JP2009062215A - Hydrogen generating material, method for manufacturing hydrogen generating material, container for hydrogen generating material, hydrogen fuel vehicle, and portable apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrogen generating material decreasing supplied calories upon generating hydrogen from a hydrogenated metal and downsizing a heating device. <P>SOLUTION: The hydrogen generating material contains a metal hydride 1 and a water-releasing material 2. The hydrogen generating material has a particle structure such as a particle structure having the water-releasing material 2 included inside the metal hydride 1, a structure having a layer of the water-releasing material 2 on the surface of the metal hydride 1, or a structure having the water-releasing material 2 on the surface of a metal oxide covering the surface of the metal hydride 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a hydrogen generating material and peripheral technologies thereof, and more particularly to a hydrogen generating material suitable for supplying hydrogen to a moving body, a method for manufacturing the hydrogen generating material, a container for the hydrogen generating material, a hydrogen fuel vehicle, and a portable device. Regarding equipment.

  Conventionally, as a method of supplying hydrogen to a portable fuel cell or a hydrogen fuel vehicle, a method of supplying hydrogen from a cryogenic liquid hydrogen storage device, a method of supplying hydrogen from a high-pressure hydrogen gas tank, and a moving body from a material containing hydrogen A method for generating and supplying hydrogen is known.

  However, the liquid hydrogen storage device has a drawback that even if it has a high-performance heat insulating container, it cannot suppress evaporation of several percent of liquid hydrogen per day, and the device becomes large. In addition, the high-pressure hydrogen gas tank must have strength against high pressure, and there is a drawback that the volume and weight per unit storage hydrogen increase. For this reason, attention is focused on a method for generating hydrogen from a raw material other than hydrogen in a portable fuel cell or a hydrogen fuel vehicle.

  As a prior art of such a hydrogen generation method, it is known that when aluminum hydride is heated at a temperature of about 200 ° C., it is decomposed into metallic aluminum and hydrogen as shown in the formula (a) (non- Patent Document 1).

AlH ₃ → Al + (3/2) H ₂ (Chemical Formula a)
Further, as a hydrogen supply system for a fuel cell, between a first hydrogen storage system that supplies hydrogen by hydrolysis of a metal hydride and a second hydrogen storage system that supplies hydrogen using a hydrogen storage material. A hydrogen supply system that performs heat exchange is known (Patent Document 1). According to this hydrogen supply system, the heat generated in the first hydrogen storage system is supplied to the second hydrogen storage system, so that no external heating is required at the time of hydrogen generation, and wasteful heat is generated outside. There is no need to dispose of it and overall energy efficiency can be improved.
Decomposition Kinetics of the AlH3 Polymorphs Jason Greatz and James J. Reilly J. Phys. Chem. B 2005, 109, 22181-22185. JP 2004-206950 A (6th page, FIG. 2)

  However, the decomposition reaction of the metal hydride described in Non-Patent Document 1 is an endothermic reaction, and a large amount of heat supply is required at the time of hydrogen generation, so that the volume and weight of the heating device for heating the metal hydride increases. There was a problem that the supply of the necessary amount of heat had to be continued.

  Moreover, in a hydrogen supply system provided with the 1st hydrogen storage system which supplies hydrogen by hydrolysis of the metal hydride of patent document 1, and the 2nd hydrogen storage system which supplies hydrogen using a hydrogen storage material However, it is necessary to provide two different hydrogen storage systems, and there is a problem that a larger weight and volume are required than existing hydrogen storage tanks.

  In order to solve the above-mentioned problems, the present invention is a hydrogen generating material including a metal hydride and a substance that induces heat generation by heating.

  Moreover, this invention is a manufacturing method of the hydrogen generating material which makes the summary the layer which discharge | releases water to a metal hydride by making the compound and metal hydride which have a hydroxyl group contact.

  According to the hydrogen generating material according to the present invention, the hydrogen generating material includes a metal hydride and a substance that induces heat generation by heating, so that in parallel with the thermal decomposition reaction of the metal hydride during heating, Since the substance that induces exotherm induces an exothermic reaction, the amount of heat to be supplied for hydrogen generation can be greatly reduced, and the hydrogen generating material that can reduce the volume and weight of the heating device can be provided. There is.

  Further, according to the method for producing a hydrogen generating material according to the present invention, a hydrogen generating material in which a layer for releasing water can be easily formed on the surface of the metal hydride, and if this hydrogen generating material is heated, Since the released water reacts with the metal hydride or the metal from which the metal hydride is decomposed to induce an exothermic reaction, it is possible to provide a hydrogen generating material that greatly reduces the amount of heat to be supplied for hydrogen generation. There is an effect that can be done.

  Embodiments of the present invention will be described in detail. The hydrogen generating material according to the present invention is characterized by containing a metal hydride and a water release material that releases water, which is a compound having a hydroxyl group, by heating. When the metal hydride is M, the metal hydride generates hydrogen by the following thermal decomposition reaction (endothermic reaction) of the formula (Chemical Formula 1).

MH ₂ → M + H ₂ (Chemical formula 1)
The water released from the water discharge by heating undergoes a water splitting reaction (exothermic reaction) with the metal hydride to generate a metal oxide and hydrogen as shown in the formula (2).

MH ₂ + H ₂ O → MO + 2H ₂ (Chemical formula 2)
Since this water splitting reaction is an exothermic reaction, the water discharge that releases water by heating is a substance that induces heat generation by heating when present together with a metal hydride.

Further, as shown in (Chemical Formula 3), the reaction between the metal obtained by decomposition of the metal hydride and water is also an exothermic reaction. The MO includes not only metal oxides but also metal hydroxides and metal oxide hydrates. In the case of Al, Al ₂ O ₃ , Al (OH) ₃ , and AlOOH are listed.

M + H ₂ O → MO + H ₂ (Chemical formula 3)
Therefore, the heat of the water splitting reaction by (Chemical Formula 2) and (Chemical Formula 3) can be utilized for the thermal decomposition reaction (endothermic reaction) of the metal hydride shown in (Chemical Formula 1). Thereby, when generating hydrogen from a hydrogen generating material, the amount of heat to be supplied from the outside can be reduced.

  Examples of the substance that induces heat generation by heating include substances having a hydroxyl group by heating, for example, lower alcohols such as methyl alcohol and ethyl alcohol, in addition to substances that release water by heating. Furthermore, the same effect can be obtained with a substance that releases a substance such as a lower carboxylic acid having a carboxyl group. Substances such as lower alcohols and lower carboxylic acids can release hydrogen through an exothermic reaction with metal hydrides, like water.

  Next, with reference to FIG. 1, various structures of the hydrogen generating material including the metal hydride 1 according to the present invention and the water discharge material 2 which is a substance that releases water by heating will be described. FIG. 1A is a schematic diagram showing a state where the metal hydride 1 and the water discharge 2 are contained in the hydrogen generating material as individual particles. When the metal hydride 1 and the water discharge 2 are contained as individual particles in the hydrogen generating material, it is necessary to mix the two types of particles so that the distribution of the two types of particles is uniform and to fill the container.

  FIG. 1 (b) is a diagram showing a particle structure of a hydrogen generating material in which a water discharge 2 is contained inside a metal hydride 1. Thus, when the metal hydride 1 and the water discharge material 2 are closer to each other, the exothermic reaction proceeds more easily, and it is convenient to use the reaction heat of (Chemical Formula 2) and (Chemical Formula 3) in (Chemical Formula 1). is there. In addition, because the structure shown in FIG. 1B includes the metal hydride 1 and the water discharge 2 in one particle, it is necessary to uniformly mix the two types of particles when filling the container with the hydrogen generating material. This is preferable because the uniformity of the water discharge distribution and the utilization efficiency of the discharged water are increased.

  FIG. 1 (c) is a view showing a structure in which a layer of water discharge 2 is formed on the surface layer of metal hydride 1. Since the method of forming the water release 2 layer on the surface of the metal hydride 1 is easier than the formation of the water discharge 2 layer inside the metal hydride 1, the practicality is high.

  FIG. 1 (d) is a diagram showing a structure in which a water discharge 2 is formed on the surface of the metal oxide 3 covering the surface of the metal hydride 1. This structure can also be said to be a structure in which a metal oxide 3 layer is provided between the metal hydride 1 and the water discharge 2. When the metal hydride 1 and the water discharge 2 are in direct contact, the metal hydride 1 may be decomposed. In order to avoid this, the metal oxide 3 is sandwiched between the metal hydride 1 and the water discharge 2 to provide a highly stable hydrogen generating material.

  Next, the composition of the hydrogen generating material according to the present invention will be described in the order of metal hydride, metal oxide, and water discharge.

The metal constituting the metal hydride 1 contained in the hydrogen generating material of the present invention is at least one of alkali metal, alkaline earth metal, boron (B), and aluminum (Al). Specific examples include metal hydrides such as LiH, NaH, BeH ₂ , MgH ₂ , CaH ₂ , and AlH ₃ . A metal complex compound represented by M (AlH ₄ ) n or M (BH ₄ ) n (M = alkali metal or alkaline earth metal) can also be used as the metal hydride 1.

  When the structure of the hydrogen generating material is the structure shown in FIG. 1D, the metal constituting the metal oxide 3 may be an alkali metal (Li, Na, K, Rb, Cs, Fr), an alkaline earth metal (Be , Mg, Ca, Sr, Ba, Ra), boron (B), or aluminum (Al).

  The water discharge 2 is a metal hydroxide, a hydrate of metal oxide, or a water adsorbing material, and is a material that can release water near the decomposition temperature of the metal hydride 1. .

  When the water discharge material 2 is a metal hydroxide, the metal hydroxide can usually be easily synthesized from the metal oxide covering the surface of the metal hydride. For this reason, water discharge can be formed at low cost.

  Here, the decomposition temperature Td1 of the metal hydride and the decomposition temperature Td2 of the metal hydroxide must be approximately the same. For example, if the decomposition temperature Td1 of the metal hydride is sufficiently lower than the decomposition temperature Td2 of the metal hydroxide (Td1 << Td2), the hydrogen generating material is heated to near Td1 to generate hydrogen from the metal hydride. No water is released from the metal hydroxide, and the metal hydroxide as a water discharge does not contribute to hydrogen generation. Conversely, if the decomposition temperature Td1 of the metal hydride is sufficiently higher than the decomposition temperature Td2 of the metal hydroxide (Td1 >> Td2), the hydrogen generating material is heated to near Td2 to release water from the metal hydroxide. However, since the temperature is considerably lower than the decomposition temperature Td1 of the metal hydride, it is difficult for the released water to contribute to hydrogen generation.

For example, when using a combination of AlH ₃ as the metal hydride and Al (OH) ₃ as the metal hydroxide, the decomposition temperatures of both are close, and the water released from Al (OH) ₃ is AlH ₃ or AlH _3. It effectively acts on Al, which is a decomposition product, and the heat generated by the water splitting reaction promotes the decomposition of AlH ₃ .

  Also, when the water release material 2 is a metal oxide hydrate, the decomposition temperature Td1 of the metal hydride and the decomposition temperature Td3 of the metal oxide hydrate need to be approximately the same.

For example, a combination of AlH ₃ as a metal hydride and boehmite [Al ₂ O _3. (H ₂ O)] which is a monohydrate of alumina as a hydrate of a metal oxide can be given. When AlH ₃ is used for the metal hydride, even if boehmite having high crystallinity or amorphous boehmite is used, the effect can be obtained.

  When the water release 2 is a metal oxide hydrate, the metal oxide hydrate can usually be easily synthesized from the metal oxide covering the surface of the metal hydride. For this reason, water discharge can be formed at low cost.

  Furthermore, the water discharge material 2 can also be used as a water adsorbing material. Also in this case, a material having a water release temperature close to the decomposition temperature of the metal hydride 1 is selected from various water adsorbing materials. Examples of the water adsorbing material include zeolite and silica gel. However, the process for forming a zeolite or silica gel film on the surface of the metal hydride is expensive. In addition, a water adsorbing material capable of storing a large amount of water, such as zeolite or silica gel, can release a necessary amount of water by simply attaching a small amount of water discharge material 2 to metal hydride 1.

  Next, a method for producing a hydrogen generating material according to the present invention will be described.

[Production Method 1]
The first embodiment for forming a layer for releasing water on the surface of the metal hydride is a method for forming a layer for releasing water on the surface of the metal hydride by bringing the metal hydride into contact with a humidified atmosphere. . Usually, the surface of the metal hydride particles is covered with a metal oxide. By storing the metal hydride particles in a humidified atmosphere at room temperature, preferably 25 ° C. or less, part of the metal oxide on the surface changes to a hydroxide or changes to a metal oxide hydrate. To do. This forms a water release layer on the surface of the metal hydride particles. This method is the simplest method for producing a hydrogen generating material according to the present invention, but takes a long time to process.

[Production Method 2]
The second embodiment of forming a water releasing layer on the surface of the metal hydride forms a layer releasing water on the surface of the metal hydride by contacting the metal hydride with a liquid having a hydroxyl group. Is the method. When the most common water (H ₂ O) is used as a compound having a hydroxyl group, it is easy to obtain and at the time of hydrogen generation, compared with a carbon-containing material such as a lower alcohol as a compound having a hydroxyl group. It is preferable because impurity gas can be prevented from being by-produced. In addition, when the metal hydride is brought into contact with liquid water rather than in contact with the humidified atmosphere, the water release layer can be formed in a short time. In addition, it is preferable that the contact time when contacting with water at room temperature is within 3 days.

FIG. 2 shows an outline of a method for forming a water release layer on the surface of a metal hydride using aluminum hydride (AlH ₃ ) as a metal hydride and water (H ₂ O) most commonly used as a compound having a hydroxyl group. It is explanatory drawing.

  In FIG. 2, boehmite [AlO (OH)] 12 is formed on the surface of the aluminum hydride 11 in the particles 10 before treatment. 100 mg of this pre-treatment particle 10 is put in a container 20 of a glass sample bottle (volume of about 10 cc), and 0.15 cc of ion exchange water is poured as water 21. Mixing is performed so that the volume ratio of aluminum hydride to ion-exchanged water is about 1: 2. Then, an underwater milling step of stirring with a stir bar (substitute with SUS spatula) 22 for 5 minutes every 8 hours was performed at room temperature (20 to 25 ° C.) in the atmosphere for 48 hours. By keeping the container at room temperature, decomposition of the metal hydride during contact between the metal hydride and water can be avoided.

  By stirring the container containing the metal hydride particles and water, the particles come into contact with each other and easily contain water. The treated particles 15 have a secondary effect that a water adsorbing layer 13 is formed on the boehmite layer 12 on the surface, and cracks 14 are formed on the boehmite layer 12 to facilitate hydrogen release during hydrogen generation. is there. When this process was performed, the sample was almost naturally dried after 48 hours, and the sample that was allowed to stand at room temperature for about 1 week was used for the hydrogen generation ability measurement. In addition, when performing said underwater milling in large quantities, it can implement with the ball milling apparatus which can mix a liquid and solid. Moreover, it is preferable that the ratio of aluminum hydride and water is about 0.1-10.

  In Example 2 described above, the water release layer was formed on the surface of the metal hydride by stirring the mixture of the metal hydride particles and water. However, in addition to the stirring, the metal hydride particles and water A water release layer can also be formed on the surface of the metal hydride by vibrating the container containing the mixture with a device such as a vibrator. By vibrating the container, the particles are brought into contact with each other in the same manner as the stirring, so that the water adsorption layer 13 is formed on the boehmite layer 12 on the particle surface and the crack 14 is formed on the boehmite layer 12.

  FIG. 3 is a diagram showing the hydrogen release performance of the hydrogen generating material treated in a humidified atmosphere of Example 1, the hydrogen generating material milled in water of Example 2, and the hydrogen generating material of a comparative example that does not perform these treatments. It is. FIG. 3 (a) is a diagram showing the time course of the hydrogen release amount when the sample is heated by a heating device having a constant output. Compared with the comparative example, the hydrogen release rate is increased in both Example 1 and Example 2. For example, the time required to release 4 wt% hydrogen is significantly reduced to about 0.9 h for Example 1 and about 0.6 for Example 2 compared to about 1.3 h for the Comparative Example ( The release rate is greatly improved). This indicates that since the output of the heating device is constant, the amount of heat necessary to release a certain amount of hydrogen is reduced in Examples 1 and 2 compared to the comparative example. Further, it can be seen that the final hydrogen release amount is increased in Examples 1 and 2 with respect to the comparative example.

  FIG. 3B is a diagram showing the hydrogen release temperature between Example 1 and the comparative example. In Example 1, the hydrogen release temperature is lowered by about 15 ° C. with respect to the comparative example.

  FIG. 4 is a diagram showing the hydrogen release rate (arbitrary unit) when the water content (wt%) of the hydrogen generating material according to the present invention is variously changed. When the water content is from about 3% to about 13%, the hydrogen release rate is improved. When the water content is less than about 3%, the absolute amount of water discharge is small and the effect is small. If the water content exceeds 15%, it is considered that the ratio of the metal hydride of the hydrogen generating material is reduced due to the inclusion of excess water, and the hydrogen release rate is reduced.

  Next, application of the hydrogen generating material according to the present invention will be described. First, as a material for the container for containing the hydrogen generating material of the present invention, austenite-based (SUS304, 316, etc., face-centered cubic structure) stainless steel, a composite material in which carbon fiber or the like is hardened with a resin, which hardly causes hydrogen embrittlement. Or aluminum. The heat-resistant temperature of the container varies depending on the decomposition temperature of the metal hydride to be used, but at least about 200 ° C. is necessary, and the pressure resistance of the container needs a pressure-resistant performance of about 1 MPa. In particular, a composite material in which carbon fibers or the like are hardened with a resin has low high-temperature resistance, so attention must be paid to the temperature range to be used.

  The hydrogen generating material according to the present invention is suitable for supplying hydrogen to a moving body because it has a high hydrogen release amount and requires less heat to be supplied from the outside during hydrogen release. Examples of the mobile body that supplies hydrogen from the hydrogen generating material of the present invention include a hydrogen fuel vehicle that uses a fuel cell that uses hydrogen as a fuel, such as a solid polymer fuel cell or a solid oxide fuel cell, as a power source, A hydrogen fuel vehicle using a hydrogen fuel internal combustion engine as a power source is suitable. Moreover, it is suitable not only for hydrogen fuel vehicles but also for applications such as electric carts and electric wheelchairs powered by fuel cells.

  Furthermore, since the hydrogen generating material of the present invention has a high hydrogen release amount and requires less heat to be supplied from the outside at the time of hydrogen release, portable electronic devices such as notebook personal computers, portable navigation devices, and mobile phones, and portable phones can be used. The hydrogen generating material of the present invention is suitable for supplying hydrogen to a fuel cell as a power source for an electric appliance for a vehicle.

(A) Schematic of a state in which the metal hydride 1 and the water discharge 2 are each contained in the hydrogen generation material as individual particles, (b) the hydrogen generation material in which the water discharge 2 is contained inside the metal hydride 1 (C) The figure which shows the structure in which the layer of the water discharge | release material 2 was formed in the surface layer of the metal hydride 1, (d) On the surface of the metal oxide 3 which covers the surface of the metal hydride 1 It is a figure which shows the structure in which the water discharge 2 was formed. It is a schematic illustration of a method of forming a water-releasing layer on the surface of the aluminum hydride as a metal hydride (AlH _3). (A) The time lapse of the hydrogen release amount of the hydrogen generating material treated with the humidified atmosphere of Example 1, the hydrogen generating material milled in water of Example 2, and the comparative example when the sample was heated with a heating device having a constant output (B) It is a figure which shows the hydrogen releasing temperature of Example 1 and a comparative example. It is a figure which shows the hydrogen release speed | velocity at the time of changing the water content of the hydrogen generating material which concerns on this invention variously.

Explanation of symbols

1 Metal hydride 2 Water discharge 3 Metal oxide 10 Particles before treatment 11 AlH ₃
12 AlO (OH)
13 Water adsorption layer 14 Crack 15 Particles after treatment 20 Container 21 Water 22 Stirring rod

Claims (21)

  A hydrogen generating material comprising a metal hydride and a substance that induces heat generation by heating.   The hydrogen generating material according to claim 1, wherein the substance that induces heat generation by heating is a substance that releases a compound having a hydroxyl group by heating.   The substance that induces heat generation by heating is a substance that releases water by heating, and generates heat when the metal hydride or a decomposition product of the metal hydride reacts with the released water. The hydrogen generating material according to claim 1.   The hydrogen generating material according to claim 3, wherein a layer of a substance that releases water by the heating is formed inside the metal oxide particles.   The hydrogen generating material according to claim 3, wherein a layer of a substance that releases water by the heating is formed on a part of the particle surface of the metal oxide.   6. The hydrogen generating material according to claim 5, further comprising a metal oxide layer between the metal oxide and the layer of the substance that releases water by the heating.   The hydrogen generating material according to any one of claims 3 to 6, wherein the substance that releases water by heating is a metal hydroxide.   The hydrogen generating material according to any one of claims 3 to 6, wherein the substance that releases water by heating is a hydrate of a metal oxide.   The hydrogen generating material according to any one of claims 3 to 6, wherein the substance that releases water by heating is a water adsorbing material.   10. The hydrogen according to claim 1, wherein the metal constituting the metal hydride includes at least one of an alkali metal, an alkaline earth metal, boron, and aluminum. Generating material.   The material covering the surface of the metal hydride is an oxide or hydroxide of one or more kinds of metals selected from alkali metals, alkaline earth metals, boron, and aluminum. Item 11. The hydrogen generating material according to any one of Items 10.   A method for producing a hydrogen generating material, wherein a layer for releasing water is formed on a metal hydride by contacting a compound having a hydroxyl group with the metal hydride.   The method for producing a hydrogen generating material according to claim 12, wherein the compound having a hydroxyl group is water.   14. The hydrogen generation according to claim 12 or 13, wherein a layer for releasing water is formed in the metal hydride by contacting an atmosphere containing a vapor of a compound having a hydroxyl group with the metal hydride. Material manufacturing method.   When the liquid of the compound having a hydroxyl group is brought into contact with the metal hydride, a layer for releasing water is formed on the metal hydride by vibrating the container containing the liquid and the metal hydride. A method for producing a hydrogen generating material according to claim 12 or claim 13.   When the liquid of the compound having a hydroxyl group and the metal hydride are brought into contact with each other, the container containing the liquid and the metal hydride is stirred to form a layer for releasing water in the metal hydride. A method for producing a hydrogen generating material according to claim 12 or claim 13.   17. When contacting a liquid of a compound having a hydroxyl group with a metal hydride, the temperature environment is set to room temperature, and a layer for releasing water into the metal hydride is formed. 2. A method for producing a hydrogen generating material according to item 1.   A hydrogen generation material containing the hydrogen generation material according to any one of claims 1 to 11, wherein the material is any one of stainless steel, a carbon-based material, and aluminum. Material container.   A hydrogen-fueled vehicle equipped with a fuel cell that uses hydrogen generated from the hydrogen-generating material according to any one of claims 1 to 11 as fuel.   A hydrogen-fueled vehicle comprising an internal combustion engine that uses hydrogen generated from the hydrogen-generating material according to any one of claims 1 to 11 as fuel.   A portable device using as a power source a fuel cell using hydrogen generated from the hydrogen generating material according to any one of claims 1 to 11.

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