Three stage process for obtaining a xylene isomer from a 7-10 carbon aromatic cut by stages of transalkylation, separation and isomerization

摘要

The initial transalkylation stage enables the use of a recyclate comprising 9-10 carbon (C) aromatics after elimination of heavy coke precursor aromatics. Process for the production of a xylene isomer comprises: (a) introduction of the 7-10C aromatic charge, optionally mixed with the effluent from the isomerization zone into a two column distillation zone to recover a fraction comprising most of the 8C aromatics, a fraction containing most of the 9C aromatics and a fraction comprising the main part of the 10C aromatics containing most of the heavy aromatic coke precursors; (b) treatment of the 9C fraction from (a), toluene (fresh or recycled) and a 9C/10C recyclate in a catalytic transalkylation zone; (c) treatment of the effluent from the transalkylation zone in a distillation zone to withdraw fractions rich in benzene, toluene (partly recycled to the transalkylation zone) and an 8C aromatic fraction(partly recycled to the transalkylation zone) and a fraction comprising 10C + aromatics; (d) treatment of the 8C enriched aromatic fraction from (c), optionally part of the effluent from the isomerization zone, and the fraction from (a) in a xylene separation zone, to recover a primary isomer-enriched fraction and a second fraction depleted in the required isomer; and (e) treating the isomer-depleted fraction in a catalytic xylene isomerization zone in the presence of a catalyst comprising a EUO-type zeolite and group VIII element, to produce an effluent comprising the xylene isomers; the effluent is partly recycled to the inlet of the separation zone and/or to the entry of the distillation zone described in (a).