Enhanced Ethylene Glycol Selectivity of CuO–La2O3/ZrO2 Catalyst: The Role of Calcination Temperatures

The CuO–La2O3/ZrO2 catalysts calcined at different temperatures from 500 to 800 °C were studied for the hydrogenation of oxalates to ethylene glycol (EG). Along with the increase of calcination temperatures, the BET surface area, pore volume, and Cu dispersion decreased, whereas the crystallite sizes of Cu species increased. Interestingly, the superior performance such as a 98% selectivity of EG in dimethyl oxalate hydrogenation or a 96.5% selectivity of EG in diethyl oxalate hydrogenation was obtained over the catalyst calcined at 700 °C. Essentially, the surface synergism between Cu species and monoclinic ZrO2 was enhanced by the higher calcination temperature, resulting in the remarkable surface adsorption and activation of H2. Besides, the increase of calcination temperature significantly reduced the surface acidity and basicity, which could effectively suppress the byproduct formation.