Molecular modeling studies on zeolite catalysts for shape-selective electrophilic substitution: I acylation of 2-methoxynaphthalene

Abstract

The diffusion characteristics of acylated 2-methoxynaphthalene inside large pore zeolites were investigated. The interaction of the three isomers with fully siliceous zeolite lattices was studied by energy-minimization calculations. The favorable adsorption sites and the orientation of the acylated products of 2-methoxynaphthalene were analyzed in detail. Three large pore zeolites having 12 m channels were selected: (i) mordenite with an elliptical 1-d channel, (ii) zeolite-L with a circular channel and 2-d cages, and (iii) zeolite-β with circular 3-d channel systems. It was observed that the shape selectivity properties of the zeolites could be profitably used to produce 2-acyl-6-methoxynaphthalene. In the case of mordenite, the diffusion of all three isomers is facile, whereas in the case of zeolite-L, the diffusion of 1-acyl-7-methoxynaphthalene is more facile than 2-acyl-6-methoxynaphthalene and 1-acyl-2-methoxynaphthalene. In the case of zeolite-β, the energy barrier for the diffusion of 2-acyl-6-methoxynaphthalene is significantly smaller than those of the other two isomers. Thus zeolite-β is predicted to be a suitable catalyst for the shape-selective acylation of 2-methoxynaphthalene to 2-acyl-6-methoxynaphthalene.