To simply purify a crude carboxylic acid amide into the highly pure product useful as an organic synthetic material, etc., in a high yield by feeding a crude carboxylic acid amide into a specific tower type continuous crystallization device, subjecting the obtained crystals to repeated melting-recrystallizing treatments, precipitating the purified crystals and subsequently melting, separating and recovering the purified product.
This method for purifying a carboxylic acid amide comprises feeding a crude carboxylic acid amide containing the carboxylic acid amide (e.g. a crude acetamide obtained by the reaction of acetic acid with ammonia) in an amount of ≥50wt.% into a tower type continuous crystallization device having an upper cooling and crystallizing section (A section), a lower crystal-purifying section (B section) and a bottom crystal-melting section (C section) and set at such temperatures as to gradually increase from the section A to the section C, crystallizing the carboxylic acid amide in the section A, bringing the obtained crystals into counter-current contact with the crude carboxylic acid amidecontaining solution in the section B so as to repeat the melting-recrystallizing treatments and precipitating the purified carboxylic acid amide crystals, and subsequently melting the crystals and separating and recovering the melted pure carboxylic acid amide in the section C.
NISHI MAKOTO
NAKAMURA HITOSHI
AIZAWA TOSHIYUKI
KUWABARA HIROYUKI
WATANABE TAKEHIKO
NOMA NOBUMASA
HORIBE KAZUYOSHI
NIPPON STEEL CHEMICAL CO