A method for purifying 8-hydroxyquinoline reaction solution

Abstract

The application discloses a kind of 8-hydroxyquinoline reaction liquid purification methods, belong to fine chemical technology field, with propenal as raw material after reaction 8-hydroxyquinoline is obtained, concentrated removal reaction liquid is dissolved with water, 8-hydroxyquinoline is obtained after aqueous solution is adjusted by liquid alkali;During the adjustment process, the polymer generated in the solution is precipitated by controlling the pH value of the solution, the filtrate is continuously adjusted to 7~7.5 to precipitate 8-hydroxyquinoline crude product, and the filtrate is used to the next batch of experiments after filtration;8-hydroxyquinoline crude product is recrystallized with methanol as solvent to obtain pure 8-hydroxyquinoline, the content is more than 99%, and the recrystallization mother liquor is continuously used to the next batch of experiments.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of fine chemical industry, and particularly relates to a purification method of 8-hydroxyquinoline reaction liquid. BACKGROUND

[0002] Hydroxyquinoline is also known as hydroxyquinoline and quinolinol, and is an important medicine, dye and pesticide intermediate. It is mainly used for producing medicine intermediates such as quinolone and chloroquinoxaline, and dye and pesticide intermediates. Its sulfate and copper salt is an excellent preservative, disinfectant and antitoxic agent, and is also a complex titration indicator for chemical analysis, and is a main raw material for low-toxicity and high-efficiency pesticides and some medicines.

[0003] At present, 8-hydroxyquinoline is mainly produced by quinoline sulfonation alkali fusion method, chloroquinoline hydrolysis method, aminoquinoline hydrolysis method and Skraup synthesis method. In 2017, the International Agency for Research on Cancer of the World Health Organization announced that 8-hydroxyquinoline is a class III carcinogen. In addition, the synthesis process needs to go through processes such as sulfonation and alkali fusion, and a large amount of wastewater is generated, and the preparation cost is high, so the actual production capacity gradually shrinks. Because a large amount of polymer exists, post-treatment is difficult, and there are disadvantages such as high cost and difficult separation of pollutants, so it is not the optimal synthesis scheme. The raw material used in the Skraup synthesis method is low, non-toxic or less toxic, but the amount of waste salt generated by sulfuric acid dehydration is large, and the amount of excess glycerol is large, and the polymer in the reaction is obvious, and the still residue is difficult to handle. SUMMARY

[0004] To solve the above problems, the purpose of the present application is to provide a purification method of 8-hydroxyquinoline reaction liquid. After the polymer is precipitated in advance, high-purity products are obtained by recrystallization, so as to achieve the purposes of reducing energy consumption, simplifying post-treatment steps and reducing product loss in the post-treatment process.

[0005] To achieve the above purposes, the following technical solutions are adopted in the present application:

[0006] A purification method of 8-hydroxyquinoline reaction liquid, comprising the following steps:

[0007] 1) The reaction liquid obtained by synthesizing 8-hydroxyquinoline by improved Skraup method is concentrated under reduced pressure to remove the solvent, water is added to the obtained residue, and after stirring and dissolving, 30-40% sodium hydroxide aqueous solution is added dropwise at 25-30 DEG C, the pH of the system is adjusted to 3.7-3.9, after the solid is precipitated, continue to stir for 20-30 min, then filter, the obtained solid is polymer, and the obtained filtrate is used;

[0008] 2) At 25-30 DEG C, continue to add 30-40% sodium hydroxide aqueous solution to the filtrate obtained in step 1), adjust the pH of the system to 7-7.5, filter to obtain 8-hydroxyquinoline crude product;

[0009] 3) The 8-hydroxyquinoline crude product obtained in step 2) is added into methanol, heated to 50 DEG C, after stirring and dissolving, cooled to 30-40 DEG C, continue to keep warm and stir for 30 min, then keep warm and filter to obtain 8-hydroxyquinoline.

[0010] The amount of water added in step 1) is 1-2 times the mass of 8-hydroxyquinoline in the reaction solution.

[0011] The amount of methanol added in step 3) is 1-1.5 times the mass of 8-hydroxyquinoline crude product.

[0012] Preferably, the amount of water added in step 1) is 1.5 times the mass of 8-hydroxyquinoline in the reaction solution.

[0013] Preferably, the pH of the adjusting solution in step 1) is adjusted to 3.85-3.9.

[0014] Preferably, the mass concentration of the aqueous sodium hydroxide solution in step 1) and step 2) is 32%.

[0015] Preferably, the amount of methanol added in step 3) is 1.2 times the mass of 8-hydroxyquinoline crude product.

[0016] Preferably, the temperature is cooled to 35 DEG C in step 3).

[0017] A large amount of polymers is generated in the synthesis of 8-hydroxyquinoline, and the reaction types mainly include propylene aldehyde self-polymerization, polymerization of reaction intermediates and propylene aldehyde, further reaction of propylene aldehyde polymer and o-aminophenol, and the generated polymers are a mixture of polymers with different types and different polymerization degrees.

[0018] The pKa (acidity coefficient) of 8-hydroxyquinoline is 5.017 at 20 DEG C, and based on this, experiments are carried out, and after the reaction is completed, 8-hydroxyquinoline and polymers are in the form of hydrochloride in the reaction solution, and finally it is determined by adjusting different pH values, when the pH of the system is greater than or equal to 4, 8-hydroxyquinoline begins to precipitate, and when the pH is about 3.9, most of the polymer hydrochloride has reacted into polymers, and the solubility of the polymers in water is very low, at this time, the polymers are precipitated in large amounts, therefore, by accurately controlling the pH, most of the polymers can be precipitated and no 8-hydroxyquinoline is precipitated.

[0019] Compared with the prior art, the present application has the following advantages:

[0020] (1) The purification method of the 8-hydroxyquinoline reaction solution of the present application gets rid of the problems of high energy consumption, large amount of waste water and difficult polymer treatment in the stripping recovery of products, and greatly shortens the time required for post-treatment.

[0021] (2) The 8-hydroxyquinoline crude product is recrystallized in methanol, the mother liquor can be repeatedly used, so as to reduce cost and reduce product loss.

[0022] (3) The polymer separated by the method is in powder state, easy to handle, and the product is less wrapped, the purity of the obtained 8-hydroxyquinoline can reach 99.9%, and the recovery rate is above 96%. DETAILED DESCRIPTION

[0023] In order to better understand the technical scheme of the present application, the above content of the present application will be further explained in detail through the form of examples, but this should not be understood as the scope of the above subject matter of the present application is limited to the following examples. Any technology realized based on the above content of the present application belongs to the scope of the present application.

[0024] The reaction solution obtained by synthesizing 8-hydroxyquinoline by the improved Skraup method in the following examples is prepared according to the method in Liu Duan, Li Xiang. Research on preparation of 8-hydroxyquinoline by improved Skraup method [J], Chemical and Biological Engineering, 2009, 26(8): 43-44.

[0025] Example 1 The reaction solution obtained by synthesizing 8-hydroxyquinoline by the improved Skraup method is detected, containing 110.5g of 8-hydroxyquinoline, the solvent is removed by vacuum concentration, 110.5g of water is added to the obtained residue, after stirring and dissolving, 30% sodium hydroxide aqueous solution is added dropwise at 25℃, the pH of the solution is adjusted to 3.7, after the solid is precipitated, continue to stir for 20min, then filter, the obtained solid is polymer, after drying, the polymer precipitation rate is 94.5%, continue to add 30% sodium hydroxide aqueous solution to the obtained filtrate, adjust the pH of the solution to 7, filter, obtain 101g of 8-hydroxyquinoline crude product.

[0026] The obtained 8-hydroxyquinoline crude product is added to 101g of methanol, heated to 50℃, stirred and dissolved, then cooled to 30℃, continue to heat and stir for 30min, then heat and filter, obtain 8-hydroxyquinoline, the purity is more than 99.9%, the mother liquor is used for the next batch, after 20 batches, the mother liquor is recovered and treated, the still residue is separately treated to remove polymer and purify, the comprehensive recovery rate of the product 8-hydroxyquinoline is 96.3%.

[0027] Example 2 The reaction solution obtained by synthesizing 8-hydroxyquinoline by the improved Skraup method was detected, containing 505.8 g of 8-hydroxyquinoline, the solvent was removed by concentration under reduced pressure, 1011.6 g of water was added to the obtained residue, after stirring and dissolving, 40% sodium hydroxide aqueous solution was added dropwise to the solution at 30°C, the pH of the solution was adjusted to 3.9, after the solid precipitated, the stirring was continued for 30 min, then filtration was performed, the obtained solid was a polymer, after drying, the polymer precipitation rate was 95.3%, 40% sodium hydroxide aqueous solution was continuously added dropwise to the filtrate, the pH of the solution was adjusted to 7.5, and filtration was performed, obtaining 498.6 g of 8-hydroxyquinoline crude product.

[0028] The obtained 8-hydroxyquinoline crude product was added to 747.9 g of methanol, heated to 50°C, stirred and dissolved, then cooled to 40°C, continued to stir for 30 min, then filtered under insulation, obtaining 8-hydroxyquinoline with purity of more than 99.9%, the mother liquor was recycled to the next batch, after 20 batches of recycling, the mother liquor was treated for recovery, the residue was treated for polymer removal and purification, and the comprehensive recycling rate of the product 8-hydroxyquinoline was 96.6%.

[0029] Example 3 The reaction solution obtained by synthesizing 8-hydroxyquinoline by the improved Skraup method was detected, containing 1.5 kg of 8-hydroxyquinoline, the solvent was removed by concentration under reduced pressure, 2.25 kg of water was added to the obtained residue, after stirring and dissolving, 35% sodium hydroxide aqueous solution was added dropwise to the solution at 25°C, the pH of the solution was adjusted to 3.85, after the solid precipitated, the stirring was continued for 20 min, then filtration was performed, the obtained solid was a polymer, after drying, the polymer precipitation rate was 95.2%, 35% sodium hydroxide aqueous solution was continuously added dropwise to the filtrate, the pH of the solution was adjusted to 7.1, and filtration was performed, obtaining 1.47 kg of 8-hydroxyquinoline crude product.

[0030] The obtained 8-hydroxyquinoline crude product was added to 747.9 g of methanol, heated to 50°C, stirred and dissolved, then cooled to 40°C, continued to stir for 30 min, then filtered under insulation, obtaining 8-hydroxyquinoline with purity of more than 99.9%, the mother liquor was recycled to the next batch, after 20 batches of recycling, the mother liquor was treated for recovery, the residue was treated for polymer removal and purification, and the comprehensive recycling rate of the product 8-hydroxyquinoline was 96.6%.

[0031] Example 4 The reaction solution obtained by synthesizing 8-hydroxyquinoline by improved Skraup method was detected, containing 8-hydroxyquinoline 2 kg, the solvent was removed by vacuum concentration, 3 kg of water was added to the obtained residue, after stirring and dissolving, 32% sodium hydroxide aqueous solution was added dropwise at 27°C, the pH of the solution was adjusted to 3.87, after the solid precipitated, continue to stir for 25 min, then filter, the obtained solid is polymer, after drying, the polymer precipitation rate is 95.4%, continue to add 32% sodium hydroxide aqueous solution to the filtrate, adjust the pH of the solution to 7.3, filter, obtain 1.95 kg of 8-hydroxyquinoline crude product.

[0032] The obtained 8-hydroxyquinoline crude product was added to 2.34 kg of methanol, heated to 50°C, stirred and dissolved, then cooled to 35°C, continue to stir for 30 min, then filter under insulation, the purity of 8-hydroxyquinoline is more than 99.9%, the mother liquor is used for the next batch, after 20 batches of recycling, the mother liquor is treated, the polymer is removed from the residue, the product 8-hydroxyquinoline is recovered with a comprehensive recovery rate of 97.1%.

[0033] Example 5 The reaction solution obtained by synthesizing 8-hydroxyquinoline by improved Skraup method was detected, containing 8-hydroxyquinoline 2 kg, the solvent was removed by vacuum concentration, 3.2 kg of water was added to the obtained residue, after stirring and dissolving, 32% sodium hydroxide aqueous solution was added dropwise at 29°C, the pH of the solution was adjusted to 3.9, after the solid precipitated, continue to stir for 27 min, then filter, the obtained solid is polymer, after drying, the polymer precipitation rate is 95.8%, continue to add 32% sodium hydroxide aqueous solution to the filtrate, adjust the pH of the solution to 7.4, filter, obtain 1.93 kg of 8-hydroxyquinoline crude product.

[0034] The obtained 8-hydroxyquinoline crude product was added to 2.7 kg of methanol, heated to 50°C, stirred and dissolved, then cooled to 37°C, continue to stir for 30 min, then filter under insulation, the purity of 8-hydroxyquinoline is more than 99.9%, the mother liquor is used for the next batch, after 20 batches of recycling, the mother liquor is treated, the polymer is removed from the residue, the product 8-hydroxyquinoline is recovered with a comprehensive recovery rate of 97%.

[0035] The reaction solution obtained by synthesizing 8-hydroxyquinoline by improving the Skraup method was detected, containing 110.5 g of 8-hydroxyquinoline, the solvent was removed by concentration under reduced pressure, 166 g of water was added to the obtained residue, after stirring and dissolving, 32% sodium hydroxide aqueous solution was added dropwise at 25°C, and the pH of the solution was adjusted to 7, at this time, 8-hydroxyquinoline and polymers were precipitated in large amounts, after filtration under reduced pressure, 161 g of 8-hydroxyquinoline crude product was obtained, and the mother liquor was used in the next batch of experiments.

[0036] The obtained 8-hydroxyquinoline crude product was added to 195 g of methanol, heated to 50°C, stirred and dissolved, cooled to 35°C, continued to stir for 30 min, and then filtered under insulation to obtain 8-hydroxyquinoline, the purity was detected to be 85%, because the polymers were not removed in advance, too much polymers were left in the solid, the recrystallization effect was limited, and after recrystallization, there were still a lot of polymers left in the solid, which needed to be recrystallized for many times.

[0037] Although the specific embodiments of the present application are described above, it is not a limitation on the protection scope of the present application, various modifications or changes made by those skilled in the art on the basis of the technical solutions of the present application without creative labor are still within the protection scope of the present application.

Claims

1. A method for purifying an 8-hydroxyquinoline reaction solution, characterized in that, Comprising the following steps: 1) The reaction solution obtained by synthesizing 8-hydroxyquinoline by improved Skraup method is concentrated under reduced pressure to remove the solvent, water is added to the obtained residue, after stirring and dissolving, 30-40% sodium hydroxide aqueous solution is added dropwise at 25-30℃, the pH of the system is adjusted to 3.7-3.9, after the solid is precipitated, continue to stir for 20-30min, then filter, the obtained solid is a polymer, and the obtained filtrate is used for the next step; 2) At 25-30℃, continue to add 30-40% sodium hydroxide aqueous solution to the filtrate obtained in step 1), adjust the pH of the system to 7-7.5, filter to obtain 8-hydroxyquinoline crude product; 3) The 8-hydroxyquinoline crude product obtained in step 2) is added into methanol, heated to 50℃, after stirring and dissolving, cool to 30-40℃, continue to stir for 30min, then filter under insulation to obtain 8-hydroxyquinoline.

2. The method for purifying the 8-hydroxyquinoline reaction solution according to claim 1, wherein The amount of water added in step 1) is 1-2 times the mass of 8-hydroxyquinoline in the reaction solution.

3. The method for purifying the 8-hydroxyquinoline reaction solution according to claim 1, wherein The amount of methanol added in step 3) is 1-1.5 times the mass of 8-hydroxyquinoline crude product.

4. The method for purifying the 8-hydroxyquinoline reaction solution according to claim 1, wherein The amount of water added in step 1) is 1.5 times the mass of 8-hydroxyquinoline in the reaction solution.

5. The method of purifying an 8-hydroxyquinoline reaction solution according to claim 1, wherein The pH of the solution in step 1) is adjusted to 3.85-3.

9.

6. The method for purifying the 8-hydroxyquinoline reaction solution according to claim 1, wherein The mass concentration of sodium hydroxide aqueous solution in step 1) and step 2) is 32%.

7. The method for purifying the 8-hydroxyquinoline reaction solution according to claim 1, wherein The amount of methanol added in step 3) is 1.2 times the mass of 8-hydroxyquinoline crude product.

8. The method for purifying the 8-hydroxyquinoline reaction solution according to Claim 1, wherein The temperature is cooled to 35℃ in step 3).