Enhanced catalytic activity of H2 heat-treated porous ceria for direct conversion of carbon dioxide into dimethyl carbonate
Zhuxian Yang, Monica Mengdie Lin, Xinhuan Lu, Justin Tay Zheng, Wen‐Yueh Yu, Yanqiu Zhu, Hong Chang, Yongde Xia
Abstract
It has been demonstrated that the specific surface area, acid–base properties, morphologies, and oxygen-vacancies (Ov) play a role in the catalytic performance of CeO2-based catalysts. In this study, porous CeO2 and Zr-doped CeO2 catalysts with high surface area have been prepared via a low temperature synthesis strategy and evaluated for the conversion of CO2 and methanol into dimethyl carbonate (DMC). Results show that the Zr doping (Zr:Ce = 1:9) could slightly increase the DMC formation rate of CeO2, whereas the H2 heat-treatment of CeO2 could lead to a DMC formation rate of 18.22 ± 0.64 mmol g-1h−1, which is amongst the highest for CeO2 catalysts at 140 °C reported so far. Such enhancement in DMC formation rate is attributed to (1) the balanced crystallinity and defects of the CeO2, (2) a shift of acid and base activity to lower temperature, and (3) the (1 1 1) plane only surface termination of the catalyst resulted from the heat-treatment process. Excluding the best performed H2 heat-treated CeO2 catalyst, the DMC formation rate of the rest catalysts shows a positive link to the BET surface area, acid property (NH3-TPD), OV%, Ce3+%, and the Raman peak intensity ratio of ID/IF2g of the catalyst. The low temperature preparation strategy in this study could be applicable to the synthesis of CeO2 catalyst towards to other reactions (e.g., non-reductive CO2 conversions to various carbonates, carbamates, urea derivatives, etc.).