Process for recovering 2,3,5,6-tetrachloropyridine from mixtures of chlorinated pyridines
申请人:THE DOW CHEMICAL COMPANY
公开号:EP0022885A1
公开(公告)日:1981-01-28
Substantially pure 2,3,5,6-tetrachloropyridine is recovered from a mixture of chlorinated pyridines containing 2,3,5,6-tetrachloropyridine, at least one of 2,3,4,5-tetrachloropyridine and 2,3,4,6-tetrachloropyridine and certain other chlorinated pyridines in an improved process which comprises (a) reacting, by contacting, a first such mixture of chlorinated pyridines with chlorine in the presence of a strong Lewis acid catalyst thereby to obtain a second mixture consisting essentially of 2,3,5,6-tetrachloropyridine and pentachloropyridine, and (b) recovering the 2,3,5,6-tetrachloropyridine from the second mixture, especially by fractional distillation. The reaction is normally conducted at a temperature of from 150°C to 300°C by pressurizing chlorine into a molten mixture of the chlorinated pyridines and main- ' taining such conditions until substantially all of the isomers have been converted to the symmetrical tetrachloropyridine or pentachloropyridine.
从含有 2,3,5,6-四氯吡啶、2,3,4,5-四氯吡啶和 2,3,4,6-四氯吡啶中的至少一种以及某些其他氯化吡啶的氯化吡啶混合物中回收纯度相当高的 2,3,5,6-四氯吡啶、(a) 在强路易斯酸催化剂存在下,使第一种氯化吡啶混合物与氯反应,从而得到第二 种混合物,该混合物主要由 2,3,5,6-四氯吡啶和五氯吡啶组成;以及 (b) 从第二种混合物中回收 2,3,5,6-四氯吡啶,特别是通过分馏回收。反应通常在 150°C 至 300°C 的温度下进行,方法是将氯气加压到氯化吡啶的熔融混合物中,并保持这样的条件,直到基本上所有的异构体都转化为对称的四氯吡啶或五氯吡啶。