An efficient and stable Cu/SiO2 catalyst for the syntheses of ethylene glycol and methanol via chemoselective hydrogenation of ethylene carbonate

Abstract

The efficient synthesis of methanol and ethylene glycol via the chemoselective hydrogenation of ethylene carbonate (EC) is important for the sustainable utilization of CO2 to produce commodity chemicals and fuels. In this work, a series of β-cyclodextrin-modified Cu/SiO2 catalysts were prepared by ammonia evaporation method for the selective hydrogenation of EC to co-produce methanol and ethylene glycol. The structure and physicochemical properties of the catalysts were characterized in detail by N2 physisorption, XRD, N2O titration, H2-TPR, TEM, and XPS/XAES. Compared with the unmodified 25Cu/SiO2 catalyst, the involvement of β-cyclodextrin in 5β-25Cu/SiO2 could remarkably increase the catalytic activity—excellent activity of 1178 mgEC gcat−1 h−1 with 98.8% ethylene glycol selectivity, and 71.6% methanol selectivity could be achieved at 453 K. The remarkably improved recyclability was primarily attributed to the remaining proportion of Cu+/(Cu0+Cu+). Furthermore, the DFT calculation results demonstrated that metallic Cu0 dissociated adsorbed H2, while Cu+ activated the carbonyl group of EC and stabilized the intermediates. This study is a facile and efficient method to prepare highly dispersed Cu catalysts—this is also an effective and stable heterogeneous catalyst system for the sustainable synthesis of ethylene glycol and methanol via indirect chemical utilization of CO2.