Synthesis of MoVNbTe catalyst having a reduced content of niobium and tellurium, and higher activity for the oxidative dehydrogenation of ethane

The invention relates to a mixed oxide comprising the elements molybdenum, vanadium, niobium and tellurium, the h XRD, when using Cu-Ka radiation, reflections, i, k and 1, whose vertices approximately at the diffraction angles (2θ) 26, are 2 ° ± 0.5 ° (h), 27.0 ° ± 0.5 ° (i), 7.8 ° ± 0.5 ° (k), and 28.0 ° ± 0.5 ° (1) , characterized in that it comprises the following stoichiometry: Mo a = 0.2 to 0.35, b = greater than 0 to 0.08, c = greater than 0 to 0.08, n = a number which is determined by the valency and frequency of the elements other than oxygen in (I).