Method and system for extracting long-chain dicarboxylic acid

Abstract

The invention provides a method and system for extracting long-chain dicarboxylic acid, and the method comprises the following steps: (1) carrying out primary membrane filtration treatment on long-chain dicarboxylic acid fermentation liquor to obtain first filtrate; carrying out decoloration treatment, acidification crystallization and solid-liquid separation treatment on the first filtrate to obtain a first solid; (2) mixing the first solid, alkali and water to form a solution, and performing secondary membrane filtration treatment on the solution to obtain a second filtrate; carrying out decoloration treatment, acidification crystallization and solid-liquid separation treatment on the second filtrate to obtain a second solid; and (3) mixing the second solid with water to form a mixture, carrying out heat preservation treatment on the mixture at 105-150 DEG C, then carrying out cooling crystallization, and carrying out solid-liquid separation treatment. According to the extraction method of the long-chain dicarboxylic acid in one embodiment of the invention, the obtained long-chain dicarboxylic acid product is high in purity, extremely low in alkane residue and even free of residue, and does not contain an organic solvent.

Description

[0001] This application is a divisional application with an application date of December 19, 2019, application number 2019113208392 and invention name “A method and system for extracting long-chain dibasic acids”. Technical Field

[0002] The invention relates to a long-chain dibasic acid, in particular to a method and a system for extracting the long-chain dibasic acid produced by a biological fermentation method. Background Art

[0003] Long chain dicarboxylic acids (LCDA, DCn for short, n=9-18) are an important organic intermediate, which is widely used in the fields of chemical industry, light industry, pesticides, medicine, new materials, etc. Long chain dicarboxylic acids do not exist in nature and can generally be prepared by chemical synthesis and biological fermentation. The chemical synthesis method has a long synthesis route and strict reaction conditions. There are few varieties of long chain dicarboxylic acids synthesized by chemical methods, and there are only a few varieties such as dodecane dicarboxylic acid. At present, the most conventional method for preparing long chain dicarboxylic acids is to obtain them by biological fermentation of long carbon chain alkanes, fatty acids, fatty acid esters or fatty acid salts under specific strains. The extraction and purification technology of long chain dicarboxylic acids also affects the quality and cost of the final industrially produced dicarboxylic acids.

[0004] Patent application with publication number CN102476987A discloses a method for refining long-chain dibasic acids by combining ultrafiltration and liquid-liquid extraction. After the fermentation broth in the fermentation process is filtered through a microfiltration membrane to remove solid particles, it is first filtered through an organic ultrafiltration membrane with a molecular flux of 3000 to 50000 Daltons to remove some proteins and pigments in the filtrate. Then, the ultrafiltrate is mixed with an extractant (one or more C4 to C 12 The extractant and the ultrafiltrate are mixed and stirred for a certain period of time under a certain pH value and temperature, and then liquid-liquid separation is performed, and the extract phase is cooled and crystallized, and the purified product is obtained after removing the solvent.

[0005] Since organic solvents are used in the above purification process, there will be residual solvents in the wet crystal product. During the drying process, a solvent recovery device needs to be added. At the same time, the solvent in the product cannot be completely removed during the drying process, thus affecting the final performance of the product. In addition, organic solvents are easy to volatilize and lose, and the cost is high.

[0006] In addition, in the existing process of refining long-chain dibasic acids from fermentation broth, the fermentation substrate alkanes are usually difficult to remove by conventional filtration or centrifugation. The reason is that the residual alkanes in the fermentation broth exist in liquid form, with a molecular size close to that of long-chain dibasic acids. Sometimes they form emulsion droplets with complex components in the system, or adsorb with solids therein, making them difficult to remove by conventional means such as centrifugation.

[0007] If the long-chain dibasic acid product contains high levels of impurities such as ash, nitrogen-containing compounds, alkanes, organic solvents, and miscellaneous acids, these impurities will affect the polymerization of the dibasic acid and diamine during the preparation of polyamide using the dibasic acid as raw material, thereby affecting the performance of the polyamide obtained. For example, when the content of miscellaneous acids (such as monobasic acids) is high, the degree of polymerization of the polyamide obtained 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 the 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 and produce colored groups, thereby causing the polyamide product to change color.

[0008] In summary, most of the existing methods for purifying long-chain dibasic acids from fermentation broth have the problem of complex processes, and the dibasic acid products have high impurity content, alkane and solvent residues, which will affect the performance of polyamide products prepared from dibasic acids. Summary of the invention

[0009] The present invention provides a method for extracting a long-chain dibasic acid, comprising the following steps:

[0010] (1) filtering the long-chain dibasic acid fermentation broth through a primary membrane to obtain a first filtrate; subjecting the first filtrate to decolorization, acidification, crystallization, and solid-liquid separation to obtain a first solid;

[0011] (2) mixing the first solid, alkali and water to form a solution, subjecting the solution to secondary membrane filtration to obtain a second filtrate; subjecting the second filtrate to decolorization, acidification crystallization and solid-liquid separation to obtain a second solid;

[0012] (3) The second solid is mixed with water to form a mixture, the mixture is kept at 105-150° C., then cooled to crystallize, and solid-liquid separation is performed.

[0013] The invention also provides a long-chain dibasic acid obtained by extraction using the above method.

[0014] The present invention further provides a long-chain dibasic acid extraction system, comprising:

[0015] The primary membrane filtration unit is used for the first membrane filtration of the long-chain dibasic acid fermentation broth;

[0016] A first acidification crystallization unit, used for acidifying and crystallizing the first filtrate obtained after the first membrane filtration to obtain a first solid-liquid mixture;

[0017] A first separation unit, used for performing solid-liquid separation on the first solid-liquid mixture;

[0018] A secondary membrane filtration unit, used to form a solution from the solid separated by the first separation unit and perform a second membrane filtration;

[0019] A second acidification crystallization unit, used for acidifying and crystallizing the second filtrate obtained after the second membrane filtration to obtain a second solid-liquid mixture;

[0020] a second separation unit, configured to perform solid-liquid separation on the second solid-liquid mixture; and

[0021] a crystallization unit, used to convert the solid separated by the second separation unit into a solution, and perform heat preservation and cooling crystallization to obtain a third solid-liquid mixture; and

[0022] The third separation unit is used for performing solid-liquid separation on the third solid-liquid mixture.

[0023] The long-chain dibasic acid extraction method of one embodiment of the present invention can obtain a long-chain dibasic acid product with high purity, extremely low alkane residue, and no organic solvent residue. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of a system for extracting long-chain dibasic acids according to one embodiment of the present invention. DETAILED DESCRIPTION

[0025] 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 variations in different embodiments without departing from the scope of the present invention, and the descriptions and illustrations therein are essentially for illustrative purposes rather than for limiting the present invention. Among them, "primary", "secondary", "tertiary", "first", "second", "third", etc. are used to distinguish multiple processes or products with the same name, but are not intended to limit them.

[0026] One embodiment of the present invention provides a method for extracting a long-chain dibasic acid, which is used to extract a long-chain dibasic acid from a long-chain dibasic acid fermentation broth. The method comprises:

[0027] (1) filtering the long-chain dibasic acid fermentation broth through a primary membrane to obtain a first filtrate; subjecting the first filtrate to decolorization, acidification, crystallization, and solid-liquid separation to obtain a first solid;

[0028] (2) adding the first solid to water, adding alkali to dissolve the first solid to form a solution, subjecting the solution to secondary membrane filtration to obtain a second filtrate; subjecting the second filtrate to decolorization, acidification crystallization, and solid-liquid separation to obtain a second solid;

[0029] (3) The second solid is mixed with water to form a mixture, and the mixture is kept at 105-150° C., then cooled to crystallize and perform solid-liquid separation.

[0030] In the present invention, the long-chain dibasic acid fermentation broth can be a fermentation broth obtained by using alkanes, fatty acids and their derivatives as substrates and utilizing a microbial fermentation method; wherein the microorganisms are used to convert the terminal methyl groups of alkanes, fatty acids and fatty acid derivatives into carboxyl groups through oxidation, thereby generating long-chain dibasic acids.

[0031] In one embodiment, the long chain dibasic acid is C9 to C 18 of dicarboxylic acids.

[0032] In one embodiment, the long-chain dibasic acid is a straight-chain saturated or unsaturated dicarboxylic acid.

[0033] In one embodiment, the long-chain dibasic acid can be one or more of azelaic acid, decanedioic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedicarboxylic acid, hexadecanedioic acid, heptadecanedioic acid, octadecanedicarboxylic acid, and 9-ene-octadecanedicarboxylic acid.

[0034] In one embodiment, the long-chain dibasic acid fermentation broth may be heated to 50-100° C., or further to 70-90° C., and then subjected to a primary membrane filtration.

[0035] In one embodiment, before the primary membrane filtration, the temperature of the long-chain dibasic acid fermentation broth can be 65°C, 68°C, 72°C, 74°C, 75°C, 76°C, 78°C, 80°C, 82°C, 84°C, 85°C, 86°C, 88°C, 90°C, 92°C, 95°C, 96°C, or 98°C.

[0036] In one embodiment, the pH value of the long-chain dibasic acid fermentation broth can be adjusted to 6.0-12 to dissolve the long-chain dibasic acid, and further to 8-11, followed by a primary membrane filtration.

[0037] In one embodiment, before the primary membrane filtration, the pH value of the long-chain dibasic acid fermentation broth can be 8.2, 8.4, 8.5, 8.6, 8.8, 9.0, 9.2, 9.4, 9.5, 9.8, 10, 10.2, 10.4, 10.5, 10.6, 10.8, 11.0, 11.2, 11.5, 11.6, 11.8.

[0038] In one embodiment, the pH value of the fermentation broth can be adjusted by adding alkali, and the types of alkali include but are not limited to sodium hydroxide and / or potassium hydroxide.

[0039] In one embodiment, the temperature of the primary membrane filtration is 50-100°C, and can further be 60-100°C, for example, 50°C, 52°C, 55°C, 58°C, 60°C, 62°C, 64°C, 65°C, 66°C, 68°C, 70°C, 72°C, 75°C, 78°C, 80°C, 82°C, 85°C, 88°C, 90°C, 92°C, 95°C, and 98°C.

[0040] In one embodiment, the primary membrane filtration adopts microfiltration membrane filtration or ultrafiltration membrane filtration; through the primary membrane filtration, most of the alkanes, cell tissues of the fermentation microorganisms, pigments and other impurities in the fermentation broth can be removed.

[0041] In one embodiment, during the primary membrane filtration process, the pressure difference between the two sides of the membrane is 0.05-0.6 MPa, for example, 0.06 MPa, 0.08 MPa, 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa.

[0042] In one embodiment, the secondary membrane filtration adopts ultrafiltration membrane filtration. The acidification crystallization process can remove some impurities that are different from the dibasic acid crystal structure or dibasic acid solubility. After the crystallized long-chain dibasic acid solid is dissolved again, the distribution and type of impurities in the long-chain dibasic acid solution change. Combined with ultrafiltration membrane filtration, impurities that cannot be removed in a simple multi-stage filtration process can be removed.

[0043] In one embodiment, the temperature of the secondary membrane filtration is 20-100°C, further can be 20-45°C, further can be 30-40°C, for example, 22°C, 24°C, 25°C, 26°C, 28°C, 30°C, 32°C, 34°C, 35°C, 36°C, 38°C, 39°C, 41°C, 42°C, 44°C.

[0044] In one embodiment, the method further includes performing a third-stage membrane filtration after the first-stage membrane filtration and the second-stage membrane filtration.

[0045] In one embodiment, the three-stage membrane filtration uses ultrafiltration membrane filtration.

[0046] In one embodiment, the temperature of the tertiary membrane filtration is 20-45°C, and can further be 30-40°C, for example, 22°C, 24°C, 25°C, 26°C, 28°C, 30°C, 32°C, 34°C, 35°C, 36°C, 38°C, 39°C, 41°C, 42°C, and 44°C.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] In one embodiment, the decolorization treatment is achieved by contacting the liquid to be decolorized (the filtrate of step (1) or (2)) with a decolorizing agent.

[0051] In one embodiment, the decolorization process may include mixing the liquid to be decolorized with a solid decolorizer for solid-liquid decolorization; further, the decolorization effect may be improved by stirring the solid-liquid mixture. After decolorization, the filtrate may be filtered, such as plate and frame filtration, to remove the decolorizer. The amount of the decolorizer may be 0.05-5wt%, 0.2-4wt% of the mass of the filtrate, for example 0.5wt%, 3.0wt%, 3.5wt%.

[0052] The concentration of the filtrate after each stage of membrane filtration is controlled to be 2-10 wt %, preferably 2-8 wt %, such as 3 wt %, 6 wt %, based on the long-chain dibasic acid. The concentration of the filtrate can be controlled by dilution or concentration.

[0053] In another embodiment, the liquid to be decolorized may be passed through a decolorizing agent, and the effluent may be collected to obtain a decolorized solution.

[0054] In one embodiment, the decolorizing agent includes, but is not limited to, powdered activated carbon, granular activated carbon, activated carbon fiber, activated clay, and diatomaceous earth.

[0055] In one embodiment, the temperature of the decolorization treatment is 50-100°C, and may further be 60-80°C, for example, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, or 95°C.

[0056] In one embodiment, the decolorization treatment time is 10 to 180 minutes, and can further be 15 to 120 minutes, for example, 20 minutes, 25 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes, 80 minutes, 100 minutes, or 150 minutes.

[0057] In one embodiment, the solid-liquid separation in steps (1) to (3) may be centrifugal separation or filtration separation.

[0058] In one embodiment, the filtrate obtained by solid-liquid separation in steps (1) and (2) can be treated to recover inorganic salts for use as a culture medium in the dibasic acid fermentation process. In addition to sodium sulfate, potassium sulfate or potassium nitrate, the filtrate may also contain impurities such as pigments and organic acids. It can be purified and refined to obtain crystals such as sodium sulfate, potassium sulfate or potassium nitrate, which can be directly used as chemical additives or agricultural additives. The obtained sodium sulfate, potassium sulfate or potassium nitrate salts can also be electrolyzed by bipolar membranes to obtain corresponding sulfuric acid and alkali, which can be reused in the long-chain dibasic acid production process. Comprehensive resource utilization and circular economy are achieved, and emissions are reduced.

[0059] In one embodiment, the acidification crystallization in steps (1) and (2) comprises adjusting the pH value of the solution after the filtrate decolorization treatment to 2-5.5, and further to 2.5-4, for example, 2.2, 2.5, 2.8, 3.0, 3.2, 3.5, 3.7, 3.8, 4.0, 4.2, 4.3, 4.5, 4.7, 5.2, and then performing crystallization.

[0060] In one embodiment, the pH value of the filtrate is adjusted by adding an acid to the filtrate, and the acid may be an inorganic acid and / or an organic acid.

[0061] In one embodiment, the inorganic acid includes but is not limited to hydrochloric acid, sulfuric acid, and nitric acid; the organic acid includes but is not limited to acetic acid.

[0062] In one embodiment, the water content of the first solid is 3-10 wt %, for example, 5 wt %, 7 wt %, or 8 wt %.

[0063] In one embodiment, before dispersing the first solid or the second solid in water, the first solid or the second solid may be washed with water.

[0064] In step (2) of one embodiment, a base is added to water to promote the dissolution of the first solid, and the added base includes but is not limited to sodium hydroxide and / or potassium hydroxide.

[0065] In step (2) of one embodiment, heating and stirring may be performed during the process of adding alkali to dissolve the first solid to promote the dissolution of the first solid.

[0066] In step (2) of one embodiment, the first solid may be mixed with an aqueous solution of an alkali to promote dissolution of the first solid.

[0067] In one embodiment, after the filtrate is decolorized in step (2) and before the acidification and crystallization, a three-stage membrane filtration may be performed.

[0068] In step (3) of one embodiment, the mass ratio of the second solid to the solvent water may be 1:(2-20), further may be 1:(3-15), further may be 1:(3-10).

[0069] In step (3) of one embodiment, the temperature of the heat preservation treatment is 120-140°C.

[0070] In step (3) of one embodiment, the temperature of the insulation treatment can be 106°C, 108°C, 109°C, 110°C, 112°C, 114°C, 115°C, 116°C, 118°C, 120°C, 122°C, 124°C, 125°C, 126°C, 128°C, 130°C, 132°C, 133°C, 135°C, 136°C, 138°C, 139°C, 140°C, 142°C, 145°C, 146°C, 148°C.

[0071] In step (3) of one embodiment, the heat preservation treatment time is 15 to 150 minutes, and can further be 30 to 90 minutes, for example, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes, 70 minutes, 80 minutes, 100 minutes, 120 minutes, etc.

[0072] In step (3) of one embodiment, after the heat preservation treatment, the terminal temperature of the cooling is 25-65°C, and can further be 30-50°C, for example, 28°C, 32°C, 34°C, 35°C, 36°C, 38°C, 40°C, 42°C, 44°C, 45°C, 46°C, 48°C, 50°C, 52°C, 55°C, 58°C, 60°C, and 62°C.

[0073] In step (3) of one embodiment, after the heat preservation treatment, the temperature is first lowered to 85-115°C, and then lowered to the end point temperature. For example, the temperature is first lowered to 88°C, 90°C, 92°C, 95°C, 98°C, 100°C, 105°C, 108°C, 110°C, 112°C, 114°C, and then lowered to the end point temperature.

[0074] In step (3) of one embodiment, after the heat preservation treatment, the temperature is first lowered to 97-115°C (first stage cooling process), such as 98°C, 99°C, 100°C, 105°C, 108°C, 110°C, 112°C, 114°C; then lowered to 85-95°C (second stage cooling process), such as 88°C, 90°C, 91°C, 93°C, 94°C; and then lowered to the terminal temperature (third stage cooling process). Furthermore, the average cooling rate of the first stage cooling process is 0.5-12°C / h, and can further be 0.5-8°C / h, such as 3°C / h, 5°C / h, 6°C / h, 10°C / h, 12°C / h, 14°C / h. The average cooling rate of the second cooling process is 2 to 15°C / h, and can further be 2 to 8°C / h, such as 3°C / h, 5°C / h, 6°C / h, 10°C / h, 12°C / h, and 14°C / h. The average cooling rate of the third cooling process is 12 to 25°C / h, and can further be 16 to 20°C / h, such as 12.5°C / h, 13°C / h, 14°C / h, 15°C / h, 16°C / h, 17°C / h, 18°C / h, and 19°C / h.

[0075] By controlling the cooling process of step (3), the difference in properties between impurities and dibasic acid crystals is utilized. On the one hand, the dissolution of impurities at high temperature is controlled by thermodynamics, such as solubility difference, so that impurities remain in water; on the other hand, by programmed cooling, there is a difference in the growth rate of impurities and dibasic acid crystals, that is, the crystallization / precipitation kinetic rate is controlled, so that dibasic acid crystals and impurities are further separated. After cooling to the end point for solid-liquid separation, the purity of the dibasic acid product can be further improved.

[0076] In one embodiment, the filtrate obtained from the solid-liquid separation in step (3) can be used to dissolve the first solid in step (2).

[0077] The long-chain dibasic acid extraction method of one embodiment of the present invention can make no alkane residues detected in the long-chain dibasic acid product by adjusting the process parameters and steps such as the temperature of some steps, and can reduce the content of various impurities, thereby improving the quality of the long-chain dibasic acid product and the subsequently prepared polyamide product.

[0078] The method for extracting long-chain dibasic acids according to one embodiment of the present invention can overcome the drawbacks of poor product quality and environmental pollution caused by organic solvent crystallization, and is suitable for the extraction and purification of long-chain dibasic acids prepared by biological fermentation.

[0079] According to one embodiment of the present invention, by adopting two-stage membrane filtration, alkali dissolution-acid precipitation, and high-temperature crystallization processes, the obtained dibasic acid product has high purity, white color, low ash content, low metal ion and nitrogen content, and does not contain organic solvents, and the alkane residue is extremely low or even no residue, thereby improving the quality of the long-chain dibasic acid product and the subsequently prepared polyamide product.

[0080] One embodiment of the present invention provides a long-chain dibasic acid obtained by using the above extraction method.

[0081] One embodiment of the present invention provides an extraction system for long-chain dibasic acids for implementing the above-mentioned extraction method, comprising a primary membrane filtration unit, a first acidification crystallization unit, a first separation unit, a secondary membrane filtration unit, a second acidification crystallization unit, a second separation unit, a crystallization unit and a third separation unit.

[0082] Reference Figure 1 In one embodiment, the primary membrane filtration unit is used for the first membrane filtration of the long-chain dibasic acid fermentation broth, and a filtration membrane, such as a microfiltration membrane or an ultrafiltration membrane, may be provided in the primary membrane filtration unit.

[0083] In one embodiment, the primary membrane filtration unit can also dilute or concentrate the filtrate after the membrane filtration treatment.

[0084] In one embodiment, the extraction system includes a fermentation liquid storage tank, which can be connected to the primary membrane filtration unit to hold the long-chain dibasic acid fermentation liquid.

[0085] In one embodiment, the extraction system includes a heating device for heating the fermentation liquid storage tank, so that the long-chain dibasic acid fermentation liquid is subjected to primary membrane filtration at a certain temperature, such as 50-100°C.

[0086] In one embodiment, the long-chain dibasic acid fermentation broth is treated by membrane filtration in the primary membrane filtration unit to obtain a filtrate (first filtrate), and the first acidification and crystallization unit is used for acidification and crystallization of the first filtrate.

[0087] In one embodiment, the first acidification and crystallization unit includes an acidification tank, and the first filtrate can be acidified and crystallized in the acidification tank to obtain a solid-liquid mixture.

[0088] In one embodiment, a first decolorization unit may be further provided between the primary membrane filtration unit and the first acidification crystallization unit to decolorize the first filtrate before acidification crystallization.

[0089] In one embodiment, the first decolorization unit may include a decolorization tank and a filter separator; the decolorization tank is used to decolorize the liquid to be decolorized and the solid decolorizer by solid-liquid mixing; after decolorization, the solid decolorizer can be removed by the filter separator. The filter separator may be a plate and frame filter.

[0090] In one embodiment, the first decolorization unit includes a heating device for heating the decolorization tank, so that the decolorization process is performed at a certain temperature (eg, 50-100° C.).

[0091] In one embodiment, the first separation unit is used to perform solid-liquid separation on the solid-liquid mixture in the first acidification crystallization unit.

[0092] In one embodiment, the first separation unit may include a filter separator or a centrifugal separator.

[0093] In one embodiment, the solid separated by the first separation unit enters the secondary membrane filtration unit for further dissolution and membrane filtration treatment.

[0094] In one embodiment, the secondary membrane filtration unit can also dilute or concentrate the filtrate after the membrane filtration treatment. By controlling the concentration of the filtrate within a certain range, the flux of the membrane filtration can be increased, concentration polarization and membrane pollution can be reduced, and the decolorization and acidification crystallization steps can be used to better purify the dibasic acid.

[0095] In one embodiment, the secondary membrane filtration unit includes a dissolution tank and an ultrafiltration membrane. The solid obtained from the first separation unit can be dissolved in the dissolution tank to re-form a solution. The formed solution can be subjected to a second membrane filtration through the ultrafiltration membrane to obtain a filtrate (second filtrate).

[0096] In one embodiment, the secondary membrane filtration unit includes a heating device to allow the solution in the dissolution tank to be subjected to secondary membrane filtration at a certain temperature, such as 20-100°C.

[0097] In one embodiment, the pore size of the microfiltration membrane in the primary membrane filtration unit may be 0.01 to 1 micron, further may be 0.01 to 0.2 micron, and further may be 0.05 to 0.1 micron.

[0098] In one embodiment, the molecular weight cutoff of the ultrafiltration membrane in the primary membrane filtration unit or the secondary membrane filtration unit may be 1000 to 200000 Da, further 2000 to 100000 Da, and further 2000 to 20000 Da.

[0099] 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.

[0100] In one embodiment, the second acidification crystallization unit is used for acidification crystallization of the second filtrate.

[0101] In one embodiment, the second acidification and crystallization unit comprises an acidification tank, and the second filtrate can be acidified and crystallized in the acidification tank to obtain a solid-liquid mixture.

[0102] In one embodiment, a second decolorization unit may be further provided between the secondary membrane filtration unit and the second acidification crystallization unit to decolorize the second filtrate.

[0103] In one embodiment, the structure of the second decolorizing unit may be the same as that of the first decolorizing unit.

[0104] In one embodiment, a three-stage membrane filtration unit may be provided between the second decolorization unit and the second acidification crystallization unit to perform membrane filtration on the decolorized liquid; wherein an ultrafiltration membrane may be provided in the three-stage membrane filtration unit.

[0105] In one embodiment, the second separation unit is used to perform solid-liquid separation on the solid-liquid mixture in the second acidification crystallization unit.

[0106] In one embodiment, the second separation unit may include a filter separator or a centrifugal separator.

[0107] In one embodiment, the solid separated by the second separation unit enters the crystallization unit for crystallization treatment.

[0108] In one embodiment, the crystallization unit includes a crystallization tank, through which the solid separated by the second separation unit can be mixed with water to form a mixture, and the obtained mixture is subjected to heat preservation treatment and then cooled for crystallization to obtain a solid-liquid mixture.

[0109] In one embodiment, the crystallization unit includes a heating device for heating the crystallization tank, so that the mixture in the crystallization tank is kept at a certain temperature, for example, 105-150°C.

[0110] In one embodiment, the third separation unit is used to perform solid-liquid separation on the solid-liquid mixture of the crystallization unit.

[0111] In one embodiment, the third separation unit may include a filter separator or a centrifugal separator.

[0112] In one embodiment, a drying unit may be further included to dry the solid separated by the third separation unit to obtain a long-chain dibasic acid product.

[0113] In one embodiment, the drying unit includes a dryer.

[0114] In the present invention, the acidification tank, decolorization tank, dissolution tank, crystallization tank, heating device, etc. can all be existing devices.

[0115] 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:

[0116] 1. Gas chromatography detection of long-chain dibasic acids

[0117] Standard long-chain dibasic acid samples were used as controls, with reference to GB5413.27-2010 Determination of fatty acids in infant foods and dairy products.

[0118] 2. Ash content detection

[0119] Take the sample to be tested and burn it in a crucible, then burn it in a muffle furnace at 700-800℃ for 2 hours, measure the weight after cooling to constant weight, and calculate the percentage weight.

[0120] 3. Total nitrogen determination

[0121] The Kjeldahl method was used for nitrogen determination.

[0122] 4. Alkane residue detection

[0123] 4.1 Instruments

[0124] GC-14C gas chromatograph, chromatographic column: SPB-1701 30m x 0.25mm x 0.25um.

[0125] 4.2 Detection process

[0126] 4.2.1 Methylation

[0127] Weigh 0.75g of sample into a reaction tube, add 5ml of methanol and 1ml of 6mol / L hydrochloric acid methanol solution, seal, heat at 100℃ for 30min, and cool to room temperature. Add 3g of solid sodium bicarbonate and react until no bubbles emerge from the solution, let stand to obtain a clear solution, then slowly add sodium bicarbonate to neutralize until the solution does not produce CO2 gas.

[0128] 4.2.2 Alkane residue detection

[0129] Use a 0.45um syringe filter to take 1ml of the sample after methyl esterification and inject it into a GC-14C gas chromatograph. The area normalization method is used to calculate the alkane residue.

[0130] 5. Light transmittance test:

[0131] 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.

[0132] 6. Polyamide Yellow Index (YI) Test:

[0133] The yellow index is the yellow value based on the International Commission on Illumination (CIE) standard C light source and magnesium oxide as the benchmark. The calculation method of the yellow index YI is as follows:

[0134] YI=(100(1.28X-1.06Z)) / Y

[0135] Among them, X, Y, and Z are the measured three stimulus values.

[0136] Yellow index instrument test, test temperature: 25±5℃; relative humidity: 50±20%;

[0137] Detection method:

[0138] For transparent samples, the spectral transmittance relative to air is determined (transmission method); for opaque and semi-transparent samples, the spectral reflectance relative to the reference white plate or working white plate should be measured (reflection method). The background is a white working plate; powdery and granular samples need to be measured from the bottom in a glass container using the reflection method. In order to prevent the influence of external light, a black cover is placed on the glass container.

[0139] The spectral tristimulus values ​​X, Y, and Z of the sample relative to the standard illuminant C are automatically integrated by the instrument.

[0140] Both colorimeters and colorimeter are filter-type tristimulus colorimeter, which can directly read X, Y, and Z values.

[0141] For homogeneous plastics, the diameter of the measuring light hole should be ≥12 mm; for inhomogeneous plastics, the diameter of the measuring light hole should be ≥10 mm.

[0142] Example 1

[0143] According to the fermentation method of Example 4 of patent document CN1570124A, dodecanedioic acid fermentation liquid was obtained.

[0144] (1) adding alkali to the fermentation liquid of dodecanedioic acid to adjust the pH value to 9.7, heating to 90° C., filtering the fermentation liquid through a ceramic microfiltration membrane at 90° C. to obtain a dodecanedioic acid filtrate; wherein the pore size of the ceramic microfiltration membrane is 0.05 μm, and the pressure difference between the two sides of the membrane is 0.3 MPa;

[0145] The concentration of the filtrate after microfiltration is controlled to be 5.7 wt % based on dodecanedioic acid, and the dodecanedioic acid filtrate is decolorized by heating at 90° C. for 25 minutes with 2.5 wt % activated carbon, and filtered to obtain a dodecanedioic acid clear solution;

[0146] The dodecanedioic acid clear liquid obtained by decolorization is adjusted to pH 3.0 with sulfuric acid for acidification and crystallization, and filtered to obtain a first solid containing dodecanedioic acid;

[0147] (2) adding the first solid (water content of 3 wt%) into water, adding sodium hydroxide to dissolve the crude product, and filtering with an ultrafiltration membrane at a filtration temperature of 35° C. and a molecular weight cutoff of 3000 Da;

[0148] The concentration of the filtrate after ultrafiltration membrane filtration is controlled to be 5.7 wt % based on dodecanedioic acid, and the filtrate is decolorized at 90° C. for 25 minutes using 2.5 wt % activated carbon, and filtered through a plate and frame to obtain a decolorized liquid;

[0149] The decolorized solution was adjusted to pH 2.8 with sulfuric acid for acidification and crystallization, and filtered to obtain a second solid containing dodecanedioic acid.

[0150] (3) adding the second solid to water in a mass ratio of the second solid to water of 1:10, keeping the temperature at 120° C. for 60 minutes, cooling the temperature to 100° C. over 4 hours, cooling the temperature to 90° C. over 2 hours, and further cooling the temperature to 40° C. over 4 hours, crystallizing, filtering, and obtaining a solid, and drying the solid to obtain a dodecanedioic acid product.

[0151] Example 2

[0152] According to the fermentation method of Example 6 of patent document CN1570124A, tetradecanedioic acid fermentation liquid was obtained.

[0153] (1) adding alkali to the fermentation liquid of tetradecanedioic acid to adjust the pH value to 9.0, heating to 90° C., filtering the fermentation liquid through a ceramic microfiltration membrane at 90° C. to obtain a tetradecanedioic acid filtrate; wherein the pore size of the ceramic microfiltration membrane is 0.05 μm, and the pressure difference between the two sides of the membrane is 0.5 MPa;

[0154] The concentration of the filtrate after microfiltration is controlled to be 4.5 wt % based on tetradecanedioic acid, and the tetradecanedioic acid filtrate is decolorized by heat preservation at 90° C. for 25 minutes with 2.5 wt % activated carbon, and filtered to obtain a tetradecanedioic acid clear solution;

[0155] The decolorized tetradecanedioic acid clear solution is adjusted to pH 3.0 with sulfuric acid for acidification and crystallization, and filtered to obtain a first solid containing tetradecanedioic acid;

[0156] (2) adding the first solid (water content of 5 wt%) into water, adding sodium hydroxide to dissolve the crude product, and filtering with an ultrafiltration membrane at a filtration temperature of 35° C. and a molecular weight cutoff of 10,000 Da;

[0157] The concentration of the filtrate after ultrafiltration membrane filtration is controlled to be 4.5wt% based on tetradecanedioic acid, and the filtrate is decolorized at 90°C for 25 minutes using 2.5wt% activated carbon, and filtered through a plate and frame to obtain a decolorized liquid;

[0158] The decolorized solution was adjusted to pH 2.8 with sulfuric acid for acidification and crystallization, and filtered to obtain a second solid containing tetradecanedioic acid.

[0159] (3) adding the second solid to water in a mass ratio of the second solid to water of 1:10, keeping the temperature at 130° C. for 30 minutes, cooling the temperature to 100° C. over 5 hours, cooling the temperature to 90° C. over 2 hours, and further cooling the temperature to 40° C. over 4 hours, crystallizing, filtering, and obtaining a solid, and drying the solid to obtain a tetradecanedioic acid product.

[0160] Example 3

[0161] According to the fermentation method of Example 8 of patent document CN1570124A, hexadecanedioic acid fermentation liquid was obtained.

[0162] (1) adding alkali to the fermentation liquid of hexadecanedioic acid to adjust the pH value to 8.3, heating to 80° C., filtering the fermentation liquid through a ceramic microfiltration membrane at 80° C. to obtain a hexadecanedioic acid filtrate; wherein the pore size of the ceramic microfiltration membrane is 0.1 μm, and the pressure difference between the two sides of the membrane is 0.2 MPa;

[0163] The concentration of the filtrate after microfiltration is controlled to be 3.7 wt % based on 16-carbon dicarboxylic acid, and the filtrate of 16-carbon dicarboxylic acid is decolorized by heat preservation at 80° C. for 25 minutes with 4 wt % activated carbon, and filtered through a plate and frame to obtain a 16-carbon dicarboxylic acid clear solution;

[0164] The hexadecanedioic acid clear solution obtained by decolorization is adjusted to pH 3.0 with sulfuric acid for acidification and crystallization, and filtered to obtain a first solid containing hexadecanedioic acid;

[0165] (2) adding the first solid (water content of 8 wt%) into water, adding sodium hydroxide to dissolve the crude product, and filtering with an ultrafiltration membrane at a filtration temperature of 35° C. and a molecular weight cutoff of 5000 Da;

[0166] The concentration of the filtrate after ultrafiltration membrane filtration is controlled to be 3.7 wt % based on hexadecanedioic acid, and the filtrate is decolorized at 90° C. for 25 minutes using 2.5 wt % activated carbon, and filtered through a plate and frame to obtain a decolorized liquid;

[0167] The decolorized solution was adjusted to pH 3.5 with sulfuric acid for acidification and crystallization, and filtered to obtain a second solid containing hexadecanedioic acid.

[0168] (3) adding the second solid to water in a mass ratio of the second solid to water of 1:10, keeping the temperature at 135° C. for 60 minutes, cooling the temperature to 100° C. after 5 hours, cooling the temperature to 90° C. after 1 hour, and further cooling the temperature to 50° C. after 3 hours, crystallizing, filtering, and obtaining a solid, and drying the solid to obtain a 16-carbon dicarboxylic acid product.

[0169] Example 4

[0170] According to the fermentation method of Example 5 of patent document CN1570124A, tridecanedioic acid fermentation liquid was obtained.

[0171] (1) adding alkali to the fermentation liquid of tridecanedioic acid to adjust the pH value to 10.0, heating to 90° C., filtering the fermentation liquid through a ceramic microfiltration membrane at 90° C. to obtain a tridecanedioic acid filtrate; wherein the pore size of the ceramic microfiltration membrane is 0.05 μm, and the pressure difference between the two sides of the membrane is 0.5 MPa;

[0172] The concentration of the filtrate after microfiltration is controlled to be 5.0 wt % based on tridecanedioic acid, and the tridecanedioic acid filtrate is decolorized by heat preservation at 90° C. for 60 minutes with 3 wt % activated carbon, and filtered to obtain a tridecanedioic acid clear solution;

[0173] The tridecanedioic acid clear liquid obtained by decolorization is adjusted to pH 2.5 with sulfuric acid for acidification and crystallization, and filtered to obtain a first solid containing tridecanedioic acid;

[0174] (2) adding the first solid (water content of 5 wt%) into water, adding sodium hydroxide to dissolve the crude product, and filtering with an ultrafiltration membrane at a filtration temperature of 35° C. and a molecular weight cutoff of 2000 Da;

[0175] The concentration of the filtrate after ultrafiltration membrane filtration is controlled to be 5.0 wt % based on tridecanedioic acid, and the filtrate is decolorized at 90° C. for 40 minutes using 3 wt % activated carbon, and filtered through a plate and frame to obtain a decolorized liquid;

[0176] The decolorized solution was adjusted to pH 2.8 with sulfuric acid for acidification and crystallization, and filtered to obtain a second solid containing tridecanedioic acid.

[0177] (3) adding the second solid to water in a mass ratio of the second solid to water of 1:5, keeping the temperature at 115° C. for 30 minutes, cooling the temperature to 100° C. over 4 hours, cooling the temperature to 90° C. over 2 hours, and further cooling the temperature to 40° C. over 4 hours, crystallizing, filtering, and obtaining a solid, and drying the solid to obtain a tridecanedioic acid product.

[0178] Example 5

[0179] According to the fermentation method of Example 4 of patent document CN1570124A, dodecanedioic acid fermentation liquid was obtained.

[0180] (1) adding alkali to the fermentation liquid of dodecanedioic acid to adjust the pH value to 8.0, heating to 65° C., filtering the fermentation liquid through a ceramic microfiltration membrane at 65° C. to obtain a dodecanedioic acid filtrate; wherein the pore size of the ceramic microfiltration membrane is 0.05 μm, and the pressure difference between the two sides of the membrane is 0.3 MPa;

[0181] The concentration of the filtrate after microfiltration is controlled to be 5.7 wt % based on dodecanedioic acid, and the dodecanedioic acid filtrate is decolorized by heating at 90° C. for 25 minutes with 2.5 wt % activated carbon, and filtered to obtain a dodecanedioic acid clear solution;

[0182] The dodecanedioic acid clear liquid obtained by decolorization is adjusted to pH 3 with sulfuric acid for acidification and crystallization, and filtered to obtain a first solid containing dodecanedioic acid;

[0183] (2) adding the first solid (water content of 3 wt%) into water, adding sodium hydroxide to dissolve the crude product, and filtering with an ultrafiltration membrane at a filtration temperature of 35° C. and a molecular weight cutoff of 3000 Da;

[0184] The concentration of the filtrate after ultrafiltration membrane filtration is controlled to be 5.7 wt % based on dodecanedioic acid, and the filtrate is decolorized at 90° C. for 25 minutes using 2.5 wt % activated carbon, and filtered through a plate and frame to obtain a decolorized liquid;

[0185] The decolorized solution was adjusted to pH 2.8 with sulfuric acid for acidification and crystallization, and filtered to obtain a second solid containing dodecanedioic acid.

[0186] (3) adding the second solid to water in a mass ratio of the second solid to water of 1:10, keeping the temperature at 120° C. for 60 minutes, cooling the temperature to 40° C. over 3 hours, crystallizing, filtering, and obtaining a solid, and drying the solid to obtain the dodecanedioic acid product.

[0187] Example 6

[0188] According to the fermentation method of Example 6 of patent document CN1570124A, tetradecanedioic acid fermentation liquid was obtained.

[0189] (1) adding alkali to the fermentation liquid of tetradecanedioic acid to adjust the pH value to 9.0, heating to 90° C., filtering the fermentation liquid through a ceramic microfiltration membrane at 90° C. to obtain a tetradecanedioic acid filtrate; wherein the pore size of the ceramic microfiltration membrane is 0.05 μm, and the pressure difference between the two sides of the membrane is 0.5 MPa;

[0190] The concentration of the filtrate after microfiltration is controlled to be 9.6 wt % based on tetradecanedioic acid, and the tetradecanedioic acid filtrate is decolorized by heat preservation at 90° C. for 25 minutes with 2.5 wt % activated carbon, and filtered to obtain a tetradecanedioic acid clear solution;

[0191] The decolorized tetradecanedioic acid clear solution is adjusted to pH 4.7 with sulfuric acid for acidification and crystallization, and filtered to obtain a first solid containing tetradecanedioic acid;

[0192] (2) adding the first solid (water content of 5 wt%) into water, adding sodium hydroxide to dissolve the crude product, and filtering with an ultrafiltration membrane at a filtration temperature of 35° C. and a molecular weight cutoff of 50,000 Da;

[0193] The concentration of the filtrate after microfiltration membrane filtration is controlled to be 9.6 wt % based on tetradecanedioic acid, and the filtrate is decolorized at 90° C. for 25 minutes using 2.5 wt % activated carbon, and filtered through a plate and frame to obtain a decolorized liquid;

[0194] The decolorized solution was adjusted to pH 2.8 with sulfuric acid for acidification and crystallization, and filtered to obtain a second solid containing tetradecanedioic acid.

[0195] (3) adding the second solid to water in a mass ratio of the second solid to water of 1:10, keeping the temperature at 130° C. for 30 minutes, cooling the temperature to 100° C. over 5 hours, cooling the temperature to 90° C. over 2 hours, and further cooling the temperature to 40° C. over 4 hours, crystallizing, filtering, and obtaining a solid, and drying the solid to obtain a tetradecanedioic acid product.

[0196] Example 7

[0197] According to the fermentation method of Example 8 of patent document CN1570124A, hexadecanedioic acid fermentation liquid was obtained.

[0198] (1) adding alkali to the fermentation liquid of hexadecanedioic acid to adjust the pH value to 8.3, heating to 80° C., filtering the fermentation liquid through a ceramic microfiltration membrane at 80° C. to obtain a hexadecanedioic acid filtrate; wherein the pore size of the ceramic microfiltration membrane is 0.1 μm, and the pressure difference between the two sides of the membrane is 0.2 MPa;

[0199] The concentration of the filtrate after microfiltration is controlled to be 3.7 wt % based on 16-carbon dicarboxylic acid, and the filtrate of 16-carbon dicarboxylic acid is decolorized by heat preservation at 80° C. for 25 minutes with 4 wt % activated carbon, and filtered through a plate and frame to obtain a 16-carbon dicarboxylic acid clear solution;

[0200] The hexadecanedioic acid clear solution obtained by decolorization is adjusted to pH 3.0 with sulfuric acid for acidification and crystallization, and filtered to obtain a first solid containing hexadecanedioic acid;

[0201] (2) adding the first solid (water content of 8 wt%) into water, adding sodium hydroxide to dissolve the crude product, and filtering with an ultrafiltration membrane at a filtration temperature of 35° C. and a molecular weight cutoff of 5000 Da;

[0202] The concentration of the filtrate after ultrafiltration membrane filtration is controlled to be 3.7 wt % based on hexadecanedioic acid, and the filtrate is decolorized at 55° C. for 40 minutes using 2.5 wt % activated carbon, and filtered through a plate and frame to obtain a decolorized liquid;

[0203] The decolorized solution was adjusted to pH 4.5 with sulfuric acid for acidification and crystallization, and filtered to obtain a second solid containing hexadecanedioic acid.

[0204] (3) adding the second solid to water in a mass ratio of the second solid to water of 1:10, keeping the temperature at 108°C for 60 minutes, cooling the temperature to 100°C after 4 hours, cooling the temperature to 90°C after 1 hour, and further cooling the temperature to 60°C after 2 hours, crystallizing, filtering, and obtaining a solid, and drying the solid to obtain a 16-carbon dicarboxylic acid product.

[0205] Example 8

[0206] According to the fermentation method of Example 5 of patent document CN1570124A, tridecanedioic acid fermentation liquid was obtained.

[0207] (1) adding alkali to the fermentation liquid of tridecanedioic acid to adjust the pH value to 10.0, heating to 65° C., filtering the fermentation liquid through a ceramic microfiltration membrane at 65° C. to obtain a tridecanedioic acid filtrate; wherein the pore size of the ceramic microfiltration membrane is 0.05 μm, and the pressure difference between the two sides of the membrane is 0.5 MPa;

[0208] The concentration of the filtrate after microfiltration is controlled to be 5.0 wt % based on tridecanedioic acid, and the tridecanedioic acid filtrate is decolorized by heat preservation at 90° C. for 60 minutes with 3 wt % activated carbon, and filtered to obtain a tridecanedioic acid clear solution;

[0209] The tridecanedioic acid clear liquid obtained by decolorization is adjusted to pH 4.8 with sulfuric acid for acidification and crystallization, and filtered to obtain a first solid containing tridecanedioic acid;

[0210] (2) adding the first solid (water content of 5 wt%) into water, adding sodium hydroxide to dissolve the crude product, and filtering with an ultrafiltration membrane at a filtration temperature of 35° C. and a molecular weight cutoff of 2000 Da;

[0211] The concentration of the filtrate after ultrafiltration membrane filtration is controlled to be 5.0 wt % based on tridecanedioic acid, and the filtrate is decolorized at 90° C. for 40 minutes using 3 wt % activated carbon, and filtered through a plate and frame to obtain a decolorized liquid;

[0212] The decolorized solution was adjusted to pH 2.8 with sulfuric acid for acidification and crystallization, and filtered to obtain a second solid containing tridecanedioic acid.

[0213] (3) adding the second solid to water in a mass ratio of the second solid to water of 1:5, keeping the temperature at 105°C for 30 minutes, cooling the temperature to 90°C after 1 hour, and then cooling the temperature to 40°C after 2 hours, filtering to obtain a solid, and drying the solid to obtain a tridecanedioic acid product.

[0214] Example 9

[0215] According to the fermentation method of Example 4 of patent document CN1570124A, dodecanedioic acid fermentation liquid was obtained.

[0216] (1) adding alkali to the fermentation liquid of dodecanedioic acid to adjust the pH value to 9.7, heating to 40° C., filtering the fermentation liquid through a ceramic microfiltration membrane at 40° C. to obtain a dodecanedioic acid filtrate; wherein the pore size of the ceramic microfiltration membrane is 0.05 μm, and the pressure difference between the two sides of the membrane is 0.3 MPa;

[0217] The concentration of the filtrate after microfiltration is controlled to be 13.5 wt % based on dodecanedioic acid, and the dodecanedioic acid filtrate is decolorized by heating at 90° C. for 25 minutes with 2.5 wt % activated carbon, and filtered to obtain a dodecanedioic acid clear solution;

[0218] The dodecanedioic acid clear liquid obtained by decolorization is adjusted to pH 3.0 with sulfuric acid for acidification and crystallization, and filtered to obtain a first solid containing dodecanedioic acid;

[0219] (2) adding the first solid (water content of 3 wt%) into water, adding sodium hydroxide to dissolve the crude product, and filtering with an ultrafiltration membrane at a filtration temperature of 35° C. and a molecular weight cutoff of 3000 Da;

[0220] The concentration of the filtrate after ultrafiltration membrane filtration is controlled to be 13.5wt% based on dodecanedioic acid, and the filtrate is decolorized at 90°C for 25 minutes using 2.5wt% activated carbon, and filtered through a plate and frame to obtain a decolorized liquid;

[0221] The decolorized solution was adjusted to pH 2.8 with sulfuric acid for acidification and crystallization, and filtered to obtain a second solid containing dodecanedioic acid.

[0222] (3) adding the second solid to water in a mass ratio of the second solid to water of 1:10, keeping the temperature at 122° C. for 60 minutes, cooling the temperature to 15° C. over 5 hours, crystallizing, filtering, and obtaining a solid, and drying the solid to obtain the dodecanedioic acid product.

[0223] Comparative Example

[0224] According to the fermentation method of Example 4 of patent document CN1570124A, a fermentation liquid of dodecanedioic acid is obtained. The fermentation liquid of dodecanedioic acid is heated to 90°C, the pH is adjusted to 8.5 by adding alkali, and centrifuged at 90°C. The clear liquid is decolorized at 90°C for 30 minutes using 5wt% activated carbon, and filtered through a plate and frame to obtain a dodecanedioic acid clear liquid. The pH of the dodecanedioic acid clear liquid is adjusted to 3.0 for acidification and crystallization, filtration, and washing to obtain a dodecanedioic acid product.

[0225] The products obtained from the above examples and comparative examples were subjected to relevant performance tests, and the specific results are shown in Table 1.

[0226] Table 1 Performance of long chain dibasic acid products

[0227]

[0228] Application Examples

[0229] Polyamide 512 and polyamide 513 are prepared using the obtained dodecacarbon long-chain dibasic acid and tridecacarbon long-chain dibasic acid as raw materials. The specific process is as follows:

[0230] The air in a 100-liter polymerization kettle (K / SY166-2007 model) 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 dodecanedioic acid or tridecanedioic acid was added, and the pH value was adjusted to 7.23 (the test result of diluting a 30°C salt solution to 10%) to obtain a polyamide salt solution.

[0231] Under a nitrogen environment, the oil bath temperature was gradually increased to 288°C. After the pressure in the polymerization kettle increased to 1.5 MPa, exhaust was started. When the temperature in the kettle reached 262°C, the vacuum was evacuated to -0.07 MPa and the vacuum was maintained for 35 minutes to obtain polyamide 512 or polyamide 513. The yellowness index of the obtained polyamide slices was tested. The specific results are shown in Tables 2 and 3.

[0232] Table 2 Polyamide 512 Yellow Index Test Results

[0233] Yellowness Index (YI) Example 1 3.10 Example 5 6.25 Example 9 9.44 Comparative Example 23.71

[0234] Table 3 Polyamide 513 yellow index test results

[0235] Yellowness Index (YI) Example 4 3.75 Example 8 10.24

[0236] Unless otherwise defined, the terms used in the present invention have the meanings commonly understood by those skilled in the art.

[0237] 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 a long-chain dibasic acid, comprising the following steps: (1) filtering the long-chain dibasic acid fermentation broth through a primary membrane filtration process to obtain a first filtrate, wherein the primary membrane filtration process uses a microfiltration membrane filtration process, and the pore size of the microfiltration membrane is 0.01 to 1 micron; subjecting the first filtrate to decolorization, acidification crystallization, and solid-liquid separation to obtain a first solid; (2) mixing the first solid, alkali and water to form a solution, and subjecting the solution to secondary membrane filtration to obtain a second filtrate, wherein the secondary membrane filtration is performed by ultrafiltration membrane filtration, and the molecular weight cutoff of the ultrafiltration membrane is 2000 to 20000 Da; The second filtrate is subjected to decolorization, acidification crystallization, and solid-liquid separation to obtain a second solid; (3) mixing the second solid with water to form a mixture, heat-insulating the mixture at 105 to 150° C., then cooling it for crystallization and performing solid-liquid separation; The concentrations of the first filtrate and the second filtrate are controlled at 2-10 wt %; the temperature of the primary membrane filtration treatment is 50-100° C., and the temperature of the secondary membrane filtration treatment is 20-100° C.

2. The method according to claim 1, wherein: The temperature of the first-stage membrane filtration treatment is 60-100°C.

3. The method according to claim 1, wherein: The pore size of the microfiltration membrane is 0.01 to 0.2 microns, further 0.05 to 0.1 microns; And / or, during the primary membrane filtration process, the pressure difference on both sides of the membrane is 0.05-0.6 MPa.

4. The method according to claim 1, wherein the temperature of the secondary membrane filtration treatment is 20-45°C, and further can be 30-40°C.

5. The method according to claim 1, wherein: The temperature of the heat preservation treatment is 120-140°C.

6. The method according to claim 1, wherein: Before the primary membrane filtration treatment, the pH value of the long-chain dibasic acid fermentation broth is 6.0-12, further 8-11.

7. The method according to claim 1, wherein: In the step (1) and the step (2), the temperature of the decolorization treatment is 50 to 100°C, and further 60 to 80°C.

8. The method according to claim 1 or 7, wherein: In the step (1) and the step (2), the decolorization treatment time is 10 to 180 minutes, and further 15 to 120 minutes.

9. The method according to claim 1, comprising adjusting the pH values ​​of the decolorized solutions of the first filtrate and the second filtrate to 2 to 5.5, and further to 2.5 to 4 for acidification and crystallization.

10. The method according to claim 1, wherein: In the step (3), the temperature of the heat preservation treatment is 120-140°C.

11. The method according to claim 1 or 10, wherein: In the step (3), the heat preservation treatment time is 15 to 150 minutes, and further 30 to 90 minutes.

12. The method according to claim 1 or 10, wherein: In the step (3), the mass ratio of the second solid to the solvent water is 1:(2-20), further 1:(3-15), further 1:(3-10).

13. The method according to claim 1, wherein: In the step (3), the terminal temperature of the cooling crystallization is 25 to 65°C, and further 30 to 50°C.

14. The method according to claim 1 or 13, wherein: In the step (3), after the heat preservation treatment, the temperature is first lowered to 85-115° C., and then lowered to the end point.

15. The method according to claim 1 or 13, wherein: In the step (3), after the heat preservation treatment, the temperature is firstly lowered to 97-115°C (the first stage of the temperature reduction process), then lowered to 85-95°C, and finally lowered to the end point.

16. The method according to claim 15, wherein: The average cooling rate during the cooling process to 97-115°C is 0.5-12°C / h, and further 0.5-8°C / h.

17. The method according to claim 15, wherein: The average cooling rate during the cooling process to 85-95°C is 2-15°C / h, and further 2-8°C / h.

18. The method according to claim 15, wherein: The average cooling rate during the cooling process to the end point is 12 to 25°C / h, and further 16 to 20°C / h.

19. The method according to claim 1, wherein: Before dispersing the first solid or the second solid in water, the first solid or the second solid may be washed with water; And / or, the filtrate obtained from the solid-liquid separation in step (3) is used to dissolve the first solid in step (2).

20. The method according to claim 1, wherein: Long chain dibasic acid is C9~C 18 dicarboxylic acid, further, the long-chain dicarboxylic acid is one or more of azelaic acid, sebacic acid, undecanedicarboxylic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedicarboxylic acid, hexadecanedioic acid, heptadecanedioic acid, octadecanedicarboxylic acid, and 9-ene-octadecanedicarboxylic acid.

21. The method according to claim 1, wherein: After the decolorization treatment in step (2) and before the acidification crystallization, three-stage membrane filtration is performed. Furthermore, the three-stage membrane filtration adopts ultrafiltration membrane filtration.

22. A system for extracting a long-chain dibasic acid, comprising: Fermentation liquid storage tank, used to hold long-chain dibasic acid fermentation liquid; A primary membrane filtration unit is used for the first membrane filtration of the long-chain dibasic acid fermentation broth, wherein the primary membrane filtration unit is provided with a microfiltration membrane, and the pore size of the microfiltration membrane is 0.01-1 micron; A first acidification crystallization unit, used for acidifying and crystallizing the first filtrate obtained after the first membrane filtration to obtain a first solid-liquid mixture; A first separation unit, used for performing solid-liquid separation on the first solid-liquid mixture; A secondary membrane filtration unit, used to form a solution from the solid separated by the first separation unit and perform a second membrane filtration, wherein the secondary membrane filtration unit is provided with an ultrafiltration membrane, and the molecular weight cutoff of the ultrafiltration membrane is 2000-20000Da; A second acidification crystallization unit, used for acidifying and crystallizing the second filtrate obtained after the second membrane filtration to obtain a second solid-liquid mixture; a second separation unit, for performing solid-liquid separation on the second solid-liquid mixture; as well as a crystallization unit, for mixing the solid separated by the second separation unit with water to form a mixture, and performing heat preservation and cooling crystallization on the mixture to obtain a third solid-liquid mixture; as well as The third separation unit is used for performing solid-liquid separation on the third solid-liquid mixture.

23. The extraction system according to claim 22, wherein: A decolorization unit is provided between the primary membrane filtration unit and the first acidification crystallization unit to decolorize the first filtrate.

24. The extraction system of claim 22, wherein: A dissolution tank is provided in the secondary membrane filtration unit.

25. The extraction system of claim 22, wherein: A decolorization unit is provided between the secondary membrane filtration unit and the second acidification crystallization unit to decolorize the second filtrate.

26. The extraction system of claim 25, wherein: A three-stage membrane filtration unit is arranged between the decolorization unit and the second acidification crystallization unit to perform membrane filtration on the decolorized liquid.

27. The extraction system of claim 22, wherein: The first acidification crystallization unit and the second acidification crystallization unit each include an acidification tank, the first separation unit, the second separation unit and the third separation unit each include a filter separator or a centrifugal separator, and the crystallization unit includes a crystallization tank.

28. The extraction system of claim 22, wherein: A drying unit is included to dry the solid separated by the third separation unit to obtain a long-chain dibasic acid product.

29. The extraction system of claim 22, wherein: The utility model comprises a heating device for heating the fermentation liquid storage tank.

30. The method of claim 22, wherein: Long chain dibasic acid is C9~C 18 dicarboxylic acid, further, the long-chain dicarboxylic acid is one or more of azelaic acid, sebacic acid, undecanedicarboxylic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedicarboxylic acid, hexadecanedioic acid, heptadecanedioic acid, octadecanedicarboxylic acid, and 9-ene-octadecanedicarboxylic acid.

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