JP2006142281A - Aluminum type nanocomposite catalyst, its manufacturing method and hydrogen occluding composite material using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum type nanocomposite catalyst capable of increasing the speed of hydrogen occlusion and release of hydrogen occlusion material and making the temperature of hydrogen occlusion and release lower, to provide a manufacturing method of the aluminum type nanocomposite catalyst and, further, to provide a hydrogen occlusion composite material capable of occluding and releasing a large amount of hydrogen at lower temperature. <P>SOLUTION: The aluminum type nanocomposite catalyst includes nanometer-sized aluminum (Al) and nano-particles consisting of a compound between at least transition metal and Al to produce composites of the nanometer-sized Al and the nano-particles in the high dispersed state. The aluminum type nanocomposite catalyst is manufactured by mechanically crushing a raw material mixture consisting of: a composite hydride between at least one kind selected from alkali metal element and alkali earth metal element and Al; and a chloride including transition metal. The composites as the hydrogen occlusion composite material are obtained by highly dispersing the aluminum type nanocomposite catalyst to hydrogen occlusion material. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an aluminum-based nanocomposite catalyst that improves the hydrogen storage / release characteristics of a hydrogen storage material, a method for producing the same, and a hydrogen storage composite material using the same.

  In recent years, hydrogen energy has attracted attention as a clean alternative energy due to environmental problems such as global warming caused by carbon dioxide emissions and energy problems such as exhaustion of petroleum resources. For the practical application of hydrogen energy, it is important to develop technology for safely storing and transporting hydrogen. There are several candidates for the hydrogen storage method, and among them, a method using a hydrogen storage material capable of reversibly storing and releasing hydrogen is promising. As hydrogen storage materials, carbon materials such as activated carbon, fullerene, and nanotubes and various metal hydrides are known.

As a metal hydride, it is lightweight and has a large hydrogen occlusion amount. Therefore, a hydride containing lithium (Li) or magnesium (Mg) as a constituent element, or a hydride of alkali metal and aluminum (Al) (LiAlH ₄ , NaAlH _4, etc.) are attracting attention (see, for example, Non-Patent Documents 1 and 2).
Non-Patent Document 3 describes that when AlH ₃ is ball milled, the hydrogen release start temperature decreases from around 180 ° C. to about 100 ° C.
Furthermore, Patent Document 1 discloses a method for synthesizing AlH ₃ . This document describes that AlH ₃ can be obtained by reacting LiH with AlCl ₃ and that this reaction is preferably carried out in a solvent such as ether.
Viktor P. Balema and three others, "Rapid solid-state transformation of tetrahedral [AlH4]-into octahedral [AlH6] 3-in lithium aluminohydride", "Chem. Commun", 2000, p. 1665-1666 Jun Chen and four others, “Reversible Hydrogen Strage via Titanium-Catalyzed LiAlH4 and Li3AlH6”, “J.Phys.Chem.B”, 2001, vol. 105, p. 11214-11220 Sandrock et al., Appl.Phys. A, 80 (2005) 687-690 US Pat. No. 2,567,972

However, the hydride is not suitable for practical use because of its slow hydrogen storage / release rate. For example, Non-Patent Documents 1 and 2 disclose attempts to improve the hydrogen release characteristics of LiAlH ₄ using TiCl ₄ and TiCl ₃ · AlCl ₃ as catalysts. However, the hydrogen storage / release temperature has not been lowered, and the hydrogen storage / release characteristics are still not sufficient for practical use.
AlH ₃ has a relatively high hydrogen density per unit weight, and its hydrogen storage amount reaches about 10 wt%. In addition, AlH ₃ is thermally unstable as compared with other hydrogen storage materials, and the hydrogen release start temperature can be lowered only by mechanical pulverization. However, in order to increase the efficiency of the hydrogen storage / release system, it is desired to further lower the hydrogen release start temperature. Furthermore, there has been no example in which a catalyst for a hydrogen storage material utilizing the high activity of AlH ₃ has been produced.

  The present invention has been made in view of such circumstances, an aluminum-based nanocomposite catalyst capable of increasing the hydrogen storage and release speed of the hydrogen storage material, and realizing the hydrogen storage and lowering of the release temperature, and It is an object to provide a manufacturing method thereof. Another object of the present invention is to provide a hydrogen storage composite material that can store and release a large amount of hydrogen at a lower temperature by using an aluminum-based nanocomposite catalyst.

The aluminum-based nanocomposite catalyst according to the present invention includes nanometer-sized aluminum (Al) and nanoparticles composed of a compound of at least a transition metal and Al, and these are composited in a highly dispersed state. Features.
The method for producing an aluminum-based nanocomposite catalyst according to the present invention comprises a raw material mixture comprising a composite hydride of at least one selected from an alkali metal element and an alkaline earth metal element and Al, and a chloride containing a transition metal. A raw material mixture preparation step to be prepared, and mechanically pulverizing the raw material mixture to include nanometer-sized Al and nanoparticles composed of a compound of at least a transition metal and Al, which are combined in a highly dispersed state. And a mechanical pulverization step for obtaining an aluminum-based nanocomposite catalyst.
Furthermore, the hydrogen storage composite material according to the present invention is characterized in that the aluminum-based nanocomposite catalyst according to the present invention is combined with a hydrogen storage material in a highly dispersed state.

The second of the aluminum-based nanocomposite catalyst according to the present invention includes nanometer-sized Al and nanoparticles composed of at least a transition metal, a transition metal compound or an alkali metal compound, and these are composited in a highly dispersed state. Yes.
The second method for producing an aluminum-based nanocomposite catalyst according to the present invention is a raw material containing a hydride containing AlH ₃ and one or more selected from transition metals, transition metal halides, and alkali metal halides. A raw material mixture preparation step for preparing a mixture, and mechanically pulverizing the raw material mixture to include nanometer-sized Al and nanoparticles composed of at least a transition metal, a transition metal compound, or an alkali metal compound, which are highly dispersed And a mechanical pulverization process for obtaining an aluminum-based nanocomposite catalyst that is composited in a state.
A second hydrogen storage composite material according to the present invention includes a hydrogen storage material and a second aluminum-based nanocomposite catalyst according to the present invention dispersed in the hydrogen storage material.
Further, the third of the hydrogen storage composite material according to the present invention is a raw material mixture containing a hydride containing AlH ₃ and one or more selected from transition metals, transition metal halides, and alkali metal halides. It consists of what was prepared and obtained by carrying out the mechanical grinding | pulverization process of the said raw material mixture.

  The aluminum-based nanocomposite catalyst of the present invention includes nanometer-sized Al and nanoparticles composed of a compound of at least a transition metal and Al, and these are composited in a highly dispersed state. According to the aluminum-based nanocomposite catalyst of the present invention, the hydrogen storage / release speed of the hydrogen storage material can be increased, and the hydrogen storage / release temperature can be lowered. Moreover, according to the manufacturing method of this invention, the aluminum-type nano composite catalyst of this invention can be manufactured simply. Moreover, the hydrogen storage composite material of the present invention is formed by combining the hydrogen storage material with the aluminum-based nanocomposite catalyst of the present invention in a highly dispersed state. The aluminum-based nanocomposite catalyst of the present invention increases the hydrogen storage and release speed, and the hydrogen storage composite material of the present invention can store and release a large amount of hydrogen at a lower temperature.

Further, when a transition metal, a halide of a transition metal, and / or a halide of an alkali metal is added to a hydride containing AlH ₃ and mechanically mixed and pulverized, nanometer-sized Al and transition metal are obtained. In addition, a composite catalyst is obtained which includes nanoparticles made of a transition metal compound or an alkali metal compound and is composited in a highly dispersed state. Nanometer-sized Al and nanoparticles act as a catalyst that lowers the starting temperature of the hydrogen storage / release reaction of the hydrogen storage material. Therefore, when the composite catalyst and the hydrogen storage material are combined, a hydrogen storage composite material capable of storing and releasing a large amount of hydrogen at a low temperature is obtained.
Furthermore, a hydride containing AlH ₃ has a relatively high hydrogen density per unit weight, but a relatively high hydrogen release start temperature. However, when a transition metal, a transition metal halide or an alkali metal halide is added to this and mechanically pulverized, the hydride containing AlH ₃ becomes thermally unstable. Therefore, a hydrogen storage composite material capable of storing and releasing a large amount of hydrogen at a low temperature can be obtained.

  Hereinafter, the aluminum-based nanocomposite catalyst, the production method thereof, and the hydrogen storage composite material of the present invention will be described in detail. The aluminum-based nanocomposite catalyst of the present invention, the production method thereof, and the hydrogen storage composite material are not limited to the following embodiments, and can be changed by those skilled in the art without departing from the gist of the present invention. It can be implemented in various forms with improvements and the like.

<Aluminum-based nanocomposite catalyst according to the first embodiment of the present invention>
The aluminum-based nanocomposite catalyst according to the present embodiment includes nanometer-sized Al and nanoparticles composed of a compound of at least a transition metal and Al, and these are composited in a highly dispersed state.

As will be described later, the composite catalyst according to the present embodiment is obtained by mechanically pulverizing a composite hydride containing Al and a transition metal chloride and causing a starting material to undergo a mechanochemical reaction. Therefore, the composite catalyst may contain unreacted starting materials and intermediate products in addition to nanometer-sized Al and nanoparticles which are reaction products.
For example, the hydrogen releasing process of LiAlH ₄ , which is a kind of composite hydride containing Al, is represented by the following formulas (a) to (c).
3LiAlH ₄ → Li ₃ AlH ₆ + 2Al + 3H ₂ (a)
Li ₃ AlH ₆ → 3LiH + Al + 3 / 2H ₂ (b)
3LiH → 3Li + 3 / 2H ₂ (c)
When a transition metal chloride is added to LiAlH ₄ and mechanically pulverized, LiAlH ₄ is decomposed according to the formula (a) to (c) according to the type and blending amount of the transition metal chloride, pulverization conditions, and the like. Proceeding to any stage, hydrogen and Al are produced. A part of the produced Al remains in the composite catalyst in the metal state, and the other part reacts with the transition metal to form a compound. When the mechanochemical reaction stops halfway, the composite catalyst may contain unreacted LiAlH ₄ and / or Li ₃ AlH _{6 that} is by-produced when LiAlH ₄ decomposes to produce Al. is there. These may be contained in the composite catalyst. The same applies when other complex hydrides are used as starting materials.

“Nanoparticle” means a composite hydride containing Al as a starting material (for example, LiAlH ₄ ), Al generated when the starting material is decomposed, and a secondary material when the starting material is decomposed to generate Al. This refers to nanometer-sized fine particles made of a material other than hydride containing Al (eg, Li ₃ AlH ₆ ).
In the present embodiment, the nanoparticles include at least a compound of a transition metal and Al generated by a mechanochemical reaction of a starting material.
The transition metal is not particularly limited. For example, it is a kind selected from titanium (Ti), zirconium (Zr), cobalt (Co), nickel (Ni), chromium (Cr), and vanadium (V) because of its high catalytic ability to accelerate hydrogen storage and release. The above is desirable. Of these, Ti and Zr are preferable.

In addition, “a nanoparticle composed of a compound of at least a transition metal and Al” does not exclude an aspect in which nanoparticles other than the compound are combined in addition to a nanoparticle composed of a compound of a transition metal and Al. It is.
For example, in the case of mechanically pulverizing the LiAlH ₄ and TiCl _3, amount or TiCl _3, depending on the milling conditions and the like, other compounds of transition metals and _{Al (Al 3 Ti), Ti} , TiH, Various simple substances and compounds produced by the reaction of starting materials such as LiCl may be produced. Depending on the reaction conditions, unreacted TiCl ₃ may remain. These are all included in “nanoparticles”. The same applies when other complex hydrides and other transition metal chlorides are used as starting materials.
Among these, transition metals or compounds thereof are particularly suitable as materials constituting the nanoparticles because of their high catalytic activity. In particular, Al ₃ Ti, Ti, and TiCl ₃ are suitable as nanoparticles because of their high activity.

  The average particle diameter of the nanoparticles is preferably 10 nm or more and 50 nm or less. It is more preferable that it is 10 nm or more and 20 nm or less. The average particle diameter of the nanoparticles can be determined by observing with a transmission electron microscope (TEM) or the like. In this case, the maximum length when the observed nanoparticles are sandwiched between two parallel lines may be the particle diameter. In this specification, the average particle diameter obtained by observing with TEM is adopted.

“Nanometer-sized Al and nanoparticles are combined in a highly dispersed state” means a state where nanometer-sized Al and nanoparticles are uniformly dispersed.
For example, when the ratio of the composite hydride in the starting material is relatively large, the composite catalyst contains unreacted composite hydride and Al as an intermediate product in addition to Al generated by mechanochemical reaction. Including hydrides. These are primary particles of nanometer size, and these primary particles are aggregated to form a cluster shape (tuft shape). The size of the primary particles and the entire cluster varies depending on the production conditions, but is preferably about 5 to 50 nm and about 100 to 200 nm, respectively. The nanoparticles are mainly uniformly dispersed in such a cluster-like matrix.
For example, when the ratio of the composite hydride in the starting material is relatively small, Al or the like is uniformly dispersed in the form of clusters or primary particles in the nanoparticles.
“Complexed in a highly dispersed state” includes any of these states.

Furthermore, the aluminum-based nanocomposite catalyst according to the present embodiment has various compositions depending on the type of starting material, the blending ratio, pulverization conditions, and the like. In addition, although hydrogen contained in the starting material remains in the composite catalyst, even if the amount of residual hydrogen is relatively large, in order to lower the starting temperature of the hydrogen storage / release reaction of the hydrogen storage material. It functions as a catalyst.
In general, as the residual hydrogen ratio in the composite catalyst (ratio of the amount of hydrogen remaining in the composite catalyst to the total amount of hydrogen contained in the starting material) decreases, the content of Al in the composite catalyst increases, and / or As the content of the transition metal and Al compound in the composite catalyst increases, a composite catalyst with higher activity can be obtained.
Specifically, when the composition of the starting material and the mechanical grinding conditions are optimized, the residual hydrogen ratio is 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% A composite catalyst of 20% or less is obtained below.
In addition, when the composition of the starting material and the mechanical pulverization conditions are optimized, a composite catalyst having a metal Al content of 30 wt% or more, 40 wt% or more, 50 wt% or more, or 60 wt% or more is obtained. It is done.
Furthermore, when the composition of the starting material and the mechanical grinding treatment conditions are optimized, a composite catalyst in which the content of the compound of transition metal and Al in the composite catalyst is 10 wt% or more, 20 wt% or more, or 30 wt% or more is obtained. can get.

Next, the operation of the aluminum-based nanocomposite catalyst according to the present embodiment will be described.
In the aluminum-based nanocomposite catalyst according to the present embodiment, the transition metal mainly serves as a catalyst for increasing the hydrogen storage / release rate. Transition metals exist mainly as compounds with Al. The compound of the transition metal and Al is a nanoparticle, that is, a nanometer-sized particle. Although the transition metal is miniaturized, it is hardly poisoned (oxidized) because it exists mainly as a compound with Al.

  Further, according to the study by the present inventors, it has been confirmed that nanometer-sized Al also has a catalytic ability to increase the hydrogen storage and release rate. Thus, since the Al and transition metal contained in the composite catalyst are both in a nanometer size and highly active state, the aluminum-based nano composite catalyst according to the present embodiment has many active sites. For this reason, the aluminum-based nanocomposite catalyst according to the present embodiment has high catalytic ability to increase the hydrogen storage / release rate of the hydrogen storage material. Therefore, according to the composite catalyst according to the present embodiment, the hydrogen storage / release speed of the hydrogen storage material is increased, and the hydrogen storage / release temperature can be lowered.

<Method for producing an aluminum-based nanocomposite catalyst according to the first embodiment of the present invention>
The method for producing an aluminum-based nanocomposite catalyst according to the present embodiment includes a raw material mixture preparation step and a mechanical pulverization treatment step. Hereinafter, each step will be described.

(1) Raw material mixture preparation step This step is a step of preparing a raw material mixture comprising a composite hydride of at least one selected from an alkali metal element and an alkaline earth metal element and Al, and a chloride containing a transition metal. It is. The “raw material mixture” in this step is a concept including not only a mixture of a composite hydride and a chloride but also a mixture of a composite hydride and a chloride.

As the first raw material, at least one selected from alkali metal elements such as Li, sodium (Na), potassium (K), and alkaline earth metal elements such as beryllium (Be), Mg, calcium (Ca), and Al A complex hydride of For example, at least one selected from LiAlH ₄ , NaAlH ₄ , KAlH ₄ , MgAlH ₄ , and Ca (AlH ₄ ) composed of a relatively light metal may be used as the composite hydride. One of these may be used alone, or two or more may be mixed and used.

As a second raw material, a chloride containing a transition metal (hereinafter simply referred to as “chloride”) is used. This chloride may contain other metals in addition to the transition metal. The transition metal is not particularly limited. For example, it is desirable to include one or more selected from Ti, Zr, Co, Ni, Cr, and V because of their high catalytic ability to increase hydrogen storage and release rates. Of these, Ti and Zr are preferable. For example, chlorides of these transition metals [composition formula XCl _y (X: transition metal, y = 1 to 4)] may be used as the second raw material.

  The blending ratio of the composite hydride and chloride may be determined in consideration of the rate of progress of the reaction between the composite hydride and chloride, the catalytic ability of the produced aluminum-based nanocomposite catalyst, and the like. That is, the larger the compounding ratio of the chloride, the easier the hydrogen release from the composite hydride and the reaction between Al and the transition metal proceed. Thus, when the reaction rate of the composite hydride and chloride is fast, the particle diameter of the nanoparticles becomes small, and the amount of unreacted raw material also decreases. In addition, the catalytic performance of the aluminum-based nanocomposite catalyst is increased. Therefore, it is desirable that the proportion of chloride is 1 wt% or more when the weight of the raw material mixture is 100 wt%. It is preferable to set it to 2.5 wt% or more, further 5 wt% or more. On the other hand, when the compounding ratio of the chloride is increased to some extent, the effect of improving the reaction rate and catalytic ability is not changed. Thus, it is desirable that the compounding ratio of chloride is 50 wt% or less. More preferably, it is 10 wt% or less.

  The form of the starting material is not particularly limited, but usually powder is used. Moreover, when using powder as a starting material, the particle size is not specifically limited. In general, the smaller the particle size used as a starting material, the less the load required to produce a composite composed of nanoparticles. On the other hand, if a finer powder than necessary is used as a starting material, the powder surface may be poisoned by oxidation or the like. Therefore, it is preferable to select an optimum particle size in consideration of workability, cost, presence / absence of poisoning, and the like.

(2) Mechanical pulverization treatment step This step is a mechanical pulverization treatment of the raw material mixture prepared in the previous raw material mixture preparation step, and nanometer-sized Al and at least nanoparticles composed of a compound of transition metal and Al. And a process for obtaining an aluminum-based nanocomposite catalyst in which these are composited in a highly dispersed state.

In this step, the raw material mixture is accommodated in a processing apparatus that performs mechanical pulverization, and is processed in a predetermined atmosphere. The mechanical pulverization treatment may be performed at a temperature near room temperature and atmospheric pressure. In addition, it is desirable to perform in an atmosphere free of oxygen and moisture, such as an inert gas atmosphere, a hydrogen atmosphere, or a vacuum atmosphere.
The type of the mechanical pulverization process is not particularly limited, and a process that uses an already known injection pressure or collision force may be used. For example, a mechanical gliding (MG) process, a mechanical milling process, a mechanical alloying process, etc. are mentioned. In particular, a mechanical gliding process is suitable. In addition, it is desirable to perform a process by a dry type. Specifically, for example, a planetary ball mill, a vibration ball mill, a jet mill, a hammer mill or the like may be used.
There are no particular limitations on the materials for the container for containing the raw material mixture and the balls for grinding. For example, a container made of structural alloy steel such as chrome steel, nickel chrome steel, nickel chrome molybdenum steel, chrome molybdenum steel, a ball for pulverization, or the like may be used.
Various conditions for the pulverization may be appropriately determined according to the apparatus to be used and in consideration of the amount of the raw material mixture to be processed. For example, the grinding energy is desirably 5 times (5G) or more of the gravitational acceleration.

In the mechanical pulverization treatment, it is necessary to advance the hydrogen release from the composite hydride and the reaction between Al and the transition metal. Further, the longer the treatment time, the finer the Al and starting material, and the smaller the particle size of the nanoparticles. In consideration of these points, the treatment time may be appropriately determined according to the type of raw material to be used, the blending ratio of chloride, and the like.
In general, since the reaction between the raw materials proceeds as the treatment time becomes longer, a composite catalyst having a small amount of residual hydrogen, a high content of metal Al, and / or a high content of a compound of transition metal and Al can be obtained. . For example, in the case of mechanical pulverization using MG treatment, in order to obtain a composite catalyst having high catalytic activity, the treatment time is preferably 5 minutes or longer, more preferably 30 minutes or longer, more preferably 1 hour or longer. More preferably, it is 4 hours or longer, more preferably 10 hours or longer, more preferably 24 hours or longer.

  By the mechanical pulverization treatment, the composite hydride and chloride are mixed and pulverized. As a result, nanometer-sized Al and nanoparticles composed of a compound of at least a transition metal and Al are generated, and these are composited in a highly dispersed state. The preferred embodiment of the produced aluminum-based nanocomposite catalyst according to the present embodiment is as described above.

Next, the operation of the manufacturing method according to the present embodiment will be described.
For example, LiAlH ₄ , which is a kind of complex hydride, releases hydrogen in a three-stage reaction, as shown by formulas (a) to (c). Complex hydrides are generally thermally stable and usually require heating to a relatively high temperature (150 ° C.) or higher in order to cause reactions such as formulas (a) to (c). Therefore, even if the composite hydride is mechanically pulverized alone at room temperature, the decomposition reaction of the composite hydride does not proceed easily, and hydrogen is hardly released.

  On the other hand, when a composite hydride and a chloride containing a transition metal are mixed and mechanically pulverized, the composite hydride is refined by the mechanical pulverization process and also decomposed at room temperature. Release. At the same time, the chloride containing the transition metal is also refined by mechanical grinding. Part of the fine Al generated during the mechanical grinding process chemically binds with the transition metal to form a nanometer-sized compound. The remaining Al is uniformly dispersed in the composite catalyst. As a result, an aluminum-based nanocomposite catalyst containing nanometer-sized Al and nanoparticles composed of a compound of at least a transition metal and Al, which are composited in a highly dispersed state, is obtained.

<Hydrogen storage composite material according to the first embodiment of the present invention>
The hydrogen storage composite material according to the present embodiment is obtained by combining the hydrogen storage material with the aluminum-based nanocomposite catalyst according to the first embodiment of the present invention in a highly dispersed state.
The kind of hydrogen storage material is not particularly limited. For example, when an ion-bonded biohydride having a slow hydrogen storage / release rate is used, the effect of the aluminum-based nanocomposite catalyst of the present invention is fully exhibited. In particular, a Li-based or Mg-based material that is relatively light and has a large hydrogen storage capacity is suitable. For example, LiH, LiBH ₄ , LiAlH ₄ , Li ₂ NH, LiNH ₂ , MgH ₂ , Mg (NH ₂ ) ₂ , Mg (BH ₄ ) ₂ , Mg (AlH ₄ ) ₂ , Li ₂ Mg (NH ₂ ) _2, etc. Is mentioned. One of these may be used alone, or two or more may be mixed and used.
In addition, although metal hydride was mentioned here as a hydrogen storage material, the hydrogen storage material which comprises the hydrogen storage composite material of this invention is a concept also including the state from which the said metal hydride discharge | released hydrogen. That is, the hydrogen storage material includes both a metal hydride in a state of storing hydrogen and a material in a state in which hydrogen is released therefrom.

  The content ratio of the aluminum-based nanocomposite catalyst according to the present embodiment in the hydrogen storage composite material according to the present embodiment is desirably 0.1 wt% or more when the weight of the hydrogen storage composite material is 100 wt%. . When the amount is less than 0.1 wt%, the catalytic effect of increasing the hydrogen storage / release rate cannot be obtained sufficiently. More preferably, it is 2 wt% or more. On the other hand, as a practical range for obtaining the catalytic effect, the content ratio is desirably 10 wt% or less. More preferably, it is 5 wt% or less.

The hydrogen storage composite material according to the present embodiment includes, for example, a hydrogen storage material and the aluminum-based nanocomposite catalyst according to the present embodiment blended at a predetermined ratio as a raw material, and this raw material is mechanically pulverized. Can be manufactured. The mechanical pulverization treatment may be performed in accordance with the contents described in the above-mentioned << Method for producing aluminum-based nanocomposite catalyst according to first embodiment of the present invention> (2) Mechanical pulverization treatment step>. The mechanical pulverization process is not limited to the case of strong pulverization using a planetary ball mill or the like. Any method may be used as long as mechanical energy can be applied to the starting material by rotation, vibration, impact, etc., and the mixture can be uniformly mixed while being pulverized. For example, a method of mixing in a mortar or the like may be used.
Generally, as the energy during pulverization increases and / or as the pulverization time increases, the hydrogen storage material becomes thermally unstable, and hydrogen can be stored and released at a lower temperature. On the other hand, excessive grinding has no real benefit. Therefore, it is preferable to select optimum conditions for the pulverization conditions according to the type and purpose of the raw material.
When excessively pulverized, most of the hydrogen contained in the hydride is released during pulverization. In this case, the obtained material contains a relatively small amount of hydrogen, but when this is reacted with hydrogen, it becomes a material (hydride composite) in a state where hydrogen is occluded.

Next, the operation of the hydrogen storage composite material according to the present embodiment will be described.
The aluminum-based nanocomposite catalyst according to the present embodiment contains nanometer-sized Al or a compound of a transition metal and Al, and therefore has high catalytic ability to increase the hydrogen storage / release rate of the hydrogen storage material. When this composite catalyst is combined with a hydrogen storage material in a highly dispersed state, at least nanoparticles composed of a compound of a transition metal and Al are dispersed in the hydrogen storage material in a substantially uniform state. Thereby, the hydrogen molecules adsorbed on the surface of the hydrogen storage material are easily dissociated, and the dissociated hydrogen atoms are easily diffused inside. Therefore, the hydrogen storage composite material according to the present embodiment can store and release a large amount of hydrogen at a lower temperature.

<Aluminum-based nanocomposite catalyst according to the second embodiment of the present invention>
The aluminum-based nanocomposite catalyst according to the present embodiment includes nanometer-sized Al and nanoparticles composed of at least a transition metal, a transition metal compound, or an alkali metal compound, and these are composited in a highly dispersed state. Consists of.

In the present embodiment, the nanoparticles do not necessarily contain a transition metal and Al compound. This is because the starting materials used are different as will be described later.
Nanoparticles have a variety of compositions depending on the type of starting material and the extent of reaction that occurs during the mechanical grinding process. In particular,
(1) transition metals such as Ti, Zr, Co, Ni, Cr, V,
(2) transition metal hydrides such as TiH,
(3) transition metal halides such as TiCl ₃ ;
(4) Al ₃ Ti and other transition metals and Al compounds,
(5) Alkali metal halides such as NaCl and LiCl,
(6) Alkali metal hydrides such as NaH and LiH,
and so on. Any one of these may be contained in the composite catalyst, or two or more of them may be contained.
Among these, transition metals (particularly Ti, Zr) and transition metal compounds (particularly transition metal and Al compounds) have a high catalytic activity for decomposing the hydrogen storage material, and are particularly useful as materials constituting the nanoparticles. Is preferred.
Since it is the same as that of the aluminum-type nano composite catalyst which concerns on 1st Embodiment about another point, description is abbreviate | omitted.

<Method for producing an aluminum-based nanocomposite catalyst according to the second embodiment of the present invention>
The method for producing an aluminum-based nanocomposite catalyst according to the present embodiment includes a raw material mixture preparation step and a mechanical pulverization step.

The raw material mixture preparation step is a step of preparing a raw material mixture containing a hydride containing AlH ₃ and one or more selected from transition metals, halides of transition metals, and halides of alkali metals.

The first raw material is made of a hydride containing AlH ₃ .
AlH ₃ has various synthesis methods as will be described later, but the way it is produced varies depending on the starting material used, the type of solvent, and the like. At present, there is no standard reagent, so researchers have created it using a unique process. At present, AlH ₃ is known to show seven kinds of crystal structures and is named α, α ′, β, δ, ε, γ, ζ. AlH ₃ produced by the liquid phase synthesis method described later is supposed to be α, β, γ.
In the present invention, the crystal structure of AlH ₃ contained in the first raw material is not particularly limited, and may have any of the crystal structures described above. Further, the first raw material may contain only one kind of AlH ₃ , or may contain two or more kinds of AlH ₃ having different crystal structures.

The first raw material may contain only AlH ₃ or may contain other substances. Other substances, unreacted starting material used in the synthesis of AlH ₃ (e.g., LiH, etc.), by-products in the synthesis of AlH ₃ (e.g., LiCl, LiAlH _4, etc.) and the like.
A hydride containing AlH ₃ can be synthesized by reacting a hydride containing an alkali metal with a halide of Al.
As a hydride containing an alkali metal,
(1) Alkali metal hydrides such as LiH and NaH,
(2) Alkali metal-aluminum complex hydrides such as LiAlH ₄ and NaAlH ₄ ,
and so on. These may be used alone or in combination of two or more.
Examples of Al halides include AlCl ₃ , AlBr ₃ , AlF ₃ , and AlI ₃ . These may be used alone or in combination of two or more. In particular, AlCl ₃ is particularly suitable as a starting material because it is soluble in a solvent.

The mixing ratio of the hydride containing alkali metal and the halide of Al is selected in accordance with the type of the starting material and the target composition. For example, when LiH or LiAlH ₄ is used as a hydride containing an alkali metal, assuming that the molar ratio (x / y) of the hydride containing alkali metal (x) to the halide of aluminum (y) is 3, the following: As shown in formula (d) or formula (e), almost single-phase AlH ₃ is obtained. The same applies to the case of using a hydride containing other alkali metal (for example, NaH or NaAlH ₄ ).
3LiH + AlCl ₃ → AlH ₃ + 3LiCl (d)
3LiAlH ₄ + AlCl ₃ → 4AlH ₃ + LiCl (e)
When the molar ratio (x / y) between the hydride containing an alkali metal and the halide of Al is changed, a hydride other than AlH ₃ is also generated. For example, when the molar ratio (x / y) is 4, LiAlH ₄ can be synthesized as shown in the following formula (f).
4LiH + AlCl ₃ → LiAlH ₄ + 3LiCl (f)
It is thought that a mixture containing these hydrides can be obtained by further increasing the molar ratio (x / y) of the starting materials.

In the method of reacting a hydride containing an alkali metal with a halide of Al,
(1) A solid phase synthesis method in which a starting material is mechanically pulverized and subjected to a mechanochemical reaction,
(2) A liquid phase synthesis method in which starting materials are dissolved or dispersed in a suitable solvent and reacted in the solvent.
and so on. In the present invention, a hydride synthesized by any method can be used.

In particular, the liquid phase synthesis method is suitable as a method for synthesizing a hydride containing AlH ₃ because the reaction can be controlled relatively easily. In this case, the solvent is preferably a solvent capable of dissolving at least an Al halide. Specific examples of such a solvent include diethyl ether, tetrahydrofuran (THF), dioxane and the like.
When a hydride containing an appropriate amount of an alkali metal and an Al halide are added to a solvent and this solution is stirred at room temperature for a predetermined time, AlH ₃ and an alkali metal halide are produced. In addition to these, the solution may contain hydrides other than AlH ₃ produced by the reaction, unreacted starting materials, intermediate products, and the like. A compound other than AlH ₃ may be separated from the synthesized product by filtration or the like, or may be used in a state containing a compound other than AlH ₃ . If necessary, a compound other than AlH ₃ is removed, and then the solvent is removed to obtain a hydride containing AlH ₃ .

The second raw material is made of at least one of a transition metal, a transition metal halide, and an alkali metal halide.
The transition metal is not particularly limited. In particular, Ti, Zr, Co, Ni, Cr and V are suitable as constituent elements of the second raw material because of their high catalytic ability to increase the hydrogen storage / release rate. In particular, Ti and Zr are preferable.
Examples of transition metal halides include TiCl ₃ , TiF ₄ , TiBr ₄ , ZrF ₄ , ZrI ₄ , VF ₄ , and VI ₃ .
Furthermore, examples of the alkali metal halide include NaCl, LiCl, NaF, LiF, NaBr, LiBr, NaI, and LiI.
These may be used alone or in combination of two or more.

What is necessary is just to determine the mixture ratio of a 1st raw material and a 2nd raw material in consideration of the advancing speed of these reaction, the catalyst ability of the aluminum-type nanocomposite catalyst manufactured, etc. That is, the larger the blending ratio of the second raw material, the easier the hydrogen release from the first raw material proceeds. Further, in the case where the second raw material contains a transition metal, the larger the blending ratio of the second raw material,
(1) The reaction between Al and the transition metal easily proceeds.
(2) The particle size of the nanoparticles produced by the reaction between Al and the transition metal is reduced.
(3) Less unreacted raw materials,
There is an advantage. As a result, the catalytic performance of the aluminum-based nanocomposite catalyst is also increased.
Specifically, the blending ratio of the second raw material is desirably 1 wt% or more when the weight of the raw material mixture is 100 wt%. The blending ratio of the second raw material is more preferably 2.5 wt% or more, and further preferably 5 wt% or more.
On the other hand, when the blending ratio of the second raw material is increased to some extent, the effect of improving the reaction rate and catalytic ability is not changed. Therefore, the blending ratio of the second raw material is preferably 50 wt% or less, more preferably 10 wt% or less.

The mechanical pulverization process includes mechanically pulverizing the raw material mixture to include nanometer-size Al and nanoparticles composed of at least a transition metal, a transition metal compound, or an alkali metal compound, which are combined in a highly dispersed state. This is a step of obtaining the aluminum-based nanocomposite catalyst.
In the mechanical pulverization process, it is necessary to release hydrogen from the first raw material. Further, when the second raw material contains a transition metal, it is desirable to advance the reaction between Al and the transition metal. In general, the longer the treatment time, the finer the starting materials and reaction products, or the hydrogen release reaction and the reaction between Al and transition metals proceed. In consideration of these points, it is preferable to appropriately determine the treatment time according to the type of raw material to be used, the blending ratio, and the like.
In general, since the reaction between the raw materials proceeds as the treatment time becomes longer, a composite catalyst having a small amount of residual hydrogen, a high content of metal Al, and / or a high content of a compound of transition metal and Al can be obtained. . For example, in the case of mechanical pulverization using MG treatment, in order to obtain a composite catalyst having high catalytic activity, the treatment time is preferably 5 minutes or longer, more preferably 30 minutes or longer, more preferably 1 hour or longer. More preferably, it is 4 hours or longer, more preferably 10 hours or longer, more preferably 24 hours or longer.
Since other points regarding the mechanical pulverization process are the same as those in the first embodiment, description thereof is omitted.

<Hydrogen storage composite material according to second embodiment of the present invention>
The hydrogen storage composite material according to the present embodiment includes a hydrogen storage material and the aluminum-based nanocomposite catalyst according to the second embodiment of the present invention dispersed in the hydrogen storage material. The hydrogen storage composite material according to the present embodiment is the same as the hydrogen storage composite material according to the first embodiment, except that the aluminum-based nanocomposite catalyst according to the second embodiment of the present invention is used as a catalyst. Since it is the same, description is abbreviate | omitted.

Next, the operation of the aluminum-based nanocomposite catalyst and the manufacturing method thereof and the hydrogen storage composite material according to the present embodiment will be described.
AlH ₃ is thermally unstable compared to other hydrides. Therefore, when the first raw material and the second raw material mixed at a predetermined ratio are mechanically pulverized, the raw material is refined and AlH ₃ is decomposed by the catalytic action of the second raw material at room temperature. Releases a large amount of hydrogen. At the same time, nanometer-sized metal Al is produced. Further, when the second raw material contains a transition metal, a part of the fine Al produced by the mechanical pulverization treatment reacts with the transition metal to produce a compound of Al and the transition metal.
The composite catalyst thus obtained contains nanometer-sized metal Al and nanoparticles composed of a transition metal, a transition metal compound, or an alkali metal compound, and has a structure in which these are uniformly dispersed. Many of them have high catalytic ability to increase the hydrogen storage / release speed of hydrogen storage materials. Therefore, if this is added to the hydrogen storage material, the start temperature of the hydrogen storage / release reaction can be lowered.

<Hydrogen storage composite material and manufacturing method thereof according to the third embodiment of the present invention>
The method for producing a hydrogen storage composite material according to the third embodiment of the present invention includes a raw material mixture preparation step and a mechanical pulverization step. Moreover, the hydrogen storage composite material which concerns on this Embodiment consists of what was obtained by the method which concerns on this Embodiment.

The raw material mixture preparation step is a step of preparing a raw material mixture containing a hydride containing AlH ₃ and one or more selected from transition metals, halides of transition metals, and halides of alkali metals. Since the raw material mixture preparation step is the same as the manufacturing method of the aluminum-based nanocomposite catalyst according to the second embodiment described above, description thereof is omitted.

The mechanical pulverization process is a process of mechanically pulverizing the raw material mixture.
The mechanical pulverization process is a process in which mechanical energy is applied to the starting material by rotation, vibration, impact, etc., and the mixture is uniformly mixed while pulverizing. As such mechanical mixing and grinding treatment,
(1) A process of mixing and crushing raw material powder in a mortar,
(2) Processing to mix and pulverize raw material powder using a pulverizer such as a planetary ball mill, rotary mill, vibration mill, etc. (so-called “mechanical grinding (MG) processing” described above),
and so on.

In general, as the energy during mechanical pulverization increases and / or as the processing time of mechanical pulverization increases, the hydride containing AlH ₃ becomes thermally unstable and the hydrogen storage / release reaction starts. The temperature drops.
In order to lower the starting temperature of the hydrogen storage / release reaction, the treatment time of the mechanical pulverization treatment is preferably at least 1 minute. The treatment time of the mechanical pulverization treatment is more preferably 5 minutes or more, and further preferably 10 minutes or more. On the other hand, excessive grinding has no real benefit. Therefore, it is preferable to select optimum conditions for the pulverization conditions according to the type and purpose of the raw material.
When excessively pulverized, most of the hydrogen contained in the hydride is released during pulverization. In this case, the amount of hydrogen contained in the obtained material is relatively small, but when this is reacted with hydrogen, a material (hydride complex) in a state of storing hydrogen is obtained. Moreover, since the catalytic activity increases as the residual hydrogen ratio in the material decreases, a material with a relatively small amount of residual hydrogen can also be used as a composite catalyst.
Other points regarding the mechanical pulverization process are the same as those in the method of manufacturing the aluminum-based nanocomposite catalyst according to the second embodiment, and thus the description thereof is omitted.

AlH ₃ has a larger amount of hydrogen storage (about 10 wt%) than other hydrogen storage materials and is thermally unstable. Therefore, when a hydride containing AlH ₃ is mechanically pulverized alone, a certain amount of hydrogen is released during pulverization. In addition, the starting temperature of the hydrogen storage / release reaction is lowered to some extent by the mechanical pulverization treatment.
In contrast, when a transition metal or the like is added to a hydride containing AlH ₃ and mechanically pulverized, the hydride containing AlH ₃ becomes thermally unstable, and the start temperature of the hydrogen storage / release reaction is significantly reduced. . Furthermore, when the energy of the mechanical grinding process is increased and / or the processing time is increased, a large amount of hydrogen is released only by the mechanical grinding process.

(Comparative Example 1)
5 g of LiAlH ₄ was placed in a chrome steel container (volume: 300 ml) together with 40 chrome steel balls (outer diameter 9.5 mm), and subjected to MG treatment with a planetary ball mill P-5 (manufactured by FRITSCH). The MG treatment was performed under an argon gas atmosphere, room temperature, 0.1 MPa, and the grinding energy was 5 G (motor rotation speed 1300 rpm). The MG treatment time was 0 hour, 4 hours, 24 hours, or 96 hours.

For LiAlH ₄ before and after MG treatment, the hydrogen release characteristics were measured using a thermal desorption method. FIG. 1 shows the hydrogen release rate during the temperature rising process. FIG. 2 shows an integrated value of the amount of hydrogen released during the temperature raising process.
As shown in FIG. 1 and FIG. 2, the release of hydrogen shows a first peak around 150 to 200 ° C., and a second peak around 200 to 250 ° C., although there is a slight difference depending on the presence or absence of MG treatment. A third peak is shown around 400-450 ° C. The hydrogen release process of LiAlH ₄ is divided into three stages as shown in the formulas (a) to (c). The reactions of the formulas (a) to (c) correspond to these peaks in order. .
1 and 2,
(1) When the reaction proceeds to the second peak, that is, the reaction of formula (b) (decomposition reaction of Li ₃ AlH ₆ ), about ₇ to 8 wt% of hydrogen is released from LiAlH ₄ .
(2) hydrogen release initiation temperature of LiAlH ₄ by MG process is reduced extent 50 ° C., even if MG processes the LiAlH ₄ alone, hydrogen is hardly released,
I understand that.
Note that the reason why the hydrogen release start temperature is slightly lowered by the MG treatment is considered to be that metal Al is generated by the MG treatment and the hydrogen is easily released by the catalytic ability of the metal Al.

Example 1
An aluminum-based nanocomposite catalyst was prepared using LiAlH ₄ and TiCl ₃ as the composite hydride and transition metal chloride, respectively.
First, a raw material mixture was prepared by adding TiCl ₃ to LiAlH ₄ . The blending ratio of TiCl ₃ was 5 wt% (LiAlH ₄ : TiCl ₃ = 95: 5 (weight ratio)). Next, 5 g of the prepared raw material mixture is put into a chrome steel container (volume: 300 ml) together with 40 chrome steel balls (outer diameter 9.5 mm), and the planetary ball mill P-5 (manufactured by FRITSCH) uses MG. Processed. The MG treatment was performed under an argon gas atmosphere, room temperature, 0.1 MPa, and the grinding energy was 5 G (motor rotation speed 1300 rpm). The MG treatment time was 5 minutes, 0.5 hours, 1 hour, 4 hours, or 24 hours.
(Comparative Example 2)
The raw material mixture obtained in Example 1 was used for the test as it was.

For the composite catalyst obtained in Example 1 and the raw material mixture of Comparative Example 2, the amount of remaining hydrogen was measured using a thermal desorption method. FIG. 3 shows the result. In FIG. 3, the curve shown as “Mix.” Is the hydrogen release behavior of a mixture of LiAlH ₄ and TiCl ₃ (Comparative Example 2). FIG. 3 shows that the amount of released hydrogen decreases as the treatment time increases, that is, the longer the treatment time, the more hydrogen is released during the MG treatment.
In particular, when the MG treatment was performed for 24 hours, there was almost no hydrogen release at 400 ° C. or lower, and the total hydrogen release amount was about 3 wt%. As shown in FIG. 2, the total hydrogen release amount of LiAlH ₄ is about 10 wt%. Further, when the reaction proceeds to the second stage reaction of the formula (b), about 7 wt% of hydrogen is released (residual hydrogen amount: 10 −7 = 3 wt%). From this, it is considered that when the MG treatment is performed for 24 hours, LiAlH ₄ hydrogen release proceeds to the second stage, and about 7 wt% of hydrogen is released from LiAlH ₄ . Therefore, for example, when the aluminum-based nanocomposite catalyst of the present invention is produced using LiAlH ₄ and TiCl ₃ , it can be said that the treatment time is desirably about 24 hours.

Next, X-ray diffraction measurement by a powder method using CuKα rays was performed on the catalyst of Example 1 (MG treatment time: 24 hours). FIG. 4 shows the X-ray diffraction pattern. As shown in FIG. 4, peaks of Al, LiAlH ₄ , Li ₃ AlH ₆ , TiH, Al ₃ Ti, TiCl ₃ , and LiCl are observed. From this, the composition of the catalyst of Example 1 (MG treatment time: 24 hours) is Al: about 60 wt%, LiAlH ₄ + Li ₃ AlH ₆ : about 30 wt%, and other Al ₃ Ti, etc .: about 10 wt%. I found out.

When observed with a scanning electron microscope (SEM), the catalyst of Example 1 (MG treatment time: 24 hours) was an aggregate of clusters of about 100 to 200 nm. Although not shown here, nanoparticles (Al ₃ Ti, TiCl ₃ , Ti, etc.) of about 10 to 50 nm are dispersed in a matrix (Al, LiAlH ₄ , Li ₃ AlH ₆ ) by TEM observation and elemental analysis. It was confirmed that

From the above, the catalyst of Example 1 is a composite in which nanoparticles such as Al ₃ Ti particles, TiCl ₃ particles, and Ti particles are combined in a highly dispersed state in a matrix containing Al, LiAlH ₄ , and Li ₃ AlH _6. I can say that.

(Example 2)
An aluminum-based nanocomposite catalyst under the same conditions as in Example 1 except that the compounding ratio of TiCl ₃ was 50 wt% (LiAlH ₄ : TiCl ₃ = 50: 50 (weight ratio)) and the MG treatment time was 24 hours. Was made.

The catalyst of Example 2 was subjected to X-ray diffraction measurement in the same manner as described above. FIG. 5 shows an X-ray diffraction pattern of the catalyst of Example 2. As shown in FIG. 5, peaks of LiCl, Al, Al ₃ Ti, and LiH are observed. From this, it was found that the composition of the catalyst of Example 2 was Al: about 35 wt%, Al ₃ Ti: about 35%, and other LiCl, etc .: about 30 wt%. In the catalyst of Example 2, the proportion of TiCl ₃ used is larger than that of Example 1. Therefore, it is considered that the reaction between LiAlH ₄ and TiCl ₃ proceeded rapidly and almost no unreacted raw material remained. From this, it can be said that the catalyst of Example 2 is a composite of nanometer-sized Al and nanoparticles made of Al ₃ Ti or the like in a highly dispersed state.

(Example 3)
The hydrogen storage composite material of the present invention was produced using the catalyst of Example 1 (MG treatment time: 24 hours). LiAlH ₄ was used as the hydrogen storage material. LiAlH ₄ and the catalyst of Example 1 (hereinafter appropriately referred to as “LiAlH ₄ / TiCl ₃ ”) were blended in a weight ratio of 95: 5 to obtain a raw material. 5 g of this raw material was subjected to MG treatment as described above. The MG treatment was performed for 24 hours under an argon gas atmosphere, room temperature, 0.1 MPa, and a grinding energy of 5G.
(Comparative Examples 3-5)
LiAlH ₄ similar to the above is used as the hydrogen storage material, and TiCl ₃ (Comparative Example 3), Ti (Comparative Example 4), or Ni (Comparative Example 5) is used as the catalyst, respectively. A composite material was produced. LiAlH ₄ and each catalyst were blended in a weight ratio of 95: 5 to obtain raw materials. 5 g of this raw material was subjected to MG treatment in the same manner as in Example 3 except for the treatment time. The MG treatment time was 5 minutes for TiCl ₃ and 1 hour for Ti and Ni, respectively.

[Evaluation of hydrogen release characteristics]
(A) Change with time of hydrogen release amount Each of the hydrogen storage composite materials of Example 3 and Comparative Examples 3 to 5 was heated to 120 ° C. in an argon gas atmosphere of 0.1 MPa, and in that state for 6 hours. Retained. Thereafter, the temperature was further raised to 450 ° C. The amount of hydrogen released in this process was measured by a thermal desorption method. The results are shown in FIGS.
FIG. 6 shows the change over time of the hydrogen release amount of the hydrogen storage composite material of Example 3 (catalyst: LiAlH ₄ / TiCl ₃ ). FIG. 7 shows the change over time in the hydrogen release amount of the hydrogen storage composite material of Comparative Example 3 (catalyst: TiCl ₃ ). FIG. 8 shows the change over time of the hydrogen release amount of the hydrogen storage composite material of Comparative Example 4 (catalyst: Ti). FIG. 9 shows the change over time in the hydrogen release amount of the hydrogen storage composite material of Comparative Example 5 (catalyst: Ni). Of the hydrogen release amounts shown in each figure, the solid line indicates the actual measurement value. A one-dot chain line indicates a value obtained by adding the amount of hydrogen released at room temperature (including the amount released during MG treatment) to the actual measurement value. The dotted line indicates the hydrogen release rate.

  In FIG. 6, the hydrogen storage composite material of Example 3 released about 5 wt% of hydrogen from room temperature to 120 ° C., including during MG treatment, as indicated by the alternate long and short dash line. This shows that the hydrogen storage composite material of Example 1 can release about 5 wt% of hydrogen even at room temperature to 120 ° C. Further, after holding at 120 ° C. for 6 hours, the hydrogen release amount was about 6 wt%. On the other hand, in the hydrogen storage composite material of Comparative Example 3, as shown by the one-dot chain line in FIG. 7, the amount of hydrogen released between room temperature and 120 ° C. including during MG treatment is about 4 wt%, and 120 ° C. × The amount of hydrogen released after holding for 6 hours was about 5 wt%.

  Here, when the combined amount of Ti is compared between the hydrogen storage composite material of Example 3 and the hydrogen storage composite material of Comparative Example 3, the hydrogen storage composite material of Example 3 is the same as that of Comparative Example 3. It is only about 1/100 of the composite material. That is, the hydrogen storage composite material of Example 3 released more hydrogen at a low temperature despite the extremely small amount of Ti.

  Further, in the hydrogen storage composite materials of Comparative Examples 4 and 5, as shown by the alternate long and short dash lines in FIGS. 8 and 9, the amount of hydrogen released until the temperature is raised from room temperature to 120 ° C. is 1 wt%. The amount of hydrogen released after holding at 120 ° C. for 6 hours did not reach 4 wt%. Thus, even if a transition metal is simply used as a catalyst, hydrogen cannot be sufficiently released from the hydrogen storage material at a relatively low temperature of room temperature to 120 ° C.

  From the above, it was confirmed that the hydrogen storage composite material of the present invention releases a large amount of hydrogen at room temperature even if the amount of transition metal contained is small. This confirmed the catalytic effect of the aluminum-based nanocomposite catalyst of the present invention.

(B) Hydrogen release behavior in the temperature raising process The hydrogen storage composite materials of Example 3 and Comparative Examples 3 to 5 were heated in an argon gas atmosphere of 0.1 MPa, and the hydrogen release behavior in the temperature raising process was examined. . The results are shown in FIGS.
FIG. 10 shows the hydrogen release amount of the hydrogen storage composite material of Example 3 (catalyst: LiAlH ₄ / TiCl ₃ ). FIG. 11 shows the hydrogen release amount of the hydrogen storage composite material of Comparative Example 3 (catalyst: TiCl ₃ ). FIG. 12 shows the hydrogen release amount of the hydrogen storage composite material of Comparative Example 4 (catalyst: several μm Ti). FIG. 13 shows the hydrogen release amount of the hydrogen storage composite material of Comparative Example 5 (catalyst: several μm Ni). Of the hydrogen release amounts shown in each figure, the solid line indicates the actual measurement value. A one-dot chain line indicates a value obtained by adding the amount of hydrogen released during MG treatment to the actual measurement value. The dotted line indicates the hydrogen release rate.

As indicated by the alternate long and short dash line in FIG. 10, the hydrogen storage composite material of Example 3 had already released about 2.4 wt% of hydrogen during the MG treatment. Then, hydrogen was gradually released from around 50 ° C., and when it reached 250 ° C., the hydrogen release amount exceeded 7 wt%. As described above, the hydrogen release rate of LiAlH ₄ shows a first peak around 150 to 200 ° C., a second peak around 200 to 250 ° C., and a third peak around 400 to 450 ° C. Show. However, the hydrogen storage composite material of Example 3 releases hydrogen even at room temperature. For this reason, as shown by a dotted line in FIG. 10, the first peak and the second peak overlap and are shifted to the low temperature side.

  On the other hand, in the hydrogen storage composite material of Comparative Example 3, as shown in FIG. 11, no hydrogen was released during the MG treatment, and hydrogen was gradually released from around 100 ° C. Further, in the hydrogen storage composite material of Comparative Example 4, as shown in FIG. 12, hydrogen was not released during the MG treatment, and hydrogen was gradually released from around 150 ° C. Further, in the hydrogen storage composite material of Comparative Example 5, about 0.65 wt% of hydrogen was released during the MG treatment, as indicated by a one-dot chain line in FIG. However, the hydrogen release start temperature was around 130 ° C.

  From the above, it was confirmed that the hydrogen storage composite material of the present invention releases a large amount of hydrogen at room temperature even if the amount of transition metal contained is small. That is, if the aluminum-based nanocomposite catalyst of the present invention is used, the hydrogen release temperature can be lowered.

(C) Hydrogen release behavior with and without catalyst In order to confirm the catalytic effect of the aluminum-based nanocomposite catalyst of the present invention, the change over time in the hydrogen release amount of the hydrogen storage composite material of Example 3 and the MG treatment without using the catalyst The hydrogen storage amount of the obtained hydrogen storage material (LiAlH ₄ ) was compared with the change over time. The hydrogen release conditions were 0.1 MPa, argon gas atmosphere, and 120 ° C. FIG. 14 shows the change over time in the amount of hydrogen released from each material.

  As described above, the hydrogen storage composite material of Example 3 releases about 5 wt% of hydrogen from the room temperature to 120 ° C., including during the MG treatment. For this reason, in FIG. 14, the hydrogen release amount at the start of measurement is about 5 wt%. Then, about 6 wt% of hydrogen was released 6 hours after the start of measurement. On the other hand, none of the hydrogen storage materials containing no catalyst released hydrogen at room temperature. Further, even when the MG treatment was performed for 96 hours, the hydrogen release amount after 6 hours was only about 5 wt%. Thus, it can be seen that a large amount of hydrogen can be released at a low temperature by using the aluminum-based nanocomposite catalyst of the present invention.

Example 4
[1. Synthesis of AlH ₃ (1)]
To 30 cc of diethyl ether, 2.3 to 6.3 g of LiH and 2.9 g of AlCl ₃ were added, and the mixture was stirred at room temperature for 10 minutes under an inert gas (Ar) atmosphere. The molar ratio (x / y) between LiH (x) and AlCl ₃ (y) was 3-8. After completion of the reaction, precipitates (LiCl, etc.) were removed by filtration, and diethyl ether was volatilized.
The sample from which the precipitate was removed was measured for hydrogen release characteristics by a thermal desorption method. FIG. 15 shows the hydrogen release amount of each sample. FIG. 16 shows the hydrogen release amount (solid line) and hydrogen release rate (dotted line) of the sample with x / y = 3. In FIG. 15 and FIG. 16, the vertical axis is an arbitrary scale. As shown in FIGS. 15 and 16, in the case of the sample of x / y = 3, hydrogen release started from about 130 ° C., and a large amount of hydrogen was released around 150 ° C.
From FIG. 15 and FIG. 16, when x / y = 3, it is estimated that a single substance (AlH ₃ ) was generated according to the equation (d). Further, when x / y = 4, it is estimated that LiAlH ₄ is mainly generated according to the equation (f). Furthermore, when x / y = 5 to 8, the composition is unknown, but it is estimated that a mixture of a plurality of hydrides containing AlH ₃ was formed.

[2. Synthesis of AlH ₃ (2)]
Except for using LiAlH ₄ instead of LiH, [1. The hydride was synthesized following the same procedure as above. The molar ratio (x / y) between LiAlH ₄ (x) and AlCl ₃ (y) was 3.
The sample from which the precipitate was removed was measured for hydrogen release characteristics by a thermal desorption method. FIG. 17 shows the hydrogen release amount (solid line) and the hydrogen release rate (dotted line). In FIG. 17, the vertical axis is an arbitrary scale. FIG. 17 shows that this sample starts releasing hydrogen at about 100 ° C. In the case of this sample, it is estimated that a single substance (AlH ₃ ) was generated according to the equation (e). [1. The reason why the hydrogen release start temperature is lower than that of the sample obtained in the above is considered to be due to the difference in how AlH ₃ is formed depending on the type of starting material. When the obtained sample was subjected to X-ray diffraction, it was confirmed that the sample was composed of a compound having a structure similar to β-AlH ₃ (JCPDS file: 38-0757).

[3. Preparation of hydrogen storage composite material]
5% by weight of transition metal, transition metal halide or alkali metal halide was added to AlH ₃ (x / y = 3) synthesized according to the formula (d) and mixed with MG treatment or mortar. The MG treatment conditions were the same as in Example 1 except that the MG treatment time was 5 minutes to 1 hour.
[4. Evaluation]
The obtained hydrogen storage composite material was heated in an argon gas atmosphere of 0.1 MPa, and the hydrogen release behavior in the temperature rising process was examined. A thermal desorption method was used to measure the amount of hydrogen. Table 1 shows the amount of hydrogen contained in the hydrogen storage composite material (total amount of hydrogen released before being heated to 450 ° C.) and the hydrogen release start temperature. In Table 1, AlH _3, AlH ₃ was synthesized according to the equation (e) was synthesized in accordance with equation (d), and, only AlH ₃ was synthesized according to the equation (d) MG (treatment time: 1 hour) was Sample results are also shown.

The amount of hydrogen of AlH ₃ synthesized according to the formula (d) was 10 wt%, and the hydrogen release start temperature was 130 ° C. In addition, the amount of hydrogen of AlH ₃ synthesized according to the formula (e) was 10 wt%, and the hydrogen release start temperature was 100 ° C. Furthermore, when only AlH ₃ was treated with MG, about 5 wt% of hydrogen was released during the MG treatment process, and the amount of hydrogen in the sample was about 5 wt%. Moreover, the hydrogen release start temperature decreased to 75 ° C. by the MG treatment. FIG. 18 shows the hydrogen release amount (solid line) and hydrogen release rate (dotted line) of a sample obtained by subjecting AlH ₃ synthesized according to the formula (d) to MG treatment (treatment time: 1 hour). In FIG. 18, the vertical axis is an arbitrary scale.

On the other hand, when MG treatment was performed by adding a transition metal or the like to AlH ₃ , the hydrogen release start temperature decreased to 45 to 70 ° C. The amount of hydrogen contained in the hydrogen storage composite material depended on the MG processing time, and decreased as the processing time increased. This is because hydrogen was released during the MG treatment process.
In particular, transition metals or transition metal halides have a large effect of thermally destabilizing AlH ₃ , and the hydrogen release start temperature decreased to 45 to 60 ° C. by MG treatment for only 10 minutes. Moreover, the hydrogen release start temperature decreased to 95 ° C. by simply mixing in a mortar for 5 minutes.

(Example 5)
[1. Preparation of aluminum nanocomposite catalyst]
AlH ₃ synthesized according to the formula (d) and halides of various transition metals were blended at a weight ratio of 50/50 and subjected to MG treatment for 24 hours. The MG processing method was the same as in Example 1.
[2. Preparation of hydrogen storage composite material]
LiAlH ₄ [1. ] Was added, and MG treatment or mixing with a mortar was performed. The addition amount of the composite catalyst was 5 wt%. The MG processing conditions were the same as those in Example 1 except that the MG processing time was 5 minutes.
[3. Evaluation]
The obtained hydrogen storage composite material was heated in an argon gas atmosphere of 0.1 MPa, and the hydrogen release behavior in the temperature rising process was examined. A thermal desorption method was used to measure the amount of hydrogen. Table 2 shows the amount of hydrogen contained in the hydrogen storage composite material (total amount of hydrogen released before being heated to 450 ° C.) and the hydrogen release start temperature. Table 1 also shows the results of only LiAlH ₄ that was not subjected to MG treatment, and samples that were subjected to MG treatment for 5 minutes by adding 5 wt% of TiCl ₃ to LiAlH ₄ .

LiAlH _{4 had} a hydrogen content of 10.5 wt% and a hydrogen release start temperature of 150 ° C. In addition, when MG treatment was performed for 5 minutes using TiCl ₃ as a catalyst, the hydrogen release start temperature was 100 ° C.
On the other hand, when various composite catalysts were used, the hydrogen release start temperature decreased to 60 to 70 ° C. by MG treatment for only 5 minutes. Moreover, even if the composite catalyst (AlH ₃ / TiCl ₃ ) was added and mixed in an mortar for 5 minutes (inert gas atmosphere), the hydrogen release start temperature decreased to 130 ° C. From Table 2, it can be seen that the aluminum-based nanocomposite catalyst according to the present invention is effective as a catalyst for an alkali metal hydride.

The aluminum-based nanocomposite catalyst and the method for producing the same according to the present invention can be used as a catalyst for lowering the starting temperature of the hydrogen storage / release reaction of the hydrogen storage material and the method for producing the same.
In addition, the hydrogen storage composite material according to the present invention can be used for hydrogen storage means for fuel cell systems, ultra-high purity hydrogen production equipment, chemical heat pumps, actuators, hydrogen storage bodies for metal-hydrogen storage batteries, and the like.

Is a graph showing the rate of hydrogen release of LiAlH ₄ in the Atsushi Nobori process. Is a graph showing the hydrogen release amount of LiAlH ₄ in the Atsushi Nobori process. It is a graph which shows the hydrogen discharge | release behavior of five types of aluminum nanocomposite catalysts from which MG processing time differs. 2 is an X-ray diffraction pattern of the catalyst of Example 1 (MG treatment time: 24 hours). 2 is an X-ray diffraction pattern of the catalyst of Example 2. 6 is a graph showing a change over time in the hydrogen release amount of the hydrogen storage composite material of Example 3. 6 is a graph showing a change over time in the amount of hydrogen released from the hydrogen storage composite material of Comparative Example 3; 6 is a graph showing a change over time in the amount of hydrogen released from the hydrogen storage composite material of Comparative Example 4; 6 is a graph showing a change with time in hydrogen release amount of the hydrogen storage composite material of Comparative Example 5. 6 is a graph showing a hydrogen release amount in a temperature rising process of the hydrogen storage composite material of Example 3. 10 is a graph showing a hydrogen release amount in a temperature rising process of the hydrogen storage composite material of Comparative Example 3. 6 is a graph showing a hydrogen release amount in a temperature rising process of a hydrogen storage composite material of Comparative Example 4. 6 is a graph showing a hydrogen release amount in a temperature rising process of a hydrogen storage composite material of Comparative Example 5. It is a graph which shows the difference in hydrogen discharge | release behavior by the presence or absence of the aluminum-type nano composite catalyst of this invention. Changing LiH (x) and the molar ratio of AlCl ₃ (y) a (x / y), it is a graph showing the hydrogen release amount of synthesized hydride in diethyl ether. Illustrates been hydrogen release amount and rate of hydrogen release of AlH ₃ synthesized according to formula (d). Illustrates been hydrogen release amount and rate of hydrogen release of AlH ₃ synthesized according to formula (f). After MG processing AlH ₃ synthesized according to formula (d) (processing time: 1 hour) is a graph showing the hydrogen release amount and rate of hydrogen release of.

Claims (24)

  An aluminum-based nanocomposite catalyst comprising nanometer-sized aluminum (Al) and nanoparticles composed of a compound of at least a transition metal and Al, which are composited in a highly dispersed state.   The aluminum-based nanocomposite catalyst according to claim 1, wherein an average particle size of the nanoparticles is 10 nm or more and 50 nm or less.   The aluminum-based nanostructure according to claim 1, wherein the transition metal is at least one selected from titanium (Ti), zirconium (Zr), cobalt (Co), nickel (Ni), chromium (Cr), and vanadium (V). Composite catalyst. In addition to Al, LiAlH ₄ and / or Li ₃ AlH ₆ are included,
The transition metal is Ti;
The aluminum-based nanocomposite catalyst according to claim 1, wherein the nanoparticles include TiCl ₃ particles and / or Ti particles in addition to Al ₃ Ti particles.   2. The composition according to claim 1, which is obtained by mechanically pulverizing a raw material mixture composed of a composite hydride of one or more selected from alkali metal elements and alkaline earth metal elements and Al, and a chloride containing a transition metal. Aluminum-based nanocomposite catalyst. A raw material mixture preparation step for preparing a raw material mixture comprising a composite hydride of one or more selected from alkali metal elements and alkaline earth metal elements and Al, and a chloride containing a transition metal;
The raw material mixture is mechanically pulverized to include an aluminum-based nanocomposite catalyst containing nanometer-sized Al and nanoparticles composed of a compound of at least a transition metal and Al, which are complexed in a highly dispersed state. A mechanical grinding process step to obtain;
The manufacturing method of the aluminum type nano composite catalyst containing this. The method for producing an aluminum-based nanocomposite catalyst according to claim 6, wherein the composite hydride is one or more selected from LiAlH ₄ , NaAlH ₄ , KAlH ₄ , MgAlH ₄ , and Ca (AlH ₄ ) ₂ .   The method for producing an aluminum-based nanocomposite catalyst according to claim 6, wherein the transition metal is one or more selected from Ti, Zr, Co, Ni, Cr, and V.   The method for producing an aluminum-based nanocomposite catalyst according to claim 6, wherein the compounding ratio of the transition metal chloride is 1 wt% or more and 50 wt% or less when the weight of the raw material mixture is 100 wt%.   A hydrogen storage composite material obtained by combining the aluminum-based nanocomposite catalyst according to claim 1 in a highly dispersed state with a hydrogen storage material.   The hydrogen storage composite material according to claim 10, wherein the hydrogen storage material is a lithium (Li) -based or magnesium (Mg) -based material.   11. The hydrogen storage composite material according to claim 10, wherein a content ratio of the aluminum-based nanocomposite catalyst is 0.1 wt% or more and 10 wt% or less when the weight of the hydrogen storage composite material is 100 wt%.   An aluminum-based nanocomposite catalyst comprising nanometer-sized Al and nanoparticles composed of at least a transition metal, a transition metal compound or an alkali metal compound, and these are composited in a highly dispersed state.   The aluminum-based nanostructure according to claim 13, wherein the transition metal is at least one selected from titanium (Ti), zirconium (Zr), cobalt (Co), nickel (Ni), chromium (Cr), and vanadium (V). Composite catalyst.   The aluminum-based nanocomposite catalyst according to claim 13, wherein the transition metal compound is a compound of the transition metal and the Al.   The aluminum-based nanocomposite catalyst according to claim 13, wherein the alkali metal compound is an alkali metal chloride. A raw material mixture preparation step of preparing a raw material mixture containing a hydride containing AlH ₃ and at least one selected from a transition metal, a halide of a transition metal, and a halide of an alkali metal;
The raw material mixture is mechanically pulverized to contain nanometer-size Al and at least nanoparticles composed of a transition metal, a transition metal compound or an alkali metal compound, and these are compounded in a highly dispersed state. The manufacturing method of the aluminum type nano composite catalyst provided with the mechanical grinding | pulverization process process of obtaining a composite catalyst. The method for producing an aluminum-based nanocomposite catalyst according to claim 17, wherein the hydride containing AlH ₃ is obtained by reacting a hydride containing an alkali metal with a halide of Al.   An aluminum-based nanocomposite catalyst obtained by the method according to claim 17 or 18. A hydrogen storage material;
A hydrogen storage composite material comprising the aluminum-based nanocomposite catalyst according to claim 13 dispersed in the hydrogen storage material.   21. The hydrogen storage composite material according to claim 20, wherein the hydrogen storage material is a lithium (Li) -based or magnesium (Mg) -based material.   21. The hydrogen storage composite material according to claim 20, wherein a content ratio of the aluminum-based nanocomposite catalyst is 0.1 wt% or more and 10 wt% or less when the weight of the hydrogen storage composite material is 100 wt%. A raw material mixture preparation step for preparing a raw material mixture containing a hydride containing AlH ₃ and at least one selected from a transition metal, a halide of a transition metal, and a halide of an alkali metal;
A method for producing a hydrogen storage composite material, comprising: a mechanical grinding treatment step of mechanically grinding the raw material mixture. The hydrogen storage composite material obtained by the method of Claim 23.

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