JP2021038127A - Method for producing porous carbon and method for producing porous carbon molded body - Google Patents

Abstract

To provide a method for producing porous carbon which can produce porous carbon having a large bulk density and a large specific surface area per unit volume at a low production cost.SOLUTION: A method for producing porous carbon comprises a step of solidifying a graphitizable carbon raw material without passing through a melt, and a step of converting a solid content having undergone the solidifying step into a solid phase carbon.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing porous carbon and a method for producing a porous carbon molded product.

Porous carbon having pores on the surface having a diameter on the order of microns or nanometers and having a high specific surface area is useful as an adsorbent. Examples of the method for producing the porous carbon include a method in which a phenol resin or the like is used as a carbon raw material and activated by water vapor or an alkaline substance to increase the specific surface area (Japanese Patent Laid-Open No. 2012-41199), or an organic resin such as magnesium oxide. Examples thereof include a method of removing the oxide after mixing with an oxide (template particles) and carbonizing (Japanese Patent Laid-Open No. 2016-41656).

In the above-mentioned conventional method for producing porous carbon, in addition to the step of carbonizing the raw material, a step of activating with an alkaline substance and removing template particles is required, which lowers the manufacturing efficiency and raises the manufacturing cost. To do.

In the above-mentioned conventional method for producing porous carbon, voids are formed on the surface of the carbon by erosion treatment. In such a method, the specific surface area is roughly proportional to the degree of erosion. On the other hand, if the degree of erosion is increased in order to increase the specific surface area, the space formed inside also increases, and the bulk of the porous carbon itself increases. In the case of porous carbon having an increased bulk, that is, a reduced bulk density, the specific surface area per unit volume tends to decrease even if the specific surface area per unit mass increases.

Here, considering the usage state of the porous carbon, for example, when it is used for a storage battery, the porous carbon is used by filling a container having a constant volume with the porous carbon. That is, the porous carbon is required to have a large specific surface area per unit volume as well as a large specific surface area per unit area. Therefore, it is preferable that the porous carbon has a large bulk density.

Further, since the decrease in bulk density means a decrease in the strength of the porous carbon, it is required that the bulk density of the porous carbon is large from the viewpoint of durability.

Japanese Unexamined Patent Publication No. 2012-41199 Japanese Unexamined Patent Publication No. 2016-41656

The present invention has been made based on the above circumstances, and is a method for producing porous carbon capable of producing porous carbon having a large bulk density and a large specific surface area per unit volume at a low production cost. An object of the present invention is to provide a method for producing a porous carbon molded product.

In the above-mentioned conventional method for producing porous carbon, a non-graphitized carbon raw material such as a phenol resin is generally used as a raw material for producing porous carbon. It is considered that this is mainly due to the fact that a porous body cannot be obtained when an inexpensive easily graphitized carbon raw material is used. The cause of this difference is not clear, but the present inventors speculate as follows. First, when a non-graphitized carbon raw material is used, a randomly crosslinked aromatic polymer having a small laminated structure of aromatic rings is directly solid-phase carbonized. In the process, it is considered that the voids formed between the carbon mesh surfaces function as micropores and a porous body can be obtained. On the other hand, when an easily graphitized carbon raw material is used, it is carbonized via a melt. In the melt, it is stable that the aromatic rings are oriented in parallel (laminated), so that a laminated structure (mesophase, liquid crystal) between aromatic molecules is generated. After that, the graphitized carbon raw material is infusible and carbonized in the solid phase. Since the voids between aromatic molecules are minimized in this mesophase, it is considered that solid-phase carbonization does not result in porosity. Based on the above discussion, the present inventors have found that even when an easily graphitizable carbon raw material is used, porous carbon can be produced by solid-phase carbonization without passing through a melt. Completed the invention.

That is, the method for producing porous carbon of the present invention includes a step of solidifying the graphitized carbon raw material without passing through a melt and a step of solid-phase carbonizing the solid content after the solidification step. ..

In the method for producing porous carbon, the easily graphitized carbon raw material is solidified without passing through a melt, so that a porous body can be obtained as a solid content even if the easily graphitized carbon raw material is used. Therefore, by solid-phase carbonizing this solid content, it is possible to produce porous carbon having a large specific surface area per unit volume at a low production cost. Further, the porous carbon produced by the method for producing the porous carbon has a high proportion of micropores having pores having a diameter of less than 2 nm, and the bulk density can be increased.

It is preferable that the graphitized carbon raw material contains ashless charcoal. Compared to coal pitch generally obtained by carbonization and distillation of coal performed at 1000 ° C or higher, ashless coal obtained by extraction from coal at 400 ° C or lower contains a large amount of heteroatomic atoms such as oxygen and has a laminated structure. hard. Therefore, by including ashless carbon in the graphitized carbon raw material, it is easy to obtain porous carbon having a large specific surface area per unit volume. Further, since ashless coal has a large content of heteroatoms and a large molecular weight, the yield in the solid phase carbonization step can be increased.

The solidification step is a step of dissolving the easily graphitized carbon raw material in the good solvent, a step of mixing the solution obtained in the above dissolution step with the poor solvent of the easily graphitized carbon raw material, and the above poor solvent mixing. It is preferable to have a step of precipitating solid content from the mixed solution obtained in the step. As described above, by using the so-called poor solvent method having the above-mentioned steps in the solidification step, the porous carbon can be easily produced and no special equipment or the like is required. Therefore, the production cost of the porous carbon is high. Can be further reduced.

The solidification step includes a step of mixing coal with a good solvent of ashless coal, a step of eluting ashless coal from the coal into the good solvent by heating the slurry obtained in the good solvent mixing step, and the above. A step of solid-liquid separation of the slurry obtained in the dissolution step, a step of mixing the solution obtained in the solid-liquid separation step with the poor solvent of the ashless coal, and a mixed solution obtained in the poor solvent mixing step. It is preferable to have a step of precipitating the solid content from the coal. The ashless coal can be eluted into a good solvent by the solvent extraction treatment of coal in the above elution step. Therefore, by using the solution obtained by eluting the ashless coal in a good solvent as the solution in the poor solvent mixing step, it is not necessary to take out the ashless coal as a solid substance, so that the production cost of porous carbon can be further reduced.

It is preferable that the good solvent contains a nitrogen-containing compound and the poor solvent does not contain a nitrogen-containing compound. By including the nitrogen-containing compound in the good solvent in this way, the solubility of the graphitized carbon raw material can be increased. Further, by not including the nitrogen-containing compound in the poor solvent, the precipitation efficiency of the solid content can be improved. Therefore, by combining the good solvent and the poor solvent as described above, the production efficiency of the porous carbon can be improved.

The content of the easily graphitized carbon raw material in the solution is preferably 5% by mass or more and 50% by mass or less, and the mass ratio of the poor solvent to the solution mixed in the poor solvent mixing step is 3 times. It is preferably 20 times or more and 20 times or less. By setting the content of the graphitized carbon raw material within the above range in this way, it is possible to increase the production efficiency of porous carbon while reducing the undissolved graphitized carbon raw material. Further, by setting the mass ratio of the poor solvent within the above range, it is possible to improve the production efficiency of porous carbon while suppressing the use of unnecessary poor solvent.

The solidification step may include a step of freezing the solution containing the graphitized carbon raw material and a step of drying the graphitized carbon raw material after the freezing step in a frozen state. As described above, by using the so-called freeze-drying method having the above-mentioned steps in the above-mentioned solidification step, porous carbon can be easily produced and a bulk bulk can be easily obtained.

The solidification step may include a step of preparing a spinning liquid containing the graphitized carbon raw material and a step of fiberizing the graphitized carbon raw material by discharging the spinning liquid into a coagulating liquid. As described above, by using the so-called wet spinning method having the above-mentioned steps in the solidification step, the porous carbon can be easily produced and the fibrous porous carbon can be easily obtained.

The method for producing a porous carbon molded product of the present invention includes a step of solidifying an easily graphitized carbon raw material without passing through a melt, a step of solidifying the solid content after the solidification step, and the above. It includes a step of pressure molding the porous carbon after the solidification step so that the bulk density is 0.8 g / cm ^{3 or more.}

In the method for producing the porous carbon molded product, the graphitized carbon raw material is solidified without passing through a melt, so that the porous body can be obtained as a solid content even if the graphitized carbon raw material is used. Therefore, by solid-phase carbonizing this solid content, it is possible to produce a porous carbon molded product having a large specific surface area per unit volume at a low production cost. Further, in the method for producing the porous carbon molded product, the proportion of micropores having pores having a diameter of less than 2 nm is high, and the bulk density can be increased. By setting the bulk density to be equal to or higher than the above lower limit in the pressure molding step, a high capacitance can be obtained with respect to a unit volume when used as an electric double layer capacitor, for example.

Here, the "graphitized carbon raw material" refers to a carbon material that is graphitized when heat-treated at a high temperature of 2500 ° C. or higher at normal pressure. Further, "solid phase carbonization" means carbonization without softening (melting).

A "good solvent" for a substance refers to a solvent having a solubility of the substance of 5% by mass or more at 25 ° C., and a "poor solvent" means a solvent having a solubility of the substance of less than 5% by mass at 25 ° C. Point to.

"Ashless coal" (Hypercoal, HPC) is a type of reformed coal that is reformed from coal, and is a reformed coal in which ash and insoluble components are removed from the coal as much as possible using a solvent. is there. However, the ashless coal may contain ash as long as the fluidity and expandability of the ashless coal are not significantly impaired. Generally, coal contains ash content of 7% by mass or more and 20% by mass or less, but ashless coal may contain about 2% by mass, and in some cases, about 5% by mass. The "ash content" means a value measured in accordance with JIS-M8812: 2004.

The "bulk density" of the molded body is a value obtained by dividing the mass after molding by its volume.

As described above, the method for producing porous carbon and the method for producing a porous carbon molded product of the present invention have a low production cost, a large bulk density, and a large specific surface area per unit volume. A quality carbon molded product can be produced.

FIG. 1 is a flow chart showing a method for producing porous carbon according to an embodiment of the present invention. FIG. 2 is a flow chart showing a method for producing a porous carbon molded product according to an embodiment of the present invention. FIG. 3 is a detailed flow chart showing the solidification steps of FIGS. 1 and 2. FIG. 4 is a detailed flow chart showing a solidification process different from that of FIG. FIG. 5 is a detailed flow chart showing a solidification process different from that of FIGS. 3 and 4. FIG. 6 is a detailed flow chart showing a solidification process different from those in FIGS. 3, 4, and 5. FIG. 7 is a schematic view showing a schematic configuration of a wet spinning apparatus used in the solidification step of FIG.

[First Embodiment]
Hereinafter, the first embodiment of the method for producing porous carbon and the method for producing a porous carbon molded product according to the present invention will be described.

As shown in FIG. 1, the method for producing porous carbon includes a solidification step S1 and a solid phase carbonization step S2. Further, as shown in FIG. 2, the method for producing the porous carbon molded product includes a pressure molding step S3 in addition to the solidification step S1 and the solid phase carbonization step S2 described above.

[Solidization process]
In the solidification step S1, the graphitized carbon raw material is solidified without going through a melt.

Examples of the easily graphitized carbon raw material include coal pitch, petroleum asphalt, and ashless coal. These raw materials may be used alone or in combination of two or more. Further, the graphitized carbon raw material may be produced through a melt.

The graphitized carbon raw material preferably contains ashless charcoal, and it is more preferable to use ashless charcoal alone. Compared to coal pitch generally obtained by carbonization and distillation of coal performed at 1000 ° C or higher, ashless coal obtained by extraction from coal at 400 ° C or lower contains a large amount of heteroatomic atoms such as oxygen and has a laminated structure. hard. Therefore, by including ashless carbon in the graphitized carbon raw material, it is easy to obtain porous carbon having a large specific surface area per unit volume. Further, since ashless coal has a large content of heteroatoms and a large molecular weight, the yield in the solid phase carbonization step can be increased.

Here, the ashless coal will be described in more detail. Since the ashless coal is a coal extract, it is a mixture composed of various molecules, and has a polycyclic aromatic having a heteroatom such as oxygen and nitrogen as a basic structure. Since the polycyclic aromatics are flat, such ashless coal molecules have relatively flatness and high softening and melting properties. In the process of raising the temperature for carbonizing ashless coal, the liquid state is usually softened and melted at around 400 ° C., and the carbonization reaction (liquid phase carbonization) proceeds at about 900 ° C. In this liquid phase carbonization process, the plane portions of the ashless coal molecules are laminated to stabilize the entire system, resulting in an oriented molecular aggregate. That is, ashless coal is a carbon raw material having graphitability (easy graphitizing carbon raw material).

In the method for producing the porous carbon and the method for producing the porous carbon molded product, the solidification step S1 includes a dissolution step S11, a poor solvent mixing step S12, and a precipitation step S13, as shown in FIG.

<Melting process>
In the dissolution step S11, the graphitized carbon raw material is dissolved in a good solvent thereof.

The good solvent is not particularly limited as long as the easily graphitized carbon raw material can be dissolved, but it is preferable that the good solvent contains a nitrogen-containing compound. By including the nitrogen-containing compound in the good solvent in this way, the solubility of the graphitized carbon raw material can be increased.

Examples of the nitrogen-containing compound include pyridine (C ₅ H ₅ N), quinoline (C ₉ H ₇ N), N-methylpyrrolidone (C ₅ H ₉ NO) and the like. Of these, pyridine is preferable because it has a high dissolving power and has a relatively low boiling point and is easy to handle.

The lower limit of the content of the graphitized carbon raw material in the dissolved solution is preferably 5% by mass, more preferably 10% by mass. On the other hand, the upper limit of the content of the graphitized carbon raw material is preferably 40% by mass, more preferably 30% by mass. If the content of the graphitized carbon raw material is less than the above lower limit, a good solvent may be excessive and the production efficiency of the porous carbon may be lowered. On the contrary, when the content of the easily graphitized carbon raw material exceeds the above upper limit, the undissolved easily graphitized carbon raw material may increase and the yield of porous carbon may decrease.

<Solvent mixing step>
In the poor solvent mixing step S12, the solution obtained in the dissolution step S11 is mixed with the poor solvent of the graphitized carbon raw material.

The poor solvent is not particularly limited as long as the solubility of the graphitized carbon raw material is small, but a solvent that mixes well with the good solvent is preferable. Further, it is preferable that the poor solvent does not contain a nitrogen-containing compound. By not including the nitrogen-containing compound in the poor solvent in this way, the precipitation efficiency of the solid content can be increased. Further, by using a combination in which the good solvent contains a nitrogen-containing compound and the poor solvent does not contain a nitrogen-containing compound, the production efficiency of porous carbon can be particularly enhanced.

Examples of the poor solvent include water (H ₂ O), methanol (CH ₄ O), ethanol (C ₂ H ₆ O), acetone (C ₃ H ₆ O), toluene (C ₇ H ₈ ), and hexane (C _6). H ₁₄ ) and the like can be mentioned. As the poor solvent, when a highly polar nitrogen-containing compound is used as the good solvent, a highly polar solvent containing oxygen that is easily mixed with the good solvent is preferable. Examples of such a poor solvent include water, methanol, ethanol, and acetone. When methylnaphthalene or the like is used as the good solvent, toluene or hexane having a sufficiently smaller dissolving power of the graphitized carbon raw material than methylnaphthalene or the like is preferable as the poor solvent.

The method for mixing the solution and the poor solvent is not particularly limited, but a method of adding the solution to the poor solvent is preferable. By adding the graphitized carbon raw material dissolved in the good solvent to a large amount of poor solvent, the graphitized carbon raw material instantly becomes a powdery solid content, so that the production efficiency of porous carbon can be improved.

The lower limit of the mass ratio of the poor solvent to the solution mixed in the poor solvent mixing step S12 is preferably 3 times, more preferably 5 times. On the other hand, the upper limit of the mass ratio is preferably 20 times, more preferably 10 times. If the mass ratio is less than the above lower limit, the amount of the graphitized carbon raw material that does not precipitate increases, and the yield of porous carbon may decrease. On the contrary, when the mass ratio exceeds the upper limit, the amount of poor solvent is unnecessarily increased, which may reduce the production efficiency or increase the production cost.

<Precipitation process>
In the precipitation step S13, the solid content is precipitated from the mixed solution obtained in the poor solvent mixing step S12.

Specifically, when the above solution and the above solvent are mixed as described above, solids are precipitated. Therefore, the precipitated solids are separated by filtration and dried under reduced pressure, for example.

Most of the solids precipitated in this way are pores with a diameter of less than 2 nm (micropores), and pores with a diameter of 2 nm or more and less than 50 nm (mesopores) and pores with a diameter of 50 nm or more (macropores) are compared. There are few targets. Therefore, the solid content is highly dense with respect to the specific surface area.

Further, by using the so-called poor solvent method having the above-mentioned step in the solidification step S1 as described above, the porous carbon can be easily produced and no special equipment or the like is required. The manufacturing cost can be further reduced.

[Solid phase carbonization process]
In the solid phase carbonization step S2, the solid content after the solidification step S1 is solid phase carbonized. Specifically, the solid content obtained in the solidification step S1 is heat-treated. Porous carbon is obtained by this carbonization. This solid phase carbonization step S2 can be performed by the heating unit.

<Heating part>
The heating unit carbonizes the solid content by heating while substantially maintaining its aggregated state (solid phase carbonization). As the heating unit, for example, a known electric furnace or the like can be used. A low crystalline solid content is inserted into the heating unit, the inside is replaced with an inert gas, and then the inert gas is blown into the heating unit. By heating, the solid content can be carbonized in a solid phase. The inert gas is not particularly limited, and examples thereof include nitrogen and argon. Of these, inexpensive nitrogen is preferable.

The lower limit of the heating temperature in the solid phase carbonization step S2 is preferably 600 ° C. or higher, more preferably 900 ° C. or higher. On the other hand, as the upper limit of the heating temperature, 1300 ° C. is preferable, and 1100 ° C. is more preferable. If the heating temperature is less than the above lower limit, carbonization and pore development may be insufficient. On the contrary, when the heating temperature exceeds the above upper limit, the specific surface area (porousness) decreases, and the manufacturing cost may increase from the viewpoint of improving the heat resistance of the equipment and the fuel consumption. The rate of temperature rise can be, for example, 0.01 ° C./min or more and 10 ° C./min or less.

The lower limit of the heating time is preferably 10 minutes, more preferably 20 minutes. On the other hand, the upper limit of the heating time is preferably 10 hours, more preferably 8 hours. If the heating temperature is less than the above lower limit, carbonization may be insufficient. On the contrary, if the heating time exceeds the above upper limit, the production efficiency of the porous carbon may decrease.

<Infusibilization treatment>
It should be noted that insolubilization may be performed before solid phase carbonization. This infusibilization treatment can prevent the solids from fusing to each other. The infusibilization is performed by heating in an atmosphere containing oxygen using, for example, a known heating furnace. Air is generally used as the atmosphere containing oxygen.

The lower limit of the infusibilization treatment temperature at the time of insolubilization is preferably 150 ° C., more preferably 180 ° C. On the other hand, the upper limit of the infusibilization treatment temperature is preferably 300 ° C., more preferably 280 ° C. If the infusibilization treatment temperature is less than the above lower limit, the infusibilization may be insufficient or the infusification treatment time may become long, resulting in inefficiency. On the contrary, if the infusibilization treatment temperature exceeds the upper limit, the solid content may melt before being infusible. The rate of temperature rise can be, for example, 0.01 ° C./min or more and 10 ° C./min or less.

Further, as the lower limit of the infusibilization treatment time when performing infusibilization, 10 minutes is preferable, and 20 minutes is more preferable. On the other hand, the upper limit of the infusibilization treatment time is preferably 120 minutes, more preferably 90 minutes. If the infusibilization treatment time is less than the above lower limit, the infusibilization may be insufficient. On the contrary, if the infusibilization treatment time exceeds the upper limit, the production cost of the porous carbon may increase unnecessarily.

<Activation process>
In the method for producing porous carbon, porous carbon in which micropores occupy the majority can be obtained without activation treatment, but micropores can be further increased by performing light activation treatment.

As the activation treatment, a known method can be used. For example, after the heat treatment, or simultaneously with the heat treatment, using an inert gas containing CO ₂ as a inert gas, partially gasified surface of solids _{(C + CO 2 → 2CO ↑} ) causes CO ₂ Activation can be used.

_{The CO 2} concentration in the inert gas is not particularly limited, but _{the lower limit of the CO 2} concentration is preferably 10% by mass. On the other hand, _{the upper limit of the CO 2} concentration may be 100% by mass (pure CO _2). If the CO ₂ concentration is less than the above lower limit, a higher temperature and longer treatment is required to obtain a desired activation effect, which may increase the production cost or decrease the production efficiency. ..

The weight reduction of the porous carbon due to CO ₂ activation is preferably 105% by mass or more and 150% by mass or less with respect to the weight reduction when the carbonization treatment is performed in an inert gas containing no _{CO 2.} If the weight reduction is less than the above lower limit, the activation effect (porousization) may be insufficient. On the contrary, when the weight reduction exceeds the upper limit, a large activation effect can be obtained, but carbon may be unnecessarily consumed and the production efficiency may be lowered.

<Porous carbon>
By using the method for producing porous carbon, for example, porous carbon having pores having an average diameter of 0.5 nm or more and 2 nm or less can be produced. The porous carbon obtained by the method for producing the porous carbon is in the form of particles.

The porous carbon can be suitably used for gas adsorbents such as nitrogen, hydrogen and carbon monoxide, adsorbents for water treatment, electronic parts and the like. Due to its high bulk density, the porous carbon can obtain high performance per unit volume when used as an electrode for an EDLC (Electrical Double Layer Capacitor) or the like.

Hereinafter, the characteristics of the porous carbon produced by using the method for producing the porous carbon will be described.

Examples of the lower limit of the porous carbon of pore volume, preferably 0.02 cm ³ / g, more preferably 0.1 cm ³ / g, more preferably 0.15 cm ³ / g. If the pore volume is less than the lower limit, it may be difficult to use it as a porous material. On the other hand, the upper limit of the pore volume is not particularly limited, but is usually ^{about 0.5 cm 3} / g. The "pore volume" refers to the integrated pore volume when the pore distribution is measured by the HK method and the pores are assumed to be cylindrical.

It is preferable that the pores of the porous carbon have many micropores and few mesopores and macropores. That is, among the pores of the porous carbon, the Log differential pore volume of the pores having a diameter of 0.5 nm or less ^{is preferably 0.1 cm 3} / g or more, and more preferably 0.15 cm ³ / g or more. The Log differential pore volume of pores having a diameter of 2 nm or more and 4 nm or less is preferably less than ^{0.05 cm 3} / g, more preferably less than ^{0.03 cm 3 / g.} When the Log differential pore volume of pores having a diameter of 0.5 nm or less is less than the above lower limit, or when the Log differential pore volume of pores having a diameter of 2 nm or more and 4 nm or less is more than the above upper limit, the density of the porous carbon is low. Therefore, the mechanical strength may decrease. The upper limit of the Log differential pore volume of pores having a diameter of 0.5 nm or less is not particularly limited, but is usually ^{about 0.5 cm 3} / g. The lower limit of the Log differential pore volume of pores ^{having a diameter of 2 nm or more and 4 nm or less is preferably 0 cm 3} / g, and it is not necessary to have pores having a diameter of 2 nm or more and 4 nm or less. The "Log differential pore volume of the pores" at a certain diameter is a value calculated as follows. First, the pore distribution is measured by the HK method. By this measurement, the integrated pore volume distribution V with respect to the diameter D of the bottom surface when the pores are assumed to be cylindrical can be obtained. The Log differential pore volume can be calculated by dividing the difference pore volume dV between the measurement points by the difference value d (LogD) in logarithmic treatment of the pore diameter D based on this distribution.

Since the pores of the porous carbon have many micropores, the porous carbon is dense but has a large specific surface area per unit mass. Above for porous specific surface area lower limit per unit mass of carbon is preferably 300 meters ² / g, more preferably ^{350m 2 / g, 400m 2 /} g is more preferred. If the specific surface area per unit mass is less than the above lower limit, it may be difficult to use it as a porous material. On the other hand, the upper limit of the specific surface area per unit mass is not particularly limited, but is usually ^{about 3000 m 2} / g. The specific surface area of the porous carbon per unit mass can be adjusted, for example, by adjusting the content of the graphitized carbon raw material in the solution, the type of good solvent or poor solvent, and the like.

[Pressure molding process]
In the pressure molding step S3, the porous carbon after the solid phase carbonization step S2 after the solidification step S1 is pressure molded so ^{that the bulk density is 0.8 g / cm 3 or more.}

As the molding method in the pressure molding step S3, known compression molding, extrusion molding, granulation method and the like can be used.

This molding step S3 can be performed using a known molding machine. The size and shape of the cavity of the mold used in the molding machine are appropriately determined according to the purpose of use of the porous carbon, and can be, for example, a cylindrical shape having a diameter of 15 mm or more and 25 mm or less and a depth of 25 mm or more and 35 mm or less.

Further, when the porous carbon lacks flexibility, the molding in the pressure molding step S3 is preferably performed by adding a binder to the porous carbon. If the porous carbon is flexible, it can be molded without including a binder.

When molding is performed by adding a binder, it is preferable to use a substance having a low carbon yield and hardly penetrating into the pores of porous carbon, for example, water or a water-soluble polymer. Examples of the water-soluble polymer include starch, molasses, polyvinyl alcohol and the like. By using the binder as a substance having a low carbon yield and hardly penetrating into the pores of the porous carbon, it is possible to suppress a decrease in the porosity of the obtained porous carbon molded product.

When molding is performed by adding a binder, the lower limit of the amount of the binder added to the obtained porous carbon molded product is preferably 2% by mass, more preferably 4% by mass. On the other hand, the upper limit of the amount of the binder added is preferably 10% by mass, more preferably 8% by mass. If the amount of the binder added is less than the above lower limit, the moldability may be insufficient. On the contrary, if the amount of the binder added exceeds the above upper limit, the production cost may become too large for the effect of improving the moldability.

The lower limit of the bulk density of the porous carbon molded body after molding in a press-molding step S3, preferably ^{0.8g / cm 3, 0.9g / cm} 3 or more is more preferable. On the other hand, the upper limit of the bulk density of the porous carbon molded body is preferably ^{1.1g / cm 3, 1.0g / cm} 3 or more is more preferable. If the bulk density of the porous carbon molded product is less than the above lower limit, the capacitance per unit volume may be insufficient when used as an EDLC electrode, for example. On the contrary, if the bulk density of the porous carbon molded product exceeds the above upper limit, the micropores may be crushed during molding in order to increase the bulk density, and the specific surface area per unit volume may rather decrease.

As the lower limit of the molding pressure, 0.8 ton / cm ² is preferable, and 1.0 ton / cm ² is more preferable. On the other hand, as the upper limit of the molding pressure, 3.0 ton / cm ² is preferable, and 2.5 ton / cm ² is more preferable. If the molding pressure is less than the above lower limit, the bulk density of the obtained porous carbon molded product may be insufficient, and the strength and the specific surface area per unit volume may be insufficient. On the contrary, when the molding pressure exceeds the above upper limit, the micropores of the solid content are easily crushed, and the specific surface area per unit volume of the obtained porous particles may be reduced.

The pressurization time in the pressure molding step S3 is appropriately determined from the viewpoint of stabilizing the shape of the porous carbon molded product after molding and manufacturing efficiency, and is, for example, 0.5 minutes or more and 3 minutes or less. ..

Further, the molding of the porous carbon is preferably performed at room temperature (for example, 25 ° C.) without heating from the viewpoint of manufacturing cost. Alternatively, heating may be performed to improve moldability. The mold temperature at that time is preferably 200 ° C. or lower. If the mold temperature exceeds the above upper limit, the production cost may increase too much for the improvement effect of the obtained porous carbon molded product, or the porosity of the obtained porous carbon molded product may decrease. ..

<Advantage>
In the method for producing the porous carbon and the method for producing the porous carbon molded product, the graphitized carbon raw material is solidified without passing through a melt, so that even if the graphitized carbon raw material is used, the solid content is porous. The body is obtained. Therefore, by solid-phase carbonizing this solid content, it is possible to produce porous carbon and a porous carbon molded product having a large specific surface area per unit volume at a low production cost. Further, the porous carbon and the porous carbon molded product produced by the method for producing the porous carbon and the method for producing the porous carbon molded product have a high proportion of micropores having pores having a diameter of less than 2 nm. The bulk density can be increased.

[Second Embodiment]
Hereinafter, a second embodiment of the method for producing porous carbon and the method for producing a porous carbon molded product according to the present invention will be described.

As shown in FIG. 1, the method for producing porous carbon includes a solidification step S1 and a solid phase carbonization step S2, similarly to the method for producing porous carbon in the first embodiment. Further, as shown in FIG. 2, the method for producing the porous carbon molded product includes a pressure molding step S3 in addition to the solidification step S1 and the solid phase carbonization step S2 described above.

[Solidization process]
In the solidification step S1, the graphitized carbon raw material is solidified without passing through a melt.

In the present embodiment, the graphitized carbon raw material is ashless charcoal.

In the method for producing the porous carbon and the method for producing the porous carbon molded product, the solidification step S1 includes a good solvent mixing step S21, an elution step S22, and a solid-liquid separation step S23, as shown in FIG. It has a poor solvent mixing step S24 and a precipitation step S25.

<Good solvent mixing process>
In the good solvent mixing step S21, coal is mixed with a good solvent of ashless coal.

As the good solvent, the same solvent as in the first embodiment can be used.

This good solvent mixing step S21 can be performed by, for example, a coal input unit, a solvent supply unit, and a mixing unit.

(Coal input section)
The coal input section inputs coal to the mixing section. As the coal input section, known coal hoppers such as a normal pressure hopper used in a normal pressure state and a pressure hopper used in a normal pressure state and a pressurized state can be used.

The coal input from the coal input section is coal that is a raw material for ashless coal. As the above-mentioned coal, coal of various qualities can be used. For example, bituminous coal with a high extraction rate of ashless coal and cheaper low-grade coal (subbituminous coal or lignite) are preferably used. Further, when coal is classified by particle size, finely crushed coal is preferably used. Here, the "finely crushed coal" means, for example, coal in which the mass ratio of coal having a particle size of less than 1 mm to the total mass of coal is 80% or more. In addition, lump coal can be used as the coal to be input from the coal input section. Here, "lump coal" means, for example, coal in which the mass ratio of coal having a particle size of 5 mm or more to the mass of the entire coal is 50% or more. Since the lump coal keeps the particle size of the undissolved solid coal larger than that of the finely crushed coal, it is possible to improve the efficiency of separation at the separation part described later. Here, the "particle size (particle size)" means a value measured in accordance with the general rules for sieving tests of JIS-Z8815: 1994. For sorting by grain size of coal, for example, a metal net sieve specified in JIS-Z8801-1: 2006 can be used.

The lower limit of the carbon content of the low-grade coal is preferably 70% by mass. On the other hand, the upper limit of the carbon content of the low-grade coal is preferably 85% by mass, more preferably 82% by mass. If the carbon content of the low-grade coal is less than the above lower limit, the elution rate of the solvent-soluble component may decrease. On the contrary, if the carbon content of the low-grade coal exceeds the above upper limit, the cost of the coal to be input may increase.

As the coal to be charged from the coal charging section to the mixing section, coal that has been slurried by mixing a small amount of solvent may be used. By charging the slurried coal from the coal charging section to the mixing section, the coal can be easily mixed with the solvent in the mixing section, and the coal can be melted faster. However, if the amount of the solvent to be mixed at the time of slurrying is large, the amount of heat for raising the temperature of the slurry to the elution temperature in the temperature raising section described later becomes unnecessarily large, which may increase the manufacturing cost.

(Solvent supply unit)
The solvent supply unit supplies the solvent to the mixing unit. The solvent supply unit has a solvent tank for storing the solvent, and the solvent is supplied from the solvent tank to the mixing unit. The solvent supplied from the solvent supply unit is mixed with the coal charged from the coal supply unit in the mixing unit.

The solvent supplied from the solvent supply unit is the above-mentioned good solvent. When ashless coal is used as the graphitized carbon raw material, as the good solvent, in addition to the above solvent, methylnaphthalene oil, which is a distilled oil of by-product oil when carbonizing coal to produce coke, is used. Naphthalene oil or the like can also be used.

(Mixing part)
The mixing unit mixes the coal input from the coal input unit and the solvent supplied from the solvent supply unit.

A preparation tank can be used as the mixing unit. The solvent is supplied to this preparation tank via a supply pipe, and coal is charged into the supplied solvent. In the preparation tank, the coal and the solvent are mixed to prepare a slurry. Further, the preparation tank has a stirrer, and maintains the mixed state of the slurry by holding the mixed slurry while stirring with the stirrer.

The coal concentration in the slurry in the preparation tank based on anhydrous coal is appropriately determined depending on the type of solvent and the like, but the lower limit of the coal concentration is preferably 5% by mass, more preferably 10% by mass. On the other hand, the upper limit of the coal concentration is preferably 65% by mass, more preferably 40% by mass. When the coal concentration is less than the above lower limit, the elution amount of the solvent-soluble component eluted in the elution step S22 is smaller than the slurry processing amount, so that the content of ashless coal contained in the liquid component is insufficient. There is a risk of becoming. On the contrary, when the coal concentration exceeds the upper limit, the solvent-soluble component is likely to be saturated in the solvent, so that the elution rate of the solvent-soluble component may decrease.

The slurry prepared in the preparation tank of the mixing section is processed in the ashless coal elution step S22.

<Elution process>
In the elution step S22, ashless coal is eluted from the coal into the good solvent by heating the slurry obtained in the good solvent mixing step S21. The elution step S22 can be performed by the temperature raising unit and the elution unit.

(Temperature temperature riser)
The temperature raising unit raises the temperature of the slurry obtained in the good solvent mixing step S21.

The temperature raising unit is not particularly limited as long as it can raise the temperature of the slurry passing through the inside, and examples thereof include a resistance heating type heater and an induction heating coil. Further, the temperature raising unit may be configured to raise the temperature using a heat medium. For example, the heating tube has a heating tube arranged around the flow path of the slurry passing through the inside, and the heating tube has a heating tube. The slurry may be configured to be able to raise the temperature by supplying a heat medium such as steam or oil.

The temperature of the slurry after the temperature is raised by the temperature raising unit is appropriately determined depending on the solvent used, but is at least equal to or lower than the boiling point of the solvent. For example, when methylnaphthalene is used as a solvent, the temperature is set to 300 ° C. or higher and 400 ° C. or lower in a pressure-resistant container. If the temperature of the slurry is less than the lower limit, the elution rate may decrease. On the contrary, if the temperature of the slurry exceeds the upper limit, the solvent may be vaporized too much, and it may be difficult to control the concentration of the slurry.

The pressure of the temperature rising portion is not particularly limited, but can be normal pressure (0.1 MPa). For example, when methylnaphthalene is used as the solvent, the pressure may be 2 MPa or less in the pressure-resistant container.

(Elution part)
The elution unit is obtained in the mixing unit, and the solvent-soluble coal component is eluted from the coal in the slurry that has been heated in the temperature raising unit. The main component of this solvent-soluble component is ashless coal. Here, the "main component" means a component having the highest content, for example, a component having a content of 50% by mass or more.

An extraction tank can be used as the elution portion, and the slurry after the temperature rise is supplied to the extraction tank. In the extraction tank, the solvent-soluble coal component is eluted from the coal while maintaining the temperature and pressure of this slurry. In addition, the extraction tank has a stirrer. The elution can be promoted by stirring the slurry with this stirrer.

The elution time at the elution portion is not particularly limited, but is preferably 10 minutes or more and 120 minutes or less from the viewpoint of the extraction amount of the solvent-soluble component and the extraction efficiency.

<Solid-liquid separation process>
In the solid-liquid separation step S23, the slurry obtained in the elution step S22 is solid-liquid separated. Specifically, in the solid-liquid separation step S23, the slurry is separated into a solution in which a solvent-soluble component is eluted and an extraction residue. This solid-liquid separation step S23 can be performed by the separation unit. The extraction residue mainly contains ash and insoluble coal that are insoluble in the extraction solvent, and further contains an extraction solvent in addition to these.

(Separation part)
As a method for separating the liquid component and the extraction residue in the separation unit, for example, a gravity settling method, a filtration method, and a centrifugation method can be used, and a settling tank, a filter, and a centrifuge are used, respectively.

Hereinafter, the separation method will be described by taking the gravity sedimentation method as an example. The gravity sedimentation method is a separation method in which the extraction residue is sedimented in a sedimentation tank using gravity to separate solid and liquid. When the separation is performed by the gravity settling method, the liquid content in which the ashless coal is dissolved collects in the upper part of the settling tank. This liquid component is filtered using a filter unit as needed and then discharged. On the other hand, the extraction residue is discharged from the lower part of the separation part.

Further, when the separation is performed by the gravity sedimentation method, the liquid component and the extraction residue can be discharged from the sedimentation tank while continuously supplying the slurry into the separation portion. This enables continuous solid-liquid separation processing.

The time for maintaining the slurry in the separation section is not particularly limited, but can be, for example, 30 minutes or more and 120 minutes or less, and sedimentation separation in the separation section is performed within this time. When lump coal is used as the coal, the sedimentation separation is efficient, so that the time for maintaining the slurry in the separation portion can be shortened.

The temperature and pressure inside the separation unit can be the same as the temperature and pressure of the slurry after the temperature is raised by the temperature raising unit.

<Solvent mixing step>
In the poor solvent mixing step S24, the solution obtained in the solid-liquid separation step S23 is mixed with the ashless coal poor solvent.

As described above, the main component of the solvent-soluble component eluted in this solution is ashless coal. That is, the above solution is obtained by dissolving ashless coal, which is a raw material for graphitized carbon, in a good solvent for ashless coal.

The content of the graphitized carbon raw material (ash-free charcoal) in the solution can be the same as the content of the graphitized carbon raw material in the solution in the first embodiment. Further, as the poor solvent, the same solvent as in the first embodiment can be used.

The method for mixing the solution and the poor solvent is the same as in the poor solvent mixing step S12 in the first embodiment.

<Precipitation process>
In the precipitation step S25, the solid content is precipitated from the mixed solution obtained in the poor solvent mixing step S24. Since the precipitation step S25 is the same as the precipitation step S13 in the first embodiment, detailed description thereof will be omitted.

[Solid phase carbonization process and pressure molding process]
Since the solid phase carbonization step S2 and the pressure molding step S3 are the same as the solid phase carbonization step S2 and the pressure molding step S3 in the first embodiment, detailed description thereof will be omitted. Further, the obtained porous carbon is the same as that of the porous carbon in the first embodiment.

<Advantage>
In the method for producing porous carbon and the method for producing a porous carbon molded product, ashless coal can be eluted into a good solvent by the solvent extraction treatment of coal in the elution step S21. Therefore, by using the solution in which the ashless coal is eluted in a good solvent as the solution in the poor solvent mixing step S24, it is not necessary to take out the ashless coal as a solid substance, so that the production cost of porous carbon can be further reduced.

[Third Embodiment]
Hereinafter, a third embodiment of the method for producing porous carbon and the method for producing a porous carbon molded product according to the present invention will be described.

As shown in FIG. 1, the method for producing porous carbon includes a solidification step S1 and a solid phase carbonization step S2, similarly to the method for producing porous carbon in the first embodiment. Further, as shown in FIG. 2, the method for producing the porous carbon molded product includes a pressure molding step S3 in addition to the solidification step S1 and the solid phase carbonization step S2 described above.

[Solidization process]
In the solidification step S1, the graphitized carbon raw material is solidified without passing through a melt.

As the graphitized carbon raw material, those described in the method for producing porous carbon in the first embodiment can be used. Hereinafter, as in the first embodiment, the case where ashless carbon is used alone as the graphitized carbon raw material will be described as an example, but it means that the graphitized carbon raw material is limited to ashless carbon. It's not something to do.

In the method for producing porous carbon and the method for producing a porous carbon molded product, the solidification step S1 includes a freezing step S31 and a drying step S32 as shown in FIG.

<Freezing process>
In the freezing step S31, the solution containing the graphitized carbon raw material is frozen.

In this freezing step S31, first, a solution prepared by dissolving the graphitized carbon raw material in a solvent is prepared. Examples of the solvent include pyridine (C ₅ H ₅ N), tetrahydrofuran (C ₄ H ₈ O), dimethylformamide ((CH ₃ ) ₂ NCHO), N-methylpyrrolidone (C ₅ H ₉ NO) and the like. Of these, low boiling point pyridine and tetrahydrofuran, which have a high affinity for ashless coal and can reduce the load in the drying step S32 described later, are preferable.

The content of the graphitized carbon raw material (ash-free charcoal in the method for producing porous carbon) in the solution can be the same as that of the graphitized carbon raw material in the solution of the first embodiment. Further, the method of eluting the ashless charcoal, which is a raw material for graphitized carbon, into the good solvent can be the same as the elution method of the first embodiment.

Next, the solution is cooled to a temperature below the melting point of the solvent and frozen. For example, when tetrahydrofuran (melting point −108 ° C.) is used, it is cooled to −130 ° C. and frozen.

The temperature difference between the melting point of the solvent and the cooling temperature is not particularly limited, but can be, for example, 10 ° C. or higher and 50 ° C. or lower. If the temperature difference is less than the above lower limit, it takes time to freeze, which may reduce the production efficiency. On the contrary, if the temperature difference exceeds the upper limit, energy is unnecessarily required for cooling, which may increase the manufacturing cost.

<Drying process>
In the drying step S32, the graphitized carbon raw material after the freezing step S31 is dried in a frozen state.

In this step, the solvent is sublimated without passing through a melt by reducing the pressure while maintaining the freezing temperature in the freezing step S31. Then, the temperature is returned to room temperature (for example, 25 ° C.) to obtain a dry solid content. The main component of this solid content is ashless coal, which is a raw material for graphitized carbon.

The pressure at the time of depressurization is not particularly limited as long as the solvent can be sublimated, but when tetrahydrofuran is used as the solvent, it can be, for example, 10 Pa or more and 100 Pa or less. If the pressure is less than the lower limit, the cost for depressurization may increase and the production cost of porous carbon may increase. On the contrary, when the pressure exceeds the upper limit, the amount of the solvent that evaporates through the melt increases, and the porosity of the obtained porous carbon may decrease.

[Solid phase carbonization process and pressure molding process]
Since the solid phase carbonization step S2 and the pressure molding step S3 are the same as the solid phase carbonization step S2 and the pressure molding step S3 in the first embodiment, detailed description thereof will be omitted. Further, the obtained porous carbon is the same as that of the porous carbon in the first embodiment.

<Advantage>
When frozen and solidified in the freezing step S31 in this way, the lamination (crystallization) of the graphitizable carbon raw material is difficult to proceed. Then, in order to obtain a solid of a graphitizable carbon raw material without passing through a melt in the drying step S32, it is possible to obtain a shaped solid in which crystallization has not progressed even though the graphitizable carbon raw material is used. it can.

Further, by using a so-called freeze-drying method having a freezing step S31 and a drying step S32 in the solidification step S2, porous carbon can be easily produced and a bulky bulk can be easily obtained.

[Fourth Embodiment]
Hereinafter, a fourth embodiment of the method for producing porous carbon and the method for producing a porous carbon molded product according to the present invention will be described.

As shown in FIG. 1, the method for producing porous carbon includes a solidification step S1 and a solid phase carbonization step S2, similarly to the method for producing porous carbon in the first embodiment. Further, as shown in FIG. 2, the method for producing the porous carbon molded product includes a pressure molding step S3 in addition to the solidification step S1 and the solid phase carbonization step S2 described above.

[Solidization process]
In the solidification step S1, the graphitized carbon raw material is solidified without passing through a melt.

As the graphitized carbon raw material, those described in the method for producing porous carbon in the first embodiment can be used. Hereinafter, as in the first embodiment, the case where ashless carbon is used alone as the graphitized carbon raw material will be described as an example, but it means that the graphitized carbon raw material is limited to ashless carbon. It's not something to do.

In the method for producing porous carbon and the method for producing a porous carbon molded product, the solidification step S1 includes a preparation step S41 and a fibrosis step S42 as shown in FIG.

<Preparation process>
In the preparation step S41, a spinning liquid containing the above-mentioned easily graphitized carbon raw material is prepared.

Specifically, a spinning solution in which the above-mentioned easily graphitized carbon raw material is dissolved in a solvent is prepared. As the solvent, the good solvent described in the first embodiment can be used.

The content of the graphitized carbon raw material (ash-free charcoal in the method for producing porous carbon) in the solution can be the same as that of the graphitized carbon raw material in the solution of the first embodiment. Further, the method of eluting the ashless charcoal, which is a raw material for graphitized carbon, into the good solvent can be the same as the elution method of the first embodiment.

<Filamentation process>
In the filamentation step S42, the easily graphitized carbon raw material is fibrated by discharging the spinning liquid into the coagulating liquid. As the coagulating solution, the poor solvent described in the first embodiment can be used.

The filamentation step S42 can be performed using, for example, a wet spinning apparatus as shown in FIG. 7. First, as shown in FIG. 7, the spinning liquid X is discharged from the syringe N in the coagulating liquid Y. Of the discharged spinning liquid X, the solvent dissolves in the coagulating liquid Y, and as a result, the graphitizable carbon raw material is covered with the coagulating liquid Y. As a result, the graphitizable carbon raw material rapidly solidifies to a solid content W. This solid content W is taken up by the roller R and filamented.

[Solid phase carbonization process and pressure molding process]
Since the solid phase carbonization step S2 and the pressure molding step S3 are the same as the solid phase carbonization step S2 and the pressure molding step S3 in the first embodiment, detailed description thereof will be omitted. Further, the obtained porous carbon is the same as the porous carbon in the first embodiment except that it is fibrous, and thus detailed description thereof will be omitted.

<Advantage>
As described above, the rapid solidification in the fiber addition step S42 makes it difficult for the graphitizable carbon raw material to be laminated (crystallized). Therefore, although it is an easily graphitizable carbon raw material, it is possible to obtain a fibrous shaped solid with less lamination.

Further, by using the so-called wet spinning method having the preparation step S41 and the fibration step S42 in the solidification step S1 as described above, fibrous porous carbon can be easily obtained.

[Other Embodiments]
The present invention is not limited to the above embodiment.

In the second embodiment, the configuration in which the mixing section of the good solvent mixing step has a preparation tank has been described, but the mixing section is not limited to this configuration, and if the solvent and coal can be mixed, the preparation tank is omitted. May be good. For example, when the above mixing is completed by a line mixer, the preparation tank may be omitted and a line mixer may be provided between the supply pipe and the separation portion. As described above, the apparatus configuration used in each step is not limited to the above embodiment.

Further, in the above embodiment, the case where the poor solvent method, freeze-drying method and wet spinning method are used as the solidification step has been described, but other methods as long as the graphitized carbon raw material can be solidified without passing through a melt. Can also be used.

In the above embodiment, as a method for producing the porous carbon molded body, a case where the solidification step, the solid phase carbonization step and the pressure molding step are performed in this order has been described, but the solid phase carbonization step and the pressure molding step have been described. May change the order. That is, the method for producing a porous carbon molded product of the present invention includes a case where a solidification step, a pressure molding step, and a solid phase carbonization step are performed in this order.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

[Example 1]
As a raw material for graphitized carbon, ashless coal produced by solvent extraction of bituminous coal was prepared. Table 1 shows the elemental analysis values of this ashless coal. In addition, pyridine (C ₅ H ₅ N, boiling point 115 ° C.) was prepared as a good solvent. The ashless coal was dissolved in the good solvent and prepared so that the content of the ashless coal in the solution was 15% by mass.

In Table 1, the amount of oxygen in ashless coal means the amount of components other than carbon, hydrogen, nitrogen and sulfur, and is obtained by subtracting the amount of components of carbon, hydrogen, nitrogen and sulfur from 100% by mass.

2.0 L of water was prepared as a poor solvent. 100 g of the above solution was added to the stirred poor solvent to precipitate a solid content. Then, the precipitated solid content was separated by filtration and dried under reduced pressure.

Further, the temperature was raised to 900 ° C. at a heating rate of 5 ° C./min in a nitrogen atmosphere, and heat treatment (solid phase carbonization) was performed for 30 minutes to produce the carbon material of Example 1.

[Example 2]
The carbon material of Example 2 in the same manner as in Example 1 except that _{quinoline (C 9} H ₇ N, boiling point 238 ° C.) was used as a good solvent and _{ethanol (C 2} H _{6 O, boiling point 78 ° C.) was used as a poor solvent.} Manufactured.

[Example 3]
A spinning solution prepared by dissolving ashless coal of the same type as in Example 1 in pyridine was prepared. The content of ashless charcoal in the spinning solution was 30% by mass. 100 g of this spinning solution was discharged into 2.0 L of ethanol from a syringe having an inner diameter of 1.1 mm to obtain a fibrous solid content. The obtained solid content was solid-phase carbonized under the same conditions as in Example 1 to produce the carbon material of Example 3.

[Comparative Example 1]
After crushing ashless coal of the same type as in Example 1 to a particle size of 250 μm or less, the temperature is raised to 900 ° C. at a heating rate of 5 ° C./min in a nitrogen atmosphere, and heat treatment (carbonization) is performed for 30 minutes. The carbon material of Comparative Example 1 was produced.

[Comparative Example 2]
The ashless coal of the same type as in Example 1 was heated to 280 ° C. in a nitrogen atmosphere to melt the ashless coal (fluidization). This melt was pressurized and discharged from a nozzle having a diameter of 0.5 mm, and the discharged fibers were wound up to obtain a fibrous solid content. The obtained solid content was carbonized under the same conditions as in Example 1 to produce a carbon material of Comparative Example 2.

[Reference example 1]
A commercially available coconut shell activated carbon powder was prepared and used as the carbon material of Reference Example 1. The coconut husk is a non-graphitized carbon, and the activated carbon powder of the activated carbon powder has a specific surface area increased by the activation treatment.

[Evaluation methods]
The following measurements were carried out on the obtained carbon materials of Examples 1 to 3, Comparative Example 1, Comparative Example 2 and Reference Example 1. The results are shown in Table 2.

<Specific surface area>
The specific surface area was measured by the BET method.

<Capacitance>
The obtained carbon material, acetylene black as a conductive auxiliary agent, and polytetrafluoroethylene (PTFE) as a binder are mixed at a mass ratio of 8: 1: 1 and molded into a coin shape to form an EDLC. A electrode for use was prepared.

The thickness of the obtained electrode was measured, and the volume was calculated by multiplying by the electrode area. Further, using a battery charging / discharging device (“HJ1001SD8” manufactured by Hokuto Denko Co., Ltd.), the charging characteristics in a 40 mass% sulfuric acid electrolytic solution were measured, and the capacitance at 50 mA / h was determined.

In Table 2, it means that the "ND" of the specific surface area was below the measurement limit. In addition, "-" means that it has not been measured.

From Table 2, the carbon materials of Examples 1 to 3 in which the graphitized carbon was solid-phase carbonized without passing through the melt were Comparative Examples 1 to 1 in which the graphitized carbon was carbonized via the melt. It can be seen that the specific surface area is larger than that of the carbon material of Comparative Example 2 and the carbon is porous.

On the other hand, in the carbon material of Comparative Example 1, it is considered that carbon having pores could not be obtained because the carbon material was normally carbonized via the melt. Further, in the carbon material of Comparative Example 2, carbonization itself is performed without softening (melting), but as a preliminary step, the carbon material is melted and spun, and in this process, it passes through a melt. It is probable that carbon having pores could not be obtained.

From the above, it can be said that even when an easily graphitizable carbon raw material is used, porous carbon can be produced by solid-phase carbonization without passing through a melt.

Further, comparing Example 1 and Reference Example 1, although the specific surface area of Example 1 is smaller, the capacitance when the EDLC electrode is produced is rather large. From this, it is possible to manufacture an EDLC electrode suitable for charging because the porous carbon obtained by solid-phase carbonization using an easily graphitizable carbon raw material without passing through a melt has abundant micropores. I understand.

As described above, the method for producing porous carbon and the method for producing a porous carbon molded product of the present invention have a low production cost, a large bulk density, and a large specific surface area per unit volume. A quality carbon molded product can be manufactured.

X Spinning liquid Y Coagulant liquid N Syringe R Roller W Solid content

Claims (9)

The process of solidifying the graphitized carbon raw material without going through a melt,
A method for producing porous carbon, which comprises a step of solid-phase carbonizing the solid content after the solidification step. The method for producing porous carbon according to claim 1, wherein the graphitized carbon raw material contains ashless charcoal. The solidification process is
The step of dissolving the graphitized carbon raw material in the good solvent and
A step of mixing the solution obtained in the dissolution step with the poor solvent of the graphitized carbon raw material, and a step of mixing the solution.
The method for producing porous carbon according to claim 1 or 2, further comprising a step of precipitating solid content from the mixed solution obtained in the poor solvent mixing step. The solidification process is
The process of mixing coal with a good solvent for ashless coal,
A step of eluting ashless coal from the coal into the good solvent by heating the slurry obtained in the good solvent mixing step, and
A step of solid-liquid separation of the slurry obtained in the above elution step and a step of solid-liquid separation
A step of mixing the solution obtained in the solid-liquid separation step with the poor solvent of the ashless coal, and a step of mixing the solution.
The method for producing porous carbon according to claim 2, further comprising a step of precipitating a solid content from the mixed solution obtained in the poor solvent mixing step. The good solvent contains a nitrogen-containing compound and contains
The method for producing porous carbon according to claim 3 or 4, wherein the poor solvent does not contain a nitrogen-containing compound. The content of the graphitized carbon raw material in the solution is 5% by mass or more and 50% by mass or less.
The method for producing porous carbon according to claim 3, claim 4 or claim 5, wherein the mass ratio of the poor solvent to the solution mixed in the poor solvent mixing step is 3 times or more and 20 times or less. The solidification process is
The step of freezing the solution containing the graphitized carbon raw material and
The method for producing porous carbon according to claim 1 or 2, further comprising a step of drying the graphitized carbon raw material after the freezing step in a frozen state. The solidification process is
The process of preparing a spinning solution containing the above-mentioned easily graphitized carbon raw material, and
The method for producing porous carbon according to claim 1 or 2, further comprising a step of fiberizing the easily graphitized carbon raw material by discharging the spinning liquid into a coagulating liquid. The process of solidifying the graphitized carbon raw material without going through a melt,
The step of solid-phase carbonizing the solid content after the solidification step and
A method for producing a porous carbon molded product, which comprises a step of pressure-molding the porous carbon after the solidification step so that the bulk density is 0.8 g / cm ^{3 or more.}

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