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

Abstract

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 N₂ physical adsorption. The Brønsted–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–SBA-15/[mim-ps]Cl–ZnCl₂) was prepared by a wet impregnation method and characterized by XRD, BET, FT-IR 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/[mim-ps]Cl–ZnCl₂ was found to be an outstanding catalyst for esterification.