JPS6344938A - Preparation of monolithic base material for purifying exhaust gas - Google Patents

Abstract

PURPOSE:To eliminate the delamination of an alumina coating layer, by coating the surface of a monolithic base material with a slurry formed by adding combustible fine particles and a liquid to a kneaded substance of clay mineral and subsequently drying and baking the coated base material. CONSTITUTION:An org. binder and water is added to a clay mineral raw material based on kaolin and talc, and the resulting mixture is kneaded, subjected to extrusion molding and dried to form a monolithic base material 1 having a large number of cells 2. Separately, water and a carbon powder having an average particle size of 10mum are stirred along with the mixture of the aforementioned clay mineral to prepare a slurry. The monolithic base material is immersed in the slurry and drawn up to coat the entire surface containing the interiors of the cells 2 of the base material 12. Subsequently, the coated base material 1 is dried and subsequently baked at about 1,400 deg.C for about 5hr to form a cordierite layer 3 on the surface of the base material 1 and an alumina coating layer 4 is further formed thereon.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a monolith base material for exhaust gas purification, and in particular to a method for improving the peeling resistance of an alumina coat layer formed on the surface of the monolith base material. The present invention relates to a method for manufacturing a monolith base material for use in manufacturing.

[Conventional technology]

As carriers for automobile exhaust gas purification catalysts, spherical pellet carriers and monolithic carriers in which a honeycomb-shaped base material is coated with alumina or the like are known.

In recent years, the specific gravity of monolithic carriers has become extremely high due to their advantages such as light weight, excellent abrasion resistance, and small heat capacity. As monolithic carrier base materials, those with a Corjelai l-composition made from clay minerals such as kaolin and talc have been found to have excellent properties such as a low coefficient of thermal expansion, and are currently widely used (for example, 1234
No. 08 eIl).

In automotive catalysts, a monolith base material coated with alumina is used as a carrier. This technology was developed in the 1980s.
It is publicly known from the publication No.-27295. This is because a catalyst in which the active ingredient is directly attached to a monolithic carrier has an insignificant catalytic activity, so an alumina film of several tens of micrometers is usually formed on the surface of the carrier, and the active ingredient is added to this alumina coat layer. I try to attach it.

[Problem that the invention seeks to solve]

However, forming an alumina coat layer on the surface of a monolith base material is difficult because the alumina coat layer and the monolith base material have different physical properties such as coefficient of thermal expansion, and the alumina coat layer may fall apart during use. This often occurred and became a problem. Particularly when the temperature of the carrier changes drastically, there is a problem that this is a major cause of deterioration of the catalyst.

In order to solve the above problems, the present invention aims to solve the above problems.
An object of the present invention is to provide a method for producing monolith base +4 in which the alumina coat layer formed on the surface of A is difficult to peel off even at extreme temperatures.

[Bottom section for solving problems]

The method for manufacturing a monolithic base material for exhaust gas purification according to the present invention, which meets the objective 1), is to form a kneaded material of clay mineral into a predetermined shape and dry it, then apply a kneaded material of clay mineral to the surface of the monolithic base material. The manufacturing method consists of coating a slurry produced by adding flammable fine particles and a liquid, and then drying the monolith base +4 coated with the slurry, followed by firing.

[Function] In the method for producing a monolithic base material for purifying 1+ gases, combustible fine particles in the slurry are burned out by firing the monolithic base material coated with the slurry.
Many pores are always formed on the surface of the monolith base material. In other words, a very fine uneven surface is formed on the surface of the monolithic group H, and the monolithic group +4
An alumina coat layer is formed on the surface. Therefore,
The contact area between the alumina coat layer and the monolith base material increases, and the part of the alumina coat F layer penetrates into the pores of the monolith 2'S. Therefore, the bonding state between the alumina coat layer and the monolith base material is significantly improved, and the peeling resistance of the alumina coat layer is significantly improved.

〔Example〕

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the method for manufacturing a monolith base material for exhaust gas purification according to the present invention will be described below with reference to the drawings.

First, three examples of monolith base materials formed by this manufacturing method and a comparative example formed by another method will be described.

First Embodiment FIGS. 1 to 4 show a monolith base material formed by a method for manufacturing a monolith base material for exhaust gas purification according to a first embodiment of the present invention.

Clay mineral raw materials mainly composed of kaolin and talc are mixed with an organic binder and water, extruded, and then dried for a predetermined period of time to form a large number of clay minerals as shown in Figures 3 and 4. A monolith substrate 1 having cells 2 of
is formed.

Thereafter, the surface of the dried monolith base material 1 is coated with the slurry. This slurry is produced by sufficiently stirring a mixture of a clay mineral kneaded material having the same composition as Monolith Group +11, water and carbon powder having an average particle size of 10 μm as flammable fine particles.

That is, the monolith base material 1 after drying is immersed in this slurry for a lifetime, and by pulling up the monolith base material 1, the entire surface of the monolith base material 1 including the inside of the cells 2 is covered with the slurry. Then, the excess slurry adhered to the monolith base material 1 is blown away by compressed air.

The monolith substrate 1 covered with the slurry is dried for a predetermined time and then fired at 1400° C. for 5 hours. As a result, a new cordierite layer 3 is formed on the surface of the monolith base material 1, as shown in FIG. In this cordierite layer 3, a large number of pores with an average size of 10 μm are formed by burning off the carbon powder described above, and the surface of the monolith base material 1 is formed into a very fine uneven surface.

An alumina coat layer is formed on the surface of the cordierite layer 3 of the monolith base material 1 thus formed. In other words, the fired monolith base material 1 described in 1-
Thereafter, it is immersed in an alumina coating slurry containing alumina powder with an average grain size of 10 μm, and the alumina coating slurry is adhered to the surface of the cordierite layer 3 by pulling up the monolith substrate 1 . Then, the alumina coating slurry deposited in excess is blown off with compressed air as in the case described above. Thereafter, the monolith substrate is dried for a predetermined time and then fired at 700°C for 2 hours. As a result, an alumina cord I layer 4 is formed on the surface of the cordierite layer 3 of the monolith base material 1, as shown in FIG.

In this case, a part of the alumina coat layer 4 penetrates into the many pores C formed in each layer of Corjelai 1.
7- The adhesion between the aluminum layer 1 layer 3 and the alumina layer 1 layer 4 is improved, and the alumina layer 1 layer 4 (monolith base material) 11
becomes difficult to peel off.

Then, alumina: 7-1 layer 4, platinum (P 1.
) using ammine solution, rhodium chloride 1, solution, catalyst 1
7! A monolithic catalyst is obtained by supporting 0.1 g of Pt, (platinum) Ig, and Rh (U-A) per catalyst.

Second Example The monolith base +4 used in this example is manufactured by the same manufacturing method as in the first example, but the average particle size of the carbon powder used is different. Of course, in this example, carbon powder with an average particle size of 5 μn'l is used, and as a result, many pores of 5 It m are formed on the surface of the monolith base material. Note that the manufacturing method for catalyticization is similar to that of the first embodiment.

Third Example The monolith base material in this example is manufactured by the same method as in the first example, similar to the above jAX. Zunawachi,
In this example, carbon powder having an average particle size of 20 μm, which is larger than that of the first example, is used, and many pores with an average size of 20 μm are formed on the surface of the monolith base material. Incidentally, the manufacturing method for catalyzing is also the same as in the first embodiment.

Comparative Example In this comparative example, a kneaded material of clay minerals having the same composition was extruded and molded seven times in the same manner as in each of the above-mentioned Examples, dried and fired to form a monolith base material. Therefore, the pores formed by burning off the carbon powder described in each example do not exist. The monolith substrate thus formed was catalyzed by the same method as in each of the above-mentioned examples.

Experimental Examples Next, the results of tests on the peeling resistance of the alumina coat layers in the monolithic catalysts obtained in each of the Examples and the monolithic catalysts obtained in the Comparative Examples will be explained.

The three monolithic catalysts obtained in each example and the monolithic catalyst obtained in the comparative example were heated in an electric furnace at 800'c for 15 minutes, taken out, and cooled in an air stream for 15 minutes (S TJ 2
The test was carried out over 200 cycles, with one cycle being 00,0OOh-'). Thereafter, the weight of each monolithic catalyst was measured, and the amount of peeling of the Alumina Two 1 to layer layers was determined. The results are shown in Table-1.

Table 1 As can be seen from this result, in the first example, 0.5%
The amount of peeling is 0.8% in the second example and 0.9% in the third example, which is significantly smaller than 5.0% in the comparative example. From this result, it can be seen that the peeling resistance is the best when the particle size of the carbon powder and the particle size of the alumina powder are made to be approximately the same.

In each of the examples, a slurry of clay minerals such as kaolin and talc was used, but cordierite which has been calcined in advance may also be used.

〔Effect of the invention〕

As explained above, when using the method for manufacturing a monolith base material for exhaust gas purification of the present invention, the surface of the 1000-110S base material is coated with a slurry to which flammable fine particles are added, and then this slurry is coated with the slurry. Since the monolith substrate was dried and fired, a large number of fine f. h: 1. It can be formed. As a result, the bonding state between the monolithic base material and the alumina coat layer formed on the surface of the monolithic base material is significantly improved, and the peeling resistance of the alumina layer 1 can be significantly improved.

[Brief explanation of drawings]

FIG. 1 is a partially enlarged sectional view of a monolith base +A manufactured by the method of manufacturing a monolith base +2 for exhaust gas purification according to the present invention. Figure 3 is an overall view of the monolith base material in Figure 1, and Figure 4 is a partially enlarged sectional view of the monolith base material in Figure 1.
A side view of the figure. 1... Monolith base material 2... Cell 3... Part where many pores exist in the monolith base material (newly formed on the monolith base H by coating with slurry) Cordierite layer) 4... Alumina coat layer patent applicant Toyota Motor Corporation Figure 1 Figure 2

Claims (1)

[Claims] (1) A slurry produced by adding flammable fine particles and a liquid to the clay mineral kneading product is coated on the surface of a monolith base material, which is formed by molding a clay mineral kneading product into a predetermined shape and drying. A method for producing a monolith base material for exhaust gas purification, characterized in that the monolith base material coated with slurry is dried and fired.