JPH0634906B2 - Hydrogen separator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION “Industrial field of application” The present invention can be suitably used for recovery, purification, removal, etc. of hydrogen gas, and can also be used for hydrogen electrodes of fuel cells and primary and secondary batteries. It relates to the separating material.

“Problems to be Solved by Prior Art and Invention” In the semiconductor industry, as a method for selectively collecting and separating high-purity hydrogen gas, a low temperature adsorption method or P
The d film method or the like is used.

However, the low-temperature adsorption method has a problem that it requires liquid nitrogen and is therefore subject to the regulations of the High Pressure Gas Control Law, and that it requires the use of cryogenic technology in order to be implemented.

Further, the Pd film method has a problem that an expensive film needs to be used and the operating temperature is high.

In order to deal with such a problem, a hydrogen separation method has been proposed in which an inexpensive hydrogen storage alloy is used to selectively collect or separate hydrogen gas.

However, in the conventionally proposed hydrogen separation method, since the hydrogen storage alloy used is crystalline, it is pulverized during repeated storage and release of hydrogen. Therefore, there is a problem that it is necessary to take measures so that the finely divided hydrogen storage alloy is not released to the outside of the system.

As a solution to this problem, it has been proposed to use a hydrogen separating material having a thin film of a hydrogen storage alloy. However, since the thin film of the hydrogen storage alloy proposed above is crystalline, there is a problem that the thin film undergoes volume expansion at the time of hydrogen storage and peels from the substrate or causes pinholes.

Therefore, it was proposed to use amorphous hydrogen storage alloy by compression processing and use it as a hydrogen separating material, but this method makes the separating material porous and it is difficult to separate high-purity hydrogen gas. Met.

The present invention has been made in view of the above circumstances, and is a hydrogen separation material that can be suitably used for a hydrogen separation method using an inexpensive hydrogen storage alloy, and is a peeling or pinhole generation from a substrate of a hydrogen storage alloy thin film. The object is to provide a hydrogen separation material free from problems such as.

"Means for Solving the Problem" The hydrogen separating material according to claim 1 is a hydrogen separating material in which a thin film made of a hydrogen storage alloy is laminated on a surface of a porous substrate having small pores, and the thin film has the following general formula: It is formed by the hydrogen storage alloy shown in (1) and becomes an amorphous state by absorbing hydrogen, and the porous substrate has an underlayer made of a transition metal, a group IIIb element or glass on the surface. It is a thing.

RNi ₂ (1) In the hydrogen separation material according to claim 2, the thin film has the following general formula:
It consists of (2).

RNi ₂₋ xMx (2) (In the formulas (1) and (2), R represents a rare earth metal element, and M
Represents a transition metal or a group IIIb element, and x has a value of 2.0 or less. ) In formulas (1) and (2), R is not only a single rare earth metal element, but also a mixture of rare earth metals such as Misch metal (M
It may be an alloy of lanthanum (La) and cerium (Ce) known as m).

(2) In the formula, the transition metal element represented by M includes copper (Cu), zinc (Zn), cobalt (Co), iron (FE), molybdenum (Mo), palladium (P2), niobium (Nb), Tungsten (W), zirconium (Zr), vanadium (V), and the like, and aluminum (Al), boron (B), and the like as IIIb group elements can be mentioned, among which Cu, Co, and Al are preferably used. To be

The thickness of the thin film made of the hydrogen storage alloy represented by the formula (1) or (2) is preferably 50 μm or less. When the film thickness is set to 50 μm or less, the hydrogen permeation rate per unit area is improved.

The porous substrate supporting the thin film of hydrogen storage alloy,
When the average pore diameter is 1 μm or less, peeling of the hydrogen storage alloy thin film can be more reliably suppressed. Also, the porous substrate is
It is desirable that the pore size distribution is uniform, especially the pore size distribution is within ± 5% of the average pore size. Distribution ± 5%
If it exceeds the range, inconveniences such as pinholes are likely to occur.

As the porous substrate, a stainless steel filter, a ceramics filter such as alumina, or porous glass can be used. Among them, the porous glass is SiO ₂ : 7
5 to 99,9 wt%, Al ₂ O ₃ : 12 wt% or less, B ₂ O ₃ : 1
It is desirable to have a composition in the range of 2 wt% or less, Na ₂ O: 8 wt% or less, K ₂ O: 8 wt% or less, MgO: 8 wt% or less.

Further more SiO ₂ is _{large, Al 2 O 3, B 2} O 3, Na
It is preferable that many oxides such as ₂ O, K ₂ O and MgO exist. Such a porous glass has the above formula (1) or
Since it has a strong affinity with the hydrogen storage alloy represented by formula (2),
When this substrate is used, the adhesion between the substrate and the thin film is further improved, and peeling of the thin film can be surely suppressed.

An underlayer is formed on the surface of this porous substrate. The underlayer enhances the affinity between the hydrogen-absorbing alloy thin film and the substrate, relaxes the difference in the coefficient of thermal expansion between the substrate and the thin film in the operating temperature range, and causes the thin film to peel or pinholes to occur in the thin film. It is to prevent it. Such an underlayer is preferably formed of a transition metal, a Group IIIb element, or glass. For example, when the porous substrate is made of porous glass, the affinity between the hydrogen storage alloy thin film and the substrate can be further enhanced by forming the underlayer with soda glass or copper plating.

The underlayer is preferably formed in a range of 50% by weight or less of the entire porous substrate. If the amount of the underlayer exceeds 50% by weight of the entire porous substrate, the hydrogen permeation rate will be reduced.

The hydrogen storage alloy thin film of the hydrogen separation material according to claim 1 or 2 is a physical vapor deposition method (PVD method) such as a vacuum vapor deposition method, a sputtering method, an ion beam vapor deposition method, or an ion plating method.
It can be formed by a dry thin film forming technique such as a vapor deposition method (CVD method). In particular, when the thin film is formed by the PVD method, the composition of the hydrogen storage alloy can be easily controlled.

When the hydrogen storage alloy thin film is formed by these methods, the formed hydrogen storage alloy is in an amorphous state or C14, C
15 or C36 Laves structure crystalline state,
Once hydrogen is occluded, it becomes amorphous. Therefore, the hydrogen separating material according to the present invention is used in an amorphous state.

The hydrogen separation operation using the hydrogen separation material of the present invention is 10
It is desirable to be performed in a temperature range of 0 ° C to 300 ° C. When the operation is performed at a temperature higher than 300 ° C., the hydrogen storage alloy represented by the formulas (1) and (2) forming the thin film is crystallized, so that the thin film is peeled from the substrate or pinholes are formed in the thin film. There is a danger.

The pressure during the hydrogen separation operation mainly depends on the bending strength of the porous substrate, but is preferably set within the pressure range regulated by the high pressure gas control method.

Further, since the thin film made of the hydrogen storage alloy of the hydrogen separating material of the present invention is easily oxidized, it is desirable that the gas to be treated during the hydrogen separating operation has a small oxidizing gas component. Specifically, the oxidizing gas component contained in the gas to be treated is preferably 0.1% or less of the entire gas.

"Operation" The hydrogen separation process using the hydrogen separation material of the present invention is performed by supplying the hydrogen-containing gas to be processed to one side of the separation material. Among various molecules contained in the gas to be processed, only hydrogen molecules are dissociated on the surface of the hydrogen-absorbing alloy thin film. The dissociated hydrogen diffuses in the hydrogen-absorbing alloy thin film due to the pressure difference between the one side and the other side of the hydrogen separating material supplied with the gas to be processed, permeates through the film, and then the pores of the porous substrate. Pass through. As a result, hydrogen is separated and purified on the other side of the hydrogen separating material.

The thin film of the hydrogen separation material of the present invention is made of the hydrogen storage alloy represented by the general formula (1) or (2), and becomes an amorphous state by hydrogen storage, so that the volume fluctuation due to the change of the hydrogen content. Is extremely small, and cracks due to grain boundaries do not occur.

Therefore, the hydrogen separating material of the present invention suppresses the peeling of the thin film from the porous substrate and makes it difficult for pinholes to occur in the thin film.

Further, since the hydrogen separation material of the present invention has a thin film made of a hydrogen storage alloy laminated on a porous substrate, the thin film can be formed extremely thin. Therefore, according to the hydrogen separating material of the present invention, the hydrogen absorbing alloy thin film can be formed thin to improve the hydrogen permeation rate.

"Example" Hereinafter, the hydrogen separation material of the present invention will be described in detail with reference to Examples.

Example 1 A hydrogen separating material according to an example of the present invention was manufactured and subjected to a hydrogen pressure test and a hydrogen separation test.

As shown in FIG. 1, this hydrogen separating material is used for the porous substrate 1
The thin film 2 is laminated on one surface. The porous substrate 1 was a porous glass having a shirasu composition coated with an underlayer made of copper, and had an average pore diameter of 3000 Å. The pore size distribution of this porous glass was extremely sharp as shown in FIG. Other properties of this porous glass are summarized in Table 1.

The thin film 2 had a thickness of 5 μm, and the composition of the hydrogen storage alloy forming this thin film 2 was LaNi ₂ . This thin film 2
A part of the film was in a crystalline state with a C15 Laves structure, but once hydrogen was absorbed, it became a completely amorphous state.

This hydrogen separation material was manufactured as follows.

First, the porous glass to be the substrate 1 is washed with acetone, and C
u was electroless plated to form a base layer.

Then, this was set in a sputtering device to form a thin film 2. A split type target was used as the target. The division angle was 40 degrees for La and 50 degrees for Ni. Each of these 4 sheets was prepared and used as a bonding target. The sputtering conditions were as follows.

The X-ray diffraction result of the thin film 2 immediately after the film formation is shown in FIG.
FIG. 4 shows the X-ray diffraction results after hydrogen pressure treatment at 0 ° C. and 15 atm to absorb hydrogen. Comparing FIG. 3 and FIG. 4, it can be seen that although crystallinity (C15 Laves structure) is observed after film formation, it is completely in an amorphous state after hydrogen storage. It was also found that the crystallization temperature of the alloy forming the thin film 2 was around 350 ° C.

FIG. 5 shows the relationship between the hydrogen pressure and the hydrogen release amount of the alloy forming the thin film 2. FIG. 5 shows a typical tendency that the amorphous state shows, and since there is no plateau region, it was confirmed that the alloy forming the thin film 2 does not cause a rapid volume change.

The hydrogen separation material manufactured as described above was subjected to a hydrogen pressure test.
After exposure to a hydrogen gas atmosphere at 15 ° C. and 15 atm, this thin film 2 was examined by a scanning electron microscope (SEM).

As a result, no pinholes were observed in the hydrogen separating material after the hydrogen pressure test and no peeling between the thin film 2 and the substrate 1 was observed, and it was confirmed that the thin film 2 was kept in a healthy state. It was

The produced hydrogen separation material was attached to the separation device shown in FIG. 6 to perform a hydrogen separation treatment test. Reference numeral 3 in FIG. 6 is a hydrogen separating material. The hydrogen separating material 3 is fixed in the container 4 through O-rings 6 and 6 so as to divide the container 4 into two chambers. As a result, the to-be-processed gas supply chamber 7 is formed on the thin film 2 side of the hydrogen separation material, and the collection chamber 8 is formed on the substrate 1 side. A to-be-processed gas supply pipe 7 having an open / close valve 9 is connected to the to-be-processed gas supply chamber 7.
A purge flow rate adjusting valve 11 is connected to the valve. Further, the separation hydrogen collection chamber 8 has a lead-out pipe 14 equipped with a valve 13.
Are lined up.

The container 4 is housed in a constant temperature device 17 including a heater 15 and a heat insulating material 16. The temperature of the heater 15 is controlled by the temperature controller 18 according to the measurement result of the temperature sensor 19 inserted in the gas supply chamber 7.

He gas was supplied to the gas supply chamber 7 of this hydrogen separator to measure the amount of He gas leaking to the collection chamber 8 side.
It was 2.7 × 10 ⁻⁹ atm · cc / sec or less, and it was confirmed that the thin film 2 of the hydrogen separating material 3 had no pinholes.

Then, in the process gas supply chamber 7 of this hydrogen separator, A
Gas of r; 30 vol% and H ₂ ; 70 vol% was supplied. At this time, the atmosphere of the gas supply chamber 7 is 300 ° C. and 10 atm.
Was set to. As a result, 99,99 vol from the collection room 8
Hydrogen gas purified to a purity of% was obtained. At this time, the hydrogen permeation rate was 0.56 cm ³ / cm ² · sec.

From this result and the observation result after the hydrogen separation test, in this hydrogen separation material, the thin film 2 was firmly adhered to the substrate 1,
It was confirmed that there were no pinholes and that it could be used sufficiently as a hydrogen separation material.

(Comparative Example) LaNi _2.5 has the composition Co _2.5 and crystallinity of the hydrogen separation member which the thin film 2 is formed in the hydrogen storage alloy, manufactured in substantially the same manner as in Example 1, subjected to a hydrogen pressure test did. A split target was used as the sputtering target.
The division angle was La23 degrees, Ni48.5 degrees, and Co48.5 degrees, and these three sheets were laminated together.

As a result of a hydrogen pressure test, it was found that the thin film 2 peeled off from the substrate 1 when the hydrogen separating material was brought into contact with a hydrogen atmosphere.

(Example 2) A hydrogen separating material of Example 1 and a hydrogen storage alloy forming the thin film 2 were different from each other only in composition.

In this hydrogen separating material, the thin film 2 is made of a crystallizable hydrogen storage alloy having a composition of LaNi ₁ Co ₁ . A split-type target was used as the sputtering target during manufacturing. The division angle was 40 degrees for La, 25 degrees for Ni, and 25 degrees for Co.

When this hydrogen separating material was subjected to a hydrogen pressure test and a hydrogen separating test similar to those in Example 1, this hydrogen separating material also showed good adhesion between the substrate 1 and the thin film 2 as in Example 1. Since pinholes are unlikely to occur, it has been confirmed that the hydrogen separator can withstand sufficient use.

"Effects of the Invention" As described above, the hydrogen separating material according to claim 1 or 2 comprises: a porous substrate having an underlayer made of a transition metal, a Group IIIb element or glass formed on its surface; It is made of the hydrogen storage alloy represented by the general formula (1) or (2) and has a Laves structure of C14, C15 or C36 at the time of film formation or is in an amorphous state, and becomes amorphous by hydrogen absorption. Since the thin film is laminated on the porous substrate, the volume variation is small due to the change in the amount of hydrogen contained in the hydrogen storage alloy thin film, and cracks due to grain boundaries do not occur.

Therefore, the hydrogen separating material of the present invention suppresses the peeling of the thin film from the porous substrate and makes it difficult for pinholes to occur in the thin film.

Further, since the hydrogen separation material of the present invention has a thin film made of a hydrogen storage alloy laminated on a porous substrate, the thin film can be formed extremely thin. Therefore, according to the hydrogen separating material of the present invention, the thin film can be thinned to improve the hydrogen permeation rate.

Therefore, according to the hydrogen separation material of the present invention, it is possible to realize a hydrogen separation method using an inexpensive hydrogen storage alloy. Further, since the hydrogen separation material of the present invention uses a porous substrate having an underlayer made of a transition metal, a Group IIIb element or glass formed on the surface, the affinity between the substrate and the hydrogen storage alloy thin film is high. It is stronger and can reliably prevent peeling of the thin film.

Further, in the hydrogen separation material according to the third aspect, since the film thickness of the hydrogen storage alloy thin film is 50 μm or less, the hydrogen permeation rate per unit area is high.

In the hydrogen separating material according to the fourth aspect, since the average pore diameter of the porous substrate is 1 μm or less, the adhesion between the porous substrate and the hydrogen-absorbing alloy thin film is better. Therefore, with this hydrogen separation material, peeling of the hydrogen storage alloy thin film can be prevented more reliably.

The hydrogen separation material according to claim 5 has a pore size distribution of ± 5% of the average pore size.
Within the range of distribution, SiO ₂ : 75 to 99,
9 wt%, Al ₂ O ₃ : 12 wt% or less, B ₂ O ₃ : 12 wt% or less, Na ₂ O: 8 wt% or less, K ₂ O: 8 wt% or less, Mg
O: Since it is composed of a porous substrate having a composition in the range of 8 wt% or less, the affinity between the substrate and the hydrogen storage alloy thin film is extremely strong. Therefore, in this hydrogen separator, peeling of the thin film from the substrate can be reliably prevented.

When a physical vapor deposition method or a vapor deposition method is used as a method for forming the hydrogen storage alloy thin film of the hydrogen separating material of the present invention, it has a Laves structure of C14, C15 or C36 at the time of film formation, or is amorphous. In this state, it is possible to easily form a hydrogen-absorbing alloy thin film which becomes amorphous by hydrogen absorption.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the hydrogen separation material of the present invention,
FIG. 2 is a graph showing the pore size distribution of the porous glass forming the hydrogen separating material of the same example, and FIG. 3 is an X-ray diffraction analysis of the hydrogen separating material thin film of the hydrogen separating material of the same example immediately after film formation. Fig. 4 is a graph showing the results, Fig. 4 is a graph showing the X-ray diffraction results of the hydrogen storage alloy thin film examined after hydrogen pressure storage treatment, and Fig. 5 is a graph showing the hydrogen pressure and hydrogen release amount of the hydrogen storage alloy thin film. FIG. 6 is a graph showing the relationship, and FIG. 6 is a schematic configuration diagram of the apparatus used for the hydrogen separation test of the example. 1 ... Porous substrate, 2 ... Thin film, 3 ... Hydrogen separator

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Hazaka 4-320 Tsukagoshi, Sachi-ku, Kawasaki City, Kanagawa Prefecture Yasuyuki Yamada, Examiner, Nihon Oxygen Co., Ltd. (56) References JP 62-273030 (JP, A) ) JP-A-58-8510 (JP, A)

Claims (5)

[Claims] 1. A hydrogen separation material comprising a porous substrate having small holes and a hydrogen-absorbing alloy thin film laminated on the porous substrate, wherein the thin film comprises a hydrogen storage alloy represented by the following general formula (1): And a porous substrate having an underlayer made of a transition metal, a group IIIb element or glass formed on the surface thereof. RNi ₂ (1) (R in the formula (1) represents a rare earth metal element.) 2. A hydrogen separating material comprising a porous substrate having small pores and a hydrogen absorbing alloy thin film laminated on the porous substrate, wherein the thin film comprises a hydrogen storage alloy represented by the following general formula (2): And a porous substrate having an underlayer made of a transition metal, a group IIIb element or glass formed on the surface thereof. RNi ₂ -xMx (2) (In the formula (2), R represents a rare earth metal element, M represents a transition metal or a group IIIb element, and x has a value of 2.0 or less.) 3. The hydrogen separating material according to claim 1 or 2, wherein the thin film of the hydrogen storage alloy has a thickness of 50 μm or less. 4. The hydrogen separating material according to claim 1 or 2, wherein the porous substrate has an average pore diameter of 1 μm or less. 5. The pore size distribution of the porous substrate is within ± the average pore size.
The distribution range is within 5%, and the composition is SiO ₂ : 7
5 to 99.9 wt%, Al ₂ O ₃ : 12 wt% or less, B ₂ O ₃ :
The hydrogen separation material according to claim 3, wherein the hydrogen separation material is in the range of 12 wt% or less, Na ₂ O: 8 wt% or less, K ₂ O: 8 wt% or less, and MgO: 8 wt% or less.