The Influence of Sulfate‐Doping on the Nature of V Sites in VO x /TiO 2 Catalysts

EPR, UV/Vis and FTIR spectroscopy as well as thermal analysis (TA/MS) were applied to study the influence of sulfate species present in the anatase support on the specific nature of VO x species in supported VO x /TiO 2 catalysts. Those sulfate species modify the local structure of the supported vanadyl species and lead to the formation of two types of VO 2+ sites instead of only one type being formed on sulfate‐free anatase. EPR and FTIR spectroscopic measurements revealed that a part of the VO 2+ species are directly bound to the surface sulfate species. By TA/MS it was found that SO 2 is released at lower temperature from VO x /TiO 2 in comparison to the vanadium‐free support. The direct bonding between sulfate and VO x species stabilizes the latter on the surface of VO x /TiO 2 resulting in three effects: 1) a higher V site dispersion in comparison to sulfate‐free TiO 2 , 2) a better resistance of surface vanadyls against diffusion into the bulk of the support and 3) a much faster reoxidation of reduced V sites than observed on sulfate‐free TiO 2 .