Modeling of para-Xylene Synthesis via Nonselective Toluene Disproportionation

Abstract

The effective parameters on p-Xylene yield in the nonselective disproportionation reaction over unmodified ZSM-5 catalyst were investigated using the validated model developed in this study. The results of this study indicate that toluene conversion and benzene/xylene ratio is increased by increasing feed temperature and reactor residence time. Even though an adiabatic operation is applied, an almost isothermal reactor temperature profile is predicted by the model due to the low heat of reaction. At different feed operating temperatures, different maximum para-Xylene yields are reached at different weight hourly space velocities (WHSV)-1. Since the model numerical predictions demonstrate that the lower feed temperature requires larger reactor to obtain the maximum p-Xylene yield, therefore, selection of optimum conditions is a function of two independent variables, feed temperature, and (WHSV)-1, and should be selected in order to minimize the objective function of total manufacturing and operating costs.