| 摘要 |
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 DEG C to 300 DEG C by pressurizing chlorine into a molten mixture of the chlorinated pyridines and maintaining such conditions until substantially all of the isomers have been converted to the symmetrical tetrachloropyridine or pentachloropyridine.
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