The kinetics and mechanism of methanol dehydration over anatase TiO2 nanoplates and truncated bi-pyramidal nanocrystals were investigated at 300 °C to understand surface structure effect of TiO2 in methanol chemistry. The reaction mechanism for the redox and oxidative coupling of methanol was also probed under dilute oxygen concentration. TiO2 nanoplates displayed a higher fraction of (001) facet while truncated bi-pyramidal nanocrystals were dominated by (101). In situ titration experiments show that the active sites for dehydration are acidic and non-equivalent compared to redox and oxidative coupling, while FTIR spectroscopy reveals that adsorbed methoxy is the dominant surface species. Kinetic isotope experiments using partially and fully deuterated methanol (CD3OH and CD3OD) indicate that the cleavage of C-H bond is the rate limiting step for methanol conversion over TiO2, which is good agreement with density functional theory calculations of both (101) and (001) surfaces. Comparison between estimated kinetic parameters for methanol dehydration over various TiO2 nanocrystals indicates that (001) has a higher reactivity compared to (101). This work clearly shows a cooperative effect between surface oxygen atoms and Lewis acid sites in the conversion of methanol via dehydration, redox and oxidative coupling pathways over TiO2 surfaces.

Kinetics and mechanism of methanol conversion over anatase titania nanoshapes

254th National Meeting (2017)

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