Method for effectively recycling 2,4-dichloro-5-fluoro acetophenone from crystallization mother liquor

Abstract

The invention discloses a method for effectively recycling 2,4-dichloro-5-fluoro acetophenone from crystallization mother liquor, which comprises the following steps of: (a) reacting 2,4-dichloro-5-fluoro acetophenone crystallized mother liquor and neopentyl glycol as raw materials in an inert organic solution A under the action of an acidic catalyst A, then removing water continuously produced in the reaction process, and after sufficient reaction, separating and purifying to respectively obtain 2,6-dichloro-3-fluoro acetophenone and 2,4-dichloro-5-fluoro acetophenone ketal; and (b) carrying out the hydrolysis on the 2,4-dichloro-5-fluoro acetophenone ketal and water in an inert organic solution B under the action of an acidic catalyst B, and after sufficient reaction, carrying out aftertreatment to obtain the 2,4-dichloro-5-fluoro acetophenone. The invention has advanced process route, simple operation, mild reaction condition, high recycle rate of the 2,4-dichloro-5-fluoro acetophenone, environment protection and low production cost; and the neopentyl glycol of the auxiliary reagent can be recycled repeatedly, and the solidoid acidic catalyst can be recycled, thereby the invention is suitable for industrialized large-scale production.

Description

(1) Technical field [0001] The invention relates to a method for efficiently recovering 2,4-dichloro-5-fluoroacetophenone from 2,4-dichloro-5-fluoroacetophenone crystallization mother liquor. (2) Background technology [0002] 2,4-Dichloro-5-fluoroacetophenone is a key intermediate for the production of quinolones such as ciprofloxacin, enrofloxacin, and norfloxacin, with an annual market demand of more than 3,000 tons. 2,4-dichloro-5-fluoroacetophenone is prepared by using 2,4-dichlorofluorobenzene, acetyl chloride and aluminum trichloride as raw materials through the Friedel-Crafts acylation reaction. Chloro-5-fluoroacetophenone inevitably produces its isomer by-product 2,6-dichloro-3-fluoroacetophenone, and the main component of the reaction solution is 2,4-dichloro-5-fluoro Acetophenone and 2,6-dichloro-3-fluoroacetophenone, of which 2,4-dichloro-5-fluoroacetophenone content is about 80%, 2,6-dichloro-3-fluoroacetophenone The ketone content is about 20%. The melting po...

AI Technical Summary

Problems solved by technology

2,4-dichloro-5-fluoroacetophenone is prepared by using 2,4-dichlorofluorobenzene, acetyl chloride and aluminum trichloride as raw materials through the Friedel-Crafts acylation reaction. Chloro-5-fluoroacetophenone inevitably produces its isomer by-product 2,6-dichloro-3-fluoroacetophenone, and the main component of the reaction solution is 2,4-dichloro-5-fluoro Acetophenone and 2,6-dichloro-3-fluoroacetophenone, of which 2,4-dichloro-5-fluoroacetophenone content is about 80%, 2,6-dichloro-3-fluoroacetophenone The ketone content is about 20%. The melting points of 2,4-dichloro-5-fluoroacetophenone and 2,6-dichloro-3-fluoroacetophenone differ by about 10°C. Post-treatment is exactly repeated crystallization at low temperature, and 2,4-dichloro-5-fluoroacetophenone is preferentially separated out, but as the content of 2,6-dichloro-3-fluoroacetophenone in the crystallization mother liquor increases as reaching 50% or so, the two cannot be separated by repeated crystallization

2,4-dichloro-5-fluoroacetophenone phenylhydrazone is hydrolyzed under the catalysis of sulfuric acid to obtain 2,4-dichloro-5-fluoroacetophenone. This process has many disadvantages: the amount of hydrochloric acid and sulfuric acid is large, and the amount of waste water is large. The environmental pollution is serious, and at the same time, the auxiliary separation reagent hydrazine hydrate is used in a large amount and is not easy to recycle. - Method for dichloro-5-fluoroacetophenone

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