A method for refining dodecanedioic acid crude product produced by biological fermentation

Abstract

The application discloses a refining method of dodecanedioic acid crude product produced by a biological fermentation method, adopts 1,4-dioxane as a crystallization solvent, and after dissolving, activated carbon decoloring and filtering, the filtrate is kept warm, cooled and crystallized, and then filtered, the filter cake is washed and dried, and then dodecanedioic acid pure product is obtained, and the filtrate can be directly recycled and used as a solvent for refining dodecanedioic acid crude product, and is reused.The purity of dodecanedioic acid product prepared by the method reaches 99.25%, the yield can reach 92%, the colority can reach 10, and the purity is increased by more than 2%.The solvent is non-corrosive, non-irritating and low in volatility, and no special protection is needed in the crystallization operation process, the requirements for production environment, operation conditions and equipment are lower, the refining cost can be obviously reduced, and the solvent is suitable for industrialized refining production of dodecanedioic acid.

Description

(I) Technical Field

[0001] This invention belongs to the field of refining technology for crude dodecanoic acid produced by bio-fermentation, and particularly relates to a refining method for crude dodecanoic acid produced by bio-fermentation. (II) Background Technology

[0002] Dodecanedioic acid (DC) 12 ( ) refers to aliphatic dicarboxylic acids containing 12 carbon atoms in their carbon chain. They are an important class of fine chemical products with a wide range of industrial applications, playing an irreplaceable role in industries such as the synthesis of polyamides, high-grade coatings, adhesives, cold-resistant plasticizers, and high-grade lubricants.

[0003] Dodecanoic acid (DCA) does not exist in nature. Currently, there are two main methods for producing DCA: chemical synthesis and microbial fermentation. Chemical synthesis of DCA is complex, requires harsh reaction conditions (high temperature, high pressure, large amounts of catalysts, etc.), causes severe environmental pollution, and poses significant safety hazards, thus limiting its industrial application. Microbial fermentation offers advantages such as milder production conditions, simpler processes, wider availability of raw materials, and lower costs, overcoming the shortcomings of chemical synthesis. Currently, microbial fermentation has gradually replaced chemical synthesis as the main method for industrial production of DCA. However, due to the lack of breakthroughs in extraction and purification methods and the influence of patent technology monopolies, most domestic DCA producers can only produce crude products with high ash and other impurity content, low purity, and poor thermal stability, failing to meet the quality requirements of polymerization-grade products, thus limiting its application.

[0004] In existing technologies, the purification method for crude dodecanoic acid mainly uses crude dodecanoic acid produced by bio-fermentation as raw material and employs an organic solvent method for purification and refining through recrystallization. The organic solvents used mainly include alcohols, acids, esters, ethers, ketones, etc., such as ethanol, acetic acid, diethyl ether, ethyl acetate, acetone, and mixtures thereof.

[0005] Patent application CN201010160266.4 describes a method using acetic acid (90% or higher) as a solvent. Crude dodecanoic acid is dissolved in a hot acetic acid solution at a specific ratio. After decolorization with activated carbon, cooling crystallization, and separation, a wet dodecanoic acid product is obtained, which is then dried to obtain a refined dodecanoic acid product. The advantage of this method is the high purity of the refined dodecanoic acid product. However, acetic acid solvent is highly volatile, irritating, and corrosive, requiring specially customized equipment selection and operation with appropriate protection. Furthermore, due to the high solubility of long-chain dicarboxylic acids in high-concentration acetic acid solutions at room temperature, the product yield is generally low. To improve the yield, a secondary extraction or reuse of the mother liquor after purification is necessary.

[0006] Clearly, improving the existing crude dodecanoic acid extraction and purification technologies in China to enhance product quality is a crucial technical challenge that urgently needs to be addressed for the sustainable development of dodecanoic acid production via fermentation. Since the crystallization behavior of compounds varies significantly in different solvents, exploring new purification and crystallization solvents based on their physicochemical parameters, solubility, and crystallization properties is an important goal of process innovation. (III) Summary of the Invention

[0007] The purpose of this invention is to provide a method for refining crude dodecanoic acid produced by bio-fermentation. By using 1,4-dioxane as a crystallization solvent and employing a specific refining process route, a dodecanoic acid product with high yield, purity, color, and transmittance can be obtained with low energy consumption, thus solving the problems of low yield and high energy consumption of dodecanoic acid in the prior art.

[0008] The technical solution adopted in this invention is:

[0009] This invention provides a method for refining crude dodecanoic acid produced by bio-fermentation. The refining method is carried out according to the following steps: (1) Decolorization: using crude dodecanoic acid produced by bio-fermentation as raw material, dissolving it in a solvent, adding activated carbon, stirring and decolorizing at a temperature of 65-85℃ for 30-120 min, and then filtering while hot to obtain a clear dodecanoic acid solution; the solvent is 1,4-dioxane; (2) Crystallization: keeping all the clear dodecanoic acid solution obtained in step (1) (preferably added to a crystallization tank) at a temperature of 60-80℃ for 1-2 hours, cooling to 20-35℃, filtering to obtain a dodecanoic acid filter cake and a crystallization mother liquor; the filter media used for filtration include medium-speed qualitative filter paper, polypropylene filter membrane, and glass fiber filter paper; (3) Washing: washing the dodecanoic acid filter cake obtained in step (2) with pure water and vacuum drying to obtain the dodecanoic acid product.

[0010] Preferably, the solvent volume in step (1) is 2-6 mL / g, more preferably 4-5 mL / g, based on the mass of the crude dodecanoic acid; the activated carbon mass addition is 0.5-3%, more preferably 1.5-2%, based on the mass of the crude dodecanoic acid. The crude dodecanoic acid is purchased from Shandong Guiyuan Biotechnology Co., Ltd., and the purity of the crude dodecanoic acid is 97%.

[0011] Preferably, step (1) is carried out in a closed dissolution vessel, and the solvent dissolution temperature is 70-85℃, preferably 75℃. The decolorization conditions are preferably 70-75℃ for 80-100 min.

[0012] Preferably, step (2) involves cooling down to 20-35°C at a rate of 5°C-15°C / h, and more preferably to 25°C at a rate of 8-10°C / h.

[0013] Preferably, step (2) involves keeping the temperature at 70°C for 1.5 hours.

[0014] Preferably, the pore size of the polypropylene filter membrane in step (2) is 0.1 μm.

[0015] Preferably, the mother liquor from step (2) is used as a solvent to dissolve the raw materials and is reused in step (1).

[0016] Preferably, the volume of purified water used in step (3) is 2-11 mL / g based on the weight of the dodecanoic acid filter cake, more preferably 4-8 mL / g; the vacuum drying is carried out in a vacuum drying oven at 60℃~80℃ for 6-10 hours, more preferably at 80℃ for 5 hours.

[0017] The dodecanoic acid product prepared by the method of the present invention can be repeatedly purified to further improve its purity.

[0018] Compared with existing technologies, the beneficial effects of this invention are mainly reflected in the following aspects: The purification method for crude dodecanoic acid produced by bio-fermentation provided by this invention uses 1,4-dioxane as a crystallization solvent. The process involves heating and dissolving, decolorizing with activated carbon, filtration, heat preservation of the filtrate, cooling and crystallization, followed by filtration again. In particular, filtration is performed using a specific filter medium. The filter cake is then washed and dried to obtain pure dodecanoic acid. Furthermore, the filtrate can be directly recycled as a solvent for the purification of crude dodecanoic acid. On one hand, the dodecanoic acid product prepared by this invention achieves a purity of 99.25%, a yield of 92%, and a color of 10, representing a purity improvement of over 2%. On the other hand, compared with previous purification methods, solvent volatility and irritating odors are significantly reduced. No special protection is required during the crystallization process. The solvent of this invention is non-corrosive, non-irritating, and has low volatility, resulting in lower requirements for the production environment, operating conditions, and equipment, and significantly reducing purification costs. Furthermore, when 1,4-dioxane is used as the crystallization solvent in this invention, the 1,4-dioxane crystallization mother liquor obtained after the precipitation of dodecanoic acid product has a low impurity content and can be reused more than twice without distillation purification, which greatly reduces solvent consumption and production energy consumption, making it suitable for the industrial refining production of dodecanoic acid. (iv) Description of the attached drawings

[0019] Figure 1 This is an appearance diagram of the refined product of dodecanoic acid. 'a' represents the 1,4-dioxane refined DC from Example 1. 12 Product; b represents purified DC acetic acid from Comparative Example 1. 12 Product. c represents the DMSO refined DC of Comparative Example 2. 12 Product; d represents DMF refined DC of Comparative Example 4. 12 product.

[0020] Figure 2 For the X-ray diffraction pattern of the product, (a) 1,4-dioxane refined DC from Example 1 12 (a) Sample; (b) DC purified acetic acid of Comparative Example 1 12 sample.

[0021] Figure 3 For the gas chromatogram of the product, (a) 1,4-dioxane purified DC from Example 1 12 (a) Sample; (b) DC purified acetic acid of Comparative Example 1 12 Sample; (c) DC purified acetic acid from Comparative Example 1 12 And the 1,4-dioxane refined DC of Example 1 12 Mixed samples. (V) Detailed Implementation

[0022] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto:

[0023] In this embodiment of the invention, crude dodecanoic acid was purchased from Shandong Guiyuan Biotechnology Co., Ltd. (item number: 22221080737), and the purity of the crude dodecanoic acid was 97%. The activated carbon was purchased from Hangzhou Shuangmu Chemical Co., Ltd. (item number: shmu-A805338-500g), and the particle size of the activated carbon was 200 mesh. The medium-speed qualitative filter paper was purchased from Hangzhou Jigong Biotechnology Co., Ltd. (item number: jghc0414). The polypropylene filter membrane was purchased from Haining Haichang Yibo Filter Material Store (item number: f329491), and the pore size was 0.1 μm. The glass fiber filter paper was purchased from Hangzhou Shuangmu Chemical Co., Ltd. (item number: smsyhc-0374), and the pore size was 0.1 μm.

[0024] The detection method involved in the embodiments of the present invention:

[0025] 1. Total acidity test: Refer to GB541327-2010 Determination of fatty acids in infant food and dairy products.

[0026] 2. DC 12 Purity testing (DC) 12 Monoacid Content): DC in the sample was calculated using peak area normalization. 12 Purity. Pretreatment of dodecanoic acid sample: Accurately weigh 0.15g of purified DC... 12 The sample was dissolved by sonication at 35 Hz with 1 mL of 25% tetramethylammonium hydroxide aqueous solution, followed by dilution with water to a final volume of 10 mL for gas chromatography. The purified DC was then determined by gas chromatography (Agilent 7820A). 12The chromatographic analysis conditions for the samples were as follows: flame ionization (FID) detector; Agilent J&WHP-5 column (30m × 0.320 × 0.25mm); carrier gas: nitrogen, flow rate: 25 mL / min, split ratio: 50:1; combustion gas: hydrogen, flow rate: 40 mL / min; oxidizing gas: air, flow rate: 400 mL / min; injector temperature: 270℃; detector temperature: 300℃; injection volume: 1 μL. The temperature program was as follows: initial column temperature 180℃, held for 2 min, then increased to 190℃ at a rate of 10℃ / min, held for 5 min, then increased to 240℃ at a rate of 25℃ / min, held for 6 min.

[0027] 3. Total nitrogen content determination: Kjeldahl method was used.

[0028] 4. Ash content detection: Take a dodecanoic acid sample and ignite it in a crucible, then ignite it in a muffle furnace at 700-800℃ for 2 hours. After cooling and constant weight, measure the weight and calculate the percentage weight.

[0029] 5. Transmittance detection: Take 10g of dodecanoic acid sample and add it to dimethyl sulfoxide (DMSO) to prepare a 10% solution. Using DMSO as a blank, read the transmittance at 440nm and 550nm on a spectrophotometer.

[0030] 6. Colorimetric detection: Platinum-cobalt colorimetric method.

[0031] Example 1

[0032] (1) Decolorization: Weigh 40g of crude dodecanoic acid and place it in a 250mL three-hole flask equipped with a stirrer. Then add 160mL of 1,4-dioxane solvent and heat to 75℃ in a digital display constant temperature water bath while stirring to completely dissolve the dodecanoic acid. Add 0.8g of activated carbon and decolorize by stirring at 75℃ for 80 minutes under sealed conditions. Then filter while hot and collect the clear dodecanoic acid solution.

[0033] (2) Crystallization: All the dodecanoic acid clear liquid obtained in step (1) was placed in a primary crystallization vessel and kept at 70°C for 1.5 hours. Then, the temperature was slowly reduced to 25°C in the crystallization vessel at a rate of 10°C / h. The solution was then vacuum filtered at 0.08 MPa using medium-speed qualitative filter paper as the filter medium, resulting in 36 g of dodecanoic acid filter cake and 135 mL of crystallization mother liquor.

[0034] (3) Washing: The 36g dodecanoic acid filter cake obtained in step (2) was washed with 160mL of purified water and then dried in a vacuum drying oven at 80℃ for 5 hours to obtain 35.2g of dodecanoic acid product, namely 1,4-dioxane purified DC. 12Sample. Product purity is 98.8%, crystallization yield is 88% (product weight g / crude product weight g). The appearance of the obtained product is as follows. Figure 1 As shown in Figure a. The obtained product was analyzed for total acid content and DC... 12 The content of monoacids, total nitrogen, ash, transmittance, color, and yield were measured and calculated, and the results are shown in Table 1.

[0035] 1,4-Dioxane Refined DC 12 The X-ray diffraction pattern of the sample is as follows Figure 2 As shown in Figure a, gas chromatography analysis is as follows: Figure 3 As shown in Figure a, Figure 2 and Figure 3 The product is confirmed to be a DC. 12 .

[0036] Example 2

[0037] (1) Decolorization: Weigh 30g of crude dodecanoic acid and place it in a 250mL three-hole flask equipped with a stirrer. Then add 120mL of the crystallization mother liquor recovered in Example 1. Heat the mixture to 75°C in a digital display constant temperature water bath while stirring until all the dodecanoic acid is dissolved. Add 0.6g of activated carbon and decolorize by stirring at 75°C for 80 minutes under sealed conditions. Then filter while hot and collect the clear dodecanoic acid solution.

[0038] (2) Crystallization: All the dodecanoic acid clear liquid obtained in step (1) was placed in a primary crystallization vessel and kept at 70°C for 1.5 hours. Then, the temperature was slowly reduced to 25°C in the crystallization vessel at a rate of 10°C / h. The solution was then vacuum filtered at 0.08 MPa using medium-speed qualitative filter paper as the filter medium, resulting in 28 g of dodecanoic acid filter cake and 100 mL of crystallization mother liquor.

[0039] (3) Washing: 28g of the dodecanoic acid filter cake obtained in step (2) was washed with 120mL of purified water and then dried in a vacuum drying oven at 80℃ for 5 hours to obtain 27.3g of dodecanoic acid product. The product purity was 98.7%, and the crystallization yield was 91% (product weight g / crude product weight g). The total acid content and DC content of the obtained product were analyzed. 12 The content of monoacids, total nitrogen, ash, transmittance, color, and yield were measured and calculated, and the results are shown in Table 1.

[0040] Example 3

[0041] (1) Decolorization: Weigh 20g of crude dodecanoic acid and place it in a 250mL three-hole flask equipped with a stirrer. Then add 80mL of the crystallization mother liquor recovered in Example 2. Heat the mixture to 75°C in a digital display constant temperature water bath while stirring until all the dodecanoic acid is dissolved. Add 0.4g of activated carbon and decolorize by stirring at 75°C for 80 minutes under sealed conditions. Then filter while hot and collect the clear dodecanoic acid solution.

[0042] (2) Crystallization: All the dodecanoic acid clear liquid obtained in step (1) was placed in a primary crystallization vessel and kept at 70°C for 1.5 hours. Then, the temperature was slowly reduced to 25°C in the crystallization vessel at a rate of 10°C / h. The solution was then vacuum filtered at 0.08 MPa using medium-speed qualitative filter paper as the filter medium. 19.2 g of dodecanoic acid filter cake and 60 mL of crystallization mother liquor were obtained.

[0043] (3) Washing: 19.2 g of the dodecanoic acid filter cake obtained in step (2) was washed with 80 mL of purified water and dried in a vacuum drying oven at 80 °C for 5 hours to obtain 18.6 g of dodecanoic acid product. The product purity was 98.5%, and the crystallization yield was 93% (product weight g / crude product weight g). The total acid content and DC content of the obtained product were analyzed. 12 The content of monoacids, total nitrogen, ash, transmittance, color, and yield were measured and calculated, and the results are shown in Table 1.

[0044] Example 4

[0045] (1) Decolorization: Weigh 30g of crude dodecanoic acid and place it in a 250mL three-hole flask equipped with a stirrer. Then add 90mL of 1,4-dioxane solvent and heat to 85℃ in a digital display constant temperature water bath while stirring to completely dissolve the dodecanoic acid. Add 0.45g of activated carbon and decolorize by stirring at 85℃ for 60 minutes under sealed conditions. Then filter while hot and collect the clear dodecanoic acid solution.

[0046] (2) Crystallization: All the dodecanoic acid clear liquid obtained in step (1) was placed in a primary crystallization vessel and kept at 80°C for 2 hours. Then, the temperature was slowly reduced to 25°C in the crystallization vessel at a rate of 12°C / h. The solution was then vacuum filtered at 0.08MPa using medium-speed qualitative filter paper as the filter medium, resulting in 27g of dodecanoic acid filter cake and 70mL of crystallization mother liquor.

[0047] (3) Washing: 27g of the dodecanoic acid filter cake obtained in step (2) was washed with 120mL of purified water and dried in a vacuum drying oven at 80℃ for 5 hours to obtain 26.1g of dodecanoic acid product. The product purity was 98.7%, and the crystallization yield was 87% (product weight g / crude product weight g). The total acid content and DC content of the obtained product were analyzed. 12The content of monoacids, total nitrogen, ash, transmittance, color, and yield were measured and calculated, and the results are shown in Table 1.

[0048] Example 5

[0049] (1) Decolorization: Weigh 30g of crude dodecanoic acid and place it in a 250mL three-hole flask equipped with a stirrer. Then add 150mL of 1,4-dioxane solvent and heat to 70℃ in a digital display constant temperature water bath while stirring to completely dissolve the dodecanoic acid. Add 0.45g of activated carbon and decolorize by stirring at 70℃ for 100 minutes under sealed conditions. Then filter while hot and collect the clear dodecanoic acid solution.

[0050] (2) Crystallization: All the dodecanoic acid clear liquid obtained in step (1) was placed in a primary crystallization vessel and kept at 65°C for 1 hour. Then, the temperature was slowly reduced to 25°C in the crystallization vessel at a rate of 8°C / h. The solution was then vacuum filtered at 0.08MPa using medium-speed qualitative filter paper as the filter medium, resulting in 28g of dodecanoic acid filter cake and 120mL of crystallization mother liquor.

[0051] (3) Washing: 28g of the dodecanoic acid filter cake obtained in step (2) was washed with 160mL of purified water and dried in a vacuum drying oven at 80℃ for 5 hours to obtain 26.7g of dodecanoic acid product. The product purity was 98.6%, and the crystallization yield was 89% (product weight g / crude product weight g). The total acid content and DC content of the obtained product were analyzed. 12 The content of monoacids, total nitrogen, ash, transmittance, color, and yield were measured and calculated, and the results are shown in Table 1.

[0052] Example 6

[0053] (1) Decolorization: Weigh 30g of crude dodecanoic acid and place it in a 250mL three-hole flask equipped with a stirrer. Then add 150mL of 1,4-dioxane solvent and heat to 75℃ in a digital display constant temperature water bath while stirring to completely dissolve the dodecanoic acid. Add 0.45g of activated carbon and decolorize by stirring at 70℃ for 100 minutes under sealed conditions. Then filter while hot and collect the clear dodecanoic acid solution.

[0054] (2) Crystallization: All the dodecanoic acid clear liquid obtained in step (1) was placed in a primary crystallization vessel and kept at 70°C for 1.5 hours. Then, the temperature was slowly reduced to 25°C in the crystallization vessel at a rate of 8°C / h. The mixture was then vacuum filtered at 0.08MPa. The filter medium was glass fiber filter paper (pore size 0.1μm). 26.3g of dodecanoic acid filter cake and 120mL of crystallization mother liquor were obtained.

[0055] (3) Washing: The 26.3g dodecanoic acid filter cake obtained in step (2) was washed with 160mL of purified water and dried in a vacuum drying oven at 80℃ for 5 hours to obtain 25.2g of dodecanoic acid product. The product purity was 98.4%, and the crystallization yield was 84% ​​(product weight g / crude product weight g). The total acid content and DC content of the obtained product were analyzed. 12 The content of monoacids, total nitrogen, ash, transmittance, color, and yield were measured and calculated, and the results are shown in Table 1.

[0056] Example 7

[0057] (1) Decolorization: Weigh 30g of crude dodecanoic acid and place it in a 250mL three-hole flask equipped with a stirrer. Then add 150mL of 1,4-dioxane solvent and heat to 75℃ in a digital display constant temperature water bath while stirring to completely dissolve the dodecanoic acid. Add 0.45g of activated carbon and decolorize by stirring at 70℃ for 100 minutes under sealed conditions. Then filter while hot and collect the clear dodecanoic acid solution.

[0058] (2) Crystallization: All the dodecanoic acid clear liquid obtained in step (1) was placed in a primary crystallization vessel and kept at 70°C for 1.5 hours. Then, the temperature was slowly reduced to 25°C in the crystallization vessel at a rate of 8°C / h. The mixture was then vacuum filtered at 0.08MPa. The filter medium was a polypropylene filter membrane (pore size 0.1μm). 28.5g of dodecanoic acid filter cake and 120mL of crystallization mother liquor were obtained.

[0059] (3) Washing: 28.5 g of the dodecanoic acid filter cake obtained in step (2) was washed with 160 mL of purified water and dried in a vacuum drying oven at 80 °C for 5 hours to obtain 27.6 g of dodecanoic acid product. The product purity was 99.25%, and the crystallization yield was 92% (product weight g / crude product weight g). The total acid content and DC content of the obtained product were analyzed. 12 The content of monoacids, total nitrogen, ash, transmittance, color, and yield were measured and calculated, and the results are shown in Table 1.

[0060] Example 8

[0061] (1) Decolorization: Weigh 30g of crude dodecanoic acid and place it in a 250mL three-hole flask equipped with a stirrer. Then add 120mL of the crystallization mother liquor from Example 7. Heat the mixture to 75°C in a digital display constant temperature water bath while stirring until all the dodecanoic acid is dissolved. Add 0.6g of activated carbon and decolorize by stirring at 70°C for 100 minutes under sealed conditions. Then filter while hot and collect the clear dodecanoic acid solution.

[0062] (2) Crystallization: All the dodecanoic acid clear liquid obtained in step (1) was placed in a primary crystallization vessel and kept at 70°C for 1.5 hours. Then, the temperature was slowly reduced to 25°C in the crystallization vessel at a rate of 8°C / h. The mixture was then vacuum filtered at 0.08MPa. The filter medium was a polypropylene filter membrane (pore size 0.1μm). 29.1g of dodecanoic acid filter cake and 100mL of crystallization mother liquor were obtained.

[0063] (3) Washing: The 29.1g dodecanoic acid filter cake obtained in step (2) was washed with 160mL of purified water and dried in a vacuum drying oven at 80℃ for 5 hours to obtain 28.2g of dodecanoic acid product. The product purity was 99.15%, and the crystallization yield was 94% (product weight g / crude product weight g). The total acid content and DC content of the obtained product were analyzed. 12 The content of monoacids, total nitrogen, ash, transmittance, color, and yield were measured and calculated, and the results are shown in Table 1.

[0064] Example 9

[0065] (1) Decolorization: Weigh 20g of crude dodecanoic acid and place it in a 250mL three-hole flask equipped with a stirrer. Then add 80mL of the crystallization mother liquor from Example 8. Heat the mixture to 75°C in a digital display constant temperature water bath while stirring until all the dodecanoic acid is dissolved. Add 0.4g of activated carbon and decolorize by stirring at 70°C for 100 minutes under sealed conditions. Then filter while hot and collect the clear dodecanoic acid solution.

[0066] (2) Crystallization: All the dodecanoic acid clear liquid obtained in step (1) was placed in a primary crystallization vessel and kept at 70°C for 1.5 hours. Then, the temperature was slowly reduced to 25°C in the crystallization vessel at a rate of 8°C / h. The mixture was then vacuum filtered at 0.08MPa. The filter medium was a polypropylene filter membrane (pore size 0.1μm). 19.4g of dodecanoic acid filter cake and 60mL of crystallization mother liquor were obtained.

[0067] (3) Washing: 19.4 g of the dodecanoic acid filter cake obtained in step (2) was washed with 160 mL of purified water and dried in a vacuum drying oven at 80 °C for 5 hours to obtain 19 g of dodecanoic acid product. The product purity was 99.10%, and the crystallization yield was 95% (product weight g / crude product weight g). The total acid content and DC content of the obtained product were analyzed. 12 The content of monoacids, total nitrogen, ash, transmittance, color, and yield were measured and calculated, and the results are shown in Table 1.

[0068] Example 10

[0069] (1) Decolorization: Weigh 30g of the dodecanoic acid product (crystals) obtained in step (3) of Example 7 and place it in a 250mL three-hole flask equipped with a stirrer. Then add 150mL of 1,4-dioxane solvent and heat to 75°C in a digital display constant temperature water bath while stirring to completely dissolve the dodecanoic acid. Add 0.45g of activated carbon and decolorize by stirring at 70°C for 100 minutes under sealed conditions. Then filter while hot and collect the clear dodecanoic acid solution.

[0070] (2) Crystallization: All the dodecanoic acid clear liquid obtained in step (1) was placed in a primary crystallization vessel and kept at 70°C for 1.5 hours. Then, the temperature was slowly reduced to 25°C in the crystallization vessel at a rate of 8°C / h. The mixture was then vacuum filtered at 0.08MPa. The filter medium was a polypropylene filter membrane (pore size 0.1μm). 28.5g of dodecanoic acid filter cake and 120mL of crystallization mother liquor were obtained.

[0071] (3) Washing: The 29.1g dodecanoic acid filter cake obtained in step (2) was washed with 160mL of purified water and dried in a vacuum drying oven at 80℃ for 5 hours to obtain 27.9g of dodecanoic acid product. The product purity was 99.3%, and the crystallization yield was 93% (product weight g / crude product weight g). The total acid content and DC content of the obtained product were analyzed. 12 The content of monoacids, total nitrogen, ash, transmittance, color, and yield were measured and calculated, and the results are shown in Table 1.

[0072] Table 1. Quality indicators of dodecanoic acid products produced in Examples 1-10

[0073]

[0074] Table 1 shows that by using 1,4-dioxane as a crystallization solvent, a dodecanoic acid product with a purity of 99.3% can be obtained. Furthermore, the 1,4-dioxane crystallization mother liquor can be directly applied to the next crystallization process without distillation purification, thereby significantly reducing solvent consumption, reducing production energy consumption, and improving the crystallization yield of dodecanoic acid.

[0075] Compare with Example 1

[0076] (1) Decolorization: Weigh 20g of crude dodecanoic acid and place it in a 250mL three-hole flask equipped with a stirrer. Then add 80mL of 99% acetic acid solvent. Heat the flask to 75℃ while stirring in a digital display constant temperature water bath until the dodecanoic acid is completely dissolved. Add 0.4g of activated carbon and decolorize by stirring at 75℃ for 80 minutes under sealed conditions. Then filter while hot and collect the clear dodecanoic acid solution.

[0077] (2) Crystallization: All the dodecanoic acid clear liquid obtained in step (1) was placed in a primary crystallization vessel and kept at 70°C for 1.5 hours. Then, the temperature was slowly reduced to 25°C in the crystallization vessel at a rate of 10°C / h. The solution was then vacuum filtered at 0.08 MPa using medium-speed qualitative filter paper as the filter medium, resulting in 18.2 g of dodecanoic acid filter cake and 60 mL of crystallization mother liquor.

[0078] (3) Washing: 18.2 g of the dodecanoic acid filter cake obtained in step (2) was washed with 80 mL of purified water and dried in a vacuum drying oven at 80 °C for 5 hours to obtain 16.9 g of dodecanoic acid product. The product purity was 99.2%, and the crystallization yield was 84.4%. The appearance of the obtained product is as follows. Figure 1 As shown in b. The obtained product was analyzed for total acid content and DC. 12 The content of monoacids, total nitrogen, ash, transmittance, color, and yield were measured and calculated, and the results are shown in Table 2.

[0079] Acetic acid purified DC 12 The X-ray diffraction pattern of the sample is as follows Figure 2 As shown in Figure b, gas chromatography analysis is as follows: Figure 3 As shown in b.

[0080] Compare with Example 2

[0081] (1) Decolorization: Weigh 20g of crude dodecanoic acid and place it in a 250mL three-hole flask equipped with a stirrer. Then add 80mL of DMSO solvent and heat to 75℃ in a digital display constant temperature water bath while stirring to completely dissolve the dodecanoic acid. Add 0.4g of activated carbon and decolorize by stirring at 75℃ for 80 minutes under sealed conditions. Then filter while hot and collect the clear dodecanoic acid solution.

[0082] (2) Crystallization: All the dodecanoic acid clear liquid obtained in step (1) was placed in a primary crystallization vessel and kept at 70°C for 1.5 hours. Then, the temperature was slowly reduced to 25°C in the crystallization vessel at a rate of 10°C / h. The solution was then vacuum filtered at 0.08 MPa using medium-speed qualitative filter paper as the filter medium, resulting in 7.3 g of dodecanoic acid filter cake and 60 mL of crystallization mother liquor.

[0083] (3) Washing: The 7.3g dodecanoic acid filter cake obtained in step (2) was washed with 80mL of purified water and dried in a vacuum drying oven at 80℃ for 5 hours to obtain 6.4g of dodecanoic acid product. The product purity was 97.2%, and the crystallization yield was 32%. The appearance of the obtained product is as follows. Figure 1 As shown in Figure c. The obtained product was analyzed for total acid content and DC. 12 The content of monoacids, total nitrogen, ash, transmittance, color, and yield were measured and calculated, and the results are shown in Table 2.

[0084] Compare with Example 3

[0085] (1) Decolorization: Weigh 20g of crude dodecanoic acid and place it in a 250mL three-hole flask equipped with a stirrer. Then add 80mL of DMSO solvent and heat to 40℃ in a digital display constant temperature water bath while stirring to completely dissolve the dodecanoic acid. Add 0.4g of activated carbon and decolorize by stirring at 40℃ for 80 minutes under sealed conditions. Then filter while hot and collect the clear dodecanoic acid solution.

[0086] (2) Crystallization: All the dodecanoic acid clear solution obtained in step (1) was placed in a primary crystallization vessel and kept at 35°C for 1 hour. Then, 60 mL of purified water was added as the solvent at a dropping rate of 2 mL / min, and the crystallization time was 60 min. The solution was then vacuum filtered at 0.08 MPa using medium-speed qualitative filter paper to obtain 18.4 g of dodecanoic acid filter cake and 60 mL of crystallization mother liquor.

[0087] (3) Washing: 18.4 g of the dodecanoic acid filter cake obtained in step (2) was washed with 80 mL of purified water and dried in a vacuum drying oven at 80 °C for 5 hours to obtain 17.6 g of dodecanoic acid product. The product purity was 97.2%, and the crystallization yield was 88%. The total acid content and DC content of the obtained product were analyzed. 12 The content of monoacids, total nitrogen, ash, transmittance, color, and yield were measured and calculated, and the results are shown in Table 2.

[0088] Compare with Example 4

[0089] (1) Decolorization: Weigh 20g of crude dodecanoic acid and place it in a 250mL three-hole flask equipped with a stirrer. Then add 80mL of DMF solvent and heat to 75℃ in a digital display constant temperature water bath while stirring to completely dissolve the dodecanoic acid. Add 0.4g of activated carbon and decolorize by stirring at 75℃ for 80 minutes under sealed conditions. Then filter while hot and collect the clear dodecanoic acid solution.

[0090] (2) Crystallization: All the dodecanoic acid clear liquid obtained in step (1) was placed in a primary crystallization vessel and kept at 70°C for 1.5 hours. Then, the temperature was slowly reduced to 25°C in the crystallization vessel at a rate of 10°C / h. The solution was then vacuum filtered at 0.08 MPa using medium-speed qualitative filter paper as the filter medium. 8.1 g of dodecanoic acid filter cake and 60 mL of crystallization mother liquor were obtained.

[0091] (3) Washing: The 8.1g dodecanoic acid filter cake obtained in step (2) was washed with 80mL of purified water and dried in a vacuum drying oven at 80℃ for 5 hours to obtain 7.2g of dodecanoic acid product. The product purity was 97.3%, and the crystallization yield was 36% (product weight g / crude product weight g). The appearance of the obtained product is as follows. Figure 1 As shown in d. The total acid content and DC of the obtained product were analyzed. 12 The content of monoacids, total nitrogen, ash, transmittance, color, and yield were measured and calculated, and the results are shown in Table 2.

[0092] Compare with Example 5

[0093] (1) Decolorization: Weigh 20g of crude dodecanoic acid and place it in a 250mL three-hole flask equipped with a stirrer. Then add 80mL of DMF solvent and heat to 40℃ in a digital display constant temperature water bath while stirring to completely dissolve the dodecanoic acid. Add 0.4g of activated carbon and decolorize by stirring at 40℃ for 80 minutes under sealed conditions. Then filter while hot and collect the clear dodecanoic acid solution.

[0094] (2) Crystallization: The entire dodecanoic acid solution obtained in step (1) was placed in a primary crystallization vessel and kept at 35°C for 1.5 hours. Then, 60 mL of purified water was added as the solvent at a dropping rate of 2 mL / min, and the crystallization time was 60 min. The solution was then vacuum filtered at 0.08 MPa using medium-speed qualitative filter paper to obtain 17.2 g of dodecanoic acid filter cake and 60 mL of crystallization mother liquor.

[0095] (3) Washing: 17.2 g of the dodecanoic acid filter cake obtained in step (2) was washed with 80 mL of purified water and dried in a vacuum drying oven at 80 °C for 5 hours to obtain 16.4 g of dodecanoic acid product. The product purity was 97.3%, and the crystallization yield was 82% (product weight g / crude product weight g). The total acid content and DC content of the obtained product were analyzed. 12 The content of monoacids, total nitrogen, ash, transmittance, color, and yield were measured and calculated, and the results are shown in Table 2.

[0096] Compare with Example 6

[0097] (1) Decolorization: Weigh 20g of crude dodecanoic acid and place it in a 250mL three-hole flask equipped with a stirrer. Then add 80mL of ethanol solvent and heat to 75℃ in a digital display constant temperature water bath while stirring to completely dissolve the dodecanoic acid. Add 0.4g of activated carbon and decolorize by stirring at 75℃ for 80 minutes under sealed conditions. Then filter while hot and collect the clear dodecanoic acid solution.

[0098] (2) Crystallization: All the dodecanoic acid clear liquid obtained in step (1) was placed in a primary crystallization vessel and kept at 70°C for 1.5 hours. Then, the temperature was slowly reduced to 25°C in the crystallization vessel at a rate of 10°C / h. The solution was then vacuum filtered at 0.08 MPa using medium-speed qualitative filter paper as the filter medium, resulting in 15.4 g of dodecanoic acid filter cake and 60 mL of crystallization mother liquor.

[0099] (3) Washing: 15.4 g of the dodecanoic acid filter cake obtained in step (2) was washed with 80 mL of purified water and dried in a vacuum drying oven at 80 °C for 5 hours to obtain 14.6 g of dodecanoic acid product. The product purity was 98.23%, and the crystallization yield was 73% (product weight g / crude product weight g). The total acid content and DC content of the obtained product were analyzed. 12 The content of monoacids, total nitrogen, ash, transmittance, color, and yield were measured and calculated, and the results are shown in Table 2.

[0100] Compare with Example 7

[0101] (1) Decolorization: Weigh 20g of crude dodecanoic acid and place it in a 250mL three-hole flask equipped with a stirrer. Then add 80mL of propyl ether solvent and heat to 75℃ in a digital display constant temperature water bath while stirring to completely dissolve the dodecanoic acid. Add 0.4g of activated carbon and decolorize by stirring at 75℃ for 80 minutes under sealed conditions. Then filter while hot and collect the clear dodecanoic acid solution.

[0102] (2) Crystallization: All the dodecanoic acid clear liquid obtained in step (1) was placed in a primary crystallization vessel and kept at 70°C for 1.5 hours. Then, the temperature was slowly reduced to 25°C in the crystallization vessel at a rate of 10°C / h. The solution was then vacuum filtered at 0.08 MPa using medium-speed qualitative filter paper as the filter medium, resulting in 16.3 g of dodecanoic acid filter cake and 60 mL of crystallization mother liquor.

[0103] (3) Washing: 16.3 g of the dodecanoic acid filter cake obtained in step (2) was washed with 80 mL of purified water and dried in a vacuum drying oven at 80 °C for 5 hours to obtain 15.2 g of dodecanoic acid product. The product purity was 98.5%, and the crystallization yield was 76% (product weight g / crude product weight g). The total acid content and DC content of the obtained product were analyzed. 12 The content of monoacids, total nitrogen, ash, transmittance, color, and yield were measured and calculated, and the results are shown in Table 2.

[0104] Compare with Example 8

[0105] (1) Decolorization: Weigh 20g of crude dodecanoic acid and place it in a 250mL three-hole flask equipped with a stirrer. Then add 80mL of ethylene glycol dimethyl ether solvent. Heat the flask to 75℃ while stirring in a digital display constant temperature water bath until the dodecanoic acid is completely dissolved. Add 0.4g of activated carbon and decolorize by stirring at 75℃ for 80 minutes under sealed conditions. Then filter while hot and collect the clear dodecanoic acid solution.

[0106] (2) Crystallization: All the dodecanoic acid clear liquid obtained in step (1) was placed in a primary crystallization vessel and kept at 70°C for 1.5 hours. Then, the temperature was slowly reduced to 25°C in the crystallization vessel at a rate of 10°C / h. The solution was then vacuum filtered at 0.08 MPa using medium-speed qualitative filter paper as the filter medium, resulting in 13.4 g of dodecanoic acid filter cake and 60 mL of crystallization mother liquor.

[0107] (3) Washing: 12.6 g of the dodecanoic acid filter cake obtained in step (2) was washed with 80 mL of purified water and dried in a vacuum drying oven at 80 °C for 5 hours to obtain 12.6 g of dodecanoic acid product. The product purity was 98.1%, and the crystallization yield was 63% (product weight g / crude product weight g). The total acid content and DC content of the obtained product were analyzed. 12 The content of monoacids, total nitrogen, ash, transmittance, color, and yield were measured and calculated, and the results are shown in Table 2.

[0108] Compare with Example 9

[0109] (1) Decolorization: Weigh 20g of crude dodecanoic acid and place it in a 250mL three-hole flask equipped with a stirrer. Then add 80mL of tetrahydrofuran solvent. Heat the flask to 55℃ while stirring in a digital display constant temperature water bath until the dodecanoic acid is completely dissolved. Add 0.4g of activated carbon and decolorize by stirring at 55℃ for 80 minutes under sealed conditions. Then filter while hot and collect the clear dodecanoic acid solution.

[0110] (2) Crystallization: All the dodecanoic acid clear liquid obtained in step (1) was placed in a primary crystallization vessel and kept at 50°C for 1.5 hours. Then, the temperature was slowly reduced to 25°C in the crystallization vessel at a rate of 10°C / h. The solution was then vacuum filtered at 0.08 MPa using medium-speed qualitative filter paper as the filter medium, resulting in 14.7 g of dodecanoic acid filter cake and 60 mL of crystallization mother liquor.

[0111] (3) Washing: 14.7 g of the dodecanoic acid filter cake obtained in step (2) was washed with 80 mL of purified water and dried in a vacuum drying oven at 80 °C for 5 hours to obtain 13.6 g of dodecanoic acid product. The product purity was 98.2%, and the crystallization yield was 68% (product weight g / crude product weight g). The total acid content and DC content of the obtained product were analyzed. 12The content of monoacids, total nitrogen, ash, transmittance, color, and yield were measured and calculated, and the results are shown in Table 2.

[0112] Table 2. Quality Indicators of Dodecanoic Acid Products Produced in Comparative Examples 1-9

[0113]

[0114] A comparison of Table 2 and Table 1 shows that using 1,4-dioxane as the refining solvent for crude dodecacarbonyl dicarboxylic acid produced by bio-fermentation, the total acid content and DC content of the product in Example 7 of Table 1 are significantly improved. 12 In terms of monoacid content, total nitrogen content, ash content, transmittance, color, and product yield, its effect is superior to acetic acid, DMSO, DMF, ethanol, propyl ether, ethylene glycol dimethyl ether, and tetrahydrofuran solvents. The 1,4-dioxane filtrate from Example 7 can be reused twice without treatment (Table 1 Examples 8 and 9). Furthermore, using 1,4-dioxane as a recrystallization solvent (Table 1 Example 10) can further improve product quality.

Claims

1. A method for purifying crude dodecanoic acid produced by bio-fermentation, characterized in that, The refining method is carried out according to the following steps: (1) Decolorization: using crude dodecanoic acid produced by bio-fermentation as raw material, dissolving it in solvent, adding activated carbon, stirring and decolorizing at a temperature of 65~85℃ for 30~120 min, filtering while hot to obtain dodecanoic acid clear liquid; the solvent is 1,4-dioxane; (2) Crystallization: keeping all the dodecanoic acid clear liquid obtained in step (1) at a temperature of 60~80℃ for 1-2 hours, cooling it to 25℃ at a rate of 8℃~10℃ / h, filtering it with a polypropylene filter membrane with a pore size of 0.1 μm to obtain dodecanoic acid filter cake and crystallization mother liquor, the crystallization mother liquor is directly recycled for reuse as a solvent for refining crude dodecanoic acid; (3) Washing: washing the dodecanoic acid filter cake obtained in step (2) with pure water, vacuum drying to obtain dodecanoic acid product.

2. The refining method as described in claim 1, characterized in that, In step (1), the volume of solvent used is 2-6 mL / g based on the mass of crude dodecanoic acid; the mass of activated carbon added is 0.5-3% based on the mass of crude dodecanoic acid.

3. The refining method as described in claim 1, characterized in that, Step (1) is carried out in a sealed dissolution vessel at a temperature of 70-85℃.

4. The refining method as described in claim 1, characterized in that, The mother liquor from step (2) is used as a solvent to dissolve the raw materials and is reused in step (1).

5. The refining method as described in claim 1, characterized in that, Step (3) The volume of pure water used is 2-11 mL / g based on the weight of the dodecanoic acid filter cake; the vacuum drying is carried out in a vacuum drying oven at 60℃~80℃ for 6-10 hours.

Images