To provide high-quality ε-caprolactam by efficiently refining crude ε-caprolactam obtained by the Beckmann rearrangement of cyclohexanon oxime.
A method for producing high-quality ε-caprolactam includes: a step of crystallizing ε-caprolactam at a crystallization temperature from 10°C to a temperature less than a melting point of lactam from a mixed solution prepared by mixing crude ε-caprolactam, which is obtained by the Beckmann rearrangement of cyclohexanone oxime, with an organic solvent, and thereby obtaining a slurry liquid containing ε-caprolactam crystals; a step of separating the obtained slurry liquid into a liquid phase containing the organic solvent and a solid phase containing the ε-caprolactam crystals, and thereby obtaining the ε-caprolactam crystals; a step of subjecting the obtained ε-caprolactam crystals to repulp cleaning using an organic solvent at a temperature not less than the crystallization temperature but less than a melting point of ε-caprolactam, and thereby obtaining a slurry liquid containing ε-caprolactam crystals; and a step of separating the slurry liquid into a liquid phase containing the organic solvent and a solid phase containing the ε-caprolactam crystals, and thereby obtaining the high-quality ε-caprolactam.
OZAKI TATSUYA
Naozumi Hiroyasu
Norihiko Ara
Hiroyuki Kato
Mitsunaga Igarashi
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