Mesostructured CeO2 as Catalyst in the Direct Synthesis of Dimethyl Carbonate

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Abstract
The direct synthesis of dimethyl carbonate (DMC) from methanol and CO2 requires the use of a dehydrating agent such as 2-cyanopyridine (2-CP) to overcome thermodynamic limitations, alongside controlled catalyst surfaces to limit competing side reactions. In this study, mesostructured CeO2 catalysts were synthesized via a nanocasting approach using SBA-15 as a hard template. The specific impact of the precursor infiltration method and the final thermal treatment on catalytic performance were evaluated. While a one-step precursor infiltration route yielded the most ordered mesostructure after template removal, the final calcination step emerged as the dominant variable governing catalyst activity and selectivity. Textural analysis confirmed that calcination preserved the interconnected nanorod morphology with only a minor decrease in specific surface area. Temperature-programmed desorption (TPD) revealed that the thermal treatment induced a redistribution of surface acid-base sites, specifically increasing the ratio of medium-strength basic to acidic sites. In situ DRIFTS demonstrated that this tailored surface chemistry facilitated CO2 activation, promoted the formation of bidentate carbonates, and favored the monomethyl carbonate (MMC) intermediate formation. Consequently, the calcined CeO2-OS catalyst achieved 74% methanol conversion and 91% DMC yield at 120 °C and 5 MPa, outperforming its uncalcined counterpart by suppressing 2-CP-related secondary reactions.

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