Effect of boric oxide doping on the stability and activity of a Cu-SiO2 catalyst for vapor-phase hydrogenation of dimethyl oxalate to ethylene glycol

Stable and efficient B-Cu-SiO2 catalysts for the hydrogenation of dimethyl oxalate (DMO) to ethylene glycol were prepared through urea-assisted gelation followed by postimpregnation with boric acid. Auger electron spectroscopy and CO adsorption by in situ Fourier transform infrared spectroscopy revealed that the Cu+ species on the catalyst surface increased together with an increase in the amount of boric oxide dopant. X-ray diffraction and N2O chemisorption indicated that a suitable amount of boric oxide doping tended to improve copper dispersion and retard the growth of copper particles during DMO hydrogenation. Catalytic stability was greatly enhanced in the B-Cu-SiO2 catalyst with an optimized Cu/B atomic ratio of 6.6, because of the formation and preservation of appropriate distributions of Cu+ and Cu-0 species on the catalyst surfaces. The effect of boric oxide was attributed to its relatively high affinity for electrons, which tended to lower the reducibility of the Cu+ species. (C) 2010 Elsevier Inc. All rights reserved.