Catalytic esterification of benzyl alcohol with acetic acid by zirconia-loaded on mesoporous material

Abstract

This research focuses on the synthesis and characterization of metalcontaining mesoporous silica for catalytic esterification of benzyl alcohol with acetic acid. In this study Zr-containing MCM-41 (Zr-MCM-41) with different molar ratios were synthesized successfully, and the influence of the Si/Zr molar ratio on the crystalline structure, textural properties, morphological features and surface acidity of Zr-MCM-41 mesoporous molecular sieves was investigated by X-ray diffraction (XRD), N2 adsorption-desorption measurement, SEM and FTIR (Fourier transform infrared) Spectroscopy, UV-Vis diffuse reflectance (UV-Vis DR), spectroscopy and single point BET. It is observed that the structural ordering of Zr-MCM-41 varies with the Si/Zr ratio, and highly ordered mesoporous molecular sieves could be earned for a Si/Zr molar ratio larger than 5. Calcination may significantly improve the structural regularity. After impregnation with 15 wt % of H3PW12O40 (denoted as HWP hereafter),in esterification reaction of benzyl alcohol with acetic acid, the benzyl alcohol conversion over all the HPW/Zr-MCM-41catalysts linearly increases with increasing the reaction temperature, and selectivity to benzyl acetate was 100 %. The molar ratios of reactants also were investigated for final product yield; the molar ratio of acetic acid to benzyl alcohol can be 2:1 for high yield. The presence of zirconium in tetrahedral coordination was indicated by UV-Vis DR spectra, which shows an absorption band around 220 nm in Zr-MCM41. The catalyst had more active sites than pure Si-MCM-41 due to enhanced hydrophobicity properties and the presence of framework zirconium species as Lewis active sites. Kinetics studies have shown that the esterification reaction follows the Eley-Ridel mechanism. The energy of activation for the reaction follows the order: HPW/Zr-MCM-41(Si/Zr=5) > Zr- MCM-41(Si/Zr=10) > Zr-MCM-41(Si/Zr=20).