Production of maleic anhydride and catalysts therefor

A catalyst for the production of maleic anhydride by the oxidation of a hydrocarbon, which comprises a phosphorus/vanadium mixed oxide with at least one promoter selected from the group consisting of tungsten, antimony, niobium, and molybdenum, the atomic ratio of vanadium to phosphorus being in the range 0.5:1 to 2:1 and the total atomic ratio of molybdenum, tungsten, antimony or niobium to vanadium being in the range 0.025:1 to 1:1, the surface area of the catalyst being at least 10 m.sup.2 /g, wherein said catalyst comprises a phase having a characteristic powder x-ray diffraction pattern using copper K.alpha.-radiation as follows:

• ______________________________________ Line position d (Angstrom 2.0 degrees Intensity, I ______________________________________ 6.3 14.2 10 4.8 18.5 7 3.9 23.0 100 3.13 28.5 58 2.98 30.0 29 2.65 33.8 7 ______________________________________ .