Highly efficient supported CeO2/HMOR bicomponent catalyst for the direct synthesis of diethyl carbonate from CO2 and ethanol assisted by triethyl orthoformate hydrolysis

Abstract

The direct synthesis of diethyl carbonate (DEC) from CO2 and ethanol represents an attractive and environmentally benign approach. However, it still faces significant challenges related to CO2 activation and thermodynamic limitations. In this work, a highly efficient supported CeO2/HMOR bicomponent catalyst was developed for the synthesis of DEC from CO2 and ethanol, assisted by the hydrolysis of triethyl orthoformate (TEOF). The CeO2/HMOR bicomponent catalyst was composed of CeO2 and HMOR via a stepwise initial wet impregnation method. CeO2 is considered an effective catalyst for DEC synthesis from CO2 and ethanol, while HMOR zeolite is identified as an ideal catalyst for the TEOF hydrolysis reaction. The optimized CeO2/HMOR-25% demonstrates an excellent DEC yield of 35.38%, which is almost 15 times that obtained using pure CeO2 (2.36%). Through the study of structure–performance relationship, it was found that the synergistic combination of CeO2 and HMOR zeolite can significantly enhance the DEC synthesis rate by timely removing the generated water through the TEOF hydrolysis reaction. The closer proximity between CeO2 and HMOR promotes the transfer of H2O molecules from the CeO2 surface to the HMOR surface. Meanwhile, the abundant basic sites and oxygen vacancies on the CeO2 surface enhance CO2 adsorption and activation, while the suitable acidic sites accelerate TEOF hydrolysis, thereby improving both the DEC synthesis reaction rate and yield. This study introduces an efficient catalytic system for the direct synthesis of DEC from CO2 and ethanol, providing significant reference value for CO2 utilization applications.