A method for preparing glyphosate from aminomethylphosphonic acid

Abstract

The invention discloses a method for preparing glyphosate from aminomethylphosphonic acid. The method comprises the following steps: stirring aminomethylphosphonic acid, chloroacetic acid, an alkali catalyst and a co-catalyst in a solvent at 25-100 DEG C for 1-10 hours, acidifying with hydrochloric acid and separating to obtain glyphosate. The method optimizes the overall process of a key preparation process and the parameter conditions of each reaction step (including the ratio of reaction raw materials, the alkali catalyst, the co-catalyst, the reaction temperature and time, etc.). Compared with a traditional glyphosate synthesis method, the method has the advantages of good route economy, high reaction selectivity, great industrial application value, etc., reduces the oxidation process of diglyphosate in the traditional process of preparing glyphosate from aminomethylphosphonic acid, and significantly improves the yield of preparing glyphosate from aminomethylphosphonic acid and chloroacetic acid.

Description

Technical Field

[0001] The invention belongs to the technical field of fine chemical preparation, and more specifically, relates to a method for preparing glyphosate technical. Background Art

[0002] Glyphosate's chemical name is N-(phosphomethyl)glycine, and its chemical formula is C3H8NO5P. It is an organophosphine herbicide and a systemic broad-spectrum herbicide. Glyphosate is widely used in rubber, mulberry, tea, orchards and sugarcane fields. It mainly inhibits the phosphoenolpyruvyl shikimate synthase in plants, thereby inhibiting the conversion of shikimate to phenylalanine, tyrosine and tryptophan, interfering with protein synthesis and causing plant death. Glyphosate is absorbed by lotus leaves and then transmitted to various parts of the plant. It can prevent and control plants of many families, including monocots and dicots, annuals and perennials, herbs and shrubs. After entering the soil, glyphosate quickly combines with metal ions such as iron and loses its activity. It has no adverse effects on seeds and soil microorganisms hidden in the soil.

[0003] Traditional industrial synthesis of glyphosate mainly includes IDA method and alkyl ester method. Foreign companies, mainly Monsanto and Syngenta, generally use high-concentration hydrocyanic acid produced as a byproduct of acrylonitrile as raw material to catalyze the synthesis of iminodiacetic acid, and then use diglycol as raw material, oxygen as raw material, and highly activated carbon as catalyst to prepare glyphosate. The characteristics of this process are easy to obtain raw materials, low production cost, high product quality and yield, and it is suitable for large-scale industrial production. In recent years, foreign companies have successfully developed a process that uses diethanolamine as raw material, dehydrogenates under high pressure under the action of a composite catalyst to obtain IDA, and then oxidizes diglycol to obtain glyphosate. As the process route continues to mature, Monsanto is converting some of the devices using hydrocyanic acid as raw material into this process device. The advantages of this method are: short process flow, wide source of main raw materials, and low price. The disadvantage is that highly toxic hydrocyanic acid is required.

[0004] Shenyang Institute of Chemical Industry in my country began research and development in 1973 and established a production unit for producing 10% glyphosate aqueous solution using chloroacetic acid as the starting raw material at Jiangnan Chemical Plant in 1980. By the late 1980s, there were more than a dozen manufacturers of this process, which made a great contribution to the promotion and application of glyphosate in my country. In 1987, the institute launched the glycine-alkyl ester method for synthesizing glyphosate. This method uses dimethyl phosphite, glycine and polyformaldehyde as the main raw materials, triethylamine as the catalyst, and produces glyphosate through addition, condensation and hydrolysis, with a total yield of up to 80%. The product purity can reach 95%. The advantages of this process are simple process, easy availability of raw materials, and relatively low cost. The disadvantages are long process reaction cycle, difficulty in wastewater treatment, and large amount of waste salt crystallization mother liquor.

[0005] Therefore, the current industry is in urgent need of a glyphosate synthesis route with low production cost, simple synthesis method and high selectivity for the target product. Summary of the invention

[0006] In view of the above defects or improvement needs of the prior art, the object of the present invention is to provide a method for preparing the herbicide glyphosate, wherein the overall process of the key preparation process and the parameter conditions of each reaction step (including the ratio of reaction raw materials, base catalyst, co-catalyst, reaction temperature and time, etc.) are improved. Compared with the traditional glyphosate synthesis method, the method has the advantages of high reaction selectivity, low cost, simple operation, high industrial application value, etc.

[0007] To achieve the above object, according to the present invention, a method for preparing glyphosate is provided, characterized in that it comprises the following steps:

[0008] Aminomethylphosphonic acid, chloroacetic acid, a base catalyst and a co-catalyst are stirred in a solvent at 25-100° C. for 1-8 hours, and then hydrochloric acid is added for acidification. The precipitated glyphosate solid is filtered, washed, dried and weighed to calculate the yield.

[0009] As further preferred embodiment of the present invention, in the step, the base catalyst is any one of inorganic bases or organic bases selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium methoxide, sodium tert-butoxide, triethylamine and n-butylamine.

[0010] As a further preferred embodiment of the present invention, in the step, the co-catalyst is at least one of elemental iodine, sodium iodide, potassium iodide, ammonium iodide or tetrabutylammonium iodide.

[0011] As a further preferred embodiment of the present invention, in the step, the solvent is any one of methanol, ethanol, isopropanol, acetonitrile or water.

[0012] As further preferred embodiment of the present invention, in the steps, the molar ratio of the aminomethylphosphonic acid to the chloroacetic acid is 1:2 to 2:1; the molar ratio of the chloroacetic acid to the base catalyst is 1:1 to 1:4; and the molar ratio of the chloroacetic acid to the co-catalyst is 1:0.3 to 1:3.

[0013] By the above technical scheme described in the present invention, compared with the traditional synthesis route, a new method for preparing glyphosate is provided. The method does not involve the highly toxic hydrocyanic acid material in the IDA method, directly uses chloroacetic acid as a raw material, does not need to use glycine as a substrate, avoids the environmental problems caused by "red water" in the glycine synthesis process, and only requires one step. The chemical synthesis of aminomethylphosphonic acid is usually prepared by acetamide, paraformaldehyde and phosphorous acid / phosphorus trichloride through Mannich reaction, and aminomethylphosphonic acid can also be prepared by biocatalysis. Chloroacetic acid is one of the raw materials for synthesizing glyphosate by the glycine method at present. Therefore, the raw materials used in the preparation method of the present invention are cheap and easy to obtain, and the reaction conditions are optimized (especially for the material ratio of the reactants, the type of co-catalyst, the reaction temperature and time, etc.), so that the reaction selectivity is good, with less three wastes, simple operation steps, and the advantages of low by-products.

[0014] The present invention uses aminomethylphosphonic acid and chloroacetic acid as raw materials to prepare glyphosate, which has the characteristics of high synthesis efficiency, low cost and simple operation compared with the existing technology. The preparation method of the present invention first uses aminomethylphosphonic acid and chloroacetic acid as raw materials to react and prepare glyphosate in the presence of an alkaline catalyst and a co-catalyst. The main reactions involved are as follows:

[0015]

[0016] In the synthesis steps involved in the present invention, the selection of iodine-containing catalyst is the key. The yield of glyphosate synthesized from aminomethylphosphonic acid and chloroacetic acid reported by Gao Jiangtao's research group in Fujian Agriculture and Forestry is only 13% (doi.org / 10.1038 / s41467-022-29188-6), and the inorganic base sodium bicarbonate used, aminomethylphosphonic acid, has low selectivity and conversion rate. The present invention can significantly improve the yield of glyphosate by adding an iodine-containing catalyst to the system, increasing the nucleophilicity of the halogenated reagent by the replacement of iodine and chloride ions, and both chloroacetic acid and iodinated reagents are cheap and easy to obtain, and have been industrialized bulk chemical basic chemicals. The synthesis reaction can ensure a high yield, only requires one step, and does not involve dangerous processes such as chlorination, oxidation and nitration. In summary, compared with the traditional industrialized IDA method and glycine method for synthesizing glyphosate, the present invention has the advantages of high reaction selectivity, low cost, simple operation, and great industrial application value. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0018] The preparation method of glyphosate in the present invention is mainly achieved by the following steps:

[0019] The method comprises the following steps: sequentially adding aminomethylphosphonic acid, chloroacetic acid, a solvent, an alkaline catalyst and a co-catalyst into a reactor equipped with a mechanical stirrer, mixing the above materials, stirring and reacting at 25-100° C. for 1-8 hours; adjusting the pH of the reaction system to 1.0-2.5 with hydrochloric acid after the reaction, and precipitating glyphosate solid in the reaction system; crystallizing the precipitated solid, washing the filter cake and drying to obtain a white solid.

[0020] The base catalyst is any one of inorganic bases or organic bases such as sodium hydroxide, potassium hydroxide, sodium methoxide, sodium tert-butoxide, triethylamine and n-butylamine.

[0021] The promoter is at least one of elemental iodine, sodium iodide, potassium iodide, ammonium iodide or tetrabutylammonium iodide.

[0022] The solvent is any one of water, methanol, ethanol, isopropanol and acetonitrile.

[0023] The above scheme is described in detail below with different reaction conditions.

[0024] Example 1

[0025] Glyphosate is prepared using aminomethylphosphonic acid and chloroacetic acid as substrates, the steps are as follows: 11.1 g (0.1 mol) of aminomethylphosphonic acid and 9.5 g (0.1 mol) of chloroacetic acid are dissolved in an organic solvent, methanol (400 mL), and then 10.8 g (0.2 mol) of sodium methoxide and 16.6 g (0.1 mol) of potassium iodide are added in sequence, and the reaction solution is stirred at 80° C. in a reactor equipped with a mechanical stirrer for 4 hours. After the reaction is completed, dilute hydrochloric acid is added dropwise to the reaction system under an ice bath to acidify to a pH of about 2, a large amount of solid is precipitated in the system, and the filter cake is filtered with suction, and washed with a small amount of methanol, dried, and weighed to obtain 8.7 g of white solid. The purity of glyphosate measured by high performance liquid chromatography is 97.2%, and the glyphosate yield is calculated to be 50.1%.

[0026] Example 2

[0027] The method and steps are the same as those in Example 1, except that the solvent is isopropanol, and the purity is 97.0% and the yield is 45.4%.

[0028] The method and steps are the same as those in Example 1, except that the solvent is acetonitrile, and the purity is 96.4% and the yield is 48.5%.

[0029] Example 3

[0030] Glyphosate is prepared using aminomethylphosphonic acid and chloroacetic acid as substrates, the steps are as follows: 11.1 g (0.1 mol) of aminomethylphosphonic acid and 19.0 g (0.2 mol) of chloroacetic acid are dissolved in solvent water (400 mL), and then 12.0 g (0.3 mol) of sodium hydroxide and 10.1 g (0.04 mol) of elemental iodine are added in sequence, and the reaction solution is stirred and reacted at room temperature for 8 hours in a reactor equipped with mechanical stirring. After the reaction is completed, dilute hydrochloric acid is added dropwise to the reaction system under an ice bath to acidify to a pH of about 1.5, a large amount of solid is precipitated in the system, and suction filtration is performed, the filter cake is washed with a small amount of water, dried, and weighed to obtain 8.3 g of white solid, and the purity of glyphosate measured by high performance liquid chromatography is 96.9%, and the glyphosate yield is calculated to be 47.6%.

[0031] Example 4

[0032] Glyphosate is prepared using aminomethylphosphonic acid and chloroacetic acid as substrates, the steps are as follows: 11.1 g (0.1 mol) of aminomethylphosphonic acid and 19.0 g (0.2 mol) of chloroacetic acid are dissolved in an organic solvent ethanol (500 mL), and then 30.3 g (0.3 mol) of triethylamine and 21.8 g (0.15 mol) of ammonium iodide are added in sequence, and the reaction solution is stirred at 50° C. in a reactor equipped with a mechanical stirrer for 6 hours. After the reaction is completed, dilute hydrochloric acid is added dropwise to the reaction system under an ice bath to acidify to a pH of about 2, a large amount of solid is precipitated in the system, and the filter cake is filtered with suction, and washed with a small amount of ethanol, dried, and weighed to obtain 7.9 g of white solid. The purity of glyphosate measured by high performance liquid chromatography is 98.8%, and the glyphosate yield is calculated to be 46.2%.

[0033] The technical solution of the present application uses elemental iodine or iodine salt as a catalyst for the catalytic reaction. Through implementation, it is found that other halides, such as AlCl3 (glyphosate yield 11.2%), NaBr (glyphosate yield 12.5%), and KBr (glyphosate yield 10.8%), cannot significantly increase the yield of glyphosate. When no halogenated promoter is added, the formation of glyphosate cannot be monitored in the liquid phase. Therefore, the addition of an iodine-containing promoter can significantly increase the activity of chloroacetic acid and improve the yield of glyphosate.

[0034] Example 5

[0035] Glyphosate is prepared using aminomethylphosphonic acid and chloroacetic acid as substrates, the steps are as follows: 11.1 g (0.1 mol) of aminomethylphosphonic acid and 9.5 g (0.1 mol) of chloroacetic acid are dissolved in solvent water (500 mL), and then 8.0 g (0.2 mol) of sodium hydroxide and 18.5 g (0.05 mol) of tetrabutylammonium iodide are added in sequence, and the reaction solution is stirred at 100° C. in a reactor equipped with a mechanical stirrer for 4 hours. After the reaction is completed, dilute hydrochloric acid is added dropwise to the reaction system under an ice bath to acidify to a pH of about 1.5, a large amount of solid is precipitated in the system, and the filter cake is filtered with suction, and washed with a little water, dried, and weighed to obtain 8.9 g of white solid. The purity of glyphosate measured by high performance liquid chromatography is 96.6%, and the glyphosate yield is calculated to be 50.9%.

[0036] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing glyphosate from aminomethylphosphonic acid, characterized in that: The steps include: (1) stirring aminomethylphosphonic acid, chloroacetic acid, a base catalyst and a co-catalyst in a solvent to react to obtain a reaction solution, and monitoring the reaction solution by liquid phase and TLC thin layer chromatography until the reaction is completed, wherein the base catalyst is selected from any one of sodium hydroxide, potassium hydroxide, sodium methoxide, sodium tert-butoxide, triethylamine, and n-butylamine, and the co-catalyst is selected from at least one of elemental iodine, sodium iodide, potassium iodide, ammonium iodide and tetrabutylammonium iodide, the reaction temperature is 25-100° C., the reaction time is 1-8 hours, and the molar ratio of the chloroacetic acid, aminomethylphosphonic acid, base catalyst, and co-catalyst is 1:0.5-2:1-4:0.3-3; (2) Add hydrochloric acid to the reaction solution in step (1) to acidify it, adjust the pH of the system, precipitate glyphosate solid, filter the crystals, wash the filter cake and dry it to obtain glyphosate.

2. The method for preparing glyphosate from aminomethylphosphonic acid according to claim 1, characterized in that: In the step (1), the solvent is selected from any one of water, methanol, ethanol, isopropanol and acetonitrile.

3. The method for preparing glyphosate from aminomethylphosphonic acid according to claim 1, characterized in that: During the acidification process of adding hydrochloric acid in step (2), the pH value is adjusted to 1.0-2.5.

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