Process for the production of N-phenylmaleimide

摘要

Process for the manufacture of N-phenylmaleimide, in which maleic anhydride is reacted with aniline in a single stage at elevated temperature in the presence of a water-immiscible organic solvent capable of forming an azeotrope with water and of p-toluenesulphonic acid as catalyst. …According to the invention the recovery of N-phenylmaleimide comprises the following successive stages: … …  (a) the reaction mixture is treated in a dilution and filtration zone in which it is diluted with an additional quantity of solvent, the dilute mixture being subjected to a low-temperature filtration in order to separate off a solid cake containing the catalyst and the impurities, and a filtrate consisting of a solution of N-phenylmaleimide in the solvent, and …  (b) this solution of N-phenylmaleimide is subjected to a distillation at reduced pressure so as to separate off successively the solvent and N-phenylmaleimide of at least 99% purity, whereas the distillation residue is treated exactly as indicated in (a) above in a dilution and filtration zone for recovering the N-phenylmaleimide therefrom, the filtrate being returned to stage (a) to be used for diluting the reaction mixture for the synthesis which follows. … …In addition, the filter cakes from stages (a) and (b) are washed with the solvent obtained by distillation in stage (b) and the washing solvents are recycled to the stage of synthesis of N-phenylmaleimide and/or to the dilution zones. …A N-phenylmaleimide of high purity is obtained in an overall yield which exceeds 86 mol%; the problem of water pollution is reduced to a minimum.