Method for preparing glyphosate by catalytic oxidation method

Abstract

This invention discloses a method for oxidizing N-(carboxymethyl)-N-(phosphonomethyl)-glycine into glyphosate by using carbon nanotubes or modified nanotubes as a novel catalyst. The method has such advantages as high reaction selectivity, no need for reductant such as ferrous sulfate or sodium sulfite, repeated use of the catalyst, high product yield, high product quality, and little mother liquor. The method can avoid the problems of low solid glyphosate yield, low quality and large wastewater discharge faced by sodium tungstate-ferrous sulfate method.

Description

technical field [0001] The invention relates to a method for synthesizing glyphosate by catalytic oxidation of diglyphosate. In the method, carbon nanotubes are used as catalysts. Background technique [0002] Glyphosate (glyphosate, N-(phosphonomethyl)-glycine) is a herbicide screened and synthesized by Monsanto Chemical Company in the United States in the 1960s, which belongs to amino acid derivatives. The good biological activity of glyphosate makes it a widely used high-efficiency, low-toxicity, post-emergent herbicide, and its current annual sales rank first among pesticide products. [0003] The iminodiacetic acid (IDA) method is one of many methods for synthesizing glyphosate. It reacts IDA with formaldehyde and phosphorous acid to prepare diglyphosate (PMIDA), and then oxidizes PMIDA to obtain glyphosate. This method has simple operation, mild process conditions, small equipment investment, and high product yield, but there are problems such as high raw material cos...

AI Technical Summary

Problems solved by technology

[0009] Monsanto reported a method for preparing glyphosate by catalytic oxidation of diglyphosate with sodium tungstate / sodium molybdate-hydrogen peroxide-ferrous sulfate / sulfite system. This method has the advantage of high reaction selectivity, but also has many defects For example, the price of the catalyst sodium tungstate is high, the catalyst cannot be effectively recovered or recycled after the reaction is completed, and it needs to be reduced with ferrous sulfate after the oxidation, but the introduction of iron ions makes the product color yellow, and the yield of glyphosate raw powder is low , a considerable part of the product still remains in the mother liquor, the glyphosate water dosage is large, etc.

Compared with sodium tungstate, sodium molybdate does not use iron salt for reduction after oxidation, and the catalyst can be applied mechanically, but the number of applications is very limited, about 2-4 times. It is difficult to recover sodium molybdate, and the price of sodium molybdate is much higher Sodium tungstate, and molybdenum resources are scarce, these factors limit the large-scale application of this method

[0010] CN1183100A, CN1480460A, CN1066152C patents have reported activated carbon catalysts, the method for preparing glyphosate by hydrogen peroxide oxidation, the advantage of this method is that the catalyst is cheap and easy to get, and the process is easy to control, but its defect is that the activated carbon used is amorphous , different preparation methods and sources of raw materials lead to large differences in performance, and the effect of activated carbon is poor, which easily leads to fluctuations and instability in production. Therefore, it is necessary to develop new catalysts with stable performance and reliable quality

Glyphosate is synthesized by the method of precious metal catalyzed oxidation of diglyphosate, the content of glyphosate obtained by the reaction is high, and the selectivity and conversion rate of the reaction are also very good. Monsanto Company of the United States uses this method to synthesize glyphosate, but due to the precious metal The price is expensive, the recovery is difficult, the catalyst is easy to deactivate, and the reasons for patent restrictions require the development of new methods

Images