Method for separating succinic acid from fermentation liquor

Abstract

The invention discloses a method for separating succinic acid from fermentation liquor. Adding a flocculating agent and an ethanol solution into the succinic acid fermentation liquor, stirring, and carrying out centrifugal separation to obtain succinic acid fermentation clear liquor; dropwise adding alpha-methylbenzylamine into the succinic acid fermentation clear liquid, wherein succinic acid and alpha-methylbenzylamine form crystals; filtering the obtained crystal; the method comprises the following steps: dissolving alpha-methylbenzylamine in pure water for dissociation, extracting alpha-methylbenzylamine with an extractant, and dissolving succinic acid in water to obtain a succinic acid aqueous solution; carrying out rotary evaporation on the organic phase containing alpha-methylbenzylamine to obtain alpha-methylbenzylamine, and carrying out rotary evaporation on the aqueous solution of succinic acid to obtain succinic acid. The method is simple and mild in preparation process and suitable for large-scale separation and purification of succinic acid.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical engineering, and particularly relates to a method for separating succinic acid and malonic acid. Background Art

[0002] Succinic acid, also known as amber acid, is a key raw material for the production of biodegradable plastics (such as polybutylene succinate, PBS) due to its wide range of applications and huge market potential. PBS has good biodegradability and can be used in fields such as packaging and agricultural films to reduce environmental pollution caused by traditional plastics. It is an important intermediate for the synthesis of chemicals such as 1,4-butanediol (BDO) and tetrahydrofuran (THF), and is widely used in the textile, pharmaceutical, and chemical industries. In the food industry, succinic acid is used as an acidulant and preservative, and is also used in the pharmaceutical field for the synthesis of antibiotics, vitamins, and anticancer drugs.

[0003] At present, the commonly used production methods for preparing succinic acid are as follows: First, chemical synthesis method. The most commonly used is the catalytic hydrogenation method, with maleic anhydride as the raw material and noble metals such as nickel as the catalyst, and succinic acid is produced through a hydrogenation reaction. Second, biological conversion method. In this method, fumaric acid is used as the raw material, and under the catalytic action of fumarate reductase, it can be converted into succinic acid. Third, microbial fermentation method. Microbial fermentation is the conversion of reducing sugars of renewable resources (such as sugarcane or starch) into succinic acid by microorganisms.

[0004] At present, great research results have been achieved in the aspect of preparing succinic acid by fermentation method. However, in the production process, in addition to succinic acid, there will be a large amount of bacteria, proteins, residual sugars, cytochromes, water-soluble inorganic salts, and by-product organic acids. The generation of these impurities gradually hinders the separation and purification of succinic acid. At present, the downstream separation and purification process accounts for more than 60% of the total industrial investment (Song Guangtao. Separation of succinic acid from simulated fermentation broth by nanofiltration membrane and modeling [D]. East China University of Science and Technology, 2018.), which will be the main technical problem in the production of succinic acid and directly determines the yield and purity of succinic acid. At present, the separation and purification of succinic acid mostly use methods such as calcium salt method, ammonium salt method, membrane separation method, and direct crystallization method.

[0005] The calcium salt method (US5168055, CN101665428) is used to extract succinic acid from the succinic acid fermentation broth. The method is to add calcium hydroxide or calcium oxide to obtain calcium succinate. After filtration and washing, pure calcium succinate precipitate can be obtained; treating calcium succinate with concentrated sulfuric acid can separate succinic acid from the by-product calcium sulfate. The solution removing the by-product calcium sulfate can use ion exchange resin to remove impurities, and then concentrate and crystallize succinic acid to obtain succinic acid crystals with a purity of 80-99%. It is very difficult to obtain succinic acid crystals by this method and the yield is relatively low. It is found that the main disadvantage of the calcium salt method is that the content of the by-product calcium sulfate is high, which will increase the input cost of treating the by-product calcium sulfate, and unpleasant odors and impurities of other colors will also be generated during the fermentation process, and industrial production cannot be carried out; another problem is that a large amount of reagents such as calcium hydroxide, calcium oxide and sulfuric acid will be consumed, and recycling or regeneration treatment cannot be carried out during the whole process, which will lead to high additional costs.

[0006] The ammonium salt precipitation method (US5958744) is used to extract succinic acid from the succinic acid fermentation broth. Ammonia water is added to the fermentation broth or during the fermentation process to adjust the pH value of the solution to convert it into diammonium succinate; then sulfuric acid or ammonium bisulfate is added to the reaction tank to lower the pH value to 1.5-1.8, so that diammonium succinate is converted into succinic acid and ammonium sulfate. Finally, the filtrate is obtained by filtration, and it is cooled and crystallized with methanol, and the methanol is recycled after condensation. After high-temperature decomposition, ammonium sulfate is decomposed into ammonium bisulfate and ammonia gas by high-temperature decomposition, and the generated ammonia gas is recycled again, and the process of multiple filtration, reflux and reuse can also be passed through. The advantage of this process is that there are basically no redundant by-products and not many reagents are consumed, so that the acid value and alkali value in the internal circulation system can be maintained. By using the ammonium salt precipitation method, the recovery rate of succinic acid can be as high as 93.3%.

[0007] The membrane separation method (US5143834) is used to extract succinic acid from the fermentation broth. The first step of the desalting electrodialysis process is to use uncharged substances such as residual sugar, weak acid, protein and other substances that cannot pass through the cell membrane, and all charged ions pass through the cell membrane (such as sodium succinate) and are separated from succinic acid. About 23% of succinic acid is lost in this process; in the second step, sodium succinate can be converted into succinic acid and caustic soda by bipolar membrane electrodialysis, and the recovered caustic soda can be used to adjust the pH during the succinic acid fermentation process. After two-step electrodialysis, the yield of succinic acid is 60%. The disadvantages of electrodialysis are large losses, low cost of membrane materials and low selectivity for succinic acid. There is also another biggest problem, which is that the electrodialysis membrane cannot solve the problem of treating binary ions. Summary of the Invention

[0008] The object of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing high-purity succinic acid.

[0009] The technical solution of the present invention is as follows:

[0010] The present invention provides a method for separating succinic acid from a fermentation broth, which comprises the following steps:

[0011] 1) In the succinic acid fermentation broth, a flocculant and an ethanol solution are added, stirred, and centrifuged to obtain a clear succinic acid fermentation broth;

[0012] 2) α-Methylbenzylamine is added dropwise to the clear succinic acid fermentation broth, and succinic acid and α-methylbenzylamine form crystals;

[0013] 3) The obtained crystals are filtered; dissolved in pure water for dissociation, and then α-methylbenzylamine is extracted with an extractant, and succinic acid is dissolved in water to obtain an aqueous succinic acid solution;

[0014] 4) The organic phase containing α-methylbenzylamine is rotary evaporated to obtain α-methylbenzylamine, and the aqueous solution of succinic acid is rotary evaporated to obtain succinic acid.

[0015] According to the preferred embodiment of the present invention, in step 1), the flocculant is polyacrylamide, and the flocculant is used to remove substances such as bacteria in the fermentation broth. The addition amount of polyacrylamide in the succinic acid fermentation broth is 0.1-100 ppm (0.1-100 mg / L fermentation broth). Preferably, in the ethanol solution, the volume percentage of ethanol is 10%-30%; when the volume of the ethanol solution is converted into the added volume of pure ethanol, the volume percentage of the added volume of pure ethanol compared to the volume of the succinic acid fermentation broth is 0.01%-1%. Excessive ethanol will not be able to obtain the required crystals. Preferably, in step 1), the stirring time is 1-3 h, and the stirring temperature is 20-30 °C.

[0016] According to the preferred embodiment of the present invention, in step 2), the molar amount of α-methylbenzylamine is 1-2 times the mass amount of succinic acid in the clear succinic acid fermentation broth; after the addition of α-methylbenzylamine is completed, it is maintained at 20-30 °C for 24-48 h to form crystals.

[0017] According to the preferred embodiment of the present invention, in step 3), the dissociation is carried out at 50-60 °C, and the dissociation time is 2-4 h. The amount of pure water used is not critical, and its amount can make the crystals completely dissolve. Preferably, the amount of pure water can be reduced to reduce the energy consumption of subsequent rotary evaporation under the condition of complete dissolution. Preferably, in step 3), the extractant is n-hexane, cyclohexane or toluene.

[0018] According to the preferred embodiment of the present invention, the α-methylbenzylamine obtained in step 4) is recycled to step 2) to realize the recycling of α-methylbenzylamine.

[0019] According to a preferred embodiment of the present invention, the concentration of succinic acid in the succinic acid fermentation broth is 10 - 100 g / L, preferably 50 - 100 g / L.

[0020] Compared with the prior art, the present invention discovers that α-methylbenzylamine can form a salt solvate with succinic acid in an ethanol-water solvent and precipitate. This selectively formed salt solvate has 100% selectivity and is easily dissociated in pure water. Therefore, it is very suitable for the purification and separation of succinic acid. After dissociation, the mixture can be separated into α-methylbenzylamine and succinic acid by extraction, and the α-methylbenzylamine in the organic phase is easy to recover and recycle. The present invention has no requirement for the configuration of α-methylbenzylamine. The preparation process of this method is simple and mild, and is suitable for large-scale separation and purification of succinic acid. Description of the Drawings

[0021] Figure 1 It is the infrared spectrum of succinic acid-α-methylbenzylamine ethanol solvate;

[0022] Figure 2 It is the powder X-ray diffraction pattern of succinic acid-α-methylbenzylamine ethanol solvate. Detailed Embodiments

[0023] The following examples provide to those of ordinary skill in the art how to make and evaluate the present invention. The examples are merely illustrative of the present disclosure and do not delimit the scope of limitation. Although efforts have been made to ensure the accuracy of numerical values (e.g., amounts, temperatures, etc.), some errors and deviations should be considered. Unless otherwise stated, the temperature is in °C or at ambient temperature, and the pressure is at or near atmospheric pressure.

[0024] The preparation method described for the disclosed compounds of the present invention in this embodiment is one of many methods. There are many other methods for the preparation of the disclosed compounds of the present invention, and the scope of the present application is not delimited. Therefore, those skilled in the art of the present disclosure can easily modify the described method or use different methods to prepare one or more of the disclosed compounds. The following methods are merely exemplary, and the temperature, concentration, reactant composition, and other process conditions can be changed. For the desired compounds, those skilled in the art of the present disclosure can easily select suitable reactants and conditions for preparation.

[0025] In view of the characteristics that the succinic acid fermentation broth contains a certain concentration of succinic acid, bacteria, residual fermentation medium and by-products, the method proposed by the present invention includes steps such as removing bacteria and forming and dissociating the α-methylbenzylamine ethanol solvate of succinic acid. Since the solvate has 100% selectivity for succinic acid, the method of the present invention can be applied to succinic acid microbial fermentation broth from any source, so the present invention does not make specific limitations on the succinic acid fermentation broth. The succinic acid fermentation has been industrially applied, and its fermentation process and the obtained fermentation broth are well-known in the art. In the art, the succinic acid microbial fermentation broth mostly directly uses glucose as a raw material, or can also use the hydrolysate obtained after processing cheap renewable cellulose resources such as straw, corncob, and bagasse as a raw material. The fermentation strain can be a natural succinic acid-producing strain, such as Actinobacillus, Anaerobiospirillum, Mannheimia, or can also be an engineered strain (mainly Escherichia coli and yeast) modified through the metabolic process; the obtained fermentation broth contains a certain concentration of succinic acid. According to existing research reports, the succinic acid concentration in the fermentation broth generally reaches 50-100 g / L. Through fed-batch fermentation, continuous fermentation and other process optimizations, the succinic acid concentration in some fermentation broths can be further increased.

[0026] The same succinic acid fermentation broth was used in the following examples of the present invention. The succinic acid fermentation broth was obtained by the following process: Take out Actinobacillus succinogenes, ATCC55618 (purchased from Shanghai Rechu Biotechnology Co., Ltd.) stored at -80°C, and anaerobically culture it at 38°C for 12 h to obtain a seed solution. Fermentation in a 50 L fermenter: 105 g.L -1 of the bagasse primary sugar solution, add inorganic salts, sterilize at 120°C for 60 min, inoculate 5% (v / v) of the seed solution, at 37°C, the rotation speed of the fermenter is 150 r.min-1, control the pH to be about 6.0, and anaerobically ferment for 24 h to obtain the succinic acid fermentation broth.

[0027] Example 1

[0028] 1) Add 30 L of succinic acid fermentation broth (containing 50 g / L of succinic acid), 1 g of flocculant polyacrylamide, and 0.5 L of 10% (V / V) ethanol. Stir at 20 °C for 1 hour and then perform centrifugal separation to obtain the filtrate, the succinic acid fermentation clear broth. Slowly add dropwise 1500 g of α-methylbenzylamine and maintain at 20 °C for 24 hours. Succinic acid and α-methylbenzylamine form crystals (succinic acid-α-methylbenzylamine ethanol solvate); filter the obtained crystals to get 2950 g; dissolve them in 10 L of pure water and dissociate at 50 °C for 2 hours. Extract α-methylbenzylamine with 1 L of n-hexane. Succinic acid dissolves in water to obtain an aqueous solution of succinic acid; rotary evaporate the organic solution of α-methylbenzylamine to obtain 1480 g of α-methylbenzylamine for recycling, and rotary evaporate the aqueous solution of succinic acid to obtain 1220 g of succinic acid. Analyze the content by liquid chromatography. The test result shows that the content of succinic acid is 99.1%. Liquid chromatography analysis conditions: chromatographic column: Agilent liquid chromatography column ZORBAX SB-Aq, 4.6 mm × 250 mm, 5 μm, mobile phase: phosphoric acid aqueous solution with pH 2.5, column temperature: 40 °C, flow rate: 1.2 mL / min, detection wavelength of ultraviolet detector: 210 nm, injection volume: 5 μL, detection time: 25 min.

[0029] Figure 1 The infrared spectrum of succinic acid-α-methylbenzylamine ethanol solvate obtained during the process of the example is shown as follows; Figure 2 The powder X-ray diffraction pattern of succinic acid-α-methylbenzylamine ethanol solvate; the single crystal data is shown in Table 1, triclinic system, α = 81.2390(10)°, β = 89.8800(10)°, γ = 78.0470(10)°

[0030] Table 1 Single crystal data of succinic acid-α-methylbenzylamine ethanol solvate

[0031]

[0032] Example 2

[0033] Add 30 L of succinic acid fermentation broth (containing 50 g / L of succinic acid), 1 g of flocculant polyacrylamide, and 1 L of 30% ethanol. Stir at 30 °C for 3 hours and then perform centrifugal separation to obtain the filtrate, the succinic acid fermentation clear broth; slowly add dropwise 1500 g of α-methylbenzylamine and maintain at 30 °C for 48 hours. Succinic acid and α-methylbenzylamine form crystals; filter the obtained crystals to get 2900 g; dissolve them in 10 L of pure water and dissociate at 60 °C for 4 hours. Extract α-methylbenzylamine with 1 L of cyclohexane. Succinic acid dissolves in water to obtain an aqueous solution of succinic acid; rotary evaporate the organic solution of α-methylbenzylamine to obtain 1480 g of α-methylbenzylamine, and rotary evaporate the aqueous solution of succinic acid to obtain 1185 g of succinic acid. The content of succinic acid is 98.9%.

[0034] Example 3

[0035] Add 30 L of succinic acid fermentation broth (containing 50 g / L of succinic acid), 1 g of flocculant polyacrylamide, and 0.80 L of 20% ethanol, stir at 25°C for 2 hours, and perform centrifugal separation to obtain the filtrate, succinic acid fermentation clear broth. Slowly add dropwise 1600 g of α-methylbenzylamine, maintain at 25°C for 36 hours, and succinic acid and α-methylbenzylamine form crystals; filter the obtained crystals to obtain 3520 g; dissolve in 10 L of pure water, dissociate at 55°C for 3 hours, extract α-methylbenzylamine with 1 L of toluene, and succinic acid dissolves in water to obtain an aqueous solution of succinic acid; rotary evaporate the organic solution of α-methylbenzylamine to obtain 1565 g of α-methylbenzylamine, and rotary evaporate the aqueous solution of succinic acid to obtain 1450 g of succinic acid, and the succinic acid content is 99.0%.

[0036] Example 4

[0037] Take 30 L of succinic acid fermentation broth (containing 50 g / L of succinic acid), add 1 g of flocculant polyacrylamide, and 0.5 L of 10 (V / V)% ethanol, stir at 20°C for 1 hour, and perform centrifugal separation to obtain the filtrate, succinic acid fermentation clear broth. Slowly add dropwise 1500 g of aniline, maintain at 20°C for 24 hours, and no crystals precipitate.

[0038] Example 5

[0039] Take 30 L of succinic acid fermentation broth (containing 50 g / L of succinic acid), add 1 g of flocculant polyacrylamide, and 0.5 L of 10 (V / V)% methanol, stir at 20°C for 1 hour, and perform centrifugal separation to obtain the filtrate, succinic acid fermentation clear broth. Slowly add dropwise 1500 g of α-methylbenzylamine, maintain at 20°C for 24 hours, and no crystals precipitate.

[0040] Example 6

[0041] Take 30 L of succinic acid fermentation broth (containing 50 g / L of succinic acid), add 1 g of flocculant polyacrylamide, and 5 L of 10 (V / V)% ethanol, stir at 20°C for 1 hour, and perform centrifugal separation to obtain the filtrate, succinic acid fermentation clear broth. Slowly add dropwise 1500 g of α-methylbenzylamine, maintain at 20°C for 24 hours, and no crystals precipitate. Raise the temperature, recover 0.45 L of ethanol, cool down, maintain at 20°C for 24 hours, and crystals precipitate. Filter the obtained crystals to obtain 2800 g; dissolve in 10 L of pure water, dissociate at 50°C for 2 hours, extract α-methylbenzylamine with 1 L of n-hexane, and succinic acid dissolves in water to obtain an aqueous solution of succinic acid; rotary evaporate the organic solution of α-methylbenzylamine to obtain 1350 g of α-methylbenzylamine for recycling, and rotary evaporate the aqueous solution of succinic acid to obtain 1105 g of succinic acid, and the succinic acid content is 99.3%.

[0042] The above-described embodiments merely represent several implementation manners of the present invention. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent for the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the appended claims.

Claims

1. A method for separating succinic acid from a fermentation broth, characterized in that, It includes the following steps: 1) Add a flocculant and an ethanol solution to the succinic acid fermentation broth, stir, and perform centrifugal separation to obtain a clear succinic acid fermentation broth; 2) Drop α-methylbenzylamine into the clear succinic acid fermentation broth, and succinic acid and α-methylbenzylamine form crystals; 3) Filter the obtained crystals; dissolve them in pure water for dissociation, and then extract α-methylbenzylamine with an extractant, and succinic acid dissolves in water to obtain an aqueous succinic acid solution; 4) Rotate-evaporate the organic phase containing α-methylbenzylamine to obtain α-methylbenzylamine, and rotate-evaporate the aqueous solution of succinic acid to obtain succinic acid.

2. The method according to claim 1, wherein In step 1), the flocculant is polyacrylamide, and the addition amount of polyacrylamide in the succinic acid fermentation broth is 0.1-100 ppm.

3. The method according to claim 1, characterized in that, In step 1), in the ethanol solution, the volume percentage of ethanol is 10% to 30%; based on the volume of the added ethanol, the volume usage percentage of ethanol compared to the volume of the succinic acid fermentation broth is 0.01%-1%.

4. The method according to claim 1, wherein In step 1), the stirring time is 1-3 h, and the stirring temperature is 20-30 °C.

5. The method according to claim 1, characterized in that In step 2), the mass ratio of α-methylbenzylamine to succinic acid in the clear succinic acid fermentation broth is 1-2:1; after the addition of α-methylbenzylamine is completed, it is kept at 20-30 °C for 24-48 h to form crystals.

6. The method according to claim 1, wherein In step 3), the dissociation is carried out at 50-60 °C, and the dissociation time is 2-4 h.

7. The method according to claim 1, wherein In step 3), the extractant is n-hexane, cyclohexane or toluene.

8. The method according to claim 1, characterized in that, The α-methylbenzylamine obtained in step 4) is recycled to step 2) to realize the recycling of α-methylbenzylamine.

9. The method according to claim 1, wherein In the succinic acid fermentation broth, the concentration of succinic acid is 10-100 g / L.

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