JP6509643B2 - Method of producing activated carbon - Google Patents

Description

  The present invention relates to a method of producing activated carbon and activated carbon produced by the method.

  Conventionally, activated carbon is used for applications such as polarizable electrodes of capacitors, adsorbents, etc. because of its high specific surface area. Such activated carbon is generally produced by steam activation or chemical activation of raw materials such as coconut shell carbide, phenol resin carbide, coal and the like.

  Also, the capacitor is known as a large capacity capacitor that uses the electric double layer generated at the interface between the polarizable electrode and the electrolyte as the storage principle, and is expected to have higher performance as the electronics field progresses. Therefore, in order to realize fast charge and discharge of the capacitor, various activated carbons having pores in the mesopore region and various methods for producing the same have been developed so that ions in the electrolytic solution can easily move.

  As activated carbon for capacitors, it is considered preferable to have a large specific surface area, but even if the specific surface area is too large, the discharge capacity per volume decreases, so the specific surface area is not increased. It is important to improve the discharge capacity per specific surface area.

  For that purpose, it is said that it is preferable to have many nitrogen atoms while maintaining the specific surface area by increasing the amount of pores of a desired size (especially about 1 to 2 nm), for example, patent Document 1 describes porous carbon containing a nitrogen atom.

Unexamined-Japanese-Patent No. 2010-135647

  However, when the amount of the desired pore size (particularly, about 1 to 2 nm) is increased, the pores having other sizes are also inevitably increased, and thus it is not possible to increase only the desired pores. Therefore, the specific surface area is increased to obtain a large discharge capacity, and the discharge capacity per specific surface area is not sufficient.

  An object of the present invention is to provide an activated carbon for a capacitor in which the discharge capacity per specific surface area is improved by having a large number of desired pores while having a certain specific surface area.

As a result of intensive studies, the present inventors have impregnated a carbonaceous material in a mixture of high pressure carbon dioxide and an oxidizing agent, and then making the material porous by reacting the carbonaceous material with the oxidizing agent, By finding out that activated carbon can be obtained and optimizing the conditions, while having a certain specific surface area suitable for use in a capacitor, it has a large number of desired pores and a discharge per specific surface area It has been found that activated carbon with improved capacity can also be obtained. The present invention has been completed by further research based on such findings. That is, the present invention includes the following configurations.
Item 1. A method of producing activated carbon,
An impregnating step of impregnating a carbonaceous material and / or a resin in a mixture of high pressure carbon dioxide and an oxidizing agent, and a porosifying step of making porous by reaction of the carbonaceous material and / or the resin with the oxidizing agent The manufacturing method.
Item 2. The pressure of the high pressure carbon dioxide is 0.2 to 30 MPa. The manufacturing method according to Item 1.
Item 3. Item 3. The production method according to Item 1 or 2, wherein the porosifying step is performed at 300 ° C. or less.
Item 4. The shape of the carbonaceous material and / or resin is particulate, and the average particle diameter of the carbonaceous material and / or resin is 100 μm or less and the particle size distribution is in the range of 40 μm, or
The method according to any one of Items 1 to 3, wherein the shape of the carbonaceous material and / or the resin is fibrous, and the average fiber diameter of the carbonaceous material and / or the resin is 50 μm or less.
Item 5. The carbonaceous material and / or resin is at least one selected from the group consisting of activated carbon, wood material, coconut shell, fruit shell, thermosetting resin and its carbide, thermoplastic resin and its carbide, coal pitch, and petroleum pitch The manufacturing method according to any one of Items 1 to 4, which is
Item 6. The oxidizing agent is at least one selected from the group consisting of oxygen, ozone, nitrogen dioxide, hydrogen peroxide, sulfur dioxide, persulfate, peracetic acid, formic acid, nitric acid, nitric acid, concentrated nitric acid, fuming nitric acid and t-butyl hydroperoxide. Item 5. The method according to any one of Items 1 to 5, which is a species.
Item 7. Item 7. The production method according to any one of Items 1 to 6, wherein the impregnating step and the porosifying step are performed sequentially and continuously.
Item 8. Item 8. The production method according to any one of Items 1 to 7, wherein the impregnating step and the porosifying step are repeated.
Item 9. The BET specific surface area is 200 to 2000 m ² / g, the bulk density is 0.1 to 1.2 g / mL, the discharge capacity is 5 to 20 F / cc, and the discharge capacity per specific surface area (discharge capacity / ratio Activated carbon for capacitors having a surface area of 1 × 10 ⁻³ to 1 × 10 ⁻¹ F / m ² .
Item 10. Item 10, at least one functional group selected from the group consisting of a nitro group, a nitroso group, an azo group, an amino group, a lactone group, a phenyl group, a phenol group, a carbonyl group, a carboxy group, and a sulfone group. The activated carbon for capacitors according to.
Item 11. Item 11. The activated carbon for a capacitor according to item 9 or 10, which contains nitrogen atoms in an atomic ratio of 0.7 to 5% with respect to carbon atoms.
Item 12. Item 12. The activated carbon for a capacitor according to any one of Items 9 to 11, which contains an oxygen atom in an atomic ratio of 1.2 to 30% with respect to a carbon atom.
Item 13. Item 13. An electrode for a capacitor using the activated carbon for a capacitor according to any one of Items 9 to 12.
Item 14. Item 14. A capacitor comprising the capacitor electrode according to item 13.
Item 15. A method of increasing the number of pores having a pore diameter of 1 to 2 nm possessed by a carbonaceous material and increasing the content of nitrogen atoms,
A method comprising the steps of: impregnating a carbonaceous material into a mixture of high pressure carbon dioxide and an oxidizing agent; and porosifying the reaction by the reaction of the carbonaceous material with the oxidizing agent.

  According to the present invention, activated carbon is obtained by impregnating a carbonaceous material in a mixture of high pressure carbon dioxide and an oxidizing agent, and then making the material porous by reaction of the carbonaceous material with the oxidizing agent. This method is a novel method which has not been made before.

  Moreover, since this method can be performed at a low temperature and in a short time as compared with the conventional method using steam activation, the manufacturing cost of activated carbon can be reduced.

  Furthermore, by optimizing the conditions, activated carbon having a large number of desired pores and improved discharge capacity per specific surface area while having a constant specific surface area suitable for use in a capacitor It is also possible to get. The activated carbon thus obtained can also increase the content of nitrogen atoms and further improve the discharge capacity per specific surface area.

It is a graph which shows pore distribution of Example 1, and the pore volume of the pore of a specific magnitude | size. 15 is a graph showing the pore distribution of Example 6. 15 is a graph showing the pore distribution of Example 7. It is a Raman spectrum which shows the result of the crystal | crystallization characteristic analysis of Example 4 and 5. It is a FE-SEM image which shows the result of shape observation of Examples 2 and 3. It is a FE-SEM image which shows the result of shape observation of Example 2. FIG. It is drawing which shows the structure of the electric double layer capacitor produced as an experiment in the Example.

1. Method for Producing Activated Carbon The method for producing activated carbon according to the present invention comprises an impregnating step of impregnating a carbonaceous material and / or a resin in a mixture of high pressure carbon dioxide and an oxidizing agent, and the carbonaceous material and / or the resin and the oxidant. And a process for making porous by reaction with the

<Impregnation process>
In the impregnation step, the carbonaceous material and / or the resin is impregnated in a mixture of high pressure carbon dioxide and an oxidizing agent. By this step, the oxidizing agent can be sorbed on the surface of the carbonaceous material and / or resin as the raw material.

Carbonaceous Material and / or Resin In the present invention, the carbonaceous material and / or resin used as a raw material is not particularly limited as long as it is a material that can be made porous by reacting with an oxidizing agent described later, an activated carbon precursor Not only activated carbon can also be used as a raw material. In addition, resins such as thermosetting resins and thermoplastic resins can also be used as a raw material.

  As such a carbonaceous material and / or resin, for example, a carbonaceous material such as activated carbon, wood material, coconut shell, fruit shell, coal coke, coal pitch, thermosetting resin and its carbide, thermoplastic resin, and the like Resins such as carbides can also be used.

  As the activated carbon, activated carbon produced by a conventional method such as steam activation (for example, JP-A-2002-33249 etc.) may be used, or activated carbon obtained by the production method of the present invention is used again as a raw material You may

  The wood material may be appropriately selected according to the application, but, for example, charcoal (wood char etc.), plate material, chip, sawdust, wood powder, bark powder, wood fiber, paper, cloth, etc. And processed plywood, medium quality fiber board (hereinafter sometimes referred to as MDF), particle board and the like.

  The fruit shell is not particularly limited, and examples thereof include hut, peach, plum, almond and the like.

  The thermosetting resin is not particularly limited, and examples thereof include epoxy resins, phenol resins, melamine resins, polyimides, urea resins, unsaturated polyesters, polyurethanes, crosslinked polymers and the like, and carbides thereof may also be suitably used.

  The thermoplastic resin is not particularly limited, but polyethylene, polypropylene, polystyrene, polyester, polycarbonate, polyacrylonitrile, polyvinyl alcohol, polyvinyl chloride, polyvinylidene fluoride, polyimide, polyamide, polyamide imide, polysulfone, polyether sulfone, poly Ether imide, polyphenylene oxide, polyether ketone, acrylonitrile butadiene styrene copolymer, styrene acrylonitrile acrylonitrile copolymer, polystyrene acrylonitrile copolymer, plastic waste, waste tire, etc. may be mentioned, and carbides thereof are also suitably used. obtain.

  Among these, from the viewpoint of specific surface area, discharge capacity, discharge capacity per specific surface area, etc., activated carbon (in particular, ordinary water vapor activated activated carbon (eg, JP-A-2002-33249 etc.)) is preferable. That is, activated carbon (especially, ordinary steam activated activated carbon) is preferable for capacitor applications. Moreover, although a wood material is preferable from the viewpoint of low raw material cost and reactivity with an oxidizing agent described later, a high density raw material is preferable from the viewpoint of discharge capacity per volume.

  When the shape of the carbonaceous material and / or the resin is particulate, the average particle diameter is preferably 100 μm or less, and more preferably 45 to 75 μm. Further, the particle size distribution of the carbonaceous material and / or the resin is preferably in the range of 100 μm or less and 40 μm. Moreover, when a carbonaceous material and / or resin are fibrous form, 50 micrometers or less are preferable and, as for an average fiber diameter, 10-20 micrometers is more preferable. The uniform particle diameter and fiber diameter of the carbonaceous material and / or resin enables uniform reaction, and the reproducibility of porosification is further enhanced. In the present invention, the average particle size, particle size distribution, average fiber size and the like of the carbonaceous material and / or resin are selected and controlled with a sieve and measured with a microscope. However, when the carbonaceous material and / or the resin is in the form of fibers, it is only measured by a microscope.

The oxidizing agent is not particularly limited as long as the above-mentioned carbonaceous material can be made porous to produce activated carbon, and oxygen (O ₂ ), ozone (O ₃ ), nitrogen dioxide (NO ₂ ), nitric acid (HNO ₃ ), concentrated nitric acid, fuming nitric acid (concentrated nitric acid blown with gaseous nitrogen dioxide), hydrogen peroxide (H ₂ O ₂ ), sulfur dioxide (SO ₂ ), persulfuric acid (H ₂ SO ₅ ), etc. Organic peroxides such as peracetic acid (CH ₃ COOOH) and periodate (HCOOOH); organic peroxides such as t-butyl hydroperoxide ((CH ₃ ) ₃ COOH) and the like; Can be used alone or in combination of two or more.

Although these oxidizing agents are preferably inorganic oxidizing agents, they may be used depending on the application, and depending on the type of oxidizing agent, select functional groups on the surface of the activated carbon to be obtained, hetero atoms doped in the activated carbon, etc. Can. For example, the electric double layer capacitor application, as described above, since it is preferable to include a nitrogen atom, as an oxidant, nitrogen dioxide (NO _2), nitric acid, concentrated nitric acid, it is preferable to use fuming nitric acid and the like. Further, when it is desired to include a sulfur atom in the activated carbon, sulfur dioxide (SO ₂ ), persulfuric acid (H ₂ SO ₅ ) or the like may be used.

High Pressure Carbon Dioxide High pressure carbon dioxide is used in the impregnation process of the present invention. The high pressure carbon dioxide may be in a liquid, gas or supercritical state. However, liquid can dissolve substances, but it is difficult for it to get into pores like activated carbon. On the other hand, gases tend to enter the pores but lack the ability to dissolve substances. Supercritical carbon dioxide, which is in a state intermediate between gas and liquid, can dissolve oxidizing agents like liquids and can feed them into pores like gases, so the surface of carbonaceous material It is most preferable in that the oxidizing agent can be surely impregnated.

When a strong oxidizing agent such as NO ₂ is directly added to the carbonaceous material and / or resin, the heat of adsorption generated may accumulate in the carbonaceous material and lead to an oxidation reaction with temperature rise. In the present invention, by diluting the oxidizing agent with high-pressure carbon dioxide, the adsorption rate can be decreased, and the generated heat of adsorption can be diffused to more safely supply the oxidizing agent without reaching the oxidation reaction. .

  In the present invention, high-pressure carbon dioxide means carbon dioxide in a state where high pressure is applied, and specifically, the pressure is 0.2 to 30 MPa, and in the oxidizing agent supply process described later, 1 to 6 MPa Carbon dioxide in the liquid or near the liquid is preferred, and in the impregnation step, carbon dioxide in a supercritical state in the range of 5 to 20 MPa (especially 7 to 10 MPa) or near supercritical is preferable.

  Although high-pressure carbon dioxide may be produced by controlling the pressure, it can also be produced by introducing liquid carbon dioxide into a closed vessel.

  The essential manufacturing method of the present invention comprises an impregnating step and a porosifying step, but it is preferable from the viewpoint of safe manufacturing to also include an oxidant supplying step described later prior to the porosifying step.

<Oxidizing agent supply process>
In the present invention, when the carbonaceous material and the oxidizing agent are mixed, it is preferable to add the oxidizing agent to the carbonaceous material. In this case, it is preferable to first add the carbonaceous material to the closed vessel. The amount of the carbonaceous material to be added to the closed container is preferably 0.2 to 10 w / v%, more preferably 2 to 4 w / v%, based on the volume of the container. It is preferable to add 1 to 40 w / v% (especially 10 to 20 w / v%) of carbon dioxide with respect to the vessel volume and to cool the closed vessel to -10 to 20 ° C (especially 0 to 10 ° C). On the other hand, 50 to 300 parts by weight (particularly 100 to 200 parts by weight) of the oxidizing agent is collected in 100 parts by weight of the carbonaceous material in an oxidizing agent collection pipe (a container other than the above-mentioned closed container). After that, it is preferable to connect the oxidizing agent collecting pipe containing the oxidizing agent to the closed container containing the carbonaceous material and / or the resin, and introduce the oxidizing agent into the closed container.

<Impregnation process>
In the impregnation step, it is preferable that the above-mentioned impregnation of the carbonaceous material improve the impregnation amount while suppressing the reaction between the carbonaceous material and the oxidizing agent (porosity of the carbonaceous material).

  In order to further suppress the reaction between the carbonaceous material and the oxidizing agent (porosity of the carbonaceous material), it is preferable to stir when impregnating the carbonaceous material. As described later, the impregnation step and the porosification step may be performed sequentially (simultaneously) sequentially, but in this case, it is performed at a higher temperature, for example, 20 to 300 ° C. (particularly 40 to 250 ° C.) It is also possible.

  In the impregnation step, the above-mentioned impregnation of the carbonaceous material is preferably performed for 5 minutes to 40 hours to improve the sorption amount of the oxidizing agent to the carbonaceous material more, and may be performed for 1 to 20 hours. More preferable.

<Porporation process>
In the porosifying step, the carbonaceous material is made porous by the reaction of the carbonaceous material and the oxidizing agent after the above-mentioned impregnation step.

  Specifically, it is preferable to perform heat treatment so that the carbonaceous material and the oxidizing agent easily react. After the impregnation step, heating may be performed as it is, or after the sealed container is cooled, pressure may be reduced to remove carbon dioxide and then heating may be performed. Further, after removing the oxidizing agent remaining without being sorbed by the carbonaceous material, heating may be performed after pressurization with carbon dioxide, nitrogen, argon or the like. Furthermore, after removing the oxidizing agent remaining without being sorbed by the carbonaceous material, heating may be performed after adding a new oxidizing agent such as oxygen or hydrogen peroxide water. In the present invention, the reaction can be triggered at low temperature as compared to the conventional method, and can be performed at 300 ° C. or less, preferably 20 to 250 ° C., more preferably 120 to 220 ° C. Thereby, the carbonaceous material and the oxidizing agent can be sufficiently reacted to make the carbonaceous material porous to produce activated carbon.

  The reaction time (heating time) is not particularly limited as long as the carbonaceous material can be made sufficiently porous, but it is preferably 0.5 to 60 minutes, and more preferably 2 to 10 minutes.

  The heating method is not particularly limited, and various conventionally known methods can be employed. For example, a method of heating in an oil bath, a method of heating while being in contact with a panel heater, a ceramic heater or the like, an infrared lamp Non-contact heating methods can be adopted such as laser, warm air, microwave and the like. Among them, a method of heating in an oil bath is preferable from the viewpoint of simply raising the temperature in a short time.

<Manufacturing method>
The above-mentioned impregnation step and porosification step may be performed as separate steps or may be performed sequentially (simultaneously).

  Further, in the production method of the present invention, the impregnation step and the porosification step may be performed only once or plural times. In the case where it is carried out a plurality of times, the impregnating step and the porosifying step can be carried out using the activated carbon obtained through the impregnating step and the porosifying step again as a raw material.

  When the impregnation step and the porosification step are repeated, the pore volume of the obtained activated carbon can be further improved and the average pore diameter can be further increased, as compared with the case where it is performed only once. For this reason, by repeating the impregnation step and the porosification step a plurality of times, it is possible to reduce the pores having a small diameter and to increase the number of desired pores, which is more suitable for capacitor applications. The preferred number of repetitions is about 2 to 10, and the more preferred number of repetitions is about 2 to 5.

According to the production method of the present invention, the pore volume can be increased and the pores with a pore diameter of less than 1 nm can be reduced as described above by passing through the impregnation step and the porosification step at least once. The desired pores can be increased. For this reason, the pore diameter of the carbonaceous material can be increased to 1 to 2 nm.

  In general, if it is attempted to increase the number of pores having a pore diameter of 1 to 2 nm, pores of other sizes are also inevitably increased. Although it was difficult to increase only the pores having the pore size, according to the production method of the present invention, it is possible to maintain the number of pores of other sizes while maintaining fine pores with a pore size of 1 to 2 nm. It is possible to increase only the pores with pore size.

  After that, if necessary, the pressure is reduced to normal pressure to obtain activated carbon, but high pressure carbon dioxide may be sprayed to remove excess oxidant, or a washing step may be provided.

2. Activated Carbon The activated carbon of the present invention is obtained by the above-mentioned production method of the present invention. When performing the manufacturing method of the present invention, by setting the conditions appropriately, it is possible to obtain activated carbon suitable for use in a capacitor. More specifically, it is preferable to use activated carbon (in particular, ordinary steam activated activated carbon) as a raw material.

  The activated carbon for capacitors of the present invention thus obtained may have a pore distribution peak at a pore diameter of 0.7 to 5 nm, particularly 1 to 2 nm.

The BET specific surface area of the activated carbon for a capacitor of the present invention thus obtained is 200 to 2000 m ² / g, preferably 600 to 1500 m ² / g. The pore characteristics of the activated carbon for capacitors of the present invention are analyzed using a gas adsorption analyzer (for example, BELSORP-mini II (manufactured by Japan BEL)). For example, first, at -196 ° C, the adsorption amount of nitrogen gas as a function of the relative pressure of nitrogen gas (this is referred to as a nitrogen adsorption isotherm) is obtained. The BET specific surface area and the total pore volume are calculated from this nitrogen adsorption isotherm. Also, a pore volume of 1 to 2 nm is calculated using the GCMC method.

The bulk density of the activated carbon for a capacitor of the present invention thus obtained is 0.1 to 1.2 g / mL, preferably 0.2 to 1.0 g / mL .

  Furthermore, the discharge capacity of the activated carbon for a capacitor of the present invention thus obtained is 5 to 20 F / cc, preferably 8 to 18 F / cc, more preferably 10 to 16 F / cc.

The discharge capacity of the activated carbon for capacitor of the present invention is evaluated using the capacitor characteristic evaluation of the activated carbon: initial performance. The specific evaluation method is described below. A polarizable electrode mainly composed of activated carbon is mainly composed of activated carbon and a binder, but a conductive material may be further added to impart conductivity to the electrode. A solvent is appropriately added to the mixture, and the mixture is molded on a current collector by a known method such as a coating method or a sheet molding method, or a solvent is appropriately added, and a known method such as a coating method or a sheet molding method The molded body formed by the above method is adhered to a current collector to form an electrode. The obtained positive electrode molded body (activated carbon / Ketjenburuck (conductive material) / PTFE (binder) = 86/7/7; area: 2.8 cm ² ), negative electrode molded body (activated carbon / Ketjen black (conductive material) / After drying the PTFE (binder) = 86/7/7; area: 2.8 cm ² ) in vacuum at 170 ° C. for 10 hours and transferring the two dried molded articles into a dry box in an argon gas atmosphere Then, laminating via a cellulose-based separator, a capacitor of an aluminum laminate is prepared by using a propylene carbonate solution in which TEMA · BF ₄ (triethyl methyl ammonium tetrafluoro ester) is dissolved at 1.4 M / L as an electrolytic solution. A voltage of 2.5 V is applied to the obtained capacitor for 2 hours (maximum current 0.7 mA) and then discharged with a constant current of 0.7 mA, and the slope of the obtained discharge curve (between 2.5 V and 0 V) Determine the initial capacitance (F) from).

For this reason, in the activated carbon for capacitors of the present invention, the discharge capacity (discharge capacity / specific surface area) per specific surface area can be increased, and specifically, 1 × 10 ⁻³ to 1 × 10 ⁻¹ F / m. ^{It can be 2} preferably 1 × 10 ^{−2 to} 5 × 10 ⁻² F / m ² .

  Moreover, according to the manufacturing method of this invention mentioned above, the functional group which exists on the surface of the activated carbon obtained can be set by selecting an oxidizing agent suitably. Thereby, depending on the application, at least one functional group such as nitro group, nitroso group, azo group, amino group, lactone group, phenyl group, phenol group, carbonyl group, carboxy group and sulfone group is formed on the activated carbon surface It is possible. In addition, when using the activated carbon of this invention for a capacitor use, it is preferable to have an activated carbon surface at least 1 sort (s) of functional groups, such as a nitro group, a nitroso group, an azo group, an amino group.

  Moreover, according to the manufacturing method of this invention mentioned above, the density | concentration of the nitrogen atom, oxygen atom, etc. which exist in the activated carbon obtained can be set by selecting an oxidizing agent suitably. For example, by selecting nitrogen dioxide as the oxidizing agent, nitrogen atoms can be contained in an atomic ratio to carbon atoms of 0.7 to 5%, particularly 1.3 to 4%. In addition, oxygen atoms can be contained in an atomic ratio of 1.2 to 30%, particularly 1 to 3%, to carbon atoms. As described above, since it is possible to include a large amount of nitrogen atoms (increasing the content of nitrogen atoms) as compared to conventional activated carbon, it is suitable for capacitor applications.

3. Electrodes for Capacitors The electrodes for capacitors according to the present invention are prepared by adding a conductive additive and a binder at a predetermined ratio to the above-mentioned activated carbon for capacitors according to the present invention, kneading as required, and shaping into an arbitrary shape, It can be manufactured.

  The conductive aid used here is not particularly limited, and examples thereof include acetylene black, carbon black and graphite. The binder is not particularly limited, and examples thereof include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer, styrene-butadiene rubber, polyacrylonitrile and the like.

  The mixing ratio of the activated carbon for a capacitor of the present invention, the conductive additive and the binder may be appropriately determined. In addition, since the shapes of activated carbon for capacitors, conductive assistants and binders are usually in the form of particles or powders, when these are mixed, an organic solvent such as N-methyl-2-pyrrolidone (NMP) is mixed. It is preferable to make it paste-like.

4. Capacitor The capacitor of the present invention has the capacitor electrode of the present invention described above. Specifically, the capacitor of the present invention covers the periphery of the cell in which the electrode for a capacitor of the present invention is disposed on both sides of the separator, as necessary, with gasket-like packings. It is preferable to arrange the aluminum current collector foils and to arrange the current collector terminals in contact with the respective aluminum current collector foils. It is possible to apply the existing material conventionally known as materials, such as packing and a current collection terminal.

  Although the present invention will be specifically described based on examples, the present invention is not limited to these.

Example 1
<Impregnation process>
Woody steam activated carbon was used as a raw material.

The aforementioned raw materials and a stirrer were charged into a 50 mL pressure vessel, sealed, and replaced with CO ₂ . _Next, high pressure injected into the vessel in the order of NO 2, CO _2, while kept at 60 ° C., and stirred for 1 hour.

<Porporation process>
The recovered product obtained in the above sorption step was placed in a 50 mL pressure vessel and sealed. Thereafter, CO ₂ was injected into the pressure vessel, and the reaction was carried out in an oil bath of 180 ° C. for 10 minutes.

[Examples 2 to 17]
The procedure of Example 1 was repeated except that the raw materials and the respective conditions were changed as described in Tables 1 and 2. The results are shown in Tables 1 and 2 (Table 1 is the impregnation step and Table 2 is the porosification step). In Examples 2 and 3, woody char was used as a raw material. In Examples 4 and 5, coal pitch (JC / 2J10-17) manufactured by Osaka Gas Chemical Co., Ltd. was used. In Example 6, as a melamine resin (melamine foam, manufactured by Nakatani), a carbonized melamine resin product which was carbonized at 400 ° C. for 30 minutes in a nitrogen atmosphere was used. In Example 7, kainol (manufactured by Nippon Kainol) was used as a phenol resin. In Example 8, polyimide (JC / 2J10-17) manufactured by Osaka Gas Chemical Co., Ltd. was used. In Example 9, coconut shell activated carbon manufactured by Osaka Gas Chemical Co., Ltd. was used. In Example 10, ACF (A15) manufactured by Osaka Gas Chemical Co., Ltd. was used. In Example 11, a fruit shell carbonized product was used. In Example 12, a PAN-based carbonized product manufactured by Osaka Gas Chemical Co., Ltd. was used. In Example 13, porous step adds the _H 2 _{O 2,} was used NO ₂ and _H 2 _{O 2} as an oxidizing agent. In Example 14, porous step adds the _{O 2,} was used NO ₂ and _{O 2} as an oxidizing agent. In Examples 15 and 16, the impregnation step and the porosification step used fuming nitric acid as an oxidizing agent. In Example 17, the porosifying step was performed using microwave (700 W).

  The above results are summarized below.

  It has been confirmed that supercritical activation can be performed using carbonaceous materials such as woody char, activated carbon, coconut shells, and fruit shells, and resins such as phenol resins, polyimide resins, and melamine resins as raw materials.

[Specific surface area]
The specific surface areas of Examples 1 to 4, 8 to 11 and 14 to 16 were measured. The results are shown in Table 3.

  Among the above, taking Example 1 as an example in particular, FIG. 1 shows the results of comparing the pore distribution and the pore volume of pores of a specific size with the steam activated activated carbon as a raw material.

  As a result, while the pore volume was increased by the method of the present invention, the peak diameter of the pore distribution was shifted to the right, and the pore volume of small pores was reduced. Moreover, it was suggested that the pore volume of the pore about 1-2 nm of pore diameters preferable as an electric double layer capacitor use is increasing.

  Moreover, from the result of the pore volume of pores of a specific size, it is possible to increase only the pore volume of pores having a pore diameter of about 1 to 2 nm, which is preferable for electric double layer capacitor applications, and to form pores of other sizes. The pore volume of is substantially maintained. From this, it was suggested that by adopting the method of the present invention, it is possible to increase only pores having a diameter of about 1 to 2 nm, which is preferable for electric double layer capacitor applications. In addition, in the right figure of FIG. 1, each bar graph is "from 0 to 1 nm pore volume", "1 to 2 nm pore volume", "2 to 50 nm mesopore volume", "50 nm or more macropore volume" sequentially from the left. , "Total pore product".

  Pore distribution is shown in FIG. 2 about Example 6 using a melamine resin carbonized product, and the melamine resin carbonized product which is a raw material. In addition, in FIG. 2, each graph shows Example 6, melamine resin carbonization goods in an order from the top. Moreover, pore distribution is shown in FIG. 3 about Example 7 which used the phenol resin. As a result, the pore diameter, pore volume, etc. could be controlled depending on the difference of the starting material. In particular, melamine resin does not have pores of 2 nm or less, pore diameter of about 2 to 10 nm, phenol resin does not have pores of 1 nm or less, and pore volume of pores of about 1 to 2 nm is retained. It has been suggested that it can be used for double layer capacitor applications. Similar results were seen in Examples 4 and 5 where coal pitch was used as the feedstock.

[Surface characteristics]
As surface property evaluation, FT-IR measurement was performed. From the results of FT-IR, in Examples 2 and 3, nitrate / nitrite ion, aromatic / alkene, non-conjugated alkene, N-containing functional group (amine, amide) and the like were also observed.

[Crystal properties]
Raman spectroscopy measurement was performed as crystal characteristic analysis. The results are shown in FIG. In the spectrum of FIG. 4, the results are Example 4, Example 5, coal pitch in order from the top. As a result, in Examples 4 and 5, as compared to the wood char before applying the method of the present invention, a peak attributable to SP3 and defects 1360 cm ^-1, sharper peak attributable to SP2 of 1580 cm ^-1 It was suggested that a change in carbon structure appeared in the process of the production method of the present invention.

[Shape observation]
FE-SEM observation was performed as shape observation of the sample before and behind applying the method of this invention. The results are shown in FIGS. As a result of measuring the raw wood char and Examples 2 and 3, while the raw wood char has a wide range of pore distribution, regular round holes are observed in Examples 2 and 3. The It is suggested that this circular hole was generated by the reaction of the woody char and NO ₂ which is an oxidizing agent. Also, very small pores were also observed in Examples 2 and 3. From this, it was possible to visually grasp the porosification by the method of the present invention. Similar results were obtained in Example 7 as well.

[XPS analysis]
In order to determine the form (functional group) of each element from the spectrum of C / N / O / S / Si element, XPS analysis is performed using a commercially available water vapor activated activated carbon (specific surface area: 2853 m ² / g) in Comparative Example 1 Did. XPS analysis was performed in Examples 1 and 15. In Comparative Example 1, the amount of nitrogen was detected 9 times or more from the sample in Example 1 and 11 times or more in Example 15 with respect to the slight presence of nitrogen. The oxidizing agent can change the nitrogen content. The origin of the nitrogen element was cyanide, ammonium salt, nitrate and the like. As a result of the functional groups, carboxy, lactone, phenol, cyano, ammonium and nitrate groups were detected on the surface of the sample in any of the examples.

[Capacitor application]
As shown in FIG. 7, using the activated carbons obtained in Examples 1, 25, 27 and 33 as active materials, evaluation electrodes were produced, and an electric double layer capacitor was produced by using this. The components of the prototype electric double layer capacitor are
Cell type: Single layer laminated cell electrode type: 14 × 20 mm ²
Positive electrode: Evaluation sample produced: Negative electrode produced: Evaluation sample separator produced: Cellulose-based electrolyte: 1.4 M-TEMA, BF ₄ (PC)
Reference pole: None. In addition, said activated carbon was grind | pulverized to a 5 micrometer level using the planetary mill (revolution type ball mill).

The results of the evaluation are shown in Table 5. Discharge capacity in Example 1 is 13.0F / cc (discharge capacity is 1.26 × ^{10 -2} per specific surface area), further, the discharge capacity in Example 15, per surface area 17.9F / cc (specific discharge capacity could be improved with 1.47 × ^{10 -2).} As compared with the commercially available steam activated carbon according to Comparative Example 1, higher values were obtained for the supercritical activated carbon in terms of discharge capacity and discharge capacity per specific surface area . Particularly, in the case of Example 15, improved relative to Comparative Example 1 of a commercially available activated carbon, the discharge capacity (F / cc) was 1.6 times, the discharge capacity per specific surface area of about 3.7 times It shows that it was possible. From Comparative Example 1, Example 1 contained a nitrogen atom, so the discharge capacity was improved. Moreover, the specific surface area is controlled to about 1000 m 2 / ^g, the discharge capacity per specific surface area was increased about 3 times higher than Comparative Example 1. Then, in Example 15, contains more pore volume of 1 to 2 nm, and, because it has many more nitrogen atom content, discharge capacity of the discharge capacity and the specific surface area per could further improve both.

DESCRIPTION OF SYMBOLS 1 positive electrode 2 negative electrode 3 separator 4 positive electrode collector 5 negative electrode collector 6 aluminum laminated exterior 20 electric double layer capacitor

Claims (14)

A method of producing activated carbon,
An impregnating step of impregnating a carbonaceous material and / or a resin in a mixture of high pressure carbon dioxide and an oxidizing agent, and a porosifying step of making porous by reaction of the carbonaceous material and / or the resin with the oxidizing agent with the pressure of the high-pressure carbon dioxide, Ru 0.2~30MPa der method. The manufacturing method according to claim 1, wherein the porosifying step is performed at 300 ° C. or less. The shape of the carbonaceous material and / or resin is particulate, and the average particle diameter of the carbonaceous material and / or resin is 100 μm or less and the particle size distribution is in the range of 40 μm or more , or
The method according to claim 1 or 2 , wherein the shape of the carbonaceous material and / or the resin is fibrous, and the average fiber diameter of the carbonaceous material and / or the resin is 50 μm or less. The carbonaceous material and / or resin is at least one selected from the group consisting of activated carbon, wood material, coconut shell, fruit shell, thermosetting resin and its carbide, thermoplastic resin and its carbide, coal pitch, and petroleum pitch The method according to any one of claims 1 to 3 , which is The oxidizing agent is at least one selected from the group consisting of oxygen, ozone, nitrogen dioxide, hydrogen peroxide, sulfur dioxide, persulfate, peracetic acid, formic acid, nitric acid, nitric acid, concentrated nitric acid, fuming nitric acid and t-butyl hydroperoxide. The manufacturing method according to any one of claims 1 to 4 , which is a species. The manufacturing method according to any one of claims 1 to 5 in which said impregnation process and said porosification process are performed one by one continuously. The manufacturing method in any one of Claims 1-6 which repeat the said impregnation process and porosification process. The BET specific surface area is 200 to 1,500 m ² / g ,
Discharge capacity is 5~20F / cc,
Discharge capacity per specific surface area of ^{1 × 10 -3 ~1 × 10 -1} F / m 2, activated carbon capacitor. The surface has at least one functional group selected from the group consisting of a nitro group, a nitroso group, an azo group, an amino group, a lactone group, a phenyl group, a phenol group, a carbonyl group, a carboxy group, and a sulfone group. The activated carbon for capacitors according to 8 . The nitrogen atom, containing from 0.7 to 5% by atomic ratio to carbon atoms, activated carbon for capacitor according to claim 8 or 9. The activated carbon for a capacitor according to any one of claims 8 to 10 , which contains an oxygen atom in an atomic ratio of 1.2 to 30% with respect to a carbon atom. Capacitor electrode using activated carbon for capacitor according to any one of claims 8-11. A capacitor comprising the capacitor electrode according to claim 12 . A method of increasing the number of pores having a pore diameter of 1 to 2 nm possessed by a carbonaceous material and increasing the content of nitrogen atoms,
The method comprises an impregnating step of impregnating a carbonaceous material in a mixture of high pressure carbon dioxide and an oxidizing agent, and a porosifying step of making porous by reaction of the carbonaceous material with the oxidizing agent, the pressure of the high pressure carbon dioxide There, Ru 0.2~30MPa der, method.