First-Principles Study of Methanol Oxidation into Methyl Formate on Rutile TiO2(110)

Abstract

The detailed oxidation of methanol into methyl formate on perfect and defect rutile TiO2(110) surfaces was explored based on first-principles calculations. Based on the calculated energy barriers of elementary steps, a pathway was identified for methanol oxidation on both surfaces. The reaction proceeds through a direct coupling of methoxy and formaldehyde to produce the intermediate hemiacetal, which leads to methyl formate. Kinetics of elementary steps further shows that methanol dissociation at surface oxygen vacancy greatly changes the reaction rates of the sequential reaction steps on the defect surface, making them quite different from those occurring at the Ti5c sites on both surfaces. In addition, small diffusion barriers of formaldehyde demonstrate that it can move freely from the adsorption sites to the reactive sites on the surfaces to produce the hemiacetal. These findings may provide insights into the complete oxidation mechanism for methanol on TiO2, and demonstrate a green and benign route for the synthesis of ester directly from alcohols or from alcohols and aldehydes.