A method for extracting and refining high carbon number dibasic acid

Abstract

The present invention provides a method for extracting and refining a high-carbon dibasic acid, comprising: (1) heating a high-carbon dibasic acid fermentation liquid, separating the bacterial cells by centrifugation or membrane filtration, and obtaining a fermentation liquid clear liquid; adding acid to the clear liquid until the pH value is 2-4 to precipitate and crystallize the high-carbon dibasic acid, and obtaining a crystal liquid; (2) extracting the crystal liquid with an organic solvent, decolorizing the separated extract phase, cooling it, separating the solid matter, and obtaining a first solid; (3) washing the first solid with water, drying it, and then subjecting it to molecular distillation, and collecting the light phase after molecular distillation. The high-carbon dibasic acid includes any one or a combination of two or more of aliphatic straight-chain dicarboxylic acids with 14 to 20 carbon atoms; the organic solvent is selected from any one or a combination of alcohols and ethers. The extraction process of the present invention can achieve the separation of high-carbon dibasic acids from most of the impurities such as monobasic miscellaneous acids, nitrogen, ash, etc., and the obtained product has high purity and low impurity content, and can reach the polymerization level.

Description

Technical Field

[0001] The invention relates to the technical field of long-chain dibasic acids, in particular to a method for extracting and refining dibasic acids with high carbon numbers produced by a biological fermentation method. Background Art

[0002] Long chain dicarboxylic acids refer to aliphatic dicarboxylic acids with more than 10 carbon atoms in the carbon chain, including saturated and unsaturated dicarboxylic acids. They are a kind of fine chemical products with important and extensive industrial applications. They are important basic raw materials for synthesizing advanced fragrances, high-performance nylon engineering plastics, high-grade nylon hot melt adhesives, high-temperature dielectrics, advanced paints and coatings, advanced lubricants, cold-resistant plasticizers, resins, medicines and pesticides in the chemical industry. Due to the broad development potential of downstream products of long chain dicarboxylic acids, the demand for long chain dicarboxylic acids at home and abroad will continue to increase, and its market potential is huge.

[0003] The biological method (fermentation method) to produce long-chain dibasic acids is the application of microbial technology in the field of petrochemicals that emerged in the 1970s. Its characteristics are that it uses abundant petroleum resources as raw materials, utilizes the unique oxidation ability of microorganisms and the action of microbial intracellular enzymes, and oxidizes the two methyl groups at both ends of long-chain n-alkanes to carboxyl groups at room temperature and pressure to generate various long-chain dibasic acids of corresponding chain lengths; the biological method of producing long-chain dibasic acids overcomes the various shortcomings of simple chemical synthesis methods and vegetable oil cracking methods, and opens up a new way for the mass production of long-chain dibasic acids. Compared with chemical synthesis methods, the biological method of producing long carbon chain dibasic acids has unquestionable advantages and is widely valued at home and abroad. The biological method can not only provide a series of long carbon chain dibasic acid monomers from C9 to C18 and even C22, but also produce dibasic acids with high carbon atoms (such as dibasic acids above C14) that cannot be produced by chemical synthesis, which greatly expands the application of dibasic acids in the industrial field.

[0004] In the process of preparing polyamide using high-carbon dibasic acid as raw material, if the high-carbon dibasic acid product has high content of impurities such as ash, nitrogen-containing compounds, organic solvents, and miscellaneous acids, these impurities will affect the polymerization of dibasic acid and diamine during the process of preparing polyamide using it as raw material, and further affect the performance of the obtained polyamide; for example, when the content of miscellaneous acid (such as monobasic acid) is high, the degree of polymerization of the obtained polyamide will not reach the theoretical value, and the molecular weight, viscosity, and fluidity of the polyamide resin will deviate from expectations; for another example, since the polymerization process of dibasic acid and diamine is carried out under high temperature and high pressure conditions, the presence of nitrogen-containing compounds can easily lead to side reactions, produce colored groups, and thus cause the polyamide product to change color.

[0005] Therefore, strictly controlling the impurity content in the finished high-carbon dibasic acid products and improving product quality are of great significance for the downstream applications of high-carbon dibasic acids, such as polymerization-grade raw materials for polyamides. Summary of the invention

[0006] The present invention provides a method for extracting and refining a high carbon number dibasic acid, comprising the following steps:

[0007] (1) heating the high carbon number dibasic acid fermentation liquid to 60-150° C., separating the bacterial cells by centrifugation or membrane filtration, and obtaining a fermentation liquid clear liquid; adding acid to the fermentation liquid clear liquid to a pH value of 2-4 to precipitate and crystallize the high carbon number dibasic acid, and obtaining a crystal liquid;

[0008] (2) extracting the crystallization liquid with an organic solvent, decolorizing the separated extract phase, cooling it to precipitate and crystallize the high carbon number dibasic acid, and separating the solid matter to obtain a first solid;

[0009] (3) washing and drying the first solid and then performing molecular distillation, collecting the light phase after molecular distillation, and obtaining a purified high-carbon dibasic acid product;

[0010] The high carbon number dibasic acid includes any one or a combination of two or more aliphatic straight-chain dicarboxylic acids having 14 to 20 carbon atoms;

[0011] The organic solvent is selected from any one of alcohol and ether or a combination thereof.

[0012] The extraction process of high-carbon dibasic acid in one embodiment of the present invention can separate high-carbon dibasic acid from most of the monobasic acids, nitrogen, ash and other impurities. The obtained product has high purity and low impurity content and can reach the polymerization grade level. DETAILED DESCRIPTION

[0013] Typical embodiments that embody the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various changes in different embodiments without departing from the scope of the present invention.

[0014] One embodiment of the present invention provides a method for extracting and refining a high carbon number dibasic acid, comprising the following steps:

[0015] (1) heating the high carbon number dibasic acid fermentation liquid to 60-150° C., separating the bacterial cells by centrifugation or membrane filtration, and obtaining a fermentation liquid clear liquid; adding acid to the fermentation liquid clear liquid to a pH value of 2-4 to precipitate and crystallize the high carbon number dibasic acid, and obtaining a crystal liquid;

[0016] (2) extracting the crystallization liquid with an organic solvent, decolorizing the separated extract phase, cooling it to precipitate and crystallize the high carbon number dibasic acid, and separating the solid matter to obtain a first solid;

[0017] (3) washing and drying the first solid and then performing molecular distillation, collecting the light phase after molecular distillation, and obtaining a purified high-carbon dibasic acid product;

[0018] The high carbon number dibasic acid includes any one or a combination of two or more aliphatic straight-chain dicarboxylic acids having 14 to 20 carbon atoms;

[0019] The organic solvent is selected from any one of alcohol and ether or a combination thereof.

[0020] In one embodiment, the high carbon number dibasic acid is prepared by biological method. It is obtained by microbial fermentation using alkanes, fatty acids or fatty acid derivatives as substrates. The microorganism can oxidize the terminal methyl of alkanes, fatty acids or fatty acid derivatives to carboxyl groups to generate high carbon number dibasic acids.

[0021] In one embodiment, the high carbon number dibasic acid includes any one of linear tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, heptadecanedioic acid, octadecanedioic acid or 9-ene-octadecanedioic acid, or a combination of two or more thereof.

[0022] In one embodiment, in step (1), the high carbon number dibasic acid fermentation broth is heated to 70-90°C.

[0023] In one embodiment, the pH of the high-carbon dibasic acid fermentation liquid is 6.0 to 12, and further 7.5 to 10.5.

[0024] In one embodiment, the pH value of the high carbon number dibasic acid fermentation broth can be adjusted by adding alkali, and the types of alkali include sodium hydroxide, calcium hydroxide, potassium hydroxide, and ammonia water.

[0025] In one embodiment, the membrane filtration separation adopts microfiltration membrane filtration and / or ultrafiltration membrane filtration.

[0026] In one embodiment, the temperature of the membrane filtration separation is 70-130°C.

[0027] In one embodiment, the pore size of the microfiltration membrane is 0.01 to 1 micrometer, further can be 0.01 to 0.2 micrometer, further can be 0.05 to 0.1 micrometer.

[0028] In one embodiment, the molecular weight cutoff of the ultrafiltration membrane is 1000-200000 Da, further can be 2000-100000 Da, further can be 2000-20000 Da, for example 3000 Da, 5000 Da, 10000 Da, 50000 Da.

[0029] In one embodiment, the ultrafiltration membrane includes but is not limited to a ceramic membrane, a polypropylene membrane, a polysulfone membrane, a polyethersulfone membrane, and the like.

[0030] In one embodiment, in the step (2), the ratio of the organic solvent to the high carbon dibasic acid in the crystallization solution is (1.5-7) L:1 kg, and further is (3-7) L:1 kg.

[0031] In one embodiment, in the step (2), the organic solvent is a composition of alcohol and ether, and the volume ratio of the alcohol to the ether is 1:(15-50), further 1:(25-50).

[0032] In one embodiment, in step (2), the alcohol has 2 to 5 carbon atoms, further comprising any one or a combination of two or more of ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, 2-methyl-1-propanol, and 2-methyl-2-propanol.

[0033] In one embodiment, in step (2), the ether has 2 to 8 carbon atoms, further 2 to 6 carbon atoms, and further includes any one of ethyl ether, propyl ether, n-butyl ether, isobutyl ether, amyl ether, isopentyl ether, and n-hexyl ether, or a combination of two or more thereof.

[0034] In one embodiment, in the step (2), the extraction temperature is 70 to 120° C., further 80 to 100° C. The extraction can be performed by heating to the above temperature in a sealed device.

[0035] In one embodiment, the extraction time is 30 to 180 min, further 30 to 90 min.

[0036] In one embodiment, after extraction, the mixture is allowed to stand for separation to obtain an extract phase.

[0037] In one embodiment, after extraction, decolorization and crystallization with an organic solvent, most of the impurities are removed. However, there are still a small amount of impurities that are soluble in organic solvents and have crystallization properties similar to those of high-carbon dibasic acids and cannot be removed by organic solvent crystallization.

[0038] In one embodiment, the decolorization process is achieved by contacting the liquid to be decolorized with a decolorizing agent.

[0039] In one embodiment, the decolorization process may include mixing the liquid to be decolorized with activated carbon for solid-liquid decolorization; further, the decolorization effect may be improved by stirring the solid-liquid mixture. It is generally known to those skilled in the art that the decolorization process includes separating the decolorizing agent by filtering or centrifuging to obtain a decolorized liquid.

[0040] In one embodiment, the temperature of the decolorization treatment is 70-100°C.

[0041] In one embodiment, the decolorization treatment time is 25 to 120 minutes, and further 25 to 90 minutes.

[0042] In one embodiment, the decolorization treatment uses activated carbon as a decolorizing agent, and the mass ratio of activated carbon to high carbon number dibasic acid in the decolorization system is (0.5-5):100.

[0043] In one embodiment, in the step (2), the terminal temperature of the cooling is 25 to 65°C, and further 25 to 45°C.

[0044] In one embodiment, in the step (3), the temperature of the evaporation surface of the molecular distillation treatment is 120 to 200°C, further 130 to 185°C, further 130 to 160°C.

[0045] In one embodiment, the temperature of the condensation surface is 95 to 160°C, further 115 to 145°C, and further 115 to 135°C.

[0046] In one embodiment, the feed rate is 10 to 90 kg / h / m 2 , further 15~60kg / h / m 2 .

[0047] In one embodiment, from the perspective of further improving the yield of the dibasic acid product, the method may further include the following steps: recovering the residual high-carbon dibasic acid from the bacterial cells or the slurry containing the bacterial cells separated in step (1).

[0048] In one embodiment, from the perspective of further improving the yield of the dibasic acid product, the method may further include the following steps: recovering the residual high carbon number dibasic acid from the residue after separating the extraction phase in step (1).

[0049] In one embodiment, from the perspective of further improving the yield of the dibasic acid product, the method may further include the following steps: recovering the residual high carbon number dibasic acid from the mother liquor after separating the crystals in step (2).

[0050] In one embodiment, the aqueous phase remaining after separation of the extraction phase in step (2) can be treated to recover inorganic salts for use as a culture medium in the dibasic acid fermentation process. The remaining aqueous phase contains inorganic salts, which can be purified and refined to obtain purified inorganic salt crystals, which can be directly used as chemical additives and agricultural additives. Comprehensive resource utilization and circular economy are achieved, and emissions are reduced.

[0051] In the extraction process of one embodiment of the present invention, the organic mixed solvent can be recycled.

[0052] The extraction process of one embodiment of the present invention can effectively remove impurities such as bacteria, pigments, proteins, miscellaneous acids, nitrogen, ash, etc. by a simple separation method.

[0053] The extraction process of one embodiment of the present invention can extract a high-carbon dibasic acid product with high purity and low impurity content, and can be widely used in hot melt adhesives, rust inhibitors, fragrances, coatings, lubricating oils, and nylon polymerization raw materials, and can reach polymerization grade level.

[0054] The long-chain dibasic acid extraction method of one embodiment of the present invention can reduce the content of various impurities in the high-carbon dibasic acid by adjusting the type and proportion of the extractant and combining it with the molecular distillation process, and improve the quality of the long-chain dibasic acid product and the subsequently prepared polyamide product.

[0055] In one embodiment, the purity of the purified high-carbon dibasic acid product is ≥99.0%, further ≥99.6%.

[0056] In one embodiment, the monoacid content of the purified high-carbon dibasic acid product is ≤1500 ppm, further ≤1000 ppm, further ≤500 ppm.

[0057] In one embodiment, the light transmittance of the purified high-carbon dibasic acid product is ≥98%, further ≥99%.

[0058] In one embodiment, the total nitrogen content of the purified high-carbon dibasic acid product is ≤100 ppm, further ≤60 ppm, further ≤40 ppm.

[0059] The following is a further description of the method for extracting long-chain dibasic acids according to one embodiment of the present invention through specific examples. The raw materials used, unless otherwise specified, are commercially available, and the test methods used are as follows:

[0060] 1. Purity and residual monoacid content detection of high carbon number dibasic acid products

[0061] Gas chromatography.

[0062] 2. Total nitrogen content detection

[0063] Kjeldahl method.

[0064] 3. Light transmittance test:

[0065] Taking advantage of the different colors of substances, different transmittances and absorption properties at certain wavelengths, the transmittance of a 25% dimethyl sulfoxide solution of the dibasic acid sample at 440nm is used to indicate the color of the dibasic acid product.

[0066] 4. Polyamide Yellow Index (YI) Test:

[0067] Tested according to HG / T 3862.

[0068] 5. Polyamide viscosity fluctuation test:

[0069] First, the average value of the relative viscosity of 10 batches of samples is calculated, and then the absolute value of the difference between the relative viscosity of the 10 batches of samples and the average value is calculated. The average value of the obtained 10 absolute values ​​is calculated as the viscosity fluctuation.

[0070] Example 1

[0071] The fermentation liquid of hexadecanedioic acid was obtained by referring to the fermentation method of Example 8 of CN1570124A.

[0072] The fermentation liquid of 16-carbon dicarboxylic acid (pH 8.1) is heated to 85°C, filtered through a microfiltration membrane (pore size 0.5um) to separate the bacterial cells, and a fermentation liquid clear liquid is obtained. Sulfuric acid is added to the fermentation liquid clear liquid to acidify it to a pH value of 2.5 to precipitate and crystallize the 16-carbon dicarboxylic acid, and a crystal liquid is obtained.

[0073] (2) extracting the crystallized liquid with an organic solvent at an extraction temperature of 92° C. for 50 min, allowing the liquid to stand and separate into layers to form an extraction phase (organic phase) and an aqueous phase, separating the extraction phase, and decolorizing the extraction phase at a decolorization temperature of 92° C. for 45 min. The mass ratio of activated carbon to hexadecane dicarboxylic acid in the decolorization system is 2:100. After decolorization, separating the activated carbon, cooling the decolorized liquid to 35° C. to allow the hexadecane dicarboxylic acid to precipitate and crystallize, and separating the solid to obtain a first solid.

[0074] The organic solvent is a combination of ethanol and propyl ether, and the volume ratio of ethanol to propyl ether is 1:30. The ratio of the total volume of the organic solvent to the hexadecane dibasic acid in the crystallization solution is 4L:1kg.

[0075] (3) The first solid is washed and dried with a paddle dryer before molecular distillation. The feed rate for molecular distillation is 30 kg / h / m 2 The temperature of the evaporation surface is 145°C, the temperature of the condensation surface is 125°C, and the light phase is collected to obtain the product. The purity, impurity content and light transmittance of the product are tested and calculated, and the results are shown in Table 1.

[0076] Example 2

[0077] The method is substantially the same as Example 1, except that the organic solvent is a combination of ethanol and propyl ether, and the volume ratio of ethanol to propyl ether is 1:45.

[0078] Example 3

[0079] The method is basically the same as Example 1, except that the organic solvent is a combination of ethanol and propyl ether, and the volume ratio of ethanol to propyl ether is 1:15.

[0080] Example 4

[0081] The method is substantially the same as Example 1, except that the organic solvent is a combination of ethanol and propyl ether, and the volume ratio of ethanol to propyl ether is 1:50.

[0082] Example 5

[0083] The method is substantially the same as Example 1, except that the organic solvent is a combination of ethanol and ether, and the volume ratio of ethanol to ether is 1:30.

[0084] Example 6

[0085] The method is substantially the same as Example 1, except that the organic solvent is a combination of ethanol and n-hexyl ether, and the volume ratio of ethanol to n-hexyl ether is 1:30.

[0086] Example 7

[0087] The method is substantially the same as Example 1, except that the organic solvent is a combination of isopropanol and ether, and the volume ratio of isopropanol to ether is 1:30.

[0088] Example 8

[0089] The method is basically the same as Example 1, except that the organic solvent is a combination of ethanol, isopropanol and propyl ether, and the volume ratio of ethanol, isopropanol and propyl ether is 1:1:60.

[0090] Example 9

[0091] The method is basically the same as Example 1, except that the ratio of the total volume of the organic solvent to the hexadecane dibasic acid in the crystallization solution is 1.5 L:1 kg.

[0092] Example 10

[0093] The same as Example 1, the only difference is that the feed rate of molecular distillation is 15kg / h / m 2 .

[0094] Embodiment 11

[0095] The same as Example 1, the only difference is that the feed rate of molecular distillation is 90kg / h / m 2 .

[0096] Example 12

[0097] It is basically the same as Example 1, except that the temperature of the evaporation surface is 180°C and the temperature of the condensation surface is 140°C.

[0098] Embodiment 13

[0099] It is basically the same as Example 1, except that the temperature of the evaporation surface is 120°C and the temperature of the condensation surface is 95°C.

[0100] Embodiment 14

[0101] The fermentation liquid of pentadecadienoic acid was obtained according to the fermentation method of Example 7 of CN1570124A.

[0102] The fermentation liquid of 15-carbon dicarboxylic acid (pH 8.0) is heated to 90°C, filtered through a microfiltration membrane (pore size 0.5um) to separate the bacterial cells, and a fermentation liquid is obtained. Sulfuric acid is added to the fermentation liquid to acidify the pH value to 2.8 to precipitate and crystallize the 15-carbon dicarboxylic acid, and a crystal liquid is obtained.

[0103] (2) extracting the crystallized liquid with an organic solvent at an extraction temperature of 95° C. for 45 min, allowing the liquid to stand and separate into layers to form an extraction phase (organic phase) and an aqueous phase, separating the extraction phase, and decolorizing the extraction phase at a decolorization temperature of 97° C. for 40 min. The mass ratio of activated carbon to 15-carbon dicarboxylic acid in the decolorization system is 2.5:100. After decolorization, separating the activated carbon, cooling the decolorized liquid to 40° C. to precipitate and crystallize the 15-carbon dicarboxylic acid, and separating the solid to obtain a first solid.

[0104] The organic solvent is a combination of ethanol and propyl ether, and the volume ratio of ethanol to propyl ether is 1:30. The ratio of the total volume of the organic solvent to the 15-carbon dicarboxylic acid in the crystallization solution is 3.5 L:1 kg.

[0105] (3) The first solid was washed and dried by a paddle dryer before molecular distillation. The feed rate of molecular distillation was 50 kg / h / m 2 The temperature of the evaporation surface is 140°C, the temperature of the condensation surface is 117°C, and the light phase is collected to obtain the product. The purity, impurity content and light transmittance of the product are tested and calculated, and the results are shown in Table 1.

[0106] Embodiment 15

[0107] According to the fermentation method of Example 1 of CN101121653A, linoleic acid is used as a substrate for fermentation to obtain a fermentation liquid of octadecenoic acid.

[0108] The fermentation liquid of octadecenoic acid (pH 8.1) is heated to 85°C, filtered through a microfiltration membrane (pore size 0.5um) to separate the bacterial cells, and a fermentation liquid is obtained. Sulfuric acid is added to the fermentation liquid to acidify the pH value to 2.5 to precipitate and crystallize octadecenoic acid, and a crystal liquid is obtained.

[0109] (2) extracting the crystallized liquid with an organic solvent at an extraction temperature of 92° C. for 50 min, allowing the liquid to stand and separate into layers to form an extraction phase (organic phase) and an aqueous phase, separating the extraction phase, and decolorizing the extraction phase at a decolorization temperature of 97° C. for 50 min. The mass ratio of activated carbon to octadecenoic acid in the decolorization system is 2:100. After decolorization, the activated carbon is separated, the decolorized liquid is cooled to 42° C. to precipitate and crystallize octadecenoic acid, and the solid is separated to obtain a first solid.

[0110] The organic solvent is a combination of ethanol and propyl ether, and the volume ratio of ethanol to propyl ether is 1:30. The ratio of the total volume of the organic solvent to the octadecenoic acid in the crystallization solution is 4.5L:1kg.

[0111] (3) The first solid was washed and dried by a paddle dryer before molecular distillation. The feed rate of molecular distillation was 20 kg / h / m 2 The temperature of the evaporation surface is 147°C, the temperature of the condensation surface is 123°C, and the light phase is collected to obtain the product. The purity, impurity content and light transmittance of the product are tested and calculated, and the results are shown in Table 1.

[0112] Example 16

[0113] The fermentation liquid of 15-carbon dicarboxylic acid was obtained according to the fermentation method of Example 6 of CN110218661A.

[0114] The fermentation liquid of 15-carbon dicarboxylic acid (pH 5.7) is heated to 115°C, filtered through a microfiltration membrane (pore size 0.5um) to separate the bacterial cells, and a fermentation liquid is obtained. Sulfuric acid is added to the fermentation liquid to acidify the pH value to 2.7 to precipitate and crystallize the 15-carbon dicarboxylic acid, and a crystal liquid is obtained.

[0115] (2) extracting the crystallized liquid with an organic solvent at an extraction temperature of 95° C. for 45 min, allowing the liquid to stand and separate into layers to form an extraction phase (organic phase) and an aqueous phase, separating the extraction phase, and decolorizing the extraction phase at a decolorization temperature of 90° C. for 35 min. The mass ratio of activated carbon to 15-carbon dicarboxylic acid in the decolorization system is 3:100. After decolorization, separating the activated carbon, cooling the decolorized liquid to 38° C. to allow the 15-carbon dicarboxylic acid to precipitate and crystallize, and separating the solid to obtain a first solid.

[0116] The organic solvent is a combination of ethanol and ether, and the mass ratio of ethanol to ether is 1:45. The ratio of the total mass of the organic solvent to the dry weight of 15-carbon dicarboxylic acid in the crystallization solution is 3L:1kg.

[0117] (3) The first solid was washed and dried by a paddle dryer before molecular distillation. The feed rate of molecular distillation was 45 kg / h / m 2The temperature of the evaporation surface is 142°C, the temperature of the condensation surface is 115°C, and the light phase is collected to obtain the product. The purity, impurity content and light transmittance of the product are tested and calculated, and the results are shown in Table 1.

[0118] Table 1:

[0119] purity(%) Monoacid content (ppm) Total nitrogen content (ppm) Light transmittance (%) Example 1 99.6 860 55 98.8 Example 2 99.8 260 28 99.5 Example 3 99.2 1520 77 98.2 Example 4 99.7 450 38 99.6 Example 5 99.7 475 41 99.4 Example 6 99.8 280 27 99.6 Example 7 99.0 1885 95 98.1 Example 8 99.7 492 35 99.5 Example 9 99.0 1952 182 98.0 Example 10 99.7 389 35 99.7 Embodiment 11 99.4 680 60 99.1 Example 12 99.5 561 51 99.2 Embodiment 13 99.2 1750 72 98.4 Embodiment 14 99.7 543 33 99.5 Embodiment 15 99.6 496 42 99.6 Example 16 99.8 526 35 99.5

[0120] Polyamide was prepared using the high carbon number dibasic acid obtained in Examples 1 to 16 as a raw material, and the specific process was as follows:

[0121] The air in a 100-liter polymerization kettle was replaced with nitrogen, 15 kg of pure water was added to the reactor, and then 115.2 mol of pentamethylenediamine was added. After stirring, 115.2 mol of a dibasic acid with a high carbon number was added, and the pH value was adjusted to 7.21 (detection result at 30° C. and diluted to 10%) to obtain a polyamide salt aqueous solution.

[0122] Under nitrogen environment, the oil bath temperature was gradually raised to 288°C. After the pressure in the polymerization reactor rose to 1.7 MPa, exhaust began. When the temperature in the reactor reached 265°C, the reactor was evacuated to -0.05 MPa and the vacuum was maintained for 40 minutes to obtain polyamide. The yellowness index and viscosity fluctuation of the obtained polyamide were tested, and the results are shown in Table 2.

[0123] Table 2:

[0124] Polyamide Yellow Index Polyamide viscosity fluctuations Example 1 8 0.034 Example 2 5 0.018 Example 3 14 0.089 Example 4 6 0.022 Example 5 6 0.029 Example 6 5 0.017 Example 7 12 0.062 Example 8 7 0.031 Example 9 13 0.072 Example 10 6 0.027 Embodiment 11 9 0.051 Example 12 10 0.056 Embodiment 13 13 0.085 Embodiment 14 5 0.023 Embodiment 15 5 0.029 Example 16 5 0.027

[0125] Unless otherwise defined, the terms used in the present invention have the meanings commonly understood by those skilled in the art.

[0126] The embodiments described in the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Those skilled in the art may make various other substitutions, changes and improvements within the scope of the present invention. Therefore, the present invention is not limited to the above embodiments, but is only limited by the claims.

Claims

1. A method for extracting and refining a high carbon number dibasic acid, comprising the following steps: (1) heating the high carbon number dibasic acid fermentation liquid to 60-150° C., separating the bacterial cells by centrifugation or membrane filtration, and obtaining a fermentation liquid clear liquid; adding acid to the fermentation liquid clear liquid to a pH value of 2-4 to precipitate and crystallize the high carbon number dibasic acid, and obtaining a crystal liquid; (2) extracting the crystallization liquid with an organic solvent, decolorizing the separated extract phase, cooling it to precipitate and crystallize the high carbon number dibasic acid, and separating the solid matter to obtain a first solid; (3) washing and drying the first solid and then performing molecular distillation, collecting the light phase after molecular distillation, and obtaining a purified high-carbon dibasic acid product; The high carbon number dibasic acid includes any one or a combination of two or more aliphatic straight-chain dicarboxylic acids having 14 to 20 carbon atoms; The organic solvent is selected from any one of alcohol and ether or a combination thereof.

2. The method according to claim 1, wherein in step (1), the membrane filtration separation adopts microfiltration membrane filtration and / or ultrafiltration membrane filtration; and / or, The temperature of the membrane filtration separation is 70 to 130° C.; and / or, The pH value of the high carbon number dibasic acid fermentation liquid is 6.0 to 12; and / or, The high carbon number dibasic acid includes any one or a combination of two or more of linear tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, heptadecanedioic acid, octadecanedioic acid or 9-ene-octadecanedioic acid.

3. The method according to claim 1, wherein in step (2), the ratio of the organic solvent to the high carbon number dibasic acid in the crystallization solution is (1.5-7) L:1 kg, further (3-7) L:1 kg.

4. The method according to claim 1 or 3, wherein in step (2), the organic solvent is a composition of alcohol and ether, and the volume ratio of the alcohol to the ether is 1:(15-50), further 1:(25-50).

5. The method according to claim 1 or 3, wherein in step (2), the alcohol has 2 to 5 carbon atoms, further comprising any one or a combination of two or more of ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, 2-methyl-1-propanol, and 2-methyl-2-propanol.

6. The method according to claim 1 or 3, wherein in step (2), the ether has 2 to 8 carbon atoms, further 2 to 6 carbon atoms, and further comprises any one of ethyl ether, propyl ether, n-butyl ether, isobutyl ether, amyl ether, isopentyl ether, and n-hexyl ether, or a combination of two or more thereof.

7. The method according to claim 1, wherein in step (2), the extraction temperature is 70 to 120°C; and / or, The extraction time is 30 to 180 minutes; and / or, After extraction, the extract phase is separated by standing and stratification; and / or, The temperature of the decolorization treatment is 70 to 100°C; and / or, The decolorization time is 25 to 120 minutes; and / or, The decolorization treatment uses activated carbon as a decolorizing agent, and the mass ratio of activated carbon to high carbon number dibasic acid in the decolorization system is (0.5-5):100; and / or, The terminal temperature of the cooling is 25-65°C.

8. The method according to claim 1, wherein in step (3), the temperature of the evaporation surface treated by molecular distillation is 120 to 200°C, further 130 to 185°C, further 130 to 160°C; and / or, The temperature of the condensation surface is 95 to 160° C., further 115 to 145° C., further 115 to 135° C.; and / or, Feeding speed is 10~90kg / h / m 2 , further 15~60kg / h / m 2 .

9. The method according to claim 1, wherein: The following steps are also included: Recovering residual high-carbon dibasic acid from the bacterial cells separated in step (1) or the slurry containing the bacterial cells; and / or, Recovering the residual high carbon number dibasic acid from the residue after separation of the extraction phase in step (1); and / or, The residual high carbon number dibasic acid is recovered from the mother liquor after the crystals are separated in the step (2).

10. The method according to claim 1, wherein the purity of the purified high-carbon dibasic acid product is ≥99.0%, further ≥99.6%; and / or the monoacid content is ≤1500ppm, further ≤1000ppm, further ≤500ppm; and / or the transmittance is ≥98%, further ≥99%; and / or the total nitrogen content is ≤100ppm, further ≤60ppm, further ≤40ppm.