Preparation, Characterization and Catalytic Properties of SBA-15-SO₃H Supported Tungstophosphoric Acid for Esterification Reaction

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.