Investigation of synthesis parameters to fabricate CeO2 with a large surface and high oxygen vacancies for dramatically enhanced performance of direct DMC synthesis from CO2 and methanol

Abstract

Hierarchically porous CeO2 with excellent catalytic performance for direct dimethyl carbonate (DMC) from CO2 and methanol was successfully prepared by a simple hydrothermal method due to the abundant oxygen vacancies (Ovs, ∼17%) and large surface area (137 m2·g−1). The effects of template dosage as well as synthesis parameters including hydrothermal time and calcination temperature on the physicochemical properties of as-synthesized CeO2 were studied, and the reaction conditions were investigated and optimized. The obtained results indicated that the Ovs varied with prolonging hydrothermal time and more Ovs were formed by etching due to longer crystal time. And the fabricated Ovs acting as acid sites and basic sites effectively activated CO2 and methanol, respectively, which was further confirmed by the simulation results, however, the strong acid sites are detrimental to catalyst stability due to their strong chemical interactions with nicotinamide. And a high DMC yield of 260.12 mmol∙g−1 was obtained under the optimal reaction conditions: reaction time 5 h, initial CO2 pressure 4.0 MPa, and reaction temperature 140 °C.