JPH01107818A - Method for coating wall flow type filter - Google Patents

Abstract

PURPOSE:To allow a catalyst slurry to flow in a wall flow type filter from the bottom and to simply support the catalyst when the filter is coated with the slurry by connecting a slurry storage tank to a filter vessel with a communicating pipe and positioning the surface of the slurry in the storage tank above the top of the filter. CONSTITUTION:When a wall flow type filter 1 is coated with a catalyst slurry, the bottom of a filter vessel 3 contg. the filter 1 is connected to a slurry storage tank 6 with a communicating pipe 5 and the surface of the slurry in the tank 6 is positioned above the top of the filter 1. By the difference in head, the slurry is allowed to flow in the filter 1 from the bottom to coat the inner wall of each cell with a prescribed amt. of the catalyst. The flow of the slurry is regulated with a cock 4. The filter 1 has been covered with rubber 2 for hermetical sealing so as to prevent the slurry from entering the filter 1 from the side wall.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of coating a wall flow type filter. More specifically, the present invention applies to the production of an exhaust gas purification catalyst that collects and burns particulates contained in the exhaust gas of diesel automobiles, etc.
The present invention relates to a method of coating a catalyst slurry only in cells having openings in the exhaust gas inlet direction of a wall flow filter.

(Prior Art) Filters for collecting particulates discharged from diesel engines and the like include ceramic filters such as ceramic foam and honeycomb filters having a three-dimensional mesh structure, metal foam, and wire mesh.

Among these, every other cell of the honeycomb filter is sealed, and as shown in Figure 1, cells whose inlet side is sealed are open at the outlet side, and cells whose inlet side is open are sealed at the outlet side. The so-called wall flow type filter is considered to be a particulate trapping filter with high particulate trapping efficiency.

Furthermore, when catalyst is supported on this wall-flow type filter, the catalyst component is supported on the cell wall (1 in Figure 2), but particulates adhere to the wall 2 on the cell entrance side. Mostly, it does not collect much on the wall of the cell exit side 3. Therefore, in terms of burning particulates using a catalyst component, it is sufficient to support the catalyst only on the inlet side of the A-leflow type filter, which is both cost-effective and simple in terms of process. it is conceivable that.

A method of supporting catalyst components only on the inlet side is to plug the honeycomb filter with a flammable plug, burn the plug at high temperature after impregnating the honeycomb filter, and then plug it again with a cordierite plug like a wall flow type. (Unexamined Japanese Patent Publication No. 60-2168
No. 19), and a method in which a catalyst component is dropped from above onto the filter's population side and suctioned by a vacuum pump from the lower outlet side (Japanese Patent Application Laid-Open No. 129016/1983). However, in the former method, the process is quite complicated and the cost is high. Furthermore, in the latter case, the slurry support m is controlled by drawing a vacuum, but this is quite difficult and may result in pressure loss holes.

(Problems to be Solved by the Invention) Therefore, the purpose of the present invention is to solve the above-mentioned problems of the prior art, and to make it easier to support a catalyst component on a wall-flow type filter and to use less precious metals. Moreover, it is an object of the present invention to provide a coating method for a wall flow type filter, which makes it possible to control the amount of catalyst slurry supported.

(Means for Solving the Problems) According to the present invention, the above object is such that every other cell on the exhaust gas inlet side is sealed, and the cells sealed on the inlet side are not opened on the exhaust gas outlet side. When coating a catalyst slurry on a wall-flow type filter, which has an open cell on the inlet side and is closed on the outlet side, the catalyst slurry storage tank and the filter container are connected via a communication pipe, and the catalyst slurry storage tank is closed. The catalyst slurry is caused to flow from below the filter by arranging the liquid level above the position of the upper end surface of the filter, and the slurry is coated on the inner wall of the cell having an opening in the direction of inflow of the slurry. This is accomplished by a wall-flow type filter coating method.

It will be explained in detail below.

Specifically, when a wall flow type filter is impregnated with catalyst slurry, the present invention connects the lower part of the filter container in which the filter is delivered to a catalyst slurry storage tank with a communication pipe, and the slurry is extracted from the storage tank connected with the communication pipe. This is done by feeding the filter into the filter cell. In this case, the pressure at which the slurry is fed can be changed depending on the difference in height between the slurry storage tank and the filter installation port. Therefore, if it is desired to impregnate a filter with a predetermined amount of catalyst slurry, the slurry storage tank or filter container can be set to a corresponding height. As shown in FIG. 3, a catalyst filter 1 is covered with a sealing rubber 2 and installed in a filter container 3. As shown in FIG. The slurry stored in the slurry storage W16 is transferred to the communication pipe 5
It flows into the filter container 3 through the filter. ] Tuk 4 adjusts the flow of the slurry.

Here, the sealing rubber is provided to prevent the catalyst slurry from entering through the side wall of the filter and coating the outer circumference of the filter with the catalyst slurry unevenly. As the rubber, it is preferable to use hydrophobic rubber such as vinyl, acrylic, or nitrile resins, or fluorine-based pyton. Furthermore, instead of using the rubber, the entire side wall of the filter may be treated to be water repellent. This treatment method involves applying water-repellent paints such as silicone-based or fluorine-based paints, wax emulsions for ceramics, or other paints that impart water-repellent or water-repellent properties to the side walls of the filter by spacing, spraying, etc. This can be easily done by doing this.

When changing the supported ω of the catalyst slurry, the specific gravity of the slurry,
Viscosity, particle size distribution, etc. are parameters and usage conditions vary depending on the case, but - The head difference between the liquid level in the catalyst slurry storage tank and the upper end surface of the filter is such that the solid content of the slurry is 15 to 53%, and the specific gravity is 15% to 53%. 1.10-1.65,
When the viscosity is about 5 to 100 cps, the height of the liquid level in the slurry storage tank is 5 to 300 an above the upper end surface of the filter.
+ It is appropriate to lift it up high.

In the present invention, it is preferable to create a head difference between the liquid level in the slurry storage tank and the upper end surface of the filter so that the slurry flows naturally from the bottom of the filter. The present invention can also be carried out by reducing the pressure and providing a head difference.

Furthermore, although the slurry is stored in a storage tank for use, it is possible that the slurry may settle at the bottom of the tank during impregnation, so it is also considered a good idea to feed the slurry into the tank while stirring it.

When impregnating with slurry, the impregnation time is a factor that can change the amount of slurry supported. If this impregnation time is not long enough, the slurry will pass through the pores in the cell wall to all the cells in the filter, so there is no point in impregnating only one side. The impregnation time is appropriately determined depending on the size of the carrier, but is preferably about 10 to 60 seconds.

EXAMPLES The present invention will be explained below using Examples, but the present invention is not limited to these Examples.

In implementation, the approximate diameter is 6011111 as shown in Figure 2.
A cylindrical cordierite wall flow filter with a length of 150,111 ffl and an average pore diameter of 20 μm in partition walls was used.

As a supporting slurry, γ-alumina powder and Pd C were used.
12 aqueous solution was added thereto, dried, baked, supported, and then ground for about 1 hour using a wet grinder (capacity FF151).

The specific gravity solid content was 1.25.30%, respectively.

The slurry pressure is the height from the upper end surface of the filter to the liquid level of the slurry storage tank when the filter is impregnated with the slurry.

Furthermore, the effects of the present invention were evaluated based on the back pressure difference before and after slurry loading, particulate collection rate, particulate ignition temperature, and Pd loading per catalyst filter, and these definitions were as follows.

Back pressure difference before and after slurry is supported on the O filter (m aq) = (filter back pressure after slurry is supported) - (filter back pressure before slurry is supported) ○ Particulate collection rate (%) (filter population side particulate Curate concentration) - (Particulate concentration on the filter outlet side) = X10
0 (particulate concentration on the filter population side) O A 2.814-cylinder direct injection diesel engine was used as the engine for evaluating the particulate ignition temperature, and particulates were collected for 3 hours to raise the exhaust gas temperature and reduce the back pressure of the catalyst layer. The starting temperature was defined as the particulate ignition temperature.

Amount of Pd supported per catalyst filter A portion of the catalyst filter was crushed and the Pd content was measured by fluorescent X-ray analysis.

Example 1 A sealing rubber 2 was wrapped around the side wall of the wall-flow type filter as shown in FIG. 3, and the filter was packed into a filter container 3. The cock 4 is initially closed, and the slurry is poured into the storage tank 6.
The storage tank was set so that the difference between the storage tank and the filter installation port was 15 mm. After confirming that the slurry was in the communication tube (5), the cock was opened and the slurry was poured into the filter container. After impregnating for 15 seconds, remove the excess slurry, dry at 150℃ for 2 hours, and then dry at 500℃ for 2 hours.
Baked for an hour.

Regarding the wall flow type filter obtained in this way, the back pressure difference before and after slurry loading, particulate collection rate, ignition temperature, Pdft per catalyst filter
was measured and the results shown in Table 1 were obtained.

Example 2 Impregnation, drying, and firing were performed under the same conditions as in Example 1, except that the storage tank was set to 60111 m, and the results shown in Table 1 were obtained.

Examples 3 and 4 The impregnation time was 30 seconds, and in Example 3, the setting of the liquid storage tank was 1.
5111I111 In Example 4, the diameter was 60 mm, and impregnation, drying, and firing were performed under the same conditions as in Example 1, and the results shown in Table 1 were obtained.

Comparative Example 1 The same procedure as in Example 1 was carried out, except that the slurry was allowed to flow into the upper cell opening of the filter without wrapping vinyl rubber, and both cells were impregnated for a total of 15 seconds. Table 1 shows the back pressure difference before and after slurry loading, particulate collection rate, firing temperature, and Pd loading per catalyst filter.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the groove structure of a wall flow type filter, and FIG. 2 is a schematic diagram not showing the flow of exhaust gas when the filter is used for exhaust gas treatment. FIG. 3 is a schematic diagram showing an embodiment of an apparatus used in the method of the present invention. Patent applicant Nippon Shokubai Kagaku Kogyo Co., Ltd. Figure 1 1: Cell wall 4: Cornoelite sealing 2:
Cell entrance side 5. Catalyst component 3: Cell outlet side

Claims (3)

[Claims] (1) Every other cell on the exhaust gas inlet side is sealed, and cells that are sealed on the inlet side are open on the exhaust gas outlet side, and cells that are open on the inlet side are closed on the outlet side. When coating a wall flow type filter with catalyst slurry, the catalyst slurry storage tank and the filter container are connected via a communication pipe, and the liquid level in the catalyst slurry storage tank is arranged above the position of the upper end surface of the filter. A method for coating a wall-flow type filter, characterized in that a catalyst slurry is introduced from below the filter, and the slurry is coated on an inner wall of a cell having an opening in the direction of inflow of the slurry. (2) The method according to claim 1, wherein the catalyst slurry has a specific gravity of 1.10 to 1.65, a solid content of 15 to 53%, and a viscosity of 5 to 100 cps. (3) The wall-flow type filter has the entire side wall treated with water repellency in advance, or is further provided with a weir on the upper end surface of the filter to prevent the catalyst slurry from entering the filter. The method described in section.