WO2010001226A1 - Layered exhaust gas purification catalyst comprising different noble metals - Google Patents

Layered exhaust gas purification catalyst comprising different noble metals Download PDF

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Publication number
WO2010001226A1
WO2010001226A1 PCT/IB2009/006122 IB2009006122W WO2010001226A1 WO 2010001226 A1 WO2010001226 A1 WO 2010001226A1 IB 2009006122 W IB2009006122 W IB 2009006122W WO 2010001226 A1 WO2010001226 A1 WO 2010001226A1
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Prior art keywords
catalyst layer
layer
length
support
exhaust gas
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PCT/IB2009/006122
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French (fr)
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WO2010001226A8 (en
Inventor
Tomoaki Sunada
Toshitaka Tanabe
Naoki Takahashi
Hirohisa Tanaka
Mari Uenishi
Masashi Taniguchi
Shingo Sakagami
Masaaki Kawai
Hirotak Ori
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Toyota Jidosha Kabushiki Kaisha
Daihatsu Motor Co., Ltd.
Cataler Corporation
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Publication of WO2010001226A1 publication Critical patent/WO2010001226A1/en
Publication of WO2010001226A8 publication Critical patent/WO2010001226A8/en

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    • B01J35/19—
    • 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
    • B01D53/9445—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC]
    • B01D53/945—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC] characterised by a specific catalyst
    • 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
    • B01J23/002—Mixed oxides other than spinels, e.g. perovskite
    • 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
    • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
    • 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
    • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
    • B01J23/46—Ruthenium, rhodium, osmium or iridium
    • B01J23/464—Rhodium
    • 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
    • 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
    • B01J37/024—Multiple impregnation or coating
    • B01J37/0244—Coatings comprising several layers
    • 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
    • B01J37/024—Multiple impregnation or coating
    • B01J37/0248—Coatings comprising impregnated particles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/10—Noble metals or compounds thereof
    • B01D2255/102—Platinum group metals
    • B01D2255/1021—Platinum
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/10—Noble metals or compounds thereof
    • B01D2255/102—Platinum group metals
    • B01D2255/1023—Palladium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/10—Noble metals or compounds thereof
    • B01D2255/102—Platinum group metals
    • B01D2255/1025—Rhodium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/204—Alkaline earth metals
    • B01D2255/2042—Barium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/206—Rare earth metals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/209—Other metals
    • B01D2255/2092—Aluminium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/40—Mixed oxides
    • B01D2255/407—Zr-Ce mixed oxides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/90—Physical characteristics of catalysts
    • B01D2255/902—Multilayered catalyst
    • B01D2255/9022—Two layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/01—Engine exhaust gases
    • B01D2258/014—Stoichiometric gasoline engines
    • 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
    • B01D53/9459—Removing one or more of nitrogen oxides, carbon monoxide, or hydrocarbons by multiple successive catalytic functions; systems with more than one different function, e.g. zone coated catalysts
    • B01D53/9477—Removing one or more of nitrogen oxides, carbon monoxide, or hydrocarbons by multiple successive catalytic functions; systems with more than one different function, e.g. zone coated catalysts with catalysts positioned on separate bricks, e.g. exhaust systems
    • 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
    • B01J2523/00—Constitutive chemical elements of heterogeneous catalysts
    • B01J35/56—
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
    • Y02C20/00—Capture or disposal of greenhouse gases
    • Y02C20/10—Capture or disposal of greenhouse gases of nitrous oxide (N2O)
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

Definitions

  • the invention relates to an exhaust gas purification catalyst suitable as a three-way catalyst.
  • Three-way catalysts have been widely used for purification of HC, CO, and NOx contained in exhaust gases of automobiles.
  • a three-way catalyst for example, as disclosed in Japanese Patent Application Publication No. 63-236541 (JP-A-63-236541), a noble metal such as Pt (platinum), Pd (palladium), and Rh (rhodium) is supported on a base material and performs purification by oxidizing HC and CO and reducing NOx. These reactions most effectively proceed in atmosphere in which the oxidized components and reduced components are present in substantially identical amounts. Therefore, in a vehicle that carries a three-way catalyst, the air-fuel ratio is controlled so that combustion is performed in the vicinity of a stoichiometric air-fuel ratio.
  • Rh has a high NOx reduction purification activity, and Pt and Pd have high HC and CO oxidation purification activity.
  • the NOx purification capacity is increased by disposing Rh in the upper layer.
  • the invention provides an exhaust gas purification catalyst that can demonstrate both the NOx purification capacity and the HC purification capacity.
  • the first aspect of the invention relates to an exhaust gas purification catalyst including: a base material having a gas passage through which exhaust gas flows; a lower catalyst layer formed on a surface of the base material wherein the lower catalyst layer supports Pd and/or Pt; and an upper catalyst layer that is formed on a surface of the lower catalyst layer wherein the upper catalyst layer supports Rh, a length of the upper catalyst layer in a gas flow direction along the gas passage is less than a length of the lower catalyst layer in the gas flow direction.
  • the upper catalyst layer supports Rh
  • the lower catalyst layer supports Pd and/or Pt. Because Rh and Pd and/or Pt are in different layers, alloying of Rh with Pd and/or Pt is inhibited and decrease in HC purification capacity of Pd and/or Pt is inhibited.
  • Rh is supported by the upper catalyst layer. Because Rh excels in NOx purification capacity and is disposed in the upper layer that comes into contact with the gas passage, the diffusability of the exhaust gas flowing in the gas passage to the upper catalyst layer increases, contact ⁇ vith NOx contained in the exhaust gas is facilitated, and NOx purification capacity of Rh can be effectively demonstrated.
  • a length of the upper catalyst layer in a gas flow direction along the gas passage is less than a length of the lower catalyst layer in the gas flow direction. Therefore, part of the lower catalyst layer is exposed in the gas passage and not covered with the upper catalyst layer. For this reason, the exhaust gas easily diffuses into the lower catalyst layer and the HC purification capacity and CO purification capacity of Pd and/or Pt can be effectively demonstrated.
  • a ratio of the length of the upper catalyst layer in the gas flow direction to the length of the lower catalyst layer in the gas flow direction may be 50 to 90%.
  • the ratio of the length of the upper catalyst layer in the gas flow direction to the length of the lower catalyst layer in the gas flow direction is 50 to 90%. Therefore, the lower catalyst layer can be exposed, by a certain length thereof, in the gas passage, while the length of the upper -catalyst layer is being maintained. For this reason, the NOx purification capacity of Rh supported on the upper catalyst layer can be effectively demonstrated together with the HC purification capacity of Pd and/or Pt supported on the lower catalyst layer.
  • the lower catalyst layer includes an oxygen absorbing/releasing material such as ceria
  • the fluctuations of the air-to-fuel ratio (AJF) of the exhaust gas flowing in the gas channel can be relaxed. For this reason, the lower catalyst layer and upper catalyst layer can demonstrate stable purification capacity.
  • the upper catalyst layer may be provided on a surface of the lower catalyst layer at a portion that includes a downstream end in the gas flow direction.
  • the upper catalyst layer is provided on a surface of the lower catalyst layer at a portion that includes a downstream end in the gas flow direction.
  • the downstream side of the base material is lower in temperature than the upstream side. Therefore, by providing the upper catalyst layer that supports Rh at the downstream side, it is possible to inhibit thermal deterioration of Rh at a high temperature.
  • the lower catalyst layer may be formed by a Pd support layer that supports Pd upstream in the gas flow direction and a Pt support layer that supports Pt downstream of the Pd support layer in the gas flow direction.
  • the lower catalyst layer is formed by a Pd support on the upstream side and a Pt support layer on the downstream side.
  • Pd and/or Pt contained in the lower catalyst layer consumes oxygen contained in the exhaust gas and conducts oxidation purification of HC and CO contained in the exhaust gas. Therefore, oxygen concentration on the downstream side becomes lower than that on the upstream side.
  • the Pd support layer that demonstrates high endurance at a high temperature in an atmosphere with a high oxygen concentration is disposed on the upstream side where the concentration of oxygen is high, and the Pt support layer is disposed on the downstream side.
  • the Pt support layer is disposed in an atmosphere with a comparatively low temperature and a low oxygen concentration on the downstream side, thermal deterioration of Pt is prevented and the endurance of the entire lower catalyst layer is increased.
  • FIG. 1 is a cross-sectional view of the exhaust gas purification catalyst of Example 1 in the gas flow direction;
  • FIG, 2 is a perspective view of the exhaust gas purification catalyst of Example 1;
  • FIG. 3 is a cross-sectional view along the arrow 2A-2A in FIG. 2;
  • FIG. 4 is a cross-sectional view along the arrow 2B-2B in FIG. 2;
  • FIG. 5 is a cross-sectional view of the exhaust gas purification catalyst of Example 2 in the gas flow direction;
  • FIG 6 is a cross-sectional view of the exhaust gas purification catalyst of Comparative Example 1 in the gas flow direction.
  • FIG. 7 is a diagram illustrating the relationship between the length of the upper catalyst layer and HC discharge amount as well as NOx discharge amount.
  • the exhaust gas purification catalyst of an embodiment of the invention includes a base material that has a gas passage, a lower catalyst layer formed on the base material surface, and an upper catalyst layer formed on the surface of the lower catalyst layer.
  • the base material is provided with a structure having a gas channel.
  • a base material of a honeycomb shape or foam shape can be used.
  • the type of the base material is not particularly limited, and a conventional material such as a metal or a ceramic, e.g. cordierite and SiC, can be used.
  • the lower catalyst layer is formed on the base material surface. In a case where the base material has a honeycomb shape, the lower catalyst layer is formed on the surface of partition walls of the honeycomb base material that partition a plurality of gas passages.
  • the lower catalyst layer may be formed on the entire base material in the gas flow direction.
  • the lower catalyst layer is composed of a support and Pd and/or Pt as a noble metal catalyst that is supported on the support.
  • the lower catalyst layer supports Pd and/or Pt, and it is desirable that no Rh be supported thereon. Pd and/or Pt enhance the HC and CO oxidation purification reaction.
  • the lower catalyst layer is preferably composed of a Pd support layer that supports Pd on the upstream side in the gas flow direction and a Pt support layer that supports Pt on the downstream side of the Pd support layer.
  • Pd that has excellent endurance at a high temperature in an atmosphere with a high oxygen concentration is disposed on the upstream side where the temperature and oxygen concentration are high, deterioration of Pt is inhibited, and endurance of the entire lower catalyst layer can be increased.
  • the ratio of the length of the Pd support layer in the gas flow direction to the length of the base material in the gas flow direction is preferably 20 to 45%. Where this ratio is less than 20%, the Pt support layer that supports Pt that shows comparatively low endurance at a high temperature will be close to the upstream side where the temperature is high and Pt may undergo thermal deterioration. Where the ratio is more than 45%, the concentration of Pd on the upstream side becomes low and warm-up capacity may decrease.
  • the Pd support ratio amount of the Pd support layer of the lower catalyst layer is preferably 0.25 to 5.0 g/L (liter). Where this amount is less than 0.25 g/L, the HC and CO oxidation activity may decrease, and where the amount is more than 5.0 g/L, the effect reaches saturation and cost rises.
  • the Pt support ratio amount of the Pt support layer of the lower catalyst layer is preferably 0.25 to 5.0 g/L. Where this amount is less than 0.25 g/L, the HC and CO oxidation activity may decrease, and where the amount is more than 5.0 g/L, the effect reaches saturation and cost rises.
  • the support of the Pd support layer of the lower catalyst layer can be from alumina, ceria, ceria-zirconia complex oxide, and the complex oxide having added thereto an oxide of lanthanum, yttrium, neodymium, or praseodymium.
  • the support of the Pt support layer of the lower catalyst layer can be from alumina, ceria, ceria-zirconia complex oxide, and the complex oxide having added thereto an oxide of lanthanum, yttrium, neodymium, or praseodymium.
  • the thickness of the lower catalyst layer is preferably 10 to 20 ⁇ m.
  • the thickness is less than 10 ⁇ m, catalytic activity of Pd and/or Pt contained in the lower catalyst layer may decrease, and where the thickness is more than 20 ⁇ m, diffusability of exhaust gas into Pd and/or Pt in the deep portions of the lower catalyst layer may decrease.
  • the lower catalyst layer may be formed by wash coating a slurry including a support powder for the lower catalyst layer on the base material, and then supporting Pd and/or Pt thereon, or by wash coating a slurry including a catalyst powder obtained in advance by supporting Pd and/or Pt on a support powder on the base material having the lower catalyst layer.
  • the upper catalyst layer is formed on the surface of the lower catalyst layer.
  • the length of the upper catalyst layer in the gas flow direction is less than the length of the lower catalyst layer in the gas flow direction.
  • the ratio of the length of the upper catalyst layer in the gas flow direction to the length of the lower catalyst layer in the gas flow direction is equal to or less than 100%, preferably 50 to 90%, more preferably 60 to 85%. In a case where the ratio is less than 50%, the length of the upper catalyst layer is too short by comparison with the length of the lower catalyst layer, and NOx purification activity of Rh supported on the upper catalyst layer can decrease. Where the ratio is above 90%, most of the lower catalyst layer is covered by the upper catalyst layer and gas diffusability into the lower catalyst layer can decrease.
  • the upper catalyst layer may be provided on the surface of a portion including the downstream end of the lower catalyst layer in the gas flow direction.
  • the portion including the downstream end in the lower catalyst layer is covered by the upper catalyst layer and the portion on the upstream side is exposed in the gas passage.
  • the upper catalyst layer is composed of a support and Rh as a catalytic noble metal supported on the support.
  • the upper catalyst layer supports Rh, and it is desirable that neither Pd nor Pt be supported thereon.
  • the Rh support ratio amount of the upper catalyst layer is preferably 0.1 to 1,2 g/L. Where this amount is less than 0.1 g/L, the NOx reduction activity may decrease, and where the amount is more than 1.2 g/L, the effect reaches saturation and cost rises.
  • the support of the upper catalyst layer may be from alumina, zirconia, ceria-zirconia complex oxide, and the complex oxide having added thereto an oxide of lanthanum, yttrium, neodymium, or praseodymium.
  • the thickness of the upper catalyst layer is preferably 10 to 20 ⁇ m.
  • the thickness is less than 10 ⁇ m, catalytic activity of Rh contained in the upper catalyst layer may decrease, and where the thickness is more than 20 ⁇ m, diffusability of exhaust gas into the portion of the lower catalyst layer that is covered by the upper catalyst layer may decrease.
  • the upper catalyst layer may be formed by wash coating a slurry including a support powder for the upper catalyst layer on the base material having the lower catalyst layer formed thereon, and then supporting at least Rh thereon, or by wash coating a slurry including a catalyst powder obtained in advance by supporting Rh on a support powder on the base material having the lower catalyst layer formed thereon.
  • a material that functions as an oxygen absorbing/releasing material capable of absorbing and releasing oxygen contained in the exhaust gas flowing through the gas passage is used as the support contained in the upper catalyst layer and/or lower catalyst layer.
  • the oxygen absorbing/releasing material include ceria and a ceria-zirconia complex oxide.
  • the exhaust gas purification catalyst of the embodiment of the invention can be used as a three-way catalyst. [0040] The invention will be described below in greater detail by using examples and comparative examples thereof.
  • Example 1 includes a honeycomb base material 1 having a gas passage 10 through which the exhaust gas flows, a lower catalyst layer 2 that is formed on the surface of the honeycomb base material 1, and an upper catalyst layer 3 that is formed on the surface of the lower catalyst layer 2.
  • he honeycomb base material 1 is a cylindrical part with a length (Ll) of 105 mm that is produced from cordierite, As shown in FIGS. 3 and 4, in the honeycomb base material 1, a large number of cells 11 with a hexagonal cross section that extend in the longitudinal direction are bounded by partition walls 12.
  • the lower catalyst layer 2 and upper catafyst layer 3 are formed on the surface of partition walls 12 constituting each cell 11, and a gas passage 10 is formed in the spatial portions at the surface thereof.
  • the lower catalyst layer 2 is constituted by a Pd support layer 21 that supports Pd and a Pt support layer 22 that supports Pt.
  • the Pd support layer 21 is disposed in a portion with a length of 20 mm from an upstream end Ia of the base material 1 in the flow direction of the gas flowing in the gas passage 10.
  • the Pt support layer 22 is disposed in a portion with a length of 85 mm from a downstream end 21b of the Pd support layer 21 to a downstream end Ib of the base material 1. Therefore, as shown in FIG. 3, on the upstream side of the base material 1, a single layer constituted only by the Pd support layer 21 of the lower catalyst layer 2 is provided, and as shown in FIG 4, on the downstream side of the base material 1, two layers, namely, the Pt support layer 22 of the lower catalyst layer 2 and the upper catalyst layer 3 are provided.
  • the upper catalyst layer 3 supports Rh.
  • a length L3 of the upper catalyst layer 3 in the gas flow direction is 85 mm, and the upper catalyst layer is disposed in a portion with a length of 85 mm from the downstream end Ib of the base material 1 toward the upstream side. Therefore, a portion of the lower catalyst layer 2 with a length of 20 ram from the upstream end 2a is exposed in the gas passage 10.
  • the thickness of the lower catalyst layer 2 is 15 ⁇ m, and the thickness of the upper catalyst layer 3 is 12 ⁇ m.
  • a method for manufacturing the exhaust gas purification catalyst of Example 1 will be explained below.
  • a complex oxide powder of CeO 2 -ZrO 2 -Y 2 O 3 -La 2 O 3 (CeO 2 : 30 wt.%, ZrO 2 : 60 wt.%, Y 2 O 3 : 5 wt.%, La 2 O 3 : 5 wt.%) serving as a support for forming a Pt support layer was prepared and immersed in a dinitrodiamine Pt solution serving as a noble metal catalyst solution and then evaporation to dryness was performed to prepare a Pt/support powder that supported Pt at 1.4 wt.%.
  • a slurry for the Pt support layer was prepared by mixing 60 parts by weight of the Pt/support powder, 25 parts by weight of an Al 2 Os-La 2 O 3 complex oxide (Al 2 O 3 : 96 wt.%, La 2 O 3 : 4 wt.%), 15 parts by weight of BaSO 4 , 3 parts by weight (absolute amount of alumina) of alumina sol as a binder (Al 2 Oa: 10 wt.%), and distilled water.
  • a portion of the cordierite honeycomb base material 1 (diameter 103 mm, total length 105 mm) with a length of 85 mm from the downstream end Ib in the upstream direction was immersed in the prepared slurry and then pulled up.
  • the excess slurry was blown off and then drying and firing were performed to form the Pt support layer 22.
  • the Pt support layer 22 was formed at a ratio of 103 g per 1 L of the honeycomb base material 1, and Pt was supported at a ratio of 0.45 g per 1 L of the honeycomb base material 1.
  • a CeO 2 -ZrO 2 -La 2 O 3 -Pr 6 On complex oxide powder (CeO 2 : 60 wt.%, ZrO ⁇ : 40 wt.%, La 2 O 3 : 3 wt.%, Pr 6 Ou: 7 wt.%) was prepared as a support for forming the Pd support layer and immersed in an aqueous solution of Pd nitrate as a noble metal catalyst solution and then evaporation to dryness was performed to prepare a Pd/support powder that supported Pd.
  • a slurry for the Pd support layer was prepared by mixing 9 parts by weight of the Pd/support powder, 3 parts by weight of an Al 2 O 3 -La 2 O 3 complex oxide (AJ 2 O 3 : 96 wt.%, La 2 O 3 : 4 wt.%), 3 parts by weight of BaSO 4 , 2 parts by weight (absolute amount of alumina) of alumina sol as a binder (Al 2 O 3 : 10 wt.%), and distilled water.
  • a portion with a length of 20 mm from the upstream end Ia in the downward direction of the cordierite honeycomb base material 1 having the abovementioned Pt support layer 22 formed thereon was immersed in the prepared slurry for the Pd support layer and then pulled up. The excess slurry was blown off and then drying and firing were performed to form the Pd support layer 21.
  • the Pd support layer 21 was formed at a ratio of 17 g per 1 L of the honeycomb base material 1, and Pd was supported at a ratio of 0.9 g per 1 L of the honeycomb base material 1.
  • a CeO 2 -ZrO 2 -Y 2 O 3 -Nd 2 O 3 complex oxide powder (CeO 2 : 20 wt.%, ZrO 2 : 60 wt.%, Y 2 O 3 : 8 wt.%, Nd 2 O 3 : 12 wt.%) was prepared as a support for forming the upper catalyst layer and immersed in an aqueous solution of Rh nitrate as a noble metal catalyst solution and then evaporation to dryness was performed to prepare a Rh/support powder that supported Rh.
  • a slurry for the upper catalyst layer was prepared by mixing 50 parts by weight of the Rh/support powder, 25 parts by weight of an Al 2 O 3 -La 2 O 3 complex oxide (AI 2 O 3 : 96 wt.%, La ⁇ Cb: 4 wt.%), 3 parts by weight (absolute amount of alumina) of alumina sol as a binder (AI2O3: 10 wt.%), and distilled water.
  • a portion with a length of 85 mm from the downstream end Ib of the cordierite honeycomb base material 1 in the upstream direction that was a surface portion of the Pd support layer 21 and Pt support layer 22 located on the surface of the honeycomb base material 1 was immersed in the prepared slurry and then pulled up.
  • the excess slurry was blown off and then drying and firing were performed to form the upper catalyst layer 3 supporting Rh.
  • the upper catalyst layer 3 was formed at a ratio of 78 g per 1 L of the honeycomb base material 1, and Rh was supported at a ratio of 0.13 g per 1 L of the honeycomb base material 1.
  • Example 2 differs from Example 1 in that the upper catalyst layer 3 was formed on a portion with a length of 75 mm from the downstream end 2b of the lower catalyst layer 2 toward the upstream side. Other features are similar to those of Example 1.
  • Example 3 differs from Example 1 in that the upper catalyst layer 3 was formed on a portion with a length of 65 mm from the downstream end 2b of the lower catalyst layer 2 toward the upstream side. Other features are similar to those of Example 1.
  • Example 4 differs from Example 1 in that the upper catalyst layer 3 was formed on a portion with a length of 55 mm from the downstream end 2b of the lower catalyst layer 2 toward the upstream side. Other features are similar to those of Example 1.
  • Example 5 differs from Example 1 in that the upper catalyst layer 3 was formed on a portion with a length of 95 mm from the downstream end 2b of the lower catalyst layer 2 toward the upstream side. Other features are similar to those of Example 1.
  • FIG. 7 demonstrates that the HC discharge amount of the catalyst increased, but the NOx discharge amount decreased with the increase in the length of the upper catalyst layer. This result indicates that the NOx reduction purification activity of Rh that was supported on the upper catalyst layer increased with the increase in the length of the upper catalyst layer. This is apparently because the spatial velocity (SV) of exhaust gas relative to the upper catalyst layer decreased with the increase in the length of the upper catalyst layer and therefore gas diffusability of the exhaust gas into the upper catalyst layer increased.
  • SV spatial velocity
  • the ratio of the length of the upper catalyst layer to the length of the lower catalyst layer was 100% and the HC discharge amount was the highest, but the NOx discharge amount was the lowest. This result indicates that the NOx purification activity of Rh in the upper catalyst layer was high, but the HC purification activity of Pt and Pd in the lower catalyst layer was suppressed.

Abstract

An exhaust gas purification catalyst includes a base material having a gas passage through which exhaust gas flows, a lower catalyst layer formed on a surface of the base material, and an upper catalyst layer that is formed on a surface of the lower catalyst layer. The upper catalyst layer supports Rh. The lower catalyst layer is formed by a Pd support layer that supports Pd and/or a Pt support layer that supports Pt. A length of the upper catalyst layer in a gas flow direction is less than a length of the lower catalyst layer in the gas flow direction.

Description

EXHAUST GAS PURIFICATION CATALYST
BACKGROUND OF THE INVENTION
1. Field of the Invention [0001] The invention relates to an exhaust gas purification catalyst suitable as a three-way catalyst.
2. Description of the Related Art
[0002] Three-way catalysts have been widely used for purification of HC, CO, and NOx contained in exhaust gases of automobiles. In a three-way catalyst, for example, as disclosed in Japanese Patent Application Publication No. 63-236541 (JP-A-63-236541), a noble metal such as Pt (platinum), Pd (palladium), and Rh (rhodium) is supported on a base material and performs purification by oxidizing HC and CO and reducing NOx. These reactions most effectively proceed in atmosphere in which the oxidized components and reduced components are present in substantially identical amounts. Therefore, in a vehicle that carries a three-way catalyst, the air-fuel ratio is controlled so that combustion is performed in the vicinity of a stoichiometric air-fuel ratio.
[0003] However, a demand has recently been created for reduction in use of noble metals, so as to save limited natural resources. Even among the noble metals, Rh is mined in a limited amount and has a high cost. Accordingly, as disclosed in Japanese Patent Application Publication No. 2004-298813 (JP-A-2004-298813) and Japanese Patent Application Publication No. 2001-79403 (JP- A-2001 -79403), in order to use Rh effectively, the catalyst layer is divided into two layers and the Rh activity is increased by disposing Rh in the upper layer. More specifically, JP-A-2004-298813 describes disposing Rh in the upper layer and Pt in the lower layer, and JP-A-2001-79403 describes disposing at least either of Rh and Pt in the upper layer and Pd in the lower layer.
[0004] Rh has a high NOx reduction purification activity, and Pt and Pd have high HC and CO oxidation purification activity. The NOx purification capacity is increased by disposing Rh in the upper layer.
[0005] However, as disclosed in JP-A-2004-298813 and JP-A-2001-79403, in a case where the catalyst layer is divided into two layers — an upper layer and a lower layer — , because the lower layer is covered by the upper layer, diffusability of gas into the lower layer is lower than that in the upper layer and catalytic activity of the lower layer is suppressed.
[0006] In the configuration described in JP-A-2004-298813, because Pt is disposed in the lower layer, the HC purification capacity of Pt is suppressed. In the configuration described in JP-A-2001-79403, because Pd is disposed in the lower layer, the HC purification capacity of Pd is suppressed. In particular, Examples 1 and 4 of JP-A-2001-79403 indicate that both Rh and Pt are present in the upper layer. Therefore, Rh and Pt are alloyed together, and the HC purification capacity of Pt is decreased.
SUMMARY OF THE INVENTION [0007T The invention provides an exhaust gas purification catalyst that can demonstrate both the NOx purification capacity and the HC purification capacity.
[0008] The first aspect of the invention relates to an exhaust gas purification catalyst including: a base material having a gas passage through which exhaust gas flows; a lower catalyst layer formed on a surface of the base material wherein the lower catalyst layer supports Pd and/or Pt; and an upper catalyst layer that is formed on a surface of the lower catalyst layer wherein the upper catalyst layer supports Rh, a length of the upper catalyst layer in a gas flow direction along the gas passage is less than a length of the lower catalyst layer in the gas flow direction.
[0009] In the above-described configuration, the upper catalyst layer supports Rh, and the lower catalyst layer supports Pd and/or Pt. Because Rh and Pd and/or Pt are in different layers, alloying of Rh with Pd and/or Pt is inhibited and decrease in HC purification capacity of Pd and/or Pt is inhibited.
[0010] Rh is supported by the upper catalyst layer. Because Rh excels in NOx purification capacity and is disposed in the upper layer that comes into contact with the gas passage, the diffusability of the exhaust gas flowing in the gas passage to the upper catalyst layer increases, contact λvith NOx contained in the exhaust gas is facilitated, and NOx purification capacity of Rh can be effectively demonstrated.
[0011] Furthermore, a length of the upper catalyst layer in a gas flow direction along the gas passage is less than a length of the lower catalyst layer in the gas flow direction. Therefore, part of the lower catalyst layer is exposed in the gas passage and not covered with the upper catalyst layer. For this reason, the exhaust gas easily diffuses into the lower catalyst layer and the HC purification capacity and CO purification capacity of Pd and/or Pt can be effectively demonstrated. [0012] A ratio of the length of the upper catalyst layer in the gas flow direction to the length of the lower catalyst layer in the gas flow direction may be 50 to 90%.
[0013] In the above-described configuration, the ratio of the length of the upper catalyst layer in the gas flow direction to the length of the lower catalyst layer in the gas flow direction is 50 to 90%. Therefore, the lower catalyst layer can be exposed, by a certain length thereof, in the gas passage, while the length of the upper -catalyst layer is being maintained. For this reason, the NOx purification capacity of Rh supported on the upper catalyst layer can be effectively demonstrated together with the HC purification capacity of Pd and/or Pt supported on the lower catalyst layer.
[0014] Further, in a case where the lower catalyst layer includes an oxygen absorbing/releasing material such as ceria, because the lower catalyst layer is exposed in the gas passage, the fluctuations of the air-to-fuel ratio (AJF) of the exhaust gas flowing in the gas channel can be relaxed. For this reason, the lower catalyst layer and upper catalyst layer can demonstrate stable purification capacity.
[0015] The upper catalyst layer may be provided on a surface of the lower catalyst layer at a portion that includes a downstream end in the gas flow direction.
[0016] In the above- described configuration, the upper catalyst layer is provided on a surface of the lower catalyst layer at a portion that includes a downstream end in the gas flow direction. The downstream side of the base material is lower in temperature than the upstream side. Therefore, by providing the upper catalyst layer that supports Rh at the downstream side, it is possible to inhibit thermal deterioration of Rh at a high temperature.
[0017] The lower catalyst layer may be formed by a Pd support layer that supports Pd upstream in the gas flow direction and a Pt support layer that supports Pt downstream of the Pd support layer in the gas flow direction.
[0018] In the above-described configuration, the lower catalyst layer is formed by a Pd support on the upstream side and a Pt support layer on the downstream side. Pd and/or Pt contained in the lower catalyst layer consumes oxygen contained in the exhaust gas and conducts oxidation purification of HC and CO contained in the exhaust gas. Therefore, oxygen concentration on the downstream side becomes lower than that on the upstream side. Accordingly, the Pd support layer that demonstrates high endurance at a high temperature in an atmosphere with a high oxygen concentration is disposed on the upstream side where the concentration of oxygen is high, and the Pt support layer is disposed on the downstream side. As a result, since the Pt support layer is disposed in an atmosphere with a comparatively low temperature and a low oxygen concentration on the downstream side, thermal deterioration of Pt is prevented and the endurance of the entire lower catalyst layer is increased.
BRIEF DESCRIPTION OF THE DRAWINGS [0019] The features, advantages, and technical and industrial significance of this invention will be described in the following detailed description of the example embodiments of the invention with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:
FIG. 1 is a cross-sectional view of the exhaust gas purification catalyst of Example 1 in the gas flow direction;
FIG, 2 is a perspective view of the exhaust gas purification catalyst of Example 1;
FIG. 3 is a cross-sectional view along the arrow 2A-2A in FIG. 2;
FIG. 4 is a cross-sectional view along the arrow 2B-2B in FIG. 2;
FIG. 5 is a cross-sectional view of the exhaust gas purification catalyst of Example 2 in the gas flow direction;
FIG 6 is a cross-sectional view of the exhaust gas purification catalyst of Comparative Example 1 in the gas flow direction; and
FIG. 7 is a diagram illustrating the relationship between the length of the upper catalyst layer and HC discharge amount as well as NOx discharge amount.
DETAILED DESCRIPTION OF EMBODIMENTS
[0020] The exhaust gas purification catalyst of an embodiment of the invention includes a base material that has a gas passage, a lower catalyst layer formed on the base material surface, and an upper catalyst layer formed on the surface of the lower catalyst layer. The base material is provided with a structure having a gas channel. For example, a base material of a honeycomb shape or foam shape can be used. The type of the base material is not particularly limited, and a conventional material such as a metal or a ceramic, e.g. cordierite and SiC, can be used. [0021] The lower catalyst layer is formed on the base material surface. In a case where the base material has a honeycomb shape, the lower catalyst layer is formed on the surface of partition walls of the honeycomb base material that partition a plurality of gas passages. The lower catalyst layer may be formed on the entire base material in the gas flow direction. [0022] The lower catalyst layer is composed of a support and Pd and/or Pt as a noble metal catalyst that is supported on the support. The lower catalyst layer supports Pd and/or Pt, and it is desirable that no Rh be supported thereon. Pd and/or Pt enhance the HC and CO oxidation purification reaction.
[0023] The lower catalyst layer is preferably composed of a Pd support layer that supports Pd on the upstream side in the gas flow direction and a Pt support layer that supports Pt on the downstream side of the Pd support layer. In this case, Pd that has excellent endurance at a high temperature in an atmosphere with a high oxygen concentration is disposed on the upstream side where the temperature and oxygen concentration are high, deterioration of Pt is inhibited, and endurance of the entire lower catalyst layer can be increased.
[0024] The ratio of the length of the Pd support layer in the gas flow direction to the length of the base material in the gas flow direction is preferably 20 to 45%. Where this ratio is less than 20%, the Pt support layer that supports Pt that shows comparatively low endurance at a high temperature will be close to the upstream side where the temperature is high and Pt may undergo thermal deterioration. Where the ratio is more than 45%, the concentration of Pd on the upstream side becomes low and warm-up capacity may decrease.
[0025] The Pd support ratio amount of the Pd support layer of the lower catalyst layer is preferably 0.25 to 5.0 g/L (liter). Where this amount is less than 0.25 g/L, the HC and CO oxidation activity may decrease, and where the amount is more than 5.0 g/L, the effect reaches saturation and cost rises.
[0026] The Pt support ratio amount of the Pt support layer of the lower catalyst layer is preferably 0.25 to 5.0 g/L. Where this amount is less than 0.25 g/L, the HC and CO oxidation activity may decrease, and where the amount is more than 5.0 g/L, the effect reaches saturation and cost rises.
[0027] The support of the Pd support layer of the lower catalyst layer can be from alumina, ceria, ceria-zirconia complex oxide, and the complex oxide having added thereto an oxide of lanthanum, yttrium, neodymium, or praseodymium. The support of the Pt support layer of the lower catalyst layer can be from alumina, ceria, ceria-zirconia complex oxide, and the complex oxide having added thereto an oxide of lanthanum, yttrium, neodymium, or praseodymium.
[0028] The thickness of the lower catalyst layer is preferably 10 to 20 μm.
Where the thickness is less than 10 μm, catalytic activity of Pd and/or Pt contained in the lower catalyst layer may decrease, and where the thickness is more than 20 μm, diffusability of exhaust gas into Pd and/or Pt in the deep portions of the lower catalyst layer may decrease.
[0029] The lower catalyst layer may be formed by wash coating a slurry including a support powder for the lower catalyst layer on the base material, and then supporting Pd and/or Pt thereon, or by wash coating a slurry including a catalyst powder obtained in advance by supporting Pd and/or Pt on a support powder on the base material having the lower catalyst layer.
[0030] In a case where the lower catalyst layer is separated into the Pd support layer on the upstream side and the Pt support layer on the downstream side, when the Pd support layer is formed, a portion of a predetermined length from the upstream end of the base material is immersed in a slurry including a support powder for the Pd support layer, and Pd is then supported. The same also relates to a slurry including a catalyst powder that supports Pd. When a Pt support layer is formed, a portion with a predetermined length from the downstream end of the base material is immersed in a slurry including a support powder for the Pt support layer, and Pt is then supported. The same also relates to a slurry including a catalyst powder that supports Pt.
[0031] The upper catalyst layer is formed on the surface of the lower catalyst layer. The length of the upper catalyst layer in the gas flow direction is less than the length of the lower catalyst layer in the gas flow direction. The ratio of the length of the upper catalyst layer in the gas flow direction to the length of the lower catalyst layer in the gas flow direction is equal to or less than 100%, preferably 50 to 90%, more preferably 60 to 85%. In a case where the ratio is less than 50%, the length of the upper catalyst layer is too short by comparison with the length of the lower catalyst layer, and NOx purification activity of Rh supported on the upper catalyst layer can decrease. Where the ratio is above 90%, most of the lower catalyst layer is covered by the upper catalyst layer and gas diffusability into the lower catalyst layer can decrease.
[0032] Where the ratio of the length of the upper catalyst layer in the gas flow direction to the length of the lower catalyst layer in the gas flow direction is 60 to 85%, the HC oxidation activity of Pd and/or Pt supported on the lower catalyst layer and NOx reduction activation of Rh supported on the upper catalyst layer can be effectively demonstrated with good balance.
[0033] The upper catalyst layer may be provided on the surface of a portion including the downstream end of the lower catalyst layer in the gas flow direction. In this case, the portion including the downstream end in the lower catalyst layer is covered by the upper catalyst layer and the portion on the upstream side is exposed in the gas passage.
[0034] The upper catalyst layer is composed of a support and Rh as a catalytic noble metal supported on the support. The upper catalyst layer supports Rh, and it is desirable that neither Pd nor Pt be supported thereon. The Rh support ratio amount of the upper catalyst layer is preferably 0.1 to 1,2 g/L. Where this amount is less than 0.1 g/L, the NOx reduction activity may decrease, and where the amount is more than 1.2 g/L, the effect reaches saturation and cost rises. [0035] The support of the upper catalyst layer may be from alumina, zirconia, ceria-zirconia complex oxide, and the complex oxide having added thereto an oxide of lanthanum, yttrium, neodymium, or praseodymium.
[0036] The thickness of the upper catalyst layer is preferably 10 to 20 μm.
Where the thickness is less than 10 μm, catalytic activity of Rh contained in the upper catalyst layer may decrease, and where the thickness is more than 20 μm, diffusability of exhaust gas into the portion of the lower catalyst layer that is covered by the upper catalyst layer may decrease.
[0037] The upper catalyst layer may be formed by wash coating a slurry including a support powder for the upper catalyst layer on the base material having the lower catalyst layer formed thereon, and then supporting at least Rh thereon, or by wash coating a slurry including a catalyst powder obtained in advance by supporting Rh on a support powder on the base material having the lower catalyst layer formed thereon.
[0038] A material that functions as an oxygen absorbing/releasing material capable of absorbing and releasing oxygen contained in the exhaust gas flowing through the gas passage is used as the support contained in the upper catalyst layer and/or lower catalyst layer. Examples of the oxygen absorbing/releasing material include ceria and a ceria-zirconia complex oxide.
[0039] The exhaust gas purification catalyst of the embodiment of the invention can be used as a three-way catalyst. [0040] The invention will be described below in greater detail by using examples and comparative examples thereof.
[0041] (Example 1) As shown in FIG 1, an exhaust gas purification catalyst of
Example 1 includes a honeycomb base material 1 having a gas passage 10 through which the exhaust gas flows, a lower catalyst layer 2 that is formed on the surface of the honeycomb base material 1, and an upper catalyst layer 3 that is formed on the surface of the lower catalyst layer 2.
[0042] As shown in FIG. 2, he honeycomb base material 1 is a cylindrical part with a length (Ll) of 105 mm that is produced from cordierite, As shown in FIGS. 3 and 4, in the honeycomb base material 1, a large number of cells 11 with a hexagonal cross section that extend in the longitudinal direction are bounded by partition walls 12. The lower catalyst layer 2 and upper catafyst layer 3 are formed on the surface of partition walls 12 constituting each cell 11, and a gas passage 10 is formed in the spatial portions at the surface thereof. [0043] As shown in FIG 1, the lower catalyst layer 2 is constituted by a Pd support layer 21 that supports Pd and a Pt support layer 22 that supports Pt. The Pd support layer 21 is disposed in a portion with a length of 20 mm from an upstream end Ia of the base material 1 in the flow direction of the gas flowing in the gas passage 10. The Pt support layer 22 is disposed in a portion with a length of 85 mm from a downstream end 21b of the Pd support layer 21 to a downstream end Ib of the base material 1. Therefore, as shown in FIG. 3, on the upstream side of the base material 1, a single layer constituted only by the Pd support layer 21 of the lower catalyst layer 2 is provided, and as shown in FIG 4, on the downstream side of the base material 1, two layers, namely, the Pt support layer 22 of the lower catalyst layer 2 and the upper catalyst layer 3 are provided.
[0044] The upper catalyst layer 3 supports Rh. A length L3 of the upper catalyst layer 3 in the gas flow direction is 85 mm, and the upper catalyst layer is disposed in a portion with a length of 85 mm from the downstream end Ib of the base material 1 toward the upstream side. Therefore, a portion of the lower catalyst layer 2 with a length of 20 ram from the upstream end 2a is exposed in the gas passage 10.
[0045] The thickness of the lower catalyst layer 2 is 15 μm, and the thickness of the upper catalyst layer 3 is 12 μm.
[0046] A method for manufacturing the exhaust gas purification catalyst of Example 1 will be explained below. First, a complex oxide powder of CeO2-ZrO2-Y2O3-La2O3 (CeO2: 30 wt.%, ZrO2: 60 wt.%, Y2O3: 5 wt.%, La2O3: 5 wt.%) serving as a support for forming a Pt support layer was prepared and immersed in a dinitrodiamine Pt solution serving as a noble metal catalyst solution and then evaporation to dryness was performed to prepare a Pt/support powder that supported Pt at 1.4 wt.%. [0047] A slurry for the Pt support layer was prepared by mixing 60 parts by weight of the Pt/support powder, 25 parts by weight of an Al2Os-La2O3 complex oxide (Al2O3: 96 wt.%, La2O3: 4 wt.%), 15 parts by weight of BaSO4, 3 parts by weight (absolute amount of alumina) of alumina sol as a binder (Al2Oa: 10 wt.%), and distilled water. A portion of the cordierite honeycomb base material 1 (diameter 103 mm, total length 105 mm) with a length of 85 mm from the downstream end Ib in the upstream direction was immersed in the prepared slurry and then pulled up. The excess slurry was blown off and then drying and firing were performed to form the Pt support layer 22. The Pt support layer 22 was formed at a ratio of 103 g per 1 L of the honeycomb base material 1, and Pt was supported at a ratio of 0.45 g per 1 L of the honeycomb base material 1.
[0048] Then, a CeO2-ZrO2-La2O3-Pr6On complex oxide powder (CeO2: 60 wt.%, ZrO∑: 40 wt.%, La2O3: 3 wt.%, Pr6Ou: 7 wt.%) was prepared as a support for forming the Pd support layer and immersed in an aqueous solution of Pd nitrate as a noble metal catalyst solution and then evaporation to dryness was performed to prepare a Pd/support powder that supported Pd.
[0049] A slurry for the Pd support layer was prepared by mixing 9 parts by weight of the Pd/support powder, 3 parts by weight of an Al2O3-La2O3 complex oxide (AJ2O3: 96 wt.%, La2O3: 4 wt.%), 3 parts by weight of BaSO4, 2 parts by weight (absolute amount of alumina) of alumina sol as a binder (Al2O3: 10 wt.%), and distilled water. A portion with a length of 20 mm from the upstream end Ia in the downward direction of the cordierite honeycomb base material 1 having the abovementioned Pt support layer 22 formed thereon was immersed in the prepared slurry for the Pd support layer and then pulled up. The excess slurry was blown off and then drying and firing were performed to form the Pd support layer 21. The Pd support layer 21 was formed at a ratio of 17 g per 1 L of the honeycomb base material 1, and Pd was supported at a ratio of 0.9 g per 1 L of the honeycomb base material 1.
[0050] Then, a CeO2-ZrO2-Y2O3-Nd2O3 complex oxide powder (CeO2: 20 wt.%, ZrO2: 60 wt.%, Y2O3: 8 wt.%, Nd2O3: 12 wt.%) was prepared as a support for forming the upper catalyst layer and immersed in an aqueous solution of Rh nitrate as a noble metal catalyst solution and then evaporation to dryness was performed to prepare a Rh/support powder that supported Rh.
[0051] A slurry for the upper catalyst layer was prepared by mixing 50 parts by weight of the Rh/support powder, 25 parts by weight of an Al2O3-La2O3 complex oxide (AI2O3: 96 wt.%, LaβCb: 4 wt.%), 3 parts by weight (absolute amount of alumina) of alumina sol as a binder (AI2O3: 10 wt.%), and distilled water. A portion with a length of 85 mm from the downstream end Ib of the cordierite honeycomb base material 1 in the upstream direction that was a surface portion of the Pd support layer 21 and Pt support layer 22 located on the surface of the honeycomb base material 1 was immersed in the prepared slurry and then pulled up. The excess slurry was blown off and then drying and firing were performed to form the upper catalyst layer 3 supporting Rh. The upper catalyst layer 3 was formed at a ratio of 78 g per 1 L of the honeycomb base material 1, and Rh was supported at a ratio of 0.13 g per 1 L of the honeycomb base material 1.
[0052] (Example 2) Example 2 differs from Example 1 in that the upper catalyst layer 3 was formed on a portion with a length of 75 mm from the downstream end 2b of the lower catalyst layer 2 toward the upstream side. Other features are similar to those of Example 1.
[0053] (Example 3) Example 3 differs from Example 1 in that the upper catalyst layer 3 was formed on a portion with a length of 65 mm from the downstream end 2b of the lower catalyst layer 2 toward the upstream side. Other features are similar to those of Example 1.
[0054] (Example 4) As shown in FIG 5, Example 4 differs from Example 1 in that the upper catalyst layer 3 was formed on a portion with a length of 55 mm from the downstream end 2b of the lower catalyst layer 2 toward the upstream side. Other features are similar to those of Example 1.
[0055] (Example 5) Example 5 differs from Example 1 in that the upper catalyst layer 3 was formed on a portion with a length of 95 mm from the downstream end 2b of the lower catalyst layer 2 toward the upstream side. Other features are similar to those of Example 1.
[0056] (Comparative Example 1) As shown in FIG 6, in the comparative example, the upper catalyst layer 3 was formed on a portion with a length of 105 mm from the downstream end 2b of the lower catalyst layer 2 toward the upstream side. Thus, the upper catalyst layer 3 covered the entire lower catalyst layer 2. [0057] <Test> Each of the catalysts of Examples 1 to 5 and Comparative example 1 was mounted on an exhaust system of a V-type 8-cylinder 4.3 L engine and an endurance test was conducted for 50 h by using gasoline under the following conditions: stationary conditions, oscillations with a frequency of 1 Hz between A/F = 14.0 and A/F = 15.0, and a central temperature of the catalyst of 10000C. [0058] Each catalyst after the endurance test was installed in an exhaust system of a linear 4-cylinder 2.4 L engine, combustion was induced at a stoichiometric air/fuel ratio (A/F = 14.2) till the temperature of gas flowing into the catalyst reached 55O0C, and the NOx amount and HC amount discharged within this period was measured. The measurement results are shown in FIG 7. In FIG 7, the measurement results are arranged in the order of increasing length of the upper catalyst layer. In FIG. 7, El to E5 and Cl indicate Examples 1 to 5 and Comparative Example 1.
[0059] FIG. 7 demonstrates that the HC discharge amount of the catalyst increased, but the NOx discharge amount decreased with the increase in the length of the upper catalyst layer. This result indicates that the NOx reduction purification activity of Rh that was supported on the upper catalyst layer increased with the increase in the length of the upper catalyst layer. This is apparently because the spatial velocity (SV) of exhaust gas relative to the upper catalyst layer decreased with the increase in the length of the upper catalyst layer and therefore gas diffusability of the exhaust gas into the upper catalyst layer increased. Furthermore, it is clear that as the length of the upper catalyst layer increased, the length of the lower catalyst layer that is covered by the upper catalyst layer increased, gas diffusability into the lower catalyst layer decreased, and HC oxidation purification activity of Pt and Pd supported on the lower catalyst layer decreased, [0060] Conversely, as the length of the upper catalyst layer decreased, the HC oxidation purification activity of Pt and Pd supported on the lower catalyst layer increased. This is apparently because the exposure of the lower catalyst layer increased and gas diffusability into Pt that has high activity with respect to combustion of HC contained in exhaust gas increased with the decrease in the length of the upper catalyst layer.
[0061] Further, where the length of the upper catalyst layer was 80 mm, that is, the length of the upper catalyst layer was 76% that of the lower catalyst layer, both the HC discharge amount and the NOx discharge amount decreased. This result suggests that HC and NOx purification activity can be demonstrated with good balance when the length of the upper catalyst layer is 50 to 90%, preferably 60 to 85%.
[0062] Meanwhile, in the comparative example, the ratio of the length of the upper catalyst layer to the length of the lower catalyst layer was 100% and the HC discharge amount was the highest, but the NOx discharge amount was the lowest. This result indicates that the NOx purification activity of Rh in the upper catalyst layer was high, but the HC purification activity of Pt and Pd in the lower catalyst layer was suppressed.

Claims

1. An exhaust gas purification catalyst comprising: a base material having a gas passage through which exhaust gas flows; a lower catalyst layer formed on a surface of the base material, wherein the lower catalyst layer supports Pd and/or Pt; and an upper catalyst layer that is formed on a surface of the lower catalyst layer, wherein the upper catalyst layer supports Rh, and a length of the upper catalyst layer in a gas flow direction along the gas passage is less than a length of the lower catalyst layer in the gas flow direction.
2. The exhaust gas purification catalyst according to claim 1, wherein a ratio of the length of the upper catalyst layer in the gas flow direction to the length of the lower catalyst layer in the gas flow direction is 50 to 90%.
3. The exhaust gas purification catalyst according to claim 1 or 2, wherein the upper catalyst layer is provided on a surface of the lower catalyst layer at a portion that includes a downstream end in the gas flow direction.
4. The exhaust gas purification catalyst according to any one of claims 1 to 3, wherein the lower catalyst layer is formed by a Pd support layer that supports Pd upstream in the gas flow direction and a Pt support layer that supports Pt downstream of the Pd support layer in the gas flow direction.
5. The exhaust gas purification catalyst according to claim 4, wherein a ratio of a length of the Pd support layer in the gas flow direction to a length of the lower catalyst layer in the gas flow direction is 20 to 45%.
6. The exhaust gas purification catalyst according to claim 4 or 5, wherein a Pd support ratio of the Pd support layer is 0.25 to 5.0 g/L.
7. The exhaust gas purification catalyst according to any of claims 4 to 6, wherein a Pt support ratio of the Pt support layer is 0.25 to 5.0 g/L.
8. The exhaust gas purification catalyst according to any of claims 1 to 7, wherein a thickness of the lower catalyst layer is 10 to 20 μm.
9. The exhaust gas purification catalyst according to any of claims 1 to 8, wherein a ratio of the length of the upper catalyst layer in the gas flow direction to the length of the lower catalyst layer in the gas flow direction is 60 to 85%.
10. The exhaust gas purification catalyst according to any of claims 1 to 9, wherein an Rh support ratio of the upper catalyst layer is 0.1 to 1.2 g/L.
11. The exhaust gas purification catalyst according to any of claims 1 to 10, wherein a thickness of the upper catalyst layer is 10 to 20 μm.
PCT/IB2009/006122 2008-06-30 2009-06-29 Layered exhaust gas purification catalyst comprising different noble metals WO2010001226A1 (en)

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US10071365B2 (en) 2013-01-23 2018-09-11 Toyota Jidosha Kabushiki Kaisha Catalytic converter
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Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5720949B2 (en) * 2011-12-08 2015-05-20 トヨタ自動車株式会社 Exhaust gas purification catalyst
EP3488928B1 (en) 2016-07-20 2020-08-19 Umicore Shokubai Japan Co., Ltd. Exhaust gas purification catalyst for internal combustion engine, and exhaust gas purifying method using exhaust gas purification catalyst
US11149603B2 (en) 2017-04-28 2021-10-19 Umicore Shokubai Japan Co., Ltd. Exhaust gas purification catalyst and exhaust gas purification method using the same
CN110785231B (en) 2017-04-28 2022-09-23 优美科触媒日本有限公司 Exhaust gas purifying catalyst and exhaust gas purifying method using same
US11141713B2 (en) 2017-04-28 2021-10-12 Umicore Shokubai Japan Co., Ltd. Exhaust gas purification catalyst and exhaust gas purification method using the same
JP7434489B1 (en) * 2022-10-18 2024-02-20 株式会社キャタラー Exhaust gas purification catalyst and catalyst body using the same

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0566401A1 (en) * 1992-04-15 1993-10-20 Ngk Insulators, Ltd. Catalyst for exhaust gas purification and method for exhaust gas purification
US20040001781A1 (en) * 2002-06-27 2004-01-01 Engelhard Corporation Multi-zone catalytic converter
US6887444B1 (en) * 1999-11-26 2005-05-03 Nissan Motor Co., Ltd. Exhaust gas purifying catalyst

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6384635A (en) * 1986-09-26 1988-04-15 Nissan Motor Co Ltd Catalyst for purifying exhaust gas
JPS63236541A (en) * 1987-03-24 1988-10-03 Nissan Motor Co Ltd Catalyst for purifying exhaust gas
JPH05293384A (en) * 1992-04-15 1993-11-09 Nissan Motor Co Ltd Catalyst for purifying exhaust gas and method therefor
JP4015328B2 (en) * 1999-09-14 2007-11-28 ダイハツ工業株式会社 Exhaust gas purification catalyst
JP4350250B2 (en) * 2000-01-27 2009-10-21 株式会社キャタラー Exhaust gas purification catalyst
JP4238056B2 (en) * 2003-03-31 2009-03-11 三井金属鉱業株式会社 Layered catalyst for exhaust gas purification

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0566401A1 (en) * 1992-04-15 1993-10-20 Ngk Insulators, Ltd. Catalyst for exhaust gas purification and method for exhaust gas purification
US6887444B1 (en) * 1999-11-26 2005-05-03 Nissan Motor Co., Ltd. Exhaust gas purifying catalyst
US20040001781A1 (en) * 2002-06-27 2004-01-01 Engelhard Corporation Multi-zone catalytic converter

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* Cited by examiner, † Cited by third party
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US8968690B2 (en) 2010-11-22 2015-03-03 Umicore Ag & Co. Kg Three-way catalyst having an upstream single-layer catalyst
WO2012069404A1 (en) * 2010-11-22 2012-05-31 Umicore Ag & Co. Kg Three-way catalytic system having an upstream single -layer catalyst
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