Interaction of oxygen with the surface of vanadia catalysts

Kinetics of the re-oxidation of the H2-reduced or vacuum treated VOx/TiO2 catalyst was studied. It was found that oxygen does not adsorb in the form of ad-atoms on the fully oxidized surface of the catalyst but re-oxidizes oxygen vacancies. On the basis of the surface potential measurements it was concluded that nucleophillic oxygen O(s)2− is almost exclusively present above 550 K on the catalyst surface. The quantum-chemical calculations were supported by the experimental results. The implications of these results for the reaction mechanism of the oxidative dehydrogenation of propane are discussed.

The kinetics of the reoxidation of the reduced VOx/TiO2 catalysts was studied. It was found that oxygen does not adsorb in form of ad-atoms on the fully oxidized surface of the catalyst but re-oxidizes oxygen vacancies. The oxygen vacancies formed are quickly replenished with oxygen from the gaseous phase at temperatures above 473 K. On the basis of the surface potential measurements it was concluded that above 550 K the nucleophyllic oxygen O(s)2− is the dominant form of oxygen on the surface of the catalyst. The results of the quantum-chemical calculations were supported by experimental findings. Implications of these results on the mechanism reactions of the ODH of propane were discussed.Figure optionsDownload as PowerPoint slideFigure optionsDownload as PowerPoint slideFigure optionsDownload as PowerPoint slide