Effect of the Cu/SBA-15 catalyst preparation method on methyl acetate hydrogenation for ethanol production

Methyl acetate (MA) hydrogenation to ethanol was investigated over SBA-15 supported copper (Cu/SBA-15) catalysts prepared by different methods, including impregnation, deposition precipitation, and homogeneous deposition precipitation. The catalysts were characterized by means of the Brunauer-Emmett-Teller method, X-ray diffraction, transmission electron microscopy, temperature-programmed reduction and X-ray photoelectron spectroscopy. Of the three catalysts, it was found that the Cu/SBA-15 catalyst prepared by the homogeneous deposition precipitation method has the smallest particle size, and the appropriate Cu+/(Cu+ + Cu-0) molar ratio of 53.5%. The high dispersion of the active components, and the synergetic effect between Cu-0 and Cu+ contributed to the high activity of Cu/SBA-15 prepared via the homogeneous deposition precipitation method. A MA conversion of 93.6% with an ethanol selectivity of 98.5% was obtained for MA hydrogenation in methanol solution under mild reaction conditions. Both of these values were much higher than those obtained over catalysts prepared by the other two methods. The catalyst still maintained good performance in the co-hydrogenation of acetic acid and MA in methanol solution. A high MA conversion of 99.5% and an ethanol selectivity of 99.5% were obtained for pure MA hydrogenation over the best catalyst. It was found that methanol solution inhibited the conversion of MA, and suppressed the side reaction of MA trans-esterification with the product ethanol at higher LHSV.