Method for efficiently synthesizing 3-aminofurazan-4-carboxylic acid from 1, 2, 3-glycerol trioxime

Abstract

The invention discloses a method for efficiently synthesizing 3-amino furazan-4-carboxylic acid from 1, 2, 3-glycerol trioxime, and belongs to the technical field of chemical engineering. The invention solves the problems that the existing 3-aminofurazan-4-carboxylic acid synthesis method uses toxic raw materials and highly toxic and flammable reagents, and lacks green and safety. According to the method, 1, 2, 3-glycerol trioxime and a hydroxylamine solution are dissolved in an alkaline water phase, the reaction temperature is adjusted, the catalytic reaction, the dehydration reaction and the neutralization reaction are carried out in sequence, finally, the 3-amino furazan-4 carboxylic acid is synthesized, the yield reaches 55%, and the method is suitable for industrial production. The method disclosed by the invention has the advantages of safe and non-toxic raw materials, short synthesis reaction time, simple reaction steps, easily controlled reaction temperature, high product yield, few pollutants and the like, and compared with the traditional 3-aminofurazan-4 carboxylic acid synthesis method, the production cost is saved, the product preparation process is green and environment-friendly, and the method is suitable for industrial production. And the method is suitable for green sustainable development of industrial production of 3-aminofurazan-4 carboxylic acid.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical engineering, and particularly relates to a method for efficiently synthesizing 3-aminofurazan-4-carboxylic acid from 1,2,3-propanetrioxime. Background Art

[0002] 3-Aminofurazan-4-carboxylic acid (AFCA) is an important multifunctional oxidized furazan compound. Due to its unique molecular structure, it has a wide range of application prospects, especially in the fields of pharmaceuticals, materials, and industry. Oxidized furazan compounds are an important class of NO donors with potential application value in the medical field. They can be used to synthesize drugs with medical functions such as preventing leukemia, antiviral and cancer spread, and inhibiting HIV. In other industrial applications, furazan compounds are often used as metal polishing agents, preservatives, photographic photosensitizers, etc.

[0003] At present, the synthesis of AFCA mainly relies on two chemical methods. One is to use methyl cyanoacetate as raw material and react with hydroxylamine hydrochloride to synthesize AFCA (Reference: "Synthesis and Performance Research of New Insensitive Energetic Plasticizer 3-Nitrofurazan-4-Methyl Ether", Energetic Materials, 2011, 19 (6): 735-738). The second method is to use cyanoacetamide as the starting material and prepare AFCA through three steps of nitrosation, addition and cyclization (Reference: "Synthesis and Characterization of 3-Aminofurazan-4-Carboxylic Acid", Chemical Reagents, 2019, 41 (01): 93-95). Although these methods have made progress in the synthesis of AFCA, they use toxic cyano compounds as raw materials and highly toxic and flammable reagents, which poses challenges to the safety and environmental friendliness of the AFCA synthesis process. Therefore, it is necessary to explore new green synthesis routes and methods for AFCA to significantly reduce the use of toxic raw materials and solvents in the traditional AFCA synthesis, thereby promoting its industrialization process and its wide application in various fields. Summary of the invention

[0004] The invention provides a method for efficiently synthesizing 3-aminofurazan-4-carboxylic acid from 1,2,3-propanetrioxime in order to solve the problems that the existing synthesis method of 3-aminofurazan-4-carboxylic acid uses toxic raw materials, highly toxic and flammable reagents, lacks environmental friendliness and safety, and the like.

[0005] In order to solve the above technical problems, the present invention is implemented through the following technical solutions:

[0006] The object of the present invention is to provide a method for efficiently synthesizing 3-aminofurazan-4-carboxylic acid from 1,2,3-propanetrioxime, comprising:

[0007] (1) Mixed dissolution: Weigh three raw materials: 1,2,3-propanetrioxime, hydroxylamine salt and inorganic base, mix and dissolve the three raw materials at below 40° C. to obtain a reaction solution;

[0008] (2) Catalytic reaction: Control the temperature of the reaction liquid below 40° C., carry out the catalytic reaction under stirring conditions, then raise the temperature of the reaction liquid to a certain temperature and continue the catalytic reaction;

[0009] (3) Dehydration reaction: the reaction solution after the catalytic reaction in (2) is heated and dehydration reaction is carried out under stirring;

[0010] (4) Neutralization reaction: cooling the reaction solution after the dehydration reaction in (3), adding acid to adjust the pH under stirring, and then cooling the reaction solution after the pH adjustment to below 20° C. to obtain a suspended reaction solution;

[0011] (5) Post-treatment: The suspended reaction liquid was filtered to obtain a solid, and the solid was washed with water, recrystallized, and filtered again to obtain 3-aminofurazan-4-carboxylic acid.

[0012] It is further defined that the molar ratio of 1,2,3-propanetrioxime, hydroxylamine salt and inorganic base in (1) is 1:(2-13):(2-20).

[0013] It is further defined that the hydroxylamine salt in (1) is one of hydroxylamine hydrochloride, hydroxylamine sulfate, and hydroxylamine aqueous solution.

[0014] It is further defined that the inorganic base in (1) is one of sodium hydroxide and potassium hydroxide.

[0015] Further defined, in (2), the reaction solution is heated to 40-50°C.

[0016] It is further defined that the total catalytic reaction time in (2) is 1 to 24 hours.

[0017] It is further defined that in (3), the reaction solution is heated to 60-120°C.

[0018] It is further defined that the dehydration reaction time in (3) is 0.5 to 12 hours.

[0019] It is further defined that in (4), the reaction solution is cooled to below 60°C.

[0020] It is further defined that the pH in (4) is adjusted to 1-4.

[0021] It is further defined that the recrystallization process in (5) is as follows: dissolving the solid obtained by washing with water in a recrystallization solvent to form a solution, heating the solution to 80°C to 150°C under stirring conditions to obtain a recrystallization mixture, maintaining the recrystallization mixture at 80°C to 150°C for 0.5 to 3h and then cooling it to 0 to 50°C.

[0022] The beneficial effects of the present invention are:

[0023] The present invention uses 1,2,3-propanetrioxime as a substrate and synthesizes 3-aminofurazan-4-carboxylic acid (AFCA) through chemical conversion. 1,2,3-propanetrioxime has a simple structure and is non-toxic. Under alkaline conditions, two aldoxime groups of 1,2,3-propanetrioxime undergo a dehydration reaction (the dehydration here corresponds to the catalytic reaction of (2) rather than the dehydration reaction in (3)) to generate 2-oxime-1,3-malononitrile. 2-oxime-1,3-malononitrile and a hydroxylamine aqueous solution undergo an addition reaction under an alkaline environment, and a cyano group and a hydroxylamine generate an oxime group to obtain 1,3-diamino-1,2 , 3-propanetrioxime intermediate, the intermediate is subjected to high temperature dehydration cyclization to generate 3-amino-4-aminoximitofurazan, and finally acidified to obtain 3-aminofurazan-4-carboxylic acid. The method of the invention avoids the toxicity caused by the use of traditional cyano raw materials, has the advantages of safe, non-toxic and non-explosive raw materials, short synthesis reaction time, simple reaction steps, easy to control reaction temperature, high product yield, simple purification, less pollutants, etc. Compared with the traditional synthesis method, it saves production cost and time, makes the production process more efficient and quick, and the product preparation process is green and environmentally friendly, which is suitable for the green and sustainable development of industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 HPLC detection chromatogram of 3-aminofurazan-4-carboxylic acid prepared in Example 1;

[0025] Figure 2 The UHPLC-MS detection chromatogram (extracted ion chromatogram EIC diagram) of 3-aminofurazan-4-carboxylic acid prepared in Example 1;

[0026] Figure 3 The UHPLC-MS detection chromatogram (primary spectrum) of 3-aminofurazan-4-carboxylic acid prepared in Example 1;

[0027] Figure 4 The carbon NMR spectrum (deuterated DMSO) of 3-aminofurazan-4-carboxylic acid prepared in Example 1;

[0028] Figure 5 This is the hydrogen nuclear magnetic resonance spectrum (deuterated DMSO) of 3-aminofurazan-4-carboxylic acid prepared in Example 1. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0030] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0031] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0032] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.

[0033] The synthesis route of 1,2,3-propanetrioxime to synthesize 3-aminofurazan-4-carboxylic acid provided by the present invention is as follows:

[0034]

[0035] Example 1

[0036] (1) Mixed dissolution: 100 mL of water and 30 g of sodium hydroxide were added to a 500 mL three-necked flask equipped with a mechanical stirrer, a thermometer and a reflux condenser and dissolved, and then 17.5 g of 1,2,3-propanetrioxime was added, and the system temperature was controlled within 20° C., and then 46.5 g of hydroxylamine hydrochloride was slowly added, and the system temperature was controlled within 40° C. Under stirring conditions, the raw materials were mixed and dissolved to obtain a reaction solution;

[0037] (2) Catalytic reaction: After the raw materials in (1) are mixed and dissolved, the temperature of the reaction solution is still controlled to be below 40° C., and the catalytic reaction is carried out at room temperature with stirring for 2 h, and then the temperature is rapidly raised to 42° C., and the catalytic reaction is continued with stirring for 2 h;

[0038] (3) Dehydration reaction: The reaction solution after the catalytic reaction in (2) was heated to 90° C. and subjected to dehydration reaction for 6 h under stirring;

[0039] (4) Neutralization reaction: After the dehydration reaction in (3) is completed, the reaction solution is cooled to 60° C., and the pH of the reaction solution is adjusted to 1 using 36% concentrated hydrochloric acid at room temperature with stirring. The reaction solution is then cooled to below 20° C. to obtain a suspended reaction solution.

[0040] (5) Filtration and separation: Use a suction filtration bottle to filter the suspended reaction liquid to separate the solid from the reaction liquid, rinse the filtered solid with deionized water to remove most of the inorganic salts, and obtain a white solid, which is the crude 3-aminofurazan-4-carboxylic acid. Use deionized water to fully dissolve the crude product. The mass ratio of the crude product to deionized water is 1:5. The mixture is heated to 100°C under stirring to obtain a recrystallized mixture. After reacting for 1 hour, the temperature of the mixture is reduced to 30°C, and the mixture is cooled and precipitated. The precipitated substance is filtered to obtain 3-aminofurazan-4-carboxylic acid containing water, which is dried to obtain the product, that is, the white solid is 3-aminofurazan-4-carboxylic acid.

[0041] All steps in (1) to (4) are carried out under stirring conditions.

[0042] The product 3-aminofurazan-4-carboxylic acid was dissolved in water and deuterated DMSO (dimethyl sulfoxide-d6) respectively to obtain a reaction solution for testing, which was subjected to high performance liquid chromatography (HPLC), ultra high performance liquid chromatography mass spectrometry (UHPLC-MS) and nuclear magnetic resonance (NMR) detection. According to calculation, the actual yield of 3-aminofurazan-4-carboxylic acid was 40%, and the purity of the product detected by ultra high performance liquid chromatography was 99.1%.

[0043] High performance liquid chromatography (HPLC) detection method: Take 1mL of the reaction solution, centrifuge at 12000g for 1min, take the supernatant, pass through a 0.22μm filter membrane, and place it in a liquid phase vial for testing. Detection conditions: HPLC instrument model is Shimadzu LC-20AT; chromatographic column Agilent ZORBAX SB-C18 (4.6×250mm); detection wavelength is 272nm; column temperature is 30℃; flow rate is 0.5mL / min; injection volume: 10μL; mobile phase A is water, and mobile phase B is acetonitrile. Gradient elution program: 0-5min, 5% B liquid; 5-12min, linear change to 40% B liquid; 12-20min, 40% B liquid; 20-30min, 5% B liquid.

[0044] Ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS) detection method: Take 1 mL of the reaction solution, centrifuge at 12000g for 1 min, take the supernatant and filter it and place it in a liquid vial for testing. Chromatographic separation conditions: The instrument is Thermo SCIENTIFICUltiMate 3000UHPLC, the chromatographic column is Aglient Poroshell 120SB-Aq, the column temperature is 30°C, the mobile phase A liquid is water, the B liquid is acetonitrile, and the gradient elution conditions are: 0-2min is 5% B liquid; B liquid changes linearly to 95% from 2 to 6min and keeps for 4min; 10min is quickly reduced to 5% B liquid and kept for 5min. Flow rate 0.2mL / min. Mass spectrometry conditions: The instrument is a Bruker CompactQ-TOF time-of-flight mass spectrometer, electrospray ion source, positive ion mode detection, drying oven temperature 200°C, flow rate 2.0L / min, mass scanning range m / z 0-600.

[0045] HPLC test results are as follows Figure 1 As shown, in Figure 1 It can be seen from B that the product prepared in this example has an obvious peak at around 4 minutes, and its retention time is completely consistent with that of the standard product ( Figure 1 A) This example successfully prepared 3-aminofurazan-4-carboxylic acid. The UHPLC-MS test results are as follows Figure 2 As shown in FIG. 1 , the parent ion current of m / z=130.02 was extracted, and the peak time was consistent with that of the 3-aminofurazan-4-carboxylic acid standard, which also shows that the product prepared in this example is indeed 3-aminofurazan-4-carboxylic acid. The primary spectrum of the UHPLC-MS detection result is shown in FIG. Figure 3 As shown, it can be seen that both the product prepared in this example and the standard product contain ions in the form of sodium salt (m / z=173.988). Figure 4 As shown, the chemical shifts and ratios of the three carbons in the carbon spectrum are consistent with 3-aminofurazan-4-carboxylic acid. Figure 5 ), the chemical shifts of amino hydrogen and carboxyl hydrogen in the product are consistent with those of the standard product, but the ratio is inconsistent. Combined with the sodium salt information detected by UHPLC-MS, it can be seen that the difference in ratio is due to the presence of sodium salt in the product prepared in this example. This result is mutually confirmed by UHPLC-MS analysis, further confirming the chemical composition of the product prepared in this example.

[0046] Example 2

[0047] (1) Mixed dissolution: 100 mL of water and 10.6 g of sodium hydroxide were added to a 500 mL three-necked flask equipped with a mechanical stirrer, a thermometer and a reflux condenser and dissolved, and then 17.5 g of 1,2,3-propanetrioxime was added, and the system temperature was controlled within 20° C., and then 18.5 g of hydroxylamine hydrochloride was slowly added, and the system temperature was controlled within 40° C. Under stirring conditions, the raw materials were mixed and dissolved to obtain a reaction solution;

[0048] (2) Catalytic reaction: After the raw materials in (1) are mixed and dissolved, the temperature of the reaction solution is still controlled to be below 40° C., and the catalytic reaction is carried out at room temperature with stirring for 2 h, and then the temperature is rapidly raised to 42° C., and the catalytic reaction is continued with stirring for 2 h;

[0049] (3) Dehydration reaction: The reaction solution after the catalytic reaction in (2) was heated to 90° C. and subjected to dehydration reaction for 6 h under stirring;

[0050] (4) Neutralization reaction: After the dehydration reaction in (3) is completed, the reaction solution is cooled to 60° C., and the pH of the reaction solution is adjusted to 1 using 36% concentrated hydrochloric acid at room temperature with stirring. The reaction solution is then cooled to below 20° C. to obtain a suspended reaction solution.

[0051] (5) Filtration and separation: Use a suction filtration bottle to filter the suspended reaction liquid to separate the solid from the reaction liquid, rinse the filtered solid with deionized water to remove most of the inorganic salts, and obtain a white solid, which is the crude 3-aminofurazan-4-carboxylic acid. Use deionized water to fully dissolve the crude product. The mass ratio of the crude product to deionized water is 1:5. The mixture is heated to 100°C under stirring to obtain a recrystallized mixture. After reacting for 1 hour, the temperature of the mixture is reduced to 30°C, and the mixture is cooled and precipitated. The precipitated substance is filtered to obtain 3-aminofurazan-4-carboxylic acid containing water, which is dried to obtain the product, that is, the white solid is 3-aminofurazan-4-carboxylic acid.

[0052] All steps in (1) to (4) are carried out under stirring conditions.

[0053] The product 3-aminofurazan-4-carboxylic acid was dissolved in water and detected by high performance liquid chromatography (HPLC). According to calculation, the actual yield of 3-aminofurazan-4-carboxylic acid was 23%, and the purity of the product detected by ultra-high performance liquid chromatography was 97.8%.

[0054] Example 3

[0055] (1) Mixed dissolution: 100 mL of water and 53.2 g of sodium hydroxide were added to a 500 mL three-necked flask equipped with a mechanical stirrer, a thermometer and a reflux condenser and dissolved, and then 35 g of 1,2,3-propanetrioxime was added, and the system temperature was controlled within 20° C., and then 60 g of hydroxylamine hydrochloride was slowly added, and the system temperature was controlled within 40° C. Under stirring conditions, the raw materials were mixed and dissolved to obtain a reaction solution;

[0056] (2) Catalytic reaction: After the raw materials in (1) are mixed and dissolved, the temperature of the reaction solution is still controlled to be below 40° C., and the catalytic reaction is carried out at room temperature with stirring for 2 h, and then the temperature is rapidly raised to 42° C., and the catalytic reaction is continued with stirring for 2 h;

[0057] (3) Dehydration reaction: The reaction solution after the catalytic reaction in (2) was heated to 90° C. and subjected to dehydration reaction for 6 h under stirring;

[0058] (4) Neutralization reaction: After the dehydration reaction in (3) is completed, the reaction solution is cooled to 60° C., and the pH of the reaction solution is adjusted to 1 using 36% concentrated hydrochloric acid at room temperature with stirring. The reaction solution is then cooled to below 20° C. to obtain a suspended reaction solution.

[0059] (5) Filtration and separation: Use a suction filtration bottle to filter the suspended reaction liquid to separate the solid from the reaction liquid, rinse the filtered solid with deionized water to remove most of the inorganic salts, and obtain a white solid, which is the crude 3-aminofurazan-4-carboxylic acid. Use deionized water to fully dissolve the crude product. The mass ratio of the crude product to deionized water is 1:5. The mixture is heated to 100°C under stirring to obtain a recrystallized mixture. After reacting for 1 hour, the temperature of the mixture is reduced to 30°C, and the mixture is cooled and precipitated. The precipitated substance is filtered to obtain 3-aminofurazan-4-carboxylic acid containing water, which is dried to obtain the product, that is, the white solid is 3-aminofurazan-4-carboxylic acid.

[0060] All steps in (1) to (4) are carried out under stirring conditions.

[0061] The product 3-aminofurazan-4-carboxylic acid was dissolved in water and tested by high performance liquid chromatography (HPLC). According to calculation, the actual yield of 3-aminofurazan-4-carboxylic acid was 31%, and the purity of the product was 92.8% as tested by ultra-high performance liquid chromatography.

[0062] Example 4

[0063] (1) Mixed dissolution: 100 mL of water and 30 g of sodium hydroxide were added to a 500 mL three-necked flask equipped with a mechanical stirrer, a thermometer and a reflux condenser and dissolved, and then 17.5 g of 1,2,3-propanetrioxime was added, and the system temperature was controlled within 20° C., and then 46.5 g of hydroxylamine hydrochloride was slowly added, and the system temperature was controlled within 40° C. Under stirring conditions, the raw materials were mixed and dissolved to obtain a reaction solution;

[0064] (2) Catalytic reaction: After the raw materials in (1) are mixed and dissolved, the temperature of the reaction solution is still controlled to be below 40° C., and the catalytic reaction is carried out at room temperature with stirring for 2 h, and then the temperature is rapidly raised to 42° C., and the catalytic reaction is continued with stirring for 2 h;

[0065] (3) Dehydration reaction: The reaction solution after the catalytic reaction in (2) was heated to 120° C. and subjected to dehydration reaction for 4 h under stirring;

[0066] (4) Neutralization reaction: After the dehydration reaction in (3) is completed, the reaction solution is cooled to 60° C., and the pH of the reaction solution is adjusted to 1 using 36% concentrated hydrochloric acid at room temperature with stirring. The reaction solution is then cooled to below 20° C. to obtain a suspended reaction solution.

[0067] (5) Filtration and separation: Use a suction filtration bottle to filter the suspended reaction liquid to separate the solid from the reaction liquid, rinse the filtered solid with deionized water to remove most of the inorganic salts, and obtain a white solid, which is the crude 3-aminofurazan-4-carboxylic acid. Use deionized water to fully dissolve the crude product. The mass ratio of the crude product to deionized water is 1:5. The mixture is heated to 100°C under stirring to obtain a recrystallized mixture. After reacting for 1 hour, the temperature of the mixture is reduced to 30°C, and the mixture is cooled and precipitated. The precipitated substance is filtered to obtain 3-aminofurazan-4-carboxylic acid containing water, which is dried to obtain the product, that is, the white solid is 3-aminofurazan-4-carboxylic acid.

[0068] All steps in (1) to (4) are carried out under stirring conditions.

[0069] The product 3-aminofurazan-4-carboxylic acid was dissolved in water and detected by high performance liquid chromatography (HPLC). According to calculation, the actual yield of 3-aminofurazan-4-carboxylic acid was 55%, and the purity of the product detected by ultra-high performance liquid chromatography was 99.3%.

[0070] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for efficiently synthesizing 3-aminofurazan-4-carboxylic acid from 1,2,3-propanetrioxime, characterized in that: include: (1) Mixed dissolution: Weigh three raw materials: 1,2,3-propanetrioxime, hydroxylamine salt and inorganic base, mix and dissolve the three raw materials at below 40° C. to obtain a reaction solution; (2) Catalytic reaction: Control the temperature of the reaction liquid below 40° C., carry out the catalytic reaction under stirring conditions, then raise the temperature of the reaction liquid to a certain temperature and continue the catalytic reaction; (3) Dehydration reaction: the reaction solution after the catalytic reaction in (2) is heated and dehydration reaction is carried out under stirring; (4) Neutralization reaction: cooling the reaction solution after the dehydration reaction in (3), adding acid to adjust the pH under stirring, and then cooling the reaction solution after the pH adjustment to below 20° C. to obtain a suspended reaction solution; (5) Post-treatment: The suspended reaction liquid was filtered to obtain a solid, and the solid was washed with water, recrystallized, and filtered again to obtain 3-aminofurazan-4-carboxylic acid.

2. The method according to claim 1, characterized in that The molar ratio of 1,2,3-propanetrioxime, hydroxylamine salt and inorganic base in (1) is 1:(2-13):(2-20).

3. The method according to claim 1, characterized in that The hydroxylamine salt in (1) is one of hydroxylamine hydrochloride, hydroxylamine sulfate and hydroxylamine aqueous solution.

4. The method according to claim 1, characterized in that: The inorganic base in (1) is one of sodium hydroxide and potassium hydroxide.

5. The method according to claim 1, characterized in that In the step (2), the reaction solution is heated to 40-50°C.

6. The method according to claim 1, characterized in that The total catalytic reaction time in (2) is 1 to 24 hours.

7. The method according to claim 1, characterized in that In the step (3), the reaction solution is heated to 60-120°C.

8. The method according to claim 1, characterized in that The dehydration reaction time in (3) is 0.5 to 12 hours.

9. The method according to claim 1, characterized in that: The reaction solution in (4) is cooled to below 60°C and the pH is adjusted to 1-4.

10. The method according to claim 1, characterized in that The recrystallization process in (5) is as follows: dissolving the solid obtained by washing with water in a recrystallization solvent to form a solution, heating the solution to 80°C to 150°C under stirring conditions to obtain a recrystallization mixed solution, maintaining the recrystallization mixed solution at 80°C to 150°C for 0.5 to 3 hours, and then cooling it to 0 to 50°C.

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