US EPA

5175851 

Journal Article 

The interaction of V2O5 with Ti02(anatase): Catalyst evolution with calcination temperature and O-xylene oxidation 

Saleh, RY; Wachs, IE; Chan, SS; Chersich, CC 

1986 

Yes 

Journal of Catalysis
ISSN: 0021-9517
EISSN: 1090-2694 

98 

102-114 

10.1016/0021-9517(86)90300-3 

http://www.sciencedirect.com/science/article/pii/0021951786903003
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The interaction of V2O5 with the surface of TiO2(anatase) was studied over the temperature range 110–750 °C. The V2O5TiO2(anatase) system was characterized with laser Raman spectroscopy, X-ray photoelectron spectroscopy, Fourier transform infrared, X-ray diffraction, thermal gravimetric analysis, BET, and catalytic performance for o-xylene oxidation to phthalic anhydride. The state of V2O5TiO2(anatase) possessing high loadings of vanadia is strongly dependent on calcination temperature. In the presence of vanadia the TiO2(anatase) support exhibits a simultaneous loss in surface area and structural transformation to rutile at elevated calcination temperatures. The morphology of the supported vanadia phase also depends on calcination temperature. At low calcination temperatures, 110–200 °C, the vanadia exists as vanadyl oxalate, the starting vanadia salt. At intermediate calcination temperatures, 350–575 °C, vanadia is present as a complete monolayer of surface vanadia species coordinated to the titania support and V2O5 crystallites. At calcination temperature of 575 °C and above, the supported vanadia phase reacts with the TiO2(anatase) support to yield VxTi1 −xO2(rutile). These structural changes have a pronounced effect on the catalytic performance of V2O5TiO2(anatase) catalysts for the oxidation of o-xylene. The optimum catalytic performance is observed for prolonged calcination at intermediate temperatures, 350–575 °C, where a complete monolayer of surface vanadia exists on the TiO2(anatase) support. The complete monolayer of surface vanadia and crystalline vanadia phases remain intact during the o-xylene oxidation reaction and become partially reduced by the reaction environment.