The effect of support on redox properties and methanol-oxidation activity of vanadia catalysts Original Research Article

The effect of support composition on the catalytic properties of isolated mono-vanadates was studied using reaction rates for the methanol-oxidation reaction and oxygen binding from coulometric titration measurements on 2.5 wt% V2O5/ZrO2, 2.5 wt% V2O5/TiO2, and 5 wt% V2O5/Al2O3. Although a review of the redox properties for the bulk oxides V2O5, ZrV2O7, AlVO4, Mg3(VO4)2, and CeVO4 showed that the environment surrounding the V cations can have a dramatic effect on the redox properties, the majority of sites on supported catalysts showed nearly identical properties, with ΔG of oxidation being −375 ± 25 kJ/mol at 748 K. The steady-state turnover frequencies for methanol oxidation were also similar (within a factor of 3) on each of the supports over the temperature range from 463 to 528 K. Finally, methanol-oxidation rates in the absence of oxygen over the oxidized vanadia/titania catalyst at 443 K demonstrated that all of the vanadia sites were active for the reaction and exhibited a similar rate to that observed in the presence of oxygen, showing that the reaction follows a Mars-van Krevelen mechanism.