Enhanced Selectivity and Stability of Cu/SiO2 Catalysts for Dimethyl Oxalate Hydrogenation to Ethylene Glycol by Using Silane Coupling Agents for Surface Modification

• Published in: Industrial & engineering chemistry research Vol. 59; no. 20; pp. 9414 - 9422
• Main Authors: Wang, Meilin, Yao, Dawei, Li, Antai, Yang, Youwei, Lv, Jing, Huang, Shouying, Wang, Yue, Ma, Xinbin
• Format: Journal Article
• Language: English
• Published: American Chemical Society 20-05-2020
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/acs.iecr.0c00789

Hydrogenation of dimethyl oxalate (DMO) is one of the key steps in the route of ethylene glycol (EG) production from syngas. Cu/SiO2 catalysts prepared by the ammonia evaporation method are reported to present excellent catalytic performance for selective DMO hydrogenation and used in industry. However, the selectivity of EG and the long-term stability of catalysts still require improvement. Herein, we used silane coupling agents to selectively and efficiently cover the surface isolated hydroxyl groups on Cu/SiO2 by the post-grafting method, which exhibited a prominently promotion effect on reducing the selectivity of by-products (C3-C4OH) and enhancing the catalytic stability. Characterization results suggested that both the density and intensity of the basic sites decreased significantly after the coverage of hydroxyl groups, resulting in the reduction of C3-C4OH selectivity, thus increasing the EG selectivity. Meanwhile, the coke and blocked pore structure induced by excessive methyl glycolate (MG) adsorption and polymerization on surface hydroxyl groups could be the main reason for catalyst deactivation. After the surface modification, MG desorption was greatly facilitated, which improved the stability in DMO hydrogenation. Furthermore, the effect of different silane coupling agents ended with amino or alkyl groups was studied as well. These insights concerning the effect of covering hydroxyl groups by silane coupling agents on selectivity and stability may provide practical guidance for the design and fabrication of Cu/SiO2 catalysts for the industrial application.