Preparation of Highly Dispersed Cs-Tungstophosphoric Acid Salt on MCM-41 Silica

Abstract

This paper describes a grafting technique that we developed for preparing highly dispersed Cs-tungstophosphoric acid (Cs-TPA) salt on a mesoporous silica carrier (MCM-41) using alcohols as solvents during impregnation. It is shown that this procedure leads to a novel class of catalysts with high dispersion of Cs-TPA salts which exhibit significantly improved catalytic performances for the alkylation of 1,3,5-trimethylbenzene with cyclohexene than those prepared using water as the solvent. Catalyst activity demonstrated to have a clear correlation with the type of alcohol used during impregnation which decreased in the following order: 1-butanol > 1-propanol ≈ ethanol > water. Adsorption data using molecules of various sizes suggest that our novel catalysts maintained open pore structures after the impregnation with tungstophosphoric acid (TPA). For comparison purposes, we also used a prior published method to prepare Cs-TPA on MCM-41, which seemed to have suffered unfavorable structural changes such as partial pore clogging leading to significant transport limitations for the reactants examined here.