JP2011046584A - Method of manufacturing active carbon, and electric double layer capacitor using the active carbon prepared by the method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing active carbon capable of enlarging a pore size without increasing an amount used of an alkali activator, and without excessively elevating a specific surface area of the resultant active carbon in activation treatment using the alkali activator. <P>SOLUTION: The method of manufacturing the active carbon comprises an activation process of alkali-activating by housing a mixture of a carbon material and an alkali activator in a furnace, and heating the inside of the furnace; a hydration process of supplying water in the furnace after the activation process and a heating process of heating the inside of the furnace after supplying the water. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing activated carbon, and more particularly to a technique for controlling the pore structure of the obtained activated carbon.

  Conventionally, since activated carbon has a high specific surface area, it has been used as an electrode material for electric double layer capacitors, or as an adsorbent for wastewater treatment, water purifiers, and exhaust gas treatment. Such activated carbon production methods include gas activation in which a carbon raw material is heated in the presence of an activation gas such as water vapor and carbon dioxide; chemical activation in which an activation agent such as an alkali metal compound and a carbon raw material are mixed and heated is known. It has been.

  In addition, since activated carbon has different physical properties depending on its application, various production methods have been proposed to obtain desired physical properties. For example, a method for producing activated carbon in which a phenol resin having an average particle size of 20 to 500 μm is activated after carbonization and pulverized the activated product (Patent Document 1, Claim 4, Paragraph [0024]); Then, a method for producing activated carbon in which the ratio of the specific surface area with a pore diameter of 2.0 nm (20 mm) or more and the total specific surface area is 0.30 or more is further activated with alkali (Patent Document 2, Claim) Item 2, paragraph [0013]); a process for producing activated carbon that is calcined in the presence of an alkali metal hydroxide, removed the alkali metal compound, and further activated with water vapor (Patent Document 3, claim 7, paragraph [ [0009] After capturing the alkali metal generated during the alkali activation of the carbon material using the alkali metal compound as an activator with the other carbon material, the alkali metal in the other carbon material is hydrated and the alkali activator. Back, which activation method of the carbon material to alkali activation (Patent Document 4, claim 1, paragraph [0007]); and the like have been proposed.

JP 2003-203829 A JP-A-8-119614 JP 2000-40645 A Japanese Patent Laid-Open No. 2001-19415

  In recent years, there has been a demand for activated carbon capable of reducing the internal resistance of a capacitor, particularly in applications of electrode materials for electric double layer capacitors. Such reduction of the internal resistance of the electric double layer capacitor can be achieved by increasing the diameter of the pores formed in the activated carbon. As described above, various methods for producing activated carbon have been proposed, and a method for increasing the diameter of the formed pores has also been proposed. However, since the pore diameter of activated carbon increases as the degree of activation increases, increasing the pore diameter also increases the specific surface area, making it difficult to increase the pore diameter while maintaining an equivalent specific surface area. Met. Further, in the case of activation treatment using an alkali activator, in order to increase the pore diameter, that is, to increase the degree of activation, a large amount of alkali activator is required, resulting in an increase in production cost. was there.

  This invention is made | formed in view of the said situation, In the activation process using an alkali activator, without increasing the usage-amount of an alkali activator, and without raising the specific surface area of the activated carbon obtained excessively. An object of the present invention is to provide a method for producing activated carbon capable of increasing the pore diameter.

  The method for producing activated carbon according to the present invention that has solved the above-described problems includes an activation process in which a mixture of a carbon raw material and an alkali activator is accommodated in a furnace, and the interior of the furnace is heated; after the activation process, water is introduced into the furnace. A hydration step of supplying; a heating step of heating the inside of the furnace after supplying water.

  In the hydration step, it is preferable to supply 100 parts by mass to 1000 parts by mass of water with respect to 100 parts by mass of the alkali activator used in the activation step. Moreover, in the said hydration process, the furnace temperature at the time of supplying water has preferable activation treatment temperature or less. In the hydration step, it is preferable to supply the water in a steam state. The alkali activator is preferably at least one selected from the group consisting of sodium hydroxide, potassium hydroxide and lithium hydroxide.

  The present invention also includes an electrode for an electric double layer capacitor containing activated carbon obtained by the above production method and an electric double layer capacitor using the electrode for an electric double layer capacitor.

  According to the present invention, in the activation treatment using the alkali activator, the pore diameter is increased without increasing the amount of the alkali activator used and without excessively increasing the specific surface area of the obtained activated carbon. Activated carbon is obtained.

It is a figure which shows the pore diameter distribution of the activated carbon obtained by manufacture examples 1-4. It is a figure which shows the pore diameter distribution of the activated carbon obtained by manufacture examples 5-7. It is a figure for demonstrating the electric double layer capacitor manufactured using the activated carbon of an Example or a comparative example.

  The activated carbon production method of the present invention includes an activation process in which a mixture of a carbon raw material and an alkali activator is housed in a furnace and heats the interior of the furnace; a hydration process in which water is supplied into the furnace after the activation process; water is supplied And a heating step of heating the inside of the furnace.

  The reason why the pore diameter can be increased by suppressing the increase in the specific surface area of the activated carbon by supplying water and heating after the alkali activation treatment is not necessarily clear, but can be considered as follows. That is, for example, when potassium hydroxide is used as the alkali activator, as the activation reaction proceeds, potassium hydroxide reacts with the carbon raw material to produce an inactive potassium compound such as potassium carbonate. Since this inactive potassium compound no longer has an action of eroding the carbon raw material, the activation reaction does not proceed any further. However, by supplying water vapor, the inactive potassium compound reacts with water vapor to return to potassium hydroxide, and further heating activates locally, increasing the pore size while maintaining the specific surface area. It is thought that it is done.

Hereafter, the manufacturing method of the activated carbon of this invention is demonstrated in detail.
In the activation step, a mixture of the carbon raw material and the alkali activator is housed in a furnace, and the inside of the furnace is heated for activation treatment. Here, the “activation process” is to increase the specific surface area and the pore volume by forming pores on the surface of the carbon raw material.

  Examples of the carbon raw material include wood, sawdust, coconut shell, cellulosic fiber (including paper), synthetic resin (for example, phenol resin, polyvinyl chloride, polyimide, polyacrylonitrile (PAN)), petroleum pitch, coal tar pitch, and mesophase. Carbonaceous materials such as pitch and composites thereof; carbides of the carbonaceous materials; carbides such as coal, petroleum coke, coal coke, petroleum pitch coke, coal pitch coke, and charcoal. These carbon raw materials may be used alone or in combination of two or more. Among these, the carbon raw material is at least selected from the group consisting of coal pitch coke, coal, petroleum coke, coal coke, petroleum pitch coke, synthetic resin, composite of synthetic resin and cellulosic fiber, and carbides thereof. One is preferred.

  When the carbonaceous material carbide is used as the carbon raw material, the carbonaceous material is normally carbonized by heat treatment in an inert gas atmosphere. The temperature of the carbonization treatment is preferably 400 ° C. or higher, more preferably 500 ° C. or higher, preferably 950 ° C. or lower, more preferably 900 ° C. or lower. Further, the carbonization time is preferably 0.5 hours or longer, more preferably 1.0 hours or longer, 4.0 hours or shorter, more preferably 3.0 hours or shorter.

  The carbon raw material preferably has an average particle size of 10 mm or less, more preferably 5 mm or less, and even more preferably 2 mm or less. The lower limit of the average particle size of the carbon raw material is not particularly limited, but if the average particle size is too small, the handling of the powder tends to be poor (for example, the powder will rise during operation). Therefore, the average particle diameter of the carbon raw material is preferably 1 μm or more, more preferably 3 μm or more, and further preferably 5 μm or more. The average particle diameter is a volume-based median obtained by measuring a sample dispersed in water with a laser diffraction particle size distribution measuring apparatus (for example, “SALD (registered trademark) -2000” manufactured by Shimadzu Corporation). Is the diameter.

  As the alkali activator, an alkali metal compound is preferable. Examples of the alkali metal compound include hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide; carbonates such as sodium carbonate, potassium carbonate, and lithium carbonate; These alkali activators may be used alone or in combination of two or more. Among these, hydroxide is preferable, and potassium hydroxide is more preferable.

  The mass ratio of the carbon raw material to the alkali activator (alkali activator / carbon raw material) is preferably 1.0 or more, more preferably 1.5 or more, still more preferably 2.0 or more, and 4.5 or less. Is more preferable, 4.0 or less, more preferably 3.5 or less.

  Moreover, when adding an alkali activator, in order to fully mix with a carbon raw material, you may use an alkali activator as aqueous solution. The amount of water used at this time is preferably 0.05 times by mass to 10 times by mass of the alkali activator. In addition, when using an alkali activator as an aqueous solution, before performing heating for the activation treatment, heating at a temperature lower than the heating temperature in the activation treatment is performed to prevent bumping of moisture derived from the alkaline activator aqueous solution. It is preferable to remove moisture by performing treatment.

  The mixing method of the carbon raw material and the alkali activator is not particularly limited, and may be mechanically mixed. Although it does not specifically limit as a furnace used in order to heat the mixture of the said carbon raw material and an alkali activator, For example, a tunnel furnace, a rotary kiln, a batch furnace etc. are mentioned.

  When the inside of the furnace is heated, an inert gas is introduced. What is necessary is just to adjust the inflow amount of inert gas suitably according to the volume of a furnace, and the preparation amount of a carbon raw material. Note that nitrogen, argon, helium, or the like can be used as the inert gas.

  The heating temperature (furnace temperature) at the time of activation treatment (hereinafter sometimes referred to as “activation treatment temperature”) is preferably 600 ° C. or higher, more preferably 650 ° C. or higher, and preferably 950 ° C. or lower, more Preferably it is 900 degrees C or less. Since the alkali activator contains a small amount of moisture, it is preferable to remove the moisture contained in the alkali activator before reaching the activation treatment temperature. The heat treatment condition for removing moisture in the alkali activator is, for example, about 400 minutes at 400 ° C. In addition, the heating time in performing the activation treatment is preferably 0.1 hour or longer, more preferably 1.5 hours or longer, 3.5 hours or shorter, more preferably 3.0 hours or shorter. The atmosphere during heating is preferably an inert gas atmosphere such as argon, helium, or nitrogen.

  In the hydration step, water is supplied into the furnace. By supplying water into the furnace after the activation step, the inert alkali compound generated in the activation step can be reacted with water vapor to form a hydroxide. Thereby, in the heating process mentioned later, the average pore diameter of the activated carbon from which activated carbon can be further eroded can be enlarged more. In addition, as an aspect which supplies water in a furnace, the method of supplying water, without taking out the activated charcoal which passed through the activation process from a furnace is the simplest.

  The water supplied into the furnace may be supplied in a liquid state or in a gaseous state (water vapor) as long as it can be reacted with an inert alkali compound. In order to react with the inert alkali compound existing inside the pores of the activated carbon, it is preferable to supply water vapor. In addition, even if it supplies with a liquid form, it will be thought that it becomes gaseous (water vapor | steam) in the heating process mentioned later, and can be made to react with the inert alkali compound which exists in the inside of the pore of activated carbon. Moreover, as an aspect which supplies water vapor | steam, both the aspect which supplies water vapor | steam without diluting; The aspect which dilutes and supplies water vapor | steam with an inert gas are possible.

  The furnace temperature at the time of supplying water is not particularly limited, and water may be supplied at the furnace temperature at which the activation treatment is performed, or water may be supplied after cooling. In addition, there exists a tendency for the average pore diameter of the activated carbon finally obtained to become large and the hydration effect of the inactive alkali compound by water becomes high, so that the furnace temperature is low. Therefore, what is necessary is just to adjust suitably the temperature at the time of supplying water vapor | steam according to the desired average pore diameter.

  When it is desired to further suppress the increase in the specific surface area of the obtained activated carbon, the furnace temperature at the time of supplying water is preferably the activation treatment temperature or less, more preferably 500 ° C. or less, and further preferably 400 ° C. or less. By making the furnace temperature at the time of supplying water below the activation treatment temperature, the steam activation does not proceed and the increase in the specific surface area of the activated carbon can be further suppressed. The furnace temperature when supplying water is preferably room temperature (15 ° C.) or higher. Even if the temperature in the furnace is lowered below room temperature (15 ° C.), the hydration effect of the inert alkali compound by water becomes saturated, which is not economical.

  In the hydration step, the amount of water supplied into the furnace is preferably 100 parts by mass or more, more preferably 150 parts by mass or more, and still more preferably 200 masses, with respect to 100 parts by mass of the alkali activator used in the activation process. Part or more, preferably 1000 parts by mass or less, more preferably 750 parts by mass or less, and still more preferably 500 parts by mass or less. If the supply amount of water is 100 parts by mass or more with respect to 100 parts by mass of the alkali activator, most of the inactive alkali compound generated as the activation proceeds can be converted to hydroxides, and the pore diameter If the diameter increase effect is further improved and the amount is 1000 parts by mass or less, most of the supplied water contributes to the reaction with the inert alkali compound, which is more economical.

  In the heating step, after supplying water, the inside of the furnace is heated. Here, the heating includes both an aspect of heating to raise the temperature in the furnace lowered when water is supplied; and an aspect of heating continuously from the activation step.

  The heating temperature (furnace temperature) is preferably 600 ° C. or higher, more preferably 650 ° C. or higher, preferably 950 ° C. or lower, more preferably 900 ° C. or lower. The heating time is preferably 0.1 hour or longer, more preferably 1.5 hours or longer, 3.5 hours or shorter, more preferably 3.0 hours or shorter. The atmosphere during heating is preferably an inert gas atmosphere such as argon, helium, or nitrogen.

  The production method of the present invention may further include a cleaning step, a heat treatment step, and a pulverization step.

  The washing step is a step of washing and drying the activated carbon after the activation step. Since the alkali metal hydroxide used as the alkali activator adheres to the surface of the activated charcoal after the activation process, the activated charcoal is washed to remove such deposits.

Examples of the activated charcoal washing include water washing and acid washing.
The washing method is not particularly limited, but it is preferable to carry out, for example, by putting activated charcoal into water, stirring and dispersing as necessary, and then filtering. The stirring and dispersion can be performed by mechanical stirring, gas blowing, and ultrasonic irradiation, but can also be performed by heating and boiling. The water temperature during washing is preferably 30 ° C. or higher, more preferably 40 ° C. or higher, and further preferably 50 ° C. or higher. The stirring and dispersing time is preferably 0.5 hours or more, more preferably 1 hour or more, and further preferably 1.5 hours or more.

  In acid cleaning, activated charcoal is cleaned using a cleaning liquid containing an inorganic acid, an organic acid, or the like. The solvent for the cleaning liquid is not particularly limited, but is usually water. By performing the acid cleaning, the alkali metal hydroxide used as the alkali activator can be efficiently removed.

  Examples of the inorganic acid include hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, and carbonic acid. These inorganic acids may be used alone or in combination of two or more. When the inorganic acid is used, the concentration of the inorganic acid in the cleaning liquid is preferably 0.5 mol / L or more, more preferably 1.0 mol / L or more, still more preferably 1.5 mol / L or more, and 3.5 mol / L. L or less is preferable, More preferably, it is 3.0 mol / L or less, More preferably, it is 2.5 mol / L or less. When acid cleaning is performed using an inorganic acid, for example, activated charcoal and a cleaning liquid containing an inorganic acid may be mixed and stirred at a temperature of 50 ° C. to 100 ° C. for 30 minutes to 120 minutes.

  Examples of the organic acid include formic acid, oxalic acid, malonic acid, succinic acid, acetic acid, propionic acid, and the like. These organic acids may be used alone or in combination of two or more. The concentration of the organic acid in the cleaning liquid containing the organic acid is preferably 1 vol% or more, more preferably 2 vol% or more, still more preferably 5 vol% or more, preferably 100 vol% or less, more preferably 80 vol% or less, More preferably, it is 60 vol% or less. By setting the concentration of the organic acid to 1 vol% or more, the metal component removal effect by the organic acid can be obtained, but if the concentration becomes too high, the manufacturing cost increases. When acid cleaning is performed using an organic acid, for example, activated charcoal and a cleaning liquid containing an organic acid are mixed, and the resulting mixture is stirred at a temperature of 20 ° C. to 80 ° C. for 1 minute to 120 minutes. Good.

  In the manufacturing method of this invention, it is preferable to perform acid washing and water washing as a washing | cleaning process, More preferably, after performing acid washing, it is the aspect which performs water washing several times. The activated charcoal after washing is preferably dried at 50 to 120 ° C. for 0.5 to 2.0 hours.

  The heat treatment step is a step of further heat-treating the activated charcoal after the activation step or after the cleaning step in an inert gas atmosphere. By performing heat treatment on the activated charcoal, the amount of functional groups on the surface of the obtained activated carbon can be adjusted.

  Examples of the heat treatment include an aspect in which activated charcoal immediately after the activation process is heat-treated in an inert gas atmosphere; an activated charcoal after the activation process is heat-treated in an inert gas atmosphere after acid washing and / or water washing, and the like. Can be mentioned. As said inert gas, argon, nitrogen, helium etc. can be used, for example. The heat treatment temperature is not particularly limited, but is preferably 400 ° C. or higher and 1000 ° C. or lower.

  The pulverization step is a step of performing pulverization for adjusting the particle size of the activated carbon. The method for pulverizing the activated carbon is not particularly limited, and may be performed using a disk mill, a ball mill, a bead mill, or the like. The average particle diameter of the activated carbon is preferably 1 μm or more, more preferably 2 μm or more, and preferably 15 μm or less, more preferably 10 μm or less. If the average particle diameter is too small, the binding property between the current collector plate and the electrode material layer in the electrode is deteriorated, and the amount of binder required for the electrode material layer may be increased in order to maintain the practical binding property. is there.

The specific surface area of the activated carbon obtained by the production method of the present invention is preferably 1500 m ² / g or more, more preferably 1700 m ² / g or more, still more preferably 1800 m ² / g or more, and preferably 3500 m ² / g or less. Preferably it is 3200 m < ² > / g or less, More preferably, it is 3000 m < ² > / g or less. Here, in the present invention, the specific surface area is a value determined by the BET method for measuring the nitrogen adsorption isotherm of activated carbon.

Pore volume of the resulting activated carbon in the production process of the present invention is preferably at least 0.5 cm ³ / g, more preferably 0.7 cm ³ / g or more, is preferably from 2.0 cm ³ / g, more preferably It is 1.6 cm ³ / g or less. Here, in the present invention, the total pore volume means that the relative pressure P / P ₀ (P: pressure of the adsorbate gas in the adsorption equilibrium, P ₀ : saturated vapor pressure of the adsorbate at the adsorption temperature) is 0.93. It is a value calculated | required by BET method which measures the nitrogen adsorption amount until.

  The average pore diameter of the activated carbon obtained by the production method of the present invention is preferably 1.9 nm or more, more preferably 2.0 nm or more, still more preferably 2.1 nm or more, and preferably 3.0 nm or less, more preferably 2 .6 nm or less. Here, in the present invention, the average pore diameter is a value determined by the BJH method.

  Activated carbon obtained by the production method of the present invention can be used as an electrode material for an electric double layer capacitor, and an electrode for an electric double layer capacitor or an electric double layer capacitor can be produced using the electrode material. is there. According to the production method of the present invention, the pore diameter can be increased while suppressing an increase in the specific surface area of the activated carbon. That is, it is possible to easily adsorb and desorb ions in the electrolytic solution while suppressing a decrease in the density of the activated carbon. Therefore, if the activated carbon obtained by the production method of the present invention is used for an electric double layer capacitor, the internal resistance can be reduced while maintaining the capacitance per electrode volume.

  Next, the electric double layer capacitor of the present invention will be described. The electric double layer capacitor of the present invention is characterized in that activated carbon obtained by the above-described manufacturing method is used as an electrode constituent material.

  As an electrode for an electric double layer capacitor, for example, activated carbon, a conductivity-imparting agent and a binder are kneaded, a solvent is further added to prepare a paste, and this paste is applied to a current collector plate such as an aluminum foil. Is obtained by drying and removing.

  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.

1. Specific surface area, total pore volume, average pore diameter After 0.2 g of activated carbon was heated under vacuum at 150 ° C., an adsorption isotherm was measured using a nitrogen adsorption device (“ASAP-2400” manufactured by Micromeritics). 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.

2. Capacitance, internal resistance The charging / discharging terminal of the charging / discharging device (manufactured by Enomoto Kasei Co., Ltd., “ETAC (registered trademark) Ver. 4.4”) is connected to the current collecting plate of the electric double layer capacitor, and the voltage between the current collecting plates The battery was charged at a constant current of 40 mA until the voltage reached 2.5 V, and then charged at 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 obtained capacitance was divided by the total volume of the electrode material layer in the capacitor electrode to obtain a volume-based capacitance (F / cm ³ ). Moreover, internal resistance was calculated | required using following formula (3). The capacitance was 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
V0: 2.5 (V)
V1: 2.0 (V)
V2: 1.0 (V)

Production and production example 1 of activated carbon
Carbon hydroxide (purity 85% by mass) with respect to 25.0 g of phenol resin carbide (phenol resin (manufactured by Sumitomo Bakelite Co., Ltd.) carbonized at a processing temperature of 700 ° C. (average particle diameter: 5 mm to 15 mm)) as a carbon raw material ) 73.5 g (potassium hydroxide / carbon raw material (mass ratio) = 2.5) was added and mixed well. Next, the mixture was placed in a cylindrical furnace (manufactured by Osaka Seiko Co., Ltd.), heated to 400 ° C. at a heating rate of 10 ° C./min under a nitrogen flow (1 L / min), and kept at 400 ° C. for 30 minutes. It heated to 850 degreeC with the temperature increase rate of 10 degree-C / min, and heated at 850 degreeC for 2 hours, and performed the activation process.

Next, after the furnace temperature was cooled to room temperature (25 ° C.), 200 g of water vapor was supplied. The water vapor was diluted with nitrogen to form a mixed gas (water vapor partial pressure 81.6 kPa, total pressure: 101.3 kPa) and supplied at a flow rate of 1 L / min.
After supplying water vapor, it was heated again to 850 ° C. at a temperature rising rate of 10 ° C./min under a nitrogen flow (1 L / min), and heated at 850 ° C. for 2 hours.

  To the obtained mixture of activated material and potassium component, 1.6 L of water and 0.4 L of hydrochloric acid (concentration: 35% by mass) were added, heated at 100 ° C. for 2 hours, and then the activated material was collected by filtration to wash hydrochloric acid. went. Thereafter, 2 L of water was added to the activated product after washing with hydrochloric acid, heated to 100 ° C. and boiled for 2 hours, and then the activated product was filtered to perform warm water washing. The same operation was repeated, and washing with warm water was further performed once. The activated product that had been washed once with hydrochloric acid and washed twice with hot water was dried at 110 ° C. for 2 hours. A was obtained. The obtained activated carbon was evaluated, and the results are shown in Table 1 and FIG.

Production Example 2
The activation process was performed in the same manner as in Production Example 1. Next, after the furnace temperature was cooled to 400 ° C., 200 g of water vapor was supplied. The water vapor was diluted with nitrogen to form a mixed gas (water vapor partial pressure 81.6 kPa, total pressure: 101.3 kPa) and supplied at a flow rate of 1 L / min. After supplying water vapor, it was heated again to 850 ° C. at a temperature rising rate of 10 ° C./min under a nitrogen flow (1 L / min), and heated at 850 ° C. for 2 hours. The obtained activated product was washed and dried in the same manner as in Production Example 1, and activated carbon No. B was obtained. The obtained activated carbon was evaluated, and the results are shown in Table 1 and FIG.

Production Example 3
The activation process was performed in the same manner as in Production Example 1. Next, after the furnace temperature was cooled to 700 ° C., 200 g of water vapor was supplied. The water vapor was diluted with nitrogen to form a mixed gas (water vapor partial pressure 81.6 kPa, total pressure: 101.3 kPa) and supplied at a flow rate of 1 L / min. After supplying water vapor, it was heated again to 850 ° C. at a temperature rising rate of 10 ° C./min under a nitrogen flow (1 L / min), and heated at 850 ° C. for 2 hours. The obtained activated product was washed and dried in the same manner as in Production Example 1, and activated carbon No. C was obtained. The obtained activated carbon was evaluated, and the results are shown in Table 1 and FIG.

Production Example 4
The activation process was performed in the same manner as in Production Example 1. Next, 200 g of water vapor was supplied without lowering the furnace temperature. The water vapor was diluted with nitrogen to form a mixed gas (water vapor partial pressure 81.6 kPa, total pressure: 101.3 kPa) and supplied at a flow rate of 1 L / min. After supplying water vapor, it was again heated at 850 ° C. for 2 hours under a nitrogen flow (1 L / min). The obtained activated product was washed and dried in the same manner as in Production Example 1, and activated carbon No. D was obtained. The obtained activated carbon was evaluated, and the results are shown in Table 1 and FIG.

Production Example 5
Carbon hydroxide (purity 85% by mass) with respect to 25.0 g of phenol resin carbide (phenol resin (manufactured by Sumitomo Bakelite Co., Ltd.) carbonized at a processing temperature of 700 ° C. (average particle diameter: 5 mm to 15 mm)) as a carbon raw material ) 73.5 g (potassium hydroxide / carbon raw material (mass ratio) = 2.5) was added and mixed well. Next, the mixture was placed in a cylindrical furnace (manufactured by Osaka Seiko Co., Ltd.), heated to 400 ° C. at a heating rate of 10 ° C./min under a nitrogen flow (1 L / min), and kept at 400 ° C. for 30 minutes. It heated to 850 degreeC with the temperature increase rate of 10 degrees C / min, and heated at 850 degreeC for 2 hours, and performed the activation process. The obtained activated product was washed and dried in the same manner as in Production Example 1, and activated carbon No. E was obtained. The obtained activated carbon was evaluated, and the results are shown in Table 1 and FIG.

Production Example 6
In the same manner as in Production Example 5 except that the amount of potassium hydroxide (purity 85% by mass) used was changed to 147.6 g (potassium hydroxide / carbon raw material (mass ratio) = 5.0), activated carbon No. F was obtained. The obtained activated carbon was evaluated, and the results are shown in Table 1 and FIG.

Production Example 7
Carbon hydroxide (purity 85% by mass) with respect to 25.0 g of phenol resin carbide (phenol resin (manufactured by Sumitomo Bakelite Co., Ltd.) carbonized at a processing temperature of 700 ° C. (average particle diameter: 5 mm to 15 mm)) as a carbon raw material ) 73.5 g (potassium hydroxide / carbon raw material (mass ratio) = 2.5) was added and mixed well. Next, the mixture was placed in a cylindrical furnace (manufactured by Osaka Seiko Co., Ltd.), heated to 400 ° C. at a heating rate of 10 ° C./min under a nitrogen flow (1 L / min), and kept at 400 ° C. for 30 minutes. It heated to 850 degreeC with the temperature increase rate of 10 degree-C / min, and heated at 850 degreeC for 2 hours, and performed the activation process.

  Next, after the furnace temperature was cooled to room temperature (25 ° C.), it was again heated to 850 ° C. at a temperature rising rate of 10 ° C./min under nitrogen flow (1 L / min), and heated at 850 ° C. for 2 hours. The obtained activated product was washed and dried in the same manner as in Production Example 1, and activated carbon No. G was obtained. The obtained activated carbon was evaluated, and the results are shown in Table 1 and FIG.

  Production Examples 1 to 4 are cases where water is supplied into the furnace after the activation process and heat treatment is performed. In these production examples, the average pore diameter is increased without excessively increasing the specific surface area compared to Production Example 5 in which only alkali activation is performed. Comparing these production examples 1 to 4, it can be seen that the average pore diameter can be increased while the increase in the specific surface area is suppressed as the furnace temperature at the time of introducing the steam is lower. In particular, in Production Example 1 in which water was supplied after the furnace temperature was lowered to 25 ° C., the specific surface area hardly changed, and the average pore diameter was greatly increased. Production Example 6 is a case where the amount of the alkali activator used is increased by a factor of 2, but the specific surface area is excessively increased. In Production Example 7, after the activation step, the furnace temperature was lowered to room temperature and then heated again, but the average pore diameter was not increased.

Production of electric double layer capacitor Electric double layer capacitors were manufactured using A to G. 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 500 micrometers stainless steel sieve, 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. 3 has a separator (Celgard, “Celguard (registered trademark) # 3501”) 1 impregnated with the electrolytic solution 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.

  Table 2 shows the evaluation results of the activated carbons obtained in Production Examples 1 to 7 and the evaluation results of the electric double layer capacitors produced using these activated carbons.

  Activated carbon No. When AD is used, activated carbon No. Compared with the case where E is used, the internal resistance of the obtained electric double layer capacitor is greatly reduced both at 25 ° C. and at −30 ° C. In addition, these activated carbon No. When A to D are used, a sufficiently high value is obtained for the capacitance.

  The method for producing activated carbon of the present invention relates to a method for producing activated carbon, and can increase the pore diameter without excessively increasing the specific surface area of the obtained activated carbon.

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

Claims (7)

An activation process in which a mixture of a carbon raw material and an alkali activator is housed in a furnace and the interior of the furnace is heated;
A hydration step of supplying water into the furnace after the activation step;
A method for producing activated carbon, comprising: a heating step of heating the inside of the furnace after supplying water.   The manufacturing method of the activated carbon of Claim 1 which supplies 100 mass parts-1000 mass parts water with respect to 100 mass parts of alkali activators used at the activation process in the said hydration process.   The method for producing activated carbon according to claim 1 or 2, wherein in the hydration step, the furnace temperature when supplying water is equal to or lower than the activation treatment temperature.   The manufacturing method of the activated carbon as described in any one of Claims 1-3 which supplies the said water in the state of water vapor | steam in the said hydration process.   The method for producing activated carbon according to any one of claims 1 to 4, wherein the alkali activator is at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, and lithium hydroxide.   6. An electrode for an electric double layer capacitor, comprising activated carbon obtained by the production method according to any one of claims 1 to 5.   An electric double layer capacitor using the electric double layer capacitor electrode according to claim 6.