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WO2023182481A1 - Catalyseur de purification de gaz d'échappement - Google Patents

Catalyseur de purification de gaz d'échappement Download PDF

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Publication number
WO2023182481A1
WO2023182481A1 PCT/JP2023/011744 JP2023011744W WO2023182481A1 WO 2023182481 A1 WO2023182481 A1 WO 2023182481A1 JP 2023011744 W JP2023011744 W JP 2023011744W WO 2023182481 A1 WO2023182481 A1 WO 2023182481A1
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WO
WIPO (PCT)
Prior art keywords
catalyst layer
exhaust gas
mass
base material
equivalent amount
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/JP2023/011744
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English (en)
Japanese (ja)
Inventor
真吾 秋田
広樹 栗原
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mitsui Kinzoku Co Ltd
Original Assignee
Mitsui Mining and Smelting Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Mitsui Mining and Smelting Co Ltd filed Critical Mitsui Mining and Smelting Co Ltd
Publication of WO2023182481A1 publication Critical patent/WO2023182481A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/56—Platinum group metals
    • B01J23/63—Platinum group metals with rare earths or actinides
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/022—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
    • F01N3/28—Construction of catalytic reactors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/50—Catalysts, in general, characterised by their form or physical properties characterised by their shape or configuration
    • B01J35/56—Foraminous structures having flow-through passages or channels, e.g. grids or three-dimensional monoliths

Definitions

  • the present invention relates to an exhaust gas purifying catalyst.
  • Exhaust gas emitted from internal combustion engines such as automobiles and motorcycles contains harmful components such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx).
  • harmful components such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx).
  • Three-way catalysts are used to purify these harmful components and render them harmless.
  • a catalyst containing noble metal elements such as Pt, Pd, and Rh is used as Pt, Pd, and Rh is used as Pt, Pd, and Rh.
  • the wall flow type base material has an inflow side cell with an open end on the exhaust gas inflow side and a closed end on the exhaust gas outflow side, and a closed end on the exhaust gas inflow side and a closed cell on the exhaust gas outflow side. It includes an outflow side cell with an open end, and a porous partition wall that partitions the inflow side cell and the outflow side cell.
  • exhaust gas flows in from the exhaust gas inflow side end (opening) of the inflow side cell, passes through the porous partition wall, and flows out from the exhaust gas outflow side end (opening) of the outflow side cell. At this time, PM in the exhaust gas is collected in the pores inside the partition wall.
  • the mounting space for exhaust gas purification catalysts is limited, so a catalyst layer containing noble metal elements such as Pt, Pd, and Rh is provided on a wall flow type base material to collect PM and to collect HC, CO, NOx, etc. Purification of harmful components is being considered.
  • Patent Documents 1 and 2 disclose a wall flow type base material, a first catalyst layer formed from an end on the exhaust gas inflow side in the direction in which the partition wall extends, and a wall flow type base material in which the partition wall extends from the end on the exhaust gas outflow side.
  • An exhaust gas purifying catalyst is described that includes a second catalyst layer formed in the direction of the exhaust gas purifying catalyst.
  • the first catalyst layer is formed inside the partition so as to be in contact with the inflow side cells, and the second catalyst layer is formed inside the partition so as to be in contact with the outflow side cells.
  • the first catalyst layer contains, for example, Rh
  • the second catalyst layer contains, for example, Pd.
  • Patent Document 3 discloses a wall flow type base material, a first catalyst layer formed from an end on the exhaust gas inflow side in the extending direction of the partition wall, and a first catalyst layer formed in the extending direction of the partition wall from the end on the exhaust gas outflow side.
  • a catalyst for exhaust gas purification is described that includes a second catalyst layer formed facing toward the patent and a third catalyst layer formed on the second catalyst layer.
  • the first catalyst layer is formed on the outer surface of the partition wall on the inflow side cell side
  • the second catalyst layer is formed on the outer surface of the partition wall on the outflow side cell side.
  • the first catalyst layer contains, for example, Rh
  • the second catalyst layer contains, for example, Rh
  • the third catalyst layer contains, for example, Pd.
  • Patent Documents 1 and 2 Due to the soaring price of precious metals, there is a demand for the use of Pt, which is relatively inexpensive among precious metals.
  • exhaust gas purifying catalysts using Pt exhaust gas purifying catalysts described in Patent Documents 1 and 2 are known.
  • the exhaust gas purification catalysts described in Patent Documents 1 and 2 do not sufficiently achieve both the purification performance of low-temperature NOx generated during low-speed operation of the internal combustion engine and the purification performance of high-temperature NOx generated during ultra-high-speed operation of the internal combustion engine. could not be realized.
  • the present invention provides an exhaust gas purifying catalyst comprising a wall flow type base material and a catalyst layer containing Pt, which has the ability to purify low-temperature NOx generated during low-speed operation of an internal combustion engine and ultra-high-speed operation of an internal combustion engine.
  • An object of the present invention is to provide an exhaust gas purifying catalyst that can achieve both purification performance of high-temperature NOx that is sometimes generated.
  • the present invention provides the following exhaust gas purifying catalyst.
  • a base material extending in the exhaust gas flow direction; a first catalyst layer containing Rh and optionally containing one or more noble metal elements other than Rh; a second catalyst layer containing Rh and optionally containing one or more noble metal elements other than Rh; a third catalyst layer containing Pt and optionally containing one or more noble metal elements other than Pt;
  • An exhaust gas purification catalyst comprising:
  • the base material is The inflow side cell extends in the exhaust gas flow direction, and has an open end on the exhaust gas inflow side and a closed end on the exhaust gas outflow side;
  • the outflow side cell extends in the exhaust gas flow direction, and has a closed end on the exhaust gas inflow side and an open end on the exhaust gas outflow side; a porous partition that partitions the inflow side cell and the outflow side cell; Equipped with The first catalyst layer is formed on the inflow-side cell side of the partition wall part along the exhaust gas flow direction from the exhaust gas inflow-side end of
  • the metal equivalent amount of Rh in the second catalyst layer is larger than the metal equivalent amount of each noble metal element other than Rh in the second catalyst layer
  • the metal equivalent amount of Pt in the third catalyst layer is larger than the metal equivalent amount of each noble metal element other than Pt in the third catalyst layer
  • the mass of the second catalyst layer per unit volume of the portion of the base material where the second catalyst layer is formed is per unit volume of the portion of the base material where the third catalyst layer is formed.
  • the mass ratio of the third catalyst layer is 0.3 or more and 1.9 or less.
  • the metal equivalent amount of Rh in the first catalyst layer is larger than the total metal equivalent amount of all noble metal elements other than Rh in the first catalyst layer
  • the metal equivalent amount of Rh in the second catalyst layer is larger than the total metal equivalent amount of all noble metal elements other than Rh in the second catalyst layer
  • the first catalyst layer according to any one of [1] to [3], wherein at least a portion of the first catalyst layer protrudes from the outer surface of the partition wall on the inflow side cell side toward the inflow side cell side. Catalyst for exhaust gas purification.
  • an exhaust gas purification catalyst that can achieve both the purification performance of low-temperature NOx generated during low-speed operation of an internal combustion engine and the purification performance of high-temperature NOx generated during ultra-high-speed operation of the internal combustion engine.
  • FIG. 1 is a partial sectional view showing a state in which an exhaust gas purifying catalyst according to an embodiment of the present invention is arranged in an exhaust path of an internal combustion engine.
  • FIG. 2 is an end view taken along line AA in FIG. 1.
  • FIG. 3 is an end view taken along line BB in FIG. 1.
  • FIG. 4 is an enlarged view of the area indicated by the symbol R1 in FIG.
  • FIG. 5 is an enlarged view of the area indicated by the symbol R2 in FIG.
  • FIG. 6 is an end view taken along line CC in FIG. 1.
  • an exhaust gas purifying catalyst 1 is arranged in an exhaust path in an exhaust pipe P of an internal combustion engine.
  • the internal combustion engine is, for example, a gasoline engine (eg, a GDI engine, etc.), a diesel engine, or the like.
  • the exhaust gas purifying catalyst 1 is arranged in the exhaust path of the internal combustion engine so that the axial direction of the base material 10 substantially coincides with the exhaust gas flow direction E.
  • length means the axial dimension of the base material 10, unless otherwise specified.
  • the exhaust gas purifying catalyst 1 includes a base material 10, a first catalyst layer 20, a second catalyst layer 30, and a third catalyst layer 40.
  • the material constituting the base material 10 can be appropriately selected from known materials.
  • the material constituting the base material 10 include ceramic materials, metal materials, and the like, with ceramic materials being preferred.
  • ceramic materials include carbide ceramics such as silicon carbide, titanium carbide, tantalum carbide, and tungsten carbide, nitride ceramics such as aluminum nitride, silicon nitride, boron nitride, and titanium nitride, alumina, zirconia, cordierite, mullite, and zircon. , aluminum titanate, magnesium titanate, and other oxide ceramics.
  • the metal material include alloys such as stainless steel.
  • the length L 10 of the base material 10 can be adjusted as appropriate 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 10 of the base material 10 is preferably 50 mm or more and 160 mm or less, more preferably 80 mm or more and 130 mm or less.
  • the volume of the base material 10 can be adjusted as appropriate 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 base material 10 is preferably 0.5L or more and 2.5L or less, more preferably 0.5L or more and 2.0L or less, and even more preferably 0.5L or more and 2.0L or less. It is 7L or more and 1.8L or less.
  • the base material 10 is a wall flow type base material. As shown in FIGS. 2 to 6, the base material 10 includes a cylindrical portion 11, cells 13 (inflow side cells 13a and outflow side cells 13b), and adjacent cells 13 (inflow side cells 13a and outflow side cells 13b). A porous partition wall portion 12 is provided. It is preferable that the base material 10 is a honeycomb structure.
  • the cylindrical part 11 defines the outer shape of the base material 10, and the axial direction of the cylindrical part 11 coincides with the axial direction of the base material 10.
  • the shape of the cylindrical portion 11 is cylindrical, but it may have other shapes such as an elliptical shape or a polygonal shape.
  • the cells 13 each extend in the exhaust gas flow direction E, and have an end on the exhaust gas inflow side and an end on the exhaust gas outflow side. has.
  • the base material 10 includes a first sealing part 14 that seals the ends of some of the cells 13 on the exhaust gas outflow side, and a first sealing part 14 that seals the ends of the remaining cells 13 on the exhaust gas inflow side.
  • some of the cells 13 are open at the end on the exhaust gas inflow side, and the end on the exhaust gas outflow side is opened at the first sealing section 14.
  • the remaining cells 13 have their exhaust gas inflow ends closed with the second sealing part 15 and their exhaust gas outflow ends open. This is the outflow side cell 13b.
  • a partition wall 12 exists between adjacent cells 13 (inflow side cell 13a and outflow side cell 13b), and adjacent cells 13 (inflow side cell 13a and outflow side cell 13b) are partitioned by partition walls 12.
  • a plurality of (four in this embodiment) outflow cells 13b are arranged around one inflow cell 13a, and an inflow cell 13a, The inflow cell 13 a is separated from the outflow cell 13 b arranged around it by a partition wall 12 .
  • plan view shape of the exhaust gas inflow side end (opening) of the inflow side cell 13a and the plan view shape of the exhaust gas outflow side end (opening) of the outflow side cell 13b are shown.
  • each of the shapes in plan view is a quadrilateral, other shapes such as a hexagon or an octagon may be used.
  • the partition wall portion 12 is provided within the cylindrical portion 11.
  • the partition wall portion 12 has a porous structure through which exhaust gas can pass.
  • the partition wall portion 12 has an outer surface S1a on the inflow side cell 13a side and an outer surface S1b on the outflow side cell 13b side.
  • Outer surface S1a on the inflow side cell 13a side is a region on the inflow side cell 13a side that extends in the exhaust gas flow direction E (i.e., a region in contact with the inflow side cell 13a) among the outer surfaces that define the outer shape of the partition wall portion 12. It is.
  • the outer surface S1b on the outflow side cell 13b side is the area on the outflow side cell 13b side that extends in the exhaust gas flow direction E (i.e., the area in contact with the outflow side cell 13b) among the outer surfaces that define the outer shape of the partition wall 12. It is.
  • the thickness of the partition wall portion 12 can be adjusted as appropriate in consideration of PM trapping performance, pressure loss, etc. From the viewpoint of improving PM trapping performance and suppressing an increase in pressure loss, the thickness of the partition wall portion 12 is preferably 110 ⁇ m or more and 380 ⁇ m or less, more preferably 150 ⁇ m or more and 330 ⁇ m or less, and even more preferably 180 ⁇ m or more and 310 ⁇ m or less.
  • the cell density per square inch of the base material 10 can be adjusted as appropriate in consideration of PM trapping performance, pressure loss, etc. From the viewpoint of improving PM trapping performance and suppressing an increase in pressure loss, the cell density per square inch of the base material 10 is preferably 180 cells or more and 350 cells or less.
  • the cell density per square inch of the base material 10 is the cell density per square inch of the base material 10 in a cross section obtained by cutting the base material 10 along a plane perpendicular to the axial direction of the base material 10. This is the total number of side cells 13b).
  • the first catalyst layer 20 will be explained below.
  • the first catalyst layer 20 contains Rh.
  • Rh is present in the first catalyst layer in the form of a catalytically active component containing Rh, such as a metal Rh, an alloy containing Rh, a compound containing Rh (for example, an oxide of Rh), etc., which can function as a catalytically active component. Included in 20. From the viewpoint of improving exhaust gas purification performance, the catalytically active component containing Rh is preferably in the form of particles.
  • the metal equivalent amount of Rh in the first catalyst layer 20 is preferably 0.1% by mass or more and 10.0% by mass based on the mass of the first catalyst layer 20.
  • the content is more preferably 0.2% by mass or more and 5.0% by mass or less, even more preferably 0.3% by mass or more and 3.0% by mass or less.
  • the first catalyst layer 20 may contain one or more noble metal elements other than Rh.
  • the noble metal elements other than Rh can be selected from, for example, Pt, Pd, Ru, Ir, Os, and the like.
  • the noble metal element other than Rh includes a noble metal element other than Rh in a form that can function as a catalytically active component, for example, a metal, an alloy containing a noble metal element, a compound containing a noble metal element (e.g., an oxide of a noble metal element), etc. It is contained in the first catalyst layer 20 in the form of a catalytically active component. From the viewpoint of improving exhaust gas purification performance, the catalytically active component containing a noble metal element other than Rh is preferably in the form of particles.
  • the total metal equivalent amount of all noble metal elements in the first catalyst layer 20 is preferably 0.1% by mass or more based on the mass of the first catalyst layer 20.
  • the content is 0% by mass or less, more preferably 0.2% by mass or more and 5.0% by mass or less, even more preferably 0.3% by mass or more and 3.0% by mass or less.
  • the metal equivalent amount of Rh in the first catalyst layer 20 should be larger than the metal equivalent amount of each noble metal element other than Rh in the first catalyst layer 20. is preferred. Further, from the same viewpoint, the metal equivalent amount of Rh in the first catalyst layer 20 is preferably larger than the total metal equivalent amount of all noble metal elements other than Rh in the first catalyst layer 20.
  • the ratio of the metal equivalent amount of each noble metal element other than Rh in the first catalyst layer 20 to the metal equivalent amount of Rh in the first catalyst layer 20 is preferably 0.9 or less, more preferably 0. .5 or less, and even more preferably 0.3 or less.
  • the lower limit of this ratio is zero.
  • the ratio may be, for example, 0.01 or more, 0.1 or more, or 0.15 or more. Each of these lower limits may be combined with any of the above upper limits.
  • the ratio of the total metal equivalent amount of all noble metal elements other than Rh in the first catalyst layer 20 to the metal equivalent amount of Rh in the first catalyst layer 20 is preferably 0.9 or less, more preferably It is 0.5 or less, more preferably 0.3 or less.
  • the lower limit of this ratio is zero.
  • the ratio may be, for example, 0.01 or more, 0.1 or more, or 0.2 or more. Each of these lower limits may be combined with any of the above upper limits.
  • the first catalyst layer 20 may contain Pt.
  • Pt is present in the first catalyst layer in the form of a catalytically active component containing Pt, such as metal Pt, an alloy containing Pt, a compound containing Pt (for example, an oxide of Pt), etc., which can function as a catalytically active component. Included in 20. From the viewpoint of improving exhaust gas purification performance, the catalytically active component containing Pt is preferably in the form of particles.
  • the ratio of the metal equivalent amount of Pt in the first catalyst layer 20 to the total metal equivalent amount of all noble metal elements in the first catalyst layer 20 is preferably 0.3 or less in terms of mass ratio. If the ratio is 0.3 or less, the catalytic activity of Rh can be stabilized.
  • the lower limit of this ratio is zero.
  • the ratio may be, for example, 0.01 or more, 0.5 or more, or 0.1 or more. Each of these lower limits can be combined with the above upper limits.
  • the metal equivalent amount of each noble metal element in the first catalyst layer 20 is It can be determined from information on the raw materials used in the production of. If information on the raw materials used to manufacture the first catalyst layer 20 is not known, the metal equivalent amount of each noble metal element in the first catalyst layer 20 can be determined using an inductively coupled plasma optical emission spectrometer (ICP-OES), It can be determined using an X-ray fluorescence analyzer (XRF), a scanning electron microscope-energy dispersive X-ray analyzer (SEM-EDX), or the like. Specifically, it is as follows.
  • ICP-OES inductively coupled plasma optical emission spectrometer
  • XRF X-ray fluorescence analyzer
  • SEM-EDX scanning electron microscope-energy dispersive X-ray analyzer
  • Elemental analysis is performed on the sample obtained from the first catalyst layer 20 using a conventional method such as SEM-EDX, and the types of constituent elements of the entire sample are identified, as well as the metal equivalent amount of each identified metal element. Find (mass%). For each of the 10 fields of view of the SEM, the metal equivalent amount (mass%) of each metal element is determined, and the average value of the metal equivalent amount (mass %) of each metal element in the 10 fields of view is determined for each metal in the first catalyst layer 20. It is expressed as the metal equivalent amount (mass%) of the element.
  • the mass of the first catalyst layer 20 per unit volume of the portion of the base material 10 where the first catalyst layer 20 is formed is preferably 11 g/L or more and 133 g/L. L or less, more preferably 22 g/L or more and 89 g/L or less, even more preferably 22 g/L or more and 67 g/L or less.
  • the mass of the first catalyst layer 20 per unit volume of the portion of the base material 10 where the first catalyst layer 20 is formed is calculated by the formula: (mass of the first catalyst layer 20)/((volume of the base material 10) It is calculated from ⁇ (average length L 20 of first catalyst layer 20 / length L 10 of base material 10)).
  • the “mass of the first catalyst layer 20” refers to the mass of noble metal elements in metal terms among all the metal elements contained in the first catalyst layer 20, and the oxidized mass of metal elements other than the noble metal elements. It means the sum of the calculated mass in physical terms. That is, “the mass of the first catalyst layer 20” is the mass of the noble metal element contained in the first catalyst layer 20 in terms of metal, and the mass of the metal element other than the noble metal element contained in the first catalyst layer 20 in terms of oxide. means the calculated mass obtained by summing the Note that the term “metal element” also includes metalloid elements such as Si and B.
  • non-noble metal element includes Pt, Pd, Rh, Au, Ag, Ru, Ir, and Os.
  • oxides of rare earth elements other than Ce, Pr and Tb are referred to as sesquioxides (M 2 O 3 , M represents rare earth elements other than Ce, Pr and Tb), and oxides of Ce are referred to as CeO 2 , Pr oxide is Pr 6 O 11 , Tb oxide is Tb 4 O 7 , Al oxide is Al 2 O 3 , Zr oxide is ZrO 2 , Si oxide is SiO 2 , B oxide is B 2 O 3 , Cr oxide is Cr 2 O 3 , Mg oxide is MgO, Ca oxide is CaO, Sr oxide is SrO, Ba The oxide of is BaO, the oxide of Fe is Fe 3 O 4 , the oxide of Mn is Mn 3 O 4 , the oxide of Ni is NiO, the oxide of Ti is TiO 2 , the oxide of Zn. means ZnO, and oxide of Sn means SnO2 .
  • An example of a method for measuring the average length L 20 of the first catalyst layer 20 is as follows.
  • a sample extending in the axial direction of the base material 10 and having the same length as the length L10 of the base material 10 is cut out from the exhaust gas purifying catalyst 1.
  • the sample is, for example, cylindrical with a diameter of 25.4 mm. Note that the value of the diameter of the sample can be changed as necessary.
  • the sample was cut at intervals of 5 mm along a plane perpendicular to the axial direction of the base material 10, and the first cut piece, the second cut piece, ..., the nth cut piece were cut in order from the end of the sample on the exhaust gas inflow side. obtain.
  • the length of the cut piece is 5 mm.
  • the composition of the cut pieces was determined using an inductively coupled plasma optical emission spectrometer (ICP-OES), an X-ray fluorescence spectrometer (XRF), a scanning electron microscope-energy dispersive X-ray spectrometer (SEM-EDX), etc. Based on the composition of the cut piece, it is determined whether the cut piece includes a part of the first catalyst layer 20 or not.
  • ICP-OES inductively coupled plasma optical emission spectrometer
  • XRF X-ray fluorescence spectrometer
  • SEM-EDX scanning electron microscope-energy dispersive X-ray spectrometer
  • the cut surface can be observed using a scanning electron microscope (SEM), an electron beam microanalyzer (EPMA), etc., and it can be confirmed whether the cut piece includes a part of the first catalyst layer 20 or not.
  • SEM scanning electron microscope
  • EPMA electron beam microanalyzer
  • elemental mapping of the cut surface may be performed. Elemental mapping can be performed using, for example, a SEM-EDX, an electron beam microanalyzer (EPMA), a transmission type X-ray inspection device, or the like.
  • the first cut piece to the kth cut piece include a part of the first catalyst layer 20, but the (k+1)th to nth cut pieces do not include a part of the first catalyst layer 20, they are not included in the sample.
  • the length of the first catalyst layer 20 is (5 ⁇ k) mm.
  • An example of a more detailed method for measuring the length of the first catalyst layer 20 included in the sample is as follows.
  • the k-th cut piece (that is, the cut piece obtained from the closest exhaust gas outflow side of the sample among the cut pieces including a part of the first catalyst layer 20) is cut in the axial direction of the base material 10, and then SEM, EPMA
  • SEM, EPMA By observing a portion of the first catalyst layer 20 present on the cut surface using a tool such as a cutting tool, the length of the portion of the first catalyst layer 20 at the k-th cut section is measured.
  • the length of the first catalyst layer 20 included in each sample is measured, and the average value thereof is determined as the average length of the first catalyst layer 20.
  • L be 20 .
  • the amount per unit volume of the portion of the base material 10 on which the first catalyst layer 20 is formed is The mass of the first catalyst layer 20 can be determined from information on the raw materials used to manufacture the first catalyst layer 20.
  • the first catalyst layer 20 includes one or more types of carriers, and at least a part of the catalytically active component is supported on the one or more types of carriers.
  • 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 or the state in which it is maintained. It can be confirmed that at least a portion of the catalytically active component is supported on the carrier using, for example, SEM-EDX. Specifically, in the elemental mapping obtained by analyzing the cross section of the catalyst layer with SEM-EDX, if at least part of the catalytically active component and the support are present in the same area, at least part of the catalytically active component is It can be determined that the part is supported on the carrier.
  • the carrier can be selected from, for example, inorganic oxides.
  • the inorganic oxide is, for example, particulate. From the viewpoint of improving the ability to support the catalytically active component, the inorganic oxide is preferably porous.
  • the inorganic oxide may or may not have oxygen storage capacity (OSC).
  • OSC oxygen storage capacity
  • Inorganic oxides used as supports are distinguished from inorganic oxides used as binders (eg, inorganic oxide binders such as alumina binders, zirconia binders, titania binders, silica binders, etc.).
  • the inorganic oxide used as the binder is derived from the sol used as a raw material (for example, an inorganic oxide sol such as alumina sol, zirconia sol, titania sol, silica sol, etc.).
  • inorganic oxides include Al-based oxides, rare earth element (hereinafter sometimes referred to as "Ln") oxides, Ln-Zr-based composite oxides, zirconia (ZrO 2 ), and silica (SiO 2 ), titania (TiO 2 ), zeolite (aluminosilicate), MgO, ZnO, SnO 2 and the like-based oxides.
  • Ln rare earth element
  • ZrO 2 zirconia
  • silica SiO 2
  • TiO 2 titania
  • zeolite aluminosilicate
  • an Al-based oxide refers to an oxide containing Al, in which Al is the element with the highest content on a mass basis among the elements other than oxygen constituting the oxide. .
  • Al-based oxides are distinguished from alumina, which is used as a binder. In this specification, alumina used as a binder may be referred to as "alumina binder”.
  • Al-based oxides generally have higher heat resistance than other inorganic oxides (for example, Ln-Zr-based composite oxides). Therefore, by including the Al-based oxide in the first catalyst layer 20, the heat resistance of the first catalyst layer 20 is improved, and the exhaust gas purification performance of the first catalyst layer 20 is improved.
  • Al-based oxide examples include alumina (Al 2 O 3 ), modified alumina, and the like.
  • Modified alumina contains one or more elements other than Al and O.
  • modified alumina examples include oxides obtained by modifying the surface of alumina with elements other than Al and O, and oxides obtained by dissolving elements other than Al and O in alumina.
  • Elements other than Al and O can be selected from, for example, B, Si, Zr, Cr, rare earth elements, alkaline earth metal elements, and the like.
  • the modified alumina include alumina-silica, alumina-zirconia, alumina-chromia, alumina-ceria, and alumina-lanthana.
  • the Al 2 O 3 equivalent amount of Al in the Al-based oxide is preferably 50% by mass or more, more preferably 70% by mass or more, and more preferably 50% by mass or more, more preferably 70% by mass or more, based on the mass of the Al-based oxide. More preferably, it is 80% by mass or more. The upper limit is 100% by mass.
  • the amount of Al in the Al-based oxide in terms of Al 2 O 3 is It can be determined from information on the raw materials used in the production of. If the information on the raw materials used for manufacturing the first catalyst layer 20 is not known, the amount of Al in the Al-based oxide in terms of Al 2 O 3 can be calculated using an energy dispersive X-ray spectrometer. (EDX) analysis and obtained elemental mapping and EDX elemental analysis of specified particles.
  • EDX energy dispersive X-ray spectrometer.
  • the oxide equivalent amount of a predetermined element in a specified particle can be determined.
  • the amount of the Al-based oxide in the first catalyst layer 20 is preferably based on the mass of the first catalyst layer 20.
  • the content is 5% by mass or more and 50% by mass or less, more preferably 5% by mass or more and 40% by mass or less, even more preferably 7% by mass or more and 30% by mass or less. If information on the raw materials used to manufacture the first catalyst layer 20 (for example, composition, amount, etc.) is known, the amount of Al-based oxide in the first catalyst layer 20 can be determined by It can be determined from information on raw materials used in manufacturing.
  • the amount of Al-based oxide in the first catalyst layer 20 can be determined using ICP-OES, XRF, SEM-EDX, etc. You can ask for it. Specifically, it is as follows.
  • the Ln-Zr-based composite oxide is a composite oxide containing one or more types of Ln and Zr, and the mass of Ln in the composite oxide in terms of oxide is less than the mass of the composite oxide.
  • oxidation is 3% by mass or more and 97% by mass or less
  • the mass of Zr in the composite oxide in terms of ZrO 2 is 3% by mass or more and 97% by mass or less, based on the mass of the composite oxide.
  • the mass of one or more types of Ln in terms of oxide means, when the Ln-Zr-based composite oxide contains one type of Ln, the amount of the one type of Ln in terms of oxide, When the Ln-Zr-based composite oxide contains two or more types of Ln, it means the total amount of the two or more types of Ln in terms of oxide.
  • Ln-Zr-based composite oxides have oxygen storage ability (that is, the ability to store oxygen when the oxygen concentration in the exhaust gas is high and release oxygen when the oxygen concentration in the exhaust gas is low). Expanding the operating window of catalytically active components by mitigating concentration fluctuations. Therefore, by including the Ln-Zr-based composite oxide in the first catalyst layer 20, the exhaust gas purifying ability of the first catalyst layer 20 is improved.
  • the Ln--Zr-based composite oxide (hereinafter referred to as "first Ln--Zr-based composite oxide") according to one embodiment includes Ce and Zr.
  • the first Ln--Zr-based composite oxide may be referred to as a "Ce--Zr-based composite oxide.”
  • Ce, Zr, and O preferably form a solid solution phase.
  • Ce, Zr, and O may form a single phase (CeO 2 phase, ZrO 2 phase, etc.) that is a crystalline phase or an amorphous phase in addition to a solid solution phase. It can be confirmed using X-ray diffraction (XRD), SEM-EDX, etc. that Ce, Zr, and O form a solid solution.
  • the first Ln-Zr-based composite oxide may contain one or more metal elements other than Ce and Zr.
  • metal elements other than Ce and Zr include rare earth elements other than Ce.
  • rare earth elements other than Ce include Y, Pr, Sc, La, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.
  • Metal elements other than Ce and Zr may form a solid solution phase together with Ce, Zr, and O, or may form a single phase that is a crystalline phase or an amorphous phase, or may form a solid solution phase or an amorphous phase. Both may form a single phase. Formation of a solid solution phase can be confirmed using XRD, SEM-EDX, etc.
  • the CeO 2 equivalent amount of Ce in the first Ln-Zr composite oxide is preferably 3% by mass based on the mass of the first Ln-Zr composite oxide.
  • the content is 40% by mass or less, more preferably 5% by mass or more and 30% by mass or less, even more preferably 5% by mass or more and 25% by mass or less.
  • the CeO 2 equivalent amount of Ce in the first Ln-Zr based composite oxide can be determined in the same manner as the Al 2 O 3 equivalent amount of Al in the Al based oxide.
  • the amount of Zr in the first Ln-Zr composite oxide converted to ZrO 2 is preferably 30% by mass or more based on the mass of the first Ln-Zr composite oxide.
  • the content is 90% by mass or less, more preferably 40% by mass or more and 80% by mass or less, even more preferably 50% by mass or more and 80% by mass or less.
  • the amount of Zr in the first Ln--Zr-based composite oxide in terms of ZrO 2 can be determined in the same manner as the amount of Al in the Al-based oxide in terms of Al 2 O 3 .
  • the total amount of Ce in terms of CeO 2 and the amount of Zr in terms of ZrO 2 in the first Ln-Zr complex oxide is It is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, based on the mass of .
  • the upper limit is 100% by mass.
  • the first Ln-Zr composite oxide in the first catalyst layer 20 includes the first Ln-Zr composite oxide, from the viewpoint of improving oxygen storage capacity and heat resistance, the first Ln-Zr composite oxide in the first catalyst layer 20
  • the amount is preferably 40% by mass or more and 95% by mass or less, more preferably 50% by mass or more and 93% by mass or less, even more preferably 60% by mass or more and 90% by mass or less, based on the mass of the first catalyst layer 20. be.
  • the amount of the first Ln--Zr-based composite oxide in the first catalyst layer 20 can be determined in the same manner as the amount of Al-based oxide in the first catalyst layer 20.
  • the Ln-Zr-based composite oxide according to another embodiment contains one or more types of Ln other than Ce and Zr, Contains no Ce.
  • second Ln-Zr-based composite oxide contains one or more types of Ln other than Ce and Zr, Contains no Ce.
  • one or more types of Ln, Zr, and O other than Ce preferably form a solid solution phase.
  • One or more types of Ln, Zr, and O other than Ce may be present in a single phase that is a crystalline phase or an amorphous phase (an oxide phase of one or more types of Ln other than Ce) in addition to a solid solution phase. , ZrO 2 phase, etc.). It can be confirmed using XRD, SEM-EDX, etc. that one or more types of Ln, Zr, and O other than Ce form a solid solution.
  • the second Ln-Zr-based composite oxide may contain one or more metal elements other than Ln and Zr.
  • metal elements other than Ln and Zr include alkaline earth metal elements.
  • alkaline earth metal elements include Ca, Sr, and Ba.
  • Metal elements other than Ln and Zr may form a solid solution phase with one or more types of Ln other than Ce, Zr, and O, or may form a single phase that is a crystalline phase or an amorphous phase. or may form both a solid solution phase and a single phase. Formation of a solid solution phase can be confirmed using XRD, SEM-EDX, etc.
  • the oxide equivalent amount of one or more types of Ln other than Ce in the second Ln-Zr composite oxide is Based on the mass, the content is preferably 10% by mass or more and 80% by mass or less, more preferably 20% by mass or more and 70% by mass or less, even more preferably 30% by mass or more and 70% by mass or less.
  • the oxide equivalent amount of one or more types of Ln other than Ce in the second Ln-Zr based composite oxide means that the second Ln-Zr based composite oxide contains one type of Ln other than Ce.
  • the oxide equivalent amount of one type of Ln other than Ce is Based on the mass, the content is preferably 10% by mass or more and 80% by mass or less, more preferably 20% by mass or more and 70% by mass or less, even more preferably 30% by mass or more and 70% by mass or less.
  • the oxide-equivalent amount of one or more types of Ln other than Ce in the second Ln-Zr-based composite oxide is determined in the same manner as the Al 2 O 3- equivalent amount of Al in the Al-based oxide. I can do it.
  • the amount of Zr in the second Ln-Zr composite oxide converted to ZrO 2 is preferably 30% by mass or more based on the mass of the second Ln-Zr composite oxide.
  • the content is 90% by mass or less, more preferably 35% by mass or more and 80% by mass or less, even more preferably 40% by mass or more and 75% by mass or less.
  • the ZrO 2 equivalent amount of Zr in the second Ln-Zr based composite oxide can be determined in the same manner as the Al 2 O 3 equivalent amount of Al in the Al based oxide.
  • the sum of the oxide equivalent amount of one or more types of Ln other than Ce and the ZrO 2 equivalent amount of Zr in the second Ln-Zr-based composite oxide is: It is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, based on the mass of the second Ln-Zr complex oxide.
  • the upper limit is 100% by mass.
  • the second Ln-Zr-based composite oxide in the first catalyst layer 20 includes the second Ln-Zr-based composite oxide, from the viewpoint of improving oxygen storage capacity and heat resistance, the second Ln-Zr-based composite oxide in the first catalyst layer 20
  • the amount is preferably 40% by mass or more and 95% by mass or less, more preferably 50% by mass or more and 93% by mass or less, even more preferably 60% by mass or more and 90% by mass or less, based on the mass of the first catalyst layer 20. be.
  • the amount of the second Ln-Zr based composite oxide in the first catalyst layer 20 can be determined in the same manner as the amount of the Al based oxide in the first catalyst layer 20.
  • the first and second Ln-Zr-based composite oxides may be used together.
  • the first and second Ln-Zr-based composite oxides from the viewpoint of improving oxygen storage capacity and heat resistance, the first and second Ln- The total amount of the Zr-based composite oxide is preferably 40% by mass or more and 95% by mass or less, more preferably 50% by mass or more and 93% by mass or less, even more preferably 60% by mass, based on the mass of the first catalyst layer 20. % or more and 90% by mass or less.
  • the total amount of inorganic oxides other than Al-based oxides and Ln-Zr-based composite oxides in the first catalyst layer 20 is based on the mass of the first catalyst layer 20. , preferably from 0% by mass to 20% by mass, more preferably from 0.5% by mass to 15% by mass, even more preferably from 1% by mass to 15% by mass.
  • the total amount of inorganic oxides other than Al-based oxides and Ln-Zr-based composite oxides in the first catalyst layer 20 can be determined in the same manner as the amount of Al-based oxides in the first catalyst layer 20. .
  • the first catalyst layer 20 may contain a stabilizer, a binder, and the like.
  • the binder include inorganic oxide binders such as alumina binder, zirconia binder, titania binder, and silica binder.
  • the inorganic oxide binder is derived from an inorganic oxide sol such as alumina sol, zirconia sol, titania sol, and silica sol.
  • the stabilizer include nitrates, carbonates, oxides, and sulfates of alkaline earth metal elements.
  • the first catalyst layer 20 is formed on the inflow side cell 13a side of the partition wall portion 12.
  • the first catalyst layer 20 extends along the exhaust gas flow direction E from the end of the partition wall 12 on the exhaust gas inflow side. In this embodiment, the first catalyst layer 20 does not reach the end of the partition wall 12 on the exhaust gas outflow side, but may reach the end of the partition wall 12 on the exhaust gas outflow side.
  • the catalyst layer 20 has a portion that protrudes from the outer surface S1a of the partition wall portion 12 on the inflow side cell 13a side toward the inflow side cell 13a side (hereinafter referred to as “raised portion”). This improves the contact between the exhaust gas and PM, making it possible to more effectively improve the exhaust gas purification performance and the PM trapping performance.
  • the first catalyst layer 20 may be composed of only a raised portion, or may include a portion existing inside the partition wall portion 12 (hereinafter referred to as “internal portion”) together with the raised portion. Since the partition wall portion 12 is porous, when forming the first catalyst layer 20, an internal portion may be formed together with a raised portion. The raised portion and the internal portion may be continuous. The first catalyst layer 20 may be composed only of an internal portion. “The first catalyst layer 20 is formed on the inflow side cell 13a side of the partition wall 12” includes an embodiment in which the first catalyst layer 20 is formed only of a raised portion, and an embodiment in which the first catalyst layer 20 is internally formed.
  • first catalyst layer 20 includes only a portion and embodiments in which the first catalyst layer 20 has a raised portion and an inner portion are included.
  • the region where the raised 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 internal portion of the first catalyst layer 20 exists overlaps with the region where the partition wall portion 12 exists. Therefore, the exhaust gas purifying catalyst 1 was cut along a plane perpendicular to the axial direction of the base material 10, and the first catalyst layer 20 present on the cut surface was observed, and the morphology between the first catalyst layer 20 and the partition wall portion 12 was observed. Based on the difference, the raised portion and the inner portion of the first catalyst layer 20 can be identified.
  • elemental mapping of the cut surface may be performed. Elemental mapping can be performed, for example, by using a combination of observation of the cut surface using SEM and compositional analysis of the cut surface.
  • Elemental mapping can be performed using, for example, a SEM-EDX, an electron beam microanalyzer (EPMA), a transmission type X-ray inspection device, or the like.
  • EMA electron beam microanalyzer
  • the protruding portion and the internal portion can be identified based on the difference in morphology and composition between the first catalyst layer 20 and the partition wall portion 12.
  • the average length L 20 of the first catalyst layer 20 can be adjusted as appropriate in consideration of exhaust gas purification performance, PM trapping performance, and the like. From the viewpoint of improving exhaust gas purification performance and PM trapping performance, the percentage of the average length L 20 of the first catalyst layer 20 to the length L 10 of the base material 10 (L 20 /L 10 ⁇ 100) is preferably 15 % or more and 90% or less, more preferably 20% or more and 80% or less, even more preferably 30% or more and 80% or less.
  • the second catalyst layer 30 contains Rh.
  • Rh is present in the second catalyst layer in the form of a catalytically active component containing Rh, such as a metal Rh, an alloy containing Rh, a compound containing Rh (for example, an oxide of Rh), etc., which can function as a catalytically active component. Included in 30. From the viewpoint of improving exhaust gas purification performance, the catalytically active component containing Rh is preferably in the form of particles.
  • the metal equivalent amount of Rh in the second catalyst layer 30 is preferably 0.1% by mass or more and 10.0% by mass based on the mass of the second catalyst layer 30.
  • the content is more preferably 0.2% by mass or more and 5.0% by mass or less, even more preferably 0.3% by mass or more and 3.0% by mass or less.
  • the second catalyst layer 30 may contain one or more noble metal elements other than Rh.
  • the noble metal elements other than Rh can be selected from, for example, Pt, Pd, Ru, Ir, Os, and the like.
  • the noble metal element other than Rh includes a noble metal element other than Rh in a form that can function as a catalytically active component, for example, a metal, an alloy containing a noble metal element, a compound containing a noble metal element (e.g., an oxide of a noble metal element), etc. It is contained in the second catalyst layer 30 in the form of a catalytically active component. From the viewpoint of improving exhaust gas purification performance, the catalytically active component containing a noble metal element other than Rh is preferably in the form of particles.
  • the total metal equivalent amount of all noble metal elements in the second catalyst layer 30 is preferably 0.1% by mass or more based on the mass of the second catalyst layer 30.
  • the content is 0% by mass or less, more preferably 0.2% by mass or more and 5.0% by mass or less, even more preferably 0.3% by mass or more and 3.0% by mass or less.
  • the metal equivalent amount of Rh in the second catalyst layer 30 should be larger than the metal equivalent amount of each noble metal element other than Rh in the second catalyst layer 30. is preferred. Further, from the same viewpoint, the metal equivalent amount of Rh in the second catalyst layer 30 is preferably larger than the total metal equivalent amount of all noble metal elements other than Rh in the second catalyst layer 30.
  • the ratio of the metal equivalent amount of each noble metal element other than Rh in the second catalyst layer 30 to the metal equivalent amount of Rh in the second catalyst layer 30 is preferably 0.9 or less, more preferably 0. .5 or less, and even more preferably 0.3 or less.
  • the lower limit of this ratio is zero.
  • the ratio may be, for example, 0.01 or more, 0.1 or more, or 0.15 or more. Each of these lower limits may be combined with any of the above upper limits.
  • the ratio of the total metal equivalent amount of all noble metal elements other than Rh in the second catalyst layer 30 to the metal equivalent amount of Rh in the second catalyst layer 30 is preferably 0.9 or less, more preferably It is 0.5 or less, more preferably 0.3 or less.
  • the lower limit of this ratio is zero.
  • the ratio may be, for example, 0.01 or more, 0.1 or more, or 0.2 or more. Each of these lower limits may be combined with any of the above upper limits.
  • the metal equivalent amount of each noble metal element in the second catalyst layer 30 is It can be determined from information on the raw materials used in the production of. If information on the raw materials used to manufacture the second catalyst layer 30 is not known, the amount of each noble metal element in the second catalyst layer 30 in terms of metal is the amount of each noble metal element in the first catalyst layer 20 It can be determined in the same way as the quantity.
  • the mass of the second catalyst layer 30 per unit volume of the portion of the base material 10 where the second catalyst layer 30 is formed is preferably 7 g/L or more and 86 g/L. L or less, more preferably 14 g/L or more and 57 g/L or less, even more preferably 14 g/L or more and 43 g/L or less.
  • the mass of the second catalyst layer 30 per unit volume of the portion of the base material 10 where the second catalyst layer 30 is formed is calculated by the formula: (mass of the second catalyst layer 30)/((volume of the base material 10) It is calculated from ⁇ (average length L 30 of second catalyst layer 30 / length L 10 of base material 10)).
  • first catalyst layer 20 also applies to the mass of the second catalyst layer 30.
  • second catalyst layer 30 is read as “second catalyst layer 30.”
  • the above description regarding the method for measuring the average length L 20 of the first catalyst layer 20 also applies to the method for measuring the average length L 30 of the second catalyst layer 30 .
  • the "first catalyst layer 20" is read as the "second catalyst layer 30”
  • the "average length L 20 " is read as "average length L 30 ".
  • the sample is cut at 5 mm intervals along a plane perpendicular to the axial direction of the base material 10, and the samples are cut in order from the end of the sample on the exhaust gas outflow side.
  • a first cut piece, a second cut piece, . . . , an nth cut piece are obtained.
  • the amount per unit volume of the portion of the base material 10 on which the second catalyst layer 30 is formed is known.
  • the mass of the second catalyst layer 30 can be determined from information on the raw materials used to manufacture the second catalyst layer 30.
  • the second catalyst layer 30 includes one or more types of carriers, and at least a part of the catalytically active component is supported on the one or more types of carriers.
  • the meaning and confirmation method of "at least a portion of the catalytically active component is supported on the carrier" are as described in the above description regarding the first catalyst layer 20.
  • the above explanation regarding the carrier in the first catalyst layer 20 also applies to the second catalyst layer 30.
  • first catalyst layer 20 is read as "second catalyst layer 30.”
  • the second catalyst layer 30 may contain a stabilizer, a binder, and the like. A description of the binder and stabilizer is given above.
  • the second catalyst layer 30 is formed on the outflow side cell 13b side of the partition wall portion 12.
  • the second catalyst layer 30 extends from the end of the partition wall 12 on the exhaust gas outflow side in a direction opposite to the exhaust gas flow direction E.
  • the second catalyst layer 30 does not reach the end of the partition wall 12 on the exhaust gas inflow side, but may reach the end of the partition wall 12 on the exhaust gas inflow side.
  • the second catalyst layer 30 protrudes from the outer surface S1b of the partition wall 12 on the outflow side cell 13b side toward the outflow side cell 13b side, that is, the second It is preferable that the catalyst layer 30 has a portion that protrudes from the outer surface S1b of the partition wall portion 12 on the outflow side cell 13b side toward the outflow side cell 13b side (hereinafter referred to as “raised portion”). This improves the contact between the exhaust gas and PM, making it possible to more effectively improve the exhaust gas purification performance and the PM trapping performance.
  • the second catalyst layer 30 may be composed of only a raised portion, or may include a portion existing inside the partition wall portion 12 (hereinafter referred to as “internal portion”) together with the raised portion. Since the partition wall portion 12 is porous, when forming the second catalyst layer 30, an internal portion may be formed together with a raised portion. The raised portion and the internal portion may be continuous. The second catalyst layer 30 may be composed only of an internal portion. “The second catalyst layer 30 is formed on the outflow cell 13b side of the partition wall 12” includes an embodiment in which the second catalyst layer 30 is formed only of a raised portion, and an embodiment in which the second catalyst layer 30 is internally formed.
  • both embodiments in which the second catalyst layer 30 includes only a portion and embodiments in which the second catalyst layer 30 has a raised portion and an inner portion are included.
  • first catalyst layer 20 is read as “second catalyst layer 30.”
  • the average length L 30 of the second catalyst layer 30 can be adjusted as appropriate in consideration of exhaust gas purification performance, PM trapping performance, and the like. From the viewpoint of improving exhaust gas purification performance and PM trapping performance, the percentage of the average length L 30 of the second catalyst layer 30 to the length L 10 of the base material 10 (L 30 /L 10 ⁇ 100) is preferably 15 % or more and 90% or less, more preferably 20% or more and 80% or less, even more preferably 30% or more and 80% or less.
  • the percentage ((L 20 +L 30 )/L 10 ⁇ 100) is preferably 100% or more and 180% or less, more preferably 105% or more and 150% or less, even more preferably 110% or more and 130% or less.
  • the third catalyst layer 40 will be explained below.
  • the third catalyst layer 40 contains Pt.
  • Pt is present in the third catalyst layer in the form of a catalytically active component containing Pt, such as metal Pt, an alloy containing Pt, a compound containing Pt (for example, an oxide of Pt), etc., which can function as a catalytically active component. Included in 40. From the viewpoint of improving exhaust gas purification performance, the catalytically active component containing Pt is preferably in the form of particles.
  • the metal equivalent amount of Pt in the third catalyst layer 40 is preferably 0.1% by mass or more and 20% by mass or less, based on the mass of the third catalyst layer 40. More preferably 0.5% by mass or more and 15% by mass or less, even more preferably 1.0% by mass or more and 10% by mass or less.
  • the third catalyst layer 40 may contain one or more noble metal elements other than Pt.
  • the noble metal element other than Pt can be selected from, for example, Au, Ag, Rh, Pd, Ru, Ir, Os, and the like.
  • the noble metal element other than Pt includes a noble metal element other than Pt in a form that can function as a catalytically active component, for example, a metal, an alloy containing a noble metal element, a compound containing a noble metal element (e.g., an oxide of a noble metal element), etc. It is contained in the third catalyst layer 40 in the form of a catalytically active component. From the viewpoint of improving exhaust gas purification performance, the catalytically active component containing a noble metal element other than Pt is preferably in the form of particles.
  • the total metal equivalent amount of all precious metal elements in the third catalyst layer 40 is preferably 0.1% by mass or more and 20% by mass based on the mass of the third catalyst layer 40. % or less, more preferably 0.5% by mass or more and 15% by mass or less, even more preferably 1.0% by mass or more and 10% by mass or less.
  • the metal equivalent amount of Pt in the third catalyst layer 40 should be larger than the metal equivalent amount of each noble metal element other than Pt in the third catalyst layer 40. is preferred. Further, from the same viewpoint, it is preferable that the metal equivalent amount of Pt in the third catalyst layer 40 is larger than the total metal equivalent amount of all noble metal elements other than Pt in the third catalyst layer 40.
  • the ratio of the metal equivalent amount of each noble metal element other than Pt in the third catalyst layer 40 to the metal equivalent amount of Pt in the third catalyst layer 40 is preferably 0.9 or less, more preferably 0. .5 or less, and even more preferably 0.3 or less.
  • the lower limit of this ratio is zero.
  • the ratio may be, for example, 0.01 or more, 0.1 or more, or 0.15 or more. Each of these lower limits may be combined with any of the above upper limits.
  • the ratio of the total metal equivalent amount of all noble metal elements other than Pt in the third catalyst layer 40 to the metal equivalent amount of Pt in the third catalyst layer 40 is preferably 0.9 or less, more preferably It is 0.5 or less, more preferably 0.3 or less.
  • the lower limit of this ratio is zero.
  • the ratio may be, for example, 0.01 or more, 0.1 or more, or 0.2 or more. Each of these lower limits may be combined with any of the above upper limits.
  • the metal equivalent amount of each noble metal element in the third catalyst layer 40 is It can be determined from information on the raw materials used in the production of. If information on the raw materials used for manufacturing the third catalyst layer 40 is not known, the amount of each noble metal element in the third catalyst layer 40 in terms of metal is It can be determined in the same way as the quantity.
  • the mass of the third catalyst layer 40 per unit volume of the portion of the base material 10 where the third catalyst layer 40 is formed is preferably 7 g/L or more and 86 g/L. L or less, more preferably 14 g/L or more and 57 g/L or less, even more preferably 14 g/L or more and 43 g/L or less.
  • the mass of the third catalyst layer 40 per unit volume of the portion of the base material 10 where the third catalyst layer 40 is formed is calculated by the formula: (mass of the third catalyst layer 40)/((volume of the base material 10) It is calculated from ⁇ (average length L 40 of third catalyst layer 40 / length L 10 of base material 10)).
  • first catalyst layer 20 also applies to the mass of the third catalyst layer 40.
  • first catalyst layer 20 is read as “third catalyst layer 40.”
  • first catalyst layer 20 is read as “third catalyst layer 40.”
  • the sample is cut at 5 mm intervals along a plane perpendicular to the axial direction of the base material 10, and the samples are cut in order from the end of the sample on the exhaust gas outflow side.
  • a first cut piece, a second cut piece, . . . , an nth cut piece are obtained.
  • the amount per unit volume of the portion of the base material 10 where the third catalyst layer 40 is formed is The mass of the third catalyst layer 40 can be determined from information on the raw materials used to manufacture the third catalyst layer 40.
  • the total mass of the portion where the layer 40 is formed and the mass of the third catalyst layer 40 per unit volume is preferably 14 g/L or more and 129 g/L or less, more preferably 21 g/L or more and 100 g/L or less, and even more Preferably it is 29 g/L or more and 86 g/L or less.
  • the mass of the second catalyst layer 30 per unit volume of the portion of the base material 10 where the second catalyst layer 30 is formed is The ratio of the masses of the three catalyst layers 40 is preferably 0.3 or more and 1.9 or less, more preferably 0.5 or more and 1.5 or less, and even more preferably 0.7 or more and 1.3 or less.
  • the third catalyst layer 40 includes one or more types of carriers, and at least a part of the catalytically active component is supported on the one or more types of carriers.
  • the meaning and confirmation method of "at least a portion of the catalytically active component is supported on the carrier" are as described in the above description regarding the first catalyst layer 20.
  • the above explanation regarding the carrier in the first catalyst layer 20 also applies to the third catalyst layer 40.
  • first catalyst layer 20 is read as "third catalyst layer 40.”
  • the third catalyst layer 40 may contain a stabilizer, a binder, and the like. A description of the binder and stabilizer is given above.
  • the third catalyst layer 40 is formed on the second catalyst layer 30.
  • the expression “the third catalyst layer 40 is formed on the second catalyst layer 30” means that the main surface of the second catalyst layer 30 is opposite to the main surface on the partition wall 12 side of the base material 10. This means that at least a portion (preferably all) of the third catalyst layer 40 is present on the main surface of the side.
  • the main surface of the second catalyst layer 30 means the outer surface of the second catalyst layer 30 that extends in the exhaust gas flow direction E.
  • the third catalyst layer 40 may be provided directly on the main surface of the second catalyst layer 30, or may be provided via another layer.
  • the third catalyst layer 40 extends from the end of the partition wall 12 on the exhaust gas outflow side in a direction opposite to the exhaust gas flow direction E.
  • the third catalyst layer 40 does not reach the end of the partition wall 12 on the exhaust gas inflow side, but may reach the end of the partition wall 12 on the exhaust gas inflow side.
  • the third catalyst layer 40 protrudes from the outer surface S1b of the partition wall portion 12 on the outflow side cell 13b side toward the outflow side cell 13b side. It is preferable that the catalyst layer 40 has a portion that protrudes from the outer surface S1b of the partition wall portion 12 on the outflow side cell 13b side toward the outflow side cell 13b side (hereinafter referred to as “raised portion”). This improves the contact between the exhaust gas and PM, making it possible to more effectively improve the exhaust gas purification performance and the PM trapping performance.
  • the third catalyst layer 40 may be composed of only a raised portion, or may have a portion that exists inside the partition wall portion 12 (hereinafter referred to as “internal portion”) together with the raised portion. Since the partition wall portion 12 is porous, when forming the third catalyst layer 40, an internal portion may be formed together with a raised portion. The raised portion and the internal portion may be continuous.
  • the third catalyst layer 40 may be composed only of an internal portion. "The third catalyst layer 40 is formed on the second catalyst layer 30" includes embodiments in which the third catalyst layer 40 is comprised only of raised parts, and embodiments in which the third catalyst layer 40 is comprised only of internal parts. Embodiments in which the third catalyst layer 40 has a raised portion and an embedded portion are both included. Among these, preferred are embodiments in which the third catalyst layer 40 includes only raised portions, and embodiments in which the third catalyst layer 40 includes raised portions and internal portions.
  • the raised portion of the third catalyst layer 40 exists on the outflow side cell 13b side rather than the outer surface S1b of the partition wall section 12 on the outflow side cell 13b side. It does not need to be in contact with the surface S1b.
  • the raised portion of the third catalyst layer 40 is formed on the internal portion of the second catalyst layer 30
  • the raised portion of the third catalyst layer 40 is formed on the outer surface of the partition wall portion 12 on the outflow side cell 13b side. come into contact with
  • the raised portion of the third catalyst layer 40 is formed on the raised portion of the second catalyst layer 30
  • the raised portion of the third catalyst layer 40 is formed on the outer surface of the partition wall portion 12 on the outflow side cell 13b side. Not in contact.
  • first catalyst layer 20 is read as “third catalyst layer 40.”
  • the average length L 40 of the third catalyst layer 40 can be adjusted as appropriate in consideration of exhaust gas purification performance, PM trapping performance, and the like. From the viewpoint of improving exhaust gas purification performance and PM trapping performance, the percentage of the average length L 40 of the third catalyst layer 40 to the length L 10 of the base material 10 (L 40 /L 10 ⁇ 100) is preferably 15 % or more and 90% or less, more preferably 20% or more and 80% or less, even more preferably 30% or more and 80% or less.
  • the percentage ((L 20 +L 40 )/L 10 ⁇ 100) is preferably 100% or more and 180% or less, more preferably 105% or more and 150% or less, even more preferably 110% or more and 130% or less.
  • the average length L 40 of the third catalyst layer 40 may be the same as or different from the average length L 30 of the second catalyst layer 30. Good too.
  • the percentage of the average length L 40 of the third catalyst layer 40 to the average length L 30 of the second catalyst layer 30 is preferably 50% or more and 150% or less, more preferably 70%. 130% or less.
  • the exhaust gas purification catalyst 1 when the exhaust gas flowing in from the end (opening) on the exhaust gas inflow side of the inflow side cell 13a passes through the porous partition wall 12, particulate matter (PM) in the exhaust gas is removed. ) is collected in the pores of the partition wall 12 , the pores of the first catalyst layer 20 , the pores of the second catalyst layer 30 , and the pores of the third catalyst layer 40 . Therefore, the exhaust gas purifying catalyst 1 is useful as a gasoline engine particulate filter or a diesel engine particulate filter.
  • the exhaust gas flowing in from the end (opening) on the exhaust gas inflow side of the inflow side cell 13a comes into contact with the first catalyst layer 20, passes through the porous partition wall 12, and enters the second It contacts the catalyst layer 30 and the third catalyst layer 40 in this order.
  • NOx in the exhaust gas is purified by Rh in the first catalyst layer 20.
  • NOx that has passed through the first catalyst layer 20 without being purified is sequentially purified by Rh in the second catalyst layer 30 and Pt in the third catalyst layer 40.
  • Per unit volume of the portion of the base material 10 where the third catalyst layer 40 is formed relative to the mass of the second catalyst layer 30 per unit volume of the portion of the base material 10 where the second catalyst layer 30 is formed When the mass ratio of the third catalyst layer 40 is more than 1.9, Pt in the third catalyst layer 40 can sufficiently contact exhaust gas, but Rh in the second catalyst layer 30 can sufficiently contact exhaust gas. This results in a decrease in NOx purification performance.
  • the third catalyst layer 40 is formed in the base material 10 relative to the mass of the second catalyst layer 30 per unit volume of the portion of the base material 10 where the second catalyst layer 30 is formed.
  • Rh in the second catalyst layer 30 can sufficiently contact the exhaust gas, and the third catalyst layer 40 The Pt inside can make sufficient contact with the exhaust gas, improving NOx purification performance.
  • the exhaust gas purification catalyst 1 can achieve both the purification performance of low-temperature NOx generated during low-speed operation of the internal combustion engine and the purification performance of high-temperature NOx generated during ultra-high-speed operation of the internal combustion engine. . That is, the exhaust gas purification catalyst 1 can exhibit excellent NOx purification performance in a wide temperature range from low to high temperatures.
  • Purification performance of low-temperature NOx generated during low-speed operation of an internal combustion engine refers to the performance of NOx emitted from the start of operation to 589 seconds after the start of operation in WLTC mode, which is one of the internationally regulated driving modes.
  • the "purification performance of high-temperature NOx generated during ultra-high-speed operation of an internal combustion engine” can be evaluated based on the amount of NOx emitted from 1477 seconds to 1800 seconds after the start of operation in the same WLTC mode. can be evaluated based on The specific evaluation method is as described in Examples.
  • a base material 10 a slurry for forming the first catalyst layer 20, a slurry for forming the second catalyst layer 30, and a slurry for forming the third catalyst layer 40 are prepared.
  • the composition of the slurry for forming the first catalyst layer 20, the second catalyst layer 30, and the third catalyst layer 40 depends on the composition of the first catalyst layer 20, the second catalyst layer 30, and the third catalyst layer 40, respectively. It is adjusted accordingly.
  • the slurry includes, for example, a source of a noble metal element, inorganic oxide particles, a binder, a pore-forming material, a solvent, and the like.
  • Examples of the source of the noble metal element include salts of the noble metal element, and examples of the salt of the noble metal element include nitrates, ammine complex salts, acetates, and chlorides.
  • the explanation regarding the inorganic oxide constituting the inorganic oxide particles is as above.
  • Examples of the binder include alumina sol, zirconia sol, titania sol, silica sol, and ceria sol.
  • Examples of the pore-forming material include crosslinked methyl poly(meth)acrylate particles, crosslinked butyl poly(meth)acrylate particles, crosslinked polystyrene particles, crosslinked polyacrylate particles, and melamine resins.
  • Examples of the solvent include water, organic solvents, and the like. Examples of the organic solvent include alcohol, acetone, dimethyl sulfoxide, and dimethyl formamide.
  • the solvent may be one type of solvent or a mixture of two or more types of solvents. Examples of the mixture of two or more solvents include a mixture of water and one or more organic solvents, a mixture of two or more organic solvents, and the like.
  • the end of the base material 10 on the exhaust gas inflow side is immersed in the slurry for forming the first catalyst layer 20, and after the slurry is sucked from the opposite side, it is dried. As a result, a precursor of the first catalyst layer 20 is formed.
  • the length of the precursor of the first catalyst layer 20 (and thus the average length L 20 of the first catalyst layer 20) can be adjusted.
  • the thickness of the precursor of the first catalyst layer 20 (and thus the thickness of the first catalyst layer 20) can be adjusted.
  • the mass of the precursor of the first catalyst layer 20 per unit volume of the portion of the base material 10 on which the precursor of the first catalyst layer 20 is formed can be adjusted.
  • the drying temperature is, for example, 40° C. or more and 150° C. or less, and the drying time is, for example, 5 minutes or more and 1 hour or less.
  • the firing temperature is, for example, 350° C. or more and 600° C. or less
  • the firing time is, for example, 20 minutes or more and 5 hours or less.
  • the atmosphere during firing is usually an atmospheric atmosphere.
  • the end of the base material 10 on the exhaust gas outflow side is immersed in the slurry for forming the second catalyst layer 30, and after the slurry is sucked from the opposite side, it is dried. As a result, a precursor for the second catalyst layer 30 is formed.
  • the length of the precursor of the second catalyst layer 30 (and thus the average length L 30 of the second catalyst layer 30) can be adjusted.
  • the thickness of the precursor of the second catalyst layer 30 (and thus the thickness of the second catalyst layer 30) can be adjusted.
  • the mass of the precursor of the second catalyst layer 30 per unit volume of the portion of the base material 10 on which the precursor of the second catalyst layer 30 is formed can be adjusted.
  • the drying temperature is, for example, 40° C. or more and 150° C. or less, and the drying time is, for example, 5 minutes or more and 1 hour or less.
  • the end of the base material 10 on the exhaust gas outflow side is immersed in the slurry for forming the third catalyst layer 40, and after sucking the slurry from the opposite side, it is dried. let As a result, a precursor for the third catalyst layer 40 is formed on the precursor for the second catalyst layer 30.
  • the length of the precursor of the third catalyst layer 40 (and thus the average length L 40 of the third catalyst layer 40) can be adjusted.
  • the thickness of the precursor of the third catalyst layer 40 (and thus the thickness of the third catalyst layer 40) can be adjusted. thickness) and the mass of the precursor of the third catalyst layer 40 per unit volume of the portion of the base material 10 on which the precursor of the third catalyst layer 40 is formed (thickness of the third catalyst layer of the base material 10) The mass of the third catalyst layer 40 per unit volume of the portion where the third catalyst layer 40 is formed can be adjusted.
  • the drying temperature is, for example, 40° C. or more and 150° C. or less, and the drying time is, for example, 5 minutes or more and 1 hour or less.
  • the firing temperature is, for example, 350° C. or more and 600° C. or less
  • the firing time is, for example, 20 minutes or more and 5 hours or less.
  • the atmosphere during firing is usually an atmospheric atmosphere.
  • the median D 50 of the pore-forming material is preferably 0.5 ⁇ m or more and 50 ⁇ m or less, preferably 1 ⁇ m or more and 30 ⁇ m or less, from the viewpoint of suppressing peeling, suppressing increase in pressure loss, and improving PM trapping performance.
  • D50 is the particle size at which the cumulative volume is 50% in the volume-based particle size distribution measured by laser diffraction scattering particle size distribution measuring method.
  • the D 90 of the inorganic oxide particles is preferably 3 ⁇ m or more and 50 ⁇ m or less, more preferably 5 ⁇ m or more and 40 ⁇ m or less, from the viewpoint of suppressing peeling, suppressing increase in pressure loss, and improving PM trapping performance.
  • D90 is the particle size at which the cumulative volume is 90% in the volume-based particle size distribution measured by laser diffraction scattering particle size distribution measuring method.
  • D 50 or D 90 use a laser diffraction scattering particle size distribution analyzer automatic sample feeder (Microtorac SDC manufactured by Microtrac Bell), add the sample to be measured to an aqueous dispersion medium, and add 26 mL After irradiating with 40W ultrasonic waves for 360 seconds at a flow rate of /sec, the measurement is performed using a laser diffraction scattering particle size distribution analyzer (Microtrac MT3300EXII manufactured by Microtrac Bell). The measurement was performed twice under the following conditions: particle refractive index of 1.5, particle shape of perfect sphere, solvent refractive index of 1.3, set zero for 30 seconds, and measurement time of 30 seconds. Let the average value be D50 or D90 . Pure water is used as the aqueous dispersion medium.
  • Example 1 (1) Preparation of first slurry In rhodium nitrate aqueous solution, Ce-Zr composite oxide powder (Ce equivalent to CeO 2 : 15% by mass, Zr equivalent to ZrO 2 : 70% by mass, 3 types other than Ce) After adding rare earth elements (La, Nd, Y) oxide equivalent amount: 15% by mass) and alumina powder, a pore-forming material (crosslinked poly(meth)methyl acrylate particles with a median diameter D50 of 5 ⁇ m) was added. , alumina sol, zirconia sol, and water as a solvent were added to prepare a first slurry.
  • the amount of each component in the first slurry is based on the mass of the catalyst layer formed by drying and firing the first slurry, rhodium is 0.5% by mass in terms of metal, and Ce-Zr composite oxide powder is 0.5% by mass.
  • the content of the alumina powder was 74.6% by mass
  • the alumina powder was 16.9% by mass
  • the alumina sol was 3.0% by mass in terms of solid content
  • the zirconia sol was 5.0% by mass in terms of solid content.
  • the amount of the pore former in the first slurry was adjusted to be 30% by mass of the catalyst layer formed by drying and firing the first slurry.
  • the mass of the catalyst layer formed by drying and firing the first slurry is calculated by subtracting the mass of components (e.g., solvent, pore-forming material, etc.) that disappear by drying and firing the first slurry from the mass of the first slurry. It is determined by subtracting the amount.
  • D 90 of the metal oxide powder (Ce-Zr composite oxide powder and alumina powder) in the first slurry was 20 ⁇ m.
  • the amount of each component in the third slurry is based on the mass of the catalyst layer formed by drying and firing the third slurry, platinum is 7.8% by mass in terms of metal, and Ce-Zr composite oxide powder is 7.8% by mass.
  • the content of the alumina powder was 15.7% by mass
  • the alumina sol was 7.4% by mass in terms of solid content
  • the content of zirconia sol was 1.8% by mass in terms of solid content.
  • the amount of the pore former in the third slurry was adjusted to be 30% by mass of the catalyst layer formed by drying and firing the third slurry.
  • the mass of the catalyst layer formed by drying and firing the third slurry is calculated by subtracting the mass of components (e.g., solvent, pore-forming material, etc.) that disappear by drying and firing the third slurry from the mass of the third slurry. It is determined by subtracting the amount.
  • D 90 of the metal oxide powder (Ce-Zr composite oxide powder and alumina powder) in the third slurry was 20 ⁇ m.
  • first catalyst layer Wall-flow type substrates shown in FIGS. 1 to 6 were prepared.
  • the thickness of the partition wall part is 200 to 250 ⁇ m
  • the total number of inflow side cells and outflow side cells in a cross section perpendicular to the axial direction of the base material is 300 cells per square inch
  • the volume of the base material is 1.0L
  • the base material The length was 91 mm.
  • the upstream end of the base material in the exhaust gas flow direction was immersed in the first slurry, suctioned from the downstream side, and then dried at 90° C. for 10 minutes.
  • a first precursor layer (a layer consisting of the solid content of the first slurry) extending from the exhaust gas inflow side end of the base material along the exhaust gas flow direction is formed on the inflow side cell side of the partition wall portion of the base material.
  • the substrate was fired at 450° C. for 1 hour.
  • a first catalyst layer was formed on the inflow side cell side of the partition wall portion of the base material, extending from the exhaust gas inflow side end of the base material along the exhaust gas flow direction.
  • the percentage of the length of the first catalyst layer to the length of the base material was 45%.
  • the mass of the first catalyst layer per unit volume of the portion of the base material where the first catalyst layer was formed (hereinafter referred to as "WC1") was 37.8 g/L.
  • the metal equivalent amount of Rh in the first catalyst layer per unit volume of the portion of the base material where the first catalyst layer was formed was 5.6 g/cft. Note that "cft" means cubic feet.
  • the downstream end of the base material in the exhaust gas flow direction was immersed in the third slurry, suctioned from the upstream side, and then dried at 90° C. for 10 minutes.
  • a third precursor layer (a layer consisting of the solid content of the third slurry) was formed on the second precursor layer, extending from the end of the base material on the exhaust gas outflow side in a direction opposite to the exhaust gas flow direction. .
  • the base material was baked at 450° C. for 1 hour.
  • a second catalyst layer extending from the exhaust gas outflow side end of the base material along a direction opposite to the exhaust gas flow direction, and a second catalyst layer on the second catalyst layer.
  • a third catalyst layer was formed extending from the end of the base material on the exhaust gas outflow side in a direction opposite to the exhaust gas flow direction.
  • the percentage of the length of the second catalyst layer with respect to the length of the base material was 70%.
  • at least a portion of the second catalyst layer was found to be protruding from the outer surface of the partition wall of the base material on the outflow side cell side toward the outflow side cell side.
  • the mass of the second catalyst layer per unit volume (hereinafter referred to as "WC2") of the portion of the base material where the second catalyst layer was formed was 27.1 g/L.
  • the metal equivalent amount of Rh in the second catalyst layer per unit volume of the portion of the base material where the second catalyst layer was formed was 3.6 g/cft.
  • the percentage of the length of the third catalyst layer to the length of the base material was 70%.
  • the mass of the third catalyst layer per unit volume (hereinafter referred to as "WC3") of the portion of the base material where the third catalyst layer was formed was 12.9 g/L.
  • the ratio of WC3 to WC2 was 0.47.
  • the metal equivalent amount of Pt in the third catalyst layer per unit volume of the portion of the base material where the third catalyst layer was formed was 28.6 g/cft.
  • a vehicle equipped with an exhaust gas purification catalyst after durability treatment was operated according to the operating conditions of the internationally harmonized exhaust gas test mode (WLTC). Measures the emissions (emission values) of nitrogen oxides (NOx), non-methane hydrocarbons (HC), and carbon monoxide (CO) in the exhaust gas that has passed through the exhaust gas purification catalyst for 1800 seconds from the start of operation. Then, the emissions of NOx, HC, and CO per unit traveling distance (mg/km) were determined.
  • a passenger car equipped with a 1.5L direct injection turbo engine was used as the vehicle, a certification test fuel was used as the gasoline, and an exhaust gas measuring device manufactured by Horiba, Ltd. was used as the exhaust gas measuring device.
  • Table 1 shows the measurement results of NOx, HC, and CO emissions per unit traveling distance.
  • the emissions of NOx, HC, and CO per unit traveling distance are shown as relative values to the emissions of NOx, HC, and CO per unit traveling distance in Comparative Example 3, which will be described later.
  • low temperature NOx means the amount of NOx emitted from the start of operation to 589 seconds after the start of operation
  • high temperature NOx means the amount of emissions from 1477 seconds to 1800 seconds after the start of operation. Means NOx emissions.
  • Example 2 The amounts of each component in the second slurry were determined based on the mass of the catalyst layer formed by drying and firing the second slurry, rhodium was 0.6% by mass in terms of metal, and Ce-Zr composite oxide powder was The content was adjusted to 74.5% by mass, the alumina powder was 16.9% by mass, the alumina sol was 3.0% by mass in terms of solid content, and the zirconia sol was adjusted to be 5.0% by mass in terms of solid content, The amounts of each component in the third slurry were determined based on the mass of the catalyst layer formed by drying and firing the third slurry, platinum was 5.0% by mass in metal terms, and Ce-Zr composite oxide powder was 5.0% by mass in terms of metal.
  • alumina powder was adjusted to 16.1% by mass
  • alumina sol was adjusted to 7.6% by mass in terms of solid content
  • zirconia sol was adjusted to 1.9% by mass in terms of solid content
  • WC2 was changed to 20.0g/L
  • An exhaust gas purification catalyst was produced in the same manner as in Example 1, except that WC3 was changed to 20.0 g/L, and the exhaust gas purification performance was evaluated. The results are shown in Table 1.
  • the ratio of WC3 to WC2 was 1.00.
  • the second catalyst layer was found to be protruding from the outer surface of the partition wall of the base material on the outflow side cell side toward the outflow side cell side.
  • the third catalyst layer also protruded from the outer surface of the partition wall of the base material on the outflow side cell side toward the outflow side cell side.
  • the metal equivalent amount of Rh in the first catalyst layer per unit volume of the portion of the base material where the first catalyst layer is formed is 5.6 g/cft, and the second catalyst layer is formed in the base material.
  • the metal equivalent amount of Rh in the second catalyst layer per unit volume of the portion is 3.6 g/cft, and the Pt in the third catalyst layer per unit volume of the portion of the base material where the third catalyst layer is formed.
  • the metal equivalent amount was 28.6 g/cft.
  • the ratio of WC3 to WC2 was 2.11.
  • the second catalyst layer was found to be protruding from the outer surface of the partition wall of the base material on the outflow side cell side toward the outflow side cell side.
  • the third catalyst layer also protruded from the outer surface of the partition wall of the base material on the outflow side cell side toward the outflow side cell side.
  • the metal equivalent amount of Rh in the first catalyst layer per unit volume of the portion of the base material where the first catalyst layer is formed is 5.6 g/cft, and the second catalyst layer is formed in the base material.
  • the metal equivalent amount of Rh in the second catalyst layer per unit volume of the portion is 3.6 g/cft, and the Pt in the third catalyst layer per unit volume of the portion of the base material where the third catalyst layer is formed.
  • the metal equivalent amount was 28.6 g/cft.
  • the ratio of WC3 to WC2 was 0.47.
  • the second catalyst layer was found to be protruding from the outer surface of the partition wall of the base material on the outflow side cell side toward the outflow side cell side.
  • the third catalyst layer also protruded from the outer surface of the partition wall of the base material on the outflow side cell side toward the outflow side cell side.
  • the metal equivalent amount of Rh in the first catalyst layer per unit volume of the portion of the base material where the first catalyst layer is formed is 5.6 g/cft, and the second catalyst layer is formed in the base material.
  • the metal equivalent amount of Pt in the second catalyst layer per unit volume of the portion is 28.6 g/cft
  • the amount of Rh in the third catalyst layer per unit volume of the portion of the base material where the third catalyst layer is formed is 28.6 g/cft.
  • the metal equivalent amount was 3.6 g/cft.
  • the second catalyst layer was found to be protruding from the outer surface of the partition wall of the base material on the outflow side cell side toward the outflow side cell side.
  • the metal equivalent amount of Rh in the first catalyst layer per unit volume of the portion of the base material where the first catalyst layer is formed is 11.1 g/cft, and the second catalyst layer is formed in the base material.
  • the metal equivalent amount of Pt in the second catalyst layer per unit volume of the part was 28.6 g/cft.

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Abstract

L'invention concerne un catalyseur de purification de gaz d'échappement comprenant : un substrat pourvu de cellules côté entrée, de cellules côté sortie, et de parois de séparation poreuses ; une première couche catalytique ; et une seconde couche catalytique et une troisième couche catalytique dans lesquelles l'élément de métal noble qui présente la plus grande teneur équivalente en métal est Rh et Pt, respectivement, la première couche catalytique étant formée sur le côté cellule côté entrée des parois de séparation, le long d'une direction d'écoulement de gaz d'échappement à partir d'une extrémité côté entrée de gaz d'échappement des parois de séparation ; la seconde couche catalytique étant formée sur le côté cellule côté sortie des parois de séparation, le long d'une direction opposée à la direction d'écoulement de gaz d'échappement à partir d'une extrémité côté sortie de gaz d'échappement des parois de séparation ; la troisième couche catalytique étant formée sur la seconde couche catalytique de sorte qu'au moins une partie de la troisième couche catalytique fasse saillie vers l'extérieur vers le côté cellule côté sortie à partir d'une surface externe côté cellule côté sortie des parois de séparation ; et le rapport de la masse de la troisième couche catalytique par unité de volume au niveau d'une partie du substrat où la troisième couche catalytique est formée à la masse de la seconde couche catalytique par unité de volume au niveau d'une partie du substrat où la seconde couche catalytique est formée étant de 0,3 à 1,9.
PCT/JP2023/011744 2022-03-25 2023-03-24 Catalyseur de purification de gaz d'échappement Ceased WO2023182481A1 (fr)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2016060049A1 (fr) * 2014-10-16 2016-04-21 株式会社キャタラー Catalyseur pour purification des gaz d'échappement
WO2020039650A1 (fr) * 2018-08-22 2020-02-27 三井金属鉱業株式会社 Catalyseur de purification de gaz d'échappement
JP2020193568A (ja) * 2019-05-24 2020-12-03 トヨタ自動車株式会社 排ガス浄化装置
WO2021029098A1 (fr) * 2019-08-09 2021-02-18 三井金属鉱業株式会社 Catalyseur de purification de gaz d'échappement et procédé de production associé
WO2021125256A1 (fr) * 2019-12-18 2021-06-24 三井金属鉱業株式会社 Catalyseur de purification de gaz d'échappement

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2016060049A1 (fr) * 2014-10-16 2016-04-21 株式会社キャタラー Catalyseur pour purification des gaz d'échappement
WO2020039650A1 (fr) * 2018-08-22 2020-02-27 三井金属鉱業株式会社 Catalyseur de purification de gaz d'échappement
JP2020193568A (ja) * 2019-05-24 2020-12-03 トヨタ自動車株式会社 排ガス浄化装置
WO2021029098A1 (fr) * 2019-08-09 2021-02-18 三井金属鉱業株式会社 Catalyseur de purification de gaz d'échappement et procédé de production associé
WO2021125256A1 (fr) * 2019-12-18 2021-06-24 三井金属鉱業株式会社 Catalyseur de purification de gaz d'échappement

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