JP2010269205A - Catalyst for cleaning exhaust gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst for cleaning exhaust gas, which restrains the increase of a pressure loss of a diesel particulate filter, whose capacity for removing HC or CO is increased and whose durability is improved. <P>SOLUTION: An inlet-side catalyst layer 2 which has a length shorter than the full length of an inflow-side cell 10 from the exhaust gas inlet-side end face thereof to the downstream side, and an outlet-side catalyst layer 3 which has the length shorter than the full length of an outflow-side cell 11 from the exhaust gas outlet-side end face thereof to the upstream side, are formed of a filter base material of a wall flow structure having the inflow-side cell plugged at the exhaust gas downstream side, the outflow-side cell which is adjacent to the inflow-side cell and is plugged at the exhaust gas upstream side, and a porous cell partition wall for separating the inflow-side cell from the outflow-side cell. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an exhaust gas purifying catalyst that purifies exhaust gas from a diesel engine or the like by forming a catalyst layer on a cell partition wall of a filter base material.

  As for gasoline engines, toxic components in exhaust gas are steadily decreasing due to strict regulations on exhaust gas and technological advances that can cope with it. On the other hand, in the case of diesel engines, exhaust gas purification is more effective than gasoline engines due to the peculiar situation that harmful components are discharged as PM (carbon fine particles, sulfur fine particles such as sulfate, high molecular weight hydrocarbon fine particles (SOF), etc.). Is difficult.

  Therefore, a ceramic plug-type honeycomb body (diesel particulate filter (hereinafter referred to as DPF)) has been known. This DPF is formed by alternately sealing both ends of the openings of the cells of the ceramic honeycomb structure, for example, in a checkered pattern, and is adjacent to the inflow side cells and the inflow side cells clogged on the exhaust gas downstream side. It consists of an outflow side cell clogged on the exhaust gas upstream side and a cell partition wall that partitions the inflow side cell and the outflow side cell, and collects PM by filtering the exhaust gas through the pores of the cell partition wall.

  However, in DPF, pressure loss (hereinafter referred to as pressure loss) increases due to PM accumulation, so it is necessary to periodically remove and regenerate PM (mainly soot) accumulated by some means. Therefore, conventionally, when pressure loss increases, DPF is regenerated (forced regeneration) by flowing high-temperature exhaust gas and burning PM. For example, an oxidation catalyst is placed upstream of the DPF, exhaust gas rich in HC and CO is supplied, the exhaust gas temperature is raised by the reaction heat in the oxidation catalyst, and the high temperature exhaust gas is supplied to the DPF to oxidize the deposited PM. A forced regeneration method is known. However, in this case, if the amount of PM deposited is large, acceleration combustion occurs, and sometimes thermal runaway occurs, causing thermal damage to the center or downstream end of the DPF.

  Therefore, in recent years, for example, as described in Japanese Patent Publication No. 07-106290, a coating layer is formed on the surface of the cell partition wall of DPF from alumina or the like, and a catalytic metal such as platinum (Pt) is supported on the coating layer. Filter catalysts have been developed. According to this filter catalyst, the collected PM is oxidized and burned by the catalytic reaction of the catalytic metal, so that the filter catalyst can be regenerated continuously by burning simultaneously with the collection or continuously with the collection. . Since the catalytic reaction occurs at a relatively low temperature and can be burned while the amount collected is small, there is an advantage that the thermal stress acting on the filter catalyst is small and breakage is prevented.

  However, even with a filter catalyst, depending on the use conditions, there is a case where accumulation of PM increases and forced regeneration needs to be performed. For example, when forcibly regenerating a filter catalyst carrying Pt as a catalyst metal, the exhaust gas temperature needs to be about 600 ° C. or higher. However, in the conventional filter catalyst in which the catalyst layer is formed on the cell partition wall over the entire length in both the inflow side cell and the outflow side cell, the exhaust gas temperature in the outflow side cell is particularly high due to the reaction heat during forced regeneration, When forced regeneration was repeated, there was a problem that the catalyst metal deteriorated in grain growth. Further, there is a problem that ash remains in the filter partition wall, and it becomes difficult to oxidize PM by the catalyst metal when the ash is interposed between the catalyst metal and PM. Further, there is a problem that pressure loss increases due to the catalyst layer and ash.

  Japanese Patent Laid-Open No. 2003-154223 proposes a filter catalyst in which the catalyst layer of the cell partition wall of the inflow side cell is formed in a range shorter than the full length from the input side end face. According to this filter catalyst, since the catalyst layer is not formed in the outflow side cell, it is possible to suppress the grain growth deterioration of the catalyst metal during forced regeneration. And since the catalyst layer is not formed in the downstream of an inflow side cell, it is suppressed that the gas permeability in a downstream is prevented, and the raise of a pressure loss can be suppressed.

Japanese Patent Publication No. 07-106290 JP 2003-154223 A

  However, the filter catalyst described in Patent Document 2 has a problem in that purification of HC and CO is insufficient because the catalyst layer is not formed on the outflow side cell.

  This invention is made | formed in view of such a situation, It is set as the problem which should be solved while improving the purification | cleaning performance while suppressing the raise of a pressure loss.

The exhaust gas purifying catalyst of the present invention that solves the above problems is characterized in that an inflow side cell clogged on the exhaust gas downstream side, an outflow side cell adjacent to the inflow side cell and clogged on the exhaust gas upstream side, and the inflow side A filter substrate having a wall flow structure having a cell and a porous cell partition wall defining an outflow side cell;
An inlet side catalyst layer formed on the cell partition wall surface of the inflow side cell from the exhaust gas inlet side end face to the downstream side within a length less than the total length of the filter base material and supporting a noble metal on a porous oxide carrier, and an outlet side cell And an outlet catalyst layer formed on the surface of the cell partition wall from the exhaust gas outlet end face to the upstream side in a range of less than the total length of the filter base material and having a noble metal supported on a porous oxide carrier.

  The inlet side catalyst layer is preferably formed in the range of 1/6 to 1/2 of the total length of the filter base material from the exhaust gas inlet side end face to the downstream side. Moreover, it is desirable that the exit catalyst layer be formed in the range of 1/6 to 1/2 of the total length of the filter base material from the exhaust gas exit end face to the upstream side.

  Further, it is desirable that at least Pt is supported on the inlet catalyst layer and at least Pd is supported on the outlet catalyst layer.

  According to the exhaust gas purifying catalyst of the present invention, the cell partition wall in which the catalyst layer is not formed in a predetermined length range from the clogged portion of the inflow side cell to the upstream side is exposed. The site near the clogged portion of the inflow side cell is a site where ash is likely to accumulate, but since a catalyst layer is not formed at that site, a problem that the contact between precious metal and PM is impaired by ash is avoided. The Accordingly, the precious metal can be effectively used, and even if the amount of the precious metal supported is reduced, the same purification performance can be ensured as before, so that the cost can be reduced. And since the cell partition which does not have a catalyst layer in part in both the inflow side cell and the outflow side cell has exposed, an initial pressure loss can be made low and the raise of a pressure loss is also suppressed.

  Further, according to the exhaust gas purifying catalyst of the present invention, the outlet catalyst layer is formed within a predetermined length from the exhaust gas outlet end face of the outflow side cell to the upstream side. The vicinity of the exhaust gas outlet side end face of the outflow side cell is less susceptible to the heat generated when the accumulated PM burns, so that deterioration of the noble metal can be suppressed. During forced regeneration, where a liquid reducing agent such as fuel is added to the exhaust gas and burned with an oxidation catalyst, and the exhaust gas whose temperature has risen thereby flows into the filter catalyst, a large amount of HC and CO flows into the inlet catalyst layer. Then, HC and CO that cannot be oxidized may pass through the cell partition wall. However, since such slip-through HC can be oxidized in the outgoing catalyst layer, emission during forced regeneration is reduced.

Furthermore, if Pd is supported at least on the outlet catalyst layer, Pd has a high ability to oxidize high concentrations of HC, so that it can efficiently oxidize slip-through HC during forced regeneration, and a part of SO _{x in} the exhaust gas flows in. since the captured as ash on the side cell durability can be suppressed sO _x poisoning of Pd is increased.

1 is a schematic cross-sectional view of an exhaust gas purifying catalyst according to an embodiment of the present invention. It is typical sectional drawing of the exhaust gas purification catalyst which concerns on the 2nd Example of this invention. It is typical sectional drawing of the exhaust gas purification catalyst which concerns on the 3rd Example of this invention. It is typical sectional drawing of the catalyst for exhaust gas purification which concerns on the comparative example 1 of this invention. It is typical sectional drawing of the catalyst for exhaust gas purification which concerns on the comparative example 2 of this invention. It is typical sectional drawing of the catalyst for exhaust gas purification which concerns on the comparative example 3 of this invention.

  The exhaust gas purifying catalyst of the present invention comprises a filter base material and a catalyst layer formed on a cell partition wall of the filter base material. Among these, the filter base material is divided into an inflow side cell clogged on the exhaust gas downstream side, an outflow side cell adjacent to the inflow side cell and clogged on the exhaust gas upstream side, and an inflow side cell and an outflow side cell. The wall flow structure is the same as that of the conventional DPF, which has a porous cell partition wall having a number of pores. As the filter base material, one produced from heat-resistant ceramics such as cordierite and silicon carbide can be used.

  In order to manufacture the filter base material, for example, a clay-like slurry containing cordierite powder as a main component is prepared, and the slurry is formed by extrusion molding or the like and fired. Instead of cordierite powder, each powder of alumina, magnesia, and silica can be blended so as to have a cordierite composition. Thereafter, the cell opening on one end surface is sealed in a checkered pattern or the like with the same clay-like slurry, and the cell opening of the cell adjacent to the cell sealed on the one end surface is sealed on the other end surface. Thereafter, a filter substrate having a honeycomb structure can be manufactured by fixing the plugging material by firing or the like. The shapes of the inflow side cell and the outflow side cell are not particularly limited, such as a cross-sectional triangle, a cross-sectional square, a cross-sectional hexagon, and a cross-sectional circle.

  The cell partition wall has a porous structure through which exhaust gas can pass. In order to form pores in the cell partition walls, carbon powder, wood powder, starch, resin powder and other combustible powders are mixed in the above-mentioned slurry, and the combustible powder disappears during firing to form pores. The diameter and pore volume of the pores can be controlled by adjusting the particle size and the amount of the combustible powder. The inflow side cell and the outflow side cell communicate with each other through this pore, and PM is collected in the pore, but gas can pass through the pore from the inflow side cell to the outflow side cell.

  The porosity of the cell partition walls is preferably 40 to 70%, and the average pore diameter is preferably 10 to 40 μm. When the porosity and average pore diameter are in this range, an increase in pressure loss can be suppressed even when the catalyst layer is formed at 100 to 200 g / L, and a decrease in strength can be further suppressed. And PM can be collected more efficiently.

  On the surface of the cell partition wall of the inflow side cell, an entrance side catalyst layer formed by supporting a noble metal on a porous oxide carrier is formed. This inlet side catalyst layer is formed in a range of a length less than the total length of the filter base material from the exhaust gas inlet side end surface to the downstream side, and a range of a predetermined length from the clogging portion existing at the most downstream side of the inflow side cell to the upstream side. No inlet catalyst layer is formed in the cell partition walls. Although the inlet side catalyst layer is formed on the surface of the cell partition wall, a part of it may be formed on the inner surface of the pores of the cell partition wall. Here, the total length of the filter base material means the length from the exhaust gas inlet side end surface to the inflow side cell clogging portion on the exhaust gas outlet side end surface side.

  The inlet side catalyst layer is preferably formed in the range of 1/6 to 1/2 of the total length of the filter base material from the exhaust gas inlet side end face to the downstream side. When it is formed in the range of less than 1/6 of the total length of the filter base material from the exhaust gas inlet side end face to the downstream side, the pressure loss can be reduced, but the amount of precious metal necessary for purifying HC and CO contacts with the exhaust gas. The area is small and sufficient purification performance cannot be obtained. Moreover, when it forms exceeding 1/2 of the filter base material full length, since the contact with a noble metal and PM is inhibited by ash while a pressure loss rises, the purification | cleaning performance of PM will fall.

  On the surface of the cell partition wall of the outflow side cell, an exit side catalyst layer formed by supporting a noble metal on a porous oxide carrier is formed. This exit side catalyst layer is formed in a range of a length less than the total length of the filter base material from the exhaust gas exit side end surface to the upstream side, and a range of a predetermined length from the clogged portion existing in the uppermost stream of the outflow side cell to the downstream side. In this case, the outlet catalyst layer is not formed, and the cell partition walls are exposed. Although the exit side catalyst layer is formed on the surface of the cell partition wall, a part thereof may be formed up to the inner surface of the pores of the cell partition wall. The total length of the filter base means the length from the exhaust gas outlet side end surface to the clogging portion of the outflow side cell on the exhaust gas inlet side end surface side.

The exit side catalyst layer is preferably formed in the range of 1/6 to 1/2 of the total length of the filter base material from the exhaust gas exit end face to the upstream side. When formed in the range of less than 1/6 of the total length of the filter base material from the exhaust gas outlet side end face to the upstream side, the effect of forming the catalyst layer is difficult to be achieved. Further, when formed beyond the half of the filter substrate full length, with a pressure loss is increased, noble metals such as Pd carried on the outlet side catalyst layer tends to deteriorate by SO _x poisoning.

  The porous oxide carrier constituting the inlet catalyst layer and the outlet catalyst layer is selected from alumina, titania, zirconia, ceria, or a porous oxide selected from one or a mixture of multiple oxides selected from these. An oxide can be used. Different oxide species may be used for the inlet catalyst layer and the outlet catalyst layer, or the same oxide species may be used.

Pt, Rh, Pd, etc. are illustrated as a noble metal carry | supported by the entrance side catalyst layer and the exit side catalyst layer. In addition to noble metals, base metals such as Sr, La, Pr, and Nd, and NO _x storage materials such as Ba, K, and Li can be supported.

It is desirable that at least Pt is supported on the inlet side catalyst layer and at least Pd is supported on the outlet side catalyst layer. By supporting Pt with high oxidation activity on the inlet side catalyst layer, HC and CO can be oxidized and purified from a relatively low temperature range, and PM is also combusted by NO ₂ with high oxidation activity generated by oxidation of the reaction heat and NO. Therefore, the time until forced regeneration can be lengthened. Further, by supporting Pd on the exit side catalyst layer, high concentration of HC can be oxidized, and the purification performance during forced regeneration is improved. Further, since a part of SO _x is captured as ash in the inflow side cell, the deterioration of poisoning of Pd supported on the output side catalyst layer is suppressed and durability is improved.

  Each of the inlet catalyst layer and the outlet catalyst layer can be formed in an amount of 10 to 200 g per liter of the filter base material. If it is less than 10 g / L, the amount of the noble metal relative to the porous oxide increases, so that the density of the noble metal supported becomes high and the grain growth is liable to occur, and if it exceeds 200 g / L, the pressure loss increases, which is not preferable.

  The amount of noble metal supported on the inlet catalyst layer and the outlet catalyst layer is preferably 0.1 to 10 g per liter of the filter substrate. If the loading amount is less than this range, the purification performance becomes insufficient, and even if the loading amount exceeds this range, the purification activity is saturated and the cost is increased.

  FIG. 1 shows a schematic cross-sectional view of an exhaust gas purifying catalyst according to the present embodiment. This exhaust gas purifying catalyst uses a filter base material 1 made of cordierite as a base material. The filter base 1 includes an inflow side cell 10 clogged on the exhaust gas downstream side, an outflow side cell 11 adjacent to the inflow side cell 10 and clogged on the exhaust gas upstream side, an inflow side cell 10 and an outflow side cell 11. Wall flow structure having a porous cell partition wall 12 for partitioning.

  An inlet side catalyst layer 2 is formed on the surface of the cell partition wall 12 of the inflow side cell 10 from the exhaust gas inlet side end face to the downstream side in a range of ½ of the total length of the filter base material 1. The surface of the cell partition wall 12 is exposed in the inflow side cell 10 in the range from the end portion to the clogging portion 100 of the inflow side cell 10. In addition, on the surface of the cell partition wall 12 of the outflow side cell 11, an exit side catalyst layer 3 is formed in the range of ½ of the total length of the filter base 1 from the exhaust gas exit side end surface to the upstream side. The surface of the cell partition wall 12 is exposed in the outflow side cell 11 in the range from the side end portion to the clogging portion 110 of the outflow side cell 11.

  Hereinafter, a method for producing the exhaust gas-purifying catalyst will be described, and a detailed description of the configuration will be substituted.

First, after preparing an aqueous slurry of alumina, the filter substrate 1 (total length 150 mm, diameter 130 mm, 200 cells / inch ² , apparent volume 2 liters) is immersed in this slurry in a range of 1/2 of the total length from the exhaust gas inlet side end face. The inlet side coating layer was formed on the surface of the cell partition wall 12 of the inflow side cell 10 by pulling up, drying at 120 ° C., and firing at 500 ° C. The entrance coat layer was formed in an amount of 25 g per liter of the filter substrate 1. Next, in the same slurry as above, a range of ½ (75 mm) of the entire length from the exhaust gas outlet side end face of the filter base material 1 on which the inlet side coating layer is formed is pulled up, dried at 120 ° C., dried at 500 ° C. Baking was performed to form an exit coat layer on the surface of the cell partition wall 12 of the outflow cell 11. The outgoing coating layer was formed in an amount of 25 g per liter of the filter substrate 1.

  Subsequently, a predetermined amount of dinitrodiammine platinum nitric acid aqueous solution with a predetermined concentration is impregnated in the range of 1/2 (75mm) of the entire length from the exhaust gas inlet side end face, dried at 120 ° C and baked at 500 ° C to form an inlet side coating layer. The inlet catalyst layer 2 was formed by supporting Pt. The supported amount of Pt is 1 g per catalyst. Further, impregnated with a predetermined amount of palladium nitrate aqueous solution with a predetermined concentration in the range of 1/2 of the total length from the exhaust gas outlet side end face, dried at 120 ° C and baked at 500 ° C to carry Pd on the outlet side coating layer. A side catalyst layer 3 was formed. The amount of Pd supported is 1 g per catalyst. That is, the total amount of noble metal supported per catalyst is 2 g.

  FIG. 2 is a schematic cross-sectional view of the exhaust gas purifying catalyst according to this embodiment. This exhaust gas purifying catalyst uses the same filter base material 1 as in Example 1, and the inlet side catalyst layer 2 falls within the range of 1/6 (25 mm) of the entire length of the filter base material 1 from the exhaust gas inlet side end face to the downstream side. It is formed in the same manner as in Example 1 except that it is formed.

  The inlet-side coating layer is formed in an amount of 25 g per liter of the filter substrate 1, and the inlet-side catalyst layer 2 carries 1 g of Pt per catalyst. That is, the total amount of noble metal supported per catalyst is 2 g as in Example 1.

  FIG. 3 is a schematic cross-sectional view of the exhaust gas purifying catalyst according to the present embodiment. This exhaust gas purifying catalyst uses the same filter base material 1 as in Example 1, and the inlet side catalyst layer 2 falls within the range of 1/6 (25 mm) of the entire length of the filter base material 1 from the exhaust gas inlet side end face to the downstream side. It is formed in the same manner as in Example 1 except that it is formed and the outlet catalyst layer 3 is formed in the range of 1/6 (25 mm) of the total length of the filter base material 1 from the exhaust gas outlet side end face to the upstream side. Has been.

Each of the inlet side coating layer and the outlet side coating layer is formed in an amount of 25 g per liter of the filter base material 1, 1 g of Pt is supported per catalyst on the inlet side catalyst layer 2, and the catalyst 1 on the outlet side catalyst layer 3. 1 g of Pd is supported per piece. That is, the total amount of noble metal supported per catalyst is 2 g as in Example 1.
(Comparative Example 1)

  FIG. 4 shows a schematic cross-sectional view of the exhaust gas purifying catalyst according to this comparative example. This exhaust gas-purifying catalyst uses the same filter base material 1 as in Example 1. The inlet catalyst layer 2 is formed over the entire length of the filter base material 1 from the exhaust gas inlet side end face, and the outlet catalyst layer 3 is It is formed in the same manner as in Example 1 except that it is formed over the entire length of the filter base 1 from the exhaust gas outlet side end face.

Each of the inlet side coating layer and the outlet side coating layer is formed in an amount of 50 g per liter of the filter base material 1, 1 g of Pt is supported per catalyst on the inlet side catalyst layer 2, and the catalyst 1 on the outlet side catalyst layer 3. 1 g of Pd is supported per piece. That is, the total amount of noble metal supported per catalyst is 2 g as in Example 1.
(Comparative Example 2)

  FIG. 5 shows a schematic cross-sectional view of an exhaust gas purifying catalyst according to this comparative example. This exhaust gas purifying catalyst uses the same filter base material 1 as in Example 1, and the inlet side catalyst layer 2 falls within the range of 1/2 (75 mm) of the entire length of the filter base member 1 from the exhaust gas inlet side end face to the downstream side. It is formed in the same manner as in Example 1 except that the outlet side cell 11 is not formed with the outlet side coating layer and the outlet side catalyst layer.

The inlet side coating layer is formed in an amount of 50 g per liter of the filter substrate 1, and the inlet side catalyst layer 2 carries 2 g of Pt per catalyst. That is, the total amount of noble metal supported per catalyst is 2 g as in Example 1.
(Comparative Example 3)

  FIG. 6 shows a schematic cross-sectional view of an exhaust gas purifying catalyst according to this comparative example. This exhaust gas purifying catalyst uses the same filter base material 1 as in Example 1, and is the same as Example 1 except that the same catalyst layer 4 is formed over the entire length of the inflow side cell 10 and the outflow side cell 11. Is formed.

The catalyst layer 4 is formed in an amount of 50 g per liter of the filter substrate 1, and 1 g of Pt per catalyst and 1 g of Pd per catalyst are supported. That is, the total amount of noble metal supported per catalyst is 2 g as in Example 1.
(Test example)

  Table 1 summarizes the structures of the exhaust gas purifying catalysts of each Example and each Comparative Example.

  The exhaust gas purification catalyst of each Example and each Comparative Example was subjected to a durability test in which steady operation and forced regeneration were repeated, and the subsequent purification performance and pressure loss were evaluated.

In the test method, a catalytic converter in which each exhaust gas purification catalyst is arranged downstream of the exhaust gas of a straight flow structure oxidation catalyst is attached to the exhaust pipe of a diesel engine, and 10 g of PM is deposited on each exhaust gas purification catalyst in steady operation. It was. Next, the operation was performed for 5 minutes under the condition that the temperature of the gas entering the oxidation catalyst was 300 ° C., and the operation was performed for 5 minutes while adding light oil at an addition amount of 2 g / min upstream of the oxidation catalyst. After 100 cycles of this cycle, the HC and CO purification rates during 11-mode driving were measured. Air was supplied at a flow rate of 5 m ³ / min at room temperature, and the pressure loss was measured. These results are shown in Table 2.

As an oxidation catalyst, a cordierite honeycomb substrate with a straight flow structure (diameter 130 mm, 400 cells / inch ² , apparent volume 1 liter) was coated with 150 g of alumina coat layer per liter of honeycomb substrate, and the alumina coat layer A honeycomb substrate carrying 2 g of Pt per liter was used.

  Each of the exhaust gas purifying catalysts of each example shows a higher purification rate than Comparative Example 1. The reason why the catalyst of Comparative Example 1 is inferior in purification performance after the endurance test is that the ingress side catalyst layer is formed over the entire length, so that ash is deposited downstream of the inflow side cell during the endurance test of 100 cycles. This is because the contact between the noble metal supported in the vicinity and the exhaust gas is hindered.

  Each of the exhaust gas purifying catalysts of each Example shows a higher purification rate than that of Comparative Example 2. The reason why the catalyst of Comparative Example 2 is inferior in purification performance after the endurance test is that no exit side catalyst layer is formed and no noble metal is supported on the outflow side cell.

  Further, when Comparative Example 1 and Comparative Example 3 are compared, Comparative Example 1 has a higher purification rate. The catalyst of Comparative Example 1 carries Pd on the outlet catalyst layer, whereas the catalyst of Comparative Example 3 carries Pd separately on the inlet catalyst layer and the outlet catalyst layer. Although it is known that Pd is poisoned by the sulfur component in the exhaust gas, since the sulfur component is partially captured by the inflow side cell as calcium sulfate, a comparative example in which the entire amount of Pd is supported on the output side catalyst layer No. 1 is considered to have a higher purification rate with less poisoned Pd.

  From Table 2, it can be seen that the catalyst of each example has both a high purification rate and a low pressure loss, and it is clear that this is an effect of the configuration described in the claims.

  The exhaust gas purifying catalyst of the present invention can be used not only for purifying exhaust gas from a diesel engine but also for purifying exhaust gas from a boiler or the like.

1: Filter base material 2: Incoming catalyst layer 3: Outlet catalyst layer
10: Inflow side cell
11: Outflow cell
12: Cell bulkhead
100, 110: Clogging part

Claims (4)

An inflow side cell packed on the exhaust gas downstream side, an outflow side cell adjacent to the inflow side cell and plugged on the exhaust gas upstream side, and a porous cell partition wall that partitions the inflow side cell and the outflow side cell A filter substrate having a wall flow structure having
An inlet side catalyst layer formed on the surface of the cell partition wall of the inflow side cell from the exhaust gas inlet side end face to the downstream side and having a length less than the total length of the filter base material and supporting a noble metal on a porous oxide carrier;
An exit side catalyst layer formed on the surface of the cell partition wall of the outflow side cell from the exhaust gas exit end face to the upstream side in a range of a length less than the total length of the filter base material and supporting a noble metal on a porous oxide carrier; An exhaust gas purifying catalyst comprising:   2. The exhaust gas purifying catalyst according to claim 1, wherein the inlet catalyst layer is formed in a range of 1/6 to 1/2 of the total length of the filter base material from the exhaust gas inlet side end surface to the downstream side.   The exhaust gas purification catalyst according to claim 1 or 2, wherein the outlet catalyst layer is formed in a range of 1/6 to 1/2 of the total length of the filter base material from the exhaust gas outlet end face to the upstream side.   The exhaust gas purifying catalyst according to any one of claims 1 to 3, wherein at least Pt is supported on the inlet catalyst layer, and at least Pd is supported on the outlet catalyst layer.

Images