JP2006219322A - Monodisperse spherical carbon porous body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a monodisperse spherical carbon porous body which is spherical, monodisperse and has radially-formed fine pores, and also to provide another monodisperse spherical carbon porous body in which noble metal particulates are supported and/or nitrogen is doped inside the above fine pores. <P>SOLUTION: The monodisperse spherical carbon porous body comprises a spherical carbon particulate having fine pores extending radially from its center to its surface, and has a monodisperse degree of ≤10%. Inside the carbon particulate, a noble metal particulate may be supported, or nitrogen may be doped. Such a monodisperse spherical carbon porous body is obtained by allowing a spherical monodisperse mesoporous silica with the radially-formed fine pores to adsorb an organic material being a carbon source, polymerizing and carbonizing the organic material, and then removing the mesoporous silica. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a monodispersed spherical carbon porous body, and more particularly to a monodispersed spherical carbon porous body used for an adsorbent, a catalyst, a catalyst carrier, an electric double layer capacitor, a sensor, an electrode and the like.

Since the carbon porous body is excellent in thermal stability, hydrothermal stability, chemical durability, fat solubility, etc., the energy of catalyst carriers for various electrochemical devices such as adsorbents and fuel cells, and energy of electric double layer capacitors Application to storage materials, packing materials for liquid chromatography, etc. is expected. In the case of using a carbon porous body for a specific application, it is important to control the particle size, shape, pore distribution and the like of the carbon porous body in order to develop high performance.
Conventionally, the use of activated carbon has been mainly studied for this type of application. However, activated carbon has the disadvantages of irregular shape, wide pore distribution, and a large proportion of micro-sized pores. For this reason, various proposals have conventionally been made regarding carbon porous bodies instead of activated carbon.

  For example, Patent Document 1 discloses spherical porous carbon particles obtained by dehydrating condensation (preliminary carbonization) of spherical cellulose and carbonizing and firing at 2000 ° C. or higher. According to this document, by such a method, graphitized spherical porous carbon particles having an average particle diameter of 6 to 25 μm and a specific surface area of 52 to 375 μm can be obtained. It describes that it functions as a better packing material for liquid chromatography.

Patent Document 2 discloses that
(1) Adsorbing furfuryl alcohol in the pores of mesoporous silica (for example, AlMCM-48),
(2) This is heated at 140 ° C. for 2 hours to polymerize furfuryl alcohol,
(3) By further heating this at 900 ° C. in vacuum, the furfuryl alcohol is thermally decomposed,
(4) removing mesoporous silica from the obtained composite with an aqueous NaOH solution;
A method for producing a carbon molecular sieve is disclosed.
This document describes that a carbon molecular sieve having a uniform diameter and regularly arranged pores can be obtained by such a method.

Non-Patent Document 1 includes
(1) impregnating silica having a mesostructure with furfuryl alcohol;
(2) This is heated in N ₂ at 353 K for 2 hours to polymerize furfuryl alcohol,
(3) This was further heated in N ₂ at 1073 K for 1 hour,
(4) 48% HF is added to the obtained carbon-silica composite to remove the template.
A method for producing mesoporous carbon is disclosed.
In the same document, when synthesizing mesoporous silica, if the stirring conditions are changed, 2-8 μm polydispersed spherical particles, 0.2-0.5 μm submicron particle aggregates, or 10-20 nm nanoparticles It describes that mesoporous silica composed of agglomerates can be obtained, and that when this is used as a template, mesoporous carbon retaining the shape of mesoporous silica can be obtained.

  Furthermore, Non-Patent Document 2 discloses a method for producing spherical carbon in which metallic sodium and polytetrafluoroethylene powder are placed in a stainless steel container, benzene is further added thereto, and the stainless steel container is heated at 250 ° C. for 24 hours. It is disclosed. This document describes that a spherical carbon composed of an aggregate of fibers having a diameter of 300 to 400 nm can be obtained by such a method.

Japanese Patent No. 2989201 US Pat. No. 6,585,948 A.B.Fuertes, J.Mater.Chem., 2003, 13, 3085-3088 Y.Ni et al., Chem. Lett., 2004, 33, 494-495

The carbon porous body used for various electrochemical devices preferably has a high filling property. For that purpose, the carbon porous body is preferably spherical and monodispersed.
In addition, when a carbon porous body is used as a catalyst carrier or the like, in order to obtain high activity, it is necessary to facilitate the supply of reactants and electrons to the catalyst surface supported by the carbon porous body. To that end, the pore structure should be as simple as possible, i.e. the pores are connected at the shortest distance from the surface of the sphere to the center, e.g., the pores are radial from the center of the sphere toward the surface. It is preferable to be formed.

Moreover, a noble metal is generally used for the catalyst supported on the carbon porous body. Since noble metals are extremely expensive, in order to produce an electrochemical device having high performance at low cost, it is necessary to develop high activity with a small amount of catalyst supported. For that purpose, the smaller the particle size of the noble metal particles supported, the better.
Furthermore, when the carbon porous body is doped with nitrogen, the adsorption characteristics change. In order to synthesize a porous carbon body with high filling properties, pores formed radially, and various adsorption properties, the nitrogen doping amount is controlled while maintaining the particle shape, pore structure, etc. There is a need to.
However, a spherical carbon monodispersed porous carbon body having pores formed radially, and a carbon porous body having such a structure, in which noble metal fine particles are supported, and / or There is no example in which a material doped with nitrogen is produced.

The problem to be solved by the present invention is to provide a monodispersed spherical carbon porous body that is spherically monodispersed and has pores formed radially.
Another problem to be solved by the present invention is spherical monodisperse, monodisperse spherical particles in which pores are formed radially and noble metal fine particles are supported therein and / or nitrogen is doped. The object is to provide a carbon porous body.

  In order to solve the above problems, a monodispersed spherical carbon porous body according to the present invention comprises spherical carbon particles, has pores extending radially from the center toward the surface, and has a monodispersity. The gist is that it is 10% or less. The monodispersed spherical carbon porous body may be one in which noble metal fine particles are supported inside the carbon particles, or nitrogen may be doped into the carbon particles.

  The monodispersed spherical carbon porous body according to the present invention has a spherical particle shape and a small monodispersity. Therefore, when producing a structure using this, or when filling a column, carbon particles The packing density of can be remarkably improved. In addition, since the monodispersed spherical carbon porous body according to the present invention has pores extending radially, the diffusion path of the substance into the sphere is shortened, and the utilization efficiency of the pores is improved.

  Hereinafter, an embodiment of the present invention will be described in detail. The monodispersed spherical carbon porous body according to the present invention comprises spherical carbon particles, has pores extending radially from the center toward the surface, and has a monodispersity of 10% or less. Features.

“Spherical” means that the average sphericity of each particle is 13% or less when a plurality of (preferably 20 or more) particles manufactured under the same conditions are observed with a microscope. Say. The “sphericity” is an index representing the degree of deviation of the outer shape of each particle from the perfect circle, and the circumscribed circle and the particle with respect to the radius (r ₀ ) of the smallest circumscribed circle in contact with the particle surface. This is a value represented by the ratio (= Δr _max × 100 / r ₀ (%)) of the maximum value (Δr _max ) of the distance in the radial direction from each point on the surface. In order to obtain a high filling property, the smaller the sphericity of the carbon particles, the better. When the method described later is used, carbon particles having a sphericity of 7% or less or 3% or less can be obtained.

  The carbon particles have an internal structure in which carbon rods extend radially from the center of the sphere toward the surface, and the gaps form pores that extend radially from the center to the surface. In order to improve the utilization efficiency of pores, the higher the proportion of pores extending radially, the better. When the method described later is used, carbon particles in which most of the pores extend radially from the center toward the surface can be obtained. Whether or not the pores extend radially can be directly observed with a transmission electron microscope. When carbon particles in which most of the pores extend radially are observed with a transmission electron microscope, a radial contrast can be confirmed in the vicinity of the outer periphery of the particles.

“Monodispersion” means that the degree of monodispersion represented by the following formula (1) is 10% or less. In order to obtain a high filling property, the smaller the monodispersity, the better. When the method described later is used, carbon particles having a monodispersity of 10% or less or 5% or less can be obtained.
Monodispersity = (standard deviation of particle diameter / average particle diameter) × 100 (%) (1)

The monodispersed spherical carbon porous body according to the present invention is synthesized using a spherical mesoporous body as a template, as will be described later. Therefore, the average particle diameter, specific surface area, and pore distribution of the monodispersed spherical carbon porous body are almost determined by the template used.
Specifically, a monodispersed spherical carbon porous body having an average particle size of 50 nm or more and 2 μm or less is obtained by using the method described later. Moreover, the monodispersed spherical carbon porous body whose specific surface area is 1000 m < ² > / g or more is obtained. Furthermore, a monodispersed spherical carbon porous body whose pore distribution has a peak at 0.5 nm or more and 2.0 nm or less is obtained.

The monodispersed spherical carbon porous body according to the present invention may have noble metal fine particles supported therein. Specifically, the noble metal fine particles are fine particles made of Pt, Rh, Pd, Ru, Ir, Ag, Au, or an alloy thereof.
The size of the noble metal fine particles is substantially determined by the pore diameter of the spherical mesoporous material used as the template. When a method described later is used, a monodispersed spherical carbon porous body carrying noble metal fine particles having a particle size of 5.0 nm or less can be obtained.
In addition, the maximum amount of the precious metal fine particles that can be supported on the monodispersed spherical carbon porous body is almost determined by the porosity (porosity) of the spherical mesoporous body used as a template. When a method described later is used, a monodispersed spherical carbon porous body having a precious metal fine particle loading of 80 wt% or less can be obtained.

Furthermore, the monodispersed spherical carbon porous body according to the present invention may be doped with nitrogen in addition to or instead of supporting the noble metal fine particles.
The monodispersed spherical carbon porous body doped with nitrogen can be synthesized by using a nitrogen-containing organic substance as a carbon source, as will be described later. The nitrogen doping amount can be adjusted by controlling the type and amount of the nitrogen-containing organic substance.

Next, a method for producing a spherical mesoporous material used as a template for synthesizing the monodispersed spherical carbon porous material according to the present invention will be described.
The monodispersed spherical carbon porous material according to the present invention can be obtained by carbonizing a carbon source adsorbed in the pores of a spherical mesoporous material containing silica and removing the spherical mesoporous material. Therefore, in order to synthesize carbon particles having a predetermined average particle diameter, spherical monodisperse, and pores extending radially from the center to the surface, a spherical mesoporous material having such a structure is used. The body needs to be used as a template.

In this case, spherical mesoporous material may be made of only silica, or may comprise oxides of the metal element M ₁ other than silica. The metal element M ₁ is not particularly limited, those capable of producing a divalent or more metal alkoxides are preferred. If the metal element M ₁ can produce a metal alkoxide having a valence of 2 or more, mesoporous silica containing an oxide of the metal element M ₁ can be easily produced. Examples of the metal element _{M 1,} specifically, is Al, Ti, Mg, Zr and the like. In particular, the spherical mesoporous material containing Al has an advantage of functioning also as a solid acid for polymerizing organic substances described later.

  It is preferable that the content of silica contained in the spherical mesoporous material is relatively large. The removal of the spherical mesoporous material is facilitated as the silica content is relatively increased. Specifically, the content of silica in the spherical mesoporous material is preferably 20 wt% or more, more preferably 50 wt% or more, and still more preferably 80 wt% or more.

A spherical mesoporous material containing silica can be obtained by three-dimensionally polymerizing a raw material containing a silica raw material using a surfactant as a template. In particular,
(1) Add appropriate amount of surfactant and silica raw material (and other raw materials if necessary) to water, and hydrolyze silica raw material (and other raw materials added as needed) under basic conditions Let
(2) separating the product from the solution and removing the surfactant;
(See, for example, JP-A-10-328558 and JP-A-2004-2161).

  At this time, when the concentration of the surfactant in the solution, the concentration of the silica raw material, and the ratio of the two are optimized, a spherical mesoporous body in which mesopores are radially arranged from the center toward the outside is obtained. Furthermore, when a specific kind of alcohol and / or hydrophilic polymer is added to the solution, a spherical mesoporous material having a fine particle size of 2 μm or less and a narrow particle size distribution is obtained.

Silica raw materials include
(1) Tetraalkoxysilanes (silane compounds) such as tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, dimethoxydiethoxysilane,
(2) Trimethoxysilanol, triethoxysilanol, trimethoxymethylsilane, trimethoxyvinylsilane, triethoxyvinylsilane, triethoxy-3-glycidoxypropylsilane, 3-mercaptopropyltrimethoxysilane, 3-chloropropyltrimethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, γ- (methacryloxypropyl) trimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, etc. Trialkoxysilane (silane compound),
(3) dialkoxysilanes (silane compounds) such as dimethoxydimethylsilane, diethoxydimethylsilane, diethoxy-3-glycidoxypropylmethylsilane, dimethoxydiphenylsilane, dimethoxymethylphenylsilane,
(4) Sodium metasilicate (Na ₂ SiO ₃ ), sodium orthosilicate (Na ₄ SiO ₄ ), sodium disilicate (Na ₂ Si ₂ O ₅ ), sodium tetrasilicate (Na ₂ Si ₄ O ₉ ), water Sodium silicate such as glass (Na ₂ O · nSiO ₂ , n = 2 to 4),
(5) Kanemite (NaHSi ₂ O ₅ .3H ₂ O), sodium disilicate crystals (α, β, γ, δ-Na ₂ Si ₂ O ₅ ), macatite (Na ₂ Si ₄ O ₉ ), eyelite ( _{Na 2 Si 8 O 17 · xH} 2 O), magadiite _{(Na 2 Si 14 O 17 ·} xH 2 O), kenyaite _{(Na 2 Si 20 O 41 ·} xH 2 O) layered silicates, such as,
(6) Precipitating silica such as Ultrasil (Ultrasil), Cab-O-Sil (Cabot), HiSil (Pittsburgh Plate Glass), colloidal silica, fumed silica such as Aerosil (Degussa-Huls),
Etc. can be used.

Among these, tetraalkoxysilane is suitable as a silica raw material because it has a large number of silanol bonds generated by hydrolysis and can form a strong skeleton.
In addition, these silica raw materials may be used alone or in combination of two or more. However, when two or more kinds of silica raw materials are used, the reaction conditions during the production of mesoporous silica may be complicated. In such a case, the silica raw material is preferably used alone.

In addition, the raw material containing the metal element M ₁ includes
(1) Al-containing alkoxides such as aluminum butoxide (Al (OC ₄ H ₉ ) ₃ ), aluminum ethoxide (Al (OC ₂ H ₅ ) ₃ ), aluminum isopropoxide (Al (OC ₃ H ₇ ) ₃ ) And salts such as sodium aluminate and aluminum chloride,
(2) Ti such as titanium isopropoxide (Ti (Oi-C ₃ H ₇ ) ₄ ), titanium butoxide (Ti (OC ₄ H ₉ ) ₄ ), titanium ethoxide (Ti (OC ₂ H ₅ ) ₄ ), etc. Containing alkoxide,
(3) Alkoxide containing Mg such as magnesium methoxide (Mg (OCH ₃ ) ₂ ), magnesium ethoxide (Mg (OC ₂ H ₅ ) ₂ ),
(4) Zr such as zirconium isopropoxide (Zr (Oi-C ₃ H ₇ ) ₄ ), zirconium butoxide (Zr (OC ₄ H ₉ ) ₄ ), zirconium ethoxide (Zr (OC ₂ H ₅ ) ₄ ) Containing alkoxide,
Etc. can be used.

Moreover, what is represented by following (2) Formula is preferable for surfactant.
_{CH 3 - (CH 2) n} -N + (R 1) (R 2) (R 3) X - ··· (2)
_{(Wherein, R 1, R 2, R} 3 is a 1 to 3 carbon atoms, the same or different alkyl group, X is a halogen atom, n represents 8-21 integer.)
Among the surfactants represented by the formula (1), alkyltrimethylammonium halides (for example, hexadecyltrimethylammonium halide, octadecyltrimethylammonium halide, nonyltrimethylammonium halide, decyltrimethylammonium halide, undecyltrimethylammonium halide, dodecyltrimethyl) Ammonium halide etc.) are preferable, and alkyltrimethylammonium bromide or alkyltrimethylammonium chloride is particularly preferable.

In order to obtain a spherical mesoporous material having mesopores radially arranged from the center to the outside, the concentration of the silica raw material (and other raw materials added as necessary) in the solution is 0.005 mol / L or more and 0.05 mol / L or less are preferable, more preferably 0.007 mol / L or more and 0.045 mol / L or less, and still more preferably 0.009 mol / L or more and 0.04 mol / L or less.
Similarly, the concentration of the surfactant in the solution is preferably 0.005 mol / L or more and 0.04 mol / L or less, more preferably 0.007 mol / L or more and 0.03 mol / L or less, more preferably 0. It is 0.008 mol / L or more and 0.018 mol / L or less.
Furthermore, the ratio (molar ratio) of the surfactant / silica raw material (and other raw materials added as necessary) is preferably 0.1 or more and 3 or less, more preferably 0.2 or more and 2.7 or less. More preferably, it is 0.3 or more and 2.5 or less.

  When alcohol is added to the solution, the alcohol may be any of monovalent alcohols such as methanol, ethanol, and propanol, divalent alcohols such as ethylene glycol, and trivalent alcohols such as glycerin. In this case, in order to obtain a spherical mesoporous material having a fine particle size of 2 μm or less and a narrow particle size distribution, the amount of alcohol added is preferably 5 to 80, more preferably 100% of the water volume. Is 7 to 70, more preferably 10 to 60.

  In the case where a hydrophilic polymer is added to the solution in addition to or in place of the alcohol, the hydrophilic polymer is preferably polyvinyl alcohol or polyethylene glycol. In this case, the molecular weight of the hydrophilic polymer is preferably 200 to 50000, more preferably 300 to 30000. In order to obtain mesoporous silica having a fine particle size of 2 μm or less and a narrow particle size distribution, the concentration of the hydrophilic polymer in the solution is preferably 0.1 to 20% by weight, more preferably 0.5 to 10% by weight.

A basic substance is added to the solution containing these raw materials in order to make the solution basic and hydrolyze the silica raw materials. Specific examples of the basic substance include sodium hydroxide and aqueous ammonia. The addition amount of the basic substance is selected in accordance with the type and concentration of the raw material, the characteristics of the spherical mesoporous material to be produced, and the like. Generally, when the addition amount of the basic substance is too small, the yield is extremely lowered. On the other hand, when the addition amount of the basic substance is too large, it may be difficult to form a porous body. The addition amount of the basic substance is specifically the alkali equivalent of a basic substance by a value obtained by dividing the number of moles of silicon and the metal element M ₁ in the raw material, if the basic substance is a strong base, 0 0.1 to 0.9 is preferable, 0.2 to 0.5 is more preferable, and 0.2 to 5 is preferable when the basic substance is a weak base, and 1 to 3 is more preferable.

When a silane compound such as tetraalkoxysilane is used as the silica material, this is used as a starting material as it is.
On the other hand, when a compound other than a silane compound is used as the silica raw material, a basic material such as sodium hydroxide is added in advance to the silica raw material in water (or an alcohol aqueous solution to which an alcohol is added if necessary). Add. The addition amount of the basic substance is preferably about equimolar to the silicon atom in the silica raw material. When a basic substance is added to a solution containing a silica raw material other than the silane compound, a part of the Si— (O—Si) ₄ bond already formed in the silica raw material is cleaved to obtain a uniform solution. The amount of the basic substance contained in the solution affects the yield and porosity of the spherical mesoporous material. Therefore, after a uniform solution is obtained, a dilute acid solution is added to the solution, and the excess present in the solution is added. Neutralize basic substances. The addition amount of the dilute acid solution is preferably an amount corresponding to 1/2 to 3/4 times mol of silicon atoms in the silica raw material.

Silica materials preliminary process is performed as necessary to a predetermined amount of water and surfactant, and, optionally, a raw material, an alcohol and / or a hydrophilic polymer added containing a metal element M _1, which Further, a basic substance is added to hydrolyze under basic conditions. Thereby, the surfactant functions as a template, and a silicon-containing oxide (hereinafter referred to as “precursor”) containing the surfactant therein is obtained.

Next, if the precursor obtained from the solution is separated, and the surfactant is removed from this precursor, it contains silica, has an average particle size of 50 nm to 2.0 μm, is monodispersed, and has pores Can be obtained as a spherical mesoporous material (monodispersed spherical mesoporous silica) formed radially.
As a method for removing the surfactant, specifically,
(1) A firing method in which the precursor is fired at a predetermined temperature (300 to 1000 ° C., preferably 400 to 700 ° C.) for a predetermined time (30 minutes or more, preferably 1 hour or more) in the air or in an inert atmosphere. ,
(2) The precursor is immersed in a good solvent for a surfactant (for example, methanol containing a small amount of hydrochloric acid), and stirred while heating at a predetermined temperature (for example, 50 to 70 ° C.), and the interface in the precursor An ion exchange method to extract the active agent,
and so on.

  Next, the manufacturing method of the monodispersed spherical carbon porous body concerning this invention is demonstrated. The method for producing a monodispersed spherical carbon porous body according to the first embodiment of the present invention is a method for producing a monodispersed spherical carbon porous body made of only carbon, and includes an adsorption step, a polymerization step, a carbonization step, And a removing step. Depending on the manufacturing method, the adsorption process and the polymerization process may be performed, or the adsorption process, the polymerization process, and the carbonization process may be performed in one process.

The adsorption step is a step of adsorbing an organic substance in the pores of a monodispersed spherical mesoporous material (hereinafter simply referred to as “mesoporous silica”) containing silica and having radial pores.
The organic substance is a carbon source and may be any substance that can generate carbon by thermal decomposition. Specifically, as such an organic substance,
(1) A liquid polymer precursor at room temperature and thermally polymerizable (for example, furfuryl alcohol, aniline, etc.),
(2) A mixture of an aqueous carbohydrate solution and an acid (for example, monosaccharides such as sucrose (sucrose), xylose (wood sugar), glucose (glucose)), disaccharides, polysaccharides, sulfuric acid, hydrochloric acid, nitric acid, phosphorus Mixtures with acids such as acids),
(3) a polymerizable gas having an unsaturated bond (for example, acetylene, propylene, etc.),
(4) A mixture of two-component curable polymer precursors (for example, phenol and formalin),
and so on.
Among these, since the polymer precursor can be impregnated into the pores of mesoporous silica without diluting with a solvent, a relatively large amount of carbon is introduced into the pores with a relatively small number of impregnations. Can be generated. Further, there is an advantage that a polymerization initiator is unnecessary and handling is easy.

When adsorbing a liquid or solution carbon source, it is only necessary to add a predetermined amount of liquid or solution to mesoporous silica. Since mesoporous silica is extremely excellent in adsorption properties, the liquid or solution can be impregnated in the pores by simply adding a liquid or solution to the silica and applying a slight vibration from the outside at room temperature.
Alternatively, mesoporous silica may be placed in a sealable container, and after the container is evacuated, the liquid or solution carbon source vapor may be introduced into the container. Thereby, a carbon source can be adsorbed in the pores of mesoporous silica.

When a liquid or solution carbon source is used, the larger the amount of adsorption of the liquid or solution per time, the better. The amount by which all pores in the mesoporous silica are filled with the liquid or solution is preferable.
Further, when a mixture of an aqueous carbohydrate solution and an acid is used as the carbon source, the amount of the acid is preferably set to a minimum amount capable of polymerizing the organic matter.
Furthermore, when a mixture of a two-component curable polymer precursor is used as the carbon source, an optimal ratio is selected according to the type of the polymer precursor.

The polymerization step is a step of polymerizing organic substances adsorbed in the pores.
For example, when the organic substance is a polymer precursor, a mixture of an aqueous solution of carbohydrate and an acid, or a mixture of a two-part curable polymer precursor, the polymerization of the organic substance is performed at a predetermined temperature on mesoporous silica adsorbed with the organic substance at a predetermined temperature. Perform by heating for hours. The optimum polymerization temperature and polymerization time vary depending on the type of organic substance, but the polymerization temperature is usually 50 ° C. to 400 ° C., and the polymerization time is 5 minutes to 24 hours.

The carbonization step is a step of carbonizing the polymerized organic substance in the pores.
Carbonization of the organic substance is performed by heating mesoporous silica to a predetermined temperature in a non-oxidizing atmosphere (for example, in an inert atmosphere or vacuum). Specifically, the heating temperature is preferably 500 ° C. or higher and 1200 ° C. or lower. When the heating temperature is less than 500 ° C., carbonization of the organic matter becomes insufficient. On the other hand, when the heating temperature exceeds 1200 ° C., silica and carbon react with each other, which is not preferable. As the heating time, an optimum time is selected according to the heating temperature.
On the other hand, when a polymerizable gas having an unsaturated bond is used as a carbon source, it is diluted with an inert gas (N ₂ , argon, helium, etc.), and flows into a flow-through reaction tube provided with mesoporous silica. Heat at a temperature for a predetermined time (so-called “thermal CVD method”). As a result, polymerization and carbonization occur simultaneously with the adsorption of the carbon source into the pores. In the same manner, a liquid carbon source can be bubbled with an inert gas, and carbon can be deposited in mesoporous silica in one step. As the heating temperature, an optimum temperature is selected according to the type of gas.

Note that the amount of carbon generated in the pores may be more than the amount that can maintain the shape when the mesoporous silica is removed. Therefore, when the amount of carbon produced in one adsorption step, polymerization step and carbonization step is relatively small, it is preferable to repeat these steps a plurality of times. In this case, the conditions of the repeated steps may be the same or different.
When each of the adsorption, polymerization, and carbonization steps is repeated a plurality of times, each carbonization step is carbonized at a relatively low temperature, and after the last carbonization treatment is completed, carbonization is performed again at a higher temperature. Processing may be performed. When the final carbonization treatment is performed at a higher temperature than the previous carbonization treatment, the carbon introduced into the pores in a plurality of times is easily integrated.

The removing step is a step of removing mesoporous silica from the mesoporous silica / carbon composite in which carbon is generated in the pores. Thereby, the monodispersed spherical carbon porous body according to the present invention is obtained.
As a method for removing mesoporous silica, specifically,
(1) A method of heating the composite in sodium hydroxide,
(2) A method of etching the composite with an aqueous hydrofluoric acid solution,
and so on.

  Next, the manufacturing method of the monodispersed spherical carbon porous body concerning the 2nd Embodiment of this invention is demonstrated. The production method according to the present embodiment is a production method of a monodispersed spherical carbon porous body on which noble metal fine particles are supported, and includes a noble metal support step, an adsorption step, a polymerization step, a carbonization step, and a removal step. I have. Among these, the adsorption process, the polymerization process, the carbonization process, and the removal process are the same as those in the first embodiment, and thus description thereof is omitted.

The noble metal supporting step is a step of supporting noble metal fine particles in the pores of mesoporous silica before adsorbing organic substances.
Specifically, the precious metal fine particles are supported by
(1) A solution in which a noble metal compound is dissolved is adsorbed in the pores of mesoporous silica (noble metal compound adsorption step),
(2) Precipitating a noble metal compound in the pores by drying mesoporous silica (drying step),
(3) The deposited noble metal compound is reduced and converted into noble metal fine particles (reduction process).
By doing.

The noble metal compound only needs to be soluble in an appropriate solvent. In particular,
(1) Hexachloroplatinum (IV) acid hexahydrate, dinitrodiammineplatinum (II), hexaammineplatinum (IV) chloride, tetraammineplatinum (II) chloride, bis (acetylacetonato) platinum (II), etc. A Pt compound,
(2) Pd compounds such as palladium sulfate, palladium chloride, palladium nitrate, dinitrodiammine palladium (II), bis (acetylacetonato) palladium (II), trans-dichlorobis (triphenylphosphine) palladium (II),
(3) Rhodium chloride, rhodium sulfate, rhodium nitrate, rhodium acetate (II), tris (acetylacetonato) rhodium (III), chlorotris (triphenylphosphine) rhodium (I), acetylacetonatodicarbonyl rhodium (I), Rh compounds such as tetracarbonyldi-μ-chlorodirhodium (I),
(4) Ru compounds such as ruthenium chloride, ruthenium nitrate, dodecacarbonyltriruthenium (0), tris (acetylacetonato) ruthenium (III),
(5) Ir compounds such as hexachloroiridium (IV) hexahydrate, dodecacarbonyltetriiridium (0), carbonylchlorobis (triphenylphosphine) iridium (I), tris (acetylacetonato) iridium (III),
(6) Au compounds such as hexachlorogold (IV) acid hexahydrate, gold cyanide ammonium,
(7) Ag compounds such as silver nitrate and silver cyanide,
and so on. These may be used alone or in combination of two or more.

The solvent for dissolving the noble metal compound is not particularly limited, and may be water or an organic solvent such as alcohol.
The amount of the noble metal compound dissolved in the solution can be arbitrarily selected depending on the solubility of the noble metal compound in the solvent, the target loading amount, and the like. Generally, the higher the concentration of the noble metal compound, the greater the amount of adsorption of the noble metal compound per time.
Adsorption is performed by adding a solution in which a noble metal compound is dissolved in mesoporous silica and stirring at room temperature for a predetermined time (usually about several hours). Since mesoporous silica is excellent in adsorption characteristics, the noble metal compound solution can be easily adsorbed in the pores simply by adding it to the noble metal compound solution and stirring.

  Next, the mesoporous silica to which the noble metal compound solution is adsorbed is dried to deposit the noble metal compound in the pores. The heating temperature at the time of drying is not particularly limited, but is preferably equal to or higher than the boiling point of the solvent. As the heating time, an optimal time is selected according to the heating temperature so that the solvent in the pores is completely volatilized.

Next, the mesoporous silica on which the noble metal compound is supported is reduced to convert the noble metal compound in the pores into noble metal fine particles.
The reduction of the noble metal compound is performed in a hydrogen atmosphere. The optimal reduction temperature and reduction time are selected according to the type of noble metal compound. For example, when the noble metal compound is chloroplatinic acid, it is preferably heated at 150 ° C. or higher and 500 ° C. or lower for 0.5 hour or longer in a 5% hydrogen-nitrogen stream.
In addition, when the amount of noble metal fine particles supported per time is relatively small, the above-described noble metal compound adsorption step, drying step, and reduction step may be repeated a plurality of times.

  After the noble metal fine particles are supported in the pores, when the organic matter is adsorbed, polymerized and carbonized, and the mesoporous silica is removed according to the same procedure as in the first embodiment, the monodispersion in which the noble metal fine particles are supported A spherical carbon porous body is obtained.

  Next, a method for producing a monodispersed spherical carbon porous body according to the third embodiment of the present invention will be described. The manufacturing method according to the present embodiment is a manufacturing method of a monodispersed spherical carbon porous body doped with nitrogen, and includes an adsorption step, a polymerization step, a carbonization step, and a removal step. Among these, the polymerization step, the carbonization step, and the removal step are the same as those in the first embodiment, and thus description thereof is omitted.

The adsorption step is a step of adsorbing a nitrogen-containing organic substance in the pores of mesoporous silica.
The “nitrogen-containing organic substance” refers to an organic substance containing nitrogen that can generate carbon containing nitrogen by thermal decomposition. Therefore, the nitrogen-containing organic substance is preferably a nitrogen-containing heterocyclic compound.

Specifically, as nitrogen-containing organic substances,
(1) pyrrole and derivatives thereof, which are nitrogen-containing five-membered ring compounds, diazoles and derivatives thereof, triazoles and derivatives thereof,
(2) Nitrogen-containing six-membered ring compounds such as pyridine and derivatives thereof, diazines and derivatives thereof, triazines and derivatives thereof,
(3) Quinoline, phenanthroline, purine and the like obtained from nitrogen-containing condensed heterocyclic compounds.
Nitriles such as acetonitrile, acrylonitrile and benzonitrile, imines such as pyridine and ethyleneimine, and various amines can also be used.
Each of these nitrogen-containing organic substances may be used alone or in combination of two or more. Moreover, you may use combining 1 type, or 2 or more types of nitrogen-containing organic substance, and the various organic substance mentioned above. The amount of nitrogen dope can be arbitrarily changed by changing the type of the nitrogen-containing organic material and the blending ratio with various organic materials serving as the carbon source.
Since other points such as the adsorption method and adsorption conditions of the nitrogen-containing organic substance are the same as those in the adsorption step according to the first embodiment, description thereof will be omitted.

  A nitrogen-doped monodispersed spherical carbon porous body is obtained by adsorbing nitrogen-containing organic matter and, if necessary, organic matter as a carbon source into the pores, followed by polymerization, carbonization, and removal of mesoporous silica. It is done. In addition, if the noble metal fine particles are supported in the pores of the mesoporous silica before the adsorption of the nitrogen-containing organic material (and the organic material that serves as the carbon source), nitrogen is doped and the single particles on which the noble metal fine particles are supported are supported. A dispersed spherical carbon porous body is obtained.

  Since the manufacturing method according to the present invention uses a spherical mesoporous material containing silica that is monodispersed and whose pores are radially formed as a template, carbon in which the pore shape of the template is transferred as it is. A monodispersed spherical carbon porous body having an internal structure in which the carbon rods branch radially from the center of the particle, that is, from the center of the sphere to the surface, is obtained. In this case, the average particle diameter, pore diameter, specific surface area and the like of the monodispersed spherical carbon porous body can be changed by controlling the average particle diameter, wall thickness, specific surface area and the like of the template.

  The monodispersed spherical carbon porous body obtained in this way has a spherical particle shape and a small monodispersity. Therefore, when producing a structure using this, or when filling a column The packing density of carbon particles can be significantly improved. Further, the monodispersed spherical carbon porous body according to the present invention has a radial structure, and the gaps form radial pores extending from the center of the sphere toward the surface, so that the diffusion path of the substance to the inside of the sphere Becomes shorter and the utilization efficiency of the pores is improved.

  Further, when the noble metal compound is supported on the mesoporous silica before the organic substance is adsorbed, the periphery of the noble metal compound is constrained by the pore walls of the mesoporous silica. Therefore, the grain growth of the noble metal fine particles can be suppressed when the noble metal compound is reduced.

  Furthermore, in addition to or in place of the organic substance serving as the carbon source, when a nitrogen-containing organic substance is adsorbed in the pores and carbonized, a monodispersed spherical carbon porous body doped with nitrogen is obtained. When the monodispersed spherical carbon porous body is doped with nitrogen, the adsorption characteristics can be changed according to the nitrogen doping amount. For example, carbon particles are inherently hydrophobic, but hydrophilicity can also be imparted to the carbon particles by optimizing the nitrogen doping amount.

Example 1
[1. Preparation of mesoporous silica]
To 5 L of water and 5 L of methanol, 35.2 g (0.014 mol / L) of hexadecyltrimethylammonium chloride and 22.8 mL of 1N sodium hydroxide were added. To this solution, 13.2 g (0.011 mol / L) of tetramethoxysilane was added and completely dissolved. After dissolution, a white powder precipitated in about 200 seconds. The solution was further stirred at room temperature for 8 hours, and then the solution was left overnight. After standing, filtration and washing of the solution were repeated three times to obtain a white powder. The white powder was dried with a hot air dryer for 3 days and then baked at 550 ° C. to remove organic components.

[2. Preparation of monodispersed spherical carbon porous body]
0.70 mL of furfuryl alcohol was added to 1.0 g of the synthesized mesoporous silica powder and impregnated in the pores. This was heated at 150 ° C. for 24 hours to polymerize furfuryl alcohol in the pores. Further, this was baked in a nitrogen stream at 500 ° C. for 6 hours to carbonize polyfurfuryl alcohol.
Next, 0.28 mL of furfuryl alcohol was additionally added to this powder, and again heating (polymerization) at 150 ° C. for 4 hours and baking (carbonization) at 500 ° C. for 6 hours in a nitrogen stream were performed. After the second firing, the powder was further fired in a nitrogen stream at 900 ° C. for 6 hours to completely carbonize furfuryl alcohol.
The obtained powder was immersed in a 48% HF solution and stirred at room temperature for 3 hours. After the mesoporous silica was completely dissolved, the solution was filtered and washed to obtain a black powder.

[3. Evaluation]
In FIG. 1, the scanning electron micrograph of the mesoporous silica powder after baking is shown. 1 that spherical mesoporous silica particles having a uniform particle diameter are obtained. The average particle diameter of arbitrary 100 particles was 0.72 μm (monodispersity is 2.5%).
FIG. 2 shows a scanning electron micrograph of the synthesized carbon particles. FIG. 2 shows that spherical carbon particles having a uniform particle diameter are obtained. The average particle diameter of arbitrary 100 particles was 0.66 μm (monodispersity is 2.2%).
FIG. 3 shows the pore distribution of the synthesized spherical carbon particles. FIG. 3 shows that the pore distribution has a peak at 1 nm. The BET specific surface area of the spherical carbon particles obtained in this example was 1200 m ² / g.
Further, FIG. 4 shows a transmission electron micrograph of the synthesized carbon particles. As can be seen from FIG. 4, the monodispersed spherical carbon porous body obtained in this example has a particle internal structure that is radial, that is, the pores extend radially from the center toward the surface.

(Example 2)
[1. Preparation of mesoporous silica]
To 4 L of water and 6 L of methanol, 38.3 g (0.014 mol / L) of octadecyltrimethylammonium chloride and 22.8 mL of 1N sodium hydroxide were added. To this solution, 13.2 g (0.011 mol / L) of tetramethoxysilane was added and completely dissolved. After dissolution, a white powder precipitated in about 200 seconds. The solution was further stirred at room temperature for 8 hours, and then the solution was left overnight. After standing, filtration and washing of the solution were repeated three times to obtain a white powder. The white powder was dried with a hot air dryer for 3 days and then baked at 550 ° C. to remove organic components.

[2. Preparation of monodispersed spherical carbon porous body]
0.80 mL of furfuryl alcohol was added to 1.0 g of the synthesized mesoporous silica powder and impregnated in the pores. This was heated at 150 ° C. for 24 hours to polymerize furfuryl alcohol in the pores. Further, this was baked in a nitrogen stream at 500 ° C. for 6 hours to carbonize polyfurfuryl alcohol.
Next, 0.32 mL of furfuryl alcohol was additionally added to this powder, and again heating (polymerization) at 150 ° C. for 4 hours and baking (carbonization) at 500 ° C. for 6 hours in a nitrogen stream were performed. After the second firing, the powder was further fired in a nitrogen stream at 900 ° C. for 6 hours to completely carbonize furfuryl alcohol.
The obtained powder was immersed in a 48% HF solution and stirred at room temperature for 3 hours. After the mesoporous silica was completely dissolved, the solution was filtered and washed to obtain a black powder.

[3. Evaluation]
The average particle diameter of arbitrary 100 particles obtained from the scanning electron micrograph of the powder obtained in this example was 0.90 μm (monodispersity is 4.0%).

(Example 3)
[1. Supporting Pt fine particles]
0.067 g of hexachloroplatinic (IV) acid hexahydrate was dissolved in 50 mL of methanol. To this solution, [1. ] 0.5 g of the mesoporous silica powder synthesized in the above was added and stirred at room temperature for 1 hour. After evaporating methanol with a rotary evaporator, it was heated in a 5% hydrogen-nitrogen stream at 400 ° C. for 2 hours to obtain Pt-dispersed silica powder.

[2. Preparation of Pt-supported monodispersed spherical carbon porous body]
0.16 mL of furfuryl alcohol was added to 0.3 g of Pt-dispersed silica powder and impregnated in the pores. This was heated at 150 ° C. for 24 hours to polymerize furfuryl alcohol in the pores. Further, this was baked in a nitrogen stream at 500 ° C. for 6 hours to carbonize polyfurfuryl alcohol.
Next, 0.07 mL of furfuryl alcohol was additionally added to this powder, and again heating (polymerization) at 150 ° C. for 4 hours and baking (carbonization) at 500 ° C. for 6 hours in a nitrogen stream were performed. After the second firing, the powder was further fired in a nitrogen stream at 900 ° C. for 6 hours to completely carbonize furfuryl alcohol.
The obtained powder was immersed in a 48% HF solution and stirred at room temperature for 3 hours. After the mesoporous silica was completely dissolved, the solution was filtered and washed to obtain a black powder.

[3. Evaluation]
FIG. 5 shows an X-ray diffraction pattern of the obtained powder. As can be seen from FIG. 5, a peak corresponding to Pt is recognized, and carbon powder in which Pt is dispersed is obtained. The crystallite diameter of Pt obtained from the half width of the X-ray diffraction peak by the Scherrer equation was about 2 nm. Moreover, the BET specific surface area of the obtained powder was 1100 m < ² > / g. Furthermore, the pore distribution had a peak at 1 nm.

Example 4
[1. Preparation of nitrogen-doped monodispersed spherical carbon porous body]
0.952 g (0.01 mol) of pyrrole-2-carboxaldehyde was completely dissolved in 1 mL of furfuryl alcohol. To this solution, [1. ] 1.0 g of mesoporous silica synthesized in the above was added and impregnated in the pores. This was heated at 150 ° C. for 24 hours to polymerize organic substances in the pores. Further, this was baked at 500 ° C. for 6 hours in a nitrogen stream to carbonize the organic polymer.
Next, 0.28 mL of a furfuryl alcohol solution of pyrrole-2-carboxaldehyde was added to this powder, and again heating (polymerization) at 150 ° C. for 4 hours and firing at 500 ° C. for 6 hours in a nitrogen stream (carbonization) ) After the completion of the second firing, this powder was further fired in a nitrogen stream at 900 ° C. for 6 hours to completely carbonize the organic polymer.
The obtained powder was immersed in a 48% HF solution and stirred at room temperature for 3 hours. After the mesoporous silica was completely dissolved, the solution was filtered and washed to obtain a black powder.

[2. Evaluation]
The BET specific surface area of the powder obtained in this example was 1100 m ² / g. The pore distribution had a peak at 1 nm. Furthermore, as a result of analyzing by X-ray photoelectron spectroscopy (XPS) method, it was confirmed that nitrogen was doped 5%.
When XPS spectral peak separation was performed, it was found that peaks exist at positions of 401.1 eV and 398.6 eV. The former corresponds to a quaternary nitrogen atom surrounded by three sp ² carbons and located inside the graphene layer, and the latter is sandwiched between ^two sp ² carbons at the end of the graphene layer. Corresponds to the pyridinic nitrogen atom located. When the ratio was calculated from the peak area, the ratio of the nitrogen atom in the quaternary state to the nitrogen atom in the pyridinic state was 2: 1. From this result, it was confirmed that in the nitrogen-doped monodispersed spherical carbon porous body, the nitrogen atoms are not lost from the skeleton and form a skeleton together with the carbon atoms in two kinds of chemical bonds.
FIG. 6 shows the result of comparing the water vapor adsorption isotherm of the monodispersed spherical carbon porous body synthesized in Example 1 and the nitrogen-doped monodispersed spherical carbon porous body synthesized in Example 4. The nitrogen-doped monodispersed spherical carbon porous body adsorbs water vapor from a lower water vapor pressure, indicating that the hydrophilicity was improved by nitrogen doping.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the present invention.

  The monodispersed spherical carbon porous material according to the present invention can be used for an adsorbent, a catalyst, a catalyst carrier, an electric double layer capacitor, a sensor, an electrode, a filler for liquid chromatography, and the like.

2 is a scanning electron micrograph of mesoporous silica particles obtained in Example 1. FIG. 2 is a scanning electron micrograph of monodisperse spherical carbon porous particles obtained in Example 1. FIG. FIG. 3 is a diagram showing the pore distribution of the monodispersed spherical carbon porous body obtained in Example 1. 2 is a transmission electron micrograph of monodispersed spherical carbon porous particles obtained in Example 1. FIG. 3 is an X-ray diffraction pattern of a Pt-supported monodispersed spherical carbon porous body obtained in Example 3. It is a figure which shows the water vapor | steam adsorption characteristic of the monodispersed spherical carbon porous body obtained in Example 1, and the nitrogen dope monodispersed spherical carbon porous body obtained in Example 4.

Claims (8)

Consisting of spherical carbon particles,
It has pores extending radially from the center to the surface inside, and
A monodispersed spherical carbon porous body having a monodispersity represented by the following formula (1) of 10% or less.
Monodispersity = (standard deviation of particle diameter / average particle diameter) × 100 (%) (1)   The monodispersed spherical carbon porous body according to claim 1, wherein the average particle size is 50 nm or more and 2 µm or less. The monodispersed spherical carbon porous body according to claim 1 or 2, which has a specific surface area of 1000 m ² / g or more.   The monodispersed spherical carbon porous body according to any one of claims 1 to 3, wherein the pore distribution has a peak at 0.5 nm or more and 2.0 nm.   The monodispersed spherical carbon porous body according to any one of claims 1 to 4, wherein noble metal fine particles are supported inside the carbon particles.   The monodispersed spherical carbon porous body according to claim 5, wherein a particle diameter of the noble metal fine particles is 5.0 nm or less.   The monodispersed spherical carbon porous body according to claim 5 or 6, wherein the supported amount of the noble metal fine particles is 80 wt% or less.   The monodispersed spherical carbon porous body according to any one of claims 1 to 7, wherein the carbon particles are doped with nitrogen.

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