Long carbon chain dicarboxylic acid, preparation method and application thereof

Abstract

The invention relates to long-carbon-chain dibasic acid, a preparation method and application thereof. The method comprises the following steps: S1, inoculating a long-carbon-chain dibasic acid production strain on a fermentation culture medium for fermentation culture; step S2, in the fermentation acid production process, performing in-situ neutralization regulation and control on the fermentation liquor by feeding a potassium hydroxide solution so as to maintain the pH value of the fermentation liquor in a range of 6.0-8.0; wherein long carbon chain dibasic acid generated in the fermentation process is instantly converted into soluble long carbon chain dibasic acid dipotassium salt through in-situ neutralization regulation and control, and a long carbon chain dibasic acid dipotassium salt solution with the concentration larger than 150 g / L is formed in a fermentation solution in situ; and S3, after fermentation is finished, performing post-treatment on the fermentation liquor to obtain the long-carbon-chain dibasic acid. KOH is used, so that sodium ions are fundamentally prevented from entering a production system, and the thallus activity and the product tolerance are favorably improved. The problems of difficulty in downstream extraction and environmental protection caused by a traditional sodium salt route are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of dicarboxylic acid preparation, in particular to a long carbon chain dicarboxylic acid, a preparation method and application thereof. BACKGROUND

[0002] Long-chain dicarboxylic acids (LCDA) are key monomers for the synthesis of high-performance polyamides, hot melt adhesives, perfumes and plasticizers. Currently, the industrial production of long-chain dicarboxylic acids mainly adopts the biological fermentation method, that is, using engineered microorganisms (such as Candida tropicalis) to carry out omega-oxidation on alkane or fatty acid substrates.

[0003] In this fermentation process, the continuous acid production by microorganisms leads to a sharp decrease in the pH value of the fermentation broth. In order to maintain the optimal pH environment and relieve product inhibition, it is necessary to add an alkaline neutralizing agent to the fermentation broth. The existing technology generally uses sodium hydroxide (NaOH) solution as the neutralizing agent. After neutralization, the product exists in the form of sodium salt such as sodium dicarboxylate in the fermentation broth.

[0004] CN115595337A discloses a method for producing high-purity long-chain dicarboxylic acid using coal-to-alkane, using alkane products containing n-alkanes with carbon number distribution in C9-C18 obtained from coal indirect liquefaction reaction as fermentation substrate to produce long-chain dicarboxylic acid by fermentation; the long-chain dicarboxylic acid is any one or several selected from azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, heptadecanedioic acid and octadecanedioic acid.

[0005] CN110218746A discloses a method for fermenting long-chain dicarboxylic acid, fermentation broth, fermentation treatment liquid and sewage. The fermentation method controls the salt content in the fermentation broth to be 20% or less.

[0006] The disadvantages of the existing sodium type technology are as follows: 1. Difficulty in downstream extraction and environmental pressure. After using sodium neutralizing agent (NaOH), the dicarboxylic acid in the fermentation broth exists in the form of sodium salt. During subsequent acidification extraction, sulfuric acid needs to be added, generating a large amount of sodium sulfate by-product. These by-products have low value, high separation and treatment cost, and improper treatment can cause environmental pollution. 2. Influence on the physical properties and mass transfer of the fermentation broth. The solubility of sodium salt (especially the salt formed with dicarboxylic acid) is relatively low, which easily leads to an increase in the viscosity of the fermentation broth. High viscosity can cause uneven mixing of the fermentation broth and difficulty in oxygen transfer, thereby inhibiting the growth of the bacterial cells and the efficiency of acid production. 3. Introduction of unnecessary ions: high concentration of sodium ions is not necessary and may have a slight impact on the activity of some enzyme systems or the function of the cell membrane, thereby limiting the fermentation conversion rate and the final acid concentration.

[0007] Therefore, it is evident that the existing methods for preparing long-chain dicarboxylic acids still have inconveniences and shortcomings, and urgently require further improvement. To address these problems, manufacturers have spared no effort in seeking solutions, but a suitable design has yet to be developed. Furthermore, there are currently no appropriate methods, manufacturing processes, processing techniques, or structures to solve these issues, which is clearly a problem that relevant industries urgently need to resolve.

[0008] In view of the shortcomings of existing methods for preparing long-chain dicarboxylic acids, the inventor, based on years of practical experience and professional knowledge in the design and manufacture of such products, and in conjunction with theoretical application, actively researched and innovated to create a new method for preparing long-chain dicarboxylic acids that can improve upon existing methods and make them more practical. Through continuous research, design, and repeated trials and improvements, this invention, with genuine practical value, was finally created. Summary of the Invention

[0009] The main objective of this invention is to overcome the shortcomings of existing methods for preparing long-chain dicarboxylic acids and provide a new method for doing so. The technical problem to be solved is that the use of KOH fundamentally eliminates the entry of sodium ions into the production system, which helps to improve cell activity and product tolerance. This method also solves the downstream extraction difficulties and environmental problems associated with the traditional sodium salt route, making it more practical and possessing industrial value.

[0010] Compared with the prior art, the present invention has significant advantages and beneficial effects. As can be seen from the above technical solution, in order to achieve the aforementioned objectives, the main technical contents of the present invention are as follows:

[0011] This invention proposes a method for preparing long-chain dicarboxylic acids, comprising:

[0012] Step S1: Inoculate the long-chain dicarboxylic acid producing strain into the fermentation medium for fermentation culture;

[0013] Step S2: During the fermentation process, potassium hydroxide solution is added to neutralize and regulate the fermentation broth in situ to maintain the pH value of the fermentation broth within the range of 6.0-8.0; wherein, the in-situ neutralization and regulation causes the long-chain dicarboxylic acid produced during the fermentation process to be converted into soluble long-chain dicarboxylic acid dipotassium salt in an instant, and a long-chain dicarboxylic acid dipotassium salt solution with a concentration greater than 150 g / L is formed in situ in the fermentation broth;

[0014] Step S3: After fermentation, the fermentation broth is post-treated to obtain long-chain dicarboxylic acid.

[0015] In one optional embodiment, the mass concentration of the potassium hydroxide solution is 15-25%.

[0016] In one alternative implementation, the potassium-type neutralizing agent is added via an automatic pH control system to maintain the pH of the fermentation broth within the range of 6.0-8.0.

[0017] In one optional implementation, the in-situ neutralization regulation is performed by an automatic pH control system, with pH 4.5-5.0 as the feed start signal and pH 7.0-7.5 as the feed stop signal.

[0018] In one alternative embodiment, the potassium ion source contained in the fermentation medium provides less than 30% of the total amount of potassium ions required for the entire fermentation process.

[0019] In one optional embodiment, the post-processing includes: adding acid to the fermentation broth for acidification, causing the dipotassium salt of the long-chain dicarboxylic acid to be converted into long-chain dicarboxylic acid crystals that precipitate out.

[0020] In one alternative implementation, sulfuric acid is used for acidification, with the endpoint pH controlled at 2.0-3.0.

[0021] In one optional embodiment, after the solid-liquid separation, the method further includes a step of washing the obtained crude long-chain dicarboxylic acid with a washing solution.

[0022] In another aspect, a long-chain dicarboxylic acid product prepared by any of the above methods is provided, wherein the sodium ion content of the long-chain dicarboxylic acid product is less than 100 ppm.

[0023] On the other hand, an application of a long-chain dicarboxylic acid product is provided, including its use in the preparation of polyamides, hot melt adhesives, fragrances, or plasticizers.

[0024] As described above, this invention relates to a long-chain dicarboxylic acid, its preparation method, and its application. The method includes: Step S1, inoculating a long-chain dicarboxylic acid producing strain into a fermentation medium for fermentation culture; Step S2, during the acid production process, neutralizing and regulating the fermentation broth in situ by adding potassium hydroxide solution to maintain the pH value of the fermentation broth within the range of 6.0-8.0; wherein, the in-situ neutralization and regulation causes the long-chain dicarboxylic acid produced during fermentation to be immediately converted into a soluble long-chain dicarboxylic acid dipotassium salt, and forming a long-chain dicarboxylic acid dipotassium salt solution with a concentration greater than 150 g / L in situ in the fermentation broth; Step S3, after fermentation, post-processing the fermentation broth to obtain the long-chain dicarboxylic acid. This invention uses KOH to fundamentally prevent sodium ions from entering the production system, which helps to improve cell activity and product tolerance. It solves the difficulties in downstream extraction and environmental problems caused by the traditional sodium salt route.

[0025] By employing the above technical solution, the method for preparing long-chain dicarboxylic acids of the present invention has at least the following advantages:

[0026] This invention avoids the introduction of sodium ions at the source: Unlike existing technologies that use sodium hydroxide, the use of KOH fundamentally eliminates the introduction of sodium ions (Na₂O₃). + 1) Entering the production system. 2) Utilizing the physiological advantages of potassium ions: Potassium ions (K... + ) It is the main cation in microbial cells and a cofactor for many key enzymes, creating a superior physiological and metabolic environment for the cells and helping to improve cell activity and product tolerance. 3) It lays the foundation for downstream purification: The generation of potassium dicarboxylate provides the prerequisite for obtaining high-purity products with low metal ion content through acidification and separation, solving the difficulties in downstream extraction and environmental problems caused by the traditional sodium salt route.

[0027] In summary, the unique long-chain dicarboxylic acid preparation method of this invention, using KOH, fundamentally eliminates the entry of sodium ions into the production system, which helps improve cell activity and product tolerance. It solves the downstream extraction difficulties and environmental problems associated with traditional sodium salt routes. It possesses numerous advantages and practical value, and is truly innovative as no similar design has been publicly disclosed or used in similar preparation methods. It represents a significant improvement in both preparation method and function, demonstrating substantial technological advancement and producing user-friendly and practical effects. Furthermore, it offers several enhanced benefits compared to existing long-chain dicarboxylic acid preparation methods, making it more suitable for practical application and possessing broad industrial value. It is indeed a novel, progressive, and practical new design.

[0028] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0029] The specific preparation method of the present invention is given in detail in the following embodiments and accompanying drawings. Attached Figure Description

[0030] Appendix Figure 1 This is a schematic diagram of the process for preparing long-chain dicarboxylic acids according to an embodiment of the present invention. Detailed Implementation

[0031] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation methods, steps, structures, features, and effects of the long-chain dicarboxylic acid preparation method proposed in this invention.

[0032] Please see Figure 1As shown, the preferred embodiment of the present invention for preparing long-chain dicarboxylic acids mainly includes the following steps:

[0033] Step S1: Inoculate the long-chain dicarboxylic acid producing strain into the fermentation medium for fermentation culture;

[0034] Step S2: During the fermentation process, potassium hydroxide solution is added to neutralize and regulate the fermentation broth in situ to maintain the pH value of the fermentation broth within the range of 6.0-8.0. In situ neutralization and regulation converts the long-chain dicarboxylic acid produced during fermentation into soluble long-chain dicarboxylic acid dipotassium salts in real time, and forms a long-chain dicarboxylic acid dipotassium salt solution with a concentration greater than 150 g / L in situ in the fermentation broth.

[0035] Step S3: After fermentation, the fermentation broth is post-treated to obtain long-chain dicarboxylic acids.

[0036] The core technical principle of this invention is based on "metal ion replacement and biological regulation": 1. In-situ neutralization principle: Fermentation is essentially a process in which microorganisms oxidize the substrate (alkane) into a dicarboxylic acid, and this process continuously produces H₂. + This causes the pH to drop, and the addition of KOH solution can react with H+. + Instant reaction (`KOH + H) + →K + +H₂O) maintains pH stability and simultaneously converts the generated dicarboxylic acid into a soluble potassium dicarboxylic acid salt, relieving product feedback inhibition. 2. Ion effect principle: K + It is a major intracellular cation, a cofactor in the active sites of many enzymes, and crucial for maintaining cellular osmotic pressure and pH stability. Compared to Na+... + Provide K + This better meets the physiological needs of cells and theoretically creates a superior metabolic environment for the bacteria, potentially improving cell activity and tolerance. 3. Terminal purification principle: In subsequent extraction processes, through acidification (usually with the addition of sulfuric acid), potassium dicarboxylate is converted into the target dicarboxylic acid product (`R(COO-K)). + The reaction is: K₂ + H₂SO₄ → R(COOH)₂ + K₂SO₄. The resulting potassium sulfate (K₂SO₄) has extremely high solubility in water and is easily separated from the target dicarboxylic acid during the crystallization step, thus being completely eluted and finally yielding a pure dicarboxylic acid product with extremely low metal ion content.

[0037] This invention avoids the introduction of sodium ions at the source: Unlike existing technologies that use sodium hydroxide, the use of KOH fundamentally eliminates the introduction of sodium ions (Na₂O₃). + 1) Entering the production system. 2) Utilizing the physiological advantages of potassium ions: Potassium ions (K... +) It is the main cation in microbial cells and a cofactor for many key enzymes, creating a superior physiological and metabolic environment for the cells and helping to improve cell activity and product tolerance. 3) It lays the foundation for downstream purification: The generation of potassium dicarboxylate provides the prerequisite for obtaining high-purity products with low metal ion content through acidification and separation, solving the difficulties in downstream extraction and environmental problems caused by the traditional sodium salt route.

[0038] In one optional embodiment, the mass concentration of the potassium hydroxide solution is 15-25%.

[0039] In this embodiment of the invention, the concentration range of the potassium hydroxide solution is limited to 15-25%, which is an optimized range. Too low a concentration will result in an excessively large feed volume, diluting the fermentation broth and affecting fermentation efficiency; too high a concentration may damage the cells due to localized excessive alkalinity and easily cause crystallization and blockage of the pipes. This concentration range ensures neutralization efficiency while maintaining operational stability and a smooth fermentation process.

[0040] In one alternative implementation, the potassium-type neutralizing agent is added via an automatic pH control system to maintain the pH of the fermentation broth within the range of 6.0-8.0.

[0041] This invention introduces automatic pH control and limits the pH range to 6.0-8.0, which is crucial for achieving efficient fermentation. This pH range is the optimal range for acid production by long-chain dicarboxylic acid-producing strains (such as Candida tropicalis). Automatic control can neutralize the produced acid in real time and precisely, effectively eliminating product feedback inhibition and avoiding the negative impact of pH fluctuations on cell activity and metabolic pathways, thereby significantly improving the acid production rate and final acid concentration.

[0042] In one alternative implementation, in-situ neutralization and regulation are performed using an automatic pH control system, with pH 4.5-5.0 as the feed start signal and pH 7.0-7.5 as the feed stop signal.

[0043] This invention further defines specific upper and lower limits for pH control (start-up: 4.5-5.0; stop-up: 7.0-7.5), achieving more precise process control. This "range-based" control strategy avoids frequent start-up and stop-up of the neutralizing agent, reduces mechanical wear, and stabilizes the pH during the acid-producing period within a narrower, more optimal window (e.g., 7.0 ± 0.2), providing an extremely stable external environment for the cells and maximizing fermentation performance.

[0044] In one alternative embodiment, the potassium ion source contained in the fermentation medium provides less than 30% of the total amount of potassium ions required for the entire fermentation process.

[0045] This invention emphasizes that the supply of potassium primarily relies on the neutralizing agent KOH, rather than the basal culture medium. This quantitative limitation (culture medium supply of K+ < 30% of total demand) brings significant advantages: 1) Reduced costs: It reduces the initial addition of expensive potassium salts such as potassium dihydrogen phosphate. 2) Optimized metabolism: It synchronizes the supply of K+ with the acid production process (i.e., H+ generation), better meeting the requirements of fermentation kinetics and avoiding the osmotic pressure shock that may be caused by high potassium ion concentrations in the early stages.

[0046] In one optional embodiment, the post-processing includes: acidifying the fermentation broth to convert long-chain dicarboxylic acid potassium salt into long-chain dicarboxylic acid crystals, and then performing solid-liquid separation.

[0047] This invention directly stems from the use of potassium sulfate (K₂SO₄) as a byproduct of acidification with KOH. Compared to sodium sulfate (Na₂SO₄) produced by the sodium salt route, K₂SO₄ has extremely high solubility in water. This makes it readily separate from the target dicarboxylic acid crystals during subsequent water washing, allowing for more thorough removal and ultimately yielding metal ions (especially Na₂SO₄). + High-purity long-chain dicarboxylic acid products with extremely low content.

[0048] In one alternative implementation, sulfuric acid is used for acidification, with the endpoint pH controlled at 2.0-3.0.

[0049] This invention specifies the use of sulfuric acid as the acidifying agent and controls the endpoint pH to be between 2.0 and 3.0. Under these pH conditions, long-chain dicarboxylic acids (with lower pKa) exist almost entirely in molecular form, resulting in the highest crystallization yield. Simultaneously, this pH range ensures complete conversion of the potassium dicarboxylic acid salt and avoids equipment corrosion or side reactions that may be caused by excessive acidification. Combined with neutralization with KOH, this constitutes a complete "potassium cycle" process.

[0050] In one alternative embodiment, after solid-liquid separation, the method further includes washing the obtained crude long-chain dicarboxylic acid with a washing solution.

[0051] This invention adds a washing step, utilizing the high solubility of potassium sulfate to efficiently remove residual K2SO4 from the surface and pores of diacid crystals through water washing. This step is crucial for achieving high product purity, is simple to operate, and low in cost, overcoming the difficulties in washing and improving product purity caused by the relatively low solubility of Na2SO4 in the sodium salt route.

[0052] In another aspect, a long-chain dicarboxylic acid product prepared by any of the above methods is provided, characterized in that the sodium ion content of the long-chain dicarboxylic acid product is less than 100 ppm.

[0053] On the other hand, an application of a long-chain dicarboxylic acid product is provided, including its use in the preparation of polyamides, hot melt adhesives, fragrances, or plasticizers.

[0054] The method of the present invention will be further explained and described below through specific embodiments.

[0055] Step 1: Fermentation Preparation

[0056] 1. Strain activation: The preserved long-chain dicarboxylic acid producing strain is inoculated onto slant culture medium and activated.

[0057] 2. Seed culture preparation: Inoculate the activated strain into a shake flask containing seed culture medium and incubate at 29℃ and 200rpm for 16-24 hours until the cells grow vigorously.

[0058] 3. Preparation of Fermentation Medium: Add the fermentation medium to the fermenter, which mainly includes: carbon source (n-alkanes), nitrogen source (ammonium sulfate, urea, etc.), inorganic salts (MgSO4·7H2O, KH2PO4, etc.), and trace elements. Note: Potassium sulfate is not needed here or should be added in small amounts, as the neutralizing agent KOH will provide the main potassium. + source.

[0059] Step 2: Fermentation Start

[0060] 1. Transfer the seed culture prepared in step one to the fermenter at an inoculation rate of 5%-15%.

[0061] 2. Set the culture conditions: temperature 30±1℃, tank pressure 0.05MPa, stirring speed 350-800rpm, aeration rate 0.8-1.5vvm, and maintain dissolved oxygen (DO) at a level of 40-50% saturation.

[0062] 3. In the early stage of fermentation, microorganisms mainly grow and reproduce, consuming nutrients in the culture medium, and the pH may naturally decrease due to the consumption of ammonia nitrogen.

[0063] Step 3: KOH neutralization and regulation (core of this invention)

[0064] 1. When the pH of the fermentation broth drops to the preset lower limit (4.7) due to the large-scale generation of dicarboxylic acid, the pH controller automatically starts the alkali pump.

[0065] 2. The alkali pump precisely pumps a predetermined 20% concentration KOH solution from the potassium hydroxide solution storage tank into the fermenter.

[0066] 3. After KOH is added, the pH rises. When the pH reaches the preset upper limit (7.0), the controller shuts off the alkali pump.

[0067] 4. This process is repeated cyclically, and through dynamic feedback control, the pH is precisely stabilized within the optimal range (e.g., 7.0 ± 0.2) throughout the acid production stage. During this process, the generated dicarboxylic acid is neutralized into potassium salt in real time and dissolved in the fermentation broth, ensuring smooth fermentation and a high acid concentration (up to 200 g / L or more).

[0068] Step 4: Fermentation Termination and Product Extraction

[0069] 1. When the substrate is depleted (or the residual hydrocarbon content is less than 1%), and the acid concentration no longer increases significantly, the fermentation is terminated.

[0070] 2. Sterilize the fermentation broth by heating it to 80-90℃ for 10-20 minutes, and then cool it.

[0071] 3. Acidification crystallization: Add sulfuric acid (H2SO4) to the fermentation broth to adjust the pH to 2.0-3.0, causing the potassium dicarboxylate to completely convert into water-insoluble dicarboxylic acid crystals, which then precipitate out. + It remains in the mother liquor as potassium sulfate (K2SO4).

[0072] 4. Centrifugal separation: The acidified slurry is centrifuged to obtain a crude diacid wet cake and a mother liquor containing potassium sulfate.

[0073] 5. Washing and drying: The wet cake is thoroughly washed with deionized water to completely remove residual K2SO4 and water-soluble impurities. Finally, it is dried to obtain a high-purity long-chain dicarboxylic acid product.

[0074] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the methods and techniques disclosed above without departing from the scope of the present invention to create equivalent embodiments. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing long-chain dicarboxylic acid, characterized by, The application relates to a method for preparing long-chain dicarboxylic acid, comprising the following steps: S1, inoculating a long-chain dicarboxylic acid producing strain on a fermentation medium to carry out fermentation culture; S2, in the process of acid production by fermentation, in-situ neutralization control is carried out on the fermentation liquor by adding potassium hydroxide solution to maintain the pH value of the fermentation liquor in the range of 6.0-8.0; wherein, the in-situ neutralization control makes the long-chain dicarboxylic acid produced in the fermentation process be instantaneously converted into soluble long-chain dicarboxylic acid dipotassium salt, and a long-chain dicarboxylic acid dipotassium salt solution with a concentration greater than 150 g / L is formed in-situ in the fermentation liquor; S3, after the fermentation is completed, post-treatment is carried out on the fermentation liquor to obtain long-chain dicarboxylic acid.

2. The method of claim 1, wherein the long-chain dicarboxylic acid is prepared by the process comprising: The mass concentration of the potassium hydroxide solution is 15-25%. ​ 3. The method of claim 1, wherein, The pH value of the fermentation liquor is maintained in the range of 6.0-8.0 by adding the potassium-type neutralizing agent through a pH automatic control system.

4. The method of claim 3, wherein, The in-situ neutralization control is carried out through the pH automatic control system, the pH value of 4.5-5.0 is used as the flow adding starting signal, and the pH value of 7.0-7.5 is used as the flow adding stopping signal.

5. The method for preparing long-chain dicarboxylic acids according to claim 1, characterized in that, The potassium ion source contained in the fermentation medium provides potassium ions in an amount less than 30% of the total amount of potassium ions required in the whole fermentation process.

6. The method of claim 1, wherein, The post-treatment comprises adding acid into the fermentation liquor to carry out acidification, so that the long-chain dicarboxylic acid dipotassium salt is converted into long-chain dicarboxylic acid to be crystallized and precipitated.

7. The method of claim 6, wherein, Sulfuric acid is used to carry out acidification, and the end-point pH value is controlled in the range of 2.0-3.

0.

8. The method of claim 7, wherein, After the solid-liquid separation, a step of washing the obtained long-chain dicarboxylic acid crude product with a washing liquid is further included.

9. A long-chain diacid product prepared by the process of any one of claims 1 to 8, characterized in that, The sodium ion content of the long-chain dicarboxylic acid product is less than 100 ppm.

10. Use of a long-chain dicarboxylic acid product, characterized in that The application is used in the preparation of polyamide, hot melt adhesive, perfume or plasticizer.

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