Numerical Simulation of p-Xylene Synthesis via Selective Toluene Disproportionation over Modified ZSM-5 Catalyst

Abstract

Numerical modeling of selective toluene disproportionation reaction over modified ZSM-5 zeolites to produce p-Xylene was developed and validated. The results of parametric analysis using the authenticated model provide an optimum guideline for the selection of appropriate operating conditions to achieve maximum toluene conversion and p-Xylene selectivity and yield. The predicted data indicate that increasing feed temperature from 450 to 600°C at constant (WHSV)-1 enhances the toluene conversion by 150%. Low weight hourly space velocities ((WHSV)-1=100 g.h/mol) and feed temperature (450°C) provides 99% p-Xylene selectivity. Moreover, at constant feed temperatures of 450, 500, 550 and 600°C, the maximum p-Xylene yield (? 0.087) occurs at 1300, 650, 330, and 175 g.h/mol, respectively, which clearly demonstrates that operation at higher feed temperature reduces the needed reactor residence time. Despite of imposed adiabatic condition, the model prediction demonstrates that an almost isothermal behavior prevails inside the reactor (2°C decrease in reactor temperature) due to the low heat of reaction (<1kJ/mol).