JP2018150197A - Hollow carbon particle containing nitrogen element, and method for producing hollow carbon particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hollow carbon particle having a high content of nitrogen elements, and a method for efficiently and safely producing the hollow carbon particle.SOLUTION: A hollow carbon particle has one cavity inside, where a content of nitrogen elements is more than 30 mass% and is 40 mass% or less relative to a mass of the hollow carbon particle.SELECTED DRAWING: None

Description

  The present invention relates to a hollow carbon particle containing nitrogen element and a method for producing the hollow carbon particle.

  Carbon materials are widely used in various applications because they are thermally and chemically stable and have electrical conductivity. Furthermore, carbon materials are widely used as adsorbents for separating gases such as nitrogen or carbon dioxide. In recent years, in various particle materials, attempts have been made to hollow out the particle material in order to increase the surface area while reducing the particle diameter, to reduce the density, and to increase the surface area effectively. ing.

  As a method for producing hollow particles using a phenol resin, polystyrene latex particles are dispersed in a phenol resin aqueous solution, and the dispersion is spray-pyrolyzed to produce hollow particles (for example, see Non-Patent Document 1). And a method using silica as a template (nucleating agent) (for example, see Non-Patent Document 2) is known.

Ratna Balgis et al., "Morphology control of hierarchical porous carbon particles from phenolic resin and polystyrene latex template via aerosol process", Carbon, 2015, 84, 281-289. Xianglin Yu et al., “Aerosol assisted synthesis of silica / phenolic resin composite mesoporous hollow spheres”, Colloid Polymer Science, 2008, 286, 1361-1368.

  However, since the method described in Non-Patent Document 1 is produced by spray pyrolysis, the amount of spray and heat conduction are limited, and the productivity is extremely low. Further, in the method described in Non-Patent Document 2, it is necessary to use toxic hydrogen fluoride to remove silica as a template, and a special container must be used. There is a big problem. Furthermore, hollow carbon particles containing a high content of nitrogen element are not known in the prior art.

  An object of the present invention is to provide hollow carbon particles containing a high content of nitrogen element and an efficient and safe method for producing hollow carbon particles.

  In order to solve the above-mentioned problems, the present inventors have conducted detailed studies on hollow carbon particles containing a high content of nitrogen element and a method for producing the hollow carbon particles. As a result, the present invention has been completed. It came.

That is, the present invention includes the following preferred embodiments.
[1] Hollow carbon particles having one void inside, wherein the content of nitrogen element is greater than 30% by mass and equal to or less than 40% by mass with respect to the mass of the hollow carbon particles.
[2] The hollow carbon particles according to [1], wherein an average diameter of the voids is 50 nm or more and 200 nm or less, and an average thickness of a carbon wall forming the hollow carbon particles is 1 nm or more and 200 nm or less.
[3] A coating step of coating the surface of the core made of the resin composition with melamine resin to obtain a coated core,
A curing step of heating the coated core to cure the melamine resin to obtain a cured coated core;
In the above [1] or [2], including a heat treatment step of heat-treating the cured coated core to thermally decompose the core to obtain a hollow carbon particle precursor, and a carbonization step of carbonizing the hollow carbon particle precursor The manufacturing method of the hollow carbon particle of description.
[4] The production method according to [3], wherein the resin composition comprises polystyrene.
[5] The production method according to [3] or [4], wherein the curing step is performed in a liquid phase.
[6] The production method according to any one of [3] to [5], wherein the heat treatment step and the carbonization step are performed simultaneously.
[7] The manufacturing method according to any one of [3] to [6], wherein the heat treatment step and / or the carbonization treatment is performed in an inert gas atmosphere at a temperature of 300 ° C. or higher and 1000 ° C. or lower.

  According to the present invention, there are provided hollow carbon particles having advantages such as a high specific surface area and a low density and containing a high content of nitrogen element, and an efficient and safe method for producing hollow carbon particles.

1 is an electron microscopic observation view of a core manufactured according to Example 1. FIG. 1 is an electron microscopic observation view of hollow carbon particles produced according to Example 1. FIG. 1 is a transmission microscope observation view of hollow carbon particles produced according to Example 1. FIG. 2 is an electron microscopic observation view of a product manufactured according to Comparative Example 1. FIG.

  The hollow carbon particles of the present invention have one void inside and contain a high content of nitrogen element.

<Content of nitrogen element>
The amount of nitrogen element contained in the hollow carbon particles of the present invention is greater than 30% by mass and equal to or less than 40% by mass with respect to the mass of the hollow carbon particles. In the hollow carbon particles, if the amount of the nitrogen element is less than 30% by mass, the physical properties derived from carbon dominate, and the effect of introducing nitrogen cannot be obtained, and the amount of the nitrogen element is more than 40% by mass. If it is large, the thermal stability is low and the shape cannot be maintained. The amount of the nitrogen element is preferably 31% by mass or more and 40% by mass or less with respect to the mass of the hollow carbon particles. By using a melamine resin as a starting material for the hollow carbon particles and adjusting a heat treatment temperature and a carbonization temperature described later, the amount of nitrogen element contained in the hollow carbon particles easily falls within the above range. When the amount of elemental nitrogen contained in the hollow carbon particles is within the above range, the effect brought about by the presence of elemental nitrogen (for example, basic effects such as selective adsorption of acidic substances such as carbon dioxide and formaldehyde) ) Is preferably easily obtained. In the present invention, the content of nitrogen element is measured using an oxygen / nitrogen / hydrogen analyzer (for example, EMGA-930 manufactured by Horiba, Ltd.).

<Gap>
The average diameter of the voids of the hollow carbon particles of the present invention can be adjusted by the average diameter of the core made of the resin composition described later, and the average thickness of the carbon walls forming the hollow carbon particles, preferably 50 nm or more and 200 nm. Hereinafter, it is more preferably 60 nm or more and 180 nm or less. When the average diameter of the voids of the hollow carbon particles is within the above range, voids inside the hollow carbon particles (hereinafter, sometimes referred to as hollow regions) are preferably used and a good surface area increase is likely to be brought about. In the present invention, the average diameter of the voids is obtained by observing the hollow carbon particles with a transmission electron microscope (for example, JEM3200-FS manufactured by JEOL Ltd.), measuring the diameter of the voids of 10 hollow carbon particles, and calculating the average value. It is calculated | required by calculating.

  The porosity of the hollow carbon particles of the present invention is preferably 1% or more and 90% or less, more preferably 5% or more and 90% or less, and further preferably 10% or more and 85% or less with respect to the volume of the hollow carbon particles. . When the porosity of the hollow carbon particles is within the above range, it is easy to provide a suitable utilization of the hollow region, and it is easy to obtain good mechanical strength.

  The shape of the void is not particularly limited. It is preferable from the viewpoint that the mechanical strength is easily maintained and the uneven distribution is less likely to occur when the third component is injected into the hollow region, when the shape of the void is spherical.

<Average thickness of carbon wall>
The average thickness of the carbon wall forming the hollow carbon particles can be controlled by the amount of the melamine resin relative to the core, and is preferably 1 nm to 200 nm, more preferably 10 nm to 100 nm. When the average thickness of the carbon wall is within the above range, the preferred mechanical strength of the hollow carbon particles can be obtained, the hollowness can be easily maintained, and melamine is not used excessively, so that adhesion between the particles is easily prevented. In the present invention, the average thickness of the carbon wall is obtained by observing a hollow carbon particle with a transmission electron microscope (for example, JEM3200-FS manufactured by JEOL Ltd.), measuring the thickness of the carbon wall of ten hollow carbon particles, It is obtained by calculating an average value.

<Average particle size>
The average particle size of the hollow carbon particles of the present invention is preferably 52 nm or more and 500 nm or less, more preferably 60 nm or more and 400 nm or less. If the average particle diameter of the hollow carbon particles is within the above range, the hollow carbon particles are likely to have good mechanical strength, easily maintain the hollow, and the hollow region is suitably used to provide a good surface area increase. Cheap. In the present invention, the average particle diameter is, for example, an observation figure of hollow carbon particles obtained by a transmission electron microscope (for example, JEM3200-FS manufactured by JEOL Ltd.), the particle diameter of 10 hollow carbon particles is measured, and the average value is obtained. It is calculated | required by calculating.

<Method for producing hollow carbon particles>
The hollow carbon particles of the present invention are, for example,
A coating step of coating the surface of the core made of the resin composition with a melamine resin to obtain a coated core;
A curing step of heating the coated core to cure the melamine resin to obtain a cured coated core;
The hardened coated core can be manufactured by a manufacturing method including a heat treatment step of thermally decomposing the core to obtain a hollow carbon particle precursor, and a carbonization step of carbonizing the hollow carbon particle precursor.

<Core>
In the present invention, the core is made of a resin composition. The resin composition preferably includes a resin that can be produced by polymerization of an aromatic vinyl monomer such as styrene, a vinyl monomer such as vinyl acetate, and a (meth) acrylic acid monomer such as methyl methacrylate. It becomes. From the standpoint that it can be easily decomposed thermally and does not generate an activation gas such as water or carbon dioxide during decomposition, the resin composition comprises a resin produced using styrene, that is, a resin composition More preferably, the article comprises polystyrene. The content of polystyrene is preferably 10% by mass or more and 100% by mass, more preferably 40% by mass or more and 98% by mass or less, and still more preferably 60% by mass or more and 95% by mass or less based on the resin composition. The resin composition may further contain an additive such as an emulsifier such as dodecylbenzenesulfonic acid as long as the performance as a core is not impaired. The content of the additive is preferably 5% by mass or less, more preferably 1% by mass or less, based on the resin composition.

  It is preferred that the core has a positive zeta potential. “Zeta potential” is the difference between the potential of the core surface and the potential of a solution sufficiently away from it, and “the core has a positive zeta potential” means that the core is positively charged. That's what it means. The zeta potential of the core is not particularly limited as long as it is positive. The zeta potential of the core is preferably 30 mV to 70 mV, more preferably 40 mV to 60 mV.

  Depending on the surface potential of the core, the state of fixing of the melamine resin to the core changes when the surface of the core is coated with the melamine resin. Specifically, the fixing is homogenized or the coated cores are fused together. When the coated cores adhere to each other, the melamine resin coating layer is locally thinned after the curing step, so that it is difficult to withstand the thermal decomposition treatment and carbonization treatment described later, and the hollow carbon particles are not easily formed.

  The average diameter of the core used in the present invention is not particularly limited because it depends on the desired average diameter of the voids of the hollow carbon particles. The average diameter of the core is preferably 50 nm to 200 nm, more preferably 60 nm to 180 nm. When the average diameter of the core is within the above range, a suitable hollow region is likely to be obtained, a favorable increase in surface area is likely to be obtained, and the hollow region is easily maintained without being blocked by the carbonization treatment described later.

  The manufacturing method of the core in this invention is not specifically limited. The core can be polymerized by adding a monomer to distilled water, purified water or ion-exchanged water as a solvent and suspending it with sufficient stirring, adding a polymerization initiator and heating it with stirring, or polymerizing into the solvent. It can be produced by adding an initiator and stirring well, adding a monomer and heating with stirring.

  A monomer will not be specifically limited if a core can be manufactured. One or more monomers such as aromatic vinyl monomers such as styrene, vinyl monomers such as vinyl acetate, and (meth) acrylic acid monomers such as methyl methacrylate can be used. It is preferable to use a styrenic monomer from the viewpoint that it can be thermally decomposed easily and does not generate an activating gas such as water or carbon dioxide during decomposition. It is more preferable to use styrene having a structural unit derived from a hydrophobic monomer such as styrene or alkyl (meth) acrylate, and styrene having another copolymerizable monomer structural unit, for example, having 3 to 22 carbon atoms. Alkyl (meth) acrylate styrene having an alkyl group, and 2-methylstyrene can be used.

  The concentration of the monomer in the solvent is not particularly limited. The amount is preferably 0.01 mol or more and 1 mol or less, and more preferably 0.02 mol or more and 0.8 mol or less per liter of the solvent. When the concentration of the monomer in the solvent is within the above range, the coarsening of the core due to aggregation is easily avoided, and the stability of the emulsion is easily secured.

  The zeta potential of the core can be adjusted by the polymerization initiator. When a core is produced using a styrene monomer, an azo compound can be used as a polymerization initiator in order to make the zeta potential of the core positive. The azo compound is not particularly limited. For example, 2,2′-azobisisobutyronitrile (azobisisobutyronitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), dimethyl 2 2,2′-azobisisobutyrate, 2,2′-azobis (N-butyl-2-methylpropioamide), and the like can be used. From the viewpoint of price and stability in use, the use of 2,2′-azobisisobutyronitrile (azobisisobutyronitrile) and 2,2′-azobis (2,4-dimethylvaleronitrile) preferable.

The concentration of the polymerization initiator is not particularly limited as long as the polymerization proceeds. It is preferably 0.1 × 10 ⁻⁴ mol or more and 2 × 10 ⁻⁴ mol or less, and more preferably 0.2 × 10 ⁻⁴ mol or more and 1 × 10 ⁻⁴ mol or less per liter of the solvent. When the concentration of the polymerization initiator is within the above range, a suitable molecular weight of the polymer can be obtained, so that the shape of the core is easily maintained, and the polymerization easily proceeds sufficiently.

  There is no particular limitation on the temperature at which the polymerization of the monomer is carried out. The temperature may be any temperature at which polymerization proceeds, and is usually from 40 ° C. to 90 ° C., preferably from 50 ° C. to 80 ° C. If the temperature at which the polymerization of the monomer is within the above range, the polymerization is likely to proceed sufficiently so that the residual monomer is easily avoided, and the average diameter of the core is easily controlled because the polymerization rate is not too high.

  The reaction time of the polymerization of the monomer depends on the polymerization temperature and cannot be particularly specified. Usually, it is 1 hour or more and 100 hours or less, preferably 2 hours or more and 80 hours or less.

  A core having a desired average diameter and zeta potential can be manufactured by the manufacturing method described above.

<Coating process>
In the coating step, the surface of the core made of the resin composition is coated with a melamine resin to obtain a coated core.

  The melamine resin is produced by a condensation (polymerization) reaction between melamine and formaldehyde.

  The mixing ratio of melamine and formaldehyde is not particularly limited as long as a large amount of formaldehyde is mixed to completely react and consume the melamine content. Formaldehyde is usually used in a mixing ratio of 1.0 to 10 mol times, preferably 1.0 to 8 mol times with respect to 1 mol of melamine. When the mixing ratio is within the above range, the melamine content is completely consumed by the reaction, and it is easy to avoid the formation of insoluble paraformaldehyde by the self-condensation of too much formaldehyde.

  In the present invention, the composition ratio of melamine and core is not particularly limited. Melamine is usually used in an amount of 0.01 g to 50 g, preferably 0.05 g to 20 g, relative to 1 g of the core. When the composition ratio between the melamine and the core is within the above range, the core is likely to be satisfactorily coated, and it is easy to avoid the formation of a product consisting only of the melamine resin before the coating.

  The temperature at which the polymerization reaction between melamine and formaldehyde is performed is not particularly limited. Usually, it is carried out at a temperature of 40 to 200 ° C., preferably 60 to 180 ° C. If the temperature at which the polymerization reaction between melamine and formaldehyde is performed is within the above range, the polymerization reaction proceeds within an appropriate time, so that an economic advantage is easily secured, and the melamine before the polymerization reaction proceeds on the core surface. It is easy to avoid polymerization of aldehyde with formaldehyde.

  The heating method is not particularly limited. An autoclave can be used for pressurization and heating, and heating can be performed by irradiating microwaves to accelerate the polymerization reaction.

  In the coating step of the present invention, instead of melamine and formaldehyde, melamine and formaldehyde may be previously condensed to form a melamine (formylol). Formalization is the hydroxymethylation of N atoms not contained in the aromatic ring of melamine. The degree of formalization is not particularly limited, and is usually in the range of 1-6, preferably in the range of 3-6. Trihydroxymethyl melamine, tetrahydroxymethyl melamine, pentahydroxymethyl melamine, hexahydroxymethyl melamine can be used. These may be used alone or in combination. From the viewpoint of the stability of the compound, it is preferable to use hexahydroxymethylmelamine.

  A product obtained by reacting the methylol body with an alcohol such as methanol, ethanol, or a mixture of methanol and butanol, for example, may be used instead of the methylol body. Examples of such reaction products include hexamethoxymethyl melamine, hexaethoxymethyl melamine, and hexabutoxymethyl melamine. These may be used alone or in combination. From the viewpoint of the stability of the compound, it is preferable to use hexamethoxymethylmelamine.

  In the present invention, a radical initiator is used in the polymerization reaction of melamine and formaldehyde, the polymerization reaction of the melamine methylol body, or the reaction product of the reaction product of the methylol body and alcohol. With the addition of the radical initiator, the polymer is uniformly coated on the core.

The radical initiator is not particularly limited, and for example, organic peroxides, inorganic peroxides, azo compounds, and the like are used.
Examples of the organic peroxide include t-butyl hydroperoxide, di-t-butyl peroxide, cumene hydroperoxide, performic acid, peracetic acid and perbenzoic acid.
Examples of inorganic peroxides include potassium persulfate, ammonium persulfate, and sodium persulfate.
An azo compound (RN = NR) is decomposed into two carbon radicals and a nitrogen molecule by heat or light. Examples of the azo compound include azobisisobutyronitrile (AIBN), 1,1′-azobis (cyclohexanecarbonitrile) (ABCN), and 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile). ), 2,2′-azobis [2- (2-imidazolin-2-yl) propane], 2,2′-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, 2,2 '-Azobis (2-methylpropionamidine) dihydrochloride (AIBA), 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) propionamidine] and 4,4'-azobis (4-cyano Valeric acid).
From the viewpoint of initiation efficiency of the radical initiator and solubility in water, 2,2′-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, or 2,2′-azobis (2- Preference is given to using methylpropionamidine) dihydrochloride (AIBA).

  In the present invention, the amount of radical initiator used is not particularly limited as long as the polymerization proceeds. The radical initiator is usually used in the range of 0.01 to 50% by mass, preferably 0.02 to 30% by mass, based on the melamine used.

The coating method is not particularly limited as long as the melamine resin is coated on the surface of the core.
When the core is produced in a solvent as described above, the core is obtained in a state dispersed in the solvent. In this case, melamine and formaldehyde, a methylol body of melamine, or a reaction product of the methylol body and alcohol is added to the dispersion and stirred, and a radical initiator is added and heated while stirring, or this The dispersion was coated with a melamine resin by adding a radical initiator and stirring, adding melamine and formaldehyde, a melamine methylol body, or a reaction product of the methylol body and alcohol and heating with stirring. A core (coated core) can be obtained. The coated core dispersed in the solvent can be separated, for example, by filtration or centrifugation.

<Curing process>
In the curing step, the melamine resin is cured by heating the coated core, and a cured coated core is obtained.

  The temperature at which the curing reaction is carried out depends on the type of melamine used, the methylol body of melamine, and the reaction product of the methylol body and alcohol. Usually, the curing reaction can be carried out at a temperature of 40 to 200 ° C., preferably 60 to 180 ° C., more preferably 120 to 180 ° C.

  The coating process and the curing process can be performed simultaneously. By carrying out at the same time, the adhesion between the coated cores and the cured coated cores can be further suppressed. The temperature at which the coating step and the curing step are performed simultaneously is preferably 100 ° C. or higher and 200 ° C. or lower, more preferably 120 ° C. or higher and 180 ° C. or lower. When the temperature at which the coating step and the curing step are simultaneously performed is within the above range, the reaction product of melamine and formaldehyde, a melamine methylol body, or the methylol body and alcohol easily polymerizes on the core surface, and the melamine resin is cured. Is easy to progress sufficiently.

  The heating method in the curing step is not particularly limited. An autoclave can be used as a method of pressurization and heating, and in order to promote the reaction, it can be heated by irradiation with microwaves.

  As described above, when the core is produced in a solvent, the core is obtained in a state dispersed in the solvent, and the coated core is obtained in a state dispersed in the solvent. In such a case, the curing step performed after or simultaneously with the coating step is performed in a liquid phase (in a solvent) from the viewpoint of avoiding adhesion between the coated cores and the cured coated cores. preferable. The cured coated core can be separated, for example, by filtration or centrifugation.

  The separated cured coated core may be dried, and the method is not particularly limited. It can be dried under atmospheric pressure or reduced pressure. It can also heat at the time of drying, Usually, it can heat at 40 to 200 degreeC, Preferably it can heat at 60 to 180 degreeC. When the heating temperature at the time of drying the cured coated core is within the above range, the cured coated core is easily dried within an appropriate time without melting the core.

<Heat treatment process>
In the heat treatment step, the core is thermally decomposed by heat-treating the cured coated core to obtain a hollow carbon particle precursor.

  The heat treatment temperature is not particularly limited as long as the core is decomposed and volatilized while suppressing thermal decomposition of the melamine resin. Usually, it is 300 ° C. or higher and 1000 ° C. or lower, preferably 350 ° C. or higher and 900 ° C. or lower, more preferably 400 ° C. or higher and 800 ° C. or lower. When the heat treatment temperature is within the above range, the core is easily decomposed and volatilized without remaining, and a hollow region is likely to be produced.

  The heat treatment time is not particularly limited. Usually, it is 1 minute to 300 minutes, preferably 5 minutes to 270 minutes, more preferably 10 minutes to 240 minutes. When the heat treatment time is within the above range, the core is easily decomposed and volatilized easily, and a hollow region is easily provided.

  The rate of temperature increase when heat-treating the cured coated core is not particularly limited. Usually, it is 0.1 ° C. or more and 200 ° C. or less per minute, preferably 0.5 ° C. or more and 180 ° C. or less per minute. If the temperature rising rate when heat-treating the cured coated core is within the above range, the thermal decomposition rate of the core is not too high, so that the structure of the hollow carbon particle precursor is easily maintained, and the core is melted and carbonized. Since it is difficult to occur, a decrease in carbon purity is easily avoided.

  Depending on the conditions of the heat treatment step and the types of melamine, melamine methylol body, and reaction product of the methylol body and alcohol, a part of the carbonization step described later may proceed in the heat treatment step.

<Carbonization process>
In the carbonization step, the hollow carbon particle precursor obtained in the heat treatment step is carbonized to obtain hollow carbon particles.

  The carbonization temperature is not particularly limited as long as the carbonization temperature can be applied to the hollow carbon particle precursor while suppressing thermal decomposition of the melamine resin. Usually, it is 300 ° C. or higher and 1000 ° C. or lower, preferably 350 ° C. or higher and 900 ° C. or lower, more preferably 400 ° C. or higher and 800 ° C. or lower. When the carbonization temperature is within the above range, the carbonization treatment is sufficiently performed, and a decrease in the melamine resin-derived nitrogen content is easily avoided.

  The carbonization time is not particularly limited. Usually, it is 1 minute to 300 minutes, preferably 5 minutes to 270 minutes, more preferably 10 minutes to 240 minutes. When the carbonization time is within the above range, the carbonization treatment is sufficiently performed, and an excessive decrease in the melamine resin-derived nitrogen content is easily avoided.

  The rate of temperature increase during the carbonization treatment is not particularly limited. Usually, it is 0.1 ° C. or more and 200 ° C. or less per minute, preferably 0.5 ° C. or more and 180 ° C. or less per minute. If the rate of temperature increase during the carbonization treatment is within the above range, the structure of the hollow carbon particles is easily maintained because of the carbonization rate that is not too fast, so that a decrease in carbonization yield is easily avoided.

  The carbonization treatment is preferably performed in an inert gas atmosphere. Nitrogen and argon can be used as the inert gas. In consideration of economy and availability, it is preferable to carry out under nitrogen. By subjecting the hollow carbon particle precursor to carbonization treatment under an inert gas atmosphere, a decrease in yield due to the combustion, oxidation, and thermal decomposition of the melamine resin is easily suppressed.

  From the viewpoint of shortening the process and saving the heat energy, it is preferable to simultaneously perform the heat treatment process and the carbonization process. The temperature at which the heat treatment step and the carbonization step are simultaneously performed is preferably 300 ° C. or higher and 1000 ° C. or lower, more preferably 350 ° C. or higher and 900 ° C. or lower. When the temperature at which the heat treatment step and the carbonization step are simultaneously performed is within the above range, the thermal decomposition and desorption of nitrogen content is suppressed, and desired hollow carbon particles are easily obtained. For the reasons described above, when the heat treatment step and the carbonization step are performed simultaneously, it is preferably performed in an inert gas atmosphere.

  The hollow carbon particles obtained by subjecting the hollow carbon particle precursor to carbonization can be recovered after cooling. The recovered hollow carbon particles can be stored under nitrogen as necessary, thereby suppressing the oxidation of the carbon content and maintaining the physical properties immediately after the carbonization treatment.

<Content of nitrogen element>
The amount of nitrogen element contained in the hollow carbon particles obtained by the production method of the present invention is greater than 30% by mass and 40% by mass or less with respect to the mass of the hollow carbon particles. In the hollow carbon particles, if the amount of the nitrogen element is less than 30% by mass, the physical properties derived from carbon dominate, and the effect of introducing nitrogen cannot be obtained, and the amount of the nitrogen element is more than 40% by mass. If it is large, the thermal stability is low and the shape cannot be maintained. The amount of the nitrogen element is preferably 31% by mass or more and 40% by mass or less with respect to the mass of the hollow carbon particles. By using a melamine resin as a starting material for the hollow carbon particles and adjusting the heat treatment temperature and the carbonization temperature, the amount of nitrogen element contained in the hollow carbon particles easily falls within the above range. The content of the nitrogen element depends on the melamine used, the methylol body of melamine, the kind of reaction product of the methylol body and alcohol, the heat treatment temperature and the carbonization temperature. When the amount of elemental nitrogen contained in the hollow carbon particles is within the above range, the effect produced by the presence of elemental nitrogen (for example, basic adsorption such as selective adsorption of acidic substances such as carbon dioxide and formaldehyde) Effect) is easily obtained. The content of elemental nitrogen is measured by the procedure described above.

<Gap>
The hollow carbon particles obtained by the production method of the present invention have one void inside.
The average diameter of the voids of the hollow carbon particles obtained by the production method of the present invention can be adjusted by the average diameter of the core and the average thickness of the carbon wall forming the hollow carbon particles, preferably 50 nm or more and 200 nm or less, more Preferably they are 60 nm or more and 180 nm or less. When the average diameter of the voids of the hollow carbon particles is within the above range, the voids inside the hollow carbon particles are preferably used and a good increase in surface area is likely to occur. The average diameter of the voids is measured by the procedure described above.

  The porosity of the hollow carbon particles obtained by the production method of the present invention is preferably 1% or more and 90% or less, more preferably 5% or more and 90% or less, and still more preferably 10% or more with respect to the volume of the hollow carbon particles. 85% or less. When the porosity of the hollow carbon particles is within the above range, it is easy to provide a suitable utilization of the hollow region, and it is easy to obtain good mechanical strength.

  The shape of the voids of the hollow carbon particles obtained by the production method of the present invention is not particularly limited. It is preferable from the viewpoint that the mechanical strength is easily maintained and the uneven distribution is less likely to occur when the third component is injected into the hollow region, when the shape of the void is spherical.

<Average thickness of carbon wall>
The average thickness of the carbon wall forming the hollow carbon particles obtained by the production method of the present invention can be controlled by the amount of the melamine resin relative to the core, and is preferably 1 nm to 200 nm, more preferably 10 nm to 100 nm. . When the average thickness of the carbon wall is within the above range, the preferred mechanical strength of the hollow carbon particles can be obtained, the hollowness can be easily maintained, and melamine is not used excessively, so that adhesion between the particles is easily prevented. The average thickness of the carbon wall is measured by the procedure described above.

<Average particle size>
The average particle diameter of the hollow carbon particles obtained by the production method of the present invention is preferably 52 nm or more and 500 nm or less, and more preferably 60 nm or more and 400 nm or less. If the average particle diameter of the hollow carbon particles is within the above range, the hollow carbon particles are likely to have good mechanical strength, easily maintain the hollow, and the hollow region is suitably used to provide a good surface area increase. Cheap. The average particle size is measured by, for example, the procedure described above.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited at all by this Example. The characteristics of the hollow carbon particles obtained in the respective examples and comparative examples were evaluated as follows.

Average diameter of the core:
Using the observation drawing of the core obtained with an electron microscope (manufactured by Keyence Corporation), the diameter of 10 cores was measured, and the average value was taken as the average diameter of the core.

Elemental nitrogen content:
Measurement was performed using an oxygen / nitrogen / hydrogen analyzer (EMGA-930 manufactured by Horiba, Ltd.).

Average diameter of voids:
The observation figure of the hollow carbon particles was obtained with a transmission electron microscope (JEM3200-FS, manufactured by JEOL Ltd.), the diameter of 10 voids of the hollow carbon particles was measured, and the average value was calculated.

Average thickness of carbon wall:
The observation figure of the hollow carbon particles was obtained with a transmission electron microscope (JEM3200-FS manufactured by JEOL Ltd.), the thickness of the carbon wall of 10 hollow carbon particles was measured, and the average value was calculated.

Average particle size of hollow carbon particles:
Using the observation drawing of hollow carbon particles obtained by a transmission electron microscope (JEM3200-FS manufactured by JEOL Ltd.), the particle diameter of 10 hollow carbon particles was measured, and the average value was calculated as the average particle diameter of the hollow carbon particles. did.

から算出した。 Porosity:
The porosity is given by the following formula:

Calculated from

Example 1
A stirrer, a reflux tube and a thermometer were connected to a 1 L three-necked flask, and 600 mL of ion-exchanged water was introduced. 2 g of styrene and 0.01 g of azobisisobutyronitrile were added to ion-exchanged water, and the resulting system was heated to 70 ° C. while flowing nitrogen. The system was agitated at 70 ° C. for 24 hours while maintaining a rotation speed of 400 rpm. The reaction solution was cooled to room temperature, and the obtained dispersion was dropped onto a cover glass, dried, and then observed using an electron microscope. An electron microscope observation diagram is shown in FIG. In this observation figure, the diameter of 10 cores was measured, and the average value thereof was 81.6 nm. The zeta potential of the obtained core dispersion was measured using Zeta Sizer Nano ZSP (manufactured by Malvern) and found to be 46.0 mV.
To this core dispersion, 1.0 g of hexamethoxymethylmelamine was added, and 0.225 g of 2,2′-azobis (2-methylpropionamidine) dihydrochloride was added. The resulting mixture was stirred and reacted at 60 ° C. for 30 minutes while being irradiated with microwaves.
After cooling the reaction solution, the hardened coated core was separated using a centrifuge. The cured coated core was dried at 100 ° C. and 13 Pa for 4 hours, and then heat-treated and carbonized in a fast reactor (manufactured by Motoyama) at 550 ° C. for 2 hours under nitrogen. The mixture was cooled to room temperature to obtain 0.46 g of hollow carbon particles. The electron microscope observation figure of the obtained hollow carbon particle is shown in FIG. 2, and the transmission microscope observation figure is shown in FIG. Table 1 shows the results of elemental analysis.

Example 2
To the core dispersion obtained in Example 1, 2.0 g of hexamethoxymethylmelamine was added, and 0.225 g of 2,2′-azobis (2-methylpropionamidine) dihydrochloride was added. The resulting mixture was stirred and reacted at 60 ° C. for 30 minutes while being irradiated with microwaves.
After cooling the reaction solution, the hardened coated core was separated using a centrifuge. The cured coated core was dried at 100 ° C. and 13 Pa for 4 hours, and then heat-treated and carbonized in a fast reactor (manufactured by Motoyama) at 550 ° C. for 2 hours under nitrogen. After cooling to room temperature, 0.90 g of hollow carbon particles were obtained. Table 1 shows the results of elemental analysis.

Comparative Example 1
To the core dispersion obtained in Example 1, 1.0 g of hexamethoxymethylmelamine was added, and the reaction was performed at 60 ° C. for 30 minutes while irradiating with microwaves.
After cooling the reaction solution, the product was collected using a centrifuge. The product was dried at 100 ° C. and 13 Pa for 4 hours, then heat-treated and carbonized at 550 ° C. for 2 hours in a fast reactor (manufactured by Motoyama) and cooled to room temperature. The electron microscope observation figure of a product is shown in FIG. It can be seen that the particles adhere to each other and do not exist as single particles. In addition, a clear hollow region could not be observed.

Comparative Example 2
A stirrer, a reflux tube and a thermometer were connected to a 1 L three-necked flask, and 600 mL of ion-exchanged water was introduced. 2 g of styrene and 0.03 g of potassium persulfate were added to ion-exchanged water, and the resulting system was heated to 70 ° C. while flowing nitrogen. The system was agitated at 70 ° C. for 24 hours while maintaining a rotation speed of 400 rpm. The reaction solution was cooled to room temperature, and the obtained dispersion was dropped onto a cover glass, dried, and then observed using an electron microscope. In the obtained observation drawing, the diameter of 10 cores was measured, and the average value thereof was 81.6 nm. When the zeta potential of the obtained core dispersion was measured using Zeta Sizer Nano ZSP (manufactured by Malvern), it was -50.4 mV.
To this core dispersion, 2 g of 3-aminophenol was added, and 2 mL of a 17% aqueous ammonia solution and 100 g of ethanol were added. While stirring the resulting mixed solution, 1.88 g of a 30% formaldehyde solution (an equimolar amount of 3-aminophenol) was added, and the mixture was reacted at 150 ° C. for 30 minutes while being irradiated with microwaves.
After cooling the reaction solution, the hardened coated core was separated using a centrifuge. The cured coated core was dried at 100 ° C. and 13 Pa for 4 hours, and then heat-treated and carbonized in a fast reactor (manufactured by Motoyama) at 550 ° C. for 2 hours under nitrogen. The mixture was cooled to room temperature to obtain 1.22 g of hollow carbon particles. The content of nitrogen element in the obtained hollow carbon particles was 15.97% by mass.

  According to the present invention, it is possible to provide a hollow carbon particle containing nitrogen element and an efficient and safe method for producing a hollow carbon particle, which have advantages such as a high specific surface area and a low density. The hollow carbon particles of the present invention can be extremely usefully used for battery materials, catalyst carriers, and adsorbents for separating gases such as nitrogen or carbon dioxide.

Claims (7)

  Hollow carbon particles having one void inside, wherein the content of nitrogen element is greater than 30% by mass and equal to or less than 40% by mass with respect to the mass of the hollow carbon particles.   The hollow carbon particles according to claim 1, wherein an average diameter of the voids is 50 nm or more and 200 nm or less, and an average thickness of carbon walls forming the hollow carbon particles is 1 nm or more and 200 nm or less. A coating step of coating the surface of the core made of the resin composition with a melamine resin to obtain a coated core;
A curing step of heating the coated core to cure the melamine resin to obtain a cured coated core;
The hollow according to claim 1, comprising a heat treatment step of heat-treating the cured coated core to thermally decompose the core to obtain a hollow carbon particle precursor, and a carbonization step of subjecting the hollow carbon particle precursor to carbonization. A method for producing carbon particles.   The manufacturing method according to claim 3, wherein the resin composition comprises polystyrene.   The manufacturing method of Claim 3 or 4 which performs the said hardening process by a liquid phase.   The manufacturing method in any one of Claims 3-5 which performs the said heat processing process and the said carbonization process simultaneously.   The manufacturing method according to claim 3, wherein the heat treatment step and / or the carbonization treatment is performed in an inert gas atmosphere at a temperature of 300 ° C. or higher and 1000 ° C. or lower.

Images