The Dow Chemical Company

Norman L Dean

Donald J Perettie

Wallace E Embrey

John Thomas Marshall

Highly chlorinated pyridines are prepared by reacting 2,6-dichloropyridine with chlorine at temperatures of from about 150.degree. to about 300.degree. C. in the presence of an aluminum, iron or silica oxide catalyst and under sufficient pressure to maintain the 2,6-dichloropyridine reactant as a liquid.

Preparation of highly chlorinated pyridines

Substantially pure 2,3,5,6-tetrachloropyridine is recovered from a mixture of chlorinated pyridines containing initially 2,3,5,6-tetrachloropyridine and other chlorinated pyridines in an improved process which comprises (a) reacting by contacting a first mixture of chlorinated pyridines with chlorine in the presence of a strong Lewis acid catalyst to thereby obtain a second mixture consisting essentially of 2,3,5,6-tetrachloropyridine and pentachloropyridine, and (b) recovering the 2,3,5,6-tetrachloropyridine from said second mixture. The reaction is normally conducted at a temperature of from about 150.degree. C. to about 300.degree. 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.

Process for recovering 2,3,5,6-tetrachloropyridine

Tetrachloropyridine is prepared by heating pentachloropyridine in an aqueous medium under pressure, with agitation, in the presence of a particulate oxidizable metal, e.g., zinc and a hydrogen-producing acid, e.g., hydrogen chloride. The tetrachloropyridine is then conveniently extracted with an inert, water-immiscible solvent, e.g., a halogenated hydrocarbon.

Growing community of inventors

Lake Jackson, TX, United States of America

Norman L Dean