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.