Maleic anhydride is an organic compound with the formula C2H2(CO)2O. It is the anhydride of maleic acid. It is a colorless or white solid with a pungent odor. It is industrially produced on a large scale and used in coatings and polymers.
Maleic anhydride is produced by the gas phase oxidation of n-butane. The whole process converts methyl groups to carboxylates and dehydrogenates the backbone. The selectivity of this process reflects the robustness of maleic anhydride and its conjugated double bond system. Maleic anhydride is traditionally produced by oxidation of benzene or other aromatic compounds. As of 2006, only a few smaller plants continue to use benzene.

In both cases, benzene and butane are fed into a stream of hot air, and the mixture is passed through the catalyst bed at high temperature. The ratio of air to hydrocarbons is controlled to prevent the mixture from igniting. Vanadium pentoxide and molybdenum trioxide are catalysts used for the benzene route, while vanadium phosphate is used for the butane route