Ion-Exchange Temperature Effect on Cu/HMS Catalysts for the Hydrogenation of Dimethyl Oxalate to Ethylene Glycol

A series of Cu/HMS (HMS = hexagonal mesoporous silica) catalysts, synthesized by ion exchange at temperatures from 303 to 363 K, are extensively investigated as catalysts for the hydrogenation of dimethyl oxalate to ethylene glycol. The physicochemical properties and catalytic activity are compared with those of a catalyst prepared by the conventional impregnation method. Characterization of the Cu/HMS catalysts shows that the surface and textural structure of the HMS support as well as the dispersion and nature of copper species depend strongly on the ion-exchange temperature. Temperature-programmed reduction patterns reveal the presence of three types of copper species. N2O titration experiments show that the catalyst prepared by ion-exchange treatment at 333 K has the highest metallic copper surface area. A 98% ethylene glycol yield is attained over the catalyst ion-exchanged at 333 K, illustrating that an optimum ion-exchange temperature is beneficial for the generation of copper catalysts with enhanced activity.