The Cu/SiO2 catalyst for gas-phase hydrogenation of diethyl oxalate (DEO) to ethylene glycol (EG) was prepared through the incipient wetness impregnation with the aid of complex agents (such as citric acid and ammonia) or not. The relative activity enhancement lied within the preparation of the catalyst by employment carriers having specific ranges of physical parameters, e.g., average pore diameter. For the Cu/SiO2 catalyst employed SiO2 with an average pore diameter of 3.0 nm, the selectivity and space time yield to EG of 94.6% and 0.46, which corresponded to 99.1% conversion of DEO, was achieved. In addition, the one also had excellent performance with no deactivation through severe conditions during 200 h run time. It was believed that the Cu particles with sub-3-nm size induced by spatial restriction were in favor of its superior activity; furthermore, the spatial restriction strategy by filling the Cu nanoparticles on mesoporous silica (ca. 3.0 nm of pore diameter) to conquer the sintering problem and help the stability (>200 h at 220-270 degrees C) has latent values in exothermic reactions. More interestingly, we found a close relationship between the amount of H-2-associative adsorption and the hydrogenation of DEO. Thus, the spatial restriction created by the small pores of the support was helpful to increase the proportion of the filled Cu particles (sub-3-nm) and the more metal-active sites, which afforded the enhanced H-2 activation ability. Besides, the nature of the metallic precursor derived from metal complexes interacting with the support was also important for the dispersing of metal copper particles. (C) 2015 Elsevier B.V. All rights reserved.