JP5202460B2 - Activated carbon and electric double layer capacitor using the activated carbon - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide activated carbon which satisfies both of the adsorption amount and the moving speed of an adsorbate in a good balance. <P>SOLUTION: The activated carbon is characterized in that the BET specific surface area is 1,000-3,000 m<SP>2</SP>/g, the area ratio of pores each having a pore diameter of 1.0-2.0 nm in the BET specific surface area is &ge;40%, and the volume ratio of pores each having pore diameter of &gt;2.0 nm and &lt;50.0 nm in the total pore volume is &ge;40%. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to activated carbon having both micropores and mesopores.

  Activated carbon is used for adsorption and the like because of its high specific surface area. In recent years, it is also used for electronic materials such as electrodes for electric double layer capacitors. Since activated carbon has many micropores having a diameter of 2.0 nm or less, it has a feature that the specific surface area is higher than other porous materials. However, micropores have a high specific surface area per pore volume, but their pore size is small, so when used as an adsorbent, the movement of adsorbent into the pores is slow, and the electrode for electric double layer capacitors When it is used for electrolyte, diffusion and movement of electrolyte ions are slow. Therefore, even if it has a high specific surface area, the adsorption sites in the fine pores were not fully utilized.

  In order to solve such a problem, it is conceivable to increase the diffusion rate of adsorbed substances and electrolyte ions into the pores by simply increasing the diameter of each pore. However, when the pore diameter is simply increased, the specific surface area per pore volume decreases, and the mass of activated carbon, the amount of adsorption per activated carbon volume, and the capacitance decrease. Therefore, various types of activated carbon having fine pores for improving the amount of adsorption of activated carbon and relatively large pores for rapid mass transfer have been proposed.

  For example, Patent Document 1 discloses activated carbon in which the pore size distribution measured by the Cranston-Inclay method has a peak between 1.0 to 2.0 nm and 2.0 nm to 10.0 nm, respectively. Yes. In Patent Document 2, in the pore size distribution, at least one peak in the pore diameter range of 1.0 to 4.0 nm and at least one peak in the pore diameter range of 0.6 to 0.9 nm are disclosed. And activated carbon in which small-diameter pores having a pore diameter of 0.6 to 0.9 nm are formed on the inner surface of large-diameter pores having a pore diameter of 1.0 to 5.0 nm. . Patent Document 3 discloses a pore volume (A) having a pore volume of 0.01 ml / g or more and 0.2 ml / g or less, a pore diameter of 10.0 to 30.0 nm, and a pore diameter of An activated carbon having a pore volume (B) ratio of 2.0 to 3.0 nm (A / B) of 0.6 or more is disclosed.

In Patent Document 4, in the pore volume distribution, a pore diameter range of 2.1 to 2.4 nm, a range of 1.7 to 2.1 nm, a range of 1.4 to 1.7 nm, and a 1.1 to 1. Activated carbon having a peak in the range of 4 nm is disclosed. Patent Document 5 discloses activated carbon having at least two peak tops at least less than 4.0 nm and a specific surface area of 1200 to 2500 m ² / g in a pore distribution curve. In Patent Document 6, the specific surface area of mesopores having a pore diameter of 2.0 or more and less than 50.0 nm is 100-2500 m ² / g, and the specific surface area of micropores having a pore diameter of less than 2.0 nm is 600- Fibrous activated carbon with 2500 m ² / g and a mesopore volume to total pore volume ratio of 10-40% is disclosed.

JP-A-9-328308 JP 2000-351613 A JP 2006-143494 A JP 2007-186411 A JP 2007-269552 A JP 2008-149267 A

  As in Patent Documents 1 to 6, activated carbon having fine pores and relatively large pores has been proposed. However, from the viewpoint of achieving both the amount of adsorption and the moving speed of the adsorbed material, the existence ratio of micropores having a diameter of 2.0 nm or less and mesopores having a diameter of more than 2.0 nm and less than 50 nm formed on activated carbon has not yet been examined. There was room for.

  This invention is made | formed in view of the said situation, and it aims at providing the activated carbon which made the adsorption amount and the moving speed of adsorption material balance compatible.

The activated carbon of the present invention that has solved the above problems has a BET specific surface area of 1000 m ² / g or more and 3000 m ² / g or less, and has a pore diameter of 1.0 nm or more and 2.0 nm or less in the BET specific surface area of the pores. And the volume ratio in the total pore volume of pores having a pore diameter of more than 2.0 nm and less than 50.0 nm is 40% or more. The activated carbon preferably has a volume ratio of 8% or more in the total pore volume of pores having a pore diameter of 10.0 nm or more and less than 50.0 nm.

The activated carbon has a pore size of 1 in a pore distribution diagram (vertical axis: log differential pore volume dV / dlogD (cm ³ / g), horizontal axis: pore diameter D (nm)) measured by a nitrogen adsorption method. It is preferable to have a maximum peak in the range of not less than 0.0 nm and not more than 2.0 nm. Further, in the pore distribution diagram, when the log differential pore volume values when the pore diameter is 3.0 nm, 4.0 nm and 10.0 nm are V ₃ , V ₄ and V ₁₀ , respectively, V ₁₀ / It is preferable that V ₃ ≧ 0.4 and V ₁₀ / V ₄ ≧ 0.5.

  The average pore diameter of the activated carbon is preferably 2.0 nm or more and 3.0 nm or less.

  The present invention also includes an electrode material for an electric double layer capacitor containing the activated carbon, an electrode for an electric double layer capacitor using the electrode material, and an electric double layer capacitor using the electrode.

  Since the activated carbon of the present invention has micropores and mesopores in a well-balanced manner, the amount of adsorption and the moving speed of the adsorbed material are balanced. Therefore, for example, when the activated carbon of the present invention is used as an electrode material, an electric double layer capacitor excellent in capacitance and internal resistance can be obtained.

Activated carbon No. It is a pore distribution map of 1-5. Activated carbon No. 3 is a pore distribution diagram of 3, 6, and 7. FIG. Activated carbon No. 3 is a pore distribution diagram of 3, 8, and 9. FIG. Activated carbon No. 3 is a pore distribution diagram of 3, 10, and 11. FIG. It is a figure for demonstrating the electric double layer capacitor manufactured using the activated carbon of an Example.

  The activated carbon of the present invention has a high specific surface area, a pore having a pore diameter of 1.0 nm or more and 2.0 nm or less (hereinafter sometimes referred to as “micropore”), a pore diameter of more than 2.0 nm and 50.0 nm. It is characterized by having a well-balanced number of pores (hereinafter sometimes referred to as “mesopores”) of less than. Adsorption in the deep pores of the adsorbed material is accelerated by allowing the adsorbed material to diffuse and move more quickly in the activated carbon by making the micropores acting as the adsorption site and the mesopores, which serve as the movement route of the adsorbed material, in good balance. Even the site can be fully utilized. Therefore, for example, when the activated carbon of the present invention is used as an electrode material for an electric double layer capacitor, an electric double layer capacitor having a high capacitance and a low internal resistance can be obtained. Further, when the activated carbon of the present invention is used as an adsorbent such as a gas adsorbent, an adsorbent for water purification, and an adsorbent for wastewater purification, the adsorption capacity and the adsorption rate can be improved.

  Hereinafter, the activated carbon of the present invention will be specifically described.

The activated carbon has a BET specific surface area (S _total ) of 1000 m ² / g or more and 3000 m ² / g or less. When the BET specific surface area is less than 1000 m ² / g, the adsorption ability of the activated carbon becomes low. Therefore, for example, when activated carbon is used for the electrode for an electric double layer capacitor, a sufficient capacitance per unit mass (F / g) cannot be obtained. On the other hand, if the BET specific surface area exceeds 3000 m ² / g, the density of the activated carbon is excessively lowered. Therefore, for example, when activated carbon is used for an electrode for an electric double layer capacitor, the capacitance per volume (F / cm ³ ) is lowered. The BET specific surface area is preferably 1200 m ² / g or more, more preferably 1500 m ² / g or more, preferably 2500 m ² / g or less, more preferably 2200 m ² / g or less.

The activated carbon has an area ratio of a BET specific surface area (S _1-2 ) of pores having a pore diameter of 1.0 nm to 2.0 nm in a BET specific surface area (S _total ) of 40% or more. When the area ratio of micropores in the BET specific surface area is less than 40%, the ratio of micropores acting as adsorption sites becomes too low. Therefore, for example, when used as an electrode for an electric double layer capacitor, a sufficient capacitance per unit mass (F / g) cannot be obtained. The area ratio of the micropores in the BET specific surface area is preferably 50% or more, more preferably 60% or more. The upper limit of the area ratio of micropores in the BET specific surface area varies depending on the area ratio of mesopores, but is usually 80%.

The activated carbon may have an area ratio of a BET specific surface area (S _2-50 ) of pores having a pore diameter of more than 2.0 nm and less than 50.0 nm in the BET specific surface area (S _total ) of 40% or less. Preferably, it is 36% or less, more preferably 32% or less. If the area ratio of mesopores in the BET specific surface area is 40% or less, the area ratio of micropores is relatively increased. Therefore, for example, when used for an electrode for an electric double layer capacitor, the capacitance per unit mass (F / g) becomes better. The lower limit of the area ratio of mesopores in the BET specific surface area is usually 20%.

Total pore volume of the activated carbon (V _total) is preferably at least 0.7 cm ³ / g, more preferably 0.8 cm ³ / g or more, more preferably 0.9 cm ³ / g or more, 3.0 cm ³ / g or less is preferable, More preferably, it is 2.5 cm < ³ > / g or less, More preferably, it is 2.0 cm < ³ > / g or less.

The activated carbon has a volume ratio of the pore volume (V _2-50 ) of pores having a pore diameter of more than 2.0 nm and less than 50.0 nm in the _total pore volume (V _total ) of 40% or more. If the volume ratio of mesopores in the total pore volume is less than 40%, the ratio of mesopores that become the migration path of the adsorbed material becomes too low. Therefore, for example, when used for an electric double layer capacitor electrode, the internal resistance increases. The volume ratio of mesopores in the total pore volume is preferably 45% or more, more preferably 50% or more. The upper limit of the volume ratio of mesopores in the total pore volume varies depending on the volume ratio of micropores, but is usually 70%.

The activated carbon has a pore volume (V ₁₀ ) of pores (hereinafter sometimes referred to as “large diameter mesopores”) having a pore diameter of 10.0 nm or more and less than 50.0 nm in the _total pore volume (V _total ). _-50 ) is preferably 8% or more, more preferably 10% or more, and even more preferably 12% or more. If the volume ratio of the large-diameter mesopores in the total pore volume is 8% or more, the movement path having a large inner diameter increases, so that the adsorbed substance can be moved and diffused inside the activated carbon more easily. Therefore, for example, when used for an electrode for an electric double layer capacitor, the internal resistance is further reduced. The volume ratio of large diameter mesopores in the total pore volume is preferably 20% or less.

  The average pore diameter of the activated carbon is preferably 2.0 nm or more, more preferably 2.1 nm or more, still more preferably 2.2 nm or more, preferably 3.0 nm or less, more preferably 2.6 nm or less, still more preferably 2.4 nm or less. When the average pore diameter is within the above range, the adsorbed material easily enters and exits the activated carbon. Therefore, for example, when used as an electrode for an electric double layer capacitor, rapid charge / discharge characteristics are improved.

The activated carbon has a pore diameter of 1.0 nm in a pore distribution diagram (vertical axis: log differential pore volume dV / dlogD (cm ³ / g), horizontal axis: pore diameter D (nm)) measured by a nitrogen adsorption method. It is preferable to have a maximum peak in the range of 2.0 nm or less. If the pore distribution diagram has the maximum peak in the micropore region, the activated carbon has many micropores and many adsorption sites. In the pore distribution diagram, activated carbon having a maximum peak in the mesopore region tends to have a high mesopore ratio and a low specific surface area.

In the pore distribution diagram, when the log differential pore volume values when the pore diameter is 3.0 nm, 4.0 nm, and 10.0 nm are V ₃ , V _4, and V ₁₀ , respectively, V ₁₀ / It is preferable that V ₃ ≧ 0.4 and V ₁₀ / V ₄ ≧ 0.5. If V ₁₀ / V ₃ and V ₁₀ / V ₄ are in the above ranges, the micropores and the mesopores communicate with each other efficiently. For example, when used as an electric double layer capacitor, an electrolyte, ions, etc. As a result, the amount of ions adsorbed increases and the capacitance increases.

  Next, the manufacturing method of the said activated carbon is demonstrated. The activated carbon can be produced by activating the activated raw material. Here, the “activation process” is a process for forming pores on the surface of the activation raw material to increase the specific surface area and the pore volume. As the activation treatment, both chemical activation and gas activation can be employed, and both chemical activation and gas activation may be performed. Moreover, the activation process may be performed only once or multiple times. An activation raw material will not be specifically limited if it is used as a raw material of normal activated carbon.

  In addition, as the manufacturing method of the activated carbon, an activation raw material in which relatively large pores (mesopores) are easily formed (hereinafter may be referred to as “mesopore forming raw material”) and relatively small pores (micropores). It is preferable to steam-activate a composite with an activation raw material (hereinafter sometimes referred to as a “micropore forming raw material”) that is easily formed. If a composite of mesopore-forming raw material and micropore-forming raw material is used as the activation raw material, activated carbon having a good balance of micropores and mesopores can be obtained by a single activation treatment without performing the activation treatment multiple times. .

  Examples of the mesopore forming raw material include cellulosic raw materials such as paper, cotton fiber, and woody material. Examples of the micropore forming raw material include synthetic resin raw materials such as phenol resin and furan resin. At least one or more of these mesopore forming raw materials and micropore forming raw materials are used. In addition, what is necessary is just to change suitably the compounding ratio of a mesopore formation raw material and a micropore formation raw material according to the physical property of the desired activated carbon. Examples of the composite of the mesopore-forming raw material and the micropore-forming raw material include a paper phenolic resin laminate.

  The mixture or composite of the mesopore forming raw material and the micropore forming raw material is preferably used after being carbonized. The carbonization treatment is usually performed by heat treatment in an inert gas atmosphere. The carbonization temperature is preferably 500 ° C. or higher, more preferably 550 ° C. or higher, preferably 850 ° C. or lower, more preferably 800 ° C. or lower.

  The average particle size of the mixture or composite of the mesopore-forming raw material and the micropore-forming raw material used for steam activation, or the carbide thereof is preferably 1 μm or more, more preferably 3 μm or more, further preferably 5 μm or more, and 10 cm or less. Is more preferably 7 cm or less, and further preferably 5 cm or less. Here, in the present application, the average particle size is obtained by measuring a sample dispersed in water with a laser diffraction particle size distribution measuring device (for example, “SALD (registered trademark) -2000” manufactured by Shimadzu Corporation). Volume average particle size. In addition, what is necessary is just to adjust the average particle diameter of an activation raw material by a grinding | pulverization. Moreover, what is necessary is just to size-size using a sieve, when the average particle diameter of an activation raw material is 200 micrometers or more.

  In the steam activation, the activation raw material is heated to a predetermined temperature and then activated by supplying steam. It is preferable to heat the activation raw material in an inert gas atmosphere. Note that nitrogen, argon, helium, or the like can be used as the inert gas.

  The temperature at the time of activation treatment (furnace temperature) is preferably 400 ° C. or higher, more preferably 450 ° C. or higher, preferably 1500 ° C. or lower, more preferably 1300 ° C. or lower. Moreover, the heating time at the time of performing an activation process has preferable 0.5 hours or more, More preferably, it is 1.0 hours or more, 10 hours or less are preferable, More preferably, it is 5 hours or less.

  50 mass parts or more are preferable with respect to 100 mass parts of activation raw materials, as for the total amount of the water vapor | steam supplied during an activation process, More preferably, it is 100 mass parts or more, More preferably, it is 200 mass parts or more, and shall be 10000 mass parts or less. More preferably, it is 5000 parts by mass or less, and still more preferably 3000 parts by mass or less. If the total amount of water vapor to be supplied is 50 parts by mass or more with respect to 100 parts by mass of the activation raw material, pore formation by the activation reaction is better, and if it is 10000 parts by mass or less, the activation reaction proceeds more efficiently. Productivity can be improved.

  As an aspect for supplying water vapor, either an aspect for supplying water vapor without dilution or an aspect for supplying water vapor diluted with an inert gas can be used, but in order to advance the activation reaction efficiently, it is inactive. An embodiment in which the gas is supplied after being diluted with gas is preferable. When supplying water vapor diluted with an inert gas, the water vapor partial pressure in the mixed gas (total pressure 101.3 kPa) is preferably 40 kPa or more, more preferably 50 kPa or more, and further preferably 70 kPa or more.

  The activated carbon after steam activation may be further washed, heat-treated and pulverized. Washing is performed using activated carbon after steam activation using a solvent such as water, an acid, or an organic solvent. By washing the activated carbon, metal impurities, ash, organic solvent soluble components and the like can be removed. In the heat treatment, the activated carbon after steam activation or after washing is further heated in an inert gas atmosphere. The amount of functional groups on the surface of the activated carbon can be adjusted by heat treating the activated carbon. The pulverization is performed using a disk mill, a ball mill, a bead mill or the like. In addition, what is necessary is just to adjust the particle diameter of activated carbon suitably according to a use.

  Next, the electric double layer capacitor of the present invention will be described. The electric double layer capacitor of the present invention is characterized by using the activated carbon.

  As an electrode for an electric double layer capacitor, for example, knead activated carbon, a conductivity imparting agent, and a binder, further add a solvent to prepare a paste, and after applying this paste to a current collector plate such as an aluminum foil, What removed the solvent by drying is mentioned.

  As the binder used for the electrode for the electric double layer capacitor, fluorine-based polymer compounds such as polytetrafluoroethylene and polyvinylidene fluoride, carboxymethyl cellulose, styrene-butadiene rubber, petroleum pitch, phenol resin, and the like can be used. As the conductivity imparting agent, acetylene black, ketjen black, or the like can be used.

  An electric double layer capacitor generally has a structure in which an electrode, an electrolytic solution, and a separator are main components, and a separator is disposed between a pair of electrodes. Examples of the electrolytic solution include an electrolytic solution in which an amidine salt is dissolved in an organic solvent such as propylene carbonate, ethylene carbonate, and methyl ethyl carbonate; an electrolytic solution in which a quaternary ammonium salt of perchloric acid is dissolved; quaternary ammonium or lithium An electrolytic solution in which an alkali metal boron tetrafluoride salt or phosphorous hexafluoride salt is dissolved; an electrolytic solution in which a quaternary phosphonium salt is dissolved may be mentioned. Examples of the separator include cellulose, glass fiber, or a nonwoven fabric, cloth, or microporous film mainly composed of polyolefin such as polyethylene or polypropylene.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to the following examples, and may be appropriately modified and implemented within a range that can meet the purpose described above and below. All of which are within the scope of the present invention.

Measuring method of specific surface area, total pore volume and average pore diameter After 0.2 g of activated carbon was heated under vacuum at 150 ° C., adsorption was performed using a nitrogen adsorption device (“ASAP-2400” manufactured by Micromeritics). An isotherm was determined, and the specific surface area and total pore volume were calculated by the BET method. Further, assuming that the shape of the pores formed in the activated carbon is cylindrical, the average pore size was calculated by the following formula (1) based on the pore volume and specific surface area in the pore size range of 1.0 nm to 30 nm.

Electric double layer capacitor performance evaluation Capacitance Charge / discharge device (Etamoto Kasei Co., Ltd., “ETAC (registered trademark) Ver. 4.4”) charge / discharge terminal is connected to the current collector plate of the electric double layer capacitor to collect current The battery was charged with a constant current of 40 mA until the voltage between the plates reached 2.5 V, and then charged with a constant voltage of 2.5 V for 30 minutes. After charging, the electric double layer capacitor was discharged with a constant current (discharge current 10 mA). At this time, the discharge times t1 and t2 required until the voltage between the current collector plates became V1 and V2 were measured, and the capacitance was obtained using the following formula (2). The mass-based capacitance (F / g) is calculated by dividing the obtained capacitance by the mass of activated carbon in the electrode material layer in the capacitor electrode, and divided by the total volume of the electrode material layer in the capacitor electrode. Thus, a volume-based capacitance (F / cm ³ ) was calculated. Moreover, internal resistance was calculated | required using following formula (3). The capacitance and internal resistance were measured at 25 ° C. and −30 ° C.

I: 10 (mA)
t1: Discharge time required for the electric double layer capacitor voltage to reach V1 (sec)
t2: Discharge time (sec) required for the electric double layer capacitor voltage to reach V2
V1: 2.0 (V)
V2: 1.0 (V)

1. Production of activated carbon Production example 1
As an activation raw material, 100 g of carbonized paper phenolic resin laminate (average particle size: 5 mm to 15 mm) was put into a rotary kiln (Tanaka Tech Co., Ltd. (volume: 2.5 L)), and under nitrogen flow (1 L / min) ) To 900 ° C. (temperature increase rate: 10 ° C./min).
After reaching 900 ° C., steam (steam partial pressure: 71 kPa) was supplied together with nitrogen into the rotary kiln, and steam activation treatment was performed for 2.0 hours to obtain activated carbon No. 1 was obtained. The flow rate of nitrogen to be supplied was 1.0 L / min. At this time, the total amount of water vapor used was 240 g, that is, 240 parts by mass with respect to 100 parts by mass of the activation raw material. The obtained activated carbon was evaluated and the results are shown in Table 1.

Production Example 2
Activated carbon No. 1 was prepared in the same manner as in Production Example 1 except that the steam activation treatment time was changed to 3.0 hours. 2 was obtained. At this time, the total amount of steam used was 360 g, that is, 360 parts by mass with respect to 100 parts by mass of the activation raw material. The obtained activated carbon was evaluated and the results are shown in Table 1.

Production Example 3
Activated carbon No. 1 was prepared in the same manner as in Production Example 1 except that the steam activation treatment time was changed to 3.5 hours. 3 was obtained. At this time, the total amount of water vapor used was 420 g, that is, 420 parts by mass with respect to 100 parts by mass of the activation raw material. The obtained activated carbon was evaluated and the results are shown in Table 1.

Production Example 4
In the same manner as in Production Example 1 except that the steam activation treatment time was changed to 4.0 hours, activated carbon No. 4 was obtained. At this time, the total amount of water vapor used was 480 g, that is, 480 parts by mass with respect to 100 parts by mass of the activation raw material. The obtained activated carbon was evaluated and the results are shown in Table 1.

Production Example 5
Activated carbon No. 1 was prepared in the same manner as in Production Example 1 except that the steam activation treatment time was changed to 4.5 hours. 5 was obtained. At this time, the total amount of water vapor used was 540 g, that is, 540 parts by mass with respect to 100 parts by mass of the activation raw material. The obtained activated carbon was evaluated and the results are shown in Table 1.

Production Example 6
In the same manner as in Production Example 3 except that the water vapor partial pressure when supplying water vapor with nitrogen into the rotary kiln was changed to 54 kPa. 6 was obtained. The flow rate of nitrogen to be supplied was 1.6 L / min. At this time, the total amount of water vapor used was 300 g, that is, 300 parts by mass with respect to 100 parts by mass of the activation raw material. The obtained activated carbon was evaluated and the results are shown in Table 1.

Production Example 7
In the same manner as in Production Example 3 except that the water vapor partial pressure when supplying water vapor with nitrogen into the rotary kiln was changed to 41 kPa. 7 was obtained. The flow rate of nitrogen to be supplied was 1.8 L / min. At this time, the total amount of water vapor used was 200 g, that is, 200 parts by mass with respect to 100 parts by mass of the activation raw material. The obtained activated carbon was evaluated and the results are shown in Table 1.

Production Example 8
Activated carbon No. 1 was prepared in the same manner as in Production Example 3 except that the charging amount of the activation raw material was changed to 125 g. 8 was obtained. At this time, the total amount of water vapor used was 420 g, that is, 336 parts by mass with respect to 100 parts by mass of the activation raw material. The obtained activated carbon was evaluated and the results are shown in Table 1.

Production Example 9
Activated carbon No. 2 was prepared in the same manner as in Production Example 3 except that the amount of the activation raw material was changed to 150 g. 9 was obtained. At this time, the total amount of water vapor used was 420 g, that is, 280 parts by mass with respect to 100 parts by mass of the activation raw material. The obtained activated carbon was evaluated and the results are shown in Table 1.

Production Example 10
As an activation raw material, 100 g of carbonized phenol resin (manufactured by Sumitomo Bakelite Co., Ltd.) (average particle diameter: 5 mm to 15 mm) is put into a rotary kiln (manufactured by Tanaka Tech Co., Ltd. (volume: 2.5 L)), under nitrogen circulation ( The temperature was raised to 900 ° C. at 1 L / min (temperature raising rate: 10 ° C./min).

  After reaching 900 ° C., water vapor (water vapor partial pressure: 71 kPa) was supplied into the rotary kiln together with nitrogen, and steam activation treatment was performed for 4.0 hours to obtain activated carbon No. 10 was obtained. At this time, the total amount of water vapor used was 480 g, that is, 480 parts by mass with respect to 100 parts by mass of the activation raw material. The obtained activated carbon was evaluated and the results are shown in Table 1.

Production Example 11
In Example No. 11 of Japanese Patent Laid-Open No. 11-87190. In the same manner as in No. 1, activated carbon no. 11 was obtained. That is, a paper base phenolic resin laminate crushed to about 2.5 mm square was carbonized at 700 ° C. for 4 hours in an inert gas atmosphere, and then subjected to steam activation using a rotary kiln device to activate activated carbon. No. 11 was obtained. The conditions for the steam activation treatment were: sample charge: 500 g, water usage: 500 g / hour, nitrogen inflow: 12 L / min, activation temperature: 900 ° C., activation time: 3.0 hours. The obtained activated carbon was evaluated and the results are shown in Table 1.

  Activated carbon No. 1 obtained in Production Examples 1-9. Each of Nos. 1 to 9 has a large specific surface area and has micropores and mesopores in a balanced manner. From these results, it can be seen that activated carbon having a good balance of micropores and mesopores can be easily produced by using a mixture or composite of the mesopore-forming raw material and the micropore-forming raw material as the activation raw material. Activated carbon No. Nos. 10 and 11 have a high BET specific surface area and a large area ratio of micropores in the BET specific surface area, but a small volume ratio of mesopores in the total pore volume, that is, many micropores are formed. The mesopore ratio is small.

2. Production of electric double layer capacitor Activated carbon No. obtained above. The electric double layer capacitor was manufactured using 1-3. Specifically, polytetrafluoroethylene (PTFE) powder and acetylene black are mixed with activated carbon so as to be activated carbon: PTFE: acetylene black = 8: 1: 1 (mass ratio), until a paste is obtained. Kneaded. Subsequently, it grind | pulverized with the mini blender and sieved with the stainless steel sieve of 500 micrometers, and the particle size was arrange | equalized. Next, using a mold having a diameter of 2.54 cm (1 inch), adjusting the preparation amount so that the thickness after pressing becomes 0.5 mm, press-molding with a pressure of 50.4 MPa, and the capacitor electrode Created.

  The obtained capacitor electrode was dried under vacuum conditions at 200 ° C. for 1 hour, and then an electrolyte (1M tetraethylammonium tetrafluoroborate propylene carbonate solution) was used as an electrode in a glove box in which nitrogen gas was circulated. Vacuum impregnated. Using this electrode, an electric double layer capacitor was assembled as shown in FIG. The electric double layer capacitor shown in FIG. 5 includes a separator (Celgard, “Celgard (registered trademark) # 3501”) 1 impregnated with the electrolytic solution 1 sandwiched between the capacitor electrodes 2, and the electrodes are surrounded by an O-ring 3. Then, it was further sandwiched between aluminum plates 4 as current collector plates. The evaluation results of the obtained electric double layer capacitor are shown in Table 2.

  Activated carbon No. The electric double layer capacitors using No. 1 to No. 3 have a high capacitance, and in particular, activated carbon No. 1 having a volume ratio of mesopores in the total pore volume of 50% or more. 2 and 3 show that the internal resistance of the electric double layer capacitor is greatly reduced. Activated carbon No. The electric double layer capacitor using No. 10 is activated carbon No. Compared with the electric double layer capacitor using No. 1, the internal resistance is slightly lower, but the capacitance is also lower. From this, activated carbon No. 10 shows that the ratio of mesopores serving as the movement path of the adsorbed material is low, so that the adsorption sites in the deep pores are not fully utilized.

  The activated carbon of the present invention is suitable for electrode materials for electric double layer capacitors and adsorbents.

1: Separator, 2: Electrode for capacitor, 3: O-ring, 4: Aluminum plate, 5: Polytetrafluoroethylene plate, 6: Stainless steel plate

Claims (7)

The BET specific surface area is 1000 m ² / g or more and 3000 m ² / g or less,
The area ratio in the BET specific surface area of pores having a pore diameter of 1.0 nm or more and 2.0 nm or less is 40% or more, and
The volume ratio in the total pore volume of pores having a pore diameter of more than 2.0 nm and less than 50.0 nm is 40% or more ,
Activated carbon characterized in that the volume ratio in the total pore volume of pores having a pore diameter of 10.0 nm or more and less than 50.0 nm is 10% or more . In a pore distribution diagram (vertical axis: log differential pore volume dV / dlogD (cm ³ / g), horizontal axis: pore diameter D (nm)) measured by the nitrogen adsorption method, a pore diameter of 1.0 nm to 2.0 nm The activated carbon according to claim 1 , having a maximum peak in the following range. In the pore distribution diagram, when the log differential pore volume values when the pore diameter is 3.0 nm, 4.0 nm, and 10.0 nm are V ₃ , V _4, and V ₁₀ , respectively,
V ₁₀ / V ₃ ≧ 0.4, and
The activated carbon according to claim 2 , wherein V ₁₀ / V ₄ ≧ 0.5. The activated carbon according to any one of claims 1 to 3 , wherein the average pore diameter is 2.0 nm or more and 3.0 nm or less. An electrode material for an electric double layer capacitor comprising the activated carbon according to any one of claims 1 to 4 . An electrode for an electric double layer capacitor, wherein the electrode material according to claim 5 is used. An electric double layer capacitor using the electrode according to claim 6 .