Cellular filter

Abstract

Provided is a honeycomb filter that can improve exhaust gas purification performance while suppressing an increase in pressure loss. The honeycomb filter is provided with: a columnar honeycomb structure (4) having porous partition walls (1) arranged so as to surround a plurality of cells (2) that become fluid flow paths extending from a first end face (11) to a second end face (12); a plugged portion (5) provided at an opening portion on the first end face (11) side or the second end face (12) side of each cell (2); and a catalyst (14) for exhaust gas purification supported on the partition walls (1) of the honeycomb structure (4), the partition walls (1) having a pore volume of pores having a pore diameter of 10 μm or less of 0.07 to 0.30 cc / g, an average pore diameter of 11 to 23 μm, and a porosity of 56 to 65% in a state in which the catalyst (14) is not supported.

Description

Technical Field

[0001] This invention relates to a honeycomb filter. More specifically, it relates to a honeycomb filter capable of suppressing the rise in pressure loss and improving exhaust gas purification performance. Background Technology

[0002] Previously, honeycomb filters using a honeycomb structure were known as filters for capturing particulate matter in exhaust gases emitted from internal combustion engines such as automobile engines. The honeycomb structure has partitions made of porous ceramics such as cordierite, which divide the gas into multiple compartments. In contrast to the aforementioned honeycomb structure, the honeycomb filter is configured with sealing portions arranged such that the openings on the inflow end face and the openings on the outflow end face of the multiple compartments are alternately sealed. That is, the honeycomb filter has a structure in which inflow compartments with openings on the inflow end face and sealed outlet compartments with sealed inflow end face and open outlet side are alternately arranged with partitions. Furthermore, in the honeycomb filter, the porous partitions function as filters for capturing particulate matter (e.g., soot) in the exhaust gases. Hereinafter, particulate matter contained in exhaust gases will sometimes be referred to as "PM." "PM" is an abbreviation for "particulate matter." Furthermore, for the aforementioned honeycomb filter, in order to purify toxic gas components other than PM in the exhaust gas, a catalyst for exhaust gas purification is sometimes supported in the porous partitions constituting the honeycomb filter. Hereinafter, the honeycomb filter with a catalyst for exhaust gas purification supported in the porous partitions as described above will sometimes be referred to as a "catalyst-supported honeycomb filter".

[0003] Due to the increasingly stringent restrictions on exhaust gas emissions in recent years, there is a need to improve the exhaust gas purification performance of catalyst-supported honeycomb filters. Here, in the technology of supporting a catalyst in the partition wall of a honeycomb filter, the following attempt is proposed: by sharpening the pore size distribution of the porous partition wall, the flow of gases such as exhaust gas through the partition wall is made more uniform, thereby reducing pressure loss and improving collection efficiency (for example, see Patent Document 1).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2002-219319 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] Techniques like those in Patent Document 1, which sharpen the pore size distribution of the partition wall, reduce pressure loss and improve collection efficiency by homogenizing gas flow. However, sharpening the pore size distribution can lead to a decrease in exhaust gas purification efficiency. For example, sharpening the pore size distribution reduces the number of relatively small pores in the porous partition wall. This reduction in small pores decreases the surface area of ​​the catalyst-supporting pores in the porous partition wall, thus reducing the catalyst loading capacity. Consequently, if the pore size distribution of the partition wall becomes too sharp, the exhaust gas purification efficiency may sometimes deteriorate.

[0009] In addition, if you want to increase the size of the pores while maintaining the sharpness of the pore distribution in the partition wall, you need to shift the pore distribution in the partition wall towards the smaller pores. If the pore distribution in the partition wall shifts towards the smaller pores, the pressure loss of the honeycomb filter will increase.

[0010] Here, to suppress the increase in pressure loss of the honeycomb filter, a countermeasure of increasing the size of the pores to be larger is considered. However, increasing the size of the pores will reduce the PM collection performance. Furthermore, when shifting the pore size distribution of the separator wall as described above towards smaller pores, or increasing the number of larger pores, the porosity of the separator wall sometimes changes. The porosity of the separator wall affects the catalyst loading capacity of the separator wall and the mechanical strength of the honeycomb filter. Therefore, it is desirable to develop a technology that can improve exhaust gas purification performance without significantly changing the porosity of the separator wall.

[0011] This invention was made in view of the problems inherent in the prior art. According to the invention, a honeycomb filter is provided that can improve exhaust gas purification performance while suppressing the increase in pressure loss.

[0012] Solution for solving the problem

[0013] According to the present invention, a cellular filter as shown below is provided.

[0014] [1] A honeycomb filter, characterized in that it comprises: a columnar honeycomb structure having a porous partition wall arranged to surround a plurality of compartments extending from a first end face to a second end face that form a fluid flow path; a sealing portion disposed at either the end face of the compartment on the first end face side or the end face of the compartment on the second end face side; and a catalyst for purifying exhaust gas supported on the partition wall, wherein the partition wall, in a state without the catalyst supported, has a pore volume of pores with a pore size of 10 μm or less of 0.07 to 0.30 cc / g, an average pore size of 11 to 23 μm, and a porosity of 56 to 65%.

[0015] [2] According to the honeycomb filter described in [1] above, wherein the pore volume of the pores with a diameter of less than 10 μm in the partition wall when the catalyst is not supported is 0.07 to 0.20 cc / g.

[0016] [3] According to the honeycomb filter described in [1] or [2] above, wherein the partition wall has an average pore size of 14 μm to 23 μm when it is not loaded with the catalyst.

[0017] [4] The honeycomb filter according to any one of [1] to [3] above, wherein the septum has a porosity of 56% to 63% when the catalyst is not loaded.

[0018] [5] The honeycomb filter according to any one of [1] to [4] above, wherein the partition is made of a material comprising at least one selected from the group consisting of cordierite, silicon carbide and aluminum titanate.

[0019] [6] The honeycomb filter according to any one of [1] to [5] above, wherein the catalyst is a ternary catalyst, an oxidation catalyst or a selective reduction catalyst.

[0020] Invention Effects

[0021] The honeycomb filter of the present invention effectively suppresses the increase in pressure loss and improves the exhaust gas purification performance. In particular, compared with conventional honeycomb filters, the honeycomb filter of the present invention can suppress the increase in pressure loss and improve the exhaust gas purification performance without changing the porosity of the partition walls (in other words, maintaining the same level of porosity as in the past). Attached Figure Description

[0022] Figure 1 This is a perspective view, taken from the first end face, schematically illustrating one embodiment of the honeycomb filter of the present invention.

[0023] Figure 2 From Figure 1 The top view of the first end face of the shown cellular filter.

[0024] Figure 3 It is a schematic representation Figure 2 A cross-sectional view of section A-A'.

[0025] In the picture:

[0026] 1—Block; 2—Compartment; 2a—Inflow compartment; 2b—Outflow compartment; 3—Outer peripheral wall; 4—Honeycomb structure; 5—Sealing part; 11—First end face; 12—Second end face; 14—Catalyst; 100—Honeycomb filter. Detailed Implementation

[0027] The embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments. Therefore, it should be understood that appropriate modifications, improvements, etc., to the following embodiments based on ordinary knowledge of those skilled in the art, without departing from the spirit of the present invention, also fall within the scope of the present invention.

[0028] (1) Honeycomb filter:

[0029] like Figures 1-3 As shown, one embodiment of the honeycomb filter of the present invention is a honeycomb filter 100 comprising a honeycomb structure 4, a sealing portion 5, and a catalyst 14 for purifying exhaust gas supported on the partitions 1 of the honeycomb structure 4. The honeycomb structure 4 is columnar with porous partitions 1 arranged to surround a plurality of compartments 2 that form a flow path for fluid extending from a first end face 11 to a second end face 12. In the honeycomb filter 100, the honeycomb structure 4 is columnar and has an outer peripheral wall 3 on its outer peripheral side. That is, the outer peripheral wall 3 is arranged to surround the partitions 1 arranged in a lattice pattern.

[0030] Figure 1 This is a perspective view, schematically illustrating one embodiment of the cellular filter of the present invention, viewed from the first end face side (e.g., the inflow end face side). Figure 2 From Figure 1 A top view of the first end face (e.g., the inflow end face) of the shown cellular filter. Figure 3 It is a schematic representation Figure 2 A cross-sectional view of section A-A'.

[0031] The honeycomb filter 100 possesses particularly important characteristics in the structure of the partitions 1 constituting the honeycomb structure 4. Specifically, in the state without the catalyst 14 supported, the partitions 1 constituting the honeycomb structure 4 have a pore volume of 0.07 to 0.30 cc / g for pores with a pore size of 10 μm or less. Furthermore, the average pore size of these partitions 1 is 11 to 23 μm. Moreover, the porosity of these partitions 1 is 56% to 65%. The honeycomb filter 100 constructed in this way can suppress the increase in pressure loss and improve exhaust gas purification performance. Specifically, by making the pore volume of the pores with a pore size of 10 μm or less in the partitions 1 0.07 to 0.30 cc / g, the surface area of ​​the pores in the partitions 1 carrying the catalyst 14 is increased. This ensures a catalyst loading capacity that achieves excellent exhaust gas purification performance and increases the contact area between the catalyst 14 and the exhaust gas, thereby improving the exhaust gas purification performance of the honeycomb filter 100. Furthermore, by setting the average pore size of the partition wall 1 to 11 μm to 23 μm and the porosity to 56% to 65%, as described above, the exhaust gas purification performance can be improved, and the increase in pressure loss can be effectively suppressed. The characteristics of the partition wall 1 described above will be explained in more detail below.

[0032] Regarding partition wall 1, the pore volume of pores with a diameter of 10 μm or less is 0.07 to 0.30 cc / g. The pore volume of pores with a diameter of 10 μm or less in partition wall 1 is determined by mercury infiltration. The determination of the pore volume (cc / g) of pores with a diameter of 10 μm or less in partition wall 1 can be performed, for example, using an Autopore 9500 (trade name) manufactured by Micromeritics. If the pore volume of pores with a diameter of 10 μm or less is less than 0.07 cc / g, the surface area of ​​the pores supporting catalyst 14 decreases, making it difficult to sufficiently improve the exhaust gas purification performance. On the other hand, if the pore volume of pores with a diameter of 10 μm or less exceeds 0.30 cc / g, the pressure loss increases when the average pore diameter and porosity of partition wall 1 are set within the aforementioned range. The pore volume of the pores with a diameter of less than 10 μm can be 0.07 to 0.30 cc / g, preferably 0.07 to 0.20 cc / g, and more preferably 0.07 to 0.15 cc / g.

[0033] Furthermore, the average pore size of the partition wall 1 is 11 μm to 23 μm. The average pore size of the partition wall 1 is measured by mercury infiltration. The average pore size of the partition wall 1 can be measured, for example, using an Autopore 9500 (trade name) manufactured by Micromeritics. If the average pore size of the partition wall 1 is less than 11 μm, the pressure loss increases when the average pore size and porosity of the partition wall 1 are set within the aforementioned range. On the other hand, if the average pore size of the partition wall 1 exceeds 23 μm, the collection performance of the honeycomb filter 100 decreases. An average pore size of 11 to 23 μm is acceptable, preferably 14 to 23 μm, and more preferably 15 to 23 μm.

[0034] Furthermore, the porosity of partition 1 is 56% to 65%. The porosity of partition 1 is measured by mercury infiltration. For example, the porosity of partition 1 can be measured using an Autopore 9500 (trade name) manufactured by Micromeritics. If the porosity of partition 1 is less than 56%, the pressure loss increases when the average pore size and porosity of partition 1 are set within the aforementioned range. On the other hand, if the porosity of partition 1 exceeds 65%, the mechanical strength (e.g., isostatic strength) of the honeycomb filter 100 decreases. A porosity of 56% to 65% for partition 1 is acceptable, preferably 56% to 63%, and more preferably 56% to 62%.

[0035] The determination of the pore volume (cc / g), average pore diameter (μm), and porosity (%) of the pores with a pore diameter of less than 10 μm described so far can be performed by cutting a portion of the pore 1 from the honeycomb filter 100 as a test piece and using the test piece obtained in this way.

[0036] There are no particular limitations on the thickness of the partition wall 1, but it is preferably 0.203 to 0.406 mm, more preferably 0.229 to 0.356 mm, and particularly preferably 0.254 to 0.330 mm. For example, if the thickness of the partition wall 1 is less than 0.203 mm, the mechanical strength of the partition wall 1 may sometimes decrease. On the other hand, if the thickness of the partition wall 1 exceeds 0.406 mm, the pressure loss of the honeycomb filter 100 may sometimes increase when the partition wall 1 carries the catalyst for exhaust gas purification. The thickness of the partition wall 1 can be measured, for example, using a scanning electron microscope or a microscope.

[0037] There are no particular limitations on the shape of the compartments 2 formed in the honeycomb structure 4. For example, the shape of the compartment 2 in a cross-section orthogonal to the direction in which the compartment 2 extends can be polygonal, circular, elliptical, etc. As polygons, examples include triangles, quadrilaterals, pentagons, hexagons, octagons, etc. Furthermore, the shape of the compartment 2 is preferably triangular, quadrilateral, pentagonal, hexagonal, or octagonal. Regarding the shape of the compartments 2, all compartments 2 can have the same shape or different shapes. For example, although the illustration is omitted, a mixture of quadrilateral and octagonal compartments is also possible. Regarding the size of the compartments 2, all compartments 2 can have the same size or different sizes. For example, although the illustration is omitted, the size of some of the multiple compartments can be increased while the size of the other compartments is relatively decreased. It should be noted that, in this invention, compartment 2 refers to the space surrounded by partition walls 1.

[0038] The preferred compartment density of compartment 2, formed by partition 1, is 31 compartments / cm². 2 ~70 pieces / cm 2 More preferably 39 per cm 2 ~54 pieces / cm 2 With this configuration, the honeycomb filter 100 can be appropriately used as a filter for purifying exhaust gases emitted from the engine of a car.

[0039] The partition 1 is preferably made of a porous ceramic material, and more preferably of a material comprising at least one selected from the group consisting of cordierite, silicon carbide and aluminum titanate. The material constituting the partition 1 preferably contains 30% by mass or more of the components contained in the group mentioned above (i.e., cordierite, silicon carbide and aluminum titanate), and more preferably 40% by mass or more.

[0040] The outer peripheral wall 3 of the honeycomb structure 4 can be integrally formed with the partition wall 1, or it can be an outer peripheral coating formed by applying an outer peripheral coating material to the outer peripheral side of the partition wall 1. For example, although the figure is omitted, the outer peripheral coating can be provided on the outer peripheral side of the partition wall after the partition wall and the outer peripheral wall are integrally formed during manufacturing, and the outer peripheral wall is removed by known methods such as grinding.

[0041] There are no particular restrictions on the shape of the honeycomb structure 4. Examples of the shape of the honeycomb structure 4 include the first end face 11 (e.g., the inflow end face) and the second end face 12 (e.g., the outflow end face) being cylindrical, elliptical, polygonal, or similar shapes.

[0042] There are no particular restrictions on the size of the honeycomb structure 4, such as its length from the first end face 11 to the second end face 12, and the size of the cross-section of the honeycomb structure 4 orthogonal to the direction in which the compartment 2 extends. When using the honeycomb filter 100 as a filter for exhaust gas purification, the sizes can be appropriately selected in a way that yields the best purification performance.

[0043] In the honeycomb filter 100, sealing portions 5 are provided at the openings on the first end face 11 side of the predetermined compartment 2 and at the openings on the second end face 12 side of the remaining compartment 2. Here, when the first end face 11 is designated as the inflow end face and the second end face 12 as the outflow end face, the compartment 2 with the sealing portion 5 provided at the opening on the outflow end face side and the opening on the inflow end face side is designated as the inflow compartment 2a. In addition, the compartment 2 with the sealing portion 5 provided at the opening on the inflow end face side and the opening on the outflow end face side is designated as the outflow compartment 2b. The inflow compartment 2a and the outflow compartment 2b are preferably arranged alternately with partition walls 1 in between. Moreover, it is preferable to form a grid pattern on both ends of the honeycomb filter 100 using the sealing portions 5 and the openings of the compartment 2.

[0044] There are no particular restrictions on the material of the sealing part 5. For example, it can be the same material as the material of the partition 1, or it can be a different material from the material of the partition 1.

[0045] The honeycomb filter 100 has a partition wall 1 that divides the filter into multiple compartments 2, on which a catalyst 14 for purifying exhaust gas is carried. Carrying the catalyst 14 on the partition wall 1 means coating the surface of the partition wall 1 and the inner walls of the pores formed in the partition wall 1 with the catalyst 14. With this configuration, hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx), etc., in the exhaust gas can be converted into harmless substances through a catalytic reaction. Furthermore, the partition wall 1 can be used to promote the oxidation of PM such as coal particles captured in the filter.

[0046] There are no particular limitations on the catalyst 14 supported on the partition 1. For example, three-way catalysts, oxidation catalysts, and selective reduction catalysts can be cited as such catalysts 14.

[0047] Three-way catalysts are catalysts that primarily purify hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). Examples of three-way catalysts include those containing platinum (Pt), palladium (Pd), and rhodium (Rh).

[0048] Oxidation catalysts containing noble metals can be cited as examples. Specifically, an oxidation catalyst containing at least one selected from the group consisting of platinum, palladium, and rhodium is preferred.

[0049] Selective reduction catalysts are catalysts that selectively reduce the components being purified. Selective reduction catalysts are also known as "SCR catalysts." "SCR" is an abbreviation for "Selective Catalytic Reduction." Examples of SCR catalysts include those for the selective reduction of NOx in exhaust gases. For instance, metal-substituted zeolites are examples of SCR catalysts. Examples of metals used for metal substitution in zeolites include iron (Fe) and copper (Cu). β-zeolite is a preferred example of a zeolite.

[0050] There is no particular limitation on the amount of catalyst 14 supported on the partition 1 (hereinafter referred to as the "loading amount" of catalyst 14). For example, the loading amount of catalyst 14 is preferably 50 to 150 g / L, more preferably 70 to 140 g / L. It should be noted that the loading amount (g / L) of catalyst 14 in this specification represents the amount (g) of catalyst supported per unit volume (L) of the honeycomb filter 100.

[0051] (2) Manufacturing method of honeycomb filter:

[0052] for Figures 1-3 The method for manufacturing the honeycomb filter of this embodiment shown is not particularly limited, and can be manufactured, for example, by the following method. First, a plastic clay for making the honeycomb structure is prepared. The clay for making the honeycomb structure can be prepared, for example, as follows. As raw material powder, silicon carbide, silicon-bonded silicon carbide, sintered ceramic materials with binder, mullite, cordierite, cordierite raw materials, and aluminum titanate can be used. It should be noted that "silicon-bonded silicon carbide" refers to a substance in which silicon carbide particles, for example, are bonded together with metallic silicon. In addition, "sintered ceramic materials with binder" refers to a material in which aggregates such as silicon carbide and mullite are bonded together with binder materials such as cordierite, and is a ceramic material produced by sintering. The cordierite raw material is a mixture of raw materials such as talc, kaolin, alumina, silicon dioxide, and aluminum hydroxide in a predetermined proportion, such that its chemical composition is 42-56% by mass of SiO2, 30-45% by mass of Al2O3, and 12-16% by mass of MgO.

[0053] The honeycomb filter of this embodiment has key characteristics in terms of the structure of the porous partitions (especially the structure of porous pores and micropores). As a method for manufacturing such a honeycomb filter, for example, in the preparation of the blank, a mixed raw material is prepared by mixing silicon carbide (SiC) powder and metallic silicon (Si) in a mass ratio of 80:20. Then, as a pore-forming material to be added to this mixed raw material, a variety of pore-forming materials with different average particle sizes are selected from a variety of pore-forming materials with an average particle size of 25 μm to 45 μm. The blank is prepared by adding a variety of pore-forming materials to the previously prepared mixed raw material in a way that increases the proportion of pore-forming materials with smaller average particle sizes among the selected pore-forming materials. Thus, the pore-forming material added to the mixed raw material during the preparation of the blank preferably exhibits a unimodal or multimodal particle size distribution, with a distribution biased towards the smaller diameter side, when viewed as a whole.

[0054] Next, by extruding the resulting clay into shape, a honeycomb structure is made having partitions that divide the space into multiple compartments, and a honeycomb structure arranged around the outer perimeter of the partitions.

[0055] The resulting honeycomb molded body is dried, for example, using microwaves and hot air. The openings of the compartments are then sealed with the same material used to make the honeycomb molded body, thereby creating sealed sections. After creating the sealed sections, the honeycomb molded body can be further dried.

[0056] Next, the honeycomb molded body with sealed sections is fired to produce a honeycomb filter before catalyst loading (hereinafter also referred to as "honeycomb filter before catalyst loading"). The firing temperature and firing atmosphere vary depending on the raw materials, and those skilled in the art can select the firing temperature and firing atmosphere most suitable for the selected materials.

[0057] Next, the prepared honeycomb filter, before the catalyst is loaded, is loaded with a catalyst for exhaust gas purification. There are no particular limitations on the method of loading the catalyst; for example, a method can be used where a catalyst slurry containing catalyst components is washed and coated, then heat-treated at high temperature and sintered. As described above, the honeycomb filter of this embodiment can be manufactured.

[0058] [Example]

[0059] The present invention will be described in more detail below by way of examples, but the present invention is not limited to these examples in any way.

[0060] (Example 1)

[0061] As a raw material powder for adjusting the clay, a mixed raw material is prepared by mixing silicon carbide (SiC) powder and metallic silicon (Si) in a mass ratio of 80:20. To 100 parts by mass of this mixed raw material, 25 parts by mass of a pore-forming material, a trace amount of dispersant, and 7 parts by mass of an organic binder are added, and the mixture is then mixed and kneaded to prepare the clay. Methylcellulose is used as the organic binder. Polyethylene glycol monooleate is used as the dispersant. The pore-forming material is prepared by selecting several pore-forming materials with different average particle sizes from a variety of pore-forming materials with an average particle size of 25 μm to 45 μm, and increasing the proportion of pore-forming materials with smaller average particle sizes.

[0062] Next, the obtained clay is shaped using an extrusion molding machine to create a honeycomb molded body. Then, the honeycomb molded body is dried using high-frequency induction heating, followed by further drying using a hot air dryer. The compartments in the honeycomb molded body are quadrilateral in shape.

[0063] Next, sealing portions are formed on the dried honeycomb molded body. First, a mask is applied to the inflow end face of the honeycomb molded body. Then, the masked end (the end on the inflow end face side) is immersed in sealing slurry, and the openings of the unmasked compartments (outflow compartments) are filled with sealing slurry. In this way, sealing portions are formed on the inflow end face side of the honeycomb molded body. Then, sealing portions are also formed on the inflow compartments on the outflow end face of the dried honeycomb molded body in the same way.

[0064] Next, the honeycomb molded body with sealed pores is dried using a microwave dryer, and then further dried completely using a hot air dryer. The two ends of the honeycomb molded body are then cut off and adjusted to the predetermined dimensions. Next, the dried honeycomb molded body is degreased and sintered to manufacture a honeycomb filter before the catalyst is supported.

[0065] The diameter of the end face of the honeycomb filter before the catalyst loading is 165 mm, and the length of the compartment in the extending direction is 140 mm. Additionally, the thickness of the compartment wall is 0.318 mm, and the compartment density is 46.5 cells / cm³. 2 .

[0066] In addition, for the honeycomb filter before catalyst loading, the porosity (%) and average pore size (μm) of the partition walls were determined using the following method. Furthermore, using the apparatus shown below for determining porosity and average pore size, the pore size distribution of the partition walls was determined, and the pore volume (cc / g) of pores with a pore size of 10 μm or less was calculated from the determined pore size distribution. The results are shown in Table 1.

[0067] [Table 1]

[0068]

[0069] [Table 2]

[0070]

[0071] [Porosity (%) and average pore size (μm)]

[0072] The porosity and average pore size of the septum were measured using an Autopore 9500 (trade name) manufactured by Micromeritics. For the porosity and average pore size measurements, a portion of the septum was cut from the honeycomb filter to serve as a test piece, and the porosity was measured using this test piece. The test piece was a cuboid with lengths of approximately 10 mm, widths of approximately 10 mm, and height of approximately 20 mm. The sampling location for the test piece was set near the axial center of the honeycomb structure.

[0073] Next, the catalyst for exhaust gas purification was loaded onto the honeycomb filter before catalyst loading using the following method. First, the materials were mixed to prepare a catalyst slurry containing zeolite. Next, the prepared catalyst slurry was washed onto the honeycomb filter before catalyst loading. Then, it was dried at 120°C and then heat-treated at 500°C for 3 hours to sinter the catalyst and load it onto the septa of the honeycomb filter. The honeycomb filter of Example 1 was prepared using the above procedures. The catalyst loading of the honeycomb filter of Example 1 was 120 g / L. Table 1 shows the catalyst loading (g / L).

[0074] For the honeycomb filter of Example 1, the exhaust gas purification performance, isostatic strength, pressure loss, and collection performance were evaluated using the following methods. Furthermore, based on the above evaluation results, a comprehensive judgment was made using the following methods. The results are shown in Table 1.

[0075] (Exhaust gas purification performance)

[0076] The exhaust gas purification performance (%) of the honeycomb filter was determined by measuring the model gas using a catalytic reaction evaluation device. The exhaust gas purification performance was measured using an FTIR gas analyzer; for example, an FTIR gas analyzer manufactured by Horiba Corporation (model: MEXA-6000FT) could be used. The exhaust gas performance (%) was calculated by measuring the gas concentrations of nitric oxide and nitrogen dioxide at both the inlet and outlet ends of the honeycomb filter. The simulated gas was a mixture of nitrogen, oxygen, carbon dioxide, carbon monoxide, nitric oxide, and ammonia water, evaluated at a temperature of approximately 200°C and a gas flow rate SV = 40000 (1 / h). The honeycomb filters of each embodiment were evaluated based on the following evaluation criteria in the exhaust gas purification performance evaluation.

[0077] Evaluation "A": When the exhaust gas purification performance of the honeycomb filter in Comparative Example 1 is set to 100%, the exhaust gas purification performance of the honeycomb filter in the evaluation object is 130% or higher.

[0078] Evaluation "B": When the exhaust gas purification performance value of the honeycomb filter of Comparative Example 1 is set to 100%, the exhaust gas purification performance value of the honeycomb filter of the evaluated object is 100% or more and less than 130%.

[0079] Evaluation "C": When the exhaust gas purification performance value of the honeycomb filter of Comparative Example 1 is set to 100%, the exhaust gas purification performance value of the honeycomb filter of the evaluated object is less than 100%.

[0080] (Isostatic strength)

[0081] The isostatic pressure strength (MPa) of the honeycomb filter was determined using a hydrostatic isostatic strength test device. The evaluation of the isostatic pressure strength was conducted based on the following evaluation criteria for each embodiment of the honeycomb filter.

[0082] Evaluation "A": When the isostatic pressure of the cellular filter of Comparative Example 1 is set to 100%, the isostatic pressure of the cellular filter of the evaluated object is 90% or higher.

[0083] Evaluation "B": When the isostatic pressure of the honeycomb filter of Comparative Example 1 is set to 100%, the isostatic pressure of the honeycomb filter of the evaluation object is 80% or more and less than 90%.

[0084] Evaluation "C": When the isostatic pressure of the cellular filter of Comparative Example 1 is set to 100%, the isostatic pressure of the cellular filter of the evaluation object is less than 80%.

[0085] (Capture performance)

[0086] The capture performance (particles / km) of the exhaust gas purification device using a honeycomb filter was determined through evaluation tests in vehicles. Specifically, the exhaust gas purification device was connected to the outlet side of the exhaust manifold of a 3.0L diesel engine vehicle, and the number of soot particles in the gas discharged from the outlet of the exhaust gas purification device was measured using the PN measurement method. The "PN measurement method" is a measurement method proposed by the Particulate Matter Procedure (PMP) of the Exhaust Gas Energy Experts Meeting (GRPE) of the World Forum for Harmonization of Automotive Benchmarks (WP29) of the United Nations Economic Commission for Europe (ECE). It should be noted that, specifically, in determining the number of soot particles, the number of soot particles discharged after driving in WLTC (Worldwide Harmonized Light Duty Test Cycle) mode was accumulated as the number of soot particles in the exhaust gas purification device (i.e., the honeycomb filter used in the exhaust gas purification device) under evaluation. In the evaluation of capture performance, the honeycomb filters of each embodiment were evaluated based on the following evaluation criteria.

[0087] Evaluation "A": When the capture performance value of the cellular filter of Comparative Example 1 is set to 100%, the capture performance value of the cellular filter of the evaluated object is 120% or higher.

[0088] Evaluation "B": When the capture performance value of the cellular filter of Comparative Example 1 is set to 100%, the capture performance value of the cellular filter of the evaluated object is 80% or more and less than 120%.

[0089] Evaluation "C": When the capture performance value of the cellular filter of Comparative Example 1 is set to 100%, the capture performance value of the cellular filter of the evaluated object is less than 80%.

[0090] (Comprehensive judgment)

[0091] "Excellent" rating: The evaluation of exhaust gas purification performance, isostatic strength and pressure loss are all "A", and the evaluation of collection performance is "A" or "B".

[0092] "Good" rating: The performance of exhaust gas purification is rated "A", and other ratings are rated "A" or "B" (except for ratings equivalent to "Excellent").

[0093] Evaluation "Acceptable": The evaluation of the exhaust gas purification performance is "B" or "C", or the evaluation other than the exhaust gas purification performance includes a result of "C".

[0094] (Examples 2 to 16)

[0095] In Examples 2 through 16, honeycomb filters were manufactured using the raw materials shown below in the preparation of the clay for making honeycomb molded bodies. For the obtained honeycomb filters, the porosity of the septa and the average pore size were measured using the same method as in Example 1. Furthermore, the pore volume (cc / g) of pores smaller than 10 μm was determined using the above method. The results are shown in Tables 1 and 2. It should be noted that Examples 2, 10, and 15 are honeycomb filters with substantially the same characteristics manufactured from the same raw materials, but they are described as different examples in Table 1 for ease of comparison with other examples.

[0096] In Examples 2 to 16, when selecting multiple pore-forming materials with different average particle sizes from a variety of pore-forming materials with average particle sizes of 25 μm to 45 μm, the types of pore-forming materials selected (i.e., the average particle size of the selected pore-forming materials) and their mixing ratios were changed, but the honeycomb filter was manufactured using the same method as in Example 1. However, in Examples 2 to 16, pore-forming materials were also selected in a manner that increased the proportion of pore-forming materials with smaller average particle sizes.

[0097] (Comparative Examples 1 to 7)

[0098] In Comparative Examples 1 to 7, honeycomb filters were manufactured using the raw materials shown below during the preparation of the clay for making honeycomb molded bodies. For the obtained honeycomb filters, the porosity of the septa and the average pore size were measured using the same method as in Example 1. Furthermore, the pore volume (cc / g) of pores smaller than 10 μm was determined using the above method. The results are shown in Tables 1 and 2. In Comparative Example 1, a mixed raw material was prepared by mixing silicon carbide (SiC) powder and metallic silicon (Si) in a mass ratio of 80:20 in the raw material powder used for preparing the clay. In Comparative Examples 2 to 7, the raw material powder was prepared according to the preparation methods of the raw material powders in Examples 2 to 4, 5 to 8, 9 to 12, and 13 to 16.

[0099] For the honeycomb filters of Examples 2 to 16 and Comparative Examples 1 to 7, the exhaust gas purification performance, isostatic strength, pressure loss, and collection performance were evaluated using the same method as in Example 1. Furthermore, based on the above evaluation results, a comprehensive judgment was made using the following method. The results are shown in Tables 1 and 2.

[0100] (result)

[0101] It was confirmed that, as with the honeycomb filters of Examples 1 to 6, increasing the pore volume (cc / g) of pores smaller than 10 μm improved the exhaust gas purification performance compared to the honeycomb filter of Comparative Example 1. However, it was found that if the pore volume (cc / g) of pores smaller than 10 μm was excessively increased, as with the honeycomb filter of Comparative Example 3, the pressure loss of the honeycomb filter increased significantly.

[0102] It is evident that, as with the honeycomb filters of Examples 7 to 11, by setting the porosity of the partition walls to a predetermined range, the increase in pressure loss can be suppressed while maintaining the isostatic strength of the honeycomb filter. On the other hand, if the porosity of the partition walls is excessively increased, although the evaluation results of pressure loss become good, a tendency to reduce the mechanical strength of the honeycomb filter is confirmed. For example, as with the honeycomb filter of Comparative Example 5, if the porosity of the partition walls is 66%, the isostatic strength is significantly reduced, which may cause problems when canning the honeycomb filter into a can such as a metal casing. On the other hand, it is evident that, as with the honeycomb filter of Comparative Example 4, if the porosity of the partition walls is 53%, although the isostatic strength is excellent, the pressure loss of the honeycomb filter increases significantly.

[0103] As with the honeycomb filters of Examples 12 to 16, by setting the average pore size of the partition walls to a predetermined range, high collection performance can be achieved, pressure loss can be suppressed, and exhaust gas purification performance can be improved. It should be noted that if the average pore size of the partition walls is too large, a tendency for reduced collection performance is observed. On the other hand, if the average pore size of the partition walls is too small, a tendency for increased pressure loss is observed.

[0104] Industrial availability

[0105] The honeycomb filter of the present invention can be used as a trapping filter for removing particles and the like contained in exhaust gas.

Claims

1. A honeycomb filter, characterized in that, have: A columnar honeycomb structure having porous partitions configured to surround multiple compartments that form fluid flow paths extending from a first end face to a second end face. A sealing portion, disposed on either the end portion on the first end face side or the end portion on the second end face side of the compartment; and The catalyst used for waste gas purification is supported on the partition wall. In the absence of catalyst loading, the partition wall has a pore volume of 0.07–0.30 cc / g for pores with a diameter of less than 10 μm, an average pore diameter of 11–23 μm, and a porosity of 56–65%. The thickness of the partition wall is 0.229–0.356 mm.

2. The honeycomb filter according to claim 1, characterized in that, When the partition wall is not loaded with the catalyst, the pore volume of the pores with a diameter of less than 10 μm is 0.07 to 0.20 cc / g.

3. The honeycomb filter according to claim 1 or 2, characterized in that, The partition wall, when not loaded with the catalyst, has an average pore size of 14 μm to 23 μm.

4. The honeycomb filter according to claim 1 or 2, characterized in that, The partition wall has a porosity of 56% to 63% when it is not loaded with the catalyst.

5. The honeycomb filter according to claim 1 or 2, characterized in that, The partition is made of a material comprising at least one selected from the group consisting of cordierite, silicon carbide and aluminum titanate.

6. The honeycomb filter according to claim 1 or 2, characterized in that, The catalyst is a ternary catalyst, an oxidation catalyst, or a selective reduction catalyst.

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