Formation of active phases in MoVTeNb oxide catalysts for ammoxidation of propane

The method of drying, heat evaporation or spray drying, of the aqueous suspension of starting chemicals has a pronounced effect on the phase composition of the final MoVTeNb catalyst, which ultimately influences the catalytic properties in propane ammoxidation reaction. The sample synthesized by spray drying is active and selective; it contains two main crystalline phases, orthorhombic M1 and hexagonal M2. The activity of the sample prepared by heat evaporation is low. This sample does not contain the active M1 phase and consists of hexagonal M2, TeMo5O16, and Mo5−x(V/Nb)xO14 phases. The different mechanisms of phase composition formation in the samples synthesized by heat evaporation or spray drying arise from the different chemical nature of corresponding solid precursors.