Exhaust purification device

Abstract

The invention relates to an exhaust gas purification device. Provided is an exhaust gas purification device capable of reducing pressure loss and improving exhaust gas purification performance. The exhaust gas purification device is characterized in that the exhaust gas purification device is provided with a honeycomb base material and an outflow cell-side catalyst, the honeycomb base material is provided with a porous partition wall which divides a plurality of cells extending from an inflow-side end surface to an outflow-side end surface, the plurality of cells include inflow cells and outflow cells which are adjacent to each other with the partition wall therebetween, and the outflow cell-side catalyst is arranged between the inflow cells and the outflow cells. The inflow-side end of the inflow cell is open and the outflow-side end is sealed, and the inflow-side end of the outflow cell is sealed and the outflow-side end is open. The flow-out-cell-side catalyst is provided in a region inside the partition wall on the flow-out-cell side in a flow-out-cell-side catalyst installation range extending in the extension direction from the flow-out-side end of the partition wall to a position separated from the flow-out-side end of the partition wall by a predetermined distance in the extension direction. The minimum value of the porosity in the thickness direction of the flow-out cell-side catalyst arrangement wall of the flow-out cell-side catalyst arrangement range including the partition wall and the flow-out cell-side catalyst arrangement wall of the flow-out cell-side catalyst is within the range of from 20% to 30% (inclusive).

Description

Technical Field

[0001] The present invention relates to an exhaust gas purification device in which a catalyst is provided on a filter of a wall flow structure. Background Art

[0002] Exhaust gas discharged from an internal combustion engine in a car or the like contains particulate matter (PM: Particulate Matter, hereinafter sometimes referred to as "PM") mainly composed of carbon, which is a cause of air pollution, and ash, which is an incombustible component. As a filter for collecting and removing PM from exhaust gas, a filter with a wall flow structure is widely used.

[0003] The filter of the wall flow structure usually has a honeycomb substrate, and the honeycomb substrate has a porous partition wall that divides a plurality of pores extending from the inlet side end face to the outlet side end face, and the plurality of pores include an inlet pore chamber and an outflow pore chamber that are adjacent to each other across the partition wall. Moreover, the inlet side end of the inlet pore chamber is open, and the outflow side end is sealed, and the inlet side end of the outflow pore chamber is sealed, and the outflow side end is open. Therefore, the exhaust gas that flows into the inlet pore chamber from the inlet side end flows into the outflow pore chamber by passing through the partition wall, and is discharged from the outflow side end of the outflow pore chamber. Moreover, when the exhaust gas passes through the partition wall, PM accumulates in the gaps existing in the partition wall. As filters with a wall flow structure, for example, a diesel particulate filter (DPF) for a diesel engine and a gasoline particulate filter (GPF, hereinafter sometimes referred to as "GPF") for a gasoline engine are known.

[0004] On the other hand, in addition to PM, exhaust gas also contains harmful components such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx). Harmful components can be removed from exhaust gas using a catalyst containing a catalyst metal disposed on the partition wall of the filter. In recent years, in order to remove both PM and harmful components from exhaust gas, an exhaust gas purification device in which a catalyst is disposed on a filter has been used.

[0005] As such an exhaust purification device, a device is known in which a catalyst is appropriately arranged in an internal area or surface of a cell side of a partition wall in an inlet side portion or an outlet side portion of the partition wall in order to ensure the purification performance of the exhaust gas and suppress the reduction of the PM capture rate and the suppression of the pressure loss. For example, Patent Document 1 describes an exhaust purification device, which comprises: an upstream catalyst layer, which is arranged inside the partition wall and arranged in an upstream side portion (inlet side portion) of an end portion of the exhaust gas inlet side including a substrate; and a downstream catalyst layer, which is arranged inside the partition wall and arranged in a downstream side portion (outlet side portion) of an end portion of the exhaust gas outflow side including a substrate, the upstream catalyst layer and the downstream catalyst layer contain at least one precious metal (catalyst metal) among Pt, Pd and Rh, and the type of precious metal contained in the upstream catalyst layer is different from the type of precious metal contained in the downstream catalyst layer. According to this device, by arranging the catalyst in the internal area of ​​the cell side of the partition wall, it is possible to achieve a reduction in pressure loss and significantly improve the exhaust purification performance.

[0006] Prior Art Literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2016-78016 Summary of the invention

[0009] In the past, in an exhaust purification device in which a catalyst is provided in a filter, for example, an exhaust purification device as described in Patent Document 1 has been attempted to improve the characteristics of pressure loss and purification performance by setting a suitable structure in which the catalyst is arranged in the internal area of ​​the pore chamber side of the next door. On the other hand, in recent years, in response to stricter fuel consumption restrictions than before in various regions of the world, various efforts have been made as internal combustion engines in addition to electrification. One of them is the miniaturization of exhaust volume. From the necessity of increasing the output per unit exhaust volume, the requirement for reducing the back pressure of the exhaust system has become higher. Under such circumstances, it is required to maintain the exhaust purification performance and PM capture performance, and to further reduce the pressure loss. However, in the previous structure in which the catalyst is arranged in the internal area of ​​the pore chamber side of the next door, the reduction in pressure loss is not sufficient.

[0010] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an exhaust gas purification device capable of reducing pressure loss and improving exhaust gas purification performance.

[0011] In order to solve the above-mentioned problems, the exhaust purification device of the present invention is characterized in that it has a honeycomb substrate and an outflow chamber side catalyst, the honeycomb substrate has a porous partition wall that divides a plurality of chambers extending from the inflow side end face to the outflow side end face, the plurality of chambers include an inflow chamber and an outflow chamber adjacent to each other across the partition wall, the inflow side end of the inflow chamber is open and the outflow side end is sealed, the inflow side end of the outflow chamber is sealed and the outflow side end is open, the outflow chamber side catalyst is arranged in an inner area of ​​the outflow chamber side of the partition wall in the outflow chamber side catalyst setting range extending from the outflow side end of the partition wall along the extension direction to the following position, the position is a position away from the outflow side end of the partition wall along the extension direction by a specified distance, the minimum value of the porosity of the outflow chamber side catalyst configuration wall in the thickness direction is within the range of more than 20% and less than 30%, and the outflow chamber side catalyst configuration wall includes the outflow chamber side catalyst setting range of the partition wall and the outflow chamber side catalyst.

[0012] According to the exhaust gas purification device of the present invention, it is possible to reduce pressure loss and improve exhaust gas purification performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a perspective view schematically showing the exhaust gas purification device according to the first embodiment.

[0014] Figure 2 This is a cross-sectional view schematically showing a main part of a cross section parallel to the extending direction of the cell in the exhaust purification device of the first embodiment.

[0015] Figure 3 It is a cross-sectional view schematically showing a main part of a cross section parallel to the extending direction of the cell in the exhaust purification device of the second embodiment.

[0016] Figure 4 It is a cross-sectional view schematically showing a main part of a cross section parallel to the extending direction of the cell in the exhaust purification device according to the third embodiment.

[0017] Figure 5 This is a cross-sectional image based on X-ray CT of a region between adjacent corners of an inlet cell in a cross section perpendicular to the extending direction at a reference position of the outflow cell-side catalyst arrangement wall of the exhaust purification device of Example 1.

[0018] Figure 6 This is a flowchart showing the steps of obtaining the minimum value of the porosity in the thickness direction at a reference position in the extending direction of the outflow cell side catalyst arrangement wall.

[0019] Figure 7This is a cross-sectional image showing a cross section perpendicular to the extending direction at one imaging position (reference position) in a reference region of the outflow cell-side catalyst arrangement wall of the exhaust purification device of the first embodiment.

[0020] Figure 8 It is a graph showing the relationship between the initial pressure loss and the maximum NOx purification rate obtained by the exhaust purification devices of Examples 1 and 2 and Comparative Examples 1 to 4 relative to the minimum value of the porosity in the thickness direction at the reference position in the extension direction of the catalyst configuration wall on the outflow cell side.

[0021] Description of Reference Numerals

[0022] 1: exhaust gas purification device, 10: honeycomb substrate, 10Sa: inflow side end surface, 10Sb: outflow side end surface, 11: frame, 12: cell, 12A: inflow cell, 12Aa: inflow side end, 12Ab: outflow side end, 12B: outflow cell, 12Ba: inflow side end, 12Bb: outflow side end, 14: partition wall, 14a: inflow side end, 14b: position away from the inflow side end by a predetermined distance in the extension direction, 14c: outflow cell side catalyst configuration wall in the extension direction Reference position, 14d: outflow side end, 14e: position away from the outflow side end by a specified distance along the extension direction, 14X: catalyst setting range on the inflow chamber side, 14Y: catalyst setting range on the outflow chamber side, 14SA: the surface of the partition wall on the inflow chamber side, 14NA: the inner area of ​​the partition wall on the inflow chamber side, 14SB: the surface of the partition wall on the outflow chamber side, 14NB: the inner area of ​​the partition wall on the outflow chamber side, 16: sealing part, 20: catalyst on the inflow chamber side, 30: catalyst on the outflow chamber side DETAILED DESCRIPTION

[0023] Hereinafter, embodiments of the exhaust gas purification device of the present invention will be described.

[0024] An exhaust purification device of an embodiment is characterized in that it has a honeycomb substrate and an outflow chamber side catalyst, the honeycomb substrate has a porous partition wall that divides a plurality of chambers extending from an inlet side end face to an outflow side end face, the plurality of chambers include an inflow chamber and an outflow chamber adjacent to each other across the partition wall, the inflow side end of the inflow chamber is open and the outflow side end is sealed, the inflow side end of the outflow chamber is sealed and the outflow side end is open, the outflow chamber side catalyst is arranged in an inner area of ​​the outflow chamber side of the outflow chamber within an outflow chamber side catalyst setting range extending from the outflow side end of the partition wall along an extension direction to a position away from the outflow side end of the partition wall by a specified distance along the extension direction, the minimum value of the porosity of the outflow chamber side catalyst setting range including the partition wall and the outflow chamber side catalyst configuration wall of the outflow chamber side catalyst in the thickness direction is within a range of greater than 20% and less than 30%.

[0025] In the exhaust purification device of the embodiment, the "inflow side" refers to the side of the exhaust purification device where the exhaust gas flows in, and the "outflow side" refers to the side of the exhaust purification device where the exhaust gas flows out. The "extension direction of the partition wall" refers to the direction in which the partition wall extends. The axial direction of the honeycomb substrate is usually roughly the same as the extension direction of the partition wall, and the extension direction of the cell (the direction in which the cell extends) is usually roughly the same as the extension direction of the partition wall. The "thickness direction of the partition wall" refers to the direction perpendicular to the surface of the partition wall on the cell (inflow cell and outflow cell) side of the partition wall. The "width direction of the partition wall" refers to the direction perpendicular to both the extension direction and the thickness direction of the partition wall. In the following description, the "extension direction" refers to the extension direction of the partition wall, which is roughly the same direction as the axial direction of the honeycomb substrate and the extension direction of the cell. The "thickness direction" refers to the thickness direction of the partition wall. The "width direction" refers to the width direction of the partition wall.

[0026] First, regarding the outline of the exhaust gas purification device according to the embodiment, the exhaust gas purification device according to the first to third embodiments will be described by way of example.

[0027] [First embodiment]

[0028] Figure 1 It is a perspective view schematically showing the exhaust gas purification device according to the first embodiment. Figure 2 This is a cross-sectional view schematically showing a main part of a cross section parallel to the extending direction of the cell in the exhaust purification device of the first embodiment.

[0029] like Figure 1 and Figure 2As shown, the exhaust gas purification device 1 of the first embodiment includes a honeycomb substrate 10, a sealing portion 16, an inflow cell side catalyst 20, and an outflow cell side catalyst 30. The honeycomb substrate 10 is a substrate formed by integrally forming a cylindrical frame portion 11 and a partition wall 14 that divides the space inside the frame portion 11 into a honeycomb shape. The partition wall 14 is a porous body that divides a plurality of cells 12 extending from the inflow side end face 10Sa of the honeycomb substrate 10 to the outflow side end face 10Sb. Regarding the shape of the partition wall 14, the partition wall 14 includes a plurality of wall portions 14A that are separated from each other and parallelly arranged in a manner that makes the cross-sectional shape of the plurality of cells 12 perpendicular to the extension direction become rectangular, and a plurality of wall portions 14B that are orthogonal to these plurality of wall portions 14A and are separated from each other and parallelly arranged, and the cross section perpendicular to the extension direction becomes a grid shape.

[0030] The plurality of cells 12 include an inlet cell 12A and an outlet cell 12B adjacent to each other via a partition wall 14. The inlet side end 12Aa of the inlet cell 12A is open, and the outlet side end 12Ab is sealed by a sealing portion 16, and the inlet side end 12Ba of the outlet cell 12B is sealed by a sealing portion 16, and the outlet side end 12Bb is open. The cross-sectional shape of the inlet cell 12A and the outlet cell 12B perpendicular to the extension direction is a rectangle with four corners.

[0031] The inflow cell side catalyst 20 is arranged on the partition wall surface 14SA on the inflow cell 12A side in the inflow cell side catalyst installation range 14X, which is a range extending from the inflow side end 14a of the partition wall 14 along the extension direction to a position 14b which is away from the inflow side end 14a of the partition wall 14 along the extension direction toward the outflow side by a distance of 50% of the length of the partition wall 14 in the extension direction. The inflow cell side catalyst 20 includes a powdered carrier, catalyst metal particles containing platinum (Pt) or palladium (Pd) supported on the carrier, and an OSC material.

[0032] The outflow cell side catalyst 30 is provided in a gap existing in the partition wall inner region 14NB on the outflow cell 12B side in the outflow cell side catalyst installation range 14Y, which is a range extending from the outflow side end 14d of the partition wall 14 along the extension direction to a position 14e which is away from the outflow side end 14d of the partition wall 14 along the extension direction toward the inflow side by a distance of 70% of the extension direction length of the partition wall 14. The outflow cell side catalyst 30 includes a powdered carrier, catalyst metal particles containing rhodium (Rh) supported on the carrier, and an OSC material.

[0033] The outflow cell side catalyst configuration wall is a wall including the outflow cell side catalyst installation range 14Y of the partition wall 14 and the outflow cell side catalyst 30. The reference position 14c of the outflow cell side catalyst configuration wall in the extension direction is a position close to the outflow side within a range that does not overlap with the configuration area of ​​the sealing portion 16 in the extension direction. Figure 2 In the white box of , a portion of a cross-sectional image obtained by photographing the region between the adjacent corners of the inflow cell 12A (outflow cell 12B) in the cross section perpendicular to the extension direction at the reference position 14c of the outflow cell side catalyst arrangement wall using X-ray CT is shown. In addition, a graph illustrating the change in the porosity in the thickness direction (Z direction) at the reference position 14c in the extension direction of the outflow cell side catalyst arrangement wall (the porosity of the outflow cell side catalyst arrangement wall in the thickness direction) is shown while showing a portion of the cross-sectional image.

[0034] like Figure 2 As shown in the white box, the minimum value of the porosity in the thickness direction at the reference position 14c in the extension direction of the catalyst configuration wall on the outflow chamber side (the minimum value of the porosity in the thickness direction of the catalyst configuration wall on the outflow chamber side) is within the range of 20% to 30%. The minimum value of the porosity in the thickness direction at the reference position 14c in the extension direction of the catalyst configuration wall on the outflow chamber side, specifically, the area between adjacent corners of the inflow chamber 12A (outflow chamber 12B) within the range of ±1 mm in the extension direction from the reference position 14c of the catalyst configuration wall on the outflow chamber side is taken as the reference area, and is the minimum value of the porosity (the proportion of voids) at each position in the thickness direction in the reference area of ​​the catalyst configuration wall on the outflow chamber side. Furthermore, the portion where the porosity in the thickness direction becomes minimum at the reference position 14c in the extension direction of the catalyst configuration wall on the outlet chamber side (the portion where the porosity in the thickness direction of the catalyst configuration wall on the outlet chamber side becomes minimum) is sometimes called a "neck".

[0035] In the exhaust purification device that is different from the exhaust purification device 1 of the first embodiment in that the minimum value of the porosity in the thickness direction at the reference position 14c of the outflow hole chamber side catalyst configuration wall is less than 20%, when the exhaust gas is about to pass through the outflow hole chamber side catalyst configuration wall from the inflow hole chamber 12A side to the outflow hole chamber 12B side in the thickness direction, the neck where the porosity in the thickness direction at the reference position 14c of the outflow hole chamber side catalyst configuration wall becomes the minimum value (less than 20%) may hinder the passage of the exhaust gas. As a result, the pressure loss may increase significantly. In addition, due to the excessively small porosity of the outflow hole chamber side catalyst configuration wall, the frequency of contact between the exhaust gas and the outflow hole chamber side catalyst 30 is insufficient, resulting in a decrease in the exhaust purification performance in the gas diffusion rate region.

[0036] On the other hand, in the exhaust purification device which is different from the exhaust purification device 1 of the first embodiment in that the minimum value of the porosity in the thickness direction at the reference position 14c of the outlet hole chamber side catalyst configuration wall exceeds 30%, the configuration amount of the outlet hole chamber side catalyst 30 in the outlet hole chamber side catalyst configuration wall is insufficient. Therefore, when the exhaust gas attempts to pass through the outlet hole chamber side catalyst configuration wall, the exhaust purification performance in the gas diffusion rate region may be significantly reduced due to the insufficient frequency of contact between the exhaust gas and the outlet hole chamber side catalyst 30.

[0037] In contrast, in the exhaust purification device 1 of the first embodiment, the minimum value of the porosity in the thickness direction at the reference position 14c of the outflow hole chamber side catalyst configuration wall is greater than 20%. As a result, when the exhaust gas is about to pass through the outflow hole chamber side catalyst configuration wall from the inflow hole chamber 12A side to the outflow hole chamber 12B side in the thickness direction, the passage of the exhaust gas will not be hindered in the entire area including the neck of the outflow hole chamber side catalyst configuration wall in the thickness direction. Therefore, a significant increase in pressure loss can be avoided. In addition, since the porosity of the outflow hole chamber side catalyst configuration wall is not too small, the frequency of contact between the exhaust gas and the outflow hole chamber side catalyst 30 will not be insufficient, and a reduction in the exhaust purification performance in the gas diffusion rate region can be avoided. Moreover, the minimum value of the porosity in the thickness direction at the reference position 14c of the outflow hole chamber side is less than 30%. As a result, the amount of the outflow cell side catalyst 30 in the outflow cell side catalyst arrangement wall is sufficient, so when the exhaust gas is about to pass through the outflow cell side catalyst arrangement wall, the exhaust gas contacts the outflow cell side catalyst 30 with sufficient frequency. Therefore, it is possible to avoid a significant reduction in the exhaust gas purification performance in the gas diffusion rate region.

[0038] [Second embodiment]

[0039] Figure 3 It is a cross-sectional view schematically showing a main part of a cross section parallel to the extending direction of the cell in the exhaust purification device of the second embodiment.

[0040] like Figure 3As shown, the exhaust gas purification device 1 of the second embodiment is provided with the honeycomb substrate 10, the sealing portion 16 and the outflow cell side catalyst 30 similar to the first embodiment, and is also provided with the inflow cell side catalyst 20 different from the first embodiment. The inflow cell side catalyst 20 is arranged in the partition wall internal area 14NA on the inflow cell 12A side in the inflow cell side catalyst setting range 14X of the partition wall 14 similar to the first embodiment. The inflow cell side catalyst 20 includes a powdered carrier, catalyst metal particles containing platinum (Pt) or palladium (Pd) supported on the carrier, and an OSC material. In such an exhaust gas purification device 1, by having the honeycomb substrate 10 and the outflow cell side catalyst 30 similar to the first embodiment, the minimum value of the porosity in the thickness direction at the reference position 14c in the extension direction of the outflow cell side catalyst configuration wall is within the range of 20% or more and 30% or less, similar to the first embodiment. Thus, similarly to the first embodiment, when the exhaust gas is about to pass through the outlet cell side catalyst arrangement wall from the inlet cell 12A side to the outlet cell 12B side in the thickness direction, the exhaust gas is not blocked from passing through the entire region including the neck of the outlet cell side catalyst arrangement wall in the thickness direction, and the exhaust gas contacts the outlet cell side catalyst 30 with sufficient frequency. Therefore, a significant increase in pressure loss can be avoided, and a significant decrease in exhaust gas purification performance in the gas diffusion rate region can be avoided.

[0041] [Third Embodiment]

[0042] Figure 4 It is a cross-sectional view schematically showing a main part of a cross section parallel to the extending direction of the cell in the exhaust purification device according to the third embodiment.

[0043] like Figure 4 As shown, the exhaust gas purification device 1 of the third embodiment includes the honeycomb substrate 10, the sealing portion 16, and the outflow cell side catalyst 30 similar to those of the first embodiment, but unlike the first embodiment, does not include the inflow cell side catalyst 20. In such an exhaust gas purification device 1, by including the honeycomb substrate 10 and the outflow cell side catalyst 30 similar to those of the first embodiment, the minimum value of the porosity in the thickness direction at the reference position 14c in the extension direction of the outflow cell side catalyst arrangement wall is within the range of 20% or more and 30% or less, similar to the first embodiment. Therefore, similar to the first embodiment, when the exhaust gas is about to pass through the outflow cell side catalyst arrangement wall from the inflow cell 12A side to the outflow cell 12B side in the thickness direction, the exhaust gas is not blocked in the entire region including the neck of the outflow cell side catalyst arrangement wall in the thickness direction, and the exhaust gas contacts the outflow cell side catalyst 30 with sufficient frequency. Therefore, it is possible to avoid a significant increase in pressure loss and a significant decrease in exhaust gas purification performance in the gas diffusion rate region.

[0044] Therefore, according to the exhaust gas purification device of the embodiment, for example, as in the first to third embodiments, it is possible to reduce pressure loss and improve exhaust gas purification performance. Next, the details of each structure of the exhaust gas purification device of the embodiment will be described.

[0045] 1. Honeycomb substrate

[0046] The honeycomb substrate has a porous partition wall that divides a plurality of cells extending from the inlet side end face to the outlet side end face. Moreover, the plurality of cells include an inlet cell and an outlet cell that are adjacent to each other across the partition wall, the inlet side end of the inlet cell is open and the outlet side end is sealed, and the inlet side end of the outlet cell is sealed and the outlet side end is open. The honeycomb substrate is a so-called wall-flow type honeycomb substrate, which is a substrate formed integrally of a frame portion and a partition wall that divides the space inside the frame portion into a honeycomb shape.

[0047] The axial length of the honeycomb substrate is not particularly limited, and a general length can be used, but for example, it is preferably in the range of 10 mm to 500 mm, and particularly preferably in the range of 50 mm to 300 mm. The capacity of the honeycomb substrate, that is, the total volume of the cells, is not particularly limited, and a general capacity can be used, for example, it is preferably in the range of 0.1 L to 5 L.

[0048] The material of the honeycomb substrate is not particularly limited, and general materials can be used, and examples thereof include ceramics such as cordierite, silicon carbide (SiC), and aluminum titanate, and alloys such as stainless steel.

[0049] The shape of the frame is not particularly limited, and a general shape can be used, for example, in addition to a cylindrical shape, there can be mentioned cylindrical shapes such as an elliptical cylindrical shape and a polygonal cylindrical shape. The other structures of the frame are not particularly limited, and a general structure can be used.

[0050] The shape of the partition wall is not particularly limited, and a general shape can be used, but it usually includes a plurality of wall portions extending in the extension direction in a manner such that the cross-sections of the plurality of cells perpendicular to the extension direction have the desired shape, and other plurality of wall portions extending in the extension direction and separated from each other and arranged in parallel, intersecting with the plurality of wall portions and extending in the extension direction. The length of the partition wall in the extension direction is not particularly limited, but it is usually approximately the same as the axial length of the honeycomb substrate. The thickness of the partition wall is not particularly limited, and a general thickness can be used, but for example, it is preferably within the range of 50 μm or more and 2000 μm or less, and particularly preferably within the range of 100 μm or more and 300 μm or less. This is because, by having the thickness of the partition wall within these ranges, the strength of the substrate can be ensured, and sufficient PM capture performance can be obtained, and the pressure loss can be sufficiently suppressed.

[0051] The partition wall is a porous structure containing voids consisting of pores through which exhaust gas can pass. The porosity of the partition wall (the porosity of the partition wall monomer) is not particularly limited, and a general porosity can be used, but for example, it is preferably in the range of 40% to 70%, and particularly preferably in the range of 50% to 70%. This is because, by having a porosity above the lower limit of these ranges, pressure loss can be effectively suppressed, and by having a porosity below the upper limit of these ranges, sufficient mechanical strength can be ensured. The average pore diameter of the voids of the partition wall (the average pore diameter of the voids of the partition wall monomer) is not particularly limited, and a general average pore diameter can be used, but for example, it is preferably in the range of 1 μm to 60 μm, and particularly preferably in the range of 5 μm to 30 μm, and particularly preferably in the range of 5 μm to 20 μm. This is because, by having an average pore diameter of the voids within these ranges, sufficient PM capture performance can be obtained and pressure loss can be sufficiently suppressed. In addition, "the average pore diameter of the voids in the cell walls" refers to the average pore diameter measured by mercury penetration, for example.

[0052] The inlet cell and the outlet cell are formed by partitioning the inner space of the frame portion by the partition wall, and are adjacent to each other via the partition wall. Usually, the inlet cell and the outlet cell are surrounded by the partition wall in a direction perpendicular to the extending direction.

[0053] Typically, the outflow side end of the inflow hole chamber is sealed by a sealing portion. Typically, the inflow side end of the outflow hole chamber is sealed by a sealing portion. The length of the sealing portion in the extension direction is not particularly limited, and can be a general length, but for example, it is preferably within the range of more than 2 mm and less than 20 mm, and particularly preferably within the range of more than 2 mm and less than 10 mm. The material of the sealing portion is not particularly limited, and can be a general material.

[0054] The cross-sectional shape of the inlet and outlet chambers perpendicular to the extension direction is not particularly limited, and general shapes can be used, and can be appropriately set in consideration of the flow rate and composition of the exhaust gas passing through the exhaust purification device. Examples of cross-sectional shapes include rectangles such as squares, polygons including hexagons, and circles. The cross-sectional area of ​​the inlet and outlet chambers perpendicular to the extension direction is not particularly limited, and general cross-sectional areas can be used, such as 1 mm 2 Above and 7mm 2 The length of the inlet cell and the outlet cell in the extension direction is not particularly limited, but is generally substantially the same as the length obtained by subtracting the length of the sealing portion in the extension direction from the axial length of the honeycomb substrate. As an arrangement of the inlet cell and the outlet cell, for example, a checkered pattern of alternately arranging the inlet cell and the outlet cell as in the arrangement of the first embodiment can be cited.

[0055] 2. Catalyst on the outflow chamber side and catalyst configuration wall on the outflow chamber side

[0056] The outflow hole chamber side catalyst is arranged in the inner region of the outflow hole chamber side of the outflow hole chamber in the outflow hole chamber side catalyst setting range extending from the outflow side end of the outflow hole chamber along the extension direction to a position away from the outflow side end of the outflow hole chamber along the extension direction by a predetermined distance (the gap existing in the inner region of the outflow hole chamber). The minimum value of the porosity in the thickness direction of the outflow hole chamber side catalyst setting range including the outflow hole chamber side catalyst and the outflow hole chamber side catalyst configuration wall of the outflow hole chamber side catalyst is within the range of more than 20% and less than 30%. By making the minimum value of the porosity greater than the lower limit of the range, the pressure loss can be reduced, and by making the minimum value of the porosity less than the upper limit of the range, the exhaust purification performance can be improved.

[0057] The range of the catalyst installation on the outlet hole chamber side of the partition wall is not particularly limited as long as it is a region extending from the outlet side end of the partition wall along the extension direction to a position away from the outlet side end of the partition wall along the extension direction to the inflow side by a predetermined distance, but for example, as in the first to third embodiments, it is preferably a region extending from the outlet side end of the partition wall along the extension direction to a position away from the outlet side end of the partition wall along the extension direction to the inflow side by a distance of more than 50% and less than 100% of the length of the partition wall in the extension direction, and is particularly preferably a region extending to a position away from a distance of more than 55% and less than 90% of the length of the partition wall in the extension direction, and is particularly preferably a region extending to a position away from a distance of more than 60% and less than 80% of the length of the partition wall in the extension direction. This is because, by having the length of the extension direction of the catalyst installation range on the outlet hole chamber side (the length of the catalyst on the outlet hole chamber side in the extension direction) being within the range of these distances, the pressure loss can be effectively reduced, and the exhaust purification performance can be effectively improved.

[0058] The outflow hole chamber side catalyst configuration wall is a wall including the outflow hole chamber side catalyst setting range of the next wall and the outflow hole chamber side catalyst. That is, the outflow hole chamber side catalyst configuration wall is a catalyst configuration wall provided with the outflow hole chamber side catalyst in the outflow hole chamber side catalyst setting range of the next wall. The porosity of the outflow hole chamber side catalyst configuration wall is smaller than the porosity of the next wall monomer by the amount of reduction caused by filling the outflow hole chamber side catalyst into the gap of the next wall monomer.

[0059] “The minimum value of the porosity in the thickness direction of the catalyst configuration wall on the outlet chamber side” refers, for example, to the minimum value of the porosity in the thickness direction at the reference position in the extension direction of the catalyst configuration wall on the outlet chamber side. The reference position of the catalyst configuration wall on the outlet chamber side is not particularly limited as long as it is any position in the extension direction of the catalyst configuration wall on the outlet chamber side, but it is preferably a position as close to the outlet side as possible within a range that does not overlap with the configuration area of ​​the sealing portion that seals the outlet side end of the inflow chamber in the extension direction. Since the porosity in the thickness direction at such a position has a great influence on the pressure loss and the exhaust purification performance, by setting the minimum value of the porosity to be greater than 20% and less than 30%, the pressure loss can be effectively reduced and the exhaust purification performance can be effectively improved.

[0060] As a method for obtaining the minimum value of the porosity in the thickness direction at a reference position in the extension direction of the catalyst configuration wall on the outflow hole chamber side, for example, the following method can be cited: the area between the adjacent corners of the inflow hole chamber (outflow hole chamber) in the range of ±1 mm in the extension direction from the reference position of the catalyst configuration wall on the outflow hole chamber side (limited to the range included in the catalyst configuration wall on the outflow hole chamber side) is taken as the reference area, the porosity at each position in the thickness direction in the reference area of ​​the catalyst configuration wall on the outflow hole chamber side is measured, and the minimum value among the measured values ​​of these porosities is taken as the minimum value of the porosity. Furthermore, as the porosity at each position in the thickness direction in the reference area of ​​the catalyst configuration wall on the outflow hole chamber side, for example, it can also be the ratio of the area of ​​the voids to the total area of ​​the cross section perpendicular to the thickness direction at each position in the thickness direction in the reference area of ​​the catalyst configuration wall on the outflow hole chamber side.

[0061] As the outflow cell side catalyst configuration wall, there is no particular limitation as long as the minimum value of the porosity in the thickness direction at the reference position in the extension direction of the outflow cell side catalyst configuration wall is within the range of 20% to 30%, but it is preferably an outflow cell side catalyst configuration wall in which the average value of the minimum value of the porosity in the thickness direction at different multiple calculated positions in the extension direction of the outflow cell side catalyst configuration wall is within the range of 20% to 30%. This is because it can effectively reduce the pressure loss and effectively improve the exhaust purification performance. As the different multiple calculated positions, there is no particular limitation as long as they are any multiple positions in the extension direction of the outflow cell side catalyst configuration wall, but for example, it is preferably a plurality of positions arranged at equal intervals in the extension direction, including a position as close to the outflow side as possible within the range that does not overlap with the configuration area of ​​the sealing portion that seals the outflow side end of the inflow cell in the extension direction and a position of the inflow side end of the outflow cell side catalyst configuration wall in the extension direction. Furthermore, as a method for obtaining the minimum value of the void ratio in the thickness direction at each calculated position in the extension direction of the outflow hole chamber side catalyst configuration wall, for example, the following method can be cited: the area between the adjacent corners of the inflow hole chamber (outflow hole chamber) in the range of ±1 mm in the extension direction from each calculated position of the outflow hole chamber side catalyst configuration wall (limited to the range included in the outflow hole chamber side catalyst configuration wall) is taken as the calculation area, the void ratio at each position in the thickness direction in the calculation area of ​​the outflow hole chamber side catalyst configuration wall is measured, and the minimum value among the measured values ​​of the void ratio is taken as the minimum value of the void ratio. Furthermore, as the void ratio at each position in the thickness direction in the calculation area of ​​the outflow hole chamber side catalyst configuration wall, for example, it can also be the ratio of the area of ​​the voids to the total area of ​​the cross section perpendicular to the thickness direction at each position in the thickness direction in the calculation area of ​​the outflow hole chamber side catalyst configuration wall. In addition, as the outflow hole chamber side catalyst configuration wall, it is preferred that the outflow hole chamber side catalyst configuration wall has a minimum porosity in the thickness direction in the overall extension direction of the outflow hole chamber side catalyst configuration wall within the range of 20% to 30%. This is because it can effectively reduce pressure loss and effectively improve exhaust purification performance. Furthermore, as a method for obtaining the minimum porosity in the thickness direction in the overall extension direction of the outflow hole chamber side catalyst configuration wall, the following method can be cited: the area between adjacent corners of the inflow hole chamber (outflow hole chamber) in the overall extension direction of the outflow hole chamber side catalyst configuration wall is used as the calculation area in the overall extension direction of the outflow hole chamber side catalyst configuration wall, the porosity at each position in the thickness direction in the calculation area in the overall extension direction of the outflow hole chamber side catalyst configuration wall is measured, and the minimum value among these measured values ​​of the porosity is obtained as the minimum value of the porosity.Furthermore, the porosity at each position in the thickness direction in the calculated area in the overall extension direction of the catalyst configuration wall on the outlet hole chamber side may be, for example, the ratio of the area of ​​the voids to the total area of ​​the cross section perpendicular to the thickness direction at each position in the thickness direction in the calculated area in the overall extension direction of the catalyst configuration wall on the outlet hole chamber side.

[0062] The outflow cell side catalyst generally includes catalyst metal particles and a carrier that supports the catalyst metal particles. The outflow cell side catalyst is, for example, a sintered body with a catalyst carrier in which the catalyst metal particles are supported on the carrier.

[0063] The material of the catalyst metal particles is not particularly limited, and general materials can be used, for example, catalyst metals such as platinum (Pt), palladium (Pd), and rhodium (Rh). The material of the catalyst metal particles can be one metal or two or more metals, or an alloy containing two or more metals. As the material of the catalyst metal particles, rhodium is preferred.

[0064] The average particle size of the catalyst metal particles is not particularly limited, and a general average particle size can be used, but it is preferably within a range of 0.1 nm or more and 20 nm or less, for example. This is because the contact area with the exhaust gas can be increased by making the average particle size below the upper limit of the range. In addition, the average particle size of the catalyst metal particles refers to an average value calculated from the particle size measured using a transmission electron microscope (TEM), for example.

[0065] The content of the catalyst metal particles is not particularly limited, and a general content can be used, but it varies according to the material of the catalyst metal particles. For example, when the material is at least one of Pt, Pd and Rh, it is preferably in the range of 0.01 g or more and 2 g or less per 1L of honeycomb substrate. When the content is above the lower limit of the range, a sufficient catalytic effect can be obtained, and when the content is below the upper limit of the range, the particle growth of the catalyst metal particles can be suppressed, and it becomes advantageous in terms of cost. Here, the content of the catalyst metal particles per 1L volume of the substrate refers to the value obtained by dividing the mass of the catalyst metal particles contained in the outflow cell side catalyst by the volume of a part of the axial direction of the honeycomb substrate having the same axial length as the length of the outflow cell side catalyst in the extension direction.

[0066] The material of the carrier is not particularly limited, and general materials can be used, but for example, metal oxides such as aluminum oxide (Al2O3), ceria (CeO2), zirconium oxide (ZrO2), silicon dioxide (SiO2), magnesium oxide (MgO), titanium oxide (TiO2), such as solid solutions such as aluminum oxide-zirconia (Al2O3-ZrO2) composite oxides, ceria-zirconia (CeO2-ZrO2) composite oxides, etc. can be listed. As the material of the carrier, it can be one of them, or it can be two or more of them. As the material of the carrier, at least one of aluminum oxide and ceria-zirconia composite oxides, etc. is preferred.

[0067] The shape of the carrier is not particularly limited, and a general shape can be used, but a powdered shape is preferred. This is because a larger specific surface area can be ensured. The average particle size D50 of the powdered carrier is not particularly limited, and can be a general average particle size, but for example, it is preferably in the range of 1 μm or more and 15 μm or less, and particularly preferably in the range of 4 μm or more and 10 μm or less. This is because, by having an average particle size D50 above the lower limit of these ranges, sufficient heat resistance can be obtained. This is because, by having an average particle size D50 below the upper limit of these ranges, the dispersibility of the catalyst metal particles can be fully ensured, thereby effectively improving the purification performance. Furthermore, the average particle size D50 of the powdered carrier is obtained, for example, by a laser diffraction / scattering method, and can be measured, for example, by using a laser diffraction / scattering particle size distribution measuring device LA-960 (manufactured by Horiba, Ltd.).

[0068] The mass ratio of the mass of the catalyst metal particles to the total mass of the catalyst metal particles and the carrier is not particularly limited, and a general mass ratio can be used, but for example, it is preferably in the range of 0.01 mass % or more and 10 mass % or less. This is because, by having a mass ratio of more than the lower limit of the range, a sufficient catalytic effect can be obtained. This is because, by having a mass ratio of less than the upper limit of the range, the particle growth of the catalyst metal particles can be suppressed, and it is advantageous in terms of cost.

[0069] The method for loading the catalyst metal particles on the carrier is not particularly limited, and general methods can be used, but examples thereof include: immersing the carrier in an aqueous solution containing a catalyst metal salt (such as nitrates, etc.) or a catalyst metal complex (such as a tetraamine complex, etc.), drying it, and calcining it.

[0070] The outflow cell side catalyst may contain, in addition to the catalyst metal particles and the carrier, a promoter such as an OSC (Oxygen Storage Capacity) material.

[0071] The material of the co-catalyst is not particularly limited, and may be a general material, but for example, the same material as the carrier can be cited. Among the co-catalysts, the materials of the OSC material in particular can be, for example, ceria, composite oxides containing ceria, etc. As composite oxides containing ceria, for example, ceria-zirconia composite oxides, etc. can be cited. The shape of the co-catalyst is not particularly limited, and may be a general shape, but for example, the same shape as the carrier can be cited. The average particle size D50 of the powdered co-catalyst is not particularly limited, and may be a general average particle size, but for example, the same average particle size as the powdered carrier can be cited. The mass ratio of the mass of the co-catalyst to the total mass of the catalyst metal particles, the carrier and the co-catalyst is not particularly limited, and a general mass ratio can be used, but for example, it is preferably in the range of 30% by mass or more and 80% by mass or less.

[0072] The density of the outflow hole chamber side catalyst is not particularly limited, but for example, it is preferably in the range of 5 g / L or more and 100 g / L or less, particularly preferably in the range of 10 g / L or more and 65 g / L or less, and particularly preferably in the range of 30 g / L or more and 60 g / L or less. This is because the purification performance can be effectively improved by making the density of the outflow hole chamber side catalyst above the lower limit of the range. This is because the pressure loss can be effectively suppressed by making the density of the outflow hole chamber side catalyst below the upper limit of the range. Furthermore, the "density of the outflow hole chamber side catalyst" refers to the mass of the outflow hole chamber side catalyst divided by the volume of the axial part of the honeycomb substrate having the same axial length as the length of the outflow hole chamber side catalyst in the extension direction.

[0073] The method for forming the catalyst on the outlet hole chamber side is not particularly limited, and a general method can be used, but for example, the following method can be listed: a slurry prepared by mixing catalyst metal particles and a carrier for supporting the catalyst metal particles in a solvent is supplied to the inner area of ​​the outlet hole chamber side of the outlet hole chamber within the catalyst setting range of the outlet hole chamber side of the outlet hole chamber, and then dried and calcined.

[0074] In the method of forming the outflow cell side catalyst by supplying the slurry to the partition wall, drying it, and calcining it, the slurry may contain any components such as a co-catalyst, a binder, and an additive in addition to the catalyst metal particles, the carrier, and the solvent. The average particle size of the solid components such as the powdered carrier and the co-catalyst contained in the slurry may be appropriately adjusted so that the slurry penetrates into the inner area of ​​the outflow cell side of the partition wall within the range where the outflow cell side catalyst of the partition wall is set.

[0075] The preparation method of the slurry is not particularly limited, and can be a general method, but for example, the following method can be cited. First, after the powdered carrier is impregnated in a solution (such as an aqueous solution) containing a catalyst metal salt or a catalyst metal complex, they are dried and calcined to prepare a catalyst metal-supported powder carrying the catalyst metal. Then, OSC material, a co-catalyst, a binder and ion exchange water are added to the catalyst metal-supported powder, which are fully stirred and wet-pulverized so that the average particle size D50 of the solid component becomes the desired value. Thus, a slurry is prepared.

[0076] The average particle size D50 of the solid content of the slurry is not particularly limited and may be a general average particle size. The average particle size D50 of the solid content of the slurry can be measured, for example, by using a laser diffraction / scattering particle size distribution measuring device LA-960 (manufactured by Horiba, Ltd.).

[0077] As a method for supplying the slurry to the inner area of ​​the next door on the outflow hole chamber side in the catalyst setting range of the outflow hole chamber side of the next door, there is no particular limitation, and it can be a general method, but for example, the following method can be cited: immersing the honeycomb substrate in the slurry from the outflow side, and taking it out from the slurry after a predetermined time. In this method, the solid content concentration, viscosity and other properties of the slurry can be appropriately adjusted so that the slurry is supplied to the inner area of ​​the next door on the outflow hole chamber side in the catalyst setting range of the outflow hole chamber side of the next door. As a method for supplying the slurry to the inner area of ​​the next door on the outflow hole chamber side in the catalyst setting range of the outflow hole chamber side of the next door, a method can be used in which a blower is used to blow off the slurry when supplying the slurry so that the slurry is not supplied to the inner area of ​​the next door and the part on the surface where the catalyst is not required.

[0078] In the method of drying and firing the slurry after supplying it to the partition wall, the drying conditions are not particularly limited, and are affected by the shape and size of the honeycomb substrate, the carrier, etc., but for example, it is preferably a condition of drying for a time in the range of 1 hour to 10 hours at a temperature in the range of 80°C to 300°C. The firing conditions are not particularly limited, but for example, it is preferably a condition of firing for a time in the range of 1 hour to 4 hours at a temperature in the range of 400°C to 1000°C.

[0079] The minimum value of the porosity of the catalyst configuration wall on the outlet chamber side in the thickness direction, the thickness of the catalyst on the outlet chamber side, the porosity of the catalyst on the outlet chamber side, etc., can be adjusted by, for example, adjusting the average particle size D50 of the solid component of the slurry, the solid component concentration of the slurry, the properties of the slurry, the supply amount of the slurry, the drying conditions, the calcination conditions, etc.

[0080] 3. Exhaust purification device

[0081] The exhaust gas purification device includes a honeycomb substrate and an outflow cell-side catalyst. The exhaust gas purification device generally further includes a sealing portion that seals the outflow-side end of the inflow cell and a sealing portion that seals the inflow-side end of the outflow cell.

[0082] (1) Catalyst on the inflow chamber side

[0083] The exhaust purification device may also include an inlet chamber side catalyst arranged in an inlet chamber side catalyst setting range extending from the inlet side end of the partition wall along the extension direction to a position away from the inlet side end of the partition wall along the extension direction by a predetermined distance as in the first and second embodiments, or may not include an inlet chamber side catalyst as in the third embodiment. In the exhaust purification device, regardless of the presence or absence of an inlet chamber side catalyst, when the exhaust gas is about to pass through the outlet chamber side catalyst configuration wall from the inlet chamber side to the outlet chamber side in the thickness direction, whether the passage of the exhaust gas is obstructed at the neck has a great influence on the pressure loss. Moreover, regardless of the presence or absence of an inlet chamber side catalyst, the configuration amount of the outlet chamber side catalyst in the outlet chamber side catalyst configuration wall affects the exhaust purification performance. Therefore, regardless of the presence or absence of an inlet chamber side catalyst, the effect of reducing the pressure loss and improving the exhaust purification performance can be obtained.

[0084] The inflow cell side catalyst is provided on at least one of the inflow cell side partition wall surface in the inflow cell side catalyst provision range of the partition wall and the inflow cell side partition wall internal region (voids present in the internal region).

[0085] The catalyst setting range on the inflow chamber side of the partition wall is not particularly limited as long as it is an area extending from the inflow side end of the partition wall along the extension direction to a position away from the inflow side end of the partition wall along the extension direction to the outflow side by a predetermined distance, but for example, it is preferably an area extending along the extension direction to a position overlapping with the catalyst setting range on the outflow chamber side, and an area extending from the inflow side end of the partition wall along the extension direction to a position away from the inflow side end of the partition wall along the extension direction to the outflow side by a distance of less than 80% of the length of the extension direction of the partition wall. This is because, by extending the catalyst setting range on the inflow chamber side to a position overlapping with the catalyst setting range on the outflow chamber side, it is possible to suppress the exhaust gas from passing through the area of ​​the partition wall where the catalyst is not set and being discharged from the exhaust gas purification device in an unpurified state. This is because, by the length of the extension direction of the catalyst setting range on the inflow chamber side (the length of the catalyst on the inflow chamber side) being less than 80% of the length of the partition wall in the extension direction, it is possible to suppress the increase in pressure loss.

[0086] The cell-inflow side catalyst generally includes catalyst metal particles and a carrier that supports the catalyst metal particles. The cell-inflow side catalyst is, for example, a sintered body with a catalyst carrier in which the catalyst metal particles are supported on the carrier.

[0087] The material of the catalyst metal particles is the same as that of the catalyst metal particles contained in the outflow cell side catalyst, except that it is preferably at least one of platinum and palladium. The average particle size of the catalyst metal particles is the same as that of the catalyst metal particles contained in the outflow cell side catalyst.

[0088] The content of the catalyst metal particles is not particularly limited, and a general content can be used, but it varies according to the material of the catalyst metal particles. For example, when the material is at least one of Pt, Pd and Rh, it is preferably within the range of 0.05 g or more and 5 g or less per 1L of honeycomb substrate. This is because, by having a content above the lower limit of the range, a sufficient catalytic effect can be obtained, and by having a content below the upper limit of the range, the particle growth of the catalyst metal particles can be suppressed, and at the same time, it becomes advantageous in terms of cost. Here, the content of the catalyst metal particles per 1L volume of the substrate refers to the value obtained by dividing the mass of the catalyst metal particles contained in the inflow cell side catalyst by the volume of a portion of the honeycomb substrate in the axial direction having the same length as the length of the inflow cell side catalyst in the extension direction.

[0089] The material and shape of the carrier are the same as those of the carrier contained in the outflow pore chamber side catalyst. The average particle size D50 of the powdered carrier is not particularly limited and can be a general average particle size. The mass ratio of the mass of the catalyst metal particles to the total mass of the catalyst metal particles and the carrier is the same as that of the outflow pore chamber side catalyst. The method of making the catalyst metal particles supported on the carrier is the same as that in the outflow pore chamber side catalyst. The inflow pore chamber side catalyst can contain a co-catalyst, etc., like the outflow pore chamber side catalyst. Regarding the co-catalyst, it is the same as the co-catalyst contained in the outflow pore chamber side catalyst.

[0090] The density of the inflow hole side catalyst is not particularly limited, but is preferably within the range of 5 g / L or more and 100 g / L or less, particularly preferably within the range of 10 g / L or more and 65 g / L or less, and particularly preferably within the range of 10 g / L or more and 30 g / L or less. This is because, by making the density of the inflow hole side catalyst above the lower limit of these ranges, the exhaust gas can be effectively purified using the inflow hole side catalyst. In addition, this is because, by making the density of the inflow hole chamber side catalyst below the upper limit of these ranges, the increase in pressure loss can be effectively suppressed. Furthermore, the "density of the inflow hole chamber side catalyst" refers to the value obtained by dividing the mass of the inflow hole chamber side catalyst by the volume of the axial part of the honeycomb substrate whose axial length is the same as the length of the inflow hole chamber side catalyst in the extension direction.

[0091] The method for forming the catalyst on the inflow chamber side is not particularly limited and can be a general method, but for example the following method can be listed: a slurry prepared by mixing catalyst metal particles and a carrier supporting the catalyst metal particles in a solvent is supplied to at least one of the surface of the partition wall on the inflow chamber side within the catalyst setting range of the inflow chamber side of the partition wall and the internal area of ​​the partition wall on the inflow chamber side, and then dried and calcined.

[0092] In the method of forming the inflow cell side catalyst by drying and calcining the slurry after supplying it to the next wall, the slurry may also appropriately contain any components such as a co-catalyst, a binder, and an additive in addition to the catalyst metal particles, the carrier, and the solvent. The average particle size of the solid components such as the powdered carrier and the co-catalyst contained in the slurry, for example, in the case where the inflow cell side catalyst is mainly formed on the surface of the next wall on the inflow cell side of the next wall as in the first embodiment, it can be appropriately adjusted so that the slurry is not impregnated into the next wall internal area. In addition, for example, in the case where the inflow cell side catalyst is mainly formed on the next wall internal area on the inflow cell side of the next wall as in the second embodiment, it can be appropriately adjusted so that the slurry is impregnated into the next wall internal area. As a preparation method of the slurry, it is the same as the preparation method of the slurry used in the formation of the outflow cell side catalyst. The average particle size D50 of the solid components of the slurry is not particularly limited and can be a general average particle size.

[0093] As a method for supplying the slurry to at least one of the surface of the wall on the inflow cell side and the internal area of ​​the wall on the inflow cell side in the range of the catalyst on the inflow cell side of the next wall, there is no particular limitation, and it can be a general method, but for example, the following method can be cited: immersing the honeycomb substrate in the slurry from the inflow side, and taking it out from the slurry after a predetermined time. In this method, for example, in the case where the inflow cell side catalyst is mainly formed on the surface of the wall on the inflow cell side of the next wall, the solid content concentration, viscosity and other properties of the slurry can be appropriately adjusted so that the slurry is not supplied to the internal area of ​​the next wall, and the outflow cell can be pressurized from the outflow side to generate a pressure difference between the outflow cell and the inflow cell. In addition, for example, in the case where the inflow cell side catalyst is mainly formed in the internal area of ​​the wall on the inflow cell side of the next wall, the solid content concentration, viscosity and other properties of the slurry can be appropriately adjusted so that the slurry is supplied to the internal area of ​​the wall on the inflow cell side of the next wall. In addition, in a method of supplying slurry to at least one of the surface of the partition wall on the inflow chamber side and the internal area of ​​the partition wall on the inflow chamber side within the catalyst setting range of the inflow chamber side of the partition wall, a method of using a blower to blow off the slurry when supplying the slurry can be used so that the slurry is not supplied to the portion of the partition wall surface and the internal area of ​​the partition wall where the catalyst is not required.

[0094] The drying conditions and the calcining conditions in the method of supplying the slurry to the partition walls, drying it, and then calcining it are the same as the drying conditions and the calcining conditions used in forming the outflow cell side catalyst.

[0095] The thickness of the catalyst on the inflow chamber side, the porosity of the catalyst on the inflow chamber side, the setting range of the catalyst on the inflow chamber side including the partition wall, and the porosity of the catalyst configuration wall on the inflow chamber side of the catalyst on the inflow chamber side can be adjusted, for example, by adjusting the average particle size D50 of the solid component of the slurry, the solid component concentration of the slurry, the properties of the slurry, the supply amount of the slurry, the drying conditions, the calcination conditions, etc.

[0096] (2) Others

[0097] In the case where the exhaust gas purification device further includes an inflow cell side catalyst, the exhaust gas purification device is preferably an exhaust gas purification device in which the catalyst metal particles contained in the inflow cell side catalyst contain at least one of platinum (Pt) and palladium (Pd), and the catalyst metal particles contained in the outflow cell side catalyst contain rhodium (Rh) as in the first embodiment. This is because after hydrocarbons (HC) contained in the exhaust gas are effectively purified by the catalyst metal particles contained in the inflow cell side catalyst, the exhaust gas contacts the outflow cell side catalyst, so that the rhodium (Rh) contained in the catalyst metal particles contained in the outflow cell side catalyst can be suppressed from being poisoned by hydrocarbons (HC).

[0098] [Example]

[0099] Hereinafter, the exhaust gas purification device according to the embodiment will be described in more detail with reference to examples and comparative examples.

[0100] [Example 1]

[0101] An example of the exhaust gas purification device of the first embodiment was produced. Specifically, first, a GPF including the honeycomb substrate 10 and the sealing portion 16 and not provided with a catalyst was prepared. The details of the configuration of the honeycomb substrate 10 and the sealing portion 16 of the GPF are as follows.

[0102] (Constitution of Honeycomb Base Material and Sealing Section)

[0103] Honeycomb substrate material: Cordierite

[0104] Honeycomb substrate dimensions: outer diameter x axial length = 117 mm x 122 mm

[0105] Thickness of the partition wall: 240 μm

[0106] The void ratio of the partition wall (void ratio of the partition wall alone): 61%

[0107] Average pore diameter of voids in partition walls (average pore diameter of voids in partition walls alone): 7 μm

[0108] Cell density: 200 per square inch

[0109] Length of the seal in the extension direction: 5 mm

[0110] Next, a catalyst carrier with catalyst metal particles loaded on a powdered carrier is mixed with a solvent to prepare a slurry for the catalyst flowing into the pore chamber side. Specifically, after the powdered alumina (carrier) is immersed in an aqueous solution containing Pt nitrate (catalyst metal salt), they are dried and calcined to prepare a Pt-loaded powder in which the powdered alumina is loaded with platinum (Pt). Next, ceria-zirconia composite oxide (OSC material), barium sulfate (co-catalyst), a binder, and ion exchange water (solvent) are added to the Pt-loaded powder, which are fully stirred and wet-pulverized. Thus, a slurry for the catalyst flowing into the pore chamber side is prepared.

[0111] Next, the slurry for the inflow cell side catalyst is supplied to the wall surface 14SA on the inflow cell 12A side in the inflow cell side catalyst setting range 14X of the partition wall 14 by flowing the inflow cell side catalyst slurry from the inflow side end 12Aa into the inflow cell 12A. At this time, the supply amount of the slurry is adjusted so that the density of the inflow cell side catalyst 20 becomes the desired value. The inflow cell side catalyst setting range 14X of the partition wall 14 is an area extending from the inflow side end 14a of the partition wall 14 along the extension direction to the position 14b that is 50% of the length of the extension direction of the partition wall 14 away from the inflow side end 14a of the partition wall 14 along the extension direction to the outflow side. Then, the honeycomb substrate 10 supplied with the slurry for the inflow cell side catalyst is heated at 120°C for 2 hours using a dryer, thereby drying and removing moisture, and then calcined at 500°C for 2 hours using an electric furnace. Thus, the inflow cell side catalyst 20 is formed.

[0112] Next, a catalyst carrier with a powdered carrier loaded with catalyst metal particles is mixed with a solvent to prepare a slurry for the outflow chamber side catalyst. Specifically, after the powdered ceria-zirconia composite oxide (carrier) is immersed in an aqueous solution containing Rh nitrate (catalyst metal salt), they are dried and calcined to prepare a Rh-loaded powder in which the powdered ceria-zirconia composite oxide is loaded with rhodium (Rh). Next, ceria-zirconia composite oxide (OSC material), alumina (co-catalyst), a binder, and ion exchange water (solvent) are added to the Rh-loaded powder, which are fully stirred and wet-pulverized. Thus, a slurry for the outflow chamber side catalyst is prepared.

[0113] Next, the outflow cell side catalyst slurry is supplied to the inner region 14NB of the outflow cell 12B side in the outflow cell side catalyst setting range 14Y of the partition wall 14 by flowing from the outflow side end 12Bb into the outflow cell 12B. The outflow cell side catalyst setting range 14Y of the partition wall 14 is a region extending from the outflow side end 14d of the partition wall 14 along the extension direction to a position 14e which is 70% of the length of the extension direction of the partition wall 14 away from the outflow side end 14d of the partition wall 14 along the extension direction toward the inflow side. Then, the honeycomb substrate 10 supplied with the outflow cell side catalyst slurry is heated at 120° C. for 2 hours using a dryer, thereby drying and removing moisture, and then calcined at 500° C. for 2 hours using an electric furnace. Thus, the outflow cell side catalyst 30 is formed.

[0114] Based on the above, the following Figure 2 As shown, the exhaust gas purification device 1 includes the honeycomb substrate 10, the sealing portion 16, the inflow cell side catalyst 20, and the outflow cell side catalyst 30. The density of the outflow cell side catalyst 30 is 49 g / L.

[0115] [Example 2]

[0116] When the slurry for the outlet hole chamber side catalyst is supplied to the inner area 14NB of the partition wall on the outlet hole chamber 12B side in the outlet hole chamber side catalyst setting range 14Y of the partition wall 14, the density of the outlet hole chamber side catalyst 30 is made to be 39 g / L by adjusting the supply amount of the slurry for the outlet hole chamber side catalyst. Except for this, the exhaust purification device 1 is manufactured by the same manufacturing method as Example 1.

[0117] [Comparative Example 1]

[0118] When the slurry for the outflow hole chamber side catalyst is supplied to the inner area 14NB of the partition wall on the outflow hole chamber 12B side in the outflow hole chamber side catalyst setting range 14Y of the partition wall 14, the density of the outflow hole chamber side catalyst 30 is made to be 109 g / L by adjusting the supply amount of the slurry for the outflow hole chamber side catalyst. Except for this, the exhaust purification device 1 is manufactured by the same manufacturing method as Example 1.

[0119] [Comparative Example 2]

[0120] When the slurry for the outlet hole chamber side catalyst is supplied to the inner area 14NB of the partition wall on the outlet hole chamber 12B side in the outlet hole chamber side catalyst setting range 14Y of the partition wall 14, the density of the outlet hole chamber side catalyst 30 is made to be 94g / L by adjusting the supply amount of the slurry for the outlet hole chamber side catalyst. Except for this, the exhaust purification device 1 is manufactured by the same manufacturing method as Example 1.

[0121] [Comparative Example 3]

[0122] When the slurry for the outflow hole chamber side catalyst is supplied to the inner area 14NB of the partition wall on the outflow hole chamber 12B side in the outflow hole chamber side catalyst setting range 14Y of the partition wall 14, the density of the outflow hole chamber side catalyst 30 is made to be 79 g / L by adjusting the supply amount of the slurry for the outflow hole chamber side catalyst. Except for this, the exhaust purification device 1 is manufactured by the same manufacturing method as Example 1.

[0123] [Comparative Example 4]

[0124] The exhaust gas purification device 1 was manufactured by the same manufacturing method as in Example 1 except that the outflow cell side catalyst 30 was not formed.

[0125] [evaluate]

[0126] For the exhaust purification device 1 manufactured in Examples 1 and 2 and Comparative Examples 1 to 4, the cross section perpendicular to the extension direction of the reference position 14c of the outflow chamber side catalyst configuration wall was observed, and the minimum value of the porosity in the thickness direction at the reference position 14c of the outflow chamber side catalyst configuration wall in the extension direction, the initial pressure loss, and the exhaust purification performance after the durability test were evaluated. Furthermore, the outflow chamber side catalyst configuration wall is a wall including the outflow chamber side catalyst setting range 14Y of the partition wall 14 and the outflow chamber side catalyst 30. The reference position 14c of the outflow chamber side catalyst configuration wall in the extension direction is a position that is 15 mm away from the outflow side end 14d of the partition wall 14 along the extension direction toward the inflow side (a position close to the outflow side within a range that does not overlap with the configuration area of ​​the sealing portion 16 in the extension direction).

[0127] (Cross-section observation)

[0128] In the exhaust purification device 1 of Examples 1 and 2 and Comparative Examples 1 to 4, the area between adjacent corners of the inflow chamber 12A (outflow chamber 12B) in a cross section perpendicular to the extension direction of the reference position 14c of the catalyst configuration wall on the outflow chamber side was photographed by X-ray CT. Figure 5 This is a cross-sectional image based on X-ray CT of the region between the adjacent corners of the inflow cell in the cross section perpendicular to the extension direction at the reference position of the outflow cell side catalyst configuration wall of the exhaust purification device of Example 1. In this image, the void of the outflow cell side catalyst configuration wall (the portion of the void of the partition wall monomer that is not filled with the outflow cell side catalyst), the substrate portion of the partition wall 14, and the outflow cell side catalyst 30 are shown together with the partition wall 14 and the region of the inflow cell 12A and the outflow cell 12B.

[0129] (Minimum value of the porosity in the thickness direction at the reference position of the catalyst arrangement wall on the outflow cell side)

[0130] In the exhaust purification device 1 of Examples 1 and 2 and Comparative Examples 1 to 4, the minimum value of the porosity in the thickness direction is obtained at the reference position 14c in the extension direction of the catalyst configuration wall on the outlet cell side (the minimum value of the porosity in the thickness direction of the catalyst configuration wall on the outlet cell side).

[0131] Hereinafter, a description will be given of a procedure for obtaining the minimum value of the porosity in the thickness direction at the reference position 14 c in the extending direction of the outflow cell-side catalyst arrangement wall in the exhaust purification device 1 of each example. Figure 6 This is a flowchart showing the steps of obtaining the minimum value of the porosity in the thickness direction at a reference position in the extending direction of the outflow cell side catalyst arrangement wall.

[0132] In this step, if Figure 6As shown, first, the area between the adjacent corners of the inflow cell 12A (outflow cell 12B) within the range of ±1 mm in the extension direction from the reference position 14c of the outflow cell side catalyst arrangement wall is taken as the reference area, and the cross sections perpendicular to the extension direction at 1000 shooting positions set at 2 μm intervals in the reference area of ​​the outflow cell side catalyst arrangement wall are photographed by X-ray CT to obtain 1000 cross-sectional images (step 1). Specifically, the cross sections perpendicular to the extension direction at each shooting position in the reference area of ​​the outflow cell side catalyst arrangement wall are photographed at a magnification of 150 times, and each cross-sectional image is obtained in an 8-bit format of 1280×960 pixels. Figure 7 This is a cross-sectional image showing a cross section perpendicular to the extending direction at one imaging position (reference position) in a reference region of the outflow cell-side catalyst arrangement wall of the exhaust purification device of the first embodiment.

[0133] Then, if Figure 6 As shown, by using the CAE software GEODICT (registered trademark) made by Math2Market, using the Import Geo module of GEODICT, all 1000 cross-sectional images are read, and the 1000 cross-sectional images are integrated, thereby constructing a 3D (three-dimensional) model of the reference area of ​​the outflow hole chamber side catalyst configuration wall (step 2). At this time, according to the specification of the Import Geo module, 1000 cross-sectional images are read and integrated.

[0134] Then, if Figure 6 As shown in FIG. 1 , by using GEODICT, the calculation target area in the center of the extension direction and the width direction is cut out from the 3D model and voxelized, thereby obtaining a 3D voxel model (step 3). At this time, a three-dimensional space is used in which the width direction is set as the X-axis direction, the extension direction is set as the Y-axis direction, and the thickness direction is set as the Z-axis direction, and the calculation target area of ​​the 3D model is expressed by voxels arranged in the X-axis direction, the Y-axis direction, and the Z-axis direction, thereby obtaining a 3D voxel model.

[0135] Then, if Figure 6 As shown, using the Threshold menu of the PoroDict module of GEODICT, the pattern method is adopted to set the threshold for binarizing each voxel of the 3D voxel model to a specified value, and then each voxel of the 3D voxel model is binarized, thereby classifying each voxel of the 3D voxel model into the gaps of the catalyst configuration wall on the outflow pore chamber side and other areas (the substrate portion of the partition wall 14 and the outflow pore chamber side catalyst 30) (step 4).

[0136] Then, if Figure 6As shown, the 1D statistics menu of the PoroDict module of GEODICT is used to set the parameters (Input Map) as shown in Table 1 below, and the porosity at each position in the Z-axis direction (thickness direction) in the binarized 3D voxel model is calculated (step 5). Then, the porosity at each position in the Z-axis direction in the binarized 3D voxel model thus calculated is obtained as the porosity at each position in the thickness direction in the reference area of ​​the catalyst configuration wall on the outflow cell side.

[0137] Table 1

[0138] parameter Settings BackgroundMode Pore DirectionX false DirectionY false DirectionZ true AnalyzeLayerThickness false ResultFileName 1DStatistics.gdr Method 3 WriteFile false

[0139] Then, if Figure 6 As shown, using Excel (registered trademark) manufactured by Microsoft Corporation, the minimum value of the porosity at each position in the Z-axis direction in the binarized 3D voxel model is extracted (step 6). Then, the minimum value of the porosity thus extracted (the minimum value of the porosity at each position in the thickness direction in the reference region of the outflow cell side catalyst arrangement wall) is obtained as the minimum value of the porosity in the thickness direction at the reference position 14c in the extension direction of the outflow cell side catalyst arrangement wall.

[0140] For the exhaust gas purification devices 1 of Examples 1 and 2 and Comparative Examples 1 to 4, the minimum value of the porosity in the thickness direction at the reference position 14c in the extending direction of the outflow cell side catalyst arrangement wall obtained by the above steps is shown in Table 2 below.

[0141] (Initial pressure loss)

[0142] For the exhaust gas purification devices 1 of Examples 1 and 2 and Comparative Examples 1 to 4, the initial pressure loss at the reference position 14c in the extension direction of the catalyst configuration wall on the outflow cell side was calculated. Specifically, the pressure loss when air was allowed to flow through the exhaust gas purification device 1 of each example under the conditions of 0.01 m / s and 226.85°C was calculated by using the software GEODICT FilterDict module manufactured by Math2Market, as the initial pressure loss at the reference position 14c in the extension direction of the catalyst configuration wall on the outflow cell side. The initial pressure loss in each example is shown in Table 2 below.

[0143] (Exhaust purification performance after endurance test)

[0144] For the exhaust gas purification devices 1 of Examples 1 and 2 and Comparative Examples 1 to 4, the NOx maximum purification rate was measured as an index of the exhaust gas purification performance after the endurance test. Specifically, first, the exhaust gas purification device of each example was installed in the exhaust system of a V-type 8-cylinder engine, and the exhaust gas of the stoichiometric ratio and the lean atmosphere was repeatedly flowed for a certain time (ratio of 3:1) at a catalyst bed temperature of 900°C for 50 hours, thereby implementing the endurance test. Next, the exhaust gas purification device of each example after the endurance test was installed in the exhaust system of an L-type 4-cylinder engine, and the exhaust gas with an A / F (air-fuel ratio) of 14.4 was supplied, and the intake air temperature was raised from 200°C to 600°C (20°C / minute) under the condition of Ga=28g / s. Then, the NOx concentration of the intake air and the exhaust gas was measured during the temperature increase of the intake air temperature to calculate the NOx purification rate, and the maximum value of the NOx purification rate was obtained as the NOx maximum purification rate. The NOx maximum purification rate in each example is shown in Table 2 below.

[0145] Table 2

[0146]

[0147] *Minimum value of the porosity in the thickness direction at the same position as the reference position in the partition wall

[0148] Figure 8 It is a graph showing the relationship between the initial pressure loss and the maximum NOx purification rate obtained in the exhaust purification devices of Examples 1 and 2 and Comparative Examples 1 to 4 with respect to the minimum value of the porosity in the thickness direction at the reference position in the extension direction of the catalyst configuration wall on the outflow cell side. As shown in Table 2 and Figure 8 As shown in the figure, when the minimum value of the porosity in the thickness direction at the reference position in the extension direction of the catalyst arrangement wall on the outflow cell side is less than 20%, the initial pressure loss increases sharply, while on the contrary, when the minimum value of the porosity is 20% or more, the increase of the initial pressure loss is suppressed. On the other hand, when the minimum value of the porosity exceeds 20% and becomes larger, there is a tendency that the maximum NOx purification rate decreases, while on the contrary, when the minimum value of the porosity is 20% or more and 30% or less, the maximum NOx purification rate increases.

[0149] Although the embodiments of the exhaust gas purification device of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various design changes can be made within the scope of the spirit of the present invention described in the claims.

Claims

1. An exhaust gas purification device, characterized in that: It has a honeycomb substrate and a catalyst on the outflow cell side. The honeycomb substrate has porous partition walls that define a plurality of cells extending from an inlet-side end surface to an outlet-side end surface. The plurality of cells include an inlet cell and an outlet cell adjacent to each other via the partition wall. The inflow side end of the inflow hole chamber is open, and the outflow side end is sealed, The inflow side end of the outflow hole chamber is sealed, and the outflow side end is open, The outflow chamber side catalyst is arranged in an inner region of the outflow chamber side partition wall within an outflow chamber side catalyst arrangement range extending from the outflow side end of the partition wall along an extension direction to the following position, wherein the position is a position away from the outflow side end of the partition wall along the extension direction by a predetermined distance, The minimum value of the porosity of the outflow cell side catalyst configuration wall in the thickness direction is within the range of 20% to 30%, and the outflow cell side catalyst configuration wall includes the outflow cell side catalyst setting range of the partition wall and the outflow cell side catalyst.

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