Process for the preparation of p-xylene

A process for the manufacture of xylene from 2,2,4-trimethylpentane, comprising:

• (a) feeding to a reactor a reactor feed comprising 2,2,4-trimethylpentane and a diluent gas selected from the group consisting of methane, ethane, propane and mixtures thereof wherein the molar concentration of 2,2,4-trimethylpentane in the reactor feed is about 50% or less;
• (b) contacting, in the vapor phase, said reactor feed with a catalyst comprising chromium to produce a reactor effluent containing xylene and by-products comprising 2,2,4-trimethylpentenes, isobutane, isobutylene, and unreacted 2,2,4-trimethylpentane;
• (c) separating methane, ethane, propane or a mixture thereof from the effluent produced in step (b), and recycling the methane, ethane, propane or mixture thereof to the reactor of step (a);
• and
• (d) separating 2,2,4-trimethylpentenes and unreacted 2,2,4-trimethylpentane from the other by-products and xylene in the effluent produced in step (b), and recycling the 2,2,4-trimethylpentenes and unreacted 2,2,4-trimethylpentane to the reactor of step (a).