| 摘要 |
PROBLEM TO BE SOLVED: To suppress polymer formation, reduce the pressure difference rise, enable long-term continuous operation for a purification process and cut cleaning operation involved in the process by preventing nitriles from being polymerized by adding piperidine-oxyl compounds to a (meth)acrylonitrile purification process liquor. SOLUTION: Nitriles are prevented from being polymerized by adding a piperidine-oxyl compound to a (meth)acrylonitrile purification process liquor containing 5-100 ppm of aldehyde(s) and/or 0.0005-10 wt.% of hydrogen cyanide; where it is preferable that the piperidine-oxyl compound is a compound of the formula (R1 is a 1-3C alkyl; R2 is H, O, OH or the like) (pref. 2,2,6,6- tetramethylpiperidine-1-oxyl), its amount being >=5 ppm based on the liquor flow in the purification process, and its concentration being 1-50 wt.%.
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