Response surface optimization of toluene disproportionation over mordenite catalyst under hydrogen atmosphere

Abstract

The catalytic disproportionation of toluene with parallel transalkylation of C9 aromatics over a mordenite catalyst was investigated in a xed-bed reactor under hydrogen atmosphere, and the effects of key operating parameters were optimized using Response Surface Methodology (RSM) based on a Box–Behnken design (BBD). Six independent variables, including pressure (27.0–33.0 barg), temperature (375.0–395.0 ◦C), hydrogen-tohydrocarbon ratio (3.0–6.0 mol/mol), liquid hourly space velocity (1.50–4.50 h-1), hydrogen mole fraction (0.70–1.00), and C9 aromatic content (0–6.0 wt.%), were evaluated with respect to seven performance indicators. The developed quadratic models were statistically signicant and provided satisfactory predictive capability for most responses, while selectivity-related responses exhibited comparatively lower predictive accuracy. Within the investigated experimental domain, multi-response optimization identied the highestdesirability solution at approximately 394.5 ◦C, 27.0 barg, H2/HC ratio of 3.02, LHSV of 1.63 h-1, hydrogen mole fraction of 0.70, and C9 aromatics content of 6.0 wt.%. Under these conditions, the process achieved a toluene conversion of 42.12 wt.% and a combined benzene + xylenes yield of 38.78 wt.%, with para-xylene yield reaching 5.98 wt.% and xylene selectivity of 63.34 wt.%. The results demonstrate that appropriate control of reaction severity and hydrogen availability signicantly enhances aromatic yields. This study conrms the effectiveness of statistical optimization for improving the performance of mordenite catalysts in toluene upgrading processes.