Recovery of p-xylene and benzene from eight carbon atom aromatic fractions

Claim 1

In a process for recovery of p-xylene from a fresh feed of eight carbon atom alkyl aromatic compounds including ethyl benzene and the three xylene isomers by separating p-xylene from a mixture of said fresh feed with xylene recycle as hereinafter defined, subjecting the mixture depleted of p-xylene to isomerization by contact with hydrogen in the presence of a catalyst consisting essentially of a metal having hydrogenation/dehydrogenation catalyst properties and a crystalline aluminosilicate zeolite having a silica/alumina ratio of at least 12 and a constraint index of about 1 to about 12, separating hydrogen from the isomerate so produced, recycling separated hydrogen to the feed to the isomerization step, separating C 9 + and C 7 - hydrocarbons from the hydrogen free isomerate and adding the remaining C 8 hydrocarbons to said fresh feed as said xylene recycle; the improvement which comprises conducting said isomerization at a temperature of about 550° to 700° F., admixing the separated C 9 + hydrocarbons with hydrogen, contacting the hydrogen/C 9 + mixture with a porous acidic solid catalyst at a temperature of about 750° to 900° F., blending the product of such contacting with said isomerate, and recycling a portion of said separated hydrogen to admixture with said C 9 + hydrocarbons.