Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
9607956 | Applied Catalysis A: General | 2005 | 12 Pages |
Abstract
A vanadium oxide powder catalyst supported on titanium oxide (VOx/TiO2(anatase)) was investigated with in situ X-ray absorption spectroscopy (XAS). This system is applied in industry for partial oxidation processes. The structural changes of the supported vanadium oxide due to different treatments were determined: during a reduction-oxidation cycle at 623Â K after calcination in air and after heating in inert atmosphere. Unsupported crystalline V2O5 powder was used as a reference system. After calcination in air of the VOx/TiO2(anatase) a V2O5 bulk crystal structure appears, while an octahedral co-ordination with a VO vanadyl bond is present after heating in inert atmosphere. The redox cycle performed on fully oxidized supported vanadium oxide induces similar structural changes as for unsupported V2O5: a reduction to V4+ with a slightly distorted VO octahedron and a re-oxidation to the initial V2O5 structure. However, when the supported vanadium oxide is reduced after heating in inert, a valence lower than V4+ is obtained and a different structure is found: a symmetrical VO octahedron is present with VO and VV distances identical to the TiO and TiTi distances in TiO2(anatase or rutile). After re-oxidation the V2O5 bulk structure is again obtained for the supported vanadium oxide.
Keywords
Related Topics
Physical Sciences and Engineering
Chemical Engineering
Catalysis
Authors
Geert Silversmit, Jeroen A. van Bokhoven, Hilde Poelman, Ad M.J. van der Eerden, Guy B. Marin, Marie-Françoise Reyniers, Roger De Gryse,