Influence of zeolite composition on the selectivity of alkylation reactionfor the synthesis of p-isobutylethylbenzene: a computational study

In this paper, we describe our computational approach to understand the fac tors influencing the selectivity of alkylation reactions over zeolite catal ysts. Firstly, the shape, size and flexibility of the alkylated products ar e correlated to their diffusion behaviour inside zeolites. Secondly, the in fluence of pore architecture and the dimension of various large pore zeolit es on diffusion characteristics of alkylaromatics are brought out. Further, we study the isomorphous substitution of Al, Ga or B in the place of Si an d their consequent influence in the selectivity of alkylation reaction. We apply hard-soft acid-base (HSAB) principle which provides the properties to describe the acidity and reactivity of zeolites. The analysis of the resul ts indicates that the shape selectivity in the alkylation reaction is also controlled by the molecular orbital properties in addition to the geometry constraints. (C) 1999 Elsevier Science B.V. All rights reserved.