Interaction of oxygen with the surface of vanadia catalysts

• Published in: Journal of molecular catalysis. A, Chemical Chemical, 2007-11, Vol.277 (1), p.27-34
• Main Authors: Słoczyński, J., Grabowski, R., Kozłowska, A., Tokarz-Sobieraj, R., Witko, M.
• Format: Article
• Language: English
• Subjects: Catalysis; Chemistry; Exact sciences and technology; General and physical chemistry; Oxygen forms; Quantum-chemical calculations; Re-oxidation; Reduction; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Vanadia–titania catalyst
• ISSN: 1381-1169; 1873-314X
• DOI: 10.1016/j.molcata.2007.07.022

The kinetics of the reoxidation of the reduced VO x /TiO 2 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. ▪ ▪ ▪ Kinetics of the re-oxidation of the H 2-reduced or vacuum treated VO x /TiO 2 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.