JPH02271902A - Production of hydrogen separating medium - Google Patents

Abstract

PURPOSE:To easily and inexpensively obtain the hydrogen separating medium having an excellent hydrogen separating capacity by coating a porous base body with an inorg. material without closing the pores of the base body and then depositing a hydrogen occluding metal on the base body to form a hydrogen occluding thin film. CONSTITUTION:The porous base body such as a ceramic filter and prous glass is coated with an inorg. material without closing the pores of the base body. Concretely, an aq. metal silicate soln., a metal alkoxide soln., a metal acetylacetonate soln. or a metal carboxylate soln. are deposited on the base body, gelled and fixed to coat the inorg. material. A hydrogen occluding metal (e.g. LaNi5) is then deposited on the base body by sputtering, etc., to form a hydrogen occluding thin film, and the hydrogen separating medium appropriate for the recovery, refining, removal, etc., of gaseous hydrogen is obtained.

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] Low temperature adsorption method, Pd model film method, etc. are conventionally known 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.
Furthermore, 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 becomes pulverized due to repeated absorption and release of hydrogen, so there are disadvantages 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 heat is absorbed during release, complex 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 narrows the pore diameter of the substrate and reduces hydrogen permeability. In addition, especially when the surface is plated, the process becomes complicated, which increases the production cost, and there still remains the problem that it is difficult to remove moisture remaining on the substrate.

The present invention has been made in view of the above problems, and its purpose 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, a substrate made of a porous material is coated with an inorganic material without clogging the pores of the substrate, and then a hydrogen storage medium is coated on the substrate. The solution to the above problem was to deposit a hydrogen-absorbing thin film to form a hydrogen-absorbing thin film to obtain a hydrogen separation medium.

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. As the porous body, one made of a material with high heat resistance such as an SUS filter, a ceramic filter, or porous glass is preferably used, and one with an average pore diameter of 18 m or less is preferable, especially one with a uniform pore size distribution. Something is desirable.

Next, an inorganic material is coated on the surface of the substrate without blocking the pores of the substrate. Inorganic materials to be coated include S io , T io 21 Z ro
1Alt03. BaTiO3, LiNbO3, In
to-3nOL iA 102+ N atO-B 2
03-3 io and the like are preferred, and these may be further doped with a metal. When selecting an inorganic material for coating, it is best to use a material that has a coefficient of thermal expansion that is intermediate between the coefficient of thermal expansion of the substrate material used and the coefficient of thermal expansion of the hydrogen-absorbing metal described below. , is preferable in terms of improving the bondability between the substrate and the hydrogen storage metal. In addition, since it is necessary to avoid clogging the pores of the substrate during coating, it is preferable that the coating thickness be 50 μm or less, particularly 10 μm or less.
The following is desirable.

A specific method for coating with an inorganic material is, for example, applying one or more of a metal silicate aqueous solution, a metal alkoxide solution, a metal acetylacetonate solution, or a metal carboxylate solution to the substrate, and gelling and fixing the solution. A method of obtaining a coating film is adopted. Here, examples of the metal silicate aqueous solution include a cassium silicate aqueous solution and a sodium silicate aqueous solution.

As a method for attaching the solution, any method such as a spinner method, dipping method, spraying method, brush coating method, etc., or a method using a combination of these methods is adopted, and among them, the thickness of the coating film to be produced is determined. Since it is necessary to make the film thin, the spinner method and dipping method are preferably employed. In this case, the viscosity of the solution used is suitably adjusted in advance according to the above-mentioned deposition method so that the coating film has a desired thickness. and,
When the spinner method or dipping method is employed, the thickness of the resulting coating film is determined by the relationship between the rotation speed or pulling speed and the viscosity of the solution used.

In addition, in gelling the adhered solution and fixing it on the substrate, it is preferable to heat-treat the substrate at a temperature range of 50 to 1200°C, particularly 50 to 500°C.
It is preferable to perform the heat treatment at a temperature within the range of 100 to 100%, so that the average pore diameter of the pores does not change due to thermal expansion of the substrate.

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 n, , s, etc., 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 is
When adopting alloy groups such as , T iMn+, s,
Physical methods such as sputtering are 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, since the substrate is coated with an inorganic material, the resulting thin film of hydrogen-absorbing metal is firmly bonded to the substrate through the inorganic material. to be joined to.

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 crystalline alloys generally have less volumetric expansion of the lattice during hydrogen absorption, and are less likely to crack because they do not have grain boundaries.Also, the thickness of the thin film is determined by hydrogen storage alloys such as LaNi6+TiMn+, s, etc. When forming a film, the thickness is preferably 50 μm or less because the hydrogen permeation rate per unit area is improved.

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 100℃~500'
A temperature range of approximately 500°C is desirable, but if the operation is performed at a temperature of 500°C or higher, the pores of the porous substrate will become smaller due to thermal expansion of the substrate (this will increase the ventilation resistance, and furthermore, the heating cost will increase. In addition, the pressure at which the raw hydrogen gas is vented to 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.

"Operation" According to the method according to claim 1 of the present invention, a substrate made of a porous material is coated with an inorganic material without clogging the pores of the substrate, and then a hydrogen-absorbing metal is deposited on the substrate. Since the hydrogen separation medium is produced by forming a hydrogen-absorbing thin film, the production process is simplified, and since an inorganic material is coated on the substrate as a pre-treatment, the coating film can be used as a pre-treatment. The bonding strength of the hydrogen-absorbing metal to the substrate is improved, and the generation of pinholes in the obtained thin film is suppressed.

Further, according to the method of claim 2, when coating with the inorganic material, the coating thickness is set to 50 μm or less, so that clogging of the pores of the porous substrate is suppressed.

According to the method of claim 3, when footing an inorganic material, one or more of a metal silicate aqueous solution, a metal alkoxide solution, a metal acetylacetonate solution, or a metal carboxylate solution is deposited on the substrate, and then this is gelled. Because it is solidified and fixed, unlike when plating metal as a pretreatment, it does not clog the pores of the substrate.

According to the method of claim 4, in depositing one or more of metal silicate aqueous solution, metal alkoxide solution, metal acetylacetonate solution, or metal carboxylate solution on the substrate, spinner method, dipping method, spraying method, brushing method, etc. Since the solution is applied by one of the coating methods or a combination thereof, the thickness of the coating film can be adjusted as appropriate.

According to the method of claim 5, in gelling and immobilizing the solution adhered to the substrate, the substrate is heated to a temperature of 50 to 120
Since the heat treatment is performed at a temperature of 0° C., the solvent remaining on the substrate is sufficiently removed, and therefore, 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, 50nv×50m
A square plate-shaped porous glass having a thickness of 0.5n+n+ 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 washed with acetone. Separately, solutions were prepared to have the compositions shown in Table 1 below.

Table 1 Next, a solution having the composition shown in Table 1 (BaT io
3; 4, 28 wt%), and the substrate was coated with B aT io by a dipping method while changing the pulling speed.
After performing the surface treatment in step 3, vitrification treatment was performed by heating at 500° C. for 10 minutes. After the treatment, the thickness of the coating film on the obtained substrate was measured, and the results are shown in FIG.

Furthermore, the surface treatment by the dipping method was repeated in the same manner, and the results are also shown in FIG.

From the results shown in FIG. 1, it was found that as the pulling speed increases, the film thickness increases, and as the number of treatments increases, the film thickness becomes thicker.

Based on the above results, in this example, the pulling speed was 0 and 6.
The coating that had been coated three times at i+m/sec was used to perform the treatment described below. In addition, the nitrogen permeability of the substrate after three coating treatments was measured at room temperature.
When examined at a pressure of K g/cm"G, the permeability coefficient was 33.2 N cc/sec-cm!cmHg, which was almost the same value as the substrate before coating.

Thereafter, LaNi was deposited on the surface of the substrate using high frequency magnetron sputtering under the following conditions to form a thin film to 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: 50', and four sheets of each were prepared and pasted together in a disk shape to serve as a target.

Moreover, the sputtering conditions were as follows.

(1) Atmosphere 4XIO-3Torr (Ar) (
ii) Substrate drying 150℃ + 300se
c.

(iii) x Notching 150'C, 200L
30 seconds.

(1v) Press sputter 200W, 180
sec.

(v) Sputtering 100°C, 8001. 180
0sec.

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

Immediately after film formation, the hydrogen separation medium thus obtained was pressurized with hydrogen at 1-30°C + 15 atal, and the state after hydrogen absorption was analyzed by X-ray diffraction. It was confirmed that it was in a crystalline state.

Furthermore, when this hydrogen separation medium was pressurized with hydrogen at 300'0.15 atm and its state was observed using a scanning electron microscope, no pinholes were observed in the thin film. ) and the substrate remained in good condition with no peeling observed.

Next, the hydrogen separation medium obtained in this manner was loaded into the hydrogen separation apparatus shown in FIG. 2, and the amount of He') was measured. In FIG. 2, 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 l 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 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 inside the processing chamber 4. The space before and after the separation medium 2 was hermetically sealed off by the separation medium 2.

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. Note that during measurement, a temperature sensor 10 connected to a temperature controller 9 is used.
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. Further, the flow rate 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-”atIIl-cc/
It was confirmed that the produced thin film had no pinholes.

Next, the hydrogen separation medium was poured into the hydrogen separation apparatus shown in FIG.
%, Hy Near 0 vo 1% mixed raw material hydrogen gas 3
00'C.

A hydrogen separation ability test was conducted by aerating at 10 atm. 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 according to 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, and the results are shown in Table 2.

Table 2 From the results shown in Table 2, 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%, confirming that water has been almost completely removed. Ta. On the other hand, Cu electroless method.

The purified hydrogen obtained from the raw-treated sample has a higher dew point than the raw hydrogen gas, and it is therefore thought that water is mixed in the purified hydrogen, so it is inferred that more water is generated than in the sample. be done. In addition, the hydrogen permeation rate at this time is 0.56c shoulder 3/cxffi・se
It was c.

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 has been confirmed that the hydrogen separation medium according to the present invention is sufficient for use.

"Effects of the Invention" As explained below, the manufacturing method of claim 1 of the present invention involves coating a substrate made of a porous material with an inorganic material without clogging the pores of the substrate, and then Since the hydrogen separation medium is manufactured by depositing a hydrogen storage metal on the substrate to form a hydrogen storage thin film, the hydrogen separation medium can be manufactured through a simple process. Since it is inexpensive, the cost of refining hydrogen can be reduced by using it. In addition, since the inorganic material is coated as a pretreatment, the bonding strength of the hydrogen-absorbing metal to the substrate can be increased by interposing the coating film, and the resulting hydrogen separation medium expands in volume during hydrogen absorption. The peeling of the hydrogen-absorbing metal from the substrate due to this phenomenon 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 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, in the manufacturing method according to claim 2, when coating the inorganic material, the coating thickness is set to 50 μm or less, so that it is possible to prevent the pores of the porous substrate from being blocked.

In the manufacturing method of claim 3, when coating an inorganic material, one or more of a metal silicate aqueous solution, a metal alcokind solution, a metal acetylacetonate solution, or a metal carboxylate solution is adhered to the substrate, and then this is gelled. Since it is immobilized, the pores are not blocked unlike when metal is plated as a pre-treatment, and the hydrogen permeation ability of the resulting hydrogen separation medium is not reduced. It is fully exerted and has a high permeation rate.

The manufacturing method according to claim 4 includes a metal silicate aqueous solution in the substrate;
When depositing one or more of the metal alkoxide solution, metal acetylacetonate solution, or metal carboxylate solution, the solution is coated by a spinner method, a dipping method, a spraying method, a brush coating method, or a combination thereof. The thickness of the coating film can be adjusted as appropriate.

In the manufacturing method according to claim 5, when the solution adhered to the substrate is kelized and fixed, the substrate is heated to a temperature of 50 to 1200
Since the heat treatment is carried out at a temperature of 10°C, the solvent remaining on the substrate is sufficiently removed, and if the obtained hydrogen separation medium is used to purify hydrogen, there is no risk that moisture from the solvent etc. may remain in the separation medium. Highly purified hydrogen gas can be obtained because there is no hydrogen gas.

[Brief explanation of drawings]

Fig. 1 is a graph showing the relationship between the film thickness obtained by coating treatment and the processing conditions in one embodiment of the present invention, and Fig. 2 is a graph showing the relationship between the film thickness obtained by the coating process and the processing conditions, and Fig. 2 is a graph for investigating the hydrogen separation ability of the hydrogen separation medium obtained by the present invention. FIG. 2 is a diagram for explaining the test method of the present invention, and is a schematic configuration diagram of a hydrogen separation device. 1...Hydrogen separation device, 2...Hydrogen separation medium.

Claims (5)

[Claims] (1) A substrate made of a porous material is coated with an inorganic material without clogging the pores of the substrate, and then a hydrogen-absorbing metal is deposited on the substrate to form a hydrogen-absorbing thin film. A method for producing a hydrogen separation medium. (2) The method for producing a hydrogen separation medium according to claim 1, characterized in that when coating the inorganic material, the coating thickness is 50 μm or less. (3) In the method for producing a hydrogen separation medium according to claim 1, when coating the inorganic material, one or more of a metal silicate aqueous solution, a metal alkoxide solution, a metal acetylacetonate solution, or a metal carboxylate solution is attached to the substrate. , and then gelling and immobilizing it. A method for producing a hydrogen separation medium. (4) In the method for producing a hydrogen separation medium according to claim 3, when attaching one or more of metal silicate aqueous solution, metal alkoxide solution, metal acetylacetonate solution, or metal carboxylate solution to the substrate, spinner method or dipping method is used. A method for producing a hydrogen separation medium, characterized in that the solution is applied by any one of a spraying method, a brush coating method, or a combination thereof. (5) In the method for producing a hydrogen separation medium according to claim 3, in gelling and immobilizing the solution attached to the substrate, the substrate is heat-treated at a temperature of 50 to 1200°C. Method for producing separation media.