Mg-Mo-O catalysts have been investigated with different techniques (XR
D, XPS, IR, and EPR spectroscopies) in order to explain the difference
in catalytic behavior in the oxidative dehydrogenation of propane to
propene. The active site would be a coordinatively unsaturated form of
Mo5+. Th, active Mo5+ could be generated on the surface by propane re
duction. The slight excess of MoO3 which is necessary for the catalyst
to become an active one probably contributes to the formation of Mo5.