Surface modification of HMS material with silica sol leading to a remarkable enhanced catalytic performance of Cu/SiO2

Cu/SiO2 catalysts with different bimodal pore structures adjusted by the ratio of HMS and silica sol were prepared via modified impregnation method. Structure evolutions of the catalyst were systematically characterized by N2-physisorption, X-ray diffraction, H2 temperature-programmed reduction, N2O titration and X-ray photoelectron spectroscopy. The results show that the composite silica supported copper catalysts showed remarkably enhanced catalytic performance in the selective hydrogenation of dimethyl oxalate to ethylene glycol compared to the individual silica supported ones obtained by the same method. The dimethyl oxalate conversion and the ethylene glycol selectivity can reach 100% and 98% at 473 K with 2.5 MPa H2 pressure and 1.5 h−1 liquid hour space velocity of dimethyl oxalate over the optimized Cu/SiO2 catalyst. The remarkably enhanced catalytic performance of Cu/SiO2 catalysts might be attributed to the homogeneous dispersion and uniformity of the active copper species and to the larger copper surface areas attained on the HMS supports with large pore diameters and surface areas.