JP6714470B2 - Exhaust gas purifying catalyst, manufacturing method thereof, and exhaust gas purifying catalytic converter - Google Patents
Exhaust gas purifying catalyst, manufacturing method thereof, and exhaust gas purifying catalytic converter Download PDFInfo
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- JP6714470B2 JP6714470B2 JP2016164574A JP2016164574A JP6714470B2 JP 6714470 B2 JP6714470 B2 JP 6714470B2 JP 2016164574 A JP2016164574 A JP 2016164574A JP 2016164574 A JP2016164574 A JP 2016164574A JP 6714470 B2 JP6714470 B2 JP 6714470B2
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- exhaust gas
- gas purifying
- catalyst
- purifying catalyst
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- 239000003054 catalyst Substances 0.000 title claims description 154
- 230000003197 catalytic effect Effects 0.000 title claims description 22
- 238000004519 manufacturing process Methods 0.000 title claims description 21
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 claims description 96
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims description 83
- 239000002245 particle Substances 0.000 claims description 70
- 239000010419 fine particle Substances 0.000 claims description 69
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 54
- 239000000463 material Substances 0.000 claims description 46
- 229910017771 LaFeO Inorganic materials 0.000 claims description 43
- 238000000746 purification Methods 0.000 claims description 39
- 239000007864 aqueous solution Substances 0.000 claims description 18
- 229910052742 iron Inorganic materials 0.000 claims description 18
- 229910052746 lanthanum Inorganic materials 0.000 claims description 18
- 229910052761 rare earth metal Inorganic materials 0.000 claims description 16
- 239000006104 solid solution Substances 0.000 claims description 10
- 150000002500 ions Chemical class 0.000 claims description 4
- 239000007789 gas Substances 0.000 description 92
- 239000002585 base Substances 0.000 description 31
- 239000000843 powder Substances 0.000 description 24
- 238000000034 method Methods 0.000 description 22
- 230000000052 comparative effect Effects 0.000 description 18
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical group [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 17
- 239000012298 atmosphere Substances 0.000 description 15
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 15
- 238000005259 measurement Methods 0.000 description 14
- 238000012360 testing method Methods 0.000 description 14
- -1 eurobium Chemical compound 0.000 description 12
- 238000010304 firing Methods 0.000 description 11
- 239000002131 composite material Substances 0.000 description 10
- 238000000921 elemental analysis Methods 0.000 description 9
- 238000004453 electron probe microanalysis Methods 0.000 description 8
- 229910000510 noble metal Inorganic materials 0.000 description 8
- 229910052684 Cerium Inorganic materials 0.000 description 7
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 description 7
- 230000006866 deterioration Effects 0.000 description 7
- GJKFIJKSBFYMQK-UHFFFAOYSA-N lanthanum(3+);trinitrate;hexahydrate Chemical compound O.O.O.O.O.O.[La+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O GJKFIJKSBFYMQK-UHFFFAOYSA-N 0.000 description 7
- 239000000203 mixture Substances 0.000 description 7
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 6
- 239000001301 oxygen Substances 0.000 description 6
- 229910052760 oxygen Inorganic materials 0.000 description 6
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 5
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 5
- 239000000446 fuel Substances 0.000 description 5
- QZRHHEURPZONJU-UHFFFAOYSA-N iron(2+) dinitrate nonahydrate Chemical compound O.O.O.O.O.O.O.O.O.[Fe+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O QZRHHEURPZONJU-UHFFFAOYSA-N 0.000 description 5
- 150000002910 rare earth metals Chemical class 0.000 description 5
- 150000003839 salts Chemical class 0.000 description 5
- 238000005245 sintering Methods 0.000 description 5
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 4
- 229910002651 NO3 Inorganic materials 0.000 description 4
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 4
- 150000004703 alkoxides Chemical class 0.000 description 4
- 229910002091 carbon monoxide Inorganic materials 0.000 description 4
- 239000010949 copper Substances 0.000 description 4
- 239000013078 crystal Substances 0.000 description 4
- 238000001035 drying Methods 0.000 description 4
- 229930195733 hydrocarbon Natural products 0.000 description 4
- 150000002430 hydrocarbons Chemical class 0.000 description 4
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 4
- 238000002156 mixing Methods 0.000 description 4
- 229910052726 zirconium Inorganic materials 0.000 description 4
- 206010021143 Hypoxia Diseases 0.000 description 3
- 229910052779 Neodymium Inorganic materials 0.000 description 3
- 229910052777 Praseodymium Inorganic materials 0.000 description 3
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 3
- 229910052783 alkali metal Inorganic materials 0.000 description 3
- 150000001340 alkali metals Chemical class 0.000 description 3
- 229910000287 alkaline earth metal oxide Inorganic materials 0.000 description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 238000002485 combustion reaction Methods 0.000 description 3
- 239000000470 constituent Substances 0.000 description 3
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- 238000011156 evaluation Methods 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 230000001590 oxidative effect Effects 0.000 description 3
- 239000011148 porous material Substances 0.000 description 3
- 238000000634 powder X-ray diffraction Methods 0.000 description 3
- PUDIUYLPXJFUGB-UHFFFAOYSA-N praseodymium atom Chemical compound [Pr] PUDIUYLPXJFUGB-UHFFFAOYSA-N 0.000 description 3
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- 239000010948 rhodium Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
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- 229910052727 yttrium Inorganic materials 0.000 description 3
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 description 3
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 2
- KRKNYBCHXYNGOX-UHFFFAOYSA-K Citrate Chemical compound [O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O KRKNYBCHXYNGOX-UHFFFAOYSA-K 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 229910052692 Dysprosium Inorganic materials 0.000 description 2
- 229910052691 Erbium Inorganic materials 0.000 description 2
- 229910052688 Gadolinium Inorganic materials 0.000 description 2
- 229910052689 Holmium Inorganic materials 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- 229910021193 La 2 O 3 Inorganic materials 0.000 description 2
- 229910052765 Lutetium Inorganic materials 0.000 description 2
- 229910017493 Nd 2 O 3 Inorganic materials 0.000 description 2
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 2
- 229910019142 PO4 Inorganic materials 0.000 description 2
- 229910052773 Promethium Inorganic materials 0.000 description 2
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 description 2
- 229910052772 Samarium Inorganic materials 0.000 description 2
- 229910052771 Terbium Inorganic materials 0.000 description 2
- 229910052775 Thulium Inorganic materials 0.000 description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 229910052769 Ytterbium Inorganic materials 0.000 description 2
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 2
- 230000033228 biological regulation Effects 0.000 description 2
- 238000001354 calcination Methods 0.000 description 2
- 238000006555 catalytic reaction Methods 0.000 description 2
- 238000000975 co-precipitation Methods 0.000 description 2
- 239000010941 cobalt Substances 0.000 description 2
- 229910017052 cobalt Inorganic materials 0.000 description 2
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 230000002950 deficient Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- KBQHZAAAGSGFKK-UHFFFAOYSA-N dysprosium atom Chemical compound [Dy] KBQHZAAAGSGFKK-UHFFFAOYSA-N 0.000 description 2
- UYAHIZSMUZPPFV-UHFFFAOYSA-N erbium Chemical compound [Er] UYAHIZSMUZPPFV-UHFFFAOYSA-N 0.000 description 2
- UIWYJDYFSGRHKR-UHFFFAOYSA-N gadolinium atom Chemical compound [Gd] UIWYJDYFSGRHKR-UHFFFAOYSA-N 0.000 description 2
- 239000010931 gold Substances 0.000 description 2
- 229910052735 hafnium Inorganic materials 0.000 description 2
- VBJZVLUMGGDVMO-UHFFFAOYSA-N hafnium atom Chemical compound [Hf] VBJZVLUMGGDVMO-UHFFFAOYSA-N 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- KJZYNXUDTRRSPN-UHFFFAOYSA-N holmium atom Chemical compound [Ho] KJZYNXUDTRRSPN-UHFFFAOYSA-N 0.000 description 2
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- 229910052741 iridium Inorganic materials 0.000 description 2
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 description 2
- 238000011068 loading method Methods 0.000 description 2
- OHSVLFRHMCKCQY-UHFFFAOYSA-N lutetium atom Chemical compound [Lu] OHSVLFRHMCKCQY-UHFFFAOYSA-N 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 239000012299 nitrogen atmosphere Substances 0.000 description 2
- 229910052762 osmium Inorganic materials 0.000 description 2
- SYQBFIAQOQZEGI-UHFFFAOYSA-N osmium atom Chemical compound [Os] SYQBFIAQOQZEGI-UHFFFAOYSA-N 0.000 description 2
- 229910052763 palladium Inorganic materials 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 2
- 239000010452 phosphate Substances 0.000 description 2
- 229910052697 platinum Inorganic materials 0.000 description 2
- VQMWBBYLQSCNPO-UHFFFAOYSA-N promethium atom Chemical compound [Pm] VQMWBBYLQSCNPO-UHFFFAOYSA-N 0.000 description 2
- 229910052703 rhodium Inorganic materials 0.000 description 2
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 2
- 229910052707 ruthenium Inorganic materials 0.000 description 2
- 239000012266 salt solution Substances 0.000 description 2
- KZUNJOHGWZRPMI-UHFFFAOYSA-N samarium atom Chemical compound [Sm] KZUNJOHGWZRPMI-UHFFFAOYSA-N 0.000 description 2
- 239000000523 sample Substances 0.000 description 2
- 229910052706 scandium Inorganic materials 0.000 description 2
- SIXSYDAISGFNSX-UHFFFAOYSA-N scandium atom Chemical compound [Sc] SIXSYDAISGFNSX-UHFFFAOYSA-N 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
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- 238000003860 storage Methods 0.000 description 2
- GZCRRIHWUXGPOV-UHFFFAOYSA-N terbium atom Chemical compound [Tb] GZCRRIHWUXGPOV-UHFFFAOYSA-N 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- 229910052723 transition metal Inorganic materials 0.000 description 2
- NAWDYIZEMPQZHO-UHFFFAOYSA-N ytterbium Chemical compound [Yb] NAWDYIZEMPQZHO-UHFFFAOYSA-N 0.000 description 2
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonium chloride Substances [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 1
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- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
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- 229910025794 LaB6 Inorganic materials 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
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- 235000011114 ammonium hydroxide Nutrition 0.000 description 1
- 229910052788 barium Inorganic materials 0.000 description 1
- XDFCIPNJCBUZJN-UHFFFAOYSA-N barium(2+) Chemical compound [Ba+2] XDFCIPNJCBUZJN-UHFFFAOYSA-N 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 229910052790 beryllium Inorganic materials 0.000 description 1
- ATBAMAFKBVZNFJ-UHFFFAOYSA-N beryllium atom Chemical compound [Be] ATBAMAFKBVZNFJ-UHFFFAOYSA-N 0.000 description 1
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- 230000007423 decrease Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- JSKIRARMQDRGJZ-UHFFFAOYSA-N dimagnesium dioxido-bis[(1-oxido-3-oxo-2,4,6,8,9-pentaoxa-1,3-disila-5,7-dialuminabicyclo[3.3.1]nonan-7-yl)oxy]silane Chemical compound [Mg++].[Mg++].[O-][Si]([O-])(O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2)O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2 JSKIRARMQDRGJZ-UHFFFAOYSA-N 0.000 description 1
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Description
本発明は、母材粒子上にＬａＦｅＯ３及び酸化鉄が共担持された排気ガス浄化用触媒、及びその製造方法、並びに排気ガス浄化用触媒コンバータに関する。 The present invention relates to an exhaust gas purifying catalyst in which LaFeO 3 and iron oxide are co-loaded on a base material particle, a method for producing the same, and an exhaust gas purifying catalytic converter.
自動車等の内燃機関から排出される炭化水素（ＨＣ）、一酸化炭素（ＣＯ）、及び窒素酸化物（ＮＯｘ）の浄化において、プラチナ、パラジウム、ロジウム、イリジウム、ルテニウム、オスミウム等の白金族元素（ＰＧＭ：Platinum Group Metal）を触媒活性成分として用いた三元触媒（ＴＷＣ：Three-Way Catalyst）が広く用いられている。しかしながら、ＰＧＭは比較的に高価であり、また中長期的な安定供給の確保に懸念がある。そのため、ＰＧＭを必須としない新たな触媒材料の開発が検討されている。 In purification of hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) emitted from internal combustion engines such as automobiles, platinum group elements such as platinum, palladium, rhodium, iridium, ruthenium, osmium ( A three-way catalyst (TWC) using PGM (Platinum Group Metal) as a catalytically active component is widely used. However, PGM is relatively expensive, and there is concern about securing a stable supply in the medium to long term. Therefore, development of a new catalyst material that does not require PGM is under study.
例えば、特許文献１（特開２００５−１２５３１７号公報）には、特定の細孔径及び細孔容積を有するセリア−ジルコニア固溶体を含む担体と、該担体に混合又は担持された活性種としての酸化鉄と、よりなることを特徴とする酸素貯蔵放出材が開示されている。 For example, in Patent Document 1 (JP 2005-125317 A), a carrier containing a ceria-zirconia solid solution having a specific pore size and pore volume, and iron oxide as an active species mixed or carried by the carrier. And an oxygen storage/release material comprising:
また、特許文献２（特開平１０−２１６５０９号公報）には、Ｙ固溶セリア−ジルコニアＣｅ0.6 Ｚｒ0.30 Ｙ0.10 Ｏ1.95のセリウム系複合酸化物と、このセリウム系複合酸化物に担持されたＦｅとを有する、酸素吸蔵性セリウム系複合酸化物が開示されている。 Further, in Patent Document 2 (JP-A-10-216509), a cerium-based composite oxide of Y solid solution ceria-zirconia Ce 0.6 Zr 0.30 Y 0.10 O 1.95 and Fe supported on the cerium-based composite oxide are disclosed. An oxygen-storing cerium-based composite oxide having and is disclosed.
一方、特許文献３（特開２０１０−０６９４５１号公報）には、ペロブスカイト型構造を有する酸化物焼成体からなる球状粒子であって、該粒子の平均粒子径が１０〜５０μｍの範囲、比表面積が１０ｍ２／ｇ〜４０ｍ２／ｇの範囲にあることを特徴とするペロブスカイト型酸化触媒が開示されている。 On the other hand, Patent Document 3 (Japanese Patent Laid-Open No. 2010-069451) discloses spherical particles made of an oxide calcined body having a perovskite structure, in which the average particle diameter of the particles is in the range of 10 to 50 μm and the specific surface area is perovskite oxide catalyst lies in the range of 10m 2 / g~40m 2 / g are disclosed.
さらに、ペロブスカイト型複合酸化物に、アルカリ土類金属酸化物やアルカリ金属を併用した排ガス浄化触媒が検討されている。
例えば、特許文献４（特開２０１０−１９４４８７号公報）には、欠陥ペロブスカイト型複合酸化物（ＢａＹ２−ｘＳｃｘＯ４又はＢａＹ２−ｘＩｎｘＯ４）とアルカリ土類金属酸化物（ＢａＯ）とを含み、粉末Ｘ線回折において、実質的に上記欠陥ペロブスカイト型複合酸化物の回折パターンのみが検出される、ＮＯｘ浄化触媒が開示されている。
Further, an exhaust gas purifying catalyst in which an alkaline earth metal oxide or an alkali metal is used in combination with a perovskite type complex oxide is being studied.
For example, in Patent Document 4 (JP 2010-194487A), a defective perovskite complex oxide (BaY 2−x Sc x O 4 or BaY 2−x In x O 4 ) and an alkaline earth metal oxide ( BaO), and a NOx purification catalyst in which only the diffraction pattern of the defective perovskite-type composite oxide is substantially detected in powder X-ray diffraction is disclosed.
近年、内燃機関の排気ガス浄化においては、世界的な排気ガス規制の強化にともない、触媒の浄化性能のさらなる向上が求められている。また、エンジン始動直後の所謂コールドスタート時の浄化性能を向上させるため、或いは寒冷地での使用時の浄化性能を向上させるため、排気ガス温度が高いエキゾーストマニホールド直下に触媒コンバータを配置する、直下型の触媒コンバータ等の採用が進展している。これにともない、排気ガス浄化触媒には、耐熱性のさらなる向上も求められてきている。 In recent years, in purification of exhaust gas from internal combustion engines, further improvement in catalyst purification performance has been demanded along with tightening of exhaust gas regulations worldwide. Also, in order to improve the purification performance at the time of so-called cold start immediately after the engine is started, or to improve the purification performance when used in cold regions, a catalyst converter is placed directly below the exhaust manifold with high exhaust gas temperature. The adoption of catalytic converters and the like is progressing. Along with this, exhaust gas purifying catalysts are required to have further improved heat resistance.
さらに、排気ガス規制や燃費向上に対応するための空燃比（Ａ／Ｆ）制御の高度化にともない、リーン環境（酸化性雰囲気）、ストイキ環境（理論空燃比）、及びリッチ環境（還元性雰囲気）の処理雰囲気の切り替えが精密に行われるようになってきている。ここで、特許文献１の触媒系では、リッチ環境において、酸化鉄（Ｆｅ２Ｏ３）から鉄（Ｆｅ）が還元生成され、これが高活性な活性種として機能している。しかしながら実際は、特許文献１の触媒系は、高温環境に曝されると担体上の粒子同士がシンタリングして粒成長して、触媒活性サイト（担体上の活性種の粒子）の数が著しく減少してしまい、高温曝露後に触媒性能が大きく劣化するという問題があった。すなわち、特許文献１の酸素貯蔵放出材は、合成直後の性能（初期性能）と高温曝露後の性能（ランニング性能）との乖離が大きく、また高温曝露後の触媒活性サイトの数が少ないという点で、改善の余地が大きく、高温環境下で使用する排気ガス浄化触媒として実用性に乏しかった。これらの問題は、特許文献２の触媒系においても、同様に当てはまる。 Furthermore, along with the sophistication of air-fuel ratio (A/F) control to cope with exhaust gas regulations and fuel efficiency improvement, lean environment (oxidizing atmosphere), stoichiometric environment (theoretical air-fuel ratio), and rich environment (reducing atmosphere) ) The process atmosphere is being changed more precisely. Here, in the catalyst system of Patent Document 1, iron (Fe) is reduced and produced from iron oxide (Fe 2 O 3 ) in a rich environment, and this functions as a highly active active species. However, in reality, in the catalyst system of Patent Document 1, when exposed to a high-temperature environment, particles on the carrier sinter and grow to each other, and the number of catalytically active sites (particles of active species on the carrier) is significantly reduced. However, there is a problem that the catalyst performance is greatly deteriorated after exposure to high temperature. That is, in the oxygen storage/release material of Patent Document 1, the difference between the performance immediately after synthesis (initial performance) and the performance after high temperature exposure (running performance) is large, and the number of catalytically active sites after high temperature exposure is small. However, there is a lot of room for improvement, and it was not practical as an exhaust gas purification catalyst used in a high temperature environment. These problems similarly apply to the catalyst system of Patent Document 2.
一方、ペロブスカイト型酸化触媒は、表面積が小さく、所望の活性が得られにくいという問題がある。これを解決するために、特許文献３の触媒系では、ＣａＭｎＯ３触媒を数十μｍオーダーに造粒し、所定の比表面積を確保することで、プロピレンの酸化触媒性能を高めている。しかしながら、特許文献３の触媒系は、依然として触媒活性サイトが十分ではなく、また、これを高温環境に曝される排気ガス浄化触媒として用いた場合、高温曝露後においてもその比表面積を維持することが難しく、高温環境下で使用する排気ガス浄化触媒として実用性に乏しかった。 On the other hand, the perovskite type oxidation catalyst has a problem that the surface area is small and it is difficult to obtain a desired activity. In order to solve this, in the catalyst system of Patent Document 3, the CaMnO 3 catalyst is granulated in the order of several tens of μm and a predetermined specific surface area is secured to improve the propylene oxidation catalyst performance. However, the catalyst system of Patent Document 3 still has insufficient catalytically active sites, and when it is used as an exhaust gas purifying catalyst exposed to a high temperature environment, it maintains its specific surface area even after high temperature exposure. However, it was not practical as an exhaust gas purifying catalyst used in a high temperature environment.
特許文献４の触媒系では、アルカリ土類金属酸化物やアルカリ金属を併用することで、触媒活性、特に低温活性を向上させているものの、これらは耐熱性が不十分であり、高温環境下で使用する排気ガス浄化触媒として実用性に乏しかった。 In the catalyst system of Patent Document 4, although the alkaline earth metal oxide or the alkali metal is used in combination to improve the catalytic activity, particularly the low temperature activity, these have insufficient heat resistance and therefore, in a high temperature environment. It was not practical as an exhaust gas purification catalyst to be used.
本発明は、上記課題に鑑みてなされたものである。すなわち本発明の目的は、優れた耐熱性を有するのみならず、高温曝露後にも優れた触媒性能を有する、排気ガス浄化用触媒、及びその製造方法、並びに排気ガス浄化用触媒コンバータ等を提供することにある。 The present invention has been made in view of the above problems. That is, an object of the present invention is to provide an exhaust gas purifying catalyst, which has not only excellent heat resistance but also excellent catalytic performance even after exposure to high temperatures, a method for producing the same, an exhaust gas purifying catalytic converter, and the like. Especially.
本発明者らは、上記課題を解決すべく鋭意検討した。その結果、所定の母材粒子上にＬａＦｅＯ３微粒子及び酸化鉄微粒子がそれぞれ高分散に付着した新規構造を採用することにより、上記課題を解決できることを見出し、本発明を完成するに至った。 The present inventors diligently studied to solve the above problems. As a result, they have found that the above-mentioned problems can be solved by adopting a novel structure in which LaFeO 3 fine particles and iron oxide fine particles are highly dispersed and adhered on predetermined base material particles, and have completed the present invention.
すなわち、本発明は、以下に示す種々の具体的態様を提供する。
（１）ジルコニア系酸化物を含有する母材粒子と、前記母材粒子の表面に共担持された、ＬａＦｅＯ３微粒子及び酸化鉄微粒子と、を少なくとも含有することを特徴とする、排気ガス浄化用触媒。
（２） Ｌａ及びＦｅの含有割合が、モル比で、下記式（１）：
０．６＜ Ｆｅ／Ｌａ ≦１．６ ・・・（１）
を満たす上記（１）に記載の排気ガス浄化用触媒。
That is, the present invention provides various specific embodiments shown below.
(1) For exhaust gas purification, containing at least base material particles containing a zirconia-based oxide, and LaFeO 3 fine particles and iron oxide fine particles co-loaded on the surfaces of the base material particles. catalyst.
(2) The content ratios of La and Fe are the following formula (1):
0.6<Fe/La≦1.6 (1)
The exhaust gas purifying catalyst according to (1), which satisfies the above condition.
（３）前記ＬａＦｅＯ３微粒子が、１〜５０ｎｍの平均結晶子径を有する上記（１）又は（２）に記載の排気ガス浄化用触媒。
（４）前記ジルコニア系酸化物が、希土類元素固溶ジルコニアである上記（１）〜（３）のいずれか一項に記載の排気ガス浄化用触媒。
（５）前記母材粒子が、３〜３０μｍの平均粒子径Ｄ５０を有する上記（１）〜（４）のいずれか一項に記載の排気ガス浄化用触媒。
（６）触媒担体と、前記触媒担体の少なくとも一部に保持された、上記（１）〜（５）のいずれか一項に記載の排気ガス浄化用触媒と、を少なくとも備えることを特徴とする、排気ガス浄化用触媒コンバータ。
(3) The exhaust gas purifying catalyst according to (1) or (2), wherein the LaFeO 3 fine particles have an average crystallite size of 1 to 50 nm.
(4) The exhaust gas purifying catalyst according to any one of (1) to (3), wherein the zirconia-based oxide is a rare earth element solid-solution zirconia.
(5) The exhaust gas purifying catalyst according to any one of (1) to (4), wherein the base material particles have an average particle diameter D 50 of 3 to 30 μm.
(6) A catalyst carrier, and at least the exhaust gas purifying catalyst according to any one of (1) to (5), which is held by at least a part of the catalyst carrier. , Catalytic converters for exhaust gas purification.
（７）ジルコニア系酸化物を含有する母材粒子の表面に、ＬａイオンとＦｅイオンとを少なくとも含有する水溶液を付与する工程、及び処理後の前記母材粒子を５００〜１４９０℃で熱処理して、前記母材粒子の表面にＬａＦｅＯ３微粒子及び酸化鉄微粒子を共担持させる工程と、を少なくとも有することを特徴とする、排気ガス浄化用触媒の製造方法。
（８） 前記水溶液中のＬａ及びＦｅの含有割合が、モル比で、下記式（１）：
０．６＜ Ｆｅ／Ｌａ ≦１．６ ・・・（１）
を満たす、上記（７）に記載の排気ガス浄化用触媒の製造方法。
(7) A step of applying an aqueous solution containing at least La ions and Fe ions to the surface of the base material particles containing the zirconia-based oxide, and heat treating the base material particles after the treatment at 500 to 1490°C. And a step of co-supporting LaFeO 3 fine particles and iron oxide fine particles on the surface of the base material particles, the method for producing an exhaust gas purifying catalyst.
(8) The content ratios of La and Fe in the aqueous solution are represented by the following formula (1):
0.6<Fe/La≦1.6 (1)
The method for producing an exhaust gas purifying catalyst according to (7), which satisfies the above condition.
（９）前記ＬａＦｅＯ３微粒子が、１〜５０ｎｍの平均結晶子径を有する上記（７）又は（８）に記載の排気ガス浄化用触媒の製造方法。
（１０）前記ジルコニア系酸化物が、希土類元素固溶ジルコニアである上記（７）〜（９）のいずれか一項に記載の排気ガス浄化用触媒の製造方法。
（１１）前記母材粒子が、３〜３０μｍの平均粒子径Ｄ５０を有する上記（７）〜（１０）のいずれか一項に記載の排気ガス浄化用触媒の製造方法。
(9) The method for producing an exhaust gas purifying catalyst according to (7) or (8), wherein the LaFeO 3 fine particles have an average crystallite size of 1 to 50 nm.
(10) The method for producing an exhaust gas purification catalyst according to any one of (7) to (9) above, wherein the zirconia-based oxide is a rare earth element solid-solution zirconia.
(11) The method for producing an exhaust gas purifying catalyst according to any one of (7) to (10), wherein the base material particles have an average particle diameter D 50 of 3 to 30 μm.
本発明によれば、優れた耐熱性を有し、高温曝露後にも優れた触媒性能を有する、排気ガス浄化用触媒、及びその製造方法、並びに排気ガス浄化用触媒コンバータ等を実現することができる。本発明の排気ガス浄化用触媒は、母材粒子上に数多くの微小な活性点（ＬａＦｅＯ３微粒子及び酸化鉄微粒子）が担持された複合構造の触媒粒子であり、その組成及び構造に基づいて、排ガス中のＮＯｘ、ＣＯ、ＨＣ等を削減する三元触媒（TWC：Tree Way Catalyst）として、特に好適に用いることができる。また、本発明の排気ガス浄化用触媒は、白金族元素（ＰＧＭ）や貴金属元素（ＰＭ）を必須成分として用いていないので、経済性にも優れる。しかも、耐熱性に劣る従来のゼオライト等を用いた触媒とは異なり、本発明の排気ガス浄化用触媒は、エンジン直下型触媒コンバータやタンデム配置の直下型触媒コンバータ等に搭載することができ、これにより、キャニングコストの削減などを図ることができる。 According to the present invention, it is possible to realize an exhaust gas purifying catalyst having excellent heat resistance and excellent catalytic performance even after exposure to high temperatures, a method for producing the same, an exhaust gas purifying catalytic converter, and the like. .. The exhaust gas purifying catalyst of the present invention is a catalyst particle having a composite structure in which many minute active sites (LaFeO 3 fine particles and iron oxide fine particles) are supported on the base material particles, and based on the composition and structure, It can be particularly suitably used as a three-way catalyst (TWC: Tree Way Catalyst) for reducing NOx, CO, HC, etc. in exhaust gas. Further, the exhaust gas purifying catalyst of the present invention does not use a platinum group element (PGM) or a noble metal element (PM) as an essential component, and therefore is excellent in economical efficiency. Moreover, unlike conventional catalysts using inferior heat resistance, such as zeolite, the exhaust gas purifying catalyst of the present invention can be mounted on an engine direct type catalytic converter or a tandem type direct type catalytic converter. As a result, the canning cost can be reduced.
以下、本発明の実施の形態について、図面を参照して詳細に説明する。なお、上下左右等の位置関係は、特に断らない限り、図面に示す位置関係に基づくものとする。また、図面の寸法比率は、図示の比率に限定されるものではない。但し、以下の実施の形態は、本発明を説明するための例示であり、本発明はこれらに限定されるものではない。なお、本明細書において、例えば「１〜１００」との数値範囲の表記は、その上限値「１」及び下限値「１００」の双方を包含するものとする。また、他の数値範囲の表記も同様である。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the positional relationship such as top, bottom, left, and right is based on the positional relationship shown in the drawings unless otherwise specified. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios. However, the following embodiments are examples for explaining the present invention, and the present invention is not limited to these. In the present specification, for example, the notation of a numerical range of "1 to 100" includes both the upper limit value "1" and the lower limit value "100". The same applies to other numerical ranges.
図１は、本発明の一実施形態の排気ガス浄化用触媒１００の概略構成を示す模式図である。この排気ガス浄化用触媒１００は、ジルコニア系酸化物を含有する母材粒子１１と、この母材粒子１１の表面１１ａに共担持されたＬａＦｅＯ３微粒子２１及び酸化鉄微粒子３１と、を少なくとも含有することを特徴とする。以下、各成分について詳述する。 FIG. 1 is a schematic diagram showing a schematic configuration of an exhaust gas purifying catalyst 100 according to an embodiment of the present invention. The exhaust gas purifying catalyst 100 contains at least base material particles 11 containing a zirconia-based oxide, and LaFeO 3 fine particles 21 and iron oxide fine particles 31 co-loaded on the surfaces 11a of the base material particles 11. It is characterized by Hereinafter, each component will be described in detail.
母材粒子１１に含有されるジルコニア系酸化物としては、ジルコニア、ジルコニアに他元素がドープされたジルコニア複合酸化物が挙げられる。ジルコニウムは、耐熱性に優れているため、高温環境下で使用する排気ガス浄化触媒の母材として適している。また、ジルコニウムは、６００℃以上の高温での酸素交換速度が速く、排気ガスの処理雰囲気の切り替えの応答性に優れている。そのため、ジルコニア系酸化物を母材粒子１１に用いることで、触媒反応に必要な酸素の吸放出が行われ、触媒反応が促進されて、高いＮＯｘ浄化性能が得られる。さらに、本触媒系においては、ジルコニア系酸化物を用いることで、アルミナに比して、共担持させるＬａ及びＦｅの固溶が抑制されるというメリットもある。なお、ジルコニア系酸化物は、鉱石中に通常１〜２質量％程度含まれているハフニウム（Ｈｆ）を不可避不純物として含有していても構わない。また、ハフニウムを除く不可避不純物の総量は、０．３質量％以下であることが好ましい。例えば、セリウムやジルコニウムの一部が、アルカリ金属元素やアルカリ土類金属元素等で置換されていてもよい。また、鉄（Ｆｅ）、コバルト（Ｃｏ）、ニッケル（Ｎｉ）、チタン（Ｔｉ）及び銅（Ｃｕ）等の遷移金属元素を含有していてもよい。 Examples of the zirconia-based oxide contained in the base material particles 11 include zirconia and zirconia composite oxide in which zirconia is doped with another element. Since zirconium has excellent heat resistance, it is suitable as a base material for an exhaust gas purification catalyst used in a high temperature environment. Further, zirconium has a fast oxygen exchange rate at a high temperature of 600° C. or higher, and is excellent in responsiveness of switching the exhaust gas processing atmosphere. Therefore, by using the zirconia-based oxide for the base material particles 11, oxygen required for the catalytic reaction is absorbed and released, the catalytic reaction is promoted, and high NOx purification performance is obtained. Furthermore, in the present catalyst system, the use of a zirconia-based oxide has an advantage that the solid solution of La and Fe to be co-supported is suppressed as compared with alumina. The zirconia-based oxide may contain hafnium (Hf), which is usually contained in the ore in an amount of about 1 to 2% by mass, as an unavoidable impurity. The total amount of unavoidable impurities other than hafnium is preferably 0.3% by mass or less. For example, part of cerium or zirconium may be replaced with an alkali metal element, an alkaline earth metal element, or the like. Moreover, you may contain transition metal elements, such as iron (Fe), cobalt (Co), nickel (Ni), titanium (Ti), and copper (Cu).
なかでも、ジルコニア系酸化物は、これらに希土類元素がさらに固溶したもの、すなわち希土類元素固溶ジルコニアが好ましい。希土類元素が固溶したジルコニア系酸化物を用いることで、格子酸素欠損（δ）の調整が容易となり、排ガス浄化性能が高められる傾向にある。また、共担持されるＬａＦｅＯ３微粒子２１及び酸化鉄微粒子３１の分散性が高められ、さらには高熱曝露時のシンタリングによる粒成長も抑制される傾向にある。希土類元素としては、イットリウム、セリウム、スカンジウム、ランタン、プラセオジム、ネオジム、プロメチウム、サマリウム、ユウロビウム、ガドリニウム、テルビウム、ジスプロシウム、ホルミウム、エルビウム、ツリウム、イッテルビウム、及びルテチウムが挙げられる。これらの中でも、結晶構造の安定性や耐熱性等の観点から、イットリウム（Ｙ）、セリウム（Ｃｅ）、Ｌａ（ランタン）、プラセオジム（Ｐｒ）及びネオジム（Ｎｄ）が好ましい。なお、これらの希土類金属Ｒは、１種を単独で、又は２種以上を適宜組み合わせて用いることができる。これらの希土類元素は、ジルコニア系酸化物の総量に対する、上記列挙した希土類元素の酸化物換算の総量（例えばＹ２Ｏ３、Ｎｄ２Ｏ３等の総和）で、５〜４５質量％が好ましく、より好ましくは１０〜４０質量％である。 Among them, the zirconia-based oxide is preferably a zirconia in which a rare earth element is further solid-solved therein, that is, a rare earth element-solid-solution zirconia. By using a zirconia-based oxide in which a rare earth element is solid-dissolved, it is easy to adjust the lattice oxygen deficiency (δ) and the exhaust gas purification performance tends to be improved. Further, the dispersibility of the LaFeO 3 fine particles 21 and the iron oxide fine particles 31 to be co-supported is enhanced, and further, grain growth due to sintering during high heat exposure tends to be suppressed. Examples of the rare earth element include yttrium, cerium, scandium, lanthanum, praseodymium, neodymium, promethium, samarium, eurobium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. Among these, yttrium (Y), cerium (Ce), La (lanthanum), praseodymium (Pr), and neodymium (Nd) are preferable from the viewpoint of stability of crystal structure, heat resistance, and the like. In addition, these rare earth metals R can be used individually by 1 type or in combination of 2 or more types. These rare earth elements are preferably 5 to 45% by mass in the total amount of the rare earth elements listed above in terms of oxides (for example, the total of Y 2 O 3 , Nd 2 O 3, etc.) with respect to the total amount of zirconia-based oxides. It is more preferably 10 to 40% by mass.
ジルコニア系酸化物の好ましい例としては、ペロブスカイト型酸化物／複合酸化物であって、Ｙ−Ｚｒ−Ｏｘ、Ｎｄ−Ｚｒ−Ｏｘ、Ｌａ−Ｚｒ−Ｏｘ、Ｐｒ−Ｚｒ−Ｏｘ、Ｙ−Ｎｄ−Ｚｒ−Ｏｘ、Ｙ−Ｌａ−Ｚｒ−Ｏｘ、Ｙ−Ｐｒ−Ｚｒ−Ｏｘ、Ｎｄ−Ｌａ−Ｚｒ−Ｏｘ、Ｎｄ−Ｐｒ−Ｚｒ−Ｏｘ、Ｌａ−Ｐｒ−Ｚｒ−Ｏｘ、Ｙ−Ｎｄ−Ｌａ−Ｚｒ−Ｏｘ、Ｙ−Ｎｄ−Ｐｒ−Ｚｒ−Ｏｘ、Ｙ−Ｌａ−Ｐｒ−Ｚｒ−Ｏｘ、Ｎｄ−Ｌａ−Ｐｒ−Ｚｒ−Ｏｘ、Ｙ−Ｚｒ−Ｃｅ−Ｏｘ、Ｎｄ−Ｚｒ−Ｃｅ−Ｏｘ、Ｌａ−Ｚｒ−Ｃｅ−Ｏｘ、Ｐｒ−Ｚｒ−Ｃｅ−Ｏｘ、Ｙ−Ｎｄ−Ｚｒ−Ｃｅ−Ｏｘ、Ｙ−Ｌａ−Ｚｒ−Ｃｅ−Ｏｘ、Ｙ−Ｐｒ−Ｚｒ−Ｃｅ−Ｏｘ、Ｎｄ−Ｌａ−Ｚｒ−Ｃｅ−Ｏｘ、Ｎｄ−Ｐｒ−Ｚｒ−Ｃｅ−Ｏｘ、Ｌａ−Ｐｒ−Ｚｒ−Ｃｅ−Ｏｘ、Ｙ−Ｎｄ−Ｌａ−Ｚｒ−Ｃｅ−Ｏｘ、Ｙ−Ｎｄ−Ｐｒ−Ｚｒ−Ｃｅ−Ｏｘ、Ｙ−Ｌａ−Ｐｒ−Ｚｒ−Ｃｅ−Ｏｘ、Ｎｄ−Ｌａ−Ｐｒ−Ｚｒ−Ｃｅ−Ｏｘ等の希土類元素固溶ジルコニアが挙げられるが、これらに特に限定されない。ジルコニア系酸化物は、１種を単独で、又は２種以上を適宜組み合わせて用いることができる。なお、これらの例示においては、それぞれの複合酸化物に含まれる構成元素の組み合わせに着目して表示したものであり、各構成元素の化学量論比を表示するものではない。すなわち、各構成元素の化学量論比は、任意に調整可能である。 A preferable example of the zirconia-based oxide is a perovskite-type oxide/complex oxide, which is Y-Zr-Ox, Nd-Zr-Ox, La-Zr-Ox, Pr-Zr-Ox, Y-Nd-. Zr-Ox, Y-La-Zr-Ox, Y-Pr-Zr-Ox, Nd-La-Zr-Ox, Nd-Pr-Zr-Ox, La-Pr-Zr-Ox, Y-Nd-La-. Zr-Ox, Y-Nd-Pr-Zr-Ox, Y-La-Pr-Zr-Ox, Nd-La-Pr-Zr-Ox, Y-Zr-Ce-Ox, Nd-Zr-Ce-Ox, La-Zr-Ce-Ox, Pr-Zr-Ce-Ox, Y-Nd-Zr-Ce-Ox, Y-La-Zr-Ce-Ox, Y-Pr-Zr-Ce-Ox, Nd-La-. Zr-Ce-Ox, Nd-Pr-Zr-Ce-Ox, La-Pr-Zr-Ce-Ox, Y-Nd-La-Zr-Ce-Ox, Y-Nd-Pr-Zr-Ce-Ox, Examples thereof include rare earth element solid solution zirconia such as Y-La-Pr-Zr-Ce-Ox and Nd-La-Pr-Zr-Ce-Ox, but are not particularly limited thereto. The zirconia-based oxides may be used alone or in appropriate combination of two or more. It should be noted that in these examples, the display is made by focusing on the combination of the constituent elements contained in each composite oxide, and the stoichiometric ratio of each constituent element is not displayed. That is, the stoichiometric ratio of each constituent element can be adjusted arbitrarily.
ここで、大きな比表面積を保持させてＬａＦｅＯ３及び酸化鉄の担持量を増大させるとともに、耐熱性を高めて自身の触媒活性サイトの数を増大させる等の観点から、母材粒子１１は３〜３０μｍの平均粒子径Ｄ５０を有することが好ましく、より好ましくは３〜１５μｍであり、さらに好ましくは４〜１０μｍである。なお、本明細書において、平均粒子径Ｄ５０は、レーザー回折式粒度分布測定装置（例えば、島津製作所社製、レーザ回折式粒度分布測定装置ＳＡＬＤ−７１００等）で測定されるメディアン径を意味する。 Here, from the viewpoint of maintaining a large specific surface area and increasing the carried amounts of LaFeO 3 and iron oxide, and also increasing the heat resistance and increasing the number of catalytically active sites of itself, the base material particles 11 have a particle size of 3 to 3. It preferably has an average particle diameter D 50 of 30 μm, more preferably 3 to 15 μm, still more preferably 4 to 10 μm. In the present specification, the average particle diameter D 50 means a median diameter measured by a laser diffraction type particle size distribution measuring device (for example, laser diffraction type particle size distribution measuring device SALD-7100 manufactured by Shimadzu Corporation). ..
母在粒子１１は、各種グレードの市販品を用いることができる。また、上述した各種組成のジルコニア系酸化物からなる母在粒子１１は、当業界で公知の方法で製造することもできる。ジルコニア系酸化物の製造方法は、特に限定されないが、共沈法やアルコキシド法が好ましい。 As the mother particles 11, various grades of commercial products can be used. Further, the mother particles 11 made of the zirconia-based oxide having various compositions described above can also be manufactured by a method known in the art. The method for producing the zirconia-based oxide is not particularly limited, but a coprecipitation method and an alkoxide method are preferable.
共沈法としては、例えば、ジルコニウム塩、及び必要に応じて配合する希土類金属元素を所定の化学量論比で混合した水溶液に、アルカリ物質を添加して加水分解させ或いは前駆体を共沈させ、その加水分解生成物或いは共沈物を焼成する製法が好ましい。ここで用いる各種塩の種類は、特に限定されない。一般的には、塩酸塩、オキシ塩酸塩、硝酸塩、オキシ硝酸塩、炭酸塩、リン酸塩、酢酸塩、シュウ酸塩、クエン酸塩等が好ましい。また、アルカリ性物質の種類も、特に限定されない。一般的には、アンモニア水溶液が好ましい。アルコキシド法としては、例えば、ジルコニウムアルコキシド、及び必要に応じて配合する希土類金属元素を所定の化学量論比で混合した混合物を加水分解し、その後に焼成する製法が好ましい。ここで用いるアルコキシドの種類は、特に限定されない。一般的には、メトキシド、エトキシド、プロポキシド、イソプロポキシド、ブトキシドや、これらのエチレンオキサイド付加物等が好ましい。また、希土類金属元素は、金属アルコキシドとして配合しても、上述した各種塩として配合してもよい。 As the coprecipitation method, for example, a zirconium salt and an aqueous solution in which a rare earth metal element to be blended if necessary is mixed at a predetermined stoichiometric ratio, an alkaline substance is added to cause hydrolysis or a precursor is coprecipitated. A preferred method is to calcine the hydrolysis product or coprecipitate. The type of various salts used here is not particularly limited. Generally, hydrochloride, oxyhydrochloride, nitrate, oxynitrate, carbonate, phosphate, acetate, oxalate, citrate and the like are preferable. Also, the type of alkaline substance is not particularly limited. Generally, an aqueous ammonia solution is preferred. As the alkoxide method, for example, a production method of hydrolyzing a mixture obtained by mixing zirconium alkoxide and a rare earth metal element to be blended if necessary at a predetermined stoichiometric ratio and then firing is preferable. The type of alkoxide used here is not particularly limited. Generally, methoxide, ethoxide, propoxide, isopropoxide, butoxide, ethylene oxide adducts thereof and the like are preferable. Further, the rare earth metal element may be blended as a metal alkoxide or may be blended as the above-mentioned various salts.
焼成条件は、常法にしたがえばよく、特に限定されない。焼成雰囲気は、酸化性雰囲気、還元性雰囲気、中性雰囲気のいずれの雰囲気でもよい。焼成温度及び処理時間は、所望するジルコニア系酸化物の組成及びその化学量論比によって変動するが、生産性等の観点からは、一般的には、１５０℃〜１３００℃で１〜１２時間が好ましく、より好ましくは３５０℃〜８００℃で２〜４時間である。なお、高温焼成に先立って、真空乾燥機等を用いて減圧乾燥を行い、約５０℃〜２００℃で約１〜４８時間程度の乾燥処理を行うことが好ましい。 The firing conditions are not particularly limited as long as they are in the usual manner. The firing atmosphere may be an oxidizing atmosphere, a reducing atmosphere, or a neutral atmosphere. The firing temperature and the treatment time vary depending on the desired composition of the zirconia-based oxide and the stoichiometric ratio thereof, but from the viewpoint of productivity and the like, generally, the temperature is 150°C to 1300°C for 1 to 12 hours. It is more preferably 350° C. to 800° C. for 2 to 4 hours. Prior to the high temperature firing, it is preferable to perform vacuum drying using a vacuum dryer or the like, and to perform a drying treatment at about 50° C. to 200° C. for about 1 to 48 hours.
この排気ガス浄化用触媒１００においては、上述した母材粒子１１の表面１１ａに、ＬａＦｅＯ３微粒子２１及び酸化鉄微粒子３１が共担持されているという複合構造を有する点に、１つの特徴を有する。すなわち、排気ガス浄化用触媒１００は、ＬａＦｅＯ３微粒子２１及び酸化鉄微粒子３１が母材粒子１１の表面１１ａにそれぞれ高分散に付着した複合構造を有する。このような複合構造を採用することにより、この排気ガス浄化用触媒１００においては、高温曝露後の触媒性能の劣化が大幅に抑制されている。その理由は定かではないが、母材粒子１１の表面１１ａに存在するＬａＦｅＯ３微粒子２１が、母材粒子１１の表面１１ａにおいて酸化鉄微粒子３１同士の接触機会を減じさせ、これにより、高温曝露による酸化鉄微粒子３１のシンタリング及び粒成長が阻害されているためと推察される。 The exhaust gas purifying catalyst 100 has one feature in that it has a composite structure in which the LaFeO 3 fine particles 21 and the iron oxide fine particles 31 are co-supported on the surface 11a of the base material particles 11 described above. That is, the exhaust gas purifying catalyst 100 has a composite structure in which the LaFeO 3 fine particles 21 and the iron oxide fine particles 31 are highly dispersed and adhered to the surfaces 11 a of the base material particles 11. By adopting such a composite structure, in the exhaust gas purifying catalyst 100, deterioration of the catalyst performance after exposure to high temperatures is significantly suppressed. Although the reason is not clear, the LaFeO 3 fine particles 21 present on the surface 11a of the base material particle 11 reduce the chances of contact between the iron oxide fine particles 31 on the surface 11a of the base material particle 11, and thereby the high temperature exposure It is presumed that the sintering and grain growth of the iron oxide fine particles 31 are inhibited.
また、ＬａＦｅＯ３は、ペロブスカイト型酸化物であって、自身の格子酸素欠損に基づいてＮＯｘ等の排ガスを浄化する触媒活性を呈する。このＬａＦｅＯ３による触媒作用は、格子酸素欠損の量に応じて増減するものの、リーン環境〜ストイキ環境〜リッチ環境の全域にわたって触媒活性を呈する。一方、酸化鉄は、外部環境に応じて種々の酸化状態（例えば、Ｆｅ２Ｏ３、Ｆｅ３Ｏ４、ＦｅＯ）を採る。とりわけ、還元状態では高活性な活性種であるＦｅ（単体）の状態で存在し、それ故にストイキ環境〜リッチ環境において特に強い触媒活性を呈することとなる。そのため、ＬａＦｅＯ３を酸化鉄と併用することで、リーン環境〜ストイキ環境〜リッチ環境の全域にわたって排ガス浄化の触媒作用が補強され、白金族元素（ＰＧＭ）を必須成分として用いていない場合であっても、優れた排ガス浄化性能が示される。 Further, LaFeO 3 is a perovskite type oxide, and exhibits catalytic activity for purifying exhaust gas such as NOx based on its lattice oxygen deficiency. The catalytic action of LaFeO 3 increases or decreases according to the amount of lattice oxygen deficiency, but exhibits catalytic activity over the entire lean environment, stoichiometric environment, and rich environment. On the other hand, iron oxide takes various oxidation states (for example, Fe 2 O 3 , Fe 3 O 4 , and FeO) depending on the external environment. In particular, it exists in the state of Fe (single substance) which is a highly active active species in the reduced state, and therefore exhibits particularly strong catalytic activity in the stoichiometric environment to the rich environment. Therefore, when LaFeO 3 is used in combination with iron oxide, the catalytic action of exhaust gas purification is reinforced over the entire range from the lean environment to the stoichiometric environment to the rich environment, and the platinum group element (PGM) is not used as an essential component. Also shows excellent exhaust gas purification performance.
そして、触媒活性をより高めるとともに酸化鉄微粒子３１のシンタリング及び粒成長を阻害する観点から、ＬａＦｅＯ３微粒子２１は、１〜５０ｎｍの平均結晶子径を有することが好ましく、より好ましくは３〜４０ｎｍである。また、同様の理由から、酸化鉄微粒子３１は、１〜５０ｎｍの平均結晶子径を有することが好ましく、より好ましくは３〜４０ｎｍである。このような微細なＬａＦｅＯ３微粒子２１及び酸化鉄微粒子３１を母材粒子１１の表面１１ａに存在させることで、表面積を高く維持し触媒活性サイトを多く維持することができる。 From the viewpoint of further enhancing the catalytic activity and inhibiting the sintering and grain growth of the iron oxide fine particles 31, the LaFeO 3 fine particles 21 preferably have an average crystallite diameter of 1 to 50 nm, more preferably 3 to 40 nm. Is. For the same reason, the iron oxide fine particles 31 preferably have an average crystallite size of 1 to 50 nm, more preferably 3 to 40 nm. By allowing such fine LaFeO 3 fine particles 21 and iron oxide fine particles 31 to exist on the surface 11a of the base material particle 11, it is possible to maintain a high surface area and a large number of catalytically active sites.
なお、結晶子とは、一般に単結晶とみなせる最大の集まりのことをいい、その結晶子の大きさのことを結晶子径という。また、本明細書において、平均結晶子径は、Ｘ線回折装置を用いて回折パターンを測定し、その測定結果に基づいて下記式（２）で表されるScherrerの式より算出した値を意味する。
結晶子径 Ｄ（Å）＝Ｋ・λ／（β・ｃｏｓθ） ・・・（２）
式（２）中、ＫはScherrer定数であり、ここではＫ＝０．９とする。また、λは使用したＸ線管球の波長、βは半値幅、θは回折角（ｒａｄ）である。
Note that the crystallite generally refers to the largest collection that can be regarded as a single crystal, and the size of the crystallite is referred to as the crystallite diameter. In addition, in the present specification, the average crystallite size means a value calculated from a Scherrer's formula represented by the following formula (2) based on the measurement result of a diffraction pattern measured using an X-ray diffractometer. To do.
Crystallite diameter D(Å)=K・λ/(β・cosθ) (2)
In Expression (2), K is a Scherrer constant, and here K=0.9. Further, λ is the wavelength of the X-ray tube used, β is the half width, and θ is the diffraction angle (rad).
ここで、ＬａＦｅＯ３微粒子２１及び酸化鉄微粒子３１の存在割合（含有割合）は、触媒活性をより高めるとともに酸化鉄微粒子３１のシンタリング及び粒成長を阻害して高温曝露後の触媒性能の劣化を抑制する観点から、Ｌａ及びＦｅのモル比換算で、０．６＜ Ｆｅ／Ｌａ ≦１．６の範囲内にあることが好ましい。 Here, the abundance ratio (content ratio) of the LaFeO 3 fine particles 21 and the iron oxide fine particles 31 further enhances the catalytic activity and inhibits the sintering and particle growth of the iron oxide fine particles 31 to deteriorate the catalytic performance after the high temperature exposure. From the viewpoint of suppression, the molar ratio of La and Fe is preferably in the range of 0.6<Fe/La≦1.6.
酸化鉄微粒子３１の含有量は、特に限定されないが、触媒性能及び低温活性を向上させる等の観点から、排気ガス浄化用触媒１００の総量に対して、Ｆｅ２Ｏ３換算で０．０５〜１０質量％が好ましく、より好ましくは０．１〜５質量％である。 The content of the iron oxide fine particles 31 is not particularly limited, but is 0.05 to 10 in terms of Fe 2 O 3 based on the total amount of the exhaust gas purifying catalyst 100 from the viewpoint of improving catalyst performance and low temperature activity. Mass% is preferable, and 0.1 to 5 mass% is more preferable.
また、ＬａＦｅＯ３微粒子２１の含有量は、特に限定されないが、リーン環境〜ストイキ環境〜リッチ環境の全域にわたる触媒性能を向上させる等の観点から、排気ガス浄化用触媒１００の総量に対して、０．０５〜１０質量％が好ましく、より好ましくは０．１〜５質量％である。 Further, the content of the LaFeO 3 fine particles 21 is not particularly limited, but from the viewpoint of improving the catalyst performance over the entire range from the lean environment to the stoichiometric environment to the rich environment, it is 0 with respect to the total amount of the exhaust gas purifying catalyst 100. 0.05 to 10 mass% is preferable, and 0.1 to 5 mass% is more preferable.
なお、排気ガス浄化用触媒１００は、金（Ａｕ）、銀（Ａｇ）、プラチナ（Ｐｔ）、パラジウム（Ｐｄ）、ロジウム（Ｒｈ）、イリジウム（Ｉｒ）、ルテニウム（Ｒｕ）、オスミウム（Ｏｓ）等の貴金属元素（ＰＭ）や白金族元素（ＰＧＭ）を必須成分として用いなくとも、優れた耐熱性を有し、高温曝露後にも優れた触媒性能を有する。したがって、経済性及び安定供給等の観点から、排気ガス浄化用触媒１００は、貴金属元素（ＰＭ）及び白金族元素（ＰＧＭ）を実質的に含有しないことが好ましい。ここで、実質的に含有しないとは、貴金属元素（ＰＭ）及び白金族元素（ＰＧＭ）の総量が、排気ガス浄化用触媒１００の全量に対して、０〜１．０質量％の範囲内にあることを意味し、より好ましくは０〜０．５質量％、さらに好ましくは０〜０．３質量％である。ここで排気ガス浄化用触媒１００が貴金属元素（ＰＭ）や白金族元素（ＰＧＭ）を含有する場合は、これらは母材粒子１１、ＬａＦｅＯ３微粒子２１及び／又は酸化鉄微粒子３１の表面に担持されていればよい。 The exhaust gas purifying catalyst 100 includes gold (Au), silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru), osmium (Os), etc. Even if the precious metal element (PM) or platinum group element (PGM) is not used as an essential component, it has excellent heat resistance and excellent catalytic performance even after exposure to high temperature. Therefore, it is preferable that the exhaust gas purifying catalyst 100 does not substantially contain the noble metal element (PM) and the platinum group element (PGM) from the viewpoints of economy and stable supply. Here, “not substantially contain” means that the total amount of the noble metal element (PM) and the platinum group element (PGM) is within a range of 0 to 1.0 mass% with respect to the total amount of the exhaust gas purifying catalyst 100. It means that it is present, more preferably 0 to 0.5% by mass, and further preferably 0 to 0.3% by mass. Here, when the exhaust gas purifying catalyst 100 contains a noble metal element (PM) or a platinum group element (PGM), these are supported on the surfaces of the base material particles 11, the LaFeO 3 fine particles 21, and/or the iron oxide fine particles 31. It should be.
排気ガス浄化用触媒１００の形状は、特に限定されない。母材粒子１１上にＬａＦｅＯ３微粒子２１及び酸化鉄微粒子３１が共担持された触媒粒子の集合体である触媒粉末のまま用いることができる。また、例えば、触媒粉末を任意の形状に成形して、粒状やペレット状の成形触媒とすることができる。また、この排気ガス浄化用触媒１００を触媒担体に担持させることもできる。ここで用いる触媒担体としては、当業界で公知のものを適宜選択することができる。代表的には、コージェライト製等のセラミックモノリス担体、ステンレス製等のメタルハニカム担体、ステンレス製等のワイヤメッシュ担体等が挙げられるが、これらに特に限定されない。なお、これらは、１種を単独で、又は２種以上を適宜組み合わせて用いることができる。 The shape of the exhaust gas purifying catalyst 100 is not particularly limited. The catalyst powder, which is an aggregate of catalyst particles in which LaFeO 3 fine particles 21 and iron oxide fine particles 31 are co-supported on the base material particles 11, can be used as it is. Further, for example, the catalyst powder can be molded into an arbitrary shape to form a granular or pelletized molded catalyst. Further, the exhaust gas purifying catalyst 100 can be supported on a catalyst carrier. As the catalyst carrier used here, those known in the art can be appropriately selected. Typical examples include, but are not limited to, a ceramic monolith carrier made of cordierite, a metal honeycomb carrier made of stainless steel, a wire mesh carrier made of stainless steel, and the like. In addition, these can be used individually by 1 type or in combination of 2 or more types.
上述した排気ガス浄化用触媒１００は、例えば内燃機関の排気ガス浄化用触媒、とりわけ自動車の排ガス浄化用触媒として有用である。 The above-described exhaust gas purifying catalyst 100 is useful, for example, as an exhaust gas purifying catalyst for an internal combustion engine, especially as an automobile exhaust gas purifying catalyst.
排気ガス浄化用触媒１００の製造方法は、上述したとおり母材粒子１１上にＬａＦｅＯ３微粒子２１及び酸化鉄微粒子３１が共担持された構成のものが得られる限り、特に限定されない。排気ガス浄化用触媒１００を再現性よく簡易且つ低コストで製造する観点からは、蒸発乾固法（含浸法）等が好ましい。 The method for manufacturing the exhaust gas purifying catalyst 100 is not particularly limited as long as a structure in which the LaFeO 3 fine particles 21 and the iron oxide fine particles 31 are co-supported on the base material particles 11 is obtained as described above. From the viewpoint of manufacturing the exhaust gas purifying catalyst 100 with good reproducibility, simply and at low cost, the evaporation dryness method (impregnation method) or the like is preferable.
蒸発乾固法としては、上述した母材粒子１１に、ランタンイオン及び鉄イオンを少なくとも含有する水溶液を含浸させ、その後に焼成する製法が好ましい。この含浸処理により、ランタンイオン及び鉄イオンが、母材粒子１１の表面１１ａにそれぞれ高分散状態で吸着（付着）される。ここで、ランタンイオン及び鉄イオンは、ランタン及び鉄の各種塩として水溶液に配合することができる。ここで用いる各種塩の種類は、特に限定されない。一般的には、塩酸塩、オキシ塩酸塩、硝酸塩、オキシ硝酸塩、炭酸塩、リン酸塩、酢酸塩、シュウ酸塩、クエン酸塩等が好ましい。 As the evaporation-drying method, a manufacturing method in which the above-described base material particles 11 are impregnated with an aqueous solution containing at least lanthanum ions and iron ions and then baked is preferable. By this impregnation treatment, lanthanum ions and iron ions are adsorbed (adhered) on the surface 11a of the base material particle 11 in a highly dispersed state. Here, the lanthanum ion and the iron ion can be mixed in the aqueous solution as various salts of lanthanum and iron. The type of various salts used here is not particularly limited. Generally, hydrochloride, oxyhydrochloride, nitrate, oxynitrate, carbonate, phosphate, acetate, oxalate, citrate and the like are preferable.
焼成条件は、常法にしたがえばよく、特に限定されない。焼成雰囲気は、酸化性雰囲気、大気雰囲気が好ましい。焼成温度及び処理時間は、所望するジルコニア系酸化物の組成及びその化学量論比によって変動するが、ＬａＦｅＯ３の生成及び生産性等の観点からは、一般的には、５００〜１４９０℃で０．１〜１２時間が好ましく、より好ましくは５５０℃〜８００℃で０．５〜６時間である。なお、高温焼成に先立って、真空乾燥機等を用いて減圧乾燥を行い、約５０℃〜２００℃で約１〜４８時間程度の乾燥処理を行ってもよい。この焼成処理により、ナノオーダーサイズに高分散したＬａＦｅＯ３微粒子及び酸化鉄微粒子が、母材粒子１１の表面１１ａ上で生成（合成）される。 The firing conditions are not particularly limited as long as they are in the usual manner. The firing atmosphere is preferably an oxidizing atmosphere or an air atmosphere. The calcination temperature and the treatment time vary depending on the desired composition of the zirconia-based oxide and the stoichiometric ratio thereof, but from the viewpoint of LaFeO 3 production and productivity, it is generally 0 to 500 to 1490° C. 1 to 12 hours are preferable, and more preferably 550 to 800° C. and 0.5 to 6 hours. In addition, prior to the high temperature firing, vacuum drying may be performed using a vacuum dryer or the like to perform a drying treatment at about 50° C. to 200° C. for about 1 to 48 hours. By this firing treatment, highly dispersed LaFeO 3 fine particles and iron oxide fine particles having a nano-order size are generated (synthesized) on the surface 11 a of the base material particle 11.
前記水溶液中のＬａ及びＦｅの含有割合は、得られる排気ガス浄化用触媒１００においてＬａＦｅＯ３微粒子及び酸化鉄微粒子が所望の含有割合となるように調整すればよい。高温曝露による触媒性能の劣化を抑制する観点から、前記水溶液中のＬａ及びＦｅの含有割合は、モル比で、下記式（１）を満たすことが好ましい。
０．６＜ Ｆｅ／Ｌａ ≦１．６ ・・・（１）
The content ratios of La and Fe in the aqueous solution may be adjusted so that the LaFeO 3 fine particles and the iron oxide fine particles have a desired content ratio in the obtained exhaust gas purifying catalyst 100. From the viewpoint of suppressing deterioration of catalyst performance due to high temperature exposure, the content ratios of La and Fe in the aqueous solution preferably satisfy the following formula (1) in terms of molar ratio.
0.6<Fe/La≦1.6 (1)
なお、前記水溶液は、イットリウム、セリウム、スカンジウム、ランタン、プラセオジム、ネオジム、プロメチウム、サマリウム、ユウロビウム、ガドリニウム、テルビウム、ジスプロシウム、ホルミウム、エルビウム、ツリウム、イッテルビウム、及びルテチウム等の希土類元素、リチウム、ナトリウム、カリウム等のアルカリ金属元素、ベリリウム、マグネシウム、カルシウム、ストロンチウム、バリウム等のアルカリ土類金属元素、コバルト、ニッケル、チタン、銅等の遷移金属元素を含有していてもよい。なお、これらは、１種を単独で、又は２種以上を適宜組み合わせて用いることができる。 The aqueous solution is a rare earth element such as yttrium, cerium, scandium, lanthanum, praseodymium, neodymium, promethium, samarium, eurobium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium, lithium, sodium, potassium. And the like, alkaline earth metal elements such as beryllium, magnesium, calcium, strontium, and barium, and transition metal elements such as cobalt, nickel, titanium, and copper. In addition, these can be used individually by 1 type or in combination of 2 or more types.
ここで、上記のようにして得られる排気ガス浄化用触媒１００に、必要に応じて、貴金属元素や白金族元素をさらに担持させてもよい。貴金属元素や白金族元素の担持方法は、公知の手法を適用でき、特に限定されない。例えば、貴金属元素や白金族元素を含む塩の溶液を調製し、排気ガス浄化用触媒１００にこの含塩溶液を含浸させ、その後に焼成することにより、貴金属元素や白金族元素の担持を行うことができる。含塩溶液としては、特に限定されないが、硝酸塩水溶液、ジニトロジアンミン硝酸塩溶液、塩化物水溶液等が好ましい。また、焼成処理も、特に限定されないが、３５０℃〜１０００℃で約１〜１２時間が好ましい。なお、高温焼成に先立って、真空乾燥機等を用いて減圧乾燥を行い、約５０℃〜２００℃で約１〜４８時間程度の乾燥処理を行うことが好ましい。 Here, the exhaust gas-purifying catalyst 100 obtained as described above may be further loaded with a noble metal element or a platinum group element, if necessary. A known method can be applied to the method for supporting the noble metal element or the platinum group element, and is not particularly limited. For example, a salt solution containing a noble metal element or a platinum group element is prepared, the exhaust gas purifying catalyst 100 is impregnated with the salt solution, and then baked to carry the noble metal element or the platinum group element. You can The salt-containing solution is not particularly limited, but a nitrate aqueous solution, a dinitrodiammine nitrate solution, a chloride aqueous solution and the like are preferable. Further, the calcination treatment is not particularly limited, but is preferably about 350°C to 1000°C for about 1 to 12 hours. Prior to the high temperature firing, it is preferable to perform vacuum drying using a vacuum dryer or the like, and to perform a drying treatment at about 50° C. to 200° C. for about 1 to 48 hours.
かくして得られる排気ガス浄化用触媒１００は、触媒粒子の集合体である触媒粉末のまま用いることができるが、触媒粉末を任意の形状に成形して粒状やペレット状の成形触媒としたり、触媒担体に保持させることでモノリス担体とすることができる。なお、成形触媒の作製時には、各種公知の分散装置、混練装置、成形装置を用いることができる。また、触媒担体に排気ガス浄化用触媒１００を保持させる際には、各種公知のコーティング法、ウォッシュコート法、ゾーンコート法を適用することができる。 The exhaust gas-purifying catalyst 100 thus obtained can be used as it is as a catalyst powder, which is an aggregate of catalyst particles. However, the catalyst powder is molded into an arbitrary shape to form a granular or pelletized molded catalyst, or a catalyst carrier. It can be used as a monolithic carrier by holding it on. Note that various known dispersing devices, kneading devices, and molding devices can be used when manufacturing the molded catalyst. Further, when the exhaust gas purifying catalyst 100 is held on the catalyst carrier, various known coating methods, wash coating methods, and zone coating methods can be applied.
以下に試験例、実施例と比較例を挙げて本発明の特徴をさらに具体的に説明するが、本発明は、これらによりなんら限定されるものではない。すなわち、以下の実施例に示す材料、使用量、割合、処理内容、処理手順等は、本発明の趣旨を逸脱しない限り、適宜変更することができる。 The features of the present invention will be described more specifically below with reference to Test Examples, Examples and Comparative Examples, but the present invention is not limited to these. That is, the materials, usage amounts, ratios, processing contents, processing procedures, and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention.
（試験例１）
母材粒子として、ジルコニア系酸化物（Ｙ−ＺｒＯ２と記載，Ｙ２Ｏ３：３５質量％、ＺｒＯ２：６５質量％：Ｄ５０＝６．４μｍ：ＢＥＴ比表面積：７２ｍ２／ｇ）を用いた。なお、本明細書において、ＢＥＴ比表面積は、比表面積／細孔分布測定装置（商品名：BELSORP-mini II、マイクロトラック・ベル株式会社製）及び解析用ソフトウェア（商品名：BEL_Master、マイクロトラック・ベル株式会社製）を用い、ＢＥＴ一点法により求めた値を意味する。硝酸鉄９水和物（Ｆｅ２Ｏ３換算で４０質量％含有）１．２５質量部を、水３．２５質量部に溶解して、Ｆｅ含有水溶液を調製した。上記ジルコニア系酸化物に鉄含有水溶液を含浸させ、６００℃で３０ｍｉｎ焼成することにより、試験例１の排気ガス浄化用触媒として、酸化鉄を担持したＹ−ＺｒＯ２パウダー触媒１０質量部（Ｆｅ２Ｏ３換算担持量：０．５質量部）を得た。
(Test Example 1)
As the base material particles, zirconia oxide (Y-ZrO 2 with the description, Y 2 O 3: 35 wt%, ZrO 2: 65 wt%: D 50 = 6.4μm: BET specific surface area: 72m 2 / g) to Using. In the present specification, the BET specific surface area means a specific surface area/pore distribution measuring device (trade name: BELSORP-mini II, manufactured by Microtrac Bell Co., Ltd.) and analysis software (trade name: BEL_Master, Microtrac. Bell Co., Ltd.) and the value obtained by the BET one-point method. 1.25 parts by mass of iron nitrate nonahydrate (containing 40% by mass in terms of Fe 2 O 3 ) was dissolved in 3.25 parts by mass of water to prepare an Fe-containing aqueous solution. By impregnating the zirconia-based oxide with an iron-containing aqueous solution and firing at 600° C. for 30 minutes, as an exhaust gas purifying catalyst of Test Example 1, 10 parts by mass of Fe-loaded Y-ZrO 2 powder catalyst (Fe 2 O 3 equivalent supported amount: 0.5 parts by mass) was obtained.
＜パウダー粒子のＮＯ浄化率のラボ測定＞
得られた試験例１のパウダー触媒を用いて、フューエルカット（Ｆ／Ｃ）制御からの復帰時の、ストイキ空燃比におけるＮＯ浄化率の測定を行った。このＮＯ浄化率の測定は、ガス分析計（商品名：ＢＥＬ Ｍａｓｓ、マイクロトラック・ベル株式会社製）を用い、測定温度７００℃、触媒量５０ｍｇの条件で測定した。また、Ｆ／Ｃ制御及びモデルガス組成は、図２に示すとおりである。
なお、ＮＯ浄化率は、下記式（３）に基づいて算出した。
ＮＯ浄化率（％）＝１００−（ＮＯ−ＭＡＳＳピーク強度（測定時）／ＮＯ−ＭＡＳＳピーク強度（Ｂｌａｎｋ））×１００ ・・・（３）
<Lab measurement of NO purification rate of powder particles>
Using the obtained powder catalyst of Test Example 1, the NO purification rate at the stoichiometric air-fuel ratio at the time of returning from the fuel cut (F/C) control was measured. The NO purification rate was measured using a gas analyzer (trade name: BEL Mass, manufactured by Microtrac Bell Co., Ltd.) under the conditions of a measurement temperature of 700° C. and a catalyst amount of 50 mg. The F/C control and model gas composition are as shown in FIG.
The NO purification rate was calculated based on the following equation (3).
NO purification rate (%)=100−(NO-MASS peak intensity (during measurement)/NO-MASS peak intensity (Blank))×100 (3)
（試験例２）
母材粒子として、ジルコニア系酸化物（Ｎｄ−ＺｒＯ２と記載，Ｎｄ２Ｏ３：１５質量％、ＺｒＯ２：８５質量％、Ｄ５０＝５．７μｍ、ＢＥＴ比表面積：６３ｍ２／ｇを用いること以外は、試験例１と同様に行い、試験例２の排気ガス浄化用触媒として、酸化鉄を担持したＮｄ−ＺｒＯ２パウダー触媒１０質量部（Ｆｅ２Ｏ３換算担持量：０．５質量部）を得た。
(Test Example 2)
As the base material particles, zirconia oxide (Nd-ZrO 2 with the description, Nd 2 O 3: 15 wt%, ZrO 2: 85 wt%, D 50 = 5.7μm, BET specific surface area: using 63m 2 / g Other than the above, the same procedure as in Test Example 1 was performed, and as an exhaust gas purifying catalyst in Test Example 2, 10 parts by mass of iron oxide-supported Nd-ZrO 2 powder catalyst (Fe 2 O 3 conversion supported amount: 0.5 mass). Part).
（比較試験例１）
母材粒子として、アルミナ（Ａｌ２Ｏ３、Ｄ５０＝２８μｍ、ＢＥＴ比表面積：１４１ｍ２／ｇ）を用いること以外は、試験例１と同様に行い、比較試験例１の排気ガス浄化用触媒として、酸化鉄を担持したＡｌ２Ｏ３パウダー触媒１０質量部（Ｆｅ２Ｏ３換算担持量：０．５質量部）を得た。
(Comparative Test Example 1)
Exhaust gas purifying catalyst of Comparative Test Example 1 was performed in the same manner as in Test Example 1 except that alumina (Al 2 O 3 , D 50 =28 μm, BET specific surface area: 141 m 2 /g) was used as the base material particles. As a result, 10 parts by mass of Al 2 O 3 powder catalyst supporting iron oxide (Fe 2 O 3 conversion supported amount: 0.5 parts by mass) was obtained.
評価結果を、図３に示す。図３から明らかなように、試験例１〜２は、比較試験例１に比して、ＮＯ浄化率が有意に優れていることが確認された。これらの結果から、活性種を担持させる母材粒子として、アルミナよりもジルコニア系酸化物が優れていることが示された。 The evaluation result is shown in FIG. As is clear from FIG. 3, it was confirmed that Test Examples 1 and 2 were significantly superior in NO purification rate to Comparative Test Example 1. From these results, it was shown that zirconia-based oxide is superior to alumina as the base material particles for supporting the active species.
（実施例１）
母材粒子として、Ｎｄ固溶ジルコニア系酸化物（Ｎｄ−ＺｒＯ２と記載，Ｎｄ：１５質量％、ＺｒＯ２：８５質量％、Ｄ５０＝５．７μｍ、ＢＥＴ比表面積：６３ｍ２／ｇ）を用いた。硝酸鉄９水和物（Ｆｅ２Ｏ３換算で４０質量％含有）１．２５質量部と硝酸ランタン６水和物（Ｌａ２Ｏ３換算で７５質量％含有）２．０質量部を、水３．２５質量部に溶解して、Ｆｅ及びＬａ含有水溶液を調製した。上記ジルコニア系酸化物にＦｅ及びＬａ含有水溶液を含浸させ、６００℃で３０ｍｉｎ焼成することにより、ＬａＦｅＯ３微粒子及び酸化鉄微粒子が共担持されたＮｄ−ＺｒＯ２パウダー触媒１０質量部（Ｆｅ２Ｏ３換算担持量：０．５質量部）を得た。
その後、得られたパウダー触媒を耐久炉内で高温曝露処理を行い、実施例１の排気ガス浄化用触媒を得た。なお、高温曝露処理としては、外部雰囲気をＡ／Ｆ＝１２．５、窒素雰囲気、及び酸素雰囲気に順次切り替えを繰り返しながら、９８０℃で６時間の熱処理を行った。
(Example 1)
Nd solid solution zirconia-based oxide (described as Nd-ZrO 2 ; Nd: 15 mass %, ZrO 2 : 85 mass %, D 50 =5.7 μm, BET specific surface area: 63 m 2 /g) was used as a base material particle. Using. 1.25 parts by mass of iron nitrate 9-hydrate (containing 40% by mass in terms of Fe 2 O 3 ) and 2.0 parts by mass of lanthanum nitrate hexahydrate (containing 75% by mass in terms of La 2 O 3 ) were added to water. It melt|dissolved in 3.25 mass parts and prepared Fe and La containing aqueous solution. The above-mentioned zirconia-based oxide was impregnated with an aqueous solution containing Fe and La, and baked at 600° C. for 30 minutes to obtain 10 parts by mass of an Nd—ZrO 2 powder catalyst (Fe 2 O 3) on which LaFeO 3 particles and iron oxide particles were co-supported. Converted loading: 0.5 parts by mass) was obtained.
Then, the obtained powder catalyst was subjected to high temperature exposure treatment in an endurance furnace to obtain an exhaust gas purifying catalyst of Example 1. As the high-temperature exposure treatment, heat treatment was performed at 980° C. for 6 hours while sequentially switching the external atmosphere to A/F=12.5, a nitrogen atmosphere, and an oxygen atmosphere.
（実施例２）
硝酸鉄９水和物及び硝酸ランタン６水和物の配合量を、１．２５質量部及び１．３５質量部に変更すること以外は、実施例１と同様に行い、ＬａＦｅＯ３微粒子及び酸化鉄微粒子が共担持されたＮｄ−ＺｒＯ２パウダー触媒１０質量部（Ｆｅ２Ｏ３換算担持量：０．５質量部）を得た。
その後、実施例１と同様に行い、実施例２の排気ガス浄化用触媒を得た。
(Example 2)
LaFeO 3 fine particles and iron oxide were prepared in the same manner as in Example 1 except that the blending amounts of iron nitrate nonahydrate and lanthanum nitrate hexahydrate were changed to 1.25 parts by mass and 1.35 parts by mass. 10 parts by mass of Nd-ZrO 2 powder catalyst on which fine particles were co-supported (Fe 2 O 3 conversion supported amount: 0.5 parts by mass) was obtained.
Then, the same procedure as in Example 1 was carried out to obtain an exhaust gas purifying catalyst of Example 2.
（実施例３）
硝酸鉄９水和物及び硝酸ランタン６水和物の配合量を、１．２５質量部及び０．９質量部に変更すること以外は、実施例１と同様に行い、ＬａＦｅＯ３微粒子及び酸化鉄微粒子が共担持されたＮｄ−ＺｒＯ２パウダー触媒１０質量部（Ｆｅ２Ｏ３換算担持量：０．５質量部）を得た。
その後、実施例１と同様に行い、実施例３の排気ガス浄化用触媒を得た。
(Example 3)
LaFeO 3 fine particles and iron oxide were prepared in the same manner as in Example 1 except that the blending amounts of iron nitrate nonahydrate and lanthanum nitrate hexahydrate were changed to 1.25 parts by mass and 0.9 parts by mass. 10 parts by mass of Nd-ZrO 2 powder catalyst on which fine particles were co-supported (Fe 2 O 3 conversion supported amount: 0.5 parts by mass) was obtained.
Then, the same procedure as in Example 1 was carried out to obtain an exhaust gas purifying catalyst of Example 3.
（実施例４）
硝酸鉄９水和物及び硝酸ランタン６水和物の配合量を、１．２５質量部及び０．３４質量部に変更すること以外は、実施例１と同様に行い、ＬａＦｅＯ３微粒子及び酸化鉄微粒子が共担持されたＮｄ−ＺｒＯ２パウダー触媒１０質量部（Ｆｅ２Ｏ３換算担持量：０．５質量部）を得た。
その後、実施例１と同様に行い、実施例４の排気ガス浄化用触媒を得た。
(Example 4)
LaFeO 3 fine particles and iron oxide were prepared in the same manner as in Example 1 except that the blending amounts of iron nitrate nonahydrate and lanthanum nitrate hexahydrate were changed to 1.25 parts by mass and 0.34 parts by mass. 10 parts by mass of Nd-ZrO 2 powder catalyst on which fine particles were co-supported (Fe 2 O 3 conversion supported amount: 0.5 parts by mass) was obtained.
Then, the same procedure as in Example 1 was carried out to obtain an exhaust gas purifying catalyst of Example 4.
（比較例１）
硝酸ランタン６水和物の配合を省略すること以外は、実施例１と同様に行い、酸化鉄微粒子が担持されたＮｄ−ＺｒＯ２パウダー触媒１０質量部（Ｆｅ２Ｏ３換算担持量：０．５質量部）を得た。
その後、実施例１と同様に行い、比較例１の排気ガス浄化用触媒を得た。
(Comparative Example 1)
The same procedure as in Example 1 was carried out except that the compound of lanthanum nitrate hexahydrate was omitted, and 10 parts by mass of the Nd-ZrO 2 powder catalyst supporting the iron oxide fine particles (Fe 2 O 3 conversion supported amount: 0. 5 parts by mass) was obtained.
Then, the same procedure as in Example 1 was carried out to obtain an exhaust gas purifying catalyst of Comparative Example 1.
（実施例５）
母材粒子として、Ｙ固溶ジルコニア系酸化物（Ｙ−ＺｒＯ２と記載，Ｙ２Ｏ３：３５質量％、ＺｒＯ２：６５質量％：Ｄ５０＝６．４μｍ：ＢＥＴ比表面積：７２ｍ２／ｇ）を用いた。硝酸鉄９水和物（Ｆｅ２Ｏ３換算で４０質量％含有）１．２５質量部と硝酸ランタン６水和物（Ｌａ２Ｏ３換算で７５質量％含有）０．９質量部を、水３．２５質量部に溶解して、Ｆｅ及びＬａ含有水溶液を調製した。上記ジルコニア系酸化物にＦｅ及びＬａ含有水溶液を含浸させ、６００℃で３０ｍｉｎ焼成することにより、ＬａＦｅＯ３微粒子及び酸化鉄微粒子が共担持されたＹ−ＺｒＯ２パウダー触媒１０質量部（Ｆｅ２Ｏ３換算担持量：０．５質量部）を得た。
その後、得られたパウダー触媒を耐久炉内で高温曝露処理を行い、実施例５の排気ガス浄化用触媒を得た。なお、高温曝露処理としては、外部雰囲気をＡ／Ｆ＝１２．５、窒素雰囲気、酸素雰囲気に順次切り替えながら、９８０℃で６時間の熱処理を行った。
(Example 5)
As the base material particles, Y solute zirconia oxide (Y-ZrO 2 with the description, Y 2 O 3: 35 wt%, ZrO 2: 65 wt%: D 50 = 6.4μm: BET specific surface area: 72m 2 / g) was used. 1.25 parts by mass of iron nitrate nonahydrate (containing 40% by mass in terms of Fe 2 O 3 ) and 0.9 parts by mass of lanthanum nitrate hexahydrate (containing 75% by mass in terms of La 2 O 3 ) were added to water. It melt|dissolved in 3.25 mass parts and prepared Fe and La containing aqueous solution. The above zirconia-based oxide was impregnated with an aqueous solution containing Fe and La, and was baked at 600° C. for 30 minutes to obtain 10 parts by mass of a Y—ZrO 2 powder catalyst (Fe 2 O 3) on which LaFeO 3 particles and iron oxide particles were co-supported. Converted loading: 0.5 parts by mass) was obtained.
Then, the obtained powder catalyst was subjected to high temperature exposure treatment in a durable furnace to obtain an exhaust gas purifying catalyst of Example 5. As the high temperature exposure treatment, a heat treatment was performed at 980° C. for 6 hours while sequentially switching the external atmosphere to A/F=12.5, a nitrogen atmosphere and an oxygen atmosphere.
（比較例２）
硝酸ランタン６水和物の配合を省略すること以外は、実施例５と同様に行い、実施例２の排気ガス浄化用触媒として、酸化鉄微粒子が担持されたＹ−ＺｒＯ２パウダー触媒１０質量部（Ｆｅ２Ｏ３換算担持量：０．５質量部）を得た。
その後、実施例５と同様に行い、比較例２の排気ガス浄化用触媒を得た。
(Comparative example 2)
The same procedure as in Example 5 was carried out except that the compound of lanthanum nitrate hexahydrate was omitted, and as an exhaust gas purifying catalyst in Example 2, 10 parts by mass of Y-ZrO 2 powder catalyst carrying iron oxide fine particles was carried out. (Fe 2 O 3 equivalent supported amount: 0.5 parts by mass) was obtained.
Then, the same procedure as in Example 5 was carried out to obtain an exhaust gas purifying catalyst of Comparative Example 2.
＜粉末Ｘ線回折測定＞
Ｘ線回折装置（商品名：Ｘ’Ｐｅｒｔ ＰＲＯ ＭＰＤ，ヤマト科学株式会社製）を用いて、得られたＬａＦｅＯ３微粒子及び酸化鉄微粒子を担持したＹ−ＺｒＯ２パウダー触媒について下記条件で粉末Ｘ線回折測定を行ったところ、実施例１〜５ではＬａＦｅＯ３結晶の固有ピークが確認された。図４に、実施例１のＸ線回折パターンを示す。
ターゲット：Ｃｕ
Ｋ−Ａｌｐｈａ１［Ａ］：１．５４０６
Ｘ線出力設定：４０ ｍＡ，４５ｋＶ
＜平均結晶子径の測定＞
また、上記式（２）の基づき平均結晶子径を算出したところ、実施例３の排気ガス浄化用触媒のＬａＦｅＯ３の平均結晶子径は１９．４ｎｍであり、実施例５の排気ガス浄化用触媒では３８．１ｎｍであった。なお、シェラー法による計算は、３２°付近の強いピーク（００２）に基づいて、市販のソフトウェア（スペクトリス社製、PANalytical X'Pert High Score Plus 3.0）を用いて行った。
<Powder X-ray diffraction measurement>
Using a X-ray diffractometer (trade name: X'Pert PRO MPD, manufactured by Yamato Scientific Co., Ltd.), the obtained LaFeO 3 fine particles and Y-ZrO 2 powder catalyst supporting iron oxide fine particles were powdered under the following conditions. When the diffraction measurement was performed, the intrinsic peak of the LaFeO 3 crystal was confirmed in Examples 1 to 5. FIG. 4 shows the X-ray diffraction pattern of Example 1.
Target: Cu
K-Alpha1 [A]: 1.5406
X-ray output setting: 40 mA, 45 kV
<Measurement of average crystallite size>
Further, when the average crystallite size was calculated based on the above formula (2), the average crystallite size of LaFeO 3 of the exhaust gas purification catalyst of Example 3 was 19.4 nm, and It was 38.1 nm for the catalyst. The calculation by the Scherrer method was performed using commercially available software (PANalytical X'Pert High Score Plus 3.0) manufactured by Spectris, based on the strong peak (002) near 32°.
＜ＥＰＭＡ元素分析＞
電子プローブマイクロアナライザ（商品名：ＪＸＡ−８１００，日本電子株式会社製）を用いて、下記条件で実施例及び比較例のパウダー触媒及び排気ガス浄化用触媒の元素分析を行った。
＜条件＞
電子銃 熱電子（ＬａＢ６）
前処理 樹脂包埋（Ｓｐｅｃｉｆｉｘ）−湿式研磨
導電処理 カーボン蒸着
加速電圧 １５ｋＶ
照射電流 ４．５×１０−８Ａ
ステップ幅 ０．８μｍ
ステップ数 ２５０×２５０
計測時間 ３８ｍｓｅｃ
プローブ径 Ｆｏｃｕｓｅｄ
測定元素［結晶］：Zr(Lα), Fe(Kα), Ce(Lα), Nd(Lβ), Pr(Lβ), La(Lα), Y(Lα)
<EPMA elemental analysis>
Using an electron probe microanalyzer (trade name: JXA-8100, manufactured by JEOL Ltd.), elemental analysis was performed on the powder catalyst and the exhaust gas purifying catalyst of Examples and Comparative Examples under the following conditions.
<Condition>
Electron gun Thermoelectron (LaB6)
Pretreatment Resin embedding (SPECIFIX)-wet polishing Conductive treatment Carbon vapor deposition Accelerating voltage 15kV
Irradiation current 4.5×10 −8 A
Step width 0.8 μm
Number of steps 250 x 250
Measurement time 38msec
Probe diameter Focused
Measurement element [Crystal]: Zr(Lα), Fe(Kα), Ce(Lα), Nd(Lβ), Pr(Lβ), La(Lα), Y(Lα)
図５に、実施例３のパウダー触媒及び排気ガス浄化用触媒のＥＰＭＡ元素分析結果、及び比較例１の排気ガス浄化用触媒のＥＰＭＡ元素分析結果を示す。また、図６に、実施例５及び比較例２の排気ガス浄化用触媒のＥＰＭＡ元素分析結果を示す。 FIG. 5 shows the EPMA elemental analysis results of the powder catalyst and the exhaust gas purification catalyst of Example 3, and the EPMA elemental analysis results of the exhaust gas purification catalyst of Comparative Example 1. Further, FIG. 6 shows the EPMA elemental analysis results of the exhaust gas purifying catalysts of Example 5 and Comparative Example 2.
これら粉末Ｘ線回折測定及びＥＰＭＡ元素分析の結果から、実施例１〜５の排気ガス浄化用触媒では、母材粒子上にＬａＦｅＯ３微粒子及び酸化鉄微粒子が担持（付着）されていることが確認された。また、実施例１〜５の排気ガス浄化用触媒は、ＬａＦｅＯ３微粒子及び酸化鉄微粒子が、高分散な状態で一様に均一分布していることがわかる。一方、比較例１及び２の排気ガス浄化用触媒では、高温曝露により酸化鉄微粒子がシンタリングして粒成長していることがわかる。これらのことから、母材粒子上にＬａＦｅＯ３微粒子及び酸化鉄微粒子が共担持された構造を有する本発明の排気ガス浄化用触媒では、高温曝露時の酸化鉄微粒子のシンタリング及び粒成長が抑制されていることが裏付けられた。 From the results of these powder X-ray diffraction measurements and EPMA elemental analysis, it was confirmed that in the exhaust gas purifying catalysts of Examples 1 to 5, LaFeO 3 fine particles and iron oxide fine particles were carried (adhered) on the base material particles. Was done. Further, it can be seen that in the exhaust gas purifying catalysts of Examples 1 to 5, LaFeO 3 fine particles and iron oxide fine particles are uniformly distributed in a highly dispersed state. On the other hand, in the exhaust gas purifying catalysts of Comparative Examples 1 and 2, it is found that the iron oxide fine particles are sintered and grain-formed due to the high temperature exposure. From these, in the exhaust gas purifying catalyst of the present invention having a structure in which LaFeO 3 fine particles and iron oxide fine particles are co-supported on the base material particles, sintering and particle growth of the iron oxide fine particles during high temperature exposure are suppressed. It is confirmed that this is done.
＜排気ガス浄化用触媒のランニング性能のラボ評価＞
実施例１〜４及び比較例１において、高温曝露による性能劣化（ＮＯ浄化率）を評価した。ここでは、実施例１〜４及び比較例１において、高温曝露前後のＮＯ浄化率をそれぞれ測定し、高温曝露処理前のＮＯ浄化率（パウダー触媒）を基準として、高温曝露処理後のＮＯ浄化率の劣化率を算出した。なお、ここでのＮＯ浄化率の測定は、上述したパウダー粒子のＮＯ浄化率の測定と同条件で実施した。評価結果を表１に示す。なお、表１では、高温曝露前の比較例１のパウダー触媒のＮＯ浄化率を基準として、規格化した数値でそれぞれ表した。
<Lab evaluation of running performance of exhaust gas purification catalyst>
In Examples 1 to 4 and Comparative Example 1, performance deterioration (NO purification rate) due to high temperature exposure was evaluated. Here, in Examples 1 to 4 and Comparative Example 1, the NO purification rate before and after high temperature exposure was measured, respectively, and the NO purification rate after high temperature exposure treatment (powder catalyst) was used as a reference, and the NO purification rate after high temperature exposure treatment was performed. The deterioration rate was calculated. The measurement of the NO purification rate here was carried out under the same conditions as the measurement of the NO purification rate of the powder particles described above. The evaluation results are shown in Table 1. In Table 1, the NO purification rate of the powder catalyst of Comparative Example 1 before exposure to high temperature was used as a reference and expressed as normalized values.
表１から明らかなように、酸化鉄微粒子のみ担持した比較例１の排気ガス浄化用触媒は、触媒作製直後はＮＯ浄化性能に優れるものの、高温曝露によって酸化鉄微粒子がシンタリングして粒成長するために劣化度が大きく、その結果、高温曝露後のＮＯ浄化性能に劣るものであることがわかる。これに対して、ＬａＦｅＯ３微粒子及び酸化鉄微粒子を共担持した実施例１〜４の排気ガス浄化用触媒は、高温曝露による劣化度が小さく、高温曝露後においても比較的に大きなＮＯ浄化性能を維持していることがわかる。とりわけ、Ｆｅ：Ｌａが４：６〜６：４の範囲内において、高温曝露による劣化度が特に小さいことが判明した。 As is clear from Table 1, the exhaust gas purifying catalyst of Comparative Example 1 supporting only iron oxide fine particles has excellent NO purifying performance immediately after the catalyst is produced, but the iron oxide fine particles are sintered due to high temperature exposure to grow grains. Therefore, the degree of deterioration is large, and as a result, the NO purification performance after high temperature exposure is inferior. On the other hand, the exhaust gas purifying catalysts of Examples 1 to 4 in which LaFeO 3 fine particles and iron oxide fine particles were co-loaded showed a low degree of deterioration due to high temperature exposure, and exhibited a relatively large NO purification performance even after high temperature exposure. You can see that you are maintaining. In particular, it was found that the degree of deterioration due to high temperature exposure was particularly small when Fe:La was in the range of 4:6 to 6:4.
本発明は、排ガス中のＮＯｘ、ＣＯ、ＨＣ等を削減する三元触媒（TWC: Three Way Catalyst）として広く且つ有効に利用することができ、特に耐熱性が要求されるエンジン直下型触媒コンバータやタンデム配置の直下型触媒コンバータ等のTWCとして殊に有効に利用することができる。 INDUSTRIAL APPLICABILITY The present invention can be widely and effectively utilized as a three-way catalyst (TWC: Three Way Catalyst) for reducing NOx, CO, HC and the like in exhaust gas, and is particularly useful for a catalyst converter directly below an engine, which requires heat resistance. It can be used particularly effectively as a TWC for a direct-type catalytic converter in a tandem arrangement.
１１ ・・・母材粒子
１１ａ・・・表面
２１ ・・・ＬａＦｅＯ３微粒子
３１ ・・・酸化鉄微粒子
１００ ・・・排気ガス浄化用触媒
11 ... base particles 11a ... surface 21 ... LaFeO 3 particles 31 ... iron oxide particles 100 ... exhaust gas purifying catalyst
Claims (11)
前記母材粒子の表面に共担持された、ＬａＦｅＯ３微粒子及び酸化鉄微粒子と、
を少なくとも含有することを特徴とする、排気ガス浄化用触媒。 Base material particles containing a zirconia-based oxide,
LaFeO 3 fine particles and iron oxide fine particles, which are co-supported on the surface of the base material particles,
An exhaust gas purification catalyst comprising at least:
０．６＜ Ｆｅ／Ｌａ ≦１．６ ・・・（１）
を満たす
請求項１に記載の排気ガス浄化用触媒。 The content ratios of La and Fe are represented by the following formula (1):
0.6<Fe/La≦1.6 (1)
The exhaust gas purifying catalyst according to claim 1, which satisfies the above condition.
請求項１又は２に記載の排気ガス浄化用触媒。 The exhaust gas purifying catalyst according to claim 1, wherein the LaFeO 3 fine particles have an average crystallite size of 1 to 50 nm.
請求項１〜３のいずれか一項に記載の排気ガス浄化用触媒。 The exhaust gas purifying catalyst according to any one of claims 1 to 3, wherein the zirconia-based oxide is rare earth element solid solution zirconia.
請求項１〜４のいずれか一項に記載の排気ガス浄化用触媒。 The base material particles, the exhaust gas purifying catalyst according to claim 1 having an average particle diameter D 50 of 3 to 30 .mu.m.
前記触媒担体の少なくとも一部に保持された、請求項１〜５のいずれか一項に記載の排気ガス浄化用触媒と、
を少なくとも備えることを特徴とする、排気ガス浄化用触媒コンバータ。 A catalyst carrier,
An exhaust gas purifying catalyst according to any one of claims 1 to 5, which is held on at least a part of the catalyst carrier.
An exhaust gas purifying catalytic converter, comprising:
処理後の前記母材粒子を５００〜１４９０℃で熱処理して、前記母材粒子の表面にＬａＦｅＯ３微粒子及び酸化鉄微粒子を共担持させる工程と、
を少なくとも有することを特徴とする、排気ガス浄化用触媒の製造方法。 A step of applying an aqueous solution containing at least La ions and Fe ions to the surface of the base material particles containing the zirconia-based oxide, and heat treating the base material particles after the treatment at 500 to 1490° C. A step of co-supporting LaFeO 3 fine particles and iron oxide fine particles on the surface of the material particles,
A method for producing an exhaust gas purifying catalyst, comprising:
０．６＜ Ｆｅ／Ｌａ ≦１．６ ・・・（１）
を満たす
請求項７に記載の排気ガス浄化用触媒の製造方法。 The content ratios of La and Fe in the aqueous solution are represented by the following formula (1):
0.6<Fe/La≦1.6 (1)
The method for producing an exhaust gas purifying catalyst according to claim 7, which satisfies the above condition.
請求項７又は８に記載の排気ガス浄化用触媒の製造方法。 The method for producing an exhaust gas purifying catalyst according to claim 7, wherein the LaFeO 3 fine particles have an average crystallite size of 1 to 50 nm.
請求項７〜９のいずれか一項に記載の排気ガス浄化用触媒の製造方法。 The method for producing an exhaust gas purifying catalyst according to any one of claims 7 to 9, wherein the zirconia-based oxide is rare earth element solid solution zirconia.
請求項７〜１０のいずれか一項に記載の排気ガス浄化用触媒の製造方法。 The method for producing an exhaust gas purifying catalyst according to claim 7, wherein the base material particles have an average particle diameter D 50 of 3 to 30 μm.
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