Efficient synthesis of methanol and ethylene glycol via the hydrogenation of CO2-derived ethylene carbonate on Cu/SiO2 catalysts with balanced Cu+–Cu0 sites

Abstract

Achieving high catalytic performance with Cu-based catalysts is crucial for the hydrogenation of CO₂-derived ethylene carbonate (EC) to simultaneously yield methanol (MeOH) and ethylene glycol (EG). Although Cu-based catalysts are widely studied for the target reaction, there are still some issues to be clarified. In this study, we prepared a 29.1 wt% Cu/SiO₂-MHT catalyst by a modified hydrothermal method and successfully applied it to the hydrogenation of EC. In comparison with its three analogues having similar Cu loading and comparable Cu particle size but prepared by different methods, we found that the catalytic performance of the Cu/SiO₂ catalysts, including the activity and the selectivity to MeOH, could be tuned by adjusting the Cu⁺/(Cu⁰ + Cu⁺) ratio via different preparation methods. As a result, the Cu/SiO₂-MHT catalyst furnished 89% MeOH yield and 37.6 h⁻¹ turnover frequency. To our best knowledge, these values are one of the highest among all heterogeneous Cu catalysts up to now. The results reveal that a cooperative effect exists between Cu⁰ and Cu⁺. When the Cu⁰ species are sufficient to activate H₂, a more favorable formation of MeOH can be achieved with more Cu⁺ species and greater Cu⁺ surface areas. Furthermore, a greater amount of Lewis acid on the Cu/SiO₂-MHT catalyst is also beneficial for MeOH formation.