JP2808914B2 - Hydrogen gas production method and hydrogen isotope analysis method using microcrystalline metal zinc - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing hydrogen gas as a sample in a hydrogen isotope ratio analysis method in which water is reduced and the resulting hydrogen gas is used as a sample.

[0002]

2. Description of the Related Art In general, when the concentration of deuterium contained in water is known, the water is reduced, the hydrogen contained in the water is completely gasified, and the hydrogen gas is used as a sample for stable isotope analysis. A method has been adopted in which hydrogen isotope analysis is performed by a mass spectrometer and the deuterium concentration is calculated from the results.

As a method for reducing water to generate hydrogen gas, a method using depleted uranium or zinc has been known. In the former, the hydrogen gasified by passing sample water through depleted uranium at a certain temperature is recovered using a Tepler pump, and is called a uranium reduction method. On the other hand, the latter is a method in which water is reacted with metallic zinc under high-temperature vacuum to gasify hydrogen, and is called a zinc reduction method.

[0004] According to each of the above methods, hydrogen contained in the sample water is completely gasified. Therefore, the deuterium concentration of the sample water can be known by analyzing the isotope ratio of hydrogen using the generated hydrogen gas as a sample.

[0005]

However, among the above methods, in the uranium reduction method, it is difficult to obtain depleted uranium, it takes time to recover the generated hydrogen gas, and the isotope ratio is different. When water is continuously passed through depleted uranium, there is a problem that the analysis accuracy is reduced due to the influence of the previous sample. On the other hand, in the zinc reduction method, there is a problem that hydrogen contained in the sample water cannot be completely gasified unless specific properties of metal zinc used in the reaction are used.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a hydrogen gas producing method in which water is reduced by reacting water with metallic zinc under a high temperature vacuum to generate hydrogen gas. It is set to 5 μm or less.

[0007] Metal zinc particles are usually granulated by heating and dissolving zinc at least at a temperature equal to or higher than its melting point, followed by dropping into water and cooling and solidifying by using other methods. In the present invention, when dissolving zinc in the above step, by adding nickel at a concentration of 10 ppm to 10000 ppm with respect to zinc, the crystal grain size of zinc constituting metal zinc grains is reduced from the usual 20 μm to 50 μm to 5 μm. It can be refined to the following. Also, in this case, the particle diameter of the metal zinc particles is suitably about 1 mm to 2 mm.

Here, the substance added to the metallic zinc grains in order to make the crystal grain size of zinc 5 μm or less is not particularly limited to nickel. It can be arbitrarily selected from substances having an effect of reducing the diameter and not hindering the reduction of water by the metal zinc particles.

Further, the crystal condition of zinc is suppressed by rapidly changing the temperature conditions at the time of granulating the metallic zinc, such as by dripping dissolved zinc into liquid nitrogen or other cryogenic liquid and rapidly cooling the same. The grain size of zinc should be 5 μm or less,
By the above-mentioned quenching and other operations, the fine structure of the zinc metal particles is changed to a thin layer or a porous material having a high porosity, and the crystal grain size of the zinc is reduced to 5 μm or less. it can.

On the other hand, metallic zinc may be formed into a fine powder having a diameter of 5 μm or less by spray granulation, pulverization, or a combination thereof. Further, it is of course possible to use a plurality of the above operations in combination.

When zinc metal having a microcrystalline structure having a particle diameter of 5 μm or less prepared by each of the above means and a sample water are reacted under a high temperature vacuum, the sample water is all reduced, and zinc oxide and hydrogen gas are converted. Generated. That is, by using the metal zinc, hydrogen contained in the sample water can be completely gasified. Therefore, if the hydrogen gas generated as a result of the above reaction is used as a sample, a hydrogen isotope ratio analysis by a stable isotope mass spectrometer can be performed.

In the above-described hydrogen gas production method, the reaction temperature between water and metallic zinc particles is about 42 which is the melting point of zinc.
The temperature is set to 0 ° C. or lower and as high as possible according to the particle size of the metal zinc particles used in the reaction. The reaction time is standard for 2 to 3 hours, but when the reaction temperature is lower, the reaction time needs to be extended accordingly.

[0013]

EXAMPLES Next, the effects of the present invention will be described with reference to examples. In the production process of metal zinc particles, 0 ppm, 6 ppm, 15 ppm, and 400 p
Nickel is added at a concentration of pm, and the crystal grain size is 40 μm,
Four types of metal zinc particles of μm, 5 μm, and 1 μm were prepared. Here, all of the metal zinc particles had a particle diameter of 2 mm.

Further, using these metallic zinc particles, hydrogen gas was produced from the same sample water by the following methods, and the hydrogen gas was used as a sample to measure the gasification rate of hydrogen contained in the sample water.

(1) About 1 g of metallic zinc particles 2 are put into a glass reaction tube 1 having a greaseless stopcock 4 as shown in FIG. And heated at about 250 ° C.
Removes moisture adsorbed on (2) After adding 5 μl of sample water using a fine pipette, freeze the sample water with liquid nitrogen. (3) After exhausting the air in the reaction tube 1 from the suction unit 3, the stop cock 4 is closed and the reaction tube 1 is kept in a vacuum state.
Heating is performed for 2 to 4 hours using a heater maintained at 420 ° C., and hydrogen is generated by reducing sample water with zinc.

The results are shown in Table 1. The crystal grain size of zinc in each of the metal zinc particles was measured with a reflection microscope, and the gasification rate was represented by the gasification rate (%) of hydrogen in the sample water 4 hours after the start of the reaction.

[0017]

[Table 1]

As shown in Table 1, in the production of hydrogen gas by the above method, 100% of the hydrogen in the sample water was gasified because the crystal grain size of zinc constituting the metal zinc grains was 5 μm.
The case was as follows. As a result of various studies, the crystal grain size of zinc in the metal zinc grains was 5 μm or less when nickel was added in the range of 10 ppm to 10000 ppm.

As a result, when metal zinc particles having a crystal grain size of 5 μm or less are used as a sample and hydrogen gas obtained by the above method is used as a sample, the sample water obtained by the mass spectrometer for stable isotope analysis is used. Was available for hydrogen isotope analysis. Further, the deuterium concentration of the sample water could be calculated from the analysis result.

[0020]

As described above, in the present invention, zinc metal grains having a crystal grain size of 5 μm or less are prepared,
The sample zinc was reacted with the sample water under a high-temperature vacuum to reduce the sample water and generate hydrogen gas. As a result, hydrogen contained in the sample water was completely gasified. Therefore, hydrogen isotope ratio analysis by a stable isotope mass spectrometer using the resulting hydrogen gas as a sample has become possible.

[Brief description of the drawings]

FIG. 1 is a side view of a reaction tube used for hydrogen generation by a zinc reduction method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reaction tube 2 Metal zinc particles 3 Suction unit 4 Stopcock

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C01B 3/08 C01B 4/00 G01N 31/00

Claims (2)

(57) [Claims] 1. A method for producing hydrogen gas by reducing water by reacting water with metallic zinc under high-temperature vacuum to produce hydrogen gas, characterized in that the crystal grain size of metallic zinc used in the reaction is 5 μm or less. Hydrogen gas production method. 2. A hydrogen isotope analysis method for water using the hydrogen gas production method according to claim 1.