Succinic acid composition and preparation method therefor and use thereof

Abstract

Disclosed herein are a succinic acid composition and a preparation method therefor and a use thereof. The succinic acid composition comprises a combination of succinic acid and fumaric acid, and the mass content of fumaric acid in the succinic acid composition is 10-200 ppm. The succinic acid composition provided in the present application is derived from biomass, and comprises succinic acid and a specific amount of fumaric acid. By controlling the fumaric acid content in the succinic acid composition, the succinic acid composition has markedly improved storage stability and a prolonged storage life, and maintains excellent quality characterized by high succinic acid purity and low impurity content even after long-term storage. When used in polyester synthesis, the succinic acid composition can effectively suppress polymerization side reactions and improve polymerization efficiency, so as to obtain polyester products having high yield and high quality.

Description

A succinic acid composition, its preparation method and application Technical Field

[0001] This application relates to the field of biochemical technology, such as a succinic acid composition, its preparation method, and its application. Background Technology

[0002] Succinic acid, also known as succinic acid, is a colorless crystal. Its important uses include the preparation of five-membered heterocyclic compounds, alkyd resins, and the biodegradable plastic polybutylene succinate (PBS). Succinic acid can be obtained through chemical synthesis, such as the catalytic reduction of butenedioic acid, the hydrolysis of succinic anhydride, or the production of succinic acid from butane via maleic anhydride. It can also be produced through microbial fermentation. Currently, the sales volume of industrial-grade succinic acid exceeds 15,000 tons, mostly produced through chemical synthesis; only succinic acid for the food market is produced through fermentation.

[0003] The chemical synthesis of succinic acid is costly due to its susceptibility to petroleum prices and the environmental pollution it causes, failing to meet current sustainable development requirements. Microbial fermentation, on the other hand, fully utilizes renewable resources and boasts a high conversion rate, making it a highly environmentally friendly, efficient, and green method for succinic acid production, and has garnered significant attention in recent years.

[0004] Microbial fermentation uses suitable succinic acid-producing bacteria to synthesize succinic acid through metabolic processes using renewable resources such as sugars. Common bacteria include succinic acid-producing anaerobic spirochetes, succinic acid-producing actinobacilli, Escherichia coli, Corynebacterium glutamicum, and Mannheim succinic acid-producing bacteria. Studies have shown that the metabolic acid-producing pathways of succinic acid-producing bacteria include three categories: (1) the reduction tricarboxylic acid pathway for succinic acid synthesis, which is the main pathway for succinic acid synthesis under anaerobic conditions; (2) the aerobic tricarboxylic acid cycle pathway, in which oxaloacetate and acetyl-CoA are first catalyzed into citrate in the mitochondria under aerobic conditions, and then succinic acid is generated through multiple oxidation reactions; (3) the glyoxylate cycle pathway, in which acetyl-CoA and oxaloacetate condense to form citrate under the action of citrate synthase, and then isocitric acid is formed by cis-aconitase catalysis; subsequently, isocitrate lyase decomposes isocitric acid into succinic acid and glyoxylate; the generated glyoxylate combines with another molecule of acetyl-CoA under the action of malate synthase to form malic acid, and then generates oxaloacetate for the next round of glyoxylate cycle. From the perspective of metabolic acid production pathways, regardless of the synthetic route, the production of succinic acid inevitably generates byproduct organic acids such as formic acid, acetic acid, citric acid, or malic acid. Moreover, sugars used as carbon sources in the culture medium will also remain in the fermentation broth. In the purification process of succinic acid fermentation broth, impurities and residual sugars are difficult to remove and will remain as impurities in the final succinic acid product. These impurities will affect the subsequent synthesis efficiency of PBS and the performance of polyester.

[0005] In recent years, with the rapid development of biodegradable polyester (PBS) synthesis technology, the quality of succinic acid, a monomer for polymerization, has become increasingly important. Impurities such as miscellaneous acids and residual sugars in succinic acid not only affect the efficiency of the polymerization reaction and cause side reactions, but may also affect the polymer's color, reduce its molecular weight, affect its molecular weight distribution, or increase the branching degree of the molecular chains, thus significantly impacting the synthesis process and physical properties of biodegradable polyesters. Besides impurities introduced during the preparation process affecting product quality, succinic acid products also exhibit poor storage stability, are hygroscopic, and are sensitive to light, temperature, and humidity. Long-term storage can lead to clumping, decomposition, and denaturation, resulting in a decline in product quality and hindering its application in polyester synthesis.

[0006] Therefore, developing high-purity, high-storage-stability, and high-quality succinic acid products to meet their application needs in polyester synthesis and other fields is an urgent problem to be solved in this field. Summary of the Invention

[0007] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0008] In view of the shortcomings of related technologies, the purpose of this application is to provide a succinic acid composition, its preparation method and application. By controlling the fumaric acid content in the succinic acid composition, the succinic acid composition has better storage stability, high purity and low impurity content. When applied to polyester synthesis, it can effectively suppress side reactions, improve polymerization efficiency and obtain polyester products with excellent performance.

[0009] To achieve this objective, the following technical solution is adopted in this application:

[0010] In a first aspect, this application provides a succinic acid composition comprising a combination of succinic acid and fumaric acid, wherein the mass content of fumaric acid in the succinic acid composition is 10-200 ppm.

[0011] The succinic acid composition provided in this application is of biomass origin, containing succinic acid and a specific amount of fumaric acid. The fumaric acid has excellent antibacterial and antifungal properties, and as one of the strongest-tasting solid acids, it has a low absorption rate. By controlling the fumaric acid content in the succinic acid composition, the composition exhibits significantly improved storage stability, extended shelf life, and maintains high purity and low impurity content even after long-term storage. When used in polyester synthesis, the succinic acid composition effectively inhibits polymerization side reactions, improves polymerization efficiency, and yields high-yield and high-quality polyester products.

[0012] The following are optional technical solutions for this application, but are not intended to limit the technical solutions provided in this application. The purpose and beneficial effects of this application can be better achieved through the following optional technical solutions.

[0013] In this application, the term "ppm" means parts per million, and 1 ppm means one part per million.

[0014] The mass content of fumaric acid in the succinic acid composition is 10-200 ppm, for example, it can be 15 ppm, 20 ppm, 30 ppm, 40 ppm, 50 ppm, 60 ppm, 70 ppm, 80 ppm, 90 ppm, 100 ppm, 120 ppm, 150 ppm, 160 ppm, 180 ppm or 190 ppm, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range. It can be 20-100 ppm, or more preferably 20-60 ppm.

[0015] This application controls and optimizes the mass content of fumaric acid to achieve a succinic acid composition that combines high succinic acid content (high purity), low impurity content, excellent storage stability, and a longer shelf life. If fumaric acid is absent or present in too low a content, it cannot extend the shelf life of the succinic acid composition, resulting in poor storage performance and easy deterioration after long-term storage. If the fumaric acid content is too high, the succinic acid composition is prone to side reactions in polyester synthesis, affecting the polyester preparation efficiency, yield, and polyester quality.

[0016] Optionally, the succinic acid composition contains ≥99.75% by mass, for example, 99.78%, 99.8%, 99.82%, 99.85%, 99.88%, 99.9%, 99.92%, 99.93%, 99.94%, 99.95%, 99.96%, 99.97%, 99.98%, 99.99%, or 99.999%, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range, but further options include 99.78%-99.99%.

[0017] Optionally, the succinic acid composition further includes water.

[0018] Optionally, the water content in the succinic acid composition is 300-3000 ppm by mass, for example, 300 ppm, 500 ppm, 800 ppm, 1000 ppm, 1200 ppm, 1500 ppm, 1800 ppm, 2000 ppm, 2200 ppm, 2500 ppm or 2800 ppm, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0019] Optionally, the succinic acid composition has a residue content of 20-100 ppm, for example, 25 ppm, 30 ppm, 35 ppm, 40 ppm, 45 ppm, 50 ppm, 55 ppm, 60 ppm, 65 ppm, 70 ppm, 75 ppm, 80 ppm, 85 ppm, 90 ppm or 95 ppm, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0020] Optionally, the succinic acid composition may further include other organic acids; “other organic acids” means organic acids that are different from succinic acid and different from fumaric acid.

[0021] Optionally, the other organic acids include any one or a combination of at least two of formic acid, acetic acid, or lactic acid.

[0022] Optionally, the mass content of other organic acids in the succinic acid composition is ≤200 ppm, for example, it can be 0, 0.0001 ppm, 0.0005 ppm, 0.001 ppm, 0.005 ppm, 0.01 ppm, 0.05 ppm, 0.1 ppm, 0.5 ppm, 1 ppm, 2 ppm, 5 ppm, 8 ppm, 10 ppm, 20 ppm, 30 ppm, 40 ppm, 50 ppm, 60 ppm, 80 ppm, 100 ppm, 120 ppm, 150 ppm, 180 ppm or 190 ppm, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range. Further, it can be ≤100 ppm, and even more preferably ≤10 ppm.

[0023] Optionally, the succinic acid composition further includes a carbohydrate compound.

[0024] Optionally, the carbohydrate compound includes glucose and / or maltose.

[0025] Optionally, the mass content of carbohydrate compounds in the succinic acid composition is ≤5 ppm, for example, it can be 0, 0.0001 ppm, 0.0005 ppm, 0.001 ppm, 0.005 ppm, 0.01 ppm, 0.05 ppm, 0.08 ppm, 0.1 ppm, 0.2 ppm, 0.3 ppm, 0.5 ppm, 0.8 ppm, 1 ppm, 1.5 ppm, 2 ppm, 2.5 ppm, 3 ppm, 3.5 ppm, 4 ppm or 4.5 ppm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0026] Optionally, the melting point of the succinic acid composition is 185-188°C, for example, it can be 185.5°C, 186°C, 186.5°C, 187°C or 187.5°C, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0027] For example, the contents of succinic acid, fumaric acid, other organic acids and sugar compounds in the succinic acid composition can be determined by high performance liquid chromatography (HPLC).

[0028] Optionally, high performance liquid chromatography (HPLC, Thermo Fisher Vanquish core) was used for testing. The HPLC chromatographic conditions were as follows: Rio-Rad column, injection volume of 30 μL, mobile phase of 10 mmol / L dilute sulfuric acid, flow rate of 0.5 mL / min, elution gradient of isocratic elution, column temperature of 40℃, and detector wavelength of 410 nm.

[0029] For example, the melting point, residue on ignition content, and water content of the succinic acid composition can be obtained by the method in GB / T 34686-2017.

[0030] Secondly, this application provides a method for preparing the succinic acid composition as described in the first aspect, the method comprising:

[0031] Seed culture of *Actinomyces succinate* was inoculated into a culture medium for anaerobic fermentation to obtain fermentation broth;

[0032] The fermentation broth was filtered, and the filtrate was purified to obtain the succinic acid composition.

[0033] Optionally, the inoculation amount of the seed liquid is 1-10%, for example, it can be 2%, 3%, 4%, 5%, 6%, 7%, 8% or 9%, and specific point values ​​between the above point values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific point values ​​included in the range.

[0034] In this application, the term "inoculation amount" refers to the volume percentage of the seed culture relative to the culture medium.

[0035] Optionally, the culture medium comprises a combination of a carbon source, a nitrogen source, and inorganic salts.

[0036] Optionally, the carbon source includes sugar, and more preferably glucose.

[0037] Optionally, the nitrogen source includes an organic nitrogen source, and may further be any one or a combination of at least two of yeast powder, peptone, or fish meal.

[0038] Optionally, the inorganic salt includes any one or a combination of at least two of NaHCO3, NaH2PO4, K2HPO4, CaCl2, or MgCl2.

[0039] Optionally, the dissolved oxygen content of the anaerobic fermentation is 0-0.5%, for example, it can be 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4% or 0.45%, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0040] It should be noted that the term "dissolved oxygen" refers to the volume percentage of oxygen in the fermentation broth.

[0041] Optionally, the anaerobic fermentation is carried out under stirred conditions.

[0042] Optionally, the stirring speed of the anaerobic fermentation is 100-500 r / min, for example, it can be 120 r / min, 150 r / min, 180 r / min, 200 r / min, 220 r / min, 240 r / min, 250 r / min, 260 r / min, 270 r / min, 280 r / min, 290 r / min, 300 r / min, 320 r / min, 350 r / min, 380 r / min, 400 r / min, 420 r / min, 450 r / min or 480 r / min, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range. Further, 200-300 r / min can be selected.

[0043] Optionally, the pH value of the anaerobic fermentation is 6.0-8.0, for example, it can be 6.2, 6.5, 6.6, 6.8, 7.0, 7.2, 7.4, 7.5, 7.6 or 7.8, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0044] As an optional technical solution of this application, an alkaline neutralizing agent is added to the system during the anaerobic fermentation process to make the pH value of the anaerobic fermentation 6.0-8.0.

[0045] Optionally, the alkaline neutralizing agent includes any one or a combination of at least two of sodium hydroxide, sodium carbonate, magnesium carbonate, magnesium chloride, calcium carbonate, or calcium chloride.

[0046] Optionally, the temperature of the anaerobic fermentation is 33-45℃, for example, it can be 34℃, 35℃, 36℃, 37℃, 38℃, 39℃, 40℃, 41℃, 42℃, 43℃ or 44℃, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0047] Optionally, the anaerobic fermentation time is 48-72 h, for example, it can be 50 h, 52 h, 55 h, 58 h, 60 h, 62 h, 65 h, 68 h, 70 h or 71 h, as well as specific point values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific point values ​​included in the range.

[0048] Optionally, the filtration method includes any one or a combination of at least two of microfiltration, ultrafiltration, nanofiltration, or reverse osmosis.

[0049] Optionally, the pore size of the filter membrane used for microfiltration is 0.1-10 μm, for example, it can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm or 9 μm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0050] Optionally, the pore size of the filter membrane used for nanofiltration is 10-100 nm, for example, it can be 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm or 90 nm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0051] Optionally, the pore size of the filter membrane used for ultrafiltration is 20-80 nm, for example, it can be 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm or 75 nm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0052] Optionally, the concentration factor of the filtration is 10-30 times, for example, it can be 12 times, 15 times, 18 times, 20 times, 22 times, 25 times or 28 times, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific point values ​​included in the range.

[0053] Optionally, the filtration temperature is 40-60℃, for example, it can be 42℃, 45℃, 48℃, 50℃, 52℃, 55℃ or 58℃, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0054] Optionally, the purification process includes sequential ion exchange, decolorization, concentration, and crystallization to obtain a crude product; the crude product is subjected to at least one redissolution-recrystallization to obtain the succinic acid composition; the redissolution solvent includes a combination of water and an organic solvent, wherein the organic solvent includes ether solvents and / or ketone solvents.

[0055] As an optional technical solution of this application, a fermentation broth containing succinic acid is obtained through anaerobic fermentation. A purification method including filtration, ion exchange treatment, decolorization, concentration, and crystallization is then designed to separate impurities and succinic acid, obtaining a crude product with high purity. The crude product is then reconstituted in a specific solvent and then recrystallized. Since fumaric acid has poor solubility in the organic solvent, while other organic acids and sugars have excellent solubility in the organic solvent, the reconstitution-recrystallization process can effectively remove other organic acids and sugar impurities, and control the fumaric acid content to 10-200 ppm as specified in this application, to obtain the succinic acid composition.

[0056] It should be noted that "resolution-recrystallization" includes resolution and recrystallization performed sequentially. It is a combination, that is, one resolution-recrystallization means that the crude product is resolution in the solvent and then recrystallized to obtain crystals; two resolution-recrystallization means that the crude product is resolution in the solvent and then recrystallized to obtain crystals, then the crystals are resolution in the solvent and then recrystallized again to obtain crystals, thus completing two resolution-recrystallization; and so on.

[0057] Optionally, the ion exchange includes sequential cation exchange and anion exchange.

[0058] In this application, the cation exchange resin may be a strong acid type cation exchange resin, and more preferably a macroporous strong acid type cation exchange resin, wherein the exchange groups include sulfonic acid groups, and the matrix resin includes styrene polymers and / or acrylic polymers. The macroporous strong acid type cation exchange resin is commercially available, and exemplary examples include, but are not limited to, D001 type cation exchange resin, 001×7 cation exchange resin, or ZG C180 type cation exchange resin.

[0059] Optionally, the cation exchange resin includes a macroporous strong acid type cation exchange resin.

[0060] In this application, the anion exchange resin may be a weakly basic anion exchange resin, and more preferably a macroporous weakly basic anion exchange resin. The exchange groups include any one or a combination of at least two of primary, secondary, or tertiary amine groups. The matrix resin includes a styrene-based polymer and / or an acrylic polymer. The macroporous weakly basic anion exchange resin is commercially available, and exemplary examples include, but are not limited to, D301 type anion exchange resin, WA-30 type anion exchange resin, IRA-94 type anion exchange resin, or J-18 type anion exchange resin.

[0061] Optionally, the anion exchange resin includes a macroporous weakly basic anion exchange resin.

[0062] Optionally, the decolorizing agent used for decolorization includes any one or a combination of at least two of activated carbon, kaolin, or adsorption resin, with activated carbon being a further option.

[0063] Optionally, the activated carbon includes granular activated carbon and / or powdered activated carbon.

[0064] Optionally, the packing density of the granular activated carbon is 0.4-0.5 g / cm³. 3 The particle size of the powdered activated carbon is 0.2-0.5 mm.

[0065] Optionally, the decolorization temperature is 50-60℃, for example, it can be 51℃, 52℃, 53℃, 54℃, 55℃, 56℃, 57℃, 58℃ or 59℃, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0066] Optionally, the decolorization time is 30-60 min, for example, it can be 32 min, 35 min, 38 min, 40 min, 42 min, 45 min, 48 min, 50 min, 52 min, 55 min or 58 min, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific point values ​​included in the range.

[0067] Optionally, the transmittance of the decolorized liquid obtained by decolorization is ≥96%, for example, it can be 96.2%, 96.5%, 96.8%, 97%, 97.2%, 97.5%, 97.8%, 98%, 98.2%, 98.5% or 99%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0068] For example, the transmittance of the decolorizing solution can be obtained by testing with a UV-Vis spectrophotometer.

[0069] Optionally, the concentration method includes evaporation concentration.

[0070] Optionally, the concentration temperature is 60-80℃, for example, it can be 62℃, 65℃, 68℃, 70℃, 72℃, 75℃ or 78℃, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0071] Optionally, the concentration system pressure is 10-40 kPa, for example, it can be 12 kPa, 15 kPa, 18 kPa, 20 kPa, 22 kPa, 25 kPa, 28 kPa, 30 kPa, 32 kPa, 35 kPa or 38 kPa, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0072] Optionally, the concentration factor is 2-10 times, for example, it can be 2.5 times, 3 times, 3.5 times, 4 times, 4.5 times, 5 times, 5.5 times, 6 times, 6.5 times, 7 times, 7.5 times, 8 times, 8.5 times, 9 times or 9.5 times, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific point values ​​included in the range.

[0073] Optionally, the crystallization temperature is 10-30℃, for example, it can be 12℃, 15℃, 18℃, 20℃, 22℃, 25℃ or 28℃, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0074] Optionally, the system pressure for crystallization is 60-80 kPa, for example, it can be 62 kPa, 65 kPa, 68 kPa, 70 kPa, 72 kPa, 75 kPa or 78 kPa, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0075] Optionally, the crystallization process further includes a drying step.

[0076] Optionally, the drying temperature is 75-85℃, for example, it can be 76℃, 78℃, 80℃, 82℃ or 84℃, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0077] Optionally, the crude product is subjected to n resolution-recrystallization cycles, where n is an integer from 1 to 10, such as 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10. Further, n can be an integer from 2 to 8. Considering both purification effect and production efficiency, n can be 3 to 6.

[0078] Optionally, the organic solvent includes diethyl ether and / or acetone.

[0079] Optionally, the mass content of the organic solvent in each resolution is independently 5%-30%, for example, 6%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25% or 28%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0080] Optionally, the crude product undergoes n resolution-recrystallization cycles, where n is an integer from 2 to 10; the mass content of the organic solvent in the solvent of the nth resolution is ≤ the mass content of the organic solvent in the solvent of the (n-1)th resolution.

[0081] As an optional technical solution of this application, with the repeated resolution-recrystallization, the mass content of organic solvent in the solvent used for resolution is reduced, which can further optimize the removal effect of other organic acids and sugar compounds, while controlling the fumaric acid content to 18-100 ppm and obtaining a high succinic acid yield.

[0082] Optionally, the temperature for each reconstitution is independently 60-80°C, for example, 62°C, 65°C, 68°C, 70°C, 72°C, 75°C or 78°C, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0083] Optionally, the reconstitution time for each reconstitution is independently 2-10 h, for example, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h, 6 h, 6.5 h, 7 h, 7.5 h, 8 h, 8.5 h, 9 h or 9.5 h, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific point values ​​included in the range.

[0084] Optionally, the recrystallization temperature for each instance is independently between 10-30°C, for example, 12°C, 15°C, 18°C, 20°C, 22°C, 25°C, or 28°C, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list all the specific values ​​included in the range.

[0085] Optionally, the system pressure for each recrystallization is independently 60-80 kPa, for example, 62 kPa, 65 kPa, 68 kPa, 70 kPa, 72 kPa, 75 kPa or 78 kPa, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0086] Optionally, a drying step is also included after each recrystallization.

[0087] Optionally, the drying temperature for each drying step is independently 75-85°C, for example, 76°C, 78°C, 80°C, 82°C or 84°C, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0088] In one optional technical solution, the method for preparing the succinic acid composition includes the following steps:

[0089] (1) Inoculate the seed liquid of Actinobacillus succinate into the culture medium at an inoculation rate of 1-10% for anaerobic fermentation. The anaerobic fermentation is carried out at a stirring speed of 150-350 r / min, a pH of 6.0-8.0, a temperature of 33-45℃, and a time of 48-72 h to obtain the fermentation broth.

[0090] (2) The fermentation broth is filtered, and the filtrate is subjected to cation exchange, anion exchange, decolorization, concentration, crystallization and drying in sequence to obtain crude product;

[0091] The decolorization temperature is 50-60℃ and the time is 30-60 min, so that the transmittance of the decolorized solution is ≥96%.

[0092] The concentration temperature is 60-80℃, the system pressure is 10-40 kPa, and the concentration ratio is 2-10 times.

[0093] The crystallization temperature is 10-30℃, and the system pressure is 60-80 kPa;

[0094] The drying temperature is 75-85℃;

[0095] (3) The crude product is subjected to n resolution-recrystallization cycles, where n is an integer from 2 to 10, to obtain the succinic acid composition;

[0096] Each resolution uses a combination of water and an organic solvent, wherein the mass content of each organic solvent is independently 5%-30%, and the mass content of the organic solvent in the nth resolution is ≤ the mass content of the organic solvent in the (n-1)th resolution; the organic solvent includes diethyl ether and / or acetone.

[0097] Each reconstitution was carried out at a temperature of 60-80°C and for a time of 2-10 h.

[0098] Each recrystallization was carried out at a temperature of 10-30°C and a system pressure of 60-80 kPa.

[0099] Thirdly, this application provides the use of the succinic acid composition as described in the first aspect in the preparation of five-membered heterocyclic compounds or polyesters.

[0100] For example, the five-membered heterocyclic compound includes succinic anhydride (i.e., succinic anhydride) or succinimide.

[0101] Optionally, the polyester comprises polybutylene succinate (PBS) or alkyd resin.

[0102] For example, the preparation method of the polybutylene succinate includes the following steps: esterifying the succinic acid composition with 1,4-butanediol to obtain an esterified product; and subjecting the esterified product to a polycondensation reaction to obtain the polybutylene succinate.

[0103] Optionally, the molar ratio of the succinic acid composition to 1,4-butanediol is 1:(1.2-1.6), for example, it can be 1:1.22, 1:1.25, 1:1.28, 1:1.3, 1:1.32, 1:1.35, 1:1.38, 1:1.4, 1:1.42, 1:1.45, 1:1.48, 1:1.5, 1:1.52, 1:1.55, or 1:1.58, etc.

[0104] Optionally, the temperature of the esterification reaction is 150-170℃, for example, it can be 152℃, 154℃, 155℃, 156℃, 158℃, 160℃, 162℃, 164℃, 165℃, 166℃ or 168℃, etc.

[0105] Optionally, the esterification reaction time is 2-4 h, for example, 2.2 h, 2.5 h, 2.8 h, 3 h, 3.2 h, 3.5 h or 3.8 h.

[0106] Optionally, the polycondensation reaction is carried out in the presence of a catalyst, which may include a titanate catalyst, and may further include any one or a combination of at least two of tetramethyl titanate, tetraethyl titanate, tetraisopropyl titanate, tetran-n-butyl titanate, and tetraisooctyl titanate.

[0107] Optionally, based on the total mass of the succinic acid composition and 1,4-butanediol as 100%, the amount of catalyst used is such that the mass of Ti element is 50-200 ppm, for example, 60 ppm, 80 ppm, 100 ppm, 120 ppm, 140 ppm, 150 ppm, 160 ppm or 180 ppm, etc.

[0108] Optionally, the polycondensation reaction includes a prepolymerization reaction and a final polymerization reaction carried out sequentially.

[0109] Optionally, the temperature of the prepolymerization reaction is 180-260℃, for example, it can be 185℃, 190℃, 195℃, 200℃, 205℃, 210℃, 215℃, 220℃, 225℃, 230℃ or 235℃, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0110] Optionally, the pressure of the prepolymerization reaction is 1-5 kPa, for example, it can be 1.5 kPa, 2 kPa, 2.5 kPa, 3 kPa, 3.5 kPa, 4 kPa or 4.5 kPa, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0111] Optionally, the prepolymerization reaction time is 0.5-4 h, for example, it can be 1 h, 1.2 h, 1.5 h, 1.8 h, 2 h, 2.2 h, 2.5 h, 2.8 h, 3 h or 3.5 h, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific point values ​​included in the range.

[0112] Optionally, the temperature of the final polymerization reaction is 220-260℃, for example, it can be 222℃, 225℃, 228℃, 230℃, 232℃, 235℃, 238℃, 240℃, 242℃, 245℃, 248℃, 250℃, 252℃, 255℃ or 258℃, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0113] Optionally, the pressure of the final polymerization reaction is 10-100 Pa, for example, it can be 20 Pa, 25 Pa, 30 Pa, 35 Pa, 40 Pa, 45 Pa, 50 Pa, 55 Pa, 60 Pa, 65 Pa, 70 Pa, 75 Pa, 80 Pa, 85 Pa, 90 Pa or 95 Pa, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0114] Optionally, the time for the final polymerization reaction is 1-6 h, for example, it can be 1.5 h, 2 h, 2.2 h, 2.5 h, 2.8 h, 3 h, 3.2 h, 3.5 h, 3.8 h, 4 h, 4.2 h, 4.5 h, 4.8 h, 5 h, 5.2 h, 5.5 h or 5.8 h, etc.

[0115] Optionally, after the final polymerization reaction is completed, the process further includes an extrusion granulation step to obtain granular polybutylene succinate.

[0116] Compared with related technologies, this application has the following advantages:

[0117] The succinic acid composition provided in this application is derived from biomass and contains succinic acid and a specific amount of fumaric acid. Through the compounding of fumaric acid and succinic acid, the succinic acid composition exhibits significantly improved storage stability, a long shelf life, and maintains its high purity and low impurity content even after long-term storage. When used in polyester synthesis, the succinic acid composition effectively suppresses polymerization side reactions, improves polymerization efficiency, and yields high-yield and high-quality polyester products, especially imparting excellent solvent resistance to the polyester products.

[0118] After reading and understanding the detailed description, other aspects can be understood. Detailed Implementation

[0119] The technical solution of this application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely to help understand this application and should not be regarded as specific limitations on this application.

[0120] The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used herein, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not limited to those elements and may also include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0121] In the following specific embodiments of this application, all components of the culture medium and all reagents used for filtrate purification are commercially available chemicals; *Actinomyces succinate* is a commercially available strain. The cation exchange resin is a commercially available macroporous strong acid cation exchange resin, specifically ZG C180 type cation exchange resin (Ningbo Zhengguang Resin Co., Ltd.); the anion exchange resin is a commercially available macroporous weak base anion exchange resin, specifically J-18 type anion exchange resin (Ningbo Zhengguang Resin Co., Ltd.).

[0122] The specific component information for some materials is as follows:

[0123] (1) Seed culture medium, with the following components: glucose 12 g / L, yeast extract 8 g / L, corn steep liquor 3 g / L, NaHCO3 3 g / L, NaH2PO4 8 g / L, K2HPO4 4 2.5 g / L, solvent is water.

[0124] (2) Fermentation medium, with the following components: glucose 90 g / L, peptone 15 g / L, potassium dihydrogen phosphate 2 g / L, sodium bicarbonate 2 g / L, calcium chloride 0.5 g / L, magnesium chloride 0.3 g / L, and water as solvent.

[0125] In the following specific embodiments of this application, the water content, residue on ignition content, and melting point of the succinic acid composition are all tested according to the methods in standard GB / T 34686-2017; the test methods for the content of succinic acid, fumaric acid, other organic acids, and carbohydrate compounds in the succinic acid composition, as well as the shelf life, are as follows:

[0126] (1) Content test of succinic acid, fumaric acid, other organic acids and sugar compounds: The test was performed by high performance liquid chromatography (HPLC, Thermo Fisher Vanquish core). The HPLC was equipped with an autosampler, a quaternary gradient pump and a differential refractive index detector. The sample to be tested was prepared into a 10 g / L aqueous solution. The chromatographic conditions were as follows: a Rio-Rad column was used, the mobile phase was 10 mmol / L dilute sulfuric acid, isocratic elution was performed, the detection wavelength was 410 nm and the column temperature was 40℃. The content of fumaric acid, other organic acids and sugar compounds was obtained by chromatogram.

[0127] (2) Shelf life: Place the succinic acid composition to be tested in a ton bag (plastic inner film + woven bag), keep it away from light, and store it at room temperature with an air humidity of 50%. Test its water content every month (using the method in GB / T 34686-2017) and observe whether there is clumping, odor, deterioration, etc. When any of the following occurs, such as water content >1000 ppm, clumping, odor, or deterioration, record the storage time, which is the time when the succinic acid composition can be stably stored.

[0128] Example 1

[0129] A succinic acid composition and its preparation method, the preparation method comprising the following steps:

[0130] (1) Preparation of seed liquid:

[0131] A single colony of *Actinomyces succinate* on the plate was inoculated into a sterilized seed culture medium and cultured at 34°C for 12 h to obtain the seed solution.

[0132] (2) Preparation of fermentation broth:

[0133] The fermentation medium was added to a 5 L fermenter. After sterilization, the seed liquid obtained in step (1) was inoculated into the medium at an inoculation rate of 10% for anaerobic fermentation. During the fermentation process, the pH value was monitored and sodium carbonate solution (sodium carbonate mass concentration of 5%) was introduced to control the pH value to 6.5. The anaerobic fermentation temperature was 35℃, the dissolved oxygen content was 0.05%, the rotation speed was 280 r / min, and the anaerobic fermentation was carried out for 48 h to obtain the fermentation broth.

[0134] (3) Filtration and purification:

[0135] The fermentation broth obtained in step (2) was filtered (at a temperature of 45°C): first microfiltration (filter membrane pore size of 5 μm), then nanofiltration (filter membrane pore size of 80 nm), and the filtrate was collected.

[0136] The filtrate is subjected to cation exchange and anion exchange in sequence to obtain the permeate;

[0137] The permeate was decolorized using activated carbon at a temperature of 50°C for 45 minutes, resulting in a decolorized solution with a transmittance of 96%.

[0138] The decolorizing solution was evaporated and concentrated at a temperature of 65°C and a system pressure of 20 kPa, with a concentration factor of 4 times, to obtain a concentrated solution.

[0139] The concentrated liquid was crystallized at 20°C and 60 kPa, the solid was collected and dried at 75°C to obtain the crude product.

[0140] (4) Resolution-recrystallization

[0141] The crude product was subjected to four resolution-recrystallization cycles. Each resolution was performed using a combination of water and acetone as the solvent. The mass content of acetone in the solvents for the first to fourth resolution cycles was 30%, 20%, 20%, and 10%, respectively. Each resolution was performed at a temperature of 65°C for 3 hours. Each recrystallization was performed at a temperature of 10°C and a system pressure of 70 kPa. The resulting solid was dried at 80°C to obtain the succinic acid composition, the composition of which is shown in Table 1.

[0142] Example 2

[0143] A succinic acid composition and its preparation method, the preparation method comprising the following steps:

[0144] (1) Preparation of seed liquid:

[0145] A single colony of *Actinomyces succinate* on the plate was inoculated into a sterilized seed culture medium and cultured at 35°C for 10 h to obtain the seed liquid.

[0146] (2) Preparation of fermentation broth:

[0147] The fermentation medium was added to a 5 L fermenter. After sterilization, the seed liquid obtained in step (1) was inoculated into the medium at an inoculation rate of 8% for anaerobic fermentation. During the fermentation process, the pH value was monitored and sodium carbonate solution was introduced to control the pH value to 6.8. The anaerobic fermentation temperature was 37℃, the dissolved oxygen content was 0.1%, and the rotation speed was 300 r / min. The fermentation liquid was obtained after 56 h of anaerobic fermentation.

[0148] (3) Filtration and purification:

[0149] The fermentation broth obtained in step (2) was subjected to ultrafiltration at 40°C (the pore size of the filter membrane was 50 nm), and the filtrate was collected.

[0150] The filtrate is subjected to cation exchange and anion exchange in sequence to obtain the permeate;

[0151] The permeate was decolorized using an adsorption resin at a temperature of 55°C for 60 minutes, resulting in a decolorized solution with a transmittance of 96.5%.

[0152] The decolorizing solution was evaporated and concentrated at a temperature of 75°C and a system pressure of 30 kPa, with a concentration factor of 6 times, to obtain a concentrated solution.

[0153] The concentrated liquid was crystallized at 30°C and 75 kPa, the solid was collected and dried at 80°C to obtain the crude product.

[0154] (4) Resolution-recrystallization

[0155] The crude product was subjected to five resolution-recrystallization cycles. Each resolution was performed using a combination of water and diethyl ether as the solvent. The mass content of diethyl ether in the solvents for the first to fifth resolution cycles was 25%, 25%, 20%, 20%, and 10%, respectively. Each resolution was performed at a temperature of 60°C for 2 hours. Each recrystallization was performed at a temperature of 15°C and a system pressure of 60 kPa. The resulting solid was dried at 80°C to obtain the succinic acid composition, the composition of which is shown in Table 1.

[0156] Example 3

[0157] A succinic acid composition and its preparation method differ from Example 1 only in that the method of redissolution-recrystallization in step (4) is different, specifically:

[0158] The crude product was subjected to six resolution-recrystallization cycles. Each resolution was performed using a combination of water and diethyl ether as the solvent. The mass content of diethyl ether in the solvents for the first to sixth resolution cycles was 30%, 30%, 20%, 20%, 10%, and 10%, respectively. Each resolution was performed at a temperature of 70°C for 2 hours. Each recrystallization was performed at a temperature of 15°C and a system pressure of 70 kPa. The resulting solid was dried at 80°C to obtain the succinic acid composition, the composition of which is shown in Table 1.

[0159] Example 4

[0160] A succinic acid composition and its preparation method differ from Example 1 only in that the method of redissolution-recrystallization in step (4) is different, specifically:

[0161] The crude product was subjected to three resolution-recrystallization cycles. Each resolution was performed using a combination of water and acetone as the solvent. The mass content of acetone in the solvents for the first to third resolution cycles was 30%, 20%, and 10%, respectively. Each resolution was performed at a temperature of 70°C for 5 hours. Each recrystallization was performed at a temperature of 12°C and a system pressure of 70 kPa. The resulting solid was dried at 80°C to obtain the succinic acid composition, the composition of which is shown in Table 1.

[0162] Example 5

[0163] A succinic acid composition and its preparation method differ from Example 1 only in that the method of redissolution-recrystallization in step (4) is different, specifically:

[0164] The crude product was subjected to four resolution-recrystallization cycles. Each resolution was performed using a combination of water and acetone as the solvent. The mass content of acetone in the solvents for the first to fourth resolution cycles was 30%, 25%, 20%, and 10%, respectively. Each resolution was performed at a temperature of 70°C for 2 hours. Each recrystallization was performed at a temperature of 20°C and a system pressure of 70 kPa. The resulting solid was dried at 80°C to obtain the succinic acid composition, the composition of which is shown in Table 1.

[0165] Example 6

[0166] A succinic acid composition and its preparation method differ from Example 2 only in that the method of redissolution-recrystallization in step (4) is different, specifically:

[0167] The crude product was subjected to six resolution-recrystallization cycles. The solvents for the first to third resolutions were a combination of water and acetone, with acetone content of 28%, 25%, and 20% by mass, respectively. The solvents for the fourth to sixth resolutions were a combination of water and diethyl ether, with diethyl ether content of 15%, 10%, and 8% by mass, respectively. The temperature for each resolution was 60°C, and the time was 2 h. The temperature for each recrystallization was 15°C, and the system pressure was 70 kPa. The resulting solid was dried at 80°C to obtain the succinic acid composition, the composition of which is shown in Table 1.

[0168] Example 7

[0169] A succinic acid composition and its preparation method differ from Example 1 only in that the method of redissolution-recrystallization in step (4) is different, specifically:

[0170] The crude product was subjected to two resolution-recrystallization processes. The solvent for each resolution was a combination of water and acetone. The mass content of acetone in the solvents for the first and second resolutions was 30% and 20%, respectively. The temperature for each resolution was 65°C and the time was 3 h. The temperature for each recrystallization was 10°C and the system pressure was 70 kPa. The obtained solid was dried at 80°C to obtain the succinic acid composition, the composition of which is shown in Table 1.

[0171] Example 8

[0172] A succinic acid composition and its preparation method differ from Example 1 only in that the method of redissolution-recrystallization in step (4) is different, specifically:

[0173] The crude product was subjected to a single resolution-recrystallization process. The resolution solvent was a combination of water and acetone, with the acetone content being 30% by mass. The resolution temperature was 65°C and the time was 3 h. The recrystallization temperature was 10°C and the system pressure was 70 kPa. The resulting solid was dried at 80°C to obtain the succinic acid composition, the composition of which is shown in Table 2.

[0174] Example 9

[0175] A succinic acid composition and its preparation method differ from Example 1 only in that the method of redissolution-recrystallization in step (4) is different, specifically:

[0176] The crude product was subjected to four resolution-recrystallization cycles. Each resolution was performed using a combination of water and acetone, with the acetone content being 30% by mass. The resolution temperature was 65°C and the time was 3 h. Each recrystallization was performed at 10°C and the system pressure was 70 kPa. The resulting solid was dried at 80°C to obtain the succinic acid composition, the composition of which is shown in Table 2.

[0177] Example 10

[0178] A succinic acid composition and its preparation method differ from Example 1 only in that the method of redissolution-recrystallization in step (4) is different, specifically:

[0179] The crude product was subjected to four resolution-recrystallization cycles. Each resolution was performed using a combination of water and acetone, with the acetone content being 10% by mass. The resolution temperature was 65°C and the time was 3 h. Each recrystallization was performed at 10°C and the system pressure was 70 kPa. The resulting solid was dried at 80°C to obtain the succinic acid composition, the composition of which is shown in Table 2.

[0180] Comparative Example 1

[0181] A succinic acid composition and its preparation method are disclosed. The only difference between this composition and Example 1 is that step (4) involves only one resolution-recrystallization. The solvent for resolution is water. Other parameters are the same as in Example 1. The succinic acid composition is obtained, and its component information is shown in Table 2.

[0182] Comparative Example 2

[0183] A succinic acid composition and its preparation method differ from Example 1 only in that the method of redissolution-recrystallization in step (4) is different, specifically:

[0184] The crude product was subjected to 12 resolution-recrystallization cycles. Each resolution was performed using a combination of water and acetone as the solvent. The mass content of acetone in the solvent for the 1st to 12th resolution cycles was 30%, 30%, 30%, 20%, 20%, 20%, 10%, 10%, 10%, 5%, 5%, and 5%, respectively. Each resolution was performed at a temperature of 65°C for 3 hours. Each recrystallization was performed at a temperature of 10°C and a system pressure of 70 kPa. The resulting solid was dried at 80°C to obtain the succinic acid composition, the composition of which is shown in Table 2.

[0185]

[0186]

[0187] According to the data in Tables 1 and 2, the succinic acid composition provided in this application contains ≥99.78% succinic acid, 20-80 ppm fumaric acid, ≤1000 ppm water, and ≤10 ppm other organic acids. The succinic acid has high purity, low impurity content, and ≤85 ppm residue on ignition. It also exhibits good storage stability, remaining stable for more than six months without clumping, increased water content, deterioration, or off-odors, thus extending its shelf life. This succinic acid composition, when used in the preparation of polyesters, effectively inhibits polymerization side reactions and improves polymerization efficiency.

[0188] According to the data in Table 2, the succinic acid composition of Comparative Example 1 has an excessively high content of fumaric acid. Although it has a long shelf life, it will lead to an increase in side reactions in downstream applications, affecting the production efficiency and quality of downstream products. The succinic acid composition of Comparative Example 2 has an extremely low content of fumaric acid, resulting in poor storage stability and easy deterioration.

[0189] The following are exemplary examples of the application of the succinic acid composition described in this application in the preparation of polybutylene succinate (PBS). In the following detailed embodiments of this application, reagents whose preparation methods are not specified are all conventional commercially available chemicals.

[0190] Application Example 1-10

[0191] The preparation method of PBS includes the following steps: succinic acid composition (from Examples 1-10, respectively) and 1,4-butanediol (purity ≥99.7%, purchased from Liaoning Kingfa Biotechnology Co., Ltd.) are mixed at a molar ratio of 1:1.4 and esterified at 160℃ for 3 h to obtain an esterified product; then, using tetrabutyl titanate as a catalyst, the amount of catalyst is such that the mass of Ti element is 80 ppm (based on the total mass of succinic acid composition and 1,4-butanediol being 100%), a prepolymerization reaction is carried out at 220℃ and 5 kPa for 3 h to obtain a prepolymer; the reaction is continued at 230℃ and 20 Pa for 4 h, and the product is extruded and granulated to obtain the polymerized product PBS.

[0192] Comparative Examples 1-2

[0193] The preparation method of PBS includes the following steps: succinic acid composition (from Comparative Examples 1-2) and 1,4-butanediol (purity ≥99.7%, purchased from Liaoning Kingfa Biotechnology Co., Ltd.) are mixed at a molar ratio of 1:1.4 and esterified at 160℃ for 3 h to obtain an esterified product; subsequently, using tetrabutyl titanate as a catalyst, the catalyst dosage is such that the mass of Ti element is 80 ppm (based on the total mass of succinic acid composition and 1,4-butanediol being 100%), a prepolymerization reaction is carried out at 220℃ and 5 kPa for 4 h to obtain a prepolymer; the reaction is continued at 230℃ and 20 Pa for 6 h, and the product is extruded and granulated to obtain the polymerized product PBS.

[0194] The PBS prepared in Application Examples 1-10 and Comparative Examples 1-2 were subjected to the following performance tests:

[0195] The tensile strength of the PBS sample was tested according to the method in standard GB / T 1040.1-2018 to obtain the test value before immersion. The sample was then immersed in tetrahydrofuran (THF) for 72 h, dried, and the tensile strength was tested again using the same method to obtain the test value after immersion. The retention rate of tensile strength before and after solvent immersion was calculated (100% × test value after immersion / test value before immersion), and the data are shown in Table 3.

[0196]

[0197] According to the test data in Table 3, the PBS prepared using the succinic acid compositions provided in Examples 1-10 of this application helps to improve the cross-linking degree of the PBS molecular chains, giving the PBS of Examples 1-10 better solvent resistance. The tensile strength retention rate after immersion in THF for 72 h is ≥63%. The succinic acid composition used in Comparative Example 1 has an excessively high fumaric acid content. On the one hand, this leads to a certain degree of disruption to the continuity of the PBS resin molecular chains. This structural disruption makes the molecular chains more susceptible to attack by solvent molecules when the material is immersed in THF, thus reducing the tensile strength retention rate. On the other hand, the high fumaric acid content reduces the crystallinity of PBS, thereby reducing the toughness of the material and affecting the tensile strength retention rate. The succinic acid composition used in Comparative Example 2 has an insufficient fumaric acid content. Its molecular structure is too regular, and the molecular weight of the synthesized PBS resin is too tightly packed, causing local stress concentration. This results in a significant decrease in the mechanical properties of the prepared PBS after immersion in organic solvents, and poor solvent resistance.

Claims

A succinic acid composition comprising a combination of succinic acid and fumaric acid, wherein the fumaric acid content in the succinic acid composition is 10-200 ppm by mass. The succinic acid composition of claim 1, wherein, The mass content of fumaric acid in the succinic acid composition is 20-100 ppm; Optionally, the succinic acid composition contains ≥99.75% succinic acid by mass, and more preferably 99.8%-99.99%. The succinic acid composition of claim 1, wherein, The succinic acid composition also includes water; Optionally, the water content in the succinic acid composition is 300-3000 ppm by mass; Optionally, the succinic acid composition has a residue content of 20-100 ppm on ignition. The succinic acid composition of claim 1, wherein, The succinic acid composition also includes other organic acids, which include any one or a combination of at least two of formic acid, acetic acid or lactic acid. Optionally, the mass content of other organic acids in the succinic acid composition is ≤200 ppm, and more preferably ≤100 ppm; Optionally, the succinic acid composition further includes a carbohydrate compound; Optionally, the carbohydrate compound includes glucose and / or maltose; Optionally, the succinic acid composition contains ≤5 ppm of carbohydrate compounds by mass. A method for preparing a succinic acid composition according to any one of claims 1-4, comprising: Seed culture of *Actinomyces succinate* was inoculated into a culture medium for anaerobic fermentation to obtain fermentation broth; The fermentation broth was filtered, and the filtrate was purified to obtain the succinic acid composition. The production method according to claim 5, wherein The pH value of the anaerobic fermentation is 6.0-8.0; Optionally, the anaerobic fermentation is carried out at a temperature of 33-45°C for a time of 48-72 h. The production method according to claim 5, wherein The filtration method includes any one or a combination of at least two of microfiltration, ultrafiltration, nanofiltration or reverse osmosis; Optionally, the purification process includes sequential ion exchange, decolorization, concentration, and crystallization to obtain a crude product; the crude product is subjected to at least one redissolution-recrystallization to obtain the succinic acid composition; the redissolution solvent includes a combination of water and an organic solvent, wherein the organic solvent includes ether solvents and / or ketone solvents. The method of preparation according to claim 7, wherein, The ion exchange includes sequential cation exchange and anion exchange; Optionally, the decolorizing agent used for decolorization includes any one or a combination of at least two of activated carbon, kaolin, or adsorption resin; Optionally, the decolorization temperature is 50-60℃ and the time is 30-60 min; Optionally, the concentration temperature is 60-80℃ and the system pressure is 10-40 kPa; Optionally, the concentration factor is 2-10 times; Optionally, the crystallization temperature is 10-30℃ and the system pressure is 60-80 kPa. The method of preparation according to claim 7, wherein, The crude product is subjected to n resolution-recrystallization cycles, where n is an integer from 1 to 10, and may be an integer from 2 to 8. Optionally, the organic solvent includes diethyl ether and / or acetone; Optionally, the mass content of the organic solvent in each resolution is independently 5%-30%; Optionally, the crude product undergoes n resolution-recrystallization cycles, where n is an integer from 2 to 10; the mass content of the organic solvent in the solvent of the nth resolution is ≤ the mass content of the organic solvent in the solvent of the (n-1)th resolution. The method of preparation according to claim 9, wherein, Each reconstitution is carried out at an independent temperature of 60-80°C. Optionally, the reconstitution time for each reconstitution is independently 2-10 h; Optionally, the recrystallization temperature for each instance is independently 10-30°C; Optionally, the system pressure for each recrystallization is independently 60-80 kPa. The use of a succinic acid composition as described in any one of claims 1-4 in the preparation of a five-membered heterocyclic compound or polyester. The use according to claim 11, wherein The polyester includes polybutylene succinate or alkyd resin.

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