Efficient cerium oxide catalysts for the direct synthesis of dimethyl carbonate from carbon dioxide: characterization, catalytic activity, and thermodynamic studies

Abstract

Using oxygen vacancies to modify the surface properties of catalysts to enhance catalytic activity, inhibiting reverse reactions can effectively increase synthetic yield. This study presents an M-CeO₂ catalyst derived from MOF-808(Ce), which was successfully applied to the synthesis of dimethyl carbonate (DMC) under dehydration agent-free conditions. Particularly, it has been found that M-CeO₂ catalyst enables the formation of defective microporous structure in ceria catalysts, enriching the surfaces with oxygen vacancy sites, and slowing down the reverse reaction. This leads to the yield of DMC reaching 4.184 mmol/g, corresponding to a significant improvement in the conversion rate of methanol up to 1.42%. Moreover, the M-CeO₂ catalyst exhibited over 1.6 times higher methanol conversion rate than reflux-synthesized ceria nanorods, which can be attributed to their superior CO₂ adsorption and activation capability, as well as the inhibition of reverse reactions. These conclusions are supported by combined surface characterizations and thermodynamic calculations. We developed a novel method for surface engineering of catalysts whose function was combined with dehydrating agents. A possible reaction mechanism for the synthesis of DMC from CO₂ and CH₃OH on M-CeO₂ was proposed.