The activity and selectivity in the oxidation of butane (a saturated hydrocarbon) on unsupported and supported V2O5 catalysts were investigated in connection with the catalyst structure. It was found that the reaction rate at various concentrations of O2 was proportional to the amount of V5+=O species in the catalyst, indicating that the surface V=O plays the active oxygen species for the reaction. The specific activity of surface V=O species on unsupported V2O5 changed greatly with the surface structure of the catalyst: The fusion of V2O5 markedly decreased the specific activity, while the severe redox treatment of the fused catalyst increased the activity. This means that the butane oxidation on V2O5 catalyst is a structure-sensitive reaction The specific activity of the surface V=O species on the V2O5/TiO2 (anatase) and V2O5/TiO2 (rutile) catalysts was smaller than that of the unsupported V2O5, indicating the retarding effect of the support on the activity. This is in contrast to the known promoting effect of TiO2 support on the activity of V2O5. The selectivity to CO or CO2 was also found to be sensitive to the surface structure of V2O5: A rough V2O5 surface is favorable for the formation of CO while a smooth surface leads to the selective formation of CO2.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry