| 摘要 |
1,175,079. Citraconic, maleic acids and anhydrides. PRODUITS CHIMIQUES PECHINEY-SAINT-GOBAIN. 12 June, 1967 [13 June, 1966], No. 26941/67. Heading C2C. Citraconic anhydride is obtained by separating at least part of the maleic acid present in an aqueous solution obtained as by-product during the manufacture of phthalic anhydride and heating the resulting solution with a solvent having a boiling point of not more than 140‹ C., whereby the solution is dehydrated and the citraconic acid present is converted to citraconic anhydride which dissolves in said solvent, separating the residue from the resulting solution and evaporating the solvent. The preliminary separation of the maleic acid may be effected by concentrating the initial aqueous solution whereby maleic acid crystallizes out and is separated from the solution, by converting it to fumaric acid and separating the fumaric acid from the aqueous solution, or by partially neutralizing the initial aqueous solution so that the maleic acid present is converted to an acid metal maleate, which is separated off, and then acidifying this solution. The citraconic anhydride and maleic acid thus obtained may be converted, into citraconic acid and maleic anhydride respectively. |
