Hydrogen-permeable membrane and method for manufacturing same

Abstract

To provide a hydrogen permeable membrane which is inexpensive and is excellent in hydrogen permeability.SOLUTION: A hydrogen permeable membrane includes a lamination structure structured of a cylindrical porous body 3 with an average pore diameter of 0.05-20 μm, a Pd or Pd alloy film 2 with a thickness formed on a surface of the porous body 3 of 0.05-5 μm, a sprayed coating film 1 with a thickness formed on a surface of the Pd or Pd alloy film 2 of 1-500 μm, the sprayed coating film containing Zr, Nb, and Ni, and the Pd or Pd alloy film 2 with a thickness formed on a surface of the sprayed coating film 1 of 0.05-5 μm. The hydrogen permeable membrane is manufactured by a process of forming the Pd or Pd alloy film 2 on the surface of the cylindrical porous body 3, a process of forming the sprayed coating film 1 by a plasma sprayed coating method on the surface of the Pd or Pd alloy film 2, and a process of forming the Pd or Pd alloy film 2 on the surface of the sprayed coating film 1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hydrogen-permeable membrane that selectively separates hydrogen gas from a mixture of hydrogen gas and impure gases, and a method for manufacturing the same. [Background technology]

[0002] Traditionally, fossil fuels such as oil and coal have been used as energy sources, but the Ministry of Economy, Trade and Industry and other national governments are promoting the expanded use of environmentally friendly hydrogen, which is being used to curb global warming. The reaction produces water from hydrogen and oxygen, and does not emit any carbon dioxide, making it an important technology for realizing a clean society.

[0003] To date, PSA (pressure swing adsorption) and Pd membrane methods have been used as known technologies for extracting only hydrogen from hydrogen-containing gases (see, for example, Patent Document 1). In the PSA method, impurities other than hydrogen are adsorbed and removed from gases containing hydrogen, carbon monoxide, water vapor, etc. produced by steam reforming in a large adsorption / separation tower, and hydrogen gas is extracted. However, this method has issues such as the large size and noise of the equipment required, and the need for processing to recover the impurities after a certain amount of impurities has been adsorbed. In the Pd membrane method, the expensive precious metal Pd is used as the main material, and a thickness is used that takes durability into consideration, which poses a cost obstacle.

[0004] As metal membrane methods other than Pd, methods using crystalline metals such as V alloys and amorphous metals containing metals that allow hydrogen to permeate have been proposed (for example, Patent Documents 2 and 3). However, methods using crystalline metals such as V alloys have the problem of reduced durability due to embrittlement during hydrogen permeation.

[0005] On the other hand, methods using amorphous metals include sputtering and single-roll processes. The sputtering process has a low deposition rate, posing productivity challenges. Furthermore, the single-roll process produces ribbons with limited width, making it difficult to increase the surface area. Furthermore, amorphous metals change to a crystalline state at high temperatures, making them unsuitable for welding. Therefore, ribbons produced by the single-roll process are difficult to join into cylindrical units. Furthermore, ribbon-shaped amorphous films produced by the single-roll process are not integrated with the substrate, requiring a process of bonding them to a porous substrate to increase their strength. The unbonded portions of the film are prone to deformation and destruction during hydrogen permeation.

[0006] On the other hand, Patent Document 4 proposes a method of forming a film by high-velocity flame spraying of metallic glass powder. Paragraph 0022 of Patent Document 4 states that metals such as Nb, V, Ti, Ta, and Zr are known to have hydrogen permeability, and that metallic glasses containing such metals as the main component can exhibit selective hydrogen permeability. However, the hydrogen permeability of metallic glasses containing such metals as the main component is insufficient.

[0007] For these reasons, metal membranes other than Pd membranes have not yet been widely used industrially as hydrogen-permeable membranes. However, as mentioned above, the Pd membrane method has a problem in terms of cost, as it mainly uses Pd, an expensive precious metal, at a thickness that takes durability into consideration. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-289948 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-264740 [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-334828 [Patent Document 4] Japanese Patent Application Laid-Open No. 2006-159108 Summary of the Invention [Problem to be solved by the invention]

[0009] The problem to be solved by the present invention is to provide a hydrogen-permeable membrane that is inexpensive and has excellent hydrogen permeability. [Means for solving the problem]

[0010] The hydrogen-permeable membrane of the present invention comprises a cylindrical porous body having an average pore size of 0.05 to 20 μm, a Pd or Pd alloy film having a thickness of 0.05 to 5 μm formed on the surface of the porous body, and a thermal spray coating containing Zr, Nb, and Ni having a thickness of 1 to 500 μm formed on the surface of the Pd or Pd alloy film. A thermal spray coating having a composition of Zr: 25 to 55 atomic %, Ni: 25 to 65 atomic %, and Nb: 10 to 25 atomic %, and an amorphous ratio of 90% or more. The thermal spray coating has a laminated structure composed of a Pd or Pd alloy film having a thickness of 0.05 to 5 μm formed on the surface of the thermal spray coating.

[0011] The method for producing a hydrogen-permeable membrane includes the steps of forming a Pd or Pd alloy membrane with a thickness of 0.05 to 5 μm on the surface of a cylindrical porous body with an average pore size of 0.05 to 20 μm, and spraying a thermal spray coating containing Zr, Nb, and Ni with a thickness of 1 to 500 μm on the surface of the Pd or Pd alloy membrane. A thermal spray coating having a composition of Zr: 25 to 55 atomic %, Ni: 25 to 65 atomic %, and Nb: 10 to 25 atomic %, and an amorphous ratio of 90% or more. and forming a Pd or Pd alloy film having a thickness of 0.05 to 5 μm on the surface of the sprayed coating. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a hydrogen-permeable membrane that is inexpensive and has excellent hydrogen permeability. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view schematically illustrating the configuration of a hydrogen-permeable membrane according to one embodiment of the present invention. [Figure 2] 1 is a cross-sectional view of a plasma spraying device for forming a thermal spray coating by a plasma spraying method. [Figure 3] 1 is an SEM photograph showing a cross section of a thermal spray coating formed by a plasma spraying method. [Figure 4] FIG. 2 is a schematic diagram showing the measurement of hydrogen permeability of a hydrogen-permeable membrane produced in an example of the present invention. [Figure 5] 1 shows the results of measuring the hydrogen permeability of a hydrogen-permeable film produced in an example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] The hydrogen-permeable membrane of the present invention will be described below with reference to the drawings. 1 is a cross-sectional view showing a schematic configuration of a hydrogen-permeable membrane according to one embodiment of the present invention. The hydrogen-permeable membrane has a laminated structure comprising a cylindrical porous body 3 having an average pore size of 0.05 to 20 μm, a Pd or Pd alloy film 2 having a thickness of 0.05 to 5 μm formed on the surface of the porous body 3, an amorphous thermal sprayed coating 1 containing Zr, Nb, and Ni having a thickness of 1 to 500 μm formed on the surface of the Pd or Pd alloy film 2, and another Pd or Pd alloy film 2 having a thickness of 0.05 to 5 μm formed on the surface of the thermal sprayed coating 1.

[0015] By using a thermal spray coating in this way, welding is not required when manufacturing a cylindrical unit, simplifying the manufacturing process. Furthermore, since welding is not required, the amorphous state of the thermal spray coating 1 can be maintained. Furthermore, by forming a Pd or Pd alloy film 2 on the thermal spray coating 1, which has an uneven surface, the surface area can be increased, improving the hydrogen permeation rate. Furthermore, compressive stress is generated in the thermal spray coating 1, improving adhesion to the cylindrical porous body 3.

[0016] Because the thermal spray coating 1 contains elements such as Zr, Ni, and Nb that are easily oxidized, it is formed using a plasma spraying device such as the one shown in Figure 2. This device is the plasma spraying device disclosed in JP 2017-222921 A, and includes a plasma spraying unit 5 that sprays a plasma jet, a double cylindrical unit 6 with an open tip that is positioned to surround the plasma jet sprayed from the plasma spraying unit 5, an inert gas supply unit 7 that supplies an inert gas into the inner cylinder of the double cylindrical unit 6, a material supply unit 9 that supplies a spray material into the inner cylinder of the double cylindrical unit 6, and an inert gas spraying unit 8 that supplies and sprays an inert gas between the outer and inner cylinders of the double cylindrical unit 6. An amorphous thermal spray coating can be formed by melting the supplied powder and then rapidly cooling it, which is a method that can be suitably used in the production of hydrogen-permeable membranes.

[0017] The Pd or Pd alloy film 2 that serves as a catalyst is formed between the porous body 3 and the thermal spray coating 1 and on the surface of the thermal spray coating 1 by a method such as plating, vapor deposition, or sputtering.

[0018] The pores in the thermal spray coating 1 are filled with the sealant 4 by applying it to the surface of the thermal spray coating 1, immersing the thermal spray coating in the sealant, or by vacuuming the thermal spray coating after either of these procedures. Excess sealant on the surface is removed by wiping it off before curing, blowing it with a gas, or polishing and blasting it after the sealant has cured. In other words, there is essentially no sealant between the thermal spray coating 1 and the Pd or Pd alloy film 2, and a hydrogen permeation path is ensured by the contact between the thermal spray coating 1 and the Pd or Pd alloy film 2. Note that the sealant is preferably primarily made of an inorganic material that is relatively stable even at high temperatures; specifically, an inorganic sealant primarily made of an alkoxysilane compound is preferably used.

[0019] The composition of thermal spray coating 1 is Zr: 25-55 atomic %, Ni: 25-65 atomic %, and Nb: 10-25 atomic %. Thermal spray coating 1 becomes the main layer of the hydrogen-permeable film, and when hydrogen embrittlement resistance, thermal embrittlement resistance, mechanical properties, etc. were examined by varying the contents of Zr, Ni, and Nb, the above range was found to be desirable for suppressing the tendency toward embrittlement. Furthermore, the amorphous fraction of thermal spray coating 1 at this time was 90% or more. The amorphous fraction of thermal spray coating 1 can be determined by thermal analysis.

[0020] The average pore diameter of the porous body 3 is preferably 0.05 to 20 μm. If the diameter is less than 0.05 μm, the adhesion between the Pd or Pd alloy film 2 or thermal spray coating 3 formed on the surface of the porous body 3 will be weak, and the porous body 3 will be prone to peeling. On the other hand, if the average pore diameter is 20 μm or more, the surface will become uneven, and a large film thickness will be required to form a continuous thermal spray coating 3. This will not only reduce the hydrogen permeability, but will also increase the cost of the thermal spray material, making it unsuitable for practical use. The average pore diameter of the porous body 3 can be determined by mercury intrusion porosimetry.

[0021] The thickness of the thermal spray coating 1 is preferably 1 to 500 μm. If the thickness is less than 1 μm, it is difficult to form a continuous coating using current thermal spraying technology. Furthermore, when a powder with a relatively small particle size is sprayed using the above-mentioned plasma spraying device, it is known that a dense sprayed layer is easily formed at a certain thickness, as shown in Figure 3. On the other hand, if the thickness of the thermal spray coating is too large, the amount of hydrogen permeation is significantly reduced, so a thickness of 500 μm or less is suitable. Considering the ease of forming a continuous, dense thermal spray coating, hydrogen permeability, and manufacturing costs, a thickness of 10 to 300 μm is more preferable.

[0022] The thickness of the Pd or Pd alloy film 2 is preferably 0.05 to 5 μm. If the thickness is 0.05 μm or more, the catalytic effect can be exerted. Furthermore, as the catalytic effect saturates as the thickness of the catalyst layer increases, the thickness of the catalyst layer is preferably 5 μm or less. In order to obtain a sufficient catalytic effect and to reduce the amount of expensive Pd used, the thickness of the catalyst layer is more preferably 0.1 to 2 μm. [Example]

[0023] The area of the porous part is 1188mm 2 A 0.5 μm thick Pd film was formed by plating on the surface of a cylindrical porous body (average pore diameter = 4.37 μm) made of SUS316. A 280 μm thick thermal spray coating containing 30 atomic % Zr, 52 atomic % Ni, and 18 atomic % Nb was then plasma sprayed on top of it. The plasma spraying equipment shown in Figure 2 was used to minimize pores, unmelted particles, and oxidation in the sprayed coating, and the plasma output was set to 100 kW. After the sealant penetrated and solidified into the pores of the sprayed coating and the excess sealant remaining on the surface was removed, a 0.5 μm thick Pd film was plated on top to create a hydrogen-permeable membrane.

[0024] The hydrogen permeation rate of the fabricated hydrogen-permeable membrane was measured using the measuring device shown in Figure 4. Hydrogen gas flows in through gas supply port 10, permeates from the outside of cylindrical porous body 12 on which hydrogen-permeable membrane 11 is formed, passes through hydrogen-permeable membrane 11 to the inside, and then flows into hydrogen gas recovery port 13 connected to a flow meter. Gas that does not permeate flows into gas outlet 14.

[0025] The hydrogen-permeable membrane was then tested at 300°C under a primary pressure (outside the cylinder) of 20 kPa and a secondary pressure (inside the cylinder) of 0 kPa. As shown in Figure 5, the hydrogen permeability was 4.08 cm. 3 The hydrogen permeation rate was calculated as 6.70 × 10 -9 mol m -1 Pa -1 / 2 The hydrogen permeable membrane was 4.58×10 -9 mol m -1 Pa -1 / 2 It was.

[0026] As described above, the present invention can reduce the amount of Pd used compared to conventional Pd membrane methods, while still achieving a hydrogen permeability coefficient close to that of conventional Pd membrane methods. In other words, the present invention can provide an inexpensive hydrogen-permeable membrane with excellent hydrogen permeability. [Explanation of symbols]

[0027] 1: Thermal spray coating 2: Pd or Pd alloy film 3: Cylindrical porous body 4: Sealer 5: Plasma injection unit 6: Double cylindrical section 7: Inert gas supply unit 8: Inert gas injection section 9: Material supply section 10: Gas supply unit 11: Hydrogen permeable membrane 12: Cylindrical porous body 13: Hydrogen gas recovery port 14: Gas outlet

Claims

1. A hydrogen-permeable membrane having a laminated structure composed of a cylindrical porous body having an average pore size of 0.05 to 20 μm, a Pd or Pd alloy film having a thickness of 0.05 to 5 μm formed on the surface of the porous body, a thermal sprayed coating containing Zr, Nb, and Ni having a thickness of 1 to 500 μm formed on the surface of the Pd or Pd alloy film, the thermal sprayed coating having a composition of Zr: 25 to 55 atomic %, Ni: 25 to 65 atomic %, and Nb: 10 to 25 atomic %, with an amorphous proportion of 90% or more, and a Pd or Pd alloy film having a thickness of 0.05 to 5 μm formed on the surface of the thermal sprayed coating.

2. 2. The hydrogen-permeable film according to claim 1, wherein the pores in the thermal spray coating are filled with a sealant.

3. forming a Pd or Pd alloy film having a thickness of 0.05 to 5 μm on the surface of a cylindrical porous body having an average pore diameter of 0.05 to 20 μm; forming a thermal spray coating containing Zr, Nb, and Ni and having a thickness of 1 to 500 μm on the surface of the Pd or Pd alloy film by a plasma spraying method, the thermal spray coating having a composition of Zr: 25 to 55 atomic %, Ni: 25 to 65 atomic %, and Nb: 10 to 25 atomic % and an amorphous ratio of 90% or more; The method for producing a hydrogen-permeable film includes a step of forming a Pd or Pd alloy film having a thickness of 0.05 to 5 μm on the surface of the thermal sprayed coating.

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