XANES Study of Hydrothermal Mo-V-Based Mixed Oxide. M1-Phase Catalysts for the (Amm)oxidation of Propane

The hydrothermal Mo-V-based mixed oxide catalysts possessing the M1-phase structure were investigated by XANES and in situ X-ray diffraction under ambient and dynamic redox conditions in the presence of O-2 and H-2 at 693 K. Under ambient conditions, XANES, with the use of model compounds, suggested oxidation states of Nb, Te, Mo, and V close to 5+, 4+, 6+, and 4+, respectively, in the bulk M I phase. The oxidation state changes of Nb, Te, and Mo were not detected under the dynamic redox conditions employed, while the pre-edge peak of vanadium in the M I phase exhibited small, reproducible shifts, suggesting that VOx is the active catalytic species in the bulk M1-phase catalysts for selective (amin)oxidation of propane.