Crystalline Structure and Propylene Oxidation in Complex Bismuth‐Molybdenum Oxide Catalysts

Complex BiMo oxide catalysts supported on amorphous SiO 2 were prepared by coprecipitation and tested in the reaction of selective oxidation of propylene to acrolein. They consist of a mixture of molybdate phases and excess MoO 3 . The Fe 2 (MoO 4 )( 3 ) phase was found to have a high concentration of lattice defects, induced by a Mo excess. These defects could be related to the catalytic conversion and to the selectivity to total oxidation by varying the calcination temperature. Calcination above 500°C induced also the transition of the metastable modification β‐NiMoO 4 to the stable form α, accompanied by a loss of conversion. A complex Bi molybdate with scheelitic structure was found to have a high selectivity to acrolein.