JPH02268817A - Production of hydrogen separating medium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method for producing a hydrogen separation medium used for recovery, purification, removal, etc. of hydrogen gas.

``Prior Art and Its Issues J'' Conventionally, low-temperature adsorption method and Pd patterning method are known as methods for selectively recovering or separating high-purity hydrogen gas.
These methods are mainly employed in the semiconductor industry. However, since the low-temperature adsorption method requires liquid nitrogen, it is subject to regulations under the High Pressure Gas Control Law and requires cryogenic technology.
Further, the Pd patterning method has disadvantages in that the film is expensive and the operating temperature is high. Therefore, both the low-temperature adsorption method and the Pd patterning method have major problems in device fabrication and operation, and also have the disadvantage of high device cost.

By the way, in view of this situation, a hydrogen separation method using an inexpensive hydrogen storage alloy has been proposed.

However, with this method, the hydrogen storage alloy is pulverized by repeated absorption and desorption of hydrogen, so there are inconveniences such as the need to take measures against particles to prevent the hydrogen storage alloy from leaving the system, and it also generates heat during storage. However, since it absorbs heat when released, complicated thermal operations are required, and the container structure must be able to withstand the stress caused by the volumetric expansion of the alloy, making it impractical.

Recently, as a solution to this problem, a hydrogen separation material has been proposed in which a hydrogen storage alloy is deposited on a porous substrate and the hydrogen storage alloy is made into a thin film. However, when a hydrogen storage alloy is directly deposited on a substrate, there is a drawback that the substrate and the alloy peel off due to the volumetric expansion of the alloy when hydrogen is stored. In order to solve this drawback, the substrate is subjected to surface treatment such as plating with a transition metal or a metal of Group MB of the periodic table to increase its affinity with the alloy.
Attempts have also been made to reduce the difference in thermal expansion coefficients. However, this method has the problem that the metal film attached to the surface of the substrate becomes thicker, which pinches the pore diameter of the substrate and lowers the hydrogen 1B overcapacity. Also, especially if the surface is plated, is it a process? fs
Problems still remain, such as high production costs due to the use of He, and furthermore, it is difficult to remove moisture remaining on the substrate.

The present invention was made in view of the above problems, and an object thereof is to provide a method for producing a hydrogen separation medium having excellent hydrogen permeability through simple steps.

In the method for producing a hydrogen separation medium of the present invention, an alkali metal or an alkaline earth metal is attached to a substrate made of a porous material, and then the substrate is heated to remove the inside of the surface layer of the substrate. The solution to the above problem is to obtain a hydrogen separation medium by diffusing the alkali metal or alkaline earth metal into a substrate and depositing a hydrogen storage metal on the substrate to form a hydrogen storage thin film.

Hereinafter, the method for producing the hydrogen separation medium of the present invention will be explained in detail.

First, a substrate (substrate) made of a porous material is prepared. The porous body is preferably made of a material with high heat resistance such as a SUS filter, a ceramic filter, or porous glass, and preferably has an average pore diameter of 1 μm or less, especially one with a uniform pore size distribution. something desirable.

Next, an alkali metal or an alkaline earth metal is attached to the surface of this substrate. The alkali metals or alkaline earth metals that adhere here include K, Na +
Car M g, etc. are used, among which K.

Na is more preferably used.

A specific method for attaching an alkali metal or alkaline earth metal to a substrate is to contact the substrate with a nitrate solution, hydroxide solution, halide solution, carbonate solution, or sulfate solution of the alkali metal or alkaline earth metal. Among these methods, it is preferable to use a nitrate solution, since there is no risk of thermal diffusion or residual impurities such as sulfate (desirable).

As a method for contacting the metal solution with the substrate, for example, a method is adopted in which the pH of the metal solution used is adjusted appropriately, and then the substrate is immersed in this solution for several minutes to perform a dipping treatment on the substrate surface.

Next, this substrate is heated to diffuse the previously deposited alkali metal or alkaline earth metal into the surface layer of the substrate. Here, when alkali metals or alkaline earth metals are attached using a metal salt solution as described above,
The substrate can be dried and then heated and diffused.

In this case, the drying/diffusion temperature is 50 to 1
A temperature range of 200'C is preferred, but especially 50,000
It is preferable to perform the following steps since there is no risk of damage to the substrate due to rapid heating. Further, after the substrate is brought into contact with the metal salt solution in this manner, the moisture in the hydrogen separation medium to be prepared can be effectively removed by drying the substrate before depositing the hydrogen-absorbing metal described below.

In addition, when performing diffusion treatment of alkali metals or alkaline earth metals on a substrate, repeating the treatment multiple times can strengthen the affinity between the substrate and the hydrogen-absorbing metal described later, and therefore hydrogen can be absorbed from the substrate. This is preferable because it can suppress the peeling of the storage metal.

Thereafter, a hydrogen-absorbing metal is deposited on the substrate to form a hydrogen-absorbing thin film to obtain a hydrogen separation medium.

Here, the hydrogen storage metal is a metal or alloy that reversibly stores or releases only hydrogen under certain conditions, and also permeates it. A typical example of such a metal is L aN i5. There is a group of alloys such as T iM 11 s, which are generally referred to as hydrogen storage alloys.

Further, metals such as P d , V 2 , and N b also have hydrogen storage properties, and are used together with the above alloys as the hydrogen storage metals of the present invention.

As a method for depositing the hydrogen-absorbing metal, either a physical method or a chemical method can be employed. As a physical method, a thermal evaporation method, a sputtering method, an ion blating method, etc. can be used, and as a chemical method, a plating method, a chemical vapor deposition method, etc. can be used. In addition, as a hydrogen storage metal, L aN 15
When using an alloy group such as + TiM n+ , 5, etc., a physical method such as a sputtering method is more suitable because the alloy composition can be easily controlled.

When a hydrogen-absorbing metal is deposited on a substrate by such a deposition method, the resulting thin film of hydrogen-absorbing metal contains a large amount of alkali metal or alkaline earth metal, since alkali metals or alkaline earth metals are present on the substrate. This provides a strong bond with the substrate.

The thin film deposited by such a physical or chemical method may be in an amorphous state or a crystalline state, but the amorphous state is more preferable. This is because, compared to crystalline alloys, amorphous alloys generally have less lattice volumetric expansion during hydrogen absorption, and are less likely to crack because they have no grain boundaries. Further, the thickness of the thin film is preferably 50 μm or less when forming a film of a hydrogen storage alloy such as [, 3N is+T IM n+ 5, etc., since this improves the hydrogen permeation rate per unit area.

In order to purify, for example, a raw material hydrogen gas containing impurities using the hydrogen separation medium obtained in this way, this raw material hydrogen gas is passed through the hydrogen separation medium at an appropriate pressure. Then, the hydrogen molecules in the raw material hydrogen gas dissociate as hydrogen atoms on the surface of the thin film made of the hydrogen-absorbing metal, and are separated from the raw material hydrogen gas by preferentially diffusing into the thin film. In this case, hydrogen atoms are diffused into the hydrogen storage metal due to the difference between the pressure of the raw hydrogen gas and the pressure of pure hydrogen gas in the raw hydrogen gas.

In addition, the operating temperature at this time is IOO'C ~ 500
A temperature range of approximately 500°C is preferable, but if the operation is performed at a temperature of 500°C or higher, the pores in the porous substrate will become smaller due to thermal expansion of the substrate (this will increase ventilation resistance and increase heating costs. In addition, the pressure at which the raw hydrogen gas is vented into the hydrogen separation medium is mainly determined by the bending strength of the substrate at the operating temperature, but according to the High Pressure Gas Control Law. It is desirable to operate below the pressure range.

In addition, when refining raw material hydrogen gas in this way, the purity of the raw material hydrogen gas used should preferably be low in oxidizing gas, considering the surface oxidation of the metal thin film for hydrogen separation in the hydrogen separation medium. is 0.1% in total
It is advantageous to use the following raw material hydrogen gas in terms of durability of the hydrogen separation medium.

"Function" According to the method according to claim 1 of the present invention, an alkali metal or an alkaline earth metal is attached to a substrate made of a porous material, and then the substrate is heated so that the alkali metal or alkaline metal is added to the surface layer of the substrate. Alternatively, the hydrogen separation medium is manufactured by diffusing an alkaline earth metal and then depositing a hydrogen storage metal on the substrate to form a hydrogen storage thin film, which simplifies the manufacturing process and pre-treatments. Since the alkali metal or alkaline earth metal is diffused into the surface layer of the substrate, the presence of this metal improves the bonding strength of the hydrogen storage metal to the substrate and prevents the formation of pinholes in the resulting thin film. suppressed.

Further, according to the method of claim 2, the adhesion of an alkali metal or alkaline earth metal to the substrate can be carried out using a nitrate solution, a hydroxide solution, a halide solution, or a carbonate solution of the alkali metal or alkaline earth metal. Since this is carried out by contacting with a solution or a sulfate solution, unlike when plating metal as a pretreatment, the pores of the substrate are not clogged.

According to the method according to claim 3, after the alkali metal or alkaline earth metal is attached to the substrate, a drying treatment and a diffusion treatment are performed at a temperature of 50 to 1200° C. prior to depositing the hydrogen storage metal on the substrate. Therefore, the solvent remaining on the substrate is sufficiently removed, and when hydrogen is purified using the obtained hydrogen separation medium, there is no possibility that the solvent will remain in the hydrogen.

“Examples” The manufacturing method of the present invention will be explained in more detail below with reference to Examples.

First, the substrate has a shirasu composition and has a size of 50 mm x 50 m.
A square plate-shaped porous glass with a thickness of 0 and 5 mm was prepared. Note that the average pore diameter of this porous glass is 300
There were 0 people.

Next, the prepared porous glass substrate was cleaned with acetone,
Thereafter, surface treatment was performed according to the operating procedures (1) to (3) shown below to diffuse sodium into the surface layer of the substrate.

(1) Immerse the substrate in a 10% sodium nitrate solution for 2 minutes.

(2) The substrate is pulled out of the solution and heated at a temperature of 500° C. for 1 hour to dry and diffuse sodium.

(3) Repeat steps (1) and (2) three times each to diffuse sodium into the surface layer of the substrate.

Next, using a high frequency magnetron sputtering method, LaN1t was deposited on the surface of the substrate under the following conditions to form a thin film and obtain a hydrogen separation medium.

Here, a split target was used as the sputtering target. The dividing angle of this split target is L
A: 40°, Ni: 5G°, and four sheets of each were prepared and pasted together into a disk shape to serve as a target. Moreover, the sputtering conditions were as follows.

(i) Atmosphere 4XlO-”Torr(Ar)(
11) Substrate drying 150℃, 300se
c.

(iii) Etching 150°C, 2001.
30 seconds.

(iv) Press sputter 2QOW, 180
sec.

(v) Sputtering 100°C, 8001f, 18
00sec.

The thin film obtained by sputtering under the above conditions had a thickness of 5 μm and a composition of LaN1t.

Immediately after film formation, the hydrogen separation medium thus obtained was pressurized with hydrogen at 130°C + 15 atm, and the state after hydrogen absorption was analyzed by X-ray diffraction. It has been confirmed that the condition is

Furthermore, when this hydrogen separation medium was pressurized with hydrogen at 300°C and 15 atm and its state was observed using a scanning electron microscope, no pinholes were observed in the thin film. No peeling from the substrate was observed and a good condition was maintained.

Next, the hydrogen separation medium obtained in this manner was loaded into the hydrogen separation apparatus shown in FIG. 1, and the amount of He'J was measured. In FIG. 1, reference numeral 1 indicates a hydrogen separation device, and 2 indicates a hydrogen separation medium obtained in the above embodiment.

To explain the measurement operation method, first, the hydrogen separation medium 2 is set in the processing chamber of the hydrogen separation apparatus 1 as shown in FIG. Here, the hydrogen separator 1 has an outer wall 3 made of a heat insulating material.
A processing chamber 4 is formed inside the processing chamber 4, and a heater 5 connected to a temperature controller to be described later is arranged between the outer wall 3 and the processing chamber 4. A gas supply pipe 6 and a gas exhaust pipe are arranged in the front and rear directions of the processing chamber 4, respectively. The pipe 7 is connected to the outside of the outer wall.

In addition, when setting the hydrogen separation medium 2, the thin film side made of a hydrogen-absorbing metal should be placed on the gas supply pipe 6 side, and the front and back of the separation medium 2 should be fixed with two O-rings 8', 8, and placed in the processing chamber 4. The space before and after the separation medium 2 in the separation medium 2
It was sealed off airtight.

Next, the processing chamber 4 is covered with a lid to make the processing chamber 4 airtight, and then a certain amount of He gas is supplied into the processing chamber 4 from the gas supply pipe 6, and the He gas from the gas exhaust pipe 7 is The amount of He leakage was investigated by measuring the amount of discharge. In addition, when measuring, the temperature sensor 1 connected to the temperature controller 9
0 was inserted into the gas supply pipe 6 in advance, and the temperature controller 10 controlled the heater 5 based on the gas temperature detected by the temperature sensor 9 to keep the temperature of the supplied gas constant. Also,
The total amount of the supply gas supplied into the processing chamber 4 was kept constant by letting a part of the supply gas escape to the bypass pipe 11 connected to the gas supply pipe 6.

When the leakage amount of He gas was investigated in this way, the leakage amount was 2, OX 10-”atm-cc/se
c or less, and it was confirmed that there were no pinholes in the produced thin film.

Next, using the hydrogen separation apparatus shown in FIG. 1, the hydrogen separation medium was set therein, and Ar: 30 vol.
, H2 near 0 vo1% mixed raw material hydrogen gas 30
A hydrogen separation ability test was conducted by aerating at 0° C. and 11 Oat.

As a result, the mixed raw material hydrogen gas was purified to hydrogen with a purity of 99.99 vol%, and it was confirmed that the hydrogen separation medium obtained by the present invention has a high hydrogen gas separation ability.

In addition, C
The above-mentioned hydrogen separation ability test was conducted using a sample in which a hydrogen-absorbing alloy membrane was prepared under the same conditions as in the example. Hydrogen was purified under the same conditions, and the dew point of the obtained purified hydrogen was measured. The results are shown in Table 1.

From the results shown in Table 1, it is confirmed that the hydrogen purified by the sample of the present invention has a lower dew point than the raw material hydrogen gas with a purity of 99.99%, and that water is almost completely removed. Ta. On the other hand, purified hydrogen obtained from a sample subjected to electroless plating of Cu has a higher dew point than the raw hydrogen gas, and therefore it is thought that water is mixed in the purified hydrogen. It is assumed that this is occurring. Note that the hydrogen permeation rate at this time was Q, 56 cm37c1-sec.

From the above results, it was found that in the hydrogen separation medium obtained by the manufacturing method of the present invention, water is almost completely removed, which means that the peeling of the hydrogen storage alloy from the substrate is suppressed. It was confirmed that the hydrogen separation medium according to the present invention is sufficiently usable.

"Effects of the Invention" As explained above, the manufacturing method according to claim 1 of the present invention involves depositing an alkali metal or alkaline earth metal on a porous substrate, and then heating the substrate. Since the hydrogen separation medium is produced by diffusing the alkali metal or alkaline earth metal into the surface layer of the substrate and then depositing a hydrogen-absorbing metal on the substrate to form a hydrogen-absorbing thin film, Since the hydrogen separation medium can be produced through a simple process and the hydrogen separation medium is therefore inexpensive, the hydrogen purification cost can be reduced by using this medium. In addition, since an alkali metal or alkaline earth metal is diffused into the surface layer of the substrate as a pretreatment, the presence of the metal can increase the bonding strength of the hydrogen-absorbing metal to the substrate. The separation medium is one in which peeling of the hydrogen-absorbing metal from the substrate due to volume expansion during hydrogen absorption is suppressed. Furthermore, by increasing the bonding strength of the hydrogen-absorbing metal to the substrate, the generation of pinholes in the obtained hydrogen-absorbing metal thin film is suppressed, and therefore a hydrogen separation medium with high hydrogen separation ability can be obtained. . In addition, since it is possible to form a uniform thin film without pinholes, the thickness of the thin film can be made thinner than that of conventional ones. Therefore, the hydrogen separation medium itself can be made compact.

Furthermore, since the hydrogen separation medium obtained by this production method can store hydrogen without the hydrogen storage metal peeling off, it can be used as a hydrogen electrode in fuel cells and primary and secondary batteries. can.

Further, the manufacturing method according to claim 2 provides a method for attaching an alkali metal or alkaline earth metal to a substrate by applying an alkali metal or alkaline earth metal nitrate solution, hydroxide solution, halide solution, carbonate solution or Because it is carried out by contacting with a sulfate solution, unlike when plating metal as a pretreatment, the pores of the substrate are not clogged, and the resulting hydrogen separation medium does not have a decrease in hydrogen permeation ability. , the characteristics of the hydrogen separation medium are fully exhibited, resulting in a high permeation rate.

In the manufacturing method according to claim 3, after adhering an alkali metal or alkaline earth metal to a substrate, a drying treatment and a diffusion treatment are performed at a temperature of 50 to 1200° C. prior to depositing a hydrogen storage metal on the substrate. Therefore, if the solvent remaining on the substrate is sufficiently removed and the resulting hydrogen separation medium is used to purify hydrogen, there is no risk of water from the solvent remaining in the separation medium, so high purity precision can be achieved. It is possible to obtain dihydrogen gas.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining a test method for determining the hydrogen separation ability of a hydrogen separation medium obtained according to the present invention, and is a schematic diagram of a hydrogen separation apparatus. 1...Hydrogen separation device, 2...Hydrogen separation medium.

Claims (3)

[Claims] (1) An alkali metal or alkaline earth metal is attached to a substrate made of a porous material, and then this substrate is heated to diffuse the alkali metal or alkaline earth metal into the surface layer of the substrate. 1. A method for producing a hydrogen separation medium, comprising depositing a hydrogen-absorbing metal on a hydrogen-absorbing metal to form a hydrogen-absorbing thin film. (2) In the method for producing a hydrogen separation medium according to claim 1, the adhesion of an alkali metal or alkaline earth metal to the substrate is performed by applying an alkali metal or alkaline earth metal nitrate solution, hydroxide solution, or halide to the substrate. 1. A method for producing a hydrogen separation medium, which is carried out by contacting a solution, a carbonate solution, or a sulfate solution. (3) In the method for producing a hydrogen separation medium according to claim 2, after adhering the alkali metal or alkaline earth metal to the substrate, and before depositing the hydrogen storage metal on the substrate, the temperature is set at 50 to 1200°C. 1. A method for producing a hydrogen separation medium, comprising drying and diffusion treatment.