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

A technology of hydroxybenzoic acid and hydroxybenzoate, applied in the field of synthesis of 3,6-dichloro-2-hydroxybenzoic acid, which can solve the problems of reduced reaction yield and achieve the effect of reducing production costs

Inactive Publication Date: 2013-04-03
ZHEJIANG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

But, according to prior art, if reduce the consumption of salt of wormwood, can cause the undesirable result that occurs reaction yield to reduce

Method used

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

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Experimental program
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Effect test

Embodiment 1

[0031] Embodiment 1, a kind of preparation method of 3,6-dichloro-2-hydroxybenzoic acid, carries out following steps successively:

[0032] 1) Weigh 146g (0.83 mol) of 2,5-dichlorophenol (95% purity) in a 1000ml three-neck flask and dissolve it in 98g of KOH aqueous solution (mass concentration 48%, containing 0.84mol of KOH), and then add Mix 640ml of xylene as a solvent evenly, heat up to 142~145°C, dehydrate with a water separator until almost no water is evaporated, and obtain 2,5-dichlorophenoxide potassium solution.

[0033] 2), transfer the potassium 2,5-dichlorophenate solution obtained in the above step 1) to the autoclave, and then add 12gK 2 CO 3 and 14g of activated carbon as a co-catalyst, filled with CO in the autoclave 2 To 3Mpa, after being stabilized, empty the air, and continue the same operation for 3 times, so as to fully replace the air in the kettle; then fill with CO 2 to 5Mpa and heated; finally, control the reaction temperature to 145°C and the reac...

Embodiment 2

[0036] 14g of activated carbon in Example 1 was changed to 13.8g of recovered activated carbon (obtained in Example 1) + 0.2g of activated carbon, and the rest were the same as in Example 1. The result is:

[0037] 13.9 g of activated carbon was recovered and 73 g (0.437 mol) of 3,5-dichlorophenol was recovered, and the calculated recovery rate was 52.7%. 80 g (0.386 mol) of 3,6-dichloro-2-hydroxybenzoic acid solid was obtained, and the calculated yield was 46.5%. The calculated total yield of starting material and product was 99.2%.

Embodiment 3

[0039] Change the activated carbon 14g in Example 1 into 13.9g of recovered activated carbon (obtained in Example 2)+0.1g activated carbon, and the rest are the same as in Example 1. The result is:

[0040] 13.9 g of activated carbon was recovered and 72.1 g (0.432 mol) of 3,5-dichlorophenol was recovered, with a calculated recovery rate of 52.0%. 80.8 g (0.390 mol) of 3,6-dichloro-2-hydroxybenzoic acid solid was obtained, and the calculated yield was 47.0%. The total yield of starting material and product was calculated to be 99.0%.

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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 ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C07C65/05C07C51/15
Inventor 章国林陈俊倪航程俞永平
Owner ZHEJIANG UNIV
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