Influence of La-doping on the CuO/ZrO2 catalysts with different Cu contents for hydrogenation of dimethyl oxalate to ethylene glycol

Herein, Cu/ZrO2 catalysts containing different Cu contents with or without La-doping were used for the selective hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG). Effects of La addition and the optimal Cu content were thoroughly investigated. It was found that the Cu-0/Cu+ pairs located at interfacial sites for CuO/ZrO2 catalysts with different Cu contents played an important role in the hydrogenation of DMO to EG. Interestingly, the La-doping could make the copper dispersion increase obviously. Besides, it greatly inhibited the crystal phase transformation from tetragonal to monoclinic zirconia regardless of being calcined at 750 degrees C. Meanwhile, the incorporation of La promoted the activation of hydrogen although resulting in a small increase in acidic/basic sites over the catalyst surface, which led to a higher conversion of DMO while the selectivity of EG decreased slightly. As a result, 97.2% selectivity of EG, which corresponds to 100% conversion of DMO, was achieved over the La-doped CuO/ZrO2 catalyst with 33 wt% Cu content, which was also stable for more than 168 h on stream. This results revealed that the strong interaction between La promoters and Cu species was another type of important active site with high catalytic efficiency in addition to the Cu-0/Cu+ site of La-doped CuO/ZrO2 catalyst.

Automated summary

The effects of La addition and optimal Cu content on Cu/ZrO2 catalysts for selective hydrogenation of DMO to EG were investigated. La-doping effectively increased Cu dispersion and inhibited crystal phase transformation, leading to higher hydrogen activation and DMO conversion with slightly lower EG selectivity. Strong interaction between La promoters and Cu species was found to be another important active site with high catalytic efficiency in addition to Cu-0/Cu+ site on La-doped CuO/ZrO2 catalyst.