Abstract
The aim of this study was to test the suitability of oxygen uptake measurements for the characterization of titania-supported vanadia catalysts. Before oxygen uptake measurements, the two catalysts (EL10V1 and EL10V8) were reduced in flowing hydrogen (623 K, 2 and 6 h). The subsequent oxygen adsorption at different temperatures was determined by using a static (microbalance) and a dynamic (GC pulse experiments) method. There was only a significant influence of reduction time on oxygen uptake for catalyst EL10V8. Considering the oxygen uptake of the two catalysts (μmol O 2/μmol V 2O 5), EL10V1 shows a higher degree of reduction for all temperatures, which is explained by the higher dispersion of the vanadia leading to stronger support interaction and easier reducibility of these species. The static and the dynamic method are both suitable for oxygen uptake measurements for characterizing supported vanadia catalysts. However, it seems unlikely that the reduction and oxidation processes are confined to the outermost surface layer of vanadia. The following reference conditions are proposed: reduction of the catalyst for 6 h at 623 K and subsequent exposure to oxygen at the same temperature.
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