JP2009000663A - Exhaust gas purifying filter and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas purifying filter having a sufficient mechanical strength and more efficiently burning PM than before. <P>SOLUTION: The exhaust gas purifying filter 10 used for purifying PM in the exhaust gas discharged from an internal combustion engine has a carrier 13 and the catalyst layer 12 supported by the carrier 13, and the catalyst layer 12 has a large number of spherical pores 11a and a large number of columnar pores 11b for mutually connecting a large number of the spherical pores 11a. This exhaust gas purifying filter has a sufficient mechanical strength and more efficiently burns PM than before. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to an exhaust gas purification filter used for purification of particulate matter in exhaust gas discharged from an internal combustion engine and a method for manufacturing the same, and in particular, it is suitably used for purification of particulate matter in exhaust gas discharged from a diesel engine. The present invention relates to an exhaust gas purification filter and a method for manufacturing the same.

  Conventionally, in order to purify particulate matter (PM) contained in exhaust gas discharged from an internal combustion engine, in particular, a diesel engine, a diesel particulate filter (DPF) or a catalyzed soot is used. A filter (CSF: catalytic soot filter) is used.

  The combustion temperature of PM is as high as 550 ° C. to 650 ° C., and high temperature is required for PM combustion. For this reason, the current state is that the combustion of PM in the DPF is forcibly performed by using an additional technique such as a regeneration technique or an additive. On the other hand, even when a catalyst is used as in CSF, a low temperature cannot be expected. This is because the reaction between PM and the catalyst is a solid-solid reaction, and thus PM having poor contact with the catalyst is difficult to burn.

  For example, the total opening area of the open pores existing on the cell partition wall surface is 30% or more with respect to the total surface area of the cell partition wall, and the total opening area of large open pores having an opening hole diameter of 30 μm or more is open. A diesel exhaust gas purification filter characterized by being 50% or more of the total opening area of the pore has been proposed (see Patent Document 1). According to this diesel exhaust gas purification filter, PM can be collected not only on the surface of the cell partition wall but also inside the pores. For this reason, it is said that the inner surface of the pore can also be used as a reaction field of the catalyst, and PM combustion efficiency can be increased.

  In addition, in the distribution of surface vacancies opening on the surface of the cell partition walls of the pores, the total open area of the surface vacancies having a maximum diameter of 10 μm to 50 μm determined by the direct observation method is 8% of the total open area of all the surface vacancies. In the distribution of internal pores obtained by cross-sectional observation by CT scan, the total cross-sectional area of pores having a cross-sectional area corresponding to a circle having a diameter of 300 μm or more is 20% of the total cross-sectional area of all pores. An exhaust gas purifying filter catalyst base material that occupies the above has been proposed (see Patent Document 2). According to this exhaust gas purifying filter catalyst base material, even when PM is concentrated in a short time and discharged in a large amount, the PM is dispersed and collected in each pore, so that the collection efficiency is high. In addition, it is said that an increase in pressure loss can be suppressed because PM accumulation is suppressed.

  In addition, ceramic oxide particles having pores are provided on the surface of the silicon carbide particles constituting the porous silicon carbide sintered body, and further in the pores of the ceramic oxide particles, the particles in the collected exhaust gas A wall flow type exhaust gas purification filter containing an oxidation catalyst for oxidizing and burning a substance, wherein an average particle diameter of ceramic oxide particles is 0.002 times to an average particle diameter of silicon carbide particles An exhaust gas purifying filter characterized by being 0.2 times has been proposed (see Patent Document 3). According to this exhaust gas purification filter, it is said that even under practical conditions, the catalyst does not fall off, and high catalytic activity can be maintained for a long time. Further, it is said that an exhaust gas purifying filter with high PM collection efficiency and low pressure loss can be provided.

  An exhaust gas purification catalyst comprising at least a carrier and a catalyst layer formed on the carrier, wherein the catalyst layer has voids, and the catalyst layer and / or the carrier are fine particles in the exhaust gas. There has been proposed an exhaust gas purification catalyst characterized in that it can be supplemented with particulate matter (see Patent Document 4). According to this exhaust gas purification catalyst, it is possible to improve the gas diffusibility of the exhaust gas, particularly the gas SOF in the exhaust gas, and the diffusivity of hydrocarbons having a large molecular size. And can be processed.

  Further, in a filter catalyst having a catalyst carrier substrate made of a heat-resistant porous body having continuous pores and a catalyst layer for burning PM formed on the surface of the catalyst carrier substrate, the filter catalyst has a thickness of 1 μm to 20 μm. A filter catalyst characterized by having pores with a porosity of 11% or more has been proposed (see Patent Document 5). According to this filter catalyst, an increase in pressure loss can be suppressed even when a large amount of PM is accumulated.

As described above, in any of Patent Documents 1 to 5, it is possible to improve the contact between PM and the catalyst and promote the combustion of PM by optimally controlling the pores in the DPF wall on which the catalyst is supported. It is supposed to be possible. Here, “contactability” means the contact ratio between PM and catalyst with respect to the amount of deposited PM. The case where the contact property is high is a case where most of the deposited PM has a contact point with the catalyst, and the case where the contact property is low is a case where most of the deposited PM does not have a contact point with the catalyst. In addition, by providing pores with an appropriate diameter, it is said that even when PM is deposited, the pores are blocked by PM and the increase in pressure loss can be suppressed.
JP 2002-349234 A JP 2004-261644 A JP 2004-330118 A JP 2005-21818 A JP 2005-224667 A

  However, in Patent Documents 1 to 5, since the pores 41 are randomly formed in the DPF wall (carrier wall) 43 and the catalyst layer 42 as shown in the schematic diagram 4, the adjacent pores 41 are connected to each other. There are independent pores 41 that are not connected. In such independent pores 41, exhaust gas cannot pass through, so the frequency of use for PM combustion is small.

  Moreover, in the pore which can burn PM only at a slight speed, when PM significantly exceeding the combustion capacity flows, PM accumulates and the flow path is blocked. If the flow path is blocked, the exhaust gas cannot flow in, so the number of pores used for PM combustion decreases, and as a result, the PM combustion efficiency decreases.

  Furthermore, in order to improve the combustion efficiency of PM, when many pores are provided to connect all the pores, the mechanical strength of the DPF wall and the catalyst layer is lowered. Eventually, problems such as breakage of the DPF and peeling of the catalyst are caused.

  This invention is made | formed in view of the above subjects, The objective is to provide the exhaust gas purification filter which can combust PM more efficiently compared with the past.

  The inventors of the present invention have made extensive studies to solve the above problems. As a result, it has been found that by connecting spherical pores with columnar pores to form a network, an exhaust gas purification filter capable of efficiently burning PM can be provided without lowering the mechanical strength of the DPF or catalyst layer. The present invention has been completed. More specifically, the present invention provides the following.

  (1) An exhaust gas purification filter used for purification of particulate matter in exhaust gas discharged from an internal combustion engine, comprising a carrier and a catalyst layer carried on the carrier, wherein the catalyst layer comprises a plurality of An exhaust gas purification filter having spherical pores and a plurality of columnar pores connecting the plurality of spherical pores.

  (2) The total capacity of the capacity of the plurality of spherical pores and the capacity of the plurality of columnar pores is 0.08 ml to 0.2 ml with respect to 1 g of the weight of the catalyst layer (1) The exhaust gas purification filter as described.

  (3) The exhaust gas purification filter according to (1) or (2), wherein the carrier has pores having a major axis of 1 μm to 50 μm and a porosity of 40% to 60%.

  (4) The catalyst layer includes at least one active catalyst element selected from the group consisting of Ag, Au, Cu, Pd, Rh, Pt, Ru, and Ir. Exhaust gas purification filter.

  (5) The catalyst layer further includes a support catalyst element, and the support catalyst element includes at least one element selected from the group consisting of Ni, Co, Fe, Mn, V, Mo, W, and Ce; The exhaust gas purification filter according to any one of (1) to (4), comprising at least one element selected from the group consisting of rare earth elements and alkali metal elements.

  (6) A method for producing an exhaust gas purification filter used for purification of particulate matter in exhaust gas discharged from an internal combustion engine, comprising: a step of preparing a catalyst containing at least an active catalytic element; A step of adding a predetermined amount of a pore-forming agent, a columnar pore-forming agent, and an inorganic binder, preparing a catalyst slurry, and immersing the carrier in the prepared catalyst slurry, then lifting and firing, And a step of burning and extinguishing the spherical pore former and the columnar pore former to form a catalyst layer having spherical pores and columnar pores.

  (7) The method for producing an exhaust gas purification filter according to (6), wherein a spherical pore-forming agent having a diameter of 1 μm to 30 μm is used as the spherical pore-forming agent.

  (8) The exhaust gas purification filter according to (6) or (7), wherein as the columnar pore former, a columnar pore former having a major axis of an opening surface of 30 μm or less and an aspect ratio of 10 to 1000 is used. Production method.

  According to the present invention, since the spherical pores in the catalyst layer are connected by the columnar pores and networked, the utilization rate of the pores for PM combustion can be improved, and PM is efficiently burned. be able to. In addition, since the catalyst layer has sufficient mechanical strength, it is possible to suppress separation of the catalyst layer and to suppress pressure loss due to PM deposition.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  The exhaust gas purification filter according to the present embodiment is provided in an exhaust system of an internal combustion engine, and is suitably used for purification of particulate matter in exhaust gas discharged from the internal combustion engine, particularly particulate matter mainly composed of carbon. The configuration includes a carrier and a catalyst layer carried on the carrier.

<Carrier>
The carrier of the exhaust gas purification filter according to the present embodiment is not particularly limited, and a conventionally known carrier can be used. Preferably, a ceramic wall flow type honeycomb DPF carrier is used. As the material, cordierite, silicon carbide, mullite, alumina or the like is preferably used. If it is a wall flow type, the number of cells and the wall thickness are not particularly limited.

  The carrier preferably has a filtration function, and preferably has pores having a major axis of 1 μm to 50 μm. When the major diameter of the pores is less than 1 μm, it is smaller than the main peak of the particle size distribution of the PM secondary particles discharged from the internal combustion engine, so that the pores are easily blocked by the PM secondary particles, and the pressure loss increases. Since it invites, it is not preferable. Further, the contact state between the PM and the catalyst deteriorates due to the clogging of the pores, which is not preferable for PM combustion. On the other hand, when the thickness exceeds 50 μm, there are problems that the strength of the carrier and the PM collection rate are lowered, which is not preferable. More preferably, it is 9 μm to 30 μm.

  The porosity of the carrier is preferably 40% to 60%. A porosity of less than 40% is not preferable because it tends to cause pore clogging by PM secondary particles, leading to an increase in pressure loss. Further, the contact state between the PM and the catalyst deteriorates due to the clogging of the pores, which is not preferable for PM combustion. More preferably, it is 45% to 55%.

<Catalyst layer>
The catalyst layer of the exhaust gas purification filter according to the present embodiment has a plurality of spherical pores and a plurality of columnar pores that connect the plurality of spherical pores. That is, a plurality of adjacent spherical pores are connected by a plurality of columnar pores to form a network.

  In the exhaust gas purification filter according to the present embodiment, the total capacity of the capacity of the plurality of spherical pores and the capacity of the plurality of columnar pores is 0.08 ml to 0.2 ml with respect to 1 g of the weight of the catalyst layer. Preferably there is. When the amount is less than 0.08 ml, the amount of pores suitable for PM combustion is small, which is not preferable for PM combustion. On the other hand, when it exceeds 0.2 ml, the pore volume in the catalyst layer becomes too large, so that the strength of the catalyst layer is lowered and the catalyst may be peeled off. More preferably, it is 0.1-0.2 ml.

  The catalyst layer of the exhaust gas purification filter according to the present embodiment contains an active catalyst element. The active catalyst element is preferably at least one selected from the group consisting of Ag, Au, Cu, Pd, Rh, Pt, Ru, and Ir. Of these, Ag is more preferably used as the active catalyst element.

  Moreover, the catalyst layer of the exhaust gas purification filter according to the present embodiment includes a support catalyst element. The support catalyst element is at least one element selected from the group consisting of Ni, Co, Fe, Mn, V, Mo, W, and Ce, and at least one element selected from the group consisting of rare earth elements and alkali metal elements. Elements. Of the elements of the former group, Ce is more preferably used.

Alkali metal elements are used as carbonates and sulfates. Except for alkali metal elements, oxides of these elements such as Fe ₂ O ₃ and Co ₃ O ₄ are used as they are, or K ₂ NiO ₄ and K _{2 are used.} It is preferable to use it as a complex oxide like MnOx. In addition, a polymer can be supported on a high specific surface area carrier such as alumina or silica.

<Manufacturing method>
The exhaust gas purification filter according to this embodiment includes a step of preparing a catalyst containing an active catalyst element and a promoter element, and adding a predetermined amount of a spherical pore forming agent, a columnar pore forming agent, and an inorganic binder to the prepared catalyst. And mixing to prepare a catalyst slurry, and after immersing the carrier in the prepared catalyst slurry, raising and firing, the spherical pore-forming agent and the columnar pore-forming agent are burned off and the spherical fine particles are burned. And a step of forming a catalyst layer having pores and columnar pores.

  That is, the network pores, which are the characteristics of the exhaust gas purifying filter according to the present embodiment, are formed by mixing the spherical pore forming agent and the columnar pore forming agent into the catalyst slurry at the same time and disappearing at the time of firing. The method for preparing the catalyst or catalyst slurry, the dipping method, the drying method, and the firing method are not particularly limited, and conventionally known methods can be used.

  Although it does not specifically limit as a spherical pore making agent, For example, combustible powders, such as carbon powder, wood powder, starch powder, resin powder, can be used. Further, the columnar pore-forming agent is not particularly limited, but flammable fibers such as carbon fiber, resin fiber, and wool can be used.

  The diameter of the spherical pore forming agent is preferably 1 μm to 30 μm. When the diameter of the spherical pore forming agent is less than 1 μm, the PM combustion effect is low, and when it is larger than 30 μm, the PM burning effect is low because the pore forming agent does not enter the DPF. More preferably, it is 1 μm to 20 μm.

  The major axis of the opening surface of the columnar pore former is preferably 30 μm or less. When the major axis exceeds 30 μm, the size of the columnar pores is increased, and the pore size is not suitable for PM combustion, and thus adversely affects PM combustion. The aspect ratio is preferably 10 to 1000. When the aspect ratio exceeds 1000, since it does not enter the DPF pores, the pore coupling rate is lowered, which adversely affects PM combustion. More preferably, it is 10-100.

<Action and effect>
The operation and effect of the exhaust gas purification filter 10 according to the present embodiment will be described with reference to FIG. As shown in FIG. 1, in the catalyst layer 12 of the exhaust gas purification filter 10 according to the present embodiment, a plurality of spherical pores 11 a and a plurality of columnar pores 11 b that connect the plurality of spherical pores 11 a to each other. There are a plurality of pores 11 networked by. For this reason, the exhaust gas containing the particulate matter discharged from the internal combustion engine can flow smoothly, and the blockage of the flow path by the particulate matter is suppressed. Thereby, the utilization factor of the pore 11 with respect to combustion of PM can be improved, and PM can be burned efficiently. Also, unlike the conventional one that forms a large amount of spherical pores, the columnar pores 11b are bridged between the spherical pores 11a, and the total pore volume is suppressed. . For this reason, the catalyst layer 12 of the exhaust gas purification filter 10 according to the present embodiment has sufficient mechanical strength, can suppress the separation of the catalyst, and can also suppress the pressure loss due to PM deposition.

  Next, although this invention is demonstrated based on an Example, this invention is not limited to this.

<Example 1>
[Preparation of Ag / CeO ₂ catalyst]
A predetermined amount of silver nitrate was dissolved in water so that the weight of Ag with respect to CeO ₂ was 30 wt%, and this silver nitrate aqueous solution and CeO ₂ powder were placed in an eggplant flask and evaporated to dryness with a rotary evaporator. This was calcined at 700 ° C. for 2 hours to produce an Ag / CeO ₂ catalyst.

[Honeycomb support]
With respect to the Ag / CeO ₂ catalyst prepared as described above, the spherical pore former is 25% by catalyst weight ratio, the columnar pore former is 25% catalyst weight ratio, and the SiO ₂ binder is catalyst weight ratio. After blending to 10%, a predetermined amount of water was added, and the mixture was stirred with a ball mill to form a catalyst slurry. As the spherical pore-forming agent, a spherical corn starch powder having an average diameter of 30 μm and a diameter distribution of 1 μm to 100 μm was used. Moreover, in order to connect spherical pores, carbon fibers having an average diameter of 150 nm and an aspect ratio of 0 to 500 were used as columnar pore formers.

  Next, a 300-cell SiC-DPF honeycomb was prepared, and the honeycomb was immersed in the catalyst slurry obtained above. After soaking, the honeycomb was pulled up and the excess catalyst slurry was cut well with an air knife, and then the drying process at 200 ° C. was repeated until a predetermined weight was reached, so that the inside of the cell was filled with the dried catalyst slurry.

  The obtained honeycomb with catalyst was fired at 600 ° C. for 2 hours to burn and remove the corn starch powder and the carbon fiber pore former component. As a result, a catalyst-attached DPF (exhaust gas purification filter) having a catalyst layer in which 30 g / L of catalyst per 1 L of catalyst-attached DPF was filled and spherical pores were connected by columnar pores in the honeycomb cell was obtained.

<Example 2>
The catalyst was prepared in the same manner as in Example 1. The honeycomb was supported by the same method as in Example 1 except that both the spherical pore former and the columnar pore former were used in an amount twice that of Example 1.

<Comparative Example 1>
The catalyst was prepared in the same manner as in Example 1. The honeycomb was supported by the same method as in Example 1 except that neither a spherical pore forming agent nor a columnar pore forming agent was used.

<Comparative Example 2>
The catalyst was prepared in the same manner as in Example 1. The honeycomb was supported by the same method as in Example 1 except that the columnar pore former was not used.

<Comparative Example 3>
The catalyst was prepared in the same manner as in Example 1. The honeycomb was supported by the same method as in Example 1 except that the spherical pore former was not used.

<Evaluation>
All the DPFs with catalysts obtained in the examples and comparative examples were evaluated under the initial state.

[PM collection method]
The PM was collected by circulating the exhaust gas discharged from the diesel generator through the DPF with catalyst obtained in each of the examples and comparative examples. The weight of the collected PM was calculated by measuring the weight of the DPF with catalyst before and after the collection. In measuring the weight, in order to remove the influence of water and hydrocarbon, it was held at 200 ° C. for 15 min and dried in a dryer.

[PM combustion performance evaluation]
A gas containing 10% O ₂ , 700 ppm NOx, and N ₂ balance gas is circulated at 500 ° C. (SV = 50000 h ⁻¹ ) in a DPF with a catalyst that collects PM, and 90% of PM burns. The PM combustion performance of the catalyst was evaluated using the time until (hereinafter referred to as T90) as an index. Until the target temperature reached 500 ° C., the temperature was raised by flowing N ₂ so that PM would not burn during the temperature rise.

[Pore volume measurement]
The catalyst-attached DPF produced in Examples and Comparative Examples was broken into a predetermined size, and the pore distribution of the DPF and the pore distribution in the catalyst layer were measured using a mercury porosimeter.

<Evaluation results>
Table 1 shows the catalyst type, pore forming agent type, pore forming agent addition amount, and 90% PM combustion time (T90) of Examples and Comparative Examples. Table 2 shows the pore volume formed by the pore former types and the pore formers of Examples and Comparative Examples. Table 3 shows the pore volume, T90, formed by the pore formers of Examples and Comparative Examples.

  Comparing Comparative Example 1 with Comparative Examples 2 and 3, it can be seen that Comparative Examples 2 and 3 using a pore-forming agent clearly burn PM more efficiently. This is considered to be because the contact property between the PM and the catalyst is improved and the combustion efficiency of the PM is improved.

  When Example 1 and Comparative Examples 2 and 3 are compared, spherical pores and columnar pores as in Example 1 are produced rather than spherical pores or columnar pores alone as in Comparative Example 2 or 3. It can be seen that the exhaust gas flows more smoothly and PM can be burned efficiently if both are generated simultaneously (see FIG. 2). In addition, since PM combustion efficiency does not depend on the pore volume in the catalyst (see Table 3), it can be seen that it is important that spherical pores and columnar pores exist simultaneously.

  The reason why the PM combustion efficiency of Comparative Example 2 is lower than that of Example 1 is that the generated pores are only spherical pores as shown in FIG. This is probably because the number of pores that are effectively used is small.

  The reason why the PM combustion efficiency of Comparative Example 3 is lower than that of Example 1 is considered that the columnar pores are not in a shape suitable for burning PM. Due to the shape of the columnar pores, PM tends to deposit near the opening compared to the spherical pores, so the internal pores are not used and are effectively used for PM combustion as in Comparative Example 2. This is probably because the number of pores formed is small. However, the carbon fibers for generating columnar pores used this time have a large volume per weight (see Table 2), and thus the connection rate is considered to be high. Therefore, although the columnar pores are in a shape unsuitable for burning PM, the coupling rate is high, and as a result, it is considered that the PM combustion efficiency equivalent to that of Comparative Example 2 was obtained in Comparative Example 3.

  The diameter of the spherical pore former used this time is about 1 μm to 30 μm. If the diameter of the spherical pore former is within this range, the PM combustion efficiency can be increased. In addition, considering that the pore size of the carrier is 9 μm to 30 μm and pores larger than the pore size of the carrier cannot be generated in principle, the effect of using a pore forming agent larger than the maximum diameter is small. Conceivable.

  In view of the role of connecting the spherical pores, it is considered that the fibrous pore-forming agent for generating the columnar pores is desirably smaller in diameter than the spherical pore diameter. Moreover, the aspect ratio of the carbon fiber pore-forming agent used this time is 10 to 1000, and it was confirmed that the combustion efficiency of PM can be improved by the connection effect of the spherical pores within this range.

  In Example 2, the amount of pore-forming agent was twice that of Example 1, and the PM combustion efficiency was further improved as compared with Example 1. This is considered to be due to an increase in pores where PM and the catalyst can come into contact. From this, the amount of pore-forming agent is effective even when blended up to the same amount as the catalyst weight, and the capacity of the pores formed by the pore-forming agent at that time includes spherical pores and columnar pores. The combined amount was 0.17 ml per 1 g of the DPF with catalyst.

It is a schematic diagram for demonstrating the exhaust gas purification filter of this invention. It is a schematic diagram for demonstrating the exhaust gas purification filter of a present Example. 6 is a schematic diagram for explaining an exhaust gas purification filter of Comparative Example 2. FIG. It is a schematic diagram for demonstrating the conventional exhaust gas purification filter.

Explanation of symbols

10, 20, 30, 40 Exhaust gas purification filter 11, 21, 31, 41 Pore 11a, 21a, 31a, 41a Spherical pore 11b, 21b, 31b, 41b Columnar pore 12, 22, 32, 42 Catalyst layer 13, 23, 33, 43 Carrier wall

Claims (8)

An exhaust gas purification filter used for purification of particulate matter in exhaust gas discharged from an internal combustion engine,
A support and a catalyst layer supported on the support;
The exhaust gas purification filter, wherein the catalyst layer has a plurality of spherical pores and a plurality of columnar pores connecting the plurality of spherical pores.   2. The exhaust gas according to claim 1, wherein a total capacity of the plurality of spherical pores and the plurality of columnar pores is 0.08 ml to 0.2 ml with respect to 1 g of the weight of the catalyst layer. Purification filter.   The exhaust gas purification filter according to claim 1 or 2, wherein the carrier has pores having a major axis of 1 µm to 50 µm and a porosity of 40% to 60%.   4. The exhaust gas purification filter according to claim 1, wherein the catalyst layer includes at least one active catalyst element selected from the group consisting of Ag, Au, Cu, Pd, Rh, Pt, Ru, and Ir. The catalyst layer further includes a support catalyst element,
The support catalyst element is at least one element selected from the group consisting of Ni, Co, Fe, Mn, V, Mo, W, and Ce, and at least one element selected from the group consisting of rare earth elements and alkali metal elements. The exhaust gas purification filter according to claim 1, comprising: A method of manufacturing an exhaust gas purification filter used for purification of particulate matter in exhaust gas discharged from an internal combustion engine,
Preparing a catalyst comprising at least an active catalytic element;
A step of adding a predetermined amount of a spherical pore-forming agent, a columnar pore-forming agent, and an inorganic binder to the prepared catalyst and mixing them to prepare a catalyst slurry;
After the carrier is immersed in the prepared catalyst slurry, the spherical pore-forming agent and the columnar pore-forming agent are burned and disappeared by raising and firing to form a catalyst layer having spherical pores and columnar pores. And a method for manufacturing an exhaust gas purification filter.   The method for producing an exhaust gas purification filter according to claim 6, wherein a spherical pore-forming agent having a diameter of 1 µm to 30 µm is used as the spherical pore-forming agent.   The method for producing an exhaust gas purification filter according to claim 6 or 7, wherein a columnar pore former having a major axis of an opening surface of 30 µm or less and an aspect ratio of 10 to 1000 is used as the columnar pore former.

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