Partial oxidation of propane over Keggin type molybdovanadophosphoric acids was studied. The physico-chemical properties of the catalysts were investigated by means of BET, UV-visible diffuse reflectance spectra, IR and TPR, and the preliminary structure-performance relationship was established. The substitution of Mo^6＋ with V^5＋ in Keggin structure decreased the vibration strength of bridging M—O bonds and significantly increased the oxidation and oxygen insertion abilities of Keggin oxoanion, thus influencing the catalytic activity and selectivity to oxygenated products. Optimized vanadium atom substitution enhanced the selectivity to acid products and the optimal selectivity could be obtained on the H₅PMo₁₀V₂O₄₀ catalyst. However, excessive vanadium substitution led to deep oxidation of the acid products. It was thought that appropriate amount of (VO)^2＋and small amount of vanadic oxide species segregating from the primary and the secondary structures of the oxo-anions have an impact on the reaction performance.

Key words: molybdovanadophosphoric acid, propane oxidation, vanadium species