Abstract: This invention relates to a process and a chemical plant for the production primarily of paraxylene. In particular the process and chemical plant utilise zeolite membranes for enhanced paraxylene production.

Abstract: A method for producing 1,2-bis(indenyl)ethanes in good yield is described. An agent and its application for isomerizing kinetic EBI to thermodynamic EBI and for isomerizing meso TMS-EBI to rac TMS-EBI are exemplified.

Abstract: Process for isomerization of a feedstock that contains aromatic compounds with eight carbon atoms characterized in that it comprises at least one isomerization stage a) that is carried out in the presence of a catalyst that contains at least one metal of group VIII and that is activated according to an activation process that comprises at least one sulfurization stage and at least one stage for passivation with ammonia, and at least one dehydrogenation stage b).

Abstract: The method for removing ethylbenzene from a feed stream for use in producing para-xylene product, the stream containing para-xylene, ortho-xylene, meta-xylene and ethylbenzene. The method incorporates provision of a reactor unit used in a pretreatment step, the reactor containing an isomerization catalyst in an amount sufficient to convert substantially all the ethylbenzene in the feed stream to benzene, and provides for removal of the converted benzene from the stream prior to cyclic retreatments of the stream by a para-xylene separator and an isomerization unit, respectively.

Abstract: A process for isomerising aromatic compounds containing eight carbon atoms is described in which the catalyst used contains at least one zeolite with structure type EUO and a group VIII element. In FIG. 1, the feed to be isomerised is introduced into reactor R via line 1. This fresh feed is enriched via lines 6 and 11 with a mixture containing at least one compound selected from the group formed by paraffins containing eight carbon atoms, benzene, toluene and naphthenes containing eight carbon atoms. Hydrogen is added via line 15.

Abstract: Low temperature hydrothermal treatment of an LTL zeolite-producing mixture produces a colloidal suspension of the zeolite; the suspension may be used as seeds in Al— and Ga—LTL zeolite manufacture.

Abstract: A process for isomerising a feed comprising aromatic compounds containing 8 carbon atoms is carried out in two steps: an isomerisation step and a dehydrogenation step. In FIG. 1, the feed to be treated is introduced into isomerisation zone R1 via line 1. Substantially pure hydrogen is introduced into line 1 via line 12 and recycled hydrogen is introduced into line 1 via line 13. Hydrogen which circulates in line 13 is purged via line 15. The effluent from isomerisation zone R1 is sent to a separation zone S1 via line 2. In S1, hydrogen contained in the effluent is isolated and recycled to the inlet to isomerisation zone R1 via line 13, the remaining effluent being evacuated from this separation zone S1 via line 3. The fluid contained in line 3 is heated in an oven F1 then evacuated therefrom via line 4. The effluent leaving the oven is enriched in recycled hydrogen via line 14 then it is introduced into dehydrogenation zone R2. The effluent from zone R2 is sent via line 5 to separation zone S2.

Abstract: For isomerising aromatic compounds containing eight carbon atoms in the presence of hydrogen, a mixture containing compounds with a boiling point of about 80° C. to 135° C. comprising at least one paraffin containing eight carbon atoms, at least one naphthene containing eight carbon atoms, at least benzene and at least toluene is added to the feed before introducing it into the isomerisation reactor R via line 1. These additions are made by a recycle via line 6 or by adding fresh compounds via line 11, or be a combination of fresh and recycled compounds via lines 6 and 11. Hydrogen is added via line 15.

Abstract: Hydroprocessing of petroleum and chemical feedstocks using bulk Group VIII/Group VIB catalysts. Preferred catalysts include those comprised of Ni--Mo--W.

Abstract: A C.sub.8 aromatic feedstock is isomerized by an isomerization stage conducted at 320-380.degree. C. with a catalyst containing at least one EUO-structure-type zeolite and at least one metal of group VIII, to obtain an effluent containing isomerized alkyl aromatics and about 10-30% by weight of naphthenes. The effluent is then subjected to a dehydrogenation stage so as to convert the naphthenes to additional alkyl aromatics.

Abstract: A catalytic material is provided which effectuates the aromatization, reformation, and dehydrogenation of aliphatic, cycloaliphatic, and mixtures of aliphatic and cycloaliphatic hydrocarbons. The catalyst comprises an L-zeolite associated with a Group VIII metal such as platinum and having a rare earth metal ion incorporated therein. A method of using the catalytic material is also provided.

Abstract: A method for increasing the efficiency of xylene isomerization by using a two stage isomerization process. In the first stage of the process, a C.sub.9.sup.+ aromatics feedstock is subjected to ethylbenzene conversion and xylene isomerization. Non-C.sub.8 aromatics are removed from the effluent, which is then processed in a second stage of the process to remove para-xylene and isomerize the para-xylene depleted effluent. The effluent from the second stage isomerization unit is then recycled into the inlet of the second stage of the process and a slip stream from the para-xylene separator is recycled to the feedstock and to the effluent of the ethylbenzene conversion unit. In this way, the production of para-xylene is maximized. In a preferred embodiment, toluene is co-fed into the feedstock to minimize the loss of xylenes during the ethylbenzene conversion reaction.

Abstract: Hydrocarbon conversion processes are described which use a sulfur tolerant catalyst system. The catalyst is tolerant to large amounts (about 30,000 ppm sulfur) in the feedstream and comprises a first component which comprises at least one Group VIII metal dispersed on an inorganic oxide support and a second component comprising a metal phthalocyanine dispersed on an inorganic oxide support. Preferred Group VIII metals are platinum and palladium, while preferred metal phthalocyanines are cobalt or nickel phthalocyanine. Preferred inorganic oxide supports are molecular sieves, aluminas and mixtures thereof. Processes which can be carried out using this catalyst system include reforming, hydrocracking, dehydrogenation and isomerization.

Abstract: A process for producing highly pure 2,6-dimethylnaphthalene in a high yield from a mixture of dimethylnaphthalene isomers in the presence of a solvent, such as an aliphatic or alicyclic saturated hydrocarbon. Highly pure 2,6-dimethylnaphthalene can be produced steadily for a long time by filtering the 2,6-dimethylnaphthalene crystal precipitated by the crystallizing by using a filtration apparatus, such as a rotary vacuum filter, peeling-off the filtered cake from a filter cloth and cleaning the filter cloth with a solvent, at a temperature not lower than a filtration temperature.

Abstract: This invention provides a method for preparing non-zeolitic molecular sieves using inexpensive reagents and at lower manufacturing cost. The method includes using a low density, small size particulate hydrated alumina, such as aluminum hydroxide, in place of aluminum alkoxides and other more costly reagents. The preferred particulate hydrated alumina has a density of less than 1.0 g/cm.sup.3, an average particle size of less than about 40 microns and an alkali content of less than 0.12 wt %.

Abstract: The present invention relates to a zeolite beta catalyst characterized by critical limits of weak and strong acid species and exceptionally high catalytic activity. The catalyst is activated at a temperature effective to substantially reduce the concentration of strong acid species, i.e., hydronium cations, without substantially reducing the concentration of weak acid species, i.e., hydroxoaluminum cations, preferably following a calcining step wherein a synthesized zeolite beta catalyst containing a templating agent is calcined at a temperature in the range of from about 200.degree. to 1000.degree. C. in order to remove a substantial portion of the catalyst templating agent and an ion-exchanging step wherein the calcined catalyst is ion-exchanged with a salt solution containing at least one hydrogen forming cation selected from NH.sub.4.sup.+ and quaternary ammonium.

Abstract: A process is provided for catalytic conversion of feedstock comprising aromatic compounds to product comprising aromatic compounds which differs from said feedstock. The catalyst required in the process comprises a crystalline material having the structure of MCM-58. Said crystalline material may have been treated with one or more monomeric or polymeric siloxane compounds which decompose to oxide or non-oxide ceramic or solid-state carbon species.

Abstract: An improvement to a known process in which C.sub.8 aromatic hydrocarbons are treated to recover a desired isomer of xylene, and in particular o-xylene or p-xylene. A step in recovering isomers of xylene typically includes subjecting a mixture of xylenes to fractional distillation and drawing a stream rich in o-xylene from the fractionation column. The current improvement involves the steps of contacting the contents of the fractionation column with an isomerization catalyst, thereby isomerizing C.sub.8 aromatic hydrocarbons in the fractionation column toward equilibrium and consequently enhancing the effectiveness of the fractional distillation in the recovery of the desired xylene isomer. The process can be carried out in the xylene splitter of existing apparatus by making appropriate modifications thereto. It also can be carried out in newly-designed and fabricated apparatus. Embodiments are disclosed for favoring the production either of o-xylene or p-xylene.

Abstract: A ex situ selectivated catalytic molecular sieve for enhanced shape selective hydrocarbon conversions in which a catalytic molecular sieve is modified by being exposed to at least two selectivation sequences, each sequence including an impregnation of the molecular sieve with a selectivating agent and a subsequent calcination of the impregnated molecular sieve. The ex situ selectivation method is also described, including the use of aqueous carriers for the selecting agent. Also a method for in situ trim-selectivating the modified catalytic molecular sieve. Also, a method for moderate steaming of the selectivated molecular sieve. Also a method for in situ trim-selectivating the modified catalytic molecular sieve. Also described is the process for shape selective hydrocarbon conversion comprising contacting a hydrocarbon feedstream under conversion conditions with the selectivated molecular sieve.

Abstract: A method for isomerizing dimethylnaphthalene (DMN) in the gaseous phase in the presence of a solvent comprising an aromatic hydrocarbon having a boiling point of at most 150.degree. C., e.g., benzene, under atmospheric pressure by using a catalyst comprising a hydrogen-form of mordenite. According to the method, the objective 2,6-DMN can be produced with a minimal content of impurities and the 2,6-DMN can be stably produced in high selectivity and high yield under mild reaction conditions for a long period of time, while suppressing side reactions.

Abstract: A process of effecting an acid catalyzed reaction wherein a reactant capable of undergoing an acid catalyzed reaction is contacted with an acid functionalized organically-bridged polysilsesquioxane catalyst where all of the acid functionality is covalently bonded to the organic portion of an organically-bridged polysilsesquioxane framework has been developed. The acid functionalized organically-bridged polysilsesquioxane is formed by polymerizing a monomer through sol-gel processing to form an organically-bridged polysilsesquioxane, reacting an acid group onto the organic portion of the organically-bridged polysilsesquioxane, and recovering the acid functionalized product. An embodiment of the invention is where the acid catalyzed reaction is the hydration of olefins, alkylation, acylation, isomerization, or aldol condensation/elimination.

Abstract: A hydrocarbon feedstock is catalytically reformed in a sequence comprising a reforming zone containing a catalyst comprising a platinum-group metal and a nonacidic L-zeolite and an aromatics-isomerization zone containing a catalyst comprising a platinum-group metal, a metal attenuator and a refractory inorganic oxide. The process combination features high selectivity in producing a high-purity BTX product from naphtha.

Abstract: A catalyst for chemical and petrochemical reactions and a process for its production. The catalyst comprises an oxide of one of the transition metals, rare earth elements, or actinide elements, e.g., molybdenum, having on its surface carbides and oxycarbides, the core being the metal or the metal oxide. In the process for catalyst production, the reaction gas mixture containing carbon products is passed onto the oxide, leading to a progressive carburization of the surface of the oxide and to a progressive increase in the efficiency of the catalyst.

Abstract: A method for preparing one or more specific dimethyltetralins from either 5-(o-, m-, or p-tolyl)-pent-1- or -2-ene or 5-phenyl-hex-1- or -2-ene, and optionally for preparing one or more specific dimethylnaphthalenes from the aforesaid dimethyltetralins is disclosed wherein the orthotolylpentene or phenylhexane is cyclized to the dimethyltetralin using an ultra-stable crystalline aluminosilicate molecular sieve Y-zeolite.

Abstract: There is provided a vacancy titanate intercalated with a cationic hydroxy aluminum complex, such as a Keggin ion. A method for making this material and a process for using this material as a catalyst are also provided.

Abstract: A process for a shape selective hydrocarbon conversion such as toluene disproportionation, involves contacting a reaction stream under conversion conditions with a catalytic molecular sieve which has been preselectivated by agglomerating with an organosilicon compound. The invention also includes a method for agglomeration-preselectivation and the shape selective catalyst which results from the agglomeration preselectivation.

Abstract: A process for a shape selective hydrocarbon conversion such as toluene disproportionation involves contacting a reaction stream under conversion conditions with a catalytic molecular sieve which has been pre-selectivated and concurrently activated by contact with a substantially aqueous solution of an organosilicon compound. The invention also includes a method for concurrently preselectivating and activating a catalyst and the shape selectivated, activated catalyst which results from this method.

Abstract: A pretreatment method for a C.sub.8 aromatic isomerization process wherein the isomerization catalyst is initially contacted with a C.sub.8 aromatic feedstock under high severity isomerization conditions for a period of time sufficient to deposit a substantial amount to carbonaceous material on the catalyst. After pretreatment, the carbon-laden catalyst continues to be contacted by the C.sub.8 aromatic feedstock under less severe conditions than that of the pretreatment mode of operation.

Abstract: There is provided a process for producing 3,3',4,4'-tetramethyldiphenylmethane which comprises subjecting tetramethyldiphenylmethane containing at least one of 2,3,3',4'-tetramethyldiphenylmethane and 2,2',3,3'-tetramethyldiphenylmethane to isomerization reaction in the presence of a catalyst to convert into 3,3',4,4'-tetramethyldiphenylmethane. According to the process of the present invention, the objective 3,3',4,4'-tetramethyldiphenylmethane is efficiently obtained from tetramethyldiphenylmethane obtainable in particular by the reaction of o-xylene with formaldehyde. The 3,3',4,4'-tetramethyldiphenylmethane thus obtained can be converted by oxidation into 3,4,3',4'-benzophenonetetracarboxylic acid dianhydride which is important as a raw material for heat-resistant high molecular compounds.

Abstract: Dimethylnaphthalenes are isomerized into 2,6-dimethylnaphthalene by utilizing hydrogen fluoride as a catalyst and straight chain saturated aliphatic hydrocarbons having carbon atoms in the range from 5 to 12 as the solvent. Isomerization to other undesirable isomers such as 2,7-dimethylnaphthalene and side reactions such as disproportionation are suppressed and a very high degree of the isomerization to 2,6-DMN can be attained.

Abstract: Alkylaromatic hydrocarbons are produced in a process which comprises concentrating a feed aromatic hydrocarbon into a sidecut stream removed from a fractionation column. A feed acyclic olefin is then admixed with the aromatic hydrocarbon and passed through an alkylation reaction zone operated at optimum alkylation conditions. The reaction zone effluent is returned to the fractionation column to recover the product and to recycle untreated feed aromatics. This technique can be applied to hydrocarbon conversion processes in general to obtain benefits of catalytic distillation while operating the reaction zone at conditions not suitable for catalytic distillation. Hydrogen and other light gases are preferably separated from the reaction zone effluent by cooling and vapor-liquid separation external to the column.

Abstract: The invention relates to a catalyst for isomerizing a C.sub.8 aromatic fraction containing a mordenite and at least one metal from group VIII of the periodic classification of elements (such as Pt or Pd), characterized in that the mordenite is such that its skeleton Si/Al atomic ratio is between 6 and 10.5, its sodium weight content is below 2000 ppm, its unit cell volume is between 2.73 and 2.78 nm.sup.3, its benzene adsorption capacity is between 4 and 10% based on the dry mordenite weight and its 1,3,5-trimethylbenzene adsorption capacity is between 0.5 and 2.5% by weight based on the dry mordenite weight. The invention also relates to the preparation of said mordenite.

Abstract: Compositions containing sulfuric acid and one or more of certain chalcogen-containing compounds in which the chalcogen compound/H.sub.2 SO.sub.4 molar ratio is below 2 contain the mono-adduct of sulfuric acid which is catalytically active for promoting organic chemical reactions. Suitable chalcogen-containing compounds have the empirical formula ##STR1## wherein X is a chalcogen, each of R.sub.1 and R.sub.2 is independently selected from hydrogen, NR.sub.3 R.sub.4, and NR.sub.5, at least one of R.sub.1 and R.sub.2 is other than hydrogen, each of R.sub.3 and R.sub.4 is hydrogen or a monovalent organic radical, and R.sub.5 is a divalent organic radical. Such compositions are useful for catalyzing organic reactions such as oxidation, oxidative addition, reduction, reductive addition, esterification, transesterification, hydrogenation, isomerication (including racemization of optical isomers), alkylation, polymerization, demetallization of organometallics, nitration, Friedel-Crafts reactions, and hydrolysis.

Abstract: Improved processes for the production of secondary alkyl indanes, particularly mixtures of 1,1,3,5-tetramethyl-3-isopropylindanes and 1,3,3,5-tetramethyl-3-isopropylindane, and alkylated tetrahydronaphthalenes, particularly mixtures of 1,1,3,4,4,6-hexametyl-1,2,3,4-tetrahydronaphthalene and 1,1,2,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphthalene, are described. In the processes of the invention, alkylated tetrahydronaphthalenes or secondary alkyl indanes are isomerized in the presence of a Lewis acid and a solvent which may be a halogenated or unhalogenated solvent and, optionally, a phase transfer agent, to produce, in the case of an alkylated tetrahydronaphthalene starting material, a secondary alkyl indane, and in the case of a secondary alkyl indane starting material, an aklylated tetrahydronaphthalene. The Lewis acid is present in the reaction medium in an amount of less than about 50 mole percent based on the amount of the alkylated tetrahydronaphthalene or secondary alkylindane charged.

Abstract: A dual function composite catalyst for isomerizing an isomerization feed containing an aromatic C.sub.8 mixture of ethyl benzene and xylene, comprises (a) a crystalline aluminosilicate zeolite having a low acid activity as measured by an alpha value of from 0.02 to 11, an average crystal size of not more than 0.4 microns for at least 50% by weight of the crystals, a silica to alumina ratio of at least about 12, a constraint index of about 1 to 12, a xylene sorption capacity greater than 1 gram per 100 grams of zeolite, and an ortho-xylene sorption time for 30 percent of said capacity less than 10 minutes, said sorption capacity and sorption time being measured at 120.degree. C. and a xylene pressure of 4.5.+-.0.8 mm of mercury, and (b) a supported metal of Group VIII of the Periodic Table having a high hydrogenation/dehydrogenation activity to provide the catalyst with a dehydrogenation activity of at least 10. The catalyst has an alpha value of 0.005 to 3.

Abstract: A method for preparing one or more specific dimethyltetralins from either 5-(o-, m-, or p-tolyl)-pent-1-or -2-ene or 5-phenyl-hex-1- or -2-ene, and optionally for preparing one or more specific dimethylnaphthalenes from the aforesaid dimethyltetralins is disclosed.

Abstract: A process for producing methylnaphthalenes is disclosed, comprising subjecting a fraction containing at least 50% by volume of components within the boiling range of 195.degree.-215.degree. C., which is obtained by distilling a raffinate resulting from the recovery of normal paraffins from a hydrodesulfurized kerosene fraction, to reforming reaction and then recovering methylnaphthalenes from the product oil.

Abstract: A catalyzed process for the isomerization of a xylene-containing stream containing a major amount of ethylbenzene under supercritical temperature and pressure which contacts the stream under supercritical conditions with a catalyst and subsequently reduces the temperature of the isomerization product at a pressure above the critical pressure.

Abstract: A dual function composite catalyst for isomerizing an isomerization feed containing an aromatic C.sub.8 mixture of ethyl benzene and xylene, comprises (a) a crystalline aluminosilicate zeolite having a low acid activity as measured by an alpha value of from 0.02 to 11, an average crystal size of not more than 0.4 microns for at least 50% by weight of the crystals, a silica to alumina ratio of at least about 12, a constraint index of about 1 to 12, a xylene sorption capacity greater than 1 gram per 100 grams of zeolite, and an ortho-xylene sorption time for 30 percent of said capacity less than 10 minutes, said sorption capacity and sorption time being measured at 120.degree. C. and a xylene pressure of 4.5.+-.0.8 mm of mercury, and (b) a supported metal of Group VIII of the Periodic Table having a high hydrogenation/dehydrogenation activity to provide the catalyst with a dehydrogenation activity of at least 10. The catalyst has an alpha value of 0.005 to 3.

Abstract: Removal of the small amount of lower molecular weight olefins produced by certain isomerization catalysts during the catalytic isomerization of xylene results in reduced xylene loss. Such removal can be conveniently effected by use of a mild hydrogenation catalyst separate from the isomerization catalyst in the process.

Abstract: A process for production of dimethylnaphthalenes is disclosed, comprising subjecting a raffinate resulting from the recovery of normal paraffins from a hydrodesulfurized kerosene fraction to reforming reaction and then recovering dimethylnaphthalenes from the product oil.

Abstract: A method for preparing one or more specific dimethyltetralins from either 5-(o-, m-, or p-tolyl)-pent-1- or -2-ene or 5-phenyl-hex-1- or -2-ene, and optionally for preparing one or more specific dimethylnaphthalenes from the aforesaid dimethyltetralins is disclosed.

Abstract: A method for producing efficiently a highly pure 1-(m-ethylphenyl)-1-phenylethane or m-ethylphenylphenylmethane which are used as the starting materials for preparing medicines and other organic compounds. The method comprises the step of reacting a diaryl compound with benzene or alkylbenzene in the presence of an acid catalyst selected from the group consisting of AlCl.sub.3, AlBr.sub.3, HF.BF.sub.3 complex and Y-type zeolites.

Abstract: The improved, heterogeneous catalysts are in the form of gas-impervious, hollow, thin-walled spheres (10) suitably formed of a shell (12) of metal such as aluminum having a cavity (14) containing a gas at a pressure greater than atmospheric pressure. The wall material may be, itself, catalytic or the catalyst can be coated onto the sphere as a layer (16), suitably platinum or iron, which may be further coated with a layer (18) of activator or promoter. The density of the spheres (30) can be uniformly controlled to a preselected value within .+-.10 percent of the density of the fluid reactant such that the spheres either remain suspended or slowly fall or rise through the liquid reactant.

Abstract: A process is disclosed for the production of a desired xylene isomer, preferably paraxylene, and high quality benzene. The desired isomer (11) is recovered from the feed (1) and recycle (3) streams in a xylene separation zone (2). The raffinate (5) from the separation zone is passed into a catalytic xylene isomerization zone (6). The isomerization zone effluent stream is passed into a high severity transalkylation zone (14) which contains a catalyst comprising both a ZSM-5 zeolite and mordenite. Ethylbenzene in the feed stream is subjected to staged conversion in the two catalytic reaction zones to both xylenes and benzene. The overall ethylbenzene conversion efficiency is improved.

Abstract: Process for the isomerization of a xylene feedstock employing a silicalite catalyst. A xylene feedstock containing a mixture of xylene isomers and ethylbenzene is passed to a reaction zone containing the silicalite catalyst. Para-xylene is present in the feedstock in less than an equilibrium amount, and ethylbenzene is present in a concentration greater than the para-xylene concentration. Hydrogen and/or water are also supplied to the reaction zone. The reaction zone is operated under conditions to effect isomerization of xylene isomers to provide an increased para-xylene content, and disproportionation of ethylbenzene to provide a decreased ethylbenzene content.

Abstract: Boron, aluminum and gallium C.sub.1 -C.sub.18 perfluoroalkanesulfonates (CF.sub.3 (CF.sub.2).sub.n SO.sub.3).sub.3 M (M=B, A1, Ga; n=0-17) as well as perfluororesin sulfonates such as Nafionates are new, highly effective Friedel-Crafts catalysts. In contrast to volatile aluminum and boron trihalides, the Group III-B perfluoroalkanesulfonates are generally of low or no volatility and, except for boron triflate and some of its homologs, only sparingly soluble incommon organic solvents. This allows their use as solid or supported Friedel-Crafts catalysts of wide utility and scope in continuous heterogenous catalytic processes. At the same time, boron triflate and related lower perfluoroalkanesulfonates are particularly efficient soluble catalysts in solution reactions.

Abstract: A process is disclosed for the production of a desired xylene isomer, preferably paraxylene, and high quality benzene. The desired isomer is recovered from the feed and recycle streams in a xylene separation zone. The net effluent or raffinate from the separation zone is passed into a catalytic xylene isomerization zone. The isomerization zone effluent stream is passed into a high severity transalkylation zone. Ethylbenzene in the feed stream is subjected to staged conversion in the two catalytic reaction zones and thereby converted to both xylenes and benzene.

Abstract: An improved catalyst composition for isomerizing xylene containing a minor amount of ethylbenzene comprising a HAMS-1B crystalline borosilicate molecular sieve incorporated into an inorganic matrix impregnated with a small amount of a phosphorus compound. The catalyst composition when contacted with an ethylbenzene containing xylene under isomerization conditions results in a greater yield of paraxylene and a conversion of ethylbenzene to more useful products.

Abstract: A process is disclosed for the production of high quality benzene and a desired xylene isomer, preferably paraxylene, from a mixture of C.sub.7 -plus alkylaromatic hydrocarbons. The desired xylene isomer is recovered by absorptive separation from a stream of two or three xylene isomers. The resultant isomer-depleted stream is passed into a transalkylation zone together with both feed and recycled toluene and C.sub.9 aromatic hydrocarbons instead of being passed into a xylene isomerization zone. Benzene and xylenes are fractionated from the transalkylation zone effluent stream, with the xylenes being passed into the absorptive separation zone. A nonmetal catalyst is employed in the transalkylation zone, which must be operated at high severity (high temperature) conditions.