PROCESS FOR ISOMERIZATION OF XYLENES

摘要

A process for isomerizing xylenes, which comprises contacting an aromatic hydrocarbon feedstock containing mainly a xylene isomeric mixture containing ethylbenzene with a catalyst of a palladium-containing crystalline aluminosilicate in the vapor phase in the presence of hydrogen to continuously isomerize xylenes and simultaneously de-ethylate the ethylbenzene selectively; interrupting the isomerization reaction; introducing an oxygen-containing gas into a bed of the catalyst in which coke has been deposited during the isomerization reaction, to contact the catalyst with the oxygen-containing gas; burning off the coke deposits on the catalyst with the oxygen-containing gas by gradually increasing the temperature of introduction of the oxygen-containing gas from not more than 200 DEG C. to a temperature in the range of 330 DEG to 390 DEG C. with no part of the catalyst bed exceeding a maximum temperature of 400 DEG C. while controlling the hot spot temperature of the catalyst bed not to exceed 50 DEG C. throughout the burn-off period; reducing in hydrogen the catalyst from which the burnable coke deposits have been removed at least partly; and thereafter resuming the isomerization reaction in the presence of the regenerated catalyst.