A method and apparatus for purifying polyacrylonitrile-based carbon fiber polymerization raw material

Abstract

The application provides a purification method and device for polyacrylonitrile-based carbon fiber polymerization raw materials, which comprises a distillation kettle, a rectifying tower, a vacuum pump, a reflux tank and a product tank, the distillation kettle is connected with the rectifying tower, the rectifying tower is connected with the vacuum pump, the top end of the rectifying tower is connected with the reflux tank, the side surface of the rectifying tower is connected with the product tank, a heating unit is arranged on the distillation kettle, a condenser is arranged between the rectifying tower and the reflux tank, a cooler is arranged between the rectifying tower and the product tank, and a stirrer is arranged in the distillation kettle. The technical problem that organic impurities and metal ions contained in the existing polyacrylonitrile-based high-performance carbon fiber polymerization raw material acrylonitrile cannot be effectively removed, resulting in carbon fiber defects and affecting product performance is solved. The application can be widely applied in the polymerization production of polyacrylonitrile-based high-performance carbon fibers.

Description

Technical Field

[0001] This invention relates to a method for purifying polymer raw materials, and more particularly to a method and apparatus for purifying polyacrylonitrile-based carbon fiber polymer raw materials. Background Technology

[0002] Polyacrylonitrile-based carbon fiber possesses comprehensive material properties such as low density, high strength, high modulus, resistance to high and low temperatures, good electrical conductivity, radiation resistance, good biocompatibility, chemical corrosion resistance, and low coefficient of thermal expansion. It is an important reinforcing material in the field of advanced composite materials and is known as the king of new materials in the 21st century. It is widely used in aerospace, pressure vessels, wind turbine blades, automotive lightweighting, carbon-carbon composite materials, composite cable cores, building reinforcement, and sports and leisure.

[0003] The production of high-performance polyacrylonitrile-based carbon fiber is challenging and involves high technological barriers. Its production hinges on high-quality precursor fibers, which in turn require a high-quality spinning solution. In other words, the polymerization process is fundamental to producing high-performance carbon fiber, and the quality of acrylonitrile, the main raw material for polymerization, is crucial. Currently, domestic acrylonitrile manufacturers produce their products using propylene and ammonia oxidation processes. The superior or first-grade products leaving the factory contain trace amounts of organic impurities such as acetaldehyde, hydrogen cyanide, peroxides, acrolein, acetone, acetonitrile, propionitrile, oxazole, methacrylonitrile, butadiene nitrile, and p-hydroxyanisole (polymerization inhibitor), as well as metallic ions such as copper and iron ions. These impurities sequentially enter the spinning solution, precursor fibers, and carbon fibers during the polymerization reaction, ultimately leading to a decrease in the strength and performance of the carbon fibers. This is because these impurities partially create defects in the precursor fibers and carbon fibers, and these defects cannot be eliminated during subsequent processing. Therefore, acrylonitrile must be purified before the polymerization reaction to effectively remove organic impurities such as acetaldehyde, hydrogen cyanide, peroxides, acrolein, acetone, acetonitrile, propionitrile, oxazole, methacrylonitrile, butadiene nitrile, and p-hydroxyanisole (polymerization inhibitor), as well as metallic ion impurities such as copper and iron ions, in order to produce high-quality, high-performance carbon fibers. Thus, the production of high-performance polyacrylonitrile-based carbon fibers is inseparable from the purification of the polymerization raw material, acrylonitrile.

[0004] CN212187850U ​​introduces a purification device for acrylonitrile, employing vacuum distillation to lower the boiling point of the polymerization raw materials. This facilitates distillation using circulating water with low-pressure steam as the primary heat source to heat the reboiler, improving the utilization efficiency of the low-pressure steam's thermal energy and achieving energy conservation and emission reduction. Lowering the distillation temperature also facilitates the recovery of heat dissipation after condensation of the evaporated raw materials through a heat exchanger, utilizing waste heat to achieve energy conservation and emission reduction. A scrubbing system absorbs trace amounts of uncondensed polymerization raw material vapor, preventing it from entering the atmosphere and causing pollution. Nitrogen gas is added to the system during distillation to disrupt and regulate the vacuum, simultaneously preventing the raw materials from self-polymerizing.

[0005] The aforementioned literature describes a purification device for acrylonitrile, but this device can only partially remove high-boiling-point substances, including polymerization inhibitors. It does not target small-molecule organic compounds such as acetaldehyde, hydrogen cyanide, acrolein, and acetone in acrylonitrile. Furthermore, high-boiling-point impurities such as p-hydroxyanisole (polymerization inhibitor), copper ions, and iron ions at the bottom of the tower are difficult to completely remove. Oxazoles and acetonitrs, which have boiling points close to acrylonitrile, cannot be removed at all. Therefore, the acrylonitrile purification in this patent is not complete. Summary of the Invention

[0006] This invention addresses the technical problem that organic impurities and metal ions contained in acrylonitrile, the raw material for high-performance polyacrylonitrile-based carbon fiber polymerization, cannot be effectively removed, causing carbon fiber defects and affecting product performance. It provides a purification method and apparatus for polyacrylonitrile-based carbon fiber polymerization raw materials that can effectively remove organic matter and metal ions from acrylonitrile that have a harmful effect on carbon fibers, improve acrylonitrile purity, and further ensure carbon fiber performance.

[0007] Therefore, the technical solution of the present invention is a purification device for polyacrylonitrile-based carbon fiber polymerization raw materials, comprising a distillation kettle, a distillation column, a vacuum pump, a reflux tank, and a product tank. The distillation kettle is connected to the distillation column, the distillation column is connected to the vacuum pump, the top of the distillation column is connected to the reflux tank, the side of the distillation column is connected to the product tank, a heating unit is provided on the distillation kettle, a condenser is provided between the distillation column and the reflux tank, a cooler is provided between the distillation column and the product tank, and a stirrer is provided inside the distillation kettle.

[0008] Preferably, the heating unit is a jacket, which is located outside the distillation vessel, and a steam feed pipe is provided at the bottom of the jacket.

[0009] Preferably, the distillation column is located at the upper end of the distillation vessel, the upper part of the distillation vessel is provided with an acrylonitrile inlet and a sodium hydroxide solution inlet, the distillation vessel is also provided with a vapor condensate outlet, and the bottom of the distillation vessel is provided with a discharge pipe.

[0010] Preferably, the distillation column is equipped with packing and trays, a demister made of metal wire mesh, a side outlet, and a collection tray at the position corresponding to the side outlet.

[0011] A purification method for polyacrylonitrile-based carbon fiber polymerization raw materials involves mixing industrial acrylonitrile and sodium hydroxide solution evenly in a distillation kettle, followed by distillation in a distillation column using negative pressure distillation to remove impurities in acrylonitrile that affect the polymerization reaction in carbon fiber precursor production. The method includes the following steps:

[0012] (2) Pretreatment: Under the protection of inert nitrogen gas, acrylonitrile for industrial production is added to a distillation vessel equipped with a stirrer, sodium hydroxide solution is added to the distillation vessel, and the stirrer is started to stir the mixture so that the acrylonitrile and sodium hydroxide aqueous solution in the distillation vessel are fully mixed.

[0013] (2) Removal of light components: Start the vacuum pump to evacuate the distillation kettle and the distillation column, and heat the distillation kettle at the same time. Under negative pressure, heat the acrylonitrile in the distillation kettle and distill it. Light component impurities and some acrylonitrile are collected through the top of the distillation column and condensed by the condenser before entering the reflux tank.

[0014] (3) Removal of heavy components: Continue heating the distillation kettle, collect acrylonitrile at the collection plate, and then collect acrylonitrile through the side outlet. After being cooled by the cooler, the acrylonitrile enters the product tank to complete the purification of acrylonitrile.

[0015] Preferably, in steps (2) and (3), the distillation vessel is heated by introducing steam into the jacket through the steam feed line at the bottom of the distillation vessel to raise the temperature inside the distillation vessel; or by using an external heat exchanger to heat the distillation vessel.

[0016] Preferably, in step (1), the mass concentration of the added sodium hydroxide solution is in the range of 5% to 8%, and the weight ratio of the added sodium hydroxide solution to the acrylonitrile in the distillation vessel is in the range of 1:2000 to 1:1500.

[0017] Preferably, in steps (2) and (3), the distillation column and the distillation kettle are operated under negative pressure by a vacuum pump. The operating pressure at the top of the distillation column is 20 kPaA and the operating temperature is 33°C. The operating pressure of the distillation kettle is 40-50 kPaA and the operating temperature is 50.9-56.8°C.

[0018] Preferably, in steps (2) and (3), the cold source for the condenser and the cooler is low-temperature water at 7-17°C.

[0019] The beneficial effects of this invention are:

[0020] (1) By thoroughly mixing sodium hydroxide solution with acrylonitrile raw material, it can solidify acidic substances, p-hydroxyanisole (polymerization inhibitor) and copper and iron ions in acrylonitrile. After mixing, distillation can effectively remove organic impurities such as acetaldehyde, hydrogen cyanide, peroxide, acrolein, acetone, acetonitrile, propionitrile, oxazole, methacrylonitrile, butenyl nitrile, p-hydroxyanisole (polymerization inhibitor) and metal ion impurities such as copper and iron ions from acrylonitrile raw material, and obtain acrylonitrile with oxazole content less than 3 ppm, acetonitrile content less than 5 ppm, methacrylonitrile content less than 5 ppm and no other impurities. Since oxazole, acetonitrile and methacrylonitrile have similar boiling points to acrylonitrile and cannot be completely removed, but acetonitrile and methacrylonitrile have similar structures to acrylonitrile and have a content of less than 5 ppm, so they have no effect on the polymerization reaction of acrylonitrile.

[0021] (2) By setting a liquid collection tray at the side outlet of the distillation column, the product can be easily collected through the side outlet. By using a metal wire mesh demister, the liquid entrainment of heavy components in the collected acrylonitrile can be effectively reduced. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the device used in Embodiments 1-4 of the present invention.

[0023] Explanation of symbols in the diagram:

[0024] 1. Distillation vessel; 2. Stirrer; 3. Distillation vessel jacket; 4. Distillation column; 5. Vacuum pump; 6. Condenser; 7. Reflux tank; 8. Reflux pump; 9. Cooler; 10. Product tank; 11. Product pump; 12. Packing; 13. Collection tray; 14. Demister; 15. Acrylonitrile feed line; 16. Sodium hydroxide solution feed line; 17. Residue discharge line; 18. Steam feed line; 19. Steam condensate discharge line; 20. High-concentration light component acrylonitrile conveying line; 21. Purified acrylonitrile conveying line; 22. Side discharge port. Detailed Implementation

[0025] The present invention will be further described below with reference to embodiments.

[0026] like Figure 1As shown, a purification device for polyacrylonitrile-based carbon fiber polymerization raw materials includes a distillation kettle 1, a distillation column 4, a vacuum pump 5, a reflux tank 7, and a product tank 10. The distillation kettle 1 is connected to the distillation column 4, the distillation column 4 is connected to the vacuum pump 5, the top of the distillation column 4 is connected to the reflux tank 7, and the side of the distillation column 4 is connected to the product tank 10. The distillation kettle 1 is equipped with a heating unit. A condenser 6 is provided between the distillation column 4 and the reflux tank 7, and a cooler 9 is provided between the distillation column 4 and the product tank 10. Both the condenser 6 and the cooler 10 are connected to low-temperature water at 7-17℃ as a cold source. A stirrer 2 is provided inside the distillation kettle 1, and the stirrer 2 includes, but is not limited to, paddle-type and anchor-type stirrers.

[0027] The heating unit can be a jacket 3, located outside the distillation vessel 1, with a steam feed line 18 at the bottom. Other heating methods, such as an external heat exchanger, can also be used. The distillation column 4 is located above the distillation vessel 1. An acrylonitrile feed line 15 and a sodium hydroxide solution feed line 16 are located on the upper part of the distillation vessel 1 for adding acrylonitrile feedstock and sodium hydroxide solution to the distillation vessel 1. A steam condensate discharge line 19 is also provided on the distillation vessel 1, and a vessel residue discharge line 17 is located at the bottom of the distillation vessel 1.

[0028] The distillation column 4 is equipped with packing 12 and trays. The packing 12 is either random packing or structured packing. The distillation column 4 is equipped with a metal wire mesh demister 14 to reduce the liquid entrainment of heavy components in the acrylonitrile. The distillation column 4 is equipped with a side stream outlet 22. A liquid collection tray 13 is installed at the position corresponding to the side stream outlet 22 in the distillation column 4 to facilitate the side stream collection of the finished product.

[0029] Example 1

[0030] A purification method for polyacrylonitrile-based carbon fiber polymerization raw materials involves mixing acrylonitrile raw materials and sodium hydroxide solution in a distillation vessel 1 using a stirrer 2, followed by distillation in a distillation column 4 under negative pressure to remove impurities from the acrylonitrile raw materials that affect the polymerization reaction in carbon fiber precursor production. The method includes the following steps:

[0031] (1) Pretreatment: Under the protection of inert nitrogen gas, the acrylonitrile material is transported to the distillation vessel 1 equipped with a stirrer 2. In this embodiment, the composition of the acrylonitrile raw material is determined to be: acrylonitrile 99.6%, water 0.37%, acidity (calculated as acetic acid) 5ppm, total aldehyde (calculated as acetaldehyde) 8ppm, total cyanide (calculated as hydrogen cyanide) 2ppm, acrolein 5ppm, acetone 10ppm, oxazole 10ppm, acetonitrile 29ppm, methacrylonitrile 80ppm, propionitrile 10ppm, butadiene nitrile 19ppm, p-hydroxyanisole 37ppm, peroxide (calculated as hydrogen peroxide) 0.18ppm, copper ions 0.05ppm, and iron ions 0.06ppm. Add a 5% sodium hydroxide solution to distillation vessel 1. The weight ratio of the added sodium hydroxide solution to acrylonitrile is 1:2000. Start stirrer 2 and stir for 0.5 hours to fully mix the sodium hydroxide solution with the acrylonitrile raw material. This can solidify impurities such as acidic substances, p-hydroxyanisole (polymerization inhibitor), and copper and iron ions in acrylonitrile.

[0032] (2) Removal of light components: The distillation column 4 has 50 trays, and a side outlet 22 is located at the position of the 30th tray. The vacuum pump 5 is started, and steam is introduced into the jacket 3 of the distillation vessel. The operating pressure at the top of the distillation column 4 is set to 20 kPaA, the operating temperature at the top of the distillation column 4 is set to 33°C, the operating pressure at the distillation vessel 1 is set to 50 kPaA, and the operating temperature at the distillation vessel 1 is set to 56.8°C. Steam is slowly introduced into the steam feed line 18 through the distillation vessel jacket 3 for heating. The light components in acrylonitrile are slowly distilled off from the top of the distillation column 4, condensed by the condenser 6, and then enter the reflux tank 7. The liquid in the reflux tank 7 is partially pumped into the distillation column 4 by the reflux pump 8, and partially pumped into the high-concentration light component acrylonitrile delivery line 20. The reflux ratio is set to 2. After slow distillation for 0.5 hours, when the liquid in the reflux tank 7 reaches 10% of the acrylonitrile added to the distillation vessel 1, the condensate from the top condenser 6 of the distillation column 4 is changed from entering the reflux tank 7 to being completely refluxed back into the distillation column 4.

[0033] (3) Removal of heavy components: Continue to slowly heat the distillation vessel 1, collect acrylonitrile at the collection pan 13, and then gradually extract acrylonitrile through the side outlet 22. After being cooled by the cooler 9, the purified acrylonitrile enters the product tank 10, and the purified acrylonitrile is transported to the subsequent polymerization process by the product pump 11. When the acrylonitrile in the product tank 10 reaches 70% of the acrylonitrile added to the distillation vessel 1, the side outlet is stopped, and the high concentration of heavy component acrylonitrile remaining in the distillation vessel 1 is discharged from the bottom discharge line 17.

[0034] The composition of acrylonitrile in product tank 10 was determined to be: acrylonitrile 99.58%, water 0.41%, oxazole 1.2 ppm, acetonitrile 4 ppm, and methacrylonitrile 5 ppm. Acidity, total aldehydes, total cyanides, acrolein, acetone, propionitrile, butadiene nitrile, p-hydroxyanisole, peroxides, copper ions, and iron ions were not detected.

[0035] Example 2

[0036] Compared with Example 1, the difference in Example 2 is that the acrylonitrile material is fed into the distillation vessel 1, and an 8% sodium hydroxide solution is added at 1 / 1500 of the mass of the acrylonitrile material.

[0037] Distillation column 4 has 50 trays, with a side feed outlet 22 located at the 30th tray position. Agitator 2 is started and stirred for 0.5 hours. Vacuum pump 5 is started, and the operating pressure at the top of distillation column 4 is set to 20 kPaA, and the operating temperature to 33°C. The operating pressure of retort 1 is set to 50 kPaA, and the operating temperature of retort 4 is set to 56.8°C. Steam is slowly introduced into the retort jacket 3 for heating. The light components of acrylonitrile are slowly distilled from the top of distillation column 4, condensed by condenser 6, and then enter reflux tank 7. The reflux is then pumped back to the top of distillation column 4 by reflux pump 8, with a reflux ratio set to 2. After slow distillation for 0.5 hours, the liquid in reflux tank 7 reaches 10% of the acrylonitrile added to retort 1. The condensate from the top condenser 6 is then redirected from entering reflux tank 7 to being completely refluxed back into distillation column 4.

[0038] The composition of acrylonitrile in product tank 10 was determined to be: acrylonitrile 99.56%, water 0.43%, oxazole 1.5ppm, acetonitrile 3ppm, and methacrylonitrile 3.8ppm. Acidity, total aldehydes, total cyanides, acrolein, acetone, propionitrile, butadiene nitrile, p-hydroxyanisole, peroxides, copper ions, and iron ions were not detected.

[0039] Example 3

[0040] Compared with Example 1, the difference in Example 3 is that the distillation column 4 has 40 trays and a side outlet 22 is located at the position of the 25th tray. The pressure at the top of the column is the same as in Example 1. Due to the reduction in the number of trays, the pressure at the bottom of the column is reduced.

[0041] Acrylonitrile material is fed into distillation vessel 1. A 5% sodium hydroxide solution is added at 1 / 2000 of the acrylonitrile material mass, and stirrer 2 is started for 0.5 hours. Vacuum pump 5 is started, and the operating pressure at the top of distillation column 4 is set to 20 kPaA, the operating temperature at the top of the column is set to 33°C, the operating pressure at distillation vessel 1 is set to 40 kPaA, and the operating temperature at distillation vessel 1 is set to 50.9°C. Steam is slowly introduced into the jacket of distillation vessel 3 for heating. The lighter components of acrylonitrile are slowly distilled off from the top of the column, condensed by condenser 6, and then enter reflux tank 7. The reflux is then pumped back to the top of the column by reflux pump 8, with a reflux ratio set to 2. After slow distillation for 0.5 hours, the liquid in reflux tank 7 reaches 10% of the acrylonitrile added to distillation vessel 1. The condensate from the top of condenser 6 is then switched from entering reflux tank 7 to being completely refluxed back into distillation column 4.

[0042] The composition of acrylonitrile in product tank 10 was determined to be: acrylonitrile 99.53%, water 0.46%, oxazole 0.9ppm, acetonitrile 2ppm, and methacrylonitrile 4.5ppm. Acidity, total aldehydes, total cyanides, acrolein, acetone, propionitrile, butadiene nitrile, p-hydroxyanisole, peroxides, copper ions, and iron ions were not detected.

[0043] Example 4

[0044] Compared with Example 1, Example 4 differs in that the distillation column 4 has 50 trays and a side outlet 22 is located at the position of the 25th tray.

[0045] Acrylonitrile material is fed into distillation vessel 1. A 5% sodium hydroxide solution is added at 1 / 2000 of the acrylonitrile material mass. Stirring is started by agitator 2 for 0.5 hours. Vacuum pump 5 is started, and the operating pressure at the top of distillation column 4 is set to 20 kPaA, and the operating temperature at the top of the column is set to 33°C. The operating pressure at distillation vessel 1 is set to 50 kPaA, and the operating temperature at distillation vessel 1 is set to 56.8°C. Steam is slowly introduced into the jacket 3 of the distillation vessel for heating. The lighter components of acrylonitrile are slowly distilled off from the top of distillation column 4, condensed by condenser 6, and then enter reflux tank 7. The reflux is then pumped back to the top of distillation column 4 by reflux pump 8, with a reflux ratio set to 2. After slow distillation for 0.5 hours, when the liquid in reflux tank 7 reaches 10% of the acrylonitrile added to distillation vessel 1, the condensate from the top of distillation column 4 condenser 6 is changed from entering reflux tank 7 to being completely refluxed back into distillation column 4.

[0046] The composition of acrylonitrile in product container 10 was determined to be: acrylonitrile 99.43%, water 0.55%, oxazole 2.5ppm, acetonitrile 3ppm, and methacrylonitrile 6ppm. Acetic acid, acetaldehyde, hydrogen cyanide, acrolein, acetone, propionitrile, butadiene nitrile, p-hydroxyanisole, peroxide, copper ions, and iron ions were not detected.

[0047] The main parameters of the purification methods in Examples 1-4 are shown in Table 1, and the test results are shown in Table 2. By comparison, it can be seen that when the mass ratio of acrylonitrile material to sodium hydroxide solution is 1 / 2000 to 1 / 500, the mass concentration of sodium hydroxide solution is 5% to 10%, the operating temperature of distillation vessel 1 is 43.7 to 56.8℃, the operating pressure is 30 to 50 kPaA, the top temperature of distillation column 4 is 18.4 to 33℃, the top pressure is 10 to 20 kPaA, the number of trays is 30 to 50, the side outlet 22 is located at 1 / 2 to 2 / 3 of the total number of trays, and the reflux ratio is 1 to 2.5, acrylonitrile raw material containing organic impurities and metal ion impurities such as copper ions and iron ions can be purified into finished acrylonitrile with oxazole content less than 3 ppm, acetonitrile content less than 5 ppm, methacrylonitrile content less than 5 ppm, and no other impurities. Since oxazole, acetonitrile, and methacrylonitrile have similar boiling points to acrylonitrile and cannot be completely removed, but acetonitrile and methacrylonitrile have similar structures to acrylonitrile and their content is less than 5 ppm, they have no effect on the polymerization reaction of acrylonitrile and can be widely used in the polymerization production of polyacrylonitrile-based high-performance carbon fibers.

[0048] Table 1 Comparison of Parameters in Examples

[0049]

[0050]

[0051] Table 2 Comparison of Detection Results of Examples

[0052]

[0053] However, the above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the present invention. Therefore, any substitution of equivalent components or equivalent changes and modifications made in accordance with the scope of protection of the present invention should still fall within the scope of the claims of the present invention.

Claims

1. A method for purifying polyacrylonitrile-based carbon fiber polymerization raw materials, characterized in that, After the acrylonitrile raw material and sodium hydroxide solution are stirred and mixed evenly in a distillation kettle, they are then distilled in a distillation column using negative pressure distillation to remove impurities in the acrylonitrile that affect the polymerization reaction in the production of carbon fiber precursor. This process includes the following steps: (1) Pretreatment: Under the protection of inert nitrogen gas, acrylonitrile for industrial production is added to a distillation vessel equipped with a stirrer, sodium hydroxide solution is added to the distillation vessel, and the stirrer is started to stir the mixture so that the acrylonitrile and sodium hydroxide aqueous solution in the distillation vessel are fully mixed. (2) Removal of light components: Start the vacuum pump to evacuate the distillation kettle and the distillation column, and heat the distillation kettle at the same time. Under negative pressure, heat the acrylonitrile in the distillation kettle and distill it. Light component impurities and some acrylonitrile are collected through the top of the distillation column and condensed by the condenser before entering the reflux tank. (3) Removal of heavy components: Continue heating the distillation kettle, collect acrylonitrile at the collection plate, and then collect acrylonitrile through the side outlet. After being cooled by the cooler, the acrylonitrile enters the product tank to complete the purification of acrylonitrile.

2. The purification method for polyacrylonitrile-based carbon fiber polymerization raw materials according to claim 1, characterized in that, In steps (2) and (3), the distillation vessel is heated by introducing steam into the jacket through the steam feed line at the bottom of the distillation vessel to raise the temperature inside the distillation vessel; or by using an external heat exchanger to heat the distillation vessel.

3. The purification method for polyacrylonitrile-based carbon fiber polymerization raw materials according to claim 1, characterized in that, In step (1), the mass concentration of the added sodium hydroxide solution ranges from 5% to 8%, and the weight ratio of the added sodium hydroxide solution to the acrylonitrile in the distillation vessel ranges from 1:2000 to 1:1500.

4. The purification method for polyacrylonitrile-based carbon fiber polymerization raw materials according to claim 1, characterized in that, In steps (2) and (3), the distillation column and the distillation kettle are operated under negative pressure by a vacuum pump. The operating pressure at the top of the distillation column is 20 kPaA and the operating temperature is 33°C. The operating pressure of the distillation kettle is 40-50 kPaA and the operating temperature is 50.9-56.8°C.

5. The purification method for polyacrylonitrile-based carbon fiber polymerization raw materials according to claim 1, characterized in that, In steps (2) and (3), the cold source for the condenser and the cooler is low-temperature water at 7-17°C.

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