Catalytic activity comparison of Zr-SBA-15 immobilized by a Bronsted-Lewis acidic ionic liquid in different esterifications

Zirconium-incorporated SBA-15 mesoporous molecular sieves (Zr-SBA-15) with different Si/Zr molar ratios were one-pot synthesized and characterized by XRD, TEM and N-2 physical adsorption. The Bronsted-Lewis acidic ionic liquid 1-(3-sulfonic acid)-propy l-3-methylimidazole chlorozincinate ([mim-ps] Cl-ZnCl2) was prepared by a hydrothermal process and its acidity was measured by FT-IR spectroscopy using acetonitrile and pyridine as probes. The Zr-SBA-15 catalyst immobilized by [mim-ps] Cl-ZnCl2 (Zr-SBA15/[ mim-ps] Cl-ZnCl2) was prepared by a wet impregnation method and characterized by XRD, BET, FTIR spectroscopy, TEM, XPS and TG. In particular, the catalytic activities of Zr-SBA-15 and Zr-SBA-15/[mim-ps] Cl-ZnCl2 in the esterification of acetic acid were evaluated with n-butyl alcohol (n-BuOH), benzyl alcohol (BnOH) and cyclohexanol (Naxol). The results show that Zr-SBA-15/[mim-ps] Cl-ZnCl2 exhibited enhanced catalytic properties compared to Zr-SBA-15. Under optimal conditions, the acetic acid conversion over Zr-SBA-15/[mim-ps] Cl-ZnCl2 reached 89.7, 93.6, and 84.9% for n-BuOH, BnOH and Naxol, respectively. After 5 cycles, the acetic acid conversion decreased slightly. Zr-SBA-15/[mimps] Cl-ZnCl2 was found to be an outstanding catalyst for esterification.