KINETICS OF ZEOLITE-CATALYZED TOLUENE DISPROPORTIONATION

Y zeolites containing 0-6% Ni were prepared and tested as model disproportionation catalysts at 613-774 K and toluene partial pressures to 0.43 bar with H2as the carrier gas. At these conditions deactivation was slow, side reactions insignificant, and intraparticle concentration gradients negligible; similar results were obtained in some cases when disproportionation kinetics data from other studies were examined. All kinetics data shown to be characteristic of the intrinsic disproportionation were fitted to a set of 42 Langmuir-Hinshelwood rate models, which were derived assuming previously proposed alkyl-transfer and biphenylalkane mechanisms. Most of the data were adequately fit by a second-order rate expression with toluene inhibition, which is in accord with previous findings for non-zeolite solid acid catalysts. These results are in contrast to previous work on Cu/AlF3-Y zeolites, which follow a first-order rate expression with toluene inhibition; possible reasons for the disagreement are discussed. © 1990, American Chemical Society. All rights reserved.