While the catalytic performances of stoichiometric nickel molybdate in the oxidative dehydrogenation of isobutane into isobutene and methacrolein are improved by the addition of potassium oxides, the oxidation of propane to propene is mainly affected by calcium oxides. The selectivity towards the corresponding alkenes and specifically the methacrolein selectivity are also affected by the active catalyst phase and the oxygen/alkane ratio in the feed.