KR20190128737A - Manufacturing method of porous carbon fiber sheet and manufacturing method of porous carbon electrode - Google Patents

Abstract

An object of this invention is to provide the manufacturing method of the porous carbon fiber sheet with comparatively low manufacturing cost, and high manufacturing efficiency, and the manufacturing method of the porous carbon electrode using this porous carbon fiber sheet. The manufacturing method of the porous carbon fiber sheet of this invention is a process of felt-depositing a fine fiber on the surface of a board | substrate by the electric field spinning of the solution which ash-free coal dissolves, and the process of heating the fine fiber deposit obtained by the said deposition process. It is provided. As the deposition step, a step of mixing coal and a solvent, a step of eluting a component soluble in the solvent from the coal in the slurry obtained in the mixing step, and the slurry after elution in the elution step, What is necessary is just to include the process of isolate | separating into the liquid component and solvent insoluble component to contain. The manufacturing method of the porous carbon electrode of this invention is equipped with the process of shape | molding the porous carbon fiber sheet manufactured by the manufacturing method of the said porous carbon fiber sheet by an electrode.

Description

Manufacturing method of porous carbon fiber sheet and manufacturing method of porous carbon electrode

The present invention relates to a method for producing a porous carbon fiber sheet and a method for producing a porous carbon electrode.

As a method for producing a porous carbon fiber sheet having fluid or gas-liquid diffusibility, a method is known in which short carbon fibers are mixed with a binder material to harden in a felt form. In this conventional method for producing a porous carbon fiber sheet, since it is necessary to perform molding with a binder material, there is room for improvement in the production efficiency.

As a manufacturing method of the porous carbon fiber sheet which does not require molding, a method of carbonizing the field-spun fibers has been proposed (see Japanese Patent Application Laid-Open No. 2011-157668 and International Publication No. 2011/070893). In this conventional field emission method, a preheating gas is supplied to the pitch-based material for spinning, or a composition containing a field-spinable polymer material, an organic compound, and a transition metal is spun.

As described above, in the conventional method for producing the porous carbon fiber sheet by electric field spinning, a material specific to the carbon raw material and a substance other than carbon are required. For this reason, the manufacturing cost of the conventional porous carbon fiber sheet by electric field spinning has room for improvement.

Japanese Patent Laid-Open No. 2011-157668 International Publication No. 2011/070893

The present invention has been made on the basis of the above circumstances, and an object of the present invention is to provide a method for producing a porous carbon fiber sheet having a relatively low production cost and high production efficiency, and a method for producing a porous carbon electrode using the porous carbon fiber sheet. It is done.

The invention made in order to solve the above problems includes a step of depositing fine fibers in the form of felt on a substrate surface by electric field spinning of a solution in which ashless coal is dissolved, and a step of heating the fine fiber deposits obtained in the deposition step. It is a manufacturing method of the porous carbon fiber sheet.

In the manufacturing method of the said porous carbon fiber sheet, ashless coal is used as a carbon raw material. Ashless coal is relatively inexpensive, has good field radiation and does not require materials other than carbon. Moreover, in the manufacturing method of the said porous carbon fiber sheet, based on the excellent graphitization property of ashless coal, a fine fibrous porous carbon fiber can be easily obtained by a high specific surface area by electric field spinning, without performing a process, such as shaping | molding. Therefore, the manufacturing method of the said porous carbon fiber sheet is comparatively low in manufacturing cost, and high in manufacturing efficiency.

As the deposition step, a step of mixing coal and a solvent, a step of eluting a component soluble in the solvent from the coal in the slurry obtained in the mixing step, and the slurry after elution in the elution step, What is necessary is just to include the process of isolate | separating into the liquid component and solvent insoluble component to contain. By using the solvent extracted as ashless coal in this manner, the production efficiency can be further increased, and the production cost can be reduced.

What is necessary is just to adjust the voltage of electric field emission or content of the ashless coal in the said solution so that the average diameter of the carbon fiber obtained may be 0.5 micrometer or more and 5 micrometers or less. By adjusting the average diameter of the carbon fiber thus obtained in the above range, the fibers are appropriately entangled at the time of electric field spinning, and the fluid diffusivity is increased.

Another invention made in order to solve the said subject is a manufacturing method of the porous carbon electrode provided with the process of shape | molding the porous carbon fiber sheet manufactured by the manufacturing method of the said porous carbon fiber sheet to an electrode.

In the method for producing a porous carbon electrode, since the porous carbon fiber sheet produced by the method for producing a porous carbon fiber sheet is formed into an electrode, an electrode having fluid diffusibility can be efficiently produced at a relatively low production cost. .

As explained above, the manufacturing method of the porous carbon fiber sheet of this invention, and the manufacturing method of the porous carbon electrode using this porous carbon fiber sheet are comparatively low in manufacturing cost, and high in manufacturing efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic flowchart which shows the manufacturing method of the porous carbon fiber sheet which concerns on one Embodiment of this invention.
FIG. 2 is a schematic flowchart of the deposition process of FIG. 1.
3 is a schematic diagram illustrating the electric field radiating part.
4 is an optical micrograph of the porous carbon fiber sheet of Example 1. FIG.
5 is a scanning electron micrograph of the carbon fibers of the porous carbon fiber sheet of Example 1. FIG.
6 is a graph showing the pore diameter distribution of the porous carbon fiber sheet of Example 1. FIG.

EMBODIMENT OF THE INVENTION Hereinafter, one Embodiment of the manufacturing method of the porous carbon fiber sheet which concerns on this invention, and the manufacturing method of a porous carbon electrode is demonstrated.

[Method for producing porous carbon fiber sheet]

As shown in FIG. 1, the method for producing the porous carbon fiber sheet mainly includes a deposition step S1 and a heating step S2. The manufacturing method of the said porous carbon fiber sheet is a manufacturing apparatus mainly provided with a coal supply part, a solvent supply part, a mixing part, a temperature rising part, an elution part, a separation part, an electric field spinning part, and a heating part, for example. This can be done by.

[Deposition process]

In the deposition step S1, fine fibers are felt-deposited on the surface of the substrate by electric field spinning of a solution in which ashless coal is dissolved. The deposition step S1 includes a first mixing step S11, an elution step S12, a solid-liquid separation step S13, an evaporation separation step S14, a second mixing step S15, and an electric field spinning step S16. .

<1st mixing process>

In 1st mixing process S11, coal and a solvent are mixed. This 1st mixing process S11 can be performed by a coal supply part, a solvent supply part, and a mixing part, for example.

(Coal supply)

The coal supply unit supplies coal to the mixing unit. As a coal supply part, well-known coal hoppers, such as the normal pressure hopper used in a normal pressure state, the pressurized hopper used in a normal pressure state and a pressurized state, can be used.

Coal supplied from a coal supply part is coal used as a raw material of ashless coal. As said coal, coal of various quality can be used. For example, bituminous coal having a high extraction rate of ashless coal and cheaper low-grade coal (sub-bituminous coal and lignite) are suitably used. In addition, when coal is classified into particle sizes, finely pulverized coal is suitably used. The term "finely pulverized coal" herein means coal having a mass ratio of coal having a particle size of less than 1 mm to 80% or more of the mass of the entire coal. In addition, lump coal can also be used as coal supplied from a coal supply part. Here, "got coal" means the coal whose mass ratio of the coal whose particle size is 5 mm or more with respect to the mass of the whole coal is 50% or more. Since lump coal has a larger coal particle size of the undissolved solid than the finely pulverized coal, the separation in the separating section described later can be made more efficient. Here, "particle size (particle size)" means the value measured based on the sieve classification test general rule of JIS-Z8815: 1994. In addition, the metal mesh prescribed | regulated to JIS-Z8801-1: 2006 can be used for the division by the particle size of coal.

As a minimum of the carbon content rate of the said low grade carbon, 70 mass% is preferable. On the other hand, as an upper limit of the carbon content rate of the said low grade coal, 85 mass% is preferable, and 82 mass% is more preferable. When the carbon content rate of the said low grade coal is less than the said minimum, there exists a possibility that the dissolution rate of a solvent-soluble component may fall. On the contrary, when the carbon content rate of the said low grade coal exceeds the said upper limit, there exists a possibility that the cost of the coal to supply may become high.

In addition, as coal supplied from the coal supply part to the mixing part, coal which is slurryed by mixing a small amount of solvent may be used. By supplying coal slurried from a coal supply part to a mixing part, coal becomes easy to mix with a solvent in a mixing part, and can dissolve coal more quickly. However, if the amount of the solvent to be mixed at the time of slurrying is large, the amount of heat for raising the slurry to the elution temperature is unnecessarily increased in the temperature raising section described later, which may increase the manufacturing cost.

(Solvent supply)

The solvent supply part supplies the solvent to the mixing part. The said solvent supply part has a solvent tank which stores a solvent, and supplies a solvent from this solvent tank to a mixing part. The solvent supplied from the said solvent supply part is mixed in coal and a mixing part supplied from the coal supply part.

The solvent supplied from the solvent supply unit is not particularly limited as long as it dissolves coal. For example, a bicyclic aromatic compound derived from coal is suitably used. This bicyclic aromatic compound has a high affinity with coal in that its basic structure is similar to that of coal, and a relatively high extraction rate can be obtained. As a bicyclic aromatic compound derived from coal, methylnaphthalene oil, naphthalene oil, etc. which are by-product oil at the time of distilling coal and manufacturing coke, etc. are mentioned.

Although the boiling point of the said solvent is not specifically limited, For example, as a minimum of the boiling point in the normal pressure (0.1 MPa) of the said solvent, 180 degreeC is preferable and 230 degreeC is more preferable. On the other hand, as an upper limit of the boiling point in the normal pressure of the said solvent, 300 degreeC is preferable and 280 degreeC is more preferable. If the boiling point of the solvent is less than the above lower limit, the solvent tends to be volatilized, and thus, there is a fear that adjustment and maintenance of the mixing ratio of coal and solvent in the slurry are difficult. On the contrary, when the boiling point of the said solvent exceeds the said upper limit, separation of a solvent-soluble component and a solvent will become difficult and there exists a possibility that the recovery rate of a solvent may fall.

(Mixing part)

The mixing unit mixes the coal supplied from the coal supply unit and the solvent supplied from the solvent supply unit.

As said mixing part, preparation preparation can be used. In this preparation, the said coal and a solvent are supplied through a supply pipe. In the said preparation, this supplied coal and a solvent are mixed and a slurry is prepared. Moreover, the said preparation manufacturing has a stirrer, and maintains the mixed state of a slurry by hold | maintaining the mixed slurry with stirring.

Although the coal concentration in the anhydrous carbon standard in the slurry in preparation manufacture is suitably determined by the kind of solvent, etc., as a minimum of the said coal concentration, 10 mass% is preferable and 13 mass% is more preferable. On the other hand, as an upper limit of the said coal concentration, 25 mass% is preferable, and 20 mass% is more preferable. If the said coal concentration is less than the said minimum, since the elution amount of the solvent soluble component eluted in elution process S12 will become small compared with the slurry throughput, there exists a possibility that content of the ashless coal contained in a solution may become inadequate. On the contrary, when the said coal concentration exceeds the said upper limit, since the said solvent soluble component tends to be saturated in a solvent, there exists a possibility that the dissolution rate of the said solvent soluble component may fall.

<Elution process>

In elution process S12, the soluble coal component is eluted from a coal in the slurry obtained by the said 1st mixing process S11 to a solvent. Elution process S12 can be performed by a temperature rising part and an elution part, for example.

(Heating part)

A temperature rising part heats up the slurry obtained at the said 1st mixing process S11.

The temperature raising part is not particularly limited as long as it can heat up the slurry passing through the inside, but examples thereof include a resistance heating heater and an induction heating coil. In addition, the temperature increase part may be comprised so that a temperature may be heated using a heat medium, For example, it has a heating tube arrange | positioned around the flow path of the slurry which passes inside, and heat mediums, such as steam and oil, are supplied to this heating tube. You may be comprised so that a temperature can be heated up by supplying.

Although the temperature of the slurry after temperature rising by a temperature rising part is suitably determined according to the solvent used, 300 degreeC is preferable and 360 degreeC is more preferable as a minimum of the said slurry temperature. On the other hand, as an upper limit of the said slurry temperature, 420 degreeC is preferable and 400 degreeC is more preferable. If the temperature of the said slurry is less than the said minimum, there exists a possibility that a dissolution rate may fall. On the contrary, when the temperature of the said slurry exceeds the said upper limit, since a solvent vaporizes too much, there exists a possibility that it may become difficult to control the density | concentration of a slurry.

In addition, it does not specifically limit as a pressure of a temperature rising part, It can be set as normal pressure (0.1MPa).

(Elution part)

The eluting unit is obtained by the mixing unit and elutes the coal component soluble in the solvent from the coal in the slurry heated at the temperature raising unit.

As an elution part, an extraction tank can be used and the slurry after the said temperature rising is supplied to this extraction tank. In the said extraction tank, the coal component soluble in a solvent is eluted from coal, holding the temperature and pressure of this slurry. Moreover, the said extraction tank has a stirrer. The elution can be promoted by stirring the slurry with this stirrer.

The elution time in the elution section is not particularly limited, but is preferably 10 minutes or more and 70 minutes or less from the viewpoint of extraction amount and extraction efficiency of the solvent-soluble component.

<Solid-Liquid Separation Process>

In solid-liquid separation process S13, the said slurry after eluting in the said eluting process S12 is isolate | separated into the liquid component and solvent insoluble component containing a solvent-soluble component. This solid-liquid separation process S13 can be performed by a separating part. In addition, a solvent-insoluble component says the extraction residue which mainly contains ash and insoluble coal insoluble in an extraction solvent, and further contains an extraction solvent further in these.

(Separation part)

As a method of separating the said liquid component and the solvent insoluble component in a separation part, the gravity sedimentation method, the filtration method, and the centrifugal separation method can be used, for example, A sedimentation tank, a filter, and a centrifugal separator are used, respectively.

Hereinafter, the separation method will be described taking the gravity sedimentation method as an example. The gravity sedimentation method is a separation method in which a solvent-insoluble component is sedimented and solid-liquid separated using gravity in a sedimentation tank. When separating by the gravity sedimentation method, the liquid component containing the solvent soluble component accumulates in the upper part of the sedimentation tank. This liquid powder is filtered using a filter unit as necessary, and then discharged to a spraying unit described later. On the other hand, the solvent insoluble component is discharged | emitted from the lower part of a separation part.

In addition, in the case of separation by gravity sedimentation, the liquid component and the solvent insoluble component including the solvent soluble component can be discharged from the sedimentation tank while the slurry is continuously supplied into the separation portion. This enables continuous solid-liquid separation treatment.

Although the time to hold a slurry in a separation part is not specifically limited, For example, it can be 30 minutes or more and 120 minutes or less, and sedimentation separation in a separation part is performed within this time. In addition, when lump coal is used as coal, sedimentation separation becomes more efficient, and the time which holds a slurry in a separation part can be shortened.

In addition, as temperature and pressure in a separating part, it can carry out similarly to the temperature and pressure of the slurry after temperature rising by a temperature rising part.

<Evaporation Separation Process>

In the evaporation separation step S14, the solvent is evaporated from the liquid fraction separated in the solid-liquid separation step S13. Ashless charcoal (HPC) is obtained by evaporative separation of this solvent. Ash-free coal obtained in this way has ash content of 5 mass% or less or 3 mass% or less, hardly contains ash, and has no moisture.

As a method for evaporating the solvent, a separation method including a general distillation method or an evaporation method (spray drying method or the like) can be used. By separating the solvent from the liquid powder, an ashless coal substantially free of ash can be obtained from the liquid powder.

On the other hand, from the said solvent insoluble component, a by-product coal can be obtained by evaporating a solvent. By-product coal does not exhibit softening meltability, but the oxygen-containing functional group is detached. Therefore, by-product coal does not impair the softening meltability of the other coal contained in this coal blend when it is used as a coal blend. Therefore, this coal blend can be used, for example as a part of coal blend of a coke raw material. In addition, by-product coal may be used as a fuel similar to general coal.

<2nd mixing process>

In the second mixing step S15, the ashless coal obtained in the evaporation separation step S14 is dissolved in a solvent. By dissolving the ashless coal, a solution in which ashless coal is dissolved is obtained.

The solvent for dissolving the ashless coal is not particularly limited as long as the ashless coal is dissolved, but may be an organic compound containing an oxygen atom or a nitrogen atom as a main component. Thus, by making the main component of the said solvent into the organic compound containing an oxygen atom or a nitrogen atom, the affinity of a solvent and ashless coal becomes high and it is easy to raise content of ashless coal in the solution which is electrospun. As a result, since the quantity of porous carbon fiber increases, the manufacturing cost of a porous carbon fiber sheet can be reduced. As such a solvent, pyridine (C ₅ H ₅ N), tetrahydrofuran (C ₄ H ₈ O), dimethylformamide ((CH ₃ ) ₂ NCHO), N-methylpyrrolidone (C ₅ H ₉ NO) Etc. can be mentioned. Among them, pyridine and tetrahydrofuran having high affinity for ashless coal are preferable. In addition, one type of organic compound containing an oxygen atom or a nitrogen atom may be sufficient, and two or more types of organic compounds may be mixed.

As a minimum of content of the ashless coal in the said solution, 20 mass% is preferable and 25 mass% is more preferable. On the other hand, as an upper limit of content of the ashless coal in the said solution, 60 mass% is preferable, 50 mass% is more preferable, 40 mass% is further more preferable. When content of the said ashless coal is less than the said minimum, since it will become easy to droplet at the time of electric field spinning, there exists a possibility that it may become difficult to obtain a fine fiber in the field spinning process S16 mentioned later. On the contrary, when content of the said ashless coal exceeds the said upper limit, the diameter of the fine fiber obtained by electric field spinning will become large too much, and there exists a possibility that the specific surface area of a porous carbon fiber sheet may fall.

<Field emission process>

In the field spinning step S16, fine fibers are deposited in a felt form on the surface of the substrate by performing field spinning using the solution obtained in the second mixing step S15.

For example, as shown in FIG. 3, the electric field radiation can be performed by the electric field radiator having the syringe 1 and the substrate 2. Specifically, the field emission is performed by placing the solution in the syringe 1 and applying a voltage E between the nozzle 1a of the syringe 1 and the substrate 2. When a voltage E is applied between the nozzle 1a and the substrate 2, electric charges are collected on the surface of the droplet at the tip of the nozzle 1a, repel each other, and become conical. In addition, the voltage E is increased so that when the repulsive force of the charge exceeds the surface tension, the solution is ejected toward the substrate 2 from the tip of the nozzle 1a. As the ejected solution stream 3 becomes thinner, the surface charge density becomes larger, so that the repulsive force of the charge is increased, and the solution stream 3 becomes longer. At that time, the specific surface area of the solution 3 rapidly increases, and the solvent is volatilized, and the fine fibers 4 are spun onto the surface of the substrate 2. As described above, in the field spinning, the fine fibers 4 can be produced by a relatively simple device. In addition, although the nozzle 1a is one in FIG. 3, you may be provided with the some nozzle 1a, and a some fine fiber may be produced simultaneously.

The substrate 2 is not particularly limited as long as it is conductive, but a metal plate, a metal foil, a carbon substrate, or the like can be used.

As a minimum of the inner diameter (nozzle inner diameter) of the tip part of the said nozzle 1a, 0.2 mm is preferable and 0.4 mm is more preferable. On the other hand, as an upper limit of the said nozzle inner diameter, 0.7 mm is preferable and 0.6 mm is more preferable. If the said nozzle inner diameter is less than the said minimum, since the fine fiber 4 obtained becomes thin, it will be easy to be broken and will be short fiber. For this reason, there exists a possibility that it may become difficult to deposit the fine fiber 4 in felt form on the board | substrate 2 surface. On the contrary, when the nozzle inner diameter exceeds the upper limit, the diameter of the fine fibers 4 to be obtained increases, so there is a fear that the specific surface area of the porous carbon fiber sheet to be produced decreases.

As a lower limit of the distance between radiations (distance of the tip of the nozzle 1a, and the board | substrate 2), 10 cm is preferable and 12 cm is more preferable. On the other hand, as an upper limit of the distance between radiations, 20 cm is preferable and 18 cm is more preferable. If the distance between the radiations is less than the above lower limit, the solvent may not be volatilized sufficiently, and the electric field radiation may be difficult. On the contrary, when the distance between spinning exceeds the said upper limit, since the fine fiber 4 obtained becomes thin, it will be easy to be broken and will be short fiber. For this reason, there exists a possibility that it may become difficult to deposit the fine fiber 4 in felt form on the board | substrate 2 surface.

As a minimum of the applied voltage E between the said nozzle 1a and the board | substrate 2, 10 kV is preferable and 12 kV is more preferable. On the other hand, as an upper limit of the said applied voltage E, 30 kV is preferable and 20 kV is more preferable. There exists a possibility that the fine fiber 4 may not be formed stably if the said applied voltage E is less than the said minimum. On the contrary, when the said applied voltage E exceeds the said upper limit, since the diameter distribution of the fine fiber 4 obtained becomes easy to spread, there exists a possibility that the porous carbon fiber sheet manufactured may become heterogeneous.

As a minimum of the flow volume (discharge amount of the solution from one nozzle 1a) of the said solution 3, 1 ml / h is preferable and 1.5 ml / h is more preferable. On the other hand, as an upper limit of the flow volume of the said solution 3, 3 ml / h is preferable and 2.5 ml / h is more preferable. If the flow volume of the said solution 3 is less than the said minimum, there exists a possibility that the fine fiber 4 may not be formed stably. On the contrary, when the flow volume of the said solution 3 exceeds the said upper limit, since the diameter of the fine fiber 4 obtained becomes large, there exists a possibility that the specific surface area of the porous carbon fiber sheet manufactured may fall. In addition, the flow volume of the said solution 3 can be controlled by the nozzle internal diameter and the applied voltage E. FIG.

As a minimum of the average diameter of the fine fiber 4 deposited on the surface of the board | substrate 2, 0.5 micrometer is preferable and 0.7 micrometer is more preferable. On the other hand, as an upper limit of the average diameter of the said fine fiber 4, 5 micrometers is preferable and 3 micrometers is more preferable. If the average diameter of the fine fibers 4 is less than the above lower limit, the fine fibers 4 tend to break and become short fibers, so that the fine fibers 4 become difficult to be deposited on the surface of the substrate 2 in a felt form. There is concern. On the contrary, when the average diameter of the said fine fiber 4 exceeds the said upper limit, there exists a possibility that the specific surface area of the porous carbon fiber sheet manufactured may fall. In addition, the average diameter of the said fine fiber 4 is mainly controlled by the applied voltage E of field emission from a viewpoint of controllability. In addition, the average diameter of the said fine fiber 4 can also be adjusted with nozzle internal diameter and the distance between spinning.

In addition, the fine fiber 4 which felt-deposited on the surface of the board | substrate 2 peels from the board | substrate 2. As shown in FIG. In the method for producing the porous carbon fiber sheet, the fine fibers 4 are not cut by the excellent field spinning of ashless coal, and are continuously and randomly deposited on the substrate 2. For this reason, since the fine fibers 4 are appropriately entangled with each other, it is possible to maintain the felt form after peeling without using a binder material or the like, for example. In addition, in the manufacturing method of the said porous carbon fiber sheet, the fine fiber 4 can be carbonized in the heating process S2 mentioned later, maintaining this felt form.

[Heating process]

In the heating step S2, the fine fiber deposits obtained in the deposition step S1 are heated. This heating process S2 can be performed by a heating part.

(Heating part)

The heating unit carbonizes the fine fiber deposits while maintaining the aggregated state thereof substantially by heating. By this carbonization, a porous carbon fiber sheet is obtained.

As said heating part, a well-known electric furnace etc. can be used, for example, Fine fiber deposits are inserted into a heating part, the inside is replaced with an inert gas, and it heats, blowing inert gas into a heating part, and making fine fiber Carbonization of the deposits is possible. Although it does not specifically limit as said inert gas, For example, nitrogen, argon, etc. are mentioned. Among them, inexpensive nitrogen is preferable.

As a minimum of the said heating temperature, 500 degreeC is preferable and 700 degreeC is more preferable. On the other hand, as an upper limit of the said heating temperature, 3000 degreeC is preferable and 2800 degreeC is more preferable. There exists a possibility that carbonization may become inadequate when the said heating temperature is less than the said minimum. On the contrary, when heating temperature exceeds the said upper limit, there exists a possibility that manufacturing cost may rise from the viewpoint of the heat resistance improvement of a facility, or fuel consumption. In addition, as a temperature increase rate, it can be 0.01 degreeC / min or more and 10 degrees C / min or less, for example.

Moreover, as a minimum of a heat time, 10 minutes are preferable and 20 minutes are more preferable. On the other hand, as an upper limit of a heat time, 10 hours are preferable and 8 hours are more preferable. If heating temperature is less than the said minimum, there exists a possibility that carbonization may become inadequate. On the contrary, when heating time exceeds the said upper limit, there exists a possibility that the manufacturing efficiency of a porous carbon fiber sheet may fall.

The inventors have found that the carbon fibers constituting the porous carbon fiber sheet thus obtained are mainly composed of fine pores having a pore diameter of 10 nm or less, and have a high specific surface area. The mechanism by which such micropores are formed is not necessarily clear, but ashless coal has a high oxygen content and a low carbon content as compared to, for example, coal pitch. For this reason, ashless coal is considered to have low planarity of molecules as a mixture of polycyclic aromatic compounds, is considered small in ring size, and is difficult to be molecularly aligned. That is, when the solution is ejected from the nozzle 1a by electric field spinning in the deposition step S1, and the solvent is rapidly volatilized, ashless coal is condensed, but the molecules are randomly stacked on each other. In heating process S2, since such a molecule | numerator does not align and carbonizes, maintaining a random structure, it is thought that porous carbon is produced | generated. On the other hand, in the coal pitch having high aromaticity, it is considered that since the molecules are condensed while forming molecular orientations in which molecules are stacked in parallel with each other, relatively high crystalline carbon, that is, carbon fibers in which fine pores do not develop, is produced.

As an upper limit of the oxygen content rate of the carbon fiber which comprises a porous carbon fiber sheet, 0.6 mass% is preferable and 0.55 mass% is more preferable. When the oxygen content rate of the said carbon fiber exceeds the said upper limit, there exists a possibility that the strength of a carbon fiber may run short.

As a minimum of the specific surface area of the porous carbon fiber sheet manufactured, 300 m <2> / g is preferable, 400 m <2> / g is more preferable, and 450 m <2> / g is still more preferable. When the said specific surface area is less than the said minimum, there exists a possibility that it may become difficult to use as a porous material. On the other hand, it is although it does not specifically limit as an upper limit of the said specific surface area, Usually, it is about 3000 m <2> / g.

As a minimum of the average diameter of the carbon fiber obtained, 0.5 micrometer is preferable and 0.7 micrometer is more preferable. On the other hand, as an upper limit of the average diameter of the said carbon fiber, 5 micrometers is preferable and 3 micrometers is more preferable. When the average diameter of the said carbon fiber is less than the said minimum, since carbon fiber is easy to be broken and it becomes short fiber, there exists a possibility that it may become difficult to obtain a felt-type carbon fiber sheet. On the contrary, when the average diameter of the said carbon fiber exceeds the said upper limit, there exists a possibility that the specific surface area of the porous carbon fiber sheet manufactured may fall. In addition, the average diameter of the said carbon fiber is determined by the average diameter of the fine fiber 4, and the average diameter of the fine fiber 4 is mainly from the controllability viewpoint, the applied voltage E of an electric field emission or ashless coal in a solution. It is controlled by the content of. In addition, the average diameter of the said fine fiber 4 can also be adjusted with nozzle internal diameter and the distance between spinning.

[advantage]

In the manufacturing method of the said porous carbon fiber sheet, ashless coal is used as a carbon raw material. Ashless coal is relatively inexpensive and has good field radiation and does not require materials other than carbon. Moreover, in the manufacturing method of the said porous carbon fiber sheet, based on the excellent graphitization property of ashless coal, a fine fibrous porous carbon fiber can be easily obtained by a high specific surface area by electric field spinning, without performing a process, such as shaping | molding. Therefore, the manufacturing method of the said porous carbon fiber sheet is comparatively low in manufacturing cost, and high in manufacturing efficiency.

Moreover, in the manufacturing method of the said porous carbon fiber sheet, by using what was solvent-extracted as ashless coal, manufacturing efficiency can be improved further and manufacturing cost can be reduced.

[Method for producing porous carbon electrode]

The manufacturing method of the said porous carbon electrode is equipped with the shaping | molding process. In the said molding process, the porous carbon fiber sheet manufactured by the manufacturing method of the said porous carbon fiber sheet is shape | molded, and it is set as an electrode. For this reason, the electrode which has fluid diffusibility can be manufactured efficiently with comparatively low manufacturing cost. Although it does not specifically limit as a shaping | molding method, For example, the method by the punching of the said porous carbon fiber sheet is mentioned.

[Other Embodiments]

In addition, this invention is not limited to the said embodiment.

In the above embodiment, as a method for producing a porous carbon fiber sheet, a method of manufacturing ashless coal by solvent extraction has been described. However, the method of manufacturing ashless coal is not limited thereto, for example, mixing coal and a hydrogen donor solvent. Anthracite produced by heating may also be used.

Moreover, in the said embodiment, as a manufacturing method of a porous carbon fiber sheet, after a solvent extraction of ashless coal in the evaporation separation process, the ashless coal was melt | dissolved in the 2nd mixing process to prepare the solution which electrospins, but extracts ashless coal By using the solvent of the solvent and the solution of the electrospinning as the same kind of solvent, the evaporation separation step and the second mixing step may be omitted. In this case, the liquid component obtained by the solid-liquid separation process can be used as a solution of electric field spinning.

In the said embodiment, although the structure which the mixing part of a 1st mixing process has preparation manufacturing was demonstrated as a manufacturing method of a porous carbon fiber sheet, it is not limited to this structure, If a solvent and coal can be mixed, preparation preparation May be omitted. For example, when the said mixing is completed by a line mixer, preparation manufacturing is abbreviate | omitted and it is good also as a structure provided with a line mixer between a supply pipe and a separation part. Thus, the apparatus structure used by each process is not limited to the said embodiment.

In addition, the use of the porous carbon fiber sheet manufactured by the manufacturing method of a porous carbon fiber sheet is not limited to an electrode, For example, it can be used suitably for the sheet | seat requiring porous properties, such as an adsorption material and a catalyst carrier.

Example

Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.

Example 1

Anthracite produced by solvent extraction of bituminous coal was prepared as a carbon raw material. The elemental analysis value of this ashless coal is shown in Table 1 as "anthracite A". In addition, pyridine was prepared as a solvent.

By mixing this ashless coal and a solvent, the solution which ashless coal dissolved in a solvent was prepared so that content of the ashless coal in a solution might be 39 mass%.

Using this solution, field spinning was performed under the conditions shown in Table 2, and fine fibers were deposited on the aluminum foil substrate. After peeling this fine fiber deposit from aluminum foil, it heated up to 900 degreeC at the temperature increase rate of 3.3 degree-C / min, heat-processed for 30 minutes (carbonization), and manufactured the porous carbon fiber sheet of Example 1. The optical micrograph of the obtained porous carbon fiber sheet is shown in FIG.

Example 2

By the solvent extraction of bituminous coal, the ashless coal which differs in a composition from Example 1 was prepared as a carbon raw material. The elemental analysis value of this ashless coal is shown in Table 1 as "anthracite B". A porous carbon fiber sheet of Example 2 was produced in the same manner as in Example 1, except that this ashless coal was used.

Comparative Example 1

Coal-based pitches prepared from tar by-produced in the high-temperature drying process of coal were prepared. Table 1 shows the elemental analysis of this coal-based pitch. Except having made this coal-based pitch the carbon raw material, it carried out similarly to Example 1, and manufactured the porous carbon fiber sheet of the comparative example 1.

In addition, in Table 1, oxygen amount means component amounts other than carbon, hydrogen, nitrogen, and sulfur, and removes the component amounts of carbon, hydrogen, nitrogen, and sulfur from 100 mass%.

[Assessment Methods]

The following measurements were performed about the said Example 1, 2 and the comparative example 1.

<Average fiber diameter>

The average diameter (average fiber diameter) of the carbon fibers was measured by scanning electron microscopy. The measurement measured the diameter of ten arbitrary fibers in the visual field of a scanning electron microscope, and calculated | required the average. The scanning electron micrograph of the carbon fiber of the porous carbon fiber sheet of Example 1 is shown in FIG. In addition, the measurement results are shown in Table 3.

<Specific surface area>

The specific surface area of the porous carbon fiber sheet was measured using "BELSOR-max" by Micro Track Bell Co., Ltd. The measurement results are shown in Table 3.

<Pore distribution>

About the porous carbon fiber sheet of Example 1, the pore distribution of carbon fiber was measured using the HK method. The measurement result is shown in FIG.

From Table 3, it turns out that Example 1 and Example 2 which used ashless coal for a carbon material have a large specific surface area compared with the comparative example 1. 6 shows that the carbon fibers of the porous carbon fiber sheet of Example 1 are mainly composed of fine pores having a pore diameter of 10 nm or less, and the porous properties of each carbon fiber are high. In addition, the carbon fiber is not cut from FIG. 5 and is continuously and randomly gathered. In the porous carbon fiber sheet of Example 1, the felt form can be maintained without using a binder or the like, and the gas or liquid It can be seen that the fluid diffusivity is excellent.

On the other hand, the comparative example 1 which used the coal pitch for the carbon material is small in specific surface area, and it is thought that pore is not developed. Therefore, it is understood that the fine fiber-like porous carbon fibers can be easily obtained with high specific surface area by electric field spinning without performing molding or the like by the method for producing the porous carbon fiber sheet using ashless coal as a carbon raw material. Can be.

As explained above, the manufacturing method of the porous carbon fiber sheet of this invention, and the manufacturing method of the porous carbon electrode using this porous carbon fiber sheet are comparatively low in manufacturing cost, and high in manufacturing efficiency.

S1: deposition process
S2: heating process
S11: first mixing process
S12: elution process
S13: solid-liquid separation process
S14: Evaporative Separation Process
S15: second mixing process
S16: field emission process
1: syringe
1a: nozzle
2: substrate
3: solutions
4: fine fiber
E: voltage

Claims (4)

A process of felt-depositing fine fibers on the substrate surface by field spinning of a solution in which ashless coal is dissolved;
Heating the fine fiber deposits obtained in the deposition step
The manufacturing method of the porous carbon fiber sheet provided with the. The method of claim 1, wherein as the deposition process,
Mixing the coal and the solvent,
Eluting a component soluble in the solvent from the coal in the slurry obtained in the mixing step;
A step of separating the slurry after eluting in the elution step into a liquid component containing a solvent soluble component and a solvent insoluble component
The manufacturing method of the porous carbon fiber sheet provided with the. The manufacturing method of the porous carbon fiber sheet of Claim 1 which adjusts the voltage of electric field emission or content of the ashless coal in the said solution so that the average diameter of the carbon fiber obtained may be 0.5 micrometer or more and 5 micrometers or less. The manufacturing method of the porous carbon electrode provided with the process of shape | molding the porous carbon fiber sheet manufactured by the manufacturing method of the porous carbon fiber sheet of Claim 1, 2 or 3 to an electrode.

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