Preparation method of dicamba

Abstract

The invention provides a preparation method of dicamba. The preparation method comprises the steps as follows: A) 3,6-dichlorosalicylic acid is salified under an alkaline condition; B) 3,6-dichlorosalicylate and halomethane are subjected to a methylation reaction under the action of a catalyst, and 3,6-dichloro-2-methyl methoxybenzoate is obtained, wherein the catalyst comprises tertiary amine andquaternary ammonium salt; C) methyl 3,6-dichloro-2-methoxybenzoate is subjected to acidification and drying, and dicamba is obtained. A compound phase transfer catalyst is adopted in the etherification process, so that salicylic acid is completely converted into dicamba methyl ester, separation of oil and water phases is realized, alkaline hydrolysis and acidification routes in the prior art arereplaced by distillation and acidification, the production process in the whole process is simple, the product quality is good and industrial production is facilitated.

Description

technical field [0001] The invention relates to the technical field of herbicides, in particular to a preparation method of dicamba. Background technique [0002] Dicamba (dicamba), also known as Baicao, has a chemical name of 3,6-dichloro-2-methoxybenzoic acid, a herbicide of the benzoic acid family, and is a low-toxicity, high-efficiency, broad-spectrum herbicide , It has a significant control effect on annual and perennial broad-leaved weeds, but it is relatively safe on grass crops such as wheat, corn, millet, and rice. With the prohibition and restriction of metsulfuron-methyl and chlorsulfuron-methyl preparations, the safety, human health and super weed problems caused by glyphosate have become increasingly prominent. As a traditional high-efficiency herbicide, dicamba has gradually attracted attention. With the continuous development of transgenic crops, dicamba ushers in new opportunities for development. [0003] At present, the mainstream synthesis route of dicam...

AI Technical Summary

Problems solved by technology

[0003] At present, the mainstream synthesis route of dicamba is to use 3,6-dichlorosalicylic acid as the raw material, and undergo processes such as beating, etherification, alkaline hydrolysis, decolorization, acidification, pressure filtration, recrystallization, centrifugation and drying to obtain dicamba , the conversion rate of salicylic acid in this route is low, resulting in low reaction yield and purity, and the product is yellow or light yellow, with poor product phase and easy to agglomerate. In order to improve product quality, a step of activated carbon decolorization is also added. The dust is large, the workers' work site is not controlled, the recrystallization, centrifugation and drying processes have a strong smell, and the pressure on environmental protection is high, which makes it difficult to industrialize production