JP6287687B2 - Exhaust gas purification catalyst - Google Patents
Exhaust gas purification catalyst Download PDFInfo
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- JP6287687B2 JP6287687B2 JP2014170847A JP2014170847A JP6287687B2 JP 6287687 B2 JP6287687 B2 JP 6287687B2 JP 2014170847 A JP2014170847 A JP 2014170847A JP 2014170847 A JP2014170847 A JP 2014170847A JP 6287687 B2 JP6287687 B2 JP 6287687B2
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- 239000003054 catalyst Substances 0.000 title claims description 38
- 238000000746 purification Methods 0.000 title description 11
- 239000002131 composite material Substances 0.000 claims description 98
- 239000000203 mixture Substances 0.000 claims description 25
- 229910052684 Cerium Inorganic materials 0.000 claims description 21
- 229910052746 lanthanum Inorganic materials 0.000 claims description 18
- 229910052726 zirconium Inorganic materials 0.000 claims description 13
- 229910000510 noble metal Inorganic materials 0.000 claims description 9
- 239000012071 phase Substances 0.000 description 68
- 239000007789 gas Substances 0.000 description 36
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 29
- 239000001301 oxygen Substances 0.000 description 29
- 229910052760 oxygen Inorganic materials 0.000 description 29
- 230000000052 comparative effect Effects 0.000 description 22
- 238000003860 storage Methods 0.000 description 20
- 238000002441 X-ray diffraction Methods 0.000 description 18
- 239000000047 product Substances 0.000 description 13
- 239000012298 atmosphere Substances 0.000 description 12
- UJVRJBAUJYZFIX-UHFFFAOYSA-N nitric acid;oxozirconium Chemical compound [Zr]=O.O[N+]([O-])=O.O[N+]([O-])=O UJVRJBAUJYZFIX-UHFFFAOYSA-N 0.000 description 12
- 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 11
- 239000000463 material Substances 0.000 description 11
- 238000005259 measurement Methods 0.000 description 11
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 10
- 239000007864 aqueous solution Substances 0.000 description 9
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 9
- NIPNSKYNPDTRPC-UHFFFAOYSA-N N-[2-oxo-2-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)ethyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 NIPNSKYNPDTRPC-UHFFFAOYSA-N 0.000 description 8
- XMPZTFVPEKAKFH-UHFFFAOYSA-P ceric ammonium nitrate Chemical compound [NH4+].[NH4+].[Ce+4].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O XMPZTFVPEKAKFH-UHFFFAOYSA-P 0.000 description 8
- 150000003839 salts Chemical class 0.000 description 8
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 7
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 7
- 229910002091 carbon monoxide Inorganic materials 0.000 description 7
- QBEGYEWDTSUVHH-UHFFFAOYSA-P diazanium;cerium(3+);pentanitrate Chemical compound [NH4+].[NH4+].[Ce+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O QBEGYEWDTSUVHH-UHFFFAOYSA-P 0.000 description 7
- 229910052751 metal Inorganic materials 0.000 description 7
- 238000000034 method Methods 0.000 description 7
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 6
- -1 cerium (III) compound Chemical class 0.000 description 6
- 239000000446 fuel Substances 0.000 description 6
- 239000002184 metal Substances 0.000 description 6
- 238000002360 preparation method Methods 0.000 description 6
- 239000000243 solution Substances 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 150000001785 cerium compounds Chemical class 0.000 description 5
- 150000002604 lanthanum compounds Chemical class 0.000 description 5
- 239000010948 rhodium Substances 0.000 description 5
- 238000006467 substitution reaction Methods 0.000 description 5
- 150000003755 zirconium compounds Chemical class 0.000 description 5
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 4
- 239000008139 complexing agent Substances 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 230000001590 oxidative effect Effects 0.000 description 4
- 229910052697 platinum Inorganic materials 0.000 description 4
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 3
- OFOBLEOULBTSOW-UHFFFAOYSA-N Malonic acid Chemical compound OC(=O)CC(O)=O OFOBLEOULBTSOW-UHFFFAOYSA-N 0.000 description 3
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 3
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 description 3
- 150000001805 chlorine compounds Chemical class 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 229930195733 hydrocarbon Natural products 0.000 description 3
- 150000002430 hydrocarbons Chemical class 0.000 description 3
- 238000012423 maintenance Methods 0.000 description 3
- 150000002823 nitrates Chemical class 0.000 description 3
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 3
- 229910052763 palladium Inorganic materials 0.000 description 3
- 229910052703 rhodium Inorganic materials 0.000 description 3
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
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- DHMQDGOQFOQNFH-UHFFFAOYSA-N Glycine Chemical compound NCC(O)=O DHMQDGOQFOQNFH-UHFFFAOYSA-N 0.000 description 2
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 description 2
- MKYBYDHXWVHEJW-UHFFFAOYSA-N N-[1-oxo-1-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propan-2-yl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(C(C)NC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 MKYBYDHXWVHEJW-UHFFFAOYSA-N 0.000 description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- YRKCREAYFQTBPV-UHFFFAOYSA-N acetylacetone Chemical compound CC(=O)CC(C)=O YRKCREAYFQTBPV-UHFFFAOYSA-N 0.000 description 2
- WNLRTRBMVRJNCN-UHFFFAOYSA-N adipic acid Chemical compound OC(=O)CCCCC(O)=O WNLRTRBMVRJNCN-UHFFFAOYSA-N 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
- 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 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- ZSWFCLXCOIISFI-UHFFFAOYSA-N cyclopentadiene Chemical compound C1C=CC=C1 ZSWFCLXCOIISFI-UHFFFAOYSA-N 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- XBDQKXXYIPTUBI-UHFFFAOYSA-N dimethylselenoniopropionate Natural products CCC(O)=O XBDQKXXYIPTUBI-UHFFFAOYSA-N 0.000 description 2
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 2
- 229910044991 metal oxide Inorganic materials 0.000 description 2
- 150000004706 metal oxides Chemical class 0.000 description 2
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 description 2
- 239000011259 mixed solution Substances 0.000 description 2
- 229910052758 niobium Inorganic materials 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 125000004430 oxygen atom Chemical group O* 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 2
- VSZWPYCFIRKVQL-UHFFFAOYSA-N selanylidenegallium;selenium Chemical compound [Se].[Se]=[Ga].[Se]=[Ga] VSZWPYCFIRKVQL-UHFFFAOYSA-N 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- JOXIMZWYDAKGHI-UHFFFAOYSA-N toluene-4-sulfonic acid Chemical compound CC1=CC=C(S(O)(=O)=O)C=C1 JOXIMZWYDAKGHI-UHFFFAOYSA-N 0.000 description 2
- RTBFRGCFXZNCOE-UHFFFAOYSA-N 1-methylsulfonylpiperidin-4-one Chemical compound CS(=O)(=O)N1CCC(=O)CC1 RTBFRGCFXZNCOE-UHFFFAOYSA-N 0.000 description 1
- VZSRBBMJRBPUNF-UHFFFAOYSA-N 2-(2,3-dihydro-1H-inden-2-ylamino)-N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]pyrimidine-5-carboxamide Chemical compound C1C(CC2=CC=CC=C12)NC1=NC=C(C=N1)C(=O)NCCC(N1CC2=C(CC1)NN=N2)=O VZSRBBMJRBPUNF-UHFFFAOYSA-N 0.000 description 1
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 description 1
- LSNNMFCWUKXFEE-UHFFFAOYSA-M Bisulfite Chemical compound OS([O-])=O LSNNMFCWUKXFEE-UHFFFAOYSA-M 0.000 description 1
- FEWJPZIEWOKRBE-JCYAYHJZSA-N Dextrotartaric acid Chemical compound OC(=O)[C@H](O)[C@@H](O)C(O)=O FEWJPZIEWOKRBE-JCYAYHJZSA-N 0.000 description 1
- ZSBXGIUJOOQZMP-JLNYLFASSA-N Matrine Chemical compound C1CC[C@H]2CN3C(=O)CCC[C@@H]3[C@@H]3[C@H]2N1CCC3 ZSBXGIUJOOQZMP-JLNYLFASSA-N 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
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- KDYFGRWQOYBRFD-UHFFFAOYSA-N Succinic acid Natural products OC(=O)CCC(O)=O KDYFGRWQOYBRFD-UHFFFAOYSA-N 0.000 description 1
- FEWJPZIEWOKRBE-UHFFFAOYSA-N Tartaric acid Natural products [H+].[H+].[O-]C(=O)C(O)C(O)C([O-])=O FEWJPZIEWOKRBE-UHFFFAOYSA-N 0.000 description 1
- 229910010413 TiO 2 Inorganic materials 0.000 description 1
- XBALSZKLRNNSRC-UHFFFAOYSA-N [Zr+4].[Ce+3] Chemical compound [Zr+4].[Ce+3] XBALSZKLRNNSRC-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 235000011054 acetic acid Nutrition 0.000 description 1
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- 235000011037 adipic acid Nutrition 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 150000001298 alcohols Chemical class 0.000 description 1
- 150000004703 alkoxides Chemical class 0.000 description 1
- 125000005233 alkylalcohol group Chemical group 0.000 description 1
- JFCQEDHGNNZCLN-UHFFFAOYSA-N anhydrous glutaric acid Natural products OC(=O)CCCC(O)=O JFCQEDHGNNZCLN-UHFFFAOYSA-N 0.000 description 1
- 239000003125 aqueous solvent Substances 0.000 description 1
- SRSXLGNVWSONIS-UHFFFAOYSA-N benzenesulfonic acid Chemical compound OS(=O)(=O)C1=CC=CC=C1 SRSXLGNVWSONIS-UHFFFAOYSA-N 0.000 description 1
- 229940092714 benzenesulfonic acid Drugs 0.000 description 1
- KDYFGRWQOYBRFD-NUQCWPJISA-N butanedioic acid Chemical compound O[14C](=O)CC[14C](O)=O KDYFGRWQOYBRFD-NUQCWPJISA-N 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
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- 150000001732 carboxylic acid derivatives Chemical class 0.000 description 1
- 150000001733 carboxylic acid esters Chemical class 0.000 description 1
- 150000001735 carboxylic acids Chemical class 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 239000012876 carrier material Substances 0.000 description 1
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 description 1
- 229910000420 cerium oxide Inorganic materials 0.000 description 1
- VYLVYHXQOHJDJL-UHFFFAOYSA-K cerium trichloride Chemical compound Cl[Ce](Cl)Cl VYLVYHXQOHJDJL-UHFFFAOYSA-K 0.000 description 1
- OZECDDHOAMNMQI-UHFFFAOYSA-H cerium(3+);trisulfate Chemical compound [Ce+3].[Ce+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O OZECDDHOAMNMQI-UHFFFAOYSA-H 0.000 description 1
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 235000015165 citric acid Nutrition 0.000 description 1
- 239000003426 co-catalyst Substances 0.000 description 1
- KDUIUFJBNGTBMD-VXMYFEMYSA-N cyclooctatetraene Chemical compound C1=C\C=C/C=C\C=C1 KDUIUFJBNGTBMD-VXMYFEMYSA-N 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- 235000019253 formic acid Nutrition 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 229960002449 glycine Drugs 0.000 description 1
- 235000013905 glycine and its sodium salt Nutrition 0.000 description 1
- 229910052735 hafnium Inorganic materials 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 229910010272 inorganic material Inorganic materials 0.000 description 1
- 239000011147 inorganic material Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 229910052741 iridium Inorganic materials 0.000 description 1
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- VQEHIYWBGOJJDM-UHFFFAOYSA-H lanthanum(3+);trisulfate Chemical compound [La+3].[La+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O VQEHIYWBGOJJDM-UHFFFAOYSA-H 0.000 description 1
- ICAKDTKJOYSXGC-UHFFFAOYSA-K lanthanum(iii) chloride Chemical compound Cl[La](Cl)Cl ICAKDTKJOYSXGC-UHFFFAOYSA-K 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- VZCYOOQTPOCHFL-UPHRSURJSA-N maleic acid Chemical compound OC(=O)\C=C/C(O)=O VZCYOOQTPOCHFL-UPHRSURJSA-N 0.000 description 1
- 239000011976 maleic acid Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 229910052762 osmium Inorganic materials 0.000 description 1
- SYQBFIAQOQZEGI-UHFFFAOYSA-N osmium atom Chemical compound [Os] SYQBFIAQOQZEGI-UHFFFAOYSA-N 0.000 description 1
- 235000006408 oxalic acid Nutrition 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 description 1
- CMOAHYOGLLEOGO-UHFFFAOYSA-N oxozirconium;dihydrochloride Chemical compound Cl.Cl.[Zr]=O CMOAHYOGLLEOGO-UHFFFAOYSA-N 0.000 description 1
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 description 1
- 239000010970 precious metal Substances 0.000 description 1
- 235000019260 propionic acid Nutrition 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- IUVKMZGDUIUOCP-BTNSXGMBSA-N quinbolone Chemical compound O([C@H]1CC[C@H]2[C@H]3[C@@H]([C@]4(C=CC(=O)C=C4CC3)C)CC[C@@]21C)C1=CCCC1 IUVKMZGDUIUOCP-BTNSXGMBSA-N 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 229910052707 ruthenium Inorganic materials 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- 238000010532 solid phase synthesis reaction Methods 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 150000003460 sulfonic acids Chemical class 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- 239000011975 tartaric acid Substances 0.000 description 1
- 235000002906 tartaric acid Nutrition 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- VZCYOOQTPOCHFL-UHFFFAOYSA-N trans-butenedioic acid Natural products OC(=O)C=CC(O)=O VZCYOOQTPOCHFL-UHFFFAOYSA-N 0.000 description 1
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- 229910001928 zirconium oxide Inorganic materials 0.000 description 1
- ZXAUZSQITFJWPS-UHFFFAOYSA-J zirconium(4+);disulfate Chemical compound [Zr+4].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O ZXAUZSQITFJWPS-UHFFFAOYSA-J 0.000 description 1
Images
Description
本発明は、セリウム（Ｃｅ）、ランタン（Ｌａ）及びジルコニウム（Ｚｒ）を含む複合酸化物及び該複合酸化物を用いた排ガス浄化用触媒に関する。 The present invention relates to a composite oxide containing cerium (Ce), lanthanum (La), and zirconium (Zr), and an exhaust gas purifying catalyst using the composite oxide.
自動車等の内燃機関から排出される排ガスには、一酸化炭素（ＣＯ）、炭化水素（ＨＣ）、窒素酸化物（ＮＯｘ）等の有害成分が含まれており、これらの有害成分は排ガス浄化用触媒によって浄化されてから大気中に放出されている。従来、この排ガス浄化用触媒には、ＣＯ、ＨＣの酸化とＮＯｘの還元とを同時に行う三元触媒が用いられており、三元触媒としては、アルミナ（Ａｌ２Ｏ３）、シリカ（ＳｉＯ２）、ジルコニア（ＺｒＯ２）、チタニア（ＴｉＯ２）等の多孔質酸化物担体に、白金（Ｐｔ）、パラジウム（Ｐｄ）、ロジウム（Ｒｈ）等の貴金属を担持したものが広く用いられている。 Exhaust gas discharged from internal combustion engines such as automobiles contains harmful components such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NO x ). After being purified by the catalyst for use, it is released into the atmosphere. Conventionally, a three-way catalyst that simultaneously performs oxidation of CO and HC and reduction of NO x is used as the exhaust gas purification catalyst. As the three-way catalyst, alumina (Al 2 O 3 ), silica (SiO 2 ) 2 ), porous oxide carriers such as zirconia (ZrO 2 ), titania (TiO 2 ), etc., on which a noble metal such as platinum (Pt), palladium (Pd), rhodium (Rh) is supported are widely used. .
このような三元触媒を用いて効率的に排ガス中の上記有害成分を浄化するためには、内燃機関に供給される混合気の、空気と燃料の比率である空燃比（Ａ／Ｆ）が理論空燃比（ストイキ）近傍でなければならない。しかし、実際の空燃比は、自動車の走行条件等によって、ストイキを中心に、リッチ（燃料過剰：Ａ／Ｆ＜１４．７）又はリーン（酸素過剰：Ａ／Ｆ＞１４．７）になり、これに対応して排ガスもリッチ又はリーンになる。 In order to efficiently purify the harmful components in the exhaust gas using such a three-way catalyst, the air-fuel ratio (A / F), which is the ratio of air to fuel, of the air-fuel mixture supplied to the internal combustion engine is set. Must be near stoichiometric air-fuel ratio (stoichiometric). However, the actual air-fuel ratio becomes rich (excess fuel: A / F <14.7) or lean (excess oxygen: A / F> 14.7), mainly due to stoichiometry, depending on the driving conditions of the automobile, Correspondingly, the exhaust gas becomes rich or lean.
近年では、排ガス中の酸素濃度の変動に対して三元触媒の排ガス浄化能を高めるために、酸素吸蔵能(OSC:Oxygen Storage Capacity)を有する無機材料であるＯＳＣ材が排ガス浄化用触媒の担体として用いられている。セリウムの酸化物は優れた酸素吸蔵能を有することが知られており、ＯＳＣ材として広く用いられてきた。 In recent years, an OSC material, which is an inorganic material having an oxygen storage capacity (OSC), has been used as a carrier for an exhaust gas purification catalyst in order to enhance the exhaust gas purification performance of a three-way catalyst against fluctuations in oxygen concentration in the exhaust gas. It is used as. Cerium oxide is known to have an excellent oxygen storage capacity and has been widely used as an OSC material.
排ガス浄化用触媒にＯＳＣ材として用いられるセリウムの酸化物として、特許文献１には、セリウム（ＩＩＩ）化合物とジルコニウム（ＩＶ）化合物との混合物又は共沈物を不活性又は非酸化性雰囲気下に加熱し、熱分解して、セリウム（ＩＩＩ）−ジルコニウム（ＩＶ）複合酸化物を形成し、次いで、これを酸化性雰囲気下に加熱することを特徴とする排ガス浄化用助触媒のためのセリア−ジルコニア複合酸化物の製造方法が記載されている。
As an oxide of cerium used as an OSC material for an exhaust gas purification catalyst,
また、特許文献２には、ＣｅとＺｒとを含む複合酸化物であって、Ｃｅの価数が３価の時、以下の組成式：（Ｃｅ１−ｘ−ｙ，ＲＥｘ，ＡＥｙ）２（Ｚｒ１−ｙ，Ｍｙ）２Ｏ７（ＲＥはＣｅ以外の希土類イオンの少なくとも１種類、ＡＥはＣａ、Ｓｒ、Ｂａの少なくとも１種類、ＭはＮｂ、Ｔａの少なくとも１種類、０≦ｘ≦０．９、０≦ｙ≦０．９、０．４≦ｘ＋ｙ≦０．９）で表されるパイロクロア構造を有することを特徴とする複合酸化物が記載されている。特許文献２には、複合酸化物のＣｅ１ｍｏｌ当りの酸素吸蔵能が優れていたことが記載されている。
近年、自動車用の排ガス浄化用触媒について、省資源、コストダウン及びエンジン性能の改良等のために、触媒の貴金属使用量を低減することや触媒の圧損を低減することが求められている。しかし、貴金属の使用量を低減すると触媒の酸素吸蔵能が低下するため、ＯＳＣ材の性能をさらに向上させることが望まれている。また、エンジン性能に悪影響を与える触媒の圧損を低減するために各種技術の開発が進められており、触媒体格を低減させることがその一つとして挙げられる。触媒体格を低減させることによって、ＯＳＣ材の使用量を減少させることも可能になり、自動車の軽量化にもつながるため、コストを低減することもできる。従って、排ガス浄化用触媒の担体として用いられるＯＳＣ材の単位重量当りの酸素吸蔵能を高めることが求められている。 In recent years, regarding exhaust gas purification catalysts for automobiles, it has been required to reduce the amount of noble metal used in the catalyst and the pressure loss of the catalyst in order to save resources, reduce costs, improve engine performance, and the like. However, if the amount of noble metal used is reduced, the oxygen storage capacity of the catalyst is lowered, so that it is desired to further improve the performance of the OSC material. In addition, various technologies have been developed in order to reduce the pressure loss of the catalyst that adversely affects the engine performance, and one example is to reduce the catalyst size. By reducing the catalyst size, it is possible to reduce the amount of OSC material used, leading to a reduction in the weight of the automobile, and thus the cost can be reduced. Therefore, it is required to increase the oxygen storage capacity per unit weight of the OSC material used as a carrier for the exhaust gas purification catalyst.
上記のように、排ガス浄化用触媒の担体にＯＳＣ材として用いられる複合酸化物について、省資源、コストダウン及びエンジン性能の改良等のため、触媒の貴金属使用量の低減や触媒圧損の低減が求められているが、従来の排ガス浄化用触媒では、触媒の担体の単位重量当りの酸素吸蔵能について改善の余地がある。 As described above, the composite oxide used as the OSC material for the exhaust gas purification catalyst carrier is required to reduce the amount of precious metal used in the catalyst and reduce the catalyst pressure loss in order to save resources, reduce costs and improve engine performance. However, conventional exhaust gas purifying catalysts have room for improvement in oxygen storage capacity per unit weight of catalyst support.
従って、本発明は、単位重量当りの酸素吸蔵能が向上した、Ｃｅを含む複合酸化物を提供することを目的とする。 Accordingly, an object of the present invention is to provide a composite oxide containing Ce having an improved oxygen storage capacity per unit weight.
本発明者らは、上記課題を解決するための手段を種々検討した結果、Ｃｅ、Ｌａ及びＺｒを含むパイロクロア構造を有する複合酸化物のＣｅの組成比を特定することによって、該複合酸化物の単位重量当りの酸素吸蔵能を向上させることができることを見出し、本発明を完成した。 As a result of various studies on means for solving the above problems, the present inventors have identified the composition ratio of Ce of the composite oxide having a pyrochlore structure containing Ce, La, and Zr. It has been found that the oxygen storage capacity per unit weight can be improved, and the present invention has been completed.
すなわち、本発明の要旨は以下の通りである。
（１）Ｃｅ、Ｌａ及びＺｒを含み、式Ａ２Ｂ２Ｏ７で表されるパイロクロア構造を有する複合酸化物であって、ＡサイトがＣｅ及びＬａからなり、ＢサイトがＺｒを含み、ＡサイトのＣｅの組成比が０．６〜０．８である複合酸化物。
（２）ＡサイトのＣｅの組成比が０．６５〜０．７５であり、Ｌａの組成比が１．２５〜１．３５である（１）の複合酸化物。
（３）（１）又は（２）の複合酸化物に貴金属を担持した排ガス浄化用触媒。
That is, the gist of the present invention is as follows.
(1) A composite oxide containing Ce, La and Zr and having a pyrochlore structure represented by the formula A 2 B 2 O 7 , wherein the A site consists of Ce and La, the B site contains Zr, and A A composite oxide having a Ce composition ratio of 0.6 to 0.8.
(2) The composite oxide according to (1), wherein the composition ratio of Ce at the A site is 0.65 to 0.75 and the composition ratio of La is 1.25 to 1.35.
(3) An exhaust gas purifying catalyst in which a noble metal is supported on the composite oxide of (1) or (2).
本発明により、単位重量当りの酸素吸蔵能が向上した、Ｃｅを含む複合酸化物を提供することが可能となる。 According to the present invention, it is possible to provide a composite oxide containing Ce with improved oxygen storage capacity per unit weight.
以下、本発明の好ましい実施形態について詳細に説明する。 Hereinafter, preferred embodiments of the present invention will be described in detail.
本発明は、セリウム（Ｃｅ）、ランタン（Ｌａ）及びジルコニウム（Ｚｒ）を含む、式Ａ２Ｂ２Ｏ７で表されるパイロクロア構造を有する複合酸化物に関する。本発明の複合酸化物は、式Ａ２Ｂ２Ｏ７のＡサイトがＣｅ及びＬａからなり、他の元素を含まない。本発明の複合酸化物は、式Ａ２Ｂ２Ｏ７のＢサイトがＺｒを含む。 The present invention relates to a composite oxide having a pyrochlore structure represented by the formula A 2 B 2 O 7 containing cerium (Ce), lanthanum (La), and zirconium (Zr). In the composite oxide of the present invention, the A site of the formula A 2 B 2 O 7 is composed of Ce and La and does not contain other elements. In the composite oxide of the present invention, the B site of the formula A 2 B 2 O 7 contains Zr.
本発明の複合酸化物において、パイロクロア構造を有するとは、式Ａ２Ｂ２Ｏ７で表される構造を有し、Ｃｅ、Ｌａ及びＺｒによるパイロクロア型の規則配列構造を有する結晶相（パイロクロア相）が構成されていることを意味する。パイロクロア相は酸素欠陥サイトを有し、そのサイトに酸素原子が入り込むことでパイロクロア相は、式Ａ２Ｂ２Ｏ８−α（αはＬａの原子組成／２である）で表されるκ相に相変化する。一方、κ相は酸素原子を放出することによりパイロクロア相に相変化することができる。本発明のＣｅ、Ｌａ及びＺｒを含む複合酸化物の酸素吸蔵能は、パイロクロア相とκ相との間で相互に相変化して酸素を吸放出することによるものである。パイロクロア相の複合酸化物を排ガス浄化用触媒のＯＳＣ材として用いる場合、リッチ時にはパイロクロア相に変化し、リーン時にはκ相に変化することになる。 In the composite oxide of the present invention, having a pyrochlore structure means a crystal phase (pyrochlore phase) having a structure represented by the formula A 2 B 2 O 7 and having a pyrochlore type ordered arrangement structure of Ce, La and Zr. ) Is configured. The pyrochlore phase has an oxygen defect site, and oxygen atoms enter the site, whereby the pyrochlore phase is expressed by the formula A 2 B 2 O 8-α (α is the atomic composition of La / 2). Phase change. On the other hand, the κ phase can change into a pyrochlore phase by releasing oxygen atoms. The oxygen storage capacity of the composite oxide containing Ce, La and Zr of the present invention is due to the absorption and release of oxygen by mutually changing the phase between the pyrochlore phase and the κ phase. When the composite oxide of the pyrochlore phase is used as the OSC material of the exhaust gas purification catalyst, it changes to the pyrochlore phase when rich and changes to the κ phase when lean.
本発明の複合酸化物の結晶相は、Ｘ線回折（ＸＲＤ）測定により判別することができる。ＸＲＤパターンにおいて、２θ＝１４°付近の回折線は規則相（κ相）の（１１１）面に帰属する回折線であり、２θ＝２９°付近の回折線は規則相の（２２２）面に帰属する回折線である。本発明では、（１１１）面に帰属する回折線の（２２２）面に帰属する回折線に対する強度の比（（１１１）回折線の強度／（２２２）回折線の強度）をＩ値とし、Ｉ値を規則相の耐久性（維持率）を示す指標として用いる。 The crystal phase of the composite oxide of the present invention can be determined by X-ray diffraction (XRD) measurement. In the XRD pattern, diffraction lines near 2θ = 14 ° are diffraction lines belonging to the (111) plane of the regular phase (κ phase), and diffraction lines near 2θ = 29 ° belong to the (222) plane of the regular phase. Diffraction lines. In the present invention, the ratio of the intensity of the diffraction line belonging to the (111) plane to the diffraction line belonging to the (222) plane (the intensity of the (111) diffraction line / the intensity of the (222) diffraction line) is defined as I value. The value is used as an index indicating the durability (maintenance rate) of the ordered phase.
本発明の複合酸化物において、ＡサイトのＣｅの組成比は０．６〜０．８であり、好ましくは、０．６５〜０．７５である。本発明の複合酸化物は、ＡサイトのＣｅの組成比を０．６〜０．８にすることによって、複合酸化物の単位重量当りの酸素吸蔵能が向上するため、触媒体格の低減及び触媒圧損の低減が達成され、さらに、ＯＳＣ材の使用量も減少させることができるため、コストの面でも優れる。 In the composite oxide of the present invention, the composition ratio of Ce at the A site is 0.6 to 0.8, preferably 0.65 to 0.75. In the composite oxide of the present invention, the oxygen storage capacity per unit weight of the composite oxide is improved by setting the composition ratio of Ce at the A site to 0.6 to 0.8. Reduction in pressure loss is achieved, and furthermore, the amount of OSC material used can be reduced, which is excellent in terms of cost.
本発明の複合酸化物において、ＡサイトのＬａの組成比は、Ｃｅの組成比に対応して１．２〜１．４であり、好ましくは１．２５〜１．３５である。本発明の複合酸化物では、ＡサイトがＬａを含むことによって、規則相のパイロクロア相の耐久性が向上し、Ｃｅの利用率が向上する。 In the composite oxide of the present invention, the composition ratio of La at the A site is 1.2 to 1.4, preferably 1.25 to 1.35, corresponding to the composition ratio of Ce. In the composite oxide of the present invention, when the A site contains La, durability of the ordered pyrochlore phase is improved, and Ce utilization is improved.
本発明の複合酸化物において、Ｚｒを含むＢサイトの組成比は２である。ＢサイトはＺｒ以外の金属元素を含むこともできる。Ｚｒ以外の金属元素としては、Ｔｉ、Ｆｅ、Ｙ、Ｎｂ、Ｈｆ等を挙げることができる。 In the composite oxide of the present invention, the composition ratio of the B site containing Zr is 2. The B site can also contain a metal element other than Zr. Examples of metal elements other than Zr include Ti, Fe, Y, Nb, and Hf.
本発明の複合酸化物は、好ましくは、式ＣｅｘＬａ２−ｘＺｒ２Ｏ７（式中、ｘは０．６〜０．８であり、好ましくは０．６５〜０．７５である）で表されるパイロクロア構造を有する複合酸化物である。 The composite oxide of the present invention preferably has the formula Ce x La 2-x Zr 2 O 7 (wherein x is 0.6 to 0.8, preferably 0.65 to 0.75). A composite oxide having a pyrochlore structure represented by
本発明の複合酸化物は、上記のＣｅ及びＬａの組成比とすることにより、Ｌａの置換量の増大に伴い、規則相のパイロクロア相の耐久性が向上し、Ｃｅ利用率が向上して酸素吸蔵能が向上する効果と、Ｌａ置換量の増大に伴い、単位重量当りのＣｅ量が減少し、酸素吸蔵能が低下する影響とのバランスが最適化されている。これによって、本発明の複合酸化物は、Ｃｅ及びＬａの組成比がこの範囲にない複合酸化物と比較して、単位重量当りの酸素吸蔵能が優れる。 By setting the composition ratio of Ce and La in the composite oxide of the present invention, the durability of the ordered pyrochlore phase is improved as the amount of substitution of La is increased, and the Ce utilization rate is improved. The balance between the effect of improving the storage capacity and the effect of decreasing the amount of Ce per unit weight and decreasing the oxygen storage capacity as the La substitution amount increases is optimized. As a result, the composite oxide of the present invention is superior in oxygen storage capacity per unit weight as compared with a composite oxide in which the composition ratio of Ce and La is not in this range.
ここで、本発明の複合酸化物において、Ｌａの置換量が増大することにより規則相のパイロクロア相の耐久性が向上するのは、（１）３価のＬａが置換固溶することにより、κ相でも酸素欠陥が生じ、Ｃｅ、Ｚｒサイトの酸素配位数に差が生じるため、（２）Ｃｅサイトにイオンサイズの大きい３価のＬａが置換することによるため、（３）安定相であるＬａ２Ｚｒ２Ｏ７に組成が近づくため等の理由が可能性として考えられる。 Here, in the composite oxide of the present invention, the durability of the ordered pyrochlore phase is improved by increasing the substitution amount of La. (1) The trivalent La is substituted and dissolved, and κ Oxygen vacancies also occur in the phase, resulting in a difference in the number of oxygen coordination at the Ce and Zr sites. (2) Since trivalent La having a large ion size is substituted at the Ce site, (3) a stable phase A possible reason is that the composition is close to La 2 Zr 2 O 7 .
本発明の複合酸化物は、幅広い温度範囲にわたって優れた酸素吸蔵能を発揮することができるが、好ましくは、３５０℃〜５５０℃程度の低・中温域で用いられる。 The composite oxide of the present invention can exhibit excellent oxygen storage capacity over a wide temperature range, but is preferably used in a low / medium temperature range of about 350 ° C. to 550 ° C.
本発明のパイロクロア構造を有する複合酸化物は、固相法、液相法、アルコキシド法等の通常の方法で製造することができる。例えば、本発明の複合酸化物は、セリウム化合物、ジルコニウム化合物及びランタン化合物の水溶液と、錯形成剤の水溶液とを混合し、乾燥してＣｅ、Ｌａ及びＺｒを含む生成物を析出させた後、還元性雰囲気にて焼成を行うことによって製造される。セリウム化合物、ジルコニウム化合物及びランタン化合物は、非水溶剤、例えば、アルコールや有機カルボン酸エステルの溶液として用いることもできる。 The composite oxide having a pyrochlore structure of the present invention can be produced by a usual method such as a solid phase method, a liquid phase method, or an alkoxide method. For example, in the composite oxide of the present invention, an aqueous solution of a cerium compound, a zirconium compound and a lanthanum compound and an aqueous solution of a complexing agent are mixed and dried to precipitate a product containing Ce, La and Zr. Manufactured by firing in a reducing atmosphere. A cerium compound, a zirconium compound, and a lanthanum compound can also be used as a solution of a non-aqueous solvent, for example, an alcohol or an organic carboxylic acid ester.
セリウム化合物としては、例えば、硝酸セリウム、硝酸二アンモニウムセリウム等の硝酸塩、硫酸セリウム等の硫酸塩、塩化セリウム等の塩化物等の水溶性化合物を用いることができる。また、ジルコニウム化合物としては、オキシ硝酸ジルコニウム等の硝酸塩、硫酸ジルコニウム等の硫酸塩、オキシ塩化ジルコニウム等の塩化物等の水溶性化合物を用いることができる。また、ランタン化合物としては硝酸ランタン等の硝酸塩、硫酸ランタン等の硫酸塩、塩化ランタン等の塩化物等の水溶性化合物を用いることができる。 Examples of the cerium compound include water-soluble compounds such as nitrates such as cerium nitrate and diammonium cerium nitrate, sulfates such as cerium sulfate, and chlorides such as cerium chloride. Further, as the zirconium compound, water-soluble compounds such as nitrates such as zirconium oxynitrate, sulfates such as zirconium sulfate, and chlorides such as zirconium oxychloride can be used. As the lanthanum compound, water-soluble compounds such as nitrates such as lanthanum nitrate, sulfates such as lanthanum sulfate, and chlorides such as lanthanum chloride can be used.
錯形成剤としては、特に限定されずに、例えば、有機カルボン酸、有機スルホン酸、β−ジケトン、シクロポリエン、アルコール等を挙げることができる。有機カルボン酸としては、例えば、ギ酸、酢酸、プロピオン酸、シュウ酸、マロン酸、コハク酸、グルタル酸、アジピン酸、マレイン酸、クエン酸、酒石酸、アミノ酢酸等を挙げることができるが、クエン酸が好ましい。有機スルホン酸としては、例えば、ベンゼンスルホン酸やｐ−トルエンスルホン酸等を挙げることができる。β−ジケトンとしては、例えば、アセチルアセトン等を挙げることができる。シクロポリエンとしては、例えば、シクロオクタテトラエンやシクロペンタジエン等を挙げることができる。アルコールとしては、例えば、ブチルアルコールのようなアルキルアルコールを挙げることができる。 The complexing agent is not particularly limited, and examples thereof include organic carboxylic acids, organic sulfonic acids, β-diketones, cyclopolyenes, alcohols and the like. Examples of the organic carboxylic acid include formic acid, acetic acid, propionic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, citric acid, tartaric acid, aminoacetic acid and the like. Is preferred. Examples of the organic sulfonic acid include benzenesulfonic acid and p-toluenesulfonic acid. Examples of β-diketone include acetylacetone. Examples of cyclopolyene include cyclooctatetraene and cyclopentadiene. Examples of the alcohol include alkyl alcohols such as butyl alcohol.
セリウム化合物、ジルコニウム化合物及びランタン化合物の水溶液と、錯形成剤の水溶液との混合により沈殿物が生成した場合には、この沈殿物をろ過した後に乾燥してもよい。 When a precipitate is formed by mixing an aqueous solution of a cerium compound, a zirconium compound and a lanthanum compound and an aqueous solution of a complexing agent, the precipitate may be filtered and dried.
セリウム化合物、ジルコニウム化合物及びランタン化合物の水溶液と、錯形成剤の水溶液との混合溶液の乾燥は、通常、５０℃〜８０℃で５時間〜４８時間行うことができる。 Drying of a mixed solution of an aqueous solution of a cerium compound, a zirconium compound and a lanthanum compound and an aqueous solution of a complexing agent can be usually performed at 50 to 80 ° C. for 5 to 48 hours.
Ｃｅ、Ｌａ及びＺｒを含む生成物の焼成は、通常、還元性雰囲気下にて、６００℃〜１５００℃で２時間〜１０時間加熱保持することで行うことができる。還元性雰囲気は不活性ガス雰囲気又は非酸化性雰囲気とすることもできるが、Ｈ２、ＣＯ等の還元性ガスを含む雰囲気とすることが好ましい。 Calcination of the product containing Ce, La and Zr can be usually performed by heating and holding at 600 ° C. to 1500 ° C. for 2 hours to 10 hours in a reducing atmosphere. The reducing atmosphere can be an inert gas atmosphere or a non-oxidizing atmosphere, but is preferably an atmosphere containing a reducing gas such as H 2 or CO.
パイロクロア構造を有する複合酸化物は、大気中や酸素雰囲気等の酸化雰囲気下で５００℃〜１０００℃で１時間〜１０時間保持することにより、Ｃｅの価数が４価になったκ相の複合酸化物にすることができる。 The composite oxide having a pyrochlore structure is a composite of κ phase in which the valence of Ce becomes tetravalent by holding at 500 ° C. to 1000 ° C. for 1 hour to 10 hours in an oxidizing atmosphere such as air or an oxygen atmosphere. It can be an oxide.
本発明の複合酸化物は、自らを担体として貴金属を担持することにより、自動車等の排ガス浄化用触媒とすることができる。よって本発明は、上記複合酸化物に貴金属を担持した排ガス浄化用触媒にも関する。本発明の排ガス浄化用触媒は、主触媒として白金族貴金属を含むことが好ましい。白金族貴金属としては、ルテニウム(Ｒｕ)、ロジウム(Ｒｈ)、パラジウム(Ｐｄ)、オスミウム(Ｏｓ)、イリジウム(Ｉｒ)及び白金(Ｐｔ)が挙げられ、特にＲｈ、Ｐｔ及びＰｄを用いることが好ましい。その担持量は従来の排ガス浄化用触媒と同様でよいが、排ガス浄化用触媒に対して０．０１重量％〜５重量％であることが好ましい。本発明の排ガス浄化用触媒は、担体として本発明の複合酸化物以外の担体材料を含んでいてもよい。本発明の複合酸化物以外の担体材料としては、多孔質であり、かつ、耐熱性に優れた金属酸化物が挙げられ、例えば、酸化アルミニウム（アルミナ：Ａｌ２Ｏ３）、酸化ジルコニウム（ジルコニア：ＺｒＯ２）、酸化ケイ素（シリカ：ＳｉＯ２）、又はこれらの金属酸化物を主成分とした複合酸化物等を用いることができる。本発明の排ガス浄化用触媒において、担持方法は、吸着担持法、吸水担持法等従来の担持法を利用することができる。 The composite oxide of the present invention can be used as an exhaust gas purifying catalyst for automobiles or the like by supporting a noble metal by itself as a carrier. Therefore, the present invention also relates to an exhaust gas purification catalyst in which a noble metal is supported on the composite oxide. The exhaust gas purifying catalyst of the present invention preferably contains a platinum group noble metal as a main catalyst. Examples of the platinum group noble metal include ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), and platinum (Pt), and it is particularly preferable to use Rh, Pt, and Pd. . The supported amount may be the same as that of the conventional exhaust gas purifying catalyst, but is preferably 0.01% by weight to 5% by weight with respect to the exhaust gas purifying catalyst. The exhaust gas purifying catalyst of the present invention may contain a support material other than the composite oxide of the present invention as a support. Examples of the carrier material other than the composite oxide of the present invention include metal oxides that are porous and have excellent heat resistance. For example, aluminum oxide (alumina: Al 2 O 3 ), zirconium oxide (zirconia: ZrO 2 ), silicon oxide (silica: SiO 2 ), or composite oxides mainly composed of these metal oxides can be used. In the exhaust gas purifying catalyst of the present invention, a conventional supporting method such as an adsorption supporting method or a water absorbing supporting method can be used as the supporting method.
以下、実施例を用いて本発明をさらに具体的に説明する。但し、本発明の技術的範囲はこれら実施例に限定されるものではない。 Hereinafter, the present invention will be described more specifically with reference to examples. However, the technical scope of the present invention is not limited to these examples.
（実施例１）
Ｃｅ０．７Ｌａ１．３Ｚｒ２Ｏ７．３５（κ相）の調製
硝酸二アンモニウムセリウム（ＩＶ）７ｍｍｏｌ／純水５ｍｌ、オキシ硝酸ジルコニウム２０ｍｍｏｌ／純水１０ｍｌ及び硝酸ランタン１３ｍｍｏｌ／純水１０ｍｌの各水溶液を調製し、これらの水溶液を混合し、撹拌した。クエン酸４０ｍｍｏｌ／純水１０ｍｌの水溶液を調製し、調製したクエン酸溶液に、上記のＣｅ塩、Ｚｒ塩及びＬａ塩の混合溶液を加え、３００ｒｐｍで３０分間撹拌した。撹拌中に、この溶液を約６０℃で加熱し、水分を蒸発させた。この溶液の粘性が高くなり、撹拌子の回転数に乱れが出てきたのを確認した後、溶液を真空乾燥器に移し、６０℃で１晩真空乾燥した。乾燥して析出した生成物を粉砕した後、これをガラス容器に移し、ホットプレート上で加熱した。加熱は、１５０℃から開始し、１０℃ずつ昇温して、硝酸塩が分解するまで昇温した（本試料は１９０℃で分解した）。得られたＣｅ、Ｚｒ及びＬａを含む生成物を電気炉にて６００℃で５時間焼成し、Ｃｅ、Ｚｒ及びＬａの複合酸化物を得た。得られた複合酸化物を管状路に移し、５％Ｈ２／Ａｒバランスガスを流速１Ｌ／分で２時間流通させた。その後、５％Ｈ２／Ａｒバランスガスを流速３００ｍＬ／分で流しながら、電気炉を室温から１３００℃まで２時間１０分かけて昇温し、１３００℃で３時間保持して複合酸化物を焼成した。その後、熱源を切り、自然放熱させて、式Ｃｅ０．７Ｌａ１．３Ｚｒ２Ｏ７で表されるパイロクロア相の複合酸化物を得た。パイロクロア相の複合酸化物の一部をＸＲＤ分析に供試し、初期のパイロクロア相の複合酸化物の回折パターンを測定した。
Example 1
Preparation of Ce 0.7 La 1.3 Zr 2 O 7.35 (κ phase) Diammonium cerium (IV) nitrate 7 mmol / pure water 5 ml, zirconium oxynitrate 20 mmol / pure water 10 ml and lanthanum nitrate 13 mmol / pure water 10 ml Each aqueous solution was prepared, and these aqueous solutions were mixed and stirred. An aqueous solution of citric acid 40 mmol / pure water 10 ml was prepared, and the mixed solution of the Ce salt, Zr salt and La salt was added to the prepared citric acid solution, and the mixture was stirred at 300 rpm for 30 minutes. While stirring, the solution was heated at about 60 ° C. to evaporate the water. After confirming that the viscosity of the solution became high and the rotational speed of the stirring bar was disturbed, the solution was transferred to a vacuum dryer and vacuum-dried at 60 ° C. overnight. The dried and precipitated product was pulverized and then transferred to a glass container and heated on a hot plate. Heating was started at 150 ° C., and the temperature was increased by 10 ° C. until the nitrate was decomposed (this sample decomposed at 190 ° C.). The obtained product containing Ce, Zr and La was baked in an electric furnace at 600 ° C. for 5 hours to obtain a composite oxide of Ce, Zr and La. The obtained composite oxide was transferred to a tubular channel, and 5% H 2 / Ar balance gas was circulated at a flow rate of 1 L / min for 2 hours. Then, while flowing 5% H 2 / Ar balance gas at a flow rate of 300 mL / min, the electric furnace was heated from room temperature to 1300 ° C. over 2 hours and 10 minutes and held at 1300 ° C. for 3 hours to sinter the composite oxide did. Thereafter, the heat source was turned off and naturally dissipated to obtain a composite oxide of a pyrochlore phase represented by the formula Ce 0.7 La 1.3 Zr 2 O 7 . A part of the pyrochlore phase composite oxide was subjected to XRD analysis, and the diffraction pattern of the initial pyrochlore phase composite oxide was measured.
得られたパイロクロア相の複合酸化物を電気炉にて、大気中、５５０℃で２時間焼成して、式Ｃｅ０．７Ｌａ１．３Ｚｒ２Ｏ７．３５で表されるκ相の複合酸化物を得た。κ相の複合酸化物の一部をＸＲＤ分析に供試し、初期のκ相の複合酸化物の回折パターンを測定した。また、κ相の複合酸化物を空気中、１０００℃で５時間耐久し、この耐久品についてＸＲＤ分析及びＯＳＣ測定を実施した。 The obtained pyrochlore phase composite oxide was baked in an electric furnace in the atmosphere at 550 ° C. for 2 hours to form a composite of κ phase represented by the formula Ce 0.7 La 1.3 Zr 2 O 7.35. An oxide was obtained. A part of the κ-phase composite oxide was subjected to XRD analysis, and the diffraction pattern of the initial κ-phase composite oxide was measured. In addition, the composite oxide of κ phase was durable in air at 1000 ° C. for 5 hours, and XRD analysis and OSC measurement were performed on this durable product.
（実施例２）
Ｃｅ０．８Ｌａ１．２Ｚｒ２Ｏ７．４（κ相）の調製
金属塩の使用量を、硝酸二アンモニウムセリウム（ＩＶ）７ｍｍｏｌ、オキシ硝酸ジルコニウム２０ｍｍｏｌ及び硝酸ランタン１３ｍｍｏｌから、硝酸二アンモニウムセリウム（ＩＶ）８ｍｍｏｌ、オキシ硝酸ジルコニウム２０ｍｍｏｌ及び硝酸ランタン１２ｍｍｏｌとした以外は実施例１と同様にして、式Ｃｅ０．８Ｌａ１．２Ｚｒ２Ｏ７で表されるパイロクロア相の複合酸化物及び式Ｃｅ０．８Ｌａ１．２Ｚｒ２Ｏ７．４で表されるκ相の複合酸化物を得て、各々ＸＲＤ分析を行い、また、得られたκ相の複合酸化物を空気中、１０００℃で５時間耐久し、この耐久品についてＸＲＤ分析及びＯＳＣ測定を実施した。
(Example 2)
Preparation of Ce 0.8 La 1.2 Zr 2 O 7.4 (κ phase) The amount of metal salt used was changed from 7 mmol of diammonium cerium (IV) nitrate, 20 mmol of zirconium oxynitrate and 13 mmol of lanthanum nitrate to diammonium cerium nitrate. (IV) Pyrochlore phase complex oxide and formula represented by the formula Ce 0.8 La 1.2 Zr 2 O 7 in the same manner as in Example 1 except that 8 mmol, zirconium oxynitrate 20 mmol and lanthanum nitrate 12 mmol were used. A composite oxide of κ phase represented by Ce 0.8 La 1.2 Zr 2 O 7.4 was obtained, each was subjected to XRD analysis, and the obtained composite oxide of κ phase was 1000 in the air. Durability was performed at 5 ° C. for 5 hours, and XRD analysis and OSC measurement were performed on the durable product.
（比較例１）
Ｃｅ２Ｚｒ２Ｏ８（κ相）の調製
金属塩の使用量を、硝酸二アンモニウムセリウム（ＩＶ）７ｍｍｏｌ、オキシ硝酸ジルコニウム２０ｍｍｏｌ及び硝酸ランタン１３ｍｍｏｌから、硝酸二アンモニウムセリウム（ＩＶ）２０ｍｍｏｌ、オキシ硝酸ジルコニウム２０ｍｍｏｌとした以外は実施例１と同様にして、式Ｃｅ２Ｚｒ２Ｏ７で表されるパイロクロア相の複合酸化物及び式Ｃｅ２Ｚｒ２Ｏ８で表されるκ相の複合酸化物を得て、各々ＸＲＤ分析を行い、また、得られたκ相の複合酸化物を空気中、１０００℃で５時間耐久し、この耐久品についてＸＲＤ分析及びＯＳＣ測定を実施した。
(Comparative Example 1)
Preparation of Ce 2 Zr 2 O 8 (κ phase) The amount of metal salt used was 7 mmol of diammonium cerium (IV) nitrate, 20 mmol of zirconium oxynitrate and 13 mmol of lanthanum nitrate, 20 mmol of diammonium cerium (IV) nitrate, zirconium oxynitrate A composite oxide of a pyrochlore phase represented by the formula Ce 2 Zr 2 O 7 and a composite oxide of a κ phase represented by the formula Ce 2 Zr 2 O 8 were obtained in the same manner as in Example 1 except that the amount was 20 mmol. Then, XRD analysis was performed, and the obtained composite oxide of κ phase was durable in air at 1000 ° C. for 5 hours, and XRD analysis and OSC measurement were performed on this durable product.
（比較例２）
ＣｅＬａＺｒ２Ｏ７．５（κ相）の調製
金属塩の使用量を、硝酸二アンモニウムセリウム（ＩＶ）７ｍｍｏｌ、オキシ硝酸ジルコニウム２０ｍｍｏｌ及び硝酸ランタン１３ｍｍｏｌから、硝酸二アンモニウムセリウム（ＩＶ）１０ｍｍｏｌ、オキシ硝酸ジルコニウム２０ｍｍｏｌ及び硝酸ランタン１０ｍｍｏｌとした以外は実施例１と同様にして、式ＣｅＬａＺｒ２Ｏ７で表されるパイロクロア相の複合酸化物及び式ＣｅＬａＺｒ２Ｏ７．５で表されるκ相の複合酸化物を得て、各々ＸＲＤ分析を行い、また、得られたκ相の複合酸化物を空気中、１０００℃で５時間耐久し、この耐久品についてＸＲＤ分析及びＯＳＣ測定を実施した。
(Comparative Example 2)
Preparation of CeLaZr 2 O 7.5 (κ phase) The amount of metal salt used was 7 mmol of diammonium cerium (IV) nitrate, 20 mmol of zirconium oxynitrate and 13 mmol of lanthanum nitrate, 10 mmol of diammonium cerium (IV) nitrate, zirconium oxynitrate A composite oxide of pyrochlore phase represented by the formula CeLaZr 2 O 7 and a composite oxide of κ phase represented by the formula CeLaZr 2 O 7.5 are the same as in Example 1 except that 20 mmol and 10 mmol of lanthanum nitrate were used. Each was subjected to XRD analysis, and the obtained composite oxide of κ phase was durable in air at 1000 ° C. for 5 hours, and XRD analysis and OSC measurement were performed on this durable product.
（比較例３）
Ｃｅ０．５Ｌａ１．５Ｚｒ２Ｏ７．２５（κ相）の調製
金属塩の使用量を、硝酸二アンモニウムセリウム（ＩＶ）７ｍｍｏｌ、オキシ硝酸ジルコニウム２０ｍｍｏｌ及び硝酸ランタン１３ｍｍｏｌから、硝酸二アンモニウムセリウム（ＩＶ）５ｍｍｏｌ、オキシ硝酸ジルコニウム２０ｍｍｏｌ及び硝酸ランタン１５ｍｍｏｌとした以外は実施例１と同様にして、式Ｃｅ０．５Ｌａ１．５Ｚｒ２Ｏ７で表されるパイロクロア相の複合酸化物及び式Ｃｅ０．５Ｌａ１．５Ｚｒ２Ｏ７．２５で表されるκ相の複合酸化物を得て、各々ＸＲＤ分析を行い、また、得られたκ相の複合酸化物を空気中、１０００℃で５時間耐久し、この耐久品についてＸＲＤ分析及びＯＳＣ測定を実施した。
(Comparative Example 3)
Preparation of Ce 0.5 La 1.5 Zr 2 O 7.25 (κ phase) The amount of the metal salt was changed from 7 mmol of diammonium cerium (IV) nitrate, 20 mmol of zirconium oxynitrate and 13 mmol of lanthanum nitrate to diammonium cerium nitrate. (IV) Pyrochlore phase composite oxide and formula represented by the formula Ce 0.5 La 1.5 Zr 2 O 7 in the same manner as in Example 1 except that 5 mmol, zirconium oxynitrate 20 mmol and lanthanum nitrate 15 mmol were used. A composite oxide of κ phase represented by Ce 0.5 La 1.5 Zr 2 O 7.25 was obtained, each was subjected to XRD analysis, and the obtained composite oxide of κ phase was 1000 in the air. Durability was performed at 5 ° C. for 5 hours, and XRD analysis and OSC measurement were performed on the durable product.
（比較例４）
Ｌａ２Ｚｒ２Ｏ７（パイロクロア相）の調製
金属塩の使用量を、硝酸二アンモニウムセリウム（ＩＶ）７ｍｍｏｌ、オキシ硝酸ジルコニウム２０ｍｍｏｌ及び硝酸ランタン１３ｍｍｏｌから、オキシ硝酸ジルコニウム２０ｍｍｏｌ及び硝酸ランタン２０ｍｍｏｌとした以外は実施例１と同様にして、式Ｌａ２Ｚｒ２Ｏ７で表されるパイロクロア相の複合酸化物を得て、初期品及び空気中、１０００℃で５時間耐久した耐久品について、ＸＲＤ分析及びＯＳＣ測定を実施した。比較例４の複合酸化物は酸素吸蔵能を有していないが、パイロクロア相の耐久性の比較試料とした。
(Comparative Example 4)
Preparation of La 2 Zr 2 O 7 (pyrochlore phase) The amount of metal salt used was changed from 7 mmol of diammonium cerium (IV) nitrate, 20 mmol of zirconium oxynitrate and 13 mmol of lanthanum nitrate to 20 mmol of zirconium oxynitrate and 20 mmol of lanthanum nitrate. In the same manner as in Example 1, a pyrochlore phase composite oxide represented by the formula La 2 Zr 2 O 7 was obtained, and XRD analysis and OSC were performed on the initial product and the durable product that was durable in air at 1000 ° C. for 5 hours. Measurements were performed. The composite oxide of Comparative Example 4 did not have oxygen storage capacity, but was used as a comparative sample for durability of the pyrochlore phase.
実施例１、２及び比較例１−４の複合酸化物のＣｅ、Ｌａ、Ｚｒ組成分析は下記のＮａ２Ｏ２溶融−ＩＣＰ分析法で実施した。 The Ce, La, and Zr composition analyzes of the composite oxides of Examples 1 and 2 and Comparative Example 1-4 were performed by the following Na 2 O 2 melting-ICP analysis method.
［Ｃｅ、Ｌａ、Ｚｒ組成分析］
試料０．１ｇを秤量し、融解剤のＮａ２Ｏ２ ２ｇを試料に加え、４００℃に加熱した電気炉に入れた。電気炉を昇温し、試料を８００℃で３０分間加熱して溶融させた。得られた溶融物をビーカーに移し、ＨＣｌ（１＋１）４０ｍｌを添加し、ヒーター上で加熱溶解させた。これを１００ｍｌに定容し、ＩＣＰ分析を行った。ＩＣＰ分析は３回行った。
[Ce, La, Zr composition analysis]
A 0.1 g sample was weighed and 2 g of the melting agent Na 2 O 2 was added to the sample and placed in an electric furnace heated to 400 ° C. The electric furnace was heated and the sample was heated at 800 ° C. for 30 minutes to melt. The obtained melt was transferred to a beaker, 40 ml of HCl (1 + 1) was added, and the mixture was heated and dissolved on a heater. The volume was adjusted to 100 ml and ICP analysis was performed. ICP analysis was performed three times.
（試験例１）
実施例１、２、比較例１−３のκ相及び比較例４のパイロクロア相の複合酸化物の初期品及び耐久品（空気中、１０００℃で５時間耐久）のＸＲＤ分析を行った。複合酸化物（κ相）のＸＲＤパターンにおいて、２θ＝１４°付近の（１１１）面に帰属する回折線は、規則相の倍周期を表す回折線の一つである。測定した各試料のＸＲＤパターンにおいて、規則相（κ相）の（１１１）面に帰属する回折線である２θ＝１４°付近の回折線の強度の、規則相の（２２２）面に帰属する回折線である２θ＝２９°付近の回折線の強度に対する比（（１１１）回折線の強度／（２２２）回折線の強度）をＩ値として算出した。Ｉ値は規則相の耐久性（維持率）を示す指標とすることができる。結果を表１及び図１に示す。
(Test Example 1)
The XRD analysis of the initial product and durable product (durability in air at 1000 ° C. for 5 hours) of the composite oxides of the κ phase of Examples 1 and 2 and Comparative Example 1-3 and the pyrochlore phase of Comparative Example 4 was performed. In the XRD pattern of the complex oxide (κ phase), the diffraction line belonging to the (111) plane near 2θ = 14 ° is one of the diffraction lines representing the double period of the regular phase. In the measured XRD pattern of each sample, the diffraction attributed to the (222) plane of the ordered phase having the intensity of the diffraction line near 2θ = 14 °, which is the diffraction line attributed to the (111) plane of the ordered phase (κ phase). A ratio ((111) diffraction line intensity / (222) diffraction line intensity) to the intensity of the diffraction line near 2θ = 29 °, which is a line, was calculated as an I value. The I value can be used as an index indicating the durability (maintenance rate) of the ordered phase. The results are shown in Table 1 and FIG.
表１及び図１より、実施例１、２の複合酸化物の耐久後のＩ値は、比較例１、２のものより大きいが、比較例３、４のものより小さかったことが示された。また、Ｌａの置換量の増加とともに、耐久後のＩ値が増大し、規則相が維持されるが、Ｌａ＝１．５（比較例３）以上ではほぼ一定のＩ値となることが示された。 From Table 1 and FIG. 1, it was shown that the I value after durability of the composite oxides of Examples 1 and 2 was larger than that of Comparative Examples 1 and 2, but smaller than that of Comparative Examples 3 and 4. . Further, as the substitution amount of La increases, the post-endurance I value increases and the ordered phase is maintained, but it is shown that the La value is almost constant at La = 1.5 (Comparative Example 3) or more. It was.
また、Ｌａの置換量と、ＸＲＤパターンの（１１１）、（２２２）のｄ値間との関係が比例関係にあり、Ｖｅｇａｒｄ則が成立していたことから、ＬａがＣｅサイトに置換されていることが確認された。 In addition, since the relationship between the amount of substitution of La and the d values of (111) and (222) of the XRD pattern is proportional, and the Vegard rule is established, La is substituted for the Ce site. It was confirmed.
（試験例２）
実施例１、２及び比較例１−３のκ相の複合酸化物を排ガス浄化用触媒に用いて酸素吸蔵能（ＯＳＣ）を測定した。測定試料として、実施例１、２及び比較例１−３のκ相の複合酸化物の耐久品１ｇと、１重量％Ｐｔ／Ａｌ２Ｏ３（Ａｌ２Ｏ３の比表面積（ＳＳＡ）：１００ｍ２／ｇ）１ｇとを物理的に混合したもの２ｇを用いた。
(Test Example 2)
The oxygen storage capacity (OSC) was measured using the κ-phase composite oxides of Examples 1 and 2 and Comparative Example 1-3 as exhaust gas purifying catalysts. As a measurement sample, 1 g of the composite oxide of κ phase of Examples 1 and 2 and Comparative Example 1-3 and 1 wt% Pt / Al 2 O 3 (specific surface area (SSA) of Al 2 O 3 : 100 m) 2 / g) 2 g of 1 g physically mixed was used.
測定条件は下記の通りである：
測定ガス流量：１０Ｌ／分にて一酸化炭素（ＣＯ）２容量％のガス（バランスガスは窒素）と、酸素（Ｏ２）１容量％のガス（バランスガスは窒素）を２分間サイクルで３回パルス導入させた。
測定温度：４００℃、５００℃
ＯＳＣデータ：３回目のＣＯガスのパルス導入時に、２分間のＣＯ２生成量から吸蔵されたＯ２分子のｍｏｌ数を計算し、ＯＳＣとした。
The measurement conditions are as follows:
Measurement gas flow rate: Carbon dioxide (CO) 2 volume% gas (balance gas is nitrogen) and oxygen (O 2 ) 1 volume% gas (balance gas is nitrogen) at a rate of 10 L / min. The pulse was introduced twice.
Measurement temperature: 400 ° C, 500 ° C
OSC data: At the time of introducing the third CO gas pulse, the number of moles of O 2 molecules occluded was calculated from the amount of CO 2 produced for 2 minutes and used as OSC.
耐久後の複合酸化物１ｇ当りのＯＳＣを表２及び図２に示す。
表２及び図２より、実施例１、２の複合酸化物を用いた排ガス浄化用触媒は、４００℃、５００℃のいずれの温度においても、ＯＳＣ材（複合酸化物）１ｇ当りの２分間のＯＳＣが優れていた。 From Table 2 and FIG. 2, the exhaust gas purifying catalyst using the composite oxides of Examples 1 and 2 is 2 minutes per gram of OSC material (composite oxide) at both 400 ° C. and 500 ° C. OSC was excellent.
次に、式ＣｅｘＬａ２−ｘＺｒ２Ｏ７で表される複合酸化物のＣｅ量と耐久後の単位重量当りの酸素吸蔵能との関係を下記のようにして求めた。 Next, the relationship between the Ce content of the composite oxide represented by the formula Ce x La 2 -x Zr 2 O 7 and the oxygen storage capacity per unit weight after durability was determined as follows.
複合酸化物の耐久後の単位重量当りのＯＳＣは、下記式（Ｉ）：
耐久後の単位重量当りのＯＳＣ＝Ｃｅ利用率×ＯＳＣ理論値 （Ｉ）
で表される。
The OSC per unit weight after durability of the composite oxide is represented by the following formula (I):
OSC per unit weight after endurance = Ce utilization factor x OSC theoretical value (I)
It is represented by
まず、Ｃｅ利用率を耐久後のＩ値に対する関係式として求めた。Ｉ値は規則相の維持率の程度を示す。 First, the Ce utilization was determined as a relational expression for the I value after durability. The I value indicates the degree of regular phase maintenance rate.
実施例１、２及び比較例１−３の複合酸化物のＣｅ利用率について、各試料の複合酸化物１ｇ当りのＯＳＣ理論値（Ｃｅが１００％ＯＳＣに使用された場合のＯＳＣ）を計算し、ＯＳＣ実測値（４００℃、５００℃）の理論値に対する割合（実測値／理論値）を算出することで求めた。結果を表３に示す。 Regarding the Ce utilization ratio of the composite oxides of Examples 1 and 2 and Comparative Example 1-3, the theoretical value of OSC per gram of composite oxide of each sample (OSC when Ce was used for 100% OSC) was calculated. The ratio (actual value / theoretical value) of the OSC actual value (400 ° C., 500 ° C.) to the theoretical value was calculated. The results are shown in Table 3.
各試料の耐久後のＩ値とＣｅ利用率との関係を図３に示す。図３より、Ｉ値とＣｅ利用率は比例関係にあり、パイロクロア構造が維持されるとＣｅの利用率が高くなることが示された。これは、パイロクロア相には酸素欠陥が存在するので、Ｃｅの酸化・還元に伴う酸素の吸蔵・放出が容易に起こり、バルク内の拡散速度が速いためであると考えられる。 The relationship between the I value after the durability of each sample and the Ce utilization rate is shown in FIG. FIG. 3 shows that the I value and the Ce utilization rate are in a proportional relationship, and that the Ce utilization rate increases when the pyrochlore structure is maintained. This is considered to be because oxygen defects are present in the pyrochlore phase, so that oxygen is readily occluded / released due to the oxidation / reduction of Ce, and the diffusion rate in the bulk is high.
図３より、４００℃におけるＣｅ利用率は、下記式（ＩＩ）：
Ｃｅ利用率（ｙ）＝９．３７６８×Ｉ値（ｘ）−０．０２１７ （ＩＩ）
で表され、５００℃におけるＣｅ利用率は、下記式（ＩＩＩ）：
Ｃｅ利用率（ｙ）＝１５．６７１×Ｉ値（ｘ）＋０．００１２ （ＩＩＩ）
で表される。
From FIG. 3, the Ce utilization rate at 400 ° C. is represented by the following formula (II):
Ce utilization rate (y) = 9.3768 × I value (x) −0.0217 (II)
The Ce utilization at 500 ° C. is represented by the following formula (III):
Ce utilization rate (y) = 15.671 × I value (x) +0.0012 (III)
It is represented by
次に、耐久後のＩ値とＣｅ量の関係を図４に示す。図４より、耐久後のＩ値は、Ｃｅ量を変数とする下記指数関数式（ＩＶ）：
耐久後のＩ値（ｙ）＝０．０３９６ｅｘｐ（−１．１６２×ｘ） （ＩＶ）
で近似することができる。
Next, the relationship between the I value after endurance and the Ce amount is shown in FIG. From FIG. 4, the I value after endurance is the following exponential function formula (IV) with Ce amount as a variable:
I value after endurance (y) = 0.0396exp (−1.162 × x) (IV)
Can be approximated by
また、複合酸化物の単位重量当りのＯＳＣ理論値とＣｅ量の関係を図５に示す。図５より、ＯＳＣ理論値は下記式（Ｖ）：
ＯＳＣ理論値＝４２７．３２×ｘ＋３．３９４７ （Ｖ）
で表される。
FIG. 5 shows the relationship between the OSC theoretical value per unit weight of the composite oxide and the Ce amount. From FIG. 5, the OSC theoretical value is the following formula (V):
OSC theoretical value = 427.32 × x + 3.3947 (V)
It is represented by
式（Ｉ）の複合酸化物の耐久後の単位重量当りのＯＳＣは、式（ＩＩ）〜（Ｖ）から、
ＯＳＣ＝［ａ（０．０３９６ｅｘｐ（−１．１６２×ｘ）＋ｂ］×［４２７．３２×ｘ＋３．３９４７］
（ａ、ｂは、図３に示される４００℃、５００℃についての各式における係数である）
で表される。この式から計算した複合酸化物の耐久後の単位重量当りのＯＳＣと、Ｃｅ量との関係を、４００℃及び５００℃の各温度について図６に示す。図６より、Ｃｅ＝０．６〜０．８の組成比で、耐久後の単位重量当りのＯＳＣが優れており、特に、４００℃では、この範囲の組成比で単位重量当りのＯＳＣが最大となったことが示された。
The OSC per unit weight after endurance of the composite oxide of the formula (I) is calculated from the formulas (II) to (V):
OSC = [a (0.0396exp (−1.162 × x) + b] × [427.32 × x + 3.3947]
(A and b are coefficients in the respective equations for 400 ° C. and 500 ° C. shown in FIG. 3)
It is represented by FIG. 6 shows the relationship between the OSC per unit weight after endurance of the composite oxide calculated from this equation and the Ce amount at 400 ° C. and 500 ° C., respectively. From FIG. 6, the OSC per unit weight after endurance is excellent at a composition ratio of Ce = 0.6 to 0.8. Particularly, at 400 ° C., the OSC per unit weight is maximum at this composition ratio. It was shown that it became.
以上より、実施例１、２の複合酸化物は、比較例３、４のものと比較して、規則相の耐久性が劣るが、複合酸化物中のＣｅ量は多い。また、実施例１、２の複合酸化物は、比較例１、２のものと比較して、複合酸化物中のＣｅ量は少ないが、規則相の耐久性が高く、Ｃｅの利用率が高い。 As described above, the composite oxides of Examples 1 and 2 are inferior in the durability of the ordered phase as compared with those of Comparative Examples 3 and 4, but the amount of Ce in the composite oxide is large. In addition, the composite oxides of Examples 1 and 2 have less Ce content in the composite oxide than those of Comparative Examples 1 and 2, but the ordered phase has high durability and Ce utilization is high. .
実施例１、２の複合酸化物は、Ｃｅサイトの一部をＬａで置換することにより、規則相のパイロクロア相の耐久性が向上し、Ｃｅ利用率が向上して酸素吸蔵能が向上する効果と、Ｌａで置換することにより、単位重量当りのＣｅ量が減少し、酸素吸蔵能が低下する影響とのバランスが最適化されているため、比較例１−３のものと比べて、耐久後の単位重量当りのＯＳＣが最大となったと考えられる。 In the composite oxides of Examples 1 and 2, by replacing part of the Ce site with La, durability of the ordered pyrochlore phase is improved, Ce utilization is improved, and oxygen storage capacity is improved. And by replacing with La, the balance between the effect of reducing the amount of Ce per unit weight and reducing the oxygen storage capacity is optimized. It is considered that the OSC per unit weight became the maximum.
本発明の排ガス浄化用触媒を用いることにより、単位重量当りのＯＳＣ性能が向上した排ガス浄化用触媒を提供することが可能となる。 By using the exhaust gas purifying catalyst of the present invention, it is possible to provide an exhaust gas purifying catalyst having improved OSC performance per unit weight.
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