A refining method and device for long-chain dibasic acid

Abstract

The present invention relates to a method and apparatus for refining long-chain dibasic acids, comprising: (1) mixing and dissolving crude acids with an organic solvent in a crystallizer, allowing it to stand for layering, and discharging the aqueous phase; cooling the solvent phase for crystallization to precipitate long-chain dibasic acids, and filtering to obtain a refined product, and the filtrate is the crystallization mother liquor; (2) transporting the crystallization mother liquor to an oxidizer, adjusting the pH to slightly alkaline, adding an oxidant for reaction, performing adsorption treatment after the reaction, and filtering the filtrate for recycling as the solvent in step (1). The present invention does not require rectification treatment of the crystallization mother liquor, which can improve the solvent recovery rate, reduce the loss of long-chain dibasic acids in the crystallization mother liquor, improve the overall refining yield, and is easy to be applied in large-scale production.

Description

Technical Field

[0001] The present invention belongs to the technical field of biochemistry, and particularly relates to a method and device for refining long-chain dicarboxylic acids. Background Art

[0002] Long chain dicarboxylic acids refer to aliphatic dicarboxylic acids (abbreviated as DCn) with more than 10 carbon atoms in the carbon chain, including saturated and unsaturated dicarboxylic acids. They are a class of fine chemical products with important and wide industrial uses and are important raw materials for synthesizing high-grade fragrances, high-performance nylon engineering plastics, high-grade nylon hot-melt adhesives, high-temperature dielectrics, high-grade paints and coatings, high-grade lubricating oils, cold-resistant plasticizers, resins, medicines, pesticides, etc. in the chemical industry.

[0003] The preparation of long-chain dicarboxylic acids usually uses alkanes as substrates and is obtained by microbial transformation. Long-chain dicarboxylic acids account for about 9% - 16% of the total mass of the fermentation broth. To extract long-chain dicarboxylic acids from the fermentation broth, unit operations such as demulsification, acid precipitation, and filtration are generally performed. Since the preparation of long-chain dicarboxylic acids uses the method of microbial transformation and the fermentation period is more than 120 hours, the content of solids such as cell proteins generated by cell autolysis in the fermentation broth is relatively high. The quality of the crude long-chain dicarboxylic acids obtained only through one acid precipitation separation is not high, and protein-like molecular solids will remain in the product. Therefore, in order to improve the product purity, refining is usually required after the extraction of crude acids.

[0004] At present, various technical solutions have been formed around the refining process of long-chain dicarboxylic acids, such as melt crystallization refining, extraction and recrystallization refining, etc. CN104418725A discloses a long-chain dicarboxylic acid and its preparation method, in which the long-chain dicarboxylic acid obtained after solvent treatment is heated to a molten state under reduced pressure and then cooled, where the heating temperature is 135 - 200°C and the pressure ≤ 0.07 MPa. This refining method is a melt crystallization refining of the dicarboxylic acid after solvent treatment, which is a secondary crystallization refining and requires a certain temperature and pressure, and the refining energy consumption is relatively high.

[0005] CN103965035A discloses a method for refining a long-chain dibasic acid, comprising the following steps: 1) mixing a crude long-chain dibasic acid with an alkane, heating and dissolving; 2) separating the clear phase; and 3) cooling and crystallizing or precipitating to obtain a long-chain dibasic acid product. CN102911036A discloses a method for obtaining a high-purity dicarboxylic acid, comprising: I. heating and inactivating a terminated fermentation broth; II. acidifying to precipitate the dicarboxylic acid, and filtering to obtain a dicarboxylic acid filter cake; III. mixing the dicarboxylic acid filter cake with an ether solvent to dissolve the dicarboxylic acid, and separating the organic phase and the aqueous phase, the ether solvent being ethyl ether, propyl ether, propyl ether, butyl ether, pentyl ether or hexyl ether; IV. adding an adsorbent to the organic phase obtained in step III, and filtering to remove solids; V. cooling the organic phase obtained in step IV until the dicarboxylic acid crystallizes out, filtering to obtain a dicarboxylic acid crystal filter cake, and drying the dicarboxylic acid crystal filter cake to obtain a dicarboxylic acid product with a purity greater than 98.5% by weight. The above two patented methods will produce secondary crystallization mother liquor, which mainly contains a solvent, a long-chain dibasic acid, water and impurities. If the crystallization mother liquor is used as a substitute for the solvent for recycling, the impurity components will accumulate continuously after multiple cycles, thereby affecting the product quality. Therefore, at present, rectification technology is generally used to refine the solvent from the crystallization mother liquor for reuse, which has the problem of high energy consumption. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the present invention provides a method and an apparatus for refining a long-chain dibasic acid. The present invention does not require rectification treatment of the crystallization mother liquor, can improve the solvent recovery rate, reduce the loss of the long-chain dibasic acid in the crystallization mother liquor, improve the refining yield, and is easy to be applied in large-scale production.

[0007] A method for refining a long-chain dibasic acid provided by the present invention comprises the following steps:

[0008] (1) Mixing and dissolving a crude long-chain dibasic acid with an organic solvent in a crystallizer, standing for layering, and discharging the aqueous phase; cooling and crystallizing the solvent phase to precipitate the long-chain dibasic acid, and filtering to obtain a refined product, and the filtrate is the crystallization mother liquor;

[0009] (2) Sending the crystallization mother liquor to an oxidizer, adjusting the pH to slightly alkaline, adding a basic oxidant for reaction, and performing an adsorption treatment after the reaction, and filtering to obtain a filtrate for recycling as the solvent in step (1).

[0010] In the method of the present invention, the general molecular formula of the long-chain dibasic acid in step (1) is C n H 2n-2 O4, where n is 10-18.

[0011] In the method of the present invention, the purity of the crude acid in step (1) is generally 95% - 98.5%, and the water content is 2% - 5%. The crude acid can be obtained by commercial purchase or self - preparation. The self - prepared crude acid can be specifically obtained by demulsifying, filtering, and acid - precipitation of the fermentation broth in which microorganisms ferment alkanes to produce long - chain dibasic acids. The demulsification is generally heating the fermentation broth to 70 - 100°C; the filtration can adopt membrane filtration methods such as microfiltration and ultrafiltration. The acid - precipitation is to precipitate the long - chain dibasic acid in the filtrate by adjusting the acidity, and the controlled acidity range is 3 - 5, preferably 4.5 - 5.0. The acid used for acidity adjustment can be at least one of sulfuric acid, hydrochloric acid, nitric acid, etc. After acid - precipitation, filtration and drying are carried out. Plate - and - frame filtration is used, and the filtration pressure is 0.1 - 1.0 MPa. The drying conditions are that the drying temperature is 80 - 105°C.

[0012] In the method of the present invention, the organic solvent in step (1) is at least one of straight - chain alkanes, ether solvents, etc. that can extract long - chain dibasic acids. The straight - chain alkanes are selected from at least one of n - dodecane, n - tridecane, etc.; the ether solvents are selected from at least one of butyl ether, pentyl ether, hexyl ether, etc., and ether solvents are preferred.

[0013] In the method of the present invention, the mass - to - volume ratio of the long - chain dibasic acid crude acid to the organic solvent in step (1) is 1:2 - 1:10 (g:mL), preferably 1:4 - 1:5 (g:mL).

[0014] In the method of the present invention, in step (1), the long - chain dibasic acid crude product and the organic solvent are mixed in a crystallizer and dissolved by heating. The heating temperature is 85 - 95°C, preferably 90 - 95°C. After dissolution, it is kept at a constant temperature and left to stand for 20 - 40 min, preferably 20 - 30 min.

[0015] In the method of the present invention, in step (1), under the heat - preservation state, that is, at 85 - 95°C, the lower - layer aqueous phase is discharged, and the upper - layer solvent phase remaining in the crystallizer is cooled and crystallized to precipitate the long - chain dibasic acid, generally down to room temperature. Further, a programmed - cooling method is preferably adopted, specifically: after naturally cooling to 80 - 85°C, it is cooled to room temperature through the circulation of cooling water. After the long - chain dibasic acid is precipitated, the long - chain dibasic acid filter cake and the crystallization mother liquor are collected after filtration.

[0016] In the method of the present invention, in step (1), the collected crystallization mother liquor is transported to an oxidizer for pH adjustment and oxidation treatment.

[0017] In the method of the present invention, the slightly alkaline pH range in step (2) is 7.5 - 8.5. The base used for pH adjustment is a solid inorganic base, such as at least one of calcium hydroxide, sodium hydroxide, potassium hydroxide, etc.

[0018] In the method of the present invention, the oxidant described in step (2) is an alkaline oxidant, such as at least one of sodium hypochlorite, calcium hypochlorite, etc. The addition amount is 0.1% - 2% by mass concentration, preferably 0.5% - 1%.

[0019] In the method of the present invention, after adding the alkaline oxidant in step (2) and reacting, it is left standing at room temperature for 20 - 40 min, preferably 20 - 30 min.

[0020] In the method of the present invention, the adsorbent used in the adsorption treatment in step (2) is selected from at least one of activated carbon, diatomite, activated clay, etc. The addition amount of the adsorbent is 0.1% - 2% by mass concentration, preferably 0.5% - 1%.

[0021] In the method of the present invention, after adsorption in step (2), filtration can be carried out, such as plate - frame filtration, etc., and the filtration pressure is 0.1 - 1.0 MPa.

[0022] In the method of the present invention, the filtrate obtained by filtration in step (2) is recycled as the organic solvent in step (1). The clear liquid contains organic solvent, a small amount of water, dissolved long - chain dibasic acid, etc. The dissolved long - chain dibasic acid can enter the refined product during the subsequent refining of crude acid.

[0023] The present invention also provides a device for the above - mentioned long - chain dibasic acid refining method, which mainly includes a crystallizer, filter F1, oxidizer, filter F2, etc. The crystallizer is used for mixing and dissolving crude acid and organic solvent in the crystallizer, standing for layering, and discharging the aqueous phase; the solvent phase is cooled and crystallized to precipitate long - chain dibasic acid, which enters filter F1. The filter cake is the refined product of dibasic acid, and the filtrate is the crystallization mother liquor; the crystallization mother liquor is transported to the oxidizer, the pH is adjusted to slightly alkaline with alkali, an alkaline oxidant is added for reaction, adsorption treatment is carried out after the reaction, and finally the filtrate is obtained through filter F2 and recycled as the organic solvent.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The purity of the long - chain dibasic acid refined by the solvent crystallization method is relatively high. However, in the existing solvent crystallization refining process for long - chain dibasic acid, there are technical problems such as the direct reuse of the solvent affecting the product quality, high energy consumption and large losses in the rectification recovery process, resulting in a relatively high refining cost. In view of the characteristics of the solvent crystallization method for long - chain dibasic acid, the inventors of this application combined with the slightly alkaline condition in the refining process, used a specific organic solvent, and carried out slightly alkaline adjustment, oxidation treatment and adsorption treatment on the crystallization mother liquor, realizing the efficient purification of the organic solvent in the crystallization mother liquor to meet the requirements of long - term recycling. After multiple cycles of use, on the basis of ensuring a relatively high refining yield of long - chain dibasic acid, the quality of the obtained refined product is relatively high.

[0026] (2) Since a small amount of dibasic acid is still dissolved in the organic solvent at room temperature, the dibasic acid in the crystallization mother liquor of the present invention can be re-refined as the crystallization mother liquor is purified and recycled. After being recycled multiple times, the total yield of dibasic acid extraction is increased.

[0027] (3) In the existing solvent method for refining long-chain dibasic acids, distillation is usually used to recover the organic solvent, which has high energy consumption and the dibasic acid dissolved in the solvent will be lost. The filtration, oxidation, adsorption, etc. of the present invention are all carried out at room temperature, which can realize the recycling of the solvent and will not affect the product quality, thus forming a low-energy consumption refining process.

[0028] (4) In the solvent refining process of the present invention, an alkaline oxidant is used for treatment, which effectively removes the dissolved impurity components in cooperation with the organic solvent, and the nitrogen content of the obtained refined product is further reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a schematic flow diagram of a refining device of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0030] The method and effect of the present invention will be further described below with reference to embodiments. The embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0031] Unless otherwise specified, the experimental methods in the following examples are all conventional methods in the art. Unless otherwise specified, the experimental materials used in the following examples can all be obtained from biochemical reagent stores.

[0032] The collection of the present invention is detected by the dry weight method, and the detection method of nitrogen content is determined according to NB / SH / T 0704-2010 "Determination Method of Nitrogen Content in Petroleum and Petroleum Products - Boat Injection Chemiluminescence Method". The purity of dibasic acid is determined according to GB5009.168-2016 "National Food Safety Standard - Determination of Fatty Acids in Foods".

[0033] Total yield of refined product of long-chain dibasic acid The calculation formula is:

[0034]

[0035] Among them, M1 is the mass of crude long-chain dibasic acid, g; M2 is the mass of refined product of long-chain dibasic acid, g; a is the moisture content of crude long-chain dibasic acid, %.

[0036] Example 1

[0037] Take 500 L of dodecanedioic acid fermentation broth, with the concentration of dodecanedioic acid being 140 g / L. Adjust the pH of the fermentation broth to 9, and raise the temperature to 90 °C for constant temperature for 20 min. Cool to room temperature, filter through a 25-nm membrane with the inlet pressure of the membrane being 0.15 MPa. Let the clarified fermentation broth stand, and collect 380 L of the lower aqueous phase clarified liquid layer in total. Add sulfuric acid to adjust the pH to 5, and let it stand until the dodecanedioic acid in the system completely precipitates. Filter through a plate-and-frame filter with the filtration pressure being 0.1 MPa, and then dry at 90 °C to obtain a crude acid product with a moisture content of 2%. After detection, the monoacid purity of the crude acid is 97.0%. Use the refining method and device of the present invention for treatment, and the specific steps are as follows:

[0038] (1) Take 5.10 kg of crude acid and mix it with 20.4 L of butyl ether in a crystallizer, heat to 92 °C to completely dissolve the crude acid. After constant temperature and standing for 20 min, drain the lower aqueous phase under the heat preservation state. Naturally cool the upper solvent phase to 82 °C, and then use a jacketed water bath to assist in cooling to room temperature. After the long-chain dibasic acid crystallizes out, filter through a plate-and-frame filter to obtain a refined filter cake of long-chain dibasic acid and crystallization mother liquor.

[0039] (2) Transport the crystallization mother liquor collected in step (1) to an oxidizer, and adjust the pH of the mixed system to 7.5 with calcium hydroxide. Add calcium hypochlorite at a mass concentration of 1%, fully mix, and then let it stand at room temperature for 20 min. Add activated carbon at a mass concentration of 1%, fully mix, and then filter through a plate-and-frame filter with the filtration pressure of 0.8 MPa, and collect the filtered clarified liquid.

[0040] Use the filtered clarified liquid as the organic solvent for the next batch of step (1), without adding fresh organic solvent. Carry out a total of 10 batches of cycles according to the same process and conditions of steps (1) to (2), and process about 51 kg of crude acid in total. Collect the refined filter cakes of long-chain dibasic acid obtained in step (2) of each batch, and dry at 90 °C to obtain 48.75 kg of refined long-chain dibasic acid product with a monoacid purity of 99.85%, a nitrogen content of 2.5 µg / g, and a total yield of the refined product of 97.54%.

[0041] Example 2

[0042] Take 500 L of dodecanedioic acid fermentation broth, with the concentration of dodecanedioic acid being 140 g / L. Adjust the pH of the fermentation broth to 8, and raise the temperature to 85 °C for constant temperature for 20 min. Cool to room temperature, filter through a 25-nm membrane with the inlet pressure of the membrane being 0.12 MPa. Let the clarified fermentation broth stand, and collect 375 L of the lower aqueous phase clarified liquid layer in total. Add sulfuric acid to adjust the pH to 4.5, and let it stand until the dodecanedioic acid in the system completely precipitates. Filter through a plate-and-frame filter with the filtration pressure being 0.1 MPa, and then dry at 80 °C to obtain a crude acid product with a moisture content of 5%. After detection, the monoacid purity of the crude acid is 97.1%. Use the refining method and device of the present invention for treatment, and the specific steps are as follows:

[0043] (1) Mix 5.08 kg of crude acid with 25.42 L of butyl ether in a crystallizer, heat to 90 °C until all the crude acid is dissolved, keep the temperature constant and let it stand for 20 min, then drain the lower aqueous phase under the heat preservation state. Naturally cool the upper solvent phase to 80 °C, and then use a jacketed water bath to assist in cooling to room temperature. After the long-chain dibasic acid crystallizes out, filter it through a plate-and-frame filter to obtain a refined filter cake of long-chain dibasic acid and crystallization mother liquor.

[0044] (2) Transfer the crystallization mother liquor collected in step (1) to an oxidizer, adjust the pH of the mixed system to 7.5 with calcium hydroxide, then add calcium hypochlorite at a mass concentration of 0.5%, mix well, and let it stand for 20 min. Add diatomaceous earth at a mass concentration of 0.5%, mix well, and then filter it through a plate-and-frame filter with a filtration pressure of 0.1 MPa, and collect the filtered clear liquid.

[0045] The filtered clear liquid is used as the organic solvent for the next batch of step (1) without adding fresh organic solvent. Carry out 10 batches of cycles according to the same process and conditions of steps (1) to (2). A total of about 50.8 kg of crude acid is processed. Collect the refined filter cake of long-chain dibasic acid obtained in step (2) of each batch, dry it at 90 °C to obtain 47.81 kg of refined long-chain dibasic acid product, with a monoacid purity of 99.70%, a nitrogen content of 3.4 μg / g, and a total yield of the refined product of 99.07%.

[0046] Example 3

[0047] Take 500 L of dodecanedioic acid fermentation broth with a dodecanedioic acid concentration of 140 g / L. Adjust the pH of the fermentation broth to 10 and heat it to 90 °C and keep it constant for 20 min. Cool it to room temperature and filter it through a 20 nm membrane with an inlet pressure of 0.15 MPa. Let the clarified fermentation broth stand and collect 378 L of the lower aqueous phase clarified liquid layer. Add sulfuric acid to adjust the pH to 5 and let it stand until all the dodecanedioic acid in the system precipitates out. Filter it through a plate-and-frame filter with a filtration pressure of 1.0 MPa, and then dry it at 105 °C to obtain a crude acid product with a moisture content of 2%. After testing, the monoacid purity of the crude acid is 97.08%. Use the refining method and device of the present invention for treatment, and the specific steps are as follows:

[0048] (1) Mix 4.902 kg of crude acid with 24.5 L of butyl ether in a crystallizer, heat to 95 °C until all the crude acid is dissolved, keep the temperature constant and let it stand for 30 min, then drain the lower aqueous phase under the heat preservation state. Naturally cool the upper solvent phase to 85 °C, and then use a jacketed water bath to assist in cooling to room temperature. After the long-chain dibasic acid crystallizes out, filter it through a plate-and-frame filter to obtain a refined filter cake of long-chain dibasic acid and crystallization mother liquor.

[0049] (2) Transfer the crystallization mother liquor collected in step (1) to an oxidizer, and adjust the pH of the mixed system to 8.5 with calcium hydroxide. Then, add calcium hypochlorite with a mass concentration of 1%, mix well, and let it stand for 30 min. Add activated clay with a mass concentration of 1%, mix well, and then filter through a plate-and-frame filter with a filtration pressure of 1.0 MPa. Collect the filtered clear liquid.

[0050] The filtered clear liquid is used as the organic solvent for the next batch of step (1) without adding fresh organic solvent. The same process and conditions as in steps (1) to (2) are carried out for 10 batches of cycles, and about 49.02 kg of crude acid is processed in total. Collect the refined filter cake of long-chain dibasic acid obtained in step (2) of each batch, dry it at 90 °C, and obtain 46.83 kg of refined long-chain dibasic acid product. The purity of the monoacid is 99.80%, the nitrogen content is 1.9 µg / g, and the total yield of the refined long-chain dibasic acid product is 97.48%.

[0051] Example 4

[0052] Take 500 L of hexadecanedioic acid fermentation broth, in which the concentration of hexadecanedioic acid is 100 g / L. Adjust the pH of the fermentation broth to 9, and heat it to 90 °C and keep it constant for 20 min. Cool it to room temperature, filter through a 25 nm membrane with an inlet pressure of 0.15 MPa at the membrane, and let the obtained fermentation clear liquid stand. Collect the lower aqueous phase clear liquid layer, a total of 385 L, add sulfuric acid to adjust the pH to 5, and let it stand until the hexadecanedioic acid in the system is completely precipitated. Filter through a plate-and-frame filter with a filtration pressure of 0.1 MPa, and then dry it at 90 °C to obtain a crude acid product with a moisture content of 2%. After testing, the purity of the monoacid of the crude acid is 97.2%. Use the refining method and device of the present invention for treatment, and the specific steps are as follows:

[0053] (1) Take 3.6 kg of crude acid and mix it with 14.4 L of butyl ether in a crystallizer, heat it to 92 °C to completely dissolve the crude acid, keep it at a constant temperature and let it stand for 20 min, and then drain the lower aqueous phase under the heat preservation state. Naturally cool the upper solvent phase to 82 °C, and then use a jacket water bath to assist in cooling it to room temperature. After the long-chain dibasic acid crystallizes out, filter through a plate-and-frame filter to obtain a refined filter cake of long-chain dibasic acid and crystallization mother liquor.

[0054] (2) Transfer the crystallization mother liquor collected in step (1) to an oxidizer, and adjust the pH of the mixed system to 7.5 with calcium hydroxide. Add calcium hypochlorite with a mass concentration of 1%, mix well, and let it stand at room temperature for 20 min. Add activated carbon with a mass concentration of 1%, mix well, and then filter through a plate-and-frame filter with a filtration pressure of 0.8 MPa. Collect the filtered clear liquid.

[0055] The filtered clear liquid was used as the organic solvent for the next batch of step (1), and no fresh organic solvent was added. A total of 10 batches of cycles were carried out according to the same process and conditions of steps (1) to (2), and about 36.1 kg of crude acid was processed. The test results showed that 34.74 kg of refined long-chain dibasic acid product was obtained, the purity of monoacid was 99.81%, the nitrogen content was 2.3 μg / g, and the total yield of refined long-chain dibasic acid product was 99.20%.

[0056] Example 5

[0057] Same as Example 1, except that: the crude long-chain dibasic acid was commercially purchased, and the purity of the crude acid was detected to be 97% and the water content was 0.6%. The water content of this crude product was adjusted to 2.05%.

[0058] The filtered clear liquid was used as the organic solvent for the next batch of step (1), and no fresh organic solvent was added. A total of 10 batches of cycles were carried out according to the same process and conditions of steps (1) to (2), and about 50 kg of crude acid was processed. The test results showed that 48.26 kg of refined long-chain dibasic acid product was obtained, the purity of monoacid was 99.83%, the nitrogen content was 2.6 μg / g, and the total yield of refined long-chain dibasic acid product was 98.54%.

[0059] Example 6

[0060] Same as Example 1, except that: in step (1), program cooling was not adopted, and the temperature was directly reduced to room temperature by circulating water.

[0061] The test results showed that 48.52 kg of refined long-chain dibasic acid product was obtained, the purity of monoacid was 99.55%, the nitrogen content was 7.6 μg / g, and the total yield of refined long-chain dibasic acid product was 97.08%.

[0062] Example 7

[0063] Same as Example 1, except that: in step (2), sodium hypochlorite was used as the oxidant.

[0064] The test results showed that 48.46 kg of refined long-chain dibasic acid product was obtained, the purity of monoacid was 99.81%, the nitrogen content was 2.2 μg / g, and the total yield of refined long-chain dibasic acid product was 96.96%.

[0065] Example 8

[0066] Same as Example 1, except that: in step (1), n-pentyl ether was used instead of butyl ether as the organic solvent.

[0067] The test results showed that 48.09 kg of refined long-chain dibasic acid product was obtained, the purity of monoacid was 99.83%, the nitrogen content was 2.9 μg / g, and the total yield of refined long-chain dibasic acid product was 96.22%.

[0068] Example 9

[0069] Same as Example 1, except that: in step (1), n-dodecane is used as the organic solvent instead of butyl ether.

[0070] The test results show that 47.89 kg of refined long-chain dibasic acid product is obtained, the purity of monoacid is 99.80%, the nitrogen content is 2.5 μg / g, and the total yield of refined long-chain dibasic acid product is 95.82%.

[0071] Example 10

[0072] Same as Example 1, except that: in step (1), n-tridecane is used as the organic solvent instead of butyl ether.

[0073] The test results show that 47.59 kg of refined long-chain dibasic acid product is obtained, the purity of monoacid is 99.79%, the nitrogen content is 3.6 μg / g, and the total yield of refined long-chain dibasic acid product is 95.22%.

[0074] Example 11

[0075] Same as Example 1, except that: in step (2), sodium hydroxide is used as the solid inorganic base.

[0076] The test results show that 48.77 kg of refined long-chain dibasic acid product is obtained, the purity of monoacid is 99.72%, the nitrogen content is 3.4 μg / g, and the total yield of refined long-chain dibasic acid product is 97.58%.

[0077] Comparative Example 1

[0078] Same as Example 1, except that: in step (2), the oxidation treatment is omitted.

[0079] The test results show that 48.61 kg of refined long-chain dibasic acid product is obtained, the purity of monoacid is 99.15%, the nitrogen content is 18.2 μg / g, and the total yield of refined long-chain dibasic acid product is 97.26%.

[0080] Comparative Example 2

[0081] Same as Example 1, except that: in step (2), the slightly alkaline condition is not adjusted and the pH is natural.

[0082] The test results show that 48.81 kg of refined long-chain dibasic acid product is obtained, the purity of monoacid is 99.76%, the nitrogen content is 27.4 μg / g, and the total yield of refined long-chain dibasic acid product is 97.66%.

[0083] Comparative Example 3

[0084] Same as Example 1, except that: in step (2), the treatment with adsorbent is omitted.

[0085] The test results showed that 48.88 kg of refined long-chain dibasic acid product was obtained, with the purity of monoacid being 99.56%, the nitrogen content being 13.6 μg / g, and the total yield of the refined long-chain dibasic acid product being 97.80%.

[0086] Comparative Example 4

[0087] Same as Example 1, except that in step (2), rectification treatment was used instead of the treatment method of the present invention. Since the recovery rate of butyl ether by rectification for each batch was 80.1%, a total of 36.5 L of butyl ether was replenished during the refining process of 10 batches.

[0088] The test results showed that 40.57 kg of refined long-chain dibasic acid product was obtained, with the purity of monoacid being 99.82%, the nitrogen content being 1.6 μg / g, and the total yield of the refined long-chain dibasic acid product being 81.17%.

[0089] Comparative Example 5

[0090] Same as Example 1, except that in step (1), ethanol was used as the organic solvent instead of butyl ether.

[0091] The test results showed that 39.65 kg of refined long-chain dibasic acid product was obtained, with the purity of monoacid being 99.16%, the nitrogen content being 6.5 μg / g, and the total yield of the refined long-chain dibasic acid product being 79.33%.

[0092] Comparative Example 6

[0093] Same as Example 1, except that in step (2), potassium permanganate was used as the oxidant.

[0094] The test results showed that 48.24 kg of refined long-chain dibasic acid product was obtained, with the purity of monoacid being 99.81%, the nitrogen content being 17.6 μg / g, and the total yield of the refined long-chain dibasic acid product being 96.52%.

Claims

1. A method for refining long-chain dibasic acid, characterized in that It includes the following steps: (1) Mix and dissolve the crude long-chain dibasic acid with an organic solvent in a crystallizer, let it stand for layering, and drain the aqueous phase; cool the solvent phase for crystallization to precipitate the long-chain dibasic acid, and filter to obtain the refined product. The filtrate is the crystallization mother liquor; the organic solvent is at least one of a straight-chain alkane and an ether solvent for extracting the long-chain dibasic acid; the crude long-chain dibasic acid and the organic solvent are mixed in the crystallizer and dissolved by heating, and the heating temperature is 85-95°C; the molecular general formula of the long-chain dibasic acid is C n H 2n-2 O4, where n is 10-18; the purity of the crude dibasic acid is 95%-98.5%, and the water content is 2%-5%; (2) Transport the crystallization mother liquor to an oxidizer, adjust the pH to slightly alkaline, add an alkaline oxidant for reaction, and perform adsorption treatment after the reaction. Filter the filtrate and recycle it as the solvent in step (1); the pH range of the slightly alkaline is 7.5 - 8.5, and the base used to adjust the pH is a solid inorganic base; the alkaline oxidant is at least one of sodium hypochlorite and calcium hypochlorite.

2. The method according to claim 1, wherein: The crude acid is obtained by commercial purchase or self - preparation. The self - prepared crude acid is obtained by demulsifying, filtering, and acid precipitation of the fermentation broth in which microorganisms ferment alkanes to produce long - chain dibasic acids.

3. The method according to claim 2, characterized in that: When self - preparing the crude acid, the demulsification is to heat the fermentation broth to 70 - 100 °C; the filtration adopts microfiltration and ultrafiltration membrane filtration methods; the acid precipitation is to adjust the acidity to precipitate the long - chain dibasic acid in the filtrate, and the pH range of the controlled acidity is 3 - 5; after acid precipitation, filtration and drying are carried out. Plate - and - frame filtration is used, and the filtration pressure is 0.1 - 1.0 MPa; the drying temperature is 80 - 105 °C.

4. The method according to claim 3, wherein: The pH range of the controlled acidity is 4.5 - 5.

0.

5. The method according to claim 1, characterized in that: The straight - chain alkane is at least one of n - dodecane and n - tridecane.

6. The method according to claim 1, wherein: The ether solvent is at least one of butyl ether, pentyl ether, and hexyl ether.

7. The method according to claim 1, 5 or 6, characterized in that: In step (1), the mass - to - volume ratio of the long - chain dibasic acid crude acid to the organic solvent is 1:2 - 1:10, g / mL.

8. The method according to claim 7, characterized in that: The mass - to - volume ratio of the long - chain dibasic acid crude acid to the organic solvent is 1:4 - 1:5, g / mL.

9. The method according to claim 1, wherein: In step (1), the long - chain dibasic acid crude acid and the organic solvent are mixed in a crystallizer and dissolved by heating, and the heating temperature is 90 - 95 °C.

10. The method according to claim 1 or 9, characterized in that: In step (1), the lower aqueous phase is discharged under the heat - preservation state, and the remaining upper solvent phase in the crystallizer is cooled and crystallized to precipitate the long - chain dibasic acid.

11. The method according to claim 1, wherein: In step (1), the solvent phase is cooled and crystallized by a programmed cooling method, specifically: after naturally cooling to 80 - 85 °C, it is cooled to room temperature through the circulation of cooling water.

12. The method according to claim 1, characterized in that: The inorganic base is at least one of calcium oxide, sodium hydroxide, and potassium hydroxide.

13. The method according to claim 1, wherein: In step (2), the addition amount of the alkaline oxidant is 0.1% - 2% in terms of mass concentration.

14. The method according to claim 13, characterized in that: The addition amount of the alkaline oxidant is 0.5% - 1% in terms of mass concentration.

15. The method according to claim 1, characterized in that: After adding the alkaline oxidant in step (2) and reacting, it is left standing at room temperature for 20 - 40 min.

16. The method according to claim 15, wherein: After adding the alkaline oxidant and reacting, it is left standing at room temperature for 20 - 30 min.

17. The method according to claim 1, characterized in that: In step (2), the adsorbent used for the adsorption treatment is selected from at least one of activated carbon, diatomite, and activated clay; the addition amount of the adsorbent is 0.1% - 2% in terms of mass concentration.

18. The method according to claim 17, characterized in that: The addition amount of the adsorbent is 0.5% - 1% in terms of mass concentration.

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