JP2007203160A - Catalyst support for purification of exhaust gas, catalyst for purification of exhaust gas using it and method of purifying exhaust gas - Google Patents
Catalyst support for purification of exhaust gas, catalyst for purification of exhaust gas using it and method of purifying exhaust gas Download PDFInfo
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- JP2007203160A JP2007203160A JP2006023003A JP2006023003A JP2007203160A JP 2007203160 A JP2007203160 A JP 2007203160A JP 2006023003 A JP2006023003 A JP 2006023003A JP 2006023003 A JP2006023003 A JP 2006023003A JP 2007203160 A JP2007203160 A JP 2007203160A
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- exhaust gas
- alumina
- titania
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- catalyst
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- 239000003054 catalyst Substances 0.000 title claims abstract description 116
- 238000000746 purification Methods 0.000 title claims abstract description 52
- 238000000034 method Methods 0.000 title claims abstract description 28
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims abstract description 165
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 123
- 239000002245 particle Substances 0.000 claims abstract description 116
- 229910044991 metal oxide Inorganic materials 0.000 claims abstract description 45
- 150000004706 metal oxides Chemical class 0.000 claims abstract description 45
- 239000006104 solid solution Substances 0.000 claims abstract description 30
- 239000007789 gas Substances 0.000 claims description 146
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 32
- 229910052760 oxygen Inorganic materials 0.000 claims description 32
- 239000001301 oxygen Substances 0.000 claims description 32
- 239000002243 precursor Substances 0.000 claims description 24
- 238000003860 storage Methods 0.000 claims description 23
- 229910000510 noble metal Inorganic materials 0.000 claims description 17
- 238000005259 measurement Methods 0.000 claims description 13
- 239000011163 secondary particle Substances 0.000 claims description 8
- 239000013078 crystal Substances 0.000 claims description 4
- 238000002441 X-ray diffraction Methods 0.000 claims description 3
- 238000001354 calcination Methods 0.000 claims 1
- 230000000694 effects Effects 0.000 abstract description 39
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 abstract description 32
- 229910052717 sulfur Inorganic materials 0.000 abstract description 32
- 239000011593 sulfur Substances 0.000 abstract description 32
- 231100000572 poisoning Toxicity 0.000 abstract description 26
- 230000000607 poisoning effect Effects 0.000 abstract description 26
- XTQHKBHJIVJGKJ-UHFFFAOYSA-N sulfur monoxide Chemical class S=O XTQHKBHJIVJGKJ-UHFFFAOYSA-N 0.000 abstract description 15
- 229910052815 sulfur oxide Inorganic materials 0.000 abstract description 12
- 239000000243 solution Substances 0.000 abstract description 5
- 230000015572 biosynthetic process Effects 0.000 description 42
- 238000003786 synthesis reaction Methods 0.000 description 40
- 230000000052 comparative effect Effects 0.000 description 37
- 239000002131 composite material Substances 0.000 description 29
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 24
- 239000010936 titanium Substances 0.000 description 22
- 238000006243 chemical reaction Methods 0.000 description 19
- 230000008859 change Effects 0.000 description 14
- 239000000843 powder Substances 0.000 description 14
- 239000007788 liquid Substances 0.000 description 13
- 239000007864 aqueous solution Substances 0.000 description 12
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 11
- 230000007423 decrease Effects 0.000 description 11
- 238000010304 firing Methods 0.000 description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 10
- 238000004519 manufacturing process Methods 0.000 description 9
- 229910052719 titanium Inorganic materials 0.000 description 9
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 description 8
- 239000000446 fuel Substances 0.000 description 8
- 238000002156 mixing Methods 0.000 description 8
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 8
- 239000000203 mixture Substances 0.000 description 7
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 6
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 description 6
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 5
- -1 titanium alkoxide Chemical class 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 4
- 239000000969 carrier Substances 0.000 description 4
- 239000008367 deionised water Substances 0.000 description 4
- 229910021641 deionized water Inorganic materials 0.000 description 4
- 238000000921 elemental analysis Methods 0.000 description 4
- 239000011259 mixed solution Substances 0.000 description 4
- 238000002360 preparation method Methods 0.000 description 4
- VXUYXOFXAQZZMF-UHFFFAOYSA-N titanium(IV) isopropoxide Chemical compound CC(C)O[Ti](OC(C)C)(OC(C)C)OC(C)C VXUYXOFXAQZZMF-UHFFFAOYSA-N 0.000 description 4
- PAWQVTBBRAZDMG-UHFFFAOYSA-N 2-(3-bromo-2-fluorophenyl)acetic acid Chemical compound OC(=O)CC1=CC=CC(Br)=C1F PAWQVTBBRAZDMG-UHFFFAOYSA-N 0.000 description 3
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 3
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 3
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N ammonia Natural products N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 3
- 235000011114 ammonium hydroxide Nutrition 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 3
- 238000004140 cleaning Methods 0.000 description 3
- 238000002485 combustion reaction Methods 0.000 description 3
- TXKMVPPZCYKFAC-UHFFFAOYSA-N disulfur monoxide Inorganic materials O=S=S TXKMVPPZCYKFAC-UHFFFAOYSA-N 0.000 description 3
- 230000001747 exhibiting effect Effects 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 3
- 229910052697 platinum Inorganic materials 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 239000010948 rhodium Substances 0.000 description 3
- 239000000758 substrate Substances 0.000 description 3
- XNDZQQSKSQTQQD-UHFFFAOYSA-N 3-methylcyclohex-2-en-1-ol Chemical compound CC1=CC(O)CCC1 XNDZQQSKSQTQQD-UHFFFAOYSA-N 0.000 description 2
- 229910052684 Cerium Inorganic materials 0.000 description 2
- 229910052777 Praseodymium Inorganic materials 0.000 description 2
- 229910052772 Samarium Inorganic materials 0.000 description 2
- 238000003917 TEM image Methods 0.000 description 2
- YRKCREAYFQTBPV-UHFFFAOYSA-N acetylacetone Chemical compound CC(=O)CC(C)=O YRKCREAYFQTBPV-UHFFFAOYSA-N 0.000 description 2
- IXSUHTFXKKBBJP-UHFFFAOYSA-L azanide;platinum(2+);dinitrite Chemical compound [NH2-].[NH2-].[Pt+2].[O-]N=O.[O-]N=O IXSUHTFXKKBBJP-UHFFFAOYSA-L 0.000 description 2
- IWOUKMZUPDVPGQ-UHFFFAOYSA-N barium nitrate Chemical compound [Ba+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O IWOUKMZUPDVPGQ-UHFFFAOYSA-N 0.000 description 2
- 229910002091 carbon monoxide Inorganic materials 0.000 description 2
- HSJPMRKMPBAUAU-UHFFFAOYSA-N cerium(3+);trinitrate Chemical compound [Ce+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O HSJPMRKMPBAUAU-UHFFFAOYSA-N 0.000 description 2
- 239000011651 chromium Substances 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 230000003301 hydrolyzing effect Effects 0.000 description 2
- 238000005342 ion exchange Methods 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 238000011068 loading method Methods 0.000 description 2
- 239000011572 manganese Substances 0.000 description 2
- 239000010955 niobium Substances 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 229910052763 palladium Inorganic materials 0.000 description 2
- 239000008188 pellet Substances 0.000 description 2
- SCVFZCLFOSHCOH-UHFFFAOYSA-M potassium acetate Chemical compound [K+].CC([O-])=O SCVFZCLFOSHCOH-UHFFFAOYSA-M 0.000 description 2
- PUDIUYLPXJFUGB-UHFFFAOYSA-N praseodymium atom Chemical compound [Pr] PUDIUYLPXJFUGB-UHFFFAOYSA-N 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 229910052703 rhodium Inorganic materials 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- KZUNJOHGWZRPMI-UHFFFAOYSA-N samarium atom Chemical compound [Sm] KZUNJOHGWZRPMI-UHFFFAOYSA-N 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- BNGXYYYYKUGPPF-UHFFFAOYSA-M (3-methylphenyl)methyl-triphenylphosphanium;chloride Chemical compound [Cl-].CC1=CC=CC(C[P+](C=2C=CC=CC=2)(C=2C=CC=CC=2)C=2C=CC=CC=2)=C1 BNGXYYYYKUGPPF-UHFFFAOYSA-M 0.000 description 1
- ATRRKUHOCOJYRX-UHFFFAOYSA-N Ammonium bicarbonate Chemical compound [NH4+].OC([O-])=O ATRRKUHOCOJYRX-UHFFFAOYSA-N 0.000 description 1
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- 229910052693 Europium Inorganic materials 0.000 description 1
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 description 1
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 description 1
- 229910052771 Terbium Inorganic materials 0.000 description 1
- 229910052775 Thulium Inorganic materials 0.000 description 1
- 229910010413 TiO 2 Inorganic materials 0.000 description 1
- 229910052769 Ytterbium Inorganic materials 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 1
- 150000001342 alkaline earth metals Chemical class 0.000 description 1
- SMZOGRDCAXLAAR-UHFFFAOYSA-N aluminium isopropoxide Chemical compound [Al+3].CC(C)[O-].CC(C)[O-].CC(C)[O-] SMZOGRDCAXLAAR-UHFFFAOYSA-N 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 239000001099 ammonium carbonate Substances 0.000 description 1
- 235000012501 ammonium carbonate Nutrition 0.000 description 1
- 229910052787 antimony Inorganic materials 0.000 description 1
- WATWJIUSRGPENY-UHFFFAOYSA-N antimony atom Chemical compound [Sb] WATWJIUSRGPENY-UHFFFAOYSA-N 0.000 description 1
- 229910052797 bismuth Inorganic materials 0.000 description 1
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 description 1
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000003426 co-catalyst Substances 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 229910052878 cordierite Inorganic materials 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000009849 deactivation Effects 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 230000006866 deterioration Effects 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
- 239000006185 dispersion Substances 0.000 description 1
- 238000000635 electron micrograph Methods 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- OGPBJKLSAFTDLK-UHFFFAOYSA-N europium atom Chemical compound [Eu] OGPBJKLSAFTDLK-UHFFFAOYSA-N 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 229910052741 iridium Inorganic materials 0.000 description 1
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000002923 metal particle Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 230000003472 neutralizing effect Effects 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- UJVRJBAUJYZFIX-UHFFFAOYSA-N nitric acid;oxozirconium Chemical compound [Zr]=O.O[N+]([O-])=O.O[N+]([O-])=O UJVRJBAUJYZFIX-UHFFFAOYSA-N 0.000 description 1
- QBHQQYMEDGADCQ-UHFFFAOYSA-N oxozirconium(2+);dinitrate;dihydrate Chemical compound O.O.[Zr+2]=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O QBHQQYMEDGADCQ-UHFFFAOYSA-N 0.000 description 1
- 125000004430 oxygen atom Chemical group O* 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 235000011056 potassium acetate Nutrition 0.000 description 1
- 239000010970 precious metal Substances 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000010992 reflux Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 1
- VXNYVYJABGOSBX-UHFFFAOYSA-N rhodium(3+);trinitrate Chemical compound [Rh+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VXNYVYJABGOSBX-UHFFFAOYSA-N 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 229910052707 ruthenium Inorganic materials 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000006228 supernatant Substances 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 229910052714 tellurium Inorganic materials 0.000 description 1
- PORWMNRCUJJQNO-UHFFFAOYSA-N tellurium atom Chemical compound [Te] PORWMNRCUJJQNO-UHFFFAOYSA-N 0.000 description 1
- GZCRRIHWUXGPOV-UHFFFAOYSA-N terbium atom Chemical compound [Tb] GZCRRIHWUXGPOV-UHFFFAOYSA-N 0.000 description 1
- FRNOGLGSGLTDKL-UHFFFAOYSA-N thulium atom Chemical compound [Tm] FRNOGLGSGLTDKL-UHFFFAOYSA-N 0.000 description 1
- 230000001988 toxicity Effects 0.000 description 1
- 231100000419 toxicity Toxicity 0.000 description 1
- 230000001052 transient effect Effects 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 1
- NAWDYIZEMPQZHO-UHFFFAOYSA-N ytterbium Chemical compound [Yb] NAWDYIZEMPQZHO-UHFFFAOYSA-N 0.000 description 1
Abstract
Description
本発明は、排ガス浄化用触媒担体、それを用いた排ガス浄化用触媒並びに排ガス浄化方法に関する。 The present invention relates to an exhaust gas purification catalyst carrier, an exhaust gas purification catalyst using the same, and an exhaust gas purification method.
セリアをはじめとする酸素を吸蔵、放出する酸素貯蔵能を有する金属酸化物は内燃機関用排ガス浄化用触媒の助触媒として広く用いられている。排ガス中に存在する一酸化炭素、並びに炭化水素の酸化、窒素酸化物の還元は理論空燃比付近で排ガス浄化用触媒により行われるが、過渡域では理論空燃比からずれる場合がある。このような場合に前記助触媒の酸素吸放出作用により酸素濃度を一定に保ち理論空燃比近傍に制御することで、空燃比の幅が広がり、排ガス浄化用触媒は安定した三元活性を維持することができる。また、このような排ガス浄化用触媒においては、アルミナに代表される耐熱性に優れた担体を混合することにより、酸素貯蔵能を有する金属酸化物の耐熱性向上を図り、高温度下においても安定した三元活性を提供している。 Metal oxides having oxygen storage capacity for storing and releasing oxygen such as ceria are widely used as promoters for exhaust gas purifying catalysts for internal combustion engines. The oxidation of carbon monoxide, hydrocarbons, and nitrogen oxides present in the exhaust gas is carried out by the exhaust gas purifying catalyst in the vicinity of the stoichiometric air-fuel ratio, but it may deviate from the stoichiometric air-fuel ratio in the transient region. In such a case, the oxygen concentration is kept constant by the oxygen absorption / release action of the co-catalyst, and the air / fuel ratio is widened by controlling the oxygen concentration to be close to the theoretical air / fuel ratio, and the exhaust gas purifying catalyst maintains stable three-way activity. be able to. In addition, in such exhaust gas purifying catalysts, the heat resistance of metal oxides having oxygen storage ability is improved by mixing a carrier having excellent heat resistance typified by alumina, which is stable even at high temperatures. Provides ternary activity.
しかしながら、このような排ガス浄化用触媒においては、燃料に由来する硫黄酸化物に常に晒されているため、硫黄が付着しやすいアルミナ等の担体表面を介した貴金属への硫黄被毒により三元活性の低下が生じることが分かってきた。 However, such exhaust gas purifying catalysts are always exposed to sulfur oxides derived from fuel, so three-way activity is caused by sulfur poisoning to noble metals via the carrier surface such as alumina where sulfur easily adheres. It has been found that a decrease in
そのため、このような硫黄酸化物による被毒を抑制するために担体として酸性酸化物担体、特にチタニアが用いられてきた。そして、このようなチタニアは担体表面への硫黄酸化物の付着抑制や付着後の脱離性に優れているため、排ガス浄化用触媒の活性低下の抑制に有効であることが提案されている。 For this reason, acidic oxide carriers, particularly titania, have been used as carriers in order to suppress such poisoning by sulfur oxides. And since such titania is excellent in the suppression of the attachment of sulfur oxides to the surface of the carrier and the detachability after the adhesion, it has been proposed to be effective in suppressing the decrease in the activity of the exhaust gas purification catalyst.
例えば、特開２００４−３２１８４７号公報（特許文献１）においては、チタニアが固溶したアルミナ系酸化物と他の酸化物とがナノレベルで混合した複合酸化物と、該複合酸化物の少なくとも一部の表面に少なくとも一部がアルミナに固溶した状態で存在するチタニア粒子とからなる触媒担体が開示されている。また、特開平９−１２２４８６号公報（特許文献２）においては、（ｉ）アルカリ金属、アルカリ土類金属及び希土類元素から選ばれるＮＯｘ吸蔵元素の酸化物と、（ｉｉ）アルミナ（Ａｌ２Ｏ３）と、（ｉｉｉ）チタニア（ＴｉＯ２）、ジルコニア（ＺｒＯ２）及びシリカ（ＳｉＯ２）から選ばれる少なくとも一種との非晶質の複合酸化物からなる高耐熱性触媒担体が開示されている。そして、特許文献２においては、高耐熱性触媒担体に、更にセリアを含むことができることが記載されている。しかしながら、特許文献１及び２に記載の触媒担体においては、理論空燃比近傍において、硫黄酸化物を含む排ガスを浄化する際の三元活性が必ずしも十分なものではなかった。
本発明は、上記従来技術の有する課題に鑑みてなされたものであり、高い耐硫黄被毒性を有し、硫黄酸化物を含む排ガス中においても優れた三元活性を発揮することを可能とする排ガス浄化用触媒担体、それを用いた排ガス浄化用触媒、並びにその排ガス浄化用触媒を用いた排ガス浄化方法を提供することを目的とする。 The present invention has been made in view of the above-described problems of the prior art, has high sulfur poisoning resistance, and can exhibit excellent ternary activity even in exhaust gas containing sulfur oxides. An object of the present invention is to provide an exhaust gas purification catalyst carrier, an exhaust gas purification catalyst using the same, and an exhaust gas purification method using the exhaust gas purification catalyst.
本発明者らは、上記目的を達成すべく鋭意研究を重ねた結果、従来の触媒担体が理論空燃比近傍における硫黄酸化物を含む排ガスを浄化する際の三元活性が必ずしも十分なものではない理由について、先ず、特許文献１に記載の触媒担体においては耐硫黄被毒性には優れるものの、十分な酸素貯蔵能を有さないため、酸素濃度の変動が大きくなることに加え、アルミナ系酸化物以外の他の酸化物にもチタニアが固溶しているため他の酸化物の構造が変化し、硫黄酸化物を含む排ガス中において三元活性が必ずしも十分なものとはならないと推察した。また、特許文献２に記載の触媒担体においては、例えば、アルミナとチタニアの固溶体とセリア粒子とを含む触媒担体が挙げられるが、前記固溶体はアルミナとチタニアとが均一に固溶したものであり、粒子表面にチタニアが濃化していないために耐硫黄被毒性が十分でなく、しかも得られる触媒担体の比表面積が十分に大きなものではないことから前記担体に貴金属を十分に分散させることができないため、硫黄酸化物を含む排ガス中において三元活性が必ずしも十分なものとならないと推察した。 As a result of intensive studies to achieve the above object, the inventors of the present invention do not always have sufficient three-way activity when purifying exhaust gas containing sulfur oxides in the vicinity of the theoretical air-fuel ratio. Regarding the reason, first, the catalyst carrier described in Patent Document 1 is excellent in sulfur poisoning resistance, but does not have sufficient oxygen storage capacity, so that the fluctuation of oxygen concentration is increased, and in addition, the alumina-based oxide It was speculated that because the titania dissolved in other oxides, the structure of the other oxides changed and the ternary activity was not always sufficient in the exhaust gas containing sulfur oxides. In addition, in the catalyst carrier described in Patent Document 2, for example, a catalyst carrier containing a solid solution of alumina and titania and ceria particles can be mentioned, and the solid solution is a solid solution of alumina and titania uniformly. Since titania is not concentrated on the particle surface, the sulfur poisoning resistance is not sufficient, and the specific surface area of the resulting catalyst support is not sufficiently large, so the noble metal cannot be sufficiently dispersed in the support. It was speculated that the ternary activity was not always sufficient in the exhaust gas containing sulfur oxides.
そこで、本発明者らは、上記目的を達成すべく更に鋭意研究を重ねた結果、表面近傍にアルミナとチタニアとの固溶体層を有するアルミナ粒子と、酸素貯蔵能を有する金属酸化物を含有する金属酸化物粒子とを含むことによって、高い耐硫黄被毒性を有し、硫黄酸化物を含む排ガス中においても優れた三元活性を発揮する排ガス浄化用触媒担体が得られることを見出し、本発明を完成するに至った。 Thus, as a result of further earnest research to achieve the above object, the present inventors have obtained a metal containing an alumina particle having a solid solution layer of alumina and titania near the surface, and a metal oxide having an oxygen storage capacity. It was found that by containing oxide particles, an exhaust gas purification catalyst carrier having high sulfur poisoning resistance and exhibiting excellent ternary activity even in exhaust gas containing sulfur oxides can be obtained. It came to be completed.
すなわち、本発明の排ガス浄化用触媒担体は、表面近傍にアルミナとチタニアとの固溶体層を有するアルミナ粒子と、酸素貯蔵能を有する金属酸化物を含有する金属酸化物粒子とを含むことを特徴とするものである。 That is, the exhaust gas purifying catalyst carrier of the present invention comprises alumina particles having a solid solution layer of alumina and titania in the vicinity of the surface, and metal oxide particles containing a metal oxide having an oxygen storage ability. To do.
上記本発明にかかる前記固溶体層としては、前記アルミナ粒子の表面から、該粒子の半径の５０％未満の深さの領域に存在することが好ましい。 The solid solution layer according to the present invention is preferably present in a region having a depth of less than 50% of the radius of the particles from the surface of the alumina particles.
また、上記本発明にかかる前記アルミナ粒子としては、前記アルミナにチタニア前駆体を担持せしめて５００℃以上で焼成して得られるものであることが好ましい。 Further, the alumina particles according to the present invention are preferably obtained by carrying a titania precursor on the alumina and firing at 500 ° C. or higher.
さらに、上記本発明の排ガス浄化用触媒担体においては、前記アルミナ粒子中における前記チタニアの含有量が、前記粒子中のアルミナとチタニアの総量に対して１〜２０ｍｏｌ％の範囲であることが好ましい。 Further, in the exhaust gas purifying catalyst carrier of the present invention, the titania content in the alumina particles is preferably in the range of 1 to 20 mol% with respect to the total amount of alumina and titania in the particles.
また、上記本発明の排ガス浄化用触媒担体においては、前記アルミナ粒子と前記金属酸化物粒子の平均２次粒子径が、それぞれ０．５〜５０μｍであることが好ましい。 In the exhaust gas purifying catalyst carrier of the present invention, it is preferable that the average secondary particle diameters of the alumina particles and the metal oxide particles are 0.5 to 50 μm, respectively.
上記本発明にかかる前記アルミナ粒子としては、Ｘ線回折法による測定において前記チタニアの結晶相に帰属するピークを持たないものであることが好ましい。 The alumina particles according to the present invention preferably do not have a peak attributed to the titania crystal phase in the measurement by an X-ray diffraction method.
また、本発明の排ガス浄化用触媒は、上記本発明の排ガス浄化用触媒担体と、該担体に担持された貴金属とを含むことを特徴とするものである。 The exhaust gas purifying catalyst of the present invention includes the exhaust gas purifying catalyst carrier of the present invention and a noble metal supported on the carrier.
さらに、本発明の排ガス浄化方法は、上記本発明の排ガス浄化用触媒を排ガスと接触させることを特徴とする方法である。 Furthermore, the exhaust gas purification method of the present invention is a method characterized by bringing the exhaust gas purification catalyst of the present invention into contact with exhaust gas.
本発明によれば、高い耐硫黄被毒性を有し、硫黄酸化物を含む排ガス中においても優れた三元活性を発揮することを可能とする排ガス浄化用触媒担体、それを用いた排ガス浄化用触媒、並びにその排ガス浄化用触媒を用いた排ガス浄化方法を提供することが可能となる。 According to the present invention, an exhaust gas purification catalyst carrier having high sulfur poisoning resistance and capable of exhibiting excellent ternary activity even in exhaust gas containing sulfur oxide, and for exhaust gas purification using the same It is possible to provide an exhaust gas purification method using the catalyst and the exhaust gas purification catalyst.
以下、本発明をその好適な実施形態に即して詳細に説明する。 Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.
先ず、本発明の排ガス浄化用触媒担体について説明する。すなわち、本発明の排ガス浄化用触媒担体は、表面近傍にアルミナとチタニアとの固溶体層を有するアルミナ粒子と、酸素貯蔵能を有する金属酸化物を含有する金属酸化物粒子とを含むことを特徴とするものである。 First, the exhaust gas purifying catalyst carrier of the present invention will be described. That is, the exhaust gas purifying catalyst carrier of the present invention comprises alumina particles having a solid solution layer of alumina and titania in the vicinity of the surface, and metal oxide particles containing a metal oxide having an oxygen storage ability. To do.
このように、本発明にかかる前記アルミナ粒子は、その粒子の表面近傍にアルミナとチタニアとの固溶体層を有する。ここにいう「固溶体層」とは、アルミナ粒子中において、アルミナとチタニアが固溶している領域をいう。本発明においては、このような領域は電界放射型透過電子顕微鏡（ＦＥ-ＴＥＭ）による元素分析によって測定する。このようなＦＥ-ＴＥＭによる元素分析においては、粒子を透過する形で元素分析を行うことから表面に高い濃度で存在しているチタン（Ｔｉ）元素の存在が粒子内部の元素分析にまで影響を及ぼす。そのため、本発明においてチタニアが固溶している領域とは、ＦＥ-ＴＥＭにより測定されるＡｌ元素に対するＴｉ元素の存在強度比が０．１以上の値となる領域をいう。 Thus, the alumina particles according to the present invention have a solid solution layer of alumina and titania near the surface of the particles. The “solid solution layer” as used herein refers to a region where alumina and titania are in solid solution in alumina particles. In the present invention, such a region is measured by elemental analysis using a field emission transmission electron microscope (FE-TEM). In such elemental analysis by FE-TEM, elemental analysis is performed in such a way that it penetrates the particle, so the presence of titanium (Ti) element present at a high concentration on the surface affects the elemental analysis inside the particle. Effect. Therefore, the region in which titania is dissolved in the present invention refers to a region in which the existing intensity ratio of Ti element to Al element measured by FE-TEM is a value of 0.1 or more.
また、本発明にかかるアルミナ粒子には、アルミナ粒子の表面近傍においてチタニアが固溶した固溶体層が形成されているため、触媒の劣化成分である硫黄酸化物（ＳＯ２）の付着を防ぎ、且つＳＯ２が付着した場合においても脱離し易いというチタニアの特性が付与されている。また、アルミナとともにチタニアを単独で存在させた場合においてはチタニアが耐熱性に劣るため構造変化が生じ易いが、本発明においてはチタニアとアルミナとが固溶しているため、高熱下においても構造変化が生じにくい。そして、このようなアルミナ粒子を排ガス浄化用触媒に用い、これに貴金属を担持させた場合には、硫黄酸化物の流通下で使用しても硫黄の付着が抑制されるとともに付着した硫黄の脱離が促進されて貴金属の硫黄被毒が十分に抑制される。したがって、このようなアルミナ粒子を含有する排ガス浄化用触媒担体を用いた触媒においては、触媒の三元活性の低下が十分に防止され、優れた三元活性を発揮することができる。 In addition, since the alumina particles according to the present invention have a solid solution layer in which titania is dissolved in the vicinity of the surface of the alumina particles, it prevents adhesion of sulfur oxide (SO 2 ), which is a deterioration component of the catalyst, and The titania characteristic of being easily desorbed even when SO 2 is attached is provided. In addition, when titania alone is present together with alumina, structural change tends to occur because titania is inferior in heat resistance, but in the present invention, structural change occurs even under high heat because titania and alumina are in solid solution. Is unlikely to occur. When such alumina particles are used as an exhaust gas purifying catalyst and a noble metal is supported on the catalyst, the adhesion of sulfur is suppressed and the attached sulfur is removed even when used under the flow of sulfur oxides. Separation is promoted, and sulfur poisoning of precious metals is sufficiently suppressed. Therefore, in a catalyst using such an exhaust gas purifying catalyst carrier containing alumina particles, a decrease in the ternary activity of the catalyst is sufficiently prevented, and an excellent ternary activity can be exhibited.
また、このようなアルミナ粒子においては表面近傍に前記固溶体層を有しており、前記固溶体層が前記アルミナ粒子の表面から、前記アルミナ粒子の半径の５０％未満（より好ましくは２５％未満）の深さの領域に存在することが好ましい。前記領域を超えて前記固溶体層が存在すると粒子表面から、その粒子の半径の５０％未満までに存在するチタニアの濃度が低下するため、十分な耐硫黄被毒性を得ることが困難となる傾向にある。なお、ここにいう「半径」とは、粒子が真球ではない場合には粒子半径の平均値をいう。 In addition, such alumina particles have the solid solution layer in the vicinity of the surface, and the solid solution layer is less than 50% (more preferably less than 25%) of the radius of the alumina particles from the surface of the alumina particles. It is preferable to exist in the region of depth. When the solid solution layer is present beyond the region, the concentration of titania existing from the particle surface to less than 50% of the radius of the particle is lowered, and thus it tends to be difficult to obtain sufficient sulfur poisoning resistance. is there. Here, “radius” refers to the average value of particle radii when the particles are not true spheres.
また、前記アルミナ粒子の平均２次粒子径としては、０．５〜５０μｍであることが好ましく、１〜３０μｍであることがより好ましい。前記アルミナ粒子の平均粒径が前記下限未満では、ガスの拡散に有効なマクロ細孔の形成が困難となる傾向にあり、前記上限を超えると、ハニカム基材への触媒コート層の形成が困難となる傾向にある。 Further, the average secondary particle diameter of the alumina particles is preferably 0.5 to 50 μm, and more preferably 1 to 30 μm. When the average particle diameter of the alumina particles is less than the lower limit, it tends to be difficult to form macropores effective for gas diffusion, and when the upper limit is exceeded, formation of a catalyst coat layer on the honeycomb substrate is difficult. It tends to be.
また、前記アルミナ粒子の比表面積としては、８０〜２５０ｍ２／ｇであることが好ましく、１３０〜２００ｍ２／ｇであることがより好ましい。前記比表面積が前記下限未満では、貴金属の分散度が低下し、十分な三元活性を得ることが困難となる傾向にあり、他方、前記上限を超えると酸素貯蔵能を有する金属酸化物の比表面積が相対的に低下し、酸素貯蔵能による酸素濃度の変動抑制が困難となる傾向にある。なお、このような比表面積は、吸着等温線からＢＥＴ等温吸着式を用いてＢＥＴ比表面積として算出することができる。 As the specific surface area of the alumina particles is preferably 80~250m 2 / g, more preferably 130~200m 2 / g. If the specific surface area is less than the lower limit, the degree of dispersion of the noble metal tends to be reduced, and it is difficult to obtain sufficient ternary activity. On the other hand, if the upper limit is exceeded, the ratio of the metal oxide having oxygen storage capacity The surface area is relatively reduced, and it tends to be difficult to suppress fluctuations in oxygen concentration due to oxygen storage capacity. Such a specific surface area can be calculated as a BET specific surface area from an adsorption isotherm using a BET isotherm adsorption formula.
また、前記アルミナ粒子中における前記チタニアの含有量としては、前記粒子中のアルミナとチタニアの総量に対してチタン（Ｔｉ）換算で１〜２０ｍｏｌ％の範囲であることが好ましく、２．５〜１０ｍｏｌ％の範囲であることがより好ましい。前記チタニアの含有量が前記下限未満では、得られる排ガス浄化用触媒担体の耐硫黄被毒性が低下する傾向にあり、他方、前記上限を超えると、含有される全てのチタニアがアルミナ粒子へ固溶できず、チタニア単独粒子が存在するため、得られる排ガス浄化用触媒担体の耐熱性が低下する傾向にある。 The titania content in the alumina particles is preferably in the range of 1 to 20 mol% in terms of titanium (Ti) with respect to the total amount of alumina and titania in the particles, and preferably 2.5 to 10 mol. % Is more preferable. If the content of the titania is less than the lower limit, the sulfur poisoning resistance of the obtained exhaust gas purification catalyst carrier tends to be reduced. On the other hand, if the content exceeds the upper limit, all the titania contained is dissolved in the alumina particles. However, since titania single particles exist, the heat resistance of the obtained exhaust gas-purifying catalyst carrier tends to decrease.
さらに、前記アルミナ粒子としては、Ｘ線回折法による測定において前記チタニアの結晶相に帰属するピークを持たないものが好ましい。すなわち、前記アルミナ粒子とは別に単独のチタニア粒子が存在しないものであることが好ましい。チタニアの結晶層、すなわちチタニア単独粒子が存在すると、熱によりチタニア粒子の粒成長が進行し、比表面積低下や貴金属の粒成長を引き起こし、十分な活性を得ることが困難となる傾向にある。 Further, the alumina particles preferably do not have a peak attributed to the titania crystal phase in measurement by X-ray diffraction. That is, it is preferable that a single titania particle does not exist separately from the alumina particle. In the presence of a titania crystal layer, that is, titania single particles, the growth of titania particles progresses due to heat, leading to a decrease in specific surface area and growth of noble metal particles, which tends to make it difficult to obtain sufficient activity.
また、前記アルミナ粒子としては、前記アルミナにチタニア前駆体を担持せしめて５００℃以上（より好ましくは５００〜９００℃）で焼成して得られるものが好ましい。前記焼成温度が前記下限未満では、アルミナとチタニアに固溶が生じないためアルミナの表面にチタニア粒子が存在した状態となってしまい、アルミナ粒子にチタニアの有する特性を付与することが不十分となり、耐硫黄被毒性が低下する傾向にある。 The alumina particles are preferably those obtained by carrying a titania precursor on the alumina and firing at 500 ° C. or higher (more preferably 500 to 900 ° C.). When the firing temperature is less than the lower limit, since the solid solution does not occur in alumina and titania, the titania particles are present on the surface of the alumina, and it becomes insufficient to impart the characteristics of titania to the alumina particles. Sulfur poisoning resistance tends to decrease.
このようなアルミナ粒子を製造するための好適な製造方法としては、アルミナにチタニア前駆体を担持した後に５００℃以上で焼成して、表面近傍にチタニアとアルミナの固溶体層が形成されたアルミナ粒子を得る方法を挙げることができる。 As a preferred production method for producing such alumina particles, alumina particles having a titania / alumina solid solution layer formed in the vicinity of the surface after firing a titania precursor on alumina and firing at 500 ° C. or higher are used. The method of obtaining can be mentioned.
このようなアルミナ粒子を製造するために用いられるアルミナとしては特に制限されないが、例えば、公知のアルミナの製造方法を適宜採用して得られるアルミナや、市販のアルミナを用いることができる。このようなアルミナの製造方法としては、例えば、硝酸アルミニウム溶液にアンモニア水を添加して中和して得られる沈殿物を５００〜１２００℃程度で０．５〜１０時間程度焼成した後、乾式粉砕してアルミナを得る方法が挙げられる。 Although it does not restrict | limit especially as an alumina used in order to manufacture such an alumina particle, For example, the alumina obtained by employ | adopting suitably the manufacturing method of a well-known alumina, and a commercially available alumina can be used. As a method for producing such alumina, for example, a precipitate obtained by neutralizing by adding ammonia water to an aluminum nitrate solution is calcined at about 500 to 1200 ° C. for about 0.5 to 10 hours, and then dry pulverized. Thus, there is a method of obtaining alumina.
また、前記チタニア前駆体としては、例えば、チタンの可溶性塩から析出沈殿された水酸化物等の前駆体や、チタンアルコキシドを加水分解することによって形成される前駆体等が挙げられる。このようなチタニア前駆体の好適な製造方法としては、例えば、クエン酸を含有するイオン交換水中に６５〜９５℃程度に加熱しながらチタンアルコキシドを添加し、室温に冷却する方法を挙げることができる。 Examples of the titania precursor include a precursor such as a hydroxide precipitated and precipitated from a soluble salt of titanium, a precursor formed by hydrolyzing titanium alkoxide, and the like. As a suitable production method of such a titania precursor, for example, a method in which titanium alkoxide is added to ion-exchanged water containing citric acid while heating at about 65 to 95 ° C. and cooled to room temperature can be mentioned. .
さらに、前記アルミナに前記チタニア前駆体を担持させる方法としては、例えば、前記アルミナをチタンの可溶性塩の水溶液中に混合し、その混合液中においてチタニア前駆体を沈殿析出もしくは蒸発乾固させることでアルミナにチタニア前駆体を担持させる方法、チタンアルコキシドが溶解したアルコール溶液中にアルミナを混合し、その混合液中においてチタンアルコキシドを加水分解して析出させることでアルミナにチタニア前駆体を担持させる方法を採用することができる。 Further, as a method for supporting the titania precursor on the alumina, for example, the alumina is mixed in an aqueous solution of a soluble salt of titanium, and the titania precursor is precipitated or evaporated to dryness in the mixed solution. A method of supporting a titania precursor on alumina, mixing alumina in an alcohol solution in which titanium alkoxide is dissolved, and a method of supporting a titania precursor on alumina by hydrolyzing and depositing titanium alkoxide in the mixed solution. Can be adopted.
また、前述のように、アルミナにチタニア前駆体を担持させた後に焼成する際の温度条件は５００℃以上（より好ましくは５００〜９００℃）である。このような焼成の温度条件が５００℃未満では、アルミナとチタニアに固溶が生じずアルミナの表面にチタニア粒子が存在した状態となるため、アルミナへのチタンの酸性質の付与が不十分となって耐硫黄被毒性が低下する傾向にある。また、５００℃以上で焼成することで、アルミナとチタニアの固溶体層を形成させるのと同時にチタニア前駆体の構成成分の一つである有機物を燃焼除去することも可能となり、更には、既に５００℃以上の高温で焼成されているためアルミナ粒子を触媒として使用する際の比表面積の低下が抑制される傾向にある。一方、９００℃以上で焼成すると、アルミナが結晶化したり、相転移が生じたりして比表面積が低下する傾向にある。 Further, as described above, the temperature condition for firing after supporting the titania precursor on alumina is 500 ° C. or more (more preferably 500 to 900 ° C.). If the temperature condition for such firing is less than 500 ° C., solid solution does not occur in alumina and titania, and titania particles are present on the surface of alumina, so that the acidity of titanium to alumina is insufficiently imparted. Therefore, the sulfur poisoning resistance tends to decrease. In addition, by firing at 500 ° C. or higher, it is possible to burn and remove the organic substance that is one of the constituent components of the titania precursor at the same time as forming a solid solution layer of alumina and titania. Since it is fired at the above high temperature, the decrease in specific surface area when using alumina particles as a catalyst tends to be suppressed. On the other hand, when firing at 900 ° C. or higher, the specific surface area tends to decrease due to crystallization of alumina or phase transition.
また、本発明にかかる金属酸化物粒子は、酸素貯蔵能を有する金属酸化物を含有するものである。ここにいう「酸素貯蔵能を有する金属酸化物」とは、価数変化することによって酸素原子を吸放出することができる金属の酸化物をいう。本発明においては、このような酸素貯蔵能を有する金属酸化物を含有させることで、排ガス処理中において酸素濃度の変動を抑制し、理論空燃比近傍に保つことができ、得られる排ガス浄化用触媒の三元活性及び耐硫黄被毒性を向上させることが可能となる。 Moreover, the metal oxide particle concerning this invention contains the metal oxide which has oxygen storage ability. The term “metal oxide having oxygen storage ability” as used herein refers to a metal oxide capable of absorbing and releasing oxygen atoms by changing the valence. In the present invention, by containing such a metal oxide having an oxygen storage capacity, it is possible to suppress fluctuations in oxygen concentration during exhaust gas treatment, and to maintain the vicinity of the theoretical air-fuel ratio. It is possible to improve the ternary activity and sulfur poisoning resistance.
このような酸素貯蔵能を有する金属酸化物としては、例えば、セリウム（Ｃｅ）、プラセオジウム（Ｐｒ）、サマリウム（Ｓｍ）、ユウロピウム（Ｅｕ）、テルビウム（Ｔｂ）、ツリウム（Ｔｍ）、イッテルビウム（Ｙｂ）、アンチモン（Ｓｂ）、テルル（Ｔｅ）、ビスマス（Ｂｉ）、バナジウム（Ｖ）、クロム（Ｃｒ）、マンガン（Ｍｎ）、鉄（Ｆｅ）、コバルト（Ｃｏ）、ニッケル（Ｎｉ）、銅（Ｃｕ）、ニオブ（Ｎｂ）、モリブデン（Ｍｏ）及びタングステン（Ｗ）等の金属の酸化物が挙げられる。また、このような酸素貯蔵能を有する金属酸化物の中でも、より高い酸素貯蔵放出性能を発揮できることから、セリア、プラセオジウム及びサマリウムを用いることが好ましい。また、前記酸素貯蔵能を有する金属酸化物は１種を単独で、また、複数種類を混合あるいは複合化して用いてもよい。 Examples of such metal oxides having oxygen storage ability include cerium (Ce), praseodymium (Pr), samarium (Sm), europium (Eu), terbium (Tb), thulium (Tm), ytterbium (Yb). , Antimony (Sb), tellurium (Te), bismuth (Bi), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu) , Oxides of metals such as niobium (Nb), molybdenum (Mo), and tungsten (W). Among metal oxides having such an oxygen storage ability, it is preferable to use ceria, praseodymium and samarium because they can exhibit higher oxygen storage / release performance. Further, the metal oxide having oxygen storage ability may be used alone, or a plurality of kinds may be mixed or combined.
また、前記酸素貯蔵能を有する金属酸化物粒子としては、前述のような酸素貯蔵能を有する金属酸化物を含有しているものであればよく特に制限されないが、例えば、前記酸素貯蔵能を有する金属酸化物と他の金属酸化物とを複合化させたものを好適に用いることができる。このような他の金属酸化物としては、アルミナ、チタニア、ジルコニア、シリカ、シリカ−アルミナ等の従来の排ガス浄化用触媒の担体に用いられる多孔質酸化物が挙げられる。また、前記他の金属酸化物は１種を単独で、また、複数種類を混合あるいは複合化して用いることができる。 Further, the metal oxide particles having the oxygen storage ability are not particularly limited as long as they contain the metal oxide having the oxygen storage ability as described above. For example, the metal oxide particles have the oxygen storage ability. A composite of a metal oxide and another metal oxide can be suitably used. Examples of such other metal oxides include porous oxides used for carriers of conventional exhaust gas purification catalysts such as alumina, titania, zirconia, silica, silica-alumina and the like. Further, the other metal oxides can be used alone or in combination of a plurality of types.
このような金属酸化物粒子としては、例えば、アルミナ−セリア−ジルコニア複合酸化物、セリア−ジルコニア複合酸化物、アルミナ−セリア複合酸化物、シリカ−セリア−ジルコニア複合酸化物、シリカ−セリア複合酸化物等が挙げられ、ジルコニアによるセリアの構造安定化に基づく、高い酸素貯蔵能の保持の観点から、アルミナ−セリア−ジルコニア複合酸化物、セリア−ジルコニア複合酸化物、シリカ−セリア−ジルコニア複合酸化物を用いることが好ましい。 Examples of such metal oxide particles include alumina-ceria-zirconia composite oxide, ceria-zirconia composite oxide, alumina-ceria composite oxide, silica-ceria-zirconia composite oxide, silica-ceria composite oxide. From the viewpoint of maintaining high oxygen storage capacity based on the structural stabilization of ceria by zirconia, alumina-ceria-zirconia composite oxide, ceria-zirconia composite oxide, silica-ceria-zirconia composite oxide are used. It is preferable to use it.
このような金属酸化物粒子中における前記酸素貯蔵能を有する金属酸化物の含有量としては、１〜９０ｍｏｌ％であることが好ましく、５〜６０ｍｏｌ％であることがより好ましい。前記酸素貯蔵能を有する金属酸化物の含有量が前記下限未満では、排ガス処理中において酸素濃度の変動を抑制する効果が不十分となる傾向にあり、他方、前記上限を超えると他の酸化物の特性を得ることが困難となる傾向にある。 The content of the metal oxide having oxygen storage capacity in such metal oxide particles is preferably 1 to 90 mol%, and more preferably 5 to 60 mol%. If the content of the metal oxide having oxygen storage capacity is less than the lower limit, the effect of suppressing fluctuations in oxygen concentration during exhaust gas treatment tends to be insufficient. It tends to be difficult to obtain these characteristics.
また、このような金属酸化物粒子の平均２次粒子径としては、０．５〜５０μｍであることが好ましく、１〜３０μｍであることがより好ましい。前記金属酸化物粒子の平均粒径が前記下限未満では、ガス拡散に有効なマクロ細孔の形成が困難となる傾向にあり、前記上限を超えると、ハニカム基材への触媒コート層の形成が困難となる傾向にある。 Moreover, as an average secondary particle diameter of such a metal oxide particle, it is preferable that it is 0.5-50 micrometers, and it is more preferable that it is 1-30 micrometers. If the average particle diameter of the metal oxide particles is less than the lower limit, it tends to be difficult to form macropores effective for gas diffusion, and if the upper limit is exceeded, formation of a catalyst coat layer on the honeycomb substrate is likely to occur. It tends to be difficult.
また、前記金属酸化物粒子の比表面積としては、１〜３００ｍ２／ｇであることが好ましく、１〜１００ｍ２／ｇであることがより好ましい。前記比表面積が前記下限未満では、排ガス処理中における酸素濃度の変動を抑制する効果が不十分となる傾向にあり、他方、前記上限を超えると硫黄被毒される部分が増加し、前記アルミナ粒子を混合しても効果的な耐硫黄被毒性を得ることが困難となる傾向にある。 As the specific surface area of the metal oxide particles is preferably from 1~300m 2 / g, and more preferably 1 to 100 m 2 / g. If the specific surface area is less than the lower limit, the effect of suppressing fluctuations in oxygen concentration during exhaust gas treatment tends to be insufficient. On the other hand, if the upper limit is exceeded, sulfur poisoned portions increase, and the alumina particles Even if these are mixed, it tends to be difficult to obtain effective sulfur poisoning resistance.
また、本発明の金属酸化物粒子の製造方法は特に制限されず、公知の方法を適宜採用することができ、例えば、本発明にかかる金属酸化物粒子として好適なアルミナ−セリア−ジルコニア複合酸化物を製造する場合には特開平１０−１８２１５５号公報に記載された製造方法を参照することができ、本発明にかかる金属酸化物粒子として好適なセリア−ジルコニア複合酸化物を製造する場合には特開２００３−２７５５８０号公報に記載の製造方法を参照することができる。 Further, the method for producing the metal oxide particles of the present invention is not particularly limited, and a known method can be appropriately employed. For example, an alumina-ceria-zirconia composite oxide suitable as the metal oxide particles according to the present invention. Can be referred to the production method described in JP-A-10-182155, and when producing ceria-zirconia composite oxide suitable as metal oxide particles according to the present invention, it can be referred to. Reference can be made to the production method described in Japanese Unexamined Patent Publication No. 2003-275580.
また、本発明の排ガス浄化用触媒担体は、前記アルミナ粒子と前記金属酸化物とを含むものである。このような排ガス浄化用触媒担体においては、前記アルミナ粒子１００質量部に対して前記金属酸化物粒子を４０〜２５０質量部含有させることが好ましく、６０〜１５０質量部含有させることがより好ましい。前記金属酸化物粒子の含有量が前記下限未満では、排ガス処理中において、酸素濃度の変動を抑制する効果が不十分となる傾向にあり、他方、前記上限を超えると前記アルミナ粒子による耐硫黄被毒性を得ることが困難となる傾向にある。 The exhaust gas purifying catalyst carrier of the present invention contains the alumina particles and the metal oxide. In such an exhaust gas purifying catalyst carrier, the metal oxide particles are preferably contained in an amount of 40 to 250 parts by mass, more preferably 60 to 150 parts by mass with respect to 100 parts by mass of the alumina particles. If the content of the metal oxide particles is less than the lower limit, the effect of suppressing fluctuations in oxygen concentration tends to be insufficient during exhaust gas treatment. It tends to be difficult to obtain toxicity.
また、このような排ガス浄化用触媒担体は、前記アルミナ粒子と前記金属酸化物粒子とを混合することで製造することができる。このような混合の方法は特に制限されず、例えば、ボールミルを用いて湿式混合する方法等を挙げることができる。 Moreover, such an exhaust gas purifying catalyst carrier can be produced by mixing the alumina particles and the metal oxide particles. Such a mixing method is not particularly limited, and examples thereof include a wet mixing method using a ball mill.
次に、本発明の排ガス浄化用触媒について説明する。すなわち、本発明の排ガス浄化用触媒は、上記本発明の排ガス浄化用触媒担体と、該担体に担持された貴金属とを含むことを特徴とするものである。このように、本発明の排ガス浄化用触媒は、上記本発明の排ガス浄化用触媒担体に貴金属を担持させたものであるため、硫黄酸化物の流通下で使用しても硫黄の付着が抑制されるとともに付着した硫黄の脱離が促進されて貴金属の硫黄被毒が十分に抑制されることから、触媒の三元活性の低下が十分に防止され、優れた三元活性を発揮する。 Next, the exhaust gas purifying catalyst of the present invention will be described. That is, the exhaust gas purifying catalyst of the present invention is characterized by including the exhaust gas purifying catalyst carrier of the present invention and a noble metal supported on the carrier. As described above, the exhaust gas purifying catalyst of the present invention is obtained by supporting a noble metal on the exhaust gas purifying catalyst carrier of the present invention, so that the adhesion of sulfur is suppressed even when used under the flow of sulfur oxide. In addition, the elimination of adhering sulfur is promoted and sulfur poisoning of the noble metal is sufficiently suppressed, so that a reduction in the ternary activity of the catalyst is sufficiently prevented and excellent ternary activity is exhibited.
本発明にかかる貴金属としては、白金（Ｐｔ）、ロジウム（Ｒｈ）、パラジウム（Ｐｄ）、イリジウム（Ｉｒ）、ルテニウム（Ｒｕ）等が挙げられ、三元活性が高いという観点から、Ｐｔ、Ｒｈ、Ｐｄが好ましい。 Examples of the noble metal according to the present invention include platinum (Pt), rhodium (Rh), palladium (Pd), iridium (Ir), ruthenium (Ru), etc. From the viewpoint of high ternary activity, Pt, Rh, Pd is preferred.
このような貴金属の担持量としては、排ガス浄化用触媒担体１００質量部当たり０．０１〜１０質量部であることが好ましく、０．１〜４質量部であることがより好ましい。前記貴金属の担持量が前記下限未満ではＨＣ、ＣＯ及びＮＯｘの浄化率が低下する傾向にあり、他方、前記上限を超えると、貴金属により得られる効果が飽和するとともにコストが増大する傾向にある。 The amount of such noble metal supported is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 4 parts by mass, per 100 parts by mass of the exhaust gas purifying catalyst carrier. If the loading amount of the noble metal is less than the lower limit, the purification rate of HC, CO and NO x tends to decrease. On the other hand, if the upper limit is exceeded, the effect obtained by the noble metal tends to be saturated and the cost tends to increase. .
また、本発明の排ガス浄化用触媒を製造する方法は特に制限されず、例えば、上記本発明の排ガス浄化用触媒担体に前記貴金属のイオンを含有する水溶液（例えば、ジニトロジアンミン白金水溶液、硝酸ロジウム水溶液）を所定量含浸させ、これを蒸発乾固もしくは選択担持により濾過させた後、２５０〜５００℃程度で０．５〜５時間焼成する方法や、上記本発明の排ガス浄化用触媒担体を脱イオン水中に分散させ、これに前記貴金属のイオンを含有する水溶液を所定量添加して十分に撹拌した後、これを蒸発乾固せしめ、その後に２５０〜５００℃程度で０．５〜５時間焼成する方法を採用することができる。 The method for producing the exhaust gas purifying catalyst of the present invention is not particularly limited. For example, an aqueous solution containing the noble metal ions in the exhaust gas purifying catalyst carrier of the present invention (for example, dinitrodiammine platinum aqueous solution, rhodium nitrate aqueous solution). ), And by evaporating to dryness or filtering by selective loading, followed by baking at about 250 to 500 ° C. for 0.5 to 5 hours, or deionizing the exhaust gas purification catalyst carrier of the present invention. Disperse in water, add a predetermined amount of the aqueous solution containing the noble metal ions and stir well, evaporate to dryness, and then bake at about 250-500 ° C. for 0.5-5 hours The method can be adopted.
また、本発明の排ガス浄化用触媒の形態も特に制限されず、例えば、定法によりペレット化してペレット触媒としても、本発明の排ガス浄化用触媒を主成分とするスラリーをコーディエライトや金属箔からなるハニカム基材にコートし焼成してモノリス触媒としてもよい。 Further, the form of the exhaust gas purifying catalyst of the present invention is not particularly limited, and for example, a pellet containing the exhaust gas purifying catalyst of the present invention as a main component is prepared from cordierite or a metal foil. The resulting honeycomb substrate may be coated and fired to form a monolith catalyst.
次に、本発明の排ガス浄化方法について説明する。すなわち、本発明の排ガス浄化方法は、上記本発明の排ガス浄化用触媒を排ガスと接触させることを特徴とする方法である。このように、本発明の排ガス浄化方法においては、本発明の排ガス用浄化触媒を用いているため、ＳＯ２を含む排ガスに曝されても排ガスを十分に浄化することが可能である。そのため、本発明の排ガス浄化方法は、例えば、自動車の内燃機関等から排出される排ガスを浄化するための方法に採用することができる。 Next, the exhaust gas purification method of the present invention will be described. That is, the exhaust gas purification method of the present invention is a method characterized by bringing the exhaust gas purification catalyst of the present invention into contact with exhaust gas. Thus, in the exhaust gas purification method of the present invention, since the exhaust gas purification catalyst of the present invention is used, the exhaust gas can be sufficiently purified even when exposed to exhaust gas containing SO 2 . Therefore, the exhaust gas purification method of the present invention can be employed in a method for purifying exhaust gas discharged from, for example, an internal combustion engine of an automobile.
以下、実施例及び比較例に基づいて本発明をより具体的に説明するが、本発明は以下の実施例に限定されるものではない。 EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.
（合成例１：表面近傍にアルミナとチタニアが固溶したアルミナ粒子の調製）
先ず、８８２ｇの硝酸アルミニウム９水和物を２Ｌのイオン交換水に溶解させ、２８％アンモニア水４６０ｇを添加し、中和して得られた沈殿物を４００℃で５時間仮焼し、８００℃で５時間焼成した後、１５０μm以下に乾式粉砕してγ−Ａｌ２Ｏ３粉末を得た。次に、得られたγ−Ａｌ２Ｏ３粉末に対して、Ｔｉ換算でγ−Ａｌ２Ｏ３比５ｍｏｌ％となるようにチタニア前駆体を担持せしめ、大気中にて８００℃で３時間焼成してボールミルにより粉砕し、表面近傍にアルミナとチタニアが固溶したアルミナ粒子（平均２次粒子径１７μｍ）を得た。
(Synthesis Example 1: Preparation of alumina particles in which alumina and titania are dissolved in the vicinity of the surface)
First, 882 g of aluminum nitrate nonahydrate was dissolved in 2 L of ion exchange water, 460 g of 28% ammonia water was added, and the precipitate obtained by neutralization was calcined at 400 ° C. for 5 hours, And then pulverized to 150 μm or less to obtain γ-Al 2 O 3 powder. Next, a titania precursor is supported on the obtained γ-Al 2 O 3 powder so that the ratio of γ-Al 2 O 3 is 5 mol% in terms of Ti, and fired at 800 ° C. for 3 hours in the air. Then, it was pulverized by a ball mill to obtain alumina particles (average secondary particle diameter: 17 μm) in which alumina and titania were dissolved in the vicinity of the surface.
なお、前記チタニア前駆体としては、クエン酸０．９ｍｏｌをイオン交換水４５０ｍｌに溶解させた水溶液中に、７５℃に加熱しながらチタンイソプロポキシド０．３molを添加し、その後、室温に冷却することにより調製したものを用いた。 As the titania precursor, 0.3 mol of titanium isopropoxide is added to an aqueous solution in which 0.9 mol of citric acid is dissolved in 450 ml of ion exchange water while heating to 75 ° C., and then cooled to room temperature. Was used.
（合成例２：アルミナ−セリア−ジルコニア複合酸化物の調製）
先ず、硝酸アルミニウム９水和物２．３５モル、硝酸ジルコニル２水和物０．２５モル、硝酸セリウム（III）０．２５モル、硝酸バリウム０．０５モル、脱イオン水５７６８ｍｌを混合溶解した水溶液（Ａ液）と、アンモニア水８．３１２モルと、炭酸アンモニウム０．０７５モルと、脱イオン水２４００ｍｌとを混合した水溶液（Ｂ液）を調整した。
(Synthesis Example 2: Preparation of alumina-ceria-zirconia composite oxide)
First, an aqueous solution in which 2.35 mol of aluminum nitrate nonahydrate, 0.25 mol of zirconyl nitrate dihydrate, 0.25 mol of cerium (III) nitrate, 0.05 mol of barium nitrate, and 5768 ml of deionized water are mixed and dissolved. An aqueous solution (Liquid B) prepared by mixing (Liquid A), 8.31 mol of aqueous ammonia, 0.075 mol of ammonium carbonate, and 2400 ml of deionized water was prepared.
次に、高速混合装置の回転盤をおよそ５０００ｒｐｍの速度で回転させつつ、その回転盤上に１秒以内に両液が均一に混合されるような速度で前記Ａ液と前記Ｂ液とを同時に注入し、その混合液中において複合酸化物前駆体を析出させた。そして、このようにして得られた混合液と析出された複合酸化物前駆体とを、遠心力により器壁にぶつけて下方に流下せしめ、複合酸化物前駆体含有液体を捕集した。 Next, the A liquid and the B liquid are simultaneously mixed at a speed such that both liquids are uniformly mixed within 1 second on the rotating disk while rotating the rotating disk of the high speed mixing device at a speed of approximately 5000 rpm. The mixed oxide precursor was precipitated in the mixed solution. Then, the mixed liquid thus obtained and the deposited composite oxide precursor were made to flow downward by colliding against the vessel wall by centrifugal force, and the composite oxide precursor-containing liquid was collected.
次に、このようにして捕集された複合酸化物前駆体含有液体を攪拌して、複合酸化物前駆体が液体中で均一になるように保持しながら、脱イオン水により５倍に希釈した。その後、これを１日静置して上澄みを除去し、更に脱イオン水からなる洗浄液を添加して複合酸化物前駆体を洗浄し、洗浄液に含まれる硝酸アンモニウム塩の量が初期洗浄液における含有量の１０％以下になるまで繰り返し洗浄液を加えて洗浄を行った。 Next, the composite oxide precursor-containing liquid collected in this way was stirred and diluted 5 times with deionized water while keeping the composite oxide precursor uniform in the liquid. . Thereafter, this is left to stand for one day to remove the supernatant, and further, a cleaning liquid composed of deionized water is added to clean the composite oxide precursor, and the amount of ammonium nitrate contained in the cleaning liquid is the content of the initial cleaning liquid. Washing was performed by repeatedly adding a washing solution until the concentration became 10% or less.
その後、フィルタープレスにより複合酸化物前駆体と液体とを濾別し、フィルタープレスにより生成されたケーキ中に含まれる硝酸アンモニウム塩の量を質量比で約１％程度となるまで低下させた。このようにして得られた複合酸化物前駆体は１０５℃にて約２０時間乾燥させた後、６５０℃で１時間焼成した。次いで、このように焼成して得られた焼成物の塊をボールミルにより粉砕してアルミナとセリアとジルコニアとが均一に分散した平均２次粒子径１５μｍのアルミナ−セリア−ジルコニア複合酸化物（金属酸化物粒子）を得た。 Thereafter, the composite oxide precursor and the liquid were separated by a filter press, and the amount of ammonium nitrate contained in the cake produced by the filter press was reduced to about 1% by mass ratio. The composite oxide precursor thus obtained was dried at 105 ° C. for about 20 hours and then calcined at 650 ° C. for 1 hour. Next, the mass of the fired product obtained by firing in this manner is pulverized by a ball mill, and an alumina-ceria-zirconia composite oxide (metal oxide having an average secondary particle diameter of 15 μm) in which alumina, ceria, and zirconia are uniformly dispersed. Product particles).
（合成例３：セリア−ジルコニア複合酸化物の調製）
先ず、硝酸セリウム（III）と硝酸ジルコニルを、モル比で５０／５０（Ｚｒ／（Ｃｅ＋Ｚｒ）＝０．５０）となるように混合した水溶液を調製し、これをガラスビーカ中で撹拌しながらアンモニア水を滴下して中和し沈殿を生成させた。次に、この混合水溶液に含まれるセリウムイオンの１／２のモル数の過酸化水素を含む過酸化水素水と、得られる酸化物の重量の１０％のアルキルベンゼンスルホン酸を含む水溶液を添加し、混合撹拌した。
(Synthesis Example 3: Preparation of ceria-zirconia composite oxide)
First, an aqueous solution in which cerium (III) nitrate and zirconyl nitrate were mixed so as to have a molar ratio of 50/50 (Zr / (Ce + Zr) = 0.50) was prepared, and ammonia was stirred in a glass beaker. Water was added dropwise to neutralize to form a precipitate. Next, a hydrogen peroxide solution containing hydrogen peroxide having a mole number of ½ of cerium ions contained in the mixed aqueous solution and an aqueous solution containing 10% of alkylbenzenesulfonic acid by weight of the resulting oxide are added, The mixture was stirred.
次いで、このようにして得られたスラリーをガラスビーカ中に入れたまま５０℃／時の昇温速度で４００℃まで加熱し、４００℃で５時間保持して、共存する硝酸アンモニウムを蒸発または分解し、セリア−ジルコニア複合酸化物粉末を調製した。 Next, the slurry thus obtained is heated to 400 ° C. at a temperature rising rate of 50 ° C./hour while being put in a glass beaker, and kept at 400 ° C. for 5 hours to evaporate or decompose the coexisting ammonium nitrate. A ceria-zirconia composite oxide powder was prepared.
その後、得られたセリア−ジルコニア複合酸化物粉末を黒鉛粉末とともに蓋付き坩堝に入れ、黒鉛の部分的な酸化によるＣＯを含む還元雰囲気下にて、１２００℃で５時間熱処理してボールミルにより粉砕し、平均２次粒子径が１５μｍのセリア−ジルコニア複合酸化物（金属酸化物粒子）を得た。なお、この際に試料と黒鉛粉末が混合しないように二重の坩堝を用い、内側を試料、外側を黒鉛粉末として両者を分離した。 Thereafter, the obtained ceria-zirconia composite oxide powder is put in a crucible with a lid together with graphite powder, and is heat-treated at 1200 ° C. for 5 hours in a reducing atmosphere containing CO by partial oxidation of graphite and pulverized by a ball mill. A ceria-zirconia composite oxide (metal oxide particles) having an average secondary particle diameter of 15 μm was obtained. At this time, a double crucible was used so that the sample and the graphite powder were not mixed, and the inside was separated and the outside was separated from the graphite powder.
（比較合成例１：γ−Ａｌ２Ｏ３粉末とルチル型チタニア粉末を混合したアルミナ混合物の調製）
合成例１で得られたチタニアを固溶させる前のγ−Ａｌ２Ｏ３粉末を用い、そのγ−Ａｌ２Ｏ３粉末にＴｉ換算でγ−Ａｌ２Ｏ３比５ｍｏｌ％となるようにルチル型チタニア粉末を物理混合してアルミナ混合物を得た。
(Comparative Synthesis Example 1: Preparation of alumina mixture obtained by mixing γ-Al 2 O 3 powder and rutile-type titania powder)
Using the γ-Al 2 O 3 powder before solidifying the titania obtained in Synthesis Example 1, the γ-Al 2 O 3 powder was rutile so that the γ-Al 2 O 3 ratio was 5 mol% in terms of Ti. Type titania powder was physically mixed to obtain an alumina mixture.
（比較合成例２：粒子全体にチタニアとアルミナが均一に固溶したアルミナ−チタニア均質固溶体）
酢酸カリウム９．８ｇ、アルミニウムトリイソプロポキシド６１．２ｇ、チタニウムテトライソプロポキシド１４．２ｇを２−プロパノール３４５ｍｌに溶解した。この溶液を８０℃で２時間還流攪拌した後、２，４−ペンタンジオン１８．０ｇを混合しさらに３時間攪拌した。ここにイオン交換水３９．６ｍｌと２−プロパノール４０ｍｌの混合溶液を８０℃に保ちながら滴下した。そして８０℃で５時間攪拌した後、減圧乾燥して白色粉末を得た。この白色粉末を大気中にて８００℃で５時間焼成し、ボールミルにより粉砕した後、チタニアとアルミナが均一に固溶したアルミナ−チタニア均質固溶体（平均２次粒子径２０μｍ）を得た。
(Comparative synthesis example 2: Alumina-titania homogeneous solid solution in which titania and alumina are uniformly dissolved in the whole particle)
9.8 g of potassium acetate, 61.2 g of aluminum triisopropoxide, and 14.2 g of titanium tetraisopropoxide were dissolved in 345 ml of 2-propanol. The solution was stirred under reflux at 80 ° C. for 2 hours, mixed with 18.0 g of 2,4-pentanedione, and further stirred for 3 hours. A mixed solution of 39.6 ml of ion-exchanged water and 40 ml of 2-propanol was added dropwise thereto while maintaining at 80 ° C. And after stirring at 80 degreeC for 5 hours, it dried under reduced pressure and obtained white powder. This white powder was calcined at 800 ° C. for 5 hours in the air and pulverized by a ball mill, and then an alumina-titania homogeneous solid solution (average secondary particle size 20 μm) in which titania and alumina were uniformly dissolved.
〈ＸＲＤ測定〉
合成例１で得られたアルミナ粒子及び比較合成例１で得られたアルミナ混合物に対してＸＲＤ測定を行った。測定の結果得られたＸＲＤチャートを図１に示す。
<XRD measurement>
XRD measurement was performed on the alumina particles obtained in Synthesis Example 1 and the alumina mixture obtained in Comparative Synthesis Example 1. An XRD chart obtained as a result of the measurement is shown in FIG.
図１に示す回折強度に関するグラフからも明らかなように、比較合成例１で得られた前記アルミナ混合物はルチル型チタニアに帰属されるピークが２７．３°付近に存在していたのに対し、合成例１で得られた前記アルミナ粒子にはチタニアに帰属されるピークは存在しなかった。このような結果から、合成例１で得られた前記アルミナ粒子においては、チタニアの単独粒子はほとんど存在せず、チタニアの大部分がγ−Ａｌ２Ｏ３と固溶していることが確認された。 As apparent from the graph relating to the diffraction intensity shown in FIG. 1, the alumina mixture obtained in Comparative Synthesis Example 1 had a peak attributed to rutile-type titania near 27.3 °, The alumina particles obtained in Synthesis Example 1 did not have a peak attributed to titania. From these results, it was confirmed that in the alumina particles obtained in Synthesis Example 1, there were almost no single titania particles, and most of the titania was dissolved in γ-Al 2 O 3. It was.
次に、比較合成例２で得られたアルミナ−チタニア均質固溶体に対してもＸＲＤ測定を行ったところ、ＴｉがＡｌに対して高分散されており、チタニアがアルミナ中に均一に固溶していることが確認された。 Next, XRD measurement was also performed on the alumina-titania homogeneous solid solution obtained in Comparative Synthesis Example 2. As a result, Ti was highly dispersed in Al, and titania was uniformly dissolved in alumina. It was confirmed that
〈電界放射型透過電子顕微鏡（ＦＥ-ＴＥＭ）による測定〉
合成例１で得られたアルミナ粒子に対してＦＥ-ＴＥＭによる測定を行った。合成例１で得られたアルミナ粒子の表面からの距離とＡｌ元素に対するＴｉ元素の存在強度比との関係を示すグラフを図２に示し、合成例１で得られたアルミナ粒子の電界放射型透過電子顕微鏡写真を図３に示す。なお、合成例１で得られたアルミナ粒子に関しては、直径約２０ｎｍのものを測定試料として用いた。
<Measurement with Field Emission Transmission Electron Microscope (FE-TEM)>
The alumina particles obtained in Synthesis Example 1 were measured by FE-TEM. A graph showing the relationship between the distance from the surface of the alumina particles obtained in Synthesis Example 1 and the intensity ratio of Ti element to Al element is shown in FIG. 2, and the field emission transmission of the alumina particles obtained in Synthesis Example 1 is shown in FIG. An electron micrograph is shown in FIG. In addition, about the alumina particle obtained by the synthesis example 1, the thing about 20 nm in diameter was used as a measurement sample.
図２に示す結果からも明らかなように、合成例１で得られたアルミナ粒子においては、表面から粒子中心に向かうにつれＴｉ元素の存在割合は低下し、表面から２．５nmまでの範囲にＴｉ元素は高い濃度で存在していることが確認され、また、Ａｌ元素に対するＴｉ元素の存在強度比が０．１以下のアルミナ粒子の内部の領域では、測定上、粒子の断面を透過する部分の元素を測定するため、見かけ上Ｔｉが存在する形となっていることから、表面から５ｎｍ以降の領域にはＴｉ元素がほとんど存在しないと考えられる。また、図３に示す電界放射型透過電子顕微鏡写真からも明らかなように、合成例１で得られたアルミナ粒子においては、チタニアの単独粒子が存在せず、チタニアが固溶したアルミナ粒子のみであることが確認された。 As is clear from the results shown in FIG. 2, in the alumina particles obtained in Synthesis Example 1, the proportion of Ti element decreases as it goes from the surface toward the particle center, and Ti is within a range of 2.5 nm from the surface. It is confirmed that the element is present at a high concentration, and in the region inside the alumina particle where the ratio of the intensity of the Ti element to the Al element is 0.1 or less, the portion of the portion that permeates the cross section of the particle is measured. Since Ti is apparently present in order to measure the element, it is considered that there is almost no Ti element in the region after 5 nm from the surface. Further, as is clear from the field emission transmission electron micrograph shown in FIG. 3, the alumina particles obtained in Synthesis Example 1 do not contain single titania particles, but only alumina particles in which titania is dissolved. It was confirmed that there was.
〈合成例１で得られたアルミナ粒子と比較合成例２で得られたアルミナ−チタニア均質固溶体の比較〉
合成例１で得られたアルミナ粒子と比較合成例２で得られたアルミナ−チタニア均質固溶体の比表面積を測定したところ、合成例１で得られたアルミナ粒子の比表面積は１３９ｍ２／ｇであり、比較合成例２で得られたアルミナ−チタニア均質固溶体の比表面積は１２５ｍ２／ｇであった。このような比表面積の相違から、合成例１で得られたアルミナ粒子は、比較合成例２で得られたアルミナ−チタニア均質固溶体と比較して、貴金属をより高濃度で担持させることが可能となるため、より分散した反応場が得られることが分かった。
<Comparison of Alumina Particles Obtained in Synthesis Example 1 and Alumina-Titania Homogeneous Solid Solution Obtained in Comparative Synthesis Example 2>
When the specific surface areas of the alumina particles obtained in Synthesis Example 1 and the alumina-titania homogeneous solid solution obtained in Comparative Synthesis Example 2 were measured, the specific surface area of the alumina particles obtained in Synthesis Example 1 was 139 m 2 / g. The specific surface area of the alumina-titania homogeneous solid solution obtained in Comparative Synthesis Example 2 was 125 m 2 / g. Due to the difference in specific surface area, the alumina particles obtained in Synthesis Example 1 can support a noble metal at a higher concentration than the alumina-titania homogeneous solid solution obtained in Comparative Synthesis Example 2. Therefore, it was found that a more dispersed reaction field can be obtained.
（実施例１）
合成例１で得られたアルミナ粒子９４．５ｇと、合成例２で得られたアルミナ−セリア−ジルコニア複合酸化物９９．３ｇとをボールミルにより湿式混合して本発明の排ガス浄化用触媒担体を得た。次いで、得られた排ガス浄化用触媒担体１９３．８ｇにＰｔを４．５ｗｔ％含有するジニトロジアンミン白金水溶液４４ｇを含浸させ、これを蒸発乾固せしめた後、大気中にて５００℃で３時間焼成して前記排ガス浄化用触媒担体にＰｔが２ｇ担持された本発明の排ガス浄化用触媒を得た。
Example 1
94.5 g of the alumina particles obtained in Synthesis Example 1 and 99.3 g of the alumina-ceria-zirconia composite oxide obtained in Synthesis Example 2 are wet mixed by a ball mill to obtain an exhaust gas purifying catalyst carrier of the present invention. It was. Next, 193.8 g of the obtained exhaust gas purification catalyst carrier was impregnated with 44 g of a dinitrodiammine platinum aqueous solution containing 4.5 wt% Pt, evaporated and dried, and then calcined at 500 ° C. in the atmosphere for 3 hours. Thus, the exhaust gas purifying catalyst of the present invention in which 2 g of Pt was supported on the exhaust gas purifying catalyst carrier was obtained.
（実施例２）
合成例１で得られたアルミナ粒子１２０ｇと、合成例３で得られたセリア−ジルコニア複合酸化物８４ｇを用い、担体２０４ｇに対してＰｔを担持した以外は実施例１と同様にして本発明の排ガス用浄化用触媒を得た。
(Example 2)
Using the alumina particles 120 g obtained in Synthesis Example 1 and 84 g of the ceria-zirconia composite oxide obtained in Synthesis Example 3, except that Pt was supported on 204 g of the carrier, the same as in Example 1 was applied. An exhaust gas purification catalyst was obtained.
（比較例１）
合成例１で得られたアルミナ粒子の代わりに、合成例１で得られたチタニアを固溶する前のγ−Ａｌ２Ｏ３粉末を９４．５ｇ用いた以外は、実施例１と同様にして比較としての排ガス用浄化用触媒を得た。
(Comparative Example 1)
Instead of the alumina particles obtained in Synthesis Example 1, 94.5 g of the γ-Al 2 O 3 powder before dissolving the titania obtained in Synthesis Example 1 was used in the same manner as in Example 1. As a comparison, an exhaust gas purification catalyst was obtained.
（比較例２）
合成例１で得られたアルミナ粒子の代わりに、合成例１で得られたチタニアを固溶する前のγ−Ａｌ２Ｏ３粉末を１２０ｇ用いた以外は実施例２と同様にして比較としての排ガス用浄化用触媒を得た。
(Comparative Example 2)
Instead of the alumina particles obtained in Synthesis Example 1, 120 g of the γ-Al 2 O 3 powder before dissolving the titania obtained in Synthesis Example 1 was used in the same manner as in Example 2 for comparison. An exhaust gas purification catalyst was obtained.
（比較例３）
合成例１で得られたアルミナ粒子の代わりに、比較合成例２で得られたアルミナ−チタニア均質固溶体の粉末を１２０ｇ用いた以外は、実施例２と同様にして比較としての排ガス用浄化用触媒を得た。
(Comparative Example 3)
Exhaust gas purification catalyst as a comparison in the same manner as in Example 2 except that 120 g of the alumina-titania homogeneous solid solution powder obtained in Comparative Synthesis Example 2 was used instead of the alumina particles obtained in Synthesis Example 1. Got.
＜硫黄被毒耐久試験後の排ガス浄化用触媒の排ガス浄化活性＞
以下の方法で硫黄被毒耐久試験を行い、硫黄被毒耐久試験後の排ガス浄化用触媒の排ガス浄化活性を測定した。なお、このような試験には、実施例１〜２及び比較例１〜２で得られた排ガス浄化用触媒を定法により０．３ｍｍ−１ｍｍのペレットに成型したものを用いた。
<Exhaust gas purification activity of exhaust gas purification catalyst after sulfur poisoning durability test>
The sulfur poisoning endurance test was performed by the following method, and the exhaust gas purifying activity of the exhaust gas purifying catalyst after the sulfur poisoning endurance test was measured. For such tests, the exhaust gas purifying catalysts obtained in Examples 1-2 and Comparative Examples 1-2 were molded into 0.3 mm-1 mm pellets by a conventional method.
先ず、実施例１〜２及び比較例１〜２で得られた排ガス浄化用触媒に表１に示すガス組成でリッチとリーン雰囲気を１２０秒毎に変動させながら４００℃で１００分間硫黄被毒耐久試験を行った。次に、このような硫黄被毒耐久試験後の各排ガス浄化用触媒をそれぞれ０．５ｇ使用して、表２に示すモデルガスのリッチ雰囲気とリーン雰囲気を２秒毎に変動させながら、１２℃／ｍｉｎの昇温速度で１００℃から５００℃まで昇温して、各排ガス浄化用触媒のＣＯ、ＴＨＣ及びＮＯｘの排ガス浄化活性を測定した。 First, sulfur poisoning endurance for 100 minutes at 400 ° C. while changing the rich and lean atmosphere every 120 seconds with the gas composition shown in Table 1 for the exhaust gas purifying catalysts obtained in Examples 1-2 and Comparative Examples 1-2 A test was conducted. Next, using 0.5 g of each exhaust gas purifying catalyst after such a sulfur poisoning endurance test, while changing the rich atmosphere and lean atmosphere of the model gas shown in Table 2 every 2 seconds, The temperature was raised from 100 ° C. to 500 ° C. at a rate of temperature increase of / min, and the exhaust gas purification activity of CO, THC and NO x of each exhaust gas purification catalyst was measured.
〈実施例１及び比較例１で得られた各排ガス浄化用触媒の排ガス浄化活性に関して〉
実施例１及び比較例１で得られた排ガス浄化用触媒においては、上述の排ガス浄化活性の測定において、ＣＯ、ＴＨＣ及びＮＯｘの各成分の入りガス温度に対する転化率の変化を測定した。実施例１及び比較例１で得られた排ガス浄化用触媒によってＣＯとＴＨＣとが入りガス濃度に対して８０％転化される温度（８０％転化温度）とＮＯｘが入りガス濃度に対して５０％転化される温度（５０％転化温度）とを表３に示す。また、このような測定の結果得られた入りガス温度に対するＣＯの転化率の変化を示すグラフを図４に示し、入りガス温度に対するＴＨＣの転化率の変化を示すグラフを図５に示し、入りガス温度に対するＮＯｘの転化率の変化を示すグラフを図６に示す。
<Regarding Exhaust Gas Purifying Activity of Exhaust Gas Purifying Catalysts Obtained in Example 1 and Comparative Example 1>
In the exhaust gas purifying catalyst obtained in Example 1 and Comparative Example 1, in the measurement of the exhaust gas purifying activity described above, the change in the conversion rate of each component of CO, THC and NO x with respect to the entering gas temperature was measured. The temperature at which CO and THC are converted by 80% of the incoming gas concentration by the exhaust gas purifying catalyst obtained in Example 1 and Comparative Example 1 (80% conversion temperature) and NO x are 50% of the incoming gas concentration. Table 3 shows the temperature at which the% conversion is performed (50% conversion temperature). Further, FIG. 4 shows a graph showing the change in the CO conversion rate with respect to the inlet gas temperature obtained as a result of such measurement, and FIG. 5 shows a graph showing the change in the THC conversion rate with respect to the inlet gas temperature. A graph showing the change in the conversion rate of NO x with respect to the gas temperature is shown in FIG.
表３及び図４〜６に示す結果からも明らかなように、実施例１で得られた排ガス浄化用触媒は、比較例１で得られた排ガス浄化用触媒と比べてＣＯ、ＴＨＣ及びＮＯｘの各転化温度が低かった。このような結果から、実施例１で得られた排ガス浄化用触媒は、比較例１で得られた排ガス浄化用触媒よりも硫黄被毒による浄化活性の低下が十分に抑制され、硫黄被毒後においても優れた三元活性を示すことが確認された。 As is clear from the results shown in Table 3 and FIGS. 4 to 6, the exhaust gas purification catalyst obtained in Example 1 is more CO, THC and NO x than the exhaust gas purification catalyst obtained in Comparative Example 1. Each conversion temperature of was low. From these results, the exhaust gas purifying catalyst obtained in Example 1 is more sufficiently suppressed from lowering the purifying activity due to sulfur poisoning than the exhaust gas purifying catalyst obtained in Comparative Example 1, and after sulfur poisoning. Also showed excellent ternary activity.
〈実施例２、比較例２及び比較例３で得られた各排ガス浄化用触媒の排ガス浄化活性に関して〉
実施例２及び比較例２で得られた排ガス浄化用触媒においては、上述の排ガス浄化活性の測定において、ＣＯ、ＴＨＣ及びＮＯｘの各成分の入りガス温度に対する転化率の変化を測定した。実施例２、比較例２及び比較例３で得られた排ガス浄化用触媒によってＣＯ、ＴＨＣ及びＮＯｘの各成分がそれぞれ５０％転化される温度を表４に示す。また、このような測定の結果得られた入りガス温度に対するＴＨＣの転化率の変化を示すグラフを図７に示し、入りガス温度に対するＮＯｘの転化率の変化のグラフを示す図８に示す。
<Regarding Exhaust Gas Purifying Activity of Each Exhaust Gas Purifying Catalyst Obtained in Example 2, Comparative Example 2 and Comparative Example 3>
In the exhaust gas purifying catalysts obtained in Example 2 and Comparative Example 2, in the measurement of the exhaust gas purifying activity described above, the change in the conversion rate of each component of CO, THC, and NO x with respect to the entering gas temperature was measured. Table 4 shows the temperatures at which the respective components of CO, THC and NO x are converted by 50% by the exhaust gas purifying catalysts obtained in Example 2, Comparative Example 2 and Comparative Example 3. Further, FIG. 7 shows a graph showing the change in the conversion rate of THC with respect to the inlet gas temperature obtained as a result of such measurement, and FIG. 8 shows a graph of the change in the conversion rate of NO x with respect to the inlet gas temperature.
表４及び図７〜８に示す結果からも明らかなように、実施例２で得られた排ガス浄化用触媒は、比較例２及び比較例３で得られた排ガス浄化用触媒と比べてＣＯ、ＴＨＣ及びＮＯｘの５０％転化温度が低く、ＴＨＣ及びＮＯｘの各転化温度も低かった。このような結果から、実施例２で得られた排ガス浄化用触媒は、比較例２及び比較例３で得られた排ガス浄化用触媒よりも硫黄被毒による浄化活性の低下が十分に抑制され、硫黄被毒後においても優れた三元活性を示すことが確認された。
これらの実施例が示す効果は、担体中にチタニアが存在することにより硫黄の触媒表面への付着が抑制され、比較例よりもPtの失活が抑えられたことに由来すると考えられる。
As is clear from the results shown in Table 4 and FIGS. 7 to 8, the exhaust gas purification catalyst obtained in Example 2 is CO, compared with the exhaust gas purification catalyst obtained in Comparative Example 2 and Comparative Example 3. 50% conversion temperature of THC and NO x is low, the conversion temperature of THC and NO x was low. From such a result, the exhaust gas purification catalyst obtained in Example 2 is sufficiently suppressed from lowering the purification activity due to sulfur poisoning than the exhaust gas purification catalyst obtained in Comparative Example 2 and Comparative Example 3, It was confirmed that excellent ternary activity was exhibited even after sulfur poisoning.
The effects shown by these examples are considered to be derived from the fact that the adhesion of sulfur to the catalyst surface is suppressed due to the presence of titania in the support, and the deactivation of Pt is suppressed as compared with the comparative example.
以上説明したように、本発明によれば、高い耐硫黄被毒性を有し、硫黄酸化物を含む排ガス中においても優れた三元活性を発揮することを可能とする排ガス浄化用触媒担体、それを用いた排ガス浄化用触媒、並びにその排ガス浄化用触媒を用いた排ガス浄化方法を提供することが可能となる。 As described above, according to the present invention, an exhaust gas purifying catalyst carrier having high sulfur poisoning resistance and capable of exhibiting excellent ternary activity even in exhaust gas containing sulfur oxide, It is possible to provide an exhaust gas purifying catalyst using the catalyst and an exhaust gas purifying method using the exhaust gas purifying catalyst.
したがって、本発明の排ガス浄化用触媒は、硫黄酸化物を含む排ガス中においても三元活性に優れるため、自動車等の内燃機関から排出される排ガスを浄化するための排ガス浄化用触媒等として特に有用である。 Accordingly, the exhaust gas purifying catalyst of the present invention is particularly useful as an exhaust gas purifying catalyst for purifying exhaust gas discharged from an internal combustion engine such as an automobile because it has excellent three-way activity even in exhaust gas containing sulfur oxides. It is.
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| US10052615B2 (en) | 2013-11-29 | 2018-08-21 | Umicore Ag & Co. Kg | Oxygen storage materials |
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