JP2018177564A - Method for producing porous carbon particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing porous carbon particles having a large specific surface area which is relatively excellent in production cost.SOLUTION: A porous carbon particle production method of the present invention includes the steps of: spray drying a solution where ashless coal and a group 2 metal compound are dissolved in a solvent; heating solids obtained in the spray drying step; and acid washing the solids after the heating step. The solvent contains, as a main component, an organic compound containing an oxygen atom or a nitrogen atom and having a boiling point at atmospheric pressure of not less than 50°C and less than 250°C. It is advisable that the group 2 metal compound is magnesium oxide. It is preferable that the mass ratio of the group 2 metal compound to the ashless coal is 1 or more and 10 or less. It is preferable that the content of the ashless coal in the solution is 5 mass% or more and 50 mass% or less.SELECTED DRAWING: Figure 1

Description

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

  Porous carbon particles having pores of micron or nanometer order in diameter on the surface and high specific surface area are used as adsorbents for water treatment or gas separation, electric double layer capacitor electrodes and the like.

  As a method for producing the porous carbon particles, for example, a steam activation method (Japanese Patent Laid-Open No. 2014-34475) in which a carbon source is activated by steam to increase a specific surface area, or a carbon material is an alkaline activator such as sodium hydroxide. An alkaline activation method (Japanese Patent Laid-Open No. 2011-41199) in which activation treatment is carried out by

  In the above-described steam activation method, in order to obtain a high specific surface area, it is necessary to increase the erosion (the amount of consumption) of carbon, and the carbon yield is low and the production cost tends to be large. In addition, the carbon particles obtained are excessively porous to reduce the bulk density, and the specific surface area tends to be low with respect to the pore volume. In addition, in the alkaline activation method, since the alkaline reagent is expensive and the processing cost is also increased, the manufacturing cost tends to be further increased.

JP 2014-34475 A JP, 2011-41199, A

  The present invention has been made based on the circumstances as described above, and an object thereof is to provide a method for producing porous carbon particles having a relatively high production cost and a large specific surface area.

  The invention made to solve the above-mentioned problems comprises a step of spray-drying a solution in which ash-free charcoal and a Group 2 metal compound are dissolved in a solvent, and a step of heat-treating solids obtained in the spray-drying step And acid-washing the solid content after the heating step, wherein the solvent mainly contains an organic compound containing an oxygen atom or a nitrogen atom and having a boiling point of 50 ° C. or more and less than 250 ° C. at atmospheric pressure. It is a manufacturing method of porous carbon particles.

  In the method for producing porous carbon particles, in the spray drying step, the solvent is rapidly detached from the state in which the ash-free coal is dissolved, whereby a large number of micropores are induced in the obtained solid content. That is, in the method for producing porous carbon particles, the carbon material can be made porous without being corroded, so that the carbon yield can be enhanced. In addition, ash-free charcoal has a high carbon yield compared to polyvinyl alcohol and other resin materials, so the specific surface area is large relative to the pore volume of the porous carbon particles obtained. Furthermore, in the method for producing porous carbon particles, since the Group 2 metal compound is dissolved in the solvent, porous carbon particles are formed by ashless coal on the surface or grain boundaries of the Group 2 metal compound, The pore structure is likely to be developed by the different pores of the above-mentioned solvent and the pores of the group 2 metal compound. Moreover, in the manufacturing method of the said porous carbon particle, the solvent which has an oxygen atom or a nitrogen atom, and uses as a main component the organic compound whose boiling point in atmospheric pressure is in the said range is used. Since ashless coal can be dissolved in such a solvent at a high concentration, the interaction between the ashless coal and the Group 2 metal compound is enhanced, and the production efficiency can be enhanced. Therefore, by using the method for producing porous carbon particles, it is possible to produce porous carbon particles relatively excellent in production cost and having a large specific surface area.

  The Group 2 metal compound is preferably magnesium oxide. By using magnesium oxide as the group 2 metal compound, the interaction with ashless coal can be further enhanced, and the production efficiency can be improved.

  The mass ratio of the group 2 metal compound to the ashless coal is preferably 1 or more and 10 or less. Thus, by setting the mass ratio of the group 2 metal compound to the ashless coal within the above range, the effect of increasing pores can be enhanced, and the specific surface area can be further increased.

  As content of ash-free charcoal in the above-mentioned solution, 5 mass% or more and 50 mass% or less are preferred. By setting the content of ash-free coal in the above solution to the above range, the solvent is rapidly and easily detached from the state in which ash-free coal is dissolved in the spray drying step, so many micropores are obtained in the obtained solid content. It is induced. Therefore, the specific surface area of the obtained porous carbon particles can be further increased.

  In the spray drying 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 The method may further comprise the steps of: separating the liquid component containing the solvent-soluble component and the solvent-insoluble component; and dissolving the Group 2 metal compound in the liquid component. Ash-free charcoal can be eluted to a solvent by the solvent extraction process of coal in the said elution process. Therefore, the production cost of the porous carbon particles can be further reduced by using a solution in which the polymer component is mixed with the liquid component in which the ash-free charcoal is dissolved in the solvent.

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

  The solution preferably further contains a polymer compound. Thus, when the solution contains a polymer compound, carbonization in the heating step mainly causes mesopores in the solid content to increase due to decomposition and dissipation of the polymer compound. Thereby, the specific surface area of the porous carbon particles can be further increased.

  As mass ratio of the said high molecular compound with respect to the said ashless coal, 0.01 or more and 0.1 or less are preferable. As described above, by setting the mass ratio of the polymer compound to the ashless coal within the above range, the effect of increasing pores can be enhanced, and the specific surface area can be further increased.

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

  As explained above, by using the method for producing porous carbon particles of the present invention, porous carbon particles having a large specific surface area can be produced at relatively low production cost.

FIG. 1 is a schematic flow diagram showing a method of producing porous carbon particles according to an embodiment of the present invention. It is a schematic flowchart of the spray-drying process of FIG. It is a schematic flow figure which shows the manufacturing method of the porous carbon particle which concerns on embodiment different from FIG.

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

  The method for producing the porous carbon particles mainly includes a spray drying step S1, a heating step S2, and an acid washing step S3, as shown in FIG. The manufacturing method of the porous carbon particles mainly includes, for example, a coal supply unit, a solvent supply unit, a mixing unit, a temperature raising unit, an elution unit, a separation unit, a spray unit, and a heating unit. It can be done by the device.

[Spray drying process]
In the spray drying step S1, solid content is obtained by spray drying of a solution in which ashless coal and a group 2 metal compound are dissolved. Spray drying process S1 is provided with 1st mixing process S11, elution process S12, solid-liquid separation process S13, 2nd mixing process S14, and solid content generation process S15, as shown in FIG.

<First mixing step>
In the first mixing step S11, coal and a solvent are mixed. This first mixing step S11 can be performed by, for example, a coal supply unit, a solvent supply unit, and a mixing unit.

(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 by a normal pressure state, a pressurized hopper used by 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 ash-free coal. As said coal, coal of various quality can be used. For example, bituminous coal having a high extraction ratio of ash-free coal, and cheaper low-grade coal (sub-bituminous coal or lignite) are preferably used. Also, when coal is classified by particle size, finely crushed coal is suitably used. Here, "finely pulverized coal" 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. Moreover, lump coal can also be used as coal supplied from a coal supply part. Here, "mass coal" means coal in which the mass ratio of coal having a particle size of 5 mm or more with respect to the mass of the entire coal is 50% or more. Since the particle size of undissolved solid coal is maintained large as compared with finely pulverized coal, bulk coal can streamline separation in the separation section described later. Here, “particle size (particle size)” refers to a value measured in accordance with the general rule of sieving test in JIS-Z8815: 1994. In addition, the metal mesh screen defined, for example to JIS-Z8801-1: 2006 can be used for the classification by the particle size of coal.

  As a minimum of the carbon content rate of the above-mentioned low grade coal, 70 mass% is preferred. On the other hand, as a maximum of the carbon content rate of the above-mentioned low grade coal, 85 mass% is preferred, and 82 mass% is more preferred. If the carbon content of the low-grade coal is less than the above lower limit, the elution rate of the solvent-soluble component may be reduced. On the contrary, if the carbon content of the low grade coal exceeds the upper limit, the cost of the supplied coal may be high.

  In addition, you may use the coal which mixed and slurried a small amount of solvents as coal supplied from a coal supply part to a mixing part. By supplying the slurryed coal from the coal supply unit to the mixing unit, the coal can be easily mixed with the solvent in the mixing unit, and coal can be dissolved faster. However, if the amount of the solvent to be mixed in forming the slurry is large, the amount of heat for raising the temperature of the slurry to the elution temperature in the temperature rising 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 to a mixing part from this solvent tank. The solvent supplied from the solvent supply unit is mixed with the coal supplied from the coal supply unit in the mixing unit.

The solvent supplied from the solvent supply unit contains an organic compound containing an oxygen atom or a nitrogen atom as a main component. As described above, when the main component of the solvent is an organic compound containing an oxygen atom or a nitrogen atom, the affinity between the solvent and the ashless coal is enhanced, and the content of the ashless coal in the solution to be extracted can be easily increased. As a result, since the yield of porous carbon particles is increased, the production cost of porous carbon particles can be reduced. Such solvents include pyridine (C ₅ H ₅ N), tetrahydrofuran (C ₄ H ₈ O), dimethylformamide ((CH ₃ ) ₂ NCHO), N-methyl pyrrolidone (C ₅ H ₉ NO), etc. Be Among them, pyridine and tetrahydrofuran having high affinity to ashless coal are preferable. The organic compound containing an oxygen atom or a nitrogen atom may be of one type, or two or more types of organic compounds may be mixed.

  The lower limit value 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 still more preferably less than 160 ° C. If the boiling point of the solvent is less than the lower limit, ashless coal may not be sufficiently dissolved, and the content of ashless coal may not be increased. On the other hand, when the boiling point of the solvent is equal to or more than the upper limit, the pressure involved in the detachment of the solvent is insufficient in the solid content generation step S15, and the pores of the porous carbon particles may not be formed sufficiently.

(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 said mixing part. The coal and the 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. Further, the preparation tank has a stirrer, and the mixed slurry is kept stirred by the stirrer to maintain the mixed state of the slurry.

  The concentration of coal on the basis of anhydrous coal in the slurry in the preparation tank is appropriately determined depending on the type of solvent and the like, but the lower limit of the concentration of coal is preferably 5% by mass, and more preferably 10% by mass. On the other hand, as an upper limit of the above-mentioned coal concentration, 65 mass% is preferred, and 40 mass% is more preferred. When the coal concentration is less than the above lower limit, the elution amount of the solvent-soluble component eluted in the elution step S12 decreases relative to the slurry treatment amount, so that the content of ashless coal contained in the solution is insufficient May be 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.

<Elution step>
In the elution step S12, the coal component soluble in the solvent is eluted from the coal in the slurry obtained in the first mixing step S11. The elution step S12 can be performed by the temperature rising portion and the elution portion.

(Heating section)
The temperature raising unit raises the temperature of the slurry obtained in the first mixing step S11.

  The temperature raising portion is not particularly limited as long as it can heat the slurry passing through the inside, and examples thereof include a resistance heating heater and an induction heating coil. In addition, the temperature raising unit may be configured to perform temperature raising using a heat medium, and has, for example, a heating pipe disposed around the flow path of the slurry passing through the inside, The temperature of the slurry may be increased by supplying a heat medium such as steam or oil.

  Although the temperature of the slurry after temperature rising by a temperature rising part is suitably determined according to the solvent to be used, it can be 80 degreeC or more and 120 degrees C or less, for example. When the temperature of the above-mentioned slurry is less than the above-mentioned minimum, there is a possibility that a dissolution rate may fall. Conversely, if the temperature of the above-mentioned slurry exceeds the above-mentioned upper limit, there is a possibility that it becomes difficult to control the concentration of the slurry because the solvent is excessively vaporized.

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

(Elution part)
The elution part is obtained in the mixing part, and the coal component soluble in the solvent is eluted from the coal in the slurry heated in the heating part.

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

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

Solid-liquid separation process
In the solid-liquid separation step S13, the slurry after elution in the elution step S12 is separated into a liquid component containing a solvent-soluble component and a solvent-insoluble component. This solid-liquid separation step S13 can be performed by the separation unit. The solvent-insoluble component mainly refers to an extraction residue which mainly contains ash and insoluble coal which are insoluble in a solvent for extraction, and additionally contains a solvent for extraction.

(Separation section)
As a method of separating the liquid component and the solvent-insoluble component in the separation part, 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 settling method as an example. The gravity settling method is a separation method in which solvent insoluble components are precipitated and solid-liquid separated in the settling tank using gravity. In the case of separation by gravity sedimentation, the liquid containing solvent-soluble components accumulates at the top of the sedimentation tank. The liquid component is filtered using a filter unit, if necessary, and then discharged to a spray unit described later. On the other hand, the solvent insoluble component is discharged from the lower part of the separation unit.

  In addition, when separation is performed by the gravity sedimentation method, it is possible to discharge the liquid component including the solvent-soluble component and the solvent-insoluble component from the sedimentation tank while continuously supplying the slurry into the separation unit. This enables continuous solid-liquid separation processing.

  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 within this time, sedimentation in the separation part is performed. In addition, when using lumped coal as coal, since sedimentation separation is made efficient, time to maintain a slurry in a isolation | 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 raising by the temperature raising unit.

  The main component of the solvent-soluble component contained in the liquid component is ashless coal. Ash-free coal has an ash content of 5% by mass or less or 3% by mass or less, hardly contains ash, has no water, and exhibits a higher calorific value than, for example, raw material coal.

  On the other hand, the solvent can be evaporated and separated from the solvent insoluble component to obtain by-product carbon. The byproduct coal does not show softening and melting properties, but the oxygen-containing functional group is eliminated. Therefore, by-produced coal does not inhibit the softening and melting properties of other coals contained in this blended coal when used as blended coal. Therefore, this blended coal can be used, for example, as a part of blended coke of coke raw material. Also, by-product coal may be used as a fuel like general coal.

<2nd mixing process>
In the second mixing step S14, the group 2 metal compound is mixed with the liquid portion in which the ashless coal obtained in the solid-liquid separation step S13 is dissolved. As a result of this dissolution, a solution in which ashless coal and a Group 2 metal compound are dissolved is obtained.

  Examples of the Group 2 metal compound include oxides, hydroxides, chlorides, and carbonates with beryllium (Be), magnesium (Mg), calcium (Ca), barium (Ba), etc., which are Group 2 metals. A sulfate etc. can be mentioned. Among them, magnesium oxide is preferred. By using magnesium oxide as the above-mentioned Group 2 metal compound, the interaction with ash-free charcoal can be further enhanced, and the production efficiency of porous carbon particles is improved.

  As a minimum of mass ratio of the above-mentioned group 2 metal compound to the above-mentioned ash-free charcoal, 1 is preferred and 3 is more preferred. On the other hand, the upper limit of the mass ratio of the group 2 metal compound to the ashless coal is preferably 10, and more preferably 5. If the mass ratio of the group 2 metal compound to the ashless coal is less than the lower limit, the pore increasing effect may be insufficient. Conversely, when the mass ratio of the Group 2 metal compound to the ashless coal exceeds the upper limit, the amount of ashless coal is relatively reduced, which may lower the production efficiency.

  In addition, as a method of mixing the Group 2 metal compound in the liquid, the Group 2 metal compound may be directly dissolved in the solution, and a liquid in which the Group 2 metal compound is dissolved in a solvent is combined with the liquid. You may mix and prepare.

<Solid content generation process>
In the solid content generation step S15, the above-mentioned solution in which ashless coal and a group 2 metal compound are dissolved in a solvent is spray-dried. The solid content generation step S15 can be performed by the spray unit.

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

  Such a sprayer has a spray nozzle that sprays a spray gas onto the solution supplied to the spray unit through the supply pipe from the separation unit. 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 sprayer, the heated spray gas is caused to collide with the solution by the spray nozzle to make the solution fine and disperse. Among the solution atomized by the collision of the gas for spraying, the solvent evaporates by self-sensible heat and heat application from the heated gas for spraying in a flash distiller or a cyclone. 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 detached from the droplets of the misty solution. The atomized solution is dried by rapid desorption of the solvent to obtain a solid containing ash-free charcoal as a main component. It is thought that this solid content is formed mainly from carbon, although the solvent is desorbed from the state in which the solvent is trapped inside the carbon-based carbon layer derived from ashless coal, and this solid content is formed. As a component, it has a carbon layer that constitutes a hollow portion. In addition, the carbon layer has a plurality of micropores induced by the desorption of the solvent.

  An inert gas such as nitrogen is preferably used as the spray gas. The inert gas has less influence on the composition of the solid produced because of its low reactivity. In addition, 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.

  As a minimum of pressure (spray pressure) of the above-mentioned spray gas made to collide with solution, 0.1MPa is preferred and 0.2MPa is more preferred. On the other hand, 1 MPa is preferable as an upper limit of the said spraying pressure, and 0.5 MPa is more preferable. Dispersion | distribution of the solution by collision of gas for sprays runs short that the said spray pressure is less than the said minimum, and the diameter of the porous carbon particle obtained tends to become large. For this reason, the specific surface area of the porous carbon particles may be insufficient. On the other hand, when the spray pressure exceeds the upper limit, the solvent is difficult to vaporize and desorption of the solvent becomes insufficient, so that micropores may not be formed sufficiently.

  As a minimum of the temperature of the above-mentioned spray gas, 100 ° C is preferred and 150 ° C is more preferred. On the other hand, as a maximum of the temperature of the above-mentioned spray gas, 450 ° C is preferred and 400 ° C is more preferred. If the temperature of the spray gas is less than the lower limit, desorption of the solvent is insufficient, and micropores may not be formed sufficiently. Conversely, when the temperature of the spray gas exceeds the upper limit, the energy consumption for heating may be unnecessarily increased.

  The lower limit of the liquid transfer speed of the solution supplied to the spray 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 transfer rate is preferably 2 kg / h, more preferably 1.5 kg / h. When the liquid transfer rate is less than the above lower limit, the amount of porous carbon particles obtained per unit time is reduced, which may lower the production efficiency. On the other hand, when the liquid transfer speed exceeds the upper limit, the heat quantity applied to the solution is insufficient, and the desorption of the solvent is insufficient, so that micropores may not be formed sufficiently.

  As a minimum of temperature of the above-mentioned solution supplied to a spraying part through supply piping from a separation part, 60 ° C is preferred, 70 ° C is more preferred, and 90 ° C is still more preferred. On the other hand, as an upper limit of the temperature of the above-mentioned solution, 160 ° C is preferred and 150 ° C is more preferred. If the temperature of the solution is less than the lower limit, the amount of heat given to the solution is insufficient, and the desorption of the solvent is insufficient, so that micropores may not be formed sufficiently. Conversely, if the temperature of the solution exceeds the upper limit, the energy consumption for heating may be unnecessarily increased.

  The temperature of the solution is above the boiling point of the solvent. As a minimum of a temperature difference of the temperature of the above-mentioned solution, and a boiling point of a solvent, 10 ° C is preferred and 20 ° C is more preferred. On the other hand, as an upper limit of the above-mentioned temperature difference, 50 ° C is preferred and 40 ° C is more preferred. If the temperature difference is less than the above lower limit, the removal of the solvent is insufficient, so that micropores may not be formed sufficiently. Conversely, if the temperature difference exceeds the upper limit, the energy consumption for heating may be unnecessarily increased.

  In addition, the solid content obtained by the spray unit is naturally cooled in the spray unit and discharged at a temperature of 40 ° C. or more and 80 ° C. or less.

  As a minimum of an average diameter of the above-mentioned solid content, 1 micrometer is preferred and 2 micrometers is more preferred. On the other hand, as an upper limit of an average diameter of the above-mentioned solid content, 20 micrometers is preferred and 10 micrometers is more preferred. The average diameter of the solid content is mainly determined by the size of droplets of the solution sprayed in the solid content generation step S15. Since the size of droplets of the solution to be sprayed is mainly determined by the spray pressure and the liquid transfer rate, it is preferable to adjust the spray pressure and the liquid transfer rate so that the average diameter of the solid content is in the above range. When the average diameter of the solid content is less than the lower limit, it means that the size of the droplet of the solution to be sprayed is small, and the amount of the solvent desorbed from the solution is small. Therefore, micropores may not be formed sufficiently. On the other hand, when the average diameter of the solid content exceeds the upper limit, the surface area relative to the volume decreases, and thus the specific surface area of the solid content may be insufficient.

<Heating process>
In the heating step S2, the solid content obtained in the spray drying step S1 is heat-treated. The heating step S2 can be performed by the heating unit.

(Heating unit)
The heating unit carbonizes the solid content obtained by the spraying unit. This carbonization gives porous carbon particles.

  For example, a known electric furnace or the like can be used as the heating unit, and solid content is inserted into the heating unit, the inside is replaced with an inert gas, and heating is performed while blowing the inert gas into the heating unit. The carbon content of solids can be The inert gas is not particularly limited, and examples thereof include nitrogen and argon. Among them, inexpensive nitrogen is preferable.

  For example, when using a coal pitch etc. as a carbon raw material, the micropore which arose by the rapid detachment | desorption of a solvent in a spraying part volatilizes components other than carbon of solid content, and crystallization of carbon by heat processing in this heating part. As a result, the micropores tend to shrink and be clogged, resulting in fine (not porous) carbon particles. On the other hand, ash-free charcoal is used as a carbon raw material in the manufacturing method of the said porous carbon particle. As ash-free coal has a high proportion of heteroelements such as oxygen as compared to coal and petroleum pitch, it is difficult to grow crystals during heat treatment and the proportion of components other than carbon is small. Therefore, in the method for producing porous carbon particles, micropores are easily maintained even if heat treatment is performed in the heating unit, and the porosity of carbon particles to be produced is easily maintained.

  In addition, porous carbon particles of ashless coal are generated on the surface or grain boundaries of the Group 2 metal compound dispersed in the solid content in the spray drying step S1, and there are pores different from the pores derived from the solvent. It is generated.

  As a minimum of the above-mentioned heating temperature, 500 ° C is preferred and 700 ° C is more preferred. On the other hand, as an upper limit of the above-mentioned heating temperature, 3000 ° C is preferred and 2800 ° C is more preferred. If the heating temperature is below the lower limit, carbonization may be insufficient. On the other hand, if the heating temperature exceeds the above upper limit, the manufacturing cost may increase from the viewpoint of improving the heat resistance of the equipment and the fuel consumption. In addition, as a temperature rising rate, it can be set, for example as 0.01 degrees C / min or more and 10 degrees C / min or less.

  Moreover, as a minimum of heating time, 10 minutes are preferable and 20 minutes are more preferable. On the other hand, as an upper limit of heating time, 10 hours are preferable and 8 hours are more preferable. If the heating temperature is less than the above lower limit, carbonization may be insufficient. Conversely, if the heating time exceeds the above upper limit, the production efficiency of the porous carbon fiber may be reduced.

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

  As a minimum of infusibilization processing temperature in the case of performing infusibilization, 150 ° C is preferred and 180 ° C is more preferred. On the other hand, as an upper limit of the above-mentioned infusibilization treatment temperature, 300 ° C is preferred and 280 ° C is more preferred. If the infusibilization treatment temperature is less than the lower limit, the infusibilization may be insufficient, or the infusibilization treatment time may be prolonged, and the production efficiency may be lowered. Conversely, if the infusibilization treatment temperature exceeds the above upper limit, the solid content may be melted before being infusibilized.

  Moreover, as a minimum of infusibilization processing time, 10 minutes are preferable and 20 minutes are more preferable. On the other hand, as an upper limit of the above-mentioned infusibilization treatment time, 120 minutes are preferred and 90 minutes are more preferred. If the infusibilization treatment time is less than the lower limit, infusibilization may be insufficient. On the contrary, when the above-mentioned infusibilization treatment time exceeds the above-mentioned upper limit, there is a possibility that production efficiency of porous carbon particles may fall.

<Acid washing process>
In the acid washing step S3, porous carbon particles are obtained by acid washing the solid content after the heating step S2. Specifically, the solid content after the heating step S2 is dipped in an acidic solution to remove the unnecessary Group 2 metal compound.

  As the above acidic solution, sulfuric acid, hydrochloric acid or the like can be used. The concentration of the acidic solution can be 1 M or more and 3 M or less. If the concentration of the acidic solution is less than the above lower limit, the Group 2 metal compound may not be sufficiently removed. Conversely, if the concentration of the acidic solution exceeds the upper limit, the cost of post-treatment of the acid used may increase.

  Moreover, the acid adhering to porous carbon particles is removed by performing water washing and drying after being immersed in an acidic solution. The drying can be, for example, flash drying at 40 ° C. or more and 60 ° C. or less and 10 hours or more and 30 hours or less.

  As a minimum of carbon yield in a manufacturing method of the porous carbon particles concerned, 30 mass% is preferred, and 50 mass% is more preferred. If the carbon yield is less than the above lower limit, the effect of reducing the production cost may be insufficient, or the micropores may be blocked by volatile components other than carbon, and the specific surface area of the produced porous carbon particles may be reduced. There is a risk of In the method of producing porous carbon particles, since ashless coal is used, this carbon yield is high. Also, the carbon yield can be adjusted, for example, by the content of ashless coal in the solution. On the other hand, the upper limit of the carbon yield is not particularly limited, and may be 100% by mass, but when using ashless coal, it is usually about 75% by mass. In addition, a "carbon yield" represents the mass ratio of the carbon substance obtained by heat processing with respect to the mass of the organic substance in the raw material before heating process S2, and, in the manufacturing method of the said porous carbon particle, a spray-drying process It represents the mass ratio of porous carbon particles to the mass of the solid content obtained in S1.

The The porous specific surface lower limit of the carbon particles is preferably from 600 meters ² / g, more preferably from 700 meters ² / g, more preferably 750m ² / g. There exists a possibility that it may become difficult to use as a porous material as the said specific surface area is less than the said minimum. 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 the content of ash-free charcoal in a solution, the kind of solvent, spraying conditions etc., for example.

  The lower limit of the total pore volume of the porous carbon particles is preferably 0.3 ml / g, more preferably 0.4 ml / g. On the other hand, the upper limit of the total pore volume of the porous carbon particles is preferably 1 ml / g, and more preferably 0.95 ml / g. If the total pore volume of the porous carbon particles is less than the above lower limit, it may be difficult to use as a porous material. On the other hand, when the total pore volume of the porous carbon particles exceeds the above upper limit, the bulk density is lowered to be too porous, and the strength may be insufficient.

<Advantage>
In the method for producing porous carbon particles, in the spray drying step, the solvent is rapidly detached from the state in which the ash-free coal is dissolved, whereby a large number of micropores are induced in the obtained solid content. That is, in the method for producing porous carbon particles, the carbon material can be made porous without being corroded, so that the carbon yield can be enhanced. In addition, ash-free charcoal has a high carbon yield compared to polyvinyl alcohol and other resin materials, so the specific surface area is large relative to the pore volume of the porous carbon particles obtained. Furthermore, in the method for producing porous carbon particles, since the Group 2 metal compound is dissolved in the solvent, porous carbon particles are formed by ashless coal on the surface or grain boundaries of the Group 2 metal compound, The pore structure is likely to be developed by the different pores of the above-mentioned solvent and the pores of the group 2 metal compound. Moreover, in the manufacturing method of the said porous carbon particle, the solvent which has an oxygen atom or a nitrogen atom, and uses as a main component the organic compound whose boiling point in atmospheric pressure is in the said range is used. Since ashless coal can be dissolved in such a solvent at a high concentration, the interaction between the ashless coal and the Group 2 metal compound is enhanced, and the production efficiency can be enhanced. Therefore, by using the method for producing porous carbon particles, it is possible to produce porous carbon particles relatively excellent in production cost and having a large specific surface area.

  Moreover, in the manufacturing method of the said porous carbon particle, ashless coal can be eluted to a solvent by the solvent extraction process of coal in elution process S12. Therefore, the manufacturing cost of porous carbon particles can be further reduced by using a solution in which a group 2 metal compound is mixed with a liquid component in which the ash-free charcoal is dissolved in a solvent.

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 the porous carbon particles mainly includes a dissolving step S4, a spray drying step S5, a heating step S6, and an acid washing step S7, as shown in FIG.

<Dissolution process>
In the dissolving step S4, ashless coal and the Group 2 metal compound are dissolved in a solvent. As a result of this dissolution, a solution in which ashless coal and a Group 2 metal compound are dissolved 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 said solvent has an organic compound containing an oxygen atom or a nitrogen atom as a main component, and the thing similar to the solvent of 1st embodiment is mentioned. The solvent has a boiling point of 50 ° C. or more and less than 250 ° C. at atmospheric pressure.

  As said group 2 metal compound, the thing similar to 1st embodiment is mentioned.

  Moreover, the said ash-free charcoal can be obtained, for example by the manufacturing method of ash-free charcoal provided with a mixing process, an elution process, a solid-liquid separation process, and an evaporation process.

(Mixing process)
The mixing step in the method of producing ashless coal can be performed in the same manner as the first mixing step S11 of the first embodiment.

  In addition, the solvent mixed at a mixing process is not limited to what has an organic compound containing an oxygen atom or a nitrogen atom as a main component, What is necessary is just to melt | dissolve coal. Examples of such a solvent include methyl naphthalene oil, naphthalene oil and the like, which are bicyclic aromatic compounds derived from coal.

(Elution step)
The elution step in the method for producing ashless coal can be performed in the same manner as the elution step S12 of the first embodiment.

  As a minimum of the temperature of the slurry after temperature rising by the temperature rising part in the above-mentioned elution process, 300 ° C is preferred and 360 ° C is more preferred. On the other hand, as a maximum of the temperature of the above-mentioned slurry, 420 ° C is preferred and 400 ° C is more preferred. If the temperature of the above-mentioned slurry is less than the above-mentioned lower limit, the bond between molecules which constitute coal can not be weakened sufficiently, and there is a possibility that the elution rate may be lowered. Conversely, if the temperature of the above-mentioned slurry exceeds the above-mentioned 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 lower limit 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, as an upper limit of the internal pressure of the said temperature rising part, 5 MPa is preferable and 4 MPa is more preferable. If the internal pressure of the temperature raising portion is less than the lower limit, the solvent may be evaporated to reduce the dissolution of coal. On the contrary, when the internal pressure of the temperature rising portion exceeds the upper limit, there is a possibility that the improvement effect of coal dissolution obtained to the cost increase for maintaining the pressure becomes insufficient.

(Solid-liquid separation process)
The solid-liquid separation step in the method of producing ash-free coal can be performed in the same manner as the solid-liquid separation step S13 of the first embodiment.

  The inside of the separation unit in the separation step is preferably heated and pressurized. 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, as a maximum of the above-mentioned heating temperature, 420 ° C is preferred and 400 ° C is more preferred. When 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 be high.

  Moreover, as a lower limit of the pressure in a isolation | separation part, 1 MPa is preferable and 1.4 MPa is more preferable. On the other hand, as an upper limit of the above-mentioned pressure, 3MPa is preferred and 2MPa is more preferred. When the pressure is less than the above lower limit, the solvent-soluble component may be reprecipitated to lower the separation efficiency. Conversely, if the pressure exceeds the upper limit, the operating cost for pressurization may be increased.

(Evaporation process)
In the evaporation step, the solvent is evaporated from the liquid separated in the separation step. Evaporative separation of this solvent gives ashless coal (HPC).

  As a method of evaporating and separating the above-mentioned solvent, a separation method including a general distillation method or evaporation method (spray dry method etc.) can be used. By separating the solvent from the liquid, it is possible to obtain ashless coal substantially free of ash from the liquid.

  The content of ash-free charcoal and the content of polymer compound of the solution in which the ash-free charcoal and the Group 2 metal compound are dissolved by the above-mentioned dissolution can be the same as in the first embodiment.

<Spray drying process>
In the spray drying step S5, the solution is spray dried. The spray drying step S5 can be performed in the same manner using an apparatus similar to the solid content generation step S15 of the first embodiment.

<Heating process>
In the heating step S6, the solid content obtained in the spray drying step S5 is heat-treated. This heating process S6 can be performed similarly using the same apparatus as the heating process S2 of the first embodiment.

<Acid washing process>
In the acid washing step S7, the solid content after the heating step S6 is acid washed to obtain porous carbon particles. This acid cleaning step S7 can be performed in the same manner as the acid cleaning step S3 of the first embodiment.

<Advantage>
In the method for producing porous carbon particles, the ashless coal and the Group 2 metal compound are directly dissolved in the solvent to obtain a solution in which the ashless coal and the Group 2 metal compound are dissolved in the solvent. For this reason, the kind of solvent used when extracting ash-free charcoal and the solvent used for the solution for obtaining porous carbon particles can be changed. Therefore, since the extraction of ashless coal and the production of porous carbon particles can be optimized, the yield of porous carbon particles can be increased.

Third Embodiment
Hereinafter, a third embodiment of the method for producing porous carbon particles according to the present invention will be described. Although the manufacturing method of the said porous carbon particles can be performed by the flow similar to the manufacturing method of the porous carbon particles of 1st embodiment or 2nd embodiment, it is a solution in 2nd mixing process S14 or melt process S4. It differs in that the polymer compound is further contained.

  The above-mentioned polymer compound is not particularly limited as long as it has a solvent which can be dissolved together with ash-free carbon, but organic polymer compounds are preferable, among which organic polymer compounds having a lower carbon yield than ash-free charcoal preferable. Since the carbon yield of ash-free charcoal is usually 30% by mass to 70% by mass, the upper limit of the carbon yield of the above-mentioned polymer compound is preferably 25% by mass, more preferably 15% by mass, 5% by mass Is more preferred. Thus, the increase effect of the mesopores in the heating step S2 to be described later is easily promoted by using the polymer compound having a low carbon yield. On the other hand, the lower limit of the carbon yield of the above-mentioned polymer compound is not particularly limited and may be 0% by mass. Examples of such a polymer compound include poly (methyl methacrylate) (carbon yield: 4% by mass), polyvinylpyrrolidone (carbon yield: 0% by mass), polystyrene (carbon yield: 10% by mass) and the like.

  As a lower limit of the mass ratio of the above-mentioned high molecular compound to the above-mentioned ash-free charcoal, 0.01 is preferred and 0.015 is more preferred. On the other hand, the upper limit of the mass ratio of the polymer compound to the ashless coal is preferably 0.1, and more preferably 0.05. If the mass ratio of the polymer compound to the ashless coal is less than the lower limit, the pore increasing effect may be insufficient. Conversely, if the mass ratio of the polymer compound to the ashless coal exceeds the upper limit, layer separation from the ashless coal is likely to occur, and the pore increase effect may be insufficient.

  In addition, as a method of mixing the polymer compound, the polymer compound may be directly dissolved in the above solution, or a solution in which the polymer compound is dissolved in a solvent may be mixed with the above solution to prepare.

<Advantage>
In the method for producing porous carbon particles, when carbonizing in the heating step, mesopores in the solid content are mainly increased due to decomposition and dissipation of the polymer compound. For this reason, in the method of producing porous carbon particles, the specific surface area of the porous carbon particles can be further increased.

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

  Although the said 1st embodiment demonstrated the structure which the mixing part of a 1st mixing process has a preparation tank, if a solvent and coal can be mixed not only in this structure, a preparation tank may be abbreviate | omitted. 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 device configuration used in each process is not limited to the above embodiment.

  In the second embodiment, the method of producing ash-free charcoal by solvent extraction has been described, but the method of producing ash-free charcoal is not limited thereto, and for example, it is produced by mixing heating of coal and a hydrogen donating solvent Ash-free coal can also be used.

  Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

Example 1
Ashless coal manufactured by solvent extraction of bituminous coal was prepared as a carbon raw material. Elemental analysis values of this ashless coal are shown in Table 1.

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

  Magnesium oxide (MgO) was prepared as a group 2 metal compound.

  As a solvent, pyridine having a boiling point of 115 ° C. at atmospheric pressure was prepared. Pyridine is a nitrogen-containing organic compound (aromatic compound).

  The ashless coal and the Group 2 metal compound were dissolved in this solvent so that the content of the ashless coal was 10% by mass, and the mass ratio of the Group 2 metal compound to the ashless coal was 4.

  This solution was sprayed into a cyclone using a two-fluid nozzle under the conditions of a spray pressure of 0.3 MPa and a solution feed rate of 1 kg / h to obtain solid content. The inlet temperature of the cyclone 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 in a nitrogen stream, and heat treatment (carbonization) was performed for 30 minutes.

  The carbonized solid was acid-washed with a 2 M aqueous sulfuric acid solution, and after removing the group 2 metal compound, it was air-dried at 50 ° C. for 24 hours to produce porous carbon particles of Example 1.

Example 2
As a high molecular compound, polymethyl methacrylate (PMMA, carbon yield 4% by mass) was prepared, and this high molecular compound was further dissolved in a solution used for dry spraying. The solution was prepared such that the mass ratio of the polymer compound to ashless coal was 0.02. Porous carbon particles of Example 2 were produced in the same manner as in Example 1 except that the above solution was used.

[Example 3]
The porous carbon particles of Example 3 were the same as Example 2 except that the solvent was tetrahydrofuran (THF) having a boiling point of 66 ° C. at atmospheric pressure, the inlet temperature of the cyclone was 100 ° C., and the outlet temperature was 50 ° C. Manufactured. THF is an oxygen-containing organic compound (polar organic compound).

[Examples 4 to 7]
Polymer compounds using PMMA in Examples 4 and 5, polyvinyl pyrrolidone (PVP, carbon yield 0 mass%) in Example 6, and polystyrene (PSt, carbon mass 10 mass%) in Example 7 as polymer compounds The solution was prepared so that the content of. Porous carbon particles of Examples 4 to 7 were produced in the same manner as in Example 2 except that the above solution was used.

Comparative Example 1
Porous carbon particles of Comparative Example 1 were produced in the same manner as in Example 1 except that the same solution as in Example 1 was used and solid content was obtained by vacuum distillation at 100 ° C. for 1 hour in a nitrogen stream.

Comparative Example 2
Porous carbon particles of Comparative Example 2 were produced in the same manner as Example 1, except that the Group 2 metal compound was not dissolved in the solution used for spray drying.

[Evaluation method]
The specific surface area and total pore volume of the obtained porous carbon particles were measured for the above Examples 1 to 7 and Comparative Examples 1 and 2. The BET method was used to measure the specific surface area, and the BJH method was used to measure the total pore volume. The results are shown in Table 2.

  In Table 2, "-" in the column of MgO or the polymer compound means that MgO or the polymer compound was not dissolved in the solution. Also, "-" in the column of total pore volume means that it has not been measured.

  From the results in Table 2, Example 1 in which the solution contains magnesium oxide which is a Group 2 metal compound and produces a solid content by spray drying is Comparative Example 1 using atmospheric distillation or a Group 2 metal compound in a solution It can be seen that the specific surface area is larger than that of Comparative Example 2 not including. That is, it is thought that the specific surface area can be increased by spray drying a solution in which ashless coal and a Group 2 metal compound are dissolved in a solvent.

  The porous carbon particles of Examples 2, 6 and 7 in which the polymer compound was added to the solution to be spray-dried of Example 1 had a specific surface area of Example 1 regardless of the type of the polymer compound. Larger than the ones. Moreover, the porous carbon particle of Example 4 is increasing the total pore volume by adding a polymer compound. That is, it is understood that the specific surface area or the total pore volume can be increased by adding the polymer compound to the solution to be spray-dried.

  Furthermore, the specific surface area of the porous carbon particle of Example 2 is large when Example 2, 4 and 5 from which the mass ratio of the high molecular compound with respect to ashless coal differs is compared. From this, it is understood that the specific surface area can be increased by setting the mass ratio of the polymer compound to the ashless coal to be 0.015 or more and 0.05 or less.

  As explained above, by using the method for producing porous carbon particles of the present invention, porous carbon particles having a large specific surface area can be produced at relatively low production cost.

S1, S5 spray drying step S2, S6 heating step S3, S7 acid washing step S4 dissolution step S11 first mixing step S12 elution step S13 solid-liquid separation step S14 second mixing step S15 solid content generation step

Claims (8)

Spray drying a solution in which ashless coal and a Group 2 metal compound are dissolved in a solvent;
Heat treating the solid content obtained in the spray drying step;
Acid-washing the solid content after the heating step;
The method for producing porous carbon particles, wherein the solvent contains an oxygen atom or a nitrogen atom and an organic compound whose boiling point at atmospheric pressure is 50 ° C. or more and less than 250 ° C. as a main component.   The method for producing porous carbon particles according to claim 1, wherein the group 2 metal compound is magnesium oxide.   The method for producing porous carbon particles according to claim 1 or 2, wherein a mass ratio of the group 2 metal compound to the ashless coal is 1 or more and 10 or less.   The method for producing porous carbon particles according to claim 1, wherein the content of ashless coal in the solution is 5% by mass or more and 50% by mass or less. As said spray-drying process,
Mixing the coal and the solvent;
Eluting the component soluble in the solvent from the coal in the slurry obtained in the mixing step;
Separating the slurry after elution in the elution step into a liquid component containing a solvent-soluble component and a solvent-insoluble component;
And D. dissolving the Group 2 metal compound in the liquid component. The method for producing porous carbon particles according to any one of claims 1 to 4, further comprising:   The method for producing porous carbon particles according to any one of claims 1 to 5, wherein the spray pressure and the liquid transfer speed are adjusted so that the average diameter of the solid content is 1 μm to 20 μm.   The method for producing porous carbon particles according to any one of claims 1 to 6, wherein the solution further contains a polymer compound. The method for producing porous carbon particles according to claim 7, wherein the mass ratio of the polymer compound to the ashless coal is 0.01 or more and 0.1 or less.

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