Effect of Pd Doping on the Cu 0 /Cu + Ratio of Cu‐Pd/SiO 2 Catalysts for Ethylene Glycol Synthesis from Dimethyl Oxalate

The Cu 0 /Cu + ratio is very important in many copper‐catalyzed reactions. A series of Cu−Pd/SiO 2 catalysts were prepared by composite evaporation of ammonia with subsequent Pd impregnation. The Cu 0 /Cu + ratio could be controlled by changing the Pd content in the catalysts during reduction. The catalysts were applied to the hydrogenation of dimethyl oxalate, and experimental results showed that a suitable amount of Pd doping remarkably improved the activity and prolonged the lifetime of the catalyst. The optimized Cu‐0.5 % Pd/SiO 2 catalyst showed complete conversion with 96.0 % ethylene glycol selectivity over a lifetime of 300 h. Enhancements in the activity and stability of the Cu−Pd/SiO 2 catalysts were ascribed to the stable generation of hydrogen spillover, which tended to adjust the Cu 0 /Cu + ratio with changes in Pd content in the reduced catalysts. Hydrogen spillover also promoted the release of intermediates in contact with Cu + to inhibit copper sintering.