Transition through various regimes of reaction kinetics and selectivity driven by progressing modification of the external surface of zeolites

Abstract

HZSM5 crystals were silanised in a novel stepwise manner. This technique led to a stepwise increase of the amount of material, which was deposited on the external surface of the crystals, resulting in a stepwise inactivation of the external surface and simultaneous pore mouth narrowing. A set of model reactions was selected, which covered a wide range of spatial demands, in order to analyse and monitor the effect on the catalytic performance of the zeolite. The paper presents the fundamental relations between the variation of catalytic activity and specifity and the modification of the external surface of HZSM5 zeolite crystals by deposition of non-active material.