TiO2 nanofibers of different crystal phases for transesterification of alcohols with dimethyl carbonate

• TiO2 nanofibers of different crystal phases are efficient catalysts.
• An active order is TiO2(B), TiO2(A + B), TiO2(A), commercial anatase, P25, TiO2(A + R), TiO2(R).
• TiO2(B) shows high selectivity, general suitability to alcohols, and reusability.
• TiO2 nanofibers are easy to prepare and recycle.
• The isotope labeling of oxygen-18 demonstrates the reaction pathway.

TiO2 nanofibers with different crystal phases have been discovered to be efficient catalysts for the transesterification of alcohols with dimethyl carbonate to produce corresponding methyl carbonates. Advantages of this catalytic system include excellent selectivity (>99%), general suitability to alcohols, reusability and ease of preparation and separation of fibrous catalysts. Activities of TiO2 catalysts were found to correlate with their crystal phases which results in different adsorption abilities and activation energies on the catalyst surfaces. The kinetic isotope effect (KIE) investigation identified the rate-determining step, and the isotope labeling of oxygen-18 of benzyl alcohol clearly demonstrated the reaction pathway. Finally, the transesterification mechanism of alcohols with dimethyl carbonate catalyzed by TiO2 nanofibers was proposed, in which the alcohol released the proton to form benzyl alcoholic anion, and subsequently the anion attached the carbonyl carbon of dimethyl carbonate to produce the target product of benzyl methyl carbonate.

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