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。