8194
Ind. Eng. Chem. Res. 2004, 43, 8194-8199
O Methylation of Phenol in Liquid Phase over Basic Zeolites Marı´a D. Romero, Gabriel Ovejero, Araceli Rodrı´guez, Jose´ M. Go´ mez,* and Ismael A Ä gueda Department of Chemical Engineering, Faculty of Chemistry, Complutense University of Madrid, Madrid 28040, Spain
Liquid-phase O methylation of phenol was carried out with dimethyl carbonate (DMC) over as-synthesized KNaX zeolite with impregnated alkaline metal hydroxides. The presence of alkaline hydroxides is associated with hydroxysodalite impurity in the X zeolite. This zeolite exhibited better properties as basic catalyst than those prepared by postsynthesis treatments (ionic exchange). Phenol conversion and selectivity toward anisole were 100% and 85%, respectively, at 438 K with a DMC/phenol molar ratio of 2. The crystallinity and composition of the KNaX zeolite were retained after reaction, making it possible to recover the catalyst without loss of the impregnated alkaline hydroxides during the reaction. The reactivation of the KNaX zeolite was carried out at low temperature (373 K), achieving the same conversion and selectivity to anisole in the phenol methylation as in the first reaction. 1. Introduction In recent years, considerable emphasis has been placed on improvement in the environmental impact of industrial chemical processes.1 It is well recognized that solid catalysts can play a significant role in the development of cleaner technologies. As such, one may expect that in the future an important development in this field will be carried out. Of particular interest will be the exploitation of heterogeneous catalysts to replace currently used homogeneous catalysts. These catalysts can work with the same activity and even better selectivity without the formation of byproducts and wastes more usually associated with homogeneous catalysis. Among the materials that can be used as heterogeneous catalysts are zeolites. Zeolites are aluminosilicates with crystalline structure and pore size in the microporous range (
