A method for preparing spherical glyphosate

Abstract

The present application relates to a method for preparing glyphosate spherical crystal, and belongs to the technical field of pesticide production. The steps include: taking the glyphosate synthesis solution obtained by the glycine-phosphite dimethyl ester method as a raw material, adding concentrated hydrochloric acid with a molar ratio of 2-5 to glycine and a concentration of 30% or more to the glyphosate synthesis solution for acidolysis; heating the acidolysis solution to 95-125 DEG C and keeping it for 0.5-2 hours for dealcoholization; after dealcoholization, the temperature of the system is reduced to 50-80 DEG C within 1-2 hours, and an alkali solution with a mass concentration of 35-42% is added while reducing the temperature, the pH of the system is controlled to be 0.5-3.5, and the stirring speed is kept at 180-250 rpm; then the temperature of the material is reduced to 20-40 DEG C within 1-2 hours, and the glyphosate spherical crystal product is obtained after filtration and washing. The spherical glyphosate obtained by the present application has good flowability, is not easy to agglomerate, has a larger tap density, and is easy to store and transport.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of glyphosate production and relates to a preparation method of spherical glyphosate by the glycine method. BACKGROUND

[0002] Glyphosate, also known as Lasso, Phosylate, Roundup, etc., is a herbicide developed by the American Monsanto Company in 1971, and is the most widely used herbicide in the world. The main production routes of glyphosate include the glycine method and the imino diacetic acid (IDA) method, etc. The glycine-phosphite dimethyl ester method in the glycine method is the mainstream method in China. The main raw materials of the method include paraformaldehyde, glycine, triethylamine, phosphite dimethyl ester, methanol and hydrochloric acid. Paraformaldehyde is depolymerized in a methanol solution under the catalysis of triethylamine, then glycine is added to undergo an addition reaction, then phosphite dimethyl ester is added to undergo an esterification reaction, then hydrochloric acid is added to undergo acidolysis, and then the glyphosate crystal product is obtained through dealcoholization and crystallization.

[0003] At present, the glyphosate crystal is in a rod-like or block-like morphology, the crystal is fine and has poor flowability. Since the spherical crystal has the advantages of good flowability, difficulty in caking and large tap density, it is of great significance to develop a simple preparation process of the spherical glyphosate crystal.

[0004] At present, the glyphosate crystal is in a rod-like or block-like morphology, the crystal is fine and has poor flowability. Since the spherical crystal has the advantages of good flowability, difficulty in caking and large tap density, it is necessary to develop a simple preparation method of the spherical glyphosate crystal. SUMMARY

[0005] In order to improve the product flowability of glyphosate, increase the tap density of the product and overcome the problem of caking of glyphosate, the application provides a method for preparing spherical glyphosate, which is suitable for glyphosate produced by the glycine-phosphite dimethyl ester method.

[0006] To achieve the above-mentioned purpose, the following technical scheme is adopted in the application.

[0007] The application provides a preparation method of spherical glyphosate, which comprises the following steps:

[0008] (1) adding concentrated hydrochloric acid to a glyphosate synthesis solution to perform acidolysis and obtain an acidolysis solution;

[0009] (2) performing dealcoholization on the acidolysis solution obtained in step (1) under stirring and heating to 95-125 DEG C, then cooling to 50-80 DEG C, adding liquid alkali during the cooling process, and then cooling the material to 20-40 DEG C to obtain a spherical glyphosate crystal product.

[0010] Step (1) the glyphosate synthesis solution is prepared by glycine-dimethyl phosphite method, the mass concentration of concentrated hydrochloric acid in the acidolysis process is 25-35%, and the molar ratio of the mass concentration of 30-35% to glycine is 2-5.

[0011] Step (1) the acidolysis temperature is 10-40℃.

[0012] After the dealcoholization is completed, the temperature is decreased to 50-80℃ at a rate of 0.5-3℃ / min, preferably at a rate of 0.5-1.5℃ / min.

[0013] The stirring rate is 180-250rpm during the temperature decreasing process, preferably 180-200rpm.

[0014] The liquid alkali is sodium hydroxide, potassium hydroxide or a mixture of the two, and the mass concentration of the liquid alkali is 35-40%.

[0015] The pH of the material is adjusted to 0.5-3.5 by the liquid alkali during the temperature decreasing process.

[0016] The pH of the material is adjusted to 0.8-1.5 by the liquid alkali during the temperature decreasing process.

[0017] The rate of decreasing the temperature of the material to 20-40℃ is 0.5-3℃ / min. The solid-liquid ratio during the formation of glyphosate crystals is 1:3 to 1:2.

[0018] In the present application, the stirring rate is controlled to be 180-250rpm during the crystallization process. If the stirring is too slow, the friction of the crystals is not enough, and it is not easy to form spherical crystals. If the stirring is too fast, the crystals are easily broken, and it is also not easy to form spherical crystals. In addition, the over-saturation is controlled by adjusting the alkali and the temperature at the same time. If the over-saturation is too small, the growth is slow, and it is not easy to form spherical crystals. If the over-saturation is too large, it is easy to burst nucleation, and it is also not easy to form spherical crystals. Therefore, the over-saturation needs to be controlled to be 2-5 by adjusting the temperature and adding the alkali at the same time. The increase of the pH value increases the solubility of glyphosate, thereby reducing the over-saturation. If the temperature decreasing rate is too fast, the over-saturation is too large, and a large number of small crystals are precipitated. In addition, the solid-liquid ratio (1:3 to 1:2) also plays a key role in forming spherical crystals. If the solid-liquid ratio is small, the friction between the solids is small, and it is not easy to form spherical crystals.

[0019] Advantages

[0020] The spherical glyphosate has good flowability, is not easy to cake, and has large tap density. The method does not need to add spherical forming reagents, but uses the suitable over-saturation controlled by adding alkali and decreasing the temperature at the same time, and combines the friction conditions formed by the large solid-liquid ratio and the stirring speed, thereby forming spherical crystals. The rest angle of the spherical glyphosate crystal is 26℃ or lower, and is further preferably 20℃ or lower, which has the technical effect of good flowability.

[0021] Key points and protection points of the present application

[0022] The key protection is to form spherical glyphosate crystals by synergistically regulating supersaturation through alkali addition and temperature reduction, combined with a large solid-liquid ratio and strong stirring. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 Optical microscope image of glyphosate prepared in Example 1. DETAILED DESCRIPTION

[0024] To better illustrate the present application and facilitate understanding of the technical solutions of the present application, the typical but non-limiting embodiments of the present application are as follows:

[0025] Example 1

[0026] A method for preparing spherical glyphosate, the method comprising the following steps:

[0027] (1) In a reaction kettle, using methanol, triethylamine, glycine and dimethyl phosphite as raw materials, a synthesis solution is obtained by the glycine-dimethyl phosphite method;

[0028] (2) The temperature of the synthesis solution is controlled at 30ºC, 4 times the molar amount of glycine of hydrochloric acid (25% concentration) is added to the synthesis solution, then the temperature is raised to 120ºC and maintained for 60 minutes;

[0029] (3) The temperature is reduced to 70ºC at a rate of 0.8K / min, and the stirring speed is maintained at 180rpm;

[0030] (4) While reducing the temperature, 38% liquid caustic is slowly added to the crystallization kettle 1, and the pH is adjusted to 3;

[0031] (5) Then reduce the temperature to 40ºC at a rate of 0.5K / min, and maintain the stirring speed during the temperature reduction;

[0032] (6) The material is filtered, the mass ratio of glyphosate wet crystals to crystallization mother liquor is 1:3, and the crystals are washed with clean water to obtain the spherical glyphosate product as shown in the accompanying Figure 1

[0033] (7) The rest angle of the spherical glyphosate crystal is 20ºC. The rest angle detection instrument is a HR-S4 type instrument produced by Dandong Hengrui Instrument Co., Ltd.

[0034] Example 2

[0035] A method for preparing spherical glyphosate, the method comprising the following steps:

[0036] ​(1) A synthesis solution was obtained in a reactor using methanol, triethylamine, glycine and dimethyl phosphite as raw materials via the glycine-dimethyl phosphite method;

[0037] (2) Control the temperature of the synthesis solution to 35°C, add hydrochloric acid (concentration 31%) with 2.8 times the molar amount of glycine to the synthesis solution, and then raise the temperature to 110°C and keep it at that temperature for 90 minutes;

[0038] (3) Cool down to 60ºC at a cooling rate of 0.4-0.6K / min, while maintaining a stirring speed of 200rpm;

[0039] (4) While cooling, slowly add 35% liquid alkali to the crystallization vessel and adjust the pH to 1.5;

[0040] (5) Reduce the temperature to 30 degrees Celsius at a cooling rate of 0.25-0.35 K / min;

[0041] (6) Filter the material. The mass ratio of glyphosate wet crystals to crystallization mother liquor is 1:2. Wash the crystals with water to obtain spherical glyphosate product. Its morphology and structure are similar to those in Example 1.

[0042] (7) The angle of repose of the glyphosate spherical crystals was determined to be 26°C.

[0043] Example 3

[0044] A method for preparing spherical glyphosate, the method comprising the following steps:

[0045] (1) A synthesis solution was obtained in a reactor using methanol, triethylamine, glycine and dimethyl phosphite as raw materials via the glycine-dimethyl phosphite method;

[0046] (2) Control the temperature of the synthesis solution to 20ºC, add hydrochloric acid (concentration 32%) with twice the molar amount of glycine to the synthesis solution, and then raise the temperature to 125ºC and keep it at that temperature for 40 minutes;

[0047] (3) Reduce the temperature to 65ºC at a cooling rate of 0.6-1K / min, while maintaining the stirring speed at 220rpm;

[0048] (4) While cooling, slowly add 40% liquid alkali to the system and adjust the pH to 0.5;

[0049] (5) Reduce the temperature to 35ºC at a cooling rate of 0.3-0.5K / min;

[0050] (6) Filter the material. The mass ratio of glyphosate wet crystals to crystallization mother liquor is 1:2.5. Wash the crystals with water to obtain spherical glyphosate product. Its morphology and structure are similar to those in Example 1.

[0051] (7) The rest angle of the glyphosate spherical crystal is 25°C.

[0052] Example 4

[0053] As a comparison of the spherical glyphosate example, this example provides a preparation method of a non-spherical glyphosate, which comprises the following steps:

[0054] (1) In a reaction kettle, methanol, triethylamine, glycine and dimethyl phosphite are used as raw materials to obtain a synthesis solution by the glycine-dimethyl phosphite method;

[0055] (2) The temperature of the synthesis solution is controlled at 30°C, 2 times the molar amount of glycine of hydrochloric acid (concentration 28%) is added to the synthesis solution, then the temperature is raised to 122°C, and the temperature is maintained for 45 minutes;

[0056] (3) It is placed in a room temperature environment, and naturally cooled to 25°C;

[0057] (6) The material is filtered, the mass ratio of glyphosate wet crystal and crystallization mother liquor is 1:4.5, and the glyphosate product obtained by washing the crystal with clean water is a block crystal.

[0058] (7) The rest angle of the glyphosate crystal is 40°C.

[0059] Example 5

[0060] As a comparison of the spherical glyphosate example, this example provides a preparation method of a non-spherical glyphosate, which comprises the following steps:

[0061] (1) In a reaction kettle, methanol, triethylamine, glycine and dimethyl phosphite are used as raw materials to obtain a synthesis solution by the glycine-dimethyl phosphite method;

[0062] (2) The temperature of the synthesis solution is controlled at 40°C, 2.5 times the molar amount of glycine of hydrochloric acid (concentration 33%) is added to the synthesis solution, then the temperature is raised to 118°C, and the temperature is maintained for 50 minutes;

[0063] (3) The temperature is lowered to 30°C at a rate of 0.2K / min, and liquid alkali is slowly added to control the pH value to 4 during the cooling process;

[0064] (6) The material is filtered, the mass ratio of glyphosate wet crystal and crystallization mother liquor is 1:4.8, and the glyphosate product obtained by washing the crystal with clean water is a block crystal.

[0065] (7) The rest angle of the glyphosate spherical crystal is 38°C.

Claims

1. A method for preparing spherical glyphosate, characterized in that, The method includes the following steps: (1) Concentrated hydrochloric acid was added to the glyphosate synthesis solution for acid hydrolysis to obtain the acid hydrolysate; (2) The acid hydrolysate obtained in step (1) is heated to 95-125℃ under stirring to remove alcohol. After the alcohol removal is completed, the temperature is lowered to 50-80℃ at a rate of 0.5-3℃ / min. During the cooling process, the stirring rate is 180-250rpm. Liquid alkali is added during the cooling process. During the cooling process, the pH of the material is adjusted to 0.5-3.5 using liquid alkali. The material is then cooled to 20-40℃ to obtain spherical glyphosate crystals. The material is cooled to 20-40℃ at a rate of 0.5-3℃ / min. During the formation of glyphosate crystals, the solid-liquid ratio is 1:3 to 1:

2.

2. The method for preparing spherical glyphosate according to claim 1, characterized in that, Step (1) The glyphosate synthesis solution was prepared by the glycine-dimethyl phosphite method. During the acid hydrolysis process, the mass concentration of concentrated hydrochloric acid was 30-35%, and the molar ratio of the mass concentration of 30-35% to glycine was 2-5.

3. The method for preparing spherical glyphosate according to claim 2, characterized in that, The acid hydrolysis temperature in step (1) is 10-40℃.

4. The method for preparing spherical glyphosate according to claim 3, characterized in that, After the alcohol removal is completed, the temperature is reduced to 50-80℃ at a rate of 0.5-1.5℃ / min.

5. The method for preparing spherical glyphosate according to claim 1, characterized in that, The stirring rate during the cooling process is 180-200 rpm.

6. The method for preparing spherical glyphosate according to claim 1, characterized in that, The liquid alkali is sodium hydroxide, potassium hydroxide, or a mixture of both, and the mass concentration of the liquid alkali is 35-40%.

7. The method for preparing spherical glyphosate according to claim 6, characterized in that, During the cooling process, liquid alkali is used to adjust the pH of the material to 0.8-1.5.

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