8. Phase Development in the Catalytic System V2O5/Tio2 Under Oxidizing Conditions
- William M. Mullins,
- Andrew Wereszczak and
- Egar Lara-Curzio
Published Online: 26 MAR 2008
Copyright © 2007 The American Ceramic Society
Synthesis and Processing of Nanostructured Materials: Ceramic Engineering and Science Proceedings, Volume 27, Issue 8
How to Cite
Habel, D., Feike, E., Schroder, C., Schubert, H., Hösch, A., Stelzer, J. B., Caro, J., Hess, C. and Knop-Gericke, A. (2007) Phase Development in the Catalytic System V2O5/Tio2 Under Oxidizing Conditions, in Synthesis and Processing of Nanostructured Materials: Ceramic Engineering and Science Proceedings, Volume 27, Issue 8 (eds W. M. Mullins, A. Wereszczak and E. Lara-Curzio), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470291375.ch8
- Published Online: 26 MAR 2008
- Published Print: 1 JAN 2007
Print ISBN: 9780470080511
Online ISBN: 9780470291375
The target of this work was to investigate phase development in the catalyst system consisting of TiO2 (Anatase) and V2O5 (Shcherbinaite). Thus a set of V2O5/TiO2 specimens was prepared by ball milling and exposed to subsequent annealing in air in the temperature range from 400 to 700 °C. The XRD-results showed the presence of Anatase and Shcherbinaite as the only phases up to 525 °C. For temperatures above 525 °C Rutile as a new TiO2-phase occured. Peak intensities and positions were shifted. No loss of oxygen or vanadium was detected. The reaction involves the formation of a Rutile solid solution containing VOx species. XPS studies showed an oxidation state of 4.75 for V in the Rutile solid solution as compared to 4.65 in the Shcherbinaite. The Rutile solid solution was first found at 525 °C < T < 550 °C for compositions of 3 mole % < V2O5 < 5 mole %. The phase field for Rutile solid solutions extends to 10 mole% < V2O5 < 12.5 mole % at 675 °C. For very high V2O5 concentrations an eutectic reaction was found at 631 °C (95 mole% V2O5). A Shcherbinaite structure remained with shifted peak intensities and positions due to the alloying of Ti-ions.
SEM inspections showed that the Rutile formation and the eutectic reaction both cause a substantial grain growth and a loss of surface area. The catalytic activity is entirely lost. The knowledge of phase relations helps to find the appropriate processing conditions and to understand the aging phenomena of catalysts.