Exhaust gas purification catalyst

Abstract

The purpose of the present invention is to provide an exhaust gas purification catalyst that comprises a wall-flow substrate and a catalyst part, and that can improve PM collection performance and suppress an increase in pressure loss. Provided is an exhaust gas purification catalyst (1), comprising: a substrate (10) that extends in an exhaust gas circulation direction (E); and at least one among a first catalyst part (20) and a second catalyst part (30) provided to the substrate (10), wherein the first catalyst part (20) satisfies following formulas (11) and (12): (11) 0.20≤R11≤0.80, (12) 0.30≤R12≤0.85, and the second catalyst part (30) satisfies following formulas (21) and (22): (21) 0.20≤R21≤0.80, (22) 0.30≤R22≤0.85.

Description

[Technical Field]

[0001] The present invention relates to a catalyst for purifying exhaust gases. [Background technology]

[0002] Exhaust gases emitted from internal combustion engines of automobiles, motorcycles, and other vehicles contain harmful components such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). Three-way catalysts are used to purify and neutralize these harmful components. Three-way catalysts contain precious metals such as platinum (Pt), palladium (Pd), and rhodium (Rh). Pt and Pd are primarily involved in the oxidation of HC and CO, while Rh is primarily involved in the reduction of NOx.

[0003] Exhaust gas contains particulate matter (PM) in addition to harmful components such as HC, CO, and NOx, and is known to cause air pollution.

[0004] In order to comply with environmental regulations regarding PM, vehicles equipped with gasoline engines such as direct injection engines (GDI: Gasoline Direct Injection engines) are now required to be equipped with filters that have PM collection functions (GPF: Gasoline Particulate Filters), just like vehicles equipped with diesel engines.

[0005] For example, a substrate having a structure known as a wall-flow type is used as a GPF. The wall-flow type substrate includes inlet cells that have an open exhaust gas inlet end and a closed exhaust gas outlet end, outlet cells that have a closed exhaust gas inlet end and an open exhaust gas outlet end, and a porous partition wall separating the inlet and outlet cells. In a wall-flow type substrate, when exhaust gas flows in through the exhaust gas inlet end (opening) of the inlet cell, passes through the porous partition wall, and flows out from the exhaust gas outlet end (opening) of the outlet cell, PM in the exhaust gas is captured in the pores inside the partition wall.

[0006] Generally, the space available for installing catalysts for purifying exhaust gas is limited, so studies are being conducted to install a catalyst section containing precious metal elements such as Pt, Pd, and Rh on a wall-flow type substrate to capture PM and purify harmful components such as HC, CO, and NOx.

[0007] For example, Patent Document 1 describes an exhaust gas purification catalyst that includes a wall-flow type substrate and a catalyst portion provided inside the partition walls of the wall-flow type substrate.

[0008] Furthermore, Patent Document 2 describes an exhaust gas purification catalyst that includes a wall-flow type substrate and a catalyst portion provided on the outer surface of the partition wall of the wall-flow type substrate. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-150305 [Patent Document 2] Special Publication No. 2018-537265 Summary of the Invention [Problem to be solved by the invention]

[0010] When the catalyst portion is provided inside the partition walls of the wall-flow type substrate, as in Patent Document 1, the large pores in the partition walls cannot be adequately filled, which may result in a decrease in PM trapping performance.On the other hand, when the catalyst portion is provided on the outer surface of the partition walls of the wall-flow type substrate, as in Patent Document 2, the pores on the outer surface of the partition walls can be filled to improve PM trapping performance, but this requires providing a high coating amount of catalyst portion, which results in a significant increase in pressure drop.

[0011] Therefore, an object of the present invention is to provide an exhaust gas purification catalyst that includes a wall-flow type substrate and a catalytic portion, and that can improve PM trapping performance and suppress an increase in pressure loss. [Means for solving the problem]

[0012] In order to solve the above problems, the present invention provides the following exhaust gas purification catalyst. [1] A catalyst for purifying exhaust gas comprising a substrate extending in an exhaust gas flow direction and at least one of a first catalytic portion and a second catalytic portion provided on the substrate, The substrate is an inlet-side cell extending in the exhaust gas flow direction, the inlet-side cell having an open end on the exhaust gas inlet side and a closed end on the exhaust gas outlet side; an outlet-side cell extending in the exhaust gas flow direction, the outlet-side cell having a closed end on an exhaust gas inlet side and an open end on an exhaust gas outlet side; a porous partition wall separating the inlet cell and the outlet cell; Equipped with the first catalyst portion is formed in a predetermined region of an inlet-side cell-side surface of the partition wall, the region extending from an exhaust gas inlet-side end of the partition wall along the exhaust gas flow direction, the second catalytic portion is formed in a predetermined region of an outlet-side cell side surface of the partition wall, the region extending from an exhaust gas outlet-side end of the partition wall along a direction opposite to the exhaust gas flow direction, a part of the predetermined region of the inlet-side cell-side surface is covered with the first catalyst portion, while the remaining portion of the predetermined region of the inlet-side cell-side surface is exposed without being covered with the first catalyst portion, whereby the surface of the first catalyst portion and the remaining portion of the predetermined region together form a first uneven surface; a part of the predetermined region of the outlet-side cell surface is covered with the second catalyst portion, while the remaining portion of the predetermined region of the outlet-side cell surface is exposed without being covered with the second catalyst portion, whereby the surface of the second catalyst portion and the remaining portion of the predetermined region together form a second uneven surface; The first catalyst portion is represented by the following formulas (11) and (12): 0.20≦R 11 ≦0.80 (11) 0.30≦R12 ≦0.85 (12) [In the formula, R 11 represents the ratio of the area of ​​the part covered by the first catalyst portion to the area of ​​the predetermined region of the inlet-side cell surface, and R 12 represents the ratio of the surface roughness of the first uneven surface to the surface roughness of the predetermined region of the inlet cell side surface.] Fulfilling The second catalyst portion is represented by the following formulas (21) and (22): 0.20≦R 21 ≦0.80 (21) 0.30≦R 22 ≦0.85 (22) [In the formula, R 21 represents the ratio of the area of ​​the portion covered by the second catalyst portion to the area of ​​the predetermined region of the outlet-side cell surface, and R 22 represents the ratio of the surface roughness of the second uneven surface to the surface roughness of the predetermined region of the outlet-side cell-side surface.] The exhaust gas purifying catalyst satisfies the above. [2] The first catalyst portion is represented by the following formula (13): 0.060≦R 13 ≦0.55 (13) [In the formula, R 13 is R 11 to R 12 represents the value obtained by multiplying by R 11 and R 12 has the same meaning as above.] Fulfilling The second catalyst portion is represented by the following formula (23): 0.060≦R 23 ≦0.55 (23) [In the formula, R 23 is R 21 to R 22 represents the value obtained by multiplying by R 21 and R 22 has the same meaning as above.] The exhaust gas purifying catalyst according to [1], which satisfies the above. [3] The exhaust gas purifying catalyst according to [1] or [2], wherein the exhaust gas purifying catalyst comprises both the first catalyst portion and the second catalyst portion. [4] The exhaust gas purification catalyst according to any one of [1] to [3], wherein the ratio of the sum of the length of the predetermined region on the inlet cell side surface and the length of the predetermined region on the outlet cell side surface to the length of the substrate is 0.30 or more and 1.8 or less. [5] The exhaust gas purification catalyst according to any one of [1] to [4], wherein the first catalytic portion and the second catalytic portion each independently contain at least one catalytically active component selected from platinum element (Pt), palladium element (Pd), and rhodium element (Rh). [Effects of the Invention]

[0013] According to the present invention, there is provided an exhaust gas purification catalyst that can improve PM trapping performance and suppress an increase in pressure loss. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a partial cross-sectional view showing a state in which an exhaust gas purifying catalyst according to one embodiment of the present invention is arranged in an exhaust passage of an internal combustion engine. [Figure 2] FIG. 2 is an end view taken along line AA in FIG. [Figure 3] FIG. 3 is an end view taken along line BB in FIG. [Figure 4] FIG. 4 is an enlarged view of the area indicated by the symbol R1 in FIG. [Figure 5] FIG. 5 is an enlarged view of the area indicated by the symbol R2 in FIG. [Figure 6] FIG. 6 is an end view taken along line CC in FIG. [Figure 7A] FIG. 7A is an enlarged view of the area indicated by the symbol R31 in FIG. [Figure 7B] FIG. 7B is an enlarged view of the area indicated by the symbol R32 in FIG. [Figure 8]FIG. 8 is a diagram for explaining the first region and the second region on the inlet-side cell-side surface of the partition wall and the first region and the second region on the outlet-side cell-side surface of the partition wall (a diagram in which the first catalyst portion and the second catalyst portion are omitted from FIG. 6). [Figure 9] FIG. 9 is a perspective view of a cut piece used to calculate R11 or R12. [Figure 10] FIG. 10 is a plan view of the cut piece shown in FIG. 9 (a plan view of the cut piece shown in FIG. 9 from the Z direction). [Figure 11] FIG. 11 is a conceptual diagram of an SEM image used to calculate R11. [Figure 12] FIG. 12 is a conceptual diagram of the surface profilometer scan image used to calculate R12. [Figure 13] FIG. 13 is a perspective view of a cut piece used to calculate R21 or R22. [Figure 14] FIG. 14 is a plan view of the cut piece shown in FIG. 13 (a plan view of the cut piece shown in FIG. 13 from the Z direction). [Figure 15] FIG. 15 is a conceptual diagram of an SEM image used to calculate R21. [Figure 16] FIG. 16 is a conceptual diagram of the surface profilometer scan image used to calculate R22. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the exhaust gas purifying catalyst of the present invention will be described with reference to the drawings.

[0016] As shown in Fig. 1, an exhaust gas purification catalyst 1 according to one embodiment of the present invention is disposed in an exhaust path in an exhaust pipe P of an internal combustion engine. The internal combustion engine is, for example, a gasoline engine (e.g., a GDI engine) or a diesel engine.

[0017] In Figure 1, the direction of exhaust gas flow in the exhaust path of the internal combustion engine is indicated by the symbol E. This is the same in other figures. In this specification, the upstream side of the exhaust gas flow direction E (for example, the left side in Figure 1) may be referred to as the "exhaust gas inflow side," and the downstream side of the exhaust gas flow direction E (for example, the right side in Figure 1) may be referred to as the "exhaust gas outflow side."

[0018] 1, the exhaust gas purification catalyst 1 is disposed in the exhaust path of an internal combustion engine so that the axial direction of the substrate 10 substantially coincides with the exhaust gas flow direction E. In this specification, "length" refers to the dimension of the substrate 10 in the axial direction, unless otherwise specified.

[0019] As shown in Figures 1 to 7, the exhaust gas purification catalyst 1 includes a substrate 10 extending in the exhaust gas flow direction E, a first catalyst portion 20 provided on the substrate 10, and a second catalyst portion 30 provided on the substrate 10.

[0020] The exhaust gas purifying catalyst 1 may include at least one of the first catalytic section 20 and the second catalytic section 30. Therefore, the present invention also includes an embodiment in which one of the first catalytic section 20 and the second catalytic section 30 is omitted. However, from the viewpoint of improving exhaust gas purification performance and PM trapping performance, it is preferable that the exhaust gas purifying catalyst 1 include both the first catalytic section 20 and the second catalytic section 30.

[0021] ≪Base material≫ The substrate 10 will now be described.

[0022] The material constituting the substrate 10 can be selected appropriately. Examples of materials constituting the substrate 10 include ceramic materials and metal materials, with ceramic materials being preferred. Examples of ceramic materials include carbide ceramics such as silicon carbide, titanium carbide, tantalum carbide, and tungsten carbide; nitride ceramics such as aluminum nitride, silicon nitride, boron nitride, and titanium nitride; oxide ceramics such as alumina, zirconia, cordierite, mullite, zircon, aluminum titanate, and magnesium titanate; and silicon-containing silicon carbide. The ceramic material is preferably a silicon-containing ceramic material such as silicon carbide, silicon nitride, cordierite, or mullite. The ceramic materials can be used alone or in combination of two or more.

[0023] As shown in FIGS. 2 to 8, the substrate 10 includes a cylindrical portion 11, porous partition walls 12 provided in the cylindrical portion 11, and cells 13 (cells 13a and 13b) separated by the partition walls 12.

[0024] The axial direction of the substrate 10 coincides with the axial direction of the tubular portion 11. In this embodiment, the shape of the tubular portion 11 is cylindrical, but it may be other shapes such as an elliptical cylinder or a polygonal cylinder.

[0025] As shown in FIGS. 2 to 8, a partition wall 12 exists between adjacent cells 13 (cells 13a and 13b), and the adjacent cells 13 (cells 13a and 13b) are separated by the partition wall 12.

[0026] As shown in FIGS. 2 to 8, the cells 13 (cells 13a and 13b) extend in the exhaust gas flow direction E, and have an exhaust gas inlet end and an exhaust gas outlet end.

[0027] As shown in Figure 6, the substrate 10 is provided with first sealing portions 14 that seal the exhaust gas outlet end portions of some of the cells 13, and second sealing portions 15 that seal the exhaust gas inlet end portions of the remaining cells 13.As a result, some of the cells 13 have open exhaust gas inlet end portions and are inlet side cells 13a whose exhaust gas outlet end portions are blocked by the first sealing portions 14, and the remaining cells 13 have closed exhaust gas inlet end portions with the second sealing portions 15 and are outlet side cells 13b whose exhaust gas outlet end portions are open.

[0028] As shown in Figures 4 to 6 and 8, multiple (four in this embodiment) outlet cells 13b are arranged around one inlet cell 13a, and the inlet cell 13a and the outlet cells 13b arranged around the inlet cell 13a are separated by a porous partition wall 12.

[0029] Exhaust gas emitted from an internal combustion engine flows through an exhaust path in the exhaust pipe P from one end to the other end, and is purified by an exhaust gas purification catalyst 1 arranged in the exhaust pipe P. At this time, the exhaust gas flows in from the exhaust gas inlet end (opening) of the inlet-side cell 13a, passes through the porous partition wall 12, and flows out from the exhaust gas outlet end (opening) of the outlet-side cell 13b. This type of system is called a wall-flow type.

[0030] In the exhaust gas purifying catalyst 1, when exhaust gas that has flowed in from the exhaust gas inlet side end (opening) of the inlet side cell 13a passes through the porous partition walls 12, particulate matter (PM) in the exhaust gas is captured in the pores of the partition walls 12, the pores of the first catalyst section 20, and the pores of the second catalyst section 30. Therefore, the exhaust gas purifying catalyst 1 is useful as a particulate filter for a gasoline engine (Gasoline Particulate Filter) or a particulate filter for a diesel engine (Diesel Particulate Filter).

[0031] In this embodiment, the shape of the exhaust gas inlet end (opening) of the inlet cell 13a in a plan view is quadrangular, but it may be other shapes such as hexagonal, octagonal, etc. The same applies to the exhaust gas inlet end (opening) of the outlet cell 13b.

[0032] The cell density per square inch of the substrate 10 can be adjusted as appropriate, but from the viewpoint of more effectively improving PM capture performance and suppressing an increase in pressure drop, it is preferably 200 cells or more and 350 cells or less. The cell density per square inch of the substrate 10 is the total number of cells 13a and 13b per square inch in a cross section obtained by cutting the substrate 10 along a plane perpendicular to the axial direction of the substrate 10.

[0033] The partition walls 12 have a porous structure that allows exhaust gas to pass through. The thickness of the partition walls 12 can be adjusted as appropriate, but from the viewpoint of more effectively realizing an improvement in PM trapping performance and suppressing an increase in pressure drop, it is preferably 150 μm or more and 350 μm or less, and more preferably 180 μm or more and 320 μm or less. The average pore diameter (average pore diameter) of the partition walls 12 can be adjusted as appropriate, but from the viewpoint of more effectively realizing an improvement in PM trapping performance and suppressing an increase in pressure drop, it is preferably 12 μm or more and 25 μm or less, and more preferably 13 μm or more and 22 μm or less. The porosity (porosity) of the partition walls 12 can be adjusted as appropriate, but from the viewpoint of more effectively realizing a suppression of an increase in pressure drop, it is, for example, 40% or more and 80% or less, preferably 45% or more and 75% or less, more preferably 50% or more and 75% or less, and even more preferably 60% or more and 70% or less.

[0034] The average pore size and porosity of the partition walls 12 can be measured by mercury intrusion porosimetry using a mercury porosimeter. In mercury intrusion porosimetry, a test piece (excluding the first sealing portion 14 and the second sealing portion 15) cut out from the substrate 10 is placed in a measurement cell of the mercury porosimeter, the pressure inside the measurement cell is reduced, mercury is introduced into the measurement cell and pressurized, and the pore size and pore volume are measured from the pressure during pressurization and the volume of mercury introduced into the pores of the partition walls 12 in the test piece. The measurement is performed, for example, at a pressure range of 0.5 to 20,000 psia. Note that 0.5 psia is 0.35 × 10 -3 kg / mm 2 20,000 psia is equivalent to 14 kg / mm 2 The pore size range corresponding to this pressure range is 0.01 to 420 μm. As constants for calculating the pore size from the pressure, for example, a contact angle of 140° and a surface tension of 480 dyn / cm are used. The average pore size of the partition walls 12 is the pore size at which the cumulative pore volume is 50% in the pore size distribution of the partition walls 12 (the pore size at which the integrated value of the pore volume is 50%). The porosity of the partition walls 12 can be calculated based on the following formula. Note that when the partition wall material is cordierite, for example, 2.52 can be used as the true specific gravity of cordierite. Porosity (%) of partition wall 12 = total pore volume / (total pore volume + 1 / true specific gravity of partition wall material) × 100

[0035] The length L10 of the substrate 10 can be adjusted as appropriate, but from the viewpoints of improving exhaust gas purification performance, improving PM collection performance, and ease of installation in the limited space of a vehicle, it is preferably 50 mm or more and 160 mm or less, more preferably 80 mm or more and 130 mm or less.

[0036] The volume of the substrate 10 can be adjusted as appropriate, but from the viewpoint of improving exhaust gas purification performance, improving PM collection performance, and ease of installation in the limited space of a vehicle, it is preferably 0.5 L to 2.5 L, more preferably 0.5 L to 2.0 L, and more preferably 0.7 L to 1.8 L. The volume of the substrate 10 means the apparent volume of the substrate 10. When the substrate 10 is cylindrical, the volume of the substrate 10 is calculated by the formula: Volume of substrate 10 = π × r, where 2r is the outer diameter of the substrate 10 and L is the length of the substrate 10. 2 It is expressed as × L.

[0037] <Catalyst section> The first catalyst section 20 and the second catalyst section 30 will be described below.

[0038] As shown in FIGS. 4 and 6 to 8, the first catalyst portion 20 is formed in the first region S1a on the surface of the partition wall 12 facing the inlet cell 13a.

[0039] The surface of the partition wall 12 facing the inlet cells 13a is the outer surface of the inlet cells 13a that defines the outer shape of the partition wall 12. As shown in FIGS. 4 to 8, the surface of the partition wall 12 facing the inlet cells 13a is composed of a first region S1a and a second region S1b.

[0040] The first region S1a is a region of the surface of the partition wall 12 on the inlet cell 13a side, extending from the exhaust gas inlet end of the partition wall 12 along the exhaust gas flow direction E. Within the first region S1a, the region where the first catalyst section 20 is formed may be a single continuous region or multiple discontinuous regions. That is, the first catalyst section 20 may be composed of a single continuous structure or multiple discontinuous structures. For example, the first catalyst section 20 may be composed of multiple discontinuous structures scattered on the first region S1a. The term "structure" refers to a material having a certain shape. Examples of the shape of the structure include layered, spherical, granular, needle-like, scaly (flake-like), irregular shapes, and shapes combining two or more of these. Note that in FIGS. 4 and 6, the first catalyst section 20 is depicted as a single layered structure for the sake of simplicity.

[0041] The fact that the first catalyst part 20 is formed in the first region S1a can be confirmed by using a scanning electron microscope-energy dispersive X-ray analyzer (SEM-EDX) or the like to confirm that elements specific to the first catalyst part 20 (elements that are contained in the first catalyst part 20 but not in the substrate 10) are present in the first region S1a.

[0042] The second region S1b is a region of the surface of the partition wall 12 on the inlet cell 13a side other than the first region S1a, and the first catalyst portion 20 is not formed in the second region S1b.

[0043] As shown in FIG. 7A, the first catalyst portion 20 protrudes from the first region S1a toward the inlet-side cell 13a, and covers a part of the first region S1a.

[0044] The first catalyst section 20 may have a first section that protrudes from the first region S1a toward the inlet-side cell 13a, and a second section that exists inside the partition wall 12. Because the partition wall 12 is porous, the second section may be formed together with the first section when the first catalyst section 20 is formed. The first section and the second section may be continuous.

[0045] As shown in FIGS. 5 to 8, the second catalyst portion 30 is formed in the first region S2a on the surface of the partition wall 12 on the outlet-side cell 13b side.

[0046] The surface of the partition wall 12 on the outflow-side cells 13b side is an outer surface on the outflow-side cells 13b side that defines the outer shape of the partition wall 12. As shown in FIGS. 4 to 8, the surface of the partition wall 12 on the outflow-side cells 13b side is configured of a first region S2a and a second region S2b.

[0047] The first region S2a is a region of the surface of the partition wall 12 on the outlet cell 13b side, extending from the exhaust gas outlet end of the partition wall 12 in the direction opposite to the exhaust gas flow direction E. Within the first region S2a, the region where the second catalyst section 30 is formed may be a single continuous region or a plurality of discontinuous regions. That is, the second catalyst section 30 may be composed of a single continuous structure or a plurality of discontinuous structures. For example, the second catalyst section 30 may be composed of a plurality of discontinuous structures scattered on the first region S2a. The meaning of the structure and specific examples of the shape of the structure are the same as those described above. Note that in FIGS. 5 and 6, the second catalyst section 30 is depicted as a single layer structure for the sake of simplicity.

[0048] The fact that the second catalyst part 30 is formed in the first region S2a can be confirmed by using a scanning electron microscope-energy dispersive X-ray analyzer (SEM-EDX) or the like to confirm that elements specific to the second catalyst part 30 (elements that are contained in the second catalyst part 30 but not in the substrate 10) are present in the first region S2a.

[0049] The second region S2b is a region of the surface of the partition wall 12 on the outlet-side cell 13b side other than the first region S2a, and the second catalyst portion 30 is not formed in the second region S2b.

[0050] As shown in FIG. 7B, the second catalyst portion 30 protrudes from the first region S2a toward the outlet-side cell 13b side, and covers a part of the first region S2a.

[0051] The second catalyst portion 30 may have a first portion that protrudes from the first region S2a toward the outlet-side cell 13b, and a second portion that is present inside the partition wall 12. Because the partition wall 12 is porous, the second portion may be formed together with the first portion when the second catalyst portion 30 is formed. The first portion and the second portion may be continuous.

[0052] The length LS1a of the first region S1a means the distance between a plane perpendicular to the axial direction of the substrate 10, which passes through a point located closest to the exhaust gas outlet side among all points on the surface of the first catalyst portion 20 formed in the first region S1a, and the end face of the substrate 10 on the exhaust gas inlet side. The length LS1a of the first region S1a can be adjusted as appropriate. The first region S1a may extend along the exhaust gas flow direction E from the exhaust gas inlet side end of the partition wall 12 to the exhaust gas outlet side end of the partition wall 12. However, it is preferable that the first region S1a extend along the exhaust gas flow direction E from the exhaust gas inlet side end of the partition wall 12 so as not to reach the exhaust gas outlet side end of the partition wall 12.

[0053] The length LS2a of the first region S2a means the distance between a plane perpendicular to the axial direction of the substrate 10, which passes through a point on the exhaust gas inlet side among all points on the surface of the second catalyst section 30 formed on the first region S2a, and the end face of the substrate 10 on the exhaust gas outlet side. The length LS2a of the first region S2a can be adjusted as appropriate. The first region S2a may extend from the exhaust gas outlet side end of the partition wall 12 to the exhaust gas inlet side end of the partition wall 12 in the direction opposite to the exhaust gas flow direction E. However, it is preferable that the first region S2a extend from the exhaust gas outlet side end of the partition wall 12 in the direction opposite to the exhaust gas flow direction E so as not to reach the exhaust gas inlet side end of the partition wall 12.

[0054] From the viewpoint of more effectively achieving improvements in exhaust gas purification performance and PM capture performance, the ratio ((LS1a+LS2a) / L10) of the sum of the length LS1a of the first region S1a and the length LS2a of the first region S2a to the length L10 of the substrate 10 is preferably 0.30 or more and 1.8 or less, more preferably 0.50 or more and 1.5 or less, and even more preferably 1.0 or more and 1.3 or less. Note that the sum of the length LS1a of the first region S1a and the length LS2a of the first region S2a means the length LS2a of the first region S2a in an embodiment in which the first catalyst section 20 is omitted, and means the length LS1a of the first region S1a in an embodiment in which the second catalyst section 30 is omitted.

[0055] From the viewpoint of more effectively achieving improvements in exhaust gas purification performance and PM collection performance, the ratio of the length LS1a of the first region S1a to the length L10 of the substrate 10 (LS1a / L10) is preferably 0.15 or more and 0.90 or less, more preferably 0.20 or more and 0.80 or less, and even more preferably 0.30 or more and 0.80 or less.

[0056] From the viewpoint of more effectively achieving improvements in exhaust gas purification performance and PM collection performance, the ratio of the length LS2a of the first region S2a to the length L10 of the substrate 10 (LS2a / L10) is preferably 0.15 or more and 0.90 or less, more preferably 0.20 or more and 0.80 or less, and even more preferably 0.30 or more and 0.80 or less.

[0057] An example of a method for measuring the length LS1a of the first region S1a is as follows.

[0058] A sample extending in the axial direction of the substrate 10 and having the same length as the length L10 of the substrate 10 is cut out from the exhaust gas purification catalyst 1. The sample is, for example, cylindrical with a diameter of 25.4 mm. The diameter of the sample can be changed as needed. The sample is cut at 5 mm intervals along a plane perpendicular to the axial direction of the substrate 10, and a first cut piece, a second cut piece, ..., and an nth cut piece are obtained in order from the end of the sample on the exhaust gas inlet side. Each cut piece is 5 mm long. The composition of the cut piece is analyzed using an inductively coupled plasma optical emission spectrometer (ICP-OES), an X-ray fluorescence spectrometer (XRF), a SEM-EDX, or the like, and it is confirmed whether the cut piece contains a part of the first catalyst portion 20 based on the composition of the cut piece.

[0059] It is not necessary to perform composition analysis on cut pieces that are clearly found to contain a portion of the first catalyst portion 20. For example, the cut surface can be observed using an SEM, EPMA, or the like to confirm whether the cut piece contains a portion of the first catalyst portion 20. When observing the cut surface, elemental mapping of the cut surface may be performed. Elemental mapping can be performed in the same manner as described above.

[0060] After confirming whether or not the cut piece includes a part of the first catalyst portion 20, the length LS1a of the first region S1a included in the sample is calculated based on the following formula. Length LS1a of the first region S1a included in the sample = 5 mm × (number of cut pieces including part of the first catalyst portion 20)

[0061] For example, if the first to kth cut pieces include a portion of the first catalyst portion 20, but the (k+1)th to nth cut pieces do not include a portion of the first catalyst portion 20, the length LS1a of the first region S1a included in the sample is (5×k) mm.

[0062] A more detailed example of a method for measuring the length LS1a of the first region S1a is as follows. The kth cut piece (i.e., the cut piece obtained from the exhaust gas outflow side of the sample among the cut pieces including a part of the first catalyst portion 20) is cut in the axial direction of the substrate 10, and the part of the first catalyst portion 20 present on the cut surface is observed using an SEM, EPMA, etc., to measure the length of the part of the first region S1a included in the kth cut piece. Then, the length LS1a of the first region S1a included in the sample is calculated based on the following formula. Length LS1a of the first region S1a included in the sample = (5 mm × (k-1)) + (length of the portion of the first region S1a included in the k-th cut piece)

[0063] For 8 to 16 samples arbitrarily cut out from the exhaust gas purifying catalyst 1, the length LS1a of the first region S1a included in each sample is measured, and the average value thereof is defined as the length LS1a of the first region S1a.

[0064] The above explanation regarding the method for measuring the length LS1a of the first region S1a also applies to the method for measuring the length LS2a of the first region S2a. When applying this, "the length LS1a of the first region S1a" should be read as "the length LS2a of the first region S2a," and "the first catalyst portion 20" should be read as "the second catalyst portion 30." However, in the method for measuring the length LS2a of the first region S2a, the sample is cut at 5 mm intervals along a plane perpendicular to the axial direction of the substrate 10, and a first cut piece, a second cut piece, ..., an n-th cut piece are obtained in order from the end of the sample on the exhaust gas outflow side.

[0065] From the viewpoint of more effectively improving PM trapping performance and suppressing an increase in pressure drop, the total mass of the first catalyst portion 20 and the second catalyst portion 30 per unit volume of the substrate 10 (total mass after drying and calcination) is preferably 5 g / L or more and 25 g / L or less, more preferably 10 g / L or more and 20 g / L or less. Note that the total mass of the first catalyst portion 20 and the second catalyst portion 30 refers to the mass of the second catalyst portion 30 in an embodiment in which the first catalyst portion 20 is omitted, and refers to the mass of the first catalyst portion 20 in an embodiment in which the second catalyst portion 30 is omitted. The total mass of the first catalyst portion 20 and the second catalyst portion 30 per unit volume of the substrate 10 is calculated using the formula: (total mass of the first catalyst portion 20 and the second catalyst portion 30) / (volume of the substrate 10).

[0066] From the viewpoint of more effectively improving PM trapping performance and suppressing an increase in pressure drop, the mass of the first catalyst portion 20 per unit volume of the substrate 10 (mass after drying and calcination) is preferably 2 g / L or more and 20 g / L or less, and more preferably 3 g / L or more and 15 g / L or less. The mass of the first catalyst portion 20 per unit volume of the substrate 10 is calculated by the formula: (mass of the first catalyst portion 20) / (volume of the substrate 10).

[0067] From the viewpoint of more effectively improving PM trapping performance and suppressing an increase in pressure drop, the mass of the second catalyst portion 30 per unit volume of the substrate 10 (total mass after drying and calcination) is preferably 2 g / L or more and 20 g / L or less, and more preferably 3 g / L or more and 15 g / L or less. The mass of the second catalyst portion 30 per unit volume of the substrate 10 is calculated by the formula: (mass of the second catalyst portion 30) / (volume of the substrate 10).

[0068] As shown in Fig. 7A, a portion of the first region S1a is covered by the first catalyst portion 20, while the remainder of the first region S1a is exposed and not covered by the first catalyst portion 20, so that the surface of the first catalyst portion 20 and the remainder of the first region S1a together form a first uneven surface 41. Note that, for the sake of simplicity of illustration, Figs. 4 and 6 are illustrated as if the entire first region S1a is covered by the first catalyst portion 20, but in reality, as shown in Fig. 7A, a portion of the first region S1a is covered by the first catalyst portion 20, while the remainder of the first region S1a is exposed and not covered by the first catalyst portion 20.

[0069] As shown in Fig. 7B, a portion of the first region S2a is covered by the second catalyst section 30, while the remainder of the first region S2a is exposed and not covered by the second catalyst section 30, so that the surface of the second catalyst section 30 and the remainder of the first region S2a together form the second uneven surface 42. Note that for convenience, Figs. 5 and 6 illustrate the first region S2a as if the entirety of the first region S2a is covered by the second catalyst section 30, but in reality, as shown in Fig. 7B, a portion of the first region S2a is covered by the second catalyst section 30, while the remainder of the first region S2a is exposed and not covered by the second catalyst section 30.

[0070] In the exhaust gas purifying catalyst 1, the first catalyst portion 20 is represented by the following formulas (11) and (12): 0.20≦R 11 ≦0.80 (11) 0.30≦R 12 ≦0.85 (12) This makes it possible to improve PM collection performance and suppress increases in pressure loss.

[0071] In the above formula (11), R 11 represents the ratio of the area of ​​the part of the first region S1a covered by the first catalyst portion 20 to the area of ​​the first region S1a.

[0072] In the above formula (12), R 12 represents the ratio of the surface roughness of the first uneven surface 41 to the surface roughness of the first region S1a.

[0073] The surface roughness of the first region S1a means the surface roughness of the first region S1a before the first catalyst portion 20 is formed.

[0074] R 11 When the above formula (11) is satisfied, it indicates that the pores in the vicinity of the first region S1a are appropriately filled with the first catalyst portion 20, and this makes it possible to suppress an increase in pressure loss.

[0075] R 12 When the above formula (12) is satisfied, it indicates that the large pores in the vicinity of the first region S1a are appropriately filled with the first catalyst portion 20, which makes it possible to realize an improvement in the PM trapping performance.

[0076] The second catalyst portion 30 is represented by the following formulas (21) and (22): 0.20≦R 21 ≦0.80 (21) 0.30≦R 22 ≦0.85 (22) Meet the following.

[0077] In the above formula (21), R 21 represents the ratio of the area of ​​the part of the first region S2a covered by the second catalyst portion 30 to the area of ​​the first region S2a.

[0078] In the above formula (22), R 22 represents the ratio of the surface roughness of the second uneven surface 42 to the surface roughness of the first region S2a.

[0079] The surface roughness of the first region S2a means the surface roughness of the first region S2a before the second catalyst portion 30 is formed.

[0080] R 21When the above formula (21) is satisfied, it indicates that the pores in the vicinity of the first region S2a are appropriately filled with the second catalytic portion 30, and this makes it possible to suppress an increase in pressure loss.

[0081] R 22 When the above formula (22) is satisfied, it indicates that the large pores in the vicinity of the first region S2a are appropriately filled with the second catalyst portion 30, which makes it possible to realize an improvement in the PM trapping performance.

[0082] From the viewpoint of more effectively suppressing the increase in pressure loss, R 11 is preferably 0.20 or more and 0.80 or less, more preferably 0.20 or more and 0.70 or less, and even more preferably 0.25 or more and 0.65 or less.

[0083] From the viewpoint of more effectively improving PM collection performance, 12 is preferably 0.30 or more and 0.85 or less, more preferably 0.40 or more and 0.80 or less, and even more preferably 0.50 or more and 0.80 or less.

[0084] From the viewpoint of more effectively suppressing the increase in pressure loss, R 21 is preferably 0.20 or more and 0.80 or less, more preferably 0.20 or more and 0.70 or less, and even more preferably 0.25 or more and 0.65 or less.

[0085] From the viewpoint of more effectively improving PM collection performance, 22 is preferably 0.30 or more and 0.85 or less, more preferably 0.40 or more and 0.80 or less, and even more preferably 0.50 or more and 0.80 or less.

[0086] From the viewpoint of more effectively realizing an improvement in PM trapping performance and suppressing an increase in pressure loss, the first catalyst portion 20 has a structure satisfying the following formula (13): 0.060≦R 13 ≦0.55 (13) It is preferable that the following is satisfied.

[0087] In the above formula (13), R13 is R 11 to R 12 It represents the value obtained by multiplying by R 11 and R 12 is synonymous with the above.

[0088] From the viewpoint of more effectively improving PM collection performance and suppressing pressure loss increases, 13 is preferably 0.10 or more and 0.55 or less, more preferably 0.10 or more and 0.50 or less, even more preferably 0.10 or more and 0.45 or less, and even more preferably 0.10 or more and 0.43 or less.

[0089] From the viewpoint of more effectively realizing an improvement in PM trapping performance and suppression of an increase in pressure loss, the second catalyst section 30 has a structure satisfying the following formula (23): 0.060≦R 23 ≦0.55 (23) It is preferable that the following is satisfied.

[0090] In the above formula (23), R 23 is R 21 to R 22 It represents the value obtained by multiplying by R 21 and R 22 is synonymous with the above.

[0091] From the viewpoint of more effectively improving PM collection performance and suppressing pressure loss increases, 23 is preferably 0.10 or more and 0.55 or less, more preferably 0.10 or more and 0.50 or less, even more preferably 0.10 or more and 0.45 or less, and even more preferably 0.10 or more and 0.43 or less.

[0092] <R 11 Calculation method> R 11 The calculation method is as follows:

[0093] The exhaust gas purifying catalyst 1 is cut along a plane parallel to the axial direction of the substrate 10 and a plane perpendicular to the axial direction of the substrate 10. A portion indicated by symbol M in FIG. 6 is cut out from the exhaust gas purifying catalyst 1 to prepare a cut piece M shown in FIGS. 9 and 10 . The cut piece M includes the first uneven surface 41 but does not include the second uneven surface 42. The length of the first uneven surface 41 included in the cut piece M is equal to the length of the cut piece M. The cut piece M can be obtained from the vicinity of the exhaust gas inlet end of the exhaust gas purifying catalyst 1. For example, by cutting the substrate 10 at two locations 5 mm and 15 mm away from the exhaust gas inlet end in the exhaust gas flow direction E along a plane perpendicular to the axial direction of the substrate 10, a cut piece M having a length of 10 mm can be obtained that includes the first uneven surface 41 but does not include the second uneven surface 42. The size of the cut piece M can be appropriately changed as needed.

[0094] As shown in FIGS. 9 and 10, in the cut piece M, the first uneven surface 41 is exposed, and the second region S2b (this region is not covered with the second catalyst portion 30) is also exposed.

[0095] The region indicated by the symbol R4 in Fig. 10 is observed with a scanning electron microscope (SEM) from the Z-axis direction (the direction perpendicular to the paper surface of Fig. 10), and an SEM image G11 shown in Fig. 11 is taken. At this time, as shown in Fig. 11, the SEM image G11 is taken so that the longitudinal direction Y of the cut piece M is aligned with the lateral direction of the SEM image G11.

[0096] The SEM image G11 includes the first uneven surface 41, the second region S2b (this region is not covered by the second catalyst part 30), and the partition wall 12 located therebetween (see FIG. 10).

[0097] The thickness of the partition 12 included in the SEM image G11 is calculated. Specifically, as shown in FIG. 11 , intersections Q1 and Q2 between a center line CL11 perpendicular to the horizontal direction of the SEM image G11 and the outline of the partition 12 are identified, and the distance D12 between the intersections Q1 and Q2 is defined as the thickness of the partition 12.

[0098] As shown in FIG. 11, a line PL1 is drawn from the intersection Q1 in parallel with the lateral direction of the SEM image G11, and a line PL2 is drawn from the intersection Q2 in parallel with the lateral direction of the SEM image G11.

[0099] 11, a rectangular measurement region MR11 is set at a position distance D1 from the line PL1 within the first uneven surface 41, and a rectangular measurement region MR12 is set at a position distance D2 from the line PL2 within the second region S2b (this region is not covered by the second catalyst section 30). The distances D1 and D2 are 0.5 times the thickness (distance D12) of the partition wall 12. The vertical dimension of the measurement regions MR11 and MR12 (the X-axis direction in FIG. 11) is 1.5 times the thickness (distance D12) of the partition wall 12, and the horizontal dimension of the measurement regions MR11 and MR12 (the Y-axis direction in FIG. 11) is 5 times the thickness (distance D12) of the partition wall 12.

[0100] A Si mapping image of the SEM image G11 is obtained. The mapping target element may be an element other than silicon (Si) as long as it is an element specific to the base material 10 (an element that is contained in the base material 10 but not contained in the first catalytic portion 20 or the second catalytic portion 30).

[0101] In the Si mapping image, areas other than the measurement areas MR11 and MR12 are masked, and then the measurement areas MR11 and MR12 are binarized under the following binarization conditions. Threshold = (average brightness value of background + average brightness value of target area) / 2

[0102] The number of dots in the binarized measurement areas MR11 and MR12 is measured, and R 11 Calculate. R 11 =1-(number of dots in binarized measurement area MR11) / (number of dots in binarized measurement area MR12)

[0103] R 11When calculating the area of ​​the first region S1a, the number of dots in the binarized measurement region MR11 is regarded as the area of ​​the portion of the first region S1a that is not covered by the first catalyst part 20, and the number of dots in the binarized measurement region MR12 is regarded as the area of ​​the first region S1a.

[0104] For each of the three cut pieces M, R 11 The average value is used as the R 11 Let's say.

[0105] R 11 The measuring equipment and conditions used to calculate are as follows: Device name: Tabletop scanning electron microscope Model: JCM-7000 Manufacturer: JEOL Ltd. Detector type: EX-54700U1L21 Accelerating voltage: 5 kV Magnification: Any Measuring element: Si (K line) Mapping pixel count: 512x384 Process time: T1 Number of sweeps: 20 Duel time: 0.02ms Filter: Average(3x3)

[0106] <R 12 Calculation method> R 12 The calculation method is as follows:

[0107] In the same manner as above, the cut pieces M shown in FIGS. 9 and 10 are prepared.

[0108] 9 and 10, in the cut piece M, the first uneven surface 41 is exposed, and the second region S2b (this region is not covered with the second catalyst part 30) is also exposed. The height MH of the partition wall 12 located between these exposed surfaces is adjusted to 500 μm or more.

[0109] The region indicated by reference symbol R5 in FIG. 10 is scanned in the Z-axis direction (the direction perpendicular to the paper surface of FIG. 10) with a surface roughness meter to capture a scanned image G12 shown in FIG. 12, and the surface roughness is measured. At this time, as shown in FIG. 12, the scanned image G12 is captured so that the length direction Y of the cut piece M is aligned with the Y-axis direction of the scanned image G12 (the vertical direction in FIG. 12). The scan magnification is adjusted so that the entire region indicated by reference symbol R5 in FIG. 10 is included in the scanned range. During scanning, focusing is performed on the second region S2b, and the scanned range in the Z-axis direction (the direction perpendicular to the paper surface of FIG. 10) is set to ±400 μm with respect to the second region S2b where focusing is performed. Note that because the height MH of the partition 12 is adjusted to 500 μm or more, the partition 12 is outside the scanned range. Therefore, the partition 12 is displayed in black as "null" in the scanned image G12, as shown in FIG. 12.

[0110] 12, a line analysis is performed on a center line CL12 perpendicular to the Y-axis direction (the vertical direction in FIG. 12) of the scanned image G12. A continuous portion outside the scanned range extending for 10 μm or more is regarded as a partition wall 12, and the x-coordinates of the left and right endpoints P1 and P2 of the first uneven surface 41 and the left and right endpoints P3 and P4 of the second region S2b are determined.

[0111] 12, a line QL1 that passes through the left end point P1 and is parallel to the Y-axis direction of the scanned image G12, and a line QL2 that passes through the right end point P2 and is parallel to the Y-axis direction of the scanned image G12 are drawn, and these lines are defined as the boundary line between the first uneven surface 41 and the partition 12. The distance DS1 between the line QL1 and the line QL2 is defined as the width (dimension in the X-axis direction) of the first uneven surface 41.

[0112] 12, a line QL3 that passes through the left end point P3 and is parallel to the Y-axis direction of the scanned image G12, and a line QL4 that passes through the right end point P4 and is parallel to the Y-axis direction of the scanned image G12 are drawn, and these lines are defined as the boundary line between the second region S2b and the partition 12. The distance DS2 between the line QL3 and the line QL4 is defined as the width of the second region S2b (the dimension in the X-axis direction).

[0113] 12, a rectangular measurement region MR21 is set at a position within the first uneven surface 41, a predetermined distance (0.25 times the width (distance DS1) of the first uneven surface 41) from the lines QL1 and QL2, and a rectangular measurement region MR22 is set at a position within the second region S2b, a predetermined distance (0.25 times the width (distance DS2) of the second region S2b) from the lines QL3 and QL4. The dimension of the measurement region MR21 in the X-axis direction (the horizontal direction in FIG. 12) is 0.5 times the width (distance DS1) of the first uneven surface 41, and the dimension of the measurement region MR21 in the Y-axis direction (the vertical direction in FIG. 12) is twice the width (distance DS1) of the first uneven surface 41. The dimension of the measurement region MR22 in the X-axis direction (horizontal direction in Figure 12) is 0.5 times the width of the second region S2b (distance DS2), and the dimension of the measurement region MR22 in the Y-axis direction (vertical direction in Figure 12) is twice the width of the second region S2b (distance DS2).

[0114] From the frequency distribution of surface roughness in the measurement region MR21, the maximum and minimum surface roughness in the area ratio range of 1% to 99% are determined, and the difference V1 between the maximum and minimum surface roughness is calculated. Similarly, from the frequency distribution of surface roughness in the measurement region MR22, the maximum and minimum surface roughness in the area ratio range of 1% to 99% are determined, and the difference V2 between the maximum and minimum surface roughness is calculated. Note that the area ratio means the cumulative area ratio from the side with the smaller surface roughness (the same applies below). Based on the following formula, the ratio R of the surface roughness of the first uneven surface 41 to the surface roughness of the first region S1a (first region S1a before the first catalyst portion 20 is formed) is calculated. 12 Calculate. R 12 =V1 / V2

[0115] R 12 In calculating V1, the difference V1 is regarded as the surface roughness of the first uneven surface 41, and the difference V2 is regarded as the surface roughness of the first region S1a (the first region S1a before the first catalyst portion 20 is formed).

[0116] For each of the three cut pieces M, R 12 The average value is calculated as R 12 Let's say.

[0117] R 12 The measuring equipment and conditions used to calculate are as follows: Equipment name: Non-contact surface profile measuring machine Model: Nexview Manufacturer: Zygo Measurement mode: CSI (Coherence Scanning Interferometry) Measuring lens: x2.75 Measurement range: 3.01mm x 3.01mm (XY range) Scan length: 800 μm (Z range)

[0118] The difference V2 is usually 20 μm or more and 120 μm or less, preferably 40 μm or more and 100 μm or less, and more preferably 50 μm or more and 80 μm or less.

[0119] <R 21 Calculation method> R 21 The calculation method is as follows:

[0120] The exhaust gas purifying catalyst 1 is cut along a plane parallel to the axial direction of the substrate 10 and a plane perpendicular to the axial direction of the substrate 10. A portion indicated by symbol N in FIG. 6 is cut out from the exhaust gas purifying catalyst 1 to prepare a cut piece N shown in FIGS. 13 and 14 . The cut piece N includes the second uneven surface 42 but does not include the first uneven surface 41. The length of the second uneven surface 42 included in the cut piece N is equal to the length of the cut piece N. The cut piece N can be obtained from the vicinity of the exhaust gas outlet end of the exhaust gas purifying catalyst 1. For example, by cutting the substrate 10 at two locations 5 mm and 15 mm away from the exhaust gas outlet end in the direction opposite to the exhaust gas flow direction E along a plane perpendicular to the axial direction of the substrate 10, a cut piece N having a length of 10 mm can be obtained that includes the second uneven surface 42 but does not include the first uneven surface 41. The size of the cut piece N can be appropriately changed as needed.

[0121] As shown in FIGS. 13 and 14, in the cut piece N, the second uneven surface 42 is exposed, and the second region S1b (this region is not covered with the first catalyst portion 20) is also exposed.

[0122] The region indicated by the symbol R6 in Fig. 14 is observed with a scanning electron microscope (SEM) from the Z-axis direction (the direction perpendicular to the paper surface of Fig. 14), and an SEM image G21 shown in Fig. 15 is taken. At this time, as shown in Fig. 15, the SEM image G21 is taken so that the longitudinal direction Y of the cut piece N is the lateral direction of the SEM image G21.

[0123] The SEM image G21 includes the second uneven surface 42, the second region S1b (this region is not covered by the first catalyst part 20), and the partition wall 12 located therebetween (see FIG. 14).

[0124] The thickness of the partition 12 included in the SEM image G21 is calculated. Specifically, as shown in Fig. 15 , intersections Q1' and Q2' between a center line CL21 perpendicular to the horizontal direction of the SEM image G21 and the outline of the partition 12 are identified, and the distance D12' between the intersections Q1' and Q2' is defined as the thickness of the partition 12.

[0125] As shown in FIG. 15, a line PL1' is drawn from the intersection Q1' parallel to the lateral direction of the SEM image G21, and a line PL2' is drawn from the intersection Q2' parallel to the lateral direction of the SEM image G21.

[0126] 15, a rectangular measurement region NR11 is set at a position within the second uneven surface 42, a distance D1' from the line PL1', and a rectangular measurement region NR12 is set at a position within the second region S1b (this region is not covered by the first catalyst section 20), a distance D2' from the line PL2'. The distances D1' and D2' are 0.5 times the thickness of the partition wall 12 (distance D12'). The vertical dimension of the measurement regions NR11 and NR12 (the X-axis direction in FIG. 15) is 1.5 times the thickness of the partition wall 12 (distance D12'), and the horizontal dimension of the measurement regions NR11 and NR12 (the Y-axis direction in FIG. 15) is 5 times the thickness of the partition wall 12 (distance D12').

[0127] A Si mapping image of the SEM image G21 is obtained. The mapping target element may be an element other than silicon (Si) as long as it is an element specific to the base material 10 (an element that is contained in the base material 10 but not contained in the first catalytic portion 20 or the second catalytic portion 30).

[0128] In the Si mapping image, areas other than the measurement areas NR11 and NR12 are masked, and then the measurement areas NR11 and NR12 are binarized under the following binarization conditions. Threshold = (average brightness value of background + average brightness value of target area) / 2

[0129] The number of dots in the binarized measurement areas NR11 and NR12 is measured, and R is calculated based on the following formula: 21 Calculate. R 21 =1-(number of dots in binarized measurement area NR11) / (number of dots in binarized measurement area NR12)

[0130] R 21 When calculating the area ratio, the number of dots in the binarized measurement area NR11 is regarded as the area of ​​the portion of the first area S2a that is not covered by the second catalyst part 30, and the number of dots in the binarized measurement area NR12 is regarded as the area of ​​the first area S2a.

[0131] For each of the three cut pieces M, R 21 The average value is used as the R 21 Let's say.

[0132] R 21 The measuring equipment and conditions used to calculate 11 is the same as:

[0133] <R 22 Calculation method> R 22 The calculation method is as follows:

[0134] In the same manner as above, the cut pieces N shown in FIGS. 13 and 14 are prepared.

[0135] 13 and 14, in the cut piece N, the second uneven surface 42 is exposed, and the second region S1b (this region is not covered with the first catalyst part 20) is also exposed. The height NH of the partition wall 12 located between these exposed surfaces is adjusted to 500 μm or more.

[0136] The region indicated by reference symbol R7 in FIG. 14 is scanned in the Z-axis direction (the direction perpendicular to the paper surface of FIG. 14) with a surface roughness meter to capture a scanned image G22 shown in FIG. 16, and the surface roughness is measured. At this time, the scanned image G22 is captured so that the length direction Y of the cut piece N is aligned with the Y-axis direction of the scanned image G22 (the vertical direction in FIG. 16). The scan magnification is adjusted so that the entire region indicated by reference symbol R7 in FIG. 14 is included in the scanned range. During scanning, the second region S1b is focused, and the scanned range in the Z-axis direction (the direction perpendicular to the paper surface of FIG. 14) is set to ±400 μm with respect to the second region S1b where the focus was adjusted. Because the height NH of the partition walls 12 is adjusted to 500 μm or more, the partition walls 12 are outside the scanned range. As shown in FIG. 16, the partition walls 12 are displayed in black as "null" in the scanned image G22.

[0137] As shown in Fig. 16, a line analysis is performed on a center line CL22 perpendicular to the Y-axis direction (the vertical direction in Fig. 16) of the scanned image G22. A continuous portion outside the scanned range extending for 10 µm or more is regarded as a partition wall 12, and the x-coordinates of the left end point P1' and the right end point P2' of the second uneven surface 42 and the x-coordinates of the left end point P3' and the right end point P4' of the second region S1b are determined.

[0138] 16, a line QL1' that passes through the left end point P1' and is parallel to the Y-axis direction of the scanned image G22, and a line QL2' that passes through the right end point P2' and is parallel to the Y-axis direction of the scanned image G22 are drawn, and these lines are defined as the boundary line between the second uneven surface 42 and the partition 12. The distance DS1' between the line QL1' and the line QL2' is defined as the width (dimension in the X-axis direction) of the second uneven surface 42.

[0139] 16, a line QL3' that passes through the left end point P3' and is parallel to the Y-axis direction of the scanned image G22, and a line QL4' that passes through the right end point P4' and is parallel to the Y-axis direction of the scanned image G22, are drawn, and these lines are defined as the boundary line between the second region S1b and the partition 12. The distance DS2' between the line QL3' and the line QL4' is defined as the width of the second region S1b (the dimension in the X-axis direction).

[0140] 16, a rectangular measurement region NR21 is set at a position within the second uneven surface 42, a predetermined distance (0.25 times the width (distance DS1') of the second uneven surface 42) from the lines QL1' and QL2', and a rectangular measurement region NR22 is set at a position within the second region S1b, a predetermined distance (0.25 times the width (distance DS2') of the second region S1b) from the lines QL3' and QL4'. The dimension of the measurement region NR21 in the X-axis direction (the horizontal direction in FIG. 16) is 0.5 times the width (distance DS1') of the second uneven surface 42, and the dimension of the measurement region NR21 in the Y-axis direction (the vertical direction in FIG. 16) is twice the width (distance DS1') of the second uneven surface 42. The dimension of the measurement region NR22 in the X-axis direction (horizontal direction in Figure 16) is 0.5 times the width of the second region S1b (distance DS2'), and the dimension of the measurement region NR22 in the Y-axis direction (vertical direction in Figure 16) is twice the width of the second region S1b (distance DS2').

[0141] From the frequency distribution of surface roughness in the measurement region NR21, the maximum and minimum surface roughness in the area ratio range of 1% to 99% are determined, and the difference V1' between the maximum and minimum surface roughness is calculated. Similarly, from the frequency distribution of surface roughness in the measurement region NR22, the maximum and minimum surface roughness in the area ratio range of 1% to 99% are determined, and the difference V2' between the maximum and minimum surface roughness is calculated. Based on the following formula, the ratio R of the surface roughness of the second uneven surface 42 to the surface roughness of the first region S2a (first region S2a before the second catalyst portion 30 is formed) is calculated. 22 Calculate. R 22 =V1' / V2'

[0142] R 22In calculating V1′, the difference V1′ is regarded as the surface roughness of the second uneven surface 42, and the difference V2′ is regarded as the surface roughness of the first region S2a (the first region S2a before the second catalyst portion 30 is formed).

[0143] For each of the three cut pieces N, R 22 The average value is calculated as R 22 Let's say.

[0144] R 22 The measuring equipment and conditions used to calculate 12 is the same as:

[0145] The difference V2' is usually 20 μm or more and 120 μm or less, preferably 40 μm or more and 100 μm or less, and more preferably 50 μm or more and 80 μm or less.

[0146] <Components of the catalyst part> Each of the first catalytic section 20 and the second catalytic section 30 contains at least one kind of precious metal element. The precious metal element can be selected from, for example, platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), iridium (Ir), osmium (Os), etc., but is preferably selected from Pt, Pd, and Rh from the viewpoint of improving exhaust gas purification performance.

[0147] The precious metal element is contained in the first catalyst section 20 or the second catalyst section 30 in a form capable of functioning as a catalytically active component, such as a precious metal, an alloy containing the precious metal element, or a compound containing the precious metal element (e.g., an oxide of the precious metal element). The catalytically active component is preferably in a particulate form from the viewpoint of enhancing exhaust gas purification performance.

[0148] The amount of precious metal elements per unit volume of the substrate 10 (if the catalyst portion contains two or more types of precious metal elements, the total amount of the two or more types of precious metal elements) is preferably 0.5 g / L or more and 1.5 g / L or less in terms of precious metal, from the viewpoint of balancing exhaust gas purification performance and cost.

[0149] It is preferable that the first catalyst section 20 and the second catalyst section 30 each include a carrier, and the catalytically active component is supported on the carrier.

[0150] The phrase "catalytically active components are supported on a support" means that the catalytically active components are physically or chemically adsorbed or held on the outer surface or the inner pore surfaces of the support. For example, when elemental mapping obtained by analyzing a cross section of a catalyst using an energy dispersive spectroscopy (EDS) reveals that the catalytically active components and the support are present in the same region, it can be determined that the catalytically active components are supported on a support.

[0151] Examples of the carrier include inorganic oxide particles, etc. The inorganic oxide constituting the inorganic oxide particles may be an inorganic oxide having oxygen storage capacity (OSC) (hereinafter, may be referred to as "oxygen storage component"), or may be an inorganic oxide other than the oxygen storage component.

[0152] Examples of oxygen storage components include cerium oxide, and composite oxides containing cerium and zirconium elements (CeO2-ZrO2 composite oxides).

[0153] In the CeO2-ZrO2-based composite oxide, cerium oxide and zirconium oxide preferably form a solid solution phase, and cerium oxide and zirconium oxide may each form a single phase (cerium oxide phase, zirconium oxide phase) in addition to the solid solution phase.

[0154] The CeO2-ZrO2 composite oxide may contain one or more metal elements other than cerium and zirconium. The metal elements or oxides thereof other than cerium and zirconium may form a solid solution phase with cerium oxide and / or zirconium oxide, or may form a single phase. Examples of metal elements other than cerium and zirconium include rare earth elements other than cerium, alkaline earth metals, and transition metals.

[0155] Examples of inorganic oxides other than the oxygen storage component include alumina, silica, silica-alumina, alumino-silicate, alumina-zirconia, alumina-chromia, alumina-ceria, alumina-lanthana, and titania.

[0156] <Method for manufacturing exhaust gas purification catalyst> A method for producing the exhaust gas purifying catalyst 1 will be described below. A substrate 10, a slurry for forming the first catalyst portion 20, and a slurry for forming the second catalyst portion 30 are prepared.

[0157] The compositions of the slurries for forming the first catalyst section 20 and the second catalyst section 30 are adjusted according to the compositions of the first catalyst section 20 and the second catalyst section 30, respectively. The slurry contains, for example, a source of a precious metal element, inorganic oxide particles, a binder, a pore-forming material, a solvent, etc. Examples of the source of a precious metal element include salts of precious metal elements, and examples of salts of precious metal elements include nitrates, ammine complex salts, acetates, chlorides, etc. Examples of inorganic oxides constituting the inorganic oxide particles include oxygen storage components and inorganic oxides other than the oxygen storage component. The oxygen storage component and inorganic oxides other than the oxygen storage component are the same as those described above. Examples of binders include alumina sol, zirconia sol, titania sol, silica sol, ceria sol, etc. Examples of pore-forming materials include cross-linked polymethyl(meth)acrylate particles, cross-linked polybutyl(meth)acrylate particles, cross-linked polystyrene particles, cross-linked polyacrylic ester particles, melamine-based resins, etc. Examples of solvents include water, organic solvents, etc. Examples of organic solvents include alcohol, acetone, dimethyl sulfoxide, and dimethylformamide. The solvent may be one type of solvent or a mixture of two or more types of solvents. Examples of mixtures of two or more types of solvents include a mixture of water and one or two or more types of organic solvents, and a mixture of two or more types of organic solvents.

[0158] The exhaust gas inlet side end of the substrate 10 is immersed in a slurry for forming the first catalyst section 20, and the slurry is sucked from the opposite side, followed by drying. In this way, a precursor of the first catalyst section 20 is formed. By adjusting the solid content concentration, viscosity, etc. of the slurry, it is possible to adjust the length LS1a of the first region S1a where the precursor of the first catalyst section 20 is formed. In addition, by adjusting the coating amount of the slurry, the type of material constituting the slurry, the particle size of the pore-forming material contained in the slurry, etc., it is possible to adjust the thickness of the precursor of the first catalyst section 20 (and therefore R 11 and R 12 ) and the mass of the precursor of the first catalyst portion 20 per unit volume of the substrate 10 (and thus the mass of the first catalyst portion 20 per unit volume of the substrate 10) can be adjusted. The drying temperature is, for example, 40 to 120°C.

[0159] The exhaust gas outlet side end of the substrate 10 is immersed in a slurry for forming the second catalyst section 30, and the slurry is sucked from the opposite side, followed by drying. In this way, a precursor of the second catalyst section 30 is formed. By adjusting the solid content concentration, viscosity, etc. of the slurry, it is possible to adjust the length LS2a of the first region S2a where the precursor of the second catalyst section 30 is formed. In addition, by adjusting the coating amount of the slurry, the type of material constituting the slurry, the particle size of the pore-forming material contained in the slurry, etc., it is possible to adjust the thickness of the precursor of the second catalyst section 30 (and therefore R 21 and R 22 ) and the mass of the precursor of the second catalyst portion 30 per unit volume of the substrate 10 (and thus the mass of the second catalyst portion 30 per unit volume of the substrate 10) can be adjusted. The drying temperature is, for example, 40 to 120°C.

[0160] The particle size of the inorganic oxide particles in the slurry can be adjusted appropriately. 11 , R 12 , R 21 and R 22 In order to easily adjust the D of the inorganic oxide particles in the slurry to a desired range, 90 is preferably 10 μm or more and 30 μm or less, more preferably 15 μm or more and 25 μm or less. 90is the particle size at which the cumulative volume is 90% in the volume-based particle size distribution measured by a laser diffraction / scattering particle size distribution measurement method.

[0161] The particle size of the pore-forming material can be adjusted as appropriate. 11 , R 12 , R 21 and R 22 In order to easily adjust the median diameter D of the pore-forming material to a desired range, 50 is preferably 1 μm or more and 30 μm or less, more preferably 3 μm or more and 25 μm or less, and even more preferably 5 μm or more and 20 μm or less. 50 is the particle size at which the cumulative volume is 50% in the volume-based particle size distribution measured by a laser diffraction / scattering particle size distribution measurement method.

[0162] D 50 or D 90 The measurement is carried out using a laser diffraction scattering particle size distribution analyzer automatic sample feeder (Microtrac SDC manufactured by Microtrac-Bell) by putting the sample to be measured into an aqueous dispersion medium, irradiating it with 40W ultrasound for 360 seconds at a flow rate of 26mL / sec, and then using a laser diffraction scattering particle size distribution analyzer (Microtrac MT3300EXII manufactured by Microtrac-Bell). The measurement is carried out twice under the following conditions: particle refractive index 1.5, particle shape spherical, solvent refractive index 1.3, set zero 30 seconds, and measurement time 30 seconds. The average of the obtained measurements is taken as D. 50 or D 90 Pure water is used as the aqueous dispersion medium.

[0163] After the precursor of the first catalytic section 20 and the precursor of the second catalytic section 30 are formed, they are calcined. This forms the first catalytic section 20 and the second catalytic section 30. From the viewpoint of preventing a decrease in catalytic activity and of successfully calcining the pore-forming material, the calcination temperature is preferably 350 to 550°C. The atmosphere during calcination is, for example, air. [Example]

[0164] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[0165] Example 1 (1) Preparation of slurry A rhodium nitrate solution and a dinitrodiammine platinum nitrate solution were mixed, and a Ce-Zr composite oxide powder and an alumina powder were added to the mixture. Next, a pore-forming material (crosslinked polymethyl(meth)acrylate particles with a median diameter D50 of 20 μm), an alumina sol, and water as a solvent were added to the mixture to prepare a slurry.

[0166] The amount of each component in the slurry was adjusted to 1 mass% rhodium (metal equivalent), 75 mass% Ce-Zr composite oxide powder, 7 mass% alumina powder, 9 mass% platinum (metal equivalent), and 8 mass% alumina sol (solids equivalent) based on the mass of the catalyst portion formed by drying and calcining the slurry. The amount of pore-forming material in the slurry was adjusted to 30.0 mass% of the mass of the catalyst portion formed by drying and calcining the slurry. The mass of the catalyst portion formed by drying and calcining the slurry can be calculated by subtracting the mass of components (e.g., solvent, pore-forming material, etc.) that disappear during drying and calcining the slurry from the mass of the slurry.

[0167] D of metal oxide powder (Ce-Zr composite oxide powder and alumina powder) in slurry 90 was 20 μm.

[0168] (2) Manufacturing of exhaust gas purification catalysts A substrate having the structure shown in Figures 2 to 8 was prepared, that is, a substrate including inlet cells extending in the axial direction of the substrate, outlet cells extending in the axial direction of the substrate, and porous partition walls separating the inlet and outlet cells. The thickness of the partition walls was 200 to 250 µm, the total number of inlet and outlet cells in a cross section perpendicular to the axial direction of the substrate was 300 cells per square inch, the volume of the substrate was 1.0 L, and the length of the substrate was 91 mm. The average pore diameter of the partition walls was 15 µm, and the porosity (porosity) of the partition walls was 63%.

[0169] The exhaust gas inlet end of the substrate was immersed in the slurry, and the slurry was sucked from the opposite side, followed by drying for 10 minutes at 90° C. As a result, a first precursor (first catalyst part before calcination) consisting of the solid content of the slurry was formed on the inlet cell side of the partition wall of the substrate.

[0170] After drying, the exhaust gas outlet end of the substrate was immersed in the slurry, and the slurry was sucked from the opposite side, followed by drying for 10 minutes at 90° C. In this way, a second precursor (second catalyst part before calcination) made of the solid content of the slurry was formed on the outlet cell side of the partition walls of the substrate.

[0171] Thereafter, the substrate was calcined at 450° C. for 1 hour to form a first catalyst portion and a second catalyst portion on the substrate, thereby obtaining the exhaust gas purifying catalyst of Example 1.

[0172] When the exhaust gas inlet-side and exhaust gas outlet-side ends of the substrate were immersed in the slurry, the immersion conditions were adjusted so that the ratio of the length of the first region, where the first catalyst portion was formed on the inlet-side cell-side surface of the partition wall, to the length of the substrate was 0.45, the ratio of the length of the first region, where the second catalyst portion was formed on the outlet-side cell-side surface of the partition wall, to the length of the substrate was 0.70, and the total mass (WC amount) of the first catalyst portion and the second catalyst portion per unit volume of the substrate was 11 g / L.

[0173] The exhaust gas purifying catalyst of Example 1 was subjected to the R 11 , R 12 , R 21 and R 22 was calculated.

[0174] (3) Pressure loss evaluation The side of the exhaust gas purification catalyst of Example 1 was supported and fixed so that the end face on the exhaust gas inlet side faced upward. Air was sucked from below the fixed exhaust gas purification catalyst (the end face on the exhaust gas outlet side) at a rate of 50 L / sec. The difference between the air pressure at the end face on the exhaust gas inlet side and the air pressure at the end face on the exhaust gas inlet side 10 seconds after the start of suction was calculated, and this was taken as the pressure loss of the exhaust gas purification catalyst of Example 1.

[0175] Instead of the exhaust gas purification catalyst of Example 1, a substrate (neither the first catalyst part nor the second catalyst part was formed) was used, and the difference between the air pressure at the end face on the exhaust gas inlet side and the air pressure at the end face on the exhaust gas inlet side 10 seconds after the start of suction was calculated in the same manner as above, and this was taken as the pressure loss of the substrate.

[0176] The pressure drop ratio (%) was calculated based on the following formula. Pressure drop ratio = (pressure drop of the exhaust gas purifying catalyst of Example 1 / pressure drop of the substrate) × 100

[0177] If the pressure loss ratio was less than 105%, it was rated as "S", if the pressure loss ratio was 105% or more but less than 125%, it was rated as "A", and if the pressure loss ratio was 125% or more, it was rated as "B".

[0178] (4) Evaluation of PM collection performance A gasoline engine vehicle using the catalyst for purifying exhaust gas of Example 1 was driven under the driving conditions of the World Wide Harmonized Exhaust Gas Test Mode (WLTC). The number of PM particles (PN cat ) was measured. In addition, the number of PM particles (PN all ) was measured, and the PM trapping performance of the exhaust gas purifying catalyst of Example 1 was calculated by the following formula. PM collection performance=1-(PN cat / PN all )

[0179] The conditions for measuring the PM trapping performance were as follows: Test vehicle: 1.5L direct injection turbo engine Gasoline used: Fuel for certification tests PM measuring device: Horiba Ltd.

[0180] Instead of the gasoline engine vehicle using the exhaust gas purification catalyst of Example 1, a gasoline engine vehicle using a substrate (neither the first catalyst section nor the second catalyst section was formed) was used, and the PM collection performance of the substrate was determined in the same manner as above.

[0181] The PM collection efficiency ratio (%) was calculated based on the following formula. PM collection performance ratio=(PM collection performance of the exhaust gas purification catalyst of Example 1 / PM collection performance of the substrate)×100

[0182] If the PM collection efficiency ratio was over 110%, it was rated as "S", if the PM collection efficiency ratio was over 100% and up to 110%, it was rated as "A", and if the PM collection efficiency ratio was 100% or less, it was rated as "B".

[0183] <Example 2> The same operation as in Example 1 was performed, except that when the exhaust gas inlet side and exhaust gas outlet side ends of the substrate were immersed in the slurry, the immersion conditions were adjusted so that the total mass (WC amount) of the first catalyst part and the second catalyst part per unit volume of the substrate was 16 g / L.

[0184] Example 3 The same operation as in Example 1 was performed, except that when the exhaust gas inlet side and exhaust gas outlet side ends of the substrate were immersed in the slurry, the immersion conditions were adjusted so that the total mass (WC amount) of the first catalyst part and the second catalyst part per unit volume of the substrate was 20 g / L.

[0185] Example 4 As a pore-forming material, the median diameter D 50 The same procedure as in Example 1 was carried out, except that crosslinked polymethyl (meth)acrylate particles having a particle size of 5 μm were used.

[0186] <Comparative Example 1> D of metal oxide powder (Ce-Zr composite oxide powder and alumina powder) in slurry 90 The same operation as in Example 1 was carried out, except that the thickness was adjusted to 0.5 μm.

[0187] <Comparative Example 2> The same operation as in Example 1 was performed, except that when the exhaust gas inlet side and exhaust gas outlet side ends of the substrate were immersed in the slurry, the immersion conditions were adjusted so that the total mass (WC amount) of the first catalyst part and the second catalyst part per unit volume of the substrate was 30 g / L.

[0188] <Comparative Example 3> The same operation as in Example 1 was performed, except that when the exhaust gas inlet side and exhaust gas outlet side ends of the substrate were immersed in the slurry, the immersion conditions were adjusted so that the total mass (WC amount) of the first catalyst part and the second catalyst part per unit volume of the substrate was 45 g / L.

[0189] The results of Examples 1 to 4 and Comparative Examples 1 to 3 are shown in Tables 1 and 2.

[0190] [Table 1]

[0191] [Table 2]

[0192] From the above results, it was confirmed that by the exhaust gas purification catalyst satisfying the above formulas (11) and (12) or the above formulas (21) and (22), it is possible to improve the PM trapping performance and suppress the increase in pressure loss.

[0193] In Examples 1 to 4 and Comparative Examples 1 to 3, R 11 , R 12 , R 21 and R 22 The values ​​calculated to determine are shown in Table 3 below.

[0194] [Table 3] [Explanation of symbols]

[0195] 1. Exhaust gas purification catalyst 10...Base material 20...1st catalyst section 30...Second catalyst section 11....Cylindrical portion of substrate 12. Substrate partition 13. Cells in the substrate 13a Inlet cell 13b Outlet cell S1a: The first region on the inlet cell surface of the partition wall S1b: The second region on the inlet cell surface of the partition wall S2a: The first region on the outflow cell surface of the partition wall S2b: The second region on the outflow cell surface of the partition 41...1st uneven surface 42...Second uneven surface

Claims

1. An exhaust gas purification catalyst comprising a substrate extending in an exhaust gas flow direction, and both a first catalytic portion and a second catalytic portion provided on the substrate, The substrate is an inlet-side cell extending in the exhaust gas flow direction, the inlet-side cell having an open end on the exhaust gas inlet side and a closed end on the exhaust gas outlet side; an outlet-side cell extending in the exhaust gas flow direction, the outlet-side cell having a closed end on an exhaust gas inlet side and an open end on an exhaust gas outlet side; a porous partition wall separating the inlet cell and the outlet cell; Equipped with the substrate is made of a ceramic material, a total number of the inlet-side cells and the outlet-side cells per square inch in a cross section obtained by cutting the substrate along a plane perpendicular to an axial direction of the substrate is 200 cells or more and 350 cells or less; the thickness of the partition wall is 150 μm or more and 350 μm or less, the first catalytic portion is formed in a predetermined region of an inlet-side cell-side surface of the partition wall, the region extending from an exhaust gas inlet-side end of the partition wall along the exhaust gas flow direction, the second catalytic portion is formed in a predetermined region of an outlet-side cell side surface of the partition wall, the region extending from an exhaust gas outlet-side end of the partition wall along a direction opposite to the exhaust gas flow direction, a part of the predetermined region of the inlet-side cell-side surface is covered with the first catalyst portion, while the remaining portion of the predetermined region of the inlet-side cell-side surface is exposed without being covered with the first catalyst portion, so that the surface of the first catalyst portion and the remaining portion of the predetermined region together form a first uneven surface; a part of the predetermined region of the outlet-side cell surface is covered with the second catalyst portion, while the remaining portion of the predetermined region of the outlet-side cell surface is exposed without being covered with the second catalyst portion, whereby the surface of the second catalyst portion and the remaining portion of the predetermined region together form a second uneven surface; The first catalyst portion is represented by the following formulas (11) and (12): 0.20≦R １１ ≦0.80 ・・・(11) 0.30≦R １２ ≦0.85 ・・・(12) [In the formula, R １１ represents the ratio of the area of ​​the part covered by the first catalyst portion to the area of ​​the predetermined region of the inlet-side cell surface, and R １２ represents the ratio of the surface roughness of the first uneven surface to the surface roughness of the predetermined region of the inlet cell side surface.] Fulfilling The second catalyst portion is represented by the following formulas (21) and (22): 0.20≦R ２１ ≦0.80 ・・・(21) 0.30≦R ２２ ≦0.85 ・・・(22) [In the formula, R ２１ represents the ratio of the area of ​​the part covered by the second catalyst portion to the area of ​​the predetermined region of the outlet-side cell surface, and R ２２ represents the ratio of the surface roughness of the second uneven surface to the surface roughness of the predetermined region of the outflow cell side surface.] The exhaust gas purifying catalyst satisfies the above.

2. The first catalyst portion is represented by the following formula (13): 0.060≦R １３ ≦0.55 ・・・(13) [In the formula, R １３ is R １１ to R １２ represents the value obtained by multiplying by R １１ and R １２ has the same meaning as above.] Fulfilling The second catalyst portion is represented by the following formula (23): 0.060≦R ２３ ≦0.55 ・・・(23) [In the formula, R ２３ is R ２１ to R ２２ represents the value obtained by multiplying by R ２１ and R ２２ has the same meaning as above.] The exhaust gas purifying catalyst according to claim 1, which satisfies the above.

3. 3. The exhaust gas purification catalyst according to claim 1, wherein a ratio of a sum of a length of the predetermined region on the inlet-side cell side surface and a length of the predetermined region on the outlet-side cell side surface to a length of the substrate is 0.30 or more and 1.8 or less.

4. 3. The exhaust gas purification catalyst according to claim 1, wherein the first catalytic portion and the second catalytic portion each independently contain at least one catalytically active component selected from the group consisting of platinum (Pt), palladium (Pd), and rhodium (Rh).

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