Oxydehydrogenation catalyst, and process for the catalytic conversion of isobutyric acid or functional derivatives thereof into corresponding alpha, beta-unsaturated compounds

Isobutyric acid or functional derivatives thereof, for example lower alkyl esters, are oxidatively dehydrogenated in order to achieve vapour-phase conversion thereof into the corresponding alpha , beta -ethylenically unsaturated derivative by contact with a heterogeneous catalyst in the presence of molecular oxygen. The catalyst comprises calcined phosphates of iron which contain silver, cobalt, lanthanum or tellurium as modifying or doping component.