Classifications

• • 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
• • 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
  • C07C2521/10—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
• • 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 relates to a process and catalyst for converting methane in the presence of oxygen into hydrogen and higher hydrocarbons which include ethane and ethylene.
• Methane is a plentiful hydrocarbon feedstock which is obtained principally from natural gas.
• the methane content of natural gas can vary from 60% to 99%, the other components being ethane, propane, butane, carbon dioxide, and nitrogen.
• World reserves are estimated to be about 2.5 x 10 12 ft 3 .
• the production of chemicals from methane is hampered by the lack of catalytic processes capable of activating methane towards chemical transformations.
• methane can be either combusted for its heating value, or steam reformed over iron or nickel catalysts to produce CO and H 2 .
• the CO and H 2 are further reacted with N 2 to produce methanol and ammonia.
• methane is an underutilized natural resource.
• 4,239,658 disclose a novel catalyst and process for converting methane into a hydrocarbon product rich in ethylene and benzene.
• the essential components of the catalyst are
• a group Ila metal selected from the group consisting of magnesium and strontium composited with a passivated, spinel-coated refractory support or calcium composited with a passivated, non-zinc containing spinel-coated refractory support.
• the process consists of contacting the catalyst with methane at elevated temperatures for a short period of time, and recovering the hydrocarbons which are produced. During the exposure to methane some of the metal oxides contained in the catalyst are reduced, and the surface of the catalyst becomes covered with coke, rendering it inactive. Before the methane can be readmitted to the reactor, the catalyst must be regenerated by contact with an oxygen or water containing gas at elevated temperature.
• U. S. Patent No. 4,450,310 discloses a process for the conversion of methane into olefins and hydrogen by passing methane in the absence of oxygen and in the absence of water over a catalyst at temperatures above 500°C.
• the catalyst is composed of mixed oxides from group 1A of the periodic table, including Li, Na, K, Rb, and Cs, and group IIA of the periodic table, including Be, Mg, Ca, Sr, and Ba, and optionally a promoter metal selected from Cu, Re, W, Zr, and Rh.
• the reducible oxides can also be promoted with alkali metals (U. S. Patent 4,499,322) or alkaline earth metals (U. S. Patent 4,495,374) and stability is enhanced by the presence of phosphorus (PCT Published Application WO 85/00804).
• alkali metals U. S. Patent 4,499,322
• alkaline earth metals U. S. Patent 4,495,374
• phosphorus PCT Published Application WO 85/00804
• Other related work includes Ru promoted by alkali and alkaline earth metals (U. S. Patent 4,489,215), and the use of reducible rare earth oxides, CeO 2 (U. S. Patent 4,499,324) and Pr 6 O 11 (U. S. Patent 4,499,323).
• Hinsen and Baerns disclose a new process for the synthesis of ethylene and ethane from methane.
• the improvement of this process over previous processes is that methane and oxygen are fed simultaneously to the catalytic reactor, thereby obviating the need to cycle between reaction and catalyst regeneration.
• the preferred method of adding the oxygen is either laterally along the length of the reactor, or to a large recirculating stream of the hydrocarbon gas. These methods of oxygen addition insure that the oxygen partial pressure is kept low, so as to maximize selectivity.
• U. S. Patent No. 2,020,671 discloses the production of oxygenated organic compounds by reaction of methane with steam at temperatures of 200°-700°C in the presence of catalysts selected from metal salts of the alkaline earth metals, aluminum, magnesium, and zinc.
• U. S. Patent No. 2,859,258 discloses the production of ethylene from methane in the presence of oxygen containing metal compound wherein the metal is selected from the second, third, and fourth groups of the periodic table, such as aluminum oxide, magnesium aluminum silicate, and magnesium aluminum molybdate.
• methane can be converted into hydrogen, ethylene, ethane, and higher hydrocarbon products by contacting a gas containing methane and oxygen with a metal oxide of Group IIA metals of the Periodic Table such as Be, Mg, Ca, Sr, and Ba; a metal oxide of Group 111A metals of the Periodic Table, such as Sc, Y, and La; a metal oxide of the lanthanide series excluding Ce, such as Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; and mixtures thereof.
• the catalytic reaction is preferably carried out at temperatures between 500 and 1000oC and pressures between 1 and 25 atmospheres. Some water, CO, and CO 2 is also produced as a byproduct of the reaction.
• the present process is distinguished from previous known processes for the synthesis of hydrocarbons from methane in the presence of oxygen by the use of metal oxides which are not reducible, such as MgO, SrO, Y 2 O 3 , and La 2 O 3 .
• a second feature of these catalysts is that they are basic and ionic metal oxides.
• metal oxides which exhibit basic character, and do not have a redox potential are generally selective catalysts for synthesizing higher hydrocarbons from a mixture of methane and oxygen.
• metal oxides of Group IIA, IIIA, and the lanthanide series excluding Ce can be improved by the addition of one or more promoter oxides selected from the following metals:
• metals of Group 11A which are Be, Mg, Ca, Sr, and Ba;
• (d) metals of the lanthanide series which are Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu;
• the promoter oxide can be added by a variety of techniques.
• the loading of the promoter can vary from a catalytically effective amount up to 50 wt%, and preferably less than 10 wt%.
• the present process is also distinguished from previous known processes for the synthesis of hydrocarbons from methane in that an inert support material for the active metal oxide is not necessary, and in some cases may be deleterious to the overall performance of the catalyst.
• the present process is further distinguished from previous known processes for the synthesis of hydrocarbons from methane by feeding methane and oxygen simultaneously to the catalytic reactor.
• the catalysts described herein By using the catalysts described herein, the synthesis of hydrocarbons from methane can be carried out in the presence of oxygen without reducing the yield of hydrocarbon product.
• Such a simultaneous and continuous feeding of a methane and oxygen mixture to the catalytic reactor eliminates the need for periodic catalyst regeneration, and it is the preferred mode of operation of the present invention.
• Fig. 1 is a graph illustrating the dependence of product selectivity (based on moles of methane converted) upon methane conversion.
• Fig. 2 is a graph illustrating the dependence of product selectivity upon operating temperature.
• the catalyst can be composed of one or more base metal oxides of Group 11A, Group 111A, and the lanthanide series. These materials can be supplied as metal oxides, or as metal salts which are subsequently decomposed to the oxide form. Some examples of suitable metal salts are acetate, acetylacetonate. carbide, carbonate, hydroxide, formate, oxalate, nitrate, phosphate, sulfate, sulfide, tartrate, and halides such as fluoride, chloride, bromide, and iodide.
• catalysts for the process described herein are the rare earth oxides which include La 2 O 3 , Y 2 O 3 , Pr 6 O 11 , Nd 2 O 3 , Sm 2 O 3 , Eu 2 O 3 , Gd 2 O 3 , TbO 2 , Dy 2 O 3 , Ho 2 O 3 , Er 2 O 3 , Tm 2 O 3 , Yb 2 O 3 , and
• Lu 2 O 3 Lu 2 O 3 . These oxides may be used in their pure form, or as a mixture such as is commonly obtained from mineral deposits. If a mixture obtained from an ore is used, for example, bastnasite or monazite is used, then it is necessary to reduce the cerium content of the ore to a low level. Cerium oxide is an acidic solid, and can readily cycle between the +3 and +4 oxidation state.
• CeO 2 converts methane in the presence of oxygen into CO and CO 2 , instead of ethylene, ethane, and higher hydrocarbons.
• the catalyst can be composed of mixtures of the base metal oxides described above with promoter oxides, such as metal oxides of Groups 1A, IIA, 111A, 1VB, VB, 1B, and the lanthanide series.
• promoter oxides such as metal oxides of Groups 1A, IIA, 111A, 1VB, VB, 1B, and the lanthanide series.
• a preferred form of the catalyst is to deposit promoter amounts of elements of Groups 1A, 11A, 1VB, VB, or 1B onto a rare earth oxide.
• Another preferred form of the catalyst is to deposit elements of Groups 1A, 111A, IVB, VB, 1B, or the lanthanide series onto an alkaline earth oxide.
• the elements of Groups 1A, 11A, 1VB, VB, or 1B can be deposited onto a rare earth oxide by a variety of techniques. The same techniques apply for depositing elements of Groups 1A, 111A, IVB, VB, 1B, or the lanthanide series onto an alkaline earth oxide. Suitable techniques are adsorption, incipient-wetness impregnation, precipitation, coprecipitation, and dry-mixing. After depositing the element from one of the groups listed above, it is converted into the oxide form by treating in an atmosphere of oxygen at elevated temperatures. The weight loading of the promoter metal oxide deposit can vary between 0% and 50%, but preferably less than 10%.
• the metal oxides described above can also be deposited on conventional supports, such as SiO 2 and Al 2 O 3 . These supports are not an essential part of the catalyst formulation, but may be used to give the catalyst pellet improved shape and/or improved mechanical strength and durability. If conventional supports are used, it is important that their acidity be reduced, otherwise the supports may catalyze the formation of carbon oxides from methane and oxygen.
• the support acidity can be reduced by a number of means, such as using a high weight loading of the active metal oxide, doping the support with alkali metal prior to depositing the metal oxide, or using supports of low porosity.
• a suitable method of preparing an unsupported catalyst is to deposit a promoter metal salt, such as from Groups 1A or 11A, onto a rare earth oxide by incipient-wetness impregnation.
• the metal salt may be dissolved in water or another solvent and then mixed with the rare earth oxide, thereby wetting the surface of the oxide.
• Aqueous solutions of the metal salt are desirable, and in this case, a water soluble salt is used.
• acids and/or bases can be added to the solution.
• the oxide is dried in an oven.
• the solid for use in the process it may be calcined at high temperature for a period of time to convert the metal or metal salts to the metal oxide form.
• the catalyst may be placed in a kiln, or a tube through which air may be passed, and heated for several hours at an elevated temperature, which preferably is between about 500 and 1000°C.
• the unsupported metal oxide used as the catalyst can be prepared in a variety of pellet shapes and sizes, the shape and size being dictated by the need to have good contact between the gas and the solid surface of the catalyst.
• the pellets can be prepared in the conventional manner using techniques well known to persons skilled in the art.
• the catalyst pellet may be prepared by extrusion of a slurry of the metal oxide. Pellets formed in this manner are then dried and calcined at elevated temperatures.
• the addition of promoter metal oxides, such as from Groups 1A or 11A of the Periodic Table, to the base metal oxide can be performed before or after the base metal oxide has been shaped into pellets.
• the catalyst described above is charged to a reactor and contacted with a gas containing methane and oxygen at elevated temperatures.
• feedstock for this process is natural gas which contains methane, ethane, propane, and other light hydrocarbons.
• the methane content of the gas is between 60 to 100 volume percent, preferably 90 to 100 volume percent.
• the natural gas is mixed with a stream containing oxygen to give a hydrocarbon to oxygen ratio (by volume) of 1 to 50, preferably between 2 and 15.
• the stream containing oxygen may contain an inert diluent, such as nitrogen or argon.
• substantially pure oxygen be used, because the diluents require a larger reactor size and must be removed from the process stream to purify the product.
• the optimum ratio of hydrocarbon to oxygen fed to the reactor is chosen such that the yield of ethylene, ethane, and higher hydrocarbons is a maximum. This choice is governed by a number of factors, such as the catalyst composition, the reaction temperature and pressure, and the desired distribution of hydrocarbon products. As the oxygen partial pressure is increased relative to the methane partial pressure, the conversion of methane in the reactor increases. However, the yield of ethylene and ethane does not increase proportionally, because at high oxygen partial pressures more carbon oxides are produced relative to the desired hydrocarbon products. This tradeoff is illustrated in Figure 1 for the catalyst described in Example 18, using an integral fixed-bed reactor.
• the selectivity (based on moles of methane converted) is cross-plotted against methane conversion and the methane to oxygen feed ratio.
• the combined selectivity to ethylene, ethane, and higher hydrocarbons is identified as All C n in the figure.
• These data were obtained at 700°C, 1 atm. pressure, a GHSV of 8x10 5 hr -1 (NTP), and an O 2 feed of 10 vol%.
• Argon diluent was used in this experiment to maintain a constant space velocity.
• Operating temperatures for contacting the methane and oxygen with the catalyst are between 500 and 1000oC, preferably between 550 and 850°C.
• the optimum choice of reaction temperature depends on a number of factors, such as the composition of the catalyst, the partial pressures of hydrocarbon and oxidant, and the desired distribution of hydrocarbon products.
• the dependence of hydrocarbon selectivity upon operating temperature is shown in Figure 2 for the catalyst described in Example 6. These data were obtained at a GHSV of 37,500 hr -1 (NTP), a methane partial pressure of 0.30 atm, an oxygen partial pressure of 0.05 atm, and an argon partial pressure of 0.65 atm. For all temperatures investigated in Figure 2 the oxygen conversion was 100%.
• the data in Figure 2 indicate that maximum selectivities to higher hydrocarbons are observed at temperatures between 650 and 850oC.
• the maximum selectivity to ethylene is observed at the highest temperature investigated, 850oC.
• Operating pressures for contacting the methane and oxygen mixture with the catalyst are not critical. However, the total system pressure does effect the performance, since increasing the pressure tends to decrease the selectivity to higher hydrocarbons.
• the effect of system pressure varies depending on the composition of the catalyst used. Preferred operating pressures are between 1 and 50 atms., more preferably between 1 and 20 atms.
• the reactor contains a fixed-bed of catalyst, and the hydrocarbon and oxygen streams are mixed and fed to the reactor.
• the reactor contains a fixed-bed of catalyst, the hydrocarbon feedstock is fed into one end of the reactor, and the oxygen is fed in at several inlets evenly spaced down the length of the reactor.
• contacting schemes can be used whereby the catalyst is suspended in a fluidized-bed, an ebullating-bed, a moving-bed, or an entrained-bed, although a fixed-bed of catalyst is particularly well suited to contacting the solid oxide with the gas containing methane and oxygen.
• Fixed-beds of catalyst can be operated in series or in parallel, depending on the desired yield and throughput of hydrocarbons required by the process.
• the catalytic reaction In addition to producing ethylene, ethane, and higher hydrocarbons, the catalytic reaction also produces large amounts of hydrogen. This hydrogen is valuable as a fuel, as well as being a desirable reactant at a refinery where there are many hydrogen consuming reactions taking place.
• This example describes the test procedure for the evaluation of the catalysts and sets forth the results.
• the pellets of metal oxide from Examples 1-11 were separately charged to a quartz tube (4 mm inside diameter) to give a catalyst bed depth of 25.4 mm.
• the quartz tube was then immersed in a fluidized sand-bath heater and brought up to reaction temperature over a 2 hr period under 50 cc/min of flowing argon.
• the feed was switched to a mixture of methane (0.30 atm), oxygen (0.05 atm), and argon (0.65 atm), and the flow rate was set at a GHSV (gas hourly space velocity) of 37,500 hr -1 (NTP).
• GHSV gas hourly space velocity
• the SrO catalyst exhibits the highest selectivity, this advantage is offset by the low oxygen and methane conversion per pass.
• the rare earth oxides including Y 2 O 3 , La 2 O 3 , Nd 2 O 3 , Sm 2 O 3 , Eu 2 O 3 , and Gd 2 O 3 , appear to offer the best overall performance characteristics, which are selectivities of approximately 60% to higher hydrocarbons, 100% O 2 conversion per pass, and a lower operating temperature (750-800°C) for achieving maximum hydrocarbon yield.
• This example illustrates the preparation of a mixture of oxide catalysts according to the present invention.
• a solution of lithium salt was prepared by dissolving LiNO 3 in distilled water. Lanthanum oxide was then impregnated to incipient-wetness by the solution of LiNO 3 . The mixture was dried in a vacuum oven at 110°C for 12 hours. The dried solid was then calcined in air at 600°C for 4 hours. Enough lithium was deposited on the La 2 O 3 to give a finished loading of 1.0 wt% Li 2 O.
• catalysts were produced with 1.0 wt% of various metal oxides on either La 2 O 3 or MgO.
• the catalysts prepared are listed in Tables 2 and 3.
• This example describes the test procedure for the evaluation of the mixed oxide catalysts and sets forth the results.
• the selectivity of the base metal oxide in this case La 2 O 3 or MgO
• the selectivity of the base metal oxide can be increased by impregnating them with other metal oxides of Groups 1A, IIA, 111A, IVB, VB, and IB of the Periodic Table.
• the especially preferred catalysts appear to be La 2 O 3 promoted with alkali metal oxides, La 2 O 3 promoted with alkaline earth oxides, and MgO promoted with Li 2 O.
• This example illustrates the use of different amounts of a promoter oxide on a base metal oxide.
• catalysts were produced with weight loadings of 0.25 to 10.0 wt% SrO on La 2 O 3 .
• the catalysts prepared are listed in Table 4.
• This example describes the test procedure for the evaluation of the strontium oxide-promoted lanthanum oxide catalysts prepared in Examples 30-33, and sets forth the results.
• This example illustrates the use of rare earth oxide mixtures as catalysts for the oxidative coupling of methane, wherein the mixture is obtained from the mineral ore, and a portion of the cerium has been removed.
• Bastnasite ore was obtained and dissolved in an acidic solution. From this solution varying levels of cerium was removed by extraction. The lanthanide concentrate was then converted into a rare earth carbonate, filtered, and dried. The carbonate was subsequently decomposed to the oxide by calcining in air at 750°C for 4 hours. Pure cerium oxide was also obtained for comparison with the rare earth oxide mixtures.
• the catalysts prepared are listed in Table 5. The amount of La 2 O 3 , CeO 2 , and other rare earth oxides (Re 2 O 3 ) contained in each catalyst is given in the Table.
• Example 39 This example describes the test procedure for the evaluation of the rare earth oxide mixtures prepared in Examples 35-38, and sets forth the results.
• Each of the catalysts of Examples 35-38 were separately pressed into pellets of mesh size between 20 and 32, charged to the quartz reactor, and exposed to the reaction conditions as described in Example 12 above.
• the experimental results for these catalyst samples are given in Table 5.
• This example compares two catalysts according to the present invention with a prior art catalyst consisting of lead oxide supported on silica.
• a lead oxide on silica catalyst was prepared according to the procedure given by W. Hinsen, W. Bytyn, and M. Baerns, Proc. 8th Intl. Cong. Catal. 3 , 581 (1984).
• Cab-O-Sil HS5 silica was impregnated to incipient-wetness by a solution of lead acetate dissolved in distilled water. The mixture was dried in a vacuum oven at 120oC for 12 hours. The dried solid was then calcined in air at 800°C for 4 hours. Enough lead was deposited on the SiO 2 to give a finished loading of 11.2 wt% PbO.
• the supported lead oxide catalyst was pressed into pellets of mesh size between 20 and 32, charged to the quartz reactor, and exposed to the reactor conditions as described in Example 12.
• the experimental results for this catalyst and for the catalysts of Examples 6 and 18 are given in Table 6.
• the 11.2% PbO/SiO 2 prior art catalyst exhibits selectivities to higher hydrocarbons similar to that of the catalysts disclosed in this invention, the activity of the prior art catalyst is low.
• a reaction temperature of 900°C only 50% of the oxygen is converted per pass.
• 100% of the oxygen is converted per pass at temperatures as low as 600°C.
• a comparison of the data shown in Table 6 indicates that the relative amount of hydrogen produced by PbO/SiO 2 is much less than that produced by either La 2 O 3 or SrO/La 2 O 3 .
• the catalysts disclosed in the present invention are superior to the prior art catalyst for the synthesis of hydrocarbons from methane in the presence of oxygen.

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• 1986
  • 1986-06-03 NZ NZ216388A patent/NZ216388A/en unknown
  • 1986-06-10 AU AU59944/86A patent/AU5994486A/en not_active Abandoned
  • 1986-06-10 EP EP19860903991 patent/EP0227750A4/de not_active Withdrawn
  • 1986-06-10 WO PCT/US1986/001254 patent/WO1986007351A1/en not_active Application Discontinuation
  • 1986-06-10 JP JP61503481A patent/JPS62503101A/ja active Pending
  • 1986-06-13 CN CN198686104014A patent/CN86104014A/zh active Pending
  • 1986-06-13 ES ES556014A patent/ES8707705A1/es not_active Expired
  • 1986-06-13 NO NO862377A patent/NO862377L/no unknown

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