Abstract: Isomerization of xylenes in admixture with ethylbenzene by contact with a zeolite catalyst such as ZSM-5 is improved by use of zeolite which has been steamed at high temperature to reduce activity, the reaction being at a temperature above about 700.degree. F. At these conditions, conversion of ethylbenzene follows a different reaction path which permits high conversion of ethylbenzene to benzene without loss of xylenes of disproportionation.

Abstract: Isomerization of xylenes admixed with other alkyl aromatics of at least eight carbon atoms is conducted at essentially atmospheric pressure at 800.degree.-1000.degree. F. with a zeolite like zeolite ZSM-5 of reduced acid activity.

Abstract: Isomerization of xylenes in admixture with ethyl benzene by contact with a zeolite catalyst such as ZSM-5 is improved by use of zeolite having a substantial alkali metal content at a temperature above about 800.degree. F. At these conditions, conversion of ethylbenzene follows a different reaction path which permits high conversion of ethylbenzene to benzene without loss of xylenes by disproportionation.

Abstract: Benzene, toluene and xylene are produced in high yield from aromatic naphtha by a processing technique which combines (1) high temperature isomerization of eight carbon atom aromatics over a catalyst having relatively low activity and constrained access to the internal pore surface and (2) processing of heavy single ring aromatics of nine or more carbon atoms together with toluene under dealkylation/transalkylation conditions. The effluents of the two reactions are blended for processing through separation and recovery equipment. The unique chemistry of the isomerization stage results in splitting off alkyl side chains of two or more carbon atoms while retaining methyl groups attached to aromatic rings. Because of these reaction characteristics, full range reformate is advantageously added to the isomerizer charge for conversion to methyl benzene and redistribution of methyl groups to the thermodynamic equilibrium values.

Abstract: Benzene, toluene and xylene are prepared from mixtures of single ring alkyl aromatic compounds of eight or more carbon atoms concurrently with isomerization of xylenes by mixing xylenes from which at least one isomer has been separated with a mixture of alkyl benzenes of eight and more carbon atoms, e.g. heavy reformate, and contacting that mixture at 800.degree. to 1000.degree. F. with a zeolite catalyst of reduced activity such as zeolite ZSM-5 having a silica to alumina ratio of at least 200.

Abstract: Isomerization of xylenes in admixture with ethyl benzene by contact with a zeolite catalyst such as ZSM-5 is improved by use of zeolite having a silica/alumina ratio of at least 500 at a temperature above about 800.degree. F. At these conditions, conversion of ethyl benzene follows a different reaction path which permits high conversion of ethyl benzene to benzene without loss of xylenes by disproportionation.

Abstract: An improved vapor phase process is provided for isomerization of monocyclic methyl-substituted aromatic hydrocarbons. The process involves contacting said aromatic hydrocarbons with a catalyst material containing a crystalline aluminosilicate zeolite characterized by a silica/alumina mole ratio of at least 12 and a constraint index, hereinafter defined, within the approximate range of 1 to 12, in a reaction zone maintained under conditions such that said isomerization is accomplished in the vapor phase. The improvement resides in the catalyst being highly diluted, such as with alumina, and the reaction temperature being maintained at greater than 800.degree. F.

Abstract: Certain acidic heterogeneous catalysts produce large yields of benzene, toluene and xylene from alkyl aromatics of at least nine carbon atoms by a mechanism different from the classical disproportionation reaction characteristic of acid catalysts. Typically, aromatic mixtures so derived from such stocks have unusually low content of ethyl benzene, thus greatly simplifying separation of xylene isomers.

Abstract: A process is provided for disproportionation of toluene in a reaction zone maintained under conditions such that said disproportionation is accomplished in the vapor-phase, with a hydrogen/hydrocarbon mole ratio of from 0 to 4, and in the presence of a catalyst comprising a crystalline aluminosilicate zeolite characterized by a silica/alumina mole ratio of at least 12 and a constraint index, hereinafter defined, within the approximate range of 1 to 12, said catalyst under said conditions being capable of long stability and of affording a high yield of disproportionation products with favorable selectivity toward para-xylene.

Abstract: Improvements in the aromatization of hydrocarbons and in the alkylation of aromatic rings effected by contacting appropriate hydrocarbon feed streams with a ZSM-5 type of catalyst at prescribed temperature, pressure and space velocity conditions to convert the feed as required and desired, which improvements go to minimizing the production of polycyclic aromatics, particularly naphthalenes in the process and reducing coking of the catalyst during aromatization and/or alkylation by using as the catalyst a ZSM-5 type of crystalline aluminosilicate zeolite which has rhenium values deposited thereon and therein by ion exchange techniques.

Abstract: Certain acidic heterogeneous catalysts produce large yields of benzene, toluene and xylene from alkyl aromatics of at least nine carbon atoms by a mechanism different from the classical disproportionation reaction characteristic of acid catalysts. These catalysts are characterized by a zeolite of the ZSM-5 type or zeolite ZSM-12 or zeolite ZSM-21. The reaction has the unique function of providing aliphatic by-products of higher molecular weight than is to be expected by splitting side chains from benzene rings. Typically, aromatic mixtures so derived from such charge stocks have unusually low content of ethyl benzene, thus greatly simplifying separation of xylene isomers.