A kind of preparation method of 2,3,6-trichloropyridine

Abstract

The invention discloses a preparation method of 2,3,6-trichloropyridine, which uses 3-picoline and chlorine gas as raw materials, and uses a molecular sieve catalyst to catalyze one-step gas phase chlorination and detrichlorination in the presence of water vapor Methyl preparation of 2,3,6‑trichloropyridine. The molecular sieve catalyst is prepared by using molecular sieve raw powder as an active component. The raw material 3-picoline used in the present invention is a by-product of pyridine synthesized by the aldehyde-ammonia method, and the source is cheap and easy to obtain. Molecular sieve catalyst has strong processing ability. Using 3-picoline and chlorine gas as raw materials, adding appropriate amount of water, under the action of molecular sieve acid center and water vapor molecules, gas-phase chlorination and detrichloromethylation reactions occur, and one-step synthesis of 2,3 , 6-trichloropyridine, the process is simple, the product is pure, the conversion rate is high, and the yield can generally be maintained at more than 85%, the highest can reach 95%, and it has a good industrial application prospect.

Description

technical field [0001] The invention belongs to the field of chemical industry and relates to a preparation method of 2,3,6-trichloropyridine. Background technique [0002] 2,3,6-Trichloropyridine is an important chemical intermediate, which is widely used in the field of pesticides and medicine, and can be used as the key raw material for the synthesis of new pesticide chlorantraniliprole, such as 2,3-dichloropyridine. [0003] The existing 2,3,6-trichloropyridine synthesis methods generally have disadvantages such as low reaction efficiency, poor selectivity, low yield, and a large amount of waste water generated during the reaction process. For example, US Pat. No. 4,515,953 uses the pyridine chlorination method to prepare 2,3,6-trichloropyridine. The disadvantages of this method are low yield, many side reactions, and harsh equipment requirements. U.S. Patents US4281135, US4785112, and US4810797 use 2,6-dichloropyridine to prepare 2,3,6-trichloropyridine by liquid-phase...

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Problems solved by technology

[0003] The existing 2,3,6-trichloropyridine synthesis methods generally have disadvantages such as low reaction efficiency, poor selectivity, low yield, and a large amount of waste water generated during the reaction process.

For example, U.S. Patent No. 4,515,953 uses the pyridine chlorination method to prepare 2,3,6-trichloropyridine. The disadvantages of this method are low yield, many side reactions, and harsh equipment requirements.

U.S. Patents US4281135, US4785112, and US4810797 use 2,6-dichloropyridine in liquid-phase chlorination or gas-phase chlorination to prepare 2,3,6-trichloropyridine. The conversion rate of raw materials is low, the reaction time is long, and the efficiency of obtaining the target product is low.

Chinese patent CN 107759512A uses 2,6-dichloropyridine as a raw material to prepare 2,3,6-trichloropyridine by gas-phase chlorination under the action of a catalyst. The preparation steps of the catalyst are cumbersome and the selectivity of the target product is low.

Chinese patent CN 108484492 A uses nicotinamide as a raw material to prepare 2,3,6-trichloropyridine through Hofmann degradation, chlorination and Sandmeyer reaction. The method has the purity and yield of 2,3,6-trichloropyridine The efficiency is above 90%, but the raw materials are expensive, the reaction steps are long, and a large amount of waste water is produced

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