WO2012165362A1 - 複合酸化物、その製造法及び排ガス浄化用触媒 - Google Patents
複合酸化物、その製造法及び排ガス浄化用触媒 Download PDFInfo
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- WO2012165362A1 WO2012165362A1 PCT/JP2012/063586 JP2012063586W WO2012165362A1 WO 2012165362 A1 WO2012165362 A1 WO 2012165362A1 JP 2012063586 W JP2012063586 W JP 2012063586W WO 2012165362 A1 WO2012165362 A1 WO 2012165362A1
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- Prior art keywords
- cerium
- oxide
- mass
- precursor
- parts
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- 239000003054 catalyst Substances 0.000 title claims abstract description 24
- 238000004519 manufacturing process Methods 0.000 title abstract description 18
- 238000000746 purification Methods 0.000 title abstract description 9
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 122
- 230000009467 reduction Effects 0.000 claims abstract description 72
- 229910052761 rare earth metal Inorganic materials 0.000 claims abstract description 49
- 150000002910 rare earth metals Chemical class 0.000 claims abstract description 43
- 230000003647 oxidation Effects 0.000 claims abstract description 27
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 27
- 239000007789 gas Substances 0.000 claims abstract description 21
- 238000005259 measurement Methods 0.000 claims abstract description 14
- 239000012300 argon atmosphere Substances 0.000 claims abstract description 4
- 229910052684 Cerium Inorganic materials 0.000 claims description 139
- 239000002131 composite material Substances 0.000 claims description 130
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 123
- 229910052814 silicon oxide Inorganic materials 0.000 claims description 110
- 229910000420 cerium oxide Inorganic materials 0.000 claims description 100
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 claims description 100
- 238000000034 method Methods 0.000 claims description 93
- 239000002243 precursor Substances 0.000 claims description 89
- 239000000725 suspension Substances 0.000 claims description 69
- 238000010438 heat treatment Methods 0.000 claims description 54
- 239000002244 precipitate Substances 0.000 claims description 41
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 27
- 239000000047 product Substances 0.000 claims description 24
- 238000010304 firing Methods 0.000 claims description 23
- 238000001354 calcination Methods 0.000 claims description 20
- -1 cerium ions Chemical class 0.000 claims description 18
- 229910052710 silicon Inorganic materials 0.000 claims description 17
- 239000010703 silicon Substances 0.000 claims description 17
- 229910052727 yttrium Inorganic materials 0.000 claims description 15
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 claims description 15
- 230000001590 oxidative effect Effects 0.000 claims description 9
- 238000004438 BET method Methods 0.000 claims description 6
- 239000001257 hydrogen Substances 0.000 abstract description 14
- 229910052739 hydrogen Inorganic materials 0.000 abstract description 14
- 230000001747 exhibiting effect Effects 0.000 abstract description 3
- 229910052681 coesite Inorganic materials 0.000 abstract 1
- 229910052906 cristobalite Inorganic materials 0.000 abstract 1
- 125000004435 hydrogen atom Chemical class [H]* 0.000 abstract 1
- 239000000377 silicon dioxide Substances 0.000 abstract 1
- 229910052682 stishovite Inorganic materials 0.000 abstract 1
- 229910052905 tridymite Inorganic materials 0.000 abstract 1
- 239000000243 solution Substances 0.000 description 76
- MRELNEQAGSRDBK-UHFFFAOYSA-N lanthanum(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[La+3].[La+3] MRELNEQAGSRDBK-UHFFFAOYSA-N 0.000 description 74
- 239000000843 powder Substances 0.000 description 50
- 238000001816 cooling Methods 0.000 description 35
- MMKQUGHLEMYQSG-UHFFFAOYSA-N oxygen(2-);praseodymium(3+) Chemical compound [O-2].[O-2].[O-2].[Pr+3].[Pr+3] MMKQUGHLEMYQSG-UHFFFAOYSA-N 0.000 description 34
- 229910003447 praseodymium oxide Inorganic materials 0.000 description 34
- 239000012298 atmosphere Substances 0.000 description 33
- 230000000704 physical effect Effects 0.000 description 26
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 26
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 15
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 15
- 235000011114 ammonium hydroxide Nutrition 0.000 description 15
- 239000011148 porous material Substances 0.000 description 14
- 238000000926 separation method Methods 0.000 description 14
- 230000007423 decrease Effects 0.000 description 13
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 12
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 12
- 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 12
- 239000012452 mother liquor Substances 0.000 description 12
- 239000002002 slurry Substances 0.000 description 12
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 10
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 10
- 239000008119 colloidal silica Substances 0.000 description 10
- 239000003795 chemical substances by application Substances 0.000 description 9
- 239000007788 liquid Substances 0.000 description 9
- 230000001376 precipitating effect Effects 0.000 description 9
- 238000003756 stirring Methods 0.000 description 9
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 description 8
- 150000001875 compounds Chemical class 0.000 description 8
- 239000012065 filter cake Substances 0.000 description 8
- 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 8
- 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 8
- 238000001914 filtration Methods 0.000 description 7
- 238000002156 mixing Methods 0.000 description 7
- 238000010583 slow cooling Methods 0.000 description 7
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 6
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 6
- 238000001035 drying Methods 0.000 description 6
- 238000011049 filling Methods 0.000 description 6
- 229910052751 metal Inorganic materials 0.000 description 6
- 239000002184 metal Substances 0.000 description 6
- 239000000203 mixture Substances 0.000 description 6
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 6
- 238000001556 precipitation Methods 0.000 description 6
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 5
- 229910021193 La 2 O 3 Inorganic materials 0.000 description 5
- 239000007864 aqueous solution Substances 0.000 description 5
- 239000003426 co-catalyst Substances 0.000 description 5
- 239000002245 particle Substances 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- 229910002651 NO3 Inorganic materials 0.000 description 4
- 229910052779 Neodymium Inorganic materials 0.000 description 4
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 4
- 229910052777 Praseodymium Inorganic materials 0.000 description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- 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 4
- KKFPIBHAPSRIPB-UHFFFAOYSA-N cerium(3+);oxygen(2-);hydrate Chemical compound O.[O-2].[O-2].[O-2].[Ce+3].[Ce+3] KKFPIBHAPSRIPB-UHFFFAOYSA-N 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 239000012702 metal oxide precursor Substances 0.000 description 4
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 description 4
- PLDDOISOJJCEMH-UHFFFAOYSA-N neodymium(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Nd+3].[Nd+3] PLDDOISOJJCEMH-UHFFFAOYSA-N 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- PUDIUYLPXJFUGB-UHFFFAOYSA-N praseodymium atom Chemical compound [Pr] PUDIUYLPXJFUGB-UHFFFAOYSA-N 0.000 description 4
- 229910001404 rare earth metal oxide Inorganic materials 0.000 description 4
- 239000002904 solvent Substances 0.000 description 4
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 3
- 239000004115 Sodium Silicate Substances 0.000 description 3
- 229910052797 bismuth Inorganic materials 0.000 description 3
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 description 3
- 229910002091 carbon monoxide Inorganic materials 0.000 description 3
- 230000003197 catalytic effect Effects 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000010908 decantation Methods 0.000 description 3
- 238000001704 evaporation Methods 0.000 description 3
- 230000008020 evaporation Effects 0.000 description 3
- 239000000446 fuel Substances 0.000 description 3
- 150000002431 hydrogen Chemical class 0.000 description 3
- 229910052746 lanthanum Inorganic materials 0.000 description 3
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 3
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 3
- 230000033116 oxidation-reduction process Effects 0.000 description 3
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 3
- 150000003839 salts Chemical class 0.000 description 3
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 description 3
- 229910052911 sodium silicate Inorganic materials 0.000 description 3
- 238000001179 sorption measurement Methods 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- YZCKVEUIGOORGS-OUBTZVSYSA-N Deuterium Chemical compound [2H] YZCKVEUIGOORGS-OUBTZVSYSA-N 0.000 description 2
- 229910052692 Dysprosium Inorganic materials 0.000 description 2
- 229910052691 Erbium Inorganic materials 0.000 description 2
- 229910052693 Europium Inorganic materials 0.000 description 2
- 229910052688 Gadolinium Inorganic materials 0.000 description 2
- 229910052689 Holmium Inorganic materials 0.000 description 2
- 229910052765 Lutetium Inorganic materials 0.000 description 2
- 229910017493 Nd 2 O 3 Inorganic materials 0.000 description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 description 2
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 description 2
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 2
- 229910052772 Samarium Inorganic materials 0.000 description 2
- 229910052771 Terbium Inorganic materials 0.000 description 2
- 229910052775 Thulium Inorganic materials 0.000 description 2
- 229910052769 Ytterbium Inorganic materials 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000007664 blowing Methods 0.000 description 2
- 150000001785 cerium compounds Chemical class 0.000 description 2
- JIHMVMRETUQLFD-UHFFFAOYSA-N cerium(3+);dioxido(oxo)silane Chemical compound [Ce+3].[Ce+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O.[O-][Si]([O-])=O JIHMVMRETUQLFD-UHFFFAOYSA-N 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 239000008367 deionised water Substances 0.000 description 2
- 229910021641 deionized water Inorganic materials 0.000 description 2
- 238000003795 desorption Methods 0.000 description 2
- 229910052805 deuterium Inorganic materials 0.000 description 2
- KBQHZAAAGSGFKK-UHFFFAOYSA-N dysprosium atom Chemical compound [Dy] KBQHZAAAGSGFKK-UHFFFAOYSA-N 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- UYAHIZSMUZPPFV-UHFFFAOYSA-N erbium Chemical compound [Er] UYAHIZSMUZPPFV-UHFFFAOYSA-N 0.000 description 2
- OGPBJKLSAFTDLK-UHFFFAOYSA-N europium atom Chemical compound [Eu] OGPBJKLSAFTDLK-UHFFFAOYSA-N 0.000 description 2
- UIWYJDYFSGRHKR-UHFFFAOYSA-N gadolinium atom Chemical compound [Gd] UIWYJDYFSGRHKR-UHFFFAOYSA-N 0.000 description 2
- 239000001307 helium Substances 0.000 description 2
- 229910052734 helium Inorganic materials 0.000 description 2
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 2
- KJZYNXUDTRRSPN-UHFFFAOYSA-N holmium atom Chemical compound [Ho] KJZYNXUDTRRSPN-UHFFFAOYSA-N 0.000 description 2
- 238000005470 impregnation Methods 0.000 description 2
- NIZHERJWXFHGGU-UHFFFAOYSA-N isocyanato(trimethyl)silane Chemical compound C[Si](C)(C)N=C=O NIZHERJWXFHGGU-UHFFFAOYSA-N 0.000 description 2
- OHSVLFRHMCKCQY-UHFFFAOYSA-N lutetium atom Chemical compound [Lu] OHSVLFRHMCKCQY-UHFFFAOYSA-N 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 239000003960 organic solvent Substances 0.000 description 2
- 125000001181 organosilyl group Chemical group [SiH3]* 0.000 description 2
- SIWVEOZUMHYXCS-UHFFFAOYSA-N oxo(oxoyttriooxy)yttrium Chemical compound O=[Y]O[Y]=O SIWVEOZUMHYXCS-UHFFFAOYSA-N 0.000 description 2
- 229910052697 platinum Inorganic materials 0.000 description 2
- 238000010298 pulverizing process Methods 0.000 description 2
- 125000001453 quaternary ammonium group Chemical group 0.000 description 2
- KZUNJOHGWZRPMI-UHFFFAOYSA-N samarium atom Chemical compound [Sm] KZUNJOHGWZRPMI-UHFFFAOYSA-N 0.000 description 2
- 150000004756 silanes Chemical class 0.000 description 2
- 150000004760 silicates Chemical class 0.000 description 2
- 125000005625 siliconate group Chemical group 0.000 description 2
- GZCRRIHWUXGPOV-UHFFFAOYSA-N terbium atom Chemical compound [Tb] GZCRRIHWUXGPOV-UHFFFAOYSA-N 0.000 description 2
- APSPVJKFJYTCTN-UHFFFAOYSA-N tetramethylazanium;silicate Chemical compound C[N+](C)(C)C.C[N+](C)(C)C.C[N+](C)(C)C.C[N+](C)(C)C.[O-][Si]([O-])([O-])[O-] APSPVJKFJYTCTN-UHFFFAOYSA-N 0.000 description 2
- 239000008096 xylene Substances 0.000 description 2
- NAWDYIZEMPQZHO-UHFFFAOYSA-N ytterbium Chemical compound [Yb] NAWDYIZEMPQZHO-UHFFFAOYSA-N 0.000 description 2
- NGDQQLAVJWUYSF-UHFFFAOYSA-N 4-methyl-2-phenyl-1,3-thiazole-5-sulfonyl chloride Chemical compound S1C(S(Cl)(=O)=O)=C(C)N=C1C1=CC=CC=C1 NGDQQLAVJWUYSF-UHFFFAOYSA-N 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 239000003082 abrasive agent Substances 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 229910000416 bismuth oxide Inorganic materials 0.000 description 1
- 239000012159 carrier gas Substances 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- VYLVYHXQOHJDJL-UHFFFAOYSA-K cerium trichloride Chemical compound Cl[Ce](Cl)Cl VYLVYHXQOHJDJL-UHFFFAOYSA-K 0.000 description 1
- 229910052878 cordierite Inorganic materials 0.000 description 1
- TYIXMATWDRGMPF-UHFFFAOYSA-N dibismuth;oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Bi+3].[Bi+3] TYIXMATWDRGMPF-UHFFFAOYSA-N 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
- 230000002708 enhancing effect Effects 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 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 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000002468 redox effect Effects 0.000 description 1
- 229910052703 rhodium Inorganic materials 0.000 description 1
- 239000010948 rhodium Substances 0.000 description 1
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 1
- 239000007784 solid electrolyte Substances 0.000 description 1
- 239000003381 stabilizer Substances 0.000 description 1
Classifications
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- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/10—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of rare earths
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/86—Catalytic processes
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
- B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
- B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
- B01J21/08—Silica
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
- B01J35/61—Surface area
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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
- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
- B01J35/61—Surface area
- B01J35/613—10-100 m2/g
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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
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
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- B01J37/0201—Impregnation
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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
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/02—Impregnation, coating or precipitation
- B01J37/03—Precipitation; Co-precipitation
- B01J37/031—Precipitation
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
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- C01F17/30—Compounds containing rare earth metals and at least one element other than a rare earth metal, oxygen or hydrogen, e.g. La4S3Br6
- C01F17/32—Compounds containing rare earth metals and at least one element other than a rare earth metal, oxygen or hydrogen, e.g. La4S3Br6 oxide or hydroxide being the only anion, e.g. NaCeO2 or MgxCayEuO
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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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- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
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- 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 can be used for catalysts, functional ceramics, solid electrolytes for fuel cells, abrasives, and the like, and can be suitably used as a promoter material in exhaust gas purification catalysts for automobiles and the like, and is highly oxidized even at low temperatures.
- the present invention relates to a composite oxide exhibiting reducing ability and having excellent heat resistance, a method for producing the same, and a catalyst for exhaust gas purification using the composite oxide.
- An exhaust gas purifying catalyst for automobiles and the like is configured, for example, by supporting a catalyst metal such as alumina or cordierite with platinum, palladium, or rhodium as a catalytic metal and a co-catalyst for enhancing their catalytic action.
- the cocatalyst material has the property of absorbing oxygen under an oxidizing atmosphere and releasing the oxygen under a reducing atmosphere.
- the co-catalyst material having such characteristics has a ratio of fuel to air amount so that the exhaust gas purifying catalyst efficiently purifies the harmful components in the exhaust gas such as hydrocarbon, carbon monoxide and nitrogen oxides. Acts to maintain optimal.
- the efficiency of exhaust gas purification by the exhaust gas purification catalyst is generally proportional to the contact area between the active species of the catalytic metal and the exhaust gas.
- Patent Document 1 proposes a CeZrBi-based composite oxide that exhibits high redox ability at 300 ° C. or lower.
- this composite oxide is exposed to a reduced state of 700 ° C. or more, bismuth oxide is reduced to metal bismuth and evaporates, and the bismuth component in the composite oxide decreases as it repeats oxidation and reduction, Redox properties are reduced. For this reason, it is difficult to put into practical use an automobile catalyst that is repeatedly oxidized and reduced at a high temperature for a long time.
- Patent Documents 2 to 4 propose composite oxides in which Ba, Ag, and Pt are added to CeZrBi as the fourth component, respectively, to improve heat resistance or phase stability.
- Ba, Ag, and Pt are added to CeZrBi as the fourth component, respectively, to improve heat resistance or phase stability.
- Patent Documents 5 to 8 propose a technique of adding a rare earth metal element or silicon as a stabilizer in order to improve the heat resistance of cerium oxide. These documents propose several composite oxides that are excellent in heat resistance at high temperatures and excellent in specific surface area retention by the BET method. However, specifically, a composite oxide containing cerium, silicon, or a rare earth metal element excluding cerium that has excellent heat resistance and exhibits a sufficient reduction rate even at low temperatures is not known.
- JP 2003-238159 A International Publication No. 2005/85137 JP 2005-281021 A JP 2010-260023 A International Publication No. 2008/156219 Japanese Patent Laid-Open No. 4-214026 JP 2000-72437 A JP-A-5-270824
- the object of the present invention is to exhibit high oxidation-reduction ability even at low temperatures, have excellent heat resistance, and maintain its characteristics stably even when repeated oxidation and reduction at high temperatures. It is an object of the present invention to provide a composite oxide suitable for a catalyst cocatalyst and an exhaust gas purification catalyst using the same. Another subject of this invention is providing the manufacturing method of the composite oxide which can obtain easily the composite oxide of the said this invention excellent in heat resistance and a reduction rate.
- a composite oxide containing silicon in an amount of more than 0 parts by mass and less than 20 parts by mass in terms of SiO 2 In a 10% hydrogen-90% argon atmosphere, a temperature-reduction (TPR) measurement was performed from 50 ° C. to 900 ° C. at a rate of temperature increase of 10 ° C./min, followed by an oxidation treatment at 500 ° C. for 0.5 hour.
- TPR temperature-reduction
- a composite oxide hereinafter, may be abbreviated as the composite oxide of the present invention having a characteristic that the reduction rate of 400 ° C.
- a step (a1) of preparing a cerium solution in which 90 mol% or more of cerium ions are tetravalent a step of heating and holding the cerium solution prepared in step (a1) at 60 ° C.
- a method for producing a complex oxide (hereinafter sometimes abbreviated as a first method), which comprises a step (g) of reducing the reduced amount and a step (h) of oxidizing the reduced product.
- a cerium suspension obtained by heating and holding the step (a1), the step (b1), and a precursor of an oxide of a rare earth metal element that contains yttrium and does not contain cerium.
- a method (hereinafter sometimes abbreviated as a second method) is provided. Furthermore, according to the present invention, a step (A1) of preparing a cerium solution in which 90 mol% or more of cerium ions are tetravalent, and a step of heating and holding the cerium solution prepared in step (A1) at 60 ° C. or higher ( B1), a step of adding a silicon oxide precursor to the heated cerium suspension (C1), a step of maintaining the cerium suspension containing the silicon oxide precursor at 100 ° C.
- a step of adding a precipitant to the cerium suspension containing the silicon oxide precursor obtained by heating and holding to obtain a precipitate (E1), and a step of firing the obtained precipitate (F) are obtained.
- a method for producing a composite oxide (hereinafter sometimes abbreviated as a third method) is provided which includes a step (G) for reducing the calcined product and a step (H) for oxidizing the reduced product.
- B2 a step of adding a precipitant to the suspension obtained in step (B2) to obtain a precipitate, the above step (F), the above step (G), and the above step (H )
- the first to fourth methods are collectively abbreviated as the production method of the present invention).
- an exhaust gas purifying catalyst comprising the composite oxide of the present invention.
- an exhaust gas purifying catalyst comprising a catalyst metal, a promoter comprising the composite oxide of the present invention, and a catalyst carrier, wherein the catalyst metal and the promoter are supported on the catalyst carrier.
- the composite oxide of the present invention contains silicon and cerium, and, if necessary, a rare earth metal element containing yttrium and not containing cerium (hereinafter sometimes referred to as a specific rare earth metal element) in a specific ratio, Since it exhibits excellent reducibility even at the following low temperatures and maintains excellent heat resistance, it is particularly useful as a co-catalyst for exhaust gas purifying catalysts.
- the method for producing a composite oxide of the present invention includes the above steps, and in particular, since the reduction / oxidation step is performed after firing, the composite oxide of the present invention can be easily obtained.
- Such a composite oxide is obtained because Si rich domains in which CeO 2 and SiO 2 are more uniformly mixed at the nano level are formed on the surface of the cerium particles by the reduction step and the oxidation step in the production method of the present invention. It is thought to be for this purpose. By doing so, it is considered that the composite oxide of the present invention has a low activation energy for cerium silicate formation when exposed to a reducing atmosphere, and a high oxygen releasing ability can be obtained even at 400 ° C. or lower. Even when oxidation / reduction is repeated, the uniform mixing of CeO 2 —SiO 2 at the nano level and the formation of cerium silicate occur reversibly, so that high oxidation-reduction ability is maintained even at temperatures below 400 ° C. It is thought that it is done.
- the composite oxide of the present invention was subjected to a temperature-reduction (TPR) measurement from 50 ° C. to 900 ° C. at a rate of temperature increase of 10 ° C./min in a 10% hydrogen-90% argon atmosphere, It has a characteristic that the reduction rate of 400 ° C. or lower calculated from the result of the oxidation treatment for 5 hours and the temperature reduction measurement again is 1.5% or higher, preferably 2.0% or higher.
- the upper limit of the reduction rate of 400 ° C. or lower is not particularly limited, but is usually 4.0%, preferably 5.0%.
- a reduction rate means the ratio by which cerium in the oxide calculated from the result of temperature-reduction measurement (TPR) from 50 ° C.
- Reduction rate (%) measured hydrogen consumption of sample below 400 ° C. ( ⁇ mol / g) / theoretical hydrogen consumption of cerium oxide in sample ( ⁇ mol / g) ⁇ 100
- the composite oxide of the present invention preferably has a heat resistance of 20 m 2 / g or more, particularly preferably 25 m 2 / g or more, by BET method after repeating the temperature reduction measurement and oxidation treatment three times. It is desirable to have characteristics.
- the upper limit of the specific surface area is not particularly limited, but is usually 40 m 2 / g, preferably 50 m 2 / g.
- the specific surface area means a value measured based on the most standard nitrogen gas adsorption BET method as a specific surface area measurement method of powder.
- the composite oxide of the present invention exhibits the above physical properties, and more than 0 parts by mass in terms of SiO 2 exceeds 20 parts by mass with respect to 100 parts by mass in terms of oxides of rare earth metal elements including cerium. , Preferably 1 to 20 parts by weight, particularly preferably 2 to 20 parts by weight, and most preferably 5 to 20 parts by weight.
- the rare earth metal element containing cerium consists of cerium alone or cerium and a specific rare earth metal element.
- the ratio of the cerium to the specific rare earth metal element is 85:15 to 99: 1, preferably 85:15 to 95: 5, in terms of mass ratio in terms of oxide.
- the heat resistance and the reduction rate may be reduced.
- Examples of the specific rare earth metal element include yttrium, lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, or a mixture of two or more thereof.
- the use of yttrium, lanthanum, praseodymium, neodymium, or a mixture of two or more of these is preferred.
- the production method of the present invention is a method by which a silicon-containing cerium composite oxide containing the composite oxide of the present invention can be obtained easily and with good reproducibility.
- the first method is 90 mol% or more of cerium ions.
- the initial concentration of the cerium solution in which 90 mol% or more of cerium ions are tetravalent is usually 5 to 100 g / L, preferably 5 to 80 g / L, particularly preferably 10 in terms of CeO 2. It can be adjusted to 70 g / L.
- concentration of the cerium solution usually water is used, and the use of deionized water is particularly preferred. If the initial concentration is too high, the crystallinity of the precipitate described later does not increase, and pores sufficient to contain the silicon oxide precursor solution described later cannot be formed. Heat resistance and reduction rate may be reduced. On the other hand, if the concentration is too low, the productivity is low, which is not industrially advantageous.
- the cerium solution is then reacted by performing step (b1) of heating and holding the cerium solution prepared in step (a1) at 60 ° C. or higher.
- the reactor used in step (b1) may be either a closed type container or an open type container.
- an autoclave reactor can be used.
- the heating and holding temperature is 60 ° C. or higher, preferably 60 to 200 ° C., particularly preferably 80 to 180 ° C., more preferably 90 to 160 ° C.
- the heating and holding time is usually 10 minutes to 48 hours, preferably 30 minutes to 36 hours, more preferably 1 hour to 24 hours.
- the heating and holding are not sufficient, the crystallinity of the precipitate described later does not increase, and pores having a volume sufficient to impregnate the silicon oxide precursor solution described later cannot be formed. There is a risk that the heat resistance and reduction rate of the product cannot be improved sufficiently. Further, even if the heating and holding time is too long, the influence on the heat resistance and the reduction rate is insignificant, which is not industrially advantageous.
- the first method includes a step (c1) of adding a precipitant to the cerium suspension obtained by heating and holding in step (b1) to obtain a precipitate.
- the precipitating agent used in the step (c1) include sodium hydroxide, potassium hydroxide, ammonia water, ammonia gas, or a base of a mixture thereof, and the use of ammonia water is particularly preferable.
- the addition of the precipitating agent is, for example, a method in which the precipitating agent is made into an aqueous solution having an appropriate concentration and added to the cerium suspension obtained in step (b1) with stirring. In the case of ammonia gas, the reactor is stirred. It can be carried out by a method of blowing in.
- the amount of precipitant added can be easily determined by following the change in pH of the suspension. In general, the amount of precipitation of cerium suspension with a pH of about 7 to 9 is sufficient, and the amount is preferably 7 to 8.5.
- Step (c1) may be performed after cooling the cerium suspension obtained by heating and holding in step (b1). Cooling can usually be performed with stirring, and a generally known method can be used. Natural slow cooling or forced cooling using a cooling pipe may be used. The cooling temperature is usually about 40 ° C or less, preferably about 20 to 30 ° C.
- a slurry containing a cerium oxide hydrate precipitate having advanced crystal growth can be obtained.
- the precipitate can be separated by, for example, Nutsche method, centrifugal separation method, or filter press method. Moreover, the precipitate can be washed with water as much as necessary. Furthermore, in order to increase the efficiency of the next step (d1), a step of appropriately drying the obtained precipitate may be added.
- the first method includes a step (d1) of calcining the precipitate to obtain cerium oxide.
- the calcination temperature is usually 250 to 500 ° C, preferably 280 to 450 ° C.
- the cerium oxide obtained by calcination in the step (d1) becomes a porous body having pores having a volume sufficient to impregnate a silicon oxide precursor solution described later, and impregnated with the silicon oxide precursor solution. And the heat resistance and reduction rate of the finally obtained composite oxide can be improved.
- the calcination time is usually 30 minutes to 36 hours, particularly 1 hour to 24 hours, and more preferably 3 to 20 hours.
- the first method includes a step (e1) of impregnating the cerium oxide obtained by the above calcination with a silicon oxide precursor solution.
- the precursor of silicon oxide used in the step (e1) is a compound that can be converted into silicon oxide by an oxidation treatment such as baking, and is a compound that can be impregnated into a porous body of cerium oxide calcined using a solvent.
- examples thereof include silicates such as sodium silicate, silane compounds such as tetraethyl orthosilicate, silyl compounds such as trimethylsilyl isocyanate, and quaternary ammonium silicates such as tetramethylammonium silicate.
- the solvent for dissolving the silicon oxide precursor can be selected depending on the type of the precursor used.
- the concentration of the silicon oxide precursor solution is not particularly limited as long as it can be impregnated with cerium oxide, but the concentration of silicon oxide precursor in terms of SiO 2 is usually 1 to 300 g / L, preferably 10 to 200 g / L. About L is preferable in terms of workability and efficiency.
- the addition amount of the silicon oxide precursor is 100 parts by mass of the cerium in the oxide converted to CeO 2, and the amount of the silicon oxide precursor to be added is converted to SiO 2 .
- it is more than 0 parts by mass and 20 parts by mass or less, preferably 1 to 20 parts by mass, more preferably 2 to 20 parts by mass, and most preferably 5 to 20 parts by mass.
- impregnation of the silicon oxide precursor solution into cerium oxide can be performed by, for example, a pore filling method, an adsorption method, or an evaporation to dryness method.
- a pore filling method include a method in which the pore volume of cerium oxide is measured in advance and a precursor solution of silicon oxide having the same volume is added so that the cerium oxide surface is uniformly wetted.
- the first method includes a step (f1) of firing cerium oxide impregnated with a precursor solution of silicon oxide.
- the firing temperature is usually 300 to 700 ° C., preferably 350 to 600 ° C.
- the firing time can be appropriately set in consideration of the firing temperature, and can usually be determined in the range of 1 to 10 hours.
- a step of drying the cerium oxide impregnated with the silicon oxide precursor solution at about 60 to 200 ° C. may be performed. it can. By performing such a drying step, the firing in the step (f1) can be performed efficiently.
- the first method includes a step (g) of reducing the obtained fired product.
- the reduction is performed, for example, under a reducing atmosphere obtained by mixing or mixing hydrogen, deuterium, carbon monoxide, etc., or under an inert atmosphere obtained by combining nitrogen, helium, argon, or the like. Or under vacuum.
- the temperature during the reduction is usually 100 to 600 ° C, preferably 150 to 500 ° C.
- the reduction time is usually 0.5 to 5 hours, preferably 1 to 3 hours.
- the first method includes a step (h) of oxidizing the obtained reduction product.
- the oxidation can be carried out in an air atmosphere, usually in the range of 100 to 900 ° C., preferably 200 to 800 ° C.
- the oxidation time is usually 0.1 to 3 hours, preferably 0.3 to 2 hours.
- the composite oxide of the present invention having the above physical properties can be obtained by the step (h).
- the cerium suspension obtained by heating and holding in the step (b1) A step (a2) of adding a precursor of an oxide of a specific rare earth metal element, that is, a precursor of an oxide of a rare earth metal element containing yttrium and not containing cerium, to the liquid;
- the precursor of the oxide of the specific rare earth metal element may be a compound that can be converted into an oxide of the specific rare earth metal element by an oxidation treatment such as firing, and examples thereof include a specific rare earth metal element-containing nitric acid solution.
- the amount of the precursor of the oxide of the specific rare earth element is calculated by converting the cerium in the cerium suspension and the specific rare earth element in the oxide precursor of the specific rare earth element into oxide equivalents.
- the mass ratio can be adjusted to usually be in the range of 85:15 to 99: 1, preferably 85:15 to 95: 5.
- the content of cerium in terms of CeO 2 in the oxide of cerium and a specific rare earth metal element is less than 85% by mass, the heat resistance and reduction rate of the resulting composite oxide may be reduced.
- Step (a2) may be performed after cooling the cerium suspension obtained by heating and holding in step (b1). Cooling can usually be performed with stirring, and a generally known method can be used. Natural slow cooling or forced cooling using a cooling pipe may be used. The cooling temperature is usually about 40 ° C or less, preferably about 20 to 30 ° C.
- step (a2) the salt concentration of the cerium suspension is adjusted by removing the mother liquor from the cerium suspension and adding water before adding the precursor of the oxide of the specific rare earth metal element. You may do it.
- the mother liquor can be removed by, for example, the decantation method, Nutsche method, centrifugal separation method, or filter press method. At this time, a small amount of cerium is removed together with the mother liquor. Thus, the amount of the following specific rare earth metal oxide precursor and water added can be adjusted.
- the cerium suspension containing the specific rare earth metal oxide precursor is heated and held at 100 ° C. or higher, preferably 100 to 200 ° C., particularly preferably 100 to 150 ° C. (b2 )including.
- the heating and holding time is usually 10 minutes to 6 hours, preferably 20 minutes to 5 hours, more preferably 30 minutes to 4 hours.
- the heating and holding in this step (b2) if it is lower than 100 ° C., the crystallinity of the precipitate described later does not increase, and the heat resistance and reduction rate of the finally obtained composite oxide may not be sufficiently improved. Further, even if the heating and holding time is too long, the influence on the heat resistance and the reduction rate is insignificant, which is not industrially advantageous.
- the first method includes the step (c2) of adding a precipitant to the suspension obtained in the step (b2) to obtain a precipitate.
- the precipitating agent used in the step (c2) include sodium hydroxide, potassium hydroxide, ammonia water, ammonia gas, or a base of a mixture thereof, and the use of ammonia water is particularly preferable.
- the addition of the precipitating agent is, for example, a method of adding the precipitating agent to an aqueous solution having an appropriate concentration and adding the suspension to the suspension obtained in step (c2) with stirring. The method can be carried out by blowing into The amount of precipitant added can be easily determined by following the change in pH of the suspension. Usually, an amount that causes precipitation at a pH of the suspension of about 7 to 9 is sufficient, and preferably an amount that results in a pH of 7 to 8.5.
- Step (c2) may be performed after cooling the heated cerium suspension in step (b2). Cooling can usually be performed with stirring, and a generally known method can be used. Natural slow cooling or forced cooling using a cooling pipe may be used. The cooling temperature is usually about 40 ° C or less, preferably about 20 to 30 ° C.
- a slurry containing a cerium oxide hydrate precipitate having advanced crystal growth can be obtained.
- the precipitate can be separated by, for example, Nutsche method, centrifugal separation method, or filter press method. Moreover, the precipitate can be washed with water as much as necessary. Furthermore, in order to increase the efficiency of the next step (f), a step of appropriately drying the obtained precipitate may be added.
- the second method includes the step (d2) of calcining the precipitate.
- the calcination temperature is usually 250 to 500 ° C., preferably 280 to 450 ° C.
- the calcination time is usually 30 minutes to 36 hours, particularly 1 hour to 24 hours, and more preferably 3 to 20 hours.
- the oxide obtained by calcining in step (d2) becomes a porous body having pores having a volume sufficient to impregnate a silicon oxide precursor solution described later, and impregnated with the silicon oxide precursor solution. And the heat resistance and reduction rate of the finally obtained composite oxide can be improved.
- the second method includes a step (e2) of impregnating the oxide obtained by the calcination with a precursor solution of silicon oxide.
- the precursor of silicon oxide used in step (e2) is a compound that can be converted into silicon oxide by an oxidation treatment such as firing, and is a compound that can be impregnated into a porous body of oxide calcined using a solvent.
- examples thereof include silicates such as sodium silicate, silane compounds such as tetraethyl orthosilicate, silyl compounds such as trimethylsilyl isocyanate, and quaternary ammonium silicates such as tetramethylammonium silicate.
- the solvent for dissolving the silicon oxide precursor can be selected depending on the type of the precursor used.
- the concentration of the silicon oxide precursor solution is not particularly limited as long as the porous body can be impregnated with the oxide, but the concentration of the silicon oxide precursor in terms of SiO 2 is usually 1 to 300 g / L, About 10 to 200 g / L is preferable from the viewpoint of workability and efficiency.
- the silicon oxide precursor is added in an amount of 100 parts by mass in terms of the oxide equivalent of cerium and the specific rare earth metal element in the oxide.
- the amount of the body in terms of SiO 2 is usually more than 0 parts by mass and 20 parts by mass or less, preferably 1 to 20 parts by mass, more preferably 2 to 20 parts by mass, and most preferably 5 to 20 parts by mass.
- the amount of silicon added is small, the heat resistance and reduction rate of the resulting composite oxide tend to decrease. Even when the amount of silicon added is too large, the heat resistance of the resulting composite oxide decreases, The specific surface area at high temperatures tends to decrease.
- the silicon oxide precursor solution is impregnated into the oxide by, for example, a pore filling method, an adsorption method, or an evaporation to dryness method.
- a pore filling method examples include a method in which the pore volume of the oxide is measured in advance, and a silicon oxide precursor solution having the same volume is added to uniformly wet the oxide surface.
- the second method includes the step (f2) of firing the oxide impregnated with the silicon oxide precursor solution.
- the firing temperature is usually 300 to 700 ° C., preferably 350 to 600 ° C.
- the firing time can be appropriately set in consideration of the firing temperature, and can usually be determined in the range of 1 to 10 hours.
- a step of drying the oxide impregnated with the silicon oxide precursor at about 60 to 200 ° C. can be performed when performing the step (f2). . By performing such a drying step, the firing in the step (f2) can be performed efficiently.
- the composite oxide of the present invention can be obtained by performing the step (g) and the step (h) after the step (f2) as in the first method.
- the third method of the present invention includes a step (A1) of preparing a cerium solution in which 90 mol% or more of cerium ions are tetravalent.
- the water-soluble cerium compound used in the step (A1) include ceric nitrate solution and ceric ammonium nitrate, and the use of ceric nitrate solution is particularly preferable.
- the initial concentration of the cerium solution in which 90 mol% or more of the cerium ions are tetravalent is usually 5 to 100 g / L, preferably 5 to 80 g / L, particularly preferably 10 in terms of CeO 2. It can be adjusted to 70 g / L.
- the concentration of the cerium solution usually water is used, and the use of deionized water is particularly preferred. If the initial concentration is too high, the crystallinity of the precipitate described later does not increase, pores having a sufficient volume cannot be formed, and the heat resistance and reduction rate of the finally obtained composite oxide may be reduced. is there. On the other hand, if the concentration is too low, the productivity is low, which is not industrially advantageous.
- the step (B1) of heating and holding the cerium solution prepared in the step (A1) at 60 ° C. or higher is performed.
- the reactor used in the step (B1) may be either a closed type container or an open type container, and an autoclave reactor can be preferably used.
- the heating and holding temperature is 60 ° C. or higher, preferably 60 to 200 ° C., particularly preferably 80 to 180 ° C., more preferably 90 to 160 ° C.
- the heating and holding time is usually 10 minutes to 48 hours, preferably 30 minutes to 36 hours, more preferably 1 hour to 24 hours.
- the heating and holding are not sufficient, the crystallinity of the precipitate described later does not increase, pores having a sufficient volume cannot be formed, and the heat resistance and reduction rate of the finally obtained composite oxide may not be sufficiently improved. is there. Further, even if the heating and holding time is too long, the influence on the heat resistance and the reduction rate is insignificant, which is not industrially advantageous.
- the step (C1) of adding a silicon oxide precursor to the cerium suspension obtained in the step (B1) is performed.
- the silicon oxide precursor added to the cerium suspension may be a compound that can be converted into silicon oxide by an oxidation treatment such as calcination, and examples thereof include colloidal silica, siliconate, and quaternary ammonium silicate.
- colloidal silica is preferable from the viewpoint of reducing production cost and environmental load.
- the addition amount of the silicon oxide precursor is 100 parts by mass of the cerium in the oxide converted to CeO 2, and the amount of the silicon oxide precursor to be added is converted to SiO 2 .
- it is more than 0 parts by mass and 20 parts by mass or less, preferably 1 to 20 parts by mass, more preferably 2 to 20 parts by mass, and most preferably 5 to 20 parts by mass.
- the salt concentration of the cerium suspension may be adjusted by removing the mother liquor from the cerium suspension and adding water before adding the silicon oxide precursor.
- the mother liquor can be removed by, for example, the decantation method, Nutsche method, centrifugal separation method, or filter press method. At this time, a small amount of cerium is removed together with the mother liquor. Then, the amount of the next silicon oxide precursor and water can be adjusted.
- Step (C1) may be performed after cooling the cerium suspension obtained by heating and holding in step (B1). Cooling can usually be performed with stirring, and a generally known method can be used. Natural slow cooling or forced cooling using a cooling pipe may be used. The cooling temperature is usually about 40 ° C or less, preferably about 20 to 30 ° C.
- the third method includes a step (D1) of heating and holding the cerium suspension containing the silicon oxide precursor at 100 ° C. or higher, preferably 100 to 200 ° C., particularly preferably 100 to 150 ° C.
- the heating and holding time is usually 10 minutes to 6 hours, preferably 20 minutes to 5 hours, more preferably 30 minutes to 4 hours.
- the heating and holding in this step (D1) if it is less than 100 ° C., the crystallinity of the precipitate described later does not increase, and the heat resistance and reduction rate of the finally obtained composite oxide may not be sufficiently improved. Further, even if the heating and holding time is too long, the influence on the heat resistance and the reduction rate is insignificant, which is not industrially advantageous.
- the third method includes a step (E1) of adding a precipitating agent to a cerium suspension containing a silicon oxide precursor which is kept heated to obtain a precipitate.
- a precipitating agent used in the step (E1) for example, sodium hydroxide, potassium hydroxide, ammonia water, ammonia gas, or a base of a mixture thereof can be used, and the use of ammonia water is particularly preferable.
- the amount of the precipitating agent added in the step (E) can be easily determined by following the change in pH of the cerium suspension containing the silicon oxide precursor that has been heated and held. In general, the amount of precipitation of cerium suspension with a pH of about 7 to 9 is sufficient, and the amount is preferably 7 to 8.5.
- Step (E1) may be performed after cooling the cerium suspension obtained by heating and holding in step (D1). Cooling can usually be performed with stirring, and a generally known method can be used. Natural slow cooling or forced cooling using a cooling pipe may be used. The cooling temperature is usually about 40 ° C or less, preferably about 20 to 30 ° C.
- the precipitate can be separated by, for example, Nutsche method, centrifugal separation method, or filter press method. Moreover, the precipitate can be washed with water as much as necessary.
- the third method includes a step (F) of calcining the obtained precipitate.
- the firing temperature is usually 300 to 700 ° C., preferably 350 to 600 ° C.
- a silicon-containing cerium composite oxide having excellent heat resistance and reduction rate can be obtained.
- the firing time is usually 1 to 48 hours, particularly 1 to 24 hours, and more preferably 3 to 20 hours.
- the third method includes a step (G) of reducing the obtained fired product.
- the reduction is performed, for example, in a reducing atmosphere obtained by mixing or mixing hydrogen, deuterium, carbon monoxide or the like, or in an inert atmosphere obtained by mixing or mixing nitrogen, helium, argon, or the like. Or under vacuum.
- the temperature during the reduction is usually 100 to 600 ° C, preferably 150 to 500 ° C.
- the reduction time is usually 0.5 to 5 hours, preferably 1 to 3 hours.
- the third method includes a step (H) of oxidizing the obtained reduction product.
- the oxidation can be carried out in an air atmosphere, usually in the range of 100 to 900 ° C., preferably 200 to 800 ° C.
- the oxidation time is usually 0.1 to 3 hours, preferably 0.3 to 2 hours.
- the composite oxide of the present invention having the above physical properties can be obtained by the step (H).
- the cerium suspension obtained in the step (B1) is used.
- the step (A2) of adding a precursor of silicon oxide and a precursor of an oxide of a specific rare earth metal element is performed.
- the silicon oxide precursor to be added to the cerium suspension may be any compound that can be converted into silicon oxide by oxidation treatment such as calcination.
- oxidation treatment such as calcination.
- colloidal silica, siliconate, quaternary ammonium silicate In particular, the use of colloidal silica is preferable from the viewpoint of reducing production cost and environmental load.
- the amount of the silicon oxide precursor added is 100 parts by mass with respect to a total amount of cerium and a specific rare earth metal element in terms of oxide in the finally obtained composite oxide.
- the amount of silicon oxide precursor to be converted to SiO 2 is more than 0 parts by mass and 20 parts by mass or less, preferably 1 to 20 parts by mass, more preferably 2 to 20 parts by mass, most preferably 5 to 20 parts by mass. is there.
- the amount of silicon added is small, the heat resistance and reduction rate of the resulting composite oxide tend to decrease. Even when the amount of silicon added is too large, the heat resistance of the resulting composite oxide decreases, The specific surface area at high temperatures tends to decrease.
- the precursor of the oxide of the specific rare earth metal element may be a compound that can become an oxide of the specific rare earth metal element by an oxidation treatment such as firing, for example, a specific rare earth metal element-containing nitric acid.
- the amount of the precursor of the oxide of the specific rare earth element is determined by converting the cerium in the cerium suspension and the specific rare earth metal element in the precursor of the oxide of the specific rare earth element into oxide equivalents.
- the mass ratio can be adjusted to usually be in the range of 85:15 to 99: 1, preferably 85:15 to 95: 5. If the content of cerium in terms of CeO 2 in the oxide of cerium and a specific rare earth metal element is less than 85% by mass or more than 99% by mass, the heat resistance and the reduction rate may be reduced.
- Step (A2) may be performed after cooling the cerium suspension obtained by heating and holding in step (B1). Cooling can usually be performed with stirring, and a generally known method can be used. Natural slow cooling or forced cooling using a cooling pipe may be used. The cooling temperature is usually about 40 ° C or less, preferably about 20 to 30 ° C.
- the cerium suspension is removed by removing the mother liquor from the cerium suspension and adding water before adding the silicon oxide precursor and the specific rare earth metal oxide precursor.
- the mother liquor can be removed by, for example, the decantation method, Nutsche method, centrifugal separation method, or filter press method. At this time, a small amount of cerium is removed together with the mother liquor. Thus, it is possible to adjust the amount of the following silicon oxide precursor, a specific rare earth metal oxide precursor and water added.
- the cerium suspension containing the silicon oxide precursor and the specific rare earth element oxide precursor is heated to 100 ° C. or higher, preferably 100 to 200 ° C., particularly preferably 100 to 150 ° C.
- the heating and holding time is usually 10 minutes to 6 hours, preferably 20 minutes to 5 hours, more preferably 30 minutes to 4 hours.
- the heating and holding in this step (B2) if it is less than 100 ° C., the crystallinity of the precipitate described later does not increase, and there is a possibility that the heat resistance and reduction rate of the finally obtained composite oxide cannot be sufficiently improved. Further, even if the heating and holding time is too long, the influence on the heat resistance and the reduction rate is insignificant, which is not industrially advantageous.
- the fourth method includes a step (E2) of adding a precipitant to the suspension obtained in the step (B2) to obtain a precipitate.
- the precipitant used in the step (E2) for example, sodium hydroxide, potassium hydroxide, ammonia water, ammonia gas, or a base of a mixture thereof can be used, and the use of ammonia water is particularly preferable.
- the amount of the precipitant added in step (E) can be easily determined by following the change in pH of the suspension. Usually, an amount that causes precipitation at a pH of the suspension of about 7 to 9 is sufficient, and preferably an amount that results in a pH of 7 to 8.5.
- Step (E2) may be performed after cooling the cerium suspension obtained by heating and holding in step (B2).
- Cooling can usually be performed with stirring, and a generally known method can be used. Natural slow cooling or forced cooling using a cooling pipe may be used.
- the cooling temperature is usually about 40 ° C or less, preferably about 20 to 30 ° C.
- the precipitate can be separated by, for example, Nutsche method, centrifugal separation method, or filter press method. Moreover, the precipitate can be washed with water as much as necessary.
- the composite oxide having the above physical properties of the present invention can be obtained by performing the step (F), the step (G) and the step (H).
- the composite oxide obtained in the step (h) or the step (H) can be pulverized and used as a powder.
- the pulverization can be carried out using a commonly used pulverizer such as a hammer mill, and a powder having a sufficiently desired particle size can be obtained.
- the particle size of the composite oxide powder obtained by the production method of the present invention can be adjusted to the desired particle size by the above-mentioned pulverization.
- the average particle size is 1 to The thickness is preferably 50 ⁇ m.
- the exhaust gas purifying catalyst of the present invention is not particularly limited as long as it includes the co-catalyst containing the composite oxide of the present invention.
- Example 1 This example relates to a composite oxide in which 1 part by mass of silicon oxide is added to 100 parts by mass of cerium oxide.
- a cerium nitrate solution containing 90 mol% or more of tetravalent cerium ions was collected in an amount of 20 g in terms of CeO 2 , and then adjusted to a total amount of 1 L with pure water.
- the obtained solution was introduced into an autoclave reactor, heated to 120 ° C., held for 6 hours, and then naturally cooled to room temperature.
- aqueous ammonia was added to neutralize to pH 8 to obtain a slurry of cerium oxide hydrate.
- the slurry was subjected to solid-liquid separation by Nutsche filtration to obtain a filter cake.
- the filter cake was baked in a box-type electric furnace in an air atmosphere at 300 ° C. for 10 hours to obtain cerium oxide.
- cerium oxide-based composite oxide powder containing 1 part by mass of silicon oxide with respect to 100 parts by mass of cerium oxide.
- 0.5 g of the obtained composite oxide powder was reduced by heating from 50 ° C. to 900 ° C. at a temperature increase rate of 10 ° C./min in a 90% argon-10% hydrogen atmosphere with a gas flow rate of 30 mL / min. Then, it baked at 500 degreeC as an air atmosphere for 0.5 hour.
- an automatic temperature programmed desorption analyzer (equipment name, TP-5000) manufactured by Okura Riken Co., Ltd., oxidation at 400 ° C or lower from the result of temperature-programmed reduction measurement (TPR) from 50 ° C to 900 ° C.
- TPR temperature-programmed reduction measurement
- Example 2 This example relates to a composite oxide in which 2 parts by mass of silicon oxide is added to 100 parts by mass of cerium oxide. Mainly cerium oxide containing 2 parts by mass of silicon oxide with respect to 100 parts by mass of cerium oxide, except that the amount of tetraethyl orthosilicate added is 1.04 g (containing 0.31 g in terms of SiO 2 ). A composite oxide powder was obtained. The physical properties of the obtained composite oxide powder were evaluated in the same manner as in Example 1. The results are shown in Table 1.
- Example 3 This example relates to a composite oxide in which 5.3 parts by mass of silicon oxide is added to 100 parts by mass of cerium oxide. Oxidation containing 5.3 parts by mass of silicon oxide per 100 parts by mass of cerium oxide in the same manner as in Example 1 except that the amount of tetraethyl orthosilicate added was 2.65 g (containing 0.79 g in terms of SiO 2 ). A cerium-based composite oxide powder was obtained. The physical properties of the obtained composite oxide powder were evaluated in the same manner as in Example 1. The results are shown in Table 1.
- Example 4 This example relates to a composite oxide in which 11 parts by mass of silicon oxide is added to 100 parts by mass of cerium oxide. Mainly cerium oxide containing 11 parts by mass of silicon oxide with respect to 100 parts by mass of cerium oxide in the same manner as in Example 1 except that the amount of tetraethyl orthosilicate added was 5.60 g (containing 1.67 g in terms of SiO 2 ). A composite oxide powder was obtained. The physical properties of the obtained composite oxide powder were evaluated in the same manner as in Example 1. The results are shown in Table 1.
- Example 5 This example relates to a composite oxide in which 20 parts by mass of silicon oxide is added to 100 parts by mass of cerium oxide. Mainly cerium oxide containing 20 parts by mass of silicon oxide with respect to 100 parts by mass of cerium oxide in the same manner as in Example 1, except that the amount of tetraethyl orthosilicate added was 10.6 g (containing 3.16 g in terms of SiO 2 ). A composite oxide powder was obtained. The physical properties of the obtained composite oxide powder were evaluated in the same manner as in Example 1. The results are shown in Table 1.
- Example 6 This example relates to a composite oxide prepared by adding 11 parts by mass of silicon oxide to 100 parts by mass of cerium oxide and prepared by a method different from that in Example 4. After collecting 20 g of a cerium nitrate solution containing 90 mol% or more of tetravalent cerium ions in terms of CeO 2 , the total amount was adjusted to 1 L with pure water. Next, after heating up the obtained solution to 100 degreeC and hold
- colloidal silica 2.2 g in terms of SiO 2
- the slurry obtained by neutralization was subjected to solid-liquid separation by Nutsche filtration to obtain a filter cake, and the cake was baked at 500 ° C. for 10 hours in the air.
- the obtained fired product was subjected to a reduction treatment by being held at 250 ° C. for 2 hours in a 90% argon-10% hydrogen atmosphere. Subsequently, it was calcined in an air atmosphere at 500 ° C. for 0.5 hour to obtain a cerium oxide-based composite oxide powder containing 11 parts by mass of silicon oxide with respect to 100 parts by mass of cerium oxide.
- the physical properties of the obtained composite oxide powder were evaluated in the same manner as in Example 1. The results are shown in Table 1.
- Comparative Example 1 This example relates to cerium oxide without silicon oxide.
- a cerium nitrate solution containing 90 mol% or more of tetravalent cerium ions was collected in an amount of 20 g in terms of CeO 2 , and then adjusted to a total amount of 1 L with pure water.
- the obtained solution was introduced into an autoclave reactor, heated to 120 ° C., held for 6 hours, and then naturally cooled to room temperature.
- aqueous ammonia was added to neutralize to pH 8 to obtain a slurry of cerium oxide hydrate.
- the slurry was subjected to solid-liquid separation by Nutsche filtration to obtain a filter cake.
- the filter cake was baked in a box-type electric furnace in an air atmosphere at 500 ° C.
- the obtained fired product was subjected to a reduction treatment by being held at 250 ° C. for 2 hours in a 90% argon-10% hydrogen atmosphere. Subsequently, it baked at 500 degreeC in the air atmosphere for 0.5 hour, and obtained the cerium oxide powder.
- the physical properties of the obtained cerium oxide powder were evaluated in the same manner as in Example 1. The results are shown in Table 1.
- Comparative Example 2 This example is a composite oxide in which 6.8 parts by mass of silicon oxide is added to 100 parts by mass of cerium oxide, and the method described in the academic paper Journal of Catalysis 194, 461-478 (2000)). Synthesized in compliance. That is, an aqueous solution of 7.69 g of sodium silicate (3.42 g in terms of SiO 2 ) and 108.24 g of cerium chloride (50.0 g in terms of CeO 2 ) were mixed to obtain a 2.23 L mixed aqueous solution. Next, the mixed aqueous solution was subjected to heat treatment at 90 ° C. for 24 hours in the reactor to obtain a yellow slurry.
- the Si content is based on 100 parts by mass of Ce converted to CeO 2 It is Si mass part of SiO 2 conversion.
- Example 7 This example relates to a composite oxide in which 1 part by mass of silicon oxide is further added to a total of 100 parts by mass of cerium oxide, lanthanum oxide and praseodymium oxide having a mass ratio of 90: 5: 5. After 50 g of a cerium nitrate solution containing 90 mol% or more of tetravalent cerium ions was collected in terms of CeO 2 , the total amount was adjusted to 1 L with pure water. Next, after heating up the obtained solution to 100 degreeC and hold
- the obtained slurry was subjected to solid-liquid separation by Nutsche filtration to obtain a filter cake.
- the cake was baked in the atmosphere at 500 ° C. for 10 hours.
- the obtained fired product was subjected to a reduction treatment by being held at 250 ° C. for 2 hours in a 90% argon-10% hydrogen atmosphere.
- it is calcined in an air atmosphere at 500 ° C. for 0.5 hour, and contains cerium oxide, lanthanum oxide and praseodymium oxide in a mass ratio of 90: 5: 5, to 100 parts by mass of cerium oxide, lanthanum oxide and praseodymium oxide.
- a cerium oxide-based composite oxide powder containing 1 part by mass of silicon oxide was obtained.
- the physical properties of the obtained composite oxide powder were evaluated in the same manner as in Example 1. The results are shown in Table 2.
- Example 8 This example relates to a composite oxide in which 2 parts by mass of silicon oxide is further added to a total of 100 parts by mass of cerium oxide, lanthanum oxide and praseodymium oxide having a mass ratio of 90: 5: 5. Cerium oxide, lanthanum oxide, and praseodymium oxide were mixed at a mass ratio of 90: 5: 5 in the same manner as in Example 7 except that the amount of colloidal silica added was 4.9 g (containing 1.0 g in terms of SiO 2 ). In addition, a cerium oxide-based composite oxide powder containing 2 parts by mass of silicon oxide with respect to 100 parts by mass of cerium oxide, lanthanum oxide and praseodymium oxide was obtained. The physical properties of the obtained composite oxide powder were evaluated in the same manner as in Example 1. The results are shown in Table 2.
- Example 9 This example relates to a composite oxide in which 5 parts by mass of silicon oxide is further added to 100 parts by mass of cerium oxide, lanthanum oxide and praseodymium oxide having a mass ratio of 90: 5: 5. Cerium oxide, lanthanum oxide and praseodymium oxide were mixed at a mass ratio of 90: 5: 5 in the same manner as in Example 7 except that the amount of colloidal silica added was 12.7 g (containing 2.6 g in terms of SiO 2 ). In addition, a cerium oxide-based composite oxide powder containing 5 parts by mass of silicon oxide with respect to 100 parts by mass of cerium oxide, lanthanum oxide and praseodymium oxide was obtained. The physical properties of the obtained composite oxide powder were evaluated in the same manner as in Example 1. The results are shown in Table 2.
- Example 10 This example relates to a composite oxide in which 10 parts by mass of silicon oxide is further added to a total of 100 parts by mass of cerium oxide, lanthanum oxide and praseodymium oxide having a mass ratio of 90: 5: 5. Cerium oxide, lanthanum oxide and praseodymium oxide were mixed at a mass ratio of 90: 5: 5 in the same manner as in Example 7 except that the amount of colloidal silica added was 25.4 g (containing 5.2 g in terms of SiO 2 ). In addition, a cerium oxide-based composite oxide powder containing 10 parts by mass of silicon oxide with respect to 100 parts by mass of cerium oxide, lanthanum oxide and praseodymium oxide was obtained. The physical properties of the obtained composite oxide powder were evaluated in the same manner as in Example 1. The results are shown in Table 2.
- Example 11 This example relates to a composite oxide in which 20 parts by mass of silicon oxide is further added to a total of 100 parts by mass of cerium oxide, lanthanum oxide and praseodymium oxide having a mass ratio of 90: 5: 5. Cerium oxide, lanthanum oxide, and praseodymium oxide at a mass ratio of 90: 5: 5 except that the amount of colloidal silica added was 50.8 g (containing 10.4 g in terms of SiO 2 ). In addition, a cerium oxide-based composite oxide powder containing 20 parts by mass of silicon oxide with respect to 100 parts by mass of cerium oxide, lanthanum oxide, and praseodymium oxide was obtained. The physical properties of the obtained composite oxide powder were evaluated in the same manner as in Example 1. The results are shown in Table 2.
- Example 12 This example is a composite oxide obtained by further adding 5 parts by mass of silicon oxide to 100 parts by mass of cerium oxide, lanthanum oxide and praseodymium oxide having a mass ratio of 90: 5: 5. It relates to an example manufactured by a different method. After 50 g of a cerium nitrate solution containing 90 mol% or more of tetravalent cerium ions was collected in terms of CeO 2 , the total amount was adjusted to 1 L with pure water. Next, after heating up the obtained solution to 100 degreeC and hold
- the cake was baked in the atmosphere at 300 ° C. for 10 hours to obtain a cerium oxide-based rare earth composite oxide containing 5% by mass of lanthanum oxide and praseodymium oxide, respectively.
- 16.1 g of the obtained rare earth composite oxide was introduced into a beaker, and 2.60 g of tetraethyl orthosilicate (containing 0.75 g in terms of SiO 2 ) was dissolved in ethanol to a total amount of 9 ml.
- the solution was added and impregnated with the silicon oxide precursor solution by the pore filling method.
- the rare earth composite oxide impregnated with the silicon oxide precursor solution was dried at 120 ° C. for 10 hours, and then fired in the air at 500 ° C. for 10 hours.
- the obtained fired product was subjected to a reduction treatment by being held at 250 ° C. for 2 hours in a 90% argon-10% hydrogen atmosphere. Next, it is calcined in an air atmosphere at 500 ° C. for 0.5 hour, and contains cerium oxide, lanthanum oxide and praseodymium oxide in a mass ratio of 90: 5: 5, to 100 parts by mass of cerium oxide, lanthanum oxide and praseodymium oxide. In contrast, a cerium oxide-based composite oxide powder containing 5 parts by mass of silicon oxide was obtained. The physical properties of the obtained composite oxide powder were evaluated in the same manner as in Example 1. The results are shown in Table 2.
- Example 13 This example relates to a composite oxide obtained by further adding 5 parts by mass of silicon oxide to 100 parts by mass of cerium oxide and lanthanum oxide having a mass ratio of 90:10.
- cerium oxide and lanthanum oxide were obtained in the same manner as in Example 12 except that only 20.8 ml of lanthanum nitrate solution (containing 5.2 g in terms of La 2 O 3 ) was added.
- the physical properties of the obtained composite oxide powder were evaluated in the same manner as in Example 1. The results are shown in Table 1.
- Example 14 This example relates to a composite oxide obtained by further adding 5 parts by mass of silicon oxide to 100 parts by mass of cerium oxide and praseodymium oxide having a mass ratio of 90:10.
- cerium oxide and praseodymium oxide were obtained in the same manner as in Example 12 except that only 20.5 ml of praseodymium nitrate solution (containing 5.2 g in terms of Pr 6 O 11 ) was added.
- the physical properties of the obtained composite oxide powder were evaluated in the same manner as in Example 1. The results are shown in Table 2.
- Example 15 This example relates to a composite oxide in which 5 parts by mass of silicon oxide is further added to 100 parts by mass of cerium oxide and neodymium oxide having a mass ratio of 90:10.
- cerium oxide and oxidation were performed in the same manner as in Example 12 except that 23.5 ml of neodymium nitrate solution (containing 5.2 g in terms of Nd 2 O 3 ) was added.
- a cerium oxide-based composite oxide powder containing neodymium at a mass ratio of 90:10 and containing 5 parts by mass of silicon oxide with respect to 100 parts by mass of cerium oxide and neodymium oxide was obtained.
- the physical properties of the obtained composite oxide powder were evaluated in the same manner as in Example 1. The results are shown in Table 2.
- Example 16 This example relates to a composite oxide obtained by adding 5 parts by mass of silicon oxide to 100 parts by mass of cerium oxide and yttrium oxide having a mass ratio of 90:10.
- cerium oxide and oxidation were performed in the same manner as in Example 12 except that 22.9 ml of yttrium nitrate solution (containing 5.2 g in terms of Y 2 O 3 ) was added.
- a cerium oxide-based composite oxide powder containing yttrium at a mass ratio of 90:10 and containing 5 parts by mass of silicon oxide with respect to 100 parts by mass of cerium oxide and yttrium oxide was obtained.
- the physical properties of the obtained composite oxide powder were evaluated in the same manner as in Example 1. The results are shown in Table 2.
- Comparative Example 3 This example is an example of a composite oxide not containing silicon oxide. After 50 g of a cerium nitrate solution containing 90 mol% or more of tetravalent cerium ions was collected in terms of CeO 2 , the total amount was adjusted to 1 L with pure water. Next, after heating up the obtained solution to 100 degreeC and hold
- the cerium suspension containing the precursors of lanthanum oxide and praseodymium oxide was kept at 120 ° C. for 2 hours, then naturally cooled, and neutralized to pH 8.5 by adding aqueous ammonia.
- the obtained slurry was subjected to solid-liquid separation by Nutsche filtration to obtain a filter cake.
- the cake was baked in the atmosphere at 500 ° C. for 10 hours to obtain a cerium oxide-based rare earth composite oxide containing 5% by mass of lanthanum oxide and praseodymium oxide, respectively.
- the obtained fired product was subjected to a reduction treatment by being held at 250 ° C.
- the Si content is Si parts by mass in terms of SiO 2 with respect to 100 parts by mass in terms of oxides of rare earth metal elements including Ce.
- Example 17 The cerium oxide, lanthanum oxide and praseodymium oxide were mixed at a mass ratio of 90: 5: 5 in the same manner as in Example 10 except that the reduction treatment at 250 ° C. for 2 hours was changed to the reduction treatment at 150 ° C. for 2 hours.
- a cerium oxide-based composite oxide powder containing 10 parts by mass of silicon oxide with respect to 100 parts by mass of cerium oxide, lanthanum oxide and praseodymium oxide was obtained.
- the physical properties of the obtained composite oxide powder were evaluated in the same manner as in Example 1. The results are shown in Table 3.
- Example 18 The cerium oxide, lanthanum oxide and praseodymium oxide were mixed at a mass ratio of 90: 5: 5 in the same manner as in Example 10 except that the reduction treatment at 250 ° C. for 2 hours was changed to the reduction treatment at 500 ° C. for 2 hours.
- a cerium oxide-based composite oxide powder containing 10 parts by mass of silicon oxide with respect to 100 parts by mass of cerium oxide, lanthanum oxide and praseodymium oxide was obtained.
- the physical properties of the obtained composite oxide powder were evaluated in the same manner as in Example 1. The results are shown in Table 3.
- Example 19 Cerium oxide, lanthanum oxide, and lanthanum oxide were the same as in Example 10 except that the firing at 500 ° C. for 0.5 hour after the reduction treatment at 250 ° C. for 2 hours was changed to 200 ° C. for 0.5 hour.
- a cerium oxide-based composite oxide powder containing praseodymium oxide at a mass ratio of 90: 5: 5 and containing 10 parts by mass of silicon oxide with respect to 100 parts by mass of cerium oxide, lanthanum oxide and praseodymium oxide was obtained.
- the physical properties of the obtained composite oxide powder were evaluated in the same manner as in Example 1. The results are shown in Table 3.
- Example 20 Cerium oxide, lanthanum oxide, and lanthanum oxide were the same as in Example 10 except that the firing at 500 ° C. for 0.5 hour after the reduction treatment at 250 ° C. for 2 hours was changed to 800 ° C. for 0.5 hour.
- a cerium oxide-based composite oxide powder containing praseodymium oxide at a mass ratio of 90: 5: 5 and containing 10 parts by mass of silicon oxide with respect to 100 parts by mass of cerium oxide, lanthanum oxide and praseodymium oxide was obtained.
- the physical properties of the obtained composite oxide powder were evaluated in the same manner as in Example 1. The results are shown in Table 3.
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Abstract
Description
排ガス浄化用触媒による排ガス浄化の効率は、一般に触媒金属の活性種と排ガスとの接触面積に比例する。また、上記燃料と空気量との比を最適に維持することも重要な問題であって、そのためには、助触媒の酸素吸収・放出能に係る還元率を高く維持する必要がある。特に、排ガス規制の強化に伴い、エンジンのコールドスタート時等、触媒の温度が低い状態でも高い酸化還元能を示し、同時に高い耐熱性を保持した助触媒材料が求められている。
また、特許文献2~4には、CeZrBiにさらに第4成分として、それぞれBa、Ag、Ptを添加し、耐熱性または相安定性の向上を図った複合酸化物が提案されている。しかしながら、高温の還元雰囲気に曝された場合に、ビスマス成分の蒸発が懸念される。
しかし、具体的に、セリウム、ケイ素や、セリウムを除く希土類金属元素を含む複合酸化物において、耐熱性に優れ、低温下においても十分な還元率を示すものについては知られていない。
本発明の別の課題は、耐熱性及び還元率に優れた上記本発明の複合酸化物を容易に得ることができる複合酸化物の製造法を提供することにある。
また本発明によれば、セリウムイオンの90モル%以上が4価であるセリウム溶液を準備する工程(a1)と、工程(a1)で準備したセリウム溶液を60℃以上に加熱保持する工程(b1)と、加熱保持して得たセリウム懸濁液に沈澱剤を添加し、沈澱物を得る工程(c1)と、酸化セリウムを得るために、沈澱物を仮焼する工程(d1)と、仮焼して得た酸化セリウムに、酸化ケイ素の前駆体溶液を含浸させる工程(e1)と、酸化ケイ素の前駆体溶液を含浸させた酸化セリウムを焼成する工程(f1)と、得られた焼成物を還元する工程(g)と、還元物を酸化する工程(h)とを含む複合酸化物の製造法(以下、第1の方法と略す場合がある)が提供される。
更に本発明によれば、上記工程(a1)と、上記工程(b1)と、加熱保持して得たセリウム懸濁液に、イットリウムを含みセリウムを含まない希土類金属元素の酸化物の前駆体を加える工程(a2)と、イットリウムを含みセリウムを含まない希土類金属元素の酸化物の前駆体を含むセリウム懸濁液を100℃以上に加熱保持する工程(b2)と、工程(b2)で得た懸濁液に、沈澱剤を添加し、沈澱物を得る工程(c2)と、沈澱物を仮焼する工程(d2)と、仮焼して得た酸化物に、酸化ケイ素の前駆体溶液を含浸させる工程(e2)と、酸化ケイ素の前駆体溶液を含浸させた酸化物を、焼成する工程(f2)と、上記工程(g)と、上記工程(h)とを含む複合酸化物の製造法(以下、第2の方法と略す場合がある)が提供される。
更にまた本発明によれば、セリウムイオンの90モル%以上が4価であるセリウム溶液を準備する工程(A1)と、工程(A1)で準備したセリウム溶液を60℃以上に加熱保持する工程(B1)と、加熱保持したセリウム懸濁液に酸化ケイ素の前駆体を加える工程(C1)と、酸化ケイ素の前駆体を含むセリウム懸濁液を100℃以上に加熱保持する工程(D1)と、加熱保持して得た酸化ケイ素の前駆体を含むセリウム懸濁液に沈澱剤を添加し、沈澱物を得る工程(E1)と、得られた沈澱物を焼成する工程(F)と、得られた焼成物を還元する工程(G)と、還元物を酸化する工程(H)とを含む複合酸化物の製造法(以下、第3の方法と略す場合がある)が提供される。
また本発明によれば、上記工程(A1)と、上記工程(B1)と、加熱保持して得たセリウム懸濁液に、酸化ケイ素の前駆体及びイットリウムを含みセリウムを含まない希土類金属元素の酸化物の前駆体を加える工程(A2)と、酸化ケイ素の前駆体及びイットリウムを含みセリウムを含まない希土類金属元素の酸化物の前駆体を含むセリウム懸濁液を100℃以上に加熱保持する工程(B2)と、工程(B2)で得た懸濁液に沈澱剤を添加し、沈澱物を得る工程(E2)と、上記工程(F)と、上記工程(G)と、上記工程(H)とを含む複合酸化物の製造法(以下、第4の方法と略す場合がある。また、第1の方法~第4の方法をまとめて本発明の製造法と略す)が提供される。
更に本発明によれば、上記本発明の複合酸化物を備えた排ガス浄化用触媒が提供される。
また本発明によれば、排ガス浄化用触媒を製造するための、上記本発明の複合酸化物の使用が提供される。
更に本発明によれば、触媒金属と、本発明の複合酸化物からなる助触媒と、触媒担持体とを備え、前記触媒金属及び助触媒が、触媒担持体に担持された排ガス浄化用触媒が提供される。
本発明の複合酸化物の製造法は、上記各工程を含み、特に、焼成後に還元・酸化工程を行うので、上記本発明の複合酸化物を容易に得ることができる。このような複合酸化物が得られるのは、本発明の製造法における還元工程及び酸化工程によりセリウム粒子表面にCeO2とSiO2とがナノレベルでより均一に混合されたSiリッチドメインが形成されるためと考えられる。そうすることで、本発明の複合酸化物は、還元雰囲気に曝された際のセリウムケイ酸塩形成に対する活性化エネルギーが低下し、400℃以下でも高い酸素放出能が得られるものと考えられる。そして、酸化・還元が繰り返された場合でも、CeO2-SiO2のナノレベルでの均一な混合とセリウムケイ酸塩の形成とが可逆的に起こるため、400℃以下においても高い酸化還元能が持続されると考えられる。
本発明の複合酸化物は、10%水素-90%アルゴン雰囲気下、10℃/分の昇温速度で50℃から900℃まで昇温還元測定(TPR)を行った後、500℃で0.5時間の酸化処理を行い、再度前記昇温還元測定を行った結果から算出した400℃以下の還元率が1.5%以上、好ましくは2.0%以上を示す特性を有する。該400℃以下の還元率の上限は特に限定されないが、通常4.0%、好ましくは5.0%である。
還元率は、50℃から900℃までの昇温還元測定(TPR)の結果から算出した酸化物中のセリウムが4価から3価に還元された比率を意味する。
前記TPRは、(株)大倉理研製、自動昇温脱離分析装置(装置名、TP-5000)を使用し、測定条件は、キャリアガス:90%アルゴン-10%水素、ガス流量:30mL/分、測定中の試料昇温速度:10℃/分、試料重量0.5gにて測定したものである。
算出は下記式に従って行った。
還元率(%)=試料の400℃以下の実測水素消費量(μmol/g)/試料中の酸化セリウムの理論水素消費量(μmol/g)×100
ここで、比表面積とは、粉体の比表面積測定法として最も標準的な窒素ガス吸着によるBET法に基づいて測定された値を意味する。
セリウムを含む希土類金属元素は、セリウム単独、もしくはセリウムと特定の希土類金属元素とからなる。該セリウムと特定の希土類金属元素との割合は、酸化物換算の質量比で、85:15~99:1、好ましくは85:15~95:5の範囲である。セリウムのCeO2換算の含有割合が85質量%未満、また、99質量%を超える場合には、耐熱性及び還元率が低下する恐れがある。
本発明においてイットリウムはY2O3、ランタンはLa2O3、セリウムはCeO2、プラセオジムはPr6O11、ネオジムはNd2O3、サマリウムはSm2O3、ユウロピウムはEu2O3、ガドリニウムはGd2O3、テルビウムはTb4O7、ジスプロシウムDy2O3、ホルミウムはHo2O3、エルビウムはEr2O3、ツリウムはTm2O3、イッテルビウムはYb2O3、ルテチウムはLu2O3として、それぞれ酸化物に換算される。
工程(a1)に用いる水溶性セリウム化合物としては、例えば、硝酸第二セリウム溶液、硝酸第二セリウムアンモニウムを挙げることができ、特に、硝酸第二セリウム溶液の使用が好ましい。
工程(a1)において、セリウムイオンの90モル%以上が4価であるセリウム溶液の初期濃度は、セリウムをCeO2換算で通常5~100g/L、好ましくは5~80g/L、特に好ましくは10~70g/Lに調整することができる。セリウム溶液の濃度の調整には、通常水を用い、脱イオン水の使用が特に好ましい。該初期濃度は、高すぎると後述する沈澱物の結晶性が上がらず、後述する酸化ケイ素の前駆体溶液を含有させるのに十分な細孔を形成できず、最終的に得られる複合酸化物の耐熱性及び還元率が低下する恐れがある。また、濃度が低すぎると生産性が低いため工業的に有利でない。
工程(b1)において加熱保持温度は、60℃以上、好ましくは60~200℃、特に好ましくは80~180℃、更に好ましくは90~160℃である。加熱保持時間は、通常10分~48時間、好ましくは30分~36時間、より好ましくは1時間~24時間である。加熱保持が十分でないと、後述する沈澱物の結晶性が上がらず、後述する酸化ケイ素の前駆体溶液を含浸させるのに十分な容積を有する細孔を形成できず、最終的に得られる複合酸化物の耐熱性及び還元率を十分改善できない恐れがある。また、加熱保持時間が長すぎても耐熱性及び還元率への影響は微々たるものであり、工業的に有利でない。
工程(c1)に用いる沈澱剤としては、例えば、水酸化ナトリウム、水酸化カリウム、アンモニア水、アンモニアガス又はこれらの混合物の塩基が挙げられ、特に、アンモニア水の使用が好ましい。
前記沈澱剤の添加は、例えば、沈澱剤を適度な濃度の水溶液とし、工程(b1)で得られたセリウム懸濁液に撹拌しながら加える方法、また、アンモニアガスの場合は撹拌しながら反応器内に吹き込む方法により実施できる。沈澱剤の添加量は、懸濁液のpHの変化を追跡することにより容易に決定できる。通常、セリウム懸濁液のpHが7~9程度の沈澱が生じる量で十分であり、好ましくはpH7~8.5となる量である。
冷却は、通常、攪拌下に行うことができ、一般的に知られている方法を用いることができる。自然徐冷又は冷却管を用いる強制冷却でも良い。冷却温度は、通常40℃以下、好ましくは20~30℃の室温程度である。
工程(d1)の仮焼により得られる酸化セリウムは、後述する酸化ケイ素の前駆体溶液を含浸させるのに十分な容積を有する細孔を保持する多孔質体となり、酸化ケイ素の前駆体溶液の含浸を容易にして、かつ最終的に得られる複合酸化物の耐熱性及び還元率を改善することができる。
仮焼時間は、通常30分~36時間、特に1時間~24時間、更には3~20時間が好ましい。
工程(e1)に用いる酸化ケイ素の前駆体は、焼成等の酸化処理により酸化ケイ素となりうる化合物であって、溶媒を用いて仮焼した酸化セリウムの多孔質体に含浸させることが可能な化合物であれば良く、例えば、ケイ酸ナトリウム等のケイ酸塩類、オルトケイ酸テトラエチル等のシラン化合物、イソシアン酸トリメチルシリル等のシリル化合物、ケイ酸テトラメチルアンモニウム等のケイ酸第四アンモニウム塩類が挙げられる。
酸化ケイ素の前駆体を溶解する溶媒は、使用する前駆体の種類に応じて使い分けることができる。例えば、水、あるいはアルコール、キシレン、ヘキサン、トルエン等の有機溶媒が挙げられる。
酸化ケイ素の前駆体溶液の濃度は酸化セリウムへの含浸が可能であれば特に限定されないが、酸化ケイ素の前駆体をSiO2換算した濃度で、通常1~300g/L、好ましくは10~200g/L程度が作業性及び効率性の点で好ましい。
ポアフィリング法としては、あらかじめ酸化セリウムの細孔容積を測定し、これと同じ容積の酸化ケイ素の前駆体溶液を加え、酸化セリウム表面が均一に濡れた状態にする方法が挙げられる。
工程(f1)において焼成時間は、焼成温度との兼ね合いで適宜設定でき、通常1~10時間の範囲で決定することができる。
第1の方法では、上記工程(e1)の後、工程(f1)を行うにあたって、酸化ケイ素の前駆体溶液を含浸させた酸化セリウムを、60~200℃程度で乾燥する工程を実施することもできる。このような乾燥工程を行うことにより、工程(f1)の焼成を効率良く実施することができる。
工程(g)において還元は、例えば、水素、重水素、一酸化炭素などを単独あるいは混合して得られる還元雰囲気下、または窒素、ヘリウム、アルゴンなどを単独あるいは混合して得られる不活性雰囲気下、もしくは真空下にて行うことができる。還元の際の温度は、通常100~600℃、好ましくは150~500℃である。還元時間は、通常0.5~5時間、好ましくは1~3時間である。
工程(h)において酸化は、空気雰囲気下、通常100~900℃、好ましくは200~800℃の範囲で行うことができる。酸化時間は、通常0.1~3時間、好ましくは0.3~2時間である。
第1の方法では、工程(h)により、上記物性を有する本発明の複合酸化物を得ることができる。
特定の希土類金属元素の酸化物の前駆体は、焼成等の酸化処理により特定の希土類金属元素の酸化物となりうる化合物であれば良く、例えば、特定の希土類金属元素含有硝酸溶液が挙げられる。
特定の希土類金属元素の酸化物の前駆体の添加量は、上記セリウム懸濁液中のセリウムと、特定の希土類金属元素の酸化物の前駆体中の特定の希土類金属元素とを酸化物換算の質量比で、通常85:15~99:1、好ましくは85:15~95:5の範囲となるように調整することができる。セリウムと、特定の希土類金属元素との酸化物におけるセリウムのCeO2換算の含有割合が85質量%未満の場合には、得られる複合酸化物の耐熱性及び還元率が低下する恐れがある。
工程(b2)において、加熱保持時間は、通常10分~6時間、好ましくは20分~5時間、より好ましくは30分~4時間である。
この工程(b2)の加熱保持において、100℃未満では後述する沈澱物の結晶性が上がらず、最終的に得られる複合酸化物の耐熱性及び還元率を十分改善できない恐れがある。また、加熱保持時間が長すぎても耐熱性及び還元率への影響は微々たるものであり、工業的に有利でない。
工程(c2)に用いる沈澱剤としては、例えば、水酸化ナトリウム、水酸化カリウム、アンモニア水、アンモニアガス又はこれらの混合物の塩基が挙げられ、特に、アンモニア水の使用が好ましい。
前記沈澱剤の添加は、例えば、沈澱剤を適度な濃度の水溶液とし、工程(c2)で得られた懸濁液に撹拌しながら加える方法、また、アンモニアガスの場合は撹拌しながら反応器内に吹き込む方法により実施できる。沈澱剤の添加量は、懸濁液のpHの変化を追跡することにより容易に決定できる。通常、懸濁液のpHが7~9程度の沈澱が生じる量で十分であり、好ましくはpH7~8.5となる量である。
冷却は、通常、攪拌下に行うことができ、一般的に知られている方法を用いることができる。自然徐冷又は冷却管を用いる強制冷却でも良い。冷却温度は、通常40℃以下、好ましくは20~30℃の室温程度である。
工程(d2)の仮焼により得られる酸化物は、後述する酸化ケイ素の前駆体溶液を含浸させるのに十分な容積を有する細孔を保持する多孔質体となり、酸化ケイ素の前駆体溶液の含浸を容易にして、かつ最終的に得られる複合酸化物の耐熱性及び還元率を改善することができる。
工程(e2)に用いる酸化ケイ素の前駆体は、焼成等の酸化処理により酸化ケイ素となりうる化合物であって、溶媒を用いて仮焼した酸化物の多孔質体に含浸させることが可能な化合物であれば良く、例えば、ケイ酸ナトリウム等のケイ酸塩類、オルトケイ酸テトラエチル等のシラン化合物、イソシアン酸トリメチルシリル等のシリル化合物、ケイ酸テトラメチルアンモニウム等のケイ酸第四アンモニウム塩類が挙げられる。
酸化ケイ素の前駆体を溶解する溶媒は、使用する前駆体の種類に応じて使い分けることができる。例えば、水、あるいはアルコール、キシレン、ヘキサン、トルエン等の有機溶媒が挙げられる。
酸化ケイ素の前駆体溶液の濃度は、前記多孔質体の酸化物への含浸が可能であれば特に限定されないが、酸化ケイ素の前駆体をSiO2換算した濃度で、通常1~300g/L、好ましくは10~200g/L程度が作業性及び効率性の点で好ましい。
ポアフィリング法としては、あらかじめ前記酸化物の細孔容積を測定し、これと同じ容積の酸化ケイ素の前駆体溶液を加え、酸化物表面が均一に濡れた状態にする方法が挙げられる。
工程(f2)において焼成時間は、焼成温度との兼ね合いで適宜設定でき、通常1~10時間の範囲で決定することができる。
第2の方法では、上記工程(e2)の後、工程(f2)を行うにあたって、酸化ケイ素の前駆体を含浸させた酸化物を、60~200℃程度で乾燥する工程を実施することもできる。このような乾燥工程を行うことにより、工程(f2)の焼成を効率良く実施することができる。
工程(A1)に用いる水溶性セリウム化合物としては、例えば、硝酸第二セリウム溶液、硝酸第二セリウムアンモニウムを挙げることができ、特に、硝酸第二セリウム溶液の使用が好ましい。
工程(A1)において、セリウムイオンの90モル%以上が4価であるセリウム溶液の初期濃度は、セリウムをCeO2換算で通常5~100g/L、好ましくは5~80g/L、特に好ましくは10~70g/Lに調整することができる。セリウム溶液の濃度の調製には、通常水を用い、脱イオン水の使用が特に好ましい。該初期濃度は、高すぎると後述する沈澱物の結晶性が上がらず、十分な容積を有する細孔を形成できず、最終的に得られる複合酸化物の耐熱性及び還元率が低下する恐れがある。また、濃度が低すぎると生産性が低いため工業的に有利でない。
工程(B1)に使用する反応器としては、密閉タイプの容器、開放タイプの容器のどちらでも良く、好ましくはオートクレーブ反応器を用いることができる。
工程(B1)において加熱保持温度は、60℃以上、好ましくは60~200℃、特に好ましくは80~180℃、更に好ましくは90~160℃である。加熱保持時間は、通常10分~48時間、好ましくは30分~36時間、より好ましくは1時間~24時間である。加熱保持が十分でないと、後述する沈殿物の結晶性が上がらず、十分な容積を有する細孔を形成できず、最終的に得られる複合酸化物の耐熱性及び還元率を十分改善できない恐れがある。また、加熱保持時間が長すぎても耐熱性及び還元率への影響は微々たるものであり、工業的に有利でない。
工程(C1)において、セリウム懸濁液に加える酸化ケイ素の前駆体としては、焼成等の酸化処理により酸化ケイ素となりうる化合物であれば良く、例えば、コロイダルシリカ、シリコネート、第4アンモニウムケイ酸塩のゾルが挙げられ、特に、生産コストと環境負荷の低減の観点からコロイダルシリカの使用が好ましい。
工程(C1)において、前記酸化ケイ素の前駆体を加える前にセリウム懸濁液から母液を除去することにより、また水を加えることにより、セリウム懸濁液の塩濃度を調整しても良い。母液の除去は、例えば、デカンテーション法、ヌッチェ法、遠心分離法、フィルタープレス法で行うことができ、この際、若干量のセリウムが母液と共に除去されるが、この除去されたセリウム量を考慮して、次の酸化ケイ素の前駆体及び水を加える量を調整することができる。
工程(D1)において、加熱保持時間は、通常10分~6時間、好ましくは20分~5時間、より好ましくは30分~4時間である。
この工程(D1)の加熱保持において、100℃未満では後述する沈澱物の結晶性が上がらず、最終的に得られる複合酸化物の耐熱性及び還元率を十分改善できない恐れがある。また、加熱保持時間が長すぎても耐熱性及び還元率への影響は微々たるものであり、工業的に有利でない。
工程(E1)に用いる沈澱剤としては、例えば、水酸化ナトリウム、水酸化カリウム、アンモニア水、アンモニアガス又はこれらの混合物の塩基を用いて行うことができ、特に、アンモニア水の使用が好ましい。工程(E)における沈澱剤の添加量は、加熱保持した酸化ケイ素の前駆体を含むセリウム懸濁液のpHの変化を追跡することにより容易に決定できる。通常、セリウム懸濁液のpHが7~9程度の沈澱が生じる量で十分であり、好ましくはpH7~8.5となる量である。
工程(E1)は、工程(D1)の加熱保持で得られたセリウム懸濁液を冷却した後に行っても良い。冷却は、通常、攪拌下に行うことができ、一般的に知られている方法を用いることができる。自然徐冷又は冷却管を用いる強制冷却でも良い。冷却温度は、通常40℃以下、好ましくは20~30℃の室温程度である。
該沈澱物は、例えば、ヌッチェ法、遠心分離法、フィルタープレス法で分離できる。また、必要程度に沈澱物の水洗を付加することもできる。
該工程(F)により、耐熱性及び還元率に優れたケイ素含有セリウム複合酸化物を得ることができる。
焼成時間は、通常1~48時間、特に1~24時間、更には3~20時間が好ましい。
工程(G)において還元は、例えば、水素、重水素、一酸化炭素などを単独あるいは混合して得られる還元雰囲気下、または窒素、ヘリウム、アルゴンなどを単独あるいは混合して得られる不活性雰囲気下、もしくは真空下にて行うことができる。還元の際の温度は、通常100~600℃、好ましくは150~500℃である。還元時間は、通常0.5~5時間、好ましくは1~3時間である。
工程(H)において酸化は、空気雰囲気下、通常100~900℃、好ましくは200~800℃の範囲で行うことができる。酸化時間は、通常0.1~3時間、好ましくは0.3~2時間である。
第3の方法では、工程(H)により、上記物性を有する本発明の複合酸化物を得ることができる。
工程(A2)において、セリウム懸濁液に加える酸化ケイ素の前駆体としては、焼成等の酸化処理により酸化ケイ素となりうる化合物であれば良く、例えば、コロイダルシリカ、シリコネート、第4アンモニウムケイ酸塩のゾルが挙げられ、特に、生産コストと環境負荷の低減の観点からコロイダルシリカの使用が好ましい。
特定の希土類金属元素の酸化物の前駆体の添加量は、上記セリウム懸濁液中のセリウムと、特定の希土類金属元素の酸化物の前駆体中の特定の希土類金属元素とを酸化物換算による質量比で、通常85:15~99:1、好ましくは85:15~95:5の範囲となるように調整することができる。セリウムと、特定の希土類金属元素との酸化物におけるセリウムのCeO2換算の含有割合が85質量%未満、また99質量%を超える場合には、耐熱性及び還元率が低下する恐れがある。
工程(B2)において、加熱保持時間は、通常10分~6時間、好ましくは20分~5時間、より好ましくは30分~4時間である。
この工程(B2)の加熱保持において、100℃未満では後述する沈澱物の結晶性が上がらず、最終的に得られる複合酸化物の耐熱性及び還元率を十分改善できない恐れがある。また、加熱保持時間が長すぎても耐熱性及び還元率への影響は微々たるものであり、工業的に有利でない。
工程(E2)に用いる沈澱剤としては、例えば、水酸化ナトリウム、水酸化カリウム、アンモニア水、アンモニアガス又はこれらの混合物の塩基を用いて行うことができ、特に、アンモニア水の使用が好ましい。工程(E)における沈澱剤の添加量は、懸濁液のpHの変化を追跡することにより容易に決定できる。通常、懸濁液のpHが7~9程度の沈澱が生じる量で十分であり、好ましくはpH7~8.5となる量である。
工程(E2)は、工程(B2)の加熱保持で得られたセリウム懸濁液を冷却した後に行っても良い。冷却は、通常、攪拌下に行うことができ、一般的に知られている方法を用いることができる。自然徐冷又は冷却管を用いる強制冷却でも良い。冷却温度は、通常40℃以下、好ましくは20~30℃の室温程度である。
該沈澱物は、例えば、ヌッチェ法、遠心分離法、フィルタープレス法で分離できる。また、必要程度に沈澱物の水洗を付加することもできる。
本発明の製造法により得られる複合酸化物粉末の粒径は、上記粉砕により所望粒径とすることができるが、例えば、排ガス浄化用触媒の助触媒として用いる場合には、平均粒径1~50μmとすることが好ましい。
実施例1
この例は、酸化セリウム100質量部に対して、1質量部の酸化ケイ素を添加した複合酸化物に関する。
4価のセリウムイオンを90モル%以上含有する硝酸第二セリウム溶液を、CeO2換算で20g分取した後、純水にて総量1Lに調整した。次に、得られた溶液をオートクレーブ反応器に導入して120℃まで昇温し、6時間保持した後、室温まで自然冷却した。
次いで、アンモニア水を加えてpH8まで中和し、酸化セリウム水和物のスラリーを得た。該スラリーをヌッチェろ過にて固液分離し、ろ過ケーキを得た。該ろ過ケーキを、箱型電気炉にて空気雰囲気中、300℃で10時間焼成して酸化セリウムを得た。
次いで、酸化ケイ素の前駆体溶液を含浸させた酸化セリウムを120℃で10時間乾燥後、大気中、500℃で10時間焼成した。
得られた焼成物を、90%アルゴン-10%水素雰囲気下において、250℃で2時間保持し還元処理を行った。次いで、空気雰囲気中、500℃で0.5時間焼成して酸化セリウム100質量部に対して酸化ケイ素を1質量部含む酸化セリウム主体の複合酸化物粉末を得た。
更に、空気雰囲気下、500℃で0.5時間焼成した後、ガス流量30mL/分の90%アルゴン-10%水素雰囲気において、昇温速度10℃/分で50℃から900℃まで加熱還元した。その後、空気雰囲気として500℃で0.5時間焼成後、比表面積をBET法により測定した。結果を表1に示す。
この例は、酸化セリウム100質量部に対して、2質量部の酸化ケイ素を添加した複合酸化物に関する。
オルトケイ酸テトラエチルの添加量を1.04g(SiO2換算で0.31g含有)とした以外は実施例1と同様にして、酸化セリウム100質量部に対して酸化ケイ素を2質量部含む酸化セリウム主体の複合酸化物粉末を得た。得られた複合酸化物粉末の物性を実施例1と同様の方法で評価した。結果を表1に示す。
この例は、酸化セリウム100質量部に対して、5.3質量部の酸化ケイ素を添加した複合酸化物に関する。
オルトケイ酸テトラエチルの添加量を2.65g(SiO2換算で0.79g含有)とした以外は実施例1と同様にして、酸化セリウム100質量部に対して酸化ケイ素を5.3質量部含む酸化セリウム主体の複合酸化物粉末を得た。得られた複合酸化物粉末の物性を実施例1と同様の方法で評価した。結果を表1に示す。
この例は、酸化セリウム100質量部に対して、11質量部の酸化ケイ素を添加した複合酸化物に関する。
オルトケイ酸テトラエチルの添加量を5.60g(SiO2換算で1.67g含有)とした以外は実施例1と同様にして、酸化セリウム100質量部に対して酸化ケイ素を11質量部含む酸化セリウム主体の複合酸化物粉末を得た。得られた複合酸化物粉末の物性を実施例1と同様の方法で評価した。結果を表1に示す。
この例は、酸化セリウム100質量部に対して、20質量部の酸化ケイ素を添加した複合酸化物に関する。
オルトケイ酸テトラエチルの添加量を10.6g(SiO2換算で3.16g含有)とした以外は実施例1と同様にして、酸化セリウム100質量部に対して酸化ケイ素を20質量部含む酸化セリウム主体の複合酸化物粉末を得た。得られた複合酸化物粉末の物性を実施例1と同様の方法で評価した。結果を表1に示す。
この例は、酸化セリウム100質量部に対して、11質量部の酸化ケイ素を添加した複合酸化物であって、実施例4とは別の方法で調製した複合酸化物に関する。
4価のセリウムイオンを90モル%以上含有する硝酸第二セリウム溶液をCeO2換算で20g分取した後、純水にて総量1Lに調整した。次に、得られた溶液を100℃まで昇温し、30分間保持した後、室温まで自然冷却し、セリウム懸濁液を得た。
次いで、得られた懸濁液中にコロイダルシリカ8.8g(SiO2換算で2.2g)を添加し120℃にて2時間保持した後、自然冷却し、アンモニア水を加えてpH8.5まで中和した。
中和して得られたスラリーをヌッチェろ過にて固液分離し、ろ過ケーキを得、該ケーキを大気中、500℃で10時間焼成した。得られた焼成物を、90%アルゴン-10%水素雰囲気下において、250℃で2時間保持し還元処理を行った。次いで、空気雰囲気中、500℃で0.5時間焼成して酸化セリウム100質量部に対して酸化ケイ素を11質量部含む酸化セリウム主体の複合酸化物粉末を得た。
得られた複合酸化物粉末の物性を実施例1と同様の方法で評価した。結果を表1に示す。
この例は、酸化ケイ素を含まない酸化セリウムに関する。
4価のセリウムイオンを90モル%以上含有する硝酸第二セリウム溶液を、CeO2換算で20g分取した後、純水にて総量1Lに調整した。次に、得られた溶液をオートクレーブ反応器に導入して120℃まで昇温し、6時間保持した後、室温まで自然冷却した。
次いで、アンモニア水を加えてpH8まで中和し、酸化セリウム水和物のスラリーを得た。該スラリーをヌッチェろ過にて固液分離し、ろ過ケーキを得た。該ろ過ケーキを、箱型電気炉にて空気雰囲気中、500℃で10時間焼成して焼成物を得た。
得られた焼成物を、90%アルゴン-10%水素雰囲気下において、250℃で2時間保持し還元処理を行った。次いで、空気雰囲気中、500℃で0.5時間焼成して酸化セリウム粉末を得た。
得られた酸化セリウム粉末の物性を実施例1と同様の方法で評価した。結果を表1に示す。
この例は、酸化セリウム100質量部に対して、6.8質量部の酸化ケイ素を添加した複合酸化物であって、学術論文Journal of Catalysis 194, 461-478 (2000))に記載の方法に準拠して合成した。
即ち、ケイ酸ナトリウム7.69g(SiO2換算で3.42g)の水溶液と塩化セリウム108.24g(CeO2換算で50.0g)の水溶液とを混合し、2.23Lの混合水溶液とした。
次に、混合水溶液を反応機内において90℃で24時間の熱処理にかけ、黄色スラリーを得た。該スラリーにアンモニア水を加えてpH11.5とし、ヌッチェろ過にて固液分離しケーキを得た後、ケーキを純水とアセトンにより洗浄した。
該洗浄ケーキを60℃にて24時間乾燥した後、箱型電気炉にて空気雰囲気中、500℃で10時間焼成して酸化セリウム100質量部に対して酸化ケイ素を6.8質量部含む酸化セリウム主体の複合酸化物粉末を得た。
得られた複合酸化物粉末の物性を実施例1と同様の方法で評価した。結果を表1に示す。
この例は、質量割合が90:5:5の酸化セリウム、酸化ランタン及び酸化プラセオジムの合計100質量部に対して、さらに1質量部の酸化ケイ素を添加した複合酸化物に関する。
4価のセリウムイオンを90モル%以上含有する硝酸第二セリウム溶液を、CeO2換算で50g分取した後、純水にて総量を1Lに調整した。次に、得られた溶液を100℃まで昇温し、30分保持した後、室温まで自然冷却し、セリウム懸濁液を得た。
得られたセリウム懸濁液から母液を除去した後、硝酸ランタン溶液10.4ml(La2O3換算で2.6g含有)、硝酸プラセオジム溶液10.3ml(Pr6O11換算で2.6g含有)、コロイダルシリカ2.5g(SiO2換算で0.5g)を添加し、純水にて総量を1Lに調整した。
次いで、酸化ランタン、酸化プラセオジム及び酸化ケイ素の前駆体を含むセリウム懸濁液を120℃にて2時間保持した後、自然冷却し、アンモニア水を加えてpH8.5まで中和した。
得られたスラリーを、ヌッチェろ過にて固液分離し、ろ過ケーキを得た。該ケーキを大気中、500℃で10時間焼成した。得られた焼成物を、90%アルゴン-10%水素雰囲気下において、250℃で2時間保持し還元処理を行った。次いで、空気雰囲気中、500℃で0.5時間焼成して、酸化セリウム、酸化ランタン及び酸化プラセオジムを、質量比で90:5:5で含み、酸化セリウム、酸化ランタン及び酸化プラセオジム100質量部に対して酸化ケイ素を1質量部含む酸化セリウム主体の複合酸化物粉末を得た。
得られた複合酸化物粉末の物性を実施例1と同様の方法で評価した。結果を表2に示す。
この例は、質量割合が90:5:5の酸化セリウム、酸化ランタン及び酸化プラセオジムの合計100質量部に対して、さらに2質量部の酸化ケイ素を添加した複合酸化物に関する。
コロイダルシリカの添加量を4.9g(SiO2換算で1.0g含有)とした以外は実施例7と同様にして、酸化セリウム、酸化ランタン及び酸化プラセオジムを、質量比で90:5:5で含み、酸化セリウム、酸化ランタン及び酸化プラセオジム100質量部に対して酸化ケイ素を2質量部含む酸化セリウム主体の複合酸化物粉末を得た。得られた複合酸化物粉末の物性を実施例1と同様の方法で評価した。結果を表2に示す。
この例は、質量割合が90:5:5の酸化セリウム、酸化ランタン及び酸化プラセオジムの合計100質量部に対して、さらに5質量部の酸化ケイ素を添加した複合酸化物に関する。
コロイダルシリカの添加量を12.7g(SiO2換算で2.6g含有)とした以外は実施例7と同様にして、酸化セリウム、酸化ランタン及び酸化プラセオジムを、質量比で90:5:5で含み、酸化セリウム、酸化ランタン及び酸化プラセオジム100質量部に対して酸化ケイ素を5質量部含む酸化セリウム主体の複合酸化物粉末を得た。得られた複合酸化物粉末の物性を実施例1と同様の方法で評価した。結果を表2に示す。
この例は、質量割合が90:5:5の酸化セリウム、酸化ランタン及び酸化プラセオジムの合計100質量部に対して、さらに10質量部の酸化ケイ素を添加した複合酸化物に関する。
コロイダルシリカの添加量を25.4g(SiO2換算で5.2g含有)とした以外は実施例7と同様にして、酸化セリウム、酸化ランタン及び酸化プラセオジムを、質量比で90:5:5で含み、酸化セリウム、酸化ランタン及び酸化プラセオジム100質量部に対して酸化ケイ素を10質量部含む酸化セリウム主体の複合酸化物粉末を得た。得られた複合酸化物粉末の物性を実施例1と同様の方法で評価した。結果を表2に示す。
この例は、質量割合が90:5:5の酸化セリウム、酸化ランタン及び酸化プラセオジムの合計100質量部に対して、さらに20質量部の酸化ケイ素を添加した複合酸化物に関する。
コロイダルシリカの添加量を50.8g(SiO2換算で10.4g含有)とした以外は実施例7と同様にして、酸化セリウム、酸化ランタン及び酸化プラセオジムを、質量比で90:5:5で含み、酸化セリウム、酸化ランタン及び酸化プラセオジム100質量部に対して酸化ケイ素を20質量部含む酸化セリウム主体の複合酸化物粉末を得た。得られた複合酸化物粉末の物性を実施例1と同様の方法で評価した。結果を表2に示す。
この例は、質量割合が90:5:5の酸化セリウム、酸化ランタン及び酸化プラセオジムの合計100質量部に対して、さらに5質量部の酸化ケイ素を添加した複合酸化物であって、実施例9とは異なる方法で製造した例に関する。
4価のセリウムイオンを90モル%以上含有する硝酸第二セリウム溶液を、CeO2換算で50g分取した後、純水にて総量を1Lに調整した。次に、得られた溶液を100℃まで昇温し、30分保持した後、室温まで自然冷却し、セリウム懸濁液を得た。
次いで、得られたセリウム懸濁液から母液を除去した後、硝酸ランタン溶液10.4ml(La2O3換算で2.6g含有)、硝酸プラセオジム溶液10.3ml(Pr6O11換算で2.6g含有)を添加し、純水にて総量を1Lに調整した。
次いで、酸化ランタン及び酸化プラセオジムの前駆体を含むセリウム懸濁液を120℃にて2時間保持した後、自然冷却し、アンモニア水を加えてpH8.5まで中和した。
得られたスラリーを、ヌッチェろ過にて固液分離し、ろ過ケーキを得た。該ケーキを大気中、300℃で10時間焼成して、酸化ランタンと酸化プラセオジムをそれぞれ質量比で5%含む酸化セリウム主体の希土類複合酸化物を得た。
次に、得られた希土類複合酸化物16.1gをビーカーに導入し、該複合酸化物中にオルトケイ酸テトラエチル2.60g(SiO2換算で0.75g含有)をエタノールに溶解し総量9mlとした溶液を添加して、ポアフィリング法によって酸化ケイ素の前駆体溶液を含浸させた。
次いで、酸化ケイ素の前駆体溶液を含浸させた希土類複合酸化物を120℃で10時間乾燥後、大気中、500℃で10時間焼成した。得られた焼成物を、90%アルゴン-10%水素雰囲気下において、250℃で2時間保持し還元処理を行った。次いで、空気雰囲気中、500℃で0.5時間焼成して、酸化セリウム、酸化ランタン及び酸化プラセオジムを、質量比で90:5:5で含み、酸化セリウム、酸化ランタン及び酸化プラセオジム100質量部に対して酸化ケイ素を5質量部含む酸化セリウム主体の複合酸化物粉末を得た。得られた複合酸化物粉末の物性を実施例1と同様の方法で評価した。結果を表2に示す。
この例は、質量割合が90:10の酸化セリウム及び酸化ランタンの合計100質量部に対して、さらに5質量部の酸化ケイ素を添加した複合酸化物に関する。
硝酸ランタン溶液及び硝酸プラセオジム溶液を添加する工程において、硝酸ランタン溶液のみを20.8ml(La2O3換算で5.2g含有)添加した以外は実施例12と同様にして、酸化セリウム及び酸化ランタンを、質量比で90:10で含み、酸化セリウム及び酸化ランタン100質量部に対して酸化ケイ素を5質量部含む酸化セリウム主体の複合酸化物粉末を得た。得られた複合酸化物粉末の物性を実施例1と同様の方法で評価した。結果を表1に示す。
この例は、質量割合が90:10の酸化セリウム及び酸化プラセオジムの合計100質量部に対して、さらに5質量部の酸化ケイ素を添加した複合酸化物に関する。
硝酸ランタン溶液及び硝酸プラセオジム溶液を添加する工程において、硝酸プラセオジム溶液のみを20.5ml(Pr6O11換算で5.2g含有)添加した以外は実施例12と同様にして、酸化セリウム及び酸化プラセオジムを、質量比で90:10で含み、酸化セリウム及び酸化プラセオジム100質量部に対して酸化ケイ素を5質量部含む酸化セリウム主体の複合酸化物粉末を得た。得られた複合酸化物粉末の物性を実施例1と同様の方法で評価した。結果を表2に示す。
この例は、質量割合が90:10の酸化セリウム及び酸化ネオジムの合計100質量部に対して、さらに5質量部の酸化ケイ素を添加した複合酸化物に関する。
硝酸ランタン溶液及び硝酸プラセオジム溶液を添加する工程に代えて、硝酸ネオジム溶液を23.5ml(Nd2O3換算で5.2g含有)添加した以外は実施例12と同様にして、酸化セリウム及び酸化ネオジムを、質量比で90:10で含み、酸化セリウム及び酸化ネオジム100質量部に対して酸化ケイ素を5質量部含む酸化セリウム主体の複合酸化物粉末を得た。得られた複合酸化物粉末の物性を実施例1と同様の方法で評価した。結果を表2に示す。
この例は、質量割合が90:10の酸化セリウム及び酸化イットリウムの合計100質量部に対して、さらに5質量部の酸化ケイ素を添加した複合酸化物に関する。
硝酸ランタン溶液及び硝酸プラセオジム溶液を添加する工程に代えて、硝酸イットリウム溶液を22.9ml(Y2O3換算で5.2g含有)添加した以外は実施例12と同様にして、酸化セリウム及び酸化イットリウムを、質量比で90:10で含み、酸化セリウム及び酸化イットリウム100質量部に対して酸化ケイ素を5質量部含む酸化セリウム主体の複合酸化物粉末を得た。得られた複合酸化物粉末の物性を実施例1と同様の方法で評価した。結果を表2に示す。
この例は、酸化ケイ素を含まない複合酸化物の例である。
4価のセリウムイオンを90モル%以上含有する硝酸第二セリウム溶液を、CeO2換算で50g分取した後、純水にて総量を1Lに調整した。次に、得られた溶液を100℃まで昇温し、30分保持した後、室温まで自然冷却し、セリウム懸濁液を得た。
次いで、得られたセリウム懸濁液から母液を除去した後、硝酸ランタン溶液10.4ml(La2O3換算で2.6g含有)、硝酸プラセオジム溶液10.3ml(Pr6O11換算で2.6g含有)を添加し、純水にて総量を1Lに調整した。
次いで、酸化ランタン及び酸化プラセオジムの前駆体を含むセリウム懸濁液を120℃にて2時間保持した後、自然冷却し、アンモニア水を加えてpH8.5まで中和した。
得られたスラリーを、ヌッチェろ過にて固液分離し、ろ過ケーキを得た。該ケーキを大気中、500℃で10時間焼成して、酸化ランタンと酸化プラセオジムをそれぞれ質量比で5%含む酸化セリウム主体の希土類複合酸化物を得た。
得られた焼成物を、90%アルゴン-10%水素雰囲気下において、250℃で2時間保持し還元処理を行った。次いで、空気雰囲気中、500℃で0.5時間焼成して、酸化セリウム、酸化ランタン及び酸化プラセオジムを、質量比で90:5:5で含む酸化セリウム主体の複合酸化物粉末を得た。得られた複合酸化物粉末の物性を実施例1と同様の方法で評価した。結果を表2に示す。
250℃で2時間の還元処理を、150℃で2時間の還元処理に変更した以外は、実施例10と同様に、酸化セリウム、酸化ランタン及び酸化プラセオジムを、質量比で90:5:5で含み、酸化セリウム、酸化ランタン及び酸化プラセオジム100質量部に対して酸化ケイ素を10質量部含む酸化セリウム主体の複合酸化物粉末を得た。得られた複合酸化物粉末の物性を実施例1と同様の方法で評価した。結果を表3に示す。
250℃で2時間の還元処理を、500℃で2時間の還元処理に変更した以外は、実施例10と同様に、酸化セリウム、酸化ランタン及び酸化プラセオジムを、質量比で90:5:5で含み、酸化セリウム、酸化ランタン及び酸化プラセオジム100質量部に対して酸化ケイ素を10質量部含む酸化セリウム主体の複合酸化物粉末を得た。得られた複合酸化物粉末の物性を実施例1と同様の方法で評価した。結果を表3に示す。
250℃で2時間の還元処理を行った後の500℃、0.5時間の焼成を、200℃、0.5時間に変更した以外は、実施例10と同様に、酸化セリウム、酸化ランタン及び酸化プラセオジムを、質量比で90:5:5で含み、酸化セリウム、酸化ランタン及び酸化プラセオジム100質量部に対して酸化ケイ素を10質量部含む酸化セリウム主体の複合酸化物粉末を得た。得られた複合酸化物粉末の物性を実施例1と同様の方法で評価した。結果を表3に示す。
250℃で2時間の還元処理を行った後の500℃、0.5時間の焼成を、800℃、0.5時間に変更した以外は、実施例10と同様に、酸化セリウム、酸化ランタン及び酸化プラセオジムを、質量比で90:5:5で含み、酸化セリウム、酸化ランタン及び酸化プラセオジム100質量部に対して酸化ケイ素を10質量部含む酸化セリウム主体の複合酸化物粉末を得た。得られた複合酸化物粉末の物性を実施例1と同様の方法で評価した。結果を表3に示す。
Claims (14)
- セリウムを含む希土類金属元素の酸化物換算による合計量100質量部に対して、ケイ素をSiO2換算で、0質量部を超え20質量部以下含む複合酸化物であって、
10%水素-90%アルゴン雰囲気下、10℃/分の昇温速度で50℃から900℃まで昇温還元測定(TPR)を行った後、500℃で0.5時間の酸化処理を行い、再度前記昇温還元測定を行った結果から算出した400℃以下の還元率が1.5%以上を示す特性を有する複合酸化物。 - 前記昇温還元測定及び酸化処理を3回繰返した後のBET法による比表面積が20m2/g以上を示す特性を有する請求項1の複合酸化物。
- 希土類金属元素が、セリウムと、イットリウムを含みセリウムを含まない希土類金属元素とを酸化物換算の質量比で、85:15~99:1の範囲で含む請求項1又は2の複合酸化物。
- セリウムを含む希土類金属元素の酸化物換算による合計量100質量部に対して、ケイ素をSiO2換算で、2~20質量部含む請求項1~3のいずれかの複合酸化物。
- 前記400℃以下の還元率が2.0%以上である請求項1~4のいずれかの複合酸化物。
- 前記BET法による比表面積が25m2/g以上である請求項2~5のいずれかの複合酸化物。
- セリウムイオンの90モル%以上が4価であるセリウム溶液を準備する工程(a1)と、
工程(a1)で準備したセリウム溶液を60℃以上に加熱保持する工程(b1)と、
加熱保持して得たセリウム懸濁液に沈澱剤を添加し、沈澱物を得る工程(c1)と、
酸化セリウムを得るために、沈澱物を仮焼する工程(d1)と、
仮焼して得た酸化セリウムに、酸化ケイ素の前駆体溶液を含浸させる工程(e1)と、
酸化ケイ素の前駆体溶液を含浸させた酸化セリウムを焼成する工程(f1)と、
得られた焼成物を還元する工程(g)と、
還元物を酸化する工程(h)とを含む複合酸化物の製造法。 - セリウムイオンの90モル%以上が4価であるセリウム溶液を準備する工程(a1)と、
工程(a1)で準備したセリウム溶液を60℃以上に加熱保持する工程(b1)と、
加熱保持して得たセリウム懸濁液に、イットリウムを含みセリウムを含まない希土類金属元素の酸化物の前駆体を加える工程(a2)と、
イットリウムを含みセリウムを含まない希土類金属元素の酸化物の前駆体を含むセリウム懸濁液を100℃以上に加熱保持する工程(b2)と、
工程(b2)で得た懸濁液に、沈澱剤を添加し、沈澱物を得る工程(c2)と、
沈澱物を仮焼する工程(d2)と、
仮焼して得た酸化物に、酸化ケイ素の前駆体溶液を含浸させる工程(e2)と、
酸化ケイ素の前駆体溶液を含浸させた酸化物を、焼成する工程(f2)と、
得られた焼成物を還元する工程(g)と、
還元物を酸化する工程(h)とを含む複合酸化物の製造法。 - セリウムイオンの90モル%以上が4価であるセリウム溶液を準備する工程(A1)と、
工程(A1)で準備したセリウム溶液を60℃以上に加熱保持する工程(B1)と、
加熱保持したセリウム懸濁液に酸化ケイ素の前駆体を加える工程(C1)と、
酸化ケイ素の前駆体を含むセリウム懸濁液を100℃以上に加熱保持する工程(D1)と、
加熱保持して得た酸化ケイ素の前駆体を含むセリウム懸濁液に沈澱剤を添加し、沈澱物を得る工程(E1)と、
得られた沈澱物を焼成する工程(F)と、
得られた焼成物を還元する工程(G)と、
還元物を酸化する工程(H)とを含む複合酸化物の製造法。 - セリウムイオンの90モル%以上が4価であるセリウム溶液を準備する工程(A1)と、
工程(A1)で準備したセリウム溶液を、60℃以上に加熱保持する工程(B1)と、
加熱保持して得たセリウム懸濁液に、酸化ケイ素の前駆体及びイットリウムを含みセリウムを含まない希土類金属元素の酸化物の前駆体を加える工程(A2)と、
酸化ケイ素の前駆体及びイットリウムを含みセリウムを含まない希土類金属元素の酸化物の前駆体を含むセリウム懸濁液を100℃以上に加熱保持する工程(B2)と、
工程(B2)で得た懸濁液に沈澱剤を添加し、沈澱物を得る工程(E2)と、
得られた沈澱物を焼成する工程(F)と、
得られた焼成物を還元する工程(G)と、
還元物を酸化する工程(H)とを含む複合酸化物の製造法。 - 工程(a1)又は工程(A1)のセリウム溶液中のセリウム濃度が、CeO2換算で5~100g/Lである請求項7~10のいずれかの製造法。
- 工程(g)又は工程(G)の還元を150~500℃の温度範囲で行う請求項7~11のいずれかの製造法。
- 工程(h)又は工程(H)の酸化を200~800℃の温度範囲で行う請求項7~12のいずれかの製造法。
- 請求項1~6のいずれかの複合酸化物を備えた排ガス浄化用触媒。
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KR20190098164A (ko) | 2016-12-28 | 2019-08-21 | 카오카부시키가이샤 | 산화세륨 지립 |
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JP7044510B2 (ja) | 2017-10-10 | 2022-03-30 | 花王株式会社 | 酸化セリウム含有複合研磨材 |
JP2019087571A (ja) * | 2017-11-02 | 2019-06-06 | 花王株式会社 | 複合砥粒 |
JP7019379B2 (ja) | 2017-11-02 | 2022-02-15 | 花王株式会社 | 複合砥粒 |
Also Published As
Publication number | Publication date |
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RU2559884C2 (ru) | 2015-08-20 |
US20140179515A1 (en) | 2014-06-26 |
ZA201308828B (en) | 2014-12-23 |
CN103596679A (zh) | 2014-02-19 |
PL2716361T3 (pl) | 2018-10-31 |
CN103596679B (zh) | 2016-12-28 |
KR20140005342A (ko) | 2014-01-14 |
RU2013158319A (ru) | 2015-07-20 |
JP5911858B2 (ja) | 2016-04-27 |
CA2836386A1 (en) | 2012-12-06 |
US11040332B2 (en) | 2021-06-22 |
KR101633166B1 (ko) | 2016-06-23 |
EP2716361A4 (en) | 2015-04-29 |
EP2716361B1 (en) | 2018-03-28 |
JPWO2012165362A1 (ja) | 2015-02-23 |
CA2836386C (en) | 2017-01-03 |
EP2716361A1 (en) | 2014-04-09 |
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