JP2019119632A - Porous carbon, and production method thereof - Google Patents

Abstract

To produce porous carbon having an oxygen-containing functional group such as a hydroxyl group, a carbonyl group, and a carboxyl group, and a functional group such as an alkyl group by a simple process of low energy consumption from an inexpensive carbon precursor (carbon source).SOLUTION: Porous carbon is produced by a simple process of low energy consumption in which a fatty acid ester of sugar as a carbon precursor (carbon source) is subjected to hydrothermal treatment at 100-350°C without using a structural mold agent (template), wherein the porous carbon has an oxygen-containing functional group such as a hydroxyl group, a carbonyl group, and a carboxyl group, and a functional group such as an alkyl group.SELECTED DRAWING: Figure 1

Description

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

  Porous carbon is a material which is very important in the industry as an adsorbent, separating material, catalyst carrier, column carrier, drug-containing material, etc. by utilizing its pores. Furthermore, in recent years, the use as a carbon electrode in secondary batteries, capacitors, sensors, etc., in which the pore space is used as an efficiency transfer space for electrolytes, has been widely put to practical use. The porous carbon which provided functionality by modification is preferably used.

Porous carbon can be produced by various methods, one of which is using amphiphilic compounds such as surfactants or block copolymers as structural templating agents, in the presence of carbon precursors (carbon sources There is a so-called organic template method in which carbonization of) is advanced.
For example, Patent Document 1 describes that after forming a micelle of a surfactant which is a template in a monomer and / or prepolymer, the monomer and / or prepolymer is polymerized and cured to form a micelle-containing organic polymer. Furthermore, a method of calcining this organic polymer to carry out carbonization is disclosed. Patent Document 2 and Non-Patent Documents 1 and 2 disclose that a block copolymer is used as a structure templating agent and a phenol-based resin such as phenol and formaldehyde or resorcinol is used as a carbon precursor. It is done.
However, in these methods, there are few oxygen-containing functional groups in the molecules of the raw material, high temperature heat treatment is necessary for carbonization, and at this time the functional groups are lost, etc. The amount of oxygenated functional groups in it is limited. Therefore, it is difficult to impart functionality to carbon by chemical modification, which is important for use as a separation carrier or an electrode material. Moreover, the carbon materials obtained by these methods are expected to have limited applications in the aqueous phase.

On the other hand, it is already known that the carbon skeleton of a carbon material comprising a hydrothermal reaction product of sugar contains a furan skeleton as a basic skeleton, and according to hydrothermal synthesis using sugar or biomass as a raw material, an oxygen-containing functional group An abundant carbon material is obtained (non-patent documents 3 and 4). Moreover, it is also known that a carbon material doped with nitrogen can be obtained by hydrothermal synthesis using a nitrogen-containing sugar such as chitin, chitosan, glucoseamine as a carbon source (Non-patent Document 5).
Porous carbon can be obtained by combining hydrothermal synthesis of such a sugar with a synthesis method using an amphiphilic compound such as a block copolymer as an organic template (Non-patent Document 6). However, currently published processes using an organic template require thermal removal of the structural templating agent by heat treatment under an inert atmosphere of several hundred degrees C. or higher (eg 550 degrees C.), and the energy cost in synthesis is It costs extra. Moreover, it can not prevent that the quantity of surface functional groups reduces at the time of heat processing.

In addition, as an inorganic template method, an inorganic porous body such as a porous silica body is used as a structural template, a carbon precursor (carbon source) such as saccharides is immersed in the pores thereof, and then hydrothermal treatment is performed. There is a method of dissolving and removing the inorganic porous material with a strong acid such as hydrofluoric acid (Non-patent Documents 7 and 8). According to this method, a porous carbon material having surface functional groups can be obtained.
However, the pore structure of the obtained porous body is the reverse structure (replica) of the silica porous body, and does not directly reflect the structure of the above-mentioned higher-order aggregate such as surfactant or amphiphilic polymer. . For example, it seems very difficult to obtain a honeycomb channel structure called a hexagonal structure. Furthermore, this method requires the synthesis of the porous silica itself and a step that is incompatible with industrial production such as etching with a strong acid, which is problematic in terms of practical application in the industrial world.

On the other hand, Patent Document 4 and Non-Patent Document 9 describe that porous carbon having mesopores is obtained without using a structural templating agent (template), using a carbohydrate such as alginic acid, pectin, amylose, or chitosan as a raw material. It is done. In the methods described in these documents, polysaccharides are dissolved in water and heated to obtain gels with high viscosity, and by cooling the gels, polysaccharide gels in which polysaccharide molecules are linked by hydrogen bonds are obtained. The obtained polysaccharide gel is then dried and then calcined at a temperature of several hundreds ° C. in a vacuum or an inert atmosphere in the presence of an organic acid to obtain porous carbon.
However, in this method, the structure formation is based on the swelling of the polysaccharide network by water and the hydrogen bond between the polysaccharide molecules, so induction of the orientation in the structure formation is not easy, and hence the nanostructure of the resulting carbon material It is difficult to give clear orientation or to control the degree and type of orientation. Moreover, the aromatization of the carbon network proceeds by firing, and when firing is performed at a temperature of about 400 ° C. or more, most of the oxygen-containing functional groups are lost.

Unexamined-Japanese-Patent No. 2004-59904 JP 2014-34475 A JP, 2010-267542, A International Publication No. 2009/037354

Y. Meng, D .; Gu, F. et al. Zhang, Y .; Shi, H. Yang, Z. Li, Z. Yu, B. Tu, D. Zhao, Angew. Chem. Int. Ed. 2005, 44, 7053-7059. C. Liang, K .; Hong, G. et al. A. Guiochon, J.J. W. Mays, S. Dai, Angew. Chem. Int. Ed. 2004, 43, 5785-5789. M-M. Titirici, M .; Antonietti, Chem. Soc. Rev. 2010, 39, 103-116. C. Falco, F., et al. P. Caballero, F .; Babonneau, C .; Gervais, G., et al. Laurent. M-M, Titirici. N. Baccile, Langmuir, 2011, 27, 14460. R. J. White, M. Antonietti, M-M. Titirici, J.J. Mater. Chem. 2009, 19, 8645. S. Kubo, R .; J. White, N.J. Yoshizawa, M .; Antonietti, M-M. Titirici, Chem. Mater. 2011, 23, 482-488. M-M. Titirici, A .; Thomas, M .; Antonietti, J.J. Mater. Chem. 2007, 17, 3412-3418. M-M. Titirici, A .; Thomas, M .; Antonietti, Adv. Funct. Mater. 2007, 17, 1010-1018. Budarin et al. , Angew. Chem. Int. Ed. 2006, 45, 378-2786.

  As described above, it is desired to obtain porous carbon having a functional group using an inexpensive raw material in a simple and energy-saving manner. In addition, it is expected to form a laminate with a thin film, a single molecule / bilayer film, and various substrates by utilizing the possibility of directly and precisely controlling the polymerization of a carbon source.

  The present invention has been made in view of the present situation, and uses an inexpensive carbon precursor (carbon source) in a simple and energy-saving manner, using an oxygen-containing compound such as a hydroxyl group, a carbonyl group or a carboxyl group. An object of the present invention is to provide porous carbon having a functional group or a functional group such as an alkyl group.

  As a result of intensive studies aimed at achieving the above object, by using a fatty acid ester of sugar as a carbon precursor (carbon source), it is possible to use a simple and energy-saving method without using a structural templating agent (template). It has been found that porous carbon having a functional group such as an oxygen-containing functional group such as a hydroxyl group, a carbonyl group or a carboxyl group, or an alkyl group can be produced.

The present invention has been completed based on these findings, and according to the present invention, the following inventions are provided.
[1] Porous carbon consisting of a hydrothermal reaction product made from fatty acid esters of sugars.
[2] The porous carbon according to [1], wherein the carbon skeleton contains an alkyl group derived from the fatty acid.
[3] The porous carbon according to [1] or [2], wherein the alkyl group of the fatty acid is an alkyl group having 1 to 100 carbon atoms which may contain a double bond.
[4] Porous carbon consisting of a fired product of a hydrothermal reaction product made from fatty acid esters of sugars.
[5] The porous carbon according to [4], which contains a hydroxyl group in its carbon skeleton.
[6] The porous carbon according to any one of [1] to [5], wherein the sugar is a monosaccharide, a disaccharide or a polysaccharide which may contain nitrogen, or a mixture of two or more of them.
[7] The porous carbon according to any one of [1] to [6], wherein the fatty acid ester of the sugar is a monoester, a diester or a polyester, or a mixture of two or more thereof.
[8] The porous carbon according to any one of [1] to [7], wherein the total pore volume calculated by nitrogen adsorption measurement is 0.04 to ⁵ cm ³ / g.
[9] The porous carbon according to any one of [1] to [8], which has an oriented nano structure.
[10] An adsorbent mainly composed of porous carbon according to any one of [1] to [9].
[11] A porous carrier comprising the porous carbon as a main component according to any one of [1] to [9].
[12] The porous carrier according to [11], wherein the porous carrier is any of a catalyst carrier, a separation carrier, a chromatography carrier, a biomolecule scaffolding material, a biomolecule capturing material, a drug-containing material or a fragrance carrier.
[13] An electrode material containing porous carbon as a main component according to any one of [1] to [9].
The secondary battery provided with the electrode using the electrode material as described in [14] [13].
[15] An electrochemical capacitor comprising an electrode using the electrode material according to [13].
[16] A fuel cell provided with an electrode using the electrode material according to [13].
The sensor provided with the electrode using the electrode material as described in [17] [13].
[18] A food additive based on porous carbon according to any one of [1] to [9].
[19] A food containing porous carbon according to any one of [1] to [9].
[20] A cosmetic additive based on porous carbon according to any one of [1] to [9].
[21] A method for producing porous carbon comprising hydrothermally treating a fatty acid ester of a sugar at 100 to 350 ° C., washing the obtained solid with water and an organic solvent, and drying it.
[22] The method for producing porous carbon according to [21], wherein the alkyl group of the fatty acid is an alkyl group having 1 to 100 carbon atoms which may contain a double bond.
[23] The method for producing porous carbon according to [21] or [22], wherein the sugar is a monosaccharide, a disaccharide or a polysaccharide which may contain nitrogen, or a mixture of two or more thereof.
[24] The method for producing porous carbon according to any one of [21] to [23], wherein the fatty acid ester of the sugar is a monoester, a diester or a polyester, or a mixture of two or more thereof.
[25] A method for producing porous carbon, comprising the steps of producing porous carbon by the method according to any one of [21] to [24], and further calcining.

  According to the present invention, using inexpensive raw materials, it is simple and energy-saving to form porous carbon while leaving functional groups derived from raw materials such as hydroxyl-containing functional groups such as hydroxyl groups, carbonyl groups and carboxyl groups and alkyl groups. It can be obtained by a method of low consumption. Moreover, according to the present invention, not only the aromaticity is enhanced but also porous carbon having an oxygen-containing functional group such as a hydroxyl group can be obtained in the porous carbon after firing in an inert atmosphere. Furthermore, according to the present invention, sheet-like carbon (carbon thin film) having a thickness of several tens to about 200 nm can be obtained.

Fourier Transform Infrared Absorption Spectra of Materials Obtained in Examples 1 to 6 and Comparative Examples 1 and 2 Fourier Transform Infrared Absorption Spectra of Materials Obtained in Examples 7 to 8 and Comparative Example 3 Nitrogen adsorption isotherm of materials obtained in Examples 1 to 8 Nitrogen adsorption isotherm of materials obtained in Comparative Examples 1 and 2 Scanning electron microscope image of the material obtained in Example 1 Transmission electron microscope image of the material obtained in Example 1 Scanning electron microscope image of the material obtained in Example 2 Transmission electron microscope image of the material obtained in Example 2 Scanning electron microscope image of the material obtained in Example 3 Scanning electron microscope image of the material obtained in Example 4 Transmission electron microscope image of the material obtained in Example 4 Scanning electron microscope image of the material obtained in Example 5 Transmission electron microscope image of the material obtained in Example 5 Scanning electron microscope image of the material obtained in Example 6 Scanning electron microscope image of the material obtained in Comparative Example 1 Transmission electron microscope image of the material obtained in Comparative Example 1 Scanning electron microscope image of the material obtained in Comparative Example 2 Scanning electron microscope image of the material obtained in Example 7 Transmission electron microscope image of the material obtained in Example 7 Scanning electron microscope image of the material obtained in Example 8 Scanning electron microscope image of the material obtained in Comparative Example 3

The porous carbon of the present invention is obtained by a hydrothermal reaction using a fatty acid ester of sugar as a raw material, and by using a fatty acid ester of sugar as a raw material, the carbon skeleton which is a basic skeleton is It is characterized in that it contains an alkyl group derived from a fatty acid ester, or consists of a calcined product of the product obtained by the hydrothermal reaction.
Moreover, the method for producing porous carbon of the present invention uses a fatty acid ester of sugar as a carbon precursor (carbon source), which is hydrothermally treated at 100 to 350 ° C., and the obtained solid is washed with water and an organic solvent It is then characterized by drying or baking.

In the present invention, since the fatty acid ester of sugar used as a raw material of the hydrothermal reaction is an amphiphilic molecule, porous carbon can be obtained without using a conventional template.
Further, according to the present invention, since the calcining step required to remove the template as in the prior art is not required, an oxygen-containing functional group such as a hydroxyl group, a carbonyl group or a carboxyl group and an alkyl derived from the above amphiphilic molecule Porous carbon having a functional group such as a group can be obtained.
Furthermore, according to the method of the present invention using sucrose fatty acid ester, which is an amphiphilic molecule, as a raw material, sheet carbon (carbon thin film) having a thickness of about several tens to 200 nm, monomolecular / bimolecular film, and various substrates It is possible to form a laminate with the

  Hereinafter, the porous carbon of the present invention and the method for producing the same will be described in more detail.

[Fatty acid ester of sugar]
In the present invention, fatty acid esters of sugar are used as a carbon source of hydrothermal reaction.
The sugar may be any of monosaccharides such as fructose and glucose, disaccharides such as sucrose, polysaccharides such as alginic acid, pectin and amylose, and nitrogen-containing sugars such as chitin, chitosan and glucoseamine, or two of these It may be a mixture of more than one kind.
In addition, as the fatty acid ester, a monoester of 1 fatty acid, a diester of 2 or a polyester of 3 or more, or a mixture of 2 or more of these is used.

  Thus, the fatty acid ester of the sugar used in the present invention is not particularly limited, and examples thereof include those represented by the following formulas 1 to 3 or mixtures thereof. However, in the formula, the fatty acid moiety may be introduced at a site different from the above-mentioned chemical structural formula. In other words, it does not matter which OH group of the sugar is esterified to extend the alkyl group.

The alkyl group of the fatty acid may contain a double bond, and in the above formula, n is 1 to 100, preferably 1 to 50, more preferably 1 to 20.
The fatty acid ester of the sugar of the present invention may be used as a mixture of fatty acid esters of sugars having different alkyl chain lengths, and further, in the case of diesters and polyesters, two or more different alkyls per molecule of fatty acid ester of one sugar. The chain length may be included. In other words, in diesters and polyesters, alkyl groups of different chain lengths may extend from the OH group in one molecule of sugar.
The fatty acid ester of sugar in the present invention may be a synthetic product or a commercially available product. Specific examples of readily available commercial products include sucrose laurate, sucrose stearate, sucrose behenate and the like.

Hydrothermal synthesis
The porous carbon of the present invention is synthesized in the following steps 1 to 3.
Step 1: Dissolve sugar fatty acid ester in water and tightly heat the solution Step 2: Recover the resulting solid, wash at room temperature, and dry Step 3: Dry the dried solid under heating A step of drying after solvent washing However, depending on the type of raw material to be used, step 3 may be omitted.
The following will be described in order.

(Step 1)
The above step 1 is carried out by heating an aqueous solution of a fatty acid ester of sugar having a concentration of 1 to 70% by weight (hereinafter sometimes referred to as “raw material aqueous solution”) at 100 to 350 ° C. in a sealed container for 1 hour or more. It will be.
For example, an amphiphilic polymer such as polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer conventionally used in a raw material aqueous solution which is a raw material of a hydrothermal reaction, or a general interface such as sodium dodecyl sulfate Activators, organic colloids such as polystyrene particles, or inorganic colloids such as silica particles may be added and used. Moreover, you may add and use inorganic porous template agents, such as the conventional silica porous body. Also, two or more of these conventional template agents may be mixed and added.
In addition, conventional monosaccharides such as fructose and glucose, disaccharides such as sucrose, polysaccharides such as alginic acid, pectin and amylose, or nitrogen-containing sugars such as chitin, chitosan and glucoseamine, or the like in the raw material aqueous solution A mixture of two or more of these may be added.
Further, an additive for doping nitrogen or sulfur may be added to the raw material aqueous solution. Such additives include cysteine, albumin, ovalbumin, thiophene aldehyde and the like.
Moreover, you may add and synthesize | combine a pH adjuster in the said raw material aqueous solution.
Furthermore, an acid such as an inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid or boronic acid or an organic acid such as toluenesulfonic acid or a base such as an inorganic base such as sodium hydroxide or ammonium hydroxide is added to the aqueous solution of the raw material. It is good.
Furthermore, as a pore swelling agent, for example, an organic additive such as hexane, trimethylbenzene or cymene may be added.
Furthermore, they may be used in combination with o / w emulsions and colloid dispersants.

(Steps 2 and 3)
The porous carbon of the present invention can be obtained by washing the solid obtained by the hydrothermal synthesis reaction with water and an organic solvent and then drying it. The organic solvent is not particularly limited, but ethanol, acetone, diethyl ether and the like are preferably used.
Specifically, the brown solid obtained after hydrothermal synthesis is washed with a sufficient amount of water and an organic solvent respectively at a temperature of room temperature or more, and then dried at a temperature of room temperature or more for 3 hours or more. It may be dried under vacuum conditions. A sufficient amount of the organic solvent is added to the brown solid after this drying, and the mixture is stirred and washed at a temperature of room temperature or more for 1 hour or more. The brown solid after stirring and washing is dried at a temperature above room temperature for 3 hours or more to obtain a porous carbon material derived from the target fatty acid of sugar. It may be dried under vacuum conditions. The stirring and washing with an organic solvent and the subsequent drying step may be omitted depending on the type of fatty acid ester of sugar used.
Instead of the first drying described above, drying by lyophilization may be performed. That is, after washing with a sufficient amount of water and an organic solvent, the organic solvent contained in the sample is replaced with water and then freeze-dried.
After the second drying described above, washing with a base may be performed.

[Hydrothermal reaction product]
In the present invention, porous carbon obtained by hydrothermal synthesis using a fatty acid ester of a sugar as a raw material has an oxygen-containing functional group derived from a sugar and an alkyl group derived from a fatty acid in a carbon skeleton, It forms a massive shape of 100 μm and a sheet-like shape with a thickness of several nm to several μm. The massive and sheet-like shapes further have a structure in which fine particles of several to several tens of nm are connected to one another or a bicontinuous structure of several to several tens of nm in thickness. Furthermore, the connection form of the present fine particles can have a gentle orientation. The obtained powder exhibits a pore volume of 0.04 to ³ cm ³ / g in pore evaluation by nitrogen adsorption.

(Firing treatment under inert atmosphere)
In general, the carbon skeleton obtained from saccharides by hydrothermal synthesis proceeds by firing in an inert atmosphere at 400 to 500 ° C. or more, the aromatization of the carbon skeleton proceeds, and the carbon material It is known that it can be used as an electrode material or the like having good electrical conductivity.
Also in the present invention, the aromaticity can be enhanced by further baking the dried porous carbon under an inert atmosphere.
Specifically, the dried porous carbon is fired at a temperature of 200 ° C. or more under an inert gas flow of 50 mL / min or more. Nitrogen, argon, helium or the like is used as the inert gas.

After calcining the carbon material obtained from the sugar, the carbon material proceeds with aromatization of the carbon network, and when calcinated usually at a temperature of about 400 ° C. or more, most of the oxygen-containing functional groups are lost ( Patent Document 4 and Non-Patent Document 9).
On the other hand, the porous carbon obtained by firing the carbon material obtained from the hydrothermal synthesis of fatty acid esters of sugars in the present invention in an inert atmosphere has relatively high aromaticity and oxygen-containing functional properties. It is characterized by containing a group (hydroxyl group).
In the present invention, the porous carbon after firing has a massive shape of several to several hundred μm in size and a sheet-like shape of several nm to several μm in thickness, and is a massive and sheet-like shape. Furthermore, it has a structure in which fine particles of several to several tens of nm are connected to each other.

Furthermore, the porous carbon after this calcination in the present invention exhibits a pore volume of 0.2 to ⁵ cm ³ / g in pore evaluation by nitrogen adsorption. Usually, the pore volume when the carbon material obtained from the sugar itself is similarly calcined under an inert atmosphere is 0.15 cm ³ g ⁻¹ or less (L. Yu et al., Langmuir, 2012, 28. From the viewpoint of 12373), it can be said that in the present invention, by using a fatty acid ester of sugar as a raw material, one having a larger pore volume can be obtained.

The porous carbon consisting of a hydrothermal reaction product starting from a fatty acid ester of a sugar according to the present invention or the porous carbon consisting of a fired product of the hydrothermal reaction product utilizes its small pores (pores) Not only can it be used as a porous carrier such as adsorbent and catalyst carrier, separation carrier, chromatography carrier, biomolecule scaffolding material, biomolecule trapping material, drug inclusion material or perfume carrier, the pore space can be used as electrolyte It can be used as a carbon electrode for secondary batteries, capacitors, fuel cells, sensors, etc., which were used as an efficient moving space.
In addition, since the porous carbon of the present invention uses fatty acid esters of sugar as a raw material, it has not only a small environmental load, but is preferably used for medical applications such as biomolecular scaffolds, biomolecular capture agents, and drug inclusion materials. It can also be used as food, food additive, cosmetic additive and the like.
In addition, since the porous carbon of the present invention has functional groups such as an oxygen-containing functional group such as a hydroxyl group, a carbonyl group and a carboxyl group or an alkyl group derived from a fatty acid ester of sugar, various kinds of functional groups can be used using these functional groups. The porous carbon which provided the functionality of (1) can be provided.

  EXAMPLES The present invention will be described in more detail based on examples given below, but the invention is not meant to be limited thereby.

[Evaluation method]
The functional groups contained in the carbon materials obtained in Examples and Comparative Examples described below were confirmed by Fourier transform infrared absorption spectroscopy.
1 (A) and (B) show Fourier transform infrared absorption spectra of the carbon materials obtained in Examples 1 to 6 and Comparative Examples 1 and 2, and (B) shows absorption peaks of alkyl groups derived from fatty acids. In order to analyze in detail, the wave number 4000-2000 cm < ^-1 > range of the spectrum of (A) is expanded.
FIG. 2 shows Fourier transform infrared absorption spectra of the carbon materials obtained in Examples 7 and 8 and Comparative Example 3.

Moreover, the total pore volume of the carbon material obtained by the Example and the comparative example was measured by the nitrogen adsorption method.
FIG. 3 is a nitrogen adsorption isotherm of the carbon materials obtained in Examples 1 to 8, and FIG. 4 is a nitrogen adsorption isotherm of the carbon materials obtained in Comparative Examples 1 and 2.

Furthermore, about the carbon material obtained by the Example and the comparative example, observation by a scanning electron microscope and a transmission electron microscope was performed. In addition, the observation by a transmission electron microscope is for observing the obtained particles in more detail, and the obtained carbon material is embedded in a thermosetting resin, and the embedding material is used as a microtome. A thin slice sample obtained by slicing to a thickness of several tens to 100 nm was observed.
5 to 21 are respective observation images of the carbon materials obtained in Examples and Comparative Examples.

Example 1
(Step 1)
Sucrose stearic acid ester (Daiichi Kogyo Seiyaku Co., Ltd. DK ester SS, HLB19, monoester ratio; about 100%) represented by molecular formula C ₃₀ H ₅₇ O ₁₂ as fatty acid ester of sugar 10 mL of deionized water Dissolved in water. After left to stand overnight, it was heated at 120 ° C. for 103 hours in a closed vessel.
(Step 2)
The resulting brown solid was collected. The top layer, which usually separates into three layers and precipitates, is the smallest in specific gravity. After pouring about 40 mL of deionized water and shaking with a shaker, it was centrifuged to precipitate a solid. The supernatant solution was removed, the same amount of deionized water was poured again, and the same operation was repeated twice more. Then, about 40 mL of ethanol was poured, and similarly shaken and centrifuged. The supernatant solution was removed, and this operation was repeated twice more. The resulting precipitate was dried at 65 ° C. overnight or more.
(Step 3)
To the dried brown solid was added 50 mL of ethanol, and the mixture was stirred and washed at 60 ° C. overnight. After washing, centrifugation was performed, and after removing the supernatant, 40 mL of ethanol was added and shaken at room temperature. After centrifugation, the supernatant was removed. This operation was repeated once more. The precipitate was dried at 65 ° C. overnight or more to obtain a target sucrose fatty acid ester-derived carbon material.

(Fourier transform infrared absorption spectrum)
In the carbon material obtained in Example 1, a peak attributed to C = O (stretching, 1800 to 1520 cm ⁻¹ ) or OH (stretching, 3700 to 3100 cm ⁻¹ ) derived from a carboxyl group or a carbonyl group is observed Thus, it was found that an oxygen-containing functional group was present in the carbon material. Furthermore, characteristic peaks are seen in the alkyl group derived from fatty acid in the vicinity of 2955 cm ⁻¹ (CH ₃ symmetric stretching vibration), in the vicinity of 2920 cm ⁻¹ (vCH ₂ antisymmetry), and in the vicinity of 2851 cm ⁻¹ (vCH ₂ symmetry) It turned out that it also has an alkyl group.

(Nitrogen adsorption isotherm)
The carbon material obtained in Example 1 showed a slight rise in the isotherm near high relative pressure, and the calculated total pore volume was 0.04 cm ³ / g (Table 2). .

(Scanning electron microscope image and transmission electron microscope image)
The scanning electron microscope image of the carbon material obtained in Example 1 is shown in FIG. It was observed that particles of several to several tens of nm were connected to one another to form particles of several to several tens of μm in size.
A transmission electron microscope image of the carbon material obtained in Example 1 is shown in FIG. It was observed that a bicontinuous structure with a stem thickness of several tens of nm was formed.

Therefore, from this example, it was found that porous carbon was obtained by hydrothermal synthesis using a fatty acid ester of sugar as a raw material, and the material had an oxygen-containing functional group and an alkyl group.
In the step 2 of Example 1, the lowermost layer having the largest specific gravity was taken out of the solid separated into three layers and the carbon material was obtained even if other operations were performed in the same manner as in Example 1. However, the carbon material did not have an alkyl group derived from fatty acid.

Example 2
In the present example, the same sucrose fatty acid ester as in Example 1 was used, and in Step 2, the intermediate layer with the second smallest specific gravity was taken out. The steps in this example are shown below.
(Step 1)
Sucrose stearic acid ester (Daiichi Kogyo Seiyaku Co., Ltd. DK ester SS, HLB19, monoester ratio; about 100%) represented by molecular formula C ₃₀ H ₅₇ O ₁₂ as fatty acid ester of sugar 10 mL of deionized water Dissolved in water. After left to stand overnight, it was heated at 120 ° C. for 103 hours in a closed vessel.
(Step 2)
The resulting brown solid was collected. Usually, the layer was separated into three layers, but the intermediate layer having the second smallest specific gravity was taken out unlike the first example. About 40 mL of deionized water was poured, shaken with a shaker, and centrifuged to precipitate a solid. The supernatant solution was removed, the same amount of deionized water was poured again, and the same operation was repeated twice more. Then, about 40 mL of ethanol was poured, and similarly shaken and centrifuged. The supernatant solution was removed, and this operation was repeated twice more. The resulting precipitate was dried at 65 ° C. overnight or more.
(Step 3)
To the dried brown solid was added 50 mL of ethanol, and the mixture was stirred and washed at 60 ° C. overnight. After washing, centrifugation was performed, and after removing the supernatant, 40 mL of ethanol was added and shaken at room temperature. After centrifugation, the supernatant was removed. This operation was repeated once more. The precipitate was dried at 65 ° C. overnight or more to obtain a target sucrose fatty acid ester-derived carbon material.

(Fourier transform infrared absorption spectrum)
In the carbon material obtained in Example 2, a peak attributed to C = O (stretching, 1800 to 1520 cm ^-1 ) or OH (stretching, 3700 to 3100 cm ^-1 ) derived from a carboxyl group or a carbonyl group is observed Thus, it was found that an oxygen-containing functional group was present in the carbon material. Furthermore, a characteristic peak is seen in the alkyl group derived from fatty acid near wave number 2955 cm ⁻¹ (CH ₃ symmetrical stretching vibration), near 2924 cm ⁻¹ (vCH ₂ antisymmetry), and near 2853 cm ⁻¹ (vCH ₂ symmetry) And alkyl groups were also found to be present.

  Here, it can not be denied that the observed alkyl group may be generated as a result of physical mixing of the fatty acid to the carbon material as the ester bond in the sucrose fatty acid ester molecule as the raw material is broken under hydrothermal conditions. Therefore, in order to confirm that the present alkyl group is not derived from the fatty acid physically mixed in the carbon material, but is generated as a result of the alkyl group being incorporated into the carbon skeleton by covalent bond, in Example 2, After performing the operation of step 3 twice, Fourier transform infrared absorption measurement was performed, and peak intensities of fatty acid-derived alkyl groups in infrared absorption spectra before and after this step were compared. Fatty acids are usually hardly soluble in water (solubility: 0.0003%, 20 ° C.) but soluble in heated ethanol. If the alkyl group and the carbon are physically mixed, more alkyl groups should be removed after washing twice, which should reduce the peak strength of the alkyl group seen above .

The Fourier transform infrared absorption spectrum after performing step 3 twice is shown in FIGS. 1 (A) and (B) (a spectrum labeled “Example 2 (after washing twice with EtOH)”). Also for the material subjected to step 3 twice, fatty acid-derived alkyl at a wavenumber of about 2957 cm ⁻¹ (CH ₃ symmetric stretching vibration), about 2924 cm ⁻¹ (vCH ₂ antisymmetry), and about 2855 cm ⁻¹ (vCH ₂ symmetry) Since a characteristic peak was observed in the group, it is considered that the alkyl group and carbon are not physically mixed, and the alkyl group is incorporated into the carbon skeleton by covalent bond.

(Nitrogen adsorption isotherm)
In the carbon material obtained in Example 2, the rise of the isotherm is larger at around the high relative pressure than in Example 1, and the calculated total pore volume is 0.16 cm ³ / g (Table 2). Yes, greater than Example 1.

(Scanning electron microscope image and transmission electron microscope image)
The scanning electron microscope image of the carbon material obtained in Example 2 is shown in FIG. It was observed that particles of several to several tens of nm were connected to one another. In addition, the connected body was in the form of a sheet having a thickness of about several tens to about 200 nm.
A transmission electron microscope image of the carbon material obtained in Example 2 is shown in FIG. FIG. 8 is considered to represent a cross section of the sheet shape, and it is observed that the sheet shape is formed by connecting particles of several to several tens of nm in a row.

  Therefore, from this example, it was found that porous carbon was obtained by hydrothermal synthesis using a fatty acid ester of sugar as a raw material, and the material had an oxygen-containing functional group and an alkyl group.

[Example 3]
In this example, in order to investigate the basic resistance of the carbon material obtained in this example, the base was subjected to washing treatment. The synthesis including this base treatment step is shown below.
(Step 1)
Sucrose stearic acid ester (Daiichi Kogyo Seiyaku Co., Ltd. DK ester SS, HLB19, monoester ratio; about 100%) represented by molecular formula C ₃₀ H ₅₇ O ₁₂ as fatty acid ester of sugar 10 mL of deionized water Dissolved in water. After left to stand overnight, it was heated at 120 ° C. for 103 hours in a closed vessel.
(Step 2)
The resulting brown solid was collected. The intermediate layer having the second smallest specific gravity was taken out as in the case of Example 2 although the precipitation was usually divided into three layers. About 40 mL of deionized water was poured, shaken with a shaker, and centrifuged to precipitate a solid. The supernatant solution was removed, the same amount of deionized water was poured again, and the same operation was repeated twice more. Then, about 40 mL of ethanol was poured, and similarly shaken and centrifuged. The supernatant solution was removed, and this operation was repeated twice more. The resulting precipitate was dried at 65 ° C. overnight or more.
(Step 3)
To the dried brown solid, 50 mL of ethanol was added, and the mixture was stirred and washed at 60 ° C. overnight. After washing, centrifugation was performed, and after removing the supernatant, 40 mL of ethanol was added and shaken at room temperature. After centrifugation, the supernatant was removed. This operation was repeated once more. The precipitate was dried at 65 ° C. overnight or more.
(Base treatment process)
The carbon material obtained in step 3 was stirred at room temperature in a 0.1 M aqueous solution of sodium hydroxide. About 40 mL of deionized water was poured onto the carbon material after stirring, the mixture was shaken with a shaker, and then centrifuged to precipitate a solid. After removing the supernatant solution, about 40 mL of EtOH was poured and shaken with a shaker, and then centrifuged to precipitate a solid. The precipitate was dried at 65 ° C. overnight or more to obtain a target sodium hydroxide-treated carbon material.

  The alkyl group of the sucrose fatty acid-derived carbon material is considered to be covalently bonded to the carbon skeleton via an ester group. Therefore, when the basic resistance of the ester bond is low, it is expected that the number of alkyl groups decreases and the peak intensity of the alkyl group in the Fourier transform infrared absorption spectrum decreases.

(Fourier transform infrared absorption spectrum)
The carbon material obtained in Example 3 is affected by the large absorption peak of OH (stretching, 3700 to 3100 cm ⁻¹ ), so although it is not clear as compared with Examples 1 and 2, the wavenumber is around 2967 cm ⁻¹ ( Some absorption is seen in CH ₃ symmetric stretching vibration). 2927Cm ^-1 vicinity (VCH ₂ antisymmetric), and 2850 cm ^-1 vicinity (VCH ₂ symmetry) the observed peaks characteristic of alkyl groups derived from fatty acids, that remain alkyl groups incorporated in the carbon backbone I understand. In addition, since a peak attributed to COO (stretching, 1800 to 1520 cm ^-1 ) or OH (stretching, 3700 to 3100 cm ^-1 ) derived from a carboxyl group or a carbonyl group is recognized, the oxygen-containing functional group is also simultaneously It turned out to be kept.

(Nitrogen adsorption isotherm)
In the carbon material obtained in Example 3, the rise of the isotherm similar to that in Example 2 is confirmed near high relative pressure, and the calculated total pore volume is 0.17 cm ³ / g (Table 2). there were. Thus, it was found that the pore volume was maintained.

(Scanning electron microscope image)
The scanning electron microscope image of the carbon material obtained in this example is shown in FIG. It was observed that particles of several to several tens of nm were connected to one another to form particles of several to several tens of μm in size.

  Therefore, it was found from this example that even when 0.1 M sodium hydroxide treatment is performed, the oxygen-containing functional group and the alkyl group of the carbon material derived from sucrose fatty acid ester and the pore volume can be maintained.

Example 4
In Examples 1 to 3, it is found that a porous carbon having an oxygen-containing functional group and an alkyl group can be obtained by hydrothermal synthesis using sucrose fatty acid ester in which an alkyl group is linked to one chain per sucrose molecule as a raw material The
Therefore, in this example, the sucrose fatty acid ester-derived carbon obtained by increasing the hydrophobicity of the sucrose fatty acid ester raw material to be used compared to the sucrose fatty acid ester used in Examples 1 to 3 to increase the surface activity. An attempt was made to increase the pore volume of the material and to impart orientation.
In Examples 1 to 3, a molecule in which an alkyl group is linked to one chain per sugar molecule is used as a raw material, but here, unlike Examples 1 to 3, a molecule in which two or more alkyl groups are linked to one sucrose molecule is used. Sucrose fatty acid ester containing 30% was used as a raw material. The present synthesis is shown below.
(Step 1)
Dissolve 1 g of a fatty acid ester of sugar represented by the molecular formula C ₃₃ H ₆₂ O ₁₂ and having an HLB of 15 and a monoester ratio of 70% (Daiichi Kogyo Seiyaku Co., Ltd. DK ester F160) in 10 mL deionized water The After standing overnight, it was heated at 120 ° C. for 182 hours in a closed vessel.
(Step 2)
The resulting brown solid was collected. Usually, the upper layer and the lower layer are separated and deposited, and the upper layer having a smaller specific gravity is taken out. After pouring about 40 mL of deionized water and shaking with a shaker, it was centrifuged to precipitate a solid. The supernatant solution was removed, the same amount of deionized water was poured again, and the same operation was repeated twice more. Then, about 40 mL of ethanol was poured, and similarly shaken and centrifuged. The supernatant solution was removed, and this operation was repeated twice more. The resulting precipitate was dried at 65 ° C. overnight or more.
(Step 3)
To the dried brown solid was added 50 mL of ethanol, and the mixture was stirred and washed at 60 ° C. overnight. After washing, centrifugation was performed, and after removing the supernatant, 40 mL of ethanol was added and shaken at room temperature. After centrifugation, the supernatant was removed. This operation was repeated once more. The precipitate was dried at 65 ° C. overnight or more to obtain a target sucrose fatty acid ester-derived carbon material.

(Fourier transform infrared absorption spectrum)
In the carbon material obtained in Example 4, a peak attributed to C = O (stretching, 1800 to 1520 cm ⁻¹ ) or OH (stretching, 3700 to 3100 cm ⁻¹ ) derived from a carboxyl group or a carbonyl group is observed Thus, it was found that an oxygen-containing functional group was present in the carbon material. Furthermore, although CH ₃ symmetric stretching vibration usually found around wave number 2963 cm ⁻¹ is not clearly seen, fatty acid derived from around 2922 cm ⁻¹ (vCH ₂ anti-symmetry) and 2853 cm ⁻¹ (vCH ₂ symmetry) A characteristic peak was observed for the alkyl group, and it was found that an alkyl group was also present.

(Nitrogen adsorption isotherm)
The carbon material obtained in Example 4 shows a slight rise in the isotherm as in Example 1 near high relative pressure, and the calculated total pore volume is 0.05 cm ³ / g ( It is Table 2).

(Scanning electron microscope image and transmission electron microscope image)
The scanning electron microscope image of the carbon material obtained in Example 4 is shown in FIG. In the carbon material obtained in this example, it was observed that particles of several to several tens of nm were connected to one another.
A transmission electron microscope image of the carbon material obtained in Example 4 is shown in FIG. It was observed that a bicontinuous structure with a stem thickness of several tens of nm was formed.

  Therefore, according to this example, porous carbon can be obtained also by hydrothermal synthesis using sucrose fatty acid ester containing 30% of molecules in which two or more alkyl groups are linked per sucrose molecule as a raw material, and the material contains It was found to have oxygen functionality and alkyl groups.

[Example 5]
In the present example, the same sucrose fatty acid ester as in Example 4 was used, and in Step 2, the lower layer having a large specific gravity was taken out. The present synthesis is shown below.
(Step 1)
Dissolve 1 g of a fatty acid ester of sugar represented by the molecular formula C ₃₃ H ₆₂ O ₁₂ and having an HLB of 15 and a monoester ratio of 70% (Daiichi Kogyo Seiyaku Co., Ltd. DK ester F160) in 10 mL deionized water The After standing overnight, it was heated at 120 ° C. for 182 hours in a closed vessel.
(Step 2)
The resulting brown solid was collected. Usually, two layers of the upper layer and the lower layer are separated and deposited, but unlike Example 4, the lower layer having a large specific gravity was taken out. After pouring about 40 mL of deionized water and shaking with a shaker, it was centrifuged to precipitate a solid. The supernatant solution was removed, the same amount of deionized water was poured again, and the same operation was repeated twice more. Then, about 40 mL of ethanol was poured, and similarly shaken and centrifuged. The supernatant solution was removed, and this operation was repeated twice more. The obtained precipitate was dried at 65 ° C. overnight or more to obtain a target sucrose fatty acid ester-derived carbon material.
(Step 3)
To the dried brown solid was added 50 mL of ethanol, and the mixture was stirred and washed at 60 ° C. overnight. After washing, centrifugation was performed, and after removing the supernatant, 40 mL of ethanol was added and shaken at room temperature. After centrifugation, the supernatant was removed. This operation was repeated once more. The precipitate was dried at 65 ° C. overnight or more to obtain a target sucrose fatty acid ester-derived carbon material.

(Fourier transform infrared absorption spectrum)
In the carbon material obtained in Example 5, a peak attributed to C = O (stretching, 1800 to 1520 cm ⁻¹ ) or OH (stretching, 3700 to 3100 cm ⁻¹ ) derived from a carboxyl group or a carbonyl group is observed Thus, it was found that an oxygen-containing functional group was present in the carbon material. Furthermore, a characteristic peak is seen in the alkyl group derived from fatty acid at wave number 2972 cm ^-1 (CH ₃ symmetric stretching vibration), 2925 cm ^-1 (vCH ₂ antisymmetry) and 2854 cm ¹ (vCH ₂ symmetry) And alkyl groups were also found to be present.

(Nitrogen adsorption isotherm)
The carbon material obtained in Example 5 shows a large rise of the isotherm near high relative pressure, and the calculated total pore volume is 0.72 cm ³ / g (Table 2). The largest pore volume was shown in the examples.

(Scanning electron microscope image and transmission electron microscope image)
The scanning electron microscope image of the carbon material obtained in Example 5 is shown in FIG. It appears that particles of several tens of nm in size (primary particles) are connected to one another with gentle but constant orientation, and particles (secondary particles) of several to several tens of μm in size are formed. It was observed. The direction of orientation is indicated by an arrow in FIG.

  Therefore, from this example, porous carbon is obtained by hydrothermal synthesis using fatty acid ester of sugar as a raw material, and the material has an oxygen-containing functional group and an alkyl group, and has a moderate orientation. I understood.

In the fifth embodiment, unlike the first to fourth embodiments, the step 3 can be omitted. As described above, the porous carbon obtained in the present invention is synthesized by the three steps of steps 1 to 3, of which step 3 aims to remove physically mixed alkyl groups and is obtained after step 2. It is only required if the material contains physically mixed alkyl groups. In Examples 1 to 4, after step 3, a decrease in the peak intensity of the alkyl group is observed in the Fourier transform infrared absorption spectrum compared to before performing step 3, and the alkyl group present physically mixed is a step. It was found that 3 was removed. Furthermore, as described above, even if step 3 is repeated once, the peak intensity of the alkyl of the Fourier transform infrared absorption spectrum does not change before and after that, so it can be said that the operation of step 3 is sufficient once.
In Example 5, as shown in FIGS. 1A and 1B, no significant change was observed in the peak intensity of the alkyl group observed in the Fourier transform infrared absorption spectrum before and after step 3 (step 3 The Fourier transform infrared absorption spectrum of the previous carbon material is described as "Example 5 (omission of step 3)". Therefore, since it is considered that the physically obtained alkyl group is hardly present in the material obtained in step 2, step 3 may not be performed.

Further, in Example 5, the observation results of the scanning electron microscope observation and the nitrogen adsorption measurement also did not significantly change regardless of the presence or absence of the step 3. In scanning electron microscope observation of the carbon material obtained by omitting step 3, similar to the carbon material obtained in step 3, particles (primary particles) with a size of about several tens of nm are loose but constant It was observed that particles (secondary particles) having a size of several to several tens of μm were formed by being connected to one another with the orientation of
Furthermore, as in the case of the carbon material obtained by performing step 3 near the nitrogen adsorption high relative pressure, a large rise of the isotherm was observed, and the calculated total pore volume was 0.70 cm ³ / g.
Furthermore, in the present example, a brown solid is obtained even if the hydrothermal treatment time of step 1 is set to 103 hours as in Examples 1 to 3, but among the material evaluations described in the above [0033] to [0035] However, the yield required for nitrogen adsorption measurement was not reached. However, also in this case, almost the same results as in Example 5 were obtained from the Fourier transform infrared absorption measurement and the scanning electron microscope.
A transmission electron microscope image of a carbon material obtained by setting step 1 to 103 hours and omitting step 3 in Example 5 is shown in FIG. It was observed that a structure in which primary particles having a size of several tens of nm were connected was uniformly formed throughout the secondary particles.

[Example 6]
In the synthesis of the sucrose fatty acid-derived carbon material of Examples 1 to 5, the steps 2 and 3 include an evaporation drying step. Here, in general, in evaporation and drying of the porous material, it is said that the porous structure shrinks and the pore volume decreases with the detachment and evaporation of the solvent from the porous body. On the other hand, in a drying method called lyophilization, the solvent is frozen once and then removed by sublimation. Therefore, it is expected that reduction in pore volume in the drying process of sucrose fatty acid-derived carbon material can be suppressed by using the lyophilization method.
Therefore, in this example, the material obtained in Example 5 having the largest pore volume up to this point was subjected to lyophilization instead of evaporation drying at 65 ° C. to further increase the pore volume. . The present synthesis is shown below.
(Step 1)
Dissolve 1 g of a fatty acid ester of sugar represented by the molecular formula C ₃₃ H ₆₂ O ₁₂ and having an HLB of 15 and a monoester ratio of 70% (Daiichi Kogyo Seiyaku Co., Ltd. DK ester F160) in 10 mL deionized water The After standing overnight, it was heated at 120 ° C. for 182 hours in a closed vessel.
(Step 2)
The resulting brown solid was collected. Usually, the upper layer and the lower layer are separated and deposited, but the lower layer having a large specific gravity was taken out as in Example 5. About 40 mL of deionized water was poured, shaken with a shaker, and centrifuged to precipitate a solid. The supernatant solution was removed, the same amount of deionized water was poured again, and the same operation was repeated twice more. Then, about 40 mL of ethanol was poured, and similarly shaken and centrifuged. The supernatant solution was removed, and this operation was repeated twice more.
(Lyophilization process)
In step 2, after the ethanol wash, the remaining ethanol was replaced with deionized water. Thereafter, it was freeze-dried to obtain a target sucrose fatty acid-derived carbon material.
Steps 1 and 2 in this example are the same as in example 5. That is, since there is almost no physically mixed alkyl group in the material obtained after step 2, step 3 can be omitted. Therefore, the lyophilization process was performed without passing through the process 3 in the present example.

(Fourier transform infrared absorption spectrum)
In the carbon material obtained in Example 6, a peak attributed to C = O (stretching, 1800 to 1520 cm ⁻¹ ) or OH (stretching, 3700 to 3100 cm ⁻¹ ) derived from a carboxyl group or a carbonyl group is observed Thus, it was found that an oxygen-containing functional group was present in the carbon material. Furthermore, characteristic peaks are observed in alkyl groups derived from fatty acids near wavenumber 2959 cm ⁻¹ (CH ₃ symmetrical stretching vibration), 2926 cm ⁻¹ (vCH ₂ antisymmetry), and 2859 cm ⁻¹ (vCH ₂ symmetrical) And alkyl groups were also found to be present.

(Nitrogen adsorption isotherm)
The carbon material obtained in Example 6 shows a large rise of the isotherm near high relative pressure, and the calculated total pore volume is 0.98 cm ³ / g (Table 2). Also showed a larger pore volume.

(Scanning electron microscope image)
The scanning electron microscope image of the carbon material obtained in Example 6 is shown in FIG. It was observed that particles of about several tens of nm in size were connected to one another with gentle but constant orientation, and particles of several to several tens of μm in size were formed. The direction of orientation is indicated by an arrow in FIG.

  Therefore, according to this example, in Example 5, instead of drying at 65 ° C. in Step 2, a porous carbon can be obtained even if a freeze-drying step is performed, and the material has an oxygen-containing functional group and an alkyl group. And it was found to have a gentle orientation.

Comparative Example 1
A comparative synthesis test was carried out in the same manner as in the above example, using sucrose itself as a raw material in which the alkyl group is not incorporated in the molecule, that is, not amphiphilic. The present synthesis is shown below.
(Step 1)
In 10 mL of deionized water was dissolved 2.3 g of sucrose, which was equivalent to the amount of sucrose stearate used in Example 1. After left to stand overnight, it was heated at 120 ° C. for 103 hours in a closed vessel.
(Step 2)
The resulting brown precipitate was collected, poured about 40 mL of deionized water, shaken with a shaker, and then centrifuged to precipitate a solid. The supernatant solution was removed, the same amount of deionized water was poured again, and the same operation was repeated twice more. Then, about 40 mL of ethanol was poured, and similarly shaken and centrifuged. This operation was repeated twice more after the supernatant solution was removed. The resulting precipitate was dried at 65 ° C. overnight or more.

(Fourier transform infrared absorption spectrum)
The carbon material obtained in Comparative Example 1 has a peak attributed to C = O (stretching, 1800 to 1520 cm ⁻¹ ) or OH (stretching, 3700 to 3100 cm ⁻¹ ) derived from a carboxyl group or a carbonyl group However, it is characteristic of fatty acid-derived alkyl groups, which are generated around normal wave number 2963 cm ^-1 (CH ₃ symmetrical stretching vibration), 2925 cm ^-1 (vCH ₂ antisymmetry) and 2854 cm ^-1 (vCH ₂ symmetry) No peak was seen.
As described above, the porous material of the example is synthesized by the three steps of steps 1 to 3, and step 3 in this step is intended to remove physically mixed alkyl groups, and is obtained after step 2. It is only needed if the material to be incorporated contains a physically mixed alkyl group. In this comparative example, the Fourier transform infrared absorption spectrum of the material obtained after step 2 showed almost no alkyl group peak. Therefore, it was also obvious that the alkyl groups were not physically mixed because they do not have an alkyl group itself derived from a fatty acid. Thus, in the synthesis of Comparative Example 1, Step 3 was omitted.

(Nitrogen adsorption isotherm)
The carbon material obtained in Comparative Example 1 showed no rise in the entire relative pressure range, and the calculated pore volume remained at 0.01 cm ³ / g (Table 2).

(Scanning electron microscope image and transmission electron microscope image)
The scanning electron microscope image of the carbon material obtained in Comparative Example 1 is shown in FIG. Spherical particles of two sizes of several μm in diameter and several hundreds of nm were observed, but both particle surfaces are smooth, and particles of several to several tens of nm in size as seen in the example are It was not observed that they were in line with each other.
A transmission electron microscope image of the carbon material obtained in Comparative Example 1 is shown in FIG.
Although some contrast was seen in the electron microscopic image, no appearance of formation of a bicontinuous structure or a fine particle linked body as seen in the example was observed throughout the inside of the microparticles.

Comparative Example 2
A comparative synthesis test was carried out in the same manner as in the above example, using a mixture of sucrose and fatty acid, which are not amphiphilic, as a raw material. The present synthesis is shown below.
(Step 1)
10 mL of deionized water was added to 2.2 g of sucrose and 1.9 g of stearic acid equivalent to the amount of sucrose stearate used in Example 1. After left to stand overnight, it was heated at 120 ° C. for 103 hours in a closed vessel.
(Step 2)
The resulting brown precipitate was collected, poured about 40 mL of deionized water, shaken with a shaker, and then centrifuged to precipitate a solid. The supernatant solution was removed, the same amount of deionized water was poured again, and the same operation was repeated twice more. Then, about 40 mL of ethanol was poured, and similarly shaken and centrifuged. This operation was repeated twice more after the supernatant solution was removed. The resulting precipitate was dried at 65 ° C. overnight or more.

(Fourier transform infrared absorption spectrum)
The carbon material obtained in Comparative Example 2 has a peak attributed to C = O (stretching, 1800 to 1520 cm ⁻¹ ) or OH (stretching, 3700 to 3100 cm ⁻¹ ) derived from a carboxyl group or a carbonyl group However, it is characteristic of fatty acid-derived alkyl groups, which are generated around normal wave number 2963 cm ^-1 (CH ₃ symmetrical stretching vibration), 2925 cm ^-1 (vCH ₂ antisymmetry) and 2854 cm ^-1 (vCH ₂ symmetry) No peak was seen. In the same manner as Comparative Example 1, also in this Comparative Example, the Fourier transform infrared absorption spectrum of the material obtained after Step 2 hardly showed the peak of the alkyl group. Therefore, step 3 was omitted in the synthesis of this comparative example.

(Nitrogen adsorption isotherm)
The carbon material obtained in Comparative Example 2 also showed no rise in the entire relative pressure range as in Comparative Example 1, and the calculated pore volume remained at 0.01 cm ³ / g (Table 2).

(Scanning electron microscope image and transmission electron microscope image)
The scanning electron microscope image of the carbon material obtained in Comparative Example 2 is shown in FIG. Similar to Comparative Example 1, spherical particles of two sizes of several μm in diameter and several hundreds of nm were observed, but both particle surfaces are smooth, and several to several tens of particles as seen in the examples. It was not observed that nm particles were lined up.

  From the above, when sucrose itself is used as a raw material and when physical mixture of sucrose itself and fatty acid is used as a raw material, porous carbon can not be obtained in either case, and the carbon material also has an alkyl group derived from fatty acid. It turned out not to do.

The carbonization of the carbon skeleton obtained from saccharides by a hydrothermal synthesis method is generally good in carbon materials as the carbonization of the carbon skeleton proceeds by calcination in an inert atmosphere at 400 ° C. to 500 ° C. or higher and the calcination temperature further increases. Can be used as an electrode material etc.
Therefore, in order to enhance the aromaticity of the carbon skeleton of the sucrose fatty acid ester-derived porous carbon obtained in Examples 1 to 6, the obtained porous carbon was fired in an inert atmosphere.
The baking treatment is carried out for Examples 2 and 5 which are particularly large in pore volume and not subjected to special treatments such as base treatment and lyophilization among Examples 1 to 6, and Examples 7 and 8 did. It is shown below.

[Example 7]
(Step 1)
Sucrose stearic acid ester (Daiichi Kogyo Seiyaku Co., Ltd. DK ester SS, HLB19, monoester ratio; about 100%) represented by molecular formula C ₃₀ H ₅₇ O ₁₂ as fatty acid ester of sugar 10 mL of deionized water Dissolved in water. After left to stand overnight, it was heated at 120 ° C. for 103 hours in a closed vessel.
(Step 2)
The resulting brown solid was collected. The intermediate layer having the second smallest specific gravity was taken out as in the case of Example 2 although the precipitation was usually divided into three layers. After pouring about 40 mL of deionized water and shaking with a shaker, it was centrifuged to precipitate a solid. The supernatant solution was removed, the same amount of deionized water was poured again, and the same operation was repeated twice more. Then, about 40 mL of ethanol was poured, and similarly shaken and centrifuged. The supernatant solution was removed, and this operation was repeated twice more. The resulting precipitate was dried at 65 ° C. overnight or more.
(Step 3)
To the dried brown solid was added 50 mL of ethanol, and the mixture was stirred and washed at 60 ° C. overnight. After washing, centrifugation was performed, and after removing the supernatant, 40 mL of ethanol was added and shaken at room temperature. After centrifugation, the supernatant was removed. This operation was repeated once more. The precipitate was dried at 65 ° C. overnight or more.
(Firing process under nitrogen)
The obtained material was calcined at 550 ° C. under a nitrogen flow of 600 mL / min to obtain a target sucrose fatty acid ester-derived carbon material.

(Fourier transform infrared absorption spectrum)
The carbon material obtained in Example 7 is usually generated near a wave number of 2963 cm ⁻¹ (CH ₃ symmetric stretching vibration), near 2925 cm ⁻¹ (vCH ₂ antisymmetry), and near 2854 cm ⁻¹ (vCH ₂ symmetry). Although no peak characteristic of the alkyl group derived from fatty acid was observed, a peak of stretching of conjugated C 共 役 C or olefinic system CCC—O was observed at 1650 to 1450 cm ⁻¹ . Further, 886cm ^-1, and loose some a ^{while, 805cm -1,} the 766cm ^-1, the carbon of the aromatic ring - absorption peak attributable to hydrogen out-of-plane deformation vibration was observed. Furthermore, the absorption peak which belongs to the stretching movement of OH group is seen in 3700-3100 cm < ^-1 >, and it turned out that the obtained carbon material has a hydroxyl group.

  Here, as described above, the porous material of the example is synthesized by the three steps of steps 1 to 3. Step 3 in this step is for the purpose of removing physically mixed alkyl groups. It is only needed if the material obtained later contains physically mixed alkyl groups. In this example, even if the alkyl group is physically mixed in step 2, the alkyl group is thermally decomposed by itself at a temperature of 550 ° C. Therefore, it is considered that this alkyl group is removed without using step 3. . Therefore, in the present example, the following measurement was performed on the carbon material obtained by performing the firing step without passing through the step 3.

(Nitrogen adsorption isotherm)
The carbon material obtained in Example 7 was found to rise on the low relative pressure side and rise on the high relative pressure side. The former indicates the presence of micropores, and the latter indicates the presence of mesopores and / or macropores. The total pore volume calculated from the nitrogen adsorption isotherm was 0.62 cm ³ / g (Table 2).

(Scanning electron microscope image and transmission electron microscope image)
The scanning electron microscope image of the carbon material obtained in Example 7 is shown in FIG. It was observed that particles of several to several tens of nm were connected to one another. In addition, the connected body was in the form of a sheet having a thickness of about several tens to 200 nm.
A transmission electron microscope image of the carbon material obtained in Example 7 is shown in FIG. The figure is considered to represent a cross section of the sheet shape, and it is observed that the sheet shape is formed by connecting particles of several to several tens of nm in a row.

(Measurement of conductivity)
The both ends of the dense particle group of the carbon material obtained in Example 7 are sandwiched between two terminals, and the resistance value is measured using a digital multimeter to confirm the presence or absence of conductivity as follows. did.
In advance, a resistance value is displayed for a conductive material (for example, conductive porous carbon described in S. Kubo et al., Chem. Mater. 2013, 25, 4781), but for an insulating material After confirming that no value is displayed, the above measurement was performed to confirm the presence or absence of the display of the resistance value.
The carbon material obtained in Example 7 exhibited a resistance value of about 10 to 20 MΩ when measured under the condition that the distance between both terminals is about 0.5 to 1 mm.

  Therefore, by baking the porous carbon material in an inert atmosphere using fatty acid esters of sugar as a raw material, conductive carbon carbon materials having high aromaticity can be obtained from fatty acid ester raw materials of sugar, and the materials Were found to have a hydroxyl group.

[Example 8]
(Step 1)
Dissolve 1 g of a fatty acid ester of sugar represented by the molecular formula C ₃₃ H ₆₂ O ₁₂ and having an HLB of 15 and a monoester ratio of 70% (Daiichi Kogyo Seiyaku Co., Ltd. DK ester F160) in 10 mL deionized water The After standing overnight, it was heated at 120 ° C. for 182 hours in a closed vessel.
(Step 2)
The resulting brown solid was collected. Usually, the upper layer and the lower layer are separated and deposited, but the lower layer having a large specific gravity was taken out as in Example 5. After pouring about 40 mL of deionized water and shaking with a shaker, it was centrifuged to precipitate a solid. The supernatant solution was removed, the same amount of deionized water was poured again, and the same operation was repeated twice more. Then, about 40 mL of ethanol was poured, and similarly shaken and centrifuged. The supernatant solution was removed, and this operation was repeated twice more. The resulting precipitate was dried at 65 ° C. overnight or more.
(Firing process under nitrogen)
The obtained material was calcined at 550 ° C. under a nitrogen flow of 600 mL / min to obtain a target sucrose fatty acid ester-derived carbon material.
Here, the processes 1 and 2 of the present embodiment are the same as those of the fifth embodiment. That is, since the step 3 may be omitted, in the present example, the firing was performed under nitrogen without the step 3.

(Fourier transform infrared absorption spectrum)
The carbon material obtained in Example 8 is usually generated near a wave number of 2963 cm ⁻¹ (CH ₃ symmetric stretching vibration), near 2925 cm ⁻¹ (vCH ₂ antisymmetry), and near 2854 cm ⁻¹ (vCH ₂ symmetry). Although no peak characteristic of the alkyl group derived from fatty acid was observed, a peak of stretching of conjugated C 共 役 C or olefinic system CCC—O was observed at 1650 to 1450 cm ⁻¹ . ^{Further, 882cm -1, 807cm -1,} the 758cm ^-1, the carbon of the aromatic ring - absorption peak attributable to hydrogen out-of-plane deformation vibration was observed. Furthermore, it was found that an absorption peak attributed to OH group stretching movement was observed at 3700 to 3100 cm ⁻¹ , and the resulting carbon material had a hydroxyl group.

(Nitrogen adsorption isotherm)
The carbon material obtained in Example 8 showed a rise on the low relative pressure side and a large rise on the high relative pressure side. The former indicates the presence of micropores, and the latter indicates the presence of mesopores and / or macropores. The total pore volume calculated from the nitrogen adsorption isotherm was 1.23 cm ³ / g (Table 2).

(Scanning electron microscope image)
The scanning electron microscope image of the carbon material obtained in Example 8 is shown in FIG. It was observed that particles of about several tens of nm in size were connected to each other, and particles of several to several tens of μm in size were formed.
(Measurement of conductivity)
When the resistance value was measured in the same manner as in Example 7, the carbon material obtained in Example 8 was 5 to 25 MΩ when measured under the condition that the distance between both terminals was about 0.5 to 1 mm. The degree of resistance is shown.

  Therefore, by baking the porous carbon material in an inert atmosphere using fatty acid esters of sugar as a raw material, conductive carbon carbon materials having high aromaticity can be obtained from fatty acid ester raw materials of sugar, and the materials Were found to have a hydroxyl group.

Comparative Example 3
A comparative synthesis test was carried out in the same manner as in the above example, using sucrose itself as a raw material in which the alkyl group is not incorporated in the molecule, that is, not amphiphilic. In particular, the carbon material obtained by hydrothermal synthesis using sucrose itself as a raw material was calcined under a nitrogen flow to compare with Examples 7 and 8. The present synthesis is shown below.
(Step 1)
In 10 mL of deionized water was dissolved 2.3 g of sucrose, equivalent to the amount of sucrose stearate used in Example 1. After left to stand overnight, it was heated at 120 ° C. for 103 hours in a closed vessel.
(Step 2)
The resulting brown precipitate was collected, poured about 40 mL of deionized water, shaken with a shaker, and then centrifuged to precipitate a solid. The supernatant solution was removed, the same amount of deionized water was poured again, and the same operation was repeated twice more. Then, about 40 mL of ethanol was poured, and similarly shaken and centrifuged. This operation was repeated twice more after the supernatant solution was removed. The resulting precipitate was dried at 65 ° C. overnight or more.
(Firing process under nitrogen)
The comparison carbon material was obtained by baking the obtained material at 550 degreeC under nitrogen flow of 600 mL / min.
In the present comparative example, the firing step was performed without passing through step 3, as in the case of Examples 7 and 8 in which firing was performed under nitrogen.

(Fourier transform infrared absorption spectrum)
The carbon material obtained in this comparative example is usually generated near a wave number of 2963 cm ⁻¹ (CH ₃ symmetric stretching vibration), near 2925 cm ⁻¹ (vCH ₂ antisymmetry), and near 2854 cm ⁻¹ (vCH ₂ symmetry). No peaks characteristic of alkyl groups derived from fatty acids were observed. The 1650~1450cm ^-1, a peak of expansion and contraction of the conjugate C = C or olefinic C = C-O ^{is, 874cm -1, 801cm -1,} the 748cm ^-1, the carbon of the aromatic ring - hydrogen out-of-plane deformation vibration However, no clear absorption peak attributable to OH group stretching movement was found at 3700 to 3100 cm ^-1, and it was found that many of the hydroxyl groups were lost in this comparative carbon material. The

(Scanning electron microscope image and transmission electron microscope image)
The scanning electron microscope image of the carbon material obtained in Comparative Example 3 is shown in FIG. Similar to Comparative Examples 1 and 2, spherical particles of two sizes of several μm in diameter and several hundreds of nm were observed, but both particle surfaces are smooth and the number as seen in the Examples ~ It was not observed that fine particles of several tens of nm were aligned.

The evaluation conditions of the production conditions and the porosity in the above examples and comparative examples are described in Table 1 below.
However, for evaluation of porosity, based on Comparative Examples 1 and 2 (x) having a nitrogen adsorption amount of 0.01 cm ³ / g, 、 → ○ → Δ was sequentially arranged in the descending order of adsorption amount.

The total pore volume of the carbon materials obtained in the above Examples and Comparative Examples is described in Table 2 below.
However, the total pore volume was calculated from the nitrogen adsorption amount at the measurement point of relative pressure 0.991 or more and 0.996 or less.

As mentioned above, the carbon material obtained from hydrothermal synthesis which used fatty acid ester of sugar of the present invention as a raw material had an oxygen-containing functional group and an alkyl group. On the other hand, the carbon materials obtained from the sucrose itself and the physical mixture of sucrose and fatty acid of Comparative Examples 1 and 2 did not have an alkyl group although they have an oxygen-containing functional group.
In addition, the alkyl group-containing carbon material of the present invention had a pore volume which exceeds that of the carbon materials obtained using the sugar itself and the physical mixture of sugar and fatty acid as the raw materials of Comparative Examples 1 and 2.
Furthermore, the carbon material obtained from the fatty acid ester raw material of sugar of the present invention is composed of particles of several to several tens of μm in size, and particles of several to several tens of nm in size are formed in a row. Furthermore, particles having a size of about several to several tens of nm are connected with moderate but constant orientation, or a sheet-like shape having a thickness of several tens to about 200 nm of a connected body. There was also one that was not. This is largely different from the spherical particles of several hundred nm to several μm in diameter having smooth surface texture obtained from sugar itself or a mixture of sugar and fatty acid in Comparative Examples 1 and 2.
Therefore, it can be said that the porous carbon derived from the fatty acid ester of the sugar of the present invention is produced utilizing the fact that the carbon source itself is amphiphilic. That is, when the sugar moiety of the raw material molecule acts as a hydrophilic moiety and the alkyl moiety acts as a hydrophobic moiety, an interfacial phenomenon of the carbon source itself is induced during hydrothermal synthesis, and carbon nanostructures such as micelles and liquid crystals are formed. Ru. It is believed that the resulting material is porous. According to the method of the present invention, since the carbon material is already made porous after hydrothermal synthesis, a porous carbon material can be obtained without using the thermal decomposition removal step which is usually required when using a template. Therefore, porous carbon in which the oxygen-containing functional group is maintained can be obtained.

On the other hand, for the application to an electrode material etc., it is necessary to enhance the aromaticity of the carbon skeleton of the porous carbon derived from the fatty acid ester of sugar obtained. Therefore, when the porous carbon derived from the fatty acid ester of the above-mentioned sugar is calcined in an inert atmosphere, the porous carbon derived from the fatty acid ester of the sugar of the present invention It had a functional group (hydroxyl group). Moreover, the pore volume was 0.62-1.23 cm < ³ > / g. In addition, the aromaticity of the carbon skeleton was enhanced, and the conductivity was also exhibited.
On the other hand, in the carbon material of Comparative Example 3 obtained from the sugar itself, when it was fired in an inert atmosphere, the aromaticity of the carbon skeleton was enhanced, but most of the oxygen-containing functional groups were lost. Furthermore, the pore volume at the time of baking the carbon material obtained normally from the sugar itself in the same inert atmosphere at 550 ° C. as in Examples 7 and 8 is 0.15 cm ³ / g or less (Non-patent Literature: L Yu et al., Langmuir, 2012, 28, 12373).
Furthermore, the carbon material of the present invention, which is a calcined product of a hydrothermally synthesized product using fatty acid esters of sugar as a raw material, has a size of several to several tens of μm formed by particles of several to several tens of nm connected to one another. Made of particles. Furthermore, some particles having a size of several to several tens of nm are connected to one another to form a sheet-like shape having a thickness of several tens to about 200 nm. This is significantly different from the spherical particles having a smooth surface texture and having a diameter of several hundred nm to several μm, which are obtained by calcining a hydrothermal compound of sugar itself, which is Comparative Example 3.
Therefore, in the present invention, by using a fatty acid ester of sugar as a raw material, a porous carbon having a large pore volume and having both the aromaticity of a carbon skeleton and an oxygen-containing functional group even after firing in an inert atmosphere Can be obtained.

Claims (25)

  Porous carbon consisting of hydrothermal reaction products made from fatty acid esters of sugars.   The porous carbon according to claim 1, wherein the carbon skeleton contains an alkyl group derived from the fatty acid.   The porous carbon according to claim 1 or 2, wherein the alkyl group of the fatty acid is an alkyl group having 1 to 100 carbon atoms which may contain a double bond.   Porous carbon consisting of a calcined product of a hydrothermal reaction product starting from a fatty acid ester of sugar.   The porous carbon according to claim 4, wherein the carbon skeleton contains a hydroxyl group.   The porous carbon according to any one of claims 1 to 5, wherein the sugar is a monosaccharide, a disaccharide or a polysaccharide which may contain nitrogen, or a mixture of two or more of them.   The porous carbon according to any one of claims 1 to 6, wherein the fatty acid ester of the sugar is a monoester, a diester or a polyester, or a mixture of two or more thereof. The porous carbon according to any one of claims 1 to 7, wherein the total pore volume calculated by nitrogen adsorption measurement is 0.04 to ⁵ cm3 / g.   The porous carbon according to any one of claims 1 to 8, which has an oriented nano structure.   The adsorbent which has porous carbon of any one of Claims 1-9 as a main component.   A porous carrier comprising the porous carbon according to any one of claims 1 to 9 as a main component.   The porous carrier according to claim 11, wherein the porous carrier is any of a catalyst carrier, a separation carrier, a chromatography carrier, a biomolecular scaffold, a biomolecular capture material, a drug-containing material or a flavor carrier.   The electrode material which has porous carbon of any one of Claims 1-9 as a main component.   The secondary battery provided with the electrode using the electrode material of Claim 13.   An electrochemical capacitor comprising an electrode using the electrode material according to claim 13.   A fuel cell comprising an electrode using the electrode material according to claim 13.   The sensor provided with the electrode using the electrode material of Claim 13.   The additive for foodstuffs which has porous carbon of any one of Claims 1-9 as a main component.   The food containing porous carbon according to any one of claims 1 to 9.   The cosmetic additive based on porous carbon according to any one of claims 1 to 9.   A method for producing porous carbon comprising hydrothermally treating a fatty acid ester of a sugar at 100 to 350 ° C., washing the obtained solid with water and an organic solvent, and drying it.   The method for producing porous carbon according to claim 21, wherein the alkyl group of the fatty acid is an alkyl group having 1 to 100 carbon atoms which may contain a double bond.   The method for producing porous carbon according to claim 21 or 22, wherein the sugar is a monosaccharide, disaccharide or polysaccharide which may contain nitrogen, or a mixture of two or more thereof.   The method for producing porous carbon according to any one of claims 21 to 23, wherein the fatty acid ester of the sugar is a monoester, a diester or a polyester, or a mixture of two or more of them.   A method for producing porous carbon, comprising producing the porous carbon by the method according to any one of claims 21 to 24, and further calcining.

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