A bipolar membrane electrodialysis system for the separation of 2-aminobutanol

Abstract

The application relates to the field of 2-amino butanol separation and purification, and particularly discloses a bipolar membrane electrodialysis system for separating 2-amino butanol. The system comprises polar liquid chambers located on two sides and an electrodialysis compartment sandwiched between the two polar liquid chambers, wherein the electrodialysis compartment is composed of an acid chamber, a feed liquid chamber and an alkali chamber unit arranged by bipolar membranes, anion exchange membranes and cation exchange membranes arranged at intervals; the separation method is specifically as follows: 2-amino butanol sulfate solution is introduced into the feed liquid chamber, electricity is supplied, and the conductivity of the feed liquid chamber is monitored; when the conductivity of the feed liquid chamber is reduced to below 5 ms / cm, the operation is stopped; the acid chamber, the feed liquid chamber and the alkali chamber respectively obtain sulfuric acid aqueous solution, residual liquid and 2-amino butanol aqueous solution; and the 2-amino butanol aqueous solution is concentrated to obtain 2-amino butanol. The application can obtain 2-amino butanol and sulfuric acid with high purity, the yield of the product is high, the energy consumption of the tail end of membrane conversion is reduced, and the production cost is saved.

Description

Technical Field

[0001] This application relates to the field of 2-aminobutanol separation and purification, and more specifically, it relates to a method for separating 2-aminobutanol using a bipolar membrane electrodialysis system. Background Technology

[0002] 2-Aminobutanol is a chiral amino alcohol, a colorless or pale yellow liquid, with wide applications in the pharmaceutical and chemical industries. It serves as an important intermediate in the production of biologically active butanol derivatives and can also be used to prepare emulsifiers, surfactants, vulcanization accelerators, and acid gas absorbents. (+)-Aminobutanol, obtained by resolving 2-aminobutanol, can be used to produce the anti-tuberculosis drug ethambutol.

[0003] Currently, 2-aminobutanol is mainly synthesized using a high-pressure hydrogenation reduction method. In this method, 2-aminobutyric acid is used as the starting material, with the addition of water, sulfuric acid, and a catalyst. Hydrogen gas is then introduced to carry out a high-pressure hydrogenation reduction reaction. The reaction solution containing an aqueous solution of 2-aminobutanol sulfate is then separated and purified to obtain the product 2-aminobutanol. Since 2-aminobutanol is a key intermediate in many chiral drugs, its purity plays a crucial role in the quality of the drugs.

[0004] Existing Chinese patent CN 102584606A discloses a method for preparing aminopropanol using a bipolar membrane electrodialysis device. This electrodialysis device consists of two electrode chambers on either side and an electrodialysis compartment sandwiched between them. The electrodialysis compartment is composed of feed chambers and acid chambers arranged in alternating layers of bipolar membranes and anion exchange membranes. The electrode chambers are divided into an anode chamber and a cathode chamber, and are powered by a DC power supply. In the preparation of aminopropanol, an aqueous solution of aminopropanol sulfate is used as the raw material. After passing through a microporous processor, it enters the feed chamber of the electrodialysis device. The device is then started, and the conductivity of the feed chamber is monitored. When the conductivity of the feed chamber drops to 2000 μS / cm, operation is stopped. At this point, the feed chamber contains an aqueous solution of aminopropanol, and the acid chamber contains an aqueous solution of sulfuric acid. The aqueous solution of aminopropanol is then concentrated to obtain aminopropanol. The aminopropanol obtained by this method has high purity and low production cost.

[0005] However, in the above method, the aminopropanol aqueous solution is gradually converted from aminopropanol sulfate in the feed chamber. After the conversion, the feed chamber contains not only the aminopropanol aqueous solution but also a small amount of incompletely converted aminopropanol sulfate aqueous solution. To improve the product conversion rate, a membrane tail-end treatment is needed to minimize the presence of aminopropanol sulfate solution in the feed chamber. However, the membrane tail-end treatment significantly increases the system's energy consumption and cannot completely convert the aminopropanol sulfate solution into the aminopropanol aqueous solution. Furthermore, because aminopropanol molecules are small, they easily diffuse into the acid chamber through the concentration gradient, reducing both the yield of aminopropanol product and the purity of the byproduct sulfuric acid. Summary of the Invention

[0006] To address the aforementioned technical problems, this application provides a bipolar membrane electrodialysis system for separating 2-aminobutanol.

[0007] This application provides a bipolar membrane electrodialysis system for separating 2-aminobutanol, which adopts the following technical solution: A bipolar membrane electrodialysis system for separating 2-aminobutanol includes two electrode chambers located on both sides and an electrodialysis compartment sandwiched between the two electrode chambers. The electrodialysis compartment is composed of an acid chamber, a feed chamber, and an alkali chamber unit arranged alternately with bipolar membranes, anion exchange membranes, and cation exchange membranes. The specific method for separating 2-aminobutanol is as follows: a 2-aminobutanol sulfate solution is introduced into the feed chamber, an electric current is applied, and the conductivity of the feed chamber is monitored. When the conductivity of the feed chamber decreases to below 5 mS / cm, the operation is stopped. Sulfuric acid aqueous solution, residual liquid, and 2-aminobutanol aqueous solution are obtained in the acid chamber, feed chamber, and alkali chamber, respectively. The 2-aminobutanol aqueous solution is concentrated to obtain 2-aminobutanol.

[0008] By adopting the above technical solution, this application sets the electrodialysis chamber as a three-compartment unit, adding an alkali chamber to the existing acid chamber and feed chamber. When the device is powered on, the SO42- in the 2-aminobutanol sulfate solution within the feed chamber... 2- Ions pass through the anion exchange membrane into the acid chamber, forming an aqueous sulfuric acid solution. Cations in the 2-aminobutanol sulfate solution pass through the cation exchange membrane into the alkali chamber, forming an aqueous 2-aminobutanol solution. After the device operation is completed, the 2-aminobutanol aqueous solution obtained in the alkali chamber can be directly concentrated to obtain 2-aminobutanol. There is no need to increase the membrane tail treatment to separate the 2-aminobutanol aqueous solution and a small amount of unreacted 2-aminobutanol sulfate solution, which greatly reduces the energy consumption of the system. Furthermore, this application obtains 2-aminobutanol directly in the alkali chamber, reducing the impact of reaction byproducts, impurities, and unreacted 2-aminobutanol sulfate on the purity of 2-aminobutanol, and significantly improving the purity of 2-aminobutanol.

[0009] Furthermore, since the 2-aminobutanol in this application is obtained directly in the alkaline chamber, the possibility of 2-aminobutanol diffusing into the acid chamber through concentration gradient is extremely low. This improves the purity of the sulfuric acid obtained in the acid chamber and reduces the loss of 2-aminobutanol, thereby increasing the yield of 2-aminobutanol. In addition, the sulfuric acid obtained in the acid chamber of this application can be directly used in the front-end reaction of the product, saving production costs.

[0010] Preferably, both the anion exchange membrane and the cation exchange membrane are heterogeneous membranes or homogeneous membranes.

[0011] Preferably, both the anion exchange membrane and the cation exchange membrane are homogeneous membranes.

[0012] By adopting the above technical solution, the anion exchange membrane and cation exchange membrane of this application are further selected as homogeneous membranes. Homogeneous membranes have strong resistance to strong acids and strong alkalis, and the resistance to ion conduction is less than that of heterogeneous membranes, thereby reducing the energy consumption of the system.

[0013] Preferably, the residual liquid is separated using a nanofiltration membrane to obtain a 2-aminobutanol sulfate solution.

[0014] By adopting the above technical solution, when the system stops operating, the remaining liquid in the feed chamber includes reaction byproducts and a small amount of incompletely converted 2-aminobutanol sulfate. This application uses a nanofiltration membrane to further separate and extract the remaining 2-aminobutanol sulfate from the residual liquid, and reuses the nanofiltration concentrate in the feed chamber for continued membrane treatment. This not only improves the yield of 2-aminobutanol but also significantly saves energy consumption at the tail end of the membrane conversion process.

[0015] Preferably, the nanofiltration membrane is prepared by the following method: First, anhydrous piperazine, triethylamine, and polyvinyl alcohol are dissolved in water to prepare an aqueous phase solution. Simultaneously, pyromellitic trimethylol chloride is dissolved in n-hexane to prepare an oil phase solution. Then, the polysulfone-based membrane is immersed in the aqueous phase solution for 3-5 minutes, removed, and excess aqueous phase solution is removed from the surface. It is then immersed in the oil phase solution for 1-3 minutes. After being removed and dried, it is heat-treated at 50-55℃ for 10-15 minutes to obtain an antifouling nanofiltration membrane. The dosage of anhydrous piperazine is 3-3.5 g / L, the dosage of triethylamine is 1.8-2 g / L, the dosage of polyvinyl alcohol is 0.54-0.63 g / L, and the dosage of pyromellitic trimethylol chloride is 1-1.2 g / L.

[0016] By adopting the above technical solution, this application uses a polysulfone ultrafiltration membrane as the base membrane and prepares a polyamide nanofiltration membrane through interfacial polymerization of piperazine (PIP) and trimesoyl chloride (TMC). Polyvinyl alcohol is added to the nanofiltration membrane, which reduces the contact angle, increases hydrophilicity, and improves film-forming properties, making its surface smoother and thus enhancing its antifouling performance. Furthermore, this application uses an antifouling nanofiltration membrane to separate and extract 2-aminobutanol sulfate from the residual liquid, reducing the possibility of performance degradation due to contamination after repeated use, improving the extraction efficiency of 2-aminobutanol sulfate, extending the service life of the nanofiltration membrane, and saving production costs.

[0017] Preferably, the concentration of the 2-aminobutanol sulfate solution is 6-25%.

[0018] Preferably, the current of the electrodialysis system is 4.4-225A, the voltage is 35-360V, and the reaction temperature is 20-40℃.

[0019] Preferably, the electrodialysis compartment is composed of 4-80 units arranged in series, consisting of acid chambers, feed chambers, and alkali chambers.

[0020] Preferably, the specific process of distillation and concentration of the 2-aminobutanol aqueous solution is as follows: first, the 2-aminobutanol aqueous solution is rotary evaporated at a temperature of 50-55°C until no distillate is distilled off, and then it is distilled under reduced pressure at a temperature of 130-132°C until no distillate is distilled off, to obtain 2-aminobutanol.

[0021] In summary, this application has the following beneficial technical effects: 1. The method of this application can obtain 2-aminobutanol and sulfuric acid with high purity and high product yield; 2. The method of this application shortens the production process route of 2-aminobutanol, has high production efficiency, and greatly reduces the energy consumption at the end of membrane conversion, thus saving production costs. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the electrodialysis compartment of this application; Figure 2 This is a process flow diagram of the bipolar membrane electrodialysis system used in this application to separate 2-aminobutanol. Detailed Implementation

[0023] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0024] The 2-aminobutanol sulfate solution in this application can be D-2-aminobutanol sulfate solution, L-2-aminobutanol sulfate solution, or DL-2-aminobutanol sulfate solution. In the embodiments of this application, DL-2-aminobutanol sulfate solution is selected.

[0025] The separation method in this application embodiment uses an electrodialysis system, such as Figure 1 and Figure 2 As shown, a bipolar membrane electrodialysis system for separating 2-aminobutanol includes a DC power supply, a cathode plate, and an anode plate. The positive terminal of the DC power supply is connected to the anode plate, and the negative terminal is connected to the cathode plate. An electrodialysis chamber is provided between the cathode and anode plates. This chamber is composed of acid, feed, and alkali units arranged in alternating layers of bipolar membranes, anion exchange membranes, and cation exchange membranes. The number of these units can range from 4 to 80 depending on production requirements. In this embodiment, the electrodialysis chamber consists of 20 units connected in series. The acid, feed, and alkali chambers are externally connected to acid, feed, and alkali tanks, respectively, and form a loop through a circulation pump. A section of pipe connected to the inlet of each chamber is a circulation coil, which is placed in ice water to ensure sufficient cooling of the feed solution and control the temperature during the reaction process. The anode plate and cathode plate, each connected to an adjacent bipolar membrane, form an electrode liquid chamber. The electrode liquid chamber is connected to an electrode liquid tank, and a circulation pump forms a loop. When the device is energized and turned on, SO42- from the 2-aminobutanol sulfate solution introduced into the feed chamber... 2- Ions pass through the anion exchange membrane into the acid chamber, forming an aqueous solution of sulfuric acid. Cations in the 2-aminobutanol sulfate solution pass through the cation exchange membrane into the alkali chamber, forming an aqueous solution of 2-aminobutanol.

[0026] <Material Source> All raw materials used in this application are commercially available products.

[0027] <Example> Example 1 A method for separating 2-aminobutanol using a bipolar membrane electrodialysis system involves adding 1000 mL of a 6% DL-2-aminobutanol sulfate solution to a feed tank, adding pure water to the acid and alkali tanks, and adding 4% sulfuric acid to the electrode liquid tank. The circulation pump is turned on, and the flow rate of each compartment is adjusted to 30 L / h. The voltage is set to 35 V and the current to 4.4 A. The electrodialysis system is then started. The DL-2-aminobutanol sulfate solution in the feed tank enters the feed chamber, the pure water in the acid and alkali tanks enters the acid and alkali chambers as receiving solutions, and the sulfuric acid in the electrode liquid tank enters the electrode liquid chamber as the electrode liquid. During operation, the conductivity of the feed chamber was monitored, and the reaction temperature was controlled at 20℃. When the conductivity of the feed chamber dropped below 5 mS / cm, the operation was stopped. Sulfuric acid aqueous solution, residual liquid, and DL-2-aminobutanol aqueous solution were obtained from the acid tank, feed tank, and alkali tank, respectively. Then, the DL-2-aminobutanol aqueous solution was first evaporated at 50℃ using a rotary evaporator until no distillate was distilled off, and then distilled under reduced pressure using a water pump at 130℃ until no distillate was distilled off, to obtain DL-2-aminobutanol. The anion exchange membrane and cation exchange membrane used in the electrodialysis system are heterogeneous membranes.

[0028] Example 2 A method for separating 2-aminobutanol using a bipolar membrane electrodialysis system involves adding 1000 mL of a 25% DL-2-aminobutanol sulfate solution to a feed tank, adding pure water to the acid and alkali tanks, and adding 4% sulfuric acid to the electrode tank. The circulation pump is turned on, and the flow rate of each compartment is adjusted to 30 L / h. The voltage is set to 360 V and the current to 225 A. The electrodialysis system is then started. The DL-2-aminobutanol sulfate solution in the feed tank enters the feed chamber, the pure water in the acid and alkali tanks enters the acid and alkali chambers as receiving solutions, and the sulfuric acid in the electrode tank enters the electrode chamber as the electrode solution. During operation, the conductivity of the feed chamber was monitored, and the reaction temperature was controlled at 40℃. Operation was stopped when the conductivity of the feed chamber dropped below 5 mS / cm. Sulfuric acid aqueous solution, residual liquid, and DL-2-aminobutanol aqueous solution were obtained from the acid tank, feed tank, and alkali tank, respectively. Then, the DL-2-aminobutanol aqueous solution was first evaporated at 55℃ using a rotary evaporator until no distillate was distilled off, and then distilled under reduced pressure using a water pump at 132℃ until no distillate was distilled off, to obtain DL-2-aminobutanol. The anion exchange membrane and cation exchange membrane used in the electrodialysis system are heterogeneous membranes.

[0029] Example 3 A method for separating 2-aminobutanol using a bipolar membrane electrodialysis system involves adding 1000 mL of a 15% DL-2-aminobutanol sulfate solution to a feed tank, adding pure water to the acid and alkali tanks, and adding 4% sulfuric acid to the electrode liquid tank. The circulation pump is turned on, and the flow rate of each compartment is adjusted to 30 L / h. The voltage is set to 120 V and the current to 60 A. The electrodialysis system is then started. The DL-2-aminobutanol sulfate solution in the feed tank enters the feed chamber, the pure water in the acid and alkali tanks enters the acid and alkali chambers as receiving solutions, and the sulfuric acid in the electrode liquid tank enters the electrode liquid chamber as the electrode liquid. During operation, the conductivity of the feed chamber was monitored, and the reaction temperature was controlled at 30℃. When the conductivity of the feed chamber dropped below 5 mS / cm, the operation was stopped. Sulfuric acid aqueous solution, residual liquid, and DL-2-aminobutanol aqueous solution were obtained from the acid tank, feed tank, and alkali tank, respectively. Then, the DL-2-aminobutanol aqueous solution was first evaporated at 53℃ using a rotary evaporator until no distillate was distilled off, and then distilled under reduced pressure using a water pump at 131℃ until no distillate was distilled off, to obtain DL-2-aminobutanol. The anion exchange membrane and cation exchange membrane used in the electrodialysis system are heterogeneous membranes.

[0030] Example 4 A method for separating 2-aminobutanol using a bipolar membrane electrodialysis system differs from Example 1 in that the anion exchange membrane and cation exchange membrane used in the electrodialysis system are homogeneous membranes.

[0031] Example 5 A method for separating 2-aminobutanol using a bipolar membrane electrodialysis system differs from Example 1 in that the residual liquid in the feed tank is passed into a nanofiltration separation system, and a commercially available nanofiltration membrane NF90-400 is used to separate the residual liquid. The nanofiltration concentrate is then reused in the feed chamber for further conversion.

[0032] Example 6 A method for separating 2-aminobutanol using a bipolar membrane electrodialysis system differs from Example 5 in that the nanofiltration membrane is prepared by the following method: First, 3g of anhydrous piperazine, 2g of triethylamine and 0.54g of polyvinyl alcohol were dissolved in 1L of water to prepare an aqueous phase solution. At the same time, 1g of trimesoyl chloride was dissolved in 1L of n-hexane to prepare an oil phase solution. Then, the polysulfone-based membrane was immersed in the aqueous phase solution for 3 minutes, removed, and excess aqueous phase solution was removed from the surface. It was then immersed in the oil phase solution for 1 minute. After being removed and dried, it was heat-treated at 50℃ for 10 minutes to obtain an antifouling nanofiltration membrane.

[0033] Example 7 A method for separating 2-aminobutanol using a bipolar membrane electrodialysis system differs from Example 5 in that the nanofiltration membrane is prepared by the following method: First, 3.5g of anhydrous piperazine, 1.8g of triethylamine and 0.63g of polyvinyl alcohol were dissolved in 1L of water to prepare an aqueous phase solution. At the same time, 1.2g of trimesoyl chloride was dissolved in 1L of n-hexane to prepare an oil phase solution. Then, the polysulfone-based membrane was immersed in the aqueous phase solution for 5 minutes, removed, and excess aqueous phase solution was removed from the surface. It was then immersed in the oil phase solution for 3 minutes. After being removed and dried, it was heat-treated at 55℃ for 15 minutes to obtain an antifouling nanofiltration membrane.

[0034] <Comparative Example> Comparative Example 1 DL-2-aminobutanol was separated using the electrodialysis apparatus described in Example 1 of Chinese Patent No. CN 102584606A.

[0035] Comparative Example 2 DL-2-aminobutanol was separated using an electrodialysis apparatus in Example 2 of Chinese Patent No. CN 102584606A.

[0036] Data Analysis The yields of DL-2-aminobutanol obtained in Examples 1-7 and Comparative Examples 1-2 were calculated, and the purity of DL-2-aminobutanol obtained in Examples 1-7 and Comparative Examples 1-2 was tested. The results are shown in Table 1.

[0037] Table 1 Test Results Example 1 98.8 99.78 Example 2 98.1 99.75 Example 3 98.6 99.78 Example 4 99.0 99.81 Example 5 99.5 99.80 Example 6 99.8 99.81 Example 7 99.7 99.80 Comparative Example 1 89.5 99.23 Comparative Example 2 94.8 99.71 As shown in Table 1, the purity of DL-2-aminobutanol obtained by the methods in Examples 1-3 of this application is greater than 99.7%, and the product yield is above 98%. This indicates that by further adding an alkali chamber to the acid chamber and feed chamber, and directly obtaining an aqueous solution of DL-2-aminobutanol in the alkali chamber, the yield and purity of the product can be significantly improved.

[0038] The yield and purity of Example 4 are higher than those of Example 1, indicating that in the electrodialysis system of this application, the use of homogeneous membranes for both anion exchange and cation exchange membranes can further improve the yield and purity of the product.

[0039] The yield of Example 5 was higher than that of Example 1, indicating that the present application can further improve the product yield by using nanofiltration membrane to separate and extract the residual liquid.

[0040] The yields of Examples 6-7 were higher than those of Example 5, indicating that the use of an antifouling nanofiltration membrane in this application can further improve the product yield.

[0041] The yields and purity of Comparative Examples 1-2 were significantly lower than those of Example 1, indicating that by further adding an alkali chamber to the acid chamber and feed chamber of this application, and directly obtaining an aqueous solution of DL-2-aminobutanol in the alkali chamber, the yield and purity of the product can be significantly improved.

[0042] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for separating 2-aminobutanol, wherein the separation method employs a bipolar membrane electrodialysis system, the system comprising two electrode chambers located on either side and an electrodialysis compartment sandwiched between the two electrode chambers, characterized in that: The electrodialysis chamber is composed of an acid chamber, a feed chamber, and an alkali chamber, which are formed by bipolar membranes, anion exchange membranes, cation exchange membranes, and bipolar membranes arranged in an alternating pattern. The specific method for separating 2-aminobutanol is as follows: a 2-aminobutanol sulfate solution is introduced into the feed chamber, an electric current is applied, and the conductivity of the feed chamber is monitored. When the conductivity of the feed chamber decreases to below 5 mS / cm, the operation is stopped. A sulfuric acid aqueous solution is obtained from the acid chamber, a residual liquid is obtained from the feed chamber, and a 2-aminobutanol aqueous solution is obtained from the alkali chamber. The 2-aminobutanol aqueous solution is then concentrated to obtain 2-aminobutanol. Both the anion exchange membrane and the cation exchange membrane are homogeneous membranes. The residual liquid was separated by nanofiltration membrane to obtain nanofiltration concentrate 2-aminobutanol sulfate solution, which was then recycled back to the feed chamber. The nanofiltration membrane is prepared by the following method: First, anhydrous piperazine, triethylamine, and polyvinyl alcohol are dissolved in water to prepare an aqueous phase solution. Simultaneously, pyromellitic trimethylol chloride is dissolved in n-hexane to prepare an oil phase solution. Then, the polysulfone-based membrane is immersed in the aqueous phase solution for 3-5 minutes, removed, and excess aqueous phase solution is removed from the surface. It is then immersed in the oil phase solution for 1-3 minutes. After being removed and dried, it is heat-treated at 50-55℃ for 10-15 minutes to obtain an antifouling nanofiltration membrane. The dosage of anhydrous piperazine is 3-3.5 g / L, the dosage of triethylamine is 1.8-2 g / L, the dosage of polyvinyl alcohol is 0.54-0.63 g / L, and the dosage of pyromellitic trimethylol chloride is 1-1.2 g / L.

2. The method for separating 2-aminobutanol according to claim 1, characterized in that: The concentration of the 2-aminobutanol sulfate solution is 6-25%.

3. The method for separating 2-aminobutanol according to claim 1, characterized in that: The electrodialysis system has a current of 4.4-225A, a voltage of 35-360V, and a reaction temperature of 20-40℃.

4. The method for separating 2-aminobutanol according to claim 1, characterized in that, The electrodialysis compartment is composed of a series of units consisting of an acid chamber, a feed chamber, and an alkali chamber, with the number of such units ranging from 4 to 80.

5. The method for separating 2-aminobutanol according to claim 1, characterized in that: The specific process of distilling and concentrating the 2-aminobutanol aqueous solution is as follows: First, at a temperature of 50-55℃, the 2-aminobutanol aqueous solution is rotary evaporated to remove water until no distillate is distilled off, and then at a temperature of 130-132℃, it is distilled under reduced pressure until no distillate is distilled off, thus obtaining 2-aminobutanol.

Images