Long-chain dibasic acids and methods for their purification

Abstract

The application relates to a long-chain dibasic acid and a purification method thereof. The purification method of the long-chain dibasic acid comprises the following steps: adjusting the pH value of a long-chain dibasic acid fermentation liquor to 8.0-8.5 to prepare an alkaline dibasic acid salt solution; performing first solid-liquid separation on the alkaline dibasic acid salt solution, taking a liquid phase and mixing the liquid phase with an oxidizing agent to perform oxidation treatment, and preparing an oxidized dibasic acid salt solution; the oxidizing agent comprises ozone; and the oxidized dibasic acid salt solution is sequentially subjected to acidification treatment and second solid-liquid separation. The purification method of the long-chain dibasic acid, the interaction of various steps and parameters can effectively reduce metal and nitrogen residues, improve the purity of the long-chain dibasic acid and improve the colority of the product.

Description

Technical Field

[0001] This application relates to the field of purification technology, and in particular to long-chain dicarboxylic acids and their purification methods. Background Technology

[0002] Long-chain dicarboxylic acids (LCDA) are key monomer raw materials for the synthesis of high-performance long-chain nylons (such as PA1012, PA1212, PA612), hot melt adhesives, fragrances, lubricants, polyester resins, and other chemicals. For example, lauric acid (DC12) is an irreplaceable core precursor for the synthesis of PA1212 and has significant application value in fields such as automotive fuel lines, pneumatic brake lines, 3D printing, electronic connectors, and fiber optic sheaths.

[0003] Bio-fermentation is the mainstream process for preparing long-chain dicarboxylic acids. This process uses n-alkanes or fatty acids as substrates and utilizes the ω-oxidation pathway of microorganisms such as *Candida tropicalis* to catalyze the oxidation of these compounds to obtain the target product. The fermentation broth after fermentation is complex, mainly containing sodium or potassium salts of long-chain dicarboxylic acids, unreacted alkanes, microbial cells and their debris, nitrogenous impurities such as soluble proteins and peptides, polysaccharides, melanoidins and quinone pigments, homologous byproducts such as ω-hydroxy acids, and various inorganic salt impurities. To obtain polymerization-grade long-chain dicarboxylic acid products that meet the requirements for polymerization, the fermentation broth needs to undergo multi-step purification treatment, including demulsification pretreatment, phase inversion, oxidative decolorization, acidification crystallization, solid-liquid separation, washing, and drying. Among these, oxidative decolorization is a key process that determines the product's color and impurity content, ensuring the performance of downstream polymerization.

[0004] Currently, in the aqueous phase purification process of long-chain dicarboxylic acids, oxidative decolorization methods mainly include potassium permanganate oxidation, activated carbon adsorption, and hydrogen peroxide oxidation. Potassium permanganate oxidation decolorization involves adding potassium permanganate to an alkaline aqueous system to complete the decolorization treatment. However, this process introduces permanganate ions into the system, generating manganese dioxide solid residue after the reaction. The manganese residue in the finished product can reach 25 ppm to 50 ppm, far exceeding the requirement of ≤5 ppm for polymer-grade products. Furthermore, the disposal of manganese dioxide waste residue is difficult, and the material recovery and treatment costs are high. Activated carbon adsorption decolorization is simple to operate, achieving decolorization and purification of fermentation broth through activated carbon adsorption. However, this method has poor selectivity for adsorbing small molecule pigments and nitrogen-containing impurities, and the treated product often fails to achieve the purity of polymer-grade products. Moreover, the amount of activated carbon added is large, typically reaching 1% to 3% of the system mass, leading to high energy consumption and significant carbon dioxide emission pressure from subsequent incineration of waste activated carbon. The hydrogen peroxide oxidation decolorization process is carried out under acidic or weakly alkaline conditions. Hydrogen peroxide has a low oxidation potential and is not capable of oxidizing and degrading some conjugated pigment structures. The decolorized product has a high color, which is difficult to meet the specifications of polymer-grade products. At the same time, hydrogen peroxide has a high safety risk when stored on an industrial scale.

[0005] Therefore, it is necessary to improve traditional technologies. Summary of the Invention

[0006] Based on this, this application provides a long-chain dicarboxylic acid that can effectively improve purity and its purification method.

[0007] The technical solution to the above-mentioned technical problems in this application is as follows.

[0008] The first aspect of this application provides a method for purifying long-chain dicarboxylic acids, comprising the following steps:

[0009] The pH of the long-chain dicarboxylic acid fermentation broth was adjusted to 8.0-8.5 to prepare an alkaline dicarboxylic acid salt solution.

[0010] The alkaline dibasic acid salt solution is subjected to a first solid-liquid separation.

[0011] The liquid phase obtained from the solid-liquid separation is mixed with an oxidant and subjected to oxidation treatment to prepare an oxidized dibasic acid salt solution; the oxidant includes ozone.

[0012] The dicarboxylate solution is subjected to acidification treatment and a second solid-liquid separation in sequence.

[0013] In some embodiments, in the purification method of long-chain dicarboxylic acids, the oxidant is a mixture of gases containing ozone, and the oxidation treatment satisfies at least one of the following conditions:

[0014] (1) The volume fraction of ozone in the mixed gas is 2% to 30%; optionally, the volume fraction of ozone in the mixed gas is 2% to 18%.

[0015] (2) The mixed gas is selected from a mixture of ozone and air, a mixture of ozone, oxygen and inert gas, or a mixture of ozone, oxygen and carbon dioxide.

[0016] (3) The oxidation treatment temperature is 75℃~85℃;

[0017] (4) The oxidation treatment time is 0.5 h to 4 h.

[0018] In some embodiments, the purification method for long-chain dicarboxylic acids includes oxidizing the liquid phase and the oxidant by mixing them:

[0019] The liquid phase is heated to the oxidation treatment temperature, and the mixed gas is introduced to perform the oxidation treatment; the flow rate of the mixed gas is 0.2 L·min. -1 ·L -1 ~3.0 L·min -1 ·L -1 .

[0020] In some embodiments, the oxidation treatment in the purification method of long-chain dicarboxylic acids further satisfies at least one of the following conditions:

[0021] (1) The step of mixing the liquid phase and the oxidant further includes: adding a transition metal catalyst; the transition metal ions in the transition metal catalyst include Co. 2+ Ni 2+ Fe 3+ Mn 2+ and Cu 2+ At least one of them;

[0022] (2) The oxidation process further includes: subjecting the reaction solution of the oxidation process to ultraviolet irradiation treatment.

[0023] In some embodiments, the oxidation treatment in the purification method of long-chain dicarboxylic acids further satisfies at least one of the following conditions:

[0024] (1) The concentration of the transition metal catalyst in the mixed solution is 5 ppm to 50 ppm;

[0025] (2) The ultraviolet light wavelength of the ultraviolet irradiation treatment is 185 nm to 400 nm, and the power density is 0.5 W·L. -1 ~5 W·L -1 .

[0026] In some embodiments, the purification method for long-chain dicarboxylic acids further includes, prior to the oxidation treatment, decolorizing the liquid phase.

[0027] In some embodiments, the purification method for long-chain dicarboxylic acids includes a decolorization process using activated carbon, wherein the activated carbon decolorization process satisfies at least one of the following conditions:

[0028] (1) The amount of activated carbon used in the activated carbon decolorization treatment is 0.1% to 2% of the mass of the liquid phase;

[0029] (2) The temperature of the activated carbon decolorization treatment is 60℃~80℃ and the time is 10 min~30 min.

[0030] In some embodiments, the acidification treatment in the purification method of long-chain dicarboxylic acids includes:

[0031] The dicarboxylate solution is heated to 60°C to 85°C, and the pH value of the dicarboxylate solution is adjusted to 3.8 to 4.2 using an acid solution.

[0032] In some embodiments, in the purification method of long-chain dicarboxylic acids, the acidification treatment satisfies at least one of the following conditions:

[0033] (1) Adjusting the pH value of the dicarboxylate solution includes: adding the acid solution to the dicarboxylate solution under ultrasonic treatment conditions, wherein the frequency of ultrasonic treatment is 20 kHz to 40 kHz;

[0034] (2) The acid solution includes a sulfuric acid solution, wherein the mass fraction of the sulfuric acid solution is 10% to 50%.

[0035] In some embodiments, the purification method for long-chain dicarboxylic acids satisfies at least one of the following conditions:

[0036] (1) The pH value of the long-chain dicarboxylic acid fermentation broth is adjusted by using an alkaline regulator, wherein the alkaline regulator is selected from at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate and ammonia water;

[0037] (2) The long-chain dicarboxylic acid is an α,ω-straight-chain saturated dicarboxylic acid with 9 to 18 carbon atoms.

[0038] The second aspect of this application provides a long-chain dicarboxylic acid, which is prepared using the purification method described above.

[0039] In some embodiments, the long-chain dicarboxylic acid satisfies at least one of the following conditions:

[0040] (1) The purity determined by HPLC normalization method is ≥99.5%;

[0041] (2) The color of a long-chain dicarboxylic acid ethanol solution with a concentration of 10 g / 100 mL is ≤15 Hazen;

[0042] (3) The color of the long-chain dicarboxylic acid ethanol solution prepared by heating at 250°C for 2 hours is ≤40 Hazen.

[0043] (4) Under the conditions of 1cm optical path and 280nm, the residual absorbance of protein is ≤0.05;

[0044] (5) Total metal content ≤ 20 ppm;

[0045] (6) Fe content ≤ 5 ppm;

[0046] (7) Sulfate content ≤100ppm.

[0047] The purification method for long-chain dicarboxylic acids disclosed in this application involves adjusting the pH of the fermentation broth to 8.0-8.5, allowing the long-chain dicarboxylic acid to dissolve in the aqueous phase as a divalent anion. Subsequent solid-liquid separation, oxidation, and acidification are carried out under these specific alkaline conditions, reducing the amount of acid and alkali reagents used and effectively lowering ion residues introduced by these reagents in the product. Simultaneously, under these specific alkaline conditions, an ozone-containing oxidant is used for oxidation treatment. Ozone decomposes at a low rate in a weakly alkaline aqueous phase, effectively controlling the generation of hydroxyl radicals and reducing the amount of long-chain dicarboxylic acids. The peroxidation loss of carboxyl groups in the acid effectively improves the yield of long-chain dicarboxylic acids. By first performing a solid-liquid separation on the alkaline dicarboxylic acid solution, and then oxidizing the resulting liquid phase, suspended impurities such as bacterial cells and their fragments can be effectively removed from the alkaline dicarboxylic acid solution. This reduces the oxidative degradation of intracellular proteins during oxidation, resulting in small-molecule nitrogenous impurities such as amides, short peptides, amino acids, and amines, thus lowering the nitrogenous impurity residue in the long-chain dicarboxylic acid product. Furthermore, it reduces the oxidation of bacterial cell pigments to form new chromophores, minimizing secondary pigment formation. The interaction of each step and parameter effectively reduces metal and nitrogen residues, improves the purity of the long-chain dicarboxylic acid, and enhances the product's color.

[0048] The long-chain dicarboxylic acid purified by the method described in this application has low metal and nitrogen residues, high purity, and low color, meeting the requirements for downstream polymerization. Detailed Implementation

[0049] The present application will be further described in detail below with reference to the embodiments and examples. It should be understood that these embodiments and examples are only used to illustrate the present application and are not intended to limit the scope of the present application. The purpose of providing these embodiments and examples is to make the disclosure of the present application more thorough and comprehensive.

[0050] It should also be understood that this application can be implemented in many different forms and is not limited to the embodiments and examples described herein. Those skilled in the art can make various alterations or modifications without departing from the spirit of this application, and the resulting equivalent forms also fall within the protection scope of this application. For example, features described or illustrated as part of one embodiment can be combined in a suitable manner in another embodiment to produce new embodiments. Furthermore, numerous specific details are set forth in the following description to provide a fuller understanding of this application; it should be understood that this application can be implemented without one or more of these details.

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for descriptive purposes only and is not intended to be limiting of the application.

[0052] Unless otherwise stated or in case of contradiction, the terms or phrases used herein shall have the following meanings:

[0053] In this application, the terms "multiple", "various", "multiple times", etc., unless otherwise specified, refer to a quantity greater than or equal to 2. For example, "one or more" means one or more than or equal to two.

[0054] The terms “combinations of,” “any combination of,” and “any combination of” used in this article include all suitable combinations of any two or more of the listed items.

[0055] In this document, the term "suitable" as used in "suitable combination", "suitable method", "any suitable method", etc., refers to the ability to implement the technical solution of this application, solve the technical problem of this application, and achieve the expected technical effect of this application.

[0056] In this document, terms such as "preferred," "better," "more suitable," and "ideal" are merely descriptions of more effective implementation methods or embodiments, and should be understood not to limit the scope of protection of this application. If multiple "preferred" terms appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "preferred" term shall be independent.

[0057] In this application, terms such as "further," "even more," and "particularly" are used for descriptive purposes and to indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0058] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0059] In this application, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0060] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0061] In this application, when numerical intervals (i.e., numerical ranges) are mentioned, unless otherwise specified, the distribution of selectable numerical values ​​within the numerical interval is considered continuous, and includes the two endpoints of the numerical interval (i.e., the minimum and maximum values), as well as every numerical value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that numerical interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints, which is equivalent to directly listing every integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical ranges disclosed herein should be understood to include any and all subranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, percentage, ratio, etc. The term "numerical interval" can be broadly included to include numerical interval types such as percentage intervals, ratio intervals, and proportion intervals.

[0062] Unless otherwise specified, the temperature parameters in this application are permitted to be either constant-temperature treatment or variations within a certain temperature range. It should be understood that the constant-temperature treatment allows temperature fluctuations within the precision range of the instrument control, such as ±5℃, ±4℃, ±3℃, ±2℃, or ±1℃.

[0063] In this application, the terms "room temperature" or "normal temperature" generally refer to 4℃ to 35℃, for example, 20℃ ± 5℃. In some embodiments of this application, "room temperature" or "normal temperature" refers to 10℃ to 30℃. In some embodiments of this application, "room temperature" or "normal temperature" refers to 20℃ to 30℃.

[0064] In this application, if the unit of a data range is only followed by the right endpoint, it indicates that the units of the left and right endpoints are the same. For example, 3~5 h means that the units of the left endpoint "3" and the right endpoint "5" are both h (hours).

[0065] The mass or weight of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship of mass or weight between the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass or weight mentioned in the embodiments of this application can be units known in the chemical industry, such as μg, mg, g, and kg.

[0066] PA: Polyamide (Nylon);

[0067] HPLC: High-Performance Liquid Chromatography;

[0068] ICP-OES: Inductively Coupled Plasma Optical Emission Spectrometry;

[0069] NTU: Nephelometric Turbidity Unit;

[0070] Hazen: Pt-Co color scale, a unit of colorimetry for platinum-cobalt.

[0071] One embodiment of this application provides a method for purifying long-chain dicarboxylic acids, comprising the following steps:

[0072] Step S100: Adjust the pH of the long-chain dicarboxylic acid fermentation broth to 8.0~8.5 to obtain an alkaline dicarboxylic acid salt solution.

[0073] It is understood that long-chain dicarboxylic acid fermentation broth is a fermentation broth containing long-chain dicarboxylic acid salts obtained by biological fermentation; the fermentation broth is an aqueous system; this application provides a method for purifying long-chain dicarboxylic acid fermentation broth in an aqueous phase.

[0074] It is understandable that the pKa1 of long-chain dicarboxylic acids is approximately 4.3~4.6, and the pKa2 is approximately 5.2~5.6. Based on acid-base dissociation equilibrium calculations, when pH ≥ 8.0, the proportion of long-chain dicarboxylic acids existing as divalent anions is ≥ 99.9%, almost completely dissolved in the aqueous phase. Adjusting the pH of the long-chain dicarboxylic acid fermentation broth to 8.0~8.5 allows the long-chain dicarboxylic acid to exist as divalent anions (… - OOC-(CH2) n -COO - It dissolves in the aqueous phase in the form of [a specific substance]. Under these specific alkaline conditions, subsequent first solid-liquid separation, oxidation treatment, and acidification treatment can reduce the amount of acid and alkali reagents used and effectively reduce the residual ions introduced by acid and alkali reagents in the product.

[0075] Studies have found that adjusting the pH of long-chain dicarboxylic acid fermentation broth to 12-14 and then introducing ozone for oxidation and decolorization presents the following problems: (i) a large amount of NaOH alkaline adjuster is required (the amount of alkali used at pH 12-14 is approximately 4-8 times that used at pH 8), leading to increased Na content in the product. + (i) High residual ions introduced by alkaline reagents (up to 80 ppm~120 ppm) affect the molecular weight distribution of downstream nylon polymerization reactions; (ii) Under strong alkaline conditions, ozone decomposes rapidly in the liquid phase, resulting in excessive ·OH free radical generation, which easily causes peroxidation loss of the carboxyl groups of long-chain dicarboxylic acids, reducing the yield of the target product (up to 3~6 percentage points); (iii) A large amount of strong acid is required to neutralize the excess alkali in the acidification stage, resulting in a large amount of waste salt generated.

[0076] Furthermore, the pH value of the long-chain dicarboxylic acid fermentation broth is adjusted to include, but is not limited to, 8.0, 8.1, 8.2, 8.3, 8.4, and 8.5; in some examples, it can be any two of these point values ​​as end values ​​within a range. Optionally, the pH value of the long-chain dicarboxylic acid fermentation broth is adjusted to 8.1~8.4.

[0077] In some of these examples, in step S100, an alkaline regulator is used to adjust the pH of the long-chain dicarboxylic acid fermentation broth.

[0078] In some of these examples, in step S100, the alkalinity regulator is selected from at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and ammonia water.

[0079] It is understandable that when ammonia is used as the alkaline regulator, the resulting ammonium salt solution will generate ammonium sulfate (NH4)2SO4 during the acidification stage, which can be used as a by-product of fertilizer.

[0080] Optionally, the alkalinity regulator is selected from at least one of sodium hydroxide aqueous solution and potassium hydroxide aqueous solution. Optionally, the mass fraction of sodium hydroxide aqueous solution and potassium hydroxide aqueous solution is independently 5% to 30%. It is understood that the mass fraction of sodium hydroxide aqueous solution and potassium hydroxide aqueous solution is independently, but not limited to, 5%, 10%, 15%, 20%, 25%, and 30%; in some examples, it can be a range formed by any two of these point values ​​as endpoints.

[0081] In some examples, in step S100, after adjusting the pH of the long-chain dicarboxylic acid fermentation broth to 8.0-8.5, the mixture is stirred for 10-40 minutes. It is understood that the stirring time includes, but is not limited to, 10, 15, 20, 25, 30, 35, and 40 minutes; in some examples, it can be any two of these values ​​forming a range. Stirring at a specific pH promotes the dissolution of the long-chain dicarboxylic acid in the aqueous phase as a divalent anion.

[0082] In some examples, in step S100, the long-chain dicarboxylic acid is an α,ω-linear saturated dicarboxylic acid with 9 to 18 carbon atoms. It can be understood that the long-chain dicarboxylic acid has 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 carbon atoms; in some examples, it can be any two of these point values ​​forming a range with end values.

[0083] In some of these examples, in step S100, the long-chain dicarboxylic acid is selected from at least one of azelaic acid (DC9), sebacic acid (DC10), undecanoic acid (DC11), dodecanoic acid (lauric acid, DC12), tridecanoic acid (DC13), tetradecanoic acid (DC14), pentadecanoic acid (DC15), hexadecanoic acid (DC16), and octadecanoic acid (DC18).

[0084] In some of these examples, in step S100, the chemical name, common name, molecular formula, number of carbon atoms, and main downstream applications of the long-chain dicarboxylic acid are shown in Table 1.

[0085] Table 1

[0086]

[0087] Step S200: Perform a first solid-liquid separation on the alkaline dicarboxylic acid salt solution.

[0088] In some examples, in step S200, the first solid-liquid separation method includes at least one of filtration and centrifugation. Optionally, filtration includes, but is not limited to, at least one of microfiltration, plate and frame filtration, etc.; further, the pore size of the microfiltration is 0.1 μm to 10 μm; optionally, centrifugation includes, but is not limited to, disc centrifugation, with a centrifugal force ≥4000 g. It is understood that a two-stage series solid-liquid separation can be used: centrifugation followed by filtration. Solid-liquid separation removes large particulate bacteria, and then filtration removes fine particulate impurities.

[0089] In some of these examples, in step S200, the liquid phase obtained from the first solid-liquid separation has a transmittance of ≥80% and a turbidity of ≤20 NTU at a wavelength of 600 nm and an optical path length of 1 cm.

[0090] In some examples, after the first solid-liquid separation, step S200 further includes:

[0091] Step S210: Decolorize the liquid phase.

[0092] In some of these examples, step S210 includes a decolorization process using activated carbon.

[0093] In some of these examples, in step S210, the amount of activated carbon used in the activated carbon decolorization treatment is 0.1% to 2% of the liquid phase mass.

[0094] It is understood that the amount of activated carbon used in activated carbon decolorization treatment is a percentage of the liquid phase mass, including but not limited to 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, and 2%; in some examples, it can be any two of these point values ​​as the end values ​​within a range.

[0095] In some of these examples, in step S210, the activated carbon decolorization treatment is carried out at a temperature of 60°C to 80°C for a time of 10 min to 30 min.

[0096] It is understood that the temperatures for activated carbon decolorization treatment include, but are not limited to, 60℃, 62℃, 64℃, 66℃, 68℃, 70℃, 72℃, 74℃, 76℃, 78℃, and 80℃; and the times include, but are not limited to, 10 min, 12 min, 14 min, 16 min, 18 min, 20 min, 22 min, 24 min, 26 min, 28 min, and 30 min. In some examples, any two of these point values ​​can be used as endpoints within a range.

[0097] Step S300: The liquid phase obtained from solid-liquid separation is mixed with an oxidant and subjected to oxidation treatment to obtain an oxidized dibasic acid salt solution; the oxidant includes ozone.

[0098] By first performing a solid-liquid separation on the alkaline dicarboxylate solution, and then oxidizing the resulting liquid phase, suspended impurities such as bacterial cells and their fragments can be effectively removed from the alkaline dicarboxylate solution. On the one hand, this reduces the oxidation and degradation of intracellular proteins during the oxidation process, generating small molecule nitrogenous impurities such as amides, short peptides, amino acids, and amines, thus reducing the residual nitrogenous impurities in long-chain dicarboxylate products. On the other hand, it reduces the oxidation of cytochrome c, heme compounds, and other bacterial cytochromes to generate new chromophores, thereby reducing the formation of secondary pigments.

[0099] Under specific alkaline conditions controlled in step S100, the liquid phase is oxidized under conditions containing ozone oxidant. Ozone decomposes at a low rate in a weakly alkaline aqueous phase, effectively controlling the amount of hydroxyl radicals generated, thereby effectively reducing the peroxidation loss of carboxyl groups in long-chain dicarboxylic acids and effectively improving the yield of long-chain dicarboxylic acids.

[0100] The liquid phase is oxidized by an oxidant including ozone, which selectively oxidizes and degrades soluble proteins, pigments and residual organic impurities, resulting in an oxidized dibasic acid salt solution that is colorless to slightly yellow.

[0101] If oxidation is performed directly without solid-liquid separation, the bacterial proteins, after being strongly oxidized and decomposed by ozone, will be converted into a large number of soluble small-molecule nitrogen-containing impurities such as amides, short peptides, amino acids, and amines. These impurities are difficult to completely remove through subsequent crystallization separation, resulting in an increased nitrogen content in the product (up to 81 ppm to 200 ppm), affecting the stability of downstream polymerization reactions. At the same time, the presence of bacteria significantly increases the ineffective consumption of ozone (accounting for approximately 30% to 50% of the total dosage), reducing ozone utilization efficiency.

[0102] This application reduces the total nitrogen content to 30 ppm to 80 ppm by first performing a solid-liquid separation on an alkaline dicarboxylate solution and then oxidizing the liquid phase obtained from the solid-liquid separation.

[0103] In some of these examples, in step S300, the oxidant is a mixture of gases containing ozone.

[0104] In some of these examples, in step S300, the volume fraction of ozone in the mixed gas is 2% to 30%.

[0105] It is understood that the volume fraction of ozone in the mixed gas includes, but is not limited to, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, and 30%; in some examples, it can be a range formed by any two of these point values ​​as endpoints. Optionally, the volume fraction of ozone in the mixed gas is 2% to 18%. Optionally, the volume fraction of ozone in the mixed gas is 4% to 12%.

[0106] By controlling the volume fraction of ozone in the mixed gas, the formation of a "peroxidation zone" near the gas-liquid interface can be effectively reduced, effectively inhibiting the peroxidation side reaction of carboxyl groups in long-chain dicarboxylic acids. Simultaneously, increasing the total volumetric flow rate of the mixed gas increases the gas-liquid contact area and the system's turbulence intensity, enhancing mass transfer efficiency. Furthermore, the total ozone dosage can be reduced (by up to 30%–50%), minimizing ineffective ozone consumption on the bacterial cell surface and significantly improving ozone utilization efficiency. The bacterial cells separated using this process can be used as high-value byproduct raw materials such as single-cell proteins and yeast extracts, achieving comprehensive resource utilization of materials.

[0107] In some of these examples, in step S300, the mixed gas is selected from a mixture of ozone and air, a mixture of ozone and oxygen and an inert gas, or a mixture of ozone and oxygen and carbon dioxide.

[0108] It is understood that inert gases include, but are not limited to, nitrogen. A mixture of air and ozone can be obtained by directly diluting ozone with air; a mixture of ozone with oxygen and inert gases, or a mixture of ozone with oxygen and carbon dioxide, is obtained by further diluting the mixture of oxygen and ozone with inert gases or carbon dioxide.

[0109] Oxygen in the mixed gas can act as a free radical scavenger, consuming excess hydroxyl·OH free radicals in the liquid phase system and further inhibiting the peroxidation of carboxyl groups in long-chain dicarboxylic acids; air can act as a safe diluent, reducing the risk of ozone explosion and facilitating the industrial-scale continuous operation of the process.

[0110] In some of these examples, in step S300, the mixed gas is bubbled in from the bottom of the reactor through a microporous distributor with a pore size ≤ 50 μm.

[0111] It is understood that the type of reactor includes, but is not limited to, any gas-liquid contact equipment such as mechanically stirred jacketed reactors, external circulation reactors, microchannel reactors, and tower-type bubbling reactors; the operation mode includes, but is not limited to, intermittent operation, continuous operation, or semi-continuous operation; the ultrasonic instrument can be in various forms such as ultrasonic pools or ultrasonic oscillators.

[0112] In some of these examples, the oxidation process in step S300 is carried out at a temperature of 75°C to 85°C.

[0113] It is understood that the oxidation treatment temperature includes, but is not limited to, 75℃, 76℃, 77℃, 78℃, 79℃, 80℃, 81℃, 82℃, 83℃, 84℃, and 85℃; in some examples, it can be any two of these point values ​​as the end values ​​within a range. Optionally, the oxidation treatment temperature is 78℃~82℃.

[0114] By controlling the temperature of the oxidation process, the rate at which ozone decomposes into ·OH radicals in water is regulated, thereby enhancing the oxidizing capacity of ozone (·OH oxidation potential +2.80V, O3 oxidation potential +2.07V), while simultaneously inhibiting excessive ·OH radical generation and reducing the peroxidation loss of carboxyl groups in long-chain dicarboxylic acids. Furthermore, this temperature reduces the viscosity of the aqueous solution (by approximately 30%–40%), improving gas-liquid mass transfer efficiency and increasing the liquid-phase absorption rate of ozone. Simultaneously, this temperature promotes the denaturation and aggregation of soluble proteins into insoluble particles, facilitating separation in subsequent processes; it also shortens the reaction time and increases the processing capacity of the production unit. In addition, it reduces the effective ozone dosage in the liquid phase caused by the violent thermal decomposition of ozone under high-temperature conditions, inhibits excessive evaporation of water in the system, reduces heat loss, and ensures the stability of long-chain dicarboxylic acid salts.

[0115] In some of these examples, the oxidation process in step S300 lasts for 0.5 h to 4 h.

[0116] It is understood that the oxidation treatment time includes, but is not limited to, 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, and 4 h; in some examples, it can be any two of these point values ​​as endpoints within a range. Optionally, the oxidation treatment time is 1 h to 2.5 h.

[0117] In some of these examples, step S300 includes the following steps:

[0118] The liquid phase is heated to the oxidation temperature, and a mixed gas is introduced for oxidation treatment.

[0119] In some of these examples, in step S300, the flow rate of the mixed gas is 0.2 L·min. -1 ·L -1 ~3.0 L·min -1 ·L -1 .

[0120] It is understood that the flow rate of the mixed gas includes, but is not limited to, 0.2 L·min. -1 ·L -1 0.4 L·min -1 ·L -1 0.6 L·min-1 ·L -1 0.8 L·min -1 ·L -1 1.0 L·min -1 ·L -1 1.2 L·min -1 ·L -1 1.4 L·min -1 ·L -1 1.6 L·min -1 ·L -1 1.8 L·min -1 ·L -1 2.0 L·min -1 ·L -1 2.2 L·min -1 ·L -1 2.4L·min -1 ·L -1 2.6 L·min -1 ·L -1 2.8 L·min -1 ·L -1 3.0 L·min -1 ·L -1 In some examples, this can be a range consisting of any two of these point values ​​as endpoints. Optionally, the flow rate of the mixed gas is 0.5 L·min. -1 ·L -1 ~2.0 L·min -1 ·L -1 .

[0121] In some of these examples, step S300, which involves mixing the liquid phase and the oxidant, further includes adding a transition metal catalyst.

[0122] In some of these examples, in step S300, the transition metal ions in the transition metal catalyst include Co. 2+ Ni 2 + Fe 3+ Mn 2+ and Cu 2+ At least one of the following. Optionally, the above-mentioned transition metal ions can be used alone or in combination; or the transition metal ions can be coordinated with organic ligands (such as porphyrins or phthalocyanines) to form metal complexes for use in combination.

[0123] In some of these examples, in step S300, the concentration of the transition metal catalyst in the mixed solution is 5 ppm to 50 ppm.

[0124] It is understood that the concentration of transition metal catalysts includes, but is not limited to, 5 ppm, 10 ppm, 15 ppm, 20 ppm, 25 ppm, 30 ppm, 35 ppm, 40 ppm, 45 ppm, and 50 ppm; in some examples, it can be any two of these point values ​​as end values ​​within a range.

[0125] Optionally, the transition metal catalyst includes ferric salts, with Fe... 3+ The concentration of transition metal catalysts is estimated to be 10 ppm to 30 ppm.

[0126] In some examples, step S300, during the oxidation process, further includes subjecting the reaction solution to ultraviolet irradiation treatment.

[0127] In some examples, in step S300, the ultraviolet light irradiation treatment uses ultraviolet light with a wavelength of 185 nm to 400 nm and a power density of 0.5 W·L. -1 ~5 W·L -1 .

[0128] It is understood that the ultraviolet wavelengths used in ultraviolet irradiation treatment include, but are not limited to, 185 nm, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 254 nm, 260 nm, 270 nm, 280 nm, 290 nm, 300 nm, 350 nm, and 400 nm; the power density is based on the volume of the reaction liquid being treated, and the power density of ultraviolet irradiation treatment includes, but is not limited to, 0.5 W·L. -1 1 W·L -1 1.5 W·L -1 2 W·L -1 2.5 W·L -1 3 W·L -1 3.5 W·L -1 4 W·L -1 4.5 W·L -1 5 W·L -1 In some examples, the range can be defined by any two of these point values ​​as endpoints. Optionally, the ultraviolet wavelength for ultraviolet irradiation is 200 nm to 300 nm.

[0129] It is understood that ultraviolet light sources include, but are not limited to, at least one of low-pressure mercury lamps, LED ultraviolet light sources, and excimer ultraviolet light sources.

[0130] Step S400: The dicarboxylate solution is subjected to acidification treatment and second solid-liquid separation in sequence.

[0131] Acidification treatment converts long-chain dicarboxylic acids into free acids (HOOC-(CH2)). n The precipitate is formed in the form of -COOH, yielding a slurry containing long-chain dicarboxylic acid crystals.

[0132] In some of these examples, step S400 includes the acidification process as follows:

[0133] Step S410: Heat the oxidized dicarboxylate solution to 60℃~85℃, and adjust the pH value of the oxidized dicarboxylate solution to 3.8~4.2 using an acid solution.

[0134] By adjusting the pH of the dicarboxylic acid salt solution to a specific range, long-chain dicarboxylic acids can be fully extracted, ensuring product yield; at the same time, short-chain impurities of the same series can be suppressed from co-precipitating with the product, ensuring that the obtained product has high purity.

[0135] It is understood that the temperature of the oxidized dicarboxylate solution includes, but is not limited to, 60℃, 62℃, 64℃, 66℃, 68℃, 70℃, 72℃, 74℃, 76℃, 78℃, 80℃, 82℃, 84℃, and 85℃; the pH value of the oxidized dicarboxylate solution is adjusted to, but is not limited to, 3.8, 3.9, 4.0, 4.1, and 4.2; in some examples, it can be any two of these point values ​​as endpoints within a range. Optionally, the temperature of the oxidized dicarboxylate solution is 70℃~80℃; optionally, the pH value of the oxidized dicarboxylate solution is adjusted to 3.9~4.1.

[0136] In some examples, step S410, adjusting the pH of the dicarboxylate solution includes adding an acid solution to the dicarboxylate solution under ultrasonic treatment conditions.

[0137] By adjusting the pH of the oxidized dicarboxylic acid salt solution to a specific range, the impurities of the mixed acids in the system are stably converted into soluble salts. Combined with ultrasonic vibration, the peritectic precipitation of impurities can be effectively inhibited, allowing the impurities of the mixed acids to remain in the aqueous phase, thus achieving efficient removal of mixed acids and significantly improving the purity of long-chain dicarboxylic acid products.

[0138] While ensuring the polymerization-grade purity of the product, alkali consumption is reduced (by up to 50%~75%), and Na... + The combined technical effects include: reduced residue (up to 60%~80%), reduced waste salt production (up to 50%~70%), and reduced total nitrogen content in products (up to 40%~60%).

[0139] In some of these examples, in step S410, the frequency of the ultrasonic treatment is 20 kHz to 40 kHz.

[0140] It is understood that the frequencies of ultrasonic processing include, but are not limited to, 20 kHz, 22 kHz, 24 kHz, 26 kHz, 28 kHz, 30 kHz, 32 kHz, 34 kHz, 36 kHz, 38 kHz, and 40 kHz; in some examples, the frequency can be any two of these point values ​​as endpoints. Optionally, the frequency of ultrasonic processing is 25 kHz to 30 kHz.

[0141] In some of these examples, in step S410, the acid solution includes at least one of sulfuric acid solution, sulfurous acid solution, and nitric acid solution.

[0142] It is understandable that when the product is intended for non-polymerization applications, at least one of hydrochloric acid solution and phosphoric acid solution may be used as the acid solution.

[0143] In some of these examples, in step S410, the acid solution includes a sulfuric acid solution.

[0144] Sulfuric acid is a non-volatile acid that does not produce hydrogen chloride gas during use. This avoids the equipment corrosion and environmental pollution problems caused by hydrogen chloride, reduces the requirements for equipment materials, and improves the on-site operating environment. Furthermore, sulfate ions have a smaller negative impact on downstream polymer polymerization reactions such as polyamides compared to chloride ions; chloride ions accelerate the thermal degradation of polyamides in the molten state, while the impact of sulfate ions on the polymerization process is negligible. In addition, sulfuric acid is an inexpensive raw material, significantly reducing overall production costs.

[0145] Optionally, the mass fraction of the acid solution is 10% to 50%. Optionally, the mass fraction of the acid solution is 20% to 40%.

[0146] It is understood that the mass fraction of the acid solution includes, but is not limited to, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, and 50%; in some examples, it can be any two of these point values ​​as the end values ​​within a range.

[0147] In some examples, in step S410, the acid solution is added to the dicarboxylate solution with stirring, the pH of the dicarboxylate solution is adjusted to 3.8~4.2, and then it is kept at a warm temperature for aging.

[0148] Optionally, the stirring speed is 30 rpm to 120 rpm. Optionally, the acid solution addition rate is ≤2% of the total volume of acid solution added per minute to the total volume of the dicarboxylate solution. Optionally, the aging time is 20 min to 60 min.

[0149] In some examples, in step S400, the second solid-liquid separation method includes at least one of filtration and centrifugation. Optionally, filtration includes, but is not limited to, at least one of microfiltration, plate and frame filtration, etc.; further, the pore size of the microfiltration is 0.1 μm to 10 μm; optionally, centrifugation includes, but is not limited to, disc centrifugation, with a centrifugal force ≥4000 g. It is understood that a two-stage series solid-liquid separation can be used: centrifugation followed by filtration. Solid-liquid separation removes large particulate bacteria, and then filtration removes fine particulate impurities.

[0150] In some examples, in step S400, the temperature for the second solid-liquid separation is 60°C to 85°C. It can be understood that the temperature for the second solid-liquid separation refers to the temperature at which the crystal slurry obtained from the acidification treatment undergoes solid-liquid separation.

[0151] In some of these examples, after the second solid-liquid separation, step S400 further includes washing and drying the solid phase sequentially.

[0152] In some examples, in step S400, the washing solution is water. Optionally, the water temperature is 40°C to 70°C. Further, the water temperature is 55°C to 65°C.

[0153] Optionally, the washing process is repeated 1 to 3 times. Optionally, the water used for each washing is 0.5 to 2 times the mass of the crystals. The mother liquor after washing is neutralized and then recycled as downstream industrial water, with a recycling rate of ≥70%.

[0154] In some of these examples, in step S400, the drying temperature is 70°C to 95°C and the vacuum degree is ≤-0.08 MPa.

[0155] It is understandable that for the purification of different long-chain dicarboxylic acids, parameters such as alkaline pH, ozonolysis temperature, and acidification pH can be fine-tuned according to the solubility characteristics and impurity profile of the product type (azelaic acid, sebacic acid, lauryl iodide, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, octadecanoic acid, etc.).

[0156] The purification method for long-chain dicarboxylic acids in this application has the following beneficial effects:

[0157] The product has high purity: the purity of the obtained product is ≥99.5% (HPLC normalization method), the color is ≤15 Hazen, and the thermal stability color is ≤40 Hazen under heating at 250℃ for 2h, meeting the raw material indicators for long-chain nylon polymerization. Taking lauryl diacid as an example, the impurities of tetradecanoic acid are reduced to about 0.1%, and the impurities of decadecanoic acid are reduced to below 0.05%.

[0158] Low metal residue levels: The resulting product has Fe content ≤5ppm, Na content ≤40ppm, and total metal content ≤20ppm. The process does not introduce heavy metal impurities such as Mn, Cr, and Cu.

[0159] Low nitrogen residue: The process mechanism of sterilization followed by oxidation ensures that the total nitrogen in the product is ≤80ppm, which effectively reduces the adverse effects of bacterial protein degradation products on the stability of the polymerization reaction.

[0160] High product yield: Relying on the dual selective protection mechanism of mild alkaline conditions and air dilution, the peroxidation loss of carboxyl groups in long-chain dicarboxylic acids is effectively reduced, thereby increasing the overall yield of the target product.

[0161] Lower alkali consumption: Effectively reduces the amount of alkalinity regulator used (up to 50% to 75%), and the alkali consumption per unit product decreases from about 0.30 t / t to 0.07 t / t to 0.15 t / t.

[0162] The amount of waste salt generated is relatively small: based on a 5000t / a production unit, the annual waste salt emissions can be reduced by 400t to 800t, significantly reducing the environmental protection treatment pressure on the unit.

[0163] The purification method for long-chain dicarboxylic acids presented in this application is simple to operate, easy to control, requires no preparation of heavy metal recovery oxidants, has low equipment investment, and is environmentally friendly, thus possessing significant industrial application value. It can be used as an independent step in the purification of long-chain dicarboxylic acids, or it can be combined with upstream fermentation broth demulsification / pretreatment steps and downstream recrystallization / flake formation / granulation and other post-processing steps. The isolated bacterial cells can be washed with water and desolvated before being utilized as single-cell protein (SCP) feed additives, yeast extract raw materials, or by-products of organic fertilizers.

[0164] One embodiment of this application provides a long-chain dicarboxylic acid, which is prepared using the purification method for the long-chain dicarboxylic acid described above.

[0165] In some of these examples, the long-chain dicarboxylic acids satisfy at least one of the following conditions:

[0166] (1) The purity determined by HPLC normalization method is ≥99.5%;

[0167] (2) The color of a long-chain dicarboxylic acid ethanol solution with a concentration of 10 g / 100 mL is ≤15 Hazen;

[0168] (3) The color of a long-chain dicarboxylic acid ethanol solution with a concentration of 10 g / 100 mL prepared after heating at 250℃ for 2 h is ≤40 Hazen.

[0169] (4) Under the conditions of 1cm optical path and 280nm, the residual absorbance of protein is ≤0.05;

[0170] (5) Total metal content ≤ 20 ppm;

[0171] (6) Fe content ≤ 5 ppm;

[0172] (7) Sulfate content ≤100ppm.

[0173] One embodiment of this application provides a polymer material, the raw materials of which include the above-mentioned long-chain dicarboxylic acid.

[0174] The aforementioned long-chain dicarboxylic acids meet the requirements for polymer-grade raw materials such as long-chain nylon.

[0175] In some of these examples, the polymeric material includes, but is not limited to, at least one of nylon, hot melt adhesive, fragrance, lubricant, and polyester resin.

[0176] Optionally, the nylon includes, but is not limited to, at least one of PA9, PA1010, PA1012, PA1212 and PA612.

[0177] The present application will be described in further detail below with reference to specific embodiments, but the embodiments of the present application are not limited thereto.

[0178] The "lauric acid fermentation broth containing lauryl diacid" in the following examples are all fermentation broths of lauryl diacid (DC12) produced by the production facilities of Ningxia Zhongke Biotechnology Co., Ltd.

[0179] Example 1: Lauric acid (DC12)

[0180] (1) Take 10L of DC12 fermentation broth (lauric acid content 140 g / L, initial pH value 7.2, color 420 Hazen, transmittance 22%) and place it in a 20 L jacketed reactor. Turn on the mechanical stirring (200 rpm). Slowly add 20% (mass fraction) NaOH aqueous solution until the pH value is 8.3, and continue stirring for 20 min to obtain a dark brown alkaline solution (sodium lauryl ester solution).

[0181] (2) The sodium lauryl salt solution was continuously separated and the bacterial cells were removed by a disc centrifuge (5000g, ALFALAVAL model), and then filtered through a 5 μm microporous precision filter to obtain 9.2 L of clear filtrate (turbidity 12 NTU, transmittance 75%).

[0182] (3) The clarified filtrate was heated to 80°C, and under stirring at 200 rpm, an air / ozone mixture (8% O3 volume fraction, generated by an industrial ozone generator and diluted with air) was bubbled into the bottom of the reactor through a microporous titanium rod distributor with a pore size of 20 μm. The gas flow rate was 1.0·min -1 ·L-1 (Fluoride volume), maintain the reaction temperature at 80℃ for 1.5 hours. After the reaction is complete, turn off the gas to obtain a colorless to very pale yellow purified sodium lauryl dichloride solution (color 18 Hazen).

[0183] (4) Insert the ultrasonic oscillator (28KHz) below the liquid surface, maintain the solution temperature at 75℃, and slowly and uniformly add 30% (mass fraction) sulfuric acid aqueous solution (addition rate 0.15L·min). -1 The pH was adjusted to 4.0, and after the addition was complete, stirring was continued for 30 minutes for aging to allow the lauryl diacid crystals to grow fully. The crystal slurry was centrifuged (3000 g, 10 min) to obtain wet crystals, which were washed twice with 60℃ hot water (each time using water equal to the mass of the wet crystals). The crystals were then dried to constant weight at 85℃ and a vacuum of -0.09 MPa to obtain 1.28 kg of purified DC12 product (91.4% yield based on fermentation broth; 96.2% yield based on crude dicarboxylic acid). Product testing: purity 99.58% (HPLC), color 9 Hazen, thermal stability 28 Hazen, Fe 2.8 ppm, Na 28 ppm, total metals 12 ppm, total nitrogen 48 ppm, sulfate 35 ppm, protein residue absorbance 0.02.

[0184] Example 2

[0185] The process is basically the same as in Example 1, except that in step (3), while introducing the air / ozone mixture, FeCl3·6H2O (Fe...) is added to the clarified filtrate. 3+ Add 20 ppm), and install a 254 nm UV lamp (power density 2 W·L) outside the reactor. -1 Irradiate the clarified filtrate.

[0186] 1.27 kg of refined DC12 product was obtained. Product testing results: purity 99.72% (HPLC), color 5 Hazen, thermal stability 20 Hazen, Fe 4.2 ppm, Na 25 ppm, total metals 15 ppm, total nitrogen 42 ppm, sulfate 28 ppm, protein residue absorbance 0.01.

[0187] Fe 3+ +UV synergistic catalysis increases the rate at which ozone is converted into ·OH radicals in the liquid phase by approximately 4 times, thereby enhancing the oxidative degradation ability of pigments; Fe 3+ Reduced to Fe by ultraviolet light 2+ It can then be re-oxidized to Fe by ozone. 3+ , forming a catalytic cycle, Fe 3+The actual consumption is low, and it can be effectively removed through final acidification precipitation and hot water washing, without affecting the Fe index of the product.

[0188] Example 3:

[0189] It is basically the same as Example 1, except that:

[0190] In step (1), 10L of DC12 fermentation broth was used (lauric acid content 138 g / L, initial pH value 7.0, color 520 Hazen, cell dry weight 42 g / L).

[0191] In step (2), after obtaining 9.0 L of clear filtrate, 90 g of activated carbon (1.0% of the filtrate mass) is added to the clear filtrate, and the mixture is stirred at 70℃ for 20 min for pre-decolorization. Then, the activated carbon is removed by fine filtration through a 5 μm microporous precision filter to obtain 8.85 L of pre-decolorized filtrate (color 220 Hazen).

[0192] In step (3), the pre-decolorized filtrate is heated to 80°C, and an air / ozone mixture (O3 volume fraction 10%) is introduced at a flow rate of 1.2 min. -1 ·L -1 The reaction takes 2 hours.

[0193] In step (4), 1.24 kg of refined DC12 product was obtained. Product testing results: purity 99.55% (HPLC), color 8 Hazen, thermal stability 25 Hazen, Fe 3.0 ppm, Na 30 ppm, total nitrogen 50 ppm.

[0194] For fermentation broths with high color and high impurities, adding an activated carbon pre-decolorization process after solid-liquid separation can reduce ozone consumption in the subsequent ozonation step by about 30% and improve the color stability of the final product.

[0195] Example 4: Sebacic acid (DC10)

[0196] (1) Take 10 L of DC10 fermentation broth (sebacic acid content 130 g / L, initial pH value 7.3, color 380 Hazen) and place it in a 20 L jacketed reactor. Turn on the mechanical stirring (200 rpm). Slowly add 20% (mass fraction) NaOH aqueous solution until the pH value is 8.2, and continue stirring for 25 min to obtain sodium sebacic acid solution.

[0197] (2) The sodium sebacate solution was continuously separated and the bacterial cells were removed by a disc centrifuge, and then filtered through a 5 μm microporous precision filter to obtain 9 L of clear filtrate.

[0198] (3) The clarified filtrate was heated to 78°C, and under stirring at 200 rpm, an air / ozone mixture (O3 volume fraction 6%) was bubbled into the bottom of the reactor through a microporous titanium rod distributor with a pore size of 20 μm. The gas flow rate was 1.2 min. -1 ·L -1 (Fluoride volume), maintain the reaction temperature for 2 hours. After the reaction is complete, turn off the gas to obtain a purified sodium sebacic acid solution.

[0199] (4) Insert the ultrasonic oscillator (28KHz) below the liquid surface, maintain the solution temperature at 75℃, and slowly and uniformly add 30% (mass fraction) sulfuric acid aqueous solution (addition rate 0.15L·min). -1 The pH was adjusted to 4.0, and after the addition was complete, stirring was continued for 30 minutes for aging to allow the sebacic acid crystals to grow fully. The crystal slurry was centrifuged (3000 g, 10 min) to obtain wet crystals, which were washed twice with 60°C hot water (each time using water equal to the mass of the wet crystals). The crystals were then dried to constant weight at 85°C and a vacuum of -0.09 MPa to obtain 1.16 kg of purified DC10 product. Product testing: purity 99.52% (HPLC), color 11 Hazen, thermal stability 26 Hazen, Fe 3.0 ppm, Na 30 ppm, total nitrogen 52 ppm, sulfate 32 ppm.

[0200] Example 5: Tetradecanoic acid (DC14)

[0201] (1) Take 10 L of DC14 fermentation broth (tetradecanoic acid content 125 g / L, initial pH value 7.1, color 160 Hazen), place it in a 20 L jacketed reactor, and turn on mechanical stirring (200 rpm). Slowly add 20% (mass fraction) KOH aqueous solution until the pH value is 8.4, and continue stirring for 30 min to obtain a potassium tetradecanoic acid solution.

[0202] (2) The potassium tetradecanoate solution was continuously separated and the bacterial cells were removed by disc centrifugation, and then filtered through a 3 μm microporous precision filter to obtain 8.8 L of clear filtrate.

[0203] (3) The clarified filtrate was heated to 82°C and stirred at 200 rpm. An air / ozone mixture (O3 volume fraction 10%) was bubbled into the bottom of the reactor through a microporous titanium rod distributor with a pore size of 20 μm. The gas flow rate was 0.8 min. -1 ·L -1 (Fluoride volume), maintain the reaction temperature for 2.5 hours. After the reaction is complete, turn off the gas to obtain a purified potassium tetradecanoate solution.

[0204] (4) Insert the ultrasonic oscillator (28KHz) below the liquid surface, maintain the solution temperature at 75℃, and slowly and uniformly add 30% (mass fraction) sulfuric acid aqueous solution (addition rate 0.15 L·min). -1 The pH was adjusted to 3.9, and after the addition was complete, stirring was continued for 40 minutes for aging to allow the tetradecanoic acid crystals to grow fully. The crystal slurry was centrifuged (3000 g, 10 min) to obtain wet crystals, which were washed twice with 60°C hot water (each time using water equal to the mass of the wet crystals). The crystals were then dried to constant weight at 90°C and a vacuum of -0.09 MPa to obtain 1.10 kg of purified DC14 product. Product testing: purity 99.48% (HPLC), color 12 Hazen, thermal stability 30 Hazen, Fe 3.5 ppm, K 35 ppm, total nitrogen 58 ppm, sulfate 38 ppm.

[0205] Example 6: Azelaic acid (DC9)

[0206] (1) Take 10 L of DC9 fermentation broth (azelaic acid content 135 g / L, initial pH value 7.4, color 360 Hazen), place it in a 20 L jacketed reactor, and turn on mechanical stirring (200 rpm). Slowly add 20% (mass fraction) NaOH aqueous solution until the pH value is 8.1, and continue stirring for 15 min to obtain sodium azelaic acid solution.

[0207] (2) The sodium azelate solution was continuously separated and the bacterial cells were removed by a disc centrifuge, and then filtered through a 5 μm microporous precision filter to obtain 9.1 L of clear filtrate.

[0208] (3) The clarified filtrate was heated to 80°C, and under stirring at 200 rpm, an air / ozone mixture (O3 volume fraction 6%) was bubbled into the bottom of the reactor through a microporous titanium rod distributor with a pore size of 20 μm. The gas flow rate was 1.0·min. -1 ·L -1 (Fluoride volume), maintain the reaction temperature for 1.5 hours. After the reaction is complete, turn off the gas to obtain a purified sodium azelate solution.

[0209] (4) Insert the ultrasonic oscillator (35KHz) below the liquid surface to maintain the solution temperature at 75℃, and slowly and uniformly add 25% (mass fraction) sulfuric acid aqueous solution (addition rate 0.15 L·min). -1The pH was adjusted to 4.1, and after the addition was complete, stirring was continued for 25 minutes for aging to allow the sebacic acid crystals to grow fully. The crystal slurry was centrifuged (3000 g, 10 min) to obtain wet crystals, which were washed twice with 55°C hot water (each time using water equal to the mass of the wet crystals). The crystals were then dried to constant weight at 80°C and a vacuum of -0.09 MPa to obtain 1.18 kg of purified DC9 product. Product testing: purity 99.55% (HPLC), color 10 Hazen, thermal stability 24 Hazen, Fe 2.5 ppm, Na 22 ppm, total nitrogen 45 ppm.

[0210] Example 7: Mixed system of undecanoic acid (DC11) and octadecanoic acid (DC18)

[0211] (1) Take 10 L of DC11 / DC18 mixed fermentation broth (DC11 content 80 g / L + DC18 content 50 g / L, initial pH value 7.2, color 480 Hazen), place it in a 20 L jacketed reactor, and turn on mechanical stirring (200 rpm). Slowly add 20% (mass fraction) NaOH aqueous solution until the pH value is 8.3, and continue stirring for 25 min to obtain a mixed diacid sodium salt solution.

[0212] (2) The mixed sodium diacid solution was continuously separated and the bacterial cells were removed by a disc centrifuge, and then filtered through a 5 μm microporous precision filter to obtain 9.0 L of clear filtrate.

[0213] (3) The clarified filtrate was heated to 82°C, and under stirring at 200 rpm, an air / ozone mixture (8% O3 volume fraction) was bubbled into the bottom of the reactor through a microporous titanium rod distributor with a pore size of 20 μm. The gas flow rate was 1.0·min. -1 ·L -1 (Fluoride volume), maintain the reaction temperature for 2 hours. After the reaction is complete, turn off the gas to obtain a purified sodium diisocyanate solution.

[0214] (4) Insert the ultrasonic oscillator (28 kHz) below the liquid surface, maintain the solution temperature at 75°C, and slowly and uniformly add 30% (mass fraction) sulfuric acid aqueous solution (addition rate 0.15 L·min). -1The pH was adjusted to 4.0, and after the addition was complete, stirring was continued for 40 minutes for aging to allow the mixed diacid crystals to grow fully. The crystal slurry was centrifuged (3000 g, 10 min) to obtain wet crystals, which were washed three times with 60°C hot water (each time using water equal to the mass of the wet crystals). The mixture was then dried to constant weight at 90°C and a vacuum of -0.09 MPa to obtain 1.21 kg of purified DC11 / DC18 mixed product (DC11 61.5%, DC18 38.5%). Product testing: purity 99.46% (HPLC), color 13 Hazen, thermal stability 32 Hazen, Fe 3.2 ppm, Na 32 ppm, total nitrogen 60 ppm.

[0215] Example 8

[0216] It is basically the same as Example 1, except that in step (3), the volume fraction of O3 is 30%.

[0217] Example 9

[0218] It is basically the same as Example 1, except that in step (3), ozone is directly introduced, that is, the volume fraction of O3 is 100%.

[0219] Comparative Example 1

[0220] It is basically the same as Example 1, except that:

[0221] In step (1), take 10 L of the same batch of DC12 fermentation broth, slowly add 30% (mass fraction) NaOH aqueous solution until the pH value is 12, and continue stirring for 30 min (the amount of NaOH used is about 4.5 times that of Example 1).

[0222] Step (2) omitted;

[0223] In step (3), an oxygen / ozone mixture (8% O3 volume fraction) is introduced and reacted for 2.5 hours;

[0224] In step (4), the pH was adjusted to 3.5 using 31% (mass fraction) HCl; finally, 1.18 kg of purified DC12 was obtained. Product testing: purity 99.05% (HPLC), color 25 Hazen, thermal stability 65 Hazen, Fe 7 ppm, Na 105 ppm, Cl - 180 ppm, total nitrogen 145 ppm.

[0225] Compared with Example 1, the strong base ozonation method in Comparative Example 1 used 4.5 times more alkali and produced more Na. + The residue was 3.75 times higher, the total nitrogen content was 3.0 times higher, the color was 2.78 times lower, and the yield decreased by 5.2 percentage points. Furthermore, due to acidification with HCl, Cl...- The residue was as high as 180 ppm, which adversely affected the stability of the downstream PA1212 polymerization reaction.

[0226] Comparative Example 2

[0227] It is basically the same as Example 1, except that:

[0228] In step (1), take 10 L of the same batch of DC12 fermentation broth, slowly add 30% (mass fraction) NaOH aqueous solution until the pH value is 12, and continue stirring for 30 min;

[0229] Step (2) is the same as step (2) in Example 1;

[0230] In step (3), the clarified filtrate is heated to 75°C, and 18 g of KMnO4 (equivalent to 1.3% of the mass of lauryl iodide) is added. The reaction is carried out for 1.5 hours. NaHSO3 is added to reduce the excess KMnO4 to MnO2 precipitate, and MnO2 is removed by filtration.

[0231] In step (4), the pH was adjusted to 3.5 using 31% (mass fraction) HCl; finally, 1.15 kg of purified DC12 product was obtained. Product testing: purity 99.10% (HPLC), color 22 Hazen, thermal stability 58 Hazen, Fe 6 ppm, Mn 35 ppm, Na 95 ppm, Cl - 165 ppm, total nitrogen 130 ppm.

[0232] The residual Mn in the product of Comparative Example 2 was as high as 35 ppm, far exceeding the requirement of Mn≤5ppm for polymer-grade raw materials; MnO2 sludge treatment burden was heavy and NaHSO3 consumption was high, with the total operating cost being about 1.6 to 1.8 times that of this application.

[0233] The product performance testing methods for each embodiment and comparative example purification are shown in Table 2.

[0234] Table 2

[0235]

[0236] The performance of the purified products from each embodiment and comparative example is shown in Table 3.

[0237] Table 3

[0238]

[0239] The purification method for long-chain dicarboxylic acids described in this application has been successfully pilot-scale verified on a 5000 t / a long-chain dicarboxylic acid production facility of Ningxia Zhongke Biotechnology Co., Ltd. Pilot-scale data shows that, using the method described in Example 1, step (1) adjusts the pH of the long-chain dicarboxylic acid fermentation broth to 8.3, and step (3) raises the temperature to 80°C, sets the O3 volume fraction to 8%, and the gas flow rate to 1.0·min⁻¹. -1 ·L -1 Under the condition of 1.5h reaction, the key indicators of DC12 product, such as purity, color, thermal stability, metal residue, and total nitrogen, stably meet the requirements of polymer-grade long-chain nylon raw materials. Compared with the strong base ozonation refining process of Comparative Example 1, the comprehensive refining cost per unit product is reduced by about 28%, and compared with the potassium permanganate oxidation refining process of Comparative Example 2, the comprehensive refining cost per unit product is reduced by about 45%.

[0240] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0241] The embodiments described above are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A method for purifying a long-chain dicarboxylic acid, characterized in that, Includes the following steps: The pH of the long-chain dicarboxylic acid fermentation broth was adjusted to 8.0-8.5 to prepare an alkaline dicarboxylic acid salt solution. The alkaline dibasic acid salt solution is subjected to a first solid-liquid separation. The liquid phase obtained from the solid-liquid separation is mixed with an oxidant and subjected to oxidation treatment to prepare an oxidized dibasic acid salt solution; the oxidant includes ozone. The dicarboxylate solution is subjected to acidification treatment and a second solid-liquid separation in sequence.

2. The purification method for long-chain dicarboxylic acids as described in claim 1, characterized in that, The oxidant is a mixture of gases containing ozone, and the oxidation treatment satisfies at least one of the following conditions: (1) The volume fraction of ozone in the mixed gas is 2% to 30%; optionally, the volume fraction of ozone in the mixed gas is 2% to 18%. (2) The mixed gas is selected from a mixture of ozone and air, a mixture of ozone, oxygen and inert gas, or a mixture of ozone, oxygen and carbon dioxide. (3) The oxidation treatment temperature is 75℃~85℃; (4) The oxidation treatment time is 0.5 h to 4 h.

3. The purification method for long-chain dicarboxylic acids as described in claim 2, characterized in that, The oxidation process of mixing the liquid phase and the oxidant includes: The liquid phase is heated to the oxidation treatment temperature, and the mixed gas is introduced to perform the oxidation treatment; the flow rate of the mixed gas is 0.2 L·min. -1 ·L -1 ~3.0 L·min -1 ·L -1 .

4. The purification method for long-chain dicarboxylic acids according to any one of claims 1 to 3, characterized in that, The oxidation treatment also satisfies at least one of the following conditions: (1) The step of mixing the liquid phase and the oxidant further includes: adding a transition metal catalyst; the transition metal ions in the transition metal catalyst include Co. 2+ Ni 2+ Fe 3+ Mn 2+ and Cu 2+ At least one of them; (2) The oxidation process further includes: subjecting the reaction solution of the oxidation process to ultraviolet irradiation treatment.

5. The purification method for long-chain dicarboxylic acids as described in claim 4, characterized in that, The oxidation treatment also satisfies at least one of the following conditions: (1) The concentration of the transition metal catalyst in the mixed solution is 5 ppm to 50 ppm; (2) The ultraviolet light wavelength of the ultraviolet irradiation treatment is 185 nm to 400 nm, and the power density is 0.5 W·L. -1 ~5W·L -1 .

6. The purification method for long-chain dicarboxylic acids according to any one of claims 1 to 3 and 5, characterized in that, Prior to the oxidation treatment, the liquid phase is further subjected to a decolorization treatment.

7. The purification method for long-chain dicarboxylic acids as described in claim 6, characterized in that, The decolorization process includes activated carbon decolorization, which satisfies at least one of the following conditions: (1) The amount of activated carbon used in the activated carbon decolorization treatment is 0.1% to 2% of the mass of the liquid phase; (2) The temperature of the activated carbon decolorization treatment is 60℃~80℃ and the time is 10 min~30 min.

8. The purification method for long-chain dicarboxylic acids according to any one of claims 1 to 3, 5, and 7, characterized in that, The acidification treatment includes: The dicarboxylate solution is heated to 60℃~85℃, and the pH value of the dicarboxylate solution is adjusted to 3.8~4.2 using an acid solution; Optionally, the acidification treatment satisfies at least one of the following conditions: (1) Adjusting the pH value of the dicarboxylate solution includes: adding the acid solution to the dicarboxylate solution under ultrasonic treatment conditions, wherein the frequency of ultrasonic treatment is 20 kHz to 40 kHz; (2) The acid solution includes a sulfuric acid solution, wherein the mass fraction of the sulfuric acid solution is 10% to 50%.

9. The purification method for long-chain dicarboxylic acids according to any one of claims 1 to 3, 5, and 7, characterized in that, At least one of the following conditions must be met: (1) The pH value of the long-chain dicarboxylic acid fermentation broth is adjusted by using an alkaline regulator, wherein the alkaline regulator is selected from at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate and ammonia water; (2) The long-chain dicarboxylic acid is an α,ω-straight-chain saturated dicarboxylic acid with 9 to 18 carbon atoms.

10. A long-chain dicarboxylic acid, characterized in that, The long-chain dicarboxylic acid is prepared by the purification method according to any one of claims 1 to 9, wherein the long-chain dicarboxylic acid satisfies at least one of the following conditions: (1) The purity determined by HPLC normalization method is ≥99.5%; (2) The color of a long-chain dicarboxylic acid ethanol solution with a concentration of 10 g / 100 mL is ≤15 Hazen; (3) The color of the long-chain dicarboxylic acid ethanol solution prepared by heating at 250°C for 2 hours is ≤40 Hazen. (4) Under the conditions of 1cm optical path and 280nm, the residual absorbance of protein is ≤0.05; (5) Total metal content ≤ 20 ppm; (6) Fe content ≤ 5 ppm; (7) Sulfate content ≤100ppm.

Images