Preparation method of 3,6-dichloro-2-hydroxybenzoic acid

Abstract

The invention discloses a preparation method of 3,6-dichloro-2-hydroxybenzoic acid, which sequentially comprises the following steps: 1) salifying 2,5-dichlorophenol; 2) carboxylation: transferring the 2,5-dichlorophenate solution into a high-pressure reaction kettle, adding a cocatalyst, and introducing CO2 to carry out high-pressure carboxylation reaction to obtain the reaction product containing 3,6-dichloro-2-hydroxybenzoate, wherein the cocatalyst is composed of potassium carbonate and activated carbon; 3) refinement: after cooling the reaction product containing 3,6-dichloro-2-hydroxybenzoate obtained in the step 2) to room temperature, adding an alkali solution, regulating the pH value to 11-13, uniformly stirring, filtering to recover activated carbon, stratifying the filtrate, and taking the water phase; and adding an acid solution into the water phase, regulating the pH value to 1-3, carrying out vapor distillation to recover the 2,5-dichlorophenol, cooling to crystallize, carrying out vacuum filtration, and drying to obtain the 3,6-dichloro-2-hydroxybenzoic acid.

Description

technical field

[0001] The invention belongs to a dicamba intermediate production process and relates to a synthesis method of 3,6-dichloro-2-hydroxybenzoic acid. Background technique

[0002] 3,6-dichloro-2-hydroxybenzoic acid, 3,6-dichlorosalicylic acid, English name 3,6-Dichlorosallicylic Acid, structural formula:

[0003] .

[0004] 3,6-dichloro-2-hydroxybenzoic acid is an intermediate in the preparation of the pesticide herbicide dicamba (3,6-dichloro-2-methoxybenzoic acid). Dicamba is a benzoic acid series herbicide first developed by the former American Siebel Chemical Company. With the prohibition and restricted use of chlorsulfuron and metsulfuron-methyl preparations, the demand for dicamba will increase, and the market prospect is promising. At present, the global sales volume of dicamba is about 15,000 t / year, and its production is mainly concentrated in Germany's BASF company and Switzerland's Sandoz company. In China, it is mainly Zhejiang Shenghua Biotech ...

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