Acylation of 2-Methoxynaphthalene and Isobutylbenzene over Zeolite Beta

Abstract

The acylation of 2-methoxynaphthalene (2MN) with acetic anhydride is carried out in the liquid phase in the presence of zeolite beta. Two main products, 1-acetyl-2-methoxynaphthalene (1,2-AMN) and the desired 2-acetyl-6-methoxynaphthalene (2,6-AMN) are obtained. Variations of reaction temperature, the concentration of the acylating agent, and the weight of the catalyst are investigated to find reaction conditions sufficient to provide for good conversion of 2MN and limited deactivation. Surface-poisoning experiments show that the formation of 1,2-AMN occurs on the external surface of the zeolite. When the external surface of zeolite beta is passivated by coating with amorphous silica, a significant increase in the selectivity of 2,6-AMN is observed and this result is a clear example of shape-selective acylation with zeolite catalysts. The acylation of isobutylbenzene with acetic anhydride is investigated also. At conversions of around 10%, the selectivity to 4-isobutylacetophenone is excellent (>97%). For the acylation of isobutylbenzene, the external surface of the zeolite contributes significantly to the formation of 4-isobutylacetophenone, so the shape-selective properties of the zeolite are not utilized.