EP1476420A1 - Ammoxidation of hydrocarbons and hydrogenated metallo oxynitride catalysts therefor - Google Patents

Ammoxidation of hydrocarbons and hydrogenated metallo oxynitride catalysts therefor

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Publication number
EP1476420A1
EP1476420A1 EP02795234A EP02795234A EP1476420A1 EP 1476420 A1 EP1476420 A1 EP 1476420A1 EP 02795234 A EP02795234 A EP 02795234A EP 02795234 A EP02795234 A EP 02795234A EP 1476420 A1 EP1476420 A1 EP 1476420A1
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EP
European Patent Office
Prior art keywords
catalyst
compound
ammoxidation
propane
process according
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP02795234A
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German (de)
French (fr)
Inventor
Ricardo Prada Silvy
Mihaela Florea Popescu
Paul Grange
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Universite Catholique de Louvain UCL
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Universite Catholique de Louvain UCL
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Priority to EP02795234A priority Critical patent/EP1476420A1/en
Publication of EP1476420A1 publication Critical patent/EP1476420A1/en
Withdrawn legal-status Critical Current

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    • CCHEMISTRY; METALLURGY
    • C07ORGANIC CHEMISTRY
    • C07CACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C253/00Preparation of carboxylic acid nitriles
    • C07C253/24Preparation of carboxylic acid nitriles by ammoxidation of hydrocarbons or substituted hydrocarbons
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/002Mixed oxides other than spinels, e.g. perovskite
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J27/00Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
    • B01J27/24Nitrogen compounds
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/12Oxidising
    • B01J37/14Oxidising with gases containing free oxygen
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B21/00Nitrogen; Compounds thereof
    • C01B21/082Compounds containing nitrogen and non-metals and optionally metals
    • C01B21/0821Oxynitrides of metals, boron or silicon
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B21/00Nitrogen; Compounds thereof
    • C01B21/082Compounds containing nitrogen and non-metals and optionally metals
    • C01B21/087Compounds containing nitrogen and non-metals and optionally metals containing one or more hydrogen atoms
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01CAMMONIA; CYANOGEN; COMPOUNDS THEREOF
    • C01C3/00Cyanogen; Compounds thereof
    • C01C3/02Preparation, separation or purification of hydrogen cyanide
    • C01C3/0208Preparation in gaseous phase
    • C01C3/0212Preparation in gaseous phase from hydrocarbons and ammonia in the presence of oxygen, e.g. the Andrussow-process
    • C01C3/0216Preparation in gaseous phase from hydrocarbons and ammonia in the presence of oxygen, e.g. the Andrussow-process characterised by the catalyst used
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/16Catalysts 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
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/16Catalysts 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
    • B01J23/20Vanadium, niobium or tantalum
    • B01J23/22Vanadium
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2523/00Constitutive chemical elements of heterogeneous catalysts
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00Technologies relating to chemical industry
    • Y02P20/50Improvements relating to the production of bulk chemicals
    • Y02P20/52Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts

Definitions

  • This invention relates to an improved catalytic ammoxidation process for converting hydrocarbons into nitriles.
  • the invention further relates to new metallo oxynitride catalysts useful for performing said ammoxidation.
  • nitriles and more specifically ⁇ , ⁇ - unsaturated nitriles is generally well recognized with acrylonitrile being among the most valuable monomers available to the polymer industry for producing useful polymeric products.
  • an unsaturated nitrile such as acrylonitrile by ammoxidation of an alkene, such as propylene, namely, by reacting an olefin or alkene with ammonia and molecular oxygen, i.e.
  • CH 3 CH 2 CH 3 + NH 3 + 2 O 2 -> CH 2 CHCN + 4 H 2 O, in the presence of a catalyst, i.e., by reacting an alkane with ammonia and molecular oxygen in the presence of a catalyst.
  • Another object of the present invention is to provide an alkane ammoxidation process with a high conversion of the alkane. It is a further object to provide an alkane ammoxidation process with a high selectivity for the desired end-product. It is another object to provide an alkane ammoxidation process with a high yield of the desired end-product. It is yet another object to provide new catalysts for performing such ammoxidation reactions.
  • the invention relates in general to a process for the ammoxidation of a hydrocarbon, comprising contacting the hydrocarbon with ammonia and molecular oxygen in the presence of a hydrogenated metallo oxynitride catalyst.
  • the invention further relates to novel metallo oxynitride catalysts. Detailed Description of the Invention
  • the present invention relates to processes for the oxidative conversion of hydrocarbons to nitriles. Processes and catalyst compositions for performing ammoxidation of hydrocarbons are provided.
  • unsaturated nitriles are prepared from saturated hydrocarbons, in for example a vapor phase process, comprising contacting at least one saturated hydrocarbon, ammonia and oxygen in the presence of a catalyst containing aluminum and a second metal "M" selected from the group comprising Ga, Si, Ge, W, Mo, Mn, Cr, Ti, Nb, V, Fe, B, and Mg under conditions suitable for converting the selected saturated hydrocarbon to the desired unsaturated nitrile.
  • a catalyst containing aluminum and a second metal "M" selected from the group comprising Ga, Si, Ge, W, Mo, Mn, Cr, Ti, Nb, V, Fe, B, and Mg under conditions suitable for converting the selected saturated hydrocarbon to the desired unsaturated nitrile.
  • new hydrogenated metallo oxynitride compounds are provided along with their preparation process for use as ammoxidation catalysts.
  • Said new catalyst compounds as used in the ammoxidation process according to the present invention for the conversion of propane allow for a high conversion of propane and a high selectivity to the desired end-product acrylonitrile while a total absence of selectivity for the intermediary compound propylene.
  • Advantages over the prior art of the avoidance of propylene production as in the ammoxidation process according to the present invention includes the avoidance of production of undesirable CO x compounds which are normally produced by reaction of propylene with oxygen.
  • the selectivity of the catalyst according to the present invention towards acrylonitrile and acetonitrile formation is substantially increased.
  • the absence of propylene production in the ammoxidation process according to the present invention avoids an otherwise difficult removal in a downstream process.
  • Different reaction mechanisms of the ammoxidation metallo oxynitride catalysts according to the present invention compared to conventional oxide ammoxidation catalysts, substantially increases the yield of the desired end products.
  • Allyl adsorbed like species formed on the metallo oxinitride catalysts surface during alkane activation are more reactive than propylene in the gas phase.
  • propylene molecules need to be adsorbed on the catalyst surface and then react with activated nitrogen species (NH, NH 2 , N * ) to produce acrylonitrile.
  • activated nitrogen species NH, NH 2 , N *
  • a key aspect of the oxynitride catalyst according to the present invention is that said activated nitrogen species are present at high concentration while, on conventional oxides, only few ammonia adsorbed species are present.
  • a nitrogen insertion reaction requires less contact time as compared to propylene production from propane which is the step controlling the reaction in oxide catalysts, requiring high contact times.
  • the process of the present invention provides for a 70-times increased turn-over with comparable propane conversions and comparable acrylonitrile selectivities.
  • the present invention provides a process for the ammoxidation of a hydrocarbon comprising contacting the hydrocarbon with ammonia and molecular oxygen in the presence of a hydrogenated metallo oxynitride catalyst.
  • the metallo oxynitride catalysts of the present invention alone or promoted with certain elements supported or unsupported provides excellent yields of desired end products in hydrocarbon ammoxidation reactions.
  • hydrocarbon capable of forming unsaturated nitriles may be used in the practice of the invention.
  • Suitable hydrocarbons include linear and branched alkanes and alkenes.
  • Suitable hydrocarbons include but are not limited to ethane, ethylene, propane, propylene, n-butane, isobutane, isobutene, n-pentane, n-pentene, isopentane, 3-methyl pentane, dimethylpentane, 2-methylpentene, n-hexane, isohexane, 2,3-dimethyl butane, heptane, isoheptane, octane, isononane, dodecane, and the like.
  • cyclic hydrocarbons such as cyclohexane and cyclohexene may be used.
  • the ammoxidation process of the present invention is particularly suitable for the conversion of a C 1-6 alkane.
  • the ammoxidation process of the present invention is particularly suitable for the conversion of a C 1-6 alkane selected from the group of methane, ethane, propane and methane.
  • the ammoxidation process of the present invention is particularly suitable for the conversion of propane and methane. In yet a further embodiment, the ammoxidation process of the present invention is particularly suitable for the conversion of propane. In yet a further embodiment, the ammoxidation process of the present invention is particularly suitable for the conversion of methane.
  • ammonia is most generally employed, other compounds may be employed.
  • ammonia may be generated in use from decomposable ammonium compounds such as ammonium carbonate, or from various amines, such as methyl amine, ethyl amine and aniline.
  • Any source of oxygen, pure or in admixture with inerts, may be employed in the process of this invention. Air is a satisfactory source of oxygen for use in this invention.
  • the process according to the present invention may be carried out as a vapor phase reaction. It is well understood that during the course of the process of the present invention, diluent inert gasses may be used such as He, N 2 and Ar and equally, steam or
  • CO 2 may be added to the gaseous reaction mixture.
  • the gaseous reactive comprising the hydrocarbon, ammonia and oxygen may be diluted with an inert diluent and/or steam and/or CO 2 as a diluent.
  • the feedstock may be a single alkane or alkene, a mixture of alkanes, a mixture of alkenes, or a mixture of alkane and alkene.
  • the oxygen/propane molar ratio in the feedstock supplied to the reactor in the present invention is within a range of from 1 :1 to 1 :4.
  • a suitable oxygen concentration feed ranges from 10% to 60% by volume of the feed. Since the catalyst used in this invention provides a high acrylonitrile selectivity a relatively low oxygen/propane molar ratio, from 2.8:1 to 3.5:1 is sufficient.
  • the ammonia/propane molar ratio in the feedstock supplied to the reactor may be varied within a range from 0.5:1 to 2:1 , preferably from 0.7:1 to 1.5:1. As previously stated, the ammoxidation process according to the present invention may be carried out as a vapor phase reaction.
  • any apparatus of the type suitable for carrying out oxidation reactions in the vapor phase may be employed for the practice of the process.
  • the process may be operated continuously or intermittently, and may employ a fixed bed with large particulate or pelleted catalyst, or so-called fluidized or moving bed of catalyst with finely divided catalyst.
  • a suitable particle size distribution is such that the catalyst particles have a size within a range from 20 microns to 200 microns
  • the ammoxidation process of the present invention is carried out at a temperature in a range from 300°C to 600°C.
  • ammoxidation process of the present invention is carried out at a temperature in a range of from 400°C to 550°C.
  • the ammoxidation process of the present invention is carried out at a temperature in a range from 490°C to 510°C.
  • Pressures other than atmospheric may be employed in the process of the present invention, however usually the process is conducted at or near atmospheric pressure, since the reaction proceeds well at such pressure.
  • the contact time between the reactants and catalyst employed in the process of this invention may be selected from a broad operable range which may vary from 0.1 to 50 seconds.
  • the contact time may be defined as the length of time in seconds representing the time measured under reaction conditions during which a unit volume of reactant gases is in contact with a volume of catalyst employed.
  • a suitable contact time will be within a range of 0.1 to 10 seconds.
  • the optimum contact time will, of course, vary depending upon the hydrocarbon being reacted, the catalyst and the reaction temperature but in general ranges between 0.1 and 5 seconds.
  • the feed mixture is commonly introduced into the catalyst bed at a W/F (defined as the weight of the catalyst in grams divided by the flow of reactant stream in moles/h at standard temperature and pressure) in a range from 100 g.h/moles to 25.000 g.h/moles, preferably from 10.000 g.h/moles to 20.000 g.h/moles.
  • W/F defined as the weight of the catalyst in grams divided by the flow of reactant stream in moles/h at standard temperature and pressure
  • the present invention provides a range of metallo catalysts and/or support materials for use in oxidation or ammoxidation reactions. These metallo catalytic materials may be composed from different basic elements as to adapt the catalyst formulation thereby meeting the technical and flexible criteria and needs of various specific catalytic reactions as demanded in a range of industrial processes.
  • the present invention provides metallo catalytic compounds with a metallic basis being composed of a metal draw on an available pool of appropriate metals including mixed metals. As such, by playing on a choice of appropriate metals, the nature, number and strength of the catalytic sites may be modulated. Therefore one may modulate the catalyst's selectivity and the conversion rate of the starting product according to one's desired end-product.
  • the ammoxidation process involves a hydrogenated metallo oxynitride catalyst comprising Al and a second metal "M" selected from the group comprising Ga, Si, Ge, W, Mo, Mn, Cr, Ti, Nb, V, Fe, B, and Mg.
  • M may represent a single metal as well as multiple metals different from one another.
  • M represents a total balanced combination of multiple metals M1 , M2, ..., Mi, said metals having respectively an oxidation degree 1 , ⁇ 2, ..., ⁇ i such that the mean is comprised between 2 and 6, including the outer limits.
  • an ammoxidation process comprising a catalyst being a compound of formula (1) Al y M ⁇ ⁇ - ⁇ O [3+ ⁇ ( - ⁇ -n)-x+C]/2 N ⁇ /3 H c
  • M is a metal selected from the group comprising Ga, Si, Ge, W, Mo, Mn, Cr, Ti, Nb, V, Fe, B, and Mg, 0,1 ⁇ y ⁇ 1 , 2 ⁇ ⁇ ⁇ 6, -1 ⁇ n ⁇ 1 , 0.1 > (n-1/y) ⁇ 1 , 0 ⁇ c ⁇ 2, 0 ⁇ x ⁇ 3 + ⁇ (1-n) + c.
  • a catalyst being a compound of the following formula
  • This catalyst is further also referred to as VAION catalyst.
  • x and "c” are chosen different from zero.
  • the VAION system shows particular acid and basic surface sites. In the frame of certain surface reactions, these two types of sites may present particular industrial interest.
  • industrial interest reactions include Canizzaro and Tishchenko type reactions, conversion reactions of ethylamine to acetonitrile, hydrogenation reactions of 1 ,3-butadiene, synthesis of ethylene amine from monoethanolamine, conversion reactions from picolin to cyanopyridine, alkylation reactions of phenol and methanol, and reduction reactions of aldehyde and ketone.
  • acid and basic surface sites refers to the acid and basic active sites on the surface of the catalyst. Those sites are applied for adsorption, which are the effective sites for a particular heterogeneous catalytic reaction.
  • active site under the present specification may also be related to an active center which describes an ensemble of sites at which a catalytic reaction takes place.
  • the "n" value of the VAION catalyst described in the present invention equals zero to define the stoichiometry linked to the vanadium atoms.
  • Such catalysts respond to the following general formulation:
  • the V/AI atomic ratio equals 1 provided that "y" equals 1.
  • the state of oxidation of vanadium " ⁇ " equals 5 which corresponds to the more stable oxidation state of vanadium.
  • Another embodiment of the present invention relates to an ammoxidation process which involves the application of a VAION catalyst with a V/AI atomic ratio comprised between 0.1 and 0.7 including the outer limits, a further embodiment relates to a V/AI atomic ratio comprised between 0.2 and 0.3 including the outer limits.
  • Another embodiment relates to a process with a catalyst Al 0.1-1.0 Vo. 1 -0.9 0 5. 2 . 6 N 0 . ⁇ -o. 7 H 0 . 1 -
  • a process according to the present invention comprises a catalyst for ammoxidation having the stoechiometric formulation selected from the group comprising
  • Control of selectivity is one of the major roles governed by heterogeneous catalysts.
  • Catalyst modification methods have been developed to tune catalysts which could then provide any desired selectivity.
  • Sustained changes in catalyst performance may be induced by the introduction of small doses of surface modifiers.
  • This practice is also referred to as doping which relates to the incorporation of impurities within the crystal lattice of a solid so as to alter its physical properties. Through a structural rearrangement of the metallic surface also an increase in catalytic activity may be induced.
  • a further embodiment of the present invention provides process comprising a modified catalyst modification procedure to the effect by addition of metallic sites chosen from the group comprising Li, Na, K, Rb, Cs, Pt, Pd, Ru, Re, Os, Ir, Cu, Ni, Co, Fe, Mo, Au, Ag, and
  • Such additional metallic sites promote the activity of the surface hydrogen.
  • the addition of metallic sites selected from the group Li, Na, K, Rb, and Cs may result in an increase in number and strength of the catalyst's surface basic sites.
  • additional metallic site refers to distinct metallic atom depositions at the catalysts' surface by impregnation that act as promoters to increase and or prolonge and or revive the activity of the surrounding active sites.
  • a VAION catalyst according to the present invention comprises from 0.01 % to 15% of additional metallic weight.
  • additional metallic weight may be from 0.1% to 3%.
  • the additional metallic weight comprising a metal selected from the group Li, Na, K, Rb, and Cs amounts to 2%.
  • catalysts of the present invention contain only a small quantity of additional metal and this catalyst modification may have the effect of delaying its de- activation which might occur during the course of certain specific uses.
  • An important proportion of the surface nitrogen atoms are linked to at least a hydrogen atom.
  • the presence of such N-H bonds may be evidenced by infrared spectroscopy (IR) technique. In fact, from the IR-spectra one can distinguish characteristic bands from different functional groups presented in the solid.
  • IR infrared spectroscopy
  • a VAION catalyst system of the present invention comprises surface hydrogen atoms in an atomic percentage comprised between 0% and 10 % including the outer limits.
  • M is a metal selected from the group comprising Ga, Si, Ge, W, Mo, Mn, Cr, Ti, Nb, V, Fe, B, and Mg, 0,1 ⁇ y ⁇ 1, 2 ⁇ 6, -1 ⁇ n ⁇ 1,
  • one embodiment of the present invention provides a compound being
  • a VAION compound wherein said compound has a V/AI atomic ratio comprised between 0.1 and 0.7 including the outer limits.
  • a compound is provided wherein said compound has a V/AI atomic ratio comprised between 0.2 and 0.3 including the outer limits.
  • the present invention provides a compound being Al 0 . 5 - o.9 Vo.1-0.9 Oi.5 -2 .6 No.1-0.7 H 0 . 1-0 .5.
  • the present invention provides a compound being Al 0.5.0.75 V 0 . ⁇ .o. 5 0-1.5-2.0 No.1-0.4 H 0 . ⁇ - 0 . 4 .
  • the present invention provides a compound having a formulation selected from the group comprising AI0.5 V0.5 O1.9 No. 4 Ho. 4
  • a preparation process by mineral way involves a reaction between a salt of metal "M" and an aluminum salt.
  • a reaction between metal "M” and aluminum may be carried out by mineral way, comprising co-precipitation, gelification and complexation.
  • a reaction between vanadium and aluminum is suitably accomplished by co-precipitation which may be effected by contacting a vanadium salt, for instance sodium meta vanadate (NaVO 3 ) or ammonium meta vanadate (NH VO 3 ) with an aluminum salt, for instance aluminum nitrate [AI(NO 3 ) 3 .9H 2 O], aluminum chloride (AICI 3 ) or aluminum sulfate [AI 2 (SO 4 ) 3 ].
  • a vanadium salt for instance sodium meta vanadate (NaVO 3 ) or ammonium meta vanadate (NH VO 3 )
  • an aluminum salt for instance aluminum nitrate [AI(NO 3 ) 3 .9H 2 O], aluminum chloride (AICI 3 ) or aluminum sulfate [AI 2 (SO 4 ) 3 ].
  • a reaction between vanadium and aluminum may also be carried out by organic way.
  • the reaction may involve an aluminum alkoxide, for instance aluminum tributoxyde; and ammonium metavanadate.
  • the vanadium compound may be acetylacetonate [V(C 5 H 7 O 2 ) 3 ] and the aluminum compound may be aluminum acetylacetonate [C 5 H 21 AIO 6 ] in an acid organic reaction environment such as citric acid.
  • the oxide or catalyst precursor is calcinated to form a catalyst with a basic activity.
  • Said drying operation may be effected at temperatures from 30°C to 150°C. Particular useful temperatures for said drying operation range from 60°C to 120°C using for example a spray-drying equipment.
  • Calcination may be conducted in two steps.
  • a first step typically comprises heating at a temperature ranging from 120°C to 250°C at a rate of heat between 5°C to 20°C per minute in a flow of air, remaining isothermally at the same conditions between 1 to 4 hours, preferably between 1 to 2 hours.
  • a second step may comprise a heating between 450°C to 550°C at a rate of heat comprised between 5°C to 20°C per minute in a flow of air, preferably between 480°C and 520°C, remaining isothermally between 1 to 2 hours.
  • Calcination may be effected in a conventional oven.
  • the oxide precursor may be treated by nitridation in order to obtain an VAION compound that correspond to the generic formulation Al z V ⁇ ⁇ -n O[3+ ⁇ (i-n)- ⁇ +c]/2 N x / 3 H c with "x" different from zero.
  • a nitridation process of the oxide precursor allow, by a selective modification of acid-base surface sites to optimize the catalytic functionality and as such a catalyst compound is obtained which is adapted to a particular chemical reaction.
  • Such nitridation step may be conducted at temperatures comprised between 200°C and 1000 °C.
  • the nitridation step is conducted at temperatures comprised between 300°C and 600 °C.
  • a nitridation step is conducted at temperatures comprised between 400°C and 500°C.
  • Nitridation may be conducted by cyano compounds using hydrocarbon mixtures with the oxide precursor or hydrogenated precursor under ammonia flow between 200°C and 1000°C. The nitridation is usually conducted at a temperature between 300°C and 800°C. Nitridation may also be done by pure or diluted organic compounds containing nitrogen molecules (e.g., monomethylamine or acetonitrile) between 200°C and 800°C.
  • nitrogen molecules e.g., monomethylamine or acetonitrile
  • the nitridation procedure may also be done progressively at different temperatures using a step by step program.
  • ammonia flow depends on the nitridation temperature, the higher the nitridation temperature, the higher is the ammonia flow.
  • Nitridation may be conducted using a flow of ammonia/propane or ammonia/hydrogen mixtures. Both propane and hydrogen are reducing agents that may help the oxygen/nitrogen exchange reaction at lower nitridation temperatures because of a coupling effect between the reduction of the catalyst and the introduction of nitrogen.
  • the amount of nitrogen in the VAION compound is a function of both the pretreatment or nitridation temperature and the reaction time.
  • a suitable nitridation duration ranges from 3 to 24 hours.
  • nitridation may be effected between 6 to 15 hours on stream.
  • the nitrogen content is determined under ammonia form by direct chemical analysis, after treatment of the solid with melted potash at high temperature. There is a good correlation between the nitrogen content and the loss of weight due to the substitution of oxygen by nitrogen introduced during the nitridation reaction.
  • a catalyst according to the present invention may comprise from 2% to 8% of nitrogen by weight. In particular, a catalyst according to the present invention may comprise from 4% to 6% of nitrogen by weight.
  • nitridation may be carried out in a catalytic reactor under high ammonia partial pressure during a period of time of about 1 hour to 24 hours, and a ammonia flow of 40 l/hr to 80 l/hr.
  • the obtained oxide compound may be optionally modified by additional metallic sites selected from the group comprising alkali metal oxides and alkali metals.
  • additional metallic sites as used in this specification refers to distinct metallic atoms deposited at the catalyst's surface by impregnation that act as promoters to increase and or prolong and or revive the activity of the surrounding active basic and acidic sites.
  • promoter herein refers to catalyst additives that facilitate the predetermined synthesis and are classified in two categories.
  • Metal oxides or structural promoters may be selected from the group comprising oxidized aluminum (AI 2 O 3 , called alumina), oxidized calcium (CaO) and oxidized Mg (MgO, magnesia) and play a structural role during the synthesis process and they also have important roles during the catalyst production where they influence the formation of the metal crystallites.
  • Alkali metals or electronic promoters may be selected from the group comprising Li, K, Na, Rb and Cs and play an electronic role towards an increased synthesis.
  • another embodiment of the present invention provides a compound, said compound modified by addition of metallic sites chosen from the group comprising Li, Na, K, Rb, Cs, Pt, Pd, Ru, Rh, Re, Os, Ir, Cu, Ni, Co, Fe, Mo, Au, Ag, and Sn.
  • the added promoter may be a single metal oxide or alkali metal, a mixture of metal oxides, a mixture of alkali metals, or a mixture of metal oxide(s) and alkali metal(s) and may be employed affecting the catalyst complexity with increasing the likelihood of co- operative promoter interactions such that a structural promoter may have indirect electronic promotional effects and vice versa.
  • Additional mono or multimetallic promoter elements may be introduced after completion of the nitridation process by deposition, impregnation or by exchange of a metallic salt, in particular using nickel formiate.
  • Additional mono or multimetallic alkaline elements may also be introduced before initiating the nitridation pre-treatment by introduction of a metallic salt, in particular using nickel formiate during the preparation stage of the oxide precursor.
  • Promoters generally make up a few percent of the catalyst weight and are inhomogenously distributed over the catalyst surface.
  • Alkaline metal content in catalysts according to the present invention may vary between 0.1 % and 15 wt% including the outer limits.
  • Metallo oxynitride compounds according to the present invention may be used as catalyst as well as support of active metals. In the latter case, the presence of nitrogen in the support is susceptible for promotion the activity of the associated oxynitride catalyst.
  • a compound according to the present invention is provided as a catalyst.
  • Catalysts according to the present invention may be employed without a support and will display excellent activities. However, in some applications, it may be advantageous to include in the catalyst a support material which functions by providing a large surface area for the catalyst and by creating a harder and more durable catalyst for use in highly abrasive environment such as found in fluidized bed reactors.
  • This support may be any of those commonly proposed for such use, such as silica, zirconia, alumina, titania, antimony pentoxide sol, or other oxide substrates. From the point of view of availability, cost, and performance, silica is usually a satisfactory material and is suitable in the form of silica sol for easy dispersion.
  • Metallo oxynitride catalysts of the present invention may be suitable for use as bifunctional catalysts.
  • the term bifunctional catalyst refers to a catalyst containing both basic and acid metallic sites.
  • Metallo oxynitride catalysts of the present invention may be suitable for oxidation reactions such as ammoxidation reactions but they may also be suitable for condensation reactions, dehydrogenation reactions, oxidative coupling reactions and the like.
  • Another embodiment provides use of a compound according to the present invention in the ammoxidation of C 1-6 alkanes.
  • Figure 1 discloses a graph wherein the methane conversion, acetonitrile selectivity and the methanol selectivity are shown in the present invention at 700°C and the prior art at 650°C and 750°C.
  • the ammoxidation process according to the present invention involves the use of a VAION catalyst which is characterized by a high performance and a high stability even when it is used over long periods of time under reaction conditions.
  • Catalyst samples were heated in the presence of the reactive from 25°C until the reaction temperature with 10°C/min.
  • the composition of the gas feed and the reaction temperature will be specified for each example.
  • the catalyst was heated to the reaction temperature, and after stabilizing for 30 minutes at the reaction temperature, the composition of the mixture at the reactor outlet was determined by gas phase chromatography.
  • the propane conversion and the product were. calculated using the following relationships:
  • Table 1 Oxynitride catalysts with differing vanadium/alumina (V/AI) atomic ratios and their activity and selectivity in the ammoxidation of propane.
  • V/AI vanadium/alumina
  • Table 1 shows that the oxynitride having a V/AI 0.25 atomic ratio corresponds to an optimal catalytic activity with a maximal selectivity and yield to acrylonitrile.
  • Example 2 Effect of the propane, oxygen and ammonia contact time on the 15 performance of the VAION catalyst system
  • the performance of the VAION catalyst system in the ammoxidation reaction of propane in function of the propane (C 3 H 8 ), oxygen (O 2 ) or ammonia (NH 3 ) contact time is presented in Table 2, Table 3 and Table 4 respectively.
  • the reaction condition is expressed by W/F which is defined as space time or the catalyst weight in grams divided by the flow of 20 reactant stream in moles per hour at standard temperature such as (e.g. 25°C) and atmospheric pressure.
  • the contact time of one reactant is changed, keeping the contact time of the two other reactants constant.
  • the amount of the catalyst is 100mg and the reaction temperature is 25 500°C.
  • the vanadium aluminum oxynitride catalyst with a V/AI 0.25 atomic ratio composition is used.
  • Example 3 Comparison among different known metallo oxynitride catalysts and the oxynitride catalyst of the present invention in the propane ammoxidation reaction
  • Performances of different metallo oxynitrides catalysts in the ammoxidation reaction of propane are presented in Table 5.
  • the feed ratio propane:oxygen:ammonia is 1 :1 :1 , the amount of the catalyst is 100mg and the reaction temperature is 500°C.
  • the metallo oxynitride catalysts in this example are: ZrPON, VAION, AIGaPON, AICrPON, AIPON.
  • Table 5 shows that the vanadium aluminum oxynitrides are the more active and selective in the conversion of propane into acrylonitrile.
  • Example 4 Yield effect of the VAION catalyst system of the present invention in the ammoxidation reaction of propane compared to known propane ammoxidation catalysts
  • Table 6 shows the activity profile of the aluminum vanadium oxynitride of the present invention over known propane ammoxidation catalysts. It is noted that, for a comparable acrylonitrile percentage yield with the three catalyst systems as shown in Table 6, the value of the propane contact time is very low when using the VAION which ultimately result in the production of a higher amount of acrylonitrile when expressed per ton of catalyst and per hour.
  • Table 6 shows that the VAION catalyst system of the present invention provides for a 70- times higher acrylonitrile yield when expressed per ton of catalyst per hour compared to the MoVNbTeOx catalyst system.
  • Both VAION and MoVNbTeO x catalyst systems show a comparable propane conversion and acrylonitrile selectivity for a comparable acrylonitrile yield expressed as percentage.
  • Example 5 Effect of the activation condition on the catalytic properties of the VAION catalyst system.
  • the catalytic activity of the vanadium aluminum oxynitride catalyst with V/AI ratio 0.25 is monitored under different feed space velocities of the reactants.
  • the molar ratio between the reactants propane, oxygen and ammonia is 1 :2:1.
  • the resulting catalytic activities are presented in Table 8.
  • the conversion of propane in function of increasing space velocities results in a curve with a maximum.
  • the selectivity to acrylonitrile increases with increasing space velocities. It is noted that space velocities for previously known metal oxide catalysts are lower.
  • the results as presented in Table 8 are highly advantageous towards the industrial production of ACN.
  • the catalysts of the present invention provide a substantial advantage with regard to the ACN production per time unit because they are operational at high space velocities maintaining a high conversion of the propane and a high selectivity for ACN.
  • Aluminum vanadate oxynitride catalyst (V/AI molar ratio 0.25) was modified with 1 wt%
  • Example 8 Comparative study of activity results between VAION catalyst system and prior art ammoxidation catalysts.
  • Table 10 shows the activity results corresponding to propane ammoxidation reactions using ammoxidation catalysts known in the prior art compared to VAION catalyst system.
  • the VAION catalyst system of the present invention operates at high space velocity (low contact time) and thereby provides substantial advantages with regard to the ACN productivity. It can be seen from these results that for equivalent propane conversion and acrylonitrile selectivity, propane ammoxidation using the VAION catalyst system is around 10.5 times more productive than
  • the ACN productivity can be enhanced if the VAION catalyst system is used in a process scheme in which propane is recycled.
  • the catalytic system according to the invention because of its low contact time value, can be advantageously used in a catalytic fluid bed reactor.

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Abstract

The present invention relates to a process for the ammoxidation of a hydrocarbon, comprising contacting the hydrocarbon with ammonia and molecular oxygen in the presence of a hydrogenated metallo oxynitride catalyst.The invention further relates to a hydrogenated metallo oxynitride compound characterized by the empirical formula (1): Aly Mα1-b O¿[3+α(1-n)-x+c]/2 N¿x/3? Hc and to a process for the preparation of a hydrogenated metallo oxynitride compound and the use of said compound.

Description

AMMOXIDATION OF HYDROCARBONS AND HYDROGENATED METALLO OXYNITRIDE CATALYSTS THEREFOR
Field of the invention This invention relates to an improved catalytic ammoxidation process for converting hydrocarbons into nitriles. The invention further relates to new metallo oxynitride catalysts useful for performing said ammoxidation.
Background to the invention The value of nitriles and more specifically α, β- unsaturated nitriles is generally well recognized with acrylonitrile being among the most valuable monomers available to the polymer industry for producing useful polymeric products.
It has been well known to commercially produce an unsaturated nitrile, such as acrylonitrile by ammoxidation of an alkene, such as propylene, namely, by reacting an olefin or alkene with ammonia and molecular oxygen, i.e.
CH3CH=CH2 + NH3 + 1.5 O2 -> CH2=CHCN + 3 H2O.
On the other hand, from the viewpoint of reducing the cost for raw materials, attention has been attracted to a process for producing an unsaturated nitrile, such as acrylonitrile, from an alkane (such as propane), which is available at low cost as compared to an alkene, by the ammoxidation reaction, i.e.:
CH3 CH2 CH3 + NH3 + 2 O2 -> CH2=CHCN + 4 H2O, in the presence of a catalyst, i.e., by reacting an alkane with ammonia and molecular oxygen in the presence of a catalyst.
The much reduced conversion rates of the relative inert alkanes (often kept low on purpose to keep selectivities up) compared to the relative high reactive alkenes have led to many efforts towards the development of an alkane conversion process being a match for the alkene counterpart conversion reaction regarding yield of the desired end-product.
Most of the efforts to date have concentrated on the development of improved catalyst systems. It is clear that the art to catalyst improvements enacts largely expert on the catalyst's atomic composition. Many multi component systems have been developed as a catalyst for use in producing acrylonitrile from propane by ammoxidation as exemplified e.g. in US patent no. 5,231 ,214 wherein an oxide catalyst containing Mo, V, Nb, Te and at least one element selected from the group consisting of Mg, Ca, Sr, Ba, Al, Ga, TI, In, Ti, Zr, Hf, Ta, Cr, Mn, W, Fe, Ru, Co, Rh, Ni, Pd, Pt, Zn, Sn, Pb, As, Sb, Bi, La and Ce is disclosed. In spite of the numerous and various approaches to develop an efficient process for the ammoxidation of propane to acrylonitrile, most solutions produced insufficient yields, increasing the capital costs over the costs for propylene-based processes.
It should be recognized by the numerous studies on catalyst systems as cited in scientific and patent literature that there is a continuos incentive to the development of new and/or improved systems for many and various reaction systems, comprising compound compositions with reduced complexity. The examples are given here by FR2741612 and FR2743796 which relate to aluminum based oxynitride catalysts.
Even if satisfactory yields are produced, those catalyst systems known to aid- in the alkane ammoxidation lack commercial utility which is highly dependent on the overall cost of the conversion process. Therefore and increasingly higher yield and selectivity of the conversion of reactants is desired to minimize purification of the product and recycle streams.
Those skilled in the ammoxidation art recognize that it would be a distinct advance in industrial catalysis and extremely beneficial for the industry if a highly efficient and economic alkane ammoxidation process would be available. Another object of the present invention is to provide an alkane ammoxidation process with a high conversion of the alkane. It is a further object to provide an alkane ammoxidation process with a high selectivity for the desired end-product. It is another object to provide an alkane ammoxidation process with a high yield of the desired end-product. It is yet another object to provide new catalysts for performing such ammoxidation reactions. Other objects, as well as aspects, features and advantages, of the present invention will become apparent from a study of the accompanying disclosure and the claims.
Summary of the invention
The invention relates in general to a process for the ammoxidation of a hydrocarbon, comprising contacting the hydrocarbon with ammonia and molecular oxygen in the presence of a hydrogenated metallo oxynitride catalyst.
The invention further relates to novel metallo oxynitride catalysts. Detailed Description of the Invention
The present invention relates to processes for the oxidative conversion of hydrocarbons to nitriles. Processes and catalyst compositions for performing ammoxidation of hydrocarbons are provided.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art.
In accordance with this invention, in one aspect, unsaturated nitriles are prepared from saturated hydrocarbons, in for example a vapor phase process, comprising contacting at least one saturated hydrocarbon, ammonia and oxygen in the presence of a catalyst containing aluminum and a second metal "M" selected from the group comprising Ga, Si, Ge, W, Mo, Mn, Cr, Ti, Nb, V, Fe, B, and Mg under conditions suitable for converting the selected saturated hydrocarbon to the desired unsaturated nitrile.
In further aspects of the present invention new hydrogenated metallo oxynitride compounds are provided along with their preparation process for use as ammoxidation catalysts.
Said new catalyst compounds as used in the ammoxidation process according to the present invention for the conversion of propane allow for a high conversion of propane and a high selectivity to the desired end-product acrylonitrile while a total absence of selectivity for the intermediary compound propylene.
Advantages over the prior art of the avoidance of propylene production as in the ammoxidation process according to the present invention includes the avoidance of production of undesirable COx compounds which are normally produced by reaction of propylene with oxygen. By avoiding the production of propylene, the selectivity of the catalyst according to the present invention towards acrylonitrile and acetonitrile formation is substantially increased. The absence of propylene production in the ammoxidation process according to the present invention avoids an otherwise difficult removal in a downstream process. Different reaction mechanisms of the ammoxidation metallo oxynitride catalysts according to the present invention, compared to conventional oxide ammoxidation catalysts, substantially increases the yield of the desired end products. Allyl adsorbed like species formed on the metallo oxinitride catalysts surface during alkane activation are more reactive than propylene in the gas phase. In fact, propylene molecules need to be adsorbed on the catalyst surface and then react with activated nitrogen species (NH, NH2, N*) to produce acrylonitrile. A key aspect of the oxynitride catalyst according to the present invention is that said activated nitrogen species are present at high concentration while, on conventional oxides, only few ammonia adsorbed species are present. Also, a nitrogen insertion reaction requires less contact time as compared to propylene production from propane which is the step controlling the reaction in oxide catalysts, requiring high contact times.
Compared to known propane ammoxidation yields, the process of the present invention provides for a 70-times increased turn-over with comparable propane conversions and comparable acrylonitrile selectivities.
In particular, the present invention provides a process for the ammoxidation of a hydrocarbon comprising contacting the hydrocarbon with ammonia and molecular oxygen in the presence of a hydrogenated metallo oxynitride catalyst.
The metallo oxynitride catalysts of the present invention alone or promoted with certain elements supported or unsupported provides excellent yields of desired end products in hydrocarbon ammoxidation reactions.
Although the specific procedures and methods as described herein are mainly exemplified for the ammoxidation of the hydrocarbon propane, they are merely illustrative for the practice of the invention.
Any hydrocarbon capable of forming unsaturated nitriles may be used in the practice of the invention. Suitable hydrocarbons include linear and branched alkanes and alkenes. Suitable hydrocarbons include but are not limited to ethane, ethylene, propane, propylene, n-butane, isobutane, isobutene, n-pentane, n-pentene, isopentane, 3-methyl pentane, dimethylpentane, 2-methylpentene, n-hexane, isohexane, 2,3-dimethyl butane, heptane, isoheptane, octane, isononane, dodecane, and the like. Also cyclic hydrocarbons such as cyclohexane and cyclohexene may be used.
In one embodiment, the ammoxidation process of the present invention is particularly suitable for the conversion of a C1-6 alkane. The ammoxidation process of the present invention is particularly suitable for the conversion of a C1-6 alkane selected from the group of methane, ethane, propane and methane.
In a further embodiment, the ammoxidation process of the present invention is particularly suitable for the conversion of propane and methane. In yet a further embodiment, the ammoxidation process of the present invention is particularly suitable for the conversion of propane. In yet a further embodiment, the ammoxidation process of the present invention is particularly suitable for the conversion of methane.
While ammonia is most generally employed, other compounds may be employed. For example, ammonia may be generated in use from decomposable ammonium compounds such as ammonium carbonate, or from various amines, such as methyl amine, ethyl amine and aniline. Any source of oxygen, pure or in admixture with inerts, may be employed in the process of this invention. Air is a satisfactory source of oxygen for use in this invention.
The process according to the present invention may be carried out as a vapor phase reaction. It is well understood that during the course of the process of the present invention, diluent inert gasses may be used such as He, N2 and Ar and equally, steam or
CO2 may be added to the gaseous reaction mixture. As such the gaseous reactive comprising the hydrocarbon, ammonia and oxygen may be diluted with an inert diluent and/or steam and/or CO2 as a diluent.
The feedstock may be a single alkane or alkene, a mixture of alkanes, a mixture of alkenes, or a mixture of alkane and alkene.
The oxygen/propane molar ratio in the feedstock supplied to the reactor in the present invention is within a range of from 1 :1 to 1 :4. A suitable oxygen concentration feed ranges from 10% to 60% by volume of the feed. Since the catalyst used in this invention provides a high acrylonitrile selectivity a relatively low oxygen/propane molar ratio, from 2.8:1 to 3.5:1 is sufficient. The ammonia/propane molar ratio in the feedstock supplied to the reactor may be varied within a range from 0.5:1 to 2:1 , preferably from 0.7:1 to 1.5:1. As previously stated, the ammoxidation process according to the present invention may be carried out as a vapor phase reaction. Accordingly, any apparatus of the type suitable for carrying out oxidation reactions in the vapor phase may be employed for the practice of the process. The process may be operated continuously or intermittently, and may employ a fixed bed with large particulate or pelleted catalyst, or so-called fluidized or moving bed of catalyst with finely divided catalyst.
A suitable particle size distribution is such that the catalyst particles have a size within a range from 20 microns to 200 microns
In one embodiment, the ammoxidation process of the present invention is carried out at a temperature in a range from 300°C to 600°C.
In a further embodiment, the ammoxidation process of the present invention is carried out at a temperature in a range of from 400°C to 550°C.
In yet a further embodiment, when ammoxidizing propane to yield acrylonitrile, the ammoxidation process of the present invention is carried out at a temperature in a range from 490°C to 510°C.
Pressures other than atmospheric may be employed in the process of the present invention, however usually the process is conducted at or near atmospheric pressure, since the reaction proceeds well at such pressure.
The contact time between the reactants and catalyst employed in the process of this invention may be selected from a broad operable range which may vary from 0.1 to 50 seconds. The contact time may be defined as the length of time in seconds representing the time measured under reaction conditions during which a unit volume of reactant gases is in contact with a volume of catalyst employed. In the case of converting propane to acrylonitrile, a suitable contact time will be within a range of 0.1 to 10 seconds. The optimum contact time will, of course, vary depending upon the hydrocarbon being reacted, the catalyst and the reaction temperature but in general ranges between 0.1 and 5 seconds.
The feed mixture is commonly introduced into the catalyst bed at a W/F (defined as the weight of the catalyst in grams divided by the flow of reactant stream in moles/h at standard temperature and pressure) in a range from 100 g.h/moles to 25.000 g.h/moles, preferably from 10.000 g.h/moles to 20.000 g.h/moles.
The present invention provides a range of metallo catalysts and/or support materials for use in oxidation or ammoxidation reactions. These metallo catalytic materials may be composed from different basic elements as to adapt the catalyst formulation thereby meeting the technical and flexible criteria and needs of various specific catalytic reactions as demanded in a range of industrial processes. The present invention provides metallo catalytic compounds with a metallic basis being composed of a metal draw on an available pool of appropriate metals including mixed metals. As such, by playing on a choice of appropriate metals, the nature, number and strength of the catalytic sites may be modulated. Therefore one may modulate the catalyst's selectivity and the conversion rate of the starting product according to one's desired end-product.
In one embodiment of the present invention the ammoxidation process involves a hydrogenated metallo oxynitride catalyst comprising Al and a second metal "M" selected from the group comprising Ga, Si, Ge, W, Mo, Mn, Cr, Ti, Nb, V, Fe, B, and Mg. "M" may represent a single metal as well as multiple metals different from one another. In the latter case "M" represents a total balanced combination of multiple metals M1 , M2, ..., Mi, said metals having respectively an oxidation degree 1 , α2, ..., αi such that the mean is comprised between 2 and 6, including the outer limits.
In a further embodiment of the present invention, an ammoxidation process is provided comprising a catalyst being a compound of formula (1) Aly Mαι O[3+α(-n)-x+C]/2/3 Hc
1 wherein
"M" is a metal selected from the group comprising Ga, Si, Ge, W, Mo, Mn, Cr, Ti, Nb, V, Fe, B, and Mg, 0,1 ≤ y ≤ 1 , 2 < α < 6, -1 < n < 1 , 0.1 > (n-1/y) <1 , 0 < c < 2, 0 < x ≤ 3 + α(1-n) + c. In a further embodiment of the present invention, an ammoxidation process is provided comprising a catalyst being a compound of the following formula
Aly Vαι-n O[3(l).x+C]/2 Nχ/3 Hc wherein 0,1 < y < 1, 3 < α < 5, -1 < n < 1 , 0 < c < 2, 0 < x ≤ 3 + α(1-n) + c.
This catalyst is further also referred to as VAION catalyst.
In order to define the stoichiometry of the VAION catalyst according to the present invention with regard to nitrogen and hydrogen, "x" and "c" are chosen different from zero. As such the VAION system shows particular acid and basic surface sites. In the frame of certain surface reactions, these two types of sites may present particular industrial interest. Non-limiting examples of industrial interest reactions include Canizzaro and Tishchenko type reactions, conversion reactions of ethylamine to acetonitrile, hydrogenation reactions of 1 ,3-butadiene, synthesis of ethylene amine from monoethanolamine, conversion reactions from picolin to cyanopyridine, alkylation reactions of phenol and methanol, and reduction reactions of aldehyde and ketone.
The wording acid and basic surface sites as used in the present specification refers to the acid and basic active sites on the surface of the catalyst. Those sites are applied for adsorption, which are the effective sites for a particular heterogeneous catalytic reaction. The term active site under the present specification may also be related to an active center which describes an ensemble of sites at which a catalytic reaction takes place.
Advantageously, the "n" value of the VAION catalyst described in the present invention equals zero to define the stoichiometry linked to the vanadium atoms. Such catalysts respond to the following general formulation:
Aly Vα O[3+α-x+C]/2 Nx/3 Hc wherein 0,1 < y < 1 , 3 < α < 5, 0 < c < 2, and 0 < x ≤ 3 + + c.
In this type of compound, the V/AI atomic ratio equals 1 provided that "y" equals 1. Preferably, the state of oxidation of vanadium "α" equals 5 which corresponds to the more stable oxidation state of vanadium.
Another embodiment of the present invention relates to an ammoxidation process which involves the application of a VAION catalyst with a V/AI atomic ratio comprised between 0.1 and 0.7 including the outer limits, a further embodiment relates to a V/AI atomic ratio comprised between 0.2 and 0.3 including the outer limits.
Another embodiment relates to a process with a catalyst Al 0.1-1.0 Vo.1-0.9 0 5.2.6 N0.ι-o.7 H0.1-
0.5-
In a further embodiment, a process according to the present invention comprises a catalyst for ammoxidation having the stoechiometric formulation selected from the group comprising
Alto V0.9 O2.3 No.7 H0.5, AI0.5 V0.5 O1.9 No. Ho.4,
Alo. 5 Vo.25 O1.5 N0.3 H0.3,
AI1.0 V0.1 O2.6 N0.i H0.ι, and
AI1.0 V0.5 O1.92 No.4 Ho.4.
Control of selectivity is one of the major roles governed by heterogeneous catalysts. Catalyst modification methods have been developed to tune catalysts which could then provide any desired selectivity. Sustained changes in catalyst performance may be induced by the introduction of small doses of surface modifiers. This practice is also referred to as doping which relates to the incorporation of impurities within the crystal lattice of a solid so as to alter its physical properties. Through a structural rearrangement of the metallic surface also an increase in catalytic activity may be induced.
A further embodiment of the present invention provides process comprising a modified catalyst modification procedure to the effect by addition of metallic sites chosen from the group comprising Li, Na, K, Rb, Cs, Pt, Pd, Ru, Re, Os, Ir, Cu, Ni, Co, Fe, Mo, Au, Ag, and
Sn. In general, such additional metallic sites promote the activity of the surface hydrogen. The addition of metallic sites selected from the group Li, Na, K, Rb, and Cs may result in an increase in number and strength of the catalyst's surface basic sites.
It is to be understood in the context of the present specification that the wording additional metallic site refers to distinct metallic atom depositions at the catalysts' surface by impregnation that act as promoters to increase and or prolonge and or revive the activity of the surrounding active sites.
A VAION catalyst according to the present invention comprises from 0.01 % to 15% of additional metallic weight. In particular when doping is accomplished with at least one of the elements selected from the group comprising Pt, Pd, Ru, Re, Os, Ir, Cu, Ni, Co, Fe, Mo, Au, Ag, and Sn the additional metal weight may be from 0.1% to 3%. In general the additional metallic weight comprising a metal selected from the group Li, Na, K, Rb, and Cs amounts to 2%.
It is observed that catalysts of the present invention contain only a small quantity of additional metal and this catalyst modification may have the effect of delaying its de- activation which might occur during the course of certain specific uses.
Advantageously, a VAION catalyst system according to this specification, present hydrogen surface atoms in the formation -AIOH and/or -VOH and/or -AINHX and/or -VNHX with x= 1 , 2, 3 or 4. An important proportion of the surface nitrogen atoms are linked to at least a hydrogen atom. The presence of such N-H bonds may be evidenced by infrared spectroscopy (IR) technique. In fact, from the IR-spectra one can distinguish characteristic bands from different functional groups presented in the solid.
Advantageously, a VAION catalyst system of the present invention comprises surface hydrogen atoms in an atomic percentage comprised between 0% and 10 % including the outer limits.
It is another aspect of the present invention to provide a metallo oxynitride compound characterized by the empirical formula (1)
Aly M ι Op+ot(i-n)-x+c]/2 Nχ3 Hc 1 wherein "M" is a metal selected from the group comprising Ga, Si, Ge, W, Mo, Mn, Cr, Ti, Nb, V, Fe, B, and Mg, 0,1 <y< 1, 2<α<6, -1 <n < 1,
0.1 >(n-1/y)<1,
0<c<2,
0<x<3 + α(1-n) + c.
Accordingly, one embodiment of the present invention provides a compound being
Aly Vα-|-n Or3+cc(i-n)-x+C]/2 Nχ/3 Hc wherein 0,1 <y<1, 3<α<5,
-1 <n< 1, 0<c<2,
0<x<3 + α(1-n) + c. Said compound is also referred to as VAION compound.
According to another embodiment, a VAION compound is provided wherein said compound has a V/AI atomic ratio comprised between 0.1 and 0.7 including the outer limits. According to a further embodiment, a compound is provided wherein said compound has a V/AI atomic ratio comprised between 0.2 and 0.3 including the outer limits.
According to another embodiment, the present invention provides a compound being Al 0.5- o.9 Vo.1-0.9 Oi.5-2.6 No.1-0.7 H0.1-0.5. According to a further embodiment, the present invention provides a compound being Al 0.5.0.75 V0.ι.o.50-1.5-2.0 No.1-0.4 H0.ι-0.4.
According to another embodiment, the present invention provides a compound having a formulation selected from the group comprising AI0.5 V0.5 O1.9 No.4 Ho.4
Alo.75 Vo.25 O1.5 No.3 Ho.3. A preparation process by mineral way involves a reaction between a salt of metal "M" and an aluminum salt. In case of the VAION catalyst the preparation process involves the reaction between a vanadium compound with an aluminum compound, followed by a drying step and a calcination step to obtain a VAION compound that correspond to the aforementioned formula Aly Vαι-n O[3+α(ι-n)_x+C]/2 Nx/3 Hc with x= 0 (= oxide precursor).
A reaction between metal "M" and aluminum may be carried out by mineral way, comprising co-precipitation, gelification and complexation. A reaction between vanadium and aluminum is suitably accomplished by co-precipitation which may be effected by contacting a vanadium salt, for instance sodium meta vanadate (NaVO3) or ammonium meta vanadate (NH VO3) with an aluminum salt, for instance aluminum nitrate [AI(NO3)3.9H2O], aluminum chloride (AICI3) or aluminum sulfate [AI2(SO4)3].
A reaction between vanadium and aluminum may also be carried out by organic way. In this case, the reaction may involve an aluminum alkoxide, for instance aluminum tributoxyde; and ammonium metavanadate. More suitable, the vanadium compound may be acetylacetonate [V(C5H7O2)3] and the aluminum compound may be aluminum acetylacetonate [C 5H21AIO6] in an acid organic reaction environment such as citric acid.
Following a drying operation, the oxide or catalyst precursor is calcinated to form a catalyst with a basic activity. Said drying operation may be effected at temperatures from 30°C to 150°C. Particular useful temperatures for said drying operation range from 60°C to 120°C using for example a spray-drying equipment.
Calcination may be conducted in two steps. A first step typically comprises heating at a temperature ranging from 120°C to 250°C at a rate of heat between 5°C to 20°C per minute in a flow of air, remaining isothermally at the same conditions between 1 to 4 hours, preferably between 1 to 2 hours. A second step may comprise a heating between 450°C to 550°C at a rate of heat comprised between 5°C to 20°C per minute in a flow of air, preferably between 480°C and 520°C, remaining isothermally between 1 to 2 hours. Calcination may be effected in a conventional oven.
In a subsequent step, the oxide precursor may be treated by nitridation in order to obtain an VAION compound that correspond to the generic formulation Alz Vαι-n O[3+α(i-n)-χ+c]/2 Nx/3 Hc with "x" different from zero. A nitridation process of the oxide precursor allow, by a selective modification of acid-base surface sites to optimize the catalytic functionality and as such a catalyst compound is obtained which is adapted to a particular chemical reaction.
Such nitridation step may be conducted at temperatures comprised between 200°C and 1000 °C.
In a particular embodiment, for the propane ammoxidation reaction, the nitridation step is conducted at temperatures comprised between 300°C and 600 °C.
In a further embodiment a nitridation step is conducted at temperatures comprised between 400°C and 500°C.
Nitridation may be conducted by cyano compounds using hydrocarbon mixtures with the oxide precursor or hydrogenated precursor under ammonia flow between 200°C and 1000°C. The nitridation is usually conducted at a temperature between 300°C and 800°C. Nitridation may also be done by pure or diluted organic compounds containing nitrogen molecules (e.g., monomethylamine or acetonitrile) between 200°C and 800°C.
The nitridation procedure may also be done progressively at different temperatures using a step by step program.
For a nitridation reaction by ammonia, used ammonia flow depends on the nitridation temperature, the higher the nitridation temperature, the higher is the ammonia flow.
Nitridation may be conducted using a flow of ammonia/propane or ammonia/hydrogen mixtures. Both propane and hydrogen are reducing agents that may help the oxygen/nitrogen exchange reaction at lower nitridation temperatures because of a coupling effect between the reduction of the catalyst and the introduction of nitrogen.
The amount of nitrogen in the VAION compound is a function of both the pretreatment or nitridation temperature and the reaction time. A suitable nitridation duration ranges from 3 to 24 hours. As a particular suitable example, nitridation may be effected between 6 to 15 hours on stream. The nitrogen content is determined under ammonia form by direct chemical analysis, after treatment of the solid with melted potash at high temperature. There is a good correlation between the nitrogen content and the loss of weight due to the substitution of oxygen by nitrogen introduced during the nitridation reaction. At the end of the nitridation process, a catalyst according to the present invention may comprise from 2% to 8% of nitrogen by weight. In particular, a catalyst according to the present invention may comprise from 4% to 6% of nitrogen by weight.
More advantageously, nitridation may be carried out in a catalytic reactor under high ammonia partial pressure during a period of time of about 1 hour to 24 hours, and a ammonia flow of 40 l/hr to 80 l/hr.
The obtained oxide compound may be optionally modified by additional metallic sites selected from the group comprising alkali metal oxides and alkali metals. The term additional metallic sites as used in this specification refers to distinct metallic atoms deposited at the catalyst's surface by impregnation that act as promoters to increase and or prolong and or revive the activity of the surrounding active basic and acidic sites. The term promoter herein refers to catalyst additives that facilitate the predetermined synthesis and are classified in two categories.
Metal oxides or structural promoters may be selected from the group comprising oxidized aluminum (AI2O3, called alumina), oxidized calcium (CaO) and oxidized Mg (MgO, magnesia) and play a structural role during the synthesis process and they also have important roles during the catalyst production where they influence the formation of the metal crystallites.
Alkali metals or electronic promoters may be selected from the group comprising Li, K, Na, Rb and Cs and play an electronic role towards an increased synthesis.
Accordingly, another embodiment of the present invention provides a compound, said compound modified by addition of metallic sites chosen from the group comprising Li, Na, K, Rb, Cs, Pt, Pd, Ru, Rh, Re, Os, Ir, Cu, Ni, Co, Fe, Mo, Au, Ag, and Sn.
The added promoter may be a single metal oxide or alkali metal, a mixture of metal oxides, a mixture of alkali metals, or a mixture of metal oxide(s) and alkali metal(s) and may be employed affecting the catalyst complexity with increasing the likelihood of co- operative promoter interactions such that a structural promoter may have indirect electronic promotional effects and vice versa.
Additional mono or multimetallic promoter elements may be introduced after completion of the nitridation process by deposition, impregnation or by exchange of a metallic salt, in particular using nickel formiate.
Additional mono or multimetallic alkaline elements may also be introduced before initiating the nitridation pre-treatment by introduction of a metallic salt, in particular using nickel formiate during the preparation stage of the oxide precursor.
Promoters generally make up a few percent of the catalyst weight and are inhomogenously distributed over the catalyst surface. Alkaline metal content in catalysts according to the present invention may vary between 0.1 % and 15 wt% including the outer limits.
Metallo oxynitride compounds according to the present invention may be used as catalyst as well as support of active metals. In the latter case, the presence of nitrogen in the support is susceptible for promotion the activity of the associated oxynitride catalyst.
Accordingly, in another embodiment, a compound according to the present invention is provided as a catalyst.
Catalysts according to the present invention may be employed without a support and will display excellent activities. However, in some applications, it may be advantageous to include in the catalyst a support material which functions by providing a large surface area for the catalyst and by creating a harder and more durable catalyst for use in highly abrasive environment such as found in fluidized bed reactors. This support may be any of those commonly proposed for such use, such as silica, zirconia, alumina, titania, antimony pentoxide sol, or other oxide substrates. From the point of view of availability, cost, and performance, silica is usually a satisfactory material and is suitable in the form of silica sol for easy dispersion.
Metallo oxynitride catalysts of the present invention may be suitable for use as bifunctional catalysts. As used herein, the term bifunctional catalyst refers to a catalyst containing both basic and acid metallic sites. Metallo oxynitride catalysts of the present invention may be suitable for oxidation reactions such as ammoxidation reactions but they may also be suitable for condensation reactions, dehydrogenation reactions, oxidative coupling reactions and the like.
Accordingly, another embodiment provides use of a compound according to the present invention in the ammoxidation of C1-6 alkanes.
Brief description of the figures Figure 1 discloses a graph wherein the methane conversion, acetonitrile selectivity and the methanol selectivity are shown in the present invention at 700°C and the prior art at 650°C and 750°C.
Examples
The ammoxidation process according to the present invention involves the use of a VAION catalyst which is characterized by a high performance and a high stability even when it is used over long periods of time under reaction conditions.
The following examples of the invention are exemplary and should not be taken as in any way limiting.
Catalyst samples were heated in the presence of the reactive from 25°C until the reaction temperature with 10°C/min. The composition of the gas feed and the reaction temperature will be specified for each example.
The catalyst was heated to the reaction temperature, and after stabilizing for 30 minutes at the reaction temperature, the composition of the mixture at the reactor outlet was determined by gas phase chromatography. The propane conversion and the product were. calculated using the following relationships:
Conversion of propane (% in moles) = converted propane/ propane in the feed Selectivity to product A (% moles) = amount of product A / converted propane. Example 1: Effect on the catalytic activity of the VAION catalyst system of the vanadium/alumina atomic ratio in the catalyst composition
The performance in the ammoxidation reaction of propane into acrylonitrile of vanadium aluminum oxynitrides with differing amounts of vanadium are presented in Table 1. The 5 feed ratio propane/oxygen/ammonia is 1 :1 :1 , the amount of the catalyst is 100mg and the reaction temperature is 500°C.
Table 1: Oxynitride catalysts with differing vanadium/alumina (V/AI) atomic ratios and their activity and selectivity in the ammoxidation of propane.
10
Table 1 shows that the oxynitride having a V/AI 0.25 atomic ratio corresponds to an optimal catalytic activity with a maximal selectivity and yield to acrylonitrile.
Example 2: Effect of the propane, oxygen and ammonia contact time on the 15 performance of the VAION catalyst system
The performance of the VAION catalyst system in the ammoxidation reaction of propane in function of the propane (C3H8), oxygen (O2) or ammonia (NH3) contact time is presented in Table 2, Table 3 and Table 4 respectively. The reaction condition is expressed by W/F which is defined as space time or the catalyst weight in grams divided by the flow of 20 reactant stream in moles per hour at standard temperature such as (e.g. 25°C) and atmospheric pressure.
The contact time of one reactant is changed, keeping the contact time of the two other reactants constant. The amount of the catalyst is 100mg and the reaction temperature is 25 500°C. The vanadium aluminum oxynitride catalyst with a V/AI 0.25 atomic ratio composition is used.
Table 2
C3H8:02:NH3 W/F Conversion Selectivity Selectivity Selectivity Selectivity Yield (molar ratios) (g.h/moles to propane to ACN to AcCN to CO to C02 ACN
Table 3
Table 4
It is concluded from the above-mentioned Tables 2, 3 and 4 that an optimal catalytic activity of the VAION catalyst system is obtained with a W/F 7.7 of propane, a W/F 3.1 of oxygen and a W/F 14.2 of ammonia.
Example 3: Comparison among different known metallo oxynitride catalysts and the oxynitride catalyst of the present invention in the propane ammoxidation reaction
Performances of different metallo oxynitrides catalysts in the ammoxidation reaction of propane are presented in Table 5. The feed ratio propane:oxygen:ammonia is 1 :1 :1 , the amount of the catalyst is 100mg and the reaction temperature is 500°C. The metallo oxynitride catalysts in this example are: ZrPON, VAION, AIGaPON, AICrPON, AIPON.
Table 5 shows that the vanadium aluminum oxynitrides are the more active and selective in the conversion of propane into acrylonitrile.
Example 4: Yield effect of the VAION catalyst system of the present invention in the ammoxidation reaction of propane compared to known propane ammoxidation catalysts
Table 6 shows the activity profile of the aluminum vanadium oxynitride of the present invention over known propane ammoxidation catalysts. It is noted that, for a comparable acrylonitrile percentage yield with the three catalyst systems as shown in Table 6, the value of the propane contact time is very low when using the VAION which ultimately result in the production of a higher amount of acrylonitrile when expressed per ton of catalyst and per hour.
Table 6.
Table 6 shows that the VAION catalyst system of the present invention provides for a 70- times higher acrylonitrile yield when expressed per ton of catalyst per hour compared to the MoVNbTeOx catalyst system. Both VAION and MoVNbTeOx catalyst systems show a comparable propane conversion and acrylonitrile selectivity for a comparable acrylonitrile yield expressed as percentage.
Example 5: Effect of the activation condition on the catalytic properties of the VAION catalyst system.
In order to verify the role of the activation process or nitridation process on the catalytic performance of the catalyst, a number of catalytic tests are conducted with pre-activated catalyst samples. The influence of the ammonia concentration in the gas feed in the presence of propane is monitored. A catalyst with a V/AI 0.25 atomic ratio is tested with a feed propane:oxygen:ammonia molar ratio composition of 1.25 :3 :1. For the activation of the catalysts the following experimental pre-activation conditions are used: (a) 7 hours under a mixture: 5 ml propane, 7 ml helium, 4 ml ammonia ( 25% ammonia)
(b) 7 hours under a mixture: 5 ml propane, 4 ml ammonia (44.4% ammonia)
(c) 1 hour under a mixture: 5 ml propane, 4 ml ammonia (44.4% ammonia)
(d) nitridation carried out with a feed oxygen:ammonia molar ratio of 3:1
The results of the catalytic activity are presented in Table 7. The results obtained with a 1.25 :3 :1 molar mixture of propane:oxygen:ammonia are included as reference.
Table 7: Effect of the nitridation condition on the catalytic activity
The results as shown in Table 7 indicate that a higher amount of ammonia in the gas mixture and a longer activation time as defined by pre-treatment (b) lead to the formation of propylene in the reaction products and the production of high COx levels and hence a decreased ACN selectivity. Consequently the existence of an optimal reduction-nitridation coupling effect determine the effectiveness of the catalyst which results in a substantially higher yield of ACN.
In the prior art the mentioned lower conversion rates for propane ammoxidation give rise to a higher waste volume which call for the necessity to recycle unreacted alkane and unreacted intermediary alkene. This high conversion rate is a main advantage of the present invention.
Example 6: Effect of the feed space velocity (GHSV)
The catalytic activity of the vanadium aluminum oxynitride catalyst with V/AI ratio 0.25 is monitored under different feed space velocities of the reactants. The molar ratio between the reactants propane, oxygen and ammonia is 1 :2:1. The resulting catalytic activities are presented in Table 8.
Table 8: Effect of GHSV (grams of catalyst per hour space velocity) on the catalytic activity
As deduced from Table 8, the conversion of propane in function of increasing space velocities results in a curve with a maximum. The selectivity to acrylonitrile increases with increasing space velocities. It is noted that space velocities for previously known metal oxide catalysts are lower. The results as presented in Table 8 are highly advantageous towards the industrial production of ACN. The catalysts of the present invention provide a substantial advantage with regard to the ACN production per time unit because they are operational at high space velocities maintaining a high conversion of the propane and a high selectivity for ACN.
Example 7
Aluminum vanadate oxynitride catalyst (V/AI molar ratio 0.25) was modified with 1 wt%
NaOH and 1 wt% from NaN3. The ratio composition between the reactants methane:oxygen:ammonia is 1 :2:1. The catalytic reaction was conducted at 700°C and atmospheric pressure. As shown in Table 9 the VAION catalyst system shows excellent properties for the production of methanol from direct conversion of methane.
Example 8: Comparative study of activity results between VAION catalyst system and prior art ammoxidation catalysts.
Table 10 shows the activity results corresponding to propane ammoxidation reactions using ammoxidation catalysts known in the prior art compared to VAION catalyst system.
Table 10: Propane ammoxidation catalyst systems and reaction conditions
(*) ml/h.g of cata ys ACN cat.
Ref. 1. Ushikubo et al. EP 0529853. Ref. 2. Guttmann, et al. US Pat. No. 4,788,317. Ref.
3. Albonetti et al. US Pat. No. 6,083,869. Ref. 4. Hinago et al. US Pat. No. 6,063,728.
During the ammoxidation reactions, propylene formation was observed for all vanadium molybdate and vanadium antimonite catalyst formulations. However this intermediate was not detected during catalytic reaction with VAION catalyst system.
The results as shown in Table 10, indicate that the amount of acrylonitrile production per hour and per amount of catalyst is higher for the VAION catalyst system than that produced by the prior art systems. The VAION catalyst system of the present invention operates at high space velocity (low contact time) and thereby provides substantial advantages with regard to the ACN productivity. It can be seen from these results that for equivalent propane conversion and acrylonitrile selectivity, propane ammoxidation using the VAION catalyst system is around 10.5 times more productive than
MoVo.3Te0.23Nbo.i5θx system (ref 1), 16.7 times more productive than VSb5W0.5Te0.5Sn0.5Ox/SiO2-AI2O5 system (ref 2), 2.5 times more productive than
VSbi2.5Fe Ox system (ref 3) and 5.2 times more productive than MoV0.32Teo.22Nbo.i2Ybo.o2Ox/SiO2 system (ref 4).
The ACN productivity can be enhanced if the VAION catalyst system is used in a process scheme in which propane is recycled. The catalytic system according to the invention, because of its low contact time value, can be advantageously used in a catalytic fluid bed reactor.

Claims

Claims
1. A process for the ammoxidation of a hydrocarbon, comprising contacting the hydrocarbon with ammonia and molecular oxygen in the presence of a hydrogenated metallo oxynitride catalyst.
2. A process according to claim 1 wherein said catalyst comprises Al and a second metal "M" selected from the group comprising Ga, Si, Ge, W, Mo, Mn, Cr, Ti, Nb, V, Fe, B, and Mg.
3. A process according to claim 2, wherein said catalyst is a compound of formula (1)
Aly Mαi-n O[3+(x(i-n)-x+c]/2 Nχ/3 Hc
1 wherein
"M" is a metal selected from the group comprising Ga, Si, Ge, W, Mo, Mn, Cr, Ti,
Nb, V, Fe, B, and Mg,
0,1 <y<1,
2<α<6, -1<n<1,
0.1 >(n-1/y)<1,
0<c<2,
0<x<3 + α(1-n) + c.
4. A process according to claim 3, wherein said catalyst is
Aly Vα 1-n O[3+oc(i-n)-x+c]/2 Nχ/3 Hc wherein
0,1 <y<1,
3<α 5, -1<n<1,
0<c<2,
0<x≤3 + α(1-n) + c.
5. A process according to claim 4 wherein said catalyst has a V/AI atomic ratio comprised between 0.1 and 0.7.
6. A process according to claim 5 wherein said catalyst has a V/AI atomic ratio comprised between 0.2 and 0.3.
5 7. A process according to claim 4, wherein said catalyst is Al 0.1-1.0 V0.ι-o.g Oι.5-2.6 N0.ι.
8. A process according to claim 7, wherein said catalyst has the stoechiometric formulation selected from the group comprising
10 A .o Vo.9 O2.3 No.7 Ho.5,
Alo.5 Vo.5 O-I.9 No.4 Ho.4, Alo.75 Vo.25 O-1.5 No.3 Ho.3,
A .o Vo.1 O2.6 N0.i Ho.ι, and A .o Vo.5 Oι.92 No.4 Ho. . 15
9. A process according to any of previous claims 1-8, wherein said catalyst is modified by addition of metallic sites chosen from the group comprising Li, Na, K, Rb, Cs, Pt, Pd, Ru, Re, Os, Ir, Cu, Ni, Co, Fe, Mo, Au, Ag, and Sn.
20 10. A process according to any of previous claims 1-9 wherein the hydrocarbon is a C1-6 alkane.
11. A process according to claim 10 wherein the alkane is selected from the group comprising propane and methane.
25
12. A process according to claim 11 wherein the alkane is propane.
13. A process according to claim 11 wherein the alkane is methane.
30 14. A process according to any of previous claims 1-13 wherein the reaction temperature in comprised between 300°C and 600°C.
15. A process according to claim 14 wherein the reaction temperature in comprised between 400°C and 550°C. 35
16. A process according to claim 15 wherein the reaction temperature in comprised between 490°C and 510°C.
17. A hydrogenated metallo oxynitride compound characterized by the empirical formula (1)
Aly Mαι-D O[3(i-n)-x+C]/2/3 Hc 1 wherein
"M" is a metal selected from the group comprising Ga, Si, Ge, W, Mo, Mn, Cr, Ti, Nb, V, Fe, B, and Mg,
0,1 <y<1,
2<α<6,
-1 <n < 1,
0.1 >(n-1/y)<1, 0<c<2,
0<χ<3 + α(1-n) + c.
18. A compound according to claim 17, being Aly Vα 1-n O[3+α(ι-n)-x+c]/2 Nx3 Hc wherein 0,1<y<1,
3< <5,
-1 <n < 1,
0<c<2,
0<x<3 + α(1-n) + c.
19. A compound according to claim 18 wherein said compound has a V/AI atomic ratio comprised between 0.1 and 0.7.
20. A compound according to claim 19 wherein said compound has a V/AI atomic ratio comprised between 0.2 and 0.3.
21. A compound according to claim 18, being Al 0.5-0.9 V0.ι.0.9 O^.^ N0-0.7 H0.1-0.5-
22. A compound according to claim 21, being Al 0.5-0.75 V0.1-0.5 Oι.5-2.o N0-04 H0.ι-o. -
23. A compound according to claim 22, having a formulation selected from the group comprising
Alo.5 Vo.5 O-i.g No.4 Ho.4 Alo.75 Vo.25 O-1.5 N0.3 Ho.3.
5
24. A compound according to any of claims 17-23 wherein said compound is modified by addition of metallic sites chosen from the group comprising Li, Na, K, Rb, Cs, Pt, Pd, Ru, Rh, Re, Os, Ir, Cu, Ni, Co, Fe, Mo, Au, Ag, and Sn.
10 25. A process for the preparation of a hydrogenated metallo oxynitride compound comprising a reaction between a vanadium compound and an aluminum compound, further characterized by a nitridation step at a temperature comprised between 300°C and 600°C.
15 26. A process for the preparation of a compound according to claim 25 wherein the nitridation step is conducted at a temperature comprised between 400°C and 500°C.
27. Use of a compound according to any of previous claims 17-24 as a catalyst. 0
28. Use of a compound according to claim 27 in the ammoxidation of C|-6 alkanes.
EP02795234A 2001-12-21 2002-12-19 Ammoxidation of hydrocarbons and hydrogenated metallo oxynitride catalysts therefor Withdrawn EP1476420A1 (en)

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US7153981B2 (en) 2004-07-27 2006-12-26 E. I. Du Pont De Nemours And Company Supercritical fluid phase synthesis of methylene lactones using oxynitride catalyst
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US7141682B2 (en) 2004-07-27 2006-11-28 E. I. Du Pont De Nemours And Company Liquid phase synthesis of methylene lactones using oxnitride catalyst
EP2007680B1 (en) 2006-03-14 2012-08-15 Max-Planck-Gesellschaft zur Förderung der Wissenschaften e.V. Use of zirconium oxynitride catalysts for ammonia decomposition
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