Polyacrylonitrile-based activated carbon fiber and method for producing the same

Abstract

The application provides a polyacrylonitrile-based activated carbon fiber and a preparation method thereof, and belongs to the technical field of carbon fibers, and comprises the following steps: S1, polyacrylonitrile fibers are pre-oxidized at 200-300 DEG C for 60-120 min to obtain pre-oxidized filaments; S2, the pre-oxidized filaments are soaked in a solution for 6-24 h; S3, natural air-drying is performed for 24-48 h, and then baking is performed at 100 DEG C for 2-6 h; S4, heating is performed to 600-1200 DEG C under the protection of inert gas, heat preservation is performed, a gas is introduced for carbonization and activation, the activation time is 10-240 min, and the activated carbon fiber is obtained after cooling. The surface pore diameter of the prepared activated carbon fiber can be controlled through the salt solution concentration, and the activated carbon fiber is a kind of activated carbon fiber with rich surface macropores, and the specific surface area of the prepared activated carbon fiber is 600-2000 m 2 / g.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber technology, specifically to a polyacrylonitrile-based activated carbon fiber and its preparation method. Background Technology

[0002] Activated carbon fiber is a highly efficient adsorption material that was successfully developed and gradually industrialized in the early 1960s. It has advantages such as large specific surface area, moderate pore size, uniform distribution, and fast adsorption speed. It is widely used in industries such as medical, water purification, air purification, aviation, military, nuclear industry, and food.

[0003] Activated carbon fiber has a surface covered with micropores. Different pore sizes on the material's surface endow activated carbon fiber with different adsorption properties and applications in various fields. Pores smaller than 2 nm are micropores, those between 2-50 nm are mesopores, and those larger than 50 nm are macropores. Its adsorption capacity for organic gases is several to tens of times higher than that of granular activated carbon in air, and 5 to 6 times higher in aqueous solutions, with an adsorption rate 100 to 1000 times faster. It is a new generation of adsorption material following activated carbon, and its use has only occurred in the last 50 years; only a few countries in the world are capable of producing it. Its products can be in the form of silk, paper, felt, cloth, etc.

[0004] The development and application of high-performance polyacrylonitrile-based, phenolic-based, and pitch-based activated carbon fibers in my country are currently in the laboratory research stage. Major research institutions include the Shanxi Coal Chemistry Institute of the Chinese Academy of Sciences, Tsinghua University, Nanjing University, Tianjin University, Jilin University, Sun Yat-sen University, Beijing University of Chemical Technology, and Donghua University. Research focuses primarily on laboratory preparation processes, modification methods, and experimental evaluation of application effects. However, polyacrylonitrile-based activated carbon fibers generally suffer from a low specific surface area, thus limiting their application.

[0005] Patent CN201611022481.1 discloses a method for preparing polyacrylonitrile-based activated carbon fibers and the application of such activated carbon fibers, including the following steps: (1) pre-oxidizing polyacrylonitrile precursor fibers in an oxidation furnace using a three-stage heat treatment; (2) subjecting the pre-oxidized polyacrylonitrile fibers to a two-stage oxygen-free carbonization treatment. This method involves complex steps and cannot produce polyacrylonitrile-based activated carbon fibers with a high specific surface area.

[0006] Patent CN201310369447.1 discloses a method and application for preparing activated carbon fiber materials with energy storage characteristics from polyacrylonitrile-based pre-oxidized fibers. The steps are as follows: (1) Washing commercially available polyacrylonitrile-based pre-oxidized fibers with water and drying them; (2) Mixing the dried pre-oxidized fibers from step (1) with a strong alkali in a certain proportion, adding a certain amount of water and mixing evenly, drying, controlling the heating rate, activating, and obtaining an activated product; (3) Soaking the activated product obtained in step (2) in hot water, filtering, washing until neutral, vacuum drying, and grinding into powder to obtain activated carbon fiber materials that can be used in electrochemical capacitors. This method is complex to operate and has a high cost. Summary of the Invention

[0007] The purpose of this invention is to provide a polyacrylonitrile-based activated carbon fiber and its preparation method. The surface pore size of the activated carbon fiber prepared by this invention can be controlled by the salt solution concentration, which is 0.5 mol / L-3.0 mol / L, resulting in an activated carbon fiber with abundant macropores on its surface. The specific surface area of ​​the activated carbon fiber can be controlled by the activation temperature, the flow rate of water vapor or a mixture of carbon dioxide and water vapor, and the activation time, so that the specific surface area of ​​the obtained activated carbon fiber is 600-2000 m². 2 / g.

[0008] The technical solution of this invention is implemented as follows:

[0009] This invention provides a method for preparing polyacrylonitrile-based activated carbon fibers, comprising the following steps:

[0010] S1. Pre-oxidize polyacrylonitrile fibers at 200-300℃ for 60-120 min to obtain pre-oxidized filaments;

[0011] S2. Soak the pre-oxidized fiber in the solution for 6-24 hours;

[0012] S3. Let it air dry naturally for 24-48 hours, then bake at 100℃ for 2-6 hours;

[0013] S4. Under inert gas protection, heat to 600-1200℃, hold at that temperature, and introduce gas for carbonization activation. The activation time is 10-240 min. After cooling, activated carbon fibers are obtained.

[0014] As a further improvement of the present invention, the polyacrylonitrile fiber in step S1 is obtained by wet spinning or dry-jet wet spinning of acrylonitrile polymerization solution.

[0015] As a further improvement of the present invention, the solution in step S2 is at least one of magnesium chloride, zinc chloride, and ammonium chloride solution.

[0016] As a further improvement of the present invention, the solute concentration in the solution is 0.5-3.0 mol / L.

[0017] As a further improvement of the present invention, the gas mentioned in step S4 is water vapor, or a mixture of water vapor and carbon dioxide, with a molar ratio of (1-5):1.

[0018] As a further improvement of the present invention, the gas flow rate is 10-100 mL per minute per kilogram of carbon fiber.

[0019] As a further improvement of the present invention, the inert gas in step S4 is N2 gas or Ar gas, and the heating rate under the protection of the inert gas is 5-30℃ / min.

[0020] The present invention further protects a polyacrylonitrile-based activated carbon fiber prepared by the above-described preparation method.

[0021] As a further improvement of the present invention, the specific surface area of ​​the polyacrylonitrile-based activated carbon fiber is 600-2000 m². 2 / g.

[0022] The present invention has the following beneficial effects: The surface pore size of the activated carbon fibers prepared by the present invention can be controlled by the salt solution concentration, which is 0.5 mol / L-3.0 mol / L, resulting in activated carbon fibers with abundant macropores on the surface. The specific surface area of ​​the activated carbon fibers can be controlled by the activation temperature, the flow rate of water vapor or a mixture of carbon dioxide and water vapor, and the activation time, so that the specific surface area of ​​the obtained activated carbon fibers is 600-2000 m². 2 / g. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1

[0025] Polyacrylonitrile (PA) fiber precursors (3K) with a single filament diameter of 15-20 μm were prepared by NaSCN solution polymerization and wet spinning. The PA fibers were pre-oxidized at 200℃ for 100 min; the pre-oxidized fibers were then immersed in a 2 mol / L zinc chloride solution for 12 h; naturally air-dried for 24 h; and pre-dried at 100℃ for 3 h. 200 g of the treated sample was heated to 800℃ under Ar atmosphere at a gas flow rate of 50 mL / min and a heating rate of 10℃ / min. Carbonization activation was then performed by introducing steam at a gas flow rate of 2 mL / min for 30 min. After cooling, activated carbon fibers were obtained with a specific surface area of ​​836 m². 2 / g, pore volume is 0.39mL / g.

[0026] Example 2

[0027] Polyacrylonitrile (PAN) fiber precursors (12K) with a single filament diameter of 15-20 μm were prepared by NaSCN solution polymerization and wet spinning. The PAN fibers were pre-oxidized at 250℃ for 80 min. The pre-oxidized fibers were then immersed in a mixed solution of 2 mol / L zinc chloride and 2 mol / L ammonium chloride (mass ratio 1:1) for 20 h, naturally air-dried for 30 h, and then dried at 100℃ for 4 h. 500 g of the treated sample was heated to 1000℃ under N2 protection at a gas flow rate of 100 mL / min and a heating rate of 15℃ / min. Carbonization activation was then performed by introducing a mixed gas of water vapor and CO2 (molar ratio 2:1) at a gas flow rate of 10 mL / min for 60 min. After cooling, activated carbon fibers were obtained. The specific surface area was 1342 m² / g. 2 / g, pore volume is 0.51mL / g.

[0028] Example 3

[0029] Polyacrylonitrile (PAN) fiber precursors (48K) with a single filament diameter of 8-10 μm were prepared by NaSCN solution polymerization and wet spinning. The PAN fibers were pre-oxidized at 300℃ for 100 min; the pre-oxidized fibers were then immersed in 3 mol / L ammonium chloride solution for 24 h; naturally air-dried for 48 h; and dried at 100℃ for 4 h. 1000 g of the treated sample was heated to 1000℃ under N2 protection at a gas flow rate of 200 mL / min and a heating rate of 20℃ / min. Carbonization activation was then performed by introducing steam at a gas flow rate of 50 mL / min for 30 min. After cooling, activated carbon fibers were obtained with a specific surface area of ​​619 m² / g. 2 / g, pore volume is 0.27mL / g.

[0030] Example 4

[0031] Polyacrylonitrile (PA) fiber precursors (3K) with a single filament diameter of 8-10 μm were prepared by DMSO solution polymerization followed by dry-jet wet spinning. The PA fibers were pre-oxidized at 240℃ for 100 min. The pre-oxidized fibers were then immersed in a mixed solution of 2.5 mol / L magnesium chloride and 3 mol / L zinc chloride (mass ratio 1:1) for 24 h, naturally air-dried for 36 h, and then dried at 100℃ for 4 h. 500 g of the treated sample was heated to 800℃ under N2 protection at a gas flow rate of 80 mL / min and a heating rate of 10℃ / min. Carbonization activation was then performed by introducing steam at a gas flow rate of 15 mL / min for 40 min. After cooling, activated carbon fibers were obtained. The specific surface area was 1123 m² / g. 2 / g, pore volume is 0.43mL / g.

[0032] Example 5

[0033] Polyacrylonitrile (PA) fiber precursors (12K) with a single filament diameter of 8-10 μm were prepared by DMSO solution polymerization followed by dry-jet wet spinning. The PA fibers were pre-oxidized at 220℃ for 120 min. The pre-oxidized fibers were then immersed in a mixed solution of 3 mol / L magnesium chloride and 3 mol / L ammonium chloride (mass ratio 1:1) for 24 h, naturally air-dried for 24 h, and pre-dried at 100℃ for 4 h. 300 g of the treated sample was heated to 900℃ under N2 protection at a gas flow rate of 50 mL / min and a heating rate of 15℃ / min. Carbonization activation was then performed by introducing steam at a gas flow rate of 12 mL / min for 60 min. After cooling, activated carbon fibers were obtained with a specific surface area of ​​1263 m². 2 / g, pore volume is 0.47mL / g.

[0034] Example 6

[0035] Polyacrylonitrile (PA) fiber precursors (3K) with a single filament diameter of 8-12 μm were prepared by DMF solution polymerization followed by dry-jet wet spinning. The PA fibers were pre-oxidized at 260℃ for 90 min. The pre-oxidized fibers were then immersed in a mixed solution of 2 mol / L magnesium chloride, 2 mol / L zinc chloride, and 2 mol / L ammonium chloride (mass ratio 1:1:1) for 24 h, naturally air-dried for 48 h, and pre-dried at 100℃ for 4 h. 100 g of the treated sample was heated to 1000℃ under N2 protection at a gas flow rate of 50 mL / min and a heating rate of 15℃ / min. Carbonization activation was then carried out by introducing a mixed gas of water vapor and CO2 (molar ratio 3:1) at a gas flow rate of 8 mL / min for 60 min. After cooling, activated carbon fibers were obtained. The specific surface area was 1863 m². 2 / g, pore volume is 0.69mL / g.

[0036] Comparative Example 1

[0037] Compared to Example 2, the difference lies in that the pre-oxidized fiber was not subjected to salt solution impregnation treatment but was directly carbonized and activated using a mixture of water vapor and CO2 gas (molar ratio 2:1), resulting in activated carbon fibers with a specific surface area of ​​436 m². 2 / g, pore volume is 0.21mL / g.

[0038] Polyacrylonitrile (PAN) fiber precursors (12K) with a single filament diameter of 15-20 μm were prepared by NaSCN solution polymerization and wet spinning. The PAN fibers were then pre-oxidized at 250℃ for 80 min to obtain pre-oxidized fibers. 500 g of the pre-oxidized fibers were heated to 1000℃ under N2 protection at a gas flow rate of 100 mL / min and a heating rate of 15℃ / min. The temperature was then maintained at this level while introducing a mixed gas of water vapor and CO2 (molar ratio 2:1) at a gas flow rate of 10 mL / min for 60 min. After cooling, activated carbon fibers were obtained with a specific surface area of ​​436 m². 2 / g, pore volume is 0.21mL / g.

[0039] Comparative Example 2

[0040] Compared to Example 5, the difference lies in that the pre-oxidized fiber was not subjected to salt solution impregnation treatment but was directly carbonized and activated using water vapor, resulting in activated carbon fibers with a specific surface area of ​​392 m². 2 / g, pore volume is 0.18mL / g.

[0041] Polyacrylonitrile (PAN) fiber 12K precursor fibers with a single filament diameter of 8-10 μm were prepared by DMSO solution polymerization followed by dry-jet wet spinning. The PAN fibers were pre-oxidized at 220℃ for 120 min to obtain pre-oxidized fibers. 300 g of the pre-oxidized fibers were heated to 900℃ under N2 protection at a gas flow rate of 50 mL / min and a heating rate of 15℃ / min. Carbonization activation was then performed by introducing steam at a gas flow rate of 12 mL / min for 60 min. After cooling, activated carbon fibers were obtained. The specific surface area was 392 m² / g. 2 / g, pore volume is 0.18mL / g.

[0042] Compared with existing technologies, the surface pore size of the activated carbon fibers prepared by this invention can be controlled by the salt solution concentration, which is 0.5 mol / L-3.0 mol / L, resulting in activated carbon fibers with abundant macropores on the surface. The specific surface area of ​​the activated carbon fibers can be controlled by the activation temperature, the flow rate of water vapor or a mixture of carbon dioxide and water vapor, and the activation time, so that the specific surface area of ​​the obtained activated carbon fibers is 600-2000 m². 2 / g.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for producing a polyacrylonitrile-based activated carbon fiber, characterized by, Includes the following steps: S1. Pre-oxidize polyacrylonitrile fibers at 200-300℃ for 60-120 min to obtain pre-oxidized filaments; S2. Soak the pre-oxidized fiber in a solution for 6-24 hours, wherein the solution is at least one of magnesium chloride, zinc chloride, and ammonium chloride, and the solute concentration is 0.5-3.0 mol / L; S3. Allow the soaked pre-oxidized yarn to air dry naturally for 24-48 hours, and then bake it at 100℃ for 2-6 hours; S4. Under inert gas protection, heat to 600-1200℃ at 5-30℃ / min, hold at the temperature and introduce gas for carbonization activation. The gas is water vapor or a mixture of water vapor and carbon dioxide, with a molar ratio of (1-5):

1. The gas flow rate is 10-100mL per kilogram of carbon fiber per minute, and the activation time is 10-240min. The specific surface area of the polyacrylonitrile-based activated carbon fiber prepared is 600-2000 m 2 / g.

2. The method for preparing polyacrylonitrile-based activated carbon fibers according to claim 1, characterized in that, The polyacrylonitrile fiber mentioned in step S1 is obtained by wet spinning or dry-jet wet spinning of acrylonitrile polymerization solution.

3. The method for preparing polyacrylonitrile-based activated carbon fibers according to claim 1, characterized in that, The inert gas mentioned in step S4 is N2 or Ar.

4. A polyacrylonitrile-based activated carbon fiber prepared by the preparation method according to any one of claims 1-3.