JP7302840B2 - Method for producing carbon dioxide storage-release material - Google Patents

Description

The present invention relates to a method for producing a carbon dioxide storage-release material capable of storing (absorbing) or releasing carbon dioxide.

In order to reduce carbon dioxide, which is a greenhouse gas, the development of materials for storing carbon dioxide is underway.
As a material for storing carbon dioxide, a nitrogen-doped carbon material having a carbon dioxide adsorption amount of 3.13 mmol/g at 25° C. and 1 atm is known (see, for example, Non-Patent Document 1). .

Rapid Synthesis of Nitrogen-Doped Porous Carbon Monolith for CO2 Capture, Guang-Ping Hao, Wen-Cui Li, Dan Qian, and An-Hui Lu, Advanced Materials, 2010, 22, 853 -857.

However, the material described in Non-Patent Document 1 was unable to retain carbon dioxide after releasing the carbon dioxide pressure during storage.

The present invention has been made in view of the above circumstances, and a carbon dioxide storage-release material capable of storing carbon dioxide at normal temperature (15° C. to 25° C.) and normal pressure (1 atm) or less, and a method for producing the same. intended to provide In addition, the present invention is a carbon dioxide that can retain carbon dioxide even when the pressure of carbon dioxide during storage is released, and can store carbon dioxide again after releasing carbon dioxide by heating at 50 ° C. or higher. It is an object of the present invention to provide a carbon storage-release material and a method for producing the same.

[1] Consisting of a two-dimensional borohydride-containing sheet having a two-dimensional network , showing peaks at 187.5 eV and 191.2 eV derived from boron B1s in X-ray photoelectron spectroscopy, and peaks derived from magnesium A method for producing a carbon dioxide storage-release material having a spectrum not shown, comprising: magnesium diboride of MgB 2 type structure _; and an exchange resin in a polar organic solvent to obtain a carbon dioxide storage-release material precursor; and a step of heat-treating the carbon dioxide storage-release material precursor at 200°C to 350°C. A method for producing a carbon dioxide storage-release material .

[2] The carbon dioxide storage-release material precursor has a molar ratio of boron to hydrogen of 1:1 calculated by thermal desorption analysis and mass measurement before and after heating (HB) n (n _≧ 4 ), and in X-ray photoelectron spectroscopy analysis, it has a spectrum showing a peak in the vicinity of 188 eV derived from B1s of negatively charged boron and showing no peak derived from magnesium, and electron beam energy The method for producing a carbon dioxide storage-release material according to [1] , which has a spectrum showing a peak at 191 eV derived from the sp2 structure of boron in loss spectroscopy .

[3] The method for producing a carbon dioxide storage-release material according to [1] or [2], wherein the ion exchange resin has a sulfo group .

[4] The method for producing a carbon dioxide storage-release material according to any one of [1] to [3], wherein the polar organic solvent is acetonitrile or methanol .

According to the present invention, it is possible to provide a carbon dioxide storage-release material capable of storing carbon dioxide at normal temperature (15° C. to 25° C.) and normal pressure (1 atm) or lower, and a method for producing the same. Further, according to the present invention, carbon dioxide can be retained even when the pressure of carbon dioxide at the time of absorption is released, and after releasing carbon dioxide by heating at 50° C. or more, carbon dioxide can be absorbed again. It is possible to provide a carbon dioxide storage-release material and a method for manufacturing the same.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic diagram showing the molecular structure of a two-dimensional boron-containing sheet that constitutes the carbon dioxide storage-release material of the present invention, where (a) is a diagram showing the XY plane, (b) is a diagram showing the YZ plane, and (c) is a diagram showing the XY plane. It is a figure which shows ZX plane. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing the molecular structure of a carbon dioxide storage-release material precursor used in a method for producing a carbon dioxide storage-release material, where (a) is a view showing the XY plane, (b) is a view showing the YZ plane, and (c). ) indicates the ZX plane. 4 is a diagram showing the results of X-ray photoelectron spectroscopy in Experimental Example 1. FIG. FIG. 10 is a diagram showing the results of X-ray photoelectron spectroscopy in Experimental Example 2; FIG. 10 is a diagram showing the results of electron beam energy loss spectroscopy in Experimental Example 3; FIG. 10 is a diagram showing the results of electron beam energy loss spectroscopy in Experimental Example 3; FIG. 10 is a diagram showing the results of thermal desorption analysis in Experimental Example 4; FIG. 11 shows the results of visible/ultraviolet spectroscopic analysis in Experimental Example 5. FIG. FIG. 11 shows the results of X-ray photoelectron spectroscopy in Experimental Example 6. FIG. FIG. 10 is a diagram showing the relationship between the pressure inside the sample charging part and the elapsed time after introduction of carbon dioxide in Experimental Example 7; FIG. 10 is a diagram showing the relationship between the carbon dioxide adsorption amount of the product after heat treatment and the number of carbon dioxide adsorptions in Experimental Example 8; FIG. 10 is a diagram showing the relationship between the amount of carbon dioxide adsorbed by the product after heat treatment and the pressure of carbon dioxide introduced into the sample inlet in Experimental Example 9;

Embodiments of the carbon dioxide storage-release material and the method for producing the same of the present invention will be described.
It should be noted that the present embodiment is specifically described for better understanding of the gist of the invention, and does not limit the invention unless otherwise specified.

[Carbon dioxide storage and release material]
The carbon dioxide storage-release material of this embodiment has n(H _x B _y ) (n≧4, 5/6≦x/y≦1/3) with a molar ratio of boron to hydrogen of 6:5 to 3:1 ) consisting of a two-dimensional borohydride-containing sheet with a two-dimensional network consisting of That is, the carbon dioxide storage-release material of the present embodiment contains boron atoms (B) and hydrogen atoms (H) in a molar ratio of 6:5 to 3:1, and is formed only from these two atoms. It is a sheet-like material composed of two-dimensional borohydride-containing sheets with a two-dimensional network.

In the carbon dioxide storage-release material of the present embodiment, the ratio (molar ratio) of boron atoms (B) and hydrogen atoms (H) is calculated by temperature-programmed desorption gas analysis and mass measurement before and after heating, which will be described later.

In addition, the two-dimensional borohydride-containing sheet constituting the carbon dioxide storage-release material of the present embodiment shows peaks at 187.5 eV and 191.2 eV derived from B1s of boron in X-ray photoelectron spectroscopy, and magnesium It has a spectrum showing no originating peaks.

X-ray photoelectron spectroscopic analysis of the carbon dioxide storage-release material of the present embodiment will be described later.

In the two-dimensional borohydride-containing sheet constituting the carbon dioxide storage-release material of the present embodiment, as shown in FIG. 1, boron atoms (B) are arranged in a hexagonal ring like a benzene ring, and the It exists at the vertexes of hexagons, and hexagons formed by boron atoms (B) are connected without gaps to form a mesh-like surface structure (two-dimensional network). Furthermore, the two-dimensional borohydride-containing sheet in the present embodiment, as shown in FIG. Randomly bound without agglomeration.
In the two-dimensional borohydride-containing sheet of the present embodiment, the hexagonal mesh formed by boron atoms (B) means, for example, a honeycomb shape.

The carbon dioxide storage-release material of this embodiment is a thin-film substance having a two-dimensional network composed of boron atoms (B) and hydrogen atoms (H). In addition, the carbon dioxide storage-release material of the present embodiment contains almost no magnesium atoms derived from magnesium diboride used in the method for producing the carbon dioxide storage-release material of the present embodiment, which will be described later, or other metal atoms. .
In the carbon dioxide storage-release material of the present embodiment, the total number of boron atoms (B) and hydrogen atoms (H) forming the network surface structure of the two-dimensional borohydride-containing sheet is 1000 or more.

The bond distance _d1 between two adjacent boron atoms (B) shown in FIG. 1(a) is 0.170 nm to 0.185 nm.

The thickness of the carbon dioxide storage-release material of this embodiment is 0.5 nm to 10 nm.
In the two-dimensional borohydride-containing sheet constituting the carbon dioxide storage-release material of the present embodiment, the length in at least one direction (for example, the length in the X direction or Y direction in FIG. 1(a)) is 100 nm or more. is preferred. In the carbon dioxide storage-release material of the present embodiment, if the two-dimensional borohydride-containing sheet has a length of 100 nm or more in at least one direction, the carbon dioxide storage-release material of the present embodiment is effective as a carbon dioxide storage-release material. can be used for
The size (area) of the carbon dioxide storage-release material of the present embodiment is not particularly limited, and can be formed to any size by the method for producing the carbon dioxide storage-release material of the present embodiment, which will be described later.

The two-dimensional borohydride-containing sheet that constitutes the carbon dioxide storage-release material of this embodiment may be terminated with an oxide. That is, the two-dimensional borohydride-containing sheet in the present embodiment may form an oxide at the end of its molecular structure. Examples of the oxide forming the ends of the molecular structure of the two-dimensional borohydride-containing sheet in the present embodiment include boric acid (B(OH) ₃ ) and boron oxide (B ₂ O ₃ ). The two-dimensional borohydride-containing sheet that constitutes the carbon dioxide storage-release material of this embodiment forms a more stable molecular structure by being terminated with an oxide.

The two-dimensional borohydride-containing sheet constituting the carbon dioxide storage-release material of this embodiment is a substance having a crystal structure. In addition, in the two-dimensional borohydride-containing sheet of the present embodiment, the bonding strength between the boron atoms (B) forming the hexagonal rings and between the boron atoms (B) and the hydrogen atoms (H) is strong. Therefore, even if the two-dimensional borohydride-containing sheet in the present embodiment forms a crystal (aggregate) in which a plurality of layers are laminated during production, it is easily cleaved along the crystal plane like graphite, and a single layer is formed. It can be separated (collected) as a two-dimensional sheet.

According to the carbon dioxide storage-release material of the present embodiment, n(H _x B _y ) (n≧4, 5/6≦x/y≦1/3), composed of a two-dimensional borohydride-containing sheet having a two-dimensional network, and derived from B1s of boron in X-ray photoelectron spectroscopy. Since it has a spectrum that shows peaks at 187.5 eV and 191.2 eV and does not show a peak derived from magnesium, carbon dioxide can be stored at room temperature and pressure below normal temperature. In addition, according to the carbon dioxide storage-release material of the present embodiment, carbon dioxide can be retained even when the carbon dioxide pressure at the time of absorption is released, and after releasing carbon dioxide by heating at 50 ° C. or higher, According to the carbon dioxide storage-release material of the present embodiment, carbon dioxide can be stored or released repeatedly.

The carbon dioxide storage-release material of the present embodiment can store (occlude) carbon dioxide in a molecular state (where carbon dioxide molecules are present as they are) at normal temperature and normal pressure or less. In the carbon dioxide storage-release material of the present embodiment, it is considered that carbon dioxide is stored by binding oxygen atoms of carbon dioxide to boron atoms contained in the carbon dioxide storage-release material. Then, by heating the carbon dioxide storage-release material of the present embodiment in which carbon dioxide is stored (occluded) to 50° C. or higher, the stored (occluded) carbon dioxide can be released. That is, unless the carbon dioxide storage-release material of the present embodiment that stores (occludes) carbon dioxide is heated to 50° C. or higher, the carbon dioxide storage-release material of the present embodiment stores carbon dioxide semipermanently. can be done. Therefore, the carbon dioxide storage-release material of the present embodiment can store (absorb) carbon dioxide and contribute to the reduction of carbon dioxide in the atmosphere.

In order to release the stored (occluded) carbon dioxide, the temperature at which the carbon dioxide storage-release material of the present embodiment is heated is preferably 300° C. or less. When the temperature for heating the carbon dioxide storage-release material exceeds 300 ° C., the structure that reduces the carbon dioxide storage capacity (188. structure having a peak at 6 eV), the temperature at which the carbon dioxide storage-release material is heated to release the stored (occluded) carbon dioxide is preferably 300° C. or less.

Further, when the carbon dioxide storage-release material of the present embodiment stores (occludes) carbon dioxide, the carbon dioxide storage-release material is washed with water or an alkaline aqueous solution such as an amine, and the water or the alkaline aqueous solution is washed. Carbon dioxide can be released by dissolving (absorbing) carbon dioxide in . Thus, the carbon dioxide storage-release material of the present embodiment can repeatedly store or release carbon dioxide by dissolving (absorbing) the stored (absorbed) carbon dioxide in water or an alkaline aqueous solution.

[Method for producing carbon dioxide storage-release material]
In _the method for producing a carbon dioxide storage-release material of the present embodiment, a polar A step of mixing in an organic solvent to obtain a carbon dioxide storage-release material precursor (hereinafter referred to as “first step”); and a step of heat-treating the carbon dioxide storage-release material precursor at 200°C to 350°C. (hereinafter referred to as a “second step”).

In _the method for producing a carbon dioxide storage-release material of the present embodiment, a polar Mix in an organic solvent to obtain a carbon dioxide storage-release material precursor (first step).

The ion-exchange resin in which magnesium ions constituting magnesium diboride and ion-exchangeable ions are coordinated is not particularly limited. styrene polymer having a functional group α (hereinafter referred to as "functional group α"), divinylbenzene polymer having a functional group α, copolymerization of styrene having a functional group α and divinylbenzene having a functional group α A coalescence etc. are mentioned.
Examples of the functional group α include a sulfo group and a carboxyl group. Among these, a sulfo group is preferable because it can easily exchange ions with magnesium ions constituting magnesium diboride in a polar organic solvent.

The polar organic solvent is not particularly limited, and examples thereof include acetonitrile, N,N-dimethylformamide, methanol and the like. Among these, acetonitrile is preferable because it does not contain oxygen.
Magnesium diboride can be easily ion-exchanged with an ion-exchange resin in a polar organic solvent.

In the first step, magnesium diboride and an ion-exchange resin are added to a polar organic solvent, the mixed solution containing the polar organic solvent, magnesium diboride and the ion-exchange resin is stirred, and magnesium diboride and the ion-exchange resin are are in full contact. As a result, magnesium ions constituting magnesium diboride and ions of the functional group α of the ion-exchange resin are ion-exchanged to form a boron atom and an atom derived from the functional group α of the ion-exchange resin. A sheet-like carbon dioxide storage-release material precursor with a dimensional network is produced.

When an ion-exchange resin having a sulfo group is used as the ion-exchange resin, magnesium ions (Mg ⁺ ) of magnesium diboride are substituted with hydrogen ions (H ⁺ ) of the sulfo group of the ion-exchange resin. A sheet-like carbon dioxide storage-release material precursor having a two-dimensional network of boron atoms (B) and hydrogen atoms (H) is produced.

In the first step, without applying ultrasonic waves or the like to the mixed solution, the reaction of ion exchange between the magnesium ions constituting magnesium diboride and the ions of the functional group α of the ion exchange resin can be gently proceeded. preferable.

When stirring the mixed solution, the temperature of the mixed solution is preferably 15°C to 35°C.
The time for stirring the mixed solution is not particularly limited, but is, for example, 700 minutes to 7000 minutes.

Also, the first step is performed under an inert atmosphere of an inert gas such as nitrogen (N ₂ ) or argon (Ar).

Next, the mixed solution after stirring is filtered.
The method for filtering the mixed solution is not particularly limited, and for example, methods such as natural filtration, vacuum filtration, pressure filtration, and centrifugal filtration are used. As the filter medium, for example, a filter paper having cellulose as a base material, a membrane filter, a filter plate formed by compressing cellulose, glass fiber, or the like, and the like are used.

The solution containing the product separated from the precipitate by filtration is air-dried or dried by heating to finally obtain only the product.
This product is a sheet-like carbon dioxide storage-release material precursor having a two-dimensional network formed by boron atoms and atoms (hydrogen: H) derived from the functional group α of the ion exchange resin.

Methods for analyzing the product obtained by the method for producing the carbon dioxide storage-release material of the present embodiment include, for example, X-ray Photoelectron Spectroscopy (XPS), Transmission Electron Microscopy. Microscope, TEM), energy dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS) performed in a transmission electron microscope.

In the X-ray photoelectron spectroscopy (XPS), for example, an X-ray photoelectron spectroscopy analyzer (trade name: JPS9010TR) manufactured by JEOL is used to irradiate the surface of the product with X-rays. The constituent elements of the product and their electronic states are analyzed by measuring the energy of the photoelectrons generated in . In this analysis, almost no photoelectron energy due to magnesium constituting the raw material magnesium diboride was detected, and only the photoelectron energy due to elements derived from boron and the functional group α of the ion exchange resin was detected. If so, it can be said that the product is composed only of boron and an element (hydrogen: H) derived from the functional group α of the ion exchange resin. By X-ray photoelectron spectroscopy analysis, almost no photoelectron energy due to magnesium constituting the raw material magnesium diboride is detected, and if only photoelectron energy due to boron and hydrogen is detected, the product is composed only of boron and hydrogen.

In observation with a transmission electron microscope (TEM), for example, by observing the product using a transmission electron microscope manufactured by JEOL (trade name: JEM-2100F TEM / STEM), the product Analyze the shape (appearance), etc. If a membranous (sheet-like) substance is observed in this analysis, it can be said that the product is a two-dimensional sheet-like substance. By performing energy dispersive X-ray analysis (EDS) in a transmission electron microscope, it is possible to observe the presence or absence of metal elements in the TEM-observed portion of the product. In this analysis, almost no X-ray energy due to magnesium constituting the raw material magnesium diboride is detected, and if no peak of magnesium (Mg) appears, it can be said that magnesium does not exist. Further, by conducting electron energy loss spectroscopy (EELS) in a transmission electron microscope, the constituent elements in the TEM observed portion of the product can be observed. In this analysis, if only the X-ray energy due to the element (hydrogen: H) derived from boron and the functional group α of the ion exchange resin is detected, the product is boron and the functional group of the ion exchange resin It can be said that it is composed only of elements (hydrogen: H) derived from α.

The sheet-like carbon dioxide storage-release material precursor obtained in the first step of the method for producing a carbon dioxide storage-release material of the present embodiment has a molar ratio of boron to hydrogen of 1:1 (HB) _n It is a sheet-shaped material having a two-dimensional network consisting of (n≧4). That is, in the sheet-like carbon dioxide storage-release material precursor, boron atoms (B) and hydrogen atoms (H) are present in a molar ratio of 1:1, and a two-dimensional network formed only from these two atoms. It is a sheet-shaped material having

In the sheet-like carbon dioxide storage-release material precursor, the ratio (molar ratio) of boron atoms (B) and hydrogen atoms (H) is calculated by temperature-programmed desorption gas analysis and mass measurement before and after heating, which will be described later. .

In addition, the sheet-like carbon dioxide storage-release material precursor has a spectrum in X-ray photoelectron spectroscopy that shows a peak in the vicinity of 188 eV derived from B1s of negatively charged boron and does not show a peak derived from magnesium.

In addition, the sheet-like carbon dioxide storage-release material precursor has a spectrum showing a peak at 191 eV derived from the sp2 structure of boron in electron beam energy loss spectroscopy.

Electron beam energy loss spectroscopy for a sheet-like carbon dioxide storage-release material precursor will be described later.

In the sheet-like carbon dioxide storage-release material precursor, as shown in FIG. 2, boron atoms (B) are arranged in a hexagonal ring like a benzene ring and are present at the vertices of the hexagon. , and the hexagons formed by the boron atoms (B) are connected without gaps to form a mesh-like planar structure (two-dimensional network). Furthermore, the sheet-like carbon dioxide storage-release material precursor has sites where two adjacent boron atoms (B) are bonded to the same hydrogen atom (H), as shown in FIG. In the sheet-like carbon dioxide storage-release material precursor, the hexagonal mesh formed by boron atoms (B) means, for example, a honeycomb shape.

A sheet-like carbon dioxide storage-release material precursor is a thin film-like substance having a two-dimensional network composed of boron atoms (B) and hydrogen atoms (H). In addition, the sheet-like carbon dioxide storage-release material precursor hardly contains magnesium atoms derived from magnesium diboride used in the method for producing the carbon dioxide storage-release material or other metal atoms.
In the sheet-like carbon dioxide storage-release material precursor, the total number of boron atoms (B) and hydrogen atoms (H) forming the network surface structure is 1000 or more.

The bond distance _D1 between two adjacent boron atoms (B) shown in FIG. 2(a) is 0.17 nm to 0.18 nm. Also, the bond distance _D2 between two adjacent boron atoms (B) through one hydrogen atom (H) shown in FIG. 2(b) is 0.17 nm to 0.18 nm. Also, the bond distance _D3 between the adjacent boron atom (B) and hydrogen atom (H) shown in FIG. 2(b) is 0.125 nm to 0.135 nm.

The thickness of the sheet-like carbon dioxide storage-release material precursor is 0.23 nm to 0.50 nm.
In the sheet-like carbon dioxide storage-release material precursor, the length in at least one direction (for example, the length in the X direction or the Y direction in FIG. 2(a)) is preferably 100 nm or more.
The size (area) of the sheet-like carbon dioxide storage-release material precursor is not particularly limited, and the carbon dioxide storage-release material precursor can be formed to an arbitrary size by the first step of the method for producing a carbon dioxide storage-release material of the present embodiment. can be done.

The sheet-like carbon dioxide storage-release material precursor may be oxide terminated. That is, the sheet-like carbon dioxide storage-release material precursor may form an oxide at the end of its molecular structure. Examples of the oxide forming the ends of the molecular structure of the sheet-like carbon dioxide storage-release material precursor include boric acid (B(OH) ₃ ) and boron oxide (B ₂ O ₃ ). The sheet-like carbon dioxide storage-release material precursor is terminated with an oxide to form a more stable molecular structure.

A sheet-like carbon dioxide storage-release material precursor is a substance having a crystalline structure. Moreover, in the sheet-like carbon dioxide storage-release material precursor, the bonding strength between the boron atoms (B) forming the hexagonal rings and between the boron atoms (B) and the hydrogen atoms (H) is strong. Therefore, even if the sheet-like carbon dioxide storage-release material precursor forms a crystal (aggregate) in which a plurality of layers are laminated during manufacturing, it can be easily cleaved along the crystal plane like graphite to form two monolayers. It can be separated (collected) as a dimensional sheet.

Next, the sheet-like carbon dioxide storage-release material precursor is heat-treated at 200° C. to 350° C. to obtain the carbon dioxide storage-release material of the present embodiment (second step).

In the second step, the time for heat-treating the sheet-like carbon dioxide storage-release material precursor is not particularly limited, but is, for example, 5 minutes to 1200 minutes.

Also, the second step is performed under vacuum or under an inert atmosphere comprising an inert gas such as nitrogen (N ₂ ) or argon (Ar).

According to the method for producing a carbon dioxide storage-release material of the present embodiment, a two-dimensional boron compound having a two-dimensional network formed by boron atoms and atoms (hydrogen: H) derived from the functional group α of the ion exchange resin is contained. A carbon dioxide storage-release material composed of sheets can be readily produced.
By using large crystals of magnesium diboride having a MgB ₂ type structure as a raw material, a sheet-like carbon dioxide storage-release material precursor having a larger area can be obtained. As a result, a sheet-like carbon dioxide storage-release material having a larger area can be obtained.

Further, according to the method for producing a carbon dioxide storage-release material of the present embodiment, in the first step of forming the sheet-like carbon dioxide storage-release material precursor, magnesium ions constituting magnesium diboride and ion exchange Since a polar organic solvent is used instead of an acidic solution for ion exchange with the ions of the functional group α of the resin, there is no need to adjust the pH of the mixed solution containing the polar organic solvent, magnesium diboride and ion exchange resin. is.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to experimental examples, but the present invention is not limited to the following experimental examples.

[Experimental example 1]
X-ray photoelectron spectroscopy (XPS) analysis of magnesium diboride (manufactured by Rare Metallic Co., Ltd.) was performed.
As an analyzer for X-ray photoelectron spectroscopy, an X-ray photoelectron spectroscopy analyzer (trade name: JPS9010TR) manufactured by JEOL was used. FIG. 3 shows the results of X-ray photoelectron spectroscopic analysis.

[Experimental example 2]
60 mg of magnesium diboride (purity: 99%, manufactured by Rare Metallic Co., Ltd.) is added to acetonitrile, and an ion-exchange resin having a sulfo group (Amberlite (registered trademark) IR120B, manufactured by Organo Corporation) is added in a volume of 30 mL, A mixed solution of magnesium diboride and an ion exchange resin was prepared by stirring with a glass rod.
After stirring this mixed solution at 25° C. for 72 hours, this mixed solution was filtered through a membrane filter with a pore size of 1.0 μm, and the filtrate was collected. Then, the filtrate was dried at 80° C. using a hot plate under a nitrogen atmosphere to obtain a product.
The obtained product was subjected to X-ray photoelectron spectroscopic analysis in the same manner as in Experimental Example 1. The results are shown in FIG.

In the results of FIG. 3, the Mg2p peak of magnesium at 51.3 eV, the B1s peak of boron at 188.2 eV, and the boron oxide (B ₂ O) covering the surface of magnesium diboride (MgB ₂ ) at 193.2 eV. ₃ ) peak appears. This is consistent with the X-ray photoelectron spectroscopy results of typical commercial _MgB2 .
From the results of FIG. 4, the Mg2p peak that appeared in FIG. 3 was not observed, so the product of Experimental Example 2 did not contain magnesium (Mg) and contained boron (B). I found out that I was In FIG. 4, the small peak appearing at 193.2 eV is the peak of boric acid as a by-product. This result suggests that the Mg ion of magnesium diboride (MgB ₂ ) and the hydrogen ion of the sulfo group of the ion exchange resin exchanged ions.

[Experimental example 3]
The product obtained in Experimental Example 2 was observed with a scanning transmission electron microscope (STEM) manufactured by JEOL (trade name: JEM-2100F TEM/STEM) and subjected to electron beam energy loss spectroscopy. Electron beam energy loss spectroscopy results for this product are shown in FIGS. As shown in FIG. 5, an electron beam energy loss spectroscopy peak at 191 eV indicating the sp2 structure of boron (B) was observed, and peaks attributed to carbon (C), nitrogen (N) and oxygen (O) were observed. It was found that the sheet material was composed only of boron having an sp2 structure. Further, from the results of FIG. 6, no peak attributed to magnesium (Mg) was observed, so it was found that the sheet-like substance was composed only of boron. In FIG. 6, peaks due to oxygen (O), sulfur (S), copper (Cu), etc. are observed, but these are noises from highly sensitive measurements.

[Experimental example 4]
The product obtained in Experimental Example 2 was subjected to thermal desorption spectrometry (TDS) using TDS1400TV manufactured by ESCO. The analysis results are shown in FIG. In FIG. 7, (a) shows the spectrum caused by water, and (b) shows the spectrum caused by hydrogen. It was found that when the product obtained in Experimental Example 2 was heated, water was desorbed at around 180°C due to the presence of boron as a by-product. It was also found that when the product obtained in Experimental Example 2 was further heated, hydrogen was desorbed at 200° C. or higher. When the amount of desorbed water and the amount of desorbed hydrogen were measured and compared, the molar ratio of boron to hydrogen contained in the precipitate obtained in Experimental Example 2 was calculated to be 0.97:1. This result suggests that the precipitate obtained in Experimental Example 2 contains boron atoms (B) and hydrogen atoms (H) at a molar ratio of 1:1.

[Experimental example 5]
The product obtained in Experimental Example 2 was subjected to visible/ultraviolet spectroscopic analysis (UV-VIS) using V-660 manufactured by JASCO Corporation. The analysis results are shown in FIG. From the results of FIG. 8, it was found that the product obtained in Experimental Example 2 had a light absorption of 2.59 eV, which neither magnesium diboride nor boric acid had.

[Experimental example 6]
The product obtained in Example 2 was heat treated under vacuum at 20° C. (293 K), 60° C. (333 K) or 350° C. (623 K) for 1 hour.
X-ray photoelectron spectroscopy (XPS) analysis of the product after heat treatment was performed.
As an analyzer for X-ray photoelectron spectroscopy, an X-ray photoelectron spectroscopy analyzer manufactured by JEOL (trade name: JPS9010TR) was used. FIG. 9 shows the results of X-ray photoelectron spectroscopic analysis.
In the results of FIG. 9, when heated at 350° C. (623 K), peaks derived from B1s of boron appear at 187.5 eV and 191.2 eV.

[Experimental example 7]
A test apparatus consisting of a gas inlet and a sample inlet was prepared. The volume of the gas introduction part was 32.00 cm ³ and the volume of the sample introduction part was 28.4 cm ³ .
The product obtained in Experimental Example 2 was placed in the sample inlet of the test apparatus.
After evacuating the inside of the sample charging section containing the heat-treated product, the product obtained in Experimental Example 2 was heat-treated at 250° C. (523 K) for 1 hour.
Carbon dioxide of 28.1 Torr (approximately 3.75 kPa) was introduced at 25° C. into the sample charging section containing the product after the heat treatment.
After that, the pressure in the sample charging portion was measured by a pressure sensor installed in the sample charging portion at predetermined time intervals. The results are shown in FIG.
From the results of FIG. 10, it was observed that the pressure inside the sample charging portion decreased with the lapse of time. This is considered to be due to the fact that the product after the heat treatment contained in the sample loading section adsorbed the carbon dioxide in the sample loading section.
In addition, it was found that the adsorption amount of carbon dioxide in the product after the heat treatment two hours after the start of the experiment, which is calculated from the amount of decrease in the pressure inside the sample insertion part, was 1.32×10 ⁻⁶ mol. . When converted to 1 g of borohydride, the carbon dioxide adsorption amount of the product after the heat treatment was found to be 4.34×10 ⁻⁵ molCO ₂ /g-HB.

[Experimental example 8]
In the same manner as in Experimental Example 7, carbon dioxide was adsorbed on the product after the heat treatment.
The heat-treated product was then heated at 150° C. for 1 hour to release carbon dioxide.
Carbon dioxide was adsorbed in the same manner as in Experimental Example 8 on the product after the heat treatment from which carbon dioxide was released.
In this way, the adsorption and release of carbon dioxide to and from the heat-treated product were repeated five times.
Each time carbon dioxide was adsorbed on the heat-treated product, the amount of carbon dioxide adsorbed on the heat-treated product was calculated. The results are shown in FIG.
From the results of FIG. 11, even if the adsorption and release of carbon dioxide to the heat-treated product were repeated five times, it was confirmed that the heat-treated product adsorbed approximately the same amount of carbon dioxide each time. rice field.

[Experimental example 9]
A test device (trade name: BELmax00067, manufactured by Microtrack Bell Co., Ltd.) consisting of a gas introduction part and a sample introduction part was prepared. The volume of the gas introduction part was 20.995 cm ³ and the volume of the sample introduction part was 23.729 cm ³ .
The product obtained in Experimental Example 2 was placed in the sample inlet of the test apparatus.
After evacuating (3.795×10 ⁻⁶ Pa) the inside of the sample loading section containing the heat-treated product, the product obtained in Experimental Example 2 was heat-treated at 200° C. (473 K) for 18 hours. .
Carbon dioxide was introduced at −78° C. or 25° C. at 1.598×10 ⁻² Pa/min into the sample charging section containing the product after the heat treatment. After reaching 100 kPa, the pressure was reduced to 1.598×10 ⁻² Pa/min. During this process, the pressure in the sample inlet was measured by a pressure sensor installed in the sample inlet. The amount of carbon dioxide adsorbed by the product after the heat treatment under each pressure condition was calculated from the amount of pressure drop in the sample charging portion. The results are shown in FIG.
From the results of FIG. 12, it was confirmed that as the pressure of carbon dioxide introduced into the sample input unit containing the product after heat treatment increases, the amount of carbon dioxide adsorbed by the product after heat treatment increases. was done. Further, it was confirmed that carbon dioxide was adsorbed on the product after the heat treatment even when the introduction of carbon dioxide into the sample charging portion was stopped and the pressure was reduced.

The carbon dioxide storage-release material of the present invention can be used as a material for storing carbon dioxide at room temperature (15° C. to 25° C.) and normal pressure (1 atm) or less. In addition, the carbon dioxide storage-release material of the present invention is suitably used for the PSA (Pressure Swing Adsorption) method among the CCS (Carbon Dioxide Capture and Storage) technologies required in natural gas plants and power plants.

Claims (4)

Constructed from a two-dimensional borohydride-containing sheet having a two-dimensional network,
A method for producing a carbon dioxide storage-release material having a spectrum showing peaks at 187.5 eV and 191.2 eV derived from B1s of boron and not showing a peak derived from magnesium in X-ray photoelectron spectroscopy,
Magnesium diboride having a MgB ₂ type structure and an ion exchange resin in which magnesium ions constituting the magnesium diboride and ion-exchangeable hydrogen ions are coordinated are mixed in a polar organic solvent to obtain a carbon dioxide storage and release material. obtaining a precursor;
and heat-treating the carbon dioxide storage-release material precursor at 200°C to 350°C. The carbon dioxide storage-release material precursor consists of (HB) _n (n≧4) having a molar ratio of boron to hydrogen of 1:1 calculated by temperature-programmed desorption gas analysis and mass measurement before and after heating. Having a two-dimensional network, in X-ray photoelectron spectroscopy, having a spectrum showing a peak in the vicinity of 188 eV derived from B1s of negatively charged boron and not showing a peak derived from magnesium, in electron beam energy loss spectroscopy , having a spectrum showing peaks at 191 eV derived from the sp2 structure of boron. 3. The method for producing a carbon dioxide storage-release material according to claim 1, wherein the ion exchange resin has a sulfo group. The method for producing a carbon dioxide storage-release material according to any one of claims 1 to 3, wherein the polar organic solvent is acetonitrile or methanol.

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