Purification method of long-chain dicarboxylic acid and product

Abstract

The invention provides a purification method of long-chain dicarboxylic acid and a product, the method comprises the following steps: S1, decolorizing a mixture containing a long-chain dicarboxylic acid crude product, water and a decolorizing agent, and carrying out crystallization treatment and solid-liquid separation treatment on a decolorizing solution to obtain a filter cake and a first crystallization mother solution; s2, applying or not applying the first crystallization mother liquor to the step S1. According to the method, the purification process is optimized, the fermentation liquor is firstly subjected to decoloration and solid-liquid separation for impurity removal, long-chain dicarboxylic acid crystallization, decoloration, crystallization mother liquor recycling and the like are combined, and the usage amount of acid, alkali and a decolorizing agent in the process is greatly reduced. And the obtained product is good in quality, high in yield and high in purity. The product application field is wide.

Description

Technical Field

[0001] The present invention relates to an extraction and purification process for long-chain dibasic acids produced by biological fermentation. Background Art

[0002] Long-chain dibasic acids refer to aliphatic dibasic carboxylic acids containing more than 10 carbon atoms (abbreviated as DCn, n≧10), which are a class of fine chemical products with important and extensive industrial uses, and are also important raw materials for synthesizing high-grade fragrances, high-performance engineering plastics, high-temperature dielectrics, high-grade hot-melt adhesives, cold-resistant plasticizers, high-grade lubricating oils, high-grade paints and coatings, etc. in the chemical industry. The production methods of long-chain dibasic acids include chemical synthesis and biological fermentation.

[0003] The production of long-chain dibasic acids by biological fermentation is the application of microbial fermentation technology in the petrochemical field that emerged in the 1970s. Using petroleum by-product wax oil as raw material, it has the advantages of wide raw material sources, simple production process, mild production conditions, etc., and has received extensive attention at home and abroad. In industrial production, the extraction and purification of long-chain dibasic acids mainly use solvent treatment and water treatment. Among them, water treatment has the advantages of low cost, simple and easily available materials, non-toxicity, less three wastes, simple recovery, low environmental protection pressure and low labor intensity of workers compared with the solvent method. Summary of the Invention

[0004] The first object of the present invention is to provide a method for purifying long-chain dibasic acids.

[0005] The method for purifying long-chain dibasic acids comprises the following steps:

[0006] S1: Decolorize a mixture containing crude long-chain dibasic acid, water and a decolorizing agent, and subject the decolorized solution to crystallization treatment and solid-liquid separation treatment to obtain a filter cake and a first crystallization mother liquor; optionally, the mixture further contains an alkaline substance;

[0007] S2: Recycle or not recycle the first crystallization mother liquor to step S1.

[0008] In one embodiment, the first crystallization mother liquor is recycled to step S1, thereby reducing the amount of the alkaline substance and / or water used.

[0009] In one embodiment, the long-chain dibasic acid is any one or a combination of two or more of sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, heptadecanedioic acid, octadecanedioic acid or 9-ene-octadecanedioic acid.

[0010] In one embodiment, in the crude long-chain dibasic acid, the long-chain dibasic acid exists in the form of long-chain dibasic acid and / or long-chain dibasic acid salt.

[0011] In one embodiment, the total content of the long-chain dibasic acid and its salts in the crude long-chain dibasic acid is 85 wt% or more, further 90 wt% or more.

[0012] In one embodiment, the long-chain dibasic acid fermentation broth is subjected to crystallization treatment and solid-liquid separation treatment with or without membrane filtration treatment to obtain the crude long-chain dibasic acid.

[0013] In one embodiment, the method includes step S0. Step S0 includes: subjecting the long-chain dibasic acid fermentation broth to crystallization treatment and solid-liquid separation treatment with or without membrane filtration treatment to obtain the crude long-chain dibasic acid and the second crystallization mother liquor.

[0014] Preferably, the crystallization treatment methods include cooling crystallization and acidification crystallization.

[0015] In one embodiment, the method further includes step S3: dispersing the filter cake obtained in step S1 in water, adjusting the pH to 2-5, performing solid-liquid separation, and drying the obtained solid to obtain the product.

[0016] In one embodiment, the method includes step S3': refining the filter cake obtained in step S1 or the product obtained in step S3.

[0017] In one embodiment, the method includes step S4: recycling the second crystallization mother liquor to step S1.

[0018] It is found that by adjusting the pH value of the decolorization system, the existence forms and aggregation states of the long-chain dibasic acid and its salts and impurities (derived from the fermentation broth, such as pigments and proteins) in the system are changed. After subsequent treatment steps such as filtration, centrifugation, decolorization, and crystallization, the impurity content is significantly reduced, which is beneficial to the purification of the product.

[0019] Those skilled in the art generally know that the long-chain dibasic acid in the fermentation broth exists in the form of long-chain dibasic acid and / or long-chain dibasic acid salts.

[0020] In one embodiment, in step S0, based on the long-chain dibasic acid, the concentration of the fermentation broth is 3 wt% to 40 wt%, further 3 wt% to 20 wt%. The concentration value of the fermentation broth includes the long-chain dibasic acid existing in the form of long-chain dibasic acid and long-chain dibasic acid salts. The concentration based on the long-chain dibasic acid means that the long-chain dibasic acid existing in the form of salt is converted into long-chain dibasic acid for concentration calculation.

[0021] In one embodiment, in step S0, the membrane filtration treatment uses microfiltration membrane filtration and / or ultrafiltration membrane treatment.

[0022] In one embodiment, in step S0, the temperature of the membrane filtration treatment is 25 to 150 °C, further 80 to 150 °C, further 88 to 125 °C, and further 88 to 98 °C.

[0023] In one embodiment, the pore size of the microfiltration membrane is 0.01 to 1 μm, further 0.01 to 0.2 μm, and further 0.01 to 0.1 μm.

[0024] In one embodiment, the molecular weight cut-off of the ultrafiltration membrane is 1000 to 30000 Da, and further 1000 to 10000 Da.

[0025] In one embodiment, in step S0, the pH value of the long-chain dibasic acid fermentation broth before membrane filtration treatment is 5.7 to 6.5, further 5.7 to 6.3, further 5.7 to 6.2, and further 5.7 to 6.1. The pH of the long-chain dibasic acid fermentation broth can be the natural pH or the adjusted pH.

[0026] In one embodiment, in step S0, the end temperature of the cooling crystallization is 25 to 45 °C, and further 30 to 40 °C.

[0027] In one embodiment, in step S0, the acidification crystallization is to adjust the pH value of the solution to 2 to 5.5, and further 2 to 4.

[0028] In one embodiment, in step S0, the temperature of the acidification crystallization is 25 to 60 °C.

[0029] In one embodiment, in step S0, the solid-liquid separation includes centrifugal separation and filtration separation. The equipment for centrifugal separation is, for example, a horizontal screw centrifuge.

[0030] In one embodiment, in step S1: the total concentration of long-chain dibasic acid and its salts in the mixture is 3 wt% to 35 wt%, and further 3 wt% to 20 wt%.

[0031] In one embodiment, in step S1: the pH value of the mixture is 5.7 to 6.5, further 5.7 to 6.3, and further 5.7 to 6.1.

[0032] In one embodiment, in step S1, the mixture further contains an alkaline substance to promote the dissolution of the crude long-chain dibasic acid in water.

[0033] In one embodiment, the alkaline substance includes but is not limited to alkali metal hydroxides, alkali metal oxides, and ammonia water.

[0034] In one embodiment, the alkaline substance includes, but is not limited to, sodium hydroxide, potassium hydroxide, ammonia water, sodium oxide, and potassium oxide.

[0035] In one embodiment, in step S1: the temperature of the decolorization treatment is 70-97 °C, further 80-97 °C, and / or the time of the decolorization treatment is 10-180 min, further 10-120 min.

[0036] In one embodiment, in step S1: the content of the decolorizing agent in the mixture is 0.05 wt% - 1 wt%, further 0.05 wt% - 0.5 wt%, further 0.05 wt% - 0.3 wt%. The decolorizing agent is preferably activated carbon.

[0037] In one embodiment, in step S1, the solid-liquid separation method is filtration separation or centrifugal separation.

[0038] In one embodiment, in step S1, the crystallization treatment is cooling crystallization treatment.

[0039] In one embodiment, in step S1, the end temperature of the cooling crystallization is 25-60 °C, further 25-45 °C.

[0040] In one embodiment, in step S2, the method of recycling the first crystallization mother liquor includes: using the first crystallization mother liquor to replace part or all of the water and / or alkaline substance in step S1, and mixing with the crude long-chain dibasic acid and the decolorizing agent to form a mixture.

[0041] The purification process of the present invention combines solution crystallization, decolorization, and recycling of the crystallization mother liquor of long-chain dibasic acid and / or its salt, etc., to reduce the consumption of materials such as acids, alkalis, and decolorizing agents.

[0042] The purification process of the present invention obtains products with good quality, and the quality of the further refined products is also good. It can meet the quality grade requirements of different customers.

[0043] In one embodiment, in step S3', the refining treatment method includes a refining method using a solvent and a refining method without using a solvent.

[0044] In one embodiment, in step S3', the refining treatment method includes any one or a combination of two or more of crystallization, extraction, distillation, rectification, chromatographic separation, decolorization, and washing treatment.

[0045] In one embodiment, the object of the refining treatment is the solid long-chain dibasic acid to be refined, that is, the filter cake obtained in step S1.

[0046] In one embodiment, in step S3', the refining process includes the following steps: dissolving the long-chain dibasic acid solid to be refined in a solvent and then recrystallizing and separating it.

[0047] In one embodiment, in step S3', after dissolution and before crystallization, a membrane filtration treatment can be performed. The membrane is a microfiltration membrane or an ultrafiltration membrane.

[0048] In one embodiment, in step S3', a decolorization treatment is performed after dissolution and before crystallization. The decolorization treatment is preferably activated carbon decolorization or resin decolorization.

[0049] In one embodiment, in step S3', a membrane filtration treatment and a decolorization treatment are performed after dissolution and before crystallization.

[0050] Preferably, the decolorization treatment is activated carbon decolorization or resin decolorization.

[0051] Preferably, the temperature of the decolorization treatment is 30 to 95 °C, further 50 to 95 °C.

[0052] Preferably, the time of the decolorization treatment is 10 to 180 min.

[0053] Preferably, the time of the membrane filtration treatment is 10 to 180 min.

[0054] Preferably, the temperature of the microfiltration membrane filtration is 80 to 150 °C, further 88 to 125 °C, further 88 to 98 °C. The pore size of the microfiltration membrane is 0.01 to 1 μm, further can be 0.01 to 0.2 μm, further can be 0.01 to 0.1 μm.

[0055] Preferably, the temperature of the ultrafiltration membrane filtration is 25 to 45 °C. The molecular weight cut-off of the ultrafiltration membrane is 1000 to 30000 Da, further can be 1000 to 10000 Da.

[0056] In one embodiment, in step S3', the crystallization is cooling crystallization. The end temperature of the cooling crystallization is 25 to 60 °C, further 30 to 40 °C.

[0057] In one embodiment, the solvent is an organic solvent.

[0058] In one embodiment, the organic solvent includes any one or a combination of two or more of hydrocarbons, esters, organic acids, alcohols, ethers, ketones, and halogenated alkanes.

[0059] The hydrocarbon compounds can be pentane, hexane, heptane, octane, decane, n - undecane, n - dodecane, n - tridecane, n - hexadecane, etc.; the ester compounds can be ethyl acetate, butyl acetate, methyl acetate, etc.; the organic acid compounds can be fatty acids with 1 - 5 carbon atoms; the alcohol compounds can be methanol, ethanol, propanol, butanol, isopropanol, ethylene glycol, etc.; the ether compounds can be diethyl ether, isopropyl ether, butyl ether, and the ketone compound can be acetone; the halogenated alkanes can be dichloromethane, chloroform, carbon tetrachloride, etc.

[0060] The organic solvent can be in the form of a solution with a concentration of 80 wt% or more.

[0061] In one embodiment, the mass ratio of the long - chain dibasic acid solid to be refined to the solvent is 1:(1 - 10).

[0062] In one embodiment, the refining treatment further includes the following steps: contacting the solid separated in step S3’ with water to reduce the impurity content; preferably including the steps of mixing the separated solid and water at a mass ratio of 1:(1 - 10), maintaining the temperature at 70 - 150 °C for 30 - 180 min, then cooling to 25 - 60 °C, performing solid - liquid separation to obtain a solid, and washing and drying the solid.

[0063] In one embodiment, the solvent is an alkaline aqueous solution, and the long - chain dibasic acid solid to be refined is dissolved in the solvent and then acidified for crystallization and separation.

[0064] The alkaline aqueous solution includes but is not limited to sodium hydroxide solution and ammonia water.

[0065] In order to further improve the purity of the product, the process of "dissolving, recrystallizing, and separating" can be repeated more than once. The solid obtained from the previous - stage dissolving, recrystallizing, and separating is used as the treatment object for dissolving, recrystallizing, and separating again.

[0066] The present invention also provides a long - chain dibasic acid product with a purity of ≥98%, further ≥99%, and / or a light transmittance of ≥95%, further ≥99%.

[0067] The positive and progressive effects of the present invention are as follows:

[0068] The purification process is optimized. First, the fermentation broth is decolorized and the solid - liquid separation is carried out to remove impurities. Combining with long - chain dibasic acid crystallization, decolorization, and recycling of the crystallization mother liquor, etc., the usage amounts of acids, alkalis, and decolorizing agents in the process are greatly reduced. The product obtained by the purification process has good quality, high yield, and high purity. The product has a wide range of application fields. Detailed Embodiments

[0069] The present invention will be further described below by way of examples, but the present invention is not limited to the scope of the described examples. For the experimental methods without specific conditions in the following examples, they are carried out according to conventional methods and conditions, or selected according to the product specifications. The reagents and raw materials used in the present invention are all commercially available.

[0070] Example 1

[0071] An undecanedioic acid fermentation broth was prepared by referring to the fermentation method of Example 1 in Patent Document CN 110218746 A.

[0072] (1) The fermentation broth with a concentration of 10 wt% and a pH of 5.9 was heated to 90 °C and filtered through a 50 nm ceramic membrane to obtain a filtrate. The filtrate was cooled to 40 °C for crystallization, and then filtered to separate the crude product (the content of undecanedioic acid and its salts was 98.5 wt%) and the crystallization mother liquor.

[0073] (2) The crude product, sodium hydroxide, water, and activated carbon were mixed to form a mixture. The total content of undecanedioic acid and its salts in the mixture was 10 wt%, the content of activated carbon was 0.2 wt%, and the pH value of the mixture was 5.9. The mixture was heated to 90 °C and kept at 90 °C for 1 h for decolorization, and then filtered to separate the decolorized liquid. The decolorized liquid was cooled to 40 °C for crystallization, and then filtered to separate the filter cake and the crystallization mother liquor.

[0074] (3) The crystallization mother liquor obtained in step (2) was recycled back to step (2) to replace the water and sodium hydroxide in step (2): The crystallization mother liquor was mixed with the crude product and activated carbon to form a mixture, in which the total content of undecanedioic acid and its salts in the mixture was 10 wt%, the content of activated carbon was 0.2 wt%, and the pH value of the mixture was adjusted to 5.9. The remaining processes and parameters were the same as those in step (2). The obtained crystallization mother liquor was recycled in the above manner 10 times. The filter cakes obtained from 10 operations of step (2) were collected.

[0075] The filter cakes in steps (2) and (3) were separately dispersed in water, and sulfuric acid was added to adjust the pH to 3 for acidification. After filtration and separation, the filter cakes were dried at 80 °C to obtain the product.

[0076] The yield of undecanedioic acid in this Example 1 was 99.4%.

[0077] In this Example 1, the crystallization conditions in steps (1) and (2) can make more impurities remain in the crystallization mother liquor, and correspondingly, the usage amount of the decolorizing agent activated carbon can be reduced. Moreover, the consumption of acid and alkali is less.

[0078] Example 2

[0079] An undecanedioic acid fermentation broth was prepared by referring to the fermentation method of Example 1 in Patent Document CN 110218746 A.

[0080] (1) Heat the fermentation broth with a concentration of 10 wt% and a pH of 6.4 to 90 °C, and filter it through a 50-nm ceramic membrane to obtain a filtrate. Cool the filtrate to 40 °C for crystallization, and then filter and separate to obtain the crude product (the content of undecanedioic acid and its salts is 98.2 wt%) and the crystallization mother liquor.

[0081] Step (2) is the same as that in Example 1.

[0082] Disperse the filter cake from step (2) with water, adjust the pH to 3 with sulfuric acid for acidification, filter and separate, and dry the filter cake at 80 °C to obtain the product.

[0083] The yield of undecanedioic acid in this Example 2 is 11.2%.

[0084] It is found that in this Example 2, the filter cake obtained in step (1) contains more pigment proteins. Even if the purification is continued according to step (2), the quality of the obtained product is poor and the crystallization mother liquor cannot be recycled.

[0085] Example 3

[0086] Prepare the undecanedioic acid fermentation broth by referring to the fermentation method in Example 1 of Patent Document CN 110218746 A.

[0087] (1) Heat the fermentation broth with a concentration of 10 wt% and a pH of 5.9 to 85 °C, and filter it through a 50-nm ceramic membrane to obtain a filtrate. Cool the filtrate to 40 °C for crystallization, and then filter and separate to obtain the crude product (the content of undecanedioic acid and its salts is 98.1 wt%) and the crystallization mother liquor.

[0088] Step (2) is the same as that in Example 1.

[0089] Step (3) is the same as that in Example 1.

[0090] Disperse the filter cakes from step (2) and step (3) with water respectively, adjust the pH to 3 with sulfuric acid for acidification, filter and separate, and dry the filter cakes at 80 °C to obtain the product.

[0091] The yield of undecanedioic acid in this Example 3 is 10.5%.

[0092] Example 4

[0093] Prepare the undecanedioic acid fermentation broth by referring to the fermentation method in Example 1 of Patent Document CN 110218746 A.

[0094] Step (1) is the same as that in Example 1.

[0095] (2) Mix the crude product obtained in step (1) with sodium hydroxide, water, and activated carbon to form a mixture. The total content of undecanedioic acid and its salts in the mixture is 10 wt%, the content of activated carbon is 0.2 wt%, and the pH value of the mixture is 6.2. Heat the mixture to 93 °C and keep it at 93 °C for 1 h for decolorization. Then, filter and separate to obtain a decolorized solution. Cool the decolorized solution to 40 °C for crystallization, and filter and separate to obtain a filter cake and a crystallization mother liquor.

[0096] (3) Recycle the crystallization mother liquor obtained in step (2) back to step (2) to replace the water and sodium hydroxide in step (2): Mix the crystallization mother liquor with the crude product and activated carbon to form a mixture. The total content of undecanedioic acid and its salts in the mixture is 11%, the content of activated carbon is 0.2 wt%, adjust the pH value of the mixture to 6.1, and the remaining processes and parameters are the same as those in step (2). The obtained crystallization mother liquor is recycled 10 times in the above manner. Collect the filter cakes obtained from 10 operations of step (2).

[0097] Disperse the filter cakes from step (2) and step (3) in water respectively, adjust the pH to 3 with sulfuric acid for acidification, filter and separate, and dry the filter cakes at 80 °C to obtain the product.

[0098] The yield of undecanedioic acid in Example 4 of this example is 15.2%.

[0099] Example 5

[0100] Prepare an undecanedioic acid fermentation broth according to the fermentation method in Example 1 of Patent Document CN 110218746 A.

[0101] (1) Heat the fermentation broth with a concentration of 10% and a pH of 5.9 to 88 °C, and filter it with a 50 nm ceramic membrane to obtain a filtrate. Acidify the filtrate to a pH value of 3, cool it to 40 °C for crystallization, and filter and separate to obtain a crude product (the content of undecanedioic acid and its salts is 97.8 wt%) and a crystallization mother liquor.

[0102] (2) Mix the crude product, alkali, water, and activated carbon to form a mixture. The total content of undecanedioic acid and its salts in the mixture is 10 wt%, the content of activated carbon is 0.2 wt%, and the pH of the mixture is 5.9. Heat the mixture to 90 °C and keep it at 90 °C for 1 h for decolorization. Then, filter and separate to obtain a decolorized solution. Cool the decolorized solution to 40 °C for crystallization, and filter and separate to obtain a filter cake and a crystallization mother liquor.

[0103] (3) The crystallization mother liquor obtained in step (2) is recycled back to step (2) to replace the water and sodium hydroxide in step (2): The crystallization mother liquor is mixed with the crude product and activated carbon to form a mixture, where the total content of undecanedicarboxylic acid and its salts in the mixture is 12 wt%, the content of activated carbon is 0.3 wt%, and the pH of the mixture is adjusted to 5.9. The remaining processes and parameters are the same as those in step (2). The obtained crystallization mother liquor is recycled 10 times in the above manner. Collect the filter cake obtained from 10 operations of recycling step (2).

[0104] Disperse the filter cakes from step (2) and step (3) separately with water, adjust the pH to 3 with sulfuric acid for acidification, filter and separate, and dry the filter cake at 80 °C to obtain the product.

[0105] The yield of undecanedicarboxylic acid in Example 5 is 99.0%.

[0106] Compared with Example 5, in Example 1, based on every 100 kg of undecanedicarboxylic acid, more than 50 wt% of alkali and acid are saved, and more than 50 wt% of activated carbon is saved.

[0107] Example 6

[0108] Refer to the fermentation method in Example 1 of Patent Document CN 110218746 A to prepare a decanedicarboxylic acid fermentation broth using decane as the fermentation substrate.

[0109] (1) Heat the fermentation broth with a concentration of 10 wt% and a pH of 5.8 to 92 °C, and filter with a 50 nm ceramic membrane to obtain a filtrate. Cool the filtrate to 38 °C for crystallization, and filter and separate to obtain a crude product (the content of decanedicarboxylic acid and its salts is 98.2 wt%) and a crystallization mother liquor.

[0110] (2) Mix the crude product, sodium hydroxide, water, and activated carbon to form a mixture. The total content of decanedicarboxylic acid and its salts in the mixture is 10 wt%, the content of activated carbon is 0.3 wt%, and the pH value of the mixture is 5.8. Heat the mixture to 92 °C and keep it at 92 °C for 1 h for decolorization, then filter and separate to obtain a decolorized liquid. Cool the decolorized liquid to 40 °C for crystallization, and filter and separate to obtain a filter cake and a crystallization mother liquor.

[0111] Disperse the filter cake from step (2) with water, adjust the pH to 3 with sulfuric acid for acidification, filter and separate, and dry the filter cake at 80 °C to obtain the product.

[0112] The yield of decanedicarboxylic acid in Example 6 is 99.5%.

[0113] Comparative Example 1

[0114] Refer to the fermentation method in Example 1 of Patent Document CN 110218746 A to prepare an undecanedicarboxylic acid fermentation broth.

[0115] The process and conditions of step (1) are the same as those in Example 1.

[0116] (2) Mix the crude product obtained in step (1) with sodium hydroxide, water, and activated carbon to form a mixture. The total content of undecanedioic acid and its salts in the mixture is 10 wt%, the content of activated carbon is 0.2 wt%, and the pH value of the mixture is adjusted to 6.7. Heat the mixture to 90 °C and keep it at 90 °C for 1 h for decolorization, and then filter at 90 °C to obtain a decolorized solution.

[0117] Cool the decolorized solution to 40 °C for crystallization, and then filter and separate to obtain a filter cake and a crystallization mother liquor.

[0118] Disperse the filter cake obtained in step (2) with water, adjust the pH to 3 with sulfuric acid for acidification, filter and separate, and dry the filter cake at 80 °C to obtain the product.

[0119] The yield of undecanedioic acid in this Comparative Example 1 is 3.7%.

[0120] Comparative Example 2

[0121] Prepare an undecanedioic acid fermentation broth by referring to the fermentation method in Example 4 of the Chinese patent in Patent Document CN200410018255.7, and the pH value of the fermentation broth is 8.1.

[0122] Adjust the pH value of the fermentation broth to 9.0 with alkali, heat it to 88 °C, and filter with a 50 nm ceramic membrane to obtain a filtrate. Add 0.5 wt% of activated carbon to the filtrate for decolorization at 90 °C for 35 minutes, and remove the activated carbon by plate-and-frame filtration to obtain a clear liquid.

[0123] Adjust the pH of the clear liquid to 3.3 with sulfuric acid for acidification crystallization, obtain a filter cake by plate-and-frame filtration, wash the filter cake, and dry it at 80 °C to obtain the product.

[0124] The yield of undecanedioic acid in this Comparative Example 2 is 99.3%.

[0125] Compared with Comparative Example 2, in Example 1, based on every 100 kg of undecanedioic acid, more than 40 wt% of alkali and acid are saved, and more than 80 wt% of activated carbon is saved.

[0126] Long-chain dibasic acids of different quality grades have different application scenarios. When the light transmittance of the product reaches 80% and the purity reaches more than 98%, it can meet the application in the field of rust inhibitors. In addition, according to customer requirements and different specific application fields, the product can be further refined according to the conventional refining process to further improve the product quality. For example, the product can be used as a raw material for polymerization reaction to prepare polymers after refining.

[0127] Example 6

[0128] The product of Example 1 was mixed with a 95% aqueous acetic acid solution (the mass ratio of the two was 1:3), heated to 90 °C, cooled to 25 °C, filtered, and the obtained filter cake was washed and dried to obtain the product. The purity of the product was detected to be 99.8%, and the light transmittance was 99.6%. The product meets the requirements of polymer-grade products.

[0129] The test / calculation methods involved are introduced as follows:

[0130] 1. Light transmittance: Due to the different colors of substances, at a certain wavelength, the different light transmittance and absorption properties are used to represent the color of the long-chain dibasic acid product by the light transmittance of a 25% dimethyl sulfoxide solution of the long-chain dibasic acid sample at 440 nm.

[0131] 2. Purity: Detected by gas chromatography.

[0132] Table 1

[0133] Type Light transmittance (%) Purity (%) Example 1 Filter cake of step (2) 95.2 99.4 Example 1 Filter cake of step (3) 95.1 99.3 Example 2 Filter cake of step (2) 94.5 98.9 Example 3 Filter cake of step (2) 93.4 99.2 Example 4 Filter cake of step (2) 94.1 99.1 Example 5 Filter cake of step (2) 80.1 98.7 Example 6 Filter cake of step (2) 95.3 99.5 Comparative example 1 Filter cake of step (2) 88.2 98.9 Comparative example 2 Filter cake 89.2 99.1

Claims

1. A method for purifying long-chain dibasic acid, the method comprising the following steps: S1: Decolorize a mixture containing crude long-chain dibasic acid, water, and a decolorizing agent. The decolorized solution is subjected to crystallization treatment and solid-liquid separation to obtain a filter cake and a first crystallization mother liquor; optionally, the mixture further contains an alkaline substance; S2: Optionally recycle the first crystallization mother liquor to step S1.

2. The method according to claim 1, wherein, The long-chain dibasic acid is any one or a combination of two or more of sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, heptadecanedioic acid, octadecanedioic acid, or 9-ene-octadecanedioic acid.

3. The method according to claim 1, wherein, The total content of the long-chain dibasic acid and its salts in the crude long-chain dibasic acid is 85 wt% or more, further 90 wt% or more.

4. The method according to claim 1, wherein, The method further includes step S0: subjecting the long-chain dibasic acid fermentation broth to crystallization treatment and solid-liquid separation treatment with or without membrane filtration treatment to obtain the crude long-chain dibasic acid and the second crystallization mother liquor. Preferably, the crystallization treatment methods include cooling crystallization and acidification crystallization.

5. The method according to claim 1, wherein, The method further includes step S3: dispersing the filter cake obtained in step S1 in water, adjusting the pH to 2-5, performing solid-liquid separation, and drying the obtained solid to obtain the product.

6. The method according to claim 1 or 5, wherein, The method further includes step S3': refining the filter cake obtained in step S1 or the product obtained in step S3.

7. The method according to claim 4, wherein, The method further includes step S4: recycling the second crystallization mother liquor to step S1.

8. The method according to claim 4, wherein, In step S0, based on the long-chain dibasic acid, the concentration of the fermentation broth is 3 wt% to 40 wt%, further 3 wt% to 20 wt%; and / or, In step S0, the membrane filtration treatment uses microfiltration membrane filtration and / or ultrafiltration membrane treatment; and / or, In step S0, the temperature of the membrane filtration treatment is 25-150 °C, further 80-150 °C, further 88-125 °C, further 88-98 °C; and / or, In step S0, the pH value of the long-chain dibasic acid fermentation broth before the membrane filtration treatment is 5.7-6.5, further 5.7-6.3, further 5.7-6.2, further 5.7-6.1; and / or, In step S0, the end temperature of the cooling crystallization is 25-45 °C; and / or, In step S0, the acidification crystallization is to adjust the pH value of the solution to 2-5.5, further 2-4; and / or, In step S0, the solid-liquid separation includes centrifugal separation and filtration separation.

9. The method according to claim 1, wherein, In step S1: the total concentration of the long-chain dibasic acid and its salts in the mixture is 3 wt% to 35 wt%, further 3 wt% to 20 wt%; and / or, In step S1: the pH value of the mixture is 5.7-6.5, further 5.7-6.3, further 5.7-6.1; and / or, In step S1: the temperature of the decolorization treatment is 70-97 °C, further 80-97 °C; and / or, In step S1: the time of the decolorization treatment is 10-180 min, further 10-120 min; and / or, In step S1: the content of the decolorizing agent in the mixture is 0.05 wt% to 1 wt%, further 0.05 wt% to 0.5 wt%, further 0.05 wt% to 0.3 wt%.

10. The method according to claim 1, wherein, In step S1: the crystallization treatment is a cooling crystallization treatment; Preferably, the end temperature of the cooling crystallization is 25-60 °C, further 25-45 °C.

11. The method according to claim 1, wherein, The way of recycling the first crystallization mother liquor includes replacing part or all of the water and / or alkaline substance in step S1 with the first crystallization mother liquor and mixing it with the crude long-chain dibasic acid and the decolorizing agent to form a mixture.

12. The method according to claim 11, wherein, The total concentration of the long-chain dibasic acid and its salt in the mixture is 3 wt% to 35 wt%, further 3 wt% to 20 wt%; and / or, The pH value of the mixture is 5.7 to 6.5, further 5.7 to 6.3, and further 5.7 to 6.

1.

13. The method according to claim 6, wherein The refining treatment method includes a refining method using a solvent and a refining method without using a solvent.

14. The method according to claim 6, wherein The refining treatment method includes any one or a combination of two or more of crystallization, extraction, distillation, rectification, chromatographic separation, decolorization, and washing treatment.

15. The method according to claim 6 or 13, wherein The refining treatment includes the following steps: dissolving the long-chain dibasic acid solid to be refined in a solvent and then recrystallizing and separating it.

16. The method according to claim 15, wherein Before crystallization after dissolution, a decolorization treatment is carried out. The decolorization treatment is preferably activated carbon decolorization or resin decolorization; and / or, Before crystallization after dissolution, a membrane filtration treatment is carried out. The membrane is a microfiltration membrane or an ultrafiltration membrane.

17. The method according to claim 15, wherein The solvent is an organic solvent. The organic solvent preferably includes any one or a combination of two or more of hydrocarbons, esters, organic acids, alcohols, ethers, ketones, and halogenated alkanes; and / or, The mass ratio of the long-chain dibasic acid solid to be refined to the solvent is 1:(1 to 10); and / or, The crystallization is cooling crystallization, and the end temperature of the cooling crystallization is 25 to 60 °C.

18. The method according to claim 15, wherein It also includes contacting the separated solid with water to reduce the impurity content; preferably, it includes the following steps: mixing the separated solid and water according to a mass ratio of 1:(1 to 10), keeping warm at 70 to 150 °C for 30 to 180 min, then cooling to 25 to 60 °C, separating the solid and liquid to obtain a solid, and washing and drying the solid.

19. The method according to claim 15, wherein The solvent is an alkaline aqueous solution. The long-chain dibasic acid solid to be refined is dissolved in the solvent and then acidified and crystallized and separated.

20. The method according to claim 19, wherein The process of dissolving, recrystallizing, and separating is repeated more than once.

21. A long-chain dibasic acid product with a purity of ≥98%, further ≥99%, and / or a light transmittance of ≥95%, further ≥99%.