WO2018154977A1

WO2018154977A1 - Method for producing porous carbon particles, and porous carbon particles

Info

Publication number: WO2018154977A1
Application number: PCT/JP2018/000033
Authority: WO
Inventors: 濱口　眞基; 祥平和田; 聡則井上; 豊田　昌宏
Original assignee: 株式会社神戸製鋼所; 国立大学法人大分大学
Priority date: 2017-02-24
Filing date: 2018-01-04
Publication date: 2018-08-30
Also published as: JP2018140883A

Abstract

The purpose of the present invention is to provide a method for producing relatively dense porous carbon particles at a low production cost, and porous carbon particles. This method for producing porous carbon particles is provided with a spray-drying step in which a solution of ashless coal dissolved in a solvent is spray-dried, and a heating step in which a solids fraction obtained in the spray-drying step is heated. The solvent has as a main component an organic compound that includes an oxygen atom or nitrogen atom and has a boiling point of at least 50°C and less than 250°C at atmospheric pressure. The ashless coal content in the solution is 5-50% by mass. These porous carbon particles have carbon as the main component and are provided with a carbon layer that encloses a hollow portion. The carbon layer has a plurality of pores. The log differential pore volume of pores having a diameter of 0.5 nm or less from among the pores is 0.1 cm3/g or higher, and the log differential pore volume of pores having a diameter of 2-4 nm is less than 0.05 cm3/g.

Description

Method for producing porous carbon particles and porous carbon particles

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

The porous carbon particles having pores with a diameter of micron or nanometer order on the surface and a high specific surface area are useful as adsorbents. As a method for producing the porous carbon particles, for example, a carbon raw material is activated with water vapor or an alkaline substance to increase the specific surface area (Japanese Patent Laid-Open No. 2012-41199), an organic resin is an oxide such as magnesium oxide (template) For example, a method of removing the oxide after mixing with carbon) and carbonizing the particles (Japanese Patent Laid-Open No. 2016-41656).

In the above conventional method for producing porous carbon particles, in addition to the step of carbonizing the raw material, a step of performing an activation treatment with an alkaline substance and a removal treatment of the template particles is necessary, which increases the production cost. Further, the pores formed by these treatments tend to have larger diameters as they are closer to the surface of the porous carbon particles. For this reason, in addition to pores (micropores) having a diameter of less than 2 nm, the conventional porous carbon particles also have pores (mesopores) having a diameter of 2 nm or more and less than 50 nm and pores (macropores) having a diameter of 50 nm or more. It has a relatively large amount and has a low density with respect to the specific surface area. Therefore, the strength of the conventional porous carbon particles tends to decrease. For this reason, the surface of the conventional porous carbon particles tends to be unstable, and it is difficult to increase the conductivity by applying a mechanical or chemical treatment.

JP 2012-41199 A JP 2016-41656 A

The present invention has been made based on the above-mentioned circumstances, and an object thereof is to provide a method for producing relatively dense porous carbon particles and porous carbon particles at a low production cost.

As a result of intensive studies on a method for producing porous carbon particles, the present inventors have spray-dried a solution in which ashless coal is dissolved in a solvent, so that the porous carbon particles can be made porous without performing activation treatment or treatment with template particles. It has been found that carbon particles can be produced. Moreover, the pores of the porous carbon particles produced in this way are mostly micropores, relatively few mesopores and macropores, and the porous carbon particles are denser than the specific surface area. I found out.

That is, the invention made in order to solve the above-mentioned problems includes a spray-drying process for spray-drying a solution in which ashless coal is dissolved in a solvent, and a heating process for heat-treating the solid content obtained in the spray-drying process. The solvent contains an oxygen atom or a nitrogen atom and has a boiling point at atmospheric pressure of 50 ° C. or higher and lower than 250 ° C. as a main component, and the content of ashless coal in the solution is 5% by mass or more 50 It is a manufacturing method of the porous carbon particle which is the mass% or less.

The method for producing the porous carbon particles includes spray drying a solution in which ashless coal is dissolved in a solvent mainly containing an organic compound containing an oxygen atom or a nitrogen atom and having a boiling point at atmospheric pressure within the above range. To do. Since ashless coal has a higher carbonization yield than coal and petroleum pitch, the production method of the porous carbon particles has high production efficiency of the porous carbon particles. Further, by using the above solvent and setting the content of ashless coal in the above solution within the above range, the solvent is rapidly desorbed from the state in which the ashless coal is dissolved in the spray drying step, so that the obtained solid content Many micropores are induced. Furthermore, since the ashless coal which is the main component of the solid content has a higher ratio of hetero elements such as oxygen than coal and petroleum pitch, it is difficult for crystals to grow during heat treatment. For this reason, micropores are maintained even in the heating step, and the method for producing the porous carbon particles can produce relatively dense porous carbon particles. Moreover, since the manufacturing method of the said porous carbon particle does not require the activation process and the process by template particle | grains, it can reduce manufacturing cost. Therefore, by using the method for producing porous carbon particles, relatively dense porous carbon particles can be produced at a low production cost.

A mixing step of mixing coal and the solvent, an elution step of eluting components soluble in the solvent from the coal in the slurry obtained in the mixing step, and the slurry after elution in the elution step It is preferable to further include a liquid component containing a soluble component and a separation step for separating into a solvent-insoluble component, and the liquid component obtained in the separation step may be used as the solution in the spray drying step. Ashless coal can be eluted into the solvent by solvent extraction of coal in the elution step. That is, ashless coal is dissolved in the solvent in the liquid. Therefore, the production cost of the porous carbon particles can be further reduced by using the liquid as it is as the solution.

The spray pressure and the liquid feeding speed may be adjusted so that the average diameter of the solid content is 1 μm or more and 20 μm or less. Thus, the specific surface area of the porous carbon particles can be further increased by adjusting the spray pressure and the liquid feeding speed so that the average diameter of the solid content is 1 μm or more and 20 μm or less.

Another invention made in order to solve the above-mentioned problem is provided with a carbon layer containing carbon as a main component and enclosing a hollow portion, wherein the carbon layer has a plurality of pores, and the diameter of the pores is 0. Porous carbon having a Log differential pore volume of 0.1 cm ³ / g or more for pores of 5 nm or less and a Log differential pore volume of pores having a diameter of 2 nm or more and 4 nm or less of less than 0.05 cm ³ / g Particles.

The porous carbon particles have a Log differential pore volume of pores having a diameter of 0.5 nm or less above the lower limit and a Log differential pore volume of pores having a diameter of 2 nm or more and 4 nm or less less than the upper limit. Precise. In addition, since the porous carbon particles include a carbon layer that encloses the hollow portion, the pores easily penetrate the carbon layer as compared with the solid porous carbon particles, and the diameter of each pore from the surface is reduced. It is easy to equalize regardless of the distance. For this reason, even if it is a pore of 0.5 nm or less in diameter, a hole is maintained to a comparatively deep position from an outer surface, without a diameter being crushed on the way. Therefore, even if the Log differential pore volume of pores having a diameter of 2 nm or more and 4 nm or less is less than the above upper limit, the specific surface area can be maintained by the pores having a diameter of 0.5 nm or less.

Here, “main component” means a component having the largest content, for example, a component having a content of 50% by mass or more, and “average diameter of solid content” is the same volume as the solid content. It means the diameter of a true sphere.

Further, “Log differential pore volume of pores” at a certain diameter is a value calculated as follows. First, the pore distribution is measured by the HK method. By this measurement, an integrated pore volume distribution V with respect to the diameter D of the bottom surface when the pore is assumed to be cylindrical is obtained. Based on this distribution, the Log differential pore volume can be calculated by obtaining a value obtained by dividing the difference pore volume dV between the measurement points by the difference value d (LogD) in the logarithmic treatment of the pore diameter D.

As described above, by using the method for producing porous carbon particles of the present invention, relatively dense porous carbon particles can be obtained at a low production cost. Further, since the porous carbon particles of the present invention are relatively dense, the surface is relatively stable, and it is easy to increase the conductivity by applying a mechanical or chemical treatment. Therefore, the porous carbon particles can be suitably used as an adsorbent or an electronic component.

FIG. 1 is a schematic flow diagram showing a method for producing porous carbon particles according to an embodiment of the present invention. FIG. 2 is a schematic flow diagram showing a method for producing porous carbon particles according to an embodiment different from FIG. FIG. 3 is a graph showing the pore size distribution of the porous carbon particles of Example 1.

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

[Method for producing porous carbon particles]
As shown in FIG. 1, the method for producing porous carbon particles mainly includes a mixing step S1, an elution step S2, a separation step S3, a spray drying step S4, and a heating step S5.

<Mixing process>
In the mixing step S1, coal and a solvent are mixed. This mixing process S1 can be performed by a coal supply part, a solvent supply part, and a mixing part, for example.

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

Coal supplied from the coal supply unit is coal that is a raw material for ashless coal. As the coal, various quality coals can be used. For example, bituminous coal with a high extraction rate of ashless coal or cheaper low-grade coal (subbituminous coal or lignite) is preferably used. Further, when coal is classified by particle size, finely pulverized coal is preferably used. Here, “finely pulverized coal” means, for example, coal in which the mass ratio of coal having a particle size of less than 1 mm to the mass of the entire coal is 80% or more. Moreover, lump coal can also be used as coal supplied from a coal supply part. Here, “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. The lump coal can maintain the particle size of undissolved solid coal larger than that of finely pulverized coal, so that the separation in the separation unit described later can be made more efficient. Here, “particle size (particle size)” refers to a value measured in accordance with JIS-Z8815: 1994 general screening test rules. For sorting according to the particle 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, and more preferably 82% by mass. There exists a possibility that the elution rate of a solvent soluble component may fall that the carbon content rate of the said low grade coal is less than the said minimum. Conversely, if the carbon content of the low-grade coal exceeds the upper limit, the cost of the coal to be supplied may increase.

In addition, as a coal supplied to a mixing part from a coal supply part, you may use the coal which mixed a small amount of solvent and made it slurry. By supplying the slurried coal from the coal supply unit to the mixing unit, the coal is easily mixed with the solvent in the mixing unit, and the coal can be dissolved more quickly. However, if the amount of the solvent to be mixed at the time of forming the slurry is large, the amount of heat for raising the slurry to the elution temperature in the temperature raising portion 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 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 solvent supply unit is mixed with coal supplied from the coal supply unit in the mixing unit.

The solvent supplied from the solvent supply unit is mainly composed of an organic compound containing an oxygen atom or a nitrogen atom. 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 increases, and it is easy to raise the content of ashless coal in the solution to be extracted. As a result, the yield of the porous carbon particles increases, so that the manufacturing cost of the porous carbon particles can be reduced. Examples of such a 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. It is done. Of these, pyridine and tetrahydrofuran having high affinity with ashless coal are preferred. In addition, the organic compound containing an oxygen atom or a nitrogen atom may be one kind, and two or more kinds of organic compounds may be mixed.

The lower limit of the boiling point of the solvent at atmospheric pressure is 50 ° C., more preferably 60 ° C., and still more preferably 65 ° C. on the other hand. The boiling point of the solvent is less than 250 ° C, more preferably less than 210 ° C, and even more preferably less than 160 ° C. If the boiling point of the solvent is less than the lower limit, the ashless coal may not be sufficiently dissolved and the content of ashless coal may not be increased. On the other hand, if the boiling point of the solvent is equal to or higher than the upper limit, the pressure associated with the desorption of the solvent is insufficient in the spray drying step S4, so that there is a possibility that the pores of the porous carbon material are not sufficiently formed.

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

A preparation tank can be used as the mixing unit. The coal and solvent are supplied to the preparation tank through a supply pipe. In the preparation tank, the supplied coal and solvent are mixed to prepare a slurry. Moreover, the said preparation tank has a stirrer, and maintains the mixing state of a slurry by hold | maintaining the mixed slurry, stirring with a stirrer.

Although the coal concentration on the basis of anhydrous carbon in the slurry in the preparation tank is appropriately determined depending on the type of solvent and the like, the lower limit of the coal concentration is preferably 5% by mass and more preferably 10% by mass. On the other hand, the upper limit of the coal concentration is preferably 65% by mass, and more preferably 40% by mass. If the coal concentration is less than the lower limit, the elution amount of the solvent-soluble component eluted in the elution step S2 is less than the slurry processing amount, and therefore the content of ashless coal contained in the solution is insufficient. There is a risk. Conversely, if the coal concentration exceeds the upper limit, the solvent-soluble component is likely to be saturated in the solvent, and the elution rate of the solvent-soluble component may be reduced.

In addition, the slurry prepared in the preparation tank of the mixing unit is processed in the elution step S2.

<Elution process>
In the elution step S2, coal components soluble in the solvent are eluted from the coal in the slurry obtained in the mixing step S1. The elution step S2 can be performed by the temperature raising part and the elution part.

(Temperature riser)
The temperature raising unit raises the temperature of the slurry obtained in the mixing step S1.

The temperature raising part 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 heater and an induction heating coil. Further, the temperature raising unit may be configured to raise the temperature using a heat medium, for example, has a heating tube disposed around the flow path of the slurry passing through the inside, and the heating tube The slurry may be heated by supplying a heat medium such as steam or oil.

The temperature of the slurry after the temperature rise by the temperature raising unit is appropriately determined according to the solvent to be used. If the temperature of the slurry is less than the lower limit, the elution rate may decrease. On the other hand, if the temperature of the slurry exceeds the upper limit, the solvent is excessively vaporized, which may make it difficult to control the concentration of the slurry.

Further, the pressure of the temperature raising portion is not particularly limited, but can be normal pressure (0.1 MPa).

(Elution part)
An elution part elutes a coal component soluble in a solvent from coal in a slurry obtained by the above-mentioned mixing part and heated at the above-mentioned temperature raising part.

As the elution part, an extraction tank can be used, and the slurry after the above temperature rise is supplied to this extraction tank. In the extraction tank, the coal components soluble in the solvent are eluted from the coal while maintaining the temperature and pressure of the slurry. The extraction tank has a stirrer. The elution can be promoted by stirring the slurry with this stirrer.

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

<Separation process>
In the separation step S3, the slurry eluted in the elution step S2 is separated into a liquid component containing a solvent-soluble component and a solvent-insoluble component. This separation step S3 can be performed by a separation unit. The solvent-insoluble component refers to an extraction residue that mainly contains ash and insoluble coal 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 solvent-insoluble component in the separation unit, for example, a gravity sedimentation method, a filtration method, and a centrifugal separation method can be used, and a sedimentation tank, a filter, and a centrifugal separator are used, respectively.

Hereinafter, the separation method will be described by taking the gravity sedimentation method as an example. The gravitational sedimentation method is a separation method in which a solvent-insoluble component is settled by using gravity in a sedimentation tank to separate it into solid and liquid. When the separation is performed by the gravity sedimentation method, the liquid component containing the solvent-soluble component is accumulated in the upper part of the sedimentation tank. This liquid content is filtered using a filter unit as necessary, and then discharged to a spraying section to be described later. On the other hand, the solvent-insoluble component is discharged from the lower part of the separation part.

Further, when separation is performed by the gravity sedimentation method, the liquid component including the solvent-soluble component and the solvent-insoluble component can be discharged from the sedimentation tank while continuously supplying the slurry into the separation unit. Thereby, continuous solid-liquid separation processing becomes possible.

The time for maintaining the slurry in the separation part is not particularly limited, but can be, for example, 30 minutes or more and 120 minutes or less, and sedimentation separation in the separation part is performed within this time. In addition, when using lump coal as coal, since sedimentation separation is made efficient, the time which maintains a slurry in a separation part can be shortened.

The temperature and pressure in 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.

The main component of the solvent-soluble component contained in the liquid component is ashless coal, and this liquid component can be used as a solution sprayed in the spraying section. Ashless coal has an ash content of 5% by mass or less or 3% by mass or less, hardly contains ash, has no moisture, and exhibits a higher calorific value than, for example, raw coal.

The lower limit of the content of ashless coal in the liquid component, that is, the solution to be sprayed, is 5% by mass, and more preferably 8% by mass. On the other hand, as an upper limit of content of ashless coal in the said solution, it is 50 mass%, 40 mass% is more preferable, and 25 mass% is further more preferable. If the content of the ashless coal is less than the lower limit, the amount of porous carbon particles obtained from the liquid content per unit amount is decreased, which may reduce the production efficiency. On the contrary, if the content of the ashless coal exceeds the upper limit, the amount of the solvent is relatively insufficient, and the momentum of detachment of the solvent becomes insufficient, so that micropores may not be sufficiently formed. . In addition, content of the said ashless coal can be adjusted with the quantity of coal added to a solvent in a mixing part.

On the other hand, by-product coal can be obtained by evaporating and separating the solvent from the solvent-insoluble component. By-product charcoal does not show softening and melting properties, but the oxygen-containing functional groups are eliminated. Therefore, by-product coal does not inhibit the softening and melting properties of other coals contained in this blended coal when used as a blended coal. Therefore, this blended coal can be used, for example, as a part of the blended coal of the coke raw material. Further, by-product coal may be used as fuel in the same manner as general coal.

<Spray drying process>
In spray drying process S4, the solution which is the said liquid component in which ashless coal melt | dissolves in a solvent is spray-dried. This spray drying process S4 can be performed by a spraying part.

(Spraying part)
A sprayer can be used as the spray unit. As this atomizer, a well-known flash distiller and a cyclone can be mentioned.

Such a sprayer has a spray nozzle that injects a spraying gas into a solution supplied to the spraying section through a supply pipe from the separation section. The spray nozzle can be configured, for example, by connecting a supply pipe to a two-fluid nozzle or a four-fluid nozzle.

In the atomizer, the solution is refined and dispersed by colliding the heated atomizing gas with the solution through a spray nozzle. The solvent in the mist-like solution due to the collision of the atomizing gas evaporates in a flash distiller or a cyclone by self-sensible heat and the application of heat from the heated atomizing gas. In the method for producing porous carbon particles, since the boiling point of the solvent at atmospheric pressure is less than 250 ° C., the solvent is rapidly desorbed from each droplet of the atomized solution. The atomized solution is dried by rapid desorption of the solvent, and a solid content mainly composed of ashless coal is obtained. This is thought to be because the solvent is released from the state where the solvent is trapped inside the carbon layer mainly composed of carbon derived from ashless coal, and this solid content is formed. As a component, a carbon layer constituting the hollow portion is provided. The carbon layer has a plurality of micropores induced by the desorption of the solvent.

It is preferable to use an inert gas such as nitrogen as the atomizing gas. Since the inert gas has low reactivity, it has little influence on the composition of the solid content produced. Further, since it is a gas even at a relatively low temperature below the boiling point of the solvent, it is easy to separate the evaporated solvent and the spray gas.

The lower limit of the pressure of the spray gas (spray pressure) that collides with the solution is preferably 0.1 MPa, and more preferably 0.2 MPa. On the other hand, the upper limit of the spray pressure is preferably 1 MPa, and more preferably 0.5 MPa. When the spray pressure is less than the lower limit, the dispersion of the solution due to the collision of the spray gas is insufficient, and the diameter of the obtained porous carbon particles tends to be large. For this reason, there exists a possibility that the specific surface area of a porous carbon particle may become inadequate. On the other hand, when the spray pressure exceeds the upper limit, the solvent is difficult to vaporize and the solvent is insufficiently desorbed, so that micropores may not be sufficiently formed.

The lower limit of the temperature of the spray gas is preferably 100 ° C, more preferably 150 ° C. On the other hand, the upper limit of the temperature of the spray gas is preferably 450 ° C., more preferably 400 ° C. If the temperature of the spray gas is lower than the lower limit, the solvent is not sufficiently released and the micropores may not be sufficiently formed. Conversely, if the temperature of the spray gas exceeds the upper limit, the energy consumption for heating may increase unnecessarily.

The lower limit of the solution feeding speed of the solution supplied to the spraying part through the supply pipe from the separation part is preferably 0.5 kg / h, more preferably 0.7 kg / h. On the other hand, the upper limit of the liquid feeding speed is preferably 2 kg / h, more preferably 1.5 kg / h. When the liquid feeding speed is less than the lower limit, the amount of porous carbon particles obtained per unit time is decreased, and thus production efficiency may be decreased. On the other hand, when the liquid feeding speed exceeds the upper limit, the amount of heat applied to the solution is insufficient, and the desorption of the solvent becomes insufficient, so that micropores may not be sufficiently formed.

The lower limit of the temperature of the solution supplied to the spraying part through the supply pipe from the separation part is preferably 60 ° C, more preferably 70 ° C, and further preferably 90 ° C. On the other hand, as an upper limit of the temperature of the said solution, 160 degreeC is preferable and 150 degreeC is more preferable. If the temperature of the solution is less than the lower limit, the amount of heat applied to the solution is insufficient, and the desorption of the solvent becomes insufficient, so that micropores may not be sufficiently formed. Conversely, if the temperature of the solution exceeds the upper limit, the energy consumption for heating may increase unnecessarily.

The temperature of the above solution is higher than the boiling point of the solvent. The lower limit of the temperature difference between the solution temperature and the boiling point of the solvent is preferably 10 ° C, more preferably 20 ° C. On the other hand, as an upper limit of the said temperature difference, 50 degreeC is preferable and 40 degreeC is more preferable. If the temperature difference is less than the lower limit, the desorption of the solvent becomes insufficient, and there is a possibility that micropores are not sufficiently formed. Conversely, if the temperature difference exceeds the upper limit, the energy consumption for heating may increase unnecessarily.

Moreover, the solid content obtained in the spraying part is naturally cooled in the spraying part and discharged at a temperature of 40 ° C. or more and 80 ° C. or less.

The lower limit of the average solid content is preferably 1 μm, more preferably 2 μm. On the other hand, the upper limit of the average diameter of the solid content is preferably 20 μm and more preferably 10 μm. The average diameter of the solid content is determined mainly by the size of the droplets of the solution sprayed in the spray drying step S4. Since the size of the droplets of the solution to be sprayed is mainly determined by the spray pressure and the liquid feeding speed, the spray pressure and the liquid feeding speed may be adjusted so that the average diameter of the solid content is within the above range. When the average diameter of the solid content is less than the lower limit, it means that the droplet size of the solution to be sprayed is small, and the amount of the solvent desorbed from the solution is small. For this reason, there is a possibility that micropores are not sufficiently formed. On the other hand, if the average diameter of the solid content exceeds the upper limit, the surface area is small with respect to the volume, so that the specific surface area of the solid content may be insufficient.

<Heating process>
In the heating step S5, the solid content obtained in the spray drying step S4 is heated. This heating step S5 can be performed by a heating unit.

(Heating part)
The heating unit carbonizes the solid content obtained in the spray unit. By this carbonization, porous carbon particles are obtained.

As the heating unit, for example, a known electric furnace or the like can be used. After inserting the solid content into the heating unit and replacing the inside with an inert gas, heating is performed while blowing the inert gas into the heating unit. Can carbonize solids. Although it does not specifically limit as said inert gas, For example, nitrogen, argon, etc. can be mentioned. Of these, inexpensive nitrogen is preferred.

For example, when coal pitch is used as a carbon raw material, micropores generated by the rapid desorption of the solvent in the spraying part are volatilization of components other than solid carbon or crystallization of carbon by heat treatment in this heating part. Therefore, the micropores are easily contracted and closed, and the carbon particles tend to be dense (not porous). On the other hand, in the manufacturing method of the said porous carbon particle, ashless coal is used for a carbon raw material. Ashless coal has a higher proportion of heteroelements such as oxygen than coal and petroleum pitch, so it is difficult for crystals to grow during heat treatment, and the proportion of components other than carbon is small. Therefore, in the method for producing porous carbon particles, the micropores are easily maintained even when heat treatment is performed in the heating unit, and the porosity of the produced carbon particles is easily maintained.

The lower limit of the heating temperature is preferably 500 ° C, more preferably 700 ° C. On the other hand, the upper limit of the heating temperature is preferably 3000 ° C and more preferably 2800 ° C. There exists a possibility that carbonization may become inadequate that the said heating temperature is less than the said minimum. Conversely, if the heating temperature exceeds the above upper limit, the production cost may increase from the viewpoint of improving the heat resistance of the equipment and fuel consumption. In addition, as a temperature increase rate, it can be 0.01 degree-C / min or more and 10 degree-C / min or less, for example.

Further, the lower limit of the heating time is preferably 10 minutes, and more preferably 20 minutes. On the other hand, the upper limit of the heating time is preferably 10 hours, more preferably 8 hours. There exists a possibility that carbonization may become inadequate that heating temperature is less than the said minimum. Conversely, if the heating time exceeds the above upper limit, the production efficiency of the porous carbon particles may be reduced.

Note that infusibilization may be performed before carbonization. This infusibilization treatment can prevent solids from fusing together. Infusibilization is performed, for example, by heating in an atmosphere containing oxygen using a known heating furnace. As an atmosphere containing oxygen, air is generally used.

The lower limit of the infusibilization temperature when infusibilizing is preferably 150 ° C., more preferably 180 ° C. On the other hand, the upper limit of the infusibilization temperature is preferably 300 ° C, and more preferably 280 ° C. If the infusibilization treatment temperature is less than the lower limit, infusibilization may be insufficient, or the infusibilization treatment time may be increased, resulting in inefficiency. Conversely, if the infusibilization temperature exceeds the upper limit, the solid content may melt before being infusible.

Also, the lower limit of the infusibilization time is preferably 10 minutes, more preferably 20 minutes. On the other hand, the upper limit of the infusibilization time is preferably 120 minutes, and more preferably 90 minutes. If the infusibilization time is less than the lower limit, infusibilization may be insufficient. Conversely, if the infusibilization treatment time exceeds the upper limit, the production cost of the porous carbon particles may increase unnecessarily.

The lower limit of the carbonization yield in the method for producing porous carbon particles is preferably 30% by mass, more preferably 50% by mass. If the carbonization yield is less than the above lower limit, the effect of reducing the production cost may be insufficient, the micropores may be blocked by volatile components other than carbon, and the specific surface area of the produced porous carbon particles is May decrease. Since the method for producing the porous carbon particles uses ashless coal, this carbonization yield is high. Further, the carbonization yield can be adjusted by, for example, the content of ashless coal in the solution. On the other hand, the upper limit of the carbonization yield is not particularly limited, and may be 100% by mass, but is usually about 75% by mass when using ashless coal. The “carbonization yield” represents the mass ratio of the carbon substance obtained by the heat treatment with respect to the mass of the organic substance in the raw material before the heating step S5. In the method for producing porous carbon particles, spray drying is used. It represents the mass ratio of the porous carbon particles to the mass of the solid content obtained in step S4.

<Advantages>
The method for producing porous carbon particles includes a solution in which ashless coal is dissolved in a solvent containing an organic compound containing oxygen atoms or nitrogen atoms and having a boiling point at atmospheric pressure of 0 ° C. or higher and lower than 250 ° C. as a main component. Spray dry. Since ashless coal has a higher carbonization yield than coal and petroleum pitch, the production method of the porous carbon particles has high production efficiency of the porous carbon particles. In addition, by using the solvent and setting the content of ashless coal in the solution to 5% by mass or more and 50% by mass or less, the solvent rapidly desorbs from the state in which the ashless coal is dissolved in the spray drying process. Many micropores are induced in the obtained solid content. Furthermore, since the ashless coal which is the main component of the solid content has a higher ratio of hetero elements such as oxygen than coal and petroleum pitch, it is difficult for crystals to grow during heat treatment. For this reason, micropores are maintained even in the heating step, and the method for producing the porous carbon particles can produce relatively dense porous carbon particles. Moreover, since the manufacturing method of the said porous carbon particle does not require the activation process and the process by template particle | grains, it can reduce manufacturing cost. Therefore, by using the method for producing porous carbon particles, relatively dense porous carbon particles can be produced at a low production cost.

Further, in the method for producing the porous carbon particles, the liquid obtained in the separation step S3 is used as the solution in the spray drying step S4. In the method for producing porous carbon particles, ashless coal can be eluted into the solvent by the solvent extraction treatment of coal in the elution step S2. That is, ashless coal is dissolved in the solvent in the liquid. Therefore, the production cost of the porous carbon particles can be further reduced by using the liquid as it is as the solution.

[Porous carbon particles]
The porous carbon particle includes a carbon layer containing carbon as a main component and enclosing a hollow portion, and the carbon layer has a plurality of pores. The said porous carbon particle can be manufactured with the manufacturing method of the said porous carbon particle mentioned above. The porous carbon particles produced by the method for producing porous carbon particles usually include a hollow portion in the carbon layer, but carbon having a recess is obtained by dividing the porous carbon particle according to the application. It can be used as porous carbon particles comprising a layer.

The porous carbon particles have many micropores and few mesopores or macropores. That is, among the pores of the porous carbon particles, the Log differential pore volume of pores having a diameter of 0.5 nm or less is 0.1 cm ³ / g or more, and more preferably 0.15 cm ³ / g or more. Further, the Log differential pore volume of pores having a diameter of 2 nm or more and 4 nm or less is less than 0.05 cm ³ / g, and 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 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 particles is The mechanical strength may be lowered. 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. Further, 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 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.

Since the porous carbon particles have many micropores, the porous carbon particles are dense and have a relatively high specific surface area. The porous the lower limit of the specific surface area of the carbon particles is preferably 100 m ² / g, more preferably ^{^{150m 2 / g, 200m 2 /}} g is more preferred. If the specific surface area is less than the lower limit, it may be difficult to use as the porous material. On the other hand, the upper limit of the specific surface area is not particularly limited, but is usually about 3000 m ² / g. In addition, the specific surface area of the said porous carbon particle can be adjusted with content of ashless coal in a solution, the kind of solvent, spray conditions, etc., for example.

<Advantages>
The porous carbon particles have a Log differential pore volume of pores having a diameter of 0.5 nm or less of 0.1 cm ³ / g or more and a Log differential pore volume of pores of 2 nm or more and 4 nm or less in diameter of 0.05 cm ^3. Since it is less than / g, it is relatively dense. In addition, since the porous carbon particles include a carbon layer that encloses the hollow portion, the pores easily penetrate the carbon layer as compared with the solid porous carbon particles, and the diameter of each pore from the surface is reduced. It is easy to equalize regardless of the distance. For this reason, even if it is a pore of 0.5 nm or less in diameter, a hole is maintained to a comparatively deep position from an outer surface, without a diameter being crushed on the way. Therefore, even if the Log differential pore volume of pores having a diameter of 2 nm or more and 4 nm or less is less than the above upper limit, the specific surface area can be maintained by the pores having a diameter of 0.5 nm or less.

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

The method for producing porous carbon particles mainly includes a dissolution step S6, a spray drying step S7, and a heating step S8 as shown in FIG.

<Dissolution process>
In the dissolution step S6, ashless coal is dissolved in a solvent. By this dissolution, a solution in which ashless coal is dissolved in the solvent is obtained.

A preparation tank can be used for this dissolution. As said adjustment tank, the adjustment tank comprised similarly to the mixing part of 1st embodiment, for example is mentioned.

The above solvent is mainly composed of an organic compound containing an oxygen atom or a nitrogen atom, and examples thereof include the same solvents as those in the first embodiment.

Further, the ashless coal can be obtained, for example, by a method for producing ashless coal including a mixing step, an elution step, a separation step, and an evaporation step.

(Mixing process)
The mixing step in the method for producing ashless coal can be performed in the same manner as the mixing step S1 of the first embodiment.

Note that the solvent to be mixed in the mixing step is not limited to a solvent mainly containing an organic compound containing an oxygen atom or a nitrogen atom, and any solvent that dissolves coal can be used. Examples of such a solvent include methyl naphthalene oil and naphthalene oil which are bicyclic aromatic compounds derived from coal.

(Elution process)
The elution step in the method for producing ashless coal can be performed in the same manner as the elution step S2 of the first embodiment.

The lower limit of the temperature of the slurry after the temperature rise by the temperature raising portion in the elution step is preferably 300 ° C, and more preferably 360 ° C. On the other hand, the upper limit of the temperature of the slurry is preferably 420 ° C., more preferably 400 ° C. If the temperature of the slurry is less than the lower limit, the bonds between the molecules constituting the coal cannot be sufficiently weakened, and the elution rate may decrease. On the contrary, when the temperature of the slurry exceeds the upper limit, the amount of heat for maintaining the temperature of the slurry becomes unnecessarily large, which may increase the production cost of the porous carbon particles.

Moreover, as a minimum of the internal pressure of the said temperature rising part, 1.1 MPa is preferable and 1.5 MPa is more preferable. On the other hand, the upper limit of the internal pressure of the temperature raising part is preferably 5 MPa, and more preferably 4 MPa. When the internal pressure of the temperature raising part is less than the lower limit, the solvent is reduced by evaporation, and there is a possibility that coal may not be sufficiently dissolved. On the contrary, when the internal pressure of the said temperature rising part exceeds the said upper limit, there exists a possibility that the improvement effect of coal melt | dissolution obtained with respect to the cost increase for maintaining a pressure may become inadequate.

(Separation process)
The separation process in the method for producing ashless coal can be performed in the same manner as the separation process S3 of the first embodiment.

It is preferable to heat and pressurize the inside of the separation part in the separation step. As a minimum of heating temperature in the above-mentioned separation part, 300 ° C is preferred and 350 ° C is more preferred. On the other hand, the upper limit of the heating temperature is preferably 420 ° C., more preferably 400 ° C. If the heating temperature is less than the lower limit, the solvent-soluble component may be reprecipitated and the separation efficiency may be reduced. Conversely, if the heating temperature exceeds the upper limit, the operating cost for heating may increase.

Also, the lower limit of the pressure in the separation part is preferably 1 MPa, more preferably 1.4 MPa. On the other hand, the upper limit of the pressure is preferably 3 MPa, more preferably 2 MPa. If the pressure is less than the lower limit, the solvent-soluble component may be reprecipitated and the separation efficiency may be reduced. Conversely, when the pressure exceeds the upper limit, the operating cost for pressurization may increase.

(Evaporation process)
In the evaporation step, the solvent is evaporated from the liquid component separated in the separation step. Ashless coal (HPC) is obtained by evaporating and separating the solvent.

As a method for evaporating and separating 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, ashless coal substantially free of ash can be obtained from the liquid.

The lower limit of the content of ashless coal in the above solution in which ashless coal is dissolved in the solvent is 5% by mass, and more preferably 8% by mass. On the other hand, as an upper limit of content of ashless coal in the said solution, it is 50 mass%, and 40 mass% is more preferable. If the content of the ashless coal is less than the lower limit, the amount of porous carbon particles obtained from the liquid content per unit amount is decreased, which may reduce the production efficiency. On the contrary, if the content of the ashless coal exceeds the upper limit, the amount of the solvent is relatively insufficient, and the momentum of detachment of the solvent becomes insufficient, so that micropores may not be sufficiently formed. .

<Spray drying process>
In the spray drying step S7, the solution is spray dried. This spray drying process S7 can be performed similarly using the apparatus similar to the spray drying process S4 of 1st embodiment.

<Heating process>
In the heating step S8, the solid content obtained in the spray drying step S4 is heat-treated. This heating process S8 can be performed similarly using the apparatus similar to heating process S5 of 1st embodiment.

<Advantages>
In the method for producing porous carbon particles, a solution in which ashless coal is dissolved in a solvent is obtained by directly dissolving ashless coal in a solvent. For this reason, the kind of solvent used when extracting ashless coal and the solvent used for the solution for obtaining porous carbon particles can be changed. For this reason, since extraction of ashless coal and manufacture of porous carbon particles can each be optimized, the yield of porous carbon particles can be increased.

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

In the first embodiment, the configuration in which the mixing unit of the mixing step S1 includes the preparation tank has been described. However, the present invention is not limited to this configuration, and the preparation tank may be omitted as long as the solvent and coal can be mixed. 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 unit. Thus, the apparatus structure used at each process is not limited to the said embodiment.

In the second embodiment, the method for producing ashless coal by solvent extraction has been described. However, the method for producing ashless coal is not limited thereto, and for example, the ashless coal is produced by mixing and heating coal and a hydrogen donating solvent. Ashless charcoal can also be used.

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]
Ashless coal produced by solvent extraction of sub-bituminous coal was prepared. Table 1 shows the elemental analysis values of the ashless coal. Further, pyridine having a boiling point of 115 ° C. at atmospheric pressure was prepared as a solvent. Pyridine is an organic compound (aromatic compound) containing nitrogen.

A solution in which the ashless coal was dissolved in the solvent was prepared by mixing the ashless coal and the solvent so that the content of the ashless coal in the solution was 10.7% by mass.

This solution was sprayed into a cyclone using a two-fluid nozzle under a spraying pressure of 0.3 MPa and a solution feeding speed of 1 kg / h to obtain a solid content. The cyclone inlet temperature was 140 ° C. and the outlet temperature was 70 ° C.

Furthermore, the solid content was heated to 900 ° C. at a temperature rising rate of 5 ° C./min, and heat treatment (carbonization) for 30 minutes was performed to produce porous carbon particles of Example 1. Table 2 shows the carbonization yield by this heat treatment.

[Example 2]
The solvent is tetrahydrofuran (THF) having a boiling point of 66 ° C. at atmospheric pressure, the content of ashless coal in the solution is 10.8% by mass, the cyclone inlet temperature is 100 ° C., and the outlet temperature is 50 ° C. In the same manner as in Example 1, porous carbon particles of Example 2 were produced. Note that THF is an organic compound (polar organic compound) containing oxygen.

[Example 3]
Porous carbon particles of Example 3 were produced in the same manner as Example 2 except that the content of ashless coal in the solution was 35.8% by mass.

[Comparative Example 1]
In place of the ashless coal of Example 1, the porous material of Comparative Example 1 was used in the same manner as in Example 1 except that coal pitch produced from tar produced as a by-product in the high temperature carbonization process of coal produced by iron making coke was used. Carbon particles were obtained. Table 1 shows the elemental analysis values of this coal pitch.

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

[Evaluation methods]
The following measurements were performed for Examples 1 to 3 and Comparative Example 1.

<Particle size>
The particle size of the solid content was measured with an optical microscope. In the measurement, the particle diameter of each particle within the field of view of the optical microscope was measured, and the range was determined. The results are shown in Table 2.

<Specific surface area>
The specific surface area of the porous carbon particles was measured by the BET method. The results are shown in Table 2.

<Pore size distribution>
For the porous carbon particles of Example 1, the pore size distribution was measured by the HK method. The results are shown in FIG. The average pore diameter of the porous carbon particles of Example 1 measured by the BET method was 2 nm.

From the results in Table 2, porous carbon particles having a specific surface area of 100 m ² / g or more can be obtained by the production methods of Examples 1 to 3 within the scope of the present invention without performing activation treatment or treatment with template particles. I understand that. On the other hand, the porous carbon particles obtained by the production method of Comparative Example 1 have a specific surface area of less than 100 m ² / g. This is presumably because carbon pitch growth was likely to occur during the heat treatment because the coal pitch was used as a raw material, and the micropores were blocked.

In addition, the carbonization yield during the heat treatment of Examples 1 to 3 is larger than the carbonization yield of Comparative Example 1, and there is a difference between Example 1 and Comparative Example 1 where the conditions other than the raw materials are the same. It is remarkable. This shows that the production efficiency of porous carbon particles can be increased by using ashless coal.

Also, the porous carbon particles of Example 1 from FIG. 3 have a log differential pore volume (denoted as dV / d (LogD) in FIG. 3) of pores having a diameter (denoted as D in FIG. 3) of 0.5 nm or less. Is 0.1 cm ³ / g or more, and the Log differential pore volume of pores having a diameter of 2 nm or more and 4 nm or less is less than 0.05 cm ³ / g. That is, the pores of the porous carbon particles of Example 1 are mostly micropores, relatively few mesopores and macropores, and the porous carbon particles of Example 1 are dense with respect to the specific surface area. I understand that there is.

Furthermore, when an Example is seen in detail, the direction of Example 2 which made content of ashless coal in the solution to spray into 10.8 mass% which is 25 mass% or less is 25 mass% of ashless coal. The carbonization yield and the specific surface area are larger than those of Example 3 in which the amount is more than 35.8% by mass. From this, it can be seen that the content of ashless coal in the solution to be sprayed should be 25% by mass or less.

S1 mixing step S2 elution step S3 separation step S4, S7 spray drying step S5, S8 heating step S6 dissolution step

Claims

A spray drying step of spray drying a solution in which ashless coal is dissolved in a solvent;
A heating step of heat-treating the solid content obtained in the spray drying step,
The solvent mainly contains an organic compound containing an oxygen atom or a nitrogen atom and having a boiling point at atmospheric pressure of 50 ° C. or higher and lower than 250 ° C.,
The manufacturing method of the porous carbon particle whose content of ashless coal in the said solution is 5 mass% or more and 50 mass% or less.
A mixing step of mixing coal and the solvent;
An elution step for eluting components soluble in the solvent from the coal in the slurry obtained in the mixing step;
A separation step of separating the slurry after the elution in the elution step into a liquid component containing a solvent-soluble component and a solvent-insoluble component;
The method for producing porous carbon particles according to claim 1, wherein the liquid obtained in the separation step is used as the solution in the spray drying step.
The method for producing porous carbon particles according to claim 1 or 2, wherein the spray pressure and the liquid feeding speed are adjusted so that the average diameter of the solid content is 1 µm or more and 20 µm or less.
A carbon layer containing carbon as a main component and enclosing a hollow part,
The carbon layer has a plurality of pores;
Among the above pores, the Log differential pore volume of pores having a diameter of 0.5 nm or less is 0.1 cm 3 / g or more, and the Log differential pore volume of pores having a diameter of 2 nm or more and 4 nm or less is 0.05 cm 3. Porous carbon particles less than / g.