A glyphosate crystallization method for eliminating fine crystals

Abstract

The present invention relates to a glyphosate crystallization method for eliminating fine crystals, and belongs to the technical field of pesticide production. A glyphosate synthetic liquid is obtained by a glycine-dimethyl phosphite method; then concentrated hydrochloric acid with a molar ratio of 3.5-5 to glycine and a concentration of more than 30% is added to the glyphosate synthetic liquid for acid hydrolysis; the acid hydrolysis liquid is heated to 110-120°C for dealcoholization, and the dealcoholization liquid is added to a crystallization kettle for crystallization in 2-5 sections in a slow-first-fast-later-fast manner within 4-10 hours, and liquid alkali is added during the crystallization process to adjust the pH value to 0.5-2.0, and glyphosate crystals with uniform particle size are obtained by filtering and washing. The present invention solves the problems of small particle size and large loss in the washing process in the glyphosate production process. The crystallization of glyphosate using this method can increase the crystal particle size, and the crystal product is easier to wash, and the glyphosate loss in the washing process can be reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of glyphosate production and relates to a glyphosate crystallization method for eliminating fine crystals. Background Art

[0002] Glyphosate, also known as glyphosate, phosphonolyic acid, and Roundup, is a herbicide developed by Monsanto in the United States in 1971. It is currently the most widely used herbicide in the world. The main production routes of glyphosate include the glycine method and the iminodiacetic acid (IDA) method, among which the glycine-dimethyl phosphite method in the glycine method is the mainstream method in China. The main raw materials of this method include polyformaldehyde, glycine, triethylamine, dimethyl phosphite, methanol, and hydrochloric acid. Polyformaldehyde is depolymerized in a methanol solution under the catalysis of triethylamine, and then glycine is added for addition reaction, and then dimethyl phosphite is added for esterification reaction. After esterification, hydrochloric acid is added for acid hydrolysis, and then dealcoholization and crystallization are performed to obtain glyphosate crystal products.

[0003] In actual production, due to the slow growth rate of glyphosate and the fast nucleation rate, problems such as small product particle size and difficulty in solid-liquid separation are prone to occur during the glyphosate crystallization process, which not only affects the filtration time, but also affects the yield of glyphosate, because small crystal particles are more easily dissolved during washing. If the crystal particle size is increased by slowly cooling, the production efficiency will be reduced. Summary of the invention

[0004] In view of the problem that there are many fine crystals in the glyphosate production process, it is difficult to filter and there is a lot of loss in the filtration process, the present invention provides a method for eliminating fine crystals in the glyphosate production process, and the method is suitable for glyphosate produced by the glycine-dimethyl phosphite method.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides a glyphosate crystallization method capable of eliminating fine crystals, the method comprising the following steps:

[0007] (1) adding hydrochloric acid with a concentration of 30% or more at a molar ratio of 3.5 to 5 with respect to glycine to a glyphosate synthesis solution prepared by a glycine-dimethyl phosphite method for acid hydrolysis;

[0008] (2) The acid hydrolyzate is heated to 110-120 degrees Celsius for dealcoholization. The dealcoholized liquid is added to a crystallization kettle and crystallized in 2-5 stages over 4-10 hours in a slow-first-fast-later manner. During the crystallization process, liquid alkali is added to adjust the pH value to 0.5-2.0. The glyphosate crystals are filtered and washed to obtain glyphosate crystals with uniform particle size.

[0009] As a preferred technical solution of the present invention, the molar ratio of hydrochloric acid to glycine in step (1) is 3.5-4.5.

[0010] As a preferred technical solution of the present invention, the segmented crystallization method in step (2) is as follows: the cooling rate of the first cooling process is lower than 10°C / h, and the cooling rate of each subsequent cooling process is faster than the cooling rate of the previous cooling process.

[0011] As a preferred technical solution of the present invention, the crystallization kettle in step (2) can be a single crystallization kettle, or it can be divided into 2-5 crystallization kettles connected in series according to the segmentation of the cooling rate.

[0012] As a preferred technical solution of the present invention, the liquid alkali in step (2) can be added to the crystallization kettle during the first or second cooling process.

[0013] As a preferred technical solution of the present invention, the concentration of the liquid caustic soda in step (2) is 30-40%, and the liquid caustic soda component is a mixture of one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, and potassium bicarbonate, and is more preferably sodium hydroxide.

[0014] The present invention is further described in detail below. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Attached Figure 1 This is an accompanying drawing of Example 1.

[0016] Attached Figure 2 This is an accompanying drawing of Example 2.

[0017] Attached Figure 3 This is an accompanying drawing of Example 3.

[0018] Attached Figure 4 This is an accompanying drawing of Example 4. DETAILED DESCRIPTION

[0019] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0020] Example 1

[0021] A glyphosate crystallization method capable of eliminating fine crystals, the method comprising the following steps:

[0022] (1) In a reaction kettle, methanol, triethylamine, glycine and dimethyl phosphite are used as raw materials to obtain a synthetic liquid through a glycine-dimethyl phosphite method;

[0023] (2) Control the temperature of the synthesis liquid to 30°C, add hydrochloric acid (concentration 30%) in an amount 3.8 times the molar amount of glycine to the synthesis liquid, then raise the temperature to 120°C and keep the temperature until crystals precipitate;

[0024] (3) The temperature was cooled in three stages at different cooling rates for 6 hours. The cooling rate in the first stage was 3.0°C / h. When the temperature dropped to 85°C, the cooling rate was kept constant and a 40% NaOH solution was added at a flow rate of 0.3 ml / min. The pH value was adjusted to 1.5, and then the temperature was further cooled at a cooling rate of 3.0°C / h to 35°C. Glyphosate crystals were obtained by filtration. Figure 1 As shown, the image of glyphosate crystals under a microscope using a uniform cooling method has relatively uniform particles and regular crystal shape, but the particle size is small (D50 is about 80μm), and most of them are fine crystals.

[0025] Example 2

[0026] A glyphosate crystallization method capable of eliminating fine crystals, the method comprising the following steps:

[0027] (1) In a reaction kettle, methanol, triethylamine, glycine and dimethyl phosphite are used as raw materials to obtain a synthetic liquid through a glycine-dimethyl phosphite method;

[0028] (2) Control the temperature of the synthesis liquid to 30°C, add hydrochloric acid (concentration 30%) in an amount 3.8 times the molar amount of glycine to the synthesis liquid, then raise the temperature to 120°C and keep the temperature until crystals precipitate;

[0029] (3) The temperature was cooled in three stages at different cooling rates for 6 hours. The cooling rate in the first stage was 5.0°C / h. When the temperature dropped to 85°C, the cooling rate was kept constant and a 40% NaOH solution was added at a flow rate of 0.3 ml / min. The pH value was adjusted to 0.5-2.0, and then the temperature was further cooled at a cooling rate of 3.0°C / h to 35°C. Glyphosate crystals were obtained by filtration. Figure 2 As shown in the figure, the image of glyphosate crystals under a microscope using a fast-then-slow cooling method shows that the particles are not very uniform, the particle sizes vary (D50 range is 50-100μm), and the crystal shape is irregular.

[0030] Example 3

[0031] A glyphosate crystallization method capable of eliminating fine crystals, the method comprising the following steps:

[0032] (1) In a reaction kettle, methanol, triethylamine, glycine and dimethyl phosphite are used as raw materials to obtain a synthetic liquid through a glycine-dimethyl phosphite method;

[0033] (2) Control the temperature of the synthesis liquid to 30°C, add hydrochloric acid (concentration 30%) in an amount 3.8 times the molar amount of glycine to the synthesis liquid, then raise the temperature to 120°C and keep the temperature until crystals precipitate;

[0034] (3) The temperature was cooled in 4 stages at different cooling rates for 6 hours. The cooling rate in the first stage was 1.0℃ / h. When the temperature dropped to 90℃, the cooling rate was set to 0.2℃ / h. When the temperature dropped to 80℃, the cooling rate was set to 0.2℃ / h. The cooling rate was kept constant, and a 40% NaOH solution was added at a flow rate of 0.6ml / min. The pH value was adjusted to 0.5-2.0, and then the temperature was continued to be cooled to 35℃ at a cooling rate of 5.0℃ / h. Glyphosate crystals were obtained by filtration. The results are shown in Figure 3 As shown in the figure, the image of glyphosate crystals under a microscope using a slow-then-fast cooling method shows that the alkali addition rate is too fast, the particles are not very uniform, the particle sizes are different (D50 range is 60-90μm), and the crystal shape is relatively regular.

[0035] Example 4

[0036] A glyphosate crystallization method capable of eliminating fine crystals, the method comprising the following steps:

[0037] (1) In a reaction kettle, methanol, triethylamine, glycine and dimethyl phosphite are used as raw materials to obtain a synthetic liquid through a glycine-dimethyl phosphite method;

[0038] (2) Control the temperature of the synthesis liquid to 30°C, add hydrochloric acid (concentration 30%) in an amount 3.8 times the molar amount of glycine to the synthesis liquid, then raise the temperature to 120°C and keep the temperature until crystals precipitate;

[0039] (3) The temperature was cooled in 4 stages at different cooling rates for 6 hours. The cooling rate in the first stage was 1.0℃ / h. When the temperature dropped to 90℃, the cooling rate was set to 0.2℃ / h. When the temperature dropped to 80℃, the cooling rate was set to 0.2℃ / h. The cooling rate was kept constant, and a 40% NaOH solution was added at a flow rate of 0.3ml / min. The pH value was adjusted to 0.5-2.0, and then the temperature was continued to be cooled to 35℃ at a cooling rate of 5.0℃ / h. Glyphosate crystals were obtained by filtration. The results are shown in Figure 4 As shown, the image of glyphosate crystals under a microscope using a slow-then-fast cooling method has uniform particles, large particle size (D50 average 130μm), and regular crystal shape.

[0040] Example 5

[0041] A glyphosate crystallization method capable of eliminating fine crystals, the method comprising the following steps:

[0042] (1) In a reaction kettle, methanol, triethylamine, glycine and dimethyl phosphite are used as raw materials to obtain a synthetic liquid through a glycine-dimethyl phosphite method;

[0043] (2) Control the temperature of the synthesis liquid to 30°C, add hydrochloric acid (concentration 30%) in an amount 3.8 times the molar amount of glycine to the synthesis liquid, then raise the temperature to 120°C and keep the temperature until crystals precipitate;

[0044] (3) The temperature was cooled in 4 stages at different cooling rates for 7 hours. The cooling rate in the first stage was 0.5°C / h. When the temperature dropped to 90°C, the cooling rate was set to 0.8°C / h. When the temperature dropped to 80°C, the cooling rate was set to 0.5°C / h. The cooling rate was kept constant, and a 40% NaOH solution was added at a flow rate of 0.3 ml / min. The pH value was adjusted to 0.5-2.0, and then the temperature was continued to be cooled to 35°C at a cooling rate of 5.5°C / h. Glyphosate crystals were obtained by filtration. The results are shown in Figure 4 As shown in the figure, the glyphosate crystals imaged under a microscope using a slow-then-fast cooling method have uniform particles, large particle size (D50 average 140μm), and regular crystal shape. Figure 4 Basically the same.

[0045] Example 6

[0046] A glyphosate crystallization method capable of eliminating fine crystals, the method comprising the following steps:

[0047] (1) In a reaction kettle, methanol, triethylamine, glycine and dimethyl phosphite are used as raw materials to obtain a synthetic liquid through a glycine-dimethyl phosphite method;

[0048] (2) Control the temperature of the synthesis liquid to 30°C, add hydrochloric acid (concentration 30%) in an amount 3.8 times the molar amount of glycine to the synthesis liquid, then raise the temperature to 120°C and keep the temperature until crystals precipitate;

[0049] (3) The temperature was cooled in 4 stages at different cooling rates. The cooling time was 6.5 hours. The cooling rate in the first stage was 0.8℃ / h. When the temperature dropped to 90℃, the cooling rate was set to 1.2℃ / h. When the temperature dropped to 80℃, the cooling rate was set to 0.8℃ / h. The cooling rate was kept constant, and a 40% NaOH solution was added at a flow rate of 0.3ml / min. The pH value was adjusted to 0.5-2.0, and then the temperature was continued to be cooled to 35℃ at a cooling rate of 6.0℃ / h. Glyphosate crystals were obtained by filtration. The results are shown in Figure 4 As shown in the figure, the glyphosate crystals imaged under a microscope using a slow-first-fast-then-fast cooling method have uniform particles, large particle size (D50 average of 125 μm), and regular crystal shape. Figure 4 Basically the same.

[0050] Example 7

[0051] A glyphosate crystallization method capable of eliminating fine crystals, the method comprising the following steps:

[0052] (1) In a reaction kettle, methanol, triethylamine, glycine and dimethyl phosphite are used as raw materials to obtain a synthetic liquid through a glycine-dimethyl phosphite method;

[0053] (2) Control the temperature of the synthesis liquid to 30°C, add hydrochloric acid (concentration 30%) in an amount 3.8 times the molar amount of glycine to the synthesis liquid, then raise the temperature to 120°C and keep the temperature until crystals precipitate;

[0054] (3) The temperature was cooled in 4 stages at different cooling rates for 7 hours. The cooling rate in the first stage was 0.3℃ / h. When the temperature dropped to 95℃, the cooling rate was set to 0.6℃ / h. When the temperature dropped to 80℃, the cooling rate was set to 0.3℃ / h. The cooling rate was kept constant, and a 40% NaOH solution was added at a flow rate of 0.3ml / min. The pH value was adjusted to 0.5-2.0, and then the temperature was continued to be cooled to 35℃ at a cooling rate of 4.0℃ / h. Glyphosate crystals were obtained by filtration. The results are shown in Figure 4 As shown in the figure, the glyphosate crystals imaged under a microscope using a slow-then-fast cooling method have uniform particles, large particle size (D50 average 150μm), regular crystal shape, and morphology. Figure 4 Basically the same.

[0055] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0056] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0057] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing glyphosate by the glycine method and eliminating fine crystals, characterized in that: The following steps are involved: (1) In a reaction kettle, methanol, triethylamine, glycine and dimethyl phosphite are used as raw materials to obtain a synthetic liquid through a glycine-dimethyl phosphite method; (2) Control the temperature of the synthesis liquid to 30°C, add hydrochloric acid with a molar amount of 3.8 times that of glycine to the synthesis liquid, with a concentration of 30%, and then raise the temperature to 120°C and keep it warm until crystals precipitate; (3) The temperature was cooled in 4 stages at different cooling rates for 6 hours. The cooling rate in the first stage was 1.0°C / h. When the temperature dropped to 90°C, the cooling rate was set to 0.2°C / h. When the temperature dropped to 80°C, the cooling rate was set to 0.2°C / h. The cooling rate was kept constant and a 40% NaOH solution was added at a flow rate of 0.3 ml / min. The pH value was adjusted to 0.5-2.

0. The temperature was then cooled to 35°C at a cooling rate of 5.0°C / h. The glyphosate crystals were filtered out.

2. A method for preparing glyphosate by the glycine method and eliminating fine crystals, characterized in that: The following steps are involved: (1) In a reaction kettle, methanol, triethylamine, glycine and dimethyl phosphite are used as raw materials to obtain a synthetic liquid through a glycine-dimethyl phosphite method; (2) Control the temperature of the synthesis liquid to 30°C, add hydrochloric acid with a molar amount of 3.8 times that of glycine to the synthesis liquid, with a concentration of 30%, and then raise the temperature to 120°C and keep it warm until crystals precipitate; (3) The temperature was cooled in 4 stages at different cooling rates for 7 hours. The cooling rate in the first stage was 0.5°C / h. When the temperature dropped to 90°C, the cooling rate was set to 0.8°C / h. When the temperature dropped to 80°C, the cooling rate was set to 0.5°C / h. The cooling rate was kept constant and a 40% NaOH solution was added at a flow rate of 0.3 ml / min. The pH value was adjusted to 0.5-2.

0. The temperature was then cooled to 35°C at a cooling rate of 5.5°C / h. The glyphosate crystals were filtered out.

3. A method for preparing glyphosate by the glycine method and eliminating fine crystals, characterized in that: The following steps are involved: (1) In a reaction kettle, methanol, triethylamine, glycine and dimethyl phosphite are used as raw materials to obtain a synthetic liquid through a glycine-dimethyl phosphite method; (2) Control the temperature of the synthesis liquid to 30°C, add hydrochloric acid with a molar amount of 3.8 times that of glycine to the synthesis liquid, with a concentration of 30%, and then raise the temperature to 120°C and keep it warm until crystals precipitate; (3) The temperature was cooled in 4 stages at different cooling rates for 6.5 hours. The cooling rate in the first stage was 0.8°C / h. When the temperature dropped to 90°C, the cooling rate was set to 1.2°C / h. When the temperature dropped to 80°C, the cooling rate was set to 0.8°C / h. The cooling rate was kept constant and a 40% NaOH solution was added at a flow rate of 0.3 ml / min. The pH value was adjusted to 0.5-2.

0. The temperature was then cooled to 35°C at a cooling rate of 6.0°C / h. The glyphosate crystals were filtered out.

4. A method for preparing glyphosate by the glycine method and eliminating fine crystals, characterized in that: The following steps are involved: (1) In a reaction kettle, methanol, triethylamine, glycine and dimethyl phosphite are used as raw materials to obtain a synthetic liquid through a glycine-dimethyl phosphite method; (2) Control the temperature of the synthesis liquid to 30°C, add hydrochloric acid with a molar amount of 3.8 times that of glycine to the synthesis liquid, with a concentration of 30%, and then raise the temperature to 120°C and keep it warm until crystals precipitate; (3) The temperature was cooled in 4 stages at different cooling rates for 7 hours. The cooling rate in the first stage was 0.3°C / h. When the temperature dropped to 95°C, the cooling rate was set to 0.6°C / h. When the temperature dropped to 80°C, the cooling rate was set to 0.3°C / h. The cooling rate was kept constant and a 40% NaOH solution was added at a flow rate of 0.3 ml / min. The pH value was adjusted to 0.5-2.

0. The temperature was then cooled to 35°C at a cooling rate of 4.0°C / h. The glyphosate crystals were filtered out.

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