Citraconic anhydride prodn. from 5C hydrocarbon - by oxidn. over catalyst contg. tungsten, molybdenum and antimony

Prodn. of citraconic anhydride (I) comprises reacting a mixt. of branched, unsatd. 5C hydrocarbons and O2 contg. gas at 300-500 degrees C with apparent contact time 0.1-20(0.2-10) sec. over a catalyst of formula WaMobSbcYdXeOx (Y is P and/or Si; X is V, Bi and/or alkali metal. a and b are 1-12; c is 2-20; d= 0.2-2; c is 0-10; x is sufficient to satisfy valency requirements of the other elements. These catalysts are made by combining a trivalent Sb cpd. (and opt. sources of X) with a soln. of Mo-W heteropoly-acid at 10-200 degrees C, then drying and calcining at 300-500 degrees C. These catalysts can be prepd. reproducibly; have long life times (no loss of activity or selectivity after 1yr), esp. no discharge of Mo or P cpds.; and provide high selectivity for (I).