Surface Amine Species Promoted Cu/SiO2 Catalysts for the Hydrogenation of Dimethyl Oxalate to Ethylene Glycol

Hydrogenation of dimethyl oxalate (DMO) to ethylene glycol(EG)is a critical step in the syngas-to-EG route. Cu/SiO2 catalystsprepared by ammonia-evaporation method exhibited stable and highlydispersed copper species during the DMO hydrogenation which has beenused in the industry. However, the catalytic activity and the selectivityof EG require further enhancement. Herein, we prepared a series ofsurface modified Cu/SiO2 catalysts with amine species bypostgrafting method using organic silane coupling agents. Detailedcharacterizations indicated that the introduced amine species couldreduce the amounts and intensity of basic sites, contributing to thereduction of byproducts (C-3-C4OH) selectivity,and consequently improve the EG selectivity. The amine species alsoshowed an electron-donating effect and significantly increased theproportion of Cu-0 species. Meanwhile, it is demonstratedthat there was a linear correlation between the TOFCu andmedium-strong basic sites induced by amine species, indicating thesynergistic catalysis between copper species and medium-strong basicsites accounted for the superior catalytic activity in DMO hydrogenation.These insights into the effects of the introduction of amine speciescould lead to new possibilities for the improvement of Cu/SiO2 catalysts for ester hydrogenations toward industrial applications.