Vapor-phase alkylation of toluene by benzyl alcohol on H 3PO 4-modified MCM-41 mesoporous silicas

Abstract

Several mesoporous aluminosilicate molecular sieves with the MCM-41 structure (SiO 2/Al 2O 3 = 20–200) have been synthesized using different aluminum sources and modifying several synthesis parameters during the preparation process, such as the temperature and the content of water and sulfuric acid in the gel mixture. All samples were characterized by element chemical analysis, X-ray diffraction, N 2 physisorption, thermal analyses, and electron microscopy. These Al-MCM-41 materials have BET surface areas up to 940 m 2 g −1. The catalytic properties of their H 3PO 4-treated derivatives for Friedel–Crafts alkylation of toluene with benzyl alcohol have been evaluated. Toluene benzylation preferentially gave p-benzyl-toluene. The conversion of toluene to monoalkylated products increased with increasing the H 3PO 4 content in the catalysts and reached a maximum value for a H 3PO 4 loading of 25%, a further increase in H 3PO 4 leading to a decrease in the activity for alkylation. The influence of H 3PO 4 loading and of the operating parameters on the performance of the catalysts was also investigated.