JP2011101871A - Hydrogen-permeable membrane structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrogen-permeable membrane structure inexpensive and highly durable, which has excellent hydrogen permeability without using a noble metal or rare metal as a main material. <P>SOLUTION: The hydrogen-permeable membrane structure 1 includes a membrane 3 having hydrogen permeability, and a porous supporting body 2 the surface portion 2a of which is made of a main material the same as that of the membrane 3 on a side on which at least the membrane 3 is formed, so that the hydrogen-permeable membrane structure is unlikely to be deformed or damaged even by thermal expansion or hydrogen adsorption, while securing excellent hydrogen permeability, to thus enable the hydrogen-permeable membrane structure 1 to be produced even from an inexpensive main material such as iron. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a hydrogen permeable membrane structure for purifying hydrogen to obtain highly purified hydrogen.

  Currently, only a palladium alloy has been put into practical use as a metal hydrogen permeable membrane used for producing high-purity hydrogen used in semiconductor manufacturing and experiments (see, for example, Patent Document 1). In the metal hydrogen permeable membrane (hydrogen permeable membrane cell) described in the same document, for example, a tube-shaped one having a thickness of 80 μm and a diameter of 1.6 mm is used, but palladium is an expensive noble metal itself. Metal hydrogen permeable membranes using palladium are also very expensive, unsuitable for mass production, and difficult to spread widely.

  Therefore, attempts have been made to reduce the amount of palladium used by reducing the thickness of the metal hydrogen permeable membrane, and a palladium alloy thin film is formed on a stainless steel or ceramic porous support by a method such as plating or ion plating. Various techniques have been developed (see, for example, Patent Document 2 and Patent Document 3).

  In addition, metallic hydrogen permeable membranes that do not contain expensive noble metals such as palladium have been developed. As such a metal hydrogen permeable membrane, a zirconium-nickel (Zr-Ni) alloy, a vanadium-nickel (V-Ni) alloy, or a niobium-titanium-nickel (Nb-Ti-Ni) alloy was used. A thing can be illustrated (for example, refer patent document 3).

  Further, as another technique, it is known that a metal film, such as iron, which is inexpensive and easily obtainable exhibits excellent hydrogen permeation characteristics by electron irradiation on the surface of the metal film (see, for example, Patent Document 5).

JP 62-017001 A Japanese Patent Laid-Open No. 05-078810 JP-A-11-267477 JP 2005-232491 A Japanese Patent Laid-Open No. 11-285613

  By the way, if the palladium alloy thin film is formed on the porous support as in the techniques described in Patent Documents 2 and 3 described above, it is possible to greatly reduce the amount of palladium used, but the porous support has a defect. However, there is a problem that the technology itself for forming a palladium alloy thin film without any problems is difficult and the yield is not good. In addition, since the hydrogen permeable membrane and the porous support are different types of materials, differences in thermal expansion and expansion due to hydrogen occur, and the hydrogen permeable membrane is distorted, so that it can be said that problems with durability are likely to occur. Furthermore, when the constituent elements of the porous support are thermally diffused into the hydrogen permeable membrane, the hydrogen permeation rate is reduced, so that it is necessary to form a barrier layer for preventing thermal diffusion.

  In addition, the main component of the metal used in the metal hydrogen permeable membrane that does not use a noble metal as described in Patent Document 4 is a rare metal, and although it is cheaper than a noble metal, it is relatively expensive and unevenly distributed. As a result, they are worried about whether it will be adequately supplied.

  Furthermore, in the technique described in Patent Document 5, a good hydrogen permeation rate can be imparted to iron or the like without using a noble metal or a rare metal. This mechanism is essential, and cost increases.

  The present invention has been made paying attention to such a problem, and a main object is to provide an inexpensive and high-quality hydrogen permeable membrane structure.

  That is, the hydrogen permeable membrane structure of the present invention comprises a thin film having hydrogen permeability and a porous support for forming and supporting the thin film on the surface, and at least the thin film in the porous support is provided. The surface portion on the side to be formed is made of the same main material.

  Here, the surface portion of the porous support means a region having a predetermined thickness including the surface on the side where the thin film is formed. For the porous support, it is preferable to apply a material whose behavior due to thermal expansion is similar to that of the thin film and whose expansion behavior due to hydrogen is similar to that of the thin film. When the same material as the main material of the thin film is used as the material of the porous support, these conditions can be satisfied, but the part other than the surface of the porous support (for example, opposite to the side on which the thin film is formed) This does not preclude the application of a material different from the main material of the thin film to the porous support. If the material which can be specifically used as a porous support body is illustrated, what was manufactured with raw materials, such as a single metal, an alloy, and ceramics, will be employable. Ceramics generally do not dissolve in hydrogen and do not expand due to hydrogen. Therefore, when pure iron or the like is applied to a thin film as a main material with little expansion due to hydrogen, ceramics is one of the porous support materials. Can be used. However, in the present invention, the porous support is required to have fine pores continuously formed at least from the surface on which the thin film is formed to the opposite surface. As the porous support having such micropores, those having open cells inside, a net or a laminate of nets can be used. The shape of the porous support is not particularly limited as long as it is a structure in which hydrogen before purification and high-purity hydrogen after purification are separated, and can be, for example, plate-shaped or tube-shaped. In the present invention, at least the surface of the porous support on the side on which the thin film is formed is made of the same main material as the thin film. The thin film may be integrally formed on the surface of such a porous support, or may be fixed integrally on the surface of the porous support.

  In such a hydrogen permeable membrane structure of the present invention, the main material of the hydrogen permeable thin film and the main material of the surface portion of the porous support on the side on which the thin film is formed are at least the same material. Because unnecessary stress is not applied to the thin film due to thermal diffusion of constituent elements between the thin film and the porous support, which was a problem in the technologies described in References 2 and 3, and differences in expansion behavior due to thermal expansion and hydrogen. The barrier layer formed to take measures for preventing thermal diffusion is unnecessary, and the distortion of the thin film hardly occurs. As a result, a highly durable hydrogen permeable membrane structure can be manufactured at a lower cost.

In particular, in the present invention, one of the main purposes is to obtain a hydrogen permeable membrane structure using a metal that can be obtained at low cost. It is preferable that both the parts are composed of a main material mainly composed of iron. Iron is an extremely abundant and inexpensive metal, but its hydrogen permeation rate coefficient is a very small value of about 1/200 of that of a palladium alloy. I did not come. However, since the hydrogen permeation rate is inversely proportional to the film thickness, a practical hydrogen permeation rate can be obtained even with iron if the thin film is sufficiently thin.
Therefore, by using a hydrogen permeable membrane structure mainly composed of iron as a thin film and at least a surface portion of the porous support on which the thin film is formed, precious metals and rare metals that are not easily available are not used. Therefore, the manufacturing cost of the hydrogen permeable membrane structure can be greatly reduced as compared with the conventional case, and a high performance hydrogen permeable membrane structure can be obtained. Furthermore, since palladium may be destroyed at a volume of about 10% due to the solid solution of hydrogen at a temperature of 300 ° C. or lower, before and after the use of a metal hydrogen permeable membrane containing palladium, It is necessary to replace the hydrogen adsorbed by nitrogen with an inert gas such as nitrogen, but since iron does not have a property of dissolving hydrogen in a large amount, there is no need for an inert gas replacement device or operation. This is an advantage of the present invention.

  Here, the porous support may have only the surface portion on the side where the thin film is formed as a main component of iron, but may be formed entirely of iron as a main component. The thin film and the porous support can be applied with high purity iron having a purity of 99.9% or more and general pure iron such as electromagnetic soft iron, and if necessary, surface activity against hydrogen, corrosion resistance, hydrogen Other elements such as nickel and titanium can be added to improve the transmission characteristics and the like. When these elements are added, powders alloyed with iron may be used, or iron powder and powders of additive elements may be mixed and sintered. However, when high-purity iron is used as the iron thin film, the surface activity against hydrogen is higher than that of general pure iron, and therefore the amount of various catalysts described below can be reduced.

  Further, in the hydrogen permeable membrane structure of the present invention, when the thin film and at least the surface of the porous support on which the thin film is formed have an uneven shape, the surface portion of the hydrogen permeable membrane structure Since the true surface area can be made larger than the apparent area on the (thin film side), the hydrogen permeation rate per apparent area can also be increased.

  Furthermore, in the present invention, at least one catalyst selected from palladium, platinum, and nickel can be added to at least the surface of the thin film. Of course, these metal catalysts and other catalysts may be added to the porous support. By adding such a catalyst, the surface activity against hydrogen on the thin film surface and further on the porous support can be improved. The catalyst may be added by applying a catalyst powder on the surface of the thin film and sintering it, or may be added by sputtering or ion plating. In addition, when a catalyst is added to the porous support, it is desirable that the catalyst be positioned in the vicinity of the thin film. Accordingly, it is possible to prevent a decrease in hydrogen permeation rate due to a slow reaction in which hydrogen molecules dissociate into atoms on the surface of the thin film or a reaction in which hydrogen atoms that have permeated the thin film are combined to form hydrogen molecules.

  In the present invention, the porous support is formed as having a plurality of layers in the thickness direction, and at least the layer on the side opposite to the surface on which the thin film is formed among the layers excluding the layer constituting the surface portion. The layer including the surface can be made of a material different from the main material constituting the thin film and the surface portion. As described above, the porous support is formed not only in a single kind of main material but also in a layered shape in the thickness direction so long as the condition that the main material of the surface portion is the same as the main material of the thin film is satisfied. It can also be composed of various main materials. That is, as the hydrogen permeable membrane structure, it is advantageous that the thickness is thinner from the viewpoint of hydrogen permeability, and thus the porous support is composed of a plurality of layers and is compared with the layers excluding the layer including the surface portion. By applying a material having high strength, the strength can be improved even if the thickness of the entire hydrogen permeable membrane structure is reduced. For example, a layer including a surface opposite to the shape on which the thin film of the porous support is formed and one or more layers adjacent to the layer are formed of the porous ceramic as described above, and includes a surface portion. Various configurations such as forming the above layers from a metal whose main material is iron or the like common to the thin film, or forming each layer from a different main material can be adopted.

  According to the present invention, since the hydrogen permeable thin film and the surface portion on the thin film side of the porous support are made of the same main material such as iron, the constituent elements between the thin film and the porous support are Low cost and high durability that can eliminate conventional problems such as thermal diffusion, stress generation in thin films due to differences in thermal expansion and expansion behavior due to hydrogen, and the necessity of barrier layer formation to prevent thermal diffusion An excellent hydrogen permeable membrane structure can be obtained. In particular, by using a common iron material for the thin film and the surface on the thin film side of the porous support, it is possible to stably produce a high-quality hydrogen permeable membrane structure at a low price without using an expensive noble metal as the main material. Can be supplied.

The typical sectional view showing the hydrogen permeable membrane structure concerning one embodiment of the present invention. The typical sectional view expanding and showing the important section of the hydrogen permeable membrane structure. The schematic diagram which shows an example of the hydrogen purification process using the hydrogen permeable membrane structure. The typical sectional view showing an example of the hydrogen refining process using the modification of the hydrogen permeable membrane structure. The typical sectional view showing other modifications of the hydrogen permeable membrane structure. FIG. 6 is a schematic cross-sectional view showing still another modification of the hydrogen permeable membrane structure.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
This embodiment shown in FIG. 1 is a hydrogen permeable membrane structure 1 obtained by integrally forming a thin film 3 having hydrogen permeability on one surface side of a porous support 2 as a preferred example of the present invention. . In the drawing, a flat hydrogen permeable membrane structure 1 is shown as a schematic sectional view. This hydrogen permeable membrane structure 1 forms a porous support 2 by filling and sintering iron powder inside an iron frame 4, and a thin film 3 on one surface of the porous support 2. Is formed. It is desirable to use high purity iron for the iron powder filled in the frame 4. This is because high-purity iron has higher surface activity against hydrogen than general pure iron such as electromagnetic soft iron.

  In the present embodiment, the porous support 2 is a porous body formed by sintering high-purity iron powder filled in the iron frame 4 as described above. The conditions may be appropriately determined by setting the porosity of the porous support 2 after formation. In the formation process on the porous support 2, pores (pores) 2x are uniformly formed at a substantially constant rate from the surface 2a on the side where the thin film 3 is formed to the surface 2b on the opposite side (hereinafter referred to as "back surface"). Alternatively, as shown in FIG. 2, the diameter of the pores 2x may gradually increase from the front surface 2a side to the back surface 2b side. That is, the porous support 2 is allowed to be formed from a plurality of layers having different pore diameters, porosity, purity, additive elements, etc. In this case, from the viewpoint of forming the thin film 3 on the surface 2a. It is desirable to use iron powder having a small particle size on the surface 2a side. Further, the particle size and shape of the iron powder may be appropriately selected in consideration of the gas (hydrogen) permeability, the ease of forming the thin film 3, and the like. FIG. 2 schematically shows the pores 2x formed from the front surface 2a to the back surface 2b of the porous support 2, and each pore 2x seems to exist independently in this figure. However, the pores 2x are actually formed so as to communicate from the front surface 2a to the back surface 2b.

  The thin film 3 is formed by a method in which the surface 2 of the porous support 2 is melted and sealed by heating with a laser or a flash lamp, or the surface 2a of the porous support 2 is sealed by shot peening and then heat treated. It is formed by a known method such as a method of forming a film. In this embodiment, the example which formed the surface 3a of the thin film 3 smoothly is shown. When the thin film 2 is formed using iron (high-purity iron) as a material as in the present embodiment, the film thickness is preferably 2 μm or less from the viewpoint of obtaining a practical hydrogen permeation rate. Thus, by processing the surface 2a of the porous support 2 to form the thin film 3, in this embodiment, a region having a predetermined thickness including the main material of the thin film 3 and at least the surface 2a of the porous support ( That is, the main material of the surface portion in the present invention is made of common high-purity iron.

  Further, on the surface of the thin film 3 or the thin film 3 or in the vicinity of the surface 2a of the porous support 2, a catalyst (as needed) may be used for the purpose of improving surface activity against hydrogen, improving corrosion resistance, and improving hydrogen permeation characteristics. A metal which is not shown and the same applies hereinafter) can be added. As the metal serving as a catalyst, one or more selected from palladium, platinum, and nickel can be applied, but this does not prevent the addition of other catalysts. The catalyst may be formed by applying a catalytic metal powder on the surface of the thin film 3 and sintering it, or may be formed by sputtering, ion plating, or the like. Further, when the porous support 2 is formed by sintering the iron powder, the catalyst is mixed in the iron powder at the site where the thin film 3 is to be formed thereafter, and the catalyst is sintered together with the iron powder. Alternatively, after forming the porous support 2 by sintering, a catalyst is applied to the surface on which the thin film 3 is formed, and the surface is subjected to the heat treatment as described above to form the thin film 3 to which the catalyst is added. Can also be adopted. In particular, when a catalyst is added also to the porous support 2, it is desirable to add the catalyst in the vicinity of the surface 2 a so that the catalyst exists in the vicinity of the thin film 3. Thereby, it is possible to avoid a decrease in the hydrogen permeation rate when the reaction in which hydrogen molecules dissociate into atoms on the surface of the thin film 3 or the reaction in which hydrogen atoms that have permeated through the thin film 3 recombine and become hydrogen molecules is slow. . In particular, when high-purity iron is used as the material of the thin film 3 (in this embodiment, the material of the porous support 2 is the same), the surface activity against hydrogen is higher than that of general pure iron as described above. The amount of catalyst used can be reduced, or the catalyst can be made non-use.

When purifying hydrogen using the hydrogen permeable membrane structure 1 having such a configuration, for example, as shown in FIG. 3, the flat hydrogen permeable membrane structure 1 is placed in a cylindrical container 5 with its internal space. Hydrogen gas A, which is arranged so as to be divided into two parts, is introduced into the cylindrical container heated to about 400 ° C. through the duct 5a from one end thereof, and purified through the duct 5b from the other end. 'Recover. At this time, the hydrogen permeable membrane structure 1 has the back surface 2b side of the porous support 2 facing the hydrogen gas A introduction side. On the introduction side of the hydrogen gas A, a mixture of the hydrogen gas A that has not been purified and the impurity gas B that is contained in the hydrogen gas A and does not permeate the thin film 3 is separately collected through the duct 5c. That is, only the hydrogen gas A out of the hydrogen gas A containing impurities is purified through the porous support 2 and the thin film 3 (only purified hydrogen gas A ′ is obtained). If the hydrogen permeable membrane structure 1 of the present embodiment is used, highly purified hydrogen gas A ′ can be obtained by purifying commercially available hydrogen gas A.
Note that, in this example, the hydrogen permeable membrane structure 1 is arranged with respect to the cylindrical container 5 so that the back surface 2b side of the porous support 2 faces the hydrogen gas A introduction side. You may arrange | position so that the thin film 3 may face the gas A introduction side.

  As described above, in the hydrogen permeable membrane structure 1 of the present embodiment, the hydrogen permeable thin film 3 and the porous support 2 that supports the thin film 3 are configured using common iron (high-purity iron) as a main material. Therefore, the thermal diffusion of the constituent elements between the thin film 3 and the porous support 2 does not occur, and there is no generation of unnecessary stress on the thin film 3 due to the difference in expansion behavior due to thermal expansion or hydrogen. It is no longer necessary to form a barrier layer formed in the conventional hydrogen permeable membrane structure for preventing thermal diffusion, and the distortion of the thin film 3 due to hydrogen permeation hardly occurs. Further, basically, the thin film 3 and the porous support 2 can be constituted by using relatively inexpensive iron as a main material without using a catalytic metal, and even when a rare metal such as palladium or a noble metal is used as a catalyst. Since the amount used is minimal, a highly durable hydrogen permeable membrane structure 1 can be obtained at an extremely low cost compared to the prior art.

In addition, this invention is not limited to embodiment mentioned above.
In addition to the example in which the flat hydrogen permeable membrane structure 1 as described above is arranged in the cylindrical container 5, for example, as shown in FIG. 4, a hydrogen permeable membrane structure 1 ′ formed in a cylindrical shape is used. Can be used to purify hydrogen. The hydrogen permeable membrane structure 1 ′ schematically shown in FIG. 1 has a hollow cylindrical shape (tube shape) in which a porous support 2 ′ is formed on the inner side and a thin film 3 ′ is formed on the outer side. The diameter is about 1 to several mm. The porous support 2 ′ and the thin film 3 ′ are substantially the same as the porous support 2 and the thin film 3 of the hydrogen permeable membrane structure 1 described above except that the shapes are different. When purifying hydrogen with such a hydrogen permeable membrane structure 1 ′, hydrogen is introduced into the internal space from one open end of the tubular hydrogen permeable membrane structure 1 ′ heated to about 400 ° C. When the gas A is introduced, only hydrogen passes through the porous support 2 ′ and the thin film 3 ′, and the purified hydrogen gas A ′ is obtained from the outer surface of the hydrogen permeable membrane structure 1 ′. The mixture of the hydrogen gas A and the impurity gas B that has not been purified is separately collected from the opposite end of the tube-shaped hydrogen permeable membrane structure 1 ′ or the take-out port provided on the hydrogen gas A introduction side. Further, as in the case of the hydrogen permeable membrane structure 1 described above, after purification from the porous support 2 ′ side by introducing hydrogen gas A from the thin film 3 ′ side, which is the outer surface side of the hydrogen permeable membrane structure 1 ′. The hydrogen gas A ′ may be collected, and a tube-shaped hydrogen permeable membrane structure in which a porous support is formed on the outer surface side and a thin film is formed on the inner surface side is applied. It doesn't matter.

  Moreover, in the said embodiment, although the example of the hydrogen permeable film structure 1 which formed the surface 3a of the thin film 3 smoothly was shown, as shown in FIG. 5, the hydrogen permeable film structure which formed the surface 30a of the thin film 30 in unevenness | corrugation 10 is also possible. The thin film 30 is the same as the thin film 3 of the above-described embodiment except for the shape of the surface 30a. Further, the iron frame 40 and the porous support 20 are equivalent to the porous support 2 of the above-described embodiment. However, the surface portion 20 a on the thin film 30 side of the porous support 20 is also formed in an uneven shape corresponding to the surface 30 a of the thin film 30 so that the thickness of the thin film 30 is constant. As described above, when the surface 30a of the thin film 30 has an uneven shape, the true surface area of the thin film 30 is larger than the apparent surface area (the area when the surface 30a is directly facing), and the apparent area is increased. The hydrogen permeation rate per hit can be increased.

  Furthermore, in the said embodiment, although the example which sintered the iron powder with which the iron frame 4 was filled and formed the porous support body 2 was shown, as shown in FIG. The thin film 300 is formed by attaching iron powder only to one surface side of the body and sintering, and the iron mesh portion 400a in which the thin film 300 is not formed in the wire mesh 400 is made to function as the porous support 200. It is also possible to make the hydrogen permeable membrane structure 100 as described above. In the illustrated example, an example in which three metal meshes 400 are stacked is shown, but an appropriate number of metal meshes 400 may be used as long as the metal mesh 400 is one or more.

  Furthermore, as a method for forming a thin film on the surface of the porous support, a technique such as plating or ion plating can be applied. In the case of plating, a technique for forming a thin film having no defect on the surface of the porous support is difficult, but it can be realized by performing a treatment for smoothing the surface of the porous support in advance. Although ion plating is an expensive process, it can be realized if the cost can be cleared.

  Further, in the porous support, as long as the surface portion on the side where the thin film is formed is made of the same main material as the thin film, the other portions may be made of different materials. In this case, the porous support can be configured to have a plurality of layers. For example, the surface portion on the side where the thin film is formed and the layer in the vicinity thereof are made of the same high-purity iron as the thin film, while one or more layers on the back side are made of a material other than iron such as ceramics as the main material. it can. When the porous support is composed of a plurality of layers as described above, the layer other than the surface portion of the porous support is mainly made of a material having a strength higher than that of the surface portion. There is an advantage that the strength can be improved while reducing the thickness.

  In addition, the specific configuration of each part is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

1, 1 ', 10, 100 ... hydrogen permeable membrane structure 2, 2', 20, 200 ... porous support 3, 3 ', 30, 300 ... thin film

Claims (4)

Comprising a thin film having hydrogen permeability and a porous support for forming and supporting the thin film on the surface;
The hydrogen permeable membrane structure characterized in that the thin film and at least the surface portion on the side where the thin film is formed in the porous support are made of the same main material. 2. The hydrogen permeable membrane structure according to claim 1, wherein both the thin film and the porous support, at least the surface portion on the side where the thin film is formed, are mainly composed of iron. 3. The hydrogen permeable membrane structure according to claim 1, wherein at least one catalyst selected from palladium, platinum, and nickel is added to at least the surface of the thin film. The porous support is formed as having a plurality of layers in the thickness direction, and a layer including at least a surface opposite to the surface on which the thin film is formed among layers excluding the layer constituting the surface portion The hydrogen permeable membrane structure according to any one of claims 1 to 3, wherein the hydrogen permeable membrane structure is made of a material different from a main material constituting the thin film and the surface portion.

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