Hydrogen storage material and method for manufacturing the same

Abstract

The present invention provides a hydrogen storage material capable of forming a packed bed with few voids, and a method for manufacturing the same. [Solution] A hydrogen storage material comprising a molded body containing a hydrogen storage alloy, a porous material, and a thermoplastic elastomer, wherein the porous material contains one or more selected from a metal-organic structure, a covalent organic structure, and a porous aromatic structure, and the hydrogen mass density of the porous material at a temperature of 77K and a pressure of 100bar is greater than that of the hydrogen storage alloy.

Description

[Technical Field]

[0001] This invention relates to a hydrogen storage material and a method for producing the same. [Background technology]

[0002] In recent years, the use of hydrogen as an energy source has attracted attention. Consequently, technologies for safely storing and transporting hydrogen are needed to ensure its effective use as an energy source. For example, fuel cell vehicles use hydrogen tanks that store and transport hydrogen at high pressures of up to 700 atmospheres. Hydrogen tanks tend to become larger and heavier to ensure safety. Therefore, development is underway to create hydrogen storage materials that can store and transport hydrogen compactly and lightly.

[0003] Hydrogen storage alloys are one example of a hydrogen storage material. Furthermore, the use of hydrogen adsorption materials such as metal-organic frameworks (MOFs) is being considered as hydrogen storage materials. Furthermore, Patent Document 1 describes a method for manufacturing a hydrogen storage container using a hydrogen storage composition. Patent Document 1 also describes a hydrogen storage composition comprising an elastic material, a thermally conductive material, and a hydrogen storage material, and states that a thermoplastic elastomer (TPE) is selected as the elastic material. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2017-78019 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, hydrogen storage alloys and metal-organic frameworks (MOF) are powder materials, and the porosity (packing rate of the powder material) in a hydrogen tank filled with hydrogen storage alloy and / or metal-organic framework (MOF) is usually about 50%. For this reason, even if a hydrogen tank is filled with a hydrogen storage alloy and / or a metal-organic framework (MOF), it has been difficult to store and release a large amount of hydrogen in the hydrogen tank.

[0006] For this reason, in the conventional art, there has been a demand for a hydrogen storage material capable of forming a packed layer with fewer voids. The present invention has been made in view of the above problems, and an object of the present invention is to provide a hydrogen storage material capable of forming a packed layer with fewer voids and a method for producing the same. [Means for Solving the Problems]

[0007] The present inventors have conducted intensive studies to solve the above problems and realize a hydrogen storage material capable of forming a packed layer with fewer voids. As a result, they have found that it is sufficient to mix a hydrogen storage alloy and a metal-organic framework (MOF) to produce a mixture, mold and compress the mixture to obtain a molded body (pellet).

[0008] However, a molded body of a mixture composed of a hydrogen storage alloy and a metal-organic framework (MOF) has a disadvantage that it cannot maintain its shape and is easily broken due to volume change accompanying hydrogen absorption and desorption of the hydrogen storage alloy. For this reason, a molded body of a mixture composed of a hydrogen storage alloy and a porous material has a short hydrogen absorption and desorption cycle in terms of maintaining a packed layer with fewer voids.

[0009] Accordingly, the present inventors have conducted intensive studies to maintain the shape of a molded body composed of a hydrogen storage alloy and a metal organic framework. As a result, they have found that a hydrogen storage material precursor containing the hydrogen storage alloy, the porous material and the thermoplastic elastomer may be produced, molded, compressed, and formed into a molded body (pellet). Furthermore, they have found that in the production method of the first embodiment, a mixture containing a hydrogen storage alloy and a metal organic framework is impregnated with a polymer solution obtained by dissolving a thermoplastic elastomer in a solvent, and then the solvent is removed to obtain a polymer-containing mixture, which is then molded, compressed, and formed into a molded body (pellet). Furthermore, they have found that in the production method of the second embodiment, a dispersion liquid containing a polymer solution obtained by dissolving the thermoplastic elastomer in a solvent and the porous material is produced, a slurry mixture of the dispersion liquid and the hydrogen storage alloy is prepared, and then the solvent is removed to produce a hydrogen storage material-containing mixture, which is then molded, compressed, and formed into a molded body (pellet). The molded body formed in this manner can form a packed layer with few voids, and is further less likely to be broken due to the volume change of the hydrogen storage alloy.

[0010] Furthermore, the present inventors have found that when a porous material containing one or more selected from the group consisting of metal organic frameworks, covalent organic frameworks and porous aromatic frameworks, and having a hydrogen mass density higher than that of a hydrogen storage alloy at a temperature of 77K and a pressure of 100 bar is used, the molded body containing the hydrogen storage alloy, the porous material and the thermoplastic elastomer has good characteristics of hydrogen mass density and hydrogen volume density, and is suitable as a hydrogen storage material, and thus arrived at the present invention. The present invention provides the following means.

[0011] [1] A hydrogen storage alloy, a porous material, and a thermoplastic elastomer, wherein the hydrogen storage alloy, the porous material and the thermoplastic elastomer are formed into a molded body,[ the porous material comprises one or more selected from the group consisting of a metal organic framework, a covalent organic framework and a porous aromatic framework,[ A hydrogen storage material wherein the hydrogen mass density of the porous material at a temperature of 77K and a pressure of 100bar is greater than that of the hydrogen storage alloy.

[0012] [2] The hydrogen storage alloy is divided into 5% to 60% by volume. The porous material is provided in an amount of 10% to 80% by volume. The above thermoplastic elastomer is contained in an amount of 1% to 25% by volume, A hydrogen storage material as described in [1], wherein the porosity is 10% to 40% by volume.

[0013] [3] The ratio of the porous material to the hydrogen storage alloy is 100% by mass or less, The hydrogen storage material according to [1], wherein the proportion of the thermoplastic elastomer is 0.4% by mass to 4% by mass.

[0014] [4] The hydrogen storage alloys are LaNi5, (Y,Mg)Co3, MmNi5 (where "Mm" indicates mischmetal), CaNi5, TiFe, and TiMn 1.5 TiCr 1.8 ,ZrMn2,V 74.5 Ti 10 Cr 12.5 A hydrogen storage material according to [1], which is one or more selected from Mn3.

[0015] [5] The hydrogen storage material according to [1], wherein the porous material comprises a metal-organic structure. [6] The hydrogen storage material according to [1], wherein the hydrogen mass density of the metal-organic structure at a temperature of 77K and a pressure of 100bar is 3% by mass or more. [7] The hydrogen storage material according to [1], wherein the metal-organic structure is one or more selected from MOF-5, UiO-66, UiO-67, and ZIF-8.

[0016] [8] The hydrogen storage material according to [1], wherein the covalent organic structure is an organic structure composed of B, H, O, and C, or an organic structure composed of B, H, O, C, and Si. [9] The hydrogen storage material according to [1], wherein the porous aromatic structure comprises C-PAF and Si-PAF, or both.

[0017]

[10] The hydrogen storage material according to [1], wherein the thermoplastic elastomer is one or more selected from styrene elastomers, olefin elastomers, urethane elastomers, and polyester elastomers.

[0018] A method for producing a hydrogen storage material according to any of the following

[11] [1] to

[10] : A precursor manufacturing step for producing a hydrogen storage material precursor comprising the hydrogen storage alloy, the porous material, and the thermoplastic elastomer, A method for producing a hydrogen storage material, comprising a compression step of molding and compressing a precursor obtained in the precursor manufacturing step to form a molded body.

[12] The precursor manufacturing process is as follows: A mixture manufacturing step for producing a mixture containing the hydrogen storage alloy and the porous material, A polymer impregnation step involves impregnating the mixture with a polymer solution obtained by dissolving the thermoplastic elastomer in a solvent, and then removing the solvent to obtain a polymer-containing mixture. A method for producing a hydrogen storage material according to

[11] , including the method described in

[11] .

[13] The precursor manufacturing process is as follows: A dispersion manufacturing step for producing a dispersion containing a polymer solution obtained by dissolving the thermoplastic elastomer in a solvent and the porous material, A hydrogen storage material-containing mixture manufacturing step involves preparing a slurry-like mixture of the dispersion obtained in the dispersion manufacturing step and the hydrogen storage alloy, and then removing the solvent to produce a hydrogen storage material-containing mixture. A method for producing a hydrogen storage material according to

[11] , including the method described in

[11] . [Effects of the Invention]

[0019] The hydrogen storage material of the present invention comprises a molded article containing a hydrogen storage alloy, a porous material, and a thermoplastic elastomer. The hydrogen storage material of the present invention includes, as the porous material, one or more selected from metal-organic structures, covalent organic structures, and porous aromatic structures, and includes a hydrogen mass density at a temperature of 77K and a pressure of 100bar that is greater than that of the hydrogen storage alloy. Therefore, the hydrogen storage material of the present invention has good hydrogen mass density and hydrogen volume density characteristics, can form a packed bed with few voids, and can be suitably used as a hydrogen storage material.

[0020] Furthermore, in the method for producing the hydrogen storage material of the present invention, a hydrogen storage material precursor containing the hydrogen storage alloy, the porous material, and the thermoplastic elastomer is produced, and this is molded and compressed to form a molded body. Thus, the hydrogen storage material of the present invention can be produced. [Brief explanation of the drawing]

[0021] [Figure 1] Figure 1 shows photographs of the hydrogen storage materials of Example 1 and Comparative Examples 2 to 5, taken before hydrogen storage and after three hydrogen storage and release cycles. [Figure 2] Figure 2 shows photographs of the hydrogen storage material of Example 2, taken before hydrogen storage and after three hydrogen storage and release cycles. [Modes for carrying out the invention]

[0022] The hydrogen storage material and its manufacturing method according to this embodiment will be described in detail below. The embodiments shown below are examples, and the hydrogen storage material and its manufacturing method according to the present invention are not limited to these, and can be modified as appropriate without changing the gist of the invention.

[0023] [Hydrogen storage materials] The hydrogen storage material of this embodiment consists of a molded body comprising a hydrogen storage alloy, a porous material, and a thermoplastic elastomer.

[0024] (Hydrogen storage alloy) The hydrogen storage alloy included in the hydrogen storage material of this embodiment can be any alloy capable of absorbing hydrogen, and known alloys can be used. As the hydrogen storage alloy included in the hydrogen storage material, for example, an intermetallic compound represented by general formula (1) can be used. CanLi x Al (2-x) ...(1) (In equation (1), x is greater than 0 and less than 2.0.)

[0025] The intermetallic compound represented by formula (1) is one in which x is greater than 0 and less than 2.0. Therefore, the intermetallic compound represented by formula (1) contains aluminum (Al) along with calcium (Ca) and lithium (Li). Aluminum (Al) is an element with poor affinity for hydrogen. For this reason, the aluminum (Al) contained in the intermetallic compound represented by formula (1) has the function of suppressing the decomposition of the intermetallic compound during hydrogenation.

[0026] The intermetallic compound represented by formula (1) can absorb a large amount of hydrogen because x in formula (1) is greater than 0. Preferably, x in formula (1) is greater than 0.93, more preferably 0.96 or greater, and most preferably 1.00 or greater. This is because it results in an intermetallic compound that can absorb a larger amount of hydrogen.

[0027] Furthermore, in the intermetallic compound represented by formula (1), since x in formula (1) is less than 2.0, the decomposition of the intermetallic compound during hydrogenation is suppressed by the inclusion of aluminum (Al). Preferably, x in formula (1) is 1.08 or less, and more preferably 1.06 or less. This is because when x is 1.08 or less, the function of suppressing the decomposition of the intermetallic compound during hydrogenation by including aluminum (Al) is obtained more effectively. As a result, when the intermetallic compound represented by formula (1) is hydrogenated, it can absorb more hydrogen.

[0028] The intermetallic compound represented by formula (1) can be produced, for example, by the following method. First, CaLi2 and CaAl2 are produced by known methods. Specifically, for example, raw materials consisting of Ca, Li, and Al are prepared. The shape of these raw materials is not particularly limited; for example, granular form can be used.

[0029] Next, a raw material consisting of Ca and a raw material consisting of Li are mixed in a molar ratio of 1:2 to obtain an alloy raw material. Then, the alloy raw material is alloyed by a melting method. Specifically, for example, the alloy raw material is heated and melted using a known melting furnace such as a vacuum arc melting furnace, and then cooled and solidified to form CaLi2.

[0030] Furthermore, a raw material consisting of Ca and a raw material consisting of Al are mixed in a molar ratio of 1:2 to obtain an alloy raw material. Next, the alloy raw material is alloyed by a melting method. Specifically, for example, the alloy raw material is heated and melted using a known melting furnace such as a vacuum arc melting furnace or a high-frequency heating melting furnace, and then cooled and solidified to form CaAl2.

[0031] Next, the CaLi2 and CaAl2 obtained in this way are mixed to form a mixture. At this time, the mixture is mixed so that the molar ratio of Li to Al in the mixture is x:2-x(Li:Al) in equation (1). Subsequently, the resulting mixture is subjected to heat treatment. The heat treatment of the mixture may be carried out after the mixture has been pelletized by a known method.

[0032] The heat treatment of the mixture is carried out, for example, in an inert gas atmosphere using an electric furnace, at a low temperature such that the vapor pressure of Li remains sufficiently low. Specifically, the heat treatment of the mixture can be performed at a heat treatment temperature of 250°C to 500°C for a heat treatment time of 1 hour to 100 hours. The above heat treatment temperature is preferably 280°C or higher, and more preferably 300°C or higher, because it is easier to obtain an intermetallic compound with few impurity phases containing Ca, Li, and Al in predetermined proportions. Furthermore, the heat treatment time is preferably 30 hours or less in order to more effectively suppress the evaporation of Li. The above heat treatment temperature is preferably 450°C or lower in order to more effectively suppress the evaporation of Li and to enable efficient production. Furthermore, the heat treatment time is preferably 5 hours or more in order to easily obtain an intermetallic compound with few impurity phases containing Ca, Li, and Al in predetermined proportions. The above heat treatment temperature and heat treatment time can be appropriately determined according to the proportions of Li and Al contained in the mixture.

[0033] In the manufacturing method of this embodiment, by performing the above heat treatment, the intermetallic compound of this embodiment, represented by formula (1), is obtained, which contains Ca, Li, and Al in a molar ratio of 1:x:2-x (where x is greater than 0 and less than 2.0).

[0034] Furthermore, as the hydrogen storage alloy included in the hydrogen storage material, an intermetallic compound represented by general formula (2) may be used. YAlM·····(2) (In formula (2), M represents at least one metallic element selected from Mn, Fe, Ni, Ti, Cr, Co, Cu, Zn, Group 1 elements, and Group 2 elements.)

[0035] In formula (2), the metallic element represented by M is selected from Mn, Fe, Ni, Ti, Cr, Co, Cu, Zn, Group 1 elements, and Group 2 elements. The metallic element represented by M may be just one type or two or more types. If the metallic element represented by M is two or more types, the proportion of each metallic element is not particularly limited.

[0036] If the metallic element represented by M is a group element, it is preferable that it be at least one selected from Li, Na, and K. This is because they are lightweight. If the metallic element represented by M is a group 2 element, it is preferable that it be at least one selected from Mg and Ca. This is because these elements are easy to handle and are also light.

[0037] The M contained in the intermetallic compound represented by formula (2) is preferably at least one element selected from Mn, Fe, Ni, Ti, Cr, Co, Cu, Zn, Li, Na, K, Be, Mg, and Ca. Since these elements are lighter than the above elements, hydrogenation can form metal hydrides with higher hydrogen density per unit mass and per unit volume.

[0038] Furthermore, the M contained in the intermetallic compound represented by formula (2) is preferably Fe or Mg among the above elements. This is because Fe and Mg are lightweight and highly versatile elements.

[0039] The intermetallic compound represented by formula (2) absorbs hydrogen atoms between the crystal lattices of the yttrium-aluminum alloy by hydrogenation to form a metal hydride. Furthermore, in the metal hydride of the intermetallic compound represented by formula (2), hydrogen atoms are absorbed by forming covalent bonds between the aluminum atoms or the metal element represented by M contained in the intermetallic compound and the hydrogen atoms. Therefore, the intermetallic compound represented by formula (2) can form a metal hydride with high hydrogen density per unit mass and per unit volume by hydrogenation.

[0040] When M contained in the intermetallic compound represented by formula (2) is at least one metal element selected from the group consisting of Mn, Fe, Ni, Ti, Cr, Co, Cu and Zn, hydrogenation to form a metal hydride causes hydrogen atoms to be occluded between the crystal lattices of the alloy composed of yttrium and aluminum, and a complex ion is formed by covalent bonding between the metal element represented by M and a hydrogen atom.

[0041] Examples of complex ions formed by covalent bonding between the element represented by M and a hydrogen atom include [MnH6 5- , [NiH4 4- , [FeH6 4- , [CoH5 4- , [CuH4 3- , [ZnH4 2- , [CrH7 5- and the like. When M contained in the intermetallic compound represented by formula (2) is at least one metal element selected from the group consisting of Mn, Fe, Ni, Ti, Cr, Co, Cu and Zn, the number of hydrogen atoms hydrogenated and occluded in the metal hydride is determined depending on the type of the metal element represented by M, the hydrogenation conditions of the metal hydride, and the like.

[0042] Furthermore, when M contained in the intermetallic compound represented by formula (2) is at least one metal element selected from group 1 elements and group 2 elements, hydrogenation to form a metal hydride causes hydrogen atoms to be occluded between the crystal lattices of the alloy composed of yttrium and aluminum, and a complex ion is formed by covalent bonding between an aluminum atom contained in the intermetallic compound and a hydrogen atom.

[0043] An example of a complex ion formed by covalent bonding between an aluminum atom contained in the intermetallic compound represented by formula (2) and a hydrogen atom is [AlH6 3- When M contained in the intermetallic compound is at least one metal element selected from group 1 elements and group 2 elements, the number of hydrogen atoms hydrogenated and occluded in the metal hydride is determined depending on the type of the metal element represented by M, the hydrogenation conditions of the metal hydride, and the like.​

[0044] When M in the intermetallic compound represented by formula (2) is at least one metal element selected from Mn, Fe, Ni, Ti, Cr, Co, Cu, and Zn, the reactivity between the metal element represented by M and the hydrogen atom is higher than the reactivity between the aluminum in the intermetallic compound and the hydrogen atom. Therefore, when M is at least one metal element selected from Mn, Fe, Ni, Ti, Cr, Co, Cu, and Zn, hydrogenation of the intermetallic compound causes the metal element represented by M and the hydrogen atom to form a covalent bond, creating a complex ion.

[0045] In contrast, when M in the intermetallic compound represented by formula (2) is at least one metallic element selected from Group 1 and Group 2 elements, the reactivity between the metallic element represented by M and the hydrogen atom is lower than the reactivity between the aluminum in the intermetallic compound and the hydrogen atom. Therefore, when M is at least one metallic element selected from Group 1 and Group 2 elements, hydrogenation of the intermetallic compound causes the aluminum atom and the hydrogen atom to form a covalent bond, creating a complex ion.

[0046] The intermetallic compound represented by formula (2) can be produced, for example, by the method shown below. First, a raw material consisting of Y, a raw material consisting of Al, and a raw material consisting of a metal element represented by M are prepared. The shape of these raw materials is not particularly limited; for example, granular or powdered forms can be used.

[0047] Next, a raw material consisting of Y, a raw material consisting of Al, and a raw material consisting of a metal element represented by M are mixed in such a molar ratio that the content of Y, Al, and M is 1:1:1 to form an alloy raw material. Next, the alloying raw materials are alloyed by a melting method. Specifically, for example, the alloying raw materials are heated and melted using a known melting furnace such as a vacuum arc melting furnace or a high-frequency heating melting furnace, and then cooled and solidified to form an alloy, which is then used to obtain a precursor compound.

[0048] Subsequently, in this embodiment, the obtained precursor compound is subjected to heat treatment, for example, using a vacuum electric furnace, at a heat treatment temperature of 600°C to 1000°C under vacuum conditions for 1 hour to 100 hours. The heat treatment temperature is preferably 600°C to 970°C. The heat treatment time is preferably 20 to 80 hours. The heat treatment temperature and time can be appropriately determined depending on the type of metal element represented by M contained in the intermetallic compound of the target product.

[0049] In this embodiment, the above heat treatment reduces the impurity phase in the precursor compound, which consists of components derived from impurities contained in the raw materials. As a result, an intermetallic compound represented by formula (2) is obtained, in which the main phase is a phase represented by formula (1) and in which metal elements represented by Y, Al, and M are contained in a molar ratio of 1:1:1.

[0050] Examples of hydrogen storage alloys included in hydrogen storage materials include LaNi5, MmNi5 (where "Mm" in the formula represents mischmetal), CaNi5, TiFe, and TiMn. 1.5 TiCr 1.8 ,ZrMn2,V 74.5 Ti 10 Cr 12.5 Mn3, LaNi 4.7 Al 0.3 YAlFe, YAlMg, CaLi 1.06 Al 0.94 These include LaNi5, MmNi5 (where "Mm" in the formula indicates mischmetal), CaNi5, TiFe, and TiMn. 1.5 TiCr 1.8 ,ZrMn2,V 74.5 Ti 10 Cr 12.5 Mn3, YAlFe, YAlMg, CaLi 1.06 Al 0.94 Preferably, it is one or more selected from (Y,Mg)Co3.

[0051] The mischmetal contained in the above MmNi5 is a mixture of rare earth elements obtained by reducing rare earth ores. Specifically, the mischmetal is a mixture consisting of 40% to 50% by mass of cerium (Ce), 20% to 40% by mass of lanthanum (La), 0% to 15% by mass of neodymium (Nd), 0% to 5% by mass of praseodymium (Pr), with the remainder being other rare earth elements.

[0052] The hydrogen storage alloy included in the hydrogen storage material of this embodiment is not particularly limited, as long as its hydrogen mass density at a temperature of 77K and a pressure of 100bar is less than that of a porous material.

[0053] Among the hydrogen storage alloys included in the hydrogen storage material of this embodiment, LaNi5 is preferred. The reason is that hydrogen storage materials containing LaNi5 as the hydrogen storage alloy are easily activated to absorb hydrogen, can absorb hydrogen at temperatures around room temperature and pressures of 1.0 MPa or less, and can release hydrogen at temperatures around room temperature.

[0054] (porous material) The porous material contained in the hydrogen storage material of this embodiment has numerous pores capable of adsorbing and releasing hydrogen. The shape and size of the pores in the porous material are not particularly limited, but for example, materials with pores of 1 nm or less in diameter can be used.

[0055] The porous material included in the hydrogen storage material of this embodiment includes one or more selected from metal-organic frameworks (MOFs), covalent-organic frameworks (COFs), and porous aromatic frameworks (PAFs).

[0056] The porous material contained in the hydrogen storage material of this embodiment has a hydrogen mass density at a temperature of 77K and a pressure of 100 bar that is higher than that of the hydrogen storage alloy. Therefore, the hydrogen storage material of this embodiment has good hydrogen mass density and hydrogen volume density characteristics, as shown below. That is, the hydrogen storage alloy has a hydrogen mass density of 100 kgH2 / m³. 3 It has a relatively high hydrogen volume density. However, hydrogen storage alloys have a low hydrogen mass density, with a hydrogen mass density of 1-2% by mass.

[0057] Unlike hydrogen storage alloys, porous materials have a high hydrogen mass density. However, porous materials have a low hydrogen volume density. Also, porous materials adsorb and desorb hydrogen at lower temperatures compared to hydrogen storage alloys. For example, metal-organic frameworks (MOFs) have a hydrogen mass density of approximately 3% by mass and a hydrogen volume density of 50 kgH2 / m³. 3 It is of a certain degree, and it adsorbs and desorbs hydrogen at low temperatures around 77K. The hydrogen storage material of this embodiment includes a porous material along with a hydrogen storage alloy, so the properties of both the hydrogen storage alloy and the porous material are exhibited, resulting in good hydrogen mass density and hydrogen volume density properties. A method to more effectively exhibit the properties of both the hydrogen storage alloy and the porous material contained in the hydrogen storage material is, for example, to store hydrogen in the hydrogen storage alloy in the hydrogen storage material at room temperature and a pressure of 1.0 MPa, and then to adsorb hydrogen onto the porous material in the hydrogen storage material at a temperature of 77 K and a pressure of 100 bar. In this case, the properties of hydrogen mass density and hydrogen volume density are better compared to when the hydrogen storage alloy and the porous material contained in the hydrogen storage material are used individually.

[0058] "Metal-organic framework (MOF)" A metal-organic framework (MOF) comprises a metal ion capable of forming a two-dimensional or three-dimensional structure, and an organic ligand that binds to the metal ion. The metal-organic framework may also contain, along with the metal ion and the organic ligand, at least one of alkali metal elements and alkaline earth metal elements.

[0059] Known metal-organic structures can be used. Specifically, examples of metal-organic structures include one or more selected from MOF-5, UiO-66, UiO-67, and ZIF-8. Among the above, UiO-66 is preferred. This is because UiO-66 can be easily manufactured and has a high hydrogen adsorption capacity at room temperature. For example, UiO-66 has pores with a diameter of 0.75 nm and pores (micropores) with a diameter of 1.2 nm, and a specific surface area of ​​1668 m². 2 At / g, the pore volume is 0.72 cm³. 3 Some items are / g.

[0060] The hydrogen mass density of these metal-organic structures at a temperature of 77K and a pressure of 100 bar is 3 mass% or more. Specifically, MOF-5 is 10 mass%, UiO-66 is 7.7 mass%, UiO-67 is 7.4 mass%, and ZIF-8 is 3.73 mass%.

[0061] "Covalent organic framework (COF)" Covalent organic structures (COFs) are two-dimensional or three-dimensional structures formed by covalent bonds between monomers consisting of organic molecules that do not contain aromatic compounds. Known covalent organic structures can be used. The hydrogen storage material may contain only one or two or more covalent organic structures.

[0062] Examples of covalent organic structures include those containing one type of covalent bond selected from BO, CN, BN, and BO-Si. Since covalent organic structures can be easily manufactured, it is preferable that they be organic structures composed of B, H, O, and C, or organic structures composed of B, H, O, C, and Si, selected from these options.

[0063] Specifically, examples of covalent organic structures include COF-1, COF-5, COF-6, COF-8, and COF-10, which are organic structures composed of B, H, O, and C, or COF-102, COF-103, and COF-104, which are organic structures composed of B, H, O, C, and Si. These covalent organic structures are preferred because they can be easily manufactured.

[0064] The hydrogen mass densities of these covalent organic structures at a temperature of 77K and a pressure of 85bar are as follows: COF-1: 1.48 mass%, COF-5: 3.58 mass%, COF-6: 2.26 mass%, COF-8: 3.50 mass%, COF-10: 3.92 mass%, COF-102: 7.24 mass%, and COF-103: 7.05 mass%.

[0065] "Porous Aromatic Structure (PAF)" Porous aromatic structures (PAFs) are three-dimensional structures formed by covalent bonds between monomers, which are organic molecules containing aromatic compounds. Known porous aromatic structures can be used. The hydrogen storage material may contain only one type of porous aromatic structure, or two or more types. Since porous aromatic structures can be easily manufactured and have a high hydrogen adsorption capacity at room temperature, it is preferable that they contain one or more covalent bonds.

[0066] Specifically, it is preferable that the porous aromatic structure includes either or both C-PAF and Si-PAF. An example of a C-PAF is PAF-1. The porous aromatic structure preferably contains PAF-1, and more preferably it is PAF-1.

[0067] C-PAF refers to a porous aromatic structure whose main component is carbon, and which is constructed from a skeleton in which the center of the tetrahedral nodes is carbon, such as polysubstituted aromatic monomers that have tetrahedral carbon atoms. PAF-1 is a representative skeleton of C-PAF, consisting of a fully aromatic three-dimensional network formed by the coupling of tetrahedral carbon center nodes (e.g., tetraphenylmethane-type units) and aromatic rings. A representative example is described in Non-Patent Document A, but the PAF-1 of the present invention is not limited to the specific polymer described in that document, but also includes derivatives and modified products having similar skeleton topologies. [Non-patent document A] Angew. Chem. Int. Ed. 2009, 48, 9457-9460. Si-PAF refers to a porous aromatic structure having a structure linked by aromatic rings, constructed from a framework in which the center of the tetrahedral nodes is silicon, such as tetraphenylsilane-type monomers. The two are distinguished by whether the “node centers” that define the three-dimensional network are carbon (C) or silicon (Si). The hydrogen mass density of these porous aromatic structures at a temperature of 77K and a pressure of 100 bar is, for example, 17.49 mass% for C-PAF and 17.49 mass% for Si-PAF.

[0068] (Thermoplastic elastomer) Examples of thermoplastic elastomers included in hydrogen storage materials include one or more selected from styrene-based elastomers, olefin-based elastomers, urethane-based elastomers, and polyester-based elastomers.

[0069] Among the above, it is preferable to use a styrene-based elastomer as the thermoplastic elastomer. This is because styrene-based elastomers can be easily dissolved in a solvent such as toluene to form a polymer solution, making them suitable for manufacturing the hydrogen storage material of this embodiment using the method described later. Furthermore, styrene-based elastomers have a high effect in bonding hydrogen storage alloys to each other and / or to porous materials. This effect is presumed to be due to the high elongation of styrene-based elastomers as measured by tensile tests (JIS K6251), indicating that they absorb the volume change of the hydrogen storage alloy.

[0070] As for the styrene-based elastomer, it is preferable to use one with an elongation of 690% to 1400% as measured by a tensile test (JIS K6251), and more preferably one with an elongation of 1200% to 1400%. This is because an elongation of 690% or higher results in a higher binding effect between hydrogen storage alloys and / or between hydrogen storage alloys and porous materials.

[0071] As styrene-based elastomers, for example, SIS (Styrene-isoprene block copolymers) and SBS (Styrene-butadiene block copolymers) represented by the following formula (I) can be preferably used. SIS represented by formula (I) is preferred because its elongation, measured by tensile testing (JIS K6251), is 1200% to 1400%, and it has an even higher effect in bonding hydrogen storage alloys to each other and / or hydrogen storage alloys to porous materials.

[0072] [ka] (In equation (I), n and m represent the number of structural units.)

[0073] As the SIS represented by formula (I), a SIS can be used in which the proportion of structural units derived from styrene is 15 moles to 22 moles (the proportion of structural units derived from isoprene is 85 moles to 78 moles) per 100 moles of SIS. Specifically, as SIS, a SIS with a molar ratio of structural units derived from styrene to structural units derived from isoprene (structural units derived from styrene / structural units derived from isoprene) of 15 / 85, 22 / 78, or 16 / 84 can be used.

[0074] Examples of olefin-based elastomers include those in which polyolefins such as polypropylene (PP) and polyethylene (PE) are used as the hard segment, and rubber components such as ethylene-propylene rubber (EPM) and ethylene-propylene diene rubber (EPDM) are used as the soft segment.

[0075] Examples of urethane-based elastomers include those with polyester or polyether as the hard segment and those with polyurethane (PU) as the soft segment. Examples of polyester-based elastomers include those with polyester as the hard segment and those with polyether as the soft segment.

[0076] (porosity) In this embodiment, the molded article preferably has a porosity of 10 to 40 volume%. If the porosity of the molded article is 40 volume% or less, a packed layer with fewer voids can be formed, resulting in a hydrogen storage material that can absorb and release more hydrogen. It is more preferable that the porosity of the molded article is 30 volume% or less. Furthermore, a molded article with a porosity of 10 volume% or more is preferable because hydrogen and the porous material can come into contact with the hydrogen more efficiently, resulting in a hydrogen storage material that can absorb and release hydrogen efficiently. It is more preferable that the porosity of the molded article is 15 volume% or more.

[0077] The molded article in this embodiment preferably contains 5% to 60% by volume of hydrogen storage alloy, 10% to 80% by volume of porous material, and 1% to 25% by volume of thermoplastic elastomer, and more preferably contains 10% to 40% by volume of hydrogen storage alloy, 40% to 70% by volume of porous material, and 2% to 10% by volume of thermoplastic elastomer.

[0078] When the proportion of hydrogen storage alloy forming the molded body is 5% by volume or more, the hydrogen storage alloy becomes a hydrogen storage material that can sufficiently absorb and release hydrogen. More preferably, the proportion of hydrogen storage alloy is 10% by volume or more. Furthermore, when the proportion of hydrogen storage alloy forming the molded body is 60% by volume or less, the proportion of porous material and thermoplastic elastomer becomes sufficiently high. Therefore, the effects of including porous material and thermoplastic elastomer together with the hydrogen storage alloy in the molded body are easily obtained. More preferably, the proportion of hydrogen storage alloy is 40% by volume or less.

[0079] When the proportion of porous material forming the molded body is 10% by volume or more, the porous material allows for sufficient absorption and release of hydrogen, resulting in a hydrogen storage material. More preferably, the proportion of porous material is 40% by volume or more. Furthermore, when the proportion of porous material forming the molded body is 80% by volume or less, the proportion of hydrogen storage alloy and thermoplastic elastomer is sufficiently high, which is preferable. More preferably, the proportion of porous material is 70% by volume or less.

[0080] When the proportion of thermoplastic elastomer forming the molded body is 1 volume% or more, the hydrogen storage material becomes more effective in absorbing the volume change of the hydrogen storage alloy due to the presence of the thermoplastic elastomer and bonding the hydrogen storage alloys together and / or the hydrogen storage alloys with the porous material. The proportion of thermoplastic elastomer is more preferably 2 volume% or more. Furthermore, when the proportion of thermoplastic elastomer forming the molded body is 25 volume% or less, it is preferable because the proportion of hydrogen storage alloy and porous material is sufficiently high. The proportion of thermoplastic elastomer is more preferably 10 volume% or less.

[0081] In this embodiment, the molded article preferably has a ratio of porous material to hydrogen storage alloy of 100% by mass (100% by mass hydrogen storage alloy: 1% to 100% by mass porous material) or less, more preferably 0.1% to 100% by mass (100% by mass hydrogen storage alloy: 1% to 100% by mass porous material), and even more preferably 1% to 100% by mass (100% by mass hydrogen storage alloy: 1% to 100% by mass porous material). When the ratio of porous material to hydrogen storage alloy is 0.1% by mass or more, the porous material becomes a hydrogen storage material that can sufficiently absorb and release hydrogen. The ratio of porous material to hydrogen storage alloy is most preferably 20% by mass or more. Furthermore, when the ratio of porous material to hydrogen storage alloy is 100% by mass or less, the ratio of hydrogen storage alloy and thermoplastic elastomer is sufficiently high, which is preferable. The ratio of porous material to hydrogen storage alloy is more preferably 70% by mass or less.

[0082] In this embodiment, the molded article preferably has a thermoplastic elastomer ratio of 0.4% to 4% by mass relative to the hydrogen storage alloy. When the ratio of thermoplastic elastomer to the hydrogen storage alloy is 0.4% by mass or more, the effect of absorbing the volume change of the hydrogen storage alloy due to the presence of the thermoplastic elastomer and bonding the hydrogen storage alloys together and / or the hydrogen storage alloys with the porous material is more effectively obtained, resulting in a hydrogen storage material. The ratio of thermoplastic elastomer to the hydrogen storage alloy is more preferably 1% by mass or more. Furthermore, when the ratio of thermoplastic elastomer to the hydrogen storage alloy is 4% by mass or less, it is preferable because the proportion of hydrogen storage alloy and porous material is sufficiently high. The proportion of thermoplastic elastomer is more preferably 3% by mass or less.

[0083] The shape of the hydrogen storage material (molded body) in this embodiment is not particularly limited and can be, for example, columnar. Specific examples of the molded body shape include cylindrical and polygonal prismatic shapes. The size of the molded body is not particularly limited and can be determined as appropriate depending on the intended use of the molded body.

[0084] [Method for manufacturing hydrogen storage materials] The hydrogen storage material of this embodiment can be manufactured, for example, by performing the following precursor manufacturing process and compression process in that order. Precursor manufacturing process: A process for manufacturing a hydrogen storage material precursor comprising the hydrogen storage alloy, the porous material, and the thermoplastic elastomer. Compression step: A step of molding and compressing the precursor to form a molded body. Examples of methods for manufacturing the hydrogen storage material of this embodiment include the manufacturing method of the first embodiment and the manufacturing method of the second embodiment, as shown below.

[0085] (Manufacturing method of the first embodiment) In the manufacturing method of this embodiment, the precursor manufacturing step includes the following mixture manufacturing step and polymer impregnation step. Mixture manufacturing process: A process for manufacturing a mixture containing the hydrogen storage alloy and the porous material. Polymer impregnation step: A step of impregnating the mixture with a polymer solution obtained by dissolving the thermoplastic elastomer in a solvent, and then removing the solvent to obtain a polymer-containing mixture. In other words, in the manufacturing method of this embodiment, the hydrogen storage material of this embodiment can be manufactured, for example, by performing the following mixture manufacturing step, polymer impregnation step, and compression step in this order.

[0086] <Mixture manufacturing process> In the mixture manufacturing process, first, a mixture containing a hydrogen storage alloy and a porous material is produced.

[0087] It is preferable to use a hydrogen storage alloy with an average particle size in the range of 1 μm to 25 μm as a raw material. If the average particle size of the hydrogen storage alloy used as a raw material is 25 μm or less, the moldability of the polymer-containing mixture described later will be good. Therefore, the manufacturing method of this embodiment makes it possible to easily produce a hydrogen storage material that consists of a molded body with few voids and is easily activated.

[0088] The porous material used as a raw material includes one or more of the above-mentioned metal-organic structures, covalent organic structures, and porous aromatic structures. The porous material used has a hydrogen mass density at a temperature of 77K and a pressure of 100 bar that is greater than that of hydrogen storage alloys. The porous material used as a raw material is preferably in powder form. The shape and size of the pores in the porous material are not particularly limited, but for example, materials with pores of 1 nm or less in diameter can be used.

[0089] <Polymer impregnation process> In the polymer impregnation process, the mixture produced in the mixture production process is impregnated with a polymer solution by a known method. The polymer solution is prepared by dissolving a thermoplastic elastomer corresponding to the thermoplastic elastomer contained in the target hydrogen storage material in a solvent at a predetermined concentration, and can be produced by a known method.

[0090] The solvent used in the polymer solution can be, for example, toluene, hexane, or cyclohexane, and can be appropriately determined depending on the type of thermoplastic elastomer. For example, when using SIS represented by formula (I) as the thermoplastic elastomer, it is preferable to use toluene or the like as the solvent.

[0091] Subsequently, the solvent is removed from the mixture impregnated with the polymer solution. Known methods can be used to remove the solvent from the mixture impregnated with the polymer solution, such as heating the mixture. This yields a polymer-containing mixture. The steps of impregnating the mixture with a polymer solution and removing the solvent from the mixture may be performed within the mold used in the compression step described later.

[0092] <Compression process> In the compression process, the polymer-containing mixture is filled into a mold and molded into a molded body (pellet) by a known method, such as compressing it at a predetermined pressure. This yields the hydrogen storage material of this embodiment, which consists of a molded body containing a hydrogen storage alloy, a porous material, and a thermoplastic elastomer.

[0093] The mold used in the compression process can be any mold that can compress the polymer-containing mixture filled inside the mold to a predetermined pressure. The shape of the mold is not particularly limited and can be determined as appropriate according to the shape of the molded product.

[0094] In the compression process, the pressure used to compress the polymer-containing mixture is preferably 60 MPa to 400 MPa. When the compression pressure of the polymer-containing mixture is 60 MPa or higher, the hydrogen storage alloy contained in the polymer-containing mixture is easily pulverized. This causes cracks to form on the surface of the hydrogen storage alloy or reduces the particle size of the hydrogen storage alloy, increasing the surface area of ​​the hydrogen storage alloy and making it an easily activated hydrogen storage alloy. Furthermore, a pressure of 60 MPa or higher is preferable because it is easier to obtain a molded body with a sufficiently low porosity. A compression pressure of 120 MPa or higher is more preferable. A compression pressure of 200 MPa or higher is even more preferable. Moreover, when the compression pressure of the polymer-containing mixture is 400 MPa or lower, the compression process can be carried out efficiently without using special equipment and molds.

[0095] (Manufacturing method of the second embodiment) In the manufacturing method of this embodiment, the precursor manufacturing step includes the dispersion manufacturing step and the hydrogen storage material-containing mixture manufacturing step described below. Dispersion manufacturing process: A process for manufacturing a dispersion containing a polymer solution obtained by dissolving the thermoplastic elastomer in a solvent and the porous material. Hydrogen storage material-containing mixture manufacturing process: A process to manufacture a hydrogen storage material-containing mixture by preparing a slurry-like mixture of the dispersion obtained in the dispersion manufacturing process and the hydrogen storage alloy, and then removing the solvent. In other words, in the manufacturing method of this embodiment, the hydrogen storage material of this embodiment can be manufactured, for example, by performing the following steps in this order: the dispersion manufacturing step, the hydrogen storage material-containing mixture manufacturing step, and the compression step.

[0096] <Dispersion manufacturing process> The polymer solution obtained by dissolving the thermoplastic elastomer in a solvent is obtained by dissolving the thermoplastic elastomer corresponding to the thermoplastic elastomer contained in the target hydrogen storage material in a solvent at a predetermined concentration, and can be produced by known methods.

[0097] The solvent used in the polymer solution can be, for example, toluene, hexane, or cyclohexane, and can be appropriately determined depending on the type of thermoplastic elastomer. For example, when using SIS represented by formula (I) as the thermoplastic elastomer, it is preferable to use toluene or the like as the solvent.

[0098] The porous material used as a raw material includes one or more of the above-mentioned metal-organic structures, covalent organic structures, and porous aromatic structures. The porous material used has a hydrogen mass density at a temperature of 77K and a pressure of 100 bar that is greater than that of hydrogen storage alloys. The porous material used as a raw material is preferably in powder form. The shape and size of the pores in the porous material are not particularly limited, but for example, materials with pores of 1 nm or less in diameter can be used. The porous material is preferably a porous aromatic structure (PAF).

[0099] After adding the polymer solution to the porous material, stirring (using a stirring bar) is performed to prepare a dispersion of the porous material.

[0100] <Manufacturing process for hydrogen storage material-containing mixture> It is preferable to use a hydrogen storage alloy with an average particle size in the range of 1 μm to 25 μm as a raw material. If the average particle size of the hydrogen storage alloy used as a raw material is 25 μm or less, the moldability of the hydrogen storage alloy-containing mixture described later will be good. Therefore, the manufacturing method of this embodiment makes it possible to easily produce a hydrogen storage material that consists of a molded body with few voids and is easily activated. The hydrogen storage material is added to the dispersion of porous material obtained in the above dispersion manufacturing process and mixed uniformly to obtain a slurry-like mixture.

[0101] Subsequently, the solvent is removed from the slurry mixture. Known methods can be used to remove the solvent from the slurry mixture, such as air drying or heat drying. This yields a hydrogen storage alloy-containing mixture. The step of removing the solvent from the slurry mixture may be performed within the mold used in the compression step described later.

[0102] <Compression process> The compression step in this embodiment is the same as the compression step in the manufacturing method of the first embodiment.

[0103] Although preferred embodiments of the present invention have been described in detail above, the present invention is not limited to any particular embodiment, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Examples]

[0104] [Example 1, Comparative Examples 1-5] The hydrogen storage materials of Example 1 and Comparative Examples 1 to 5 were manufactured using the method described below. The following materials were used as raw materials. "Hydrogen storage alloy" LaNi5;Hydrogen mass density 1.4 mass%, density 8.28g / cm 3 , particle size 25μm or less "Metal-organic framework (MOF)" UiO-66; hydrogen mass density 7.7% by mass and density 1.24 g / cm³ under hydrogen adsorption conditions of 77K temperature and 100 bar pressure. 3

[0105] "Thermoplastic elastomer" The above formula (I) represents SIS (product name; SIS5403, elongation of 1400% measured by tensile test (JIS K6251), molar ratio of structural units derived from styrene to structural units derived from isoprene (structural units derived from styrene / structural units derived from isoprene) 15 / 85, manufactured by ENEOS Material Co., Ltd.)

[0106] (Mixture manufacturing process) The above-mentioned hydrogen storage alloy and metal-organic framework (MOF) were mixed such that the ratio of the metal-organic framework (MOF) to the hydrogen storage alloy was as shown in Table 1, and a mixture was produced.

[0107] [Table 1]

[0108] (Polymer impregnation process) 0.5 g of the mixture obtained in the mixture manufacturing process was placed in a cylindrical mold together with the polymer solution, and the mixture was impregnated with the polymer solution. As the polymer solution, the above-mentioned thermoplastic elastomer was dissolved in toluene as the solvent. The amount of polymer solution used was such that the ratio of the above-mentioned thermoplastic elastomer to the hydrogen storage material contained in the hydrogen storage material was as shown in Table 1 (mass%).

[0109] Subsequently, filter paper was placed on top of the mold, and the mixture impregnated with the polymer solution was heated inside the mold at 40°C for 20 hours to remove the solvent from the mixture and obtain a polymer-containing mixture.

[0110] (Compression process) Next, the polymer-containing mixture was compressed using a hydraulic press at the compression pressure shown in Table 1 to obtain cylindrical pellet-shaped hydrogen storage materials with a diameter of 8 mm, consisting of molded bodies of Example 1 and Comparative Examples 2 to 5. Furthermore, the hydrogen storage material of Comparative Example 1, which does not contain metal-organic frameworks (MOFs) or thermoplastic elastomers (see Tables 1 and 2), could not be molded into a shape.

[0111] For the hydrogen storage materials obtained in this manner, Example 1 and Comparative Examples 1 to 5, the volume ratio of hydrogen storage alloy, metal-organic framework (MOF), and thermoplastic elastomer, as well as the porosity, were investigated using the method described below. The results are shown in Table 2.

[0112] "Volume ratio of hydrogen storage alloys" The height of the cylindrical pellet-shaped hydrogen storage material was measured using a film thickness gauge. The volume of the hydrogen storage material was calculated from the area of ​​the base and the height of the hydrogen storage material. The density of the hydrogen storage alloy used as raw material was 8.28 g / cm³. 3 From this, the volume of hydrogen storage alloy in the hydrogen storage material was calculated. Then, the volume ratio (volume %) of the hydrogen storage alloy was determined using the following formula. Volume ratio of hydrogen storage alloy (volume %) = (Volume of hydrogen storage alloy / Volume of hydrogen storage material) × 100

[0113] "Volume ratio of metal-organic frameworks (MOFs)" Density of the metal-organic structure used as raw material: 1.24 g / cm³ 3 From this, the volume of the metal-organic structure in the hydrogen storage material was calculated. Then, using the volume of the hydrogen storage material calculated by the above method, the volume ratio (volume %) of the metal-organic structure was determined using the following formula. Volume ratio of metal-organic structures (volume %) = (Volume of metal-organic structure / Volume of hydrogen storage material) × 100

[0114] "Volume ratio of thermoplastic elastomers" The mass of thermoplastic elastomer in the hydrogen storage material was calculated by subtracting the mass of the hydrogen storage alloy used as a raw material and the mass of the metal-organic structure used as a raw material from the mass of the cylindrical pellet-shaped hydrogen storage material. The density of the thermoplastic elastomer used as a raw material was 0.92 g / cm³. 3 From this, the volume of thermoplastic elastomer in the hydrogen storage material was calculated. Then, using the volume of the hydrogen storage material calculated by the above method, the volume ratio (volume %) of thermoplastic elastomer was determined using the following formula. Volume ratio of thermoplastic elastomer (volume %) = (Volume of thermoplastic elastomer / Volume of hydrogen storage material) × 100

[0115] (porosity) Using the volume ratios of hydrogen storage alloys, metal-organic frameworks (MOFs), and thermoplastic elastomers calculated by the above method, the porosity was calculated using the following formula. Porosity (%) = 1 - (Volume ratio of hydrogen storage alloy + Volume ratio of metal-organic framework (MOF) + Volume ratio of thermoplastic elastomer)

[0116] Furthermore, the hydrogen storage material of Comparative Example 1, which did not contain metal-organic frameworks (MOFs) or thermoplastic elastomers, could not be molded into a cylindrical pellet-like body. Therefore, the height of the polymer-containing mixture within the mold after compression was considered as the height of the hydrogen storage material, and the volume of the hydrogen storage material of Comparative Example 1 was calculated. Subsequently, the volume ratio and porosity of the hydrogen storage alloy were determined using the calculated volume of the hydrogen storage material.

[0117] [Table 2]

[0118] Furthermore, the hydrogen storage materials of Example 1 and Comparative Examples 2 to 5 were each subjected to the activation treatment described below. Subsequently, the hydrogen absorption and release cycle described below was performed three times at 40°C, and the appearance before hydrogen absorption (before activation treatment) and after the three hydrogen absorption and release cycles was observed and evaluated. Figure 1 shows photographs of the hydrogen storage materials of Example 1 and Comparative Examples 2 to 5 taken before hydrogen absorption and after the three hydrogen absorption and release cycles.

[0119] (Activation treatment) Hydrogen was introduced at 2.0 MPa into a sample tube containing a hydrogen storage material (molded body). Subsequently, the sample tube was evacuated, and the hydrogen absorbed by the hydrogen storage material was released from the material.

[0120] (Hydrogen storage and release cycle) After activation treatment, the initial hydrogen pressure in the sample tube was set to 1.0 MPa and maintained for 5 minutes. This allowed hydrogen to be absorbed into the hydrogen storage material (molded body). Subsequently, the initial hydrogen pressure in the sample tube was set to 0.10 MPa and maintained for 10 minutes. This released hydrogen from the hydrogen storage material (molded body). Subsequently, the sample tube was evacuated for 2 minutes to release more hydrogen from the hydrogen storage material (molded body).

[0121] As shown in Figure 1, the hydrogen storage material (molded body) of Example 1 maintained its shape even after three hydrogen absorption and release cycles. Furthermore, as shown in Table 2, the hydrogen storage material (molded body) of Example 1 had a sufficiently low porosity and was capable of absorbing and releasing a large amount of hydrogen. In contrast, as shown in Figure 1, the hydrogen storage materials (molded bodies) of Comparative Examples 2 to 4, which did not contain thermoplastic elastomers (see Tables 1 and 2), were pulverized after three hydrogen absorption and release cycles and did not maintain their shape.

[0122] Furthermore, as shown in Figure 1, the hydrogen storage material (molded body) of Comparative Example 5, which contains a thermoplastic elastomer (see Tables 1 and 2), maintained its shape even after three hydrogen absorption and release cycles. However, as shown in Table 2, the hydrogen storage material (molded body) of Comparative Example 5 had a higher porosity compared to the hydrogen storage material (molded body) of Example 1.

[0123] [Example 2] The hydrogen storage material of Example 2 was manufactured by the method described below. The following materials were used as raw materials. "Hydrogen storage alloy" LaNi5 (manufactured by Furuchi Chemical, product name: LaNi5powder); hydrogen mass density 1.4% by mass, density 8.28 g / cm³ 3 , particle size 25μm or less

[0124] "Porous Aromatic Structure (PAF)" (Example of combination) PAF-1 in this synthesis example was synthesized using the same method as described in Non-Patent Document A, except that Tetrakis(4-bromophenyl)methane was used as a starting material. Under hydrogen adsorption conditions of 77K temperature and 100bar pressure, the hydrogen mass density was 17.49% by mass and the density was 0.315 g / cm³. 3

[0125] "Thermoplastic elastomer" The above formula (I) represents SIS (product name; SIS5403, elongation of 1400% measured by tensile test (JIS K6251), molar ratio of structural units derived from styrene to structural units derived from isoprene (structural units derived from styrene / structural units derived from isoprene) 15 / 85, manufactured by ENEOS Material Co., Ltd.)

[0126] (PAF dispersion manufacturing process) A polymer solution was added to the porous aromatic structure (PAF) and then stirred (with a stirring bar) to prepare a dispersion of the porous aromatic structure (PAF). Using a centrifuge tube as a container makes it easier to stir even small amounts. As the polymer solution, the above-mentioned thermoplastic elastomer was dissolved in toluene as the solvent. The amount of polymer solution used was such that the ratio of the above-mentioned thermoplastic elastomer to the hydrogen storage material contained in the hydrogen storage material was as shown in Table 3 (mass%).

[0127] (Manufacturing process for hydrogen storage material-containing mixture) The hydrogen storage material was added to the PAF dispersion obtained in the above process and uniformly mixed by ultrasonic dispersion or by hand mixing with a spatula to obtain a slurry mixture. The mixture was collected with a syringe and transferred to a mold. The mixture was left to air dry for about a day to evaporate and remove the solvent, resulting in a mixture containing the hydrogen storage material. The above-mentioned hydrogen storage alloy and porous aromatic structure (PAF) were mixed such that the ratio of the porous aromatic structure (PAF) to the hydrogen storage alloy was as shown in Table 3, and a mixture was produced.

[0128] [Table 3]

[0129] (Compression process) Next, the hydrogen storage material-containing mixture was compressed using a hydraulic press at the compression pressure shown in Table 3 to obtain cylindrical pellet-shaped hydrogen storage material with a diameter of 8 mm, which was made from the molded body of Example 2.

[0130] For the hydrogen storage materials of Example 2 obtained in this manner, the volume ratio of hydrogen storage alloy, porous aromatic structure (PAF), and thermoplastic elastomer, as well as the porosity, were investigated using the method described below. The results are shown in Table 4.

[0131] "Volume ratio of hydrogen storage alloys" The height of the cylindrical pellet-shaped hydrogen storage material was measured using a film thickness gauge. The volume of the hydrogen storage material was calculated from the area of ​​the base and the height of the hydrogen storage material. The density of the hydrogen storage alloy used as raw material was 8.28 g / cm³. 3From this, the volume of hydrogen storage alloy in the hydrogen storage material was calculated. Then, the volume ratio (volume %) of the hydrogen storage alloy was determined using the following formula. Volume ratio of hydrogen storage alloy (volume %) = (Volume of hydrogen storage alloy / Volume of hydrogen storage material) × 100

[0132] "Volume ratio of porous aromatic structures (PAFs)" The density of the porous aromatic structure (PAF) used as a raw material was 0.315 g / cm³. 3 From this, the volume of porous aromatic structures (PAFs) in the hydrogen storage material was calculated. Then, using the volume of the hydrogen storage material calculated by the above method, the volume ratio (volume %) of porous aromatic structures (PAFs) was determined using the following formula. Volume ratio of porous aromatic structures (PAF) (volume %) = (Volume of porous aromatic structures (PAF) / Volume of hydrogen storage material) × 100

[0133] "Volume ratio of thermoplastic elastomers" The mass of thermoplastic elastomer in the hydrogen storage material was calculated by subtracting the mass of the hydrogen storage alloy used as a raw material and the mass of the porous aromatic structure (PAF) used as a raw material from the mass of the cylindrical pellet-shaped hydrogen storage material. The density of the thermoplastic elastomer used as a raw material was 0.92 g / cm³. 3 From this, the volume of thermoplastic elastomer in the hydrogen storage material was calculated. Then, using the volume of the hydrogen storage material calculated by the above method, the volume ratio (volume %) of thermoplastic elastomer was determined using the following formula. Volume ratio of thermoplastic elastomer (volume %) = (Volume of thermoplastic elastomer / Volume of hydrogen storage material) × 100

[0134] (porosity) Using the volume ratios of hydrogen storage alloys, porous aromatic structures (PAFs), and thermoplastic elastomers calculated by the above method, the porosity was calculated using the following formula. Porosity (%) = 1 - (Volume ratio of hydrogen storage alloy + Volume ratio of porous aromatic structure (PAF) + Volume ratio of thermoplastic elastomer)

[0135] [Table 4]

[0136] Furthermore, the hydrogen storage materials of Example 2 were each subjected to the activation treatment described below. Subsequently, the hydrogen absorption and release cycle described below was performed three times at 40°C, and the appearance before hydrogen absorption (before activation treatment) and after the three hydrogen absorption and release cycles was observed and evaluated. Figure 2 shows photographs of the hydrogen storage material of Example 2 taken before hydrogen absorption and after the three hydrogen absorption and release cycles.

[0137] (Activation treatment) Hydrogen was introduced at 2.0 MPa into a sample tube containing a hydrogen storage material (molded body). Subsequently, the sample tube was evacuated, and the hydrogen absorbed by the hydrogen storage material was released from the material.

[0138] (Hydrogen storage and release cycle) After activation treatment, the initial hydrogen pressure in the sample tube was set to 1.0 MPa and maintained for 5 minutes. This allowed hydrogen to be absorbed into the hydrogen storage material (molded body). Subsequently, the initial hydrogen pressure in the sample tube was set to 0.10 MPa and maintained for 10 minutes. This released hydrogen from the hydrogen storage material (molded body). Subsequently, the sample tube was evacuated for 2 minutes to release more hydrogen from the hydrogen storage material (molded body).

[0139] As shown in Figure 2, the hydrogen storage material (molded body) of Example 2 maintained its shape even after three hydrogen absorption and release cycles. Furthermore, as shown in Table 2, the hydrogen storage material (molded body) of Example 2 had a sufficiently low porosity and was capable of absorbing and releasing a large amount of hydrogen.

Claims

1. Hydrogen storage alloys, Porous materials and, It consists of a molded article containing a thermoplastic elastomer, The porous material comprises one or more selected from metal-organic structures, covalent organic structures, and porous aromatic structures. A hydrogen storage material wherein the hydrogen mass density of the porous material at a temperature of 77 K and a pressure of 100 bar is greater than that of the hydrogen storage alloy.

2. The hydrogen storage alloy is provided in an amount of 5% to 60% by volume. The porous material is provided in an amount of 10% to 80% by volume. The above thermoplastic elastomer is contained in an amount of 1% to 25% by volume, The hydrogen storage material according to claim 1, wherein the porosity is 10% by volume to 40% by volume.

3. The ratio of the porous material to the hydrogen storage alloy is 100% by mass or less. The hydrogen storage material according to claim 1, wherein the proportion of the thermoplastic elastomer is 0.4% by mass to 4% by mass.

4. The hydrogen storage alloy is LaNi ５ , MmNi ５ (where "Mm" in the formula represents misch metal), CaNi ５ , TiFe, TiMn １．５ , TiCr １．８ , ZrMn ２ , V ７４．５ Ti １０ Cr １２．５ Mn ３ The hydrogen storage material according to claim 1, which is any one or two or more selected from the group consisting of the above.

5. The hydrogen storage material according to claim 1, wherein the porous material includes a metal-organic structure.

6. The hydrogen storage material according to claim 1, wherein the hydrogen mass density of the metal-organic structure at a temperature of 77 K and a pressure of 100 bar is 3% by mass or more.

7. The hydrogen storage material according to claim 1, wherein the metal-organic structure is one or more selected from MOF-5, UiO-66, UiO-67, and ZIF-8.

8. The hydrogen storage material according to claim 1, wherein the covalent organic structure is one organic structure selected from an organic structure consisting of B, H, O, and C, or an organic structure consisting of B, H, O, C, and Si.

9. The hydrogen storage material according to claim 1, wherein the porous aromatic structure comprises one or both of C-PAF and Si-PAF.

10. The hydrogen storage material according to claim 1, wherein the thermoplastic elastomer is one or more selected from styrene-based elastomers, olefin-based elastomers, urethane-based elastomers, and polyester-based elastomers.

11. A method for producing a hydrogen storage material according to any one of claims 1 to 10, A precursor manufacturing step for producing a hydrogen storage material precursor comprising the hydrogen storage alloy, the porous material, and the thermoplastic elastomer, A method for producing a hydrogen storage material, comprising a compression step of molding and compressing a precursor obtained in the precursor manufacturing step to form a molded body.

12. The aforementioned precursor manufacturing process is: A mixture manufacturing step for producing a mixture containing the hydrogen storage alloy and the porous material, A polymer impregnation step involves impregnating the mixture with a polymer solution obtained by dissolving the thermoplastic elastomer in a solvent, and then removing the solvent to obtain a polymer-containing mixture. A method for producing a hydrogen storage material according to claim 11, including the method described in claim 11.

13. The aforementioned precursor manufacturing process is: A dispersion manufacturing step for producing a dispersion containing a polymer solution obtained by dissolving the thermoplastic elastomer in a solvent and the porous material, A hydrogen storage material-containing mixture manufacturing process involves preparing a slurry-like mixture of the dispersion obtained in the dispersion manufacturing process and the hydrogen storage alloy, and then removing the solvent to produce a hydrogen storage material-containing mixture. A method for producing a hydrogen storage material according to claim 11, including the method described in claim 11.

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