JPS6365927A - Catalytic filter for removing particulates - Google Patents

Abstract

PURPOSE:To enhance firing properties of particulates and to wholly burn and propagate the particulates fired in the front side of a honeycomb type filter up to the rear side of the filter by holding platinum group elements excellent in oxidation activity to the inlet side of gas of the honeycomb type filter. CONSTITUTION:In a catalytic filter for removing particulates, a coated filter 5 of alumina is formed on the surface of the side wall of the cell of a honeycomb type filter. On the whole alumina coated layer 5 a rare earth metal oxide in carried, and furthermore at least one kind of platinum group catalytic metal is carried at the gas inlet side of the honeycomb type filter. Further the above- mentioned coated layer 5 is coated with a copper plate 6. Therefore since the upper part of the coated layer of alumina is wholly plated by copper good in heat transfer, particulates fired in the front side of the filter can be wholly burned and propagated to the rear side of the filter.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a catalytic filter for collecting particulates used for removing particulates discharged from internal combustion engines such as diesel engines and purifying exhaust gas. .

[Conventional technology]

Particulates discharged from internal combustion engines such as diesel engines contain carcinogenic substances, so removing them has become an important issue in terms of environmental health. For this reason, the particulates are collected by a filter installed in the exhaust system, and the collected particulates are transferred to the oil burner.
Conventionally, methods of combustion using a heat source such as a light oil burner or an electric heater have been used. In addition, in diesel engine systems, the injection time of the injection pump is delayed to generate unburned hydrocarbons and -oxidized carbon, and the heat of reaction when this unburned gas is oxidized by an oxidation catalyst supported on a filter is utilized. According to
A method of burning the collected particulates has been proposed (JP-A-58-72611, JP-A-58-
(See Publication No. 187511).

In the above method, to collect particulates, a particulate filter with a honeycomb structure (hereinafter referred to as a honeycomb filter), a ceramic filter with a three-dimensional mesh structure, or a filter made of steel wool or wire mesh has been conventionally used. There is. Furthermore, among these conventional particulate collecting filters, there are known filters in which copper, silver, cobalt, manganese, palladium, etc. are supported as oxidation catalysts.

FIG. 2 shows a cross-sectional structure of a conventional honeycomb type filter disclosed in Japanese Patent Application Laid-Open No. 58-185919. In the figure, 1 is a ceramic monolith carrier having a honeycomb structure. Every other cell opening 2a on the gas inlet side of the carrier is closed with a blind plug 3. The cell openings 2b on the gas outlet side are closed with blind plugs 3 only for cells whose inlet side openings 2a are not blocked, and the openings 2b are opened for cells with blind plugs on the inlet side. Therefore, the exhaust gas flows to the cell side wall 4 as shown by the arrow in the flow diagram.
The particulates flow through the bore, and the accompanying particulates are captured and removed.

[Problem that the invention seeks to solve]

In the honeycomb type filter, as mentioned above, by blocking both ends of the honeycomb carrier alternately with blind plugs, gas can flow through the several to several dozen bores provided in the cell side walls. It has the advantage of higher particulate collection rate than other filters.

However, when the collected particulates are burned with a burner, an electric heater, etc., only the front surface of the filter or the center of the filter is burned, and there is a problem that the combustibility of the outer circumference of the filter is poor.

In view of the above circumstances, the present invention aims to solve the problems with conventional honeycomb filters and provide a catalytic filter for removing particulates that has a high particulate collection rate and excellent combustibility. It is.

[Means for solving problems]

The catalytic filter for removing particulates according to the present invention includes:
Close every other cell opening on the gas inlet side with a blind plug, and on the gas outlet side, plug the opening with a blind plug only for cells that are not plugged on the inlet side, and for cells that are plugged on the inlet side. In a honeycomb type filter that allows gas to flow through the bore in the carrier wall by leaving the opening open, the alumina filter is formed on the side wall surface of the cell where the opening on the gas inlet side is open. a coating layer, a rare earth metal oxide supported on the entire alumina coating layer, and a catalyst metal consisting of at least one platinum group element supported only on the gas inlet side portion of the alumina coating layer, and It is characterized in that at least the surface of the alumina coating layer is plated with copper to such an extent that the surface is not completely covered.

Platinum, palladium, and rhodium are suitable as the platinum group metal used in the present invention.

Further, as the rare earth metal oxide, cerium oxide, lanthanum oxide, or a composite oxide thereof is preferable. These rare earth metal oxides are usually impregnated as ions and are converted into oxides in the subsequent firing step.

Copper plating in the present invention can be formed using an electroless plating solution. At this time, if the plating layer covers the entire surface of the alumina coating layer, the supported catalyst cannot provide an effective catalyst surface. Therefore, the copper plating must be formed to such an extent that it does not form a completely metalized coating layer.

To obtain copper plating in this state, 0.0005~
A plating amount of about 0.0059/cx2 is preferable. Further, although it is sufficient to form copper plating only on the surface of the alumina coating layer, it may be applied to the entire honeycomb filter.

In order to further improve the combustibility of particulates, it is preferable to provide an electric heater in close contact with the front surface of the honeycomb filter.

Next, one aspect of the catalyst filter for removing particulates of the present invention will be described in more detail with reference to FIG. In this figure, the same parts as in the conventional example shown in FIG. 2 are given the same reference numerals.

In this catalyst filter, an alumina coating layer 6 is formed on the cell side wall surface of the conventional honeycomb type filter shown in FIG. As shown, the alumina coating layer 6 is provided only on the side walls of the cell whose gas inlet side is open. A rare earth metal oxide is supported on the entire alumina coating layer 6, and at least one platinum group catalyst metal is supported on the gas inlet side of the honeycomb filter, that is, a portion corresponding to 68 of the alumina coating layer in FIG. is carried. Therefore, both the rare earth oxide and the platinum group metal are supported on the portion 6a, and only the rare earth metal oxide is supported on the portion 6b. Further, a copper plating layer 6 is provided on the coating layer 6. The plating layer 6 is incomplete as a coating layer, and therefore the surface does not have metallic luster.

The reason why the alumina coating layer 6 is formed only on the side wall of the cell whose gas inlet side is open as described above is because the particulates contained in the gas are This is because most of the information is captured on this side. That is, the catalyst for burning particulates is placed on the side where particulates are captured.
This is because it is sufficient if the particulates exist, and it is useless to provide them in areas where there are almost no particulates.

[Effect]

The catalytic filter for removing particulates of the present invention has a platinum group element having excellent oxidation activity supported on the gas inlet side of the honeycomb type filter, and therefore has good ignitability of particulates. In addition, rare earth metal oxides that have a stabilizing effect on activated alumina and a promoter effect on platinum group metals are supported throughout the alumina coating layer, and furthermore, the alumina coating layer is coated with copper that has good heat transfer throughout the layer. Since the particulates are plated on the front side of the filter, the particulates ignited on the front side of the filter will burn and propagate all the way to the rear side of the filter.

〔Example〕

Example 1 A honeycomb type filter was subjected to water absorption treatment, coated with a slurry containing activated alumina under suction conditions of 10 to 200 miHg, and then dried at 250°C. Next, 0.3 M/i of Ce was supported with a cerium nitrate solution and heated at 700°C.
Baked for 1 hour. PdCl2 aqueous solution was applied to the gas inlet side of the honeycomb filter thus obtained.
d19/J was carried. Furthermore, this sample was
j? 2 and HC, 7? Immerse for 10 minutes in a mixed aqueous solution of
After thoroughly washing with water, it was immersed in a PdC, &2 aqueous solution for 5 minutes and washed thoroughly with water again. Furthermore, this sample was immersed in a solution with a mixing ratio of CuSO4 aqueous solution and HCHO solution of 1:1,
It was plated with CuO, 3M/no.

The particulate collection rate of the honeycomb catalyst filter thus obtained was measured and found to be S V = 88.
The ignition temperature and combustion rate were measured under conditions of 00 Hr-'. The results are shown in Table 1.

Example 2 A honeycomb type filter was coated with activated alumina in the same manner as in Example 1, dried, and then La and Cc were supported on o and I5M/i with lanthanum nitrate and cerium nitrate aqueous solutions, respectively, and further baked at 700°C for 1 hour. did. PdO, 59/l was supported on the gas inlet side of the honeycomb filter thus obtained using a PdCJ2 aqueous solution, and RhC, I? 3
Rh was supported at 0.59/ff using an aqueous solution. Furthermore, CuO, 3M/i was plated in the same manner as in Example 1.

Regarding the honeycomb type catalyst filter thus obtained, the particulate collection rate, ignition temperature, and combustion rate were measured in the same manner as in Example 1. The results are shown in Table 1.

Example 3 A honeycomb type filter was coated with activated alumina in the same manner as in Example 1, and after drying, 0.3 M/'J of lanthanum nitrate was applied.
It was supported and then calcined at 700°C for 1 hour. Using a chloroplatinic acid solution, Pt 1';j/I! was applied to the gas inlet side of the honeycomb thus obtained. was carried.

Furthermore, Cu 0.3M/J was plated in the same manner as in Example 1.

Using the honeycomb type catalyst filter obtained above, the particulate collection rate, tube flammability, and combustion rate were measured in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1 The particulate collection rate, ignition temperature, and combustion rate were measured in the same manner as in Example 1 for a honeycomb filter base (no activated alumina coat layer, no catalytic metal, no copper plating). The results are shown in Table 1.

Comparative Example 2 A honeycomb filter was subjected to water absorption treatment, coated with a slurry containing activated alumina under suction conditions of 10 to 200 MHg, dried at 250°C, and then fired at 700°C for 1 hour.

For this sample, PdO, 5g/I!, was added to the entire sample using a PdC, f2 aqueous solution. and further Rh 0
．． 5g/, l? was carried.

Regarding the honeycomb type catalyst filter thus obtained, the particulate collection rate, ignition temperature, and combustion rate were measured in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 3 A honeycomb filter was coated with activated alumina and fired in the same manner as in Comparative Example 2. This sample was converted into SnCHC
After immersing in a mixed aqueous solution with lHCl for 10 minutes and thoroughly washing with water, PdC, f? 2 aqueous solution for 5 minutes and thoroughly washed again with water. Furthermore, this sample was immersed in a solution with a mixing ratio of Cu5Oa aqueous solution and HCHO solution of 1:1.
A plating sample of 0.3M/no was obtained.

Using the honeycomb type catalyst filter thus obtained, Example 1
When the particulate collection rate, ignition temperature and combustion rate were measured in the same manner as above, the results shown in Table 1 were obtained.

Comparative Example 4 A honeycomb type filter was coated with activated alumina in the same manner as in Comparative Example 2, and then Pd19/, & was supported on the entire sample on the gas inlet side of the filter using a PdC72 aqueous solution. Further, in the same manner as in Comparative Example 3, this sample was plated with CuO, 3M.

Regarding the honeycomb type catalyst filter thus obtained, the particulate collection rate, ignition temperature, and combustion rate were measured in the same manner as in Example 1, and the results shown in Table 1 were obtained as IF3.

Comparative Example 5 A honeycomb filter was coated with activated alumina in the same manner as in Comparative Example 2, and then coated with cerium nitrate using an aqueous solution of cerium nitrate.
After supporting O, 3M/, i', it was fired at 700°C for 1 hour. This sample was plated with CuO, 3M/I in the same manner as in Comparative Example 3.

The particulate collection rate, ignition temperature, and combustion rate of the honeycomb catalyst filter obtained above were measured in the same manner as in Example 1, and the results shown in Table 1 were obtained.

Comparative Example 6 A honeycomb type filter was coated with activated alumina in the same manner as in Comparative Example 2, and a cerium nitrate aqueous solution was used.
．． 3M/l! After supporting, it was fired at 700'C for 1 hour. On the gas inlet side of this sample, PdCl! 2 aqueous solution was used to support Pd1g/,/'.

Regarding the honeycomb type catalyst filter thus obtained, the particulate collection rate, ignition temperature, and firing rate were measured in the same manner as in Example 1. The results are shown in Table 1.

Example 4 For Example 1 and Comparative Example 4, the particulate combustion rates were measured when each was regenerated 20 times, and the results shown in Table 2 were obtained.

Table 1 * The filters used in Examples 1 to 3 and Comparative Examples 1 to 6 all have the same volume *1 Human gas I degree: 200°C, engine rotation speed: 200 Orpm *2 Temperature table at which particulates start to burn 2 1-Note As is clear from comparing the results of Examples 1 to 3 with the results of Comparative Examples 2 to 6, cerium and/or lanthanum was supported on the honeycomb filter, and platinum side elements were added to the gas inlet side of the honeycomb filter. The ignition temperature of the particulates of the present invention obtained by supporting the particles and applying copper plating to the entire part is about 10 to 60°C, and the particulate combustion rate is about 10 to 60°C.
It improved by 16%. Furthermore, as is clear from the comparison between Example 1 and Comparative Example 4 in Table 2, the cerium-supported
The particulate combustion rate has improved by approximately 10 points.

〔Effect of the invention〕

As described in detail above, the catalytic filter for removing particulates according to the present invention has significant effects such as a low particulate collection rate and excellent combustibility.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram schematically showing the cross-sectional structure of a catalyst filter for removing particulates according to an embodiment of the present invention, and FIG.
The figure is an explanatory diagram schematically showing the cross-sectional structure of a conventional honeycomb filter. DESCRIPTION OF SYMBOLS 1... Ceramic monolith carrier, 2... Honeycomb cell, 2a... Cell opening on the gas inlet side, 2b... Cell opening on the gas outlet side, 3... Blind plug, 4... Cell side wall ,
5... Alumina coating layer, 5a... Portion where platinum group catalyst metal is supported, 6b... Portion where only rare earth oxide is supported, 6... Steel plating layer. Applicant's agent Patent attorney Takehiko Suzue Figure 2

Claims (2)

[Claims] (1) Close every other cell opening on the gas inlet side with a blind plug, and on the gas outlet side, close the opening with a blind plug only for cells that do not have a blind plug on the inlet side, and close the opening with a blind plug on the inlet side. In honeycomb filters, the openings of the cells are left open to allow gas to flow through the bores in the carrier wall. a rare earth metal oxide supported on the entire alumina coating layer, and a catalyst metal consisting of at least one platinum group element supported only on the gas inlet side portion of the alumina coating layer. A catalytic filter for removing particulates, characterized in that at least the surface of the alumina coating layer is plated with copper to such an extent that the surface is not completely covered. (2) The catalytic filter according to claim 1, wherein the rare earth metal oxide is cerium oxide, lanthanum oxide, or a composite oxide thereof.