KR100291886B1 - Manufacturing method of activated carbon fiber with carbonization process - Google Patents

Abstract

The present invention is activated carbon fiber having improved adsorption performance for gaseous and liquid contaminants by activating the carbon fiber mainly used as a reinforcing material of the polymer composite material after a carbonization process at a high temperature and the activation gas at various temperatures and times while introducing the activation gas It relates to a method for producing and an activated carbon fiber produced thereby.

Description

Method for producing activated carbon fiber incorporating carbonization process

The present invention relates to a method for producing activated carbon fibers as an adsorption material having a suitable adsorption performance for gaseous and liquid contaminants by varying the activation temperature and time after the carbonization process at high temperature. More specifically, PAN fibers oxidized for about 2 to 3 hours at a relatively low temperature of 200 to 300 ° C and / or carbonized for about 2 to 10 minutes in a nitrogen atmosphere of 700 to 1,500 ° C was introduced nitrogen gas at a high temperature after carbonization for 30 to 150 minutes in an inert atmosphere, activating gas is water vapor, O _2, while introducing a gas such as CO or CO ₂ activation temperature of a high strength carbon fiber is 900 to 1,300 ℃ again and The present invention relates to a method for producing activated carbon fibers having improved adsorbing performance in gas phase and liquid phase impurity treatment by producing activated carbon fibers having a well-developed surface structure and surface properties as adsorbents.

In recent years, attention has been focused on environmental pollution, and there is a need to remove pollutants in liquid and gaseous phases, and there is an urgent need for development of improved adsorbents that meet these needs.

These activated carbon fibers have a high specific surface area, excellent adsorption capacity, high surface reactivity and fine pores, so that the waste gas treatment device in the living and industrial facilities, the harmful gas removal device in the manufacturing facilities of semiconductor and precision measuring instruments, military and It is widely used in general industrial gas masks, air cleaners in offices and residential facilities.

Activated carbon fiber, which is used in various fields for purification, collection, recovery, and fractionation, is an organic adsorbent in the form of a saturated bond compared to an inorganic adsorbent in the form of a saturated bond such as silica gel, alumina gel, or synthetic zeolite. The micropore, which is a standard, is more developed, and the adsorption surface area and the size of the micropore are relatively uniform compared to the activated carbon, which is limited in the form of granules or powders. Because of the good fiber shape, the processing is easy and the demand is gradually increasing.

The conventional method for producing activated carbon fibers as an adsorbent material is to oxidize (stabilize) the fibrous precursor at a temperature of about 200 to 300 ° C. under an oxidizing atmosphere, and then maintain the original form of the fiber by high temperature treatment. The method of thermally activating directly at a high temperature of 700 to 1,000 ° C. immediately after increasing the strength was common. However, in this method, since the oxidation treatment is carried out at a relatively low temperature, the carbon content is low due to the non-carbon components remaining in the carbon fiber, such as hydrogen, oxygen, nitrogen, or sulfur, which are generally nonvolatile materials, In the activation stage, most of them are rapidly released, resulting in a lot of mass loss (Burn-off). Also, the size and distribution of the pores formed by the release of these heterogeneous components are not constant, so that the adsorption performance is significantly reduced. In addition, due to the instability of the surface structure of the carbon fiber surface surface functional group (surface functional group) formed according to the activation temperature can not continuously exhibit its function there was a problem that the adsorption performance is not satisfactory.

In the present invention, the fine pore structure and the surface formed on the surface of the carbon fiber by controlling the activation time and temperature after carbonizing the oxidized PAN-based fiber and / or its high-strength carbon fiber at high temperature in the production of activated carbon fiber To improve the adsorption performance of various adsorbates by preparing activated carbon fibers with well-developed functional groups, and to provide a method for producing activated carbon fibers which can continuously exhibit adsorption characteristics by surface functional groups formed on the surface of activated carbon fibers. It is.

1 is a process chart showing a method for producing activated carbon fibers and a method for manufacturing activated carbon fibers according to the present invention.

2 is a view showing a comparison of changes in BET specific surface area according to activation temperatures of NC-ACFs and C-ACFs based on Oxy PAN fibers;

3 is a view showing a comparison of the change in BET specific surface area according to the activation temperature of NC-ACFs and C-ACFs using high-strength carbon fiber as a raw material;

4 is a view showing a comparison of changes in micropore volume with activation temperatures of NC-ACFs and C-ACFs based on Oxy PAN fibers;

FIG. 5 is a view showing a comparison of changes in micropore volume according to activation temperatures of NC-ACFs and C-ACFs based on high-strength carbon fibers; FIG.

6 is a view showing a comparison of the nitrogen gas adsorption amount according to the increase in the relative pressure (P / P ₀ ) of NC-ACFs and C-ACFs according to Example 1 of the present invention;

7 is a view showing a comparison of the nitrogen gas adsorption amount according to the increase in the relative pressure of the NC-ACFs and C-ACFs according to Example 2 of the present invention;

8 is a view showing a comparison of nitrogen gas adsorption amount according to an increase in relative pressure of NC-ACFs and C-ACFs according to Example 3 of the present invention;

9 is a view showing a comparison of the nitrogen gas adsorption amount according to the increase in the relative pressure of the NC-ACFs and C-ACFs according to Example 4 of the present invention;

10 is a view showing a comparison of the nitrogen gas adsorption amount according to the increase in the relative pressure of the NC-ACFs and C-ACFs according to Example 5 of the present invention;

11 is a view showing a comparison of nitrogen gas adsorption amount according to the increase in relative pressure of NC-ACFs and C-ACFs according to Example 6 of the present invention;

12 is a view showing a comparison of nitrogen gas adsorption amount according to an increase in relative pressure of NC-ACFs and C-ACFs according to Example 7 of the present invention;

13 is a view showing a comparison of the nitrogen gas adsorption amount according to the increase in the relative pressure of the NC-ACFs and C-ACFs according to the eighth embodiment of the present invention.

*** Description of symbols of the main parts of the drawings

NC-ACFs: Activated carbon fiber manufactured without carbonization

Non Carbonized-Activated Carbon Fibers

C-ACFs: Activated Carbon Fibers Fabricated by Carbonization

Carbonized-Activated Carbon Fibers

The activated carbon fiber manufacturing method of the present invention is characterized by improving the adsorption performance of activated carbon fibers by introducing a carbonization process after the oxidation of the carbon fibers before the activation step.

As the carbon fiber, all general carbon fibers such as PAN (PolyAcryloNitrile-based: polyacrylonitrile), rayon, pitch, etc. may be used, and PAN-based carbon fiber is preferable.

In particular, the carbon fibers subjected to the oxidation treatment used in the present invention include PAN fibers (Oxy PAN Fibers) which have been oxidized at 200 to 300 ° C. for 2 to 3 hours and nitrogen at 700 to 1500 ° C. for the oxidation-treated PAN fibers. More preferred is a high strength carbon fiber carbonized for 2 to 10 minutes in the atmosphere.

Oxy PAN fibers and high-strength carbon fibers thereof may be used, respectively, and may be used together in some cases.

According to the method for producing activated carbon fibers of the present invention, carbonization is performed at temperatures of 900, 1,000, 1,100, 1,200, and 1,300 ° C. for about 30 to 150 minutes in a nitrogen atmosphere, which is generally used for the production of carbon fibers. The activated carbon fiber is prepared as an adsorbent through the activation process.

In the carbonization process of the present invention, the carbonization temperature is generally 900 to 1,300 ° C. When the carbonization temperature is lower than 900 ° C, the carbon content is low after carbonization and the content of heterogeneous elements is high, so that the pore structure and the adsorption specific surface area, which are the criteria for the adsorption performance of activated carbon fibers, are well developed during the activation process at low temperature. It does not have sufficient adsorption performance as the adsorbent. When the carbonization temperature exceeds 1,300 ° C, the packing density is high after carbonization, and thus the pore structure, which is a criterion for the adsorption performance of activated carbon fibers, is poorly developed during activation at low temperatures, and thus the adsorption specific surface area is well developed. It is not preferable because it does not have sufficient adsorption performance as an adsorbent.

In addition, the carbonization time of a carbonization process is 30 to 150 minutes. If the carbonization time is less than 30 minutes, the carbon content is low after carbonization and the content of heterologous elements is high, so that the pore structure and adsorption specific surface area, which are the criteria for adsorption performance of activated carbon fibers, are relatively poor during activation at low temperature. It does not have sufficient adsorption performance as an adsorbent. If the carbonization time exceeds 150 minutes, the packing density is high after carbonization, and thus the pore structure, which is a criterion for the adsorption performance of activated carbon fibers, is poorly developed during the activation of low temperature, and thus the adsorption specific surface area is not well developed. It is not preferable because it does not have sufficient adsorption performance as an adsorbent.

According to the present invention, a carbonization process is introduced prior to the activation treatment of the oxidized PAN fiber and / or its high strength carbon fiber to effectively remove the non-carbon components to increase the carbon content in the fiber and at the same time due to the release of the non-carbon components. Spotlike pore structures on the surface of carbon fibers begin to develop.

In the activation process, gas, such as water vapor, O ₂ , CO, or CO ₂ , was introduced at a constant rate as the activation gas, and activated at 30, 60, 90, and 120 minutes at temperatures of 700, 800, 900, and 1,000 ° C., respectively. .

In the activation process, the activation temperature is 700 to 1,000 ° C. When the temperature is less than 700 ° C., the pore structure and the specific surface area formed on the surface of the carbon fiber during the activation process are not well developed, and thus are not preferable because they do not have sufficient adsorption performance as the adsorbent. If the temperature exceeds 1,000 ° C., the pore structure formed on the surface of the activated carbon fiber is undesirably destroyed due to high temperature activation, or the surface structure of the activated carbon fiber is changed, thereby degrading the adsorption performance.

The activation time according to the invention is preferably 30 to 120 minutes. If the activation time is less than 30 minutes, the pore structure and the specific surface area formed on the surface of the carbon fiber during the activation process are not well developed, and thus are not preferable because they do not have sufficient adsorption performance as the adsorbent. If it exceeds 120 minutes, the pore structure formed on the surface of the activated carbon fiber is not preferable because it is destroyed by high temperature activation or the surface structure of the activated carbon fiber is changed to lower the adsorption performance.

In general, the adsorption process by activated carbon fibers can be divided into three stages:

1) Adsorbate molecules of activated carbon fibers migrate to the outer surface of the adsorbent,

2) The adsorbate diffuses through the macropore and mesopore of the adsorbent,

3) Finally, the adsorbate is adsorbed as the diffused adsorbate fills the micropores or bonds with the inner surface of the micropore.

Therefore, as in the present invention, the carbon fiber undergoes a carbonization process before the activation step, and thus, the pore traces in the form of dots generated in the carbonization process immediately before the activation step are gradually developed, and generally 20 kPa or less. It exhibits a uniform pore structure and distribution composed of fine pores.

The adsorption performance of activated carbon fibers obtained through the above process is known to depend on various surface properties of the activated carbon fibers, that is, micropores, surface polarity and oxygen compounds on the surface. Therefore, an object of the present invention is to produce an activated carbon fiber that can improve the adsorption performance and continuously exert its function.

The process for producing the activated carbon fiber in the present invention is shown in FIG. 1 compared with the conventional manufacturing process. More specifically, as shown in FIG. 1, in order to increase the carbon content of the oxidized PAN fiber and / or its high-strength carbon fiber and stabilize the pore structure of the surface, about 30 in a nitrogen atmosphere of 900 to 1,300 ° C. It was carbonized in an electric furnace for 150 minutes and then dried. Carbonized carbon fiber was activated by the activation time and temperature while introducing the above activating gases at a constant inflow rate, and then washed two or three times with distilled water, and then dried in a drier and tested for their adsorption performance.

The present invention also relates to activated carbon fibers produced by the above production method.

The activated carbon fibers produced by the process of the present invention have a BET specific surface area that is increased by 138 to 200% compared to conventional activated carbon fibers that have not undergone the carbonization process. It also has a 153 to 300% increased micropore volume compared to activated carbon fibers that have not undergone the carbonization process.

The contents of the present invention are described in more detail in the following Examples, but the scope of the present invention is not limited to the Examples.

Example 1

Oxidized polyacrylonitrile-based fibers (Oxy PAN-based fibers) of Korea Taekwang Industry Co., Ltd. were used. First, in order to increase the carbon content of Oxy-PAN fiber and stabilize the pore structure of the surface, it was carbonized in an electric furnace for about 30 minutes in a nitrogen atmosphere of 900 ℃ and dried. The carbonized carbon fiber and the non-carbon carbon fiber were activated with O ₂ as an activation gas, and the activation temperature was activated at 700 ° C. for 30 minutes at a constant inflow rate. The adsorption specific surface area and pore structure of each activated carbon fiber thus obtained are shown in Table 1 and surface properties in Table 2, respectively.

As a result, there was no significant change in surface properties such as pH in both activated carbon fibers and carbonized carbons, but BET specific surface area, total pore volume, and micropore volume were carbons. The fibers increased by 163%, 160% and 157%, respectively, compared to the activated carbon fiber without carbonization, and the average pore diameter decreased by about 600%.

Example 2

Carbonized Oxy-PAN fiber in Example 1 in a nitrogen atmosphere of 900 ℃ for 2 minutes to obtain a high-strength carbon fiber, carbonized the high-strength carbon fiber in a nitrogen atmosphere of 900 ℃ for about 30 minutes, then subjected to the carbonization process The carbon fiber and the untreated carbon fiber were activated for 30 minutes at activating gas of O ₂ and activating temperature of 700 ° C. The adsorption specific surface area and pore structure of each activated carbon fiber thus obtained are shown in Table 1 and surface properties in Table 2, respectively.

As a result, there was no significant change in surface properties, such as pH, for both activated carbon fibers and carbonized carbons. However, BET specific surface area, total pore volume, and fine pore volume were carbonized. The fibers increased by 193%, 194% and 300%, respectively, compared to the activated carbon fiber without carbonization, and the average pore diameter decreased by about 659%.

Example 3

After carbonizing the Oxy-PAN fiber of Example 1 in a nitrogen atmosphere at 1,100 ° C. for about 60 minutes, the carbonized carbon fiber and the carbon fiber that had not undergone carbonization were activated with CO ₂ and activating temperature of 800 ° C. Each activated for 60 minutes. The adsorption specific surface area and pore structure of each activated carbon fiber thus obtained are shown in Table 1 and surface properties in Table 2, respectively.

As a result, there was no significant change in surface properties, such as pH, for both activated carbon fibers and carbonized carbons. However, BET specific surface area, total pore volume, and fine pore volume were carbonized. The fibers increased by 200%, 214% and 246%, respectively, compared to the uncarbonized activated carbon fibers, and the average pore diameter decreased by about 532%.

Example 4

The high-strength carbon fiber of Example 2 was carbonized in a nitrogen atmosphere at 1,000 ° C. for about 150 minutes, and the carbonized carbon fiber and the carbon fiber which had not been subjected to this carbonization process were activated with CO ₂ and activation temperature at 800 ° C., 60 ° C. Each activated for minutes. The adsorption specific surface area and pore structure of each activated carbon fiber thus obtained are shown in Table 1 and surface properties in Table 2, respectively.

As a result, there was no significant change in surface properties, such as pH, for both activated carbon fibers and carbonized carbons. However, BET specific surface area, total pore volume, and fine pore volume were carbonized. The fibers increased by 194%, 188% and 260%, respectively, compared to the uncarbonized activated carbon fibers, and the average pore diameter decreased by about 443%.

Example 5

After carbonizing the Oxy-PAN fiber of Example 1 in a nitrogen atmosphere at 1,100 ° C. for about 90 minutes, the carbonized carbon fiber and the carbon fiber which had not been carbonized were changed to 90 ° C. with an activation gas of CO and an activation temperature of 900 ° C. Each activated for minutes. The adsorption specific surface area and pore structure of each activated carbon fiber thus obtained are shown in Table 1 and surface properties in Table 2, respectively.

As a result, there was no significant change in surface properties, such as pH, for both activated carbon fibers and carbonized carbons. However, BET specific surface area, total pore volume, and fine pore volume were carbonized. The fibers increased by 146%, 112% and 257%, respectively, and the average pore diameter decreased by about 410% compared to the activated carbon fibers without carbonization.

Example 6

The high-strength carbon fiber of Example 2 was carbonized in a nitrogen atmosphere at 1,200 ° C. for about 60 minutes, and the carbonized carbon fiber and carbon fiber which had not been subjected to this carbonization process were activated by using an activation gas as water vapor and an activation temperature of 900 ° C. for 120 minutes. Each activated. The adsorption specific surface area and pore structure of each activated carbon fiber thus obtained are shown in Table 1 and surface properties in Table 2, respectively.

As a result, there was no significant change in surface properties, such as pH, for both activated carbon fibers and carbonized carbons. However, BET specific surface area, total pore volume, and fine pore volume were carbonized. The fibers increased by 138%, 105% and 224%, respectively, compared to the uncarbonized activated carbon fibers, and the average pore diameter decreased by about 475%.

Example 7

After carbonizing the Oxy-PAN fiber of Example 1 in a nitrogen atmosphere at 1,300 ° C. for about 150 minutes, the carbonized carbon fiber and the carbon fiber which had not been subjected to this carbonization process were activated with water vapor and activation temperature 1,000 ° C. Each activated for minutes. The adsorption specific surface area and pore structure of each activated carbon fiber thus obtained are shown in Table 1 and surface properties in Table 2, respectively.

As a result, there was no significant change in surface properties, such as pH, for both activated carbon fibers and carbonized carbons. However, BET specific surface area, total pore volume, and fine pore volume were carbonized. Fibers increased by 146%, 111% and 153%, respectively, compared to uncarbonized activated carbon fibers, and the average pore diameter decreased by about 219%.

Example 8

The high-strength carbon fiber of Example 2 was carbonized in a nitrogen atmosphere at 1,300 ° C. for about 120 minutes, and the carbonized carbon fiber and carbon fiber which had not been subjected to this carbonization process were activated for 90 minutes using CO as an activation gas and 1,000 ° C. as an activation temperature. Each activated. The adsorption specific surface area and pore structure of each activated carbon fiber thus obtained are shown in Table 1 and surface properties in Table 2, respectively.

As a result, there was no significant change in surface properties, such as pH, for both activated carbon fibers and carbonized carbons. However, BET specific surface area, total pore volume, and fine pore volume were carbonized. The fiber increased by 150%, 107% and 183%, respectively, compared with the carbonized process without carbonization, and the average pore diameter decreased by about 316%.

Each of the prepared activated carbon fibers was used after drying at 100 ° C. for about 12 hours, and the BET specific surface area, iodine adsorption capacity, pH, surface acidity and surface basicity experiments of the activated carbon fibers obtained in the above examples were as follows. It carried out similarly and showed the result by each table.

BET specific surface area measurement method:

About 0.2 g of the sample was taken in a liquid nitrogen atmosphere at -196 ° C, and nitrogen gas was used as the adsorbate. P / P _o (where P is the partial pressure and P _o is the saturated vapor pressure) showed a linear slope with respect to the adsorption amount from about 0.05 to 0.3, from which the BET specific surface area and the volume of the micropores were obtained.

Iodine adsorption capacity measurement method:

According to ASTM D4607, the amount of iodine adsorbed at different weights for each sample and the residual concentration of iodine in the solution were measured, and the amount of iodine adsorption when the residual concentration was 0.02N was used as the adsorption capacity. Prior to the measurement, 5 wt% HCl solution, 0.100N sodium thiosulfate solution, 0.100 ± 0.001N standard iodine solution, 0.100N potassium iodide solution was prepared and used after expression. At this time, the potassium iodide solution was carefully prepared because it determines the concentration coefficient of sodium thiosulfate solution and standard iodine solution. 0.1, 0.3, 0.5, and 1.0 g of the prepared samples were accurately taken into a flask, 10 ml of 5 wt% HCl solution was added, and slowly warmed for about 30 seconds, and then 50 ml of standard iodine solution was added. After shaking for 15-20 minutes at room temperature, the solution was filtered and the filtrate was titrated with 0.100N sodium thiosulfate solution. The number of mg of iodine adsorbed was determined for each sample weight by titration until the yellow color of iodine disappeared.

pH measurement method:

The pH of each sample was measured according to ASTM D3838. 0.5 g of each dried sample was added to 20 ml of distilled water boiled at 100 ° C., shaken for 12 hours or more, and each solution was filtered to measure the pH of the supernatant.

Surface acidity and surface basicity measurement method:

The surface acidity of the activated carbon fibers was measured by Boehm's selective neutralization method. About 1 g of the sample was placed in 100 ml of 0.1 N sodium hydroxide solution, sealed, shaken at room temperature for 48 hours, and then filtered (0.45 μm, Nylon) and 20 ml of the supernatant was collected and titrated with 0.1 N hydrochloric acid solution. The surface basicity was measured in the same manner, and the sample addition solution and the titration solution were measured in the reverse direction, and phenolphthalein standard solution was used as an indicator.

Mass loss of activated carbon fiber according to each example

In each example, the mass of the starting carbon fiber and the mass of the carbonized activated carbon fiber were measured, and the mass loss (%) was calculated from the following equation, and the results are shown in Table 3 below.

Mass loss (%) = [mass of starting carbon fiber (g)-mass of activated carbon fiber (g)] / mass of starting carbon fiber (g) x 100

BET specific surface area [m ² / g] Total Pore Volume [cc / g] Micro Pore Volume [cc / g] Average pore diameter Example 1 NC-ACFs 229 0.15 0.07 220.3 C-ACFs 374 0.24 0.11 36.7 Example 2 NC-ACFs 272 0.18 0.08 189.9 C-ACFs 524 0.35 0.24 28.8 Example 3 NC-ACFs 354 0.21 0.13 145.7 C-ACFs 707 0.45 0.32 27.4 Example 4 NC-ACFs 404 0.24 0.15 127.6 C-ACFs 782 0.45 0.38 28.8 Example 5 NC-ACFs 872 0.52 0.21 72.5 C-ACFs 1271 0.58 0.54 17.7 Example 6 NC-ACFs 643 0.43 0.17 121.1 C-ACFs 888 0.45 0.39 25.5 Example 7 NC-ACFs 1125 0.64 0.45 37.4 C-ACFs 1637 0.71 0.69 17.1 Example 8 NC-ACFs 1012 0.62 0.35 54.6 C-ACFs 1522 0.66 0.64 17.3

* Each measured value represents the average value according to the Example.

pH Surface acidity [meq / g] Surface basicity [meq / g] Example 1 NC-ACFs 6.52 172.6 102.4 C-ACFs 6.55 166.8 105.2 Example 2 NC-ACFs 6.74 143.5 117.6 C-ACFs 6.78 135.9 109.8 Example 3 NC-ACFs 7.12 102.2 114.3 C-ACFs 7.18 98.6 118.4 Example 4 NC-ACFs 6.75 118.3 98.7 C-ACFs 6.81 115.7 104.3 Example 5 NC-ACFs 7.01 112.2 109.6 C-ACFs 6.92 109.5 98.7 Example 6 NC-ACFs 6.79 158.4 101.6 C-ACFs 6.85 149.8 118.5 Example 7 NC-ACFs 7.59 52.6 114.3 C-ACFs 7.62 45.7 147.8 Example 8 NC-ACFs 7.25 68.2 105.3 C-ACFs 7.26 70.4 108.8

* Each measured value represents the average value according to the Example.

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 NC-ACF 72 81 82 84 86 87 95 93 C-ACF 43 56 55 58 60 62 65 67

As can be clearly seen from Table 1, Table 2 and Table 3, the activated carbon fibers (C-ACFs of Examples 1 to 8) prepared according to the present invention is activated carbon fibers prepared without a conventional carbonization process ( Compared to NC-ACFs), the change in surface properties, ie pH, surface acidity and surface basicity, was not very large, but in each example, about 1.5 times in BET specific surface area, about 1.5 times in total pore volume, and micropores. The volume increased by about 2.2 times, and the average pore diameter decreased from 2.2 times to 6.6 times according to the activation temperature and time after the carbonization process.

As described above, it is possible to increase the BET specific surface area and the pore volume and to develop the fine pore structure of the activated carbon fiber prepared by newly introducing the carbonization process according to the present invention. It can be seen that greatly improved.

In addition, in the present invention, only the carbonization process in which nitrogen gas is introduced into the conventional apparatus is introduced without the need for any other apparatus in the production of activated carbon fibers, and the process is continuously performed, thereby making it easy to work.

Claims (3)

After oxidizing the carbon fiber, the oxidized carbon fiber is carbonized by heating for 30 minutes to 150 minutes at a temperature of 900 ℃ to 1,300 ℃, then activated by heating for 30 minutes to 120 minutes at a temperature of 700 ℃ to 1,000 ℃. Method for producing activated carbon fibers. The carbon fiber of claim 1, wherein the carbon fiber is PAN fiber oxidized at 200 to 300 ° C. for 2 to 3 hours or carbonized the oxidized PAN fiber at 700 to 1500 ° C. for 2 to 10 minutes. Fiber or the oxidized PAN fiber and a high strength carbon fiber. The method according to claim 1, wherein the activation gas used in the activation step is water vapor, O 2, CO, or CO 2 gas.