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 PDFInfo
- 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
- Authority
- US
- United States
- Prior art keywords
- exhaust gas
- gas purification
- purification catalyst
- aluminum borate
- carrier
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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- 239000003054 catalyst Substances 0.000 title claims abstract description 122
- 238000000746 purification Methods 0.000 title claims abstract description 84
- OJMOMXZKOWKUTA-UHFFFAOYSA-N aluminum;borate Chemical class [Al+3].[O-]B([O-])[O-] OJMOMXZKOWKUTA-UHFFFAOYSA-N 0.000 claims abstract description 126
- 229910052761 rare earth metal Inorganic materials 0.000 claims abstract description 12
- 229910052784 alkaline earth metal Inorganic materials 0.000 claims abstract description 11
- 150000001342 alkaline earth metals Chemical class 0.000 claims abstract description 11
- 239000007769 metal material Substances 0.000 claims description 10
- 239000000919 ceramic Substances 0.000 claims description 9
- 229910052684 Cerium Inorganic materials 0.000 claims description 5
- 229910052779 Neodymium Inorganic materials 0.000 claims description 5
- 229910052777 Praseodymium Inorganic materials 0.000 claims description 5
- 229910052788 barium Inorganic materials 0.000 claims description 5
- 229910052791 calcium Inorganic materials 0.000 claims description 5
- 229910052746 lanthanum Inorganic materials 0.000 claims description 5
- 229910052712 strontium Inorganic materials 0.000 claims description 5
- MRELNEQAGSRDBK-UHFFFAOYSA-N lanthanum oxide Inorganic materials [O-2].[O-2].[O-2].[La+3].[La+3] MRELNEQAGSRDBK-UHFFFAOYSA-N 0.000 description 59
- KTUFCUMIWABKDW-UHFFFAOYSA-N oxo(oxolanthaniooxy)lanthanum Chemical compound O=[La]O[La]=O KTUFCUMIWABKDW-UHFFFAOYSA-N 0.000 description 59
- 239000007789 gas Substances 0.000 description 51
- KDLHZDBZIXYQEI-UHFFFAOYSA-N palladium Substances [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 47
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 22
- 239000000047 product Substances 0.000 description 19
- 239000000243 solution Substances 0.000 description 19
- FYDKNKUEBJQCCN-UHFFFAOYSA-N lanthanum(3+);trinitrate Chemical compound [La+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O FYDKNKUEBJQCCN-UHFFFAOYSA-N 0.000 description 16
- 239000000203 mixture Substances 0.000 description 16
- 239000007864 aqueous solution Substances 0.000 description 15
- 238000005342 ion exchange Methods 0.000 description 14
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 13
- 229910002091 carbon monoxide Inorganic materials 0.000 description 13
- 239000006185 dispersion Substances 0.000 description 12
- 238000004519 manufacturing process Methods 0.000 description 12
- 229910000510 noble metal Inorganic materials 0.000 description 12
- 239000002002 slurry Substances 0.000 description 12
- 230000007774 longterm Effects 0.000 description 10
- 229910052751 metal Inorganic materials 0.000 description 10
- 239000002184 metal Substances 0.000 description 10
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 description 9
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 description 9
- 230000000052 comparative effect Effects 0.000 description 9
- 150000001875 compounds Chemical class 0.000 description 9
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 9
- GPNDARIEYHPYAY-UHFFFAOYSA-N palladium(ii) nitrate Chemical compound [Pd+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O GPNDARIEYHPYAY-UHFFFAOYSA-N 0.000 description 9
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 8
- IWOUKMZUPDVPGQ-UHFFFAOYSA-N barium nitrate Chemical compound [Ba+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O IWOUKMZUPDVPGQ-UHFFFAOYSA-N 0.000 description 8
- 238000000034 method Methods 0.000 description 8
- 229910002637 Pr6O11 Inorganic materials 0.000 description 7
- 238000002441 X-ray diffraction Methods 0.000 description 7
- 230000003197 catalytic effect Effects 0.000 description 7
- PLDDOISOJJCEMH-UHFFFAOYSA-N neodymium oxide Inorganic materials [O-2].[O-2].[O-2].[Nd+3].[Nd+3] PLDDOISOJJCEMH-UHFFFAOYSA-N 0.000 description 7
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 6
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 description 6
- 239000004327 boric acid Substances 0.000 description 6
- JKWMSGQKBLHBQQ-UHFFFAOYSA-N diboron trioxide Chemical compound O=BOB=O JKWMSGQKBLHBQQ-UHFFFAOYSA-N 0.000 description 5
- 239000002244 precipitate Substances 0.000 description 5
- 239000007787 solid Substances 0.000 description 5
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 4
- ZCCIPPOKBCJFDN-UHFFFAOYSA-N calcium nitrate Chemical compound [Ca+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O ZCCIPPOKBCJFDN-UHFFFAOYSA-N 0.000 description 4
- HSJPMRKMPBAUAU-UHFFFAOYSA-N cerium(3+);trinitrate Chemical compound [Ce+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O HSJPMRKMPBAUAU-UHFFFAOYSA-N 0.000 description 4
- 238000000975 co-precipitation Methods 0.000 description 4
- 238000002485 combustion reaction Methods 0.000 description 4
- 229910052593 corundum Inorganic materials 0.000 description 4
- 238000001914 filtration Methods 0.000 description 4
- 229930195733 hydrocarbon Natural products 0.000 description 4
- 150000002430 hydrocarbons Chemical class 0.000 description 4
- 238000010532 solid phase synthesis reaction Methods 0.000 description 4
- DHEQXMRUPNDRPG-UHFFFAOYSA-N strontium nitrate Chemical compound [Sr+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O DHEQXMRUPNDRPG-UHFFFAOYSA-N 0.000 description 4
- 229910001845 yogo sapphire Inorganic materials 0.000 description 4
- BNGXYYYYKUGPPF-UHFFFAOYSA-M (3-methylphenyl)methyl-triphenylphosphanium;chloride Chemical compound [Cl-].CC1=CC=CC(C[P+](C=2C=CC=CC=2)(C=2C=CC=CC=2)C=2C=CC=CC=2)=C1 BNGXYYYYKUGPPF-UHFFFAOYSA-M 0.000 description 3
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 3
- ATRRKUHOCOJYRX-UHFFFAOYSA-N Ammonium bicarbonate Chemical compound [NH4+].OC([O-])=O ATRRKUHOCOJYRX-UHFFFAOYSA-N 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 3
- 239000001099 ammonium carbonate Substances 0.000 description 3
- 235000012501 ammonium carbonate Nutrition 0.000 description 3
- 229910001593 boehmite Inorganic materials 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000011156 evaluation Methods 0.000 description 3
- 238000010304 firing Methods 0.000 description 3
- 239000000446 fuel Substances 0.000 description 3
- FAHBNUUHRFUEAI-UHFFFAOYSA-M hydroxidooxidoaluminium Chemical compound O[Al]=O FAHBNUUHRFUEAI-UHFFFAOYSA-M 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000000843 powder Substances 0.000 description 3
- 239000011369 resultant mixture Substances 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 229910003158 γ-Al2O3 Inorganic materials 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- 230000032683 aging Effects 0.000 description 2
- SMZOGRDCAXLAAR-UHFFFAOYSA-N aluminium isopropoxide Chemical compound [Al+3].CC(C)[O-].CC(C)[O-].CC(C)[O-] SMZOGRDCAXLAAR-UHFFFAOYSA-N 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 239000000969 carrier Substances 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 229910044991 metal oxide Inorganic materials 0.000 description 2
- 150000004706 metal oxides Chemical class 0.000 description 2
- CFYGEIAZMVFFDE-UHFFFAOYSA-N neodymium(3+);trinitrate Chemical compound [Nd+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O CFYGEIAZMVFFDE-UHFFFAOYSA-N 0.000 description 2
- 229910052763 palladium Inorganic materials 0.000 description 2
- 239000008188 pellet Substances 0.000 description 2
- 229910052697 platinum Inorganic materials 0.000 description 2
- YWECOPREQNXXBZ-UHFFFAOYSA-N praseodymium(3+);trinitrate Chemical compound [Pr+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O YWECOPREQNXXBZ-UHFFFAOYSA-N 0.000 description 2
- 230000009257 reactivity Effects 0.000 description 2
- 238000005245 sintering Methods 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- 231100000331 toxic Toxicity 0.000 description 2
- 230000002588 toxic effect Effects 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- 159000000021 acetate salts Chemical class 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- AZDRQVAHHNSJOQ-UHFFFAOYSA-N alumane Chemical group [AlH3] AZDRQVAHHNSJOQ-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- RQPZNWPYLFFXCP-UHFFFAOYSA-L barium dihydroxide Chemical compound [OH-].[OH-].[Ba+2] RQPZNWPYLFFXCP-UHFFFAOYSA-L 0.000 description 1
- 229910001863 barium hydroxide Inorganic materials 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 229910052810 boron oxide Inorganic materials 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 239000000567 combustion gas Substances 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000012790 confirmation Methods 0.000 description 1
- 229910052878 cordierite Inorganic materials 0.000 description 1
- 230000006735 deficit Effects 0.000 description 1
- 238000000151 deposition 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
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- KZHJGOXRZJKJNY-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Si]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O KZHJGOXRZJKJNY-UHFFFAOYSA-N 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 229910052733 gallium Inorganic materials 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000004570 mortar (masonry) Substances 0.000 description 1
- 229910052863 mullite Inorganic materials 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 150000002823 nitrates Chemical class 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 150000002910 rare earth metals Chemical class 0.000 description 1
- 229910052703 rhodium Inorganic materials 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- LTEHWCSSIHAVOQ-UHFFFAOYSA-N tripropyl borate Chemical compound CCCOB(OCCC)OCCC LTEHWCSSIHAVOQ-UHFFFAOYSA-N 0.000 description 1
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- 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]
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
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- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
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- B01D—SEPARATION
- B01D2255/00—Catalysts
- B01D2255/70—Non-metallic catalysts, additives or dopants
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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
- B01J2523/00—Constitutive chemical elements of heterogeneous catalysts
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- 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
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- 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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Abstract
The disclosed exhaust gas purification catalyst carrier includes 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 and which has an electronegativity of 2.732 or lower.
Description
- 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 (NOx). Hitherto, three-way catalysts have been used for removing such toxic components for detoxifying the exhaust gas.
- 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.
- Recently, the regulation of automobile exhaust gas has become more strict, and the demand and prices of Pt and Rh, which are noble metals serving as a main catalytically active component of internal combustion engine exhaust gas purification catalysts, have risen. Since a rise in Rh price is a critical issue, efforts have been made on reduction of exhaust gas purification catalyst production cost by use of inexpensive Pd as a catalytically active component, and various means therefor have been proposed (see, for example, Patent Documents 1, 2, and 3). Meanwhile, there are some cases where a catalyst carrier made of aluminum borate is used. In one case of such a catalyst, a catalyst component is deposited on a powder compact which is covered with aluminum borate whiskers and which includes voids therein, whereby gas diffusivity is enhanced (see Patent Document 4).
- However, it has been reported that Pd causes impairment in exhaust gas purification performance by sintering thereof at high temperature in a reducing atmosphere. Thus, suppression of Pd sintering is an inevitable issue for designing coming catalysts of a noble-metal saving format. Also, aluminum borate whiskers, having an acicular shape, have a small specific surface area, which causes cohesion of noble metal elements after long-term use of the relevant catalyst under high-temperature conditions. That is, durability of the catalyst is unsatisfactory.
- In order to solve such problems, the present applicant previously developed an exhaust gas purification catalyst which exhibits excellent NOx 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 - However, the exhaust gas purification catalyst disclosed in Patent Document 5, employing a substituted aluminum borate, 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.
- In the meantime, the exhaust gas purification catalyst for automobiles is designed in accordance with the type of automobile. Specifically, automobiles mainly employing a combustion mode in a lean condition (at high air-fuel ratio) are provided with an exhaust gas purification catalyst which is durable in a lean condition, while automobiles mainly employing a combustion mode in a rich region (at low air-fuel ratio) are provided with an exhaust gas purification catalyst which is durable in a rich region.
- Thus, 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.
- Notably, characteristics, its production method, etc. of aluminum borate are disclosed in, for example, Siba P. Ray, “Preparation and Characterization of Aluminum Borate”, J. Am. Ceram. Soc., 75[9], p. 2605-2609 (1992).
- Conventionally, aluminum borate is represented by a formula 9Al2O3.2B2O3 (Al18B4O33), obtained through chemical analysis. However, a thesis (Martin et al., “Crystal-chemistry of mullite-type aluminoborates Al18B4O33 and Al5BO9: A stoichiometry puzzle”, Journal of Solid State Chemistry 184(2011) p. 70 to 80), discloses crystal structure analyses revealing that aluminum borate is represented by Al5BO9 (5Al2O3:B2O3, Al20B4O36); i.e., formula 10Al2O3.2B2O3. The thesis also discloses that aluminum borate may be represented by either formula 9Al2O3.2B2O3 (Al18B4O33) or Al5BO9 (5Al2O3:B2O3, Al20B4O36), meaning that the two formulas represent a unique substance.
- Thus, as used herein, the term “aluminum borate” encompasses aluminum borate represented by formula 10Al2O3.2B2O3 (5Al2O3:B2O3, Al20B4O36) and aluminum borate represented by formula 9Al2O3.2B2O3 (Al18B4O33).
- Accordingly, 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. Another characteristic feature resides in that 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 10Al2O3.2B2O3 (5Al2O3:B2O3, Al20B4O36) and an aluminum borate represented by formula 9Al2O3.2B2O3 (Al18B4O33). The aluminum borate employed in the present invention can be identified as an aluminum borate represented by formula 10Al2O3.2B2O3 through X-ray diffractometry. However, since the formula 9Al2O3.2B2O3 (Al18B4O33) is also given in an X-ray diffraction standard chart, the aluminum borate can also be identified as an aluminum borate represented by formula 9Al2O3.2B2O3 (Al48B4O33).
- The aforementioned addition element preferably contains two or more such elements. The addition element is particularly preferably an element selected from the group consisting of Ca, Sr, Ba, La, Pr, Nd, and Ce.
- 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.
- An XRD pattern of aluminum borate produced in Referential Example 1.
- 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. Alternatively, 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. When such a modified aluminum borate is employed, 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.
- Preferably, 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. In the preferred case, the addition element is present as an oxide or the like of the addition element such as a crystal grain boundary. When such an addition element is analyzed through XRD, no substantial shift is observed for the peak attributed to aluminum borate, but a peak attributed to the addition element is observed as, for example, a corresponding oxide peak.
- Hereinafter, 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 a target compound, aluminum borate (formula: Al20B4O36), 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 about 120° C. for 12 hours or longer. After completion of drying, the dried product was fired at about 300° C. for about one hour and then at about 1,000° C. for about 5 hours, to thereby yield the target aluminum borate.
- More specifically, boric acid was weighed in such an amount that the compositional proportions of the target aluminum borate (formula: Al20B4O36) 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.
- Boric acid was weighed in such an amount that the compositional proportions of a target compound, aluminum borate (formula: Al20B4O36), 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.
- More specifically, boric acid was weighed in such an amount that the compositional proportions of the target aluminum borate (formula: Al20B4O36) 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. 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 at 120° C. for 12 hours or longer and fired in air at 300° C. for one hour. Thereafter, the dried product was fired in air at 1,000° C. for 5 hours, to thereby yield the target aluminum borate. No significant difference was observed between the aluminum borate prepared through the above reverse co-precipitation and that prepared through the aforementioned solid-phase method.
- 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.
- In one mode of the method of producing such a modified 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.)
- 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. When 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. Also, when 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. By virtue of employing Pd supported on the 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 %. When 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. In contrast, when 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. In the present specification, the amount of supported Pd is reduced to the mass of metallic Pd.
- In one mode of production, 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. Notably, in the specification and other attachments, no particular limitation is imposed on the solvent for forming the “solution,” so long as the solvent can form the solution, and water is generally used. Notably, so long as the effects of the present invention are not impaired, 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.
- 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. In such an exhaust gas purification catalyst product, 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. In the case of a honeycomb shape support, 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 (Al2O3), mullite (3Al2O3-2SiO2), and cordierite (2MgO-2Al2O3-5SiO2), 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 present invention will next be described in detail by way of Referential Examples, Examples, and Comparative Examples. Notably, the addition element content is derived as the ratio of amount of addition element oxide/total amount of aluminum borate and addition element oxide. In Tables 1 to 3, 10A2B denotes 10Al2O3.2B2O3.
- An aluminum borate (Al20B4O36) 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 fromFIG. 1 , the aluminum borate was identified as an aluminum borate represented by formula 10Al2O3.2B2O3, through X-ray diffraction analysis. - Notably, since the formula 9Al2O3.2B2O3 (Al18B4O33) is also given in an X-ray diffraction standard chart, the yielded product was also identified as an aluminum borate represented by formula 9Al2O3.2B2O3 (Al18B4O33).
- An aluminum borate (Al20B4O36) 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.
- To a three-neck flask dipped in a hot water bath at 50° C., 2-propanol (1.5 L), aluminum isopropoxide (200 g) pulverized by means of an agate mortar, and boron n-propoxide (40.9 g) were added, and the mixture was stirred under a flow of nitrogen gas. After complete dissolution of aluminum isopropoxide (confirmation of transparency of the solution), a mixture (24.6 g) of 2-propanol:water=1:1 was gradually added dropwise to the solution for hydrolysis, to thereby form a white gel substance. The thus-formed precipitates were washed sequentially with ethanol and pure water, followed by filtration. Thereafter, the solid was dried overnight (for about 15 hours) at 120° C., and fired in air at 300° C. for 3 hours and further in air at 1,000° C. for 5 hours, to thereby yield an aluminum borate as a white product. Through X-ray diffractometry, this aluminum borate was identified as an aluminum borate represented by formula 10Al2O3.2B2O3.
- 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 La2O3 content and the SrO content of the aluminum borate represented by 10Al2O3.2B2O3 modified with target La2O3 and SrO 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. for 3 hours, to thereby yield an aluminum borate represented by 10Al2O3.2B2O3 modified with La2O3 and SrO at 5 mass % and 5 mass %, respectively.
- To the aluminum borate (99 parts by mass) represented by 10Al2O3.2B2O3 modified with La2O3 and SrO at 5 mass % and 5 mass %, and palladium nitrate (1 part by mass, as reduced to Pd metal), 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 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 La2O3 content and the Pr6O11 content of the aluminum borate represented by 10Al2O3.2B2O3 modified with target La2O3 and Pr6O11 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. for 3 hours, to thereby yield an aluminum borate represented by 10Al2O3.2B2O3 modified with La2O3 and Pr6O11 at 5 mass % and 5 mass %, respectively.
- To the aluminum borate (99 parts by mass) represented by 10Al2O3.2B2O3 modified with La2O3 and Pr6O11 at 5 mass % and 5 mass %, and palladium nitrate (1 part by mass, as reduced to Pd metal), 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 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 La2O3 content and the CaO content of the aluminum borate represented by 10Al2O3.2B2O3 modified with target La2O3 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. for 3 hours, to thereby yield an aluminum borate represented by 10Al2O3.2B2O3 modified with La2O3 and CaO at 5 mass % and 5 mass %, respectively. To the aluminum borate (99 parts by mass) represented by 10Al2O3.2B2O3 modified with La2O3 and CaO at 5 mass % and 5 mass %, and palladium nitrate (1 part by mass, as reduced to Pd metal), 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 La2O3 content and the BaO content of the aluminum borate represented by 10Al2O3.2B2O3 modified with La2O3 and BaO 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. for 3 hours, to thereby yield an aluminum borate represented by 10Al2O3.2B2O3 modified with La2O3 and BaO at 5 mass % and 5 mass %, respectively.
- To the aluminum borate (99 parts by mass) represented by 10Al2O3.2B2O3 modified with La2O3 and BaO at 5 mass % and 5 mass %, and palladium nitrate (1 part by mass, as reduced to Pd metal), 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 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 La2O3 content and the Nd2O3 content of the aluminum borate represented by 10Al2O3.2B2O3 modified with target La2O3 and Nd2O3 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. for 3 hours, to thereby yield an aluminum borate represented by 10Al2O3.2B2O3 modified with La2O3 and Nd2O3 at 5 mass % and 5 mass %, respectively.
- To the aluminum borate (99 parts by mass) represented by 10Al2O3.2B2O3 modified with La2O3 and Nd2O3 at 5 mass % and 5 mass %, and palladium nitrate (1 part by mass, as reduced to Pd metal), 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 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 La2O3 content and the CeO2 content of the aluminum borate represented by 10Al2O3.2B2O3 modified with target La2O3 and CeO2 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. for 3 hours, to thereby yield an aluminum borate represented by 10Al2O3.2B2O3 modified with La2O3 and CeO2 at 5 mass % and 5 mass %, respectively.
- To the aluminum borate (99 parts by mass) represented by 10Al2O3.2B2O3 modified with La2O3 and CeO2 at 5 mass % and 5 mass %, and palladium nitrate (1 part by mass, as reduced to Pd metal), an appropriate amount of ion-exchange water was added, and the resultant slurry was stirred, dried, and fired at 500° C. for one hour.
- γ-Al2O3 (99 parts by mass) and palladium nitrate (1 part by mass, as reduced to metallic Pd) were added to an appropriate amount of ion-exchange water, and the resultant slurry was stirred. Then, the slurry was dried and fired at 500° C. for one hour.
- 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 La2O3 content of the aluminum borate represented by 10Al2O3.2B2O3 modified with target La2O3 was attained as 5 mass %. Thereafter, 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 10Al2O3.2B2O3 modified with La2O3 at 5 mass %.
- To the aluminum borate (99 parts by mass) represented by 10Al2O3.2B2O3 modified with La2O3 at 5 mass %, and palladium nitrate (1 part by mass, as reduced to Pd metal), 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 thereof and that of the barium nitrate in its aqueous solution were adjusted such that the La2O3 content and the BaO content of the aluminum borate represented by 10Al2O3.2B2O3 modified with target La2O3 and BaO were attained as 1 mass % and 2 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. for 3 hours, to thereby yield an aluminum borate represented by 10Al2O3.2B2O3 modified with La2O3 and BaO at 1 mass % and 2 mass %, respectively.
- To the aluminum borate (99 parts by mass) represented by 10Al2O3.2B2O3 modified with La2O3 and BaO at 1 mass % and 2 mass %, and palladium nitrate (1 part by mass, as reduced to Pd metal), an appropriate amount of ion-exchange water was added, and the resultant slurry was stirred, dried, and fired at 500° C. for one hour.
- 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%), C3H6 (1,200 ppmC), O2 (.4%), H2 (.1%), and H2O (10%), the balance being N2, 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).
- Each catalyst was aged at 900° C. and 25H in a rich region of A/F=14.0 (H2O=10%).
- 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). The degree of Pd dispersion was calculated by the following formula: degree of Pd dispersion=the amount (by mole) of Pd corresponding to the amount of CO adsorbed/the total amount (by mole) of Pd contained in the catalyst of interest.
- 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. As is clear from Table 1, the catalyst samples of the Examples exhibited more excellent low-temperature catalytic activity, as compared with those of the Comparative Examples. Among three components, CO removal performance was remarkably excellent.
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TABLE 1 Carrier composition NO-T50 HC-T50 CO-T70 Comp. γ-Al2O3 392.2 360.2 374.1 Ex. 1 Comp. 5 wt. % La2O3/10A2B 375.5 355.5 373.1 Ex. 2 Comp. (1 wt. % La2O3 + 371.5 353.7 372.1 Ex. 3 2 wt. % BaO)/10A2B Ex. 1 (5 wt. % La2O3 + 371.3 352.9 365.8 5 wt. % SrO)/10A2B Ex. 2 (5 wt. % La2O3 + 357.6 336.1 347.3 5 wt. % Pr6O11)/10A2B Ex. 3 (5 wt. % La2O3 + 365.2 344.3 357.3 5 wt. % CaO)/10A2B Ex. 4 (5 wt. % La2O3 + 371.3 353.8 365.9 5 wt. % BaO)/10A2B Ex. 5 (5 wt. % La2O3 + 371.3 352.5 365.5 5 wt. % Nd2O3)/10A2B Ex. 6 (5 wt. % La2O3 + 362.5 341.0 353.2 5 wt. % CeO2)/10A2B - 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.
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TABLE 2 Pd dispersion Carrier composition degree Comp. Ex. 1 γ-Al2O3 2.79% Comp. Ex. 2 5 wt. % La2O3/10A2B 3.24% Comp. Ex. 3 (1 wt. % La2O3 + 2 wt. % BaO)/10A2B 3.44% Ex. 1 (5 wt. % La2O3 + 5 wt. % SrO)/10A2B 3.68% Ex. 2 (5 wt. % La2O3 + 5 wt. % Pr6O11)/10A2B 4.77% Ex. 3 (5 wt. % La2O3 + 5 wt. % CaO)/10A2B 4.56% Ex. 4 (5 wt. % La2O3 + 5 wt. % BaO)/10A2B 3.80% Ex. 5 (5 wt. % La2O3 + 5 wt. % Nd2O3)/10A2B 5.04% Ex. 6 (5 wt. % La2O3 + 5 wt. % CeO2)/10A2B 5.11% - 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. As shown in Table 3, aluminum borate serves as an acidic carrier having an electronegativity higher than that of Al2O3. In the case where aluminum borate is modified with an electron-accepting element such as an alkaline earth metal element or a rare earth metal element, conceivably, electrons are supplied from noble metal elements to the carrier, whereby the noble metal elements are immobilized on the carrier even in a rich region. Also, presumably, the electronegativity of the carrier decreases to be almost a neutral electronegativity, which is equivalent to that of Al2O3, to thereby attain excellent reactivity (e.g., inhibition of adsorption of exhaust gas components). Thus, as is clear from Tables 1 and 2, Pd dispersion degree and component (in particular, CO) removal reactivity at low temperature are conceivably enhanced, by virtue of the above effects. The electronegativity of the carrier was found to be preferably 2.732 or lower. Also, when the amount of an oxide modifying aluminum borate is adjusted to 7 mass % or more, purification performance and Pd dispersibility can be enhanced. In comparison of Comparative Example 2 with Example 6, even though the electronegativity values of two carriers are almost the same, catalytic activity is remarkably higher in Example 6. Thus, aluminum borate is preferably modified with two or more elements.
- Notably, electronegativity can be derived through the following calculation.
- In the case of Comparative Example 2, the ratio by mass of La2O3:10Al2O3.2B2O3 in 10Al2O3.2B2O3 modified with 5 mass % La2O3 is 5:95. When 5 mass % La2O3 is reduced to the corresponding mol % value, the value is 18.72 mol % with respect to that of 10Al2O3.2B2O3 taken as 100 mol %. Pauling's electronegativity values of the elements forming the oxide are as follows: La=1.1, O=3.44, B=2.04, and Al=1.61. Thus, the weighted average is as follows: {18.72%×(2×1.1+3×3.44)+(20×1.61+4×2.04+36×3.44)}/(18.72%×5+60)=2.733.
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TABLE 3 Electronegativity Material of carrier Comp. Ex. 1 Al2O3 2.708 — 10A2B 2.737 Comp. Ex. 2 5 wt. % La2O3/10A2B 2.733 Comp. Ex. 3 (1 wt. % La2O3 + 2 wt. % BaO)/10A2B 2.733 Ex. 1 (5 wt. % La2O3 + 5 wt. % SrO)/10A2B 2.722 Ex. 2 (5 wt. % La2O3 + 5 wt. % Pr6O11)/10A2B 2.731 Ex. 3 (5 wt. % La2O3 + 5 wt. % CaO)/10A2B 2.714 Ex. 4 (5 wt. % La2O3 + 5 wt. % BaO)/10A2B 2.725 Ex. 5 (5 wt. % La2O3 + 5 wt. % Nd2O3)/10A2B 2.730 Ex. 6 (5 wt. % La2O3 + 5 wt. % CeO2)/10A2B 2.732
Claims (21)
1-6. (canceled)
7. An exhaust gas purification catalyst carrier, comprising 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 and which has an electronegativity of 2.732 or lower.
8. An exhaust gas purification catalyst carrier, comprising 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.
9. An exhaust gas purification catalyst carrier according to claim 7 , wherein the addition element contains two or more elements.
10. An exhaust gas purification catalyst carrier according to claim 8 , wherein the addition element contains two or more elements.
11. An exhaust gas purification catalyst carrier according to claim 7 , wherein the addition element is an element selected from the group consisting of Ca, Sr, Ba, La, Pr, Nd, and Ce.
12. An exhaust gas purification catalyst carrier according to claim 8 , wherein the addition element is an element selected from the group consisting of Ca, Sr, Ba, La, Pr, Nd, and Ce.
13. An exhaust gas purification catalyst carrier according to claim 9 , wherein the addition element is an element selected from the group consisting of Ca, Sr, Ba, La, Pr, Nd, and Ce.
14. An exhaust gas purification catalyst carrier according to claim 10 , wherein the addition element is an element selected from the group consisting of Ca, Sr, Ba, La, Pr, Nd, and Ce.
15. An exhaust gas purification catalyst, comprising an exhaust gas purification catalyst carrier as recited in claim 7 , and Pd supported on the carrier.
16. An exhaust gas purification catalyst, comprising an exhaust gas purification catalyst carrier as recited in claim 8 , and Pd supported on the carrier.
17. An exhaust gas purification catalyst, comprising an exhaust gas purification catalyst carrier as recited in claim 9 , and Pd supported on the carrier.
18. An exhaust gas purification catalyst, comprising an exhaust gas purification catalyst carrier as recited in claim 10 , and Pd supported on the carrier.
19. An exhaust gas purification catalyst, comprising an exhaust gas purification catalyst carrier as recited in claim 11 , and Pd supported on the carrier.
20. An exhaust gas purification catalyst, comprising an exhaust gas purification catalyst carrier as recited in claim 12 , and Pd supported on the carrier.
21. An exhaust gas purification catalyst, comprising an exhaust gas purification catalyst carrier as recited in claim 13 , and Pd supported on the carrier.
22. An exhaust gas purification catalyst, comprising an exhaust gas purification catalyst carrier as recited in claim 14 , and Pd supported on the carrier.
23. An exhaust gas purification catalyst product, comprising a catalyst support formed of a ceramic or metallic material, and a layer of an exhaust gas purification catalyst as recited in claim 15 , the layer being supported on the catalyst support.
24. An exhaust gas purification catalyst product, comprising a catalyst support formed of a ceramic or metallic material, and a layer of an exhaust gas purification catalyst as recited in claim 16 , the layer being supported on the catalyst support.
25. An exhaust gas purification catalyst product, comprising a catalyst support formed of a ceramic or metallic material, and a layer of an exhaust gas purification catalyst as recited in claim 17 , the layer being supported on the catalyst support.
26. An exhaust gas purification catalyst product, comprising a catalyst support formed of a ceramic or metallic material, and a layer of an exhaust gas purification catalyst as recited in claim 18 , the layer being supported on the catalyst support.
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JP2013-094197 | 2013-04-26 | ||
JP2013094197 | 2013-04-26 | ||
PCT/JP2014/061470 WO2014175349A1 (en) | 2013-04-26 | 2014-04-23 | Support for exhaust gas purification catalyst, catalyst for exhaust gas purification, and catalyst structure for exhaust gas purification |
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PCT/JP2014/061470 A-371-Of-International WO2014175349A1 (en) | 2013-04-26 | 2014-04-23 | Support for exhaust gas purification catalyst, catalyst for exhaust gas purification, and catalyst structure for exhaust gas purification |
PCT/US2014/061470 A-371-Of-International WO2015195158A1 (en) | 2014-06-19 | 2014-10-21 | Carsh attenuator apparatus |
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US15/358,172 Active US10220373B2 (en) | 2013-04-26 | 2016-11-22 | Carrier for exhaust gas purification catalyst |
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US (2) | US20160082419A1 (en) |
EP (1) | EP2990107B1 (en) |
JP (1) | JP6339013B2 (en) |
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Cited By (1)
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US20160279606A1 (en) * | 2013-10-31 | 2016-09-29 | Mitsui Mining & Smelting Co., Ltd. | Carrier for exhaust gas purification catalyst, and exhaust gas purification catalyst |
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JP6407030B2 (en) * | 2013-12-04 | 2018-10-17 | 三井金属鉱業株式会社 | Exhaust gas purification catalyst and exhaust gas purification catalyst structure |
WO2017022828A1 (en) * | 2015-08-06 | 2017-02-09 | 国立大学法人熊本大学 | Method for producing ammonia combustion catalyst and method for utilizing heat generated by ammonia catalyst combustion |
JP6738505B1 (en) * | 2020-05-28 | 2020-08-12 | 黒崎播磨株式会社 | Dielectric for electrostatic chuck |
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EP0522490B1 (en) * | 1991-07-09 | 1998-03-04 | Mitsubishi Jukogyo Kabushiki Kaisha | Catalyst and method for exhaust gas purification |
JPH0699069A (en) | 1992-09-18 | 1994-04-12 | Cataler Kogyo Kk | Catalyst for purification of exhaust gas |
JPH07171392A (en) | 1993-12-20 | 1995-07-11 | Cataler Kogyo Kk | Catalyst for exhaust gas purification |
JPH08281071A (en) | 1995-04-18 | 1996-10-29 | Toyota Central Res & Dev Lab Inc | Waste gas purifying method and waste gas purifying catalyst |
JP2000176298A (en) * | 1998-12-11 | 2000-06-27 | Mazda Motor Corp | Exhaust gas purification catalyst and its production |
JP2001172626A (en) * | 1999-12-21 | 2001-06-26 | Hitachi Ltd | Display and light emitting device |
JP4639536B2 (en) | 2001-06-15 | 2011-02-23 | スズキ株式会社 | Exhaust gas purification catalyst and method for producing the same |
JP2004041868A (en) * | 2002-07-09 | 2004-02-12 | Daihatsu Motor Co Ltd | Exhaust gas purifying catalyst |
CN1704381A (en) * | 2004-05-25 | 2005-12-07 | 中国科学院福建物质结构研究所 | Preparation of neodymium-doped aluminum yttrium borate nano powder by acid-base titration |
JP2006036558A (en) * | 2004-07-23 | 2006-02-09 | Dowa Mining Co Ltd | Perovskite complex oxide and catalyst |
JP5232401B2 (en) * | 2007-04-05 | 2013-07-10 | 株式会社キャタラー | Exhaust gas purification catalyst |
JP5674092B2 (en) * | 2010-07-09 | 2015-02-25 | 三井金属鉱業株式会社 | Exhaust gas purification catalyst and method for producing the same |
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JP5794908B2 (en) * | 2011-09-14 | 2015-10-14 | 三井金属鉱業株式会社 | Exhaust gas purification catalyst and exhaust gas purification catalyst structure |
-
2014
- 2014-04-23 US US14/785,417 patent/US20160082419A1/en not_active Abandoned
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US20160279606A1 (en) * | 2013-10-31 | 2016-09-29 | Mitsui Mining & Smelting Co., Ltd. | Carrier for exhaust gas purification catalyst, and exhaust gas purification catalyst |
US9687817B2 (en) * | 2013-10-31 | 2017-06-27 | Mitsui Mining & Smelting Co., Ltd. | Carrier for exhaust gas purification catalyst, and exhaust gas purification catalyst |
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CN105121007B (en) | 2018-06-26 |
EP2990107A1 (en) | 2016-03-02 |
US10220373B2 (en) | 2019-03-05 |
JPWO2014175349A1 (en) | 2017-02-23 |
EP2990107A4 (en) | 2017-01-18 |
WO2014175349A1 (en) | 2014-10-30 |
EP2990107B1 (en) | 2020-05-13 |
CN105121007A (en) | 2015-12-02 |
US20170120221A1 (en) | 2017-05-04 |
JP6339013B2 (en) | 2018-06-06 |
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