Temperature-dependent oxygen release, intercalation behaviour and catalytic properties of V{sub 2}O{sub 5}.xNb{sub 2}O{sub 5} compounds

Graphical abstract: Temperature dependent oxygen loss and uptake of V{sub 2,38}Nb{sub 10,7}O{sub 32,7} in N{sub 2} (p(O{sub 2}) = 4 x 10{sup -5} bar) and IR spectra of gas mixtures after the reactor with V{sub 2,38}Nb{sub 10,7}O{sub 32,7} (A = 16.1 m{sup 2}/g) and propane. Highlights: {yields} V{sub 2}O{sub 5}.xNb{sub 2}O{sub 5} complex oxide compounds as catalysts. {yields} The (V, Nb){sub 2}O{sub 5} phases are able to a reversible release and uptake of oxygen without a structural variation. {yields} Metastable (V, Nb){sub 2}O{sub 5} phases are able to catalyse the oxidative dehydrogenation of propane and propene. {yields} Thermodynamically stable VNb{sub 9}O{sub 25} phase shows no measurable catalytic activity. -- Abstract: In order to investigate the catalytic properties, V{sub 2,38}Nb{sub 10,7}O{sub 32,7}, VNb{sub 9}O{sub 25} and solid solutions of V{sub 2}O{sub 5} in TT-Nb{sub 2}O{sub 5} were prepared by thermal decomposition of freeze-dried oxalate precursors. The samples were characterised by X-ray diffraction and surface area determination. The crystalline samples are capable of the intercalation of sodium and lithium ions from solution. Above a temperature of about 500 {sup o}C, in dependence on the oxygen partial pressure a reversible release and uptake of oxygen without a structural variation takes place. The catalytic properties have been evaluated for the oxidative dehydrogenation (ODH) of propane and propene. There are only small differences in the catalytic activity of the different crystalline samples. Because of the relative high starting temperature, a selective catalytic oxidation of propane to propene is hardly observed.