Extraction and purification process of long-chain dicarboxylic acid and product

Abstract

The invention provides an extraction and purification process of long-chain dicarboxylic acid and a product, and the process comprises the following steps: (1) heating and dissolving a mixture containing long-chain dicarboxylic acid in a mixed solvent, then standing, and separating out an organic phase at the upper layer; (2) cooling the organic phase, standing, and separating out an organic phase which is located at the upper part of the system and accounts for 80-99 wt% of the total mass of the system as a first extraction phase; and (3) cooling the first extraction phase, separating the separated solid, washing and drying to obtain the long-chain dicarboxylic acid product. According to the method, a mixed solvent extraction method is adopted, the capability of removing impurities such as pigment, heteroacid and ash in the long-chain binary acid mixture is high, and the operation is simple and easy to implement. The high-purity long-chain dibasic acid product can be obtained through secondary cooling and phase splitting operation of the upper-layer organic phase, and can be used for a series of products such as bio-based materials such as polyamide, textile materials and the like. In addition, crystallization mother liquor can be returned to the system after distillation treatment to be recycled.

Description

Technical Field

[0001] The invention relates to an extraction and purification process of a long-chain dibasic acid and a product. Background Art

[0002] Long chain dicarboxy acids refer to aliphatic dicarboxylic acids (DCn for short) with more than 10 carbon atoms in their carbon chain, including saturated and unsaturated dicarboxylic acids. They are a type of fine chemical products with important and extensive industrial uses, and are widely used in polyamide, hot melt adhesives, fragrances, rust inhibitors, lubricants, cold-resistant plasticizers, powder coatings and other fields.

[0003] The production of long-chain dibasic acids by microbial fermentation is an application of microbial fermentation technology in the petrochemical industry that emerged in the 1970s. It generally uses petroleum by-product wax oil as raw material and has the advantages of wide raw material sources, simple production process, and mild production conditions. At present, the extraction and purification processes of long-chain dibasic acids can be summarized as follows: (1) Organic solvent crystallization method. Usually, the crude long-chain dibasic acid and organic solvent are mixed, stirred, and allowed to stand. The separated organic phase is cooled and crystallized to obtain the target dibasic acid. (2) Aqueous phase crystallization method. The crude dibasic acid is first dissolved in an alkaline solution, then acidified, and then cooled to precipitate the target dibasic acid. (3) Esterification separation crystallization method. The crude dibasic acid and low-carbon alcohol are esterified under the action of a catalyst to obtain esters, and the target dibasic acid esters are separated by distillation. Then, the target dibasic acid is separated by hydrolysis and the mother liquor is cooled and crystallized. (4) Chromatographic separation crystallization method. That is, after the crude dibasic acid is prepared into a solution, it is separated by a treatment column with selective adsorption function such as activated carbon fiber, and the target dibasic acid is obtained by crystallization of the mother liquor.

[0004] In the prior art, most of the impurities such as pigments are removed by multiple adsorption of activated carbon. However, the efficient recovery of activated carbon has always been a major problem and the cost is extremely high. CN 109456172 A mentions a method for purifying dodecanedicarboxylic acid by aqueous phase method. In this patent, the crude dibasic acid product after acidification, crystallization and drying is hot stirred in hot water at 85-95°C, and then the filtrate is cooled to separate the precipitated C12 dibasic acid; then it is transferred to an autoclave, deionized water is added, stirred at a temperature of 120°C-180°C, and then the temperature is lowered and crystallized in stages to obtain the C12 dibasic acid product. Although the process is simple, the operation is environmentally friendly, and the removal effect of N-containing impurities is significant, the removal ability of pigment impurities is limited.

[0005] In addition, in the process of extracting and refining long-chain dibasic acids from long-chain dibasic acid fermentation broth, by-products containing long-chain dibasic acids are produced. These by-products generally cannot be used efficiently, and some are even dumped as waste. However, the by-products still contain long-chain dibasic acids and also contain a large amount of impurities that are hoped to be removed during the extraction and refining process. How to extract and purify these by-products again to obtain long-chain dibasic acid products is also a technical challenge.

[0006] In summary, the development of a simple and efficient process for the extraction and purification of dibasic acids is of far-reaching significance. Summary of the invention

[0007] In order to overcome the above problems, the purpose of the present invention is to provide a long-chain dibasic acid extraction and purification process, which removes impurities such as pigments, ash, and monobasic acid generated in the long-chain dibasic acid by mixed solvent extraction. After mixed solvent extraction, the upper organic phase with a high content of dibasic acid is separated by cooling, and further impurities are removed by direct cooling to obtain a high-purity dibasic acid product. The yield of the product obtained by this method is high.

[0008] The extraction and purification process of the long-chain dibasic acid of the present invention comprises:

[0009] (1) heating a mixture containing a long-chain dibasic acid and dissolving it in a mixed solvent, then allowing the mixture to stand and separating an upper organic phase;

[0010] (2) cooling the organic phase separated in step (1), separating the organic phase located at the top of the system and accounting for 80 wt% to 99 wt% of the total mass of the system after standing, as the first extraction phase;

[0011] (3) Cooling the first extraction phase, separating the precipitated solid, washing, and drying to obtain a long-chain dibasic acid product.

[0012] In some embodiments, the melting point of the mixture containing the long-chain dibasic acid is below 130°C.

[0013] In some embodiments, the mixture containing long-chain dibasic acids includes crude dibasic acids having 10 to 18 carbon atoms and containing double bonds in the molecular chain or by-products containing long-chain dibasic acids.

[0014] In some embodiments, the composition of the by-product containing long-chain dibasic acids includes two or more dibasic acids with carbon atoms of 10 to 18, and further, the dibasic acid with carbon atoms of 10 to 18 is selected from azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecane dibasic acid, hexadecanedioic acid, heptadecanedioic acid, and octadecane dibasic acid.

[0015] It is generally known to those skilled in the art that long-chain dibasic acid fermentation broth is obtained by using alkanes, fatty acids and their derivatives as substrates and using a microbial fermentation method. The microorganism can oxidize the terminal methyl groups of alkanes, fatty acids and derivatives of fatty acids to carboxyl groups to generate long-chain dibasic acids. The microorganism is preferably Candida.

[0016] In the process of extracting the fermentation broth to obtain a crude product and refining the crude product, by-products containing long-chain dibasic acids are produced, such as the residue after recovering the solvent from the recrystallization mother liquor of the crude long-chain dibasic acid, the long-chain dibasic acid-rich precipitate recovered from the sewage treatment workshop, and other slurries containing long-chain dibasic acids.

[0017] The purity of the mixture containing long-chain dibasic acids (i.e., the content of long-chain dibasic acids) is 20 wt% or more, further 40 wt% or more, further 65% or more, further 80% or more, further 90% or more (on a dry weight basis).

[0018] In some embodiments, the purity of the crude dibasic acid having 10 to 20 carbon atoms and containing double bonds in the molecular chain is generally above 90 wt % (based on dry weight).

[0019] In some embodiments, the purity of the by-product is generally 40 wt% to 87 wt%, further 50 wt% to 87 wt%, and may be less than 40 wt% (on dry weight).

[0020] In some embodiments, the mixture containing long-chain dibasic acids contains impurities, and the impurities include monobasic acids and ash.

[0021] In some embodiments, the content of the monoacid is less than 40 wt %, further less than 30 wt %, further less than 20 wt %, and greater than 0.

[0022] In some embodiments, the ash content is 50 to 1000 ppm, further 50 to 500 ppm.

[0023] In some embodiments, when the processing raw material is the above-mentioned by-product, since it often contains pigment impurities, the color of the raw material may be light yellow, yellow, yellowish brown, brownish black, etc. due to different pigment contents.

[0024] In the present invention, it is unexpectedly found that dibasic acids such as olefinic acids or mixed dibasic acids have a low melting point, or have a low melting point due to the presence of more impurities. It is difficult to crystallize and separate when using a single polar solvent such as acids or alcohols, and it is impossible to use them in industry. When the mixed solvent in the present invention is used, the above problems can be well solved and a satisfactory purified product can be obtained.

[0025] In some embodiments, the mass ratio of the mixture of long-chain dibasic acids to the mixed solvent is 1:(1-20), further 1:(1-12), further 1:(1-8).

[0026] In some embodiments, the mixed solvent includes solvent A and solvent B.

[0027] In some embodiments, solvent A includes hydrocarbon compounds, and further includes: aliphatic hydrocarbon compounds, aromatic hydrocarbon compounds, or a combination of two or more thereof.

[0028] In some embodiments, the B solvent includes one or a combination of two or more of an ester compound, an organic acid compound, an alcohol compound, and a halogenated alkane.

[0029] Furthermore, in the mixed solvent, solvent A accounts for 80wt% to 99wt% of the mixed solvent, further 85wt% to 99wt%, further 90wt% to 99wt%.

[0030] In some embodiments, the hydrocarbon compound includes straight-chain alkanes, branched alkanes, and cycloalkanes having 5 to 18 carbon atoms.

[0031] Furthermore, the hydrocarbon compound includes any one or a combination of two or more of pentane, hexane, cyclohexane, heptane, octane, decane, n-undecane, n-dodecane, n-tridecane, n-hexadecane, benzene, gasoline, and kerosene.

[0032] In some embodiments, the ester compound includes any one of ethyl acetate, butyl acetate, and methyl acetate, or a combination of two or more thereof.

[0033] In some embodiments, the organic acid compound includes any one or a combination of two or more aliphatic monobasic acids having 1 to 5 carbon atoms.

[0034] In some embodiments, the alcohol compound includes any one of methanol, ethanol, n-propanol, butanol, isopropanol, and ethylene glycol, or a combination of two or more thereof.

[0035] In some embodiments, the halogenated alkane includes any one of dichloromethane, chloroform, and carbon tetrachloride, or a combination of two or more thereof.

[0036] In some embodiments, in order to fully dissolve, the heating temperature in step (1) is above 60° C., and further between 60° C. and 130° C. Generally, it is limited to not higher than the boiling point of the low-boiling-point solvent in the mixed solvent.

[0037] In some embodiments, in order to fully dissolve, stirring can be performed in step (1) at any one or more stages before, during, or after heating, and the stirring time can be 1 to 6 hours.

[0038] In some embodiments, the standing time in step (1) is not particularly limited, and the standing time may be, for example, more than 0.5 h, and further 0.5 to 5 h.

[0039] The present invention has found that when only the solvent in the mixed solvent is used as a single extractant, the amount of solvent required to dissolve the same mass of the mixture containing long-chain dibasic acids is larger, about 2 to 8 times that of the mixed solvent.

[0040] In some embodiments, in step (2), the temperature of the organic phase separated in step (1) is reduced to below 60° C., further to 20-60° C., further to 33-55° C. The impurities and the target dibasic acid are more fully separated by cooling.

[0041] The present invention has found that in step (2), when the temperature is lowered, the solvent and solute (impurities, long-chain dibasic acid) in the solution change due to free energy, which causes the solvent and solute phases to be redistributed, and the impurities are further separated or the target compound is further enriched until a steady state is reached. In step (2), the first extraction phase is obtained by phase separation again, which is beneficial to the purification of the dibasic acid.

[0042] The present invention has found that when the extraction phase is cooled directly, that is, when the operation of cooling and then separating the phases again is not performed in step (2), the purity of the product is low and the color is generally light yellow or light brown.

[0043] In some embodiments, after cooling and separating the upper organic phase in step (2), the long-chain dibasic acid product can be extracted from the residue. For example, the residue can be extracted and then cooled and precipitated to obtain a high-purity dibasic acid product. The dibasic acid content in the lower organic phase is generally lower than the dibasic acid content in the upper organic phase.

[0044] In some embodiments, the cooling process in step (3) is a step-by-step cooling process, and the cooling rate from 5 to 15°C before the crystallization point (of the long-chain dibasic acid) to the crystallization point is smaller than the cooling rate in other stages.

[0045] In some embodiments, during the cooling process of step (3), the temperature is kept at the crystallization point temperature.

[0046] In some embodiments, during the cooling process of step (3), the sample is kept warm at the terminal temperature of the cooling.

[0047] Preferably, during the cooling process of step (3), the temperature is slowly cooled from 5 to 15°C before the crystallization point to the crystallization point, kept warm at the crystallization point, kept warm at the terminal temperature of the cooling, and the remaining stages are rapid cooling.

[0048] In a preferred embodiment, during the cooling process of step (3), the crystallization point temperature is 35°C to 50°C.

[0049] In a preferred embodiment, during the cooling process of step (3), the holding time at the crystallization point temperature is 0.5 to 4 hours, further 1 to 3 hours.

[0050] In a preferred embodiment, during the cooling process of step (3), the slow cooling rate is 0.5 to 7°C / h, further 0.5 to 6°C / h.

[0051] In some embodiments, during the cooling process of step (3), the rapid cooling rate is 10 to 25°C / h, further 12 to 17°C / h.

[0052] In a preferred embodiment, during the cooling process of step (3), the terminal temperature of the cooling is 5 to 35°C, and further 10 to 32°C.

[0053] In a preferred embodiment, during the cooling process of step (3), the holding time at the terminal temperature of the cooling is 0.5 to 6 hours, and further 0.5 to 3 hours.

[0054] In some embodiments, in step (3), the precipitated solid can be separated by conventional methods in the art, including but not limited to centrifugation and filtration.

[0055] In some embodiments, in step (3), the separated solid is washed, and the type of the detergent can be consistent with the A solvent or the B solvent in the mixed solvent.

[0056] In some embodiments, in step (3), the amount of detergent used is 0.3 to 1.5 times the mass of the solid, and further 0.5 to 1.5 times.

[0057] It is generally known to those skilled in the art that in step (3), the washed solid usually needs to be heated to fully evaporate the solvent to obtain a dry product.

[0058] In some embodiments, in step (3), the mother liquor obtained after separation of the solid can be returned for use as a solvent.

[0059] In some embodiments, impurities in the mother liquor are separated by distillation before being returned for use.

[0060] In some embodiments, if the solvent ratio of the mother liquor is changed, the solvent ratio can be adjusted, for example, solvent A and / or solvent B can be newly added and then returned to the system for reuse as solvent.

[0061] The product obtained in step (3) mainly contains long-chain dibasic acid, which has stable quality and high purity, and can meet the needs of some markets. At the same time, since the extraction and purification process is simple and easy to operate, it is conducive to large-scale industrial production.

[0062] In some embodiments, the extraction and purification process further includes step (4): further refining the long-chain dibasic acid product obtained in step (3) to improve the purity of the product. The product is a high-purity product that meets the requirements of different customers or downstream application scenarios.

[0063] In some embodiments, the purification method can be a conventional method in the art, including a solvent method and a non-solvent method.

[0064] In some embodiments, the purification method includes: any one or a combination of two or more of decolorization, organic solvent dissolution-recrystallization, melt crystallization, extraction, distillation, and chromatographic separation.

[0065] The decolorization method is not particularly limited, for example, one of the following methods:

[0066] a. Melting and decolorizing the long-chain dibasic acid product obtained in step (3): for example, heating and melting the long-chain dibasic acid product obtained in step (3), contacting the product with activated carbon and decolorizing the product;

[0067] b. The long-chain dibasic acid product obtained in step (3) is redissolved with alkali and water, decolorized with a decolorizing agent, filtered to remove the decolorizing agent, and the filtrate is acidified and crystallized to separate the solid to obtain a long-chain dibasic acid product with improved purity;

[0068] c. The long-chain dibasic acid product obtained in step (3) is dissolved in an organic solvent, decolorized by a decolorizing agent, filtered to remove the decolorizing agent, and then cooled to separate the solid to obtain a long-chain dibasic acid product with improved purity.

[0069] In some embodiments, step (4) comprises: mixing the long-chain dibasic acid product obtained in step (3) with an organic solvent, heating it to dissolve it, adding activated carbon for heat preservation and decolorization, and then filtering, cooling the filtrate for crystallization, solid-liquid separation, and drying to obtain the product.

[0070] The organic solvent includes alcohols, acids, ketones or esters. The acid is, for example, acetic acid solution.

[0071] The present invention also provides a long-chain dibasic acid product, wherein the residual solvent content in the product is less than or equal to 700 ppm, and further less than or equal to 500 ppm.

[0072] The beneficial effects of the present invention include:

[0073] (1) The mixed solvent extraction method has a strong ability to remove impurities such as pigments, monobasic acids, and ash from the long-chain dibasic acid mixture. The operation process is simpler and easier than the traditional activated carbon depigmentation method. In addition, compared with the single solvent extraction method, it reduces the amount of solvent and also saves costs.

[0074] (2) Through the cooling and phase separation operation of the upper organic phase, different purity long-chain dibasic acid crystal liquids are obtained at low energy consumption. The separated upper organic phase can be directly cooled and crystallized to obtain high-purity long-chain dibasic acid products; and the remaining lower material can be further extracted by, for example, solvents, and further crystallized to obtain high-purity long-chain dibasic acid products. It can be used in a series of products such as bio-based materials such as polyamides and textile materials.

[0075] (3) The crystallization mother liquor can be returned to the system for reuse after distillation. DETAILED DESCRIPTION

[0076] The present invention is described in detail below through examples to make the features and advantages of the present invention clearer, but the present invention is not limited to the examples listed herein.

[0077] In the present invention, the content (purity) of the long-chain dibasic acid product is determined by gas chromatography, specifically using a standard dibasic acid sample as a control, with reference to GB5413.27-2010 Determination of fatty acids in infant foods and dairy products.

[0078] Ash content test method: refer to GB / T 7531-2008 Determination of ignition residue of organic chemical products. The content of components in the following experimental raw materials refers to the dry weight of the experimental raw materials.

[0079] Preparatory Example 1

[0080] Referring to the method of Example 30 of CN1570124A, the crude long-chain dibasic acid produced by the biological fermentation method is refined, and the solvent mother liquor remaining after filtering the crystals during the refining process is passed through a distillation tower to recover the solvent. The residue in the bottom of the distillation tower is a by-product containing long-chain dibasic acid (aliphatic dicarboxylic acid with a carbon number of 10 to 18, and the carboxyl groups are located at both ends of the molecular chain).

[0081] Example 1

[0082] The byproducts in the extraction and refining process of hexadecanedioic acid were used as experimental raw materials. The byproducts contained 58wt% long-chain dibasic acid, 8wt% monobasic acid, 81ppm ash, brown-black color, and a melting point of 113°C.

[0083] (1) Add the by-product and the mixed solvent (3 wt% butanol and 97 wt% decane) in a mass ratio of 1:4, stir and mix at 95°C for 3 hours, then stand and keep warm for 1 hour, separate the phases, and take the upper organic phase.

[0084] (2) The organic phase separated in step (1) is cooled to 45° C. while stirring, and then the organic phase located at the top of the system, accounting for 93 wt % of the total mass of the system, is separated to obtain the first extraction phase.

[0085] (3) The first extract phase is subjected to segmented cooling crystallization. The crystallization point temperature of the first extract phase is 43°C. The segmented cooling crystallization process is as follows: cool from 95°C to 10°C before the crystallization point temperature, cool at 15°C / h, then cool to the crystallization point temperature at 5°C / h, keep at the crystallization point temperature for 1h, then cool to the final temperature of 30°C at 15°C / h, keep for 1h, filter, wash the filter cake with decane, the amount of decane is 0.8 times that of the filter cake, heat the washed filter cake to evaporate the solvent, and obtain the product.

[0086] The cooling crystallization yield of the first extraction phase was calculated and the product purity was analyzed. The results are shown in Table 1.

[0087] The crystallization mother liquor of step (3) can be recycled, and the crystallization mother liquor obtained after the crystallization of the first extraction phase can be used for purification of the next batch of by-products after adjusting the solvent ratio.

[0088] Example 2

[0089] The experimental raw materials used in this Example 2 are the same as those in Example 1.

[0090] (1) Add the by-product and the mixed solvent (3 wt% acetic acid and 97 wt% kerosene) in a mass ratio of 1:5, mix at 95° C. for 3 h, let stand for 1 h, separate the phases, and take the upper organic phase.

[0091] (2) The organic phase separated in step (1) is cooled to 45° C. while stirring, and then the organic phase located at the top of the system, which accounts for 94% of the total mass of the system, is separated to obtain a first extraction phase.

[0092] The residue after separation of the organic phase was evaporated at 200°C to dry the solvent to obtain a dry solid, which was extracted with kerosene in a mass ratio of kerosene to the dry solid of 7:1. The mixture was stirred at 95°C for 3 hours and then allowed to stand for 1 hour for phase separation. The upper organic phase obtained was the second extraction phase.

[0093] (3) The first extraction phase and the second extraction phase are subjected to segmented cooling and crystallization. The crystallization point temperature of the first extraction phase is 43°C, and the crystallization point temperature of the second extraction phase is 47°C. The segmented cooling and crystallization process of the first extraction phase and the second extraction phase is as follows: the temperature is reduced from 95°C to 10°C before the crystallization point temperature, and the temperature is reduced at 15°C / h, and then the temperature is reduced to the crystallization point temperature at 5°C / h, and the temperature is kept at the crystallization point temperature for 1h, and then the temperature is reduced at 15°C / h to the terminal temperature of 30°C, and the temperature is kept for 1h, and then filtered, and the filter cake is washed with kerosene, and the amount of kerosene is 0.8 times that of the filter cake. The filter cake after washing (the filter cake obtained from the first extraction phase is crystalline solid 1, and the filter cake obtained from the second extraction phase is crystalline solid 2) is evaporated to dryness of solvent.

[0094] The crystallization yield of the first extraction phase, the total acid content, and the purity of the 16-carbon dibasic acid were calculated and recorded in Table 1. The crystallization yield of the second extraction phase was 53%, and the purity of the 16-carbon dibasic acid was 88.9%.

[0095] The crystallization mother liquor in step (3) can be recycled. The crystallization mother liquor obtained by crystallization of the first extraction phase can be used for purification of the next batch of by-products after adjusting the solvent ratio; the crystallization mother liquor of the second extraction phase can be used for extraction of the next batch of dry solid substances.

[0096] Example 3

[0097] The experimental raw materials used in this Example 3 are the same as those in Example 1.

[0098] (1) Add the byproduct and mixed solvent (3 wt% butyl acetate and 97 wt% n-tridecane) in a mass ratio of 1:4, stir and mix at 95°C for 3 h, then stand and keep warm for 1 h, separate the phases, and take the upper organic phase.

[0099] (2) The organic phase separated in step (1) was cooled to 45° C. while stirring, and then the organic phase located at the top of the system, accounting for 94 wt% of the total mass of the system, was separated to obtain a first extraction phase.

[0100] (3) The first extract phase is subjected to segmented cooling crystallization. The crystallization point temperature of the first extract phase is 42°C. The segmented cooling crystallization process is as follows: from 95°C to 10°C before the crystallization point temperature, cooling at 15°C / h, then cooling to the crystallization point temperature at 5°C / h, keeping at the crystallization point temperature for 1h, then cooling to the terminal temperature of 30°C at 15°C / h, keeping for 1h, filtering, and washing the filter cake with n-tridecane, the amount of n-tridecane used is 0.8 times that of the filter cake, and heating the washed filter cake to evaporate the solvent to obtain the product.

[0101] The crystallization yield of the first extraction phase was calculated and the product purity was analyzed. The results are shown in Table 1.

[0102] The crystallization mother liquor in step (3) can be recycled, and the crystallization mother liquor obtained by crystallization of the first extraction phase can be used for the purification of the next batch of by-products after adjusting the solvent ratio.

[0103] Example 4

[0104] The experimental raw materials used in this Example 4 are the same as those in Example 1.

[0105] (1) Add the byproduct and the mixed solvent (10 wt% butyric acid and 90 wt% n-dodecane) in a mass ratio of 1:5, stir and mix at 90° C. for 2 h, then stand and keep warm for 1 h, separate the phases, and take the upper organic phase.

[0106] (2) The organic phase separated in step (1) is cooled to 45° C. while stirring, and then the organic phase located at the top of the system and accounting for 95% of the total mass of the system is separated to obtain a first extraction phase.

[0107] (3) The first extract phase is subjected to segmented cooling crystallization. The crystallization point temperature of the first extract phase is 40°C. The segmented cooling crystallization process is as follows: from 95°C to 10°C before the crystallization point temperature, cooling at 15°C / h, then cooling to the crystallization point temperature at 5°C / h, keeping at the crystallization point temperature for 1h, then cooling to the final temperature of 30°C at 15°C / h, keeping for 1h, filtering, and washing the filter cake with n-dodecane, the amount of n-dodecane used is 1 times the amount of the filter cake, and heating the washed filter cake to evaporate the solvent to obtain the product.

[0108] The crystallization yield of the first extraction phase was calculated and the product purity was analyzed. The results are shown in Table 1.

[0109] The crystallization mother liquor in step (3) can be recycled, and the crystallization mother liquor obtained by crystallization of the first extraction phase can be used for purification of the next batch of by-products after adjusting the solvent ratio.

[0110] Example 5

[0111] The experimental raw materials used in this Example 5 are the same as those in Example 1.

[0112] (1) Add the byproduct and mixed solvent (1 wt% acetic acid and 99 wt% kerosene) in a mass ratio of 1:5, stir and mix at 95°C for 3 h, then let stand and keep warm for 1 h, separate the phases, and take the upper organic phase.

[0113] (2) The organic phase separated in step (1) is cooled to 45° C. while stirring, and then the organic phase located at the top of the system, accounting for 92 wt% of the total mass of the system, is separated to obtain the first extraction phase.

[0114] (3) The first extract phase is subjected to segmented cooling crystallization. The crystallization point temperature of the first extract phase is 46°C. The segmented cooling crystallization process is as follows: cool from 95°C to 10°C before the crystallization point temperature, cool at 15°C / h, then cool to the crystallization point temperature at 5°C / h, keep at the crystallization point temperature for 1h, then cool to the final temperature of 30°C at 15°C / h, keep for 1h, filter, and wash the filter cake with kerosene, the amount of kerosene used is 0.8 times that of the filter cake, heat the washed filter cake to evaporate the solvent, and obtain the product.

[0115] The crystallization yield of the first extraction phase was calculated and the product purity was analyzed. The results are shown in Table 1.

[0116] The crystallization mother liquor in step (3) can be recycled and reused, and the crystallization mother liquor obtained by crystallization of the first extraction phase can be used for purification of the next batch of by-products after adjusting the solvent ratio.

[0117] Example 6

[0118] The experimental raw materials used in this Example 6 are the same as those in Example 1.

[0119] (1) Add the byproduct and the mixed solvent (3 wt% acetic acid and 97 wt% kerosene) in a mass ratio of 1:5, stir and mix at 95°C for 3 h, then stand and keep warm for 1 h, separate the phases, and take the upper organic phase.

[0120] (2) The organic phase separated in step (1) was cooled to 43° C. while stirring, and then the organic phase located at the top of the system, accounting for 94 wt % of the total mass of the system, was separated to obtain the first extraction phase.

[0121] (3) The first extract phase is subjected to segmented cooling crystallization. The crystallization point temperature of the first extract phase is 46°C. The segmented cooling crystallization process is as follows: cool from 95°C to 10°C before the crystallization point temperature, cool at 20°C / h, then cool to the crystallization point temperature at 2°C / h, keep at the crystallization point temperature for 1h, then cool at 20°C / h to the final temperature of 30°C, keep for 1h, filter, and wash the filter cake with kerosene, the amount of kerosene is 0.8 times that of the filter cake, heat the washed filter cake to evaporate the solvent, and obtain the product.

[0122] The crystallization yield of the first extraction phase was calculated and the product purity was analyzed. The results are shown in Table 1.

[0123] The crystallization mother liquor in step (3) can be recycled, and the crystallization mother liquor obtained by crystallization of the first extraction phase can be used for purification of the next batch of by-products after adjusting the solvent ratio.

[0124] Example 7

[0125] The crude product of 9-enoctadicarboxylic acid prepared by biological method was used as the experimental raw material, wherein the content of 9-enoctadicarboxylic acid was 62%, the content of monoacid was 5%, the ash content was 90ppm, the color was brown-black, and the melting point was 121℃.

[0126] (1) The crude product and the mixed solvent (3 wt% acetic acid and 97 wt% kerosene) were added in a mass ratio of 1:6, wherein the mixed solvent was composed of 3% acetic acid and 97% kerosene, stirred and mixed at 95°C for 3 hours, then allowed to stand and heat for 1 hour, phase separated, and the upper organic phase was taken.

[0127] (2) The organic phase separated in step (1) is cooled to 50° C. while stirring, and then the organic phase located at the top of the system and accounting for 90 wt % of the total mass of the system is separated to obtain a first extraction phase.

[0128] (3) The first extraction phase is subjected to segmented cooling crystallization. The crystallization point temperature of the first extraction phase is 45°C. The segmented cooling crystallization process is as follows: from 95°C to 10°C before the crystallization point temperature, cooling at 15°C / h, then cooling to the crystallization point temperature at 5°C / h, keeping at the crystallization point temperature for 1h, then cooling to the terminal temperature of 30°C at 15°C / h, keeping for 1h, filtering, and washing the filter cake with raw kerosene, the amount of kerosene used is 0.8 times that of the filter cake, and heating the washed filter cake to evaporate the solvent to obtain the product. Calculate the crystallization yield of the first extraction phase and analyze the product purity. The results are shown in Table 1.

[0129] The crystallization mother liquor in step (3) can be recycled, and the crystallization mother liquor obtained by crystallization of the first extraction phase can be used for purification of the next batch of crude products after adjusting the solvent ratio.

[0130] Example 8

[0131] The byproduct of the extraction and refining process of dodecanedioic acid was used as the experimental raw material. The byproduct contained 60wt% of long-chain dibasic acid, 13wt% of monobasic acid, 100ppm of ash, brown-black color, and a melting point of 106°C.

[0132] (1) Add the byproduct and the mixed solvent (3wt% acetic acid + 97wt% kerosene) in a mass ratio of 1:10, stir and mix at 95°C for 3h, then stand and keep warm for 1h, separate the phases, and take the upper organic phase.

[0133] (2) The organic phase separated in step (1) is cooled to 50° C. while stirring, and then the organic phase located at the top of the system, which accounts for 97 wt % of the total mass of the system, is separated to obtain the first extraction phase.

[0134] (3) The first extract phase is subjected to segmented cooling crystallization. The crystallization point temperature of the first extract phase is 45°C. The segmented cooling crystallization process is as follows: cool from 95°C to 10°C before the crystallization point temperature, cool at 15°C / h, then cool to the crystallization point temperature at 5°C / h, keep at the crystallization point temperature for 1h, then cool to the final temperature of 30°C at 15°C / h, keep for 1h, filter, and wash the filter cake with kerosene, the amount of kerosene used is 0.8 times that of the filter cake, heat the washed filter cake to evaporate the solvent, and obtain the product.

[0135] The crystallization yield of the first extraction phase was calculated and the product purity was analyzed. The results are shown in Table 1.

[0136] The crystallization mother liquor in step (3) can be recycled, and the crystallization mother liquor obtained by crystallization of the first extraction phase can be used for purification of the next batch of by-products after adjusting the solvent ratio.

[0137] Example 9

[0138] The product obtained by crystallization of the first extraction phase in Example 2 was added to 95wt% acetic acid solution to dissolve, with a solid-liquid ratio (g / g) of 1:3, and then 3wt% activated carbon was added as a decolorizing agent, heated at 90°C for 1h for decolorization, filtered, and the filtrate entered a crystallization tank for cooling and crystallization, with the cooling end temperature being 35°C, and finally filtered to separate the crystalline solid, dried, and obtained a refined product. The crystallization yield was calculated, and the product purity was analyzed, and the results are shown in Table 2.

[0139] Comparative Example 1

[0140] The experimental raw materials used in this comparative example 1 are the same as those in Example 7.

[0141] (1) Add the crude product and kerosene in a mass ratio of 1:10, mix at 90°C for 2 hours, let stand for 1 hour, and separate the extract phase.

[0142] (2) The extract phase is subjected to staged cooling and crystallization. The crystallization point temperature is 50°C. The temperature is reduced from 95°C to 10°C before the crystallization point, and then reduced at 15°C / h, and then reduced to the crystallization point at 5°C / h. The temperature is kept at the crystallization point for 1 hour, and then reduced at 15°C / h to the final temperature of 20°C, and then kept at this temperature for 1 hour. Filter and wash the filter cake with kerosene, the amount of which is 0.8 times the mass of the filter cake.

[0143] (3) The washed filter cake is heated and the solvent is evaporated to obtain the product.

[0144] The crystallization yield was calculated and the product purity was analyzed. The results are shown in Table 3.

[0145] Comparative Example 2

[0146] The experimental raw materials used in this comparative example 2 are the same as those in Example 7.

[0147] (1) Add the crude product and ethanol in a mass ratio of 1:10, mix at 90°C for 2 hours, let stand for 1 hour, and separate the extract phase.

[0148] (2) The extract phase was subjected to staged cooling and crystallization. The crystallization point temperature was 50°C. The temperature was lowered from 95°C to 10°C before the crystallization point, and then lowered at 15°C / h, and then lowered to the crystallization point at 5°C / h. The temperature was kept at the crystallization point for 1h, and then lowered at 15°C / h to the final temperature of 20°C, and kept at this temperature for 1h. It was found that it was difficult to crystallize, and a paste was obtained, which was difficult to filter and separate.

[0149] Comparative Example 3

[0150] The experimental raw materials used in this comparative example 3 are the same as those in Example 7.

[0151] (1) The crude product and a mixed solvent (3 wt% acetic acid and 97 wt% kerosene) were added in a mass ratio of 1:5, mixed at 95° C. for 3 h, allowed to stand for 1 h, and the extract phase was separated.

[0152] (2) The extract phase is subjected to segmented cooling and crystallization. The crystallization point temperature is 40°C. The segmented cooling and crystallization process is as follows: from 95°C to 10°C before the crystallization point temperature, cooling at 15°C / h, then cooling to the crystallization point temperature at 5°C / h, keeping at the crystallization point temperature for 1h, then cooling at 15°C / h to the final temperature of 30°C, keeping at this temperature for 1h, filtering, and washing the filter cake with kerosene, the amount of kerosene used is 0.8 times that of the filter cake, and evaporating the solvent from the washed filter cake to obtain the product.

[0153] The crystallization yield of the extraction phase was calculated and the purity of the product was analyzed. The results are shown in Table 3.

[0154] Comparative Example 4

[0155] As in Example 1, the byproduct containing hexadecane dibasic acid was used as the experimental raw material.

[0156] (1) Add the by-product and the mixed solvent (35 wt% acetic acid and 65 wt% kerosene) in a mass ratio of 1:2, mix at 95° C. for 3 h, let stand for 1 h, separate the phases, and take the upper organic phase.

[0157] (2) The organic phase separated in step (1) is cooled to 45° C. while stirring, and then the organic phase located at the top of the system, accounting for 98 wt% of the total mass of the system, is separated to obtain a first extraction phase.

[0158] (3) The first extraction phase is subjected to segmented cooling crystallization. The crystallization point temperature of the first extraction phase is 40°C. The segmented cooling crystallization process is as follows: from 95°C to 10°C before the crystallization point temperature, cooling at 15°C / h, then cooling to the crystallization point temperature at 5°C / h, keeping at the crystallization point temperature for 1h, then cooling to the terminal temperature of 30°C at 15°C / h, keeping for 1h, filtering, and washing the filter cake with kerosene, the amount of kerosene used is 0.8 times that of the filter cake, and heating the washed filter cake to evaporate the solvent to obtain the product. The crystallization yield of the first extraction phase is calculated, and the purity of the product is analyzed. The results are shown in Table 3.

[0159] Table 1

[0160]

[0161] Table 2

[0162] Long chain dibasic acid content color Example 2 91.7％ White Example 9 99.3％ White

[0163] Table 3

[0164]

[0165]

[0166] By comparing Comparative Example 1 with the embodiment, it can be found that when pure solvent kerosene is used as the extractant, the yield of the crystallized product is low and the solvent consumption is large. By comparing Comparative Example 2 with the embodiment, it can be found that when pure solvent ethanol is used as the extractant, it is difficult to crystallize and the obtained paste is difficult to separate. By comparing Comparative Example 3 with the embodiment, it can be found that if the cooling and phase separation operation step is omitted in step (2) and the extraction phase is directly crystallized, the crystallization yield is relatively high, but the product purity is low. By comparing Comparative Example 4 with the embodiment, it can be found that when the proportion of solvent A in the mixed solvent is less than 80%, the purity of the obtained crystallized product is significantly reduced.

Claims

1. A process for extracting and purifying a long-chain dibasic acid, characterized in that: The steps include: (1) heating a mixture containing a long-chain dibasic acid and dissolving it in a mixed solvent, then allowing the mixture to stand and separating an upper organic phase; (2) cooling the organic phase separated in step (1), separating the organic phase located at the top of the system and accounting for 80 wt% to 99 wt% of the total mass of the system after standing, as the first extraction phase; (3) Cooling the first extraction phase, separating the precipitated solid, washing, and drying to obtain a long-chain dibasic acid product.

2. The extraction and purification process of long-chain dibasic acid according to claim 1, characterized in that: The purity of the mixture containing the long-chain dibasic acid is 20 wt% or more, further 40 wt% or more; and / or, The melting point of the mixture containing the long-chain dibasic acid is 130° C. or less.

3. The extraction and purification process of a long-chain dibasic acid according to claim 1 or 2, characterized in that: The mixture containing long-chain dibasic acids includes crude dibasic acids having 10 to 20 carbon atoms and containing double bonds in the molecular chain, and byproducts containing long-chain dibasic acids.

4. The extraction and purification process of the long-chain dibasic acid according to claim 3, characterized in that: The composition of the by-product containing long-chain dibasic acids includes two or more dibasic acids with carbon atoms of 10 to 18. Further, the dibasic acid with carbon atoms of 10 to 18 is selected from azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedicarboxylic acid, hexadecanedioic acid, heptadecanedioic acid, and octadecanedicarboxylic acid.

5. The extraction and purification process of a long-chain dibasic acid according to claim 1 or 2, characterized in that: The mixture containing the long-chain dibasic acid contains impurities, and the impurities include monobasic acid and ash.

6. The extraction and purification process of the long-chain dibasic acid according to claim 1, characterized in that: In step (1), the mass ratio of the mixture of long-chain dibasic acids to the mixed solvent is 1:(1-20), further 1:(1-12), further 1:(1-8); and / or, The mixed solvent includes solvent A and solvent B. Preferably, solvent A includes hydrocarbon compounds, and further includes: aliphatic hydrocarbon compounds, aromatic hydrocarbon compounds, one or a combination of more than two thereof. Preferably, solvent B includes ester compounds, organic acid compounds, alcohol compounds, halogenated alkanes, one or a combination of more than two thereof.

7. The extraction and purification process of a long-chain dibasic acid according to claim 1 or 6, characterized in that: The A solvent in the mixed solvent accounts for 80 wt% to 99.5 wt%, further 85 wt% to 99 wt%, further 90 wt% to 99 wt% of the mixed solvent; and / or, The hydrocarbon compound includes straight-chain alkanes, branched alkanes, and cycloalkanes with a carbon number of 5 to 18, and further includes any one or a combination of two or more of pentane, hexane, cyclohexane, heptane, octane, decane, n-undecane, n-dodecane, n-tridecane, n-hexadecane, benzene, gasoline, and kerosene; and / or, The ester compound includes any one of ethyl acetate, butyl acetate, and methyl acetate, or a combination of two or more thereof; and / or, The organic acid compound includes any one or a combination of two or more aliphatic monobasic acids having 1 to 5 carbon atoms; and / or, The alcohol compound includes any one or a combination of two or more of methanol, ethanol, n-propanol, butanol, isopropanol, and ethylene glycol; and / or, The halogenated alkane includes any one of dichloromethane, chloroform and carbon tetrachloride or a combination of two or more thereof.

8. The extraction and purification process of long-chain dibasic acid according to claim 1, characterized in that: In step (1), the heating temperature is 60°C or higher, and further 60°C to 130°C; and / or, In step (1), stirring may be performed at any one or more stages before, during, or after heating, and the stirring time may be, for example, 1 to 6 hours; and / or, In step (1), the standing time is 0.5 h or longer, and further 0.5 to 5 h.

9. The process for extracting and purifying a long-chain dibasic acid according to claim 1, characterized in that: In step (2), the temperature of the organic phase separated in step (1) is lowered to below 60°C, further to 20 to 60°C, and further to 33 to 55°C.

10. The extraction and purification process of long-chain dibasic acid according to claim 1, characterized in that: In step (3), the cooling process is a step-by-step cooling process, and the cooling rate from 5 to 15°C before the crystallization point to the crystallization point is smaller than the cooling rate in other stages.

11. The extraction and purification process of a long-chain dibasic acid according to claim 1 or 10, characterized in that: During the cooling process of step (3), the temperature is slowly cooled from 5 to 15°C before the crystallization point to the crystallization point, kept warm at the crystallization point, kept warm at the terminal temperature of the cooling, and the remaining stages are rapid cooling.

12. The extraction and purification process of a long-chain dibasic acid according to claim 1, 10 or 11, characterized in that: During the cooling process of step (3), the temperature is kept at the crystallization point temperature. Preferably, the heat preservation time is 0.5 to 4 hours, further 1 to 3 hours; and / or, Preferably, the crystallization point temperature is 35°C to 50°C.

13. The extraction and purification process of a long-chain dibasic acid according to claim 1, 10 or 11, characterized in that: During the cooling process of step (3), the temperature is kept at the end point of the cooling process. Preferably, the holding time is preferably 0.5 to 6 hours, and further preferably 0.5 to 3 hours; and / or, The final temperature of cooling is 5-35℃, and the further temperature is 10-32℃.

14. The extraction and purification process of long-chain dibasic acid according to claim 11, characterized in that: During the cooling process of step (3), the slow cooling rate is 0.5 to 7°C / h, further 0.5 to 6°C / h; and / or, The rapid cooling rate is 10-25°C / h, further 12-17°C / h.

15. The extraction and purification process of long-chain dibasic acid according to claim 1, characterized in that: In step (3), methods for separating the precipitated solid include, but are not limited to, centrifugation and filtration.

16. The extraction and purification process of long-chain dibasic acid according to claim 1, characterized in that: After cooling and separating the upper organic phase in step (2), extracting the long-chain dibasic acid product from the residue; and / or, In step (3), the mother liquor obtained after separation of the solid is returned for use as a solvent. Preferably, impurities in the mother liquor are separated by distillation before being returned for use.

17. The process for extracting and purifying a long-chain dibasic acid according to any one of claims 1, 6, 8 to 11, 15 or 16, characterized in that: The method comprises step (4): further refining the long-chain dibasic acid product obtained in step (3) to improve the purity of the product.

18. The extraction and purification process of long-chain dibasic acid according to claim 17, characterized in that: Refining methods include solvent method and non-solvent method.

19. The extraction and purification process of long-chain dibasic acid according to claim 17, characterized in that: The purification method of step (4) includes: any one or a combination of two or more of decolorization, organic solvent dissolution-recrystallization, melt crystallization, extraction, distillation, and chromatographic separation.

20. The extraction and purification process of a long-chain dibasic acid according to claim 17 or 19, characterized in that: Step (4) comprises: The long-chain dibasic acid product obtained in step (3) is mixed with an organic solvent, heated to dissolve it, and activated carbon is added for heat preservation and decolorization, and then filtered. The filtrate is subjected to cooling crystallization, solid-liquid separation, and drying to obtain the product. Preferably, the organic solvent includes alcohols, acids, ketones or esters, and the acid is, for example, acetic acid solution.

21. A long-chain dibasic acid product, characterized in that: The residual solvent content in the product is less than or equal to 700 ppm, and further less than or equal to 500 ppm.

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