Title of Invention	A PROCESS FOR CONVERTING A FEEDSTOCK COMPRISING C9+AROMATIC HYDROCARBONS TO PRODUCE XYLENE
Abstract	A heavy aromatic feed is converted to lighter aromatics products, such as benzene, toluene and xylenes by contacting a C9+ aromatics fraction and benzene and/or toluene over a catalyst comprising a zeolite, such as ZSM-12, and hydrogenation component, preferably platinum. The catalyst, complete with hydrogenation component, is treated to reduce aromatics loss. Treatment includes exposure to steam and/or sulfur after incorporation of the hydrogenation component. For additional stability and aromatics retention the steamed and/or sulfur treated catalyst is sulfided by cofeeding a source of sulfur. A low hydrogen partial pressure is preferably employed to assist in aromatics retention. PRICE: THIRTY RUPEES

Title of Invention

A PROCESS FOR CONVERTING A FEEDSTOCK COMPRISING C9+AROMATIC HYDROCARBONS TO PRODUCE XYLENE

Abstract

A heavy aromatic feed is converted to lighter aromatics products, such as benzene, toluene and xylenes by contacting a C9+ aromatics fraction and benzene and/or toluene over a catalyst comprising a zeolite, such as ZSM-12, and hydrogenation component, preferably platinum. The catalyst, complete with hydrogenation component, is treated to reduce aromatics loss. Treatment includes exposure to steam and/or sulfur after incorporation of the hydrogenation component. For additional stability and aromatics retention the steamed and/or sulfur treated catalyst is sulfided by cofeeding a source of sulfur. A low hydrogen partial pressure is preferably employed to assist in aromatics retention. PRICE: THIRTY RUPEES

Full Text	Field of the Invention The invention relates to the. production of xylenes from a feedstock comprising benzene and/or toluene and heavy aromatics, specifically, C9+ aromatics. More specifically, the invention relates to the production of 5 xylenes over a catalyst comprising a zeolite and a hydrogenation component. Background of the Invention Para-xylene is an important by-product of petroleum refining because it is used in significant quantities for 10 the manufacture of terephthalic acid which is reacted with polyols such as ethylene glycol in the manufacture of polyesters. The major source of para-xylene is catalytic reformate which is prepared by mixing petroleum naphtha 15 with hydrogen and contacting the mixture with a strong hydrogenation/dehydrogenation catalyst such as platinum on a moderately acidic support such as a halogen treated alumina. Usually, a C. to C, fraction is separated from the 20 reformate, extracted with a solvent selective for aromatics or aiiphatics to separate these two kinds of compounds and produce a mixture of aromatic compounds which is relatively free of aiiphatics. This mixture of aromatic compounds usually contains benzene, toluene and 25 xylenes (BTX) along with ethyl benzene. Liquids from extremely severe thermal cracking, e.g. high temperature steam nr-ocVirig of nf»pbtha are »ls'-' rich in aromatics and may be used to pieptire BTX in a similax manner. 30 Concentrated aromatic fractions are also provided by severe cracking over such catalysts as ZSH-5 and by conversion of methanol over ZSM-5. Refineries have focused on the production of xylenes by transalkylation of C,+ aromatics, which would normally 3 5 only be of value as fuel, and toluene, over zeolite containing catalysts. The stability and transalkylation selectivity of zeolite beta for this reaction is the subject of several recent publications. See Das et al. "Transalkylation and Disproportionation of Toluene c.nd Cc Aromatics over Zeolite Beta" 23 Catalyst Letters pp. 161-168 (1994)7 Das et al. "Zeolite Beta Catalyzed C, and C, Aromatics Transformation" 116 Applied Catalysis A: General, pp. 71-79 (1994) and Wang et al. "Disproportionation of Toluene and of Trimethylbenzene and Their Transalkylation over Zeolite Beta", 29 Ind. Eng. Chem. Res. pages 2005-2012 (1990). Additionally, processes for producing xylenes from hydrocarbon fractions containing substituted aromatics have been disclosed in the patent literature. U.S. Patent No. 4,380,685 discloses the para-selective alkylation, transalkylation or disprcporti.onation of a substituted aromatic compound to provide a mixture of dialkylbenzene compounds employinq as a catalyst a zeoiite characterized by a Constraint Index of .1 to 12 and a silica/alumina mole ratio of at least 12/1, the catalyst having incorporated thereon various metals and phosphorus. Various techniques for enhancing the para-seiectivity of zeoiite catalysts omployed in the production of xylenes have been described. Specific Para-selectivity enhancing techniques which have been described include treatment with a sulfur compound in U.S. Patent No.. 4,3 65,104; treatment with carbon dioxide in U.S. Patent No. 4,367,359; treatment with a nitrogen compound in 4,370,508; trearmRnr witb a group "^'A element in 3,965,208; treatment with steaiia in U.S. Patent No. 3,965,209; treatment by deposition of coke in U.S. Patent No. 4,001,346; treatment with a boron compound in U.S. Patent No. During the dealkylation reactions that, typically, accompany the conversion of substituted aromatics to xylenes, olefins are formed which tend to undergo secondary reactions resulting in the formation of coke which rapidly deactivates the catalyst. These olefins also tend to take part in the formation of heavy aromatic compounds which are undesirable refinery by-products and which can also contribute to catalyst deactivation. One approach for solving the problems posed by the olefins formed during the dealkylation reactions which accompany xylene production has been to encourage olefin hydrogenation. Hydrogenation metals, such as platinum, are known for their ability to hydrogenate olefins and prevent coke formation and have been incorporated into the catalysts. Hydrogenation metals are also employed to facilitate dealkylation. U.S. Patent No. 5,030,7 87 discloses an improved process for the vapor-phase conversion of a feedstock containing at least one C5+ aromatic compound to a product containing substantial quantities of Cg to C, compounds, e.g. benzene and xylenes. The conversion occurs over a catalyst which contains a zeolite possessing a Constraint Index of from 1 to about 3, e.g. zeolites MCM-22, ZSM-12 and zeolite beta. Steam treatment of the zeolite is proposed, see Col. 9, lines 66-67. A Group VIII metal can be included with the catalyst. In the specific examples of the disclosure the zeolite is svibjected to the steam treatment prior to incorporation of the hydrogenation metal, see Examples 20-22. U.S. Patent No. 4,418,235 also discloses increasing the catalytic activity of a zeolite used for transalkylation by steam treatment and suggests incorporating a Group VIII metal into the zeolite. U.S. Patent No. 3,965,209 discloses the production of para-xylene by methylation of toluene in the presence of a zeolite which has been steamed to reduce its alpha value. Incorporation of a metal into the zeolite by replacing the original alkali metal of the zeolite with a Group VIII metal is disclosed. U.S. Patent No. 3,948,758 discloses preparing xylenes by hydrocracking an alkyl aromatics-rich and aliphatics-lean hydrocarbon fraction and toluene as a COfeed over a zeolite catalyst with a hydrogenation/dehydrogenation component, such as a Group VIII metal. The alkyl aromatics of the feed, to some extent, are rearranged by disproportionation and transalkylation. It is disclosed that because at lower temperatures which are necessary for high conversions without excessive dealkylation, the thermodynamic equilibrium tends to increase hydrogenation of the aromatic ring so nickel, a less active hydrogenation component, as compared to platinum, is preferred. U.S. Patent No. 4,857,666 discloses transalkylating an aromatic feed over mordenite and suggests modifying the zeolite by steam deactivation or incorporating a metal modifier into the catalyst. Employing high hydrogen partial pressures or high hydrogen to hydrocarbon mole ratios have been considered for purposes of minimizing catalyst aging. However, the hydrogenation component and high hydrogen partial pressures promote saturation of the aromatic compounds resulting in low yields of the desirable lighter aromatics products such as benzene, toluene and xylenes. Also, maintaining a high hydrogen to hydrocarbon mole ratio requires large reactors which are costly to manufacture and maintain. ^ Summary of the Invention This invention reduces the problems caused by olefins which are formed during the production of xylenes from substituted aromatics by providing a catalyst that saturates olefins formed during the process while minimizing saturation of aromatics. The invention also avoids the need for the high hydrogen partial pressures and high hydrogen to hydrocarbon mole ratios thought necessary to minimize catalyst aging. The invention relates to a process for the conversion of a feedstock containing €,+ aromatic compounds to a product comprising light aromatic products and xylenes. More specifically, the invention is a process for converting a feedstock containing 0,+ aromatic hydrocarbons to light aromatic products and xylenes comprising the step of: contacting the C,+ aromatic hydrocarbons and a feedstock comprising benzene and/or toluene with a catalyst composition, the catalyst composition comprising a zeolite and a hydrogenation functionality, the zeolite has a constraint index ranging from about 0.5 to 3 under transalkylation reaction conditions to produce a product comprising xylenes. The hydrogenation functionality of the catalyst composition has sufficient olefins saturation activity to avoid rapid catalyst deactivation but has minimum aromatics saturation activity. An objective of the invention is the conversion of C,+ aromatic hydrocarbons to a product comprising light aromatic products and xylenes, without substantial loss of aromatic hydrocarbons through aromatics saturation. A feature of the invention is a catalyst of minimum aromatics hydrogenation activity comprising a zeolite and a hydrogenation component. The catalyst is achieved by incorporation of the hydrogenation component into the catalyst followed by treatment to mimimize aromatics saturation activity. A further feature of the invention is a process for subjecting the catalyst to the hydrocarbon conversion process under start-up conditions of low hydrogen partial pressure and/or low hydrogen to hydrocarbon mole ratio. An advantage of the invention is that a product rich .in xylenes is produced by contacting a feedstock comprising 0,+ aromatic hydrocarbons and toluene over a catalyst having characteristics which enable it to convert the C,+ aromatic hydrocarbons with a minimum of aromatics saturation and catalyst aging. The invention alleviates the problems of catalyst aging and heavy aromatics formation posed by olefins formed during the conversion of heavy aromatics and toluene over catalysts comprising a zeolite and a hydrogenation component. The invention also solves the problem of high hydrogen partial pressures to avoid catalyst aging by providing a more stable catalyst which permits lower hydrogen partial pressures to be employed. The invention is directed to a process for converting a feedstock comprising C„+ aromatic hydrocarbons to lighter aromatic products comprising the step of: contacting a feed comprising the C,+ aromatic hydrocarbons, benzene and/or toluene under transalkylation reaction conditions with a catalyst composition comprising a zeolite having a Constraint Index remging from about 0.5 to about 3 emd a hydrogenation functionality to produce a product comprising xylenes, the catalyst composition having a hydrogenation functionality which is treated to substantially minimize loss of aromatics as determined by comparing the aromatics content of the feed with the aromatics content of the product. The invention is also directed to a process for converting a feedstock containing benzene and/or toluene and C9+ aromatic hydrocarbons to a product comprising xylenes comprising the steps of: treating a catalyst composition comprising a zeolite and a hydrogenation component with steam and/or a source of sulfur, the zeolite having a constraint index ranging from about 0.5 to 3; contacting the treated catalyst with the feedstock in the presence of hydrogen under transalkylation reaction conditions to produce a product comprising xylenes and which comprise lower than about 10% less than the amount of aromatics in the feedstock. The invention is also directed to a pcocess for making a catalyst for C9+ aromatics transalkylation comprising the steps of forming a catalyst composite which comprises a zeolite having a Constraint Index rangmg from about 0.5 to 3, a hydrogenation component and an inorganic oxide binder followed by the steps of treating the catalyst composite by (1) exposing the catalyst composite to steam and/or a source of sulfur and (2) contacting the catalyst composite with a feedstock comprising C9+ aromatics and benzene and/or toluene under conditions of temperature ranging from about 700o^F to about 950oF and hydrogen partial pressure of below about 300 psia. Accordingly the present invention provides a process for converting a feedstock comprising C9+ aromatic hydrocarbons to produce xylene comprising the steps of: (a) contacting a feedstock comprising C9+ aromatic hydrocarbons under transalkylation reaction conditions with a catalyst composition comprising a zeolite having a Constraint Index ranging from at least 0.5 to about 3 and a Group VIII metal - hydrogenation component to produce a product containing xylene, * wherein the catalyst composition having the hydrogenation component is treated to reduce its aromatic hydrogenation activity by steaming or by contacting with a source of sulfur or nitrogen: and (b)recovering the xylene from the product of step (a) in a known manner. With reference to the accompanying drawings, in which Figure 1 is a simphfied schematic flow diagram of one embodiment of the process of this invention. Figure 2 is a plot of hydrocarbon conversion at constant pressure and hydrogen to hydrocarbon mole ratio at a temperature of about 725oF and a temperature of about 850o'F as a function of days on stream vs. average reactor temperature. Figure 3 is a plot of hydrocarbon conversions at constant temperature and pressure at a hydrogen to hydrocarbon mole ratio of 2:1 and 3:1 as a function of days on stream vs. avenge reactor temperature. The invention relates to a process for converting a feedstock containing C9+ aromatic hydrocarbons and benzene and/or toluene to xylenes and lighter aromatic products comprising the steps of: contacting the feedstocks with a catalyst composition comprising a zeolite and a hydrogenation component, the zeolite characterized by a constraint index ranging from about 0.5 to 3. The conversion is conducted in the presence of hydrogen under transalkylation reaction conditions to produce a product comprising xylenes. The conditions of reaction are sufficient to convert the feedstock to a product containing substantial quantities of Cg-C, aromatic compounds such as benzene, toluene and xylenes, especially xylenes. The product effluent is separated and distilled to remove the desired xylenes product. Any unreacted materials such as toluene and/or 0,+ hydrocarbons can be recycled to the transalkylation reaction zone. The feature of the invention which achieves the production of xylenes without substantial aromatics saturation resides in the use of a ^eolite-Go^t^i•"ing catalyst having a hydrogenation functionality which has been treated to minimize aromatics saturation and to provide stable operation. Transalkvlation Catalyst The reactions of this invention are catalyzed by contact with a transalkylation catalyst which has been specially prepared in order to accomplish the objectives of the invention. The Zeolite As previously mentioned, the transalkylation catalyst comprises a zeolite. Zeolite catalysts which are useful in the process cf this invention are those that possess a Constraint Index of from about 0.5 to 3. The method by which Constraint Index is determined is described fully in U.S. Patent No. 4,016,218, incorporated herein by reference for details of the method. Constraint Index (CI) values -for some typical zeolites including some which are suiteible as catalysts in the process of this invention are set forth in Table A: The above described Constraint Index is an important 2 5 and even critical definitio.n of those zeolitea which are useful in the instant invention. The very nature of this parameter and the recited technique by which it is determined, however, admits of the possibility that a given zeolite can be tested under somewhat different 3 0 conditions and thereby exhibit different Constraint Indices. Constraint Index seems to vary somewhat with severity of operations (conversion) and the presence or absence of binders. Likewise, other variables, such as crystal size of the zeolite, the presence of occluded 35 contaminants,, etc., may affect the Constraint Index. Therefore, it will be appreciated that it may be possible to so select test conditions, e.g., temperature, as to establish more than one value for the Constraint Index of a particlar zeolite. 40 It is to be realized that the above CI values typically characterize the specified zeolites but that such are the cumlative result of several variables useful ill the determination and calculation thereof. Thus, for a given zeolite exhibiting a CI value within 45 the range of 3 or less, depending on the temperature employed during the test method within the range of 290'C to about 538'C, with accompanying conversion between 10% and 60%, the CI may vary within the indicated range of 3 or less. Accordingly, it will be understood to those 5 skilled in the art that the CI as utilized herein, while affording a highly useful means for characterizing the zeolites of interest, is approximate taking into consideration the manner of its determination with the possibility in some instances of compounding variadale 10 extremes. However, in all instances, at a temperature within the above-specified range of 290°C to about 538C, the CI will have a value for any given zeolite of interest herein of not greater than about 3. Some zeolite catalysts which are especially useful 15 in the process of this invention include zeolites MCM-22, ZSM-12 and Beta. ZSM-12 is more particularly described in U.S. Patent No. 3,832,449, the entire contents of which are incorporated by reference herein. 20 Zeolite Beta is more particularly described in U.S. Patent No. Re. 28,341 (of original U.S. patent No. 3,308,069), the entire contents of which are incorporated by reference herein. Zeolite MCM-22, or simply "MCM-22", appears to be 25 related to the composition nsuced "PSK-3" described in U.S. Patent No. 4,439,409. Zeolite MCM-22 does not appear to contain all the components apparently present in the PSH-3 compositions. Zeolite MCM-22 is not contauninated with other crystal structures, such as ZSM- 30 12 or 2SM-5, and exhibits unusual sorption capacities and unique catalytic utility when compared to the PSH-3 compositions synthesized in accordance with U.S. Patent No. 4,439,409. Catalyst Binder 35 It may be desirable to incorporate the selected zeolite catalyst with another material which is resistant to the temperatures and other conditions employed in the process of this invention. Such materials include active and inactive materials and synthetic or naturally occurring zeolites as well as inorganic materials such as clays, silica and/or metal oxides such as alumina. The latter may be either naturally occurring or in the form 5 of gelatinous precipitates or gels including mixtures of silica and metal oxides. Use of a material in conjunction with the zeolite catalyst, i.e. combined therewith or present during its synthesis, which itself is catalytically active, may change the conversion and/or 10 selectivity of the catalyst. Inactive materials suiteibly serve as diluents to control the amount of conversion so that transalkylated products can be obtained economically and orderly without employing other means for controlling the rate of reaction. These materials may be 15 incorporated into naturally occurring clays, e.g. bentonite and kaolin to improve the crush strength of the catalyst under commercial alkylation operating conditions. The materials, i.e. clays, oxides etc. function as binders for the catalyst. It is desirable to 20 provide a catalyst having good cmsh strength because in commercial use, it is desirable to prevent the catalyst from breaking down into powder-like materials- These clay binders have been employed normally only for the purpose of improving the crush strength of the catalyst- 25 Naturally occurring clays which can be composited with the zeolite catalyst herein include the montmorillonite and kaolin family., which families include the sxibbentonites, and the kaolins commonly known as Dixie, McNamee, Georgia and Florida clays or others in 30 which the main mineral constituent is hallcysitc, 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. Binders useful for compositing with 35 zeolite also include inorganic oxides, notably alumina. In addition to the foregoing materials, the zeolite catalyst can be composited with a porous matrix material such as an inorganic oxide selected from the group consisting of silica, alumina, zirconia, titania, thoria, beryllia, magnesia, and combinations thereof such as silica-alumina, silica-magnesia, silica-zirconia, silica-thoria, silica-beryllia, silica-titania as well as 5 ternary compositions such as silica-alumina-thoria, silica-alvimina-zirconia, silica-alumina-magnesia and silica-magnesia-zirconia. It may also be advantageous to provide at least a part of the foregoing matrix materials in colloidal form so as to facilitate extrusion of the 10 bound catalyst component(s). The relative proportions of finely divided crystalline material and inorganic oxide matrix vary widely, with the crystal content ranging from about 1 to about 95 percent by weight and more usually, particularly 15 when the composite is prepared in the form of beads, in the range of about 2 to about 80 weight percent of the composite. The zeolite is usually admixed with the binder or matrix material so that the final composite catalyst 20 contains the binder in amounts ranging from about 5 to about 90 weight percent and preferably from about 10 to about 60 weight percent. The zeolite catalyst can be shaped into a wide variety of particle sizes. In general, the particles are 25 in the form of a powder, a granule or a molded product such as an extrudate having a particle size sufficient to pass through 2 mesh (Tyler) screen and be retained on a 400 mesh (Tyler) screen. In cases where the catalyst is molded such as by extrusion, the crystals can be extruded 30 before drying or partially dried and then extruded. Hvdroaenation Component The zeolite is employed in combination with a hydrogenation component such as a metal selected from Group VIII of the Periodic Table of the Elements (CAS 35 version, 1979). Specific examples of useful hydrogenation materials are iron, ruthenium., osmium, nickel, cobalt, rhodium, iridivun, or a noble metal such as platinum or palladiun. suitable platinum compounds for impregnating the catalyst with platinum include chloroplatinic acid, platinous chloride and various compounds containing platinum amine complex, such as Pt(NH3)4Cl2.HjO. 5 The amount of the hydrogenation component is selected according to a balance between hydrogenation activity and catalytic functionality. Less of the hydrogenation component is required when the most active metals such as platin\im are used as compared to palladium 10 which does not possess such strong hydrogenation activity. Generally, less than 10 wt.% is used and often not more than 1 wt.%. The hydrogenation component can be incorporated into the catalyst composition by co-crystallization, exchanged 15 into the composition to the extent a Group IIIA element, e.g., aluminum, is in the structure, impregnated therein or mixed with the zeolite and the inorganic oxide matrix. Such component can be impregnated in, or on, the zeolite such as for example, in the case of platinxim, by treating 20 the zeolite with a solution containing a platinum metal-containing ion. In this regard, the noble metal may be incorporated into the catalyst by conventional techniques such as impregnation or ion exchange (or both) and may use 25 solutions of simple or complex ions of the chosen metal, e.g. complex such as Pt(NH,)4+. Alternatively, a compoimd of the selected hydrogenation component may be added to the zeolite when it is being composited with a binder or matrix material 30 and after the matrjved catalyst has been formed into particles e.g. by extrusion or pelletizing. The catalyst may be activated by calcination after drying the particles in order to remove organic components used in the synthesis of the zeolite, after 35 which, ion-exchange may be carried out as well as impregnation. After treatment with the hydrogenation function, the catalyst composite is usually dried by heating the catalyst at a temperature of about 150 to about 320of about 65 to about 160'C) for at least about 1 minute and generally not longer than about 24 hours preferably from about 230F to about 290F (about llO'C to about r43C), 5 at pressures ranging from about 0 to about 15 psia. Thereafter, the catalyst composite is calcined in a stream of dry gas, such as air or nitrogen at temperatures of from about 500 'F to about 1200'F (about 260'C to about 649'C) for about 1 to about 20 hours. 10 Calcination is preferably conducted at pressures ranging from about 15 psia to about 30 psia. Aromatics Retention The catalyst composition should be treated to minimize the loss of aromatics, without substantially 15 inhibiting olefin saturation which prevents formation of the desirable products. Aromatics loss over the treated catalyst composition of this invention is substantially lower than the aromatics loss sustained over the untreated catalyst. 20 The activity of the catalyst composition for aromatics ring loss relative to the entire amount of aromatics in the feed, is an effective way to evaluate the aromatics hydrogenation activity of the catalyst. Ideally, aromatics ring loss is less than 1 mole %. 25 However, ring losses of less than 10 mole %, specifically, less than 5 mole %, even more specifically, less than 2 mole %, are acceptable, based on the entire eifflount of aromatics in the feed. Ring loss is determined using gas chromatography by comparing the amount of 30 aromatics in the fscd with the amount of aromatics in the product. Catalyst Treatment to Ratain Aromatics The extent and methods of treatment of the catalyst including the hydrogenation functionality for minimizing 35 loss of aromatics may vary depending upon the catalyst composition and its method of manufacture, e.g. the method of incorporating the hydrogenation functionality. Catalyst pretreatment ex situ can be used to accomplish the objectives of the invention. Typically, steam treatment of the catalyst composition is employed as an effective method for 5 mimizing the aromatics hydrogenation activity of the catalyst composition. In the steaming process the catalyst is, usually, contacted with from about 5 to 100% steeun at a temperature of at least about 500 F to about 1200'F for at least about one hour, specifically about 1 10 to about 20 hours at a pressure of 100 to 2500 kPa. Another method for minimizing the aromatics hydrogenation activity of the catalyst composition is by exposing it to a compound containing an element selected from Group VA or VIA of the Periodic Table of the 15 Elements (CAS Version, 1979). The VIA element specifically contemplated is sulfur. A specifically contemplated group VA element is nitrogen. Effective treatment is accomplished by contacting the catalyst with a source of sulfur at a temperature 20 ranging from about 600 to 900T (316 to 480'C). The source of sulfur can be contacted with the catalyst via a carrier gas, typically, an inert gas such as hydrogen or nitrogen. In this embodiment, the source of sulfur is typically hydrogen sulfide. 25 The catalyst composition can also be treated in situ to accomplish the objectives of t:he invention. A source of sulfur is contacted with the catalyst composition by adding it to the hydrocarbon feedstreeua in a concentration ranging from about 50 ppmw sulfur to 30 about 10,000 ppmw sulfur. Any piilfur compound that will decompse to form KjS and a light hydrocarbon at about 900'F or less will suffice. Typical examples of appropriate sources of sulfur include carbon disulfide and allcylsulfides such as methyl sulfide, dimethyl sulfide, 35 dimethyldisulfide, diethylsulfide and dibutyl sulfide. Sulfur treatment can be considered sufficient when sulfur bre«Octhrough occurs; that is, when sulfur appears in the liquid product. Typically, sulfur treatment is initiated by incorporating a source of sulfur into the feed and continuing sulfur treatment for a few days, typically, up to 10 days, more specifically, from one to five days. 5 The sulfur treatment can be monitored by measuring the concentration of sulfur in the product off gas. During this treatment, the sulfur concentration in the off gas should range from about 20 to about 500 ppmw sulfur, preferably about 30 to 250 ppmw. 10 Continuously cofeeding a source of sulfur has been found to maintain a sufficiently minimal benzene hydrogenation activity. The catalyst can be contacted with sulfur during service by cofeeding sulfur to the reactor in varied amounts via the hydrogen stream 15 entering the reactor or the hydrocarbon feedstock. The sulfur can be continuously added to the feedstock throughout the process cycle or the sulfur can be intermittently continuosly added in which this sulfur cofed continuously for a period of time, discontinued, 20 then cofed again. Aromatics hydrogenation activity can also be sufficiently minimized by operating the process under conditions of low hydrogen partial pressure. Typically, an appropriately low hydrogen pairtial pressure 'is below 25 about 300 psig, ranges from about 100 psia to aijout 300 psia, specifically about 150 psia to about 250 psia and hydrogen to hydrocarbon mole ratio of less than 3.0, preferaUaly ranging from 1.0 to 2.0. Temperatures, during this phase range from about 700F to about 950F, 30 pressures from about 250 to about 400 psig and w.H-S-V. of about 1.5 to about 4.0. The lower hydrogen to hydrocarbon mole ratios can be used as a catalyst treatment initially upon commencement of the process in order to obtain the desired catalyst performance or it 35 can be used to treat the catalyst after a period of time on stream. Any one or a combination of these in situ and/or ex situ methods can be employed for minimizing the aromatics ' hydrogenation activity of the catalyst. It has been found that these methods minimize aromatics hydrogenation activity while sustaining sufficient hydrogenation of olefins which avoids rapid catalyst aging. 5 The Feed The C5+ aromatics feed used in this process will usually comprise one or more aromatic compounds containing at least 9 carbon atoms such as, e.g. trimethylbenzenes, dimethylbenzenes, and diethylbenzenes, 10 etc. Specific 0,+ aromatic compounds include mesitylene (1,3,5-trimethylbenzene), durene (1,2,4,5-tetramethylbenzene), hemimellitene (1,2,4-trimethylbenzene), pseudocumene (1,2,4-trimethylbenzene), 1,2-methylethylbenzene, 1,3-methylethylbenzene, 1,4- 15 methylethylbenzene, propyl-substituted benzenes, butyl-substituted benzenes, isomers of dimethyl-ethylbenzenes, etc. Suitable sources of the feed include a C,+ fraction of any refinery process which is rich in aromatics. 20 This aromatics fraction contains a substantial proportion of C,+ aromatics, specifically C, to C^ aromatic hydrocarbons, e.g. at least CO wt.% €,+ aromatics and, usually, at least about 80 wt.%, usually more than cJaout 90 wt.%, of the hydrocarbons will range from C, to Cj2« 25 Typically such refinery strezua will contain as much as if not more than 90 wt.% C,+ aromatics. Typical refinery fractions which may be useful include catalytic reformate, FCC naphtha or TCC naphtha. The feedstock employed contains benzene and/or ?0 toluene in addition to the 0,+ compounds. The feed can also contain xylenes. This charge will normally constitute at least about 50 %, specifically about 40 % to about 90 %, more specifically, about 50 to 70 % by volume of the entire feed, the balance of the feed is 35 made up by C,+ aromatics. The process feedstock can also include recycle of unconveirted materials such as toluene, benzene and C,-i- aromatics. The amount of the recycle will, usually, cause the reactor feed composition to vary. Normally, there are no ethylbenzenes in the feed; however, if there is a significant concentration of 5 ethylbenzenes in the feed, a net conversion would be seen. Hydrocarbon Conversion Process The process can be conducted in any appropriate reactor including a radial flow, fixed bed, continuous 10 down flow or fluid bed reactor. In carrying out the process of this invention, the feed is heated to a temperature within the range of about 600'F to about 1100oF at a pressure within the range of from about atmospheric to about 1000 psig. Preferred 15 inlet temperatures for the process of the present invention fall within the range of from about 650"F to cibout 1000'F and total system pressures range from about 50 psig to about 1000 psig, catalyst inventory of about 0.5 to about 4.0 WHSV. In one embodiment of the 20 invention, the process is initiated with a relatively low hydrogen partial pressure; thereafter, the hydrogen concentration is increased, usually gradually, to achieve a hydrogen partial pressure of at least about 200 psia, typically about 220 psia to 250 psia. The hydrogen to 25 hydrocarbon mole ratio is elevated from about 1.5 to eibout 10, preferably from about 2 to about 6. The process conditions are maintained to achieve transalkylation and light olefins saturation. Referring to Figure 1, a simplified process flow 30 diagram is illustrated. The c,+ aromatics stream along with toluene and hydrogen are introduced via line 10 to reactor 12 which contains the transalkylation catalyst of this invention. The reactor is maintained under conditions sufficient so that benzene and methyl 35 aromatics (toluene, xylenes, trimethylbenzenes and tetreunethylbenzenes) approach thermodynamic equilibrium through transalkylation reactions. The C, to Cn aromatics having C2+ alkvl arouDs underao dealkvlation to form light gas and benzene, ethylbenzene and methylbenzenes which can undergo transalkylation reactions.' The conditions are maintained to promote the secondary reactions which involve hydrogenation of light 5 olefins which reduce coke. The conditions are also maintained to prevent olefins from taking part in formation of heavy aromatics compounds that can deactivate the catalyst or produce undesirable by¬products. These results are achieved without producing a 10 high yield of saturated aromatics. The product of reactor 12 is withdrawn via line 14 and introduced to hydrogen separator 16 which separates hydrogen for recycle to reactor 12 via line 18. The feed then passes via line 20 to a stabilizer section 22 which removes C,- 15 fuel gas by known techniques. Thereafter, the product is fractionated into benzene, toluene and xylenes streams in fractionators 24, 26 and 28, respectively, for separation of these streams; The remaining product which comprises unreacted 0,+ feed and any heavy aromatics is 20 separated into a C, aromatics stream 30 and a C^Q+ aromatics stream 29. Stream 30 is recycled back to the reactor feed, removed from the process, or a combination of both (partial recycle) . The Cio+ aromatics stream 29 is suitable for gasoline blending or other product such 25 as solvents. Sxapplgs The following examples demonstrate catalyst preparation and pretreatment and performance of the catalyst in the conversion of heavy aromatics and benzene 3 0 and/or toluene to xylenes. Example 1 This example demonstrates formation of a platinum exchanged alumina bound ZSM-12 catalyst. 65 parts of ZSM-12 synthesized according to U.S. 35 Patent No. 3,832,449 was mixed with 35 parts of LaRoche yersal 250 alumina on a dry basis. The mixture was dry mulled and formed into 1/16" cylindrical extrudates. The extrudates were dried, activated and calcined. Platinum (0.1 wt.%) was exchanged into the extrudates using [ (NH3)4Pt]Cl2. The extrudates were washed, dried and calcined at 660'F. The platinum containing calcined extrudates were steamed at 900°F for 4 hours. Ths 5 resulting catalyst was designated as catalyst A. The finished catalyst had an alpha activity of 53 and a surface area of 281 vx^/q. Figure 2 is a plot of average reactor temperature vs. days on stream which compared the performance of 10 sulfided catalyst A at a temperature of about 725°F and a temperature of about 850°F at constant pressure of 400 psig and hydrogen to hydrocarbon mole ratio of 4:1. The plot shows that the catalyst remained stable at both temperatures within a period from about 10 to 100 days. 15 Elevating the temperature to 850°F after 4 0 days achieved a greater CQ+ conversion which remained relatively constant for up to 55 days longer. Example 2 This example demonstrates formation of a platinum 2 0 containing alumina bound ZSM-12 catalyst. 65 parts of ZSM-12 (dry basis) synthesized according to U.S. Patent No. 3,832,449 was mixed with 35 parts of LaRoche Versal 250 alumina (dry basis) and with a platinum-containing solution using [(NHj) ^Pt]CI-. The 25 amount of platinum used gave a nominal loading of 0.1 wt.% (dry basis). The r.ixture was dry null and formed into 1/16" cyclindrical extrudates. The extrudates were dried, activated and calcined. The platinum containing calcined extrudates were steamed at 900°F for 4 hours. 30 The platinum loading of the finished catalyst was 0.09 wt.%. The resulting catalyst was designated as catalyst E. The finished catalyst had an alpha activity of 77 and a surface area of 280 m'/g- Figure 3 is a plot of average reactor tem.perature 35 vs. days on stream which compares the performance of catalyst B at a low hydrogen to hydrocarbon mole ratio (2:1) with the performance of the same catalyst at a higher hydrogen to hydrocarbon mole ratio (3:1). Catalyst B was steamed and sulfided by exposing the catalyst to HjS in a concentration ranging from between 0.05 and 4.0 wt.% in flowing hydrogen, as carrier, at temperatures ranging from about 650°F and SOOT until HjS 5 was detected in the product gas at a level of approximately 250 ppmw. The plot shows that catalyst performance is relatively stable over a period of over 100 days on stream at a relatively constant temperature of about 750°F to about 775°F. This plot demonstrates 10 how a low hydrogen to hydrocarbon mole ratio during the start-up phase of the conversion enhances catalyst stability. Examples 3-4 These examples compare the performance of catalyst A 15 which was steamed after addition of the metal (Example 3) with a catalyst made in accordance with Example 22 of U.S. Patent No. 5,030,787 which was steamed prior to incorporation of the metal (Example 4) in transalkylating C5+ aromatics and toluene. The results are reported in 20 Table 1. The data reported in Table 1 show that ring retention is significantly better when the hydrogenation metal is 20 steamed as in Example 3. Additionally, the steamed hydrogenation functionality of Example 3 enabled a lower C. to C„ aromatics feed to be converted .ro a product containing an amount of Q to Cg arom.atics which was comparable to the amount of C^ to Cg aromatics produced 25 over the higher aromatics feed of Example 4. Moreover, although not reported in the Table of the C,- to Cg aromatics produced in Example 3, 3 6.0 wt.% were xylenes. In contrast, of the C^ to Cg aromatics produced in Example 4, only 2 8.6 wt.% were xylenes. 3 0 Examples 5-6 These examples demonstrate the advantage of sulfiding catalyst A prior to introduction of the feed .and also compare the performance of the presulfided catalyst with a presulfided catalyst which is further treated by adding sulfur to the feed. In both examples catalyst A was employed and the conditions of reaction included a temperature of 800°F, pressure of 400 psig, 5 WKSV of 2.5 and hydrogen to hydrocarbon mole ratio of 4. In Example 5, sulfiding was accomplished by contacting the steamed platinum exchanged ZSM-12 catalyst with about 50 cc/minute of 2% H2S in hydrogen gas for about 40 minutes at 660°F to 750°F. In Example 6, the catalyst 10 was further sulfided in situ by cofeeding 600 ppm sulfur (in the form of dibutyl sulfide) with the hydrocarbon feed for two hours. The results of conversion over these sulfided catalysts are shown below in Table 2. 1 2 As the data in Table 2 show there are significant 3 0 advantages, particularly in the aromatic ring retention and xylenes production, to cofeeding sulfur. Examples 7-11 These examples demonstrate that a lower aromatics saturation activity of the hydrogenation functionality -35 can be established by operating the process at a low hydrogen to hydrocarbon mole ratio. In these examples, Catalyst A was employed in the transalkylation of a C9+ aromatic hydrocarbon feedstream and toluene. The catalyst was not exposed to sulfur treatment. 5 10 15 20 25 The following Table 4 demonstrates that not only did the lower hydrogen to hydrocarbon mole ratio reduce aromatics ring loss, but the ring retention v,'as maintained when the hydrogen to hydrocarbon mole ratio 30 was increased to 4:1. The feed was similar to the feed used in Table 3. In these Examples, the catalyst was treated by steaming and exposure to sulfur. 15 Examples 12-14 These examples demonstrate continuously cofeeding sulfur to treat the catalyst in situ. In these examples a Pt/ZSM-12 catalyst vias presulfided with about bO cc/min 2% H^S/H. tor about 40 20 minutes at 660°F-750°F. In each example the reaction was operated at a temperature of 800°F, pressure of 3 00 psig, W.H.S.V. of 2.5 and hydrogen to hydrocarbon mole ratio of 2. After-about 125 hours on stream 100 ppmv; sulfur was added to the feed and the sulfur was continuously cofed 25 through about 170 hours on stream, at which time the sulfur feed was discontinued to evaluate the effect that continuous addition of sulfur had on the product-Product samples were analyzed at 13 4 hours on stream (Example 12) at 158 hours on stream (Example 13) and at 30 206 hours on stream (Example 14). The following Table 5 reports the results of product analysis. The data reported in Table 5 demonstrate the 15 advantages of continuously cofeeding sulfur. Comparing the Cg to Cg aromatics of Exa-iple 14 v.'ith Examples 12 and 13, it is apparent that continuously cofeeding sulfur maintained a product of higher Cg to Cg aromatics content. Additionally, in Examples 12 and 13 fewer C.- and C,+ 20 nonaromatics (e.g. methylcyclopentane) formed and fewer aromatics were lost. Furthermore, although not reported in Table 3, the hydrogen consumption was significantly reduced virh sulfur cofeed. At 134 hours on srream, with sulfur ccfeed, the hydrogen consumption was 222.6 SCF/B 25 (Exampie I.?},, at 158 hours on stream, with sulfur cofeed, the hydrogen consumption was 202.1 SCF/B (Example 13). In Example 14, after the sulfur cofeed was discontinued, the hydrogen consumption was 312.2 SCF/B. WE CLAIM: 1. A process for converting a feedstock comprising C9+ aromatic hydrocarbons to produce xylene comprising the steps of: (a) contacting a feedstock comprising C9+ aromatic hydrocarbons under transalkylation reaction conditions with a catalyst composition comprising a zeolite having a Constraint Index ranging from at least 0.5 to about 3 and a Group VIII metal hydroenation component to produce a product containing xylene, wherein the catalyst composition having the hydrogenation component is treated to reduce its aromatic hydrogenation activity by steaming or by contacting with a source of sulfur or nitrogen: and (b) recovering the xylene from the product of step (a) in a known manner. 2. The process as claimed in claim 1, in which the catalyst composition is contacted with from about S to 100% steam at a temperature of about 500oF to about 1200of 3. The process as claimed in claim 1, in which the source of sulfur is hydrogen sulfide. 4. The process as claimed in claim 1, in which the catalyst composition is treated by contacting the catalyst composition with a sulfur cofeed. 5. The process as claimed in claim 1, in which the contacting step (a) is conducted under a hydrogen partial pressure of below 300 psia. 6. The process as claimed in claim 1, in which the Group VIII metal hydrogenation component is platinum or palladium. 7. The process as claimed in claim 1, in which the zeolite is selected from the group consisting of zeolite beta, ZSM-i2 and MCM-22. 8. The process as claimed in claim 1, in which the zeolite is ZSM-12 and the Group VIII metal hydrogenation component is platinum. 9. The process as claimed in claim 1, in which the feed comprises benzene and/or toluene in addition to C9+ aromatic hydrocarbons. 10. The process as claimed in claim 9, in which the benzene and/or toluene represents at least about 40% to about 90% by volume of the total feedstock. 11. The process as claimed in claim 1, in which the transalkylatioa conditions comprise temperatures ranging from about 650F to about 1000oF, hydrogen to hydrocarbon mole ratio ranging from about 1.0 to about 10 and pressures ranging from about 50 to about 1000 psig. 12. The process as claimed in claim 1, in which the transalkylation conditions comprise a hydrogen to hydrocarbon mole ratio of less than about 3.0. 13. The process as claimed m claim 1, in which the transalkylatioa conditions comprise a hydrogen to hydrocarbon mole ratio of about 1.0 to 2.0. 14. A process for converting a feedstock comprising C9+ aromatic hydrocarbons to produce xylene substantially as herein described with reference to the accompanying drawing.

Full Text

Field of the Invention
The invention relates to the. production of xylenes from a feedstock comprising benzene and/or toluene and heavy aromatics, specifically, C9+ aromatics. More specifically, the invention relates to the production of 5 xylenes over a catalyst comprising a zeolite and a hydrogenation component. Background of the Invention
Para-xylene is an important by-product of petroleum refining because it is used in significant quantities for 10 the manufacture of terephthalic acid which is reacted
with polyols such as ethylene glycol in the manufacture of polyesters.
The major source of para-xylene is catalytic reformate which is prepared by mixing petroleum naphtha 15 with hydrogen and contacting the mixture with a strong hydrogenation/dehydrogenation catalyst such as platinum on a moderately acidic support such as a halogen treated alumina.
Usually, a C. to C, fraction is separated from the 20 reformate, extracted with a solvent selective for
aromatics or aiiphatics to separate these two kinds of compounds and produce a mixture of aromatic compounds which is relatively free of aiiphatics. This mixture of aromatic compounds usually contains benzene, toluene and 25 xylenes (BTX) along with ethyl benzene.
Liquids from extremely severe thermal cracking, e.g. high temperature steam nr-ocVirig of nf»pbtha are »ls'-' rich in aromatics and may be used to pieptire BTX in a similax manner. 30 Concentrated aromatic fractions are also provided by severe cracking over such catalysts as ZSH-5 and by conversion of methanol over ZSM-5.
Refineries have focused on the production of xylenes by transalkylation of C,+ aromatics, which would normally 3 5 only be of value as fuel, and toluene, over zeolite

containing catalysts. The stability and transalkylation selectivity of zeolite beta for this reaction is the subject of several recent publications. See Das et al. "Transalkylation and Disproportionation of Toluene c.nd Cc Aromatics over Zeolite Beta" 23 Catalyst Letters pp. 161-168 (1994)7 Das et al. "Zeolite Beta Catalyzed C, and C, Aromatics Transformation" 116 Applied Catalysis A: General, pp. 71-79 (1994) and Wang et al. "Disproportionation of Toluene and of Trimethylbenzene and Their Transalkylation over Zeolite Beta", 29 Ind. Eng. Chem. Res. pages 2005-2012 (1990).
Additionally, processes for producing xylenes from hydrocarbon fractions containing substituted aromatics have been disclosed in the patent literature. U.S. Patent No. 4,380,685 discloses the para-selective alkylation, transalkylation or disprcporti.onation of a substituted aromatic compound to provide a mixture of dialkylbenzene compounds employinq as a catalyst a zeoiite characterized by a Constraint Index of .1 to 12 and a silica/alumina mole ratio of at least 12/1, the catalyst having incorporated thereon various metals and phosphorus.
Various techniques for enhancing the para-seiectivity of zeoiite catalysts omployed in the production of xylenes have been described. Specific Para-selectivity enhancing techniques which have been described include treatment with a sulfur compound in U.S. Patent No.. 4,3 65,104; treatment with carbon dioxide in U.S. Patent No. 4,367,359; treatment with a nitrogen compound in 4,370,508; trearmRnr witb a group "^'A element in 3,965,208; treatment with steaiia in U.S. Patent No. 3,965,209; treatment by deposition of coke in U.S. Patent No. 4,001,346; treatment with a boron compound in U.S. Patent No.
During the dealkylation reactions that, typically, accompany the conversion of substituted aromatics to xylenes, olefins are formed which tend to undergo secondary reactions resulting in the formation of coke which rapidly deactivates the catalyst. These olefins also tend to take part in the formation of heavy aromatic compounds which are undesirable refinery by-products and which can also contribute to catalyst deactivation.
One approach for solving the problems posed by the olefins formed during the dealkylation reactions which accompany xylene production has been to encourage olefin hydrogenation. Hydrogenation metals, such as platinum, are known for their ability to hydrogenate olefins and prevent coke formation and have been incorporated into the catalysts. Hydrogenation metals are also employed to facilitate dealkylation.
U.S. Patent No. 5,030,7 87 discloses an improved process for the vapor-phase conversion of a feedstock containing at least one C5+ aromatic compound to a product containing substantial quantities of Cg to C, compounds, e.g. benzene and xylenes. The conversion occurs over a catalyst which contains a zeolite possessing a Constraint Index of from 1 to about 3, e.g. zeolites MCM-22, ZSM-12 and zeolite beta. Steam treatment of the zeolite is proposed, see Col. 9, lines 66-67. A Group VIII metal can be included with the catalyst. In the specific examples of the disclosure the zeolite is svibjected to the steam treatment prior to incorporation of the hydrogenation metal, see Examples 20-22.
U.S. Patent No. 4,418,235 also discloses increasing the catalytic activity of a zeolite used for transalkylation by steam treatment and suggests incorporating a Group VIII metal into the zeolite.
U.S. Patent No. 3,965,209 discloses the production of para-xylene by methylation of toluene in the presence of a zeolite which has been steamed to reduce its alpha value. Incorporation of a metal into the zeolite by

replacing the original alkali metal of the zeolite with a Group VIII metal is disclosed.
U.S. Patent No. 3,948,758 discloses preparing xylenes by hydrocracking an alkyl aromatics-rich and aliphatics-lean hydrocarbon fraction and toluene as a COfeed over a zeolite catalyst with a
hydrogenation/dehydrogenation component, such as a Group VIII metal. The alkyl aromatics of the feed, to some extent, are rearranged by disproportionation and transalkylation. It is disclosed that because at lower temperatures which are necessary for high conversions without excessive dealkylation, the thermodynamic equilibrium tends to increase hydrogenation of the aromatic ring so nickel, a less active hydrogenation component, as compared to platinum, is preferred.
U.S. Patent No. 4,857,666 discloses transalkylating an aromatic feed over mordenite and suggests modifying the zeolite by steam deactivation or incorporating a metal modifier into the catalyst.
Employing high hydrogen partial pressures or high
hydrogen to hydrocarbon mole ratios have been considered
for purposes of minimizing catalyst aging. However, the
hydrogenation component and high hydrogen partial
pressures promote saturation of the aromatic compounds
resulting in low yields of the desirable lighter
aromatics products such as benzene, toluene and xylenes.
Also, maintaining a high hydrogen to hydrocarbon mole
ratio requires large reactors which are costly to
manufacture and maintain. ^

Summary of the Invention
This invention reduces the problems caused by olefins which are formed during the production of xylenes from substituted aromatics by providing a catalyst that saturates olefins formed during the process while minimizing saturation of aromatics. The invention also avoids the need for the high hydrogen partial pressures and high hydrogen to hydrocarbon mole ratios thought necessary to minimize catalyst aging.
The invention relates to a process for the conversion of a feedstock containing €,+ aromatic compounds to a product comprising light aromatic products and xylenes. More specifically, the invention is a process for converting a feedstock containing 0,+ aromatic hydrocarbons to light aromatic products and xylenes comprising the step of:
contacting the C,+ aromatic hydrocarbons and a feedstock comprising benzene and/or toluene with a catalyst composition, the catalyst composition comprising a zeolite and a hydrogenation functionality, the zeolite has a constraint index ranging from about 0.5 to 3 under transalkylation reaction conditions to produce a product comprising xylenes. The hydrogenation functionality of the catalyst composition has sufficient olefins saturation activity to avoid rapid catalyst deactivation but has minimum aromatics saturation activity.
An objective of the invention is the conversion of C,+ aromatic hydrocarbons to a product comprising light aromatic products and xylenes, without substantial loss of aromatic hydrocarbons through aromatics saturation.
A feature of the invention is a catalyst of minimum aromatics hydrogenation activity comprising a zeolite and a hydrogenation component. The catalyst is achieved by incorporation of the hydrogenation component into the catalyst followed by treatment to mimimize aromatics saturation activity.
A further feature of the invention is a process for subjecting the catalyst to the hydrocarbon conversion

process under start-up conditions of low hydrogen partial pressure and/or low hydrogen to hydrocarbon mole ratio.
An advantage of the invention is that a product rich .in xylenes is produced by contacting a feedstock comprising 0,+ aromatic hydrocarbons and toluene over a catalyst having characteristics which enable it to convert the C,+ aromatic hydrocarbons with a minimum of aromatics saturation and catalyst aging.
The invention alleviates the problems of catalyst aging and heavy aromatics formation posed by olefins formed during the conversion of heavy aromatics and toluene over catalysts comprising a zeolite and a hydrogenation component. The invention also solves the problem of high hydrogen partial pressures to avoid catalyst aging by providing a more stable catalyst which permits lower hydrogen partial pressures to be employed.
The invention is directed to a process for converting a feedstock comprising C„+ aromatic hydrocarbons to lighter aromatic products comprising the step of:
contacting a feed comprising the C,+ aromatic hydrocarbons, benzene and/or toluene under transalkylation reaction conditions with a catalyst composition comprising a zeolite having a Constraint Index remging from about 0.5 to about 3 emd a hydrogenation functionality to produce a product comprising xylenes, the catalyst composition having a hydrogenation functionality which is treated to substantially minimize loss of aromatics as determined by comparing the aromatics content of the feed with the aromatics content of the product.
The invention is also directed to a process for converting a feedstock containing benzene and/or toluene and C9+ aromatic hydrocarbons to a product comprising xylenes comprising the steps of:
treating a catalyst composition comprising a zeolite and a hydrogenation component with steam and/or a source

of sulfur, the zeolite having a constraint index ranging from about 0.5 to 3;
contacting the treated catalyst with the feedstock in the presence of hydrogen under transalkylation reaction conditions to produce a product comprising xylenes and which comprise lower than about 10% less than the amount of aromatics in the feedstock.
The invention is also directed to a pcocess for making a catalyst for C9+ aromatics transalkylation comprising the steps of forming a catalyst composite which comprises a zeolite having a Constraint Index rangmg from about 0.5 to 3, a hydrogenation component and an inorganic oxide binder followed by the steps of treating the catalyst composite by (1) exposing the catalyst composite to steam and/or a source of sulfur and (2) contacting the catalyst composite with a feedstock comprising C9+ aromatics and benzene and/or toluene under conditions of temperature ranging from about 700o^F to about 950oF and hydrogen partial pressure of below about 300 psia.
Accordingly the present invention provides a process for converting a feedstock comprising C9+ aromatic hydrocarbons to produce xylene comprising the steps of:
(a) contacting a feedstock comprising C9+ aromatic hydrocarbons
under transalkylation reaction conditions with a catalyst
composition comprising a zeolite having a Constraint Index
ranging from at least 0.5 to about 3 and a Group VIII metal
- hydrogenation component to produce a product containing xylene,
* wherein the catalyst composition having the hydrogenation

component is treated to reduce its aromatic hydrogenation activity by steaming or by contacting with a source of sulfur or nitrogen: and (b)recovering the xylene from the product of step (a) in a known manner.
With reference to the accompanying drawings, in which
Figure 1 is a simphfied schematic flow diagram of one embodiment of
the process of this invention.
Figure 2 is a plot of hydrocarbon conversion at constant pressure and
hydrogen to hydrocarbon mole ratio at a temperature of about 725oF and a
temperature of about 850o'F as a function of days on stream vs. average
reactor temperature.
Figure 3 is a plot of hydrocarbon conversions at constant temperature and pressure at a hydrogen to hydrocarbon mole ratio of 2:1 and 3:1 as a function of days on stream vs. avenge reactor temperature.
The invention relates to a process for converting a feedstock containing C9+ aromatic hydrocarbons and benzene and/or toluene to xylenes and lighter aromatic products comprising the steps of:

contacting the feedstocks with a catalyst composition comprising a zeolite and a hydrogenation component, the zeolite characterized by a constraint index ranging from about 0.5 to 3.
The conversion is conducted in the presence of hydrogen under transalkylation reaction conditions to produce a product comprising xylenes.
The conditions of reaction are sufficient to convert the feedstock to a product containing substantial quantities of Cg-C, aromatic compounds such as benzene, toluene and xylenes, especially xylenes. The product effluent is separated and distilled to remove the desired xylenes product. Any unreacted materials such as toluene and/or 0,+ hydrocarbons can be recycled to the transalkylation reaction zone.
The feature of the invention which achieves the production of xylenes without substantial aromatics saturation resides in the use of a ^eolite-Go^t^i•"ing catalyst having a hydrogenation functionality which has been treated to minimize aromatics saturation and to provide stable operation. Transalkvlation Catalyst
The reactions of this invention are catalyzed by contact with a transalkylation catalyst which has been specially prepared in order to accomplish the objectives of the invention. The Zeolite
As previously mentioned, the transalkylation catalyst comprises a zeolite. Zeolite catalysts which are useful in the process cf this invention are those that possess a Constraint Index of from about 0.5 to 3.
The method by which Constraint Index is determined is described fully in U.S. Patent No. 4,016,218, incorporated herein by reference for details of the method.
Constraint Index (CI) values -for some typical zeolites including some which are suiteible as catalysts

in the process of this invention are set forth in Table A:

The above described Constraint Index is an important
2 5 and even critical definitio.n of those zeolitea which are
useful in the instant invention. The very nature of this parameter and the recited technique by which it is determined, however, admits of the possibility that a given zeolite can be tested under somewhat different
3 0 conditions and thereby exhibit different Constraint
Indices. Constraint Index seems to vary somewhat with severity of operations (conversion) and the presence or absence of binders. Likewise, other variables, such as crystal size of the zeolite, the presence of occluded
35 contaminants,, etc., may affect the Constraint Index.
Therefore, it will be appreciated that it may be possible to so select test conditions, e.g., temperature, as to establish more than one value for the Constraint Index of a particlar zeolite.
40 It is to be realized that the above CI values
typically characterize the specified zeolites but that such are the cumlative result of several variables useful ill the determination and calculation thereof. Thus, for a given zeolite exhibiting a CI value within
45 the range of 3 or less, depending on the temperature

employed during the test method within the range of 290'C to about 538'C, with accompanying conversion between 10% and 60%, the CI may vary within the indicated range of 3 or less. Accordingly, it will be understood to those 5 skilled in the art that the CI as utilized herein, while affording a highly useful means for characterizing the zeolites of interest, is approximate taking into consideration the manner of its determination with the possibility in some instances of compounding variadale
10 extremes. However, in all instances, at a temperature
within the above-specified range of 290°C to about 538*C, the CI will have a value for any given zeolite of interest herein of not greater than about 3.
Some zeolite catalysts which are especially useful
15 in the process of this invention include zeolites MCM-22, ZSM-12 and Beta.
ZSM-12 is more particularly described in U.S. Patent No. 3,832,449, the entire contents of which are incorporated by reference herein.
20 Zeolite Beta is more particularly described in U.S. Patent No. Re. 28,341 (of original U.S. patent No. 3,308,069), the entire contents of which are incorporated by reference herein.
Zeolite MCM-22, or simply "MCM-22", appears to be
25 related to the composition nsuced "PSK-3" described in U.S. Patent No. 4,439,409. Zeolite MCM-22 does not appear to contain all the components apparently present in the PSH-3 compositions. Zeolite MCM-22 is not contauninated with other crystal structures, such as ZSM-
30 12 or 2SM-5, and exhibits unusual sorption capacities and unique catalytic utility when compared to the PSH-3 compositions synthesized in accordance with U.S. Patent No. 4,439,409. Catalyst Binder
35 It may be desirable to incorporate the selected
zeolite catalyst with another material which is resistant to the temperatures and other conditions employed in the process of this invention. Such materials include active

and inactive materials and synthetic or naturally occurring zeolites as well as inorganic materials such as clays, silica and/or metal oxides such as alumina. The latter may be either naturally occurring or in the form 5 of gelatinous precipitates or gels including mixtures of silica and metal oxides. Use of a material in conjunction with the zeolite catalyst, i.e. combined therewith or present during its synthesis, which itself is catalytically active, may change the conversion and/or
10 selectivity of the catalyst. Inactive materials suiteibly serve as diluents to control the amount of conversion so that transalkylated products can be obtained economically and orderly without employing other means for controlling the rate of reaction. These materials may be
15 incorporated into naturally occurring clays, e.g.
bentonite and kaolin to improve the crush strength of the catalyst under commercial alkylation operating conditions. The materials, i.e. clays, oxides etc. function as binders for the catalyst. It is desirable to
20 provide a catalyst having good cmsh strength because in commercial use, it is desirable to prevent the catalyst from breaking down into powder-like materials- These clay binders have been employed normally only for the purpose of improving the crush strength of the catalyst-
25 Naturally occurring clays which can be composited with the zeolite catalyst herein include the montmorillonite and kaolin family., which families include the sxibbentonites, and the kaolins commonly known as Dixie, McNamee, Georgia and Florida clays or others in
30 which the main mineral constituent is hallcysitc,
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. Binders useful for compositing with
35 zeolite also include inorganic oxides, notably alumina. In addition to the foregoing materials, the zeolite catalyst can be composited with a porous matrix material such as an inorganic oxide selected from the group

consisting of silica, alumina, zirconia, titania, thoria, beryllia, magnesia, and combinations thereof such as silica-alumina, silica-magnesia, silica-zirconia, silica-thoria, silica-beryllia, silica-titania as well as 5 ternary compositions such as silica-alumina-thoria, silica-alvimina-zirconia, silica-alumina-magnesia and silica-magnesia-zirconia. It may also be advantageous to provide at least a part of the foregoing matrix materials in colloidal form so as to facilitate extrusion of the
10 bound catalyst component(s).
The relative proportions of finely divided crystalline material and inorganic oxide matrix vary widely, with the crystal content ranging from about 1 to about 95 percent by weight and more usually, particularly
15 when the composite is prepared in the form of beads, in the range of about 2 to about 80 weight percent of the composite.
The zeolite is usually admixed with the binder or matrix material so that the final composite catalyst
20 contains the binder in amounts ranging from about 5 to about 90 weight percent and preferably from about 10 to about 60 weight percent.
The zeolite catalyst can be shaped into a wide variety of particle sizes. In general, the particles are
25 in the form of a powder, a granule or a molded product
such as an extrudate having a particle size sufficient to pass through 2 mesh (Tyler) screen and be retained on a 400 mesh (Tyler) screen. In cases where the catalyst is molded such as by extrusion, the crystals can be extruded
30 before drying or partially dried and then extruded. Hvdroaenation Component
The zeolite is employed in combination with a hydrogenation component such as a metal selected from Group VIII of the Periodic Table of the Elements (CAS
35 version, 1979). Specific examples of useful hydrogenation materials are iron, ruthenium., osmium, nickel, cobalt, rhodium, iridivun, or a noble metal such as platinum or palladiun.

suitable platinum compounds for impregnating the catalyst with platinum include chloroplatinic acid, platinous chloride and various compounds containing platinum amine complex, such as Pt(NH3)4Cl2.HjO. 5 The amount of the hydrogenation component is
selected according to a balance between hydrogenation activity and catalytic functionality. Less of the hydrogenation component is required when the most active metals such as platin\im are used as compared to palladium
10 which does not possess such strong hydrogenation
activity. Generally, less than 10 wt.% is used and often not more than 1 wt.%.
The hydrogenation component can be incorporated into the catalyst composition by co-crystallization, exchanged
15 into the composition to the extent a Group IIIA element, e.g., aluminum, is in the structure, impregnated therein or mixed with the zeolite and the inorganic oxide matrix. Such component can be impregnated in, or on, the zeolite such as for example, in the case of platinxim, by treating
20 the zeolite with a solution containing a platinum metal-containing ion.
In this regard, the noble metal may be incorporated into the catalyst by conventional techniques such as impregnation or ion exchange (or both) and may use
25 solutions of simple or complex ions of the chosen metal, e.g. complex such as Pt(NH,)4+.
Alternatively, a compoimd of the selected hydrogenation component may be added to the zeolite when it is being composited with a binder or matrix material
30 and after the matrjved catalyst has been formed into particles e.g. by extrusion or pelletizing.
The catalyst may be activated by calcination after drying the particles in order to remove organic components used in the synthesis of the zeolite, after
35 which, ion-exchange may be carried out as well as impregnation.
After treatment with the hydrogenation function, the catalyst composite is usually dried by heating the

catalyst at a temperature of about 150 to about 320of about 65 to about 160'C) for at least about 1 minute and generally not longer than about 24 hours preferably from about 230*F to about 290*F (about llO'C to about r43*C), 5 at pressures ranging from about 0 to about 15 psia. Thereafter, the catalyst composite is calcined in a stream of dry gas, such as air or nitrogen at temperatures of from about 500 'F to about 1200'F (about 260'C to about 649'C) for about 1 to about 20 hours.
10 Calcination is preferably conducted at pressures ranging from about 15 psia to about 30 psia. Aromatics Retention
The catalyst composition should be treated to minimize the loss of aromatics, without substantially
15 inhibiting olefin saturation which prevents formation of the desirable products.
Aromatics loss over the treated catalyst composition of this invention is substantially lower than the aromatics loss sustained over the untreated catalyst.
20 The activity of the catalyst composition for
aromatics ring loss relative to the entire amount of aromatics in the feed, is an effective way to evaluate the aromatics hydrogenation activity of the catalyst. Ideally, aromatics ring loss is less than 1 mole %.
25 However, ring losses of less than 10 mole %,
specifically, less than 5 mole %, even more specifically, less than 2 mole %, are acceptable, based on the entire eifflount of aromatics in the feed. Ring loss is determined using gas chromatography by comparing the amount of
30 aromatics in the fscd with the amount of aromatics in the product. Catalyst Treatment to Ratain Aromatics
The extent and methods of treatment of the catalyst including the hydrogenation functionality for minimizing
35 loss of aromatics may vary depending upon the catalyst composition and its method of manufacture, e.g. the method of incorporating the hydrogenation functionality.

Catalyst pretreatment ex situ can be used to accomplish the objectives of the invention.
Typically, steam treatment of the catalyst composition is employed as an effective method for 5 mimizing the aromatics hydrogenation activity of the catalyst composition. In the steaming process the catalyst is, usually, contacted with from about 5 to 100% steeun at a temperature of at least about 500 *F to about 1200'F for at least about one hour, specifically about 1
10 to about 20 hours at a pressure of 100 to 2500 kPa. Another method for minimizing the aromatics hydrogenation activity of the catalyst composition is by exposing it to a compound containing an element selected from Group VA or VIA of the Periodic Table of the
15 Elements (CAS Version, 1979). The VIA element
specifically contemplated is sulfur. A specifically contemplated group VA element is nitrogen.
Effective treatment is accomplished by contacting the catalyst with a source of sulfur at a temperature
20 ranging from about 600 to 900T (316 to 480'C). The
source of sulfur can be contacted with the catalyst via a carrier gas, typically, an inert gas such as hydrogen or nitrogen. In this embodiment, the source of sulfur is typically hydrogen sulfide.
25 The catalyst composition can also be treated in situ to accomplish the objectives of t:he invention.
A source of sulfur is contacted with the catalyst composition by adding it to the hydrocarbon feedstreeua in a concentration ranging from about 50 ppmw sulfur to
30 about 10,000 ppmw sulfur. Any piilfur compound that will decompse to form KjS and a light hydrocarbon at about 900'F or less will suffice. Typical examples of appropriate sources of sulfur include carbon disulfide and allcylsulfides such as methyl sulfide, dimethyl sulfide,
35 dimethyldisulfide, diethylsulfide and dibutyl sulfide.
Sulfur treatment can be considered sufficient when sulfur bre«Octhrough occurs; that is, when sulfur appears in the liquid product.

Typically, sulfur treatment is initiated by incorporating a source of sulfur into the feed and continuing sulfur treatment for a few days, typically, up to 10 days, more specifically, from one to five days. 5 The sulfur treatment can be monitored by measuring the concentration of sulfur in the product off gas. During this treatment, the sulfur concentration in the off gas should range from about 20 to about 500 ppmw sulfur, preferably about 30 to 250 ppmw.
10 Continuously cofeeding a source of sulfur has been found to maintain a sufficiently minimal benzene hydrogenation activity. The catalyst can be contacted with sulfur during service by cofeeding sulfur to the reactor in varied amounts via the hydrogen stream
15 entering the reactor or the hydrocarbon feedstock. The sulfur can be continuously added to the feedstock throughout the process cycle or the sulfur can be intermittently continuosly added in which this sulfur cofed continuously for a period of time, discontinued,
20 then cofed again.
Aromatics hydrogenation activity can also be sufficiently minimized by operating the process under conditions of low hydrogen partial pressure. Typically, an appropriately low hydrogen pairtial pressure 'is below
25 about 300 psig, ranges from about 100 psia to aijout 300 psia, specifically about 150 psia to about 250 psia and hydrogen to hydrocarbon mole ratio of less than 3.0, preferaUaly ranging from 1.0 to 2.0. Temperatures, during this phase range from about 700*F to about 950*F,
30 pressures from about 250 to about 400 psig and w.H-S-V. of about 1.5 to about 4.0. The lower hydrogen to hydrocarbon mole ratios can be used as a catalyst treatment initially upon commencement of the process in order to obtain the desired catalyst performance or it
35 can be used to treat the catalyst after a period of time on stream.
Any one or a combination of these in situ and/or ex situ methods can be employed for minimizing the aromatics '

hydrogenation activity of the catalyst. It has been found that these methods minimize aromatics hydrogenation activity while sustaining sufficient hydrogenation of olefins which avoids rapid catalyst aging. 5 The Feed
The C5+ aromatics feed used in this process will usually comprise one or more aromatic compounds containing at least 9 carbon atoms such as, e.g. trimethylbenzenes, dimethylbenzenes, and diethylbenzenes,
10 etc. Specific 0,+ aromatic compounds include mesitylene (1,3,5-trimethylbenzene), durene (1,2,4,5-tetramethylbenzene), hemimellitene (1,2,4-trimethylbenzene), pseudocumene (1,2,4-trimethylbenzene), 1,2-methylethylbenzene, 1,3-methylethylbenzene, 1,4-
15 methylethylbenzene, propyl-substituted benzenes, butyl-substituted benzenes, isomers of dimethyl-ethylbenzenes, etc.
Suitable sources of the feed include a C,+ fraction of any refinery process which is rich in aromatics.
20 This aromatics fraction contains a substantial proportion of C,+ aromatics, specifically C, to C^ aromatic hydrocarbons, e.g. at least CO wt.% €,+ aromatics and, usually, at least about 80 wt.%, usually more than cJaout 90 wt.%, of the hydrocarbons will range from C, to Cj2«
25 Typically such refinery strezua will contain as much as if not more than 90 wt.% C,+ aromatics. Typical refinery fractions which may be useful include catalytic reformate, FCC naphtha or TCC naphtha.
The feedstock employed contains benzene and/or
?0 toluene in addition to the 0,+ compounds. The feed can also contain xylenes. This charge will normally constitute at least about 50 %, specifically about 40 % to about 90 %, more specifically, about 50 to 70 % by volume of the entire feed, the balance of the feed is
35 made up by C,+ aromatics.
The process feedstock can also include recycle of unconveirted materials such as toluene, benzene and C,-i-

aromatics. The amount of the recycle will, usually, cause the reactor feed composition to vary.
Normally, there are no ethylbenzenes in the feed; however, if there is a significant concentration of 5 ethylbenzenes in the feed, a net conversion would be seen. Hydrocarbon Conversion Process
The process can be conducted in any appropriate reactor including a radial flow, fixed bed, continuous
10 down flow or fluid bed reactor.
In carrying out the process of this invention, the feed is heated to a temperature within the range of about 600'F to about 1100oF at a pressure within the range of from about atmospheric to about 1000 psig. Preferred
15 inlet temperatures for the process of the present
invention fall within the range of from about 650"F to cibout 1000'F and total system pressures range from about 50 psig to about 1000 psig, catalyst inventory of about 0.5 to about 4.0 WHSV. In one embodiment of the
20 invention, the process is initiated with a relatively low hydrogen partial pressure; thereafter, the hydrogen concentration is increased, usually gradually, to achieve a hydrogen partial pressure of at least about 200 psia, typically about 220 psia to 250 psia. The hydrogen to
25 hydrocarbon mole ratio is elevated from about 1.5 to eibout 10, preferably from about 2 to about 6.
The process conditions are maintained to achieve transalkylation and light olefins saturation.
Referring to Figure 1, a simplified process flow
30 diagram is illustrated. The c,+ aromatics stream along with toluene and hydrogen are introduced via line 10 to reactor 12 which contains the transalkylation catalyst of this invention. The reactor is maintained under conditions sufficient so that benzene and methyl
35 aromatics (toluene, xylenes, trimethylbenzenes and
tetreunethylbenzenes) approach thermodynamic equilibrium through transalkylation reactions. The C, to Cn aromatics having C2+ alkvl arouDs underao dealkvlation to

form light gas and benzene, ethylbenzene and methylbenzenes which can undergo transalkylation reactions.' The conditions are maintained to promote the secondary reactions which involve hydrogenation of light 5 olefins which reduce coke. The conditions are also maintained to prevent olefins from taking part in formation of heavy aromatics compounds that can deactivate the catalyst or produce undesirable by¬products. These results are achieved without producing a
10 high yield of saturated aromatics. The product of
reactor 12 is withdrawn via line 14 and introduced to hydrogen separator 16 which separates hydrogen for recycle to reactor 12 via line 18. The feed then passes via line 20 to a stabilizer section 22 which removes C,-
15 fuel gas by known techniques. Thereafter, the product
is fractionated into benzene, toluene and xylenes streams in fractionators 24, 26 and 28, respectively, for separation of these streams; The remaining product which comprises unreacted 0,+ feed and any heavy aromatics is
20 separated into a C, aromatics stream 30 and a C^Q+
aromatics stream 29. Stream 30 is recycled back to the reactor feed, removed from the process, or a combination of both (partial recycle) . The Cio+ aromatics stream 29 is suitable for gasoline blending or other product such
25 as solvents. Sxapplgs
The following examples demonstrate catalyst preparation and pretreatment and performance of the catalyst in the conversion of heavy aromatics and benzene
3 0 and/or toluene to xylenes. Example 1
This example demonstrates formation of a platinum exchanged alumina bound ZSM-12 catalyst.
65 parts of ZSM-12 synthesized according to U.S.
35 Patent No. 3,832,449 was mixed with 35 parts of LaRoche yersal 250 alumina on a dry basis. The mixture was dry mulled and formed into 1/16" cylindrical extrudates. The extrudates were dried, activated and calcined. Platinum

(0.1 wt.%) was exchanged into the extrudates using [ (NH3)4Pt]Cl2. The extrudates were washed, dried and calcined at 660'F. The platinum containing calcined extrudates were steamed at 900°F for 4 hours. Ths 5 resulting catalyst was designated as catalyst A.
The finished catalyst had an alpha activity of 53 and a surface area of 281 vx^/q.
Figure 2 is a plot of average reactor temperature vs. days on stream which compared the performance of
10 sulfided catalyst A at a temperature of about 725°F and a temperature of about 850°F at constant pressure of 400 psig and hydrogen to hydrocarbon mole ratio of 4:1. The plot shows that the catalyst remained stable at both temperatures within a period from about 10 to 100 days.
15 Elevating the temperature to 850°F after 4 0 days achieved a greater CQ+ conversion which remained relatively constant for up to 55 days longer. Example 2
This example demonstrates formation of a platinum
2 0 containing alumina bound ZSM-12 catalyst.
65 parts of ZSM-12 (dry basis) synthesized according to U.S. Patent No. 3,832,449 was mixed with 35 parts of LaRoche Versal 250 alumina (dry basis) and with a platinum-containing solution using [(NHj) ^Pt]CI-. The
25 amount of platinum used gave a nominal loading of 0.1 wt.% (dry basis). The r.ixture was dry null and formed into 1/16" cyclindrical extrudates. The extrudates were dried, activated and calcined. The platinum containing calcined extrudates were steamed at 900°F for 4 hours.
30 The platinum loading of the finished catalyst was 0.09
wt.%. The resulting catalyst was designated as catalyst E. The finished catalyst had an alpha activity of 77 and a surface area of 280 m'/g-
Figure 3 is a plot of average reactor tem.perature
35 vs. days on stream which compares the performance of
catalyst B at a low hydrogen to hydrocarbon mole ratio (2:1) with the performance of the same catalyst at a higher hydrogen to hydrocarbon mole ratio (3:1).

Catalyst B was steamed and sulfided by exposing the catalyst to HjS in a concentration ranging from between 0.05 and 4.0 wt.% in flowing hydrogen, as carrier, at temperatures ranging from about 650°F and SOOT until HjS 5 was detected in the product gas at a level of
approximately 250 ppmw. The plot shows that catalyst performance is relatively stable over a period of over 100 days on stream at a relatively constant temperature of about 750°F to about 775°F. This plot demonstrates
10 how a low hydrogen to hydrocarbon mole ratio during the start-up phase of the conversion enhances catalyst stability. Examples 3-4
These examples compare the performance of catalyst A
15 which was steamed after addition of the metal (Example 3) with a catalyst made in accordance with Example 22 of U.S. Patent No. 5,030,787 which was steamed prior to incorporation of the metal (Example 4) in transalkylating C5+ aromatics and toluene. The results are reported in
20 Table 1.

The data reported in Table 1 show that ring retention is significantly better when the hydrogenation metal is
20 steamed as in Example 3. Additionally, the steamed
hydrogenation functionality of Example 3 enabled a lower C. to C„ aromatics feed to be converted .ro a product containing an amount of Q to Cg arom.atics which was comparable to the amount of C^ to Cg aromatics produced
25 over the higher aromatics feed of Example 4. Moreover, although not reported in the Table of the C,- to Cg aromatics produced in Example 3, 3 6.0 wt.% were xylenes. In contrast, of the C^ to Cg aromatics produced in Example 4, only 2 8.6 wt.% were xylenes.
3 0 Examples 5-6
These examples demonstrate the advantage of sulfiding catalyst A prior to introduction of the feed .and also compare the performance of the presulfided

catalyst with a presulfided catalyst which is further treated by adding sulfur to the feed. In both examples catalyst A was employed and the conditions of reaction included a temperature of 800°F, pressure of 400 psig, 5 WKSV of 2.5 and hydrogen to hydrocarbon mole ratio of 4. In Example 5, sulfiding was accomplished by contacting the steamed platinum exchanged ZSM-12 catalyst with about 50 cc/minute of 2% H2S in hydrogen gas for about 40 minutes at 660°F to 750°F. In Example 6, the catalyst 10 was further sulfided in situ by cofeeding 600 ppm sulfur (in the form of dibutyl sulfide) with the hydrocarbon feed for two hours. The results of conversion over these sulfided catalysts are shown below in Table 2.
1
2
As the data in Table 2 show there are significant 3 0 advantages, particularly in the aromatic ring retention and xylenes production, to cofeeding sulfur. Examples 7-11
These examples demonstrate that a lower aromatics saturation activity of the hydrogenation functionality -35 can be established by operating the process at a low
hydrogen to hydrocarbon mole ratio. In these examples, Catalyst A was employed in the transalkylation of a C9+

aromatic hydrocarbon feedstream and toluene. The catalyst was not exposed to sulfur treatment.
5
10
15
20
25
The following Table 4 demonstrates that not only did the lower hydrogen to hydrocarbon mole ratio reduce aromatics ring loss, but the ring retention v,'as maintained when the hydrogen to hydrocarbon mole ratio 30 was increased to 4:1. The feed was similar to the feed used in Table 3. In these Examples, the catalyst was treated by steaming and exposure to sulfur.

15 Examples 12-14
These examples demonstrate continuously cofeeding sulfur to treat the catalyst in situ.
In these examples a Pt/ZSM-12 catalyst vias presulfided with about bO cc/min 2% H^S/H. tor about 40
20 minutes at 660°F-750°F. In each example the reaction was operated at a temperature of 800°F, pressure of 3 00 psig, W.H.S.V. of 2.5 and hydrogen to hydrocarbon mole ratio of 2. After-about 125 hours on stream 100 ppmv; sulfur was added to the feed and the sulfur was continuously cofed
25 through about 170 hours on stream, at which time the
sulfur feed was discontinued to evaluate the effect that continuous addition of sulfur had on the product-Product samples were analyzed at 13 4 hours on stream (Example 12) at 158 hours on stream (Example 13) and at
30 206 hours on stream (Example 14). The following Table 5 reports the results of product analysis.

The data reported in Table 5 demonstrate the 15 advantages of continuously cofeeding sulfur. Comparing the Cg to Cg aromatics of Exa-iple 14 v.'ith Examples 12 and 13, it is apparent that continuously cofeeding sulfur maintained a product of higher Cg to Cg aromatics content. Additionally, in Examples 12 and 13 fewer C.- and C,+ 20 nonaromatics (e.g. methylcyclopentane) formed and fewer aromatics were lost. Furthermore, although not reported in Table 3, the hydrogen consumption was significantly reduced virh sulfur cofeed. At 134 hours on srream, with sulfur ccfeed, the hydrogen consumption was 222.6 SCF/B 25 (Exampie I.?},, at 158 hours on stream, with sulfur cofeed, the hydrogen consumption was 202.1 SCF/B (Example 13). In Example 14, after the sulfur cofeed was discontinued, the hydrogen consumption was 312.2 SCF/B.

WE CLAIM:
1. A process for converting a feedstock comprising C9+ aromatic
hydrocarbons to produce xylene comprising the steps of:
(a) contacting a feedstock comprising C9+ aromatic hydrocarbons under transalkylation reaction conditions with a catalyst composition comprising a zeolite having a Constraint Index ranging from at least 0.5 to about 3 and a Group VIII metal hydroenation component to produce a product containing xylene, wherein the catalyst composition having the hydrogenation component is treated to reduce its aromatic hydrogenation activity by steaming or by contacting with a source of sulfur or nitrogen: and
(b) recovering the xylene from the product of step (a) in a known manner.

2. The process as claimed in claim 1, in which the catalyst composition is contacted with from about S to 100% steam at a temperature of about 500oF to about 1200of
3. The process as claimed in claim 1, in which the source of sulfur is hydrogen sulfide.
4. The process as claimed in claim 1, in which the catalyst composition is treated by contacting the catalyst composition with a sulfur cofeed.

5. The process as claimed in claim 1, in which the contacting step (a) is conducted under a hydrogen partial pressure of below 300 psia.
6. The process as claimed in claim 1, in which the Group VIII metal hydrogenation component is platinum or palladium.
7. The process as claimed in claim 1, in which the zeolite is selected from the group consisting of zeolite beta, ZSM-i2 and MCM-22.
8. The process as claimed in claim 1, in which the zeolite is ZSM-12 and the Group VIII metal hydrogenation component is platinum.
9. The process as claimed in claim 1, in which the feed comprises benzene and/or toluene in addition to C9+ aromatic hydrocarbons.
10. The process as claimed in claim 9, in which the benzene and/or toluene represents at least about 40% to about 90% by volume of the total feedstock.

11. The process as claimed in claim 1, in which the transalkylatioa
conditions comprise temperatures ranging from about 650*F to about
1000oF, hydrogen to hydrocarbon mole ratio ranging from about 1.0
to about 10 and pressures ranging from about 50 to about 1000 psig.
12. The process as claimed in claim 1, in which the transalkylation conditions comprise a hydrogen to hydrocarbon mole ratio of less than about 3.0.
13. The process as claimed m claim 1, in which the transalkylatioa conditions comprise a hydrogen to hydrocarbon mole ratio of about 1.0 to 2.0.
14. A process for converting a feedstock comprising C9+ aromatic
hydrocarbons to produce xylene substantially as herein described with
reference to the accompanying drawing.

Documents:

531-mas-95 abstract.pdf

531-mas-95 claims.pdf

531-mas-95 correspondences-others.pdf

531-mas-95 correspondences-po.pdf

531-mas-95 description (complete).pdf

531-mas-95 drawings.pdf

531-mas-95 form-1.pdf

531-mas-95 form-26.pdf

531-mas-95 form-4.pdf

531-mas-95 others document.pdf

531-mas-95 pct.pdf

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Patent Number

189340

Indian Patent Application Number

531/MAS/1995

PG Journal Number

30/2009

Publication Date

24-Jul-2009

Grant Date

12-Feb-2004

Date of Filing

02-May-1995

Name of Patentee

M/S. MOBIL OIL CORPORATION

Applicant Address

3225 GALLOWS ROAD FAIRFAX, VIRGINIA 22037

Inventors:

#	Inventor's Name	Inventor's Address
1	SADI MIZRAHI	204 SHEFFIELD ROAD CHERRY HILL, NJ 08034
2	JOHN SCOTT BUCHANAN	663AXSON AVENUE TRENTON, NJ-08649
3	ARTHUR WARREN CHESTER	517 COUNTRY CLUB DRIVE CHERRY HILL, NJ 08003
4	SHIU LUN ANTHONY FUNG	3 CRENSHAW DRIVE WILMINGTON, DELAWARE 19810
5	TIMOTHY FREDERICK KINN	120 F HEMLOCK COURT DEPTFORD, NJ 08096

PCT International Classification Number

C07C4/12

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	84103523	1995-04-11	U.S.A.
2	08/386892	1995-02-10	U.S.A.