Effects of Cu/n-Type Semiconductor Oxides on Isopropyl Acetate Hydrogenation

Ethanol and isopropanol were prepared via hydrogenation of isopropyl acetate catalyzed by six different copper-based catalysts (CuO-ZnO, CuO-Fe₂O₃, CuO-CeO₂, CuO-TiO₂, CuO-BaO and CuO-SnO₂, respectively). All of the catalysts were prepared by co-precipitation and their physiochemical properties were characterized by X-ray diffraction(XRD), H₂-temperature-programmed reduction(TPR), N₂O oxidation titration, inductively coupled plasma(ICP) element analysis, NH₃-temperature-programmed desorption(TPD) and X-ray photoelectron spectroscopy(XPS). Effects of different oxides on copper dispersion, specific surface area of copper active sites, surface acidity, copper binding energy and catalytic reaction were investigated.Results show that the catalytic activity is different with an order of Cu-ZnO > Cu-Fe₂O₃ > Cu-CeO₂ > Cu-TiO₂ > Cu-BaO > Cu-SnO₂. Cu-ZnO shows the best catalytic activity as it has the lowest reduction temperature, the highest copper dispersion and specific surface area of active sites, the smallest particle size and the strongest binding energy. Moreover, it shows the highest ethanol selectivity and lowest ethyl acetate selectivity due to the lowest acidity. Cu-BaO and Cu-SnO₂ show poor catalytic activity due to their formation of copper barium composite oxide and copper-tin alloy after reduction. Cu-Fe₂O₃ shows good ethanol selectivity due to its lower acidity.