To continuously perform the extractive distillation of the subject compound with a small loss by monitoring the distillation conditions in an acetone buffer region and maintaining and reforming the acetone buffer when carrying out the extractive distillation of low-purity propylene oxide with oxyalkylene glycols as an extractive distillation agent.
(A3) Propylene oxide contaminated with water, (A1) methanol and (A2) acetone is introduced from a pipe 120 into the lower half of an extractive distillation column 100 and (B) an A2 buffer zone is provided in a position below the point of introduction thereof. (C) An oxyalkylene glycol extractive distilling agent is then introduced into a position above the point of introduction thereof with a pipe 106 to recover a light fraction comprising an anhydrous A3 in a position above the point of introduction thereof. A heavy fraction containing water, the components A1, A2 and C is recovered from a reboiler of the extractive distillation column 100. At this time, one of the distillation conditions is continuously monitored with a sensor 306. When the distillition conditions deviate from the predetermined value, the additional A2 is added to the extractive distillation column 100 to maintain and reform the A2 buffer agent. Thereby, the objective propylene oxide is continuously extracted and distilled.
ANDORIYUU CHIYAARUZU HIISUTAA
MAAKU ERIOTSUTO TEERAA
MAAKU ARAN MIYUURAA
MAIKERU UOREN PIITAAZU
UIRIAMU PURIIJII NERUSON
