Dynamic behavior of supported vanadia catalysts in the selective oxidation of ethane: In situ Raman, UV–Vis DRS and reactivity studies

• Published in: Catalysis today 2000-08, Vol.61 (1), p.295-301
• Main Authors: Bañares, M.A, Martı́nez-Huerta, M.V, Gao, X, Fierro, J.L.G, Wachs, I.E
• Format: Article
• Language: English
• Subjects: Catalysis; Catalytic reactions; Chemistry; Ethane oxidation; Exact sciences and technology; General and physical chemistry; In situ Raman; In situ UV–Vis DRS; Oxidation state; Polymerization degree; Solid-state reaction; Support effect; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Vanadia
• ISSN: 0920-5861; 1873-4308
• DOI: 10.1016/S0920-5861(00)00388-6

The coordination and oxidation states of surface vanadia species on different oxide supports were studied by in situ UV–Vis DRS and in situ Raman spectroscopy. Surface vanadia species remain essentially oxidized during the steady-state ethane oxidation reaction. Polymeric surface vanadia species are more reducible than isolated ones, but this has only a minor effect on the ethane oxidation reactions. It appears that only one surface V site is involved in the rate-determining step for ethane oxidation. The reducibility of supported vanadium oxide species corresponds with the TOF values, but not with the average oxidation state under steady-state reaction. Ceria- and niobia-supported vanadia catalysts do not follow this trend due to solid-state reaction between the surface vanadia species and the oxide support that decreases the number of exposed vanadia sites. This solid-state reaction does not appear to affect the nature of the active site, which is associated with the V–O–Support bond rather than with the terminal VO bond.