JPH01270948A - Preparation of catalyst supported by metal - Google Patents

Abstract

PURPOSE:To uniformize the distribution of a catalytic component and to enhance the activity thereof by impregnating the surplus wall of the alumina wash coat layer formed to the corner part of a metal carrier with a filler to impregnate only the alumina wash coat layer with the catalytic component. CONSTITUTION:In a metal carrier for purifying exhaust gas, a metal corrugated plate 1 is held between two flat plates 2 at first to form a carrier and an alumina wash coat layer 3 is formed to said carrier. Then, the surplus wall parts 3a in the thick wall parts of the alumina wash coat layer 3 at the corner parts of the flat plates 2 and the corrugated plate 1 as well as the corner parts of the corrugated plate 1 are impregnated with a filler such as polyvinyl alcohol to suppress the impregnation with a noble metal catalytic component. Thereafter, the alumina coat layer 3 is impregnated with the metal catalytic component such as platinum or rhodium. By this method, the catalytic component is uniformly distributed and becomes a proper amount and the catalytic activity thereof is enhanced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for manufacturing a metal carrier catalyst for exhaust gas purification, in which an alumina washcoat layer formed on a metal carrier is impregnated with a noble metal catalyst component. be.

(Prior Art) Conventionally, as a metal carrier catalyst for exhaust gas purification, for example, as described in Japanese Patent Publication No. 58-23138,
A so-called metal carrier catalyst is known in which an alumina washcoat layer is formed on a metal carrier and this alumina washcoat layer is impregnated with a noble metal catalyst component. As shown in the enlarged cross-sectional structure of FIG. 6, this catalyst is made of γ-alumina or the like, and is mounted on a metal carrier made by sandwiching and bonding a metal corrugated plate IA between two upper and lower metal flat plates 2A. It has a structure in which an alumina washcoat layer 3A is fixed and this alumina washcoat layer 3A is impregnated with a noble metal catalyst component such as platinum or rhodium.

When manufacturing this type of metal carrier catalyst, usually after forming an aluminum film on a metal carrier, the carrier is immersed in an alumina slurry to adhere the alumina slurry to the carrier, and this is fired to form an alumina wash coat JW3A. Thereafter, this is immersed in an aqueous solution of a noble metal catalyst to impregnate the catalyst component. In this manufacturing method, Alumina Wash Coat J! When fixing i3A,
By increasing the viscosity of the alumina slurry to a certain degree in advance, a predetermined amount of the alumina slurry required to impregnate an appropriate amount of the catalyst component is deposited at once.

[Problem to be solved by the invention]

However, when the alumina slurry is deposited as described above, a large amount of alumina slurry gathers in the corner part A of the metal carrier, a thick part of the alumina wash coat layer is formed in the corner part A, and a relatively thick part of the alumina wash coat layer is formed in the flat part B. Therefore, the alumina wash coat layer 3A becomes thinner. Therefore, when impregnating the catalyst component, if the thick portion is also set to be impregnated with the required amount of the catalyst component, the distribution density of the catalyst component tends to be high in the flat portion where the alumina washcoat layer 3A is thin. In this way, when the density of the catalyst components increases, catalyst particles that are close to each other adhere to each other at high temperatures, causing sintering (agglomeration and coarsening), which reduces the surface area of the catalyst, resulting in a decrease in catalytic activity. There is a problem with doing so.

On the other hand, if the distribution density of the catalyst component in the planar part of the alumina wash coat layer 3A is set appropriately, the distribution density of the catalyst component in the thick part of the alumina wash two 1 layer 3A will be relatively low. There is a problem with this.

An object of the present invention is to provide a method for manufacturing a metal carrier catalyst for exhaust gas purification, which can uniformize the distribution of catalyst components impregnated into an alumina wash coat layer and make the appropriate amount to improve catalyst activity. shall be.

[Means to solve the problem]

The method for manufacturing a metal carrier catalyst according to the present invention includes forming a metal carrier consisting of a flat plate and a corrugated plate, forming an alumina washcoat layer on the metal carrier, and forming a corner portion between the flat plate and the corrugated plate. Among the thick parts of the alumina washcoat layer formed at the corners of the corrugated sheet, the excess thickness on the metal carrier side is impregnated with a filler substance that suppresses the impregnation of the noble metal catalyst component, and then the noble metal catalyst is applied to the alumina washcoat H. It impregnates the ingredients.

[Effect]

In the method for producing a metal carrier catalyst according to the present invention, as described above, the noble metal catalyst is added to the excess wall portion on the metal carrier side of the thick part of the alumina wash coat layer formed at the corner part of the metal carrier. Because it is impregnated with a filler substance (such as polyvinyl alcohol) that suppresses impregnation of ingredients,
The extra wall portion impregnated with the filler material loses the function of impregnating the catalyst component as an alumina wash coat layer, and the substantial alumina coat layer capable of impregnating the catalyst component has a uniform thickness throughout. .

Therefore, the uniform thickness of the alumina washcoat i
If the catalyst component is impregnated based on this, the distribution of the catalyst component can be made appropriate and uniform throughout the alumina washcoat layer.

〔Effect of the invention〕

According to the method for manufacturing a metal carrier catalyst according to the present invention, as explained above, the method is a simple method of impregnating the extra thickness of the alumina wash coat layer formed at the corner part of the metal carrier with a filler material. This allows the distribution of catalyst components in the alumina washcoat layer to be appropriate and uniform.

This prevents sintering (agglomeration and coarsening) of catalyst components and shortage of catalyst components, and improves the purification ability of the catalyst.

〔Example〕

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

First, the metal carrier catalyst manufactured by the manufacturing method of this example will be explained based on FIG. 1.

As shown in the figure, the metal carrier is made up of a metal corrugated sheet 1 sandwiched between two metal flat plates 2, and four contact portions between the corrugated sheet 1 and the flat plate 2.

The surface of the corrugated plate 1 of the metal carrier and the flat plate 2 facing the corrugated plate 1
An alumina washcoat layer is formed on the surface.

Among the thick parts of the alumina wash coat layer 3 formed at the corner parts between the flat plate 2 and the corrugated sheet 1 and the corner parts of the corrugated sheet 1, the extra wall part 3a on the metal carrier side contains a catalyst component. The material is impregnated with polyvinyl alcohol as a filler material that inhibits impregnation. The alumina wash coat N3, which has a substantially uniform thickness over the entire area except for the extra wall portion 3a impregnated with the polyvinyl alcohol, is impregnated with a noble metal catalyst component such as platinum or rhodium.

In the metal carrier catalyst lO having the above structure, since the extra wall portion 3a is impregnated with a filler material, a substantial portion of the alumina wash coat layer 3 that absorbs and supports the catalyst components is uniform throughout. It becomes thick. By impregnating the catalyst component to match this uniform thickness, the distribution of the catalyst component is uniform and appropriate over substantially the entire alumina wash coat layer 3, and the sintering of the catalyst component is achieved. Exhaust gas purification performance is improved because no ring occurs and there is no shortage of catalyst components in thick-walled parts.

Examples of the method for manufacturing the metal carrier catalyst described above will be described below.

In the first step, the corrugated metal plate 1 is inserted into two flat metal plates 2.
A metal carrier was manufactured by sandwiching the corrugated plate 1 and the flat plate 2 between each other, and joining the abutting portions of the corrugated plate 1 and the flat plate 2.

In the second step, an alumina washcoat layer was formed on the metal carrier.

In this process, 80g of γ-alumina, 0°20g of Ce1
An alumina slurry is prepared by adding 1.6 cc of nitric acid to 100 g of Beichimite and 240 cc of water, and stirring the mixture. The alumina slurry is adhered to the alumina slurry by immersing a metal carrier which has been previously fired in air at 1000° C. for 6 hours. Then, the metal carrier with the alumina slurry adhered to it was air-blown to remove excess slurry, dried at 150°C for 30 minutes, placed in a firing furnace, and fired at 550°C for 1.5 hours. A metal carrier 10 with an alumina wash coat layer was manufactured.

In the third step, (- Hz
It was impregnated with C(OH)-) n (polyvinyl alcohol).

In this process, 200 g of water is added to 50 g of polyvinyl alcohol.
cc was added, mixed and stirred to make a polyvinyl alcohol solution, and the alumina-coated metal carrier IO was immersed in this solution, washed with water, air blown to remove excess polyvinyl alcohol solution, and heated at 200°C for 2 hours. Dry for an hour.

By the water washing, air blowing, and drying described above, most of the polyvinyl alcohol in the portion other than the excess thickness portion 3a of the alumina coat N3 is removed, and the excess thickness portion 3a remains in an impregnated state with polyvinyl alcohol.

In the fourth step, the alumina coat layer 3 was impregnated with a metal catalyst component.

In this step, the alumina coated gold metal carrier is immersed in an aqueous solution in which predetermined amounts of platinum chloride and rhodium chloride are dissolved, dried at 150°C for 30 minutes, and then fired at 500°C for 2 hours to form an alumina coated layer. A noble metal catalyst component was supported on a portion other than the extra wall portion 3a of No. 3. At this time, the precious metal is
1.33g/l of platinum and 0.27g/j of rhodium! The amount of alumina coated is 14w on the metal carrier.
It was set as t%.

Comparative Example A metal carrier catalyst similar to the conventional one was manufactured by the same method except for the third step, that is, the first, second, and fourth steps. At this time, the noble metals were platinum at 1.35 g/l, rhodium at 0.29 g/1, and the amount of alumina coated on the metal carrier was 14 wt%.

Warm-up performance test: In order to compare the performance of the catalyst obtained by the production method of the above example and the catalyst obtained by the production method of the comparative example, the warm-up performance was tested using a test device as shown in Figure 2. conducted a test. This device passed the test gas through an electric furnace 11 at 650°C, bypassed it in advance, switched it to pass through the catalyst 10, and then passed it through the catalyst 10 while measuring the temperature at the inlet of the catalyst 100. This allows gas to pass through an analyzer. The test conditions were a test gas volume of 241/min and an air-fuel ratio of 14/min.
．． 7. The size of the catalyst 10 is 24mj! As the binding and aging conditions for the catalyst, the catalyst was heated in air at 900° C. for 50 hours.

The above warm-up performance test yielded results as shown in FIGS. 3 to 6. As can be seen from the test results, the catalyst according to this example has significantly improved performance in terms of HC purification rate, as well as improved performance in CO purification rate and NOx purification rate, compared to the conventional catalyst according to the comparative example. are doing.

``If we consider the reason why the performance of the catalyst according to this example was improved as mentioned above, it is because the substantially effective alumina coat N3 has a uniform thickness throughout as described above. , the distribution of the catalyst component has become uniform as a whole, and sintering due to excessive distribution of the catalyst component no longer occurs in the flat plate-shaped part of the alumina coat layer 3, or the excess thickness of the thick part of the alumina coat layer 3 has become uniform. This is because the catalyst component is not absorbed into the portion 3a, so that the distribution of the catalyst component in the thick portion is not insufficient and is in an appropriate amount.

In addition, the filling material to be impregnated into the surplus portion 3a is as follows:
The material is not limited to the above-mentioned polyvinyl alcohol, and various other synthetic resin materials, starch, etc. can also be used. The point is that the filling material can be impregnated into the alumina coat layer 3 and the excess wall portion 3a can be heated at a heating temperature of about 100 to 2°C.
Any substance that can remove impregnated parts of the alumina coat JI3 other than the above may be used.

[Brief explanation of the drawing]

Of the drawings, Fig. 1 and Fig. 6 relate to an embodiment of the present invention, in which Fig. 1 is an enlarged sectional view of a metal carrier catalyst, Fig. 2 is a schematic configuration diagram of a warm-up test device, and Fig. 3 is a schematic diagram of a warm-up test device. Figure~6th
The figures are diagrams showing the HC purification rate, CO purification rate, Nok purification rate, and catalyst inlet temperature obtained as a result of a warm-up test, respectively, and FIG. 7 is an enlarged sectional view of a conventional metal carrier catalyst. 1. Corrugated plate, 2. Flat plate, 3. Alumina wash coat layer, 3a. Excess portion, 10. Metal carrier catalyst. Figure 7 Figure 3 (%) Figure 4 (%) Time (sec) Figure 5 (%) Figure 6 (℃)

Claims (1)

[Claims] (1) Forming a metal carrier consisting of a flat plate and a corrugated plate, forming an alumina washcoat layer on the metal carrier, and forming an alumina wash coat layer on the corner between the flat plate and the corrugated plate and on the corner of the corrugated plate. A metal characterized by impregnating a filler material that suppresses impregnation of a noble metal catalyst component into the thick part of the wash coat layer on the side of the metal carrier, and then impregnating the alumina wash coat layer with the noble metal catalyst component. A method for producing a manufactured carrier catalyst.