Exhaust gas purification catalyst and method for producing same

Abstract

The purpose of the present invention is to provide an exhaust gas purification catalyst (1A) capable of improving PM collection performance and suppressing an increase in pressure loss, the exhaust gas purification catalyst (1A) being provided with a wall-flow-type substrate (10), a first catalyst layer (20), and a second catalyst layer (30), and the logarithmic differential pore volume distribution curve of the first catalyst layer (20) being in the range of at least one of the logarithmic differential pore volume distribution curve of the second catalyst layer (30), and the logarithmic differential pore volume distribution curve of the second catalyst layer (30) being in the range of at least one of the logarithmic differential pore volume distribution curve of the first catalyst layer (20). The second catalyst layer (30) has a logarithmic differential pore volume distribution curve, where the condition that a peak value (A) present in a pore diameter range of 1 [mu] m to 3 [mu] m inclusive is 0.20 mL / g or more and the condition that a peak value (B) present in a pore diameter range of more than 3 [mu] m to 10 [mu] m inclusive is 0.20 mL / g or more are defined as condition 1 and condition 2, respectively. The first catalyst layer (20) and the second catalyst layer (30) satisfy a combination of predetermined conditions, where the condition that the peak C present in the range of pore diameters of 1 [mu] m to 3 [mu] m is 0.20 mL / g or more and the condition that the peak D present in the range of pore diameters of more than 3 [mu] m to 10 [mu] m or less is 0.20 mL / g or more, respectively, are condition 3 and condition 4.

Description

Technical Field

[0001] The present invention relates to a catalyst for exhaust gas purification and a method for manufacturing the same. Background Art

[0002] Exhaust gas discharged from internal combustion engines of automobiles, motorcycles, etc. contains harmful components such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). For the purpose of purifying these harmful components and rendering them harmless, a three-way catalyst is used. As the three-way catalyst, a catalyst containing platinum group elements such as Pt, Pd, and Rh is used.

[0003] It is known that exhaust gas contains harmful components such as HC, CO, and NOx, and also contains particulate matter (PM: Particulate Matter), which causes air pollution.

[0004] In order to comply with environmental regulations related to PM, in vehicles equipped with gasoline engines such as gasoline direct injection engines (GDI), like vehicles equipped with diesel engines, it is necessary to provide a filter (GPF: Gasoline Particulate Filter) having a PM trapping function.

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

[0006] Since the mounting space for the catalyst for exhaust gas purification is generally limited, studies have been made on providing a catalyst layer containing platinum group elements such as Pt, Pd, and Rh on the wall flow type substrate to purify harmful components such as HC, CO, and NOx while trapping PM (for example, Patent Document 1). In the catalyst for exhaust gas purification having a wall flow type substrate and a catalyst layer provided on the wall flow type substrate, when the exhaust gas flowing in from the end (opening) on the exhaust gas inflow side of the inflow side chamber passes through the porous partition wall portion and flows out from the end (opening) on the exhaust gas outflow side of the outflow side chamber, the PM in the exhaust gas is trapped by the catalyst layer and the pores of the partition wall.

[0007] Prior Art Documents

[0008] Patent Documents

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

[0010] Problems to be Solved by the Invention

[0011] The smaller the pores of the catalyst layer and the partition wall portion, the higher the PM trapping performance, but the pressure loss (pressure drop) increases. On the other hand, the larger the pores of the catalyst layer and the partition wall portion, the increase in pressure drop is suppressed, but the PM trapping performance decreases. Therefore, it is difficult to balance the improvement of PM trapping performance and the suppression of the increase in pressure drop, and a technology capable of achieving both is required.

[0012] For this reason, an object of the present invention is to provide an exhaust gas purification catalyst and a method for manufacturing the same, which can achieve an improvement in PM trapping performance and a suppression of an increase in pressure drop.

[0013] Solutions to the Problems

[0014] To solve the above problems, the present invention provides an exhaust gas purification catalyst and a method for manufacturing the same as follows.

[0015] [1] An exhaust gas purification catalyst, comprising a substrate extending in the exhaust gas flow direction, a first catalyst layer, and a second catalyst layer,

[0016] The substrate includes:

[0017] An inflow side chamber extending in the exhaust gas flow direction, having an end opening on the exhaust gas inflow side and a closed end on the exhaust gas outflow side;

[0018] An outflow side chamber extending in the exhaust gas flow direction, having a closed end on the exhaust gas inflow side and an opening at the end on the exhaust gas outflow side; and

[0019] A porous partition wall portion separating the inflow side chamber and the outflow side chamber,

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

[0021] The second catalyst layer is provided on the outflow side chamber side of the partition wall portion along the direction opposite to the exhaust gas flow direction starting from the end on the exhaust gas outflow side of the partition wall portion,

[0022] When condition 1 is set as: 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 diameter of 1 μm or more and 3 μm or less, and peak A is 0.20 mL / g or more;

[0023] When condition 2 is set as: 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 diameter greater than 3 μm and 10 μm or less, and peak B is 0.20 mL / g or more;

[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 where the pore diameter is 1 μm or more and 3 μm or less, and the peak C is 0.20 mL / g or more;

[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, there is a peak D in the range where the pore diameter is greater than 3 μm and 10 μm or less, and the peak D is 0.20 mL / g or more.

[0026] 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 both Condition 3 and Condition 4, or satisfies neither Condition 3 nor Condition 4.

[0027] When the second catalyst layer satisfies Condition 3 and does not satisfy Condition 4, the first catalyst layer satisfies at least Condition 2 among Conditions 1 and 2.

[0028] When the second catalyst layer satisfies Condition 4 and does not satisfy Condition 3, the first catalyst layer satisfies at least Condition 1 among Conditions 1 and 2.

[0029] When the second catalyst layer satisfies both Condition 3 and Condition 4, the first catalyst layer satisfies at least one of Conditions 1 and 2, or satisfies neither Condition 1 nor Condition 2.

[0030] When the second catalyst layer satisfies neither Condition 3 nor Condition 4, the first catalyst layer satisfies Conditions 1 and 2.

[0031] [2] The exhaust gas purification catalyst according to [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 both Condition 3 and Condition 4.

[0032] When the second catalyst layer satisfies Condition 3 and does not satisfy Condition 4, the first catalyst layer satisfies at least Condition 2 among Conditions 1 and 2.

[0033] When the second catalyst layer satisfies Condition 4 and does not satisfy Condition 3, the first catalyst layer satisfies at least Condition 1 among Conditions 1 and 2.

[0034] When the second catalyst layer satisfies both Condition 3 and Condition 4, the first catalyst layer satisfies at least one of Conditions 1 and 2.

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

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

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

[0038] [6] A method for manufacturing a catalyst for purifying exhaust gas, the catalyst for purifying exhaust gas including a substrate extending in the exhaust gas flow direction, a first catalyst layer, and a second catalyst layer,

[0039] The substrate includes:

[0040] An inflow side chamber extending in the exhaust gas flow direction, with the end on the exhaust gas inflow side of the inflow side chamber open and the end on the exhaust gas outflow side closed;

[0041] An outflow side chamber extending in the exhaust gas flow direction, with the end on the exhaust gas inflow side of the outflow side chamber closed and the end on the exhaust gas outflow side open; and

[0042] A porous partition wall portion separating the inflow side chamber and the outflow side chamber,

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

[0044] The second catalyst layer is provided on the outflow side chamber side of the partition wall portion along the direction opposite to the exhaust gas flow direction starting from the end on the exhaust gas outflow side of the partition wall portion,

[0045] The method includes the following steps:

[0046] (1a) A step of coating a first slurry containing a first pore former on the inflow side chamber side of the partition wall portion to form a first precursor layer;

[0047] (1b) A step of coating a second slurry containing a second pore former on the outflow side chamber side of the partition wall portion to form a second precursor layer; and

[0048] (1c) A step of baking 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 former and the second pore former 50greater than 4 μm, and the median particle diameter D of the other one 50 is 4 μm or less,

[0050] The first slurry contains inorganic oxide particles, and the median particle diameter D of the inorganic oxide particles contained in the first slurry 50 is 1 μm or more and 20 μm or less,

[0051] Based on the mass of the first catalyst layer, the amount of the first pore former 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 where 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 diameter D of the inorganic oxide particles contained in the second slurry 50 is 1 μm or more and 20 μm or less,

[0054] Based on the mass of the second catalyst layer, the amount of the second pore former 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 where 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 exhaust gas, the catalyst for purifying exhaust gas including a substrate extending in the exhaust gas flow direction, a first catalyst layer, and a second catalyst layer,

[0057] The substrate includes:

[0058] An inflow side chamber extending in the exhaust gas flow direction, with an end on the exhaust gas inflow side of the inflow side chamber open and an end on the exhaust gas outflow side closed;

[0059] An outflow side chamber extending in the exhaust gas flow direction, with an end on the exhaust gas inflow side of the outflow side chamber closed and an end on the exhaust gas outflow side open; and

[0060] A porous partition wall portion separating the inflow side chamber and the outflow side chamber,

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

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

[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 step of coating a first slurry containing a first pore former on the inflow side chamber side of the partition wall portion to form a first precursor layer;

[0066] (2b) A step of coating a third slurry containing a third pore former on the outflow side chamber side of the partition wall portion to form a third precursor layer;

[0067] (2c) A step of coating a fourth slurry containing a fourth pore former on the third precursor layer to form a fourth precursor layer; and

[0068] (2d) A step of baking 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 former, the third pore former, and the fourth pore former 50 is greater than 4 μm, and the median particle size D of the remaining two or one 50 is 4 μm or less.

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

[0071] Based on the mass of the first catalyst layer, the amount of the first pore former 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 where 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 50 is 1 μm or more and 20 μm or less.

[0074] Based on the mass of the lower layer, the amount of the third pore former 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 base material where 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 diameter D of the inorganic oxide particles contained in the fourth slurry 50 is 1 μm or more and 20 μm or less.

[0077] Based on the mass of the upper layer, the amount of the fourth pore former 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 base material where the upper layer is formed is 5 g / L or more and 60 g / L or less.

[0079] [8] The method according to [7], wherein the median particle diameter D of the third pore former 50 is greater than 4 μm, and the median particle diameter D of the fourth pore former 50 is 4 μm or less.

[0080] [9] A method for manufacturing a catalyst for purifying exhaust gas, the catalyst for purifying exhaust gas including a base material extending in the exhaust gas flow direction, a first catalyst layer, and a second catalyst layer.

[0081] The base material includes:

[0082] An inflow side chamber extending in the exhaust gas flow direction, having an opening at the end on the exhaust gas inflow side of the inflow side chamber and a closed end on the exhaust gas outflow side;

[0083] An outflow side chamber extending in the exhaust gas flow direction, having a closed end on the exhaust gas inflow side of the outflow side chamber and an opening at the end on the exhaust gas outflow side; and

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

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

[0086] The second catalyst layer is provided on the outflow side chamber side of the partition wall portion along the direction opposite to the exhaust gas flow direction starting from the end on the exhaust gas outflow side of the partition wall portion.

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

[0088] The method includes the following steps:

[0089] (3a) A step of coating a second slurry containing a second pore former on the outflow side chamber side of the partition wall portion to form a second precursor layer;

[0090] (3b) A step of coating a fifth slurry containing a fifth pore former on the inflow side chamber side of the partition wall portion to form a fifth precursor layer;

[0091] (3c) A step of coating a sixth slurry containing a sixth pore former on the fifth precursor layer to form a sixth precursor layer; and

[0092] (3d) A step of baking 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 former, the fifth pore former, and the sixth pore former 50 is greater than 4 μm, and the median particle size D of the remaining two or one 50 is 4 μm or less,

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

[0095] Based on the mass of the second catalyst layer, the amount of the second pore former 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 where 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 50 is 1 μm or more and 20 μm or less,

[0098] Based on the mass of the lower layer, the amount of the fifth pore former 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 where 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 50is 1 μm or more and 20 μm or less,

[0101] Based on the mass of the upper layer, the amount of the sixth pore former 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 where 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 former 50 is greater than 4 μm, and the median particle size D of the sixth pore former 50 is 4 μm or less.

[0104] Effects of the Invention

[0105] According to the present invention, it is possible to provide an exhaust gas purification catalyst capable of improving PM capture performance and suppressing an increase in pressure loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0106] Figure 1 is a partial cross-sectional view showing a 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 is Figure 1 a sectional view taken along line A-A of

[0108] Figure 3 is Figure 1 a sectional view taken along line B-B of

[0109] Figure 4 is Figure 2 an enlarged view of the region indicated by the symbol R1 in

[0110] Figure 5 is Figure 3 an enlarged view of the region indicated by the symbol R2 in

[0111] Figure 6 is Figure 1 a sectional view taken along line C-C of

[0112] Figure 7 A to C of Figure 7 are diagrams for explaining the "peak" in the logarithmic differential pore volume distribution curve. In each of the diagrams A to C of

[0113] Figure 8 is a diagram for explaining the exhaust gas purification catalyst according to the second embodiment (a diagram corresponding to Figure 5 )

[0114] Figure 9 The figure for explaining the exhaust gas purification catalyst according to the second embodiment (the figure corresponding to Figure 6 ).

[0115] Figure 10 The figure for explaining the exhaust gas purification catalyst according to the third embodiment (the figure corresponding to Figure 5 ).

[0116] Figure 11 The figure for explaining the exhaust gas purification catalyst according to the third embodiment (the figure corresponding to Figure 6 ).

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

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

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

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

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

[0122] Figure 14B Shows the logarithmic differential pore volume distribution curve of the second catalyst layer in the exhaust gas purification catalyst of Comparative Example 2. Detailed implementation mode

[0123] Hereinafter, embodiments of the present invention will be described based on the drawings.

[0124] 《First Embodiment》

[0125] Hereinafter, based on Figures 1 - 6 the first embodiment of the present invention will be described.

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

[0127] Figure 1 In the figure, the exhaust gas flow direction of the exhaust path of the internal combustion engine is represented by the symbol E. The same applies to other figures. In this specification, the upstream side of the exhaust gas flow direction E (for example, Figure 1 the left side) is referred to as the "exhaust gas inlet side" or the "inlet side", and the downstream side of the exhaust gas flow direction E (for example, Figure 1 the right side) is referred to as the "exhaust gas outlet side" or the "inlet side".

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

[0129] As Figures 1 - 6 shown, the 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. As the material constituting the substrate 10, for example, ceramic materials, metal materials, etc. can be cited, but ceramic materials are preferred. As ceramic materials, for example, carbide ceramics such as silicon carbide, titanium carbide, tantalum carbide, tungsten carbide; nitride ceramics such as aluminum nitride, silicon nitride, boron nitride, titanium nitride; oxide ceramics such as alumina, zirconia, cordierite, mullite, zircon, aluminum titanate, magnesium titanate, etc. can be cited. As metal materials, for example, alloys such as stainless steel can be cited.

[0133] The length L of the substrate 10 10 can be appropriately adjusted in consideration of exhaust gas purification performance, PM trapping performance, etc. From the viewpoint of improving exhaust gas purification performance and PM trapping performance, the length L of the substrate 10 10 is preferably 50 mm or more and 160 mm or less, more preferably 80 mm or more and 130 mm or less.

[0134] The volume of the substrate 10 can be appropriately adjusted in consideration of exhaust gas purification performance, PM trapping performance, etc. From the viewpoint of improving exhaust gas purification performance and PM trapping performance, the volume of the substrate 10 is preferably 0.5 L or more and 2.5 L or less, more preferably 0.5 L or more and 2.0 L or less, and further preferably 0.7 L or more and 2.0 L 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 10, the volume of the substrate 10 is calculated according to the following formula: Volume of the substrate 10 = π × r 2 × L 10 .

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

[0136] As Figure 2 and 3 shown, the substrate 10 includes a cylindrical portion 11, and the chambers 13 (inflow side chamber 13a and outflow side chamber 13b) and the partition wall portion 12 are formed inside 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 the same as the axial direction of the substrate 10. As Figure 2 and 3 shown, the shape of the cylindrical portion 11 is, for example, cylindrical, but it may also be other shapes such as elliptical cylindrical or polygonal cylindrical.

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

[0138] As Figure 6 shown, a first closing portion 14 that closes the end on the exhaust gas outflow side of a partial chamber 13 and a second closing portion 15 that closes the end on the exhaust gas inflow side of the remaining chambers 13 are provided on the substrate 10. As a result, a partial chamber 13 becomes an inflow side chamber 13a with an open end on the exhaust gas inflow side and the end on the exhaust gas outflow side blocked by the first closing portion 14, and the remaining chambers 13 become an outflow side chamber 13b with the end on the exhaust gas inflow side blocked by the second closing portion 15 and an open end on the exhaust gas outflow side.

[0139] As Figures 2 - 6 shown, a partition wall portion 12 exists 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 portion 12.

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

[0141] As Figures 2 - 6 shown, the top view shape of the end portion (opening portion) on the exhaust gas inflow side of each inflow side chamber 13a and the top view shape of the end portion (opening portion) on the exhaust gas outflow side of each outflow side chamber 13b are, for example, quadrilateral, but may also be other shapes such as hexagon, octagon, etc.

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

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

[0144] As Figures 4 - 6 shown, the partition wall portion 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 among the outer surfaces defining the outer shape of the partition wall portion 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 among the outer surfaces defining the outer shape of the partition wall portion 12.

[0145] The thickness of the partition wall portion 12 can be appropriately adjusted in consideration of PM capture performance, pressure loss, etc. From the viewpoint of improving PM capture performance and suppressing an increase in pressure loss, the thickness of the partition wall portion 12 is preferably 110 μm or more and 380 μm or less, more preferably 150 μm or more and 330 μm or less, and further preferably 180 μm or more and 310 μm or less.

[0146] The average pore diameter (average gas pore diameter) of the partition wall portion 12 can be appropriately adjusted. However, from the viewpoint of more effectively improving the PM capture performance and suppressing the increase in pressure loss, 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 (pore rate) of the partition wall portion 12 can be appropriately adjusted. However, from the viewpoint of more effectively suppressing the increase in pressure loss, 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 further preferably 60% or more and 70% or less.

[0147] The average pore diameter and porosity of the partition wall portion 12 can be measured by the mercury intrusion method using a mercury porosimeter. In the mercury intrusion method, a test piece (excluding the first closing portion 14 and the second closing portion 15) cut out from the base material 10 is placed in the measurement chamber of the mercury porosimeter. The inside of the measurement chamber is depressurized, mercury is introduced into the measurement chamber and pressurized, and the pore diameter and pore volume are measured based on the pressure during pressurization and the volume of mercury introduced into the pores of the partition wall portion 12 of the test piece. The measurement is performed, for example, in the pressure range of 0.5 to 20000 psia. It should be noted that 0.5 psia is equivalent to 0.35×10 -3 kg / mm 2 , and 20000 psia is equivalent to 14 kg / mm 2 . The pore diameter range corresponding to this pressure range is 0.01 to 420 μm. As the constant for calculating the gas pore diameter from the pressure, for example, a contact angle of 140° and a surface tension of 480 dyn / cm are used. The average pore diameter of the partition wall portion 12 is the pore diameter at which the cumulative pore volume becomes 50% in the pore diameter distribution of the partition wall portion 12 (the pore diameter at the cumulative value of 50% of the pore volume). 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 the partition wall portion 12 = Total pore volume / (Total pore volume + 1 / True specific gravity of the partition wall material) × 100

[0149] <First catalyst layer>

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

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

[0152] As Figure 4 and 6 shown, it is preferable that at least a part of the first catalyst layer 20 bulges from the outer surface S1a of the partition wall portion 12 toward the inflow side chamber 13a side, that is, the first catalyst layer 20 has a portion that bulges from the outer surface S1a of the partition wall portion 12 toward the inflow side chamber 13a side (hereinafter referred to as the "bulging portion"). Thereby, the contact between the exhaust gas and the PM is improved, and the improvement of the exhaust gas purification performance and the improvement of the PM trapping performance can be more effectively achieved.

[0153] The first catalyst layer 20 may be composed only of the bulging portion, or may have a portion existing inside the partition wall portion 12 (hereinafter referred to as the "intrinsic portion") while having the bulging portion. Since the partition wall portion 12 is porous, the intrinsic portion may be formed together with the bulging portion when the first catalyst layer 20 is formed. The bulging portion and the intrinsic portion may be continuous. The first catalyst layer 20 may also be composed only of the intrinsic portion. "The first catalyst layer 20 is provided on the inflow side chamber 13a side of the partition wall portion 12" includes all of: an embodiment in which the first catalyst layer 20 is composed only of the bulging portion, an embodiment in which the first catalyst layer 20 is composed only of the intrinsic portion, and an embodiment in which the first catalyst layer 20 has the bulging portion and the intrinsic portion.

[0154] The region where the bulging portion of the first catalyst layer 20 exists does not overlap with the region where the partition wall portion 12 exists, but the region where the intrinsic portion of the first catalyst layer 20 exists overlaps with the region where the partition wall portion 12 exists. Therefore, the catalyst 1A can be cut by a plane perpendicular to the axial direction of the base material 10, and the first catalyst layer 20 and the partition wall portion 12 existing on the cut surface can be observed, and based on the morphological difference between the first catalyst layer 20 and the partition wall portion 12, the bulging portion and the intrinsic portion of the first catalyst layer 20 can be determined. When observing the cut surface, elemental mapping of the cut surface can be performed. The elemental mapping can be performed, for example, by combining the cut surface observation using SEM and the compositional analysis of the cut surface. The elemental mapping can be performed, for example, using a scanning electron microscope - energy dispersive X-ray analysis method (SEM-EDX), an electron probe microanalyzer (EPMA), or the like. The bulging portion and the intrinsic portion can be determined based on the morphological and compositional differences between the first catalyst layer 20 and the partition wall portion 12 through the elemental mapping of the cut surface.

[0155] From the viewpoint of achieving a good balance between the 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 where 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 still 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 where the first catalyst layer 20 is formed is calculated by 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 the substrate 10 10 ))

[0156] In the present specification, the "mass of the first catalyst layer 20" means the mass in terms of metal obtained for platinum group elements and the mass in terms of oxide obtained for metal elements other than platinum group elements among all the metal elements contained in the first catalyst layer 20, and the sum of them. That is, the "mass of the first catalyst layer 20" means the calculated mass obtained by adding the mass in terms of metal of the platinum group elements contained in the first catalyst layer 20 and the mass in terms of oxide of the metal elements other than platinum group elements contained in the first catalyst layer 20. It should be noted that the "metal elements" also include semi-metal elements such as Si and B

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

[0158] In the present specification, the oxides of rare earth elements other than Ce, Pr, and Tb refer to sesquioxides (M2O3, where M represents rare earth elements other than Ce, Pr, and Tb), the oxide of Ce refers to CeO2, the oxide of Pr refers to Pr6O 11 , the oxide of Tb refers to Tb4O7, the oxide of Al refers to Al2O3, the oxide of Zr refers to ZrO2, the oxide of Si refers to SiO2, the oxide of B refers to B2O3, the oxide of Cr refers to Cr2O3, the oxide of Mg refers to MgO, the oxide of Ca refers to CaO, the oxide of Sr refers to SrO, the oxide of Ba refers to BaO, the oxide of Fe refers to Fe3O4, the oxide of Mn refers to Mn3O4, the oxide of Ni refers to NiO, the oxide of Ti refers to TiO2, the oxide of Zn refers to ZnO, and the oxide of Sn refers to SnO2

[0159] An example of the method for measuring the average length L of the first catalyst layer 20 20 is as follows

[0160] A sample is cut out from Catalyst 1A, extending axially along the substrate 10 and having the same length as the length L of the substrate 10. 10 The sample is, for example, cylindrical with a diameter of 25.4 mm. It should be noted that the value of the diameter of the sample can be changed as needed. The sample is cut at intervals of 5 mm using a plane perpendicular to the axial direction of the substrate 10, and the first slice, the second slice, ……, the nth slice are obtained in sequence from the end side on the exhaust gas inflow side of the sample. The length of each slice is 5 mm. The composition of the slices is analyzed using a scanning electron microscope - energy dispersive X-ray analysis method (SEM-EDX), etc., and based on the composition of the slices, it is confirmed whether the slices contain a part of the first catalyst layer 20.

[0161] For slices that clearly contain a part of the first catalyst layer 20, it is not necessarily required to perform a composition analysis. For example, a scanning electron microscope (SEM), an electron probe microanalyzer (EPMA), etc. can be used to observe the cut surface to confirm whether the slices contain a part of the first catalyst layer 20. When observing the cut surface, elemental mapping of the cut surface can be performed. The elemental mapping can be carried out in the same manner as described above.

[0162] After confirming whether the slices contain a part 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 × (the number of slices containing a part of the first catalyst layer 20)

[0164] For example, in the case where the first slice to the kth slice contain a part of the first catalyst layer 20, but the (k + 1)th to the nth slices do not contain a part 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 measurement method for the length of the first catalyst layer 20 contained in the sample is as follows.

[0166] By cutting the kth slice (i.e., the slice closest to the exhaust gas outflow side of the sample among the slices containing a part of the first catalyst layer 20) along the axial direction of the substrate 10, and using SEM, EPMA, etc. to observe the part of the first catalyst layer 20 present on the cut surface, the length of the part of the first catalyst layer 20 in the kth slice is measured. Then, the length of the first catalyst layer 20 contained in the sample is calculated based on the following formula.

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

[0168] For 8 to 16 samples arbitrarily cut out from Catalyst 1A, measure the lengths of the first catalyst layer 20 contained in each sample, and take their average value as the average length L of the first catalyst layer 20 20 。

[0169] The average length L of the first catalyst layer 20 20 can be appropriately adjusted in consideration of the exhaust gas purification performance, PM trapping performance, etc. From the viewpoint of improving the exhaust gas purification performance and PM trapping performance, the average length L of the first catalyst layer 20 20 relative to the length L of the substrate 10 10 percentage (L 20 / L 10 × 100) is preferably 15% or more and 90% or less, more preferably 20% or more and 90% or less, and further preferably 30% or more and 85% or less.

[0170] The first catalyst layer 20 contains one or more than two platinum group elements. The platinum group elements can be selected from, for example, Pt, Pd, Rh, Ru, Ir, Os, etc., but from the viewpoint of improving the exhaust gas purification performance, they are preferably selected from Pt, Pd, and Rh. The platinum group elements are contained in the first catalyst layer 20 in a form capable of functioning as a catalytically active component, such as in the form of a metal, an alloy containing a platinum group element, a compound containing a platinum group element (such as an oxide of a platinum group element), etc., which are catalytically active components containing a platinum group element. From the viewpoint of improving the exhaust gas purification performance, the catalytically active component containing a platinum group element is preferably in particulate form.

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

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

[0173] From the viewpoint of the balance between the exhaust gas purification performance and cost, based on the mass of the first catalyst layer 20, the metal conversion amount of the platinum group elements in the first catalyst layer 20 is preferably 0.010 mass% or more and 20 mass% or less, more preferably 0.020 mass% or more and 15 mass% or less, and further preferably 0.050 mass% or more and 10 mass% or less. The "metal conversion amount of the platinum group elements in the first catalyst layer 20" refers to the metal conversion amount of one platinum group element in the case where the first catalyst layer 20 contains one platinum group element, and refers to the sum of the metal conversion amounts of two or more platinum group elements in the case where the first catalyst layer 20 contains two or more platinum group elements.

[0174] When the composition of the raw materials for manufacturing 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 materials.

[0175] When the composition of the raw materials for manufacturing 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 analysis (SEM-EDX). Specifically, as described below.

[0176] Perform elemental analysis on a sample obtained from the first catalyst layer 20 using a conventional method such as SEM-EDX to determine the types of constituent elements of the entire sample, and determine the mole % of each metal element thus determined. Determine the mole % of each metal element for each of 10 fields of view of the SEM, and use the average of the mole % of each metal element in the 10 fields of view as the mole % of each metal element in the first catalyst layer 20. Based on the mole % of each metal element in the first catalyst layer 20, calculate the mass % in terms of metal of each platinum group element in the first catalyst layer 20, and the mass % in terms of oxide of each metal element other than the platinum group elements in the first catalyst layer 20. The mass % in terms of metal of each platinum group element in the first catalyst layer 20 is calculated according to the following formula: (Mass in terms of metal of each platinum group element calculated based on mole %) / ((Mass in terms of metal of platinum group elements calculated based on mole %) + (Mass in terms of oxide of metal elements other than platinum group elements calculated based on mole %)) × 100. The mass % in terms of oxide of each metal element other than the platinum group elements in the first catalyst layer 20 is calculated according to the following formula: (Mass in terms of oxide of each metal element other than platinum group elements calculated based on mole %) / ((Mass in terms of metal of platinum group elements calculated based on mole %) + (Mass in terms of oxide of metal elements other than platinum group elements calculated based on mole %)) × 100.

[0177] The first catalyst layer 20 preferably contains one or two or more carriers, and at least a part of the catalytically active component is supported on one or two or more carriers.

[0178] "At least a part of the catalytically active component is supported on the carrier" means that at least a part 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 carrier. The fact that at least a part of the catalytically active component is supported on the carrier can be confirmed using, for example, SEM-EDX. Specifically, in the elemental mapping obtained by analyzing the cross-section of the catalyst layer by SEM-EDX, when at least a part of the catalytically active component and the carrier are present in the same region, it can be determined that at least a part of the catalytically active component is supported on the carrier.

[0179] The carrier can, for example, be selected from inorganic oxides. The inorganic oxides are, for example, particulate. From the viewpoint of improving the loadability of the catalytic active component, the inorganic oxides are preferably porous. The inorganic oxides may or may not have oxygen storage capacity (OSC: Oxygen Storage Capacity). The inorganic oxides used as the carrier are distinguished from the inorganic oxides used as the binder (such as inorganic oxide-based binders such as alumina binder, zirconia binder, titania binder, silica binder, etc.).

[0180] Examples of the inorganic oxides include Al-based oxides, Ce-based oxides, Ce-Zr composite oxides, oxides of rare earth elements other than Ce, zirconia (ZrO2), silica (SiO2), titania (TiO2), zeolites (aluminosilicates), oxides based on MgO, ZnO, SnO2, etc.

[0181] The carrier 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 than two carriers other than Al-based oxides, Ce-based oxides, and Ce-Zr composite oxides.

[0182] In the present specification, the Al-based oxide means an oxide containing Al and having Al as the element with the highest content rate on a mass basis among the elements other than O constituting the oxide. However, the oxides belonging to the Ce-Zr composite oxides do not belong to the Al-based oxides.

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

[0184] In the present specification, the Ce-based oxide means an oxide containing Ce and having Ce as the element with the highest content rate on a mass basis among the elements other than O constituting the oxide. However, the oxides belonging to the Ce-Zr composite oxides do not belong to the Ce-based oxides.

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

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

[0187] The Ce-Zr composite oxide may contain one or more elements other than Ce, Zr, and O (hereinafter referred to as "other elements"). The other elements may be selected, for example, from rare earth elements other than Ce, alkaline earth metal elements (such as Mg, Ca, Sr, Ba, etc.), Fe, Mn, Ni, Al, etc. Examples of the Ce-Zr composite oxide include a CeO2-ZrO2 solid solution, an oxide obtained by modifying the surface of the CeO2-ZrO2 solid solution with other elements, an oxide obtained by solid-solubilizing other elements in the CeO2-ZrO2 solid solution, etc.

[0188] Based on the mass of the Ce-Zr composite oxide, the oxide conversion content rate of other elements in the Ce-Zr composite oxide is, for example, 5 mass% or more and 30 mass% or less. The "oxide conversion content rate of other elements in the Ce-Zr composite oxide" refers to the oxide conversion content rate of one such element when the Ce-Zr composite oxide contains one other element, and refers to the sum of the oxide conversion content rates of two or more such elements when the Ce-Zr composite oxide contains two or more other elements.

[0189] When the composition of the Al-based oxide is known, the oxide conversion content rate of each element in the Al-based oxide can be determined from the composition of the Al-based oxide.

[0190] In the case where the composition of the Al-based oxide is unknown, the oxide conversion content rates of the respective elements in the Al-based oxide can be determined by analyzing a sample containing the Al-based oxide using energy dispersive X-ray spectroscopy (EDX) and based on the obtained elemental mapping and EDX elemental analysis of the specified particles. Specifically, the Al-based oxide particles and other particles can be qualitatively identified (color differentiation) by elemental mapping, and the composition analysis (elemental analysis) of the specified particles can be performed, thereby determining the oxide conversion content rates of the respective elements in the specified particles.

[0191] The oxide conversion content rates of the respective elements in the Ce-based oxide or Ce-Zr-based composite oxide can be determined in the same manner as the oxide conversion content rates of the respective elements in the Al-based oxide.

[0192] The first catalyst layer 20 may contain other components such as a binder and a stabilizer. Examples of the binder include inorganic oxide-based binders such as alumina sol, ceria sol, zirconia sol, titania sol, and silica sol. Examples of the stabilizer include nitrates, carbonates, oxides, sulfates, etc. of alkaline earth metal elements (such as Sr, Ba, etc.).

[0193] <Second Catalyst Layer>

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

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

[0196] As Figure 5 and 6 shown, it is preferable that at least a part of the second catalyst layer 30 bulges from the outer surface S1b of the partition wall portion 12 toward the outflow side chamber 13b side, that is, the second catalyst layer 30 has a portion (hereinafter referred to as "bulging portion") that bulges from the outer surface S1b of the partition wall portion 12 toward the outflow side chamber 13b side. Thereby, the contact between the exhaust gas and the PM is improved, and the improvement of the exhaust gas purification performance and the improvement of the PM trapping performance can be more effectively achieved.

[0197] The second catalyst layer 30 may be composed only of the raised portions, or may have portions (hereinafter referred to as "inner portions") existing inside the partition wall portion 12 while having the raised portions. Since the partition wall portion 12 is porous, the inner portions may be formed together with the raised portions when the second catalyst layer 30 is formed. The raised portions and the inner portions may be continuous. The second catalyst layer 30 may also be composed only of the inner portions. "The second catalyst layer 30 is provided on the outflow side chamber 13b side of the partition wall portion 12" includes all of the following embodiments: an embodiment in which the second catalyst layer 30 is composed only of the raised portions, an embodiment in which the second catalyst layer 30 is composed only of the inner portions, and an embodiment in which the second catalyst layer 30 has the raised portions and the inner portions.

[0198] The above description of the method for determining the raised portions and the inner portions of the first catalyst layer 20 is also applicable to the second catalyst layer 30. When applicable, it is understood by replacing "the first catalyst layer 20" with "the 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 where 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 further 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 where the second catalyst layer 30 is formed is calculated by 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 the substrate 10 10 ))

[0200] The above description of the mass of the first catalyst layer 20 is also applicable to the second catalyst layer 30. When applicable, it is understood by replacing "the first catalyst layer 20" with "the second catalyst layer 30".

[0201] Regarding the average length L of the first catalyst layer 20 20 The above description of the measurement method is also applicable to the measurement method of the average length L of the second catalyst layer 30 30 . When applicable, it is understood by replacing "the first catalyst layer 20" with "the second catalyst layer 30", and replacing "average length L 20 " with "average length L 30 ". However, in the measurement method of the average length L of the second catalyst layer 30 30 samples are cut at 5 mm intervals with a plane perpendicular to the axial direction of the substrate 10, and the first slice, the second slice,..., the nth slice are sequentially obtained from the end side of the exhaust gas outflow side of the sample.

[0202] Average length L of the second catalyst layer 30 30 It can be appropriately adjusted in consideration of exhaust gas purification performance, PM trapping performance, etc. From the viewpoint of improving exhaust gas purification performance and PM trapping performance, the average length L of the second catalyst layer 30 30 Relative to the length L of the substrate 10 10 Percentage (L 30 / L 10 × 100) is preferably 15% or more and 90% or less, more preferably 20% or more and 90% or less, and still more preferably 30% or more and 85% or less.

[0203] From the viewpoint of improving exhaust gas purification performance and PM trapping performance, the average length L of the first catalyst layer 20 20 And the average length L of the second catalyst layer 30 30 The sum of which relative to the length L of the substrate 10 10 Percentage ((L 20 + L 30 ) / L 10 × 100) is preferably 100% or more and 180% or less, more preferably 100% or more and 170% or less, and still 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 of the platinum group elements contained in the first catalyst layer 20 and their metal equivalent amounts also applies to the platinum group elements contained in the second catalyst layer 30 and their metal equivalent amounts. When applicable, understand by replacing "the first catalyst layer 20" with "the second catalyst layer 30".

[0205] In one embodiment, the second catalyst layer 30 contains Pd and / or Rh. In addition to Pd and / or Rh, the second catalyst layer 30 may further contain one or more other platinum group elements. The embodiment in which the second catalyst layer 30 contains Pd and / or Rh can be combined with the embodiment in which the first catalyst layer 20 contains Rh.

[0206] In another embodiment, the second catalyst layer 30 contains Rh. In addition to Rh, the second catalyst layer 30 may further contain one or more other platinum group elements. The embodiment in which the second catalyst layer 30 contains Rh can be combined with the embodiment in which the first catalyst layer 20 contains Pd and / or Rh.

[0207] The second catalyst layer 30 preferably contains one or more carriers, and at least a part of the catalytic active component is supported on one or more carriers. The meaning and confirmation method of support are the same as above.

[0208] The above description of the carrier contained in the first catalyst layer 20 also applies to the carrier contained in the second catalyst layer 30. When applicable, it is understood by replacing "the first catalyst layer 20" with "the second catalyst layer 30".

[0209] The second catalyst layer 30 may contain other components such as a binder and a stabilizer. The description of the binder and the stabilizer is 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 a value (logarithmic differential pore volume dV / d(logD)) obtained by dividing the pore volume increase amount (differential pore volume dV) by the difference (difference d(logD)) between the common logarithm (log) of the upper value and the lower value of the corresponding pore diameter, and a curve formed by plotting this value against the midpoint of the pore diameter increase amount (average pore diameter of each interval). It should be noted that the "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 diameter (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 the slice M1. The slice M1 will be described later.

[0213] In the logarithmic differential pore volume distribution curve of the second catalyst layer 30, the horizontal axis represents the pore diameter (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 the slice M2. The slice M2 will be described later.

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

[0215] Cut the catalyst 1A with a plane parallel to the axial direction of the substrate 10 and a plane perpendicular to the axial direction of the substrate 10 to cut out Figure 6The part shown by the symbol M1 in [the figure] gives a slice M1 that includes a part of the partition wall part 12 and a part of the first catalyst layer 20 but does not include the second catalyst layer 30. None of the slices M1 includes the first closing part 14 or the second closing part 15. The length of the part of the partition wall part 12 included in the slice M1 is equal to the length of the slice M1. The length of the part of the first catalyst layer 20 included in the slice M1 is equal to the length of the slice M1. The slice M1 can be obtained near the exhaust gas inflow side end of the catalyst 1A. For example, by cutting at two places that are 10 mm and 20 mm respectively from the exhaust gas inflow side end of the substrate 10 along the exhaust gas flow direction E with a plane perpendicular to the axial direction of the substrate 10, a slice M1 with a length of 10 mm that includes a part of the partition wall part 12 and a part of the first catalyst layer 20 but does not include the second catalyst layer 30 can be obtained. The size of the slice M1 can be appropriately changed. The slice M1 is, for example, in the shape of a cube with a side length of 10 mm.

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

[0217] The mercury intrusion method can be carried out using an automatic porosimeter "Autopore IV9520" manufactured by Shimadzu Corporation under the following conditions and procedures.

[0218] (Measurement conditions)

[0219] Measurement environment: 25 °C

[0220] Measurement chamber: Specimen chamber volume 3 cm 3 and intrusion volume 0.39 cm 3

[0221] Measurement range: 0.0048 MPa to 255.1060 MPa

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

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

[0224] Total 131 points (when plotting each pressure logarithmically, marking points at equal intervals)

[0225] Intrusion volume: Adjusted to be 25% or more and 90% or less.

[0226] (Low-pressure parameters)

[0227] Exhaust pressure: 50 μmHg

[0228] Exhaust time: 5.0 min

[0229] Mercury injection pressure: 0.0034 MPa

[0230] Equilibration time: 10 sec

[0231] (High-pressure parameters)

[0232] Equilibration time: 10 sec

[0233] (Mercury parameters)

[0234] Advancing contact angle: 130.0 degrees

[0235] Receding 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 steps)

[0239] (1) Measure 54 points in the low-pressure section in the range of 0.0048 MPa to 0.3447 MPa or less.

[0240] (2) Measure 77 points in the high-pressure section in the range of 0.3792 MPa to 255.1060 MPa or less.

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

[0242] It should be noted that the above (1), (2), and (3) can be automatically performed using the software attached to the device. Other conditions can be based on JIS R 1655:2003.

[0243] Since slice M1 includes a part of the partition wall portion 12 and a part of the first catalyst layer 20, the logarithmic differential pore volume distribution obtained by mercury intrusion porosimetry includes, in addition to the logarithmic differential pore volume distribution of the first catalyst layer 20, the logarithmic differential pore volume distribution of the partition wall portion 12. However, since the pore diameter of the partition wall portion 12 is significantly larger than that of the first catalyst layer 20, 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 can be distinguished.

[0244] The pore diameter 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, and more preferably 0.003 μm or more and 11 μm or less. The pore diameter 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, and 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] Cut the catalyst 1A with a plane parallel to the axial direction of the substrate 10 and a plane perpendicular to the axial direction of the substrate 10 to cut out Figure 6 the portion shown by the symbol M2 in, to obtain a slice M2 that includes a part of the partition wall portion 12 and a part of the second catalyst layer 30 but does not include the first catalyst layer 20. None of the slices M2 includes the first closing portion 14 or the second closing portion 15. The length of the part of the partition wall portion 12 included in the slice M2 is equal to the length of the slice M2. The length of the part of the second catalyst layer 30 included in the slice M2 is equal to the length of the slice M2. The slice M2 can be obtained near the exhaust gas outlet side end of the catalyst 1A. For example, by cutting at two places that are 10 mm and 20 mm away from the exhaust gas outlet side end of the substrate 10 in the direction opposite to the exhaust gas flow direction E with a plane perpendicular to the axial direction of the substrate 10, a slice M2 with a length of 10 mm that includes a part of the partition wall portion 12 and a part of the second catalyst layer 30 but does not include the first catalyst layer 20 can be obtained. The size of the slice M2 can be changed appropriately. The slice M2 is, for example, in the shape of a cube with a side length of 10 mm.

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

[0248] For the mercury intrusion method, an automatic porosimeter "Autopore IV9520" manufactured by Shimadzu Corporation can be used, and it can be carried out under the same conditions and steps as above.

[0249] Since the slice M2 includes the partition wall portion 12 and the second catalyst layer 30, the logarithmic differential pore volume distribution obtained by the mercury intrusion method includes, in addition to the logarithmic differential pore volume distribution of the second catalyst layer 30, the logarithmic differential pore volume distribution of the partition wall portion 12. However, since the pore diameter of the partition wall portion 12 is significantly larger than that of the second catalyst layer 30, 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 can be distinguished.

[0250] The pore diameter 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 diameter range in the logarithmic differential pore volume distribution of the dividing 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, preferably 12 μm or more and 30 μm or less.

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

[0252] In this specification, the "differential curve of 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 the horizontal axis 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 logarithmic differential pore volume distribution curve values v n corresponding to the pore diameter D n of the group (n represents an integer from 1 to 131) are set in ascending order of pore diameter as (D1, v1), (D2, v2),..., (D n , v n ),..., (D 131 , v 131 ).

[0256] (2) For each pore diameter D n where 1 ≤ n ≤ 130, the value of (v n+1 - v n ) / (D n+1 - D n ) is taken as the differential value of the logarithmic differential pore volume distribution curve at the pore diameter D n .

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

[0258] <Peak>

[0259] The "peak" in the logarithmic differential pore volume distribution curve will be described below.

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

[0261] (P2) As Figure 7 shown in B of , in the logarithmic differential pore volume distribution curve, when there is a shoulder on the small pore diameter side of a certain peak, in the differential curve of the logarithmic differential pore volume distribution curve, there is a positive minimum value in the part corresponding to the shoulder. The pore diameter that gives this minimum value is obtained from the differential curve of the logarithmic differential pore volume distribution curve, and the logarithmic differential pore volume corresponding to the obtained pore diameter is obtained from the logarithmic differential pore volume distribution curve. The obtained logarithmic differential pore volume corresponds to the "peak value". It should be noted that in the logarithmic differential pore volume distribution curve, when there is a shoulder on the small pore diameter side of a certain peak, as Figure 7 shown in B of , this shoulder usually slopes upward to the right.

[0262] (P3) As Figure 7 shown in C of , in the logarithmic differential pore volume distribution curve, when there is a shoulder on the large pore diameter side of a certain peak, in the differential curve of the logarithmic differential pore volume distribution curve, there is a negative maximum value in the part corresponding to the shoulder. The pore diameter that gives this maximum value is obtained from the differential curve of the logarithmic differential pore volume distribution curve, and the logarithmic differential pore volume corresponding to the obtained pore diameter is obtained from the logarithmic differential pore volume distribution curve. The obtained logarithmic differential pore volume corresponds to the "peak value". It should be noted that in the logarithmic differential pore volume distribution curve, when there is a shoulder on the large pore diameter side of a certain peak, as Figure 7 shown in C of , this shoulder usually slopes downward to the right.

[0263] As described above, the "peak value" in the logarithmic differential pore volume distribution curve includes not only the maximum value (logarithmic differential pore volume at the vertex) in the curve, but also the shoulder in the curve. That is, the "peak value" in the logarithmic differential pore volume distribution curve includes 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 pore volume distribution curve, it is sufficient that one or two or more of peak values P1, P2, and P3 exist, and it is not necessary for peak values P1, P2, and P3 to all exist. In the logarithmic differential pore volume distribution curve, there can be two or more peak values P1, there can be two or more peak values P2, and there can also be two or more peak values P3.

[0264] <Peak A>

[0265] Hereinafter, "in the logarithmic differential pore volume distribution curve of the first catalyst layer 20, there is a peak A in the range where the pore diameter is 1 μm or more and 3 μm or less" will be described.

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

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

[0268] Peak A can be any one of peaks P1, P2, or P3. In one embodiment, it is peak P1 or P2.

[0269] <Peak B>

[0270] Hereinafter, an explanation will be given of "in the logarithmic differential pore volume distribution curve of the first catalyst layer 20, there is peak B in the range where the pore diameter is greater than 3 μm and 10 μm or less".

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

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

[0273] Peak B can be any one of peaks P1, P2, or P3. In one embodiment, it is peak P1 or P3.

[0274] <Peak C>

[0275] Hereinafter, an explanation will be given of "in the logarithmic differential pore volume distribution curve of the second catalyst layer 30, there is peak C in the range where the pore diameter is 1 μm or more and 3 μm or less".

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

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

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

[0279] <Peak D>

[0280] Hereinafter, an explanation will be given of "in the logarithmic differential pore volume distribution curve of the second catalyst layer 30, there is a peak D in the range where the pore diameter is greater than 3 μm and 10 μm or less".

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

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

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

[0284] <Parameters of the present invention>

[0285] In this specification,

[0286] The condition that there is a peak A in the range where the pore diameter is 1 μm or more and 3 μm or less in the logarithmic differential pore volume distribution curve of the first catalyst layer 20 obtained by mercury intrusion porosimetry, and peak A is 0.20 mL / g or more is called "condition 1";

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

[0288] The condition that there is a peak C in the range where the pore diameter is 1 μm or more and 3 μm or less in the logarithmic differential pore volume distribution curve of the second catalyst layer 30 obtained by mercury intrusion porosimetry, and peak C is 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, the condition where a peak D exists in the range where the pore diameter is greater than 3 μm and 10 μm or less, and the peak D is 0.20 mL / g or more is referred to as "Condition 4".

[0290] Preferably, the second catalyst layer 30 satisfies Condition 3 and does not satisfy Condition 4, or satisfies Condition 4 and does not satisfy Condition 3, or satisfies both Condition 3 and 4, or neither Condition 3 nor 4 is satisfied.

[0291] When the second catalyst layer 30 satisfies Condition 3 and does not satisfy Condition 4, the first catalyst layer 20 preferably satisfies at least Condition 2 among Conditions 1 and 2; when the second catalyst layer 30 satisfies Condition 4 and does not satisfy Condition 3, the first catalyst layer 20 preferably satisfies at least Condition 1 among Conditions 1 and 2; when the second catalyst layer 30 satisfies both Condition 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; when the second catalyst layer 30 satisfies neither Condition 3 nor 4, the first catalyst layer 20 preferably satisfies Conditions 1 and 2.

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

[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 more the PM capture performance is improved, but the pressure loss increases. On the other hand, the larger the pores of the first catalyst layer 20 and the second catalyst layer 30, the suppression of the increase in pressure loss is achieved, but the PM capture performance decreases. Therefore, a single pore size control of reducing the pores of the first catalyst layer 20 and the second catalyst layer 30 or increasing the pores of the first catalyst layer 20 and the second catalyst layer 30 cannot achieve both the improvement of the PM capture performance and the suppression of the increase in pressure loss. In contrast, in the above modes (i) to (ix), the first catalyst layer 20 and the second catalyst layer 30 as a whole satisfy the following conditions: the peak A and / or C corresponding to the small pore diameter is 0.20 mL / g or more, and the peak B and / or D corresponding to the large pore diameter is 0.20 mL / g or more. Thereby, it is possible to sufficiently ensure the pore volume contributing to the PM capture performance and the pore volume contributing to the reduction of the pressure loss, and it is possible to achieve both the improvement of the PM capture performance and the suppression of the increase in pressure loss.

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

[0298] In condition 1, the peak A is not particularly limited as long as it is 0.20 mL / g or more. From the viewpoint of more effectively achieving both an improvement in PM capture performance and suppression of an increase in pressure loss, it is preferably 0.31 mL / g or more, and more preferably 0.40 mL / g or more.

[0299] In condition 1, the upper limit of the peak A is not particularly limited. From the viewpoint of more effectively achieving both an improvement in PM capture performance and suppression of an increase in pressure loss, it is preferably 1.00 mL / g or less, more preferably 0.80 mL / g or less, and further preferably 0.50 mL / g or less. These upper limits can be arbitrarily combined with the above lower limits respectively.

[0300] In condition 2, the peak B is not particularly limited as long as it is 0.20 mL / g or more. From the viewpoint of more effectively achieving both an improvement in PM capture performance and suppression of an increase in pressure loss, it is preferably 0.30 mL / g or more, and more preferably 0.42 mL / g or more.

[0301] In condition 2, the upper limit of the peak B is not particularly limited. From the viewpoint of more effectively achieving both an improvement in PM capture performance and suppression of an increase in pressure loss, it is preferably 1.00 mL / g or less, more preferably 0.80 mL / g or less, and further preferably 0.50 mL / g or less. These upper limits can be arbitrarily combined with the above lower limits respectively.

[0302] In condition 3, the peak C is not particularly limited as long as it is 0.20 mL / g or more. From the viewpoint of more effectively achieving both an improvement in PM capture performance and suppression of an increase in pressure loss, it is preferably 0.31 mL / g or more, and more preferably 0.40 mL / g or more.

[0303] In condition 3, the upper limit of the peak C is not particularly limited. From the viewpoint of more effectively achieving both an improvement in PM capture performance and suppression of an increase in pressure loss, it is preferably 1.00 mL / g or less, more preferably 0.80 mL / g or less, and further preferably 0.50 mL / g or less. These upper limits can be arbitrarily combined with the above lower limits respectively.

[0304] In Condition 4, the peak D is not particularly limited as long as it is 0.20 mL / g or more. From the viewpoint of more effectively achieving both an improvement in PM capture performance and suppression of an increase in pressure loss, it is preferably 0.30 mL / g or more, and more preferably 0.42 mL / g or more.

[0305] In Condition 4, the upper limit of the peak D is not particularly limited. From the viewpoint of more effectively achieving both an improvement in PM capture performance and suppression of an increase in pressure loss, it is preferably 1.00 mL / g or less, more preferably 0.80 mL / g or less, and further preferably 0.50 mL / g or less. These upper limits can be arbitrarily combined with the above-mentioned lower limits respectively.

[0306] <Effect of the catalyst for purifying exhaust gas>

[0307] The exhaust gas discharged from the internal combustion engine flows through the exhaust path in the exhaust pipe P from one end to the other end of the exhaust pipe P and is purified by the catalyst 1A disposed in the exhaust pipe P. At this time, the exhaust gas flowing in from the end portion (opening portion) on the exhaust gas inflow side of the inflow side chamber 13a passes through the first catalyst layer 20 and the porous partition portion 12, and / or through the porous partition portion 12 and the second catalyst layer 30, and / or through the first catalyst layer 20, the porous partition portion 12, and the second catalyst layer 30, and flows out from the end portion (opening portion) on the exhaust gas outflow side of the outflow side chamber 13b. This form is called a wall flow type.

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

[0309] In the above-mentioned modes (i) to (ix), the first catalyst layer 20 and the second catalyst layer 30 as a whole satisfy the following conditions: the peak A and / or C corresponding to the small pore diameter is 0.20 mL / g or more, and the peak B and / or D corresponding to the large pore diameter is 0.20 mL / g or more. Thereby, two kinds of pore diameter controls can be achieved, and both an improvement in PM capture performance and suppression of an increase in pressure loss can be achieved.

[0310] <Method for manufacturing catalyst for purifying exhaust gas>

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

[0312] The method according to this embodiment includes the following steps:

[0313] (1a) A step of coating a first slurry containing a first pore-forming agent on the inflow-side chamber side of the partition wall portion 12 of the substrate 10 to form a first precursor layer;

[0314] (1b) A step of coating a second slurry containing a second pore-forming agent on the outflow-side chamber side of the partition wall portion 12 of the substrate 10 to form a second precursor layer; and

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

[0316] <Step 1a>

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

[0318] The first slurry contains a first pore-forming agent. As the first pore-forming material, for example, crosslinked poly(methyl)acrylate particles, crosslinked poly(butyl acrylate) particles, crosslinked polystyrene particles, crosslinked polyacrylate particles, melamine-based resins, etc. can be cited.

[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 contains, for example, a supply source of platinum group elements, inorganic oxide particles, a binder, a solvent, etc. As the supply source of platinum group elements, for example, salts of platinum group elements can be cited. As salts of platinum group elements, for example, nitrates, ammonia complex salts, acetates, chlorides, etc. can be cited. The description of the inorganic oxide constituting the inorganic oxide particles is as above. As the binder, for example, alumina sol, zirconia sol, titanium dioxide sol, silica sol, ceria sol, etc. can be cited. As the solvent, for example, water, organic solvents, etc. can be cited. One solvent can be used, or a mixture of two or more solvents can be used.

[0320] The first precursor layer, which is a precursor of 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 on the inflow side chamber 13a side of the partition wall portion 12) and drying. 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 longer and 1 hour or shorter.

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

[0322] D 50 is the particle size at which the cumulative volume is 50% in the volume-based particle size distribution measured by the laser diffraction scattering method. The measurement of D 50 is carried out as follows: Using an automatic sampler of a laser diffraction scattering particle size distribution measuring device ("Microtorac SDC" manufactured by MicrotracBEL), the sample to be measured is put into an aqueous dispersion medium, and after irradiating ultrasonic waves of 40 W for 360 seconds at a flow rate of 32.5 mL / sec, it is measured using a laser diffraction scattering particle size distribution measuring device ("Microtrac MT3300EXII" manufactured by MicrotracBEL). The measurement is carried out twice under the conditions of particle refractive index: 1.5, particle shape: spherical, solvent refractive index: 1.3, zero setting: 30 seconds, and measurement time: 30 seconds, and the average value of the obtained measurement values is taken as D 50 . Pure water is used as the aqueous dispersion medium.

[0323] <Process 1b>

[0324] Process 1b is a process of forming a second precursor layer by applying a second slurry containing a second pore-forming agent to the outflow side chamber 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. The second slurry contains, for example, a supply source of platinum group elements, inorganic oxide particles, a binder, a solvent, etc., in addition to the second pore former. Examples of the supply source of platinum group elements include salts of platinum group elements, and examples of salts of platinum group elements include nitrates, ammonia complex salts, acetates, chlorides, etc. The description of the inorganic oxide constituting the inorganic oxide particles is as described above. Examples of the binder include alumina sol, zirconia sol, titanium dioxide sol, silica sol, ceria sol, etc. Examples of the solvent include water, organic solvents, etc. One solvent can be used, or a mixture of two or more solvents can be used.

[0327] By applying the second slurry to the exhaust gas outflow side of the partition portion 12 of the substrate 10 (i.e., the outer surface S1b on the outflow side chamber 13b side of the partition portion 12) and drying, a second precursor layer as a precursor of the second catalyst layer 30 is formed. 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 longer and 1 hour or shorter.

[0328] The particle size of the second pore-forming material can be appropriately adjusted. The median particle size D 50 of the second pore-forming material is preferably 0.1 μm or more and 20 μm or less, more preferably 0.5 μm or more and 17 μm or less, and further preferably 1.5 μm or more and 15 μm or less. By adjusting the particle size, amount, etc. 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 condition 3 and 4 can be formed. The meaning and measurement method of D 50 are the same as those described above.

[0329] <Process 1c>

[0330] Process 1c is a 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] By calcining the first precursor layer and the second precursor layer, the first catalyst layer 20 and the second catalyst layer 30 are respectively formed. 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 longer and 5 hours or shorter. The atmosphere during calcination is usually an air atmosphere.

[0332] By calcining the first precursor layer, the first pore former disappears, and pores are formed in the first catalyst layer 20. By calcining the second precursor layer, the second pore former disappears, and pores are formed in the second catalyst layer 30. By adjusting the particle size, amount, etc. of the first pore-forming material and the second pore-forming material, 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). Thereby, it is possible to sufficiently ensure the amount of pores contributing to PM capture performance and the amount of pores contributing to reducing the pressure loss, and it is possible to achieve both an improvement in PM capture performance and an inhibition of an increase in pressure loss. When the method according to this embodiment satisfies the following conditions (C1) to (C7), the method according to this embodiment is particularly suitable for the production of the above-described modes (i) to (ix).

[0334] (C1) The median diameter D of one of the first pore-forming agent and the second pore-forming agent 50 is greater than 4 μm, and the median diameter D of the other 50 is 4 μm or less.

[0335] (C2) The first slurry contains inorganic oxide particles, and the median diameter D of the inorganic oxide particles contained in the first slurry 50 is 1 μm or more and 20 μm or less.

[0336] (C3) Based on the mass (mass after calcination) of the first catalyst layer 20, 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.

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

[0338] (C5) The second slurry contains inorganic oxide particles, and the median diameter D of the inorganic oxide particles contained in the second slurry 50 is 1 μm or more and 20 μm or less.

[0339] (C6) Based on the mass (mass after calcination) of the second catalyst layer 30, 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.

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

[0341] The following describes the condition (C1).

[0342] From the viewpoint of more effectively achieving both an improvement in PM capture performance and an inhibition of an increase in pressure loss, the D of the pore-forming agent of one 50 is more preferably 4.5 μm or more and 20 μm or less, further preferably 4.5 μm or more and 17 μm or less, and further preferably 4.5 μm or more and 15 μm or less.

[0343] From the viewpoint of more effectively achieving both an improvement in PM capture performance and suppression of an increase in pressure loss, the D of the pore former for the other one 50 is more preferably 0.1 μm or more and 4 μm or less, further preferably 0.5 μm or more and 4 μm or less, and still further preferably 1.5 μm or more and 4 μm or less.

[0344] The following describes the condition (C2).

[0345] From the viewpoint of more effectively achieving both an improvement in PM capture performance and suppression of an increase in pressure loss, the median particle diameter D of the inorganic oxide particles contained in the first slurry 50 is more preferably 1.5 μm or more and 15 μm or less, and further preferably 2 μm or more and 10 μm or less.

[0346] The following describes the condition (C3).

[0347] From the viewpoint of more effectively achieving both an improvement in PM capture performance and suppression of an increase in pressure loss, based on the mass (mass after calcination) of the first catalyst layer 20, the amount of the first pore former contained in the first precursor layer is more preferably 20% by mass or more and 50% by mass or less, and further preferably 25% by mass or more and 45% by mass or less. The amount of the first pore former contained in the first precursor layer can be adjusted by adjusting the amount of the first pore former contained in the first slurry, the amount of the first slurry applied to the inflow side chamber side of the partition portion 12 of the substrate 10, and the like. It should be noted that the mass of the first catalyst layer 20 is obtained by subtracting the mass of the components (such as solvents, pore formers, etc.) that disappear due to drying and calcination of the first slurry from the mass of the first slurry applied to the inflow side chamber side of the partition portion 12 of the substrate 10.

[0348] The following describes the condition (C4).

[0349] From the viewpoint of more effectively achieving both an improvement in PM capture performance and suppression of an increase in pressure loss, the mass (mass after calcination) of the first catalyst layer 20 per unit volume of the portion of the substrate 10 where the first catalyst layer 20 is formed is more preferably 10 g / L or more and 100 g / L or less, and further 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 where the first catalyst layer 20 is formed can be adjusted by adjusting the amount of the first slurry applied to the inflow side chamber side of the partition portion 12 of the substrate 10 and the like.

[0350] The following describes the condition (C5).

[0351] From the viewpoint of more effectively achieving both an improvement in PM capture performance and suppression of an increase in pressure loss, the median particle diameter D of the inorganic oxide particles contained in the second slurry 50 is more preferably 1.5 μm or more and 15 μm or less, and further preferably 2 μm or more and 10 μm or less.

[0352] The following describes the condition (C6).

[0353] From the viewpoint of more effectively achieving both an improvement in PM capture performance and suppression of an increase in pressure loss, based on the mass (mass after calcination) of the second catalyst layer 30, the amount of the second pore former contained in the second precursor layer is more preferably 20% by mass or more and 50% by mass or less, and further preferably 25% by mass or more and 45% by mass or less. The amount of the second pore former contained in the second precursor layer can be adjusted by adjusting the amount of the second pore former 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, and the like. It should be noted that the mass of the second catalyst layer 30 is obtained by subtracting the mass of the components (such as solvents, pore formers, etc.) that disappear due to 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 describes the condition (C7).

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

[0356] 《Second Embodiment》

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

[0358] As Figure 8 and 9As shown, the exhaust gas purification catalyst 1B (hereinafter referred to as "catalyst 1B") according to the second embodiment is different from catalyst 1A in that the second catalyst layer 30 has a laminated 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. When the second catalyst layer 30 has a laminated structure, the PM trapping performance can be improved more than when the second catalyst layer 30 has a single-layer structure.

[0359] In catalyst 1B, the same components as those in catalyst 1A are denoted by the same reference numerals as those in catalyst 1A. Hereinafter, unless otherwise specified, the above description regarding catalyst 1A also applies to catalyst 1B. When applicable, it is understood by replacing "catalyst 1A" with "catalyst 1B".

[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 when performing the mercury intrusion method includes a part of the partition wall portion 12 and a part of the second catalyst layer 30 (a part of the lower layer 31 and a part of the upper layer 32), but does not include the first catalyst layer 20. Other contents regarding the slice M2 are the same as above.

[0362] <Lower layer>

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

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

[0365] As Figure 8 and 9 shown, preferably, at least a part of the lower layer 31 bulges toward the outflow side chamber 13b side from the outer surface S1b of the partition wall portion 12, that is, the lower layer 31 has a portion (hereinafter referred to as "bulging portion") that bulges toward the outflow side chamber 13b side from the outer surface S1b of the partition wall portion 12. Thereby, the contact between the exhaust gas and PM is improved, and the improvement of the exhaust gas purification performance and the PM trapping performance can be achieved more effectively.

[0366] The lower layer 31 may be composed only of raised portions, or may have, in addition to raised portions, portions (hereinafter referred to as "inner portions") existing inside the partition wall portion 12. Since the partition wall portion 12 is porous, the inner portions may sometimes be formed together with the raised portions when forming the lower layer 31. The raised portions and the inner portions may be continuous. The lower layer 31 may also be composed only of inner portions. "The lower layer 31 is provided on the outflow side chamber 13b side of the partition wall portion 12" includes all of the following embodiments: an embodiment in which the lower layer 31 is composed only of raised portions, an embodiment in which the lower layer 31 is composed only of inner portions, and an embodiment in which the lower layer 31 has both raised portions and inner portions.

[0367] The above description of the method for determining the raised portions and inner portions of the first catalyst layer 20 also applies to the lower layer 31. When applying, replace "the first catalyst layer 20" with "the lower layer 31" for understanding.

[0368] From the viewpoint of achieving a good balance between exhaust gas purification performance and cost, the mass (mass after calcination) of the lower layer 31 per unit volume of the portion of the substrate 10 where the lower layer 31 is formed 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 still 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 where the lower layer 31 is formed is calculated by the following formula: (mass of the lower layer 31) / ((volume of the substrate 10)×(average length L of the lower layer 31 31 / length L of the substrate 10 10 ))

[0369] The above description of the mass of the first catalyst layer 20 also applies to the lower layer 31. When applying, replace "the first catalyst layer 20" with "the 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 measurement method of the average length L of the lower layer 31 31 When applying, replace "the first catalyst layer 20" with "the lower layer 31" for understanding, and replace "average length L 20 " with "average length L 31 ". However, in the measurement method of the average length L of the lower layer 31 31 Samples are cut at 5 mm intervals with a plane perpendicular to the axial direction of the substrate 10, and the first slice, the second slice,..., the nth slice are sequentially obtained from the end side on the exhaust gas outflow side of the sample.

[0371] The average length L of the lower layer 31 31It can be appropriately adjusted in consideration of the exhaust gas purification performance, PM trapping performance, etc. From the viewpoint of improving the exhaust gas purification performance and PM trapping performance, the average length L of the lower layer 31 31 relative to the length L of the substrate 10 10 as a percentage (L 31 / L 10 × 100) is preferably 15% or more and 90% or less, more preferably 20% or more and 90% or less, and still more preferably 30% or more and 85% or less.

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

[0373] The lower layer 31 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 equivalent amounts also applies to the platinum group elements contained in the lower layer 31 and their metal equivalent amounts. When applicable, understand by replacing "the first catalyst layer 20" with "the lower layer 31".

[0374] In one embodiment, the lower layer 31 contains Pd. In addition to Pd, the lower layer 31 may further contain one or more other platinum group elements. The embodiment where the lower layer 31 contains Pd can be combined with the embodiment where the first catalyst layer 20 contains Rh.

[0375] The lower layer 31 preferably contains one or more carriers, and at least a part of the catalytic active component is supported on one or more carriers. The meaning and confirmation method of support are the same as above.

[0376] The above description regarding the carriers contained in the first catalyst layer 20 also applies to the carriers contained in the lower layer 31. When applicable, understand by replacing "the first catalyst layer 20" with "the lower layer 31".

[0377] The lower layer 31 may contain other components such as binders and stabilizers. The description of binders and stabilizers is the same as above.

[0378] <Upper layer>

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

[0380] “The upper layer 32 is arranged on the lower layer 31” means that, of the two main surfaces of the lower layer 31, part or all of the upper layer 32 exists on the main surface on the opposite side to the main surface on the side of the partition wall portion 12. “The main surface of the lower layer 31” refers to the outer surface of the lower layer 31 extending along the exhaust gas flow direction E. The upper layer 32 can be directly arranged on the main surface of the lower layer 31, or it can be arranged through other layers, but it is usually arranged directly on the main surface of the lower layer 31. The upper layer 32 can be arranged in a manner covering a part of the main surface of the lower layer 31, or it can be arranged in a manner covering the entire main surface of the lower layer 31. “The upper layer 32 is arranged on the lower layer 31” includes both an embodiment in which the upper layer 32 is directly arranged on the main surface of the lower layer 31 and an embodiment in which the upper layer 32 is arranged on the main surface of the lower layer 31 through other layers.

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

[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 further 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 the upper layer 32) / ((volume of the substrate 10)×(average length L of the upper layer 32) 32 / length L of substrate 10 10 )).

[0383] The above description about the mass of the first catalyst layer 20 also applies to the upper layer 32. When applicable, "first catalyst layer 20" is replaced with "upper layer 32".

[0384] 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 upper layer 32 32 When applicable, replace "first catalyst layer 20" with "upper layer 32" and replace "average length L 20 " is replaced by "average length L 32 " However, the average length L of the upper layer 32 32In the measurement method, the sample is cut at intervals of 5 mm using a plane perpendicular to the axis of the substrate 10, and the first slice, the second slice, ……, the nth slice are sequentially obtained from the end side on the exhaust gas outflow side of the sample.

[0385] The average length L of the upper layer 32 32 It can be appropriately adjusted in consideration of the exhaust gas purification performance, PM capture performance, etc. From the viewpoint of improving the 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 ×100) is preferably 15% or more and 90% or less, more preferably 20% or more and 90% or less, and further preferably 30% or more and 85% or less.

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

[0387] The upper layer 32 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 equivalent amounts also applies to the platinum group elements contained in the upper layer 32 and their metal equivalent amounts. When applicable, replace "the first catalyst layer 20" with "the upper layer 32" for understanding.

[0388] In one embodiment, the upper layer 32 contains Rh. In addition to Rh, the upper layer 32 may further contain one or more other platinum group elements. The embodiment in which the upper layer 32 contains Rh can be combined with the embodiment in which the first catalyst layer 20 contains Rh and / or the embodiment in which the lower layer 31 contains Pd.

[0389] The upper layer 32 preferably contains one or more carriers, and at least a part of the catalytically active component is supported on one or more carriers. The meaning and confirmation method of support are the same as above.

[0390] The above description regarding the carriers contained in the first catalyst layer 20 also applies to the carriers contained in the upper layer 32. When applicable, replace "the first catalyst layer 20" with "the upper layer 32" for understanding.

[0391] The upper layer 32 may contain other components such as a binder and a stabilizer. The descriptions of the binder and the stabilizer are the same as those above.

[0392] <Method for Manufacturing Catalyst for Exhaust Gas Purification>

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

[0394] The method according to this embodiment includes the following steps:

[0395] (2a) A step of coating a first slurry containing a first pore-forming agent on the inflow-side chamber side of the partition wall portion 12 of the substrate 10 to form a first precursor layer;

[0396] (2b) A step of coating a third slurry containing a third pore-forming agent on the outflow-side chamber side of the partition wall portion 12 of the substrate to form a third precursor layer;

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

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

[0399] <Step 2a>

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

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

[0402] <Step 2b>

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

[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 former, the third slurry contains, for example, a supply source of platinum group elements, inorganic oxide particles, a binder, a solvent, etc. As the supply source of platinum group elements, salts of platinum group elements can be cited, and as the salts of platinum group elements, nitrates, ammonia complex salts, acetates, chlorides, etc. can be cited. The description of the inorganic oxide constituting the inorganic oxide particles is as described above. As the binder, alumina sol, zirconia sol, titanium dioxide sol, silica sol, ceria sol, etc. can be cited. As the solvent, water, organic solvents, etc. can be cited. One solvent can be used, or a mixture of two or more solvents can be used.

[0406] By applying the third slurry to the exhaust gas outflow side of the partition wall portion 12 of the substrate 10 (i.e., the outer surface S1b on the outflow side chamber 13b side of the partition wall portion 12) and drying, a third precursor layer, which is a precursor of the lower layer 31 of the second catalyst layer 30, is formed. 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 longer and 1 hour or shorter.

[0407] The particle size of the third pore-forming material can be appropriately adjusted. The median particle size D 50 is preferably 0.1 μm or more and 20 μm or less, more preferably 0.5 μm or more and 17 μm or less, and further preferably 1.5 μm or more and 15 μm or less. By adjusting the particle size, amount, etc. 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. The meaning and measurement method of D 50 are the same as those described above.

[0408] <Process 2c>

[0409] Process 2c is a process of applying a fourth slurry containing a fourth pore former to the third precursor layer to form a fourth precursor layer.

[0410] The fourth slurry contains a fourth pore former. 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. The fourth slurry contains, for example, a supply source of platinum group elements, inorganic oxide particles, a binder, a solvent, etc., in addition to the fourth pore former. As the supply source of platinum group elements, for example, salts of platinum group elements can be cited, and as the salts of platinum group elements, for example, nitrates, ammonia complex salts, acetates, chlorides, etc. can be cited. The description of the inorganic oxide constituting the inorganic oxide particles is as described above. As the binder, for example, alumina sol, zirconia sol, titanium dioxide sol, silica sol, ceria sol, etc. can be cited. As the solvent, for example, water, organic solvents, etc. can be cited. One solvent can be used, or a mixture of two or more solvents can be used.

[0412] By coating the fourth slurry on the third precursor layer and drying it, a fourth precursor layer, which is a precursor of the upper layer 32 of the second catalyst layer 30, is formed. 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 longer and 1 hour or shorter.

[0413] The particle size of the fourth pore-forming material can be appropriately adjusted. The median particle size D 50 is preferably 0.1 μm or more and 20 μm or less, more preferably 0.5 μm or more and 17 μm or less, and further preferably 1.5 μm or more and 15 μm or less. By adjusting the particle size, amount, etc. 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, amount, etc. of the third pore-forming material and / or the particle size, amount, etc. 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. The meaning and measurement method of D 50 are the same as those described above.

[0414] <Process 2d>

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

[0416] By baking the first precursor layer, the third precursor layer, and the fourth precursor layer, the first catalyst layer 20, the lower layer 31 of the second catalyst layer 30, and the upper layer 32 of the second catalyst layer 30 are respectively formed. The baking temperature is, for example, 350°C or higher and 600°C or lower, and the baking time is, for example, 20 minutes or longer and 5 hours or shorter. The atmosphere during baking is usually an air atmosphere.

[0417] By calcining the first precursor layer, the first pore former disappears, thereby forming pores in the first catalyst layer 20. By calcining the third precursor layer, the third pore former disappears, thereby forming pores in the lower layer 31 of the second catalyst layer 30. By calcining the fourth precursor layer, the fourth pore former disappears, thereby forming pores in the upper layer 32 of the second catalyst layer 30. By adjusting the particle diameters, amounts, etc. of the first pore-forming material, the third pore-forming material, and the fourth pore-forming material, the 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). Thereby, it is possible to sufficiently ensure the amount of pores contributing to the PM trapping performance and the amount of pores contributing to the reduction of the pressure loss, and it is possible to achieve both an improvement in the PM trapping performance and an inhibition of the increase in the pressure loss. When the method according to this embodiment satisfies the following conditions (D1) to (D10), the method according to this embodiment is particularly suitable for the manufacturing of the above-mentioned modes (i) to (ix).

[0419] (D1) The median diameter D of one or both of the first pore former, the third pore former, and the fourth pore former 50 is greater than 4 μm, and the median diameter D of the remaining two or one 50 is 4 μm or less.

[0420] (D2) The first slurry contains inorganic oxide particles, and the median diameter D of the inorganic oxide particles contained in the first slurry 50 is 1 μm or more and 20 μm or less.

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

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

[0423] (D5) The third slurry contains inorganic oxide particles, and the median diameter D of the inorganic oxide particles contained in the third slurry 50 is 1 μm or more and 20 μm or less.

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

[0425] (D7) The mass (mass after calcination) of the lower layer 31 per unit volume of the portion of the substrate 10 where the lower layer 31 is formed 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 50 is 1 μm or more and 20 μm or less.

[0427] (D9) Based on the mass of the upper layer 32 (mass after baking), the amount of the fourth pore former contained in the fourth precursor layer is 10% by mass or more and 60% by mass or less.

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

[0429] The following describes the condition (D1).

[0430] When the median particle size D of one of the first pore former, the third pore former, and the fourth pore former 50 is greater than 4 μm, the median particle size D of the remaining two 50 is 4 μm or less. When the median particle size D of two of the first pore former, the third pore former, and the fourth pore former 50 is greater than 4 μm, the median particle size D of the remaining one 50 is 4 μm or less.

[0431] From the viewpoint of more effectively achieving both the improvement of PM capture performance and the suppression of the increase in pressure loss, the D of the pore former of one or two of the first pore former, the third pore former, and the fourth pore former 50 is more preferably 4.5 μm or more and 20 μm or less, further preferably 4.5 μm or more and 17 μm or less, and further preferably 4.5 μm or more and 15 μm or less.

[0432] From the viewpoint of more effectively achieving both the improvement of PM capture performance and the suppression of the increase in pressure loss, the D of the pore former of the remaining two or one 50 is more preferably 0.1 μm or more and 4 μm or less, further preferably 0.5 μm or more and 4 μm or less, and further preferably 1.5 μm or more and 4 μm or less.

[0433] The following describes the condition (D2).

[0434] From the viewpoint of more effectively achieving both the improvement of PM capture performance and the suppression of the increase in pressure loss, the median particle size D of the inorganic oxide particles contained in the first slurry 50 is more preferably 1.5 μm or more and 15 μm or less, and further preferably 2 μm or more and 10 μm or less.

[0435] The following describes the condition (D3).

[0436] From the viewpoint of more effectively achieving both an improvement in PM trapping performance and suppression of an increase in pressure loss, based on the mass (mass after calcination) of the first catalyst layer 20, 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 further 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, and the like. It should be noted that the mass of the first catalyst layer 20 is obtained by subtracting the mass of the components (such as solvents, pore-forming agents, etc.) that disappear due to 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 describes the condition (D4).

[0438] From the viewpoint of more effectively achieving both an improvement in PM trapping performance and suppression of an increase in pressure loss, the mass (mass after calcination) of the first catalyst layer 20 per unit volume of the portion of the substrate 10 where the first catalyst layer 20 is formed is more preferably 10 g / L or more and 100 g / L or less, and further 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 where 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 and the like.

[0439] The following describes the condition (D5).

[0440] From the viewpoint of more effectively achieving both an improvement in PM trapping performance and suppression of an increase in pressure loss, the median particle size D of the inorganic oxide particles contained in the third slurry 50 is more preferably 1.5 μm or more and 15 μm or less, and further preferably 2 μm or more and 10 μm or less.

[0441] The following describes the condition (D6).

[0442] From the viewpoint of more effectively achieving both an improvement in PM capture performance and suppression of an increase in pressure loss, based on the mass of the lower layer 31 (mass after firing), the amount of the third pore former contained in the third precursor layer is more preferably 20% by mass or more and 50% by mass or less, and further preferably 25% by mass or more and 45% by mass or less. The amount of the third pore former contained in the third precursor layer can be adjusted by adjusting the amount of the third pore former contained in the third slurry, the amount of the third slurry coated on the outflow side chamber side of the partition wall portion 12 of the substrate 10, and the like. It should be noted that the mass of the lower layer 31 is obtained by subtracting the mass of the components (such as solvents, pore formers, etc.) that disappear due to drying and firing of the third slurry from the mass of the third slurry coated on the outflow side chamber side of the partition wall portion 12 of the substrate 10.

[0443] The following describes the condition (D7).

[0444] From the viewpoint of more effectively achieving both an improvement in PM capture performance and suppression of an increase in pressure loss, the mass (mass after firing) of the lower layer 31 per unit volume of 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 further 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 where the lower layer 31 is formed can be adjusted by adjusting the amount of the third slurry coated on the outflow side chamber side of the partition wall portion 12 of the substrate 10, and the like.

[0445] The following describes the condition (D8).

[0446] From the viewpoint of more effectively achieving both an improvement in PM capture performance and suppression of an increase in pressure loss, the median particle diameter D of the inorganic oxide particles contained in the fourth slurry 50 is more preferably 1.5 μm or more and 15 μm or less, and further preferably 2 μm or more and 10 μm or less.

[0447] The following describes the condition (D9).

[0448] From the viewpoint of more effectively achieving both an improvement in PM capture performance and suppression of an increase in pressure loss, based on the mass of the upper layer 32 (mass after firing), the amount of the fourth pore former contained in the fourth precursor layer is more preferably 20% by mass or more and 50% by mass or less, and further preferably 25% by mass or more and 45% by mass or less. The amount of the fourth pore former contained in the fourth precursor layer can be adjusted by adjusting the amount of the fourth pore former contained in the fourth slurry, the amount of the fourth slurry coated on the third precursor layer, and the like. It should be noted that the mass of the upper layer 32 is obtained by subtracting the mass of the components (such as solvents, pore formers, etc.) that disappear due to drying and firing of the fourth slurry from the mass of the fourth slurry coated on the third precursor layer.

[0449] The following describes condition (D10).

[0450] From the viewpoint of more effectively achieving both an improvement in PM capture performance and suppression of an increase in pressure loss, the mass (mass after baking) of the upper layer 32 per unit volume of 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 still 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 can be adjusted by adjusting the amount of the fourth slurry coated on the third precursor layer or the like.

[0451] When the median particle size D of the third pore former 50 is larger than the median particle size D of the fourth pore former 50 , it becomes difficult for the third slurry to enter the pores in the partition wall portion 12, and it is easy to achieve an embodiment in which at least a part of the lower layer 31 bulges from the outer surface S1b of the partition wall portion 12 toward the outflow side chamber 13b (that is, an embodiment in which the lower layer 31 has a portion that bulges from the outer surface S1b of the partition wall portion 12 toward the outflow side chamber 13b). Therefore, when using a pore former with a median particle size D 50 larger than 4 μm and a pore former with a median particle size D 50 of 4 μm or less, it is preferable to use the pore former with a median particle size D 50 larger than 4 μm as the third pore former and the pore former with a median particle size D 50 of 4 μm or less as the fourth pore former.

[0452] When the median particle size D of the third pore former 50 is larger than 4 μm and the median particle size D of the fourth pore former 50 is 4 μm or less, a sufficient amount of pores contributing to PM capture performance and / or a sufficient amount of pores contributing to pressure loss reduction can be ensured in the second catalyst layer 30. In addition, when the median particle size D of the third pore former 50 is larger than 4 μm and the median particle size D of the fourth pore former 50 is 4 μm or less, the second catalyst layer 30 that satisfies either condition 3 or 4, or the second catalyst layer 30 that satisfies both condition 3 and 4, particularly the second catalyst layer 30 that satisfies both condition 3 and 4, can be formed more efficiently.

[0453] The D of the third pore former 50 is not particularly limited as long as it is larger than 4 μm. From the viewpoint of more effectively achieving both an improvement in PM capture performance and suppression of an increase in pressure loss, it is preferably 4.5 μm or more and 20 μm or less, more preferably 4.5 μm or more and 17 μm or less, and still more preferably 4.5 μm or more and 15 μm or less.

[0454] D of the fourth pore former 50 There is no particular limitation as long as it is 4 μm or less. From the viewpoint of more effectively achieving both an improvement in PM capture performance and suppression of an increase in pressure loss, it is preferably 0.1 μm or more and 4 μm or less, more preferably 0.5 μm or more and 4 μm or less, and still more preferably 1.5 μm or more and 4 μm or less.

[0455] <<Third Embodiment>>

[0456] Hereinafter, based on Figure 10 and 11 , the third embodiment of the present invention will be described.

[0457] As Figure 10 and 11 shown, the exhaust gas purification catalyst 1C (hereinafter referred to as "catalyst 1C") according to the third embodiment is different from the catalyst 1A in that the first catalyst layer 20 has a laminated 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. When the first catalyst layer 20 has a laminated structure, the PM capture performance can be improved more than when the first catalyst layer 20 has a single-layer structure.

[0458] In the catalyst 1C, the same components as those in the catalyst 1A are denoted by the same reference numerals as those in the catalyst 1A. Hereinafter, unless otherwise specified, the above description regarding the catalyst 1A also applies to the catalyst 1C. When applicable, it is understood by replacing "catalyst 1A" with "catalyst 1C".

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

[0460] The slice M1 used when performing the mercury intrusion method includes a part of the partition wall portion 12 and a part of the first catalyst layer 20 (a part of the lower layer 21 and a part of the upper layer 22), but does not include the second catalyst layer 30. Other contents of the slice M1 are the same as above.

[0461] <Lower layer>

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

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

[0464] As Figure 10 and 11 shown, it is preferable that at least a part of the lower layer 21 bulges from the outer surface S1a of the partition wall portion 12 toward the inflow side chamber 13a side, that is, the lower layer 21 has a part that bulges from the outer surface S1a of the partition wall portion 12 toward the inflow side chamber 13a side (hereinafter referred to as "bulging part"). Thereby, the contact between the exhaust gas and the PM is improved, and the improvement of the exhaust gas purification performance and the improvement of the PM trapping performance can be more effectively achieved.

[0465] The lower layer 21 may be composed only of the bulging part, or may have a part existing inside the partition wall portion 12 (hereinafter referred to as "inner part") while having the bulging part. Since the partition wall portion 12 is porous, the inner part may sometimes be formed together with the bulging part when the lower layer 21 is formed. The bulging part and the inner part may be continuous. The lower layer 21 may also be composed only of the inner part. "The lower layer 21 is provided on the inflow side chamber 13a side of the partition wall portion 12" includes all of the embodiments in which the lower layer 21 is composed only of the bulging part, the embodiments in which the lower layer 21 is composed only of the inner part, and the embodiments in which the lower layer 21 has the bulging part and the inner part.

[0466] The above description of the method for determining the bulging part and the inner part of the first catalyst layer 20 also applies to the lower layer 21. When applicable, it is understood by replacing "the first catalyst layer 20" with "the lower layer 21".

[0467] From the viewpoint of achieving a good balance between the exhaust gas purification performance and the cost, the mass (mass after calcination) of the lower layer 21 per unit volume of the portion of the base material 10 where the lower layer 21 is formed 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 still 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 base material 10 where the lower layer 21 is formed is calculated by the following formula: (mass of the lower layer 21) / ((volume of the base material 10) × (average length L of the lower layer 21 21 / length L of the base material 10 10 ))).

[0468] The above description of the mass of the first catalyst layer 20 also applies to the lower layer 21. When applicable, it is understood by replacing "the first catalyst layer 20" with "the lower layer 21".

[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 of the measurement method. When applicable, understand by replacing "the first catalyst layer 20" with "the lower layer 21", and replacing "the average length L 20 " with "the average length L 21 ".

[0470] The average length L of the lower layer 21 21 can be appropriately adjusted in consideration of the exhaust gas purification performance, PM trapping performance, etc. From the viewpoint of improving the exhaust gas purification performance and PM trapping performance, the average length L of the lower layer 21 21 relative to the length L of the substrate 10 10 percentage (L 21 / L 10 ×100) is preferably 15% or more and 90% or less, more preferably 20% or more and 90% or less, and still more preferably 30% or more and 85% or less.

[0471] From the viewpoint of improving the exhaust gas purification performance and PM trapping performance, the average length L of the second catalyst layer 30 30 and the sum of the average length L of the lower layer 21 21 relative to the length L of the substrate 10 10 percentage ((L 30 +L 21 ) / L 10 ×100) is preferably 100% or more and 180% or less, more preferably 100% or more and 170% or less, and still 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 contained in the first catalyst layer 20 and their metal equivalent amounts also applies to the platinum group elements contained in the lower layer 21 and their metal equivalent amounts. When applicable, understand by replacing "the first catalyst layer 20" with "the lower layer 21".

[0473] In one embodiment, the lower layer 21 contains Pd. In addition to Pd, the lower layer 21 may further contain one or more other platinum group elements. The embodiment in which the lower layer 21 contains Pd can be combined with the embodiment in which the second catalyst layer 30 contains Rh.

[0474] The lower layer 21 preferably contains one or more carriers, and at least a part of the catalytic active component is supported on one or more carriers. The meaning and confirmation method of the support are the same as above.

[0475] The above description of the carriers contained in the first catalyst layer 20 also applies to the carriers contained in the lower layer 21. When applicable, understand by replacing "the first catalyst layer 20" with "the lower layer 21".

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

[0477] <Upper layer>

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

[0479] "The upper layer 22 is disposed on the lower layer 21" means that in the two main surfaces of the lower layer 21, part or all of the upper layer 22 exists on the main surface opposite to the main surface on the side of the partition wall portion 12. "The main surface of the lower layer 21" refers to the outer surface of the lower layer 21 extending along the exhaust gas flow direction E. The upper layer 22 may be directly disposed on the main surface of the lower layer 21 or may be disposed with other layers therebetween, but usually it is directly disposed on the main surface of the lower layer 21. The upper layer 22 may be disposed in such a manner as to cover a part of the main surface of the lower layer 21 or in such a manner as to cover the entire main surface of the lower layer 21. "The upper layer 22 is disposed on the lower layer 21" includes both the embodiment in which the upper layer 22 is directly disposed on the main surface of the lower layer 21 and the embodiment in which the upper layer 22 is disposed on the main surface of the lower layer 21 with other layers therebetween.

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

[0481] From the viewpoint of achieving a good balance between the exhaust gas purification performance and the cost, the mass (mass after calcination) of the upper layer 22 per unit volume of the portion of the substrate 10 where the upper layer 22 is formed 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 further 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 by the following formula: (mass of the upper layer 22) / ((volume of the substrate 10) × (average length L of the upper layer 22 22 / length L of the substrate 10 10 ))).

[0482] The above description regarding the mass of the first catalyst layer 20 also applies to the upper layer 22. When applicable, understand by replacing "the first catalyst layer 20" with "the upper layer 22".

[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 2222 Measurement method. When applicable, understand by replacing "the first catalyst layer 20" with "the upper layer 22", and replacing "average length L 20 " with "average length L 22 ".

[0484] The average length L of the upper layer 22 22 can be appropriately adjusted in consideration of exhaust gas purification performance, PM trapping performance, etc. From the viewpoint of improving exhaust gas purification performance and PM trapping performance, the average length L of the upper layer 22 22 relative to the length L of the substrate 10 10 percentage (L 22 / L 10 ×100) is preferably 15% or more and 90% or less, more preferably 20% or more and 90% or less, and still more preferably 30% or more and 85% or less.

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

[0486] The upper layer 22 contains one or more platinum group elements. The above description regarding the platinum group elements and their metal equivalent amounts contained in the first catalyst layer 20 also applies to the platinum group elements and their metal equivalent amounts contained in the upper layer 22. When applicable, understand by replacing "the first catalyst layer 20" with "the upper layer 22".

[0487] In one embodiment, the upper layer 22 contains Rh. In addition to Rh, the upper layer 22 may further contain one or more other platinum group elements. The embodiment in which the upper layer 22 contains Rh can be combined with the embodiment in which the second catalyst layer 30 contains Rh and / or the embodiment in which the lower layer 21 contains Pd.

[0488] The upper layer 22 preferably contains one or more carriers, and at least a part of the catalytic active component is supported on one or more carriers. The meaning and confirmation method of support are the same as above.

[0489] The above description regarding the carriers contained in the first catalyst layer 20 also applies to the carriers contained in the upper layer 22. When applicable, understand by replacing "the first catalyst layer 20" with "the upper layer 22".

[0490] The upper layer 22 may contain other components such as a binder and a stabilizer. The descriptions of the binder and the stabilizer are the same as those above.

[0491] <Method for manufacturing catalyst for purifying exhaust gas>

[0492] Hereinafter, an embodiment of the method for manufacturing the catalyst 1C will be described. The catalyst 1C manufactured by the method according to this embodiment also includes modes other than the above modes (i) to (ix). The method according to this embodiment is suitable for the manufacturing of the above modes (i) to (ix).

[0493] The method according to this embodiment includes the following steps:

[0494] (3a) A step of coating a second slurry containing a second pore former on the outflow side chamber side of the partition wall portion 12 of the substrate 10 to form a second precursor layer;

[0495] (3b) A step of coating a fifth slurry containing a fifth pore former on the inflow side chamber side of the partition wall portion 12 of the substrate to form a fifth precursor layer;

[0496] (3c) A step of coating a sixth slurry containing a sixth pore former on the fifth precursor layer to form a sixth precursor layer; and

[0497] (3d) A step of baking 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) may be carried out before steps (3b) to (3c), or may be carried out after steps (3b) to (3c). Step (3b) is carried out before step (3c). Step (3d) is carried out after steps (3a) to (3c).

[0498] <Step 3a>

[0499] Step 3a is a step of coating a second slurry containing a second pore former on the outflow side chamber side of the partition wall portion 12 of the substrate 10 to form a second precursor layer.

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

[0501] <Step 3b>

[0502] Step 3b is a step of coating a fifth slurry containing a fifth pore former on the inflow side chamber side of the partition wall portion 12 of the substrate to form a fifth precursor layer.

[0503] The fifth slurry contains a fifth pore former. 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 former, the fifth slurry contains, for example, a supply source of platinum group elements, inorganic oxide particles, a binder, a solvent, etc. As the supply source of platinum group elements, for example, salts of platinum group elements can be cited. As the salts of platinum group elements, for example, nitrates, ammonia complex salts, acetates, chlorides, etc. can be cited. The description of the inorganic oxide constituting the inorganic oxide particles is as described above. As the binder, for example, alumina sol, zirconia sol, titanium dioxide sol, silica sol, ceria sol, etc. can be cited. As the solvent, for example, water, organic solvents, etc. can be cited. One solvent can be used, or a mixture of two or more solvents can be used.

[0505] By applying the fifth slurry to the exhaust gas inflow side of the partition wall portion 12 of the substrate 10 (that is, the outer surface S1a on the inflow side chamber 13a side of the partition wall portion 12) and drying, a fifth precursor layer, which is a precursor of the lower layer 21 of the first catalyst layer 20, is formed. 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 longer and 1 hour or shorter.

[0506] The particle size of the fifth pore-forming material can be appropriately adjusted. The median particle size D 50 of the fifth pore-forming material is preferably 0.1 μm or more and 20 μm or less, more preferably 0.5 μm or more and 17 μm or less, and further preferably 1.5 μm or more and 15 μm or less. By adjusting the particle size, amount, etc. 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. The meaning and measurement method of D 50 are the same as those described above.

[0507] <Process 3c>

[0508] Process 3c is a process of applying a sixth slurry containing a sixth pore former onto the fifth precursor layer to form a sixth precursor layer.

[0509] The sixth slurry contains a sixth pore former. 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. The sixth slurry contains, for example, a supply source of platinum group elements, inorganic oxide particles, a binder, a solvent, etc., in addition to the sixth pore-forming agent. Examples of the supply source of platinum group elements include salts of platinum group elements. Examples of salts of platinum group elements include nitrates, ammonia complex salts, acetates, chlorides, etc. The description of the inorganic oxide constituting the inorganic oxide particles is as described above. Examples of the binder include alumina sol, zirconia sol, titanium dioxide sol, silica sol, ceria sol, etc. Examples of the solvent include water, organic solvents, etc. One solvent can be used, or a mixture of two or more solvents can be used.

[0511] By applying the sixth slurry onto the fifth precursor layer and drying it, a sixth precursor layer, which is a precursor of the upper layer 22 of the first catalyst layer 20, is formed. 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 longer and 1 hour or shorter.

[0512] The particle size of the sixth pore-forming material can be appropriately adjusted. The median particle size D 50 is preferably 0.1 μm or more and 20 μm or less, more preferably 0.5 μm or more and 17 μm or less, and still more preferably 1.5 μm or more and 15 μm or less. By adjusting the particle size, amount, etc. 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, amount, etc. of the fifth pore-forming material and / or the particle size, amount, etc. of 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. The meaning and measurement method of D 50 are the same as those described above.

[0513] <Process 3d>

[0514] Process 3d is a process of baking 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] By baking the second precursor layer, the fifth precursor layer, and the sixth precursor layer, 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 respectively formed. The baking temperature is, for example, 350°C or higher and 600°C or lower, and the baking time is, for example, 20 minutes or longer and 5 hours or shorter. The atmosphere during baking is usually an air atmosphere.

[0516] By calcining the second precursor layer, the second pore former disappears, thereby forming pores in the second catalyst layer 30. By calcining the fifth precursor layer, the fifth pore former disappears, thereby forming pores in the lower layer 21 of the first catalyst layer 20. By calcining the sixth precursor layer, the sixth pore former disappears, thereby forming pores in the upper layer 22 of the first catalyst layer 20. By adjusting the particle diameters, amounts, etc. of the second pore-forming material, the fifth pore-forming material, and the sixth pore-forming material, the differential pore volume distribution per logarithm 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). Thereby, it is possible to sufficiently ensure the amount of pores contributing to the PM trapping performance and the amount of pores contributing to reducing the pressure loss, and it is possible to achieve both an improvement in the PM trapping performance and an inhibition of an increase in the pressure loss. 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 modes (i) to (ix).

[0518] (E1) The median diameter D of one or both of the second pore former, the fifth pore former, and the sixth pore former 50 is greater than 4 μm, and the median diameter D of the remaining two or one 50 is 4 μm or less.

[0519] (E2) The second slurry contains inorganic oxide particles, and the median diameter D of the inorganic oxide particles contained in the second slurry 50 is 1 μm or more and 20 μm or less.

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

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

[0522] (E5) The fifth slurry contains inorganic oxide particles, and the median diameter D of the inorganic oxide particles contained in the fifth slurry 50 is 1 μm or more and 20 μm or less.

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

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

[0525] (E8) The sixth paste contains inorganic oxide particles, and the median particle size D of the inorganic oxide particles contained in the sixth paste 50 is 1 μm or more and 20 μm or less.

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

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

[0528] The above description of condition (D1) also applies to condition (E1). When applicable, understand by replacing "the first pore former", "the third pore former", and "the fourth pore former" with "the second pore former", "the fifth pore former", and "the sixth pore former" respectively.

[0529] The above description of condition (D2) also applies to condition (E2). When applicable, understand by replacing "the first paste" with "the second paste".

[0530] The above description of condition (D3) also applies to condition (E3). When applicable, understand by replacing "the first precursor layer", "the first pore former", "the first catalyst layer 20", "the first paste", and "the inflow side chamber side of the partition wall portion 12" with "the second precursor layer", "the second pore former", "the second catalyst layer 30", "the second paste", and "the outflow side chamber side of the partition wall portion 12" respectively.

[0531] The above description of condition (D4) also applies to condition (E4). When applicable, understand by replacing "the first catalyst layer 20", "the first paste", and "the inflow side chamber side of the partition wall portion 12" with "the second catalyst layer 30", "the second paste", and "the outflow side chamber side of the partition wall portion 12" respectively.

[0532] The above description of condition (D5) also applies to condition (E5). When applicable, understand by replacing "the third paste" with "the fifth paste".

[0533] The above description of condition (D6) also applies to condition (E6). When applicable, understand by replacing "the third precursor layer", "the third pore former", "the lower layer 31", "the third paste", and "the outflow side chamber side of the partition wall portion 12" with "the fifth precursor layer", "the fifth pore former", "the lower layer 21", "the fifth paste", and "the inflow side chamber side of the partition wall portion 12" respectively.

[0534] The above description regarding condition (D7) also applies to condition (E7). When applicable, understand by replacing "lower layer 31", "the third slurry", and "the outflow side chamber side of the partition wall portion 12" with "lower layer 21", "the fifth slurry", and "the inflow side chamber side of the partition wall portion 12", respectively.

[0535] The above description regarding condition (D8) also applies to condition (E8). When applicable, understand by replacing "the fourth slurry" with "the sixth slurry".

[0536] The above description regarding condition (D9) also applies to condition (E9). When applicable, understand by replacing "the third precursor layer", "the fourth precursor layer", "the fourth pore former", "upper layer 32", and "the fourth slurry" with "the fifth precursor layer", "the sixth precursor layer", "the sixth pore former", "upper layer 22", and "the sixth slurry", respectively.

[0537] The above description regarding condition (D10) also applies to condition (E10). When applicable, understand by replacing "the third precursor layer", "upper layer 32", and "the fourth slurry" with "the fifth precursor layer", "upper layer 22", and "the sixth slurry", respectively.

[0538] When the median particle size D 50 of the fifth pore former is greater than the median particle size D 50 of the sixth pore former, it becomes difficult for the fifth slurry to enter the pores in the partition wall portion 12, and an embodiment in which at least a part of the lower layer 21 bulges 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 that bulges from the outer surface S1a of the partition wall portion 12 toward the inflow side chamber 13a) can be easily achieved. Therefore, when using a pore former with a median particle size D 50 greater than 4 μm and a pore former with a median particle size D 50 of 4 μm or less, it is preferable to use the pore former with a median particle size D 50 greater than 4 μm as the fifth pore former and the pore former with a median particle size D 50 of 4 μm or less as the sixth pore former.

[0539] When the median particle size D 50 of the fifth pore former is greater than 4 μm and the median particle size D 50 of the sixth pore former is 4 μm or less, a sufficient amount of pores contributing to PM trapping performance and / or a sufficient amount of pores contributing to reducing pressure loss can be ensured in the first catalyst layer 20. In addition, when the median particle size D 50 of the fifth pore former is greater than 4 μm and the median particle size D 50When it is 4 μm or less, the first catalyst layer 20 that satisfies any one of Conditions 1 or 2, or the first catalyst layer 20 that satisfies both Conditions 1 and 2, particularly the first catalyst layer 20 that satisfies both Conditions 1 and 2, can be formed more efficiently.

[0540] D of the fifth pore former 50 As long as it is greater than 4 μm, there is no particular limitation. From the viewpoint of more effectively achieving both the improvement of PM capture performance and the suppression of the increase in pressure loss, it is preferably 4.5 μm or more and 20 μm or less, more preferably 4.5 μm or more and 17 μm or less, and further preferably 4.5 μm or more and 15 μm or less.

[0541] D of the sixth pore former 50 As long as it is 4 μm or less, there is no particular limitation. From the viewpoint of more effectively achieving both the improvement of PM capture performance and the suppression of the increase in pressure loss, it is preferably 0.1 μm or more and 4 μm or less, more preferably 0.5 μm or more and 4 μm or less, and further preferably 1.5 μm or more and 4 μm or less.

[0542] Examples

[0543] Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to the examples.

[0544] <Example 1>

[0545] (1) Preparation of the first slurry

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

[0547] The CeO2-ZrO2 solid solution powder and the alumina powder were mixed to prepare a mixed powder. The D of the mixed powder 50 was 7 μm.

[0548] The mixed powder was added to an aqueous rhodium nitrate solution to obtain a mixed solution. The obtained mixed solution, a pore former (crosslinked poly(methyl)acrylate particles with a median particle size D 50 of 3 μm), alumina sol, zirconia sol, and water as a solvent were mixed to prepare the first slurry. The amounts of Rh and the pore former contained in the first slurry were adjusted so that they would be 0.3% by mass 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 is obtained by subtracting the mass of the components (such as the solvent, pore former, etc.) that disappear due to the drying and calcining of 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. As the Ce-Zr composite oxide powder, CeO2-ZrO2 solid solution powder was used.

[0551] The CeO2-ZrO2 solid solution powder and the alumina powder were mixed to prepare a mixed powder. The D of the mixed powder 50 was 7 μm.

[0552] The mixed powder was added to an aqueous palladium nitrate solution to obtain a mixed solution. The obtained mixed solution, a pore-forming agent (crosslinked poly(methyl)acrylate particles with a median particle size D 50 of 5 μm), barium hydroxide, alumina sol, zirconia sol, and water as a solvent were mixed to prepare the third slurry. The amounts of Pd and the pore-forming agent contained in the third slurry were adjusted so as to be 3% by mass 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 is obtained by subtracting the mass of the components (such as the solvent, pore-forming agent, etc.) that disappear 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 the pore-forming agent contained in the fourth slurry were adjusted so as to be 0.3% by mass 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 is obtained by subtracting the mass of the components (such as the solvent, pore-forming agent, etc.) that disappear due to the drying and calcining of the fourth slurry from the mass of the fourth slurry.

[0555] (4) Manufacture of the exhaust gas purification catalyst

[0556] Prepared with Figures 1 - 6A substrate having the structure shown below, i.e., the following substrate: It has an inflow-side chamber extending along the axial direction of the substrate, an outflow-side chamber extending along the axial direction of the substrate, and a porous partition wall portion separating the inflow-side chamber and the outflow-side chamber. The thickness of the partition wall portion is 216 μm, the total number of the inflow-side chamber and the outflow-side chamber in a cross-section perpendicular to the axial direction of the substrate is 300 chambers per 1 square inch, and the volume of the substrate is 1.4 L. The area of the opening of the inflow-side chamber in the inflow-side end face of the substrate is substantially 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 exhaust gas inflow side of the substrate was immersed in the first slurry, and after sucking the first slurry from the opposite side, it was dried at 70 °C for 10 minutes. Thus, a first precursor layer composed of the solid components of the first slurry was formed on the inflow-side chamber side of the partition wall portion of the substrate. The formed first precursor layer extends along the exhaust gas flow direction from the end of the exhaust gas inflow side of the substrate.

[0558] After drying, the end of the exhaust gas outflow side of the substrate was immersed in the third slurry, and after sucking the third slurry from the opposite side, it was dried at 70 °C for 10 minutes. Thus, a third precursor layer composed of the solid components of the third slurry was formed on the outflow-side chamber side of the partition wall portion of the substrate. The formed third precursor layer extends along the direction opposite to the exhaust gas flow direction from the end of the exhaust gas outflow side of the substrate. After drying, the end of the exhaust gas outflow side of the substrate was immersed in the fourth slurry, and after sucking the fourth slurry from the opposite side, it was dried at 70 °C for 10 minutes. Thus, a fourth precursor layer composed of the solid components of the fourth slurry was formed on the third precursor layer on the outflow-side chamber side of the partition wall portion of the substrate. The formed fourth precursor layer extends along the direction opposite to the exhaust gas flow direction from the end of the exhaust gas outflow side of the substrate.

[0559] Then, the substrate was calcined at 450 °C for 1 hour, and a first catalyst layer and a second catalyst layer were formed on the substrate. Thus, the exhaust gas purification catalyst of Example 1 was obtained. The first catalyst layer has a single-layer structure, and the second catalyst layer has a two-layer structure composed of a lower layer and an upper layer. The mass (wash coat amount) of the first catalyst layer per unit volume of the portion of the substrate where the first catalyst layer is formed is 69.4 g / L. The mass (wash coat amount) of the lower layer per unit volume of the portion of the substrate where the lower layer of the second catalyst layer is formed is 41.1 g / L. The mass (wash coat amount) of the upper layer per unit volume of 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 former in the first slurry was changed from 50 crosslinked poly(methyl)acrylate particles with a diameter of 3 μm to 50Crosslinked poly(methyl) methacrylate particles with a median particle size D of 5 μm, and as the fourth slurry, the same slurry as the first slurry in Example 1 was used (i.e., crosslinked poly(methyl) methacrylate particles with a median particle size D of 3 μm were included as a pore-forming agent). Except for this, the waste gas purification catalyst of Example 2 was obtained in the same manner as in Example 1. 50 Crosslinked poly(methyl) methacrylate particles with a median particle size D of 3 μm), and except for this, the waste gas purification catalyst of Example 2 was obtained in the same manner as in Example 1.

[0562] <Example 3>

[0563] The pore-forming agent in the first slurry was changed from crosslinked poly(methyl) methacrylate particles with a median particle size D of 50 3 μm to crosslinked poly(methyl) methacrylate particles with a median particle size D of 50 2 μm, and the pore-forming agent in the fourth slurry was changed from crosslinked poly(methyl) methacrylate particles with a median particle size D of 50 3 μm to crosslinked poly(methyl) methacrylate particles with a median particle size D of 50 2 μm. Except for this, the waste gas purification catalyst of Example 3 was obtained in the same manner as in Example 1.

[0564] <Example 4>

[0565] Except that the pore-forming agent in the third slurry was changed from crosslinked poly(methyl) methacrylate particles with a median particle size D of 50 5 μm to crosslinked poly(methyl) methacrylate particles with a median particle size D of 50 10 μm, the waste gas purification catalyst of Example 4 was obtained in the same manner as in Example 1.

[0566] <Example 5>

[0567] (1) Preparation of the fifth slurry

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

[0569] The CeO2-ZrO2 solid solution powder and the alumina powder were mixed to prepare a mixed powder. The D of the mixed powder 50 was 6 μm.

[0570] The mixed powder was added to an aqueous palladium nitrate solution to obtain a mixed solution. The obtained mixed solution, a pore-forming agent (median particle size D 50Crosslinked poly(methyl)acrylate particles with a size of 5 μm, alumina sol, zirconia sol, and water as a solvent were mixed to prepare the 5th slurry. The amounts of Pd and pore former contained in the 5th slurry were adjusted so that they would be 3% by mass and 40% by mass, respectively, based on the mass of the lower layer of the 1st catalyst layer formed by drying and calcining the 5th slurry (100% by mass). It should be noted that the mass of the lower layer of the 1st catalyst layer formed by drying and calcining the 5th slurry was obtained by subtracting the mass of the components that disappeared due to drying and calcining of the 5th slurry (such as the solvent, pore former, etc.) from the mass of the 5th slurry.

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

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

[0573] The CeO2-ZrO2 solid solution powder and alumina powder were mixed to prepare a mixed powder. The D 50 of the mixed powder was 6 μm.

[0574] The mixed powder was added to an aqueous rhodium nitrate solution to obtain a mixed solution. The obtained mixed solution, a pore former (crosslinked poly(methyl)acrylate particles with a median particle size D 50 of 3 μm), alumina sol, zirconia sol, and water as a solvent were mixed to prepare the 6th slurry. The amounts of Rh and pore former contained in the 6th slurry were adjusted so that they would be 0.3% by mass and 40% by mass, respectively, based on the mass of the upper layer of the 1st catalyst layer formed by drying and calcining the 6th slurry (100% by mass). It should be noted that the mass of the upper layer of the 1st catalyst layer formed by drying and calcining the 6th slurry was obtained by subtracting the mass of the components that disappeared due to drying and calcining of the 6th slurry (such as the solvent, pore former, etc.) from the mass of the 6th slurry.

[0575] (3) Preparation of the 2nd slurry

[0576] As the 2nd slurry, a slurry identical to the 6th slurry was prepared except for the amount of the pore former described later. The amounts of Rh and pore former contained in the 2nd slurry were adjusted so that they would be 0.3% by mass and 30% by mass, respectively, based on the mass of the 2nd catalyst layer formed by drying and calcining the 2nd slurry (100% by mass). It should be noted that the mass of the 2nd catalyst layer formed by drying and calcining the 2nd slurry was obtained by subtracting the mass of the components that disappeared due to drying and calcining of the 2nd slurry (such as the solvent, pore former, etc.) from the mass of the 2nd slurry.

[0577] (4) Manufacture of Catalyst for Exhaust Gas Purification

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

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

[0580] After drying, the end of the substrate on the exhaust gas outflow side was immersed in the second slurry, and after sucking the second slurry from the opposite side, it was dried at 70 °C for 10 minutes. Thus, a second precursor layer composed of the solid components of the second slurry was formed on the outflow side chamber side of the partition wall portion of the substrate. The formed second precursor layer extended along the direction opposite to the exhaust gas flow direction from the end of the substrate on the exhaust gas outflow side.

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

[0582] <Comparative Example 1>

[0583] Except that the pore-forming agent in the third slurry was changed from crosslinked poly(methyl)acrylate particles with a diameter of 5 μm to crosslinked poly(methyl)acrylate particles with a diameter of 3 μm, the catalyst for exhaust gas purification of Comparative Example 1 was obtained in the same manner as in Example 1. 50 to crosslinked poly(methyl)acrylate particles with a diameter of 3 μm 50 The catalyst for exhaust gas purification of Comparative Example 1 was obtained in the same manner as in Example 1.

[0584] <Comparative Example 2>

[0585] The pore-forming agent in the first slurry was changed from D 50The crosslinked poly(methyl) methacrylate particles with a size of 3 μm are changed to D 50 The crosslinked poly(methyl) methacrylate particles with a size of 5 μm, and the pore former in the fourth slurry is changed from D 50 The crosslinked poly(methyl) methacrylate particles with a size of 3 μm are changed to D 50 The crosslinked poly(methyl) methacrylate particles with a size of 5 μm. In addition, the exhaust gas purification catalyst of Comparative Example 2 is obtained in the same manner as in Example 1.

[0586] <Measurement of pore volume>

[0587] Each catalyst of the examples and comparative examples is cut with a plane parallel to the axial direction of the substrate and a plane perpendicular to the axial direction of the substrate, and cut out Figure 9 The part shown by the symbol M1 in or 11 is obtained, and a slice M1 is obtained which includes a part of the partition wall part and a part of the first catalyst layer but does not include the second catalyst layer. None of the slices M1 includes the first closing part or the second closing part. The length of the part of the partition wall part included in the slice M1 is equal to the length of the slice M1. The length of the part of the first catalyst layer included in the slice M1 is equal to the length of the slice M1. The slice M1 is obtained from the vicinity of the exhaust gas inlet side end of the catalyst. Specifically, by cutting at two places 10 mm and 20 mm away from the exhaust gas inlet side end of the substrate along the exhaust gas flow direction E with a plane perpendicular to the axial direction of the substrate, the slice M1 is obtained. The slice M1 is in the shape of a cube with a side length of 10 mm.

[0588] Each catalyst of the examples and comparative examples is cut with a plane parallel to the axial direction of the substrate and a plane perpendicular to the axial direction of the substrate, and cut out Figure 9 The part shown by the symbol M2 in or 11 is obtained, and a slice M2 is obtained which includes a part of the partition wall part and a part of the second catalyst layer (lower layer and upper layer) but does not include the first catalyst layer. None of the slices M2 includes the first closing part or the second closing part. The length of the part of the partition wall part included in the slice M2 is equal to the length of the slice M2. The length of the part of the second catalyst layer (lower layer and upper layer) included in the slice M2 is equal to the length of the slice M2. The slice M2 is obtained from the vicinity of the exhaust gas outlet side end of the catalyst. Specifically, by cutting at two places 10 mm and 20 mm away from the exhaust gas outlet side end of the substrate along the direction opposite to the exhaust gas flow direction E with a plane perpendicular to the axial direction of the substrate, the slice M2 is obtained. The slice M2 is in the shape of a cube with a side length of 10 mm.

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

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

[0591] As the measuring device, an automatic porosimeter "Autopore IV9520" manufactured by Shimadzu Corporation was used, and the log differential pore volume distribution was measured under the following conditions and procedures.

[0592] (Measurement conditions)

[0593] Measurement environment: 25 °C

[0594] Measurement chamber: The volume of the sample chamber is 3 cm 3 and the intrusion volume is 0.39 cm 3

[0595] Measurement range: 0.0048 MPa to 255.106 MPa

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

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

[0598] A total of 131 points (when plotting each pressure logarithmically, the points are marked at equal intervals)

[0599] The intrusion volume was adjusted to be 25% or more and 90% or less.

[0600] (Low-pressure parameters)

[0601] Exhaust pressure: 50 μmHg

[0602] Exhaust time: 5.0 min

[0603] Mercury injection pressure: 0.0034 MPa

[0604] Equilibration time: 10 sec

[0605] (High-pressure parameters)

[0606] Equilibration time: 10 sec

[0607] (Mercury parameters)

[0608] Advancing contact angle: 130.0 degrees

[0609] Receding 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 steps)

[0613] (1) In the low-pressure section, 54 points were measured in the range from 0.0048 MPa to 0.3447 MPa or less.

[0614] (2) In the high-pressure section, 77 points were measured in the range from 0.3792 MPa to 255.1060 MPa or less.

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

[0616] It should be noted that the above (1), (2), and (3) are automatically performed using the software attached to the device. Other conditions are based on JIS R 1655:2003.

[0617] The logarithmic differential pore volume distribution curves of the first catalyst layer and the second catalyst layer in the waste gas purification catalyst of Example 2 are respectively shown in 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 waste gas purification catalyst of Comparative Example 1 are respectively shown in Figure 13A and Figure 13B .

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

[0620] It was confirmed whether there was a peak A (specific value of peak A if present) in the logarithmic differential pore volume distribution curve of the first catalyst layer in the range of pore diameter of 1 μm or more and 3 μm or less; whether there was a peak B (specific value of peak B if present) in the logarithmic differential pore volume distribution curve of the first catalyst layer in the range of pore diameter greater than 3 μm and 10 μm or less; whether there was a peak C (specific value of peak C if present) in the logarithmic differential pore volume distribution curve of the second catalyst layer in the range of pore diameter of 1 μm or more and 3 μm or less; and whether there was a peak D (specific value of peak D if present) in the logarithmic differential pore volume distribution curve of the second catalyst layer in the range of pore diameter greater than 3 μm and 10 μm or less. The results are shown in Tables 2 and 3. In Tables 2 and 3, for the "presence or absence" of peak A, "none" means that peak A does not exist, "maximum value" means that peak A exists as the maximum value (logarithmic differential pore volume at the vertex) in the logarithmic differential pore volume distribution curve, and "shoulder peak" means that peak A exists as a shoulder peak in the logarithmic differential pore volume distribution curve. The same applies to peaks B, C, and D.

[0621] <Evaluation of pressure loss>

[0622] It was fixed in such a way that the side of the exhaust gas purification catalyst of Example 1 was supported and the end face on the exhaust gas inflow side faced upward. Air was sucked at a rate of 50 L / sec from below the fixed exhaust gas purification catalyst (the end face on the exhaust gas outflow side). The difference between the air pressure at the end face on the exhaust gas inflow side 10 seconds after the start of suction and the air pressure at the end face on the exhaust gas inflow side was determined and taken as the pressure loss of the exhaust gas purification catalyst of Example 1.

[0623] The substrate (without forming the first catalyst layer and the second catalyst layer) was used instead of the exhaust gas purification catalyst of Example 1, and in the same manner as above, the difference between the air pressure at the end face on the exhaust gas inflow side 10 seconds after the start of suction and the air pressure at the end face on the exhaust gas inflow side was determined and taken as the pressure loss of the substrate.

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

[0625] Pressure loss ratio = (pressure loss of the exhaust gas purification catalyst of Example 1 / pressure loss of the substrate) × 100

[0626] The case where the pressure loss ratio was less than 270% was evaluated as "A", the case where the pressure loss ratio was 270% or more and less than 300% was evaluated as "B", and the case where the pressure loss ratio was 300% or more was evaluated 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 Worldwide Harmonized Light Vehicles Test Cycle (WLTC). The number of PM particles (PNcat) in the exhaust gas passing through the exhaust gas purification catalyst during low-speed operation from the start of operation to 589 seconds, medium-speed operation from 589 seconds to 1022 seconds from the start of operation, high-speed operation from 1022 seconds to 1477 seconds from the start of operation, and ultra-high-speed operation from 1477 seconds to 1800 seconds from the start of operation was measured respectively. Further, the number of PM particles (PNall) directly discharged from the engine was measured, and the PM capture rate of the exhaust gas purification catalyst of Example 1 was calculated according to the following formula.

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

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

[0631] Evaluation vehicle: 1.5L direct injection turbo engine

[0632] Gasoline used: Certification test fuel

[0633] PM measurement device: Manufactured by Horiba, Ltd.

[0634] When the PM capture rate is 98.7% or more, it is evaluated as "A". When the PM capture rate is 98.0% or more and less than 98.7%, it is evaluated as "B". When the PM capture rate is less than 98.0%, it is evaluated as "C". The results are shown in Table 2.

[0635] [Table 2]

[0636]

[0637] [Table 3]

[0638]

[0639] Explanation of reference numerals

[0640] 1A, 1B, 1C... Exhaust gas purification catalyst

[0641] 10... Substrate

[0642] 11... Cylindrical part

[0643] 12... Partition wall part

[0644] 13... Chamber

[0645] 13a... Inflow side chamber

[0646] 13b... Outflow side chamber

[0647] 14…First closed portion

[0648] 15…Second closed portion

[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 on the inlet side chamber side of the partition wall portion

[0656] S1b…Outer surface on the outlet side chamber side of the partition wall portion

Claims

1. A catalyst for purifying exhaust gas, comprising a substrate extending in the exhaust gas flow direction, a first catalyst layer and a second catalyst layer, The substrate has: an inflow side chamber extending along the exhaust gas flow direction, wherein the end of the inflow side chamber on the exhaust gas inflow side is open and the end of the exhaust gas outflow side is closed; an outflow side chamber extending along the exhaust gas flow direction, the end of the outflow side chamber on the exhaust gas inflow side being closed and the end of the exhaust gas outflow side being open; and a porous partition wall portion that separates the inflow side chamber from the outflow side chamber, The first catalyst layer is provided on the inlet-side chamber side of the partition wall portion along the exhaust gas flow direction from the end portion of the partition wall portion on the exhaust gas inlet side. The second catalyst layer is provided on the outflow side chamber side of the partition wall portion from the end portion of the exhaust gas outflow side of the partition wall portion in a direction opposite to the exhaust gas flow direction. Condition 1 is set as: in the logarithmic differential pore volume distribution curve of the first catalyst layer obtained by mercury porosimetry, a peak A exists in the range of pore diameters of 1 μm or more and 3 μm or less, and the peak A is 0.20 mL / g or more; Condition 2 is a condition that: in the logarithmic differential pore volume distribution curve of the first catalyst layer obtained by mercury intrusion porosimetry, a peak B exists in the range of pore diameters greater than 3 μm and less than 10 μm, and the peak B is 0.20 mL / g or more; Condition 3 is a condition that in the logarithmic differential pore volume distribution curve of the second catalyst layer obtained by mercury intrusion porosimetry, a peak C exists in the range of pore diameters of 1 μm or more and 3 μm or less, and the peak C is 0.20 mL / g or more; Condition 4 is set as follows: in the logarithmic differential pore volume distribution curve of the second catalyst layer obtained by mercury porosimetry, a peak D exists in the range of pore diameter greater than 3 μm and less than 10 μm, and the peak D is 0.20 mL / g or more. The second catalyst layer satisfies condition 3 but not condition 4, or satisfies condition 4 but not condition 3, or satisfies conditions 3 and 4, or satisfies neither condition 3 nor condition 4. When the second catalyst layer satisfies condition 3 but does not satisfy condition 4, the first catalyst layer satisfies at least condition 2 among conditions 1 and 2. When the second catalyst layer satisfies condition 4 and does not satisfy condition 3, the first catalyst layer satisfies at least condition 1 among conditions 1 and 2. When the second catalyst layer satisfies conditions 3 and 4, the first catalyst layer satisfies at least one of conditions 1 and 2, or satisfies neither condition 1 nor condition 2. When the second catalyst layer satisfies neither conditions 3 nor 4, the first catalyst layer satisfies conditions 1 and 2.

2. The exhaust gas purification catalyst according to claim 1, wherein The second catalyst layer satisfies condition 3 but not condition 4, or satisfies condition 4 but not condition 3, or satisfies conditions 3 and 4, When the second catalyst layer satisfies condition 3 but does not satisfy condition 4, the first catalyst layer satisfies at least condition 2 among conditions 1 and 2. When the second catalyst layer satisfies condition 4 and does not satisfy condition 3, the first catalyst layer satisfies at least condition 1 among conditions 1 and 2. When the second catalyst layer satisfies conditions 3 and 4, the first catalyst layer satisfies at least one of conditions 1 and 2.

3. The exhaust gas purification catalyst according to claim 1 or 2, wherein: In condition 1, the peak A is 1.00 mL / g or less, and in condition 3, the peak C is 1.00 mL / g or less.

4. The exhaust gas purification catalyst according to claim 1 or 2, wherein: In condition 2, the peak value B is 1.00 mL / g or less, and in condition 4, the peak value D is 1.00 mL / g or less.

5. The exhaust gas purification catalyst according to claim 1 or 2, wherein: In condition 1, the peak A is 0.31 mL / g or more, and in condition 3, the peak C is 0.31 mL / g or more.

6. A method for producing an exhaust gas-purifying catalyst, the exhaust gas-purifying catalyst comprising a substrate extending in an exhaust gas flow direction, a first catalyst layer and a second catalyst layer, The substrate has: an inflow side chamber extending along the exhaust gas flow direction, wherein the end of the inflow side chamber on the exhaust gas inflow side is open and the end of the exhaust gas outflow side is closed; an outflow side chamber extending along the exhaust gas flow direction, the end of the outflow side chamber on the exhaust gas inflow side being closed and the end of the exhaust gas outflow side being open; and a porous partition wall portion that separates the inflow side chamber from the outflow side chamber, The first catalyst layer is provided on the inlet-side chamber side of the partition wall portion along the exhaust gas flow direction from the end portion of the partition wall portion on the exhaust gas inlet side. The second catalyst layer is provided on the outflow side chamber side of the partition wall portion from the end portion of the exhaust gas outflow side of the partition wall portion in a direction opposite to the exhaust gas flow direction. The method comprises the following steps: (1a) a step of applying a first slurry containing a first pore former to the inlet chamber side of the partition wall portion to form a first precursor layer; (1b) a step of applying a second slurry containing a second pore former to the outflow-side chamber side of the partition wall portion to form a second precursor layer; and (1c) a 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 former and the second pore former is 50 Greater than 4 μm, the median particle size D of the other 50 4μm or less, 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 is 1 μm or more and 20 μm or less, The amount of the first pore former contained in the first precursor layer is 10 mass % or more and 60 mass % or less based on the mass of the first catalyst layer, The mass of the first catalyst layer per unit volume of the portion of the substrate where 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 is 1 μm or more and 20 μm or less, The amount of the second pore former contained in the second precursor layer is 10 mass % or more and 60 mass % or less based on the mass of the second catalyst layer, The mass of the second catalyst layer per unit volume of a portion of the substrate where the second catalyst layer is formed is 5 g / L or more and 150 g / L or less.

7. A method for producing an exhaust gas-purifying catalyst, the exhaust gas-purifying catalyst comprising a substrate extending in an exhaust gas flow direction, a first catalyst layer and a second catalyst layer, The substrate has: an inflow side chamber extending along the exhaust gas flow direction, wherein the end of the inflow side chamber on the exhaust gas inflow side is open and the end of the exhaust gas outflow side is closed; an outflow side chamber extending along the exhaust gas flow direction, the end of the outflow side chamber on the exhaust gas inflow side being closed and the end of the exhaust gas outflow side being open; and a porous partition wall portion that separates the inflow side chamber from the outflow side chamber, The first catalyst layer is provided on the inlet-side chamber side of the partition wall portion along the exhaust gas flow direction from the end portion of the partition wall portion on the exhaust gas inlet side. The second catalyst layer is provided on the outflow side chamber side of the partition wall portion from the end portion of the exhaust gas outflow side of the partition wall portion in a direction opposite to the exhaust gas flow direction. The second catalyst layer includes a lower layer provided on the outflow-side chamber side of the partition wall portion, and an upper layer provided on the lower layer. The method comprises the following steps: (2a) a step of applying a first slurry containing a first pore former to the inlet chamber side of the partition wall portion to form a first precursor layer; (2b) a step of applying a third slurry containing a third pore former to the outflow-side chamber side of the partition wall portion to form a third precursor layer; (2c) a step of applying a fourth slurry containing a fourth pore former onto the third precursor layer to form a fourth precursor layer; and (2d) a step 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 former, the third pore former and the fourth pore former is 50 Greater than 4 μm, the median particle size D of the remaining two or one of them 50 4μm or less, 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 is 1 μm or more and 20 μm or less, The amount of the first pore former contained in the first precursor layer is 10 mass % or more and 60 mass % or less based on the mass of the first catalyst layer, The mass of the first catalyst layer per unit volume of the portion of the substrate where 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 is 1 μm or more and 20 μm or less, The amount of the third pore former contained in the third precursor layer is 10 mass % or more and 60 mass % or less based on the mass of the lower layer, The mass of the lower layer per unit volume of the portion of the substrate where 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 is 1 μm or more and 20 μm or less, The amount of the fourth pore former contained in the fourth precursor layer is 10 mass % or more and 60 mass % or less based on the mass of the upper layer, The mass of the upper layer per unit volume of a portion of the substrate where the upper layer is formed is 5 g / L or more and 60 g / L or less.

8. The method according to claim 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 Less than 4μm.

9. A method for producing an exhaust gas-purifying catalyst, the exhaust gas-purifying catalyst comprising a substrate extending in an exhaust gas flow direction, a first catalyst layer and a second catalyst layer, The substrate has: an inflow side chamber extending along the exhaust gas flow direction, wherein the end of the inflow side chamber on the exhaust gas inflow side is open and the end of the exhaust gas outflow side is closed; an outflow side chamber extending along the exhaust gas flow direction, the end of the outflow side chamber on the exhaust gas inflow side being closed and the end of the exhaust gas outflow side being open; and a porous partition wall portion that separates the inflow side chamber from the outflow side chamber, The first catalyst layer is provided on the inlet-side chamber side of the partition wall portion along the exhaust gas flow direction from the end portion of the partition wall portion on the exhaust gas inlet side. The second catalyst layer is provided on the outflow side chamber side of the partition wall portion from the end portion of the exhaust gas outflow side of the partition wall portion in a direction opposite to the exhaust gas flow direction. The first catalyst layer includes a lower layer provided on the inlet-side chamber side of the partition wall portion, and an upper layer provided on the lower layer. The method comprises the following steps: (3a) a step of applying a second slurry containing a second pore former to the outflow-side chamber side of the partition wall portion to form a second precursor layer; (3b) a step of applying a fifth slurry containing a fifth pore former to the inlet chamber side of the partition wall portion to form a fifth precursor layer; (3c) a step of applying a sixth slurry containing a sixth pore former onto the fifth precursor layer to form a sixth precursor layer; and (3d) a step 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 former, the fifth pore former and the sixth pore former is 50 Greater than 4 μm, the median particle size D of the remaining two or one of them 50 4μm 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 is 1 μm or more and 20 μm or less, The amount of the second pore former contained in the second precursor layer is 10 mass % or more and 60 mass % or less based on the mass of the second catalyst layer, The mass of the second catalyst layer per unit volume of the portion of the substrate where 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 is 1 μm or more and 20 μm or less, The amount of the fifth pore former contained in the fifth precursor layer is 10 mass % or more and 60 mass % or less based on the mass of the lower layer, The mass of the lower layer per unit volume of the portion of the substrate where 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 is 1 μm or more and 20 μm or less, The amount of the sixth pore former contained in the sixth precursor layer is 10 mass % or more and 60 mass % or less based on the mass of the upper layer, The mass of the upper layer per unit volume of a portion of the substrate where the upper layer is formed is 5 g / L or more and 60 g / L or less.

10. The method according to claim 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 Less than 4μm.

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