The preparation method of glyphosate

Abstract

The invention discloses a preparation method of glyphosate, which is prepared by reacting disodium salt of aminomethylphosphonic acid and chloroacetate in water; the method avoids the existing iminodiacetic acid method, dialkyl phosphonite The defects in the production of glyphosate by ester method and chloromethyl phosphonic acid method have the characteristics of cleanness, environmental protection and high efficiency. The yield and quality of glyphosate have been significantly improved. It can be recycled, reducing waste liquid discharge, reducing material loss, greatly reducing production costs, and good economic benefits.

Description

Technical field [0001] The invention belongs to the field of chemical engineering and relates to a method for synthesizing organic compounds. Background technique [0002] Glyphosate, whose chemical name is N-(phosphonomethyl)glycine, is a herbicide that has been widely used. Since its commercialization in the mid-1970s, its application range has continued to expand due to its excellent weeding performance. [0003] There are many literature reports on the methods of synthesizing glyphosate, such as iminodiacetic acid method, dialkyl phosphonite method, chloromethyl phosphonic acid method, phosphorous acid method, etc. However, the main methods for realizing industrialization at present are mainly The aminodiacetic acid method and the dialkyl phosphite method. [0004] The iminodiacetic acid method uses iminodiacetic acid or alkali metal salt of iminodiacetic acid as the starting material, and reacts with formaldehyde and phosphorous acid to prepare diglycphos; or takes iminodiacet...

AI Technical Summary

Problems solved by technology

This method has the following problems: 1) Glyphosate is prepared by oxidation of diglyphosate, and the cost of using chlorine dioxide, hydrogen peroxide and other oxidants is relatively high. Although the air oxidation method is efficient, it has high requirements for equipment and catalysts, especially the metal ions of the catalyst 2) With iminodiacetonitrile as the starting material, the production cost of glyphosate is relatively low, but nearly 10 tons of waste liquid will be generated for every ton of glyphosate produced, and these waste liquids are biochemically treated More difficult; using iminodiacetic acid as a starting material can greatly reduce the discharge of waste liquid, but still faces the problem of preparing glyphosate from the above-mentioned oxidation of diglyphosate

This method has the following problems: 1) The catalyst triethylamine is expensive, highly toxic, and difficult to recycle; 2) The solvent methanol will react to form methylal during the depolymerization process of paraformaldehyde, and every ton of glyphosate produced Phosphine produces about 0.45 tons of methylal; during the hydrochloric acid hydrolysis process, monochloromethane is also produced as a by-product, which is difficult to recover; 3) about 5.2 tons of mother liquor is produced per ton of glyphosate production, and the amount of waste water is large, and biochemical treatment is difficult. Residual glyphosate is difficult to recycle

This method has the following problems: 1) the reaction of phosphorus trichloride and paraformaldehyde needs to be carried out under high temperature and high pressure conditions, and the requirements for equipment are relatively high; 2) the molar ratio of phosphorus trichloride and paraformaldehyde is 1.5: 1. The yield of chloromethylphosphonic acid is only 80%; 3) The molar ratio of chloromethylphosphonic acid to glycine is 1:1. Since the reaction between the two belongs to the SN2 nucleophilic substitution reaction, there is a by-product of hydroxymethylphosphine acid and N,N-bis(phosphonomethyl)glycine, resulting in a low yield of glyphosate, only 40% (calculated as formaldehyde)

The process uses the catalyst aluminum trichloride, changes the molar ratio of phosphorus trichloride and paraformaldehyde to make paraformaldehyde excessive, and the whole process is completed under normal pressure conditions, which overcomes the need for high-pressure conditions in the aforementioned chloromethylphosphonic acid method However, the problem of low yield of glyphosate is still not solved