A series of metal oxide supported tungstophosphoric acid catalysts were prepared by impregnation. The physicochemical and acidic properties of these materials were characterized by a variety of different analytical and spectroscopic techniques, namely Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) method, and nuclear magnetic resonance (NMR), and exploited as heterogeneous catalysts for selective oxidation of benzyl alcohol (BzOH) with hydrogen peroxide (H2O2). Among them, 20 wt.% H3PW12O40/CeO2 catalyst exhibited the best oxidative activity. Further process optimization by response surface methodology (RSM) based on the Box-Behnken design model resulted in a benzyl alcohol conversion of 95.2% and a benzaldehyde yield of 94.2% with 98.9% selectivity, in good agreement with the experimental results. Kinetic studies based on an irreversible parallel reaction model led to an activation energy (Ea) of 44.73 kJ mol-1.
Keywords:
ceria; heteropolyacid; oxidation; reaction engineering; process optimization
