JP6933370B2 - Method for producing porous carbon - Google Patents

Description

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

Porous carbon is a very important material in the industry as an adsorbent, a separating material, a catalyst carrier, a column carrier, a drug containing material, and the like by utilizing its pores. Furthermore, in recent years, the use of the pore space as a carbon electrode for secondary batteries, capacitors, sensors, etc., which uses the pore space as an efficient moving space for electrolytes, has been widely put into practical use. Porous carbon that has been modified to impart functionality is preferably used.

Porous carbon is produced by various methods, one of which is to use an amphipathic compound such as a surfactant or a block copolymer as a structural template, and in the presence of them, a carbon precursor (carbon source). There is a so-called organic template method that promotes carbonization of).
For example, in Patent Document 1, after forming micelles of a surfactant as a template in a monomer and / or prepolymer, the monomer and / or prepolymer is polymerized and cured to form a micelle-containing organic polymer. Further, a method of calcining this organic polymer to carry out carbonization is disclosed. Further, Patent Document 2, Non-Patent Documents 1, 2 and the like disclose that a block copolymer is used as a structural template and a phenol-based resin such as phenol and formaldehyde or resorcinol is used as a carbon precursor. Has been done.
However, in these methods, the carbon material obtained is due to factors such as the fact that there are few oxygen-containing functional groups in the molecule of the raw material, high-temperature heat treatment is required for carbonization, and the functional groups are lost at that time. The amount of oxygen-containing 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 electrode material. In addition, the carbon materials obtained by these methods are expected to have limited use in the aqueous phase.

On the other hand, it is already known that the carbon skeleton of a carbon material composed of 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 is used. An abundant carbon material can be obtained (Non-Patent Documents 3 and 4). It is also known that a nitrogen-doped carbon material can be obtained by hydrothermal synthesis using a sugar containing nitrogen such as chitin, chitosan, and glucose amine as a carbon source (Non-Patent Document 5).
Porous carbon can be obtained by combining hydrothermal synthesis of such sugars with a synthesis method using an amphipathic compound such as a block copolymer as an organic template (Non-Patent Document 6). However, the currently announced process using an organic template requires thermal decomposition removal of the structural template by heat treatment in an inert atmosphere of several hundred ° C. or higher (for example, 550 ° C.), and energy cost in synthesis. Is extra. In addition, it is not possible to prevent the amount of surface functional groups from decreasing during the heat treatment.

In addition, as an inorganic template method, an inorganic porous body such as a silica porous body is used as a structural template, and a carbon precursor (carbon source) such as a saccharide is immersed in the pores, followed by hydrothermal treatment, and finally. There is a method of dissolving and removing an inorganic porous body with a strong acid such as hydrofluoric acid (Non-Patent Documents 7, 8 and the like). According to this method, a carbon material having a surface functional group and having a porous property can be obtained.
However, the pore structure of the obtained porous body is an inverse structure (replica) of the silica porous body, and does not directly reflect the structure of a higher-order aggregate such as the above-mentioned surfactant or amphipathic polymer. .. For example, it seems very difficult to obtain a honeycomb-shaped channel structure called a hexagonal structure. Further, this method requires the synthesis of the silica porous body itself and also requires steps such as etching with a strong acid that are not suitable for industrial production, so that there is a problem in terms of practical use in the industrial world.

On the other hand, Patent Document 4 and Non-Patent Document 9 describe that a porous carbon having mesopores can be obtained by using carbohydrates such as alginic acid, pectin, amylose, and chitosan as raw materials without using a structural template. Has been done. In the methods described in these documents, a polysaccharide is dissolved in water and heated to obtain a highly viscous gel, and the gel is cooled to obtain a polysaccharide gel in which polysaccharide molecules are linked by hydrogen bonds. After that, the polysaccharide gel is further dried and then fired in the presence of an organic acid at several hundred degrees Celsius in a vacuum or an inert atmosphere to obtain porous carbon.
However, in this method, since the structure formation is based on the swelling of the polysaccharide network by water and the hydrogen bond between the polysaccharide molecules, it is not easy to induce the orientation in the structure formation, and therefore, the nanostructure of the obtained carbon material is formed. It is difficult to have a clear orientation and to control the degree and type of orientation. In addition, the carbon network is aromaticized by firing, and when firing at a temperature of around 400 ° C. or higher, most of the oxygen-containing functional groups are lost.

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

Y. Meng, D. Gu, F. 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. A. Guiochon, J.M. 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. P. Caballero, F. Babonneau, C.I. Gervais, G. Laurent. M-M, Titirici. N. Baccile, Langmuir, 2011, 27, 14460. R. J. White, M. Antonietti, M-M. Titirici, J. et al. Mater. Chem. 2009, 19, 8645. S. Kubo, R. J. White, N. Yoshizawa, M. Antonietti, M-M. Titirici, Chem. Mater. 2011, 23, 4882-4885. M-M. Titirici, A. Thomas, M. Antonietti, J.M. 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, 3782-3786.

As described above, it is desired to obtain porous carbon having a functional group by a simple and low energy consumption method using an inexpensive raw material. Further, it is expected to form a laminate with a thin film, a monomolecular / bimolecular film, or various substrates by utilizing the possibility of controlling the polymerization of a carbon source more directly and precisely.

The present invention has been made in view of this situation, and uses an inexpensive carbon precursor (carbon source), and is a simple and energy-consuming method that contains oxygen such as a hydroxyl group, a carbonyl group, and a carboxyl group. It is an object of the present invention to provide a porous carbon having a functional group such as a functional group or an alkyl group.

As a result of diligent studies to achieve the above objectives, by using a sugar fatty acid ester as a carbon precursor (carbon source), a simple and low energy consumption method is used without using a structural template. It was found that a porous carbon having an oxygen-containing functional group such as a hydroxyl group, a carbonyl group or a carboxyl group or a functional group such as an alkyl group can be produced.

The present invention has been completed based on these findings, and the following inventions are provided according to the present invention.
[1] Porous carbon composed of a hydrothermal reaction product made from a fatty acid ester of sugar.
[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 composed of a calcined product of a hydrothermal reaction product made from a fatty acid ester of sugar.
[5] The porous carbon according to [4], wherein the carbon skeleton contains a hydroxyl group.
[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 kinds thereof.
[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 polyester, or a mixture of two or more of these.
[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 nanostructure.
[10] The adsorbent containing the porous carbon according to any one of [1] to [9] as a main component.
[11] The porous carrier containing the porous carbon according to any one of [1] to [9] as a main component.
[12] The porous carrier according to [11], wherein the porous carrier is any one of a catalyst carrier, a separation carrier, a chromatographic carrier, a biomolecule scaffolding material, a biomolecule trapping material, a drug containing material, and a fragrance carrier.
[13] The electrode material containing the porous carbon according to any one of [1] to [9] as a main component.
[14] A secondary battery provided with an electrode using the electrode material according to [13].
[15] An electrochemical capacitor provided with an electrode using the electrode material according to [13].
[16] A fuel cell provided with an electrode using the electrode material according to [13].
[17] A sensor including an electrode using the electrode material according to [13].
[18] The food additive containing the porous carbon according to any one of [1] to [9] as a main component.
[19] The food containing the porous carbon according to any one of [1] to [9].
[20] The cosmetic additive containing the porous carbon according to any one of [1] to [9] as a main component.
[21] A method for producing a porous carbon, which comprises 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 then drying the solid.
[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 of these.
[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 polyester, or a mixture of two or more of these.
[25] A method for producing porous carbon, which comprises producing porous carbon by the method according to any one of [21] to [24] and then firing the porous carbon.

According to the present invention, a porous carbon containing oxygen-containing functional groups such as a hydroxyl group, a carbonyl group and a carboxyl group and a functional group derived from a raw material such as an alkyl group can be easily and energy-generated by using an inexpensive raw material. It can be obtained by a method that consumes less. Further, according to the present invention, in the porous carbon after being fired in an inert atmosphere, not only the aromaticity is enhanced, but also the porous carbon having an oxygen-containing functional group such as a hydroxyl group can be obtained. Further, according to the present invention, a sheet-like carbon (carbon thin film) having a thickness of about several tens to 200 nm can be obtained.

Fourier transform infrared absorption spectra of the materials obtained in Examples 1 to 6 and Comparative Examples 1 and 2. Fourier Transform Infrared Absorption Spectroscopy of Materials Obtained in Examples 7-8 and Comparative Example 3 Nitrogen adsorption isotherm of the material obtained in Examples 1-8 Nitrogen adsorption isotherm of the 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 using a fatty acid ester of sugar as a raw material and a hydrothermal reaction thereof. By using the fatty acid ester of sugar as a raw material, the porous carbon is contained in a carbon skeleton which is a basic skeleton. It is characterized by containing an alkyl group derived from a fatty acid ester or being composed of a calcined product of a product obtained by the hydrothermal reaction.
Further, in the method for producing porous carbon of the present invention, a fatty acid ester of sugar is used 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. After that, it is dried or further fired.

In the present invention, since the fatty acid ester of the sugar used as a raw material for the hydrothermal reaction is an amphipathic molecule, porous carbon can be obtained without using a conventional template.
Further, according to the present invention, since the firing step required for removing the template as in the conventional case 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 amphipathic molecule are used. A 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 amphipathic molecule, as a raw material, a sheet-like carbon (carbon thin film) having a thickness of several tens to 200 nm, a single molecule / bimolecular film, and various substrates It is possible to form a laminated body with.

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, a fatty acid ester of sugar is used as a carbon source for a hydrothermal reaction.
The sugar may be a monosaccharide such as fructose or glucose, a disaccharide such as sucrose, a polysaccharide such as alginic acid, pectin or amylose, or a sugar containing nitrogen such as chitin, chitosan or glucose amine, or two of these. It may be a mixture of more than one kind.
Further, as the fatty acid ester, a monoester having 1 or 2 diesters of fatty acids, a polyester having 3 or more bonds, or a mixture of two or more of these is used.

As described above, 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 into a moiety different from the above chemical structural formula. In other words, it does not matter at which site of the sugar the OH group is esterified and the alkyl group is extended.

The alkyl group of the fatty acid may contain a double bond, and n in the above formula is 1 to 100, preferably 1 to 50, and 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 diesters and polyesters, two or more different alkyls are added to the fatty acid ester molecule of one sugar. It may include the chain length. In other words, in diesters and polyesters, alkyl groups having different chain lengths may be extended from the OH group in one molecule of the sugar.
Further, the fatty acid ester of the sugar in the present invention may be a synthetic product or a commercially available product. Specific examples of commercially available products that are easily available include sucrose lauric acid ester, sucrose stearic acid ester, and sucrose behenic acid ester.

[Hydrothermal synthesis]
The porous carbon of the present invention is synthesized by the following steps 1 to 3.
Step 1: Dissolve the sugar fatty acid ester in water and heat the solution tightly. Step 2: Collect the obtained solid, wash it at room temperature, and then dry it. Step 3: Dry the solid under heating. Step of washing with a solvent and then drying However, step 3 may be omitted depending on the type of raw material used.
Hereinafter, they will be described in order.

(Step 1)
The 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, also referred to as “raw material aqueous solution”) at 100 to 350 ° C. in a closed container for 1 hour or more. It is said.
Conventionally used amphipathic polymers such as polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer and general surfactants such as sodium dodecyl sulfate in the raw material aqueous solution which is the raw material of the hydrothermal reaction. A template agent such as an activator, an organic colloid such as polystyrene particles, or an inorganic colloid such as silica particles may be added and used. Further, an inorganic porous template agent such as a conventional silica porous body may be added and used. Further, two or more kinds 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 in the raw material aqueous solution, or 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. Examples of such additives include cysteine, albumin, ovalbumin, thiophenaldehyde and the like.
Further, a pH adjusting agent may be added to the aqueous solution of the raw material for synthesis.
Further, 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 raw material aqueous solution. You may.
Further, as the pore swelling agent, for example, an organic additive such as hexane, trimethylbenzene, or cymene may be added.
Furthermore, it may be used in combination with an o / w emulsion or a colloidal dispersant.

(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 at a temperature of room temperature or higher, and then dried at a temperature of room temperature or higher for 3 hours or longer. It may be dried under vacuum conditions. A sufficient amount of an organic solvent is added to the brown solid after the main drying, and the mixture is stirred and washed at a temperature of room temperature or higher for 1 hour or longer. The brown solid after stirring and washing is dried at a temperature of room temperature or higher for 3 hours or longer to obtain a porous carbon material derived from the fatty acid of the target sugar. It may be dried under vacuum conditions. Further, the stirring washing with an organic solvent and the subsequent drying step may be omitted depending on the type of fatty acid ester of the sugar used.
Instead of the first drying described above, drying by the freeze-drying method 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-drying is performed.
In addition, washing with a base may be performed after the second drying described above.

[Hydrothermal reaction product]
In the present invention, the 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 the sugar and an alkyl group derived from the fatty acid in the carbon skeleton, and has a size of several to several. It has a lump shape of 100 μm or a sheet shape with a thickness of several nm to several μm. The lump-like and sheet-like shapes further have a structure in which fine particles having a thickness of several to several tens of nm are connected to each other, or a co-continuous structure having a thickness of several to several tens of nm. Further, the connected form of the fine particles can be given a loose orientation. The obtained powder shows a pore volume of ^{0.04 to 3} cm 3 / g in the pore evaluation by nitrogen adsorption.

(Baking process in an inert atmosphere)
Usually, the carbon skeleton obtained by the hydrothermal synthesis method from sugar is aromatized by firing in an inert atmosphere at 400 to 500 ° C. or higher, and the carbon material becomes more aromatized as the firing temperature rises further. It is known that it has good electrical conductivity and can be used as an electrode material.
Also in the present invention, the aromaticity can be enhanced by further firing the dried porous carbon in an inert atmosphere.
Specifically, the dried porous carbon is calcined at a temperature of 200 ° C. or higher under an inert gas flow of 50 mL / min or higher. As the inert gas, nitrogen, argon, helium or the like is used.

After calcining the carbon material obtained from sugar, the carbon network is aromatized by calcining, and when calcined at a temperature of about 400 ° C. or higher, most of the oxygen-containing functional groups are lost (usually, most of the oxygen-containing functional groups are lost (). See Patent Document 4 and Non-Patent Document 9).
On the other hand, in the present invention, the porous carbon obtained by firing the carbon material obtained from the hydrothermal synthesis of the fatty acid ester of sugar in an inert atmosphere has relatively high aromaticity and oxygen-containing functionality. It is characterized by containing a group (hydroxyl group).
Further, in the present invention, the porous carbon after firing has a lump shape having a size of several to several hundred μm or a sheet shape having a thickness of several nm to several μm, and has a lump shape and a sheet shape. Further, it has a structure in which fine particles having a diameter of several to several tens of nm are connected to each other.

Further, in the present invention, the porous carbon after calcination shows a pore capacity of ^{0.2 to 5 cm 3 / g in the pore evaluation by nitrogen adsorption.} Normally, when a carbon material obtained from sugar itself is calcined in the same inert atmosphere, the pore volume is 0.15 cm ³ g ^-1 or less (L. Yu et al., Langmuir, 2012, 28. From the viewpoint (see 12373), it can be said that in the present invention, by using a fatty acid ester of sugar as a raw material, a substance having a larger pore capacity can be obtained.

The porous carbon made of a hydrothermal reaction product made from a sugar fatty acid ester of the present invention or the porous carbon made of a calcined product of the hydrothermal reaction product utilizes its small pores. Not only can it be used as an adsorbent and a porous carrier such as a catalyst carrier, a separation carrier, a chromato carrier, a biomolecular scaffolding material, a biomolecule trapping material, a drug containing material or a fragrance carrier, but also the pore space can be used as an electrolyte. It can be used as a carbon electrode for secondary batteries, capacitors, fuel cells, sensors, etc. used as an efficient moving space.
Further, since the porous carbon of the present invention is made from a fatty acid ester of sugar, it not only has a small environmental load, but is also preferable for medical applications such as biomolecule scaffolding materials, biomolecule trapping materials, and drug inclusion materials. It can be used, and can also be used for foods, food additives, cosmetic additives, and the like.
Further, since the porous carbon of the present invention has an oxygen-containing functional group such as a hydroxyl group, a carbonyl group and a carboxyl group, and an alkyl group derived from a fatty acid ester of a sugar, various functional groups can be used. It is possible to provide a porous carbon imparted with the same functionality.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not construed as being limited thereto.

[Evaluation method]
The functional groups contained in the carbon materials obtained in the examples and comparative examples described below were confirmed by Fourier transform infrared absorption spectroscopy.
1 (A) and 1 (B) are Fourier transform infrared absorption spectra of the carbon materials obtained in Examples 1 to 6 and Comparative Examples 1 and 2, and FIG. 1 (B) is an absorption peak of an alkyl group derived from a fatty acid. In order to analyze in detail, ^{the range of the wave number 4000-2000 cm -1} of the spectrum of (A) is expanded.
FIG. 2 is a Fourier transform infrared absorption spectrum of the carbon material obtained in Examples 7 and 8 and Comparative Example 3.

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

Furthermore, the carbon materials obtained in Examples and Comparative Examples were observed with a scanning electron microscope and a transmission electron microscope. The observation with a transmission electron microscope is for observing the obtained particles in more detail. The obtained carbon material is embedded in a thermosetting resin, and the embedded material is embedded in a microtome. A flaky sample obtained by slicing to a thickness of several tens to 100 nm was observed.
5 to 21 are observation images of carbon materials obtained in Examples and Comparative Examples.

[Example 1]
(Step 1)
As a fatty acid ester of sugar, 10 mL of deionized 4 g of sucrose stearic acid ester (DK ester SS, HLB19, monoester ratio; about 100%) represented by the _{molecular formula C 30} H ₅₇ O ₁₂ Dissolved in water. After allowing to stand overnight, it was heated at 120 ° C. for 103 hours in a closed container.
(Step 2)
The obtained brown solid was recovered. Usually, it is divided into three layers and precipitated, but the uppermost layer having the smallest specific density was taken out. About 40 mL of deionized water was poured and 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 two more times. Then, about 40 mL of ethanol was poured, and the mixture was shaken and centrifuged in the same manner. The supernatant solution was removed and this operation was repeated two more times. The resulting precipitate was dried at 65 ° C. overnight or longer.
(Step 3)
50 mL of ethanol was added to the dried brown solid, and the mixture was stirred and washed at 60 ° C. overnight or longer. After washing, centrifugation was performed to remove the supernatant, 40 mL of ethanol was added, and the mixture was shaken at room temperature. After centrifugation, the supernatant was removed. This operation was repeated once again. The precipitate was dried at 65 ° C. overnight or more to obtain a carbon material derived from the desired sucrose fatty acid ester.

(Fourier transform infrared absorption spectrum)
The carbon material obtained in Example 1, C = O (stretching, 1800~1520cm ^-1) derived from a carboxyl group and a carbonyl group or OH (stretching, 3700~3100cm ^-1) are observed peak attributed to From this, it was found that an oxygen-containing functional group is present in the carbon material. Furthermore, peaks characteristic of fatty acid-derived alkyl groups were observed ^{near 2955 cm -1} (CH ₃ symmetric stretching vibration), 2920 cm ^-1 (vCH ₂ inverse symmetry), and 2851 cm ^-1 (vCH _{2 symmetry).} It was also found to have an alkyl group.

(Nitrogen adsorption isotherm)
In the carbon material obtained in Example 1, a slight rise of isotherms was observed in the vicinity of 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 having a size of several to several tens of nm were connected to each other to form particles having a size of several to several tens of μm.
The transmission electron microscope image of the carbon material obtained in Example 1 is shown in FIG. It was observed that a co-continuous structure with a trunk 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 that the material had an oxygen-containing functional group and an alkyl group.
In step 2 of Example 1, a carbon material was obtained by taking out the lowest layer having the highest specific gravity among the solids precipitated in three layers and performing other operations 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 this example, the same sucrose fatty acid ester as in Example 1 was used, and the intermediate layer having the second lowest specific density was taken out in step 2. The steps in this example are shown below.
(Step 1)
As a fatty acid ester of sugar, 10 mL of deionized 4 g of sucrose stearic acid ester (DK ester SS, HLB19, monoester ratio; about 100%) represented by the _{molecular formula C 30} H ₅₇ O ₁₂ Dissolved in water. After allowing to stand overnight, it was heated at 120 ° C. for 103 hours in a closed container.
(Step 2)
The obtained brown solid was recovered. Normally, the precipitate is divided into three layers, but unlike Example 1, the intermediate layer having the second lowest specific density was taken out. About 40 mL of deionized water was poured, 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 two more times. Then, about 40 mL of ethanol was poured, and the mixture was shaken and centrifuged in the same manner. The supernatant solution was removed and this operation was repeated two more times. The resulting precipitate was dried at 65 ° C. overnight or longer.
(Step 3)
50 mL of ethanol was added to the dried brown solid, and the mixture was stirred and washed at 60 ° C. overnight or longer. After washing, centrifugation was performed to remove the supernatant, 40 mL of ethanol was added, and the mixture was shaken at room temperature. After centrifugation, the supernatant was removed. This operation was repeated once again. The precipitate was dried at 65 ° C. overnight or more to obtain a carbon material derived from the desired sucrose fatty acid ester.

(Fourier transform infrared absorption spectrum)
The carbon material obtained in Example 2, C = O (stretching, 1800~1520cm ^-1) derived from a carboxyl group and a carbonyl group or OH (stretching, 3700~3100cm ^-1) are observed peak attributed to From this, it was found that an oxygen-containing functional group is present in the carbon material. Furthermore, peaks characteristic of fatty acid-derived alkyl groups are observed ^{near 2955 cm -1} (CH ₃ symmetric stretching vibration), 2924 cm ^-1 (vCH ₂ inverse symmetry), and 2853 cm ^-1 (vCH _{2 symmetry).} , Alkyl groups were also found to be present.

Here, it cannot be denied that the observed alkyl group may be generated as a result of the ester bond in the sucrose fatty acid ester molecule, which is the raw material, being broken under hydrothermal conditions and the fatty acid being physically mixed with the carbon material. 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 a covalent bond, in Example 2. After performing the operation of step 3 twice, Fourier conversion infrared absorption measurement was performed, and the peak intensities of fatty acid-derived alkyl groups in the infrared absorption spectra before and after this step were compared. Fatty acids are usually almost insoluble in water (solubility: 0.0003%, 20 ° C), but slightly soluble in warmed ethanol. If the alkyl groups and carbon were physically mixed, the peak intensity of the alkyl groups seen above should be reduced by removing more alkyl groups after the second wash. ..

The Fourier transform infrared absorption spectrum after performing step 3 twice is shown in FIGS. 1 (A) and 1 (B) (the spectrum displayed as "Example 2 (after washing EtOH twice")). Alkyl derived from fatty acids ^{around 2957 cm -1} (CH ₃ symmetric expansion and contraction vibration), 2924 cm ^-1 (vCH ₂ inverse symmetry), and 2855 cm ^-1 (vCH ₂ symmetric) also for the material obtained by performing step 3 twice. Since a characteristic peak was observed in the group, it is considered that the alkyl group and carbon are not physically mixed, but the alkyl group is covalently incorporated in the carbon skeleton.

(Nitrogen adsorption isotherm)
In the carbon material obtained in Example 2, the rise of the isotherm was larger in the vicinity of high relative pressure than in Example 1, and the calculated total pore volume was 0.16 cm ³ / g (Table 2). Yes, it was larger 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 each other. Further, the present connected body had a sheet-like shape having a thickness of about several tens to 200 nm.
The 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 was observed that the present sheet shape was formed by connecting particles having a diameter of several to several tens of nm.

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 that the material had an oxygen-containing functional group and an alkyl group.

[Example 3]
In this example, in order to examine the basic resistance of the carbon material obtained in this example, a washing treatment with a base was performed. The synthesis including this base treatment step is shown below.
(Step 1)
As a fatty acid ester of sugar, 10 mL of deionized 4 g of sucrose stearic acid ester (DK ester SS, HLB19, monoester ratio; about 100%) represented by the _{molecular formula C 30} H ₅₇ O ₁₂ Dissolved in water. After allowing to stand overnight, it was heated at 120 ° C. for 103 hours in a closed container.
(Step 2)
The obtained brown solid was recovered. Usually, it is divided into three layers and precipitated, but as in Example 2, the intermediate layer having the second lowest specific density was taken out. About 40 mL of deionized water was poured, 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 two more times. Then, about 40 mL of ethanol was poured, and the mixture was shaken and centrifuged in the same manner. The supernatant solution was removed and this operation was repeated two more times. The resulting precipitate was dried at 65 ° C. overnight or longer.
(Step 3)
To the dried brown solid, 50 mL of ethanol was added, and the mixture was washed with stirring at 60 ° C. overnight or more. After washing, centrifugation was performed to remove the supernatant, 40 mL of ethanol was added, and the mixture was shaken at room temperature. After centrifugation, the supernatant was removed. This operation was repeated once again. The precipitate was dried at 65 ° C. overnight or longer.
(Base treatment process)
The carbon material obtained in step 3 was stirred at room temperature in a 0.1 M aqueous sodium hydroxide solution. About 40 mL of deionized water was poured into the stirred carbon material, 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 longer to obtain the desired 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 will decrease and the peak intensity of the alkyl groups in the Fourier transform infrared absorption spectrum will decrease.

(Fourier transform infrared absorption spectrum)
Since the carbon material obtained in Example 3 is affected by a large absorption peak of OH (expansion and contraction, 3700 to 3100 cm ^-1 ), it is not clear as compared with Examples 1 and 2, but the wave number is ^{around 2967 cm -1} (around 2967 cm -1). Some _{absorption is seen in CH 3} symmetrical expansion and contraction 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 found out. Furthermore, C = O (stretching, 1800~1520cm ^-1) derived from a carboxyl group and a carbonyl group or OH (stretching, 3700~3100cm ^-1) from the observed peaks attributed to, oxygen-containing functional groups at the same time It turned out to be kept.

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

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

Therefore, from this example, it was found that the oxygen-containing functional groups and alkyl groups and the pore capacity of the carbon material derived from the sucrose fatty acid ester were maintained even after the treatment with 0.1 M sodium hydroxide.

[Example 4]
In Examples 1 to 3, it was found that a porous carbon having an oxygen-containing functional group and an alkyl group can be obtained by hydrothermal synthesis using a sucrose fatty acid ester in which one alkyl group is linked per molecule of sucrose as a raw material. rice field.
Therefore, in this example, the sucrose fatty acid ester-derived carbon obtained by increasing the hydrophobic chain of the sucrose fatty acid ester raw material used as compared with the sucrose fatty acid ester used in Examples 1 to 3 to increase the surface activity. Attempts were made to increase the pore capacity of the material and impart orientation.
In Examples 1 to 3, a molecule in which one alkyl group was linked to one sugar molecule was 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. A sucrose fatty acid ester containing 30% of the above was used as a raw material. This synthesis is shown below.
(Step 1)
As a fatty acid ester of sugar, _{1 g of a fatty acid ester represented by the molecular formula C 33} H ₆₂ O ₁₂ having an HLB of 15 and a monoester ratio of 70% (Daiichi Kogyo Seiyaku Co., Ltd. DK ester F160) is dissolved in 10 mL of deionized water. rice field. After allowing to stand overnight, it was heated at 120 ° C. for 182 hours in a closed container.
(Step 2)
The obtained brown solid was recovered. Normally, the precipitate is divided into two layers, an upper layer and a lower layer, and the upper layer having a smaller specific density is taken out. About 40 mL of deionized water was poured and 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 two more times. Then, about 40 mL of ethanol was poured and shaken in the same manner for centrifugation. The supernatant solution was removed and this operation was repeated two more times. The resulting precipitate was dried at 65 ° C. overnight or longer.
(Step 3)
50 mL of ethanol was added to the dried brown solid, and the mixture was stirred and washed at 60 ° C. overnight or longer. After washing, centrifugation was performed to remove the supernatant, 40 mL of ethanol was added, and the mixture was shaken at room temperature. After centrifugation, the supernatant was removed. This operation was repeated once again. The precipitate was dried at 65 ° C. overnight or more to obtain a carbon material derived from the desired sucrose fatty acid ester.

(Fourier transform infrared absorption spectrum)
The carbon material obtained in Example 4, C = O (stretching, 1800~1520cm ^-1) derived from a carboxyl group and a carbonyl group or OH (stretching, 3700~3100cm ^-1) are observed peak attributed to From this, it was found that an oxygen-containing functional group is present in the carbon material. Furthermore, although the _{CH 3} symmetric expansion and contraction vibration normally seen near the ^{wave number 2963 cm -1} is not clearly seen, it is derived from fatty acids near 2922 ^{cm -1} _{(vCH 2} inverse symmetry) and 2853 cm ^-1 (vCH _{2 symmetry).} A characteristic peak was observed in the alkyl group, and it was found that the alkyl group was also present.

(Nitrogen adsorption isotherm)
In the carbon material obtained in Example 4, a slight rise of isotherms was observed in the vicinity of high relative pressure as in Example 1, and the calculated total pore volume was 0.05 cm ³ / g (). It was 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 each other.
The transmission electron microscope image of the carbon material obtained in Example 4 is shown in FIG. It was observed that a co-continuous structure with a trunk thickness of several tens of nm was formed.

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

[Example 5]
In this example, the same sucrose fatty acid ester as in Example 4 was used, and the lower layer having a large specific density was taken out in step 2. This synthesis is shown below.
(Step 1)
As a fatty acid ester of sugar, _{1 g of a fatty acid ester represented by the molecular formula C 33} H ₆₂ O ₁₂ having an HLB of 15 and a monoester ratio of 70% (Daiichi Kogyo Seiyaku Co., Ltd. DK ester F160) is dissolved in 10 mL of deionized water. rice field. After allowing to stand overnight, it was heated at 120 ° C. for 182 hours in a closed container.
(Step 2)
The obtained brown solid was recovered. Normally, the precipitation is divided into two layers, an upper layer and a lower layer, but unlike Example 4, the lower layer having a large specific density was taken out. About 40 mL of deionized water was poured and 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 two more times. Then, about 40 mL of ethanol was poured, and the mixture was shaken and centrifuged in the same manner. The supernatant solution was removed and this operation was repeated two more times. The obtained precipitate was dried at 65 ° C. overnight or more to obtain a carbon material derived from the desired sucrose fatty acid ester.
(Step 3)
50 mL of ethanol was added to the dried brown solid, and the mixture was stirred and washed at 60 ° C. overnight or longer. After washing, centrifugation was performed to remove the supernatant, 40 mL of ethanol was added, and the mixture was shaken at room temperature. After centrifugation, the supernatant was removed. This operation was repeated once again. The precipitate was dried at 65 ° C. overnight or more to obtain a carbon material derived from the desired sucrose fatty acid ester.

(Fourier transformation infrared absorption spectrum)
The carbon material obtained in Example 5, C = O (stretching, 1800~1520cm ^-1) derived from a carboxyl group and a carbonyl group or OH (stretching, 3700~3100cm ^-1) are observed peak attributed to From this, it was found that an oxygen-containing functional group is present in the carbon material. Furthermore, peaks characteristic of fatty acid-derived alkyl groups are observed near wavenumbers of 2972 cm ^-1 (CH ₃ symmetric stretching vibration), 2925 cm ^-1 (vCH ₂ inverse symmetry), and 2854 cm ^-1 (vCH _{2 symmetry).} , Alkyl groups were also found to be present.

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

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

Therefore, from this example, porous carbon can be obtained by hydrothermal synthesis using a 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 loose orientation. Do you get it.

In Example 5, unlike Examples 1 to 4, step 3 can be omitted. As described above, the porous carbon obtained in the present invention is synthesized by three steps of steps 1 to 3, of which step 3 is obtained after step 2 for the purpose of removing physically mixed alkyl groups. Only required if the material contains physically mixed alkyl groups. In Examples 1 to 4, after the step 3, the peak intensity of the alkyl group is reduced in the Fourier transform infrared absorption spectrum as compared with the case before the step 3, and the alkyl group existing as a physical mixture is the step. It was found that it was removed by 3. Further, as described above, even if step 3 is repeated once again, the peak intensity of alkyl in 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. 1 (A) and 1 (B), no significant change was observed in the peak intensity of the alkyl group observed in the Fourier transform infrared absorption spectrum before and after the step 3 (step 3). The Fourier transform infrared absorption spectrum of the previous carbon material is described as "Example 5 (step 3 omitted)"). Therefore, it is considered that there are almost no physically mixed alkyl groups in the material obtained in step 2, and therefore step 3 does not have to be performed.

Further, in Example 5, the observation results of the scanning electron microscope observation and the nitrogen adsorption measurement did not change significantly regardless of the presence or absence of the step 3. In the scanning electron microscope observation of the carbon material obtained by omitting step 3, particles (primary particles) having a size of about several tens of nm are gentle but constant, as in the case of the carbon material obtained in step 3. It was observed that particles (secondary particles) having a size of several to several tens of μm were formed by being connected to each other with the orientation of.
Further, similar to the carbon material obtained in step 3, a large rise of the isotherm was observed in the vicinity of the high relative pressure of nitrogen adsorption, and the calculated total pore volume was 0.70 cm ³ / g.
Further, in this example, even if the hydrothermal treatment time of step 1 is set to 103 hours, which is the same as in Examples 1 to 3, a brown solid can be obtained, but among the material evaluations described in [0033] to [0035] above, , The yield required for nitrogen adsorption measurement was not reached. However, in this case as well, almost the same results as in Example 5 were obtained from the Fourier transform infrared absorption measurement and the scanning electron microscope.
FIG. 13 shows a transmission electron microscope image of the carbon material obtained by setting step 1 to 103 hours in Example 5 and omitting step 3. It was observed that a structure in which primary particles having a size of several tens of nm were connected was uniformly formed inside 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, it is generally said that in the evaporation and drying of a porous material, the porous body structure shrinks and the pore volume decreases as the solvent is desorbed and evaporated from the porous body. On the other hand, in a drying method called freeze-drying, the solvent is once frozen and then removed by sublimation. Therefore, if the freeze-drying method is used, it is expected that the decrease in pore volume in the drying step of the sucrose fatty acid-derived carbon material can be suppressed.
Therefore, in this example, the material obtained in Example 5, which had the largest pore capacity so far, was freeze-dried instead of evaporative drying at 65 ° C. in order to further increase the pore capacity. .. This synthesis is shown below.
(Step 1)
As a fatty acid ester of sugar, _{1 g of a fatty acid ester represented by the molecular formula C 33} H ₆₂ O ₁₂ having an HLB of 15 and a monoester ratio of 70% (Daiichi Kogyo Seiyaku Co., Ltd. DK ester F160) is dissolved in 10 mL of deionized water. rice field. After allowing to stand overnight, it was heated at 120 ° C. for 182 hours in a closed container.
(Step 2)
The obtained brown solid was recovered. Normally, the precipitate is divided into two layers, an upper layer and a lower layer, and the lower layer having a large specific density is taken out as in Example 5. About 40 mL of deionized water was poured, 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 two more times. Then, about 40 mL of ethanol was poured, and the mixture was shaken and centrifuged in the same manner. The supernatant solution was removed and this operation was repeated two more times.
(Freeze-drying process)
In step 2, after washing with ethanol, the residual ethanol was replaced with deionized water. Then, freeze-drying was carried out to obtain a desired carbon material derived from sucrose fatty acid.
Steps 1 and 2 of this embodiment are the same as those of the fifth embodiment. That is, since there are almost no alkyl groups physically mixed in the material obtained after the step 2, the step 3 can be omitted. Therefore, in this example, the freeze-drying step was performed without going through step 3.

(Fourier transform infrared absorption spectrum)
The carbon material obtained in Example 6, C = O (stretching, 1800~1520cm ^-1) derived from a carboxyl group and a carbonyl group or OH (stretching, 3700~3100cm ^-1) are observed peak attributed to From this, it was found that an oxygen-containing functional group is present in the carbon material. Furthermore, peaks characteristic of fatty acid-derived alkyl groups are observed ^{near 2959 cm -1} (CH ₃ symmetric stretching vibration), 2926 cm ^-1 (vCH ₂ inverse symmetry), and 2859 cm ^-1 (vCH _{2 symmetry).} , Alkyl groups were also found to be present.

(Nitrogen adsorption isotherm)
In the carbon material obtained in Example 6, a large rise of the isotherm was observed near the high relative pressure, and the calculated total pore volume was 0.98 cm ³ / g (Table 2), which was compared with Example 5. Also showed a larger pore capacity.

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

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

[Comparative Example 1]
A comparative synthetic test was carried out using sucrose itself, which does not have an alkyl group incorporated in the molecule, that is, is not amphipathic, as a raw material, in almost the same manner as in the above example. This synthesis is shown below.
(Step 1)
2.3 g of sucrose, which is equivalent to the amount of substance of the sucrose stearic acid ester used in Example 1, was dissolved in 10 mL of deionized water. After allowing to stand overnight, it was heated at 120 ° C. for 103 hours in a closed container.
(Step 2)
The obtained brown precipitate was collected, and about 40 mL of deionized water was poured and 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 the mixture was shaken and centrifuged in the same manner. After removing the supernatant solution, this operation was repeated two more times. The resulting precipitate was dried at 65 ° C. overnight or longer.

(Fourier transform infrared absorption spectrum)
Carbon material obtained in Comparative Example 1, C = O (stretching, 1800~1520cm ^-1) derived from a carboxyl group and a carbonyl group or OH (stretching, 3700~3100cm ^-1) are observed peak attributed to However, it is characteristic of fatty acid-derived alkyl groups generated ^{around 2963 cm -1} (CH ₃ symmetric expansion and contraction vibration), 2925 cm ^-1 (vCH ₂ inverse symmetry), and 2854 cm ^-1 (vCH _{2 symmetry).} No peak was seen.
As described above, the porous material of the example is synthesized by three steps of steps 1 to 3, and step 3 in this step 3 is obtained after step 2 for the purpose of removing physically mixed alkyl groups. It is only needed if the material to be used 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 peak of the alkyl group. Therefore, since it does not have an alkyl group derived from a fatty acid itself, it was obvious that the alkyl group was not physically mixed. Therefore, in the synthesis of Comparative Example 1, step 3 was omitted.

(Nitrogen adsorption isotherm)
The carbon material obtained in Comparative Example 1 did not show a 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)
A scanning electron microscope image of the carbon material obtained in Comparative Example 1 is shown in FIG. Spherical particles of two sizes, several μm in diameter and several hundred nm, were observed, but the surface of both particles was smooth, and particles having a size of several to several tens of nm as seen in the examples were observed. It was not observed that they were connected to each other.
The transmission electron microscope image of the carbon material obtained in Comparative Example 1 is shown in FIG.
Although some shades were observed in the electron microscope image, the appearance of the co-continuous structure and the fine particle conjugate as seen in the examples was not 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 physically mixed sucrose and fatty acid, which are not amphipathic, as raw materials. This 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, which are equivalent to the amount of substance of the sucrose stearic acid ester used in Example 1. After allowing to stand overnight, it was heated at 120 ° C. for 103 hours in a closed container.
(Step 2)
The obtained brown precipitate was collected, and about 40 mL of deionized water was poured and 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 the mixture was shaken and centrifuged in the same manner. After removing the supernatant solution, this operation was repeated two more times. The resulting precipitate was dried at 65 ° C. overnight or longer.

(Fourier transform infrared absorption spectrum)
Carbon material obtained in Comparative Example 2, C = O (stretching, 1800~1520cm ^-1) derived from a carboxyl group and a carbonyl group or OH (stretching, 3700~3100cm ^-1) are observed peak attributed to However, it is characteristic of fatty acid-derived alkyl groups generated ^{around 2963 cm -1} (CH ₃ symmetric expansion and contraction vibration), 2925 cm ^-1 (vCH ₂ inverse symmetry), and 2854 cm ^-1 (vCH _{2 symmetry).} No peak was seen. Similar to Comparative Example 1, in this Comparative Example as well, the Fourier transform infrared absorption spectrum of the material obtained after the step 2 showed almost no peak of the alkyl group. Therefore, step 3 was omitted in the synthesis of this comparative example.

(Nitrogen adsorption isotherm)
Similarly to Comparative Example 1, the carbon material obtained in Comparative Example 2 did not show a 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)
A scanning electron microscope image of the carbon material obtained in Comparative Example 2 is shown in FIG. Similar to Comparative Example 1, spherical particles having two sizes of several μm and several hundred nm were observed, but the surface of both particles was smooth, and the number to several tens as seen in the examples. No appearance of fine particles of nm lined up was observed.

From the above, in either case, when sucrose itself is used as a raw material or when a physical mixture of sucrose itself and fatty acid is used as a raw material, porous carbon cannot be obtained, and the carbon material also has an alkyl group derived from fatty acid. I found that I wouldn't.

The carbon skeleton obtained from sugar by the hydrothermal synthesis method is usually aromatized by firing in an inert atmosphere at 400 to 500 ° C. or higher, and the carbon material is good as the firing temperature further rises. It has excellent electrical conductivity and can be used as an electrode material.
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.
In Examples 1 to 6, the main firing treatment was performed on Examples 2 and 5, which had a particularly large pore volume and did not undergo special treatment such as base treatment or freeze-drying, and were described in Examples 7 and 8, respectively. bottom. It is shown below.

[Example 7]
(Step 1)
As a fatty acid ester of sugar, 10 mL of deionized 4 g of sucrose stearic acid ester (DK ester SS, HLB19, monoester ratio; about 100%) represented by the _{molecular formula C 30} H ₅₇ O ₁₂ Dissolved in water. After allowing to stand overnight, it was heated at 120 ° C. for 103 hours in a closed container.
(Step 2)
The obtained brown solid was recovered. Usually, it is divided into three layers and precipitated, but as in Example 2, the intermediate layer having the second lowest specific density was taken out. About 40 mL of deionized water was poured and 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 two more times. Then, about 40 mL of ethanol was poured, and the mixture was shaken and centrifuged in the same manner. The supernatant solution was removed and this operation was repeated two more times. The resulting precipitate was dried at 65 ° C. overnight or longer.
(Step 3)
50 mL of ethanol was added to the dried brown solid, and the mixture was stirred and washed at 60 ° C. overnight or longer. After washing, centrifugation was performed to remove the supernatant, 40 mL of ethanol was added, and the mixture was shaken at room temperature. After centrifugation, the supernatant was removed. This operation was repeated once again. The precipitate was dried at 65 ° C. overnight or longer.
(Baking process under nitrogen)
The obtained material was calcined at 550 ° C. under a nitrogen flow of 600 mL / min to obtain a carbon material derived from the desired sucrose fatty acid ester.

(Fourier transform infrared absorption spectrum)
The carbon material obtained in Example 7 is usually produced in the vicinity of ^{wavenumber 2963 cm -1} _{(CH 3} symmetric stretching vibration), 2925 cm ^-1 (vCH ₂ inverse symmetry), and 2854 cm ^-1 (vCH ₂ symmetry). No characteristic peak was observed in the fatty acid-derived alkyl group, but a peak of expansion and contraction of conjugated C = C or olefin-based C = ^{CO was observed at 1650 to 1450 cm -1.} Absorption peaks attributable to carbon-hydrocarbon out-of-plane angular oscillations of the aromatic ring were observed at 886 cm ^-1 and, albeit moderately, 805 cm ^-1 and 766 cm ^-1. Furthermore, an absorption peak attributed to the expansion and contraction movement of the OH group was observed at 3700 to 3100 cm- ^{1, and it was found that the obtained carbon material had a hydroxyl group.}

Here, as described above, the porous material of the example is synthesized by the three steps of steps 1 to 3, and the step 3 in this step 3 aims at removing the physically mixed alkyl group, and is the step 2. It is only needed if the material obtained later contains a physically mixed alkyl group. In this embodiment, even if the alkyl groups are physically mixed in step 2, the alkyl groups are thermally decomposed by themselves when fired at 550 ° C., so it is considered that the alkyl groups are removed without using step 3. .. Therefore, in this example, the following measurements were performed on the carbon material obtained by performing the firing step without going through step 3.

(Nitrogen adsorption isotherm)
In the carbon material obtained in Example 7, a rise on the low relative pressure side and a rise on the high relative pressure side were observed. The former indicates the presence of micropores, and the latter indicates the presence of at least one of mesopores and 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 each other. Further, this connected body had a sheet-like shape having a thickness of about several tens to 200 nm.
The 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 was observed that the sheet shape was formed by connecting particles having several to several tens of nm to each other.

(Measurement of conductivity)
By sandwiching both ends of the dense particle group of carbon material obtained in Example 7 between two terminals and measuring the resistance value using a digital multimeter, the presence or absence of conductivity is confirmed as follows. bottom.
In advance, the resistance value is displayed for the conductive material (for example, the conductive porous carbon described in S. Kubo et al., Chem. Mater. 2013, 25, 4781), but the resistance value is displayed for the insulating material. After confirming that the value was not displayed, the above measurement was performed to confirm whether or not the resistance value was displayed.
The carbon material obtained in Example 7 showed a resistance value of about 10 to 20 MΩ when measured under the condition that the distance between both terminals was about 0.5 to 1 mm.

Therefore, by firing the porous carbon material using the fatty acid ester of sugar as a raw material in an inert atmosphere, a highly aromatic and conductive porous carbon material can be obtained from the fatty acid ester raw material of sugar, and the material thereof. Was found to have a hydroxyl group.

[Example 8]
(Step 1)
As a fatty acid ester of sugar, _{1 g of a fatty acid ester represented by the molecular formula C 33} H ₆₂ O ₁₂ having an HLB of 15 and a monoester ratio of 70% (Daiichi Kogyo Seiyaku Co., Ltd. DK ester F160) is dissolved in 10 mL of deionized water. rice field. After allowing to stand overnight, it was heated at 120 ° C. for 182 hours in a closed container.
(Step 2)
The obtained brown solid was recovered. Normally, the precipitate is divided into two layers, an upper layer and a lower layer, and the lower layer having a large specific density is taken out as in Example 5. About 40 mL of deionized water was poured and 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 two more times. Then, about 40 mL of ethanol was poured and shaken in the same manner for centrifugation. The supernatant solution was removed and this operation was repeated two more times. The resulting precipitate was dried at 65 ° C. overnight or longer.
(Baking process under nitrogen)
The obtained material was calcined at 550 ° C. under a nitrogen flow of 600 mL / min to obtain a carbon material derived from the desired sucrose fatty acid ester.
Here, steps 1 and 2 of this embodiment are the same as those of the fifth embodiment. That is, since step 3 may be omitted, in this embodiment, firing under nitrogen was performed without performing step 3.

(Fourier transform infrared absorption spectrum)
The carbon material obtained in Example 8 is usually produced in the vicinity of ^{wavenumber 2963 cm -1} _{(CH 3} symmetric stretching vibration), 2925 cm ^-1 (vCH ₂ inverse symmetry), and 2854 cm ^-1 (vCH ₂ symmetry). No characteristic peak was observed in the fatty acid-derived alkyl group, but a peak of expansion and contraction of conjugated C = C or olefin-based C = ^{CO 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, an absorption peak attributed to the OH group expansion and contraction movement was observed at 3700 to 3100 cm- ^{1, indicating that the obtained carbon material has a hydroxyl group.}

(Nitrogen adsorption isotherm)
In the carbon material obtained in Example 8, a rise on the low relative pressure side and a large rise on the high relative pressure side were observed. The former indicates the presence of micropores, and the latter indicates the presence of at least one of mesopores and 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 having a size of several tens of nm were connected to each other to form particles having a size of several to several tens of μm.
(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 resistance value of the degree was shown.

Therefore, by firing the porous carbon material using the fatty acid ester of sugar as a raw material in an inert atmosphere, a highly aromatic and conductive porous carbon material can be obtained from the fatty acid ester raw material of sugar, and the material thereof. Was found to have a hydroxyl group.

[Comparative Example 3]
A comparative synthetic test was carried out using sucrose itself, which does not have an alkyl group incorporated in the molecule, that is, is not amphipathic, as a raw material, in almost the same manner as in the above example. In particular, a carbon material obtained by hydrothermal synthesis using sucrose itself as a raw material was calcined under a nitrogen flow to make a comparison with Examples 7 and 8. This synthesis is shown below.
(Step 1)
2.3 g of sucrose, which is equivalent to the amount of substance of the sucrose stearic acid ester used in Example 1, was dissolved in 10 mL of deionized water. After allowing to stand overnight, it was heated at 120 ° C. for 103 hours in a closed container.
(Step 2)
The obtained brown precipitate was collected, and about 40 mL of deionized water was poured and 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 the mixture was shaken and centrifuged in the same manner. After removing the supernatant solution, this operation was repeated two more times. The resulting precipitate was dried at 65 ° C. overnight or longer.
(Baking process under nitrogen)
The obtained material was calcined at 550 ° C. under a nitrogen flow of 600 mL / min to obtain a comparative carbon material.
In this comparative example, the firing step was performed without going through step 3, as in Examples 7 and 8 in which firing under nitrogen was performed.

(Fourier transform infrared absorption spectrum)
The carbon material obtained in this comparative example is usually generated in the vicinity of ^{wave number 2963 cm -1} _{(CH 3} symmetric stretching vibration), 2925 cm ^-1 (vCH ₂ inverse symmetry), and 2854 cm ^-1 (vCH ₂ symmetry). No characteristic peak was observed in the alkyl group derived from the fatty acid. From 1650 to 1450 cm ^-1 , the expansion and contraction peaks of conjugated C = C or olefinic C = C-O are 874 cm ^-1 , 801 cm ^-1 , 748 cm ^-1 , and the carbon-hydrogen out-of-plane eccentric vibration of the aromatic ring. However, no clear absorption peak attributed to the OH group stretching motion was observed at 3700 ^{to 3100 cm -1} , indicating that most of the hydroxyl groups were lost in this comparative carbon material. rice field.

(Scanning electron microscope image and transmission electron microscope image)
A 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 having two sizes of several μm and several hundred nm were observed, but the surface of both particles was smooth, and the number as seen in Examples ~. It was not observed that fine particles of several tens of nm were lined up.

The production conditions and the evaluation results of porosity in the above Examples and Comparative Examples are shown in Table 1 below.
However, the evaluation of porosity was based on ^{Comparative Examples 1 and 2 (x) having a nitrogen adsorption amount of 0.01 cm 3} / g, and ⊚ → ○ → Δ were set in order from the one with the largest adsorption amount.

The total pore volumes of the carbon materials obtained in the above Examples and Comparative Examples are shown in Table 2 below.
However, the total pore volume was calculated from the amount of nitrogen adsorbed at the measurement points where the relative pressure was 0.991 or more and 0.996 or less.

As described above, the carbon material obtained from the hydrothermal synthesis using the fatty acid ester of the sugar as a raw material of the present invention 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 in Comparative Examples 1 and 2 had an oxygen-containing functional group but no alkyl group.
Further, the alkyl group-containing carbon material of the present invention had a pore capacity larger than that of the carbon material obtained by using the sugar itself and the physical mixture of sugar and fatty acid as raw materials in Comparative Examples 1 and 2.
Further, the carbon material obtained from the fatty acid ester raw material of the sugar of the present invention was composed of particles having a size of several to several tens of μm formed by connecting particles having a size of several to several tens of nm. Further, the above-mentioned particles having a size of several tens to several tens of nm are connected with a gentle but constant orientation, or the connected body has a sheet-like shape having a thickness of several tens to 200 nm. Some were doing it. This was significantly different from Comparative Examples 1 and 2, which had a smooth surface texture obtained from the sugar itself or a mixture of sugar and fatty acid, and had a diameter of several hundred nm to several μm.
Therefore, it can be said that the porous carbon derived from the fatty acid ester of the sugar of the present invention is produced by utilizing the fact that the carbon source itself is amphipathic. That is, the sugar moiety of the raw material molecule acts as a hydrophilic moiety and the alkyl moiety acts as a hydrophobic portion, which induces an interfacial phenomenon of the carbon source itself during hydrothermal synthesis, and forms carbon nanostructures such as micelles and liquid crystals. NS. It is considered that the resulting material becomes porous. According to the method of the present invention, since the carbon material is already porous after hydrothermal synthesis, the porous carbon material can be obtained without using the thermal decomposition removal step usually required when using a mold. Therefore, it is possible to obtain a porous carbon in which an oxygen-containing functional group is maintained.

On the other hand, for application to electrode materials and the like, it is necessary to enhance the aromaticity of the carbon skeleton of the porous carbon derived from the fatty acid ester of the obtained sugar. Therefore, when the porous carbon derived from the fatty acid ester of the sugar is fired in an inert atmosphere, the porous carbon derived from the fatty acid ester of the sugar of the present invention contains oxygen even after high-temperature firing in which the loss of functional groups usually progresses. It had a functional group (hydroxyl group). The pore volume was 0.62 to 1.23 cm ³ / g. In addition, the aromaticity of the carbon skeleton was enhanced, and it also had conductivity.
On the other hand, when the carbon material obtained from the sugar itself in Comparative Example 3 was calcined in an inert atmosphere, the aromaticity of the carbon skeleton was enhanced, but most of the oxygen-containing functional groups were lost. Further, when the carbon material usually obtained from the sugar itself is calcined in the same inert atmosphere as in Examples 7 and 8 at 550 ° C., the pore volume is 0.15 cm ³ / g or less (Non-Patent Document: L). See Yu et al., Langmuir, 2012, 28, 12373).
Further, the carbon material of the present invention made of a calcined product of a hydrothermal synthesis made from a fatty acid ester of sugar has a size of several to several tens of μm in which particles having a size of several to several tens of nm are formed in a row. It consisted of particles of fatty acid. Further, some particles having a size of several tens to several tens of nm are connected to each other and have a sheet-like shape having a thickness of several tens to 200 nm. This was significantly different from the spherical particles of Comparative Example 3 having a smooth surface texture obtained by calcining a hydrothermal synthesis of sugar itself and having a diameter of several hundred nm to several μm.
Therefore, in the present invention, by using a fatty acid ester of sugar as a raw material, a porous carbon having a large pore capacity and having both aromaticity of a carbon skeleton and an oxygen-containing functional group even after firing in an inert atmosphere. Can be said to be obtained.

Claims (9)

A method for producing porous carbon, which produces porous carbon by a hydrothermal reaction using a sugar fatty acid ester as a raw material. The method for producing porous carbon according to claim 1, 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 1 or 2 , wherein the sugar is a monosaccharide, a disaccharide or a polysaccharide, which may contain nitrogen, or a mixture of two or more kinds thereof. The method for producing a porous carbon according to any one of claims 1 to 3 , wherein the fatty acid ester of the sugar is a monoester, a diester or a polyester, or a mixture of two or more kinds thereof. The method for producing porous carbon according to any one of claims 1 to 4, wherein the hydrothermal reaction is carried out at 100 to 350 ° C. The method for producing porous carbon according to any one of claims 1 to 5, wherein the solid obtained by the hydrothermal reaction is washed with water and an organic solvent and then dried. The method for producing porous carbon according to claim 6, wherein the dried solid is washed with a solvent under heating and then dried. A method for producing porous carbon, which is obtained by producing porous carbon by the method according to any one of claims 1 to 7, and then further firing the porous carbon. The method for producing porous carbon according to any one of claims 1 to 8 , wherein the porous carbon has an oriented nanostructure.

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