Surface Amine Species Promoted Cu/SiO<sub>2</sub> Catalysts for the Hydrogenation of Dimethyl Oxalate to Ethylene Glycol
Meilin Wang, Shixin Hou, Youwei Yang, Ziheng Zhen, Jing Lv, Shouying Huang, Yue Wang, Xinbin Ma
Abstract
Hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG) is a critical step in the syngas-to-EG route. Cu/SiO 2 catalysts prepared by ammonia-evaporation method exhibited stable and highly dispersed copper species during the DMO hydrogenation which has been used in the industry. However, the catalytic activity and the selectivity of EG require further enhancement. Herein, we prepared a series of surface modified Cu/SiO 2 catalysts with amine species by postgrafting method using organic silane coupling agents. Detailed characterizations indicated that the introduced amine species could reduce the amounts and intensity of basic sites, contributing to the reduction of byproducts (C 3 –C 4 OH) selectivity, and consequently improve the EG selectivity. The amine species also showed an electron-donating effect and significantly increased the proportion of Cu 0 species. Meanwhile, it is demonstrated that there was a linear correlation between the TOF Cu and medium-strong basic sites induced by amine species, indicating the synergistic catalysis between copper species and medium-strong basic sites accounted for the superior catalytic activity in DMO hydrogenation. These insights into the effects of the introduction of amine species could lead to new possibilities for the improvement of Cu/SiO 2 catalysts for ester hydrogenations toward industrial applications.