Towards understanding the reaction network in the hydrogenation of CO2-derived ethylene carbonate

The selective hydrogenation of ethylene carbonate (EC) to produce methanol (MeOH) and ethylene glycol (EG) is a crucial route to achieve indirect and efficient utilization of CO2 under mild reaction conditions. Nonetheless, due to the cyclic carbonate structure of EC, the intricate reaction network involved in the hydrogenation process has not been systematically reported yet. Here, a series of Cu/SiO2 catalysts were designed to investigate the related reaction pathways. The catalytic evaluation results, coupled with thermodynamic calculations, reveal that there are several competitive side-reactions other than EC hydrogenation to MeOH and EG, including decarboxylation, hydrolysis and decarbonylation reactions to produce CO2 and CO as byproducts. Moreover, the distribution of products is significantly influenced by evaluation conditions. Furthermore, by doping metal oxides to adjust the surface properties of Cu/SiO2 catalyst, it is found that acidic sites could promote EC hydrolysis, whereas basic sites predominantly facilitate EC decarboxylation and decarbonylation reactions. Overall, a comprehensive reaction network of EC hydrogenation is systematically proposed to provide appropriate evaluation conditions and guidance for designing new catalysts to minimize unwanted side reactions, which is of great significance to enhance the indirect utilization of CO2.