| 摘要 |
A process for the manufacture of N-phenylmaleimide which comprises reacting maleic anhydride with aniline in a single step at elevated temperature in the presence of a water-immiscible organic solvent capable of forming an azeotrope with water and of p-toluenesulfonic acis as catalyst. According to the invention, N-phenylmaleimide recovery comprises the successive steps of: (a) treating the reaction mixture in a dilution and filtration zone, in which it is diluted with an additional amount of the solvent, the diluted mixture being filtered at low temperature in order to separate a solid cake containing the catalyst and impurities, and a liquid filtrate consisting of a solution of N-phenylmaleimide in the solvent, (b) distilling this solution of N-phenylmaleimide under reduced pressure so as to successively separate the solvent and substantially pure N-phenylmaleimide, whereas the distillation residue is treated exactly as indicated in (a) above in a dilution and filtration zone in order to recover the N-phenylmaleimide therefrom, the filtrate being recycled for use in step (a) to dilute the reaction mixture produced by a subsequent synthesis. Furthermore, the filter cakes from steps (a) and (b) are washed with solvent obtained by distillation in step (b) and the resulting wash solvents are recycled for use in the reaction and/or dilution zones. A high purity N-phenylmaleimide is obtained in an overall yield exceeding 86 mole %; the problem of waste water and pollution is reduced to a minimum.
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