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US20160082419A1 - Carrier for exhaust gas purification catalyst, catalyst for exhaust gas purification, and catalyst structure for exhaust gas purification - Google Patents

Carrier for exhaust gas purification catalyst, catalyst for exhaust gas purification, and catalyst structure for exhaust gas purification Download PDF

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Publication number
US20160082419A1
US20160082419A1 US14/785,417 US201414785417A US2016082419A1 US 20160082419 A1 US20160082419 A1 US 20160082419A1 US 201414785417 A US201414785417 A US 201414785417A US 2016082419 A1 US2016082419 A1 US 2016082419A1
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Prior art keywords
exhaust gas
gas purification
purification catalyst
aluminum borate
carrier
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Inventor
Yunosuke Nakahara
Ohki Houshito
Hironori Iwakura
Yuki Nagao
Masato Machida
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Kumamoto University NUC
Mitsui Kinzoku Co Ltd
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Mitsui Mining and Smelting Co Ltd
Kumamoto University NUC
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Assigned to MITSUI MINING & SMELTING CO., LTD. reassignment MITSUI MINING & SMELTING CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: MACHIDA, MASATO, HOUSHITO, OHKI, IWAKURA, Hironori, NAGAO, YUKI, NAKAHARA, YUNOSUKE
Publication of US20160082419A1 publication Critical patent/US20160082419A1/en
Abandoned legal-status Critical Current

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    • 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
    • B01J23/10—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of rare earths
    • 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
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/02—Boron or aluminium; Oxides or hydroxides thereof
    • 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
    • B01J23/44—Palladium
    • 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
    • B01J23/58—Platinum group metals with alkali- or alkaline earth 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
    • B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/56—Platinum group metals
    • B01J23/63—Platinum group metals with rare earths or actinides
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—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
    • F01N3/101—Three-way catalysts
    • 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
    • F01N3/105—General auxiliary catalysts, e.g. upstream or downstream of the main catalyst
    • F01N3/106—Auxiliary oxidation catalysts
    • 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
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/204—Alkaline 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
    • B01D2255/204—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
    • B01D2255/204—Alkaline earth metals
    • B01D2255/2045—Calcium
    • 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
    • B01D2255/2063—Lanthanum
    • 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
    • B01D2255/2065—Cerium
    • 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
    • B01D2255/2066—Praseodymium
    • 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
    • B01D2255/2068—Neodymium
    • 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
    • B01D2255/70—Non-metallic catalysts, additives or dopants
    • 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
    • B01J2235/00—Indexing scheme associated with group B01J35/00, related to the analysis techniques used to determine the catalysts form or properties
    • B01J2235/15—X-ray diffraction
    • 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
    • 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
    • F01N2570/00—Exhaust treating apparatus eliminating, absorbing or adsorbing specific elements or compounds
    • F01N2570/10—Carbon or carbon oxides
    • 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 present invention relates to a carrier for an exhaust gas purification catalyst (hereinafter referred to as an exhaust gas purification catalyst carrier), to an exhaust gas purification catalyst, and to an exhaust gas purification catalyst product. More particularly, the invention relates to an exhaust gas purification catalyst carrier, to an exhaust gas purification catalyst, and to an exhaust gas purification catalyst product, which exhibit excellent exhaust gas purification performance, (in particular CO removal performance), in a fuel-rich region (hereinafter referred to simply as a “rich region”), even after long-term use thereof under high-temperature conditions.
  • Exhaust gas discharged from an internal combustion engine of, for example, an automobile contains toxic components such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NO x ). Hitherto, three-way catalysts have been used for removing such toxic components for detoxifying the exhaust gas.
  • HC hydrocarbons
  • CO carbon monoxide
  • NO x nitrogen oxides
  • Such three-way catalysts include a noble metal (e.g., Pt, Pd, or Rh) serving as a catalytically active component; a material such as alumina, ceria, zirconia, or oxygen-occluding ceria-zirconia composite oxide, serving as a carrier; and a catalyst support made of a ceramic or metallic material and having a shape of honeycomb, plate, pellet, etc.
  • a noble metal e.g., Pt, Pd, or Rh
  • a material such as alumina, ceria, zirconia, or oxygen-occluding ceria-zirconia composite oxide, serving as a carrier
  • a catalyst support made of a ceramic or metallic material and having a shape of honeycomb, plate, pellet, etc.
  • the present applicant previously developed an exhaust gas purification catalyst which exhibits excellent NO x purification performance, particularly in a rich region.
  • the catalyst includes a carrier containing a substituted aluminum borate in which 2.5 to 11.5 at. % aluminum atoms are substituted by Fe, Co, Ga, or Ni atoms, and Pd supported on the carrier (see Patent Document 5).
  • Patent Document 1 Japanese Patent Application Laid-Open (kokai) No. Hei 06-099069
  • Patent Document 2 Japanese Patent Application Laid-Open (kokai) No. Hei 07-171392
  • Patent Document 3 Japanese Patent Application Laid-Open (kokai) No. Hei 08-281071
  • Patent Document 4 Japanese Patent Application Laid-Open (kokai) No. 2002-370035
  • Patent Document 5 WO 2012/005375
  • the exhaust gas purification catalyst disclosed in Patent Document 5 exhibits somewhat lower purification performance after long-term use thereof in a rich region, although the catalyst exhibits excellent purification performance after long-term use thereof under a fuel-lean or a stoichiometric condition.
  • an object of the present invention is to provide an exhaust gas purification catalyst carrier, an exhaust gas purification catalyst, and an exhaust gas purification catalyst product, which exhibit excellent exhaust gas purification performance, (in particular CO removal performance), in a rich region, even after long-term use thereof under high-temperature conditions.
  • the present inventors have conducted extensive studies in order to attain the aforementioned object, and have found that the electronegativity of a catalyst carrier made of a modified aluminum borate to which an alkaline earth element or a rare earth element has been added can be reduced, to thereby promote electron supply from noble metal elements to the carrier, whereby the noble metal elements are immobilized on the carrier even in a rich region, to thereby attain excellent Pd dispersion degree and catalytic activity, even after long-term use thereof in a rich region.
  • the present invention has been accomplished on the basis of this finding.
  • aluminum borate may be represented by either formula 9Al 2 O 3 .2B 2 O 3 (Al 18 B 4 O 33 ) or Al 5 BO 9 (5Al 2 O 3 :B 2 O 3 , Al 20 B 4 O 36 ), meaning that the two formulas represent a unique substance.
  • aluminum borate encompasses aluminum borate represented by formula 10Al 2 O 3 .2B 2 O 3 (5Al 2 O 3 :B 2 O 3 , Al 20 B 4 O 36 ) and aluminum borate represented by formula 9Al 2 O 3 .2B 2 O 3 (Al 18 B 4 O 33 ).
  • a characteristic feature of the exhaust gas purification catalyst carrier of the present invention resides in that the catalyst carrier comprises a modified aluminum borate which contains aluminum borate (in particularly aluminum borate having a cage structure) and at least one addition element selected from the group consisting of a rare earth element and an alkaline earth metal and which has an electronegativity of 2.732 or lower.
  • the catalyst carrier comprises a modified aluminum borate which contains aluminum borate and at least one addition element selected from the group consisting of a rare earth element and an alkaline earth metal, in an amount of 6 mass % or more as an oxide thereof.
  • the aluminum borate employed in the present invention encompasses aluminum borate species having an aluminum oxide to boron oxide ratio of 10:2 to 9:2; i.e., an aluminum borate represented by formula 10Al 2 O 3 .2B 2 O 3 (5Al 2 O 3 :B 2 O 3 , Al 20 B 4 O 36 ) and an aluminum borate represented by formula 9Al 2 O 3 .2B 2 O 3 (Al 18 B 4 O 33 ).
  • the aluminum borate employed in the present invention can be identified as an aluminum borate represented by formula 10Al 2 O 3 .2B 2 O 3 through X-ray diffractometry.
  • the aluminum borate can also be identified as an aluminum borate represented by formula 9Al 2 O 3 .2B 2 O 3 (Al 48 B 4 O 33 ).
  • the exhaust gas purification catalyst of the present invention includes the aforementioned exhaust gas purification catalyst carrier, and Pd supported on the carrier.
  • the exhaust gas purification catalyst product of the present invention includes a catalyst support formed of a ceramic or metallic material, and a layer of the aforementioned exhaust gas purification catalyst, the layer being supported on the catalyst support.
  • the exhaust gas purification catalyst carrier, the exhaust gas purification catalyst, and the exhaust gas purification catalyst product according to the present invention exhibit excellent exhaust gas purification performance (in particular, CO removal performance) in a rich region, after long-term use thereof under high-temperature conditions.
  • the carrier employed in the exhaust gas purification catalyst of the present invention comprises a modified aluminum borate which contains at least one addition element selected from the group consisting of a rare earth element and an alkaline earth metal and has an electronegativity of 2.732 or lower.
  • the catalyst carrier comprises a modified aluminum borate which contains aluminum borate and at least one addition element selected from the group consisting of a rare earth element and an alkaline earth metal, in an amount of 6 mass % or more as an oxide thereof, preferably 7 mass % or more.
  • an exhaust gas purification catalyst containing Pd supported on the carrier exhibits excellent Pd dispersion degree and catalytic activity in a rich region after long-term use of the catalyst under high-temperature conditions.
  • the addition element contained in the modified aluminum borate of the present invention is not a partial substitution element with respect to boron or aluminum of aluminum borate, but is supported on aluminum borate or modifies aluminum borate.
  • the addition element is present as an oxide or the like of the addition element such as a crystal grain boundary.
  • such aluminum borate species may also be referred to collectively as modified aluminum borate.
  • the aforementioned aluminum borate species may be produced through, for example, the following method.
  • boric acid was weighed in such an amount that the compositional proportions of the target aluminum borate (formula: Al 20 B 4 O 36 ) were attained, and dissolved in ion-exchange water. Subsequently, the solution was mixed with a specifically weighed boehmite acetate sol, and the resultant mixture was heated under stirring. The thus-formed gel was dried at 120° C. for 12 hours or longer. After completion of drying, the dried product was fired at 300° C. for one hour and then at 1,000° C. for 5 hours, to thereby yield the target aluminum borate.
  • the target aluminum borate formula: Al 20 B 4 O 36
  • Boric acid was weighed in such an amount that the compositional proportions of a target compound, aluminum borate (formula: Al 20 B 4 O 36 ), were attained, and dissolved in hot pure water. Subsequently, the solution was mixed with a specifically weighed aluminum nitrate, to thereby prepare a solution. The solution was added dropwise to aqueous ammonium carbonate. The thus-formed precipitates were washed with pure water with filtration, and the solid was dried overnight at about 120° C. and fired in air at about 300° C. for about one hour. Thereafter, the dried product was fired at about 1,000° C. for about 5 hours, to thereby yield the target aluminum borate.
  • aluminum borate formula: Al 20 B 4 O 36
  • the carrier of the exhaust gas purification catalyst of the present invention contains a modified aluminum borate prepared by modifying (or depositing) at least one element selected from the group consisting of a rare earth element and an alkaline earth metal with (or on) the above-produced aluminum borate.
  • aluminum borate was immersed in a solution containing a specific amount of a compound of additional element (e.g., a nitrate salt, a sulfate salt, or an acetate salt), subjecting the mixture to evaporation to dryness, and firing the solid at a specific temperature (e.g., 400 to 1,000° C.)
  • a compound of additional element e.g., a nitrate salt, a sulfate salt, or an acetate salt
  • the addition element content, reduced to the corresponding oxide content; i.e., the ratio (amount of addition element oxide)/(sum of amount of aluminum borate+amount of addition element oxide) selected in the present invention, is 0.1 to 20 mass %, preferably 3 to 15 mass %, more preferably 6 to 13 mass %, still more preferably 7 to 13 mass %.
  • the modified aluminum borate has an electronegativity of 2.732 or lower, or contains at least one element selected from the group consisting of a rare earth element and an alkaline earth metal, in an amount of 6 mass % or more as an oxide thereof, preferably 7 mass % or more.
  • the electronegativity is higher than the above upper limit, the supported Pd component tends to be undesirably stable PdO, whereby the catalyst becomes inert to reduction of NOx or the like, which is not preferred.
  • No particular limitation is imposed on the lower limit of the electronegativity, but the practical value thereof is conceivably about 2.700.
  • said at least one element selected from the group consisting of a rare earth element and an alkaline earth metal is added as an oxide in an amount of 7 mass % or more, electrons are sufficiently supplied from noble metal elements to the carrier, whereby the noble metal elements are immobilized on the carrier even in a rich region, to thereby attain excellent Pd dispersion degree and catalytic activity, even after long-term use thereof in a rich region.
  • the exhaust gas purification catalyst of the present invention contains Pd supported on a carrier containing the aforementioned modified aluminum borate.
  • the exhaust gas purification catalyst exhibits excellent exhaust gas purification performance (in particular, CO removal performance) in a rich region, after long-term use thereof under high-temperature conditions.
  • the amount of Pd supported on the carrier is preferably 0.05 to 5 mass %, based on the mass of the carrier, more preferably 0.4 to 3 mass %.
  • the amount of supported Pd based on the mass of the carrier is 0.05 mass % or more, durability of the catalyst increases, and when the amount is 5 mass % or less, Pd can be consistently supported in a highly dispersed state.
  • the amount of supported Pd based on the mass of the carrier is less than 0.05 mass %, durability is poor due to a small absolute amount of noble metal, and when the amount is in excess of 5 mass %, supporting of Pd in a highly dispersion state may fail to be attained due to an excess amount of noble metal.
  • the amount of supported Pd is reduced to the mass of metallic Pd.
  • the exhaust gas purification catalyst of the present invention may be produced by mixing the modified aluminum borate with a solution of a Pd compound (a soluble Pd compound; e.g., Pd nitrate, Pd chloride, or Pd sulfate) so that the amount of supported Pd based on the mass of the carrier is adjusted to 0.2 to 3 mass %, and then subjecting the mixture to evaporation to dryness and firing the dried product at 450 to 650° C.
  • a Pd compound a soluble Pd compound
  • Pd nitrate e.g., Pd nitrate, Pd chloride, or Pd sulfate
  • the modified aluminum borate may be used in combination with an additional carrier, such as a porous body of a compound selected from the group consisting of silica, ceria, ceria-zirconia, alumina, and titania.
  • an additional carrier such as a porous body of a compound selected from the group consisting of silica, ceria, ceria-zirconia, alumina, and titania.
  • the exhaust gas purification catalyst product of the present invention includes a catalyst support formed of a ceramic or metallic material, and a layer of the aforementioned exhaust gas purification catalyst of the present invention, the layer being formed and supported on the catalyst support.
  • a catalyst support formed of a ceramic or metallic material no particular limitation is imposed on the shape of the catalyst support formed of a ceramic or metallic material, and the support is generally in the form of honeycomb, plate, pellet, etc.
  • the amount of exhaust gas purification catalyst supported is preferably 70 to 300 g/L, more preferably 100 to 200 g/L. When the catalyst amount is less than 70 g/L, durability of the catalyst tends to decrease due to an insufficient catalyst amount.
  • Examples of the material of the catalyst support include ceramic materials such as alumina (Al 2 O 3 ), mullite (3Al 2 O 3 -2SiO 2 ), and cordierite (2MgO-2Al 2 O 3 -5SiO 2 ), and metallic materials such as stainless steel.
  • ceramic materials such as alumina (Al 2 O 3 ), mullite (3Al 2 O 3 -2SiO 2 ), and cordierite (2MgO-2Al 2 O 3 -5SiO 2 ), and metallic materials such as stainless steel.
  • the exhaust gas purification catalyst product of the present invention may be produced through the following method.
  • a modified aluminum borate (50 to 70 parts by mass, preferably 50 to 60 parts by mass), La-stabilized alumina (20 to 40 parts by mass, preferably 20 to 30 parts by mass), barium hydroxide (0 to 3 parts by mass, preferably 1 to 3 parts by mass), and an alumina-bases binder (5 to 10 parts by mass) are mixed with a Pd compound solution, and the mixture is pulverized under wet conditions, to thereby prepare a slurry.
  • the thus-prepared slurry is applied onto, through a widely known technique, a catalyst support formed of a ceramic or metallic material, preferably a honeycomb-shape catalyst support.
  • the resultant structure is dried and then fired at 450 to 650° C., to thereby produce an exhaust gas purification catalyst product which includes a catalyst support, and a layer of the exhaust gas purification catalyst, the layer being supported on the catalyst support.
  • the addition element content is derived as the ratio of amount of addition element oxide/total amount of aluminum borate and addition element oxide.
  • 10A2B denotes 10Al 2 O 3 .2B 2 O 3 .
  • An aluminum borate (Al 20 B 4 O 36 ) was prepared through the following solid-phase method. Specifically, boric acid was weighed in such an amount that the compositional proportions of a target compound were attained, and dissolved in ion-exchange water. Subsequently, the solution was mixed with a specifically weighed boehmite acetate sol, and the resultant mixture was heated under stirring. The thus-formed gel was dried at 120° C. for 12 hours or longer. After completion of drying, the dried product was fired in air at 300° C. for one hour and then at 1,000° C. for 5 hours, to thereby yield the aluminum borate of interest. The aluminum borate was found to have an XRD pattern shown in FIG. 1 . As is clear from FIG. 1 , the aluminum borate was identified as an aluminum borate represented by formula 10Al 2 O 3 .2B 2 O 3 , through X-ray diffraction analysis.
  • An aluminum borate (Al 20 B 4 O 36 ) was prepared through a reverse co-precipitation method. Specifically, boric acid was weighed in such an amount that the compositional proportions of a target compound were attained, and dissolved in ion-exchange water. Subsequently, the solution was mixed with a specifically weighed aluminum nitrate nanohydrate, to thereby prepare a solution. Then, the solution was added dropwise to aqueous ammonium carbonate, to thereby form precipitates. The precipitates were washed with pure water with filtration, and dried at 120° C. for 12 hours or longer, followed by firing in air at 300° C. for one hour and further in air at 1,000° C. for 5 hours, to thereby yield the aluminum borate of interest. No significant difference was observed between the aluminum borate prepared through the above co-precipitation and that prepared through the solid-phase method of Referential Example 1.
  • this aluminum borate was identified as an aluminum borate represented by formula 10Al 2 O 3 .2B 2 O 3 .
  • the aluminum borate produced in Production Example 1 was immersed in aqueous lanthanum nitrate and in aqueous strontium nitrate.
  • the amount of lanthanum nitrate in the aqueous solution and that of the strontium nitrate in the aqueous solution were adjusted such that the La 2 O 3 content and the SrO content of the aluminum borate represented by 10Al 2 O 3 .2B 2 O 3 modified with target La 2 O 3 and SrO were attained as 5 mass % and 5 mass %, respectively.
  • the mixture was dried overnight (for about 15 hours) at 120° C. to dryness, and then fired in air at 600° C. for 3 hours, to thereby yield an aluminum borate represented by 10Al 2 O 3 .2B 2 O 3 modified with La 2 O 3 and SrO at 5 mass % and 5 mass %, respectively.
  • the aluminum borate produced in Production Example 1 was immersed in aqueous lanthanum nitrate and in aqueous praseodymium nitrate.
  • the amount of lanthanum nitrate in the aqueous solution thereof and that of praseodymium nitrate in its aqueous solution were adjusted such that the La 2 O 3 content and the Pr 6 O 11 content of the aluminum borate represented by 10Al 2 O 3 .2B 2 O 3 modified with target La 2 O 3 and Pr 6 O 11 were attained as 5 mass % and 5 mass %, respectively.
  • the mixture was dried overnight (for about 15 hours) at 120° C. to dryness, and then fired in air at 600° C. for 3 hours, to thereby yield an aluminum borate represented by 10Al 2 O 3 .2B 2 O 3 modified with La 2 O 3 and Pr 6 O 11 at 5 mass % and 5 mass %, respectively.
  • the aluminum borate produced in Production Example 1 was immersed in aqueous lanthanum nitrate and in aqueous calcium nitrate.
  • the amount of lanthanum nitrate in the aqueous solution and that of the calcium nitrate in its aqueous solution were adjusted such that the La 2 O 3 content and the CaO content of the aluminum borate represented by 10Al 2 O 3 .2B 2 O 3 modified with target La 2 O 3 and CaO were attained as 5 mass % and 5 mass %, respectively. Thereafter, the mixture was dried overnight (for about 15 hours) at 120° C. to dryness, and then fired in air at 600° C.
  • an appropriate amount of ion-exchange water was added, and the resultant slurry was stirred, dried, and fired at 500° C. for one hour.
  • the aluminum borate produced in Production Example 1 was immersed in aqueous lanthanum nitrate and in aqueous barium nitrate.
  • the amount of lanthanum nitrate in the aqueous solution and that of the barium nitrate in its aqueous solution were adjusted such that the La 2 O 3 content and the BaO content of the aluminum borate represented by 10Al 2 O 3 .2B 2 O 3 modified with La 2 O 3 and BaO were attained as 5 mass % and 5 mass %, respectively.
  • the mixture was dried overnight (for about 15 hours) at 120° C. to dryness, and then fired in air at 600° C. for 3 hours, to thereby yield an aluminum borate represented by 10Al 2 O 3 .2B 2 O 3 modified with La 2 O 3 and BaO at 5 mass % and 5 mass %, respectively.
  • the aluminum borate produced in Production Example 1 was immersed in aqueous lanthanum nitrate and in aqueous neodymium nitrate.
  • the amount of lanthanum nitrate in the aqueous solution and that of the neodymium nitrate in its aqueous solution were adjusted such that the La 2 O 3 content and the Nd 2 O 3 content of the aluminum borate represented by 10Al 2 O 3 .2B 2 O 3 modified with target La 2 O 3 and Nd 2 O 3 were attained as 5 mass % and 5 mass %, respectively.
  • the mixture was dried overnight (for about 15 hours) at 120° C. to dryness, and then fired in air at 600° C. for 3 hours, to thereby yield an aluminum borate represented by 10Al 2 O 3 .2B 2 O 3 modified with La 2 O 3 and Nd 2 O 3 at 5 mass % and 5 mass %, respectively.
  • the aluminum borate produced in Production Example 1 was immersed in aqueous lanthanum nitrate and in aqueous cerium nitrate.
  • the amount of lanthanum nitrate in the aqueous solution and that of the cerium nitrate in its aqueous solution were adjusted such that the La 2 O 3 content and the CeO 2 content of the aluminum borate represented by 10Al 2 O 3 .2B 2 O 3 modified with target La 2 O 3 and CeO 2 were attained as 5 mass % and 5 mass %, respectively.
  • the mixture was dried overnight (for about 15 hours) at 120° C. to dryness, and then fired in air at 600° C. for 3 hours, to thereby yield an aluminum borate represented by 10Al 2 O 3 .2B 2 O 3 modified with La 2 O 3 and CeO 2 at 5 mass % and 5 mass %, respectively.
  • ⁇ -Al 2 O 3 99 parts by mass
  • palladium nitrate 1 part by mass, as reduced to metallic Pd
  • the aluminum borate produced in Production Example 1 was immersed in aqueous lanthanum nitrate.
  • the amount of lanthanum nitrate in the aqueous solution was adjusted such that the La 2 O 3 content of the aluminum borate represented by 10Al 2 O 3 .2B 2 O 3 modified with target La 2 O 3 was attained as 5 mass %.
  • the mixture was dried overnight (for about 15 hours) at 120° C. to dryness, and then fired in air at 600° C. for 3 hours, to thereby yield an aluminum borate represented by 10Al 2 O 3 .2B 2 O 3 modified with La 2 O 3 at 5 mass %.
  • the aluminum borate produced in Production Example 1 was immersed in aqueous lanthanum nitrate and in aqueous barium nitrate.
  • the amount of lanthanum nitrate in the aqueous solution thereof and that of the barium nitrate in its aqueous solution were adjusted such that the La 2 O 3 content and the BaO content of the aluminum borate represented by 10Al 2 O 3 .2B 2 O 3 modified with target La 2 O 3 and BaO were attained as 1 mass % and 2 mass %, respectively.
  • the mixture was dried overnight (for about 15 hours) at 120° C. to dryness, and then fired in air at 600° C. for 3 hours, to thereby yield an aluminum borate represented by 10Al 2 O 3 .2B 2 O 3 modified with La 2 O 3 and BaO at 1 mass % and 2 mass %, respectively.
  • Each of the samples produced in the Examples and Comparative Examples was assessed in terms of purification performance with respect to a simulated exhaust gas, by means of an immobilized bed flow-type reactor.
  • Each catalyst powder 50 mg was placed in the reactor tube, and a gas which simulated a complete combustion gas and which was composed of NO (.05%), CO (.39%), C 3 H 6 (1,200 ppmC), O 2 (.4%), H 2 (.1%), and H 2 O (10%), the balance being N 2 , was fed to the catalyst powder at a total flow rate of 1,000 cc/min.
  • the reactor tube was heated to 500° C. at a temperature elevation rate of 10° C./min, and maintained at 500° C. for 10 minutes, for carrying out a preliminary treatment. Subsequently, the reactor tube was cooled, and heated again from 100° C. to 500° C. at 10° C./min.
  • the outlet gas composition was determined by means of a CO/NO analyzer (model: PG240, product of Horiba) and an HC analyzer (model: VMF-1000F, product of Shimadzu Corporation).
  • the degree of Pd dispersion was measured according to the CO pulse adsorption method (i.e., a known technique) (T. Takeguchi, S. Manabe, R. Kikuchi, K. Eguchi, T. Kanazawa, S. Matsumoto, Applied Catalysis A: 293 (2005) 91).
  • Table 1 shows the values of the temperature (T50) at which 50% removal of NO and HC was completed in the presence of each catalyst after aging, and the temperature (T70) at which 70% removal of CO was completed in the presence of the catalyst.
  • T50 temperature at which 50% removal of NO and HC was completed in the presence of each catalyst after aging
  • T70 temperature at which 70% removal of CO was completed in the presence of the catalyst.
  • the catalyst samples of the Examples exhibited more excellent low-temperature catalytic activity, as compared with those of the Comparative Examples.
  • CO removal performance was remarkably excellent.
  • Table 2 shows Pd dispersion degrees of the tested catalyst after aging. As is clear from Table 2, Pd dispersion degree of the catalysts of the Examples was higher than that of the Comparative Examples.
  • Table 3 shows electronegativity values of the carriers.
  • the electronegativity was a weighted average of the electronegativity (Pauling's electronegativity) of a metal or metals forming the corresponding metal oxide and that of oxygen, based on the compositional proportions of the elements contained in the metal oxide.
  • aluminum borate serves as an acidic carrier having an electronegativity higher than that of Al 2 O 3 .
  • an electron-accepting element such as an alkaline earth metal element or a rare earth metal element
  • electronegativity can be derived through the following calculation.
  • Electronegativity Material of carrier Comp. Ex. 1 Al 2 O 3 2.708 — 10A2B 2.737 Comp. Ex. 2 5 wt. % La 2 O 3 /10A2B 2.733 Comp. Ex. 3 (1 wt. % La 2 O 3 + 2 wt. % BaO)/10A2B 2.733 Ex. 1 (5 wt. % La 2 O 3 + 5 wt. % SrO)/10A2B 2.722 Ex. 2 (5 wt. % La 2 O 3 + 5 wt. % Pr 6 O 11 )/10A2B 2.731 Ex. 3 (5 wt. % La 2 O 3 + 5 wt. % CaO)/10A2B 2.714 Ex.

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CN116600893A (zh) * 2020-12-24 2023-08-15 三井金属矿业株式会社 复合氧化物及其制造方法

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US9687817B2 (en) * 2013-10-31 2017-06-27 Mitsui Mining & Smelting Co., Ltd. Carrier for exhaust gas purification catalyst, and exhaust gas purification catalyst
CN116600893A (zh) * 2020-12-24 2023-08-15 三井金属矿业株式会社 复合氧化物及其制造方法

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