JPH02180644A - Catalyst and its preparation - Google Patents

Abstract

PURPOSE:To prepare a catalyst of superior resistance to oxidation, resistance to corrosion and superior in mechanical strength and simplify its preparation process by diffusion bonding plane sheets and corrugated sheets in Al bath without braizing and making a porous carrier layer without oxidation process. CONSTITUTION:A laminate is manufactured by laminating alternately plane metal sheets 2 and corrugated metal sheets 3 and said laminate is retained in the state that sections 21 where said plane sheets 2 and corrugated sheets 3 are brought into contact and immersed in molten aluminum bath. Thus the sections 21 where plane sheets 2 and corrugated sheets 3 are bonded by diffusion bonding, and a honeycomb structure material forming an alloy layer 41 constituted of a metal forming the plates and aluminum on the surfaces of both of said plates is manufactured. Then, an inorganic powder layer such as alumina, silica or the like is bonded on the surface of the alloy layer 41 of said metal honeycomb structure material and a porous layer 4 is fixed and formed by heating and then a catalyst component 5 is carried on the porous layer 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a catalyst used for purifying exhaust gas from internal combustion engines, etc., and a method for manufacturing the same.

(Prior Art) Catalysts used for exhaust purification etc. usually consist of a catalyst component that exhibits a catalytic function and a porous layer for supporting the catalyst component.

As the structure of the porous layer, a honeycomb structure is often used to obtain a large surface area. In addition, in recent years, it has been proposed that the honeycomb structure is made of metal, a porous layer of alumina powder or the like is formed thereon, and a catalyst component is supported in the porous layer.

This is because metal has high thermal conductivity, so the temperature of the porous layer and catalyst layer rises quickly. Therefore, when this is used especially for exhaust purification, the temperature of this catalyst layer rises to almost the same temperature as the exhaust gas even at the beginning of operation of the internal combustion engine, making it possible to perform exhaust purification from the beginning of operation. can.

As described above, a catalyst using a metal honeycomb structure has excellent functions, but since it is used in exhaust gas, it is required to have oxidation resistance and corrosion resistance at high temperatures.

However, such metal honeycomb structures have conventionally been made of metals containing Al (aluminum), such as Fe.
(Iron) 15Cr (Chromium)-5AII has been proposed. This material is made of alternating layers of thin flat plates and corrugated plates made of the above materials.

Alternatively, the two rolls are stacked one on top of the other and the contacting portions of the two rolls are joined with brazing material. Furthermore, since this material contains Al, it has excellent oxidation resistance and corrosion resistance against high temperature gases containing oxygen such as exhaust gas from internal combustion engines.

Further, the formation of adhesion of the porous layer on the honeycomb structure is as follows:
This is done by heating the metal honeycomb structure in an oxidizing atmosphere to form an aluminum oxide coating on its surface, and then depositing powder for a porous layer on the coating (Japanese Patent Publication No. 48-23138). ).

The honeycomb structure is made by alternately laminating flat plates and corrugated plates, as illustrated in FIGS. 1 and 2.

The porous layer and the catalyst component are supported on the surface of the catalyst, and the exhaust gas and the like flow into the gap between the two plates.

[Problem to be solved]

However, since the conventional honeycomb structure uses brazing material to join the flat plate and the corrugated plate as described above, it has poor corrosion resistance. That is.

Conventionally, for the above-mentioned joining, a plating sheet coated with a material for brazing was interposed between the flat plate and the corrugated plate, and the two were joined by heating.

However, the honeycomb structure by brazing as described in 5.

While using the catalyst prepared in this manner, the brazed portion is likely to corrode. For example, 1ooo'c.

Corrosion occurs in 20 hours. This is considered to be because the exhaust gas is a high temperature gas containing water vapor.

Corrosion of the brazed portion causes the bond between the flat plate and the corrugated plate to separate, making it impossible to use the catalyst itself.

Furthermore, conventionally, as shown in Japanese Patent Publication No. 4B-23138, the surface of a honeycomb structure is oxidized when a porous layer is supported on the honeycomb structure. That is, it is necessary to heat the honeycomb structure in an oxidizing atmosphere prior to supporting the porous layer. Furthermore, even though such an oxidation process involves a high-temperature oxidizing atmosphere, the equipment needs to be oxidation-resistant.

In view of these problems, the present invention was made as a result of intensive research into joining a flat plate and a corrugated plate without using brazing and supporting a porous layer without using an oxidation process. It is an object of the present invention to provide a catalyst that has excellent oxidation resistance and corrosion resistance during use, and a method for producing the same. The catalyst is composed of a porous layer and a catalyst component supported on the porous layer, and the honeycomb structure is formed by alternately laminating metal flat plates and corrugated plates, and a contact portion between the flat plates and the corrugated plates. are diffusion bonded to each other, and at least the surfaces of the flat plate and the corrugated plate have an alloy layer of metal and aluminum constituting the flat plate and the corrugated plate (first invention).

In the present invention, the metal plates constituting the metal honeycomb structure as the skeleton of the catalyst are both flat plates and corrugated plates made of metals that have excellent oxidation resistance and heat resistance at high temperatures. Further, it is preferable that the metal has an Al content of less than 0.1% (!II (amount).

As the Al content increases, the transition temperature increases.

This is because cold workability deteriorates. Such metals include ferritic or austenitic stainless steel. Also, what is the thickness of flat plate and corrugated plate?

0.03 to 1.0 from the viewpoint of processability, weight reduction of the honeycomb structure, and formation of a large number of cells. It is preferable to set it as 0IIn.

The first important point in the present invention is that the contact portions of the flat plate and the corrugated plate are firmly bonded to each other by diffusion bonding. Regarding this point, to explain with reference to FIG. 3, the flat plate 2 and the corrugated plate 3 are diffusion bonded to each other at a portion indicated by the reference numeral 21 (the contact portion of both plates). Such diffusion bonding mainly utilizes atomic diffusion and creep deformation to bond contact surfaces. This joining means will be described later. In addition, in the same figure, the code|symbol 4 is a porous layer provided on the honeycomb structure.

5 is a catalyst component supported on the porous layer, and 41 is an alloy layer to be described later.

The second important point in the present invention is that these temporary metals and Al
This means that an alloy layer is formed. Therefore, the thickness of the alloy layer is preferably 10 to 100 μm. If the thickness is less than 10 μm, the five-honey structure will not have sufficient oxidation resistance or corrosion resistance, and if it exceeds 100 μm, it will be difficult to obtain a commensurate effect.Furthermore, it is sufficient that these alloy layers are formed at least on the surface. Therefore, the entire flat plate and corrugated plate may form an alloy metal as described above.

Regarding this alloy layer, referring to FIG. 3 above, an alloy layer 41 with Al is formed on the surface portions of both the flat plate 2 and the corrugated plate 3. The alloy layer 41 may be present at least on the surface, but the entirety of each plate 2.3 may be made of the same alloy as described above. These A
As mentioned above, the alloy with 2 has excellent oxidation resistance and corrosion resistance.

Demonstrates excellent performance as a metal honeycomb structure.

Such an alloy layer can be formed by the manufacturing method described below.

The honeycomb structure may be a laminate made by stacking flat plates and corrugated plates alternately, as shown in Fig. 1 described later, or a laminate made by stacking long flat plates and long corrugated plates as shown in Fig. 2. However, there are also those that are rolled into a roll and made into a laminate.

Next, a porous layer is attached and formed on the surfaces of the flat plate and the corrugated plate in the honeycomb structure (see FIG. 3). The porous layer is a layer for supporting a catalyst component, and is mainly composed of a porous fired body of ceramic powder. As such a porous layer, it is preferable to use one or more of alumina, silica, alumina-silica, titania, zirconia, and cordierite. Since these powders themselves are porous, they have a large surface area necessary for the catalyst, and are also excellent in heat resistance and durability.

In addition, the catalyst components supported on the porous layer include catalyst usage purpose 1, for example, exhaust from internal combustion engines, diesel particulates (unburned carbon particles) in diesel engine exhaust, exhaust from nitric acid factories, etc. Use one that is compatible with the purification of various types of exhaust such as flue gas. For example, in the case of purifying exhaust gas from internal combustion engines, the catalyst components used are platinum (pt), palladium (Pd), and rhodium (R).
h) It is also conceivable to use a three-element catalyst using one or more types of ruthenium (Ru), ie, a pt-based oxidation catalyst, a vanadium oxide-based reduction catalyst, etc.

Next, as a method for producing the above catalyst, a laminate is made by alternately stacking flat metal plates and corrugated metal plates.

The laminate is immersed in a molten aluminum bath while keeping the contact portions of the flat plate and the corrugated sheet in contact with each other, thereby bonding the contact portions of the flat plate and the corrugated sheet by diffusion bonding, and at least A metal honeycomb structure is prepared by forming an alloy layer of metal and aluminum on the surfaces of both plates, and then an inorganic powder layer is attached to the surface of the alloy layer of the metal honeycomb structure and heated. There is a method for producing a catalyst, characterized in that a porous layer is fixedly formed, and then a catalyst component is supported on the porous layer (second invention).

In this method, first, flat metal plates and corrugated metal plates are alternately laminated to form a laminate, and the laminate is placed in a molten A2 bath while the contact portions of the flat plates and the corrugated plates are held in contact with each other. Soak in. As a result, a honeycomb structure is produced in which the contact portions of the flat plate and the corrugated plate are diffusion bonded, and the alloy layer is formed on at least the surface portion of one of the plates.

The A2 bath may be made by melting an aluminum material containing 10% or less of silicon, copper, etc., in addition to pure aluminum. To this! What is the temperature of the bath?

To diffuse bond the contact area between the above flat plate and corrugated plate 6
It is preferable to set it as 70-750 degreeC (3rd invention). 6
If the temperature is less than 70°C, the temperature will be too low and the expansion IP bonding and alloy layer formation will be insufficient, and if it exceeds 750°C, although the bonding time will be shortened, the reaction of one alloy will be inhibited and there is a risk that the process will not be completed. In addition, the immersion time in the Al bath is 10 seconds to 1
It is preferable to set it to 0 minutes. This is the above diffusion bonding and
AI on the surface of each flat plate and corrugated plate of the honeycomb structure! , in order to form an alloy layer. If it takes less than 10 seconds, these effects will be insufficient, and if it takes more than 10 minutes, it will be difficult to obtain a commensurate effect.

In the above, the surfaces of the flat plate and the corrugated plate should be as clean and smooth as possible in order to perform diffusion bonding. In particular, thin plates produced by cold rolling have excellent cleanliness and smoothness on one surface, and excellent diffusion bonding properties. Note that the surfaces of the flat plates and corrugated plates are preferably subjected to degreasing treatment before being laminated. This is to clean the surface.

Further, during immersion in the Al bath, the contact portions of the two plates are brought into sufficient contact to ensure sufficient diffusion bonding between the flat plate and the corrugated plate. Also, as shown in FIG. 2, in the case of a laminate rolled into a roll.

The corrugated sheet is deformed by this entrainment, and the repulsive force causes the contact areas of the two sheets to stick together with appropriate pressure.

Also, in the above, the material of both boards and its thickness.

The state of the diffusion bonding, the state of the alloy layer with AN, etc. are the same as those described for the honeycomb structure. Further, the cross-sectional passage of the honeycomb structure may be arbitrary, such as hexagonal, quadrangular, or triangular.

Next, in one method, inorganic powder is attached to the honeycomb structure and heated in order to form a porous layer on the surfaces of the flat plate and corrugated plate. As such powder, one or more of alumina, silica, alumina-silica titania, zirconia, and cordierite are used. Moreover, it is preferable that the average particle size of this powder is 5 to 20 μm.

Further, the adhesion is carried out by mixing the powder with a glue such as carboxymethyl cellulose (CMC) and water to form a slurry, and immersing the honeycomb structure in the slurry. For this immersion, immersion 5
It is also possible to increase the amount of the powder adhered by repeating drying.

Then, the honeycomb structure to which the powder is attached is heated to 600 to 700°C to burn the powder and fix it on the honeycomb structure. If the temperature is lower than 600°C, it will take a long time for firing and fixing.

On the other hand, if the temperature exceeds 700°C, there will be little effect commensurate with that temperature.

Through the above steps, a porous layer is formed on the honeycomb structure.

Next, a catalyst component is supported on the porous layer on the honeycomb structure to form a catalyst. However, as a method for supporting a catalyst component on a porous layer, there is a dipping method.For example, in the case of supporting PL-Rh.

A honeycomb structure provided with the above porous layer is immersed in an aqueous solution of these chlorides (platinum chloride, rhodium chloride), nitrate compounds (platinum nitrate, rhodium nitrate), etc., and the above aqueous solution is poured into the porous layer. Adsorb, dry and heat to obtain PL and Rh.

Another method for producing a catalyst is to make a laminate by alternately stacking metal flat plates and corrugated plates, and to hold the laminate in a state in which the contact portions of the flat plates and the corrugated plates are in contact with each other. By immersing it in a molten aluminum bath, coating the surfaces of the flat plate and corrugated plate with aluminum, and heating this laminate in a non-oxidizing atmosphere after taking it out from the aluminum bath,
A metal honeycomb structure is manufactured by bonding the contact portions of the flat plate and the corrugated plate by diffusion bonding, and forming an alloy layer of metal and aluminum on at least the surfaces of the flat plate and the corrugated plate of the laminate. .

Next, an inorganic powder layer is attached to the surface of the alloy layer of the metal honeycomb structure, heated to firmly form a porous layer, and then a catalyst component is supported on the porous layer. There is a method for manufacturing a metal honeycomb structure (fourth invention)
.

In this method, in the manufacturing method of the second invention, the laminate is
I! After soaking it in a bath towel, take it out.

It is heated in a non-oxidizing atmosphere. However.

The above-mentioned dipping step is to coat A2 on the flat plate and the corrugated plate except for the contact areas between the two. Then, by heating after taking it out from the AN bath, Aff was formed on the surface of both plates.
The diffusion bonding layer at the contact portion between the two plates, which forms a thicker alloy layer with i, may be formed to some extent during immersion in the Al bath, but is mainly formed during the heating described above.

This heating is performed in vacuum or in a non-oxidizing atmosphere such as nitrogen, hydrogen, or inert gas. Heating temperature is 600-1000
It is preferable to set it as °C. At temperatures below 600°C, alloying takes a long time; at temperatures above 1000°C, flat plates and corrugated plates may deform.
? There are inconveniences such as 8 losses.

Further, the heating time is preferably 1 to 30 minutes.

Further, the temperature of the AN bath is the same as in the above method.

In addition, the immersion time in the AP hot bath is
It is preferable to set it as 10 seconds - 5 minutes in order to make it adhere.

Further, in the nine method, the thickness of the nine alloy layers of the nine metal plates and the thickness thereof are the same as those described for the honeycomb structure. Furthermore, the formation of a porous layer on the metal honeycomb structure and the supporting of the catalyst component therein are the same as described above.

[Action and effect]

In the catalyst of the first invention, the metal honeycomb structure as its skeleton is diffusion bonded at the contact portion between the flat plate and the corrugated plate,
Furthermore, an alloy layer with AN is formed on the surfaces of both plates. Therefore, the catalyst has excellent oxidation resistance and corrosion resistance against oxygen-containing gases such as exhaust gas from internal combustion engines. Also 2
It also has excellent mechanical strength. This effect is due to the fact that the two plates are directly joined as described above, and there is no adhesive layer such as brazing material interposed between the two plates as in the prior art.

Thus, the catalyst includes a porous layer on the surface of the metal honeycomb structure, and a catalyst component supported on the porous layer. Therefore, when the catalyst is used for engine exhaust purification, the heat of the exhaust is quickly transferred to the metal honeycomb structure that is the skeleton of the catalyst, and the entire catalyst quickly reaches the exhaust temperature, allowing purification to occur from the beginning of engine operation. Can be done.

Therefore, according to the present invention, it is possible to provide a catalyst that has excellent oxidation resistance, corrosion resistance, and low-temperature activity.

Further, according to the manufacturing method of the second aspect of the invention, a catalyst having excellent performance as described above can be manufactured. In addition, in the 9 method, oxidation resistance.

Since 81, which exhibits corrosion resistance, is formed as an alloy layer on the surface of the flat plate and corrugated plate after forming the honeycomb laminate,
Flat plates and corrugated plates do not need to contain AP.In this way, materials that do not contain A2 can be used as flat plates and corrugated plates, so two plates can be used regardless of hot working or cold working. It can be manufactured without any problem.

That is, the thickness of the flat plate and corrugated plate is 0.03~l■ as mentioned above.
It is a thin plate. This thin plate is produced by roll rolling, etc., but if this plate material contains a large amount of Aff (for example, the conventional Fe-15Cr-5Affi steel), cold working may be poor and longitudinal cracks may occur. On the other hand, as explained in the description of the prior art, metal honeycomb structures are required to have oxidation resistance and corrosion resistance at high temperatures, and for this purpose A
It is essential to contain l. In this way, the present invention forms the A1 alloy required for the metal honeycomb structure after forming the honeycomb laminate, so it is made of 5 flat plates.

A material that can be easily processed into a corrugated plate (for example, the stainless steel mentioned above) can be used, and a flat plate or a corrugated plate can be easily processed.

Furthermore, in this method, the diffusion bonding of the flat plate and the corrugated plate and the formation of an alloy layer on the surface are performed in a molten Al bath, and then inorganic powder is attached and fired to the surface to form a porous 'ff layer. There is. However, since the alloy layer is an alloy with Al, inorganic powder such as alumina is easily attached thereto. Also, for that reason.

This method does not require an oxidation heating step to form an oxide film on the flat plates and corrugated plates of the honeycomb structure, as in the prior art. Therefore, there are three methods.

In addition to the above effects, it also has the effect of simplifying the catalyst manufacturing process.

Furthermore, according to the manufacturing method of the fourth aspect of the invention, a catalyst having excellent performance as described above can be manufactured, and the same effects as those of the second invention described above can be obtained. Further, the diffusion bonding and the growth of the A2 alloy layer can be performed outside the Al bath, which facilitates manufacturing.

Also, the third and fifth. The invention set forth in claim 6 can obtain the same effects as the second invention and the fourth invention, respectively, as well as the effects described in the previous section (means for solving the problem).

〔Example〕

1st Example As the metal material for the flat plate and the corrugated plate, 5US430, which is a ferritic stainless steel, is used. Five plates are stacked on top of each other to form a laminate, and this is immersed in an Al bath to form a metal honeycomb as shown in Fig. 1. Next, a porous layer of alumina powder was formed on the surface of the structure I, and Pt was added to the porous layer.
A catalyst according to the present invention was prepared by supporting -Rh.

That is, as a raw material, the above 5tJ formed by cold rolling
A thin plate of S430 with a thickness of 0.8 nm and a width of 100 nm was prepared. Then, the thin plate was formed into a 6-pitch corrugated shape using a corrugated roll, and was made into a corrugated plate.
After degreasing the thin flat plate and the corrugated plate, the flat plate and the corrugated plate were alternately laminated in one box to produce a laminate. Then, in these laminates, a load was applied from above to restrain the whole so that the contact parts of the flat plate and the corrugated plate were in contact with each other, and then the laminate was immersed for 3 minutes in an Al bath heated and melted at 690 ° C. Aluminized.

As shown in FIGS. 1 and 3, the honeycomb structure 1 manufactured as described above has flat plates 2 and corrugated plates 3 stacked vertically alternately in a box 10, and both plates 2.3 are stacked vertically. The contact portion 21 was diffusion bonded, and an A1 alloy layer 41 having a thickness of approximately 20 μm was formed on the surface portions of both plates. Note that reference numerals 4 and 5 shown in the same figure represent a porous layer and a catalyst component that will be formed in the next step.

Next, the honeycomb structure 1 was coated with a T
An operation of immersing the plate in a slurry liquid consisting of alumina powder, a small amount of CMC, and water and drying it was repeated three times to adhere the alumina powder to the flat plate and the corrugated plate. Furthermore, this thing 6
The powder was heated to 50° C. for 2 hours to fix the powder on the flat plate and the corrugated plate and was fired to form a porous TL? formed J.

Next, the honeycomb structure with the porous layer formed thereon was placed in a chloroplatinic acid solution and a rhodium chloride solution.

Soaked in one solution, dried, then immersed in the other solution.

After drying, this operation was repeated twice and then heated to 200° C. to support PLRh as a catalyst component on the porous layer 'a'.

In the obtained catalyst, as shown in FIGS. 1 and 3, the flat plate 2 and the corrugated plate 3 are diffusion bonded at the contact portion 21, and there is an alloy layer 41 with A2, and the flat plate 2 and the corrugated plate 3 are bonded together at the contact portion 21. A porous layer 4 of alumina powder is formed on the surface of the catalyst 3, and PL-Rh as a catalyst component 5 is supported in the porous layer 4.

The catalyst thus prepared could be used satisfactorily as a catalyst for purifying engine exhaust gas.

Next, the oxidation resistance of the above catalyst was evaluated. In this evaluation, the oxidation resistance of the catalyst was measured after heating at 1100° C. for a predetermined period of time in the atmosphere.

Also, for comparison, t171 without using the above diffusion bonding
When making the honeycomb structure described above, a plating sheet of Ni-based brazing material was interposed between the flat plate and the corrugated plate, and a honeycomb structure was prepared by heating and brazing the two together, and then applying the same method as above. Measurements were also carried out on a catalyst in which a porous layer and a catalyst component were formed and supported. The material, thickness, etc. of both the plates are the same as in this embodiment.

As a result, the catalyst according to the present invention did not show any trouble even after being heated for 500 hours under the above conditions.

It had excellent oxidation and corrosion resistance. In contrast, oxidative corrosion was observed in the comparative catalyst described above after 30 hours of heating.

In addition, compared to the conventional material Fe-15Cr-5Af steel, the stainless steel used in the present invention (containing ncAlO001%) does not contain a large amount of Al, so the workability is greatly improved and the processing yield is 10%. % also improved.

Second Embodiment Using the same 5US430 thin plates as above as the metal materials for the flat plate and corrugated plate, a long flat plate and a long corrugated corrugated plate were rolled up and placed in an outer cylinder.

After being immersed in A2 bath, it was taken out and then heated in a non-oxidizing atmosphere to produce a roll-shaped metal honeycomb structure 11 as shown in FIG.

Immediately, f't mi 0. A thin plate of 1iK gold having a thickness of 0.5 m and a thickness of 130 m was prepared, and this was made into a corrugated plate of 5I pitch in the same manner as in the first embodiment. Next, the corrugated plate and the thin plate (flat plate) were rolled together (see FIG. 2), and the resulting laminate was inserted into a cylindrical outer cylinder. Then, this product was immersed in an Af hot bath heated to 720° C. for 3 minutes to coat the surfaces of the nine plates with A2 having a thickness of about 15 μm. Thereafter, this was heated to 800°C in N2 gas as a non-oxidizing atmosphere.
and heated for 10 minutes. Note that the surfaces of both the plates were degreased prior to one-layer winding.

As shown in FIG. 2, the honeycomb structure 11 obtained as described above is made by rolling a flat plate 25 and a corrugated plate 35 into an outer cylinder 6.
The contact portions 26 of the two plates 25.35 disposed inside were joined by diffusion bonding, and A1 alloy was formed on the surfaces of the two plates 25.35.

Next, a porous layer of alumina powder was formed on the honeycomb structure 11 in the same manner as in the first embodiment, and then P was applied.
C-Pd was supported. Palladium chloride was used for P d IB retention. The rest is the same as the first embodiment.

The catalyst thus obtained could be used satisfactorily as a catalyst for purifying engine exhaust gas.Next, the catalyst was subjected to the same oxidation resistance evaluation test as in the first example. As a result, this catalyst also had a 50%
Even when heated for 0 hours, no problems occurred and excellent oxidation resistance and corrosion resistance were exhibited.

[Brief explanation of the drawing]

1 and 2 are perspective views of metal honeycomb structures according to the first and second embodiments, and FIG. 3 is a diagram for explaining the bonding state of the flat plate and the corrugated plate and the state of the catalyst. be. 1.11. ,,metal honeycomb structure. 2.25. ,, flat plate. 21.26. ,,Contact part. 3.35. ,, corrugated plate. 411. Porous layer. 41, , alloy layer. 5゜6゜Catalyst component. Outer tube 5 Applicant Aichi Steel Corporation Cataler Industries Co., Ltd. Agent

Claims (6)

[Claims] (1) A catalyst consisting of a metal honeycomb structure, a porous layer fixedly formed on the surface thereof, and a catalyst component supported on the porous layer, wherein the honeycomb structure is made up of alternating flat metal plates and corrugated metal plates. The flat plate and the corrugated plate are laminated, and the contact portions of the flat plate and the corrugated plate are diffusion bonded to each other, and at least the surfaces of the flat plate and the corrugated plate have an alloy layer of the metal and aluminum that constitute them. A catalyst characterized by: (2) A laminate is made by alternately stacking metal flat plates and corrugated plates, and the laminate is immersed in a molten aluminum bath while keeping the contact portions of the flat plate and the corrugated plate in contact with each other. By doing so, a metal honeycomb structure is produced in which the contact portions of the flat plate and the corrugated plate are bonded by diffusion bonding, and an alloy layer of the metal and aluminum forming this is formed on at least the surfaces of both plates, and then the A catalyst characterized in that an inorganic powder layer is attached to the surface of the alloy layer of a metal honeycomb structure, a porous layer is fixedly formed by heating, and then a catalyst component is supported on the porous layer. Production method. (3) The method for producing a catalyst according to claim 2, wherein the temperature of the aluminum bath is 670 to 750°C. (4) A laminate is made by alternately stacking metal flat plates and corrugated plates, and the laminate is immersed in a molten aluminum bath while holding the contact portions of the flat plate and the corrugated plate in contact with each other. , the surfaces of the flat plate and the corrugated plate are coated with aluminum, and after being taken out from the aluminum bath, this laminate is heated in a non-oxidizing atmosphere, thereby bonding the contact area between the flat plate and the corrugated plate by diffusion bonding. A metal honeycomb structure is manufactured by forming an alloy layer of metal and aluminum on at least the surfaces of the flat plates and corrugated plates of the laminate, and then an inorganic material is applied to the surface of the alloy layer of the metal honeycomb structure. A method for manufacturing a metal honeycomb structure, which comprises adhering a powder layer, fixing a porous layer by heating, and then supporting a catalyst component on the porous layer. (5) The method for producing a catalyst according to claim 4, wherein the temperature of the aluminum bath is 670 to 750°C. (6) The method for producing a catalyst according to claim 4, wherein the heating in the non-oxidizing atmosphere is from 600 to 1000°C.