Coking and Deactivation of H-ZSM-5 Zeolites during Ethylbenzene Disproportionation: I. Formation and Location of Coke

Influence of zeolite crystals external surface modification on toluene para- disproportionation selectivity

A series of catalysts with the deactivated external surface on the basis of HZSM-5 have been prepared by extracting aluminium atoms from zeolite crystals or by covering this zeolite surface by the products of tetraethoxysilane thermal destruction. The external surface deactivation has been found to be not the main factor of increasing the para-selectivity in the reaction of toluene to benzene and p-xylene disproportionation: decreasing the diffusion of o- and p-xylene from the catalyst pores on the external surface of zeolite crystals seems to be as the determinant.