Details

Autor(en) / Beteiligte

• Habel, D
• Feike, E
• Schroder, C
• Schubert, H
• Hosch, A
• Stelzer, J B
• Caro, J
• Hess, C
• Knop-Gericke, A

Titel

PHASE DEVELOPMENT IN THE CATALYTIC SYSTEM V205/T102 UNDER OXIDIZING CONDITIONS

Ist Teil von

• Ceramic Engineering and Science Proceedings, 2007-01, Vol.27 (8), p.69-80

Erscheinungsjahr

2007

Link zum Volltext

Quelle

Wiley Online Library All Obooks

Beschreibungen/Notizen

• The target of this work was to investigate phase development in the catalyst system consisting of TiO2 (Anatase) and V205 (Shcherbinaite). Thus a set of V205/TiO2 specimens was prepared by ball milling and exposed to subsequent annealing in air in the temperature range from 400 to 700 deg C. The 3M-results showed the presence of Anatase and Shcherbinaite as the only phases up to 525 deg C. For temperatures above 525 deg 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 deg C < T < 550 deg C for compositions of 3 mole % < V205 < 5 mole %. The phase field for Rutile solid solutions extends to 10 mole% < V205 < 12.5 mole % at 675 deg C. For very high V205 concentrations an eutectic reaction was found at 631 deg C (95 mole% V205). 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 fmd the appropriate processing conditions and to understand the aging phenomena of catalysts.