TixCe1−xO2 nanocomposites: a monolithic catalyst for the direct conversion of carbon dioxide and methanol to dimethyl carbonate
Dimethyl carbonate (DMC) is widely employed as a versatile reagent and solvent for green organic synthesis and fuel additives. Owing to the environmental issues of the traditional methods for DMC production, the direct synthesis of DMC from carbon dioxide and methanol has received significant interest worldwide. Here, we demonstrate the catalytic effectiveness of monolithic titanium-doped cerium oxides, TixCe1−xO2 nanocomposites, for the direct synthesis of DMC. The TixCe1−xO2 nanocomposites are characterized by BET measurements, Raman spectroscopy, powder X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and H2-temperature-programmed reduction analysis. To increase the reaction efficiency, the TixCe1−xO2 composites are uniformly coated on honeycomb ceramics in a continuous tubular fixed-bed reactor. This leads to an extended surface area of the catalyst, and therefore the reaction conversion rate toward DMC production is significantly enhanced. Results indicate that the catalyst exhibits 24.3% methanol conversion with 79% selectivity for DMC synthesis at 140 °C in the absence of any dehydrating agents. The catalytic effectiveness of the TixCe1−xO2 nanocomposites is found to be considerably higher than those of conventional catalysts. Analysis shows that the concentration of active sites can be systemically enriched by incorporating an optimal amount of Ti dopants into CeO2 to improve the catalytic activity of the reaction. The results of this study demonstrate the promise of the TixCe1−xO2 nanocomposites for the green production of DMC, and may offer guidelines for designing efficient catalysts for the selective conversion of methanol to other building blocks of chemical synthesis.