Catalysts for Waste Gas Purification and Their Manufacturing Methods

Abstract

The present invention aims to provide a catalyst for exhaust gas purification that can improve PM capture performance and suppress pressure drop. The catalyst (1A) comprises a wall-flow substrate (10), a first catalyst layer (20), and a second catalyst layer (30). In the logarithmic differential pore volume distribution curve of the first catalyst layer (20), a peak A of 0.20 mL / g or more exists in the range of pore size 1 μm or more and 3 μm or less. The conditions for peak value B, which exists in the range of pore size below μm, to be 0.20 mL / g or more are set as conditions 1 and 2, respectively. In the logarithmic differential pore volume distribution curve of the second catalyst layer (30), the conditions for peak value C, which exists in the range of pore size above 1 μm and below 3 μm, to be 0.20 mL / g or more, and the conditions for peak value D, which exists in the range of pore size above 3 μm and below 10 μm, to be 0.20 mL / g or more, respectively are set as conditions 3 and 4. The combination of the first catalyst layer (20) and the second catalyst layer (30) satisfies the specified conditions.

Description

Technical Field

[0001] This invention relates to catalysts for waste gas purification and their manufacturing methods. Background Technology

[0002] The exhaust gases from internal combustion engines in 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. These three-way catalysts utilize platinum group elements such as Pt, Pd, and Rh.

[0003] It is known that exhaust gases contain harmful components such as HC, CO, and NOx, as well as particulate matter (PM), which contributes to air pollution.

[0004] In order to comply with PM-related environmental regulations, vehicles equipped with gasoline engines such as Gasoline Direct Injection (GDI) are required to have a Gasoline Particulate Filter (GPF) with PM-capturing function, just like vehicles equipped with diesel engines.

[0005] As a GPF, for example, a substrate having a structure known as a wall flow type is used. The wall flow type substrate includes: an inflow side chamber, which is open at the end of the exhaust gas inflow side and closed at the end of the exhaust gas outflow side; an outflow side chamber, which is closed at the end of the exhaust gas inflow side and open at the end of the exhaust gas outflow side; and a porous partition wall that separates the inflow side chamber and the outflow side chamber.

[0006] Since the space for catalysts used in exhaust gas purification is usually limited, a catalyst layer containing platinum group elements such as Pt, Pd, and Rh has been studied on a wall-flow substrate to capture PM while purifying harmful components such as HC, CO, and NOx (e.g., Patent Document 1). In an exhaust gas purification catalyst having a wall-flow substrate and a catalyst layer disposed on the wall-flow substrate, when exhaust gas flows in from the exhaust gas inflow side end (opening) of the inflow side chamber, passes through a porous partition wall and flows out from the exhaust gas outflow side end (opening) of the outflow side chamber, PM in the exhaust gas is captured by the pores of the catalyst layer and the partition wall.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: International Publication No. 2021 / 029098 Summary of the Invention

[0010] The problem the invention aims to solve

[0011] Smaller pores in the catalyst layer and separator walls result in higher PM capture performance, but also increased pressure loss. Conversely, larger pores in the catalyst layer and separator walls suppress the increase in pressure loss, but reduce PM capture performance. Therefore, it is difficult to simultaneously improve PM capture performance and suppress pressure loss, and a technology that can balance both is needed.

[0012] Therefore, the purpose of this invention is to provide a catalyst for exhaust gas purification and a method for manufacturing the same, which can improve PM capture performance and suppress pressure loss.

[0013] Solution for solving the problem

[0014] To address the aforementioned issues, this invention provides the following catalyst for waste gas purification and its manufacturing method.

[0015] [1] A catalyst for purifying waste gas, comprising a substrate extending along the waste gas flow direction, a first catalyst layer, and a second catalyst layer.

[0016] The substrate comprises:

[0017] The inflow side chamber extends along the direction of the exhaust gas flow, with the exhaust gas inflow side of the inflow side chamber open and the exhaust gas outflow side closed.

[0018] An outlet side chamber extending along the exhaust gas flow direction, wherein the exhaust gas inflow end of the outlet side chamber is closed, and the exhaust gas outflow end is open; and

[0019] A porous partition wall separates the inflow side chamber and the outflow side chamber.

[0020] The first catalyst layer is disposed on the inflow side chamber side of the partition wall portion, starting from the end of the waste gas inflow side of the partition wall portion along the waste gas flow direction.

[0021] The second catalyst layer is disposed on the outflow side chamber side of the partition wall portion, starting from the end of the waste gas outflow side of the partition wall portion, in a direction opposite to the waste gas flow direction.

[0022] Condition 1 is set as follows: in the logarithmic differential pore volume distribution curve of the first catalyst layer obtained by mercury intrusion porosimetry, there is a peak A in the range of pore size greater than 1 μm and less than 3 μm, and the peak A is greater than 0.20 mL / g.

[0023] Condition 2 is set as follows: in the logarithmic differential pore volume distribution curve of the first catalyst layer obtained by mercury intrusion porosimetry, there is a peak B in the range of pore size greater than 3 μm and less than 10 μm, and the peak B is greater than 0.20 mL / g.

[0024] Condition 3 is set as follows: in the logarithmic differential pore volume distribution curve of the second catalyst layer obtained by mercury intrusion porosimetry, there is a peak C in the range of pore size greater than 1 μm and less than 3 μm, and the peak C is greater than 0.20 mL / g.

[0025] Condition 4 is set as follows: in the logarithmic differential pore volume distribution curve of the second catalyst layer obtained by mercury intrusion porosimetry, a peak D exists in the range of pore size greater than 3 μm and less than 10 μm, and the peak D is greater than 0.20 mL / g.

[0026] The second catalyst layer satisfies condition 3 but not condition 4, or satisfies condition 4 but not condition 3, or satisfies both conditions 3 and 4, or neither condition 3 nor 4 is satisfied.

[0027] If the second catalyst layer satisfies condition 3 but not condition 4, then the first catalyst layer must satisfy at least condition 2 in both conditions 1 and 2.

[0028] If the second catalyst layer satisfies condition 4 but not condition 3, then the first catalyst layer must satisfy at least condition 1 in both conditions 1 and 2.

[0029] If the second catalyst layer satisfies conditions 3 and 4, and the first catalyst layer satisfies at least one of conditions 1 and 2, or neither condition 1 nor 2 is satisfied,

[0030] If conditions 3 and 4 of the second catalyst layer are not satisfied, then conditions 1 and 2 of the first catalyst layer are satisfied.

[0031] [2] According to the catalyst for purifying waste gas described in [1], wherein the second catalyst layer satisfies condition 3 and does not satisfy condition 4, or satisfies condition 4 and does not satisfy condition 3, or satisfies conditions 3 and 4.

[0032] If the second catalyst layer satisfies condition 3 but not condition 4, then the first catalyst layer must satisfy at least condition 2 in both conditions 1 and 2.

[0033] If the second catalyst layer satisfies condition 4 but not condition 3, then the first catalyst layer must satisfy at least condition 1 in both conditions 1 and 2.

[0034] If the second catalyst layer satisfies conditions 3 and 4, the first catalyst layer satisfies at least one of conditions 1 and 2.

[0035] [3] The catalyst for purifying exhaust gas according to [1] or [2], wherein, in condition 1, the peak value A is less than 1.00 mL / g, and in condition 3, the peak value C is less than 1.00 mL / g.

[0036] [4] The catalyst for purifying exhaust gas according to any one of [1] to [3], wherein, in condition 2, the peak value B is less than 1.00 mL / g, and in condition 4, the peak value D is less than 1.00 mL / g.

[0037] [5] The catalyst for purifying exhaust gas according to any one of [1] to [4], wherein, in condition 1, the peak value A is 0.31 mL / g or more, and in condition 3, the peak value C is 0.31 mL / g or more.

[0038] [6] A method for manufacturing a catalyst for purifying waste gas, the catalyst comprising a substrate extending along the waste gas flow direction, a first catalyst layer, and a second catalyst layer.

[0039] The substrate comprises:

[0040] The inflow side chamber extends along the direction of the exhaust gas flow, with the exhaust gas inflow side of the inflow side chamber open and the exhaust gas outflow side closed.

[0041] An outlet side chamber extending along the exhaust gas flow direction, wherein the exhaust gas inflow end of the outlet side chamber is closed, and the exhaust gas outflow end is open; and

[0042] A porous partition wall separates the inflow side chamber and the outflow side chamber.

[0043] The first catalyst layer is disposed on the inflow side chamber side of the partition wall portion, starting from the end of the waste gas inflow side of the partition wall portion along the waste gas flow direction.

[0044] The second catalyst layer is disposed on the outflow side chamber side of the partition wall portion, starting from the end of the waste gas outflow side of the partition wall portion, in a direction opposite to the waste gas flow direction.

[0045] The method includes the following steps:

[0046] (1a) A process of forming a first precursor layer by coating a first slurry containing a first pore-forming agent onto the inflow side chamber side of the partition wall portion;

[0047] (1b) The process of applying a second slurry containing a second pore-forming agent to the outflow side chamber of the partition wall to form a second precursor layer; and

[0048] (1c) The step of calcining the first precursor layer and the second precursor layer to form the first catalyst layer and the second catalyst layer.

[0049] The median particle size D of one of the first pore-forming agent and the second pore-forming agent 50The median particle size D of the other is greater than 4 μm. 50 Below 4μm

[0050] The first slurry contains inorganic oxide particles, and the median particle size D of the inorganic oxide particles contained in the first slurry is... 50 The size is greater than 1μm and less than 20μm.

[0051] Based on the mass of the first catalyst layer, the amount of the first pore-forming agent contained in the first precursor layer is 10% by mass or more and 60% by mass or less.

[0052] The mass of the first catalyst layer per unit volume of the portion of the substrate in which the first catalyst layer is formed is 5 g / L or more and 150 g / L or less.

[0053] The second slurry contains inorganic oxide particles, and the median particle size D of the inorganic oxide particles contained in the second slurry is... 50 The size is greater than 1μm and less than 20μm.

[0054] Based on the mass of the second catalyst layer, the amount of the second pore-forming agent contained in the second precursor layer is 10% by mass or more and 60% by mass or less.

[0055] The mass of the second catalyst layer per unit volume of the portion of the substrate in which the second catalyst layer is formed is 5 g / L or more and 150 g / L or less.

[0056] [7] A method for manufacturing a catalyst for purifying waste gas, the catalyst comprising a substrate extending along the waste gas flow direction, a first catalyst layer, and a second catalyst layer.

[0057] The substrate comprises:

[0058] The inflow side chamber extends along the direction of the exhaust gas flow, with the exhaust gas inflow side of the inflow side chamber open and the exhaust gas outflow side closed.

[0059] An outlet side chamber extending along the exhaust gas flow direction, wherein the exhaust gas inflow end of the outlet side chamber is closed, and the exhaust gas outflow end is open; and

[0060] A porous partition wall separates the inflow side chamber and the outflow side chamber.

[0061] The first catalyst layer is disposed on the inflow side chamber side of the partition wall portion, starting from the end of the waste gas inflow side of the partition wall portion along the waste gas flow direction.

[0062] The second catalyst layer is disposed on the outflow side chamber side of the partition wall portion, starting from the end of the waste gas outflow side of the partition wall portion, in a direction opposite to the waste gas flow direction.

[0063] The second catalyst layer includes a lower layer disposed on the outflow side chamber side of the partition wall portion, and an upper layer disposed on the lower layer.

[0064] The method includes the following steps:

[0065] (2a) A process of forming a first precursor layer by coating a first slurry containing a first pore-forming agent onto the inflow side chamber side of the partition wall portion;

[0066] (2b) The process of forming a third precursor layer by coating a third slurry containing a third pore-forming agent onto the outflow side chamber side of the partition wall portion;

[0067] (2c) The step of coating the fourth slurry containing the fourth pore-forming agent onto the third precursor layer to form the fourth precursor layer; and

[0068] (2d) The process of calcining the first precursor layer, the third precursor layer, and the fourth precursor layer to form the first catalyst layer, the lower layer, and the upper layer.

[0069] The median particle size D of one or both of the first pore-forming agent, the third pore-forming agent, and the fourth pore-forming agent. 50 For particles larger than 4 μm, the median particle size D of the remaining two or one is... 50 Below 4μm

[0070] The first slurry contains inorganic oxide particles, and the median particle size D of the inorganic oxide particles contained in the first slurry is... 50 The size is greater than 1μm and less than 20μm.

[0071] Based on the mass of the first catalyst layer, the amount of the first pore-forming agent contained in the first precursor layer is 10% by mass or more and 60% by mass or less.

[0072] The mass of the first catalyst layer per unit volume of the portion of the substrate in which the first catalyst layer is formed is 5 g / L or more and 150 g / L or less.

[0073] The third slurry contains inorganic oxide particles, and the median particle size D of the inorganic oxide particles contained in the third slurry is... 50 The size is greater than 1μm and less than 20μm.

[0074] Based on the mass of the lower layer, the amount of the third pore-forming agent contained in the third precursor layer is 10% by mass or more and 60% by mass or less.

[0075] The mass of the lower layer per unit volume of the portion of the substrate in which the lower layer is formed is 5 g / L or more and 90 g / L or less.

[0076] The fourth slurry contains inorganic oxide particles, and the median particle size D of the inorganic oxide particles contained in the fourth slurry is... 50 The size is greater than 1μm and less than 20μm.

[0077] Based on the mass of the upper layer, the amount of the fourth pore-forming agent contained in the fourth precursor layer is 10% by mass or more and 60% by mass or less.

[0078] The mass of the upper layer per unit volume of the portion of the substrate in which the upper layer is formed is 5 g / L or more and 60 g / L or less.

[0079] [8] According to the method of [7], wherein the median particle size D of the third pore-forming agent 50 The median particle size D of the fourth pore-forming agent is greater than 4 μm. 50 It is below 4μm.

[0080] [9] A method for manufacturing a catalyst for purifying waste gas, the catalyst comprising a substrate extending along the waste gas flow direction, a first catalyst layer, and a second catalyst layer.

[0081] The substrate comprises:

[0082] The inflow side chamber extends along the direction of the exhaust gas flow, with the exhaust gas inflow side of the inflow side chamber open and the exhaust gas outflow side closed.

[0083] An outlet side chamber extending along the exhaust gas flow direction, wherein the exhaust gas inflow end of the outlet side chamber is closed, and the exhaust gas outflow end is open; and

[0084] A porous partition wall separates the inflow side chamber and the outflow side chamber.

[0085] The first catalyst layer is disposed on the inflow side chamber side of the partition wall portion, starting from the end of the waste gas inflow side of the partition wall portion along the waste gas flow direction.

[0086] The second catalyst layer is disposed on the outflow side chamber side of the partition wall portion, starting from the end of the waste gas outflow side of the partition wall portion, in a direction opposite to the waste gas flow direction.

[0087] The first catalyst layer includes a lower layer disposed on the inflow side chamber side of the partition wall portion, and an upper layer disposed on the lower layer.

[0088] The method includes the following steps:

[0089] (3a) A process of forming a second precursor layer by coating a second slurry containing a second pore-forming agent onto the outflow side chamber side of the partition wall portion;

[0090] (3b) The process of applying a fifth slurry containing a fifth pore-forming agent to the inflow side chamber of the partition wall to form a fifth precursor layer;

[0091] (3c) The step of coating the sixth slurry containing the sixth pore-forming agent onto the fifth precursor layer to form the sixth precursor layer; and

[0092] (3d) The process of calcining the second precursor layer, the fifth precursor layer, and the sixth precursor layer to form the second catalyst layer, the lower layer, and the upper layer.

[0093] The median particle size D of one or both of the second pore-forming agent, the fifth pore-forming agent, and the sixth pore-forming agent. 50 For particles larger than 4 μm, the median particle size D of the remaining two or one is... 50 Below 4μm

[0094] The second slurry contains inorganic oxide particles, and the median particle size D of the inorganic oxide particles contained in the second slurry is... 50 The size is greater than 1μm and less than 20μm.

[0095] Based on the mass of the second catalyst layer, the amount of the second pore-forming agent contained in the second precursor layer is 10% by mass or more and 60% by mass or less.

[0096] The mass of the second catalyst layer per unit volume of the portion of the substrate in which the second catalyst layer is formed is 5 g / L or more and 150 g / L or less.

[0097] The fifth slurry contains inorganic oxide particles, and the median particle size D of the inorganic oxide particles contained in the fifth slurry is... 50 The size is greater than 1μm and less than 20μm.

[0098] Based on the mass of the lower layer, the amount of the fifth pore-forming agent contained in the fifth precursor layer is 10% by mass or more and 60% by mass or less.

[0099] The mass of the lower layer per unit volume of the portion of the substrate in which the lower layer is formed is 5 g / L or more and 90 g / L or less.

[0100] The sixth slurry contains inorganic oxide particles, and the median particle size D of the inorganic oxide particles contained in the sixth slurry is... 50The size is greater than 1μm and less than 20μm.

[0101] Based on the mass of the upper layer, the amount of the sixth pore-forming agent contained in the sixth precursor layer is 10% by mass or more and 60% by mass or less.

[0102] The mass of the upper layer per unit volume of the portion of the substrate in which the upper layer is formed is 5 g / L or more and 60 g / L or less.

[0103]

[10] According to the method of [9], wherein the median particle size D of the fifth pore-forming agent 50 The median particle size D of the sixth pore-forming agent is greater than 4 μm. 50 It is below 4μm.

[0104] The effects of the invention

[0105] According to the present invention, a catalyst for exhaust gas purification can be provided that can improve PM capture performance and suppress pressure loss. Attached Figure Description

[0106] Figure 1 This is a partial cross-sectional view showing the state in which the exhaust gas purification catalyst according to the first embodiment is disposed in the exhaust path of an internal combustion engine.

[0107] Figure 2 for Figure 1 AA-line cross-section view.

[0108] Figure 3 for Figure 1 BB line cross-section.

[0109] Figure 4 for Figure 2 An enlarged view of the area indicated by symbol R1 in the diagram.

[0110] Figure 5 for Figure 3 An enlarged view of the area indicated by symbol R2 in the diagram.

[0111] Figure 6 for Figure 1 CC line cross-section.

[0112] Figure 7 Figures A through C are used to illustrate the "peak value" in the logarithmic differential pore volume distribution curve. Figure 7 In the charts A through C, the left side of the horizontal axis represents the small hole side, and the right side of the horizontal axis represents the large hole side.

[0113] Figure 8 A diagram illustrating the catalyst for exhaust gas purification according to the second embodiment (and) Figure 5 (Corresponding diagram).

[0114] Figure 9 A diagram illustrating the catalyst for exhaust gas purification according to the second embodiment (and) Figure 6 (Corresponding diagram).

[0115] Figure 10 A diagram illustrating the catalyst for exhaust gas purification according to the third embodiment (and) Figure 5 (Corresponding diagram).

[0116] Figure 11 A diagram illustrating the catalyst for exhaust gas purification according to the third embodiment (and) Figure 6 (Corresponding diagram).

[0117] Figure 12A The logarithmic differential pore volume distribution curve of the first catalyst layer in the catalyst for exhaust gas purification in Example 2 is shown.

[0118] Figure 12B The logarithmic differential pore volume distribution curve of the second catalyst layer in the catalyst for exhaust gas purification in Example 2 is shown.

[0119] Figure 13A The logarithmic differential pore volume distribution curve of the first catalyst layer in the exhaust gas purification catalyst of Comparative Example 1 is shown.

[0120] Figure 13B The logarithmic differential pore volume distribution curve of the second catalyst layer in the exhaust gas purification catalyst of Comparative Example 1 is shown.

[0121] Figure 14A The logarithmic differential pore volume distribution curve of the first catalyst layer in the catalyst for exhaust gas purification of Comparative Example 2 is shown.

[0122] Figure 14B The logarithmic differential pore volume distribution curve of the second catalyst layer in the exhaust gas purification catalyst of Comparative Example 2 is shown. Detailed Implementation

[0123] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0124] Implementation Method 1

[0125] The following is based on Figures 1-6 The first embodiment of the present invention will be described.

[0126] like Figure 1 As shown, the exhaust gas purification catalyst 1A (hereinafter referred to as "catalyst 1A") according to the first embodiment is disposed in the exhaust path of the exhaust pipe P of the internal combustion engine. The internal combustion engine is, for example, a gasoline engine (e.g., a GDI engine), a diesel engine, etc.

[0127] Figure 1 In the diagram, the exhaust gas flow direction of an internal combustion engine is represented by the symbol E. The same applies to other diagrams. In this specification, the upstream side of the exhaust gas flow direction E (e.g., Figure 1 The left side of the exhaust gas flow direction E is referred to as the "exhaust gas inflow side" or "inflow side". The downstream side of the exhaust gas flow direction E (e.g.) Figure 1 The right side of the exhaust gas flow is called the "exhaust gas outflow side" or "exhaust gas inflow side".

[0128] like Figure 1 As shown, catalyst 1A is disposed in the exhaust path of the internal combustion engine such that the axial direction of substrate 10 is aligned with or substantially aligned with the exhaust gas flow direction E. In this specification, unless otherwise specified, "length" refers to the axial dimension of substrate 10.

[0129] like Figures 1-6 As shown, catalyst 1A includes a substrate 10, a first catalyst layer 20, and a second catalyst layer 30.

[0130] In this embodiment, the first catalyst layer 20 and the second catalyst layer 30 each have a single-layer structure.

[0131] <Substrate>

[0132] The material constituting the substrate 10 can be appropriately selected from known materials. Examples of materials constituting the substrate 10 include ceramic materials and metallic materials, but ceramic materials are 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; and oxide ceramics such as alumina, zirconium oxide, cordierite, mullite, zircon, aluminum titanate, and magnesium titanate. Examples of metallic materials include alloys such as stainless steel.

[0133] The length L of the substrate 10 10 The length L of the substrate 10 can be adjusted appropriately, taking into account factors such as exhaust gas purification performance and PM capture performance. From the perspective of improving exhaust gas purification performance and PM capture performance, 10 Preferably, the diameter is 50mm or more and 160mm or less, and more preferably 80mm or more and 130mm or less.

[0134] The volume of the substrate 10 can be appropriately adjusted considering factors such as exhaust gas purification performance and PM collection performance. From the viewpoint of improving exhaust gas purification performance and PM collection performance, the volume of the substrate 10 is preferably 0.5L or more and 2.5L or less, more preferably 0.5L or more and 2.0L or less, and even more preferably 0.7L or more and 2.0L or less. In this specification, the volume of the substrate 10 refers to the apparent volume of the substrate 10. When the substrate 10 is cylindrical, the outer diameter of the substrate 10 is set to 2r, and the length of the substrate 10 is set to L. 10The volume of substrate 10 is calculated using the following formula: Volume of substrate 10 = π × r 2 ×L 10 .

[0135] Substrate 10 is a wall-flow type substrate. For example... Figures 2-6 As shown, the substrate 10 has porous partition walls 12 that separate chambers 13 (inflow-side chamber 13a and outflow-side chamber 13b) and chambers 13 (inflow-side chamber 13a and outflow-side chamber 13b). The substrate 10 is preferably a honeycomb structure.

[0136] like Figure 2 and 3 As shown, the substrate 10 includes a cylindrical portion 11, chambers 13 (inflow-side chamber 13a and outflow-side chamber 13b) and partition wall portions 12 formed within the cylindrical portion 11. The cylindrical portion 11 defines the outer shape of the substrate 10, and the axial direction of the cylindrical portion 11 is aligned with the axial direction of the substrate 10. Figure 2 and 3 As shown, the shape of the cylindrical part 11 is, for example, cylindrical, but it can also be other shapes such as elliptical cylindrical or polygonal cylindrical.

[0137] like Figures 2-6 As shown, chamber 13 (inflow side chamber 13a and outflow side chamber 13b) extends along the exhaust gas flow direction E, and has an end on the exhaust gas inflow side and an end on the exhaust gas outflow side.

[0138] like Figure 6 As shown, the substrate 10 is provided with a first sealing portion 14 that closes the exhaust gas outflow end of the partial chamber 13 and a second sealing portion 15 that closes the exhaust gas inflow end of the remaining chamber 13. Thus, the partial chamber 13 becomes an inflow-side chamber 13a with the exhaust gas inflow end open and the exhaust gas outflow end blocked by the first sealing portion 14, and the remaining chamber 13 becomes an outflow-side chamber 13b with the exhaust gas inflow end blocked by the second sealing portion 15 and the exhaust gas outflow end open.

[0139] like Figures 2-6 As shown, there is a partition wall 12 between adjacent chambers 13 (adjacent inflow side chamber 13a and outflow side chamber 13b), and the adjacent chambers 13 (adjacent inflow side chamber 13a and outflow side chamber 13b) are separated by the partition wall 12.

[0140] like Figures 4-6 As shown, a plurality of (four in this embodiment) outflow side chambers 13b are arranged around an inflow side chamber 13a, and the inflow side chamber 13a and the outflow side chambers 13b arranged around it are separated by a partition wall 12. Figures 4-6As shown, a plurality of (four in this embodiment) inflow side chambers 13a are arranged around an outflow side chamber 13b, and the outflow side chamber 13b and the inflow side chambers 13a arranged around the outflow side chamber 13b are separated by a partition wall 12.

[0141] like Figures 2-6 As shown, the top view shape of the end (opening) of the exhaust gas inflow side of each inflow side chamber 13a and the top view shape of the end (opening) of the exhaust gas outflow side of each outflow side chamber 13b are, for example, quadrilaterals, but may also be hexagons, octagons or other shapes.

[0142] The chamber density per square inch of substrate 10 can be appropriately adjusted taking into account PM collection performance, pressure loss, etc. From the viewpoint of improving PM collection performance and suppressing pressure loss increase, the chamber density per square inch of substrate 10 is preferably 180 chambers or more and 350 chambers or less. The chamber density per square inch of substrate 10 is the total number of chambers 13 (inflow-side chambers 13a and outflow-side chambers 13b) per square inch in the cross-section obtained by cutting substrate 10 with a plane perpendicular to the axis of substrate 10.

[0143] like Figure 2 and 3 As shown, the partition wall 12 is disposed inside the cylindrical portion 11. The partition wall 12 has a porous structure through which exhaust gas can pass.

[0144] like Figures 4-6 As shown, the partition wall 12 has an outer surface S1a on the inflow side chamber 13a side and an outer surface S1b on the outflow side chamber 13b side. The outer surface S1a is the region on the inflow side chamber 13a side (i.e., the region in contact with the inflow side chamber 13a) that extends along the exhaust gas flow direction E of the outer surface defining the shape of the partition wall 12. The outer surface S1b is the region on the outflow side chamber 13b side (i.e., the region in contact with the outflow side chamber 13b) that extends along the exhaust gas flow direction E of the outer surface defining the shape of the partition wall 12.

[0145] The thickness of the partition wall 12 can be appropriately adjusted taking into account PM collection performance, pressure loss, etc. From the viewpoint of improving PM collection performance and suppressing pressure loss increase, the thickness of the partition wall 12 is preferably 110 μm or more and 380 μm or less, more preferably 150 μm or more and 330 μm or less, and even more preferably 180 μm or more and 310 μm or less.

[0146] The average pore size (average air pore size) of the partition wall portion 12 can be appropriately adjusted, but from the viewpoint of more effectively improving PM collection performance and suppressing pressure loss rise, it is preferably 12 μm or more and 25 μm or less, more preferably 13 μm or more and 22 μm or less. The porosity (air porosity) of the partition wall portion 12 can be appropriately adjusted, but from the viewpoint of more effectively suppressing pressure loss rise, 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.

[0147] The average pore size and porosity of the partition wall portion 12 can be determined using a mercury porosimetry method with a mercury porosimetry meter. In the mercury porosimetry method, a test piece cut from the substrate 10 (excluding the first sealing portion 14 and the second sealing portion 15) is placed in the measuring chamber of the mercury porosimetry meter. The pressure inside the measuring chamber is reduced, mercury is introduced into the measuring chamber, and pressure is applied. The pore size and pore volume are determined based on the pressure applied and the volume of mercury introduced into the pores of the partition wall portion 12 of the test piece. The determination is performed, for example, at a pressure range of 0.5 to 20000 psia. It should be noted that 0.5 psia is equivalent to 0.35 × 10⁻⁶ psia. -3 kg / mm 2 20,000 psia is equivalent to 14 kg / mm 2 The pressure range corresponds to a pore size range of 0.01–420 μm. Constants used when calculating the pore size based on pressure include, for example, a contact angle of 140° and a surface tension of 480 dyn / cm. The average pore size of the partition wall portion 12 is the pore size at which the cumulative pore volume reaches 50% in the pore size distribution of the partition wall portion 12 (the pore size at which the cumulative pore volume reaches 50%). The porosity of the partition wall portion 12 can be calculated based on the following formula. It should be noted that when the partition wall material is cordierite, the true specific gravity of cordierite can be, for example, 2.52.

[0148] Porosity (%) of partition wall 12 = Total pore volume / (Total pore volume + 1 / True specific gravity of partition wall material) × 100

[0149] <First Catalyst Layer>

[0150] like Figure 4 and 6 As shown, the first catalyst layer 20 is disposed on the inflow side chamber 13a side of the partition wall portion 12.

[0151] like Figure 6 As shown, the first catalyst layer 20 extends along the exhaust gas flow direction E from the end of the partition wall portion 12 on the exhaust gas inflow side. In this embodiment, the first catalyst layer 20 does not reach the end of the partition wall portion 12 on the exhaust gas outflow side, but it may reach the end of the partition wall portion 12 on the exhaust gas outflow side.

[0152] like Figure 4 and 6 As shown, preferably, at least a portion of the first catalyst layer 20 protrudes from the outer surface S1a of the partition wall portion 12 toward the inflow side chamber 13a, that is, the first catalyst layer 20 has a portion protruding from the outer surface S1a of the partition wall portion 12 toward the inflow side chamber 13a (hereinafter referred to as the "protruding portion"). This improves the contact between exhaust gas and PM, enabling more effective improvement in exhaust gas purification performance and PM capture performance.

[0153] The first catalyst layer 20 may consist only of raised portions, or it may have both raised portions and portions existing inside the partition wall portion 12 (hereinafter referred to as "internal portions"). Since the partition wall portion 12 is porous, the internal portions and raised portions are sometimes formed together when the first catalyst layer 20 is formed. The raised portions and internal portions may be continuous. The first catalyst layer 20 may also consist only of the internal portions. The phrase "the first catalyst layer 20 is disposed on the inflow side chamber 13a side of the partition wall portion 12" includes: an embodiment where the first catalyst layer 20 consists only of raised portions, an embodiment where the first catalyst layer 20 consists only of internal portions, and an embodiment where the first catalyst layer 20 has both raised portions and internal portions.

[0154] The area containing the raised portion of the first catalyst layer 20 does not overlap with the area containing the partition wall portion 12, but the area containing the inner portion of the first catalyst layer 20 overlaps with the area containing the partition wall portion 12. Therefore, the catalyst 1A can be cut with a plane perpendicular to the axis of the substrate 10, and the first catalyst layer 20 and the partition wall portion 12 present on the cut surface can be observed. Based on the morphological differences between the first catalyst layer 20 and the partition wall portion 12, the raised portion and the inner portion of the first catalyst layer 20 can be determined. When observing the cut surface, elemental mapping of the cut surface can be performed. Elemental mapping can be performed, for example, by combining cross-sectional observation using SEM and compositional analysis of the cut surface. Elemental mapping can be performed, for example, using scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX), electron beam microanalysis (EPMA), etc. The raised portion and the inner portion can be determined by elemental mapping of the cut surface based on the morphological and compositional differences between the first catalyst layer 20 and the partition wall portion 12.

[0155] From the viewpoint of achieving a good balance between exhaust gas purification performance and cost, the mass (mass after calcination) of the first catalyst layer 20 per unit volume of the portion of the substrate 10 in which the first catalyst layer 20 is formed is preferably 5 g / L or more and 150 g / L or less, more preferably 10 g / L or more and 100 g / L or less, and even more preferably 25 g / L or more and 70 g / L or less. The mass of the first catalyst layer 20 per unit volume of the portion of the substrate 10 in which the first catalyst layer 20 is formed is calculated according to the following formula: (mass of the first catalyst layer 20) / (volume of the substrate 10) × (average length L of the first catalyst layer 20) 20 / Length L of substrate 10 10 )).

[0156] In this specification, "the mass of the first catalyst layer 20" refers to the total mass of all metal elements contained in the first catalyst layer 20, calculated by taking the metal equivalent mass for platinum group elements and the oxide equivalent mass for metal elements other than platinum group elements. In other words, "the mass of the first catalyst layer 20" is the calculated mass obtained by adding the metal equivalent mass of the platinum group elements contained in the first catalyst layer 20 to the oxide equivalent mass of the metal elements other than platinum group elements contained in the first catalyst layer 20. It should be noted that "metal elements" also includes half-metal elements such as Si and B.

[0157] In this specification, "platinum group elements" include Pt (platinum), Pd (palladium), Rh (rhodium), Ru (ruthenium), Os (osmium), and Ir (iridium).

[0158] In this specification, oxides of rare earth elements other than Ce, Pr, and Tb refer to sesquioxides (M₂O₃, where M represents a rare earth element other than Ce, Pr, and Tb), oxides of Ce refer to CeO₂, and oxides of Pr refer to Pr₆O₃. 11 The oxides of Tb are Tb4O7, Al is Al2O3, Zr is ZrO2, Si is SiO2, B is B2O3, Cr is Cr2O3, Mg is MgO, Ca is CaO, Sr is SrO, Ba is BaO, Fe is Fe3O4, Mn is Mn3O4, Ni is NiO, Ti is TiO2, Zn is ZnO, and Sn is SnO2.

[0159] The average length L of the first catalyst layer 20 20 An example of the determination method is as follows.

[0160] A section is cut from catalyst 1A and extends axially along substrate 10, having a length L equal to that of substrate 10. 10 Samples of the same length. For example, a cylindrical sample with a diameter of 25.4 mm. It should be noted that the sample diameter can be changed as needed. The samples are cut at 5 mm intervals using a plane perpendicular to the axis of the substrate 10, sequentially obtaining slices 1, 2, ..., n from the end side of the sample on the exhaust gas inflow side. Each slice is 5 mm long. The composition of the slices is analyzed using scanning electron microscopy-energy dispersive X-ray diffraction (SEM-EDX) and other methods to confirm whether the slices contain a portion of the first catalyst layer 20.

[0161] For slices that clearly contain a portion of the first catalyst layer 20, compositional analysis is not necessarily required. For example, scanning electron microscopy (SEM) or electron beam microscopy (EPMA) can be used to observe the cut surface to confirm whether the slice contains a portion of the first catalyst layer 20. When observing the cut surface, elemental mapping can be performed. Elemental mapping can be performed in the same manner as described above.

[0162] After confirming whether the slice contains a portion of the first catalyst layer 20, the length of the first catalyst layer 20 contained in the sample is calculated based on the following formula.

[0163] The length of the first catalyst layer 20 contained in the sample = 5 mm × (number of slices containing a portion of the first catalyst layer 20)

[0164] For example, if slices 1 to k contain a portion of the first catalyst layer 20, but slices (k+1) to n do not contain a portion of the first catalyst layer 20, the length of the first catalyst layer 20 contained in the sample is (5×k) mm.

[0165] An example of a more detailed method for determining the length of the first catalyst layer 20 contained in the sample is as follows.

[0166] The length of a portion of the first catalyst layer 20 in the k-th slice (i.e., the slice obtained from the side of the sample closest to the exhaust gas outlet in the slice containing a portion of the first catalyst layer 20) is determined by cutting the k-th slice along the axial direction of the substrate 10 and observing the portion of the first catalyst layer 20 present on the cut surface using SEM, EPMA, etc. The length of the first catalyst layer 20 contained in the sample is then calculated based on the following formula.

[0167] The length of the first catalyst layer 20 contained in the sample = (5mm × (k-1)) + (the length of a portion of the first catalyst layer 20 contained in the k-th slice)

[0168] For 8 to 16 samples arbitrarily cut from catalyst 1A, the length of the first catalyst layer 20 contained in each sample is measured, and their average value is taken as the average length L of the first catalyst layer 20. 20 .

[0169] The average length L of the first catalyst layer 20 20 The average length L of the first catalyst layer 20 can be adjusted appropriately, taking into account factors such as exhaust gas purification performance and PM capture performance. 20 Relative to the length L of the substrate 10 10 percentage (L) 20 / L 10 The content of (×100) is preferably 15% or more and 90% or less, more preferably 20% or more and 90% or less, and even more preferably 30% or more and 85% or less.

[0170] The first catalyst layer 20 contains one or more platinum group elements. Platinum group elements can be selected from, for example, Pt, Pd, Rh, Ru, Ir, Os, etc., but from the viewpoint of improving exhaust gas purification performance, Pt, Pd, and Rh are preferred. The platinum group elements are contained in the first catalyst layer 20 in a form capable of functioning as catalytically active components, such as metals, alloys containing platinum group elements, compounds containing platinum group elements (e.g., oxides of platinum group elements), etc. From the viewpoint of improving exhaust gas purification performance, the catalytically active components containing platinum group elements are preferably in particulate form.

[0171] In one embodiment, the first catalyst layer 20 comprises Rh. In addition to Rh, the first catalyst layer 20 may also contain one or more other platinum group elements.

[0172] In another embodiment, the first catalyst layer 20 comprises Pd and / or Rh. In addition to Pd and / or Rh, the first catalyst layer 20 may also contain one or more other platinum group elements.

[0173] From the perspective of balancing exhaust gas purification performance and cost, based on the mass of the first catalyst layer 20, the metal conversion amount of platinum group elements in the first catalyst layer 20 is preferably 0.010% by mass or more and 20% by mass or less, more preferably 0.020% by mass or more and 15% by mass or less, and even more preferably 0.050% by mass or more and 10% by mass or less. "Metal conversion amount of platinum group elements in the first catalyst layer 20" refers to the metal conversion amount of that single platinum group element when the first catalyst layer 20 contains only one platinum group element, and to the total metal conversion amount of the two or more platinum group elements when the first catalyst layer 20 contains two or more platinum group elements.

[0174] When the composition of the raw material used to manufacture the first catalyst layer 20 is known, the metal equivalent or oxide equivalent of each metal element in the first catalyst layer 20 can be determined from the composition of the raw material.

[0175] When the composition of the raw materials used to manufacture the first catalyst layer 20 is unknown, the metal equivalent or oxide equivalent of each metal element in the first catalyst layer 20 can be determined by conventional methods such as scanning electron microscopy-energy dispersive X-ray diffraction (SEM-EDX). Specifically, as described below.

[0176] Elemental analysis was performed on the sample obtained from the first catalyst layer 20 using conventional methods such as SEM-EDX to determine the constituent elements of the entire sample and to calculate the mole percentage of each metal element. The mole percentage of each metal element was calculated for each of the 10 fields of view of the SEM, and the average mole percentage of each metal element in the 10 fields of view was taken as the mole percentage of each metal element in the first catalyst layer 20. Based on the mole percentage of each metal element in the first catalyst layer 20, the metal equivalent mass percentage of each platinum group element in the first catalyst layer 20 and the oxide equivalent mass percentage of each metal element other than the platinum group elements in the first catalyst layer 20 were calculated. The metal equivalent mass percentage of each platinum group element in the first catalyst layer 20 was calculated using the following formula: (metal equivalent mass of each platinum group element calculated based on mole percentage) / ((metal equivalent mass of platinum group elements calculated based on mole percentage) + (oxide equivalent mass of each metal element other than the platinum group elements calculated based on mole percentage)) × 100. The mass percentage of oxides of metals other than platinum group elements in the first catalyst layer 20 is calculated according to the following formula: (mass of oxides of metals other than platinum group elements calculated in molar percentage) / ((mass of metals of platinum group elements calculated in molar percentage) + (mass of oxides of metals other than platinum group elements calculated in molar percentage)) × 100.

[0177] The first catalyst layer 20 preferably contains one or more supports, and at least a portion of the catalytically active components are loaded on one or more supports.

[0178] "At least a portion of the catalytically active component is loaded on the support" means that at least a portion of the catalytically active component is physically and / or chemically adsorbed and / or retained on the outer surface and / or inner surface of the pores of the support. This can be confirmed using methods such as SEM-EDX. Specifically, in the elemental mapping obtained by analyzing the cross-section of the catalyst layer using SEM-EDX, when at least a portion of the catalytically active component exists in the same region as the support, it can be determined that at least a portion of the catalytically active component is loaded on the support.

[0179] The support can be selected from inorganic oxides, for example. Inorganic oxides are, for example, particulate. From the viewpoint of improving the loading capacity of the catalytically active component, porous inorganic oxides are preferred. Inorganic oxides may or may not have oxygen storage capacity (OSC). Inorganic oxides used as supports are distinct from inorganic oxides used as binders (e.g., inorganic oxide-based binders such as alumina binders, zirconia binders, titanium dioxide binders, and silica binders).

[0180] Examples of inorganic oxides include Al-based oxides, Ce-based oxides, Ce-Zr composite oxides, oxides of rare earth elements other than Ce, zirconium oxide (ZrO2), silicon dioxide (SiO2), titanium dioxide (TiO2), zeolite (aluminosilicate), and oxides based on MgO, ZnO, SnO2, etc.

[0181] The support is preferably selected from Al-based oxides, Ce-based oxides, and Ce-Zr composite oxides. The first catalyst layer 20 may also contain one or more supports other than Al-based oxides, Ce-based oxides, and Ce-Zr composite oxides.

[0182] In this specification, Al-based oxides refer to oxides containing Al, specifically oxides in which Al is the most abundant element by mass among the elements excluding O constituting the oxide. However, oxides belonging to the Ce-Zr complex oxide system are not Al-based oxides.

[0183] Al-based oxides can contain one or more elements other than Al and O (hereinafter referred to as "other elements"). Other elements can be selected from, for example, B, Si, Zr, Cr, rare earth elements (e.g., Y, Ce, La, Nd, Pr, Sm, Gd, etc.), alkaline earth metal elements (e.g., Mg, Ca, Sr, Ba, etc.). Examples of Al-based oxides include aluminum oxide (Al₂O₃), oxides obtained by modifying the surface of aluminum oxide with other elements, and oxides obtained by dissolving other elements in aluminum oxide.

[0184] In this specification, Ce-based oxides refer to oxides containing Ce, specifically oxides in which Ce is the most abundant element by mass among the elements excluding O constituting the oxide. However, oxides belonging to the Ce-Zr complex oxide system are not considered Ce-based oxides.

[0185] Ce-based oxides can contain one or more elements other than Ce and O (hereinafter referred to as "other elements"). Other elements can be selected from rare earth elements other than Ce (e.g., Y, Pr, Sc, La, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, etc.), alkaline earth metal elements (e.g., Mg, Ca, Sr, Ba, etc.), Fe, Mn, Ni, Zr, Al, etc. Examples of Ce-based oxides include cerium oxide (CeO2), oxides obtained by modifying the surface of cerium oxide with other elements, and oxides obtained by dissolving other elements in cerium oxide.

[0186] In this specification, Ce-Zr composite oxides refer to composite oxides containing Ce and Zr, wherein, based on the mass of the composite oxide, the CeO2 content of Ce in the composite oxide is 5.0% by mass or more and 95.0% by mass or less, and the ZrO2 content of Zr in the composite oxide is 5.0% by mass or more and 95.0% by mass or less, based on the mass of the composite oxide.

[0187] Ce-Zr composite oxides may contain one or more elements other than Ce, Zr, and O (hereinafter referred to as "other elements"). Other elements may be selected from rare earth elements other than Ce, alkaline earth metal elements (e.g., Mg, Ca, Sr, Ba, etc.), Fe, Mn, Ni, Al, etc. Examples of Ce-Zr composite oxides include CeO2-ZrO2 solid solutions, oxides obtained by modifying the surface of CeO2-ZrO2 solid solutions with other elements, and oxides obtained by dissolving other elements in CeO2-ZrO2 solid solutions.

[0188] Based on the mass of Ce-Zr composite oxides, the oxide equivalent content of other elements in Ce-Zr composite oxides is, for example, 5% by mass or more and 30% by mass or less. "Oxide equivalent content of other elements in Ce-Zr composite oxides" refers to the oxide equivalent content of that single element when the Ce-Zr composite oxide contains one element, and to the sum of the oxide equivalent contents of two or more elements when the Ce-Zr composite oxide contains two or more elements.

[0189] Given the composition of Al-based oxides, the oxide equivalent content of each element in the Al-based oxides can be calculated based on the composition of the Al-based oxides.

[0190] When the composition of Al-based oxides is unknown, the oxide equivalent content of each element in Al-based oxides can be determined by energy-dispersive X-ray spectroscopy (EDX) analysis of samples containing Al-based oxides. The determination is based on the obtained elemental mapping and EDX elemental analysis of specified particles. Specifically, Al-based oxide particles and other particles can be qualitatively identified (color-coded) through elemental mapping, and compositional analysis (elemental analysis) can be performed on specified particles to determine the oxide equivalent content of each element in the specified particles.

[0191] The oxide equivalent content of each element in Ce-based oxides or Ce-Zr composite oxides can be calculated in the same way as the oxide equivalent content of each element in Al-based oxides.

[0192] The first catalyst layer 20 may contain other components such as binders and stabilizers. Examples of binders include inorganic oxide-based binders such as alumina sol, cerium oxide sol, zirconium oxide sol, titanium dioxide sol, and silica sol. Examples of stabilizers include nitrates, carbonates, oxides, and sulfates of alkaline earth metal elements (such as Sr and Ba).

[0193] <Second Catalyst Layer>

[0194] like Figure 5 and 6 As shown, the second catalyst layer 30 is disposed on the outflow side chamber 13b side of the partition wall portion 12.

[0195] like Figure 6 As shown, the second catalyst layer 30 extends from the end of the partition wall portion 12 on the exhaust gas outflow side in a direction opposite to the exhaust gas flow direction E. In this embodiment, the second catalyst layer 30 does not reach the end of the partition wall portion 12 on the exhaust gas inflow side, but it may reach the end of the partition wall portion 12 on the exhaust gas inflow side.

[0196] like Figure 5 and 6 As shown, preferably, at least a portion of the second catalyst layer 30 protrudes from the outer surface S1b of the partition wall portion 12 toward the outflow side chamber 13b, that is, the second catalyst layer 30 has a portion protruding from the outer surface S1b of the partition wall portion 12 toward the outflow side chamber 13b (hereinafter referred to as the "protruding portion"). This improves the contact between exhaust gas and PM, enabling more effective improvement in exhaust gas purification performance and PM capture performance.

[0197] The second catalyst layer 30 may consist only of the raised portion, or it may have both the raised portion and a portion existing inside the partition wall portion 12 (hereinafter referred to as the "internal portion"). Since the partition wall portion 12 is porous, the internal portion and the raised portion may sometimes be formed together when the second catalyst layer 30 is formed. The raised portion and the internal portion may be continuous. The second catalyst layer 30 may also consist only of the internal portion. The phrase "the second catalyst layer 30 is disposed on the outflow side chamber 13b side of the partition wall portion 12" includes: an embodiment where the second catalyst layer 30 consists only of the raised portion, an embodiment where the second catalyst layer 30 consists only of the internal portion, and an embodiment where the second catalyst layer 30 has both the raised portion and the internal portion.

[0198] The above description of the method for determining the raised portion and the inner portion of the first catalyst layer 20 also applies to the second catalyst layer 30. Where applicable, "first catalyst layer 20" can be understood as "second catalyst layer 30".

[0199] From the viewpoint of achieving a good balance between exhaust gas purification performance and cost, the mass (mass after calcination) of the second catalyst layer 30 per unit volume of the portion of the substrate 10 in which the second catalyst layer 30 is formed is preferably 5 g / L or more and 150 g / L or less, more preferably 10 g / L or more and 100 g / L or less, and even more preferably 25 g / L or more and 70 g / L or less. The mass of the second catalyst layer 30 per unit volume of the portion of the substrate 10 in which the second catalyst layer 30 is formed is calculated according to the following formula: (mass of the second catalyst layer 30) / (volume of the substrate 10) × (average length L of the second catalyst layer 30) 30 / Length L of substrate 10 10 )).

[0200] The above description regarding the quality of the first catalyst layer 20 also applies to the second catalyst layer 30. Where applicable, "first catalyst layer 20" can be replaced with "second catalyst layer 30" for understanding.

[0201] Regarding the average length L of the first catalyst layer 20 20 The above description of the determination method also applies to the average length L of the second catalyst layer 30. 30 The determination method. Where applicable, "first catalyst layer 20" can be understood as "second catalyst layer 30", and "average length L" can be understood as... 20 Replace “average length L” with “average length L” 30 To understand this. However, the average length L of the second catalyst layer 30 30 In the measurement method, the sample is cut at 5mm intervals using a plane perpendicular to the axial direction of the substrate 10, and the first slice, the second slice, ..., the nth slice are obtained sequentially from the end side of the sample from the exhaust gas outlet side.

[0202] The average length L of the second catalyst layer 30 30 The average length L of the second catalyst layer 30 can be adjusted appropriately, taking into account factors such as exhaust gas purification performance and PM capture performance. From the perspective of improving exhaust gas purification performance and PM capture performance, 30 Relative to the length L of the substrate 10 10 percentage (L) 30 / L 10 The content of (×100) is preferably 15% or more and 90% or less, more preferably 20% or more and 90% or less, and even more preferably 30% or more and 85% or less.

[0203] From the perspective of improving exhaust gas purification performance and PM capture performance, the average length L of the first catalyst layer 20 is... 20 The average length L of the second catalyst layer 30 30 The sum relative to the length L of the substrate 10 10 percentage ((L) 20 +L 30 ) / L 10 The content of (×100) is preferably 100% or more and 180% or less, more preferably 100% or more and 170% or less, and even more preferably 105% or more and 150% or less.

[0204] The second catalyst layer 30 contains one or more platinum group elements. The above description regarding the platinum group elements contained in the first catalyst layer 20 and their metal equivalents also applies to the platinum group elements contained in the second catalyst layer 30 and their metal equivalents. Where applicable, "first catalyst layer 20" should be replaced with "second catalyst layer 30" for understanding.

[0205] In one embodiment, the second catalyst layer 30 comprises Pd and / or Rh. In addition to Pd and / or Rh, the second catalyst layer 30 may also comprise one or more other platinum group elements. Embodiments where the second catalyst layer 30 comprises Pd and / or Rh can be combined with embodiments where the first catalyst layer 20 comprises Rh.

[0206] In another embodiment, the second catalyst layer 30 comprises Rh. In addition to Rh, the second catalyst layer 30 may also comprise one or more other platinum group elements. Embodiments where the second catalyst layer 30 comprises Rh can be combined with embodiments where the first catalyst layer 20 comprises Pd and / or Rh.

[0207] The second catalyst layer 30 preferably comprises one or more supports, with at least a portion of the catalytically active component loaded on one or more supports. The significance and confirmation method of the loading are the same as described above.

[0208] The above description of the support contained in the first catalyst layer 20 also applies to the support contained in the second catalyst layer 30. Where applicable, "first catalyst layer 20" can be understood as "second catalyst layer 30".

[0209] The second catalyst layer 30 may contain other components such as binders and stabilizers. The descriptions of binders and stabilizers are the same as above.

[0210] <Logarithmic differential pore volume distribution curve>

[0211] In this specification, the "logarithmic differential pore volume distribution curve (log differential pore volume distribution curve)" refers to the value obtained by dividing the increase in pore volume (differential pore volume dV) by the difference between the common logarithm (log) of the upper and lower values ​​of the corresponding pore diameter (d(logD)), and plotting this value relative to the midpoint of the increase in pore diameter (the average pore diameter of each interval). It should be noted that "average pore diameter" refers to the diameter.

[0212] In the logarithmic differential pore volume distribution curve of the first catalyst layer 20, the horizontal axis represents the pore size (μm) of the first catalyst layer 20, and the vertical axis represents the logarithmic differential pore volume (mL / g) of the first catalyst layer 20 per unit mass of slice M1. Slice M1 is described later.

[0213] In the logarithmic differential pore volume distribution curve of the second catalyst layer 30, the horizontal axis represents the pore size (μm) of the second catalyst layer 30, and the vertical axis represents the logarithmic differential pore volume (mL / g) of the second catalyst layer 30 per unit mass of slice M2. Slice M2 is described later.

[0214] The logarithmic differential pore volume distribution curve of the first catalyst layer 20 can be obtained by the following method.

[0215] The catalyst 1A is cut using a plane parallel to the axial direction of the substrate 10 and a plane perpendicular to the axial direction of the substrate 10, thus cutting out... Figure 6The portion indicated by symbol M1 is used to obtain a slice M1 containing a portion of the partition wall portion 12 and a portion of the first catalyst layer 20, but excluding the second catalyst layer 30. Slices M1 do not contain either the first sealing portion 14 or the second sealing portion 15. The length of the portion of the partition wall portion 12 included in slice M1 is equal to the length of slice M1. The length of the portion of the first catalyst layer 20 included in slice M1 is equal to the length of slice M1. Slices M1 can be obtained near the exhaust gas inflow side end of catalyst 1A. For example, a slice M1 with a length of 10 mm, containing a portion of the partition wall portion 12 and a portion of the first catalyst layer 20, but excluding the second catalyst layer 30, can be obtained by cutting along the exhaust gas flow direction E at two points 10 mm and 20 mm away from the exhaust gas inflow side end of substrate 10 with a plane perpendicular to the axial direction of substrate 10. The dimensions of slice M1 can be appropriately varied. Slice M1 is, for example, a cube shape with a side length of 10 mm.

[0216] By using the mercury intrusion porosimetry method with slice M1, the logarithmic differential pore volume distribution curve of the first catalyst layer 20 can be obtained.

[0217] Mercury intrusion porosimetry can be performed using the Shimadzu Corporation's Autopore IV9520 automatic porosity meter, under the following conditions and procedures.

[0218] (Measurement conditions)

[0219] Measurement environment: 25℃

[0220] Measurement chamber: Sample chamber volume 3 cm³ 3 The pressed volume is 0.39 cm³. 3

[0221] Measurement range: 0.0048 MPa to 255.1060 MPa

[0222] Measurement points: 54 points within the range of 0.0048 MPa to 0.3447 MPa.

[0223] 77 points within the range of 0.3447 MPa to 255.1060 MPa

[0224] A total of 131 points (logarithmically plotted for each pressure level, with points placed at equal intervals).

[0225] Press-in volume: Adjusted to be between 25% and 90%.

[0226] (Low-pressure parameters)

[0227] Exhaust pressure: 50 μmHg

[0228] Exhaust time: 5.0 min

[0229] Mercury injection pressure: 0.0034 MPa

[0230] Equilibrium time: 10 seconds

[0231] (High-voltage parameters)

[0232] Equilibrium time: 10 seconds

[0233] (Mercury parameters)

[0234] Forward contact angle: 130.0 degrees

[0235] Retreating contact angle: 130.0 degrees

[0236] Surface tension: 485.0 mN / m (485.0 dyne / cm)

[0237] Mercury density: 13.5335 g / mL

[0238] (Measurement Procedure)

[0239] (1) 54 points were measured in the low-pressure section within the range of 0.0048MPa to 0.3447MPa.

[0240] (2) 77 points were measured in the high-pressure section within the range of 0.3792MPa to below 255.1060MPa.

[0241] (3) Based on the mercury injection pressure, mercury injection amount and the mass of slice M1, the logarithmic differential pore volume distribution curve (log differential pore volume distribution curve) is obtained.

[0242] It should be noted that steps (1), (2), and (3) above can be performed automatically using the software provided with the device. Other conditions can be determined in accordance with JIS R 1655:2003.

[0243] Since slice M1 includes a portion of the partition wall portion 12 and a portion of the first catalyst layer 20, the logarithmic differential pore volume distribution obtained by mercury intrusion porosimetry includes not only the logarithmic differential pore volume distribution of the first catalyst layer 20 but also the logarithmic differential pore volume distribution of the partition wall portion 12. However, since the pore size of the partition wall portion 12 is significantly larger than the pore size of the first catalyst layer 20, it is possible to distinguish between the logarithmic differential pore volume distribution of the first catalyst layer 20 and the logarithmic differential pore volume distribution of the partition wall portion 12.

[0244] The pore size range in the logarithmic differential pore volume distribution of the first catalyst layer 20 is, for example, 0.001 μm or more and 12 μm or less, preferably 0.002 μm or more and 11 μm or less, more preferably 0.003 μm or more and 11 μm or less. The pore size range in the logarithmic differential pore volume distribution of the partition wall portion 12 is, for example, 11 μm or more and 80 μm or less, preferably 12 μm or more and 50 μm or less, more preferably 12 μm or more and 30 μm or less.

[0245] The logarithmic differential pore volume distribution curve of the second catalyst layer 30 can be obtained by the following method.

[0246] The catalyst 1A is cut using a plane parallel to the axial direction of the substrate 10 and a plane perpendicular to the axial direction of the substrate 10, thus cutting out... Figure 6 The portion indicated by symbol M2 is used to obtain a slice M2 containing a portion of the partition wall portion 12 and a portion of the second catalyst layer 30, but excluding the first catalyst layer 20. Slices M2 do not contain either the first sealing portion 14 or the second sealing portion 15. The length of the portion of the partition wall portion 12 included in slice M2 is equal to the length of slice M2. The length of the portion of the second catalyst layer 30 included in slice M2 is equal to the length of slice M2. Slices M2 can be obtained near the exhaust gas outlet end of catalyst 1A. For example, a slice M2 with a length of 10 mm, containing a portion of the partition wall portion 12 and a portion of the second catalyst layer 30, but excluding the first catalyst layer 20, can be obtained by cutting at two points 10 mm and 20 mm away from the exhaust gas outlet end of substrate 10 in a direction opposite to the exhaust gas flow direction E with a plane perpendicular to the axial direction of substrate 10. The dimensions of slice M2 can be appropriately varied. Slice M2 is, for example, a cube shape with a side length of 10 mm.

[0247] By using slice M2 to perform mercury intrusion porosimetry, the logarithmic differential pore volume distribution curve of the second catalyst layer 30 can be obtained.

[0248] Mercury intrusion porosimetry can be performed using the Shimadzu Corporation's Autopore IV9520 automatic porosity meter, under the same conditions and procedures as described above.

[0249] Since slice M2 includes the partition wall portion 12 and the second catalyst layer 30, the logarithmic differential pore volume distribution obtained by mercury intrusion porosimetry includes not only the logarithmic differential pore volume distribution of the second catalyst layer 30 but also the logarithmic differential pore volume distribution of the partition wall portion 12. However, since the pore size of the partition wall portion 12 is significantly larger than that of the second catalyst layer 30, it is possible to distinguish between the logarithmic differential pore volume distribution of the second catalyst layer 30 and the logarithmic differential pore volume distribution of the partition wall portion 12.

[0250] The pore size range in the logarithmic differential pore volume distribution of the second catalyst layer 30 is, for example, 0.001 μm or more and 12 μm or less, preferably 0.002 μm or more and 12 μm or less, more preferably 0.003 μm or more and 11 μm or less. The pore size range in the logarithmic differential pore volume distribution of the partition wall portion 12 is, for example, 11 μm or more and 80 μm or less, preferably 12 μm or more and 50 μm or less, more preferably 12 μm or more and 30 μm or less.

[0251] <Differential curve of logarithmic pore volume distribution>

[0252] In this specification, "the differential curve of the logarithmic pore volume distribution curve" refers to the first differential curve of the logarithmic differential pore volume distribution curve.

[0253] In the differential curve of the logarithmic pore volume distribution curve, the horizontal axis is the same as that of the logarithmic differential pore volume distribution curve, and the vertical axis represents the slope of the tangent line in the logarithmic differential pore volume distribution curve.

[0254] The differential curve of the logarithmic differential pore volume distribution curve can be obtained through the following steps.

[0255] (1) In the logarithmic differential pore volume distribution curve obtained by the above method, the pore size D n The corresponding logarithmic differential porosity distribution curve value v n The groups (n represents an integer greater than 1 and less than 131) are named in ascending order of aperture as (D1, v1), (D2, v2), ..., (D... n v n ), ..., (D 131 v 131 ).

[0256] (2) For each aperture D of 1≤n≤130 n , will (v n+1 -v n ) / (D n+1 -D n The value of ) is used as the aperture D n The differential value of the logarithmic differential pore volume distribution curve at the location.

[0257] (3) By analyzing the aperture D of each aperture n By plotting the differential value of the logarithmic differential pore volume distribution curve obtained from (2) above, the differential curve of the logarithmic differential pore volume distribution curve can be obtained.

[0258] <Peak>

[0259] The following explains the "peak value" in the logarithmic differential pore volume distribution curve.

[0260] (P1) as Figure 7As shown in A, in the logarithmic differential porosity distribution curve, when there is more than one maximum value, each maximum value (the logarithmic differential porosity of each vertex) on the logarithmic differential porosity distribution curve corresponds to a "peak value".

[0261] (P2) such as Figure 7 As shown in Figure B, in the logarithmic differential pore volume distribution curve, when a shoulder exists on the smaller pore diameter side of a certain peak, a positive minimum exists in the portion of the differential curve corresponding to that shoulder. The pore diameter that provides this minimum value is determined from the differential curve of the logarithmic differential pore volume distribution curve, and the corresponding logarithmic differential pore volume is then calculated from the logarithmic differential pore volume distribution curve. The calculated logarithmic differential pore volume corresponds to the "peak value". It should be noted that in the logarithmic differential pore volume distribution curve, when a shoulder exists on the smaller pore diameter side of a certain peak, such as... Figure 7 As shown in B, the acromion typically slopes upward to the right.

[0262] (P3) such as Figure 7 As shown in Figure C, in the logarithmic differential pore volume distribution curve, when a shoulder peak exists on the large-pore side of a certain peak, a negative maximum value exists in the portion of the differential curve corresponding to that shoulder peak. The pore size that gives this maximum value is determined from the differential curve of the logarithmic differential pore volume distribution curve, and the corresponding logarithmic differential pore volume is then calculated from the logarithmic differential pore volume distribution curve. The calculated logarithmic differential pore volume corresponds to the "peak value". It should be noted that in the logarithmic differential pore volume distribution curve, when a shoulder peak exists on the large-pore side of a certain peak, such as... Figure 7 As shown in C, the acromion typically slopes downward to the right.

[0263] As mentioned above, the "peak values" in the logarithmic differential porosity distribution curve include not only the maximum value (the logarithmic differential porosity at the vertex) but also the shoulder peaks. That is, the "peak values" in the logarithmic differential porosity distribution curve include the peak value defined by (P1) (hereinafter referred to as "peak value P1"), the peak value defined by (P2) (hereinafter referred to as "peak value P2"), and the peak value defined by (P3) (hereinafter referred to as "peak value P3"). In the logarithmic differential porosity distribution curve, the presence of one or more of the peak values ​​P1, P2, and P3 is sufficient; it is not necessary for all three peak values ​​to be present. The logarithmic differential porosity distribution curve can contain more than two peak values ​​P1, more than two peak values ​​P2, and more than two peak values ​​P3.

[0264] <Peak A>

[0265] The following explains the statement that "in the logarithmic differential pore volume distribution curve of the first catalyst layer 20, there is a peak A in the range of pore size greater than 1 μm and less than 3 μm".

[0266] In the logarithmic differential pore volume distribution curve of the first catalyst layer 20, when there is a peak in the range of pore size above 1 μm and below 3 μm (the peak can be any one of peak P1, P2 or P3), the peak corresponds to "peak A".

[0267] In the logarithmic differential pore volume distribution curve of the first catalyst layer 20, when there are more than two peaks (each peak can be any one of peaks P1, P2 or P3) in the range of pore size greater than 1 μm and less than 3 μm, the maximum value of the two or more peaks corresponds to "peak A".

[0268] Peak value A can be any one of peak values ​​P1, P2, or P3. In one implementation, it is peak value P1 or P2.

[0269] <Peak B>

[0270] The following explains the phenomenon that "in the logarithmic differential pore volume distribution curve of the first catalyst layer 20, there is a peak B in the range of pore size greater than 3 μm and less than 10 μm".

[0271] In the logarithmic differential pore volume distribution curve of the first catalyst layer 20, when there is a peak in the range of pore size greater than 3 μm and less than 10 μm (the peak can be any one of peak P1, P2 or P3), the peak corresponds to "peak B".

[0272] In the logarithmic differential pore volume distribution curve of the first catalyst layer 20, when there are more than two peaks (each peak can be any one of peaks P1, P2 or P3) in the range of pore size greater than 3 μm and less than 10 μm, the maximum value of the two or more peaks corresponds to "peak B".

[0273] Peak value B can be any one of peak values ​​P1, P2, or P3. In one implementation, it is peak value P1 or P3.

[0274] <Peak C>

[0275] The following explains the phenomenon that "in the logarithmic differential pore volume distribution curve of the second catalyst layer 30, there is a peak C in the range of pore size above 1 μm and below 3 μm".

[0276] In the logarithmic differential pore volume distribution curve of the second catalyst layer 30, when there is a peak in the range of pore size above 1 μm and below 3 μm (the peak can be any one of peak P1, P2 or P3), the peak corresponds to "peak C".

[0277] In the logarithmic differential pore volume distribution curve of the second catalyst layer 30, when there are more than two peaks (each peak can be any one of peaks P1, P2 or P3) in the range of pore size greater than 1 μm and less than 3 μm, the maximum value of the two or more peaks corresponds to "peak C".

[0278] Peak value C can be any one of peak values ​​P1, P2, or P3. In one implementation, it is peak value P1 or P2.

[0279] <Peak D>

[0280] The following explains the phenomenon that "in the logarithmic differential pore volume distribution curve of the second catalyst layer 30, there is a peak D in the range of pore size greater than 3 μm and less than 10 μm".

[0281] In the logarithmic differential pore volume distribution curve of the second catalyst layer 30, when there is a peak in the range of pore size greater than 3 μm and less than 10 μm (the peak can be any one of peak P1, P2 or P3), the peak corresponds to "peak D".

[0282] In the logarithmic differential pore volume distribution curve of the second catalyst layer 30, when there are more than two peaks (each peak can be any one of peaks P1, P2 or P3) in the range of pore size greater than 3 μm and less than 10 μm, the maximum value of the two or more peaks corresponds to "peak D".

[0283] Peak value D can be any one of peak values ​​P1, P2, or P3. In one implementation, it is peak value P1 or P3.

[0284] <Parameters of the Invention>

[0285] In this instruction manual,

[0286] In the logarithmic differential pore volume distribution curve of the first catalyst layer 20 obtained by mercury intrusion porosimetry, a peak A exists in the range of pore size greater than 1 μm and less than 3 μm. The condition where the peak A is greater than 0.20 mL / g is called "Condition 1".

[0287] In the logarithmic differential pore volume distribution curve of the first catalyst layer 20 obtained by mercury intrusion porosimetry, there is a peak B in the range of pore size greater than 3 μm and less than 10 μm. The condition where the peak B is greater than 0.20 mL / g is called "condition 2".

[0288] In the logarithmic differential pore volume distribution curve of the second catalyst layer 30 obtained by mercury intrusion porosimetry, a peak C exists in the range of pore size greater than 1 μm and less than 3 μm. The condition with a peak C of 0.20 mL / g or more is called "Condition 3".

[0289] In the logarithmic differential pore volume distribution curve of the second catalyst layer 30 obtained by mercury intrusion porosimetry, a peak D exists in the range of pore size greater than 3 μm and less than 10 μm. The condition where the peak D is greater than 0.20 mL / g is called "condition 4".

[0290] Preferably, the second catalyst layer 30 satisfies condition 3 but not condition 4, or satisfies condition 4 but not condition 3, or satisfies both conditions 3 and 4, or neither condition 3 nor 4 is satisfied.

[0291] If the second catalyst layer 30 satisfies condition 3 but not condition 4, the first catalyst layer 20 preferably satisfies at least condition 2 in both conditions 1 and 2; if the second catalyst layer 30 satisfies condition 4 but not condition 3, the first catalyst layer 20 preferably satisfies at least condition 1 in both conditions 1 and 2; if the second catalyst layer 30 satisfies conditions 3 and 4, the first catalyst layer 20 preferably satisfies at least one of conditions 1 and 2, or neither condition 1 nor 2 is satisfied; if neither condition 3 nor 4 is satisfied in the second catalyst layer 30, the first catalyst layer 20 preferably satisfies conditions 1 and 2.

[0292] That is, catalyst 1A includes the following (i) to (ix) methods.

[0293] [Table 1]

[0294] Table 1

[0295]

[0296] The smaller the pores of the first catalyst layer 20 and the second catalyst layer 30, the better the PM capture performance, but the higher the pressure drop. On the other hand, the larger the pores of the first catalyst layer 20 and the second catalyst layer 30, the more the pressure drop increase is suppressed, but the PM capture performance decreases. Therefore, pore size control by either reducing or increasing the pore size of the first catalyst layer 20 and the second catalyst layer 30 cannot achieve both improved PM capture performance and suppression of pressure drop increase. In contrast, in the above methods (i) to (ix), the first catalyst layer 20 and the second catalyst layer 30 as a whole satisfy the following conditions: the peak values ​​A and / or C corresponding to small pore sizes are 0.20 mL / g or more, and the peak values ​​B and / or D corresponding to large pore sizes are 0.20 mL / g or more. Thus, the amount of pores that contributes to PM capture performance and the amount of pores that contribute to reducing pressure drop can be sufficiently ensured, achieving both improved PM capture performance and suppression of pressure drop increase.

[0297] From the viewpoint of more effectively achieving both improved PM capture performance and suppression of pressure loss increase, the second catalyst layer 30 is more preferably satisfied with condition 3 and not satisfied with condition 4, or satisfied with condition 4 and not satisfied with condition 3, or satisfied with conditions 3 and 4; when the second catalyst layer 30 satisfies condition 3 and not satisfied with condition 4, the first catalyst layer 20 is more preferably satisfied with at least condition 2 in conditions 1 and 2; when the second catalyst layer 30 satisfies condition 4 and not satisfied with condition 3, the first catalyst layer 20 is more preferably satisfied with at least condition 1 in conditions 1 and 2; when the second catalyst layer 30 satisfies conditions 3 and 4, the first catalyst layer 20 is more preferably satisfied with at least one of conditions 1 and 2.

[0298] In condition 1, there is no particular limitation as long as the peak value A is above 0.20 mL / g. From the viewpoint of more effectively achieving both the improvement of PM collection performance and the suppression of pressure loss, it is preferred to be above 0.31 mL / g, and more preferably above 0.40 mL / g.

[0299] In condition 1, there is no particular upper limit to the peak value A. From the viewpoint of more effectively balancing the improvement of PM collection performance and the suppression of pressure drop, it is preferably 1.00 mL / g or less, more preferably 0.80 mL / g or less, and even more preferably 0.50 mL / g or less. These upper limits can be combined with the lower limits mentioned above in any way.

[0300] In condition 2, there is no particular limitation as long as the peak value B is 0.20 mL / g or higher. From the viewpoint of more effectively achieving both the improvement of PM collection performance and the suppression of pressure loss increase, it is preferred to be 0.30 mL / g or higher, and more preferably 0.42 mL / g or higher.

[0301] In condition 2, there is no particular upper limit for the peak value B. From the viewpoint of more effectively balancing the improvement of PM collection performance and the suppression of pressure drop, it is preferably 1.00 mL / g or less, more preferably 0.80 mL / g or less, and even more preferably 0.50 mL / g or less. These upper limits can be combined with the lower limits mentioned above in any way.

[0302] In condition 3, there is no particular limitation as long as the peak value C is 0.20 mL / g or higher. From the viewpoint of more effectively achieving both the improvement of PM collection performance and the suppression of pressure loss increase, it is preferred to be 0.31 mL / g or higher, and more preferably 0.40 mL / g or higher.

[0303] In condition 3, there is no particular upper limit to the peak value C. From the viewpoint of more effectively balancing the improvement of PM collection performance and the suppression of pressure drop, it is preferably 1.00 mL / g or less, more preferably 0.80 mL / g or less, and even more preferably 0.50 mL / g or less. These upper limits can be combined with the lower limits mentioned above in any way.

[0304] In condition 4, there is no particular limitation as long as the peak value D is 0.20 mL / g or higher. From the viewpoint of more effectively achieving both the improvement of PM collection performance and the suppression of pressure loss, it is preferred to be 0.30 mL / g or higher, and more preferably 0.42 mL / g or higher.

[0305] In condition 4, there is no particular upper limit for the peak value D. From the viewpoint of more effectively balancing the improvement of PM collection performance and the suppression of pressure drop, it is preferably 1.00 mL / g or less, more preferably 0.80 mL / g or less, and even more preferably 0.50 mL / g or less. These upper limits can be combined with the lower limits mentioned above in any way.

[0306] <The Effects of Catalysts in Waste Gas Purification>

[0307] Exhaust gas from the internal combustion engine flows from one end of exhaust pipe P to the other through the exhaust path within exhaust pipe P, where it is purified by catalyst 1A disposed within exhaust pipe P. Meanwhile, exhaust gas flowing in from the exhaust gas inflow side end (opening) of the inflow side chamber 13a passes through the first catalyst layer 20 and the porous partition wall 12, and / or through the porous partition wall 12 and the second catalyst layer 30, and / or through the first catalyst layer 20, the porous partition wall 12, and the second catalyst layer 30, and exits from the exhaust gas outflow side end (opening) of the outflow side chamber 13b. This configuration is called wall-flow type.

[0308] In catalyst 1A, when exhaust gas flows in from the exhaust gas inflow side end (opening) of the inflow side chamber 13a, as it passes through the first catalyst layer 20 and the porous partition wall 12, through the porous partition wall 12 and the second catalyst layer 30, or through the first catalyst layer 20, the porous partition wall 12 and the second catalyst layer 30, particulate matter (PM) in the exhaust gas is captured by the pores of the partition wall 12, the pores of the first catalyst layer 20 and / or the pores of the second catalyst layer 30. Therefore, catalyst 1A can be used as a gasline particulate filter for gasoline engines or a diesel particulate filter for diesel engines.

[0309] In methods (i) to (ix) above, the first catalyst layer 20 and the second catalyst layer 30 as a whole satisfy the following conditions: the peak values ​​A and / or C corresponding to the small pore size are 0.20 mL / g or more, and the peak values ​​B and / or D corresponding to the large pore size are 0.20 mL / g or more. Thus, two types of pore size control can be achieved, enabling a balance between improving PM capture performance and suppressing pressure drop increases.

[0310] <Method for Manufacturing Catalysts for Waste Gas Purification>

[0311] Hereinafter, embodiments of the method for manufacturing catalyst 1A will be described. Catalyst 1A manufactured by the method according to this embodiment also includes methods other than those described in (i) to (ix). The method according to this embodiment is suitable for manufacturing methods (i) to (ix).

[0312] The method involved in this embodiment includes the following steps:

[0313] (1a) A process of forming a first precursor layer by coating a first slurry containing a first pore-forming agent onto the inflow side chamber side of the partition wall portion 12 of the substrate 10.

[0314] (1b) The process of forming a second precursor layer by coating a second slurry containing a second pore-forming agent onto the outflow side of the partition wall portion 12 of the substrate 10; and

[0315] (1c) The step of calcining the first precursor layer and the second precursor layer to form the first catalyst layer 20 and the second catalyst layer 30. Step (1a) may be performed before or after step (1b). Step (1c) is performed after steps (1a) and (1b).

[0316] <Process 1a>

[0317] Step 1a is a step of forming a first precursor layer by applying a first slurry containing a first pore-forming agent to the inflow side chamber of the partition wall portion 12 of the substrate 10.

[0318] The first slurry contains a first pore-forming agent. Examples of the first pore-forming material include cross-linked poly(methyl methacrylate) particles, cross-linked poly(butyl methacrylate) particles, cross-linked polystyrene particles, cross-linked polyacrylate particles, melamine-based resins, etc.

[0319] The composition of the first slurry can be adjusted according to the composition of the first catalyst layer 20. In addition to the first pore-forming agent, the first slurry may also include, for example, a source of platinum group elements, inorganic oxide particles, a binder, and a solvent. Examples of sources of platinum group elements include, for example, salts of platinum group elements, such as nitrates, ammonium complexes, acetates, and chlorides. The inorganic oxides constituting the inorganic oxide particles are explained as described above. Examples of binders include, for example, alumina sol, zirconium oxide sol, titanium dioxide sol, silica sol, and cerium oxide sol. Examples of solvents include, for example, water and organic solvents. One solvent or a mixture of two or more solvents may be used.

[0320] A first precursor layer, serving as a precursor to the first catalyst layer 20, is formed by applying the first slurry to the exhaust gas inflow side of the partition wall portion 12 of the substrate 10 (i.e., the outer surface S1a of the inflow side chamber 13a side of the partition wall portion 12) and drying it. The drying temperature is, for example, 40°C or higher and 150°C or lower, and the drying time is, for example, 5 minutes or higher and 1 hour or lower.

[0321] The particle size of the first pore-forming material can be adjusted appropriately. 50 Preferably, the particle size is 0.1 μm or more and 20 μm or less, more preferably 0.5 μm or more and 17 μm or less, and even more preferably 1.5 μm or more and 15 μm or less. By adjusting the particle size and amount of the first pore-forming material, a first catalyst layer 20 that does not satisfy either condition 1 or 2, a first catalyst layer 20 that satisfies either condition 1 or 2, or a first catalyst layer 20 that satisfies both conditions 1 and 2 can be formed.

[0322] D 50 It refers to the particle size that constitutes 50% of the cumulative volume in the volumetric particle size distribution determined by laser diffraction scattering particle size distribution measurement method. D 50 The determination was performed as follows: Using an automated sampler (Microtrac SDC, MicrotracBEL) for laser diffraction scattering particle size distribution analysis, the sample was placed in an aqueous dispersion medium. After irradiation with 40W ultrasound for 360 seconds at a flow rate of 32.5 mL / sec, the particle size distribution was determined using a laser diffraction scattering particle size distribution analysis device (Microtrac MT3300EXII, MicrotracBEL). The determination was performed twice under the following conditions: particle refractive index: 1.5; particle shape: spherical; solvent refractive index: 1.3; zeroing time: 30 seconds; measurement time: 30 seconds. The average value of the measured values ​​was taken as D. 50 Pure water is used as the aqueous dispersion medium.

[0323] <Process 1b>

[0324] Step 1b is a step of forming a second precursor layer by applying a second slurry containing a second pore-forming agent to the outflow side of the partition wall portion 12 of the substrate 10.

[0325] The second slurry contains a second pore-forming agent. Specific examples of the second pore-forming material are the same as those of the first pore-forming material.

[0326] The composition of the second slurry can be adjusted according to the composition of the second catalyst layer 30. In addition to the second pore-forming agent, the second slurry may also include, for example, a source of platinum group elements, inorganic oxide particles, a binder, and a solvent. Examples of sources of platinum group elements include, for example, salts of platinum group elements, such as nitrates, ammonium complexes, acetates, and chlorides. The inorganic oxides constituting the inorganic oxide particles are explained as described above. Examples of binders include, for example, alumina sol, zirconium oxide sol, titanium dioxide sol, silica sol, and cerium oxide sol. Examples of solvents include, for example, water and organic solvents. One solvent or a mixture of two or more solvents may be used.

[0327] A second precursor layer, serving as a precursor to the second catalyst layer 30, is formed by applying the second slurry to the exhaust gas outlet side of the partition wall portion 12 of the substrate 10 (i.e., the outer surface S1b of the outlet side chamber 13b of the partition wall portion 12) and drying it. The drying temperature is, for example, 40°C or higher and 150°C or lower, and the drying time is, for example, 5 minutes or higher and 1 hour or lower.

[0328] The particle size of the second pore-forming material can be adjusted appropriately. 50 Preferably, the particle size is 0.1 μm or larger and 20 μm or smaller, more preferably 0.5 μm or larger and 17 μm or smaller, and even more preferably 1.5 μm or larger and 15 μm or smaller. By adjusting the particle size and amount of the second pore-forming material, a second catalyst layer 30 that does not satisfy either condition 3 or 4, a second catalyst layer 30 that satisfies either condition 3 or 4, or a second catalyst layer 30 that satisfies both conditions 3 and 4 can be formed. 50 The significance and measurement methods are the same as those described above.

[0329] <Process 1c>

[0330] Step 1c is the process of calcining the first precursor layer and the second precursor layer to form the first catalyst layer 20 and the second catalyst layer 30.

[0331] The first catalyst layer 20 and the second catalyst layer 30 are formed by calcining the first precursor layer and the second precursor layer, respectively. The calcination temperature is, for example, above 350°C and below 600°C, and the calcination time is, for example, above 20 minutes and below 5 hours. The atmosphere during calcination is usually atmospheric.

[0332] Upon calcination of the first precursor layer, the first pore-forming agent disappears, and pores are formed in the first catalyst layer 20. Upon calcination of the second precursor layer, the second pore-forming agent disappears, and pores are formed in the second catalyst layer 30. By adjusting the particle size and amount of the first and second pore-forming materials, the logarithmic differential pore volume distribution of the first catalyst layer 20 and the second catalyst layer 30 can be adjusted.

[0333] The method according to this embodiment preferably satisfies the following conditions (C1) to (C7). This ensures sufficient pore size that contributes to PM collection performance and reduces pressure loss, achieving a balance between improved PM collection performance and suppression of pressure loss increases. When the method according to this embodiment satisfies the following conditions (C1) to (C7), the method according to this embodiment is particularly suitable for manufacturing in the above-described methods (i) to (ix).

[0334] (C1) The median particle size D of either the first or second pore-forming agent. 50 The median particle size D of the other is greater than 4 μm. 50 It is below 4μm.

[0335] (C2) The first slurry contains inorganic oxide particles, and the median particle size D of the inorganic oxide particles contained in the first slurry is... 50 It is between 1μm and 20μm.

[0336] (C3) Based on the mass of the first catalyst layer 20 (mass after calcination), the amount of the first pore-forming agent contained in the first precursor layer is more than 10% by mass and less than 60% by mass.

[0337] (C4) The mass of the first catalyst layer 20 per unit volume of the portion of the substrate 10 in which the first catalyst layer 20 is formed (mass after calcination) is 5 g / L or more and 150 g / L or less.

[0338] (C5) The second slurry contains inorganic oxide particles, and the median particle size D of the inorganic oxide particles contained in the second slurry is... 50 It is between 1μm and 20μm.

[0339] (C6) Based on the mass of the second catalyst layer 30 (mass after calcination), the amount of the second pore-forming agent contained in the second precursor layer is more than 10% by mass and less than 60% by mass.

[0340] (C7) The mass of the second catalyst layer 30 per unit volume of the portion of the substrate 10 in which the second catalyst layer 30 is formed (mass after calcination) is 5 g / L or more and 150 g / L or less.

[0341] The following explains condition (C1).

[0342] From the perspective of more effectively achieving a balance between improving PM trapping performance and suppressing pressure drop, the D of the pore-forming agent... 50 More preferably, the micrometer is 4.5 μm or more and 20 μm or less; even more preferably, it is 4.5 μm or more and 17 μm or less; and even more preferably, it is 4.5 μm or more and 15 μm or less.

[0343] From the perspective of more effectively achieving a balance between improving PM trapping performance and suppressing pressure drop, the other pore-forming agent's D 50 More preferably, the micrometer is 0.1 μm or more and 4 μm or less; even more preferably, it is 0.5 μm or more and 4 μm or less; and even more preferably, it is 1.5 μm or more and 4 μm or less.

[0344] The following explains condition (C2).

[0345] From the perspective of more effectively achieving a balance between improving PM collection performance and suppressing pressure loss, the median particle size D of the inorganic oxide particles contained in the first slurry is... 50 More preferably, the micrometer is 1.5 μm or more and 15 μm or less, and even more preferably, it is 2 μm or more and 10 μm or less.

[0346] The following explains condition (C3).

[0347] From the viewpoint of more effectively achieving both improved PM capture performance and suppression of pressure drop increase, based on the mass of the first catalyst layer 20 (mass after calcination), the amount of the first pore-forming agent contained in the first precursor layer is more preferably 20% by mass or more and 50% by mass or less, and more preferably 25% by mass or more and 45% by mass or less. The amount of the first pore-forming agent contained in the first precursor layer can be adjusted by adjusting the amount of the first pore-forming agent contained in the first slurry, the amount of the first slurry coated on the inflow side chamber side of the partition wall portion 12 of the substrate 10, etc. It should be noted that the mass of the first catalyst layer 20 is obtained by subtracting the mass of components (e.g., solvent, pore-forming agent, etc.) that disappear due to the drying and calcination of the first slurry from the mass of the first slurry coated on the inflow side chamber side of the partition wall portion 12 of the substrate 10.

[0348] The following explains condition (C4).

[0349] From the viewpoint of more effectively achieving both improved PM capture performance and suppression of pressure loss increase, the mass (mass after calcination) of the first catalyst layer 20 per unit volume of the portion of the substrate 10 in which the first catalyst layer 20 is formed is more preferably 10 g / L or more and 100 g / L or less, and even more preferably 25 g / L or more and 70 g / L or less. The mass of the first catalyst layer 20 per unit volume of the portion of the substrate 10 in which the first catalyst layer 20 is formed can be adjusted by adjusting the amount of the first slurry coated on the inflow side chamber side of the partition wall portion 12 of the substrate 10, etc.

[0350] The following explains condition (C5).

[0351] From the perspective of more effectively achieving a balance between improving PM collection performance and suppressing pressure loss, the median particle size D of the inorganic oxide particles contained in the second slurry is... 50 More preferably, the micrometer is 1.5 μm or more and 15 μm or less, and even more preferably, it is 2 μm or more and 10 μm or less.

[0352] The following explains condition (C6).

[0353] From the viewpoint of more effectively achieving both improved PM capture performance and suppression of pressure drop increase, based on the mass of the second catalyst layer 30 (mass after calcination), the amount of the second pore-forming agent contained in the second precursor layer is more preferably 20% by mass or more and 50% by mass or less, and more preferably 25% by mass or more and 45% by mass or less. The amount of the second pore-forming agent contained in the second precursor layer can be adjusted by adjusting the amount of the second pore-forming agent contained in the second slurry, the amount of the second slurry coated on the outflow side chamber side of the partition wall portion 12 of the substrate 10, etc. It should be noted that the mass of the second catalyst layer 30 is obtained by subtracting the mass of components (e.g., solvent, pore-forming agent, etc.) that disappear due to the drying and calcination of the second slurry from the mass of the second slurry coated on the outflow side chamber side of the partition wall portion 12 of the substrate 10.

[0354] The following explains condition (C7).

[0355] From the viewpoint of more effectively achieving both improved PM capture performance and suppression of pressure loss increase, the mass (mass after calcination) of the second catalyst layer 30 per unit volume of the portion of the substrate 10 in which the second catalyst layer 30 is formed is more preferably 10 g / L or more and 100 g / L or less, and even more preferably 25 g / L or more and 70 g / L or less. The mass of the second catalyst layer 30 per unit volume of the portion of the substrate 10 in which the second catalyst layer 30 is formed can be adjusted by adjusting the amount of the second slurry coated on the outflow side of the partition wall portion 12 of the substrate 10, etc.

[0356] Implementation Method 2

[0357] The following is based on Figure 8 and 9 The second embodiment of the present invention will now be described.

[0358] like Figure 8 and 9As shown, the exhaust gas purification catalyst 1B (hereinafter referred to as "catalyst 1B") according to the second embodiment differs from catalyst 1A in that the second catalyst layer 30 has a stacked structure including a lower layer 31 and an upper layer 32 instead of a single-layer structure. It should be noted that the lower layer is the layer closer to the partition wall portion 12 than the upper layer. The case where the second catalyst layer 30 has a stacked structure improves PM capture performance compared to the case where the second catalyst layer 30 has a single-layer structure.

[0359] In catalyst 1B, components identical to those in catalyst 1A are designated using the same symbols as in catalyst 1A. Unless otherwise specified, the above description relating to catalyst 1A also applies to catalyst 1B. Where applicable, "catalyst 1A" shall be replaced with "catalyst 1B" for illustrative purposes.

[0360] In catalyst 1B, the logarithmic differential pore volume distribution of the second catalyst layer 30 is the sum of the logarithmic differential pore volume distribution of the lower layer 31 and the logarithmic differential pore volume distribution of the upper layer 32.

[0361] The slice M2 used in the mercury intrusion porosimetry process includes a portion of the partition wall 12 and a portion of the second catalyst layer 30 (a portion of the lower layer 31 and a portion of the upper layer 32), but does not include the first catalyst layer 20. Other details regarding slice M2 are the same as described above.

[0362] <Lower Level>

[0363] like Figure 8 and 9 As shown, the lower layer 31 is located on the outflow side chamber 13b side of the partition wall 12.

[0364] like Figure 8 and 9 As shown, the lower layer 31 extends from the end of the partition wall 12 on the exhaust gas outflow side in a direction opposite to the exhaust gas flow direction E. In this embodiment, the lower layer 31 does not reach the end of the partition wall 12 on the exhaust gas inflow side, but it may reach the end of the partition wall 12 on the exhaust gas inflow side.

[0365] like Figure 8 and 9 As shown, preferably, at least a portion of the lower layer 31 protrudes from the outer surface S1b of the partition wall portion 12 toward the outflow side chamber 13b, that is, the lower layer 31 has a portion that protrudes from the outer surface S1b of the partition wall portion 12 toward the outflow side chamber 13b (hereinafter referred to as the "protruding portion"). This improves the contact between exhaust gas and PM, enabling more effective improvement in exhaust gas purification performance and PM capture performance.

[0366] The lower layer 31 may consist only of the raised portion, or it may have both the raised portion and a portion existing inside the partition wall portion 12 (hereinafter referred to as the "inner portion"). Since the partition wall portion 12 is porous, the inner portion and the raised portion may sometimes be formed together when the lower layer 31 is formed. The raised portion and the inner portion may be continuous. The lower layer 31 may also consist only of the inner portion. The phrase "the lower layer 31 is disposed on the outflow side chamber 13b side of the partition wall portion 12" includes: an embodiment where the lower layer 31 consists only of the raised portion, an embodiment where the lower layer 31 consists only of the inner portion, and an embodiment where the lower layer 31 has both the raised portion and the inner portion.

[0367] The above description of the method for determining the raised portion and the inner portion of the first catalyst layer 20 also applies to the lower layer 31. Where applicable, "first catalyst layer 20" can be replaced with "lower layer 31" for understanding.

[0368] From the viewpoint of achieving a good balance between exhaust gas purification performance and cost, the mass of the lower layer 31 per unit volume of the portion of the substrate 10 in which the lower layer 31 is formed (mass after calcination) is preferably 5 g / L or more and 90 g / L or less, more preferably 10 g / L or more and 70 g / L or less, and even more preferably 15 g / L or more and 50 g / L or less. The mass of the lower layer 31 per unit volume of the portion of the substrate 10 in which the lower layer 31 is formed is calculated according to the following formula: (mass of lower layer 31) / (volume of substrate 10) × (average length L of lower layer 31) 31 / Length L of substrate 10 10 )).

[0369] The above description regarding the quality of the first catalyst layer 20 also applies to the lower layer 31. Where applicable, "first catalyst layer 20" can be replaced with "lower layer 31" for understanding.

[0370] Regarding the average length L of the first catalyst layer 20 20 The above description of the measurement method also applies to the average length L of the lower layer 31. 31 The determination method. Where applicable, "first catalyst layer 20" can be understood as "lower layer 31", and "average length L" can be understood as... 20 Replace “average length L” with “average length L” 31 To understand this, we need to consider the average length L of the lower layer 31. 31 In the measurement method, the sample is cut at 5mm intervals using a plane perpendicular to the axial direction of the substrate 10, and the first slice, the second slice, ..., the nth slice are obtained sequentially from the end side of the sample from the exhaust gas outlet side.

[0371] The average length L of the lower layer 31 31The average length L of the lower layer 31 can be adjusted appropriately, taking into account factors such as exhaust gas purification performance and PM capture performance. From the perspective of improving exhaust gas purification performance and PM capture performance, 31 Relative to the length L of the substrate 10 10 percentage (L) 31 / L 10 The content of (×100) is preferably 15% or more and 90% or less, more preferably 20% or more and 90% or less, and even more preferably 30% or more and 85% or less.

[0372] From the perspective of improving exhaust gas purification performance and PM capture performance, the average length L of the first catalyst layer 20 is... 20 The average length L of the lower layer 31 31 The sum relative to the length L of the substrate 10 10 percentage ((L) 20 +L 31 ) / L 10 The content of (×100) is preferably 100% or more and 180% or less, more preferably 100% or more and 170% or less, and even more preferably 105% or more and 150% or less.

[0373] The lower layer 31 contains one or more platinum group elements. The above description of the platinum group elements and their metal conversions contained in the first catalyst layer 20 also applies to the platinum group elements and their metal conversions contained in the lower layer 31. Where applicable, "first catalyst layer 20" should be replaced with "lower layer 31" for understanding.

[0374] In one embodiment, the lower layer 31 comprises Pd. In addition to Pd, the lower layer 31 may also comprise one or more other platinum group elements. Embodiments where the lower layer 31 comprises Pd can be combined with embodiments where the first catalyst layer 20 comprises Rh.

[0375] The lower layer 31 preferably contains one or more supports, and at least a portion of the catalytically active ingredient is loaded onto one or more supports. The significance and confirmation method of the loading are the same as described above.

[0376] The above description of the support contained in the first catalyst layer 20 also applies to the support contained in the lower layer 31. Where applicable, "first catalyst layer 20" can be replaced with "lower layer 31" for understanding.

[0377] The lower layer 31 may contain other components such as adhesives and stabilizers. The descriptions of adhesives and stabilizers are the same as above.

[0378] <Upper Level>

[0379] like Figure 8 and 9 As shown, the upper layer 32 is set on the lower layer 31.

[0380] "Upper layer 32 is disposed on lower layer 31" means that, among the two main surfaces of lower layer 31, a portion or all of upper layer 32 exists on the main surface opposite to the main surface of partition wall portion 12. "Main surface of lower layer 31" refers to the outer surface of lower layer 31 extending along the exhaust gas flow direction E. Upper layer 32 can be disposed directly on the main surface of lower layer 31 or disposed in between other layers, but it is usually disposed directly on the main surface of lower layer 31. Upper layer 32 can be disposed in a manner that covers a portion of the main surface of lower layer 31 or in a manner that covers the entire main surface of lower layer 31. "Upper layer 32 is disposed on lower layer 31" includes both embodiments where upper layer 32 is disposed directly on the main surface of lower layer 31 and embodiments where upper layer 32 is disposed in between other layers.

[0381] like Figure 8 and 9 As shown, the upper layer 32 extends from the end of the partition wall 12 on the exhaust gas outflow side in a direction opposite to the exhaust gas flow direction E. In this embodiment, the upper layer 32 does not reach the end of the partition wall 12 on the exhaust gas inflow side, but it may reach the end of the partition wall 12 on the exhaust gas inflow side.

[0382] From the viewpoint of achieving a good balance between exhaust gas purification performance and cost, the mass of the upper layer 32 per unit volume of the portion of the substrate 10 where the upper layer 32 is formed (mass after calcination) is preferably 5 g / L or more and 60 g / L or less, more preferably 5 g / L or more and 40 g / L or less, and even more preferably 5 g / L or more and 30 g / L or less. The mass of the upper layer 32 per unit volume of the portion of the substrate 10 where the upper layer 32 is formed is calculated according to the following formula: (mass of upper layer 32) / (volume of substrate 10) × (average length L of upper layer 32) 32 / Length L of substrate 10 10 )).

[0383] The above description regarding the quality of the first catalyst layer 20 also applies to the upper layer 32. Where applicable, "first catalyst layer 20" can be replaced with "upper layer 32" for understanding.

[0384] Regarding the average length L of the first catalyst layer 20 20 The above description of the measurement method also applies to the average length L of the upper layer 32. 32 The determination method. Where applicable, "first catalyst layer 20" can be understood as "upper layer 32", and "average length L" can be understood as... 20 Replace “average length L” with “average length L” 32 To understand this, we need to consider the average length L of the upper layer (32). 32In the measurement method, the sample is cut at 5mm intervals using a plane perpendicular to the axial direction of the substrate 10, and the first slice, the second slice, ..., the nth slice are obtained sequentially from the end side of the sample from the exhaust gas outlet side.

[0385] The average length L of the upper layer 32 32 Adjustments can be made to consider factors such as exhaust gas purification performance and PM capture performance. From the perspective of improving exhaust gas purification performance and PM capture performance, the average length L of the upper layer 32... 32 Relative to the length L of the substrate 10 10 percentage (L) 32 / L 10 The content of (×100) is preferably 15% or more and 90% or less, more preferably 20% or more and 90% or less, and even more preferably 30% or more and 85% or less.

[0386] From the perspective of improving exhaust gas purification performance and PM capture performance, the average length L of the first catalyst layer 20 is... 20 The average length L of the upper layer 32 32 The sum relative to the length L of the substrate 10 10 percentage ((L) 20 +L 32 ) / L 10 The content of (×100) is preferably 100% or more and 180% or less, more preferably 100% or more and 170% or less, and even more preferably 105% or more and 150% or less.

[0387] The upper layer 32 contains one or more platinum group elements. The above description of the platinum group elements and their metal conversions contained in the first catalyst layer 20 also applies to the platinum group elements and their metal conversions contained in the upper layer 32. Where applicable, "first catalyst layer 20" should be replaced with "upper layer 32" for understanding.

[0388] In one embodiment, the upper layer 32 comprises Rh. In addition to Rh, the upper layer 32 may also comprise one or more other platinum group elements. Embodiments where the upper layer 32 comprises Rh can be combined with embodiments where the first catalyst layer 20 comprises Rh and / or embodiments where the lower layer 31 comprises Pd.

[0389] The upper layer 32 preferably contains one or more supports, and at least a portion of the catalytically active ingredient is loaded on one or more supports. The significance and confirmation method of the loading are the same as described above.

[0390] The above description of the support contained in the first catalyst layer 20 also applies to the support contained in the upper layer 32. Where applicable, "first catalyst layer 20" can be replaced with "upper layer 32" for understanding.

[0391] The upper layer 32 may contain other components such as adhesives and stabilizers. The descriptions of adhesives and stabilizers are the same as above.

[0392] <Method for Manufacturing Catalysts for Waste Gas Purification>

[0393] Hereinafter, embodiments of the method for manufacturing catalyst 1B will be described. Catalyst 1B manufactured by the method according to this embodiment also includes methods other than those described in (i) to (ix). The method according to this embodiment is suitable for manufacturing methods (i) to (ix).

[0394] The method involved in this embodiment includes the following steps:

[0395] (2a) A process of forming a first precursor layer by coating a first slurry containing a first pore-forming agent onto the inflow side chamber side of the partition wall portion 12 of the substrate 10.

[0396] (2b) A process of forming a third precursor layer by coating a third slurry containing a third pore-forming agent onto the outflow side of the partition wall portion 12 of the substrate.

[0397] (2c) The process of coating a fourth slurry containing a fourth pore-forming agent onto the third precursor layer to form a fourth precursor layer; and

[0398] (2d) A step of calcining the first precursor layer, the third precursor layer, and the fourth precursor layer to form the lower layer 31 of the first catalyst layer 20 and the upper layer 32 of the second catalyst layer 30. Step (2a) can be performed before or after steps (2b) to (2c). Step (2b) is performed before step (2c). Step (2d) is performed after steps (2a) to (2c).

[0399] <Process 2a>

[0400] Step 2a is a step of forming a first precursor layer by applying a first slurry containing a first pore-forming agent to the inflow side chamber of the partition wall portion 12 of the substrate 10.

[0401] Step 2a can be performed in the same manner as step 1a. The above description of step 1a also applies to step 2a.

[0402] <Process 2b>

[0403] Step 2b is a step of forming a third precursor layer by applying a third slurry containing a third pore-forming agent to the outflow side of the partition wall portion 12 of the substrate.

[0404] The third slurry contains a third pore-forming agent. Specific examples of the third pore-forming material are the same as those of the first pore-forming material.

[0405] The composition of the third slurry can be adjusted according to the composition of the lower layer 31 of the second catalyst layer 30. In addition to the third pore-forming agent, the third slurry may also include, for example, a source of platinum group elements, inorganic oxide particles, a binder, and a solvent. Examples of platinum group element sources include, for example, salts of platinum group elements, such as nitrates, ammonium complexes, acetates, and chlorides. The inorganic oxides constituting the inorganic oxide particles are explained as described above. Examples of binders include, for example, alumina sol, zirconium oxide sol, titanium dioxide sol, silica sol, and cerium oxide sol. Examples of solvents include, for example, water and organic solvents. One solvent or a mixture of two or more solvents may be used.

[0406] A third precursor layer, serving as a precursor to the lower layer 31 of the second catalyst layer 30, is formed by applying the third slurry to the exhaust gas outlet side of the partition wall portion 12 of the substrate 10 (i.e., the outer surface S1b of the outlet side chamber 13b of the partition wall portion 12) and drying it. The drying temperature is, for example, 40°C or higher and 150°C or lower, and the drying time is, for example, 5 minutes or higher and 1 hour or lower.

[0407] The particle size of the third pore-forming material can be adjusted appropriately. 50 Preferably, the particle size is 0.1 μm or larger and 20 μm or smaller, more preferably 0.5 μm or larger and 17 μm or smaller, and even more preferably 1.5 μm or larger and 15 μm or smaller. By adjusting the particle size and amount of the third pore-forming material, a lower layer 31 that does not satisfy either condition 3 or 4, a lower layer 31 that satisfies either condition 3 or 4, or a lower layer 31 that satisfies both conditions 3 and 4 can be formed. 50 The significance and measurement methods are the same as those described above.

[0408] <Process 2c>

[0409] Step 2c is a step of forming a fourth precursor layer by coating a fourth slurry containing a fourth pore-forming agent onto the third precursor layer.

[0410] The fourth slurry contains a fourth pore-forming agent. Specific examples of the fourth pore-forming material are the same as those of the first pore-forming material.

[0411] The composition of the fourth slurry can be adjusted according to the composition of the upper layer 32 of the second catalyst layer 30. In addition to the fourth pore-forming agent, the fourth slurry may also include, for example, a source of platinum group elements, inorganic oxide particles, a binder, and a solvent. Examples of platinum group element sources include, for example, salts of platinum group elements, such as nitrates, ammonium complexes, acetates, and chlorides. The inorganic oxides constituting the inorganic oxide particles are explained as described above. Examples of binders include, for example, alumina sol, zirconium oxide sol, titanium dioxide sol, silica sol, and cerium oxide sol. Examples of solvents include, for example, water and organic solvents. One solvent or a mixture of two or more solvents may be used.

[0412] A fourth precursor layer is formed by coating the fourth slurry onto the third precursor layer and drying it. This fourth precursor layer serves as the precursor to the upper layer 32 of the second catalyst layer 30. The drying temperature is, for example, 40°C or higher and 150°C or lower, and the drying time is, for example, 5 minutes or higher and 1 hour or lower.

[0413] The particle size of the fourth pore-forming material can be adjusted appropriately. 50 Preferably, the particle size is 0.1 μm or more and 20 μm or less, more preferably 0.5 μm or more and 17 μm or less, and even more preferably 1.5 μm or more and 15 μm or less. By adjusting the particle size and amount of the fourth pore-forming material, an upper layer 32 that does not satisfy either condition 3 or 4, an upper layer 32 that satisfies either condition 3 or 4, or an upper layer 32 that satisfies both conditions 3 and 4 can be formed. By adjusting the particle size and amount of the third pore-forming material and / or the particle size and amount of the fourth pore-forming material, a second catalyst layer 30 that does not satisfy either condition 3 or 4, a second catalyst layer 30 that satisfies either condition 3 or 4, or a second catalyst layer 30 that satisfies both conditions 3 and 4 can be formed. 50 The significance and measurement methods are the same as those described above.

[0414] <Process 2d>

[0415] Step 2d is the process of calcining the first precursor layer, the third precursor layer and the fourth precursor layer to form the lower layer 31 of the first catalyst layer 20 and the upper layer 32 of the second catalyst layer 30.

[0416] The first precursor layer, the third precursor layer, and the fourth precursor layer are calcined to form the lower layer 31 of the first catalyst layer 20 and the upper layer 32 of the second catalyst layer 30, respectively. The calcination temperature is, for example, 350°C or higher and 600°C or lower, and the calcination time is, for example, 20 minutes or higher and 5 hours or lower. The atmosphere during calcination is usually atmospheric.

[0417] Calcination of the first precursor layer causes the first pore-forming agent to disappear, thereby forming pores in the first catalyst layer 20. Calcination of the third precursor layer causes the third pore-forming agent to disappear, thereby forming pores in the lower layer 31 of the second catalyst layer 30. Calcination of the fourth precursor layer causes the fourth pore-forming agent to disappear, thereby forming pores in the upper layer 32 of the second catalyst layer 30. By adjusting the particle size and amount of the first, third, and fourth pore-forming materials, the logarithmic differential pore volume distribution of the first catalyst layer 20 and the second catalyst layer 30 can be adjusted.

[0418] The method according to this embodiment preferably satisfies the following conditions (D1) to (D10). This ensures sufficient pore size that contributes to PM collection performance and reduces pressure loss, achieving a balance between improved PM collection performance and suppression of pressure loss increases. When the method according to this embodiment satisfies the following conditions (D1) to (D10), the method according to this embodiment is particularly suitable for manufacturing in the above-described methods (i) to (ix).

[0419] (D1) The median particle size D of one or both of the first, third, and fourth pore-forming agents. 50 For particles larger than 4 μm, the median particle size D of the remaining two or one is... 50 It is below 4μm.

[0420] (D2) The first slurry contains inorganic oxide particles, and the median particle size D of the inorganic oxide particles contained in the first slurry is... 50 It is between 1μm and 20μm.

[0421] (D3) Based on the mass of the first catalyst layer 20 (mass after calcination), the amount of the first pore-forming agent contained in the first precursor layer is more than 10% by mass and less than 60% by mass.

[0422] (D4) The mass of the first catalyst layer 20 per unit volume of the portion of the substrate 10 in which the first catalyst layer 20 is formed (mass after calcination) is 5 g / L or more and 150 g / L or less.

[0423] (D5) The third slurry contains inorganic oxide particles, and the median particle size D of the inorganic oxide particles contained in the third slurry is... 50 It is between 1μm and 20μm.

[0424] (D6) Based on the mass of the lower layer 31 (mass after calcination), the amount of the third pore-forming agent contained in the third precursor layer is more than 10% by mass and less than 60% by mass.

[0425] (D7) The mass of the lower layer 31 per unit volume of the portion in the substrate 10 where the lower layer 31 is formed (mass after calcination) is 5 g / L or more and 90 g / L or less.

[0426] (D8) The fourth slurry contains inorganic oxide particles, and the median particle size D of the inorganic oxide particles contained in the fourth slurry is... 50 It is between 1μm and 20μm.

[0427] (D9) Based on the mass of the upper layer 32 (mass after calcination), the amount of the fourth pore-forming agent contained in the fourth precursor layer is more than 10% by mass and less than 60% by mass.

[0428] (D10) The mass of the upper layer 32 per unit volume of the portion in which the upper layer 32 is formed in the substrate 10 (mass after calcination) is more than 5 g / L and less than 60 g / L.

[0429] The following explains condition (D1).

[0430] The median particle size D of one of the pore-forming agents 1, 3, and 4. 50 When the particle size is greater than 4 μm, the median particle size D of the remaining two is... 50 The median particle size D of two of the pore-forming agents (first, third, and fourth) is below 4 μm. 50 When the diameter is greater than 4 μm, the median particle size D of the remaining one is... 50 It is below 4μm.

[0431] From the perspective of more effectively achieving a balance between improving PM trapping performance and suppressing pressure drop, the median particle size of one or both of the first, third, and fourth pore-forming agents is considered in the D-strain analysis. 50 More preferably, the micrometer is 4.5 μm or more and 20 μm or less; even more preferably, it is 4.5 μm or more and 17 μm or less; and even more preferably, it is 4.5 μm or more and 15 μm or less.

[0432] From the perspective of more effectively achieving both improved PM trapping performance and suppression of pressure drop, the D of the remaining two or one of the pore-forming agents... 50 More preferably, the micrometer is 0.1 μm or more and 4 μm or less; even more preferably, it is 0.5 μm or more and 4 μm or less; and even more preferably, it is 1.5 μm or more and 4 μm or less.

[0433] The following explains condition (D2).

[0434] From the perspective of more effectively achieving a balance between improving PM collection performance and suppressing pressure loss, the median particle size D of the inorganic oxide particles contained in the first slurry is... 50 More preferably, the micrometer is 1.5 μm or more and 15 μm or less, and even more preferably, it is 2 μm or more and 10 μm or less.

[0435] The following explains condition (D3).

[0436] From the viewpoint of more effectively achieving both improved PM capture performance and suppression of pressure drop increase, based on the mass of the first catalyst layer 20 (mass after calcination), the amount of the first pore-forming agent contained in the first precursor layer is more preferably 20% by mass or more and 50% by mass or less, and more preferably 25% by mass or more and 45% by mass or less. The amount of the first pore-forming agent contained in the first precursor layer can be adjusted by adjusting the amount of the first pore-forming agent contained in the first slurry, the amount of the first slurry coated on the inflow side chamber side of the partition wall portion 12 of the substrate 10, etc. It should be noted that the mass of the first catalyst layer 20 is obtained by subtracting the mass of components (e.g., solvent, pore-forming agent, etc.) that disappear due to the drying and calcination of the first slurry from the mass of the first slurry coated on the inflow side chamber side of the partition wall portion 12 of the substrate 10.

[0437] The following explains condition (D4).

[0438] From the viewpoint of more effectively achieving both improved PM capture performance and suppression of pressure loss increase, the mass (mass after calcination) of the first catalyst layer 20 per unit volume of the portion of the substrate 10 in which the first catalyst layer 20 is formed is more preferably 10 g / L or more and 100 g / L or less, and even more preferably 25 g / L or more and 70 g / L or less. The mass of the first catalyst layer 20 per unit volume of the portion of the substrate 10 in which the first catalyst layer 20 is formed can be adjusted by adjusting the amount of the first slurry coated on the inflow side chamber side of the partition wall portion 12 of the substrate 10, etc.

[0439] The following explains condition (D5).

[0440] From the perspective of more effectively achieving a balance between improving PM collection performance and suppressing pressure loss, the median particle size D of the inorganic oxide particles contained in the third slurry is... 50 More preferably, the micrometer is 1.5 μm or more and 15 μm or less, and even more preferably, it is 2 μm or more and 10 μm or less.

[0441] The following explains condition (D6).

[0442] From the viewpoint of more effectively achieving both improved PM collection performance and suppression of pressure drop increase, based on the mass of the lower layer 31 (mass after calcination), the amount of the third pore-forming agent contained in the third precursor layer is more preferably 20% by mass or more and 50% by mass or less, and more preferably 25% by mass or more and 45% by mass or less. The amount of the third pore-forming agent contained in the third precursor layer can be adjusted by adjusting the amount of the third pore-forming agent contained in the third slurry, the amount of the third slurry coated on the outflow side of the partition wall portion 12 of the substrate 10, etc. It should be noted that the mass of the lower layer 31 is obtained by subtracting the mass of components (e.g., solvents, pore-forming agents, etc.) that disappear due to the drying and calcination of the third slurry from the mass of the third slurry coated on the outflow side of the partition wall portion 12 of the substrate 10.

[0443] The following explains condition (D7).

[0444] From the viewpoint of more effectively achieving both improved PM capture performance and suppression of pressure loss increase, the mass of the lower layer 31 per unit volume (mass after calcination) in the portion of the substrate 10 where the lower layer 31 is formed is more preferably 10 g / L or more and 70 g / L or less, and even more preferably 15 g / L or more and 50 g / L or less. The mass of the lower layer 31 per unit volume in the portion of the substrate 10 where the lower layer 31 is formed can be adjusted by adjusting the amount of the third slurry coated on the outflow side of the partition wall portion 12 of the substrate 10, etc.

[0445] The following explains condition (D8).

[0446] From the perspective of more effectively achieving both improved PM collection performance and suppression of pressure loss, the median particle size D of the inorganic oxide particles contained in the fourth slurry is... 50 More preferably, the micrometer is 1.5 μm or more and 15 μm or less, and even more preferably, it is 2 μm or more and 10 μm or less.

[0447] The following explains condition (D9).

[0448] From the viewpoint of more effectively achieving both improved PM collection performance and suppression of pressure drop increase, based on the mass of the upper layer 32 (mass after calcination), the amount of the fourth pore-forming agent contained in the fourth precursor layer is more preferably 20% by mass or more and 50% by mass or less, and more preferably 25% by mass or more and 45% by mass or less. The amount of the fourth pore-forming agent contained in the fourth precursor layer can be adjusted by adjusting the amount of the fourth pore-forming agent contained in the fourth slurry, the amount of the fourth slurry coated on the third precursor layer, etc. It should be noted that the mass of the upper layer 32 is obtained by subtracting the mass of components (e.g., solvents, pore-forming agents, etc.) that disappear due to the drying and calcination of the fourth slurry from the mass of the fourth slurry coated on the third precursor layer.

[0449] The following explains condition (D10).

[0450] From the viewpoint of more effectively achieving both improved PM capture performance and suppression of pressure loss increase, the mass of the upper layer 32 per unit volume (mass after calcination) in the portion of the substrate 10 where the upper layer 32 is formed is more preferably 5 g / L or more and 40 g / L or less, and even more preferably 5 g / L or more and 30 g / L or less. The mass of the upper layer 32 per unit volume in the portion of the substrate 10 where the upper layer 32 is formed can be adjusted by adjusting the amount of the fourth slurry coated on the third precursor layer, etc.

[0451] When the median particle size D of the third pore-forming agent 50 The median particle size D of the fourth pore-forming agent is greater than that of the fourth pore-forming agent. 50 When the third slurry becomes difficult to enter the pores in the partition wall portion 12, it is easier to achieve an embodiment in which at least a portion of the lower layer 31 protrudes from the outer surface S1b of the partition wall portion 12 toward the outflow side chamber 13b (i.e., an embodiment in which the lower layer 31 has a portion protruding from the outer surface S1b of the partition wall portion 12 toward the outflow side chamber 13b). Therefore, when using the median particle size D 50 Pore-forming agents larger than 4 μm and median particle size D 50 When the pore-forming agent is less than 4 μm, it is preferable to use a median particle size D. 50 Pore-forming agents larger than 4 μm were used as the third pore-forming agent, with a median particle size D. 50 Pore-forming agents with a diameter of less than 4 μm are used as the fourth pore-forming agent.

[0452] When the median particle size D of the third pore-forming agent 50 The median particle size D of the fourth pore-forming agent is greater than 4 μm. 50 When the particle size is below 4 μm, the second catalyst layer 30 can sufficiently ensure the amount of pores that contributes to PM trapping performance and / or reduces pressure drop. Additionally, when the median particle size D of the third pore-forming agent... 50 The median particle size D of the fourth pore-forming agent is greater than 4 μm. 50 When the size is below 4 μm, a second catalyst layer 30 that satisfies either condition 3 or 4, or a second catalyst layer 30 that satisfies both conditions 3 and 4, can be formed more efficiently, especially a second catalyst layer 30 that satisfies both conditions 3 and 4.

[0453] D of the third pore-forming agent 50 There is no particular limitation as long as it is greater than 4μm. From the viewpoint of more effectively achieving both the improvement of PM capture performance and the suppression of pressure drop, it is preferred to be 4.5μm or more and 20μm or less, more preferably 4.5μm or more and 17μm or less, and even more preferably 4.5μm or more and 15μm or less.

[0454] D of the fourth pore-forming agent 50 There are no particular limitations as long as it is 4μm or less. From the viewpoint of more effectively achieving both improved PM capture performance and suppression of pressure drop, it is preferred to be 0.1μm or more and 4μm or less, more preferably 0.5μm or more and 4μm or less, and even more preferably 1.5μm or more and 4μm or less.

[0455] Third Implementation Method

[0456] The following is based on Figure 10 and 11 The third embodiment of the present invention will now be described.

[0457] like Figure 10 and 11 As shown, the exhaust gas purification catalyst 1C (hereinafter referred to as "catalyst 1C") according to the third embodiment differs from catalyst 1A in that the first catalyst layer 20 has a stacked structure including a lower layer 21 and an upper layer 22 instead of a single-layer structure. It should be noted that the lower layer is the layer closer to the partition wall portion 12 than the upper layer. The case where the first catalyst layer 20 has a stacked structure improves PM capture performance compared to the case where the first catalyst layer 20 has a single-layer structure.

[0458] In catalyst 1C, components identical to those in catalyst 1A are designated using the same symbols as in catalyst 1A. Unless otherwise specified, the above description relating to catalyst 1A also applies to catalyst 1C. Where applicable, "catalyst 1A" shall be replaced with "catalyst 1C" for illustrative purposes.

[0459] In catalyst 1C, the logarithmic differential pore volume distribution of the first catalyst layer 20 is the sum of the logarithmic differential pore volume distribution of the lower layer 21 and the logarithmic differential pore volume distribution of the upper layer 22.

[0460] The slice M1 used in the mercury intrusion porosimetry process includes a portion of the partition wall 12 and a portion of the first catalyst layer 20 (a portion of the lower layer 21 and a portion of the upper layer 22), but does not include the second catalyst layer 30. Other details regarding slice M1 are the same as described above.

[0461] <Lower Level>

[0462] like Figure 10 and 11 As shown, the lower layer 21 is located on the inflow side chamber 13a side of the partition wall 12.

[0463] like Figure 10 and 11As shown, the lower layer 21 extends along the exhaust gas flow direction E from the end of the partition wall 12 on the exhaust gas inflow side. In this embodiment, the lower layer 21 does not reach the end of the partition wall 12 on the exhaust gas outflow side, but it may reach the end of the partition wall 12 on the exhaust gas outflow side.

[0464] like Figure 10 and 11 As shown, preferably, at least a portion of the lower layer 21 protrudes from the outer surface S1a of the partition wall portion 12 toward the inflow side chamber 13a, that is, the lower layer 21 has a portion that protrudes from the outer surface S1a of the partition wall portion 12 toward the inflow side chamber 13a (hereinafter referred to as the "protruding portion"). This improves the contact between exhaust gas and PM, enabling more effective improvement in exhaust gas purification performance and PM capture performance.

[0465] The lower layer 21 may consist only of the raised portion, or it may have both the raised portion and a portion existing inside the partition wall 12 (hereinafter referred to as the "inner portion"). Since the partition wall 12 is porous, the inner portion and the raised portion may sometimes be formed together when the lower layer 21 is formed. The raised portion and the inner portion may be continuous. The lower layer 21 may also consist only of the inner portion. The phrase "the lower layer 21 is disposed on the inflow side chamber 13a side of the partition wall 12" includes: an embodiment where the lower layer 21 consists only of the raised portion, an embodiment where the lower layer 21 consists only of the inner portion, and an embodiment where the lower layer 21 has both the raised portion and the inner portion.

[0466] The above description of the method for determining the raised portion and the inner portion of the first catalyst layer 20 also applies to the lower layer 21. Where applicable, "first catalyst layer 20" can be replaced with "lower layer 21" for understanding.

[0467] From the viewpoint of achieving a good balance between exhaust gas purification performance and cost, the mass of the lower layer 21 per unit volume of the portion of the substrate 10 in which the lower layer 21 is formed (mass after calcination) is preferably 5 g / L or more and 90 g / L or less, more preferably 10 g / L or more and 70 g / L or less, and even more preferably 15 g / L or more and 50 g / L or less. The mass of the lower layer 21 per unit volume of the portion of the substrate 10 in which the lower layer 21 is formed is calculated according to the following formula: (mass of lower layer 21) / (volume of substrate 10) × (average length L of lower layer 21) 21 / Length L of substrate 10 10 )).

[0468] The above description regarding the quality of the first catalyst layer 20 also applies to the lower layer 21. Where applicable, "first catalyst layer 20" should be replaced with "lower layer 21" for understanding.

[0469] Regarding the average length L of the first catalyst layer 20 20The above description of the measurement method also applies to the average length L of the lower layer 21. 21 The determination method. Where applicable, "first catalyst layer 20" can be understood as "lower layer 21", and "average length L" can be understood as... 20 Replace “average length L” with “average length L” 21 To understand this.

[0470] The average length L of the lower layer 21 21 The average length L of the lower layer 21 can be adjusted appropriately, taking into account factors such as exhaust gas purification performance and PM capture performance. From the perspective of improving exhaust gas purification performance and PM capture performance, 21 Relative to the length L of the substrate 10 10 percentage (L) 21 / L 10 The content of (×100) is preferably 15% or more and 90% or less, more preferably 20% or more and 90% or less, and even more preferably 30% or more and 85% or less.

[0471] From the perspective of improving exhaust gas purification performance and PM capture performance, the average length L of the second catalyst layer 30 is... 30 The average length L of the lower layer 21 21 The sum relative to the length L of the substrate 10 10 percentage ((L) 30 +L 21 ) / L 10 The content of (×100) is preferably 100% or more and 180% or less, more preferably 100% or more and 170% or less, and even more preferably 105% or more and 150% or less.

[0472] The lower layer 21 contains one or more platinum group elements. The above description of the platinum group elements and their metal conversions contained in the first catalyst layer 20 also applies to the platinum group elements and their metal conversions contained in the lower layer 21. Where applicable, "first catalyst layer 20" shall be replaced with "lower layer 21" for understanding.

[0473] In one embodiment, the lower layer 21 comprises Pd. In addition to Pd, the lower layer 21 may also comprise one or more other platinum group elements. Embodiments where the lower layer 21 comprises Pd can be combined with embodiments where the second catalyst layer 30 comprises Rh.

[0474] The lower layer 21 preferably contains one or more supports, and at least a portion of the catalytically active ingredient is loaded onto one or more supports. The significance and confirmation method of the loading are the same as described above.

[0475] The above description of the support contained in the first catalyst layer 20 also applies to the support contained in the lower layer 21. Where applicable, "first catalyst layer 20" can be replaced with "lower layer 21" for understanding.

[0476] The lower layer 21 may contain other components such as adhesives and stabilizers. The descriptions of adhesives and stabilizers are the same as above.

[0477] <Upper Level>

[0478] like Figure 10 and 11 As shown, the upper layer 22 is set on the lower layer 21.

[0479] "Upper layer 22 is disposed on lower layer 21" means that, among the two main surfaces of lower layer 21, a portion or all of upper layer 22 exists on the main surface opposite to the main surface of partition wall portion 12. "Main surface of lower layer 21" refers to the outer surface of lower layer 21 extending along the exhaust gas flow direction E. Upper layer 22 can be disposed directly on the main surface of lower layer 21 or disposed in between other layers, but it is usually disposed directly on the main surface of lower layer 21. Upper layer 22 can be disposed in a manner that covers a portion of the main surface of lower layer 21 or in a manner that covers the entire main surface of lower layer 21. "Upper layer 22 is disposed on lower layer 21" includes both embodiments where upper layer 22 is disposed directly on the main surface of lower layer 21 and embodiments where upper layer 22 is disposed in between other layers.

[0480] like Figure 10 and 11 As shown, the upper layer 22 extends along the exhaust gas flow direction E from the end of the partition wall portion 12 on the exhaust gas inflow side. In this embodiment, the upper layer 22 does not reach the end of the partition wall portion 12 on the exhaust gas outflow side, but it may reach the end of the partition wall portion 12 on the exhaust gas outflow side.

[0481] From the viewpoint of achieving a good balance between exhaust gas purification performance and cost, the mass of the upper layer 22 per unit volume of the portion of the substrate 10 where the upper layer 22 is formed (mass after calcination) is preferably 5 g / L or more and 60 g / L or less, more preferably 5 g / L or more and 40 g / L or less, and even more preferably 5 g / L or more and 30 g / L or less. The mass of the upper layer 22 per unit volume of the portion of the substrate 10 where the upper layer 22 is formed is calculated according to the following formula: (mass of upper layer 22) / (volume of substrate 10) × (average length L of upper layer 22) 22 / Length L of substrate 10 10 )).

[0482] The above description regarding the quality of the first catalyst layer 20 also applies to the upper layer 22. Where applicable, "first catalyst layer 20" should be replaced with "upper layer 22" for understanding.

[0483] Regarding the average length L of the first catalyst layer 20 20 The above description of the measurement method also applies to the average length L of the upper layer 22.22 The determination method. Where applicable, "first catalyst layer 20" can be understood as "upper layer 22", and "average length L" can be understood as... 20 Replace “average length L” with “average length L” 22 To understand this.

[0484] The average length L of the upper layer 22 22 The average length L of the upper layer 22 can be adjusted appropriately, taking into account factors such as exhaust gas purification performance and PM capture performance. From the perspective of improving exhaust gas purification performance and PM capture performance, 22 Relative to the length L of the substrate 10 10 percentage (L) 22 / L 10 The content of (×100) is preferably 15% or more and 90% or less, more preferably 20% or more and 90% or less, and even more preferably 30% or more and 85% or less.

[0485] From the perspective of improving exhaust gas purification performance and PM capture performance, the average length L of the second catalyst layer 30 is... 30 The average length L of the upper layer 22 22 The sum relative to the length L of the substrate 10 10 percentage ((L) 30 +L 22 ) / L 10 The content of (×100) is preferably 100% or more and 180% or less, more preferably 100% or more and 170% or less, and even more preferably 105% or more and 150% or less.

[0486] The upper layer 22 contains one or more platinum group elements. The above description of the platinum group elements and their metal conversions contained in the first catalyst layer 20 also applies to the platinum group elements and their metal conversions contained in the upper layer 22. Where applicable, "first catalyst layer 20" should be replaced with "upper layer 22" for understanding.

[0487] In one embodiment, the upper layer 22 comprises Rh. In addition to Rh, the upper layer 22 may also comprise one or more other platinum group elements. Embodiments where the upper layer 22 comprises Rh can be combined with embodiments where the second catalyst layer 30 comprises Rh and / or embodiments where the lower layer 21 comprises Pd.

[0488] The upper layer 22 preferably contains one or more supports, and at least a portion of the catalytically active ingredient is loaded on one or more supports. The significance and confirmation method of the loading are the same as described above.

[0489] The above description of the support contained in the first catalyst layer 20 also applies to the support contained in the upper layer 22. Where applicable, "first catalyst layer 20" can be replaced with "upper layer 22" for understanding.

[0490] The upper layer 22 may contain other components such as adhesives and stabilizers. The descriptions of adhesives and stabilizers are the same as above.

[0491] <Method for Manufacturing Catalysts for Waste Gas Purification>

[0492] The following describes an embodiment of the method for manufacturing catalyst 1C. Catalyst 1C manufactured by the method described in this embodiment also includes methods other than those described in (i) to (ix). The method described in this embodiment is suitable for manufacturing methods (i) to (ix).

[0493] The method involved in this embodiment includes the following steps:

[0494] (3a) A process of forming a second precursor layer by coating a second slurry containing a second pore-forming agent onto the outflow side of the partition wall portion 12 of the substrate 10.

[0495] (3b) A process of forming a fifth precursor layer by applying a fifth slurry containing a fifth pore-forming agent to the inflow side chamber of the partition wall portion 12 of the substrate.

[0496] (3c) The process of coating a sixth slurry containing a sixth pore-forming agent onto a fifth precursor layer to form a sixth precursor layer; and

[0497] (3d) A step of calcining the second precursor layer, the fifth precursor layer, and the sixth precursor layer to form the second catalyst layer 30, the lower layer 21 of the first catalyst layer 20, and the upper layer 22 of the first catalyst layer 20. Step (3a) can be performed before or after steps (3b) to (3c). Step (3b) is performed before step (3c). Step (3d) is performed after steps (3a) to (3c).

[0498] <Process 3a>

[0499] Step 3a is a step of forming a second precursor layer by applying a second slurry containing a second pore-forming agent to the outflow side of the partition wall portion 12 of the substrate 10.

[0500] Step 3a can be performed in the same manner as step 1b. The above description of step 1b also applies to step 3a.

[0501] <Process 3b>

[0502] Step 3b is a step of forming a fifth precursor layer by applying a fifth slurry containing a fifth pore-forming agent to the inflow side chamber of the partition wall portion 12 of the substrate.

[0503] The fifth slurry contains the fifth pore-forming agent. Specific examples of the fifth pore-forming material are the same as those of the first pore-forming material.

[0504] The composition of the fifth slurry can be adjusted according to the composition of the lower layer 21 of the first catalyst layer 20. In addition to the fifth pore-forming agent, the fifth slurry may also include, for example, a source of platinum group elements, inorganic oxide particles, a binder, and a solvent. Examples of platinum group element sources include, for example, salts of platinum group elements, such as nitrates, ammonium complexes, acetates, and chlorides. The inorganic oxides constituting the inorganic oxide particles are explained as described above. Examples of binders include, for example, alumina sol, zirconium oxide sol, titanium dioxide sol, silica sol, and cerium oxide sol. Examples of solvents include, for example, water and organic solvents. One solvent or a mixture of two or more solvents may be used.

[0505] A fifth precursor layer, serving as a precursor to the lower layer 21 of the first catalyst layer 20, is formed by applying the fifth slurry to the exhaust gas inflow side of the partition wall portion 12 of the substrate 10 (i.e., the outer surface S1a of the inflow side chamber 13a side of the partition wall portion 12) and drying it. The drying temperature is, for example, 40°C or higher and 150°C or lower, and the drying time is, for example, 5 minutes or higher and 1 hour or lower.

[0506] The particle size of the fifth pore-forming material can be adjusted appropriately. 50 Preferably, the particle size is 0.1 μm or larger and 20 μm or smaller, more preferably 0.5 μm or larger and 17 μm or smaller, and even more preferably 1.5 μm or larger and 15 μm or smaller. By adjusting the particle size and amount of the fifth pore-forming material, a lower layer 21 that does not satisfy either condition 1 or 2, a lower layer 21 that satisfies either condition 1 or 2, or a lower layer 21 that satisfies both conditions 1 and 2 can be formed. 50 The significance and measurement methods are the same as those described above.

[0507] <Process 3c>

[0508] Step 3c is the process of coating the sixth slurry containing the sixth pore-forming agent onto the fifth precursor layer to form the sixth precursor layer.

[0509] The sixth slurry contains the sixth pore-forming agent. Specific examples of the sixth pore-forming material are the same as those of the first pore-forming material.

[0510] The composition of the sixth slurry can be adjusted according to the composition of the upper layer 22 of the first catalyst layer 20. In addition to the sixth pore-forming agent, the sixth slurry may also include, for example, a source of platinum group elements, inorganic oxide particles, a binder, and a solvent. Examples of sources of platinum group elements include, for example, salts of platinum group elements, such as nitrates, ammonium complexes, acetates, and chlorides. The inorganic oxides constituting the inorganic oxide particles are explained as described above. Examples of binders include, for example, alumina sol, zirconium oxide sol, titanium dioxide sol, silica sol, and cerium oxide sol. Examples of solvents include, for example, water and organic solvents. One solvent or a mixture of two or more solvents may be used.

[0511] The sixth precursor layer is formed by coating the sixth slurry onto the fifth precursor layer and drying it. This sixth precursor layer serves as the precursor to the upper layer 22 of the first catalyst layer 20. The drying temperature is, for example, 40°C or higher and 150°C or lower, and the drying time is, for example, 5 minutes or higher and 1 hour or lower.

[0512] The particle size of the sixth pore-forming material can be adjusted appropriately. 50 Preferably, the particle size is 0.1 μm or more and 20 μm or less, more preferably 0.5 μm or more and 17 μm or less, and even more preferably 1.5 μm or more and 15 μm or less. By adjusting the particle size and amount of the sixth pore-forming material, an upper layer 22 that does not satisfy either condition 1 or 2, an upper layer 22 that satisfies either condition 1 or 2, or an upper layer 22 that satisfies both conditions 1 and 2 can be formed. By adjusting the particle size and amount of the fifth pore-forming material and / or the sixth pore-forming material, a first catalyst layer 20 that does not satisfy either condition 1 or 2, a first catalyst layer 20 that satisfies either condition 1 or 2, or a first catalyst layer 20 that satisfies both conditions 1 and 2 can be formed. 50 The significance and measurement methods are the same as those described above.

[0513] <Process 3d>

[0514] Step 3d is the process of calcining the second precursor layer, the fifth precursor layer and the sixth precursor layer to form the second catalyst layer 30, the lower layer 21 of the first catalyst layer 20 and the upper layer 22 of the first catalyst layer 20.

[0515] The second catalyst layer 30, the lower layer 21 of the first catalyst layer 20, and the upper layer 22 of the first catalyst layer 20 are formed by calcining the second precursor layer, the fifth precursor layer, and the sixth precursor layer, respectively. The calcination temperature is, for example, 350°C or higher and 600°C or lower, and the calcination time is, for example, 20 minutes or higher and 5 hours or lower. The atmosphere during calcination is usually atmospheric.

[0516] Calcination of the second precursor layer causes the second pore-forming agent to disappear, thereby forming pores in the second catalyst layer 30. Calcination of the fifth precursor layer causes the fifth pore-forming agent to disappear, thereby forming pores in the lower layer 21 of the first catalyst layer 20. Calcination of the sixth precursor layer causes the sixth pore-forming agent to disappear, thereby forming pores in the upper layer 22 of the first catalyst layer 20. By adjusting the particle size and amount of the second, fifth, and sixth pore-forming materials, the logarithmic differential pore volume distribution of the first catalyst layer 20 and the second catalyst layer 30 can be adjusted.

[0517] The method according to this embodiment preferably satisfies the following conditions (E1) to (E10). This ensures sufficient pore size that contributes to PM collection performance and reduces pressure loss, achieving a balance between improved PM collection performance and suppression of pressure loss increases. When the method according to this embodiment satisfies the following conditions (E1) to (E10), the method according to this embodiment is particularly suitable for manufacturing in the above-described methods (i) to (ix).

[0518] (E1) The median particle size D of one or both of the second, fifth, and sixth pore-forming agents. 50 For particles larger than 4 μm, the median particle size D of the remaining two or one is... 50 It is below 4μm.

[0519] (E2) The second slurry contains inorganic oxide particles, and the median particle size D of the inorganic oxide particles contained in the second slurry is... 50 It is between 1μm and 20μm.

[0520] (E3) Based on the mass of the second catalyst layer 30 (mass after calcination), the amount of the second pore-forming agent contained in the second precursor layer is more than 10% by mass and less than 60% by mass.

[0521] (E4) The mass of the second catalyst layer 30 per unit volume of the portion of the substrate 10 in which the second catalyst layer 30 is formed (mass after calcination) is 5 g / L or more and 150 g / L or less.

[0522] (E5) The fifth slurry contains inorganic oxide particles, and the median particle size D of the inorganic oxide particles contained in the fifth slurry is... 50 It is between 1μm and 20μm.

[0523] (E6) Based on the mass of the lower layer 21 (mass after calcination), the amount of the fifth pore-forming agent contained in the fifth precursor layer is 10% by mass or more and 60% by mass or less.

[0524] (E7) The mass of the lower layer 21 per unit volume of the portion in the substrate 10 where the lower layer 21 is formed (mass after calcination) is 5 g / L or more and 90 g / L or less.

[0525] (E8) The 6th slurry contains inorganic oxide particles, and the median particle size D of the inorganic oxide particles contained in the 6th slurry is... 50 It is between 1μm and 20μm.

[0526] (E9) Based on the mass of the upper layer 22 (mass after calcination), the amount of the sixth pore-forming agent contained in the sixth precursor layer is 10% by mass or more and 60% by mass or less.

[0527] (E10) The mass of the upper layer 22 per unit volume of the portion in the substrate 10 where the upper layer 22 is formed (mass after calcination) is 5 g / L or more and 60 g / L or less.

[0528] The above description of condition (D1) also applies to condition (E1). Where applicable, "first pore-forming agent", "third pore-forming agent" and "fourth pore-forming agent" should be understood as "second pore-forming agent", "fifth pore-forming agent" and "sixth pore-forming agent", respectively.

[0529] The above explanation regarding condition (D2) also applies to condition (E2). Where applicable, replace "first slurry" with "second slurry" for understanding.

[0530] The above description regarding condition (D3) also applies to condition (E3). Where applicable, "first precursor layer", "first pore-forming agent", "first catalyst layer 20", "first slurry" and "inflow side chamber of partition wall 12" can be understood as "second precursor layer", "second pore-forming agent", "second catalyst layer 30", "second slurry" and "outflow side chamber of partition wall 12", respectively.

[0531] The above description regarding condition (D4) also applies to condition (E4). Where applicable, "first catalyst layer 20", "first slurry" and "inflow side chamber of partition wall 12" can be understood as "second catalyst layer 30", "second slurry" and "outflow side chamber of partition wall 12", respectively.

[0532] The above explanation regarding condition (D5) also applies to condition (E5). Where applicable, replace "third slurry" with "fifth slurry" for understanding.

[0533] The above description regarding condition (D6) also applies to condition (E6). Where applicable, "third precursor layer", "third pore-forming agent", "lower layer 31", "third slurry" and "outflow side chamber of partition wall 12" should be replaced with "fifth precursor layer", "fifth pore-forming agent", "lower layer 21", "fifth slurry" and "inflow side chamber of partition wall 12" respectively.

[0534] The above description of condition (D7) also applies to condition (E7). When applicable, "lower layer 31", "third slurry" and "outflow side chamber of partition wall 12" can be understood as "lower layer 21", "fifth slurry" and "inflow side chamber of partition wall 12" respectively.

[0535] The above explanation regarding condition (D8) also applies to condition (E8). Where applicable, replace "4th slurry" with "6th slurry" for understanding.

[0536] The above description of condition (D9) also applies to condition (E9). Where applicable, "3rd precursor layer", "4th precursor layer", "4th pore-forming agent", "upper layer 32" and "4th slurry" should be understood as "5th precursor layer", "6th precursor layer", "6th pore-forming agent", "upper layer 22" and "6th slurry" respectively.

[0537] The above description of condition (D10) also applies to condition (E10). Where applicable, replace “3rd precursor layer”, “upper layer 32” and “4th slurry” with “5th precursor layer”, “upper layer 22” and “6th slurry” respectively.

[0538] When the median particle size D of the fifth pore-forming agent 50 The median particle size D of the 6th pore-forming agent is greater than that of the 6th pore-forming agent. 50 When the fifth slurry becomes difficult to enter the pores in the partition wall portion 12, it is easier to achieve an embodiment in which at least a portion of the lower layer 21 protrudes from the outer surface S1a of the partition wall portion 12 toward the inflow side chamber 13a (i.e., an embodiment in which the lower layer 21 has a portion protruding from the outer surface S1a of the partition wall portion 12 toward the inflow side chamber 13a). Therefore, when using the median particle size D 50 Pore-forming agents larger than 4 μm and median particle size D 50 When the pore-forming agent is less than 4 μm, it is preferable to use a median particle size D. 50 Pore-forming agents larger than 4 μm were used as the fifth pore-forming agent, with a median particle size D. 50 A pore-forming agent with a diameter of less than 4 μm is used as the sixth pore-forming agent.

[0539] When the median particle size D of the fifth pore-forming agent 50 The median particle size D of the sixth pore-forming agent is greater than 4 μm. 50 When the particle size is below 4 μm, sufficient pore size can be ensured in the first catalyst layer 20 to contribute to PM trapping performance and / or to reduce pressure drop. Additionally, when the median particle size D of the fifth pore-forming agent... 50 The median particle size D of the sixth pore-forming agent is greater than 4 μm. 50When the size is below 4 μm, the first catalyst layer 20 that satisfies either condition 1 or 2, or satisfies both conditions 1 and 2, can be formed more efficiently, especially the first catalyst layer 20 that satisfies both conditions 1 and 2.

[0540] D of the fifth pore-forming agent 50 There is no particular limitation as long as it is greater than 4μm. From the viewpoint of more effectively achieving both the improvement of PM capture performance and the suppression of pressure drop, it is preferred to be 4.5μm or more and 20μm or less, more preferably 4.5μm or more and 17μm or less, and even more preferably 4.5μm or more and 15μm or less.

[0541] D of the 6th pore-forming agent 50 There are no particular limitations as long as it is 4μm or less. From the viewpoint of more effectively achieving both improved PM capture performance and suppression of pressure drop, it is preferred to be 0.1μm or more and 4μm or less, more preferably 0.5μm or more and 4μm or less, and even more preferably 1.5μm or more and 4μm or less.

[0542] Example

[0543] The present invention will be specifically described below based on embodiments, but the present invention is not limited to the embodiments.

[0544] <Example 1>

[0545] (1) Preparation of the first slurry

[0546] Ce-Zr composite oxide powder and alumina powder were prepared. CeO2-ZrO2 solid solution powder was used as the Ce-Zr composite oxide powder.

[0547] A mixed powder was prepared by mixing CeO2-ZrO2 solid solution powder and alumina powder. The D of the mixed powder... 50 It is 7μm.

[0548] The mixed powder was added to an aqueous solution of rhodium nitrate to obtain a mixture. The resulting mixture was then combined with a pore-forming agent (median particle size D). 50 A first slurry was prepared by mixing 3 μm cross-linked poly(methyl methacrylate) particles, alumina sol, zirconium oxide sol, and water as a solvent. The amounts of Rh and pore-forming agent in the first slurry were adjusted to 0.3% and 30% by mass, respectively, based on the mass of the first catalyst layer formed by drying and calcining the first slurry (100% by mass). It should be noted that the mass of the first catalyst layer formed by drying and calcining the first slurry was calculated by subtracting the mass of components (e.g., solvent, pore-forming agent, etc.) that disappeared due to drying and calcining the first slurry from the mass of the first slurry.

[0549] (2) Preparation of the third slurry

[0550] Ce-Zr composite oxide powder and alumina powder were prepared. CeO2-ZrO2 solid solution powder was used as the Ce-Zr composite oxide powder.

[0551] A mixed powder was prepared by mixing CeO2-ZrO2 solid solution powder and alumina powder. The D of the mixed powder... 50 It is 7μm.

[0552] The mixed powder was added to an aqueous solution of palladium nitrate to obtain a mixed solution. The obtained mixed solution, a pore-forming agent (median particle size D) was then added... 50 A third slurry was prepared by mixing 5 μm cross-linked poly(methyl methacrylate) particles, barium hydroxide, alumina sol, zirconium oxide sol, and water as a solvent. The amounts of Pd and pore-forming agent in the third slurry were adjusted to 3% and 30% by mass, respectively, based on the mass of the lower layer of the second catalyst layer formed by drying and calcining the third slurry (100% by mass). It should be noted that the mass of the lower layer of the second catalyst layer formed by drying and calcining the third slurry was determined by subtracting the mass of components (e.g., solvent, pore-forming agent, etc.) that disappeared due to the drying and calcining of the third slurry from the mass of the third slurry.

[0553] (3) Preparation of the fourth slurry

[0554] As the fourth slurry, the same slurry as the first slurry was prepared. The amounts of Rh and pore-forming agent in the fourth slurry were adjusted to 0.3% and 30% by mass, respectively, based on the mass of the upper layer of the second catalyst layer formed by drying and calcining the fourth slurry (100% by mass). It should be noted that the mass of the upper layer of the second catalyst layer formed by drying and calcining the fourth slurry was determined by subtracting the mass of components (e.g., solvent, pore-forming agent, etc.) that disappeared due to the drying and calcining of the fourth slurry from the mass of the fourth slurry.

[0555] (4) Manufacturing of catalysts for waste gas purification

[0556] Prepared with Figures 1-6The substrate with the structure shown is as follows: it has an inflow-side chamber extending axially along the substrate, an outflow-side chamber extending axially along the substrate, and a porous partition wall separating the inflow-side chamber and the outflow-side chamber. The thickness of the partition wall is 216 μm, and the total number of inflow-side chambers and outflow-side chambers in a cross-section perpendicular to the substrate axial direction is 300 chambers per square inch, with a substrate volume of 1.4 L. The area of ​​the opening of the inflow-side chamber in the inflow-side end face of the substrate is approximately the same as the area of ​​the opening of the outflow-side chamber in the outflow-side end face of the substrate.

[0557] The end of the substrate on the exhaust gas inflow side is immersed in the first slurry. After the first slurry is drawn from the opposite side, it is dried at 70°C for 10 minutes. In this way, a first precursor layer composed of the solid components of the first slurry is formed on the inflow chamber side of the partition wall of the substrate. The formed first precursor layer extends from the end of the substrate on the exhaust gas inflow side along the exhaust gas flow direction.

[0558] After drying, the end of the substrate on the exhaust gas outlet side is immersed in the third slurry. The third slurry is then drawn from the opposite side and dried at 70°C for 10 minutes. This forms a third precursor layer composed of the solid components of the third slurry on the outlet side of the partition wall portion of the substrate. The formed third precursor layer extends from the end of the substrate on the exhaust gas outlet side in a direction opposite to the exhaust gas flow direction. After drying, the end of the substrate on the exhaust gas outlet side is immersed in the fourth slurry. The fourth slurry is then drawn from the opposite side and dried at 70°C for 10 minutes. This forms a fourth precursor layer composed of the solid components of the fourth slurry on the third precursor layer on the outlet side of the partition wall portion of the substrate. The formed fourth precursor layer extends from the end of the substrate on the exhaust gas outlet side in a direction opposite to the exhaust gas flow direction.

[0559] Then, the substrate was calcined at 450°C for 1 hour, forming a first catalyst layer and a second catalyst layer on the substrate. Thus, the catalyst for exhaust gas purification of Example 1 was obtained. The first catalyst layer has a single-layer structure, and the second catalyst layer has a two-layer structure consisting of a lower layer and an upper layer. The mass of the first catalyst layer per unit volume (wash coat) in the portion of the substrate where the first catalyst layer is formed is 69.4 g / L. The mass of the lower layer per unit volume (coating amount) in the portion of the substrate where the lower layer of the second catalyst layer is formed is 41.1 g / L. The mass of the upper layer per unit volume (coating amount) in the portion of the substrate where the upper layer of the second catalyst layer is formed is 21.4 g / L.

[0560] <Example 2>

[0561] The pore-forming agent in the first slurry is from D 50 The 3μm cross-linked poly(meth)acrylate particles were changed to D 50The cross-linked poly(meth)acrylate particles were 5 μm in size, and the same slurry as the first slurry in Example 1 was used as the fourth slurry (i.e., containing a median particle size D as the pore-forming agent). 50 The catalyst for exhaust gas purification of Example 2 was obtained in the same manner as in Example 1, except that the cross-linked poly(methyl methacrylate) particles were 3 μm in size.

[0562] <Example 3>

[0563] The pore-forming agent in the first slurry is from D 50 The 3μm cross-linked poly(meth)acrylate particles were changed to D 50 The cross-linked poly(meth)acrylate particles are 2 μm in size, and the pore-forming agent in the fourth slurry is changed from D... 50 The 3μm cross-linked poly(meth)acrylate particles were changed to D 50 The catalyst for exhaust gas purification of Example 3 was obtained in the same manner as in Example 1, except that it consisted of 2 μm cross-linked poly(methyl methacrylate) particles.

[0564] <Example 4>

[0565] In addition to replacing the pore-forming agent in the third slurry with D 50 The 5μm cross-linked poly(meth)acrylate particles were changed to D 50 The catalyst for exhaust gas purification of Example 4 was obtained in the same manner as in Example 1, except for cross-linked poly(meth)acrylate particles of 10 μm.

[0566] <Example 5>

[0567] (1) Preparation of the 5th slurry

[0568] Ce-Zr composite oxide powder and alumina powder were prepared. CeO2-ZrO2 solid solution powder was used as the Ce-Zr composite oxide powder.

[0569] A mixed powder was prepared by mixing CeO2-ZrO2 solid solution powder and alumina powder. The D of the mixed powder... 50 It is 6μm.

[0570] The mixed powder was added to an aqueous solution of palladium nitrate to obtain a mixed solution. The obtained mixed solution, a pore-forming agent (median particle size D) was then added... 50A fifth slurry was prepared by mixing 5 μm cross-linked poly(methyl methacrylate) particles, alumina sol, zirconium oxide sol, and water as a solvent. The amounts of Pd and pore-forming agent in the fifth slurry were adjusted to 3% and 40% by mass, respectively, based on the mass of the lower layer of the first catalyst layer formed by drying and calcining the fifth slurry (100% by mass). It should be noted that the mass of the lower layer of the first catalyst layer formed by drying and calcining the fifth slurry was determined by subtracting the mass of components (e.g., solvent, pore-forming agent, etc.) that disappeared due to the drying and calcining of the fifth slurry from the mass of the fifth slurry.

[0571] (2) Preparation of the 6th slurry

[0572] Ce-Zr composite oxide powder and alumina powder were prepared. CeO2-ZrO2 solid solution powder was used as the Ce-Zr composite oxide powder.

[0573] A mixed powder was prepared by mixing CeO2-ZrO2 solid solution powder and alumina powder. The D of the mixed powder... 50 It is 6μm.

[0574] The mixed powder was added to an aqueous solution of rhodium nitrate to obtain a mixture. The resulting mixture was then combined with a pore-forming agent (median particle size D). 50 A sixth slurry was prepared by mixing 3 μm cross-linked poly(methyl methacrylate) particles, alumina sol, zirconium oxide sol, and water as a solvent. The amounts of Rh and pore-forming agent in the sixth slurry were adjusted to 0.3% and 40% by mass, respectively, based on the mass of the upper layer of the first catalyst layer formed by drying and calcining the sixth slurry (100% by mass). It should be noted that the mass of the upper layer of the first catalyst layer formed by drying and calcining the sixth slurry was calculated by subtracting the mass of components (e.g., solvent, pore-forming agent, etc.) that disappeared due to the drying and calcining of the sixth slurry from the mass of the sixth slurry.

[0575] (3) Preparation of the second slurry

[0576] As the second slurry, the same slurry as the sixth slurry was prepared, except for the amount of pore-forming agent described later. The amounts of Rh and pore-forming agent in the second slurry were adjusted to 0.3% and 30% by mass, respectively, based on the mass of the second catalyst layer formed by drying and calcining the second slurry (100% by mass). It should be noted that the mass of the second catalyst layer formed by drying and calcining the second slurry was calculated by subtracting the mass of components (e.g., solvent, pore-forming agent, etc.) that disappeared due to the drying and calcining of the second slurry from the mass of the second slurry.

[0577] (4) Manufacturing of catalysts for waste gas purification

[0578] The same substrate as in Example 1 was prepared.

[0579] The end of the substrate on the exhaust gas inflow side is immersed in the fifth slurry. After the fifth slurry is drawn from the opposite side, it is dried at 70°C for 10 minutes. This forms a fifth precursor layer composed of the solid components of the fifth slurry on the inflow chamber side of the partition wall portion of the substrate. The formed fifth precursor layer extends from the end of the substrate on the exhaust gas inflow side along the exhaust gas flow direction. After drying, the end of the substrate on the exhaust gas inflow side is immersed in the sixth slurry. After the sixth slurry is drawn from the opposite side, it is dried at 70°C for 10 minutes. This forms a sixth precursor layer composed of the solid components of the sixth slurry on the fifth precursor layer on the inflow chamber side of the partition wall portion of the substrate. The formed sixth precursor layer extends from the end of the substrate on the exhaust gas inflow side along the exhaust gas flow direction.

[0580] After drying, the end of the substrate on the exhaust gas outlet side is immersed in the second slurry. After the second slurry is drawn from the opposite side, it is dried at 70°C for 10 minutes. Thus, a second precursor layer composed of the solid components of the second slurry is formed on the exhaust gas outlet side of the substrate partition wall. The formed second precursor layer extends from the exhaust gas outlet end of the substrate in a direction opposite to the exhaust gas flow direction.

[0581] Then, the substrate was calcined at 450°C for 1 hour, forming a first catalyst layer and a second catalyst layer on the substrate. Thus, the catalyst for exhaust gas purification of Example 5 was obtained. The first catalyst layer has a two-layer structure consisting of a lower layer and an upper layer, and the second catalyst layer has a single-layer structure. The mass (coating amount) of the lower layer per unit volume of the portion of the substrate in which the first catalyst layer is formed is 27.1 g / L. The mass (coating amount) of the upper layer per unit volume of the portion of the substrate in which the first catalyst layer is formed is 12.3 g / L. The mass (coating amount) of the first catalyst layer per unit volume of the portion of the substrate in which the second catalyst layer is formed is 34.7 g / L.

[0582] <Comparative Example 1>

[0583] In addition to replacing the pore-forming agent in the third slurry with D 50 The 5μm cross-linked poly(meth)acrylate particles were changed to D 50 The catalyst for exhaust gas purification of Comparative Example 1 was obtained in the same manner as in Example 1, except for cross-linked poly(meth)acrylate particles of 3 μm.

[0584] <Comparative Example 2>

[0585] The pore-forming agent in the first slurry is from D 50The 3μm cross-linked poly(meth)acrylate particles were changed to D 50 The cross-linked poly(meth)acrylate particles are 5 μm in size, and the pore-forming agent in the fourth slurry is changed from D... 50 The 3μm cross-linked poly(meth)acrylate particles were changed to D 50 The cross-linked poly(meth)acrylate particles were 5 μm in size. Otherwise, the catalyst for exhaust gas purification of Comparative Example 2 was obtained in the same manner as in Example 1.

[0586] <Determination of pore volume>

[0587] The catalysts of the examples and comparative examples were cut using planes parallel to the axial direction of the substrate and planes perpendicular to the axial direction of the substrate, respectively, to cut out... Figure 9 Or, as indicated by symbol M1 in section 11, a slice M1 is obtained that includes a portion of the partition wall and a portion of the first catalyst layer, but does not include the second catalyst layer. Slices M1 do not include either the first or second sealing portion. The length of the portion of the partition wall included in slice M1 is equal to the length of slice M1. The length of the portion of the first catalyst layer included in slice M1 is equal to the length of slice M1. Slices M1 are obtained near the exhaust gas inflow side end of the catalyst. Specifically, slice M1 is obtained by cutting along the exhaust gas flow direction E at two points 10 mm and 20 mm away from the exhaust gas inflow side end of the substrate with a plane perpendicular to the axial direction of the substrate. Slice M1 is a cubic shape with a side length of 10 mm.

[0588] The catalysts of the examples and comparative examples were cut using planes parallel to the axial direction of the substrate and planes perpendicular to the axial direction of the substrate, respectively, to cut out... Figure 9 Or, as indicated by symbol M2 in section 11, a slice M2 is obtained that includes a portion of the partition wall and a portion of the second catalyst layer (lower and upper layers), but does not include the first catalyst layer. Slices M2 do not include either the first or second sealing portion. The length of the portion of the partition wall included in slice M2 is equal to the length of slice M2. The length of the portion of the second catalyst layer (lower and upper layers) included in slice M2 is equal to the length of slice M2. Slices M2 are obtained near the exhaust gas outlet end of the catalyst. Specifically, slice M2 is obtained by cutting at two points, 10 mm and 20 mm away from the exhaust gas outlet end of the substrate, respectively, in a direction opposite to the exhaust gas flow direction E, using a plane perpendicular to the axial direction of the substrate. Slice M2 is a cubic shape with a side length of 10 mm.

[0589] Using slice M1, the log differential pore volume distribution of the first catalyst layer was determined by mercury porosimetry, and the log differential pore volume distribution curve of the first catalyst layer was obtained. Using slice M2, the log differential pore volume distribution of the second catalyst layer was determined by mercury porosimetry, and the log differential pore volume distribution curve of the second catalyst layer was obtained. The specific measurement conditions are as follows.

[0590] [Determination of log differential pore volume distribution]

[0591] As the measuring device, the log differential pore volume distribution was measured using the Shimadzu Corporation Autopore IV9520 automatic porosity meter under the following conditions and procedures.

[0592] (Measurement conditions)

[0593] Measurement environment: 25℃

[0594] Measurement chamber: Sample chamber volume 3 cm³ 3 The pressed volume is 0.39 cm³. 3

[0595] Measurement range: 0.0048 MPa to 255.106 MPa

[0596] Measurement points: 54 points within the range of 0.0048 MPa to 0.3447 MPa.

[0597] 77 points within the range of 0.3447 MPa to 255.1060 MPa

[0598] A total of 131 points (logarithmically plotted for each pressure level, with points placed at equal intervals).

[0599] The compressed volume was adjusted to be between 25% and 90%.

[0600] (Low-pressure parameters)

[0601] Exhaust pressure: 50 μmHg

[0602] Exhaust time: 5.0 min

[0603] Mercury injection pressure: 0.0034 MPa

[0604] Equilibrium time: 10 seconds

[0605] (High-voltage parameters)

[0606] Equilibrium time: 10 seconds

[0607] (Mercury parameters)

[0608] Forward contact angle: 130.0 degrees

[0609] Retreating contact angle: 130.0 degrees

[0610] Surface tension: 485.0 mN / m (485.0 dyne / cm)

[0611] Mercury density: 13.5335 g / mL

[0612] (Measurement Procedure)

[0613] (1) 54 points were measured in the low-pressure section within the range of 0.0048MPa to below 0.3447MPa.

[0614] (2) 77 points were measured in the high-pressure section within the range of 0.3792MPa to below 255.1060MPa.

[0615] (3) Based on the mercury injection pressure, mercury injection amount and the mass of slices M1 and M2, the logarithmic differential pore volume distribution curve (log differential pore volume distribution curve) is obtained.

[0616] It should be noted that steps (1), (2), and (3) above are performed automatically using the software provided with the device. Other conditions are in accordance with JISR 1655:2003.

[0617] The logarithmic differential pore volume distribution curves of the first catalyst layer and the second catalyst layer in the catalyst for exhaust gas purification in Example 2 are shown below. Figure 12A and Figure 12B .

[0618] The logarithmic differential pore volume distribution curves of the first catalyst layer and the second catalyst layer in the catalyst for exhaust gas purification of Comparative Example 1 are shown below. Figure 13A and Figure 13B .

[0619] The logarithmic differential pore volume distribution curves of the first and second catalyst layers in the catalyst for exhaust gas purification in Comparative Example 2 are shown below. Figure 14A and Figure 14B .

[0620] It was confirmed that: in the logarithmic differential pore volume distribution curve of the first catalyst layer, there exists a peak A (if present, the specific value of peak A) in the range of pore size greater than 1 μm and less than 3 μm; in the logarithmic differential pore volume distribution curve of the first catalyst layer, there exists a peak B (if present, the specific value of peak B) in the range of pore size greater than 3 μm and less than 10 μm; in the logarithmic differential pore volume distribution curve of the second catalyst layer, there exists a peak C (if present, the specific value of peak C); and in the logarithmic differential pore volume distribution curve of the second catalyst layer, there exists a peak D (if present, the specific value of peak D) in the range of pore size greater than 3 μm and less than 10 μm. The results are shown in Tables 2 and 3. In Tables 2 and 3, for the presence or absence of peak A, "absence" indicates that peak A does not exist, "maximum" indicates that peak A exists as a maximum (logarithmic differential porosity at the apex) in the logarithmic differential porosity distribution curve, and "shoulder peak" indicates that peak A exists as a shoulder peak in the logarithmic differential porosity distribution curve. The same applies to peaks B, C, and D.

[0621] <Evaluation of Pressure Loss>

[0622] The catalyst for exhaust gas purification in Example 1 is fixed with its side supported and the exhaust gas inflow end face facing upwards. Air is drawn from below the fixed catalyst (exhaust gas outflow end face) at a rate of 50 L / sec. The difference between the air pressure at the exhaust gas inflow end face and the air pressure at the exhaust gas outflow end face 10 seconds after the start of drawing air is calculated and used as the pressure drop of the catalyst for exhaust gas purification in Example 1.

[0623] Using a substrate (without forming the first catalyst layer and the second catalyst layer) instead of the catalyst for exhaust gas purification in Example 1, the difference between the gas pressure at the exhaust gas inflow side end face and the gas pressure at the exhaust gas inflow side end face was calculated in the same manner as described above, and this difference was taken as the pressure loss of the substrate.

[0624] The pressure loss ratio (%) is calculated based on the following formula.

[0625] Pressure drop ratio = (Pressure drop of catalyst for exhaust gas purification in Example 1 / Pressure drop of substrate) × 100

[0626] Cases with a pressure loss ratio less than 270% are rated as "A", cases with a pressure loss ratio greater than 270% but less than 300% are rated as "B", and cases with a pressure loss ratio greater than 300% are rated as "C". The results are shown in Table 2.

[0627] <Evaluation of PM Capture Performance>

[0628] A gasoline engine vehicle using the exhaust gas purification catalyst of Example 1 was operated under the operating conditions of the World Harmonized Exhaust Gas Test Mode (WLTC). The number of PM particles (PNcat) in the exhaust gas passing through the exhaust gas purification catalyst was measured during low-speed operation from start to 589 seconds, medium-speed operation from 589 seconds to 1022 seconds, high-speed operation from 1022 seconds to 1477 seconds, and ultra-high-speed operation from 1477 seconds to 1800 seconds. Furthermore, the number of PM particles (PNall) directly emitted from the engine was measured, and the PM capture rate of the exhaust gas purification catalyst of Example 1 was calculated using the following formula.

[0629] PM capture rate = (1 - (PNcat / PNall)) × 100

[0630] The conditions for measuring PM capture performance are as follows.

[0631] Vehicle being evaluated: 1.5L direct-injection turbocharged engine

[0632] Gasoline used: fuel for certification testing

[0633] PM measuring device: manufactured by Horiba Manufacturing Co., Ltd.

[0634] A PM capture rate of 98.7% or higher is rated as "A", a PM capture rate of 98.0% or higher but less than 98.7% is rated as "B", and a PM capture rate of less than 98.0% is rated as "C". The results are shown in Table 2.

[0635] [Table 2]

[0636]

[0637] [Table 3]

[0638]

[0639] Explanation of reference numerals in the attached figures

[0640] 1A, 1B, 1C… Catalysts for exhaust gas purification

[0641] 10…substrate

[0642] 11...cylindrical part

[0643] 12…Separation wall section

[0644] Room 13…

[0645] 13a…flow into the side chamber

[0646] 13b…flow from the side chamber

[0647] 14…First Enclosed Section

[0648] 15…Second Closed Section

[0649] 20…First catalyst layer

[0650] 21…lower layer of the first catalyst layer

[0651] 22… Upper layer of the first catalyst layer

[0652] 30…Second catalyst layer

[0653] 31… Lower layer of the second catalyst layer

[0654] 32… Upper layer of the second catalyst layer

[0655] S1a…Outer surface of the inflow-side chamber of the partition wall

[0656] S1b…Outer surface of the outflow chamber side of the partition wall

Claims

1. A catalyst for purifying waste gas, comprising a substrate extending along the waste gas flow direction, a first catalyst layer, and a second catalyst layer. The substrate comprises: The inflow side chamber extends along the direction of the exhaust gas flow, with the exhaust gas inflow side of the inflow side chamber open and the exhaust gas outflow side closed. An outlet side chamber extending along the exhaust gas flow direction, wherein the exhaust gas inflow end of the outlet side chamber is closed, and the exhaust gas outflow end is open; and A porous partition wall separates the inflow side chamber and the outflow side chamber. The first catalyst layer is disposed on the inflow side chamber side of the partition wall portion, starting from the end of the waste gas inflow side of the partition wall portion along the waste gas flow direction. The second catalyst layer is disposed on the outflow side chamber side of the partition wall portion, starting from the end of the waste gas outflow side of the partition wall portion, in a direction opposite to the waste gas flow direction. Condition 1 is set as follows: in the logarithmic differential pore volume distribution curve of the first catalyst layer obtained by mercury intrusion porosimetry, there is a peak A in the range of pore size greater than 1 μm and less than 3 μm, and the peak A is greater than 0.20 mL / g. Condition 2 is set as follows: in the logarithmic differential pore volume distribution curve of the first catalyst layer obtained by mercury intrusion porosimetry, there is a peak B in the range of pore size greater than 3 μm and less than 10 μm, and the peak B is greater than 0.20 mL / g. Condition 3 is set as follows: in the logarithmic differential pore volume distribution curve of the second catalyst layer obtained by mercury intrusion porosimetry, there is a peak C in the range of pore size greater than 1 μm and less than 3 μm, and the peak C is greater than 0.20 mL / g. Condition 4 is set as follows: in the logarithmic differential pore volume distribution curve of the second catalyst layer obtained by mercury intrusion porosimetry, a peak D exists in the range of pore size greater than 3 μm and less than 10 μm, and the peak D is greater than 0.20 mL / g. The second catalyst layer satisfies condition 3 but not condition 4, or satisfies condition 4 but not condition 3, or satisfies both conditions 3 and 4, or neither condition 3 nor 4 is satisfied. If the second catalyst layer satisfies condition 3 but not condition 4, then the first catalyst layer must satisfy at least condition 2 in both conditions 1 and 2. If the second catalyst layer satisfies condition 4 but not condition 3, then the first catalyst layer must satisfy at least condition 1 in both conditions 1 and 2. If the second catalyst layer satisfies conditions 3 and 4, and the first catalyst layer satisfies at least one of conditions 1 and 2, or neither condition 1 nor 2 is satisfied, If conditions 3 and 4 of the second catalyst layer are not satisfied, then conditions 1 and 2 of the first catalyst layer are satisfied.

2. The catalyst for purifying waste gas according to claim 1, wherein, In condition 1, peak value A is below 1.00 mL / g; in condition 3, peak value C is below 1.00 mL / g.

3. The catalyst for purifying waste gas according to claim 1, wherein, In condition 2, peak value B is below 1.00 mL / g; in condition 4, peak value D is below 1.00 mL / g.

4. The catalyst for purifying waste gas according to claim 1, wherein, In condition 1, peak value A is above 0.31 mL / g; in condition 3, peak value C is above 0.31 mL / g.

5. A method for manufacturing a catalyst for waste gas purification according to claim 1, wherein the catalyst for waste gas purification comprises a substrate extending in the waste gas flow direction, a first catalyst layer, and a second catalyst layer. The substrate comprises: The inflow side chamber extends along the direction of the exhaust gas flow, with the exhaust gas inflow side of the inflow side chamber open and the exhaust gas outflow side closed. An outlet side chamber extending along the exhaust gas flow direction, wherein the exhaust gas inflow end of the outlet side chamber is closed, and the exhaust gas outflow end is open; and A porous partition wall separates the inflow side chamber and the outflow side chamber. The first catalyst layer is disposed on the inflow side chamber side of the partition wall portion, starting from the end of the waste gas inflow side of the partition wall portion along the waste gas flow direction. The second catalyst layer is disposed on the outflow side chamber side of the partition wall portion, starting from the end of the waste gas outflow side of the partition wall portion, in a direction opposite to the waste gas flow direction. The method includes the following steps: (1a) A process of forming a first precursor layer by coating a first slurry containing a first pore-forming agent onto the inflow side chamber side of the partition wall portion; (1b) The process of applying a second slurry containing a second pore-forming agent to the outflow side chamber of the partition wall to form a second precursor layer; and (1c) The step of calcining the first precursor layer and the second precursor layer to form the first catalyst layer and the second catalyst layer. The median particle size D of one of the first pore-forming agent and the second pore-forming agent 50 The median particle size D of the other is greater than 4 μm. 50 Below 4μm The first slurry contains inorganic oxide particles, and the median particle size D of the inorganic oxide particles contained in the first slurry is... 50 The size is greater than 1μm and less than 20μm. Based on the mass of the first catalyst layer, the amount of the first pore-forming agent contained in the first precursor layer is 10% by mass or more and 60% by mass or less. The mass of the first catalyst layer per unit volume of the portion of the substrate in which the first catalyst layer is formed is 5 g / L or more and 150 g / L or less. The second slurry contains inorganic oxide particles, and the median particle size D of the inorganic oxide particles contained in the second slurry is... 50 The size is greater than 1μm and less than 20μm. Based on the mass of the second catalyst layer, the amount of the second pore-forming agent contained in the second precursor layer is 10% by mass or more and 60% by mass or less. The mass of the second catalyst layer per unit volume of the portion of the substrate in which the second catalyst layer is formed is 5 g / L or more and 150 g / L or less.

6. A method for manufacturing a catalyst for waste gas purification according to claim 1, wherein the catalyst for waste gas purification comprises a substrate extending in the waste gas flow direction, a first catalyst layer, and a second catalyst layer. The substrate comprises: The inflow side chamber extends along the direction of the exhaust gas flow, with the exhaust gas inflow side of the inflow side chamber open and the exhaust gas outflow side closed. An outlet side chamber extending along the exhaust gas flow direction, wherein the exhaust gas inflow end of the outlet side chamber is closed, and the exhaust gas outflow end is open; and A porous partition wall separates the inflow side chamber and the outflow side chamber. The first catalyst layer is disposed on the inflow side chamber side of the partition wall portion, starting from the end of the waste gas inflow side of the partition wall portion along the waste gas flow direction. The second catalyst layer is disposed on the outflow side chamber side of the partition wall portion, starting from the end of the waste gas outflow side of the partition wall portion, in a direction opposite to the waste gas flow direction. The second catalyst layer includes a lower layer disposed on the outflow side chamber side of the partition wall portion, and an upper layer disposed on the lower layer. The method includes the following steps: (2a) A process of forming a first precursor layer by coating a first slurry containing a first pore-forming agent onto the inflow side chamber side of the partition wall portion; (2b) The process of forming a third precursor layer by coating a third slurry containing a third pore-forming agent onto the outflow side chamber side of the partition wall portion; (2c) The step of coating a fourth slurry containing a fourth pore-forming agent onto the third precursor layer to form a fourth precursor layer; and (2d) The process of calcining the first precursor layer, the third precursor layer, and the fourth precursor layer to form the first catalyst layer, the lower layer, and the upper layer. The median particle size D of one or both of the first pore-forming agent, the third pore-forming agent, and the fourth pore-forming agent. 50 For particles larger than 4 μm, the median particle size D of the remaining two or one is... 50 Below 4μm The first slurry contains inorganic oxide particles, and the median particle size D of the inorganic oxide particles contained in the first slurry is... 50 The size is greater than 1μm and less than 20μm. Based on the mass of the first catalyst layer, the amount of the first pore-forming agent contained in the first precursor layer is 10% by mass or more and 60% by mass or less. The mass of the first catalyst layer per unit volume of the portion of the substrate in which the first catalyst layer is formed is 5 g / L or more and 150 g / L or less. The third slurry contains inorganic oxide particles, and the median particle size D of the inorganic oxide particles contained in the third slurry is... 50 The size is greater than 1μm and less than 20μm. Based on the mass of the lower layer, the amount of the third pore-forming agent contained in the third precursor layer is 10% by mass or more and 60% by mass or less. The mass of the lower layer per unit volume of the portion of the substrate in which the lower layer is formed is 5 g / L or more and 90 g / L or less. The fourth slurry contains inorganic oxide particles, and the median particle size D of the inorganic oxide particles contained in the fourth slurry is... 50 The size is greater than 1μm and less than 20μm. Based on the mass of the upper layer, the amount of the fourth pore-forming agent contained in the fourth precursor layer is 10% by mass or more and 60% by mass or less. The mass of the upper layer per unit volume of the portion of the substrate in which the upper layer is formed is 5 g / L or more and 60 g / L or less.

7. The method according to claim 6, wherein, The median particle size D of the third pore-forming agent 50 The median particle size D of the fourth pore-forming agent is greater than 4 μm. 50 It is below 4μm.

8. A method for manufacturing a catalyst for waste gas purification according to claim 1, wherein the catalyst for waste gas purification comprises a substrate extending in the waste gas flow direction, a first catalyst layer, and a second catalyst layer. The substrate comprises: The inflow side chamber extends along the direction of the exhaust gas flow, with the exhaust gas inflow side of the inflow side chamber open and the exhaust gas outflow side closed. An outlet side chamber extending along the exhaust gas flow direction, wherein the exhaust gas inflow end of the outlet side chamber is closed, and the exhaust gas outflow end is open; and A porous partition wall separates the inflow side chamber and the outflow side chamber. The first catalyst layer is disposed on the inflow side chamber side of the partition wall portion, starting from the end of the waste gas inflow side of the partition wall portion along the waste gas flow direction. The second catalyst layer is disposed on the outflow side chamber side of the partition wall portion, starting from the end of the waste gas outflow side of the partition wall portion, in a direction opposite to the waste gas flow direction. The first catalyst layer includes a lower layer disposed on the inflow side chamber side of the partition wall portion, and an upper layer disposed on the lower layer. The method includes the following steps: (3a) A process of forming a second precursor layer by coating a second slurry containing a second pore-forming agent onto the outflow side chamber side of the partition wall portion; (3b) The process of applying a fifth slurry containing a fifth pore-forming agent to the inflow side chamber of the partition wall to form a fifth precursor layer; (3c) The step of coating the sixth slurry containing the sixth pore-forming agent onto the fifth precursor layer to form the sixth precursor layer; and (3d) The process of calcining the second precursor layer, the fifth precursor layer, and the sixth precursor layer to form the second catalyst layer, the lower layer, and the upper layer. The median particle size D of one or both of the second pore-forming agent, the fifth pore-forming agent, and the sixth pore-forming agent. 50 For particles larger than 4 μm, the median particle size D of the remaining two or one is... 50 Below 4μm The second slurry contains inorganic oxide particles, and the median particle size D of the inorganic oxide particles contained in the second slurry is... 50 The size is greater than 1μm and less than 20μm. Based on the mass of the second catalyst layer, the amount of the second pore-forming agent contained in the second precursor layer is 10% by mass or more and 60% by mass or less. The mass of the second catalyst layer per unit volume of the portion of the substrate in which the second catalyst layer is formed is 5 g / L or more and 150 g / L or less. The fifth slurry contains inorganic oxide particles, and the median particle size D of the inorganic oxide particles contained in the fifth slurry is... 50 The size is greater than 1μm and less than 20μm. Based on the mass of the lower layer, the amount of the fifth pore-forming agent contained in the fifth precursor layer is 10% by mass or more and 60% by mass or less. The mass of the lower layer per unit volume of the portion of the substrate in which the lower layer is formed is 5 g / L or more and 90 g / L or less. The sixth slurry contains inorganic oxide particles, and the median particle size D of the inorganic oxide particles contained in the sixth slurry is... 50 The size is greater than 1μm and less than 20μm. Based on the mass of the upper layer, the amount of the sixth pore-forming agent contained in the sixth precursor layer is 10% by mass or more and 60% by mass or less. The mass of the upper layer per unit volume of the portion of the substrate in which the upper layer is formed is 5 g / L or more and 60 g / L or less.

9. The method according to claim 8, wherein, The median particle size D of the fifth pore-forming agent 50 The median particle size D of the sixth pore-forming agent is greater than 4 μm. 50 It is below 4μm.

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