Effect of several cationic substitutions in the M1 active phase of the MoVTeNbO catalysts used for the oxidation of propane to acrylic acid

Several cationic substitutions with Ti, Sn, Ge and W have been made in the M1 active phase of the MoVTe(Sb)NbO catalysts in order to improve their catalytic properties for the partial oxidation of propane into acrylic acid. The catalysts were characterized by BET, XRD and chemical analysis and were studied for propane oxidation. The results obtained show that these substitutions were possible but remain limited. It was noted that Ge increased the activity of the M1 phase whereas W maintained it and Ti and Sn decreased it. Concomitantly the selectivity to acrylic acid was slightly increased or decreased. The effect of Ge, which did not enter into the structure of the M1 phase has been related to an increase of the vanadium content of the M1 phase which occurs because of the formation of new Ge containing species in the slurry during the preparation of the catalyst.