Synthesis of dimethyl carbonate from CO2 and methanol over Zn modified CeO2 with 2-cyanopyridine: Theoretical calculation and experiment

In this work, the reaction mechanism of dehydration reaction on Zn-doped ceria (CeO2) for the direct dimethyl carbonate (DMC) synthesis from CO2 and methanol is investigated from experimental and density functional theory (DFT) calculation perspectives. The dehydrating agent 2-cyanopyridine can greatly promote a shift in reaction equilibrium towards DMC by eliminating the undesired H2O. However, the dehydrating agent also causes the side reaction and reduces the DMC selectivity, especially under mild conditions (low CO2 pressure). Compared to the undoped CeO2-FD, the Zn-doped CeO2 significantly improves DMC selectivity from 82 % to 99 %, meanwhile showing high DMC yield with 434.3 mmol g−1cat under 0.5 MPa CO2 pressure. The DFT calculation shows that the energy barrier of the side reaction on the Zn-doped CeO2 catalyst is much higher than that on CeO2. The charge distribution analysis demonstrates that more charge transfer creates enhanced Lewis bases, which hinders the side reactions.