Synthesis of xylene over cerium modified large pore zeolite: A kinetic study

Abstract

Synthesis of xylene by transalkylation of 1, 2, 4 trimethylbenzene with toluene over cerium modified beta zeolite has been investigated in the present study. The reaction has been carried out in a fixed bed down-flow reactor. The effect of various process parameters: temperature (623-723K), reactant ratio (0.5-4) and space time (0.88-2.9 kg h/kmol), on the toluene conversion and xylene selectivity are investigated. Zeolites with different amount of cerium loading (4.12 wt%, 6.54 wt%, 8.1 wt% and 10.34 wt%) have been prepared and characterized. Zeolite having 8.1wt% cerium loading is proved to be the most active catalyst. Maximum toluene conversion of 58.77% is achieved at a temperature-698K, reactant ratio–3:1, space time-2.9 kg h/kmol. The kinetic runs have been carried out to choose the zone in which the mass transfer effects are negligible. Based on product distribution, a mechanism for the formation of xylene over the modified catalyst is proposed along with a rate expression. The kinetic and adsorption constants of the rate equations are estimated by non-linear regression. The activation energy is found to be 122.41 kJ/mol which compares well with those reported in the literature for transalkylation reaction over similar catalysts.