Formation of acid sites in ordered pores of FSM-16 by modification with sulfated zirconia

Abstract

A mesoporous solid acid with ordered mesopores was prepared by modification of FSM-16 with sulfated zirconia (SO 4 2−/ZrO 2/FSM-16); FSM-16 precalcined at 1123 K was soaked with an ethanol solution of zirconyl chloride, followed by exposing to 0.5 mol dm −3 H 2SO 4 and calcining in air at 873 K. Measurements of XRD and nitrogen adsorption isothermo showed the structure to contain the ordered pores, though its surface area and total pore volume were reduced to 619 m 2 g −1 and 376 cm 3 g −1 compared with 886 m 2 g −1 and 490 cm 3 g −1 for the unmodified FSM-16. The acid sites of zirconia promoted by sulfate ions were formed inside of the ordered pores. The activity of (SO 4 2−/ZrO 2/FSM-16) for 1-butene isomerization was nine times larger than that of the unmodified FSM-16. Two more acid-catalyzed reactions producing relatively large molecules were examined and catalytic activities of SO 4 2−/ZrO 2/FSM-16 were compared with those of sulfated zirconia (SO 4 2−/ZrO 2), which is one of the solid superacids. The activities for Mukaiyama aldol condensation of 1 trimethylsilyloxycyclohexene with benzaldehyde were comparable to each other, but the Friedel–Crafts benzoylation of toluene with benzoyl chloride or benzoic anhydride revealed the present catalyst to be much inferior to the sulfated zirconia for lack of superacidity.