WO2014143880A1 - Catalysts for petrochemical catalysis - Google Patents

Catalysts for petrochemical catalysis Download PDF

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Publication number
WO2014143880A1
WO2014143880A1 PCT/US2014/028040 US2014028040W WO2014143880A1 WO 2014143880 A1 WO2014143880 A1 WO 2014143880A1 US 2014028040 W US2014028040 W US 2014028040W WO 2014143880 A1 WO2014143880 A1 WO 2014143880A1
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Prior art keywords
catalyst
catalysts
oxide
doping
methane
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PCT/US2014/028040
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French (fr)
Inventor
Wayne P. Schammel
Anja RUMPLECKER
Joel M. Cizeron
Erik C. Scher
Fabio R. Zurcher
Greg Nyce
Jarod Mccormick
Marian ALCID
Joel Gamoras
Daniel Rosenberg
Erik-Jan Ras
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Siluria Technologies, Inc.
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Application filed by Siluria Technologies, Inc. filed Critical Siluria Technologies, Inc.
Priority to US14/777,333 priority Critical patent/US20160107143A1/en
Priority to CA2902192A priority patent/CA2902192C/en
Priority to EP14765794.4A priority patent/EP2969184A4/en
Publication of WO2014143880A1 publication Critical patent/WO2014143880A1/en
Priority to ZA2015/09145A priority patent/ZA201509145B/en
Priority to US15/888,966 priority patent/US10865166B2/en
Priority to US17/098,027 priority patent/US20210130260A1/en

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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2/00—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms
    • C07C2/76—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation of hydrocarbons with partial elimination of hydrogen
    • C07C2/82—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation of hydrocarbons with partial elimination of hydrogen oxidative coupling
    • C07C2/84—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation of hydrocarbons with partial elimination of hydrogen oxidative coupling catalytic
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
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    • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/32—Manganese, technetium or rhenium
    • B01J23/34—Manganese
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
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    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/84—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/889—Manganese, technetium or rhenium
    • B01J23/8892—Manganese
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/50—Catalysts, in general, characterised by their form or physical properties characterised by their shape or configuration
    • B01J35/58—Fabrics or filaments
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/03—Precipitation; Co-precipitation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/08—Heat treatment
    • B01J37/082—Decomposition and pyrolysis
    • B01J37/084—Decomposition of carbon-containing compounds into carbon
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    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/08—Heat treatment
    • B01J37/082—Decomposition and pyrolysis
    • B01J37/088—Decomposition of a metal salt
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C11/00—Aliphatic unsaturated hydrocarbons
    • C07C11/02—Alkenes
    • C07C11/04—Ethylene
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2/00—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms
    • C07C2/76—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation of hydrocarbons with partial elimination of hydrogen
    • C07C2/78—Processes with partial combustion
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2523/00—Constitutive chemical elements of heterogeneous catalysts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2523/00—Constitutive chemical elements of heterogeneous catalysts
    • B01J2523/20—Constitutive chemical elements of heterogeneous catalysts of Group II (IIA or IIB) of the Periodic Table
    • B01J2523/22—Magnesium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J2523/00—Constitutive chemical elements of heterogeneous catalysts
    • B01J2523/70—Constitutive chemical elements of heterogeneous catalysts of Group VII (VIIB) of the Periodic Table
    • B01J2523/72—Manganese
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2521/00—Catalysts comprising the elements, oxides or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium or hafnium
    • C07C2521/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
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    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
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    • C07C2521/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
    • C07C2521/08—Silica
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    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2521/00—Catalysts comprising the elements, oxides or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium or hafnium
    • C07C2521/10—Magnesium; Oxides or hydroxides thereof
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2523/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00
    • C07C2523/02—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of the alkali- or alkaline earth metals or beryllium
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2523/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00
    • C07C2523/10—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of rare earths
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    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2523/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00
    • C07C2523/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • C07C2523/24—Chromium, molybdenum or tungsten
    • C07C2523/30—Tungsten
    • C—CHEMISTRY; METALLURGY
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    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2523/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00
    • C07C2523/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • C07C2523/32—Manganese, technetium or rhenium
    • C07C2523/34—Manganese
    • C—CHEMISTRY; METALLURGY
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    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2523/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00
    • C07C2523/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of the iron group metals or copper
    • C07C2523/74—Iron group metals
    • C07C2523/75—Cobalt
    • C—CHEMISTRY; METALLURGY
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    • C07C2523/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of the iron group metals or copper
    • C07C2523/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups C07C2523/02 - C07C2523/36
    • C07C2523/84—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups C07C2523/02 - C07C2523/36 with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • C07C2523/889—Manganese, technetium or rhenium
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts

Definitions

  • This invention is generally related to novel catalysts and, more specifically, to doped metal oxide catalysts useful as heterogeneous catalysts in a variety of catalytic reactions, such as the oxidative coupling of methane to C2 hydrocarbons.
  • Catalysis is the process in which the rate of a chemical reaction is either increased or decreased by means of a catalyst.
  • Positive catalysts increase the speed of a chemical reaction, while negative catalysts slow it down.
  • Substances that increase the activity of a catalyst are referred to as promoters or activators, and substances that deactivate a catalyst are referred to as catalytic poisons or deactivators.
  • a catalyst is not consumed by the chemical reaction, but instead participates in multiple chemical transformations.
  • the catalytic reaction In the case of positive catalysts, the catalytic reaction generally has a lower rate-limiting free energy change to the transition state than the corresponding uncatalyzed reaction, resulting in an increased reaction rate at the same temperature.
  • a positive catalyst tends to increase the yield of desired product while decreasing the yield of undesired side products.
  • catalysts are not consumed by the reaction itself, they may be inhibited, deactivated or destroyed by secondary processes, resulting in loss of catalytic activity.
  • Catalysts are generally characterized as either heterogeneous or homogeneous.
  • Heterogeneous catalysts exist in a different phase than the reactants (e.g., a solid metal catalyst and gas phase reactants), and the catalytic reaction generally occurs on the surface of the heterogeneous catalyst.
  • the reactants e.g., a solid metal catalyst and gas phase reactants
  • the reactants must diffuse to and/or adsorb onto the catalyst surface. This transport and adsorption of reactants is often the rate limiting step in a heterogeneous catalysis reaction.
  • Heterogeneous catalysts are also generally easily separable from the reaction mixture by common techniques such as filtration or distillation.
  • a homogenous catalyst exists in the same phase as the reactants (e.g., a soluble organometallic catalyst and solvent-dissolved reactants). Accordingly, reactions catalyzed by a homogeneous catalyst are controlled by different kinetics than a
  • heterogeneously catalyzed reaction In addition, homogeneous catalysts can be difficult to separate from the reaction mixture.
  • catalysts have shown activity for OCM, including various forms of iron oxide, V 2 O 5 , MoO 3 , Co 3 O 4 , Pt-Rh, Li/ZrO 2 , Ag-Au, Au/Co 3 O 4 , Co/Mn, CeO 2 , MgO, La 2 O 3 , Mn 3 O 4 , Na 2 WO 4 , MnO, ZnO, and combinations thereof, on various supports.
  • a number of doping elements have also proven to be useful in combination with the above catalysts.
  • the low yield of desired products is caused by the unique homogeneous/heterogeneous nature of the reaction. Specifically, due to the high reaction temperature, a majority of methyl radicals escape the catalyst surface and enter the gas phase. There, in the presence of oxygen and hydrogen, multiple side reactions are known to take place (J.A. Labinger, Cat. Lett., 1 :371 , 1988). The non-selective over-oxidation of hydrocarbons to CO and CO 2 (e.g., complete oxidation) is the principal competing fast side reaction. Other undesirable products (e.g., methanol, formaldehyde) have also been observed and rapidly react to form CO and CO 2 .
  • desired products i.e., C 2 H 4 and C 2 H 6
  • heterogeneous metal oxide catalysts and related methods are disclosed.
  • catalysts comprising oxides of magnesium, manganese, tungsten and/or rare earth elements are provided.
  • the disclosed catalysts find utility in any number of catalytic reactions, for example in the OCM reaction.
  • the catalysts are advantageously doped with one or more doping elements.
  • the doping elements may be promoters such that the catalyst comprises an improved catalytic activity.
  • the catalytic activity is such that the C2 selectivity is 50% or greater and the methane conversion is 20% or greater when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 850 °C or less, 800 °C or less, for example 750 °C or less or 700 °C or less.
  • the disclosure provides a catalyst comprising a mixed oxide of magnesium and manganese, wherein the catalyst further comprises lithium and boron dopants and at least one doping element from groups 4, 9, 12, 13 or combinations thereof, wherein the catalyst comprises a C 2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
  • a catalyst comprising a mixed oxide of manganese and tungsten, wherein the catalyst further comprises a sodium dopant and at least one doping element from groups 2, 16 or combinations thereof is provided.
  • the disclosure is directed to a catalyst comprising an oxide of a rare earth element, wherein the catalyst further comprises at least one doping element from groups 1 -16, lanthanides, actinides or combinations thereof, wherein the catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
  • a catalyst comprising a mixed oxide of manganese and tungsten, wherein the catalyst further comprises a sodium dopant and at least one doping element from groups 2, 4-6, 8-15, lanthanides or combinations thereof, wherein the catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less is provided.
  • the disclosure provides a catalyst comprising a mixed oxide of a lanthanide and tungsten, wherein the catalyst further comprises a sodium dopant and at least one doping element from groups 2, 4-15, lanthanides or combinations thereof, wherein the catalyst comprises a C 2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
  • a catalyst comprising a rare earth oxide and one or more dopants
  • the catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less
  • the dopant comprises Eu/Na, Sr/Na, Na/Zr/Eu/Ca, Mg/Na, Sr/Sm/Ho/Tm, Sr/W, Mg/La/K, Na/K/Mg/Tm, Na/Dy/K, Na/La/Dy, Na/La/Eu, Na/La/Eu/ln, Na/La/K,
  • Li/Na/Sr/La Li/Sm/Cs, Ba/Sm/Yb/S, Ba/Tm/K/La, Ba/Tm/Zn/K, Cs/K/La,
  • Sr/Cs/Zn Sm/Cs, In/K, Ho/Cs/Li/La, Cs/La/Na, La/S/Sr, K/La/Zr/Ag, Lu/TI, Pr/Zn, Rb/Sr/La, Na/Sr/Eu/Ca, K Cs/Sr/La, Na/Sr/Lu, Sr/Eu/Dy, Lu/Nb,
  • Still other catalysts of the present invention include a catalyst comprising a mixed oxide of a rare earth element and a Group 13 element, wherein the catalyst further comprises one or more Group 2 elements.
  • inventions of the present invention are directed to a catalyst comprising a lanthanide oxide doped with an alkali metal, an alkaline earth metal or combinations thereof, and at least one other dopant from groups 3-16.
  • Figure 1 schematically depicts a first part of an OCM reaction at the surface of a metal oxide catalyst.
  • Figure 2 shows a method for catalyst screening.
  • Figure 3 schematically depicts a carbon dioxide reforming reaction on a catalytic surface.
  • Figure 4 is a flow chart for data collection and processing in evaluating catalytic performance.
  • Figure 5 is a chart showing various downstream products of ethylene.
  • Figure 6 shows an OCM and ethylene oligomerization module.
  • Figure 7 is a plot of conversion, selectivity and yield of an OCM reaction catalyzed with a doped and undoped catalyst.
  • Figure 8 is a plot of conversion, selectivity and yield of an OCM reaction catalyzed comparing a catalyst on two different supports.
  • Figure 9 depicts the results of high-throughput screening on a doped Co/Na/LiMnMgB library.
  • Figure 10 depicts the results of high-throughput screening on a doped MnWO 4 on silica library.
  • Figure 1 1 depicts the results of high-throughput screening on a doped Nd 2 O 3 library.
  • Figure 12 depicts the results of high-throughput screening on a doped Yb 2 O 3 library.
  • Figure 13 depicts the results of high-throughput screening on a doped EU2O3 library.
  • Figure 14 depicts the results of high-throughput screening on a doped La2O3 library.
  • the catalyst is a solid, the reactants are gases or liquids and the products are gases or liquids.
  • a heterogeneous catalyst provides a surface that has multiple active sites for adsorption of one more gas or liquid reactants. Once adsorbed, certain bonds within the reactant molecules are weakened and dissociate, creating reactive fragments of the reactants, e.g., in free radical forms. One or more products are generated as new bonds between the resulting reactive fragments form, in part, due to their proximity to each other on the catalytic surface.
  • Figure 1 shows schematically the first part of an
  • the catalytic properties of a catalyst strongly correlate to its surface morphology.
  • the surface morphology can be defined by geometric parameters such as: (1 ) the number of surface atoms (e.g., the surface oxygen of Figure 1 ) that coordinate to the reactant; and (2) the degree of coordinative unsaturation of the surface atoms, which is the coordination number of the surface atoms with their neighboring atoms. For example, the reactivity of a surface atom decreases with decreasing
  • a surface atom with 9 surface atom neighbors will have a different reactivity than one with 8 neighbors.
  • Additional surface characteristics that may contribute to the catalytic properties include, for example, crystal dimensions, lattice distortion, surface reconstructions, defects, grain
  • the catalysts disclosed herein and methods of producing the same have general applicability to a wide variety of
  • heterogeneous catalyses including without limitation: oxidative coupling of methane (e.g., Figure 1 ), oxidative dehydrogenation of alkanes to their corresponding alkenes, selective oxidation of alkanes to alkenes and alkynes, oxidation of carbon monoxide, dry reforming of methane, selective oxidation of aromatics, Fischer-Tropsch reaction, hydrocarbon cracking, combustions of hydrocarbons and the like.
  • Figure 2 schematically shows a high throughput work flow for generating libraries of diverse catalysts and screening for their catalytic properties.
  • An initial phase of the work flow involves a primary screening, which is designed to broadly and efficiently screen a large and diverse set of catalysts that logically could perform the desired catalytic transformation.
  • certain doped metal oxides e.g., Mn, Mg, W, etc.
  • catalysts of various metal oxide compositions comprising various dopants can be prepared and evaluated for their catalytic performances in an OCM reaction.
  • the work flow 100 begins with designing synthetic experiments for making various metal oxide compositions (block 1 10).
  • the synthesis, subsequent treatments and screenings can be manual or automated.
  • catalysts can be prepared with various surface morphologies and/or compositions in respective microwells (block 1 14). The catalysts are
  • the doped and calcined catalysts are further mixed with a catalyst support (block 122).
  • a catalyst support block 122
  • all subsequent steps are carried out in a "wafer" format, in which catalysts are deposited in a quartz wafer that has been etched to create an ordered array of microwells.
  • Each microwell is a self- contained reactor, in which independently variable processing conditions can be designed to include, without limitation, respective choices of elemental compositions, catalyst support, reaction precursors, templates, reaction durations, pH values, temperatures, ratio between reactants, gas flows, and calcining conditions (block 124). Due to design constraints of some wafers, in some embodiments calcining and other temperature variables are identical in all microwells.
  • a wafer map 130 can be created to correlate the processing conditions to the catalyst in each microwell.
  • a library of diverse catalysts can be generated in which each library member corresponds to a particular set of processing conditions and corresponding compositional and/or morphological characteristics.
  • Catalysts obtained under various synthetic conditions and doping compositions are thereafter deposited in respective microwells of a wafer (140) for evaluating their respective catalytic properties in a given reaction (blocks 132 and 134).
  • the catalytic performance of each library member can be screened serially by several known primary screening technologies, including scanning mass spectroscopy (SMS) (Symyx Technologies Inc., Santa Clara, California). The screening process is fully automated, and the SMS tool can determine if a catalyst is catalytically active or not, as well as its relative strength as a catalyst at a particular temperature.
  • SMS scanning mass spectroscopy
  • the wafer is placed on a motion control stage capable of positioning a single well below a probe that flows the feed of the starting material over the catalyst surface and removes reaction products to a mass spectrometer and/or other detector technologies (blocks 134 and 140).
  • the individual catalyst is heated to a preset reaction temperature, e.g., using a CO 2 IR laser from the backside of the quartz wafer and an IR camera to monitor temperature and a preset mixture of reactant gases.
  • the SMS tool collects data with regard to the consumption of the reactant(s) and the generation of the product(s) of the catalytic reaction in each well (block 144), and at each temperature and flow rate.
  • the SMS data obtained as described above provide information on relative catalytic properties among all the library members (block 150).
  • a secondary screening (block 154).
  • secondary screening technologies include a single, or alternatively multiple channel fixed-bed or fluidized bed reactors (as described in more detail herein).
  • a single feed system supplies reactants to a set of flow restrictors.
  • the flow restrictors divide the flows evenly among parallel reactors. Care is taken to achieve uniform reaction temperature between the reactors such that the various catalysts can be differentiated solely based on their catalytic performances.
  • the secondary screening allows for accurate determination of catalytic properties such as selectivity, yield and conversion (block 160). These results serve as a feedback for designing further catalyst libraries.
  • compositional and morphologically diverse catalysts can be rationally synthesized to meet catalytic performance criteria.
  • Catalyst means a substance which alters the rate of a chemical reaction.
  • a catalyst may either increase the chemical reaction rate (i.e., a "positive catalyst") or decrease the reaction rate (i.e., a "negative catalyst”).
  • Catalysts participate in a reaction in a cyclic fashion such that the catalyst is cyclically regenerated.
  • Catalytic means having the properties of a catalyst.
  • Crystal domain means a continuous region over which a substance is crystalline.
  • “Turnover number” is a measure of the number of reactant molecules a catalyst can convert to product molecules per unit time.
  • Active or “catalytically active” refers to a catalyst which has substantial activity in the reaction of interest. For example, in some
  • a catalyst which is OCM active i.e., has activity in the OCM reaction
  • “Inactive” or “catalytically inactive” refers to a catalyst which does not have substantial activity in the reaction of interest.
  • a catalyst which is OCM inactive has a C2 selectivity of less than 5% and/or a methane conversion of less than 5% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
  • Activation temperature refers to the temperature at which a catalyst becomes catalytically active.
  • OCM activity refers to the ability of a catalyst to catalyze the OCM reaction.
  • a catalyst having "high OCM activity” refers to a catalyst having a C2 selectivity of 50% or more and/or a methane conversion of 20% or more when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a specific temperature, for example 750 °C or less.
  • a catalyst having "moderate OCM activity” refers to a catalyst having a C2 selectivity of about 20-50% and/or a methane conversion of about 10-20% or more when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
  • a catalyst having "low OCM activity" refers to a catalyst having a
  • Base material refers to the major component of a catalyst.
  • a mixed oxide of manganese and magnesium which is doped with lithium and/or boron comprises a manganese/magnesium oxide base material.
  • Dopant or "doping agent” or “doping element” is chemical compound which is added to or incorporated within a catalyst base material to optimize catalytic performance (e.g., increase or decrease catalytic activity). As compared to the undoped catalyst, a doped catalyst may increase or decrease the selectivity, conversion, and/or yield of a reaction catalyzed by the catalyst. Dopants which increase catalytic activity are referred to as “promoters” while dopants which decrease catalytic activity are referred to as "poisons”.
  • the dopant may be present in the catalyst in any form and may be derived from any suitable source of the element (e.g., chlorides, bromides, iodides, nitrates, oxynitrates, oxyhalides, acetates, formates, hydroxides, carbonates,
  • suitable source of the element e.g., chlorides, bromides, iodides, nitrates, oxynitrates, oxyhalides, acetates, formates, hydroxides, carbonates,
  • “Atomic percent” (at% or at/at) or “atomic ratio” when used in the context of catalyst dopants refers to the ratio of the total number of dopant atoms to the total number of non-oxygen atoms in the base material.
  • Weight percent when used in the context of catalyst dopants refers to the ratio of the total weight of dopant to the total combined weight of the dopant and the catalyst.
  • Group 1 elements include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr).
  • Group 2 elements include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).
  • Group 3 elements include scandium (Sc) and yttrium (Y).
  • Group 4" elements include titanium (Ti), zirconium (Zr), halfnium (Hf), and rutherfordium (Rf).
  • Group 5" elements include vanadium (V), niobium (Nb), tantalum
  • Group 6 elements include chromium (Cr), molybdenum (Mo), tungsten (W), and seaborgium (Sg).
  • Group 7 elements include manganese (Mn), technetium (Tc), rhenium (Re), and bohrium (Bh).
  • Group 8 elements include iron (Fe), ruthenium (Ru), osmium (Os), and hassium (Hs).
  • Group 9 elements include cobalt (Co), rhodium (Rh), iridium (Ir), and meitnerium (Mt).
  • Group 10 elements include nickel (Ni), palladium (Pd), platinum
  • Group 1 1 elements include copper (Cu), silver (Ag), gold (Au), and roentgenium (Rg).
  • Group 12 elements include zinc (Zn), cadmium (Cd), mercury (Hg), and copernicium (Cn).
  • Group 13 elements include boron (B), aluminum (Al),gallium (Ga), indium (In) and thallium (Tl).
  • Group 16 elements include oxygen (O), sulfur (S), selenium (Se), tellurium (Te) and polonium (Po).
  • “Lanthanides” include lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), yitterbium (Yb), and lutetium (Lu).
  • La lanthanum
  • Ce cerium
  • Pr praseodymium
  • Nd neodymium
  • promethium Pm
  • Sm samarium
  • Eu europium
  • Gd gadolinium
  • Tb terbium
  • Dy dysprosium
  • Ho holmium
  • Er erbium
  • Tm thulium
  • Yb yitterbium
  • Lu lutetium
  • Actinides include actinium (Ac), thorium (Th), protactinium (Pa), uranium (U), neptunium (Np), plutonium (Pu), americium (Am), curium (Cm), berklelium (Bk), californium (Cf), einsteinium (Es), fermium (Fm), mendelevium (Md), nobelium (No), and lawrencium (Lr).
  • Ring earth elements include the lanthanides, actinides and
  • Metal element or “metal” is any element, except hydrogen, selected from Groups 1 through 12, lanthanides, actinides, aluminum (Al), gallium (Ga), indium (In), tin (Sn), thallium (Tl), lead (Pb), and bismuth (Bi).
  • Metal elements include metal elements in their elemental form as well as metal elements in an oxidized or reduced state, for example, when a metal element is combined with other elements in the form of compounds comprising metal elements.
  • metal elements can be in the form of hydrates, salts, oxides, as well as various polymorphs thereof, and the like.
  • Si-metal element refers to an element selected from boron
  • B silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te), and polonium (Po).
  • Non-metal element refers to an element selected from carbon
  • C nitrogen (N), oxygen (O), fluorine (F), phosphorus (P), sulfur (S), chlorine (CI), selenium (Se), bromine (Br), iodine (I), and astatine (At).
  • C2 refers to a hydrocarbon (i.e., compound consisting of carbon and hydrogen atoms) having only two carbon atoms, for example ethane and ethylene.
  • C3 refers to a hydrocarbon having only 3 carbon atoms, for example propane and propylene.
  • Conversion means the mole fraction (i.e., percent) of a reactant converted to a product or products.
  • Selectivity refers to the percent of converted reactant that went to a specified product, e.g., C2 selectivity is the % of converted methane that formed ethane and ethylene, C3 selectivity is the % of converted methane that formed propane and propylene, CO selectivity is the % of converted methane that formed CO.
  • Yield is a measure of (e.g., percent) of product obtained relative to the theoretical maximum product obtainable. Yield is calculated by dividing the amount of the obtained product in moles by the theoretical yield in moles. Percent yield is calculated by multiplying this value by 100.
  • C2 yield is defined as the sum of the ethane and ethylene molar flow at the reactor outlet multiplied by two and divided by the inlet methane molar flow.
  • C3 yield is defined as the sum of propane and propylene molar flow at the reactor outlet multiplied by three and divided by the inlet methane molar flow.
  • C2+ yield is the sum of the C2 yield and C3 yield. Yield is also calculable by multiplying the methane conversion by the relevant selectivity, e.g., C2 yield is equal to the methane conversion times the C2 selectivity.
  • C2 yield is the total combined yield of ethane and ethylene.
  • C2 selectivity is the combined selectivity for ethane and ethylene.
  • Bulk catalyst or “bulk material” means a catalyst prepared by traditional techniques, for example by milling or grinding large catalyst particles to obtain smaller/higher surface area catalyst particles.
  • Nanostructured catalyst means a catalyst having at least one dimension on the order of nanometers (e.g., between about 1 and 100 nanometers).
  • nanostructured catalysts include nanoparticle catalysts and nanowire catalysts.
  • Nanoparticle means a particle having at least one diameter on the order of nanometers (e.g., between about 1 and 100 nanometers).
  • Nanowire means a nanowire structure having at least one diameter on the order of nanometers (e.g., between about 1 and 100
  • the "aspect ratio" of a nanowire is the ratio of the actual length (L) of the nanowire to the diameter (D) of the nanowire. Aspect ratio is expressed as L:D.
  • Exemplary nanowires are known in the art and described in more detail in co-pending U.S. Application Nos. 13/1 15,082 (U.S. Pub. No. 2012/0041246), 13/689,514 (U.S. Pub. No. 2013/0158322) and 13/689,61 1 (U.S. Pub. No. 2013/0165728), the full disclosures of which are hereby incorporated by reference in their entireties for all purposes.
  • Polycrystalline nanowire means a nanowire having multiple crystal domains. Polycrystalline nanowires generally have different
  • Effective length of a nanowire means the shortest distance between the two distal ends of a nanowire as measured by transmission electron microscopy (TEM) in bright field mode at 5 keV.
  • Average effective length refers to the average of the effective lengths of individual nanowires within a plurality of nanowires.
  • “Actual length” of a nanowire means the distance between the two distal ends of a nanowire as traced through the backbone of the nanowire as measured by TEM in bright field mode at 5 keV. "Average actual length” refers to the average of the actual lengths of individual nanowires within a plurality of nanowires.
  • the “diameter" of a nanowire is measured in an axis perpendicular to the axis of the nanowire's actual length (i.e., perpendicular to the nanowires backbone).
  • the diameter of a nanowire will vary from narrow to wide as measured at different points along the nanowire backbone. As used herein, the diameter of a nanowire is the most prevalent (i.e., the mode) diameter.
  • ratio of effective length to actual length is determined by dividing the effective length by the actual length.
  • a nanowire having a "bent morphology” will have a ratio of effective length to actual length of less than one as described in more detail herein.
  • a straight nanowire will have a ratio of effective length to actual length equal to one as described in more detail herein.
  • Inorganic means a substance comprising a metal element or semi-metal element. In certain embodiments, inorganic refers to a substance comprising a metal element.
  • An inorganic compound can contain one or more metals in its elemental state, or more typically, a compound formed by a metal ion (M n+ , wherein n 1 , 2, 3, 4, 5, 6 or 7) and an anion (X m" , m is 1 , 2, 3 or 4), which balance and neutralize the positive charges of the metal ion through electrostatic interactions.
  • Non-limiting examples of inorganic compounds include oxides, hydroxides, halides, nitrates, sulfates, carbonates, phosphates, acetates, oxalates, and combinations thereof, of metal elements.
  • Other non- limiting examples of inorganic compounds include Li 2 CO 3 , Li 2 PO , LiOH, Li 2 O, LiCI, LiBr, Lil, Li 2 C 2 O 4 , Li 2 SO 4 , Na 2 CO 3 ,Na 2 PO 4 , NaOH, Na 2 O, NaCI, NaBr, Nal, Na 2 C 2 O 4 , Na 2 SO 4 , K 2 CO 3 ,K 2 PO 4 , KOH, K 2 O, KCI, KBr, Kl, K 2 C 2 O 4 , K 2 SO 4 , Cs 2 CO 3 , CsPO 4 , CsOH, Cs 2 O, CsCI, CsBr, Csl, CsC 2 O 4 , CsSO 4 , Be(
  • Salt means a compound comprising negative and positive ions. Salts are generally comprised of cations and counter ions. Under appropriate conditions, e.g., the solution also comprises a template, the metal ion (M n+ ) and the anion (X m" ) bind to the template to induce nucleation and growth of a nanowire of M m X n on the template.
  • Anion precursor thus is a compound that comprises an anion and a cationic counter ion, which allows the anion (X m" ) to dissociate from the cationic counter ion in a solution. Specific examples of the metal salt and anion precursors are described in further detail herein.
  • Oxide refers to a metal compound comprising oxygen.
  • oxides include, but are not limited to, metal oxides (M x O y ), metal oxyhalides (M x O y X z ), metal oxynitrates (M x O y (NO3) z ), metal phosphates
  • M x (PO 4 )y metal oxycarbonates
  • M x O y (CO3) z metal carbonates
  • metal oxyhydroxides M x O y (OH) z
  • X is independently, at each occurrence, fluoro, chloro, bromo or iodo, and x, y and z are numbers from 1 to 100.
  • Catalytic material refers to a plurality of catalyst particles, which may optionally be combined with a support, diluent and/or binder.
  • Catalyst form or “catalytic form” refers to the physical shape of a catalytic material.
  • catalyst forms include catalysts in the shape of extrudates or pellets or disposed on various support structures, including honeycomb structures, grids, monoliths, and the like, as discussed in more detail below.
  • Catalyst formulation or “catalytic formulation” refers to the chemical composition of a catalytic material.
  • a catalyst formulation may include a catalyst and one or more support, diluent and/or binder materials.
  • extrudate refers to a material (e.g., catalytic material) prepared by forcing a semisolid material comprising a catalyst through a die or opening of appropriate shape. Extrudates can be prepared in a variety of shapes and structures by common means known in the art.
  • a “formed aggregate” refers to an aggregation of catalyst material particles, either alone, or in conjunction with one or more other materials, e.g., catalyst materials, dopants, diluents, support materials, binders, etc., formed into a single particle.
  • Formed aggregates include without limitation, extruded particles, termed “extrudates", pressed or cast particles, e.g., pellets such as tablets, ovals, spherical particles, etc., coated particles, e.g., spray, immersion or pan coated particles, impregnated particles, e.g., monoliths, foils, foams, honeycombs, or the like.
  • Formed aggregates may range in size from particles having individual cross sections in the micron range to cross sections in the millimeter range, to even larger particles such as monolithic formed aggregates, that may be on the order of centimeters or even meters in cross section.
  • pellet or “pressed pellet” refers to a material (e.g., catalytic material) prepared by applying pressure to (i.e., compressing) a material comprising a catalyst into a desired shape. Pellets having various dimensions and shapes can be prepared according to common techniques in the art.
  • “Monolith” or “monolith support” is generally a structure formed from a single structural unit preferably having passages disposed through it in either an irregular or regular pattern with porous or non-porous walls separating adjacent passages.
  • monolithic supports include, e.g., ceramic or metal foam-like or porous structures.
  • the single structural unit may be used in place of or in addition to conventional particulate or granular catalysts (e.g., pellets or extrudates).
  • irregular patterned monolith substrates include filters used for molten metals.
  • Monoliths generally have a porous fraction ranging from about 60% to 90% and a flow resistance substantially less than the flow resistance of a packed bed of similar volume (e.g., about 10% to 30% of the flow resistance of a packed bed of similar volume).
  • regular patterned substrates include monolith
  • honeycomb supports used for purifying exhausts from motor vehicles and used in various chemical processes and ceramic foam structures having irregular passages.
  • Many types of monolith support structures made from conventional refractory or ceramic materials such as alumina, zirconia, yttria, silicon carbide, and mixtures thereof, are well known and commercially available from, among others, Corning, lac; Vesuvius Hi-Tech Ceramics, Inc.; and Porvair Advanced Materials, Inc. and SiCAT (Sicatalyst.com).
  • Monoliths include foams, honeycombs, foils, mesh, gauze and the like.
  • “Alkane” means a straight chain or branched, noncydic or cyclic, saturated aliphatic hydrocarbon.
  • Alkanes include linear, branched and cyclic structures.
  • Representative straight chain alkanes include methane, ethane, n- propane, n-butane, n-pentane, n-hexane, and the like; while branched alkanes include isopropane, sec-butane, isobutane, tert-butane, isopentane, and the like.
  • Representative cyclic alkanes include cyclopropane, cyclobutane, cyclopentane, cyclohexane, and the like.
  • Alkene means a straight chain or branched, noncydic or cyclic, unsaturated aliphatic hydrocarbon having at least one carbon-carbon double bond. Alkenes include linear, branched and cyclic structures. Representative straight chain and branched alkenes include ethylene, propylene, 1 -butene, 2-butene, isobutene, 1 -pentene, 2-pentene, 3- methyl-1 -butene, 2-methyl-2-butene, 2,3-dimethyl-2-butene, and the like.
  • Cyclic alkenes include cyclohexene and cyclopentene and the like.
  • Alkyne means a straight chain or branched, noncydic or cyclic, unsaturated aliphatic hydrocarbon having at least one carbon-carbon triple bond.
  • Alkynes include linear, branched and cyclic structures. Representative straight chain and branched alkynes include acetylene, propyne, 1 -butyne, 2-butyne, 1 -pentyne, 2-pentyne, 3-methyl-1 -butyne, and the like.
  • Representative cyclic alkynes include cycloheptyne and the like.
  • Aromatic means a carbocyclic moiety having a cyclic system of conjugated p orbitals. Representative examples of aromatics include benzene, naphthalene and toluene.
  • Carbon-containing compounds are compounds which comprise carbon.
  • Non-limiting examples of carbon-containing compounds include hydrocarbons, CO and CO2.
  • Mated oxide or “mixed metal oxide” refers to a compound comprising two or more oxidized metals and oxygen (e.g.,., M1 x M2 y O z , wherein M1 and M2 are the same or different metal elements, O is oxygen and x, y and z are numbers from 1 to 100).
  • a mixed oxide may comprise metal elements in various oxidation states and may comprise more than one type of metal element. For example, a mixed oxide of manganese and magnesium
  • M x O y OH z oxy- hydroxides ⁇ e.g., M x O y OH z , wherein M is a metal element, O is oxygen, x, y and z are numbers from 1 to 100 and OH is hydroxy).
  • Mixed oxides may be represented herein as M1 -M2, wherein M1 and M2 are each independently a metal element.
  • Mixed oxides comprising, 3, 4, 5, 6 or more metal elements can be represented in an analogous manner
  • Rare earth oxide refers to an oxide of an element from group 3, lanthanides or actinides.
  • Rare earth oxides include mixed oxide containing a rare earth element. Examples of rare earth oxides include, but are not limited to, La 2 O 3 , Nd 2 O 3 , Yb 2 O 3 , Eu 2 O 3 , Sm 2 O 3 , Y 2 O 3 , Ce 2 O 3 , Pr 2 O 3 , Ln1 4-x Ln2 x O 6 , La 4- ⁇ _ ⁇ 1 ⁇ ⁇ 6 , La -xNd x O 6 , wherein Ln1 and Ln2 are each independently a lanthanide element, wherein Ln1 and Ln2 are not the same and x is a number ranging from greater than 0 to less than 4, La 3 NdO 6 , LaNd 3 O 6 , Lai. 5 Nd 2 . 5 O6,
  • O 2 -OCM catalyst refers to a catalyst having activity in the OCM reaction and which predominately uses O 2 as an oxygen source.
  • CO 2 -OCM catalyst refers to a catalyst having activity in the OCM reaction and which predominately uses CO 2 as an oxygen source.
  • O 2 -ODH catalyst refers to a catalyst having activity in the ODH reaction and which predominately uses O 2 as an oxygen source.
  • CO 2 -ODH catalyst refers to a catalyst having activity in the ODH reaction and which predominately uses CO 2 as an oxygen source. Catalysts
  • the catalysts are bulk catalysts (i.e., not nanowire or other nanostructured catalysts).
  • the catalysts comprise one or more metal elements for example, the catalysts may be mono-metallic, bi-metallic, tri-metallic, etc. (i.e., contain one, two, three, etc., metal elements).
  • the metal elements are present in the catalysts in elemental form while in other embodiments the metal elements are present in oxidized form. In other embodiments the metal elements are present in the catalysts in the form of a compound comprising a metal element.
  • the metal element or compound comprising the metal element may be in the form of oxides (e.g., mixed oxides), hydroxides, carbonates, oxy-hydroxides, oxycarbonates, salts, hydrates, and the like.
  • the metal element or compound comprising the metal element may also be in the form of any of a number of different polymorphs or crystal structures.
  • the catalysts may comprise one or more element from group 2 and one or more element from group 7 which may be in the form of an oxide.
  • the catalyst may comprise magnesium and manganese.
  • the magnesium and manganese may be in oxidized form, for example in the form of a mixed metal oxide.
  • Catalysts comprising mixed oxides of Mn and Mg are well suited for incorporation of dopants because magnesium atoms can be easily substituted by other atoms as long as their size is comparable with magnesium.
  • a family of "doped" Mg 6 MnO8 compounds with the composition M( X )Mg(6 -X )MnO8, wherein each M is independently a dopant as defined herein and x is 0 to 6, can thus be created.
  • the oxidation state of Mn can be tuned by selecting different amounts (i.e., different values of x) of M with different oxidation states, for example Li (X) Mg(6 -X) MnO8 would contain a mixture of Mn(IV) and Mn(V) with x ⁇ 1 and a mixture that may include Mn(V), Mn(VI), Mn(VII) with x > 1 .
  • the maximum value of x depends on the ability of a particular atom M to be incorporated in the Mg 6 MnO8 crystal structure and therefore varies depending on M.
  • the present disclosure provides a mixed oxide of manganese and magnesium which has been doped with lithium and boron.
  • the catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a
  • heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
  • a catalyst comprising a mixed oxide of manganese and magnesium which further comprises lithium and boron and at least one doping element from any of groups 1 -13 are effective catalysts for use in the OCM reaction.
  • the at least one doping element is from groups 4, 9, 12 or 13, and in further embodiments, the catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
  • the doping element is rhodium. In other examples, the doping element is cobalt. In yet other embodiments, the doping element is zirconium, while in other embodiments, the doping element is zinc. Other embodiments include a gallium doping element or a sodium doping element.
  • the present disclosure provides a mixed oxide of manganese and magnesium which further includes lithium, boron, cobalt and sodium as dopants.
  • the catalyst comprises a mixed oxide of manganese and magnesium which further includes lithium, boron, gallium and sodium as dopants.
  • the catalyst comprises a mixed oxide of manganese and magnesium and further comprises lithium and boron dopants and at least one doping element from groups 4, 9, 12, 13 or combinations thereof, and further comprises at least one additional doping element from group 2.
  • a catalyst comprising a mixed oxide of manganese and magnesium which further includes lithium, boron, cobalt and sodium can be further doped with beryllium, barium, aluminum, hafnium or combinations thereof.
  • the mixed oxide of manganese and magnesium is further doped with beryllium.
  • the mixed oxide of manganese and magnesium is further doped with barium.
  • the mixed oxide of manganese and magnesium is further doped with aluminum.
  • the mixed oxide of manganese and magnesium is further doped with hafnium.
  • a catalyst comprising a mixed oxide of manganese and magnesium which further includes lithium, boron, gallium and sodium can be further doped with beryllium, barium, aluminum, hafnium or combinations thereof.
  • the mixed oxide of manganese and magnesium is further doped with beryllium.
  • the mixed oxide of manganese and magnesium is further doped with barium.
  • the mixed oxide of manganese and magnesium is further doped with aluminum.
  • the mixed oxide of manganese and magnesium is further doped with hafnium.
  • Mixed oxides comprising manganese, tungsten and sodium (Na/Mn/W/O) is a promising OCM catalyst.
  • Na/Mn/W/O catalyst surface area is relatively low ⁇ 2m 2 /g.
  • addition of certain dopants to the Na/Mn/W/O catalyst system can increase the catalytic activity thereof.
  • certain catalyst supports as described below, with or without dopants can increase the catalytic activity of the Na/Mn/W/O catalyst, for example in the OCM reaction.
  • the Na/Mn/W/O catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
  • Doping elements which have been found to increase the catalytic activity of a Na/Mn/W/O catalyst include elements from groups 2, 16 or combinations thereof. Accordingly, in some embodiments the Na/Mn/W/O catalyst is doped with at least one doping element from group 2, 16 or combinations thereof. For example, some embodiments include beryllium, barium, aluminum, hafnium or combinations thereof as dopants. In other embodiments, the doping element is beryllium. In some other embodiments, the doping element is barium. In yet other embodiments, the doping element is aluminum, while in other embodiments, the doping element is hafnium.
  • the Na/Mn/W/O catalyst has also been found to benefit from various catalyst supports, including those described below.
  • the catalyst support is SiO 2 .
  • the catalyst support is S1O2, Z D2, HfO2, lnO2 or combinations thereof.
  • the rare earth oxide is a rare earth mixed oxide (i.e., an oxide of two or more rare earth elements).
  • the rare earth oxide may comprise any rare earth element, and in certain embodiments the rare earth element is La, Nd, Eu, Sm, Yb, Gd or Y. In some embodiments, the rare earth element is La. In other embodiments, the rare earth element is Nd. In other embodiments, the rare earth element is Eu. In other embodiments, the rare earth element is Sm. In other embodiments, the rare earth element is Yb. In other embodiments, the rare earth element is Gd. In other embodiments, the rare earth element is Y.
  • the catalyst may further comprise a dopant selected from alkaline earth (Group 2) elements.
  • the dopant is selected from Be, Mg, Ca, Sr and Ba.
  • the dopant is Be.
  • the dopant is Ca.
  • the dopant is Sr.
  • the dopant is Ba.
  • the rare earth oxide is a mixed rare earth oxide such as La 3 NdO 6 , LaNd 3 O 6 , La1.5Nd2.5O6, La2.5Nd1.5O6, La3.2Ndo.8O6, La3.5Ndo.5O6, La3.8Ndo.2O6 or combinations thereof and the like.
  • the degree of effectiveness of a particular dopant is a function of the rare earth used and the concentration of the dopant.
  • further embodiments of the rare earth oxide catalysts include embodiments wherein the catalysts comprise alkali elements as dopants which further promote the selectivity of the OCM catalytic activity of the doped material.
  • the catalysts comprise both an alkali element and alkali earth element as dopant.
  • the catalyst comprises a rare earth oxide (e.g., rare earth mixed oxides) and at least one dopant is selected from groups 1 -16, lanthanides actinides or combinations thereof.
  • such catalysts comprises a C 2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
  • the at least one doping element is selected from groups 1 -4, 8, 13, 14, lactinides, actinides and combinations thereof.
  • the at least one doping element is selected from groups 1 -6, 8, 1 1 , 13-15, lactinides, actinides and combinations thereof.
  • the at least one doping element is a rare earth element.
  • the at least one doping element is Na, Mg, Ca, Sr, Ga, Sc, Y, Zr, In, Nd, Eu, Sm, Ce, Gd, Hf, Ho, Tm, W, La, K, Dy, Cs, S, Zn, Rb, Ba, Yb, Ni, Lu, Ta, P, Pt, Bi, Sn, Nb, Sb, Ge, Ag, Au, Pb, Re, Fe, Al, Tl, Pr, Co, Rh, Ti, V, Cr, Mn, Ir, As, Li, Tb ,Er, Te or Mo.
  • the at least one doping element is sodium. In other embodiments, the at least one doping element is magnesium. In other embodiments, the at least one doping element is calcium. In other words, sodium. In other embodiments, the at least one doping element is magnesium. In other embodiments, the at least one doping element is calcium. In other words, sodium. In other embodiments, the at least one doping element is magnesium. In other embodiments, the at least one doping element is calcium. In other
  • the at least one doping element is strontium. In other words,
  • the at least one doping element is gallium. In other words, the at least one doping element is gallium. In other words,
  • the at least one doping element is Scandium. In other embodiments, the at least one doping element is yttrium. In other
  • the at least one doping element is zirconium. In other embodiments, the at least one doping element is indium. In other
  • the at least one doping element is neodymium. In other embodiments, the at least one doping element is europium. In other
  • the at least one doping element is cerium. In other words, the at least one doping element is cerium.
  • the at least one doping element is gadolinium. In other embodiments, the at least one doping element is hafnium. In other
  • the at least one doping element is holmium.
  • the at least one doping element is thulium.
  • the at least one doping element is tungsten.
  • the at least one doping element is lanthanum. In other embodiments, the at least one doping element is potassium. In other embodiments, the at least one doping element is dysprosium. In other embodiments, the at least one doping element is caesium. In other
  • the at least one doping element is sulfur. In other embodiments, the at least one doping element is zinc. In other embodiments, the at least one doping element is rubidium. In other embodiments, the at least one doping element is barium. In other embodiments, the at least one doping element is ytterbium. In other embodiments, the at least one doping element is nickel. In other embodiments, the at least one doping element is lutetium. In other embodiments, the at least one doping element is tantalum. In other
  • the at least one doping element is phosphorous. In other embodiments, the at least one doping element is platinum. In other
  • the at least one doping element is bismuth. In other words, the at least one doping element is bismuth.
  • the at least one doping element is tin. In other embodiments, the at least one doping element is niobium. In other embodiments, the at least one doping element is antimony. In other embodiments, the at least one doping element is germanium. In other embodiments, the at least one doping element is silver. In other embodiments, the at least one doping element is gold. In other embodiments, the at least one doping element is lead. In other embodiments, the at least one doping element is rhenium. In other
  • the at least one doping element is iron. In other embodiments, the at least one doping element is aluminum. In other embodiments, the at least one doping element is thalium. In other embodiments, the at least one doping element is praseodymium. In other embodiments, the at least one doping element is cobalt. In other embodiments, the at least one doping element is rhodium. In other embodiments, the at least one doping element is titanium. In other embodiments, the at least one doping element is vanadium. In other embodiments, the at least one doping element is chromium. In other embodiments, the at least one doping element is manganese. In other embodiments, the at least one doping element is iridium. In other embodiments, the at least one doping element is arsenic. In other
  • the at least one doping element is terbium. In other words, the at least one doping element is terbium.
  • the at least one doping element is erbium. In other words,
  • the at least one doping element is tellurium. In other words, the at least one doping element is tellurium.
  • the at least one doping element is molybdenum.
  • Certain other metal oxides and/or mixed oxides with optional dopants have been found to have advantageously superior properties when employed as a heterogeneous catalyst, for example in the OCM reaction.
  • certain embodiments are directed to a catalyst comprising an oxide of at least one metal and further comprising one or more element (a doping element) from the lanthanides or groups 2, 3, 4, 6 or 13 of the periodic table, wherein the metal is selected from groups 4, 12 and 13 of the periodic table and Ce, Pr, Nd, Sm, Eu, Gd, Tb and Ho.
  • the catalyst is a metal oxide and the element from groups 2, 3, 4, 6 or 13 is a dopant (i.e., the catalyst is a doped metal oxide).
  • the catalyst is a perovskite or perovskite-like oxide which is optionally doped.
  • the catalyst is a mixed metal oxide which is optionally doped.
  • the catalyst comprises an oxide of at least one metal and further comprising one or more element (a doping element) from the lanthanides or groups 2, 3 or 4 of the periodic table, wherein the metal is selected from groups 4, 12 and 13 of the periodic table and Ce, Eu, Gd, Tb and Ho.
  • the catalyst is a metal oxide and the element from groups 2, 3 or 4 is a dopant (i.e., the catalyst is a doped metal oxide).
  • the catalyst comprises an oxide of at least one metal and further comprising one or more element (a doping element) from groups 2, 6 or 13 of the periodic table, for example groups 6 or 13, wherein the metal is selected from Pr, Nd and Sm.
  • the catalyst is a metal oxide and the element from groups 6 or 13 is a dopant (i.e., the catalyst is a doped metal oxide).
  • the catalyst is a bulk catalyst.
  • the catalyst is a nanostructured catalyst, such as a nanowire.
  • Specific embodiments include catalysts comprising an inorganic catalytic polycrystalline nanowire, the nanowire having a ratio of effective length to actual length of less than one and an aspect ratio of greater than ten as measured by TEM in bright field mode at 5 keV, wherein the nanowire comprises one or more elements from any of Groups 1 through 7, lanthanides, actinides or combinations thereof as described in in co-pending U.S.
  • nanowire embodiments include nanowires having a ratio of effective length to actual length of one (i.e., a "straight" nanowire), for example as described in the foregoing published patent applications.
  • the catalysts comprise or have the formula AxByOz, where 'A' is the element from the lanthanides or group 2, 3, 4, 6 or 13, 'B' is the metal, O is an oxygen anion, x, y and z are numbers greater than 0.
  • x is selected such that charges of A and B and any other elements present are balanced (i.e., net zero charge).
  • x does not balance the charges of A and B and any other elements present and the catalysts are charged (i.e., salts).
  • salts include salts of the foregoing oxides.
  • a and B are not the same.
  • the catalysts comprise additional elements.
  • the catalysts comprise or have one of the following formulas E 1 a A x ByO z , E 1 a E 2 b A x ByO z or E 1 a E 2 b E 3 cA x ByO z , wherein E 1 , E 2 and E 3 are each independently elements and a, b and c are each independently numbers greater than 0.
  • the catalysts comprising or having formula A x B y O z , E 1 a A x ByO z , E 1 a E 2 b A x B y O z or E 1 aE 2 b E 3 c A x ByO z , B is selected from Zn, Hf, Zr, Al, Ti, Pr, Nd, Ce, Sm, Eu, Gd, Tb and Ho. In other words,
  • A is selected from Ba, Zr, Sr, Sm, Hf, Gd, Er, Y, Ca, La, Mg, W, B, Tb and Ce.
  • E1 , E2 and E3, when present, are selected from elements in groups 2, 3, 4 and the lanthanides.
  • the catalyst is in the form of a perovskite or perovskite-like oxide (i.e., ABO3, where 'A' is the element from the lanthanides or group 2, 3, 4, 6 or 13, 'B' is the metal, and O is an oxygen anion that bonds to both A and B) which may optionally contain additional elements (e.g., dopants).
  • the perovskite or perovskite-like oxide comprise a metal from group 4 and an element from group 2.
  • the metal from group 4 is Ti, Zr or Hf and the element from group 2 is Ba, Sr or Ca, for example Sr.
  • the perovskite or perovskite-like oxide comprise a metal from group 13 and an element from group 2.
  • the metal from group 13 is Al and the element from group 2 is Ba, Sr or Ca, for example Sr.
  • the perovskite or perovskite-like oxide comprise a metal from the lanthanides and an element from group 2.
  • the metal from the lanthanides is Ce, Sm or Tb and the element from group 2 is Ba, Sr or Ca, for example Sr.
  • the lanthanide is Sm and the element from group 2 is Ca.
  • the element from the lanthanides is Ce or Tb and the element from group 2 is Sr.
  • the perovskite or perovskite-like oxide comprise a metal from the lanthanides and an element from group 13.
  • the metal from the lanthanides is Pr and the element from group 13 is Ga.
  • the perovskite or perovskite-like oxide is BaZrO 3 , SrZrO 3 , SrAIO 3 , SrCeO 3 , SrHfO 3 , CaHfO 3 , SrTbO 3 or BaTiO 3 .
  • the perovskite or perovskite-like oxide is doped with a dopant from any one of groups 2, 3 or the lanthanides.
  • the dopant is selected from Sr, Y, La, Nd, Ca, Mg, Ce and combinations thereof.
  • the perovskite or perovskite-like oxide is doped with a dopant from group 2, for example Sr, Mg, Ca or combinations thereof.
  • the perovskite or perovskite-like oxide is doped with an element from group 3, for example Y.
  • the perovskite or perovskite-like oxide is doped with an element from the lanthanides, for example La, Nd, Ce or combinations thereof.
  • the catalyst is a mixed metal oxide.
  • the mixed metal oxide comprises a metal selected from group 13, such as Ga or In, and a lanthanide, such as Ce or Gd.
  • such mixed metal oxides further comprise an element from group 2, such as Ba, and/or an additional lanthanide, such as Pr.
  • the mixed metal oxide comprises Eu or Nd and a metal from group 2, such as Ca.
  • such mixed metal oxides optionally further comprise a lanthanide element, such as Sm.
  • these mixed metal oxides further comprise an element from group 13, such as B.
  • the mixed metal oxides comprise and element from group 12, such as Zn, and an element from group 2 and/or group 4, for example, Ba and/or Ti.
  • the mixed metal oxides comprise one or more doping elements, examples of which are provided throughout the specification, including Tables 1 -8.
  • the element from the lanthanides is Ce or Pr. In other embodiments, the element is from groups 2, 3 or 4. In some embodiments, the element is from group 2. In other embodiments, the element is from group 3. In other embodiments, the element is from group 4.
  • the element from the lanthanides or group 2, 3 or 4 is selected from any of the elements within the respective groups.
  • the element is selected from Ce, Pr, Sr, Ca, Mg, Y, Zr and Ba.
  • the element is selected from Ce, Pr, Sr, Ca, Mg, Y, Zr, Ba and Hf.
  • the element is Ce.
  • the element is Pr.
  • the element is Sr.
  • the element is Ca.
  • the element is Mg.
  • the element is Y.
  • the element is Zr.
  • the element is Ba. In certain
  • the element is Hf.
  • the catalyst comprises two of the foregoing elements (in addition to the metal).
  • the catalyst comprises two doping elements selected from groups 2 and 3, for example one element from group 2 and one element from group 3. In some of the
  • the element from group 2 is Ba. In other embodiments, the element from group 3 is Y. In some embodiments, the element from group 2 is Ba and the element from group 3 is Y.
  • the catalyst comprises two doping elements selected from groups 2 and 4, for example one element from group 2 and one element from group 4.
  • the catalyst comprises a metal from group 12 (e.g., in the form of an oxide) and doping elements selected from groups 2 and 4, for example one element from group 2 and one element from group 4.
  • the doping element from group 2 is Sr or Ba.
  • the doping element from group 2 is Sr.
  • the doping element from group 2 is Ba.
  • the doping element from group 4 is Zr or Hf.
  • the doping element from group 4 is Zr. In other embodiments, the doping element from group 4 is Hf. In certain of the foregoing embodiments, the metal from group 12 is Zn, for example in the form of a zinc oxide such as ZnO.
  • the catalyst comprises a metal from group 12 ⁇ e.g., a zinc oxide) and doping elements selected from Ba, Sr, Zr and Hf.
  • the doping elements comprise Ba and Hf.
  • the doping elements comprise Ba and Zr.
  • the doping elements comprise Sr and Zr. In more embodiments, the doping elements comprise Sr and Hf.
  • the metal is selected from group 4.
  • the metal is Zr.
  • the metal is Hf.
  • the metal is selected from group 12.
  • the metal is Zn. In some more embodiments, the metal is Zn.
  • the metal is selected from group 13, for example Ga.
  • the metal is Ce. In some other embodiments, the metal is Eu. In still other embodiments, the metal is Gd. In still other embodiments, the metal is Tb. In still other embodiments, the metal is Ho.
  • the catalyst comprises one of the following combinations: Lao.8Sro.2Gao.9Mgo.1 O3, Y/SrZrO3,
  • SrCeO 3 /SrCe 2 O 4 Ba/ZnO, Ba/Zr/ZnO, Ba/Sr/ZnO, Ba/Y/ZnO, SrHfO 3 , SrZrO 3 , Mg/SrHfOs, Sr/Gd 2 O 3 , CaHfO 3 , SrTbO 3 , Ca/Ho 2 O 3 , Sr/BaZrO 3 , Y/SrZrO 3 , La/SrAIO 3 , La/Nd/SrAIO 3 , Ca/BaZrO 3 , La/SrCeO 3 , SrZrO 3 , SrHfO 3 , Mg/SrHfO 3 , CaHfO 3 , SrTbO 3 , BaTiO 3 , Ba-Gd-ln, CaSmO 3 , Sm-Eu-Ca, Ce/GaPrO 3 , Ba,
  • the element e.g., doping element
  • the element is selected from one or more elements in groups 2, 6 and 13.
  • the element is selected from Sr, Ba, W and B.
  • the element is Sr.
  • the element is Ba.
  • the element is W.
  • the element is B.
  • the doping combination is selected from Ba/Sr, Ba/W and Ba/B.
  • the dopants comprise W/Sr. W/Ba or W/B.
  • the dopants comprise B/Sr, B/Ba or B/W.
  • the doping elements comprise one of the following combinations: Sr/Ba/W, Sr/Ba/B, Sr/W/B or Ba/W/B.
  • the dopant combination comprises Sr/Ba/W/B.
  • the elements comprise one of the following combination of elements: Ba/Zr; Ba/Hf; Ba/Hf/Sm; Ba/Zr/Sm; Ba/Zr/Er; Ba/Hf/Er; Sr/Hf; Sr/Zr; Sr/Hf/Sm; Sr/Hf/Er or Ba/Hf/Gd.
  • the metal is from group 12, such as Zn, and is the form of an oxide, such as ZnO.
  • doping elements described herein with respect to the catalysts can be present in varying concentration with respect to the base catalyst metal.
  • One of skill in the art will be able to identify doping
  • concentration appropriate for the desired application e.g., use as an OCM catalyst.
  • concentrations for doping elements are provided below.
  • the present inventors have discovered that certain doped metal carbonate catalysts have desirable catalytic properties in petrochemical catalytic reactions, such as OCM.
  • the catalyst is a group 2 metal carbonate comprising a dopant.
  • the metal carbonate is MgCO3, CaCO3 or SrCO3.
  • the metal carbonate is CaCO 3 .
  • the dopant for the metal carbonate may be selected from any one of a number of elements, for example an element from group 4.
  • the dopant is Zr.
  • the metal carbonate catalyst is Zr/CaCO3.
  • a catalyst comprising an oxide of at least one metal and further
  • certain embodiments of these catalysts are capable of methane conversions in an OCM reaction of greater than 20% and C2 selectivities of greater than 50% at temperatures ranging from about 550 C to about 750 C, for example, from about 600 C to about 700 C.
  • the methane conversion is greater than 22%, greater than 24% or even greater than 26%.
  • the C2 selectivity of the catalysts is greater than 55% or even greater than 60%.
  • the reaction proceeds with substantially no reforming of methane to CO and H 2 .
  • the product gas from the reaction comprises less 0.5% CO, less than 0.2%, and in some cases about 0.1 % or less, as compared to between about 0.6% and 2% for other high activity OCM catalysts.
  • the H 2 concentration in the outlet gas under such conditions will typically be less than about 1 .5%, less than about 1 %, less than about 0.8%, and in many cases less than about 0.5%, as compared to other high activity OCM catalysts that can typically provide H 2 concentrations in excess of 2 %. Accordingly, processes employing such catalysts recognize significant reduction in capital costs since the separations are simplified. Embodiments of the present invention include such processes (i.e., an OCM process having substantially no reforming of methane to CO and H 2 as described above).
  • the catalyst comprises a rare earth oxide and a combination of at least two different doping elements.
  • the two different doping elements are selected from Na, Mg, Ca, Sr, Ga, Sc, Y, Zr, In, Nd, Eu, Sm, Ce, Gd, Hf, Ho, Tm, W, La, K, Dy, In, Cs, S, Zn, Rb, Ba, Yb, Ni, Lu, Ta, P, Pt, Bi, Sn, Nb, Sb, Ge, Ag, Au, Pb, Re, Fe, Al, Tl, Pr, Co, Rh, Ti, V, Cr, Mn, Ir, As, Li, Tb ,Er, Te and Mo.
  • the combination of at least two doping elements is Eu/Na, Sr/Na, Mg/Na, Sr/W, K La, K Na, Li/Cs, Li/Na, Zn/K, Li/K, Rb/Hf, Ca/Cs, Hf/Bi, Sr/Sn, Sr/W, Sr/Nb, Zr/W, Y/W, Na/W, Bi/W, Bi/Cs, Bi/Ca, Bi/Sn, Bi/Sb, Ge/Hf, Hf/Sm, Sb/Ag, Sb/Bi, Sb/Au, Sb/Sm, Sb/Sr, Sb/W, Sb/Hf, Sb/Yb, Sb/Sn, Yb/Au, Yb/Ta, Yb/W, Yb/Sr, Yb/Pb, Yb/W, Yb/Ag, Au/Sr, W/Ge,
  • the combination of at least two different doping elements is La/Nd, La/Sm, La/Ce, La/Sr, Eu/Na, Eu/Gd, Ca/Na, Eu/Sm, Eu/Sr, Mg/Sr, Ce/Mg, Gd/Sm, Sr/W, Sr/Ta, Au/Re, Au/Pb, Bi/Hf, Sr/Sn, Mg/N, Ca/S, Rb/S, Sr/Nd, Eu/Y, Mg/Nd, Sr/Na, Nd/Mg, La/Mg, Yb/S, Mg/Na, Sr/W, K La, K Na, Li/Cs, Li/Na, Zn/K, Li/K, Rb/Hf, Ca/Cs, Hf/Bi, Sr/Sn, Sr/W, Sr/Nb, Zr/W, Y/W, Na/W, Bi/W, Bi/Cs,
  • the combination of two doping elements is La/Nd. In other embodiments, the combination of two doping elements is La/Sm. In other embodiments, the combination of two doping elements is La/Ce. In other embodiments, the combination of two doping elements is La/Sr. In other embodiments, the combination of two doping elements is Eu/Na. In other embodiments, the combina ion of two doping elements is Eu/Gd. In other embod ments, the comb nation of two doping e emen ts is Ca/Na In other embod ments, the comb nation of two doping e emen ts is Eu/Sm .
  • the comb nation of two doping e emen ts is Eu/Sr. In other embodments, the comb nation of two doping e emen ts is Mg/Sr. In other embod ments, the comb nation of two doping e emen ts is Ce/Mg . In other embod ments, the comb nation of two doping e emen ts is Gd/Sm . In other embod ments, the comb nation of two doping e emen ts is Sr/W. In other embod ments, the comb nation of two doping e emen ts is Sr/Ta.
  • the comb nation of two doping e emen ts is Au/Re. In other embodments, the comb nation of two doping e emen ts is Au/Pb. In other embod ments, the comb nation of two doping e emen ts is Bi/Hf. In other embod ments, the comb nation of two doping e emen ts is Sr/Sn. In other embod ments, the comb nation of two doping e emen ts is Mg/N. In other embod ments, the comb nation of two doping e emen ts is Ca/S.
  • the comb nation of two doping e emen ts is Rb/S. In other embodments, the comb nation of two doping e emen ts is Sr/Nd. In other embod ments, the comb nation of two doping e emen ts is Eu/Y. In other embod ments, the comb nation of two doping e emen ts is Mg/Nd . In other embod ments, the comb nation of two doping e emen ts is Sr/Na. In other embod ments, the comb nation of two doping e emen ts is Nd/Mg .
  • the comb nation of two doping e emen ts is La/Mg. In other embod ments, the comb nation of two doping e emen ts is Yb/S. In other embod merits, the comb nation of two doping e emen ts is Mg/Na . In other embod merits, the comb nation of two doping e emen ts is Sr/W. In other embod merits, the comb nation of two doping e emen ts is K/La. In other embod merits, the comb nation of two doping e emen ts is K/Na.
  • the comb nation of two doping e emen ts is Li/Cs. In other embod merits, the comb nation of two doping e emen ts is Li/Na. In other embod merits, the comb nation of two doping e emen ts is Zn/K. In other embod merits, the comb nation of two doping e emen ts is Li/K. In other embod merits, the comb nation of two doping e emen ts is Rb/Hf.
  • the comb nation of two doping e emen ts is Ca/Cs In other embod merits, the comb nation of two doping e emen ts is Hf/Bi. In other embod merits, the comb nation of two doping e emen ts is Sr/Sn. In other embod merits, the comb nation of two doping e emen ts is Sr/W. In other embod merits, the comb nation of two doping e emen ts is Sr/Nb. In other embod merits, the comb nation of two doping e emen ts is Zr/W.
  • the comb nation of two doping e emen ts is Y/W. n other embod merits, the comb nation of two doping e emen ts is Na/W. In other embod merits, the comb nation of two doping e emen ts is Bi/W. In other embod merits, the comb nation of two doping e emen ts is Bi/Cs. In other embod merits, the comb nation of two doping e emen ts is Bi/Ca. In other embod merits, the comb nation of two doping e emen ts is Bi/Sn.
  • the comb nation of two doping e emen ts is Bi/Sb. In other embod merits, the comb nation of two doping e emen ts is Ge/Hf. In other embod merits, the comb nation of two doping e emen ts is Hf/Sm In other embod merits, the comb nation of two doping e emen ts is Sb/Ag. In other embod merits, the comb nation of two doping e emen ts is Sb/Bi. In other embod merits, the comb nation of two doping e emen ts is Sb/Au.
  • the comb nation of two doping e emen ts is Sb/Sm . In other embod merits, the comb nation of two doping e emen ts is Sb/Sr. In other embod merits, the comb nation of two doping e emen ts is Sb/W. In other embod merits, the comb nation of two doping e emen ts is Sb/Hf.
  • the comb nation of two doping e emen ts is Sb/Yb In other embod merits, the comb nation of two doping e emen ts is Sb/Sn In other embod merits, the comb nation of two doping e emen ts is Yb/Au In other embod merits, the comb nation of two doping e emen ts is Yb/Ta. In other embod merits, the comb nation of two doping e emen ts is Yb/W. In other embod merits, the comb nation of two doping e emen ts is Yb/Sr.
  • the comb nation of two doping e emen ts is Yb/Pb In other embod merits, the comb nation of two doping e emen ts is Yb/W. In other embod merits, the comb nation of two doping e emen ts is Yb/Ag In other embod merits, the comb nation of two doping e emen ts is Au/Sr. In other embod merits, the comb nation of two doping e emen ts is W/Ge. In other embod merits, the comb nation of two doping e emen ts is Ta/Hf.
  • the comb nation of two doping e emen ts is W/Au. In other embod merits, the comb nation of two doping e emen ts is Ca/W. In other embod merits, the comb nation of two doping e emen ts is Au/Re In other embod merits, the comb nation of two doping e emen ts is Sm/Li. In other embod merits, the comb nation of two doping e emen ts is La/K. In other embod merits, the comb nation of two doping e emen ts is Zn/Cs.
  • the comb nation of two doping e emen ts is Zr/Cs. In other embod merits, the comb nation of two doping e emen ts is Ca/Ce . In other embod merits, the comb nation of two doping e emen ts is Li/Sr. In other embod merits, the comb nation of two doping e emen ts is Cs/Zn. In other embod merits, the comb nation of two doping e emen ts is Dy/K.
  • the comb nation of two doping e emen ts is La/Mg In other embod merits, the comb nation of two doping e emen ts is In/Sr. In other embod merits, the comb nation of two doping e emen ts is Sr/Cs. In other embod merits, the comb nation of two doping e emen ts is Ga/Cs . In other embod merits, the comb nation of two doping e emen ts is Lu/Fe.
  • the comb nation of two doping e emen ts is Sr/Tm
  • the comb nation of two doping e emen ts is La/Dy.
  • the comb nation of two doping e emen ts is Mg/K.
  • the comb nation of two doping e emen ts is Zr/K.
  • the comb nation of two doping e emen ts is Li/Cs.
  • the comb nation of two doping e emen ts is Sm/Cs .
  • the comb nation of two doping e emen ts is In/K. In other embod merits, the comb nation of two doping e emen ts is Lu/TI. In other embod merits, the comb nation of two doping e emen ts is Pr/Zn. In other embod merits, the comb nation of two doping e emen ts is Lu/Nb. In other embod merits, the comb nation of two doping e emen ts is Na/Pt.
  • the comb nation of two doping e emen ts is Na/Ce In other embod merits, the comb nation of two doping e emen ts is Ba/Ta. In other embod merits, the comb nation of two doping e emen ts is Cu/Sn In other embod merits, the comb nation of two doping e emen ts is Ag/Au. In other embod merits, the comb nation of two doping e emen ts is Al/Bi. In other embod merits, the comb nation of two doping e emen ts is Al/Mo.
  • the comb nation of two doping e emen ts is Al/Nb. In other embod merits, the comb nation of two doping e emen ts is Au/Pt. In other embod merits, the comb nation of two doping e emen ts is Ga/Bi. In other embod merits, the comb nation of two doping e emen ts is Mg/W. In other embod merits, the comb nation of two doping e emen ts is Pb/Au. In other embod merits, the comb nation of two doping e emen ts is Sn/Mg .
  • the comb nation of two doping e emen ts is Zn/Bi. In other embod merits, the comb nation of two doping e emen ts is Gd/Ho . In other embod merits, the comb nation of two doping e emen ts is Zr/Bi. In other embod merits, the comb nation of two doping e emen ts is Ho/Sr. In other embod merits, the comb nation of two doping e emen ts is Ca/Sr. In other embod merits, the comb nation of two doping e emen ts is Sr/Pb.
  • the comb nation of two doping e emen ts is Sr/Hf.
  • the oxide of a rare earth element comprises a combination of at least three different doping elements.
  • the three different doping elements are selected from Na, Mg, Ca, Sr, Ga, Sc, Y, Zr, In, Nd, Eu, Sm, Ce, Gd, Hf, Ho, Tm, W, La, K, Dy, In, Cs, S, Zn, Rb, Ba, Yb, Ni, Lu, Ta, P, Pt, Bi, Sn, Nb, Sb, Ge, Ag, Au, Pb, Re, Fe, Al, Tl, Pr, Co, Rh, Ti, V, Cr, Mn, Ir, As, Li, Tb ,Er, Te and Mo.
  • the combination of at least three different doping elements is Mg/La/K, Na/Dy/K, Na/La/Dy, Na/La/Eu, Na/La/K, K La/S, Li/Cs/La, Li/Sr/Cs, Li/Ga/Cs, Li/Na/Sr, Li/Sm/Cs, Cs/K/La, Sr/Cs/La, Sr/Ho/Tm, La/Nd/S, Li/Rb/Ca, Rb/Sr/Lu, Na/Eu/Hf, Dy/Rb/Gd, Na/Pt/Bi, Ca/Mg/Na, Na/K Mg, Na/Li/Cs,
  • the combination of at least three different doping elements is Nd/Sr/CaO, La/Nd/Sr, La/Bi/Sr, Mg/Nd/Fe,
  • the combination of at least three different doping elements is Nd/Sr/CaO. In other embodiments, the combination of at least three different doping elements is La/Nd/Sr. In other embodiments, the combination of at least three different doping elements is La/Bi/Sr. In other embodiments, the combination of at least three different doping elements is Mg/Nd/Fe. In other embodiments, the combination of at least three different doping elements is Mg/La/K. In other embodiments, the combination of at least three different doping elements is Na/Dy/K. In other embodiments, the combination of at least three different doping elements is Na/La/Dy. In other embodiments, the combination of at least three different doping elements is Na/La/Dy. In other embodiments, the combination of at least three different doping elements is Na/La/Eu. In other embodiments, the combination of at least three different doping elements is Na/La/K. In other embodiments, the combination of at least three different doping elements is K/La/S. In
  • combination of at least three different doping elements is Li/Cs/La. In other embodiments, the combination of at least three different doping elements is Li/Sr/Cs. In other embodiments, the combination of at least three different doping elements is Li/Ga/Cs. In other embodiments, the combination of at least three different doping elements is Li/Na/Sr. In other embodiments, the combination of at least three different doping elements is Li/Sm/Cs. In other embodiments, the combination of at least three different doping elements is Cs/K La. In other embodiments, the combination of at least three different doping elements is Sr/Cs/La. In other embodiments, the combination of at least three different doping elements is Sr/Ho/Tm.
  • the combination of at least three different doping elements is La/Nd/S. In other embodiments, the combination of at least three different doping elements is Li/Rb/Ca. In other embodiments, the combination of at least three different doping elements is Rb/Sr/Lu. In other embodiments, the combination of at least three different doping elements is Na/Eu/Hf. In other embodiments, the combination of at least three different doping elements is Dy/Rb/Gd. In other embodiments, the combination of at least three different doping elements is Na/Pt/Bi. In other embodiments, the combination of at least three different doping elements is Ca/Mg/Na. In other embodiments, the combination of at least three different doping elements is Na/K/Mg.
  • the combination of at least three different doping elements is Na/Li/Cs. In other embodiments, the combination of at least three different doping elements is La/Dy/K. In other embodiments, the combination of at least three different doping elements is Sm/Li/Sr. In other embodiments, the combination of at least three different doping elements is Li/Rb/Ga. In other embodiments, the combination of at least three different doping elements is Li/Cs/Tm. In other embodiments, the combination of at least three different doping elements is Li/K/La. In other embodiments, the combination of at least three different doping elements is Ce/Zr/La. In other embodiments, the combination of at least three different doping elements is Ca/AI/La.
  • the combination of at least three different doping elements is Sr/Zn/La. In other embodiments, the combination of at least three different doping elements is Cs/La/Na. In other embodiments, the combination of at least three different doping elements is La/S/Sr. In other embodiments, the combination of at least three different doping elements is Rb/Sr/La. In other embodiments, the combination of at least three different doping elements is Na/Sr/Lu. In other embodiments, the combination of at least three different doping elements is Sr/Eu/Dy. In other embodiments, the combination of at least three different doping elements is La/Dy/Gd. In other embodiments, the combination of at least three different doping elements is Gd/Li/K.
  • the combination of at least three different doping elements is Rb/K/Lu. In other embodiments, the combination of at least three different doping elements is Na/Ce/Co. In other embodiments, the combination of at least three different doping elements is Ba/Rh/Ta. In other embodiments, the combination of at least three different doping elements is Na/AI/Bi. In other embodiments, the combination of at least three different doping elements is Cs/Eu/S. In other embodiments, the combination of at least three different doping elements is Sm/Tm/Yb. In other embodiments, the combination of at least three different doping elements is Hf/Zr/Ta. In other embodiments, the combination of at least three different doping elements is Na/Ca/Lu.
  • the combination of at least three different doping elements is Gd/Ho/Sr. In other embodiments, the combination of at least three different doping elements is Ca/Sr/W. In other embodiments, the combination of at least three different doping elements is Na/Zr/Eu/Tm. In other embodiments, the combination of at least three different doping elements is Sr/W/Li. In other embodiments, the combination of at least three different doping elements is Ca/Sr/W.
  • the oxide of a rare earth element comprises a combination of at least four different doping elements.
  • the four different doping elements are selected from Na, Mg, Ca, Sr, Ga, Sc, Y, Zr, In, Nd, Eu, Sm, Ce, Gd, Hf, Ho, Tm, W, La, K, Dy, In, Cs, S, Zn, Rb, Ba, Yb, Ni, Lu, Ta, P, Pt, Bi, Sn, Nb, Sb, Ge, Ag, Au, Pb, Re, Fe, Al, Tl, Pr, Co, Rh, Ti, V, Cr, Mn, Ir, As, Li, Tb ,Er, Te and Mo. More specific examples include catalysts wherein the combination of at least four different doping elements is Sr/Sm/Ho/Tm, Na/K/Mg/Tm, Na/La/Eu/ln, Na/La/Li/Cs,
  • the combination of at least four different doping elements is Sr/Sm/Ho/Tm. In other embodiments, the combination of at least four different doping elements is Na/K Mg/Tm. In other embodiments, the combination of at least four different doping elements is Na/La/Eu/ln. In other embodiments, the combination of at least four different doping elements is Na/La/Li/Cs. In other embodiments, the combination of at least four different doping elements is Li/Cs/La/Tm. In other embodiments, the combination of at least four different doping elements is Li/Cs/Sr/Tm. In other embodiments, the combination of at least four different doping elements is Li/Sr/Zn/K.
  • the combination of at least four different doping elements is Li/Ga/Cs. In other embodiments, the combination of at least four different doping elements is Li/K Sr/La. In other embodiments, the combination of at least four different doping elements is Li/Na/Rb/Ga. In other embodiments, the combination of at least four different doping elements is Li/Na/Sr/La. In other embodiments, the combination of at least four different doping elements is Ba/Sm/Yb/S. In other embodiments, the combination of at least four different doping elements is Ba/Tm/K/La. In other embodiments, the combination of at least four different doping elements is Ba/Tm/Zn/K.
  • the combination of at least four different doping elements is Cs/La/Tm/Na. In other embodiments, the combination of at least four different doping elements is Cs/Li/K/La. In other embodiments, the combination of at least four different doping elements is Sm/Li/Sr/Cs. In other embodiments, the combination of at least four different doping elements is Sr/Tm/Li/Cs. In other embodiments, the combination of at least four different doping elements is Zr/Cs/K/La. In other embodiments, the combination of at least four different doping elements is Rb/Ca/ln/Ni. In other embodiments, the combination of at least four different doping elements is Tm/Lu/Ta/P.
  • the combination of at least four different doping elements is Rb/Ca/Dy/P. In other embodiments, the combination of at least four different doping elements is Mg/La/Yb/Zn. In other embodiments, the combination of at least four different doping elements is Na/Sr/Lu/Nb. In other embodiments, the combination of at least four different doping elements is Na/Nd/ln/K. In other embodiments, the combination of at least four different doping elements is K La/Zr/Ag. In other embodiments, the combination of at least four different doping elements is Ho/Cs/Li/La. In other embodiments, the combination of at least four different doping elements is K La/Zr/Ag.
  • the combination of at least four different doping elements is Na/Sr/Eu/Ca. In other embodiments, the combination of at least four different doping elements is K Cs/Sr/La. In other embodiments, the combination of at least four different doping elements is Na/Mg/TI/P. In other embodiments, the combination of at least four different doping elements is Sr/La/Dy/S. In other embodiments, the combination of at least four different doping elements is Na/Ga/Gd/AI. In other embodiments, the combination of at least four different doping elements is Sm/Tm/Yb/Fe. In other embodiments, the combination of at least four different doping elements is Rb/Gd/Li/K.
  • the combination of at least four different doping elements is Gd/Ho/AI/P. In other embodiments, the combination of at least four different doping elements is Na/Zr/Eu/T. In other embodiments, the combination of at least four different doping elements is Sr/Ho/Tm/Na. In other embodiments, the combination of at least four different doping elements is Na/Zr/Eu/Ca. In other embodiments, the combination of at least four different doping elements is Rb/Ga/Tm/Cs. In other embodiments, the combination of at least four different doping elements is La/Bi/Ce/Nd/Sr.
  • the oxide of a rare earth element is a mixed oxide.
  • the oxide of a rare earth element comprises a lanthanum oxide, a neodymium oxide, a ytterbium oxide, a europium oxide, a samarium oxide, a yttrium oxide, a cerium oxide or a praseodymium oxide.
  • the oxide of a rare earth element comprises Ln1 4-x Ln2 x O 6 , wherein Ln1 and Ln2 are each independently a lanthanide element, wherein Ln1 and Ln2 are not the same and x is a number ranging from greater than 0 to less than 4.
  • the rare earth oxide comprises La 4-x Nd x O6, wherein x is a number ranging from greater than 0 to less than 4.
  • the rare earth oxide comprises La 3 NdO 6 , LaNd 3 O 6 , La1.5Nd2.5Oe, La2.5Nd1.5Oe, La3.2Ndo.8Oe,
  • the oxide of a rare earth element comprises a mixed oxide.
  • the mixed oxide comprises Y-La, Zr-La, Pr-La, Ce-La or combinations thereof.
  • the rare earth oxide catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
  • the catalysts comprise La2O3 or
  • LaOy(OH) x wherein x and y are each independently an integer from 1 to 10 doped with Na, Mg, Ca, Sr, Ga, Sc, Y, Zr, In, Nd, Eu, Sm ,Ce, Gd or
  • the La2O3 or LaO y (OH) x catalysts are doped with binary dopant combinations of Eu/Na; Eu/Gd; Ca/Na; Eu/Sm; Eu/Sr; Mg/Sr; Ce/Mg; Gd/Sm, Mg/Na, Mg/Y, Ga/Sr or Nd/Mg.
  • the catalysts comprise Nd2O3 or
  • NdOy(OH) x wherein x and y are each independently an integer from 1 to 10, doped with Sr, Ca, Rb, Li, Na or combinations thereof.
  • the Nd 2 O 3 or NdO y (OH) x catalysts are doped with binary dopant combinations of Ca/Sr or Rb/Sr.
  • the catalysts comprise Yb2O3 or YbO y (OH) x , wherein x and y are each independently an integer from 1 to 10, doped with Sr, Ca, Ba, Nd or combinations thereof.
  • the Yb 2 O 3 or YbO y (OH) x OCM catalysts are doped with a binary combination of Sr/Nd.
  • the catalysts comprise EU2O3 or EuOy(OH) x , wherein x and y are each independently an integer from 1 to 10, doped with Sr, Ba, Sm or combinations thereof or a binary dopant combination of Sr/Na.
  • Examples of dopants for S1TI2O3 or SmO y (OH) x catalysts, wherein x and y are each independently an integer from 1 to 10, include Sr, and examples of dopants for Y2O3 or YO y (OH) x catalysts wherein x and y are each independently an integer from 1 to 10, comprise Ga, La, Nd or combinations thereof.
  • the Y2O3 or YO y (OH) x catalysts comprise a binary dopant combination of Sr/Nd, Eu/Y or Mg/Nd or a tertiary dopant combination of Mg/Nd/Fe.
  • Rare earth mixed oxide catalysts which without doping have low OCM selectivity can be greatly improved by doping to reduce their combustion activity.
  • catalysts comprising CeO2 and Pr 2 O3 tend to have strong total oxidation activity for methane, however doping with additional rare earth elements can significantly moderate the combustion activity and improve the overall utility of the catalyst.
  • dopants which improve the selectivity of the catalysts for example the Pr 2 O3 or PrO y (OH) x catalysts, wherein x and y are each independently an integer from 1 to 10, comprise binary dopants of Nd/Mg, La/Mg or Yb/Sr.
  • the rare earth element may be in the form of a metal oxyhalide, a metal oxynitrate or a metal phosphate.
  • the present disclosure provides a catalyst comprising a mixed oxide of manganese and tungsten, wherein the catalyst further comprises a sodium dopant and at least one doping element from groups 2, 4-6, 8-15, lanthanides or combinations thereof.
  • the catalyst may comprise a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
  • the at least one doping element is Fe, Co, Ce, Cu, Ni, Sr, Ga, Zr, Pb, Zn, Cr, Pt, Al, Nb, La, Ba, Bi, Sn, In, Ru, P or combinations thereof.
  • the at least one doping element may be Fe.
  • the at least one doping element may be Co.
  • the at least one doping element may be Ce.
  • the at least one doping element may be Cu.
  • the at least one doping element may be Ni.
  • the at least one doping element may be Sr.
  • the at least one doping element may be Ga.
  • the at least one doping element may be Zr.
  • the at least one doping element may be Pb.
  • the at least one doping element may be Zn.
  • the at least one doping element may be Cr.
  • the at least one doping element may be Pt.
  • the at least one doping element may be Al.
  • the at least one doping element may be Nb.
  • the at least one doping element may be La.
  • the at least one doping element may be Ba.
  • the at least one doping element may be Bi.
  • the at least one doping element may be Sn.
  • the at least one doping element may be In.
  • the at least one doping element may be Ru.
  • the at least one doping element may be P.
  • the disclosure provides a catalyst comprising a mixed oxide of a lanthanide and tungsten, wherein the catalyst further comprises a sodium dopant and at least one doping element from groups 2, 4-15, lanthanides or combinations thereof.
  • the catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
  • the lanthanide is Ce, Pr, Nd, La, Eu, Sm or Y.
  • the at least one doping element is Fe, Co, Mn, Cu, Ni, Sr, Ga, Zr, Pb, Zn, Cr, Pt, Al, Nb, La, Ba, Bi, Sn, In, Ru, P or combinations thereof. Binary and ternary combinations of the foregoing dopants are also contemplated.
  • the at least one doping element may be Fe.
  • the at least one doping element may be Co.
  • the at least one doping element may be Mn.
  • the at least one doping element may be Cu.
  • the at least one doping element may be Ni.
  • the at least one doping element may be Sr.
  • the at least one doping element may be Ga.
  • the at least one doping element may be Zr.
  • the at least one doping element may be Pb.
  • the at least one doping element may be Zn.
  • the at least one doping element may be Cr.
  • the at least one doping element may be Pt.
  • the at least one doping element may be Al.
  • the at least one doping element may be Nb.
  • the at least one doping element may be La.
  • the at least one doping element may be Ba.
  • the at least one doping element may be Bi.
  • the at least one doping element may be Sn.
  • the at least one doping element may be In.
  • the at least one doping element may be Ru.
  • the at least one doping element may be P.
  • these lanthanide compositions comprise La2O3, Nd2O3, Yb2O3, EU2O3, S1TI2O3, Ln1 4-x Ln2 x O 6 , La 4-x Ln1 x O 6 , La 4-x Nd x O 6 , wherein Ln1 and Ln2 are each independently a lanthanide element, wherein Ln1 and Ln2 are not the same and x is a number ranging from greater than 0 to less than 4, La 3 NdO 6 ,
  • LaNd 3 O 6 La1.5Nd2.5Oe, La2.5Nd1.5Oe, La3.2Ndo.8Oe, La3.5Ndo.5Oe, La3.8Ndo.2Oe, or combinations thereof.
  • Certain lanthanide mixed oxides such as Y-La, Zr-La, Pr- La or Ce-La are also useful as catalysts in the OCM reaction.
  • Applicants have discovered that certain doping combinations, when combined with the above lanthanide compositions, serve to enhance the catalytic activity of the catalysts in certain catalytic reactions, for example OCM.
  • the dopants may be present in various levels (e.g., w/w or at/at), and the catalysts may be prepared by any number of methods.
  • Various aspects of the above lanthanide catalysts are provided in the following paragraphs and in Tables 1 -7.
  • the catalyst comprises a rare earth oxide and two or more dopants, wherein the dopants are selected from Eu/Na, Sr/Na, Na/Zr/Eu/Ca, Mg/Na, Sr/Sm/Ho/Tm, Sr/W, Mg/La/K, Na/K/Mg/Tm, Na/Dy/K, Na/La/Dy, Na/La/Eu, Na/La/Eu/ln, Na/La/K, Na/La/Li/Cs, K/La, K/La/S, K/Na, Li/Cs, Li/Cs/La, Li/Cs/La/Tm,
  • Li/Cs/Sr/Tm Li/Cs/Sr/Tm, Li/Sr/Cs, Li/Sr/Zn/K, Li/Ga/Cs, Li/K/Sr/La, Li/Na, Li/Na/Rb/Ga, Li/Na/Sr, Li/Na/Sr/La, Li/Sm/Cs, Ba/Sm/Yb/S, Ba/Tm/K/La, Ba/Tm/Zn/K, Cs/K/La, Cs/La/Tm/Na, Cs/Li/K/La, Sm/Li/Sr/Cs, Sr/Cs/La, Sr/Tm/Li/Cs, Zn/K, Zr/Cs/K/La, Rb/Ca/ln/Ni, Sr/Ho/Tm, La/Nd/S, Li/Rb/Ca, Li/K, Tm/Lu/Ta/P, Rb
  • Sr/Cs/Zn Sm/Cs, In/K, Ho/Cs/Li/La, Cs/La/Na, La/S/Sr, K/La/Zr/Ag, Lu/TI, Pr/Zn, Rb/Sr/La, Na/Sr/Eu/Ca, K Cs/Sr/La, Na/Sr/Lu, Sr/Eu/Dy, Lu/Nb,
  • the dopant is selected from Cs/Eu/S, Sm/Tm/Yb/Fe, Sm/Tm/Yb, Hf/Zr/Ta,
  • Na/K Mg/Tm Na/Dy/K, Na/La/Dy, Na/La/Eu, Na/La/Eu/ln, Na/La/K,
  • Na/La/Li/Cs K La, K La/S, K Na, Li/Cs, Li/Cs/La, Li/Cs/La/Tm, Li/Cs/Sr/Tm, Li/Sr/Cs, Li/Sr/Zn/K, Li/Ga/Cs, Li/K Sr/La, Li/Na, Li/Na/Rb/Ga and Li/Na/Sr.
  • the dopant is selected from Li/Na/Sr/La, Li/Sm/Cs, Ba/Sm/Yb/S, Ba/Tm/K La, Ba/Tm/Zn/K, Cs/K La, Cs/La/Tm/Na, Cs/Li/K La, Sm/Li/Sr/Cs, Sr/Cs/La, Sr/Tm/Li/Cs, Zn/K, Zr/Cs/K La, Rb/Ca/ln/Ni, Sr/Ho/Tm, La/Nd/S, Li/Rb/Ca, Li/K, Tm/Lu/Ta/P, Rb/Ca/Dy/P, Mg/La/Yb/Zn, Rb/Sr/Lu, Na/Sr/Lu/Nb, Na/Eu/Hf, Dy/Rb/Gd, Na/Pt/Bi, Rb/
  • Sr/Cs/Zn Sm/Cs, In/K, Ho/Cs/Li/La, Cs/La/Na, La/S/Sr, K/La/Zr/Ag, Lu/TI, Pr/Zn, Rb/Sr/La, Na/Sr/Eu/Ca, K Cs/Sr/La, Na/Sr/Lu, Sr/Eu/Dy, Lu/Nb,
  • La/Dy/Gd Na/Mg/TI/P, Na/Pt, Gd/Li/K, Rb/K Lu, Sr/La/Dy/S, Na/Ce/Co, Na/Ce, Na/Ga/Gd/AI, Ba/Rh/Ta, Ba/Ta, Na/AI/Bi, Cs/Eu/S, Sm/Tm/Yb/Fe, Sm/Tm/Yb, Hf/Zr/Ta, Rb/Gd/Li/K, Gd/Ho/AI/P and Na/Ca/Lu.
  • the dopant is selected from Ta/Hf, W/Au, Ca/W, Au/Re, Sm/Li, La/K, Zn/Cs, Na/K/Mg, Zr/Cs, Ca/Ce, Na/Li/Cs, Li/Sr, Cs/Zn, La/Dy/K, Dy/K, La/Mg,
  • the catalysts comprise La2O3, Nd2O3, Yb2O3, EU2O3, Y2O3, Ce2O3, Pr2O3 Sm 2 O3, Ln1 4-x Ln2 x O6, La 4-x Ln1 x O6, La 4-x Nd x O6, wherein Ln1 and Ln2 are each independently a lanthanide element, wherein Ln1 and Ln2 are not the same and x is a number ranging from greater than 0 to less than 4, La3NdO6,
  • LaNd 3 O 6 La1.5Nd2.5Oe, La2.5Nd1.5Oe, La3.2Ndo.8Oe, La3.5Ndo.5Oe, La3.8Ndo.2Oe, Y- La, Zr-La, Pr-La or Ce-La or combinations thereof.
  • the rare earth oxide catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the rare earth oxide catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
  • the catalysts comprise La2O3, Yb2O3, Nd 2 O 3 , E112O3, Sm 2 O 3 , Y2O3, 1_ ⁇ 1 4- ⁇ _ ⁇ 2 ⁇ 6 , La 4- xLn1 x O 6 , La 4-x NdxO 6 , wherein Ln1 and Ln2 are each independently a lanthanide element, wherein Ln1 and Ln2 are not the same and x is a number ranging from greater than 0 to less than 4, La 3 NdO 6 , LaNd 3 O 6 , La1.5Nd2.5Oe, La2.5Nd1.5Oe, La3.2Ndo.8Oe,
  • the catalysts comprise Sr Ta La 2 O3,
  • the catalysts comprise Ln1 - x Ln2 x O6, La 4-x Ln1 x O6, La 4-x Nd x O6, wherein Ln1 and Ln2 are each independently a lanthanide element, wherein Ln1 and Ln2 are not the same and x is a number ranging from greater than 0 to less than 4, La 3 NdO 6 , LaNd 3 O 6 , La1 .5 Nd2 .5 O6, La2.5Nd1.5Oe, La3.2Ndo.8Oe, La3.5Ndo.5Oe, La3.8Ndo.2Oe, Y-La, Zr-La, Pr-La or Ce- La doped with Na, Sr, Ca, Yb, Cs, Sb, or combinations thereof, for example the catalysts may comprise Na/Ln1 4-x Ln2 x O6, Sr/Ln1 4-x Ln2 x O6, Ca/Ln1 4-x Ln2 x O6, Yb/
  • Nd 2 .5O 6 Na La2.5Ndi. 5 O6, Na/La3.2Ndo.8O6, Na La3. 5 Ndo.5O6, Na La3.8Ndo.2O6, Na/Y-La, Na/Zr-La, Na/Pr-La, Na/Ce-La, Sr/La 3 NdO 6 , Sr/LaNd 3 O 6 , Sr/Lai. 5 Nd2.5O6, Sr/La 2 .5Ndi.
  • the catalysts comprise a mixed oxide selected from a Y-La mixed oxide doped with Na.
  • Y ranges from 5 to 20% of La at/at
  • Zr-La mixed oxide doped with Na Zr ranges from 1 to 5% of La at/at
  • Pr-La mixed oxide doped with a group 1 element Pr ranges from 2 to 6% of La at/at
  • Ce-La mixed oxide doped with a group 1 element Ce ranges from 5 to 20% of La at/at.
  • M1 -M2 wherein M1 and M2 are each independently metals refers to a mixed metal oxide comprising the two metals. M1 and M2 may be present in equal or different amounts (at/at).
  • the catalysts comprise a mixed oxide of a rare earth element and a Group 13 element, wherein the catalyst further comprises one or more Group 2 elements.
  • the Group 13 element is B, Al, Ga or In.
  • the Group 2 element is Ca or Sr.
  • the rare earth element is La, Y, Nd, Yb, Sm, Pr, Ce or Eu.
  • the catalyst comprises
  • lanthanide oxides doped with alkali metals and/or alkaline earth metals and at least one other dopant selected from Groups 3-16 have desirable catalytic properties and are useful in a variety of catalytic reactions, such as OCM.
  • the catalysts comprise a lanthanide oxide doped with an alkali metal, an alkaline earth metal or combinations thereof, and at least one other dopant from groups 3-16.
  • the catalyst comprises a lanthanide oxide, an alkali metal dopant and at least one other dopant selected from Groups 3-16.
  • the catalyst comprises a lanthanide oxide, an alkaline earth metal dopant and at least one other dopant selected from Groups 3-16.
  • the catalyst comprises a lanthanide oxide, a lithium dopant and at least one other dopant selected from Groups 3-16.
  • the catalyst comprises a lanthanide oxide, a sodium dopant and at least one other dopant selected from Groups 3-16.
  • the catalyst comprises a lanthanide oxide, a potassium dopant and at least one other dopant selected from Groups 3-16.
  • the catalyst comprises a lanthanide oxide, a rubidium dopant and at least one other dopant selected from Groups 3-16.
  • the catalyst comprises a lanthanide oxide, a caesium dopant and at least one other dopant selected from Groups 3-16.
  • the catalyst comprises a lanthanide oxide, a beryllium dopant and at least one other dopant selected from Groups 3-16. In other embodiments, the catalyst comprises a lanthanide oxide, a magnesium dopant and at least one other dopant selected from
  • the catalyst comprises a lanthanide oxide, a calcium dopant and at least one other dopant selected from Groups 3- 16. In more embodiments, the catalyst comprises a lanthanide oxide, a strontium dopant and at least one other dopant selected from Groups 3-16. In more embodiments, the catalyst comprises a lanthanide oxide, a barium dopant and at least one other dopant selected from Groups 3-16.
  • the catalysts comprise La 2 O 3 , Nd 2 O 3 , Yb 2 O 3 , Eu 2 O 3 , Sm 2 O 3 , Ln1 4-x Ln2 x O 6 , La 4- ⁇ ⁇ _ ⁇ 1 ⁇ 6, La 4-x Nd x O6, wherein Ln1 and Ln2 are each independently a lanthanide element, wherein Ln1 and Ln2 are not the same and x is a number ranging from greater than 0 to less than 4, La 3 NdO6, LaNd 3 O6, Lai. 5 Nd 2 .5O6,
  • the lanthanide oxide catalyst comprises a C 2 selectivity of greater than 50% and a methane conversion of greater than 20% when the lanthanide oxide catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a
  • the catalyst comprises a C 2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a
  • heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less, 700 °C or less, 650 °C or less or even 600 °C or less.
  • the catalyst comprises a C 2 selectivity of greater than 50%, greater than 55%, greater than 60%, greater than 65%, greater than 70%, or even greater than 75%, and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
  • the catalyst comprises a C 2 selectivity of greater than 50%, and a methane conversion of greater than 20%, greater than 25%, greater than 30%, greater than 35%, greater than 40%, greater than 45%, or even greater than 50% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
  • the methane conversion and C2 selectivity are calculated based on a single pass basis (i.e., the percent of methane converted or C2 selectivity upon a single pass over the catalyst or catalytic bed, etc.)
  • the metal oxides disclosed herein can be in the form of oxides, oxyhydroxides, hydroxides, oxycarbonates or combination thereof after being exposed to moisture, carbon dioxide, undergoing incomplete calcination or combination thereof.
  • the foregoing doped catalysts comprise 1 , 2, 3, 4 or more doping elements.
  • each dopant may be present in the catalysts (for example any of the catalysts described above and/or disclosed in Tables 1 -8) in up to 75% by weight of the catalyst.
  • the concentration of a first doping element ranges from 0.01 % to 1 % w/w, 1 %-5% w/w, 5%-10% w/w.
  • the concentration of a second doping element ranges from 0.01 % to 1 % w/w, 1 %-5% w/w, 5%-10% w/w. 10%-20% w/w, 20%-30% w/w, 30%-40% w/w or 40%-50% w/w, for example about 1 % w/w, about 2 % w/w, about 3% w/w, about 4% w/w, about 5% w/w, about 6% w/w, about 7% w/w, about 8% w/w, about 9% w/w, about 10 %w/w, about 1 1 % w/w, about 12 % w/w, about 13% w/w, about 14% w/w, about 15% w/w, about 16% w/w, about 17% w/w, about 18% w/w, about 19% w/w or about 20% w/w.
  • the concentration of a third doping element ranges from 0.01 % to 1 % w/w, 1 %-5% w/w, 5%-10% w/w. 10%- 20% w/w, 20%-30% w/w, 30%-40% w/w or 40%-50% w/w, for example about I % w/w, about 2 % w/w, about 3% w/w, about 4% w/w, about 5% w/w, about 6% w/w, about 7% w/w, about 8% w/w, about 9 % w/w, about 10 % w/w, about
  • the concentration of a fourth doping element ranges from 0.01 % to 1 % w/w, 1 %-5% w/w, 5%-10% w/w. 10%-20% w/w, 20%-30% w/w, 30%-40% w/w or 40%-50% w/w, for example about 1 % w/w, about 2 % w/w, about 3% w/w, about 4% w/w, about 5% w/w, about 6% w/w, about 7% w/w, about 8% w/w, about 9% w/w, about 10% w/w, about 1 1 % w/w, about 12 % w/w, about 13% w/w. about 14% w/w, about 15% w/w, about 16% w/w, about 17% w/w, about 18% w/w, about 19% w/w or about 20% w/w.
  • the concentration of the dopant is measured in terms of atomic percent (at/at).
  • each dopant may be present in the catalysts (for example any of the catalysts described above and/or disclosed in Tables 1 -8) in up to 75% at/at.
  • the concentration of a first doping element ranges from 0.01 % to 1 % at/at, 1 %-5% at/at, 5%-10% at/at.
  • the concentration of a second doping element ranges from 0.01 % to 1 % at/at, 1 %-5% at/at, 5%-10% at/at. 10%-20% w/w, 20%-30% at/at, 30%-40% at/at or 40%-50% at/at, for example about 1 % at/at, about 2 % at/at, about 3% at/at, about 4% at/at, about 5% at/at, about 6% at/at, about 7% at/at, about 8% at/at, about 9 % at/at, about 10% at/at, about 1 1 % at/at, about 12 % at/at, about 13% at/at, about 14% at/at, about 15% at/at, about 16% at/at, about 17% at/at, about 18% at/at, about 19% at/at or about 20% at/at.
  • the concentration of a third doping element ranges from 0.01 %to 1 % at/at, 1 %-5% at/at, 5%-10% at/at. 10%-20% w/w, 20%-30% at/at, 30%-40% at/at or 40%-50% at/at, for example about 1 % at/at, about 2 % at/at, about 3% at/at, about 4% at/at, about 5% at/at, about 6% at/at, about 7% at/at, about 8% at/at, about 9 % at/at, about 10% at/at, about 1 1 % at/at, about 12% at/at, about 13% at/at, about 14% at/at, about 15% at/at, about 16% at/at, about 17% at/at, about 18% at/at, about 19% at/at or about 20% at/at.
  • the concentration of a fourth doping element ranges from 0.01 % to 1 % at/at, 1 %-5% at/at, 5%-10% at/at. 10%-20% w/w, 20%-30% at/at, 30%-40% at/at or 40%-50% at/at, for example about 1 % at/at, about 2 % at/at, about 3% at/at, about 4% at/at, about 5% at/at, about 6% at/at, about 7% at/at, about 8% at/at, about 9 % at/at, about 10% at/at, about 1 1 % at/at, about 12% at/at, about 13% at/at, about 14% at/at, about 15% at/at, about 16% at/at, about 17% at/at, about 18% at/at, about 19% at/at or about 20% at/at.
  • any of the doped catalysts described above or in Tables 1 -8 may comprise any of the foregoing doping concentrations.
  • Tables 1 -8 below show exemplary doped catalysts in accordance with various specific embodiments. Dopants are shown in the vertical columns and base catalyst in the horizontal rows. The resulting doped catalysts are shown in the intersecting cells. TABLE 1 -CATALYSTS (CAT) DOPED WITH SPECIFIC DOPANTS (DOP)
  • the catalysts of the disclosure may be analyzed by inductively coupled plasma mass spectrometry (ICP-MS) to determine the element content of the catalysts.
  • ICP-MS is a type of mass spectrometry that is highly sensitive and capable of the determination of a range of metals and several non-metals at concentrations below one part in 10 12 .
  • ICP is based on coupling together an inductively coupled plasma as a method of producing ions (ionization) with a mass spectrometer as a method of separating and detecting the ions.
  • ICP-MS methods are well known in the art.
  • a catalyst composition represented by E 1 /E 2 /E 3 , etc., wherein E 1 , E 2 and E 3 are each independently an element or a compound comprising one or more elements refers to a catalyst comprised of a mixture of E 1 , E 2 and E 3 .
  • E 1 , E 2 and E 3 , etc. are not necessarily present in equal amounts and need not form a bond with one another.
  • a catalyst comprising Li/MgO refers to a catalyst comprising Li and MgO, for example, Li/MgO may refer to MgO doped with Li.
  • a catalyst comprising Na/Mn/W/O refers to a catalyst comprised of a mixture of sodium, manganese, tungsten and oxygen. Generally the oxygen is in the form of a metal oxide.
  • dopants are present in the catalysts in, for example, less than 50 at%, less than 25 at%, less than 10 at%, less than 5 at% or less than 1 at%.
  • the weight ratio (w/w) of the catalyst base material to the doping element(s) ranges from 1 :1 to 10,000:1 , 1 :1 to 1 ,000:1 or 1 :1 to 500:1 .
  • the present disclosure includes a catalytic material comprising a plurality of catalysts.
  • the catalytic material comprises a support or carrier.
  • Supports and carriers useful in the context of the invention are not limited and include supports and carriers described herein as well as those known in the art, for example as described in U.S. Application Nos. 13/1 15,082 (U.S. Pub. No. 2012/0041246), 13/689,514 (U.S. Pub. No.
  • the support is preferably porous and has a high surface area.
  • the support is active (i.e., has catalytic activity).
  • the support is inactive (i.e., non-catalytic).
  • the support comprises an inorganic oxide, AI2O3, SiO 2 , ⁇ 2, MgO, CaO, SrO, ZrO 2 , ZnO, LiAIO 2 , MgAI 2 O 4 , MnO, MnO 2 , Mn 3 O 4 , La 2 O 3 , AIPO 4 , SiO 2 /AI 2 O 3 , activated carbon, silica gel, zeolites, activated clays, activated AI 2 O 3 , SiC, diatomaceous earth, magnesia, aluminosilicates, calcium aluminate, support nanowires or combinations thereof.
  • the support comprises silicon, for example SiO 2 .
  • the support comprises magnesium, for example MgO. In yet other embodiments, the support comprises yttrium, for example Y 2 O 3 . In other embodiments the support comprises zirconium, for example ZrO 2 . In yet other embodiments, the support comprises lanthanum, for example La 2 O 3 . In yet other embodiments, the support comprises lanthanum, for example La 2 O 3 . In yet other embodiments,
  • the support comprises hafnium, for example HfO 2 .
  • the support comprises aluminum, for example AI 2 O 3 .
  • the support comprises gallium, for example Ga 2 O 3 .
  • the support material comprises an inorganic oxide, AI 2 O 3 , SiO 2 , TiO 2 , MgO, ZrO 2 , HfO2, CaO, SrO, ZnO, LiAIO 2 , MgAI 2 O 4 , MnO, MnO 2 , Mn 2 O 4 , Mn 3 O 4 , La 2 O 3 , AIPO 4 , activated carbon, silica gel, zeolites, activated clays, activated AI 2 O 3 , diatomaceous earth, magnesia, aluminosilicates, calcium aluminate, support nanowires or combinations thereof.
  • a catalyst may serve as a support for another catalyst.
  • a catalyst may be comprised of catalytic support material and adhered to or incorporated within the support is another catalyst.
  • the catalytic support may comprise S1O2, MgO, T1O2, ZrO2, AI2O3, ZnO or combinations thereof.
  • the support material comprises a carbonate.
  • the support material comprises MgCOs, CaCO 3 , SrCO 3 , BaCO 3 , Y 2 (CO 3 ) 3 , La 2 (CO 3 ) 3 or combinations thereof.
  • a nanowire may serve as a support for another bulk or nanowire catalyst.
  • a nanowire may be comprised of non-catalytic metal elements and adhered to or incorporated within the support nanowire is a catalyst as described herein.
  • the support nanowires are comprised of SiO 2 , MgO, CaO, SrO, TiO 2 , ZrO 2 , AI 2 O 3 , ZnO MgCO 3 , CaCO 3 , SrCO 3 or combinations thereof.
  • the optimum amount of catalyst present on the support depends, inter alia, on the catalytic activity of the catalyst.
  • the amount of catalyst present on the support ranges from 1 to 100 parts by weight of catalyst per 100 parts by weight of support or from 10 to 50 parts by weight of catalyst per 100 parts by weight of support. In other embodiments, the amount of catalyst present on the support ranges from 100-200 parts of catalyst per 100 parts by weight of support, or 200-500 parts of catalyst per 100 parts by weight of support, or 500-1000 parts of catalyst per 100 parts by weight of support.
  • heterogeneous catalysts are used either in their pure form or blended with inert materials, such as silica, alumina, etc.
  • inert materials such as silica, alumina, etc.
  • the blending with inert materials is used in order to reduce and/or control large temperature non- uniformities within the reactor bed often observed in the case of strongly exothermic (or endothermic) reactions.
  • typical blending materials can selectively slow down or quench one or more of the reactions of the system and promote unwanted side reactions. For example, in the case of the oxidative coupling of methane, silica and alumina can quench the methyl radicals and thus prevent the formation of ethane.
  • the present disclosure provides a catalytic material which solves these problems typically associated with catalyst support material. Accordingly, in certain embodiments the catalytic activity of the catalytic material can be tuned by blending two or more catalysts and/or catalyst support materials.
  • the blended catalytic material may comprise a catalyst as described herein in combination with another catalytic material, for example an additional bulk catalyst or a catalytic nanowire as described in PCT Pub. Nos. WO
  • the blended catalytic materials comprise metal oxides, hydroxides, oxy-hydroxides, carbonates, oxalates of the groups 1 -16, lanthanides, actinides or combinations thereof.
  • the blended catalytic materials may comprise a plurality of catalysts, as disclosed herein, and any one or more of straight nanowires, nanoparticles, bulk materials and inert support materials.
  • the catalytic materials may be undoped or may be doped with any of the dopants described herein.
  • the catalyst blend comprises at least one type 1 component and at least one type 2 component.
  • Type 1 components comprise catalysts having a high OCM activity at moderately low temperatures and type 2 components comprise catalysts having limited or no OCM activity at these moderately low temperatures, but are OCM active at higher
  • the type 1 component is a catalyst having high OCM activity at moderately low temperatures.
  • the type 1 component may comprise a C2 yield of greater than 5% or greater than 10% at temperatures less than 800°C, less than 700°C or less than 600°C.
  • the type 2 component may comprise a C2 yield less than 0.1 %, less than 1 % or less than 5% at temperatures less than 800°C, less than 700°C or less than 600°C.
  • the type 2 component may comprise a C2 yield of greater than 0.1 %, greater than 1 %, greater than 5% or greater than 10% at
  • Typical type 1 components include any of the catalysts as described herein, while typical type 2 components include bulk OCM catalysts and nanowire catalysts which only have good OCM activity at higher temperatures, for example greater than 800°C.
  • Examples of type 2 components may include catalysts comprising MgO.
  • the catalyst blend may further comprise inert support materials as described above (e.g., silica, alumina, silicon carbide, etc.).
  • the type 2 component acts as diluent in the same way an inert material does and thus helps reduce and/or control hot spots in the catalyst bed caused by the exothermic nature of the OCM reaction.
  • the type 2 component is an OCM catalyst, albeit not a particularly active one, it may prevent the occurrence of undesired side reactions, e.g., methyl radical quenching. Additionally, controlling the hotspots has the beneficial effect of extending the lifetime of the catalyst.
  • the type 2 components are good oxidative dehydrogenation (ODH) catalysts at the same temperature that the type 1 components are good OCM catalysts.
  • ODH oxidative dehydrogenation
  • the type 2 components are not only good ODH catalysts at the same temperature the type 1 components are good OCM catalysts, but also have limited to moderate OCM activity at these temperatures.
  • the catalytic performance of the catalytic material is tuned by selecting specific type 1 and type 2 components of a catalyst blend. In another embodiment, the catalytic performance is tuned by adjusting the ratio of the type 1 and type 2 components in the catalytic material.
  • the type 1 catalyst may be a catalyst for a specific step in the catalytic reaction, while the type 2 catalyst may be specific for a different step in the catalytic reaction.
  • the type 1 catalyst may be optimized for formation of methyl radicals and the type 2 catalyst may be optimized for formation of ethane or ethylene.
  • the catalytic material comprises at least two different components (component 1 , component 2, component 3, etc.).
  • the different components may comprise different morphologies, e.g., nanowires, nanoparticles, bulk, etc.
  • the different components in the catalyst material can be, but not necessarily, of the same chemical composition and the only difference is in the morphology and/or the size of the particles. This difference in morphology and particle size may result in a difference in reactivity at a specific temperature. Additionally, the difference in morphology and particle size of the catalytic material components is advantageous for creating a very intimate blending, e.g., very dense packing of the catalysts particles, which can have a beneficial effect on catalyst performance.
  • the difference in morphology and particle size of the blend components would allow for control and tuning of the macro-pore distribution in the reactor bed and thus its catalytic efficiency.
  • An additional level of micro-pore tuning can be attained by blending catalysts with different chemical composition and different morphology and/or particle size. The proximity effect would be advantageous for the reaction selectivity.
  • the present disclosure provides the use of a catalytic material comprising a first catalyst and a second catalyst, for example a first catalytic nanowire and a bulk catalyst and/or a second catalytic nanowire, in a catalytic reaction, for example the catalytic reaction may be OCM or ODH.
  • the first catalytic nanowire and the bulk catalyst and/or second catalytic nanowire are each catalytic with respect to the same reaction, and in other examples the first catalytic nanowire and the bulk catalyst and/or second catalytic nanowire have the same chemical composition.
  • the catalytic material comprises a first catalytic nanowire and a second catalytic nanowire.
  • Each nanowire can have completely different chemical compositions or they may have the same base composition and differ only by the doping elements.
  • each nanowire can have the same or a different morphology.
  • each nanowire can differ by the nanowire size (length and/or aspect ratio), by ratio of actual/effective length, by chemical composition or any combination thereof.
  • the first and second nanowires may each be catalytic with respect to the same reaction but may have different activity. Alternatively, each nanowire may catalyze different reactions.
  • the catalytic material comprises a first catalytic nanowire and a bulk catalyst.
  • the first nanowire and the bulk catalyst can have completely different chemical compositions or they may have the same base composition and differ only by the doping elements.
  • the first nanowire and the bulk catalyst may each be catalytic with respect to the same reaction but may have different activity.
  • the first nanowire and the bulk catalyst may catalyze different reactions.
  • the catalytic nanowire has a catalytic activity in the catalytic reaction, which is greater than a catalytic activity of the bulk catalyst in the catalytic reaction at the same temperature. In still other embodiments, the catalytic activity of the bulk catalyst in the catalytic reaction increases with increasing temperature.
  • OCM catalysts may be prone to hotspots due to the very exothermic nature of the OCM reaction. Diluting such catalysts helps to manage the hotspots. However, the diluent needs to be carefully chosen so that the overall performance of the catalyst is not degraded. Silicon carbide for example can be used as a diluent with little impact on the OCM selectivity of the blended catalytic material whereas using silica as a diluent significantly reduces OCM selectivity. The good heat conductivity of SiC is also beneficial in minimizing hot spots.
  • embodiments of the invention include catalyst compositions comprising an OCM catalyst (e.g., any of the disclosed catalysts) in combination with a diluent or support material that is also OCM active. Methods for use of the same in an OCM reaction are also provided.
  • the above diluent comprises alkaline earth metal compounds, for example alkaline metal oxides, carbonates, sulfates or phosphates.
  • alkaline earth metal compounds for example alkaline metal oxides, carbonates, sulfates or phosphates.
  • diluents useful in various embodiments include, but are not limited to, MgO, MgCO 3 , MgSO 4 , Mg 3 (PO 4 ) 2 , MgAI 2 O 4 , CaO, CaCO 3 , CaSO 4 , Ca 3 (PO 4 ) 2 , CaAI 2 O 4 , SrO, SrCO 3 , SrSO 4 , Sr 3 (PO 4 ) 2 , SrAI 2 O 4 , BaO, BaCO 3 , BaSO 4 , Ba 3 (PO 4 ) 2 , BaAI 2 O 4 and the like.
  • magnesium, calcium and strontium compounds are environmentally friendly too.
  • an embodiment of the invention provides a catalytic material comprising a catalyst in combination with a diluent selected from one or more of MgO, MgCO 3 , MgSO 4 , Mg 3 (PO 4 ) 2 , CaO, CaCO 3 , CaSO 4 , Ca 3 (PO 4 ) 2 , SrO, SrCO 3 , SrSO 4 , Sr 3 (PO 4 ) 2 , BaO, BaCO 3 , BaSO 4 , Ba 3 (PO 4 ) 2 .
  • the diluents is MgO, CaO, SrO, MgCO 3 , CaCO 3 , SrCO 3 or combination thereof.
  • a support e.g., MgO, CaO, CaCO3, SrCOs
  • a support e.g., MgO, CaO, CaCO3, SrCOs
  • a pellet or monolith e.g.,
  • honeycomb structure, and the catalysts may be impregnated or supported thereon.
  • a core/shell arrangement is provided and the support material may form part of the core or shell.
  • a core of MgO, CaO, CaCO 3 or SrCO 3 may be coated with a shell of any of the disclosed catalyst compositions.
  • the diluent has a morphology selected from bulk (e.g., commercial grade), nano (nanowires, nanorods, nanoparticles, etc.) or combinations thereof.
  • the diluent has none to moderate catalytic activity at the temperature the OCM catalyst is operated. In some other embodiments, the diluent has moderate to large catalytic activity at a
  • the diluent has none to moderate catalytic activity at the temperature the OCM catalyst is operated and moderate to large catalytic activity at temperatures higher than the temperature the OCM catalyst is operated.
  • Typical temperatures for operating an OCM reaction according to the present disclosure are 800 °C or lower, 750 °C or lower, 700 °C or lower, 650 °C or lower, 600 °C or lower and 550 °C or lower.
  • CaCO3 is a relatively good OCM catalyst at T > 750
  • the diluent portion in the catalyst/diluent mixture is 0.01 %, 10%, 30%, 50%, 70%, 90% or 99.99% (weight percent) or any other value between 0.01 % and 99.9%.
  • the dilution is performed with the OCM catalyst ready to go, e.g., after calcination.
  • the dilution is performed prior to the final calcination of the catalyst, i.e., the catalyst and the diluent are calcined together.
  • the dilution can be done during the synthesis as well, so that, for example, a mixed oxide is formed.
  • the catalyst/diluent mixture comprises more than one catalyst and/or more than one diluent. In some other
  • the catalyst/diluent mixture is pelletized and sized, or made into shaped extrudates or deposited on a monolith or foam, or is used as it is.
  • Methods of the invention include taking advantage of the very exothermic nature of OCM by diluting the catalyst with another catalyst that is (almost) inactive in the OCM reaction at the operating temperature of the first catalyst but active at higher temperature. In these methods, the heat generated by the hotspots of the first catalyst will provide the necessary heat for the second catalyst to become active.
  • catalytic materials often refers to OCM; however, such catalytic materials find utility in other catalytic reactions including but not limited to: oxidative dehydrogenation (ODH) of alkanes to their corresponding alkenes, selective oxidation of alkanes and alkenes and alkynes, oxidation of co, dry reforming of methane, selective oxidation of aromatics, Fischer-Tropsch, combustion of hydrocarbons, etc. 3.
  • OCM oxidative dehydrogenation
  • the catalysts can be prepared using any suitable method (e.g., such that the catalyst functions as an OCM catalyst). Suitable methods, which include using a bacteriophage template and other methods known in the art, are described in U.S. Application Nos. 13/1 15,082 (U.S. Pub. No.
  • the nanowire catalysts can be synthesized in a solution phase in the absence of a template.
  • a hydrothermal or sol gel approach can be used to create straight (i.e., ratio of effective length to actual length equal to one) and substantially single crystalline nanowires.
  • nanowires comprising a metal oxide can be prepared by (1 ) forming nanowires of a metal oxide precursor (e.g., metal hydroxide) in a solution of a metal salt and an anion precursor; (2) isolating the nanowires of the metal oxide precursor; and (3) calcining the nanowires of the metal oxide precursor to provide nanowires of a corresponding metal oxide.
  • a metal oxide precursor e.g., metal hydroxide
  • the synthesis goes through an intermediate which can be prepared as a nanowire and then converted into the desired product while maintaining its morphology.
  • the nanowires comprising a metal oxide can be doped according to methods described herein.
  • nanowires comprising a core/shell structure are prepared in the absence of a biological template.
  • Such methods may include, for example, preparing a nanowire comprising a first metal and growing a shell on the outersurface of this nanowire, wherein the shell comprises a second metal.
  • the first and second metals may be the same or different.
  • a core/shell nanowire is prepared in the absence of a biological template.
  • Such methods comprise preparing a nanowire comprising an inner core and an outer shell, wherein the inner core comprises a first metal, and the outer shell comprises a second metal, the method
  • the method further comprises addition of a base to a solution obtained in step b).
  • the first metal and the second metal are different.
  • the salt comprising the second metal is a halide or a nitrate.
  • the first nanowire may be prepared by any method, for example via a template directed method (e.g., phage).
  • variable synthetic parameters include: concentration ratios of metal and anions (e.g., hydroxide); reaction temperature; reaction time; sequence of adding anion and metal ions; pH; types of metal precursor salt; types of anion precursor; number of additions; the time that lapses between the additions of the metal salt and anion precursor, including, e.g., simultaneous (zero lapse) or sequential additions followed by respective incubation times for the metal salt and the anion precursor.
  • solvents or surfactants may influence the crystal growth of the nanowires, thereby generating different nanowire dimensions (including aspect ratios).
  • solvents such as ethylene glycol, poly(ethylene glycol), polypropylene glycol and polyvinyl pyrrolidone
  • solvents can serve to passivate the surface of the growing nanowires and facilitate a linear growth of the nanowire.
  • nanowires can be prepared directly from the corresponding oxide.
  • metal oxides may be treated with halides, for example ammonium halides, to produce nanowires.
  • halides for example ammonium halides
  • Such embodiments find particular utility in the context of lanthanide oxides, for example La2O3, are particularly useful since the procedure is quite simple and economically efficient Nanowires comprising two or more metals and/or dopants may also be prepared according to these methods.
  • at least one of the metal compounds is an oxide of a lanthanide element.
  • the present disclosure provides a method for preparing a nanowire in the absence of a biological template, the method comprising treating at least one metal compound with a halide.
  • nanowires comprising more than one type of metal and/or one or more dopants can be prepared by such methods.
  • the method comprises treating two or more different metal compounds with a halide and the nanowire comprises two or more different metals.
  • the nanowire may comprise a mixed metal oxide, metal oxyhalide, metal oxynitrate or metal sulfate.
  • the halide is in the form of an ammonium halide. In yet other embodiments, the halide is contacted with the metal compound in solution or in the solid state.
  • the method is useful for incorporation of one or more doping elements into a nanowire.
  • the method may comprise treating at least one metal compound with a halide in the presence of at least one doping element, and the nanowire comprises the least one doping element.
  • the at least one doping element is present in the nanowire in an atomic percent ranging from 0.1 to 50 at %.
  • preparing a hydroxide gel by reaction of at least one metal salt and a hydroxide base may further comprise aging the gel, heating the gel or combinations thereof.
  • the method comprises reaction of two or more different metal salts, and the nanowire comprises two or more different metals.
  • Doping elements may also be incorporated by using the hydroxide gel method described above, further comprising addition of at least one doping element to the hydroxide gel, and wherein the nanowire comprises the at least one doping element.
  • the at least one doping element may be present in the nanowire in an atomic percent ranging from 0.1 to 50 at %.
  • metal oxide nanowires can be prepared by mixing a metal salt solution and an anion precursor so that a gel of a metal oxide precursor is formed. This method can work for cases where the typical morphology of the metal oxide precursor is a nanowire.
  • the gel is thermally treated so that crystalline nanowires of the metal oxide precursor are formed.
  • the metal oxide precursor nanowires are converted to metal oxide nanowires by calcination. This method can be especially useful for lanthanides and group 3 elements.
  • the thermal treatment of the gel is hydrothermal (or solvothermal) at temperatures above the boiling point of the reaction mixture and at pressures above ambient pressure, in other
  • the thermal treatment is done under reflux conditions at temperatures equal to the boiling point of the mixture.
  • the anion precursor is a hydroxide, e.g., Ammonium hydroxide, sodium hydroxide, lithium
  • This method can be used to make mixed metal oxide nanowires, by mixing at least two metal salt solutions and an anion precursor so that a mixed oxide precursor gel is formed.
  • the first metal may be a lathanide or a group 3 element, and the other metals can be from other groups, including groups 1 -14.
  • metal oxide nanowires can be prepared in a similar way as described above by mixing a metal salt solution and an anion precursor so that a gel of a metal hydroxide precursor is formed.
  • This method works for cases where the typical morphology of the metal hydroxide precursor is a nanowire.
  • the gel is treated so that crystalline nanowires of the metal hydroxide precursor are formed.
  • the metal hydroxide precursor nanowires are converted to metal hydroxide nanowires by base treatment and finally converted to metal oxide nanowires by calcination. This method may be especially applicable for group 2 elements, for example Mg.
  • the gel treatment is a thermal treatment at temperatures in the range 50-100° C. followed by hydrothermal treatment.
  • the gel treatment is an aging step. In some embodiments, the aging step takes at least one day.
  • the metal salt solution is a concentrated metal chloride aqueous solution and the anion precursor is the metal oxide.
  • the metal is Mg. In certain embodiments of the above, these methods can be used to make mixed metal oxide nanowires.
  • the first metal is Mg and the other metal can be any other metal of groups 1 -14+Ln.
  • the catalysts and/or catalytic materials can be prepared
  • the catalysts and/or catalytic materials can be prepared after preparation of the individual components by mixing the individual components in their dry form, e.g., blend of powders, and optionally, ball milling can be used to reduce particle size and/or increase mixing. Each component can be added together or one after the other to form layered particles. Alternatively, the individual components can be mixed prior to calcination, after calcination or by mixing already calcined components with uncalcined components. The catalysts and/or catalytic materials may also be prepared by mixing the individual components in their dry form and optionally pressing them together into a "pill" followed by calcination to above 400 °C.
  • the foregoing catalysts may be doped prior to, or after formation of the catalyst.
  • one or more metal salts are mixed to form a solution or a slurry which is dried and then calcined in a range of 400 °C to 900 °C, or between 500 °C and 700 °C.
  • the catalyst is formed first through calcination of one or more metal salt followed by contact with a solution comprising the doping element followed by drying and/or calcination between 300 °C and 800 °C, or between 400 °C and 700 °C.
  • the catalysts and/or catalytic materials are prepared by mixing the individual components with one or more solvents into a solution, suspension or slurry.
  • solvents useful in this context include, but are not limited to: water, alcohols, ethers, carboxylic acids, ketones, esters, amides, aldehydes, amines, alkanes, alkenes, alkynes, aromatics, etc.
  • the individual components are deposited on a supporting material such as silica, alumina, magnesia, activated carbon, and the like, or by mixing the individual components using a fluidized bed granulator. Combinations of any of the above methods may also be used.
  • the catalysts and/or catalytic materials may optionally comprise a dopant as described in more detail herein.
  • doping material(s) may be added during preparation of the individual components, after preparation of the individual components but before drying of the same, after the drying step but before calcinations or after calcination. If more than one doping material is used, each dopant can be added together or one after the other to form layers of dopants.
  • Doping material(s) may also be added as dry components and optionally ball milling can be used to increase mixing.
  • doping material(s) are added as a liquid (e.g., solution, suspension, slurry, etc.) to the dry individual catalyst components or to the blended catalytic material.
  • the amount of liquid may optionally be adjusted for optimum wetting of the catalyst, which can result in optimum coverage of catalyst particles by doping material.
  • Mixing and/or ball milling can also be used to maximize doping coverage and uniform distribution.
  • doping material(s) are added as a liquid (e.g., solution, suspension, slurry, etc.) to a suspension or slurry of the catalyst in a solvent.
  • Mixing and/or ball milling can be used to maximize doping coverage and uniform distribution. Incorporation of dopants can also be achieved using any of the methods described elsewhere herein.
  • an optional calcination step usually follows an optional drying step at T ⁇ 200C (typically 60-120C) in a regular oven or in a vacuum oven. Calcination may be performed on the individual components of the catalysts and/or catalytic material or on the blended catalysts and/or catalytic material. Calcination is generally performed in an oven/furnace at a temperature higher than the minimum temperature at which at least one of the components decomposes or undergoes a phase transformation and can be performed in inert atmosphere (e.g., N 2 , Ar, He, etc.), oxidizing atmosphere (air, O 2 , etc.) or reducing atmosphere (H 2 , H 2 /N 2 , H 2 /Ar, etc.).
  • inert atmosphere e.g., N 2 , Ar, He, etc.
  • oxidizing atmosphere air, O 2 , etc.
  • reducing atmosphere H 2 , H 2 /N 2 , H 2 /Ar, etc.
  • the atmosphere may be a static atmosphere or a gas flow and may be performed at ambient pressure, at p ⁇ 1 atm, in vacuum or at p > 1 atm.
  • High pressure treatment (at any temperature) may also be used to induce phase transformation including amorphous to crystalline. Calcinations may also be performed using
  • Calcination is generally performed in any combination of steps comprising ramp up, dwell and ramp down. For example, ramp to 500 °C, dwell at 500 °C for 5h, ramp down to RT. Another example includes ramp to 100 °C, dwell at 100 °C for 2h, ramp to 300 °C, dwell at 300 °C for 4h, ramp to 550 °C, dwell at 550 °C for 4h, ramp down to RT. Calcination conditions (pressure, atmosphere type, etc.) can be changed during the calcination.
  • calcination is performed before preparation of the blended catalytic material (i.e., individual components are calcined), after preparation of the blended catalytic material but before doping, after doping of the individual components or blended catalytic material. Calcination may also be performed multiple times, e.g., after catalyst preparation and after doping.
  • the catalytic materials may be incorporated into a reactor bed for performing any number of catalytic reactions ⁇ e.g., OCM, ODH and the like). Accordingly, in one embodiment the present disclosure provides a catalytic material as disclosed herein in contact with a reactor and/or in a reactor bed.
  • the reactor may be for performing an OCM reaction, may be a fixed bed reactor and may have a diameter greater than 1 inch.
  • the catalytic material may be packed neat (without diluents) or diluted with an inert material ⁇ e.g., sand, silica, alumina, etc.)
  • the catalyst components may be packed uniformly forming a homogeneous reactor bed.
  • the particle size of the individual components within a catalytic material may also alter the catalytic activity, and other properties, of the same. Accordingly, in one embodiment, the catalyst is milled to a target average particle size or the catalyst powder is sieved to select a particular particle size. In some aspects, the catalyst powder may be pressed into pellets and the catalyst pellets can be optionally milled and or sieved to obtain the desired particle size distribution.
  • the catalyst materials can be configured into larger aggregate forms, such as pellets, extrudates, or other aggregations of catalyst particles.
  • larger forms are generally referred to herein as "pellets”.
  • pellets may optionally include a binder and/or support material; however, the present inventors have surprisingly found that the disclosed nanowires are particularly suited to use in the form of a pellet without a binder and/or support material. Accordingly, one embodiment of the disclosure provides a catalytic material in the absence of a binder.
  • the morphology of the disclosed nanowires is believed to contribute to the nanowires' ability to be pressed into pellets without the need for a binder.
  • Catalytic materials without binders are simpler, less complex and cheaper than corresponding materials with binders and thus offer certain advantages.
  • catalytic materials may be prepared using a "sacrificial binder" or support. Because of their special properties, the nanowires allow for preparation of catalytic material forms (e.g., pellets) without the use of a binder.
  • a "sacrificial" binder can be used in order to create unique microporosity in pellets or extrudates. After removing the sacrificial binder, the structural integrity of the catalyst is ensured by the special binding properties of the nanowires and the resulting catalytic material has unique microporosity as a result of removing the binder.
  • a catalytic nanowire may be prepared with a binder and then the binder removed by any number of techniques (e.g., calcinations, acid erosion, etc.).
  • This method allows for design and preparation of catalytic materials having unique microporosity (i.e., the microporosity is a function of size, etc., of the sacrificial binder).
  • the ability to prepare different forms (e.g., pellets) of the nanowires without the use of binder is not only useful for preparation of catalytic materials from the nanowires, but also allows the nanowires to be used as support materials (or both catalytic and support material).
  • Sacrificial binders and techniques useful in this regard include sacrificial cellulosic fibers or other organic polymers that can be easily removed by calcination, non-sacrificial binders and techniques useful in this regard include, colloidal oxide binders such as Ludox Silica or Nyacol colloidal zirconia that can also be added to strengthen the formed aggregate when needed.
  • Sacrificial binders are added to increase macro-porosity (pores larger than 20nm diameter) of the catalytic materials. Accordingly, in some embodiments the catalytic materials comprise pores greater than 20 nm in diameter, greater than 50 nm in diameter, greater than 75 nm in diameter, greater than 100 nm in diameter or greater than 150 nm in diameter.
  • Catalytic materials also include any of the disclosed catalysts disposed on or adhered to a solid support.
  • the catalysts may be adhered to the surface of a monolith support.
  • the catalysts may be adhered to the surface of the monolith in the absence of a binder due to their unique morphology and packing properties.
  • Monoliths include honeycomb-type structures, foams and other catalytic support structures derivable by one skilled in the art.
  • the support is a honeycomb matrix formed from silicon carbide, and the support further comprises the disclosed catalyst disposed on the surface.
  • One way to reduce the OCM reaction rate per unit volume of reactor is to spread the active catalyst onto an inert support with interconnected large pores as in ceramic or metallic foams (including metal alloys having reduced reactivity with hydrocarbons under OCM reaction conditions) or having arrays of channel as in honeycomb structured ceramic or metal assembly.
  • a catalytic material comprising a catalyst as disclosed herein supported on a structured support.
  • structure supports include, but are not limited to, metal foams, Silicon Carbide or Alumina foams, corrugated metal foil arranged to form channel arrays, extruded ceramic honeycomb, for example Cordierite (available from Corning or NGK ceramics, USA), Silicon Carbide or Alumina.
  • Active catalyst loading on the structured support ranges from 1 to 500 mg per ml of support component, for example from 5 to 100 mg per ml of structure support.
  • Cell densities on honeycomb structured support materials may range from 100 to 900 CPSI (cell per square inch), for example 200 to 600 CPSI.
  • Foam densities may range from 10 to 100 PPI (pore per inch), for example 20 to 60 PPI.
  • the exotherm of the OCM reaction may be at least partially controlled by blending the active catalytic material with catalytically inert material, and pressing or extruding the mixture into shaped pellets or extrudates. In some embodiments, these mixed particles may then be loaded into a pack-bed reactor.
  • the Extrudates or pellets comprise between 30% to 70% pore volume with 5% to 50% active catalyst weight fraction.
  • Useful inert materials in this regard include, but are not limited to MgO, CaO, AI2O3, SiC and cordierite.
  • Another advantage of using a structured ceramic with large pore volume as a catalytic support is reduced flow resistance at the same gas hourly space velocity versus a pack-bed containing the same amount of catalyst.
  • the structured support can be used to provide features difficult to obtain in a pack- bed reactor.
  • the support structure can improve mixing or enabling patterning of the active catalyst depositions through the reactor volume.
  • Such patterning can consist of depositing multiple layers of catalytic materials on the support in addition to the OCM active component in order to affect transport to the catalyst or combining catalytic functions as adding O2-ODH activity, CO2- OCM activity or CO2-ODH activity to the system in addition to O2-OCM active material.
  • Another patterning strategy can be to create bypass within the structure catalyst essentially free of active catalyst to limit the overall
  • Yet another advantage is reduced heat capacity of the bed of the structured catalyst over a pack bed a similar active catalyst loading therefore reducing startup time.
  • Nanowire shaped catalysts are particularly well suited for incorporation into pellets or extrudates or deposition onto structured supports. Nanowire aggregates forming a mesh type structure can have good adhesion onto rough surfaces.
  • the mesh like structure can also provide improved cohesion in composite ceramic improving the mechanical properties of pellets or extrudates containing the nanowire shaped catalyst particles.
  • OCM organic compound
  • FT dry methane reforming
  • the catalysts are packed in bands forming a layered reactor bed.
  • Each layer is composed by either a catalyst of a particular type, morphology or size or a particular blend of catalysts.
  • the catalysts blend may have better sintering properties, i.e., lower tendency to sinter, then a material in its pure form. Better sintering resistance is expected to increase the catalyst's lifetime and improve the mechanical properties of the reactor bed.
  • the disclosure provides a catalytic material comprising one or more different catalysts.
  • the catalysts may be a nanowire as disclosed herein and a different catalyst for example a bulk catalysts. Mixtures of two or more nanowire catalysts are also contemplated.
  • the catalytic material may comprise a catalyst, for example a nanowire catalyst, having good OCM activity and a catalyst having good activity in the ODH reaction. Either one or both of these catalysts may be nanowires as disclosed herein.
  • a catalytic material described herein comprises a plurality of metal oxide particles.
  • the catalytic material may further comprise a support material.
  • the total surface area per gram of a catalytic material may have an effect on the catalytic performance. Pore size distribution may affect the catalytic performance as well. Surface area and pore size distribution of the catalytic material can be determined by BET (Brunauer,
  • Emmett, Teller measurements.
  • BET techniques utilize nitrogen adsorption at various temperatures and partial pressures to determine the surface area and pore sizes of catalysts.
  • BET techniques for determining surface area and pore size distribution are well known in the art.
  • the catalytic material comprises a surface area of between 0.1 and 100 m 2 /g, between 1 and 100 m 2 /g, between 1 and 50 m 2 /g, between 1 and 20 m 2 /g, between 1 and 10 m 2 /g, between 1 and 5 m 2 /g, between 1 and 4 m 2 /g, between 1 and 3 m 2 /g, or between 1 and 2 m 2 /g.
  • the present disclosure provides heterogeneous catalysts having better catalytic properties than known catalysts.
  • the catalysts disclosed herein are useful in any number of reactions catalyzed by a heterogeneous catalyst. Examples of reactions wherein the disclosed catalysts may be employed are disclosed in Farrauto and Bartholomew, "Fundamentals of Industrial Catalytic Processes” Blackie Academic and Professional, first edition, 1997, which is hereby incorporated in its entirety.
  • reactions wherein the catalysts may be employed include: the oxidative coupling of methane (OCM) to ethane and ethylene; oxidative dehydrogenation (ODH) of alkanes to the corresponding alkenes, for example oxidative dehydrogenation of ethane or propane to ethylene or propylene, respectively; selective oxidation of alkanes, alkenes, and alkynes; oxidation of CO, dry reforming of methane, selective oxidation of aromatics; Fischer-Tropsch, hydrocarbon cracking;
  • the disclosed catalysts are generally useful in methods for converting a first carbon-containing compound ⁇ e.g., a hydrocarbon, CO or CO2) to a second carbon-containing compound.
  • the methods comprise contacting a disclosed catalyst, or material comprising the same, with a gas comprising a first carbon-containing compound and an oxidant to produce a second carbon-containing compound.
  • the first carbon-containing compound is a hydrocarbon, CO, CO2, methane, ethane, propane, hexane, cyclohexane, octane or combinations thereof.
  • the second carbon-containing compound is a hydrocarbon, CO, CO2, ethane, ethylene, propane, propylene, hexane, hexene, cyclohexane, cyclohexene, bicyclohexane, octane, octene or hexadecane.
  • the oxidant is oxygen, ozone, nitrous oxide, nitric oxide, water, carbon dioxide or combinations thereof.
  • the method is OCM and the method is performed at a temperature below 600 °C, below 700 °C, below 800 °C, or below 900 °C.
  • the method for conversion of a first carbon-containing compound to a second carbon-containing compound is performed at a pressure above 0.5 ATM, above 1 ATM, above 2 ATM, above 5 ATM, above 10 ATM, above 25 ATM or above 50 ATM.
  • the catalytic reactions described herein can be performed using standard laboratory equipment known to those of skill in the art, for example as described in U.S. Patent No. 6,350,716, which is incorporated herein in its entirety.
  • the catalysts disclosed herein have better catalytic activity than a corresponding undoped catalyst.
  • the selectivity, yield, conversion, or combinations thereof, of a reaction catalyzed by the catalysts is better than the selectivity, yield, conversion, or combinations thereof, of the same reaction catalyzed by a corresponding undoped catalyst under the same conditions.
  • the catalysts are doped bulk catalysts or nanowire catalysts (doped or undoped) and the catalysts possess a catalytic activity such that conversion of reactant to product in a reaction catalyzed by the catalyst is at least 1 .1 times, at least 1 .25 times, at least 1 .5 times, at least 2.0 times, at least 3.0 times or at least 4.0 times the yield of product in the same reaction under the same conditions but catalyzed by a corresponding catalyst.
  • a "corresponding catalyst” refers to:
  • an undoped bulk catalyst i.e., a catalyst comprising the same base material but different or no dopants or different ratios or concentrations of the same dopants
  • an undoped bulk catalyst i.e., a catalyst comprising the same base material but different or no dopants or different ratios or concentrations of the same dopants
  • a bulk catalyst i.e., a catalyst prepared from bulk material having the same chemical composition as the nanowire, including any dopants
  • the catalysts are doped bulk catalysts or nanowire catalysts (doped or undoped) and the catalysts possess a catalytic activity such that selectivity for product in a reaction catalyzed by the catalyst is at least 1 .1 times, at least 1 .25 times, at least 1 .5 times, at least 2.0 times, at least 3.0 times or at least 4.0 times the yield of product in the same reaction under the same conditions but catalyzed by a corresponding catalyst.
  • the catalysts are doped bulk catalysts or nanowire catalysts (doped or undoped) and the catalysts possess a catalytic activity such that yield of product in a reaction catalyzed by the catalyst is at least 1 .1 times, at least 1 .25 times, at least 1 .5 times, at least 2.0 times, at least 3.0 times or at least 4.0 times the yield of product in the same reaction under the same conditions but catalyzed by a corresponding catalyst.
  • the catalysts are doped bulk catalysts or nanowire catalysts (doped or undoped) and the catalysts possess a catalytic activity such that the activation temperature of a reaction catalyzed by the catalyst is at least 25°C lower, at least 50°C lower, at least 75°C lower, or at least 100°C lower than the temperature of the same reaction under the same conditions but catalyzed by a corresponding catalyst.
  • a reaction e.g., OCM
  • production of unwanted oxides of carbon e.g., CO and CO2
  • the present disclosure addresses this problem and provides catalysts with a catalytic activity such that the selectivity for CO and/or CO2 in a reaction catalyzed by the catalysts is less than the selectivity for CO and/or CO2 in the same reaction under the same conditions but catalyzed by an undoped catalyst.
  • the present disclosure provides a doped bulk catalysts or nanowire catalysts (doped or undoped) and the catalysts possess a catalytic activity such that selectivity for CO x , wherein x is 1 or 2, in a reaction catalyzed by the catalyst is less than at least 0.9 times, less than at least 0.8 times, less than at least 0.5 times, less than at least 0.2 times or less than at least 0.1 times the selectivity for COx in the same reaction under the same conditions but catalyzed by a corresponding catalyst.
  • the absolute selectivity, yield, conversion, or combinations thereof, of a reaction catalyzed by the catalysts disclosed herein is better than the absolute selectivity, yield, conversion, or combinations thereof, of the same reaction under the same conditions but catalyzed by a corresponding catalyst.
  • the yield (e.g., C2 yield) of desired product(s) in a reaction catalyzed by the catalysts is greater than 10%, greater than 20%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
  • the reaction is OCM and the yield of product is greater than 10%, greater than 20%, greater than 30% or greater than 40%.
  • the selectivity for product (e.g., C2 selectivity) in a reaction catalyzed by the catalysts is greater than 10%, greater than 20%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
  • the conversion (e.g., methane conversion) of reactant to product in a reaction catalyzed by the catalysts is greater than10%, greater than 20%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
  • the morphology of the nanowires is expected to provide for improved mixing properties for the nanowires compared to standard colloidal ⁇ e.g., bulk) catalyst materials.
  • the improved mixing properties are expected to improve the performance of any number of catalytic reactions, for example, in the area of transformation of heavy hydrocarbons where transport and mixing phenomena are known to influence the catalytic activity.
  • the shape of the nanowires is expected to provide for good blending, reduce settling, and provide for facile separation of any solid material.
  • the nanowires are useful for absorption and/or incorporation of a reactant used in chemical looping.
  • the nanowires find utility as NO x traps, in unmixed combustion schemes, as oxygen storage materials, as CO2 sorption materials (e.g., cyclic reforming with high H 2 output) and in schemes for conversion of water to H 2 .
  • the present disclosure provides catalysts having catalytic activity and related approaches to catalyst design and preparation for improving the yield, selectivity and/or conversion of any number of catalyzed reactions, including the OCM reaction.
  • Reactors useful in practice of the OCM methods described herein are known in the art and are described in PCT Pub. No. WO 2013/177433, which application is hereby incorporated by reference in its entirety.
  • Ethylene has the largest carbon footprint compared to all industrial chemical products in part due to the large total volume consumed into a wide range of downstream important industrial products including plastics, surfactants and pharmaceuticals.
  • worldwide ethylene production exceeded 120 M metric tons while growing at a robust rate of 4% per year.
  • the United States represents the largest single producer at 28% of the world capacity.
  • Ethylene is primarily manufactured from high temperature cracking of naphtha (e.g., oil) or ethane that is separated from natural gas.
  • naphtha e.g., oil
  • ethane that is separated from natural gas.
  • the true measurement of the carbon footprint can be difficult as it depends on factors such as the feedstock and the allocation as several products are made and separated during the same process. However, some general estimates can be made based on published data.
  • the catalysts of this disclosure provide an alternative to the need for the energy intensive cracking step. Additionally, because of the high selectivity of the catalysts, downstream separations are dramatically simplified, as compared to cracking which yields a wide range of hydrocarbon products. The reaction is also exothermic so it can proceed via an autothermal process mechanism. Overall, it is estimated that up to a potential 75% reduction in CO2 emission compared to conventional methods could be achieved. This would equate to a reduction of one billion tons of CO2 over a ten-year period and would save over 1 M barrels of oil per day.
  • the catalysts of this disclosure also permit converting ethylene into liquid fuels such as gasoline or diesel, given ethylene's high reactivity and numerous publications demonstrating high yield reactions, in the lab setting, from ethylene to gasoline and diesel.
  • liquid fuels such as gasoline or diesel
  • MTL methane to liquid
  • Natural gas is the cleanest of all fossil fuels, and it does not contain a number of impurities such as mercury and other heavy metals found in oil. Additionally, contaminants including sulfur are also easily separated from the initial natural gas stream. The resulting fuels burn much cleaner with no measurable toxic pollutants and provide lower emissions than conventional diesel and gasoline in use today.
  • the catalysts e.g., bulk and/or nanowires
  • the catalysts can be used to not only selectively activate alkanes, but also to activate other classes of inert unreactive bonds, such as C- F, C-CI or C-O bonds.
  • C- F C- F
  • C-CI C-CI
  • C-O bonds This has importance, for example, in the destruction of man-made environmental toxins such as CFCs, PCBs, dioxins and other pollutants.
  • the nanowire catalysts are not in any way limited to this or any other particular reaction.
  • the reported performance is generally limited to ⁇ 25% CH 4 conversion at ⁇ 80% combined C2 selectivity with the performance characteristics of high selectivity at low conversion, or the low selectivity at high conversion.
  • the catalysts of this disclosure are highly active and can optionally operate at a much lower temperature.
  • the catalysts disclosed herein enable efficient conversion of methane to ethylene in the OCM reaction at temperatures less than when other known catalysts are used.
  • the catalysts disclosed herein enable efficient conversion (i.e., high yield, conversion, and/or selectivity) of methane to ethylene at temperatures of less than 900 °C, less than 800 °C, less than 700 °C, less than 600 °C, less than 550 °C, or less than 500 °C.
  • the use of staged oxygen addition, designed heat management, rapid quench and/or advanced separations may also be employed.
  • the OCM reaction is run in a mixture of oxygen and nitrogen or other inert gas.
  • gasesses are expensive and increase the overall production costs associated with preparation of ethylene or ethane from methane.
  • the present inventors have now discovered that such expensive gases are not required and high yield, conversion, selectivity, etc., can be obtained when air is used as the gas mixture instead of pre-packaged and purified sources of oxygen and other gases. Accordingly, in one embodiment the disclosure provides a method for performing the OCM reaction using air as the oxidizer source.
  • one embodiment of the present disclosure is a method for the preparation of ethane and/or ethylene, the method comprising converting methane to ethane and/or ethylene in the presence of a catalytic material, wherein the catalytic material comprises at least one catalyst as disclosed herein.
  • a stable, very active, high surface area, multifunctional catalyst having active sites that are isolated and precisely engineered with the catalytically active metal
  • catalyst compositions useful for the OCM reaction include, but are not limited to the catalyst compositions described herein, including both bulk and nanowire morphologies.
  • the presently disclosed catalysts comprise a catalytic performance better than corresponding catalysts, for example in one embodiment the catalytic performance of the catalysts in the OCM reaction is better than the catalytic performance of a corresponding catalyst.
  • various performance criteria may define the "catalytic performance" of the catalysts in the OCM (and other reactions).
  • catalytic performance is defined by C2 selectivity in the OCM reaction, and the C2 selectivity of the catalysts in the OCM reaction is >5%, >10%, >15%, >20%, >25%, >30%, >35%, >40%, >45%, >50%, >55%, >60%, >65%, >70%, >75% or >80%.
  • Other important performance parameters used to measure the catalysts' catalytic performance in the OCM reaction are selected from single pass methane conversion percentage (i.e., the percent of methane converted on a single pass over the catalyst or catalytic bed, etc.), reaction inlet gas temperature, reaction operating temperature, total reaction pressure, methane partial pressure, gas-hour space velocity (GHSV), O2 source, catalyst stability and ethylene to ethane ratio.
  • improved catalytic performance is defined in terms of the catalysts' improved performance (relative to a corresponding catalyst) with respect to at least one of the foregoing performance parameters.
  • the reaction inlet gas temperature in an OCM reaction catalyzed by the disclosed catalysts can generally be maintained at a lower temperature, while maintaining better performance characteristics ⁇ e.g., conversion, C2 yield, C2 selectivity and the like) compared to the same reaction catalyzed by a corresponding undoped catalyst under the same reaction conditions.
  • the inlet gas temperature in an OCM reaction catalyzed by the disclosed catalysts is ⁇ 700 °C, ⁇ 675 °C, ⁇ 650 °C, ⁇ 625 °C, ⁇ 600 °C, ⁇ 593 °C, ⁇ 580 °C, ⁇ 570 °C, ⁇ 560 °C, ⁇ 550 °C, ⁇ 540 °C, ⁇ 530 °C, ⁇ 520 °C, ⁇ 510 °C, ⁇ 500 °C, ⁇ 490 °C, ⁇ 480 °C or even ⁇ 470 °C.
  • the reaction operating temperature in an OCM reaction catalyzed by the disclosed catalysts can generally be maintained at a lower temperature, while maintaining better performance characteristics compared to the same reaction catalyzed by a corresponding catalyst under the same reaction conditions.
  • the reaction operating temperature (i.e., outlet temperature) in an OCM reaction catalyzed by the disclosed catalysts is ⁇ 950 °C, ⁇ 925 °C, ⁇ 900 °C, ⁇ 875 °C, ⁇ 850 °C, ⁇ 825 °C, ⁇ 800 °C, ⁇ 775 °C, ⁇ 750 °C, ⁇ 725 °C, ⁇ 700 °C, ⁇ 675 °C, ⁇ 650 °C, ⁇ 625 °C, ⁇ 600 °C, ⁇ 593 °C, ⁇ 580 °C, ⁇ 570 °C, ⁇ 560 °C, ⁇ 550 °C, ⁇ 540 °C, ⁇ 530 °C,
  • the single pass methane conversion in an OCM reaction catalyzed by the catalysts is also generally better compared to the single pass methane conversion in the same reaction catalyzed by a corresponding catalyst under the same reaction conditions.
  • For single pass methane conversion it is preferably >5%, >10%, >15%, >20%, >25%, >30%, >35%, >40%, >45%, >50%, >55%, >60%, >65%, >70%, >75%, or even >80%.
  • the inlet reaction pressure in an OCM reaction catalyzed by the catalysts is >1 atm, >1 .1 atm, >1 .2atm, >1 .3atm, >1 .4atm, >1 .5atm, >1 .6atm, >1 .7atm, >1 .8atm, >1 .9atm, >2atm, >2.1 atm, >2.1 atm, >2.2atm, >2.3atm, >2.4atm, >2.5atm, >2.6atm, >2.7atm, >2.8atm, >2.9atm, >3.0atm, >3.5atm, >4.0atm, >4.5atm, >5.0atm, >5.5atm, >6.0atm, >6.5atm, >7.0atm, >7.5atm, >8.0atm, >8.5atm, >9.0atm, >10.0atm, >1 1 .0atm, >12.0atm, >13.0atm, >14.0
  • the total reaction pressure in an OCM reaction catalyzed by the catalysts ranges from about 1 atm to about 10 atm, from about 1 atm to about 7 atm, from about 1 atm to about 5 atm, from about 1 atm to about 3 atm or from about 1 atm to about 2 atm.
  • the methane partial pressure in an OCM reaction catalyzed by the catalysts is >0.3atm, >0.4atm, >0.5atm, >0.6atm, >0.7atm, >0.8atm, >0.9atm, >1 atm, >1 .1 atm, >1 .2atm, >1 .3atm, >1 .4atm, >1 .5atm, >1 .6atm, >1 .7atm, >1 .8atm, >1 .9atm, >2.0atm, >2.1 atm, >2.2atm, >2.3atm, >2.4atm, >2.5atm, >2.6atm, >2.7atm, >2.8atm, >2.9atm, >3.0atm, >3.5atm, >4.0atm, >4.5atm, >5.0atm, >5.5atm, >6.0atm, >6.5atm, >7.0atm, >7.5atm, >8.0atm, >8.5atm, >9.0atm,
  • the GSHV in an OCM reaction catalyzed by the catalysts is >10,000/hr, >15,000/hr, >20,000/hr, >50,000/hr, >75,000/hr, >100,000/hr, >120,000/hr, >130,000/hr, >150,000/hr, >200,000/hr, >250,000/hr, >300,000/hr, >350,000/hr, >400,000/hr, >450,000/hr, >500,000/hr, >750,000/hr, >1 ,000,000/hr, >2,000,000/hr, >3,000,000/hr, >4,000,000/hr.
  • OCM reactions catalyzed by the disclosed catalysts can be performed (and still maintain high C2 yield, C2 selectivity, conversion, etc.) using O2 sources other than pure O2.
  • the O2 source in an OCM reaction catalyzed by the disclosed catalysts is air, oxygen enriched air, pure oxygen, oxygen diluted with nitrogen (or another inert gas) or oxygen diluted with CO 2 .
  • the O 2 source is O 2 diluted by >99%, >98%, >97%, >96%, >95%, >94%, >93%, >92%, >91 %, >90%, >85%, >80%, >75%, >70%, >65%, >60%, >55%, >50%, >45%, >40%, >35%, >30%, >25%, >20%, >15%, >10%, >9%, >8%, >7%, >6%, >5%, >4%, >3%, >2% or >1 % with CO 2 or an inert gas, for example nitrogen.
  • the disclosed catalysts are also very stable under conditions required to perform any number of catalytic reactions, for example the OCM reaction.
  • the stability of the catalysts is defined as the length of time a catalyst will maintain its catalytic performance without a significant decrease in performance (e.g., a decrease >20%, >15%, >10%, >5%, or greater than 1 % in C2 yield, C2 selectivity or conversion, etc.).
  • the disclosed catalysts have stability under conditions required for the OCM reaction of >1 hr, >5 hrs, >10 hrs, >20 hrs, >50 hrs, >80 hrs, >90 hrs, >100 hrs, >150 hrs, >200 hrs, >250 hrs, >300 hrs, >350 hrs, >400 hrs, >450 hrs, >500 hrs, >550 hrs, >600 hrs, >650 hrs, >700 hrs, >750 hrs, >800 hrs, >850 hrs, >900 hrs, >950 hrs, >1 ,000 hrs, >2,000 hrs, >3,000 hrs, >4,000 hrs, >5,000 hrs, >6,000 hrs, >7,000 hrs, >8,000 hrs, >9,000 hrs, >10,000 hrs, >1 1 ,000 hrs,
  • the ratio of ethylene to ethane in an OCM reaction catalyzed by the catalysts is better than the ratio of ethylene to ethane in an OCM reaction catalyzed by a corresponding undoped catalyst under the same conditions.
  • the ratio of ethylene to ethane in an OCM reaction catalyzed by the catalysts is >0.3, >0.4, >0.5, >0.6, >0.7, >0.8, >0.9, >1 , >1 .1 , >1 .2, >1 .3, >1 .4, >1 .5, >1 .6, >1 .7, >1 .8, >1 .9, >2.0, >2.1 , >2.2, >2.3, >2.4, >2.5, >2.6, >2.7, >2.8, >2.9, >3.0, >3.5, >4.0, >4.5, >5.0, >5.5, >6.0, >6.5, >7.0, >7.5, >8.0, >8.5, >9.0, >9.5, >10.0.
  • the OCM reaction employing known catalysts suffers from poor yield, selectivity, or conversion.
  • the presently disclosed catalysts possess a catalytic activity in the OCM reaction such that the yield, selectivity, and/or conversion is better than when the OCM reaction is catalyzed by a corresponding catalyst.
  • the disclosure provides a catalyst having a catalytic activity such that the conversion of methane to ethylene in the oxidative coupling of methane reaction is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the conversion of methane to ethylene compared to the same reaction under the same conditions but performed with a corresponding catalyst.
  • the conversion of methane to ethylene in an OCM reaction catalyzed by the catalysts is greater than 10%, greater than 20%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
  • the disclosure provides a catalyst having a catalytic activity such that the yield of ethylene in the oxidative coupling of methane reaction is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the yield of ethylene compared to the same reaction under the same conditions but performed with a corresponding catalyst.
  • the conversion of methane to ethylene in an OCM reaction catalyzed by the catalytic materials is greater than 10%, greater than 20%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
  • the yield of ethylene in an OCM reaction catalyzed by the catalysts is greater than 10%, greater than 20%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
  • the catalysts possess a catalytic activity in the OCM reaction such that the yield, selectivity, and/or conversion is better than when the OCM reaction is catalyzed by a corresponding catalyst.
  • the disclosure provides a catalyst having a catalytic activity such that the conversion of methane in the oxidative coupling of methane reaction is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the conversion of methane compared to the same reaction under the same conditions but performed with a corresponding catalyst.
  • the conversion of methane in an OCM reaction catalyzed by the catalyst is greater than 10%, greater than 15%, greater than 20%, greater than 25%, greater than 30% greater than 40%, greater than 50%, greater than 75% or greater than 90%.
  • the conversion of methane is determined when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less, 700 °C or less, 650 °C or less or even 600 °C or less.
  • the conversion of methane may also be determined based on a single pass of a gas comprising methane over the catalyst or may be determined based on multiple passes over the catalyst.
  • the disclosure provides a catalyst having a catalytic activity such that the C2 yield in the oxidative coupling of methane reaction is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the C2 yield compared to the same reaction under the same conditions but performed with a corresponding catalyst.
  • the C2 yield in an OCM reaction catalyzed by the catalyst is greater than 10%, greater than 15%, greater than 20%, greater than 25%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
  • the C2 yield is determined when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less, 700 °C or less, 650 °C or less or even 600 °C or less.
  • the C2 yield may also be determined based on a single pass of a gas comprising methane over the catalyst or may be determined based on multiple passes over the catalyst.
  • the disclosure provides a catalyst having a catalytic activity such that the C2 selectivity in the oxidative coupling of methane reaction is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the C2 selectivity compared to the same reaction under the same conditions but performed with a corresponding catalyst.
  • the C2 selectivity in an OCM reaction catalyzed by the catalyst is greater than 10%, greater than 20%, greater than 30%, greater than 40%, greater than 50%, greater than 60%, greater than 65%, greater than 75%, or greater than 90%.
  • the C2 selectivity is determined when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less, 700 °C or less, 650 °C or less or even 600 °C or less.
  • the C2 selectivity may also be determined based on a single pass of a gas comprising methane over the catalyst or may be determined based on multiple passes over the catalyst.
  • the disclosure provides a catalyst having a catalytic activity in the OCM reaction such that the nanowire has the same catalytic activity (i.e., same selectivity, conversion or yield), but at a lower temperature, compared to a corresponding catalyst.
  • the catalytic activity of the catalysts in the OCM reaction is the same as the catalytic activity of a corresponding catalyst, but at a temperature of at least 20 °C less.
  • the catalytic activity of the catalysts in the OCM reaction is the same as the catalytic activity of a corresponding catalyst, but at a temperature of at least 50 °C less.
  • the catalytic activity of the catalysts in the OCM reaction is the same as the catalytic activity of a corresponding catalyst, but at a temperature of at least 100 °C less. In some embodiments the catalytic activity of the catalysts in the OCM reaction is the same as the catalytic activity of a corresponding catalyst, but at a temperature of at least 200 °C less.
  • the disclosure provides a catalyst having a catalytic activity such that the selectivity for CO or CO2 in the oxidative coupling of methane reaction is less than at least 0.9 times, 0.8 times, 0.5 times, 0.2 times, or 0.1 times the selectivity for CO or CO2 compared to the same reaction under the same conditions but performed with a corresponding catalyst.
  • the above selectivity, conversion and yield values are determined at a temperature of less than 850 °C, less than 800 °C, less than 750 °C, less than 700 °C or less than 650 °C.
  • a method for converting methane into ethane and/or ethylene comprising use of catalyst mixture comprising two or more catalysts.
  • the catalyst mixture may be a mixture of a catalyst having good OCM activity and a catalyst having good ODH activity. Catalysts suitable for such uses are described in more detail above.
  • the OCM reaction is run in a mixture of oxygen and nitrogen or other inert gas.
  • gasesses are expensive and increase the overall production costs associated with preparation of ethylene or ethane from methane.
  • the present inventors have now discovered that such expensive gases are not required and high yield, conversion, selectivity, etc., can be obtained when air is used as the gas mixture instead of pre-packaged and purified sources of oxygen and other gases. Accordingly, in one embodiment the disclosure provides a method for performing the OCM reaction in air by use of one or more of the disclosed catalysts.
  • the presently disclosed catalysts and associated methods provide for use of other sources of oxygen in the OCM reaction.
  • an alternate source of oxygen such as CO2, H 2 O, SO2 or SO3 may be used either in place of, or in addition to, air or oxygen as the oxygen source.
  • Such methods have the potential to increase the efficiency of the OCM reaction, for example by consuming a reaction byproduct (e.g., CO 2 or H 2 O) and controlling the OCM exotherm as described below.
  • the oxidation agent for both the methyl radical formation and the ethane oxidation to ethylene is oxygen.
  • the methane to oxygen ratio is generally kept at 4 (i.e., full conversion of methane into methyl radicals) or above.
  • the OCM reaction is typically oxygen limited and thus the oxygen concentration in the effluent is zero.
  • the present disclosure provides a method for increasing the methane conversion and increasing, or in some embodiments, not reducing, the C2 selectivity in an OCM reaction.
  • the disclosed methods include adding to a traditional OCM catalyst another OCM catalyst that uses an oxygen source other than molecular oxygen.
  • the alternate oxygen source is CO2, H 2 O, SO2, SO3 or
  • the alternate oxygen source is CO2. In other embodiments the alternate oxygen source is H 2 O.
  • one embodiment of the present disclosure provides a catalyst (and related methods for use thereof) which is catalytic in the OCM reaction and which uses CO2, H 2 O, SO2, SO3 or another alternative oxygen source or combinations thereof as a source of oxygen.
  • a catalytic material comprising two or more catalysts, wherein the catalytic material comprises at least one catalyst which is catalytic in the OCM reaction and uses O2 for at least one oxygen source and at least one catalysts which is catalytic in the OCM reaction and uses at least of CO 2 , H 2 O, SO 2 , SO 3 NO, NO2, NO3 or another alternative oxygen source.
  • Methods for performing the OCM reaction with such catalytic materials are also provided.
  • Such catalysts comprise any of the compositions disclosed herein and are effective as catalysts in an OCM reaction using an alternative oxygen source at temperatures of 900 °C or lower, 850 °C or lower, 800 °C or lower, 750 °C or lower, 700 °C or lower or even 650 °C or lower.
  • BaO/Cr 2 O 3 BaO/MnO 2 , CaO/MnO/CeO 2 , Na 2 WO 4 /Mn/SiO 2 , Pr 2 O 3 , or Tb 2 O 3 .
  • Some embodiments provide a method for performing OCM, wherein a mixture of an OCM catalyst which use O2 as an oxygen source (referred to herein as an O2-OCM catalyst) and an OCM catalyst which use CO2 as an oxygen source (referred to herein as a CO2-OCM catalyst) is employed as the catalytic material, for example in a catalyst bed.
  • O2-OCM catalyst an OCM catalyst which use O2 as an oxygen source
  • CO2-OCM catalyst O2-OCM catalyst
  • the methods are particularly useful for controlling the exotherm of the OCM reaction.
  • the catalyst bed comprises a mixture of O2-OCM catalyst and CO2-OCM catalysts.
  • the mixture may be in a ratio of 1 :99 to 99:1 .
  • the two catalysts work synergistically as the O2-OCM catalyst supplies the CO2-OCM catalyst with the necessary carbon dioxide and the endothermic nature of the C2-OCM reaction serves to control the exotherm of the overall reaction.
  • the CO2 source may be external to the reaction (e.g., fed in from a CO2 tank, or other source) and/or the heat required for the CO2-OCM reaction is supplied from an external source (e.g., heating the reactor).
  • some embodiments of the present invention provide an OCM method wherein the catalyst bed comprises a gradient of catalysts which changes from a high concentration of O2-OCM catalysts at the front of the bed to a high concentration of CO2-OCM catalysts at the end of the catalyst bed.
  • the O2-OCM catalyst and CO 2 OCM catalyst may have the same or different compositions.
  • the O2-OCM catalyst and CO2-OCM catalyst have the same composition but different morphologies (e.g., nanowire, bent nanowire, bulk, etc.).
  • the O2-OCM and the CO2-OCM catalyst have different compositions.
  • CO 2 -OCM catalysts will typically have higher selectivity, but lower yields than an O2-OCM catalyst. Accordingly, in one embodiment the methods comprise use of a mixture of an O 2 -OCM catalyst and a CO2-OCM catalyst and performing the reaction in O2 deprived environment so that the CO2-OCM reaction is favored and the selectivity is increased. Under appropriate conditions the yield and selectivity of the OCM reaction can thus be optimized.
  • the catalyst bed comprises a mixture of one or more low temperature O2-OCM catalyst (i.e., a catalyst active at low temperatures, for example less than 700 °C) and one or more high temperature CO2-OCM catalyst (i.e., a catalyst active at high temperatures, for example 800 °C or higher).
  • the required high temperature for the CO2-OCM may be provided by the hotspots produced by the O 2 -OCM catalyst.
  • the mixture may be sufficiently coarse such that the hotspots are not being excessively cooled down by excessive dilution effect.
  • the catalyst bed comprises alternating layers of O2-OCM and CO2-OCM catalysts.
  • the catalyst layer stack may begin with a layer of O 2 -OCM catalyst, so that it can supply the next layer ⁇ e.g., a CO2-OCM layer) with the necessary CO2.
  • the O2-OCM layer thickness may be optimized to be the smallest at which 02 conversion is 100% and thus the CH 4 conversion of the layer is maximized.
  • the catalyst bed may comprise any number of catalyst layers, for example the overall number of layers may be optimized to maximize the overall CH conversion and C2 selectivity.
  • the catalyst bed comprises alternating layers of low temperature O 2 -OCM catalysts and high temperature CO 2 -OCM catalysts. Since the CO2-OCM reaction is endothermic, the layers of CO2-OCM catalyst may be sufficiently thin such that in can be "warmed up” by the hotspots of the O2-OCM layers. The endothermic nature of the CO2-OCM reaction can be advantageous for the overall thermal management of an OCM reactor. In some embodiments, the CO 2 -OCM catalyst layers act as "internal" cooling for the O2-OCM layers, thus simplifying the requirements for the cooling, for example in a tubular reactor. Therefore, an interesting cycle takes place with the endothermic reaction providing the necessary heat for the endothermic reaction and the endothermic reaction providing the necessary cooling for the exothermic reaction.
  • one embodiment of the present invention is a method for the oxidative coupling of methane, wherein the method comprises
  • the catalytic material comprises a bed of alternating layers of O2-OCM catalysts and CO2-OCM catalysts.
  • the bed comprises a mixture (i.e., not alternating layers) of O2-OCM catalysts and CO2-OCM catalysts.
  • the OCM methods include use of a jacketed reactor with the exothermic O 2 -OCM reaction in the core and the endothermic CO2-OCM reaction in the mantel.
  • the unused CO2 can be recycled and reinjected into the reactor, optionally with the recycled CH . Additional CO2 can also be injected to increase the overall methane conversion and help reduce greenhouse gases.
  • the reactor comprises alternating stages of O2-OCM catalyst beds and CO 2 -OCM catalyst beds.
  • the CO 2 necessary for the CO2-OCM stages is provided by the O2-OCM stage upstream. Additional CO2 may also be injected.
  • the O2 necessary for the subsequent O2-OCM stages is injected downstream from the CO2-OCM stages.
  • the CO2-OCM stages may provide the necessary cooling for the O2-OCM stages.
  • the inlet gas of the CO2-OCM stages can be additionally heated, the CO2-OCM bed can be heated or both.
  • the CO2 naturally occurring in natural gas is not removed prior to performing the OCM, alternatively CO2 is added to the feed with the recycled methane. Instead the CO 2 containing natural gas is used as a feedstock for CO2-OCM, thus potentially saving a separation step.
  • the amount of naturally occurring CO 2 in natural gas depends on the well and the methods can be adjusted accordingly depending on the source of the natural gas.
  • the foregoing methods can be generalized as a method to control the temperature of very exothermic reactions by coupling them with an endothermic reaction that uses the same feedstock (or byproducts of the exothermic reaction) to make the same product (or a related product).
  • This concept can be reversed, i.e., providing heat to an endothermic reaction by coupling it with an exothermic reaction. This will also allow a higher per pass yield in the OCM reactor.
  • O2-OCM and CO2-OCM catalysts were described in reference to the oxidative coupling of methane (OCM); however, the same concept is applicable to other catalytic reactions including but not limited to: oxidative dehydrogenation (ODH) of alkanes to their corresponding alkenes, selective oxidation of alkanes and alkenes and alkynes, etc.
  • ODH oxidative dehydrogenation
  • a catalyst capable of using an alternative oxygen source e.g., CO 2 , H 2 O, SO 2 , SO 3 or combinations thereof
  • Such catalysts, and uses thereof are described in more detail below.
  • the above methods are applicable for creating novel catalysts by blending catalysts that use different reactants for the same catalytic reactions, for example different oxidants for an oxidation reaction and at least one oxidant is a byproduct of one of the catalytic reactions.
  • the methods can also be generalized for internal temperature control of reactors by blending catalysts that catalyze reactions that share the same or similar products but are exothermic and endothermic, respectively. These two concepts can also be coupled together.
  • propylene is high.
  • the main sources for alkenes include steam cracking, fluid- catalytic-cracking and catalytic dehydrogenation.
  • the current industrial processes for producing alkenes, including ethylene and propylene, suffer from some of the same disadvantages described above for the OCM reaction.
  • the catalysts are useful for the oxidative dehydrogenation (ODH) of hydrocarbons (e.g., alkanes, alkenes, and alkynes).
  • ODH oxidative dehydrogenation
  • the catalysts are useful in an ODH reaction for the conversion of ethane or propane to ethylene or propylene, respectively.
  • Reaction scheme (9) depicts the oxidative dehydrogenation of hydrocarbons:
  • Representative catalysts useful for the ODH reaction include, but are not limited to any of the catalysts disclosed herein.
  • the catalysts possess a catalytic activity in the ODH reaction such that the yield, selectivity, and/or conversion is better than when the ODH reaction is catalyzed by a corresponding catalyst.
  • the disclosure provides a catalyst having a catalytic activity such that the conversion of hydrocarbon to alkene in the ODH reaction is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the conversion of alkane to alkene compared to the same reaction under the same conditions but performed with a corresponding catalyst.
  • the conversion of alkane to alkene in an ODH reaction catalyzed by the catalyst is greater than 10%, greater than 15%, greater than 20%, greater than 25%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
  • the disclosure provides a catalyst having a catalytic activity such that the yield of alkene in an ODH reaction is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the yield of alkene compared to the same reaction under the same conditions but performed with a corresponding catalyst.
  • the yield of alkene in an ODH reaction catalyzed by the catalyst is greater than 10%, greater than 20%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
  • the disclosure provides a catalyst having a catalytic activity in the ODH reaction such that the nanowire has the same catalytic activity, but at a lower temperature, compared to a corresponding catalyst.
  • the catalytic activity of the catalysts in the ODH reaction is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 20 °C less.
  • the catalytic activity of the catalysts in the ODH reaction is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 50 °C less.
  • the catalytic activity of the catalysts in the ODH reaction is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 100 °C less. In some embodiments the catalytic activity of the catalysts in the ODH reaction is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 200 °C less.
  • the disclosure provides a catalyst having a catalytic activity such that the selectivity for alkenes in an ODH reaction is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the selectivity for alkenes compared to the same reaction under the same conditions but performed with a corresponding catalyst.
  • the selectivity for alkenes in an ODH reaction catalyzed by the catalyst is greater than 50%, greater than 60%, greater than 70%, greater than 75%, greater than 80%, greater than 85%, greater than 90%, or greater than 95%.
  • the disclosure provides a catalyst having a catalytic activity such that the selectivity for CO or CO2 in an ODH reaction is less than at least 0.9 times, 0.8 times, 0.5 times, 0.2 times, or 0.1 times the selectivity for CO or CO2 compared to the same reaction under the same conditions but performed with a corresponding catalyst.
  • the catalysts disclosed herein enable efficient conversion of alkane to alkene in the ODH reaction at temperatures less than when a corresponding catalyst is used.
  • the catalysts disclosed herein enable efficient conversion (i.e., high yield, conversion, and/or selectivity) of hydrocarbon to alkene at temperatures of less than 800 °C, less than 700 °C, less than 600 °C, less than 500 °C, less than 400 °C, or less than 300 °C.
  • the stability of the catalysts is defined as the length of time a catalyst will maintain its catalytic performance without a significant decrease in performance (e.g., a decrease >20%, >15%, >10%, >5%, or greater than 1 % in ODH activity or alkene selectivity, etc.).
  • the catalysts have stability under conditions required for the ODH reaction of >1 hr, >5 hrs, >10 hrs, >20 hrs, >50 hrs, >80 hrs, >90 hrs, >100 hrs, >150 hrs, >200 hrs, >250 hrs, >300 hrs, >350 hrs, >400 hrs, >450 hrs, >500 hrs, >550 hrs, >600 hrs, >650 hrs, >700 hrs, >750 hrs, >800 hrs, >850 hrs, >900 hrs, >950 hrs, >1 ,000 hrs, >2,000 hrs, >3,000 hrs, >4,000 hrs, >5,000 hrs, >6,000 hrs, >7,000 hrs, >8,000 hrs, >9,000 hrs, >10,000 hrs, >1 1 ,000 hrs, >12,000 hrs, >13,000 hrs, >14,000 hrs, >15,000 hrs, >16,000 hrs, >17,000 hrs, >18,000 hrs, >9,000 hrs, >10,000 hrs,
  • One embodiment of the present disclosure is directed to a catalyst capable of using an alternative oxygen source (e.g., CO2, H 2 O, SO2, SO3 or combinations thereof) to catalyze the oxidative dehydrogenation of ethane.
  • an alternative oxygen source e.g., CO2, H 2 O, SO2, SO3 or combinations thereof
  • the ODH reaction may proceed according to the following reaction (10): wherein x is an integer and Y is 2x + 2.
  • Compositions useful in this regard include Fe 2 O 3 , Cr 2 O 3 , MnO 2 , Ga 2 O 3 , Cr/SiO 2 , Cr/SO 4 -SiO 2 , Cr-K/SO 4 -SiO 2 , Na 2 WO 4 -Mn/SiO2, Cr-HZSM-5, Cr/Si-MCM-41 (Cr-HZSM-5 and Cr/Si-MCM-41 refer to known zeolites) and MoC/SiO 2 .
  • any of the foregoing catalyst compositions may be supported on S1O2, ZrO2, AI2O3, T1O2 or combinations thereof.
  • the catalysts having ODH activity with alternative oxygen sources are provided.
  • a method for converting methane to ethylene comprises use of an O2-OCM catalyst in the presence of a CO2-ODH catalyst is provided.
  • Catalytic materials comprising at least one O 2 - OCM catalyst and at least one CO2-ODH catalyst are also provided in some embodiments. This combination of catalysts results in a higher yield of ethylene (and/or ratio of ethylene to ethane) since the CO2 produced by the OCM reaction is consumed and used to convert ethane to ethylene.
  • a method for preparation of ethylene comprises converting methane to ethylene in the presence of two or more catalysts, wherein at least one catalyst is an O2-OCM catalyst and at least one catalyst is a CO2-ODH catalyst.
  • the CO2-ODH reaction is endothermic and the O2-OCM reaction is exothermic, and thus if the right mixture and/or arrangement of CO2-ODH and O2-OCM catalysts is used, the methods are particularly useful for controlling the exotherm of the OCM reaction.
  • the catalyst bed comprises a mixture of O2-OCM catalyst and CO2-ODH catalysts. The mixture may be in a ratio of 1 :99 to 99:1 .
  • the two catalysts work synergistically as the O2-OCM catalyst supplies the CO2-ODH catalyst with the necessary carbon dioxide and the endothermic nature of the C 2 -OCM reaction serves to control the exotherm of the overall reaction.
  • some embodiments of the present invention provide an OCM method wherein the catalyst bed comprises a gradient of catalysts which changes from a high concentration of O2-OCM catalysts at the front of the bed to a high concentration of CO 2 -ODH catalysts at the end of the catalyst bed.
  • the O2-ODH catalyst and CO2-ODH catalyst may have the same or different compositions.
  • the O2-ODH catalyst and CO2-ODH catalyst have the same composition but different morphologies (e.g., nanowire, bent nanowire, bulk, etc.).
  • the O2-ODH and the CO 2 -ODH catalyst have different compositions.
  • the catalyst bed comprises alternating layers of O 2 -OCM and CO 2 -ODH catalysts.
  • the catalyst layer stack may begin with a layer of O2-OCM catalyst, so that it can supply the next layer (e.g., a CO2-ODH layer) with the necessary CO2.
  • the O2-OCM layer thickness may be optimized to be the smallest at which 02 conversion is 100% and thus the CH conversion of the layer is maximized.
  • the catalyst bed may comprise any number of catalyst layers, for example the overall number of layers may be optimized to maximize the overall CH 4 conversion and C2 selectivity.
  • the catalyst bed comprises alternating layers of low temperature O2-OCM catalysts and high temperature CO2-ODH catalysts. Since the CO2-ODH reaction is endothermic, the layers of CO2-ODH catalyst may be sufficiently thin such that in can be "warmed up” by the hotspots of the O 2 -OCM layers. The endothermic nature of the CO 2 -ODH reaction can be advantageous for the overall thermal management of an OCM reactor.
  • the CO2-ODH catalyst layers act as "internal" cooling for the O2-OCM layers, thus simplifying the requirements for the cooling, for example in a tubular reactor. Therefore, an interesting cycle takes place with the endothermic reaction providing the necessary heat for the endothermic reaction and the endothermic reaction providing the necessary cooling for the exothermic reaction.
  • one embodiment of the present invention is a method for the oxidative coupling of methane, wherein the method comprises
  • the catalytic material comprises a bed of alternating layers of O 2 -OCM catalysts and CO 2 -ODH catalysts.
  • the bed comprises a mixture (i.e., not alternating layers) of O2-OCM catalysts and CO2-ODH catalysts.
  • the OCM methods include use of a jacketed reactor with the exothermic O 2 -OCM reaction in the core and the endothermic CO2-ODH reaction in the mantel.
  • the unused CO 2 can be recycled and reinjected into the reactor, optionally with the recycled CH . Additional CO2 can also be injected to increase the overall methane conversion and help reduce greenhouse gases.
  • the reactor comprises alternating stages of
  • O2-OCM catalyst beds and CO2-ODH catalyst beds The CO2 necessary for the CO2-ODH stages is provided by the O 2 -OCM stage upstream. Additional
  • CO2 may also be injected.
  • the O2 necessary for the subsequent O2-OCM stages is injected downstream from the CO2-ODH stages.
  • the CO2-ODH stages may provide the necessary cooling for the O2-OCM stages.
  • the inlet gas of the CO 2 -ODH stages can be additionally heated, the CO 2 -ODH bed can be heated or both.
  • the CO2 naturally occurring in natural gas is not removed prior to performing the OCM, alternatively CO2 is added to the feed with the recycled methane. Instead the CO2 containing natural gas is used as a feedstock for CO 2 -ODH, thus potentially saving a separation step.
  • the amount of naturally occurring CO2 in natural gas depends on the well and the methods can be adjusted accordingly depending on the source of the natural gas.
  • Carbon dioxide reforming (CDR) of methane is an attractive process for converting CO2 in process streams or naturally occurring sources into the valuable chemical product, syngas (a mixture of hydrogen and carbon monoxide). Syngas can then be manufactured into a wide range of
  • FIG. 3 schematically depicts a CDR reaction 700, in which activation and dissociation of CH occurs on the metal catalyst surface 710 to form intermediate "M-C".
  • M-C metal catalyst surface
  • S-CO2 intermediate
  • the final step is the reaction between the M-C species and the activated S-CO2 to form CO.
  • the catalysts disclosed herein are useful as catalysts for the carbon dioxide reforming of methane.
  • the catalysts are useful as catalysts in a CDR reaction for the production of syn gas.
  • the catalysts possess a catalytic activity in the CDR reaction such that the yield, selectivity, and/or conversion is better than when the CDR reaction is catalyzed by a corresponding catalyst.
  • the disclosure provides a catalyst having a catalytic activity such that the
  • conversion of CO 2 to CO in the CDR reaction is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the conversion of CO2 to CO compared to the same reaction under the same conditions but performed with a corresponding catalyst.
  • the conversion of CO2 to CO in a CDR reaction catalyzed by the catalyst is greater than 10%, greater than 15%, greater than 20%, greater than 25%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
  • the disclosure provides a catalyst having a catalytic activity such that the yield of CO in a CDR reaction is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the yield of CO compared to the same reaction under the same conditions but performed with a corresponding catalyst.
  • the yield of CO in a CDR reaction catalyzed by the catalyst is greater than 10%, greater than 20%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
  • the disclosure provides a catalyst having a catalytic activity such that the selectivity for CO in a CDR reaction is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the selectivity for CO compared to the same reaction under the same conditions but performed with a corresponding catalyst.
  • the selectivity for CO in a CDR reaction catalyzed by the catalyst is greater than 10%, greater than 20%, greater than 30%, greater than 40%, greater than 50%, greater than 65%, greater than 75%, or greater than 90%.
  • the disclosure provides a catalyst having a catalytic activity in a CDR reaction such that the catalyst has the same or better catalytic activity, but at a lower temperature, compared to a
  • the catalytic activity of the catalysts in a CDR reaction is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 20 °C less. In some embodiments the catalytic activity of the catalysts in a CDR reaction is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 50 °C less. In some embodiments the catalytic activity of the catalysts in a CDR reaction is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 100 °C less. In some embodiments the catalytic activity of the catalysts in a CDR reaction is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 200 °C less.
  • the catalysts disclosed herein enable efficient conversion of CO2 to CO in the CDR reaction at temperatures less than when a corresponding catalyst is used.
  • the catalysts enable efficient conversion (i.e., high yield, conversion, and/or selectivity) of CO 2 to CO at temperatures of less than 900 °C, less than 800 °C, less than 700 °C, less than 600 °C, or less than 500 °C.
  • Fischer-Tropsch synthesis is a valuable process for converting synthesis gas (i.e., CO and H 2 ) into valuable hydrocarbon fuels, for example, light alkenes, gasoline, diesel fuel, etc.
  • FTS has the potential to reduce the current reliance on the petroleum reserve and take advantage of the abundance of coal and natural gas reserves.
  • Current FTS processes suffer from poor yield, selectivity, conversion, catalyst deactivation, poor thermal efficiency and other related disadvantages.
  • Production of alkanes via FTS is shown in reaction scheme (14), wherein n is an integer. CO + 2H 2 (1 /n)(C n H 2n ) + H 2 O (14)
  • the catalysts are useful as catalysts in FTS processes.
  • the catalysts are useful as catalysts in a FTS process for the production of alkanes. Improvements to the yield, selectivity, and/or conversion in FTS processes employing bulk catalysts are needed. Accordingly, in one
  • the catalysts possess a catalytic activity in an FTS process such that the yield, selectivity, and/or conversion is better than when the FTS process is catalyzed by a corresponding catalyst.
  • the disclosure provides a catalyst having a catalytic activity such that the
  • conversion of CO to alkane in an FTS process is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the conversion of CO to alkane compared to the same reaction under the same conditions but performed with a corresponding catalyst.
  • the conversion of CO to alkane in an FTS process catalyzed by the catalyst is greater than 10%, greater than 15%, greater than 20%, greater than 25%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
  • the disclosure provides a catalyst having a catalytic activity in an FTS process such that the catalyst has the same or better catalytic activity, but at a lower temperature, compared a corresponding catalyst.
  • the catalytic activity of the catalysts in an FTS process is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 20 °C less.
  • the catalytic activity of the catalysts in an FTS process is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 50 °C less.
  • the catalytic activity of the catalysts in an FTS process is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 100 °C less. In some embodiments the catalytic activity of the catalysts in an FTS process is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 200 °C less.
  • the disclosure provides a catalyst having a catalytic activity such that the yield of alkane in a FTS process is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the yield of alkane compared to the same reaction under the same conditions but performed with a corresponding catalyst.
  • the yield of alkane in an FTS process catalyzed by the catalyst is greater than 10%, greater than 20%, greater than 30%, greater than 40%, greater than 50%, greater than 65%, greater than 75%, or greater than 90%.
  • the disclosure provides a catalyst having a catalytic activity such that the selectivity for alkanes in an FTS process is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the selectivity for alkanes compared to the same reaction under the same conditions but performed with a corresponding catalyst.
  • the selectivity for alkanes in an FTS process catalyzed by the catalyst is greater than 10%, greater than 20%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
  • the catalysts disclosed herein enable efficient conversion of CO to alkanes in a CDR process at temperatures less than when a corresponding catalyst is used.
  • the catalysts enable efficient conversion (i.e., high yield, conversion, and/or selectivity) of CO to alkanes at temperatures of less than 400 °C, less than 300 °C, less than 250 °C, less than 200 °C, less the 150 °C, less than 100 °C or less than 50 °C.
  • Carbon monoxide (CO) is a toxic gas and can convert hemoglobin to carboxyhemoglobin resulting in asphyxiation. Dangerous levels of CO can be reduced by oxidation of CO to CO2 as shown in reaction scheme 15:
  • Catalysts for the conversion of CO into CO2 have been developed but improvements to the known catalysts are needed. Accordingly in one embodiment, the present disclosure provides catalysts useful as catalysts for the oxidation of CO to CO2. In one embodiment, the catalysts possess a catalytic activity in a process for the conversion of CO into CO 2 such that the yield, selectivity, and/or conversion is better than when the oxidation of CO into CO 2 is catalyzed by a corresponding catalyst.
  • the disclosure provides a catalyst having a catalytic activity such that the conversion of CO to CO 2 is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the conversion of CO to CO 2 compared to the same reaction under the same conditions but performed with a corresponding catalyst.
  • the conversion of CO to CO 2 catalyzed by the catalyst is greater than 10%, greater than 15%, greater than 20%, greater than 25%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
  • the disclosure provides a catalyst having a catalytic activity such that the yield of CO 2 from the oxidation of CO is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the yield of CO 2 compared to the same reaction under the same conditions but performed with a corresponding catalyst.
  • the yield of CO 2 from the oxidation of CO catalyzed by the catalyst is greater than 10%, greater than 20%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
  • the disclosure provides a catalyst having a catalytic activity in an oxidation of CO reaction such that the catalyst has the same or better catalytic activity, but at a lower temperature, compared to a corresponding catalyst.
  • the catalytic activity of the catalysts in an oxidation of CO reaction is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 20 °C less.
  • the catalytic activity of the catalysts in an oxidation of CO reaction is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 50 °C less.
  • the catalytic activity of the catalysts in an oxidation of CO reaction is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 100 °C less. In some embodiments the catalytic activity of the catalysts in an oxidation of CO reaction is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 200 °C less.
  • the disclosure provides a catalyst having a catalytic activity such that the selectivity for CO2 in the oxidation of CO is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the selectivity for CO2 compared to the same reaction under the same conditions but performed with a corresponding catalyst.
  • the selectivity for CO 2 in the oxidation of CO catalyzed by the catalyst is greater than 10%, greater than 20%, greater than 30%, greater than 40%, greater than 50%, greater than 65%, greater than 75%, or greater than 90%.
  • the catalysts disclosed herein enable efficient conversion of CO to CO2 at temperatures less than when a corresponding catalyst is used as a catalyst.
  • the catalysts enable efficient conversion (i.e., high yield, conversion, and/or selectivity) of CO to CO 2 at temperatures of less than 500 °C, less than 400 °C, less than 300 °C, less than 200 °C, less than 100 °C, less than 50 °C or less than 20 °C.
  • the disclosed catalysts are useful as catalysts in a variety of other reactions.
  • the disclosed catalysts find utility in any reaction utilizing a
  • heterogeneous catalyst and have a catalytic activity such that the yield, conversion, and/or selectivity in reaction catalyzed by the catalysts is better than the yield, conversion and/or selectivity in the same reaction catalyzed by a corresponding catalyst.
  • the present disclosure provides a catalyst having catalytic activity in a reaction for the catalyzed combustion of
  • catalytic reactions find utility in catalytic converters for automobiles, for example by removal of unburned hydrocarbons in the exhaust by catalytic combustion or oxidation of soot captured on catalyzed particle filters resulting in reduction on diesel emissions from the engine.
  • a low temperature catalyst such as the disclosed catalysts, is needed to efficiently eliminate all unburned hydrocarbons.
  • soot removal on catalyzed particulate filters intimate contact between the soot and the catalyst is require; the open mesh morphology of catalyst coating is advantageous to promote such intimate contact between soot and oxidation catalyst.
  • the disclosure provides a catalyst having a catalytic activity such that the combustion of hydrocarbons is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the combustion of hydrocarbons compared to the same reaction under the same conditions but performed with a corresponding catalyst.
  • the total combustion of hydrocarbons catalyzed by the catalyst is greater than 10%, greater than 20%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
  • the disclosure provides a catalyst having a catalytic activity such that the yield of combusted hydrocarbon products is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the yield of combusted hydrocarbon products compared to the same reaction under the same conditions but performed with a corresponding catalyst.
  • the yield of combusted hydrocarbon products in a reaction catalyzed by the catalyst is greater than 10%, greater than 20%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
  • the stability of the catalysts is defined as the length of time a catalyst will maintain its catalytic performance without a significant decrease in performance (e.g., a decrease >20%, >15%, >10%, >5%, or greater than 1 % in hydrocarbon or soot combustion activity).
  • the catalysts have stability under conditions required for the hydrocarbon combustion reaction of >1 hr, >5 hrs, >10 hrs, >20 hrs, >50 hrs, >80 hrs, >90 hrs, >100 hrs, >150 hrs, >200 hrs, >250 hrs, >300 hrs, >350 hrs, >400 hrs, >450 hrs, >500 hrs, >550 hrs, >600 hrs, >650 hrs, >700 hrs, >750 hrs, >800 hrs, >850 hrs, >900 hrs, >950 hrs, >1 ,000 hrs, >2,000 hrs, >3,000 hrs, >4,000 hrs, >5,000 hrs, >6,000 hrs, >7,000 hrs, >8,000 hrs, >9,000 hrs, >10,000 hrs, >1 1 ,000 hrs,
  • the disclosure provides a catalyst having a catalytic activity in the combustion of hydrocarbons such that the catalyst has the same or better catalytic activity, but at a lower temperature, compared to a corresponding catalyst.
  • the catalytic activity of the catalysts in the combustion of hydrocarbons is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 20 °C less.
  • the catalytic activity of the catalysts in the combustion of hydrocarbons is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 50 °C less.
  • the catalytic activity of the catalysts in the combustion of hydrocarbons is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 100 °C less. In some embodiments the catalytic activity of the catalysts in the combustion of hydrocarbons is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 200 °C less.
  • the first step comprises the selection of a reaction and catalyst. This influences the choice of reactor and how it is operated, including batch, flow, etc. (block 754).
  • the data of the reaction are compiled and analyzed (block 760) to provide insights to the mechanism, rates and process optimization of the catalytic reaction.
  • the data provide useful feedbacks for further design modifications of the reaction conditions. Additional methods for evaluating catalytic performance in the laboratory and industrial settings are described in, for example, Bartholomew, C.H. et al. Fundamentals of Industrial Catalytic Processes, Wiley-AIChE; 2Ed (1998).
  • an Altamira Benchcat 200 can be employed using a 4 mm ID diameter quartz tube with a 0.5 mm ID capillary downstream. Quartz tubes with 2 mm or 6 mm ID can also be used. Catalysts are tested in a number of different dilutions and amounts. In some embodiments, the range of testing is between 10 and 300 mg.
  • the catalysts are diluted with a non-reactive diluent. This diluent can be quartz (S1O2) or other inorganic materials, which are known to be inert in the reaction condition. The purpose of the diluent is to minimize hot spots and provide an appropriate loading into the reactor.
  • the catalyst can be blended with less catalytically active components as described in more detail above.
  • 50 mg is the total charge of catalyst, optionally including diluent.
  • a small plug of glass wool is loaded to keep the catalysts in place.
  • a thermocouple is placed on the inlet side of the catalyst bed into the glass wool to get the temperature in the reaction zone.
  • Another thermocouple can be placed on the downstream end of the catalyst bed into the catalyst bed itself to measure the exotherms, if any.
  • x (usually 10-50) mg of the catalyst (either bulk or test nanowire catalyst) is blended with (100-x) mg of diluent. Thereafter, about 2 ml of ethanol or water is added to form a slurry mixture, which is then sonicated for about 10 minutes. The slurry is then dried in an oven at about 100-140 °C for 2 hours to remove solvent. The resulting solid mixture is then scraped out and loaded into the reactor between the plugs of quartz wool.
  • the reactor is inserted into the Altamira instrument and furnace and then a temperature and flow program is started.
  • the total flow is 50 to 100 seem of gases but this can be varied and programmed with time.
  • the reactor is inserted into the Altamira instrument and furnace and then a temperature and flow program is started.
  • the total flow is 50 to 100 seem of gases but this can be varied and programmed with time.
  • the reactor is inserted into the Altamira instrument and furnace and then a temperature and flow program is started.
  • the total flow is 50 to 100 seem of gases but this can be varied and programmed with time.
  • the reactant gases comprise air or oxygen (diluted with nitrogen or argon) and methane in the case of the OCM reaction and gas mixtures comprising ethane and/or propane with oxygen for oxidative dehydrogenation (ODH) reactions.
  • ODH oxidative dehydrogenation
  • Other gas mixtures can be used for other reactions.
  • GC Chromatography
  • the GC method developed for these experiments employs 4 columns and 2 detectors and a complex valve switching system to optimize the analysis.
  • a flame ionization detector (FID) is used for the analysis of the hydrocarbons only. It is a highly sensitive detector that produces accurate and repeatable analysis of methane, ethane, ethylene, propane, propylene and all other simple alkanes and alkenes up to five carbons in length and down to ppm levels.
  • a stripper column alumina
  • PLOT column capillary alumina column
  • a Thermal Conductivity Detector For the analysis of the light non-hydrocarbon gases, a Thermal Conductivity Detector (TCD) may be employed which also employees two columns to accomplish its analysis.
  • the target molecules for this analysis are CO2, ethylene, ethane, hydrogen, oxygen, nitrogen, methane and CO.
  • the two columns used here are a porous polymer column known as the Hayes Sep N which performs some of the separation for the CO2, ethylene and ethane.
  • the second column is a molecular sieve column which uses size differentiation to perform the separation. It is responsible for the separation of H 2 , O2, N 2 , methane and CO.
  • the catalysts disclosed herein are useful in reactions for the preparation of a number of valuable hydrocarbon compounds.
  • the catalysts are useful for the preparation of ethylene from methane via the OCM reaction.
  • the catalysts are useful for the preparation of ethylene or propylene via oxidative dehydrogenation of ethane or propane respectively.
  • Ethylene and propylene are valuable compounds which can be converted into a variety of consumer products.
  • ethylene can be converted into many various compounds including low density polyethylene, high density polyethylene, ethylene dichloride, ethylene oxide, ethylbenzene, linear alcohols, vinyl acetate, alkanes, alpha olefins, various hydrocarbon-based fuels, ethanol and the like. These compounds can then be further processed using methods well known to one of ordinary skill in the art to obtain other valuable chemicals and consumer products (e.g., the downstream products shown in Figure 5). Propylene can be analogously converted into various compounds and consumer goods including polypropylenes, propylene oxides, propanol, and the like.
  • the invention is directed to a method for the preparation of C2 hydrocarbons via the OCM reaction, the method comprises contacting a catalyst as described herein with a gas comprising methane.
  • the C2 hydrocarbons are selected from ethane and ethylene.
  • the disclosure provides a method of preparing downstream products of ethylene. The method comprises converting ethylene into a downstream product of ethylene, wherein the ethylene has been prepared via a catalytic reaction employing a catalyst disclosed herein (e.g., OCM).
  • the downstream product of ethylene is low density polyethylene, high density polyethylene, ethylene dichloride, ethylene oxide, ethylbenzene, ethanol or vinyl acetate from ethylene, wherein the ethylene has been prepared as described above.
  • the downstream product of ethylene is natural gasoline.
  • the downstream product of ethylene comprises 1 -hexene, 1 -octene, hexane, octane, benzene, toluene, xylene or combinations thereof.
  • a process for the preparation of ethylene from methane comprising contacting a mixture comprising oxygen and methane at a temperature below 900 °C, below 850 °C, below 800 °C, below 750 °C, below 700 °C or below 650 °C with a catalyst as disclosed herein is provided.
  • the disclosure provides a method of preparing a product comprising low density polyethylene, high density
  • polyethylene polyethylene, ethylene dichloride, ethylene oxide, ethylbenzene, ethanol or vinyl acetate, alkenes, alkanes, aromatics, alcohols, or mixtures thereof.
  • the method comprises converting ethylene into low density polyethylene, high density polyethylene, ethylene dichloride, ethylene oxide, ethylbenzene, ethanol or vinyl acetate, wherein the ethylene has been prepared via a catalytic reaction employing a catalyst for example any of the exemplary catalysts disclosed herein.
  • the ethylene is produced via an OCM or ODH reaction or combinations thereof.
  • the disclosure provides a method of preparing a downstream product of ethylene and/or ethane, wherein the downstream product is a hydrocarbon fuel.
  • the downstream product of ethylene may be a hydrocarbon fuel such as natural gasoline or a C 4 -Ci 4 hydrocarbon, including alkanes, alkenes and aromatics.
  • alkanes alkenes and aromatics.
  • Some specific examples include 1 -butene, 1 -hexene, 1 -octene, hexane, octane, benzene, toluene, xylenes and the like.
  • the method comprises converting methane into ethylene, ethane or combinations thereof by use of a catalyst, for example any of the catalysts disclosed herein, and further oligomerizing the ethylene and/or ethane to prepare a downstream product of ethylene and/or ethane.
  • a catalyst for example any of the catalysts disclosed herein
  • the methane may be converted to ethylene, ethane or combinations thereof via the OCM reaction as discussed above.
  • the method begins with charging methane (e.g., as a component in natural gas) into an OCM reactor.
  • the OCM reaction may then be performed utilizing a catalyst under any variety of conditions.
  • Water and CO 2 are optionally removed from the effluent and unreacted methane is recirculated to the OCM reactor.
  • Ethylene is recovered and charged to an oligomerization reactor.
  • the ethylene stream may contain CO 2 , H 2 O, N 2 , ethane, C3's and/or higher hydrocarbons.
  • Oligomerization to higher hydrocarbons e.g., C -Ci
  • Oligomerization may be effected by use of any number of catalysts known to those skilled in the art. Examples of such catalysts include catalytic zeolites, crystalline borosilicate molecular sieves, homogeneous metal halide catalysts, Cr catalysts with pyrrole ligands or other catalysts.
  • the exemplary OCM and oligomerization modules depicted in Figure 6 may be adapted to be at the site of natural gas production, for example a natural gas field.
  • natural gas can be efficiently converted to more valuable and readily transportable hydrocarbon commodities without the need for transport of the natural gas to a processing facility.
  • natural gasoline refers to a mixture of oligomerized ethylene products.
  • natural gasoline comprises hydrocarbons containing 5 or more carbon atoms.
  • Exemplary components of natural gasoline include linear, branched or cyclic alkanes, alkenes and alkynes, as well as aromatic hydrocarbons.
  • natural gasoline include linear, branched or cyclic alkanes, alkenes and alkynes, as well as aromatic hydrocarbons.
  • natural gasoline comprises 1 -pentene, 1 -hexene, cyclohexene, 1 -octene, benzene, toluene, dimethyl benzene, xylenes, napthalene, or other oligomerized ethylene products or combinations thereof.
  • natural gasoline may also include C3 and C4 hydrocarbons dissolved within the liquid natural gasoline. This mixture finds particular utility in any number of industrial applications, for example natural gasoline is used as feedstock in oil refineries, as fuel blend stock by operators of fuel terminals, as diluents for heavy oils in oil pipelines and other
  • Equimolar aqueous solutions of strontium nitrate, neodymium nitrate, and lanthanum nitrate were prepared. Aliquots of each solution were mixed together to prepare a desired formulation of La x Nd y Sr z where x,y,z represent mole fractions of total metal content in moles. Representative examples of formulations are: La 5 oNd3oSr 2 o, La52Nd 45 Sr 0 5, La 7 5Nd22Sr 0 3, and the like. A solution of citric acid was added to the metal salt mixture so that citric acid mole/metal mole ratio was 3:1 .
  • Ethylene glycol was then added to the citric acid/metal salt solution so that the ethylene glycol/citric acid mole ratio was 1 :1 .
  • the solution was stirred at room temperature for 1 h.
  • the solution was placed in a 130 °C oven for 15 h to remove water and to promote resin formation. After 15h, a hard dark resin was observed.
  • the resin was placed in a furnace and heated to 500 °C for 8h. The remaining material was heated to 650 °C for 2h to yield the desired product.
  • catalysts are prepared according to an analogous procedure.
  • catalysts comprising La and Sm as well as catalysts comprising La and Ce can be prepared according to the above general procedure.
  • catalysts comprising La/Ce/Nd/Sr, La/Bi/Sr, Nd/Sr, La/Sr, La/Bi/Ce/Nd/Sr can also be prepared in this manner.
  • Catalysts comprising support materials can also be prepared by coprecipitation according to the above method.
  • rare earth oxides on MgO, CaO or AIPO 4 supports can be prepared.
  • Specific examples include, Nd/Sr/CaO (i.e., a catalyst comprising Nd and Sr on a CaO support).
  • the solids were then calcined in a furnace by ramping up to 350 °C at 5 °C /min and holding for 2 hours and then ramping again at the same rate to 700 °C and holding for 4 hours. It was then cooled to room temperature, ground and sieved to a particle size range of 180 ⁇ to 250 ⁇ .
  • Mn2O3 (325 mesh); 1 .418g of MgO (325 mesh); 0.384g Boric acid powder and 0.164g LiOH anhydrous. This corresponds to an approximate molar ratio of Li:B:Mn:Mg of 1 :1 :2:5.
  • the powders were then added to about 20 ml of water, resulting in a black slurry. This slurry was stirred for about an hour to dissolve all of the LiOH and boric acid and then dried for several hours at about 120 °C. In a crucible, the resulting powder was ground as fine as possible and calcined according to the following schedule. Ramp to 350 °C at 5 °C /min and hold for 120 minutes.
  • Sample 2 was prepared in a manner analogous to sample one, except that 0.060g of cobalt chloride was used.
  • Sample 3 was prepared in a manner analogous to sample one, except that 0.015g (+-.01 g) NaCI was used.
  • Sample 4 was prepared in a manner analogous to sample one, except that 0.015g (+-.01 g) NaCI and 0.060g of cobalt chloride were used.
  • the 4 dishes were placed in the muffle furnace and programmed to run at 350 °C for 2 hours followed by 650 °C for 2 hours followed by 950 °C for 8 hours before cooling to near room temperature.
  • the solids were ground with a pestle in the dish and run through a Gilson sieve shaker.
  • the sieves used were, from top to bottom, 300 urn, 212 m, 106 ⁇ and 75 ⁇ .
  • the 106 fraction was collected and put in a vial, and the combined other fractions were placed in another vial.
  • the resultant slurry was placed in a 100-140 °C oven overnight to dry prior to calcining in a ceramic evaporating dish with the following schedule: ramp 5 °C /min to 400 °C and hold for 2hours, ramp 5 °C/min to 850 °C and hold for 8 hours.
  • 0.410 g of ZrO2 powder were mixed with 0.0365 g of Manganese nitrate tetrahydrate (Mn (NO 3 ) 2 ) and 0.0179g of Sodium tungstate (Na 2 WO 4 ) in a beaker with enough water to make a stirrable slurry.
  • the mixture was stirred on hotplate at about 60-80 °C for 3 hours, adding water as necessary to keep from drying.
  • the resultant slurry was placed in a 100-140 °C oven overnight to dry prior to calcining in a ceramic evaporating dish with the following schedule: ramp 5 °C /min to 400 °C and hold for 2 hours, ramp 5 °C/min to 850 °C and hold for 8 hours.
  • FIG. 7 shows the onset of OCM between 700 °C and 750 °C for the Na/Co doped LiMnMgB mixed oxide sample whereas the onset of the OCM is between 800°C and 825°C for the undoped LiMnMgB mixed oxide catalyst.
  • Figure 8 shows the onset of OCM between 700 °C and 750 °C for the NaMnWO 4 supported on Zirconia whereas the onset of the OCM is between 750 °C and 800 °C for the NaMnWO 4 supported on Silica.
  • the C2 selectivity, methane conversion and C2 yield at 750 °C for the Zirconia supported catalyst were 45 %, 20 % and 9 %, respectively.
  • the effect of doping of bulk rare earth oxides or other mixed oxides was evaluated by preparing libraries of doped catalysts on a quartz wafer etched to form a 16x16 well area (4 ml per well) in which about 1 mg of the base catalyst (e.g., bulk rare earth oxide) is added. These oxides were first suspended in slurries with Butanol then the slurries were distributed to the wells using automated liquid dispensing. The wafer library was then dried.
  • the base catalyst e.g., bulk rare earth oxide
  • Aqueous salt solutions of 49 different metals were prepared and added to the wells in a pre-set pattern design with 4 repeats of each doping in 4 different area of the wafer.
  • the list of metal salts evaluated was as follows: AI(NO 3 ) 3 , CuCI, CsCI, BaCI 2 , CeCI 3 , Ga(NO 3 ) 3 , lnCI 3 , HfCI 2 O, Fe(NO 3 ) 3 , CrCI 3 , LaCIs, RuCIs, SmCI 3 , EuCI 3 , YCI 3 , Sr(NO 3 ) 2 ,ZrOCI 2 , TaCI 5 , RhAcAc, Be(NO 3 ) 2 , AuCI 4 H, NaCI ,NiCI 2 , CoCI 2 , SbCI 3 , Ba(NO 3 ) 2 , VCI 3 , PrCI 3 , AgNO 3 , TeCI 4 , ErCI 3 , Tb(NO 3 ) 3 , HfCI 2
  • the wafer was calcined again after doping at 700°C for 4 hours. Testing of the activity of the doped catalysts was conducted in a Scanning Mass Spectrometer, which allows to heat up at set temperature individual wells on the wafer while flowing a reactant mixture on top of the heated well.
  • Reaction products were aspirated through a glass capillary and analyzed using a mass spectrometer.
  • the gas mixture in contact with the catalytic material was comprised of Methane, Oxygen, Argon with a 4/1/1 molar ratio.
  • Test temperatures were typically varied from 600 °C to 800 °C in 50 °C increment with a one minute hold at each temperature.
  • Example 8-a Doped Co/Na/LiMnMgB library.
  • a SMS wafer with a base oxide from example 4-1 was prepared and tested as described above. The results of the test are presented in Figure 9. Be, Ba, Al, Hf dopants were found to promote the Co/Na/LiMnMgB catalyst activity further without affecting the selectivity towards higher hydrocarbons.
  • Example 8-b Doping of MnW on Silica library.
  • a SMS wafer with a silica supported oxide from Example 5 was prepared and tested as described above. The results of the test are presented in Figure 10. Mo, Be, Ba, Te dopants were found to promote the OCM activity of the MnW on Silica catalyst.
  • Example 8-c Doping of Nd 2 O 3 library.
  • a SMS wafer with bulk Nd2O3 was prepared and tested as described above. The results of the test are presented in Figure 1 1 .
  • Ca, Li, Na, Rb, Sm, Sr dopants were found to promote the OCM activity of the Nd 2 O 3 catalyst and improved higher hydrocarbon selectivity compared to undoped Nd 2 O3 catalyst tested under the same conditions.
  • Example 8-d Doping of Yb 2 O 3 library.
  • a SMS wafer with bulk Yb 2 O 3 was prepared and tested as described above. The results of the test are presented in Figure 12.
  • Ba, Ca, Sr dopants were found to promote the OCM activity of the Yb 2 O 3 catalyst and improved higher hydrocarbon selectivity compared to undoped Yb 2 O3 catalyst tested under the same conditions.
  • Example 8-e Doping of Eu2O3 library.
  • a SMS wafer with bulk Eu 2 O 3 was prepared and tested as described above. The results of the test are presented in Figure 13. Na, Ba, Gd, Sm dopants were found to promote the OCM activity of the Eu 2 O 3 catalyst compared to undoped Eu 2 O 3 catalyst tested under the same conditions.
  • Example 8-f Doping of La 2 O 3 library.
  • a SMS wafer with bulk La 2 O3 was prepared and tested as described above. The results of the test are presented in Figure 14. Ca, Sr, Nd, Hf dopants were found to promote the OCM activity of the La 2 O 3 catalyst compared to undoped La 2 O 3 catalyst tested under the same conditions.
  • Rh, Fe, Pr, Mn, Ir doping was found to promote unselective oxidation of methane whereas Ba, Te, V, Li doping was found to suppress methane activation.
  • Exemplary catalysts comprising La2O3, Nd2O3 or La3NdO6 with one, two, three or four different dopants selected from Eu, Na, Sr, Ho, Tm, Zr, Ca, Mg, Sm, W, La, K, Ba, Zn, and Li, were prepared and tested for their OCM activity according to the general procedures described in the above examples.
  • Each of the exemplary catalysts produced a C2 yield above 10%, a C2 selectivity above 50%, and a CH conversion above 20%, when tested as OCM catalysts at 650 °C or lower at pressures ranging from 1 to 10 atm.
  • a number of exemplary catalysts e.g., selected catalysts from those presented in tables 5 and 6, were tested for their OCM performance parameters according to the general procedures above.
  • the methane conversion and C2+ selectivities were measured at the lowest temperature required to obtain ⁇ > 50% C2+ selectivity (condition A), and at the temperature which results in maximum C2+ selectivity (condition B).
  • All catalysts under condition A showed C2+ selectivities and methane conversions greater than 50% and 15%, respectively, while providing C2+ selectivities greater than 55% and in most cases greater than 60%, while providing methane conversions greater than 18% and in most cases greater than 20%. It was noted that certain catalysts resulted in the almost total absence of reforming of methane to CO and H 2 .

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Abstract

Metal oxide catalysts comprising various dopants are provided. The catalysts are useful as heterogeneous catalysts in a variety of catalytic reactions, for example, the oxidative coupling of methane to C2 hydrocarbons such as ethane and ethylene. Related methods for use and manufacture of the same are also disclosed.

Description

CATALYSTS FOR PETROCHEMICAL CATALYSIS BACKGROUND Technical Field
This invention is generally related to novel catalysts and, more specifically, to doped metal oxide catalysts useful as heterogeneous catalysts in a variety of catalytic reactions, such as the oxidative coupling of methane to C2 hydrocarbons.
Description of the Related Art
Catalysis is the process in which the rate of a chemical reaction is either increased or decreased by means of a catalyst. Positive catalysts increase the speed of a chemical reaction, while negative catalysts slow it down. Substances that increase the activity of a catalyst are referred to as promoters or activators, and substances that deactivate a catalyst are referred to as catalytic poisons or deactivators. Unlike other reagents, a catalyst is not consumed by the chemical reaction, but instead participates in multiple chemical transformations. In the case of positive catalysts, the catalytic reaction generally has a lower rate-limiting free energy change to the transition state than the corresponding uncatalyzed reaction, resulting in an increased reaction rate at the same temperature. Thus, at a given temperature, a positive catalyst tends to increase the yield of desired product while decreasing the yield of undesired side products. Although catalysts are not consumed by the reaction itself, they may be inhibited, deactivated or destroyed by secondary processes, resulting in loss of catalytic activity.
Catalysts are generally characterized as either heterogeneous or homogeneous. Heterogeneous catalysts exist in a different phase than the reactants (e.g., a solid metal catalyst and gas phase reactants), and the catalytic reaction generally occurs on the surface of the heterogeneous catalyst. Thus, for the catalytic reaction to occur, the reactants must diffuse to and/or adsorb onto the catalyst surface. This transport and adsorption of reactants is often the rate limiting step in a heterogeneous catalysis reaction.
Heterogeneous catalysts are also generally easily separable from the reaction mixture by common techniques such as filtration or distillation.
In contrast to a heterogeneous catalyst, a homogenous catalyst exists in the same phase as the reactants (e.g., a soluble organometallic catalyst and solvent-dissolved reactants). Accordingly, reactions catalyzed by a homogeneous catalyst are controlled by different kinetics than a
heterogeneously catalyzed reaction. In addition, homogeneous catalysts can be difficult to separate from the reaction mixture.
While catalysis is involved in any number of technologies, one particular area of importance is the petrochemical industry. At the foundation of the modern petrochemical industry is the energy-intensive endothermic steam cracking of crude oil. Cracking is used to produce nearly all the fundamental chemical intermediates in use today. The amount of oil used for cracking and the volume of greenhouse gases (GHG) emitted in the process are quite large: cracking consumes nearly 10% of the total oil extracted globally and produces 200M metric tons of CO2 equivalent every year (Ren, T, Patel, M. Res.
Conserv. Recycl. 53:513, 2009). There remains a significant need in this field for new technology directed to the conversion of unreactive petrochemical feedstocks (e.g., paraffins, methane, ethane, etc.) into reactive chemical intermediates (e.g., olefins), particularly with regard to highly selective heterogeneous catalysts for the direct oxidation of hydrocarbons.
While there are multistep paths to convert methane to certain specific chemicals using first; high temperature steam reforming to syngas (a mixture of H2 and CO), followed by stoichiometry adjustment and conversion to either methanol or, via the Fischer-Tropsch (F-T) synthesis, to liquid
hydrocarbon fuels such as diesel or gasoline, this does not allow for the formation of certain high value chemical intermediates. This multi-step indirect method also requires a large capital investment in facilities and is expensive to operate, in part due to the energy intensive endothermic reforming step. For instance, in methane reforming, nearly 40% of methane is consumed as fuel for the reaction. It is also inefficient in that a substantial part of the carbon fed into the process ends up as the GHG CO2, both directly from the reaction and indirectly by burning fossil fuels to heat the reaction. Thus, to better exploit the natural gas resource, direct methods that are more efficient, economical and environmentally responsible are required.
One of the reactions for direct natural gas activation and its conversion into a useful high value chemical, is the oxidative coupling of methane ("OCM") to ethylene: 2CH4+O2 -» C2H4 + 2H2O. See, e.g., Zhang, Q., Journal of Natural Gas Chem., 12:81 , 2003; Olah, G. "Hydrocarbon
Chemistry", Ed. 2, John Wiley & Sons (2003). This reaction is exothermic (ΔΗ = -67kcals/mole) and has typically been shown to occur at very high
temperatures (>700°C). Although the detailed reaction mechanism is not fully characterized, experimental evidence suggests that free radical chemistry is involved. (Lunsford, J. Chem. Soc, Chem. Comm., 1991 ; H. Lunsford, Angew. Chem., Int. Ed. Engl., 34:970, 1995). In the reaction, methane (CH4) is activated on the catalyst surface, forming methyl radicals which then couple in the gas phase to form ethane (C2H6), followed by dehydrogenation to ethylene (C2H ). Several catalysts have shown activity for OCM, including various forms of iron oxide, V2O5, MoO3, Co3O4, Pt-Rh, Li/ZrO2, Ag-Au, Au/Co3O4, Co/Mn, CeO2, MgO, La2O3, Mn3O4, Na2WO4, MnO, ZnO, and combinations thereof, on various supports. A number of doping elements have also proven to be useful in combination with the above catalysts.
Since the OCM reaction was first reported over thirty years ago, it has been the target of intense scientific and commercial interest, but the fundamental limitations of the conventional approach to C-H bond activation appear to limit the yield of this attractive reaction. Specifically, numerous publications from industrial and academic labs have consistently demonstrated characteristic performance of high selectivity at low conversion of methane, or low selectivity at high conversion (J.A. Labinger, Cat. Lett., 1 :371 , 1988).
Limited by this conversion/selectivity threshold, no OCM catalyst has been able to exceed 20-25% combined C2 yield (i.e., ethane and ethylene), and more importantly, all such reported yields operate at extremely high temperatures (>800C).
In this regard, it is believed that the low yield of desired products (i.e., C2H4 and C2H6) is caused by the unique homogeneous/heterogeneous nature of the reaction. Specifically, due to the high reaction temperature, a majority of methyl radicals escape the catalyst surface and enter the gas phase. There, in the presence of oxygen and hydrogen, multiple side reactions are known to take place (J.A. Labinger, Cat. Lett., 1 :371 , 1988). The non-selective over-oxidation of hydrocarbons to CO and CO2 (e.g., complete oxidation) is the principal competing fast side reaction. Other undesirable products (e.g., methanol, formaldehyde) have also been observed and rapidly react to form CO and CO2.
In order to result in a commercially viable OCM process, a catalyst optimized for the activation of the C-H bond of methane at lower temperatures (e.g., 500-800°C) higher activities, and higher pressures are required. While the above discussion has focused on the OCM reaction, numerous other catalytic reactions (as discussed in greater detail below) would significantly benefit from catalytic optimization. Accordingly, there remains a need in the art for improved catalysts and, more specifically, catalysts for improving the yield, selectivity and conversion of, for example, the OCM reaction and other catalyzed reactions. The present invention fulfills these needs and provides further related advantages.
BRIEF SUMMARY
In brief, heterogeneous metal oxide catalysts and related methods are disclosed. For example, catalysts comprising oxides of magnesium, manganese, tungsten and/or rare earth elements are provided. The disclosed catalysts find utility in any number of catalytic reactions, for example in the OCM reaction. In some embodiments, the catalysts are advantageously doped with one or more doping elements. The doping elements may be promoters such that the catalyst comprises an improved catalytic activity. For example, in certain embodiments, the catalytic activity is such that the C2 selectivity is 50% or greater and the methane conversion is 20% or greater when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 850 °C or less, 800 °C or less, for example 750 °C or less or 700 °C or less.
In one embodiment, the disclosure provides a catalyst comprising a mixed oxide of magnesium and manganese, wherein the catalyst further comprises lithium and boron dopants and at least one doping element from groups 4, 9, 12, 13 or combinations thereof, wherein the catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
In another embodiment, a catalyst comprising a mixed oxide of manganese and tungsten, wherein the catalyst further comprises a sodium dopant and at least one doping element from groups 2, 16 or combinations thereof is provided.
In still another embodiment, the disclosure is directed to a catalyst comprising an oxide of a rare earth element, wherein the catalyst further comprises at least one doping element from groups 1 -16, lanthanides, actinides or combinations thereof, wherein the catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
In another embodiment, a catalyst comprising a mixed oxide of manganese and tungsten, wherein the catalyst further comprises a sodium dopant and at least one doping element from groups 2, 4-6, 8-15, lanthanides or combinations thereof, wherein the catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less is provided.
In yet other embodiments, the disclosure provides a catalyst comprising a mixed oxide of a lanthanide and tungsten, wherein the catalyst further comprises a sodium dopant and at least one doping element from groups 2, 4-15, lanthanides or combinations thereof, wherein the catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
Other embodiments are directed to a catalyst comprising a rare earth oxide and one or more dopants, wherein the catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less, and wherein the dopant comprises Eu/Na, Sr/Na, Na/Zr/Eu/Ca, Mg/Na, Sr/Sm/Ho/Tm, Sr/W, Mg/La/K, Na/K/Mg/Tm, Na/Dy/K, Na/La/Dy, Na/La/Eu, Na/La/Eu/ln, Na/La/K,
Na/La/Li/Cs, K/La, K/La/S, K/Na, Li/Cs, Li/Cs/La, Li/Cs/La/Tm, Li/Cs/Sr/Tm, Li/Sr/Cs, Li/Sr/Zn/K, Li/Ga/Cs, Li/K/Sr/La, Li/Na, Li/Na/Rb/Ga, Li/Na/Sr,
Li/Na/Sr/La, Li/Sm/Cs, Ba/Sm/Yb/S, Ba/Tm/K/La, Ba/Tm/Zn/K, Cs/K/La,
Cs/La/Tm/Na, Cs/Li/K/La, Sm/Li/Sr/Cs, Sr/Cs/La, Sr/Tm/Li/Cs, Zn/K,
Zr/Cs/K/La, Rb/Ca/ln/Ni, Sr/Ho/Tm, La/Nd/S, Li/Rb/Ca, Li/K, Tm/Lu/Ta/P, Rb/Ca/Dy/P, Mg/La/Yb/Zn, Rb/Sr/Lu, Na/Sr/Lu/Nb, Na/Eu/Hf, Dy/Rb/Gd,
Na/Pt/Bi, Rb/Hf, Ca/Cs, Ca/Mg/Na, Hf/Bi, Sr/Sn, Sr/W, Sr/Nb, Zr/W, Y/W, Na/W, Bi/W, Bi/Cs, Bi/Ca, Bi/Sn, Bi/Sb, Ge/Hf, Hf/Sm, Sb/Ag, Sb/Bi, Sb/Au, Sb/Sm, Sb/Sr, Sb/W, Sb/Hf, Sb/Yb, Sb/Sn, Yb/Au, Yb/Ta, Yb/W, Yb/Sr, Yb/Pb, Yb/W, Yb/Ag, Au/Sr, W/Ge, Ta/Hf, W/Au, Ca/W, Au/Re, Sm/Li, La/K, Zn/Cs, Na/K/Mg, Zr/Cs, Ca/Ce, Na/Li/Cs, Li/Sr, Cs/Zn, La/Dy/K, Dy/K, La/Mg, Na/Nd/ln/K, In/Sr, Sr/Cs, Rb/Ga/Tm/Cs, Ga/Cs, K La/Zr/Ag, Lu/Fe, Sr/Tm, La/Dy, Sm/Li/Sr, Mg/K, Li/Rb/Ga, Li/Cs/Tm, Zr/K, Li/Cs, Li/K/La, Ce/Zr/La, Ca/AI/La, Sr/Zn/La,
Sr/Cs/Zn, Sm/Cs, In/K, Ho/Cs/Li/La, Cs/La/Na, La/S/Sr, K/La/Zr/Ag, Lu/TI, Pr/Zn, Rb/Sr/La, Na/Sr/Eu/Ca, K Cs/Sr/La, Na/Sr/Lu, Sr/Eu/Dy, Lu/Nb,
La/Dy/Gd, Na/Mg/TI/P, Na/Pt, Gd/Li/K, Rb/K Lu, Sr/La/Dy/S, Na/Ce/Co, Na/Ce, Na/Ga/Gd/AI, Ba/Rh/Ta, Ba/Ta, Na/AI/Bi, Cs/Eu/S, Sm/Tm/Yb/Fe, Sm/Tm/Yb, Hf/Zr/Ta, Rb/Gd/Li/K, Gd/Ho/AI/P, Na/Ca/Lu, Cu/Sn, Ag/Au, Al/Bi, Al/Mo, Al/Nb, Au/Pt, Ga/Bi, Mg/W, Pb/Au, Sn/Mg, Zn/Bi, Gd/Ho, Zr/Bi, Ho/Sr, Gd/Ho/Sr, Ca/Sr, Ca/Sr/W, Na/Zr/Eu/Tm, Sr/Ho/Tm/Na, Sr/Pb, Ca, Sr/W/Li, Ca/Sr/W, Sr/Hf or combinations thereof.
Still other catalysts of the present invention include a catalyst comprising a mixed oxide of a rare earth element and a Group 13 element, wherein the catalyst further comprises one or more Group 2 elements.
Other embodiments of the present invention are directed to a catalyst comprising a lanthanide oxide doped with an alkali metal, an alkaline earth metal or combinations thereof, and at least one other dopant from groups 3-16.
Methods for use of the disclosed catalysts in catalytic reactions, for example OCM, are also provided. Furthermore, the present disclosure also provides for the preparation of downstream products of ethylene, wherein the ethylene has been prepared via a reaction employing a catalyst disclosed herein.
These and other aspects of the invention will be apparent upon reference to the following detailed description. To this end, various references are set forth herein which describe in more detail certain background
information, procedures, compounds and/or compositions, and are each hereby incorporated by reference in their entirety. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
In the drawings, the sizes and relative positions of elements in the drawings are not necessarily drawn to scale. For example, the various elements and angles are not drawn to scale, and some of these elements are arbitrarily enlarged and positioned to improve drawing legibility. Further, the particular shapes of the elements as drawn are not intended to convey any information regarding the actual shape of the particular elements, and have been selected solely for ease of recognition in the drawings.
Figure 1 schematically depicts a first part of an OCM reaction at the surface of a metal oxide catalyst.
Figure 2 shows a method for catalyst screening.
Figure 3 schematically depicts a carbon dioxide reforming reaction on a catalytic surface.
Figure 4 is a flow chart for data collection and processing in evaluating catalytic performance.
Figure 5 is a chart showing various downstream products of ethylene.
Figure 6 shows an OCM and ethylene oligomerization module. Figure 7 is a plot of conversion, selectivity and yield of an OCM reaction catalyzed with a doped and undoped catalyst.
Figure 8 is a plot of conversion, selectivity and yield of an OCM reaction catalyzed comparing a catalyst on two different supports.
Figure 9 depicts the results of high-throughput screening on a doped Co/Na/LiMnMgB library.
Figure 10 depicts the results of high-throughput screening on a doped MnWO4 on silica library.
Figure 1 1 depicts the results of high-throughput screening on a doped Nd2O3 library.
Figure 12 depicts the results of high-throughput screening on a doped Yb2O3 library. Figure 13 depicts the results of high-throughput screening on a doped EU2O3 library.
Figure 14 depicts the results of high-throughput screening on a doped La2O3 library. DETAILED DESCRIPTION
In the following description, certain specific details are set forth in order to provide a thorough understanding of various embodiments. However, one skilled in the art will understand that the invention may be practiced without these details. In other instances, well-known structures have not been shown or described in detail to avoid unnecessarily obscuring descriptions of the embodiments. Unless the context requires otherwise, throughout the
specification and claims which follow, the word "comprise" and variations thereof, such as, "comprises" and "comprising" are to be construed in an open, inclusive sense, that is, as "including, but not limited to." Further, headings provided herein are for convenience only and do not interpret the scope or meaning of the claimed invention.
Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Also, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the content clearly dictates otherwise. It should also be noted that the term "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise. As discussed above, heterogeneous catalysis takes place between several phases. Generally, the catalyst is a solid, the reactants are gases or liquids and the products are gases or liquids. Thus, a heterogeneous catalyst provides a surface that has multiple active sites for adsorption of one more gas or liquid reactants. Once adsorbed, certain bonds within the reactant molecules are weakened and dissociate, creating reactive fragments of the reactants, e.g., in free radical forms. One or more products are generated as new bonds between the resulting reactive fragments form, in part, due to their proximity to each other on the catalytic surface.
As an example, Figure 1 shows schematically the first part of an
OCM reaction that takes place on the surface of a metal oxide catalyst 10 which is followed by methyl radical coupling in the gas phase. A crystal lattice structure of metal atoms 14 and oxygen atoms 20 are shown, with an optional dopant 24 incorporated into the lattice structure. In this reaction, a methane molecule 28 comes into contact with an active site (e.g., surface oxygen 30) and becomes activated when a hydrogen atom 34 dissociates from the methane molecule 28. As a result, a methyl radical 40 is generated on or near the catalytic surface. Two methyl radicals thus generated can couple in the gas phase to create ethane and/or ethylene, which are collectively referred to as the "C2" coupling products.
It is generally recognized that the catalytic properties of a catalyst strongly correlate to its surface morphology. Typically, the surface morphology can be defined by geometric parameters such as: (1 ) the number of surface atoms (e.g., the surface oxygen of Figure 1 ) that coordinate to the reactant; and (2) the degree of coordinative unsaturation of the surface atoms, which is the coordination number of the surface atoms with their neighboring atoms. For example, the reactivity of a surface atom decreases with decreasing
coordinative unsaturation. For example, for the dense surfaces of a face- centered crystal, a surface atom with 9 surface atom neighbors will have a different reactivity than one with 8 neighbors. Additional surface characteristics that may contribute to the catalytic properties include, for example, crystal dimensions, lattice distortion, surface reconstructions, defects, grain
boundaries, and the like. See, e.g., Van Santen R.A. et al New Trends in Materials Chemistry 345-363 (1997).
Advantageously, the catalysts disclosed herein and methods of producing the same have general applicability to a wide variety of
heterogeneous catalyses, including without limitation: oxidative coupling of methane (e.g., Figure 1 ), oxidative dehydrogenation of alkanes to their corresponding alkenes, selective oxidation of alkanes to alkenes and alkynes, oxidation of carbon monoxide, dry reforming of methane, selective oxidation of aromatics, Fischer-Tropsch reaction, hydrocarbon cracking, combustions of hydrocarbons and the like.
Figure 2 schematically shows a high throughput work flow for generating libraries of diverse catalysts and screening for their catalytic properties. An initial phase of the work flow involves a primary screening, which is designed to broadly and efficiently screen a large and diverse set of catalysts that logically could perform the desired catalytic transformation. For example, certain doped metal oxides (e.g., Mn, Mg, W, etc.) are known catalysts for the OCM reaction. Therefore, catalysts of various metal oxide compositions comprising various dopants can be prepared and evaluated for their catalytic performances in an OCM reaction.
More specifically, the work flow 100 begins with designing synthetic experiments for making various metal oxide compositions (block 1 10). The synthesis, subsequent treatments and screenings can be manual or automated. As will be discussed in more detail herein, by varying the synthetic conditions, catalysts can be prepared with various surface morphologies and/or compositions in respective microwells (block 1 14). The catalysts are
subsequently calcined and then optionally doped (block 120). Optionally, the doped and calcined catalysts are further mixed with a catalyst support (block 122). Beyond the optional support step, all subsequent steps are carried out in a "wafer" format, in which catalysts are deposited in a quartz wafer that has been etched to create an ordered array of microwells. Each microwell is a self- contained reactor, in which independently variable processing conditions can be designed to include, without limitation, respective choices of elemental compositions, catalyst support, reaction precursors, templates, reaction durations, pH values, temperatures, ratio between reactants, gas flows, and calcining conditions (block 124). Due to design constraints of some wafers, in some embodiments calcining and other temperature variables are identical in all microwells. A wafer map 130 can be created to correlate the processing conditions to the catalyst in each microwell. A library of diverse catalysts can be generated in which each library member corresponds to a particular set of processing conditions and corresponding compositional and/or morphological characteristics.
Catalysts obtained under various synthetic conditions and doping compositions are thereafter deposited in respective microwells of a wafer (140) for evaluating their respective catalytic properties in a given reaction (blocks 132 and 134). The catalytic performance of each library member can be screened serially by several known primary screening technologies, including scanning mass spectroscopy (SMS) (Symyx Technologies Inc., Santa Clara, California). The screening process is fully automated, and the SMS tool can determine if a catalyst is catalytically active or not, as well as its relative strength as a catalyst at a particular temperature. Typically, the wafer is placed on a motion control stage capable of positioning a single well below a probe that flows the feed of the starting material over the catalyst surface and removes reaction products to a mass spectrometer and/or other detector technologies (blocks 134 and 140). The individual catalyst is heated to a preset reaction temperature, e.g., using a CO2 IR laser from the backside of the quartz wafer and an IR camera to monitor temperature and a preset mixture of reactant gases. The SMS tool collects data with regard to the consumption of the reactant(s) and the generation of the product(s) of the catalytic reaction in each well (block 144), and at each temperature and flow rate.
The SMS data obtained as described above provide information on relative catalytic properties among all the library members (block 150). In order to obtain more quantitative data on the catalytic properties of the catalysts, possible hits that meet certain criteria are subjected to a secondary screening (block 154). Typically, secondary screening technologies include a single, or alternatively multiple channel fixed-bed or fluidized bed reactors (as described in more detail herein). In parallel reactor systems or multi-channel fixed-bed reactor system, a single feed system supplies reactants to a set of flow restrictors. The flow restrictors divide the flows evenly among parallel reactors. Care is taken to achieve uniform reaction temperature between the reactors such that the various catalysts can be differentiated solely based on their catalytic performances. The secondary screening allows for accurate determination of catalytic properties such as selectivity, yield and conversion (block 160). These results serve as a feedback for designing further catalyst libraries.
Secondary screening is also schematically depicted in Figure 4, which depicts a flow chart for data collection and processing in evaluating catalytic performance of catalysts according to the invention. Additional description of SMS tools in a combinatorial approach for discovering catalysts can be found in, e.g., Bergh, S. et al. Topics in Catalysts 23:1 -4, 2003.
Thus, in accordance with various embodiments described herein, compositional and morphologically diverse catalysts can be rationally synthesized to meet catalytic performance criteria. These and other aspects of the present disclosure are described in more detail below.
Definitions
As used herein, and unless the context dictates otherwise, the following terms have the meanings as specified below. "Catalyst" means a substance which alters the rate of a chemical reaction. A catalyst may either increase the chemical reaction rate (i.e., a "positive catalyst") or decrease the reaction rate (i.e., a "negative catalyst"). Catalysts participate in a reaction in a cyclic fashion such that the catalyst is cyclically regenerated. "Catalytic" means having the properties of a catalyst.
"Crystal domain" means a continuous region over which a substance is crystalline.
"Turnover number" is a measure of the number of reactant molecules a catalyst can convert to product molecules per unit time.
"Active" or "catalytically active" refers to a catalyst which has substantial activity in the reaction of interest. For example, in some
embodiments a catalyst which is OCM active (i.e., has activity in the OCM reaction) has a C2 selectivity of 5% or more and/or a methane conversion of 5% or more when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
"Inactive" or "catalytically inactive" refers to a catalyst which does not have substantial activity in the reaction of interest. For example, in some embodiments a catalyst which is OCM inactive has a C2 selectivity of less than 5% and/or a methane conversion of less than 5% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
"Activation temperature" refers to the temperature at which a catalyst becomes catalytically active.
"OCM activity" refers to the ability of a catalyst to catalyze the OCM reaction.
A catalyst having "high OCM activity" refers to a catalyst having a C2 selectivity of 50% or more and/or a methane conversion of 20% or more when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a specific temperature, for example 750 °C or less. A catalyst having "moderate OCM activity" refers to a catalyst having a C2 selectivity of about 20-50% and/or a methane conversion of about 10-20% or more when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
A catalyst having "low OCM activity" refers to a catalyst having a
C2 selectivity of about 5-20% and/or a methane conversion of about 5-10% or more when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
"Base material" refers to the major component of a catalyst. For example a mixed oxide of manganese and magnesium which is doped with lithium and/or boron comprises a manganese/magnesium oxide base material.
"Dopant" or "doping agent" or "doping element" is chemical compound which is added to or incorporated within a catalyst base material to optimize catalytic performance (e.g., increase or decrease catalytic activity). As compared to the undoped catalyst, a doped catalyst may increase or decrease the selectivity, conversion, and/or yield of a reaction catalyzed by the catalyst. Dopants which increase catalytic activity are referred to as "promoters" while dopants which decrease catalytic activity are referred to as "poisons". The dopant may be present in the catalyst in any form and may be derived from any suitable source of the element (e.g., chlorides, bromides, iodides, nitrates, oxynitrates, oxyhalides, acetates, formates, hydroxides, carbonates,
phosphates, sulfates, alkoxides, and the like.)
"Atomic percent" (at% or at/at) or "atomic ratio" when used in the context of catalyst dopants refers to the ratio of the total number of dopant atoms to the total number of non-oxygen atoms in the base material. For example, the atomic percent of dopant in a lithium doped Mg6MnO8 catalyst is determined by calculating the total number of lithium atoms and dividing by the sum of the total number of magnesium and manganese atoms and multiplying by 100 (i.e., atomic percent of dopant = [Li atoms/(Mg atoms + Mn atoms)] x 100). "Weight percent" (wt/wt) " when used in the context of catalyst dopants refers to the ratio of the total weight of dopant to the total combined weight of the dopant and the catalyst. For example, the weight percent of dopant in a lithium doped Mg6MnO8 catalyst is determined by calculating the total weight of lithium and dividing by the sum of the total combined weight of lithium and Mg6MnO8 and multiplying by 100 (i.e., weight percent of dopant = [Li weight (Li weight + Mg6MnO8 weight)] x 100).
"Group 1 " elements include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr).
"Group 2" elements include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).
"Group 3" elements include scandium (Sc) and yttrium (Y).
"Group 4" elements include titanium (Ti), zirconium (Zr), halfnium (Hf), and rutherfordium (Rf).
"Group 5" elements include vanadium (V), niobium (Nb), tantalum
(Ta), and dubnium (Db).
"Group 6" elements include chromium (Cr), molybdenum (Mo), tungsten (W), and seaborgium (Sg).
"Group 7" elements include manganese (Mn), technetium (Tc), rhenium (Re), and bohrium (Bh).
"Group 8" elements include iron (Fe), ruthenium (Ru), osmium (Os), and hassium (Hs).
"Group 9" elements include cobalt (Co), rhodium (Rh), iridium (Ir), and meitnerium (Mt).
"Group 10" elements include nickel (Ni), palladium (Pd), platinum
(Pt) and darmistadium (Ds).
"Group 1 1 " elements include copper (Cu), silver (Ag), gold (Au), and roentgenium (Rg).
"Group 12" elements include zinc (Zn), cadmium (Cd), mercury (Hg), and copernicium (Cn). "Group 13" elements include boron (B), aluminum (Al),gallium (Ga), indium (In) and thallium (Tl).
"Group 16" elements include oxygen (O), sulfur (S), selenium (Se), tellurium (Te) and polonium (Po).
"Lanthanides" include lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), yitterbium (Yb), and lutetium (Lu).
"Actinides" include actinium (Ac), thorium (Th), protactinium (Pa), uranium (U), neptunium (Np), plutonium (Pu), americium (Am), curium (Cm), berklelium (Bk), californium (Cf), einsteinium (Es), fermium (Fm), mendelevium (Md), nobelium (No), and lawrencium (Lr).
"Rare earth elements" include the lanthanides, actinides and
Group 3.
"Metal element" or "metal" is any element, except hydrogen, selected from Groups 1 through 12, lanthanides, actinides, aluminum (Al), gallium (Ga), indium (In), tin (Sn), thallium (Tl), lead (Pb), and bismuth (Bi). Metal elements include metal elements in their elemental form as well as metal elements in an oxidized or reduced state, for example, when a metal element is combined with other elements in the form of compounds comprising metal elements. For example, metal elements can be in the form of hydrates, salts, oxides, as well as various polymorphs thereof, and the like.
"Semi-metal element" refers to an element selected from boron
(B) , silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te), and polonium (Po).
"Non-metal element" refers to an element selected from carbon
(C) , nitrogen (N), oxygen (O), fluorine (F), phosphorus (P), sulfur (S), chlorine (CI), selenium (Se), bromine (Br), iodine (I), and astatine (At).
"C2" refers to a hydrocarbon (i.e., compound consisting of carbon and hydrogen atoms) having only two carbon atoms, for example ethane and ethylene. Similarly, "C3" refers to a hydrocarbon having only 3 carbon atoms, for example propane and propylene.
"Conversion" means the mole fraction (i.e., percent) of a reactant converted to a product or products.
"Selectivity" refers to the percent of converted reactant that went to a specified product, e.g., C2 selectivity is the % of converted methane that formed ethane and ethylene, C3 selectivity is the % of converted methane that formed propane and propylene, CO selectivity is the % of converted methane that formed CO.
"Yield" is a measure of (e.g., percent) of product obtained relative to the theoretical maximum product obtainable. Yield is calculated by dividing the amount of the obtained product in moles by the theoretical yield in moles. Percent yield is calculated by multiplying this value by 100. C2 yield is defined as the sum of the ethane and ethylene molar flow at the reactor outlet multiplied by two and divided by the inlet methane molar flow. C3 yield is defined as the sum of propane and propylene molar flow at the reactor outlet multiplied by three and divided by the inlet methane molar flow. C2+ yield is the sum of the C2 yield and C3 yield. Yield is also calculable by multiplying the methane conversion by the relevant selectivity, e.g., C2 yield is equal to the methane conversion times the C2 selectivity.
"C2" yield is the total combined yield of ethane and ethylene. "C2" selectivity is the combined selectivity for ethane and ethylene.
"Bulk catalyst" or "bulk material" means a catalyst prepared by traditional techniques, for example by milling or grinding large catalyst particles to obtain smaller/higher surface area catalyst particles.
"Nanostructured catalyst" means a catalyst having at least one dimension on the order of nanometers (e.g., between about 1 and 100 nanometers). Non-limiting examples of nanostructured catalysts include nanoparticle catalysts and nanowire catalysts. "Nanoparticle" means a particle having at least one diameter on the order of nanometers (e.g., between about 1 and 100 nanometers).
"Nanowire" means a nanowire structure having at least one diameter on the order of nanometers (e.g., between about 1 and 100
nanometers) and an aspect ratio greater than 10:1 . The "aspect ratio" of a nanowire is the ratio of the actual length (L) of the nanowire to the diameter (D) of the nanowire. Aspect ratio is expressed as L:D. Exemplary nanowires are known in the art and described in more detail in co-pending U.S. Application Nos. 13/1 15,082 (U.S. Pub. No. 2012/0041246), 13/689,514 (U.S. Pub. No. 2013/0158322) and 13/689,61 1 (U.S. Pub. No. 2013/0165728), the full disclosures of which are hereby incorporated by reference in their entireties for all purposes.
"Polycrystalline nanowire" means a nanowire having multiple crystal domains. Polycrystalline nanowires generally have different
morphologies (e.g., bent vs. straight) as compared to the corresponding "single- crystalline" nanowires.
"Effective length" of a nanowire means the shortest distance between the two distal ends of a nanowire as measured by transmission electron microscopy (TEM) in bright field mode at 5 keV. "Average effective length" refers to the average of the effective lengths of individual nanowires within a plurality of nanowires.
"Actual length" of a nanowire means the distance between the two distal ends of a nanowire as traced through the backbone of the nanowire as measured by TEM in bright field mode at 5 keV. "Average actual length" refers to the average of the actual lengths of individual nanowires within a plurality of nanowires.
The "diameter" of a nanowire is measured in an axis perpendicular to the axis of the nanowire's actual length (i.e., perpendicular to the nanowires backbone). The diameter of a nanowire will vary from narrow to wide as measured at different points along the nanowire backbone. As used herein, the diameter of a nanowire is the most prevalent (i.e., the mode) diameter.
The "ratio of effective length to actual length" is determined by dividing the effective length by the actual length. A nanowire having a "bent morphology" will have a ratio of effective length to actual length of less than one as described in more detail herein. A straight nanowire will have a ratio of effective length to actual length equal to one as described in more detail herein.
"Inorganic" means a substance comprising a metal element or semi-metal element. In certain embodiments, inorganic refers to a substance comprising a metal element. An inorganic compound can contain one or more metals in its elemental state, or more typically, a compound formed by a metal ion (Mn+, wherein n 1 , 2, 3, 4, 5, 6 or 7) and an anion (Xm", m is 1 , 2, 3 or 4), which balance and neutralize the positive charges of the metal ion through electrostatic interactions. Non-limiting examples of inorganic compounds include oxides, hydroxides, halides, nitrates, sulfates, carbonates, phosphates, acetates, oxalates, and combinations thereof, of metal elements. Other non- limiting examples of inorganic compounds include Li2CO3, Li2PO , LiOH, Li2O, LiCI, LiBr, Lil, Li2C2O4, Li2SO4, Na2CO3,Na2PO4, NaOH, Na2O, NaCI, NaBr, Nal, Na2C2O4, Na2SO4, K2CO3,K2PO4, KOH, K2O, KCI, KBr, Kl, K2C2O4, K2SO4, Cs2CO3, CsPO4, CsOH, Cs2O, CsCI, CsBr, Csl, CsC2O4, CsSO4, Be(OH)2, BeCO3, BePO4, BeO, BeCI2, BeBr2, Bel2, BeC2O4, BeSO4, Mg(OH)2, MgCO3, MgPO4, MgO, MgCI2, MgBr2, Mgl2, MgC2O4, MgSO4, Ca(OH)2, CaO, CaCO3, CaPO4, CaCI2, CaBr2, Cal2, Ca(OH)2, CaC2O4, CaSO4, Y2O3, Y2(CO3)3,
Y2(PO4)3, Y(OH)3, YCI3, YBr3, Yl3, Y2(C2O4)3, Y2(SO4)3, Zr(OH)4, Zr(CO3)2, Zr(PO4)2, ZrO(OH)2, ZrO2, ZrCI4, ZrBr4, Zrl4, Zr(C2O4)2, Zr(SO4)2, Ti(OH)4, TiO(OH)2, Ti(CO3)2, Ti(PO4)2, TiO2, TiCI4, TiBr4, Til4, Ti(C2O4)2, Ti(SO4)2,BaO, Ba(OH)2, BaCO3, BaPO4, BaCI2, BaBr2, Bal2, BaC2O4, BaSO4, La(OH)3, La2(CO3)3, La2(PO4)3, La2O3, LaCI3, LaBr3, Lal3, La2(C2O4)3, La2(SO4)3,
Ce(OH)4, Ce(CO3)2, Ce(PO4)2, CeO2, Ce2O3, CeCI4, CeBr4, Cel4, Ce(C2O4)2, Ce(SO4)2, ThO2, Th(CO3)2, Th(PO4)2, ThCI4, ThBr4, Thl4, Th(OH)4, Th(C2O4)2, Th(SO4)2, Sr(OH)2, SrCO3, SrPO4, SrO, SrCI2, SrBr2, Srl2, SrC2O4, SrSO4, Sm2O3, Sm2(CO3)3, Sm2(PO4)3, SmCI3, SmBr3, Sml3, Sm(OH)3, Sm2(CO3)3, Sm2(C2O3)3, Sm2(SO4)3, LiCa2Bi3O4CI6, Na2WO4, K/SrCoO3, K/Na/SrCoO3, Li/SrCoO3, SrCoO3, molybdenum oxides, molybdenum hydroxides,
molybdenum carbonates, molybdenum phosphates, molybdenum chlorides, molybdenum bromides, molybdenum iodides, molybdenum oxalates, molybdenum sulfates, manganese oxides, manganese chlorides, manganese bromides, manganese iodides, manganese hydroxides, manganese oxalates, manganese sulfates, manganese tungstates, vanadium oxides, vanadium carbonates, vanadium phosphates, vanadium chlorides, vanadium bromides, vanadium iodides, vanadium hydroxides, vanadium oxalates, vanadium sulfates, tungsten oxides, tungsten carbonates, tungsten phosphates, tungsten chlorides, tungsten bromides, tungsten iodides, tungsten hydroxides, tungsten oxalates, tungsten sulfates, neodymium oxides, neodymium carbonates, neodymium phosphates, neodymium chlorides, neodymium bromides, neodymium iodides, neodymium hydroxides, neodymium oxalates, neodymium sulfates, europium oxides, europium carbonates, europium phosphates, europium chlorides, europium bromides, europium iodides, europium
hydroxides, europium oxalates, europium sulfates rhenium oxides, rhenium carbonates, rhenium phosphates, rhenium chlorides, rhenium bromides, rhenium iodides, rhenium hydroxides, rhenium oxalates, rhenium sulfates, chromium oxides, chromium carbonates, chromium phosphates, chromium chlorides, chromium bromides, chromium iodides, chromium hydroxides, chromium oxalates, chromium sulfates, potassium molybdenum oxides and the like.
"Salt" means a compound comprising negative and positive ions. Salts are generally comprised of cations and counter ions. Under appropriate conditions, e.g., the solution also comprises a template, the metal ion (Mn+) and the anion (Xm") bind to the template to induce nucleation and growth of a nanowire of MmXn on the template. "Anion precursor" thus is a compound that comprises an anion and a cationic counter ion, which allows the anion (Xm") to dissociate from the cationic counter ion in a solution. Specific examples of the metal salt and anion precursors are described in further detail herein.
"Oxide" refers to a metal compound comprising oxygen.
Examples of oxides include, but are not limited to, metal oxides (MxOy), metal oxyhalides (MxOyXz), metal oxynitrates (MxOy(NO3)z), metal phosphates
(Mx(PO4)y), metal oxycarbonates (MxOy(CO3)z), metal carbonates, metal oxyhydroxides (MxOy(OH)z) and the like, wherein X is independently, at each occurrence, fluoro, chloro, bromo or iodo, and x, y and z are numbers from 1 to 100.
"Catalytic material" refers to a plurality of catalyst particles, which may optionally be combined with a support, diluent and/or binder.
"Catalyst form" or "catalytic form" refers to the physical shape of a catalytic material. For example, catalyst forms include catalysts in the shape of extrudates or pellets or disposed on various support structures, including honeycomb structures, grids, monoliths, and the like, as discussed in more detail below.
"Catalyst formulation" or "catalytic formulation" refers to the chemical composition of a catalytic material. For example, a catalyst formulation may include a catalyst and one or more support, diluent and/or binder materials.
An "extrudate" refers to a material (e.g., catalytic material) prepared by forcing a semisolid material comprising a catalyst through a die or opening of appropriate shape. Extrudates can be prepared in a variety of shapes and structures by common means known in the art.
A "formed aggregate" refers to an aggregation of catalyst material particles, either alone, or in conjunction with one or more other materials, e.g., catalyst materials, dopants, diluents, support materials, binders, etc., formed into a single particle. Formed aggregates include without limitation, extruded particles, termed "extrudates", pressed or cast particles, e.g., pellets such as tablets, ovals, spherical particles, etc., coated particles, e.g., spray, immersion or pan coated particles, impregnated particles, e.g., monoliths, foils, foams, honeycombs, or the like. Formed aggregates may range in size from particles having individual cross sections in the micron range to cross sections in the millimeter range, to even larger particles such as monolithic formed aggregates, that may be on the order of centimeters or even meters in cross section.
A "pellet" or "pressed pellet" refers to a material (e.g., catalytic material) prepared by applying pressure to (i.e., compressing) a material comprising a catalyst into a desired shape. Pellets having various dimensions and shapes can be prepared according to common techniques in the art.
"Monolith" or "monolith support" is generally a structure formed from a single structural unit preferably having passages disposed through it in either an irregular or regular pattern with porous or non-porous walls separating adjacent passages. Examples of such monolithic supports include, e.g., ceramic or metal foam-like or porous structures. The single structural unit may be used in place of or in addition to conventional particulate or granular catalysts (e.g., pellets or extrudates). Examples of such irregular patterned monolith substrates include filters used for molten metals. Monoliths generally have a porous fraction ranging from about 60% to 90% and a flow resistance substantially less than the flow resistance of a packed bed of similar volume (e.g., about 10% to 30% of the flow resistance of a packed bed of similar volume). Examples of regular patterned substrates include monolith
honeycomb supports used for purifying exhausts from motor vehicles and used in various chemical processes and ceramic foam structures having irregular passages. Many types of monolith support structures made from conventional refractory or ceramic materials such as alumina, zirconia, yttria, silicon carbide, and mixtures thereof, are well known and commercially available from, among others, Corning, lac; Vesuvius Hi-Tech Ceramics, Inc.; and Porvair Advanced Materials, Inc. and SiCAT (Sicatalyst.com). Monoliths include foams, honeycombs, foils, mesh, gauze and the like. "Alkane" means a straight chain or branched, noncydic or cyclic, saturated aliphatic hydrocarbon. Alkanes include linear, branched and cyclic structures. Representative straight chain alkanes include methane, ethane, n- propane, n-butane, n-pentane, n-hexane, and the like; while branched alkanes include isopropane, sec-butane, isobutane, tert-butane, isopentane, and the like. Representative cyclic alkanes include cyclopropane, cyclobutane, cyclopentane, cyclohexane, and the like. "Alkene" means a straight chain or branched, noncydic or cyclic, unsaturated aliphatic hydrocarbon having at least one carbon-carbon double bond. Alkenes include linear, branched and cyclic structures. Representative straight chain and branched alkenes include ethylene, propylene, 1 -butene, 2-butene, isobutene, 1 -pentene, 2-pentene, 3- methyl-1 -butene, 2-methyl-2-butene, 2,3-dimethyl-2-butene, and the like.
Cyclic alkenes include cyclohexene and cyclopentene and the like. "Alkyne" means a straight chain or branched, noncydic or cyclic, unsaturated aliphatic hydrocarbon having at least one carbon-carbon triple bond. Alkynes include linear, branched and cyclic structures. Representative straight chain and branched alkynes include acetylene, propyne, 1 -butyne, 2-butyne, 1 -pentyne, 2-pentyne, 3-methyl-1 -butyne, and the like. Representative cyclic alkynes include cycloheptyne and the like.
"Aromatic" means a carbocyclic moiety having a cyclic system of conjugated p orbitals. Representative examples of aromatics include benzene, naphthalene and toluene.
"Carbon-containing compounds" are compounds which comprise carbon. Non-limiting examples of carbon-containing compounds include hydrocarbons, CO and CO2.
"Mixed oxide" or "mixed metal oxide" refers to a compound comprising two or more oxidized metals and oxygen (e.g.,., M1 xM2yOz, wherein M1 and M2 are the same or different metal elements, O is oxygen and x, y and z are numbers from 1 to 100). A mixed oxide may comprise metal elements in various oxidation states and may comprise more than one type of metal element. For example, a mixed oxide of manganese and magnesium
comprises oxidized forms of magnesium and manganese. Each individual manganese and magnesium atom may or may not have the same oxidation state. Mixed oxides comprising 2, 3, 4, 5, 6 or more metal elements can be represented in an analogous manner. Mixed oxides also include oxy- hydroxides {e.g., MxOyOHz, wherein M is a metal element, O is oxygen, x, y and z are numbers from 1 to 100 and OH is hydroxy). Mixed oxides may be represented herein as M1 -M2, wherein M1 and M2 are each independently a metal element. Mixed oxides comprising, 3, 4, 5, 6 or more metal elements can be represented in an analogous manner
"Rare earth oxide" refers to an oxide of an element from group 3, lanthanides or actinides. Rare earth oxides include mixed oxide containing a rare earth element. Examples of rare earth oxides include, but are not limited to, La2O3, Nd2O3, Yb2O3, Eu2O3, Sm2O3, Y2O3, Ce2O3, Pr2O3, Ln14-xLn2xO6, La4- χΙ_η1 χΟ6, La -xNdxO6, wherein Ln1 and Ln2 are each independently a lanthanide element, wherein Ln1 and Ln2 are not the same and x is a number ranging from greater than 0 to less than 4, La3NdO6, LaNd3O6, Lai.5Nd2.5O6,
La2.5Ndi.5O6, La3.2Ndo.eO6, La3.5Ndo.5Oe, La3.8Ndo.2O6, Y-La, Zr-La, Pr-La and Ce-La.
"O2-OCM catalyst" refers to a catalyst having activity in the OCM reaction and which predominately uses O2 as an oxygen source.
"CO2-OCM catalyst" refers to a catalyst having activity in the OCM reaction and which predominately uses CO2 as an oxygen source.
"O2-ODH catalyst" refers to a catalyst having activity in the ODH reaction and which predominately uses O2 as an oxygen source.
"CO2-ODH catalyst" refers to a catalyst having activity in the ODH reaction and which predominately uses CO2 as an oxygen source. Catalysts
1 . Molecular Composition of the Catalysts
As noted above, disclosed herein are catalysts useful in various catalytic reactions. In some embodiments, the catalysts are bulk catalysts (i.e., not nanowire or other nanostructured catalysts). In some embodiments, the catalysts comprise one or more metal elements for example, the catalysts may be mono-metallic, bi-metallic, tri-metallic, etc. (i.e., contain one, two, three, etc., metal elements). In some embodiments, the metal elements are present in the catalysts in elemental form while in other embodiments the metal elements are present in oxidized form. In other embodiments the metal elements are present in the catalysts in the form of a compound comprising a metal element. The metal element or compound comprising the metal element may be in the form of oxides (e.g., mixed oxides), hydroxides, carbonates, oxy-hydroxides, oxycarbonates, salts, hydrates, and the like. The metal element or compound comprising the metal element may also be in the form of any of a number of different polymorphs or crystal structures.
In other embodiments, the catalysts may comprise one or more element from group 2 and one or more element from group 7 which may be in the form of an oxide. For example, the catalyst may comprise magnesium and manganese. The magnesium and manganese may be in oxidized form, for example in the form of a mixed metal oxide.
Catalysts comprising mixed oxides of Mn and Mg are well suited for incorporation of dopants because magnesium atoms can be easily substituted by other atoms as long as their size is comparable with magnesium. A family of "doped" Mg6MnO8 compounds with the composition M(X)Mg(6-X)MnO8, wherein each M is independently a dopant as defined herein and x is 0 to 6, can thus be created. The oxidation state of Mn can be tuned by selecting different amounts (i.e., different values of x) of M with different oxidation states, for example Li(X)Mg(6-X)MnO8 would contain a mixture of Mn(IV) and Mn(V) with x < 1 and a mixture that may include Mn(V), Mn(VI), Mn(VII) with x > 1 . The maximum value of x depends on the ability of a particular atom M to be incorporated in the Mg6MnO8 crystal structure and therefore varies depending on M. It is believed that the ability to tune the manganese oxidation state as described above could have advantageous effect on the catalytic activity {e.g., selectivity, yield, conversion, etc.) of the disclosed catalysts in various reactions, including the OCM reaction. Accordingly, in some embodiments, the present disclosure provides a mixed oxide of manganese and magnesium which has been doped with lithium and boron. In further embodiments, the catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a
heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
Surprisingly, it has been found that addition of further dopants to the above described catalyst increases the catalytic activity of the catalyst in the OCM and other reactions. For example, a catalyst comprising a mixed oxide of manganese and magnesium which further comprises lithium and boron and at least one doping element from any of groups 1 -13 are effective catalysts for use in the OCM reaction. In some specific examples, the at least one doping element is from groups 4, 9, 12 or 13, and in further embodiments, the catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less. In some examples, the doping element is rhodium. In other examples, the doping element is cobalt. In yet other embodiments, the doping element is zirconium, while in other embodiments, the doping element is zinc. Other embodiments include a gallium doping element or a sodium doping element.
In addition, Applicants have discovered that further doping of the manganese/magnesium mixed oxide catalyst can further improve the catalytic activity of the catalyst. For example, although sodium itself is not a promoting dopant, it has been found that addition of sodium, together with a cobalt or gallium dopant to the above catalyst results in an effective OCM catalyst. Thus in one embodiment of the foregoing, the present disclosure provides a mixed oxide of manganese and magnesium which further includes lithium, boron, cobalt and sodium as dopants. In other examples, the catalyst comprises a mixed oxide of manganese and magnesium which further includes lithium, boron, gallium and sodium as dopants.
Inclusion of even further dopants within the above noted catalysts can improve the activity thereof. For example, in some embodiments the catalyst comprises a mixed oxide of manganese and magnesium and further comprises lithium and boron dopants and at least one doping element from groups 4, 9, 12, 13 or combinations thereof, and further comprises at least one additional doping element from group 2. For example, a catalyst comprising a mixed oxide of manganese and magnesium which further includes lithium, boron, cobalt and sodium can be further doped with beryllium, barium, aluminum, hafnium or combinations thereof. In other embodiments, the mixed oxide of manganese and magnesium is further doped with beryllium. In other embodiments, the mixed oxide of manganese and magnesium is further doped with barium. In other embodiments, the mixed oxide of manganese and magnesium is further doped with aluminum. In other embodiments, the mixed oxide of manganese and magnesium is further doped with hafnium.
Similarly, a catalyst comprising a mixed oxide of manganese and magnesium which further includes lithium, boron, gallium and sodium can be further doped with beryllium, barium, aluminum, hafnium or combinations thereof. In other embodiments of the foregoing catalyst, the mixed oxide of manganese and magnesium is further doped with beryllium. In other embodiments, the mixed oxide of manganese and magnesium is further doped with barium. In other embodiments, the mixed oxide of manganese and magnesium is further doped with aluminum. In other embodiments, the mixed oxide of manganese and magnesium is further doped with hafnium. Mixed oxides comprising manganese, tungsten and sodium (Na/Mn/W/O) is a promising OCM catalyst. The Na/Mn/W/O system is attractive due to its high C2 selectivity and yield. Unfortunately, good catalytic activity is only achievable at temperatures greater than 800 °C and although the exact active portion of the catalyst is still subject to debate, it is thought that sodium plays an important role in the catalytic cycle. In addition, the
Na/Mn/W/O catalyst surface area is relatively low < 2m2/g. However, applicants have discovered that addition of certain dopants to the Na/Mn/W/O catalyst system can increase the catalytic activity thereof. In addition, certain catalyst supports as described below, with or without dopants, can increase the catalytic activity of the Na/Mn/W/O catalyst, for example in the OCM reaction. In some embodiments, the Na/Mn/W/O catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
Doping elements which have been found to increase the catalytic activity of a Na/Mn/W/O catalyst include elements from groups 2, 16 or combinations thereof. Accordingly, in some embodiments the Na/Mn/W/O catalyst is doped with at least one doping element from group 2, 16 or combinations thereof. For example, some embodiments include beryllium, barium, aluminum, hafnium or combinations thereof as dopants. In other embodiments, the doping element is beryllium. In some other embodiments, the doping element is barium. In yet other embodiments, the doping element is aluminum, while in other embodiments, the doping element is hafnium. The Na/Mn/W/O catalyst (doped or undoped) has also been found to benefit from various catalyst supports, including those described below. For example, in some embodiments the catalyst support is SiO2. In other embodiments, the catalyst support is S1O2, Z D2, HfO2, lnO2 or combinations thereof.
Catalysts comprising rare earth oxides (i.e., lanthanides, actinides and Group 3) doped with various elements are also effective catalysts in the OCM reaction. In some embodiments the rare earth oxide is a rare earth mixed oxide (i.e., an oxide of two or more rare earth elements). The rare earth oxide may comprise any rare earth element, and in certain embodiments the rare earth element is La, Nd, Eu, Sm, Yb, Gd or Y. In some embodiments, the rare earth element is La. In other embodiments, the rare earth element is Nd. In other embodiments, the rare earth element is Eu. In other embodiments, the rare earth element is Sm. In other embodiments, the rare earth element is Yb. In other embodiments, the rare earth element is Gd. In other embodiments, the rare earth element is Y.
In certain embodiments of the catalysts comprising rare earth oxides, the catalyst may further comprise a dopant selected from alkaline earth (Group 2) elements. For example, in some embodiments the dopant is selected from Be, Mg, Ca, Sr and Ba. In other embodiments, the dopant is Be. In other embodiments, the dopant is Ca. In other embodiments, the dopant is Sr. In other embodiments, the dopant is Ba.
In some specific embodiments, the rare earth oxide is a mixed rare earth oxide such as La3NdO6, LaNd3O6, La1.5Nd2.5O6, La2.5Nd1.5O6, La3.2Ndo.8O6, La3.5Ndo.5O6, La3.8Ndo.2O6 or combinations thereof and the like.
The degree of effectiveness of a particular dopant is a function of the rare earth used and the concentration of the dopant. In addition to Alkali earth elements, further embodiments of the rare earth oxide catalysts include embodiments wherein the catalysts comprise alkali elements as dopants which further promote the selectivity of the OCM catalytic activity of the doped material. In yet other embodiments of the foregoing, the catalysts comprise both an alkali element and alkali earth element as dopant.
In still further embodiments, the catalyst comprises a rare earth oxide (e.g., rare earth mixed oxides) and at least one dopant is selected from groups 1 -16, lanthanides actinides or combinations thereof. In certain embodiments, such catalysts comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less. . In some embodiments, the at least one doping element is selected from groups 1 -4, 8, 13, 14, lactinides, actinides and combinations thereof. In some other embodiments, the at least one doping element is selected from groups 1 -6, 8, 1 1 , 13-15, lactinides, actinides and combinations thereof.
In some further embodiments of the foregoing, the at least one doping element is a rare earth element. In some embodiments, the at least one doping element is Na, Mg, Ca, Sr, Ga, Sc, Y, Zr, In, Nd, Eu, Sm, Ce, Gd, Hf, Ho, Tm, W, La, K, Dy, Cs, S, Zn, Rb, Ba, Yb, Ni, Lu, Ta, P, Pt, Bi, Sn, Nb, Sb, Ge, Ag, Au, Pb, Re, Fe, Al, Tl, Pr, Co, Rh, Ti, V, Cr, Mn, Ir, As, Li, Tb ,Er, Te or Mo.
In other embodiments, the at least one doping element is sodium. In other embodiments, the at least one doping element is magnesium. In other embodiments, the at least one doping element is calcium. In other
embodiments, the at least one doping element is strontium. In other
embodiments, the at least one doping element is gallium. In other
embodiments, the at least one doping element is Scandium. In other embodiments, the at least one doping element is yttrium. In other
embodiments, the at least one doping element is zirconium. In other embodiments, the at least one doping element is indium. In other
embodiments, the at least one doping element is neodymium. In other embodiments, the at least one doping element is europium. In other
embodiments, the at least one doping element is cerium. In other
embodiments, the at least one doping element is gadolinium. In other embodiments, the at least one doping element is hafnium. In other
embodiments, the at least one doping element is holmium. In other
embodiments, the at least one doping element is thulium. In other
embodiments, the at least one doping element is tungsten. In other
embodiments, the at least one doping element is lanthanum. In other embodiments, the at least one doping element is potassium. In other embodiments, the at least one doping element is dysprosium. In other embodiments, the at least one doping element is caesium. In other
embodiments, the at least one doping element is sulfur. In other embodiments, the at least one doping element is zinc. In other embodiments, the at least one doping element is rubidium. In other embodiments, the at least one doping element is barium. In other embodiments, the at least one doping element is ytterbium. In other embodiments, the at least one doping element is nickel. In other embodiments, the at least one doping element is lutetium. In other embodiments, the at least one doping element is tantalum. In other
embodiments, the at least one doping element is phosphorous. In other embodiments, the at least one doping element is platinum. In other
embodiments, the at least one doping element is bismuth. In other
embodiments, the at least one doping element is tin. In other embodiments, the at least one doping element is niobium. In other embodiments, the at least one doping element is antimony. In other embodiments, the at least one doping element is germanium. In other embodiments, the at least one doping element is silver. In other embodiments, the at least one doping element is gold. In other embodiments, the at least one doping element is lead. In other embodiments, the at least one doping element is rhenium. In other
embodiments, the at least one doping element is iron. In other embodiments, the at least one doping element is aluminum. In other embodiments, the at least one doping element is thalium. In other embodiments, the at least one doping element is praseodymium. In other embodiments, the at least one doping element is cobalt. In other embodiments, the at least one doping element is rhodium. In other embodiments, the at least one doping element is titanium. In other embodiments, the at least one doping element is vanadium. In other embodiments, the at least one doping element is chromium. In other embodiments, the at least one doping element is manganese. In other embodiments, the at least one doping element is iridium. In other embodiments, the at least one doping element is arsenic. In other
embodiments, the at least one doping element is lithium. In other
embodiments, the at least one doping element is terbium. In other
embodiments, the at least one doping element is erbium. In other
embodiments, the at least one doping element is tellurium. In other
embodiments, the at least one doping element is molybdenum.
Certain other metal oxides and/or mixed oxides with optional dopants have been found to have advantageously superior properties when employed as a heterogeneous catalyst, for example in the OCM reaction.
Accordingly, certain embodiments are directed to a catalyst comprising an oxide of at least one metal and further comprising one or more element (a doping element) from the lanthanides or groups 2, 3, 4, 6 or 13 of the periodic table, wherein the metal is selected from groups 4, 12 and 13 of the periodic table and Ce, Pr, Nd, Sm, Eu, Gd, Tb and Ho. In certain embodiments, the catalyst is a metal oxide and the element from groups 2, 3, 4, 6 or 13 is a dopant (i.e., the catalyst is a doped metal oxide). In some embodiments, the catalyst is a perovskite or perovskite-like oxide which is optionally doped. In other embodiments, the catalyst is a mixed metal oxide which is optionally doped.
In other embodiments, the catalyst comprises an oxide of at least one metal and further comprising one or more element (a doping element) from the lanthanides or groups 2, 3 or 4 of the periodic table, wherein the metal is selected from groups 4, 12 and 13 of the periodic table and Ce, Eu, Gd, Tb and Ho. In certain embodiments, the catalyst is a metal oxide and the element from groups 2, 3 or 4 is a dopant (i.e., the catalyst is a doped metal oxide).
In other embodiments, the catalyst comprises an oxide of at least one metal and further comprising one or more element (a doping element) from groups 2, 6 or 13 of the periodic table, for example groups 6 or 13, wherein the metal is selected from Pr, Nd and Sm. In certain embodiments, the catalyst is a metal oxide and the element from groups 6 or 13 is a dopant (i.e., the catalyst is a doped metal oxide).
In certain embodiments, the catalyst is a bulk catalyst. In other embodiments, the catalyst is a nanostructured catalyst, such as a nanowire. Specific embodiments include catalysts comprising an inorganic catalytic polycrystalline nanowire, the nanowire having a ratio of effective length to actual length of less than one and an aspect ratio of greater than ten as measured by TEM in bright field mode at 5 keV, wherein the nanowire comprises one or more elements from any of Groups 1 through 7, lanthanides, actinides or combinations thereof as described in in co-pending U.S.
Application Nos. 13/1 15,082 (U.S. Pub. No. 2012/0041246), and 13/689,61 1 (U.S. Pub. No. 2013/0165728), the full disclosures of which are hereby incorporated by reference in their entirety for all purposes. Other exemplary nanowire embodiments include nanowires having a ratio of effective length to actual length of one (i.e., a "straight" nanowire), for example as described in the foregoing published patent applications.
In some embodiments, the catalysts comprise or have the formula AxByOz, where 'A' is the element from the lanthanides or group 2, 3, 4, 6 or 13, 'B' is the metal, O is an oxygen anion, x, y and z are numbers greater than 0. In some embodiments, x is selected such that charges of A and B and any other elements present are balanced (i.e., net zero charge). In other embodiments, x does not balance the charges of A and B and any other elements present and the catalysts are charged (i.e., salts). For example, some embodiments include salts of the foregoing oxides. For clarity, it should also be noted that A and B are not the same.
In further embodiments, the catalysts comprise additional elements. For example, in some embodiments the catalysts comprise or have one of the following formulas E1 aAxByOz, E1 aE2 bAxByOz or E1 aE2 bE3cAxByOz, wherein E1 , E2 and E3 are each independently elements and a, b and c are each independently numbers greater than 0. In further embodiments of the catalysts comprising or having formula AxByOz, E1 aAxByOz, E1 aE2 bAxByOz or E1aE2 bE3 cAxByOz, B is selected from Zn, Hf, Zr, Al, Ti, Pr, Nd, Ce, Sm, Eu, Gd, Tb and Ho. In other
embodiments, A is selected from Ba, Zr, Sr, Sm, Hf, Gd, Er, Y, Ca, La, Mg, W, B, Tb and Ce. In other embodiments, E1 , E2 and E3, when present, are selected from elements in groups 2, 3, 4 and the lanthanides.
In still more embodiments, the catalyst is in the form of a perovskite or perovskite-like oxide (i.e., ABO3, where 'A' is the element from the lanthanides or group 2, 3, 4, 6 or 13, 'B' is the metal, and O is an oxygen anion that bonds to both A and B) which may optionally contain additional elements (e.g., dopants). In some embodiments, the perovskite or perovskite-like oxide comprise a metal from group 4 and an element from group 2. For example, in some embodiments the metal from group 4 is Ti, Zr or Hf and the element from group 2 is Ba, Sr or Ca, for example Sr.
In some embodiments, the perovskite or perovskite-like oxide comprise a metal from group 13 and an element from group 2. For example, in some embodiments the metal from group 13 is Al and the element from group 2 is Ba, Sr or Ca, for example Sr.
In some embodiments, the perovskite or perovskite-like oxide comprise a metal from the lanthanides and an element from group 2. For example, in some embodiments the metal from the lanthanides is Ce, Sm or Tb and the element from group 2 is Ba, Sr or Ca, for example Sr. In some embodiments, the lanthanide is Sm and the element from group 2 is Ca. In other embodiments, the element from the lanthanides is Ce or Tb and the element from group 2 is Sr.
In some embodiments, the perovskite or perovskite-like oxide comprise a metal from the lanthanides and an element from group 13. For example, in some embodiments the metal from the lanthanides is Pr and the element from group 13 is Ga. In certain other embodiments, the perovskite or perovskite-like oxide is BaZrO3, SrZrO3, SrAIO3, SrCeO3, SrHfO3, CaHfO3, SrTbO3 or BaTiO3.
In certain embodiments, the perovskite or perovskite-like oxide is doped with a dopant from any one of groups 2, 3 or the lanthanides. For example, in some embodiments the dopant is selected from Sr, Y, La, Nd, Ca, Mg, Ce and combinations thereof. In certain embodiments, the perovskite or perovskite-like oxide is doped with a dopant from group 2, for example Sr, Mg, Ca or combinations thereof. In other embodiments the perovskite or perovskite-like oxide is doped with an element from group 3, for example Y. In yet other embodiments the perovskite or perovskite-like oxide is doped with an element from the lanthanides, for example La, Nd, Ce or combinations thereof.
In other embodiments, the catalyst is a mixed metal oxide. For example, the mixed metal oxide comprises a metal selected from group 13, such as Ga or In, and a lanthanide, such as Ce or Gd. In some embodiments such mixed metal oxides further comprise an element from group 2, such as Ba, and/or an additional lanthanide, such as Pr.
In other embodiments, the mixed metal oxide comprises Eu or Nd and a metal from group 2, such as Ca. In certain embodiments, such mixed metal oxides optionally further comprise a lanthanide element, such as Sm. In other embodiments, these mixed metal oxides further comprise an element from group 13, such as B.
In other embodiments, the mixed metal oxides comprise and element from group 12, such as Zn, and an element from group 2 and/or group 4, for example, Ba and/or Ti.
In certain embodiments, the mixed metal oxides comprise one or more doping elements, examples of which are provided throughout the specification, including Tables 1 -8.
In certain of the foregoing catalyst embodiments, the element from the lanthanides is Ce or Pr. In other embodiments, the element is from groups 2, 3 or 4. In some embodiments, the element is from group 2. In other embodiments, the element is from group 3. In other embodiments, the element is from group 4.
In other embodiments, the element from the lanthanides or group 2, 3 or 4 is selected from any of the elements within the respective groups. In certain embodiments, the element is selected from Ce, Pr, Sr, Ca, Mg, Y, Zr and Ba. In other embodiments the element is selected from Ce, Pr, Sr, Ca, Mg, Y, Zr, Ba and Hf. In certain embodiments, the element is Ce. In certain embodiments, the element is Pr. In certain embodiments, the element is Sr. In certain embodiments, the element is Ca. In certain embodiments, the element is Mg. In certain embodiments, the element is Y. In certain embodiments, the element is Zr. In certain embodiments, the element is Ba. In certain
embodiments, the element is Hf. In certain specific embodiments, the catalyst comprises two of the foregoing elements (in addition to the metal).
In some embodiments of the foregoing catalyst, the catalyst comprises two doping elements selected from groups 2 and 3, for example one element from group 2 and one element from group 3. In some of the
embodiments, the element from group 2 is Ba. In other embodiments, the element from group 3 is Y. In some embodiments, the element from group 2 is Ba and the element from group 3 is Y.
In some embodiments, the catalyst comprises two doping elements selected from groups 2 and 4, for example one element from group 2 and one element from group 4. For example, in certain embodiments, the catalyst comprises a metal from group 12 (e.g., in the form of an oxide) and doping elements selected from groups 2 and 4, for example one element from group 2 and one element from group 4. In other, the doping element from group 2 is Sr or Ba. In some embodiments, the doping element from group 2 is Sr. In other embodiments the doping element from group 2 is Ba. In further embodiments, the doping element from group 4 is Zr or Hf. In some
embodiments, the doping element from group 4 is Zr. In other embodiments, the doping element from group 4 is Hf. In certain of the foregoing embodiments, the metal from group 12 is Zn, for example in the form of a zinc oxide such as ZnO.
In still more embodiments, the catalyst comprises a metal from group 12 {e.g., a zinc oxide) and doping elements selected from Ba, Sr, Zr and Hf. In some embodiments, the doping elements comprise Ba and Hf. In other embodiments, the doping elements comprise Ba and Zr. In still more
embodiments, the doping elements comprise Sr and Zr. In more embodiments, the doping elements comprise Sr and Hf.
In other embodiments, the metal is selected from group 4. For example, in some embodiments the metal is Zr. In other embodiments, the metal is Hf.
In still other embodiments, the metal is selected from group 12. For example, in some embodiments the metal is Zn. In some more
embodiments, the metal is selected from group 13, for example Ga.
In some embodiments, the metal is Ce. In some other embodiments, the metal is Eu. In still other embodiments, the metal is Gd. In still other embodiments, the metal is Tb. In still other embodiments, the metal is Ho.
In some other more specific embodiments, the catalyst comprises one of the following combinations: Lao.8Sro.2Gao.9Mgo.1 O3, Y/SrZrO3,
SrCeO3/SrCe2O4, Ba/ZnO, Ba/Zr/ZnO, Ba/Sr/ZnO, Ba/Y/ZnO, SrHfO3, SrZrO3, Mg/SrHfOs, Sr/Gd2O3, CaHfO3, SrTbO3, Ca/Ho2O3, Sr/BaZrO3, Y/SrZrO3, La/SrAIO3, La/Nd/SrAIO3, Ca/BaZrO3, La/SrCeO3, SrZrO3, SrHfO3, Mg/SrHfO3, CaHfO3, SrTbO3, BaTiO3, Ba-Gd-ln, CaSmO3, Sm-Eu-Ca, Ce/GaPrO3, Ba-Zn- Ti, Ca-Nd-B or Ce-Ga-Pr. Each of the foregoing compositions may, in certain embodiments, include one or more additional elements (e.g., as a dopant) to optimize the desired catalytic activity.
In some embodiments, the element (e.g., doping element) is selected from one or more elements in groups 2, 6 and 13. For example, in some embodiments the element is selected from Sr, Ba, W and B. In some embodiments, the element is Sr. In some embodiments, the element is Ba. In some embodiments, the element is W. In some embodiments, the element is B.
Combinations of Sr, Ba, W and B as doping elements are also within the scope of certain embodiments of the invention. For example, in addition to the base catalyst, some embodiments comprise doping
combinations selected from Sr/Ba, Sr/W and Sr/B. In other embodiments, the doping combination is selected from Ba/Sr, Ba/W and Ba/B. In other embodiments, the dopants comprise W/Sr. W/Ba or W/B. In still other embodiments, the dopants comprise B/Sr, B/Ba or B/W.
In still more embodiments, the doping elements comprise one of the following combinations: Sr/Ba/W, Sr/Ba/B, Sr/W/B or Ba/W/B. In some embodiments, the dopant combination comprises Sr/Ba/W/B.
In other embodiments of the foregoing catalysts, the elements (e.g., doping elements) comprise one of the following combination of elements: Ba/Zr; Ba/Hf; Ba/Hf/Sm; Ba/Zr/Sm; Ba/Zr/Er; Ba/Hf/Er; Sr/Hf; Sr/Zr; Sr/Hf/Sm; Sr/Hf/Er or Ba/Hf/Gd. In some of these embodiments, the metal is from group 12, such as Zn, and is the form of an oxide, such as ZnO.
The doping elements described herein with respect to the catalysts can be present in varying concentration with respect to the base catalyst metal. One of skill in the art will be able to identify doping
concentration appropriate for the desired application (e.g., use as an OCM catalyst). Exemplary concentrations for doping elements are provided below.
Advantageously, the present inventors have discovered that certain doped metal carbonate catalysts have desirable catalytic properties in petrochemical catalytic reactions, such as OCM. For example, in one embodiment the catalyst is a group 2 metal carbonate comprising a dopant. In some embodiments the metal carbonate is MgCO3, CaCO3 or SrCO3. In certain embodiments, the metal carbonate is CaCO3. The dopant for the metal carbonate may be selected from any one of a number of elements, for example an element from group 4. In some embodiments the dopant is Zr. In more specific embodiments the metal carbonate catalyst is Zr/CaCO3.
Advantageously, certain embodiments of the foregoing catalysts
(e.g., a catalyst comprising an oxide of at least one metal and further
comprising one or more element from the lanthanides or groups 2, 3 or 4 of the periodic table, wherein the metal is selected from groups 4, 12, 13 or Ce, Eu, Gd, Tb or Ho or a doped metal carbonate catalyst) have been found to have advantageous C2 selectivity and methane conversion at relatively low
temperatures. For example, certain embodiments of these catalysts are capable of methane conversions in an OCM reaction of greater than 20% and C2 selectivities of greater than 50% at temperatures ranging from about 550 C to about 750 C, for example, from about 600 C to about 700 C. In other embodiments of the foregoing, the methane conversion is greater than 22%, greater than 24% or even greater than 26%. In still other embodiments of any of the foregoing, the C2 selectivity of the catalysts is greater than 55% or even greater than 60%.
Even further advantages are obtained from certain embodiments of the foregoing catalysts. For example, in certain embodiments when the catalysts are employed in an OCM reaction, the reaction proceeds with substantially no reforming of methane to CO and H2. For example, in some embodiments wherein the foregoing catalysts are employed in an OCM reaction, at complete O2 conversion, e.g., maximum methane conversion, the product gas from the reaction comprises less 0.5% CO, less than 0.2%, and in some cases about 0.1 % or less, as compared to between about 0.6% and 2% for other high activity OCM catalysts. Likewise, the H2 concentration in the outlet gas under such conditions will typically be less than about 1 .5%, less than about 1 %, less than about 0.8%, and in many cases less than about 0.5%, as compared to other high activity OCM catalysts that can typically provide H2 concentrations in excess of 2 %. Accordingly, processes employing such catalysts recognize significant reduction in capital costs since the separations are simplified. Embodiments of the present invention include such processes (i.e., an OCM process having substantially no reforming of methane to CO and H2 as described above).
In some embodiments, the catalyst comprises a rare earth oxide and a combination of at least two different doping elements. For example, in some embodiments the two different doping elements are selected from Na, Mg, Ca, Sr, Ga, Sc, Y, Zr, In, Nd, Eu, Sm, Ce, Gd, Hf, Ho, Tm, W, La, K, Dy, In, Cs, S, Zn, Rb, Ba, Yb, Ni, Lu, Ta, P, Pt, Bi, Sn, Nb, Sb, Ge, Ag, Au, Pb, Re, Fe, Al, Tl, Pr, Co, Rh, Ti, V, Cr, Mn, Ir, As, Li, Tb ,Er, Te and Mo. In other embodiments, the combination of at least two doping elements is Eu/Na, Sr/Na, Mg/Na, Sr/W, K La, K Na, Li/Cs, Li/Na, Zn/K, Li/K, Rb/Hf, Ca/Cs, Hf/Bi, Sr/Sn, Sr/W, Sr/Nb, Zr/W, Y/W, Na/W, Bi/W, Bi/Cs, Bi/Ca, Bi/Sn, Bi/Sb, Ge/Hf, Hf/Sm, Sb/Ag, Sb/Bi, Sb/Au, Sb/Sm, Sb/Sr, Sb/W, Sb/Hf, Sb/Yb, Sb/Sn, Yb/Au, Yb/Ta, Yb/W, Yb/Sr, Yb/Pb, Yb/W, Yb/Ag, Au/Sr, W/Ge, Ta/Hf, W/Au, Ca/W, Au/Re, Sm/Li, La/K, Zn/Cs, Zr/Cs, Ca/Ce, Li/Sr, Cs/Zn, Dy/K, La/Mg, In/Sr, Sr/Cs, Ga/Cs, Lu/Fe, Sr/Tm, La/Dy, Mg/K, Zr/K, Li/Cs, Sm/Cs, In/K, Lu/TI, Pr/Zn, Lu/Nb, Na/Pt, Na/Ce, Ba/Ta, Cu/Sn, Ag/Au, Al/Bi, Al/Mo, Al/Nb, Au/Pt, Ga/Bi, Mg/W, Pb/Au, Sn/Mg, Zn/Bi, Gd/Ho, Zr/Bi, Ho/Sr, Ca/Sr, Sr/Pb or Sr/Hf.
In other embodiments, the combination of at least two different doping elements is La/Nd, La/Sm, La/Ce, La/Sr, Eu/Na, Eu/Gd, Ca/Na, Eu/Sm, Eu/Sr, Mg/Sr, Ce/Mg, Gd/Sm, Sr/W, Sr/Ta, Au/Re, Au/Pb, Bi/Hf, Sr/Sn, Mg/N, Ca/S, Rb/S, Sr/Nd, Eu/Y, Mg/Nd, Sr/Na, Nd/Mg, La/Mg, Yb/S, Mg/Na, Sr/W, K La, K Na, Li/Cs, Li/Na, Zn/K, Li/K, Rb/Hf, Ca/Cs, Hf/Bi, Sr/Sn, Sr/W, Sr/Nb, Zr/W, Y/W, Na/W, Bi/W, Bi/Cs, Bi/Ca, Bi/Sn, Bi/Sb, Ge/Hf, Hf/Sm, Sb/Ag, Sb/Bi, Sb/Au, Sb/Sm, Sb/Sr, Sb/W, Sb/Hf, Sb/Yb, Sb/Sn, Yb/Au, Yb/Ta, Yb/W, Yb/Sr, Yb/Pb, Yb/W, Yb/Ag, Au/Sr, W/Ge, Ta/Hf, W/Au, Ca/W, Au/Re, Sm/Li, La/K, Zn/Cs, Zr/Cs, Ca/Ce, Li/Sr, Cs/Zn, Dy/K, La/Mg, In/Sr, Sr/Cs, Ga/Cs, Lu/Fe, Sr/Tm, La/Dy, Mg/K, Zr/K, Li/Cs, Sm/Cs, In/K, Lu/TI, Pr/Zn, Lu/Nb, Na/Pt, Na/Ce, Ba/Ta, Cu/Sn, Ag/Au, Al/Bi, Al/Mo, Al/Nb, Au/Pt, Ga/Bi, Mg/W, Pb/Au, Sn/Mg, Zn/Bi, Gd/Ho, Zr/Bi, Ho/Sr, Ca/Sr, Sr/Pb or Sr/Hf.
In other embodiments, the combination of two doping elements is La/Nd. In other embodiments, the combination of two doping elements is La/Sm. In other embodiments, the combination of two doping elements is La/Ce. In other embodiments, the combination of two doping elements is La/Sr. In other embodiments, the combination of two doping elements is Eu/Na. In other embodiments, the combina ion of two doping elements is Eu/Gd. In other embod ments, the comb nation of two doping e emen ts is Ca/Na In other embod ments, the comb nation of two doping e emen ts is Eu/Sm . In other embod ments, the comb nation of two doping e emen ts is Eu/Sr. In other embod ments, the comb nation of two doping e emen ts is Mg/Sr. In other embod ments, the comb nation of two doping e emen ts is Ce/Mg . In other embod ments, the comb nation of two doping e emen ts is Gd/Sm . In other embod ments, the comb nation of two doping e emen ts is Sr/W. In other embod ments, the comb nation of two doping e emen ts is Sr/Ta. In other embod ments, the comb nation of two doping e emen ts is Au/Re. In other embod ments, the comb nation of two doping e emen ts is Au/Pb. In other embod ments, the comb nation of two doping e emen ts is Bi/Hf. In other embod ments, the comb nation of two doping e emen ts is Sr/Sn. In other embod ments, the comb nation of two doping e emen ts is Mg/N. In other embod ments, the comb nation of two doping e emen ts is Ca/S. In other embod ments, the comb nation of two doping e emen ts is Rb/S. In other embod ments, the comb nation of two doping e emen ts is Sr/Nd. In other embod ments, the comb nation of two doping e emen ts is Eu/Y. In other embod ments, the comb nation of two doping e emen ts is Mg/Nd . In other embod ments, the comb nation of two doping e emen ts is Sr/Na. In other embod ments, the comb nation of two doping e emen ts is Nd/Mg . In other embod ments, the comb nation of two doping e emen ts is La/Mg. In other embod ments, the comb nation of two doping e emen ts is Yb/S. In other embod merits, the comb nation of two doping e emen ts is Mg/Na . In other embod merits, the comb nation of two doping e emen ts is Sr/W. In other embod merits, the comb nation of two doping e emen ts is K/La. In other embod merits, the comb nation of two doping e emen ts is K/Na. In other embod merits, the comb nation of two doping e emen ts is Li/Cs. In other embod merits, the comb nation of two doping e emen ts is Li/Na. In other embod merits, the comb nation of two doping e emen ts is Zn/K. In other embod merits, the comb nation of two doping e emen ts is Li/K. In other embod merits, the comb nation of two doping e emen ts is Rb/Hf. In other embod merits, the comb nation of two doping e emen ts is Ca/Cs In other embod merits, the comb nation of two doping e emen ts is Hf/Bi. In other embod merits, the comb nation of two doping e emen ts is Sr/Sn. In other embod merits, the comb nation of two doping e emen ts is Sr/W. In other embod merits, the comb nation of two doping e emen ts is Sr/Nb. In other embod merits, the comb nation of two doping e emen ts is Zr/W. In other embod merits, the comb nation of two doping e emen ts is Y/W. n other embod merits, the comb nation of two doping e emen ts is Na/W. In other embod merits, the comb nation of two doping e emen ts is Bi/W. In other embod merits, the comb nation of two doping e emen ts is Bi/Cs. In other embod merits, the comb nation of two doping e emen ts is Bi/Ca. In other embod merits, the comb nation of two doping e emen ts is Bi/Sn. In other embod merits, the comb nation of two doping e emen ts is Bi/Sb. In other embod merits, the comb nation of two doping e emen ts is Ge/Hf. In other embod merits, the comb nation of two doping e emen ts is Hf/Sm In other embod merits, the comb nation of two doping e emen ts is Sb/Ag. In other embod merits, the comb nation of two doping e emen ts is Sb/Bi. In other embod merits, the comb nation of two doping e emen ts is Sb/Au. In other embod merits, the comb nation of two doping e emen ts is Sb/Sm . In other embod merits, the comb nation of two doping e emen ts is Sb/Sr. In other embod merits, the comb nation of two doping e emen ts is Sb/W. In other embod merits, the comb nation of two doping e emen ts is Sb/Hf. In other embod merits, the comb nation of two doping e emen ts is Sb/Yb In other embod merits, the comb nation of two doping e emen ts is Sb/Sn In other embod merits, the comb nation of two doping e emen ts is Yb/Au In other embod merits, the comb nation of two doping e emen ts is Yb/Ta. In other embod merits, the comb nation of two doping e emen ts is Yb/W. In other embod merits, the comb nation of two doping e emen ts is Yb/Sr. In other embod merits, the comb nation of two doping e emen ts is Yb/Pb In other embod merits, the comb nation of two doping e emen ts is Yb/W. In other embod merits, the comb nation of two doping e emen ts is Yb/Ag In other embod merits, the comb nation of two doping e emen ts is Au/Sr. In other embod merits, the comb nation of two doping e emen ts is W/Ge. In other embod merits, the comb nation of two doping e emen ts is Ta/Hf. In other embod merits, the comb nation of two doping e emen ts is W/Au. In other embod merits, the comb nation of two doping e emen ts is Ca/W. In other embod merits, the comb nation of two doping e emen ts is Au/Re In other embod merits, the comb nation of two doping e emen ts is Sm/Li. In other embod merits, the comb nation of two doping e emen ts is La/K. In other embod merits, the comb nation of two doping e emen ts is Zn/Cs. In other embod merits, the comb nation of two doping e emen ts is Zr/Cs. In other embod merits, the comb nation of two doping e emen ts is Ca/Ce . In other embod merits, the comb nation of two doping e emen ts is Li/Sr. In other embod merits, the comb nation of two doping e emen ts is Cs/Zn. In other embod merits, the comb nation of two doping e emen ts is Dy/K. In other embod merits, the comb nation of two doping e emen ts is La/Mg In other embod merits, the comb nation of two doping e emen ts is In/Sr. In other embod merits, the comb nation of two doping e emen ts is Sr/Cs. In other embod merits, the comb nation of two doping e emen ts is Ga/Cs . In other embod merits, the comb nation of two doping e emen ts is Lu/Fe. In other embod merits, the comb nation of two doping e emen ts is Sr/Tm In other embod merits, the comb nation of two doping e emen ts is La/Dy. In other embod merits, the comb nation of two doping e emen ts is Mg/K. In other embod merits, the comb nation of two doping e emen ts is Zr/K. In other embod merits, the comb nation of two doping e emen ts is Li/Cs. In other embod merits, the comb nation of two doping e emen ts is Sm/Cs . In other embod merits, the comb nation of two doping e emen ts is In/K. In other embod merits, the comb nation of two doping e emen ts is Lu/TI. In other embod merits, the comb nation of two doping e emen ts is Pr/Zn. In other embod merits, the comb nation of two doping e emen ts is Lu/Nb. In other embod merits, the comb nation of two doping e emen ts is Na/Pt. In other embod merits, the comb nation of two doping e emen ts is Na/Ce In other embod merits, the comb nation of two doping e emen ts is Ba/Ta. In other embod merits, the comb nation of two doping e emen ts is Cu/Sn In other embod merits, the comb nation of two doping e emen ts is Ag/Au. In other embod merits, the comb nation of two doping e emen ts is Al/Bi. In other embod merits, the comb nation of two doping e emen ts is Al/Mo. In other embod merits, the comb nation of two doping e emen ts is Al/Nb. In other embod merits, the comb nation of two doping e emen ts is Au/Pt. In other embod merits, the comb nation of two doping e emen ts is Ga/Bi. In other embod merits, the comb nation of two doping e emen ts is Mg/W. In other embod merits, the comb nation of two doping e emen ts is Pb/Au. In other embod merits, the comb nation of two doping e emen ts is Sn/Mg . In other embod merits, the comb nation of two doping e emen ts is Zn/Bi. In other embod merits, the comb nation of two doping e emen ts is Gd/Ho . In other embod merits, the comb nation of two doping e emen ts is Zr/Bi. In other embod merits, the comb nation of two doping e emen ts is Ho/Sr. In other embod merits, the comb nation of two doping e emen ts is Ca/Sr. In other embod merits, the comb nation of two doping e emen ts is Sr/Pb. In other embod merits, the comb nation of two doping e emen ts is Sr/Hf. In some other embodiments, the oxide of a rare earth element comprises a combination of at least three different doping elements. In certain examples, the three different doping elements are selected from Na, Mg, Ca, Sr, Ga, Sc, Y, Zr, In, Nd, Eu, Sm, Ce, Gd, Hf, Ho, Tm, W, La, K, Dy, In, Cs, S, Zn, Rb, Ba, Yb, Ni, Lu, Ta, P, Pt, Bi, Sn, Nb, Sb, Ge, Ag, Au, Pb, Re, Fe, Al, Tl, Pr, Co, Rh, Ti, V, Cr, Mn, Ir, As, Li, Tb ,Er, Te and Mo. In certain other embodiments, the combination of at least three different doping elements is Mg/La/K, Na/Dy/K, Na/La/Dy, Na/La/Eu, Na/La/K, K La/S, Li/Cs/La, Li/Sr/Cs, Li/Ga/Cs, Li/Na/Sr, Li/Sm/Cs, Cs/K/La, Sr/Cs/La, Sr/Ho/Tm, La/Nd/S, Li/Rb/Ca, Rb/Sr/Lu, Na/Eu/Hf, Dy/Rb/Gd, Na/Pt/Bi, Ca/Mg/Na, Na/K Mg, Na/Li/Cs,
La/Dy/K, Sm/Li/Sr, Li/Rb/Ga, Li/Cs/Tm, Li/K La, Ce/Zr/La, Ca/AI/La, Sr/Zn/La, Cs/La/Na, La/S/Sr, Rb/Sr/La, Na/Sr/Lu, Sr/Eu/Dy, La/Dy/Gd, Gd/Li/K, Rb/K/Lu, Na/Ce/Co, Ba/Rh/Ta, Na/AI/Bi, Cs/Eu/S, Sm/Tm/Yb, Hf/Zr/Ta, Na/Ca/Lu, Gd/Ho/Sr, Ca/Sr/W, Na/Zr/Eu/Tm, Sr/W/Li, Ca/Sr/W or Mg/Nd/Fe.
In still other embodiments, the combination of at least three different doping elements is Nd/Sr/CaO, La/Nd/Sr, La/Bi/Sr, Mg/Nd/Fe,
Mg/La/K, Na/Dy/K, Na/La/Dy, Na/La/Eu, Na/La/K, K La/S, Li/Cs/La, Li/Sr/Cs, Li/Ga/Cs, Li/Na/Sr, Li/Sm/Cs, Cs/K/La, Sr/Cs/La, Sr/Ho/Tm, La/Nd/S, Li/Rb/Ca, Rb/Sr/Lu, Na/Eu/Hf, Dy/Rb/Gd, Na/Pt/Bi, Ca/Mg/Na, Na/K Mg, Na/Li/Cs, La/Dy/K, Sm/Li/Sr, Li/Rb/Ga, Li/Cs/Tm, Li/K La, Ce/Zr/La, Ca/AI/La, Sr/Zn/La, Cs/La/Na, La/S/Sr, Rb/Sr/La, Na/Sr/Lu, Sr/Eu/Dy, La/Dy/Gd, Gd/Li/K, Rb/K/Lu, Na/Ce/Co, Ba/Rh/Ta, Na/AI/Bi, Cs/Eu/S, Sm/Tm/Yb, Hf/Zr/Ta, Na/Ca/Lu, Gd/Ho/Sr, Ca/Sr/W, Na/Zr/Eu/Tm, Sr/W/Li or Ca/Sr/W.
In other embodiments, the combination of at least three different doping elements is Nd/Sr/CaO. In other embodiments, the combination of at least three different doping elements is La/Nd/Sr. In other embodiments, the combination of at least three different doping elements is La/Bi/Sr. In other embodiments, the combination of at least three different doping elements is Mg/Nd/Fe. In other embodiments, the combination of at least three different doping elements is Mg/La/K. In other embodiments, the combination of at least three different doping elements is Na/Dy/K. In other embodiments, the combination of at least three different doping elements is Na/La/Dy. In other embodiments, the combination of at least three different doping elements is Na/La/Eu. In other embodiments, the combination of at least three different doping elements is Na/La/K. In other embodiments, the combination of at least three different doping elements is K/La/S. In other embodiments, the
combination of at least three different doping elements is Li/Cs/La. In other embodiments, the combination of at least three different doping elements is Li/Sr/Cs. In other embodiments, the combination of at least three different doping elements is Li/Ga/Cs. In other embodiments, the combination of at least three different doping elements is Li/Na/Sr. In other embodiments, the combination of at least three different doping elements is Li/Sm/Cs. In other embodiments, the combination of at least three different doping elements is Cs/K La. In other embodiments, the combination of at least three different doping elements is Sr/Cs/La. In other embodiments, the combination of at least three different doping elements is Sr/Ho/Tm. In other embodiments, the combination of at least three different doping elements is La/Nd/S. In other embodiments, the combination of at least three different doping elements is Li/Rb/Ca. In other embodiments, the combination of at least three different doping elements is Rb/Sr/Lu. In other embodiments, the combination of at least three different doping elements is Na/Eu/Hf. In other embodiments, the combination of at least three different doping elements is Dy/Rb/Gd. In other embodiments, the combination of at least three different doping elements is Na/Pt/Bi. In other embodiments, the combination of at least three different doping elements is Ca/Mg/Na. In other embodiments, the combination of at least three different doping elements is Na/K/Mg. In other embodiments, the combination of at least three different doping elements is Na/Li/Cs. In other embodiments, the combination of at least three different doping elements is La/Dy/K. In other embodiments, the combination of at least three different doping elements is Sm/Li/Sr. In other embodiments, the combination of at least three different doping elements is Li/Rb/Ga. In other embodiments, the combination of at least three different doping elements is Li/Cs/Tm. In other embodiments, the combination of at least three different doping elements is Li/K/La. In other embodiments, the combination of at least three different doping elements is Ce/Zr/La. In other embodiments, the combination of at least three different doping elements is Ca/AI/La. In other embodiments, the combination of at least three different doping elements is Sr/Zn/La. In other embodiments, the combination of at least three different doping elements is Cs/La/Na. In other embodiments, the combination of at least three different doping elements is La/S/Sr. In other embodiments, the combination of at least three different doping elements is Rb/Sr/La. In other embodiments, the combination of at least three different doping elements is Na/Sr/Lu. In other embodiments, the combination of at least three different doping elements is Sr/Eu/Dy. In other embodiments, the combination of at least three different doping elements is La/Dy/Gd. In other embodiments, the combination of at least three different doping elements is Gd/Li/K. In other embodiments, the combination of at least three different doping elements is Rb/K/Lu. In other embodiments, the combination of at least three different doping elements is Na/Ce/Co. In other embodiments, the combination of at least three different doping elements is Ba/Rh/Ta. In other embodiments, the combination of at least three different doping elements is Na/AI/Bi. In other embodiments, the combination of at least three different doping elements is Cs/Eu/S. In other embodiments, the combination of at least three different doping elements is Sm/Tm/Yb. In other embodiments, the combination of at least three different doping elements is Hf/Zr/Ta. In other embodiments, the combination of at least three different doping elements is Na/Ca/Lu. In other embodiments, the combination of at least three different doping elements is Gd/Ho/Sr. In other embodiments, the combination of at least three different doping elements is Ca/Sr/W. In other embodiments, the combination of at least three different doping elements is Na/Zr/Eu/Tm. In other embodiments, the combination of at least three different doping elements is Sr/W/Li. In other embodiments, the combination of at least three different doping elements is Ca/Sr/W.
In yet other embodiments, the oxide of a rare earth element comprises a combination of at least four different doping elements. In some examples, the four different doping elements are selected from Na, Mg, Ca, Sr, Ga, Sc, Y, Zr, In, Nd, Eu, Sm, Ce, Gd, Hf, Ho, Tm, W, La, K, Dy, In, Cs, S, Zn, Rb, Ba, Yb, Ni, Lu, Ta, P, Pt, Bi, Sn, Nb, Sb, Ge, Ag, Au, Pb, Re, Fe, Al, Tl, Pr, Co, Rh, Ti, V, Cr, Mn, Ir, As, Li, Tb ,Er, Te and Mo. More specific examples include catalysts wherein the combination of at least four different doping elements is Sr/Sm/Ho/Tm, Na/K/Mg/Tm, Na/La/Eu/ln, Na/La/Li/Cs,
Li/Cs/La/Tm, Li/Cs/Sr/Tm, Li/Sr/Zn/K, Li/Ga/Cs, Li/K/Sr/La, Li/Na/Rb/Ga, Li/Na/Sr/La, Ba/Sm/Yb/S, Ba/Tm/K/La, Ba/Tm/Zn/K, Cs/La/Tm/Na, Cs/Li/K/La, Sm/Li/Sr/Cs, Sr/Tm/Li/Cs, Zr/Cs/K/La, Rb/Ca/ln/Ni, Tm/Lu/Ta/P, Rb/Ca/Dy/P, Mg/La/Yb/Zn, Na/Sr/Lu/Nb, Na/Nd/ln/K, K/La/Zr/Ag, Ho/Cs/Li/La, K/La/Zr/Ag, Na/Sr/Eu/Ca, K/Cs/Sr/La, Na/Mg/TI/P, Sr/La/Dy/S, Na/Ga/Gd/AI, Sm/Tm/Yb/Fe, Rb/Gd/Li/K, Gd/Ho/AI/P, Na/Zr/Eu/T, Sr/Ho/Tm/Na, Na/Zr/Eu/Ca, Rb/Ga/Tm/Cs or La/Bi/Ce/Nd/Sr.
In other embodiments, the combination of at least four different doping elements is Sr/Sm/Ho/Tm. In other embodiments, the combination of at least four different doping elements is Na/K Mg/Tm. In other embodiments, the combination of at least four different doping elements is Na/La/Eu/ln. In other embodiments, the combination of at least four different doping elements is Na/La/Li/Cs. In other embodiments, the combination of at least four different doping elements is Li/Cs/La/Tm. In other embodiments, the combination of at least four different doping elements is Li/Cs/Sr/Tm. In other embodiments, the combination of at least four different doping elements is Li/Sr/Zn/K. In other embodiments, the combination of at least four different doping elements is Li/Ga/Cs. In other embodiments, the combination of at least four different doping elements is Li/K Sr/La. In other embodiments, the combination of at least four different doping elements is Li/Na/Rb/Ga. In other embodiments, the combination of at least four different doping elements is Li/Na/Sr/La. In other embodiments, the combination of at least four different doping elements is Ba/Sm/Yb/S. In other embodiments, the combination of at least four different doping elements is Ba/Tm/K/La. In other embodiments, the combination of at least four different doping elements is Ba/Tm/Zn/K. In other embodiments, the combination of at least four different doping elements is Cs/La/Tm/Na. In other embodiments, the combination of at least four different doping elements is Cs/Li/K/La. In other embodiments, the combination of at least four different doping elements is Sm/Li/Sr/Cs. In other embodiments, the combination of at least four different doping elements is Sr/Tm/Li/Cs. In other embodiments, the combination of at least four different doping elements is Zr/Cs/K/La. In other embodiments, the combination of at least four different doping elements is Rb/Ca/ln/Ni. In other embodiments, the combination of at least four different doping elements is Tm/Lu/Ta/P. In other embodiments, the combination of at least four different doping elements is Rb/Ca/Dy/P. In other embodiments, the combination of at least four different doping elements is Mg/La/Yb/Zn. In other embodiments, the combination of at least four different doping elements is Na/Sr/Lu/Nb. In other embodiments, the combination of at least four different doping elements is Na/Nd/ln/K. In other embodiments, the combination of at least four different doping elements is K La/Zr/Ag. In other embodiments, the combination of at least four different doping elements is Ho/Cs/Li/La. In other embodiments, the combination of at least four different doping elements is K La/Zr/Ag. In other embodiments, the combination of at least four different doping elements is Na/Sr/Eu/Ca. In other embodiments, the combination of at least four different doping elements is K Cs/Sr/La. In other embodiments, the combination of at least four different doping elements is Na/Mg/TI/P. In other embodiments, the combination of at least four different doping elements is Sr/La/Dy/S. In other embodiments, the combination of at least four different doping elements is Na/Ga/Gd/AI. In other embodiments, the combination of at least four different doping elements is Sm/Tm/Yb/Fe. In other embodiments, the combination of at least four different doping elements is Rb/Gd/Li/K. In other embodiments, the combination of at least four different doping elements is Gd/Ho/AI/P. In other embodiments, the combination of at least four different doping elements is Na/Zr/Eu/T. In other embodiments, the combination of at least four different doping elements is Sr/Ho/Tm/Na. In other embodiments, the combination of at least four different doping elements is Na/Zr/Eu/Ca. In other embodiments, the combination of at least four different doping elements is Rb/Ga/Tm/Cs. In other embodiments, the combination of at least four different doping elements is La/Bi/Ce/Nd/Sr.
In some embodiments, the oxide of a rare earth element is a mixed oxide.
In other embodiments, the oxide of a rare earth element comprises a lanthanum oxide, a neodymium oxide, a ytterbium oxide, a europium oxide, a samarium oxide, a yttrium oxide, a cerium oxide or a praseodymium oxide.
In yet other embodiments, the oxide of a rare earth element comprises Ln14-xLn2xO6, wherein Ln1 and Ln2 are each independently a lanthanide element, wherein Ln1 and Ln2 are not the same and x is a number ranging from greater than 0 to less than 4. For example, in some embodiments the rare earth oxide comprises La4-xNdxO6, wherein x is a number ranging from greater than 0 to less than 4. In even further embodiments, the rare earth oxide comprises La3NdO6, LaNd3O6, La1.5Nd2.5Oe, La2.5Nd1.5Oe, La3.2Ndo.8Oe,
La3.5Ndo.5O6, La3.8Ndo.2O6 or combinations thereof.
In yet other embodiments, the oxide of a rare earth element comprises a mixed oxide. For example, in some embodiments the mixed oxide comprises Y-La, Zr-La, Pr-La, Ce-La or combinations thereof.
In some embodiments, the rare earth oxide catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less. In other embodiments, the catalysts comprise La2O3 or
LaOy(OH)x, wherein x and y are each independently an integer from 1 to 10 doped with Na, Mg, Ca, Sr, Ga, Sc, Y, Zr, In, Nd, Eu, Sm ,Ce, Gd or
combinations thereof. In yet further embodiments, the La2O3 or LaOy(OH)x catalysts are doped with binary dopant combinations of Eu/Na; Eu/Gd; Ca/Na; Eu/Sm; Eu/Sr; Mg/Sr; Ce/Mg; Gd/Sm, Mg/Na, Mg/Y, Ga/Sr or Nd/Mg.
In other embodiments, the catalysts comprise Nd2O3 or
NdOy(OH)x, wherein x and y are each independently an integer from 1 to 10, doped with Sr, Ca, Rb, Li, Na or combinations thereof. In certain other embodiments, the Nd2O3 or NdOy(OH)x catalysts are doped with binary dopant combinations of Ca/Sr or Rb/Sr.
In still other examples of the doped catalysts, the catalysts comprise Yb2O3 or YbOy(OH)x, wherein x and y are each independently an integer from 1 to 10, doped with Sr, Ca, Ba, Nd or combinations thereof. In certain other embodiments, the Yb2O3 or YbOy(OH)x OCM catalysts are doped with a binary combination of Sr/Nd.
Still other examples of doped catalysts, the catalysts comprise EU2O3 or EuOy(OH)x, wherein x and y are each independently an integer from 1 to 10, doped with Sr, Ba, Sm or combinations thereof or a binary dopant combination of Sr/Na.
Examples of dopants for S1TI2O3 or SmOy(OH)x catalysts, wherein x and y are each independently an integer from 1 to 10, include Sr, and examples of dopants for Y2O3 or YOy(OH)x catalysts wherein x and y are each independently an integer from 1 to 10, comprise Ga, La, Nd or combinations thereof. In certain other embodiments, the Y2O3 or YOy(OH)x catalysts comprise a binary dopant combination of Sr/Nd, Eu/Y or Mg/Nd or a tertiary dopant combination of Mg/Nd/Fe.
Rare earth mixed oxide catalysts which without doping have low OCM selectivity can be greatly improved by doping to reduce their combustion activity. In particular, catalysts comprising CeO2 and Pr2O3 tend to have strong total oxidation activity for methane, however doping with additional rare earth elements can significantly moderate the combustion activity and improve the overall utility of the catalyst. Examples of dopants which improve the selectivity of the catalysts, for example the Pr2O3 or PrOy(OH)x catalysts, wherein x and y are each independently an integer from 1 to 10, comprise binary dopants of Nd/Mg, La/Mg or Yb/Sr.
In yet other embodiments of the rare earth oxide, the rare earth element may be in the form of a metal oxyhalide, a metal oxynitrate or a metal phosphate.
In still other embodiments, the present disclosure provides a catalyst comprising a mixed oxide of manganese and tungsten, wherein the catalyst further comprises a sodium dopant and at least one doping element from groups 2, 4-6, 8-15, lanthanides or combinations thereof. The catalyst may comprise a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
In further embodiments of the foregoing, the at least one doping element is Fe, Co, Ce, Cu, Ni, Sr, Ga, Zr, Pb, Zn, Cr, Pt, Al, Nb, La, Ba, Bi, Sn, In, Ru, P or combinations thereof. In this regard, all binary and ternary combinations of the foregoing dopants are contemplated. The at least one doping element may be Fe. The at least one doping element may be Co. The at least one doping element may be Ce. The at least one doping element may be Cu. The at least one doping element may be Ni. The at least one doping element may be Sr. The at least one doping element may be Ga. The at least one doping element may be Zr. The at least one doping element may be Pb. The at least one doping element may be Zn. The at least one doping element may be Cr. The at least one doping element may be Pt. The at least one doping element may be Al. The at least one doping element may be Nb. The at least one doping element may be La. The at least one doping element may be Ba. The at least one doping element may be Bi. The at least one doping element may be Sn. The at least one doping element may be In. The at least one doping element may be Ru. The at least one doping element may be P.
Applicants have also found that mixed oxides of lanthanides and tungsten are effective catalysts, for example in the OCM reaction. Accordingly, in one embodiment the disclosure provides a catalyst comprising a mixed oxide of a lanthanide and tungsten, wherein the catalyst further comprises a sodium dopant and at least one doping element from groups 2, 4-15, lanthanides or combinations thereof. In further embodiments, the catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
In other embodiments of the foregoing, the lanthanide is Ce, Pr, Nd, La, Eu, Sm or Y. In other embodiments, the at least one doping element is Fe, Co, Mn, Cu, Ni, Sr, Ga, Zr, Pb, Zn, Cr, Pt, Al, Nb, La, Ba, Bi, Sn, In, Ru, P or combinations thereof. Binary and ternary combinations of the foregoing dopants are also contemplated. The at least one doping element may be Fe. The at least one doping element may be Co. The at least one doping element may be Mn. The at least one doping element may be Cu. The at least one doping element may be Ni. The at least one doping element may be Sr. The at least one doping element may be Ga. The at least one doping element may be Zr. The at least one doping element may be Pb. The at least one doping element may be Zn. The at least one doping element may be Cr. The at least one doping element may be Pt. The at least one doping element may be Al. The at least one doping element may be Nb. The at least one doping element may be La. The at least one doping element may be Ba. The at least one doping element may be Bi. The at least one doping element may be Sn. The at least one doping element may be In. The at least one doping element may be Ru. The at least one doping element may be P.
In addition to the above compositions, the present inventors have determined that certain rare earth compositions are useful as catalysts in a number of reactions, for example the OCM reaction. In some embodiments, these lanthanide compositions comprise La2O3, Nd2O3, Yb2O3, EU2O3, S1TI2O3, Ln14-xLn2xO6, La4-xLn1 xO6, La4-xNdxO6, wherein Ln1 and Ln2 are each independently a lanthanide element, wherein Ln1 and Ln2 are not the same and x is a number ranging from greater than 0 to less than 4, La3NdO6,
LaNd3O6, La1.5Nd2.5Oe, La2.5Nd1.5Oe, La3.2Ndo.8Oe, La3.5Ndo.5Oe, La3.8Ndo.2Oe, or combinations thereof. Certain lanthanide mixed oxides such as Y-La, Zr-La, Pr- La or Ce-La are also useful as catalysts in the OCM reaction. Further,
Applicants have discovered that certain doping combinations, when combined with the above lanthanide compositions, serve to enhance the catalytic activity of the catalysts in certain catalytic reactions, for example OCM. The dopants may be present in various levels (e.g., w/w or at/at), and the catalysts may be prepared by any number of methods. Various aspects of the above lanthanide catalysts are provided in the following paragraphs and in Tables 1 -7.
As noted above, certain combinations of dopants have been found useful when combined with certain catalysts. In one embodiment, the catalyst comprises a rare earth oxide and two or more dopants, wherein the dopants are selected from Eu/Na, Sr/Na, Na/Zr/Eu/Ca, Mg/Na, Sr/Sm/Ho/Tm, Sr/W, Mg/La/K, Na/K/Mg/Tm, Na/Dy/K, Na/La/Dy, Na/La/Eu, Na/La/Eu/ln, Na/La/K, Na/La/Li/Cs, K/La, K/La/S, K/Na, Li/Cs, Li/Cs/La, Li/Cs/La/Tm,
Li/Cs/Sr/Tm, Li/Sr/Cs, Li/Sr/Zn/K, Li/Ga/Cs, Li/K/Sr/La, Li/Na, Li/Na/Rb/Ga, Li/Na/Sr, Li/Na/Sr/La, Li/Sm/Cs, Ba/Sm/Yb/S, Ba/Tm/K/La, Ba/Tm/Zn/K, Cs/K/La, Cs/La/Tm/Na, Cs/Li/K/La, Sm/Li/Sr/Cs, Sr/Cs/La, Sr/Tm/Li/Cs, Zn/K, Zr/Cs/K/La, Rb/Ca/ln/Ni, Sr/Ho/Tm, La/Nd/S, Li/Rb/Ca, Li/K, Tm/Lu/Ta/P, Rb/Ca/Dy/P, Mg/La/Yb/Zn, Rb/Sr/Lu, Na/Sr/Lu/Nb, Na/Eu/Hf, Dy/Rb/Gd,
Na/Pt/Bi, Rb/Hf, Ca/Cs, Ca/Mg/Na, Hf/Bi, Sr/Sn, Sr/W, Sr/Nb, Zr/W, Y/W, Na/W, Bi/W, Bi/Cs, Bi/Ca, Bi/Sn, Bi/Sb, Ge/Hf, Hf/Sm, Sb/Ag, Sb/Bi, Sb/Au, Sb/Sm, Sb/Sr, Sb/W, Sb/Hf, Sb/Yb, Sb/Sn, Yb/Au, Yb/Ta, Yb/W, Yb/Sr, Yb/Pb, Yb/W, Yb/Ag, Au/Sr, W/Ge, Ta/Hf, W/Au, Ca/W, Au/Re, Sm/Li, La/K, Zn/Cs, Na/K/Mg, Zr/Cs, Ca/Ce, Na/Li/Cs, Li/Sr, Cs/Zn, La/Dy/K, Dy/K, La/Mg, Na/Nd/ln/K, In/Sr, Sr/Cs, Rb/Ga/Tm/Cs, Ga/Cs, K/La/Zr/Ag, Lu/Fe, Sr/Tm, La/Dy, Sm/Li/Sr, Mg/K, Li/Rb/Ga, Li/Cs/Tm, Zr/K, Li/Cs, Li/K/La, Ce/Zr/La, Ca/AI/La, Sr/Zn/La,
Sr/Cs/Zn, Sm/Cs, In/K, Ho/Cs/Li/La, Cs/La/Na, La/S/Sr, K/La/Zr/Ag, Lu/TI, Pr/Zn, Rb/Sr/La, Na/Sr/Eu/Ca, K Cs/Sr/La, Na/Sr/Lu, Sr/Eu/Dy, Lu/Nb,
La/Dy/Gd, Na/Mg/TI/P, Na/Pt, Gd/Li/K, Rb/K Lu, Sr/La/Dy/S, Na/Ce/Co, Na/Ce, Na/Ga/Gd/AI, Ba/Rh/Ta, Ba/Ta, Na/AI/Bi, Cs/Eu/S, Sm/Tm/Yb/Fe, Sm/Tm/Yb, Hf/Zr/Ta, Rb/Gd/Li/K, Gd/Ho/AI/P, Na/Ca/Lu, Cu/Sn, Ag/Au, Al/Bi, Al/Mo, Al/Nb, Au/Pt, Ga/Bi, Mg/W, Pb/Au, Sn/Mg, Zn/Bi, Gd/Ho, Zr/Bi, Ho/Sr, Gd/Ho/Sr, Ca/Sr, Ca/Sr/W, Na/Zr/Eu/Tm, Sr/Ho/Tm/Na, Sr/Pb, Sr/W/Li, Ca/Sr/W and Sr/Hf.
In other embodiments of the foregoing rare earth oxide, the dopant is selected from Cs/Eu/S, Sm/Tm/Yb/Fe, Sm/Tm/Yb, Hf/Zr/Ta,
Rb/Gd/Li/K, Gd/Ho/AI/P, Na/Ca/Lu, Cu/Sn, Ag/Au, Al/Bi, Al/Mo, Al/Nb, Au/Pt, Ga/Bi, Mg/W, Pb/Au, Sn/Mg, Zn/Bi, Gd/Ho, Zr/Bi, Ho/Sr, Gd/Ho/Sr, Ca/Sr, Ca/Sr/W, Na/Zr/Eu/Tm, Sr/Ho/Tm/Na, Sr/Pb, Ca, Sr/W/Li, Ca/Sr/W, Sr/Hf, Eu/Na, Sr/Na, Na/Zr/Eu/Ca, Mg/Na, Sr/Sm/Ho/Tm, Sr/W, Mg/La/K,
Na/K Mg/Tm, Na/Dy/K, Na/La/Dy, Na/La/Eu, Na/La/Eu/ln, Na/La/K,
Na/La/Li/Cs, K La, K La/S, K Na, Li/Cs, Li/Cs/La, Li/Cs/La/Tm, Li/Cs/Sr/Tm, Li/Sr/Cs, Li/Sr/Zn/K, Li/Ga/Cs, Li/K Sr/La, Li/Na, Li/Na/Rb/Ga and Li/Na/Sr.
In still other embodiments of the rare earth oxide, the dopant is selected from Li/Na/Sr/La, Li/Sm/Cs, Ba/Sm/Yb/S, Ba/Tm/K La, Ba/Tm/Zn/K, Cs/K La, Cs/La/Tm/Na, Cs/Li/K La, Sm/Li/Sr/Cs, Sr/Cs/La, Sr/Tm/Li/Cs, Zn/K, Zr/Cs/K La, Rb/Ca/ln/Ni, Sr/Ho/Tm, La/Nd/S, Li/Rb/Ca, Li/K, Tm/Lu/Ta/P, Rb/Ca/Dy/P, Mg/La/Yb/Zn, Rb/Sr/Lu, Na/Sr/Lu/Nb, Na/Eu/Hf, Dy/Rb/Gd, Na/Pt/Bi, Rb/Hf, Ga/Cs, K/La/Zr/Ag, Lu/Fe, Sr/Tm, La/Dy, Sm/Li/Sr, Mg/K, Li/Rb/Ga, Li/Cs/Tm, Zr/K, Li/Cs, Li/K/La, Ce/Zr/La, Ca/AI/La, Sr/Zn/La,
Sr/Cs/Zn, Sm/Cs, In/K, Ho/Cs/Li/La, Cs/La/Na, La/S/Sr, K/La/Zr/Ag, Lu/TI, Pr/Zn, Rb/Sr/La, Na/Sr/Eu/Ca, K Cs/Sr/La, Na/Sr/Lu, Sr/Eu/Dy, Lu/Nb,
La/Dy/Gd, Na/Mg/TI/P, Na/Pt, Gd/Li/K, Rb/K Lu, Sr/La/Dy/S, Na/Ce/Co, Na/Ce, Na/Ga/Gd/AI, Ba/Rh/Ta, Ba/Ta, Na/AI/Bi, Cs/Eu/S, Sm/Tm/Yb/Fe, Sm/Tm/Yb, Hf/Zr/Ta, Rb/Gd/Li/K, Gd/Ho/AI/P and Na/Ca/Lu.
In still other embodiments of the foregoing rare earth oxide, the dopant is selected from Ta/Hf, W/Au, Ca/W, Au/Re, Sm/Li, La/K, Zn/Cs, Na/K/Mg, Zr/Cs, Ca/Ce, Na/Li/Cs, Li/Sr, Cs/Zn, La/Dy/K, Dy/K, La/Mg,
Na/Nd/ln/K, In/Sr, Sr/Cs, Rb/Ga/Tm/Cs, Ga/Cs, K/La/Zr/Ag, Lu/Fe, Sr/Tm, La/Dy, Sm/Li/Sr, Mg/K, Li/Rb/Ga, Li/Cs/Tm, Zr/K, Li/Cs, Li/K/La, Ce/Zr/La, Ca/AI/La, Sr/Zn/La, Sr/Cs/Zn, Sm/Cs, In/K, Ho/Cs/Li/La, Cs/La/Na, La/S/Sr, K/La/Zr/Ag, Lu/TI, Pr/Zn, Rb/Sr/La, Na/Sr/Eu/Ca, K/Cs/Sr/La, Na/Sr/Lu,
Sr/Eu/Dy, Lu/Nb, La/Dy/Gd, Na/Mg/TI/P, Na/Pt, Gd/Li/K, Li/Sr/Cs, Li/Sr/Zn/K, Li/Ga/Cs, Li/K/Sr/La, Li/Na, Li/Na/Rb/Ga, Li/Na/Sr, Li/Na/Sr/La, Li/Sm/Cs, Ba/Sm/Yb/S, Ba/Tm/K/La, Ba/Tm/Zn/K, Cs/K/La, Cs/La/Tm/Na, Cs/Li/K/La, Sm/Li/Sr/Cs, Sr/Cs/La, Sr/Tm/Li/Cs, Zn/K, Zr/Cs/K/La, Rb/Ca/ln/Ni, Sr/Ho/Tm, La/Nd/S, Li/Rb/Ca, Li/K, Tm/Lu/Ta/P, Rb/Ca/Dy/P, Mg/La/Yb/Zn, Rb/Sr/Lu, Na/Sr/Lu/Nb, Na/Eu/Hf, Dy/Rb/Gd, Na/Pt/Bi, Rb/Hf, Ca/Cs, Ca/Mg/Na, Hf/Bi, Sr/Sn, Sr/W, Sr/Nb, Zr/W, Y/W, Na/W, Bi/W, Bi/Cs, Bi/Ca, Bi/Sn, Bi/Sb, Ge/Hf, Hf/Sm, Sb/Ag, Sb/Bi, Sb/Au, Sb/Sm, Sb/Sr, Sb/W, Sb/Hf, Sb/Yb, Sb/Sn, Yb/Au, Yb/Ta, Yb/W, Yb/Sr, Yb/Pb, Yb/W, Yb/Ag, Au/Sr and W/Ge.
In various embodiments of the foregoing rare earth oxides, the catalysts comprise La2O3, Nd2O3, Yb2O3, EU2O3, Y2O3, Ce2O3, Pr2O3 Sm2O3, Ln14-xLn2xO6, La4-xLn1 xO6, La4-xNdxO6, wherein Ln1 and Ln2 are each independently a lanthanide element, wherein Ln1 and Ln2 are not the same and x is a number ranging from greater than 0 to less than 4, La3NdO6,
LaNd3O6, La1.5Nd2.5Oe, La2.5Nd1.5Oe, La3.2Ndo.8Oe, La3.5Ndo.5Oe, La3.8Ndo.2Oe, Y- La, Zr-La, Pr-La or Ce-La or combinations thereof. In other various
embodiments, the rare earth oxide catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the rare earth oxide catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less. In other embodiments, the catalysts comprise La2O3, Yb2O3, Nd2O3, E112O3, Sm2O3, Y2O3, 1_η14-χΙ_η2χΟ6, La4-xLn1 xO6, La4-xNdxO6, wherein Ln1 and Ln2 are each independently a lanthanide element, wherein Ln1 and Ln2 are not the same and x is a number ranging from greater than 0 to less than 4, La3NdO6, LaNd3O6, La1.5Nd2.5Oe, La2.5Nd1.5Oe, La3.2Ndo.8Oe,
La3.5Ndo.5O6, La3.8Ndo.2O6, Y-La, Zr-La, Pr-La or Ce-La doped with Sr/Ta, for example in some embodiments the catalysts comprise Sr Ta La2O3,
Sr/Ta/Yb2O3, Sr/Ta/Nd2O3, Sr/Ta/Eu2O3, Sr/Ta/Sm2O3, Sr/Ta/Ln14-xLn2xO6, Sr/Ta/La4-xLn1 xO6, Sr/Ta/La4-xNdxO6, Sr/Ta/La3NdO6, Sr/Ta/LaNd3O6,
Sr/Ta/Lai.5Nd2.5O6, Sr/Ta/La2.5Ndi.5O6, Sr/Ta/La3.2Nd0.8O6, Sr/Ta/Las.sNdo.sOe, Sr/Ta/La3.8Ndo.2O6, Sr/Ta/Y-La, Sr/Ta/Zr-La, Sr/Ta/Pr-La or Sr/Ta/Ce-La or combinations thereof. In other embodiments, the catalysts comprise Ln1 - xLn2xO6, La4-xLn1 xO6, La4-xNdxO6, wherein Ln1 and Ln2 are each independently a lanthanide element, wherein Ln1 and Ln2 are not the same and x is a number ranging from greater than 0 to less than 4, La3NdO6, LaNd3O6, La1.5Nd2.5O6, La2.5Nd1.5Oe, La3.2Ndo.8Oe, La3.5Ndo.5Oe, La3.8Ndo.2Oe, Y-La, Zr-La, Pr-La or Ce- La doped with Na, Sr, Ca, Yb, Cs, Sb, or combinations thereof, for example the catalysts may comprise Na/Ln14-xLn2xO6, Sr/Ln14-xLn2xO6, Ca/Ln14-xLn2xO6, Yb/Ln14-xLn2xO6, Cs/Ln14-xLn2xO6, Sb/Ln14-xLn2xO6, Na/La4-xLn1 xO6,
Na/La3NdO6, Sr/La4-xLn1 xO6, Ca/La4-xLn1 xO6, Yb/La4-xLn1 xO6, Cs/La4-xLn1 xO6, Sb/La4-xLn1 xO6, Na/La4-xNdxO6, Sr/La4-xNdxO6, Ca/La4-xNdxO6, Yb/La4-xNdxO6, Cs La4-xNdxO6, Sb/La4-xNdxO6, Na/La3NdO6, Na/LaNd3O6, Na/Lai.5Nd2.5O6, Na La2.5Ndi.5O6, Na/La3.2Ndo.8O6, Na La3.5Ndo.5O6, Na La3.8Ndo.2O6, Na/Y-La, Na/Zr-La, Na/Pr-La, Na/Ce-La, Sr/La3NdO6, Sr/LaNd3O6, Sr/Lai.5Nd2.5O6, Sr/La2.5Ndi.5O6, Sr/La3.2Ndo.8O6, Sr/Las.sNdo.sOe, Sr/La3.8Ndo.2O6, Sr/Y-La, Sr/Zr-La, Sr/Pr-La, Sr/Ce-La, Ca/La3NdO6, Ca/LaNd3O6, Ca/Lai.5Nd2.5O6, Ca/La2.5Ndi.5O6, Ca/La3.2Ndo.8O6, Ca/Las.sNdo.sOe, Ca/La3.8Ndo.2O6, Ca/Y-La, Ca/Zr-La, Ca/Pr-La, Ca/Ce-La, Yb/La3NdO6, Yb/LaNd3O6, Yb/Lai.5Nd2.5O6, Yb/La2.5Ndi.5O6, Yb/La3.2Nd0.8O6, Yb/Las.sNdo.sOe, Yb/La3.8Ndo.2O6, YbA'-La, Yb/Zr-La, Yb/Pr-La, Yb/Ce-La, Cs/La3NdO6 LaNd3O6, Cs/Lai.5Nd2.5O6, Cs/LazsNcksOe, Cs/La^Ndo.eOe, Cs/Las.sNdo.sOe, Cs/La3.8Ndo.2O6, Cs/Y-La, Cs/Zr-La, Cs/Pr-La, Cs/Ce-La, Sb/La3NdO6, Sb/LaNd3O6, Sb/Lai.sNdzsOe, Sb/Laz5Ndi.506> Sb/La3.2Ndo.8O6j Sb/Las.sNdo.sOe, Sb/La3.8Ndo.2O6, Sb/Y-La, Sb/Zr-La, Sb/Pr-La, Sb/Ce-La or combinations thereof.
In other embodiments, the catalysts comprise a mixed oxide selected from a Y-La mixed oxide doped with Na. (Y ranges from 5 to 20% of La at/at); a Zr-La mixed oxide doped with Na (Zr ranges from 1 to 5% of La at/at); a Pr-La mixed oxide doped with a group 1 element (Pr ranges from 2 to 6% of La at/at); and a Ce-La mixed oxide doped with a group 1 element (Ce ranges from 5 to 20% of La at/at). As used herein, the notation "M1 -M2", wherein M1 and M2 are each independently metals refers to a mixed metal oxide comprising the two metals. M1 and M2 may be present in equal or different amounts (at/at).
In still other embodiments, the catalysts comprise a mixed oxide of a rare earth element and a Group 13 element, wherein the catalyst further comprises one or more Group 2 elements. In certain embodiments of the foregoing, the Group 13 element is B, Al, Ga or In. In other embodiments, the Group 2 element is Ca or Sr. In still other embodiments, the rare earth element is La, Y, Nd, Yb, Sm, Pr, Ce or Eu.
Specific examples of the foregoing include, but are not limited to
CaLnBOx, CaLnAIOx, CaLnGaOx, CaLnlnOx, CaLnAISrOx and CaLnAISrOx, wherein Ln is a lanthanide or yttrium and x is number such that all charges are balanced. For example, in some embodiments the catalyst comprises
CaLaBO4, CaLaAIO4, CaLaGaO4, CaLalnO4, CaLaAISrO5, CaLaAISrO5, CaNdBO4, CaNdAIO4, CaNdGaO4, CaNdlnO4, CaNdAISrO4, CaNdAISrO4, CaYbBO4, CaYbAIO4, CaYbGaO4, CaYblnO4, CaYbAISrO5, CaYbAISrO5, CaEuBO4, CaEuAIO4, CaEuGaO4, CaEulnO4, CaEuAISrO5, CaEuAISrO5, CaSmBO4, CaSmAIO4, CaSmGaO4, CaSmlnO4, CaSmAISrO5, CaSmAISrO5, CaYBO4, CaYAIO4, CaYGaO4, CaYlnO4, CaYAISrO5, CaYAISrO5, CaCeBO4, CaCeAIO4, CaCeGaO4, CaCelnO4, CaCeAISrO5, CaCeAISrO5, CaPrBO4, CaPrAIO4, CaPrGaO4, CaPrlnO4, CaPrAISrO5 or CaPrAISrO5.
Furthermore, the present inventors have discovered that lanthanide oxides doped with alkali metals and/or alkaline earth metals and at least one other dopant selected from Groups 3-16 have desirable catalytic properties and are useful in a variety of catalytic reactions, such as OCM.
Accordingly, in one embodiment the catalysts comprise a lanthanide oxide doped with an alkali metal, an alkaline earth metal or combinations thereof, and at least one other dopant from groups 3-16. In some embodiments, the catalyst comprises a lanthanide oxide, an alkali metal dopant and at least one other dopant selected from Groups 3-16. In other embodiments, the catalyst comprises a lanthanide oxide, an alkaline earth metal dopant and at least one other dopant selected from Groups 3-16.
In some more specific embodiments of the foregoing, the catalyst comprises a lanthanide oxide, a lithium dopant and at least one other dopant selected from Groups 3-16. In still other embodiments, the catalyst comprises a lanthanide oxide, a sodium dopant and at least one other dopant selected from Groups 3-16. In other embodiments, the catalyst comprises a lanthanide oxide, a potassium dopant and at least one other dopant selected from Groups 3-16. In other embodiments, the catalyst comprises a lanthanide oxide, a rubidium dopant and at least one other dopant selected from Groups 3-16. In more embodiments, the catalyst comprises a lanthanide oxide, a caesium dopant and at least one other dopant selected from Groups 3-16.
In still other embodiments of the foregoing, the catalyst comprises a lanthanide oxide, a beryllium dopant and at least one other dopant selected from Groups 3-16. In other embodiments, the catalyst comprises a lanthanide oxide, a magnesium dopant and at least one other dopant selected from
Groups 3-16. In still other embodiments, the catalyst comprises a lanthanide oxide, a calcium dopant and at least one other dopant selected from Groups 3- 16. In more embodiments, the catalyst comprises a lanthanide oxide, a strontium dopant and at least one other dopant selected from Groups 3-16. In more embodiments, the catalyst comprises a lanthanide oxide, a barium dopant and at least one other dopant selected from Groups 3-16.
In some embodiments of the foregoing lanthanide oxide catalysts, the catalysts comprise La2O3, Nd2O3, Yb2O3, Eu2O3, Sm2O3, Ln14-xLn2xO6, La4- χΙ_η1 χθ6, La4-xNdxO6, wherein Ln1 and Ln2 are each independently a lanthanide element, wherein Ln1 and Ln2 are not the same and x is a number ranging from greater than 0 to less than 4, La3NdO6, LaNd3O6, Lai.5Nd2.5O6,
La2.5Ndi.5O6, La3.2Ndo.eO6, La3.5Ndo.5Oe, La3.8Ndo.2O6, Y-La, Zr-La, Pr-La or Ce- La or combinations thereof. In other various embodiments, the lanthanide oxide catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the lanthanide oxide catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a
temperature of 750 °C or less.
In various embodiments, of any of the above catalysts, the catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a
heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less, 700 °C or less, 650 °C or less or even 600 °C or less.
In more embodiments, of any of the above catalysts, the catalyst comprises a C2 selectivity of greater than 50%, greater than 55%, greater than 60%, greater than 65%, greater than 70%, or even greater than 75%, and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
In other embodiments, of any of the above catalysts, the catalyst comprises a C2 selectivity of greater than 50%, and a methane conversion of greater than 20%, greater than 25%, greater than 30%, greater than 35%, greater than 40%, greater than 45%, or even greater than 50% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less. In some embodiments of the foregoing, the methane conversion and C2 selectivity are calculated based on a single pass basis (i.e., the percent of methane converted or C2 selectivity upon a single pass over the catalyst or catalytic bed, etc.)
The metal oxides disclosed herein can be in the form of oxides, oxyhydroxides, hydroxides, oxycarbonates or combination thereof after being exposed to moisture, carbon dioxide, undergoing incomplete calcination or combination thereof.
The foregoing doped catalysts comprise 1 , 2, 3, 4 or more doping elements. In this regard, each dopant may be present in the catalysts (for example any of the catalysts described above and/or disclosed in Tables 1 -8) in up to 75% by weight of the catalyst. For example, in one embodiment the concentration of a first doping element ranges from 0.01 % to 1 % w/w, 1 %-5% w/w, 5%-10% w/w. 10%-20% w/w, 20%-30% w/w, 30%-40% w/w or 40%-50% w/w, for example about 1 % w/w, about 2 % w/w, about 3% w/w, about 4% w/w, about 5% w/w, about 6% w/w, about 7% w/w, about 8% w/w, about 9% w/w, about 10 %w/w, about 1 1 % w/w, about 12% w/w, about 13% w/w, about 14% w/w, about 15% w/w, about 16% w/w, about 17% w/w, about 18% w/w, about 19% w/w or about 20% w/w.
In other embodiments, the concentration of a second doping element (when present) ranges from 0.01 % to 1 % w/w, 1 %-5% w/w, 5%-10% w/w. 10%-20% w/w, 20%-30% w/w, 30%-40% w/w or 40%-50% w/w, for example about 1 % w/w, about 2 % w/w, about 3% w/w, about 4% w/w, about 5% w/w, about 6% w/w, about 7% w/w, about 8% w/w, about 9% w/w, about 10 %w/w, about 1 1 % w/w, about 12 % w/w, about 13% w/w, about 14% w/w, about 15% w/w, about 16% w/w, about 17% w/w, about 18% w/w, about 19% w/w or about 20% w/w.
In other embodiments, the concentration of a third doping element (when present) ranges from 0.01 % to 1 % w/w, 1 %-5% w/w, 5%-10% w/w. 10%- 20% w/w, 20%-30% w/w, 30%-40% w/w or 40%-50% w/w, for example about I % w/w, about 2 % w/w, about 3% w/w, about 4% w/w, about 5% w/w, about 6% w/w, about 7% w/w, about 8% w/w, about 9 % w/w, about 10 % w/w, about
I I % w/w, about 12 % w/w, about 13% w/w, about 14% w/w, about 15% w/w, about 16% w/w, about 17% w/w, about 18% w/w, about 19% w/w or about 20% w/w.
In other embodiments, the concentration of a fourth doping element (when present) ranges from 0.01 % to 1 % w/w, 1 %-5% w/w, 5%-10% w/w. 10%-20% w/w, 20%-30% w/w, 30%-40% w/w or 40%-50% w/w, for example about 1 % w/w, about 2 % w/w, about 3% w/w, about 4% w/w, about 5% w/w, about 6% w/w, about 7% w/w, about 8% w/w, about 9% w/w, about 10% w/w, about 1 1 % w/w, about 12 % w/w, about 13% w/w. about 14% w/w, about 15% w/w, about 16% w/w, about 17% w/w, about 18% w/w, about 19% w/w or about 20% w/w.
In other embodiments, the concentration of the dopant is measured in terms of atomic percent (at/at). In some of these embodiments, each dopant may be present in the catalysts (for example any of the catalysts described above and/or disclosed in Tables 1 -8) in up to 75% at/at. For example, in one embodiment the concentration of a first doping element ranges from 0.01 % to 1 % at/at, 1 %-5% at/at, 5%-10% at/at. 10%-20% at/at, 20%-30% at/at, 30%-40% at/at or 40%-50% at/at, for example about 1 % at/at, about 2% at/at, about 3% at/at, about 4% at/at, about 5% at/at, about 6% at/at, about 7% at/at, about 8% at/at, about 9% at/at, about 10% at/at, about 1 1 % at/at, about 12% at/at, about 13% at/at, about 14% at/at, about 15% at/at, about 16% at/at, about 17% at/at, about 18% at/at, about 19% at/at or about 20% at/at.
In other embodiments, the concentration of a second doping element (when present) ranges from 0.01 % to 1 % at/at, 1 %-5% at/at, 5%-10% at/at. 10%-20% w/w, 20%-30% at/at, 30%-40% at/at or 40%-50% at/at, for example about 1 % at/at, about 2 % at/at, about 3% at/at, about 4% at/at, about 5% at/at, about 6% at/at, about 7% at/at, about 8% at/at, about 9 % at/at, about 10% at/at, about 1 1 % at/at, about 12 % at/at, about 13% at/at, about 14% at/at, about 15% at/at, about 16% at/at, about 17% at/at, about 18% at/at, about 19% at/at or about 20% at/at.
In other embodiments, the concentration of a third doping element (when present) ranges from 0.01 %to 1 % at/at, 1 %-5% at/at, 5%-10% at/at. 10%-20% w/w, 20%-30% at/at, 30%-40% at/at or 40%-50% at/at, for example about 1 % at/at, about 2 % at/at, about 3% at/at, about 4% at/at, about 5% at/at, about 6% at/at, about 7% at/at, about 8% at/at, about 9 % at/at, about 10% at/at, about 1 1 % at/at, about 12% at/at, about 13% at/at, about 14% at/at, about 15% at/at, about 16% at/at, about 17% at/at, about 18% at/at, about 19% at/at or about 20% at/at.
In other embodiments, the concentration of a fourth doping element (when present) ranges from 0.01 % to 1 % at/at, 1 %-5% at/at, 5%-10% at/at. 10%-20% w/w, 20%-30% at/at, 30%-40% at/at or 40%-50% at/at, for example about 1 % at/at, about 2 % at/at, about 3% at/at, about 4% at/at, about 5% at/at, about 6% at/at, about 7% at/at, about 8% at/at, about 9 % at/at, about 10% at/at, about 1 1 % at/at, about 12% at/at, about 13% at/at, about 14% at/at, about 15% at/at, about 16% at/at, about 17% at/at, about 18% at/at, about 19% at/at or about 20% at/at.
Accordingly, any of the doped catalysts described above or in Tables 1 -8, may comprise any of the foregoing doping concentrations.
Furthermore, different catalytic characteristics of the above doped catalysts can be varied or "tuned" based on the method used to prepare them. Such methods are described in more detail herein and other methods are known in the art. In addition, the above dopants may be incorporated either before or after (or combinations thereof) an optional calcination step as described herein.
Tables 1 -8 below show exemplary doped catalysts in accordance with various specific embodiments. Dopants are shown in the vertical columns and base catalyst in the horizontal rows. The resulting doped catalysts are shown in the intersecting cells. TABLE 1 -CATALYSTS (CAT) DOPED WITH SPECIFIC DOPANTS (DOP)
Figure imgf000067_0001
Figure imgf000068_0001
Figure imgf000069_0001
Figure imgf000070_0001
Figure imgf000071_0001
Figure imgf000072_0001
Figure imgf000073_0001
Figure imgf000074_0001
Figure imgf000075_0001
Figure imgf000076_0001
Figure imgf000077_0001
Figure imgf000078_0001
Figure imgf000079_0001
Figure imgf000080_0001
Figure imgf000081_0001
Figure imgf000082_0001
Figure imgf000083_0001
Figure imgf000084_0001
Figure imgf000085_0001
Figure imgf000086_0001
TABLE 2 -CATALYSTS (CAT) DOPED WITH SPECIFIC DOPANTS (DOP)
Figure imgf000086_0002
Figure imgf000087_0001
Figure imgf000088_0001
Figure imgf000089_0001
Figure imgf000090_0001
Figure imgf000091_0001
Figure imgf000092_0001
Figure imgf000093_0001
Figure imgf000094_0001
Figure imgf000095_0001
Figure imgf000096_0001
Figure imgf000097_0001
Figure imgf000098_0001
Figure imgf000099_0001
Figure imgf000100_0001
Figure imgf000101_0001
Figure imgf000102_0001
Figure imgf000103_0001
Figure imgf000104_0001
Figure imgf000105_0001
Figure imgf000106_0001
TABLE 3 -CATALYSTS (CAT) DOPED WITH SPECIFIC DOPANTS (DOP)
Figure imgf000106_0002
Figure imgf000107_0001
Figure imgf000108_0001
Figure imgf000109_0001
Figure imgf000110_0001
Figure imgf000111_0001
Figure imgf000112_0001
Figure imgf000113_0001
Figure imgf000114_0001
Figure imgf000115_0001
Figure imgf000116_0001
Figure imgf000117_0001
Figure imgf000118_0001
Figure imgf000119_0001
Figure imgf000120_0001
Figure imgf000121_0001
Figure imgf000122_0001
Figure imgf000123_0001
Figure imgf000124_0001
Figure imgf000125_0001
TABLE 4 -CATALYSTS (CAT) DOPED WITH SPECIFIC DOPANTS (DOP)
Figure imgf000126_0001
Figure imgf000127_0001
Figure imgf000128_0001
Figure imgf000129_0001
Figure imgf000130_0001
Figure imgf000131_0001
Figure imgf000132_0001
Figure imgf000133_0001
Figure imgf000134_0001
Figure imgf000135_0001
Figure imgf000136_0001
Figure imgf000137_0001
Figure imgf000138_0001
Figure imgf000139_0001
Figure imgf000140_0001
Figure imgf000141_0001
Figure imgf000142_0001
Figure imgf000143_0001
Figure imgf000144_0001
Figure imgf000145_0001
-CATALYSTS (CAT) DOPED WITH SPECIFIC DOPANTS (DOP)
Figure imgf000145_0002
Figure imgf000146_0001
Figure imgf000147_0001
Figure imgf000148_0001
Figure imgf000149_0001
Figure imgf000150_0001
TABLE 6-CATALYSTS (CAT) DOPED WITH SPECIFIC DOPANTS (DOP)
Figure imgf000150_0002
Figure imgf000151_0001
Figure imgf000152_0001
TABLE 7-CATALYSTS (CAT) DOPED WITH SPECIFIC DOPANTS (DOP)
Figure imgf000153_0001
Figure imgf000154_0001
Figure imgf000155_0001
TABLE 8-CATALYSTS (CAT) DOPED WITH SPECIFIC DOPANTS (DOP)
Figure imgf000156_0001
Figure imgf000157_0001
Figure imgf000158_0001
The catalysts of the disclosure may be analyzed by inductively coupled plasma mass spectrometry (ICP-MS) to determine the element content of the catalysts. ICP-MS is a type of mass spectrometry that is highly sensitive and capable of the determination of a range of metals and several non-metals at concentrations below one part in 1012. ICP is based on coupling together an inductively coupled plasma as a method of producing ions (ionization) with a mass spectrometer as a method of separating and detecting the ions. ICP-MS methods are well known in the art.
As used throughout the specification, a catalyst composition represented by E1/E2/E3, etc., wherein E1 , E2 and E3 are each independently an element or a compound comprising one or more elements, refers to a catalyst comprised of a mixture of E1, E2 and E3. E1 , E2 and E3, etc., are not necessarily present in equal amounts and need not form a bond with one another. For example, a catalyst comprising Li/MgO refers to a catalyst comprising Li and MgO, for example, Li/MgO may refer to MgO doped with Li. By way of another example, a catalyst comprising Na/Mn/W/O refers to a catalyst comprised of a mixture of sodium, manganese, tungsten and oxygen. Generally the oxygen is in the form of a metal oxide.
In some embodiments, dopants are present in the catalysts in, for example, less than 50 at%, less than 25 at%, less than 10 at%, less than 5 at% or less than 1 at%.
In other embodiments of the catalysts, the weight ratio (w/w) of the catalyst base material to the doping element(s) ranges from 1 :1 to 10,000:1 , 1 :1 to 1 ,000:1 or 1 :1 to 500:1 . 2. Catalytic Materials
The present disclosure includes a catalytic material comprising a plurality of catalysts. In certain embodiments, the catalytic material comprises a support or carrier. Supports and carriers useful in the context of the invention are not limited and include supports and carriers described herein as well as those known in the art, for example as described in U.S. Application Nos. 13/1 15,082 (U.S. Pub. No. 2012/0041246), 13/689,514 (U.S. Pub. No.
2013/0158322), 13/689,61 1 (U.S. Pub. No. 2013/0165728) and 13/901 ,319 (corresponding to PCT Pub. No. WO 2013/177461 ), the full disclosures of which are hereby incorporated by reference in their entireties.
The support is preferably porous and has a high surface area. In some embodiments the support is active (i.e., has catalytic activity). In other embodiments, the support is inactive (i.e., non-catalytic). In some
embodiments, the support comprises an inorganic oxide, AI2O3, SiO2, ΤΊΟ2, MgO, CaO, SrO, ZrO2, ZnO, LiAIO2, MgAI2O4, MnO, MnO2, Mn3O4, La2O3, AIPO4, SiO2/AI2O3, activated carbon, silica gel, zeolites, activated clays, activated AI2O3, SiC, diatomaceous earth, magnesia, aluminosilicates, calcium aluminate, support nanowires or combinations thereof. In some embodiments the support comprises silicon, for example SiO2. In other embodiments the support comprises magnesium, for example MgO. In yet other embodiments, the support comprises yttrium, for example Y2O3. In other embodiments the support comprises zirconium, for example ZrO2. In yet other embodiments, the support comprises lanthanum, for example La2O3. In yet other embodiments, the support comprises lanthanum, for example La2O3. In yet other
embodiments, the support comprises hafnium, for example HfO2. In yet other embodiments, the support comprises aluminum, for example AI2O3. In yet other embodiments, the support comprises gallium, for example Ga2O3.
In still other embodiments, the support material comprises an inorganic oxide, AI2O3, SiO2, TiO2, MgO, ZrO2, HfO2, CaO, SrO, ZnO, LiAIO2, MgAI2O4, MnO, MnO2, Mn2O4, Mn3O4, La2O3, AIPO4, activated carbon, silica gel, zeolites, activated clays, activated AI2O3, diatomaceous earth, magnesia, aluminosilicates, calcium aluminate, support nanowires or combinations thereof. In yet other embodiments, a catalyst may serve as a support for another catalyst. For example, a catalyst may be comprised of catalytic support material and adhered to or incorporated within the support is another catalyst. For example, in some embodiments, the catalytic support may comprise S1O2, MgO, T1O2, ZrO2, AI2O3, ZnO or combinations thereof.
In still other embodiments, the support material comprises a carbonate. For example, in some embodiments the support material comprises MgCOs, CaCO3, SrCO3, BaCO3, Y2(CO3)3, La2(CO3)3 or combinations thereof.
In yet other embodiments, a nanowire may serve as a support for another bulk or nanowire catalyst. For example, a nanowire may be comprised of non-catalytic metal elements and adhered to or incorporated within the support nanowire is a catalyst as described herein. For example, in some embodiments, the support nanowires are comprised of SiO2, MgO, CaO, SrO, TiO2, ZrO2, AI2O3, ZnO MgCO3, CaCO3, SrCO3 or combinations thereof. The optimum amount of catalyst present on the support depends, inter alia, on the catalytic activity of the catalyst. In some embodiments, the amount of catalyst present on the support ranges from 1 to 100 parts by weight of catalyst per 100 parts by weight of support or from 10 to 50 parts by weight of catalyst per 100 parts by weight of support. In other embodiments, the amount of catalyst present on the support ranges from 100-200 parts of catalyst per 100 parts by weight of support, or 200-500 parts of catalyst per 100 parts by weight of support, or 500-1000 parts of catalyst per 100 parts by weight of support.
Typically, heterogeneous catalysts are used either in their pure form or blended with inert materials, such as silica, alumina, etc. The blending with inert materials is used in order to reduce and/or control large temperature non- uniformities within the reactor bed often observed in the case of strongly exothermic (or endothermic) reactions. In the case of complex multistep reactions, such as the reaction to convert methane into ethylene (OCM), typical blending materials can selectively slow down or quench one or more of the reactions of the system and promote unwanted side reactions. For example, in the case of the oxidative coupling of methane, silica and alumina can quench the methyl radicals and thus prevent the formation of ethane. In certain aspects, the present disclosure provides a catalytic material which solves these problems typically associated with catalyst support material. Accordingly, in certain embodiments the catalytic activity of the catalytic material can be tuned by blending two or more catalysts and/or catalyst support materials. The blended catalytic material may comprise a catalyst as described herein in combination with another catalytic material, for example an additional bulk catalyst or a catalytic nanowire as described in PCT Pub. Nos. WO
201 1/14996; WO 2013/082318 and WO 2012/162526 which are hereby incorporated by reference in their entireties, and/or inert support material.
The blended catalytic materials comprise metal oxides, hydroxides, oxy-hydroxides, carbonates, oxalates of the groups 1 -16, lanthanides, actinides or combinations thereof. For example, the blended catalytic materials may comprise a plurality of catalysts, as disclosed herein, and any one or more of straight nanowires, nanoparticles, bulk materials and inert support materials. The catalytic materials may be undoped or may be doped with any of the dopants described herein.
In one embodiment, the catalyst blend comprises at least one type 1 component and at least one type 2 component. Type 1 components comprise catalysts having a high OCM activity at moderately low temperatures and type 2 components comprise catalysts having limited or no OCM activity at these moderately low temperatures, but are OCM active at higher
temperatures. For example, in some embodiments the type 1 component is a catalyst having high OCM activity at moderately low temperatures. For example, the type 1 component may comprise a C2 yield of greater than 5% or greater than 10% at temperatures less than 800°C, less than 700°C or less than 600°C. The type 2 component may comprise a C2 yield less than 0.1 %, less than 1 % or less than 5% at temperatures less than 800°C, less than 700°C or less than 600°C. The type 2 component may comprise a C2 yield of greater than 0.1 %, greater than 1 %, greater than 5% or greater than 10% at
temperatures greater than 800°C, greater than 700°C or greater than 600°C. Typical type 1 components include any of the catalysts as described herein, while typical type 2 components include bulk OCM catalysts and nanowire catalysts which only have good OCM activity at higher temperatures, for example greater than 800°C. Examples of type 2 components may include catalysts comprising MgO. The catalyst blend may further comprise inert support materials as described above (e.g., silica, alumina, silicon carbide, etc.).
In certain embodiments, the type 2 component acts as diluent in the same way an inert material does and thus helps reduce and/or control hot spots in the catalyst bed caused by the exothermic nature of the OCM reaction. However, because the type 2 component is an OCM catalyst, albeit not a particularly active one, it may prevent the occurrence of undesired side reactions, e.g., methyl radical quenching. Additionally, controlling the hotspots has the beneficial effect of extending the lifetime of the catalyst.
For example, it has been found that diluting active lanthanide oxide OCM catalysts with as much as a 10:1 ratio of MgO, which by itself is not an active OCM catalyst at the temperature which the lanthanide oxide operates, is a good way to minimize "hot spots" in the reactor catalyst bed, while maintaining the selectivity and yield performance of the catalyst. On the other hand, doing the same dilution with quartz S1O2 is not effective because it appears to quench the methyl radicals which serves to lower the selectivity to C2s.
In yet another embodiment, the type 2 components are good oxidative dehydrogenation (ODH) catalysts at the same temperature that the type 1 components are good OCM catalysts. In this embodiment, the
ethylene/ethane ratio of the resulting gas mixture can be tuned in favor of higher ethylene. In another embodiment, the type 2 components are not only good ODH catalysts at the same temperature the type 1 components are good OCM catalysts, but also have limited to moderate OCM activity at these temperatures. In related embodiments, the catalytic performance of the catalytic material is tuned by selecting specific type 1 and type 2 components of a catalyst blend. In another embodiment, the catalytic performance is tuned by adjusting the ratio of the type 1 and type 2 components in the catalytic material. For example, the type 1 catalyst may be a catalyst for a specific step in the catalytic reaction, while the type 2 catalyst may be specific for a different step in the catalytic reaction. For example, the type 1 catalyst may be optimized for formation of methyl radicals and the type 2 catalyst may be optimized for formation of ethane or ethylene.
In other embodiments, the catalytic material comprises at least two different components (component 1 , component 2, component 3, etc.). The different components may comprise different morphologies, e.g., nanowires, nanoparticles, bulk, etc. The different components in the catalyst material can be, but not necessarily, of the same chemical composition and the only difference is in the morphology and/or the size of the particles. This difference in morphology and particle size may result in a difference in reactivity at a specific temperature. Additionally, the difference in morphology and particle size of the catalytic material components is advantageous for creating a very intimate blending, e.g., very dense packing of the catalysts particles, which can have a beneficial effect on catalyst performance. Also, the difference in morphology and particle size of the blend components would allow for control and tuning of the macro-pore distribution in the reactor bed and thus its catalytic efficiency. An additional level of micro-pore tuning can be attained by blending catalysts with different chemical composition and different morphology and/or particle size. The proximity effect would be advantageous for the reaction selectivity.
Accordingly, in one embodiment the present disclosure provides the use of a catalytic material comprising a first catalyst and a second catalyst, for example a first catalytic nanowire and a bulk catalyst and/or a second catalytic nanowire, in a catalytic reaction, for example the catalytic reaction may be OCM or ODH. In other embodiments, the first catalytic nanowire and the bulk catalyst and/or second catalytic nanowire are each catalytic with respect to the same reaction, and in other examples the first catalytic nanowire and the bulk catalyst and/or second catalytic nanowire have the same chemical composition.
In some specific embodiments of the foregoing, the catalytic material comprises a first catalytic nanowire and a second catalytic nanowire. Each nanowire can have completely different chemical compositions or they may have the same base composition and differ only by the doping elements. In other embodiments, each nanowire can have the same or a different morphology. For example, each nanowire can differ by the nanowire size (length and/or aspect ratio), by ratio of actual/effective length, by chemical composition or any combination thereof. Furthermore, the first and second nanowires may each be catalytic with respect to the same reaction but may have different activity. Alternatively, each nanowire may catalyze different reactions.
In a related embodiment, the catalytic material comprises a first catalytic nanowire and a bulk catalyst. The first nanowire and the bulk catalyst can have completely different chemical compositions or they may have the same base composition and differ only by the doping elements. Furthermore, the first nanowire and the bulk catalyst may each be catalytic with respect to the same reaction but may have different activity. Alternatively, the first nanowire and the bulk catalyst may catalyze different reactions.
In yet other embodiments of the foregoing, the catalytic nanowire has a catalytic activity in the catalytic reaction, which is greater than a catalytic activity of the bulk catalyst in the catalytic reaction at the same temperature. In still other embodiments, the catalytic activity of the bulk catalyst in the catalytic reaction increases with increasing temperature.
OCM catalysts may be prone to hotspots due to the very exothermic nature of the OCM reaction. Diluting such catalysts helps to manage the hotspots. However, the diluent needs to be carefully chosen so that the overall performance of the catalyst is not degraded. Silicon carbide for example can be used as a diluent with little impact on the OCM selectivity of the blended catalytic material whereas using silica as a diluent significantly reduces OCM selectivity. The good heat conductivity of SiC is also beneficial in minimizing hot spots. As noted above, use of a catalyst diluents or support material that is itself OCM active has significant advantages over more traditional diluents such as silica and alumina, which can quench methyl radicals and thus reduce the OCM performance of the catalyst. An OCM active diluent is not expected to have any adverse impact on the generation and lifetime of methyl radicals and thus the dilution should not have any adverse impact on the catalyst performance. Thus embodiments of the invention include catalyst compositions comprising an OCM catalyst (e.g., any of the disclosed catalysts) in combination with a diluent or support material that is also OCM active. Methods for use of the same in an OCM reaction are also provided.
In some embodiments, the above diluent comprises alkaline earth metal compounds, for example alkaline metal oxides, carbonates, sulfates or phosphates. Examples of diluents useful in various embodiments include, but are not limited to, MgO, MgCO3, MgSO4, Mg3(PO4)2, MgAI2O4, CaO, CaCO3, CaSO4, Ca3(PO4)2, CaAI2O4, SrO, SrCO3, SrSO4, Sr3(PO4)2, SrAI2O4, BaO, BaCO3, BaSO4, Ba3(PO4)2, BaAI2O4 and the like. Most of these compounds are very cheap, especially MgO, CaO, MgCO3, CaCO3, SrO, SrCO3 and thus very attractive for use as diluents from an economic point of view. Additionally, the magnesium, calcium and strontium compounds are environmentally friendly too. Accordingly, an embodiment of the invention provides a catalytic material comprising a catalyst in combination with a diluent selected from one or more of MgO, MgCO3, MgSO4, Mg3(PO4)2, CaO, CaCO3, CaSO4, Ca3(PO4)2, SrO, SrCO3, SrSO4, Sr3(PO4)2, BaO, BaCO3, BaSO4, Ba3(PO4)2. In some specific embodiments the diluents is MgO, CaO, SrO, MgCO3, CaCO3, SrCO3 or combination thereof. Methods for use of the foregoing catalytic materials in an OCM reaction are also provided. The methods comprise converting methane to ethane and or ethylene in the presence of the catalytic materials.
The above diluents and supports may be employed in any number of methods. For example, in some embodiments a support (e.g., MgO, CaO, CaCO3, SrCOs) may be used in the form of a pellet or monolith (e.g.,
honeycomb) structure, and the catalysts may be impregnated or supported thereon. In other embodiments, a core/shell arrangement is provided and the support material may form part of the core or shell. For example, a core of MgO, CaO, CaCO3 or SrCO3 may be coated with a shell of any of the disclosed catalyst compositions.
In some embodiments, the diluent has a morphology selected from bulk (e.g., commercial grade), nano (nanowires, nanorods, nanoparticles, etc.) or combinations thereof.
In some embodiments, the diluent has none to moderate catalytic activity at the temperature the OCM catalyst is operated. In some other embodiments, the diluent has moderate to large catalytic activity at a
temperature higher than the temperature the OCM catalyst is operated. In yet some other embodiments, the diluent has none to moderate catalytic activity at the temperature the OCM catalyst is operated and moderate to large catalytic activity at temperatures higher than the temperature the OCM catalyst is operated. Typical temperatures for operating an OCM reaction according to the present disclosure are 800 °C or lower, 750 °C or lower, 700 °C or lower, 650 °C or lower, 600 °C or lower and 550 °C or lower.
For example, CaCO3 is a relatively good OCM catalyst at T > 750
°C (50% selectivity, >20% conversion) but has essentially no activity below 700 °C. Experiments performed in support of the present invention showed that dilution of Nd2O3 straight nanowires with CaCO3 or SrCO3 (bulk) showed no degradation of OCM performance and, in some cases, even better performance than the neat catalyst. In some embodiments, the diluent portion in the catalyst/diluent mixture is 0.01 %, 10%, 30%, 50%, 70%, 90% or 99.99% (weight percent) or any other value between 0.01 % and 99.9%. In some embodiments, the dilution is performed with the OCM catalyst ready to go, e.g., after calcination. In some other embodiments, the dilution is performed prior to the final calcination of the catalyst, i.e., the catalyst and the diluent are calcined together. In yet some other embodiments, the dilution can be done during the synthesis as well, so that, for example, a mixed oxide is formed.
In some embodiments, the catalyst/diluent mixture comprises more than one catalyst and/or more than one diluent. In some other
embodiments, the catalyst/diluent mixture is pelletized and sized, or made into shaped extrudates or deposited on a monolith or foam, or is used as it is.
Methods of the invention include taking advantage of the very exothermic nature of OCM by diluting the catalyst with another catalyst that is (almost) inactive in the OCM reaction at the operating temperature of the first catalyst but active at higher temperature. In these methods, the heat generated by the hotspots of the first catalyst will provide the necessary heat for the second catalyst to become active.
For ease of illustration, the above description of catalytic materials often refers to OCM; however, such catalytic materials find utility in other catalytic reactions including but not limited to: oxidative dehydrogenation (ODH) of alkanes to their corresponding alkenes, selective oxidation of alkanes and alkenes and alkynes, oxidation of co, dry reforming of methane, selective oxidation of aromatics, Fischer-Tropsch, combustion of hydrocarbons, etc. 3. Preparation of Catalysts and Catalytic Materials
The catalysts can be prepared using any suitable method (e.g., such that the catalyst functions as an OCM catalyst). Suitable methods, which include using a bacteriophage template and other methods known in the art, are described in U.S. Application Nos. 13/1 15,082 (U.S. Pub. No.
2012/0041246), 13/689,514 (U.S. Pub. No. 2013/0158322) and 13/689,61 1 (U.S. Pub. No. 2013/0165728), which applications are hereby incorporated by reference in their entireties.
In some embodiments, the nanowire catalysts can be synthesized in a solution phase in the absence of a template. Typically, a hydrothermal or sol gel approach can be used to create straight (i.e., ratio of effective length to actual length equal to one) and substantially single crystalline nanowires. As an example, nanowires comprising a metal oxide can be prepared by (1 ) forming nanowires of a metal oxide precursor (e.g., metal hydroxide) in a solution of a metal salt and an anion precursor; (2) isolating the nanowires of the metal oxide precursor; and (3) calcining the nanowires of the metal oxide precursor to provide nanowires of a corresponding metal oxide. In other embodiments (for example MgO nanowires), the synthesis goes through an intermediate which can be prepared as a nanowire and then converted into the desired product while maintaining its morphology. Optionally, the nanowires comprising a metal oxide can be doped according to methods described herein.
In other certain embodiments, nanowires comprising a core/shell structure are prepared in the absence of a biological template. Such methods may include, for example, preparing a nanowire comprising a first metal and growing a shell on the outersurface of this nanowire, wherein the shell comprises a second metal. The first and second metals may be the same or different.
In other aspects, a core/shell nanowire is prepared in the absence of a biological template. Such methods comprise preparing a nanowire comprising an inner core and an outer shell, wherein the inner core comprises a first metal, and the outer shell comprises a second metal, the method
comprising:
o a) preparing a first nanowire comprising the first metal; and o b) treating the first nanowire with a salt comprising the second metal. In some embodiments of the foregoing method, the method further comprises addition of a base to a solution obtained in step b). In yet other examples, the first metal and the second metal are different. In yet further embodiments, the salt comprising the second metal is a halide or a nitrate. In certain aspects it may be advantageous to perform one or more sequential additions of the salt comprising the second metal and a base. Such sequential additions help prevent non-selective precipitation of the second metal and favor conditions wherein the second metal nucleates on the surface of the first nanowire to form a shell of the second metal. Furthermore, the first nanowire may be prepared by any method, for example via a template directed method (e.g., phage).
As with template-directed syntheses, the synthetic conditions and parameters for direct synthesis (template free) of nanowires can also be adjusted to create diverse compositions and surface morphologies (e.g., crystal faces) and dopant levels. For example, variable synthetic parameters include: concentration ratios of metal and anions (e.g., hydroxide); reaction temperature; reaction time; sequence of adding anion and metal ions; pH; types of metal precursor salt; types of anion precursor; number of additions; the time that lapses between the additions of the metal salt and anion precursor, including, e.g., simultaneous (zero lapse) or sequential additions followed by respective incubation times for the metal salt and the anion precursor.
In addition, the choice of solvents or surfactants may influence the crystal growth of the nanowires, thereby generating different nanowire dimensions (including aspect ratios). For example, solvents such as ethylene glycol, poly(ethylene glycol), polypropylene glycol and polyvinyl pyrrolidone) can serve to passivate the surface of the growing nanowires and facilitate a linear growth of the nanowire.
In some embodiments, nanowires can be prepared directly from the corresponding oxide. For example, metal oxides may be treated with halides, for example ammonium halides, to produce nanowires. Such embodiments find particular utility in the context of lanthanide oxides, for example La2O3, are particularly useful since the procedure is quite simple and economically efficient Nanowires comprising two or more metals and/or dopants may also be prepared according to these methods. Accordingly, in some embodiments at least one of the metal compounds is an oxide of a lanthanide element.
Accordingly, in one embodiment the present disclosure provides a method for preparing a nanowire in the absence of a biological template, the method comprising treating at least one metal compound with a halide. In certain embodiments, nanowires comprising more than one type of metal and/or one or more dopants can be prepared by such methods. For example, in one embodiment the method comprises treating two or more different metal compounds with a halide and the nanowire comprises two or more different metals. The nanowire may comprise a mixed metal oxide, metal oxyhalide, metal oxynitrate or metal sulfate.
In some other embodiments of the foregoing, the halide is in the form of an ammonium halide. In yet other embodiments, the halide is contacted with the metal compound in solution or in the solid state.
In certain embodiments, the method is useful for incorporation of one or more doping elements into a nanowire. For example, the method may comprise treating at least one metal compound with a halide in the presence of at least one doping element, and the nanowire comprises the least one doping element. In some aspects, the at least one doping element is present in the nanowire in an atomic percent ranging from 0.1 to 50 at %.
Other methods for preparation of nanowires in the absence of a biological template include preparing a hydroxide gel by reaction of at least one metal salt and a hydroxide base. For example, the method may further comprise aging the gel, heating the gel or combinations thereof. In certain other embodiments, the method comprises reaction of two or more different metal salts, and the nanowire comprises two or more different metals. Doping elements may also be incorporated by using the hydroxide gel method described above, further comprising addition of at least one doping element to the hydroxide gel, and wherein the nanowire comprises the at least one doping element. For example, the at least one doping element may be present in the nanowire in an atomic percent ranging from 0.1 to 50 at %.
In some embodiments, metal oxide nanowires can be prepared by mixing a metal salt solution and an anion precursor so that a gel of a metal oxide precursor is formed. This method can work for cases where the typical morphology of the metal oxide precursor is a nanowire. The gel is thermally treated so that crystalline nanowires of the metal oxide precursor are formed. The metal oxide precursor nanowires are converted to metal oxide nanowires by calcination. This method can be especially useful for lanthanides and group 3 elements. In some embodiments, the thermal treatment of the gel is hydrothermal (or solvothermal) at temperatures above the boiling point of the reaction mixture and at pressures above ambient pressure, in other
embodiments it's done at ambient pressure and at temperatures equal to or below the boiling point of the reaction mixture. In some embodiments the thermal treatment is done under reflux conditions at temperatures equal to the boiling point of the mixture. In some specific embodiments the anion precursor is a hydroxide, e.g., Ammonium hydroxide, sodium hydroxide, lithium
hydroxide, tetramethyl ammonium hydroxide, and the like. In some other specific embodiments the metal salt is LnCI3 (Ln=Lanthanide), in other embodiment the metal salt is Ln(NO3)3. In yet other embodiments, the metal salt is YCI3, SCCI3, Y(NO3)3, Sc(NOs)3- In some other embodiments, the metal precursor solution is an aqueous solution. In other embodiments, the thermal treatment is done at T=100° C. under reflux conditions.
This method can be used to make mixed metal oxide nanowires, by mixing at least two metal salt solutions and an anion precursor so that a mixed oxide precursor gel is formed. In such cases, the first metal may be a lathanide or a group 3 element, and the other metals can be from other groups, including groups 1 -14.
In some different embodiments, metal oxide nanowires can be prepared in a similar way as described above by mixing a metal salt solution and an anion precursor so that a gel of a metal hydroxide precursor is formed. This method works for cases where the typical morphology of the metal hydroxide precursor is a nanowire. The gel is treated so that crystalline nanowires of the metal hydroxide precursor are formed. The metal hydroxide precursor nanowires are converted to metal hydroxide nanowires by base treatment and finally converted to metal oxide nanowires by calcination. This method may be especially applicable for group 2 elements, for example Mg. In some specific embodiments, the gel treatment is a thermal treatment at temperatures in the range 50-100° C. followed by hydrothermal treatment. In other embodiments, the gel treatment is an aging step. In some embodiments, the aging step takes at least one day. In some specific embodiments, the metal salt solution is a concentrated metal chloride aqueous solution and the anion precursor is the metal oxide. In some more specific embodiments, the metal is Mg. In certain embodiments of the above, these methods can be used to make mixed metal oxide nanowires. In these embodiments, the first metal is Mg and the other metal can be any other metal of groups 1 -14+Ln.
The catalysts and/or catalytic materials can be prepared
according to any number of methods known in the art. For example, the catalysts and/or catalytic materials can be prepared after preparation of the individual components by mixing the individual components in their dry form, e.g., blend of powders, and optionally, ball milling can be used to reduce particle size and/or increase mixing. Each component can be added together or one after the other to form layered particles. Alternatively, the individual components can be mixed prior to calcination, after calcination or by mixing already calcined components with uncalcined components. The catalysts and/or catalytic materials may also be prepared by mixing the individual components in their dry form and optionally pressing them together into a "pill" followed by calcination to above 400 °C.
The foregoing catalysts may be doped prior to, or after formation of the catalyst. In one embodiment, one or more metal salts are mixed to form a solution or a slurry which is dried and then calcined in a range of 400 °C to 900 °C, or between 500 °C and 700 °C. In another embodiment, the catalyst is formed first through calcination of one or more metal salt followed by contact with a solution comprising the doping element followed by drying and/or calcination between 300 °C and 800 °C, or between 400 °C and 700 °C.
In other examples, the catalysts and/or catalytic materials are prepared by mixing the individual components with one or more solvents into a solution, suspension or slurry. Optional mixing and/or ball milling can be used to maximize uniformity and reduce particle size. Examples of solvents useful in this context include, but are not limited to: water, alcohols, ethers, carboxylic acids, ketones, esters, amides, aldehydes, amines, alkanes, alkenes, alkynes, aromatics, etc. In other embodiments, the individual components are deposited on a supporting material such as silica, alumina, magnesia, activated carbon, and the like, or by mixing the individual components using a fluidized bed granulator. Combinations of any of the above methods may also be used.
The catalysts and/or catalytic materials may optionally comprise a dopant as described in more detail herein. In this respect, doping material(s) may be added during preparation of the individual components, after preparation of the individual components but before drying of the same, after the drying step but before calcinations or after calcination. If more than one doping material is used, each dopant can be added together or one after the other to form layers of dopants.
Doping material(s) may also be added as dry components and optionally ball milling can be used to increase mixing. In other embodiments, doping material(s) are added as a liquid (e.g., solution, suspension, slurry, etc.) to the dry individual catalyst components or to the blended catalytic material. The amount of liquid may optionally be adjusted for optimum wetting of the catalyst, which can result in optimum coverage of catalyst particles by doping material. Mixing and/or ball milling can also be used to maximize doping coverage and uniform distribution. Alternatively, doping material(s) are added as a liquid (e.g., solution, suspension, slurry, etc.) to a suspension or slurry of the catalyst in a solvent. Mixing and/or ball milling can be used to maximize doping coverage and uniform distribution. Incorporation of dopants can also be achieved using any of the methods described elsewhere herein.
As noted herein, an optional calcination step usually follows an optional drying step at T < 200C (typically 60-120C) in a regular oven or in a vacuum oven. Calcination may be performed on the individual components of the catalysts and/or catalytic material or on the blended catalysts and/or catalytic material. Calcination is generally performed in an oven/furnace at a temperature higher than the minimum temperature at which at least one of the components decomposes or undergoes a phase transformation and can be performed in inert atmosphere (e.g., N2, Ar, He, etc.), oxidizing atmosphere (air, O2, etc.) or reducing atmosphere (H2, H2/N2, H2/Ar, etc.). The atmosphere may be a static atmosphere or a gas flow and may be performed at ambient pressure, at p < 1 atm, in vacuum or at p > 1 atm. High pressure treatment (at any temperature) may also be used to induce phase transformation including amorphous to crystalline. Calcinations may also be performed using
microwave heating.
Calcination is generally performed in any combination of steps comprising ramp up, dwell and ramp down. For example, ramp to 500 °C, dwell at 500 °C for 5h, ramp down to RT. Another example includes ramp to 100 °C, dwell at 100 °C for 2h, ramp to 300 °C, dwell at 300 °C for 4h, ramp to 550 °C, dwell at 550 °C for 4h, ramp down to RT. Calcination conditions (pressure, atmosphere type, etc.) can be changed during the calcination. In some embodiments, calcination is performed before preparation of the blended catalytic material (i.e., individual components are calcined), after preparation of the blended catalytic material but before doping, after doping of the individual components or blended catalytic material. Calcination may also be performed multiple times, e.g., after catalyst preparation and after doping.
The catalytic materials may be incorporated into a reactor bed for performing any number of catalytic reactions {e.g., OCM, ODH and the like). Accordingly, in one embodiment the present disclosure provides a catalytic material as disclosed herein in contact with a reactor and/or in a reactor bed. For example, the reactor may be for performing an OCM reaction, may be a fixed bed reactor and may have a diameter greater than 1 inch. In this regard, the catalytic material may be packed neat (without diluents) or diluted with an inert material {e.g., sand, silica, alumina, etc.) The catalyst components may be packed uniformly forming a homogeneous reactor bed.
The particle size of the individual components within a catalytic material may also alter the catalytic activity, and other properties, of the same. Accordingly, in one embodiment, the catalyst is milled to a target average particle size or the catalyst powder is sieved to select a particular particle size. In some aspects, the catalyst powder may be pressed into pellets and the catalyst pellets can be optionally milled and or sieved to obtain the desired particle size distribution.
In some embodiments, the catalyst materials, alone or with binders and/or diluents, can be configured into larger aggregate forms, such as pellets, extrudates, or other aggregations of catalyst particles. For ease of discussion, such larger forms are generally referred to herein as "pellets". Such pellets may optionally include a binder and/or support material; however, the present inventors have surprisingly found that the disclosed nanowires are particularly suited to use in the form of a pellet without a binder and/or support material. Accordingly, one embodiment of the disclosure provides a catalytic material in the absence of a binder. In this regard, the morphology of the disclosed nanowires (either bent or straight, etc.) is believed to contribute to the nanowires' ability to be pressed into pellets without the need for a binder. Catalytic materials without binders are simpler, less complex and cheaper than corresponding materials with binders and thus offer certain advantages.
In some instances, catalytic materials may be prepared using a "sacrificial binder" or support. Because of their special properties, the nanowires allow for preparation of catalytic material forms (e.g., pellets) without the use of a binder. A "sacrificial" binder can be used in order to create unique microporosity in pellets or extrudates. After removing the sacrificial binder, the structural integrity of the catalyst is ensured by the special binding properties of the nanowires and the resulting catalytic material has unique microporosity as a result of removing the binder. For example, in some embodiments a catalytic nanowire may be prepared with a binder and then the binder removed by any number of techniques (e.g., calcinations, acid erosion, etc.). This method allows for design and preparation of catalytic materials having unique microporosity (i.e., the microporosity is a function of size, etc., of the sacrificial binder). The ability to prepare different forms (e.g., pellets) of the nanowires without the use of binder is not only useful for preparation of catalytic materials from the nanowires, but also allows the nanowires to be used as support materials (or both catalytic and support material). Sacrificial binders and techniques useful in this regard include sacrificial cellulosic fibers or other organic polymers that can be easily removed by calcination, non-sacrificial binders and techniques useful in this regard include, colloidal oxide binders such as Ludox Silica or Nyacol colloidal zirconia that can also be added to strengthen the formed aggregate when needed. Sacrificial binders are added to increase macro-porosity (pores larger than 20nm diameter) of the catalytic materials. Accordingly, in some embodiments the catalytic materials comprise pores greater than 20 nm in diameter, greater than 50 nm in diameter, greater than 75 nm in diameter, greater than 100 nm in diameter or greater than 150 nm in diameter.
Catalytic materials also include any of the disclosed catalysts disposed on or adhered to a solid support. For example, the catalysts may be adhered to the surface of a monolith support. As with the binder-less materials discussed above, in these embodiments the catalysts may be adhered to the surface of the monolith in the absence of a binder due to their unique morphology and packing properties. Monoliths include honeycomb-type structures, foams and other catalytic support structures derivable by one skilled in the art. In one embodiment, the support is a honeycomb matrix formed from silicon carbide, and the support further comprises the disclosed catalyst disposed on the surface.
As the OCM reaction is very exothermic, it can be desirable to reduce the rate of conversion per unit volume of reactor in order to avoid run away temperature rise in the catalyst bed that can result in hot spots affecting performance and catalyst life. One way to reduce the OCM reaction rate per unit volume of reactor is to spread the active catalyst onto an inert support with interconnected large pores as in ceramic or metallic foams (including metal alloys having reduced reactivity with hydrocarbons under OCM reaction conditions) or having arrays of channel as in honeycomb structured ceramic or metal assembly.
In one embodiment, a catalytic material comprising a catalyst as disclosed herein supported on a structured support is provided. Examples of such structure supports include, but are not limited to, metal foams, Silicon Carbide or Alumina foams, corrugated metal foil arranged to form channel arrays, extruded ceramic honeycomb, for example Cordierite (available from Corning or NGK ceramics, USA), Silicon Carbide or Alumina.
Active catalyst loading on the structured support ranges from 1 to 500 mg per ml of support component, for example from 5 to 100 mg per ml of structure support. Cell densities on honeycomb structured support materials may range from 100 to 900 CPSI (cell per square inch), for example 200 to 600 CPSI. Foam densities may range from 10 to 100 PPI (pore per inch), for example 20 to 60 PPI. In other embodiments, the exotherm of the OCM reaction may be at least partially controlled by blending the active catalytic material with catalytically inert material, and pressing or extruding the mixture into shaped pellets or extrudates. In some embodiments, these mixed particles may then be loaded into a pack-bed reactor. The Extrudates or pellets comprise between 30% to 70% pore volume with 5% to 50% active catalyst weight fraction. Useful inert materials in this regard include, but are not limited to MgO, CaO, AI2O3, SiC and cordierite.
In addition to reducing the potential for hot spots within the catalytic reactor, another advantage of using a structured ceramic with large pore volume as a catalytic support is reduced flow resistance at the same gas hourly space velocity versus a pack-bed containing the same amount of catalyst.
Yet another advantage of using such supports is that the structured support can be used to provide features difficult to obtain in a pack- bed reactor. For example the support structure can improve mixing or enabling patterning of the active catalyst depositions through the reactor volume. Such patterning can consist of depositing multiple layers of catalytic materials on the support in addition to the OCM active component in order to affect transport to the catalyst or combining catalytic functions as adding O2-ODH activity, CO2- OCM activity or CO2-ODH activity to the system in addition to O2-OCM active material. Another patterning strategy can be to create bypass within the structure catalyst essentially free of active catalyst to limit the overall
conversion within a given supported catalyst volume.
Yet another advantage is reduced heat capacity of the bed of the structured catalyst over a pack bed a similar active catalyst loading therefore reducing startup time.
Nanowire shaped catalysts are particularly well suited for incorporation into pellets or extrudates or deposition onto structured supports. Nanowire aggregates forming a mesh type structure can have good adhesion onto rough surfaces.
The mesh like structure can also provide improved cohesion in composite ceramic improving the mechanical properties of pellets or extrudates containing the nanowire shaped catalyst particles.
Alternatively, such nanowire on support or in pellet form
approaches can be used for other reactions besides OCM, such as ODH, dry methane reforming, FT, and all other catalytic reactions.
In yet another embodiment, the catalysts are packed in bands forming a layered reactor bed. Each layer is composed by either a catalyst of a particular type, morphology or size or a particular blend of catalysts. In one embodiment, the catalysts blend may have better sintering properties, i.e., lower tendency to sinter, then a material in its pure form. Better sintering resistance is expected to increase the catalyst's lifetime and improve the mechanical properties of the reactor bed.
In yet other embodiments, the disclosure provides a catalytic material comprising one or more different catalysts. The catalysts may be a nanowire as disclosed herein and a different catalyst for example a bulk catalysts. Mixtures of two or more nanowire catalysts are also contemplated. The catalytic material may comprise a catalyst, for example a nanowire catalyst, having good OCM activity and a catalyst having good activity in the ODH reaction. Either one or both of these catalysts may be nanowires as disclosed herein.
One skilled in the art will recognize that various combinations or alternatives of the above methods are possible, and such variations are also included within the scope of the present disclosure.
4. Structure/Physical Characteristics of the Disclosed Catalysts
Typically, a catalytic material described herein comprises a plurality of metal oxide particles. In certain embodiments, the catalytic material may further comprise a support material. The total surface area per gram of a catalytic material may have an effect on the catalytic performance. Pore size distribution may affect the catalytic performance as well. Surface area and pore size distribution of the catalytic material can be determined by BET (Brunauer,
Emmett, Teller) measurements. BET techniques utilize nitrogen adsorption at various temperatures and partial pressures to determine the surface area and pore sizes of catalysts. BET techniques for determining surface area and pore size distribution are well known in the art.
In some embodiments the catalytic material comprises a surface area of between 0.1 and 100 m2/g, between 1 and 100 m2/g, between 1 and 50 m2/g, between 1 and 20 m2/g, between 1 and 10 m2/g, between 1 and 5 m2/g, between 1 and 4 m2/g, between 1 and 3 m2/g, or between 1 and 2 m2/g.
Additional structural properties of the catalysts and catalytic materials are described in U.S. Application Nos. 13/1 15,082 (U.S. Pub. No.
2012/0041246), 13/689,514 (U.S. Pub. No. 2013/0158322) and 13/689,61 1 (U.S. Pub. No. 2013/0165728), which applications are hereby incorporated by reference in their entireties.
Catalytic Reactions
The present disclosure provides heterogeneous catalysts having better catalytic properties than known catalysts. The catalysts disclosed herein are useful in any number of reactions catalyzed by a heterogeneous catalyst. Examples of reactions wherein the disclosed catalysts may be employed are disclosed in Farrauto and Bartholomew, "Fundamentals of Industrial Catalytic Processes" Blackie Academic and Professional, first edition, 1997, which is hereby incorporated in its entirety. Other non-limiting examples of reactions wherein the catalysts may be employed include: the oxidative coupling of methane (OCM) to ethane and ethylene; oxidative dehydrogenation (ODH) of alkanes to the corresponding alkenes, for example oxidative dehydrogenation of ethane or propane to ethylene or propylene, respectively; selective oxidation of alkanes, alkenes, and alkynes; oxidation of CO, dry reforming of methane, selective oxidation of aromatics; Fischer-Tropsch, hydrocarbon cracking;
combustion of hydrocarbons and the like. Reactions catalyzed by the disclosed catalysts are discussed in more detail below. While an embodiment of the invention is described in greater detail below in the context of the OCM reaction and other reactions described herein, the catalysts are not in any way limited to the particularly described reactions.
The disclosed catalysts are generally useful in methods for converting a first carbon-containing compound {e.g., a hydrocarbon, CO or CO2) to a second carbon-containing compound. In some embodiments the methods comprise contacting a disclosed catalyst, or material comprising the same, with a gas comprising a first carbon-containing compound and an oxidant to produce a second carbon-containing compound. In some
embodiments, the first carbon-containing compound is a hydrocarbon, CO, CO2, methane, ethane, propane, hexane, cyclohexane, octane or combinations thereof. In other embodiments, the second carbon-containing compound is a hydrocarbon, CO, CO2, ethane, ethylene, propane, propylene, hexane, hexene, cyclohexane, cyclohexene, bicyclohexane, octane, octene or hexadecane. In some embodiments, the oxidant is oxygen, ozone, nitrous oxide, nitric oxide, water, carbon dioxide or combinations thereof.
In other embodiments of the foregoing, the method for conversion of a first carbon-containing compound to a second carbon-containing
compound is performed at a temperature below 100 °C, below 200 °C, below 300 °C, below 400 °C, below 500 °C, below 550 °C, below 600 °C, below 700 °C, below 800 °C, below 900 °C or below 1000 °C. In certain embodiments, the method is OCM and the method is performed at a temperature below 600 °C, below 700 °C, below 800 °C, or below 900 °C. In other embodiments, the method for conversion of a first carbon-containing compound to a second carbon-containing compound is performed at a pressure above 0.5 ATM, above 1 ATM, above 2 ATM, above 5 ATM, above 10 ATM, above 25 ATM or above 50 ATM. The catalytic reactions described herein can be performed using standard laboratory equipment known to those of skill in the art, for example as described in U.S. Patent No. 6,350,716, which is incorporated herein in its entirety.
As noted above, the catalysts disclosed herein have better catalytic activity than a corresponding undoped catalyst. In some
embodiments, the selectivity, yield, conversion, or combinations thereof, of a reaction catalyzed by the catalysts is better than the selectivity, yield, conversion, or combinations thereof, of the same reaction catalyzed by a corresponding undoped catalyst under the same conditions. For example, in some embodiments, the catalysts are doped bulk catalysts or nanowire catalysts (doped or undoped) and the catalysts possess a catalytic activity such that conversion of reactant to product in a reaction catalyzed by the catalyst is at least 1 .1 times, at least 1 .25 times, at least 1 .5 times, at least 2.0 times, at least 3.0 times or at least 4.0 times the yield of product in the same reaction under the same conditions but catalyzed by a corresponding catalyst. As used herein a "corresponding catalyst" refers to:
1 ) an undoped bulk catalyst (i.e., a catalyst comprising the same base material but different or no dopants or different ratios or concentrations of the same dopants) when the comparison is to a doped bulk catalyst of the invention;
2) a bulk catalyst (i.e., a catalyst prepared from bulk material having the same chemical composition as the nanowire, including any dopants) when the comparison is to a doped or undoped nanowire catalyst of the invention; or
3) an undoped nanowire catalyst when the comparison is to a doped nanowire of the invention.
For purpose of clarity, it should be noted that this comparison (and others throughout the application) is made to an undoped bulk catalyst when the catalysts are doped bulk catalysts and to a corresponding bulk catalyst when the catalysts are nanowire catalysts.
In other embodiments, the catalysts are doped bulk catalysts or nanowire catalysts (doped or undoped) and the catalysts possess a catalytic activity such that selectivity for product in a reaction catalyzed by the catalyst is at least 1 .1 times, at least 1 .25 times, at least 1 .5 times, at least 2.0 times, at least 3.0 times or at least 4.0 times the yield of product in the same reaction under the same conditions but catalyzed by a corresponding catalyst.
In yet other embodiments, the catalysts are doped bulk catalysts or nanowire catalysts (doped or undoped) and the catalysts possess a catalytic activity such that yield of product in a reaction catalyzed by the catalyst is at least 1 .1 times, at least 1 .25 times, at least 1 .5 times, at least 2.0 times, at least 3.0 times or at least 4.0 times the yield of product in the same reaction under the same conditions but catalyzed by a corresponding catalyst. In yet other embodiments, the catalysts are doped bulk catalysts or nanowire catalysts (doped or undoped) and the catalysts possess a catalytic activity such that the activation temperature of a reaction catalyzed by the catalyst is at least 25°C lower, at least 50°C lower, at least 75°C lower, or at least 100°C lower than the temperature of the same reaction under the same conditions but catalyzed by a corresponding catalyst. In certain reactions (e.g., OCM), production of unwanted oxides of carbon (e.g., CO and CO2) is a problem that reduces overall yield of desired product and results in an environmental liability.
Accordingly, in one embodiment the present disclosure addresses this problem and provides catalysts with a catalytic activity such that the selectivity for CO and/or CO2 in a reaction catalyzed by the catalysts is less than the selectivity for CO and/or CO2 in the same reaction under the same conditions but catalyzed by an undoped catalyst. Accordingly, in one embodiment, the present disclosure provides a doped bulk catalysts or nanowire catalysts (doped or undoped) and the catalysts possess a catalytic activity such that selectivity for COx, wherein x is 1 or 2, in a reaction catalyzed by the catalyst is less than at least 0.9 times, less than at least 0.8 times, less than at least 0.5 times, less than at least 0.2 times or less than at least 0.1 times the selectivity for COx in the same reaction under the same conditions but catalyzed by a corresponding catalyst.
In some embodiments, the absolute selectivity, yield, conversion, or combinations thereof, of a reaction catalyzed by the catalysts disclosed herein is better than the absolute selectivity, yield, conversion, or combinations thereof, of the same reaction under the same conditions but catalyzed by a corresponding catalyst. For example, in some embodiments the yield (e.g., C2 yield) of desired product(s) in a reaction catalyzed by the catalysts is greater than 10%, greater than 20%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%. In some embodiments, the reaction is OCM and the yield of product is greater than 10%, greater than 20%, greater than 30% or greater than 40%. In other embodiments, the selectivity for product (e.g., C2 selectivity) in a reaction catalyzed by the catalysts is greater than 10%, greater than 20%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%. In other embodiments, the conversion (e.g., methane conversion) of reactant to product in a reaction catalyzed by the catalysts is greater than10%, greater than 20%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
In certain embodiments wherein the catalysts are nanowires, the morphology of the nanowires is expected to provide for improved mixing properties for the nanowires compared to standard colloidal {e.g., bulk) catalyst materials. The improved mixing properties are expected to improve the performance of any number of catalytic reactions, for example, in the area of transformation of heavy hydrocarbons where transport and mixing phenomena are known to influence the catalytic activity. In other reactions, the shape of the nanowires is expected to provide for good blending, reduce settling, and provide for facile separation of any solid material. In some other chemical reactions, the nanowires are useful for absorption and/or incorporation of a reactant used in chemical looping. For example, the nanowires find utility as NOx traps, in unmixed combustion schemes, as oxygen storage materials, as CO2 sorption materials (e.g., cyclic reforming with high H2 output) and in schemes for conversion of water to H2.
1 . Oxidative Coupling of Methane (OCM)
As noted above, the present disclosure provides catalysts having catalytic activity and related approaches to catalyst design and preparation for improving the yield, selectivity and/or conversion of any number of catalyzed reactions, including the OCM reaction. Reactors useful in practice of the OCM methods described herein are known in the art and are described in PCT Pub. No. WO 2013/177433, which application is hereby incorporated by reference in its entirety. As mentioned above, there exists a tremendous need for catalyst technology capable of addressing the conversion of methane into high value chemicals (e.g., ethylene and products prepared therefrom) using a direct route that does not go through syngas. Accomplishing this task will dramatically impact and redefine a non-petroleum based pathway for feedstock
manufacturing and liquid fuel production yielding reductions in GHG emissions, as well as providing new fuel sources.
Ethylene has the largest carbon footprint compared to all industrial chemical products in part due to the large total volume consumed into a wide range of downstream important industrial products including plastics, surfactants and pharmaceuticals. In 2008, worldwide ethylene production exceeded 120 M metric tons while growing at a robust rate of 4% per year. The United States represents the largest single producer at 28% of the world capacity. Ethylene is primarily manufactured from high temperature cracking of naphtha (e.g., oil) or ethane that is separated from natural gas. The true measurement of the carbon footprint can be difficult as it depends on factors such as the feedstock and the allocation as several products are made and separated during the same process. However, some general estimates can be made based on published data.
Cracking consumes a significant portion (about 65%) of the total energy used in ethylene production and the remainder is for separations using low temperature distillation and compression. The total tons of CO2 emission per ton of ethylene are estimated at between 0.9 to 1 .2 from ethane cracking and 1 to 2 from naphtha cracking. Roughly, 60% of ethylene produced is from naphtha, 35% from ethane and 5% from others sources (Ren, T.; Patel, M. Res. Conserv. Recycl. 53:513, 2009). Therefore, based on median averages, an estimated amount of CO2 emissions from the cracking process is 1 14M tons per year (based on 120M tons produced). Separations would then account for an additional 61 M tons CO2 per year.
The catalysts of this disclosure provide an alternative to the need for the energy intensive cracking step. Additionally, because of the high selectivity of the catalysts, downstream separations are dramatically simplified, as compared to cracking which yields a wide range of hydrocarbon products. The reaction is also exothermic so it can proceed via an autothermal process mechanism. Overall, it is estimated that up to a potential 75% reduction in CO2 emission compared to conventional methods could be achieved. This would equate to a reduction of one billion tons of CO2 over a ten-year period and would save over 1 M barrels of oil per day.
The catalysts of this disclosure also permit converting ethylene into liquid fuels such as gasoline or diesel, given ethylene's high reactivity and numerous publications demonstrating high yield reactions, in the lab setting, from ethylene to gasoline and diesel. On a life cycle basis from well to wheel, recent analysis of methane to liquid (MTL) using F-T process derived gasoline and diesel fuels has shown an emission profile approximately 20% greater to that of petroleum based production (based on a worst case scenario)
(Jaramillo, P., Griffin, M., Matthews, S., Env. Sci. Tech 42:7559, 2008). In the model, the CO2 contribution from plant energy was a dominating factor at 60%. Thus, replacement of the cracking and F-T process would be expected to provide a notable reduction in net emissions, and could be produced at lower CO2 emissions than petroleum based production.
Furthermore, a considerable portion of natural gas is found in regions that are remote from markets or pipelines. Most of this gas is flared, recirculated back into oil reservoirs, or vented given its low economic value. The World Bank estimates flaring adds 400M metric tons of CO2 to the atmosphere each year as well as contributing to methane emissions. The catalysts of this disclosure also provide economic and environmental incentive to stop flaring. Also, the conversion of methane to fuel has several environmental advantages over petroleum-derived fuel. Natural gas is the cleanest of all fossil fuels, and it does not contain a number of impurities such as mercury and other heavy metals found in oil. Additionally, contaminants including sulfur are also easily separated from the initial natural gas stream. The resulting fuels burn much cleaner with no measurable toxic pollutants and provide lower emissions than conventional diesel and gasoline in use today.
In view of their wide range of applications, the catalysts (e.g., bulk and/or nanowires) of this disclosure can be used to not only selectively activate alkanes, but also to activate other classes of inert unreactive bonds, such as C- F, C-CI or C-O bonds. This has importance, for example, in the destruction of man-made environmental toxins such as CFCs, PCBs, dioxins and other pollutants. Accordingly, while the invention is described in greater detail below in the context of the OCM reaction and the other reactions described herein, the nanowire catalysts are not in any way limited to this or any other particular reaction.
The selective, catalytic oxidative coupling of methane to ethylene (i.e., the OCM reaction) is shown by the following reaction (1 ):
2CH4 + O2 CH2CH2 + 2 H2O (1 )
This reaction is exothermic (Heat of Reaction -67kcals/mole) and usually occurs at very high temperatures (> 700°C). During this reaction, it is believed that the methane (CH ) is first oxidatively coupled into ethane (C2H6), and subsequently the ethane (C2H6) is oxidatively dehydrogenated into ethylene (C2H ). Because of the high temperatures used in the reaction, it has been suggested that the ethane is produced mainly by the coupling in the gas phase of the surface- generated methyl (CH3) radicals. Reactive metal oxides (oxygen type ions) are apparently required for the activation of CH to produce the CH3 radicals. The yield of C2H and C2H6 is limited by further reactions in the gas phase and to some extent on the catalyst surface. A few of the possible reactions that occur during the oxidation of methane are shown below as reactions (2) through (8):
CH4 ^ CH3 radical (2)
CH3 radical C2H6 (3)
CH3 radical + 2.5 O2 CO2 + 1 .5 H2O (4)
C2H6 C2H4 + H2 (5)
C2H6 + 0.5 O2^ C2H4 + H2O (6) C2H4 +3 O2 2CO2 + 2H2O (7)
CH3 radical + CxHy +O2 -> Higher HC's -Oxidation/ CO2 +H2O (8)
With conventional heterogeneous catalysts and reactor systems, the reported performance is generally limited to < 25% CH4 conversion at < 80% combined C2 selectivity with the performance characteristics of high selectivity at low conversion, or the low selectivity at high conversion. In contrast, the catalysts of this disclosure are highly active and can optionally operate at a much lower temperature. In one embodiment, the catalysts disclosed herein enable efficient conversion of methane to ethylene in the OCM reaction at temperatures less than when other known catalysts are used. For example, in one embodiment, the catalysts disclosed herein enable efficient conversion (i.e., high yield, conversion, and/or selectivity) of methane to ethylene at temperatures of less than 900 °C, less than 800 °C, less than 700 °C, less than 600 °C, less than 550 °C, or less than 500 °C. In other embodiments, the use of staged oxygen addition, designed heat management, rapid quench and/or advanced separations may also be employed.
Typically, the OCM reaction is run in a mixture of oxygen and nitrogen or other inert gas. Such gasses are expensive and increase the overall production costs associated with preparation of ethylene or ethane from methane. However, the present inventors have now discovered that such expensive gases are not required and high yield, conversion, selectivity, etc., can be obtained when air is used as the gas mixture instead of pre-packaged and purified sources of oxygen and other gases. Accordingly, in one embodiment the disclosure provides a method for performing the OCM reaction using air as the oxidizer source.
Accordingly, one embodiment of the present disclosure is a method for the preparation of ethane and/or ethylene, the method comprising converting methane to ethane and/or ethylene in the presence of a catalytic material, wherein the catalytic material comprises at least one catalyst as disclosed herein.
Accordingly, in one embodiment a stable, very active, high surface area, multifunctional catalyst is disclosed having active sites that are isolated and precisely engineered with the catalytically active metal
centers/sites in the desired proximity (see, e.g., Figure 1 ) for facilitating the OCM reaction, as well as other reactions.
The exothermic heats of reaction (free energy) follow the order of reactions depicted above and, because of the proximity of the active sites, will mechanistically favor ethylene formation while minimizing complete oxidation reactions that form CO and CO2. Representative catalyst compositions useful for the OCM reaction include, but are not limited to the catalyst compositions described herein, including both bulk and nanowire morphologies.
As noted above, the presently disclosed catalysts comprise a catalytic performance better than corresponding catalysts, for example in one embodiment the catalytic performance of the catalysts in the OCM reaction is better than the catalytic performance of a corresponding catalyst. In this regard, various performance criteria may define the "catalytic performance" of the catalysts in the OCM (and other reactions). In one embodiment, catalytic performance is defined by C2 selectivity in the OCM reaction, and the C2 selectivity of the catalysts in the OCM reaction is >5%, >10%, >15%, >20%, >25%, >30%, >35%, >40%, >45%, >50%, >55%, >60%, >65%, >70%, >75% or >80%.
Other important performance parameters used to measure the catalysts' catalytic performance in the OCM reaction are selected from single pass methane conversion percentage (i.e., the percent of methane converted on a single pass over the catalyst or catalytic bed, etc.), reaction inlet gas temperature, reaction operating temperature, total reaction pressure, methane partial pressure, gas-hour space velocity (GHSV), O2 source, catalyst stability and ethylene to ethane ratio. In certain embodiments, improved catalytic performance is defined in terms of the catalysts' improved performance (relative to a corresponding catalyst) with respect to at least one of the foregoing performance parameters.
The reaction inlet gas temperature in an OCM reaction catalyzed by the disclosed catalysts can generally be maintained at a lower temperature, while maintaining better performance characteristics {e.g., conversion, C2 yield, C2 selectivity and the like) compared to the same reaction catalyzed by a corresponding undoped catalyst under the same reaction conditions. In certain embodiments, the inlet gas temperature in an OCM reaction catalyzed by the disclosed catalysts is <700 °C, <675 °C, <650 °C, <625 °C, <600 °C, <593 °C, <580 °C, <570 °C, <560 °C, <550 °C, <540 °C, <530 °C, <520 °C, <510 °C, <500 °C, <490 °C, <480 °C or even <470 °C.
The reaction operating temperature in an OCM reaction catalyzed by the disclosed catalysts can generally be maintained at a lower temperature, while maintaining better performance characteristics compared to the same reaction catalyzed by a corresponding catalyst under the same reaction conditions. In certain embodiments, the reaction operating temperature (i.e., outlet temperature) in an OCM reaction catalyzed by the disclosed catalysts is <950 °C, <925 °C, <900 °C, <875 °C, <850 °C, <825 °C, <800 °C, <775 °C, <750 °C, <725 °C, <700 °C, <675 °C, <650 °C, <625 °C, <600 °C, <593 °C, <580 °C, <570 °C, <560 °C, <550 °C, <540 °C, <530 °C, <520 °C, <510 °C, <500 °C, <490 °C, <480 °C, <470 °C.
The single pass methane conversion in an OCM reaction catalyzed by the catalysts is also generally better compared to the single pass methane conversion in the same reaction catalyzed by a corresponding catalyst under the same reaction conditions. For single pass methane conversion it is preferably >5%, >10%, >15%, >20%, >25%, >30%, >35%, >40%, >45%, >50%, >55%, >60%, >65%, >70%, >75%, or even >80%.
In certain embodiments, the inlet reaction pressure in an OCM reaction catalyzed by the catalysts is >1 atm, >1 .1 atm, >1 .2atm, >1 .3atm, >1 .4atm, >1 .5atm, >1 .6atm, >1 .7atm, >1 .8atm, >1 .9atm, >2atm, >2.1 atm, >2.1 atm, >2.2atm, >2.3atm, >2.4atm, >2.5atm, >2.6atm, >2.7atm, >2.8atm, >2.9atm, >3.0atm, >3.5atm, >4.0atm, >4.5atm, >5.0atm, >5.5atm, >6.0atm, >6.5atm, >7.0atm, >7.5atm, >8.0atm, >8.5atm, >9.0atm, >10.0atm, >1 1 .0atm, >12.0atm, >13.0atm, >14.0atm, >15.0atm, >16.0atm, >17.0atm, >18.0atm, >19.0atm or >20.0atm.
In certain other embodiments, the total reaction pressure in an OCM reaction catalyzed by the catalysts ranges from about 1 atm to about 10 atm, from about 1 atm to about 7 atm, from about 1 atm to about 5 atm, from about 1 atm to about 3 atm or from about 1 atm to about 2 atm.
In some embodiments, the methane partial pressure in an OCM reaction catalyzed by the catalysts is >0.3atm, >0.4atm, >0.5atm, >0.6atm, >0.7atm, >0.8atm, >0.9atm, >1 atm, >1 .1 atm, >1 .2atm, >1 .3atm, >1 .4atm, >1 .5atm, >1 .6atm, >1 .7atm, >1 .8atm, >1 .9atm, >2.0atm, >2.1 atm, >2.2atm, >2.3atm, >2.4atm, >2.5atm, >2.6atm, >2.7atm, >2.8atm, >2.9atm, >3.0atm, >3.5atm, >4.0atm, >4.5atm, >5.0atm, >5.5atm, >6.0atm, >6.5atm, >7.0atm, >7.5atm, >8.0atm, >8.5atm, >9.0atm, >10.0atm, >1 1 .0atm, >12.0atm,
>13.0atm, >14.0atm, >15.0atm, >16.0atm, >17.0atm, >18.0atm, >19.0atm or >20.0atm.
In some embodiments, the GSHV in an OCM reaction catalyzed by the catalysts is >10,000/hr, >15,000/hr, >20,000/hr, >50,000/hr, >75,000/hr, >100,000/hr, >120,000/hr, >130,000/hr, >150,000/hr, >200,000/hr, >250,000/hr, >300,000/hr, >350,000/hr, >400,000/hr, >450,000/hr, >500,000/hr, >750,000/hr, >1 ,000,000/hr, >2,000,000/hr, >3,000,000/hr, >4,000,000/hr.
In contrast to other OCM reactions, the present inventors have discovered that OCM reactions catalyzed by the disclosed catalysts can be performed (and still maintain high C2 yield, C2 selectivity, conversion, etc.) using O2 sources other than pure O2. For example, in some embodiments the O2 source in an OCM reaction catalyzed by the disclosed catalysts is air, oxygen enriched air, pure oxygen, oxygen diluted with nitrogen (or another inert gas) or oxygen diluted with CO2. In certain embodiments, the O2 source is O2 diluted by >99%, >98%, >97%, >96%, >95%, >94%, >93%, >92%, >91 %, >90%, >85%, >80%, >75%, >70%, >65%, >60%, >55%, >50%, >45%, >40%, >35%, >30%, >25%, >20%, >15%, >10%, >9%, >8%, >7%, >6%, >5%, >4%, >3%, >2% or >1 % with CO2 or an inert gas, for example nitrogen.
The disclosed catalysts are also very stable under conditions required to perform any number of catalytic reactions, for example the OCM reaction. The stability of the catalysts is defined as the length of time a catalyst will maintain its catalytic performance without a significant decrease in performance (e.g., a decrease >20%, >15%, >10%, >5%, or greater than 1 % in C2 yield, C2 selectivity or conversion, etc.). In some embodiments, the disclosed catalysts have stability under conditions required for the OCM reaction of >1 hr, >5 hrs, >10 hrs, >20 hrs, >50 hrs, >80 hrs, >90 hrs, >100 hrs, >150 hrs, >200 hrs, >250 hrs, >300 hrs, >350 hrs, >400 hrs, >450 hrs, >500 hrs, >550 hrs, >600 hrs, >650 hrs, >700 hrs, >750 hrs, >800 hrs, >850 hrs, >900 hrs, >950 hrs, >1 ,000 hrs, >2,000 hrs, >3,000 hrs, >4,000 hrs, >5,000 hrs, >6,000 hrs, >7,000 hrs, >8,000 hrs, >9,000 hrs, >10,000 hrs, >1 1 ,000 hrs,
>12,000 hrs, >13,000 hrs, >14,000 hrs, >15,000 hrs, >16,000 hrs, >17,000 hrs,
>18,000 hrs, >19,000 hrs, >20,000 hrs, >1 yrs, >2 yrs, >3 yrs, >4 yrs or >5 yrs.
In some embodiments, the ratio of ethylene to ethane in an OCM reaction catalyzed by the catalysts is better than the ratio of ethylene to ethane in an OCM reaction catalyzed by a corresponding undoped catalyst under the same conditions. In some embodiments, the ratio of ethylene to ethane in an OCM reaction catalyzed by the catalysts is >0.3, >0.4, >0.5, >0.6, >0.7, >0.8, >0.9, >1 , >1 .1 , >1 .2, >1 .3, >1 .4, >1 .5, >1 .6, >1 .7, >1 .8, >1 .9, >2.0, >2.1 , >2.2, >2.3, >2.4, >2.5, >2.6, >2.7, >2.8, >2.9, >3.0, >3.5, >4.0, >4.5, >5.0, >5.5, >6.0, >6.5, >7.0, >7.5, >8.0, >8.5, >9.0, >9.5, >10.0.
As noted above, the OCM reaction employing known catalysts suffers from poor yield, selectivity, or conversion. In contrast, the presently disclosed catalysts possess a catalytic activity in the OCM reaction such that the yield, selectivity, and/or conversion is better than when the OCM reaction is catalyzed by a corresponding catalyst. In one embodiment, the disclosure provides a catalyst having a catalytic activity such that the conversion of methane to ethylene in the oxidative coupling of methane reaction is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the conversion of methane to ethylene compared to the same reaction under the same conditions but performed with a corresponding catalyst. In other embodiments, the conversion of methane to ethylene in an OCM reaction catalyzed by the catalysts is greater than 10%, greater than 20%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
In another embodiment, the disclosure provides a catalyst having a catalytic activity such that the yield of ethylene in the oxidative coupling of methane reaction is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the yield of ethylene compared to the same reaction under the same conditions but performed with a corresponding catalyst. In other embodiments, the conversion of methane to ethylene in an OCM reaction catalyzed by the catalytic materials is greater than 10%, greater than 20%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%. In some embodiments the yield of ethylene in an OCM reaction catalyzed by the catalysts is greater than 10%, greater than 20%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
In certain embodiments, the catalysts possess a catalytic activity in the OCM reaction such that the yield, selectivity, and/or conversion is better than when the OCM reaction is catalyzed by a corresponding catalyst. In one embodiment, the disclosure provides a catalyst having a catalytic activity such that the conversion of methane in the oxidative coupling of methane reaction is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the conversion of methane compared to the same reaction under the same conditions but performed with a corresponding catalyst. In other embodiments, the conversion of methane in an OCM reaction catalyzed by the catalyst is greater than 10%, greater than 15%, greater than 20%, greater than 25%, greater than 30% greater than 40%, greater than 50%, greater than 75% or greater than 90%. In some embodiments the conversion of methane is determined when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less, 700 °C or less, 650 °C or less or even 600 °C or less. The conversion of methane may also be determined based on a single pass of a gas comprising methane over the catalyst or may be determined based on multiple passes over the catalyst.
In another embodiment, the disclosure provides a catalyst having a catalytic activity such that the C2 yield in the oxidative coupling of methane reaction is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the C2 yield compared to the same reaction under the same conditions but performed with a corresponding catalyst. In some embodiments the C2 yield in an OCM reaction catalyzed by the catalyst is greater than 10%, greater than 15%, greater than 20%, greater than 25%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%. In some embodiments the C2 yield is determined when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less, 700 °C or less, 650 °C or less or even 600 °C or less. The C2 yield may also be determined based on a single pass of a gas comprising methane over the catalyst or may be determined based on multiple passes over the catalyst.
In another embodiment, the disclosure provides a catalyst having a catalytic activity such that the C2 selectivity in the oxidative coupling of methane reaction is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the C2 selectivity compared to the same reaction under the same conditions but performed with a corresponding catalyst. In other embodiments, the C2 selectivity in an OCM reaction catalyzed by the catalyst is greater than 10%, greater than 20%, greater than 30%, greater than 40%, greater than 50%, greater than 60%, greater than 65%, greater than 75%, or greater than 90%. In some embodiments the C2 selectivity is determined when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less, 700 °C or less, 650 °C or less or even 600 °C or less. The C2 selectivity may also be determined based on a single pass of a gas comprising methane over the catalyst or may be determined based on multiple passes over the catalyst.
In another embodiment, the disclosure provides a catalyst having a catalytic activity in the OCM reaction such that the nanowire has the same catalytic activity (i.e., same selectivity, conversion or yield), but at a lower temperature, compared to a corresponding catalyst. In some embodiments the catalytic activity of the catalysts in the OCM reaction is the same as the catalytic activity of a corresponding catalyst, but at a temperature of at least 20 °C less. In some embodiments the catalytic activity of the catalysts in the OCM reaction is the same as the catalytic activity of a corresponding catalyst, but at a temperature of at least 50 °C less. In some embodiments the catalytic activity of the catalysts in the OCM reaction is the same as the catalytic activity of a corresponding catalyst, but at a temperature of at least 100 °C less. In some embodiments the catalytic activity of the catalysts in the OCM reaction is the same as the catalytic activity of a corresponding catalyst, but at a temperature of at least 200 °C less.
In another embodiment, the disclosure provides a catalyst having a catalytic activity such that the selectivity for CO or CO2 in the oxidative coupling of methane reaction is less than at least 0.9 times, 0.8 times, 0.5 times, 0.2 times, or 0.1 times the selectivity for CO or CO2 compared to the same reaction under the same conditions but performed with a corresponding catalyst.
In other embodiments, the above selectivity, conversion and yield values are determined at a temperature of less than 850 °C, less than 800 °C, less than 750 °C, less than 700 °C or less than 650 °C.
In some other embodiments, a method for converting methane into ethane and/or ethylene comprising use of catalyst mixture comprising two or more catalysts is provided. For example, the catalyst mixture may be a mixture of a catalyst having good OCM activity and a catalyst having good ODH activity. Catalysts suitable for such uses are described in more detail above.
Typically, the OCM reaction is run in a mixture of oxygen and nitrogen or other inert gas. Such gasses are expensive and increase the overall production costs associated with preparation of ethylene or ethane from methane. However, the present inventors have now discovered that such expensive gases are not required and high yield, conversion, selectivity, etc., can be obtained when air is used as the gas mixture instead of pre-packaged and purified sources of oxygen and other gases. Accordingly, in one embodiment the disclosure provides a method for performing the OCM reaction in air by use of one or more of the disclosed catalysts.
In addition to air or O2 gas, the presently disclosed catalysts and associated methods provide for use of other sources of oxygen in the OCM reaction. In this respect, an alternate source of oxygen such a CO2, H2O, SO2 or SO3 may be used either in place of, or in addition to, air or oxygen as the oxygen source. Such methods have the potential to increase the efficiency of the OCM reaction, for example by consuming a reaction byproduct (e.g., CO2 or H2O) and controlling the OCM exotherm as described below.
As noted above, in the OCM reaction, methane is oxidatively converted to methyl radicals, which are then coupled to form ethane, which is subsequently oxidized to ethylene. In traditional OCM reactions, the oxidation agent for both the methyl radical formation and the ethane oxidation to ethylene is oxygen. In order to minimize full oxidation of methane or ethane to carbon dioxide, i.e., maximize C2 selectivity, the methane to oxygen ratio is generally kept at 4 (i.e., full conversion of methane into methyl radicals) or above. As a result, the OCM reaction is typically oxygen limited and thus the oxygen concentration in the effluent is zero.
Accordingly, in one embodiment the present disclosure provides a method for increasing the methane conversion and increasing, or in some embodiments, not reducing, the C2 selectivity in an OCM reaction. The disclosed methods include adding to a traditional OCM catalyst another OCM catalyst that uses an oxygen source other than molecular oxygen. In some embodiments, the alternate oxygen source is CO2, H2O, SO2, SO3 or
combinations thereof. For example in some embodiments, the alternate oxygen source is CO2. In other embodiments the alternate oxygen source is H2O.
Because C2 selectivity is typically between 50% and 80% in the OCM reaction, OCM typically produces significant amounts of CO2 as a byproduct (CO2 selectivity can typically range from 20-50%). Additionally, H2O is produced in copious amounts, regardless of the C2 selectivity. Therefore both CO2 and H2O are attractive oxygen sources for OCM in an O2 depleted environment. Accordingly, one embodiment of the present disclosure provides a catalyst (and related methods for use thereof) which is catalytic in the OCM reaction and which uses CO2, H2O, SO2, SO3 or another alternative oxygen source or combinations thereof as a source of oxygen. Other embodiments, provide a catalytic material comprising two or more catalysts, wherein the catalytic material comprises at least one catalyst which is catalytic in the OCM reaction and uses O2 for at least one oxygen source and at least one catalysts which is catalytic in the OCM reaction and uses at least of CO2, H2O, SO2, SO3 NO, NO2, NO3 or another alternative oxygen source. Methods for performing the OCM reaction with such catalytic materials are also provided. Such catalysts comprise any of the compositions disclosed herein and are effective as catalysts in an OCM reaction using an alternative oxygen source at temperatures of 900 °C or lower, 850 °C or lower, 800 °C or lower, 750 °C or lower, 700 °C or lower or even 650 °C or lower.
Examples of OCM catalysts that use CO2 or other oxygen sources rather than O2 include, but are not limited to, catalysts comprising La2O3/ZnO, CeO2/ZnO, CaO/ZnO, CaO/CeO2, CaO/Cr2O3, CaO/MnO2, SrO/ZnO,
SrO/CeO2, SrO/Cr2O3, SrO/MnO2, SrCO3/MnO2, BaO/ZnO, BaO/CeO2,
BaO/Cr2O3, BaO/MnO2, CaO/MnO/CeO2, Na2WO4/Mn/SiO2, Pr2O3, or Tb2O3.
Some embodiments provide a method for performing OCM, wherein a mixture of an OCM catalyst which use O2 as an oxygen source (referred to herein as an O2-OCM catalyst) and an OCM catalyst which use CO2 as an oxygen source (referred to herein as a CO2-OCM catalyst) is employed as the catalytic material, for example in a catalyst bed. Such methods have certain advantages. For example, the CO2-OCM reaction is endothermic and the O2-OCM reaction is exothermic, and thus if the right mixture and/or arrangement of CO2-OCM and O2-OCM catalysts is used, the methods are particularly useful for controlling the exotherm of the OCM reaction. In some embodiments, the catalyst bed comprises a mixture of O2-OCM catalyst and CO2-OCM catalysts. The mixture may be in a ratio of 1 :99 to 99:1 . The two catalysts work synergistically as the O2-OCM catalyst supplies the CO2-OCM catalyst with the necessary carbon dioxide and the endothermic nature of the C2-OCM reaction serves to control the exotherm of the overall reaction. Alternatively, the CO2 source may be external to the reaction (e.g., fed in from a CO2 tank, or other source) and/or the heat required for the CO2-OCM reaction is supplied from an external source (e.g., heating the reactor).
Since the gas composition will tend to become enriched in CO2 as it flows through the catalyst bed (i.e., as the OCM reaction proceeds, more CO2 is produced), some embodiments of the present invention provide an OCM method wherein the catalyst bed comprises a gradient of catalysts which changes from a high concentration of O2-OCM catalysts at the front of the bed to a high concentration of CO2-OCM catalysts at the end of the catalyst bed.
The O2-OCM catalyst and CO2 OCM catalyst may have the same or different compositions. For example, in some embodiments the O2-OCM catalyst and CO2-OCM catalyst have the same composition but different morphologies (e.g., nanowire, bent nanowire, bulk, etc.). In other embodiments the O2-OCM and the CO2-OCM catalyst have different compositions.
Furthermore, CO2-OCM catalysts will typically have higher selectivity, but lower yields than an O2-OCM catalyst. Accordingly, in one embodiment the methods comprise use of a mixture of an O2-OCM catalyst and a CO2-OCM catalyst and performing the reaction in O2 deprived environment so that the CO2-OCM reaction is favored and the selectivity is increased. Under appropriate conditions the yield and selectivity of the OCM reaction can thus be optimized.
In some other embodiments, the catalyst bed comprises a mixture of one or more low temperature O2-OCM catalyst (i.e., a catalyst active at low temperatures, for example less than 700 °C) and one or more high temperature CO2-OCM catalyst (i.e., a catalyst active at high temperatures, for example 800 °C or higher). Here, the required high temperature for the CO2-OCM may be provided by the hotspots produced by the O2-OCM catalyst. In such a scenario, the mixture may be sufficiently coarse such that the hotspots are not being excessively cooled down by excessive dilution effect. In other embodiments, the catalyst bed comprises alternating layers of O2-OCM and CO2-OCM catalysts. The catalyst layer stack may begin with a layer of O2-OCM catalyst, so that it can supply the next layer {e.g., a CO2-OCM layer) with the necessary CO2. The O2-OCM layer thickness may be optimized to be the smallest at which 02 conversion is 100% and thus the CH4 conversion of the layer is maximized. The catalyst bed may comprise any number of catalyst layers, for example the overall number of layers may be optimized to maximize the overall CH conversion and C2 selectivity.
In some embodiments, the catalyst bed comprises alternating layers of low temperature O2-OCM catalysts and high temperature CO2-OCM catalysts. Since the CO2-OCM reaction is endothermic, the layers of CO2-OCM catalyst may be sufficiently thin such that in can be "warmed up" by the hotspots of the O2-OCM layers. The endothermic nature of the CO2-OCM reaction can be advantageous for the overall thermal management of an OCM reactor. In some embodiments, the CO2-OCM catalyst layers act as "internal" cooling for the O2-OCM layers, thus simplifying the requirements for the cooling, for example in a tubular reactor. Therefore, an interesting cycle takes place with the endothermic reaction providing the necessary heat for the endothermic reaction and the endothermic reaction providing the necessary cooling for the exothermic reaction.
Accordingly, one embodiment of the present invention is a method for the oxidative coupling of methane, wherein the method comprises
conversion of methane to ethane and/or ethylene in the presence of a catalytic material, and wherein the catalytic material comprises a bed of alternating layers of O2-OCM catalysts and CO2-OCM catalysts. In other embodiments the bed comprises a mixture (i.e., not alternating layers) of O2-OCM catalysts and CO2-OCM catalysts.
In other embodiments, the OCM methods include use of a jacketed reactor with the exothermic O2-OCM reaction in the core and the endothermic CO2-OCM reaction in the mantel. In other embodiments, the unused CO2 can be recycled and reinjected into the reactor, optionally with the recycled CH . Additional CO2 can also be injected to increase the overall methane conversion and help reduce greenhouse gases.
In other embodiments, the reactor comprises alternating stages of O2-OCM catalyst beds and CO2-OCM catalyst beds. The CO2 necessary for the CO2-OCM stages is provided by the O2-OCM stage upstream. Additional CO2 may also be injected. The O2 necessary for the subsequent O2-OCM stages is injected downstream from the CO2-OCM stages. The CO2-OCM stages may provide the necessary cooling for the O2-OCM stages.
Alternatively, separate cooling may be provided. Likewise, if necessary the inlet gas of the CO2-OCM stages can be additionally heated, the CO2-OCM bed can be heated or both.
In related embodiments, the CO2 naturally occurring in natural gas is not removed prior to performing the OCM, alternatively CO2 is added to the feed with the recycled methane. Instead the CO2 containing natural gas is used as a feedstock for CO2-OCM, thus potentially saving a separation step. The amount of naturally occurring CO2 in natural gas depends on the well and the methods can be adjusted accordingly depending on the source of the natural gas.
The foregoing methods can be generalized as a method to control the temperature of very exothermic reactions by coupling them with an endothermic reaction that uses the same feedstock (or byproducts of the exothermic reaction) to make the same product (or a related product). This concept can be reversed, i.e., providing heat to an endothermic reaction by coupling it with an exothermic reaction. This will also allow a higher per pass yield in the OCM reactor.
For purpose of simplicity, the above description relating to the use of O2-OCM and CO2-OCM catalysts was described in reference to the oxidative coupling of methane (OCM); however, the same concept is applicable to other catalytic reactions including but not limited to: oxidative dehydrogenation (ODH) of alkanes to their corresponding alkenes, selective oxidation of alkanes and alkenes and alkynes, etc. For example, in a related embodiment, a catalyst capable of using an alternative oxygen source (e.g., CO2, H2O, SO2, SO3 or combinations thereof) to catalyze the oxidative dehydrogenation of ethane is provided. Such catalysts, and uses thereof are described in more detail below.
Furthermore, the above methods are applicable for creating novel catalysts by blending catalysts that use different reactants for the same catalytic reactions, for example different oxidants for an oxidation reaction and at least one oxidant is a byproduct of one of the catalytic reactions. In addition, the methods can also be generalized for internal temperature control of reactors by blending catalysts that catalyze reactions that share the same or similar products but are exothermic and endothermic, respectively. These two concepts can also be coupled together.
2. Oxidative Dehydrogenation
Worldwide demand for alkenes, especially ethylene and
propylene, is high. The main sources for alkenes include steam cracking, fluid- catalytic-cracking and catalytic dehydrogenation. The current industrial processes for producing alkenes, including ethylene and propylene, suffer from some of the same disadvantages described above for the OCM reaction.
Accordingly, a process for the preparation of alkenes which is more energy efficient and has higher yield, selectivity, and conversion than current processes is needed. The catalysts disclosed herein fulfill this need and provide related advantages.
In one embodiment, the catalysts are useful for the oxidative dehydrogenation (ODH) of hydrocarbons (e.g., alkanes, alkenes, and alkynes). For example, in one embodiment the catalysts are useful in an ODH reaction for the conversion of ethane or propane to ethylene or propylene, respectively. Reaction scheme (9) depicts the oxidative dehydrogenation of hydrocarbons:
CxHy + ½ O2 CxHy-2 +H2O (9) Representative catalysts useful for the ODH reaction include, but are not limited to any of the catalysts disclosed herein.
As noted above, improvements to the yield, selectivity, and/or conversion in the ODH reaction employing bulk catalysts are needed.
Accordingly, in one embodiment, the catalysts possess a catalytic activity in the ODH reaction such that the yield, selectivity, and/or conversion is better than when the ODH reaction is catalyzed by a corresponding catalyst. In one embodiment, the disclosure provides a catalyst having a catalytic activity such that the conversion of hydrocarbon to alkene in the ODH reaction is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the conversion of alkane to alkene compared to the same reaction under the same conditions but performed with a corresponding catalyst. In other embodiments, the conversion of alkane to alkene in an ODH reaction catalyzed by the catalyst is greater than 10%, greater than 15%, greater than 20%, greater than 25%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
In another embodiment, the disclosure provides a catalyst having a catalytic activity such that the yield of alkene in an ODH reaction is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the yield of alkene compared to the same reaction under the same conditions but performed with a corresponding catalyst. In some embodiments the yield of alkene in an ODH reaction catalyzed by the catalyst is greater than 10%, greater than 20%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
In another embodiment, the disclosure provides a catalyst having a catalytic activity in the ODH reaction such that the nanowire has the same catalytic activity, but at a lower temperature, compared to a corresponding catalyst. In some embodiments the catalytic activity of the catalysts in the ODH reaction is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 20 °C less. In some embodiments the catalytic activity of the catalysts in the ODH reaction is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 50 °C less. In some embodiments the catalytic activity of the catalysts in the ODH reaction is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 100 °C less. In some embodiments the catalytic activity of the catalysts in the ODH reaction is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 200 °C less.
In another embodiment, the disclosure provides a catalyst having a catalytic activity such that the selectivity for alkenes in an ODH reaction is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the selectivity for alkenes compared to the same reaction under the same conditions but performed with a corresponding catalyst. In other embodiments, the selectivity for alkenes in an ODH reaction catalyzed by the catalyst is greater than 50%, greater than 60%, greater than 70%, greater than 75%, greater than 80%, greater than 85%, greater than 90%, or greater than 95%.
In another embodiment, the disclosure provides a catalyst having a catalytic activity such that the selectivity for CO or CO2 in an ODH reaction is less than at least 0.9 times, 0.8 times, 0.5 times, 0.2 times, or 0.1 times the selectivity for CO or CO2 compared to the same reaction under the same conditions but performed with a corresponding catalyst.
In one embodiment, the catalysts disclosed herein enable efficient conversion of alkane to alkene in the ODH reaction at temperatures less than when a corresponding catalyst is used. For example, in one embodiment, the catalysts disclosed herein enable efficient conversion (i.e., high yield, conversion, and/or selectivity) of hydrocarbon to alkene at temperatures of less than 800 °C, less than 700 °C, less than 600 °C, less than 500 °C, less than 400 °C, or less than 300 °C. The stability of the catalysts is defined as the length of time a catalyst will maintain its catalytic performance without a significant decrease in performance (e.g., a decrease >20%, >15%, >10%, >5%, or greater than 1 % in ODH activity or alkene selectivity, etc.). In some embodiments, the catalysts have stability under conditions required for the ODH reaction of >1 hr, >5 hrs, >10 hrs, >20 hrs, >50 hrs, >80 hrs, >90 hrs, >100 hrs, >150 hrs, >200 hrs, >250 hrs, >300 hrs, >350 hrs, >400 hrs, >450 hrs, >500 hrs, >550 hrs, >600 hrs, >650 hrs, >700 hrs, >750 hrs, >800 hrs, >850 hrs, >900 hrs, >950 hrs, >1 ,000 hrs, >2,000 hrs, >3,000 hrs, >4,000 hrs, >5,000 hrs, >6,000 hrs, >7,000 hrs, >8,000 hrs, >9,000 hrs, >10,000 hrs, >1 1 ,000 hrs, >12,000 hrs, >13,000 hrs, >14,000 hrs, >15,000 hrs, >16,000 hrs, >17,000 hrs, >18,000 hrs, >19,000 hrs, >20,000 hrs, >1 yrs, >2 yrs, >3 yrs, >4 yrs or >5 yrs.
One embodiment of the present disclosure is directed to a catalyst capable of using an alternative oxygen source (e.g., CO2, H2O, SO2, SO3 or combinations thereof) to catalyze the oxidative dehydrogenation of ethane. For example, the ODH reaction may proceed according to the following reaction (10):
Figure imgf000206_0001
wherein x is an integer and Y is 2x + 2. Compositions useful in this regard include Fe2O3, Cr2O3, MnO2, Ga2O3, Cr/SiO2, Cr/SO4-SiO2, Cr-K/SO4-SiO2, Na2WO4-Mn/SiO2, Cr-HZSM-5, Cr/Si-MCM-41 (Cr-HZSM-5 and Cr/Si-MCM-41 refer to known zeolites) and MoC/SiO2. In some embodiments, any of the foregoing catalyst compositions may be supported on S1O2, ZrO2, AI2O3, T1O2 or combinations thereof.
The catalysts having ODH activity with alternative oxygen sources
(e.g., CO2, referred to herein as a CO2-ODH catalyst) have a number of advantages. For example, in some embodiments a method for converting methane to ethylene comprises use of an O2-OCM catalyst in the presence of a CO2-ODH catalyst is provided. Catalytic materials comprising at least one O2- OCM catalyst and at least one CO2-ODH catalyst are also provided in some embodiments. This combination of catalysts results in a higher yield of ethylene (and/or ratio of ethylene to ethane) since the CO2 produced by the OCM reaction is consumed and used to convert ethane to ethylene.
In one embodiment, a method for preparation of ethylene comprises converting methane to ethylene in the presence of two or more catalysts, wherein at least one catalyst is an O2-OCM catalyst and at least one catalyst is a CO2-ODH catalyst. Such methods have certain advantages. For example, the CO2-ODH reaction is endothermic and the O2-OCM reaction is exothermic, and thus if the right mixture and/or arrangement of CO2-ODH and O2-OCM catalysts is used, the methods are particularly useful for controlling the exotherm of the OCM reaction. In some embodiments, the catalyst bed comprises a mixture of O2-OCM catalyst and CO2-ODH catalysts. The mixture may be in a ratio of 1 :99 to 99:1 . The two catalysts work synergistically as the O2-OCM catalyst supplies the CO2-ODH catalyst with the necessary carbon dioxide and the endothermic nature of the C2-OCM reaction serves to control the exotherm of the overall reaction.
Since the gas composition will tend to become enriched in CO2 as it flows through the catalyst bed (i.e., as the OCM reaction proceeds, more CO2 is produced), some embodiments of the present invention provide an OCM method wherein the catalyst bed comprises a gradient of catalysts which changes from a high concentration of O2-OCM catalysts at the front of the bed to a high concentration of CO2-ODH catalysts at the end of the catalyst bed.
The O2-ODH catalyst and CO2-ODH catalyst may have the same or different compositions. For example, in some embodiments the O2-ODH catalyst and CO2-ODH catalyst have the same composition but different morphologies (e.g., nanowire, bent nanowire, bulk, etc.). In other embodiments the O2-ODH and the CO2-ODH catalyst have different compositions.
In other embodiments, the catalyst bed comprises alternating layers of O2-OCM and CO2-ODH catalysts. The catalyst layer stack may begin with a layer of O2-OCM catalyst, so that it can supply the next layer (e.g., a CO2-ODH layer) with the necessary CO2. The O2-OCM layer thickness may be optimized to be the smallest at which 02 conversion is 100% and thus the CH conversion of the layer is maximized. The catalyst bed may comprise any number of catalyst layers, for example the overall number of layers may be optimized to maximize the overall CH4 conversion and C2 selectivity.
In some embodiments, the catalyst bed comprises alternating layers of low temperature O2-OCM catalysts and high temperature CO2-ODH catalysts. Since the CO2-ODH reaction is endothermic, the layers of CO2-ODH catalyst may be sufficiently thin such that in can be "warmed up" by the hotspots of the O2-OCM layers. The endothermic nature of the CO2-ODH reaction can be advantageous for the overall thermal management of an OCM reactor. In some embodiments, the CO2-ODH catalyst layers act as "internal" cooling for the O2-OCM layers, thus simplifying the requirements for the cooling, for example in a tubular reactor. Therefore, an interesting cycle takes place with the endothermic reaction providing the necessary heat for the endothermic reaction and the endothermic reaction providing the necessary cooling for the exothermic reaction.
Accordingly, one embodiment of the present invention is a method for the oxidative coupling of methane, wherein the method comprises
conversion of methane to ethane and/or ethylene in the presence of a catalytic material, and wherein the catalytic material comprises a bed of alternating layers of O2-OCM catalysts and CO2-ODH catalysts. In other embodiments the bed comprises a mixture (i.e., not alternating layers) of O2-OCM catalysts and CO2-ODH catalysts. Such methods increase the ethylene yield and/or ratio of ethylene to ethane compared to other known methods.
In other embodiments, the OCM methods include use of a jacketed reactor with the exothermic O2-OCM reaction in the core and the endothermic CO2-ODH reaction in the mantel. In other embodiments, the unused CO2 can be recycled and reinjected into the reactor, optionally with the recycled CH . Additional CO2 can also be injected to increase the overall methane conversion and help reduce greenhouse gases.
In other embodiments, the reactor comprises alternating stages of
O2-OCM catalyst beds and CO2-ODH catalyst beds. The CO2 necessary for the CO2-ODH stages is provided by the O2-OCM stage upstream. Additional
CO2 may also be injected. The O2 necessary for the subsequent O2-OCM stages is injected downstream from the CO2-ODH stages. The CO2-ODH stages may provide the necessary cooling for the O2-OCM stages.
Alternatively, separate cooling may be provided. Likewise, if necessary the inlet gas of the CO2-ODH stages can be additionally heated, the CO2-ODH bed can be heated or both.
In related embodiments, the CO2 naturally occurring in natural gas is not removed prior to performing the OCM, alternatively CO2 is added to the feed with the recycled methane. Instead the CO2 containing natural gas is used as a feedstock for CO2-ODH, thus potentially saving a separation step. The amount of naturally occurring CO2 in natural gas depends on the well and the methods can be adjusted accordingly depending on the source of the natural gas.
3. Carbon dioxide reforming of methane
Carbon dioxide reforming (CDR) of methane is an attractive process for converting CO2 in process streams or naturally occurring sources into the valuable chemical product, syngas (a mixture of hydrogen and carbon monoxide). Syngas can then be manufactured into a wide range of
hydrocarbon products through processes such as the Fischer-Tropsch synthesis (discussed below) to form liquid fuels including methanol, ethanol, diesel, and gasoline. The result is a powerful technique to not only remove CO2 emissions but also create a new alternative source for fuels that are not derived from petroleum crude oil. The CDR reaction with methane is exemplified in reaction scheme (1 1 ). CO2 + CH4 ^ 2CO + 2H2 (1 1 )
Unfortunately, no established industrial technology for CDR exists today in spite of its tremendous potential value. While not wishing to be bound by theory, it is thought that the primary problem with CDR is due to side- reactions from catalyst deactivation induced by carbon deposition via the Boudouard reaction (reaction scheme (12)) and/or methane cracking (reaction scheme (13)) resulting from the high temperature reaction conditions. The occurrence of the coking effect is intimately related to the complex reaction mechanism, and the associated reaction kinetics of the catalysts employed in the reaction.
2CO ^ C + CO2 (12) CH4 ^ C + 2H2 (13)
While not wishing to be bound by theory, the CDR reaction is thought to proceed through a multistep surface reaction mechanism. Figure 3 schematically depicts a CDR reaction 700, in which activation and dissociation of CH occurs on the metal catalyst surface 710 to form intermediate "M-C". At the same time, absorption and activation of CO2 takes place at the oxide support surface 720 to provide intermediate "S-CO2", since the carbon in a CO2 molecule as a Lewis acid tends to react with the Lewis base center of an oxide. The final step is the reaction between the M-C species and the activated S-CO2 to form CO.
In one embodiment, the catalysts disclosed herein are useful as catalysts for the carbon dioxide reforming of methane. For example, in one embodiment the catalysts are useful as catalysts in a CDR reaction for the production of syn gas.
Improvements to the yield, selectivity, and/or conversion in the CDR reaction employing known catalysts are needed. Accordingly, in one embodiment, the catalysts possess a catalytic activity in the CDR reaction such that the yield, selectivity, and/or conversion is better than when the CDR reaction is catalyzed by a corresponding catalyst. In one embodiment, the disclosure provides a catalyst having a catalytic activity such that the
conversion of CO2 to CO in the CDR reaction is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the conversion of CO2 to CO compared to the same reaction under the same conditions but performed with a corresponding catalyst. In other embodiments, the conversion of CO2 to CO in a CDR reaction catalyzed by the catalyst is greater than 10%, greater than 15%, greater than 20%, greater than 25%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
In another embodiment, the disclosure provides a catalyst having a catalytic activity such that the yield of CO in a CDR reaction is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the yield of CO compared to the same reaction under the same conditions but performed with a corresponding catalyst. In some embodiments the yield of CO in a CDR reaction catalyzed by the catalyst is greater than 10%, greater than 20%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
In another embodiment, the disclosure provides a catalyst having a catalytic activity such that the selectivity for CO in a CDR reaction is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the selectivity for CO compared to the same reaction under the same conditions but performed with a corresponding catalyst. In other embodiments, the selectivity for CO in a CDR reaction catalyzed by the catalyst is greater than 10%, greater than 20%, greater than 30%, greater than 40%, greater than 50%, greater than 65%, greater than 75%, or greater than 90%.
In another embodiment, the disclosure provides a catalyst having a catalytic activity in a CDR reaction such that the catalyst has the same or better catalytic activity, but at a lower temperature, compared to a
corresponding. In some embodiments the catalytic activity of the catalysts in a CDR reaction is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 20 °C less. In some embodiments the catalytic activity of the catalysts in a CDR reaction is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 50 °C less. In some embodiments the catalytic activity of the catalysts in a CDR reaction is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 100 °C less. In some embodiments the catalytic activity of the catalysts in a CDR reaction is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 200 °C less.
In one embodiment, the catalysts disclosed herein enable efficient conversion of CO2 to CO in the CDR reaction at temperatures less than when a corresponding catalyst is used. For example, in one embodiment, the catalysts enable efficient conversion (i.e., high yield, conversion, and/or selectivity) of CO2 to CO at temperatures of less than 900 °C, less than 800 °C, less than 700 °C, less than 600 °C, or less than 500 °C.
4. Fischer-Tropsch synthesis
Fischer-Tropsch synthesis (FTS) is a valuable process for converting synthesis gas (i.e., CO and H2) into valuable hydrocarbon fuels, for example, light alkenes, gasoline, diesel fuel, etc. FTS has the potential to reduce the current reliance on the petroleum reserve and take advantage of the abundance of coal and natural gas reserves. Current FTS processes suffer from poor yield, selectivity, conversion, catalyst deactivation, poor thermal efficiency and other related disadvantages. Production of alkanes via FTS is shown in reaction scheme (14), wherein n is an integer. CO + 2H2 (1 /n)(CnH2n) + H2O (14)
In one embodiment, the catalysts are useful as catalysts in FTS processes. For example, in one embodiment the catalysts are useful as catalysts in a FTS process for the production of alkanes. Improvements to the yield, selectivity, and/or conversion in FTS processes employing bulk catalysts are needed. Accordingly, in one
embodiment, the catalysts possess a catalytic activity in an FTS process such that the yield, selectivity, and/or conversion is better than when the FTS process is catalyzed by a corresponding catalyst. In one embodiment, the disclosure provides a catalyst having a catalytic activity such that the
conversion of CO to alkane in an FTS process is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the conversion of CO to alkane compared to the same reaction under the same conditions but performed with a corresponding catalyst. In other embodiments, the conversion of CO to alkane in an FTS process catalyzed by the catalyst is greater than 10%, greater than 15%, greater than 20%, greater than 25%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
In another embodiment, the disclosure provides a catalyst having a catalytic activity in an FTS process such that the catalyst has the same or better catalytic activity, but at a lower temperature, compared a corresponding catalyst. In some embodiments, the catalytic activity of the catalysts in an FTS process is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 20 °C less. In some embodiments the catalytic activity of the catalysts in an FTS process is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 50 °C less. In some embodiments the catalytic activity of the catalysts in an FTS process is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 100 °C less. In some embodiments the catalytic activity of the catalysts in an FTS process is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 200 °C less.
In another embodiment, the disclosure provides a catalyst having a catalytic activity such that the yield of alkane in a FTS process is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the yield of alkane compared to the same reaction under the same conditions but performed with a corresponding catalyst. In some embodiments the yield of alkane in an FTS process catalyzed by the catalyst is greater than 10%, greater than 20%, greater than 30%, greater than 40%, greater than 50%, greater than 65%, greater than 75%, or greater than 90%.
In another embodiment, the disclosure provides a catalyst having a catalytic activity such that the selectivity for alkanes in an FTS process is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the selectivity for alkanes compared to the same reaction under the same conditions but performed with a corresponding catalyst. In other embodiments, the selectivity for alkanes in an FTS process catalyzed by the catalyst is greater than 10%, greater than 20%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
In one embodiment, the catalysts disclosed herein enable efficient conversion of CO to alkanes in a CDR process at temperatures less than when a corresponding catalyst is used. For example, in one embodiment, the catalysts enable efficient conversion (i.e., high yield, conversion, and/or selectivity) of CO to alkanes at temperatures of less than 400 °C, less than 300 °C, less than 250 °C, less than 200 °C, less the 150 °C, less than 100 °C or less than 50 °C.
5. Oxidation of CO
Carbon monoxide (CO) is a toxic gas and can convert hemoglobin to carboxyhemoglobin resulting in asphyxiation. Dangerous levels of CO can be reduced by oxidation of CO to CO2 as shown in reaction scheme 15:
CO + 1/2O2 ^ CO2 (15)
Catalysts for the conversion of CO into CO2 have been developed but improvements to the known catalysts are needed. Accordingly in one embodiment, the present disclosure provides catalysts useful as catalysts for the oxidation of CO to CO2. In one embodiment, the catalysts possess a catalytic activity in a process for the conversion of CO into CO2 such that the yield, selectivity, and/or conversion is better than when the oxidation of CO into CO2 is catalyzed by a corresponding catalyst. In one embodiment, the disclosure provides a catalyst having a catalytic activity such that the conversion of CO to CO2 is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the conversion of CO to CO2 compared to the same reaction under the same conditions but performed with a corresponding catalyst. In other embodiments, the conversion of CO to CO2 catalyzed by the catalyst is greater than 10%, greater than 15%, greater than 20%, greater than 25%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
In another embodiment, the disclosure provides a catalyst having a catalytic activity such that the yield of CO2 from the oxidation of CO is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the yield of CO2 compared to the same reaction under the same conditions but performed with a corresponding catalyst. In some embodiments the yield of CO2 from the oxidation of CO catalyzed by the catalyst is greater than 10%, greater than 20%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
In another embodiment, the disclosure provides a catalyst having a catalytic activity in an oxidation of CO reaction such that the catalyst has the same or better catalytic activity, but at a lower temperature, compared to a corresponding catalyst. In some embodiments the catalytic activity of the catalysts in an oxidation of CO reaction is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 20 °C less. In some embodiments the catalytic activity of the catalysts in an oxidation of CO reaction is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 50 °C less. In some embodiments the catalytic activity of the catalysts in an oxidation of CO reaction is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 100 °C less. In some embodiments the catalytic activity of the catalysts in an oxidation of CO reaction is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 200 °C less.
In another embodiment, the disclosure provides a catalyst having a catalytic activity such that the selectivity for CO2 in the oxidation of CO is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the selectivity for CO2 compared to the same reaction under the same conditions but performed with a corresponding catalyst. In other embodiments, the selectivity for CO2 in the oxidation of CO catalyzed by the catalyst is greater than 10%, greater than 20%, greater than 30%, greater than 40%, greater than 50%, greater than 65%, greater than 75%, or greater than 90%.
In one embodiment, the catalysts disclosed herein enable efficient conversion of CO to CO2 at temperatures less than when a corresponding catalyst is used as a catalyst. For example, in one embodiment, the catalysts enable efficient conversion (i.e., high yield, conversion, and/or selectivity) of CO to CO2 at temperatures of less than 500 °C, less than 400 °C, less than 300 °C, less than 200 °C, less than 100 °C, less than 50 °C or less than 20 °C.
Although various reactions have been described in detail, the disclosed catalysts are useful as catalysts in a variety of other reactions. In general, the disclosed catalysts find utility in any reaction utilizing a
heterogeneous catalyst and have a catalytic activity such that the yield, conversion, and/or selectivity in reaction catalyzed by the catalysts is better than the yield, conversion and/or selectivity in the same reaction catalyzed by a corresponding catalyst.
6. Combustion of Hydrocarbons
In another embodiment, the present disclosure provides a catalyst having catalytic activity in a reaction for the catalyzed combustion of
hydrocarbons. Such catalytic reactions find utility in catalytic converters for automobiles, for example by removal of unburned hydrocarbons in the exhaust by catalytic combustion or oxidation of soot captured on catalyzed particle filters resulting in reduction on diesel emissions from the engine. When running "cold", the exhausts temperature of a diesel engine is quite low, thus a low temperature catalyst, such as the disclosed catalysts, is needed to efficiently eliminate all unburned hydrocarbons. In addition, in case of soot removal on catalyzed particulate filters, intimate contact between the soot and the catalyst is require; the open mesh morphology of catalyst coating is advantageous to promote such intimate contact between soot and oxidation catalyst.
In contrast to a corresponding catalyst, Applicants have found that certain catalysts, for example the exemplary catalysts disclosed herein, possess a catalytic activity (for example because of their morphology) in the combustion of hydrocarbons or soot such that the yield, selectivity, and/or conversion is better than when the combustion of hydrocarbons is catalyzed by a corresponding catalyst. In one embodiment, the disclosure provides a catalyst having a catalytic activity such that the combustion of hydrocarbons is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the combustion of hydrocarbons compared to the same reaction under the same conditions but performed with a corresponding catalyst. In other embodiments, the total combustion of hydrocarbons catalyzed by the catalyst is greater than 10%, greater than 20%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%.
In another embodiment, the disclosure provides a catalyst having a catalytic activity such that the yield of combusted hydrocarbon products is greater than at least 1 .1 times, 1 .25 times, 1 .50 times, 2.0 times, 3.0 times, or 4.0 times the yield of combusted hydrocarbon products compared to the same reaction under the same conditions but performed with a corresponding catalyst. In some embodiments the yield of combusted hydrocarbon products in a reaction catalyzed by the catalyst is greater than 10%, greater than 20%, greater than 30%, greater than 50%, greater than 75%, or greater than 90%. The stability of the catalysts is defined as the length of time a catalyst will maintain its catalytic performance without a significant decrease in performance (e.g., a decrease >20%, >15%, >10%, >5%, or greater than 1 % in hydrocarbon or soot combustion activity). In some embodiments, the catalysts have stability under conditions required for the hydrocarbon combustion reaction of >1 hr, >5 hrs, >10 hrs, >20 hrs, >50 hrs, >80 hrs, >90 hrs, >100 hrs, >150 hrs, >200 hrs, >250 hrs, >300 hrs, >350 hrs, >400 hrs, >450 hrs, >500 hrs, >550 hrs, >600 hrs, >650 hrs, >700 hrs, >750 hrs, >800 hrs, >850 hrs, >900 hrs, >950 hrs, >1 ,000 hrs, >2,000 hrs, >3,000 hrs, >4,000 hrs, >5,000 hrs, >6,000 hrs, >7,000 hrs, >8,000 hrs, >9,000 hrs, >10,000 hrs, >1 1 ,000 hrs,
>12,000 hrs, >13,000 hrs, >14,000 hrs, >15,000 hrs, >16,000 hrs, >17,000 hrs, >18,000 hrs, >19,000 hrs, >20,000 hrs, >1 yrs, >2 yrs, >3 yrs, >4 yrs or >5 yrs.
In another embodiment, the disclosure provides a catalyst having a catalytic activity in the combustion of hydrocarbons such that the catalyst has the same or better catalytic activity, but at a lower temperature, compared to a corresponding catalyst. In some embodiments the catalytic activity of the catalysts in the combustion of hydrocarbons is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 20 °C less. In some embodiments the catalytic activity of the catalysts in the combustion of hydrocarbons is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 50 °C less. In some embodiments the catalytic activity of the catalysts in the combustion of hydrocarbons is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 100 °C less. In some embodiments the catalytic activity of the catalysts in the combustion of hydrocarbons is the same or better than the catalytic activity of a corresponding catalyst, but at a temperature of at least 200 °C less.
7. Evaluation of Catalytic Properties
To evaluate the catalytic properties of the catalysts in a given reaction, for example those reactions discussed above, various methods can be employed to collect and process data including measurements of the kinetics and amounts of reactants consumed and the products formed. In addition to allowing for the evaluation of the catalytic performances, the data can also aid in designing large scale reactors, experimentally validating models and optimizing the catalytic process.
One exemplary methodology for collecting and processing data is depicted in Figure 4. Three main steps are involved. The first step (block 750) comprises the selection of a reaction and catalyst. This influences the choice of reactor and how it is operated, including batch, flow, etc. (block 754).
Thereafter, the data of the reaction are compiled and analyzed (block 760) to provide insights to the mechanism, rates and process optimization of the catalytic reaction. In addition, the data provide useful feedbacks for further design modifications of the reaction conditions. Additional methods for evaluating catalytic performance in the laboratory and industrial settings are described in, for example, Bartholomew, C.H. et al. Fundamentals of Industrial Catalytic Processes, Wiley-AIChE; 2Ed (1998).
As an example, in a laboratory setting, an Altamira Benchcat 200 can be employed using a 4 mm ID diameter quartz tube with a 0.5 mm ID capillary downstream. Quartz tubes with 2 mm or 6 mm ID can also be used. Catalysts are tested in a number of different dilutions and amounts. In some embodiments, the range of testing is between 10 and 300 mg. In some embodiments, the catalysts are diluted with a non-reactive diluent. This diluent can be quartz (S1O2) or other inorganic materials, which are known to be inert in the reaction condition. The purpose of the diluent is to minimize hot spots and provide an appropriate loading into the reactor. In addition, the catalyst can be blended with less catalytically active components as described in more detail above.
In a typical procedure, 50 mg is the total charge of catalyst, optionally including diluent. On either side of the catalysts a small plug of glass wool is loaded to keep the catalysts in place. A thermocouple is placed on the inlet side of the catalyst bed into the glass wool to get the temperature in the reaction zone. Another thermocouple can be placed on the downstream end of the catalyst bed into the catalyst bed itself to measure the exotherms, if any.
When blending the catalyst with diluent, the following exemplary procedure may be used: x (usually 10-50) mg of the catalyst (either bulk or test nanowire catalyst) is blended with (100-x) mg of diluent. Thereafter, about 2 ml of ethanol or water is added to form a slurry mixture, which is then sonicated for about 10 minutes. The slurry is then dried in an oven at about 100-140 °C for 2 hours to remove solvent. The resulting solid mixture is then scraped out and loaded into the reactor between the plugs of quartz wool.
Once loaded into the reactor, the reactor is inserted into the Altamira instrument and furnace and then a temperature and flow program is started. In some embodiment, the total flow is 50 to 100 seem of gases but this can be varied and programmed with time. In one embodiment, the
temperatures range from 450 °C to 900 °C. The reactant gases comprise air or oxygen (diluted with nitrogen or argon) and methane in the case of the OCM reaction and gas mixtures comprising ethane and/or propane with oxygen for oxidative dehydrogenation (ODH) reactions. Other gas mixtures can be used for other reactions.
The primary analysis of these oxidation catalysis runs is the Gas
Chromatography (GC) analysis of the feed and effluent gases. From these analyses, the conversion of the oxygen and alkane feed gases can easily be attained and estimates of yields and selectivities of the products and byproducts can be determined.
The GC method developed for these experiments employs 4 columns and 2 detectors and a complex valve switching system to optimize the analysis. Specifically, a flame ionization detector (FID) is used for the analysis of the hydrocarbons only. It is a highly sensitive detector that produces accurate and repeatable analysis of methane, ethane, ethylene, propane, propylene and all other simple alkanes and alkenes up to five carbons in length and down to ppm levels.
There are two columns in series to perform this analysis, the first is a stripper column (alumina) which traps polar materials (including the water by-product and any oxygenates generated) until back-flushed later in the cycle. The second column associated with the FID is a capillary alumina column known as a PLOT column which performs the actual separation of the light hydrocarbons. The water and oxygenates are not analyzed in this method.
For the analysis of the light non-hydrocarbon gases, a Thermal Conductivity Detector (TCD) may be employed which also employees two columns to accomplish its analysis. The target molecules for this analysis are CO2, ethylene, ethane, hydrogen, oxygen, nitrogen, methane and CO. The two columns used here are a porous polymer column known as the Hayes Sep N which performs some of the separation for the CO2, ethylene and ethane. The second column is a molecular sieve column which uses size differentiation to perform the separation. It is responsible for the separation of H2, O2, N2, methane and CO.
There is a sophisticated and timing sensitive switching between these two columns in the method. In the first 2 minutes or so, the two columns are operating in series but at about 2 minutes, the molecular sieve column is by-passed and the separation of the first 3 components is completed. At about 5-7 minutes, the columns are then placed back in series and the light gases come off of the sieve according to their molecular size.
The end result is an accurate analysis of all of the aforementioned components from these fixed-beds, gas phase reactions. Analysis of other reactions and gases not specifically described above can be performed in a similar manner known to those of skill in the art.
8. Downstream Products
As noted above, the catalysts disclosed herein are useful in reactions for the preparation of a number of valuable hydrocarbon compounds. For example, in one embodiment the catalysts are useful for the preparation of ethylene from methane via the OCM reaction. In another embodiment, the catalysts are useful for the preparation of ethylene or propylene via oxidative dehydrogenation of ethane or propane respectively. Ethylene and propylene are valuable compounds which can be converted into a variety of consumer products. For example, as shown in Figure 5, ethylene can be converted into many various compounds including low density polyethylene, high density polyethylene, ethylene dichloride, ethylene oxide, ethylbenzene, linear alcohols, vinyl acetate, alkanes, alpha olefins, various hydrocarbon-based fuels, ethanol and the like. These compounds can then be further processed using methods well known to one of ordinary skill in the art to obtain other valuable chemicals and consumer products (e.g., the downstream products shown in Figure 5). Propylene can be analogously converted into various compounds and consumer goods including polypropylenes, propylene oxides, propanol, and the like.
Accordingly, in one embodiment the invention is directed to a method for the preparation of C2 hydrocarbons via the OCM reaction, the method comprises contacting a catalyst as described herein with a gas comprising methane. In some embodiments the C2 hydrocarbons are selected from ethane and ethylene. In other embodiments the disclosure provides a method of preparing downstream products of ethylene. The method comprises converting ethylene into a downstream product of ethylene, wherein the ethylene has been prepared via a catalytic reaction employing a catalyst disclosed herein (e.g., OCM). In some embodiments, the downstream product of ethylene is low density polyethylene, high density polyethylene, ethylene dichloride, ethylene oxide, ethylbenzene, ethanol or vinyl acetate from ethylene, wherein the ethylene has been prepared as described above. In other embodiments, the downstream product of ethylene is natural gasoline. In still other embodiments, the downstream product of ethylene comprises 1 -hexene, 1 -octene, hexane, octane, benzene, toluene, xylene or combinations thereof. In another embodiment, a process for the preparation of ethylene from methane comprising contacting a mixture comprising oxygen and methane at a temperature below 900 °C, below 850 °C, below 800 °C, below 750 °C, below 700 °C or below 650 °C with a catalyst as disclosed herein is provided.
In another embodiment, the disclosure provides a method of preparing a product comprising low density polyethylene, high density
polyethylene, ethylene dichloride, ethylene oxide, ethylbenzene, ethanol or vinyl acetate, alkenes, alkanes, aromatics, alcohols, or mixtures thereof. The method comprises converting ethylene into low density polyethylene, high density polyethylene, ethylene dichloride, ethylene oxide, ethylbenzene, ethanol or vinyl acetate, wherein the ethylene has been prepared via a catalytic reaction employing a catalyst for example any of the exemplary catalysts disclosed herein.
In more specific embodiments of any of the above methods, the ethylene is produced via an OCM or ODH reaction or combinations thereof.
In one particular embodiment, the disclosure provides a method of preparing a downstream product of ethylene and/or ethane, wherein the downstream product is a hydrocarbon fuel. For example, the downstream product of ethylene may be a hydrocarbon fuel such as natural gasoline or a C4-Ci4 hydrocarbon, including alkanes, alkenes and aromatics. Some specific examples include 1 -butene, 1 -hexene, 1 -octene, hexane, octane, benzene, toluene, xylenes and the like. The method comprises converting methane into ethylene, ethane or combinations thereof by use of a catalyst, for example any of the catalysts disclosed herein, and further oligomerizing the ethylene and/or ethane to prepare a downstream product of ethylene and/or ethane. For example, the methane may be converted to ethylene, ethane or combinations thereof via the OCM reaction as discussed above.
As depicted in Figure 6, the method begins with charging methane (e.g., as a component in natural gas) into an OCM reactor. The OCM reaction may then be performed utilizing a catalyst under any variety of conditions. Water and CO2 are optionally removed from the effluent and unreacted methane is recirculated to the OCM reactor.
Ethylene is recovered and charged to an oligomerization reactor. Optionally the ethylene stream may contain CO2, H2O, N2, ethane, C3's and/or higher hydrocarbons. Oligomerization to higher hydrocarbons (e.g., C -Ci ) then proceeds under any number of conditions known to those of skill in the art. For example oligomerization may be effected by use of any number of catalysts known to those skilled in the art. Examples of such catalysts include catalytic zeolites, crystalline borosilicate molecular sieves, homogeneous metal halide catalysts, Cr catalysts with pyrrole ligands or other catalysts. Exemplary methods for the conversion of ethylene into higher hydrocarbon products are disclosed in the following references: Catalysis Science & Technology (201 1 ), 1 (1 ), 69-75; Coordination Chemistry Reviews (201 1 ), 255(7-8), 861 -880; Eur. Pat. Appl. (201 1 ), EP 2287142 A1 201 10223; Organometallics (201 1 ), 30(5), 935-941 ; Designed Monomers and Polymers (201 1 ), 14(1 ), 1 -23; Journal of Organometallic Chemistry 689 (2004) 3641-3668; Chemistry-A European Journal (2010), 16(26), 7670-7676; Acc. Chem. Res. 2005, 38, 784-793;
Journal of Organometallic Chemistry, 695 (10-1 1 ): 1541 -1549 May 15 2010; Catalysis Today Volume 6, Issue 3, January 1990, Pages 329-349; U.S. Patent No. 5,968,866; U.S. Patent No. 6,800,702; U.S. Patent No. 6,521 ,806; U.S. Patent No. 7,829,749; U.S. Patent No. 7,867,938; U.S. Patent No. 7,910,670; U.S. Patent No. 7,414,006 and Chem. Commun., 2002, 858-859, each of which are hereby incorporated in their entirety by reference.
In certain embodiments, the exemplary OCM and oligomerization modules depicted in Figure 6 may be adapted to be at the site of natural gas production, for example a natural gas field. Thus the natural gas can be efficiently converted to more valuable and readily transportable hydrocarbon commodities without the need for transport of the natural gas to a processing facility. Referring to Figure 6, "natural gasoline" refers to a mixture of oligomerized ethylene products. In this regard, natural gasoline comprises hydrocarbons containing 5 or more carbon atoms. Exemplary components of natural gasoline include linear, branched or cyclic alkanes, alkenes and alkynes, as well as aromatic hydrocarbons. For example, in some
embodiments the natural gasoline comprises 1 -pentene, 1 -hexene, cyclohexene, 1 -octene, benzene, toluene, dimethyl benzene, xylenes, napthalene, or other oligomerized ethylene products or combinations thereof. In some embodiments, natural gasoline may also include C3 and C4 hydrocarbons dissolved within the liquid natural gasoline. This mixture finds particular utility in any number of industrial applications, for example natural gasoline is used as feedstock in oil refineries, as fuel blend stock by operators of fuel terminals, as diluents for heavy oils in oil pipelines and other
applications. Other uses for natural gasoline are well-known to those of skill in the art.
The following examples are provided for purposes of illustration, not limitation.
EXAMPLES
EXAMPLE 1
PREPARATION OF A CATALYST COMPRISING LA, ND AND SR
Equimolar aqueous solutions of strontium nitrate, neodymium nitrate, and lanthanum nitrate were prepared. Aliquots of each solution were mixed together to prepare a desired formulation of LaxNdySrz where x,y,z represent mole fractions of total metal content in moles. Representative examples of formulations are: La5oNd3oSr2o, La52Nd45Sr05, La75Nd22Sr03, and the like. A solution of citric acid was added to the metal salt mixture so that citric acid mole/metal mole ratio was 3:1 . Ethylene glycol was then added to the citric acid/metal salt solution so that the ethylene glycol/citric acid mole ratio was 1 :1 . The solution was stirred at room temperature for 1 h. The solution was placed in a 130 °C oven for 15 h to remove water and to promote resin formation. After 15h, a hard dark resin was observed. The resin was placed in a furnace and heated to 500 °C for 8h. The remaining material was heated to 650 °C for 2h to yield the desired product.
Other catalysts are prepared according to an analogous procedure. For example, catalysts comprising La and Sm as well as catalysts comprising La and Ce can be prepared according to the above general procedure. Furthermore, catalysts comprising La/Ce/Nd/Sr, La/Bi/Sr, Nd/Sr, La/Sr, La/Bi/Ce/Nd/Sr can also be prepared in this manner.
Catalysts comprising support materials can also be prepared by coprecipitation according to the above method. For example, rare earth oxides on MgO, CaO or AIPO4 supports can be prepared. Specific examples include, Nd/Sr/CaO (i.e., a catalyst comprising Nd and Sr on a CaO support). EXAMPLE 2
PREPARATION OF A SR DOPED ND2O3 CATALYST
To prepare this catalyst at a level of 20 mole% Sr (based on total moles of Nd2O3), 3.0g of Nd2O3 bulk from Alfa Chemicals was slurried in a solution formed by dissolving 0.378g of Sr(NO3)2 in about 20ml of Dl water. The slurry was stirred at room temperature for about 30 minutes to ensure that the Sr(NO3)2 dissolved. The slurry was then moved to an evaporating dish and placed into an oven at 100-140 °C for 2-3 hours to ensure dryness. The solids were then calcined in a furnace by ramping up to 350 °C at 5 °C /min and holding for 2 hours and then ramping again at the same rate to 700 °C and holding for 4 hours. It was then cooled to room temperature, ground and sieved to a particle size range of 180μηη to 250μηη.
EXAMPLE 3
PREPARATION OF A LIMGMNB CATALYST The following fine powders were mixed together: 1 .072g of
Mn2O3 (325 mesh); 1 .418g of MgO (325 mesh); 0.384g Boric acid powder and 0.164g LiOH anhydrous. This corresponds to an approximate molar ratio of Li:B:Mn:Mg of 1 :1 :2:5. The powders were then added to about 20 ml of water, resulting in a black slurry. This slurry was stirred for about an hour to dissolve all of the LiOH and boric acid and then dried for several hours at about 120 °C. In a crucible, the resulting powder was ground as fine as possible and calcined according to the following schedule. Ramp to 350 °C at 5 °C /min and hold for 120 minutes. Ramp to 950 °C at 5 °C /min and hold for at least 8 hours. Cool to room temperature and repeat grinding. In certain embodiments, the catalyst was sieved to between 150-300 μιτι to minimize pressure drop and then the catalyst was ready for catalyst testing. EXAMPLE 4
PREPARATION OF DOPED LIMGMNB CATALYSTS
Four doped samples of the LiMgMnB catalyst prepared according to Example 3 were prepared as follows:
1 . 1 .00g (+-.1 g) of uncalcined LiMgMnB were weighed into a small beaker. 0.060g (+-.01 g) of NaCI and 0.240g of cobalt chloride were added to this beaker. Approximately 15ml of Dl water was added and the resulting slurry was stirred for 20 minutes. The slurry was placed in a ceramic evaporating dish (small) and dried in an oven at about 1 10-140 °C overnight.
2. Sample 2 was prepared in a manner analogous to sample one, except that 0.060g of cobalt chloride was used.
3. Sample 3 was prepared in a manner analogous to sample one, except that 0.015g (+-.01 g) NaCI was used.
4. Sample 4 was prepared in a manner analogous to sample one, except that 0.015g (+-.01 g) NaCI and 0.060g of cobalt chloride were used.
After the 4 dishes were dry, they were placed in the muffle furnace and programmed to run at 350 °C for 2 hours followed by 650 °C for 2 hours followed by 950 °C for 8 hours before cooling to near room temperature. After cooling the dishes, the solids were ground with a pestle in the dish and run through a Gilson sieve shaker. The sieves used were, from top to bottom, 300 urn, 212 m, 106 μιτι and 75 μιτι. The 106 fraction was collected and put in a vial, and the combined other fractions were placed in another vial.
EXAMPLE 5
PREPARATION OF NAMNW CATALYSTS 0.2 g of Davisil 645 Silica was mixed with 0.0365g of Manganese nitrate tetrahydrate (Mn(NO3)2) and 0.0179g of Sodium tungstate (Na2WO4) in a beaker with enough water to make a stirrable slurry. The mixture was stirred on a hotplate at about 60-80 °C for 3 hours, adding water as necessary to keep from drying. The resultant slurry was placed in a 100-140 °C oven overnight to dry prior to calcining in a ceramic evaporating dish with the following schedule: ramp 5 °C /min to 400 °C and hold for 2hours, ramp 5 °C/min to 850 °C and hold for 8 hours.
0.410 g of ZrO2 powder were mixed with 0.0365 g of Manganese nitrate tetrahydrate (Mn (NO3)2) and 0.0179g of Sodium tungstate (Na2WO4) in a beaker with enough water to make a stirrable slurry. The mixture was stirred on hotplate at about 60-80 °C for 3 hours, adding water as necessary to keep from drying. The resultant slurry was placed in a 100-140 °C oven overnight to dry prior to calcining in a ceramic evaporating dish with the following schedule: ramp 5 °C /min to 400 °C and hold for 2 hours, ramp 5 °C/min to 850 °C and hold for 8 hours.
EXAMPLE 6
OCM CATALYZED WITH LIMNMGB MIXED OXIDE AND
NA-CO DOPED LIMNMGB MIXED OXIDE 50mg of prepared samples from examples 3 and 4 were placed into a reactor tube (4 mm ID diameter quartz tube with a 0.5 mm ID capillary downstream), which was then tested in an Altamira Benchcat 200. The gas flows were held constant at 46 seem methane and 54 seem air, which
correspond to a CH4/O2 ratio of 4 and a feed gas-hour space velocity (GHSV) of about 130000 h"1. The reactor temperature was varied from 700 °C to 750 °C in a 50 °C increment and from 750 °C to 875 °C in 25 °C increments. The vent gases were analyzed with gas chromatography (GC) at each temperature level. Figure 7 shows the onset of OCM between 700 °C and 750 °C for the Na/Co doped LiMnMgB mixed oxide sample whereas the onset of the OCM is between 800°C and 825°C for the undoped LiMnMgB mixed oxide catalyst. The C2 selectivity, methane conversion and C2 yield at 750 °C for the doped catalyst were 57 %, 22 % and 12 %, respectively. The undoped LiMnMgB mixed oxide catalyst reached 12% C2 yield at 850 °C. EXAMPLE 7
OCM USING A NAMNWO4 CATALYST SUPPORTED ON SILICA OR ZIRCON IA
50mg of each sample from example 5 were placed into a reactor tube (4 mm ID diameter quartz tube with a 0.5 mm ID capillary downstream), which was then tested in an Altamira Benchcat 200. The gas flows were held constant at 46 seem methane and 54 seem air, which correspond to a CH O2 ratio of 4 and a feed gas-hour space velocity (GHSV) of about 130000 h"1. The reactor temperature was varied from 650 °C to 900 °C in a 50 °C increment. The vent gases were analyzed with gas chromatography (GC) at each temperature level. Figure 8 shows the onset of OCM between 700 °C and 750 °C for the NaMnWO4 supported on Zirconia whereas the onset of the OCM is between 750 °C and 800 °C for the NaMnWO4 supported on Silica. The C2 selectivity, methane conversion and C2 yield at 750 °C for the Zirconia supported catalyst were 45 %, 20 % and 9 %, respectively. EXAMPLE 8
HIGH THROUGHPUT SCREENING OF OCM CATALYZED BY CATALYST LIBRARIES
The effect of doping of bulk rare earth oxides or other mixed oxides was evaluated by preparing libraries of doped catalysts on a quartz wafer etched to form a 16x16 well area (4 ml per well) in which about 1 mg of the base catalyst (e.g., bulk rare earth oxide) is added. These oxides were first suspended in slurries with Butanol then the slurries were distributed to the wells using automated liquid dispensing. The wafer library was then dried.
Aqueous salt solutions of 49 different metals were prepared and added to the wells in a pre-set pattern design with 4 repeats of each doping in 4 different area of the wafer. The list of metal salts evaluated was as follows: AI(NO3)3, CuCI, CsCI, BaCI2, CeCI3, Ga(NO3)3, lnCI3, HfCI2O, Fe(NO3)3, CrCI3, LaCIs, RuCIs, SmCI3, EuCI3, YCI3, Sr(NO3)2,ZrOCI2, TaCI5, RhAcAc, Be(NO3)2, AuCI4H, NaCI ,NiCI2, CoCI2, SbCI3, Ba(NO3)2, VCI3, PrCI3, AgNO3, TeCI4, ErCI3, Tb(NO3)3, HfCI2O, NaO4W, lrCI3, Mn(NO3)2, Gd(NO3)3, LiOH, Rb(NO3), Ca(NO3)2, Lu(NO3)3, KNO3, Yb(NO3)3, H3BO3, (NH4)6Mo7O24, ScCI3, NdCI3, Pd(NO3)2, Mg(NO3)2, Te(OH)4, (NH4)2TiO(C2O4)2, NbCI5
The wafer was calcined again after doping at 700°C for 4 hours. Testing of the activity of the doped catalysts was conducted in a Scanning Mass Spectrometer, which allows to heat up at set temperature individual wells on the wafer while flowing a reactant mixture on top of the heated well.
Reaction products were aspirated through a glass capillary and analyzed using a mass spectrometer. The gas mixture in contact with the catalytic material was comprised of Methane, Oxygen, Argon with a 4/1/1 molar ratio.
The products analyzed with the mass spectrometer were: H2O,
CO2, CO, C2H6, C2H4, CH4 and O2. Test temperatures were typically varied from 600 °C to 800 °C in 50 °C increment with a one minute hold at each temperature.
In the following examples the relative Ethane and CO2 concentrations are plotted for the gas effluent collected at different
temperatures for different catalyst compositions. These graphs provide the ability to quickly compare the activity and selectivity of multiple catalysts within a catalyst library. The higher the ethane concentration at a given CO2 concentration the more selective the catalyst is. The lower the CO2
concentration at a given ethane concentration the more selective the catalyst is.
The undoped samples results are shown in grey for comparison in figures 10 to
14 for comparison.
Example 8-a: Doped Co/Na/LiMnMgB library. A SMS wafer with a base oxide from example 4-1 was prepared and tested as described above. The results of the test are presented in Figure 9. Be, Ba, Al, Hf dopants were found to promote the Co/Na/LiMnMgB catalyst activity further without affecting the selectivity towards higher hydrocarbons.
Example 8-b: Doping of MnW on Silica library. A SMS wafer with a silica supported oxide from Example 5 was prepared and tested as described above. The results of the test are presented in Figure 10. Mo, Be, Ba, Te dopants were found to promote the OCM activity of the MnW on Silica catalyst.
Example 8-c: Doping of Nd2O3 library. A SMS wafer with bulk Nd2O3 was prepared and tested as described above. The results of the test are presented in Figure 1 1 . Ca, Li, Na, Rb, Sm, Sr dopants were found to promote the OCM activity of the Nd2O3 catalyst and improved higher hydrocarbon selectivity compared to undoped Nd2O3 catalyst tested under the same conditions.
Example 8-d: Doping of Yb2O3 library. A SMS wafer with bulk Yb2O3 was prepared and tested as described above. The results of the test are presented in Figure 12. Ba, Ca, Sr dopants were found to promote the OCM activity of the Yb2O3 catalyst and improved higher hydrocarbon selectivity compared to undoped Yb2O3 catalyst tested under the same conditions.
Example 8-e: Doping of Eu2O3 library. A SMS wafer with bulk Eu2O3 was prepared and tested as described above. The results of the test are presented in Figure 13. Na, Ba, Gd, Sm dopants were found to promote the OCM activity of the Eu2O3 catalyst compared to undoped Eu2O3 catalyst tested under the same conditions.
Example 8-f: Doping of La2O3 library. A SMS wafer with bulk La2O3 was prepared and tested as described above. The results of the test are presented in Figure 14. Ca, Sr, Nd, Hf dopants were found to promote the OCM activity of the La2O3 catalyst compared to undoped La2O3 catalyst tested under the same conditions. In addition to the list of OCM activators, Rh, Fe, Pr, Mn, Ir doping was found to promote unselective oxidation of methane whereas Ba, Te, V, Li doping was found to suppress methane activation.
EXAMPLE 9
OCM ACTIVITY OF VARIOUS CATALYSTS
Exemplary catalysts comprising La2O3, Nd2O3 or La3NdO6 with one, two, three or four different dopants selected from Eu, Na, Sr, Ho, Tm, Zr, Ca, Mg, Sm, W, La, K, Ba, Zn, and Li, were prepared and tested for their OCM activity according to the general procedures described in the above examples. Each of the exemplary catalysts produced a C2 yield above 10%, a C2 selectivity above 50%, and a CH conversion above 20%, when tested as OCM catalysts at 650 °C or lower at pressures ranging from 1 to 10 atm.
EXAMPLE 10
OCM ACTIVITY OF EXEMPLARY CATALYSTS
A number of exemplary catalysts, e.g., selected catalysts from those presented in tables 5 and 6, were tested for their OCM performance parameters according to the general procedures above. In particular, the methane conversion and C2+ selectivities were measured at the lowest temperature required to obtain ~> 50% C2+ selectivity (condition A), and at the temperature which results in maximum C2+ selectivity (condition B). All catalysts under condition A showed C2+ selectivities and methane conversions greater than 50% and 15%, respectively, while providing C2+ selectivities greater than 55% and in most cases greater than 60%, while providing methane conversions greater than 18% and in most cases greater than 20%. It was noted that certain catalysts resulted in the almost total absence of reforming of methane to CO and H2.
The various embodiments described above can be combined to provide further embodiments. All of the U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent
applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, are incorporated herein by reference, in their entirety. Aspects of the embodiments can be modified, if necessary to employ concepts of the various patents, applications and publications to provide yet further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.
To the extent it does not contradict this application, U.S.
Provisional Application Serial No. 61/794,486, filed March 15, 2013 is incorporated by reference as if reproduced in its entirety herein.

Claims

1 . A catalyst comprising a mixed oxide of magnesium and manganese, wherein the catalyst further comprises lithium and boron dopants and at least one doping element from groups 4, 9, 12, 13 or combinations thereof, wherein the catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
2. The catalyst of claim 1 , wherein the catalyst further comprises a sodium dopant.
3. The catalyst of claims 1 or 2, wherein the at least one doping element is cobalt.
4. The catalyst of claims 1 or 2, wherein the at least one doping element is gallium.
5. The catalyst of any of the preceding claims, wherein the catalyst further comprises at least one additional doping element from group 2.
6. The catalyst of claim 5, wherein the at least one additional doping element is beryllium, barium, hafnium or aluminum.
7. A catalyst comprising a mixed oxide of manganese and tungsten, wherein the catalyst further comprises a sodium dopant and at least one doping element from groups 2, 16 or combinations thereof.
8. The catalyst of claim 7, wherein the catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
9. The catalyst of claim 7 or 8, wherein the doping element is barium, beryllium or tellurium.
10. A catalyst comprising an oxide of a rare earth element, wherein the catalyst further comprises at least one doping element from groups 1 -16, lanthanides, actinides or combinations thereof, wherein the catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
1 1 . The catalyst of claim 10, wherein the at least one doping element is selected from groups 1 -4, 8, 13, 14, lactinides, actinides and combinations thereof.
12. The catalyst of claim 10, wherein the at least on doping element is selected from groups 1 -6, 8, 1 1 , 13-15, lactinides, actinides and combinations thereof.
13. The catalyst of claim 10, wherein the at least one doping element is a rare earth element.
14. The catalyst of claim 10, wherein the at least one doping element is Na, Mg, Ca, Sr, Ga, Sc, Y, Zr, In, Nd, Eu, Sm, Ce, Gd, Hf, Ho, Tm, W, La, K, Dy, In, Cs, S, Zn, Rb, Ba, Yb, Ni, Lu, Ta, P, Pt, Bi, Sn, Nb, Sb, Ge, Ag, Au, Pb, Re, Fe, Al, Tl, Pr, Co, Rh, Ti, V, Cr, Mn, Ir, As, Li, Tb ,Er, Te or Mo.
15. The catalyst of any of claims 10-14, wherein the catalyst comprises a combination of at least two different doping elements.
16. The catalyst of claim 15, wherein the two different doping elements are selected from Na, Mg, Ca, Sr, Ga, Sc, Y, Zr, In, Nd, Eu, Sm, Ce, Gd, Hf, Ho, Tm, W, La, K, Dy, In, Cs, S, Zn, Rb, Ba, Yb, Ni, Lu, Ta, P, Pt, Bi, Sn, Nb, Sb, Ge, Ag, Au, Pb, Re, Fe, Al, Tl, Pr, Co, Rh, Ti, V, Cr, Mn, Ir, As, Li, Tb ,Er, Te and Mo.
17. The catalyst of any of claims 15, wherein the combination of at least two different doping elements is La/Nd, La/Sm, La/Ce, La/Sr, Eu/Na, Eu/Gd, Ca/Na, Eu/Sm, Eu/Sr, Mg/Sr, Ce/Mg, Gd/Sm, Sr/W, Sr/Ta, Au/Re, Au/Pb, Bi/Hf, Sr/Sn or Mg/N, Ca/S, Rb/S, Sr/Nd, Eu/Y, Mg/Nd, Sr/Na, Nd/Mg, La/Mg, Yb/S, Mg/Na, Sr/W, K La, K Na, Li/Cs, Li/Na, Zn/K, Li/K, Rb/Hf, Ca/Cs, Hf/Bi, Sr/Sn, Sr/W, Sr/Nb, Zr/W, Y/W, Na/W, Bi/W, Bi/Cs, Bi/Ca, Bi/Sn, Bi/Sb, Ge/Hf, Hf/Sm, Sb/Ag, Sb/Bi, Sb/Au, Sb/Sm, Sb/Sr, Sb/W, Sb/Hf, Sb/Yb, Sb/Sn, Yb/Au, Yb/Ta, Yb/W, Yb/Sr, Yb/Pb, Yb/W, Yb/Ag, Au/Sr, W/Ge, Ta/Hf, W/Au, Ca/W, Au/Re, Sm/Li, La/K, Zn/Cs, Zr/Cs, Ca/Ce, Li/Sr, Cs/Zn, Dy/K, La/Mg, In/Sr, Sr/Cs, Ga/Cs, Lu/Fe, Sr/Tm, La/Dy, Mg/K, Zr/K, Li/Cs, Sm/Cs, In/K, Lu/TI, Pr/Zn, Lu/Nb, Na/Pt, Na/Ce, Ba/Ta, Cu/Sn, Ag/Au, Al/Bi, Al/Mo, Al/Nb, Au/Pt, Ga/Bi, Mg/W, Pb/Au, Sn/Mg, Zn/Bi, Gd/Ho, Zr/Bi, Ho/Sr, Ca/Sr, Sr/Pb or Sr/Hf.
18. The catalyst of claim 10, wherein the catalyst comprises a combination of at least three different doping elements.
19. The catalyst of claim 18, wherein the three different doping elements are selected from Na, Mg, Ca, Sr, Ga, Sc, Y, Zr, In, Nd, Eu, Sm, Ce, Gd, Hf, Ho, Tm, W, La, K, Dy, In, Cs, S, Zn, Rb, Ba, Yb, Ni, Lu, Ta, P, Pt, Bi, Sn, Nb, Sb, Ge, Ag, Au, Pb, Re, Fe, Al, Tl, Pr, Co, Rh, Ti, V, Cr, Mn, Ir, As, Li, Tb ,Er, Te and Mo.
20. The catalyst of claim 18, wherein the combination of at least three different doping elements is Nd/Sr/CaO, La/Nd/Sr, La/Bi/Sr,
Mg/Nd/Fe, Mg/La/K, Na/Dy/K, Na/La/Dy, Na/La/Eu, Na/La/K, K/La/S, Li/Cs/La, Li/Sr/Cs, Li/Ga/Cs, Li/Na/Sr, Li/Sm/Cs, Cs/K La, Sr/Cs/La, Sr/Ho/Tm, La/Nd/S, Li/Rb/Ca, Rb/Sr/Lu, Na/Eu/Hf, Dy/Rb/Gd, Na/Pt/Bi, Ca/Mg/Na, Na/K/Mg, Na/Li/Cs, La/Dy/K, Sm/Li/Sr, Li/Rb/Ga, Li/Cs/Tm, Li/K/La, Ce/Zr/La, Ca/AI/La, Sr/Zn/La, Cs/La/Na, La/S/Sr, Rb/Sr/La, Na/Sr/Lu, Sr/Eu/Dy, La/Dy/Gd, Gd/Li/K, Rb/K Lu, Na/Ce/Co, Ba/Rh/Ta, Na/AI/Bi, Cs/Eu/S, Sm/Tm/Yb, Hf/Zr/Ta, Na/Ca/Lu, Gd/Ho/Sr, Ca/Sr/W, Na/Zr/Eu/Tm, Sr/W/Li or Ca/Sr/W.
21 . The catalyst of claim 10, wherein the catalyst comprises a combination of at least four different doping elements.
22. The catalyst of claim 21 , wherein the four different doping elements are selected from Na, Mg, Ca, Sr, Ga, Sc, Y, Zr, In, Nd, Eu, Sm, Ce, Gd, Hf, Ho, Tm, W, La, K, Dy, In, Cs, S, Zn, Rb, Ba, Yb, Ni, Lu, Ta, P, Pt, Bi, Sn, Nb, Sb, Ge, Ag, Au, Pb, Re, Fe, Al, Tl, Pr, Co, Rh, Ti, V, Cr, Mn, Ir, As, Li, Tb ,Er, Te and Mo.
23. The catalyst of claim 21 , wherein the combination of at least four different doping elements is La/Ce/Nd/Sr, Sr/Sm/Ho/Tm,
Na/K Mg/Tm, Na/La/Eu/ln, Na/La/Li/Cs, Li/Cs/La/Tm, Li/Cs/Sr/Tm, Li/Sr/Zn/K, Li/K Sr/La, Li/Na/Rb/Ga, Li/Na/Sr/La, Ba/Sm/Yb/S, Ba/Tm/K/La, Ba/Tm/Zn/K, Cs/La/Tm/Na, Cs/Li/K La, Sm/Li/Sr/Cs, Sr/Tm/Li/Cs, Zr/Cs/K La, Rb/Ca/ln/Ni, Tm/Lu/Ta/P, Rb/Ca/Dy/P, Mg/La/Yb/Zn, Na/Sr/Lu/Nb, Na/Nd/ln/K, K La/Zr/Ag, Ho/Cs/Li/La, K La/Zr/Ag, Na/Sr/Eu/Ca, K Cs/Sr/La, Na/Mg/TI/P, Sr/La/Dy/S, Na/Ga/Gd/AI, Sm/Tm/Yb/Fe, Rb/Gd/Li/K, Gd/Ho/AI/P, Na/Zr/Eu/T,
Sr/Ho/Tm/Na, Na/Zr/Eu/Ca, Rb/Ga/Tm/Cs or La/Bi/Ce/Nd/Sr.
24. The catalyst of any one of claims 10-23, wherein the oxide of a rare earth element is a lanthanum oxide.
25. The catalyst of any one of claims 10-23, wherein the oxide of a rare earth element is a neodymium oxide.
26. The catalyst of any one of claims 10-23, wherein the oxide of a rare earth element is a ytterbium oxide.
27. The catalyst of any one of claims 10-23, wherein the oxide of a rare earth element is a europium oxide.
28. The catalyst of any one of claims 10-23, wherein the oxide of a rare earth element is a samarium oxide.
29. The catalyst of any one of claims 10-23, wherein the oxide of a rare earth element is a yttrium oxide.
30. The catalyst of any one of claims 10-23, wherein the oxide of a rare earth element is a cerium oxide.
31 . The catalyst of any one of claims 10-23, wherein the oxide of a rare earth element is a praseodymium oxide.
32. The catalyst of any one of claims 10-23, wherein the oxide of a rare earth element comprises Ln1 -xLn2xO6, wherein Ln1 and Ln2 are each independently a lanthanide element, wherein Ln1 and Ln2 are not the same and x is a number ranging from greater than 0 to less than 4.
33. The catalyst of claim 32, wherein the rare earth oxide comprises La4-xNdxO6, wherein x is a number ranging from greater than 0 to less than 4.
34. The catalyst of claim 33, wherein the rare earth oxide comprises La3NdO6, LaNd3O6, La1.5Nd2.5Oe, La2.5Nd1.5Oe, La3.2Ndo.8Oe,
La3.5Ndo.5O6, La3.8Ndo.2O6 or combinations thereof.
35. The catalyst of any one of claims 10-23, wherein the oxide of a rare earth element comprises a mixed oxide.
36. The catalyst of claim 35, wherein the mixed oxide comprises Y-La, Zr-La, Pr-La, Ce-La or combinations thereof.
37. The catalyst of any one of claims 10-23, wherein the oxide of a rare earth element is a metal oxyhydroxide, metal oxyhalide, a metal oxynitrate or a metal phosphate.
38. The catalyst of any one of claims 10-37, wherein the oxidative coupling of methane is performed at total reaction pressures ranging from 1 atm to 10 atm.
39. A catalyst comprising a mixed oxide of manganese and tungsten, wherein the catalyst further comprises a sodium dopant and at least one doping element from groups 2, 4-6, 8-15, lanthanides or combinations thereof, wherein the catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
40. The catalyst of claim 39, wherein the at least one doping element is Fe, Co, Ce, Cu, Ni, Sr, Ga, Zr, Pb, Zn, Cr, Pt, Al, Nb, La, Ba, Bi, Sn, In, Ru, P or combinations thereof.
41 . A catalyst comprising a mixed oxide of a lanthanide and tungsten, wherein the catalyst further comprises a sodium dopant and at least one doping element from groups 2, 4-15, lanthanides or combinations thereof, wherein the catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
42. The catalyst of claim 41 , wherein the lanthanide is Ce, Pr, Nd, La, Eu, Sm or Yb.
43. The catalyst of claims 41 or 42, wherein the at least one doping element is Fe, Co, Mn, Cu, Ni, Sr, Ga, Zr, Pb, Zn, Cr, Pt, Al, Nb, La, Ba, Bi, Sn, In, Ru, P or combinations thereof.
44. A catalyst comprising a rare earth oxide and two or more dopants, wherein the catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a
temperature of 750 °C or less, and wherein the dopant comprises Eu/Na, Sr/Na, Na/Zr/Eu/Ca, Mg/Na, Sr/Sm/Ho/Tm, Sr/W, Mg/La/K, Na/K/Mg/Tm, Na/Dy/K, Na/La/Dy, Na/La/Eu, Na/La/Eu/ln, Na/La/K, Na/La/Li/Cs, K/La, K/La/S, K/Na, Li/Cs, Li/Cs/La, Li/Cs/La/Tm, Li/Cs/Sr/Tm, Li/Sr/Cs, Li/Sr/Zn/K, Li/Ga/Cs, Li/K/Sr/La, Li/Na, Li/Na/Rb/Ga, Li/Na/Sr, Li/Na/Sr/La, Li/Sm/Cs, Ba/Sm/Yb/S, Ba/Tm/K/La, Ba/Tm/Zn/K, Cs/K/La, Cs/La/Tm/Na, Cs/Li/K/La, Sm/Li/Sr/Cs, Sr/Cs/La, Sr/Tm/Li/Cs, Zn/K, Zr/Cs/K/La, Rb/Ca/ln/Ni, Sr/Ho/Tm, La/Nd/S, Li/Rb/Ca, Li/K, Tm/Lu/Ta/P, Rb/Ca/Dy/P, Mg/La/Yb/Zn, Rb/Sr/Lu, Na/Sr/Lu/Nb, Na/Eu/Hf, Dy/Rb/Gd, Na/Pt/Bi, Rb/Hf, Ca/Cs, Ca/Mg/Na, Hf/Bi, Sr/Sn, Sr/W, Sr/Nb, Zr/W, Y/W, Na/W, Bi/W, Bi/Cs, Bi/Ca, Bi/Sn, Bi/Sb, Ge/Hf, Hf/Sm, Sb/Ag, Sb/Bi, Sb/Au, Sb/Sm, Sb/Sr, Sb/W, Sb/Hf, Sb/Yb, Sb/Sn, Yb/Au, Yb/Ta, Yb/W, Yb/Sr, Yb/Pb, Yb/W, Yb/Ag, Au/Sr, W/Ge, Ta/Hf, W/Au, Ca/W, Au/Re, Sm/Li, La/K, Zn/Cs, Na/K/Mg, Zr/Cs, Ca/Ce, Na/Li/Cs, Li/Sr, Cs/Zn, La/Dy/K, Dy/K, La/Mg, Na/Nd/ln/K, In/Sr, Sr/Cs, Rb/Ga/Tm/Cs, Ga/Cs,
K La/Zr/Ag, Lu/Fe, Sr/Tm, La/Dy, Sm/Li/Sr, Mg/K, Li/Rb/Ga, Li/Cs/Tm, Zr/K, Li/Cs, Li/K La, Ce/Zr/La, Ca/AI/La, Sr/Zn/La, Sr/Cs/Zn, Sm/Cs, In/K,
Ho/Cs/Li/La, Cs/La/Na, La/S/Sr, K La/Zr/Ag, Lu/TI, Pr/Zn, Rb/Sr/La,
Na/Sr/Eu/Ca, K Cs/Sr/La, Na/Sr/Lu, Sr/Eu/Dy, Lu/Nb, La/Dy/Gd, Na/Mg/TI/P, Na/Pt, Gd/Li/K, Rb/K/Lu, Sr/La/Dy/S, Na/Ce/Co, Na/Ce, Na/Ga/Gd/AI,
Ba/Rh/Ta, Ba/Ta, Na/AI/Bi, Cs/Eu/S, Sm/Tm/Yb/Fe, Sm/Tm/Yb, Hf/Zr/Ta, Rb/Gd/Li/K, Gd/Ho/AI/P, Na/Ca/Lu, Cu/Sn, Ag/Au, Al/Bi, Al/Mo, Al/Nb, Au/Pt, Ga/Bi, Mg/W, Pb/Au, Sn/Mg, Zn/Bi, Gd/Ho, Zr/Bi, Ho/Sr, Gd/Ho/Sr, Ca/Sr, Ca/Sr/W, Na/Zr/Eu/Tm, Sr/Ho/Tm/Na, Sr/Pb, Sr/W/Li, Ca/Sr/W, Sr/Hf or combinations thereof.
45. The catalyst of claim 44, wherein the rare earth oxide comprises La2O3, Nd2O3, Yb2O3, EU2O3, Sm2O3, Y2O3, Ce2O3, Pr2O3 or combinations thereof.
46. The catalyst of claim 44, wherein the catalyst comprises Ln1 -xLn2xO6, wherein Ln1 and Ln2 are each independently a lanthanide element, wherein Ln1 and Ln2 are not the same and x is a number ranging from greater than 0 to less than 4.
47. The catalyst of claim 46, wherein the rare earth oxide comprises La -xNdxO6, wherein x is a number ranging from greater than 0 to less than 4.
48. The catalyst of claim 47, wherein the rare earth oxide comprises La3NdO6, LaNd3O6, La1.5Nd2.5Oe, La2.5Nd1.5Oe, La3.2Ndo.8Oe,
La3.5Ndo.5O6, La3.8Ndo.2O6 or combinations thereof.
49. The catalyst of claim 44, wherein the rare earth oxide comprises a mixed oxide.
50. The catalyst of claim 49, wherein the mixed oxide comprises Y-La, Zr-La, Pr-La, Ce-La or combinations thereof.
51 . A catalyst comprising a mixed oxide of a rare earth element and a Group 13 element, wherein the catalyst further comprises one or more Group 2 elements.
52. The catalyst of claim 51 , wherein the Group 13 element is B, Al, Ga or In.
53. The catalyst of claim 51 , wherein the Group 2 element is
Ca or Sr.
54. The catalyst of claim 51 , wherein the rare earth elements is La, Y, Nd, Yb, Sm, Pr, Ce or Eu.
55. The catalyst of claim 51 , wherein the catalyst comprises CaLnBOx, CaLnAIOx, CaLnGaOx, CaLnlnOx, CaLnAISrOx and CaLnAISrOx, wherein Ln is a lanthanide or yttrium and x is number such that all charges are balanced.
56. The catalyst of claim 51 , wherein the catalyst comprises CaLaBO4, CaLaAIO4, CaLaGaO4, CaLalnO4, CaLaAISrO5, CaLaAISrO5, CaNdBO4, CaNdAIO4, CaNdGaO4, CaNdlnO4, CaNdAISrO4, CaNdAISrO4, CaYbBO4, CaYbAIO4, CaYbGaO4, CaYblnO4, CaYbAISrO5, CaYbAISrO5, CaEuBO4, CaEuAIO4, CaEuGaO4, CaEulnO4, CaEuAISrO5, CaEuAISrO5, CaSmBO4, CaSmAIO4, CaSmGaO4, CaSmlnO4, CaSmAISrO5, CaSmAISrO5, CaYBO4, CaYAIO4, CaYGaO4, CaYlnO4, CaYAISrO5, CaYAISrO5, CaCeBO4, CaCeAIO4, CaCeGaO4, CaCelnO4, CaCeAISrO5, CaCeAISrO5, CaPrBO4, CaPrAIO4, CaPrGaO4, CaPrlnO4, CaPrAISrO5 or CaPrAISrO5.
57. A catalyst comprising a lanthanide oxide doped with an alkali metal, an alkaline earth metal or combinations thereof, and at least one other dopant from groups 3-16.
58. The catalyst of claim 57, wherein the catalyst comprises an alkali metal dopant.
59. The catalyst of claim 58, wherein the alkali metal dopant is lithium, sodium, potassium, rubidium, or caesium.
60. The catalyst of claim 57, wherein the catalyst comprises an alkaline earth metal dopant.
61 . The catalyst of claim 57, wherein the alkaline earth metal dopant is beryllium, magnesium, calcium, strontium or barium.
62. The catalyst of claim 57, wherein the lanthanide earth oxide comprises La2O3, Nd2O3, Yb2O3, EU2O3, S1TI2O3, or Ln14-xLn2xO6, wherein Ln1 and Ln2 are each independently a lanthanide element, wherein Ln1 and Ln2 are not the same and x is a number ranging from greater than 0 to less than 4, or combinations thereof.
63. The catalyst of claim 57, wherein the catalyst comprises a C2 selectivity of greater than 50% and a methane conversion of greater than 20% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C.
64. The catalyst of any of the preceding claims, wherein the C2 selectivity is greater than 60% when the catalyst is employed as a
heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
65. The catalyst of any of the preceding claims, wherein the C2 yield is greater than 10% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
66. The catalyst of any of the preceding claims, wherein the C2 yield is greater than 15% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
67. The catalyst of any of the preceding claims, wherein the methane conversion is greater than 30% when the catalyst is employed as a heterogeneous catalyst in the oxidative coupling of methane at a temperature of 750 °C or less.
68. The catalyst of any of the preceding claims, wherein the oxidative coupling of methane is performed at a temperature of 700 °C or less.
69. The catalyst of any of the preceding claims, wherein the oxidative coupling of methane is performed at total reaction pressures ranging from 1 atm to 10 atm.
70. The catalyst of any of the preceding claims, wherein the doping element is a promoter.
71 . The catalyst of any of the preceding claims in combination with a support material.
72. The catalyst of claim 71 , wherein the support material comprises AIPO4, AI2O3, SiO2-AI2O3, CaO, TiO2, ZrO2, MgO, SiO2, ZrO2, HfO2, ln2O3, SiC or combinations thereof.
73. Use of the catalyst of any of the preceding claims in a catalytic reaction.
74. The use claim 73, wherein the catalytic reaction is oxidative coupling of methane (OCM).
75. The use of claim 74, wherein the OCM reaction is performed in the presence of air and methane.
76. A method for preparing a downstream product of ethylene, the method comprising converting ethylene into a downstream product of ethylene, wherein the ethylene has been prepared via a reaction employing a catalyst according to any of claims 1 -72.
77. The method of claim 76, wherein the downstream product of ethylene is low density polyethylene, high density polyethylene, ethylene dichloride, ethylene oxide, ethylbenzene, ethanol or vinyl acetate.
78. The method of claim 76, wherein the downstream product of ethylene is natural gasoline.
79. The method of claim 76, wherein the downstream product of ethylene comprises 1 -hexene, 1 -octene, hexane, octane, benzene, toluene, xylene or combinations thereof.
80. The method of any of claims 76-79, wherein the reaction is
OCM.
81 . A method for the preparation of a downstream product of ethane, ethylene or combinations thereof, the method comprising converting methane into ethane, ethylene or combinations thereof in the presence of the catalyst of any of claims 1 -80 and further oligomerizing the ethylene to prepare a downstream product of ethylene.
82. The method of claim 81 , wherein the methane is converted to ethylene via the OCM reaction.
83. The method of claim 81 or 82, wherein the downstream product of ethylene is low density polyethylene, high density polyethylene, ethylene dichloride, ethylene oxide, ethylbenzene, ethanol or vinyl acetate.
84. The method of claim 81 or 82, wherein the downstream product of ethylene is natural gasoline.
85. The method of any of claims 81 or 82, wherein the downstream product of ethylene comprises 1 -hexene, 1 -octene, hexane, octane, benzene, toluene, xylene or combinations thereof.
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