Improved preparation method of 3,6-dichloro salicylic acid

A technology of dichlorosalicylic acid and dichlorosalicylic acid salt, which is applied in the field of preparation of 3,6-dichlorosalicylic acid, can solve problems such as high cost, and achieves reduced operation difficulty, stable yield, and convenient improvement. Effect

Active Publication Date: 2014-10-08
SHANDONG WEIFANG RAINBOW CHEM
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, this patent involves the use of a new type of gas-solid reactor. At present, if domestic manufacturers of the same product adopt this p

Method used

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preparation example Construction

[0030] The preparation technology of 3,6-dichlorosalicylic acid of the present invention adopts the following steps:

[0031] (1) Put 2,5-dichlorophenol and potassium hydroxide aqueous solution into the dehydration kettle according to the molar ratio of 1:0.9-1.1, and then fill it with nitrogen for replacement. After the replacement, add the solvent xylene to heat up and dehydrate under negative pressure reflux. The gauge pressure is -0.05~-0.098Mpa during the reflux dehydration of xylene, and the end point of dehydration is to detect that there are no water drops in the solution, and the temperature of the end point of dehydration is about 100°C-130°C.

[0032] (2) After the dehydration is completed, replace with nitrogen, and then through the feeding port, first add potassium carbonate with a mass ratio of 0.4-0.6:1 to 2,5-dichlorophenol into the kettle, and then add reducing metals (such as zinc powder, aluminum powder or magnesium powder) and EDTA, then close the reactor a...

Embodiment 1

[0039] Add 120g of 99% 2,5-dichlorophenol into a 1L four-neck flask, then add 83g of 50% potassium hydroxide solution, then fill with nitrogen, add 400g of xylene after nitrogen filling, and start Negative pressure dehydration operation. Maintain the gauge pressure at -0.08MPa, start reflux dehydration, stop dehydration when there are no water drops in the escaping liquid, fill the kettle with nitrogen again, and then add 50g of dry potassium carbonate, 0.5g of zinc powder, and 0.1g of EDTA. Keep warm at 130°C-135°C for 30 minutes, then transfer to a 1L autoclave that has been dried and replaced with nitrogen.

[0040]After the material transfer is completed, nitrogen is replaced again, the autoclave is sealed, the temperature is raised to 130-140°C, and then CO 2 To 4MPa, keep at 150°C-155°C for 10h, then cool down to 90°C, and then vent. After emptying, add 300g of water into the kettle, keep it warm at 80-90°C for 1 hour, transfer the feed liquid into a 2L four-neck flas...

Embodiment 2

[0042] Add 95g of 99% 2,5-dichlorophenol into a 1L four-neck flask, then add 83g of 50% potassium hydroxide solution, then fill with nitrogen, and add to Example 1 for recovery after nitrogen filling is complete. Xylene layer 522.5g, start negative pressure dehydration operation. Maintain the gauge pressure at -0.06MPa, start reflux dehydration, and continue to remove 90g of xylene when the liquid does not contain water droplets, then fill the kettle with nitrogen, and then add 50g of dry potassium carbonate, 1.5g of aluminum powder, and EDTA0 .15g. Keep warm at 130°C-135°C for 30 minutes, then transfer to a 1L autoclave that has been dried and replaced with nitrogen.

[0043] After the material transfer is completed, nitrogen is replaced twice, the autoclave is sealed, the temperature is raised to 130-140°C, and then CO 2 To 6MPa, keep warm at 130°C-135°C for 16h, then cool down to 80°C, and then vent. After emptying, add 300g of water into the kettle, keep it warm at 80-...

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Abstract

The invention discloses an improved preparation method of 3,6-dichloro salicylic acid. The improved preparation method of 3,6-dichloro salicylic acid comprises the following steps: carrying out reaction on 2,5-dichlorophenol and an alkali liquor, then adding an organic solvent, and carrying out reduced pressure dehydration; adding potassium carbonate, a dehydrating agent and a stabilizer after dehydration is finished, and carrying out reaction at the temperature of 130-140 DEG C for 30-60 minutes; adding materials into a high pressure autoclave, heating to 130-140 DEG C, then introducing CO2, and carrying out high pressure carboxylation reaction; carrying out aftertreatment after the reaction is finished, so that 3,6-dichloro salicylic acid is obtained. The improved preparation method of 3,6-dichloro salicylic acid has the advantages that oxygen is isolated before dehydration and carboxylation, so that oxidation of oxygen to a product is avoided; the dehydrating agent and the stabilizer are added before carboxylation, so that water in a system and positive hydrogen ions generated during carboxylation are further removed, stability of the system is maintained, yield is guaranteed and appearance of the product is greatly improved, usage amount of potassium carbonate is reduced, and an aftertreatment process is simplified; besides, modification on equipment is less, the current production enterprises can implement improvement conveniently, and quick benefit can be obtained.

Description

technical field [0001] The invention relates to a preparation method of 3,6-dichlorosalicylic acid, in particular to an improved preparation method of 3,6-dichlorosalicylic acid based on the prior art. Background technique [0002] Industrial grade 3,6-dichlorosalicylic acid is an off-white solid with a melting point of 181-183°C. It is the main raw material for the manufacture of 3,6-dichloro-2-methoxybenzoic acid (dicamba), and it is also an important chemical intermediate. Dicamba is a high-efficiency, low-toxicity, broad-spectrum herbicide, which is widely used at home and abroad, especially the recent promotion of dicamba-resistant transgenic crops has greatly increased the market demand. Therefore, how to efficiently and simply synthesize the key intermediate 3,6-dichlorosalicylic acid is worth studying. [0003] At present, the synthesis method of 3,6-dichlorosalicylic acid mainly uses 2.5-dichlorophenol as the starting material, reacts with alkaline substances in a...

Claims

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Application Information

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IPC IPC(8): C07C51/15C07C65/05
CPCC07C37/66C07C51/15C07C65/05C07C39/30
Inventor 孙国庆侯永生陈桂元高国利张付敏谭建国孙天伟杨青林李琪范存美邢森
Owner SHANDONG WEIFANG RAINBOW CHEM
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