JP2002338201A - Method for producing hydrogen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently generate hydrogen. SOLUTION: Hydrogen is generated by irradiating water with radiation to decomposed water. The generation efficiency is improved by incorporating a metal in water and irradiating the water with radiation. When the metal is a hydrogen storage metal, the generated hydrogen is selectively taken out to increase the improvement of hydrogen production efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing hydrogen from water using radiation.

[0002]

2. Description of the Related Art As a technique for decomposing water, conventionally,
Using a solid photocatalyst such as TiO ₂ (titanium dioxide),
There are systems that radiate ultraviolet light or visible light. In such a water splitting system, photoexcited photocatalysts act on water molecules to cause a reaction, which limits the material development to being limited to semiconductor catalysts with an appropriate band gap and some insulator catalysts. was there. In addition, in order to irradiate ultraviolet light or visible light, these are limited to containers made of a material through which they are transmitted,
There was also a restriction that opaque containers such as metal containers could not be used at all. Further, as the photocatalyst, a solid powder or a sintered body thereof is often used in order to increase the surface area. Therefore, it has been difficult to recover and reuse the catalyst after the decomposition reaction.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing hydrogen which is different from the above-mentioned conventional process and free from such restrictions.

[0004]

Means for Solving the Problems In order to achieve the above object, the present inventors have made intensive studies and obtained the following findings, and completed the present invention. That is, radiation such as γ-rays and electron beams used in the present invention has a high transparency, so that the container for containing water may be made of an opaque material such as a metal. The limitation of being limited to a transparent container such as glass can be overcome. In addition, the chemical bond of water molecules can be broken only by irradiating the above-mentioned radiation to water. And so on, so that water can be decomposed more efficiently to generate hydrogen. Further, when the metal has a hydrogen absorbing property, hydrogen generated by water splitting can be selectively taken out, so that the hydrogen production efficiency can be further improved. Alternatively, the generated hydrogen can be easily separated by using a membrane that allows only hydrogen to pass therethrough without passing oxygen.

[0005] The configuration of the present invention is as follows. (1) A method for producing hydrogen by decomposing water, the method comprising irradiating water with radiation to decompose water. (2) It is preferable to make a metal exist in water and irradiate the metal with radiation. (3) As the metal, at least one selected from the group consisting of iron, copper, aluminum, nickel, lead, tungsten, molybdenum, palladium, tantalum, platinum, gold, and rare earth elements can be used. (4) It is preferable that the metal has a hydrogen absorbing property. (5) As the radiation, at least one selected from the group consisting of X-rays, α-rays, β-rays, γ-rays, electron beams, neutron beams, and particle beams can be preferably used.

[0006]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in more detail. The hydrogen production method of the present invention is carried out by irradiating water with water to decompose water, but since radiation such as γ-rays has high transparency, it can be used even in an opaque container. The term “radiation” as used in the present invention refers to one that can decompose water to generate hydrogen. In addition, it is preferable that a metal is present in water, and it is preferable to irradiate the metal with water. In this case, the form of the metal may be a simple metal, or a compound such as an oxide or an alloy. It is not limited to a solid state, but may be in a state of being dissolved by ions or the like. When the metal or metal compound is a solid, it is preferable that the irradiated area be large from the viewpoint of radiation conversion efficiency.

[0007] Further, metals have a function of converting radiation more or less into secondary electron beams or light beams such as ultraviolet rays and visible rays. Therefore, the metal species is not particularly limited, and alkali metals, alkaline earth metals, and the like can be used. Although all metals such as metals belonging to Groups 3 to 5 and transition metals can be mentioned, metals having higher atomic numbers have higher conversion efficiency and are more efficient than metals having lower atomic numbers.

[0008] From the viewpoint of easy availability and stability in water, iron, copper, aluminum, nickel,
Lead, tungsten, molybdenum, palladium, tantalum, platinum, gold and at least one selected from the group consisting of rare earth elements can be used, nickel,
When compared with a metal having a relatively small atomic number, such as aluminum, a metal having a relatively large atomic number, such as tantalum, palladium, or molybdenum, is more preferable. The term “secondary electron” generally means an electron that is emitted from a solid upon receiving the kinetic energy of an incident electron when the electron is injected into the solid from the outside. It refers to a broad concept that includes electrons emitted from a substance by irradiation.

It is preferable that the metal has a hydrogen absorbing property, because it is advantageous in terms of hydrogen separation efficiency as described above. It is needless to say that when the metal to be converted into radiation does not have hydrogen storage properties, a solid material having a hydrogen storage function can be separately added for hydrogen storage.

Further, as radiation, X-rays, α-rays, β-rays
At least one selected from the group consisting of radiation, γ-ray, electron beam, neutron beam, and particle beam can be preferably used. X-rays and γ-rays are preferred from the viewpoint of efficiently emitting secondary electrons from the metal. When a radioactive waste is used as a radiation source, high value-added hydrogen can be efficiently produced by using the radioactive waste, so that the contribution of the present invention to the field of nuclear power and the like becomes enormous.
The irradiation dose of the radiation can be appropriately set according to the amount of water to be decomposed, the type and amount of metal, and the like.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments. (Example 1) 15 ml of distilled water was put in a stainless steel container, and each metal piece of lead, tantalum, molybdenum, nickel, and aluminum (one metal piece: 60 × 1 ×
0.2 mm) was sealed by inserting the mass shown in Table 1, and the gas in the container was sufficiently evacuated and evacuated. Thereafter, γ rays were irradiated for 1 hour at room temperature using a cobalt 60 irradiation apparatus (about 3.9 kGy / h). As a result, as shown in Table 1, hydrogen is generated only by distilled water, but the amount of generated hydrogen is larger when metal pieces are inserted. In addition, for each metal, the larger the mass of the metal (the number of atoms), the greater the amount of hydrogen generated.
There is a tendency for the amount of generated hydrogen to increase.

[0012]

[Table 1] Note) The amount of hydrogen generation in parentheses indicates a correction value obtained by measuring the amount of hydrogen absorbed in the metal.

(Example 2) In the same manner as in Example 1 above, 15 ml of distilled water was placed in a stainless steel container, and as shown in Table 2, predetermined amounts of tantalum and palladium were charged and sealed, respectively. Similarly, a vacuum was applied and gamma rays were irradiated for 1 hour (about 3.9 kGy / h). As a result, as shown in Table 2, when the hydrogen generation amount is measured in a state before correction,
In the case of tantalum, it was about 5 micromoles, and in the case of palladium, it was below the detection limit. However, when each metal piece was taken out and heated to 1000 ° C. under a high vacuum, the desorption of hydrogen from each metal piece was confirmed. In this way, when the amount of hydrogen accumulated in the metal is added and corrected, the amount of hydrogen generated for each metal is about 1
It was estimated to be 1.5 micromolar and about 10.5 micromolar. As described above, when the hydrogen storage metal coexists in water, only hydrogen generated by the decomposition of water can be selectively extracted, and the hydrogen production efficiency can be improved.

[0014]

[Table 2] Note) Ta data is the same as Table 1.

[0015]

As described above, according to the present invention,
Since radiation is used, not only a conventional transparent container such as glass but also an opaque container such as stainless steel can be used, which increases the degree of freedom in selecting a container. Also,
When radiation is applied in the presence of a metal, the irradiated metal generates secondary electron beams with high chemical efficiency, so it can decompose water more efficiently to generate hydrogen. it can. Further, by using a hydrogen storage metal or a hydrogen permeable membrane, generated hydrogen can be selectively extracted, and the hydrogen production efficiency can be further improved. In addition, when the metal is in the form of a plate, granules, or the like, an effect that collection and reuse of the metal and the coexisting material are facilitated can be obtained. INDUSTRIAL APPLICABILITY The present invention is advantageously used in an industrial field in which hydrogen production and development are advanced, such as an electric power industry, a gas industry, an automobile-related industry, and a chemical manufacturer. Further, the present invention can be effectively used in the field of nuclear power for treating radioactive waste such as nuclear fuel waste.

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Claims (5)

[Claims] 1. A method for producing hydrogen by decomposing water, the method comprising irradiating water with radiation to decompose water. 2. The method for producing hydrogen according to claim 1, wherein a metal is present in water, and the metal is irradiated with radiation. 3. The method according to claim 1, wherein the metal is at least one selected from the group consisting of iron, copper, aluminum, nickel, molybdenum, tungsten, lead, platinum, gold, tantalum, palladium, and rare earth elements. Claims 1-3
The hydrogen production method according to any one of the above. 4. The hydrogen production method according to claim 1, wherein the metal has a hydrogen absorbing property. 5. The radiation according to claim 1, wherein the radiation is at least one selected from the group consisting of X-rays, α-rays, β-rays, γ-rays, electron beams, neutron beams, and particle beams. 5. The method for producing hydrogen according to any one of 4.