A process for recovering acrylonitrile in an amps production process
By separating the acrylonitrile-water azeotrope through vacuum distillation and a distillation column, the problem of unstable acrylonitrile recovery in the prior art was solved, achieving high-purity and high-yield acrylonitrile recovery, reducing energy consumption and improving the quality of AMPS synthesis.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- WEIFANG FENGHUA ENVIRONMENTAL PROTECTION TECHNOLOGY CO LTD
- Filing Date
- 2026-02-09
- Publication Date
- 2026-06-05
AI Technical Summary
Existing acrylonitrile recovery methods suffer from unstable quality, low recovery efficiency, and high energy consumption. Furthermore, acrylonitrile is difficult to separate from water, which affects the purity and yield of AMPS synthesis.
The method employs vacuum distillation, where ethyl acetate is mixed with the residue in the reactor, and then the azeotrope of acrylonitrile and water is separated by a distillation column. The azeotrope of ethyl acetate and water is collected from the top of the column, while acrylonitrile is collected from the side stream. This method reduces the distillation temperature and the risk of self-polymerization. The components are also separated through material recycling and distillation.
It achieves the recovery of acrylonitrile with high purity (99.15-99.27%) and high yield (88.48-90.51%), low water content (0.33-0.41%), reduces energy consumption, avoids additional dehydration steps, and improves the quality and economic benefits of AMPS synthesis.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of acrylonitrile recovery technology, specifically relating to a method for recovering acrylonitrile during the AMPS production process. Background Technology
[0002] 2-Acrylamido-2-methylpropanesulfonic acid (AMPS) is an important functional monomer widely used in water treatment, oilfield chemistry, polymer materials, and other fields. The commonly used industrial synthesis method for AMPS involves reacting isobutylene with fuming sulfuric acid to produce 2-methylpropenesulfonate lactone. 2-Methylpropenesulfonate lactone then undergoes a ring-opening reaction with the participation of acrylonitrile to finally generate AMPS. Acrylonitrile is not only one of the direct raw materials for chemical synthesis, participating in the construction of the molecular structure, but also serves as an organic solvent, providing a homogeneous medium for the reaction and ensuring that the reaction can proceed efficiently and smoothly. Therefore, it is used in excess during the AMPS synthesis process. After the reaction is completed, a large amount of acrylonitrile still exists in the reaction mixture (residue). Recycling and reusing this acrylonitrile has significant economic and environmental benefits.
[0003] However, water is generated during the synthesis of AMPS. If the recovered acrylonitrile contains water, then: 1. Water will react with fuming sulfuric acid to produce ordinary sulfuric acid, which directly reduces the effective concentration and activity of the sulfonating agent, resulting in incomplete sulfonation; 2. Moisture will cause the core intermediate—2-methylpropenesulfonate lactone—to undergo a hydrolysis side reaction, generating useless 2-methylpropenesulfonate, reducing the yield and purity of AMPS. Therefore, if the recovered acrylonitrile is to be reused to participate in the reaction, the main problem is to remove the moisture.
[0004] Currently, the main method for recovering acrylonitrile is distillation, which involves batch feeding, distillation, and discharge of concentrated residue in a distillation kettle. This method results in unstable quality of recovered acrylonitrile, large fluctuations in indicators, low recovery efficiency, and high energy consumption. Furthermore, during distillation, acrylonitrile is prone to self-polymerization, clogging equipment pipelines. Acrylonitrile and water form an azeotrope, which is difficult to separate. Vacuum distillation can effectively improve the quality of acrylonitrile, reduce indicator fluctuations, and decrease the probability of acrylonitrile self-polymerization. However, the problem of acrylonitrile forming an azeotrope with water has not been effectively solved. Before participating in the synthesis reaction of AMPS again, an additional dehydration step is required. Summary of the Invention
[0005] To address the problems existing in the prior art, this invention provides a method for recovering acrylonitrile during the production of AMPS, achieving the following objectives: the recovered acrylonitrile has high purity, high yield, and low moisture content, while the process is simple and energy consumption is low.
[0006] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A method for recovering acrylonitrile during AMPS production includes the following steps: 1. Reduced pressure distillation Ethyl acetate and the residue from the reactor are fed into a stirred tank and stirred until homogeneous. Then, the mixture is fed into a distillation column. An azeotrope of ethyl acetate and water is collected from the top of the column and enters condenser A. Acrylonitrile is collected from the side stream and, after passing inspection, is transferred to the raw material preparation tank to participate in the synthesis reaction of AMPS. The concentrate from the bottom of the column is fed into a distillation column. The mass ratio of ethyl acetate to the residue in the reactor is 0.9–1.1:1.2–1.6; The distillation column is configured with a top temperature of 43–46°C, a bottom temperature of 48–52°C, an internal absolute pressure of 45–55 kPa, and a reflux ratio of 1.8–2.2.
[0007] 2. Material circulation After the azeotrope of ethyl acetate and water enters condenser A, it is allowed to stand at room temperature for 1 to 2 hours. The upper layer of ethyl acetate is fed into a stirred tank, mixed with the residual liquid in the tank, and then fed into a distillation column to participate in material circulation. The lower layer of water is discharged.
[0008] 3. Distillation of concentrated liquid After the concentrate from the bottom of the column enters the distillation column, the upper light components are cooled and fed into condenser B. After cooling, they are fed into a stirred tank, while the lower heavy components are discharged. The distillation column is controlled with a top temperature of 58–62°C, a bottom temperature of 65–70°C, and an internal absolute pressure of 70–75 kPa.
[0009] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. After mixing ethyl acetate with the residue in the reactor, vacuum distillation is carried out. Under negative pressure, the boiling point of acrylonitrile decreases, which in turn lowers the distillation temperature and reduces the risk of acrylonitrile self-polymerization. 2. The azeotrope formed by ethyl acetate and water has a lower boiling point than acrylonitrile. A method is used where the azeotrope of ethyl acetate and water is collected from the top of the distillation column, while acrylonitrile is collected from the side stream. This method achieves the following advantages: S1. Lowering the distillation temperature saves costs; S2. Water, before the boiling point of acrylonitrile, is collected from the top of the column as an azeotrope with ethyl acetate. Consequently, the acrylonitrile collected from the side stream has a low water content and can be transferred to the feed preparation vessel without additional dehydration to participate in the AMPS synthesis reaction; S3. After the ethyl acetate and water are collected from the top of the column as an azeotrope, cooling allows them to separate into layers. The upper layer of ethyl acetate can be repeatedly fed into the stirred tank for reuse.
[0010] 3. The method for recovering acrylonitrile of the present invention recovers acrylonitrile with a purity of 99.15-99.27%, a yield of 88.48-90.51%, and a low moisture content of 0.33-0.41%. Detailed Implementation
[0011] Example 1 A method for recovering acrylonitrile during AMPS production includes the following steps: 1. Reduced pressure distillation Ethyl acetate and the residue from the reactor are fed into a stirred tank and stirred until homogeneous. Then, the mixture is fed into a distillation column. An azeotrope of ethyl acetate and water is collected from the top of the column and enters condenser A. Acrylonitrile is collected from the side stream and, after passing inspection, is transferred to the raw material preparation tank to participate in the synthesis reaction of AMPS. The concentrate from the bottom of the column is fed into a distillation column. The mass ratio of ethyl acetate to the residue in the reactor is 1:1.4; The distillation column is controlled with a top temperature of 44°C, a bottom temperature of 50°C, an internal absolute pressure of 50 kPa, and a reflux ratio of 2.
[0012] 2. Material circulation The azeotrope of ethyl acetate and water enters condenser A and is left to stand at room temperature for 1.5 hours. The upper layer of ethyl acetate is fed into a stirred tank, mixed with the residual liquid in the tank, and then enters a distillation column to participate in material circulation. The lower layer of water is discharged.
[0013] 3. Distillation of concentrated liquid After the concentrate from the bottom of the column enters the distillation column, the upper light components enter the condenser B, and after cooling, they are fed into the stirred tank, while the lower heavy components are discharged. The distillation column is controlled with a top temperature of 60°C, a bottom temperature of 67°C, and an absolute pressure of 73 kPa.
[0014] Example 2 A method for recovering acrylonitrile during AMPS production includes the following steps: 1. Reduced pressure distillation Ethyl acetate and the residue from the reactor are fed into a stirred tank and stirred until homogeneous. Then, the mixture is fed into a distillation column. An azeotrope of ethyl acetate and water is collected from the top of the column and enters condenser A. Acrylonitrile is collected from the side stream and, after passing inspection, is transferred to the raw material preparation tank to participate in the synthesis reaction of AMPS. The concentrate from the bottom of the column is fed into a distillation column. The mass ratio of ethyl acetate to the residue in the reactor is 0.9:1.2; The distillation column is controlled with a top temperature of 43°C, a bottom temperature of 48°C, an internal absolute pressure of 45 kPa, and a reflux ratio of 1.8.
[0015] 2. Material circulation The azeotrope of ethyl acetate and water enters condenser A and is left to stand at room temperature for 1 hour. The upper layer of ethyl acetate is fed into a stirred tank, mixed with the residual liquid in the tank, and then enters a distillation column to participate in material circulation. The lower layer of water is discharged.
[0016] 3. Distillation of concentrated liquid After the concentrate from the bottom of the column enters the distillation column, the upper light components are cooled and enter the condenser B. After cooling, they are fed into the stirred tank, while the lower heavy components are discharged. The distillation column is controlled with a top temperature of 58°C, a bottom temperature of 65°C, and an internal absolute pressure of 70 kPa.
[0017] Example 3 A method for recovering acrylonitrile during AMPS production includes the following steps: 1. Reduced pressure distillation Ethyl acetate and the residue from the reactor are fed into a stirred tank and stirred until homogeneous. Then, the mixture is fed into a distillation column. An azeotrope of ethyl acetate and water is collected from the top of the column and enters condenser A. Acrylonitrile is collected from the side stream and, after passing inspection, is transferred to the raw material preparation tank to participate in the synthesis reaction of AMPS. The concentrate from the bottom of the column is fed into a distillation column. The mass ratio of ethyl acetate to the residue in the reactor is 1.1:1.6; The distillation column is configured with a top temperature of 46°C, a bottom temperature of 52°C, an internal absolute pressure of 55 kPa, and a reflux ratio of 2.2.
[0018] 2. Material circulation The azeotrope of ethyl acetate and water enters condenser A and is left to stand at room temperature for 2 hours. The upper layer of ethyl acetate is fed into a stirred tank, mixed with the residual liquid in the tank, and then enters a distillation column to participate in material circulation. The lower layer of water is discharged.
[0019] 3. Distillation of concentrated liquid After the concentrate from the bottom of the column enters the distillation column, the upper light components are cooled and enter the condenser B. After cooling, they are fed into the stirred tank, while the lower heavy components are discharged. The distillation column is controlled with a top temperature of 62°C, a bottom temperature of 70°C, and an internal absolute pressure of 75 kPa.
[0020] Comparative Example 1 After the residue from the reactor is fed into the distillation column, the upper light component, namely acrylonitrile, enters the condenser. After cooling and removing water, it is fed into the raw material preparation reactor to participate in the synthesis reaction of AMPS, while the lower heavy component is discharged. The distillation column is controlled with a top temperature of 60°C, a bottom temperature of 67°C, and an absolute pressure of 73 kPa.
[0021] Comparative Example 2 The residue from the bottom of the distillation column is fed into distillation column A. The vapor from the top of distillation column A is fed into the rectification column. The concentrate from the bottom of distillation column A is fed into distillation column B. Acrylonitrile is collected from the top of the rectification column, cooled and dehydrated, and after passing inspection, it is transferred to the raw material preparation vessel to participate in the synthesis reaction of AMPS. The concentrate from the bottom of the rectification column enters distillation column B. The vapor from the top of distillation column B is fed into the rectification column. The concentrate from the bottom of distillation column B is discharged. The distillation column is configured with a top temperature of 44°C, a bottom temperature of 50°C, an internal absolute pressure of 50 kPa, and a reflux ratio of 2. The distillation column A is controlled with a top temperature of 60°C, a bottom temperature of 67°C, and an internal absolute pressure of 73 kPa. The distillation column B is controlled with a top temperature of 71°C and a bottom temperature of 80°C.
[0022] Test case The purity, yield, and moisture content of the acrylonitrile recovered in Examples 1-3 and Comparative Examples 1-2 were tested respectively. The test results are shown in Table 1. Yield = Actual output / Theoretical output × 100%; Table 1
[0023] The results above show that Comparative Example 1 uses single-pot distillation, which requires batch distillation and discharge of residual liquid. This results in differences in the purity, yield, and water content of each batch of acrylonitrile, leading to unstable quality and poorer quality compared to the rectification method.
[0024] Comparative Example 2 uses a method where the gas phase at the top of a distillation column (mainly composed of acrylonitrile) is pre-distilled and then distilled in a rectification column. This method achieves high purity, but the pre-distillation in the distillation column leads to a decrease in yield. Furthermore, the acrylonitrile-water azeotropic problem was not addressed, resulting in a high water content in the acrylonitrile.
Claims
1. A method for recovering acrylonitrile during AMPS production, characterized in that: The recovery method includes vacuum distillation, material recycling, and concentrate distillation; The method of vacuum distillation is as follows: ethyl acetate and the residue from the reactor are fed into a stirred tank and stirred evenly. Then, the mixture is fed into a distillation column. An azeotrope of ethyl acetate and water is collected from the top of the column and enters a condenser A. Acrylonitrile is collected from the side stream and, after passing inspection, is transferred to a raw material preparation tank. The concentrate from the bottom of the column enters a distillation column.
2. The method for recovering acrylonitrile in the AMPS production process according to claim 1, characterized in that: In the vacuum distillation method, the mass ratio of ethyl acetate to the residue in the reactor is 0.9–1.1:1.2–1.6; The distillation column is configured with a top temperature of 43–46°C, a bottom temperature of 48–52°C, an internal absolute pressure of 45–55 kPa, and a reflux ratio of 1.8–2.
2.
3. The method for recovering acrylonitrile in the AMPS production process according to claim 1, characterized in that: The material recycling method is as follows: after the azeotrope of ethyl acetate and water enters the condenser A, it is left to stand at room temperature for 1 to 2 hours. The upper layer of ethyl acetate is fed into the stirred tank, mixed with the residual liquid in the tank, and then enters the distillation column to participate in the material recycling. The lower layer of water is discharged.
4. The method for recovering acrylonitrile in the AMPS production process according to claim 1, characterized in that: The method for distilling the concentrate is as follows: after the concentrate enters the distillation column, the upper light components are cooled and fed into the condenser B. After cooling, the concentrate is fed into the stirred tank, and the lower heavy components are discharged.
5. The method for recovering acrylonitrile in the AMPS production process according to claim 1, characterized in that: In the distillation method of the concentrate, the distillation column is controlled with a top temperature of 58-62°C, a bottom temperature of 65-70°C, and an absolute pressure of 70-75 kPa.