Refining process and system of long-chain dicarboxylic acid

Abstract

The invention provides a process and a system for refining long-chain dicarboxylic acid. The process comprises the following steps: (1) carrying out membrane filtration, acidification crystallization and solid-liquid separation on fermentation liquor or treatment liquor of the long-chain dicarboxylic acid to obtain a crude product of the long-chain dicarboxylic acid; (2) carrying out reduced pressure distillation on the long-chain dicarboxylic acid crude product to obtain a long-chain dicarboxylic acid product; wherein the pressure intensity of the reduced pressure distillation is less than or equal to 100Pa. According to the refining process, the process is simplified, the obtained product is high in purity, and the defects of poor product quality and environmental pollution caused by a solvent in a solvent crystallization method can be overcome.

Description

[0001] This application is a divisional application with an application date of December 24, 2019, application number 2019113476574 and invention name “A refining process and system for long-chain dibasic acids”. Technical Field

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

[0003] Long chain dicarboxylic acids (LCDA, DCn, n=9-18) are important organic intermediates and are widely used in the fields of chemical industry, light industry, pesticides, medicine, new materials, etc. At present, the most common 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 dicarboxylic acids also affects the cost of dicarboxylic acids produced in the final industrialization. Therefore, the development of simple and efficient extraction and purification technology of dicarboxylic acids will promote the promotion and application of fermentation process technology.

[0004] At present, the method of recrystallization from an organic solvent is generally used to purify long-chain dibasic acids. A patent application with publication number CN102503800A discloses a method for refining long-chain dibasic acids, wherein a crude long-chain dibasic acid is recrystallized using alcohols or acetone as a solvent to obtain a refined long-chain dibasic acid. Although the method of using a diluent solvent can improve the yield of the refining, the process of refining long-chain dibasic acids using alcohols as solvents has the defect of esterification of dibasic acids with ethanol at high temperatures, so that new products are generated during the refining process, affecting the purity of the product.

[0005] In addition, recrystallization mainly uses the difference in solubility to remove impurities, but some impurities have similar solubility to long-chain dibasic acids. Even if recrystallization is used repeatedly for purification, it is difficult to fundamentally remove these impurities with similar solubility to long-chain dibasic acids. Products obtained by organic solvent crystallization will have the problem of solvent residue. Summary of the invention

[0006] The present invention provides a refining process for a long-chain dibasic acid, comprising the following steps:

[0007] (1) filtering the fermentation liquid of the long-chain dibasic acid or its treated liquid through a membrane, acidifying and crystallizing, solid-liquid separation, and drying to obtain a crude long-chain dibasic acid;

[0008] (2) subjecting the crude long-chain dibasic acid to vacuum distillation to obtain a long-chain dibasic acid product;

[0009] Wherein, the pressure of the reduced pressure distillation is ≤100Pa.

[0010] The invention also provides a long-chain dibasic acid obtained by extraction using the above method.

[0011] The present invention further provides a long-chain dibasic acid refining system, comprising:

[0012] A membrane filtration unit, used for membrane filtration of long-chain dibasic acid fermentation broth or its treated broth;

[0013] an acidification crystallization unit, used for acidifying and crystallizing the filtrate obtained after the membrane filtration to obtain a solid-liquid mixture;

[0014] A separation unit, used for performing solid-liquid separation on the solid-liquid mixture;

[0015] a drying unit, used for drying the solid separated from the separation unit to obtain a crude long-chain dibasic acid; and

[0016] The vacuum distillation unit is used to distill and separate the crude long-chain dibasic acid to obtain a long-chain dibasic acid product.

[0017] The refining process of one embodiment of the present invention simplifies the process flow, and the obtained product has high purity, which can overcome the shortcomings of the solvent crystallization method, such as high equipment requirements, the need for a solvent recovery system, poor solvent safety, and environmental pollution caused by the solvent. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of a long-chain dibasic acid purification system according to one embodiment of the present invention. DETAILED DESCRIPTION

[0019] 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, "first", "second", etc. are used to distinguish multiple processes or products with the same name, but are not intended to limit them.

[0020] One embodiment of the present invention provides a long-chain dibasic acid purification process for extracting long-chain dibasic acid from long-chain dibasic acid fermentation broth or its treated broth, the method comprising:

[0021] (1) filtering the fermentation liquid of the long-chain dibasic acid or its treated liquid through a membrane, acidifying and crystallizing, solid-liquid separation, and drying to obtain a crude long-chain dibasic acid;

[0022] (2) subjecting the crude long-chain dibasic acid to vacuum distillation to obtain a long-chain dibasic acid product;

[0023] The pressure of the reduced pressure distillation is ≤100Pa, preferably ≤50Pa.

[0024] 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.

[0025] In one embodiment, the treated liquid of the long-chain dibasic acid fermentation liquid is a liquid obtained by removing one or more other components other than the long-chain dibasic acid salt in the fermentation liquid or reducing their content. For example, the fermentation liquid is centrifuged or filtered through a membrane to separate the bacterial cells and the residual substrate of the fermentation to obtain the treated liquid.

[0026] In one embodiment, the long chain dibasic acid is C9 to C 18 of dicarboxylic acids.

[0027] In one embodiment, the long-chain dibasic acid is a straight-chain saturated or unsaturated dicarboxylic acid; the long-chain dibasic acid has carboxyl groups at both ends.

[0028] 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.

[0029] In one embodiment, before membrane filtration, a base is added to the fermentation broth or the treated broth thereof to dissolve the long-chain dibasic acid.

[0030] In one embodiment, the fermentation liquid or the treated liquid thereof can be adjusted to a pH of 6 to 12 by adding alkali, and can further be 8 to 11, for example, 8.2, 8.5, 8.8, 9.0, 9.2, 9.5, 9.8, 10.0, 10.2, 10.5, 10.8, 11.5. The type of alkali added can be sodium hydroxide, potassium hydroxide, etc.

[0031] In one embodiment, before membrane filtration, the fermentation broth or its treated liquid can be heated to 60-100°C, for example, 62°C, 65°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, or 98°C.

[0032] In one embodiment, the membrane filtration includes ultrafiltration membrane filtration and / or microfiltration membrane filtration.

[0033] In one embodiment, the temperature of microfiltration membrane filtration is 30-100°C, and can further be 50-100°C, and can further be 60-100°C, for example, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 62°C, 65°C, 68°C, 70°C, 72°C, 75°C, 78°C, 80°C, 82°C, 84°C, 85°C, 86°C, 88°C, 90°C, 92°C, 94°C, 95°C, 96°C, and 98°C.

[0034] In one embodiment, the pore size of the microfiltration membrane may be 0.01 to 1 micron, further may be 0.01 to 0.2 micron, further may be 0.02 to 0.1 micron, for example 0.03 micron, 0.05 micron, 0.08 micron, 0.1 micron, 0.15 micron, 0.5 micron.

[0035] In one embodiment, the temperature of ultrafiltration membrane filtration is 20-100°C, further can be 20-45°C, further can be 30-40°C, for example 25°C, 30°C, 32°C, 34°C, 35°C, 36°C, 38°C.

[0036] In one embodiment, the molecular weight cutoff of the ultrafiltration membrane can be 1000-200000 Da, further can be 1000-30000 Da, further can be 1000-10000 Da, for example, 1500 Da, 2000 Da, 3000 Da, 4000 Da, 5000 Da, 6000 Da, 8000 Da, 10000 Da, 15000 Da, 20000 Da, 25000 Da.

[0037] In one embodiment, the ultrafiltration membrane can be a polypropylene membrane, a polysulfone membrane, a polyethersulfone membrane, or an inorganic ultrafiltration membrane, such as a ceramic membrane.

[0038] In one embodiment, the membrane filtration includes microfiltration membrane filtration and ultrafiltration membrane filtration. The fermentation broth or the treated liquid thereof can be first filtered through a microfiltration membrane, and then the filtrate can be filtered through an ultrafiltration membrane.

[0039] In one embodiment, the fermentation broth or the treated broth thereof is filtered through a microfiltration membrane at 60-100° C., the resulting filtrate is cooled to 20-45° C., and then filtered through an ultrafiltration membrane.

[0040] In step (1) of one embodiment, the filtrate after membrane filtration is decolorized and then acidified and crystallized.

[0041] In step (1) of one embodiment, the temperature of the bleaching treatment can be 50-100°C, further can be 60-100°C, further can be 60-80°C, for example, 62°C, 65°C, 68°C, 70°C, 72°C, 75°C, 78°C, 80°C, 85°C, 88°C, 90°C, 95°C.

[0042] In step (1) of one embodiment, the decolorization treatment time can be 10 to 180 minutes, and further can be 15 to 120 minutes, for example, 20 minutes, 30 minutes, 40 minutes, 60 minutes, 70 minutes, 80 minutes, 90 minutes, 100 minutes, 110 minutes, 130 minutes, 150 minutes, or 170 minutes.

[0043] In step (1) of one embodiment, the decolorizing agent used for decolorization treatment can be activated carbon fiber, activated carbon particles, or activated carbon powder. The amount of the decolorizing agent can be 0.05 to 5 wt% of the mass of the decolorizing liquid, for example, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, or 4 wt%.

[0044] In one embodiment, the acidification crystallization comprises adjusting the pH of the filtrate to 2 to 5.5 for crystallization.

[0045] In one embodiment, the acidification crystallization process includes adjusting the pH value of the membrane filtrate or the clear liquid after decolorization to 2-4.5, further to 2-4, further to 2.5-4, further to 2.5-3.7, 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, so as to crystallize the long-chain dibasic acid.

[0046] In one embodiment, the pH value of the membrane filtrate or the clear solution after decolorization can be adjusted by adding an acid, which can be an inorganic acid and / or an organic acid. The added inorganic acid can be hydrochloric acid and / or sulfuric acid.

[0047] In one embodiment, step (1) comprises:

[0048] The fermentation liquid of the long-chain dibasic acid or the treated liquid thereof is heated to 30 to 100° C., the pH value is adjusted to 8 to 11, and then the mixture is filtered through a membrane at a temperature of 20 to 100° C. to obtain a filtrate;

[0049] Decolorizing the filtrate at 50-100° C. to obtain a clear solution; and

[0050] The pH of the clear solution is adjusted to 2-4.5, crystals are precipitated, filtered, and dried to obtain a crude long-chain dibasic acid.

[0051] In one embodiment, step (2) comprises: subjecting the crude long-chain dibasic acid to vacuum distillation, collecting fractions, and obtaining a long-chain dibasic acid product.

[0052] In one embodiment, the pressure of the reduced pressure distillation can be 1 to 100 Pa, and further can be 1 to 50 Pa, for example, 3 Pa, 5 Pa, 6 Pa, 10 Pa, 15 Pa, 20 Pa, 25 Pa, 30 Pa, 50 Pa, 60 Pa, and 80 Pa.

[0053] In one embodiment, the reduced pressure distillation includes molecular distillation and high vacuum distillation.

[0054] In one embodiment, the pressure of the main evaporator of molecular distillation can be 0.1-30Pa, and further can be 0.1-15Pa, for example 1Pa, 2Pa, 5Pa, 6Pa, 8Pa, 10Pa, 12Pa, 16Pa, 18Pa, 20Pa, 25Pa.

[0055] In one embodiment, the evaporation surface temperature of the main evaporator of molecular distillation is 130-250°C, and can further be 160-230°C, for example, 140°C, 150°C, 160°C, 180°C, 200°C, 210°C, 220°C, 240°C.

[0056] In one embodiment, the condensation surface temperature of the main evaporator of molecular distillation is 130-160°C, and can further be 130-150°C, such as 135°C, 140°C, 145°C, 150°C, 155°C.

[0057] In one embodiment, the feed inlet temperature of the molecular distillation is 130-160°C, and can further be 135-150°C, for example, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C.

[0058] In one embodiment, the number of theoretical plates of the distillation tower used for high vacuum distillation can be 8 to 24, and further can be 12 to 20, such as 10, 12, 18, 24. Preferably, a packed tower is used, and the packing can be a commonly used packing in the art, such as a corrugated wire mesh packing.

[0059] In one embodiment, the top pressure of the distillation tower used for high vacuum distillation may be 1-100 Pa, and further may be 1-50 Pa, for example, 20 Pa, 30 Pa, 60 Pa, 70 Pa, 80 Pa.

[0060] In one embodiment, the top temperature of the distillation tower used for high vacuum distillation can be 160-250°C, and can further be 180-240°C, for example, 170°C, 185°C, 190°C, 195°C, 200°C, 210°C, 220°C, 225°C, 228°C, 230°C, 232°C, 235°C, 238°C, 240°C, and 245°C.

[0061] In one embodiment, the bottom temperature of the distillation tower used for high vacuum distillation can be 180-270°C, for example, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 243°C, 245°C, 248°C, 250°C, 255°C, 260°C, and 265°C.

[0062] In one embodiment, the reflux ratio of the high vacuum distillation may be (1-10):1, and further may be (6-10):1, for example, 1:1, 2:1, 5:1, 6:1, 8:1, or 10:1.

[0063] In step (2) of one embodiment, the crude long-chain dibasic acid may be decolorized before the vacuum distillation, or the obtained product may be decolorized after the vacuum distillation.

[0064] In step (2) of one embodiment, the decolorization treatment may be solution decolorization or melt decolorization.

[0065] In one embodiment, the decolorizing agent used in the decolorization process may be activated carbon.

[0066] In one embodiment, melt decolorization refers to directly contacting the crude long-chain dibasic acid to be decolorized or the fraction obtained by vacuum distillation with a decolorizing agent for decolorization. For example, the crude long-chain dibasic acid or the fraction obtained by vacuum distillation is heated and melted, and then flows through the decolorizing agent in a molten state.

[0067] Decolorizing the crude long-chain dibasic acid in a molten state and then performing vacuum distillation, or decolorizing the fraction after vacuum distillation by melting, can reduce the energy consumption of heating and simplify the process.

[0068] In one embodiment, the temperature of melt bleaching may be 130-180°C, and further may be 130-150°C, for example, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C.

[0069] In one embodiment, the amount of activated carbon used for melt decolorization is 3 to 50 wt% of the mass of the crude long-chain dibasic acid or the mass of the fraction obtained by vacuum distillation, and can further be 5 to 25 wt%, for example, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%.

[0070] In one embodiment, after the melt decolorization is completed, the residual activated carbon can be removed by further filtering. Thus, the melt decolorization not only decolorizes and purifies the substance to be decolorized, but also avoids the introduction of subsequent impurities.

[0071] In one embodiment, the activated carbon used for decolorization treatment can be one or more of powdered activated carbon, activated carbon fiber, activated carbon granules, and activated carbon columns.

[0072] According to the requirements of customers and the market for product quality, the product obtained by the refining process of the present invention can be further refined to further improve the quality of the product.

[0073] The refining process of one embodiment of the present invention simplifies the process and can overcome the shortcomings of the solvent crystallization method, such as poor product quality and environmental pollution caused by the solvent.

[0074] The refining process of one embodiment of the present invention is suitable for the extraction and purification of long-chain dibasic acids prepared by biological fermentation. By using membrane filtration combined with distillation technology, especially ceramic membrane filtration, ultrafiltration membrane filtration combined with molecular distillation or high vacuum distillation technology, no organic solvent is needed, so that the obtained product has high purity, white color, low ash content, and low metal ion and nitrogen content.

[0075] One embodiment of the present invention provides a long-chain dibasic acid obtained by the above-mentioned refining process.

[0076] like Figure 1 As shown, one embodiment of the present invention provides a long-chain dibasic acid refining system for realizing the above refining process, comprising a membrane filtration unit, an acidification crystallization unit, a separation unit, a drying unit and a vacuum distillation unit arranged in sequence.

[0077] In one embodiment, the refining system includes a raw liquid storage tank, which can be connected to the membrane filtration unit and is used to hold the long-chain dibasic acid fermentation liquid or its treated liquid.

[0078] In one embodiment, the membrane filtration unit is used for membrane filtration of the long-chain dibasic acid fermentation broth or its treated liquid, and a filtration membrane, such as a microfiltration membrane and / or an ultrafiltration membrane, may be provided in the membrane filtration unit.

[0079] In one embodiment, the pore size of the microfiltration membrane may be 0.01 to 1 micron, further may be 0.02 to 0.2 micron, further may be 0.02 to 0.1 micron, for example 0.03 micron, 0.05 micron, 0.08 micron, 0.1 micron, 0.15 micron, 0.5 micron.

[0080] In one embodiment, the molecular weight cutoff of the ultrafiltration membrane can be 1000-200000 Da, further can be 1000-30000 Da, further can be 1000-10000 Da, for example, 1500 Da, 2000 Da, 3000 Da, 4000 Da, 5000 Da, 6000 Da, 8000 Da, 10000 Da, 15000 Da, 20000 Da, 25000 Da.

[0081] In one embodiment, the ultrafiltration membrane can be a polypropylene membrane, a polysulfone membrane, a polyethersulfone membrane, or an inorganic ultrafiltration membrane, such as a ceramic membrane.

[0082] In one embodiment, the refining system includes a heating device for heating the raw liquid storage tank, so that the long-chain dibasic acid fermentation liquid or its treated liquid is subjected to membrane filtration at a certain temperature, such as 50-100°C.

[0083] In one embodiment, the long-chain dibasic acid fermentation broth is treated by membrane filtration in a membrane filtration unit to obtain a filtrate, and the acidification crystallization unit is used for acidification and crystallization of the filtrate.

[0084] In one embodiment, the acidification crystallization unit includes an acidification tank, and the filtrate can be acidified and crystallized in the acidification tank to obtain a solid-liquid mixture.

[0085] In one embodiment, a first decolorization unit may be further provided between the membrane filtration unit and the acidification crystallization unit to decolorize the filtrate before performing acidification crystallization.

[0086] In one embodiment, the first decolorization unit may include a decolorization tank and a filter; the decolorization tank is used to decolorize the liquid to be decolorized and the solid decolorizer by solid-liquid mixing; after the decolorization is completed, the solid decolorizer can be removed by the filter. The filter may be a plate and frame filter.

[0087] 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.).

[0088] In one embodiment, the separation unit is used to perform solid-liquid separation on the solid-liquid mixture in the acidification crystallization unit.

[0089] In one embodiment, the separation unit may include a filter separator or a centrifugal separator.

[0090] In one embodiment, the drying unit includes a heating device for heating the solid obtained by the separation unit to dry it and obtain a crude long-chain dibasic acid.

[0091] In one embodiment, the vacuum distillation unit is used to distill and separate the dried crude long-chain dibasic acid to obtain a long-chain dibasic acid product.

[0092] In one embodiment, the vacuum distillation unit comprises a heating device, so that the crude long-chain dibasic acid is molten in the heating device.

[0093] In one embodiment, the vacuum distillation unit includes a distillation device to perform a vacuum distillation process.

[0094] In one embodiment, the distillation apparatus comprises a molecular distillation apparatus for performing molecular distillation.

[0095] In another embodiment, the distillation apparatus comprises a distillation column for performing high vacuum distillation.

[0096] In one embodiment, the number of theoretical plates of the distillation tower may be 8-24, and further may be 12-20, such as 10, 12, 18, or 24.

[0097] In one embodiment, the refining system includes a second decolorization unit.

[0098] In one embodiment, the second decolorization unit may include a decolorization tank and a filter; the decolorization tank is used to decolorize the liquid to be decolorized and the solid decolorizer by solid-liquid mixing. After the decolorization is completed, the residual solid decolorizer can be removed by the filter. The filter may be a plate and frame filter.

[0099] In one embodiment, the crude long-chain dibasic acid or the fraction obtained by vacuum distillation is directly contacted with the decolorant in the second decolorization unit for decolorization. For example, the crude long-chain dibasic acid or the fraction obtained by vacuum distillation is passed through the decolorant in the second decolorization unit in a molten state.

[0100] In one embodiment, the second decolorization unit includes a heating device for heating the decolorization tank, so that the decolorization process is performed at a certain temperature (eg, 130-180° C.).

[0101] In one embodiment, the second decolorization unit is disposed between the drying unit and the vacuum distillation unit to decolorize the crude long-chain dibasic acid before the vacuum distillation, or the second decolorization unit is disposed after the vacuum distillation unit to decolorize the product obtained after the vacuum distillation.

[0102] In another embodiment, the crude long-chain dibasic acid or the product obtained after vacuum distillation is heated to melt, and then decolorized by a decolorizer. After decolorization, the residual decolorizer can be filtered to remove the second crude long-chain dibasic acid or the long-chain dibasic acid product.

[0103] In the present invention, the acidification tank, decolorization tank, dissolution tank, heating device, etc. can all be existing devices.

[0104] The following is a further description of the refining process of the long-chain dibasic acid 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:

[0105] 1. Gas chromatography detection of long-chain dibasic acids

[0106] 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.

[0107] 2. Ash content detection

[0108] 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.

[0109] 3. Total nitrogen determination

[0110] The Kjeldahl method was used for nitrogen determination.

[0111] 4. Light transmittance test:

[0112] Taking advantage of the different colors of substances and the different transmittances at a certain wavelength, the transmittance of a dimethyl sulfoxide solution of a 25% by mass long-chain dibasic acid sample at 440nm is used to represent the color of the dibasic acid product.

[0113] 5.Fe content test

[0114] Refer to GB / T3049-2006 and measure by spectrophotometry.

[0115] Example 1 DC12 microfiltration membrane + molecular distillation

[0116] According to the fermentation method of Example 4 of patent document CN1570124A, dodecanedioic acid (DC12) fermentation liquid was obtained.

[0117] The fermentation liquid was heated to 85°C, alkali was added to adjust the pH to 8.2, and the bacteria were removed by filtration at 85°C using a ceramic microfiltration membrane with a pore size of 0.05 um to obtain a filtrate.

[0118] The filtrate was decolorized with 3 wt % activated carbon at 85° C. for 40 minutes, filtered through a plate and frame to obtain a clear liquid, and the pH value of the clear liquid was adjusted to 2.8 with sulfuric acid for acidification and crystallization, filtered, and dried to obtain a crude DC12 product.

[0119] The crude DC12 product was purified by molecular distillation. The pressure of the main evaporator of the molecular distillation device was 18 Pa, the evaporation surface temperature of the main evaporator was 180°C, the condensation surface temperature of the main evaporator was 140°C, the feed inlet temperature was 130°C, and the fractions were collected to obtain the DC12 product.

[0120] Example 2 DC12 microfiltration membrane + high vacuum distillation

[0121] According to the fermentation method of Example 4 of patent document CN1570124A, dodecanedioic acid fermentation liquid was obtained.

[0122] The fermentation liquid was heated to 85°C, alkali was added to adjust the pH to 8.2, and the bacteria were removed by filtration at 85°C using a ceramic microfiltration membrane with a pore size of 0.05 um to obtain a filtrate.

[0123] The filtrate was decolorized with 3 wt % activated carbon at 85° C. for 20 minutes, filtered through a plate and frame to obtain a clear liquid, and the pH value of the clear liquid was adjusted to 2.8 with sulfuric acid for acidification and crystallization, filtered, and dried to obtain a crude DC12 product.

[0124] The crude DC12 product was purified by high vacuum distillation. The distillation tower had 12 plates, a top pressure of 60 Pa, a top temperature of 238°C, a bottom temperature of 250°C, a reflux ratio of 5:1, and the fractions were collected and cooled to obtain the DC12 product.

[0125] Example 3 DC16 microfiltration membrane + ultrafiltration membrane + molecular distillation

[0126] According to the fermentation method of Example 8 of patent document CN1570124A, hexadecanedioic acid (DC16) fermentation liquid was obtained.

[0127] The fermentation broth was heated to 90°C, alkali was added to adjust the pH to 8.5, and the bacteria were removed by filtration at 90°C using a ceramic microfiltration membrane with a pore size of 0.05um. The broth was then cooled to 30°C and filtered at 30°C using an ultrafiltration membrane to obtain a filtrate with a molecular weight cutoff of 5000Da.

[0128] The filtrate was decolorized with 2.5 wt% activated carbon at 85°C for 20 minutes, filtered through a plate and frame to obtain a clear liquid, the pH of the clear liquid was adjusted to 3.0 with hydrochloric acid for acidification and crystallization, filtered, and dried to obtain a crude DC16 product.

[0129] The crude DC16 product was purified by molecular distillation. The pressure of the main evaporator of the molecular distillation device was 6 Pa, the evaporation surface temperature of the main evaporator was 200°C, the condensation surface temperature of the main evaporator was 150°C, the feed inlet temperature was 140°C, and the fractions were collected and cooled to obtain the DC16 product.

[0130] Example 4-1 DC12 microfiltration membrane + ultrafiltration membrane + molecular distillation

[0131] According to the fermentation method of Example 4 of patent document CN1570124A, dodecanedioic acid fermentation liquid was obtained.

[0132] The fermentation broth of DC12 was heated to 90°C, alkali was added to adjust the pH to 8.5, and the bacteria were removed by filtration at 90°C using a ceramic microfiltration membrane with a pore size of 0.05um. The broth was then cooled to 35°C and filtered at 35°C using an ultrafiltration membrane to obtain a filtrate with a molecular weight cutoff of 5000Da.

[0133] The filtrate was decolorized with 2.5 wt% activated carbon at 85°C for 20 minutes, filtered through a plate and frame to obtain a clear liquid, the pH of the clear liquid was adjusted to 3.0 with sulfuric acid for acidification and crystallization, filtered, and dried to obtain a crude DC12 product.

[0134] The crude DC12 product was purified by molecular distillation. The pressure of the main evaporator of the molecular distillation device was 5 Pa, the evaporation surface temperature of the main evaporator was 180°C, the condensation surface temperature of the main evaporator was 140°C, the feed inlet temperature was 130°C, the fractions were collected and cooled to obtain the DC12 product.

[0135] Example 4-2 DC12 microfiltration membrane + ultrafiltration membrane + molecular distillation

[0136] According to the fermentation method of Example 4 of patent document CN1570124A, dodecanedioic acid fermentation liquid was obtained.

[0137] The fermentation broth of DC12 was heated to 90°C, alkali was added to adjust the pH to 8.5, and the bacteria were removed by filtration at 90°C using a ceramic microfiltration membrane with a pore size of 0.15um. The broth was then cooled to 35°C and filtered through an ultrafiltration membrane at 35°C to obtain a filtrate with a molecular weight cutoff of 15,000Da.

[0138] The filtrate was decolorized with 2.5 wt% activated carbon at 85°C for 20 minutes, filtered through a plate and frame to obtain a clear liquid, the pH of the clear liquid was adjusted to 4 with sulfuric acid for acidification and crystallization, filtered, and dried to obtain a crude DC12 product.

[0139] The crude DC12 product was purified by molecular distillation. The pressure of the main evaporator of the molecular distillation device was 8 Pa, the evaporation surface temperature of the main evaporator was 180°C, the condensation surface temperature of the main evaporator was 140°C, the feed inlet temperature was 130°C, and the fractions were collected and cooled to obtain the DC12 product.

[0140] Example 4-3DC12 microfiltration membrane + ultrafiltration membrane + molecular distillation

[0141] According to the fermentation method of Example 4 of patent document CN1570124A, dodecanedioic acid fermentation liquid was obtained.

[0142] The fermentation broth of DC12 was heated to 90°C, alkali was added to adjust the pH to 8.5, and the bacteria were removed by filtration at 90°C using a ceramic microfiltration membrane with a pore size of 0.05um. The broth was then cooled to 35°C and filtered through an ultrafiltration membrane at 35°C to obtain a filtrate with a molecular weight cutoff of 15,000Da.

[0143] The filtrate was decolorized with 2.5 wt% activated carbon at 85°C for 20 minutes, filtered through a plate and frame to obtain a clear liquid, and the pH of the clear liquid was adjusted to 4.5 with sulfuric acid for acidification and crystallization, filtered, and dried to obtain a crude DC12 product.

[0144] The crude DC12 product was purified by molecular distillation. The pressure of the main evaporator of the molecular distillation device was 18 Pa, the evaporation surface temperature of the main evaporator was 150°C, the condensation surface temperature of the main evaporator was 130°C, the feed inlet temperature was 130°C, the fractions were collected and cooled to obtain the DC12 product.

[0145] Example 5-1 DC12 microfiltration membrane + ultrafiltration membrane + high vacuum distillation

[0146] According to the fermentation method of Example 4 of patent document CN1570124A, dodecanedioic acid fermentation liquid was obtained.

[0147] The fermentation broth of DC12 was heated to 90°C, alkali was added to adjust the pH to 8.5, and the bacteria were removed by filtration at 90°C using a ceramic microfiltration membrane with a pore size of 0.05um. The broth was then cooled to 35°C and filtered at 35°C using an ultrafiltration membrane to obtain a filtrate with a molecular weight cutoff of 5000Da.

[0148] The filtrate was decolorized with 2.5 wt% activated carbon at 85°C for 20 minutes, filtered through a plate and frame to obtain a clear liquid, the pH of the clear liquid was adjusted to 3.0 with sulfuric acid for acidification and crystallization, filtered, and dried to obtain a crude DC12 product.

[0149] The crude DC12 product was purified by high vacuum distillation. The distillation tower had 10 plates, a top pressure of 30 Pa, a top temperature of 230°C, a bottom temperature of 243°C, a reflux ratio of 5:1, and the fractions were collected and cooled to obtain the DC12 product.

[0150] Example 5-2 DC12 microfiltration membrane + ultrafiltration membrane + high vacuum distillation

[0151] According to the fermentation method of Example 4 of patent document CN1570124A, dodecanedioic acid fermentation liquid was obtained.

[0152] The fermentation broth of DC12 was heated to 90°C, alkali was added to adjust the pH to 8.5, and the bacteria were removed by filtration at 90°C using a ceramic microfiltration membrane with a pore size of 0.15um. The broth was then cooled to 35°C and filtered through an ultrafiltration membrane at 35°C to obtain a filtrate with a molecular weight cutoff of 12000Da.

[0153] The filtrate was decolorized with 2 wt % activated carbon at 85° C. for 20 minutes, filtered through a plate and frame to obtain a clear liquid, and the pH of the clear liquid was adjusted to 4.2 with sulfuric acid for acidification and crystallization, filtered, and dried to obtain a crude DC12 product.

[0154] The crude DC12 product was purified by high vacuum distillation. The distillation tower had 24 plates, a top pressure of 30 Pa, a top temperature of 240°C, a bottom temperature of 252°C, a reflux ratio of 5:1, and the fractions were collected and cooled to obtain the DC12 product.

[0155] Example 5-3DC12 microfiltration membrane + ultrafiltration membrane + high vacuum distillation

[0156] According to the fermentation method of Example 4 of patent document CN1570124A, dodecanedioic acid fermentation liquid was obtained.

[0157] The fermentation broth of DC12 was heated to 90°C, alkali was added to adjust the pH to 8.5, and the bacteria were removed by filtration at 90°C using a ceramic microfiltration membrane with a pore size of 0.05um. The broth was then cooled to 35°C and filtered at 35°C using an ultrafiltration membrane to obtain a filtrate with a molecular weight cutoff of 5000Da.

[0158] The filtrate was decolorized with 2 wt % activated carbon at 85° C. for 20 minutes, filtered through a plate and frame to obtain a clear liquid, and the pH of the clear liquid was adjusted to 3 with sulfuric acid for acidification and crystallization, filtered, and dried to obtain a crude DC12 product.

[0159] The crude DC12 product was purified by high vacuum distillation. The distillation tower had 24 plates, a top pressure of 30 Pa, a top temperature of 240°C, a bottom temperature of 252°C, a reflux ratio of 7:1, and the fractions were collected and cooled to obtain the DC12 product.

[0160] Example 6-1 DC12 microfiltration membrane + ultrafiltration membrane + crude product melting decolorization + high vacuum distillation

[0161] According to the fermentation method of Example 4 of patent document CN1570124A, dodecanedioic acid fermentation liquid was obtained.

[0162] The fermentation broth of DC12 was heated to 90°C, alkali was added to adjust the pH to 8.5, and the cells were removed by filtration with a ceramic microfiltration membrane at 90°C, the pore size of the ceramic microfiltration membrane was 0.25um, and then the temperature was lowered to 35°C, and filtered through an ultrafiltration membrane at 35°C to obtain a filtrate, the molecular weight cutoff of the ultrafiltration membrane was 20000Da. The filtrate was decolorized with 2wt% activated carbon at 85°C for 20 minutes, and filtered through a plate and frame to obtain a clear liquid.

[0163] The pH value of the clear solution was adjusted to 4.5 with sulfuric acid for acidification and crystallization, filtered and dried to obtain crude DC12.

[0164] The crude DC12 is heated and melted and then decolorized by passing through an activated carbon column composed of activated carbon particles. The decolorization temperature is 150°C and the mass of the activated carbon particles is 40% of the mass of the crude DC12.

[0165] The decolorized crude product was purified by high vacuum distillation. The distillation tower had 20 plates, a top pressure of 30 Pa, a top temperature of 230°C, a bottom temperature of 245°C, a reflux ratio of 5:1, and the fractions were collected and cooled to obtain a DC12 product.

[0166] Example 6-2 DC12 microfiltration membrane + ultrafiltration membrane + crude product melting decolorization + high vacuum distillation

[0167] According to the fermentation method of Example 4 of patent document CN1570124A, dodecanedioic acid fermentation liquid was obtained.

[0168] The fermentation broth of DC12 was heated to 90°C, alkali was added to adjust the pH to 8.5, and the cells were removed by filtration with a ceramic microfiltration membrane at 90°C, the pore size of the ceramic microfiltration membrane was 0.15um, and then the temperature was lowered to 35°C, and filtered through an ultrafiltration membrane at 35°C to obtain a filtrate, the molecular weight cutoff of the ultrafiltration membrane was 5000Da. The filtrate was decolorized with 2wt% activated carbon at 85°C for 20 minutes, and filtered through a plate and frame to obtain a clear liquid.

[0169] The pH value of the clear solution was adjusted to 3 with sulfuric acid for acidification and crystallization, filtered and dried to obtain crude DC12.

[0170] The crude DC12 is heated and melted and then decolorized by passing through an activated carbon column composed of activated carbon particles. The decolorization temperature is 150°C and the mass of the activated carbon particles is 40% of the mass of the crude DC12.

[0171] The decolorized crude product was purified by high vacuum distillation. The distillation tower had 22 plates, a top pressure of 30 Pa, a top temperature of 230°C, a bottom temperature of 252°C, a reflux ratio of 8:1, and the fractions were collected and cooled to obtain a DC12 product.

[0172] Example 6-3DC12 microfiltration membrane + ultrafiltration membrane + crude product melting decolorization + high vacuum distillation

[0173] According to the fermentation method of Example 4 of patent document CN1570124A, dodecanedioic acid fermentation liquid was obtained.

[0174] The fermentation broth of DC12 was heated to 90°C, alkali was added to adjust the pH to 8.5, and the cells were removed by filtration with a ceramic microfiltration membrane at 90°C, the pore size of the ceramic microfiltration membrane was 0.05um, and then the temperature was lowered to 35°C, and filtered through an ultrafiltration membrane at 35°C to obtain a filtrate, the molecular weight cutoff of the ultrafiltration membrane was 5000Da. The filtrate was decolorized with 2wt% activated carbon at 85°C for 20 minutes, and filtered through a plate and frame to obtain a clear liquid.

[0175] The pH value of the clear solution was adjusted to 3 with sulfuric acid for acidification and crystallization, filtered and dried to obtain crude DC12.

[0176] The crude DC12 was heated and melted and then decolorized by passing through an activated carbon column composed of activated carbon particles. The decolorization temperature was 140° C. and the mass of the activated carbon particles was 25% of the mass of the crude DC12.

[0177] The decolorized crude product was purified by high vacuum distillation. The distillation tower had 18 plates, a top pressure of 30 Pa, a top temperature of 240°C, a bottom temperature of 250°C, a reflux ratio of 5:1, and the fractions were collected and cooled to obtain a DC12 product.

[0178] Example 7 DC12 microfiltration membrane + ultrafiltration membrane + crude product melting decolorization + molecular distillation

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

[0180] The fermentation broth of DC12 was heated to 90°C, alkali was added to adjust the pH to 8.5, and the bacteria were removed by filtration at 90°C using a ceramic microfiltration membrane with a pore size of 0.05um. The broth was then cooled to 35°C and filtered at 35°C using an ultrafiltration membrane to obtain a filtrate with a molecular weight cutoff of 5000Da.

[0181] The filtrate was decolorized with 2.5 wt% activated carbon at 85°C for 20 minutes, filtered through a plate and frame to obtain a clear liquid, the pH of the clear liquid was adjusted to 3.0 with sulfuric acid for acidification and crystallization, filtered, and dried to obtain a crude DC12 product.

[0182] The crude DC12 was heated and melted and then passed through an activated carbon column composed of activated carbon particles for decolorization. The decolorization temperature was 135° C. and the mass of the activated carbon particles was 10% of the mass of the crude DC12.

[0183] The decolorized DC12 is subjected to molecular distillation. The pressure of the main evaporator of the molecular distillation device is 3 Pa, the evaporation surface temperature of the main evaporator is 220°C, the condensation surface temperature of the main evaporator is 145°C, the feed inlet temperature is 135°C, the fractions are collected and cooled to obtain the DC12 product.

[0184] Example 8 DC12 microfiltration membrane + ultrafiltration membrane + crude product melting decolorization + molecular distillation

[0185] According to the fermentation method of Example 4 of patent document CN1570124A, dodecanedioic acid fermentation liquid was obtained.

[0186] The fermentation broth of DC12 was heated to 90°C, alkali was added to adjust the pH to 8.5, and the bacteria were removed by filtration at 90°C using a ceramic microfiltration membrane with a pore size of 0.05um. The broth was then cooled to 35°C and filtered through an ultrafiltration membrane at 35°C to obtain a filtrate with a molecular weight cutoff of 15,000Da.

[0187] The filtrate was decolorized with 2.5 wt% activated carbon at 85°C for 20 minutes, filtered through a plate and frame to obtain a clear liquid, and the pH of the clear liquid was adjusted to 4.2 with sulfuric acid for acidification and crystallization, filtered, and dried to obtain a crude DC12 product.

[0188] The crude DC12 product was heated and melted and then decolorized by passing through an activated carbon column composed of activated carbon particles. The decolorization temperature was 135° C. and the mass of the activated carbon particles was 5% of the mass of the crude DC12 product.

[0189] The decolorized DC12 is subjected to molecular distillation. The pressure of the main evaporator of the molecular distillation device is 16 Pa, the evaporation surface temperature of the main evaporator is 180°C, the condensation surface temperature of the main evaporator is 140°C, the feed inlet temperature is 130°C, the fractions are collected and cooled to obtain the DC12 product.

[0190] Example 9 DC12 microfiltration membrane + ultrafiltration membrane + molecular distillation + fraction melting decolorization

[0191] The raw materials and steps used in this embodiment are basically the same as those in Example 4-1, except that the fraction obtained after molecular distillation in Example 4-1 is further decolorized: the fraction obtained by molecular distillation is heated and melted, and then decolorized by passing through an activated carbon column composed of activated carbon particles. The decolorization temperature is 135°C, and the amount of activated carbon is 15% of the fraction. After cooling, a DC12 product is obtained.

[0192] Comparative Example 1DC12 centrifugation + alkali dissolution + decolorization + acid precipitation

[0193] According to the fermentation method of Example 4 of patent document CN1570124A, dodecanedioic acid fermentation liquid was obtained.

[0194] The fermentation liquid was heated to 90°C, alkali was added to adjust the pH to 8.5, the bacteria were removed by centrifugation to obtain a clear liquid, the pH value of the clear liquid was adjusted to 3.0 with sulfuric acid for acidification and crystallization, filtered, and dried to obtain a crude DC12 product.

[0195] Take 100 grams of crude DC12, add 1000 grams of water, heat to 70°C, add caustic soda, adjust the pH to 10, stir, and completely dissolve the dodecanedioic acid. Add 10 grams of macroporous powdered sugar carbon to the resulting solution, stir for 1 hour, filter while hot to obtain a filtrate. Add 10 grams of macroporous powdered sugar carbon to the filtrate, stir for 1 hour, filter while hot to obtain a filtrate. Add 98% mass percent sulfuric acid to the obtained filtrate, adjust the pH to less than 3, cool to 25°C, filter, and obtain the DC12 product.

[0196] Comparative Example 2DC12 centrifugation + decolorization + ethyl acetate recrystallization

[0197] According to the fermentation method of Example 4 of patent document CN1570124A, dodecanedioic acid fermentation liquid was obtained.

[0198] The fermentation liquid was heated to 90°C, the pH value was adjusted to 8.5 by adding alkali, the bacteria were removed by centrifugation, 2.5% activated carbon by mass of the filtrate was added to the filtrate for decolorization, the liquid was decolorized at 90°C for 25 minutes, and the liquid was filtered through a ceramic membrane at 90°C to obtain a clear liquid, the pH value of the clear liquid was adjusted to 3.0 for acidification and crystallization, filtered, and dried to obtain a crude DC12 product.

[0199] Take 300 g of crude DC12, add 900 mL of butyl acetate, heat to 80°C to dissolve the crude product, filter, keep warm for 60 minutes, cool to 25°C to crystallize, filter, add 1000 mL of butyl acetate to the obtained primary crystallization product, heat to 80°C to dissolve DC12, keep warm for 30 minutes, cool to 25°C to crystallize within 1 hour, filter, and dry to obtain DC12 product.

[0200] Comparative Example 3DC16 centrifugation + alkali dissolution + decolorization + acid precipitation

[0201] According to the fermentation method of Example 8 of patent document CN1570124A, hexadecanedioic acid fermentation liquid was obtained.

[0202] The fermentation liquid was heated to 90°C, alkali was added to adjust the pH to 8.5, the bacteria were removed by centrifugation to obtain a clear liquid, the pH value of the clear liquid was adjusted to 3.0 with sulfuric acid for acidification and crystallization, filtered, and dried to obtain a crude DC16 product.

[0203] Take 100 grams of crude DC16, add 1500 grams of water, heat to 70°C, add caustic soda, adjust the pH to 10.2, stir, and completely dissolve the hexadecane dibasic acid. Add 9.5 grams of macroporous powdered sugar carbon to the resulting solution, stir for 1 hour, filter while hot to obtain a filtrate. Add 10 grams of macroporous powdered sugar carbon to the filtrate, stir for 1 hour, filter while hot to obtain a filtrate. Add 98% mass percent sulfuric acid to the obtained filtrate, adjust the pH to less than 3, cool to 25°C, filter, and obtain the DC16 product.

[0204] 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.

[0205] Table 1 Long chain dibasic acid product performance table

[0206]

[0207]

[0208]

[0209] Unless otherwise defined, the terms used in the present invention have the meanings commonly understood by those skilled in the art.

[0210] 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 long-chain dibasic acid refining process comprising the following steps: (1) filtering the fermentation liquid of the long-chain dibasic acid or its treated liquid through a membrane, acidifying and crystallizing, solid-liquid separation, and drying to obtain a crude long-chain dibasic acid; in, The membrane filtration is ultrafiltration membrane filtration and microfiltration membrane filtration. The pore size of the microfiltration membrane is 0.01 to 0.1 micrometers. The ultrafiltration membrane has a molecular weight cut-off of 1000 to 10000 Da. The acidification crystallization comprises adjusting the pH of the filtrate to 2 to 5.5 for crystallization, and Filtering the fermentation liquid or the treated liquid thereof through a microfiltration membrane at 60 to 100° C., cooling the obtained filtrate to 20 to 45° C., and then filtering it through an ultrafiltration membrane; (2) subjecting the crude long-chain dibasic acid to vacuum distillation to obtain a long-chain dibasic acid product; Wherein, the pressure of the reduced pressure distillation is ≤100Pa.

2. The process according to claim 1, wherein During filtration with the microfiltration membrane, the pressure difference on both sides of the membrane is controlled to be 0.05-0.5 MPa.

3. The process according to claim 1, comprising subjecting the filtrate after the membrane filtration to decolorization treatment and then subjecting the acidification crystallization to the acidification crystallization, wherein: The temperature of the decolorization treatment is 50 to 100° C., further 60 to 100° C.; and / or, The decolorization treatment time is 10 to 180 minutes, further 15 to 120 minutes; and / or, The dosage of the decolorizing agent is 0.05-5wt% of the mass of the liquid to be decolorized.

4. The process according to claim 1 or 3, wherein: The acidified crystallization is performed by adjusting the pH to 2 to 4.5, further to 2 to 4, further to 2.5 to 4, further to 2.5 to 3.

7.

5. The process according to claim 1, wherein the pressure of the reduced pressure distillation is 1 to 50 Pa.

6. According to the process described in claim 1 or 5, the reduced pressure distillation is selected from molecular distillation and high vacuum distillation.

7. The process according to claim 6, wherein: The pressure of the main evaporator of the molecular distillation is 0.1-30 Pa, and / or, The evaporation surface temperature of the main evaporator is 130-250°C, and / or, The condensing surface temperature of the main evaporator is 130-160°C, and / or The feed inlet temperature of molecular distillation is 130-160°C.

8. The process according to claim 7, wherein, The pressure of the main evaporator of the molecular distillation is 0.1-15 Pa, and / or, The evaporation surface temperature of the main evaporator is 160-230°C, and / or, The condensing surface temperature of the main evaporator is 130-150°C, and / or The feed inlet temperature of molecular distillation is 135-150°C.

9. The process according to claim 6, wherein: The number of theoretical plates of the distillation tower used in the high vacuum distillation is 8 to 24, and / or, The top pressure of the distillation tower is 1-100 Pa, and / or, The top temperature of the distillation tower is 160-250°C, and / or The bottom temperature of the distillation tower is 180-270°C, and / or The reflux ratio of the distillation tower is (1~10):

1.

10. The process according to claim 9, wherein: The number of theoretical plates of the distillation tower used in the high vacuum distillation is 12 to 20, and / or, The top pressure of the distillation tower is 1-50 Pa, and / or, The top temperature of the distillation tower is 180-240°C, and / or The reflux ratio of the distillation tower is (6~10):

1.

11. The process according to claim 1, comprising decolorizing the crude long-chain dibasic acid before the vacuum distillation, or decolorizing the obtained product after the vacuum distillation.

12. The process according to claim 11, wherein the decolorization treatment is solution decolorization.

13. The process according to claim 11, wherein: The decolorization process includes a melt decolorization process, which includes heating and melting the solid to be decolorized, and allowing the solid to flow through a decolorizer in a molten state.

14. The process according to claim 13, wherein: The temperature of the melt decolorization treatment is 130-180°C; and / or, The decolorizing agent is activated carbon. In the melting decolorization process, the amount of the activated carbon is 3-50% of the mass of the solid to be decolorized.

15. The process according to claim 14, wherein: The temperature of the melt decolorization treatment is 130-150°C; and / or, The amount of activated carbon used is 5 to 25 wt % of the mass of the solid to be decolorized.

16. The process according to claim 1, wherein before membrane filtration, alkali is added to the fermentation liquid or its treated liquid to dissolve the long-chain dibasic acid, and further, the fermentation liquid or its treated liquid is adjusted to a pH of 6 to 12, and further, 8 to 11, by adding alkali.

17. The process according to claim 1 or 16, wherein the fermentation liquid or the treated liquid thereof is heated to 60-100°C before membrane filtration.

18. The process of 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.

19. A long-chain dibasic acid refining system comprising: Raw liquid storage tank, used to hold long-chain dibasic acid fermentation liquid or its processing liquid, A membrane filtration unit is used for membrane filtration of a long-chain dibasic acid fermentation broth or a treated broth thereof, wherein a microfiltration membrane and an ultrafiltration membrane are arranged in the membrane filtration unit. The pore size of the microfiltration membrane is 0.01 to 0.1 micrometers. The ultrafiltration membrane has a molecular weight cut-off of 1000 to 10000 Da. The fermentation liquid or the treated liquid thereof is filtered through a microfiltration membrane at 60-100° C., the obtained filtrate is cooled to 20-45° C., and then filtered through an ultrafiltration membrane. an acidification crystallization unit, used for acidifying and crystallizing the filtrate obtained after the membrane filtration to obtain a solid-liquid mixture; A separation unit, used for performing solid-liquid separation on the solid-liquid mixture; A drying unit, used for drying the solid separated from the separation unit to obtain a crude long-chain dibasic acid; as well as The vacuum distillation unit is used to distill and separate the crude long-chain dibasic acid to obtain a long-chain dibasic acid product.

20. The refining system according to claim 19, wherein: A first decolorization unit is provided between the membrane filtration unit and the acidification crystallization unit to decolorize the filtrate obtained after the membrane filtration.

21. The refining system of claim 19, wherein: The vacuum distillation unit comprises a molecular distillation device for molecular distillation or a distillation tower for high vacuum distillation.

22. The refining system according to claim 19, comprising a second decolorization unit, wherein the second decolorization unit is disposed between the drying unit and the vacuum distillation unit to decolorize the crude long-chain dibasic acid; or The second decolorization unit is arranged after the vacuum distillation unit to decolorize the product obtained after the vacuum distillation. 23 . The refining system according to claim 21 , wherein the number of theoretical plates of the distillation tower is 8 to 24, and further 12 to 20.

24. The refining system according to claim 19, comprising a heating device for heating the raw liquid storage tank.

25. The process of claim 19, 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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