Method for electrical-catalytic and selective hydrogenating and dechlorinating of pentachloropyridine

Abstract

The invention discloses a method for electrical-catalytic and selective hydrogenating and dechlorinating of pentachloropyridine. The method comprises the following steps that an acid solution is used as a reaction medium, pentachloropyridine is added in the acid solution to obtain an electrolytic reaction solution, and is subjected to electrolytic reaction in an electrolytic bath which uses a metal material as the cathode and a chemical inert conductive material or a titanium material coated with noble metallic oxide as the anode, wherein the temperature is 20-40 DEG C, the current density is 1-10 A / dm<2>, and the pH is equal to 1-6, and after the electrolytic reaction is completed, the separation and purification are conducted to obtain 2,3,5,6-tetrachloropyridine or 2,3,5-trichloropyridine. The electrolytic voltage can be controlled to 3 V or below, the current efficiency of synthetized 2,3,5,6-tetrachloropyridine can be higher than 88%, and the electrolysis can be performed at room temperature, and the selectivity of synthetized 2,3,5-trichloropyridine can be higher than 98%.

Description

(1) Technical field [0001] The invention relates to a method for preparing 2,3,5,6-tetrachloropyridine and 2,3,5-trichloropyridine by electrocatalytic selective hydrogenation dechlorination of pentachloropyridine, in particular to electrocatalytic selective hydrogenation of pentachloropyridine A method for preparing 2,3,5,6-tetrachloropyridine and 2,3,5-trichloropyridine from the upper 4-position or 4-position and 6-position chlorine substituents. (2) Background technology [0002] 2,3,5,6-tetrachloropyridine as shown in formula (2) is a key intermediate for the production of chlorpyrifos, while 2,3,5-trichloropyridine as shown in formula (3) is a synthetic The key intermediate of ether. In addition, pentachloropyridine represented by formula (1) is a commercial product. [0003] [0004] Many documents or patents have been reported from the electrochemical hydrogenation dechlorination method of pentachloropyridine shown in formula (1) to prepare 2,3,5,6-tetrachloropyri...

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Problems solved by technology

[0005] The purpose of the present invention is to provide a kind of electrocatalytic selective hydrogenation dechlorination of pentachloropyridine (shown in formula 1) to prepare 2,3,5,6-tetrachloropyridine (shown in formula 2) and 2,3,5-trichloropyridine The method of pyridine (shown in formula 3), with silver or silver-plated material as cathode, in solvents such as water, C1~C4 organic alcohol, C1~C4 organic acid, acetonitrile and supporting electrolytes such as sodium benzenesulfonate, lithium chloride The pentachloropyridine shown in formula (1) is carried out electrolysis experiment in the acid cathode solution of composition, controls the pH value (1~6) of above-mentioned electrolytic reaction solution by the buffer agent that is made up of organic acid / organic acid salt, pentachloropyridine It can be reduced to 2,3,5,6-tetrachloropyridine with high selectivity, and the 2,3,5,6-tetrachloropyridine generated by increasing the electrolysis time can be further reduced to 2,3,5-trichloropyridine , the present invention solves the "high electrolysis voltage" [US4242183] and "low current efficiency" in the prior art of preparing 2,3,5,6-tetrachloropyridine or 2,3,5-trichloropyridine by electrochemical hydrogenation dechlorination [US4592810], the problem of "high reaction temperature" [US4592810] and "low dechlorination selectivity" [US4242183]

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