JPH01107819A - Method for coating wall flow-type filter - Google Patents

Abstract

PURPOSE:To easily deposit a catalyst on a wall flow-type filter by applying water repellent finish over the whole side wall of the filter, and dipping the filter in a catalyst slurry while providing a weir to prevent the infiltration of the slurry from the upper end face of the filter at the time of coating the filter with the slurry. CONSTITUTION:When a catalyst is deposited on the wall flow type filter, water repellent finish is applied over the whole side wall of the filter, and a weir is provided to prevent the infiltration of the catalyst slurry from the upper part of the filter. When the water repellent finish and the provision of the weir are simultaneously carried out, a cover 2 is wound on the whole side wall and upper part of the filter 1 to make the weir for the slurry. A hydrophobic material (e.g., vinyl rubber) having resistance to acid and alkali is used for the cover 2. The filter 1 provided with the cover 2 is sunk in the catalyst slurry and impregnated with the slurry, and the catalyst slurry is deposited only on the inner wall with the lower cell port opened.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of coating a wall 70-type filter. More specifically, when manufacturing an exhaust gas purification catalyst that collects and burns particulates contained in exhaust gas from diesel automobiles, etc.,
The present invention relates to a method of coating a catalyst slurry only within a cell having an opening in the direction of the exhaust gas inlet of a wall flow filter.

(Prior Art) As filters for collecting particulates discharged from diesel engines and the like, there are ceramic foam filters having a three-dimensional mesh structure, as well as wall-flow type filters that have a honeycomb filter structure.

As shown in Figure 2, cells with a closed inlet side are open at the outlet side, and cells with an open inlet side are closed at the outlet side. It is considered a filter for curation collection.

Furthermore, when this wall-flow type filter is used as a catalyst filter, particulates mainly accumulate on the cell wall where the inlet side is located, so if the catalyst component is mainly supported on the inlet side, the outlet side is not so necessary.

The method of supporting the catalyst component on one side of the cell wall is (
b) A method of plugging a honeycomb filter with a flammable plug, burning the plug at high temperature after impregnating the catalyst, and plugging it again with a cordierite plug like a wall flow type (Japanese Patent Application Laid-Open No. 1983-1999-
216819) and (b) a method in which a catalyst component is dropped onto the filter population side from above and suctioned by a vacuum pump from the lower outlet side (Japanese Patent Application Laid-Open No. 129016/1983).

However, in method (a), the process is quite complicated and the cost is 1~ high. Furthermore, in the method (b), the amount of slurry carried is controlled by applying a vacuum, but this is quite difficult and may result in pressure loss.

(Problems to be Solved by the Invention) Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a simpler method for supporting a catalyst component on a wall-flow type filter while also controlling the catalyst slurry supported m. The purpose of the present invention is to provide a coating method for a wall-flow type filter, which enables the coating of a wall-flow type filter, and in which catalyst components are not attached to the sides of the filter that are not related to particulate combustion.

(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. A wall 70-type filter, which has a cell open on the inlet side and sealed on the outlet side, is immersed in the catalyst slurry, and when coating the filter with the slurry, a water repellent treatment is applied to the entire side wall of the filter. Furthermore, by immersing the filter, which has a weir on the upper end face of the filter to prevent the slurry liquid from entering the filter, in the slurry to a depth below the upper end face of the filter or the top of the weir, This is achieved by a coating method for a wall-flow type filter, which is characterized in that the slurry is coated on the inner wall of a cell having an opening.

A method of applying water repellent treatment to the entire side wall of a wall-flow type filter is to apply water-repellent paint such as silicone-based or fluorine-based paint, wax emulsion for ceramics, or other paint that makes the coating film slightly water-soluble or water-repellent to the filter. Known methods such as applying the adhesive to the side wall of the housing by spraying, spraying, etc. can be employed.

However, in order to easily perform the water repellent treatment of the filter and the provision of a weir on the upper end surface of the filter at the same time, specifically, the following method is preferable.

For example, as shown in FIG. 1, this can be done by wrapping a cover around a wall-flow type filter impregnated with catalyst slurry so as to form a slurry dam on the entire side wall of the filter and on the top of the filter.

Since this cover must cover the filter, it must be made of a hydrophobic material to prevent slurry from entering the filter in the impregnation bath.

In addition, it must be acid and alkali resistant to the catalyst slurry, and it must be flexible because it will be wrapped around the filter. Preferred materials include vinyl, acrylic, and nitrile resins, and fluorine-based rubbers such as Piton.

After wrapping the rubber around the filter, it is necessary to wrap it two or three times so that it does not come off, and by wrapping it as tightly as possible, narrow the gap between the filter surface and the rubber and prevent slurry from entering.

This catalyst filter allows the catalyst slurry to be supported only on the inner wall where the lower cell opening is open by pressing the filter into the catalyst slurry and impregnating it. It also acts as a dam to prevent water from entering. By providing this weir, the filter can be pushed further below the slurry liquid level, thereby applying slurry pressure within the cells and supporting the slurry more strongly on the inner walls of the cells of the filter. The height of the weir varies depending on the shape and capacity of the filter, but is approximately 0.5 to 10C.
About 11 is preferable.

Impregnation time is an important factor when supporting slurry. If left impregnated for a long time, the slurry will flow through the pores in the cell wall, and there is no point in impregnating only one side of the cell with the slurry. The impregnation time varies somewhat depending on the specific gravity of the slurry, but is preferably 5 to 30 seconds.

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

In carrying out the experiment, a cylindrical cordierite wall flow filter having a diameter of 60 mm, a length of 150 mm, and an average pore diameter of the filter partition wall of 20 μm as shown in FIG. 2 was used.

In addition, as a slurry for supporting, Pd is added to γ-alumina powder.
Add a C12 aqueous solution, dry, bake, and use a wet grinder (capacity f).
? A slurry obtained by grinding with an i5J mill for about 1 hour was used.

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 the filter carries slurry (mmaq
) = (filter back pressure after slurry loading) - (filter back pressure before slurry loading) O particulate collection rate (%) (particulate concentration on filter population side) - (particulate concentration on filter outlet side) XJOO (Particulate concentration on the filter population side) O Particulates were collected for 3 hours using a 2.844-cylinder direct injection diesel engine as the engine for particulate ignition temperature evaluation, and the exhaust gas temperature was raised to increase the back pressure of the catalyst layer. The temperature that started to drop was defined as the particulate ignition temperature.

Amount of Pd supported per catalyst filter A part of the catalyst filter simulating particulate combustion was crushed, and the Pd content was measured by fluorescent X-ray analysis.

(Example) Example 1 As shown in Figure 1, the side wall of the wall-flow type filter was wrapped twice with a vinyl rubber agent coated with adhesive on the back side, and a weir was applied to prevent the slurry from flowing in. The filter was pushed down to 1 cn+ below the liquid level of the slurry and impregnated for 10 seconds. After impregnation, excess slurry was removed, dried at 150°C for 2 hours, and fired at 500°C for 2 hours.

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

Example 2 Impregnation, drying, and baking were carried out under the same conditions as in Example 1, except that the filter was pressed down 5 cm below the liquid level, and the results shown in Table 1 were obtained.

Examples 3 and 4 Impregnation and drying were carried out under the same conditions as in Example 1, except that the impregnation time was 30 seconds, and in Example 3, the filter was pushed down to IC11 below the liquid surface, and in Example 4, it was 5 cm below the liquid surface.

Firing was performed and the results shown in Table 1 were obtained.

Comparative Example 1 Without wrapping the vinyl rubber, the filter was pushed down to 1 cm below the liquid surface so that the slurry entered both the upper and lower cell openings.
The same procedure as in Example 1 was carried out except that the impregnation was carried out for 10 seconds. The resulting back pressure difference before and after slurry loading, particulate collection rate, ignition temperature, and amount of Pd supported per catalyst filter are shown in Table 1.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing an embodiment of implementing the method of the present invention, and FIG. 2 is a schematic diagram showing the structure of a wall-flow type filter. 1... Wall flow type filter 2...
...Coating cover patent applicant Nippon Shokubai Chemical Co., Ltd. Figure 1 Figure 2

Claims (1)

[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 a wall-flow type filter is immersed in catalyst slurry and the filter is coated with the slurry, the entire side wall of the filter is treated to be water repellent, and the upper end surface of the filter is further treated to prevent the slurry liquid from entering the filter. A filter provided with a weir is immersed in the slurry to a depth below the upper end face of the filter or the top of the weir, thereby coating the inner walls of cells having openings in the dipping direction with the slurry. Coating method for wall flow type filters.