Methods for processing mixtures containing long-chain dicarboxylic acids, mixtures of long-chain dicarboxylic acids and dibutyl esters and their applications

Abstract

This invention provides a method for processing a mixture containing long-chain dicarboxylic acids, a mixture of long-chain dicarboxylic acids and dibutyl esters, and their applications. The processing method involves butyrating the mixture containing long-chain dicarboxylic acids to obtain a mixed dibutyl ester of long-chain dicarboxylic acids. This method effectively utilizes the mixture containing long-chain dicarboxylic acids discharged during the extraction and purification of long-chain dicarboxylic acids from fermentation broth, avoiding resource waste. The long-chain dicarboxylic acid dibutyl ester mixture obtained after butyration and purification has low color and can be directly applied to cold-resistant plasticizers, effectively improving the low-temperature flexibility of polymers. This method for processing mixtures containing long-chain dicarboxylic acids is suitable for large-scale industrial production, has low equipment requirements, is easy to operate, and solves the problem of treating and reusing waste products generated during the production of long-chain dicarboxylic acids, thus possessing economic value.

Description

Technical Field

[0001] This invention relates to a method for recycling and reusing mixtures containing long-chain dicarboxylic acids. Background Technology

[0002] Plasticizers generally refer to a class of high-boiling-point, low-volatility, miscible small-molecule substances that alter the mechanical properties of polymers. The main function of plasticizers is to weaken the secondary valence bonds between polymer molecules, i.e., van der Waals forces, thereby increasing the mobility of polymer molecular chains, reducing their crystallinity, and increasing their plasticity. This manifests as a decrease in the polymer's hardness, modulus, softening temperature, and embrittlement temperature, while increasing elongation, flexural strength, and toughness. Plasticizers can be high-boiling-point, non-volatile viscous liquids or low-melting-point solids, and generally do not chemically react with polymers.

[0003] Currently, phthalate plasticizers (such as dioctyl phthalate, DOP) are still widely used plasticizers in the domestic market, and the most critical factor contributing to this situation is their low price. While phthalates, as the main plasticizers, possess relatively good performance characteristics, their potential harm to human health and environmental pollution have been discovered in recent years. Various countries and regions have formulated a series of laws and regulations or introduced a series of policies to restrict their use in children's toys, medical plastics, food, and other fields. With increasingly stringent hygiene and safety requirements in China, the replacement of traditional plasticizers with new environmentally friendly plasticizers has become an inevitable trend. Currently, plasticizers are developing towards higher relative molecular weight, environmental friendliness, and easy degradation. In recent years, research on citrate esters, epoxy vegetable oil-based plasticizers, and polyol ester plasticizers, which can replace phthalate plasticizers, has made rapid progress, and the era of in-depth research and large-scale industrialization of green and environmentally friendly plasticizer products has arrived.

[0004] Long-chain dicarboxylic acids (LCDA), with the general structural formula HOOC-(CH2)n-COOH (n=8-16), abbreviated as DC10-DC18, are important organic intermediates widely used in chemical, light industry, pesticide, pharmaceutical, and new materials fields. Currently, the most common method for preparing LCDA involves fermenting long-chain alkanes, fatty acids, fatty acid esters, or fatty acid salts under specific microbial strains. The mixture containing LCDA discharged during the fermentation process is often discarded or stockpiled, resulting in resource waste. If the mixture containing LCDA is methylated, the methylated product is an intermediate requiring further processing such as alkaline hydrolysis or transesterification to generate the corresponding long-chain dicarboxylic mixed acids or esters of long-chain dicarboxylic mixed acids. Such processes are complex and costly. Therefore, research on esterification reactions (such as butyl esterification) for the conversion and reuse of mixtures containing long-chain dicarboxylic acids has more important practical significance. Summary of the Invention

[0005] This invention provides a method for processing mixtures containing long-chain dicarboxylic acids: the mixture containing long-chain dicarboxylic acids is butyrated to synthesize a mixture of dibutyl esters of long-chain dicarboxylic acids. This butyration technology is suitable for industrial production, not only solving the resource waste problem of mixtures containing long-chain dicarboxylic acids discharged during the industrial fermentation preparation of long-chain dicarboxylic acids, but also allowing the dibutyl ester mixture of long-chain dicarboxylic acids generated after the butyration reaction to be directly used in products such as cold-resistant plasticizers.

[0006] The present invention provides a method for processing a mixture containing a long-chain dicarboxylic acid, comprising the following steps: subjecting the mixture containing the long-chain dicarboxylic acid to a butyrylation reaction.

[0007] Furthermore, the method for processing the mixture containing the long-chain dicarboxylic acid includes the following steps:

[0008] (1) Mix the mixture containing long-chain dicarboxylic acid with n-butanol and catalyst evenly to carry out butylation reaction;

[0009] (2) Wash the product after the butyrylation reaction with an alkaline solution;

[0010] (3) Distillation and purification yields a mixture of long-chain dicarboxylic acid dibutyl esters.

[0011] The mixture containing long-chain dicarboxylic acids described in this invention may include: materials containing long-chain dicarboxylic acids discharged during the extraction and purification of long-chain dicarboxylic acids from fermentation broth, or the residue after most of the solvent has been recovered from the materials, or long-chain dicarboxylic acid precipitates accumulated over a long period of time in a long-chain dicarboxylic acid wastewater treatment plant.

[0012] The long-chain dicarboxylic acid fermentation broth refers to a fermentation broth obtained by microbial fermentation using alkanes, fatty acids, and their derivatives as substrates. The microorganisms only need to be able to oxidize the terminal methyl groups of alkanes, fatty acids, and fatty acid derivatives to carboxyl groups, generating long-chain dicarboxylic acids. The preferred microorganism is *Candida*. After fermentation, the substrate is essentially completely consumed.

[0013] The extraction and purification method of the long-chain dicarboxylic acid fermentation broth can be a method known in the art.

[0014] Those skilled in the art should understand that the "long-chain dicarboxylic acid" in the phrase "extracting and refining long-chain dicarboxylic acid from fermentation broth" refers to a long-chain dicarboxylic acid with the same carbon chain length as the fermentation substrate, and may also be referred to as the target long-chain dicarboxylic acid.

[0015] Furthermore, the mixture comprising long-chain dicarboxylic acids described in this invention includes:

[0016] (1) The crude long-chain dicarboxylic acid obtained from the fermentation broth of the long-chain dicarboxylic acid is dissolved in a solvent, and the remaining material after cooling and crystallization and separation of the long-chain dicarboxylic acid precipitate is obtained.

[0017] Or (2), the residue after most of the solvent has been recovered from the material described in (1);

[0018] Or (3), acidify and crystallize the fermentation broth of long-chain dicarboxylic acid, extract the acidified crystallization liquid with solvent, separate the liquid, cool and crystallize the organic phase containing long-chain dicarboxylic acid, and separate the remaining material after the long-chain dicarboxylic acid precipitate.

[0019] Or (4), the residue after most of the solvent has been recovered from the material described in (3);

[0020] Or (5) Long-chain dicarboxylic acid precipitate obtained from long-term sedimentation and accumulation in the wastewater treatment workshop.

[0021] Further, (1) the method of obtaining crude long-chain dicarboxylic acid from the fermentation broth of the long-chain dicarboxylic acid can be achieved by separating the precipitate after acidifying and crystallizing the fermentation broth of the long-chain dicarboxylic acid. The fermentation broth can be directly acidified and crystallized. Alternatively, before acidification and crystallization, the bacterial cells in the fermentation broth can be removed by centrifugation or membrane filtration to obtain a clear dicarboxylic acid solution. Whether to perform an activated carbon decolorization step before acidification and crystallization can be selected based on the condition of the clear dicarboxylic acid solution.

[0022] Furthermore, the separation method described in (1) or (3) includes centrifugation and / or filtration.

[0023] It can be understood that after recrystallization (1), most of the impurities in the crude long-chain dicarboxylic acid (including cell tissues of fermenting microorganisms, one or more pigments), and most of the acids other than the target long-chain dicarboxylic acid (including heteroacids and long-chain dicarboxylic acids with carbon chain lengths different from those of the fermentation substrate) are removed. These heteroacids include, but are not limited to, one or more compounds represented by the general formula R2-COOH, where R2 is CH3(CH2). n - (n = 8-16) dissolves in a solvent to separate from the target long-chain dicarboxylic acid. Since the recrystallization process involves first dissolving the crude long-chain dicarboxylic acid in a solvent and then cooling (preferably controlling the temperature below 50°C but above 20°C) to precipitate it, some of the target long-chain dicarboxylic acid remains dissolved in the solvent. The solvent containing impurities, miscellaneous acids, and long-chain dicarboxylic acids (including long-chain dicarboxylic acids with carbon chain lengths equal to and unequal to those of the fermentation substrate) is collectively referred to as the solvent mother liquor. The mixture containing long-chain dicarboxylic acids described in this invention can, for example, be the solvent mother liquor. It can also be the residue after recovering a large amount of solvent from the solvent mother liquor.

[0024] Furthermore, the recovery of the bulk solvent can be performed using methods known in the art, such as evaporation or distillation. Further, the solvent includes one or more of the following: water, alcohols, organic monocarboxylic acids, ketones, ethers, esters, and benzenes; more preferably, one of methanol, ethanol, isopropanol, n-butanol, acetic acid, acetone, diethyl ether, ethyl acetate, butyl acetate, and toluene.

[0025] Preferably, the "acidification crystallization" mentioned in (3) can be performed using hydrochloric acid and / or sulfuric acid. Preferably, the "acidification crystallization" is performed by adjusting the pH to a final value of 2-5 using acid. It should be understood that the fermentation broth can be directly subjected to acidification crystallization. Alternatively, before acidification crystallization, the bacterial cells in the fermentation broth can be removed by centrifugation or membrane filtration to obtain a dibasic acid solution. Depending on the condition of the dibasic acid solution, it can be selected whether to perform an activated carbon decolorization step before acidification crystallization.

[0026] According to any of the foregoing methods for processing a mixture containing a long-chain dicarboxylic acid, the mixture comprising at least: an effective acid, the effective acid including long-chain dicarboxylic acids (including long-chain dicarboxylic acids with a carbon chain length equal to that of the fermentation substrate and long-chain dicarboxylic acids with a carbon chain length unequal to that of the fermentation substrate). Further, the effective acid includes long-chain dicarboxylic acids and heteroacids.

[0027] Further, the mixture containing long-chain dicarboxylic acids includes: an effective acid and a pigment. Even further, the mixture containing long-chain dicarboxylic acids includes: an effective acid, cell tissue of fermenting microorganisms, and pigment. The mixture containing long-chain dicarboxylic acids may also include a very small amount of water. The pigment content is generally 1-20 wt%, where the percentage is the percentage of the dry matter of the mixture containing long-chain dicarboxylic acids. The cell tissue content is generally 1-20 wt%, where the percentage is the percentage of the dry matter of the mixture containing long-chain dicarboxylic acids.

[0028] Furthermore, the long-chain dicarboxylic acid in the effective acid is one or more compounds represented by the general formula HOOC-R1-COOH, wherein R1 is -(CH2). m -and 8≤m≤16;

[0029] Furthermore, the effective acid accounts for 30% to 90% of the mass percentage of the dry matter containing the long-chain dicarboxylic acid mixture. It is generally believed that a higher effective acid content is more beneficial to the processing method of the present invention. Generally, the effective acid content accounts for 50 wt% or more of the dry matter containing the long-chain dicarboxylic acid mixture; it can also be 55 wt% or more, 60 wt% or more, 65 wt% or more, 70 wt% or more, etc. Of course, it may also be less than 50 wt%.

[0030] Furthermore, the mass of the long-chain dicarboxylic acid in the effective acid is at least 0.1 times, preferably at least 0.5 times, and most preferably at least 1 times, the mass of the heteroacid. This mass ratio characteristic is one of the most important features distinguishing the mixture containing the long-chain dicarboxylic acid from the original long-chain dicarboxylic acid fermentation broth. The fermentation broth is primarily composed of long-chain dicarboxylic acids with the same carbon number as the substrate (their mass accounts for at least 90 wt% of the total acid mass).

[0031] Furthermore, during the butyl esterification reaction in step (1), n-butanol may be added.

[0032] Furthermore, a catalyst may be added during the butyration reaction in step (1).

[0033] According to any of the methods described above, the amount of n-butanol added is 0.2-3 times the mass of the effective acid, preferably 0.5-3 times, more preferably 1-3 times, and even more preferably 1-2 times.

[0034] According to the method described in any of the above embodiments, the catalyst comprises one or more of concentrated sulfuric acid, sodium bisulfate, p-toluenesulfonic acid, p-toluenesulfonic acid monohydrate, and tetrabutyl titanate; preferably, the catalyst comprises one or more of p-toluenesulfonic acid, p-toluenesulfonic acid monohydrate, and concentrated sulfuric acid; more preferably, the catalyst comprises p-toluenesulfonic acid monohydrate and concentrated sulfuric acid; even more preferably, the catalyst is p-toluenesulfonic acid monohydrate. Preferably, the concentrated sulfuric acid has a mass fraction ≥70%, more preferably ≥90%.

[0035] According to any of the methods described above, the total amount of the catalyst used is 1-10% of the effective acid mass, preferably 3-8%, more preferably 3-7%.

[0036] According to any of the methods described above, the temperature of the butyration reaction is 50-180°C; and / or the butyration time is 3-15 h.

[0037] Preferably, the temperature of the butyl esterification reaction is 80-150°C; and / or, the butyl esterification time is preferably 5-15 hours. More preferably, the temperature of the butyl esterification reaction is 100-130°C; and / or, the butyl esterification time is 7-13 hours. Controlling the butyl esterification temperature within a reasonable range can achieve better butyl esterification results; temperatures that are too low or too high are detrimental to the butyl esterification reaction. The temperature refers to the liquid phase temperature in the esterification equipment.

[0038] According to any of the methods described above, n-butanol is recovered before the product after the butyl esterification reaction is washed with an alkaline solution. The preferred method for recovering n-butanol is distillation. More preferably, it is vacuum distillation.

[0039] Furthermore, the temperature of the vacuum distillation is 50-180℃, preferably 80-160℃, and more preferably 100-150℃.

[0040] Furthermore, the pressure of the vacuum distillation is 1-10 kPa, preferably 2-8 kPa, and more preferably 2-5 kPa.

[0041] Furthermore, the time for vacuum distillation is 2-12 hours, preferably 3-10 hours, and more preferably 4-8 hours.

[0042] According to any of the methods described above, in step (2), the alkali in the alkaline solution includes one or more of sodium hydroxide, sodium bicarbonate, and sodium carbonate, preferably sodium bicarbonate or sodium carbonate, and more preferably sodium carbonate. The alkaline solution is preferably an aqueous solution of the above-mentioned alkalis.

[0043] Furthermore, the mass fraction of alkali in the alkaline solution is 1–20 wt%, preferably 3–10 wt%, and more preferably 4–6 wt%.

[0044] According to any of the above methods, in step (2), the number of times the alkaline solution is washed can be once, or twice or more.

[0045] According to any of the above methods, in step (2), when the alkaline washing ends, the acid value of the organic phase reaches below 2 mg KOH / g, which can be below 1.5 mg KOH / g, below 1 mg KOH / g, below 0.5 mg KOH / g, or below 0.3 mg KOH / g.

[0046] According to any of the above methods, in step (2), the temperature of the alkaline solution during washing is 0 to 100°C, preferably 50 to 95°C, and more preferably 70 to 90°C.

[0047] According to any of the above methods, in step (2), the alkaline washing time is 5-80 minutes, preferably 20-80 minutes.

[0048] Alkaline washing can remove catalysts, long-chain dicarboxylic acids and / or heteroacids that have not undergone butylation, and monobutyl esters of long-chain dicarboxylic acids.

[0049] According to any of the methods described above, step (2) further includes washing with saturated brine after washing with alkaline solution to remove any residual alkali in the organic phase. The saturated brine is preferably saturated saline solution.

[0050] According to any of the methods described above, the organic phase can be dried with anhydrous sodium sulfate before step (3) distillation purification to remove residual water.

[0051] According to any of the methods described above, the distillation in step (3) is vacuum distillation, preferably scraped film distillation, and more preferably molecular distillation.

[0052] Furthermore, the pressure of the main evaporator during molecular distillation is 10-1000 Pa, and / or the evaporation surface temperature of the main evaporator is 100-250 °C.

[0053] Furthermore, the condensation surface temperature of the main evaporator of the molecular distillation is -10 to 50°C, preferably -5 to 30°C, and more preferably -5 to 5°C.

[0054] Furthermore, the scraper rotation speed of the main evaporator of the molecular distillation is 200-400 rpm, preferably 250-350 rpm, and more preferably 290-310 rpm.

[0055] Furthermore, the feed inlet temperature of the molecular distillation apparatus is 20-100°C, preferably 25-60°C, and more preferably 25-40°C.

[0056] Furthermore, the molecular distillation includes the following steps:

[0057] (A) Control the pressure of the main evaporator to 300-1000 Pa. When the evaporation surface temperature of the main evaporator of the molecular distillation main evaporator is 100-160℃, collect fraction 1.

[0058] (B) Control the pressure of the main evaporator to 10-200 Pa. When the evaporation surface temperature of the molecular distillation main evaporator is 150-250 °C, collect fraction 2 to obtain a mixture of long-chain dicarboxylic acid dibutyl ester.

[0059] The fraction 1 collected in step (A) comprises butanol and butanol esters of heteroacids.

[0060] The fraction 2 collected in step (B) includes any of the following: C10-C18 long-chain dicarboxylic acid dibutyl esters.

[0061] Preferably, the pressure of the main evaporator in step (A) is 400-800 Pa, and / or the evaporation surface temperature of the main evaporator in step (A) is 130-160 °C;

[0062] More preferably, the pressure of the main evaporator of the molecular distillation in step (A) is 500-700 Pa, and / or the evaporation surface temperature of the main evaporator of the molecular distillation in step (A) is 140-160 °C.

[0063] Preferably, the pressure of the main evaporator of the molecular distillation in step (B) is 10-200 Pa, and / or the evaporation surface temperature of the main evaporator of the molecular distillation in step (B) is 160-220 °C;

[0064] More preferably, the pressure of the main evaporator of the molecular distillation in step (B) is 50-150 Pa, and / or the evaporation surface temperature of the main evaporator of the molecular distillation in step (B) is 170-200 °C.

[0065] According to any of the methods described above, the mixture of long-chain dibutyl diacids is a mixture of any of several dibutyl diacids having 10-18 carbon atoms.

[0066] According to any of the methods described above, the mixture containing the long-chain dicarboxylic acid is dried prior to butylation. The drying process is carried out until the moisture content is below 5 wt%, preferably below 3 wt%.

[0067] Furthermore, the drying temperature is 80-130°C, preferably 90-120°C, and more preferably 110°C.

[0068] Furthermore, the drying time is 1-8 hours, preferably 2-5 hours, and more preferably 2.5-4 hours.

[0069] Before step (1), the mixture containing long-chain dicarboxylic acids is dried. The main purpose of drying is to remove water that may be present in the mixture containing long-chain dicarboxylic acids, thereby increasing the esterification rate during the butyl esterification process.

[0070] The present invention also provides a mixture of dibutyl long-chain dicarboxylic acids, which is prepared by the treatment method of the mixture containing long-chain dicarboxylic acids in the extraction and purification process of long-chain dicarboxylic acid fermentation broth as described in any of the above claims.

[0071] This invention also provides a mixture of long-chain dicarboxylic acid dibutyl esters and its application in cold-resistant plasticizers. The applicable polymers include various resins such as polyvinyl chloride, nitrocellulose, ethyl cellulose, and synthetic rubber. It is particularly suitable for manufacturing cold-resistant wire and cable materials, cling film, artificial leather, films, conveyor belts, sheets, and plates. The long-chain dicarboxylic acid dibutyl ester mixture can be used in combination with any one or more of phthalate plasticizers, vegetable oil-based plasticizers, and polyester plasticizers. Further, the phthalate plasticizers include dioctyl phthalate (DOP) and dibutyl phthalate (DBP). The vegetable oil-based plasticizers include plasticizers synthesized from natural oils (such as castor oil, soybean oil, etc.) and fatty acids (mainly octadecanoic acid fatty acids) obtained from glycerol processing. The polyester plasticizers include linear polymers obtained by polycondensation reaction of diols or polyols with diacids or polyacids.

[0072] The beneficial effects of this invention are at least as follows:

[0073] 1. A mixture containing long-chain dicarboxylic acids, after butylation and purification, yields a mixture of dibutyl esters of long-chain dicarboxylic acids with low color, which can be directly applied to cold-resistant plasticizers, effectively improving the low-temperature flexibility of polymers. The mixture containing long-chain dicarboxylic acids discharged during the extraction and purification of long-chain dicarboxylic acids from the fermentation broth is effectively utilized, avoiding waste.

[0074] 2. The method for treating mixtures containing long-chain dicarboxylic acids during the extraction and refining process of long-chain dicarboxylic acid fermentation broth of the present invention is suitable for large-scale industrial production, has low equipment requirements, is easy to operate, solves the problem of waste treatment and reuse in the production process of long-chain dicarboxylic acids, and has economic value. Detailed Implementation

[0075] Acid value determination: The cold solvent method in GB / T5530-2005 "Determination of Acidity and Acid Value of Animal and Vegetable Oils" was adopted.

[0076] Gas chromatography: A Shimadzu GC-2014 gas chromatograph from Shimadzu Corporation of Japan was used.

[0077] Platinum-cobalt colorimetry: Colorimetry was determined using the platinum-cobalt method according to GB / T 3143.

[0078] Plastic weight loss and thermal stability test: The test shall be conducted in accordance with BG / T2951.7-1997 "Plastic weight loss and thermal stability test method".

[0079] Impact embrittlement temperature test: The test shall be conducted in accordance with GB / 5T470-1985 "Plastics Impact Embrittlement Temperature Test Method".

[0080] Drying equipment: DHG-9240A electric thermostatic drying oven from Shanghai Jinghong Experimental Equipment Co., Ltd.

[0081] Molecular distillation equipment: The equipment used is the German VTA laboratory-type molecular distillation equipment (VKL70-5) and the Tianjin Junge Molecular Distillation Equipment Co., Ltd. FZL-15 production-type molecular distillation equipment.

[0082] Scraped distillation equipment: The DEA-BM-10 experimental scraped film evaporator from Shanghai Deda Tianyi Equipment Co., Ltd. was adopted.

[0083] XG-C Type Thermal Aging Test Chamber: Jiangsu Qidong County Test Instrument Factory

[0084] The mixture containing long-chain dicarboxylic acids discharged during the extraction and purification of DC10-DC18 fermentation broth includes:

[0085] (1) The crude product of DC10-DC18 obtained from the fermentation broth of DC10-DC18 is dissolved in a solvent, and the remaining material after cooling and crystallization and separation of DC10-DC18 precipitate is obtained.

[0086] Or (2), the residue after most of the solvent has been recovered from the material described in (1);

[0087] Or (3), acidify and crystallize the fermentation broth of DC10-DC18, extract the acidified crystallization liquid with solvent, separate the liquid, cool and crystallize the organic phase containing DC10-DC18, and separate the remaining material after the DC10-DC18 precipitation.

[0088] Or (4), the residue after most of the solvent has been recovered from the material described in (3);

[0089] Or (5) DC10-DC18 precipitate obtained from long-term sedimentation accumulation in the long-chain dicarboxylic acid wastewater treatment workshop.

[0090] The DC10-DC18 fermentation broth refers to a fermentation broth obtained by microbial fermentation using alkanes, fatty acids, and their derivatives with 10-18 carbon atoms as substrates. The microorganisms only need to be able to oxidize the terminal methyl groups of alkanes, fatty acids, and fatty acid derivatives to carboxyl groups, generating DC10-DC18.

[0091] Further, (1) the method for obtaining crude DC10-DC18 from the fermentation broth of DC10-DC18 is to separate the precipitate of DC10-DC18 after acidification and crystallization of the fermentation broth of DC10-DC18, thereby obtaining crude long-chain dicarboxylic acid. The fermentation broth can be directly acidified and crystallized. Alternatively, before acidification and crystallization, the bacterial cells in the fermentation broth can be removed by centrifugation or membrane filtration to obtain a clear dicarboxylic acid solution. Whether to perform an activated carbon decolorization step before acidification and crystallization can be selected based on the condition of the clear dicarboxylic acid solution.

[0092] The separation method described in (1) or (3) is centrifugation and / or filtration.

[0093] After recrystallization (1), most of the impurities in the crude long-chain dicarboxylic acid (one or two of the cell tissues and pigments of the fermenting microorganisms) and most of the acids other than the target long-chain dicarboxylic acid (including heteroacids and long-chain dicarboxylic acids with carbon chain lengths different from those of the fermentation substrate) are removed. The heteroacids include one or more compounds represented by the general formula R2-COOH, wherein R2 is CH3(CH2). n - (n = 8-16). Dissolves in a solvent to separate from the target long-chain dicarboxylic acid. Since the recrystallization process involves first dissolving the crude long-chain dicarboxylic acid in a solvent and then cooling (preferably controlling the temperature below 50°C but above 20°C) to precipitate it, some of the target long-chain dicarboxylic acid remains dissolved in the solvent. The solvent containing impurities, miscellaneous acids, and long-chain dicarboxylic acids (including long-chain dicarboxylic acids with the same carbon chain length as the fermentation substrate and long-chain dicarboxylic acids with different carbon chain lengths) is collectively referred to as the solvent mother liquor. The mixture containing long-chain dicarboxylic acids described in this invention can, for example, be a solvent mother liquor.

[0094] (3) The “acidification crystallization” mentioned uses hydrochloric acid and / or sulfuric acid. The “acidification crystallization” is to adjust the pH to 2-5 with acid to crystallize DC10-DC18.

[0095] The above-mentioned recovery of large quantities of solvent is carried out by evaporation or distillation. The solvents include any one of methanol, ethanol, isopropanol, n-butanol, acetic acid, acetone, diethyl ether, ethyl acetate, butyl acetate, and toluene.

[0096] Example 1: Extraction and purification of fermentation broth from DC10-DC18

[0097] Includes the following steps:

[0098] (1) Extraction: Heat any one of the fermentation broths of DC10-DC18 to 60-100℃, centrifuge to remove the cells, add 0.05-5% (by volume of the clear liquid) of activated carbon to the clear liquid for decolorization, filter to remove the activated carbon, heat the decolorized liquid to 50-100℃, adjust the pH to 3-4 for acidification and crystallization, separate, and obtain the crude product of DC10-DC18;

[0099] (2) Dissolve the crude DC10-DC18 in an acetic acid solution with a mass fraction of more than 90%, decolorize with activated carbon or not, cool down to crystallize, separate, and obtain DC10-DC18 product and solvent mother liquor.

[0100] (3) Acetic acid in the mother liquor is recovered and reused via a distillation column. The bottom product of the column is a mixture containing long-chain dicarboxylic acids. In the dry matter of the mixture, the content of the pigment is generally 1-20 wt%, and the content of cell tissue is generally 1-20 wt%.

[0101] Example 2: Extraction and purification of fermentation broth from DC10-DC18

[0102] Includes the following steps:

[0103] (1) Extraction: Heat any one of the fermentation broths of DC10-DC18 to 60-100℃, centrifuge to remove the cells, add 0.05-5% (by volume of the clear liquid) of activated carbon to the clear liquid for decolorization, filter to remove the activated carbon, heat the decolorized liquid to 50-100℃, and then adjust the pH to 3-4 for acidification and crystallization to obtain crude DC10-DC18.

[0104] (2) The crude DC10-DC18 product is extracted with methanol to obtain the DC10-DC18 product. The water in the residue is recovered, resulting in a mixture containing long-chain dicarboxylic acids. In the dry matter of the mixture, the content of the pigment is generally 1-20 wt%, and the content of cell tissue is generally 1-20 wt%.

[0105] Example 1

[0106] The fermentation broth of DC12 (docosahexacarboxylic acid) was taken, and after extracting and purifying DC12, the mixture containing long-chain dicarboxylic acids (Example 1 of extraction and purification) was dried at 110°C to a water content of 1 wt%, yielding 1.626 kg of dry matter. The effective acid content in the dry matter was 81.34 wt%, the content of long-chain dicarboxylic acids (composed of DC10, DC11, DC12, DC13, DC14 and DC15) was 71.76%, and the content of miscellaneous acids was 9.58%. The mass ratio of long-chain dicarboxylic acids to miscellaneous acids was 7.5:1.

[0107] The above-mentioned dry matter was added to a 5L reactor, along with 1.25 kg of n-butanol and 58 g of p-toluenesulfonic acid monohydrate. Esterification was carried out under reflux at a liquid phase temperature of 120°C for 5 hours. 460 g of a mixture of n-butanol and water was separated, and the esterification rate was determined to be 60.2% by acid value analysis. 500 g of n-butanol was added, and esterification was continued under reflux at 120°C for 3 hours. 348 g of a mixture of n-butanol and water was separated, and the esterification rate was calculated by acid value analysis.

[0108] Unreacted n-butanol was recovered by vacuum distillation at a vacuum of 2 kPa and a liquid phase temperature of 130 °C for 4 hours.

[0109] Under conditions maintained at 85℃, 300g of a 5.65wt% sodium carbonate aqueous solution was added to the organic phase remaining after vacuum distillation, and the mixture was stirred for 25 minutes. The mixture was then allowed to stand and separate into layers at 85℃, with the lower aqueous phase being separated. The alkaline washing process was repeated: the organic phase was washed again with 300g of a 5.65wt% sodium carbonate aqueous solution while maintaining the temperature at 85℃. The acid value of the organic phase was measured to be 0.15mgKOH / g. The mixture was then dried over anhydrous sodium sulfate and filtered to obtain a crude product of a dark brown long-chain dicarboxylic acid, dibutyl ester.

[0110] The crude mixture of the above-mentioned dark brown long-chain dicarboxylic acid dibutyl esters was distilled using a molecular distillation apparatus. Molecular distillation was performed under vacuum and increased temperature conditions, with the feed inlet temperature at 29°C, the main evaporator condensing surface temperature at 0°C, and the main evaporator scraper rotation speed at 295 rpm. Under vacuum conditions of 550 Pa and main evaporator evaporating surface temperature of 145°C, the feed rate was controlled at 1 kg / h, and 85 g of the low-boiling-point fraction was collected. Under vacuum conditions of 120 Pa and main evaporator evaporating surface temperature of 180°C, the feed rate was controlled at 0.5 kg / h, and the product fraction was collected as a light yellow oily substance, yielding 1.292 kg of a mixture of long-chain dicarboxylic acid dibutyl esters (composition: dibutyl sebacate, dibutyl undecanoate, dibutyl dodecanoate, dibutyl tridecanoate, dibutyl tetradecanoate, and dibutyl pentadecanoate). The mixture of long-chain dicarboxylic acid dibutyl esters was subjected to platinum-cobalt color and acid value determination.

[0111] Example 2

[0112] The fermentation broth of DC13 (decadecanoic acid) was taken, and after extracting and purifying DC13, the mixture containing long-chain dicarboxylic acids (Example 1 of extraction and purification) was dried at 110°C to a water content of 1 wt%, yielding 1.205 kg of dry matter, of which the effective acid content was 73.18 wt%, the long-chain dicarboxylic acid content was 62.35% (composed of DC11, DC12, DC13, DC14 and DC15), and the content of miscellaneous acids was 10.83%. The mass ratio of long-chain dicarboxylic acids to miscellaneous acids was 5.8:15.8:1.

[0113] The above-mentioned dry matter was added to a 5L reactor, along with 1.755 kg of n-butanol and 51 g of p-toluenesulfonic acid monohydrate. Esterification was carried out under reflux at a liquid phase temperature of 125℃ for 7 hours. A mixture of n-butanol and water was separated, and the esterification rate was calculated by measuring the acid value of the reaction solution.

[0114] Unreacted n-butanol was recovered by vacuum distillation at a vacuum of 3 kPa and a liquid phase temperature of 135 °C for 5 h.

[0115] The residual organic phase from vacuum distillation was then washed with alkaline water. While maintaining the liquid phase temperature at 90°C, 290 g of a 5.01 wt% sodium carbonate aqueous solution was added, and the mixture was stirred for 20 minutes. The mixture was allowed to stand at 90°C to separate into layers, and the lower aqueous phase was separated. The alkaline washing process was repeated: while maintaining the liquid phase temperature at 90°C, the organic phase was washed twice more with 290 g of a 5.01 wt% sodium carbonate aqueous solution. The acid value of the organic phase was measured to be 0.09 mg KOH / g. The organic phase was washed once with 300 g of saturated brine, then dried over anhydrous sodium sulfate and filtered to obtain a crude mixture of dark brown long-chain dicarboxylic acid dibutyl ester.

[0116] The crude mixture of the above-mentioned dark brown long-chain dicarboxylic acid dibutyl esters was purified by molecular distillation. Molecular distillation was performed under vacuum and increased temperature conditions: feed inlet temperature 35℃, main evaporator condenser surface temperature -5℃, and main evaporator scraper rotation speed 300 rpm. Under vacuum of 500 Pa and main evaporator evaporator surface temperature of 140℃, the feed rate was controlled at 1 kg / h, and 68 g of the low-boiling fraction was collected. Under vacuum of 130 Pa and main evaporator evaporator surface temperature of 190℃, the feed rate was controlled at 0.5 kg / h, and the product fraction, a light yellow oily substance, was collected, yielding 846 g of a mixture of long-chain dicarboxylic acid dibutyl esters (composed of undecanoic acid dibutyl ester, dodecadic acid dibutyl ester, tridecanoic acid dibutyl ester, tetradecanoic acid dibutyl ester, and pentadecanoic acid dibutyl ester). The mixture of long-chain dicarboxylic acid dibutyl esters was subjected to platinum-cobalt color and acid value analysis.

[0117] Example 3

[0118] The fermentation broth of DC11 (undecanoic acid) was extracted and purified. The mixture containing long-chain dicarboxylic acids (Example 1) was dried at 110°C to a water content of 1 wt%, yielding 1.931 kg of dry matter. The effective acid content in the dry matter was 78.04 wt%, the long-chain dicarboxylic acid content was 51.94% (composed of DC10, DC11, DC12, DC13, DC14, and DC15), and the heteroacid content was 26.1%. The mass ratio of long-chain dicarboxylic acids to heteroacids was 2:1.

[0119] The above-mentioned dry matter was added to a 5L reactor, along with 1.855 kg of n-butanol and 60 g of 98% concentrated sulfuric acid. Esterification was carried out under reflux at a liquid phase temperature of 118°C for 4 hours. A mixture of n-butanol and water was separated, and the esterification rate was determined to be 68.9% by acid value analysis. 700 g of n-butanol was added, and esterification was continued under reflux at 120°C for 3 hours. A mixture of n-butanol and water was separated, and the esterification rate was calculated by acid value analysis.

[0120] Unreacted n-butanol was recovered by vacuum distillation at a vacuum of 2.5 kPa and a liquid phase temperature of 132 °C for 5 h.

[0121] The residual organic phase from vacuum distillation was then washed with alkaline water. While maintaining the liquid phase temperature at 80°C, 400 g of a 4.78 wt% sodium carbonate aqueous solution was added, and the mixture was stirred for 30 minutes. The mixture was allowed to stand at 80°C to separate into layers, and the lower aqueous phase was separated. The alkaline washing process was repeated: while maintaining the liquid phase temperature at 80°C, the organic phase was washed again with 400 g of a 4.78 wt% sodium carbonate aqueous solution. The acid value of the organic phase was measured to be 0.19 mg KOH / g. The organic phase was then washed once with 400 g of saturated brine, dried over anhydrous sodium sulfate, and filtered to obtain a crude mixture of dark brown long-chain dicarboxylic acid dibutyl ester.

[0122] The crude mixture of the above-mentioned dark brown long-chain dicarboxylic acid dibutyl esters was purified by molecular distillation. Molecular distillation was performed under vacuum and increased temperature conditions, with the feed inlet temperature at 30°C, the main evaporator condenser surface temperature at 0°C, and the main evaporator scraper rotation speed at 305 rpm. Under vacuum conditions of 550 Pa and main evaporator evaporator surface temperature of 145°C, the feed rate was controlled at 1 kg / h, and 80 g of the low-boiling-point fraction was collected. Under vacuum conditions of 100 Pa and main evaporator evaporator surface temperature of 178°C, the feed rate was controlled at 0.5 kg / h, and 1.331 kg of the product fraction, a light yellow oily substance, was collected as a mixture of long-chain dicarboxylic acid dibutyl esters (composition: dibutyl sebacate, dibutyl undecanoate, dibutyl dodecanoate, dibutyl tridecanoate, dibutyl tetradecanoate, and dibutyl pentadecanoate). The mixture of long-chain dicarboxylic acid dibutyl esters was subjected to platinum-cobalt color and acid value determination.

[0123] Example 4

[0124] This is basically the same as Example 3, except that in this Example 4, 60g of p-toluenesulfonic acid monohydrate is used as the catalyst.

[0125] Example 5

[0126] The fermentation broth of DC12 (docosahexacarboxylic acid) was taken, and after extracting and purifying DC12, the mixture containing long-chain dicarboxylic acids (Example 1 of extraction and purification) was dried at 110°C to a water content of 1 wt%, yielding 1.811 kg of dry matter, of which the effective acid content was 74.97 wt%, the long-chain dicarboxylic acid content was 63.06% (composed of DC10, DC11, DC12, DC13, DC14 and DC15), and the content of miscellaneous acids was 11.91%. The mass ratio of long-chain dicarboxylic acids to miscellaneous acids was 5.3:1.

[0127] The above-mentioned dry matter was added to a 5L reactor, along with 1.785 kg of n-butanol and 40 g of p-toluenesulfonic acid monohydrate. Esterification was carried out under reflux at a liquid phase temperature of 120°C for 5 hours. 588 g of a mixture of n-butanol and water was separated, and the esterification rate was determined to be 58.9% by acid value analysis. Then, 600 g of n-butanol and 40 g of 98% concentrated sulfuric acid were added, and esterification was continued under reflux at 125°C for 3 hours. 495 g of a mixture of n-butanol and water was separated, and the esterification rate was calculated by acid value analysis.

[0128] Unreacted n-butanol was recovered by vacuum distillation at a vacuum of 2 kPa and a liquid phase temperature of 130 °C for 4 hours.

[0129] The residual organic phase from vacuum distillation was then washed with alkaline water. While maintaining the liquid phase temperature at 85°C, 350 g of a 5.46 wt% sodium carbonate aqueous solution was added, and the mixture was stirred for 25 minutes. The mixture was allowed to stand at 85°C to separate into layers, and the lower aqueous phase was separated. The alkaline washing process was repeated: while maintaining the liquid phase temperature at 85°C, the organic phase was washed twice more with 350 g of a 5.46 wt% sodium carbonate aqueous solution. The acid value of the organic phase was measured to be 0.05 mg KOH / g. The organic phase was washed once with 350 g of saturated brine, then dried over anhydrous sodium sulfate and filtered to obtain a crude mixture of dark brown long-chain dicarboxylic acid dibutyl ester.

[0130] The crude mixture of the above-mentioned dark brown long-chain dicarboxylic acid dibutyl esters was purified by molecular distillation. Molecular distillation was performed under vacuum and increased temperature conditions: feed inlet temperature 35℃, main evaporator condensation surface temperature 0℃, and main evaporator scraper rotation speed 300 rpm. Under vacuum of 550 Pa and main evaporator evaporation surface temperature of 145℃, the feed rate was controlled at 1 kg / h, and 67 g of the low-boiling fraction was collected. Under vacuum of 120 Pa and main evaporator evaporation surface temperature of 180℃, the feed rate was controlled at 0.5 kg / h, and the product fraction, a light yellow oily substance, was collected, yielding 1.465 kg of a mixture of long-chain dicarboxylic acid dibutyl esters (composed of dibutyl sebacate, dibutyl undecanoate, dibutyl dodecanoate, dibutyl tridecanoate, dibutyl tetradecanoate, and dibutyl pentadecanoate). The mixture of long-chain dicarboxylic acid dibutyl esters was subjected to platinum-cobalt color and acid value determination.

[0131] Example 6

[0132] The fermentation broth of DC10 (decapodic acid) was taken, and after extracting and purifying DC10, the mixture containing long-chain dicarboxylic acids (Example 1 of extraction and purification) was dried at 110°C to a water content of 1 wt%, yielding 1.536 kg of dry matter, of which the effective acid content was 53.03 wt%, the long-chain dicarboxylic acid content was 35.12% (composed of DC10, DC11, DC12, DC13, and DC14), and the content of miscellaneous acids was 17.91%. The mass ratio of long-chain dicarboxylic acids to miscellaneous acids was 2:1.

[0133] The above-mentioned dry matter was added to a 5L reactor, along with 1.2kg of n-butanol and 55g of p-toluenesulfonic acid monohydrate. Esterification was carried out under reflux at a liquid phase temperature of 120℃ for 5 hours. 401g of a mixture of n-butanol and water was separated, and the esterification rate was determined to be 55% by acid value testing. 490g of n-butanol was added, and esterification was continued under reflux at 120℃ for 3 hours. 308g of a mixture of n-butanol and water was separated, and the esterification rate was calculated by acid value testing.

[0134] Unreacted n-butanol was recovered by vacuum distillation at a vacuum of 2 kPa and a liquid phase temperature of 130 °C for 4 hours.

[0135] Under conditions maintained at 85℃, 300g of a 5.88wt% sodium carbonate aqueous solution was added to the organic phase remaining after vacuum distillation, and the mixture was stirred for 25 minutes. The mixture was then allowed to stand and separate into layers at 85℃, with the lower aqueous phase being separated. The alkaline washing process was repeated: the organic phase was washed again with 300g of a 5.88wt% sodium carbonate aqueous solution while maintaining the temperature at 85℃. The acid value of the organic phase was measured to be 0.12mgKOH / g. The mixture was then dried over anhydrous sodium sulfate and filtered to obtain a crude product of a dark brown long-chain dicarboxylic acid, dibutyl ester.

[0136] The crude mixture of the above-mentioned dark brown long-chain dicarboxylic acid dibutyl esters was distilled using a molecular distillation apparatus. Molecular distillation was performed under vacuum and increased temperature conditions: feed inlet temperature 32℃, main evaporator condensation surface temperature 0℃, and main evaporator scraper rotation speed 300 rpm. Under vacuum of 450 Pa and main evaporator evaporation surface temperature of 140℃, the feed rate was controlled at 1 kg / h, and 88 g of the low-boiling fraction was collected. Under vacuum of 100 Pa and main evaporator evaporation surface temperature of 178℃, the feed rate was controlled at 0.5 kg / h, and the product fraction, a light yellow oily substance, was collected, yielding 881 g of a mixture of long-chain dicarboxylic acid dibutyl esters (composed of dibutyl sebacate, dibutyl undecanoate, dibutyl dodecaate, dibutyl tridecanoate, and dibutyl tetradecanoate). The mixture of long-chain dicarboxylic acid dibutyl esters was subjected to platinum-cobalt color and acid value analysis.

[0137] Example 7

[0138] The process is essentially the same as in Example 6, except that Example 7 uses a mixture containing long-chain dicarboxylic acids after extraction and purification of DC11 (according to Extraction and Purification Example 1). The mixture containing long-chain dicarboxylic acids was dried at 110°C to a water content of 1 wt%, yielding 1.536 kg of dry matter, of which the effective acid content was 78.04 wt%, the long-chain dicarboxylic acid content was 51.94% (composed of DC10, DC11, DC12, DC13, DC14, and DC15), and the heteroacid content was 26.1%. The mass ratio of long-chain dicarboxylic acids to heteroacids was 2:1. The remaining steps were the same as in Example 6.

[0139] Example 8 (2000L reactor)

[0140] The fermentation broth of DC12 (docosahexacarboxylic acid) was taken, and after extracting and purifying DC12, the mixture containing long-chain dicarboxylic acids (Example 1 of extraction and purification) was dried at 110°C to a water content of 1 wt%, yielding 604 kg of dry matter. The dry matter contained 85.16 wt% effective acid, 67.99% long-chain dicarboxylic acids (composed of DC10, DC11, DC12, DC13, DC14, and DC15), and 17.17% heteroacids. The mass ratio of long-chain dicarboxylic acids to heteroacids was 4:1.

[0141] The above-mentioned dry matter was added to a 2000L reactor, along with 460kg of n-butanol and 21.5kg of p-toluenesulfonic acid monohydrate. Esterification was carried out under reflux at a liquid phase temperature of 120℃ for 8 hours. A mixture of n-butanol and water was separated, and the esterification rate was determined to be 61% by acid value testing. 150kg of n-butanol was added, and esterification was continued under reflux at 120℃ for 5 hours. A mixture of n-butanol and water was separated, and the esterification rate was calculated by acid value testing.

[0142] Unreacted n-butanol was recovered by vacuum distillation at a vacuum of 2 kPa and a liquid phase temperature of 135 °C for 4 hours.

[0143] Under conditions maintained at 90℃, 110 kg of a 5.46 wt% sodium carbonate aqueous solution was added to the organic phase remaining after vacuum distillation, and the mixture was stirred for 30 minutes. The mixture was then allowed to stand and separate into layers at 90℃, with the lower aqueous phase being separated. The alkaline washing process was repeated: the organic phase was washed again with 100 kg of a 5.46 wt% sodium carbonate aqueous solution while maintaining the temperature at 90℃. The acid value of the organic phase was measured to be 0.09 mg KOH / g. The mixture was then dried over anhydrous sodium sulfate and filtered to obtain a crude mixture of dark brown long-chain dicarboxylic acid dibutyl esters.

[0144] The crude mixture of the above-mentioned dark brown long-chain dicarboxylic acid dibutyl esters was distilled using a molecular distillation apparatus. Molecular distillation was performed under vacuum and increased temperature conditions, with the feed inlet temperature at 35°C, the main evaporator condensing surface temperature at 0°C, and the main evaporator scraper rotation speed at 300 rpm. Under vacuum conditions of 500 Pa and main evaporator evaporating surface temperature of 145°C, the feed rate was controlled at 150 kg / h, and 30 kg of the low-boiling-point fraction was collected. Under vacuum conditions of 110 Pa and main evaporator evaporating surface temperature of 180°C, the feed rate was controlled at 75 kg / h, and the product fraction, a light yellow oily substance, was collected, yielding 482 kg of a mixture of long-chain dicarboxylic acid dibutyl esters (composed of dibutyl sebacate, dibutyl undecanoate, dibutyl dodecaate, dibutyl tridecanoate, dibutyl tetradecanoate, and dibutyl pentadecanoate). The mixture of long-chain dicarboxylic acid dibutyl esters was subjected to platinum-cobalt color and acid value determination.

[0145] Example 9 (Ordinary vacuum distillation)

[0146] The fermentation broth of DC12 (docosahexacarboxylic acid) was taken, and after extracting and purifying DC12, the mixture containing long-chain dicarboxylic acids (Example 1 of extraction and purification) was dried at 110°C to a water content of 1 wt%, yielding 1.626 kg of dry matter, of which the effective acid content was 81.34 wt%, the long-chain dicarboxylic acid content was 71.76% (composed of DC10, DC11, DC12, DC13, DC14 and DC15), and the content of miscellaneous acids was 9.58%. The mass ratio of long-chain dicarboxylic acids to miscellaneous acids was 7.5:1.

[0147] The above-mentioned dry matter was added to a 5L reactor, along with 1.25 kg of n-butanol and 58 g of p-toluenesulfonic acid monohydrate. Esterification was carried out under reflux at a liquid phase temperature of 120°C for 5 hours. 460 g of a mixture of n-butanol and water was separated, and the esterification rate was determined to be 60.2% by acid value analysis. 500 g of n-butanol was added, and esterification was continued under reflux at 120°C for 3 hours. 348 g of a mixture of n-butanol and water was separated, and the esterification rate was calculated by acid value analysis.

[0148] Unreacted n-butanol was recovered by vacuum distillation at a vacuum of 2 kPa and a liquid phase temperature of 130 °C for 4 hours.

[0149] Under conditions maintained at 85℃, 300g of a 5.65wt% sodium carbonate aqueous solution was added to the organic phase remaining after vacuum distillation, and the mixture was stirred for 25 minutes. The mixture was then allowed to stand and separate into layers at 85℃, with the lower aqueous phase being separated. The alkaline washing process was repeated: the organic phase was washed again with 300g of a 5.65wt% sodium carbonate aqueous solution while maintaining the temperature at 85℃. The acid value of the organic phase was measured to be 0.15mgKOH / g. The mixture was then dried over anhydrous sodium sulfate and filtered to obtain a crude product of a dark brown long-chain dicarboxylic acid, dibutyl ester.

[0150] The crude mixture of the above-mentioned dark brown long-chain dicarboxylic acid dibutyl esters was subjected to ordinary vacuum distillation. Under a vacuum of 650 Pa and a main evaporator surface temperature of 175℃-210℃, 86 g of the low-boiling fraction was collected. Under a vacuum of 260 Pa and a main evaporator surface temperature of 235℃-250℃, the product fraction was collected; this was a dark yellow oily substance, yielding 1.19 kg of a mixture of long-chain dicarboxylic acid dibutyl esters (composed of dibutyl sebacate, dibutyl undecanoate, dibutyl dodecaate, dibutyl tridecanoate, dibutyl tetradecanoate, and dibutyl pentadecanoate). The mixture of long-chain dicarboxylic acid dibutyl esters was subjected to platinum-cobalt color and acid value analysis.

[0151] Table 1: Test results of esterification rate, platinum-cobalt color, and acid value of dibutyl ester mixture of long-chain dicarboxylic acids.

[0152]

[0153]

[0154] As shown in Table 1, the esterification rate of the mixed long-chain dicarboxylic acids in this invention is high. The resulting mixed long-chain dicarboxylic acid dibutyl ester has low color intensity, and low-color esters are better suited to meet the needs of light-colored polymer materials. The processing method of the mixture containing long-chain dicarboxylic acids in this invention can effectively separate long-chain dicarboxylic acid dibutyl ester, butylated products of miscellaneous acids, residual long-chain dicarboxylic acids, miscellaneous acids, and impurities from fermentation broth, obtaining a high-quality mixture of long-chain dicarboxylic acid dibutyl ester, which is more suitable for use as a plasticizer in polymer materials, realizing the transformation of waste into treasure.

[0155] Furthermore, the method for processing mixtures containing long-chain dicarboxylic acids of the present invention is fully applicable to the processing of mixtures containing long-chain dicarboxylic acids at the factory scale, and has great application value.

[0156] Testing of mixed long-chain dicarboxylic acid dibutyl esters for plasticizers:

[0157] Weigh the following components according to the formula: 100 parts PVC material, 35 parts dioctyl phthalate (DOP), 10 parts mixed dibutyl phthalate product or DBS reference standard, 4.5 parts disalt lead phosphite, 0.4 parts barium stearate, 0.5 parts lubricant, and 2 parts calcium carbonate. Mix the components and plasticize them on a rubber mixing mill at 160±5℃ for 5-10 minutes. Draw the mixture into sheets, then press them in a compression molding machine at 160±5℃ for 15-20 minutes to form 1mm thick test pieces. Demold the test pieces and press them into test pieces according to different test requirements. Test the aging resistance and low-temperature brittleness of the PVC test pieces. The test results are shown in Table 2.

[0158] Table 2: Performance Test Results of PVC Sheets

[0159]

[0160]

[0161] As shown in Table 2, when the mixed long-chain dicarboxylic acid dibutyl ester was used as a plasticizer, the PVC sample destruction rate at -41℃ was approximately 50%, comparable to that of DBS (dibutyl sebacate), effectively improving the low-temperature flexibility of the polymer. The PVC samples obtained using the mixed long-chain dicarboxylic acid dibutyl ester as a cold-resistant plasticizer showed low weight loss after aging, except for Example 9, which exhibited significant weight loss. This may be because conventional vacuum distillation requires higher temperatures to complete the separation, and prolonged high temperatures caused partial decomposition of the mixed long-chain dicarboxylic acid butyl ester, thus reducing its stability when used as a plasticizer.

[0162] The foregoing description of optional embodiments of the present invention is intended to teach those skilled in the art how to implement and reproduce the invention. Some conventional aspects have been simplified or omitted to teach the technical solutions of the present invention. After reading this specification, those skilled in the art can readily conceive of variations or alternatives to the technical solutions of the present invention that achieve the objectives of the invention based on common knowledge in the field of chemistry. Those skilled in the art should understand that variations or alternatives derived from these embodiments will fall within the scope of the present invention.

Claims

1. A method for treating a mixture containing long-chain dicarboxylic acids during the extraction and purification of long-chain dicarboxylic acid fermentation broth, comprising the following steps: (1) Mix the mixture containing long-chain dicarboxylic acids with n-butanol and catalyst until homogeneous, and carry out butylation reaction; (2) Wash the product after the butyration reaction with alkaline solution; (3) Distillation and purification yields a mixture of long-chain dicarboxylic acid dibutyl esters; The mixture comprising long-chain dicarboxylic acids includes: - The crude long-chain dicarboxylic acid obtained from the fermentation broth of the long-chain dicarboxylic acid is dissolved in a solvent, and the remaining material after cooling and crystallization and separation of the long-chain dicarboxylic acid precipitate is obtained. or - The residue after most of the solvent has been recovered from the above materials; The mixture comprising long-chain dicarboxylic acids includes an effective acid and a pigment; The effective acids include a variety of long-chain dicarboxylic acids, which are compounds represented by the general formula HOOC-R1-COOH, where R1 is -(CH2). m -and 8≤m≤16; The effective acid content is 50-90 wt% based on the weight of the dry matter of the mixture containing long-chain dicarboxylic acids, and the pigment content is 1-20 wt%. The effective acid also includes heteroacids, wherein the mass of the long-chain dicarboxylic acid is more than 1 times the mass of the heteroacid; The distillation in step (3) is molecular distillation, which includes the following steps: (A) Control the pressure of the main evaporator to 300-1000 Pa. When the evaporation surface temperature of the molecular distillation main evaporator is 100-160℃, collect fraction 1. (B) Control the pressure of the main evaporator to 10-200 Pa. When the evaporation surface temperature of the molecular distillation main evaporator is 150-250 °C, collect fraction 2 to obtain a mixture of long-chain dicarboxylic acid dibutyl ester.

2. According to the method of claim 1, the total amount of n-butanol added in the butyl esterification reaction process is 0.2-3 times the mass of the effective acid.

3. The method according to claim 1, wherein the catalyst comprises: One or more of concentrated sulfuric acid, sodium bisulfate, p-toluenesulfonic acid, p-toluenesulfonic acid monohydrate, and tetrabutyl titanate.

4. The method according to claim 3, wherein the total amount of catalyst used is 1-10% of the effective acid mass.

5. The method according to claim 1, wherein the temperature of the butyration reaction is 50-180°C, and / or the butyration time is 3-15 h.

6. The method according to claim 1, wherein n-butanol is recovered before the product after the butyl esterification reaction is washed with alkaline solution.

7. According to the method of claim 1, the acid value of the organic phase reaches below 2 mg KOH / g at the end of the alkaline washing in step (2).

8. The method according to claim 1, wherein the condenser surface temperature of the main evaporator of the molecular distillation is -10 to 50°C; and / or, the scraper rotation speed of the main evaporator of the molecular distillation is 200 to 400 rpm; and / or, the feed inlet temperature of the molecular distillation apparatus is 20 to 100°C.

9. The method according to claim 1, wherein the mixture containing long-chain dicarboxylic acids is dried to a moisture content of less than 5 wt% before butyration.

10. The method according to claim 1, wherein the mixture of long-chain dicarboxylic acid dibutyl esters is a mixture of any of several long-chain dicarboxylic acid dibutyl esters having 10-18 carbon atoms.

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