JPS5938292B2 - Iron-titanium-carbon ternary hydrogen storage material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention stores a large amount of hydrogen at a predetermined temperature and hydrogen gas pressure, and can easily release hydrogen by slight heating or depressurization of hydrogen gas, or both. This invention relates to Tif'e-based hydrogen storage materials.

Hydrogen is expected to form the core of secondary energy in future clean energy systems, and the storage and transportation forms for hydrogen include high-pressure gas, liquid hydrogen, and solidification using metal hydrides.

Among these methods, methods using metal hydrides are attracting attention because of their safety and ease of handling. The reason for this is (1)
The hydrogen storage density per unit volume is high, more than 1000 times that of gaseous hydrogen, and comparable to that of liquid hydrogen (2
) Hydrogen storage does not require a high-pressure container, so there are no problems with pressure resistance or hydrogen embrittlement. (3) Metal hydrides are thermodynamically stable, so there is no loss due to evaporation like liquid hydrogen. Can be stored for a long time.

(4) The dissociation pressure of metal hydrides is almost constant, and if the dissociation temperature is determined, hydrogen gas at a constant pressure can be obtained. Therefore, a wide range of applications are being considered, including hydrogen storage containers using metal hydrides, fuel cells, and fuel cylinders for internal combustion engines, as well as hydrogen purification equipment, air conditioners, compressors, and refrigerators. It has many advantages over conventional ones in terms of improvement, simplification of the device, and improved characteristics. As described above, the solidification of hydrogen using metal hydrides is attracting attention as a form of hydrogen storage and transportation, but in order to be put to practical use as a hydrogen storage material, (1) it must be easy to activate; , (2) large amount of hydrogen that can be reversibly absorbed and released (hydrogen storage amount), (3) fast hydrogen absorption and release rate, and (4) formation equilibrium pressure and dissociation of metal hydrides near room temperature. The equilibrium pressure is several atmospheres, (5) there is little deterioration of alloy performance due to repeated absorption and release of hydrogen, (6) it is inexpensive,
Various hydrogen storage materials have been proposed.

Among these, the one currently closest to practical application in terms of hydrogen storage characteristics and alloy cost is US Patent No. 3516
The TiFe alloy No. 232 is mentioned, but it is difficult to activate this alloy because a strong surface film is formed by oxide film, nitride film, or impurities in hydrogen gas. After grinding, the alloy must be heated to 250-450° C. in hydrogen at several tens of atmospheres. Also, the equilibrium pressure for metal hydride formation at room temperature is quite high. Furthermore, as a method to increase the activation of TiFe and lower the equilibrium pressure for metal hydride formation, it is known to replace about 20% of iron with manganese, but this method This results in a disadvantage that the amount of hydrogen released increases and the amount of hydrogen released decreases.

An object of the present invention is to improve the above-mentioned drawbacks of the TiFe alloy and provide a practical hydrogen storage material. The inventors of the present invention have conducted various studies to improve the drawbacks of TiFe alloy and promote its practical use. As a result, we have developed TiFexCy, in which a part of the TiFe alloy is replaced with carbon and the atomic ratio of Fe to Ti is slightly reduced. alloy (where X and y are each Ti
The atomic ratio of Fe and C to 0.8≦X≦1.0 and o<y≦0.10) significantly improves the drawbacks of TiFe alloy and is extremely excellent as a hydrogen storage material, and y in the formula The formation of metal hydrides becomes easier as y
When y becomes about 0.10 or more, the amount of decomposed hydrogen at room temperature after metal hydride formation gradually decreases.
<y≦0.10' (preferably 0.02≦y≦0.06
) The present invention was completed by discovering that the hydrogen storage characteristics are the best in the range of

The present invention relates to a hydrogen storage material that reacts with hydrogen to form a metal hydride compound, wherein the hydrogen storage material has the general formula TiF
eC (where X and y are Fe and C for Ti, respectively)
At the atomic ratio of 0.8≦X≦1.0 and o<y≦0.10
) It consists of an iron-titanium-carbon ternary hydrogen storage material having a composition represented by:

When hydrogen is applied to the hydrogen storage material of the present invention, at room temperature, TiFe
<y≦0.10, 2 is the atomic ratio of H to Ti, approximately 2.
This is a new metal hydride that can be easily formed or decomposed by changing the hydrogen pressure near room temperature, and has a low hydrogen storage capacity per unit weight of the alloy. The amount is higher than that of TiFe alloy.

TiFeC alloy of the present invention (0.8≦X≦1.0, 0<y
≦0.10) is a new product developed by the present inventors for the first time. (1) A metal hydride is formed at room temperature without activation treatment in high temperature and high pressure hydrogen, and as The waiting time to form hydrides is shorter, (2)
The production equilibrium pressure and dissociation parallel pressure of metal hydrides at room temperature decrease as X decreases, (3) hydrogen absorption and desorption rates are fast, (4) performance does not deteriorate even after repeated hydrogen absorption and desorption (5) It has excellent properties as a hydrogen storage material, such as being relatively inexpensive.

The present invention will be explained in more detail below based on Examples.

Example TiFeC? ．． G4, Tlf' E6. glc? ．． 64
and TiFe alloy were melted by arc melting and then ground to 100 to 200 mesh in the atmosphere.

2g of each alloy in a stainless steel autoclave (inner volume 8c)
c) Purity 99.999 at room temperature after being sealed inside and evacuated.
99% hydrogen was introduced and the hydrogen pressure was maintained at 40 kg/d. FIG. 1 shows the change over time in the hydrogen absorption amount determined from the pressure drop in the autoclave at 20° C. in the TiFeCOO4 alloy and TiFe alloy held under pressure.

From this result, it is clear that samples containing C easily react with hydrogen to form metal hydrides at room temperature without activation treatment at high temperatures, and that the rate of reaction becomes faster as the amount of C increases. became. Next is TiFeC? ．． .

4 and Tif'EO. After repeating the operation of absorbing hydrogen at room temperature and exhausting the 91CO,O4 alloy 10 times, the hydrogen absorption and hydrogen release equilibrium curves of both alloys were determined.

Figure 2 shows some of the results, -01 and 1E are TiFeC6O4 alloy and TIF at 20C, respectively.
e? ,GICO. Figure 3 depicts the hydrogen release equilibrium pressure curve of the O4 alloy. From this result, it is clear that Fe relative to Ti in TiFeC-based alloys
As the atomic ratio of TtFeCO. . 4, 20 per gram of alloy
0CC (converted to standard hydrogen), whereas
TIFeO. g4CO,.

4, it was revealed that the amount increased to 220 CC (converted to hydrogen in standard state).

The hydrogen absorption equilibrium pressure also showed a similar tendency. In order to promote the practical application of hydrogen storage materials, the present inventors focused on the TiFe alloy, which currently has the shortest distance.
We have developed an iron-titanium-carbon ternary alloy that improves the drawbacks of Fe alloys.

As a result, the present invention has not only made the activation process significantly easier, but also improved the production equilibrium pressure and dissociation equilibrium pressure of metal hydrides near room temperature, as well as improved hydrogen storage capacity of 200 to 240 cc. It increased more than the TiFe alloy.
Using the solution according to the present invention, the amount of alloy required to store 7 Nm3 of hydrogen gas is 32 mm in weight and 5290 i in volume.

This results in a 10% alloy saving compared to the case of using a TiFe alloy, and has many advantages such as easier handling of the alloy due to simplified activation treatment, and easier hydrogen absorption due to lower hydrogen absorption equilibrium pressure. have

[Brief explanation of the drawing]

Figure 1 is a diagram showing the temporal change in hydrogen absorption amount of TiFecO, O+ alloy and Tif'e alloy,
O. It is a figure which shows the hydrogen release equilibrium pressure curve of O4 alloy and TiFeO, 9lcOO4 alloy.

Claims (1)

[Claims] 1. In a hydrogen storage material that reacts with hydrogen to form a metal hydride compound, the hydrogen storage material has the general formula TiFe_
xC_y (where x and y are respectively the atomic ratios of Fe and C to Ti, 0.8≦x≦100 and 0<y≦0.
10) Iron-
Titanium-carbon ternary hydrogen storage material.