Kinetic and mechanistic investigations of the direct synthesis of dimethyl carbonate from carbon dioxide over ceria nanorod catalysts

The direct conversion of carbon dioxide (CO₂) to organic carbonates such as dimethyl carbonate (DMC) is favored only at low temperatures. However, these reactions are typically conducted at high temperatures due to poor reaction kinetics. In this article, the reaction kinetics were experimentally investigated for the direct conversion of CO₂ and methanol to DMC using a ceria nanorod catalyst and were compared with those of a highly crystalline commercial ceria catalyst. The apparent activation energy for this reaction over our nanorod catalyst was determined to be 65 kJ/mol whereas that of a commercial ceria catalyst was measured to be 117 kJ/mol. The reaction rate law was found to be approximately first order with respect to both catalysts, with an apparent negative one reaction order with respect to methanol. These results were found to be consistent with a Langmuir-Hinshelwood type reaction mechanism where CO₂ and methanol adsorption occurs in separate reaction steps.