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

摘要

Cu_x-Fe_y/SiO_2 catalysts were prepared using urea-assisted sol-gel method.The structure and physicochemical properties of the catalysts were characterized using N_2 adsorption-desorption,transmission electron microscopy,H_2-temperature-programmed reduction,powder X-ray diffraction,and X-ray photoelectron spectroscopy.Compared with monometallic Cu or Fe catalysts,the bimetallic Cu_x-Fe_y/SiO_2 catalysts exhibited enhanced catalytic performance for the selective hydrogenation of diethyl malonate to1,3-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 Cu^(2+) species,thereby increasing the Cu° 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 FeO_x species provided the additional adsorption sites for substrate molecules,and they activated the C=O bond.The improved catalytic performance of bimetallic Cu_x-Fe_y/SiO_2 catalyst was mainly attributed to the synergistic effect between Cu° and FeO_x species.