Preparation, characterization and catalytic properties of SBA-15-SO3H supported tungstophosphoric acid for esterification reaction

Abstract

SBA-15-SO3H supported tungstophosphoric acid (TPA, H3PW12O40) mesoporous materials were synthesized by impregnation of TPA into the hydrothermally synthesized SBA-15-SO3H and the catalytic performances were compared for the esterification reaction. The physical and chemical properties of the catalysts were characterized by XRD, SEM/EDX, FT-IR and N2 adsorption/desorption techniques. The characterization results show that TPA/SBA-15-SO3H retained the typical mesoporous structure of SBA-15-SO3H. The experimental results indicated that TPA/SBA-15-SO3H is a more efficient catalyst than SBA-15-SO3H for the esterification reaction. The higher activity of TPA/SBA-15-SO3H compared with that of SBA-15-SO3H was consistent with the material having the low pKa value, confirming that the esterification rate was mostly dependent on the acid strength of the additional functional groups of solid acid catalyst. Accordingly, the reason for the catalytic activity difference was simply explicated by the effect of TPA, having low pKa value, affecting the pore structure and the total acidity.