Influence of alkaline earth metal on acid–base characteristics of V2O5/MO–TiO2 (M = Ca, Sr and Ba) catalysts

The influence of various alkaline earth metal oxides (CaO, SrO and BaO) on the acid–base properties of TiO2 and the dispersion behaviour of V2O5 over MO−TiO2 (M = Ca, Sr and Ba) have been investigated systematically. The MO−TiO2 binary oxides (1:1 molar ratio) were synthesized by adopting a co-precipitation method from the corresponding chloride precursors by in situ hydrolysis with urea and calcined at various temperatures from 723 to 1073 K. A nominal 10 wt.% V2O5 was deposited over the calcined (773 K) MO−TiO2 supports by a wet impregnation method. The synthesized catalysts were characterized using X-ray diffraction (XRD), Raman spectroscopy (RS), X-ray photoelectron spectroscopy (XPS), thermogravimetry–differential thermal analysis (TG–DTA) and BET surface area techniques. The MO−TiO2 composite oxides exhibited reasonably high-specific surface area and high-thermal stability retaining titania-anatase phase up to 1073 K treatment temperature. The impregnated V2O5 over MO−TiO2 binary oxides remained in a highly dispersed form. A preferential interaction between the basic MO and the dispersed V2O5 lead to the formation of MVO3 at higher calcination temperatures. The surface acid–base properties of the prepared samples were examined for the conversion of cyclohexanol to cyclohexanone/cyclohexene under normal atmospheric pressure. All the investigated samples were found to exhibit interesting catalytic properties.

Graphical abstractInfluence of MO (M = Ca, Sr and Ba) on TiO2-anatase phase stabilization and dispersion of V2O5 over these have been investigated. The MO–TiO2 and V2O5/MO–TiO2 exhibit more selectivity towards cyclohexanone and cyclohexene respectively reflecting their acid–base properties.Figure optionsDownload full-size imageDownload as PowerPoint slide