Propane oxidation on MoVTeNbO mixed oxide catalysts: study of the phase composition of active and selective catalysts

Several phases reported as minor or major phases in the active MoVTeNbO catalysts have been prepared and investigated for the oxidation of propane into acrylic acid. Activity and selectivity of pure phases and mixtures of phases obtained either directly from synthesis or by co-grinding have been compared. The results obtained confirmed that the orthorhombic M1 phase is the most active and selective phase and is responsible for the major part of the efficiency of the best catalysts. However, they also clearly demonstrated that a synergism due to a cooperation between phases occurs, similar to that previously proposed between the M1 [(Te2O)M20O56] and M2 [(TeO)M3O9] phases for the ammoxidation of propane. The origin of this phase cooperation is discussed.