Method for controlling particle size and crystal form of glycine solvus-cooling coupled crystallization process

Abstract

The application provides a glycine solvation-cooling coupled crystallization process particle size and crystal form regulation method, which comprises the following steps: heating and heat preservation of a first solvation agent, then adding a crystallization mother liquor into the first solvation agent, and forming a crystal seed under the action of the solvation agent; then adding a second solvation agent into the obtained mixture and cooling; and then performing solid-liquid separation on the obtained suspension to obtain glycine. The application realizes stable preparation of pure alpha-crystal glycine with uniform particle size and low agglomeration degree by combining solvation and cooling coupling operation and by pre-mixing the mother liquor and the solvation agent to form self-generated crystal seeds, and has the advantages of simple operation, mild conditions, high yield, easy industrialization and the like.

Description

Technical Field

[0001] This invention relates to the field of glycine production technology, and in particular to a method for controlling particle size and crystal form in a glycine dissolution-cooling coupled crystallization process. Background Technology

[0002] Glycine, also known as aminoacetic acid, commonly exists in α and γ crystal forms. As an important fine chemical intermediate, it is widely used in pesticides, pharmaceuticals, food, feed, and optoelectronic materials. Currently, the world's total annual production is around 800,000 tons, with my country being the main producer, producing approximately 400,000 tons per year. my country's glycine production is primarily used in the synthesis of the herbicide glyphosate. However, existing glycine products generally suffer from uneven particle size distribution and the coexistence of α and γ crystal forms, severely impacting downstream processing efficiency. Industrially, there are many methods for synthesizing glycine: chloroacetic acid ammonolysis (MCA), the Strecker process, the Hein process, and biosynthesis. Chloroacetic acid ammonolysis is the classic method for preparing glycine, and this process is the main route for glycine production in China. The main raw materials for this method include chloroacetic acid, ammonia, and hexamethylenetetramine. Chloroacetic acid and ammonia react under the catalysis of hexamethylenetetramine. Then, glycine products are obtained by adding glycine seed crystals to the crystallization mother liquor to induce crystallization. However, adding seed crystals to the high-temperature crystallization mother liquor is not only difficult to operate, but also makes it difficult to effectively control the particle size and crystal form of the obtained glycine products.

[0003] In the prior art, Chinese patent 106748849A discloses a method for particle size control during the cooling crystallization process of glycine, which controls the particle size of the product by controlling the degree of supersaturation during the nucleation process. Chinese patent 110746314A discloses a semi-continuous dissolution crystallization method for glycine, which achieves stable production of large and uniform α-crystalline glycine at room temperature by continuously adding saturated glycine aqueous solution and ethanol aqueous solution to the crystallizer. Chinese patent CN11606319A achieves controllable synthesis of glycine crystal form by adjusting the amount of salt additives, seed crystals, temperature, and cooling rate, significantly improving the product's stability and anti-caking properties. While the above patents use different seed crystal generation methods to control the particle size and crystal form of the product, none of these methods effectively couple the dissolution and cooling crystallization processes, and they do not fully consider the impact of industrial impurities on the crystallization process, thus limiting their industrial application. For systems containing industrial impurities, it is difficult to control the crystallization process to obtain a stable α-crystalline glycine product. Using the addition method, γ-crystalline glycine is easily obtained, and the product agglomerates severely. Increasing the addition rate of the solvent results in an α-crystalline product with an excessively large aspect ratio and fragile crystals, while decreasing the addition rate fails to achieve the supersaturation condition for the α-crystalline form.

[0004] Therefore, developing a simple glycine crystallization method that is adaptable to industrial impurity environments and can stably control particle size and crystal form is of great practical significance. Summary of the Invention

[0005] In view of the problems existing in the prior art, the present invention provides a method for controlling the particle size and crystal form of glycine in the dissolution-cooling coupled crystallization process, which realizes the stable preparation of pure α-crystalline glycine with uniform particle size and low degree of agglomeration. It has the advantages of simple operation, mild conditions, high yield and easy industrialization.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] This invention provides a method for controlling particle size and crystal form in a glycine dissolution-cooling coupled crystallization process, the method comprising the following steps:

[0008] The first solvent is heated and kept at a certain temperature. Then, a crystallization mother liquor is added to the first solvent to form seed crystals through dissolution. Then, a second solvent is added to the resulting mixture and the temperature is lowered. The resulting suspension is subjected to solid-liquid separation to obtain glycine.

[0009] This invention utilizes a staged addition process of the solvent. First, a portion of the solvent is premixed with the mother liquor of crystallization to generate seed crystals. Using the large number of microcrystalline seed crystals suspended in the mixture as templates, the solvent is then added and the temperature is lowered simultaneously to promote the large-scale crystallization of glycine. By combining the solvent and cooling coupled operations, the stable preparation of pure α-crystalline glycine with uniform particle size and low agglomeration is achieved.

[0010] As a preferred embodiment of the present invention, the first solvent and the second solvent each independently comprise methanol.

[0011] As a preferred technical solution of the present invention, the final temperature of the first solvent heating is 50-60℃, for example, it can be 50℃, 51℃, 52℃, 53℃, 54℃, 55℃, 56℃, 57℃, 58℃, 59℃ or 60℃, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0012] Preferably, the time for keeping the first solvent at room temperature is 25-35 min, for example, it can be 25 min, 26 min, 27 min, 28 min, 29 min, 30 min, 31 min, 32 min, 33 min, 34 min or 35 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0013] As a preferred technical solution of the present invention, the initial temperature of the crystallization mother liquor before adding the first solvent is 55-65℃, for example, it can be 55℃, 56℃, 57℃, 58℃, 59℃, 60℃, 61℃, 62℃, 63℃, 64℃ or 65℃, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0014] Preferably, the time for adding the crystallization mother liquor to the first solvent is 2-8 minutes, for example, it can be 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes or 8 minutes, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0015] In this invention, the time for adding the crystallization mother liquor to the first solvent is controlled within the above-mentioned range, so that the crystallization mother liquor and the hot solvent are mixed quickly and uniformly to form a large number of microcrystalline seeds with uniform particle size. If the rate is too high, the mixing will be uneven, which may result in a very wide particle size distribution of the seeds and a serious local agglomeration. If the rate is too low, the generated crystal nuclei will have enough time to grow, and the final result will be a small number of crystals with large particle size, rather than a large number of microcrystalline seeds.

[0016] As a preferred technical solution of the present invention, the mass ratio of the first solvent to the crystallization mother liquor is (0.1-0.4):1, for example, it can be 0.1:1, 0.2:1, 0.3:1 or 0.4:1, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0017] This invention controls the mass ratio of the first solvent to the crystallization mother liquor within the aforementioned range, resulting in a large amount of seed crystals with fine and uniform particle size, providing sufficient growth sites for the second step. If the mass ratio of the first solvent to the crystallization mother liquor is too large, the system becomes oversaturated, leading to excessive seed crystal formation and potentially excessively fine seed crystals. Under stirring, the probability of particle collision increases, making agglomeration more likely, which in turn makes it difficult to control the particle size distribution and deteriorates the crystal morphology during the second growth step. If the mass ratio of the first solvent to the crystallization mother liquor is too small, the seed crystal nucleation process may not be fully triggered, resulting in a reduced number of microcrystals and difficulty in effectively inducing the formation of pure α-glycine. Furthermore, insufficient seed crystals in the subsequent growth process can lead to uneven particle size distribution in the product.

[0018] As a preferred technical solution of the present invention, the process of adding the crystallization mother liquor to the first solvent includes: adding the crystallization mother liquor to the first solvent under stirring, continuing to stir until crystals precipitate, and then maintaining stirring for 5-15 minutes, for example, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes or 15 minutes, etc., but not limited to the listed values, and other unlisted values ​​within the range are also applicable, and then adding the second solvent while continuing to stir.

[0019] The purpose of adding the crystallization mother liquor to the first solvent and stirring until crystals precipitate, and continuing to stir, is to cultivate crystals, further stabilize the seed crystals, and improve the uniformity of the crystal slurry. This provides a stable seed crystal base and crystal slurry environment for the subsequent crystallization process, which is beneficial for obtaining a better quality finished product.

[0020] Preferably, the stirring speed is 225-350 rpm, for example, it can be 225 rpm, 235 rpm, 245 rpm, 255 rpm, 265 rpm, 275 rpm, 285 rpm, 295 rpm, 305 rpm, 315 rpm, 325 rpm, 335 rpm or 350 rpm, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0021] As a preferred embodiment of the present invention, the second solvent is added to the mixture by means of dropwise addition.

[0022] The second solvent of the present invention is added to the mixture in the following ways: uniform addition, fast addition followed by slow addition, and slow addition followed by fast addition. The uniform addition rate is 5-6 mL / min. The fast addition followed by slow addition first uses a dropping rate of 7-7.5 mL / min, followed by a dropping rate of 3.5-4 mL / min. The slow addition followed by fast addition is the opposite. The specific addition method can be selected according to the implementation effect and is not further limited here.

[0023] In this invention, different dropping processes are employed during the addition of the second solvent to intervene in the crystal nucleation and growth process by controlling the rate of supersaturation. Uniform dropping maintains a constant supersaturation, ensuring stable crystal growth driving force and resulting in crystals with a relatively concentrated particle size distribution. Fast-then-slow dropping rapidly increases supersaturation in the initial stage to induce secondary nucleation, then reduces the rate to allow the solute to grow slowly on the surface of existing nuclei, contributing to obtaining a moderate number of crystals with uniform particle size. Slow-then-fast dropping controls supersaturation at a low level in the early stages, preferentially promoting crystal growth.

[0024] Preferably, the dripping rate is 3.5-7.5 L / min, for example, it can be 3.5 L / min, 4.5 L / min, 5.5 L / min, 6.5 L / min or 7.5 L / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] As a preferred embodiment of the present invention, the mass ratio of the second solvent to the mixture is (1.85-2.64):1, for example, it can be 1.85:1, 1.95:1, 2.05:1, 2.15:1, 2.25:1, 2.35:1, 2.45:1, 2.55:1 or 2.64:1, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] As a preferred technical solution of the present invention, after cooling to the endpoint temperature, stirring is continued for 25-35 minutes, for example, 25 minutes, 26 minutes, 27 minutes, 28 minutes, 29 minutes, 30 minutes, 31 minutes, 32 minutes, 33 minutes, 34 minutes or 35 minutes, and then the suspension is subjected to solid-liquid separation.

[0027] After cooling to the final temperature, the present invention continues to stir in order to consume the excess supersaturation.

[0028] As a preferred technical solution of the present invention, the rate is 0.15-0.35 ℃ / min, for example, it can be 0.15 ℃ / min, 0.2 ℃ / min, 0.25 ℃ / min, 0.3 ℃ / min or 0.35 ℃ / min, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] The cooling methods of this invention include uniform cooling (0.22-0.28 ℃ / min), fast cooling followed by slow cooling (0.31-0.35 ℃ / min followed by 0.15-0.19 ℃ / min), and slow cooling followed by fast cooling (0.15-0.19 ℃ / min followed by 0.31-0.35 ℃ / min). The specific cooling method can be selected according to the implementation effect and is not further limited here.

[0030] The present invention selects different cooling methods according to the implementation effect, with the aim of more accurately controlling the nucleation rate and growth rate of crystals, thereby obtaining the desired crystal product.

[0031] Preferably, the endpoint temperature for cooling is 25-35℃, such as 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, 31℃, 32℃, 33℃, 34℃ or 35℃, etc., but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0033] (1) The method for controlling the particle size and crystal form of glycine in the dissolution-cooling coupled crystallization process provided by the present invention achieves stable preparation of pure α-crystalline glycine with uniform particle size, coefficient of variation less than 0.435, average particle size greater than 321 μm and low degree of agglomeration by premixing self-generated seed crystals with mother liquor and dissolution agent and combining dissolution and cooling coupled operation.

[0034] (2) The method for controlling the particle size and crystal form of glycine in the dissolution-cooling coupled crystallization process provided by the present invention is simple to operate, mild in conditions, high in yield, easy to industrialize, and has good economic benefits and environmental friendliness. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the crystallization process provided in Embodiment 1 of the present invention;

[0036] Figure 2 This is a particle size distribution diagram of the crystallized product of Example 1 of the present invention;

[0037] Figure 3 This is the Raman spectrum of the crystalline product of Example 1 of the present invention;

[0038] Figure 4 These are microscope images of the crystallized product from Embodiment 1 of the present invention;

[0039] Figure 5 This is the Raman spectrum of the crystalline product of Example 4 of the present invention;

[0040] Figure 6 These are microscope images of the crystalline product of Comparative Example 1 of this invention. Detailed Implementation

[0041] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0042] It should be clarified that any use of the process provided in the embodiments of the present invention or any substitution or change of conventional data falls within the protection and disclosure scope of the present invention.

[0043] Example 1

[0044] This embodiment provides a method for controlling particle size and crystal form in a glycine dissolution-cooling coupled crystallization process, the method comprising the following steps:

[0045] To prepare the crystallization mother liquor, 57.48 g of glycine was dissolved in 110.26 g of ultrapure water, and 41.11 g of ammonium chloride and 2.95 g of hexamethylenetetramine were added. The solution was heated to 60˚C to obtain a clear solution.

[0046] 100 mL of the first solvent, methanol, was added to the crystallization vessel, heated to 60°C, and kept at that temperature for 30 min. After the temperature was maintained, the crystallization mother liquor was added to the first solvent, methanol, under stirring at a speed of 300 rpm. The addition was completed in 5 min. The mass ratio of the first solvent, methanol, to the crystallization mother liquor was 0.3:1. After the addition was completed, the mixture was stirred until crystals precipitated, and then stirred for another 10 min.

[0047] Continue stirring and add the second solvent, methanol, dropwise to the resulting mixture. The solvent is added quickly at first and then slowly: 7.33 mL / min for the first half and 3.67 mL / min for the second half. The mass ratio of the second solvent, methanol, to the mixture is 2:1. Then, cool the mixture to 30°C. The cooling method is also quick at first and then slow: 0.33°C / min before 40°C and 0.17°C / min after 40°C. After cooling to the final temperature, continue stirring for 30 min.

[0048] The resulting suspension was subjected to solid-liquid separation and dried in a vacuum dryer for 8 hours to obtain a crystalline product, which yielded glycine.

[0049] The crystalline product obtained in this embodiment was characterized and tested, and the particle size distribution is as follows: Figure 2 As shown, the volume fraction of the 20-80 mesh product is 70.4%; the Raman spectrum is shown below. Figure 3 As shown, it can be seen that their crystal form is α-crystal, and the characteristic peak of α-glycine is at a wavelength of 1457 cm⁻¹. -1 Location; Microscopic images as shown Figure 4 As shown, the agglomeration between crystals is significantly reduced, the particle size is increased, and the crystal quality is better.

[0050] Example 2

[0051] This embodiment provides a method for controlling particle size and crystal form in a glycine dissolution-cooling coupled crystallization process, the method comprising the following steps:

[0052] To prepare the crystallization mother liquor, 57.48 g of glycine was dissolved in 110.26 g of ultrapure water, and 41.11 g of ammonium chloride and 2.95 g of hexamethylenetetramine were added. The solution was heated to 55˚C to obtain a clear solution.

[0053] 100 mL of the first solvent, methanol, was added to the crystallization vessel, heated to 55°C, and kept at that temperature for 35 min. After the temperature was maintained, the crystallization mother liquor was added to the first solvent, methanol, under stirring at a speed of 225 rpm. The addition was completed in 2 min. The mass ratio of the first solvent, methanol, to the crystallization mother liquor was 0.4:1. After the addition was completed, the mixture was stirred until crystals precipitated, and then stirred for another 5 min.

[0054] Continue stirring and add the second solvent, methanol, dropwise to the resulting mixture at a drop rate of 5.5 mL / min. The mass ratio of the second solvent, methanol, to the mixture is 1.85:1. Cool the mixture down to 30°C using a cooling method that is fast at first and then slow: 0.33°C / min before 40°C and 0.17°C / min after 40°C. After cooling to the final temperature, continue stirring for 35 min.

[0055] The resulting suspension was subjected to solid-liquid separation and dried in a vacuum dryer for 8 hours to obtain a crystalline product, which yielded glycine.

[0056] Example 3

[0057] This embodiment provides a method for controlling particle size and crystal form in a glycine dissolution-cooling coupled crystallization process, the method comprising the following steps:

[0058] To prepare the crystallization mother liquor, 57.48 g of glycine was dissolved in 110.26 g of ultrapure water, and 41.11 g of ammonium chloride and 2.95 g of hexamethylenetetramine were added. The solution was heated to 50˚C to obtain a clear solution.

[0059] 100 mL of the first solvent, methanol, was added to the crystallization vessel, heated to 65°C, and kept at that temperature for 25 min. After the temperature was maintained, the crystallization mother liquor was added to the first solvent, methanol, under stirring at a speed of 350 rpm. The addition was completed in 8 min. The mass ratio of the first solvent, methanol, to the crystallization mother liquor was 0.1:1. After the addition was completed, the mixture was stirred until crystals precipitated, and then stirred for another 15 min.

[0060] Continue stirring and add the second solvent, methanol, dropwise to the resulting mixture. The addition rate of the solvent is fast at first and then slow: 7.33 mL / min for the first half and 3.67 mL / min for the second half. The mass ratio of the second solvent, methanol, to the mixture is 2.64:1. Then, cool the mixture to 30°C. The cooling rate is slow at first and then fast: 0.17°C / min before 40°C and 0.33°C / min after 40°C. After cooling to the final temperature, continue stirring for 25 min.

[0061] The resulting suspension was subjected to solid-liquid separation and dried in a vacuum dryer for 8 hours to obtain a crystalline product, which yielded glycine.

[0062] Example 4

[0063] This embodiment provides a method for controlling the particle size and crystal form of glycine in a coupled crystallization process of dissolution-cooling. The only difference between this method and Example 1 is that the mass ratio of the first dissolution agent methanol to the crystallization mother liquor is changed to 0.05:1, and all other aspects are the same as in Example 1.

[0064] The crystalline product obtained in this embodiment was characterized by Raman spectra as follows: Figure 5 As shown, it can be seen that its crystal form is a mixture of α and γ crystal forms. The characteristic peak of γ-glycine is at a wavelength of 1339 cm⁻¹. -1 Place.

[0065] Example 5

[0066] This embodiment provides a method for controlling the particle size and crystal form of glycine in a coupled crystallization process of dissolution and cooling. The only difference between this method and Example 1 is that the mass ratio of the first dissolution agent methanol to the crystallization mother liquor is changed to 0.45:1, while the rest is the same as in Example 1.

[0067] Example 6

[0068] This embodiment provides a method for controlling the particle size and crystal form of glycine in a coupled crystallization process of dissolution-cooling. The only difference between this method and Example 1 is that the feeding time of adding the crystallization mother liquor to the first dissolution agent methanol is changed to 10 min, and the rest is the same as Example 1.

[0069] Example 7

[0070] This embodiment provides a method for controlling the particle size and crystal form of glycine in a coupled crystallization process of dissolution-cooling. The only difference between this method and Example 1 is that the feeding time of adding the crystallization mother liquor to the first dissolution agent methanol is changed to 1 min, and the rest is the same as Example 1.

[0071] Comparative Example 1

[0072] This comparative example provides a method for controlling the particle size and crystal form of glycine in a solubilization-cooling coupled crystallization process. The only difference between this method and Example 1 is that the first solubilizing agent and crystallization mother liquor premixing step is omitted, and methanol is directly added to the crystallization mother liquor. All other aspects are the same as in Example 1.

[0073] The crystalline product obtained in this embodiment was characterized by microscopic images, as shown below. Figure 6 As shown, the experimental conditions yielded a mixed crystal of α and γ.

[0074] Comparative Example 2

[0075] This comparative example provides a method for controlling the particle size and crystal form of glycine in a solubilization-cooling coupled crystallization process. The only difference between this method and Example 1 is that the first solubilizing agent and the crystallization mother liquor premixing step is omitted. Instead, pure α-crystal glycine prepared in advance is directly added to the crystallization mother liquor as a seed crystal, and then the second solubilizing agent is added. All other aspects are the same as in Example 1.

[0076] Performance testing

[0077] The crystalline products provided in the examples and comparative examples were characterized by Raman spectroscopy, and the average particle size and volume ratio were determined based on the particle size distribution. The coefficient of variation was calculated using the following formula: The results are shown in Table 1.

[0078] Table 1

[0079]

[0080] In Table 1, "-" indicates that there is no relevant data.

[0081] As can be seen from Table 1, this invention achieves the stable preparation of pure α-crystalline glycine with uniform particle size and low agglomeration by combining the crystallization process of dissolution and cooling.

[0082] A comprehensive comparison of Examples 1 and Examples 4-7 shows that the premixing conditions of the first solvent and the mother liquor, as well as the rate at which the mother liquor is added to the first solvent, significantly affect the crystal form and particle size distribution of the final product. When the mass ratio of the first solvent to the mother liquor decreases to 0.05:1, the product obtained in Example 4 is a mixture of α and γ crystals, indicating insufficient dissolution during the premixing stage, which is not conducive to the formation of a suitable number and uniformly distributed in-situ seed crystals, thus insufficient to induce the formation of pure α crystals. When the mass ratio of the first solvent to the mother liquor increases to 0.45:1, although Example 5 can still obtain an α-crystal product, its average particle size and coefficient of variation are worse than those of Example 1, indicating that when the local supersaturation is too high during the premixing stage, it easily leads to excessively rapid nucleation and excessively fine seed crystals, resulting in a reduction in product particle size. When the mother liquor addition time was 10 min, the average particle size and coefficient of variation in Example 6 were worse than those in Example 1, indicating that excessively rapid addition reduced the uniformity of mixing, thus affecting the particle size distribution of the product. When the addition time was reduced to 1 min, although Example 7 still exhibited the α-crystal form, the coefficient of variation increased, indicating that a slow addition rate of the mother liquor allowed for a longer growth time of the crystal nuclei, which was detrimental to the formation of a sufficient number of uniform microcrystalline seeds, resulting in a poorer particle size distribution. Therefore, controlling the mass ratio of the first solvent to the mother liquor and its addition rate within the preferred range of this invention is more conducive to balancing crystal purity, particle size concentration, and agglomeration control, with the conditions shown in Example 1 demonstrating a superior overall effect.

[0083] A comprehensive comparison of Example 1 and Comparative Examples 1-2 shows that premixing to form self-generated seed crystals is a crucial factor in achieving stable crystal form and controllable particle size in this invention. Comparative Example 1 did not involve premixing the first solvent with the crystallization mother liquor; instead, the solvent was directly added to the crystallization mother liquor. Under these conditions, the resulting product was a mixture of α and γ crystals, indicating that without the premixing seeding process, the system struggles to establish a seed base conducive to the continuous growth of the α-crystal form, resulting in poor product crystal form stability. Although Comparative Example 2 used externally added pre-prepared pure α-crystal glycine microcrystals as seed crystals, its average particle size and coefficient of variation were lower than those of Example 1, indicating that simply relying on externally added seed crystals cannot replace the self-generated seed crystals formed in situ during the premixing stage. This may be due to the limited compatibility between the added seed crystals and the mother liquor system, which is not conducive to the stable control of the product particle size distribution. The present invention premixes the mother liquor with the first solvent to form a large number of microcrystalline seed crystals in situ inside the system. Combined with the addition of the second solvent and the cooling operation, it is beneficial to provide more uniform and highly active growth sites for subsequent crystallization, which is more conducive to obtaining α-crystalline glycine products with more concentrated particle size distribution, lower degree of agglomeration and stable crystal form.

[0084] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for controlling particle size and crystal form in a glycine dissolution-cooling coupled crystallization process, characterized in that, The method includes the following steps: The first solvent is heated and kept at a certain temperature. Then, a crystallization mother liquor is added to the first solvent to form seed crystals through dissolution. Then, a second solvent is added to the resulting mixture and the temperature is lowered. The resulting suspension is subjected to solid-liquid separation to obtain glycine.

2. The method according to claim 1, characterized in that, The first solvent and the second solvent each independently comprise methanol.

3. The method according to claim 1 or 2, characterized in that, The final heating temperature of the first solvent is 50-60℃; Preferably, the first solvent is kept at a constant temperature for 25-35 minutes.

4. The method according to any one of claims 1 to 3, characterized in that, The initial temperature of the crystallization mother liquor before adding the first solvent is 55-65℃; Preferably, the time for adding the crystallization mother liquor to the first solvent is 2-8 minutes.

5. The method according to any one of claims 1 to 4, characterized in that, The mass ratio of the first solvent to the crystallization mother liquor is (0.1-0.4):

1.

6. The method according to any one of claims 1 to 5, characterized in that, The process of adding the crystallization mother liquor to the first solvent includes: adding the crystallization mother liquor to the first solvent under stirring, continuing to stir until crystals precipitate, then maintaining stirring for 5-15 minutes, and then adding the second solvent while continuing to stir; Preferably, the stirring speed is 225-350 rpm.

7. The method according to any one of claims 1 to 6, characterized in that, The second solvent is added to the mixture by means of dropwise addition; Preferably, the dripping rate is 3.5-7.5 L / min.

8. The method according to any one of claims 1 to 7, characterized in that, The mass ratio of the second solvent to the mixture is (1.85-2.64):

1.

9. The method according to any one of claims 1 to 8, characterized in that, After cooling to the final temperature, continue stirring for 25-35 minutes, and then perform solid-liquid separation on the suspension.

10. The method according to any one of claims 1 to 9, characterized in that, The cooling rate is 0.15-0.35℃ / min; Preferably, the final temperature of the cooling process is 25-35°C.

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