JPH066723B2 - A method for manufacturing a carrier based on a porous sintered body of A type - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a carrier having an Al-based porous sintered body as a base, and more specifically, a metal catalyst such as Pt, Co, Cr, or an aroma. The present invention relates to a method for producing a carrier based on an Al-based porous sintered body on which an agent, an odorant, an antibacterial agent and the like are uniformly dispersed and carried.

Conventional Technology Conventionally, for example, catalysts have been used to purify various combustion gases including harmful components of automobile exhaust gas.

The catalyst for automobile exhaust gas purification has a specific surface area on a structure formed by forming cordierite, mullite, etc. into a honeycomb shape.
Γ-Al ₂ O ₃ having ₂₀ to 80 m ² / g is coated on the surface layer, and the fine pores of γ-Al ₂ O ₃ carry a metal catalyst such as Pt, Co and Cr.

This catalyst was obtained by immersing or spraying a honeycomb body-shaped structure of cordierite, mullite or the like in a viscous washcoat mixed with γ-Al ₂ O ₃ powder, water, aluminum nitrate, a surfactant, etc. After that, it is dried and calcined, and the carrier whose surface is thinly coated with γ-Al ₂ O ₃ is immersed in a stirring vessel containing a solution of the catalytic metal salt, the catalytic metal salt is attached to the surface of the carrier, dried and calcined, and the catalyst It is produced by distributing the metal in a reduced state on the surface of the carrier.

However, in the support production of this catalyst, γ-Al ₂ O
_In addition to the need for extremely delicate adjustment of the amount of aluminum nitrate mixed, the viscosity, etc., the coating of ₃ is difficult to coat cordierite or mullite of the substrate with a uniform thickness during the coating work, and also It takes several days to dry and cure, and it is also necessary to strictly control the firing conditions and the like in the step of firing the dried and cured material.

Therefore, the cost of producing the carrier becomes high and it is inevitably expensive.

From the above, it is possible to form a γ-Al ₂ O ₃ layer on the surface of a substrate without using a washcoat such as γ-Al ₂ O _{3 on} the surface of a catalyst carrier having an Al-based porous sintered body as a substrate. If it is possible, the coating work can be omitted, the cost is reduced, and moreover, a uniform thickness of γ-Al ₂ O ₃ is formed on the surface,
Since the quality is constant, the advent of such a method for producing a catalyst carrier is desired.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention An object of the present invention is to solve the above problems, and specifically, a catalyst carrier based on a porous Al-based sintered body having a coating layer made of activated alumina having a high specific surface area on its surface. It is an object of the present invention to propose a method for efficiently producing a homogeneous product by a simple method.

Means for Solving the Problem and Its Action That is, the present invention relates to Al or Al alloy or A
A porous sintered body having continuous pores formed by sintering a mixed powder of 1 and an Al alloy without pressure is exposed to boiling water or water vapor, and a boehmite layer is formed on the surface of the porous sintered body. The temperature below the melting point of the sintered body is heated to a temperature at which the substrate does not melt, and the boehmite layer has γ-Al ₂ O ₃ or γ ′ having fine pores.
-Al ₂ O ₃ (pseudo γ crystal structure) is characterized by changing the layer, and further, the sintered body obtained by this production method was dipped in a wash coat containing γ-Al ₂ O ₃ . After that, it is dried and fired to coat the surface of the sintered body with γ-Al ₂ O ₃ .

Therefore, the configuration and operation of these means will be described more specifically as follows.

The present inventors have studied a method of forming a γ-Al ₂ O ₃ layer without washcoating γ-Al ₂ O ₃ or the like on the substrate surface of a catalyst carrier. Al metal has a high affinity for oxygen,
Although the outermost surface layer easily becomes Al ₂ O ₃ even in the atmosphere, it does not become γ-Al ₂ O ₃ by atmospheric oxidation, so the surface of the Al-based sintered body is supported by boehmite (Al ₂ O ₃ · H ₂ When converted to O) and heated, activated alumina (γ-Al ₂ O ₃ or γ′-Al ₂ O ₃ )
Focusing on that, the conditions suitable for this are as follows.

(1) Use of an Al-based sintered body having communication holes, (2) Boehmite the surface of the Al-based sintered body, and then heat to remove water content to obtain activated alumina. (3) γ-Al with a washcoat containing γ-Al ₂ O _3
2 O ₃ can be easily coated, and so on.

Further research was conducted, and the present invention was established based on this research.

Hereinafter, the present invention will be described in more detail.

In the present invention, Al or Al alloy or Al and Al alloy powder is sintered into a desired shape in a non-pressurized state, and the sintered Al-based sintered body is used. Since this Al-based sintered body has communicating holes, it can allow a substrate, liquid, etc. to pass therethrough, and can form the desired γ-Al ₂ O ₃ or γ′-Al ₂ O ₃ on the surface. It is suitable as a starting material of the present invention because it has the function of being capable.

First, the present inventors treated the above Al-based sintered body in boiling water or steam, and the surface layer thereof was easily boehmite (Al ₂ O ₃ .H ₂ O), that is, hydrated alumina. Was confirmed. Furthermore, when this is heated in the air to a temperature lower than the melting point of the Al-based sintered body, preferably 400 to less than 660 ° C., hydrated components are volatilized, and γ-Al ₂ O ₃ or γ′-Al having fine pores. ₂ O ₃
It was confirmed that Γ-Al ₂ O ₃ or γ′-Al ₂ O ₃ obtained by such means has a high specific surface area comparable to that of activated alumina (γ-Al ₂ O ₃ ) used in washcoats. It turned out to be a thing.

It was also confirmed that a so-called washcoat can be formed very easily on the base body made of the Al-based sintered body having the outermost surface layer structure of γ-Al ₂ O ₃ or γ′-Al ₂ O ₃ .

It should be noted that γ-Al ₂ O ₃ purified separately from the wash coat
This is a mixed solution in which the powder is added to a mixed solution of water, aluminum nitrate, a surfactant and the like and kneaded. Usually, a catalyst carrier for automobiles is obtained by impregnating this washcoat with a substrate made of a sintered body such as cordierite or mullite having a honeycomb structure, applying γ-Al ₂ O ₃ and firing it. However, in general, when the catalyst carrier is a metal honeycomb, the washcoat is less likely to adhere, which is one of the technical problems that prevent the spread of the metal carrier. As shown in Evaluation Test Example 3 to be described later, there is a significant difference in the peel resistance of the washcoat between the sample to which the washcoat was applied as it was as the Al-based sintered body and the sample to which the washcoat which was subjected to the heat treatment after the boehmite treatment was applied. Is recognized.
That is, the carrier coated with the wash coat after the series of steps according to the present invention exhibits excellent durability even after repeated heating-cooling, and is therefore suitable for purification of high-temperature exhaust gas.

The constitution of the method of the present invention will be described below.

Since the Al-based sintered body used in the present invention is required to allow the substrate and the liquid to pass therethrough, it is essential that the Al-based sintered body has pores that are three-dimensionally communicated with each other. For this reason, the pressureless sintered body of the Al-based sintered body obtained by the method described in Japanese Patent Publication No. 56-11375 proposed by the applicant of the present invention satisfies this requirement. That is, in this method, the Al-based powder is substantially pressureless and in a non-oxidizing atmosphere,
By sintering at a temperature lower than the melting point of the powder, a porous Al-based sintered body having communicating holes is obtained. According to this method, the desired porosity can be adjusted to 30 by changing the particle size of the powder, the sintering conditions (temperature, time), and the type of binder.
~ 70% sintered body is obtained.

Next, a method for forming the boehmite layer will be described.

By subjecting the above Al-based sintered body to hot water treatment or steam treatment as described above, a boehmite layer having a thickness of several μm is uniformly formed on the outermost layer. Industrially 10 to 30 for hot water treatment
Minutes, or steam treatment, a uniform boehmite layer is formed in a few minutes, and this layer thickness should be determined in accordance with the required carrier performance. The reason why the Al-based sintered body is subjected to hot water treatment or steam treatment in this way is that different hydrates are formed depending on the treatment temperature. That is, when treated with hot water or steam, it becomes a form of boehmite (Al ₂ O ₃ .H ₂ O).

When treated with low temperature hot water such as 60 to 70 ° C. or less, it becomes an alumina hydrate in the form of bayerite (Al ₂ O ₃ .3H ₂ O),
Due to the large amount of hydration, stable γ-
This is because it is difficult to obtain Al ₂ O ₃ or γ′-Al ₂ O ₃ (pseudo γ crystal structure).

Next, a method for forming γ-Al ₂ O _{3 on} the boehmite layer of this Al-based sintered body will be described.

Boehmite releases hydrates when heated in normal air.
According to the experiments of the present inventors, when a boehmite-treated sample was inserted into a differential thermal balance apparatus and heated at a heating rate of 10 ° C./min, the weight decreased to two points of 100 ° C. and 400 ° C. I got the peak line. This means that the hydrated temperature is 100
It shows that the substance was decomposed and volatilized at ℃ and 400 ℃. At the same time, when the crystal structure of a sample heated and held at a temperature of 500 ° C. for 30 minutes was determined by X-ray analysis, γ-Al ₂ O ₃ and γ′-Al ₂
It was identified as a mixed structure of O ₃ . By the way, although the melting point of an Al-calcined compound differs depending on the contained components,
Since the melting point of pure Al is 660 ° C., heating above this temperature is not possible because it melts the substrate. Preferably, as shown in the results obtained from the previous experiment, the temperature of the secondary hydrated release is 400 ° C,
The temperature is preferably 400 ° C. or higher and lower than the melting point of the substrate.

Then, the sample that has undergone the above steps is subjected to BET method, that is, N ₂
The results of measuring the specific surface area by the gas adsorption method are shown in Table 1. In addition, Table 1 shows the specific surface area measurement results of the sample in which the steam treatment at 800 ° C. was performed for 5 minutes, the heating temperature was changed, and the heating and holding time was 30 minutes in all cases.

It can be seen from Table 1 that the specific surface area increases as the heating temperature is increased from 200 ° C.

Although the method for producing the catalyst carrier of the present invention has been described above, the method of the present invention is not only used as a catalyst carrier, but also because the surface γ-Al ₂ O ₃ layer has fine pores and the substrate has continuous pores. Since it can be impregnated with a large amount of a fragrance, an odorant, an antibacterial material, etc., it can be used as a carrier for these.

Use of the carrier according to the present invention has the effect of further extending the duration of effect as compared with conventional carriers (felt, cotton, etc.) impregnated with an aromatic agent, an odorant, an antibacterial agent, and the like.

Examples Example 1. Pure Al powder (99.7% purity, 40-150 mesh) with Al
Powder obtained by mixing 5% of -60% Cu alloy powder (100 to 150 mesh) was sprayed on a graphite tray without pressure. This is N ₂ + H ₂
When sintered in a mixed gas at 635 ° C for 20 minutes, the porosity is 45%,
An Al sintered body having a three-dimensional communication hole with a flow resistance of 150 dyne.sec / cm ⁴ was obtained.

This Al sintered body was put into an autoclave having a steam pressure of 2.2 kg / cm ² at 180 ° C. and held for about 5 minutes. After this 600 ℃
Heat treatment was performed in the atmosphere for 5 minutes to obtain a sample (1) for evaluation.

γ-Al ₂ O ₃ powder, water, aluminum nitrate were mixed and well stirred into a wash coat with a viscosity of 300 cps Sample for evaluation (1)
After immersing in, and blowing off the residual liquid with compressed air, 600 ℃ × 30
Baked in minutes.

Next, an evaluation sample (2) having a platinum catalyst supported thereon was obtained by immersing in a chloroplatinic acid solution.

Evaluation Test Example 1. The specific surface area of the evaluation sample (1) produced in Example 1 was measured by the BET method, and the result was 15 m ² / g. Next, this was impregnated with an aromatic agent (trade name "ROSE RS-6631" manufactured by Takasago International Co., Ltd.), and the volatilization amount of the aromatic agent was measured. As a comparative example, the change in the amount of volatilization is shown in the graph of FIG. 1, including an example in which felt solidified by pressing is used as a carrier. It can be seen that the carrier according to the present invention is impregnated and retained under exactly the same conditions for 18 weeks or more, whereas the conventional carrier completely vaporizes in about 4 weeks.

The shape of the sample used for the impregnation was unified to 30 mmφ × 2.5 t.

Evaluation Test Example 2. The evaluation sample (1) prepared in Example 1 was immersed in a dinitrodiamine platinum solution to support a platinum catalyst. HC, CO, NO
x Mixed standard gas was prepared, the mixed gas was heated to 400 ° C., and the catalyst purification performance was measured with an experimental device that was introduced into a catalyst container incorporating two 50 mmφ × 2.5 t supported sample pieces. . The durability time is 300 hours. The purification rate is shown in Table 2. Further, for comparison, the same test was performed using a sample of the sintered body which was not subjected to steam treatment and heat treatment. The results are shown in Table 2 as a comparative product.
It can be seen from Table 2 that the catalyst is clearly supported on the carrier of the present invention in good yield, and at the same time, there is almost no deterioration even after 300 hours of durability.

Evaluation Test Example 3. Evaluation sample (2) prepared in Example 1, that is, an evaluation sample in which chloroplatinic acid was supported in the washcoat layer.
(2) was repeatedly subjected to a thermal shock test for 300 hours in a mixed standard gas at 500 ° C. for 5 minutes and air cooling for 5 minutes. As a result, no peeling of the washcoat layer was visually observed.

<Effect of the Development> As described in detail above, the method of the present invention provides a porous sintered body having communicating holes formed by sintering Al or Al alloy or a mixed powder of Al and Al alloy without pressure. After exposing to boiling water or water vapor to form a boehmite layer on the surface of the boehmite layer, the boehmite layer is heated to a temperature at which the substrate below the melting point of the porous sintered body does not melt, and the boehmite layer has γ-Al It is characterized in that it is transformed into a layer of ₂ O ₃ or γ-Al ₂ O ₃ .

Therefore, according to the method of the present invention, a carrier having γ-Al ₂ O ₃ or γ'-Al ₂ O ₃ having fine pores on the surface of the substrate can be very easily produced, and a high ratio of activated alumina on the surface is obtained. Since it has a surface layer, the catalyst can be efficiently supported directly on the surface layer. In addition, γ of the Al-based sintered body substrate
A washcoat of γ-Al ₂ O ₃ can be firmly formed on the −Al ₂ O ₃ or γ′-Al ₂ O ₃ surface, and the layer thickness can be adjusted.

Further, the carrier obtained by the method of the present invention has a fine pore γ-Al ₂ O ₃ or γ′-Al _{2 on} the surface of an Al sintered body having a communicating hole.
Since it contains O ₃ , it can be impregnated with a large amount of deodorant and fragrance, and the duration of effect can be extended to the conventional example.

[Brief description of drawings]

FIG. 1 is a graph showing the duration of time when a catalyst carrier according to the present invention is impregnated with an aromatic, and FIG. 2 is an evaluation test for evaluating the performance of the catalyst carrier according to the present invention as a gas purification catalyst carrier. FIG.

Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location // B01J 23/89 A 8017-4G 35/04 331 B 7821-4G

Claims (4)

[Claims] 1. Al or Al alloy or Al and Al
A porous sintered body having communicating pores formed by sintering a mixed powder of an alloy without pressure is exposed to boiling water or steam, and a boehmite layer is formed on the surface of the porous sintered body. Heat to a temperature below the melting point of the body that does not melt the substrate,
Γ-Al ₂ O ₃ or γ ′ having fine pores in the boehmite layer
Method for producing a carrier for the substrate an Al-based porous sintered body characterized by changing the nature of the layer of -Al ₂ O _3. 2. A sintered body obtained by the manufacturing method according to claim 1 is dipped or sprayed in a wash coat containing γ-Al ₂ O ₃ and then dried and fired to obtain the sintered body. Al whose surface is coated with γ-Al ₂ O ₃
A method for producing a carrier having a porous porous sintered body as a substrate. 3. The method for producing a carrier based on an Al-based porous sintered body according to claim 1, wherein the porosity of the porous sintered body is 30 to 70%. 4. The heating temperature of the porous sintered body is 400 ° C. or higher 6
The method for producing a carrier based on the Al-based porous sintered body according to claim 1, which has a temperature of less than 60 ° C.