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

• Kinetics for converting CO2 and MeOH to dimethyl carbonate with ceria is studied.
• Ceria nanorods yield much lower apparent activation energy than commercial ceria.
• Langmuir–Hinshelwood mechanism where CO2 and MeOH interact with ceria is proposed.
• The adsorption of CO2 onto ceria is proposed to be rate controlling.
• Low ratio of MeOH to CO2 in the feed gas is predicted to increase reaction yields.

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.

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