JPH067929B2 - Method for producing metal catalyst carrier - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a carrier that constitutes a metal catalyst used for purifying exhaust gas of an automobile, for example.

[Conventional technology]

Heretofore, as such a metal catalyst carrier, those disclosed in, for example, JP-A-57-71898 are known.

This will be described with reference to FIG. Metal catalyst carrier 1
In order to improve so-called spalling resistance, the surface of the base material 2 formed of a ferritic alloy containing aluminum is subjected to heat treatment to form an alumina whisker layer 3 by diffusion of aluminum. Here, for example, an alloy of Fe-20Cr-5Al is used as the base material 2, and the alumina whisker layer 3 is made of α-Al ₂ O _3.
Consists of.

Furthermore, on the surface of the alumina whisker layer 3, γ-Al
An alumina layer 4 of a catalyst carrier made of ₂ O ₃ is formed, and the catalyst supporting alumina layer 4 is impregnated with a metal catalyst 5 such as Pt or Rh.

Such a metal catalyst carrier 1 was manufactured according to the manufacturing method shown in FIG. 5, for example.

First, in order to form a whisker precursor in advance, a material made of a ferritic alloy containing aluminum is preliminarily heated in a low oxygen atmosphere at 800 ° C. for about 1 minute, for example.

The precursor is specifically an extremely thin alumina layer.

After that, the material is formed into a flat plate and a corrugated plate, and as shown in FIG. 4, the flat plate 6 and the corrugated plate 7 are superposed, and these are wound in multiple layers to form the metal catalyst carrier 1. It Thereafter, the flat plate 6 and the corrugated plate 7 are brazed or welded, and the surfaces of the flat plate 6 and the corrugated plate 7 are subjected to growth heat treatment of alumina whiskers.

[Problems to be solved by the invention]

However, in such a conventional method for producing a metallic catalyst carrier, before the brazing or welding of the flat plate 6 and the corrugated plate 7, a whisker precursor is formed in advance on a material made of a ferritic alloy containing aluminum. Since the pretreatment of (1) is performed in a low oxygen atmosphere, the productivity of alumina whiskers slightly changes depending on the oxygen concentration, and it is difficult to manage to obtain uniform alumina whiskers. In addition, the strength of brazing or welding between the flat plate 6 and the corrugated plate 7 may decrease.

Besides the method of performing the preliminary treatment, there are known a method of performing a growth treatment after thinning by peeling, and a method of performing a growth treatment with carbon or oil attached.

However, the former is very difficult to manufacture and it is difficult to obtain a thin plate. On the other hand, the latter has problems that it is difficult to make the adhered amount constant and the inside of the furnace becomes dirty.

[Object of the Invention]

The present invention has been made to solve such conventional problems, and an object thereof is to easily perform a pretreatment and to reliably produce a uniform alumina whisker. It is an object of the present invention to provide a method for manufacturing a catalyst carrier.

[Means for solving problems]

In the method for producing a metal catalyst carrier according to the present invention, a material formed of a ferritic alloy containing aluminum is laminated, and then heat-treated in the atmosphere to form α-Al ₂ O _{3 on the} surface of the material.
A method for producing a metal catalyst carrier for producing whiskers is characterized by anodizing a material formed of a ferrite alloy containing aluminum.

[Operation of the invention]

In the present invention, since the material formed of the aluminum-containing ferritic alloy is anodized, stable pretreatment can be performed in an extremely short time as compared with heat treatment. Further, the surface of the material formed of the aluminum-containing ferritic alloy is cleaned by the anodizing action.

Example of Invention

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory view showing a case where a material formed of an aluminum-containing ferrite alloy is anodized in a step before being formed into a flat plate and a corrugated plate.

First, a 3% oxalic acid solution is placed in the electrolytic cell 11 and the anode is arranged so as to be connected to the material (Fe-20Cr-5Al) 10, and platinum 12 is attached to the anode side.

Next, the material 10 is supplied to the electrolytic cell 11 adjusted to a liquid temperature of 25 ° C., 18 V, and 0.8 A / cm ² . At this time, the material 10 is kept in contact with the anode side. The immersion time was 5 minutes.

Thus, the surface of the raw material 10 is dissolved and oxidized in the electrolytic bath 11, and a precursor (extremely thin alumina film) is generated. or,
In this anodizing step, the cleaning treatment of the surface of the material 10 is also performed at the same time.

This cleaning action enables not only the cleaning of impurities but also the uniform formation of the precursor even though the precursor is extremely thin, which in turn enables the uniform production of whiskers in the next step. There is.

Then, the raw material 10 taken out of the electrolytic bath 11 is subjected to a drying step, and then formed into a flat plate and a corrugated plate according to a conventional method as shown in FIG. The flat plate and the corrugated plate are overlapped with each other, these are wound in multiple layers to form a metal catalyst carrier, and then the flat plate and the corrugated plate are brazed or welded.

Then, heat treatment for 4 hours at 925 ° C. in air, to produce alumina whiskers α-Al ₂ O ₃ than the precursor.

The state of whiskers formed on the surface of the material at this time is shown in FIG. Uniform alumina whiskers as shown in FIG. 6 were formed at all locations on the carrier. For comparison, the same material as in the above example was subjected to a heat treatment (in a low oxygen atmosphere) at 800 ° C for 1 minute, and then at 925 ° C in the atmosphere.
A metal catalyst carrier was formed in the same manner as in the above-mentioned examples except that the heat treatment was performed for 4 hours to form α-Al ₂ O ₃ alumina whiskers. On the material surface of this carrier, some incompletely formed whiskers were observed, as shown in FIG.

In the above embodiment, the anodizing treatment is performed before the flat plate and the corrugated plate are formed, but the anodizing treatment may be performed after the flat plate and the corrugated plate are formed.

Further, the anodizing treatment is not limited to the continuous treatment as in the above embodiment, but may be a batch type. Furthermore,
Although 3% oxalic acid was used in the above embodiment, the electrolytic solution is not limited to this and may be any. Moreover, the current value may be in the range of 0.01 to 10 A / cm ² . Further, the processing conditions such as temperature, time and voltage can be set arbitrarily according to the electrolytic cell. The electrode on the anode side is not limited to platinum, but stainless steel or the like may be used.

Further, to the aluminum-containing ferritic alloy used in the present invention, any one can be used as long as it can be used in a converter for purification of an internal combustion engine such as an automobile,
It is desirable that the base material is Fe-15 to 20Cr-3 to 6Al. Of course, it may contain a rare earth element such as Y or Ce.

〔The invention's effect〕

INDUSTRIAL APPLICABILITY As described above, the present invention is a method for producing a metal catalyst carrier in which materials formed of a ferrite-based alloy containing aluminum are laminated and then heat-treated in the atmosphere to generate α-Al ₂ O ₃ whiskers on the surface of the material. In this case, since the material formed of an aluminum-containing ferrite alloy is anodized, the cleaning action by anodization is combined with the oxidizing action of aluminum to reliably generate the precursor in a short time, and A uniform alumina whisker can be reliably generated during the heat treatment in the atmosphere in the formation of the carrier.

At the same time, anodic oxidation cleans impurities such as rust on the surface of the material.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view showing an embodiment of the present invention, FIG. 2 is an explanatory view showing a process for producing a metal catalyst carrier using the present invention, and FIG. 3 is a metal catalyst. FIG. 4 is a cross-sectional view showing a main part of the carrier, FIG. 4 is an external view of the metal catalyst carrier, FIG. 5 is an explanatory view showing a conventional manufacturing process, and FIG. 6 is a metal catalyst carrier 8000 according to an embodiment of the present invention. Double scanning electron micrograph, FIG. 7 is a 8,000 times electron micrograph of a metallic catalyst carrier produced by a conventional method. 1 ... Metal catalyst carrier, 2 ... Substrate, 3 ... Alumina whisker, 4 ... Catalyst-supporting alumina whisker, 5 ... Metal catalyst, 6 ... Flat plate, 7 ... Corrugated plate, 10 ... Aluminum Material made of ferritic alloy, including 11 ... electrolytic cell, 12 ... platinum.

Claims (1)

[Claims] 1. A method for producing a metal catalyst carrier, which comprises laminating materials formed of aluminum-containing ferrite-based alloys and then heat-treating the materials in the atmosphere to generate α-Al ₂ O ₃ whiskers on the surface of the materials. A method of manufacturing a metal catalyst carrier, characterized in that a material formed of an aluminum-containing ferritic alloy is anodized.