JP2006272159A - Catalyst formed on surface of metal, and its forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst formed on the surface of a metal which has a catalyst layer having a catalyst metal supported on a catalyst carrier with a large specific surface area having a number of micro pores. <P>SOLUTION: The catalyst formed on the surface of the metal having the catalyst layer having micro pores is prepared by burning a substance comprised of an organic material in the sprayed film formed by spraying an oxide containing the catalyst metal coated with the organic material to form pores and reducing the sprayed film becoming a porous oxidation layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a catalyst formed on a metal surface and a method for forming the same. For example, by catalyzing a metal surface that is a hydrogen permeable membrane, hydrogen can be efficiently dissociated or bonded on the metal surface. The present invention relates to a catalyst formed on a suitable metal surface and a method for forming the catalyst.

  The hydrogen permeable membrane is capable of efficiently extracting only hydrogen gas from a mixed gas of hydrogen gas and other gas, and is being developed mainly for use in a fuel cell. For example, in a system for supplying hydrogen to a polymer electrolyte fuel cell (PEFC), in order to make the system more compact, a hydrogen supply device that combines a steam reformer with a CO remover using a hydrogen permeable membrane has been developed. It has been broken.

  Conventionally, Pd and Pd alloys that are excellent in terms of hydrogen permeability and hydrogen embrittlement have been used as the hydrogen permeable membrane. However, Pd which is a noble metal is a rare metal and a very expensive material. In recent years, since Pd is frequently used in electronic parts and the like, the price is expected to rise, and a hydrogen permeable membrane made of an inexpensive material instead of the Pd-based hydrogen permeable membrane is demanded. Therefore, for example, development of a hydrogen permeable film made of a material having hydrogen permeability such as Ta, Nb, or an alloy thereof as disclosed in Patent Document 1 below is in progress.

  However, even in a non-Pd-based hydrogen permeable membrane, it is necessary to provide a catalyst layer made of Pd or a Pd alloy on the surface of the hydrogen permeable membrane in order to dissociate or bond hydrogen. Further, the catalyst layer is preferably formed by supporting a catalyst on a porous catalyst carrier having a large specific surface area capable of supporting a catalyst sufficient to promote hydrogen dissociation (bonding). Similar demands are also being sought for catalysts formed on metal surfaces such as stainless steel, which serve as combustion catalysts in fuel reformers and the like. Here, as a method for forming a porous catalyst carrier on the metal surface, in addition to the spraying method, an electroless plating method, an anodic oxidation method, a welding method, a dip coating method, a wash coating method, and the like are known. Since the conventional thermal spraying method forms a dense thermal spray layer, formation of fine pores is insufficient, the specific surface area of the catalyst carrier is small, and the activity as a catalyst is small.

  Further, when the underlying metal is directly catalyzed by electroless plating, the underlying metal is limited to nickel or palladium, and the catalytic metal particles are relatively large, and high activity cannot be expected.

  In addition, in the anodic oxidation method, a porous alumina layer having a large number of pores of several tens of μm and a large specific surface area can be obtained. However, the base metal is limited to aluminum. In any of the electrolytic plating methods, since aluminum is used, it is difficult to use at 400 ° C. or higher, and it cannot be used at a high temperature of about 650 ° C. or higher, which is the melting point of aluminum.

Further, when a thick catalyst layer is directly formed on a metal by a dip coating method or a wash coating method, there is a problem that the catalyst layer peels off when a high temperature acts on the catalyst layer. Further, the sol-gel method cannot coat a metal with a sufficient amount as a catalyst. In these methods, since the catalyst layer is densely formed, the specific surface area is small and the catalytic activity is poor. Furthermore, when the thermal treatment was performed by spraying an aluminum alloy or the like, only the surface could be activated because the coating film was dense.
JP 2002-336655 A

  The present invention has been made in view of the above problems, and a catalyst formed on a metal surface having a catalyst layer in which a catalyst metal is supported on a catalyst carrier having a large number of fine pores and a large specific surface area. It is intended to provide.

  To solve this problem, the first invention of the present invention forms pores by burning an organic substance in a sprayed coating formed by spraying an oxide containing a catalytic metal coated with an organic substance on the metal surface. The catalyst is formed on the metal surface by reducing the sprayed coating formed into a porous oxide layer to form a catalyst layer having fine pores. Here, the organic substance may be polyvinyl alcohol, polyvinyl butyral, etc., as long as it dissolves in a solvent in which the catalyst metal and the oxide that is the catalyst carrier are dispersed. Various oxides such as zirconia, alumina or niobium oxide can be used as the oxide serving as the catalyst carrier.

  According to the first invention, the catalyst metal and the oxide described above are uniformly dispersed in, for example, a solvent in which an organic substance is dissolved to form a slurry, and then heat-treated at a temperature at which the solvent component volatilizes. A thermal spraying powder in which an organic substance is coated on an oxide containing a metal is obtained. By spraying this thermal spraying powder on the metal surface, a thermal spray coating containing a substance made of an organic substance is formed on the metal surface.

  Here, a part of the substance made of an organic substance contained in the thermal spray coating is an intermediate made of carbon or carbon, oxygen, and hydrogen obtained by decomposing the organic substance by thermal spraying heat at the time of thermal spraying. By burning these organic substances, carbon and intermediates, which are organic substances, are decomposed to form a thermal spray coating that is an oxide layer that is a catalyst carrier with fine pores and a large specific surface area. The Here, since the oxide contains a catalyst metal, a catalyst layer in which the catalyst metal is supported in the pores of the thermal spray coating, which is a catalyst carrier having a large number of fine pores and a large specific surface area, is provided. A catalyst formed on a metal surface is provided.

  According to the second aspect of the present invention, a porous oxide is formed by burning a substance made of organic matter in a sprayed coating formed by spraying an oxide serving as a catalyst carrier coated with an organic matter on a metal surface. A catalyst formed on a metal surface, characterized in that a catalytic metal is supported on a layered sprayed coating. According to the second invention, the catalyst metal is supported on the thermal spray coating formed on the metal surface and formed as an oxide layer which is a catalyst carrier having fine pores and a large specific surface area, whereby a large number of fine metals are supported. There is provided a catalyst formed on a metal surface having a catalyst layer in which a catalyst metal is supported on the pores of a thermal spray coating that is a catalyst carrier having pores and a large specific surface area.

  According to a third aspect of the present invention, an oxide containing a catalytic metal coated with an organic substance is sprayed on a metal surface to form a sprayed coating, and then carbon in the sprayed coating is burned by heat treatment to form pores. Then, the thermal spray coating formed into a porous oxide layer is reduced to form a catalyst on the metal surface for forming a catalytic metal active layer having fine pores. According to the present invention, the catalyst of the first invention can be suitably formed.

  According to a fourth aspect of the present invention, an oxide serving as a catalyst support coated with an organic substance is sprayed on a metal surface to form a sprayed coating, and then a substance made of organic matter in the sprayed coating is burned by heat treatment to form pores. Then, the catalyst is formed on the metal surface, characterized in that the catalyst metal is supported on the sprayed coating formed into a porous oxide layer. According to the present invention, the catalyst of the second invention can be suitably formed.

  Here, as a method of supporting the catalyst metal on the thermal spray coating that is the porous catalyst support obtained in the fourth invention, a dipping method, a brush coating method, a spray coating method, or the like can be used. It is particularly preferable to use an impregnation method or a precipitation method. Further, in the above invention, a substance composed of an organic substance in the thermal spray coating is burned by heat treatment to form pores having a pore diameter in the range of 1 nm to 500 μm, preferably in the range of 1 nm to 100 μm, more preferably in the range of 1 nm to 10 μm. It is preferable to make it. Moreover, in the said invention, it is preferable to adjust the coating amount of organic substance and to control the porosity and / or hole diameter in a sprayed coating.

  Since the present invention is configured as described above, a catalyst formed on a metal surface having a catalyst layer in which a catalyst metal is supported on a catalyst carrier having a large number of fine pores and a large specific surface area, and a method for forming the catalyst Can be provided.

  Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications. An organic substance is present on the surface of a metal of various shapes such as a plate containing aluminum, stainless steel, copper, nickel, niobium, titanium, zirconium or tantalum, etc. After spraying the coated thermal spraying powder to form a thermal spray coating, a substance made of organic matter in the thermal spray coating is burned by heat treatment to have a diameter of 1 nm to 500 μm, preferably 1 nm to 100 μm, more preferably 1 nm to 10 μm. The thermal spray coating which is a porous oxide layer is formed. As described above, after the oxide containing the catalyst metal coated with the organic material is sprayed on the metal plate, the porous material layer or the catalyst carrier layer is formed by decomposing and removing the organic material in the sprayed coating. It is possible to form a porous catalyst layer of any thickness on a metal with high heat resistance. Further, the thickness of the porous layer can be arbitrarily controlled according to the spraying conditions, and the porosity and pore diameter can also be arbitrarily controlled by selecting the kind and amount of the organic substance to be used.

  When this is used as a catalyst, the catalytic metal oxide is reduced with hydrogen or the like to form an active layer having fine pores. The heat treatment for decomposing the organic substance in the thermal spray coating to form pores is performed at about 200 to about 800 ° C. for about 1 to 10 hours, preferably about 400 to about 600 ° C. for about 2 to 4 hours. It is preferable. The atmosphere is preferably an oxidizing atmosphere in the case of complete decomposition, but fine pores can be formed even in a non-oxidizing atmosphere if there is no problem even if carbon remains.

  In addition, oxides serving as catalyst supports in which organic materials are coated on the surface of various shapes of metal such as aluminum, stainless steel, copper, nickel, niobium, titanium, zirconium or tantalum, etc. The material composed of organic matter in the sprayed coating is burned and decomposed by heat treatment similar to the above to form a sprayed coating, and the diameter is 1 nm to 500 μm, preferably 1 nm to 100 μm, more preferably 1 nm to 10 μm. Pores are formed, and a porous oxide layer is formed. By coating this oxide layer with a catalyst metal or a support material by dipping, brushing, spraying, precipitation or the like, a catalyst or catalyst support in which fine pores and a large specific surface area are formed is obtained. Therefore, since the catalyst carrier layer having a large specific surface area can be formed and supported on the catalyst metal by a known method later, the type of the catalyst metal is not limited. Further, the thickness of the sprayed film can be arbitrarily controlled according to the spraying conditions, and the porosity and pore diameter can be arbitrarily controlled by selecting the kind of organic substance and the amount of organic substance to be coated. Furthermore, it does not peel off even at high temperatures.

Using any of the above methods, a combustion catalyst for catalytic combustion that oxidizes hydrogen, hydrocarbons, alcohol, etc. with oxygen on the catalyst surface, or hydrogen dissociation (bonding) for dissociating or bonding hydrogen ) A catalyst can be formed. Specifically, the combustion catalyst is Pt / Al ₂ O ₃ or the like, and instead of Pt, Fe, Ni, Co, Ru, Pd, Rh, Cu, Nb, Zr, Ta or the like and oxides thereof Can also be used. The hydrogen dissociation (bonding) catalyst is Pd / Al ₂ O ₃ or the like, and Pt or Ni and oxides thereof can be used instead of Pd.

  Examples of the present invention will be described below.

[Example 1]
Zirconia powder (particle diameter 0.1 to 2 μm) and polyvinyl alcohol are mixed in a weight ratio of 90:10 using water as a solvent in a ball mill, dried at 100 ° C., then granulated, and coated with polyvinyl alcohol. A thermal spraying powder was produced. Next, the surface of the aluminum plate as a substrate was roughened by sandblasting. The powder for thermal spraying was plasma sprayed in the atmosphere to form a sprayed coating having a thickness of 70 μm on the substrate. FIG. 1 shows a schematic diagram of the cross-sectional state of the applied film. In FIG. 1, reference numeral 10 is a substrate, reference numeral 12 is a substance made of polyvinyl alcohol, reference numeral 14 is zirconia particles, and reference numeral 15 is a catalyst metal. Thereafter, heat treatment was performed in the atmosphere at 500 ° C. for 4 hours to burn and decompose the substance 12 made of polyvinyl alcohol, thereby obtaining a sprayed coating as a porous catalyst carrier. When the pores of this thermal spray coating were measured, pores having a diameter of 10 nm to 1 μm were generated. This is called substrate A.

  A water-based slurry in which polyvinyl alcohol and alumina powder (particle diameter of 0.1 to 2 μm) were made to have a weight ratio of 20:80 was dried, and then granulated to prepare a thermal spraying powder. The thermal spraying powder containing alumina powder was sprayed in the same manner as above on the substrate 10 whose surface was adjusted in the same manner as described above to form a thermal spray coating. Thereafter, the organic material in the thermal spray coating was burned by heat treatment to form a thermal spray coating as a porous catalyst carrier. The pore diameter of this sprayed coating was 100 nm to 10 μm in diameter. This is called a substrate B.

  A polyvinyl butyral and niobium oxide powder (particle diameter 0.1 to 2 μm) was made into an etal slurry having a weight ratio of 10:90, dried, and then granulated to prepare a thermal spraying powder. The thermal spraying powder was sprayed onto the substrate 10 in the same manner as described above to form a thermal sprayed coating, and a thermal sprayed coating as a porous catalyst carrier formed by burning and decomposing a substance made of organic matter from the thermal sprayed coating was formed. The spray coating had a pore diameter of 10 nm to 100 nm. This is a substrate C.

  A catalyst layer in which a Pd catalyst is supported on a porous layer of zirconia as a catalyst carrier by applying a colloidal solution containing Pd as the catalyst metal 15 to the thermal spray coating of the substrate A by an impregnation method, drying and heat-treating at 400 ° C. A catalyst having a structure formed on the substrate 10 was obtained. Even when this catalyst was heated to 500 ° C. and then allowed to cool to room temperature, the catalyst layer could be used repeatedly without peeling.

  Substrate B was immersed in an aqueous solution containing 5% by weight of ruthenium chloride as a catalyst metal at room temperature for 10 hours, and then calcined at 400 ° C. for 3 hours. The Ru catalyst was supported on a porous layer of alumina as a catalyst carrier. A catalyst having a structure in which a catalyst layer was formed on the substrate 10 was obtained. When used as a catalyst, ruthenium was reduced with hydrogen or the like. Even when this catalyst was heated to 500 ° C. and then allowed to cool to room temperature, the catalyst layer could be used repeatedly without peeling.

[Example 2]
Pd, which is a catalytic metal, zirconia powder (particle size: 0.1 to 2 μm) and polyvinyl alcohol are mixed at a weight ratio of 5:85:10 using water as a solvent in a ball mill, dried at 100 ° C., and then granulated. A powder for thermal spraying was prepared. Next, the powder for thermal spraying was plasma sprayed in vacuum on the surface of a substrate 10 (manufactured by Nilaco Co., Ltd., 3N grade, plate thickness 1 mm) mainly composed of Ta, which is a hydrogen permeable film, and a thickness of 70 μm was formed on the substrate. A sprayed coating was formed. Thereafter, a heat treatment is performed in the atmosphere at 500 ° C. for 4 hours, and a catalyst layer, which is a porous sprayed coating carrying Pd, is formed on the substrate 10 by burning and decomposing a substance made of polyvinyl alcohol. A catalyst with the structure formed was obtained. When pores of the catalyst layer were measured, pores having a diameter of 10 nm to 1 μm were generated. Even when this catalyst was heated to 500 ° C. and then allowed to cool to room temperature, the catalyst layer could be used repeatedly without peeling.

[Example 3]
Pd, which is a catalytic metal, niobium oxide powder (particle size 0.1 to 2 μm) and polyvinyl alcohol are mixed at a weight ratio of 5:85:10 using water as a solvent in a ball mill, dried at 100 ° C., and then granulated. The powder for thermal spraying was produced. Next, the thermal spraying powder is plasma sprayed in vacuum on the surface of the substrate 10 (plate thickness 1 mm) made of a Ni ₃₀ Ti ₃₁ Nb ₃₉ alloy, which is a hydrogen permeable film, to form a sprayed coating having a thickness of 70 μm on the substrate. did. Thereafter, a heat treatment is performed in the atmosphere at 500 ° C. for 4 hours, and a catalyst layer, which is a porous sprayed coating carrying Pd, is formed on the substrate 10 by burning and decomposing a substance made of polyvinyl alcohol. A catalyst with the structure formed was obtained. When pores of the catalyst layer were measured, pores having a diameter of 10 nm to 1 μm were generated. Even when this catalyst was heated to 500 ° C. and then allowed to cool to room temperature, the catalyst layer could be used repeatedly without peeling.

It is sectional drawing in the Example of this invention.

Explanation of symbols

10 Substrate 12 Organic substance 14 Oxide 15 Catalytic metal

Claims (7)

An organic substance-coated oxide containing a catalytic metal is sprayed onto the metal surface to burn the organic material in the sprayed coating to form pores, reducing the sprayed coating that has become a porous oxide layer. The catalyst formed on the metal surface formed by forming a catalyst layer having fine pores. An organic material-coated oxide carrier is sprayed onto the metal surface to form a pore by burning the organic material in the sprayed coating to form a porous oxide layer. A catalyst formed on a metal surface, characterized by supporting a metal. An oxide containing a catalytic metal coated with an organic substance is sprayed onto the metal surface to form a sprayed coating, and then the carbon in the sprayed coating is burned by heat treatment to form vacancies, and then a porous oxide layer A method of forming a catalyst on a metal surface by reducing the sprayed coating thus formed to form an active layer of catalytic metal having fine pores. The catalyst carrier coated with organic matter is thermally sprayed onto the metal surface to form a sprayed coating, and then the organic material in the sprayed coating is burned by heat treatment to form pores, and then porous. A method for forming a catalyst on a metal surface, wherein a catalytic metal is supported on a sprayed coating that has become an oxide layer. The method for forming a catalyst on a metal surface according to any one of claims 4 to 5, wherein a catalyst metal is supported on the support layer by any one of an impregnation method and a precipitation method. The method for forming a catalyst on a metal surface according to any one of claims 3 to 5, wherein a substance composed of an organic substance in the thermal spray coating is burned by heat treatment to form pores having a pore diameter in the range of 1 nm to 500 µm. The method for forming a catalyst and / or catalyst support on the metal surface according to any one of claims 3 to 6, wherein the porosity and / or pore diameter in the sprayed coating is controlled by adjusting the coating amount of the organic matter.

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