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. (C) 2007 Elsevier B.V. All rights reserved.