A porous asphalt-based carbon fiber and preparation method thereof

Abstract

The present invention provides porous asphalt-based carbon fibers and a method for preparing the same. The preparation method comprises the steps of: dissolving pretreated asphalt and sulfur in carbon disulfide; spinning the asphalt fiber precursor after the reaction; and carbonizing the asphalt fiber precursor to obtain porous asphalt-based carbon fibers. The present invention develops a process for preparing porous carbon fibers by uniformly mixing asphalt with a softening point of 120-180°C with sulfur, spinning the mixture, and then directly carbonizing the mixture. The present invention employs the addition of sulfur to the asphalt as a crosslinking agent, addressing issues such as adhesion between carbon fibers, inconsistent oxidation levels inside and outside the fibers, decreased fiber performance, and the difficulty in preparing porous carbon fibers.

Description

Technical Field

[0001] The invention relates to a porous asphalt-based carbon fiber and a preparation method thereof, belonging to the technical field of functional carbon fiber preparation. Background Art

[0002] Battery energy storage power stations are systems that use electrochemical cells to store, convert, and release cyclical electrical energy. These energy storage systems can be connected to the grid as standalone systems, providing peak load shifting and off-peak power, as well as backup power. They can also be combined with renewable energy sources to form wind, solar, and energy storage systems, smoothing power generation and consumption, or forming microgrids to improve energy utilization, power quality, and power supply reliability. Battery energy storage power stations often use lead-acid batteries, which offer advantages such as low cost and high current discharge capability, but also suffer from low efficiency and high overall weight. Lithium or lithium-ion batteries, while offering high efficiency, also come with significant cost increases and poor safety. Therefore, improving lead-acid batteries to increase storage efficiency and reduce weight is currently the preferred approach for battery energy storage power stations. Research has found that lead-acid battery plates made of porous carbon fibers are particularly effective in reducing overall weight and improving energy storage power station efficiency compared to lead plates, and also have a positive impact on battery life.

[0003] Porous carbon fiber plates can achieve high energy density and high electron / ion charging rates. When combined with materials such as lead oxide (PbO2), they are used as energy storage materials, enabling porous carbon fibers to store large amounts of energy. When the porous carbon fibers are immersed in a PbSO4 solution and used as the negative electrode for charging, a thin layer of carbon is first corroded away, and the resulting lead then anchors to the remaining carbon, forming a thin coating approximately 2 nanometers thick. This structure increases the charging and discharging rates. Tests have shown that lead-acid batteries using porous carbon fiber plates can load up to 7 mg / cm2 of lead before performance degrades. This represents 84% of the material's theoretical limit and nearly three times the amount of lead currently available to industry.

[0004] Asphalt is a relatively low-cost raw material for carbon fiber production. Currently, asphalt-based carbon fibers are produced by spinning asphalt into precursor fibers and then subjecting them to oxidation and carbonization heat treatment. Oxidation is typically performed using air oxidation, but this method has drawbacks. The required oxidation temperature for asphalt is relatively high, typically above 250°C, while asphalt has a relatively low softening point, typically below 150°C. This leads to significant melting of the asphalt before the oxidation temperature is reached, causing adhesion and slubbing between fibers, which in turn degrades the performance of the resulting carbon fibers. Some researchers have attempted to increase the softening point of asphalt by oxidizing it, aiming to match the oxidation temperature with the softening point. However, this has also resulted in decreased spinning performance. Furthermore, since asphalt precursor fibers undergo a stepwise oxidation process from the outside in, the outer layer transforms into a cross-linked, macromolecular structure, which prevents oxygen molecules from flowing inward. As a result, the interior of the fiber remains composed of the asphalt's small molecular structure, resulting in inconsistent oxidation levels. This results in poor uniformity in the carbon fiber's performance, further exacerbating the performance degradation. Importantly, producing porous carbon fibers from asphalt is challenging. Using shaped spinnerets, only large, continuous axial through-holes can be produced, not radial pores.

[0005] The present invention is proposed to solve the above-mentioned problems. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention provides porous pitch-based carbon fibers and a method for preparing the same. The present invention develops a process for producing porous carbon fibers by uniformly mixing pitch with a softening point of 120-180°C with sulfur, spinning the mixture, and then directly carbonizing the mixture to produce the porous carbon fibers. By adding sulfur to the pitch as a crosslinking agent, the present invention addresses the issues of adhesion between carbon fibers, inconsistent oxidation levels inside and outside the fibers, decreased fiber performance, and the difficulty in preparing porous carbon fibers.

[0007] The technical solutions of the present invention are as follows:

[0008] A porous asphalt-based carbon fiber having a fiber diameter of 5-20 μm, a tensile strength of ≥200 MPa, and a specific surface area of ≥2900 m 2 / g, specific pore volume ≥0.9cm 3 / g.

[0009] According to the preferred embodiment of the present invention, the carbon fiber has a fiber diameter of 8-12 μm, a tensile strength of 209-271 MPa, and a specific surface area of 2907-3629 m 2 / g, and the specific pore volume is 0.96-1.27cm 3 / g.

[0010] The method for preparing the porous pitch-based carbon fiber comprises the following steps:

[0011] (1) Dissolving the pretreated asphalt and sulfur in carbon disulfide; after the reaction, spinning to obtain asphalt fiber precursor;

[0012] (2) Asphalt fiber precursors can be carbonized to produce porous asphalt-based carbon fibers.

[0013] Preferably, in step (1) of the present invention, the asphalt pretreatment method comprises the following steps: crushing the asphalt and passing it through a 300-500 mesh sieve, removing moisture and then cooling; then dissolving the asphalt in kerosene and filtering; and drying, crushing and passing the obtained filtrate through a 500 mesh sieve to obtain pretreated asphalt.

[0014] Preferably, the softening point of the asphalt is 120-180°C.

[0015] Preferably, the method for removing moisture is: maintaining the temperature at 100-120° C. for 5-20 minutes.

[0016] Preferably, the mass ratio of kerosene to asphalt after dehydration is 100:(5-25); and the dissolution temperature is 150-250°C.

[0017] Preferably, the filtration is performed using a 1 μm microporous filter.

[0018] According to a preferred embodiment of the present invention, in step (1), the sulfur is further subjected to a step of passing through an 800-mesh sieve before use.

[0019] Preferably, according to the present invention, in step (1), the mass ratio of the pretreated asphalt to sulfur is 100:(5-20).

[0020] Preferably, according to the present invention, in step (1), the mass ratio of the pretreated asphalt to carbon disulfide is (5-25):100.

[0021] According to the present invention, preferably, in step (1), after the pretreated asphalt and sulfur are dissolved in carbon disulfide, a drying step is also included to remove carbon disulfide mixed in the asphalt, because the presence of carbon disulfide will affect subsequent spinning.

[0022] According to a preferred embodiment of the present invention, in step (1), the reaction temperature is 120-250°C, the reaction time is 20-40 minutes, and the reaction is carried out under the protection of an inert gas. Preferably, the inert gas is nitrogen or argon.

[0023] Preferably, according to the present invention, in step (1), the spinning temperature is 150-250° C., the spinning pressure is 0.50-5.00 MPa, the drawing rate is 200-500 m / min, and the spinning is carried out in air.

[0024] According to the preferred embodiment of the present invention, in step (2), the carbonization temperature is 900-1200°C, the constant temperature time is 10-60 minutes, the heating rate is 5-30°C / minute, and the carbonization atmosphere is an inert gas; preferably, the carbonization atmosphere is nitrogen or argon.

[0025] The process principle of the present invention:

[0026] 1. The melting point of sulfur is 113 degrees, and the softening point of asphalt is 120-180 degrees. After sulfur and asphalt are mixed and heated appropriately, the asphalt undergoes a cross-linking reaction in the presence of the cross-linking agent sulfur, which transforms the asphalt into a planar network macromolecule. The softening point of the asphalt is increased, and the shaping and ductility of the asphalt are improved, which is beneficial to the spinning of the asphalt.

[0027] 2. As the temperature rises during the carbonization process, the molecular weight of this planar network of macromolecular pitch increases, transforming the pitch from a thermoplastic resin into a thermosetting resin that does not deform at high temperatures. This allows the fiber to maintain its shape even at high temperatures, and subsequent higher temperatures transform the fiber into a carbon fiber. Furthermore, because the sulfur and pitch are evenly distributed within the fiber strands, the crosslinking reaction is balanced, eliminating the uneven oxidative crosslinking reaction inside and outside the fiber strands caused by air oxidation, thus ensuring consistent fiber performance.

[0028] 3. As the temperature continues to rise during the carbonization process, the sulfur inside the fiber seizes the hydrogen in the asphalt molecules to generate hydrogen sulfide, and seizes the carbon in the asphalt molecules to generate carbon disulfide. Together with the small molecular hydrocarbons generated by the high-temperature decomposition of the original asphalt molecules, these compounds can be released from the fiber by increasing the heating rate, generating a large number of holes at different positions inside and on the surface of the fiber, thereby turning the fiber into a porous carbon fiber.

[0029] Technical features and beneficial effects of the present invention

[0030] 1. The present invention adopts medium-temperature or high-temperature asphalt with a softening point of 120 to 180 degrees. First, by mixing asphalt with sulfur and raising the temperature, the softening point of the asphalt is increased, the plasticity and ductility of the asphalt are improved, which is beneficial to the spinning of the asphalt, making the spinning effect better, avoiding adhesion and bamboo knots between fibers, and improving the performance of carbon fibers; second, during the subsequent heat treatment (i.e., carbonization treatment), the sulfur and the asphalt continue to cross-link, so that the inside and outside of the asphalt raw fiber become an insoluble and infusible network planar macromolecular structure, eliminating the oxygen oxidation process, thereby preventing the internal and external unevenness of the oxidation reaction with oxygen; third, by controlling the temperature and heating rate of the carbonization treatment, during the high-temperature heat treatment, sulfides and small molecular decomposition products escape from different directions of the fiber and leave holes, so that the fiber becomes a multi-directional porous carbon fiber with pores of different sizes, solving the problem that it is difficult to manufacture porous carbon fibers with asphalt.

[0031] 2. The present invention utilizes medium- or high-temperature asphalt with a softening point of 120-180°C, which is relatively inexpensive. Furthermore, the crosslinking reaction between asphalt and sulfur within this temperature range is relatively mild, preventing a violent reaction that would affect crosslinking uniformity at various locations. Violent reactions are exothermic, and while heat from the reaction vessel is easily dissipated at the edges, heat from the interior is less readily dissipated, leading to increased reaction heterogeneity. The asphalt of the present invention requires pretreatment; otherwise, it will contain a high ash content, making spinning difficult. The ratio of asphalt to sulfur must be appropriate. If the ratio is not appropriate, the mechanical properties and specific surface area of the resulting carbon material will be significantly reduced. Furthermore, if sulfur is not added, the porosity effect will be poor, significantly reducing the performance of the resulting carbon material. The carbonization process of the present invention requires an appropriate carbonization temperature. If the carbonization temperature is too low, the mechanical properties of the resulting carbon material will be significantly reduced, resulting in a low specific surface area and porosity. If the carbonization temperature is too high, the mechanical properties of the resulting carbon material will also be reduced, while energy consumption and costs will also increase.

[0032] 3. The porous carbon fibers prepared using the process of the present invention have controllable porosity, high porosity, and a large specific surface area. They exhibit excellent mechanical properties, with a tensile strength exceeding 200 MPa. Lead-acid battery plates prepared using these materials have high charge and discharge efficiency and a large electrolyte absorption capacity. Furthermore, because the porous carbon fiber plates weigh only one-sixth of those of lead plates, the plate supports within the lead-acid battery can be greatly simplified, reducing the overall weight of the lead-acid battery and lowering overall production and storage and transportation costs. These materials are particularly suitable for the integrated transportation of energy storage components in energy storage power stations. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is the axial SEM image of the carbon fiber prepared in Example 6.

[0034] Figure 2 This is the cross-sectional SEM image of the carbon fiber prepared in Example 6.

[0035] Figure 3 This is the cross-sectional SEM image of the carbon fiber prepared in Comparative Example 4. DETAILED DESCRIPTION

[0036] The technical solution of the present invention will be further described below in conjunction with the embodiments and drawings, but the protection scope of the present invention is not limited thereto.

[0037] In the examples, the raw materials and reagents used are commercially available unless otherwise specified; the methods described are all existing methods unless otherwise specified.

[0038] Source of raw materials

[0039] The asphalt was produced by Shandong Ruicheng Aerospace Carbon Material Co., Ltd., with a softening point of 120-180°C and a density of 1.21 g / cm 3 .

[0040] Example 1

[0041] A method for preparing porous pitch-based carbon fiber comprises the following steps:

[0042] (1) Asphalt with a softening point of 120°C was crushed and passed through a 300-mesh sieve, kept at 105°C for 10 minutes to remove moisture, and then cooled;

[0043] (2) The cooled anhydrous asphalt was dissolved in kerosene at 150°C, with the mass ratio of kerosene to anhydrous asphalt being 100:5. The mixture was filtered through a 1 μm microporous filter while hot, and the filtrate was dried and the asphalt was crushed again. The asphalt was sieved through a 500-mesh stainless steel sieve to obtain pretreated asphalt.

[0044] (3) Sieve the sulfur powder through an 800-mesh stainless steel sieve;

[0045] (4) The pretreated asphalt and the sieved sulfur are mixed in a weight ratio of 100:5, and then dissolved in carbon disulfide (the mass ratio of the pretreated asphalt to carbon disulfide is 5:100), stirred, dried, and placed in a spinning cylinder;

[0046] (5) The spinning cylinder was heated to 150°C and nitrogen was introduced to maintain the temperature for 30 minutes; the pitch fiber precursor was obtained by spinning at a pressure of 0.50 MPa, a drawing rate of 500 m / min, a spinning temperature of 150°C, and a nitrogen spinning atmosphere;

[0047] (6) The asphalt fiber precursor is placed in a carbonization furnace, and the temperature is raised to 900°C at a rate of 5°C / min under nitrogen protection. After being kept at this temperature for 10 minutes, the porous carbon fiber is obtained.

[0048] Example 2

[0049] A method for preparing porous pitch-based carbon fiber comprises the following steps:

[0050] (1) Asphalt with a softening point of 120°C was crushed and passed through a 400-mesh sieve, kept at 105°C for 10 minutes to remove moisture, and then cooled;

[0051] (2) The cooled anhydrous asphalt was dissolved in kerosene at 200°C, with the mass ratio of kerosene to anhydrous asphalt being 100:10. The mixture was filtered through a 1 μm microporous filter while hot, and the filtrate was dried and the asphalt was crushed again. The asphalt was sieved through a 500-mesh stainless steel sieve to obtain pretreated asphalt.

[0052] (3) Sieve the sulfur powder through an 800-mesh stainless steel sieve;

[0053] (4) The pretreated asphalt and the sieved sulfur are mixed in a weight ratio of 100:10, and then dissolved in carbon disulfide (the mass ratio of the pretreated asphalt to carbon disulfide is 10:100), stirred, dried, and placed in a spinning cylinder;

[0054] (5) The spinning cylinder was heated to 180°C and nitrogen was introduced to maintain the temperature for 30 minutes; the pitch fiber precursor was spun at a pressure of 1.00 MPa, a drawing rate of 400 m / min, a spinning temperature of 180°C, and a nitrogen atmosphere;

[0055] (6) The asphalt fiber precursor is placed in a carbonization furnace, and the temperature is raised to 1000 degrees at a rate of 10 °C / min under nitrogen protection. After keeping the temperature constant for 20 minutes, the porous carbon fiber is obtained.

[0056] Example 3

[0057] A method for preparing porous pitch-based carbon fiber comprises the following steps:

[0058] (1) Asphalt with a softening point of 120°C was crushed and passed through a 500-mesh sieve, kept at 105°C for 10 minutes to remove moisture, and then cooled;

[0059] (2) The cooled anhydrous asphalt was dissolved in kerosene at 200°C, with the mass ratio of kerosene to anhydrous asphalt being 100:15. The mixture was filtered through a 1 μm microporous filter while hot, and the filtrate was dried and the asphalt was crushed again. The asphalt was sieved through a 500-mesh stainless steel sieve to obtain pretreated asphalt.

[0060] (3) Sieve the sulfur powder through an 800-mesh stainless steel sieve;

[0061] (4) The pretreated asphalt and the sieved sulfur are mixed in a weight ratio of 100:15, and then dissolved in carbon disulfide (the mass ratio of the pretreated asphalt to carbon disulfide is 15:100), stirred, dried, and placed in a spinning cylinder;

[0062] (5) The spinning cylinder was heated to 150°C and nitrogen was introduced to maintain the temperature for 30 minutes; the pitch fiber precursor was obtained by spinning at a pressure of 2.00 MPa, a drawing rate of 400 m / min, a spinning temperature of 150°C, and a nitrogen spinning atmosphere;

[0063] (6) The asphalt fiber precursor is placed in a carbonization furnace, and the temperature is raised to 1000 degrees at a rate of 20 degrees Celsius per minute under nitrogen protection. After keeping the temperature constant for 30 minutes, the porous carbon fiber is obtained.

[0064] Example 4

[0065] A method for preparing porous pitch-based carbon fiber comprises the following steps:

[0066] (1) Asphalt with a softening point of 150°C was crushed and passed through a 300-mesh sieve, kept at 105°C for 10 minutes to remove moisture, and then cooled;

[0067] (2) The cooled anhydrous asphalt was dissolved in kerosene at 200°C, with the mass ratio of kerosene to anhydrous asphalt being 100:20. The mixture was filtered through a 1 μm microporous filter while hot. The filtrate was dried and the asphalt was crushed again. The asphalt was sieved through a 500-mesh stainless steel sieve to obtain pretreated asphalt.

[0068] (3) Sieve the sulfur powder through an 800-mesh stainless steel sieve;

[0069] (4) The pretreated asphalt and the sieved sulfur are mixed in a weight ratio of 100:20, and then dissolved in carbon disulfide (the mass ratio of the pretreated asphalt to carbon disulfide is 20:100), stirred, dried, and placed in a spinning cylinder;

[0070] (5) The spinning cylinder was heated to 200°C and nitrogen was introduced to maintain the temperature for 30 minutes; the pitch fiber precursor was spun at a pressure of 2.00 MPa, a drawing rate of 400 m / min, a spinning temperature of 200°C, and a nitrogen spinning atmosphere;

[0071] (6) The asphalt fiber precursor is placed in a carbonization furnace, and the temperature is raised to 1000°C at a rate of 20°C / min under nitrogen protection. The temperature is kept constant for 30 minutes and then cooled to obtain porous carbon fibers.

[0072] Example 5

[0073] A method for preparing porous pitch-based carbon fiber comprises the following steps:

[0074] (1) Asphalt with a softening point of 180°C was crushed and passed through a 400-mesh sieve, kept at 105°C for 10 minutes to remove moisture, and then cooled;

[0075] (2) The cooled anhydrous asphalt was dissolved in kerosene at 200°C, with the mass ratio of kerosene to anhydrous asphalt being 100:25. The mixture was filtered through a 1 μm microporous filter while hot, and the filtrate was dried and the asphalt was crushed again. The asphalt was sieved through a 500-mesh stainless steel sieve to obtain pretreated asphalt.

[0076] (3) Sieve the sulfur powder through an 800-mesh stainless steel sieve;

[0077] (4) The pretreated asphalt and the sieved sulfur are mixed in a weight ratio of 100:20, and then dissolved in carbon disulfide (the mass ratio of the pretreated asphalt to carbon disulfide is 25:100), stirred, dried, and placed in a spinning cylinder;

[0078] (5) The spinning cylinder was heated to 250°C and nitrogen was introduced to maintain the temperature for 30 minutes; the pitch fiber precursor was obtained by spinning at a pressure of 2.00 MPa, a drawing rate of 400 m / min, a spinning temperature of 250°C, and a nitrogen atmosphere;

[0079] (6) The asphalt fiber precursor is placed in a carbonization furnace, and the temperature is raised to 1000°C at a rate of 20°C / min under nitrogen protection. The temperature is kept constant for 30 minutes and then cooled to obtain porous carbon fibers.

[0080] Example 6

[0081] A method for preparing porous pitch-based carbon fiber comprises the following steps:

[0082] (1) Asphalt with a softening point of 180°C was crushed and passed through a 400-mesh sieve, kept at 105°C for 10 minutes to remove moisture, and then cooled;

[0083] (2) The cooled anhydrous asphalt was dissolved in kerosene at 200°C, with the mass ratio of kerosene to anhydrous asphalt being 100:20. The mixture was filtered through a 1 μm microporous filter while hot. The filtrate was dried and the asphalt was crushed again. The asphalt was sieved through a 500-mesh stainless steel sieve to obtain pretreated asphalt.

[0084] (3) Sieve the sulfur powder through an 800-mesh stainless steel sieve;

[0085] (4) The pretreated asphalt and the sieved sulfur are mixed in a weight ratio of 100:20, and then dissolved in carbon disulfide (the mass ratio of the pretreated asphalt to carbon disulfide is 20:100), stirred, dried, and placed in a spinning cylinder;

[0086] (5) The spinning cylinder was heated to 250°C and nitrogen was introduced to maintain the temperature for 30 minutes; the pitch fiber precursor was obtained by spinning at a pressure of 3.00 MPa, a drawing rate of 500 m / min, a spinning temperature of 250°C, and a nitrogen spinning atmosphere;

[0087] (6) The asphalt fiber precursor is placed in a carbonization furnace, and the temperature is raised to 1200 degrees at a rate of 30 degrees Celsius per minute under nitrogen protection. After keeping the temperature constant for 30 minutes, the porous carbon fiber is obtained.

[0088] Comparative Example 1

[0089] A method for preparing pitch-based carbon fiber is as described in Example 1, except that the carbonization treatment temperature in step 6 of Example 1 is changed to 800° C., and the remaining steps are the same as in Example 1.

[0090] Comparative Example 2

[0091] A method for preparing asphalt-based carbon fiber is as described in Example 1, except that the asphalt in step 1 of Example 1 is replaced with asphalt with a softening point of 100°C, and the remaining steps are the same as Example 1.

[0092] Comparative Example 3

[0093] A method for preparing asphalt-based carbon fiber is as described in Example 6, except that the carbonization treatment temperature in step 6 of Example 6 is changed to 1300°C, and the remaining steps are the same as Example 6.

[0094] Comparative Example 4

[0095] A method for preparing asphalt-based carbon fiber is as described in Example 6, except that the asphalt in step 1 of Example 6 is replaced with asphalt with a softening point of 200°C, and the remaining steps are the same as Example 6.

[0096] Comparative Example 5

[0097] A method for preparing asphalt-based carbon fiber is as described in Example 6, except that the weight ratio of asphalt to sulfur in step 4 of Example 6 is changed to 100:25, and the remaining steps are the same as Example 6.

[0098] Test example

[0099] The carbon fibers prepared in the examples and comparative examples were subjected to performance tests, and the test data are shown in Table 1 below.

[0100] Table 1 Comparison of various indicators and properties of carbon fibers prepared in Examples and Comparative Examples

[0101]

[0102] The tensile strength in the table is measured using instron 5967 according to GB / T 3362-2017, and the specific surface area and specific pore volume are measured using BSD 660 according to GB / T 7702.21-1997.

[0103] As can be seen from the table, various preparation methods carried out within the scope of the present invention can produce porous carbon fibers with good tensile strength, specific surface area and specific pore volume. The test results of Comparative Example 3 were obtained by increasing the temperature in Step 6 of Example 6. It can be seen that increasing the carbonization temperature from 1200 degrees to 1300 degrees can achieve similar results, but energy consumption will increase. The porous carbon fibers prepared by other preparation methods beyond the scope of the present invention are unsatisfactory in terms of tensile strength and specific surface area.

[0104] Figure 1 、 Figure 2 This is the SEM image of Example 6. It can be seen that there are a large number of micropores ( Figure 1), and the cross section also shows a large number of micropores ( Figure 2 ), showing that this carbon fiber has more nanoscale microporous structures. Figure 3 This is the SEM image of the carbon fiber cross section of Comparative Example 4. The micropores are larger, so the specific surface area is smaller.

Claims

1. A porous pitch-based carbon fiber, characterized in that: The carbon fiber has a fiber diameter of 5-20 μm, a tensile strength of ≥200 MPa, and a specific surface area of ≥2900 m 2 / g, specific pore volume ≥0.9 cm 3 / g; The method for preparing the porous asphalt-based carbon fiber comprises the steps of: (1) Dissolving the pretreated asphalt and sulfur in carbon disulfide; After the reaction, the asphalt fiber precursor is obtained by spinning; (2) Asphalt fiber precursors are carbonized to produce porous asphalt-based carbon fibers; The softening point of the asphalt is 120-180°C; In step (1), the mass ratio of the pretreated asphalt to sulfur is 100:(5-20); In step (2), the carbonization temperature is 900-1200°C.

2. The porous pitch-based carbon fiber according to claim 1, characterized in that The carbon fiber has a fiber diameter of 8-12 μm, a tensile strength of 209-271 MPa, and a specific surface area of 2907-3629 m 2 / g, and the specific pore volume is 0.96-1.27 cm 3 / g.

3. The porous pitch-based carbon fiber according to claim 1, characterized in that: In step (1), the asphalt pretreatment method includes the following steps: crushing the asphalt and passing it through a 300-500 mesh sieve, removing moisture and then cooling; then dissolving it in kerosene and filtering it; and drying, crushing and passing the obtained filtrate through a 500 mesh sieve to obtain pretreated asphalt.

4. The porous pitch-based carbon fiber according to claim 3, characterized in that: Include one or more of the following conditions: i. The method for removing moisture is: keep the temperature at 100-120℃ for 5-20 minutes; ii. The mass ratio of kerosene to asphalt after dehydration is 100:(5-25); the dissolution temperature is 150-250℃; iii. Filtration is performed using a 1 μm microporous filter.

5. The porous pitch-based carbon fiber according to claim 1, characterized in that: In step (1), one or more of the following conditions are included: i. The sulfur is also screened through an 800-mesh sieve before use; ii. The mass ratio of pretreated asphalt to carbon disulfide is (5-25):100; iii. After the pretreated asphalt and sulfur are dissolved in carbon disulfide, the process further includes a drying step.

6. The porous pitch-based carbon fiber according to claim 1, characterized in that: In step (1), one or more of the following conditions are included: i. The reaction temperature is 120-250°C, the reaction time is 20-40 minutes, and the reaction is carried out under the protection of inert gas; ii. The spinning temperature is 150-250° C., the spinning pressure is 0.50-5.00 MPa, the drawing rate is 200-500 m / min, and the spinning is carried out in air.

7. The porous pitch-based carbon fiber according to claim 1, characterized in that: In step (2), the constant temperature time during the carbonization process is 10 to 60 minutes, the heating rate is 5 to 30°C / minute, and the carbonization atmosphere is an inert gas.

8. The porous pitch-based carbon fiber according to claim 6, characterized in that: The inert gas is nitrogen or argon.

9. The porous pitch-based carbon fiber according to claim 7, characterized in that: The carbonization atmosphere is nitrogen or argon.

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