JP2012223754A - Hydrogen separation membrane and manufacturing method therefor, and hydrogen manufacturing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrogen separation membrane in which a middle layer for preventing the mutual diffusion between a base metallic layer and a coated metallic layer, and the oxidation of alloy components of the base metallic layer is formed at low cost, a manufacturing method therefor, and a hydrogen manufacturing apparatus provided therewith.SOLUTION: The hydrogen separation membrane 11 includes the base metallic layer 12 composed of a group 5A metal or its alloy, the middle layer 13 formed on the surface of the base metallic layer 12 and the coated metallic layer 14 formed on the middle layer 13; and the middle layer 13 is formed by anodic oxidation of the base metallic layer 12. The manufacturing method for the hydrogen separation membrane 11 has a step of forming the middle layer 13 by anodic oxidation of the base metallic layer 12 and a step of forming the coated metallic layer 14 on the middle layer 13, and the hydrogen manufacturing apparatus has the hydrogen separation membrane 11.

Description

  The present invention relates to a hydrogen separation membrane, and more particularly to a hydrogen separation membrane having a base metal layer, an intermediate layer, and a covering metal layer. Moreover, this invention relates to the manufacturing method of this hydrogen separation membrane, and the hydrogen production apparatus using this hydrogen separation membrane.

  There is a Pd-based alloy as a hydrogen separation membrane that selectively permeates and separates hydrogen from a hydrogen-containing gas. However, in the case of a hydrogen separation membrane of a Pd-based alloy, even when rare earth elements having a large performance improvement effect such as Y and Gd are added, the hydrogen separation performance is improved only 2 to 3 times, and Pd itself is a noble metal. There is a disadvantage of high costs.

  As a substitute for the Pd-based alloy film, a film made of Nb, V or an alloy thereof is known. Group 5A metals such as Nb and V have high hydrogen permeation performance and are inexpensive compared to Pd-based hydrogen permeation alloys. Since this Nb, V or an alloy thereof is susceptible to hydrogen embrittlement due to its high hydrogen solid solution amount, various studies have been made on hydrogen separation membranes capable of achieving both high hydrogen permeation rate and hydrogen embrittlement resistance. .

  When a group 5A metal or an alloy thereof is used as the base metal layer of the hydrogen separation membrane, the group 5A metal alloy itself has no catalytic activity for hydrogen molecule dissociation and bonding reaction, so Then, a surface catalyst layer (coating metal layer) made of Pd or a Pd alloy is formed on both surfaces (both the process side and the transmission side) of the base metal layer. This covering metal layer is usually formed very thin to about several hundred nm so as not to deteriorate the hydrogen permeation performance of the base metal layer.

  In the hydrogen separation membrane having such a coated metal layer, mutual diffusion between the base metal layer and the coated metal layer, and alloy components of the base metal layer by oxygen permeating the coated metal layer (hereinafter referred to as a base alloy) Oxidation of the component may lower the hydrogen permeation performance and durability of the hydrogen separation membrane. It is also conceivable that the base alloy component diffuses in the coated metal layer and reaches the surface or near the surface and is oxidized to become an oxide, thereby inhibiting the dissociation of hydrogen molecules and the binding reaction. For this reason, it is known to provide an intermediate layer between the base metal layer and the covering metal layer for preventing mutual diffusion of metals and preventing diffusion of oxygen (Patent Documents 1 to 4). Examples of such intermediate layers are as follows.

A SiO ₂ intermediate layer formed by immersing a metal chloride layer such as SiCl _{4 on} the surface of a base metal layer by a dipping method or the like and hydrolyzing with moisture in the atmosphere (Patent Document 1). An oxide, carbide, or boride layer of WO ₃ , SiO ₂ , ZrO ₂ or the like formed by sputtering (Patent Document 2). 5A group metal or alloy layer such as Ta, Nb, Ta-V, Ta-Pd, etc. formed by liquid phase plating, PVD, CVD, etc. on a base metal layer made of V or V alloy (Patent Documents 3 and 4) ).

JP-A-7-185277 JP 2006-272167 A JP 2006-35063 A JP2007-44593

  In the method of forming an intermediate layer by hydrolysis of a metal chloride layer as in Patent Document 1, it is not easy to form a dense intermediate layer having a desired thickness. There is also concern about the adverse effects of residual chlorine components.

  In the method of forming an intermediate layer by sputtering described in Patent Document 2, the apparatus becomes large and the processing cost including the equipment cost becomes high.

  As in Patent Documents 3 and 4, the method of forming an intermediate layer made of a group 5A metal or alloy by liquid phase plating, PVD, CVD, or the like requires a group 5A metal or alloy material for the plating solution, PVD, or CVD apparatus. Cost increases. In addition, PVD and CVD increase the equipment cost.

  The present invention relates to a hydrogen separation membrane in which an intermediate layer for preventing mutual diffusion between a base metal layer and a coated metal layer and oxidation of an alloy component of the base metal layer is formed at low cost, and a method for manufacturing the same. And it aims at providing the hydrogen production apparatus provided with this hydrogen separation membrane.

  The hydrogen separation membrane of the present invention (Claim 1) includes a base metal layer made of a group 5A metal or an alloy thereof, an intermediate layer formed on the surface of the base metal layer, and a coated metal formed on the intermediate layer In the hydrogen separation membrane having a layer, the intermediate layer is formed by anodizing the base metal layer (the surface is oxidized by applying a voltage in water or a solution with the base metal layer serving as an anode to energize the surface). It is characterized by this.

  The hydrogen separation membrane according to claim 2 is characterized in that, in claim 1, the base metal layer is made of Nb, Nb alloy, Ta, Ta alloy, V or V alloy.

  A hydrogen separation membrane according to a third aspect is characterized in that, in the first or second aspect, the coating metal layer is made of Pd or a Pd alloy.

  The method for producing a hydrogen separation membrane of the present invention (Claim 4) includes a base metal layer made of a group 5A metal or an alloy thereof, an intermediate layer formed on the surface of the base metal layer, and an intermediate layer formed on the intermediate layer. The method for producing a hydrogen separation membrane having a coated metal layer includes the steps of anodizing a base metal layer to form the intermediate layer, and forming the coated metal layer on the intermediate layer. It is a feature.

  The hydrogen production apparatus of the present invention (Claim 5) is a hydrogen production apparatus having a primary chamber and a secondary chamber separated by a hydrogen separation membrane, wherein the hydrogen separation membrane is any one of Claims 1 to 3. It is a hydrogen separation membrane as described in above.

  In the present invention, since the intermediate layer is formed by a simple method of anodizing the base metal layer, the equipment cost for forming the intermediate layer is also low, and the intermediate layer can be formed easily and inexpensively. In addition, the intermediate layer formed by anodization is dense, and even if the thickness of the intermediate layer is small, mutual diffusion between the base metal layer and the coated metal layer and the oxidation of the alloy components of the base metal layer are sufficiently prevented. Is done. Therefore, the hydrogen separation membrane and the hydrogen production apparatus having the intermediate layer formed by this method have almost no deterioration in hydrogen permeation performance and good durability as compared with the case without the intermediate layer.

It is a typical sectional view of a hydrogen separation membrane. It is a graph which shows the result of an Example and a comparative example. It is a graph which shows the result of an Example and a comparative example. It is a graph which shows the result of an Example and a comparative example. It is a graph which shows the result of an Example and a comparative example. It is a block diagram of a hydrogen separator. It is sectional drawing of the module for hydrogen permeation tests. It is sectional drawing which shows the form which set the module for hydrogen permeation tests to the electric furnace.

  Hereinafter, the present invention will be described in more detail. In the present invention, as shown in FIG. 1, the intermediate layer 13 between the base metal layer 12 and the covering metal layer 14 of the hydrogen separation membrane 11 is formed by anodic oxidation of the base metal layer 11.

[Base metal layer]
In the present invention, a 5A group metal, that is, Nb, V, Ta, or an alloy thereof is used as the base metal layer, and specifically, pure Nb, Nb alloy, pure Ta, Ta alloy, pure V, V alloy is preferable. . An example of the Nb alloy is an Nb alloy containing 15 mol% or less of at least one of W, Mo, and Ru. Examples of the Ta alloy include a Ta alloy containing 15 mol% or less of at least one of W and Mo. Examples of the V alloy include a V alloy containing 15 mol% or less of at least one of W and Mo. Specifically, these alloys include Nb—W alloys (W content 0.01 to 15 mol%), Nb—W—Mo alloys (W content 0.01 to 15 mol%, Mo content 0). .01-15 mol%), Nb-Ru alloy (Ru content 0.01-15 mol%), Ta-W alloy (W content 0.01-15 mol%), VW alloy (W content) 0.01-15 mol%), V-Mo alloys (Mo content 0.01-15 mol%) and the like are exemplified, but not limited thereto.

  The thickness of the base metal layer is preferably about 1 to 500 μm, particularly about 10 to 50 μm, but is not limited thereto.

[anodization]
Anodization or anodization is a technique in which a thin oxide film is formed on a metal surface by applying a voltage to a cathode in water or a solution in the presence of a target metal as an anode.

  To anodize the above base metal layer, immerse the base metal layer in water or an electrolyte solution to make it the anode, apply a voltage between the cathode and energize, and oxidize both sides of the base metal layer It is preferable to process.

  Examples of the electrolyte include aqueous solutions containing at least one of hydrochloric acid, sulfuric acid, hydrofluoric acid, sodium sulfate, and the like. Among these, a sulfuric acid aqueous solution is preferable. Nb, Nb alloy or Ta, Ta alloy can be anodized even with water having a low specific resistance (high electrical conductivity) (specific resistance: about 0.25 to 100 Ω · m). If the concentration of the electrolyte solution is Nb and Ta and the anode potential, an oxide film can be formed in the entire pH range. In addition, as for V and V alloys, potential-pH diagrams (also referred to as corrosion diagrams or Pourbaix diagrams) (M. A similar surface treatment can be realized in the passive region due to formation.

  The pH of the anodizing bath made of this electrolyte solution is preferably 5 or less, particularly 1 or less. The bath temperature is preferably about 1 to 30 ° C, particularly about 15 to 25 ° C.

  As the cathode, stainless steel such as SUS340 or SUS316, platinum, or the like can be used.

The applied voltage for the anodizing treatment is preferably 10 to 160 V, preferably about 30 to 50 V for Nb and Nb alloys, and about 60 to 80 V for Ta and Ta alloys. The current density is preferably about 0.1 to 1 A / dm ^2, particularly about 0.2 to 0.6 A / dm ² . The anodizing time is selected so as to reach a saturated state where the current becomes zero at a constant voltage on the surface of the base metal layer, that is, so that the anodized layer is uniformly formed on the base metal layer. Although it is preferable, it is usually about 0.3 to 2 hours.

[Coated metal layer]
As the coating metal layer, pure Pd or Pd—Ag alloy is suitable, and in particular, Pd—Ag alloy or pure Pd having an Ag content of 30 mol% or less (especially 10 to 30 mol%) is suitable. The thickness of the coating metal layer is preferably about 10 to 600 nm, particularly about 100 to 300 nm. This covering metal layer can be formed by sputtering, vacuum deposition, CVD (chemical vapor deposition) or the like.

[Hydrogen production equipment]
As a hydrogen production apparatus equipped with a hydrogen separation membrane, the hydrogen separation membrane is installed in a container called a housing, casing, vessel or the like, and has a primary chamber and a secondary chamber separated by a hydrogen separation membrane. The structure is not particularly limited as long as it further has heating means as required. The form of the film may be any form such as a flat film type and a cylindrical type. The hydrogen separation membrane may be superimposed on a porous support or a support plate having a groove on the surface, or may be formed on the surface of the porous body. As a porous body, any of a metal material, a ceramic material, etc. may be sufficient.

  The raw material gas supplied to this hydrogen production apparatus may be any gas that contains hydrogen, such as a hydrocarbon steam reformed gas, a fuel cell off-gas, a biogas containing hydrogen, and a gas generated from a biomass gasification furnace. However, the present invention is not limited to this.

  The operating temperature of the device (specifically, the gas temperature on the primary side) is usually about 300 to 600 ° C., particularly about 400 to 550 ° C., although it depends on the composition of the film.

  In the present invention, the configuration and structure of the hydrogen production apparatus are not particularly limited, but examples of the configuration of the hydrogen production apparatus that can be employed in the present invention are shown in FIGS. 6 (a), 6 (b), and 6 (c). ).

  In FIG. 6A, a raw material gas such as hydrocarbon is compressed by the compressor 21 and supplied to the hydrogen separation reformer 22. The hydrogen separation type reformer 22 includes a hydrogen reforming catalyst and a hydrogen separation membrane. The hydrogen separation type reformer 22 is supplied with steam from the boiler 24 and is given heat by the combustor 23 to perform reforming and hydrogen separation. Hydrogen from the hydrogen separation reformer 22 is taken out via the heat exchanger 25. The off gas is recovered by the heat exchanger 26 and then supplied to the combustor 23 via the pressure regulating valve 29. Heat is also recovered by the heat exchangers 27 and 28 from the combustion exhaust gas of the combustor 23 and the boiler 24, respectively. Heat supplied to the boiler 24, combustion air, fuel, and the like is performed by the heat recovered by the heat exchangers 25 to 28.

  In FIG. 6B, a hydrogen-containing gas containing hydrogen gas is supplied to the hydrogen separator 31, and the hydrogen separator 31 is heated by the combustor 32. The separated hydrogen is taken out through the heat exchanger 33. The off-gas is taken out through the heat exchanger 34, and a part or all of the off-gas is supplied to the combustor 32 through the pressure regulating valve 36 as necessary. The heat of the combustion exhaust gas is recovered by the heat exchanger 35. The fuel gas and air to the combustor 32 are heated by the recovered heat.

  In FIG. 6 (b), the combustor 32 is used. However, when there is a heat source that generates high-temperature waste heat, the high-temperature waste heat is guided to the heater 37 as shown in FIG. 6 (c). The hydrogen separator 31 may be heated.

  Hereinafter, examples and comparative examples will be described.

[Example 1]
A pure Nb film (diameter 10 mm) having a thickness of 500 μm is mirror-finished by emery polishing and buffing using 0.3 μm Al ₂ O ₃ particles, and sulfuric acid having a pH of 0.7 containing 0.1 mol / L. And anodized by dipping in an acidic electrolyte solution mixed with ion-exchanged water. As the cathode, an SUS304 plate having an electrode area of 0.03 dm ² was used. An energization was performed for 1 hour at a bath temperature of 20 ° C. and an applied voltage of 40 V, and an anodized layer in an amorphous state different from Nb ₂ O ₅ was formed on both surfaces of the pure Nb film.

  The pure Nb film with the anodized layer is taken out of the bath, washed with pure water, dried, and then a coated metal layer made of pure Pd and having a thickness of about 200 nm is formed on both sides of the film by sputtering to form a hydrogen separation membrane. It was. This hydrogen separation membrane was set in the test module 1 shown in FIG. 7, and the hydrogen permeation rate was measured.

  In this hydrogen permeation test module 1, a hydrogen separation membrane 4 is disposed between a rear end face of a gas introduction pipe 2 and a front end face of a gas extraction pipe 6 via gaskets 3 and 5. A nut 7 is fitted on the introduction pipe 2, and a cap nut 8 is engaged with a flange portion 6 a at the tip of the extraction pipe 6.

  The cap nut 8 is extended to the introduction tube 2 side, and a male screw on the outer peripheral surface of the nut 7 is screwed into a female screw on the inner peripheral surface. The leading end of the nut 7 comes into contact with the flange portion 2 a at the rear end of the introduction pipe 2, whereby the extraction pipe 6 is attracted to the introduction pipe 2 side through the cap nut 8, and the rear end surface of the introduction pipe 2 and the extraction pipe 6 are The hydrogen separation membrane 4 is sandwiched between the front end face via the gaskets 3 and 5.

  The cap nut 8 is provided with a small hole 8a for a gas leak test.

The gaskets 3 and 5 have an annular shape with the same size. Although the inner hole of the gasket is 5.6 mm, the diameter of the contact portion between the gasket and the membrane sample when tightened with a VCR is 7.1 mm, and the effective membrane permeation area A is 39.6 mm ² (3.96). × 10 ⁻⁵ m ² ).

  The hydrogen permeation test module 1 is installed in the electric furnace 10 as shown in FIG. 6, the raw material gas is supplied to the introduction pipe 2, and the hydrogen gas is taken out from the extraction pipe 6.

  The gas pressure in the introduction pipe 2 was 60 kPa, and the gas pressure in the extraction pipe 6 was 10 kPa.

  As the source gas, high purity hydrogen having a purity of 99.99999% or more was used. The hydrogen gas that permeated the membrane 4 was recovered in a recovery container (not shown).

When the operation was performed with the temperature of the electric furnace 10 being 400 ° C., the gas pressure in the introduction pipe 2 was set to 60 kPa, and the gas pressure in the take-out pipe 6 was set to 10 kPa (in FIG. 2, (0.06 / 0.01) 2), the product J · d of the hydrogen permeation rate J and the thickness d is about 25 × 10 for the pure Nb subjected to anodic oxidation as shown in FIG. ^{It was −6} molH · m ⁻¹ · s ⁻¹ .

[Example 2]
A pure Pd-coated metal layer of Nb-5W alloy (Nb alloy containing 5 mol% of W) having the same thickness formed by anodizing under the same conditions as in Example 1 as in Example 1 In the same evaluation, the gas pressure in the introduction pipe 2 is 8 kPa, and the gas pressure in the take-out pipe 6 is 3 kPa (described as (0.008 / 0.003) in FIG. 2). A test was conducted. The results are shown in FIG. As shown in the figure, J · d was approximately 5 × 10 ⁻⁶ molH · m ⁻¹ · s ⁻¹ almost stably during the entire operation period. On the other hand, during the operation period of the Nb-5W alloy without anodization (Comparative Example 1 to be described later) at the same temperature, J · d shows a gradient of change with time that is almost halved at about 1 h (60 min), and the hydrogen permeation rate A sharp decline was observed.

[Comparative Example 1]
A hydrogen separation membrane was produced in the same manner as in Example 2 except that the intermediate layer was not formed, that is, for the Nb-5W alloy, the coated metal layer was formed in the same manner directly on the membrane. The same evaluation was performed on this hydrogen separation membrane, and the results are shown in FIG. FIG. 3 shows the change in hydrogen permeation performance with respect to the hydrogen permeation time after obtaining φ / φmax with normalized hydrogen permeation coefficient of this hydrogen separation membrane and showing the maximum flux. FIG. 3 also shows the results of Examples 1 and 2.

  As shown in FIG. 3, in Comparative Example 1, it is predicted that the hydrogen permeation rate will be halved in only about 1 h (60 min) after the start of operation. Membrane separation can be performed. From this figure, it can be seen that the anodic oxide film contributes to the suppression of the decrease in hydrogen permeation performance, and the durability is improved.

Example 3
Example 1 Nb-5W-5Mo alloy (Nb alloy containing 5 mol% of W and 5 mol% of Mo) having the same film thickness on which an intermediate layer was formed by anodizing under the same conditions as in Example 1 A pure Pd-coated metal layer is formed in the same manner as described above, and the same evaluation is performed. The gas pressure in the introduction pipe 2 is 16 kPa, and the gas pressure in the extraction pipe 6 is 4 kPa ((0.016 / 0.004 in FIG. 4). The hydrogen permeation test was conducted and the results are shown in FIG. As shown in the figure, J · d slightly decreases from the initial 7 × 10 ⁻⁶ molH · m ⁻¹ · s ⁻¹ , but then stable for about 5 × 10 ⁻⁶ molH · m ⁻¹ · s ^{− after that. 1}

[Comparative Example 2]
A hydrogen separation membrane was produced in the same manner as in Example 3 except that the intermediate layer was not formed, that is, for the Nb-5W-5Mo alloy, the coated metal layer was similarly formed directly on the membrane. This hydrogen separation membrane was subjected to a hydrogen permeation test under the same conditions as in Example 3, and the results are shown in FIG. As shown in the figure, J · d was 11 × 10 ⁻⁶ molH · m ⁻¹ · s ⁻¹ at the start of the test, but then suddenly in a short time as in Example 2 and Comparative Example 1. It showed a trend of decreasing time.

Example 4
Similar to Example 1 except that a Ta-5W alloy film (Ta alloy containing 5 mol% of W) having a thickness of 500 μm was used instead of the Nb film, and that the applied voltage at the time of anodization was 40 V or 80 V Thus, a hydrogen separation membrane was manufactured by forming an intermediate layer and a coated metal layer. After measuring the hydrogen permeation rate J · d normalized with the film thickness under the same conditions as in Example 1 except that the hydrogen permeation test temperature was 500 ° C., and showing φmax at the maximum flux The change of hydrogen permeation performance with respect to hydrogen permeation time was investigated. In FIG. 5, Δ and □ marks are obtained by anodizing with an applied voltage of 40 V or 80 V, respectively, and obtaining φ / φmax with normalized hydrogen permeation coefficient for each separation membrane in the same manner as in Comparative Example 1, and hydrogen permeation time It shows the change by.

[Comparative Example 3]
A hydrogen separation membrane was produced in the same manner as in Example 4 except that the intermediate layer was not formed, that is, the coated metal layer was formed in the same manner directly on the Ta-5W alloy membrane. For this hydrogen separation membrane, the time change of φ / φmax with normalized hydrogen permeation coefficient was determined in the same manner as in Example 4, and this ratio rapidly increased with the hydrogen permeation time as indicated by the circles in FIG. Diminished.

  On the other hand, in each alloy of Example 4, even when the hydrogen permeation test temperature was higher (500 ° C.) than in Examples 1 and 2, the anodic oxide film served as an intermediate layer, and the decrease in hydrogen permeation performance was suppressed. , Φ / φmax changes slowly (see Δ and □ in FIG. 5). In Example 4, the time until the hydrogen permeation coefficient was halved was about twice that of Comparative Example 3, and it was confirmed that the mutual diffusion between the Pd catalyst film and the Ta alloy was suppressed.

DESCRIPTION OF SYMBOLS 1 Hydrogen permeation test module 2 Gas introduction pipe 3, 5 Gasket 4 Hydrogen separation membrane 6 Gas extraction pipe 7 Nut 8 Cap nut 10 Electric furnace 11 Hydrogen separation membrane 12 Base metal layer 13 Intermediate layer 14 Covered metal layer 21 Compressor 22 Hydrogen Separable reformer 25-28, 33-35 Heat exchanger 31 Hydrogen separator

Claims (5)

In a hydrogen separation membrane having a base metal layer made of a group 5A metal or an alloy thereof, an intermediate layer formed on the surface of the base metal layer, and a coated metal layer formed on the intermediate layer,
The intermediate layer is formed by anodizing a base metal layer (the surface is oxidized by applying a voltage in water or a solution with the base metal layer serving as an anode to oxidize the surface). Separation membrane.   2. The hydrogen separation membrane according to claim 1, wherein the base metal layer is made of Nb, Nb alloy, Ta, Ta alloy, V or V alloy.   3. The hydrogen separation membrane according to claim 1, wherein the coating metal layer is made of Pd or a Pd alloy. In a method for producing a hydrogen separation membrane comprising a base metal layer made of a group 5A metal or an alloy thereof, an intermediate layer formed on the surface of the base metal layer, and a coated metal layer formed on the intermediate layer,
Forming an intermediate layer by anodizing a base metal layer;
And a step of forming the coated metal layer on the intermediate layer. In a hydrogen production apparatus having a primary chamber and a secondary chamber separated by a hydrogen separation membrane,
The hydrogen separation membrane according to any one of claims 1 to 3, wherein the hydrogen separation membrane is a hydrogen separation membrane.

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