Patents Assigned to Toso Steel Co., Ltd.
  • Purification of N-methyl-2-pyrrolidone
    Patent number: 4895959
    Abstract: A method for purifying N-methyl-2-pyrrolidone containing thiophenol and/or diphenyl disulfide is disclosed, comprising adding a polyhalogenated aromatic compound and an alkali metal hydroxide and/or an alkali metal carbonate to the N-methyl-2-pyrrolidone containing thiophenol and/or diphenyl disulfide, heat treating the mixture, and subjecting the mixture to separation by distillation. The thiophenol and/or diphenyl disulfide can be removed with ease and at low cost.
    Type: Grant
    Filed: June 9, 1989
    Date of Patent: January 23, 1990
    Assignees: Tosoh Corporation, Toso Steel Co., Ltd.
    Inventors: Toshikazu Kato, Hiroshi Inoue, Kensuke Ogawara