The influence of the preparation method on the structural, acidic and redox properties of V2O5-TiO2/SO42− catalysts Original Research Article

The introduction of sulfates into vanadia-titania catalysts and the influence of the preparation method on the properties of the sulfated samples have been studied. Series of V2O5-TiO2/SO42− (VTiS) catalysts were prepared by co-precipitation, sol–gel and mechanical grinding methods and calcined at different temperatures. Their structural properties were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). Co-precipitation was by far the best preparation method in terms of maximizing the surface area and the mesoporosity. Temperature-programmed reduction (TPR) revealed that only the vanadia species were reducible. The results from XRD and FT-IR showed that V2O5 was well dispersed on the surface of TiO2. XPS showed that the surface vanadium oxide was composed of stoichiometric V2O4 and V2O5, as well as V2O3 species especially for the samples prepared by mechanical grinding. Meanwhile, titanium was present in its fully oxidized state in all the VTiS samples, and the sulfur-containing species presented an oxidation state of +6. The reaction of isopropanol (IPA) conversion in air was used to characterize the surface acid/base and redox properties. The higher activity for the IPA conversion over the VTiS catalysts as compared to TiO2 was possibly due to the generation of redox sites upon the addition of V2O5. Moreover, the surface acidic properties were enhanced and the redox properties weakened upon addition of SO42− species.