Phase transformation study of titania in [formula omitted] and [formula omitted] catalysts by X-ray diffraction analysis

• Published in: Materials chemistry and physics 1994, Vol.36 (3), p.276-281
• Main Authors: Reddy, B.Mahipal, Reddy, E.Padmanabha, Mehdi, Safia
• Format: Article
• Language: English
• ISSN: 0254-0584; 1879-3312
• DOI: 10.1016/0254-0584(94)90042-6

The effect of the presence of vanadia or molybdena and the thermal treatment on the phase transformation of titania in V 2O 5/TiO 2 and MoO 3/TiO 2 catalysts was investigated using X-ray powder diffraction (XRD) analysis. The titania support used was a commercial sample from Harshaw containing anatase together with a small quantity of graphite. The XRD results suggest that when the TiO 2 support is calcined at 973 K, anatase is partially transformed into rutile, whereas at 1273 K it is totally converted to rutile. In the presence of V 2O 5 the temperature of partial conversion is reduced to 813 K, and a total transformation is noted already at 973 K. MoO 3 also induces this transformation, but is less effective than V 2O 5. XRD results further show that when the V 2O 5/TiO 2 catalyst is subjected to calcination at 973 K, no crystalline V 2O 5 phase is present. The same is not true for MoO 3, which is present in a crystalline state at this calcination temperature. This study reveals clearly that vanadia and molybdena behave differently when impregnated on the same titanium dioxide support.