DISPROPORTIONATION OF TOLUENE AND OF TRIMETHYLBENZENE AND THEIR TRANSALKYLATION OVER ZEOLITE-BETA

Zeolite Beta has been demonstrated as having the potential for catalysis in xylene production reactions, including toluene disproportionation, trimethylbenzene disproportionation, and toluene-trimethylbenzene transalkylation. It exhibits excellent catalytic stability and transalkylation selectivity. In trimethylbenzene disproportionation, blending toluene into feedstocks can shift the production selectivity of tetramethylbenzene to xylene, whereas in toluene disproportionation, mixing trimethylbenzene into feedstocks can not only reduce the reaction temperatures but also raise the xylene yield. The shift of reaction selectivity is discussed from the viewpoints of both thermodynamics and kinetics. A methyl group transfer model has been proposed to rationalize the enhancement of xylene production efficiency. © 1990, American Chemical Society. All rights reserved.