WO2026014237A1 - Catalyseur de purification de gaz d'échappement, procédé de production de celui-ci, et procédé de purification de gaz d'échappement au moyen dudit catalyseur de purification de gaz d'échappement - Google Patents

Catalyseur de purification de gaz d'échappement, procédé de production de celui-ci, et procédé de purification de gaz d'échappement au moyen dudit catalyseur de purification de gaz d'échappement

Info

Publication number
WO2026014237A1
WO2026014237A1 PCT/JP2025/022798 JP2025022798W WO2026014237A1 WO 2026014237 A1 WO2026014237 A1 WO 2026014237A1 JP 2025022798 W JP2025022798 W JP 2025022798W WO 2026014237 A1 WO2026014237 A1 WO 2026014237A1
Authority
WO
WIPO (PCT)
Prior art keywords
catalyst layer
palladium
exhaust gas
gas inlet
side region
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.)
Pending
Application number
PCT/JP2025/022798
Other languages
English (en)
Japanese (ja)
Inventor
弘尊 久野
優 中島
茂和 南
泰隆 富田
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.)
Umicore Shokubai Japan Co Ltd
Original Assignee
Umicore Shokubai Japan 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 Umicore Shokubai Japan Co Ltd filed Critical Umicore Shokubai Japan Co Ltd
Priority to JP2025559410A priority Critical patent/JP7847283B1/ja
Publication of WO2026014237A1 publication Critical patent/WO2026014237A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

Links

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
    • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
    • B01J27/02—Sulfur, selenium or tellurium; Compounds thereof
    • B01J27/053—Sulfates
    • 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 [3D] monoliths
    • B01J35/57—Honeycombs
    • 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
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • 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
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/61—Surface area
    • 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
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/63—Pore volume
    • 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/08—Heat treatment
    • 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

Definitions

  • the present invention relates to an exhaust gas purification catalyst, a method for producing the same, and a method for purifying exhaust gas using the exhaust gas purification catalyst.
  • a three-way catalyst in treating exhaust gases from internal combustion engines, a three-way catalyst has been proposed that simultaneously oxidizes carbon monoxide (CO) and hydrocarbons (HC) to carbon dioxide (CO 2 ) and water (H 2 O) and reduces nitrogen oxides (NOx) to nitrogen (N 2 ).
  • a three-way catalyst generally has a configuration in which a catalyst layer containing a precious metal and a refractory inorganic oxide is supported on a refractory three-dimensional structure (e.g., a honeycomb support).
  • Japanese Patent Application Publication No. 2019-69402 discloses an exhaust gas purification catalyst having a catalyst coating layer in which an upper layer and a lower layer are sequentially formed on the surface of a substrate; the upper layer contains Rh and Pd and a carrier; the upper layer includes a Pd outermost layer extending from the upstream end to a downstream area of 20 mm or more, the Pd concentration of which is relatively higher than in other parts of the upper layer; the lower layer contains Pd and/or Pt and a carrier; and 60 mass % or more of the Pd contained in the Pd outermost layer is present from the surface of the Pd outermost layer to 50% of the thickness of the upper layer.
  • this configuration makes it possible to provide an exhaust gas purification catalyst with excellent HC purification performance and warm-up performance.
  • the present invention was made in consideration of the above circumstances, and aims to provide a means for improving the exhaust gas purification performance (particularly HC purification performance) of exhaust gas purification catalysts at low temperatures (e.g., below 400°C).
  • the inventors conducted extensive research to solve the above-mentioned problems. As a result, they discovered that in an exhaust gas purification catalyst comprising a lower catalytic layer and an upper catalytic layer of a predetermined composition, the above-mentioned problems can be solved by controlling the ratio of the palladium concentration in the gas inlet region of the lower catalytic layer to the palladium concentration in the gas outlet region of the lower catalytic layer to fall within a predetermined range (so that the palladium concentration in the gas inlet region of the lower catalytic layer is higher than the palladium concentration in the gas outlet region of the lower catalytic layer), and thus completed the present invention.
  • an exhaust gas purification catalyst includes: a refractory three-dimensional structure having partition walls extending from a gas inlet end face along a gas outlet end face and defining a plurality of gas flow paths penetrating from the gas inlet end face to the gas outlet end face; a lower catalyst layer formed in contact with the partition walls and containing palladium, alumina, and a cerium-zirconium composite oxide; and an upper catalyst layer formed on at least a portion of the lower catalyst layer and constituting an outermost layer, containing rhodium, alumina, and a cerium-zirconium composite oxide.
  • the lower catalyst layer in this catalyst is composed of a gas inlet side region L1 located on the gas inlet side and having a palladium concentration of C L1 [g/g], and a gas outlet side region L2 located on the gas outlet side and having a palladium concentration of C L2 [g/g]; a boundary X between the gas inlet side region L1 and the gas outlet side region L2 is located within a range of 8% to 80% from the gas inlet side end face with respect to the length of the partition wall; and a ratio (C L1 /C L2 ) of the palladium concentration C L1 in the gas inlet side region L1 to the palladium concentration C L2 in the gas outlet side region L2 is 30 to 230.
  • FIG. 1 is a front cross-sectional view that schematically shows a part of an exhaust gas purifying catalyst according to one embodiment of the present invention.
  • FIG. 2 is a front cross-sectional view that schematically shows a part of an exhaust gas purifying catalyst according to another embodiment of the present invention.
  • FIG. 3 is a front cross-sectional view that schematically shows a part of an exhaust gas purifying catalyst according to still another embodiment of the present invention.
  • An exhaust gas purification catalyst (hereinafter also simply referred to as "catalyst”) according to one embodiment of the present invention comprises: a refractory three-dimensional structure having partition walls extending from a gas inlet end face along a gas outlet end face and defining a plurality of gas flow paths penetrating from the gas inlet end face to the gas outlet end face; a lower catalyst layer formed in contact with the partition walls and containing palladium, alumina, and a cerium-zirconium composite oxide; and an upper catalyst layer formed on at least a portion of the lower catalyst layer and constituting an outermost layer, containing rhodium, alumina, and a cerium-zirconium composite oxide.
  • the lower catalyst layer in this catalyst is composed of a gas inlet region L1 located on the gas inlet side and having a palladium concentration of C L1 [g/g], and a gas outlet region L2 located on the gas outlet side and having a palladium concentration of C L2 [g/g]; a boundary X between the gas inlet region L1 and the gas outlet region L2 is located within a range of 8% to 80% of the length of the partition wall from the gas inlet end face; and the ratio (C L1 /C L2 ) of the palladium concentration C L1 in the gas inlet region L1 to the palladium concentration C L2 in the gas outlet region L2 is 30 to 230.
  • a catalyst having the above configuration improves exhaust gas purification performance (particularly HC purification performance) at low temperatures (e.g., 400°C or lower).
  • low temperatures e.g. 400°C or lower.
  • the mechanism by which this effect is achieved is not completely clear, but the following mechanism is presumed. That is, during cold start-up, the catalyst temperature is higher on the gas inlet side (catalyst inlet side) than on the gas outlet side (catalyst outlet side) (the catalyst reaches its activation temperature in a shorter time).
  • the ratio of the palladium concentration in the gas inlet side region to the palladium concentration in the gas outlet side region to be within a predetermined range (so that the palladium concentration in the gas inlet side region is higher than the palladium concentration in the gas outlet side region)
  • the amount of palladium that reaches the activation temperature is increased, and exhaust gas purification performance is thought to be improved. Note that the above mechanism is based solely on speculation, and whether it is correct or incorrect does not affect the technical scope of the present invention.
  • FIG. 1 is a front cross-sectional view schematically showing a portion of an exhaust gas purification catalyst according to one embodiment of the present invention. This embodiment corresponds to catalyst A in Example 1, which will be described later.
  • the exhaust gas purification catalyst 1 has a fire-resistant three-dimensional structure 10, a lower catalyst layer 20, and an upper catalyst layer 30.
  • the fire-resistant three-dimensional structure 10 extends from the gas inlet end face 10a along the gas outlet end face 10b, and has partition walls that define multiple gas flow paths that penetrate from the gas inlet end face 10a to the gas outlet end face 10b.
  • the length of the partition walls from the gas inlet end face 10a to the gas outlet end face 10b is 130 mm.
  • the lower catalyst layer 20 is formed so as to contact the partition walls of the refractory three-dimensional structure 10.
  • the lower catalyst layer 20 is composed of a gas inlet region L1 and a gas outlet region L2, which contact each other at a boundary X.
  • the boundary X is located 30 mm from the gas inlet end face 10a (a position 23.1% of the length of the partition walls).
  • the lower catalyst layer 20 (gas inlet region L1 and gas outlet region L2) is composed of palladium (Pd), alumina (Al 2 O 3 ), cerium-zirconium composite oxide (CeO 2 —ZrO 2 ), lanthana (La 2 O 3 ), and barium sulfate (BaSO 4 ).
  • the palladium concentration C L1 in the gas inlet side region L1 was 0.08582 [g/g], and the palladium concentration was substantially uniform throughout the gas inlet side region L1.
  • the palladium concentration C L2 in the gas outlet side region L2 was 0.0006197 [g/g], and the ratio of C L1 to C L2 (C L1 /C L2 ) was 138.
  • the upper catalytic layer 30 is formed on the lower catalytic layer 20 and is located as the outermost layer.
  • the upper catalytic layer 30 is formed adjacent to the gas outlet side region L2 of the lower catalytic layer 20 and is not located on the gas inlet side region L1.
  • This configuration can further improve exhaust gas purification performance at low temperatures. That is, in a catalyst according to a preferred embodiment, the gas inlet side region L1 of the lower catalytic layer forms the outermost layer.
  • the upper catalytic layer 30 is composed of rhodium (Rh), alumina (Al 2 O 3 ), cerium-zirconium composite oxide (CeO 2 —ZrO 2 ), and lanthana (La 2 O 3 ).
  • FIG. 2 is a front cross-sectional view schematically showing a portion of an exhaust gas purification catalyst according to another embodiment of the present invention. This embodiment corresponds to catalyst B in Example 2, which will be described later.
  • the exhaust gas purification catalyst 2 shown in FIG. 2 differs from the exhaust gas purification catalyst 1 shown in FIG. 1 in that the upper catalyst layer 30 is also formed on the gas inlet side region L1 (i.e., the upper catalyst layer 30 is formed from the gas inlet side end face 10a to the gas outlet side end face 10b).
  • FIG. 3 is a front cross-sectional view schematically illustrating a portion of an exhaust gas purification catalyst according to yet another embodiment of the present invention. This embodiment corresponds to catalyst C in Example 3, which will be described later.
  • the exhaust gas purification catalyst 3 shown in FIG. 3 differs from the exhaust gas purification catalyst 2 shown in FIG. 2 in that a predetermined proportion of palladium is present in both the gas inlet side region L1 of the lower catalytic layer and the region of the upper catalytic layer that contacts the gas inlet side region L1 of the lower catalytic layer (gas inlet side region U1 of the upper catalytic layer).
  • a predetermined proportion of palladium is present in both the gas inlet side region L1 of the lower catalytic layer and the region of the upper catalytic layer that contacts the gas inlet side region L1 of the lower catalytic layer (gas inlet side region U1 of the upper catalytic layer).
  • no palladium is present in the region of the upper catalytic layer that contacts the gas outlet side region L2 of the lower catalytic layer (gas outlet side region U2 of the upper catalytic layer).
  • boundary Y between gas inlet side region U1 and gas outlet side region U2 is located 30 mm from the gas inlet side end face 10a (at a position 23.1% of the length of the partition wall).
  • the palladium concentration C L1 in the gas inlet side region L1 was 0.06031 [g/g], and the palladium concentration was substantially uniform throughout the gas inlet side region L1.
  • the palladium concentration C U1 in the gas inlet side region U1 was 0.05972 [g/g], and the ratio of C U1 to C L1 (C U1 /C L1 ) was 0.990.
  • the refractory three-dimensional structure serves as a support for the catalyst layer.
  • a honeycomb support is preferably used as the refractory three-dimensional structure. Examples of honeycomb supports include monolith honeycomb support, metal honeycomb support, and plug honeycomb support for particulate filters.
  • the material of the honeycomb support is preferably a heat-resistant metal such as cordierite, silicon carbide, silicon nitride, stainless steel, or an Fe—Cr—Al alloy.
  • the honeycomb carrier is manufactured by extrusion molding or by winding sheet-like elements.
  • the shape of its gas passage openings may be hexagonal, rectangular, square, triangular, or corrugated.
  • a cell density number of cells/unit cross-sectional area of 100 to 1200 cells/square inch (15.5 to 186 cells/square centimeter) is sufficient for use, and preferably 200 to 900 cells/square inch (31 to 139.5 cells/square centimeter).
  • the length of the fire-resistant three-dimensional structure along the gas flow path is preferably more than 15 mm and not more than 1000 mm, more preferably 30 mm or more and not more than 500 mm, and even more preferably 50 mm or more and not more than 300 mm.
  • the lower catalyst layer is formed so as to contact the partition walls of the three-dimensional structure (directly above the partition walls).
  • the lower catalyst layer is composed of a gas inlet side region L1 (hereinafter also simply referred to as "region L1") located on the gas inlet side, and a gas outlet side region L2 (hereinafter also simply referred to as "region L2") located on the gas outlet side. Region L1 and region L2 contact each other at a boundary X.
  • the lower catalyst layer (regions L1 and L2) contains palladium, alumina, and a cerium-zirconium composite oxide.
  • Palladium functions as a catalyst for the oxidation reaction.
  • the catalyst according to this embodiment is characterized in that the ratio (C L1 /C L2 ) of the palladium concentration C L1 [g/g] in region L1 to the palladium concentration C L2 [g/g] in region L2 is 30 or more and 230 or less. If this ratio is less than 30, exhaust gas purification performance (particularly HC purification performance) at low temperatures may not be sufficiently exhibited. If this ratio exceeds 230, palladium may not be sufficiently dispersed in region L1, and purification performance commensurate with the amount of palladium may not be obtained.
  • this ratio is preferably 40 or more and 220 or less, more preferably 90 or more and 210 or less, and even more preferably 100 or more and 200 or less.
  • the palladium concentration C L1 in region L1 is not particularly limited, but is preferably 0.01900 g/g or more and 0.15000 g/g or less, more preferably 0.02000 g/g or more and 0.14000 g/g or less, even more preferably 0.06000 g/g or more and 0.13000 g/g or less, and particularly preferably 0.06500 g/g or more and 0.12000 g/g or less.
  • the palladium concentration C L2 in region L2 is also not particularly limited, but is preferably 0.0001000 g/g or more and 0.001000 g/g or less.
  • the palladium concentration in the gas inlet side region L1 is preferably substantially uniform throughout the entire region L1. This configuration allows for highly dispersed palladium to be supported in region L1, further improving exhaust gas purification performance at low temperatures.
  • the palladium concentration is substantially uniform throughout the gas inlet side region L1 refers to the value of ⁇ (maximum concentration - minimum concentration) / minimum concentration ⁇ x 100 being within 10%, when the palladium concentration is measured at any 10 points in region L1 and the maximum of the 10 palladium concentrations is defined as the "maximum concentration” and the minimum as the "minimum concentration.” This value is preferably within 5%, more preferably within 3%, even more preferably within 1%, and particularly preferably 0%.
  • the composition of the catalyst layer can be confirmed by inductively coupled plasma (ICP) emission spectroscopy or X-ray fluorescence (XRF) analysis.
  • ICP inductively coupled plasma
  • XRF X-ray fluorescence
  • the palladium content per 1 L of the fire-resistant three-dimensional structure in the lower catalyst layer is preferably 0.05 g/L or more and 5 g/L or less, more preferably 0.1 g/L or more and 4.5 g/L or less, and even more preferably 1 g/L or more and 4 g/L or less.
  • Palladium raw materials include palladium nitrate, acetate, ammonium salt, amine salt, and carbonate, as well as tetraamminepalladium salt.
  • the palladium source in region L1 is palladium nitrate and tetraamminepalladium salt
  • the palladium source in region L2 is palladium nitrate.
  • Alumina functions as a carrier for the precious metal (palladium).
  • alumina include gamma alumina, delta alumina, and theta alumina, with gamma alumina being preferred.
  • Alumina may also be contained in the form of a composite oxide of alumina and an oxide of another element.
  • the other element include phosphorus, zirconium, silicon, titanium, and lanthanum.
  • Specific examples of the composite oxide include Al-P composite oxide, Al-Zr-P composite oxide, Al-Zr composite oxide, Al-Si composite oxide, Al-Si-Zr composite oxide, Al-Ti composite oxide, Al-Ti-Zr composite oxide, Al-Si-Ti-Zr composite oxide, and Al-La composite oxide.
  • the aluminum content in the composite oxide is preferably greater than 50% by mass and less than 100% by mass, more preferably 60% by mass to 99% by mass, even more preferably 70% by mass to 97% by mass, and particularly preferably 75% by mass to 95% by mass.
  • the alumina content per 1 L of the refractory three-dimensional structure in the lower catalyst layer is preferably 10 g/L or more and 300 g/L or less, more preferably 20 g/L or more and 250 g/L or less, and even more preferably 50 g/L or more and 200 g/L or less. If the alumina content is within the above range, the precious metal (palladium) can be sufficiently dispersed and supported.
  • Alumina raw materials include alumina powder (gamma alumina, delta alumina, theta alumina, and composite oxides of alumina and oxides of other elements), as well as aluminum chloride, aluminum nitrate (e.g., aluminum nitrate nonahydrate), aluminum sulfate, aluminum acetate, and aluminum hydroxide, which become alumina upon firing.
  • raw materials for the oxides of the other elements include the following: Phosphorus oxide raw materials (phosphorus sources) include, for example, phosphoric acid, phosphorous acid, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate.
  • Zirconia raw materials include, for example, zirconium oxynitrate, zirconium oxychloride, zirconium nitrate, basic zirconium sulfate, zirconium carbonate, and zirconium hydroxide. Zirconium nitrate is preferred.
  • Silica raw materials include, for example, silicon oxide, orthosilicate, metasilicic acid, and silica sol. Examples of titania raw materials (titanium sources) include inorganic titanium compounds such as titanium tetrachloride and titanium sulfate, titanium oxalate, and tetraisopropyl titanate.
  • lanthana raw materials examples include lanthanum oxide, lanthanum nitrate, lanthanum sulfate, lanthanum carbonate, and lanthanum acetate.
  • alumina raw materials are preferably alumina powder (gamma alumina, delta alumina, theta alumina, or a composite oxide of alumina and an oxide of another element).
  • Cerium-zirconium composite oxide (CeO 2 —ZrO 2 ) can mainly function as an oxygen storage/release material, which stores oxygen in an oxidizing atmosphere (lean) and releases oxygen in a reducing atmosphere (rich) in response to fluctuations in the air-fuel ratio (A/F), which changes depending on the driving conditions, thereby stably promoting oxidation/reduction reactions.
  • the content of cerium (Ce) contained in the cerium-zirconium composite oxide, calculated as oxide (CeO 2 ), is preferably 3 mass % or more and 65 mass % or less, more preferably 5 mass % or more and 50 mass % or less, and even more preferably 10 mass % or more and 47 mass % or less. Furthermore, the content of zirconium (Zr) contained in the cerium-zirconium composite oxide, calculated as oxide (ZrO 2 ), is preferably 35 mass % or more and 97 mass % or less, more preferably 50 mass % or more and 95 mass % or less, and even more preferably 53 mass % or more and 90 mass % or less. When the contents of cerium (Ce) and zirconium (Zr) are within the above ranges, oxygen occlusion and desorption can proceed even at low temperatures.
  • the cerium-zirconium composite oxide may be contained in the form of a composite oxide of cerium-zirconium composite oxide and an oxide of at least one metal selected from the group consisting of lanthanum (La), yttrium (Y), neodymium (Nd), and praseodymium (Pr).
  • Specific examples of such composite oxides include cerium-zirconium-lanthanum composite oxide and cerium-zirconium-lanthanum-yttrium composite oxide.
  • the content of cerium-zirconium composite oxide per 1 L of the refractory three-dimensional structure in the lower catalyst layer (regions L1 and L2) is preferably 5 g/L or more and 200 g/L or less, more preferably 10 g/L or more and 100 g/L or less, and even more preferably 20 g/L or more and 90 g/L or less. If the content of cerium-zirconium composite oxide is within the above range, exhaust gas purification performance (particularly HC purification performance) at low temperatures can be further improved.
  • the lower catalyst layer optionally contains at least one promoter selected from the group consisting of Group 1 elements, Group 2 elements, and rare earth elements. Specific elements include potassium, magnesium, calcium, strontium, barium, and lanthanum. These elements are contained in the catalyst in the form of oxides, sulfates, or carbonates after firing. It is preferable for the lower catalyst layer (regions L1 and L2) to contain both a rare earth element and a Group 2 element, and it is more preferable for the lower catalyst layer (regions L1 and L2) to contain lanthanum oxide ( La2O3 ) and barium sulfate ( BaSO4 ).
  • lanthanum oxide La2O3
  • BaSO4 barium sulfate
  • the inclusion of a promoter in the lower catalyst layer can improve the efficiency of exhaust gas purification performance (particularly HC purification performance).
  • the lower catalyst layer (regions L1 and L2) contains lanthanum oxide (La 2 O 3 )
  • the content of lanthanum oxide (La 2 O 3 ) per 1 L of the refractory three-dimensional structure is preferably 0.5 g/L to 20 g/L, more preferably 0.8 g/L to 10 g/L, and even more preferably 1 g/L to 5 g/L.
  • the content of barium sulfate (BaSO 4 ) per 1 L of the refractory three-dimensional structure is preferably 1 g/L to 30 g/L, more preferably 3 g/L to 25 g/L, and even more preferably 5 g/L to 20 g/L.
  • the lower catalyst layer may contain other precious metals besides palladium, as long as the effects of the present invention are not significantly impaired.
  • examples of other precious metals include platinum (Pt) and rhodium (Rh).
  • the content of other precious metals per 1 L of the refractory three-dimensional structure in the lower catalyst layer is preferably 3 g/L or less, more preferably 1 g/L or less, and even more preferably 0 g/L (not included).
  • the lower catalyst layer may contain the above-mentioned palladium, alumina, and cerium-zirconium composite oxide, an optional promoter, other optional precious metals, and other components in addition to those mentioned above, as long as the effects of the present invention are not significantly impaired.
  • other components include manganese, iron, cobalt, nickel, and copper.
  • the content of other components per 1 L of the refractory three-dimensional structure in the lower catalyst layer is preferably 10 g/L or less, more preferably 5 g/L or less, even more preferably 3 g/L or less, particularly preferably 1 g/L or less, and most preferably 0 g/L (not included).
  • the total loading amount of the lower catalyst layer is not particularly limited, but is preferably 50 g/L or more and 200 g/L or less, more preferably 80 g/L or more and 190 g/L or less, and even more preferably 120 g/L or more and 180 g/L or less. If the total loading amount is within the above range, it is possible to achieve the desired exhaust gas purification performance while suppressing an excessive increase in pressure loss.
  • the catalyst according to this embodiment is also characterized in that the boundary X between regions L1 and L2 is located within a range of 8% to 80% from the gas inlet end face relative to the length of the partition wall. If the boundary X is located within a range less than 8% or more than 80%, sufficient exhaust gas purification performance (particularly HC purification performance) at low temperatures may not be achieved. From the perspective of further improving exhaust gas purification performance (particularly HC purification performance) at low temperatures, the boundary X is preferably located within a range of 8% to 70% from the gas inlet end face, more preferably within a range of 9% to 50%, and even more preferably within a range of 10% to 30%.
  • composition and boundary positions of each catalyst layer can be confirmed using inductively coupled plasma (ICP) emission spectroscopy or X-ray fluorescence (XRF) analysis.
  • ICP inductively coupled plasma
  • XRF X-ray fluorescence
  • the upper catalytic layer is formed on the lower catalytic layer and is located as the outermost layer. Although other layers may be disposed between the lower catalytic layer and the upper catalytic layer, it is preferable that the lower catalytic layer and the upper catalytic layer are adjacent to each other.
  • the upper catalytic layer contains rhodium, alumina, and a cerium-zirconium composite oxide.
  • Rhodium functions as a catalyst for the reduction reaction.
  • the rhodium content per 1 L of the refractory three-dimensional structure in the upper catalyst layer is preferably 0.01 g/L or more and 2 g/L or less, more preferably 0.05 g/L or more and 1.5 g/L or less, and even more preferably 0.1 g/L or more and 1 g/L or less.
  • Rhodium raw materials include inorganic salts of rhodium, such as nitrates, sulfates, acetates, ammonium salts, amine salts, hexaammine salts, carbonates, bicarbonates, nitrites, and oxalates; carboxylates such as formates; and hydroxides, alkoxides, and oxides.
  • the rhodium source is at least one selected from the group consisting of nitrates, ammonium salts, amine salts, and carbonates of rhodium.
  • the upper catalytic layer preferably contains palladium at a high concentration equivalent to a concentration C L1 in a region of the upper catalytic layer that is in contact with the gas inlet-side region L1 of the lower catalytic layer (the gas inlet-side region U1 of the upper catalytic layer), as shown in Fig. 3.
  • the upper catalytic layer is composed of a gas inlet-side region U1 located on the gas inlet side and having a palladium concentration C U1 [g/g], and a gas outlet-side region U2 located on the gas outlet side and containing substantially no palladium, the boundary Y between the gas inlet-side region U1 and the gas outlet-side region U2 is located at substantially the same position as the position of the boundary X with respect to the length of the partition wall, and the ratio (C U1 /C L1 ) of the palladium concentration C U1 in the gas inlet-side region U1 of the upper catalytic layer to the palladium concentration C L1 in the gas inlet-side region L1 of the lower catalytic layer is 0.800 or more and less than 1.000.
  • substantially free of palladium refers to "free of palladium (0 g/L)" or "containing palladium, with the palladium content per 1 L of the refractory three-dimensional structure being greater than 0 g/L and not more than 0.01 g/L.”
  • substantially the same position refers to the distance between the position of boundary X and the position of boundary Y being within 5 mm.
  • the distance between the position of boundary X and the position of boundary Y is preferably within 3 mm, more preferably within 1 mm, and most preferably 0 mm (the boundary X and boundary Y are at the same position).
  • the ratio (C U1 /C L1 ) is preferably closer to 1. Specifically, the ratio (C U1 /C L1 ) is 0.800 or more and less than 1.000, preferably 0.900 or more and less than 1.000, more preferably 0.950 or more and less than 1.000, and even more preferably 0.970 or more and less than 1.000.
  • the upper catalyst layer may contain platinum (Pt) in addition to rhodium and palladium, as long as the effects of the present invention are not significantly impaired.
  • the platinum (Pt) content per 1 L of the refractory three-dimensional structure in the lower catalyst layer is preferably 0.01 g/L or less, and more preferably 0 g/L (not included).
  • the alumina and its raw materials contained in the upper catalyst layer are the same as those explained in the section on the lower catalyst layer, so a detailed explanation will be omitted here.
  • the alumina contained in the upper catalyst layer may be the same as or different from that contained in the lower catalyst layer.
  • the alumina content per L of the refractory three-dimensional structure in the upper catalyst layer is preferably 5 g/L or more and 70 g/L or less, more preferably 10 g/L or more and 60 g/L or less, and even more preferably 20 g/L or more and 50 g/L or less. If the alumina content is within the above range, the precious metal (rhodium, or rhodium and palladium) can be sufficiently dispersed and supported.
  • cerium-zirconium composite oxide (CeO 2 —ZrO 2 ) and its raw materials contained in the upper catalytic layer are the same as those described in the section on the lower catalytic layer, and therefore detailed description thereof will be omitted here.
  • the cerium-zirconium composite oxide contained in the upper catalytic layer may be the same as or different from that contained in the lower catalytic layer.
  • the content of the cerium-zirconium composite oxide per 1 L of the refractory three-dimensional structure in the upper catalytic layer (regions U1 and U2) is preferably 5 g/L or more and 70 g/L or less, more preferably 10 g/L or more and 60 g/L or less, and even more preferably 20 g/L or more and 50 g/L or less.
  • exhaust gas purification performance particularly HC purification performance
  • the upper catalyst layer (regions U1 and U2) optionally contains at least one promoter selected from the group consisting of Group 1 elements, Group 2 elements, and rare earth elements. Details of the promoter are the same as those described in the section on the lower catalyst layer, and therefore will not be described here in detail. From the viewpoint of improving the efficiency of exhaust gas purification performance (particularly HC purification performance), the upper catalyst layer (regions U1 and U2) preferably contains lanthanum oxide (La 2 O 3 ).
  • the content of lanthanum oxide (La 2 O 3 ) per 1 L of the refractory three-dimensional structure in the upper catalyst layer is preferably 0.1 g/L or more and 10 g/L or less, more preferably 0.3 g/L or more and 5 g/L or less, and even more preferably 0.5 g/L or more and 3 g/L or less.
  • the upper catalyst layer may contain the above-mentioned rhodium, alumina, and cerium-zirconium composite oxide, as well as optional components such as platinum and a promoter, and other components other than those mentioned above, to the extent that the effects of the present invention are not significantly impaired. Details of the other components are the same as those explained in the section on the lower catalyst layer, so a detailed explanation will be omitted here.
  • the content of other components per 1 L of the refractory three-dimensional structure in the upper catalyst layer is preferably 10 g/L or less, more preferably 5 g/L or less, even more preferably 3 g/L or less, particularly preferably 1 g/L or less, and most preferably 0 g/L (not included).
  • the total loading amount of the upper catalyst layer is not particularly limited, but is preferably 50 g/L or more and 200 g/L or less, more preferably 60 g/L or more and 150 g/L or less, and even more preferably 65 g/L or more and 120 g/L or less. If the total loading amount is within the above range, it is possible to achieve the desired exhaust gas purification performance while suppressing an excessive increase in pressure loss.
  • a method for producing an exhaust gas purifying catalyst includes: applying a lower catalyst layer slurry containing a palladium source, an alumina raw material, and a cerium-zirconium composite oxide raw material onto the partition walls of the refractory three-dimensional structure, drying and firing the slurry to form a lower catalyst layer (hereinafter also referred to as a "lower catalyst layer forming step (1)” or “step (1)”); applying an upper catalyst layer slurry containing a rhodium source, an alumina raw material, and a cerium-zirconium composite oxide raw material onto the lower catalyst layer, drying and firing the slurry to form an upper catalyst layer (hereinafter also referred to as an "upper catalyst layer forming step (2)" or
  • step (1) a lower catalyst layer slurry containing a palladium source, an alumina raw material, and a cerium-zirconium composite oxide raw material is applied onto the partition walls of the refractory three-dimensional structure, followed by drying and firing to form a lower catalyst layer.
  • the slurry for the lower catalyst layer contains a palladium source, an alumina raw material, and a cerium-zirconium composite oxide raw material.
  • the palladium source, alumina raw material, and cerium-zirconium composite oxide raw material are the same as those described in the section on the lower catalyst layer, so detailed description will be omitted here.
  • the alumina raw material is preferably a powder of alumina ( ⁇ -alumina, ⁇ -alumina, ⁇ -alumina, or a composite oxide of alumina and an oxide of another element), and more preferably has a large pore volume (high-porous alumina) to improve the dispersibility of the precious metal (palladium).
  • the pore volume of the alumina raw material (alumina powder) can be measured by nitrogen adsorption.
  • the pore volume of the alumina raw material (pore volume per 1 g of alumina raw material) is preferably 0.4 cm 3 /g or more and 3.0 cm 3 /g or less, more preferably 0.6 cm 3 /g or more and 2.5 cm 3 /g or less, and even more preferably 0.7 cm 3 /g or more and 1.5 cm 3 /g or less.
  • a pore volume of the alumina raw material of 0.7 cm 3 /g or more is preferable because the precious metal (palladium) supported on the alumina is highly dispersed.
  • the pore volume of the alumina raw material is 1.5 cm 3 /g or less, the alumina is not excessively bulky and an increase in pressure loss can be suppressed, which is preferable.
  • the specific surface area of the alumina raw material can be measured by the BET multipoint method in accordance with ISO 9277:2010.
  • the BET specific surface area (BET surface area per 1 g of alumina raw material) is preferably 50 m 2 /g or more and 500 m 2 /g or less, more preferably 60 m 2 /g or more and 300 m 2 /g or less, and even more preferably 80 m 2 /g or more and 200 m 2 /g or less.
  • the BET specific surface area of the alumina raw material is 80 m 2 /g or more, the noble metal (palladium) supported on the alumina is highly dispersed, which is preferable.
  • the BET specific surface area of the alumina raw material is 200 m 2 /g or less, the surface area is less likely to decrease when the alumina is exposed to high-temperature exhaust gas, which is preferable.
  • the cerium-zirconium composite oxide raw material has a small specific surface area.
  • the BET specific surface area of the cerium-zirconium composite oxide raw material is preferably 1.0 m 2 /g or more and 30 m 2 /g or less, more preferably 1.0 m 2 /g or more and 20 m 2 /g or less, and even more preferably 1.0 m 2 /g or more and 10 m 2 /g or less.
  • a BET specific surface area of the cerium-zirconium composite oxide raw material of 1.0 m 2 /g or more is preferable because sufficient oxygen storage and release performance is exhibited.
  • a BET specific surface area of the cerium-zirconium composite oxide raw material of 10 m 2 /g or less is preferable because the precious metal (palladium) is supported in a highly dispersed state on the high-porous alumina.
  • the alumina raw material contained in the slurry for the lower catalyst layer has a pore volume of 80 cm 3 /g or more and 200 cm 3 /g or less, as measured by a nitrogen adsorption method, and the cerium-zirconium composite oxide raw material contained in the slurry for the lower catalyst layer has a BET specific surface area of 1.0 m 2 /g or more and 10 m 2 /g or less.
  • the slurry for the lower catalyst layer may, as necessary, further contain optional components other than those contained in the lower catalyst layer (the promoters, “other precious metals,” and “other components” described above) and/or their raw materials.
  • the promoters, “other precious metals,” and “other components” are the same as those described in the section on the lower catalyst layer, so detailed explanations will be omitted here.
  • the solvent contained in the slurry for the lower catalyst layer is not particularly limited, but examples include water (pure water, ultrapure water, deionized water, distilled water, etc.), lower alcohols such as ethanol and 2-propanol, and organic alkaline aqueous solutions. Of these, water and lower alcohols are preferred, with water being more preferred.
  • the amount of solvent in the slurry for the lower catalyst layer is not particularly limited, but is preferably an amount such that the proportion of solids in the slurry (solids mass concentration) is preferably 5 to 60 mass%, more preferably 10 to 50 mass%.
  • the method for applying the slurry for the lower catalyst layer to the partition walls of the fire-resistant three-dimensional structure can be any known method, such as wash coating.
  • the amount of slurry applied is such that the amount of solids in the slurry and the amount of each component in the lower catalyst layer fall within the ranges described above.
  • drying refers to removing the solvent contained in the coating film
  • baking refers to further treating the coating film from which the solvent has been removed at a high temperature to adhere each component to the partition walls. Drying conditions are not particularly limited, but are preferably carried out in air at a temperature of 50°C or higher but lower than 300°C, more preferably 80°C or higher but lower than 200°C, for a period of 5 minutes to 10 hours, more preferably 30 minutes to 8 hours.
  • Baking conditions are also not particularly limited, but are preferably carried out in air at a temperature of 300°C or higher but lower than 1200°C, more preferably 400°C or higher but lower than 700°C, for a period of 10 minutes to 10 hours, more preferably 30 minutes to 5 hours.
  • step (2) an upper catalyst layer is formed by applying a slurry for the upper catalyst layer, which contains a rhodium source, an alumina raw material, and a cerium-zirconium composite oxide raw material, onto the lower catalyst layer, followed by drying and firing.
  • a slurry for the upper catalyst layer which contains a rhodium source, an alumina raw material, and a cerium-zirconium composite oxide raw material
  • the slurry for the upper catalyst layer contains a rhodium source, an alumina raw material, and a cerium-zirconium composite oxide raw material.
  • the rhodium source, alumina raw material, and cerium-zirconium composite oxide raw material are the same as those described in the section on the upper catalyst layer, so detailed description will be omitted here.
  • the alumina raw material is preferably a powder of alumina ( ⁇ -alumina, ⁇ -alumina, ⁇ -alumina, or a composite oxide of alumina and an oxide of another element).
  • the pore volume of the alumina raw material (pore volume per 1 g of alumina raw material) is not particularly limited, but is preferably 0.2 cm 3 /g or more and 1.5 cm 3 /g or less, more preferably 0.3 cm 3 /g or more and 1.2 cm 3 /g or less, and even more preferably 0.4 cm 3 /g or more and 0.7 cm 3 /g or less.
  • a pore volume of the alumina raw material of 0.4 cm 3 /g or more is preferable because it ensures the dispersion of the precious metal (rhodium).
  • a pore volume of the alumina raw material of 0.7 cm 3 /g or less is preferable because it prevents an excessive increase in the thickness of the catalytic layer and therefore inhibits gas diffusion to the lower catalytic layer.
  • the specific surface area of the alumina raw material is not particularly limited, but is preferably 50 m 2 /g or more and 500 m 2 /g or less, more preferably 60 m 2 /g or more and 300 m 2 /g or less, and even more preferably 80 m 2 /g or more and 200 m 2 /g or less.
  • a BET specific surface area of 80 m 2 /g or more is preferred because the noble metal can be dispersed efficiently.
  • a BET specific surface area of 200 m 2 /g or less is preferred because the surface area is less likely to decrease when the alumina is exposed to high-temperature exhaust gas.
  • a cerium-zirconium composite oxide raw material having a BET specific surface area of 150 m 2 /g or less is preferred because the surface area is less likely to decrease when the cerium-zirconium composite oxide is exposed to high-temperature exhaust gas.
  • the upper catalyst layer slurry may, as necessary, further contain optional components other than those contained in the upper catalyst layer (the promoters, “other precious metals,” and “other components” described above) and/or their raw materials.
  • the promoters, “other precious metals,” and “other components” are the same as those described in the section on the upper catalyst layer, so detailed explanations will be omitted here.
  • the solvent and its amount contained in the slurry for the upper catalyst layer are the same as those described in the section on step (1), so a detailed explanation will be omitted here.
  • the method for applying the upper catalyst layer slurry to the lower catalyst layer can be any known method, such as wash coating.
  • the amount of slurry applied is such that the amount of solids in the slurry and the amount of each component in the upper catalyst layer fall within the ranges described above. If, as in the embodiment shown in Figure 1, a portion of the lower catalyst layer (the portion that will become the gas inlet side region L1) is to be exposed, the upper catalyst layer slurry can be applied from the gas outlet side end surface 10b to a predetermined length.
  • step (1) The drying and firing methods are the same as those described in step (1), so a detailed explanation will be omitted here.
  • step (3) a palladium solution containing a palladium-containing complex salt and a thickener is applied from the gas inlet side end face to a position within a range of 8% to 80% from the gas inlet side end face with respect to the length of the partition wall from the gas inlet side end face to the gas outlet side end face, followed by drying and firing.
  • the complex salt containing palladium is not particularly limited, but is preferably a complex salt containing tetraamminepalladium ion ([Pd(NH 3 ) 4 ] 2+ ) as a complex ion.
  • the anion of the complex salt is not particularly limited.
  • tetraaminepalladium salts include tetraaminepalladium(II) acetate ([Pd( NH3 ) 4 ]( CH3COO ) 2 ), tetraaminepalladium(II) chloride ([Pd( NH3 ) 4 ] Cl2 ), tetraaminepalladium(II) hydroxide ([Pd( NH3 ) 4 ](OH) 2 ), tetraaminepalladium(II) nitrate ([Pd( NH3 ) 4 ]( NO3 ) 2 ), and tetraaminepalladium(II) hydrogen carbonate ([Pd( NH3 ) 4 ]( HCO3 ) 2 ).
  • tetraaminepalladium(II) acetate and tetraaminepalladium(II) nitrate are preferred, and tetraaminepalladium(II) acetate is more preferred.
  • the amount of tetraamminepalladium salt in the palladium solution is preferably 1% by mass or more and 30% by mass or less, and more preferably 3% by mass or more and 20% by mass or less, relative to 100% by mass of the palladium solution.
  • Thickeners are added to control the amount of palladium loaded and the position of the boundary (X, or X and Y) to the desired position.
  • thickeners include ⁇ -1,3 glucans such as scleroglucan, curdlan, paramylon, patiman, and laminaran; and polysaccharides such as xanthan gum and guar gum. Among these, scleroglucan, xanthan gum, and guar gum are preferred from the perspective of ease of control, with scleroglucan being more preferred.
  • the amount of thickener in the palladium solution is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 0.15% by mass or more and 5.0% by mass or less, relative to 100% by mass of the palladium solution.
  • the solvent contained in the palladium solution is not particularly limited, but examples include water (pure water, ultrapure water, deionized water, distilled water, etc.), lower alcohols such as ethanol and 2-propanol, and organic alkaline aqueous solutions. Of these, water is preferred.
  • the method for applying the palladium solution is not particularly limited, but examples include immersing the catalyst precursor that has been subjected to step (2) from the gas inlet end face into a container containing the palladium solution.
  • the region to which the palladium solution is applied is controlled so that the boundary (X, or X and Y) is located at the desired position.
  • the region to which the palladium solution is applied, starting from the gas inlet end face, ends at a position within 8% to 80% of the length of the partition wall from the gas inlet end face to the gas outlet end face.
  • this end point is preferably within the range of 8% to 70%, more preferably within the range of 9% to 50%, and even more preferably within the range of 10% to 30%.
  • the region to which the palladium solution is applied becomes the gas inlet region (L1, or L1 and U1) after subsequent drying and firing.
  • step (1) The drying and firing methods are the same as those described in step (1), so a detailed explanation will be omitted here.
  • a method for purifying exhaust gas comprising contacting the above-mentioned exhaust gas purification catalyst with exhaust gas emitted from an internal combustion engine.
  • the internal combustion engine include a gasoline engine, a gasoline hybrid engine, a diesel engine, a diesel hybrid engine, and an engine that uses natural gas, ethanol, dimethyl ether, or the like as fuel.
  • a gasoline engine or a gasoline hybrid engine is preferred, and a gasoline engine is more preferred.
  • One method for bringing exhaust gas into contact with a catalyst is, for example, to place an exhaust gas purification catalyst in the exhaust flow path of an exhaust port of an internal combustion engine and allow the exhaust gas to flow into the exhaust flow path.
  • exhaust gas purification performance (particularly HC purification performance) can be improved at low temperatures even after high-temperature endurance.
  • High-temperature endurance is achieved by exposing the catalyst to an atmosphere of preferably 650°C or higher and 1200°C or lower for 5 hours or longer and 500 hours or shorter, and more preferably to an atmosphere of 800°C or higher and 1100°C or lower for 10 hours or longer and 100 hours or shorter.
  • the temperature of the exhaust gas there are no particular restrictions on the temperature of the exhaust gas, as long as it is within the temperature range of exhaust gas during operation of a normal internal combustion engine (e.g., a gasoline engine), but it is preferably between 0°C and 800°C, and more preferably between 50°C and 700°C.
  • the air-fuel ratio (A/F) of the exhaust gas is usually between 10 and 30, and preferably between 11 and 14.7.
  • exhaust gas temperature refers to the temperature of the exhaust gas at the catalyst inlet.
  • catalyst inlet refers to the portion of the exhaust pipe in which the exhaust gas purification catalyst is installed, extending from the catalyst end face on the exhaust gas inlet side toward the internal combustion engine by 10 cm, and also refers to the central portion of the exhaust pipe in the longitudinal (axial) direction.
  • catalyst bed refers to the central portion of the exhaust pipe between the catalyst end face on the exhaust gas inlet side and the catalyst end face on the exhaust gas outlet side, and also refers to the central portion of the cross section of the exhaust pipe (if the cross section of the exhaust pipe is not circular, the center of gravity of the cross section of the exhaust pipe).
  • the exhaust gas purification catalyst according to claim 1 having the characteristics of claim 2; the exhaust gas purification catalyst according to claim 1 or 2 having the characteristics of claim 3; the exhaust gas purification catalyst according to any one of claims 1 to 3 having the characteristics of claim 4; a manufacturing method for the exhaust gas purification catalyst according to any one of claims 1 to 4 having the characteristics of claim 5; the manufacturing method according to claim 5 having the characteristics of claim 6; and a method for purifying exhaust gas using the exhaust gas purification catalyst according to any one of claims 1 to 4 having the characteristics of claim 7.
  • Example 1 (Formation of Lower Catalyst Layer Precursor) Palladium nitrate (Pd(NO 3 ) 2 ), ⁇ -alumina (Al 2 O 3 , pore volume 0.9 cm 3 /g, BET specific surface area 150 m 2 /g, average particle size (D50) 30 ⁇ m), cerium-zirconium composite oxide (CeO 2 -ZrO 2 , CeO 2 content 44 mass%, BET specific surface area 1.7 m 2 /g), lanthanum acetate (La(CH 3 COO) 3 ), and barium sulfate (BaSO 4 ) were weighed out so that the mass ratio of Pd:Al 2 O 3 :CeO 2 -ZrO 2 :La 2 O 3 :BaSO 4 after firing would be 0.1:95:50:3:15.
  • the weighed raw materials were added to deionized water and wet-pulverized to prepare a slurry a1.
  • a refractory three-dimensional structure A2 provided with a lower catalyst layer (a gas inlet region L1 with a palladium concentration C L1 of 0.08582 [g / g] and a gas outlet region L2 with a palladium concentration C L2 of 0.0006197 [g / g]).
  • slurry a3 was applied to A2 up to a position 100 mm from the outlet end face so that the loading amount after firing would be 76.2 g/L, and the coating was dried at 150°C for 15 minutes and then fired at 550°C for 30 minutes to obtain catalyst A having a refractory three-dimensional structure provided with a lower catalyst layer and an upper catalyst layer.
  • Example 2 (Formation of Lower Catalyst Layer Precursor) A1 was obtained in the same manner as in Example 1 (formation of lower catalyst layer precursor).
  • Example 3 (Formation of Lower Catalyst Layer Precursor) A1 was obtained in the same manner as in Example 1 above.
  • Example 2 The palladium solution P1 in Example 1 (formation of lower catalytic layer) was applied to a position 30 mm from the inlet-side end face of C2 (23.1% of the length of the partition wall) so that the palladium loading after firing would be 3.51 g/L, and the applied solution was dried at 150°C for 15 minutes and then fired at 550°C for 30 minutes, thereby obtaining catalyst C, which had a refractory three-dimensional structure provided with a lower catalytic layer (comprising a gas inlet-side region L1 with a palladium concentration C L1 of 0.06031 [g/g] and a gas outlet-side region L2 with a palladium concentration C L2 of 0.0006197 [g/g]) and an upper catalytic layer (comprising a gas inlet-side region U1 with a palladium concentration C U1 of 0.05972 [g/g] and a gas outlet-side region U2 with
  • Example 2 The palladium solution P1 in Example 1 (formation of lower catalytic layer) was applied to a position 10 mm from the inlet-side end face of C2 (7.7% of the length of the partition wall) so that the palladium loading after firing would be 3.51 g/L, and the applied solution was dried at 150°C for 15 minutes and then fired at 550°C for 30 minutes, thereby obtaining catalyst D, which had a refractory three-dimensional structure provided with a lower catalytic layer (comprising a gas inlet-side region L1 with a palladium concentration C L1 of 0.1606 [g/g] and a gas outlet-side region L2 with a palladium concentration C L2 of 0.0006197 [g/g]) and an upper catalytic layer (comprising a gas inlet-side region U1 with a palladium concentration C U1 of 0.1601 [g/g] and a gas outlet-side region U2 with a palla
  • Example 4 (Formation of Lower Catalyst Layer Precursor) A1 was obtained in the same manner as in Example 1 above.
  • Example 2 The palladium solution P1 in Example 1 (formation of lower catalytic layer) was applied to a position 15 mm from the inlet-side end face of C2 (11.5% of the length of the partition wall) so that the palladium loading after firing would be 3.51 g/L, and the applied solution was dried at 150°C for 15 minutes and then fired at 550°C for 30 minutes, thereby obtaining catalyst E in which a lower catalytic layer (comprising a gas inlet-side region L1 with a palladium concentration C L1 of 0.1133 [g/g] and a gas outlet-side region L2 with a palladium concentration C L2 of 0.0006197 [g/g]) and an upper catalytic layer (comprising a gas inlet-side region U1 with a palladium concentration C U1 of 0.1127 [g/g] and a gas outlet-side region U2 with a palladium concentration C U2 of 0 [g/g]
  • Example 5 (Formation of Lower Catalyst Layer Precursor) A1 was obtained in the same manner as in Example 1 above.
  • Example 2 The palladium solution P1 in Example 1 (formation of lower catalytic layer) was applied to a position 65 mm from the inlet-side end face of C2 (50.0% of the length of the partition wall) so that the palladium loading after firing would be 3.51 g/L, and the applied solution was dried at 150°C for 15 minutes and then fired at 550°C for 30 minutes, thereby obtaining catalyst F, in which a lower catalytic layer (comprising a gas inlet-side region L1 with a palladium concentration C L1 of 0.02908 [g/g] and a gas outlet-side region L2 with a palladium concentration C L2 of 0.0006197 [g/g]) and an upper catalytic layer (comprising a gas inlet-side region U1 with a palladium concentration C U1 of 0.02848 [g/g] and a gas outlet-side region U2 with a palladium concentration C U2 of 0 [
  • Example 6 (Formation of Lower Catalyst Layer Precursor) A1 was obtained in the same manner as in Example 1 above.
  • Example 2 The palladium solution P1 in Example 1 (formation of lower catalytic layer) was applied to a position 100 mm from the inlet-side end face of C2 (76.9% of the length of the partition wall) so that the palladium loading after firing would be 3.51 g/L, and the applied solution was dried at 150°C for 15 minutes and then fired at 550°C for 30 minutes, thereby obtaining a catalyst G in which a lower catalytic layer (comprising a gas inlet-side region L1 with a palladium concentration C L1 of 0.01931 [g/g] and a gas outlet-side region L2 with a palladium concentration C L2 of 0.0006197 [g/g]) and an upper catalytic layer (comprising a gas inlet-side region U1 with a palladium concentration C U1 of 0.01870 [g/g] and a gas outlet-side region U2 with a palladium concentration C U2 of 0
  • Example 7 (Formation of Lower Catalyst Layer Precursor) A1 was obtained in the same manner as in Example 1 above.
  • Example 2 The palladium solution P1 in Example 1 (formation of lower catalytic layer) was applied to a position 30 mm from the inlet-side end face of C2 (23.1% of the length of the partition wall) so that the palladium loading after firing would be 1.75 g/L, and the applied solution was dried at 150°C for 15 minutes and then fired at 550°C for 30 minutes, thereby obtaining catalyst H, which had a refractory three-dimensional structure provided with a lower catalytic layer (comprising a gas inlet-side region L1 with a palladium concentration C L1 of 0.03138 [g/g] and a gas outlet-side region L2 with a palladium concentration C L2 of 0.0006197 [g/g]) and an upper catalytic layer (comprising a gas inlet-side region U1 with a palladium concentration C U1 of 0.03078 [g/g] and a gas outlet-side region U2 with a
  • Example 8 (Formation of Lower Catalyst Layer Precursor) A1 was obtained in the same manner as in Example 1 above.
  • Example 2 The palladium solution P1 in Example 1 (formation of lower catalytic layer) was applied to a position 30 mm from the inlet-side end face of C2 (23.1% of the length of the partition wall) so that the palladium loading after firing would be 2.63 g/L, and the applied solution was dried at 150°C for 15 minutes and then fired at 550°C for 30 minutes, thereby obtaining catalyst I in which a lower catalytic layer (comprising a gas inlet-side region L1 with a palladium concentration C L1 of 0.04606 [g/g] and a gas outlet-side region L2 with a palladium concentration C L2 of 0.0006197 [g/g]) and an upper catalytic layer (comprising a gas inlet-side region U1 with a palladium concentration C U1 of 0.04547 [g/g] and a gas outlet-side region U2 with a palladium concentration C U2 of 0 [g
  • An upper catalyst layer was formed in the same manner as in Example 1, to obtain catalyst J in which a lower catalyst layer and an upper catalyst layer were provided on a fire-resistant three-dimensional structure.
  • slurry k1 was applied to a position 100 mm from the outlet end face of A1 so that the loading amount after firing would be 79.7 g/L, and after drying at 150°C for 15 minutes, it was fired at 550°C for 30 minutes to obtain catalyst K, which had a lower catalyst layer and an upper catalyst layer provided on a refractory three-dimensional structure.
  • ⁇ Durability test> A V8, 5.6-liter engine was operated for 50 seconds with the A/F at the catalyst inlet being 14.6 and the temperature at the catalyst bed being 1000°C, followed by operation for 5 seconds at an A/F of 12.0, and then operation for 5 seconds with the fuel supply stopped. This cycle was repeated for a total of 50 hours, and heat treatment was performed.
  • ⁇ Catalyst performance test> An in-line 4-cylinder, 2.0-liter engine was operated at an A/F of 14.6, and the exhaust gas temperature was raised from 70°C to 400°C at a rate of 1300°C/min. Gas discharged from the catalyst outlet was sampled, and the THC (total hydrocarbons) purification rate was calculated. The temperature at which each purification rate reached 50% was defined as T50, and catalyst performance was evaluated based on the time required to reach T50. The results are shown in Table 1 below. The shorter the time required to reach T50, the higher the exhaust gas purification performance.
  • catalyst A in which the gas inlet region L1 of the lower catalyst layer forms the outermost layer (the gas inlet region L1 of the lower catalyst layer is not covered by another catalyst layer), has even better exhaust gas purification performance at low temperatures.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Physics & Mathematics (AREA)
  • General Engineering & Computer Science (AREA)
  • Thermal Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Toxicology (AREA)
  • Biomedical Technology (AREA)
  • Environmental & Geological Engineering (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Catalysts (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)

Abstract

La présente divulgation concerne un moyen permettant d'améliorer les performances de purification de gaz d'échappement (en particulier les performances de purification d'hydrocarbures) à basse température dans un catalyseur de purification de gaz d'échappement. Le problème mentionné ci-dessus est résolu par un catalyseur de purification de gaz d'échappement comprenant une couche de catalyseur inférieure et une couche de catalyseur supérieure ayant des compositions prescrites, le rapport de la concentration en palladium sur une région côté entrée de gaz de la couche de catalyseur inférieure à la concentration de palladium sur une région côté sortie de gaz de la couche de catalyseur inférieure étant défini de manière à être dans une plage prescrite.
PCT/JP2025/022798 2024-07-09 2025-06-25 Catalyseur de purification de gaz d'échappement, procédé de production de celui-ci, et procédé de purification de gaz d'échappement au moyen dudit catalyseur de purification de gaz d'échappement Pending WO2026014237A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP2025559410A JP7847283B1 (ja) 2024-07-09 2025-06-25 排気ガス浄化用触媒、その製造方法および当該排気ガス浄化用触媒を用いた排気ガス浄化方法

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2024-110282 2024-07-09
JP2024110282 2024-07-09

Publications (1)

Publication Number Publication Date
WO2026014237A1 true WO2026014237A1 (fr) 2026-01-15

Family

ID=98386546

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2025/022798 Pending WO2026014237A1 (fr) 2024-07-09 2025-06-25 Catalyseur de purification de gaz d'échappement, procédé de production de celui-ci, et procédé de purification de gaz d'échappement au moyen dudit catalyseur de purification de gaz d'échappement

Country Status (2)

Country Link
JP (1) JP7847283B1 (fr)
WO (1) WO2026014237A1 (fr)

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013119075A (ja) * 2011-12-08 2013-06-17 Toyota Motor Corp 排ガス浄化用触媒
JP2013130146A (ja) * 2011-12-22 2013-07-04 Toyota Motor Corp 排ガス浄化装置
WO2017163985A1 (fr) * 2016-03-22 2017-09-28 株式会社キャタラー Catalyseur de purification de gaz d'échappement
JP2018199094A (ja) * 2017-05-25 2018-12-20 株式会社キャタラー 排ガス浄化触媒装置
JP2019136695A (ja) * 2018-02-13 2019-08-22 三井金属鉱業株式会社 排ガス浄化用触媒
JP2023502225A (ja) * 2019-11-22 2023-01-23 ビーエーエスエフ コーポレーション 富化ｐｇｍゾーンを有する排気浄化触媒物品

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013119075A (ja) * 2011-12-08 2013-06-17 Toyota Motor Corp 排ガス浄化用触媒
JP2013130146A (ja) * 2011-12-22 2013-07-04 Toyota Motor Corp 排ガス浄化装置
WO2017163985A1 (fr) * 2016-03-22 2017-09-28 株式会社キャタラー Catalyseur de purification de gaz d'échappement
JP2018199094A (ja) * 2017-05-25 2018-12-20 株式会社キャタラー 排ガス浄化触媒装置
JP2019136695A (ja) * 2018-02-13 2019-08-22 三井金属鉱業株式会社 排ガス浄化用触媒
JP2023502225A (ja) * 2019-11-22 2023-01-23 ビーエーエスエフ コーポレーション 富化ｐｇｍゾーンを有する排気浄化触媒物品

Also Published As

Publication number Publication date
JP7847283B1 (ja) 2026-04-16

Similar Documents

Publication Publication Date Title
KR102852325B1 (ko) 연료 차단 NOx 제어용 TWC 시스템
JP3704279B2 (ja) 排ガス浄化用触媒
CN101610844B (zh) 抗热老化的NOx储存材料和捕集器
JP7615208B2 (ja) 卑金属をドープした酸化ジルコニウム触媒担体材料
JP7518763B2 (ja) 排気ガス浄化触媒
CN101069845A (zh) 废气净化用催化剂、其制备方法、及用该催化剂的废气净化法
JP5014845B2 (ja) 排ガス浄化用触媒、その製造方法、およびかかる触媒を用いた排ガスの浄化方法
JP7248616B2 (ja) 排ガス浄化用触媒
EP3097977A1 (fr) Catalyseur de purification des gaz d'échappement pour moteur à gaz pauvre
JP7078521B2 (ja) 排ガス浄化用触媒
JP2021133334A (ja) ガソリンリーンバーンエンジン用ｌｎｔ積層触媒、及びこれを用いた排ガス浄化装置
JP6106197B2 (ja) ＮＯｘ吸蔵還元型排ガス浄化用触媒および当該触媒を用いた排ガス浄化方法
CN112638523B (zh) 排气净化催化剂、排气的净化方法和排气净化催化剂的制造方法
JP5023950B2 (ja) 排ガス成分浄化用触媒材及び同触媒材付パティキュレートフィルタ
CN109937088B (zh) 废气净化用催化剂及废气净化方法
JP7847283B1 (ja) 排気ガス浄化用触媒、その製造方法および当該排気ガス浄化用触媒を用いた排気ガス浄化方法
JP2010022892A (ja) 排ガス浄化用触媒
JP6767603B1 (ja) 排気ガス浄化用触媒、その製造方法及びそれを用いた排気ガス浄化方法
JP5029273B2 (ja) パティキュレートフィルタ
JP7847273B2 (ja) 排気ガス浄化用触媒、その製造方法および当該排気ガス浄化用触媒を用いた排気ガスの浄化方法
JP5949520B2 (ja) 触媒付パティキュレートフィルタ
CN111315476A (zh) 氮氧化物吸留材料和废气净化用催化剂
WO2023153116A1 (fr) Dispositif catalytique de purification de gaz d'échappement
KR20250048185A (ko) 백금, 팔라듐, 및 로듐을 포함하는 구역화된 삼원 전환 촉매
WO2023276793A1 (fr) Catalyseur d'oxydation d'épuration des gaz d'échappement

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 25836799

Country of ref document: EP

Kind code of ref document: A1