A PROCESS FOR PRODUCING A MIXTURE OF HYDROCARBONS RICH IN BENZENE, TOLUENE, AND XYLENE

Abstract: In a process for producing a mixture of hydrocarbons rich in benzene, toluene and xylene, a fossil fuel is converted to a synthesis gas which in turn is catalytically reduced to oxygenated hydrocarbons. The oxygenated hydrocarbons are then contacted with a ZSM-5 type zeolite to produce a hydrocarbon stream, which is thereafter contacted with a catalyst comprising a metal promoted porous crystalline zeolite having a constraint index within the range 1 to 12 and a silica to alumina ratio of at least 12 under conditions to produce an effluent stream rich in benzene, toluene and xylene, and other aromatic compounds. The benzene, toluene and xylene and said other aromatic compounds are subsequently removed from said effluent stream.

Description: PROCESS FOR PRODUCING A MIXTURE OF HIDROCARBONS RICH IN BENZENE, TOLUENE, AND XYLENE This invention relates to a process for producing a mixture of hydrocarbons rich in benzene, toluene, and xylene. Benzene, toluene, and xylenes (BTX) are basic building blocks of tne petrochemical industry. Tne source of these compounds primarily is the refining of petroleum. As petroleum supplies dwindle so does the supply of benzene, toluene and xylene. Alternative sources must be developed for these compounds. we have discovered a process for making benzene, toluene and xylene which utilizes materials which can be indirectly derived from a readily available source, synthesis gas. The conversion of synthesis gas directly to dimethyl ether nas been described in British Patent 278,353 (1926) to F.R. BechowsKy and U.S. Patent 4,098,809 to G. Pagani (1978). The conversion of synthesis gas to oxygenated organic compounds containing mixtures of alcohols, ethers and other compounds is disclosed in a number of patent. U.S. Patent 4,237,063 to Bell et al discloses the conversion of synthesis gas to oxyqenated hydrocarbons using metal cyanide complexes. U.S. Patent 4,:11,275 discloses tne conversion of synthesis gas to methanol and dimethyl ether oy passing the mixture over a zinc-cnromium acia or copper-zinc-alumlna acia catalyst. U.S. Patent 4,076,761 discloses 8 process for making hyarocarbons from synthesis qas wnerein an intermediate product formed is a mixture of methanol and dimethyl ether. Processes for tne conversion of coal and other nydrocaroons to a gaseous mixture consisting essentially o, hydrogen ano carbon monoxide, or of nydroqen and carbon dioxide, or of nydrogen and caroon monoxide ano carbon dioxide, are well known. Sucn a gaseous mixture nereinafter Will be referred to simoly as synthesis gas. Although various processes may be employed for tne gasification, those of major interest for depend either on the partial comoustion of the fuel with oxygen, or on the high temperature reaction of tne fuel with steam, or on a combination of these two reactions. In one known variant, for example, coal may be completely gasified by first coking, and then subjecting the coke to a cyclic blue water gas process in which the coke oed is alternately blasted with air to increase the Ded temperature and then reacted with steam to produce the synthesis gas. The gases generated by the coking step may be used as fuel or steam-reformed to additional synthesis gas. In another process coal or coke may be reacted with highly superheated steam or with oxygen and steam to produce synthesis gas. Regardless of the process variants chosen, oxyqen rather than air is often used in the chemical step in which the fuel is converted to synthesis gas since the use of air would result in a qas that contains excessive amounts of inert nitrogen. A summary of the art of gas manufacture, including synthesis gas, from solid and liquid fuels, is given in Encyclopedia of Chemical Technology, Edited by Kirk-Othmer, Second Edition, Volume 10, pages 353-433, (1966), Interscience Publsihers, New York, N.Y. It is known that raw synthesis gas contains one or more of tne following impurities; sulfur compounds, nitrogen compounds, particulate matter and condensibles. Methods of removing these contaminants are well known, and are described in the above reference and elsewhere Particular attention is called to tne sulfur compounds. It is desiraDle to reduce this contaminant below a crescribed level for ecological purposes. Purified synthesis qas ordinarily contains a volume ratio of nydrogen to carbon monoxide plus carbon dioxioe of from as little as 0.O to as much as 1.1, depending on the particular fuel and process used; ia most instances, the camposition has a volune ratio from 0.30 to O.b5. -Lt is well Known tnat this ratio may oe increased by tne catalytic carbon- monoxide shift reaction described by the equation: EMI2.1 with subsequent removal o f at least part of the produced CO2 to bring said volume ratio into a desired high range. The catalytic carbon monoxide shift reaction is commonly conducted with a chromia promoted iron oxide catalyst at a flow rate of 300-1000 standard cubic feet of gas per cubic foot of catalyst bed per hour, and at sufficiently elevated temperature to allow quasi-equilibration, which is usually 3710C (7000F). Synthesis gas will undergo conversion to form reduction products of carbon monoxide, such as alcohols, at from 1490C (3000F) to 4540C (8500F), under from 1 to 1000 atmospheres (1 x 102 to 1 x low kPa) pressure, over a fairly wide variety of catalysts. Tne types of catalyst that induce conversion include ZnO, Fe, Co, Ni, Ru, ThO2, Rh and Os. Catalysts based on ZnO are particuarly suited for the production of methanol and dimethyl ether. Catalysts based on Fe, Co, and Ni, and especially Fe, are particuarly suited for the production of oxygenated and hydrocarbon products that have at least one carbon-to-carbon bond in their structure. with tne exception of ruthenium, all practical synthesis catalysts contain chemical and structural promoters. These promoters include copper, chromia, alumina and alKali. Alkali is of particular importance with iron catalysts, since it greatly enhances the conversion efficiency of the iron catalyst. Supports such as kieselguhr sometimes act beneficially. The catalyzed reduction of carbon monoxide or carbon dioxide Dy hydrogen produces various oxygenated and hydrocarbon products, depending on the particuar catalyst and reaction conditions cnosen. Tne products that are formed include methanol, dimethyl ether, acetone, acetic aciD, normal propyl alcohol, higner alcohols, methane, gaseous, liquid, and solid olefins and paraffins. It should De noted that this spectrum of products consists of aliphatic compounds; aromatic hydrocarbons either are totally absent or are formed in minor quantities. In general, when operating at tne ioweL end of tne temperature range, ie. from 3000 to 5000F (1490 to 2600C), in the reduction of carton monoxide, and with pressures greater than 20 atmosDheres (2 x low kPa), thermodynamic considerations suggest that aliphatic hydrocarbons are likely to form in preference to their aromatic counterparts. Furthermore, in some catalytic systems it has been noted that aromatic hydrocarbon impurities in the synthesis gas inactivate the synthesis catalyst, and one may speculate that a number of known synthesis catalysts intrinsically are not capaDle of producing aromatic hydrocarbons. The wide range of catalysts and catalyst modifications disclosed in the art and an equally wide range of conversion conditions for the reduction of carbon monoxide by hydrogen provide considerable flexibility toward obtaining selected products. A review of tne status of this art is given in "Carbon Monoxide-Hydrogen Reactions,n Encyclopedia of Chemical Technology, Edited By Kirk-Othmer, 2nd Edition, Volume 4, pp. 446-488, Interscience Publishers, New York, N.Y. Oxygenated compounds and hydrocarbons are produced in varying proportions in the conversion of synthesis gas. This is understandable if, as proposed by some researcners in the field, the hydrocarbons arise via oxygenated intermediates such as alcohols. By selection of less active catalysts such as zinc oxide, it is possible to obtain oxygenated compounds as the major product. One particular commercial conversion is used to produce methanol from synthesis gas with suostantially no coproduction of hydrocarbons. Suitable catalysts are those comprising zinc oxide, in admixture with promoters. Copper or copper oxide may be included in the catalyst composition. Particuarly suitaole are oxide catalysts of the zinc-copper-alumina type. Compositions of tne type described are those currently used in commercial methanol synthesis. Contact of the synthesis gas with the methanol synthesis catalyst is conducted under pressure of 25 to 600 atmospheres (2.53 x 103 to 6.06 x 104), preferably 50 to 400 atmospheres (5.05 x 103 to 4.04 x kPa), and at a temperature of 4000 to 7500F (2040 to 3?90C). Tne preferred gas space velocity is within the range of 1,000 to 50,000 volume hourly space velocity measured at standard temperature and pressu.-e. it is noted tnat tne conversion per pass is trom about l of the carbon monoxide fed to about 30s, i.e. in this process the unconverted syntnesis gas must be separated from the method product and recycled. Crystalline zeolites have been contacted with methanol under catalytic conversion conditions. U. S. Pat. No. 3,036,134 ShOWS a 98.44 conversion of methanol to dimethyl ether over sodium X zeolite at 2600C; 1.6 mole % of the product is a mixture of olefins up to pentene, with Dutene tne predominant product. Conversion of methanol over rare earth exchanged and zinc exchanged X zeolite has been reported to produce some hexanes and lighter hydrocarbons (see Advances in Catalysis, Vol. 18, p. 309, Academic Press, New York, 1968). It has recently been discovered that alconols, ethers, carbonyl and their analogous compounds may be converted to higher hydrocarbons, particuarly high octane gasoline, by catalytic contact with a special type zeolite catalyst. This conversion is described in U.S. Patents 3,894,106; 3,894,107; 3,907,915. An object of this invention therefor is to increase the yiela of products rich in benzene, toluene, and xylenes (i.e. greater than 50 percent aromatics) when oxygenated hydrocarbons such as methanol and dimethyl ether and product streams containing these and other oxygenated hydrocaroon comoounds are converted to benzene, toluene and xylene. Accordingly, the invention resides in a process for producing a mixture of hydrocarbons rich in benzene, toluene and xylene which comprises: (a) converting a fossil fuel to a synthesis gas; (D) converting said synthesis gas to oxygenated hydrocarbons; (c) contacting said oxygenated hydrocarbons with a ZSm-5 type zeolite to produce a hydrocarbon stream; (d) contacting at least the hydrocarbon stream from (c) witn a catalyst conprising a metal pronotea porous crystalline zeolite havering a constraint index within the range of 1 to 12 and a silica to alumina ratio of at least 12 under conditions to produce an effluent stream rich in benzene, toluene and xylene, and other aromatic compolJnds; ; (e) removing oenzene, toluene and xylene fiom said effluent stream. Preferably, tne synthesis oas has a voljn.etric ratio of nylon to caroon monoxide plus caroon dioxide of from 1.0 to 6.0. Preferably the zeolite used in step (d) is of the ZSM-5 type and is impregnated with one or more metals selected from the yroup consisting of Group VIIIA transition metals, and metals from Group IIss and IIIB. Group VIIIA metals include iron, cobalt, nicKel, ruthenium, rhodium, palladium, osmium, iridium and platinum. The Group IIb metals include zinc, cadmium, and mercury. The Group IIId metals include aluminum, gallium, indium and thallium. Preferred metals are platinum, gallium and zinc, and mixtures of two or more thereof, with gallium being particularly preferred. The platinum, zinc or gallium in the catalyst composition preferably used in step (d) can be present as the metal oxide and/or as metal ions if cations in the ZSM-5 type zeolite have been exchanged with the metal ions therein. In the case where the cations in the zeolite have been exchanged for metal ions, the metal ion is suitably provided as an aqueous solution of metal salts, such as, for instance, the soluole nitrate, chloride or sulfate salts of platinum, zinc or gallium. Such catalysts may be produced by conventional ion exchange techniques and the catalysts so produced Subsequently dried. For example, an aqueous solution of the metal compouna such as tetramine platinum chloride, zinc chloride, or gallium nitrate may be placed in contact with zeolite at ambient or elevated temperature, e.g. by refluxing. The exchangea zeolite is then seoarated by decantation followed by filtration, washed several times witn deionized water and finally dried. before addition to tne aqueous solution of the metal compound, the zeolite may oe acid treated. Alternatively the platinum, zinc, o gallium may only be impregnated on tne surface of the zeolite or incorporatea in the intra-crystalline zeolite cavities as a metal compound which gives rise to a metal oxide during activation of the catalyst prior to contact with tne hy:;)caroon ae-stock. It is, however, to be aPsreciated that where the catalyst comoosition is prepared by using a metal compound which ionizes in aqueous solJíon, for exam31e, gallium nitrate, it is inevitable rhdv some of the metal ions will be exchanged with the cations in tne zeolite even if the preparation was directed to impregnation of the zeolite. Whichever method of catalyst preparation is used, tne amount of metal present in the catalyst compositions (metal plus zeolite) may suitably vary between 0.01 and 5 percent, preferably between 0.05 and 2 percent by weight. Obviously, a mixture of two or more metals can be incorporated into the zeolite by the methods discussed above. If zinc is present in the catalyst, it is preferred also to include palladium and gallium. The ZSM-5 type crystalline zeolites utilized herein are members of a class of zeolitic materials which exhibit unusual properties. Although these zeolites have unusually low alumina contents, i.e. high silica to alumina mole ratios, they are very active even when tne silica to alumina mole ratio exceeds 30. The activity is surprising since catalytic activity is generally attriouted to framework aluminum atoms and/or cations associated with these aluminum atoms. These zeolites retain their crystallinity for long periods in spite of the presence of steam at high temperature which induces irreversible collapse of tne framework of other zeolites, e.g. of tne X and A type. Furthermore, carbonaceous deposits, when formed, may be removed by burning at higher than usual temperatures to restore activity. These zeolites, used as catalysts, generally have low coke-forming activity and therefore are conducive to long times on stream between regenerations by burning carbonaceous deposits with oxygen-containing gas such as air. An important characteristic of the crystal structure of this class of zeolites is that it provides a selective constrained access to and egress from tne intracrystalline free space oy virtue of haviny an effective pore size intermediate between the small pore Linde A and the large pore Linde X, i.e. the pore windows of the structure are of about a size such as would be provided by 10-memberea rings of silicon atoms interconnecteo Dy oxygen atoms. It is to be understood of course, than these rings are those formed oy the regular disposition of tne tetraneora making up the anionic framework of tne crystalline zeolite, the oxyn atoms tnenselves oeinq bonded to tne silicon (or aluminum, etc.) atoms at the centers of the tetranedra. The silica to alumina mole ratio referred to may be determined by conventional analysis. This ratio is meant to represent, as closely as possible, the ratio in the rigid anionic framework of the zeolite crystal and to exclude aluminum in the binder or in cationic or other form within the channels. Although zeolites with silica to alumina mole ratios of at least 12 are useful, it is preferred in some instances to use zeolites having substantially higher silica/alumina ratios, e.g. 1600 and above. In addition, zeolites as otherwise characterized herein but which are substantially free of aluminum, that is zeolites having silica to alumina mole ratios of up to infinity, are found to be useful and even preferable in some instances. Sucn "high silica" or "highly siliceous" zeolites are intended to be included within this description. Also included within this definition are substantially pure silica analogs of the useful zeolites described herein, that is to say those zeolites having no measurable amount of aluminum (silica to alumina mole ratio of infinity) but which otherwise embody the characteristics disclosed. This class of zeolites, after activation, acquire an intracrystalline sorption capacity for normal hexane which is greater than that for water, i.e. they exhibit "hydrophobic" properties. This hydrophobic character can be used to advantage in some applications. The class of zeolites useful herein have an effective pore size such as to freely sorb normal hexane. In addition, the structure must provide constrained access to larger molecules. It is sometimes possible to judge from a known crystal structure whether such constrained access exists. For example, if the only pore windows in a crystal are formea Dy 3-memoe ed rings of silicon and aluminum atoms, then access by molecules of larger cross-section tnan normal hexane is excludea and the zeolite is not of the desired tyDe. Windows of 10-membered rings are preferred, although in some instances excessive puckering of the rinks or po-e bincKage Tiay render these zeolites ineffective. Althougn 12-membered rings in theory wola not offer sufficient constraint to produce advantageous conversions, it is noted that the puckered 12-ring structure of TMA offretite ooes show some constrained access. Other 12-ring structures may exist which may be operative for other reasons and, therefore, it is not the present intention to entirely judge the usefulness of a particular zeolite solely from theoretical structural considerations. Rather than attempt to judge from crystal structure whether or not a zeolite possesses the necessary constrained access to molecules of larger cross-section than normal paraffins, a simple determination of the "Constraint Index" may be used. The meaning of Constraint Index and its method of determination are fully described in, for example, U.S. Patent No. 3,905,915. The oreferred zeolites used herein are ZSM-5, LSM-ll, ZSM-12, ZSM-23, ZSM-35, ZSM-38, ZSM-48, and other similar materials, ZSM-5 being especially preferred. ZSM-5 is described in U.S. Patent Nos. 3,702,886 ana Re 29,948. ZSM-ll is described in U.S. Patent No. 3,709,979. ZSM-12 is described in U.S. Patent No. 3,832,449. ZSM-23 is described in U.S. Patent No. 4,075,842. ZSM-35 is described in U.S. Patent No. 4,016,245. ZS -38 is descrined in U.S. Patent No. 4,046,859. ZSM-48 is described in publisned European Patent Application No. 15,132. These specific zeolites described, when prepared in the presence of organic cations, are substantially catalytically inactive, possibly because the intra-crystalline free space is occupied by organic cations from the forming solution. They may be activated by heating in an inert atmosohere at 5400C for one hour, for example, followed by oase exchange with ammonium salts followed by calcination at 5400C in air. The presence of organic cations in the forming solution may not be absolutely essential to the formation of this type zeolite; however, the presence of these cations does appear to favor the formation of this class of zeolite. More generally, it is aesiraole to activate this type catalyst by base exchange with ammonium salts followed by calcination in air at about 540 C for from aoout 15 minutes to about 24 hours. 'a ural zeolites may sornatiTes be converted to zeolite structures of tne class herein identified oy various activation procedures and other treatments such as base exchange, steaming, alumina extraction and calcination, alone or in combinations. Natural minerals which may be so treated include ferrierite, brewsterite, stiloite, dacniardite, epistibite, heulandite, and clinoptilolite. Preferably, the zeolites have a crystal framework density, in the dry hydrogen form, of not less than about 1.6 grams per cubic centimeter. The dry density for known structures may be calculated from the number of silicon plus aluminum atoms per 1000 cubic Angstroms, as described on page 19 of the article ZEOLITE STRUCTURE by W. M. Meier, included in PROCEEDINGS OF THE CONFERENCE ON MOLECULAR SIEVES, (London, April 1967) published by the Society of Chemical Industry, London, 1968. When the crystal structure is unknown, the crystal framework density may be determined by classical pyknometer techniques. For example, it may be determined by immersing the dry hydrogen form qf the zeolite in an organic solvent which is not sorted by the crystal. Or, the crystal density may be determined by mercury porosimetry, since mercury will fill the interstices between crystals but will not penetrate the intracrystalline free space. When syntnesized in tne alkali metal form, tne zeolite is conveniently converted to the hydrogen form, generally by intermediate formation of tne ammonium form as a result of ammonium ion exchange and calcination of the ammonium form to yield the hydrogen form. In addition to the hydrogen form, other forms of the zeolite wherein the original alkali metal has been reduced to less than about 1.5 percent Dy weight may be used. Thus, the original alkali metal of the zeolite may be replaced by ion exchange witn other suitable metal cations of Groups I throuqh VIII of tne Periodic Table, including, by way of example, nickel, cooper, zinc, palladium, calcium or rare earth metals. In practicing a particularly desired chemical conversion process, it my De useful to incorporate the above-oescrioed crystall:ne zeolite jith a matrix comprising another material resistant to the temperature and other conditions employed in tne process. Sucn matrix material is useful as a bin and -ma2.ts p-eater resistance to tne catalyst for the severe temperature, pressure and reactant feed stream velocity conditions encountereo in many cracking processes. Useful matrix materials include both synthetic and naturally occurring substances, as well as inorganic materials such as clay, silica and/or metal oxides. The latter may De either naturally occurring or in the form of gelatinous precipitates or gels including mixtures of silica and metal oxides. Naturally occurring clays which can be composited with the zeolite include those of the montmorillonite and kaolin families, which families include the sub-bentonites and the kaolins commonly known as Dixie, McNamee-Georgia and Florida clays or others in which the main mineral constituent is halloysite, kaolinite, dickite, nacrite or anauxite. Such clays can be used in the raw state as originally mined or initially subjected to calcination, acid treatment or chemical modification. In addition to the foregoing materials, the zeolites employed herein may be composited with a porous matrix material, such as alumina, silica-alumina, silica-magnesia, silica-zirconia, silica-thoria, silica-Deryllia, ana silica-titania, as well as ternary compositions, such as silica-alumina-thoria, silica-alumina-zirconia, silicaalumina-magnesia and silica-magnesia-zirconia. The matrix may be in the form of a cogel. Tne relative proportions of zeolite component and inorganic oxide gel matrix, on an anhydrous basis, may vary widely with the zeolite content ranging from between 1 to 99 percent by weight and more usually in the range of 5 to 80 percent by weight of the dry composite. In the process of the invention, the oxygenated hydrocarbon stream obtained by conversion of synthesis gas is contacted witn ZSM-5 and then tne resultant hydrocaroon stream is contacted with a catalyst comprising a zeolite as descriDed above, preferably ZSM-5, and a Group VIII metal, preferably platinum, a Group Ilti metal, preferably zinc, and/or a Croup 1113 metal, preferaoly gallium. The acconpanying drawing is a flow diagram of a process according to one example of the invention. fe-ring to tne o-avino, coal, shale oil, or resieua, o a comDination thereof, is conveyea via line 1, 2 or 3, respectively ana thence via line 4 to a synthesis gas plant, 5, where it is converted to synthesis gas. If hydrogen sulfide is produced in this plant, it may be separated and sent via line 6 to a treatment plant (not shown) for sulfur recovery. Synthesis gas, previously treated in a catalytic carbon monoxide shift converter and then reduced in carbon dioxide content by selective sorption, is then conveyed via line 7 to a first reaction zone 8, where it is at least partially catalytically converted to produce a carbon monoxide reduction product that contains at least 20% by weight of oxygenated products, preferably methanol and/or dimethyl ether. Part or all of tne unconverted synthesis gas may be separated from such reduction product and recycled via line 10. That portion of reaction product not recycled through line 10 is conveyed to the second reaction zone 11 where catalytic conversion to hydrocarbons and steam occurs. The reaction products from the second reaction zone 11 can then be diverted through line 27, open valve 31 and conduit 29 to the reactor 33 where it is contacted with the ZiM-5 type metal impregnated porous crystalline zeolite. The conversion in the second reaction zone 11 is conducted at a temperature of 250 to 6500C, preferably 300 to 6500C, a pressure of subatmospheric to 50 atmospheres, and at a liquid hourly space velocity of 0.1 to 50 LHSV. In an alternative the reaction products in line 12 are conveyed to a cooler, 13, and the cooled products are then conveyed via line 14 to a separator 15; note that tne cooler 13, line 14 and separator 15 may be one integral unit. Water is removed from the separator 15 via line 16, gas is removed via line 17, and liquid hydrocarbon product via line 18. The liquid hydrocarbon product is conveyed via line ia to reactor 33 where it is contacted with the metal impregnated crystalline zeolite preferaoly ZSM-5. Effluent from tne reactor 33 is conveyed through to a cooler ana separator (not snown) ana the liquid portion thereof is fractionateo in e distillation tower 19 into fractions consisting of oenzene, toluene and xylene. Any fraction conraInlng nydrocarDons in excess of 9 cartoon atoms can be recycled via line 35 through reactor 33 for conversion to benzene, toluene and xylene. Additional details of the operating conditions in carbon oxide converter 8 and converter 11 are set forth in U.S. Patent 4,076,761. As indicated previously the reactor 33 contains ZSM-5 type zeolite, preferably in the form of a fixed bed. Preferably the ZSM-5 zeolite is in the hydrogen or acid form and has deDosited thereon tne equivalent in metal of between .01 and 1 percent of gallium of the total composition. In a typical, and preferred embodiment, the feedstream of oxygenated hydrocarbons is introduced into the reaction zone 33 at a temperature within the range of 3500C to 6500C, a pressure within the range of 1. x 105 to 30 x 105 pascal (0 to 400 psig), and a wHSV of 0.1 to 10. Preferred temperatures in the reaction zone 33 fall within the range of 400 C to 600 C and preferred pressures fall within the range of 1. x 105 to 15 x 105 pascal (0 to 200 psig). A preferred WHSV is between 0.2 and 3. EXAMPLE 1 Samples of acid or hydrogen-form ZSM-5 zeolite catalyst prepared in the form of extrudate were impregnated respectively with gallium, zinc, oalladium, and platinum in the concentrations shown in Table 1. hydrocarbon feedstock obtained from tne treatment of methanol through a aehydration reactor and tnen furtner passed over a ZSM-5 catalyst zone corresponding to reaction zone 11 was then flowed over each catalyst under the conditions shown in Table 1. Tne results obtained show a substantial increase in tne production of aromatics, namely benzenes, toluene and xylene. In Tables II-V are shown tne results obtained with the same feedstock and catalysts at different conditions of temperature and pressure. In Tables I-V the composition of the feedstock is shown in the column headed "Feed." TABLE I Example No. Feed 1 2 3 4 5 CATALYSTS HZSM-5 Ga/HZSM-5 Zn/Pd HZSM-5* Pt/HZSM-5 Ga/HZSM-5 Metal Concentra tion, wt. % 0 0.5 2/1 0.1 0.5 Temp., C ( F) ---------------- 537.8 (1000) -------------------- Pressure kPa, (psig) ---------------- 101.4 (0) -------------------- WHSV -------------------- 1 ----------------------- 0.5 Conc. Benzene, Toluene and Xylene in Product, Wt % 14.3 49.5 60.3 63.8 51.7 77.5 Conc. of C9 + in Product, Wt % 26.4 15.8 7.5 8.8 11.0 10.3 C9 + Converted, Wt % 40.1 71.6 66.7 58.3 61.0 * 40/1 mole ratio of SiO2 to Al2O3 HZSM-5, all others 70/1 SiO2/Al2O3 TABLE II Run No. Feed 1-1 1-2 1-3 Catalyst -------HZSM-5*----------- Temperature, ( F) C (1000) 537.8 (1050) 565.6 (1100) 593.3 Pressure: 101.4 kPa, (0 psig) WHSV: 1 Conc. of BTX in Prod. wt. % 14.3 49.5 55.6 58.7 Prod. Distribution, wt % C1-C3 1.3 32.8 30.5 21.8 C2-C9 (non-aromatics) 58.0 1.7 0.5 0.2 HB 0.2 11.0 16.5 18.1 Toluene 2.7 23.0 25.7 26.9 Xylenes 11.4 15.5 13.4 13.7 C9 + Aromatics 19.6 9.6 9.0 7.8 Durenes 6.8 6.2 4.4 11.5 Total 100.0 100.0 100.0 100.0 * 70/1 SiO2/Al203 HZSM-5, no added metal. TABLE II1 Run No. 2-1 2-2 2-3 2-4 2-5 Catalyst Feed --------- Ga/HZSM-5* Temperature, C 537.8 532.8 565.6 510 510 Temperature F 1000 1000 1050 950 950 Pressure: 101.4 kPa, (0 psig) WHSV 1 0.5 1 1 0.5 Conc. of BTX in Prod. Wt % 14.3 60.3 77.5 59.6 51.2 72.7 Product Distribution C1-C3 1.3 31.0 11.7 23.7 32.8 16.2 C4-C9 58.0 0.4 0.1 0.3 2.8 0.8 BZ 0.2 15.7 15.6 17.6 11.4 12.6 Toluene 2.7 28.9 39.6 27.5 24.6 36.2 Xylenes 11.4 15.7 21.7 14.5 15.2 23.9 C9 + Aromatics 19.6 5.8 5.4 11.2 7.8 7.2 Durenes 6.8 1.7 4.9 5.1 5.1 3.0 Total 100.0 99.2 99.6 100.0 100.0 100.0 *70/1 SiO2/A1203 HZSM-5, containing 0.5 weight percent of gallium TABLE IV Run No. Feed 3-1 3-2 3-3 3-4 Catalyst Zn/Pd/HZ5M5* Zn/Pd/HZSM-5** Temperature, C 371.1 426.7 426.7 537.8 Temperature, F 700 800 800 1000 Pressure, 101.4 kPa, (0 psig) wHSV 1 1 3 1 Conc. of dTX in Prod. wt. % 14.3 37.6 35.9 39.8 63.8 Prod. Distribution wt. % Cl-C3 1.3 13.3 26.1 18.7 27.2 C4-C9 BZ 0.2 2.7 3.6 3.0 18.8 Toluene 2.7 14.5 12.9 15.5 30.5 Xylenes 11.4 20.6 19.4 21.3 14.5 C9 + Aromatics 19.6 14.6 15.1 12.4 5.9 Durenes 6.8 8.2 8.7 10.2 2.9 Total 100.0 100.0 100.0 100.1 99.9 *70/1 Si02/A1203 HZSM-5 containing 2 Percent by weight of zinc and 1% by weight of palladium. **40/1 SiO2/Al2O3 HZSM-5 containing 2 percent by weight of zinc and 1% by weight of palladium. TABLE V Run No. Feed 4-1 4-2 4-3 4-4 4-4 Catalyst ----------- Pt/HZSM-5* Temperature, C 371.1 426.7 482.2 537.8 565.6 Temperature, of 700 800 900 1000 1050 Pressure, 101.4 kPa (0 psig) WHSV: 1 Conc. of BTX in Prod. wt. % 14.3 36.9 29.6 39.4 51.7 56.2 Prod. Distribution wt. % C1-C3 1.3 18.3 41.5 36.0 36.7 33.0 C4-C9 58.0 30.2 22.6 7.4 0.5 0.2 BZ 0.2 2.6 5.0 6.3 13.1 17.9 Toluene 2.7 13.3 13.7 17.1 24.4 26.7 Xylenes 11.4 21.0 10.9 16.0 14.2 11.6 C9 + Aromatics 19.6 11.1 5.3 9.9 7.0 8.0 Durenes 6.8 4.0 1.0 7.4 4.0 2.5 Total 100.0 100.0 100.0 100.0 100.0 100.0 *70/1 SiO2/A1203 HZSM-5, containing 0.1 percent by weight of platinum.

Claims: CLAIMS: 1. A process for producing a mixture of hydrocarbons rich in benzene, toluene and xylene which comprises: (a) converting a fossil fuel to a synthesis gas; converting said synthesis gas to oxygenated hydrocarbons; (c) contacting said oxygenated hydrocarbons with a ZSM-5 type zeolite to produce a hydrocarbon stream; (d) contacting at least the hydrocarbon stream from (c) with a catalyst comprising a metal promoted porous crystalline zeolite having a constraint index within the range 1 to 12 and a silica to alumina ratio of at least 12 under conditions to produce an effluent stream rich in benzene, toluene and xylene, and other aromatic compounds; (e) removing benzene, toluene and xylene from said effluent stream. 2. Tne process of Claim 1 wherein the metal of said catalyst composition of (d) comprises zinc, cadmium, mercury, aluminum, gallium, tlium, iron, cobalt, nickel, ruthenium, rhodium, Palladium, esmium, indium, platinum or a mixture of two or more of these. 3. The process of Claim 1 or Claim 2 wherein said 2SM-5 type zeolite of (c) is a catalytically active porous crystalline zeolite having a silica to alumina ratio of at least 12, a constraint index of 1 to 12 and a crystal density, in the hydrogen form, of not substantially below 1.6 qrams per cubic centimeter, and said contacting is conducted at a temperature of 2500 to 6500C, a space velocity of 0.1 to 50 liquid hourly space velocity, and a pressure of 1 to 50 atmospheres. 4. The process of any preceding Claim wherein the hyorocarbon stream from (c) is cooled and the non-aqueous liquid fraction thereof is contacted with said catalyst of step (d). 5. The process of any preceding Claim wherein the conditions of (d) include a temperature of from 300 to 650 C, a pressure of from 1 x 105 to 30. x 105 pascal and a WHSV of from 0.1 to about 10. 6. The process of any preceding Claim wherein said zeolite of (d) is selected from the group consisting of ZSM-5, ZSM-ll, ZSM-12, ZSM-23, ZSM-35, ZSM-38, and ZSM-48. 7. Tne process of Claim 6 wherein said zeolite of (d) is ZSM-5. 8. Tne process of any preceding Claim wherein the catalyst of (d) contains between 0.01 and 5 percent of metal by weight of the overall catalyst. 9. The process of any preceding Claim wherein the metal in the catalyst of (dais gallium. 10. The process of any one of Claims 1 to 8 wherein the metal of the catalyst of (d) is zinc toyether with palladium and/or gallium.

Inventors: CHESTER, ARTHUR WARREN, CHU, YUNG-FENG
Applicants: MOBIL OIL CORPORATION
Application year: 1982
Main classification: C07C15
IPC codes: C07C2, C07B61, C07C15, C07C67, B01J29, C07C1