JPS58177118A - Preparation of diesel particulate filter - Google Patents

Abstract

PURPOSE:To obtain a filter through the burning and removing of fine particles in an exhaust gas, by a method wherein the predetermined part of a filter carrier is masked by a masking material and, after a catalyst is supported, the masking material is removed. CONSTITUTION:After the part of a filter carrier not desiring the support of a catalyst is masked by a masking material comprising a substance melted and removed by heat or capable of being removed by combustion, a noble metal alone such as platinum and a catalyst such as alkali metal salt or molybdate are supported by the masked filter carrier and the masking material is subsequently removed. In order to support the metal salt catalyst, the filter carrier is immersed in an aqueous solution of a metal salt several times or coated with the same by spraying and, after drying, the supported carrier is baked.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a filter for collecting Patikiere (9 particles) contained in exhaust gas from a diesel engine.

The fine particles are mainly composed of carbon, hydrocarbons, and metals, and are generated due to incomplete combustion of hydrocarbon fuel. When these particulates are released into the atmosphere, they are undesirable in terms of environmental hygiene and conservation. Therefore, various techniques have been proposed to remove these particulates or minimize the need for discharge lids, one of which is the use of filters. There is processing by Treatment with this filter is carried out by trapping particulates in the pores of the filter, which is made of an inorganic porous material such as alumina. It has become saturated or inoperable. Therefore, in order to prevent or remove excessively accumulated particulates, various catalysts or combustion means are used to burn off the particulates. There have also been proposals to do so. However, this technology for removing fine particles by combustion is still not sufficient, and problems such as poor bed firing often occur due to insufficient amount of fine particles.

An object of the present invention is to provide a method for manufacturing a filter for collecting diesel particulate matter that solves the above-mentioned problems in the combustion removal of particulates in exhaust gas and facilitates the ignition and combustion of particulates. 0 The diesel/citrate collecting filter produced by the method of the present invention is characterized in that only a portion thereof does not have a catalytic action. In other words, the first method of the present invention consists of supporting a catalyst on the filter carrier, or masking a portion of the filter carrier with an appropriate material after supporting the catalyst on the filter carrier. After masking the part with a masking material made of a substance that can be melted away or dephosphorized with heat, such as wax, resin, low melting point metal, etc., the catalyst is supported on the filter carrier, and then the masking material is removed. A second method of the present invention is characterized in that after a catalyst is supported on the entire filter carrier, the portion of the filter carrier that is not desired to have a catalytic action is masked with an inorganic substance.

As the filter carrier that can be used in the method of the present invention, those used for collecting particulates can be used as they are. Examples of the filter carrier include a porous skeleton obtained by applying alumina slurry 11- or the like to a foamed plastic body such as open-cell polyurethane foam and then firing it. In addition to this, there is also a cylindrical shape made of alumina particles!・Nicum-shaped sintered body can be used.O The masking material that can be used in the first method of the present invention can be any substance that can be melted away or dephosphorized with heat, but the heat treatment temperature when supporting the catalyst can be used. Alternatively, it is preferable to use one that thermally melts or disappears at the temperature at which the filter is used. Examples of such materials include Wavx, polyolefin resins such as polyethylene, linear polymers such as vinyl resins, and low melting point metals or alloys such as lead and solder alloys. Wax, polyolefin, etc. are preferable because when the filter carrier 1 is immersed in a catalyst-carrying chamber after masking, the masking becomes sufficient due to its water repellency, and it can be removed or disappeared by low-temperature melting.

These materials are preferable because they do not contain any elements other than carbon and hydrogen, and therefore cannot poison the catalyst. Masking of the filter carrier with these materials is advantageously carried out by immersing part of the filter carrier in the molten material, but it is also possible to apply or impregnate it with wax or plastic suspensions. It's okay.

As the inorganic masking material used in the second method of the present invention, a slurry of heat-resistant inorganic materials such as alumina, activated alumina, corsilite, spinel, etc. can be used. Albas is particularly preferred because it provides a porous film.@Masking is obtained by immersing a portion of the filter in a masking material slurry, drying, and firing.

As a catalyst, a noble metal such as platinum or an alkali metal I! Metal salts such as 4 salts, alkaline earth metal salts, molybdates or silver fences are used. These metal salts are
Usually used as an aqueous solution, the carrier is immersed in these catalyst-supporting solutions a required number of times and dried, or a required amount of the solution is applied to the carrier by spraying, dried, and then baked to support the catalyst.

Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Example a)-7 Rica (8i01) 51% by weight, alumina (A
I, 0. ) 55% by weight and magnesia (MgO)
A compound consisting of talc, aluminum hydroxide (or alumina) and viscosity selected to have a chemical composition of 14% by weight is mixed with water and sufficiently stirred to form a slurry in advance. Commercially available foamed foam 11 urethane foam (
Average pore diameter; 0,5 wr) 100mφX 100
A cylindrical piece of m in size was cut out, immersed in the slurry, then taken out from the slurry, excess slurry was blown off, and then dried and solidified. Thereafter, the filter carrier was fired in an electric furnace at 1400'C for 5 hours to obtain a filter carrier having a three-dimensional mesh structure.

Next, the filter carrier was immersed in a slurry consisting of activated alumina, alumina sol, and water, then taken out, excess slurry was blown off, dried at 120°C for 5 hours, and then calcined at 800°C for 1 hour. By this operation, an alumina coating layer of 20% by weight based on the total amount was formed on the surface of the filter carrier. ). This was then cooled and solidified at room temperature.

The filter carrier masked with wax was immersed in sufficient distilled water for 50 minutes, taken out and the excess water was blown off, then immersed in an aqueous palladium chloride (PdC1,) solution, and the aqueous solution was stirred for 1 hour. The filter carrier was taken out of the aqueous solution and dried at 120°C for 3 hours to melt and remove the wax, and then fired at 500°C for 1 hour to obtain a filter in which only one end was not catalyzed. Example 2 Example 1 a) A filter carrier with an alumina coat layer formed thereon obtained by the same procedure as above was immersed in sufficient distilled water for 30 minutes, taken out and the excess water was blown off, and then immersed in a palladium chloride (PdC1t) aqueous solution. Stirred for 1 hour. Thereafter, the filter carrier was taken out from the aqueous solution, dried at 120°C for 5 hours, and then fired at 500°C for 1 hour. One axial end (1 to 2 wheels) of this filter carrier was immersed in the alumina slurry described in Example 1a), the excess slurry was blown off, and the filter was dried at 120°C for 5 hours. The filter was fired at 400'C for 1 hour to obtain a filter in which the catalytic activity at one end in the axial direction was eliminated.

The filters obtained in Examples 1 and 2 are shown in the attached drawings. In the figure, 1 represents a portion that is not catalyzed or has no catalytic activity, and 2 represents a portion that has catalytic activity.

Comparative Example Example 1 A filter carrier with an alumina coat layer formed on the surface was made using a) and IW1's hands J1, and then PdCl
The filter carrier was immersed in an aqueous solution so that 115 of the carrier appeared above the liquid level, and the solution was stirred for 1 hour. After that, it was taken out and dried at 120℃ for 3 hours, and then heated to 500℃.
The filter was baked for 1 hour to obtain a filter.

According to the methods of Examples 1 and 2 according to the present invention, by masking with wax, γ-AI, and 03, respectively, it was possible to manufacture a filter in which only a portion of the filter had no catalytic effect.

However, in the method of the comparative example, the catalyst was supported on the entire filter due to capillarity.

As described above, according to the method of the present invention, it is possible to obtain a filter in which only a desired portion of the filter is not completely catalyzed or the catalytic action is eliminated. part of the filter
For example, by making only one end in the axial direction (usually 1 to 2 cslI) the catalyst inactive region, it is possible to increase the amount of particulates accumulated in this part, and therefore the prevention of combustion of particulates in the exhaust gas is greatly improved. This combined with the fact that the amount of particulates accumulated in areas other than the catalyst inactive area is reduced.
The combustion removal of particulates can be performed more completely and quickly.

[Brief explanation of the drawing]

The accompanying drawing is a perspective view showing an example of a filter obtained by the method of the present invention. 1... Portion that does not have catalytic activity 2... Catalyzed portion Patent applicant Toyota Motor Corporation (1 person) JP-A-1983-! 77118 (4) 1 no 80-

Claims (1)

[Claims] (11 Diesel patties characterized by masking a predetermined portion of the filter carrier with a masking material made of a substance that can be melted and removed or dephosphorized, then supporting the catalyst on the filter carrier, and then removing the masking material. Method of manufacturing a curate filter.