JP2006077672A - Exhaust emission control filter and exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently capture PM while suppressing increase of pressure loss and quickly burn and purify captured PM even at an outer circumference part. <P>SOLUTION: A filter concentration part which consists of a first layer 23 through which at least part of PM passes including an oxidation catalyst 3 toward a flow out side cell 21 from a flow in side cell 20, a third layer 25 suppressing pass of PM, and a second layer 24 formed between the first layer 23 and the third layer 25 and capturing PM which is prevented from passing through the third layer 25. Since exhaust gas of which temperature is raised by reaction heat by the oxidation catalyst 3 directly flows in the second layer 24, PM captured by the second layer is efficiently oxidized by the oxidation catalyst 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exhaust gas purification filter for purifying exhaust gas for purifying exhaust gas containing particulates such as exhaust gas from a diesel engine, and an exhaust gas purification apparatus using the exhaust gas purification filter.

  As for gasoline engines, harmful components in exhaust gas have been steadily reduced due to strict regulations on exhaust gas and advances in technology that can cope with it. However, for diesel engines, harmful components are discharged as particulates (particulate matter: carbon fine particles, sulfur fine particles such as sulfate, high molecular weight hydrocarbon fine particles (SOF), etc., hereinafter referred to as PM)) Regulations and technological advancements are slow compared to gasoline engines.

  As exhaust gas purification devices for diesel engines that have been developed so far, a trap type exhaust gas purification device (wall flow) and an open type exhaust gas purification device (straight flow) are known. Among these, as a trap type exhaust gas purification device, a ceramic plug-type honeycomb body (diesel PM filter (hereinafter referred to as DPF)) is known. The DPF is formed by alternately sealing both ends of the opening of the cell of the ceramic honeycomb structure, for example, in a checkered pattern, adjacent to the inflow side cell clogged on the exhaust gas downstream side and the inflow side cell. Outflow side cell clogged upstream of exhaust gas and filter partition wall that separates inflow side cell and outflow side cell, and controls exhaust by filtering exhaust gas through pores of filter partition wall and collecting PM To do.

  However, in the DPF, pressure loss (hereinafter referred to as pressure loss) increases due to the accumulation of PM. Therefore, it is necessary to periodically remove and regenerate PM accumulated by some means. Therefore, conventionally, when pressure loss increases, the DPF is regenerated by flowing high-temperature exhaust gas and burning PM. However, in this case, as the amount of accumulated PM increases, the temperature during combustion rises, and the DPF may be melted or damaged due to thermal stress.

  Therefore, in recent years, an exhaust gas purification device in which an oxidation catalyst body is arranged upstream of the DPF, or a coat layer made of alumina or the like is formed on the surface of the filter partition wall of the DPF, and a catalytic metal such as platinum (Pt) is supported on the coat layer. Thus, a continuous regeneration type DPF having a catalyst layer has been developed. According to this continuous regeneration type DPF, the collected PM is oxidized and combusted by the catalytic reaction of the catalytic metal. Therefore, the DPF can be regenerated by combusting simultaneously with the collection or continuously in the collection. Since the catalytic reaction occurs at a relatively low temperature and can be combusted while the collected amount is small, there is an advantage that the DPF can be prevented from being melted and the thermal stress acting is small, so that the damage is also prevented.

For example, Japanese Patent Laid-Open No. 01-318715 discloses an exhaust gas purification device in which an oxidation catalyst body is arranged upstream of the DPF, and Japanese Patent Application Laid-Open No. 2001-303932 discloses an oxidation catalyst body arranged upstream of the DPF with catalyst. An exhaust gas purifying apparatus is disclosed. According to these purification apparatuses, PM collected in the DPF by NO ₂ generated by the oxidation catalyst body can be oxidized and removed.

  However, since PM has a particle size distribution, if the average pore size of the filter partition is large, an increase in pressure loss due to deposition can be suppressed, but more PM passes through without being collected. Conversely, when the average pore diameter is small, the PM collection efficiency is improved, but an increase in pressure loss becomes a problem.

  Therefore, in JP-A-10-159552, JP-A-2002-097929, JP-A-2002-320807, etc., the pores of the filter partition wall are made coarse to dense in the thickness direction from the inflow side cell to the outflow side cell. A DPF distributed in such a manner is disclosed. Japanese Patent Laid-Open No. 2001-317326 discloses a DPF in which the porosity is gradually reduced from the exhaust gas inlet side to the outlet side. By comprising in this way, the raise of pressure loss and PM collection efficiency can be balanced, and both can be satisfied together.

  However, although the temperature of the center portion of the DPF rises quickly, the outer peripheral portion has a small exhaust gas flow velocity and is closest to the outside air, so that the temperature hardly rises and is easy to cool. For this reason, even in an exhaust gas purification apparatus in which an oxidation catalyst is disposed upstream of the DPF or the DPF with catalyst, there is a problem of an increase in pressure loss due to PM remaining unburned and deposited on the outer peripheral portion. In addition, when the exhaust gas temperature becomes high, generation of thermal stress due to burning of accumulated PM at a time becomes a problem.

Even in an exhaust gas purification device in which an oxidation catalyst body is arranged on the exhaust gas upstream side of the DPF, the exhaust gas temperature decreases before reaching the DPF from the oxidation catalyst body, so the reaction heat in the oxidation catalyst body is used sufficiently effectively. There was also a problem that it was not done.
JP-A-10-159552 JP2001-317326 JP2002-097929 JP2002-320807

  The present invention has been made in view of the above circumstances, and efficiently collects PM, suppresses an increase in pressure loss, and further, exhaust gas purification that can quickly burn and purify the collected PM at the outer periphery. Making it a filter is a problem to be solved.

A feature of the exhaust gas purification filter of the present invention that solves the above problems is an exhaust gas purification filter that purifies exhaust gas containing particulates discharged from an internal combustion engine,
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 a filter partition wall that partitions the inflow side cell and the outflow side cell. At least a part of the first layer including an oxidation catalyst in the thickness direction from the inflow side cell toward the outflow side cell, and a third layer that suppresses the passage of the particulates. And a second layer in which particulates formed between the first layer and the third layer and whose passage is suppressed by the third layer are collected, and a filtration concentration portion.

  The average pore diameter of the second layer is preferably larger than the average pore diameter of the first layer and the average pore diameter of the third layer. Moreover, it is desirable that the filtration concentration part is formed at least on the outer peripheral part.

  A feature of the exhaust gas purifying apparatus of the present invention is that an oxidation catalyst body is disposed on the exhaust gas upstream side of the exhaust gas purifying filter of the present invention.

  According to the exhaust gas purification filter and the exhaust gas purification filter device of the present invention, since PM is suppressed in the third layer and collected in the second layer, a high PM collection rate is expressed. Since the first layer containing the oxidation catalyst is formed adjacent to the second layer where PM is collected, the exhaust gas that has passed through the first layer passes through the second layer and the third layer. The PM collected in the second layer is oxidized and burned efficiently. Accordingly, a high PM purification rate is exhibited, and PM non-burning is suppressed even in the outer peripheral portion, so that an increase in pressure loss due to PM deposition is suppressed, and damage due to thermal stress is also suppressed.

  Furthermore, if the PM purification rate is the same as that of the prior art, the amount of catalyst metal supported on the oxidation catalyst or the oxidation catalyst body can be reduced, and the cost can be reduced.

In the exhaust gas purification filter of the present invention, the exhaust gas that has entered the inflow side cell first passes through the first layer in the filtration concentration portion. This first layer has a pore distribution such that at least a part of the PM passes, and most or all of the PM in the exhaust gas passes through the first layer and reaches the third layer from the second layer. . Further, HC, CO and NO in the exhaust gas are continuously oxidized by the oxidation catalyst contained in the first layer, and HC and CO are purified and NO is oxidized to NO ₂ .

  Here, even if the exhaust gas temperature is low, the oxidation reaction proceeds if the temperature is equal to or higher than the activation temperature of the oxidation catalyst, and the exhaust gas whose temperature is increased by the reaction heat continuously reaches the second layer and the third layer. To do.

  Since the third layer has a pore distribution at least enough to suppress the passage of PM, only the gas in the exhaust gas passes through the third layer and is discharged to the outside from the outflow side cell. The two layers will be collected at a high collection rate.

Therefore, although there is concern about PM accumulation on the second layer, as described above, the temperature of the exhaust gas passing through the second layer is higher than the temperature of the exhaust gas flowing into the inflow side cell due to the oxidation reaction of HC or the like. In addition, since the second layer exists between the first layer and the third layer, the heat retaining property is high. Further, since the exhaust gas passing through the second layer contains NO ₂ having high oxidation activity, PM is oxidized and purified by combustion and reaction promotion by heat and oxidation by NO ₂ . In addition, since the second layer is adjacent to the first layer containing the oxidation catalyst, the probability that the oxidation reaction PM by the oxidation catalyst comes into contact with the oxidation catalyst is increased, and the oxidation reaction by the oxidation catalyst is added. Oxidation of the collected PM is promoted, and an increase in pressure loss due to PM deposition is suppressed.

  Further, the temperature of the exhaust gas flowing into the outer peripheral portion is lower than the temperature of the exhaust gas flowing into the central portion as in the conventional case, but the first layer is formed by forming the filtration concentration portion at least on the outer peripheral portion. The exhaust gas temperature passing through the second layer can be increased even at the outer peripheral portion by the oxidation reaction. Accordingly, unburned PM is suppressed in the outer peripheral portion, and an increase in pressure loss is also suppressed.

  And by suppressing the accumulation of PM, a large amount of PM deposited when high-temperature exhaust gas flows in does not burn at a stretch, so that damage due to thermal stress can also be prevented.

Further, if the oxidation catalyst body is arranged on the exhaust gas upstream side of the exhaust gas purification filter of the present invention, since the high-temperature exhaust gas immediately after the internal combustion engine flows into the oxidation catalyst body, HC in the exhaust gas from a relatively early stage after the start, CO and NO can be oxidized, and the temperature further rises due to the heat of reaction, and exhaust gas containing NO ₂ flows into the filtration concentration part. And since the above-described reaction proceeds from a relatively early stage after start-up by the exhaust gas purification filter of the present invention on the downstream side, PM deposition at a low temperature can be further suppressed, and an increase in pressure loss and damage due to thermal stress can be prevented. Further suppression can be achieved.

  The exhaust gas purification filter of the present invention partitions 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 cell and the outflow side cell. And a filter partition. This filter can be formed from heat-resistant ceramics such as cordierite, silicon carbide, silicon nitride, or metal foil as in the case of the conventional DPF.

  At least a part of the cell partition wall is formed with a filtration concentration portion in which the first layer, the second layer, and the third layer are formed in this order from the inflow side cell to the outflow side cell in the thickness direction. Yes. This filtration concentration part may be formed on the entire filter, or at least on the outer peripheral part where PM unburnt residue is likely to occur. When the filtration concentration part is partially formed on the filter, the part where the filtration concentration part is not formed has a porosity of 40 to 80% and an average pore diameter of 10 to 40 μm, as in the conventional DPF. A range is preferable, and it is particularly desirable that the porosity is 60 to 75% and the average pore diameter is 22 to 35 μm.

  The first layer has a hole distribution such that at least a part of PM passes. General PM contained in exhaust gas from a diesel engine or the like has a particle size distribution with an average particle size of about several tens of nm to several hundreds of nm, but the average pore size of the first layer is more than 50 μm, more preferably Most of PM can be passed by setting it as 100 micrometers or more. When the average pore diameter of the first layer is less than 50 μm, PM that is filtered by the first layer exists, whereby PM is deposited on the surface of the first layer or inside the first layer. In this case, the exhaust gas passing through the first layer is reduced, and the action of the first layer described above is also impaired, so that the pressure loss increases. In addition, even if the average pore size of the first layer is too large or the average pore size is appropriate, if the amount of pores is large, the filter strength may be impaired, so the first layer has a porosity of 80% or less. Is desirable.

The first layer contains an oxidation catalyst. This oxidation catalyst is formed by supporting a catalytic metal on a porous oxide. As the porous oxide, oxides such as Al ₂ O ₃ , ZrO ₂ , CeO ₂ , TiO ₂ , SiO ₂ or the like can be used. A complex oxide composed of a plurality of types or a plurality of types of complex oxides selected from these can be used. This oxidation catalyst may be contained in the first layer, or may be formed as a coating layer on the surface of the first layer, but it is formed in layers on the surface of the pores existing in the first layer. Is desirable.

  This oxidation catalyst is preferably contained in an amount of 50 to 200 g per liter of filter volume. If the content is less than 50 g / L, a decrease in the durability of the catalyst activity is inevitable, and if it exceeds 200 g / L, the pressure loss becomes too high and is not practical.

  In order to include the oxidation catalyst, the oxide powder or the composite oxide powder is made into a slurry together with a binder component such as alumina sol and water, and the slurry is attached to the first layer and then fired. An ordinary dipping method can be used to attach the slurry to the first layer, but it is desirable to remove excess slurry that has entered the pores by air blowing or suction.

The catalyst metal supported on the porous oxide can be used as long as it promotes the oxidation of PM by a catalytic reaction, but is selected from at least platinum group noble metals such as Pt, Rh, Pd, and Ir. It is preferable to carry one kind or plural kinds. In some cases, a transition metal can be used, and it is also preferable to support a NO _x storage material. The amount of noble metal supported is preferably in the range of 1 to 5 g per liter of filter volume. If the loading amount is less than this, the activity is too low to be practical, and if the loading amount exceeds this range, the activity is saturated and the cost is increased.

  Further, in order to support the noble metal, a solution in which nitrate of noble metal is dissolved may be used and supported on the coat layer made of oxide powder or composite oxide powder by an adsorption support method, an impregnation support method or the like. Alternatively, a noble metal may be supported beforehand on the oxide powder or composite oxide powder, and the catalyst powder may be included in the first layer.

  In addition, the preferable average void | hole diameter of an above-mentioned 1st layer says the average void | hole diameter after including an oxidation catalyst.

  The third layer has a pore distribution such that most or all of the PM is filtered and only gas can pass through. As described above, the average particle size of PM is about several tens of nm to several hundreds of nm. If the average pore size of the third layer is 50 μm or less, more preferably 30 μm or less, most or all of PM does not pass. Can be. However, if the average pore diameter and the porosity are too small, the pressure loss increases. Therefore, the third layer preferably has a porosity of 40 to 80% and an average pore diameter of 10 μm or more.

  The second layer is a layer in which PM filtered by the third layer is collected, and may be a gap. However, in order to ensure the strength of the filtration concentration part, it is layered in the same manner as the first layer and the third layer. It is preferable to form. In this case, the average pore diameter of the second layer is preferably larger than the average pore diameter of the first layer and the average pore diameter of the third layer. When the average pore diameter of the second layer is smaller than the average pore diameter of the first layer, PM is collected in the first layer, and the PM oxidation efficiency is lowered. On the other hand, if it is smaller than the average pore diameter of the third layer, the pressure loss increases, which is not preferable.

  In order to manufacture a filter having such a filtration concentration part, at the time of extrusion molding of a honeycomb body having a straight flow structure, it is possible to manufacture by simultaneously extruding a plurality of kinds of materials for forming each layer and firing it. it can. Further, as shown in the embodiment, it is also possible to manufacture by first forming a honeycomb body having cell partition walls made of only the third layer, and inserting square tubes made of the second layer and the first layer into the inflow side cells. .

  The exhaust gas purifying apparatus of the present invention includes the exhaust gas purifying filter of the present invention and an oxidation catalyst body disposed on the upstream side of the exhaust gas. The oxidation catalyst body may be the same as the oxidation catalyst disposed directly under the conventional engine. For example, a coating layer is formed from a porous oxide carrier selected from alumina, ceria, zirconia, titania, etc. on a honeycomb substrate of straight flow structure formed from cordierite or metal foil, and Pt, Rh, Pd It carries a noble metal or transition metal. It is particularly preferable that at least Pt is supported on a coating layer containing at least alumina.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

Example 1
FIG. 1 shows an exhaust gas purification apparatus of this embodiment, and FIGS. 2 and 3 show an exhaust gas purification filter of this embodiment used in the exhaust gas purification apparatus. This exhaust gas purification device is composed of an oxidation catalyst body 1 disposed in the vicinity of an exhaust manifold of the diesel engine 100, and an exhaust gas purification filter 2 disposed on the under floor at the downstream side of the exhaust gas.

The oxidation catalyst body 1 is composed of a honeycomb substrate (400 cells / in ² , 130 mm in diameter, 1 liter) made of cordierite and an oxidation catalyst layer formed on the cell surface. The oxidation catalyst layer is made of alumina powder supporting Pt, and is formed in an amount of 150 g per liter of honeycomb substrate. 2 g of Pt is supported per liter of honeycomb substrate.

The exhaust gas purification filter 2 has a honeycomb flow wall structure (200 cells / in ² , φ 130 mm, 1 liter) made of cordierite, and an inflow side cell 20 clogged downstream of the exhaust gas, and an inflow side cell 20 And an outflow side cell 21 that is clogged upstream of the exhaust gas, and a filter partition wall 22 that partitions the inflow side cell 10 and the outflow side cell 11. The inflow side cell 20 and the outflow side cell 21 are opened in a checkered pattern on the inflow side end surface and the outflow side end surface, respectively.

  The filter partition wall 22 is formed by laminating a first layer 23, a second layer 24, and a third layer 25 in this order from the inflow side cell 20 toward the outflow side cell 21 in the thickness direction.

  The first layer 23 is formed with a porosity of 50%, an average pore diameter of 150 μm, and a thickness of 100 μm, and the oxidation catalyst 3 is formed in layers on the inner surface of the pores as shown in FIG. The oxidation catalyst 3 is made of alumina powder carrying Pt, and is formed in an amount of 150 g per liter of the exhaust gas purification filter 2. The amount of Pt supported is 2 g per liter volume of the exhaust gas purification filter 2.

  The second layer 24 is composed of a gap formed between the first layer 23 and the third layer 25 and has a thickness of 100 μm. The third layer 25 is formed with a porosity of 50%, an average pore diameter of 30 μm, and a thickness of 100 μm.

  Hereinafter, a method for manufacturing the exhaust gas purification filter 2 will be described, and a detailed description of the configuration will be given.

As shown in FIG. 4, a cordierite-made straight honeycomb substrate 200 having a square cell of 200 cells / in ² , 130 mm in diameter and 1 liter in volume was prepared. The cell partition wall 201 has a thickness of 100 μm, and the pore distribution is the same as that of the third layer 25.

  Next, a rectangular tube 202 having an outer diameter that is slightly smaller than the cell diameter of the substrate 200 and the same length as the cell was prepared. This square tube 202 is made of cordierite, and the thickness of each wall on each side is 100 μm, and the pore distribution is the same as that of the first layer 23. The square tube 202 was inserted into the cell of the base material 200 so as to have a checkered shape when viewed from the end face.

  Next, a predetermined amount of an organic binder and water are mixed with a cordierite composition powder composed of alumina, talc, kaolin, and silica to prepare a cream-like paste having stable shape retention. Using this paste, the upstream end surface of the base material 200 is alternately packed one by one using a paste injection machine (dispenser), and the downstream end surface is packed with cells where the upstream end surface is not clogged. did. Thereafter, firing was performed at 1400 ° C. to form an inflow side cell 20 and an outflow side cell 21. At this time, the space between the rectangular tube 202 and the cell partition wall 201 is simultaneously clogged, the rectangular tube 202 is the first layer 23, the cell partition wall 201 is the third layer 25, and the second layer is between the square tube 202 and the cell partition wall 201. 24 was formed.

  After allowing to cool to room temperature, a slurry containing mainly catalyst powder with Pt supported on alumina powder is poured into the inflow side cell 20, the excess slurry is discharged, dried at 110 ° C, and calcined at 450 ° C. Thus, the oxidation catalyst 3 was formed on the first layer 23.

  FIG. 5 shows an enlarged view of a part surrounded by a dotted circle in FIG. In the exhaust gas purification filter 2, the exhaust gas flowing into the inflow side cell 20 first passes through the first layer 23. Since the first layer 23 has a porosity of 50% and an average pore diameter of 150 μm, almost all PM passes through the first layer 23. Further, when the exhaust gas comes into contact with the oxidation catalyst 3, HC, CO, and NO are oxidized by Pt, and the exhaust gas is further heated by reaction heat.

  The exhaust gas that has passed through the first layer 23 passes through the second layer 24 as it is, but since the third layer 25 has a porosity of 50% and an average pore diameter of 30 μm, almost all of the PM passes through the third layer 25. It becomes difficult to pass through, and only the gas passes through the third layer 25 and is discharged. PM filtered by the third layer 25 is collected inside the second layer 24.

The PM collected in the second layer 24 is oxidized and purified by the oxidation catalyst 3 in the first layer 23. In the second layer 24, exhaust gas having passed through the first layer 23 and having a temperature increased by reaction heat is circulated. Moreover, since it is the closed space enclosed by the 1st layer 23, the 3rd layer 25, and the clogging, the 2nd layer 24 is excellent in heat retention. Further, there are many oxidizing agents such as NO ₂ produced by the reaction in the first layer 23. Therefore, the oxidation of PM is further promoted, and the PM collected in the second layer 24 is quickly burned and removed. As a result, an increase in pressure loss is suppressed, and there is no damage to the filter due to the accumulated PM burning at once.

(Examples 2-3)
As shown in FIG. 6 which is an enlarged view of the opening of the inflow side cell 20, the second layer 24 of the exhaust gas purification filter 2 is made of cordierite having the porosity and average pore diameter shown in Table 1 in place of the air gap. Example 1 is the same as Example 1 except that it is formed from a square tube.

(Examples 4 to 6)
Except that the material of the exhaust gas purification filter 2 is SiC instead of cordierite, it is the same as in Examples 1-3.

(Examples 7 to 9)
Example 1 except that a stainless steel corrugated plate and a honeycomb substrate formed by winding a flat plate are used and a cylindrical body made of stainless steel foil having the same shape as the cell cross section is inserted into the inflow side cell. The exhaust gas purification filter 2 similar to -3 is used. A stainless corrugated plate and a flat plate are formed with through holes each having a porosity of 50% and an average pore diameter of 30 μm. Further, in the cylindrical body, through holes having a porosity of 50% and an average pore diameter of 150 μm are formed in Example 7, and in Examples 8 to 9, the through holes are formed between the cylindrical body of Example 7 and the cell partition walls. A cylinder having a through hole having a porosity and an average pore diameter shown in Table 1 is further inserted.

(Examples 10 to 12)
The same as in Examples 1, 4, and 7 except that the oxidation catalyst body 1 was not used.

(Comparative Example 1)
Using the same oxidation catalyst body 1 as in Example 1, a honeycomb substrate having a cell partition wall with a porosity of 50%, an average pore diameter of 30 μm, and a thickness of 300 μm was used to form the first layer 23 and the second layer 24. Exhaust gas purification filter 2 similar to Example 1 was used except that it was not present.

(Comparative Example 2)
The material of the exhaust gas purification filter 2 is the same as that of Comparative Example 1 except that SiC is used instead of cordierite.

(Comparative Example 3)
Comparative Example 1 except that the oxidation catalyst body 1 similar to that of Example 1 was used and the exhaust gas purification filter 2 was formed using a honeycomb substrate formed by winding and winding a stainless corrugated plate and a flat plate. It is the same. The corrugated plate and the flat plate are each formed with a through hole having a porosity of 50% and an average pore diameter of 30 μm.

(Comparative Example 4)
The same as Comparative Example 1 except that the oxidation catalyst body 1 was not used.

<Test and evaluation>
The diesel engine 100 was operated in a steady operation, and 10 g of PM was deposited on each of the exhaust gas purifying apparatuses of the examples and comparative examples. Next, the operation is performed for 5 minutes under the condition that the exhaust gas temperature flowing into the oxidation catalyst body 1 is 300 ° C., and then the oxidation catalyst body 1 is added while adding light oil to the upstream side of the oxidation catalyst body 1 at an addition amount of 2 g / min. The operation was performed for 5 minutes under the condition that the temperature of the exhaust gas flowing into the tank reached 600 ° C.

  After the operation was completed, the weight of the exhaust gas purification filter 2 was measured, and the PM removal rate was calculated from the difference from the weight before the test. The results are shown in Table 1.

表１より、実施例１〜９の排ガス浄化装置は対応する比較例１〜３の排ガス浄化装置に比べてＰＭ除去率が高いことが明らかである。また実施例10〜12では、比較例４に比べて格段に高いＰＭ除去率を示し、酸化触媒体１を用いず排ガス浄化フィルタ２のみでも効果が奏されていることが明らかである。

From Table 1, it is clear that the exhaust gas purification apparatuses of Examples 1 to 9 have a higher PM removal rate than the corresponding exhaust gas purification apparatuses of Comparative Examples 1 to 3. In Examples 10 to 12, the PM removal rate is remarkably higher than that in Comparative Example 4, and it is clear that the effect is achieved only by the exhaust gas purification filter 2 without using the oxidation catalyst body 1.

It is explanatory drawing which shows the state which has arrange | positioned the exhaust gas purification apparatus of one Example of this invention in the exhaust system of the diesel engine. It is a front view of the exhaust gas purification filter of one Example of this invention. It is a principal part expanded sectional view of the exhaust gas purification filter of one Example of this invention. It is explanatory drawing which shows the manufacturing method of the exhaust gas purification filter of one Example of this invention. It is a principal part expanded sectional view which shows the effect | action of the exhaust gas purification filter of one Example of this invention. It is a principal part enlarged view of the inflow side end surface of the exhaust gas purification filter of the other Example of this invention.

Explanation of symbols

1: Oxidation catalyst body 2: Exhaust gas purification filter 3: Oxidation catalyst
20: Inflow side cell 21: Outflow side cell 22: Cell bulkhead
23: First layer 24: Second layer 25: Third layer

Claims (6)

An exhaust gas purification filter for purifying exhaust gas containing particulates discharged from an internal combustion engine,
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 a filter partition wall that partitions the inflow side cell and the outflow side cell. Become
At least a part of the filter partition wall includes, in the thickness direction from the inflow side cell toward the outflow side cell, a first layer that includes an oxidation catalyst and at least a part of the particulates pass, and the passage of the particulates. A third layer to be suppressed, a second layer formed between the first layer and the third layer, in which particulates whose passage is suppressed by the third layer are collected, and a filtration concentration portion. An exhaust gas purification filter characterized by that.   2. The exhaust gas purification filter according to claim 1, wherein an average pore diameter of the second layer is larger than an average pore diameter of the first layer and an average pore diameter of the third layer.   The exhaust gas purification filter according to claim 1 or 2, wherein the average pore diameter of the first layer is 50 µm or more.   The exhaust gas purification filter according to any one of claims 1 to 3, wherein the average pore diameter of the third layer is 50 µm or less.   The exhaust gas purification filter according to claim 1, wherein the filtration concentration part is formed at least on an outer peripheral part.   An exhaust gas purification apparatus comprising an oxidation catalyst body disposed upstream of the exhaust gas of the exhaust gas purification filter according to any one of claims 1 to 5.

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