In situ study of structural transformation of the (TeO)ₓ(Mo,V,Nb)₅O₁₄ mixed oxide nanocatalyst with a tunnel structure

The nano oxides (TeO)_x(Mo,V,Nb)₅O₁₄ with so-called M1 structure are highly attractive objects due to unsurpassed catalytic properties. In situ X-ray powder diffraction method with high time resolution (0.4 seconds per diffraction pattern) was applied to study the structure stability and the mechanism of phase transformation under heating in the reductive conditions. It was shown that M1 structure gradually transforms into the rutile-type (Mo,V,Nb)O₂ phase without intermediate phases and/or amorphisation at temperatures >480°C in a reductive media. The process is initiated by tellurium reduction and its sublimation to the gas phase.