Abstract: The oxidation of butane vapor with air produces an impure maleic anhydride which when fractionated to first remove materials boiling lower than maleic anhydride and then a maleic anhydride product, leads to a maleic anhydride product fraction which when held at 140.degree. C. for 90 minutes discolors and is not a commercially acceptable product. Such discoloration can be substantially reduced by maintaining the impure maleic anhydride at a temperature from 60.degree. up to 200.degree. C. in the presence of small amounts of either hydrogen peroxide and/or sulfuric acid.