A kind of preparation method of improved 3,6-dichlorosalicylic 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, reduce operation difficulty, improve product appearance, and see benefits Effect
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[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, fill it with nitrogen for replacement, and then add potassium carbonate with a mass ratio of 0.4-0.6:1 to 2,5-dichlorophenol into the kettle through the feeding port, and then add reducing metals (such as zinc powder, aluminum powder or magnesium powder) and EDTA, then close the ...
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 2To 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 flask...
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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