Direct synthesis of dimethyl carbonate from methanol and carbon dioxide over nickel loaded ceria as improved catalysts

The direct synthesis of dimethyl carbonate (DMC) without a dehydrating agent is challenging but has a significant value. Here we demonstrate the catalytic activity of inexpensive nickel loaded ceria in both batch and continuous processes for this reaction. The prepared catalysts were characterized by various physicochemical characterization techniques. The nickel-loaded ceria catalysts exhibited good catalytic activity for the synthesis of DMC in good yield (4.6 mmol) and 100% selectivity. The yield obtained is nearly six times higher than pristine CeO2, which clearly depicts the role of nickel. Reaction under high pressure continuous flow also provided a similar trend wherein a maximum yield of 15 mmol with 100% liquid phase selectivity of DMC was noted. Density functional theory calculations were carried out to investigate the adsorption energies of CO2 and methanol on pristine ceria and Ni modified ceria. The high catalytic activity of Ni-modified catalyst was attributed to the presence of strong acidic and moderate basic sites as elucidated from temperature-programmed desorption and pyridine adsorption monitored via FT-IR studies. The experiment result revealed that the CexNix-yO2-delta could be a reusable and longer active catalyst for the direct synthesis of DMC.