JP2007117989A - Hydrogen storage material and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the decomposition of a hydrogen storage material caused by its contact with water and deterioration in its hydrogen storage or discharge properties, and to reduce the discharge starting temperature of hydrogen in the hydrogen storage material. <P>SOLUTION: The hydrogen storage material comprises one or more kinds of first hydrides including an M<SB>1</SB>element(s), boron and hydrogen, and one or more kinds of first chlorides including an M<SB>2</SB>element(s); wherein, the M<SB>1</SB>element(s) and M<SB>2</SB>element(s) are at least one or more kinds of elements selected from Li, Na, K, Ca, Zn, Cu, Mg, Sc, Zr, Mn, Hf, Al, Ti, Cr, V, Ga, Fe, Co, Ni, Y and rare earth elements, respectively. The production method uses the same. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hydrogen storage material and a method for producing the same.

  In recent years, hydrogen energy has attracted attention as a clean alternative energy because of environmental problems such as global warming caused by carbon dioxide emissions and energy problems such as the depletion of petroleum resources. For the practical application of hydrogen energy, it is important to develop technologies for storing and transporting hydrogen safely and efficiently. There are several candidates for hydrogen storage methods. Among them, methods using hydrogen storage materials that can store and release hydrogen reversibly are considered the safest means of storing and transporting hydrogen. It is expected as a hydrogen storage medium mounted on fuel cell vehicles.

Known hydrogen storage materials include carbon materials such as activated carbon, fullerene, and nanotubes, and hydrogen storage alloys such as LaNi ₅ and TiFe. Among these, hydrogen storage alloys are promising as hydrogen storage materials for storing and transporting hydrogen because they have a higher hydrogen density per unit volume than carbon materials.
However, since hydrogen storage alloys such as LaNi ₅ and TiFe contain rare metals such as La, Ni, and Ti, there are problems that it is difficult to secure resources and the cost is high. In addition, the conventional hydrogen storage alloy has a problem that since the weight of the alloy itself is large, the hydrogen density per unit weight is small, that is, an extremely heavy alloy is required to store a large amount of hydrogen.

In order to solve this problem, attempts have been made to develop hydrogen storage materials containing light elements. As hydrogen storage materials containing light elements that have been developed so far,
(1) Complex hydrides containing lithium (Li) such as LiNH ₂ and LiBH ₄ (see, for example, Patent Document 1 and Non-Patent Document 1),
(2) Complex hydride containing sodium (Na) such as NaAlH ₄ ,
(3) a complex hydride containing magnesium (Mg) such as Mg (NH ₂ ) ₂ ;
Etc. are known.
Attempts have been made to increase the hydrogen storage amount or lower the hydrogen storage / release temperature by combining a plurality of phases instead of a single-phase intermetallic compound. LiNH ₂ + LiH, LiBH ₄ + MgH _{2 and the} like are known as a hydrogen storage material containing a light element and composed of a composite of a plurality of phases.
Non-Patent Document 2 proposes a reaction mechanism when a complex of LiNH ₂ + LiH is decomposed to release hydrogen. In this document, it is considered that NH ₃ is released by decomposition of LiNH ₂ , and the released NH ₃ reacts quickly with LiH to generate hydrogen, and the complex releases hydrogen at a relatively low temperature. It is described that this is thought to be due to the interaction between LiH and LiNH ₂ .

Japanese translation of PCT publication No. 2002-526658 P. Chen, 4 others, "Interaction of hydrogen with metal nitrides and imides", "Nature", 2002, vol.420 / 21, p.302-304 T. Ichikawa et al., J. Phys. Chem. B, 2004, 108, 7887-7892

Complex hydrides containing light elements are relatively light in weight, relatively easy to secure resources, and relatively low in cost. However, conventionally known complex hydrides have the disadvantage that they are thermally excessively stable and difficult to extract hydrogen.
Further, the complex hydride is easily hydrolyzed when it comes into contact with water, releasing hydrogen, and at the same time, easily forms an oxide or hydroxide. This tendency becomes more prominent as the complex hydride becomes thermally unstable (that is, the more complex hydride is likely to release hydrogen). Unintentional contact between the complex hydride and water results in unintended hydrogen release (ie, hydrogen loss). Further, the oxidation or hydroxylation of the complex hydride causes the re-occlusion of hydrogen to be extremely difficult.

The problem to be solved by the present invention is to suppress decomposition of the hydrogen storage material due to contact with water.
Another problem to be solved by the present invention is to suppress deterioration of the hydrogen storage / release characteristics of the hydrogen storage material due to contact with water.
Furthermore, another problem to be solved by the present invention is to thermally destabilize the hydrogen storage material and lower the hydrogen release start temperature.

The hydrogen storage material according to the present invention includes one or more first hydrides containing M ₁ element, boron and hydrogen, and one or more first chlorides containing M ₂ element, including. However, the M ₁ element and the M ₂ element are Li, Na, K, Ca, Zn, Cu, Mg, Sc, Zr, Mn, Hf, Al, Ti, Cr, V, Ga, Fe, Co, respectively. , Ni, Y, and at least one element selected from rare earth elements.
The first method for producing a hydrogen storage material according to the present invention includes one or more second hydrides containing M ₃ element, boron and hydrogen, and one or two kinds containing M ₄ element. A blending step of blending the second chloride described above, and a mixing and grinding step of mixing the blend obtained in the blending step while providing mechanical energy. However, the M ₃ element and the M ₄ element are Li, Na, K, Ca, Zn, Cu, Mg, Sc, Zr, Mn, Hf, Al, Ti, Cr, V, Ga, Fe, Co, respectively. , Ni, Y, and at least one element selected from rare earth elements.
Further, the second method for producing the hydrogen storage material according to the present invention is one or two kinds including one or more fourth hydrides composed of M ₇ element, boron and hydrogen, and M ₈ element. The above-mentioned fourth chloride is dissolved in a solvent, the reaction step of reacting the fourth hydride and the fourth chloride in the solvent, and all or part of the solvent is removed. And a solvent removing step. However, the M ₇ element is Li, Na, K, Ca, Zn, Cu, Mg, Sc, Zr, Mn, Hf, Al, Ti, Cr, V, Ga, Fe, Co, Ni, Y, and rare earth. It is at least one element selected from elements. The M ₈ element includes Li, Na, K, Ca, Zn, Cu, Mg, Sc, Zr, Mn, Hf, Al, Ti, Cr, V, Ga, Fe, Co, Ni, Y, and rare earth. It contains at least one element selected from elements that is different from the M ₇ element.

When the second hydride and the second chloride compounded at a predetermined ratio are mixed while applying mechanical energy, mixing and pulverization of the starting materials proceed and at the same time, both do not react or react. Thus, a hydrogen storage material in which the fine first hydride and the fine first chloride are uniformly dispersed is obtained. Similarly, when the fourth hydride and the fourth chloride compounded in a predetermined ratio are dissolved in a solvent and reacted with each other, the fine first hydride and the fine first chloride are reacted. Thus, a hydrogen storage material in which is uniformly dispersed can be obtained.
In the obtained hydrogen storage material, the first hydride is protected from water, which is a decomposition promoting substance, by the first chloride, so that deterioration of characteristics due to contact with water is suppressed. In addition, when the composition of the first chloride is optimized, the first hydride becomes thermally unstable, and the hydrogen release start temperature decreases.

Hereinafter, an embodiment of the present invention will be described in detail.
The hydrogen storage material according to the present invention includes one or more first hydrides containing M ₁ element, boron and hydrogen, and one or more first chlorides containing M ₂ element, including.
In the present invention, “hydrogen storage material” refers to a material capable of releasing stored hydrogen. The hydrogen storage material may be capable of re-storing hydrogen after releasing the hydrogen.

The “first hydride” is a compound in which a molecule or ion containing hydrogen is bound around the M ₁ element or its ion (that is, a complex hydride), which contains the M ₁ element, boron and hydrogen. Say.
The anion constituting the complex hydride is not particularly limited, and specific examples include [BH ₄ ] ⁻ and [B ₁₂ H ₁₂ ] ²⁻ .
M ₁ elements include Li, Na, K, Ca, Zn, Cu, Mg, Sc, Zr, Mn, Hf, Al, Ti, Cr, V, Ga, Fe, Co, Ni, Y, and rare earth elements (La ~ Lu) at least one element selected from.

Specifically, as the first hydride, LiBH ₄ , NaBH ₄ , Zn (BH ₄ ) ₂ , Ti (BH ₄ ) ₃ , Zr (BH ₄ ) ₄ , (Mg _0.5 Li _0.5 ) (BH ₄ ) _1.5 , (Zn, Na) BH ₄ and the like. Any one of these first hydrides may be included in the hydrogen storage material, or two or more thereof may be included. Moreover, when 2 or more types of 1st hydrides are contained in a hydrogen storage material, the ratio is not specifically limited, It can select arbitrarily according to the objective.

“First chloride” refers to a chloride containing M ₂ element.
M ₂ elements include Li, Na, K, Ca, Zn, Cu, Mg, Sc, Zr, Mn, Hf, Al, Ti, Cr, V, Ga, Fe, Co, Ni, Y, and rare earth elements (La ~ Lu) at least one element selected from. The M ₂ element contained in the first chloride may be the same as or different from the M ₁ element contained in the _first hydride. Further, the combination of the M ₂ element and the M ₁ element is not particularly limited, and can be arbitrarily selected.

Specific examples of the first chloride include NaCl, LiCl, ZnCl ₂ , ZrCl ₄ , TiCl ₃ , MgCl ₂ , (Mg _0.25 Li _0.75 ) Cl _1.25 , (Zn, Na) Cl, and the like. The hydrogen storage material may contain any one of these first chlorides, or may contain two or more. Moreover, when 2 or more types of 1st chloride is contained in a hydrogen storage material, the ratio is not specifically limited, It can select arbitrarily according to the objective.

The mixing ratio of the first hydride and the first chloride is not particularly limited. In general, the higher the mixing ratio of the first chloride, the higher the protective action or catalytic action of the first chloride. On the other hand, if the mixing ratio of the second chloride is too large, the amount of hydrogen contained in the entire hydrogen storage material is reduced, and the hydrogen density per unit weight is reduced.
In order to obtain a relatively high protection or catalysis and a relatively high hydrogen density, the mixing ratio of the first hydride and the first chloride (x = molar amount of the first chloride / first The molar amount of 1 hydride is preferably 0.005 ≦ x ≦ 5.0.

  The hydrogen storage material according to the present invention is in a state in which the above-described one or more first hydrides and one or more second chlorides are uniformly dispersed. The particle sizes of the first hydride and the second chloride are not particularly limited, but in general, the smaller the particle size, the better the hydrogen storage material with excellent hydrogen release characteristics.

Next, the manufacturing method of the hydrogen storage material which concerns on this invention is demonstrated.
The method for producing a hydrogen storage material according to the first embodiment of the present invention includes a blending step and a mixing and grinding step.
Combining step, M ₃ element, boron and one or more second hydride containing hydrogen, in the step of mixing the one or more second chloride containing M ₄ element is there.

Second hydride, instead of the M ₁ element, except that it includes an M ₃ element has the same configuration as the first hydride. The second hydride as the starting material may be the same as or different from the first hydride contained in the hydrogen storage material as the final product.

That is, the “second hydride” is a compound in which a molecule or ion containing hydrogen is bonded around the M ₃ element or its ion (that is, a complex hydride), and the M ₃ element, boron and hydrogen are combined. This includes things.
The anion constituting the complex hydride is not particularly limited, and specific examples include [BH ₄ ] ⁻ and [B ₁₂ H ₁₂ ] ²⁻ .
M ₃ elements include Li, Na, K, Ca, Zn, Cu, Mg, Sc, Zr, Mn, Hf, Al, Ti, Cr, V, Ga, Fe, Co, Ni, Y, and rare earth elements (La ~ Lu) at least one element selected from.

Specific examples of the second hydride include LiBH ₄ , NaBH ₄ , Zn (BH ₄ ) ₂ , Ti (BH ₄ ) ₃ , Zr (BH ₄ ) ₄ , (Mg _0.5 Li _0.5 ) (BH ₄ ). _1.5 , (Zn, Na) BH ₄ and the like. The starting material may contain any one of these second hydrides, or may contain two or more. Moreover, when 2 or more types of 2nd hydrides are contained in a starting material, the ratio is not specifically limited, According to the objective, it can select arbitrarily.

The second chloride, instead of the M ₂ element, except that it includes an M ₄ element, has the same configuration as the first chloride. The second chloride as the starting material may be the same as or different from the first chloride contained in the hydrogen storage material as the final product.

That is, the “second chloride” refers to a chloride containing the M ₄ element.
M ₄ elements include Li, Na, K, Ca, Zn, Cu, Mg, Sc, Zr, Mn, Hf, Al, Ti, Cr, V, Ga, Fe, Co, Ni, Y, and rare earth elements (La ~ Lu) at least one element selected from. The M ₄ element contained in the second chloride may be the same as or different from the M ₃ element contained in the second hydride. Further, the combination of the M ₄ element and the M ₃ element is not particularly limited, and can be arbitrarily selected.

Specific examples of the second chloride include NaCl, LiCl, ZnCl ₂ , ZrCl ₄ , TiCl ₃ , MgCl ₂ , (Mg _0.25 Li _0.75 ) Cl _1.25 , (Zn, Na) Cl, and the like. The starting material may contain any one of these second chlorides, or may contain two or more. Moreover, when 2 or more types of 2nd chloride is contained in a starting material, the ratio is not specifically limited, According to the objective, it can select arbitrarily.

The form of the second hydride and the second chloride which are starting materials is not particularly limited, but usually powder is used.
Moreover, when using powder as a starting material, the particle size is not specifically limited. Generally, the load at the time of mixing and pulverizing can be reduced as the powder having a smaller particle diameter is used as a starting material. 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.

The combination of the second hydride and the second chloride is not particularly limited, and can be arbitrarily selected according to the composition of the hydrogen storage material to be produced, the required characteristics, and the like. Further, depending on the combination of the second hydride and the second chloride, they may or may not react in a mechanochemical reaction in the mixing and pulverizing step described later. Moreover, when using 2 or more types of 2nd hydrides, these may react depending on the composition. In the present invention, any combination may be used.
Specific combinations that may react with the starting materials include:
(1) When the M ₃ element and the M ₄ element is different,
(2) if it contains more elements to M ₃ element and / or M ₄ element,
(3) When two or more second hydrides having different M ₃ elements are used,
(4) When two or more second chlorides having different M ₄ elements are used,
and so on.

The compounding ratio of the second hydride and the second chloride is not particularly limited, and can be arbitrarily selected according to the purpose.
For example, when the second hydride and the second chloride do not react in the mixing and grinding step described later, a hydrogen storage material in which the composition at the time of blending is substantially maintained can be obtained. That is, when the compounding ratio of the second chloride to the second hydride (y = molar amount of the second chloride / molar amount of the second hydride) is 0.005 ≦ y ≦ 5.0, A hydrogen storage material in which the mixing ratio x of the first chloride to the first hydride is 0.005 ≦ x ≦ 5.0 is obtained.
On the other hand, when the second hydride and the second chloride react, when the compounding ratio y of the second chloride to the second hydride deviates from the stoichiometric ratio, or during the reaction When stopped, a hydrogen storage material comprising a mixture of the first hydride and first chloride as reaction products and the second hydride and / or second chloride as unreacted raw materials is obtained. .

An example of the reaction formula is shown in the following formulas (a) to (e).
2NaBH ₄ + ZnCl ₂ → Zn (BH ₄ ) ₂ + 2NaCl (a)
2LiBH ₄ + ZnCl ₂ → Zn (BH ₄ ) ₂ + 2LiCl (b)
LiBH ₄ + yMgCl ₂ → (Mg, Li) BH ₄ + x (Mg, Li) Cl (c)
4LiBH ₄ + ZrCl ₄ → Zr (BH ₄ ) ₄ + 4LiCl (d)
NaBH ₄ + yZnCl ₂ → (Zn, Na) BH ₄ + x (Zn, Na) Cl (e)
For example, as shown in the formula (a), the compounding ratio y of ZnCl ₂ (second chloride) to NaBH ₄ (second hydride) is 1/2, and the reaction of the formula (a) is performed. When completed, ideally, a hydrogen storage material having a mixing ratio x of NaCl (first chloride) to Zn (BH ₄ ) ₂ of 2 is obtained. On the other hand, when the blending ratio y is not 1/2 or when the reaction of the formula (a) is stopped halfway, ideally, in addition to NaCl and Zn (BH ₄ ) ₂ , unreacted starting materials ( A hydrogen storage material comprising ZnCl ₂ and / or NaBH ₄ ) is obtained. The same applies when other starting materials are used.

The mixing and grinding step is a step of mixing the compound obtained in the compounding step while applying mechanical energy.
“Mixing while applying mechanical energy” refers to mixing uniformly while applying mechanical stress to the starting material using rotation, vibration, impact, or the like. As a method for performing such processing, specifically,
(1) A method of mixing and pulverizing raw material powder with a pulverizer such as a planetary ball mill, rotary mill, vibration mill, etc. (so-called mechanical grinding (MG) treatment),
(2) There is a method of mixing and pulverizing raw material powder in a mortar. In particular, MG treatment is suitable as a treatment method because the compound can be mixed and ground in a relatively short time.

The mixed pulverization is preferably performed in a non-oxidizing atmosphere (for example, in an argon atmosphere, a hydrogen atmosphere, etc.) in order to prevent oxidation of the starting material.
The processing time for the mixing and pulverization depends on the processing method, the type and form of the starting material, so that a uniform and fine mixture of starting materials can be obtained, or the reaction of the starting materials can proceed sufficiently. Select the optimal processing time. In general, the longer the treatment time, the finer the starting material is pulverized, so that a composite in which the pulverized powder is uniformly dispersed or a composite with little unreacted raw material is obtained. However, the treatment more than necessary does not have a difference in effect and has no actual profit. For example, in the case of mixing and pulverizing using a planetary ball mill, when using powder as a starting material, the treatment time is preferably 1 to several tens of hours.

The material obtained by mixing and pulverization may be used as it is as a hydrogen storage material, or may be used after removing a part of the first chloride.
As a method of removing the first chloride,
(1) The hydrogen storage material is dissolved in a solvent (for example, ether, THF (tetrahydrofuran), etc.) in which the solubility of the first hydride is relatively large and the solubility of the first chloride is relatively small. A method of separating the supernatant by filtration and removing the solvent,
(2) A method in which a hydrogen storage material is dissolved in a solvent in which the solubility of the first hydride is relatively small and the solubility of the first chloride is relatively large, and the precipitate is separated by filtration or the like,
and so on.
Moreover, the hydrogen storage material obtained in this way may be used in a powder state, or may be used in a state of a green compact formed into an appropriate size. The hydrogen storage material may be one in which a solvent such as ether or THF remains. Furthermore, the surface of the powder may be coated with a film made of another material (for example, a material having good thermal conductivity such as copper) and used after being molded. In this case, it is preferable to use a physical method such as a PVD method or a CVD method as the coating method.

Next, the manufacturing method of the hydrogen storage material which concerns on the 2nd Embodiment of this invention is demonstrated.
The manufacturing method according to the present embodiment includes a blending step, a mixing and grinding step, a separation step, and a mixing step. Among these, the blending step and the mixing and pulverizing step are the same as those in the manufacturing method according to the first embodiment, and thus description thereof is omitted.

The separation step is a step of separating and collecting one or more third hydrides by dissolving the mixture obtained in the mixing and grinding step in a solvent.
The “third hydride” is a hydride contained in a mixture and containing M ₅ element, boron and hydrogen. Further, the M ₅ element means Li, Na, K, Ca, Zn, Cu, Mg, Sc, Zr, Mn, Hf, Al, Ti, Cr, V, Ga, Fe, Co, Ni, Y, and rare earth It means at least one element selected from elements (La to Lu). Since the other points regarding the third hydride are the same as those of the second hydride, description thereof will be omitted.
As a method of separating and collecting the third hydride,
(1) The mixture is dissolved in a solvent (for example, ether, THF (tetrahydrofuran), etc.) in which the solubility of the third hydride is relatively large and the solubility of the chloride contained in the mixture is relatively small. The method of separating the supernatant liquid by etc. and removing the solvent,
(2) A method in which the mixture is dissolved in a solvent in which the solubility of the third hydride is relatively small and the solubility of the chloride contained in the mixture is relatively large, and the precipitate is separated by filtration,
and so on. In the separated and collected third hydride, a solvent such as ether or THF may remain. Moreover, the chloride contained in the mixture may be completely removed or a part thereof may be removed.

The mixing step is a step of adding one or two or more third chlorides to the separated and collected third hydride and mixing them.
“Third chloride” refers to a chloride different from the chloride contained in the mixture and containing M ₆ element. Further, the M ₆ element means Li, Na, K, Ca, Zn, Cu, Mg, Sc, Zr, Mn, Hf, Al, Ti, Cr, V, Ga, Fe, Co, Ni, Y, and rare earth It means at least one element selected from elements (La to Lu). The third chloride may react with the third hydride or may not react. Since the other points regarding the third chloride are the same as those of the second chloride, description thereof is omitted.
The amount of the third chloride added to the third hydride is not particularly limited and can be arbitrarily selected according to the purpose. Further, the mixing of the third hydride and the third chloride may be performed while applying mechanical energy, or may be performed without substantially applying mechanical energy. good. The other points regarding the mixing method are the same as the mixing and pulverizing step, and thus the description thereof is omitted.

Next, the manufacturing method of the hydrogen storage material which concerns on the 3rd Embodiment of this invention is demonstrated.
The manufacturing method according to the present embodiment includes a reaction step and a solvent removal step.
Reaction step, dissolved M ₇ element, boron and one or more fourth hydride consisting of hydrogen, and one or fourth chloride two or more including M ₈ element in a solvent And a fourth hydride and a fourth chloride are reacted in a solvent.

The “fourth hydride” is a compound in which a molecule or ion containing hydrogen is bound around the M ₇ element or its ion (that is, a complex hydride), which contains M ₇ element, boron and hydrogen. Say.
The anion constituting the complex hydride is not particularly limited, and specific examples include [BH ₄ ] ⁻ and [B ₁₂ H ₁₂ ] ²⁻ .
M ₇ elements include Li, Na, K, Ca, Zn, Cu, Mg, Sc, Zr, Mn, Hf, Al, Ti, Cr, V, Ga, Fe, Co, Ni, Y, and rare earth elements (La ~ Lu) at least one element selected from.

  In this embodiment, the fourth hydride is soluble in a solvent described later. The starting material may contain any one kind of the fourth hydride, or may contain two or more kinds. Moreover, when 2 or more types of 4th hydrides are contained in a starting material, the ratio is not specifically limited, It can select arbitrarily according to the objective. Since the other points regarding the fourth hydride are the same as those of the second hydride, description thereof will be omitted.

The “fourth chloride” refers to a chloride containing M ₈ element.
M ₈ elements include Li, Na, K, Ca, Zn, Cu, Mg, Sc, Zr, Mn, Hf, Al, Ti, Cr, V, Ga, Fe, Co, Ni, Y, and rare earth elements (La ~ Lu) at least one element selected from. Further, due to the nature of the process of reacting the fourth hydride and the fourth chloride, the M ₈ element contains an element different from the M ₇ element.

  In the present embodiment, the fourth chloride is soluble in a solvent described later. The starting material may contain any one type of fourth chloride, or may contain two or more types. Moreover, when 2 or more types of 4th chloride is contained in a starting material, the ratio is not specifically limited, According to the objective, it can select arbitrarily. Since the other points regarding the fourth chloride are the same as those of the second chloride, description thereof is omitted.

As the solvent, a solvent capable of dissolving the fourth hydride and the fourth chloride described above is used. Further, the solvent may be capable of dissolving the first hydride and / or the first chloride as the reaction product, or may be one that does not dissolve the solvent. In particular, when one of the first hydride and the first chloride which is a reaction product has a relatively high solubility and the other has a relatively low solubility, the mixture ratio of chlorides There is an advantage that it is relatively easy to control. Examples of such a solvent include various ethers and THF (tetrahydrofuran). These solvents may be used alone or in combination of two or more.
The amount of the fourth hydride and the fourth chloride dissolved in the solvent and the ratio thereof depend on the starting material and the kind of the solvent so that the desired first hydride can be obtained efficiently. Select the most suitable one.

  A solvent removal process is a process of removing all or one part of a solvent from the solution after completion | finish of reaction. The removal of the solvent may be carried out in a state including all reaction products and unreacted raw materials, or after removing a part of the chloride by utilizing the difference in solubility between the hydride and the chloride in the solvent. May be.

The following formula (f) shows an example of a synthesis reaction using a liquid phase synthesis method.
2NaBH ₄ + ZnCl ₂ → Zn (BH ₄ ) ₂ + 2NaCl (f)
NaBH ₄ (fourth hydride), ZnCl ₂ (fourth chloride), and Zn (BH ₄ ) ₂ (first hydride) are all dissolved in anhydrous ether. On the other hand, NaCl (first chloride) is insoluble in anhydrous ether. Accordingly, in the case of liquid phase synthesis of Zn (BH ₄ ) ₂ according to the formula (f), it is preferable to use anhydrous ether as a solvent when controlling the compounding ratio of NaCl.

Specifically, the synthesis of Zn (BH ₄ ) ₂ using anhydrous ether is carried out by the following procedure. That is, first, an appropriate amount of ZnCl ₂ is dissolved in anhydrous ether, and the supernatant is collected. Separately, an appropriate amount of NaBH ₄ is dissolved in anhydrous ether. To this solution, the previously prepared ZnCl ₂ / ether solution supernatant is added and allowed to stir for a predetermined time. When the reaction is allowed to proceed completely and then dried as it is, a hydrogen storage material having a mixing ratio x of 2 is obtained. On the other hand, when the supernatant is collected after the reaction and dried, the hydrogen storage material having a mixing ratio x of less than 2 can be obtained by optimizing the conditions for collecting the supernatant. The same applies when other starting materials are used.

Note that a composite of the solvent and the first hydride may be obtained depending on the composition of the first hydride generated by the reaction and the type of the solvent used for the synthesis. For example, when the first hydride is Ca (BH ₄ ) ₂ and THF is used as a solvent, a complex represented by the general formula: Ca (BH ₄ ) ₂ · 2THF is obtained. This complex is a solid, and THF is coordinated to Ca (BH ₄ ) ₂ . Even such a composite can be used as a constituent material of the hydrogen storage material according to the present invention.

  Each of the various first hydrides produced by the liquid phase synthesis method may be used alone or in combination of two or more. Also, one or two or more first hydrides synthesized by a liquid phase method and one or two or more first hydrides produced by a method other than the liquid phase method are used in combination. May be.

Next, the manufacturing method of the hydrogen storage material which concerns on the 4th Embodiment of this invention is demonstrated.
The manufacturing method according to the present embodiment includes a reaction process, a solvent removal process, a separation process, and a mixing process. Among these, the reaction step and the solvent removal step are the same as those in the third embodiment, and thus description thereof is omitted.

The separation step is a step of separating and collecting one or more fifth hydrides by dissolving the mixture obtained in the solvent removal step in a solvent.
The “fifth hydride” is a hydride contained in a mixture and containing a M ₉ element, boron and hydrogen. The M ₉ element is Li, Na, K, Ca, Zn, Cu, Mg, Sc, Zr, Mn, Hf, Al, Ti, Cr, V, Ga, Fe, Co, Ni, Y, and rare earth. It means at least one element selected from elements (La to Lu). Since the other points of the fifth hydride are the same as those of the fourth hydride, description thereof will be omitted. Further, since other points regarding the separation step are the same as those in the second embodiment, the description thereof is omitted.

The mixing step is a step of adding one or two or more fifth chlorides to the separated / collected fifth hydride and mixing them.
The “fifth chloride” refers to a chloride that is different from the chloride contained in the mixture and contains M ₁₀ element. The M ₁₀ element is Li, Na, K, Ca, Zn, Cu, Mg, Sc, Zr, Mn, Hf, Al, Ti, Cr, V, Ga, Fe, Co, Ni, Y, and rare earth. It means at least one element selected from elements (La to Lu). The fifth chloride may react with the fifth hydride or may not react. Since the other points regarding the fifth chloride are the same as those of the second chloride, description thereof will be omitted. Further, since other points regarding the mixing step are the same as those in the second embodiment, the description thereof is omitted.

Next, the operation of the hydrogen storage material and the method for producing the same according to the present invention will be described.
When the second hydride and the second chloride compounded at a predetermined ratio are mixed while applying mechanical energy, mixing and pulverization of the starting materials proceed and at the same time, both do not react or react. Thus, a hydrogen storage material in which the fine first hydride and the fine first chloride are uniformly dispersed is obtained. Similarly, when the fourth hydride and the fourth chloride compounded in a predetermined ratio are dissolved in a solvent and reacted with each other, the fine first hydride and the fine first chloride are reacted. Thus, a hydrogen storage material in which is uniformly dispersed can be obtained. Furthermore, when all or a part of the chloride is removed from the mixture obtained by the solid phase synthesis method or the liquid phase synthesis method, and a chloride different from the removed chloride is added and mixed, a fine first A hydrogen storage material in which hydride and fine first chloride are uniformly dispersed is obtained.
In the obtained hydrogen storage material, the first hydride is protected from water, which is a decomposition promoting substance, by the first chloride, so that deterioration of characteristics due to contact with water is suppressed. In addition, certain types of chloride have the effect of destabilizing the hydride thermally and lowering the hydrogen release start temperature. Therefore, when the first hydride and the first chloride are combined and their compositions are optimized, a hydrogen storage material that releases a large amount of hydrogen at a relatively low temperature can be obtained.

Further, in the hydride represented by the general formula: M (BH ₄ ) _n (n is the valence of the M element), the M element is stabilized by giving electrons to (BH ₄ ) and ionic bonding. . Therefore, if the electron donation from the M element can be suppressed, the ionic bond between the cation and the anion is weakened, and it is considered that the thermodynamic stability is lowered. The strength of electron donation is closely related to the electronegativity of the M element, which provides an effective guideline for controlling the thermodynamic stability of M (BH ₄ ) _n . For example, according to Japanese Patent Application No. 2003-319915, by replacing a part of Li in LiBH ₄ with Cu, which has a higher electronegativity than Li, it becomes thermodynamically unstable and lowers the hydrogen release temperature. Is possible.
In addition, FIG. 1 shows the relationship between the heat of formation ΔH of various borohydrides theoretically obtained from first-principles calculations and the electronegativity χ of the M element (quoted from the 2004 Annual Meeting of the Metallurgy Society of Japan, p170). ). From this figure, it is clear that the greater the electronegativity of the M element, the smaller the absolute value of the heat of formation and the lower the thermodynamic stability of M (BH ₄ ) _n .
In the present invention, it is considered that when the first hydride containing an M ₁ element having an appropriate electronegativity is used, its thermodynamic stability is controlled and the thermal decomposition temperature is remarkably lowered. Furthermore, when this is combined with the first chloride having a catalytic action, the thermal decomposition temperature is further lowered.
Furthermore, the first hydride containing a specific M ₁ element is not only relatively thermally unstable, but also has a significantly larger amount of hydrogen (about 5 mass% or more) than other hydrides. Therefore, when this is combined with the first chloride, a hydrogen storage material that is stable against water, has a low hydrogen release start temperature, and a large amount of hydrogen release can be obtained.

Example 1
NaBH ₄ and ZnCl ₂ were mixed at a molar ratio of 2: 1. The blend was mixed and ground in a high energy ball mill for 5 hours. When the obtained hydrogen storage material was subjected to X-ray diffraction, a NaCl diffraction pattern was observed. In the Raman spectrum, a vibration mode of BH bond was observed. From the above, it is considered that Zn (BH ₄ ) ₂ is generated in the material.
Next, thermal decomposition characteristics of the obtained hydrogen storage material were measured by a temperature programmed desorption method. LiBH ₄ was used as a comparative material. As a result, it was found that the decomposition start temperature of LiBH ₄ was 580K, whereas the decomposition start temperature of the hydrogen storage material was 350K.

(Example 2)
A composite was prepared under the same conditions as in Example 1 except that LiBH ₄ was used instead of NaBH ₄ . When the obtained hydrogen storage material was subjected to X-ray diffraction, a LiCl diffraction pattern was observed. In the Raman spectrum, a vibration mode of BH bond was observed. From the above, it seems that Zn (BH ₄ ) ₂ is generated in the material.
Next, thermal decomposition characteristics of the obtained hydrogen storage material were measured by a temperature programmed desorption method. FIG. 2 shows the result. FIG. 2 also shows the thermal decomposition characteristics of LiBH ₄ . FIG. 2 shows that the decomposition start temperature of LiBH ₄ is 580K, whereas the decomposition start temperature of the composite is 355K.

(Example 3)
LiBH ₄ and ZrCl ₄ were blended at a molar ratio of 4: 1. The blend was mixed and ground in a high energy ball mill for 5 hours. When the obtained hydrogen storage material was subjected to X-ray diffraction, a LiCl diffraction pattern was observed (FIG. 3). In the Raman spectrum, a vibration mode of BH bond was observed. From the above, it is considered that Zr (BH ₄ ) ₄ is generated in the material. The decomposition start temperature of this complex was 350K.
Next, the obtained hydrogen storage material was heated to 300 ° C. to advance the hydrogen releasing reaction. Then, rehydrogenation was performed at 80 ° C. and 10 MPa. The rehydrogenation was confirmed by the volume method (PCT measurement). As a result, pressure reduction due to rehydrogenation occurred, and rehydrogenation was confirmed.

Example 4
LiBH ₄ and TiCl ₃ were mixed at a molar ratio of 3: 1. The blend was mixed and ground in a high energy ball mill for 5 hours. When the obtained hydrogen storage material was subjected to X-ray diffraction, a LiCl diffraction pattern was observed. In the llama spectrum, a vibration mode of BH bond was observed. From the above, it is considered that Ti (BH ₄ ) ₃ is generated in the material. The decomposition start temperature of this complex was 360K.

(Example 5)
A hydrogen storage material was prepared under the same conditions as in Example 1 except that LiBH ₄ and MgCl ₂ were used as starting materials. When the obtained hydrogen storage material was subjected to X-ray diffraction, a diffraction pattern of (Mg _0.25 Li _0.75 ) Cl _1.25 was observed. In the Raman spectrum, a vibration mode of BH bond was observed. From the above, it is considered that (Mg _0.5 Li _0.5 ) (BH ₄ ) _1.5 is generated in the material.

(Example 6)
NaBH ₄ and ZnCl ₂ were mixed at a molar ratio of 2: 1. The blend was mixed and ground in a high energy ball mill for 1-12 hours. When the obtained hydrogen storage material was subjected to X-ray diffraction, a (Zn, Na) Cl diffraction pattern was observed. In the Raman spectrum, a vibration mode of BH bond was observed. From the above, it is considered that (Zn, Na) BH ₄ is generated in the material. In addition, the longer the milling time, the greater the amount of (Zn, Na) BH ₄ and (Zn, Na) Cl produced.

(Example 7)
The hydrogen storage material obtained in Example 1 was dissolved in ether or THF and the chloride was precipitated to control the desired mixing ratio. Next, the solvent was removed by volatilization to obtain a hydrogen storage material. The obtained hydrogen storage material is a composite having a mixing ratio x of chloride to hydride of 0.05, and this composite is also excellent in hydrogen release characteristics at a low temperature as in Example 1. all right.

(Example 8)
LiBH ₄ and ZrCl ₄ were blended at a molar ratio of 5: 1. The blend was pulverized and mixed in a high energy ball mill for 5 hours under an Ar atmosphere. When the obtained hydrogen storage material was subjected to X-ray diffraction, a LiCl diffraction pattern was observed (FIG. 3). In the Raman spectrum, a vibration mode of BH bond was observed (FIG. 4). From the above, it seems that ZrLi (BH ₄ ) ₅ is generated in the material.
Next, the thermal decomposability of the obtained hydrogen storage material was measured by a temperature programmed desorption method. As a result, it was found that the decomposition temperature of the hydrogen storage material obtained in this example was between the decomposition temperature of the LiBH ₄ and Zr (BH ₄ ) ₄ + 4LiCl mixture.

Example 9
LiBH ₄ and ZrCl ₄ were blended at a molar ratio of 6: 1. The blend was pulverized and mixed in a high energy ball mill for 5 hours under an Ar atmosphere. When the obtained hydrogen storage material was subjected to X-ray diffraction, a LiCl diffraction pattern was observed. In the Raman spectrum, a vibration mode of BH bond was observed. From the above, it is considered that ZrLi ₂ (BH ₄ ) ₆ is generated in the material.
Next, the thermal decomposability of the obtained hydrogen storage material was measured by a temperature programmed desorption method. As a comparative material, a mixture of LiBH ₄ and ZrLi (BH ₄ ) ₅ + 4LiCl (Example 8) was used. As a result, it was found that the decomposition temperature of the hydrogen storage material obtained in this example was between the decomposition temperature of the LiBH ₄ and ZrLi (BH ₄ ) ₅ + 4LiCl mixture.
In FIG. 5, the thermal decomposition characteristic of the hydrogen storage material obtained in Example 3, Example 8, and Example 9 is shown. FIG. 5 also shows the results of LiBH ₄ . FIG. 5 shows that the decomposition temperature increases as the blending ratio of LiBH ₄ increases.

(Example 10)
NaBH ₄ and ZrCl ₄ were blended at a molar ratio of 5: 1. The blend was pulverized and mixed in a high energy ball mill for 5 hours under an Ar atmosphere. When the obtained hydrogen storage material was subjected to X-ray diffraction, a NaCl diffraction pattern was observed. In the Raman spectrum, a vibration mode of BH bond was observed. From the above, it seems that ZrNa (BH ₄ ) ₅ is generated in the material.
Next, the thermal decomposability of the obtained hydrogen storage material was measured by a temperature programmed desorption method. As a comparative material, a NaBH ₄ and Zr (BH ₄ ) ₄ +4 NaCl mixture (ZrCl ₄ and NaBH ₄ were blended at a molar ratio of 1: 4 and then mixed and ground in a ball mill for 5 hours) was used. As a result, it was found that the decomposition temperature of the hydrogen storage material obtained in this example was between the decomposition temperature of the NaBH ₄ and Zr (BH ₄ ) ₄ + 4NaCl mixture.

(Example 11)
NaBH ₄ and ZrCl ₄ were blended at a molar ratio of 6: 1. The blend was pulverized and mixed in a high energy ball mill for 5 hours under an Ar atmosphere. When the obtained hydrogen storage material was subjected to X-ray diffraction, a NaCl diffraction pattern was observed. In the Raman spectrum, a vibration mode of BH bond was observed. From the above, it is considered that ZrNa ₂ (BH ₄ ) ₆ is generated in the material.
Next, the thermal decomposability of the obtained hydrogen storage material was measured by a temperature programmed desorption method. As a comparative material, a mixture of NaBH ₄ and ZrNa (BH ₄ ) ₅ + 4NaCl (Example 10) was used. As a result, it was found that the decomposition temperature of the hydrogen storage material obtained in this example was between the decomposition temperatures of the NaBH ₄ and ZrNa (BH ₄ ) ₅ + 4NaCl mixture.

(Example 12)
LiBH ₄ , CaCl ₂ and TiCl ₃ were mixed at a molar ratio of 5: 1: 1. The blend was pulverized and mixed in a high energy ball mill for 5 hours under an Ar atmosphere. When the obtained hydrogen storage material was subjected to X-ray diffraction, a LiCl diffraction pattern was observed. In the Raman spectrum, a vibration mode of BH bond was observed. From the above, it is considered that CaTi (BH ₄ ) ₅ is generated in the material.
Next, the thermal decomposability of the obtained hydrogen storage material was measured by a temperature programmed desorption method. As a comparative material, a Ca (BH ₄ ) ₂ + 2LiCl mixture and a Ti (BH ₄ ) ₃ + 3LiCl mixture were used. As a result, it was found that the decomposition temperature of the hydrogen storage material obtained in this example was between the decomposition temperatures of the Ca (BH ₄ ) ₂ + 2LiCl mixture and the Ti (BH ₄ ) ₃ + 3LiCl mixture.

(Example 13)
Ca (BH ₄ ) ₂ + 0.005NaCl and Ti (BH ₄ ) ₃ + 0.01LiCl were mixed at a molar ratio of 1: 1. The blend was pulverized and mixed in a high energy ball mill for 5 hours under an Ar atmosphere. In the Raman spectrum of the obtained hydrogen storage material, a vibration mode of BH bond was observed. From the above, it is considered that CaTi (BH ₄ ) ₅ is generated in the material.
Next, the thermal decomposability of the obtained hydrogen storage material was measured by a temperature programmed desorption method. Ca (BH ₄ ) ₂ and Ti (BH ₄ ) ₃ were used as comparative materials. As a result, it was found that the decomposition temperature of the hydrogen storage material obtained in this example was between the decomposition temperatures of Ca (BH ₄ ) ₂ and Ti (BH ₄ ) ₃ .

(Example 14)
LiBH ₄ and ScCl ₃ were mixed at a molar ratio of 3: 1. The mixture was mixed and ground in a high energy ball mill for 5 hours in an Ar atmosphere. When the obtained hydrogen storage material was subjected to X-ray diffraction, Sc (BH ₄ ) ₃ and LiCl diffraction peaks were observed (see FIG. 6A). When the obtained hydrogen storage material was evacuated at 150 ° C., Sc (BH ₄ ) ₃ was decomposed, and hydrogen releasing reaction was confirmed. In the sample after hydrogen release, the Sc (BH ₄ ) ₃ diffraction peak disappeared (see FIG. 6B). Furthermore, when held at 100 ° C. in a 10 MPa hydrogen atmosphere for 1 hour, the diffraction peak of Sc (BH ₄ ) ₃ was confirmed again (see FIG. 6C), and rehydrogenation was possible.

(Example 15)
LiBH ₄ and ScCl ₃ were mixed at a molar ratio of 4: 1. The mixture was mixed and ground in a high energy ball mill for 5 hours in an Ar atmosphere. When the obtained hydrogen storage material was subjected to X-ray diffraction, Sc (BH ₄ ) ₃ and LiCl diffraction peaks were observed. The thermal decomposition characteristics of the obtained hydrogen storage material were measured. FIG. 7 shows the result. FIG. 7 also shows the results of the hydrogen storage material of Example 14 (LiBH ₄ : ScCl ₃ = 3: 1). From FIG. 7, it can be seen that the hydrogen storage material obtained in this example has a larger hydrogen release amount than the hydrogen storage material of Example 14.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the present invention.

  A hydrogen storage material and a method for producing the same according to the present invention include a hydrogen storage means for a fuel cell system, an ultra-high purity hydrogen production apparatus, a chemical heat pump, an actuator, a hydrogen storage body for a metal-hydrogen storage battery, and the like. It can be used as a material and its manufacturing method.

It is a figure which shows the relationship between production | generation heat | fever (DELTA) H of various hydrides, and the electronegativity χ of a cation. Zn (BH _{4) 2} + 2LiCl complex, and is a diagram showing the thermal decomposition characteristics of LiBH _4. It is an X-ray diffraction pattern of the hydrogen storage material obtained in Example 3 and Example 8. 6 is a Raman spectrum of the hydrogen storage material obtained in Example 8. Example 3, the hydrogen storage material obtained in Examples 8 and 9, and a diagram showing the thermal decomposition characteristics of LiBH _4. FIG. 6A is an X-ray diffraction pattern of the hydrogen storage material obtained in Example 14, and FIG. 6B is an X-ray diffraction after heating the hydrogen storage material at 150 ° C. in vacuum. FIG. 6C shows an X-ray diffraction pattern after heating in vacuum at 150 ° C. and further reacting with 10 MPa of hydrogen at 100 ° C. It is a figure which shows the thermal decomposition characteristic of the hydrogen storage material obtained in Example 14 and Example 15.

Claims (6)

_One or more first hydrides containing M ₁ element, boron and hydrogen;
A hydrogen storage material comprising one or more first chlorides containing M ₂ element.
However, the M ₁ element and the M ₂ element are Li, Na, K, Ca, Zn, Cu, Mg, Sc, Zr, Mn, Hf, Al, Ti, Cr, V, Ga, Fe, Co, respectively. At least one element selected from Ni, Y, and rare earth elements.   The mixing ratio x of the first chloride to the first hydride (= molar amount of the first chloride / molar amount of the first hydride) is 0.005 ≦ x ≦ 5.0. The hydrogen storage material according to claim 1, wherein A blending step of blending one or more second hydrides containing M ₃ element, boron and hydrogen with one or more second chlorides containing M ₄ element;
A method for producing a hydrogen storage material, comprising: a mixing and pulverizing step of mixing the compound obtained in the compounding step while applying mechanical energy.
However, the M ₃ element and the M ₄ element are Li, Na, K, Ca, Zn, Cu, Mg, Sc, Zr, Mn, Hf, Al, Ti, Cr, V, Ga, Fe, Co, respectively. At least one element selected from Ni, Y, and rare earth elements. By dissolving the mixture obtained in the mixing and grinding step in the solvent, a separation step of separating and collecting one or more of the third hydride containing M ₅ element, boron and hydrogen,
A mixture which is a chloride different from the chloride contained in the mixture and adds one or more third chlorides containing the element M ₆ to the third hydride and mixes them. The method for producing a hydrogen storage material according to claim 3, further comprising a step.
However, the M ₅ element and the M ₆ element are Li, Na, K, Ca, Zn, Cu, Mg, Sc, Zr, Mn, Hf, Al, Ti, Cr, V, Ga, Fe, Co, respectively. At least one element selected from Ni, Y, and rare earth elements. One or two or more fourth hydrides comprising M ₇ element, boron and hydrogen and one or more fourth chlorides containing M ₈ element are dissolved in a solvent, and the solvent A reaction step of reacting the fourth hydride with the fourth chloride;
A method for producing a hydrogen storage material, comprising a solvent removal step of removing all or part of the solvent.
However, the M ₇ element is Li, Na, K, Ca, Zn, Cu, Mg, Sc, Zr, Mn, Hf, Al, Ti, Cr, V, Ga, Fe, Co, Ni, Y, and rare earth. At least one element selected from elements.
The M ₈ element includes Li, Na, K, Ca, Zn, Cu, Mg, Sc, Zr, Mn, Hf, Al, Ti, Cr, V, Ga, Fe, Co, Ni, Y, and rare earth elements. It contains at least one element selected from elements different from the M ₇ element. A separation step of separating and collecting one or more fifth hydrides containing M ₉ element, boron and hydrogen by dissolving the mixture obtained in the solvent removal step in a solvent;
A different chlorides and chloride contained in the mixture, in addition to one or more of the 5 the fifth hydride chloride containing M ₁₀ elements, mixing the mixture The method for producing a hydrogen storage material according to claim 5, further comprising a step.
However, the M ₉ element and the M ₁₀ element are Li, Na, K, Ca, Zn, Cu, Mg, Sc, Zr, Mn, Hf, Al, Ti, Cr, V, Ga, Fe, Co, respectively. At least one element selected from Ni, Y, and rare earth elements.

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