Process for producing p-xylene

Abstract

In a process for producing p-xylene which comprises catalytically methylating toluene with a methylating agent in the gaseous phase, the improvement wherein (a) said methylation is carried out continuously in a multi-stage reaction system consisting of a plurality of separate series-connected fixed catalyst layers without separating the resulting xylenes in an intermediate stage, (b) said toluene is fed together with hydrogen gas into only the first-stage fixed catalyst layer and passed successively through the subsequent fixed catalyst layers, the amount of toluene fed being such that the total weight hourly space velocity of toluene is from 1 to 300 hr.sup.-1, (c) said methylating agent is fed into each of said fixed catalyst layers, if desired together with hydrogen gas, the amount of the methylating agent fed into each catalyst layer being 0.01/t moles to 1/t moles, in which t is the number of methyl groups in the methylating agent, per mole of toluene fed into the first-stage catalyst layer, and the total amount of the methylating agent fed into all of the catalyst layers being within the range of 0.1/t moles to 2/t moles, in which t is as defined, per mole of toluene fed into the first-stage catalyst layer, and (d) each fixed catalyst layer is filled with a catalyst composed of a crystalline aluminosilicate containing magnesium oxide or lanthanide oxide.