Synergistic effects of bimetallic Cu-Fe/SiO2 nanocatalysts in selective hydrogenation of diethyl malonate to 1,3-propanediol

Abstract

CuxFey/SiO2 catalysts were prepared using urea-assisted sol−gel method. The structure and physicochemical properties of the catalysts were characterized using N2 adsorption–desorption, transmission electron microscopy, H2-temperature-programmed reduction, powder X-ray diffraction, and X-ray photoelectron spectroscopy. Compared with monometallic Cu or Fe catalysts, the bimetallic CuxFey/SiO2 catalysts exhibited enhanced catalytic performance for the selective hydrogenation of diethyl malonate to 1,3-propanediol. The bimetallic catalyst with an optimal Cu/Fe atomic ratio of 2 exhibited the highest activity, which yielded 96.3% conversion to diethyl malonate and 93.3% selectivity to 1,3-propanediol under the optimal reaction conditions. Characterization results revealed that interactions between Cu and Fe contributed to the improvement of diethyl malonate conversion and selectivity to 1,3-propanediol. The X-ray photoelectron spectroscopy results revealed that the addition of appropriate amount of Fe species enhanced the reduction of Cu2+ species, thereby increasing the Cu0 species on the surface of bimetallic catalyst. It led to a better chemisorption capacity of hydrogen and further promoted of the activation of hydrogen molecule. The ethyl acetate temperature-programmed desorption results indicated that the FeOx species provided the additional adsorption sites for substrate molecules, and they activated the CO bond. The improved catalytic performance of bimetallic CuxFey/SiO2 catalyst was mainly attributed to the synergistic effect between Cu0 and FeOx species.