Method for separating and extracting succinic acid

Abstract

The invention relates to a method for efficiently separating and extracting succinic acid. Specifically, the invention provides a method for separating and extracting succinic acid from a sample solution containing succinic acid, which comprises the following steps: carrying out chromatographic treatment on the sample solution to obtain a succinic acid chromatographic clear solution; the succinic acid chromatographic clear liquid is subjected to steam stripping treatment, the gas-liquid ratio of steam stripping treatment is 1: (10-20), and the temperature ranges from 160 DEG C to 200 DEG C.

Description

Technical Field

[0001] The invention belongs to the field of preparation and purification of succinic acid, and relates to a method for separating and extracting succinic acid, and in particular to a method for separating and extracting polymerization-grade succinic acid from succinic acid mother liquor by utilizing chromatography and steam stripping technology. Background Art

[0002] Succinic acid, also known as succinic acid, is an important "C4 platform compound". As an important organic chemical raw material and intermediate, it is widely used in synthetic plastics, food, medicine, agriculture and other fields. Among them, the main application of succinic acid in the field of synthetic plastics is the synthesis of degradable plastics such as PBS, PBST and PBSA. In recent years, with the increasingly stringent environmental supervision, the demand for degradable plastics has continued to increase, especially PBS materials, which have become the largest biodegradable materials in the world due to their safety, non-toxicity, biocompatibility and absorbability. With the improvement of PBS industrialization technology and the continuous expansion of demand for fully biodegradable plastics at home and abroad, as well as the continuous development of new application fields of succinic acid, the market prospects of succinic acid in the future are very broad, and it has been listed by the US Department of Energy as one of the 12 most valuable platform compounds in the future.

[0003] At present, the production of succinic acid mainly uses butane as raw material and is chemically synthesized through catalytic hydrogenation and other steps. This traditional production process relies on fossil fuels. Although the yield is high and the process is mature, there are problems such as the cost being greatly affected by the fluctuation of crude oil prices, the unsustainability of resources and environmental pollution. Under the dual pressure of the oil crisis and environmental pollution, the production of succinic acid by microbial fermentation has become a hot topic of research at home and abroad in recent years because of its utilization of renewable resources, environmental protection and high efficiency. There are many studies on the production of succinic acid by microbial fermentation in the prior art, such as CN118086168A, US5958744 (1999), etc.

[0004] However, in the microbial fermentation method, various impurities such as pigments, proteins, salts, and malic acid and pyruvic acid similar to the structure of succinic acid exist in the succinic acid fermentation broth. The conventional and effective purification method is to obtain crystalline succinic acid by concentration and crystallization. However, the solubility of succinic acid is relatively high, and part of succinic acid still exists in the form of salt, which has a higher solubility. As a result, most of the succinic acid remains in the mother liquor during the cooling and crystallization separation. In order to improve the product yield, the succinic acid in the mother liquor is usually further recovered by secondary concentration and crystallization of the mother liquor, but the recovery rate of this method is still not high, and the recovered crude succinic acid is rich in impurities. Too much, can not meet the quality requirements of polymerization-grade succinic acid products (purity above 99.7%). If it is used for downstream polyester polyol synthesis, it will cause yellowing of the product (yellowing of the product is caused by a variety of reasons, mainly organic yellowing and inorganic yellowing. The reason for organic yellowing is that the product contains some impurities that are easily oxidized and discolored (such as aldehydes, ketones and other unsaturated structures). Impurities with a weight ratio of one part per million (PPM level) will cause the product to turn yellow to varying degrees. The higher the residue, the more serious the yellowing. Inorganic yellowing is mainly caused by metals. For example, non-ferrous metals such as iron can also cause yellowing of the product under oxygen and other conditions). Based on this, patent CN117902974A discloses a method for effectively recovering succinic acid from succinic acid mother liquor by continuous chromatography, wherein the purity of the recovered succinic acid is about 97% and the yield is about 82%. It can be seen that although the recovery method greatly improves the purity and yield of succinic acid, the polymer-grade succinic acid product requires a purity of more than 99.7% and an ash content of less than 0.025%, and its product quality still cannot meet the polymer-grade requirements. Therefore, it is necessary to develop a more efficient succinic acid extraction process to obtain a succinic acid product that meets the polymer-grade quality requirements. Summary of the invention

[0005] As can be seen from the above, in the prior art, the conventional and effective means of purifying succinic acid is to obtain crystalline succinic acid by concentration and crystallization. Because the solubility of succinic acid is relatively high, and the succinic acid part still exists in the form of salt (higher solubility), most of the products remain in the mother liquor during the cooling and crystallization separation. Generally, in order to improve the product yield, the mother liquor will be concentrated and crystallized twice, but the recovery rate of this method is still not high, and the recovered succinic acid crude product is rich in impurities, which cannot meet the quality requirements of polymerization-grade products. It will cause the product to turn yellow when used in downstream polyester polyol synthesis. Although the chromatographic technology disclosed in the prior art, such as patent CN117902974A, can effectively remove impurities such as malic acid, soluble protein, inorganic salts, pigments, etc., the purity and ash content of succinic acid obtained by this method cannot meet the requirements of polymerization grade, and the yield of succinic acid needs to be improved.

[0006] Therefore, the technical problem to be solved by the present invention is to provide an improved method, which combines chromatographic technology to effectively remove most of the pigments, proteins and various salts contained in the mother liquor, and can also remove impurities such as malic acid and pyruvic acid that affect the purification of succinic acid and are similar in structure to succinic acid, and then the chromatographic clear liquid is stripped to significantly remove trace impurity components in the product to prevent affecting the hydrogenation reaction of downstream customers. This process technology greatly improves the recovery rate of succinic acid, the highest recovery rate can reach 100% recovery, and the recovered succinic acid is of high quality and can meet the standards of polymerization grade.

[0007] Specifically, based on boiling point differences and concentration polarization, the present application further removes trace impurities remaining in the succinic acid chromatographic clear liquid through gas stripping technology and recovers succinic acid. The highest recovery rate can reach 100%, the purity of succinic acid can reach more than 99.9%, and the ignition residue (ash content) is far less than 0.025%. The product is white in color and of high quality, meeting polymerization grade standards.

[0008] The core improvement of the present invention is to perform stripping treatment on the chromatographic clear liquid of succinic acid to improve the recovery rate and purity of succinic acid, wherein the condition parameters of the stripping treatment are: gas-liquid ratio (1:10-20), temperature (160-200°C), time (1-3min), and normal pressure.

[0009] The method of the present invention comprises the following steps:

[0010] First, the succinic acid fermentation broth is extracted and separated by conventional techniques (impurity removal, cooling crystallization, centrifugation) to obtain succinic acid; however, as mentioned above, due to the high solubility of succinic acid, although a portion of succinic acid crystals can be obtained during cooling crystallization separation, most of the succinic acid remains in the remaining fermentation broth (also known as succinic acid mother liquor, which corresponds to Figure 1 The content of succinic acid in the centrifuged mother liquor can reach more than 100 g / L.

[0011] In order to separate the succinic acid dissolved in the succinic acid mother liquor from the succinic acid mother liquor, the succinic acid mother liquor is purified by chromatography, specifically as follows: the succinic acid mother liquor is acidified, heated (or heated first and then acidified), filtered and impurities are removed to obtain a filtered clear liquid, the filtered clear liquid is chromatographed (which can remove most of the pigments, proteins and various salts contained in the mother liquor, as well as organic impurities such as malic acid and pyruvic acid that are similar in structure to succinic acid), and the eluent containing succinic acid and trace impurities is collected, which is the chromatographic clear liquid; wherein the chromatographic column filler is a uniform-particle gel cationic chromatographic resin, preferably LX-1850 resin (resin particle size 280-320 μm, purchased from Xi'an Lanxiao Technology New Materials Co., Ltd.).

[0012] Regarding the treatment of the chromatographic clear liquid, the present invention has made improvements over the prior art. Based on the boiling point difference and concentration polarization between succinic acid and impurity components, the chromatographic clear liquid is subjected to a stripping treatment to further remove the trace impurity components remaining in the chromatographic clear liquid and recover succinic acid. The maximum recovery rate can reach 100%, the purity of succinic acid can reach more than 99.9%, and the ignition residue (ash content) is far less than 0.025%. The product is white in color and of high quality, reaching the polymerization grade standard. The method for treating the chromatographic clear liquid includes the following steps:

[0013] 1. Decolorizing the chromatographic clear liquid, wherein the decolorization may include resin decolorization, carbon fiber decolorization, chemical decolorization or activated carbon decolorization; preferably activated carbon decolorization.

[0014] The operation of activated carbon decolorization is as follows: the chromatographic clear liquid is pumped into a decolorization tank through a material pump, and activated carbon is added for decolorization, the amount of activated carbon added is controlled to be at least 0.5%, for example, 0.5-2.0%, preferably 0.5-1.5%, and more preferably 0.5-1.0% (mass volume ratio, i.e., the number of grams of activated carbon added per liter of chromatographic clear liquid), the decolorization temperature is controlled at 60-80°C, the decolorization time is controlled at 0.5-1.0h, and stirring is maintained at 20-30Hz throughout the process to obtain a decolorized clear liquid.

[0015] Among them, the transmittance of the original succinic acid mother liquor is 5-10%, and the color is dark yellow; after chromatographic treatment, the transmittance of the chromatographic clear liquid is increased to 50-70%, and the color is light yellow. After decolorization treatment, the transmittance is increased to 95-99%, and the color is clear.

[0016] 2. Add the decolorized clear liquid to a concentration and crystallization tank for concentration and water removal. The concentration treatment is preferably evaporation concentration. The parameters of the concentration and crystallization are 60-80°C, vacuum degree -0.085-0.095MPa, and stirring speed 25Hz.

[0017] After the concentration and water removal is completed, the concentrated liquid is added to the supergravity bed stripping device for stripping and impurity removal operation, the gas-liquid ratio is 1: (10-20), the stripping steam temperature is controlled at 160-200°C, and the stripping time is 1-3min. After stripping and impurity removal, the temperature is slowly lowered and crystallized, and the temperature is stirred and lowered to 10-20°C, maintained for 2-3h to grow crystals. After the growth of crystals, centrifugation is performed to obtain succinic acid crystals.

[0018] Among them, the stripping principle is based on the boiling point difference and concentration polarization between succinic acid and residual impurities in the decolorized clear liquid. Through the gas-liquid ratio and temperature optimization design of the stripping, trace impurities such as calcium ions, sodium ions, magnesium ions, zinc ions, manganese ions, etc., or trace impurities that affect downstream polymerization, such as saturated aldehydes, ketones and other pigments, can be effectively removed. For example, with regard to the gas-liquid ratio, a too low gas-liquid ratio will lead to low efficiency in removing trace impurities, which will in turn lead to low product purity and fail to meet the polymerization grade product purity; while a too high gas-liquid ratio will also take away succinic acid while removing trace impurities, resulting in more succinic acid losses and low product recovery. The present application has carried out a series of optimizations on the gas-liquid ratio, so that it can ensure both product purity and product recovery rate (not less than 85%).

[0019] In a specific embodiment of the present invention, during the stripping process, the gas-liquid ratio is 1:(10-20), for example, 1:(12-18), 1:(10-18), 1:(12-15) or 1:(12-20), or 1:12, 1:15, 1:18 or 1:20; the temperature is 160-200°C, for example, 160-180°C, 160-190°C, 170-190°C, 170-180°C.

[0020] In this article, the stripping technology refers to the process of directly contacting the above-mentioned concentrated liquid with water vapor, so that the impurities in the concentrated liquid are diffused into the gas phase in a certain proportion, thereby achieving the purpose of removing impurities. In addition, since the present invention is to prepare polymerization-grade succinic acid, the purity of the stripping steam is required to be relatively high, and the steam used for stripping must be prepared from pure water.

[0021] The stripping technology is operated by conventional devices in the prior art, such as a supergravity bed stripping device.

[0022] 3. Then, the crude succinic acid obtained by centrifugation is subjected to slurry washing to wash away impurities on the surface of the crystal or in the shallow layer of the crystal surface. The specific operation is as follows: the crude succinic acid is added into the slurry washing tank, and pure water is added for slurry washing to obtain crystal slurry, wherein the amount of water added for slurry washing is 70-100% of the mass of the crystal, and the slurry washing time is controlled at 1-2h.

[0023] 4. After the pulp washing is completed, the crystal pulp is subjected to secondary centrifugation to obtain centrifuged fine succinic acid, which is then dried by air flow drying to obtain the dried finished succinic acid. The single recovery rate of the entire process exceeds 90%, the product purity is ≥99.7%, the ash content is ≤0.025%, and the color is white.

[0024] Specifically, the present invention provides the following technical solutions:

[0025] 1. A method for separating and extracting succinic acid from a sample solution containing succinic acid, comprising subjecting the sample solution to chromatographic treatment to obtain a succinic acid chromatographic clear solution; subjecting the succinic acid chromatographic clear solution to steam stripping treatment, wherein the steam stripping treatment has a gas-liquid ratio of 1:(10-20) and a temperature of 160-200°C;

[0026] Preferably, the stripping treatment time is 1-3 min.

[0027] 2. The method according to item 1, wherein the sample solution is succinic acid mother liquor or succinic acid fermentation broth;

[0028] Preferably, the succinic acid content in the sample solution is 110-140 g / L;

[0029] Preferably, when the sample liquid is succinic acid fermentation liquid, the method further includes a sample liquid pretreatment step including a filtration step.

[0030] 3. The method according to item 2, wherein the chromatographic column filler used in the chromatographic treatment is a uniform particle gel cationic chromatographic resin, preferably LX-1850.

[0031] 4. The method according to item 3, wherein the sample solution is pretreated as follows before the chromatographic treatment:

[0032] Adjust the pH of the sample solution to 1.0-3.0, and heat and filter the acidified sample solution;

[0033] Preferably, the heating temperature is 80-90°C.

[0034] 5. The method according to item 1 or 2, wherein before the stripping treatment, the method further comprises decolorizing the succinic acid chromatographic clear liquid.

[0035] 6. The method according to item 5, wherein activated carbon is added to the succinic acid chromatographic clear solution for decolorization;

[0036] Preferably, the added amount of the activated carbon is at least 0.5%, preferably 0.5-2.0%, more preferably 0.5-1.5%.

[0037] 7. The method according to item 5, wherein the decolorization treatment is carried out at a temperature of 60-70°C and for a time of 20-60 minutes.

[0038] 8. The method according to any one of items 5 to 7, further comprising concentrating the decolorized clear liquid and then stripping the obtained concentrated liquid.

[0039] 9. The method according to item 1 or 2, wherein after the stripping treatment, it further comprises cooling crystallization and centrifugation to obtain succinic acid crystals;

[0040] Optionally, the temperature reduction crystallization treatment comprises reducing the temperature to 10-30° C. and maintaining it for at least 1.5 hours.

[0041] 10. The method according to item 9 further comprises pulp washing and centrifuging the succinic acid crystals to obtain fine succinic acid.

[0042] Beneficial Effects

[0043] Existing steam stripping technology is mostly used for separation and purification of chemical feed liquids. The chemical feed liquid has a simple composition, and the relevant steam stripping conditions are easy to explore and control. However, the fermentation feed liquid has a complex composition and contains impurities such as malic acid and pyruvic acid that are similar in structure to succinic acid. Therefore, during separation and purification, it is necessary to consider both the separation and purification effect and the succinic acid yield, and it is difficult to explore the industrial process conditions. The present invention is based on boiling point differences and concentration polarization, and uses steam stripping technology. After a large number of experiments, it is obtained that the trace impurities remaining in the succinic acid chromatographic clear liquid can be effectively removed and succinic acid can be recovered, thereby obtaining a separation and extraction process for polymerization-grade succinic acid products. Specifically:

[0044] This method is based on chromatographic technology and can effectively remove most of the pigments, proteins and various salts contained in the mother liquor. It can also remove impurities such as malic acid and pyruvic acid that affect the purification of succinic acid and have a similar structure to succinic acid. By adopting a stripping process and optimizing the design of its process conditions, the trace impurities remaining in the product are greatly removed, reducing the impact of easily discolored impurities on the product color, and the impact of residual metal impurities on downstream customers' hydrogenation reactions such as polyester polyol synthesis. The quality of the finished succinic acid product is high and can meet the standards of polymerization grade. At the same time, the recovery rate of the diacid is greatly improved (the recovery rate is greater than 85%), and the maximum recovery rate can reach 100%, which is suitable for industrial preparation or separation and purification of polymerization-grade succinic acid products. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 The operation flow of the method of Example 1 of the present invention is shown;

[0046] Figure 2 The actual pictures of the finished succinic acid products of Example 1 and Comparative Example 3 are shown. DETAILED DESCRIPTION

[0047] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0048] The methods used in the following examples are conventional methods unless otherwise specified, and the reagents used are commercially available reagents unless otherwise specified.

[0049] In the following examples, the residual amount of inorganic impurities in the finished succinic acid product is detected by ignition residue (ignition residue is also called ash content, which is usually used to determine the inorganic impurities contained in organic drugs, such as metal oxides or salts); the detection steps are as follows:

[0050] Take a specified amount of the sample, place it in a crucible that has been ignited to constant weight, and weigh it accurately. Slowly ignite it on an electric furnace until it is carbonized, then cool it to room temperature. Add 0.5-1ml of sulfuric acid to moisten it, and heat it at low temperature to remove sulfuric acid vapor. Place the crucible in a high-temperature electric furnace and ignite it at 700-800℃ to constant weight. Calculate the percentage of ignition residue based on the amount of residue left and the amount of the sample.

[0051] Inorganic impurities are mainly heavy metal residues. A high content of these impurities will lead to the deactivation of the catalyst (modified precious metal catalyst) and affect the subsequent polymerization effect. Therefore, the lower the content of the ignition residue, the more suitable it is for downstream polyester polyol synthesis.

[0052] In the following embodiments, the salt removal rate is calculated as follows: Chromatographic salt removal rate calculation formula:

[0053] Salt removal rate = 1-(chromatographic clear liquid volume × chromatographic clear liquid conductivity - chromatographic clear liquid volume × chromatographic clear liquid succinic acid blank conductivity) ÷ (chromatographic clear liquid volume × chromatographic clear liquid conductivity + chromatographic residual liquid volume × chromatographic residual liquid conductivity). Among them, the chromatographic clear liquid succinic acid blank conductivity is defined as the conductivity of succinic acid in pure water, where the succinic acid concentration is consistent with the chromatographic clear liquid succinic acid concentration.

[0054] Note: The calculation method in the prior application CN117902974A is as follows: desalination rate = 1-(amount of extract × conductivity of extract) ÷ (amount of extract × conductivity of extract + amount of raffinate × conductivity of raffinate).

[0055] This detection method differs from the present application in that the contribution of succinic acid to the conductivity of the extract is not deducted.

[0056] The treatment object is a chromatographic clear solution, which is a succinic acid mother solution (corresponding to Figure 1 The mother liquor from the centrifuge is acidified, heated, filtered, and the filtrate is purified by chromatography.

[0057] Among them, the succinic acid content in the succinic acid mother liquor is 110-140g / L, the malic acid content is 1-5g / L, and it also contains 10-25g / L of inorganic salts. The pH of the succinic acid mother liquor is between 3.2-3.8; the main components of the inorganic salts in the succinic acid mother liquor are sodium sulfate, sodium phosphate, potassium sulfate, potassium phosphate, magnesium sulfate, etc.

[0058] The mother liquor of succinic acid is acidified, and concentrated sulfuric acid is added to the mother liquor tank with stirring through a pipeline flow method to adjust the pH value of the mother liquor to 1.0-3.0; after the acid adjustment is completed, the temperature is indirectly raised to 80-90°C through the jacket steam and maintained for about 1 hour; the insoluble matter in the mother liquor is filtered through a filter, including the insoluble protein precipitated during the acid adjustment process, and the filtered clear liquid is temporarily stored in the chromatographic stock liquid tank. After the chromatographic debugging is completed, the relevant valves and material pumps of the chromatographic stock liquid are opened, and the raw materials are pumped into the chromatographic device according to the process requirements, and the water-to-material ratio is controlled to be 2.0-3.5:1, and the clear residual liquid ratio is 0.6-0.8:1, and the corresponding chromatographic residual liquid and chromatographic clear liquid with qualified indicators are finally obtained. In this process, the protein removal rate is as high as more than 95%, the salt removal rate is about 97%, the pigment removal rate is more than 75%, and the removal rate of by-product impurities such as malic acid is greater than 99%.

[0059] The succinic acid mother liquor in the following embodiment is the fermentation liquor remaining after succinic acid is extracted and separated from the succinic acid fermentation liquor by conventional techniques (impurity removal, cooling crystallization, centrifugation) in the prior art. Specifically, the succinic acid fermentation liquor is first filtered through a ceramic membrane to remove macromolecular particles such as bacterial protein in the system, and then filtered and purified through an ultrafiltration membrane (molecular weight cutoff: 1000), and then decolorized, concentrated, and cooled and crystallized by activated carbon, and then centrifuged to separate the remaining fermentation liquor after succinic acid crystallization; the succinic acid content in the succinic acid mother liquor is 130 g / L, the malic acid content is 4 g / L, the inorganic salt content is 21 g / L, and the pH of the succinic acid mother liquor is 3.5.

[0060] The following water-to-material ratio is the volume ratio of pure water to the sample material; the following clear liquid-to-residue ratio is the volume ratio of the chromatographic clear liquid to the chromatographic residual liquid.

[0061] Example 1

[0062] First, the succinic acid mother liquor is subjected to continuous chromatography. The specific operation is as follows: the succinic acid mother liquor is acidified, and concentrated sulfuric acid is added to the stirring mother liquor tank through a pipeline flow method to adjust the mother liquor pH value to 2.0; after the acid adjustment is completed, the temperature is indirectly raised to 80°C through the jacket steam and maintained for about 1 hour; then the insoluble matter in the mother liquor is filtered through a filter to remove the insoluble protein precipitated during the acid adjustment process, and the filtered clear liquid is temporarily stored in the chromatography stock liquid tank. After the chromatography is debugged, the relevant valves and material pumps of the chromatography stock liquid are opened, and the raw materials are pumped into the chromatography device according to the process requirements. The chromatography filler is LX-1850, the water-to-material ratio is controlled to 2.5, the clear-to-residue ratio is 0.67, and the pure water feed flow rate is controlled to 0.1-0.5BV / h, and finally the corresponding chromatography residual liquid and chromatography clear liquid are obtained.

[0063] The protein removal rate in the chromatographic clear liquid was 95.3%, the salt removal rate was 97.6%, the pigment removal rate was 78.3%, and the removal rate of by-product impurities such as malic acid was 99.3%.

[0064] Secondly, the chromatographic clear liquid is decolorized. The specific operation is as follows: the chromatographic clear liquid is pumped into a decolorization tank through a material pump, and activated carbon is added into the decolorization tank for decolorization. The amount of activated carbon added is controlled at 0.5% (mass volume ratio, i.e., the number of grams of activated carbon added per liter of chromatographic clear liquid), the decolorization temperature is controlled at 65°C, the decolorization time is controlled at 40 minutes, and stirring is maintained at 15-35rpm throughout the process to obtain a decolorized clear liquid.

[0065] The transmittance of the original succinic acid mother liquor is 5-10%, and the color is dark yellow. After chromatographic treatment, the transmittance is increased to 67%, and the color is light yellow. After decolorization treatment, the transmittance is increased to 97.9%, and the color is clear.

[0066] Finally, the decolorized clear liquid is sent to a concentration crystallization tank for concentration and dehydration. The parameters of the concentration crystallization are 60-80°C, vacuum degree -0.085- -0.095MPa, stirring speed 25Hz. After the concentration is completed, the material is sent to a supergravity bed stripping device for stripping and impurity removal. The gas-liquid ratio is 1:15, the stripping steam temperature is controlled at 180°C, and the treatment is 2min. After stripping and impurity removal, the temperature is slowly reduced and crystallized, stirred and cooled to 15°C, maintained for 2h to grow crystals, and after the growth of crystals, centrifugation is performed to obtain crude succinic acid. The crude succinic acid obtained by centrifugation is then added to a pulp washing tank, and pure water is added for pulp washing to wash away impurities on the surface of the crystal or the shallow layer on the surface of the crystal. The amount of water added for pulp washing is added according to 85% of the mass of the crystal, and the pulp washing time is controlled at 1.5h. After washing, secondary centrifugation is performed to obtain centrifugal fine succinic acid, which is then dried by airflow drying to obtain the dried finished succinic acid. The single recovery rate of the entire process reaches 90.6%, the product purity is 99.98%, the ignition residue is 0.005%, and the color is white (such as Figure 2 A). It was used in the synthesis reaction of polyester polyols, and the polyester polyol products did not show yellowing.

[0067] Example 2

[0068] The difference between this embodiment and embodiment 1 is that the pulp washing operation is not performed, that is, the crude succinic acid prepared by chromatography and steam stripping process is directly dried to obtain the finished succinic acid, the single recovery rate of the whole process reaches 92.8%, the product purity is 99.85%, the ignition residue is 0.015%, and the color is white. No yellowing phenomenon occurs when used for polyester polyol synthesis reaction.

[0069] Example 3

[0070] The difference between this embodiment and embodiment 1 is that in the stripping, the gas-liquid ratio is 1:10, the stripping steam temperature is controlled at 160°C, the stripping time is 3 minutes, the single recovery rate of the whole process reaches 91.3%, the product purity is 99.81%, the ignition residue is 0.008%, and the color is white. No yellowing occurs when used in the polyester polyol synthesis reaction.

[0071] Example 4

[0072] The difference between this embodiment and embodiment 1 is that in the stripping, the gas-liquid ratio is 1:20, the stripping steam temperature is controlled at 200°C, the stripping time is 1min, the single recovery rate of the whole process reaches 85.4%, the product purity is 99.99%, the ignition residue is 0.004%, and the color is white. No yellowing occurs when used in the polyester polyol synthesis reaction.

[0073] Comparative Example 1

[0074] The difference between this embodiment and embodiment 1 is that in the stripping, the gas-liquid ratio is 1:21, the stripping steam temperature is controlled at 150°C, the stripping time is 5 minutes, the single recovery rate of the entire process reaches 91.9%, the product purity is 99.59%, the ignition residue is 0.014%, and the color is white. Among them, the product purity is lower than the purity of 99.7% required by the polymerization grade quality, and yellowing occurs when used in the polyester polyol synthesis reaction.

[0075] Comparative Example 2

[0076] The difference between this embodiment and embodiment 1 is that in the stripping, the gas-liquid ratio is 1:8, the stripping steam temperature is controlled at 210°C, the stripping is 30s, the single recovery rate of the whole process is 83.9%, the product purity is 99.99%, the ignition residue is 0.003%, and the color is white. No yellowing occurs when used for the polyester polyol synthesis reaction. In this embodiment, although the product purity meets the polymerization grade quality requirements, due to the excessively high gas-liquid ratio, more succinic acid is lost, and the product recovery rate is less than 85%.

[0077] Comparative Example 3

[0078] The difference between this embodiment and embodiment 1 is that the amount of activated carbon is reduced to 0.3%. The single recovery rate of the entire process reaches 90.3%, the purity of the obtained succinic acid product is 99.49%, the ignition residue is 0.013%, and the color is slightly yellow (such as Figure 2 B). Among them, the product purity is lower than the 99.7% purity required for polymerization grade quality, and yellowing occurs when used in polyester polyol synthesis reaction.

[0079] Comparative Example 4:

[0080] The difference between this embodiment and embodiment 1 is that no stripping treatment is performed, that is, the decolorized clear liquid obtained by chromatography and activated carbon decolorization is sent to a concentration crystallization tank for concentration and water removal. After the concentration is completed, the material is directly subjected to slow cooling and crystallization, stirred and cooled to 15°C, maintained for 2 hours to grow crystals, and after the growth of crystals, centrifugation is performed to obtain crude succinic acid. The crude succinic acid obtained by centrifugation is then added to a pulp washing tank, and pure water is added for pulp washing. The amount of water added for pulp washing is added according to 85% of the mass of the crystals, and the pulp washing time is controlled at 1.5 hours. After the pulp washing is completed, a secondary centrifugation is performed to obtain centrifuged fine succinic acid, and then the dried finished succinic acid is obtained by airflow drying. The single recovery rate of the entire process reaches 90.6%, the product purity is 99.56%, the ignition residue is 0.012%, and the color is white. However, the purity of succinic acid products is lower than the 99.7% required by polymerization grade quality. When it is used in polyester polyol synthesis reaction, the heavy metal residues will lead to catalyst deactivation and affect the polymerization effect. In addition, the residues of unsaturated organic impurities such as aldehydes and ketones will also cause the polyester polyol products to appear slightly yellow.

[0081] Comparative Example 5

[0082] The difference between this embodiment and embodiment 1 is that the stripping treatment is not carried out, but the activated carbon dosage is increased to 1.5% in order to improve the impurity removal effect. It is found that the single recovery rate of the whole process reaches 91.8%, the product purity is 99.65%, the ignition residue is 0.023%, and the color is white. Yellowing occurs in the polyester polyol synthesis reaction. It can be seen that the activated carbon randomly removes the trace impurities remaining in the diacid chromatographic clear liquid, and the removal efficiency is low only by increasing its dosage, and the polymerization grade requirements cannot be met, and the cost is relatively high.

[0083] Comparative Example 6:

[0084] In this comparative example, a method commonly used in the prior art for recovering succinic acid is provided, namely, a method of applying evaporation and concentration of mother liquor (i.e., directly concentrating and crystallizing the mother liquor to recover succinic acid). This method does not perform chromatography, nor does it combine chromatography with stripping. The specific operation is as follows:

[0085] 1. Put the succinic acid mother liquor into a single-effect concentration tank for secondary concentration and crystallization. After the concentration is completed, slowly cool down and crystallize. Stir and cool down to 15°C, maintain for 2 hours to grow crystals. After the growth of crystals, centrifuge to obtain crude succinic acid. The crude succinic acid content is 95.3%, the ignition residue is 1.32%, the moisture is 6.2%, and the color is yellowish.

[0086] 2. Add the crude succinic acid to the decolorization tank filled with pure water to prepare a 250g / L succinic acid solution, and add activated carbon for decolorization. The amount of activated carbon added is controlled at 1.0% (mass volume ratio), the decolorization temperature is controlled at 65℃, the decolorization time is controlled at 40min, and the stirring is maintained at 15-35rpm throughout the process. The transmittance before decolorization is 24%, and the color is yellowish. After decolorization, the transmittance is increased to 92.9%, and the color is slightly clear.

[0087] 3. The decolorized clear liquid is sent to the ion exchange equipment for ion exchange to remove sodium and other salt ions. The ion exchange type cationic resin is used, and the column flux is controlled at 3-5BV / h. The desalted clear liquid is sent to the concentration crystallization tank again for concentration and water removal. After concentration, the crystallization is carried out by slow cooling and stirring, cooling to 15°C, maintaining crystallization for 2 hours, and after crystallization, centrifugation is carried out to obtain crude succinic acid.

[0088] 4. Add crude succinic acid to the pulp washing tank, add pure water for pulp washing, add 85% of the crystal mass of water for pulp washing, and control the pulp washing time to 1.5h. After pulp washing, perform secondary centrifugation to obtain centrifuged fine succinic acid; then obtain the dried finished succinic acid by airflow drying. The single recovery rate of the whole process reaches 84.7%, the product purity is 99.14%, the ignition residue is 0.017%, and the color is white. The purity of the succinic acid product is far lower than the 99.7% purity required by the polymerization grade quality, and yellowing occurs when used in the polyester polyol synthesis reaction.

[0089] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for separating and extracting succinic acid from a sample solution containing succinic acid, comprising subjecting the sample solution to chromatographic treatment to obtain a succinic acid chromatographic clear solution; subjecting the succinic acid chromatographic clear solution to steam stripping treatment, wherein the steam stripping treatment has a gas-liquid ratio of 1:(10-20) and a temperature of 160-200°C; Preferably, the stripping treatment time is 1-3 min.

2. The method according to claim 1, wherein: The sample solution is succinic acid mother liquor or succinic acid fermentation liquid; Preferably, the succinic acid content in the sample solution is 110-140 g / L; Preferably, when the sample liquid is succinic acid fermentation liquid, the method further includes a sample liquid pretreatment step including a filtration step.

3. The method according to claim 2, wherein: The chromatographic column filler used in the chromatographic treatment is a uniform particle gel cationic chromatographic resin, preferably LX-1850.

4. The method according to claim 3, wherein: The sample solution is subjected to the following pretreatment before the chromatographic treatment: Adjust the pH of the sample solution to 1.0-3.0, and heat and filter the acidified sample solution; Preferably, the heating temperature is 80-90°C.

5. The method according to claim 1 or 2, wherein: Before the steam stripping treatment, the succinic acid chromatographic clear liquid is also subjected to a decolorization treatment.

6. The method according to claim 5, wherein: Adding activated carbon to the succinic acid chromatographic clear solution for decolorization; Preferably, the added amount of the activated carbon is at least 0.5%, preferably 0.5-2.0%, more preferably 0.5-1.5%.

7. The method according to claim 5, wherein: The temperature of the decolorization treatment is 60-70°C and the time is 20-60min.

8. The method according to any one of claims 5 to 7, wherein: The method also includes concentrating the decolorized clear liquid and then performing a stripping treatment on the obtained concentrated liquid.

9. The method according to claim 1 or 2, wherein: After the steam stripping treatment, the method further includes cooling crystallization and centrifugation treatment to obtain succinic acid crystals; Optionally, the temperature reduction crystallization treatment comprises reducing the temperature to 10-30° C. and maintaining it for at least 1.5 hours.

10. The method according to claim 9, further comprising pulp washing and centrifuging the succinic acid crystals to obtain fine succinic acid.

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