Abstract: VPO catalyst precursors were prepared by reducing V ⁵⁺ in organic phase，and added the promoter selected from compounds of Fe, Co, Cu elements which have the similar radius with V ⁴⁺. Techniques of X-ray diffraction，X-ray photoelectron spectroscopy and X-ray fluorescence analysis were used to investigate the effect of the promoters on the active of VPO catalysts which were tested for the selective oxidation of n-butane to malefic anhydride. Results have revealed that the active phase of the catalyst for oxidation of n-butane to malefic anhydride is the phase (VO)₂P₂O₇ and a few VOPO₄. The mass yield of malefic anhydride is increased by adding the promoter .The property of the catalyst of adding promoter is better than the single one.

Key words: VPO catalyst, promoter, compounded component