Synthesis and characterization of supported copper phyllosilicate catalysts for acetic ester hydrogenation to ethanol

Supported copper phyllosilicate (Cu/SiO2) catalysts were prepared by a simple co-precipitation method (CP), and compared with the urea hydrolysis deposition–precipitation method (DP) in terms of phase evolution during synthesis, physicochemical properties, chemical states of copper species after reduction, and catalytic performance in ester hydrogenation to ethanol. Catalysts were characterized by N2-physisorption, X-ray powder diffraction (XRD), IR spectroscopy, H2 temperature programmed reduction (TPR), transmission electron microscopy (TEM), in situ X-ray photoelectron spectroscopy (XPS), and FTIR/CO spectroscopy. It was confirmed that copper phyllosilicates species existed in all catalysts but the exact form differed in the Cu-CP catalysts and the Cu-DP catalysts. While the Cu-DP catalyst favored the form of 1:1 copper phyllosilicate, the Cu-CP catalysts tended to have more species of 2:1 copper phyllosilicate which led to only small amount of active copper species on surface after reduction and thus low ester conversion. Addition of ammonium ion and zinc ion during the CP method synthesis promoted the copper silicate phase evolution from 2:1 copper phyllosilicate to 1:1 copper phyllosilicate, and the reactivity of ester hydrogenation was greatly enhanced. Conversion of 99.67%, selectivity of 99.07%, and space-time yield of 1.23 g_EtOH/(g_cat·h) were achieved at 250 °C using a Cu–Zn-NCP catalyst.