Vacant cerium oxide-catalyzed synthesis of dimethyl carbonate from CO2

Abstract

Given the increasing global focus on climate change and the pressing need to reduce greenhouse gas emissions, the efficient conversion and utilization of CO2 have become pivotal research areas in chemical engineering and catalysis. However, the high thermodynamic stability and low reactivity of CO2 present significant challenges in its conversion processes, making the development of efficient and stable catalysts essential. This study investigates the application of cerium oxide (CeO2) catalysts in the direct esterification of CO2 and methanol for the synthesis of dimethyl carbonate (DMC). CeO2 catalysts with different morphologies (spherical and cubic) were synthesized and characterized using advanced techniques such as X-ray photoelectron spectroscopy (XPS). The results show that hydrogen treatment significantly increases the concentration of oxygen vacancies on the catalyst surface, thereby enhancing its catalytic activity. Experimental data reveal that the spherical CeO2 catalyst treated with hydrogen at 500 °C achieves the highest DMC yield, reaching 16.31 mmol/g, with excellent stability maintained over multiple cycles. Secondary kinetic isotope effect (SKIE) experiments further demonstrate that C–H bond cleavage is not the rate-determining step, confirming the crucial role of oxygen vacancies in the reaction mechanism. A detailed reaction pathway analysis reveals the key intermediates involved in DMC synthesis and elucidates the substantial enhancement of catalytic performance resulting from hydrogen treatment. This study provides theoretical insights into the industrial application of CeO2 catalysts for CO2 conversion and opens new avenues for the optimization of catalytic materials.