NZ216388A - Catalytic conversion of methane into hydrogen and higher hydrocarbons - Google Patents

Description

P: • , led: ...,2ta.jANJ9sa.., 2 1 6388 No.' Date.

NEW ZEALAND PATENTS ACT. 1953 COMPLETE SPECIFICATION "METHOD AND CATALYST FOR THE CONVERSION OF ['ETHANE" XK/We. W R GRACE & CO, a corporation of the State of Connecticut, United States of America, of 1114 Avenue of the Americas, Mew York, New York 10036, United States of America, hereby declare the invention for which )&£ we pray that a patent may be granted to>®oedais, and the method by which it is to be performed, to be particularly described in and by the following statement: - 2 16388 Background of the Invention 1. Field of the Invention This invention relates to a process and catalyst for converting methane in the presence of 5 oxygen into hydrogen and higher hydrocarbons which include ethane ar.c ethylene. 2. Description of the Previously Published Art r**'" 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, ar.c nitrogen. World reserves are estimated to be about 2.5 x 10 ftJ. The 15 production of chemicals from methane, however, is hampered by the lack of catalytic processes capable of activating methane towards chemical transformations. Today methane can be either combusted for its heating value, or steam reformed over iron or nickel catalysts 20 to produce CO anc K^. The CO and are further reacted with to produce methanol and ammonia. As yet no attractive processes exist to convert methane directly into higher valued hydrocarbons, such as ethylene or propylene, which can then be used to 25 produce liquid fuels, plastics, fibers, solvents, and a myriad of other organic compounds used by the chemical process industry. As a consequence, methane is an underutilized natural resource.

U. S. Patent Nos. 4,172,810, 4,205,194, and 30 4,239,658 disclose a novel catalyst and process for 2 1 63 converting methane into a hydrocarbon product rich in ethylene and benzene. The essential components of the catalyst are (1) a group VIII noble metal having an atomic number of 45 or greater, nickel, or group lb noble metal having an atomic number of 47 or greater, (2) a group Via metal oxide which is capable of being reduced to a lower oxide, and (3) a group Ila metal selected from the group consisting of magnesium and strontium composited with a passivatec, spinel-coated refractory support or calcium composited with a passivated, non-zinc containing 15 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 2 0 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 25 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 30 500°C. The catalyst is composed of mixed oxides from group 1A of the periodic table, including Li, Na, K, 2 1 63 Rb, and Cs, ar.c croup 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 improvement of this process over the one described l' previously is the reduced amount of coke deposited on the catalyst during reaction, which presumably allows the reaction to proceed for a longer period of time before the catalyst must be regenerated.

G. E. Keller and M. M. Bhasin in J. Catal. _73, 9 10 (1982) disclose a process to produce ethylene and ethane from methane whereby pure methane is fed over a catalyst at atmospheric pressure and temperatures of 500 to 1000°C. As the methane is passed through the reactor it reacts with the metal oxide catalyst 15 producing ethane and ethylene, while simultaneously reducing the metal oxide. After a short exposure to methane, the catalyst must be regenerated, ar.c the feed is switched to pure oxygen which reoxidizes the metal oxice. All catalysts were prepared by supporting a 20 metal oxide on A^CU. Active catalysts are supported oxides of Sr., Pb, Sb, Bi, T1, Ca, and Mr.. The authors suggest that the ability of these oxides to cycle between two oxidation states is essential for having ( good activity and selectivity for the conversion of 25 methane into hydrocarbon products.

Jones, Leonard, and Sofranko issued a series of patents which disclose a process similar to that of Keller and Bhasin for producing ethane and ethylene from methane. The reaction is carried out at 30 atmospheric pressure, temperatures of 500 to 1000°C, and the methane and oxygen are fed separately in a 63 cyclic fashion. The improvements of the Jones process over the Keller process appear to be: (1) the use of a fluidized-bed catalytic reactor, instead of a fixed-bed catalytic reactor, anc (2) supporting the active metal oxides on Si0o, instead of Al-O,. Jones, Z. o Leonard, and Sofranko also suggest that "reducible" metal oxides must be used as catalysts for this process, and these are oxides of Sb, Mn, Ge, Pb, Sn, In, and Bi. These oxides are claimed in U. S. Patent 10 Nos. 4,443,644; 4,443,649; 4,443,645; 4,443,647; 4,444,984; 4,443,648; and 4,443,646, respectively. 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 15 enhanced by the presence cf phosphorus (PCT Published Application WO 85/00804). Other related work includes Ru promoted by alkali ar.c alkaline earth metals (U. S. Patent 4,489,215), and the use of reducible rare earth oxides, Ce07 (U. S. Patent 4,499,324) and ?rg°2.1 S* Patent 4,499,323).

Hinsen and 3aerns (German Patent 3,237,079, Chem.-Ztg. 107, 223 (1983) and Proc. 8th Intl. Cong. Catal. _3, 581 (1984)) disclose a new process for the W" 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 30 laterally along the length of the reactor, or to a large recirculating stream of the hydrocarbon gas. 2 1 63 These methods of oxygen addition insure that the oxygen partial pressure is kept low, so as to maximize selectivity. Good selectivities are observed at reaction temperatures of 650 to 750°C anc at low partial pressures (Rq2 = 0-05 to 0.10 atm) relative to methane (P^„. = 0.25 to 0.50 atir.) . For the continuous CH4 feeding case, Baerns found that reducible oxides of Pb, Sb, Sn, Bi, Cd, Tl, and In are active and selective catalysts. Reducing the acidity of the support is also 10 essential for maintaining good selectivity, and this can be achieved by using SiO^ support instead of TiO SiO^/Al^O^ > or Al?0.,, by increasing the PbO weight loading above 10.0%, and by promoting the catalyst with alkali.

U. S. Patent N'o. 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 2 0 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 25 the periodic table, such as aluminum oxide, magnesium aluminum silicate, and magnesium aluminum molvbcate. 3. Objects of the Invention It is an object of this invention to obtain a 'w' catalytic process to convert methane in the presence of oxygen to hydrogen, ethylene, ethane, and higher 21638c hydrocarbons with high selectivities ar.c high methane conversion per pass.

It is a further object cf this invention to develop an active and selective catalyst for the synthesis of hycrccen, ethylene, ethane, and higher hydrocarbons from methane in the presence of oxygen.

It is a further object cf this invention to operate the process with simultaneous addition of methane ar.c oxygen to the catalytic reactor, so as to avoid intermittent regeneration of the catalyst, thereby obtaining a continuous synthesis of hydrogen, ethylene, ethane, ar.c higher hydrocarbons from methane.

These ar.c further objects will become apparent as the description cf the invention proceeds.

Summary of the Invention It has been four.c that methane can be converted ir.to hycrocer., ethylene, ethane, ar.c higher hydrocarbon products by contacting a gas containing methane and oxygen with a metal oxice of Group 11A metals of the Periodic Table excluding >5g, such as Be, Ca, Sr, and 3a; a metal oxide of Group 111A metals of the Periodic Table, such as Sc, Y, and La; a metal oxice of the lanthar.ide series excluding Ce, Pr and lb, such as Nd, Sm, Eu, Gd, Dy, Ko, Er, Tm, Yb, ar.c Lu; and mixtures thereof. The catalytic reaction is preferably carried out at temperatures between 500 and 1000°C and pressures between 1 and 25 atmospheres. Some water, CO, and CO2 is also produced as a byproduct of the reaction.

The present process is distinguished from previous known processes for the synthesis of hydrocarbons from "2 8 NOV 1989^' 216388 methane in the presence cf oxygen by the use cf metal oxides which are not reducible, such as McO, SrO, anc La_0„. A second feature of these catalvsts is tha_ 2 j they are basic anc ionic metal oxides. Thus, metal oxides which exhibit basic character, ar.c co not have a redox potential, are generally selective catalysts for synthesizing higher hydrocarbons from a mixture of methane ar.c oxygen.

It has further beer, found that the metal oxices of Group IIA excluding >'g, IILA, and the lanthanide series excluding Ce, Pr and Tb, can be improved by the addition of one or more promoter oxices selected frcm the following metals: (a) metals cf Group 1A, which are Li, N'a, anc X; (b) metals of Group IIA, which are Be, Mc, Ca, Sr, and 3a; (c) metals cf Group I11A, which are Sc, Y, anc LiC 7 (c) metals cf the lanthanide series , excluding Ce, Pr ar.c Tb, which are Nd, Sm, Eu, Gd, Dy, Ho, Er, Tir., Yo, cr.c LU; (e) metals of Group 1V3, which are Sr. ar.c ?b; provided the first metal oxice is not an oxice of a metal of Group IaA; (f) metals cf Group VB, which are Sb ar.c 3i provided the firs metal oxide is not an oxide or a metal frcm Group IIA; and (g) metals of Group IB, which are Cu, Ag, anc Au. (h) mixtures thereof.

The promoter oxice 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 necess: 216388 4 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 5 hydrocarbons from methane by feeding methane and oxygen simultaneously to the catalytic reactor. 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 ar.c cxvger. mixture to the catalytic reactor eliminates the need for periodic catalyst regeneration, ar.c it is the preferred mode of operation of the present invention.

This invention is further described in the following description cf its preferred embodiments.

Srief Description of the Drawjncs Fig. 1 is a graph illustrating the dependence of 2 0 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.

Description of the Preferred Embodiments The catalyst can be composed of one or more base metal oxides of Group 11A, excluding >5g, Group 111A, and the lanthanide series, excluding Ce. These materials can be supplied as metal oxides, or as metal salts which are subsequently 3 0 decomposed to the oxide form. Some examples of suitable metal salts are acetate, acetylacetonate, 2 1 63 t carbide, carbonate, hydroxide, formate, oxalate, nitrate, phosphate, sulfate, sulfide, tartrate, and halides such as fluoride, chloride, bromide, and iocice.

Particularly suitable catalysts for the process described herein are the rare earth oxides which include La,03, ^'703, PrgO., , Nc2C>3, Sm2C>3, Eu2C>3, Ga^O3, TbG^, Dy20,, Hon0^r Er^O^, Yb2°3, and Lu^03- These oxices may be used in their pure form, or 10 as a mixture such as is commonly obtained from mineral deposits. If a mixture obtained from an ore is used, for example, bastnasite or mcr.azite 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 15 readily cycle between the +3 anc +4 oxidation state.

Consequently, CeO, converts methane in the presence of oxygen into CO ar.c C02, instead of ethylene, ethane, and higher hydrocarbons.

In another embodiment of the invention the 20 catalyst can be composed of mixtures of the base metal oxices described above with promoter oxides, such as metal oxices of Groups 1A, IIA, 111A, 1VB, VB, IB, and y the lanthanide series. A preferred form of the catalyst is to deposit promoter amounts of elements of 25 Groups 1A, IIA, 1VB, V3, or 13 onto a rare earth oxide. Another preferred form of the catalyst is to deposit elements of Groups 1A, 111A, 1VB, VB, 13, or the lanthanide series onto an alkaline earth oxide.

The elements of Groups 1A, 11A, 1VB, VB, or IB can 3 0 be deposited onto a rare earth oxide by a variety of techniques. The same techniques apply for depositing 2 1 63 elements of Groups 1A, 111A, 1VB, VB, IB, or the lanthanide series onto an alkaline earth oxide.

Suitable techniques are adsorption, incipient-wetness impregnation, precipitation, coprecipitation, anc 5 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% ar.c 50%, but 10 preferably less than 10%.

The metal oxices described above can also be deposited on conventional supports, such as SiO^ anc Al703. These supports are not an essential part of the catalyst formulation, but may be used to cive the 15 catalyst pellet improved shape arc/or improved mechanical strength anc curability. If conventional supports are used, it is important that their acidity be reduced, otherwise the supports may catalyze the formation of carbon oxices from methane and oxygen. 20 The support acidity car. be reduced by a number of means, such as using a high weight loading of the active metal oxice, doping the support with alkali metal prior to depositing the metal oxice, 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 IIA, onto a rare earth oxide by incipient-wetness impregnation. The metal salt may be dissolved in water or another solvent and then mixed 30 with the rare earth oxide, thereby wetting the surface of the oxide. Acueous solutions of the metal salt are 2 163 desirable, and in this case, a water soluble salt is used. To facilitate dissolution of the metal salt, acids and/or bases can be added to the solution. After wetting the rare earth oxide with the salt solution, 5 the oxide is dried in an oven. Finally, to prepare 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. For example, the catalyst may be placed in a kiln, or a 10 tube through which air may be passed, anc heated for several hours at an elevated temperature, which preferably is between about 500 and 1000°C.

The unsupported metal oxice used as the catalyst can be prepared in a variety of pellet shapes anc 15 sizes, the shape and size being dictated by the need to have good contact between the gas anc 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. For example, the catalyst 20 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 IIA of the Periodic Table, to the base metal 25 oxide can be performed before or after the base metal oxide has been shaped into pellets.

The method of catalyst preparation is further illustrated in the examples given below.

The catalyst described above is charged to a 30 reactor and contacted with a gas containing methane and oxygen at elevated temperatures. The hydrocarbon 216388 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 5 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. However, it is 10 preferable that substantially pure oxygen be used, because the diluents require a larger reactor size anc must be removed from the process stream to purify the product.

The optimum ratio of hydrocarbon to oxygen fed to 15 the reactor is chosen such that the yield of ethylene, ethane, anc higher hydrocarbons is a maximum. This choice is governed by a number cf factors, such as the catalyst composition, the reaction temperature and pressure, anc the desired distribution of hydrocarbon 20 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 25 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. In c this figure, the selectivity (based on moles of methane 30 converted) is cross-plotted against methane conversion and the methane to oxygen feed ratio. The combined 2 1 63 selectivity to ethylene, ethane, and higher hydrocarbons is identified as All C in the figure. These data were obtained at 700°C, 1 atm. pressure, a GHSV of 8xl05 hr"1 (NTP), anc an C>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 1000°C, preferably between 550 anc 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, anc 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 ^ (NTP), a methane partial pressure of 0.30 atm, an oxygen partial pressure of 0.05 atm, ar.c 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 85 0°C. The maximum selectivity to ethylene is observed at the highest temperature investigated, 850°C.

Operating pressures for contacting the methane anc 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 2 1 63 composition of the catalyst used. Preferred operating pressures are between 1 and 50 atms., more preferably between 1 and 20 atms.

Several different contacting schemes can be used 5 to maximize the conversion of methane to ethylene, ethane, anc higher hydrocarbons in the catalytic reactor. In one preferred embodiment, the reactor contains a fixed-bed of catalyst, anc the hydrocarbon and oxygen streams are mixed and fed to the reactor. 10 In a second preferred embodiment, the reactor contains a fixed-bed of catalyst, the hydrocarbon feedstock is fed into one end of the reactor, and the cxycen is fed in at several inlets evenly spaced down the length of the reactor. Other contacting schemes can be used 15 whereby the catalyst is suspended in a fluidizec-bec, an ebullating-bed, a noving-bec, 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 2 0 can be operated in series or in parallel, depending on the desired yield and throughput of hydrocarbons required by the process.

In addition to producing ethylene, ethane, and higher hydrocarbons, the catalytic reaction also 25 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.

Having described the basic aspects of the 30 invention, the following examples are given to illustrate specific embodiments thereof. Conversions * 2 163 ar.d selectivities reported in the examples are given on a per mole of methane basis.

EXAMPLES 1-11 5 These examples illustrate the preparation of pure oxide catalysts according to the present invention.

Pure metal oxides of Groups 11A anc 111A of the Periodic Table, and metal oxides of the lanthanide series were obtained and calcined at 900 °C in a kiln 10 for 4 hours. These solids were then pressed into pellets, crushed, and sieved to a mesh size between 20 and 32. The oxides are listed in Table 1.

Example 12 This example describes the test procedure for the evaluation of the catalysts and sets forth the results.

The pellets of metal oxice 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 20 quartz tube was then immersed in a fluidized sand-bath heater anc brought up to reaction temperature over a 2 hr period under 50 cc/mir. of flowing argon. Once at reaction temperature, the feed was switched to a mixture of methane (0.30 atm), oxygen (0.05 atm), and 25 argon (0.65 atm), anc the flow rate was set at a GHSV (gas hourly space velocity) of 37,500 hr (NTP). Periodically, the effluent from the reactor was analyzed by on-line gas chromatography. The reactions were carried out from 4 to 12 hours, during which time 30 little or no deactivation of the catalysts occurred. Results for several of the metal oxides tested are 2 1 6388 shown in Table 1. In these tests the reaction temperature was chosen to give the maximum yield of hydrocarbon products. The bed ir.let temperature corresponding to this optimum is shown in Table 1. The 5 combined selectivity to ethylene, ethane, and higher hydrocarbons is listed under All C in the Table, and the last column gives the mole ratio of hydrogen to ethylene and ethane in the reactor effluent. Oxygen and s carbon material balances were closed to within + 5%.

CO CO n vO r TABLE 1 ACTIVITY AND MAXIMUM SELECTIVITY OF PURE OXIDES FOR THE CONVERSION OF METHANE Selectivity (%) Conversion (%) Example CatalyBt T(»C) -2-4 £2.

Se All Cn CO V £°2- 22 ch4_ »2^2.

S?4- 1 MgO 900 32.1 17 .9 52 . 1 17 . 7 . 2 100 18.1 1 .6 2 CaO 750 .1 26 . 1 42 .0 14 . 9 43.2 100 .3 1 .7 3 SrO 850 22. 1 46 .5 70 . 5 6 . 2 23.4 36 8.0 0 .4 4 Sc2°3 900 .7 16 .5 48 .8 21 . 7 29.5 100 17.6 2 .0 Y2°3 800 26.8 27 . 4 56 . 2 12 . 5 31.0 100 18.0 1 .0 6 La^O j 750 .7 .9 59 .1 8.1 32.8 100 19.6 1 .1 7 Pr6°ll 850 8.7 16 . 6 .6 8 .0 66.4 100 11.3 1 .6 8 Nd2°3 750 22.5 31 .5 57 .0 7 .2 .8 100 17.9 0 .9 9 Sm^O ^ 750 23.5 29 .5 55 .8 .5 33.7 100 17.9 1 .0 Eu2°3 700 24.4 28 . 2 55 .9 9 .8 34.3 100 18.2 1 .2 11 Gd2o3 800 31.1 27 . 2 61 .0 9 . 6 29. 4 100 19.2 1 .1 _ 18 - ( o ) 2 16388 From the data shown in Table 1, it is evident that all of the pure metal oxide catalysts exhibit high selectivities to ethylene, ethane, and higher hydrocarbons. It is also evident that a large amount of hydrogen is produced along with the hydrocarbons, such that the mole ratio of H_ to C-K. and C_K, in the 2 2 4 2 6 product varies between 0.4 and 1.7. This hydrogen can be used as a fuel, or in a refinery complex where there are many hydrogen consuming reactions taking place. 10 Particularly high selectivities to hydrocarbon products are exhibited by McO, SrO, ^2°3' La2°3' Nd2°3' Sir,2°3' Eu-jO^, and Gd^O^. Although the SrO catalyst exhibits the highest selectivity, this advantage is offset by the low oxygen and methane conversion per pass. Of the 15 oxides listed, the rare earth oxides, including ¥20^, La^O^, Nc^O^, Sm^O,, Eu^O^, and Gd203, appear to offer the best overall performance characteristics, which are selectivities of approximately 60% to higher hydrocarbons, 100% 00 conversion per pass, and a lower 20 operating temperature (750-800°C) for achieving maximum hydrocarbon yield.

EXAMPLE 13 This example illustrates the preparation of a 25 mixture of oxide catalysts according to the present invention - A solution of lithium salt was prepared by dissolving LiNO^ in distilled water. Lanthanum oxide was then impregnated to incipient-wetness by the 3 0 solution of LiNO^. The mixture was dried in a vacuum oven at 110°C for 12 hours. The dried solid was then 2163B® calcined in air at 600°C for 4 hours. Enough lithium was deposited on the La^O^ to give a finished loading of 1.0 wt% Li^O.

EXAMPLES 14-28 These examples illustrate the preparation of additional mixtures of oxide catalysts according to the present invention.

Following the procedure of Example 13, catalysts 10 were produced with 1.0 wt% of various metal oxides on either La^O^ or MgO. The catalysts prepared are listed in Tables 2 and 3.

Example 29 This example describes the test procedure for the 15 evaluation of the mixed oxice catalysts anc sets forth the results.

Each of the catalysts of Examples 13-28 were separately pressed ir.to pellets of mesh size between 20 and 32, charged to the quartz reactor, and exposed to 2 0 the reaction conditions as described in Example 12 above. The experimental results for these catalyst samples are given in Tables 2 ar.c 3. 00 00 n v0 TABLE 2 ACTIVITY AND MAXIMUM SELECTIVITY OF OXIDE MIXTURES CONTAINING LajOj FOR THE CONVERSION OF METHANE Selectivity (%) Conversion (%) ample Catalyst T(°C) —2—4 CM 6 All C n H CO co2 - 22 £»4_ H J (C^H 6 La203 750 .7 . 9 59. 1 8. 1 32. 8 100 19.6 1.1 13 Li ^O/La^Oj 800 32.6 37. 6 75, ,9 1 . 6 22. 100 21.6 0.2 14 Na20/La203 800 31.4 33 . 2 69, ,2 2.4 28. 4 100 .0 0.4 K20/La203 800 . 1 . 3 64. ,0 7.7 28. 3 100 .6 0.8 16 Mg0/La203 750 28.0 32. 1 65, .4 8.5 26. 1 100 . 7 0.7 17 Ca0/La20j 750 28.6 31 . 1 64, ,3 9.4 26. 3 100 19.4 0.8 18 Sr0/La203 750 28.7 34. 9 69 .0 4.8 26. 2 100 .9 0.6 19 Da0/La20j 800 .5 33. 6 68 .2 3.2 28. 7 100 .3 0.5 PbO/La^Oj 750 24.9 33. 2 60 .6 3.5 .9 100 18.5 0.5 21 Bi203/La?03 750 27.0 34. 6 65.2 2.1 32.7 100 18.4 0.3 22 AgO/I.a 20 j 800 27 . 8 31 . 9 62, .8 .4 31. 8 100 .0 0.7 V CO 00 r> vO r' TABLE 3 ACTIVITY AND MAXIMUM SELECTIVITY OF OXIDE MIXTURES CONTAINING MgO FOR CONVERSION OF METHANE Selectivity <%) Conversion (%) Example Catalyst TCC) C^ C2»i6 All Cn CO C02_ 02 CH4_ 112/122-4^2-6 1 MgO 900 32. , 1 17.9 52, , 1 V 17.7 . ,2 100 18. 1 1.6 23 Li jO/HgO 850 38, ,0 29. 1 70, ,6 .4 23, ,9 100 21, ,1 0.7 24 Na^O/MgO 800 27, ,5 31.6 61 , .4 6.8 31. ,8 100 19. ,4 0.9 K^O/MgO 900 37, ,5 \o CO 59, ,3 11.7 29, ,0 100 19, ,3 1.1 26 Y203/Mg0 900 , .6 . 2 58, ,2 12.2 29, .6 100 16, ,5 1.3 27 La^Oj/MgO 850 28, .8 23. 1 53, .8 11.1 , , 1 100 18, ,0 1.3 28 BaO/MgO 850 27 .6 28.5 57 .8 8.3 33, .9 100 17, ,4 0.9 216388 Comparison of the data in Tables 2 and 3 indicates that the selectivity of the base metal oxide, in this case La^O^ or MgO, car. be increased by impregnating them with other metal oxides of Groups 1A, IIA, 111A, 5 1VB, VB, ar.c IB of the Periodic Table. The especially preferred catalysts appear to be La^O^ promoted with alkali metal oxides, La^O^ promoted with alkaline earth oxides, and MgO promoted with Li^O.

Examples 30-33 This example illustrates the use of different amounts of a promoter oxide or. a base metal oxide.

Following the procedure of Example 13 and using Sr(NO^)2 instead of LiNO^, catalysts were produced with 15 weight loadings of 0.25 to 10.0 vt% SrO on l^O^. The catalvsts oreoared are listed in Table 4.

Example 34 This example describes the test procedure for the 2 0 evaluation of the strontium oxice-promoted lanthanum oxide catalysts prepared in Examples 30-33, and sets forth the results.

Each of the catalysts of Examples 30-34 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 4.

TABLE 4 ACTIVITY AND SELECTIVITY OF MIXTURES OP SrO AND La^ FOR THE CONVERSION OF METHANE AT 750°C Example SrO (wti) c2!!4 Selectivity (t) All C. -n CO CO 2- Conversion It) o2 ch4_ H2/i£2»4i£2ii6i 6 0.00 . , 7 . ,9 . 59.1 " 8.1 32.8 100 19.6 1, ,1 0.25 28, , 9 . , 2 68.9 4.6 26.5 100 21.2 0, ,5 31 0.50 29. ,0 36. , 2 70.2 4.1 .6 100 21.4 0. ,5 18 1 .00 28, , 7 34, ,9 69.0 4.8 26.2 100 .9 0, ,6 32 2.00 28, ,9 , ,8 69.9 .1 .0 100 21.0 0, .5 33 .00 28, .0 , . 2 67.6 3.4 29.0 100 .6 0, .5 ( > 163 Comparison of the data in Table 4 indicates that the weight loading of the promoter oxide is not critical. An increase in selectivity to higher hydrocarbons of 10 percentage points is achieved by 5 depositing SrO onto 1^20^, irrespective of whether the weight loading cf strontium oxide is 0.25% or 10.0%.

Example 35-38 This example illustrates the use of rare earth 10 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 anc dissolved in an 15 acidic solution. Froir, 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 20 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 La203, CeO^r and other rare earth oxides (Re^O^ contained in each catalyst is given in 25 the Table.

Example 39 This example describes the test procedure for the evaluation of the rare earth oxide mixtures prepared in 30 Examples 35-38, and sets forth the results. 2 16388 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 5 above. The experimental results for these catalyst samples are given in Table 5.

TABLE 5 ACTIVITY AND SELECTIVITY OF RARE EARTH OXIDE MIXTURES FOR THE CONVERSION OF METHANE AT 750eC Oxide Composition (%) Selectivity (») Conversion (%) Example La203 Ce02 ££203 C2JI4 £2H6 AU_£n CO _£02- -2 -4- H^/ (C..H 1+C:;H(.) 6 100 0 0 .7 .9 59.1 8. , 1 32.8 100 19.6 1.1 67 1 32 17.8 .0 49.8 * 8. , 7 41.5 100 16.5 1.0 36 60 18.4 31.8 52.2 3, .8 44.0 100 .5 0.5 37 40 40 7.9 16.2 24.5 8, .7 66.8 100 11.6 2.2 38 0 100 0 0.3 1.6 2.0 9, .3 88.7 100 9.3 32.9 - 27 / " 63 A comparison of the data in Table 5 indicates that a decrease in the selectivity to higher hydrocarbons occurs as the CeC^ content of the rare earth oxide increases. Mixtures containing up to 10 wt% CeC>2 give 5 acceptable results. However, at higher concentrations of cerium the selectivity decreases to a low value, and pure CeO? converts essentially all of the methane to carbon oxides.

Example 40 This example compares two catalysts according to the present invention with a prior art catalyst consisting of lead oxice supported on silica.

A lead oxice on silica catalyst was prepared 15 according to the procedure given by w. Hinsen, K. 3ytyn, 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 20 a vacuum oven at 120°C for 12 hours. The dried solid was then calcined in air at 800CC for 4 hours. Enough lead was deposited on the SiC^ to give a finished loading of 11.2 wt% PbO.

The supported lead oxide catalyst was pressed into 25 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.

TABLE 6 ACTIVITY AND MAXIMUM SELECTIVITY OF PRIOR ART CATALYST FOR THE CONVERSION OF METHANE Example Catalyst T(°C) Select iv ity (%) Conversion (4) »2ZJC2»4: 0.2 c2«4 £2H6 All C_ CO C°2- o2 CH4 40 Pb0/Si02 900 27.0 31.1 60.0 11.8 28.2 50 8.5 6 L«2O3 750 .7 .9 59.1 1 8.1 32.8 100 19.6 1.1 18 SrO/La.O, 750 28.7 34.9 69.0 4.8 26.2 100 .9 0.6 (> o ;■) 1 63 Although the 11.2% PbO/SiC^ 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. For a reaction temperature of 900°C, only 50% of the oxygen is converted per Dass. For the La_0^ and Sr0/La_0_ 2 j 2 3 catalysts, on the other hand, 100% of the oxygen is converted per pass at temperatures as low as 600°C. Also, a comparison of the data shown in Table 6 10 indicates that the relative amount of hydrogen produced by Pb0/Si07 is nuch less than that produced by either or SrO/La^O^- Thus, the catalysts disclosed in the present invention are superior to the prior art catalyst for the synthesis of hydrocarbons from methane 15 in the presence of oxygen.

It is understood that the foregoing detailed description is given merely by way of illustration ar.c that many variations may be mace therein without departing from the spirit of this invention.

Claims (1)

1. 2 WIIAT WE CIALM IS: 1. A process for converting -ethane into hydrogen, ethylene, ethane, and higher hydrocarbon products by contacting a gas containing a mixture cf methane ar.c oxygen with a catalyst, comprising the improvement • of using as the catalyst one or mere netal cxices where the metal is selected from the group consisting of metals of (a) Group IIA metals cf the Periccic Table, excluding Mg, which are He, Ca, Sr, or 3a; and 2. A process according to Claim 1, wherein the catalyst is SrO. 21638S i 1 j 1 3. A process according tc Claim 1, wherein the gas containing methane ar.c oxygen is contacted with the 3 catalyst at temperatures between 5 00 and 1000°C. 1 4. A process according tc Claim 1, wherein the pressure of the cas in the contacting zone is between 1 3 and 50 atmospheres. 1 "5. A process acccrcir.g to Claim 1, wherein the mole ratio of methane to oxygen fed tc the reactor is 3 between 0.5 and 50. 1 6. A process according to Claim 1, wherein the gas containing methane ar.c oxygen is contacted with the 3 catalyst at temperatures between 550 and 850°C, the pressure cf the gas in the contacting zone is between 1 5 and 20 atmospheres, anc the mole ratio cf methane to oxygen fed to the reactor is between 2 and 20. 1 7. A process according to Claim 1, wherein the oxygen feed consists of 20 to 100 volume percent 3 oxygen. 1 8. a process according to Claim 7, wherein the oxygen feed is essentially pure oxygen. 1 9. A process according to Claim 1, wherein the methane feed consists of 6 0 to 100 volume percent 3 methane. 4 218388 iO. A process accordir.c to Claim 9, wherein the methane feec is essentially pure methane. 11. Ir. a process fcr converting methane into hydrogen, ethylene, ethane, and higher hydrocarbon products by contacting a gas containing a mixture of methane and oxygen with a catalyst, the improvement comprising using as the catalyst a first base metal oxide where the metal is selected from the group consisting of (a) Group IIA metals of the Periodic Table excluding Mg. which are 3e. Ca. Sr. or 3a: (b) Group IIIA metals of the Periodic Table, which are Sc. V or La: (c) the lanthanide series metals excluding Ce. Pr and Tb which are Nc. Sm. Eu. Gd. Dy. Ho. Er. Tm. Yb. or Lu: and (d) mixtures thereof: and a second promoter metal oxide where the metal is selected from the group consisting of (a) metals of Group IA. which are Li. Na. and K: (b) metals of Group IIA excluding Mg. which are 3e, Ca, Sr, and 5a: (c) metals of Group IIIA. which are Sc. Y, and La: (d) metals of the lanthanide series excluding Ce, Pr and Tb. which are Nd, Sm. Eu. Gd. Dy. Nc, Er. Tm, Yb. and Lu; (e) metals of Group IV3. which are Sr. and Pb. provided the first metal oxide is not an oxide of a metal from Group IIA: (f) metals of Group VS. which are Sb and 3i. provided the first metal oxide is not an oxide of a metal from Group IIA; (g) metals of Group 13. which are Cu. Ag, and Au. and (h) mixtures thereof. 12. A process according tc Claim 11, wherein said second promoter oxice is present in an amount from a catalytically effective amount to 50% fay weight cf the mixture. 13. A process according to Claim 11, wherein the base metal oxide is CaO, or SrO anc the promoter oxide is I^O. "e 1 3 5 3 1 3 5 7 1 3 1 3 1 3 1 3 216388 14. A process acccrcir.g tc Clair. 11, wherein the base metal oxice is V-,0, ar.c the promoter oxice is antimony oxice, bismuth oxice, copper oxice, silver oxide, or gold oxice. 15. A process according to Claim n, wherein the base metal oxide is La,0^ ar.c the promoter oxice is antimor.v oxide, bismuth oxide, copper oxide, silver oxide, or gold oxice. 16. A process according tc Claim n, wherein the base metal oxide is a mixture of rare earth oxides, as is formed in rare earth minerals, but with a portion cf the CeC„ removed, and the promoter cxice is Li.,0, 3e0, CaO, SrO, BaC, tin cxice, lead cxice, antimony oxide, bismuth oxice, copper oxide, silver oxice, or gold cxice. 17. A process according tc Claim wherein the gas containing methane and oxygen is contacted with the catalyst at temperatures between 500 and 1000°C. 18. A process according to Claim 11, wherein the pressure of the gas in the contacting zone is between 1 and 50 atmospheres. IS. A process according to Claim H, wherein the mole ratio of methane to oxygen fed to the reactor is between 0.5 and 50. 20. A process according to Claim 11, wherein the gas containing methane and oxygen is contacted with the catalyst at temperatures between 550 and 850°C, the pressure of the gas in the contacting zone is between 1 L2.2O, BeO, CaO, SrO, BaC, tin cxice, lead oxice Li20, 3e0, CaO, SrO, 3aO, tin oxice, lead oxide 34 21G388 I 5 ar.c 20 atmospheres, ar.c the mole ratio of methane tc cxycer. fed tc the reactcr is between 2 ar.c 20. 1 21. A process acccrcir.c to Claim wherein the cxycer. feed consists of 20 to 100 volume percent 2 oxygen. - 22. A process according tc Claim n, wherein the cxyger. feed is essentially pure oxygen. 1 23- A process according tc Claim 11, wherein the methane feec consists of 60 to 100 volume percent 3 methane. 1 24. A process according tc Claim H, wherein the methane feec is essentially pure methane. 25. A catalyst: for converting methane in the presence of oxygen into higher hydrocarbon products consisting essentially of (1) a base metal oxide where the metal is selected from the group consisting of metals of (a} Group IIA metals of the Periodic Table excluding Mg, which are Be. Ca, Sr. Ba and mixtures thereof: and (b) Sc. Y. rare earth metals of the Periodic Table excluding Ce. Pr and Tb. which are La. Nd, Sm. Eu. Gd. Dy, Ko, Er, Tm, Yb, and Lu and mixtures thereof: and (2) a promoter oxide present in an amount of up to 50 wt Z of the mixture where the metal is selected from the group consisting of (a) Group IA metals of the Periodic Table, which are Li, Na, and K provided that the base metal oxide is not just selected from (I)(a) alone; (b) Group IIA metals of the Periodic Table excluding Mg, which are Be. Ca, Sr. and Ba provided that base metal oxide is not just selected from (I)(a) alone: (c) Sc. Y, and rare earth metals of the Periodic Table excluding Ce. Pr and Tb, which are La, Nd. Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb. and Ly, provided that the base metal oxide is not just selected from (l)(b) alone; and (d) mixtures thereof. -3S>- 12 8 NOV 1989 a /6 3.S5 26. A catalyst according to claim25, wherein the promoter oxide is pr-?n»nt in an amount up to to wt : of the mixture. 27. a catalyst accoiding to ciaimZS, vher®in the base metal oxide is and the promoter oxide is Li^O. ?^0. CaO. SrO. or 3aO. 23. A catalyst according to claim 25, wherein the base m»tal oxide is La£03 and the promoter oxide is Li^C. 3e0. CaO. SrO. or BaO. 29. A catalyst for converting methane irs the presence of oxygen into higher hydrocarbon products consisting essentially of as the sole catalytic component a base metal oxide in the form cf a mixture of rare earth oxides, as is formed in rare earth minerals, but with a portion of CeC>2 removed, anc a promoter oxide of Li-O. 5e0. CaO, SrO. or BaO. 3c. A catalyst according to claim25, wherein the promoter oxide is deposited onto the base metal oxide. 31. A process as claimed in any one of claims 1-24 when performed substantial7v as hereinbefore cescribec with reference tc any example thereof anc/or any of the accompanying drawings. 32. Hydrogen, ethylene, ethane, anc higher hydrocarbon products prepared frcm methane by a process as claimed in any one of claims 1-24 and 31. 33. A catalyst as claimed in any one of claims 25-30 substantially as hereinbefore described with reference to any example thereof. w fku*i\ker itS"? t ^ A. 1. PARK * SON ^ fBL AGEMT3 Ft* THf APTUCANT*