Method for refining long-chain dicarboxylic acid and method for continuously refining long-chain dicarboxylic acid

Abstract

The invention provides a method for refining long-chain dicarboxylic acid, which comprises the following steps: dissolving a long-chain dicarboxylic acid crude product at 88 DEG C or above by using a mixed solvent of ethers and low-carbon alcohols, fully dissolving, keeping the temperature of a system at 92 DEG C or below, adding water at 92 DEG C or below to precipitate the long-chain dicarboxylic acid, and separating a water phase from the precipitated long-chain dicarboxylic acid and the mixed solvent to obtain the refined long-chain dicarboxylic acid. And filtering and drying to obtain refined long-chain dicarboxylic acid. According to the invention, multi-batch continuous production can be realized, the low-carbon alcohol and the long-chain dicarboxylic acid crude product are added into the mixed solvent phase from which the water phase is separated again to be dissolved, then water is added to separate out the long-chain dicarboxylic acid, and continuous refining can be carried out for 5-10 batches. The solubility of the dibasic acid in the mixed solvent is not lower than 66%, so that the one-way treatment capacity is greatly improved; the binary acid is spontaneously nucleated, crystallized and separated out in the process of taking out the binary acid, and refining equipment cannot be influenced; the binary acid is obtained from a water phase, so that the solvent loss in the transportation and drying processes is reduced, the solvent cannot be adsorbed on the surface and inside of the product, and the environmental harm is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of organic matter refining, and specifically relates to a refining method and a continuous refining method for long-chain dicarboxylic acid. Background Art

[0002] The preparation of long-chain dicarboxylic acids usually uses alkanes as substrates and is obtained through microbial transformation. The components of long-chain dicarboxylic acid fermentation broth are complex, and in addition to dicarboxylic acids, they mainly include bacteria, proteins, macromolecular pigments, inorganic salts and other intermediate metabolites. The extraction of long-chain dicarboxylic acids from fermentation broth generally undergoes unit operations such as demulsification, acid precipitation, and filtration. The process flow is relatively complicated, resulting in a large share of the production cost due to its separation cost.

[0003] At present, there are two main separation and purification processes for long-chain dibasic acids: solvent method and water phase method. Among them, there is no relevant industrialization report on the water phase purification technology, and it is difficult to obtain high-quality long-chain dibasic acid products that meet the requirements of polymerization-grade processes.

[0004] The process that can stably obtain long-chain dibasic acids of polymerization grade quality is mainly solvent refining technology. The main domestic long-chain dibasic acid production enterprises that adopt this process are represented by Kaisai, which uses the acetic acid dissolution refining process. However, due to the strong corrosiveness of acetic acid, the equipment investment and energy consumption of the solvent recycling treatment section of this process are high, the process flow is complex, and the environmental damage is relatively large. Sinopec Dalian Institute uses the difference in solubility of dibasic acids and impurities in water and organic solvents to develop a unique solvent extraction coupled phase transfer impurity removal and refining process that can stably obtain polymerization-grade products. However, the production capacity of solvent refining technology is limited by the solubility of dibasic acids in solvents. Its solubility does not exceed 25% (w / v), and the single-pass processing volume is low. At the same time, it is difficult to achieve continuous production due to the rigid requirements of impurity removal. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a method for refining long-chain dicarboxylic acids with a large single-pass processing volume. The reverse dissolution method is adopted to greatly increase the single-pass processing volume of dicarboxylic acids, and the product has high precision and meets the requirements of polymerization-grade products. In addition, continuous production can be achieved, the overall process is greatly shortened, and the refining efficiency is improved.

[0006] In order to achieve the above technical objectives, the technical solutions adopted by the present invention are as follows:

[0007] The technical purpose of the first aspect of the present invention is to provide a method for refining long-chain dicarboxylic acids, wherein a crude long-chain dicarboxylic acid is dissolved in a mixed solvent of ethers and low-carbon alcohols at a temperature above 88°C, and after the crude long-chain dicarboxylic acid is fully dissolved, the system temperature is maintained below 92°C, and water below 92°C is added to precipitate the long-chain dicarboxylic acid, the aqueous phase and the precipitated long-chain dicarboxylic acid are separated from the mixed solvent, and the refined long-chain dicarboxylic acid is obtained by filtering and drying.

[0008] Furthermore, the ether is selected from at least one of propyl ether, butyl ether, pentyl ether, hexyl ether and heptyl ether, preferably butyl ether; the low-carbon alcohol is selected from at least one of methanol, ethanol and propanol, preferably ethanol or isopropanol.

[0009] Furthermore, by weight, the low-carbon alcohol in the mixed solvent accounts for 0.5-20%, preferably 5-10%.

[0010] Furthermore, the crude long-chain dicarboxylic acid is mixed with the mixed solvent in a weight ratio of 1:1.5-2.3, preferably in a weight ratio of 1:1.8-2.2.

[0011] Furthermore, the crude long-chain dicarboxylic acid is a crude product obtained by at least filtering the fermentation broth for pretreatment, and it is further preferred that the water content of the crude product is ≤5wt%.

[0012] Furthermore, water is added when the temperature of the refining system is 83-92°C, preferably 84-88°C; the temperature of the added water is 83-92°C, preferably 84-88°C, preferably consistent with the temperature of the insulation system.

[0013] Further, the amount of water added is 2.5-7 times the weight of the crude product, preferably 4-6 times the weight of the crude product.

[0014] Furthermore, during the addition of water, the stirring speed of the system must be strictly controlled and cannot be too fast to prevent the system from emulsifying and causing difficulty in separating the two phases. Preferably, the stirring speed of the system is ≤150 rpm, preferably 75-100 rpm.

[0015] Furthermore, the process of dissolving the crude long-chain dicarboxylic acid with the mixed solvent is carried out under heat preservation for 20-60 minutes, and after adding water, the mixture is also kept warm and mixed for 20-60 minutes until the long-chain dicarboxylic acid is fully precipitated.

[0016] Furthermore, the method further comprises the steps of adding cold water to the mixed solvent phase to cool it down, filtering the obtained long-chain dicarboxylic acid and drying it to collect it as a low-quality product, and refining and recovering the mixed solvent phase.

[0017] The technical purpose of the second aspect of the present invention is a method for continuously refining long-chain dicarboxylic acids, comprising the process of refining the long-chain dicarboxylic acids by the above method, adding low-carbon alcohols and crude long-chain dicarboxylic acids to the mixed solvent phase from which the water phase is separated to dissolve them again, and then adding water to precipitate the long-chain dicarboxylic acids; refining 5-10 batches.

[0018] Furthermore, in the above-mentioned continuous refining process, in the second batch and subsequent batches, the weight of the low-carbon alcohol added each time is equivalent to the weight of the low-carbon alcohol added in the previous batch, and the weight of the crude long-chain dicarboxylic acid added each time is equivalent to the weight (dry weight) of the product obtained by the previous refined batch.

[0019] Furthermore, in the above-mentioned continuous refining method, after refining 5-10 batches, it also includes adding cold water to the mixed solvent phase to cool the mixed solvent, filtering the obtained long-chain dicarboxylic acid and drying it, and collecting it as a low-quality product, and refining and recovering the mixed solvent phase.

[0020] Furthermore, one of the specific methods of refining and recovery is: cooling the mixed solvent phase to room temperature, adding sodium hydroxide solution, heating to above 80°C, stirring and discharging the lower aqueous phase, then adding pure water, stirring at a temperature above 80°C and discharging the lower aqueous phase. The second specific method of refining and recovery is: recovering the light components by vacuum distillation, and collecting the kettle residue as a low-quality product.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] (1) Under the refining system of the present invention, the solubility of the dibasic acid in the mixed solvent is not less than 66% (w / w); compared with the prior art (about 30%), the single-pass processing capacity is greatly improved.

[0023] (2) The dicarboxylic acid is removed by spontaneous nucleation and crystallization, which will not affect the refining equipment; the dicarboxylic acid is obtained from the aqueous phase, which reduces the loss of solvent during transportation and drying, and the product surface and interior will not adsorb solvent, reducing environmental damage; the product yield of long-chain dicarboxylic acid reaches more than 80%, and the purity of the dicarboxylic acid product refined in the first batch reaches more than 99.4%. When multiple batches are refined, the purity is more than 99%.

[0024] (3) The present invention can realize multi-batch continuous refining, and the solvent utilization rate is greatly improved. The solvent is uniformly recovered after being used in multiple batches, which reduces the cost, greatly shortens the overall process, and improves the refining efficiency.

[0025] Other features and advantages of the present invention will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0026] The method of the present invention is further described in detail below by way of examples. The examples are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following examples.

[0027] The purity of the long-chain dibasic acid in the crude product and the purity of the long-chain dibasic acid in the refined product in the following examples and comparative examples were determined by a hydrogen flame ionization detector and an area normalization method. Specifically, the long-chain dibasic acid was esterified to generate long-chain dibasic acid dimethyl ester. Chromatographic conditions: chromatographic column HP-innowax column, 30m×0.320mm×0.25μm; nitrogen was used as the carrier gas; programmed temperature was used, the initial column temperature was 130°C, maintained for 1min, and then heated to 220°C at 8°C / min.

[0028] Example 1

[0029] This example provides a process for refining long-chain dicarboxylic acids in a single batch using a mixed solvent of butyl ether and ethanol:

[0030] (1) Take 100 g of crude dodecanedioic acid filtered by plate and frame, and measure the water content to be 4.53%, the purity of dodecanedioic acid to be 98.27%, and the Pt-Co color value to be 151. Mix the crude product with a mixed solvent consisting of 190 g of butyl ether and 10 g of ethanol, heat to 95° C., and keep stirring for 30 minutes;

[0031] (2) After the crude product is observed to be completely dissolved (the solubility of a single batch of dicarboxylic acid is 50%), the temperature is slowly lowered to 85°C, the stirring speed is reduced to 100 rpm, and 500 mL of 85°C hot water is added. It can be seen that the crystals are rapidly transferred from the upper mixed solvent phase to the lower water phase. The speed is reduced to prevent the three-phase emulsification of butyl ether-crystal-water caused by fine crystals.

[0032] (3) After stirring for 15 minutes, the mixture was allowed to stand for 15 minutes, and the lower aqueous phase containing long-chain dicarboxylic acid crystals was cut out, filtered, and dried to obtain 80.74 g of a crystalline product with a yield of 82.2%, a purity of 99.61%, and a Pt-Co chromaticity value of 7.

[0033] (4) Add 500 g of cold pure water to the upper mixed solvent phase to lower the system temperature to about 30-40° C., cut out the lower aqueous phase containing crystals, and obtain a dicarboxylic acid crystal product of lower quality by filtering and drying.

[0034] (5) The temperature in the kettle was raised to 80°C, 50 mL of 2 wt% sodium hydroxide solution was added, and the lower phase was cut out after stirring for 30 minutes. 50 mL of pure water was added, and the lower phase was cut out after stirring for 30 minutes. The system was cooled to obtain a refined solvent, which can be directly used as the raw material for the next batch.

[0035] Example 2

[0036] This example provides a process for continuously refining long-chain dicarboxylic acids in multiple batches using a mixed solvent of butyl ether and ethanol:

[0037] (1) Take 100 g of crude dodecanedioic acid filtered by plate and frame, and determine that the water content is 3.93%, the purity is 98.11%, and the Pt-Co color value is 157. The crude product is mixed with a mixed solvent consisting of 190 g of butyl ether and 10 g of ethanol, heated to 95° C., and stirred for 30 minutes.

[0038] (2) After the crude product was completely dissolved, the temperature was slowly lowered to 85°C, the stirring speed was reduced to 100 rpm, and 500 mL of 85°C hot water was added. It was observed that crystals were rapidly transferred from the upper mixed solvent phase to the lower aqueous phase.

[0039] (3) After stirring for 15 minutes, the mixture was allowed to stand for 15 minutes, and the lower aqueous phase containing long-chain dicarboxylic acid crystals was cut out, filtered, and dried to obtain the first batch of crystalline products of 80.75 g, with a yield of 82.3%, a purity of 99.53%, and a Pt-Co chromaticity value of 7.

[0040] (4) Continue to add 80.75 g of the crude dodecanedioic acid and 10 g of ethanol in step (1) to the upper mixed solvent phase, and repeat the operation process (1) to (3) to obtain a second batch of crystalline product 78.17 g with a purity of 99.47% and a Pt-Co chromaticity value of 9.

[0041] (5) Continue to add 78.17 g of the crude dodecanedioic acid and 10 g of ethanol in step (1) to the upper mixed solvent phase, and repeat the process of (4) to (6) to obtain a third batch of crystalline product of 77.85 g with a purity of 99.39% and a Pt-Co chromaticity value of 11.

[0042] (6) Continue to add 77.85 g of the crude dodecanedioic acid and 10 g of ethanol in step (1) to the upper mixed solvent phase, and repeat the process of (4) to (6) to obtain a fourth batch of crystalline product of 76.29 g with a purity of 99.23% and a Pt-Co color value of 14.

[0043] (7) Continue to add 76.29 g of the crude dodecanedioic acid and 10 g of ethanol in step (1) to the upper mixed solvent phase, and repeat the process of (4) to (6) to obtain the fifth batch of crystalline product 75.11 g with a purity of 99.15% and a Pt-Co color value of 19.

[0044] (8) After five batches of refining, the mixed solvent phase was heated to 80°C, 50 mL of 2 wt% sodium hydroxide solution was added, and the lower phase was cut out after stirring for 30 minutes. Then 50 mL of pure water was added, and the lower phase was cut out after stirring for 30 minutes. The temperature was lowered to obtain a refined solvent, which could be directly used as the raw material for the next batch.

[0045] It should be noted that in step (3), although the yield of the first batch of refined products is only 82.3%, this is because in step (2), water is added at a relatively high temperature to precipitate the long-chain dicarboxylic acid to obtain the refined product. At this temperature, part of the long-chain dicarboxylic acid is dissolved in the butyl ether, resulting in a yield of only 82.3%. However, despite this, the single-pass processing capacity of the present invention is much higher than that of the prior art, and the part of the long-chain dicarboxylic acid dissolved in the butyl ether is not actually lost, and can be recycled in subsequent continuous multiple refining. For example, in step (4), 80.75 g of crude dodecanedioic acid is added, and the purity of the dicarboxylic acid is 98.11%, and 78.17 g of the second batch of crystalline products are obtained. For this batch alone, the yield of the dicarboxylic acid is as high as 98.6%.

[0046] Example 3

[0047] Except for using amyl ether instead of dibutyl ether, the other steps were the same as in Example 1. After purification, 80.27 g of a crystalline product was obtained with a yield of 81.7%, a purity of 99.48%, and a Pt-Co chromaticity value of 7.

[0048] Example 4

[0049] Except for using hexyl ether instead of butyl ether, the other steps were the same as in Example 1. After purification, 79.15 g of a crystalline product was obtained with a yield of 80.5%, a purity of 99.45%, and a Pt-Co chromaticity value of 7.

[0050] Example 5

[0051] Except for using propylene glycol instead of ethanol, the other procedures were the same as in Example 1. After purification, 80.19 g of a crystalline product was obtained with a yield of 81.1%, a purity of 99.39%, and a Pt-Co chromaticity value of 8.

[0052] Comparative Example 1

[0053] The same as Example 1, except that the water content of the crude product was 7.31wt%. During the refining process, the presence of excessive water greatly affected the solubility of the crude product. Under the same proportion conditions as in Example 1, the crude product was not completely dissolved, and finally 55.7g of crystalline product was obtained with a purity of 98.94%.

[0054] Comparative Example 2

[0055] The same as Example 1, except that the mixed solvent is 140 g of butyl ether and 60 g of ethanol. 65.82 g of crystalline product is obtained, with a purity of 99.42 and a Pt-Co chromaticity value of 9.

[0056] Comparative Example 3

[0057] Except for adding 93° C. hot water when the temperature is lowered to 93° C. in step (2), other operations are the same as those in Example 1. 47.25 g of a crystalline product is obtained with a purity of 99.46% and a Pt-Co chromaticity value of 8.

[0058] Comparative Example 4

[0059] Except that the stirring speed in step (2) was kept at 200 rpm, the other steps were the same as in Example 1. After the crystals were precipitated, emulsification occurred, and the interface between the solvent and water was blurred, making it difficult to separate completely. 69.20 g of the crystalline product was obtained, with a purity of 99.53% and a Pt-Co chromaticity value of 7.

Claims

1. A method for refining long-chain dicarboxylic acids, characterized in that: The crude long-chain dicarboxylic acid is dissolved in a mixed solvent of ethers and low-carbon alcohols at a temperature above 88°C. After the crude long-chain dicarboxylic acid is fully dissolved, the system temperature is maintained below 92°C, and water below 92°C is added to precipitate the long-chain dicarboxylic acid. The aqueous phase and the precipitated long-chain dicarboxylic acid are separated from the mixed solvent, and the refined long-chain dicarboxylic acid is obtained by filtering and drying.

2. The method according to claim 1, characterized in that The ether is selected from at least one of propyl ether, butyl ether, pentyl ether, hexyl ether and heptyl ether, and the low-carbon alcohol is selected from at least one of methanol, ethanol and propanol.

3. The method according to claim 1, characterized in that By weight, the low-carbon alcohol accounts for 0.5-20% of the mixed solvent.

4. The method according to claim 1, characterized in that: The crude long-chain dicarboxylic acid is mixed with a mixed solvent at a weight ratio of 1:1.5-2.

3.

5. The method according to claim 1, characterized in that The crude long-chain dicarboxylic acid product is a crude product obtained by at least filtering the fermentation broth for pretreatment, and the water content of the crude product is ≤5wt%.

6. The method according to claim 1, characterized in that When the temperature of the refining system is 83-92°C, water is added, and the temperature of the added water is 83-92°C.

7. The method according to claim 1, characterized in that The amount of water added is 2.5-7 times the weight of the crude product.

8. The method according to claim 1, characterized in that During the addition of water, control the rotation speed to avoid emulsification of the refined system.

9. The method according to claim 1, characterized in that: The process of dissolving the crude long-chain dicarboxylic acid with the mixed solvent is carried out under the condition of keeping warm for 20-60 minutes, and after adding water, the mixture is kept warm and mixed for 20-60 minutes until the long-chain dicarboxylic acid is fully precipitated.

10. The method according to claim 1, characterized in that The method also includes the steps of adding cold water to the mixed solvent phase to cool it down, filtering the obtained long-chain dicarboxylic acid and drying it to collect it as a low-quality product, and refining and recovering the mixed solvent phase.

11. A method for continuously refining long-chain dicarboxylic acids, characterized in that: The method comprises the following steps: after refining the long-chain dicarboxylic acid by the method of claim 1, adding low-carbon alcohol and crude long-chain dicarboxylic acid to the mixed solvent phase from which the aqueous phase is separated to dissolve the crude product, and then adding water to precipitate the long-chain dicarboxylic acid; and refining 5-10 batches.

12. The method for continuous purification of long-chain dicarboxylic acids according to claim 11, characterized in that: In the second batch and subsequent batches, the weight of the low-carbon alcohol added each time is equivalent to the weight of the low-carbon alcohol added in the previous batch, and the weight of the crude long-chain dicarboxylic acid added each time is equivalent to the weight of the product obtained by refining in the previous batch.

13. The method for continuous purification of long-chain dicarboxylic acid according to claim 11, characterized in that: After refining 5-10 batches, the method further includes adding cold water to the mixed solvent phase to cool the mixed solvent, filtering the obtained long-chain dicarboxylic acid and drying it, and collecting it as a low-quality product, and refining and recovering the mixed solvent phase.

14. The method for continuous purification of long-chain dicarboxylic acids according to claim 13, characterized in that: The method for refining and recovering the mixed solvent phase is as follows: cooling the mixed solvent phase to room temperature, adding sodium hydroxide solution, heating to above 80°C, stirring and discharging the lower aqueous phase, adding pure water, stirring at a temperature above 80°C and discharging the lower aqueous phase; Alternatively, the light components are recovered by vacuum distillation and the still residue is collected as a low-quality product.