A method for separating and purifying succinic acid

Abstract

The application discloses a method for separating and purifying succinic acid, which comprises the following steps: (a) adding water into a mixed solution of succinic acid and a solvent to make the succinic acid completely dissolved; and (b) performing crystallization separation on the mixed solution of succinic acid obtained in the step (a) to obtain succinic acid crystals. The application provides more favorable crystallization conditions for succinic acid crystallization by controlling the ratio of water and the solvent, improves the crystallization rate of the succinic acid, reduces the production cost, and is simple in method and can effectively separate inorganic sodium salt and other impurities remaining in the succinic acid fermentation.

Description

Technical Field

[0001] This invention relates to the field of chemical separation, and in particular to a method for separating and purifying succinic acid. Background Technology

[0002] Succinic acid, also known as succinic acid, is an intermediate product in the tricarboxylic acid cycle. It is listed by the U.S. Department of Energy as one of the "12 Bio-based Platform Compounds" and is considered to have the potential to replace petrochemical intermediates as a next-generation bio-based chemical intermediate. In the food processing industry, succinic acid can be used as an acidulant and stabilizer to improve food flavor. In agriculture, it serves as a substrate for the synthesis of plant growth regulators, regulating nutrient absorption and promoting crop growth. In manufacturing and cleaning processes, it acts as a surfactant to enhance cleaning power.

[0003] Significant progress has been made in the fermentation production of succinic acid. However, the presence of large amounts of miscellaneous acids, inorganic salts, and other substances during the production process poses challenges to the separation and purification of succinic acid. Currently, downstream extraction and purification processes account for 60% or more of the total industrial production cost. Current methods for separating succinic acid from fermentation broths include liquid-liquid extraction, ammonium salt extraction, one-step crystallization, ion exchange adsorption, and bipolar membrane electrodialysis. These methods all have unavoidable drawbacks. For example, liquid-liquid extraction requires expensive tertiary amine extractants; the ammonium salt method requires high-temperature sulfate pyrolysis, which can easily cause equipment corrosion; the calcium salt method has a long route and generates a large amount of calcium sulfate waste; one-step crystallization yields products with low purity, low recovery rate, and long crystallization time; the ion exchange method has a low effective exchange capacity of the resin and requires large amounts of acid and alkali; and electrodialysis has membrane wear, high energy consumption, and requires extremely low divalent ion content, exhibiting significant limitations.

[0004] The large volume of saline wastewater generated during succinic acid separation is a major challenge for the industry. Conventional desalination processes are complex, cause severe equipment corrosion, result in low product purity or yield, and are energy-intensive, significantly impacting the advantages of bio-based succinic acid and thus limiting its market growth. Furthermore, existing literature indicates that succinic acid obtained through single-crystallization has low purity and significant pigment residue. High-purity succinic acid often requires secondary crystallization or repeated melt-crystallization processes. Multiple crystallizations result in low yields and prolonged crystallization times. Therefore, industrial production urgently needs a process that shortens crystallization time and improves crystallization efficiency to address the shortcomings of existing technologies. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a method for separating and purifying succinic acid, which can quickly remove inorganic salt solids from succinic acid crystals, has a high crystallization rate, and significantly improves crystallization efficiency.

[0006] To achieve the objectives of this invention, the following technical solution is provided:

[0007] A method for separating and purifying succinic acid includes the following steps:

[0008] (a) Add solvent and water to succinic acid to completely dissolve the succinic acid;

[0009] (b) The succinic acid mixed solution obtained in step (a) is crystallized to obtain succinic acid crystals.

[0010] Preferably, in step (a), the solvent is selected from one or a mixture of several of acetone, glycerol, methanol, ethanol or n-butanol.

[0011] In step (a), the volume ratio of water to solvent is 1:4 to 1:8, preferably 1:5 to 1:7.

[0012] Preferably, in step (a), the concentration of succinic acid is 350-450 g / L, more preferably 350-400 g / L, and the mixture is heated and stirred until the succinic acid is completely dissolved.

[0013] Preferably, in step (a), the heating temperature is 50-80°C and the stirring speed is 200-400 rpm.

[0014] Preferably, in step (a), a solvent is added to the succinic acid crystals and mixed evenly to dissolve the succinic acid. Insoluble matter is removed by solid-liquid separation to obtain a mixed solution of succinic acid and solvent.

[0015] Preferably, the succinic acid in step (a) is succinic acid containing an inorganic salt, preferably containing an inorganic sodium salt.

[0016] Preferably, the succinic acid in step (a) is succinic acid obtained by crystallization during the succinic acid fermentation process.

[0017] In this process, solvent is first added to succinic acid crystals containing inorganic salts and stirred until homogeneous. Then, inorganic salts that are insoluble in the solvent and / or impurities such as pigments and proteins that are difficult to dissolve in the solvent can be removed by common solid-liquid separation methods (centrifugation or filtration) before water is added.

[0018] Preferably, the inorganic salt can be a sodium salt such as sodium carbonate or sodium sulfate.

[0019] Preferably, after adding the solvent, the mixture should be stirred for 1-3 hours at room temperature or 20-30°C. This process is carried out under short-term low-temperature conditions to avoid or reduce side reactions such as esterification and to prevent the generation of new impurities.

[0020] Preferably, the amount of solvent in step (a) is 10 to 30 times the total mass of succinic acid and the inorganic salt crystals contained in succinic acid.

[0021] The separated inorganic sodium salt solids can be directly reused in the fermentation stage after drying.

[0022] The succinic acid crystals obtained by crystallization can be dried to obtain high-purity succinic acid crystals.

[0023] Preferably, the crystallization method is cooling crystallization, with a crystallization temperature of 10-25°C and a crystallization time of 2-5 hours.

[0024] The separated inorganic salt solids can be reused in the succinic acid fermentation stage after being prepared into a solution. The concentration of inorganic salts is in the range of 10-100 g / L, preferably 30-60 g / L.

[0025] Preferably, the succinic acid crystals are dried by baking or freeze-drying, and crystals with a purity greater than 99.8% can be obtained after drying.

[0026] The beneficial effects of this invention are as follows:

[0027] (1) In the fermentation process of succinic acid, inorganic salts, mainly inorganic sodium salts, are added. They are easy to precipitate together with succinic acid during crystallization, which affects the purity of succinic acid. The solvent of the present invention can selectively precipitate inorganic salts and other insoluble impurities. The inorganic salts are separated by solid-liquid separation method. The separation and purification method is simple and easy to operate.

[0028] (2) The inventors made an unexpected discovery that mixing the solvent and water in a certain proportion is beneficial to the crystallization of succinic acid, which can significantly shorten the crystallization time and improve the crystallization efficiency.

[0029] (3) During the process of adding solvent to remove inorganic salts, a short time and low temperature are adopted. At the same time, the negative catalyst effect of inorganic sodium salt is utilized to prevent side reactions such as esterification during the desalination process, so as to obtain high-purity succinic acid crystals.

[0030] (4) The inorganic salts separated in this invention can be reused in the fermentation stage, reducing the cost of fermentation and treatment of inorganic salt waste. Detailed Implementation

[0031] The technical solution of the present invention will be further described below with reference to specific embodiments, but this does not limit the present invention. The scope of this application includes the description of the claims and the specification, but is not limited to the implementation schemes in the embodiments.

[0032] Unless otherwise specified, all reagents used in this invention are commercially available products. Sulfuric acid was purchased from Tianjin Kemei Chemical Reagent Co., Ltd.; methanol was purchased from Xilong Chemical Co., Ltd.; ethanol was purchased from Xilong Chemical Co., Ltd.; and activated carbon was purchased from Aladdin.

[0033] Preparation of mixed crystals of succinic acid and sodium sulfate to be separated and purified: The succinic acid fermentation broth was filtered through a filter membrane to remove bacterial cells and insoluble particulate matter, yielding a clear fermentation broth. Activated carbon was added to the clear fermentation broth for decolorization, resulting in a decolorized solution. Under stirring, 85% sulfuric acid (by volume) was slowly added to the decolorized solution to adjust the pH to 2.0. The decolorized solution was concentrated using a rotary evaporator, and the concentrate was cooled overnight at 10°C. Solid-liquid separation was then performed using vacuum filtration to obtain mixed crystals of succinic acid and sodium sulfate.

[0034] Example 1

[0035] Add 20 times the mass of ethanol solution to a mixed crystal of succinic acid and sodium sulfate, stir at 30°C for about 3 hours, centrifuge the mixture at 8000 rpm for 10 minutes, and collect the supernatant and inorganic salt solids separately. Rotary evaporate the supernatant at 30°C to remove some solvent. Add ultrapure water at a water-to-solvent volume ratio of 1:6 to make the succinic acid concentration approximately 360 g / L. Heat and stir at 60°C (stirring speed 350 rpm) until the solution is clear and transparent. Pour the dissolved liquid into a crystallization flask and crystallize at 20°C for 5 hours. After crystallization, separate the succinic acid crystals by vacuum filtration. Freeze-dry the succinic acid crystals to obtain a high-purity product; HPLC determination shows the succinic acid crystal purity to be 99.8%. Add ultrapure water to the inorganic salt solid to prepare a 50 g / L inorganic salt solution, which is then reused in the fermentation process.

[0036] Example 2

[0037] Add acetone solution at 30 times its weight to a mixture of succinic acid and sodium sulfate crystals, stir at 20°C for about 1 hour, centrifuge the mixture at 8000 rpm for 10 minutes, and collect the supernatant and inorganic salt solids separately. Rotary evaporate the supernatant at 35°C to remove some solvent. Add ultrapure water at a water-to-solvent volume ratio of 1:5 to make the succinic acid concentration approximately 380 g / L. Heat and stir at 70°C (stirring speed 250 rpm) until the solution is clear and transparent. Pour the dissolved liquid into a crystallization flask and crystallize at 25°C for 2 hours. After crystallization, separate the succinic acid crystals by vacuum filtration. Freeze-dry the succinic acid crystals to obtain a high-purity product; HPLC determination shows the succinic acid crystal purity to be 99.4%. Add ultrapure water to the inorganic salt solids to prepare a 60 g / L inorganic salt solution, which is then reused in the fermentation process.

[0038] Example 3

[0039] Add 15 times the mass of glycerol solution to a mixture of succinic acid and sodium sulfate crystals, stir at 30°C for about 2 hours, centrifuge the mixture at 8000 rpm for 10 minutes, and collect the supernatant and inorganic salt solids separately. Rotary evaporate the supernatant at 30°C to remove some solvent. Add ultrapure water at a water-to-solvent volume ratio of 1:8 to make the succinic acid concentration approximately 350 g / L. Heat and stir at 60°C (stirring speed 300 rpm) until the solution is clear and transparent. Pour the dissolved liquid into a crystallization flask and crystallize at 10°C for 4 hours. After crystallization, separate the succinic acid crystals by vacuum filtration. Freeze-dry the succinic acid crystals to obtain a high-purity product; HPLC determination shows the succinic acid crystal purity to be 99.5%. Add ultrapure water to the inorganic salt solids to prepare an 80 g / L inorganic salt solution, which is then reused in the fermentation process.

[0040] Example 4

[0041] Add 20 times its weight of acetone and n-butanol (volume ratio 1:1) to a mixed crystal of succinic acid and sodium sulfate, and stir at 23°C for about 1.5 h. Centrifuge the mixture at 8000 rpm for 10 min, and collect the supernatant and inorganic salt solids separately. Rotary evaporate the supernatant at 30°C to remove some solvent. Add ultrapure water at a water-to-solvent volume ratio of 1:4 to make the succinic acid concentration approximately 450 g / L. Heat and stir at 80°C (stirring speed 250 rpm) until the solution is clear and transparent. Pour the dissolved liquid into a crystallization flask and crystallize at 15°C for 3 h. After crystallization, separate the succinic acid crystals by vacuum filtration. Freeze-dry the succinic acid crystals to obtain a high-purity product; HPLC determination shows the succinic acid crystal purity to be 99.7%. Add ultrapure water to the inorganic salt solid to prepare a 100 g / L inorganic salt solution, which is then reused in the fermentation process.

[0042] Example 5

[0043] Add 25 times its mass of n-butanol and glycerol (volume ratio 1:1) to a mixed crystal of succinic acid and sodium sulfate, and stir at 28°C for about 2.5 h. Centrifuge the mixture at 8000 rpm for 10 min, and collect the supernatant and inorganic salt solids separately. Rotary evaporate the supernatant at 50°C to remove some solvent. Add ultrapure water at a water-to-solvent volume ratio of 1:7 to make the succinic acid concentration approximately 300 g / L. Heat and stir at 60°C (stirring speed 300 rpm) until the solution is clear and transparent. Pour the dissolved liquid into a crystallization flask and crystallize at 25°C for 4.5 h. After crystallization, separate the succinic acid crystals by vacuum filtration. Freeze-dry the succinic acid crystals to obtain a high-purity product; HPLC determination shows the succinic acid crystal purity to be 99.2%. Add ultrapure water to the inorganic salt solid to prepare a 10 g / L inorganic salt solution, which is then reused in the fermentation process.

[0044] Example 6

[0045] Add 10 times the mass of ethanol and n-butanol (volume ratio 1:1) to a mixed crystal of succinic acid and sodium sulfate. Stir at 25°C for about 2 hours. Centrifuge the mixture at 8000 rpm for 10 minutes, collecting the supernatant and inorganic salt solids separately. Rotary evaporate the supernatant at 22°C to remove some solvent. Add ultrapure water at a water-to-solvent volume ratio of 1:5 to achieve a succinic acid concentration of approximately 400 g / L. Heat and stir at 75°C (250 rpm) until the solution is clear and transparent. Pour the dissolved liquid into a crystallization flask and crystallize at 5°C for 3.5 hours. After crystallization, separate the succinic acid crystals by vacuum filtration. Freeze-dry the succinic acid crystals to obtain a high-purity product; HPLC analysis showed a purity of 99.5%. Add ultrapure water to the inorganic salt solid to prepare a 30 g / L inorganic salt solution, which is then reused in the fermentation process.

[0046] Example 7

[0047] A mixture of ethanol and n-butanol (volume ratio 1:1) was added to an aqueous solution of succinic acid, wherein the total mass of ethanol and n-butanol was 6 times the mass of water. The solution was heated and stirred at 60°C (stirring speed 250 rpm) until the solution became clear and transparent. The dissolved liquid was poured into a crystallization flask and crystallized at 5°C for 5 hours. After crystallization, the succinic acid crystals were separated by vacuum filtration. The succinic acid crystals were then lyophilized to obtain a high-purity product. HPLC analysis showed that the purity of the succinic acid crystals was 99.3%.

[0048] Comparative Example 1

[0049] Add 20 times the mass of ethanol solution to a mixed crystal of succinic acid and sodium sulfate, stir at 30°C for about 3 hours, centrifuge the mixture at 8000 rpm for 10 minutes, and collect the supernatant and inorganic salt solid separately. Rotary evaporate the supernatant at 30°C to completely remove the solvent, obtaining solid succinic acid. Add ultrapure water to the solid to make the succinic acid concentration approximately 360 g / L, and heat and stir at 60°C until the solution is clear and transparent. Pour the dissolved liquid into a crystallization flask and crystallize at 20°C for 24 hours. After crystallization, separate the succinic acid crystals by vacuum filtration. The succinic acid crystals are then freeze-dried to obtain a high-purity product; HPLC analysis shows the succinic acid crystal purity to be 99.6%. Add ultrapure water to the inorganic salt solid to prepare a 50 g / L inorganic salt solution, which is then reused in the fermentation process.

[0050] Comparative Example 2

[0051] Add 20 times the mass of ethanol solution to a mixed crystal of succinic acid and sodium sulfate, stir at 30°C for about 3 hours, centrifuge the mixture at 8000 rpm for 10 minutes, and collect the supernatant and inorganic salt solids separately. Rotary evaporate the supernatant at 30°C to remove some solvent, making the succinic acid concentration approximately 360 g / L. Heat and stir at 60°C until the solution is clear and transparent. Pour the dissolved liquid into a crystallization flask and crystallize at 20°C for 10 hours. After crystallization, separate the succinic acid crystals by vacuum filtration. Freeze-dry the succinic acid crystals to obtain a high-purity product; HPLC analysis showed the succinic acid crystal purity to be 92.5%. Add ultrapure water to the inorganic salt solid to prepare a 50 g / L inorganic salt solution, which is then reused in the fermentation process.

[0052] Comparative Example 3

[0053] Fermentation broth with a succinic acid content of approximately 85 g / L was filtered through a microfiltration membrane with a pore size of 500 nm to remove bacterial cells and insoluble particulate matter, yielding a clear fermentation broth. Under stirring at 200 rpm, 85% sulfuric acid (by volume) was slowly added to the clear fermentation broth to adjust the pH to 2.0. Activated carbon (by mass / volume) was added to the acidified broth, and the mixture was stirred at 80°C for 3 hours to decolorize, yielding a decolorized solution. The decolorized solution was concentrated using a rotary evaporator at 70°C until the succinic acid content reached 360 g / L. The concentrated solution was then cooled and crystallized at 10°C for 4 hours, and a mixed crystal of succinic acid and sodium sulfate was obtained by vacuum filtration. A 20-fold dilution of aqueous solution was added to the mixed crystals of succinic acid and sodium sulfate, and the solid was collected after low-temperature centrifugation. Four times the dilution of ultrapure water was added to the solid, and the mixture was heated at 60°C to dissolve it. The dissolved liquid was poured into a crystallization flask and crystallized at 20°C for 15 hours. Succinic acid crystals were obtained by vacuum filtration. After freeze-drying, high-purity succinic acid crystals were obtained. The purity of the succinic acid crystals was determined to be 72.3% by HPLC. Ultrapure water was added to the inorganic salt solid to prepare an inorganic salt solution with a concentration of 50 g / L, which was then reused in the fermentation process.

[0054] Comparative Example 4

[0055] Add 20 times the mass of ethanol solution to a mixed crystal of succinic acid and sodium sulfate, stir at 30°C for about 3 hours, centrifuge the mixture at 8000 rpm for 10 minutes, and collect the supernatant and inorganic salt solids separately. Rotary evaporate the supernatant at 30°C to remove some solvent. Add ultrapure water at a water-to-solvent volume ratio of 1:3 to make the succinic acid concentration approximately 360 g / L. Heat and stir at 60°C (stirring speed 350 rpm) until the solution is clear and transparent. Pour the dissolved liquid into a crystallization flask and crystallize at 20°C for 5 hours. After crystallization, separate the succinic acid crystals by vacuum filtration. Freeze-dry the succinic acid crystals to obtain a high-purity product; HPLC determination shows the succinic acid crystal purity to be 93.2%. Add ultrapure water to the inorganic salt solid to prepare a 50 g / L inorganic salt solution, which is then reused in the fermentation process.

[0056] Comparative Example 5

[0057] Add 20 times the mass of ethanol solution to a mixed crystal of succinic acid and sodium sulfate, stir at 30°C for about 3 hours, centrifuge the mixture at 8000 rpm for 10 minutes, and collect the supernatant and inorganic salt solids separately. Rotary evaporate the supernatant at 30°C to remove some solvent. Add ultrapure water at a water-to-solvent volume ratio of 1:10 to make the succinic acid concentration approximately 360 g / L. Heat and stir at 60°C (stirring speed 350 rpm) until the solution is clear and transparent. Pour the dissolved liquid into a crystallization flask and crystallize at 20°C for 5 hours. After crystallization, separate the succinic acid crystals by vacuum filtration. Freeze-dry the succinic acid crystals to obtain a high-purity product; HPLC determination shows the succinic acid crystal purity to be 94.5%. Add ultrapure water to the inorganic salt solid to prepare a 50 g / L inorganic salt solution, which is then reused in the fermentation process.

[0058] Comparative Example 6

[0059] Add 20 times the mass of ethanol solution to a mixed crystal of succinic acid and sodium sulfate, stir at 30°C for about 3 hours, centrifuge the mixture at 8000 rpm for 10 minutes, and collect the supernatant and inorganic salt solid separately. Rotary evaporate the supernatant at 30°C to completely remove the solvent, obtaining solid succinic acid. Add ultrapure water to the solid to make the succinic acid concentration approximately 360 g / L, and heat and stir at 60°C until the solution is clear and transparent. Pour the dissolved liquid into a crystallization flask and crystallize at 20°C for 5 hours. After crystallization, separate the succinic acid crystals by vacuum filtration. The succinic acid crystals are then freeze-dried to obtain pure product. HPLC analysis shows the purity of the succinic acid crystals to be 99.1%. The crystals are irregular in shape, small in size, contain many fragments, and the yield is significantly low. Add ultrapure water to the inorganic salt solid to prepare a 50 g / L inorganic salt solution, which is then reused in the fermentation process.

Claims

1. A method for separating and purifying succinic acid, characterized in that, Includes the following steps: (a) First, add solvent to succinic acid crystals containing inorganic salts and stir to mix well. Remove inorganic salts that are insoluble in the solvent and / or pigments and protein impurities that are difficult to dissolve in the solvent by solid-liquid separation. Then add water to completely dissolve the succinic acid. (b) The succinic acid mixed solution obtained in step (a) is subjected to crystallization separation to obtain succinic acid crystals; In step (a), the solvent is selected from one or a mixture of several of acetone, glycerol, methanol, ethanol or n-butanol; In step (a), the volume ratio of water to solvent added is 1:4 to 1:8; The succinic acid crystals in step (a) are succinic acid crystals obtained during the succinic acid fermentation process.

2. The separation and purification method according to claim 1, characterized in that, In step (a), the volume ratio of water to solvent added is 1:5 to 1:

7.

3. The separation and purification method according to claim 1, characterized in that, In step (a), the concentration of succinic acid is 350-450 g / L, and the mixture is heated and stirred until the succinic acid is completely dissolved.

4. The separation and purification method according to claim 3, characterized in that, In step (a), the concentration of succinic acid is 350–400 g / L.

5. The separation and purification method according to claim 3, characterized in that, The heating and stirring conditions in step (a) are: heating to a temperature of 50-80℃ and stirring speed of 200-400 rpm.

6. The separation and purification method according to claim 1, characterized in that, The inorganic salt in the succinic acid containing inorganic salt is an inorganic sodium salt.

7. The separation and purification method according to claim 6, characterized in that, The inorganic salts mentioned are sodium carbonate and sodium sulfate.

8. The separation and purification method according to claim 1, characterized in that, After adding the solvent, stir at 20-30℃ for 1-3 hours.

9. The separation and purification method according to claim 1, characterized in that, In step (a), the amount of solvent is 10 to 30 times the total mass of succinic acid and the inorganic salt crystals contained in succinic acid.

10. The separation and purification method according to claim 1, characterized in that, The crystallization method is cooling crystallization, with a crystallization temperature of 10-25℃ and a crystallization time of 2-5 hours.