JP2008073582A - Manufacturing method of hydrogen storage material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a hydrogen storage material containing lithium hydride LiH and lithium amide LiNH<SB>2</SB>capable of suppressing lowering of a hydrogen release amount by preventing aggregation of particles after applying mechanical energy such as crushing. <P>SOLUTION: The manufacturing method of hydrogen storage material comprises: a process S101 of preparing a raw material composition containing carbon material particles, metal hydride particles and metal amide particles; and a process S103 of applying the mechanical energy to the raw material composition. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a novel hydrogen storage material that is lightweight and capable of releasing a large amount of hydrogen at low temperature and low pressure.

  Due to the problems of global environmental conservation and fossil fuel depletion, fuel cells are considered as an alternative energy source to replace fossil fuels. Fuel cells are attracting attention because they use hydrogen and oxygen as raw materials and their exhaust gas is clean. However, when the fuel is hydrogen, the method using the reforming of methanol or natural gas has disadvantages that it takes time at start-up and is difficult to cope with rapid load fluctuations. Therefore, it is necessary to store hydrogen. In the conventional method, assuming that it is mounted on an automobile, about 5 kg of hydrogen is required to travel 400 to 500 km with one hydrogen filling, and this amount of hydrogen is compressed. It must be a high-pressure cylinder or low-temperature liquid hydrogen. However, when compressed hydrogen is used, even if hydrogen compressed to 35 to 70 MPa is stored in a high-pressure cylinder, the volume does not decrease so much because of a decrease in the compression rate of hydrogen, and the high-pressure cylinder filling it becomes heavy There is. Moreover, in the case of liquid hydrogen, hydrogen must be always cooled and stored at −252 ° C., and there is a disadvantage that a storage container including a cooling mechanism becomes large.

  Therefore, there is a need for a hydrogen storage material that can solve these problems and has a small storage volume and is lightweight. Currently, the closest to practical use is a hydrogen storage alloy, which stores hydrogen as a metal hydride. However, since the hydrogen adsorption amount per unit weight of the hydrogen storage alloy is small, there is a problem that the alloy weight exceeds 400 kg for in-vehicle use that requires a large amount of hydrogen, and it has not yet been put into practical use. Also, in the case of hydrogen storage alloys, when hydrogen is adsorbed and released, it is necessary to expose the alloy to high pressure and high temperature conditions. Have problems such as resource depletion.

Under such circumstances, an alanade-based material (LiAlH ₄ ) has attracted attention as an inorganic material that is lightweight and can store a large amount of hydrogen (Patent Documents 1 and 2). As for alanade materials, hydrogen release and rehydrogenation reaction of NaAlH ₄ doped with 2 mol% of Ti under practical conditions has been studied by improving the Ti doping method of Bogdanovic et al.
NaAlH ₄ ⇒ 1/3 Na ₃ AlH ₆ + Al + H ₂

This material is known to be produced from LiH and LiAlH ₄ by mechanochemical method over 5 hours and to show a hydrogen storage amount of 5.6 wt%. According to this material, when the hydrogen storage amount is up to 3 wt%, it is possible to ensure the repetition of hydrogen release and storage until the repetition of hydrogen release and storage is up to about 100 cycles. However, when a storage amount of 3 to 5.6 wt% is ensured, the number of repeated hydrogen release and storage cycles is extremely small. In other words, the amount of hydrogen that can be used reversibly is about 3 wt% compared to a conventional alloy. In addition, there are drawbacks in that the hydrogen release temperature is higher and the hydrogen storage pressure is higher than that of the hydrogen storage alloy.

It is known that LiBH ₄ releases a large amount of hydrogen as well as an alanade material. To date, 9 wt% hydrogen release has been observed by 400 ° C. with the addition of SiO ₂ catalyst. However, since this material has a melting point of 275 ° C., its performance is unstable, and there is a drawback that it is inferior in reversibility, such as hardly resorbing hydrogen.

Lithium amide materials reported in Non-Patent Document 1 and Patent Document 3 by Chen of Singapore University are attracting attention. Chen et al. Uses Li ₃ N (lithium nitride) as a starting material, and uses hydrogenated material obtained by hydrogenation at high temperature and high pressure according to the following reaction formula.
_{Li 3 N + 2H 2 ⇒LiNH 2} + 2 LiH

  According to this reaction, theoretically, a hydrogen storage amount of about 9 wt% can be obtained. However, since the enthalpy (ΔH) is large, high-temperature heating of 600 ° C. or higher is necessary to release all of the stored hydrogen.

Non-patent document 2 reported that Ichikawa et al. Of Hiroshima University can separate the above reaction into the following two stages by examining the reaction of Chen et al.
Li ₃ N + H ₂ ⇔Li ₂ NH + LiH
Li ₂ NH + H ₂ ⇔LiNH ₂ + LiH

Ichikawa et al. Focused on Li ₂ NH + H ₂ ⇔LiNH ₂ + LiH, which has a small ΔH in the reaction of Chen et al., And started using a raw material composition of LiNH ₂ (lithium amide) and LiH (lithium hydride) as a starting material. Crushing treatment was performed. As a result, Non-Patent Document 2 reports that a reaction space in which fine particles of LiNH ₂ and fine particles of LiH are entangled can be created, and the amount of ammonia produced as a by-product can be reduced. Moreover, this hydrogen storage material has a hydrogen storage amount of about 6 wt% (a change in weight before and after hydrothermal treatment), which is the same as the theoretical amount.

However, in order to create a reaction space in which fine particles of LiNH ₂ and fine particles of LiH are entangled more uniformly, if the mechanical pulverization process is performed for a long time, the particles are sufficiently aggregated after the pulverization process. There was a problem that a large amount of hydrogen release could not be obtained. This agglomeration will be specifically mentioned in the column of Examples described later.

Japanese National Patent Publication No. 11-510133 Special Table 2002-522209 International Publication No. 03/037784 Pamphlet P. Chen, et al. Nature, 420, 302-304, (2002) Ichikawa et al., J. Phys. Chem. B, 2004, 108, 7887-7892

The present invention has been made in view of such problems of the prior art, and a hydrogen storage material containing a hydrogenated metal such as LiH (lithium hydride) and a metal amide such as LiNH ₂ (lithium amide). It is an object of the present invention to provide a method for producing a hydrogen storage material having a high hydrogen release amount by preventing particles from aggregating after applying mechanical energy such as grinding treatment.

  As a result of intensive studies on the above object, the present inventors have given mechanical energy to a raw material composition in which carbon material particles are added to metal hydride particles and metal amide particles, and when carbon material particles are not added. It has been found that there is an effect of suppressing aggregation of generated particles.

The present invention is based on the above knowledge, the step (a) of producing a raw material composition containing carbon material particles, metal hydride particles and metal amide particles, and the step of imparting mechanical energy to the raw material composition And (b), a method for producing a hydrogen storage material.
The carbon material particles have an excellent effect of preventing aggregation in the process of imparting mechanical energy to the raw material composition containing metal hydride particles and metal amide particles, and the carbon material particles have a gap between the metal hydride particles and metal amide particles. By intervening, hydrogen release / occlusion reaction of the hydrogen storage material is promoted, which contributes to a decrease in hydrogen release temperature or an increase in hydrogen release amount. As the carbon material particles exhibiting this action effect, it is preferable to use one or two of graphite and activated carbon. Graphite and activated carbon are relatively inexpensive and are preferable in terms of the production cost of the hydrogen storage material.

In the method for producing a hydrogen storage material of the present invention, it is preferable to use one or more kinds selected from lithium hydride particles, magnesium hydride particles and calcium hydride particles as metal hydride particles. In this case, the term “two or more types” means a mixture. The same applies to the following.
The metal amide particles are preferably one or more selected from lithium amide particles, magnesium amide particles, and calcium amide particles.

  In the method for producing a hydrogen storage material of the present invention, it is preferable for the raw material composition to contain metal chloride particles in order to lower the hydrogen release amount temperature and increase the hydrogen release amount. The metal chloride particles are preferably one or more selected from magnesium chloride particles, copper chloride particles and zinc chloride particles.

  In the method for producing a hydrogen storage material of the present invention, mechanical pulverization is preferable as the mechanical energy application method in step (b). This is because the particles in the raw material composition can join each other or the same kind of particles if energy is applied to such an extent that mechanical pulverization is performed.

In the method for producing a hydrogen storage material of the present invention, hydrogenated carbon material particles can be used as the carbon material particles. The hydrogen storage capacity of the entire hydrogen storage material can be increased by utilizing the hydrogen storage capacity of the carbon material itself. In particular, when a hydrogen storage material is composed of a carbon material alone, the hydrogen release temperature is about 300 ° C. or higher, whereas mechanical energy is used together with metal hydride particles and metal amide particles as in the present invention. By giving, it is characterized in that hydrogen can be released even at a temperature of 250 ° C. or lower. Hydrogenation of the carbon material particles may be performed simultaneously with application of mechanical energy. That is, according to the present invention, mechanical energy can be applied in step (b) in an atmosphere containing hydrogen gas. Moreover, you may add the carbon material particle | grains previously hydrogenated to the raw material composition containing a hydrogenation metal particle and a metal amide particle.
Here, it is understood that the hydrogenated carbon material does not have hydrogen atoms or molecules hydrogen bonded to the surface, but has hydrogen bonded by removing the carbon double bond. Therefore, it is not simply adsorbed on the surface as in physical adsorption. When graphite is hydrogenated, it is called hydrogenated graphite.

  As described above, according to the present invention, in a hydrogen storage material containing metal hydride particles and metal amide particles, by mixing carbon material particles, it is possible to prevent particle aggregation and obtain a high hydrogen release amount. . By hydrogenating the carbon material particles themselves, the hydrogen storage amount of the entire hydrogen storage material can be increased. Further, by selecting graphite and activated carbon as carbon material particles and adding metal chloride particles, it is possible to further increase the amount of hydrogen released. Moreover, since this hydrogen storage material can be obtained by adding inexpensive carbon material particles as a material and imparting mechanical energy, the hydrogen storage material can be obtained at low cost.

In the method for producing a hydrogen storage material of the present invention, first, as shown in FIG. 1, a raw material composition containing carbon material particles, metal hydride particles, and metal amide particles is obtained (S101 in FIG. 1). In this raw material composition, carbon material particles, metal hydride particles and metal amide particles are preferably blended in a ratio of 0.7 to 1.5: 0.7 to 1.5: 1.
If the ratio of the carbon material particles to the metal amide particles is less than 0.7, the above-described effects cannot be sufficiently obtained. Further, when the ratio of the carbon material particles exceeds 1.5, excessive hydrogenation of the carbon material occurs, and the hydrogen release temperature is shifted to the high temperature side, or the hydrogen release temperature cannot be lowered. A more preferable ratio of the carbon material particles to the metal amide particles is 0.8 to 1.2, and a more preferable ratio is 1.0 to 1.2.

When the ratio of metal hydride particles to metal amide particles is less than 0.7, the amount of ammonia generated from the metal amide particles increases. In addition, when the ratio of metal hydride particles to metal amide particles exceeds 1.5, the hydrogen release amount tends to decrease. A more preferred ratio of metal hydride particles to metal amide particles is 0.8 to 1.2, and a more preferred ratio is 1.0 to 1.2.
The carbon material particles, metal hydride particles, and metal amide particles as raw materials may have a particle size of about 10 to 1000 μm, but are not limited thereto.

  As the carbon material to be used, materials such as graphite, activated carbon, carbon black, and carbon nanotube can be used. Among them, graphite and activated carbon are preferably used.

As the metal hydride to be used, lithium hydride (LiH), magnesium hydride (MgH ₂ ) and calcium hydride (CaH ₂ ) are preferable, but lithium hydride is most preferable in terms of hydrogen storage density and hydrogen release amount.
As the metal amide to be used, lithium amide (LiNH ₂ ), magnesium amide (Mg (NH ₂ ) ₂ ) and calcium amide (Ca (NH ₂ ) ₂ ) are preferable. Amides are preferred.

What is necessary is just to mix | blend at this stage, when manufacturing the hydrogen storage material containing a metal chloride particle and a catalyst particle.
It has been said that adding hydrogen chloride to metal hydride and metal amide may improve hydrogen storage performance, but adding metal chloride as a metal chloride reduces the hydrogen storage density by the weight of chlorine. was there. Here, for example, hydrogenated graphite has a hydrogen storage density of about 7.5 wt%, but has a problem that it is difficult to use as a hydrogen storage material because the hydrogen release temperature is about 400 ° C. This is because the bond between hydrogen and carbon is very stable. However, when metal hydride (for example, LiH) or metal amide (for example, LiNH ₂ ) that easily forms a strong bond with hydrogen gathers in the vicinity, the bond between carbon and hydrogen is relaxed by surrounding atoms and molecules, and the bond is unstable. become. Therefore, hydrogen is released at a temperature lower than 400 ° C. in hydrogenated graphite. This means that in addition to hydrogen contained in metal hydrides and metal amides, hydrogen contained in hydrogenated graphite is released, and more hydrogen can be released at low temperatures. And
As the metal chloride to be used, magnesium chloride (MgCl ₂ ), copper chloride (CuCl ₂ ), nickel chloride (NiCl ₂ ), zinc chloride (ZnCl ₂ ) and calcium chloride (CaCl ₂ ) are preferable. Particularly preferred are magnesium chloride, copper chloride and zinc chloride.
The metal chloride particles are preferably included at a molar ratio of 0.2 to 1.5 with respect to the metal amide particles. This is because if it is less than 0.2, a sufficient effect cannot be obtained. On the other hand, if it exceeds 1.5, the hydrogen storage density decreases due to an increase in weight due to excess chloride. A more preferable ratio of metal chloride particles to metal amide particles is 0.2 to 1.0, and a more preferable ratio is 0.5 to 0.7.

The catalyst particles are composed of a substance capable of promoting the reaction of Li ₂ NH + H ₂ ⇔LiNH ₂ + LiH. Specifically, transition metals, transition metal oxides, and transition metal chlorides can be used. Among these, Ti and / or Al are preferably used, and metal Ti and / or metal Al, titanium oxide (TiO ₂ ) and / or aluminum oxide (Al ₂ O ₃ ), titanium chloride (TiCl ₃ ) and It is preferable to use aluminum chloride (AlCl ₃ ). The catalyst particles are preferably included in a molar ratio of 0.001 to 0.1 with respect to the metal amide particles. If it is less than 0.001, the function as a catalyst cannot be fully exhibited. Further, even if it exceeds 0.1, the function as a catalyst is not improved, and the hydrogen storage amount and the hydrogen release amount per unit weight of the hydrogen storage material are reduced. A more preferable ratio of the catalyst particles to the metal amide particles is 0.005 to 0.08, and a more preferable ratio is 0.01 to 0.05.

  Mechanical energy is given to the raw material composition as shown in FIG. 1 (S103 in FIG. 1). By applying mechanical energy, the carbon material particles, the metal hydride particles, and the metal amide particles repeatedly collide with each other. In this process, mechanical energy such as compression, friction, and impact is applied to the carbon material particles, metal hydride particles, and metal amide particles, and the particles are activated to increase the reactivity. As the reactivity increases, the metal hydride particles and metal amide particles tend to aggregate, but the carbon material particles function as a lubricant to prevent aggregation. Thereby, the hydrogen storage material with the favorable dispersion state of the metal hydride particles and the metal amide particles can be obtained.

  In addition to the effect of preventing aggregation of metal hydride particles and metal amide particles, the carbon material particles also have a hydrogen storage capacity capable of reversibly extracting hydrogen. Therefore, it contributes to an increase in the amount of hydrogen stored in the entire hydrogen storage material. This increase in the amount of hydrogen occlusion can be obtained by using carbon material particles that have been previously hydrogenated or by applying mechanical energy in a hydrogen atmosphere to a raw material composition that includes carbon material particles that have not been hydrogenated. Can do.

Hydrogen storage materials consisting of metal hydride particles and metal amide particles that do not contain carbon material particles form metal imides at a high temperature after releasing hydrogen, but the composition of metal imides when cooled because this temperature is close to the melting point Becomes non-uniform, and the hydrogen release performance decreases. Since the hydrogen storage material of the present invention includes carbon material particles, even if the cycle of hydrogen release and hydrogen storage is repeatedly performed, a decrease in hydrogen release performance can be suppressed.
This is because the metal particles that have released hydrogen due to the presence of the carbon material are uniformly dispersed on the surface of the carbon fine particles having a large surface area, so that the reaction efficiency with hydrogen increases.

  A mechanical pulverizer can be used for applying mechanical energy. The pulverizer is intended to pulverize a substance, but in the present invention, it is not intended to pulverize itself, but to the carbon material particles, metal hydride particles and metal amide particles, compression, friction, impact, etc. The purpose is to impart mechanical energy. However, it is not excluded that the carbon material particles, metal hydride particles, and metal amide particles are pulverized in the process of achieving this object. It is because it can be said that it is preferable for the present invention to apply mechanical energy to such an extent that grinding is performed. This is because the particles in the raw material composition can join each other or the same kind of particles if energy is applied to such an extent that mechanical pulverization is performed.

A rocking mill can be used for applying mechanical energy according to the present invention. The rocking mill is a crusher that can vibrate in a three-dimensional manner while rotating a mill vessel, and can impart mechanical energy several tens of times that of a ball mill to an untreated object.
FIG. 2 shows a front view of the appearance of the rocking mill 1. In the examples described later, the rocking mill 1 was used for mechanical pulverization (milling). In FIG. 2, the mill container 2 is fixed to a vibration table 3 provided on the upper surface of the rocking mill 1. A branch pipe is attached to the mill vessel 2 so that the inside can be filled with vacuum exhaust and hydrogen gas, and the pressure of the hydrogen gas can be constantly measured by a pressure sensor. The rocking mill 1 performs milling with the center of the vibration table 3 as the vibration center.

  FIG. 3 shows a cross-sectional view of the internal structure of the mill container 2. As shown in FIG. 3, a processing object (carbon material particles, metal hydride particles, metal amide particles, etc.) 4 is filled inside the mill vessel 2. For milling, steel balls 5 are placed inside the mill vessel 2 and pulverized by the movement of the rocking mill 1 (indicated by arrows). By this treatment, the carbon material particles, metal hydride particles, and metal amide particles form a fine mixed powder. The particle size of the mixed powder is about 0.1 to 10 μm.

  The time for performing the mechanical pulverization treatment as described above is preferably selected from the range of 0.01 to 200 hours. If it is less than 0.01 hour, sufficient mechanical energy cannot be imparted to the carbon material particles, metal hydride particles, and metal amide particles. Moreover, it is because sufficient mechanical energy can be imparted to the carbon material particles, metal hydride particles, and metal amide particles if pulverization is performed for about 200 hours. A preferable pulverization time is 0.1 to 100 hours, and a more preferable pulverization time is 0.5 to 40 hours.

Moreover, it is preferable that the atmosphere which gives mechanical energy including a mechanical grinding | pulverization process shall be an inert gas atmosphere and the atmosphere containing hydrogen gas. The pressure of the atmospheric gas is preferably 0.1 to 5 MPa.
As the inert gas, it is preferable to use argon gas since many materials are inert to Ar.
The atmosphere containing hydrogen gas is preferably an atmosphere containing hydrogen gas or a mixed gas of hydrogen gas and inert gas. When mechanical energy is applied, the carbon material particles can be hydrogenated if the atmosphere contains hydrogen gas. As described above, the carbon material particles previously hydrogenated can be used as the carbon material particles. The carbon material particles can also be hydrogenated by exposing the carbon material particles to a high temperature and high pressure hydrogen atmosphere. For example, carbon material particles that have been previously hydrogenated can be obtained by exposure to an atmosphere with a hydrogen pressure of 5 MPa and 500 ° C. for several hours.

  In the production method described above, the reactivity is improved by applying mechanical energy to the carbon material particles, metal hydride particles, metal amide particles, metal chloride particles, and catalyst particles constituting the raw material composition in advance. It is also effective to perform the above-described manufacturing method after the increase.

<Initialization process>
After mechanical energy application, particularly mechanical pulverization, is completed, the hydrogen bonding state in the object to be processed may become unstable, and some hydrogen may be detached from the object to be processed. Therefore, it is preferable to supply hydrogen to the object to be processed by exposing the object to be processed in a hydrogen atmosphere. This process is called initialization process. The initialization process can be performed by exposing the workpiece to an atmosphere of a temperature of 100 to 300 ° C. and a hydrogen pressure of 1 to 5 MPa for 1 to 12 hours. However, this condition varies depending on the amount of the object to be processed and the amount of hydrogen to be supplied. This initialization process is effective when mechanical energy is applied in an inert gas atmosphere. Moreover, the carbonization material particle in a to-be-processed object contains hydrogen by this initialization process, and it contributes to the increase in a hydrogen storage amount.

<How to use hydrogen storage materials>
The hydrogen storage material of the present invention obtained as described above can release hydrogen by heating in the range of 100 to 250 ° C.
The hydrogen storage material of the present invention basically becomes a mixture of metal imide such as lithium imide (Li ₂ NH) and carbon material particles after releasing hydrogen. Hydrogen can be occluded again by heating the metal imide obtained by hydrogen release in a hydrogen gas atmosphere. The hydrogen storage material of this invention is comprised by this hydrogen occlusion. Heating for hydrogen storage may be in the range of 100 to 250 ° C. The hydrogen gas atmosphere is preferably a pressurized atmosphere.

Graphite: 0, 0.1, 0.2 g, Lithium hydride (LiH): 0.1 g, Lithium amide (LiNH ₂ ): 0.26 g, Titanium oxide (TiO ₂ ): 0.1 g are weighed and high purity The mill container 2 shown in FIG. 2 was filled in a glove box in an argon atmosphere (moisture ≦ 1 ppm). The mill container 2 was fixed to the rocking mill 1, and after confirming that there was no leak with a pressure sensor, mechanical milling (chemical milling) was performed at a frequency of 50 Hz for 2 hours. This mixture was subjected to the initialization process described above. The condition for the initialization treatment is to hold at 200 ° C. under a hydrogen atmosphere of 2 MPa for 3 hours. Next, the initialized sample was heated stepwise to 250 ° C., and the amount of hydrogen released from the sample was measured by gas chromatography. Table 1 shows the measurement results of the hydrogen release amount (released hydrogen weight / hydrogen storage material weight). The hydrogen storage material weight is the total weight of the raw material composition.

As shown in Table 1, it was confirmed that the hydrogen release amount can be increased by adding graphite. That is, according to the present invention, since the re-aggregation of the sample after the mechanical pulverization treatment can be prevented in the production of the hydrogen storage material, the efficiency of the hydrogen releasing reaction is improved, and the amount of hydrogen released can be increased. Inferred. In addition, the amount of hydrogen released is increased by utilizing the hydrogen release from the carbon material at low temperature, and the reaction efficiency is improved by the carbon material particles entering the gap between the metal amide particles and the metal hydride particles. It is understood.
In addition, when not adding graphite (addition amount 0g), it was confirmed that a to-be-processed object aggregates in the form as shown in FIG. On the other hand, when graphite was added, the object to be treated did not aggregate.

  Table 2 shows the results of a similar experiment performed on activated carbon instead of graphite. By adding 0.1 g of activated carbon, the hydrogen release amount was 5.4 wt%, and it was confirmed that activated carbon increased the hydrogen release amount compared to graphite. Furthermore, the amount of hydrogen released increased by increasing the amount of activated carbon added, suggesting that the amount of hydrogen released from the carbon material at a low temperature increased. This is the same result as graphite.

  In this embodiment, an example in which the milling time is 2 hours is shown. However, the milling time depends on the properties of the sample and is determined by the ease and difficulty of pulverization of the material. You can choose an appropriate time between them. The same applies to the second and third embodiments.

  The amount of hydrogen released was measured in the same manner as described above except that the metal hydrides and metal amides shown in Table 3 were used and the amount of graphite shown in Table 3 was added. The results are shown in Table 3.

Graphite: 0.1 g, lithium hydride (LiH): 0.36 g, lithium amide (LiNH ₂ ): 0.26 g, titanium oxide (TiO ₂ ): 0.1 g are weighed, and the hydrogen pressure inside the mill vessel 2 is determined. A hydrogen storage material was produced in the same manner as in Example 1 except that the raw material composition was filled at 0 MPa (argon gas), 1 MPa, and 3 MPa, and the hydrogen release amount was measured in the same manner as in Example 1. Note that initialization processing is not performed. The results are shown in Table 4. In addition, Table 5 shows the results of manufacturing the hydrogen storage material and measuring the hydrogen release amount in the same manner as above except that activated carbon was used instead of graphite.

From Table 4, it was confirmed that the hydrogen release amount can be increased to 6.1 wt% by performing chemical milling in a 1 MPa hydrogen atmosphere. By increasing the hydrogen pressure, the amount of hydrogen released can be further increased. Next, as shown in Table 5, it was confirmed that the hydrogen release amount can be further increased by using activated carbon as the carbon material.
Hydrogen of carbon materials that have been hydrogenated or carbon materials that have been hydrogenated by mechanically crushing the raw material composition of metal amide and metal hydride added with carbon materials in a hydrogen atmosphere are also stored hydrogen. It can be released.
Here, in the case of hydrogenation with a carbon material alone, the hydrogen release temperature is about 300 ° C. or higher, which is not practical. However, according to this example, it was confirmed that a large amount of hydrogen can be released at a temperature of 250 ° C. or lower. The reason for the decrease in the hydrogen release temperature is that the lithium amide and lithium hydride are bonded to the graphite surface, so that the hydrogen bond is destabilized and easily released.

Graphite: 0.2 g, lithium hydride (LiH): 0.1 g, lithium amide (LiNH ₂ ): 0.36 g, metal chloride: 0.2 g, titanium oxide (TiO ₂ ): 0.1 g were weighed, The mill container 2 was filled in a glove box in a high purity argon atmosphere (moisture ≦ 1 ppm), and thereafter, pulverization was performed by the rocking mill 1 under the same conditions as in Example 1. Note that magnesium chloride (MgCl ₂ ), copper chloride (CuCl ₂ ), and zinc chloride (ZnCl ₂ ) were used as metal chlorides. A hydrogen storage material was obtained in the same manner as described above except that magnesium amide (MgNH ₂ ) was used instead of lithium amide.
For the obtained hydrogen storage material, the hydrogen release amount was measured in the same manner as in Example 1. The results using lithium amide as the metal amide are shown in Table 6, and the results using magnesium amide are shown in Table 7.

From Table 6, the peak hydrogen release temperature can be reduced to about 150 ° C. by adding metal chloride. Furthermore, from this table, it was confirmed that the hydrogen release amount can be increased by using copper chloride and further zinc chloride as the metal chloride.
Next, as shown in Table 7, it was confirmed that the hydrogen release amount increased by changing lithium amide to magnesium amide.

It is a figure which shows the manufacture procedure of the hydrogen storage material by this invention. It is a figure which shows the structure of a rocking mill. It is the figure which showed the grinding | pulverization by a rocking mill typically. It is the figure which showed the grinding | pulverization by a rocking mill typically, Comprising: It is a figure which shows the state which the to-be-processed object raise | generated aggregation.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Rocking mill, 2 ... Mill container, 3 ... Vibration table, 4 ... Processing object, 5 ... Ball

Claims (8)

Producing a raw material composition comprising carbon material particles, metal hydride particles and metal amide particles;
Applying mechanical energy to the raw material composition (b);
A method for producing a hydrogen storage material, comprising:   The method for producing a hydrogen storage material according to claim 1, wherein the carbon material particles are one or two of graphite and activated carbon.   The hydrogen storage material according to claim 1 or 2, wherein the metal hydride particles are one or more selected from lithium hydride particles, magnesium hydride particles, and calcium hydride particles. Production method.   The said metal amide particle is 1 type, or 2 or more types selected from lithium amide particle, magnesium amide particle, and calcium amide particle, The manufacture of the hydrogen storage material in any one of Claims 1-3 characterized by the above-mentioned. Method.   The said raw material composition contains a metal chloride particle | grain, The manufacturing method of the hydrogen storage material in any one of Claims 1-4 characterized by the above-mentioned.   The method for producing a hydrogen storage material according to claim 5, wherein the metal chloride particles are one or more selected from magnesium chloride particles, copper chloride particles, and zinc chloride particles.   The method for producing a hydrogen storage material according to any one of claims 1 to 6, wherein the mechanical energy application in the step (b) is performed by a mechanical pulverization process.   The method for producing a hydrogen storage material according to claim 1, wherein the mechanical energy application in the step (b) is performed in an atmosphere containing hydrogen gas.

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