JP6272303B2 - Alumina material containing barium sulfate and method for producing the same, and exhaust gas purification catalyst using the same - Google Patents
Alumina material containing barium sulfate and method for producing the same, and exhaust gas purification catalyst using the same Download PDFInfo
- Publication number
- JP6272303B2 JP6272303B2 JP2015508312A JP2015508312A JP6272303B2 JP 6272303 B2 JP6272303 B2 JP 6272303B2 JP 2015508312 A JP2015508312 A JP 2015508312A JP 2015508312 A JP2015508312 A JP 2015508312A JP 6272303 B2 JP6272303 B2 JP 6272303B2
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- Prior art keywords
- alumina
- barium sulfate
- exhaust gas
- oxide
- catalyst
- Prior art date
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- TZCXTZWJZNENPQ-UHFFFAOYSA-L barium sulfate Chemical compound [Ba+2].[O-]S([O-])(=O)=O TZCXTZWJZNENPQ-UHFFFAOYSA-L 0.000 title claims description 573
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 title claims description 378
- 239000003054 catalyst Substances 0.000 title claims description 233
- 239000000463 material Substances 0.000 title claims description 97
- 238000000746 purification Methods 0.000 title claims description 75
- 238000004519 manufacturing process Methods 0.000 title claims description 15
- 239000002245 particle Substances 0.000 claims description 241
- 229910052788 barium Inorganic materials 0.000 claims description 162
- 239000007789 gas Substances 0.000 claims description 154
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims description 84
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 claims description 83
- 239000011148 porous material Substances 0.000 claims description 51
- 239000002002 slurry Substances 0.000 claims description 38
- 229910000510 noble metal Inorganic materials 0.000 claims description 33
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 33
- 239000010948 rhodium Substances 0.000 claims description 33
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 30
- MRELNEQAGSRDBK-UHFFFAOYSA-N lanthanum(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[La+3].[La+3] MRELNEQAGSRDBK-UHFFFAOYSA-N 0.000 claims description 28
- 239000000203 mixture Substances 0.000 claims description 28
- 229910001404 rare earth metal oxide Inorganic materials 0.000 claims description 28
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 26
- PLDDOISOJJCEMH-UHFFFAOYSA-N neodymium(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Nd+3].[Nd+3] PLDDOISOJJCEMH-UHFFFAOYSA-N 0.000 claims description 26
- 229910052760 oxygen Inorganic materials 0.000 claims description 26
- 239000001301 oxygen Substances 0.000 claims description 26
- 229910052763 palladium Inorganic materials 0.000 claims description 24
- 229910052782 aluminium Inorganic materials 0.000 claims description 23
- 239000006185 dispersion Substances 0.000 claims description 21
- 238000004453 electron probe microanalysis Methods 0.000 claims description 21
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 claims description 20
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 claims description 20
- 229910052809 inorganic oxide Inorganic materials 0.000 claims description 20
- 238000002156 mixing Methods 0.000 claims description 19
- 238000005469 granulation Methods 0.000 claims description 18
- 230000003179 granulation Effects 0.000 claims description 18
- 229910052697 platinum Inorganic materials 0.000 claims description 17
- 238000003860 storage Methods 0.000 claims description 17
- SIWVEOZUMHYXCS-UHFFFAOYSA-N oxo(oxoyttriooxy)yttrium Chemical compound O=[Y]O[Y]=O SIWVEOZUMHYXCS-UHFFFAOYSA-N 0.000 claims description 13
- MMKQUGHLEMYQSG-UHFFFAOYSA-N oxygen(2-);praseodymium(3+) Chemical compound [O-2].[O-2].[O-2].[Pr+3].[Pr+3] MMKQUGHLEMYQSG-UHFFFAOYSA-N 0.000 claims description 13
- 229910003447 praseodymium oxide Inorganic materials 0.000 claims description 13
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 12
- 238000000576 coating method Methods 0.000 claims description 12
- 239000011248 coating agent Substances 0.000 claims description 11
- 238000010304 firing Methods 0.000 claims description 11
- 229910052751 metal Inorganic materials 0.000 claims description 11
- 239000002184 metal Substances 0.000 claims description 11
- 238000010298 pulverizing process Methods 0.000 claims description 11
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 10
- 229910052703 rhodium Inorganic materials 0.000 claims description 10
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 claims description 8
- 229910001593 boehmite Inorganic materials 0.000 claims description 7
- FAHBNUUHRFUEAI-UHFFFAOYSA-M hydroxidooxidoaluminium Chemical compound O[Al]=O FAHBNUUHRFUEAI-UHFFFAOYSA-M 0.000 claims description 7
- 239000011324 bead Substances 0.000 claims description 6
- 239000007921 spray Substances 0.000 claims description 6
- 229910021536 Zeolite Inorganic materials 0.000 claims description 5
- 238000004458 analytical method Methods 0.000 claims description 5
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 claims description 5
- 239000000377 silicon dioxide Substances 0.000 claims description 5
- 239000010457 zeolite Substances 0.000 claims description 5
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 246
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 132
- 239000010410 layer Substances 0.000 description 47
- 239000002131 composite material Substances 0.000 description 44
- 230000000052 comparative effect Effects 0.000 description 42
- 239000000843 powder Substances 0.000 description 42
- 238000000354 decomposition reaction Methods 0.000 description 39
- 238000009826 distribution Methods 0.000 description 33
- 238000000034 method Methods 0.000 description 27
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 25
- 230000007423 decrease Effects 0.000 description 24
- 230000009467 reduction Effects 0.000 description 23
- 239000003502 gasoline Substances 0.000 description 21
- 238000005259 measurement Methods 0.000 description 21
- 230000000694 effects Effects 0.000 description 20
- 230000006870 function Effects 0.000 description 20
- 238000011156 evaluation Methods 0.000 description 18
- 239000000523 sample Substances 0.000 description 18
- 239000000243 solution Substances 0.000 description 17
- 239000012298 atmosphere Substances 0.000 description 14
- 239000011268 mixed slurry Substances 0.000 description 14
- GPNDARIEYHPYAY-UHFFFAOYSA-N palladium(ii) nitrate Chemical compound [Pd+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O GPNDARIEYHPYAY-UHFFFAOYSA-N 0.000 description 14
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 13
- 229910002091 carbon monoxide Inorganic materials 0.000 description 13
- 238000006243 chemical reaction Methods 0.000 description 13
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 12
- QVQLCTNNEUAWMS-UHFFFAOYSA-N barium oxide Chemical compound [Ba]=O QVQLCTNNEUAWMS-UHFFFAOYSA-N 0.000 description 12
- 230000008093 supporting effect Effects 0.000 description 12
- 230000001133 acceleration Effects 0.000 description 11
- 238000009792 diffusion process Methods 0.000 description 11
- 229930195733 hydrocarbon Natural products 0.000 description 11
- 150000002430 hydrocarbons Chemical class 0.000 description 11
- 230000000704 physical effect Effects 0.000 description 11
- DTQVDTLACAAQTR-UHFFFAOYSA-N Trifluoroacetic acid Chemical compound OC(=O)C(F)(F)F DTQVDTLACAAQTR-UHFFFAOYSA-N 0.000 description 10
- 239000003463 adsorbent Substances 0.000 description 10
- 239000006069 physical mixture Substances 0.000 description 10
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 9
- 230000003197 catalytic effect Effects 0.000 description 9
- 238000002485 combustion reaction Methods 0.000 description 9
- 239000000446 fuel Substances 0.000 description 9
- 238000002360 preparation method Methods 0.000 description 9
- 239000002994 raw material Substances 0.000 description 9
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 8
- 150000001342 alkaline earth metals Chemical class 0.000 description 8
- 230000033228 biological regulation Effects 0.000 description 8
- 229910000420 cerium oxide Inorganic materials 0.000 description 8
- 239000010419 fine particle Substances 0.000 description 8
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 description 8
- 239000000126 substance Substances 0.000 description 8
- -1 sulfuric acid compound Chemical class 0.000 description 7
- 229910052779 Neodymium Inorganic materials 0.000 description 6
- 239000002253 acid Substances 0.000 description 6
- 230000009471 action Effects 0.000 description 6
- 239000002585 base Substances 0.000 description 6
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 description 6
- 230000008569 process Effects 0.000 description 6
- 239000007858 starting material Substances 0.000 description 6
- 230000007704 transition Effects 0.000 description 6
- ITHZDDVSAWDQPZ-UHFFFAOYSA-L barium acetate Chemical compound [Ba+2].CC([O-])=O.CC([O-])=O ITHZDDVSAWDQPZ-UHFFFAOYSA-L 0.000 description 5
- 229910052878 cordierite Inorganic materials 0.000 description 5
- 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 5
- 230000009257 reactivity Effects 0.000 description 5
- 150000003839 salts Chemical class 0.000 description 5
- 238000001179 sorption measurement Methods 0.000 description 5
- 238000000629 steam reforming Methods 0.000 description 5
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 4
- 229910017493 Nd 2 O 3 Inorganic materials 0.000 description 4
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 4
- 230000002411 adverse Effects 0.000 description 4
- 239000007864 aqueous solution Substances 0.000 description 4
- 239000011230 binding agent Substances 0.000 description 4
- 239000000460 chlorine Substances 0.000 description 4
- 229910052801 chlorine Inorganic materials 0.000 description 4
- 238000001035 drying Methods 0.000 description 4
- 239000011361 granulated particle Substances 0.000 description 4
- 239000003960 organic solvent Substances 0.000 description 4
- 229910052761 rare earth metal Inorganic materials 0.000 description 4
- 239000011347 resin Substances 0.000 description 4
- 229920005989 resin Polymers 0.000 description 4
- 229910052938 sodium sulfate Inorganic materials 0.000 description 4
- 235000011152 sodium sulphate Nutrition 0.000 description 4
- 230000002195 synergetic effect Effects 0.000 description 4
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 3
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 3
- 239000012736 aqueous medium Substances 0.000 description 3
- 159000000009 barium salts Chemical class 0.000 description 3
- 238000009835 boiling Methods 0.000 description 3
- 238000004364 calculation method Methods 0.000 description 3
- RCFVMJKOEJFGTM-UHFFFAOYSA-N cerium zirconium Chemical compound [Zr].[Ce] RCFVMJKOEJFGTM-UHFFFAOYSA-N 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 230000003247 decreasing effect Effects 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 230000001976 improved effect Effects 0.000 description 3
- 238000003801 milling Methods 0.000 description 3
- 239000004570 mortar (masonry) Substances 0.000 description 3
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 description 3
- 239000011164 primary particle Substances 0.000 description 3
- 238000005245 sintering Methods 0.000 description 3
- 238000011144 upstream manufacturing Methods 0.000 description 3
- 229910001928 zirconium oxide Inorganic materials 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- QBPWTAFKBTUDPG-UHFFFAOYSA-N FC(C(=O)O)(F)F.C(CCCCCCCCCCC)(=O)O Chemical compound FC(C(=O)O)(F)F.C(CCCCCCCCCCC)(=O)O QBPWTAFKBTUDPG-UHFFFAOYSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 2
- 230000010718 Oxidation Activity Effects 0.000 description 2
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 2
- XUBKPYAWPSXPDZ-UHFFFAOYSA-N [Ba].OS(O)(=O)=O Chemical compound [Ba].OS(O)(=O)=O XUBKPYAWPSXPDZ-UHFFFAOYSA-N 0.000 description 2
- 150000007513 acids Chemical class 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
- AYJRCSIUFZENHW-DEQYMQKBSA-L barium(2+);oxomethanediolate Chemical compound [Ba+2].[O-][14C]([O-])=O AYJRCSIUFZENHW-DEQYMQKBSA-L 0.000 description 2
- 238000001354 calcination Methods 0.000 description 2
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 239000001569 carbon dioxide Substances 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 239000000969 carrier Substances 0.000 description 2
- 238000006555 catalytic reaction Methods 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 230000002596 correlated effect Effects 0.000 description 2
- 238000001784 detoxification Methods 0.000 description 2
- 238000006073 displacement reaction Methods 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 150000007529 inorganic bases Chemical class 0.000 description 2
- 229910052746 lanthanum Inorganic materials 0.000 description 2
- 229910052749 magnesium Inorganic materials 0.000 description 2
- 239000011777 magnesium Substances 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- CLSUSRZJUQMOHH-UHFFFAOYSA-L platinum dichloride Chemical compound Cl[Pt]Cl CLSUSRZJUQMOHH-UHFFFAOYSA-L 0.000 description 2
- CJWLZBLADIYQOV-UHFFFAOYSA-L platinum(2+);dinitrite Chemical compound [Pt+2].[O-]N=O.[O-]N=O CJWLZBLADIYQOV-UHFFFAOYSA-L 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 150000002910 rare earth metals Chemical class 0.000 description 2
- SVOOVMQUISJERI-UHFFFAOYSA-K rhodium(3+);triacetate Chemical compound [Rh+3].CC([O-])=O.CC([O-])=O.CC([O-])=O SVOOVMQUISJERI-UHFFFAOYSA-K 0.000 description 2
- 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 2
- 239000012266 salt solution Substances 0.000 description 2
- 238000000790 scattering method Methods 0.000 description 2
- 159000000000 sodium salts Chemical class 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 239000013585 weight reducing agent Substances 0.000 description 2
- 229910052726 zirconium Inorganic materials 0.000 description 2
- OERNJTNJEZOPIA-UHFFFAOYSA-N zirconium nitrate Chemical compound [Zr+4].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O OERNJTNJEZOPIA-UHFFFAOYSA-N 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
- DUFCMRCMPHIFTR-UHFFFAOYSA-N 5-(dimethylsulfamoyl)-2-methylfuran-3-carboxylic acid Chemical compound CN(C)S(=O)(=O)C1=CC(C(O)=O)=C(C)O1 DUFCMRCMPHIFTR-UHFFFAOYSA-N 0.000 description 1
- 238000004438 BET method Methods 0.000 description 1
- 229910015999 BaAl Inorganic materials 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 230000010757 Reduction Activity Effects 0.000 description 1
- 229910052581 Si3N4 Inorganic materials 0.000 description 1
- HDYRYUINDGQKMC-UHFFFAOYSA-M acetyloxyaluminum;dihydrate Chemical compound O.O.CC(=O)O[Al] HDYRYUINDGQKMC-UHFFFAOYSA-M 0.000 description 1
- 239000004480 active ingredient Substances 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 229940009827 aluminum acetate Drugs 0.000 description 1
- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical compound N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 description 1
- 229910052921 ammonium sulfate Inorganic materials 0.000 description 1
- 235000011130 ammonium sulphate Nutrition 0.000 description 1
- RQPZNWPYLFFXCP-UHFFFAOYSA-L barium dihydroxide Chemical compound [OH-].[OH-].[Ba+2] RQPZNWPYLFFXCP-UHFFFAOYSA-L 0.000 description 1
- 229910001863 barium hydroxide Inorganic materials 0.000 description 1
- SSJVTIOFGIUKMI-UHFFFAOYSA-J barium(2+);disulfate Chemical compound [Ba+2].[Ba+2].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O SSJVTIOFGIUKMI-UHFFFAOYSA-J 0.000 description 1
- QKYBEKAEVQPNIN-UHFFFAOYSA-N barium(2+);oxido(oxo)alumane Chemical compound [Ba+2].[O-][Al]=O.[O-][Al]=O QKYBEKAEVQPNIN-UHFFFAOYSA-N 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 230000003139 buffering effect Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 239000003426 co-catalyst Substances 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 230000002939 deleterious effect Effects 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000003795 desorption Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 239000012065 filter cake Substances 0.000 description 1
- 239000000295 fuel oil Substances 0.000 description 1
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- 238000000227 grinding Methods 0.000 description 1
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- 239000004615 ingredient Substances 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000002105 nanoparticle Substances 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- UYXRCZUOJAYSQR-UHFFFAOYSA-N nitric acid;platinum Chemical compound [Pt].O[N+]([O-])=O UYXRCZUOJAYSQR-UHFFFAOYSA-N 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 231100000989 no adverse effect Toxicity 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 239000003002 pH adjusting agent Substances 0.000 description 1
- PIBWKRNGBLPSSY-UHFFFAOYSA-L palladium(II) chloride Chemical compound Cl[Pd]Cl PIBWKRNGBLPSSY-UHFFFAOYSA-L 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 238000005504 petroleum refining Methods 0.000 description 1
- NWAHZABTSDUXMJ-UHFFFAOYSA-N platinum(2+);dinitrate Chemical compound [Pt+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O NWAHZABTSDUXMJ-UHFFFAOYSA-N 0.000 description 1
- 231100000614 poison Toxicity 0.000 description 1
- 230000007096 poisonous effect Effects 0.000 description 1
- 230000008092 positive effect Effects 0.000 description 1
- 239000010970 precious metal Substances 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 239000013074 reference sample Substances 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- YWFDDXXMOPZFFM-UHFFFAOYSA-H rhodium(3+);trisulfate Chemical compound [Rh+3].[Rh+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O YWFDDXXMOPZFFM-UHFFFAOYSA-H 0.000 description 1
- SONJTKJMTWTJCT-UHFFFAOYSA-K rhodium(iii) chloride Chemical compound [Cl-].[Cl-].[Cl-].[Rh+3] SONJTKJMTWTJCT-UHFFFAOYSA-K 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 description 1
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- XTQHKBHJIVJGKJ-UHFFFAOYSA-N sulfur monoxide Chemical class S=O XTQHKBHJIVJGKJ-UHFFFAOYSA-N 0.000 description 1
- 229910052815 sulfur oxide Inorganic materials 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 230000004580 weight loss Effects 0.000 description 1
- 238000001238 wet grinding Methods 0.000 description 1
- 150000003755 zirconium compounds Chemical class 0.000 description 1
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Description
本発明は、硫酸バリウムを含むアルミナ材料とその製造方法、それを用いた排気ガス浄化用触媒に関し、より詳しくは、硫酸バリウムを含むアルミナ材料とその製造方法、それを用いた触媒や吸着剤、特にガソリン車などの内燃機関から排出される排気ガス中の窒素酸化物（ＮＯｘ）の浄化性能に優れた排気ガス浄化用触媒に関する。 The present invention relates to an alumina material containing barium sulfate and a production method thereof, and an exhaust gas purifying catalyst using the same, and more specifically, an alumina material containing barium sulfate and a production method thereof, a catalyst and an adsorbent using the same, In particular, the present invention relates to an exhaust gas purifying catalyst having excellent purifying performance of nitrogen oxide (NOx) in exhaust gas discharged from an internal combustion engine such as a gasoline vehicle.
重油や軽油などの高沸点炭化水素をより低沸点の炭化水素に分解する触媒、あるいは石油精製の際に生じる硫黄酸化物の放出を抑制する吸着剤として、アルカリ土類元素の硫酸化合物である硫酸マグネシウムの他、硫酸カルシウム、硫酸バリウムなどを含むアルミナ材料が知られている（特許文献１参照）。
一方、ガソリン車等の内燃機関から排出される排気ガスを浄化する触媒装置には、その目的に応じて様々な触媒が使用されてきた。この主要な触媒成分には白金族金属があり、通常、活性アルミナ等の高表面積の耐火性無機酸化物上に高分散に担持して使用されている（特許文献２参照）。Sulfuric acid, a sulfuric acid compound of alkaline earth elements, as a catalyst that decomposes high-boiling hydrocarbons such as heavy oil and light oil into lower-boiling hydrocarbons, or as an adsorbent that suppresses the release of sulfur oxides generated during petroleum refining An alumina material containing calcium sulfate, barium sulfate, etc. in addition to magnesium is known (see Patent Document 1).
On the other hand, various catalysts have been used in catalyst devices for purifying exhaust gas discharged from an internal combustion engine such as a gasoline vehicle depending on the purpose. This main catalyst component includes a platinum group metal, and is usually used in a highly dispersed state on a high surface area refractory inorganic oxide such as activated alumina (see Patent Document 2).
排気ガスを浄化する触媒成分としての白金族金属には、白金（Ｐｔ）、パラジウム（Ｐｄ）、ロジウム（Ｒｈ）が知られており、広くガソリン車等の内燃機関から排出される排気ガス浄化用触媒に使用されてきた。具体的には、Ｐｔ、Ｐｄなど酸化活性に優れる触媒活性種は、ＮＯｘの浄化活性に優れるＲｈと組み合わせて使用されることが多い。
近年、排気ガス中に含まれる有害物質、特にＮＯｘ（ＮＯ及びＮＯ２）に対する規制が厳しさを増しており、ＮＯｘの浄化活性に優れるＲｈを効果的に使用する必要があるが、Ｒｈは産出量も少なく、高価であり、近年市場価格も高騰している。そのため、Ｒｈの代替として、Ｐｄを活用する試みも近年積極的に行われている。ＰｄはＲｈほどではないがＮＯｘ浄化性能を示すことが知られており、Ｐｄを活用してＲｈなみのＮＯｘ浄化活性が得られれば資源保護の観点、コスト面から非常に有意義なものとなる。Platinum (Pt), palladium (Pd), and rhodium (Rh) are known as platinum group metals as catalyst components for purifying exhaust gas, and are widely used for purifying exhaust gas discharged from internal combustion engines such as gasoline cars. It has been used for catalysts. Specifically, catalytically active species having excellent oxidation activity such as Pt and Pd are often used in combination with Rh having excellent NOx purification activity.
In recent years, regulations on harmful substances contained in exhaust gas, especially NOx (NO and NO 2 ) are becoming more stringent, and it is necessary to effectively use Rh, which is excellent in NOx purification activity. The amount is small and expensive, and the market price has been rising in recent years. For this reason, attempts to utilize Pd as an alternative to Rh have been actively made in recent years. Pd is known to exhibit NOx purification performance, although not as high as Rh, and if Pd is used to obtain Rh-like NOx purification activity, it will be very meaningful from the viewpoint of resource protection and cost.
また、排気ガス浄化触媒では、更なる浄化性能の向上を図るため、触媒には白金族金属の他、様々な助触媒成分の添加が検討されている。このような助触媒成分としては、酸素吸蔵放出成分（Ｏｘｇｅｎ Ｓｔｏｒａｇｅ Ｃｏｍｐｏｎｅｎｔ：ＯＳＣ）や、アルカリ土類金属や、ジルコニウム酸化物、ゼオライト等が知られている。
このうち、排気ガス中の酸素を吸蔵・放出するＯＳＣとして、酸化セリウムが知られている。酸化セリウムは、排気ガス中の酸素濃度が高い時にはＣｅＯ２として酸素を吸蔵し、酸素濃度が低い時にはＣｅ２Ｏ３になって酸素を放出する。放出された酸素は活性な酸素であり、ＰｔやＰｄによる酸化作用に利用されることでＨＣ、ＣＯの浄化を促進する。また、ＯＳＣは酸素の吸蔵・放出により、排気ガス中の酸素濃度変化を緩衝する働きもする。この働きによりＴＷＣでは排気ガスの浄化性能が向上する。ＴＷＣは一つの触媒で酸化と還元を行うものであり、設計上、浄化に適した排気ガス成分の範囲がある。この範囲は空燃比に依存することが多い。このような範囲はウィンドウといわれ、多くの場合、Ｓｔｏｉｃｈｉｏと呼ばれる理論空燃比の近傍で燃焼した排気ガスをウィンドウ域に設定している。排気ガス中の酸素濃度の変化が緩衝されることで、このウィンドウ域が長時間保たれて排気ガスの浄化が効果的に行なわれる。これは特にＯ２共存下で進行しにくいＮＯｘの浄化特性に大きく影響すると言われている。Further, in the exhaust gas purification catalyst, in order to further improve the purification performance, addition of various promoter components in addition to platinum group metals has been studied for the catalyst. As such a promoter component, oxygen storage component (Oxgen Storage Component: OSC), alkaline earth metal, zirconium oxide, zeolite, and the like are known.
Of these, cerium oxide is known as an OSC that stores and releases oxygen in exhaust gas. Cerium oxide occludes oxygen as CeO 2 when the oxygen concentration in the exhaust gas is high, and releases oxygen as Ce 2 O 3 when the oxygen concentration is low. The released oxygen is active oxygen and promotes the purification of HC and CO by being used for the oxidizing action by Pt and Pd. The OSC also functions to buffer changes in oxygen concentration in the exhaust gas by storing and releasing oxygen. This action improves the exhaust gas purification performance of TWC. TWC performs oxidation and reduction with a single catalyst, and has a range of exhaust gas components suitable for purification by design. This range often depends on the air-fuel ratio. Such a range is called a window, and in many cases, the exhaust gas burned in the vicinity of the stoichiometric air-fuel ratio called “Stoichio” is set as the window region. Since the change in the oxygen concentration in the exhaust gas is buffered, this window region is maintained for a long time, and the exhaust gas is effectively purified. This is said to have a great influence on the purification characteristics of NOx that are difficult to proceed especially in the presence of O 2 .
このような酸化セリウムとしては、純粋なセリウム酸化物も使用できるが、ジルコニウムとの複合酸化物として使用されることが多い（特許文献３参照）。セリウム・ジルコニウム複合酸化物は耐熱性が高く、酸素の吸蔵・放出速度も速いといわれている。それはセリウム・ジルコニウム複合酸化物の結晶構造が安定で、主要なＯＳＣ成分であるセリウム酸化物の働きを促進して、粒子の内部までＯＳＣとして機能するためと考えられる。 As such cerium oxide, pure cerium oxide can also be used, but it is often used as a complex oxide with zirconium (see Patent Document 3). Cerium-zirconium composite oxide has high heat resistance and is said to have a high oxygen storage / release rate. This is probably because the crystal structure of the cerium-zirconium composite oxide is stable and promotes the action of cerium oxide, which is the main OSC component, to function as an OSC up to the inside of the particle.
一方、空燃比（Ａｉｒ／Ｆｕｅｌ Ｒａｔｉｏ：以下、Ａ／Ｆということがある）を理論空燃比近傍で制御しているガソリン車では、ＲｈによるＮＯｘ（ＮＯ及びＮＯ２）の浄化が重要となり、例えばスチームリフォーミング反応｛反応式（２）｝やＣＯ＋ＮＯ反応｛反応式（４）｝がＲｈ成分を介して以下のように促進され、生成したＨ２がＮＯｘを浄化｛反応式（３）｝するものと考えられている。
そして、ジルコニウム酸化物は、Ｒｈ成分と共に用いるとスチームリフォーミング反応やＣＯ＋ＮＯ反応を促進することが公知の技術となっている（特許文献４参照）。
ＨＣ ＋ Ｈ２Ｏ → ＣＯｘ ＋ Ｈ２ ・・・ （２）
Ｈ２ ＋ ＮＯｘ → Ｎ２ ＋ Ｈ２Ｏ ・・・ （３）
ＣＯ ＋ ＮＯ → ＣＯ２ ＋ １／２Ｎ２ ・・・ （４）On the other hand, in a gasoline vehicle in which the air-fuel ratio (Air / Fuel Ratio: hereinafter sometimes referred to as A / F) is controlled near the theoretical air-fuel ratio, purification of NOx (NO and NO 2 ) by Rh is important. Steam reforming reaction {reaction formula (2)} and CO + NO reaction {reaction formula (4)} are promoted through the Rh component as follows, and the generated H 2 purifies NOx {reaction formula (3)}. It is considered a thing.
And when zirconium oxide is used together with the Rh component, it is a known technique to promote a steam reforming reaction and a CO + NO reaction (see Patent Document 4).
HC + H 2 O → COx + H 2 (2)
H 2 + NOx → N 2 + H 2 O (3)
CO + NO → CO 2 + 1 / 2N 2 (4)
加えて最近では、Ｒｈの使用量を低減するための方法として、ＰｔやＰｄにおいてもスチームリフォーミング反応｛反応式（２）｝やウォーターガスシフト反応｛反応式（５）｝により発生するＨ２を用いてＮＯｘの浄化を促進することが考えられ、助触媒成分として水溶性の酢酸バリウムを原料とするアルカリ土類金属の使用が検討されている（特許文献５参照）。
ＣＯ ＋ Ｈ２Ｏ → ＣＯ２ ＋ Ｈ２ ・・・ （５）In addition, recently, as a method for reducing the amount of Rh used, H 2 generated by the steam reforming reaction {reaction formula (2)} or the water gas shift reaction {reaction formula (5)} also in Pt and Pd. It is conceivable to promote the purification of NOx, and the use of alkaline earth metals made of water-soluble barium acetate as a promoter component has been studied (see Patent Document 5).
CO + H 2 O → CO 2 + H 2 (5)
その他、Ｂａ成分に代表されるアルカリ土類金属は、助触媒成分として排気ガス中に含まれるＮＯｘを一時的に吸蔵し、吸蔵したＮＯｘを排気ガスに含まれる還元成分によりＮ２に還元して浄化する（特許文献６参照）。
一般に、エンジンに供給される燃料が少ないとき、空気の量が多いとき、燃焼温度が高いときにＮＯｘが多量に発生する。Ｂａ成分は、このように発生するＮＯｘをＢａ（ＮＯ３）２として一時的に吸収する。
Ｂａ成分に吸収されたＮＯｘは、排気ガス中のＮＯｘの濃度が低く炭酸ガス（ＣＯ２）濃度が高くなったときにＢａ成分から放出される。これは前記Ｂａ（ＮＯ３）２が水蒸気共存下で炭酸ガスと反応し、ＢａＣＯ３になるものであり、化学平衡であるといえる。Ｂａ成分から放出されたＮＯｘは、前述したようにＲｈ成分表面で還元成分と反応して還元浄化される。In addition, alkaline earth metals represented by the Ba component temporarily store NOx contained in the exhaust gas as a promoter component, and reduce the stored NOx to N 2 by the reducing component contained in the exhaust gas. Purify (see Patent Document 6).
Generally, a large amount of NOx is generated when the amount of fuel supplied to the engine is small, when the amount of air is large, and when the combustion temperature is high. The Ba component temporarily absorbs NOx generated in this way as Ba (NO 3 ) 2 .
The NOx absorbed in the Ba component is released from the Ba component when the concentration of NOx in the exhaust gas is low and the concentration of carbon dioxide (CO 2 ) is high. This is because the Ba (NO 3 ) 2 reacts with carbon dioxide in the presence of water vapor to form BaCO 3 , which is a chemical equilibrium. As described above, NOx released from the Ba component reacts with the reducing component on the surface of the Rh component and is reduced and purified.
このような助触媒成分は、２種以上を併用することもでき、例えば、Ｂａ成分（酢酸バリウム、又は硝酸バリウム）と酸化セリウムを使用したＴＷＣ（特許文献７参照）や本出願人が提案した硫酸バリウム、セリウム・ジルコニウム複合酸化物を使用したＴＷＣ（特許文献８参照）などが知られている。ところが、触媒材料の組み合わせによっては浄化性能を低下してしまうことがあり、例えば、Ｒｈ成分とＢａ成分が同一組成中に存在するとＮＯｘの浄化性能が低下することが報告されている（特許文献９参照）。この理由は、アルカリ土類金属成分がＮＯｘを吸蔵する作用を有することから、Ｒｈ成分におけるＮＯｘの浄化作用が妨害されたり、ＢａからＲｈへの電子供与作用による不活性な酸化Ｒｈ構造の安定化によるためと考えられる。
一方、Ｐｄ成分とＢａ成分が近接して存在するとＮＯｘ浄化性能が向上することが知られている（特許文献１０参照）。これはＢａからＰｄへの電子供与によりＰｄが部分的に安定化され、Ｐｄのシンタリングが抑制されることやＮＯｘ吸着特性の低いＰｄの機能をＢａ成分が補填し、Ｐｄ近傍のＮＯｘを滞留させるためであると考えられる。
他方、バリウムに代表されるアルカリ土類金属が、ＯＳＣ（セリウム酸化物、特許文献１１参照）及びＣｅ・Ｚｒ系複合酸化物（特許文献１２参照）とは互いに分離されて異なる触媒層に含まれるようにした排気ガス浄化用触媒が提案されている。
このように貴金属（Ｒｈ、Ｐｄなど）やＯＳＣ（セリウム酸化物、Ｃｅ・Ｚｒ系複合酸化物など）と助触媒（Ｂａなど）の関係が研究され、触媒性能に好影響を与える組み合わせが次第に明らかになりつつあるが、まだ、解析が十分に進んでいるとは言い難い状況にある。
実際、上記のように触媒による排気ガスの浄化では、触媒成分相互の相関作用による複雑な反応経路を経ることから、これらを総合的に検討して、最も浄化作用が発揮される触媒成分の組み合わせと配置（位置関係）は、現在も依然として模索中であり、未だ、確立されていない。Two or more kinds of such co-catalyst components can be used in combination. For example, TWC (see Patent Document 7) using a Ba component (barium acetate or barium nitrate) and cerium oxide or the present applicant has proposed. TWC using barium sulfate, cerium-zirconium composite oxide (see Patent Document 8) and the like are known. However, depending on the combination of the catalyst materials, the purification performance may be lowered. For example, it has been reported that the purification performance of NOx is lowered when the Rh component and the Ba component are present in the same composition (Patent Document 9). reference). This is because the alkaline earth metal component has an action of occluding NOx, so that the NOx purification action in the Rh ingredient is hindered, or the inert oxidized Rh structure is stabilized by the electron donating action from Ba to Rh. It is thought to be due to this.
On the other hand, it is known that the NOx purification performance improves when the Pd component and the Ba component are close to each other (see Patent Document 10). This is because Pd is partially stabilized by electron donation from Ba to Pd, Pd sintering is suppressed, and the function of Pd with low NOx adsorption characteristics is compensated by the Ba component, and NOx in the vicinity of Pd is retained. It is thought that it is to make it.
On the other hand, the alkaline earth metal represented by barium is separated from OSC (cerium oxide, see Patent Document 11) and Ce.Zr-based composite oxide (see Patent Document 12) and is contained in different catalyst layers. There has been proposed an exhaust gas purifying catalyst.
In this way, the relationship between noble metals (Rh, Pd, etc.), OSC (cerium oxide, Ce / Zr composite oxide, etc.) and cocatalyst (Ba, etc.) has been studied, and combinations that have a positive effect on catalyst performance are gradually becoming apparent However, it is still difficult to say that the analysis is sufficiently advanced.
In fact, as described above, exhaust gas purification using a catalyst involves a complicated reaction path due to the mutual interaction of the catalyst components. The arrangement (positional relationship) is still being explored and has not yet been established.
ところで、排気ガス浄化触媒は、排気ガス流路の中に一つ配置されれば良いが、２個以上配置される場合もある。これは、排ガス規制の強化に伴って、排気ガス浄化触媒の特性をより生かすための処置であり、白金、パラジウム、ロジウムのそれぞれの貴金属が有する耐久性（耐熱性、耐雰囲気性、耐被毒性）、触媒特性（酸化活性、還元活性）等に応じてそれぞれ最適の位置を設定するためである。
また、高価な貴金属や希土類の使用量を削減することは、限りある資源の効率的な活用に繋がっているため、それぞれの貴金属や希土類の特性に応じて排気ガス流路の最適の位置に排気ガス浄化触媒を設置することが求められている。By the way, one exhaust gas purifying catalyst may be arranged in the exhaust gas flow path, but two or more exhaust gas purifying catalysts may be arranged. This is a measure to make the best use of the characteristics of exhaust gas purifying catalysts in accordance with the strengthening of exhaust gas regulations. ), The optimum positions are set in accordance with the catalyst characteristics (oxidation activity, reduction activity) and the like.
In addition, reducing the amount of expensive noble metals and rare earths used leads to the efficient use of limited resources, so the exhaust gas flow is optimally positioned according to the characteristics of each noble metal and rare earth. It is required to install a gas purification catalyst.
さらに、近年、排ガス規制は、ますます厳しくなる一方であり、複数の触媒を使用して、より優れた排気ガス浄化性能を発揮する触媒の登場が望まれている。排気ガスの中でも特にＮＯｘに対する規制値が厳しくなっており、ＮＯｘの浄化性能に優れた排気ガス浄化用触媒の必要性が高まっている。 Further, in recent years, exhaust gas regulations are becoming more and more stringent, and it is desired to introduce a catalyst that exhibits a superior exhaust gas purification performance using a plurality of catalysts. Among exhaust gases, the regulation value for NOx is particularly strict, and the need for an exhaust gas purification catalyst having excellent NOx purification performance is increasing.
このような中で、ＴＷＣの材料として、硫酸バリウムとＰｄを含むアルミナ材料を用いることが提案されている（特許文献１０参照）。
ＰｄはＨＣの低温浄化に優れるが、熱により粒子同士が接合して粒径が肥大化するという現象（シンタリング）が生じやすく、Ｐｄがシンタリングすると排気ガス中に含まれるＨＣとの接触面積が減少するため、ＨＣの低温浄化性能が低減してしまう。ＢａはＰｄと共存することで、Ｂａの電子的作用により、Ｐｄのシンタリングを抑制し、Ｐｄの活性を維持することができる。一方、ＲｈはＴＷＣの材料としてＮＯｘの浄化性能に優れるが、Ｂａは、ＲｈによるＮＯｘの浄化反応に対してはネガティブに働き、Ｒｈの活性を低下させる可能性がある。そこで、アルミナ上にＰｄとＢａを共存させる一方、スラリー中でＢａが溶出してＲｈと接触することを避けＢａ成分の配置をコントロールするため、しばしば難溶性の硫酸バリウムが使用される。Under such circumstances, it has been proposed to use an alumina material containing barium sulfate and Pd as a TWC material (see Patent Document 10).
Pd is excellent in low-temperature purification of HC, but a phenomenon (sintering) in which particles are joined by heat and the particle size is enlarged is likely to occur. When Pd is sintered, the contact area with HC contained in the exhaust gas As a result, the low temperature purification performance of HC is reduced. By coexisting with Pd, Ba can suppress the sintering of Pd and maintain the activity of Pd by the electronic action of Ba. On the other hand, although Rh is excellent in NOx purification performance as a TWC material, Ba acts negatively on the NOx purification reaction by Rh and may reduce the activity of Rh. Therefore, while coexisting Pd and Ba on alumina, Ba is often used in order to control the arrangement of the Ba component while avoiding Ba from eluting in the slurry and coming into contact with Rh.
しかしながら、硫酸バリウムは、排気ガス中７００℃以上の還元雰囲気下で分解して触媒層中に無作為に分散するという特徴を有する。触媒層中のＢａの配置をコントロールするためには、難溶性の硫酸バリウムを例えばアルミナのような多孔質無機酸化物担体に担持し、硫酸バリウムの分散範囲を制限することが望ましい。さらに硫酸バリウムをアルミナのような多孔質無機酸化物上に高分散に担持すればＢａの有効表面積が増大し、Ｂａ成分の機能を十分に発揮できるため好ましい。
ところが、特許文献１０の場合、硫酸バリウムのアルミナへの担持方法や硫酸バリウムの粒子径およびアルミナに対する硫酸バリウムの分散性についてはほとんど言及されず、また、原料の水への溶解度が小さいこと、触媒毒となる恐れのある成分を使用していることもあり、粒子径が数μｍのように大きな硫酸バリウムが沈殿したり、ナトリウムや塩素などの不純物が除去できなかったりして、所望の触媒性能が得られないことが多い。However, barium sulfate has a feature that it is decomposed in a reducing atmosphere at 700 ° C. or higher in exhaust gas and randomly dispersed in the catalyst layer. In order to control the arrangement of Ba in the catalyst layer, it is desirable to support a sparingly soluble barium sulfate on a porous inorganic oxide support such as alumina to limit the dispersion range of barium sulfate. Furthermore, it is preferable to support barium sulfate on a porous inorganic oxide such as alumina in a highly dispersed state because the effective surface area of Ba increases and the function of the Ba component can be fully exhibited.
However, in the case of
その他、貴金属塩を含む水溶液と、アルミナと、ＯＳＣと、平均粒子径が０．０５〜０．７μｍの硫酸バリウムとクエン酸とを混合してスラリー化した後、担体に塗布する方法（特許文献１３参照）や、さらに浄化性能を向上させるために、アルミナ粉末と、トルエンなどの有機溶剤と、カルボン酸であるラウリン酸とトリフルオロ酢酸とを含んだスラリーを調製した後、酸化バリウムなどのアルカリ土類金属の酸化物を添加し、硫酸ナトリウム水溶液などを添加して得られたスラリーを、特定条件で撹拌し濾過した濾過ケークを乾燥、焼成することにより、平均粒子径が５〜２００ｎｍの硫酸バリウムがアルミナ表面上に選択的に分散された材料が同一出願人より提案されている（特許文献１４参照）。
しかし、数ｎｍ〜数十ｎｍの細孔径を有するアルミナ粒子の細孔内で、硫酸ナトリウム水溶液を添加することにより酸化バリウムなどのバリウム塩から硫酸バリウムの粒子を形成させると、バリウムの含有量が多くなるにつれてバリウムの粒子成長が盛んになり、細孔の閉塞や狭小が生じ易くなることにより、排気ガスが粒子内の奥深くまで拡散し難くなることが想定される。
さらに、排気ガス浄化用触媒を大量に製造することを念頭に置くと、トリフルオロ酢酸は、国際化学物質安全性カード（ＩＣＳＣ）で、人の身体への暴露について「あらゆる接触を避ける」と記され、特に水中生物への有害性が高いため、漏洩物処理について「環境中に放出してはならない」とされており、当該トリフルオロ酢酸や、常温で揮発性を有するトルエンなどの有機溶剤は、人体にとって有害であり、使用後の無害化処理に膨大な費用がかかることから実用的ではない。In addition, an aqueous solution containing a noble metal salt, alumina, OSC, barium sulfate having an average particle size of 0.05 to 0.7 μm and citric acid are mixed to form a slurry, which is then applied to a carrier (Patent Document) 13), and in order to further improve the purification performance, after preparing a slurry containing alumina powder, an organic solvent such as toluene, lauric acid trifluoroacetic acid and trifluoroacetic acid, an alkali such as barium oxide is prepared. A slurry obtained by adding an oxide of an earth metal and adding an aqueous sodium sulfate solution, etc., is stirred under specific conditions, filtered, dried and fired, and a sulfuric acid having an average particle size of 5 to 200 nm. A material in which barium is selectively dispersed on an alumina surface has been proposed by the same applicant (see Patent Document 14).
However, when barium sulfate particles are formed from a barium salt such as barium oxide by adding a sodium sulfate aqueous solution in the pores of alumina particles having a pore diameter of several nm to several tens of nm, the content of barium is reduced. As the number of particles increases, the growth of barium particles becomes active, and pores are likely to be clogged or narrowed. As a result, it is assumed that the exhaust gas hardly diffuses deep into the particles.
In addition, with the goal of producing large quantities of exhaust gas purifying catalysts, trifluoroacetic acid is listed on the International Chemical Safety Card (ICSC) as “Avoid all contact” for human exposure. In particular, because it is highly harmful to aquatic organisms, it is said that it should not be released into the environment for the treatment of spills. Organic solvents such as trifluoroacetic acid and toluene that are volatile at room temperature It is harmful to the human body and is not practical because it takes a huge amount of detoxification treatment after use.
このような状況下、安全かつ効率的に生産でき、ガソリン車などの内燃機関から排出される排気ガスに含まれるＮＯｘの浄化性能に優れた排気ガス浄化用触媒が必要とされていた。 Under such circumstances, there has been a need for an exhaust gas purification catalyst that can be produced safely and efficiently, and that is excellent in the purification performance of NOx contained in exhaust gas discharged from an internal combustion engine such as a gasoline vehicle.
本発明の目的は、上記従来技術の課題に鑑み、硫酸バリウムを含むアルミナ材料とその製造方法、それを用いた触媒や吸着材、特にガソリン車などの内燃機関から排出される排気ガスに含まれる有害物質を浄化するための触媒として好適なＮＯｘ浄化性能に優れた排気ガス浄化用触媒を提供することにある。 An object of the present invention is included in the exhaust material exhausted from an internal combustion engine such as an alumina material containing barium sulfate and a method for producing the same, a catalyst and an adsorbent using the alumina material, and in particular, a gasoline vehicle in view of the above-described problems of the prior art. An object of the present invention is to provide an exhaust gas purification catalyst having excellent NOx purification performance suitable as a catalyst for purifying harmful substances.
本発明者らは、上記従来の課題を解決するために鋭意研究を重ね、ガソリン車などの内燃機関から排出される排気ガス中の炭化水素（ＨＣ）、一酸化炭素（ＣＯ）、窒素酸化物（ＮＯｘ）の内、特にＮＯｘを浄化する排気ガス浄化触媒として、各々特定の粒子径を有する硫酸バリウム（ＢａＳＯ４）とアルミナを均一に分散し造粒した、特定の粒子径を有する硫酸バリウムを含むアルミナ材料を用い、このアルミナ材料が特定のＢａ−Ａｌ間の相関係数を満たすことで、これに貴金属と酸素吸蔵放出成分（ＯＳＣ）を特定の仕様で組み合わせると窒素酸化物（ＮＯｘ）の浄化が促進されることを見出して、本発明を完成するに至った。The inventors of the present invention have made extensive studies to solve the above-described conventional problems, and hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides in exhaust gas discharged from an internal combustion engine such as a gasoline vehicle. (NOx) In particular, as an exhaust gas purifying catalyst for purifying NOx, barium sulfate having a specific particle diameter is obtained by uniformly dispersing and granulating barium sulfate (BaSO 4 ) and alumina each having a specific particle diameter. When the alumina material contains a specific Ba-Al correlation coefficient and the noble metal and the oxygen storage / release component (OSC) are combined with the specific specification, the oxide of nitrogen oxide (NOx) It was found that purification was promoted, and the present invention was completed.
すなわち、本発明の第１の発明によれば、硫酸バリウムがアルミナ（Ｉ）粒子間に微細かつ均一に分散した平均粒子径が５〜５０μｍの硫酸バリウムを含むアルミナ材料であって、
アルミナ（Ｉ）粒子が平均粒子径３００ｎｍ〜５μｍに、また、硫酸バリウムが平均粒子径１０〜８００ｎｍになるように粉砕・分散処理されたスラリーを造粒し焼成して得られ、かつ、アルミナ（Ｉ）への硫酸バリウムの分散状態が、ＥＰＭＡ断面分析の測定値を基に算出されるアルミナ材料粒子内のＢａ−Ａｌ間の相関係数で０．３以上であることを特徴とする硫酸バリウムを含むアルミナ材料が提供される。That is, according to the first aspect of the present invention, an alumina material containing barium sulfate having an average particle diameter of 5 to 50 μm in which barium sulfate is finely and uniformly dispersed between alumina (I) particles,
It is obtained by granulating and firing a slurry that has been pulverized and dispersed so that alumina (I) particles have an average particle diameter of 300 nm to 5 μm and barium sulfate has an average particle diameter of 10 to 800 nm, and alumina (I) Barium sulfate is characterized in that the barium sulfate dispersion state in I) is 0.3 or more in terms of the correlation coefficient between Ba-Al in alumina material particles calculated based on the measured value of EPMA cross-sectional analysis. An alumina material is provided.
また、本発明の第２の発明によれば、第１の発明において、硫酸バリウムの含有量が、アルミナ（Ｉ）に対して５〜１００重量％であることを特徴とする硫酸バリウムを含むアルミナ材料が提供される。
また、本発明の第３の発明によれば、第１又は２の発明において、アルミナ（Ｉ）が、γ−アルミナ、δ−アルミナ、θ−アルミナ、およびベーマイトの群から選ばれる１種以上であることを特徴とする硫酸バリウムを含むアルミナ材料が提供される。
また、本発明の第４の発明によれば、第１〜３のいずれかの発明において、アルミナ（Ｉ）が、さらにセリア、酸化ランタン、酸化ネオジム、酸化プラセオジム、および酸化イットリウムの群から選ばれる１種以上の希土類酸化物を含有することを特徴とする硫酸バリウムを含むアルミナ材料が提供される。
また、本発明の第５の発明によれば、第１〜４のいずれかの発明において、アルミナ（Ｉ）に含有される希土類酸化物の含有量が、３０重量％以下であることを特徴とする硫酸バリウムを含むアルミナ材料が提供される。
また、本発明の第６の発明によれば、第１〜５のいずれかの発明において、造粒後の平均細孔径が５〜１００ｎｍであることを特徴とする硫酸バリウムを含むアルミナ材料が提供される。According to a second aspect of the present invention, in the first aspect, the barium sulfate-containing alumina according to the first aspect, wherein the barium sulfate content is 5 to 100% by weight with respect to the alumina (I). Material is provided.
According to the third invention of the present invention, in the first or second invention, the alumina (I) is one or more selected from the group consisting of γ-alumina, δ-alumina, θ-alumina, and boehmite. An alumina material comprising barium sulfate is provided.
According to the fourth invention of the present invention, in any one of the first to third inventions, alumina (I) is further selected from the group of ceria, lanthanum oxide, neodymium oxide, praseodymium oxide, and yttrium oxide. An alumina material comprising barium sulfate is provided that contains one or more rare earth oxides.
According to a fifth invention of the present invention, in any one of the first to fourth inventions, the content of the rare earth oxide contained in the alumina (I) is 30% by weight or less. An alumina material comprising barium sulfate is provided.
According to a sixth aspect of the present invention, there is provided an alumina material containing barium sulfate, characterized in that, in any one of the first to fifth aspects, the average pore diameter after granulation is 5 to 100 nm. Is done.
一方、本発明の７の発明によれば、第１〜６のいずれかの発明において、アルミナ（Ｉ）および硫酸バリウムを単独で、または両方を混合し水でスラリー化した後、粉砕機で平均粒子径が１０ｎｍ〜５μｍになるまで粉砕・分散処理を行い、平均粒子径が３００ｎｍ〜５μｍのアルミナ（Ｉ）粒子と平均粒子径が１０〜８００ｎｍの硫酸バリウムを含む混合分散スラリーを調製し、引き続き、乾燥機で５〜５０μｍまで造粒させた後、焼成することを特徴とする硫酸バリウムを含むアルミナ材料の製造方法が提供される。
また、本発明の８の発明によれば、第７の発明において、粉砕・分散処理工程で、ビーズミル、またはミキサーおよびビーズミルを使用することを特徴とする硫酸バリウムを含むアルミナ材料の製造方法が提供される。
また、本発明の９の発明によれば、第７の発明において、造粒工程で、スプレードライヤー、または流動層造粒乾燥機を使用することを特徴とする硫酸バリウムを含むアルミナ材料の製造方法が提供される。
また、本発明の１０の発明によれば、第７の発明において、焼成処理で、造粒物を３００〜７００℃で２０〜１２０分加熱することを特徴とする硫酸バリウムを含むアルミナ材料の製造方法が提供される。On the other hand, according to the seventh invention of the present invention, in any one of the first to sixth inventions, alumina (I) and barium sulfate alone or a mixture of both are slurried with water, and then averaged by a pulverizer. Crushing / dispersing treatment is performed until the particle size becomes 10 nm to 5 μm, and a mixed dispersion slurry containing alumina (I) particles having an average particle size of 300 nm to 5 μm and barium sulfate having an average particle size of 10 to 800 nm is prepared. There is provided a method for producing an alumina material containing barium sulfate, which is granulated to 5 to 50 μm with a dryer and then fired.
Further, according to the eighth invention of the present invention, in the seventh invention, there is provided a method for producing an alumina material containing barium sulfate, wherein a bead mill or a mixer and a bead mill are used in the pulverization / dispersion treatment step. Is done.
Further, according to the ninth invention of the present invention, in the seventh invention, a method for producing an alumina material containing barium sulfate, characterized by using a spray dryer or a fluidized bed granulation dryer in the granulation step. Is provided.
Further, according to the tenth invention of the present invention, in the seventh invention, the granulated material is heated at 300 to 700 ° C. for 20 to 120 minutes by the baking treatment, and the production of the alumina material containing barium sulfate, A method is provided.
一方、本発明の第１１の発明によれば、第１〜６のいずれかの発明における硫酸バリウムを含むアルミナ材料、貴金属、無機酸化物、及び酸素吸蔵放出成分（ＯＳＣ）を含み、かつ貴金属が硫酸バリウムを含むアルミナ材料、無機酸化物、及び／又は、酸素吸蔵放出成分に担持されてなる排気ガス浄化用触媒が提供される。 On the other hand, according to the eleventh aspect of the present invention, the alumina material containing barium sulfate according to any one of the first to sixth aspects, the noble metal, the inorganic oxide, and the oxygen storage / release component (OSC), There is provided an exhaust gas purifying catalyst supported on an alumina material containing barium sulfate, an inorganic oxide, and / or an oxygen storage / release component.
また、本発明の第１２の発明によれば、第１１の発明において、貴金属の種類が、パラジウム、ロジウム、および白金の群から選ばれる１種以上であることを特徴とする排気ガス浄化用触媒が提供される。
また、本発明の第１３の発明によれば、第１１の発明において、無機酸化物が、アルミナ（ＩＩ）、ジルコニア、チタニア、シリカ、シリカ−アルミナ、およびゼオライトの群から選ばれる１種以上であることを特徴とする排気ガス浄化用触媒が提供される。
また、本発明の第１４の発明によれば、第１３の発明において、アルミナ（ＩＩ）が、γ−アルミナ、δ−アルミナ、θ−アルミナ、およびベーマイトの群から選ばれる１種以上であることを特徴とする排気ガス浄化用触媒が提供される。
また、本発明の第１５の発明によれば、第１３又は１４の発明において、アルミナ（ＩＩ）が、さらにセリア、酸化ランタン、酸化ネオジム、酸化プラセオジム、および酸化イットリウムの希土類酸化物の群から選ばれる少なくとも１種以上を含有することを特徴とする排気ガス浄化用触媒が提供される。
また、本発明の第１６の発明によれば、第１３〜１５のいずれかの発明において、アルミナ（ＩＩ）に含有される希土類酸化物の含有量が、３０重量％以下であることを特徴とする排気ガス浄化用触媒が提供される。
また、本発明の第１７の発明によれば、第１３の発明において、ジルコニアが、さらにセリア、酸化ランタン、酸化ネオジム、酸化プラセオジム、および酸化イットリウムの希土類酸化物の群から選ばれる少なくとも１種類以上を含有することを特徴とする排気ガス浄化用触媒が提供される。
また、本発明の第１８の発明によれば、第１３又は１７の発明において、ジルコニアに含有される希土類酸化物の含有量が、４０重量％以下であることを特徴とする排気ガス浄化用触媒が提供される。
また、本発明の第１９の発明によれば、第１１の発明において、酸素吸蔵放出成分（ＯＳＣ）が、セリア、及び／又は、セリア−ジルコニアであることを特徴とする排気ガス浄化用触媒が提供される。According to a twelfth aspect of the present invention, in the eleventh aspect, the exhaust gas purifying catalyst is characterized in that the noble metal is one or more selected from the group consisting of palladium, rhodium and platinum. Is provided.
According to the thirteenth aspect of the present invention, in the eleventh aspect, the inorganic oxide is one or more selected from the group consisting of alumina (II), zirconia, titania, silica, silica-alumina, and zeolite. There is provided an exhaust gas purifying catalyst.
According to the fourteenth aspect of the present invention, in the thirteenth aspect, the alumina (II) is at least one selected from the group consisting of γ-alumina, δ-alumina, θ-alumina, and boehmite. An exhaust gas purifying catalyst is provided.
According to the fifteenth aspect of the present invention, in the thirteenth or fourteenth aspect, the alumina (II) is further selected from the group consisting of ceria, lanthanum oxide, neodymium oxide, praseodymium oxide, and a rare earth oxide of yttrium oxide. There is provided an exhaust gas purifying catalyst characterized by containing at least one selected from the above.
According to a sixteenth aspect of the present invention, in any one of the thirteenth to fifteenth aspects, the content of the rare earth oxide contained in the alumina (II) is 30% by weight or less. An exhaust gas purifying catalyst is provided.
According to the seventeenth aspect of the present invention, in the thirteenth aspect, the zirconia is further at least one selected from the group consisting of ceria, lanthanum oxide, neodymium oxide, praseodymium oxide, and a rare earth oxide of yttrium oxide. There is provided an exhaust gas purifying catalyst characterized by containing.
According to an eighteenth aspect of the present invention, in the thirteenth or seventeenth aspect, the content of the rare earth oxide contained in zirconia is 40% by weight or less. Is provided.
According to a nineteenth aspect of the present invention, there is provided an exhaust gas purification catalyst according to the eleventh aspect, wherein the oxygen storage / release component (OSC) is ceria and / or ceria-zirconia. Provided.
また、本発明の第２０の発明によれば、第１９の発明において、セリア−ジルコニアが、ジルコニアを１０〜７０重量％含有することを特徴とする排気ガス浄化用触媒が提供される。
また、本発明の第２１の発明によれば、第１９又は２０の発明において、セリア−ジルコニアが、さらに、酸化ランタン、酸化ネオジム、酸化プラセオジム、および酸化イットリウムの希土類酸化物の群から選ばれる少なくとも１種以上を含有することを特徴とする排気ガス浄化用触媒が提供される。
また、本発明の第２２の発明によれば、第１９〜２１のいずれかの発明において、セリア−ジルコニアが、希土類酸化物を２０重量％以下含有することを特徴する排気ガス浄化用触媒が提供される。According to a twentieth aspect of the present invention, there is provided the exhaust gas purifying catalyst according to the nineteenth aspect, wherein the ceria-zirconia contains 10 to 70% by weight of zirconia.
According to the twenty-first aspect of the present invention, in the nineteenth or twentieth aspect, the ceria-zirconia is further selected from the group consisting of lanthanum oxide, neodymium oxide, praseodymium oxide, and a rare earth oxide of yttrium oxide. There is provided an exhaust gas purifying catalyst characterized by containing one or more kinds.
According to a twenty-second aspect of the present invention, there is provided an exhaust gas purification catalyst according to any one of the nineteenth to twenty-first aspects, wherein the ceria-zirconia contains 20% by weight or less of a rare earth oxide. Is done.
また、本発明の第２３の発明によれば、第１１〜２２のいずれかの発明において、前記排気ガス浄化用触媒が、一体構造型担体に一層以上に被覆されることを特徴とする排気ガス浄化用触媒が提供される。
また、本発明の第２４の発明によれば、第２３の発明において、触媒層の被覆量が、１００〜３００ｇ／Ｌであることを特徴とする排気ガス浄化用触媒が提供される。
さらに、本発明の第２５の発明によれば、第２３又は２４の発明において、貴金属の総担持量が、金属換算で０．２〜５．０ｇ／Ｌであることを特徴とする排気ガス浄化用触媒が提供される。According to a twenty-third aspect of the present invention, in any one of the first to twenty-second aspects, the exhaust gas purifying catalyst is further covered with an integral structure type carrier. A purification catalyst is provided.
According to a twenty-fourth aspect of the present invention, there is provided the exhaust gas purifying catalyst according to the twenty-third aspect, wherein the catalyst layer has a coating amount of 100 to 300 g / L.
Further, according to the twenty-fifth aspect of the present invention, in the twenty-third or twenty-fourth aspect, the exhaust gas purification is characterized in that the total supported amount of the noble metal is 0.2 to 5.0 g / L in terms of metal. A catalyst is provided.
本発明は、硫酸バリウムを含む特定の平均粒子径を有するアルミナ材料であって、アルミナ材料中に分散している硫酸バリウムが、特定値以下の平均粒子径であり、かつ、アルミナ材料のＢａ−Ａｌ間の相関係数が特定の要件を満たすために、排気ガス浄化用触媒の材料として用いると、窒素酸化物の除去活性に優れ、各種燃焼装置から排出される窒素酸化物に対して高い浄化性能を発揮する。
さらに、本発明の排気ガス浄化用触媒は、高価な活性金属の使用量が少なくて済むため低コストで製造する事ができ、排気ガス浄化装置を安定的に生産し供給することができる。The present invention is an alumina material having a specific average particle size containing barium sulfate, wherein the barium sulfate dispersed in the alumina material has an average particle size of a specific value or less, and Ba- Since the correlation coefficient between Al meets specific requirements, it is excellent in nitrogen oxide removal activity and highly purified against nitrogen oxides emitted from various combustion devices when used as a material for exhaust gas purification catalysts. Demonstrate performance.
Furthermore, the exhaust gas purifying catalyst of the present invention can be manufactured at low cost because the amount of expensive active metal used is small, and the exhaust gas purifying device can be stably produced and supplied.
以下、本発明の硫酸バリウムを含むアルミナ材料とその製造方法、及びそれを用いた排気ガス浄化用触媒について詳細に説明する。なお、ガソリンエンジンにおける実施形態を中心に述べるが、本発明は、自動車用途に限定されるものではなく、排気ガス中の窒素酸化物の脱硝技術に広く適用可能である。 Hereinafter, the alumina material containing barium sulfate of the present invention, a method for producing the same, and an exhaust gas purifying catalyst using the same will be described in detail. Although an embodiment of a gasoline engine will be mainly described, the present invention is not limited to automobile use, and can be widely applied to a denitration technique for nitrogen oxides in exhaust gas.
１．硫酸バリウムを含むアルミナ材料
本発明の硫酸バリウムを含むアルミナ材料は、平均粒子径が３００ｎｍ〜５μｍのアルミナ（Ｉ）粒子と平均粒子径が１０〜８００ｎｍの硫酸バリウムとを均一に分散したスラリーを造粒し焼成してなり、平均粒子径が５〜５０μｍの粒子で、かつ、アルミナ（Ｉ）への硫酸バリウムの分散状態が、ＥＰＭＡ断面分析の測定値を基に算出されるアルミナ材料粒子内のＢａ−Ａｌ間の相関係数で０．３以上のものである。1. Alumina Material Containing Barium Sulfate The alumina material containing barium sulfate of the present invention is a slurry in which alumina (I) particles having an average particle diameter of 300 nm to 5 μm and barium sulfate having an average particle diameter of 10 to 800 nm are uniformly dispersed. In the alumina material particles in which the particles are sintered and fired, the average particle size is 5 to 50 μm, and the dispersion state of barium sulfate in alumina (I) is calculated based on the measured value of EPMA cross-sectional analysis. The correlation coefficient between Ba and Al is 0.3 or more.
（１）硫酸バリウム
硫酸バリウム（ＢａＳＯ４、以下、Ｂａ成分ともいう）は、水および酸に極めて難溶である。そのため、硫酸バリウム単体、又は、硫酸バリウムを含有するアルミナ、ジルコニア等の無機酸化物材料の場合でも、スラリー中にバリウムが溶け出さないので、バリウムの近傍にあると触媒性能を悪化させるロジウム（Ｒｈ）のような活性成分とスラリー中に共存させることが可能になる。また、硫酸バリウム自体は融点が１，３４５℃、沸点が１，６００℃（分解して揮発）と、熱的に非常に安定な物質であり、加熱により凝集することの少ない材料である。
さらに、硫酸バリウムは、水に極めて難溶であり、酸、アルカリにもほとんど溶けないため、他のバリウム塩が劇物に指定されているなかで唯一、劇物から除外されており安全面の上でも問題がない。(1) Barium sulfate Barium sulfate (BaSO 4 , hereinafter also referred to as Ba component) is extremely hardly soluble in water and acid. For this reason, even in the case of barium sulfate alone or inorganic oxide materials such as alumina and zirconia containing barium sulfate, barium does not dissolve in the slurry. It is possible to coexist in the slurry with an active ingredient such as Further, barium sulfate itself has a melting point of 1,345 ° C. and a boiling point of 1,600 ° C. (decomposes and volatilizes), and is a thermally stable material that hardly aggregates by heating.
Furthermore, since barium sulfate is extremely insoluble in water and hardly soluble in acids and alkalis, it is the only barium salt that has been designated as a deleterious substance. There is no problem even above.
本発明におけるＢａ成分の役割は、使用分野・用途にも依るが、例えば排気ガス浄化用触媒ではＮＯｘの一時的な吸着および拡散緩衝作用である。触媒が７００℃を超える排気ガスに晒されるなか、硫酸バリウムは、還元雰囲気下で分解し、Ａ／Ｆ＝１４．７（理論空燃比）近傍に空燃比を制御する間に排気ガス中のＣＯ２やＯ２、Ｈ２Ｏなどと反応することで炭酸バリウム、酸化バリウム、水酸化バリウムなどに変化する。ここで、Ｂａ成分のＮＯｘ吸着機能を発現させるためには、硫酸バリウムから炭酸バリウム、バリウムアルミネート（ＢａＡｌ２Ｏ４）、酸化バリウムなどに変化する温度（還元雰囲気下での硫酸バリウムの分解温度）が非常に重要な因子となる。
一般に、硫酸バリウムは、単独ではＢＥＴ比表面積が２０ｍ２／ｇ以下と小さいため、還元雰囲気下でもガス接触面積が低く、分解しにくい（分解温度が高い）。硫酸バリウムの分解性を向上させる、つまり分解温度を下げるには還元雰囲気のガスに触れる面積を増やすため、硫酸バリウムの粒子径を小さくして硫酸バリウム自身の表面積を増やすか、高表面積でかつ高耐熱性を有する母材に硫酸バリウムを担持することにより還元性ガスの接触確率を向上させることが有効である。
また、ＮＯｘの吸着量を増やすためには、硫酸バリウム自体を増量するか、硫酸バリウムの粒子径を小さくして有効表面積を増やすか、高表面積でかつ高耐熱性を有する母材に硫酸バリウムを担持することによりバリウム成分の有効表面積を増大させることが不可欠であり、両者は、多くの部分で共通している。Although the role of the Ba component in the present invention depends on the field of use and application, for example, in an exhaust gas purifying catalyst, it is temporary adsorption and diffusion buffering action of NOx. While the catalyst is exposed to exhaust gas exceeding 700 ° C., barium sulfate decomposes in a reducing atmosphere, and the CO in the exhaust gas is controlled while controlling the air-fuel ratio in the vicinity of A / F = 14.7 (theoretical air-fuel ratio). It changes to barium carbonate, barium oxide, barium hydroxide, etc. by reacting with 2 , O 2 , H 2 O and the like. Here, in order to develop the NOx adsorption function of the Ba component, the temperature at which barium sulfate is changed to barium carbonate, barium aluminate (BaAl 2 O 4 ), barium oxide, etc. (decomposition temperature of barium sulfate in a reducing atmosphere) ) Is a very important factor.
In general, barium sulfate alone has a BET specific surface area as small as 20 m 2 / g or less, and therefore has a low gas contact area even under a reducing atmosphere and is not easily decomposed (high decomposition temperature). In order to improve the decomposability of barium sulfate, that is, to lower the decomposition temperature, to increase the area in contact with the gas in the reducing atmosphere, reduce the barium sulfate particle size to increase the surface area of the barium sulfate itself, or to increase the surface area of the barium sulfate. It is effective to improve the contact probability of reducing gas by supporting barium sulfate on a base material having heat resistance.
In order to increase the amount of NOx adsorbed, the amount of barium sulfate itself is increased, or the effective surface area is increased by reducing the particle diameter of barium sulfate, or barium sulfate is added to a base material having a high surface area and high heat resistance. It is essential to increase the effective surface area of the barium component by supporting it, and both are common in many parts.
そのため本発明では、アルミナ材料中に分散される硫酸バリウムの平均粒子径を１０〜８００ｎｍとする。平均粒子径は、１０〜６００ｎｍが好ましく、１０〜４００ｎｍがより好ましく、２０〜３００ｎｍが特に好ましい。
硫酸バリウムの平均粒子径が８００ｎｍを越えると、バリウム成分の有効表面積が小さくなり、十分なＮＯｘ吸着特性が得られないため、好ましくない。また、高表面積を有する母材上に８００ｎｍを超える硫酸バリウムが存在する場合、硫酸バリウムが母材上に局所的に位置することになり、同母材上に担持されるパラジウム、白金等の貴金属と距離が遠くなるため、バリウム−貴金属間のＮＯｘ浄化に関する相乗効果が減少するので、好ましくない。
一方、硫酸バリウムは、平均粒子径が小さいほど幾何学表面積が増大するので好ましいが、ミリング装置で破砕する場合、小さく砕くための粉砕時間が急激に増大するため、作業効率という点では好ましくない。そのため、砕け易くなるよう一次粒子径の小さな原料を選択したり、一次粒子径が大きい場合は予め微粉砕するなどの方法が考えられ、原料の購入価格と粉砕の費用を比較検討しながら、原料を選ぶことが肝要である。Therefore, in this invention, the average particle diameter of the barium sulfate disperse | distributed in an alumina material shall be 10-800 nm. The average particle diameter is preferably 10 to 600 nm, more preferably 10 to 400 nm, and particularly preferably 20 to 300 nm.
When the average particle diameter of barium sulfate exceeds 800 nm, the effective surface area of the barium component becomes small, and sufficient NOx adsorption characteristics cannot be obtained, which is not preferable. In addition, when barium sulfate exceeding 800 nm exists on a base material having a high surface area, the barium sulfate is locally located on the base material, and noble metals such as palladium and platinum supported on the base material Since the synergistic effect regarding the NOx purification between barium and noble metal is reduced, the distance is not preferable.
On the other hand, barium sulfate is preferable because the geometric surface area increases as the average particle size decreases. However, when crushing with a milling apparatus, the crushing time for crushing to a small size increases rapidly, which is not preferable in terms of work efficiency. Therefore, it is possible to select a raw material with a small primary particle size so that it can be easily crushed, or to finely pulverize the material when the primary particle size is large. It is important to choose.
（２）アルミナ（Ｉ）
本発明において、アルミナは、無機酸化物母材として、Ｂａの他、貴金属であるＰｄ、Ｐｔを担持するために使用される（以下、硫酸バリウムを担持する場合、アルミナ（Ｉ）といい、貴金属であるＰｄ、Ｐｔを担持する場合、アルミナ（ＩＩ）という）。アルミナの種類は、γ−アルミナ、δ−アルミナ、θ−アルミナ、又はベーマイトのいずれかである。(2) Alumina (I)
In the present invention, alumina is used as an inorganic oxide base material for supporting Pd and Pt, which are noble metals, in addition to Ba (hereinafter referred to as alumina (I) when supporting barium sulfate, In the case of supporting Pd and Pt, which are alumina (II)). The kind of alumina is either γ-alumina, δ-alumina, θ-alumina, or boehmite.
これらの中でもＢＥＴ比表面積の大きいγ−アルミナのようなアルミナが好ましい。これに対して、α−アルミナはＢＥＴ比表面積が２０ｍ２／ｇ以下と小さいため、低ＢＥＴ比表面積を有する硫酸バリウムを担持する材料としては好ましくなく、また、ガス滞留性が低く、Ｐｄ分散性も低いためＰｄを担持する母材としても好ましくない。また、ＢＥＴ比表面積が４００ｍ２／ｇを超えるようなアルミナは、アルミナの細孔径が小さすぎて、細孔内でのガスの拡散性が低下するため、好ましくない。さらにＢＥＴ比表面積が４００ｍ２／ｇを超えるようなアルミナは耐熱性が低く、耐久処理後のＢＥＴ比表面積の低下率が大きいため、ＰｄやＢａの凝集を招くため、好ましくない。
このようなことから、アルミナのＢＥＴ比表面積は、６０〜４００ｍ２／ｇが好ましい。８０〜３００ｍ２／ｇがより好ましく、さらには１００〜２５０ｍ２／ｇが特に好ましい。
本発明において、アルミナは、細孔径（モード径、以下同じ）が３〜１５０ｎｍであることが好ましく、５〜１５０ｎｍであることがより好ましく、５〜１００ｎｍであることがさらに好ましい。アルミナの細孔径が３ｎｍより小さいと細孔内でのガスの拡散が遅くなる上、被覆物質などにより細孔が閉塞される恐れがある。一方、細孔径が１５０ｎｍより大きいと相対的にＢＥＴ比表面積が小さくなり、貴金属や助触媒などの分散性が低下するので好ましくない。Among these, alumina such as γ-alumina having a large BET specific surface area is preferable. On the other hand, α-alumina has a small BET specific surface area of 20 m 2 / g or less, so it is not preferable as a material supporting barium sulfate having a low BET specific surface area, and has low gas retention and Pd dispersibility. Therefore, it is not preferable as a base material supporting Pd. Further, alumina having a BET specific surface area exceeding 400 m 2 / g is not preferable because the pore diameter of alumina is too small and gas diffusibility in the pores is lowered. Furthermore, alumina having a BET specific surface area exceeding 400 m 2 / g is not preferable because it has low heat resistance and a large decrease rate of the BET specific surface area after the durability treatment, which causes aggregation of Pd and Ba.
For these reasons, the BET specific surface area of alumina is preferably 60 to 400 m 2 / g. 80~300m more preferably 2 / g, more 100 to 250 m 2 / g is particularly preferred.
In the present invention, the alumina preferably has a pore diameter (mode diameter, hereinafter the same) of 3 to 150 nm, more preferably 5 to 150 nm, and still more preferably 5 to 100 nm. When the pore diameter of alumina is smaller than 3 nm, the diffusion of gas in the pores is slowed and the pores may be blocked by a coating substance or the like. On the other hand, if the pore diameter is larger than 150 nm, the BET specific surface area becomes relatively small, and the dispersibility of noble metals, promoters and the like is not preferable.
そのため本発明では、アルミナ（Ｉ）の平均粒子径は３００ｎｍ〜５μｍでなければならず、４００ｎｍ〜４μｍがより好ましく、５００ｎｍ〜３μｍが特に好ましい。アルミナの平均粒子径が５μｍを越えると、アルミナの幾何学表面積が小さくなり、アルミナ表面上に存在する硫酸バリウムの分散性が低くなるので、好ましくない。一方、３００ｎｍ未満では粒子−粒子間の空隙が小さくなり過ぎて、空隙間のガスの拡散が遅くなるので好ましくない。
アルミナの耐久性を向上させるため、さらにセリア、酸化ランタン、酸化ネオジム、酸化プラセオジム、酸化イットリウムなどの希土類酸化物、マグネシウムなどのアルカリ土類金属、シリカ、ジルコニアなどを付与してもよい。ただし、希土類酸化物などの添加量は、アルミナの高ＢＥＴ比表面積の大幅な低減を避けるためにも３０重量％以下が好ましい。Therefore, in the present invention, the average particle diameter of alumina (I) must be 300 nm to 5 μm, more preferably 400 nm to 4 μm, and particularly preferably 500 nm to 3 μm. When the average particle diameter of alumina exceeds 5 μm, the geometric surface area of alumina becomes small, and the dispersibility of barium sulfate existing on the alumina surface becomes low. On the other hand, if it is less than 300 nm, the particle-particle voids become too small, and gas diffusion between the voids becomes slow, which is not preferable.
In order to improve the durability of alumina, ceria, lanthanum oxide, neodymium oxide, praseodymium oxide, rare earth oxides such as yttrium oxide, alkaline earth metals such as magnesium, silica, zirconia and the like may be added. However, the addition amount of the rare earth oxide or the like is preferably 30% by weight or less in order to avoid a significant reduction in the high BET specific surface area of alumina.
また、本発明では、アルミナに対して硫酸バリウムが十分に分散しており、硫酸バリウムを含むアルミナ粒子内のＢａ−Ａｌ間の相関係数が正の値を取るものでなければならない。相関係数の値は、０．３以上とし、０．４以上が好ましく、０．５以上がより好ましい。特に好ましいのは、０．６〜１．０である。ここで、相関係数は、ＥＰＭＡを用いて硫酸バリウムを含むアルミナ粒子の断面分析を行い、以下の式に従って算出した。 Moreover, in this invention, barium sulfate must fully disperse | distribute with respect to an alumina, and the correlation coefficient between Ba-Al in the alumina particle containing barium sulfate must take a positive value. The value of the correlation coefficient is 0.3 or more, preferably 0.4 or more, and more preferably 0.5 or more. Particularly preferred is 0.6 to 1.0. Here, the correlation coefficient was calculated according to the following equation by performing a cross-sectional analysis of alumina particles containing barium sulfate using EPMA.
（相関係数の計算方法）
すなわち、本発明においては、ＥＰＭＡ測定により得られたＢａとＡｌの特性Ｘ線の強度値から、ＢａとＡｌの粒子内分布の相関係数Ｒを以下の式（６）により算出する。(Correlation coefficient calculation method)
That is, in the present invention, the correlation coefficient R of the intra-particle distribution of Ba and Al is calculated by the following equation (6) from the intensity values of the characteristic X-rays of Ba and Al obtained by EPMA measurement.
本手法により計算されるＢａとＡｌの粒子内分布の相関係数は、アルミナ粒子内にどの程度Ｂａ粒子が分散しているか、言い換えればアルミナ粒子内でのＢａの分散度の指標となる。相関係数が例えば＋０．６より大きい場合、つまり強い正の相関がある場合はＡｌとＢａの分布がよく一致していることを示しており、アルミナ粒子中にＢａが非常に高分散していると言える。また、相関係数が正であっても小さいと、ＡｌとＢａの分布に相関性が低いことを示しており、アルミナ粒子中のＢａ分散性が低いことを意味する。
一方、ＢａとＡｌの分布の相関係数が負の場合には、Ａｌの分布とＢａの分布が負の相関性にある、つまりＢａが多い個所にＡｌが少なく、Ｂａが少ない個所にＡｌが多いこととなり、アルミナ粒子と硫酸バリウム粒子が個別に存在していることを示している。以上より、本発明では、硫酸バリウムを含むアルミナ粒子中のＢａ分散度を相関係数によって推定することができる。The correlation coefficient between the intra-particle distributions of Ba and Al calculated by this method is an index of how much Ba particles are dispersed in the alumina particles, in other words, the degree of dispersion of Ba in the alumina particles. For example, when the correlation coefficient is larger than +0.6, that is, when there is a strong positive correlation, the distribution of Al and Ba is well matched, and Ba is very highly dispersed in the alumina particles. I can say that. Further, even if the correlation coefficient is positive, if it is small, it indicates that the correlation between the Al and Ba distribution is low, which means that the Ba dispersibility in the alumina particles is low.
On the other hand, when the correlation coefficient between the distributions of Ba and Al is negative, the distribution of Al and the distribution of Ba are negatively correlated, that is, Al is present where there is a lot of Ba and Al is present where there is less Ba. This indicates that alumina particles and barium sulfate particles exist separately. As described above, in the present invention, the degree of Ba dispersion in alumina particles containing barium sulfate can be estimated from the correlation coefficient.
以上により、本発明では、粒子内のＢａ−Ａｌ間の相関係数が０．３以上でなければならず、０．３未満になると硫酸バリウム粒子とアルミナ粒子がほぼ完全に分離していることになり、バリウム成分の有効表面積が小さくなり、十分なＮＯｘ吸着特性が得られなくなるため、好ましくない。また、０．３未満であると、バリウムとパラジウム、白金等の貴金属との距離が遠くなるため、バリウム−貴金属間のＮＯｘ浄化に関する相乗効果が期待できないので、好ましくない。 From the above, in the present invention, the correlation coefficient between Ba-Al in the particles must be 0.3 or more, and when it is less than 0.3, the barium sulfate particles and the alumina particles are almost completely separated. Therefore, the effective surface area of the barium component is reduced, and sufficient NOx adsorption characteristics cannot be obtained. On the other hand, if it is less than 0.3, the distance between barium and noble metals such as palladium and platinum is increased, and a synergistic effect regarding NOx purification between barium and noble metals cannot be expected.
２．硫酸バリウムを含むアルミナ材料の調製法
硫酸バリウムを含むアルミナ材料を調製するには、例えば、硫酸バリウム、アルミナのスラリーを粉砕および／または分散処理（以下、粉砕・分散処理）した後に、所定の粒径となるように造粒する工程を含む以下のような方法が挙げられる。2. Method for preparing alumina material containing barium sulfate To prepare an alumina material containing barium sulfate, for example, a slurry of barium sulfate and alumina is pulverized and / or dispersed (hereinafter, pulverized / dispersed), and then given particles are obtained. Examples of the method include the step of granulating to obtain a diameter.
（粉砕・分散処理工程）
まず、硫酸バリウム、アルミナを水などの溶媒中に添加した後、撹拌機などを用いて十分に撹拌することでよく馴染ませてスラリー化する。その後、ビーズミルなどの粉砕機を用いて、硫酸バリウムの平均粒子径が１０〜８００ｎｍに、アルミナの平均粒子径が３００ｎｍ〜５μｍになるまで粉砕・分散処理を行う。
その際、硫酸バリウムとアルミナを別々にスラリー化した後、粉砕し、その後に両方を混合しても、両方を混合してスラリー化した後、一度に粉砕してもよい。
ここで、平均粒子径は、レーザー散乱法により粉末サンプルの粒度分布を測定し、ｄ５０（５０％粒度：フルイ下の粒子量の体積基準の積算値が、全体の５０％に達した時の粒子の直径、メディアン径）の測定値である。なお、硫酸バリウムとアルミナ両方を混合してスラリー化した後、一度に粉砕する場合は、粒度分布に二つのピークが出現することがある。その場合は、各々のピークのモード径を算出し、大粒子側をアルミナに起因する平均粒子径とする。
また、硫酸バリウムやアルミナの原料は特に限定されず、原料費と粉砕に要するコストを勘案して、安価な方が選択される。すなわち、原料として粉砕の手間を省くため予め微粉砕されている市販品を用いてもよいし、粉砕に要するコストを低減するため、一次粒子径の小さい原料を採用することもできる。
具体的には、結晶径が１０〜５００ｎｍと小さい硫酸バリウムや、γ−アルミナの前躯体であるベーマイトを原料として使用すればより分散しやすく、好ましい。(Crushing / dispersing process)
First, after adding barium sulfate and alumina into a solvent such as water, the mixture is thoroughly mixed by using a stirrer or the like to make a slurry. Thereafter, using a pulverizer such as a bead mill, pulverization / dispersion treatment is performed until the average particle diameter of barium sulfate is 10 to 800 nm and the average particle diameter of alumina is 300 nm to 5 μm.
At that time, barium sulfate and alumina may be separately slurried and then pulverized, and then both may be mixed, or both may be mixed to form a slurry and then pulverized at once.
Here, the average particle size is measured when the particle size distribution of the powder sample is measured by the laser scattering method, and d50 (50% particle size: particles when the volume-based integrated value of the amount of particles under the sieve reaches 50% of the total particle size. (Diameter, median diameter). When both barium sulfate and alumina are mixed to form a slurry and then pulverized at one time, two peaks may appear in the particle size distribution. In that case, the mode diameter of each peak is calculated, and the large particle side is defined as the average particle diameter attributable to alumina.
Moreover, the raw material of barium sulfate or alumina is not particularly limited, and an inexpensive one is selected in consideration of the raw material cost and the cost required for pulverization. That is, a commercially available product that has been finely pulverized in advance may be used as a raw material in order to save pulverization, and a raw material having a small primary particle diameter may be employed in order to reduce the cost required for pulverization.
Specifically, barium sulfate having a small crystal diameter of 10 to 500 nm or boehmite, which is a precursor of γ-alumina, is preferably used because it is easier to disperse.
（造粒工程）
次に、上記粉砕・分散処理により得られた硫酸バリウムとアルミナの混合スラリーをスプレードライヤー、流動層造粒乾燥機などを用いて造粒処理を行う。その際、硫酸バリウムとアルミナの混合スラリーは、攪拌機などで十分に混合することにより、造粒前には両方をスラリー中で均一にしておく必要がある。
造粒後の平均粒子径は、５〜５０μｍが好ましく、５〜４０μｍがより好ましく、１０〜３０μｍが特に好ましい。平均粒子径が５μｍ以下になると、ハニカム等の構造体にコーティングした後、触媒層内の造粒粒子を含む粒子間の空隙が狭くなることで触媒層内のガスの拡散が滞ってしまうので好ましくない。一方、造粒粒子の平均粒子径が５０μｍを超えると、ガスが細孔内を通って造粒粒子の中心部まで拡散するのに時間がかかるので好ましくない。(Granulation process)
Next, the mixed slurry of barium sulfate and alumina obtained by the above pulverization / dispersion treatment is subjected to a granulation treatment using a spray dryer, a fluidized bed granulation dryer or the like. At that time, the mixed slurry of barium sulfate and alumina must be sufficiently mixed in the slurry before granulation by sufficiently mixing with a stirrer or the like.
The average particle diameter after granulation is preferably 5 to 50 μm, more preferably 5 to 40 μm, and particularly preferably 10 to 30 μm. When the average particle size is 5 μm or less, it is preferable because the gap between the particles including the granulated particles in the catalyst layer is narrowed after coating on a structure such as a honeycomb, so that gas diffusion in the catalyst layer is delayed. Absent. On the other hand, if the average particle diameter of the granulated particles exceeds 50 μm, it is not preferable because it takes time for the gas to diffuse through the pores and reach the center of the granulated particles.
（焼成工程）
その後、上記処理により得られた造粒品は、バッチ式電気炉、連続式電気炉、ロータリーキルンなどを用いて焼成処理を行う。焼成温度は３００〜７００℃が好ましく、４００〜６００℃がより好ましい。温度が３００℃より低いとアルミナと硫酸バリウムとの結合力が不十分となり、７００℃を超えると、焼成に要する経費がかかる上、装置の耐久性の面からも好ましくない。
また、焼成時間は２０〜１２０分が好ましく、３０〜９０分がより好ましい。(Baking process)
Thereafter, the granulated product obtained by the above treatment is fired using a batch electric furnace, a continuous electric furnace, a rotary kiln or the like. The firing temperature is preferably 300 to 700 ° C, more preferably 400 to 600 ° C. If the temperature is lower than 300 ° C., the bonding strength between alumina and barium sulfate becomes insufficient, and if it exceeds 700 ° C., the cost required for firing is increased, and the durability of the apparatus is not preferable.
The firing time is preferably 20 to 120 minutes, more preferably 30 to 90 minutes.
上記の調製法で得られたアルミナ材料は、硫酸バリウム量の多少によらず硫酸バリウムがアルミナの表面、内部に均一に含有される。但し、ビーズミルなどの粉砕機により微粒子にした後、スプレードライヤー、流動層造粒乾燥機等で再造粒するため、再造粒された粒子の物性の内、特に、細孔径、細孔容積などは調製前のアルミナ、硫酸バリウムとは異なることがある。 The alumina material obtained by the above preparation method contains barium sulfate uniformly on the surface and inside of the alumina regardless of the amount of barium sulfate. However, since it is granulated with a pulverizer such as a bead mill and then re-granulated with a spray dryer, fluidized bed granulator, etc., among the physical properties of the re-granulated particles, in particular, pore diameter, pore volume, etc. May differ from the pre-prepared alumina and barium sulfate.
実際、上記の方法により調製されるアルミナ材料は、ＢＥＴ比表面積、細孔径、細孔容積、不純物レベルなどの物性が、調製前のバリウムを含有する出発材料、使用量及びアルミナの性状に影響される。
これらの影響を避けるために、本発明では、後述するように、硫酸バリウムとアルミナの平均粒子径を各々所定の範囲内に制御することにより、平均細孔径が元のアルミナ粒子と同レベルになるように制御している。In fact, the alumina material prepared by the above method has physical properties such as BET specific surface area, pore diameter, pore volume, and impurity level affected by the starting material containing barium before preparation, the amount used, and the properties of alumina. The
In order to avoid these influences, in the present invention, as will be described later, by controlling the average particle diameter of barium sulfate and alumina within a predetermined range, the average pore diameter becomes the same level as the original alumina particles. So that it is controlled.
すなわち、アルミナに対する硫酸バリウムの混合割合を５〜１００重量％にすること、上記調製法（プロセス）を用いることにより、硫酸バリウムの分散が良好で、かつ、ガスが拡散し易い２０〜２５０ｍ２／ｇのＢＥＴ比表面積となる。That is, when the mixing ratio of barium sulfate to alumina is 5 to 100% by weight and the above preparation method (process) is used, the dispersion of barium sulfate is good and the gas easily diffuses to 20 to 250 m 2 / g BET specific surface area.
本発明では、アルミナに対する硫酸バリウムの混合量は、５〜１００重量％とし、好ましい混合量は１０〜９０重量％であり、１２〜８０重量％であることがより好ましい。硫酸バリウムの混合量が５重量％未満であると、アルミナ単独の脱硝性能に対して十分なＢａ添加効果が得られないため好ましくない。一方、硫酸バリウムの混合量が１００重量％を越えると、相対的にアルミナの含有量が減少し、硫酸バリウムを高ＢＥＴ比表面積のアルミナに担持する効果が薄れ、Ｂａ成分の有効表面積が減少するため硫酸バリウム単独の効果しか得られず、好ましくない。
本発明において、ＢＥＴ比表面積は２０〜２５０ｍ２／ｇであり、好ましくは３０〜２００ｍ２／ｇで、４０〜２００ｍ２／ｇがより好ましい。
また、同様にして細孔径についても、硫酸バリウムの分散が良好で、かつ、ガスが拡散し易い５〜１００ｎｍとなり、好ましくは５〜８０ｎｍで、１０〜５０ｎｍがより好ましい。さらに、細孔容積についても、同様に硫酸バリウムの分散が良好で、かつ、ガスが拡散し易い０．４〜２．５ｃｃ／ｇとなり、好ましくは０．５〜２．０ｃｃ／ｇで、０．５〜１．５ｃｃ／ｇがより好ましい。In the present invention, the mixing amount of barium sulfate with respect to alumina is 5 to 100% by weight, the preferable mixing amount is 10 to 90% by weight, and more preferably 12 to 80% by weight. If the amount of barium sulfate mixed is less than 5% by weight, a sufficient Ba addition effect cannot be obtained for the denitration performance of alumina alone, which is not preferable. On the other hand, when the mixing amount of barium sulfate exceeds 100% by weight, the content of alumina is relatively reduced, the effect of supporting barium sulfate on alumina having a high BET specific surface area is reduced, and the effective surface area of the Ba component is reduced. Therefore, only the effect of barium sulfate can be obtained, which is not preferable.
In the present invention, BET specific surface area of 20~250m 2 / g, preferably at 30~200m 2 / g, 40~200m 2 / g is more preferable.
Similarly, the pore size is 5 to 100 nm, preferably 5 to 80 nm, and more preferably 10 to 50 nm, in which the dispersion of barium sulfate is good and the gas easily diffuses. Further, the pore volume is similarly 0.4 to 2.5 cc / g, preferably 0.5 to 2.0 cc / g, and 0 to 0.5 cc / g, in which the barium sulfate dispersion is good and the gas easily diffuses. More preferably, it is 5-1.5 cc / g.
前記特許文献１３では、アルミナ粉末と、トルエンなどの有機溶剤と、カルボン酸であるラウリン酸とトリフルオロ酢酸とを含んだスラリーを調製した後、酸化バリウムなどのアルカリ土類金属の酸化物を添加し、更に、必要に応じて硫酸ナトリウム水溶液などのナトリウム塩水溶液を添加し、得られたスラリーを６５℃で２４時間に亘って撹拌した後、濾過した濾過ケークを乾燥、焼成（２４０℃、１２時間）することにより、平均粒子径５〜２００ｎｍの硫酸バリウムがアルミナ表面上に選択的に分散された材料を調製している。
この様に、従来の含浸法を利用した触媒調製法では、アルミナなどの高ＢＥＴ比表面積を有する無機酸化物粒子内の数〜数十ｎｍの細孔内に硫酸バリウムなどの微粒子を分散させている。ところが、硫酸バリウムなどの含有量が少ない条件下では、硫酸バリウムなどの微粒子の粒子径も小さいので細孔径内でも悪影響を及ぼさないものの、含有量が多くなるにつれ、細孔径内で細孔径の縮小や閉塞を起こすことが多くなり、それによりガスの拡散も悪化し、延いては、排気ガスの浄化反応が抑制されてしまう。In Patent Document 13, a slurry containing alumina powder, an organic solvent such as toluene, lauric acid trifluoroacetic acid and trifluoroacetic acid is prepared, and then an oxide of an alkaline earth metal such as barium oxide is added. Further, an aqueous sodium salt solution such as an aqueous sodium sulfate solution is added as necessary, and the resulting slurry is stirred at 65 ° C. for 24 hours, and then the filtered filter cake is dried and calcined (240 ° C., 12 Time), a material in which barium sulfate having an average particle diameter of 5 to 200 nm is selectively dispersed on the alumina surface is prepared.
Thus, in the catalyst preparation method using the conventional impregnation method, fine particles such as barium sulfate are dispersed in pores of several to several tens of nm in inorganic oxide particles having a high BET specific surface area such as alumina. Yes. However, under conditions where the content of barium sulfate or the like is low, the particle size of the fine particles such as barium sulfate is small, so there is no adverse effect even within the pore size. However, as the content increases, the pore size decreases within the pore size. Or gas clogging, and the gas diffusion is also worsened. As a result, the exhaust gas purification reaction is suppressed.
また、特許文献１３には、アルミナと硫酸バリウムの比率を９０ｇ：８０ｇにした調製法が記載されており、硫酸バリウムが平均粒子径２０２ｎｍとなるまで粒子成長している。しかし、数〜数十ｎｍの細孔径を有するアルミナ粒子の細孔内で、硫酸ナトリウム水溶液などのナトリウム塩水溶液を添加することにより、可溶性の酸化バリウムなどのバリウム塩から硫酸バリウムの粒子を形成させると、バリウムの含有量が多くなるにつれて細孔の閉塞や狭小が生じ易くなるので、排気ガスが粒子内の奥深くまで拡散し難くなり、反応への寄与が低下する。 Patent Document 13 describes a preparation method in which the ratio of alumina to barium sulfate is 90 g: 80 g. The particles grow until the barium sulfate has an average particle diameter of 202 nm. However, by adding an aqueous sodium salt solution such as an aqueous sodium sulfate solution within the pores of alumina particles having a pore diameter of several to several tens of nm, particles of barium sulfate are formed from a barium salt such as soluble barium oxide. As the barium content increases, the pores are more likely to be clogged or narrowed, making it difficult for the exhaust gas to diffuse deep into the particles and reducing the contribution to the reaction.
これに対し、本発明では、硫酸バリウムの微粒子とアルミナの粒子を予め、スラリー中で均一混合した後、スプレードライヤー、流動層造流乾燥機などで造粒する。そのため、造粒されたアルミナ粒子内に硫酸バリウムの微粒子がほぼ均一に存在し、かつ、細孔径が粉砕前のアルミナ粒子と同程度の細孔径に再構成されるので、アルミナ粒子内の細孔を閉塞もしくは狭小させることなく、硫酸バリウム等の粒子をアルミナ粒子の内部まで高分散させることでき、ガス拡散を低下させることなく、安定的な触媒性能を期待することができる。
しかも、本発明ではトリフルオロ酢酸の様な有害性の高い薬品や、常温で揮発性を有し肺呼吸の他、皮膚からも吸収されるトルエンなどの有機溶剤を使用しないので安全性が高いだけでなく、最終的な薬品の無害化処理も不要で量産プロセスも簡便である。On the other hand, in the present invention, barium sulfate fine particles and alumina particles are previously uniformly mixed in a slurry and then granulated by a spray dryer, a fluidized bed flow dryer or the like. Therefore, the fine particles of barium sulfate are present almost uniformly in the granulated alumina particles, and the pore size is reconfigured to the same pore size as the alumina particles before pulverization. Without blocking or narrowing the particles, particles such as barium sulfate can be highly dispersed into the alumina particles, and stable catalyst performance can be expected without reducing gas diffusion.
In addition, the present invention does not use highly harmful chemicals such as trifluoroacetic acid or volatile organic solvents such as toluene that are volatile at room temperature and absorbed by the skin, so it is only highly safe. In addition, the final chemical detoxification process is unnecessary and the mass production process is simple.
３．排気ガス浄化用触媒
本発明の排気ガス浄化用触媒（以下、触媒組成物ともいう）は、少なくとも貴金属、上記のアルミナ材料、及び無機酸化物からなる。中でも硫酸バリウムを含むアルミナ材料が触媒層として一体構造型担体に被覆されており、触媒層がさらに貴金属を含有し、硫酸バリウムを含むアルミナ材料が貴金属と同一層にあることが好ましい。
パラジウム及び／又は白金は、硫酸バリウムを含むアルミナ材料に担持させてもよい。これにより、触媒層内でＰｄ及び／又はＰｔの一部はＢａと近接し、相乗効果によって高いＮＯｘ浄化性能を示す。また、ＲｈはＢａ成分と近接すると触媒性能が悪化するため、硫酸バリウムを含むアルミナ材料以外の無機酸化物担体に担持することが望ましい。ただし、Ｒｈ成分と同一層に乖離してＢａ成分が存在すると、その相乗効果により高いＮＯｘ浄化性能を示すことから、Ｒｈ担持粒子と硫酸バリウム担持アルミナが同一層に配置させることが望ましい。3. Exhaust gas purification catalyst The exhaust gas purification catalyst of the present invention (hereinafter also referred to as catalyst composition) comprises at least a noble metal, the above-mentioned alumina material, and an inorganic oxide. In particular, it is preferable that an alumina material containing barium sulfate is coated on the monolithic support as a catalyst layer, the catalyst layer further contains a noble metal, and the alumina material containing barium sulfate is in the same layer as the noble metal.
Palladium and / or platinum may be supported on an alumina material containing barium sulfate. Thereby, a part of Pd and / or Pt is close to Ba in the catalyst layer, and shows high NOx purification performance by a synergistic effect. In addition, when Rh is close to the Ba component, the catalyst performance deteriorates. Therefore, it is desirable that Rh be supported on an inorganic oxide carrier other than an alumina material containing barium sulfate. However, when the Ba component is present in the same layer as the Rh component, high NOx purification performance is exhibited by the synergistic effect. Therefore, it is desirable that the Rh-supported particles and the barium sulfate-supported alumina be arranged in the same layer.
（１）無機酸化物
無機酸化物としては、具体的には、アルミナ（ＩＩ）、ジルコニア、セリア、セリア−ジルコニア、チタニア、シリカ、シリカ−アルミナ、ゼオライトなどが挙げられる。これらは単独で用いてもよいし、二種以上の無機酸化物を組み合わせてもよい。
アルミナ（ＩＩ）は、貴金属を担持する無機母材であり、アルミナ（Ｉ）の項で詳述した。アルミナ（ＩＩ）の種類や物性は、Ｂａを担持するアルミナ（Ｉ）と同様であり、γ−アルミナ、δ−アルミナ、θ−アルミナ、およびベーマイトの群から選ばれる１種以上が使用できる。また、アルミナ（ＩＩ）は、さらにセリア、酸化ランタン、酸化ネオジム、酸化プラセオジム、および酸化イットリウムの希土類酸化物からなる群の１種以上を含有することができ、アルミナ（ＩＩ）に含有される希土類酸化物の含有量は、３０重量％以下であることが好ましい。
次に、貴金属や助触媒を担持するための無機酸化物（無機母材）の一例として、ジルコニアの場合を以下に述べる。
ジルコニアは、ジルコニウムと希土類元素などとの複合酸化物とすることが好ましい。これは、ジルコニウム単一成分の酸化ジルコニウムでは耐熱性が低い為である。希土類酸化物としては、セリア、酸化ランタン、酸化ネオジム、酸化プラセオジム、および酸化イットリウムの群から選ばれる１種以上が好ましい。また、ジルコニア材料に占める希土類元素の割合は、酸化物基準で４０重量％以下であり、２重量％〜４０重量％であることが好ましく、５重量％〜３０重量％がより好ましい。
希土類酸化物の割合が２重量％未満であると、ジルコニア材料の耐熱性が低下し、４０重量％を超えると、ジルコニアが有するスチームリフォーミング機能が低下することがある。また、希土類酸化物の割合が４０重量％を超えるとジルコニアの特性であるスチームリフォーミング機能が低下するばかりか、他の相への相転移が生じやすくなるため、またレアアース高騰によりコスト面からも好ましくない。
希土類酸化物を含むジルコニア材料は、例えば無機または有機ジルコニウム化合物の１種以上を大気中、４５０〜６００℃で焼成し、得られた酸化物粒子を粉砕したものを原料粉末とし、これに希土類酸化物の原料粉末を混合して製造できる。
以上、ジルコニアの場合で説明したが、セリア、セリア‐ジルコニア、チタニア、シリカ、シリカ−アルミナ、ゼオライトでも同様である。(1) Inorganic oxide Specific examples of the inorganic oxide include alumina (II), zirconia, ceria, ceria-zirconia, titania, silica, silica-alumina, and zeolite. These may be used alone or in combination of two or more inorganic oxides.
Alumina (II) is an inorganic base material supporting a noble metal, and has been described in detail in the section of alumina (I). The kind and physical properties of alumina (II) are the same as those of alumina (I) supporting Ba, and one or more selected from the group of γ-alumina, δ-alumina, θ-alumina, and boehmite can be used. Alumina (II) can further contain one or more members selected from the group consisting of ceria, lanthanum oxide, neodymium oxide, praseodymium oxide, and rare earth oxides of yttrium oxide, and the rare earth contained in alumina (II) The oxide content is preferably 30% by weight or less.
Next, the case of zirconia will be described below as an example of an inorganic oxide (inorganic base material) for supporting a noble metal or a promoter.
Zirconia is preferably a composite oxide of zirconium and rare earth elements. This is because zirconium oxide having a single component has low heat resistance. The rare earth oxide is preferably at least one selected from the group consisting of ceria, lanthanum oxide, neodymium oxide, praseodymium oxide, and yttrium oxide. The ratio of the rare earth element in the zirconia material is 40% by weight or less on the oxide basis, preferably 2% to 40% by weight, and more preferably 5% to 30% by weight.
When the ratio of the rare earth oxide is less than 2% by weight, the heat resistance of the zirconia material is lowered, and when it exceeds 40% by weight, the steam reforming function of the zirconia may be lowered. In addition, when the ratio of the rare earth oxide exceeds 40% by weight, not only the steam reforming function, which is a characteristic of zirconia, is deteriorated, but also phase transition to other phases is likely to occur. It is not preferable.
A zirconia material containing a rare earth oxide is, for example, one or more inorganic or organic zirconium compounds calcined at 450 to 600 ° C. in the atmosphere, and the resulting oxide particles are pulverized as a raw material powder. It can be manufactured by mixing raw material powders.
As described above, the case of zirconia has been described, but the same applies to ceria, ceria-zirconia, titania, silica, silica-alumina, and zeolite.
（２）酸素吸蔵放出成分（ＯＳＣ）
酸素吸蔵放出成分（ＯＳＣ）としては、具体的には、セリア、セリア−ジルコニアなどが挙げられる。排気ガスの温度が低い条件下ではセリア単独でも使用できるが、排気ガスの温度が高い条件下では、セリアにジルコニアを組み合わせた複合酸化物が使用される。
セリア−ジルコニアに含有されるジルコニアの含有量は、特に限定されないが、セリアが高温下でも安定的に酸素吸蔵放出機能を発揮するためには、１０〜７０重量％が好ましく、２０〜７０重量％がより好ましく、３０〜６０重量％が特に好ましい。セリア−ジルコニアにおけるジルコニアの含有量が１０重量％を下回ると、セリアの耐熱性が低下することがあり、一方、ジルコニアの含有量が７０重量％を超えると、セリアの量が減ることにより酸素吸蔵放出機能が低下することがある。
また、セリア−ジルコニアは、排気ガス浄化用触媒の搭載位置によっては排気ガス温度が著しく高くなるため、さらに耐熱性を向上させる必要がある。そのため、さらに、酸化ランタン、酸化ネオジム、酸化プラセオジム、酸化イットリウムなどの希土類酸化物が加えられる。
セリア−ジルコニアに含有される上記希土類酸化物の含有量は、特に限定されないが、セリア−ジルコニアが著しい高温に曝されても、安定的に酸素吸蔵放出機能を発揮するためには、２０重量％以下が好ましく、２〜２０重量％がより好ましく、３〜１０重量％が特に好ましい。セリア−ジルコニア中の希土類酸化物の量が２０重量％を超えるとセリアの酸素吸蔵放出機能が低下することがあり、また、上述したように、希土類酸化物の過剰な使用は、コスト面から望ましくない。(2) Oxygen storage / release component (OSC)
Specific examples of the oxygen storage / release component (OSC) include ceria and ceria-zirconia. Ceria alone can be used under conditions where the temperature of the exhaust gas is low, but a composite oxide in which zirconia is combined with ceria is used under conditions where the temperature of the exhaust gas is high.
The content of zirconia contained in ceria-zirconia is not particularly limited, but is preferably 10 to 70% by weight for ceria to stably exhibit an oxygen storage / release function even at high temperatures, and is preferably 20 to 70% by weight. Is more preferable, and 30 to 60% by weight is particularly preferable. If the zirconia content in the ceria-zirconia is less than 10% by weight, the heat resistance of the ceria may be reduced. Release function may be reduced.
Ceria-zirconia needs to be further improved in heat resistance because the exhaust gas temperature becomes extremely high depending on the mounting position of the exhaust gas purification catalyst. Therefore, further rare earth oxides such as lanthanum oxide, neodymium oxide, praseodymium oxide, yttrium oxide are added.
The content of the rare earth oxide contained in the ceria-zirconia is not particularly limited, but in order to stably exhibit the oxygen storage / release function even when the ceria-zirconia is exposed to a very high temperature, it is 20% by weight. The following is preferable, 2 to 20% by weight is more preferable, and 3 to 10% by weight is particularly preferable. If the amount of rare earth oxide in ceria-zirconia exceeds 20% by weight, the oxygen storage / release function of ceria may be reduced. As described above, excessive use of rare earth oxide is desirable from the viewpoint of cost. Absent.
（３）パラジウム（Ｐｄ）
本発明においては、活性金属として、貴金属元素のパラジウムを使用することができる。
パラジウムは、前記硫酸バリウムを含むアルミナ材料に担持され、その際に使用する出発塩としては硝酸パラジウム、塩化パラジウム、ジニトロジアンミンパラジウム等が好ましい。特に、焼成後に塩素、硫化物等の残渣が残らない硝酸パラジウム、またはジニトロジアンミンパラジウムの使用が好ましい。
パラジウムの担持量は、０．２〜５．０ｇ／Ｌが好ましく、０．４〜４．０ｇ／Ｌがより好ましい。パラジウムの量が０．２ｇ／Ｌより少ないと脱硝性能が急激に低下することがあり、５．０ｇ／Ｌより多いと脱硝性能には問題はないが、価格の面で好ましくない。(3) Palladium (Pd)
In the present invention, the noble metal element palladium can be used as the active metal.
Palladium is supported on the alumina material containing barium sulfate, and the starting salt used at that time is preferably palladium nitrate, palladium chloride, dinitrodiammine palladium or the like. In particular, it is preferable to use palladium nitrate or dinitrodiammine palladium which does not leave a residue such as chlorine or sulfide after firing.
The supported amount of palladium is preferably 0.2 to 5.0 g / L, and more preferably 0.4 to 4.0 g / L. When the amount of palladium is less than 0.2 g / L, the denitration performance may be drastically lowered.
（４）白金（Ｐｔ）
本発明においては、活性金属として、貴金属元素の白金を使用することができる。
白金は、前記硫酸バリウムを含むアルミナ材料に担持され、その際に使用する出発塩としては塩化白金（ＩＶ）酸、亜硝酸ジアンミン白金（ＩＩ）、水酸化白金酸アミン溶液、塩化白金酸、硝酸白金等が好ましい。特に、焼成後に塩素、硫化物等の残渣が残らない亜硝酸ジアンミン白金（ＩＩ）、水酸化白金酸アミン溶液、または硝酸白金等の使用が好ましい。
白金の担持量は、０．２〜５．０ｇ／Ｌが好ましく、０．４〜４．０ｇ／Ｌがより好ましい。白金の量が０．２ｇ／Ｌより少ないと脱硝性能が急激に低下することがあり、５．０ｇ／Ｌより多いと脱硝性能には問題はないが、価格の面で好ましくない。(4) Platinum (Pt)
In the present invention, the noble metal element platinum can be used as the active metal.
Platinum is supported on the alumina material containing barium sulfate, and as the starting salt used in this case, platinum chloride (IV) acid, diammine platinum nitrite (II), platinum hydroxide amine solution, chloroplatinic acid, nitric acid Platinum or the like is preferable. In particular, it is preferable to use diammine platinum (II) nitrite, amine amine platinate, or platinum nitrate that does not leave residues such as chlorine and sulfide after firing.
The supported amount of platinum is preferably 0.2 to 5.0 g / L, and more preferably 0.4 to 4.0 g / L. If the amount of platinum is less than 0.2 g / L, the denitration performance may be drastically lowered. If it is more than 5.0 g / L, there is no problem with the denitration performance, but it is not preferable in terms of price.
（５）ロジウム（Ｒｈ）
本発明においては、活性金属として、ＮＯｘの浄化活性に優れる貴金属元素のロジウムを使用することができる。
ロジウムは、上記多孔質の無機酸化物に担持し、硫酸バリウムを含むアルミナ材料には担持しない。硫酸バリウムを含むアルミナ材料に直接Ｒｈを担持すると、ＲｈとＢａが近接して触媒性能が悪化するためである。使用する出発塩としては、硝酸ロジウム、塩化ロジウム、酢酸ロジウム、硫酸ロジウム等が好ましい。特に、焼成後に塩素、硫化物等の残渣が残らない硝酸ロジウム、または酢酸ロジウムの使用が好ましい。
多孔質の無機酸化物へのロジウムの担持量は、０．０５〜２．０ｇ／Ｌが好ましく、０．１〜１．５ｇ／Ｌがより好ましい。ロジウムの量が０．０５ｇ／Ｌより少ないと脱硝性能が急激に低下し、２．０ｇ／Ｌより多いと脱硝性能には問題はないが、価格の面で好ましくない。(5) Rhodium (Rh)
In the present invention, rhodium, a noble metal element that is excellent in NOx purification activity, can be used as the active metal.
Rhodium is supported on the porous inorganic oxide and is not supported on the alumina material containing barium sulfate. This is because when Rh is directly supported on an alumina material containing barium sulfate, Rh and Ba come close to each other and the catalyst performance deteriorates. The starting salt used is preferably rhodium nitrate, rhodium chloride, rhodium acetate, rhodium sulfate or the like. In particular, it is preferable to use rhodium nitrate or rhodium acetate in which no residue such as chlorine and sulfide remains after firing.
The supported amount of rhodium on the porous inorganic oxide is preferably 0.05 to 2.0 g / L, more preferably 0.1 to 1.5 g / L. If the amount of rhodium is less than 0.05 g / L, the denitration performance is drastically lowered. If it is more than 2.0 g / L, there is no problem in the denitration performance, but it is not preferable in terms of price.
（６）バインダー
本発明においては、必要に応じ、バインダー成分を添加してもよい。
バインダー成分としては、アルミナゾル、シリカゾル、ジルコニアゾル、チタニアゾル等のような種々のゾルを使用できる。また、硝酸アルミニウム、酢酸アルミニウム、硝酸ジルコニウム、酢酸ジルコニウム等の可溶性の塩も使用できる。その他、溶媒（ｐＨ調整剤）として、酢酸、硝酸、塩酸、硫酸等の酸も使用できる。(6) Binder In the present invention, a binder component may be added as necessary.
As the binder component, various sols such as alumina sol, silica sol, zirconia sol, titania sol and the like can be used. Soluble salts such as aluminum nitrate, aluminum acetate, zirconium nitrate, and zirconium acetate can also be used. In addition, acids such as acetic acid, nitric acid, hydrochloric acid, and sulfuric acid can also be used as a solvent (pH adjuster).
（７）硫酸バリウムを含むアルミナ材料とＯＳＣの関係
本発明においては、排気ガス浄化用触媒に使用するＯＳＣと硫酸バリウムの位置関係も重要である。
従来、硫酸バリウムがＯＳＣ表面上に直接担持されたり、硫酸バリウム粒子とＯＳＣ粒子が直接接したりする場合には、酸素吸蔵放出機能が著しく低下していた。そのため、前記特許文献１１、特許文献１２では、ＯＳＣとバリウムに代表されるアルカリ土類金属が、お互いに悪影響を及ぼし合うとして、互いに分離され異なる触媒層に含まれるようにしていた。
ところが、本発明では、後述するように、硫酸バリウムとＯＳＣが同一触媒層内であっても硫酸バリウムの微粒子は、アルミナ粒子にほぼ均一に分散包囲されて存在するため、ＯＳＣの酸素吸蔵放出機能にはほとんど悪影響を及ぼさない。(7) Relationship between OSC and alumina material containing barium sulfate In the present invention, the positional relationship between OSC and barium sulfate used for the exhaust gas purifying catalyst is also important.
Conventionally, when barium sulfate is directly supported on the OSC surface, or when barium sulfate particles and OSC particles are in direct contact with each other, the oxygen storage / release function has been significantly reduced. For this reason, in Patent Document 11 and Patent Document 12, OSC and alkaline earth metal typified by barium are separated from each other and included in different catalyst layers because they adversely affect each other.
However, in the present invention, as will be described later, even if barium sulfate and OSC are in the same catalyst layer, the fine particles of barium sulfate are dispersed and surrounded almost uniformly by alumina particles, so that the oxygen storage / release function of OSC Has little adverse effect.
４．一体構造型担体
本発明の排気ガス浄化用触媒は、上記触媒組成物単独でも使用できるが、触媒成分が各種担体、特に一体構造型担体の表面に被覆された構造型触媒として用いることが好ましい。ここで担体の形状は、特に限定されるものではなく、角柱状、円筒状、球状、ハニカム状、シート状などの構造型担体から選択可能である。構造型担体のサイズは、特に制限されないが、角柱状、円筒状、球状のいずれかであれば、例えば数ミリから数センチの直径（長さ）のものが使用できる。中でも、ハニカム状のハニカム構造担体の使用が好ましい。4). Monolithic structure type carrier The exhaust gas purifying catalyst of the present invention can be used as the catalyst composition alone, but it is preferably used as a structural type catalyst in which the catalyst component is coated on the surface of various carriers, particularly the monolithic structure type carrier. Here, the shape of the carrier is not particularly limited, and can be selected from a structural carrier such as a prismatic shape, a cylindrical shape, a spherical shape, a honeycomb shape, and a sheet shape. The size of the structure-type carrier is not particularly limited, and a structural carrier having a diameter (length) of several millimeters to several centimeters can be used as long as it is any of a prismatic shape, a cylindrical shape, and a spherical shape. Among these, the use of a honeycomb-shaped honeycomb structure carrier is preferable.
（ハニカム構造担体）
ハニカム構造担体とは、コージェライト、シリコンカーバイド、窒化珪素等のセラミックや、ステンレス等の金属からなるもので、その構造は構造型担体中の全体に渡って伸びている平行な多数の微細な気体流路を有している。材質としてはコージェライトが耐久性、コストの理由で好ましい。
また、このようなハニカム構造担体としては、さらに開口部の孔数についても処理すべき排気ガスの種類、ガス流量、圧力損失あるいは除去効率などを考慮して適正な孔数が決められる。そのセル密度は、１００〜９００セル／ｉｎｃｈ２（１５．５〜１３９．５セル／ｃｍ２）であることが好ましく、２００〜６００セル／ｉｎｃｈ２（３１〜９３セル／ｃｍ２）がより好ましい。セル密度が９００セル／ｉｎｃｈ２（１３９．５セル／ｃｍ２）を超えると、付着した粒子状成分（ＰＭ）で目詰まりが発生しやすく、１００セル／ｉｎｃｈ２（１５．５セル／ｃｍ２）未満では幾何学的表面積が小さくなるため、触媒の有効使用率が低下してしまう。なお、セル密度とは、ハニカム構造担体を気体流路に対して直角に切断した際の断面における単位面積あたりのセル数のことである。
また、ハニカム構造担体には、気体流路が連通しているフロースルー型構造体と、気体流路の一部端面が目封じされ、かつ気体流路の壁面を通して気体が流通可能になっているウォールフロー型構造体とが広く知られている。フロースルー型構造体であれば空気抵抗が少なく、排気ガスの圧力損失が少ない。また、ウォールフロー型構造体であれば、排気ガス中に含まれる粒子状成分を濾し取ることが可能である。本発明の排気ガス浄化用触媒は、そのどちらの構造体にも用いる事ができる。(Honeycomb structure carrier)
A honeycomb structure carrier is made of a ceramic such as cordierite, silicon carbide, silicon nitride, or a metal such as stainless steel, and the structure is a large number of parallel fine gases extending throughout the structure type carrier. It has a channel. As a material, cordierite is preferable for reasons of durability and cost.
Further, for such a honeycomb structure carrier, an appropriate number of holes is determined in consideration of the type of exhaust gas to be processed, gas flow rate, pressure loss, removal efficiency, etc. with respect to the number of holes in the opening. The cell density is preferably 100 to 900 cells / inch 2 (15.5~139.5 cells / cm 2), more preferably 200 to 600 cells / inch 2 (31~93 cells / cm 2) . When the cell density exceeds 900 cells / inch 2 (139.5 cells / cm 2 ), clogging is likely to occur due to adhering particulate components (PM), and 100 cells / inch 2 (15.5 cells / cm 2). ), The effective surface area of the catalyst decreases because the geometric surface area becomes small. The cell density is the number of cells per unit area in a cross section when the honeycomb structure carrier is cut at right angles to the gas flow path.
In addition, the honeycomb structure carrier has a flow-through structure in which the gas flow path communicates with a part of the end face of the gas flow path, and gas can flow through the wall surface of the gas flow path. A wall flow structure is widely known. The flow-through structure has low air resistance and low exhaust gas pressure loss. Moreover, if it is a wall flow type structure, it is possible to filter out the particulate component contained in exhaust gas. The exhaust gas purifying catalyst of the present invention can be used for either structure.
（層構成）
本発明の排気ガス浄化用触媒は、前記触媒組成物をハニカム構造担体に一層以上被覆したものである。層構成は、一層でもよいが、排気ガス浄化性能を高めるために、二層以上とすることが好ましい。(Layer structure)
The exhaust gas purifying catalyst of the present invention is obtained by coating one or more honeycomb structure carriers with the catalyst composition. The layer structure may be one layer, but it is preferable to have two or more layers in order to improve the exhaust gas purification performance.
触媒層となる触媒組成物の被覆量は、１００〜３００ｇ／Ｌであることが好ましく、１２０〜２５０ｇ／Ｌであることがより好ましい。触媒組成物の被覆量が、１００ｇ／Ｌ未満であると、担持される白金等の貴金属の分散性が悪化することにより活性が低下し、３００ｇ／Ｌを超えると、セル内が狭くなることで圧損が増大するので好ましくない。
上下二層になる構成の場合は、上層、下層で貴金属の担持比率や触媒層の被覆量を変えることが好ましい。具体的には、上層に総貴金属量の５０重量％以上、より好ましくは、６０重量％以上を担持することが好ましい。また、触媒層の被覆量は、取り付け位置に関係なく、上層を総被覆量の５０重量％未満とすることが好ましい。The coating amount of the catalyst composition that becomes the catalyst layer is preferably 100 to 300 g / L, and more preferably 120 to 250 g / L. When the coating amount of the catalyst composition is less than 100 g / L, the activity decreases due to deterioration of the dispersibility of noble metals such as platinum carried, and when it exceeds 300 g / L, the inside of the cell becomes narrow. Since pressure loss increases, it is not preferable.
In the case of an upper and lower two-layer configuration, it is preferable to change the loading ratio of the noble metal and the coating amount of the catalyst layer between the upper layer and the lower layer. Specifically, it is preferable to support 50% by weight or more, more preferably 60% by weight or more of the total noble metal amount in the upper layer. Further, the coating amount of the catalyst layer is preferably less than 50% by weight of the total coating amount regardless of the attachment position.
排気ガス浄化用触媒として様々な層の構成が考えられる。すなわち、層の構成を一層にするか、上下二層にするか、また、上下二層の構成にするにしても、単純な二層とするか、上層を被覆する範囲を上流側に偏らせるか、その他、貴金属のみを上流側に偏らせるかは、排気ガスの規制値、使用される燃料の品質、ガソリンエンジン等の排気量、触媒の設置位置、排気ガス浄化システムに許容されるコスト等々、様々な要因を加味して決める必要がある。
本発明では、排気ガス浄化用触媒の一例として、単純な二層の構成について以下に述べるが、排気ガス浄化用触媒はこれに限定されるものではない。Various layer configurations are conceivable as exhaust gas purifying catalysts. In other words, even if the layer structure is one layer, two upper and lower layers, or two upper and lower layers, the two layers are simple, or the range covering the upper layer is biased upstream. In addition, whether to preferentially bias only precious metals to the upstream side depends on the exhaust gas regulation value, the quality of fuel used, the displacement of gasoline engines, etc., the installation position of the catalyst, the cost allowed for the exhaust gas purification system, etc. It is necessary to take into account various factors.
In the present invention, a simple two-layer structure will be described below as an example of an exhaust gas purification catalyst, but the exhaust gas purification catalyst is not limited to this.
（触媒調製法）
本発明の排気ガス浄化用触媒を調製するには、前記触媒組成物と、必要に応じてバインダーなどを水系媒体と混合してスラリー状混合物にしてから、一体構造型担体へ塗工して、乾燥、焼成する。
すなわち、まず、触媒組成物と水系媒体を所定の比率で混合してスラリー状混合物を得る。本発明においては、水系媒体は、スラリー中で触媒組成物が均一に分散できる量を用いれば良い。
この際、必要に応じてｐＨ調整のための酸、塩基を配合したり、粘性の調整やスラリー分散性向上のための界面活性剤、分散用樹脂等を配合する事ができる。スラリーの混合方法としては、ボールミルなどによる粉砕混合が適用可能であるが、他の粉砕、もしくは混合方法を適用しても良い。(Catalyst preparation method)
In order to prepare the exhaust gas purifying catalyst of the present invention, the catalyst composition and, if necessary, a binder or the like are mixed with an aqueous medium to form a slurry mixture, and then applied to a monolithic structure type carrier. Dry and fire.
That is, first, the catalyst composition and the aqueous medium are mixed at a predetermined ratio to obtain a slurry mixture. In the present invention, the aqueous medium may be used in such an amount that the catalyst composition can be uniformly dispersed in the slurry.
At this time, if necessary, an acid or a base for adjusting the pH, a surfactant for adjusting the viscosity or improving the slurry dispersibility, a dispersing resin or the like can be added. As a mixing method of the slurry, pulverization and mixing by a ball mill or the like can be applied, but other pulverization or mixing methods may be applied.
次に、一体構造型担体へスラリー状混合物を塗工する。塗工方法は、特に限定されないが、ウオッシュコート法が好ましい。
塗工した後、乾燥、焼成する事により、触媒組成物が担持された排気ガス浄化用触媒が得られる。なお、乾燥温度は、７０〜１５０℃が好ましく、８０〜１２０℃がより好ましい。また、焼成温度は、３００〜７００℃が好ましく、４００〜６００℃が好ましい。加熱手段については、電気炉やガス炉等の公知の加熱手段によって行う事ができる。Next, the slurry-like mixture is applied to the monolithic structure type carrier. A coating method is not particularly limited, but a wash coat method is preferable.
After the coating, the exhaust gas purifying catalyst carrying the catalyst composition is obtained by drying and firing. In addition, 70-150 degreeC is preferable and, as for drying temperature, 80-120 degreeC is more preferable. Moreover, 300-700 degreeC is preferable and, as for baking temperature, 400-600 degreeC is preferable. About a heating means, it can carry out by well-known heating means, such as an electric furnace and a gas furnace.
５．排気ガス浄化用触媒を用いた触媒装置
本発明においては、上記排気ガス浄化用触媒をエンジンからの排気系に配置して触媒装置を構成する。
エンジンからの排気系における触媒の位置および個数は、排気ガス規制の程度に応じて適宜設計できる。排気ガス規制が厳しくない車種では、１個使いが可能である。しかし、排ガス規制の厳しい車種では２個使いとし、排気系の上流に直下触媒を配置し、その後方床下位置に、脱硝性能に優れた効果を発揮しうる本発明の触媒を配置することができる。
また、エンジンの排気量が大きくて、床下位置の触媒だけでは優れた脱硝性能を発揮することが困難な場合には、直下触媒にも本発明の触媒を用いて、脱硝性能を向上させることも可能である。
その際、本発明の触媒の層構成は、ＮＯｘの排出濃度、稼動システムに応じて決定でき、硫酸バリウムを含むアルミナ材料と単一の貴金属又は複数の貴金属からなる単層触媒とするか、硫酸バリウムを含むアルミナ材料と単一の貴金属又は複数の貴金属からなる複層触媒とするなど使い分けることができる。5). In the present invention, the catalyst device is configured by arranging the exhaust gas purification catalyst in an exhaust system from the engine.
The position and number of catalysts in the exhaust system from the engine can be appropriately designed according to the degree of exhaust gas regulation. One vehicle can be used in a vehicle model that does not have strict exhaust gas regulations. However, in vehicles with strict exhaust gas regulations, two catalysts can be used, and a catalyst directly below can be arranged upstream of the exhaust system, and a catalyst of the present invention capable of exhibiting an excellent effect of denitration performance can be arranged below the rear floor of the exhaust system. .
In addition, when the engine displacement is large and it is difficult to achieve excellent denitration performance with only the catalyst under the floor, the catalyst of the present invention can also be used for the direct catalyst to improve the denitration performance. Is possible.
At that time, the layer structure of the catalyst of the present invention can be determined according to the NOx emission concentration and the operating system, and it can be a single layer catalyst composed of an alumina material containing barium sulfate and a single noble metal or a plurality of noble metals, or sulfuric acid. For example, a multi-layer catalyst composed of an alumina material containing barium and a single noble metal or a plurality of noble metals can be used.
以下、本発明の実施例、比較例を示すが、本発明は、この実施例に限定して解釈されるものではない。なお、製造した触媒サンプルは、次の要領で物性を測定した。 Examples of the present invention and comparative examples are shown below, but the present invention is not construed as being limited to these examples. In addition, the manufactured catalyst sample measured the physical property in the following way.
＜ＳＥＭ測定＞
実施例及び比較例の粉末サンプルに対して樹脂埋め、カーボン蒸着の前処理を行なった後、ＳＥＭ測定を行った。ＳＥＭ測定では、Ｃａｒｌ Ｚｅｉｓｓ社製走査型電子顕微鏡ＵＬＴＲＡ５５を用いて触媒構造を観察した。加速電圧５ｋＶ、対物絞り６０μｍ、後方散乱電子検出器（ＲＢＳＤ）の条件で測定を行った。また、Ｒｏｎｔｅｃ社製のエネルギー分散型検出器Ｘ−Ｆｒｅｓｈを用いて、観察した粉末粒子の定性分析を行った。さらに、画像解析ソフトＷｉｎＲＯＯＦを用いて、粉末粒子内のＢａＳＯ４の粒子径（円相当径：粒子の面積と等しい円面積を持つ円の直径。Ｈｅｙｗｏｏｄ径とも呼ぶ）を１００個以上計測し、その平均値をＢａＳＯ４の平均粒子径（円相当径の平均値）とした。<SEM measurement>
The powder samples of Examples and Comparative Examples were filled with resin and subjected to pretreatment for carbon deposition, and then SEM measurement was performed. In the SEM measurement, the catalyst structure was observed using a scanning electron microscope ULTRA55 manufactured by Carl Zeiss. Measurement was performed under the conditions of an acceleration voltage of 5 kV, an objective aperture of 60 μm, and a backscattered electron detector (RBSD). Further, the observed powder particles were qualitatively analyzed using an energy dispersive detector X-Fresh manufactured by Rontec. Furthermore, using image analysis software WinROOF, 100 or more particle diameters of BaSO 4 in the powder particles (equivalent circle diameter: diameter of a circle having a circular area equal to the area of the particle, also referred to as Heywood diameter) are measured. The average value was defined as the average particle diameter of BaSO 4 (average value of equivalent circle diameter).
＜ＥＰＭＡ測定＞
実施例及び比較例のサンプルについて、ＥＰＭＡ測定にて元素分布の解析を行った。サンプルの測定面を下にしてモールドに貼り付け、樹脂と硬化剤を２０／３の割合で混合した液を流し込み、一晩静置し硬化させた。樹脂埋めしたサンプルを研磨して、カーボン蒸着させて、サンプルの前処理を行った。
測定はＪＥ０Ｌ社製の電子プローブマイクロアナライザーＪＸＡ−８１００を用いた。加速電圧１５ＫＶ、照射電流０．０２μＡの条件で測定を行った。検出器には波長分散型検出器を用いた。<EPMA measurement>
About the sample of an Example and a comparative example, the element distribution was analyzed by EPMA measurement. The sample was attached to the mold with the measurement surface facing down, and a liquid in which a resin and a curing agent were mixed at a ratio of 20/3 was poured, and the sample was allowed to stand overnight to be cured. The resin-filled sample was polished and carbon deposited, and the sample was pretreated.
The measurement was performed using an electronic probe microanalyzer JXA-8100 manufactured by JE0L. Measurement was performed under the conditions of an acceleration voltage of 15 KV and an irradiation current of 0.02 μA. A chromatic dispersion detector was used as the detector.
（相関係数の計算方法）
ＢａとＡｌの粒子内分布の相関係数Ｒは、ＥＰＭＡ測定により得られたＢａとＡｌの特性Ｘ線の強度値から、以下の式（６）により算出した。(Correlation coefficient calculation method)
The correlation coefficient R of the intraparticle distribution of Ba and Al was calculated by the following formula (6) from the intensity values of the characteristic X-rays of Ba and Al obtained by EPMA measurement.
本手法により計算されるＢａとＡｌの粒子内分布の相関係数は、アルミナ粒子内にどの程度Ｂａ粒子が分散しているか、言い換えればアルミナ粒子内でのＢａの分散度の指標となる。相関係数が例えば＋０．６より大きい場合、つまり強い正の相関がある場合はＡｌとＢａの分布がよく一致していることを示しており、アルミナ粒子中にＢａが非常に高分散していると言える。また、相関係数が正であっても小さいと、ＡｌとＢａの分布に相関性が低いことを示しており、アルミナ粒子中のＢａ分散性が低いことを意味する。一方、ＢａとＡｌの分布の相関係数が負の場合には、Ａｌの分布とＢａの分布が負の相関性にある、つまりＢａが多い個所にＡｌが少なく、Ｂａが少ない個所にＡｌが多いこととなり、アルミナ粒子と硫酸バリウム粒子が個別に存在していることを示している。 The correlation coefficient between the intra-particle distributions of Ba and Al calculated by this method is an index of how much Ba particles are dispersed in the alumina particles, in other words, the degree of dispersion of Ba in the alumina particles. For example, when the correlation coefficient is larger than +0.6, that is, when there is a strong positive correlation, the distribution of Al and Ba is well matched, and Ba is very highly dispersed in the alumina particles. I can say that. Further, even if the correlation coefficient is positive, if it is small, it indicates that the correlation between the Al and Ba distribution is low, which means that the Ba dispersibility in the alumina particles is low. On the other hand, when the correlation coefficient between the distributions of Ba and Al is negative, the distribution of Al and the distribution of Ba are negatively correlated, that is, Al is present where there is a lot of Ba and Al is present where there is less Ba. This indicates that alumina particles and barium sulfate particles exist separately.
＜ＢＥＴ比表面積＞
ＢＥＴ法により、下記耐久処理前後の粉末サンプルのＢＥＴ比表面積を測定した。
（耐久方法）
粉末サンプルの耐久処理は以下の手順に基づいて実施した。
まず、管状炉用石英管の中に粉末サンプルの入ったセラミック容器を置き、表１の組成のガスを２．０Ｌ／分で流しながら、９００℃、１時間還元処理を行った。その後、粉末サンプルを入れたまま容器を電気炉に移し、１，１００℃、１２時間かけて空気雰囲気下で焼成した。<BET specific surface area>
The BET specific surface area of the powder sample before and after the following durability treatment was measured by the BET method.
(Durability method)
The durability treatment of the powder sample was performed based on the following procedure.
First, a ceramic container containing a powder sample was placed in a quartz tube for a tubular furnace, and reduction treatment was performed at 900 ° C. for 1 hour while flowing a gas having the composition shown in Table 1 at 2.0 L / min. Then, the container was moved to the electric furnace with the powder sample put therein, and baked in an air atmosphere at 1,100 ° C. for 12 hours.
（ＢＥＴ比表面積低下率の算出）
ＢＥＴ比表面積低下率（％）は、調製時のＢＥＴ比表面積値と耐久後のＢＥＴ比表面積値から以下の式（７）により算出した。(Calculation of BET specific surface area reduction rate)
The BET specific surface area reduction rate (%) was calculated by the following formula (7) from the BET specific surface area value at the time of preparation and the BET specific surface area value after durability.
＜粒度分布測定＞
粉末サンプルの粒度分布は、ＳＨＩＭＡＤＺＵ社製のナノ粒子径分布測定装置ＳＡＬＤ−７１００を用いて、レーザー散乱法により測定し、ｄ５０（５０％粒度：フルイ下の粒子量の体積基準の積算値が全体の５０％に達した時の粒子の直径、以下同じ）の他、ｄ５７．５、ｄ７０も測定し、メディアン径（ｄ５０）を平均粒子径とした。また、モード径も測定し、アルミナに起因する平均粒子径とした（粒度分布に二つのピークが出現した場合は、各々のピークのモード径を算出し、大粒子側をアルミナに起因する平均粒子径とした）。<Particle size distribution measurement>
The particle size distribution of the powder sample was measured by a laser scattering method using a nano particle size distribution measuring device SALD-7100 manufactured by SHIMADZU, and d50 (50% particle size: the volume-based integrated value of the amount of particles under the sieve is the whole. In addition to the diameter of the particles when reaching 50% of the same (hereinafter the same), d57.5 and d70 were also measured, and the median diameter (d50) was defined as the average particle diameter. In addition, the mode diameter was also measured, and the average particle diameter attributable to alumina was determined (when two peaks appeared in the particle size distribution, the mode diameter of each peak was calculated, and the average particle diameter attributable to alumina was calculated on the large particle side. Diameter).
＜細孔分布測定＞
各種粉末サンプルを乾燥後、Ｔｈｅｒｍｏ社製ＰＡＳＣＡＬ１４０−４４０を用いて、Ｈｇ圧入法により、粉末サンプルの平均細孔径および細孔容積（細孔分布）を測定した。なお、平均細孔径としてモード径（直径）を採用した。<Measurement of pore distribution>
After drying various powder samples, the average pore diameter and pore volume (pore distribution) of the powder samples were measured by Hg intrusion method using PASCAL140-440 manufactured by Thermo. The mode diameter (diameter) was adopted as the average pore diameter.
＜ＸＲＤ測定＞
ＰＡＮａｌｙｔｉｃａｌ社製のＸ線回折測定装置Ｘ‘Ｐｅｒｔ ＰＲＯ ＭＰＤを用いて、各種粉末サンプルの回折パターンを測定し、ＩＣＳＤカードデータと照合することで、成分の同定を行なった。得られた回折パターンからガウス関数によるピーク分離を行い、半値幅を求めて、シェラーの式を用いて成分の結晶子径（直径）を算出した。<XRD measurement>
Components were identified by measuring diffraction patterns of various powder samples using an X-ray diffractometer X'Pert PRO MPD manufactured by PANalytical and collating with ICSD card data. Peak separation by a Gaussian function was performed from the obtained diffraction pattern, the half width was obtained, and the crystallite diameter (diameter) of the component was calculated using Scherrer's formula.
＜硫酸バリウムの分解温度測定＞
硫酸バリウム−アルミナ中の硫酸バリウムの分解温度は、各種粉末サンプル１０ｍｇをメノウ乳鉢で粉砕して、アルミナ製サンプルホルダーに入れ、熱重量分析装置（ＴＧ）にて測定した。ガスとして１％Ｈ２／Ｎ２ガスを用い、流量を１００ｍＬ／分とした。１０℃／分の昇温速度で１，１００℃まで昇温させ、含水分が脱離した後の重量減少が開始する温度を各サンプルの硫酸バリウムの分解温度とした。<Measurement of decomposition temperature of barium sulfate>
The decomposition temperature of barium sulfate in barium sulfate-alumina was measured with a thermogravimetric analyzer (TG) by grinding 10 mg of various powder samples with an agate mortar and placing them in an alumina sample holder. 1% H 2 / N 2 gas was used as the gas, and the flow rate was 100 mL / min. The temperature was raised to 1,100 ° C. at a rate of temperature increase of 10 ° C./min, and the temperature at which weight reduction after the desorption of moisture started was taken as the decomposition temperature of barium sulfate in each sample.
＜ＯＳＣ容量の測定方法＞
実施例および比較例の粉末材料１０ｍｇをサンプリングして、ＴＧ−ＤＴＡで、ＯＳＣ容量を測定した。ＴＧ―ＤＴＡの測定にはＲｉｇａｋｕ社製ＴＧ−８１２０を用いた。初めに空気中で６５０℃、１０分の前処理を行った。前処理終了後３５０℃まで降温し、同温度で５分間保持した。その後１．０％Ｈ２／Ｎ２雰囲気に切り替えて５分保持し、その時の重量減少値ΔＴＧ（３５０℃）を測定した。再び空気中に戻して５分保持した。同様の手法で６５０℃での重量減少値ΔＴＧ（６５０℃）を測定した。各温度のΔＴＧとＣｅＯ２からＣｅＯ１．５への分子量変化からＯＳＣ容量を算出した。<OSC capacity measurement method>
10 mg of the powder materials of Examples and Comparative Examples were sampled, and the OSC capacity was measured by TG-DTA. For measurement of TG-DTA, TG-8120 manufactured by Rigaku was used. First, pretreatment was performed at 650 ° C. for 10 minutes in air. After completion of the pretreatment, the temperature was lowered to 350 ° C. and kept at that temperature for 5 minutes. Then switching to 1.0% H 2 / N 2 atmosphere for 5 minutes, to measure the weight reduction value? Tg (350 ° C.) at that time. It was returned to the air again and held for 5 minutes. The weight loss value ΔTG (650 ° C.) at 650 ° C. was measured in the same manner. The OSC capacity was calculated from ΔTG at each temperature and the molecular weight change from CeO 2 to CeO 1.5 .
＜実機耐久処理＞
後述する直下用触媒を２個、床下用触媒を６個（実施例１〜５及び比較例１）用意し、直下用触媒と床下用触媒を１個ずつ触媒コンバーター内に格納した後、耐久ベンチに設置された耐久用エンジンの排気ラインの直下位置と床下位置にそれぞれ設置した。その後、エンジンを稼動し、Ａ／Ｆ変動下、直下用触媒は触媒床温度を９５０℃になるように設定して１５０時間、床下用触媒は触媒床温度を８００℃に設定して５０時間の耐久処理をそれぞれ行った。<Real machine durability treatment>
After preparing two below-mentioned catalysts for direct use and six under-bed catalysts (Examples 1 to 5 and Comparative Example 1), storing the direct-use catalyst and the under-floor catalyst one by one in the catalytic converter, and then the durability bench Were installed at the position directly below the exhaust line of the engine for durability and the position below the floor. After that, the engine was operated, and under the A / F fluctuation, the catalyst for the directly underneath was set so that the catalyst bed temperature was set to 950 ° C. for 150 hours, and the catalyst for the under bed was set to 800 ° C. for 50 hours. Each endurance treatment was performed.
＜実機触媒の性能試験＞
実施例７〜１０及び比較例４では、実施例１〜５及び比較例１と同様にして実機耐久処理を行った後、実機触媒の性能を評価するために、評価用車両の排気ラインの直下位置に直下触媒を収納した触媒コンバーターを、床下位置に床下用触媒を収納した触媒コンバーターを各々配置した。
触媒性能は、走行モードＬＡ−４にて評価を行なった。触媒のＮＯｘ浄化性能は、ＬＡ−４モードを走行した際の加速領域の平均ＮＯｘ浄化率を測定して比較した。具体的には、ＬＡ−４走行モードの中で、特にＮＯｘ浄化反応の進み難い１９０〜２２０秒の加速領域、すなわちＳＶが高く、ＮＯｘ排出量が多い領域を抽出して、直下触媒通過後のＮＯｘ排出量に対する床下触媒通過後のＮＯｘ排出量より平均ＮＯｘ浄化率を算出した。<Performance test of actual catalyst>
In Examples 7 to 10 and Comparative Example 4, in order to evaluate the performance of the actual machine catalyst after performing the actual machine durability treatment in the same manner as in Examples 1 to 5 and Comparative Example 1, immediately below the exhaust line of the vehicle for evaluation. A catalytic converter storing the catalyst immediately below at the position and a catalytic converter storing the catalyst for underfloor at the position below the floor were respectively arranged.
The catalyst performance was evaluated in the running mode LA-4. The NOx purification performance of the catalyst was compared by measuring the average NOx purification rate in the acceleration region when traveling in the LA-4 mode. Specifically, in the LA-4 traveling mode, an acceleration region of 190 to 220 seconds in which the NOx purification reaction is difficult to proceed, that is, a region where the SV is high and the NOx emission amount is large is extracted, and after passing through the direct catalyst. The average NOx purification rate was calculated from the NOx emission amount after passing through the underfloor catalyst with respect to the NOx emission amount.
（実施例１）
下記の要領で本発明の硫酸バリウムが担持されたアルミナ材料を調製し、その物性を測定した。
＜ＢａＳＯ４−Ａｌ２Ｏ３＞
ＢＥＴ比表面積１５０ｍ２／ｇ、平均細孔径１５ｎｍ、平均粒子径３５μｍのγ−アルミナ粉末Ａ ８４８ｇに純水を加え、湿式ミリング装置で粉砕処理を行ない、メディアン径（ｄ５０）が１．５μｍのアルミナ分散スラリーを得た。そこに結晶子径４５０ｎｍの硫酸バリウムＢ １５２ｇを添加し、ミキサーで分散混合した。この混合スラリーをスプレードライヤーで平均粒子径１５μｍまで造粒させて、さらに４５０℃、１時間の焼成を行なうことで、実施例１の１５．２重量％硫酸バリウム−アルミナ １，０００ｇを得た。Example 1
The alumina material carrying the barium sulfate of the present invention was prepared in the following manner, and its physical properties were measured.
<BaSO 4 -Al 2 O 3>
Pure water is added to 848 g of γ-alumina powder A having a BET specific surface area of 150 m 2 / g, an average pore size of 15 nm, and an average particle size of 35 μm, and pulverized by a wet milling apparatus, and the median diameter (d50) is 1.5 μm. A dispersed slurry was obtained. Thereto, 152 g of barium sulfate B having a crystallite diameter of 450 nm was added and dispersed and mixed with a mixer. This mixed slurry was granulated to an average particle size of 15 μm with a spray dryer and further calcined at 450 ° C. for 1 hour to obtain 1,000 g of 15.2 wt% barium sulfate-alumina of Example 1.
（物性測定と結果）
ＳＥＭの画像解析ソフトを用いて、硫酸バリウム−アルミナ粒子内の１００個以上の硫酸バリウムの粒子径（円相当径）を計測し、それらの値から硫酸バリウムの平均粒子径（円相当径の平均値）を求め、その結果を図１及び表２に示した。
また、図２に示す硫酸バリウム−アルミナのＥＰＭＡ粒子断面図からＢａ−Ａｌ間の相関係数を求め、その結果を図８にまとめた。その他、造粒前の混合スラリーの粒度を表２に、耐久処理前後の硫酸バリウム−アルミナのＢＥＴ比表面積、硫酸バリウムの分解温度を計測し、その結果を表３に、平均細孔径を表４にまとめた。また、耐久処理前後のＢＥＴ比表面積からＢＥＴ比表面積の低下率を求め、その結果を図９にまとめた。さらに、熱重量分析装置（ＴＧ）を用い、硫酸バリウム−アルミナ中の硫酸バリウムの分解温度を求め、その結果を図１０にまとめた。その他、Ｂａ−Ａｌ間の相関係数とＢＥＴ比表面積の低下率の関係を図１１に、硫酸バリウムの分解温度との関係を図１２にまとめた。(Measurement of physical properties and results)
Using the image analysis software of SEM, the particle diameter (equivalent circle diameter) of 100 or more barium sulfate in the barium sulfate-alumina particles was measured, and the average particle diameter of barium sulfate (average of equivalent circle diameter) was calculated from these values. Value) and the results are shown in FIG.
Moreover, the correlation coefficient between Ba-Al was calculated | required from EPMA particle | grain sectional drawing of the barium sulfate-alumina shown in FIG. 2, and the result was put together in FIG. In addition, the particle size of the mixed slurry before granulation is shown in Table 2, the BET specific surface area of barium sulfate-alumina before and after the endurance treatment, and the decomposition temperature of barium sulfate are measured. The results are shown in Table 3, and the average pore diameter is shown in Table 4. Summarized in Moreover, the reduction rate of the BET specific surface area was calculated | required from the BET specific surface area before and behind an endurance process, and the result was put together in FIG. Furthermore, the decomposition temperature of barium sulfate in barium sulfate-alumina was determined using a thermogravimetric analyzer (TG), and the results are summarized in FIG. In addition, the relationship between the correlation coefficient between Ba-Al and the reduction rate of the BET specific surface area is summarized in FIG. 11, and the relationship with the decomposition temperature of barium sulfate is summarized in FIG.
（評価）
本発明の実施例１では、得られた硫酸バリウム−アルミナ粒子内の硫酸バリウムをＳＥＭで測定すると、平均粒子径が３００ｎｍであった（図１及び表２参照）。一方、アルミナについては、ＳＥＭを用いた測定では切断面に生じたアルミナ粒子間の境が明確でないため、大きさを特定することが困難な上、アルミナ粒子断面が正確に最長径であるとはいえないため、径長を特定することは不可能であった。そのため、代理特性として、造粒前の硫酸バリウムとアルミナの混合スラリーの粒度分布を基に、アルミナの平均粒子径の算出を試みた。すなわち、硫酸バリウムとアルミナの混合スラリーの粒度分布において、両方の平均粒子径が大きく異なれば粒度分布が硫酸バリウムとアルミナの二つのピークに分離することを利用し、大粒子側のピークのモード径をアルミナに起因する平均粒子径とした。
実施例１で得られた硫酸バリウム−アルミナの場合は、粒度分布のピークは１つしか生じなかったが、モード径は１．３μｍで、混合前のアルミナの平均粒子径である１．５μｍや、５７．６％粒度（ｄ５７．６：硫酸バリウムの混合比率１５．２重量％とアルミナの混合比率８４．８重量％、その１／２の値４２．４重量％の場合、硫酸バリウムが５７．６重量％の時の粒度）である１．２μｍに近似していた。ちなみに、後述する他の実施例、比較例においても同様の結果が得られていることから、アルミナの平均粒子径の代用特性として混合スラリー中のモード径を用いることが妥当であると考えられる（表２参照）。また、同粒子内のＢａ−Ａｌ間の相関係数は０．５１と良好な相関が見られた（図８参照）。これらの結果は、硫酸バリウムの微粒子が硫酸バリウム−アルミナ粒子内でよく分散されていることを示している。
この様な状況にある実施例１の硫酸バリウム−アルミナは、モデルガスによる耐久処理前後におけるＢＥＴ比表面積の低下が２６．５％に抑えられており（表３参照）、触媒の材料として使用される場合においても優れた耐久性能を発揮することが期待される。また、酸化雰囲気下での硫酸バリウムの分解温度は１，６００℃であるが、還元雰囲気下での硫酸バリウムの分解温度は表２に示すように８３２℃であり、反応性に乏しい硫酸バリウムからＮＯｘの吸着材として機能するバリウム成分への移行が実際のガソリンエンジン稼働下でも容易に起こることが期待される。さらに、硫酸バリウム−アルミナの平均細孔径（１４ｎｍ）も出発原料であるγ−アルミナＡ（同１５ｎｍ）とほぼ同等であり（表４参照）、硫酸バリウムを添加しても細孔の閉塞も狭小も起こらず、硫酸バリウム−アルミナ粒子内のガスの拡散はγ−アルミナと同レベルであることが示唆される。(Evaluation)
In Example 1 of this invention, when the barium sulfate in the obtained barium sulfate-alumina particle was measured by SEM, the average particle diameter was 300 nm (refer FIG. 1 and Table 2). On the other hand, for alumina, since the boundary between alumina particles generated on the cut surface is not clear in the measurement using SEM, it is difficult to specify the size, and the alumina particle cross section has the longest diameter accurately. Since it was not possible, it was impossible to specify the diameter. Therefore, an attempt was made to calculate the average particle size of alumina based on the particle size distribution of the mixed slurry of barium sulfate and alumina before granulation as surrogate characteristics. That is, in the particle size distribution of the mixed slurry of barium sulfate and alumina, if the average particle size of both is greatly different, the particle size distribution is separated into two peaks of barium sulfate and alumina, and the mode diameter of the peak on the large particle side Was the average particle size attributable to alumina.
In the case of the barium sulfate-alumina obtained in Example 1, only one particle size distribution peak occurred, but the mode diameter was 1.3 μm, and the average particle diameter of alumina before mixing was 1.5 μm. 57.6% particle size (d57.6: Barium sulfate mixing ratio 15.2% by weight, alumina mixing ratio 84.8% by weight, half of the value 42.4% by weight, barium sulfate 57 The particle size was approximately 1.2 μm. Incidentally, since similar results are obtained in other examples and comparative examples described later, it is considered appropriate to use the mode diameter in the mixed slurry as a substitute characteristic of the average particle diameter of alumina ( (See Table 2). Further, the correlation coefficient between Ba and Al in the same particle was found to be 0.51, which was a good correlation (see FIG. 8). These results indicate that the fine particles of barium sulfate are well dispersed in the barium sulfate-alumina particles.
In the barium sulfate-alumina of Example 1 in such a situation, the decrease in the BET specific surface area before and after the endurance treatment with the model gas is suppressed to 26.5% (see Table 3), and is used as a catalyst material. It is expected to exhibit excellent durability even when Moreover, the decomposition temperature of barium sulfate under an oxidizing atmosphere is 1,600 ° C., but the decomposition temperature of barium sulfate under a reducing atmosphere is 832 ° C. as shown in Table 2, and is based on barium sulfate having poor reactivity. It is expected that the transition to a barium component that functions as an adsorbent for NOx will easily occur even under actual gasoline engine operation. Furthermore, the average pore diameter (14 nm) of barium sulfate-alumina is almost the same as that of the starting material γ-alumina A (15 nm) (see Table 4), and even when barium sulfate is added, the pore clogging is narrow. This suggests that gas diffusion in the barium sulfate-alumina particles is at the same level as that of γ-alumina.
（実施例２）
実施例１において、アルミナ粉末に硫酸バリウムを添加後に粉砕処理したが、ミキサーではなく、ミリング装置でアルミナ粉末Ａと硫酸バリウムＢを含むスラリーの粉砕処理を行い、両方の混合物のメディアン径（ｄ５０）が６００ｎｍのアルミナ−硫酸バリウム分散スラリーを得た。この混合スラリーを実施例１と同様な方法で平均粒子径が１５μｍとなるまで造粒し、実施例２の１５．２重量％硫酸バリウム−アルミナ １，０００ｇを得た。
次いで、実施例１と同様にして、実施例２の硫酸バリウム−アルミナ中の硫酸バリウムの物性を測定し、平均粒子径を図１及び表２に、分解温度を図１０にまとめた。また、実施例２の硫酸バリウム−アルミナのＥＰＭＡ粒子断面図を図３に、造粒前の混合スラリーの粒度を表２に、ＢＥＴ比表面積、硫酸バリウムの分解温度を表３に、平均細孔径を表４に、Ｂａ−Ａｌ間の相関係数を図８に、硫酸バリウムの平均粒子径とＢＥＴ比表面積の低下率の関係を図９に、硫酸バリウムの分解温度との関係を図１０にまとめた。また、Ｂａ−Ａｌ間の相関係数とＢＥＴ比表面積の低下率の関係を図１１に、硫酸バリウムの分解温度との関係を図１２にまとめた。
（評価）
本発明の実施例２で得られた硫酸バリウム−アルミナは、その粒子内の硫酸バリウムの平均粒子径が２００ｎｍ（図１及び表２参照）であり、アルミナの平均粒子径（モード径）が０．７μｍであって、ｄ５７．６（０．７μｍ）と一致し（表２参照）、実施例１よりさらに小さくなり（図１参照）、同粒子内のＢａ−Ａｌ間の相関係数も０．６９と、実施例１よりさらに強い相関が見られた（図８参照）。これらの結果は、硫酸バリウムのより細かな微粒子が硫酸バリウム−アルミナ粒子内で非常によく分散されていることを示している。
この様な状況にある実施例２の硫酸バリウム−アルミナは、モデルガスによる耐久処理前後におけるＢＥＴ比表面積の低下が２５．７％に抑えられており（表３参照）、触媒の材料として使用される場合においても優れた耐久性能を発揮することが期待される。また、還元雰囲気下での硫酸バリウムの分解温度が８４７℃（表３参照）であり、反応性に乏しい硫酸バリウムからＮＯｘの吸着材として機能するバリウムへの移行が実際のガソリンエンジン稼働下でも容易に起こることが期待される。さらに、硫酸バリウム−アルミナの平均細孔径（１３ｎｍ）も出発原料であるγ−アルミナＡ（同１５ｎｍ）とほぼ同等であり（表４参照）、硫酸バリウムを添加しても細孔の閉塞も狭小も起こらず、硫酸バリウム−アルミナ粒子内のガスの拡散はγ−アルミナと同レベルであることが示唆される。(Example 2)
In Example 1, the alumina powder was pulverized after adding barium sulfate, but the slurry containing the alumina powder A and barium sulfate B was pulverized by a milling apparatus instead of a mixer, and the median diameter (d50) of both the mixtures was determined. Of 600 nm alumina-barium sulfate dispersion slurry was obtained. This mixed slurry was granulated in the same manner as in Example 1 until the average particle size became 15 μm, and 1,000 g of 15.2 wt% barium sulfate-alumina in Example 2 was obtained.
Subsequently, the physical properties of barium sulfate in barium sulfate-alumina of Example 2 were measured in the same manner as in Example 1. The average particle diameters are summarized in FIG. 1 and Table 2, and the decomposition temperatures are summarized in FIG. Moreover, the EPMA particle sectional view of barium sulfate-alumina of Example 2 is shown in FIG. 3, the particle size of the mixed slurry before granulation is shown in Table 2, the BET specific surface area, the decomposition temperature of barium sulfate in Table 3, and the average pore diameter Table 4 shows the correlation coefficient between Ba and Al, FIG. 8 shows the relationship between the average particle diameter of barium sulfate and the reduction rate of the BET specific surface area, and FIG. 10 shows the relationship between the decomposition temperature of barium sulfate and FIG. Summarized. FIG. 11 shows the relationship between the correlation coefficient between Ba—Al and the reduction rate of the BET specific surface area, and FIG. 12 shows the relationship between the decomposition temperature of barium sulfate.
(Evaluation)
In the barium sulfate-alumina obtained in Example 2 of the present invention, the average particle diameter of barium sulfate in the particles is 200 nm (see FIG. 1 and Table 2), and the average particle diameter (mode diameter) of alumina is 0. 0.7 μm, which coincides with d57.6 (0.7 μm) (see Table 2), is smaller than that of Example 1 (see FIG. 1), and the correlation coefficient between Ba and Al in the particles is also 0. .69, a stronger correlation was found than in Example 1 (see FIG. 8). These results indicate that the finer particles of barium sulfate are very well dispersed within the barium sulfate-alumina particles.
In the barium sulfate-alumina of Example 2 in such a situation, the decrease in the BET specific surface area before and after the endurance treatment with the model gas is suppressed to 25.7% (see Table 3), and is used as a catalyst material. It is expected to exhibit excellent durability even when In addition, the decomposition temperature of barium sulfate in a reducing atmosphere is 847 ° C (see Table 3), so it is easy to shift from poorly reactive barium sulfate to barium, which functions as an adsorbent for NOx, even under actual gasoline engine operation. Is expected to happen. Furthermore, the average pore diameter (13 nm) of barium sulfate-alumina is almost the same as that of the starting material γ-alumina A (15 nm) (see Table 4), and even when barium sulfate is added, the pores are not clogged. This suggests that gas diffusion in the barium sulfate-alumina particles is at the same level as that of γ-alumina.
（実施例３）
実施例２の硫酸バリウムＢの代わりに、結晶子径が３０ｎｍの硫酸バリウムＣを用いた他は実施例２と同様な方法で、実施例３の１５．２重量％硫酸バリウム−アルミナ １，０００ｇを得た。
次いで、実施例１と同様にして、実施例３の硫酸バリウム−アルミナ中の硫酸バリウムの物性を測定し、平均粒子径を図１及び表２に、分解温度を図１０にまとめた。また、実施例３の硫酸バリウム−アルミナのＥＰＭＡ粒子断面図を図４に、造粒前の混合スラリーの粒度を表２に、ＢＥＴ比表面積、硫酸バリウムの分解温度を表３に、平均細孔径を表４に、Ｂａ−Ａｌ間の相関係数を図８に、硫酸バリウムの平均粒子径とＢＥＴ比表面積の低下率の関係を図９に、硫酸バリウムの分解温度との関係を図１０にまとめた。また、Ｂａ−Ａｌ間の相関係数とＢＥＴ比表面積の低下率の関係を図１１に、硫酸バリウムの分解温度との関係を図１２にまとめた。
（評価）
本発明の実施例３で得られた硫酸バリウム−アルミナは、その粒子内の硫酸バリウムの平均粒子径が６５ｎｍと非常に小さくなって（図１及び表２参照）、アルミナの平均粒子径（モード径）も１．３μｍであり、ｄ５７．６（１．２μｍ）とほぼ一致し（表２参照）、実施例１と同等であった。さらに、同粒子内のＢａ−Ａｌ間の相関係数は０．９５と、きわめて強い相関が見られた（図８参照）。これらの結果は、硫酸バリウムの非常に細かな微粒子が硫酸バリウム−アルミナ粒子内でほぼ均一に分散されていることを示している。
この様な状況にある実施例３の硫酸バリウム−アルミナは、モデルガスによる耐久処理前後におけるＢＥＴ比表面積の低下が２４．１％に抑えられており（表３参照）、触媒の材料として使用される場合においても優れた耐久性能を発揮することが期待される。また、還元雰囲気下での硫酸バリウムの分解温度が７５２℃（表３参照）と実施例１より著しく低く、実施例３中の硫酸バリウムは非常に分解しやすいことが分かる。これにより、反応性に乏しい硫酸バリウムからＮＯｘの吸着材として機能するバリウムへの移行が実際のガソリンエンジン稼働下でも非常に容易に起こることが考えられ、優れた脱硝性能を示すことが期待される。さらに、硫酸バリウム−アルミナの平均細孔径（１４ｎｍ）も出発原料であるγ−アルミナＡ（同１５ｎｍ）とほぼ同等であり（表４参照）、硫酸バリウムを添加しても細孔の閉塞も狭小も起こらず、硫酸バリウム−アルミナ粒子内のガスの拡散はγ−アルミナと同レベルであることが示唆される。(Example 3)
In place of barium sulfate B of Example 2, barium sulfate C having a crystallite diameter of 30 nm was used in the same manner as in Example 2, except that 15.2 wt% barium sulfate-alumina of Example 3 1,000 g Got.
Subsequently, the physical properties of barium sulfate in the barium sulfate-alumina of Example 3 were measured in the same manner as in Example 1. The average particle diameter was summarized in FIG. 1 and Table 2, and the decomposition temperature was summarized in FIG. Moreover, the EPMA particle sectional view of barium sulfate-alumina of Example 3 is shown in FIG. 4, the particle size of the mixed slurry before granulation is shown in Table 2, the BET specific surface area, the decomposition temperature of barium sulfate in Table 3, and the average pore diameter Table 4 shows the correlation coefficient between Ba and Al, FIG. 8 shows the relationship between the average particle diameter of barium sulfate and the reduction rate of the BET specific surface area, and FIG. 10 shows the relationship between the decomposition temperature of barium sulfate and FIG. Summarized. FIG. 11 shows the relationship between the correlation coefficient between Ba—Al and the reduction rate of the BET specific surface area, and FIG. 12 shows the relationship between the decomposition temperature of barium sulfate.
(Evaluation)
In the barium sulfate-alumina obtained in Example 3 of the present invention, the average particle diameter of barium sulfate in the particles was very small at 65 nm (see FIG. 1 and Table 2), and the average particle diameter of alumina (mode) (Diameter) was 1.3 μm, which was almost the same as d57.6 (1.2 μm) (see Table 2), and was equivalent to Example 1. Furthermore, the correlation coefficient between Ba-Al in the same particle was 0.95, showing a very strong correlation (see FIG. 8). These results indicate that very fine particles of barium sulfate are dispersed almost uniformly within the barium sulfate-alumina particles.
In the barium sulfate-alumina of Example 3 in such a situation, the decrease in the BET specific surface area before and after the endurance treatment with the model gas is suppressed to 24.1% (see Table 3), and is used as a catalyst material. It is expected to exhibit excellent durability even when In addition, the decomposition temperature of barium sulfate in a reducing atmosphere is 752 ° C. (see Table 3), which is significantly lower than that of Example 1. It can be seen that barium sulfate in Example 3 is very easily decomposed. As a result, the transition from barium sulfate, which is poor in reactivity, to barium, which functions as an adsorbent for NOx, may occur very easily even under actual gasoline engine operation, and is expected to exhibit excellent denitration performance. . Furthermore, the average pore diameter (14 nm) of barium sulfate-alumina is almost the same as that of the starting material γ-alumina A (15 nm) (see Table 4), and even when barium sulfate is added, the pore clogging is narrow. This suggests that gas diffusion in the barium sulfate-alumina particles is at the same level as that of γ-alumina.
（実施例４）
実施例２の硫酸バリウムＢの代わりに、結晶子径が１０μｍの硫酸バリウムＤを用いた他は実施例２と同様な方法で、実施例４の１５．２重量％硫酸バリウム−アルミナ １，０００ｇを得た。
次いで、実施例１と同様にして、実施例４の硫酸バリウム−アルミナ中の硫酸バリウムの物性を測定し、平均粒子径を図１に、分解温度を図１０にまとめた。また、実施例４の硫酸バリウム−アルミナのＥＰＭＡ粒子断面を図５に、造粒前の混合スラリーの粒度を表２に、ＢＥＴ比表面積、硫酸バリウムの分解温度を表３に、平均細孔径を表４に、Ｂａ−Ａｌ間の相関係数を図８に、硫酸バリウムの平均粒子径とＢＥＴ比表面積の低下率の関係を図９に、硫酸バリウムの分解温度との関係を図１０にまとめた。また、Ｂａ−Ａｌ間の相関係数とＢＥＴ比表面積の低下率の関係を図１１に、硫酸バリウムの分解温度との関係を図１２にまとめた。
（評価）
本発明の実施例４で得られた硫酸バリウム−アルミナは、その粒子内の硫酸バリウムの平均粒子径が５５０ｎｍ（図１及び表２参照）、アルミナの平均粒子径（モード径）が３．６μｍであって、ｄ５７．６（３．６μｍ）と一致し（表２参照）、実施例の中では比較的大きく（図１参照）、同粒子内のＢａ−Ａｌ間の相関係数も０．３４と、硫酸バリウムの粒子が大きくなった分、相関関係もやや低下した（図８参照）。この結果は、硫酸バリウムの粒子が大きくなると、硫酸バリウム−アルミナ粒子内での分散性がやや低下することを示している。
この様な状況にある実施例４の硫酸バリウム−アルミナは、モデルガスによる耐久処理前後におけるＢＥＴ比表面積の低下も３２．０％となり、実施例１よりやや悪化しており（表３参照）、硫酸バリウムの分散性が材料の熱耐久性を向上しうると考えられる。また、還元雰囲気下での硫酸バリウムの分解温度は８８９℃（表３参照）と実施例１よりやや高く、硫酸バリウムが分解しにくいことが分かる。それは、反応性に乏しい硫酸バリウムからＮＯｘの吸着材として機能するバリウムへの移行が実際のガソリンエンジン稼働下では他の実施例に比べやや劣ることが考えられる。さらに、硫酸バリウム−アルミナの平均細孔径（１５ｎｍ）も出発原料であるγ−アルミナＡ（同１５ｎｍ）と同じであり（表４参照）、硫酸バリウムを添加しても細孔の閉塞も狭小も起こらず、硫酸バリウム−アルミナ粒子内のガスの拡散はγ−アルミナと同レベルであることが示唆される。Example 4
The same procedure as in Example 2 was used except that barium sulfate D having a crystallite diameter of 10 μm was used instead of barium sulfate B in Example 2, and 1,000 g of 15.2 wt% barium sulfate-alumina in Example 4 was used. Got.
Subsequently, the physical properties of barium sulfate in barium sulfate-alumina of Example 4 were measured in the same manner as in Example 1, and the average particle diameter was summarized in FIG. 1 and the decomposition temperature was summarized in FIG. Moreover, the EPMA particle cross section of the barium sulfate-alumina of Example 4 is shown in FIG. 5, the particle size of the mixed slurry before granulation is shown in Table 2, the BET specific surface area, the decomposition temperature of barium sulfate in Table 3, and the average pore diameter Table 4 summarizes the correlation coefficient between Ba and Al, FIG. 8 summarizes the relationship between the average particle diameter of barium sulfate and the reduction rate of the BET specific surface area, and FIG. 10 summarizes the relationship between the decomposition temperature of barium sulfate and FIG. It was. FIG. 11 shows the relationship between the correlation coefficient between Ba—Al and the reduction rate of the BET specific surface area, and FIG. 12 shows the relationship between the decomposition temperature of barium sulfate.
(Evaluation)
In the barium sulfate-alumina obtained in Example 4 of the present invention, the average particle diameter of barium sulfate in the particles is 550 nm (see FIG. 1 and Table 2), and the average particle diameter (mode diameter) of alumina is 3.6 μm. It corresponds to d57.6 (3.6 μm) (see Table 2), is relatively large in the examples (see FIG. 1), and the correlation coefficient between Ba and Al in the particles is also 0. 34 and the correlation of the barium sulfate particles were slightly reduced (see FIG. 8). This result shows that the dispersibility in the barium sulfate-alumina particles is slightly reduced when the barium sulfate particles are enlarged.
In the barium sulfate-alumina of Example 4 in such a situation, the decrease in the BET specific surface area before and after the durability treatment with the model gas was also 32.0%, which is slightly worse than Example 1 (see Table 3). It is believed that the dispersibility of barium sulfate can improve the thermal durability of the material. Moreover, the decomposition temperature of barium sulfate in a reducing atmosphere is 889 ° C. (see Table 3), which is slightly higher than that of Example 1, and it can be seen that barium sulfate is difficult to decompose. It is conceivable that the transition from barium sulfate, which is poor in reactivity, to barium, which functions as an adsorbent for NOx, is slightly inferior to the other examples under actual gasoline engine operation. Further, the average pore diameter (15 nm) of barium sulfate-alumina is the same as that of the starting material γ-alumina A (15 nm) (see Table 4). Even if barium sulfate is added, the pores are blocked or narrowed. It does not occur, suggesting that the gas diffusion within the barium sulfate-alumina particles is at the same level as γ-alumina.
（実施例５）
ミリング装置でγ−アルミナ粉末Ａ ６００ｇと硫酸バリウムＢ ４００ｇを含むスラリーの粉砕処理を行ない、両方の混合物のメディアン径（ｄ５０）が５００ｎｍのアルミナ−硫酸バリウム分散スラリーを得た。この混合スラリーを実施例１と同様な方法で１５μｍまで造粒し、実施例５の４０重量％硫酸バリウム−アルミナ １，０００ｇを得た。
次いで、実施例１と同様にして、実施例５の硫酸バリウム−アルミナ中の硫酸バリウムの物性を測定し、平均粒子径を図１に、分解温度を図１０にまとめた。さらに、実施例５の硫酸バリウム−アルミナのＥＰＭＡ粒子断面図を図６に、造粒前の混合スラリーの粒度を表２に、ＢＥＴ比表面積、硫酸バリウムの分解温度を表３に、平均細孔径を表４に、Ｂａ−Ａｌ間の相関係数を図８に、硫酸バリウムの平均粒子径とＢＥＴ比表面積の低下率の関係を図９に、硫酸バリウムの分解温度との関係を図１０にまとめた。また、Ｂａ−Ａｌ間の相関係数とＢＥＴ比表面積の低下率の関係を図１１に、硫酸バリウムの分解温度との関係を図１２にまとめた。
（評価）
本発明の実施例５で得られた硫酸バリウム−アルミナは、その粒子内の硫酸バリウムの平均粒子径が８０ｎｍと、実施例３並みに非常に小さく（図１及び表２参照）、アルミナの平均粒子径（モード径）も０．７μｍ｛ｄ７０：硫酸バリウムの混合比率４０重量％とアルミナの混合比率６０重量％の場合、その１／２の値３０重量％と硫酸バリウム７０重量％を混合した時の粒度（０．６μｍ）とほぼ一致し（表２参照）、実施例２並に小さかった。さらに、同粒子内のＢａ−Ａｌ間の相関係数も０．９７と、極めて強い相関が見られた（図８参照）。これらの結果は、硫酸バリウムの非常に細かな微粒子が硫酸バリウム−アルミナ粒子内でほぼ均一に分散されていることを示している。
一方で、実施例５の硫酸バリウム−アルミナは、モデルガスによる耐久処理前後におけるＢＥＴ比表面積の低下は３４．４％と、硫酸バリウムの平均粒子径がほぼ同レベル（６５ｎｍ）の実施例３に比べかなり悪化している（表３参照）。これは、実施例５で得られた硫酸バリウム−アルミナ内の硫酸バリウムの混合比率が４０重量％と実施例３（同１５．２重量％）の２．６倍にもなっているため、硫酸バリウム自体のＢＥＴ比表面積が低下する影響によるものと考えられる。但し、還元雰囲気下での硫酸バリウムの分解温度は７８２℃（表３参照）と実施例３（同７５２℃）よりやや高い程度と非常に優れており、実施例５中の硫酸バリウムは実施例３同様、非常に分解しやすいことが分かる。これにより、反応性に乏しい硫酸バリウムからＮＯｘの吸着材として機能するバリウムへの移行が実際のガソリンエンジン稼働下でも非常に容易に起こると考えられ、優れた脱硝性能が期待される。さらに、硫酸バリウム−アルミナの平均細孔径（１４ｎｍ）も出発原料であるγ−アルミナＡ（同１５ｎｍ）とほぼ同等であり（表４参照）、硫酸バリウムを添加しても細孔の閉塞も狭小も起こらず、硫酸バリウム−アルミナ粒子内のガスの拡散はγ−アルミナと同レベルであると示唆される。(Example 5)
A slurry containing 600 g of γ-alumina powder A and 400 g of barium sulfate B was pulverized by a milling apparatus, and an alumina-barium sulfate dispersion slurry having a median diameter (d50) of both of the mixtures of 500 nm was obtained. This mixed slurry was granulated to 15 μm in the same manner as in Example 1 to obtain 1,000 g of 40 wt% barium sulfate-alumina of Example 5.
Subsequently, the physical properties of barium sulfate in barium sulfate-alumina of Example 5 were measured in the same manner as in Example 1, and the average particle diameter was summarized in FIG. 1 and the decomposition temperature was summarized in FIG. Further, FIG. 6 shows a cross-sectional view of the barium sulfate-alumina EPMA particles of Example 5, Table 2 shows the particle size of the mixed slurry before granulation, Table 3 shows the BET specific surface area, and the decomposition temperature of barium sulfate. Table 4 shows the correlation coefficient between Ba and Al, FIG. 8 shows the relationship between the average particle diameter of barium sulfate and the reduction rate of the BET specific surface area, and FIG. 10 shows the relationship between the decomposition temperature of barium sulfate and FIG. Summarized. FIG. 11 shows the relationship between the correlation coefficient between Ba—Al and the reduction rate of the BET specific surface area, and FIG. 12 shows the relationship between the decomposition temperature of barium sulfate.
(Evaluation)
In the barium sulfate-alumina obtained in Example 5 of the present invention, the average particle diameter of barium sulfate in the particles is 80 nm, which is very small as in Example 3 (see FIG. 1 and Table 2). The particle diameter (mode diameter) is also 0.7 μm {d70: when the mixing ratio of barium sulfate is 40% by weight and the mixing ratio of alumina is 60% by weight, a half value of 30% by weight and 70% by weight of barium sulfate are mixed. It almost coincided with the particle size (0.6 μm) of time (see Table 2) and was as small as Example 2. Furthermore, the correlation coefficient between Ba-Al in the same particle was also 0.97, showing a very strong correlation (see FIG. 8). These results indicate that very fine particles of barium sulfate are dispersed almost uniformly within the barium sulfate-alumina particles.
On the other hand, in the barium sulfate-alumina of Example 5, the decrease in the BET specific surface area before and after the endurance treatment with the model gas was 34.4%, and the average particle diameter of barium sulfate was almost the same level (65 nm). Compared to the table (see Table 3). This is because the mixing ratio of barium sulfate in the barium sulfate-alumina obtained in Example 5 is 40% by weight, which is 2.6 times that in Example 3 (15.2% by weight). This is considered to be due to the effect that the BET specific surface area of barium itself decreases. However, the decomposition temperature of barium sulfate in a reducing atmosphere is 782 ° C. (see Table 3), which is slightly higher than that of Example 3 (752 ° C.), and barium sulfate in Example 5 is an example. As with No. 3, it can be seen that it is very easy to decompose. As a result, the transition from barium sulfate, which is poor in reactivity, to barium, which functions as an adsorbent for NOx, is considered to occur very easily even under actual gasoline engine operation, and excellent denitration performance is expected. Furthermore, the average pore diameter (14 nm) of barium sulfate-alumina is almost the same as that of the starting material γ-alumina A (15 nm) (see Table 4), and even when barium sulfate is added, the pore clogging is narrow. This suggests that the gas diffusion in the barium sulfate-alumina particles is at the same level as that of γ-alumina.
（比較例１）
上記実施例に対して、γ−アルミナ粉末Ａ ８４８ｇと硫酸バリウムＢ １５２ｇを乾式ミキサーにて１０分程度混合して、比較例１の硫酸バリウムとγ―アルミナ混合物 １，０００ｇを得た。
次いで、実施例１と同様にして、比較例１の硫酸バリウム−アルミナ中の硫酸バリウムの物性を測定し、平均粒子径を図１に、分解温度を図１０にまとめた。また、実施例２の硫酸バリウム−アルミナのＥＰＭＡ粒子断面図を図７に、造粒前の混合スラリーの粒度を表２に、ＢＥＴ比表面積、硫酸バリウムの分解温度を表３に、Ｂａ−Ａｌ間の相関係数を図８に、硫酸バリウムの平均粒子径とＢＥＴ比表面積の低下率の関係を図９に、硫酸バリウムの分解温度との関係を図１０にまとめた。また、Ｂａ−Ａｌ間の相関係数と、硫酸バリウムの平均粒子径の関係を図１１に、ＢＥＴ比表面積の低下率との関係を図１２にまとめた。
（評価）
比較例１で得られた硫酸バリウム−アルミナは、その粒子内の硫酸バリウムの平均分散粒子径が１，０００ｎｍとなり（図１及び表２参照）、アルミナの平均粒子径（モード径）は３４．４μｍであって、ｄ５７．６（３４．６μｍ）とほぼ一致し（表２参照）、大きいままで存在した。さらに、同粒子内のＢａ−Ａｌ間の相関係数も−０．５６と比較的強い負の相関が見られた（図８参照）。この結果は、硫酸バリウム粒子が大きいままで、しかも、硫酸バリウム−アルミナ粒子内で、ほとんど分散しておらず個別に存在していることを示している。
この様な状況にある比較例１の硫酸バリウム−アルミナは、モデルガスによる耐久処理前後におけるＢＥＴ比表面積の低下率が４１．２％であり（表３参照）、触媒の材料として使用される場合、耐久性能に問題を生じる恐れがある。また、モデルガスによる還元雰囲気下での硫酸バリウムの分解温度は９３２℃（表３参照）と高く、硫酸バリウムが分解し難いことが分かる。つまり、反応性に乏しい硫酸バリウムからＮＯｘの吸着材として機能するバリウムへの移行が実際のガソリンエンジン稼働下では起こり難い恐れがあり、Ｂａ添加によりＮＯｘ浄化性能の向上があまり期待できない。
(Comparative Example 1)
848 g of γ-alumina powder A and 152 g of barium sulfate B were mixed with a dry mixer for about 10 minutes to obtain 1,000 g of the barium sulfate and γ-alumina mixture of Comparative Example 1.
Subsequently, the physical properties of barium sulfate in barium sulfate-alumina of Comparative Example 1 were measured in the same manner as in Example 1. The average particle diameter was summarized in FIG. 1 and the decomposition temperature was summarized in FIG. Moreover, the EPMA particle sectional view of barium sulfate-alumina of Example 2 is shown in FIG. 7, the particle size of the mixed slurry before granulation is shown in Table 2, the BET specific surface area, the decomposition temperature of barium sulfate in Table 3, and Ba-Al FIG. 8 shows the correlation coefficient between them, FIG. 9 shows the relationship between the average particle diameter of barium sulfate and the reduction rate of the BET specific surface area, and FIG. 10 shows the relationship between the decomposition temperature of barium sulfate. Further, the relationship between the correlation coefficient between Ba-Al and the average particle diameter of barium sulfate is summarized in FIG. 11, and the relationship between the reduction rate of the BET specific surface area is summarized in FIG.
(Evaluation)
The barium sulfate-alumina obtained in Comparative Example 1 has an average dispersed particle diameter of barium sulfate in the particles of 1,000 nm (see FIG. 1 and Table 2), and the average particle diameter (mode diameter) of alumina is 34. It was 4 μm, almost coincident with d57.6 (34.6 μm) (see Table 2), and remained large. Furthermore, the correlation coefficient between Ba-Al in the same particle was -0.56, which was a relatively strong negative correlation (see FIG. 8). This result shows that the barium sulfate particles remain large and are present in the barium sulfate-alumina particles with little dispersion and exist individually.
The barium sulfate-alumina of Comparative Example 1 in such a situation has a reduction rate of the BET specific surface area of 41.2% before and after the durability treatment with the model gas (see Table 3), and is used as a catalyst material. There is a risk of causing problems in durability performance. In addition, the decomposition temperature of barium sulfate in a reducing atmosphere with model gas is as high as 932 ° C. (see Table 3), and it can be seen that barium sulfate is difficult to decompose. That is, there is a risk that the transition from barium sulfate, which has poor reactivity, to barium that functions as an adsorbent for NOx may hardly occur under actual gasoline engine operation, and the addition of Ba cannot be expected to improve the NOx purification performance.
（実施例６）
下記の要領で、Ｐｄ担持ＢａＳＯ４−Ａｌ２Ｏ３、Ｐｄ担持Ａｌ２Ｏ３、及びＰｄ担持ＣｅＯ２−ＺｒＯ２系複合酸化物を調製し、種々の状態の硫酸バリウムと組み合わせることで、酸素吸蔵放出能力（ＯＳＣ容量）がどの様に変化するかを測定した。
＜Ｐｄ担持ＢａＳＯ４−Ａｌ２Ｏ３＞
硝酸パラジウム溶液をＰｄ重量で１．２ｇ量り取り、純水で希釈して、実施例５の４０重量％硫酸バリウム−アルミナ ５０ｇに含浸担持した。この含水粉末を５００℃、１時間かけて空気中で焼成することで、２．３４重量％Ｐｄ担持硫酸バリウム―アルミナａを調製した。
＜Ｐｄ担持Ａｌ２Ｏ３＞
硝酸パラジウム溶液をＰｄ重量で１．２ｇ量り取り、純水で希釈して、γ−アルミナ粉末Ａ ５０ｇに含浸担持した。この含水粉末を５００℃、１時間かけて空気中で焼成することで、２．３４重量％Ｐｄ担持アルミナｂを調製した。
＜Ｐｄ担持ＣｅＯ２−ＺｒＯ２系複合酸化物＞
硝酸パラジウム溶液をＰｄ重量で０．８ｇ量り取り、純水で希釈して、ＢＥＴ比表面積７０ｍ２／ｇ、平均細孔径１６ｎｍの４５．０重量％セリア−５．０重量％酸化ランタン−５０．０重量％ジルコニア複合酸化物粉末Ｅ ８０ｇに含浸担持した。この含水粉末を５００℃、１時間かけて空気中で焼成することで、０．９９重量％Ｐｄ担持セリア−ジルコニア系複合酸化物ｃを調製した。
この０．９９重量％Ｐｄ担持セリア−ジルコニア系複合酸化物ｃ ８．０８ｇに、２．３４重量％Ｐｄ担持アルミナｂと２．３４重量％Ｐｄ担持硫酸バリウム―アルミナａを合計で５．１２ｇになるように３水準（３．８４ｇ＋１．２８ｇ、２．５６ｇ＋２．５６ｇ、０．０ｇ＋５．１２ｇ）振って加え、乳鉢と乳棒でよく混合し、実施例６の３水準のＯＳＣ容量測定用サンプル（硫酸バリウム含有量：３．８重量％、７．６重量％、１５．２重量％）を製造した。
また、ＯＳＣ容量の基準サンプルとして、硫酸バリウムを含まないサンプル（０．９９重量％Ｐｄ担持セリア−ジルコニア系複合酸化物ｃ ８．０８ｇと２．３４重量％Ｐｄ担持アルミナｂ ５．１２ｇの物理的混合物）も製造した。
次いで、実施例６の３水準のＰｄ担持Ａｌ２Ｏ３、Ｐｄ担持ＣｅＯ２−ＺｒＯ２系複合酸化物、及びＰｄ担持ＢａＳＯ４−Ａｌ２Ｏ３の物理的混合物とＰｄ担持Ａｌ２Ｏ３及びＰｄ担持ＣｅＯ２−ＺｒＯ２系複合酸化物の物理的混合物のＯＳＣ容量を各々測定し、両者の差異を図１３にまとめた。
（ＯＳＣ量の増減）
図１３を参照すると、実施例６のＰｄ担持Ａｌ２Ｏ３、Ｐｄ担持ＣｅＯ２−ＺｒＯ２系複合酸化物、及びＰｄ担持ＢａＳＯ４−Ａｌ２Ｏ３の物理的混合物は硫酸バリウムを含まないＰｄ担持Ａｌ２Ｏ３及びＰｄ担持ＣｅＯ２−ＺｒＯ２系複合酸化物の物理的混合物に比べ、ＢａＳＯ４含有量が９重量％以下ではＯＳＣの量は硫酸バリウムを含まない物を上回っている。また、ＢａＳＯ４含有量が９重量％を超えるとＯＳＣの量が硫酸バリウムの影響により硫酸バリウムを含まない物を下回るものの、減少量が約２０μｍｏｌ／ｇ以内とその影響は軽微といえる。
この結果から、本発明の硫酸バリウム−アルミナが、ＯＳＣと物理的混合している程度であれば、硫酸バリウムがＯＳＣに及ぼす悪影響は軽微であると考えられる。(Example 6)
In the following manner, Pd-supported BaSO 4 —Al 2 O 3 , Pd-supported Al 2 O 3 , and Pd-supported CeO 2 —ZrO 2 -based composite oxides were prepared and combined with barium sulfate in various states. It was measured how the occlusion / release capacity (OSC capacity) changes.
<Pd supported BaSO 4 -Al 2 O 3>
A palladium nitrate solution was weighed 1.2 g by Pd weight, diluted with pure water, and impregnated and supported on 50 g of 40 wt% barium sulfate-alumina of Example 5. This water-containing powder was fired in air at 500 ° C. for 1 hour to prepare 2.34 wt% Pd-supported barium sulfate-alumina a.
<Pd-supported Al 2 O 3 >
A palladium nitrate solution was weighed 1.2 g by Pd weight, diluted with pure water, and impregnated and supported on 50 g of γ-alumina powder A. This hydrous powder was fired in air at 500 ° C. for 1 hour to prepare 2.34 wt% Pd-supported alumina b.
<Pd-supported CeO 2 —ZrO 2 -based composite oxide>
A palladium nitrate solution was weighed out by 0.8 g in terms of Pd weight, diluted with pure water, and 45.0 wt% ceria-5.0 wt% lanthanum oxide having a BET specific surface area of 70 m 2 / g and an average pore diameter of 16 nm-50. It was impregnated and supported on 80 g of 0 wt% zirconia composite oxide powder E. The hydrated powder was fired in air at 500 ° C. for 1 hour to prepare a 0.99 wt% Pd-supported ceria-zirconia composite oxide c.
A total of 5.12 g of 2.34 wt% Pd-supported alumina b and 2.34 wt% Pd-supported barium sulfate-alumina a was added to 8.08 g of the 0.99 wt% Pd-supported ceria-zirconia composite oxide c. Add 3 levels (3.84 g + 1.28 g, 2.56 g + 2.56 g, 0.0 g + 5.12 g) by shaking and mix well with a mortar and pestle. Sample for measuring OSC capacity of Example 6 (sulfuric acid) Barium content: 3.8 wt%, 7.6 wt%, 15.2 wt%).
As a reference sample for the OSC capacity, a sample containing no barium sulfate (8.08 g of 0.99 wt% Pd-supported ceria-zirconia-based composite oxide c and 2.12 g of Pd-supported alumina b 5.12 g was physically used. A mixture) was also produced.
Next, a physical mixture of the three levels of Pd-supported Al 2 O 3 , Pd-supported CeO 2 —ZrO 2 -based composite oxide, and Pd-supported BaSO 4 —Al 2 O 3 and Pd-supported Al 2 O 3 in Example 6 and The OSC capacities of the physical mixtures of Pd-supported CeO 2 —ZrO 2 -based composite oxides were measured, and the differences between the two were summarized in FIG.
(Increase / decrease OSC amount)
Referring to FIG. 13, the physical mixture of Pd-supported Al 2 O 3 , Pd-supported CeO 2 —ZrO 2 -based composite oxide, and Pd-supported BaSO 4 —Al 2 O 3 in Example 6 is Pd free of barium sulfate. Compared with a physical mixture of supported Al 2 O 3 and Pd-supported CeO 2 —ZrO 2 -based composite oxide, the amount of OSC exceeds that containing no barium sulfate when the BaSO 4 content is 9% by weight or less. Further, when the BaSO 4 content exceeds 9% by weight, the amount of OSC is less than that containing no barium sulfate due to the effect of barium sulfate, but the decrease is within about 20 μmol / g, and the effect is slight.
From this result, if the barium sulfate-alumina of the present invention is physically mixed with OSC, it is considered that the adverse effect of barium sulfate on OSC is slight.
（比較例２）
酢酸バリウム結晶を硫酸バリウム換算で２水準（０．５ｇ、２．０ｇ）秤量した後、純水に溶解して、酢酸バリウム水溶液を２種類調製した。実施例６に対して、２．３６重量％Ｐｄ担持硫酸バリウム―アルミナａを用いず、０．９９重量％Ｐｄ担持セリア−ジルコニア系複合酸化物ｃ ８．０８ｇ、２．３４重量％Ｐｄ担持アルミナｂ ５．１２ｇを純水に分散させ、そこに先ほどの２種類の酢酸バリウム水溶液を各々添加し、３０分ほど撹拌してバリウムをアルミナに吸着させた。さらに、このバリウム、Ｐｄ担持アルミナ、及びＰｄ担持セリア−ジルコニア系複合酸化物を含む懸濁液に、硫酸アンモニウム（０．２６ｇ、１．０４ｇ）を純水に溶解させた水溶液を３０分ほど撹拌しながら添加し（Ｓ／Ｂａ比＝１．０）、硫酸バリウムを析出させた遠心分離器にて固形分を回収後、５００℃、１時間かけて空気中で焼成することで、比較例２の２水準のＯＳＣ容量測定用サンプル（硫酸バリウム含有量：３．６重量％、１３．２重量％）を製造した。
次いで、比較例２の２水準のＰｄ担持Ａｌ２Ｏ３及びＰｄ担持ＣｅＯ２−ＺｒＯ２系複合酸化物に硫酸バリウムを含浸担持した物のＯＳＣ容量を測定し、Ｐｄ担持Ａｌ２Ｏ３及びＰｄ担持ＣｅＯ２−ＺｒＯ２系複合酸化物の物理的混合物のＯＳＣ容量との差異を図１３にまとめた。
（ＯＳＣ量の増減）
図１３を参照すると、比較例２のＰｄ担持Ａｌ２Ｏ３及びＰｄ担持ＣｅＯ２−ＺｒＯ２系複合酸化物に硫酸バリウムを含浸担持した物は、硫酸バリウムを含まないＰｄ担持Ａｌ２Ｏ３及びＰｄ担持ＣｅＯ２−ＺｒＯ２系複合酸化物の物理的混合物に比べ、ＯＳＣの減少量が約７５μｍｏｌ／ｇと著しく小さい上、硫酸バリウムの含有量とは無関係に一定であった。
この結果は、硫酸バリウムが、ＯＳＣに直接担持されると、ＯＳＣの能力が極端に悪化することを示唆している。(Comparative Example 2)
The barium acetate crystals were weighed in two levels (0.5 g, 2.0 g) in terms of barium sulfate and then dissolved in pure water to prepare two types of barium acetate aqueous solutions. For Example 6, without using 2.36 wt% Pd-supported barium sulfate-alumina a, 0.99 wt% Pd-supported ceria-zirconia composite oxide c 8.08 g, 2.34 wt% Pd-supported alumina b 5.12 g was dispersed in pure water, and the two kinds of the aqueous barium acetate solution were added thereto, and stirred for about 30 minutes to adsorb barium onto alumina. Further, an aqueous solution in which ammonium sulfate (0.26 g, 1.04 g) was dissolved in pure water was stirred for 30 minutes in a suspension containing the barium, Pd-supported alumina, and Pd-supported ceria-zirconia composite oxide. (S / Ba ratio = 1.0), and after collecting the solid content in a centrifugal separator in which barium sulfate was deposited, the mixture was calcined in the air at 500 ° C. for 1 hour. Samples for measuring OSC capacity at two levels (barium sulfate content: 3.6% by weight, 13.2% by weight) were produced.
Next, the OSC capacity of the two-level Pd-supported Al 2 O 3 and Pd-supported CeO 2 —ZrO 2 composite oxide impregnated and supported in Comparative Example 2 was measured, and Pd-supported Al 2 O 3 and Pd were measured. The difference from the OSC capacity of the physical mixture of the supported CeO 2 —ZrO 2 composite oxide is summarized in FIG.
(Increase / decrease OSC amount)
Referring to FIG. 13, the Pd-supported Al 2 O 3 and the Pd-supported CeO 2 —ZrO 2 -based composite oxide of Comparative Example 2 impregnated and supported with barium sulfate are Pd-supported Al 2 O 3 not containing barium sulfate and Compared with the physical mixture of Pd-supported CeO 2 —ZrO 2 -based composite oxide, the decrease in OSC was extremely small, about 75 μmol / g, and was constant regardless of the barium sulfate content.
This result suggests that the ability of OSC is extremely deteriorated when barium sulfate is directly supported on OSC.
（比較例３）
実施例６に対して、２．３６重量％Ｐｄ担持硫酸バリウム―アルミナａを用いず、０．９９重量％Ｐｄ担持セリア−ジルコニア系複合酸化物ｃ ８．０８ｇ、２．３４重量％Ｐｄ担持アルミナｂ ５．１２ｇに硫酸バリウムＢを３水準（０．５ｇ、１．０ｇ、２．０ｇ）振って加え、乳鉢と乳棒でよく混合し、比較例３の３水準のＯＳＣ容量測定用サンプル（硫酸バリウム含有量：３．６重量％、７．０重量％、１３．２重量％）を製造した。
次いで、比較例３の３水準のＰｄ担持Ａｌ２Ｏ３、Ｐｄ担持ＣｅＯ２−ＺｒＯ２系複合酸化物、及びＢａＳＯ４の物理的混合物のＯＳＣ容量を測定し、Ｐｄ担持Ａｌ２Ｏ３及びＰｄ担持ＣｅＯ２−ＺｒＯ２系複合酸化物の物理的混合物のＯＳＣ容量との差異を図１３にまとめた。
（ＯＳＣ量の増減）
図１３を参照すると、比較例３のＰｄ担持Ａｌ２Ｏ３、Ｐｄ担持ＣｅＯ２−ＺｒＯ２系複合酸化物、及びＢａＳＯ４の物理的混合物は、硫酸バリウムを含まないＰｄ担持Ａｌ２Ｏ３及びＰｄ担持ＣｅＯ２−ＺｒＯ２系複合酸化物の物理的混合物に比べ、ＢａＳＯ４含有量が３重量％以下では、ＯＳＣの量が硫酸バリウムを含まない物を上回っている。また、ＢａＳＯ４含有量が３重量％を超えると、ＯＳＣの量は硫酸バリウムの影響により硫酸バリウムを含まない物を下回る上、ＯＳＣの量は減少量が約１３０μｍｏｌ／ｇまで急激に減少している。(Comparative Example 3)
For Example 6, without using 2.36 wt% Pd-supported barium sulfate-alumina a, 0.99 wt% Pd-supported ceria-zirconia composite oxide c 8.08 g, 2.34 wt% Pd-supported alumina b Add barium sulfate B to 5.12 g by shaking at 3 levels (0.5 g, 1.0 g, 2.0 g), mix well with a mortar and pestle, and sample for OSC capacity measurement of 3 levels of Comparative Example 3 (sulfuric acid Barium content: 3.6 wt%, 7.0 wt%, 13.2 wt%).
Subsequently, the OSC capacity of the physical mixture of the three levels of Pd-supported Al 2 O 3 , Pd-supported CeO 2 —ZrO 2 -based composite oxide, and BaSO 4 of Comparative Example 3 was measured, and Pd-supported Al 2 O 3 and Pd The difference from the OSC capacity of the physical mixture of the supported CeO 2 —ZrO 2 composite oxide is summarized in FIG.
(Increase / decrease OSC amount)
Referring to FIG. 13, Pd-loaded Al 2 O 3, Pd-supported CeO 2 -ZrO 2 -based composite oxide of Comparative Example 3, and physical mixtures of BaSO 4 is and Pd supported Al 2 O 3 does not contain barium sulfate Compared with the physical mixture of Pd-supported CeO 2 —ZrO 2 -based composite oxide, the amount of OSC exceeds that containing no barium sulfate when the BaSO 4 content is 3% by weight or less. When the BaSO 4 content exceeds 3% by weight, the amount of OSC falls below that which does not contain barium sulfate due to the effect of barium sulfate, and the amount of OSC decreases rapidly to about 130 μmol / g. Yes.
（実施例７）
下記の要領で、Ｐｄ担持Ａｌ２Ｏ３、Ｐｄ担持ＣｅＯ２−ＺｒＯ２系複合酸化物、Ｐｄ担持ＢａＳＯ４−Ａｌ２Ｏ３、及びＰｄ担持Ｎｄ２Ｏ３−ＺｒＯ２を調製した。
＜Ｐｄ担持Ａｌ２Ｏ３＞
硝酸パラジウム溶液をＰｄ重量で１．８４ｇ量り取り、純水で希釈して、γ−アルミナ粉末Ａ ４００ｇに含浸担持した。この含水粉末を５００℃、１時間かけて空気中で焼成することで、０．４５８重量％Ｐｄ担持アルミナｄを調製した。
＜Ｐｄ担持ＣｅＯ２−ＺｒＯ２系複合酸化物＞
硝酸パラジウム溶液をＰｄ重量で１．３５ｇ量り取り、純水で希釈して、セリア−酸化ランタン−ジルコニア複合酸化物粉末Ｅ ４００ｇに含浸担持した。この含水粉末を５００℃、１時間かけて空気中で焼成することで、０．３３６重量％Ｐｄ担持セリア−ジルコニア系複合酸化物ｅを調製した。
＜Ｐｄ担持ＢａＳＯ４−Ａｌ２Ｏ３＞
硝酸パラジウム溶液をＰｄ重量で１．７６ｇ量り取り、純水で希釈して、実施例１の硫酸バリウム−アルミナ ２００ｇに含浸担持した。この含水粉末を５００℃、１時間かけて空気中で焼成することで、０．８７重量％Ｐｄ担持硫酸バリウム―アルミナｆを調製した。
また、硝酸パラジウム溶液をＰｄ重量で３．６ｇ、実施例１の硫酸バリウム−アルミナを４５０ｇ用いて同様の処理を行うことにより、０．７９４重量％Ｐｄ担持硫酸バリウム―アルミナｇを調製した。
＜Ｐｄ担持Ｎｄ２Ｏ３−ＺｒＯ２＞
硝酸パラジウム溶液をＰｄ重量で３．６ｇ量り取り、純水で希釈して、ＢＥＴ比表面積６５ｍ２／ｇ、平均細孔径２５ｎｍの１５重量％酸化ネオジム−５重量％酸化ランタン−８０重量％ジルコニア複合酸化物粉末Ｆ ５５０ｇに含浸担持した。この含水粉末を５００℃、１時間かけて空気中で焼成することで、０．６５重量％Ｐｄ担持酸化ネオジム−ジルコニア系複合酸化物ｈを調製した。(Example 7)
Pd-supported Al 2 O 3 , Pd-supported CeO 2 —ZrO 2 -based composite oxide, Pd-supported BaSO 4 —Al 2 O 3 , and Pd-supported Nd 2 O 3 —ZrO 2 were prepared in the following manner.
<Pd-supported Al 2 O 3 >
A palladium nitrate solution was weighed 1.84 g by weight of Pd, diluted with pure water, and impregnated on 400 g of γ-alumina powder A. The water-containing powder was fired in air at 500 ° C. for 1 hour to prepare 0.458 wt% Pd-supported alumina d.
<Pd-supported CeO 2 —ZrO 2 -based composite oxide>
A palladium nitrate solution was weighed 1.35 g in terms of Pd weight, diluted with pure water, and impregnated and supported on 400 g of ceria-lanthanum oxide-zirconia composite oxide powder E. The hydrous powder was fired in air at 500 ° C. for 1 hour to prepare 0.336 wt% Pd-supported ceria-zirconia composite oxide e.
<Pd supported BaSO 4 -Al 2 O 3>
The palladium nitrate solution was weighed 1.76 g by Pd weight, diluted with pure water, and impregnated and supported on 200 g of barium sulfate-alumina of Example 1. This hydrous powder was fired in air at 500 ° C. for 1 hour to prepare 0.87 wt% Pd-supported barium sulfate-alumina f.
Further, the same treatment was carried out using 3.6 g of palladium nitrate solution by weight of Pd and 450 g of barium sulfate-alumina of Example 1 to prepare 0.794 wt% Pd-supported barium sulfate-alumina g.
<Pd-supported Nd 2 O 3 —ZrO 2 >
3.6 g of palladium nitrate solution was weighed out by Pd weight, diluted with pure water, and 15 wt% neodymium oxide-5 wt% lanthanum oxide-80 wt% zirconia composite with a BET specific surface area of 65 m 2 / g and an average pore diameter of 25 nm. The oxide powder F was impregnated and supported on 550 g. The water-containing powder was fired in air at 500 ° C. for 1 hour to prepare 0.65 wt% Pd-supported neodymium oxide-zirconia composite oxide h.
次に、これらの材料を用いて、下記の要領でコージェライト製ハニカム担体に二層に塗布し、本発明の触媒（床下触媒）を得た。
＜床下触媒の下層＞
０．４５８重量％Ｐｄ担持アルミナｄ ４００．２３ｇ、０．３３６重量％Ｐｄ担持セリア−ジルコニア系複合酸化物ｅ ４０１．３５ｇ、０．８７重量％Ｐｄ担持硫酸バリウム―アルミナｆ ２００．２２ｇに純水を加え、ポットミルで混合粉砕してスラリーを調製した。このスラリーを容積１．０Ｌのコージェライト製ハニカム担体｛（４００セル／ｉｎｃｈ２（６２０ｋ／ｍ２）、３．５ミル（０．０８９ｍｍ）｝に所定量塗布し、８０℃、２０分かけて乾燥後、４５０℃で１時間焼成を行ない、実施例６の床下触媒の下層（触媒重量：１００．１８ｇ／Ｌ、Ｐｄ：０．４９ｇ／Ｌ）を得た。
＜床下触媒の上層＞
０．６５重量％Ｐｄ担持酸化ネオジム−ジルコニア系複合酸化物ｈ ５５３．６ｇ、０．７９４重量％Ｐｄ担持硫酸バリウム―アルミナｇ ４５３．６ｇ、アルミナゾル（アルミナ換算で５ｇ）に純水を加え、ポットミルで混合粉砕してスラリーを調製した。このスラリーを上記床下触媒の下層をコートしたハニカム担体に塗布して、実施例６の床下触媒の上層（触媒重量：１０１．２２ｇ／Ｌ、Ｐｄ：０．７２ｇ／Ｌ）を得た。
以上の一連の触媒調製法により、実施例７の床下触媒（触媒総重量：２０１．４ｇ／Ｌ、Ｐｄ：１．２１ｇ／Ｌ）を得た。Next, using these materials, a cordierite honeycomb carrier was applied in two layers in the following manner to obtain a catalyst of the present invention (underfloor catalyst).
<Lower layer of underfloor catalyst>
0.458 wt% Pd-supported alumina d 400.23 g, 0.336 wt% Pd-supported ceria-zirconia composite oxide e 401.35 g, 0.87 wt% Pd-supported barium sulfate-alumina f 200.22 g pure water And mixed and pulverized with a pot mill to prepare a slurry. A predetermined amount of this slurry is applied to a cordierite honeycomb carrier {(400 cells / inch 2 (620 k / m 2 ), 3.5 mil (0.089 mm)}) having a volume of 1.0 L, and the slurry is applied at 80 ° C. for 20 minutes. After drying, calcination was performed at 450 ° C. for 1 hour to obtain a lower layer (catalyst weight: 100.18 g / L, Pd: 0.49 g / L) of the underfloor catalyst of Example 6.
<Upper layer of underfloor catalyst>
Add pure water to 553.6 g of 0.65 wt% Pd-supported neodymium oxide-zirconia composite oxide h, 0.794 wt% Pd-supported barium sulfate-alumina g 453.6 g, alumina sol (5 g in terms of alumina), A slurry was prepared by mixing and pulverizing. This slurry was applied to a honeycomb carrier coated with the lower layer of the underfloor catalyst to obtain an upper layer (catalyst weight: 101.22 g / L, Pd: 0.72 g / L) of the underfloor catalyst of Example 6.
The underfloor catalyst of Example 7 (total catalyst weight: 201.4 g / L, Pd: 1.21 g / L) was obtained by the above series of catalyst preparation methods.
（触媒性能）
上記の床下触媒を下記の要領で調製した直下触媒と共に、各々を触媒コンバーター内に格納した後、耐久用ガソリンエンジンの排気システム内の直下位置、床下位置に各々のコンバーターを設置し、直下触媒は触媒床温度を９５０℃にして１５０時間、床下触媒は触媒床温度を８００℃にして５０時間耐久した。
その後、評価用車両の排気システムの直下位置、床下位置に各々の耐久処理済みコンバーターを設置し、走行モードＬＡ−４にて評価を行った。図１４はＬＡ−４モード走行時の加速領域の平均ＮＯｘ浄化率を示している。本発明の硫酸バリウム−アルミナを用いた床下触媒は８０．４％という高い脱硝性能を発揮した。
（直下触媒）
まず、下記の要領で、Ｐｄ担持Ａｌ２Ｏ３、Ｐｄ担持ＣｅＯ２−ＺｒＯ２系複合酸化物、Ｐｄ担持Ｎｄ２Ｏ３−ＺｒＯ２を調製し、次にこれらをハニカム担体に被覆し触媒層を形成した。
＜Ｐｄ担持Ａｌ２Ｏ３＞
硝酸パラジウム溶液をＰｄ重量で１２．０ｇ量り取り、純水で希釈して、γ−アルミナ粉末Ａ ３００ｇに含浸担持した。この含水粉末を５００℃、１時間空気中で焼成することで、３．８５重量％Ｐｄ担持アルミナｉを調製した。
また、硝酸パラジウム溶液をＰｄ重量で８．０ｇ、アルミナ粉末Ａを４００ｇ用いて同様の処理を行うことにより、１．９６重量％Ｐｄ担持アルミナｊを調製した。
＜Ｐｄ担持ＣｅＯ２−ＺｒＯ２系複合酸化物＞
硝酸パラジウム溶液をＰｄ重量で８．０ｇ量り取り、純水で希釈して、セリア−ジルコニア系複合酸化物粉末Ｃ １，２００ｇに含浸担持した。この含水粉末を５００℃、１時間空気中で焼成することで、０．６６２重量％Ｐｄ担持セリア−ジルコニア系複合酸化物ｋを調製した。
＜Ｐｄ担持Ｎｄ２Ｏ３−ＺｒＯ２＞
硝酸パラジウム溶液をＰｄ重量で８．０ｇ量り取り、純水で希釈して、酸化ネオジム−ジルコニア系複合酸化物粉末Ｆ ４００ｇに含浸担持した。この含水粉末を５００℃、１時間空気中で焼成することで、１．９６重量％Ｐｄ担持酸化ネオジム−ジルコニア系複合酸化物ｌを調製した。
＜直下触媒の下層＞
３．８５重量％Ｐｄ担持アルミナｉ ３１２ｇ、０．６６２重量％Ｐｄ担持セリア−ジルコニア系複合酸化物ｋ １，２０８ｇ、硫酸バリウム １００ｇに純水を加え、ポットミルで混合粉砕してスラリーを調製した。容積１．０Ｌのコージェライト製ハニカム担体｛（４００セル／ｉｎｃｈ２（６２０ｋ／ｍ２）、３．５ミル（０．０８９ｍｍ）｝にこのスラリーを所定量コーティングし、８０℃、２０分乾燥後、４５０℃１時間の焼成を行ない、直下触媒下層（触媒重量：１６２．０ｇ／Ｌ、Ｐｄ：２．０ｇ／Ｌ）を得た。
＜直下触媒の上層＞
１．９６重量％Ｐｄ担持酸化ネオジム−ジルコニア系複合酸化物ｌ ４０８ｇ、１．９６重量％Ｐｄ担持アルミナｊ ４０８ｇ、アルミナゾル（アルミナ換算で３５ｇ）に純水を加え、ポットミルで混合粉砕してスラリーを調製した。このスラリーを上記床下触媒の下層をコートしたハニカム担体にコーティングして、直下触媒上層（触媒重量：８５．１ｇ／Ｌ、Ｐｄ：１．６ｇ／Ｌ）を得た。
この様な一連の触媒調製法により、直下触媒（触媒総重量：２４７．１ｇ／Ｌ、Ｐｄ：３．６ｇ／Ｌ）を得た。(Catalyst performance)
After storing each of the above underfloor catalysts in the catalyst converter together with the direct catalyst prepared in the following manner, each converter is installed at the position directly below the floor in the exhaust system of the durable gasoline engine. The catalyst bed temperature was set at 950 ° C. for 150 hours, and the underbed catalyst was set at a catalyst bed temperature of 800 ° C. for 50 hours.
Thereafter, each endurance-treated converter was installed immediately below the exhaust system of the vehicle for evaluation and below the floor, and the evaluation was performed in the driving mode LA-4. FIG. 14 shows the average NOx purification rate in the acceleration region during the LA-4 mode traveling. The underfloor catalyst using the barium sulfate-alumina of the present invention exhibited a high denitration performance of 80.4%.
(Direct catalyst)
First, Pd-supported Al 2 O 3 , Pd-supported CeO 2 —ZrO 2 -based composite oxide, and Pd-supported Nd 2 O 3 —ZrO 2 were prepared in the following manner, and then these were coated on a honeycomb support to form a catalyst layer. Formed.
<Pd-supported Al 2 O 3 >
A palladium nitrate solution was weighed 12.0 g by weight of Pd, diluted with pure water, and impregnated and supported on 300 g of γ-alumina powder A. This hydrous powder was fired in air at 500 ° C. for 1 hour to prepare 3.85 wt% Pd-supported alumina i.
Further, the same treatment was performed using 8.0 g of palladium nitrate solution by Pd weight and 400 g of alumina powder A to prepare 1.96 wt% Pd-supported alumina j.
<Pd-supported CeO 2 —ZrO 2 -based composite oxide>
8.0 g of palladium nitrate solution was weighed out by weight of Pd, diluted with pure water, and impregnated and supported on 1,200 g of ceria-zirconia composite oxide powder C. The water-containing powder was fired in air at 500 ° C. for 1 hour to prepare 0.662 wt% Pd-supported ceria-zirconia composite oxide k.
<Pd-supported Nd 2 O 3 —ZrO 2 >
8.0 g of palladium nitrate solution was weighed out by weight of Pd, diluted with pure water, and impregnated and supported on 400 g of neodymium oxide-zirconia composite oxide powder F. The hydrous powder was fired in air at 500 ° C. for 1 hour to prepare 1.96 wt% Pd-supported neodymium oxide-zirconia composite oxide l.
<Lower layer of the direct catalyst>
Pure water was added to 3.85 wt% Pd-supported alumina i 312 g, 0.662 wt% Pd-supported ceria-zirconia composite oxide k 1,208 g, and barium sulfate 100 g, and the mixture was pulverized in a pot mill to prepare a slurry. A predetermined amount of this slurry was coated on a cordierite honeycomb carrier {(400 cells / inch 2 (620 k / m 2 ), 3.5 mil (0.089 mm)}) having a volume of 1.0 L, and dried at 80 ° C. for 20 minutes. And calcination at 450 ° C. for 1 hour to obtain a catalyst layer immediately below (catalyst weight: 162.0 g / L, Pd: 2.0 g / L).
<Upper layer of catalyst directly below>
Pure water is added to 408 g of 1.96 wt% Pd-supported neodymium oxide-zirconia composite oxide l 408 g, 1.96 wt% Pd-supported alumina j 408 g, alumina sol (35 g in terms of alumina), and the mixture is pulverized and mixed in a pot mill. Prepared. The slurry was coated on a honeycomb carrier coated with the lower layer of the underfloor catalyst to obtain an upper layer (catalyst weight: 85.1 g / L, Pd: 1.6 g / L) immediately below the catalyst.
By such a series of catalyst preparation methods, a catalyst directly underneath (total catalyst weight: 247.1 g / L, Pd: 3.6 g / L) was obtained.
（実施例８）
実施例１の硫酸バリウム−アルミナの代わりに、実施例２の硫酸バリウム−アルミナを用いた他は実施例７と同様な方法で、実施例８の床下触媒（触媒総重量：２０１．４ｇ／Ｌ、Ｐｄ：１．２１ｇ／Ｌ）を得た。
（触媒性能）
上記の床下触媒を直下触媒と共に、各々を触媒コンバーター内に格納した後、耐久用ガソリンエンジンの排気システム内の直下位置、床下位置に各々のコンバーターを設置し、直下触媒は触媒床温度を９５０℃にして１５０時間、床下触媒は触媒床温度を８００℃にして５０時間耐久した。その後、評価用車両の排気システムの直下位置、床下位置に各々の耐久処理済みコンバーターを設置し、走行モードＬＡ−４にて評価を行った。図１４はＬＡ−４モード走行時の加速領域の平均ＮＯｘ浄化率を示している。本発明の硫酸バリウム−アルミナを用いた床下触媒は８５．６％という高い脱硝性能を発揮した。(Example 8)
The underfloor catalyst of Example 8 (total catalyst weight: 201.4 g / L) was used in the same manner as in Example 7, except that barium sulfate-alumina in Example 2 was used instead of barium sulfate-alumina in Example 1. , Pd: 1.21 g / L).
(Catalyst performance)
After storing the above-mentioned underfloor catalyst together with the direct catalyst in each catalytic converter, each converter is installed in the exhaust gas exhaust system of the durable gasoline engine at the position directly below and below the floor. The underfloor catalyst was durable for 50 hours at a catalyst bed temperature of 800 ° C. for 150 hours. Thereafter, each endurance-treated converter was installed immediately below the exhaust system of the vehicle for evaluation and below the floor, and the evaluation was performed in the driving mode LA-4. FIG. 14 shows the average NOx purification rate in the acceleration region during the LA-4 mode traveling. The underfloor catalyst using the barium sulfate-alumina of the present invention exhibited a high denitration performance of 85.6%.
（実施例９）
実施例１の硫酸バリウム−アルミナの代わりに、実施例３の硫酸バリウム−アルミナを用いた他は実施例７と同様な方法で、実施例９の床下触媒（触媒総重量：２０１．４ｇ／Ｌ、Ｐｄ：１．２１ｇ／Ｌ）を得た。
（触媒性能）
上記の床下触媒を直下触媒と共に、各々を触媒コンバーター内に格納した後、耐久用ガソリンエンジンの排気システム内の直下位置、床下位置に各々のコンバーターを設置し、直下触媒は触媒床温度を９５０℃にして１５０時間、床下触媒は触媒床温度を８００℃にして５０時間耐久した。その後、評価用車両の排気システムの直下位置、床下位置に各々の耐久処理済みコンバーターを設置し、走行モードＬＡ−４にて評価を行った。図１４はＬＡ−４モード走行時の加速領域の平均ＮＯｘ浄化率を示している。本発明の硫酸バリウム−アルミナを用いた床下触媒は８９．２％という高い脱硝性能を発揮した。Example 9
The underfloor catalyst of Example 9 (total catalyst weight: 201.4 g / L) was used in the same manner as in Example 7, except that barium sulfate-alumina in Example 3 was used instead of barium sulfate-alumina in Example 1. , Pd: 1.21 g / L).
(Catalyst performance)
After storing the above-mentioned underfloor catalyst together with the direct catalyst in each catalytic converter, each converter is installed in the exhaust gas exhaust system of the durable gasoline engine at the position directly below and below the floor. The underfloor catalyst was durable for 50 hours at a catalyst bed temperature of 800 ° C. for 150 hours. Thereafter, each endurance-treated converter was installed immediately below the exhaust system of the vehicle for evaluation and below the floor, and the evaluation was performed in the driving mode LA-4. FIG. 14 shows the average NOx purification rate in the acceleration region during the LA-4 mode traveling. The underfloor catalyst using the barium sulfate-alumina of the present invention exhibited a high denitration performance of 89.2%.
（実施例１０）
実施例１の硫酸バリウム−アルミナの代わりに、実施例４の硫酸バリウム−アルミナを用いた他は実施例７と同様な方法で、実施例１０の床下触媒（触媒総重量：２０１．４ｇ／Ｌ、Ｐｄ：１．２１ｇ／Ｌ）を得た。
（触媒性能）
上記の床下触媒を直下触媒と共に、各々を触媒コンバーター内に格納した後、耐久用ガソリンエンジンの排気システム内の直下位置、床下位置に各々のコンバーターを設置し、直下触媒は触媒床温度を９５０℃にして１５０時間、床下触媒は触媒床温度を８００℃にして５０時間耐久した。その後、評価用車両の排気システムの直下位置、床下位置に各々の耐久処理済みコンバーターを設置し、走行モードＬＡ−４にて評価を行った。図１４はＬＡ−４モード走行時の加速領域の平均ＮＯｘ浄化率を示している。本発明の硫酸バリウム−アルミナを用いた床下触媒は７８．２％と比較的高い脱硝性能を発揮した。(Example 10)
The underfloor catalyst of Example 10 (total catalyst weight: 201.4 g / L) was used in the same manner as in Example 7 except that barium sulfate-alumina in Example 4 was used instead of barium sulfate-alumina in Example 1. , Pd: 1.21 g / L).
(Catalyst performance)
After storing the above-mentioned underfloor catalyst together with the direct catalyst in each catalytic converter, each converter is installed in the exhaust gas exhaust system of the durable gasoline engine at the position directly below and below the floor. The underfloor catalyst was durable for 50 hours at a catalyst bed temperature of 800 ° C. for 150 hours. Thereafter, each endurance-treated converter was installed immediately below the exhaust system of the vehicle for evaluation and below the floor, and the evaluation was performed in the driving mode LA-4. FIG. 14 shows the average NOx purification rate in the acceleration region during the LA-4 mode traveling. The underfloor catalyst using the barium sulfate-alumina of the present invention exhibited a relatively high denitration performance of 78.2%.
（比較例４）
実施例１の硫酸バリウム−アルミナの代わりに、比較例１の硫酸バリウム−アルミナ混合物を用いた他は実施例６と同様な方法で、比較例４の床下触媒（触媒総重量：２０１．４ｇ／Ｌ、Ｐｄ：１．２１ｇ／Ｌ）を得た。
上記実施例６で用いた直下触媒と比較例１の床下触媒を各々１個ずつ触媒コンバーターに格納した後、耐久エンジンの排気ラインの直下位置と床下位置に各々を設置した。その後、エンジンを稼動し、直下触媒の触媒床温度を９５０℃に、床下触媒の８５０℃に調節した後、直下触媒は１５０時間、床下触媒は５０時間耐久処理した。その後、評価用車両の排気ラインの直下位置、床下位置に各々の触媒コンバーターを設置し、走行モードＬＡ−４にて評価を実施した。触媒のＮＯｘ浄化性能は直下触媒と床下触媒の総和の脱硝性能で、ＬＡ−４モードの加速領域の平均ＮＯｘ浄化率を図１４にまとめた。
また、図１に示した比較例１の硫酸バリウム−アルミナ中の硫酸バリウムの平均粒子径と、図１４の平均ＮＯｘ浄化率の関係を図１５にまとめた。さらに、図８に示した比較例１の硫酸バリウム−アルミナのＢａ−Ａｌ間の相関係数と、図１４の平均ＮＯｘ浄化率の関係を図１６にまとめた。
（触媒性能）
上記の床下触媒を直下触媒と共に、各々を触媒コンバーター内に格納した後、耐久用ガソリンエンジンの排気システム内の直下位置、床下位置に各々のコンバーターを設置し、直下触媒は触媒床温度を９５０℃にして１５０時間、床下触媒は触媒床温度を８００℃にして５０時間耐久した。その後、評価用車両の排気システムの直下位置、床下位置に各々の耐久処理済みコンバーターを設置し、走行モードＬＡ−４にて評価を行った。図１４はＬＡ−４モード走行時の加速領域の平均ＮＯｘ浄化率を示している。比較用の硫酸バリウム−アルミナを用いた床下触媒は７１．８％と脱硝性能が低かった。(Comparative Example 4)
The underfloor catalyst of Comparative Example 4 (total catalyst weight: 201.4 g / wt) was prepared in the same manner as in Example 6 except that the barium sulfate-alumina mixture of Comparative Example 1 was used instead of the barium sulfate-alumina of Example 1. L, Pd: 1.21 g / L).
After storing each of the direct catalyst used in Example 6 and the underfloor catalyst of Comparative Example 1 in the catalytic converter, each was installed at the position directly below the exhaust line of the durable engine and the position below the floor. After that, the engine was operated, and the catalyst bed temperature of the catalyst directly below was adjusted to 950 ° C. and the catalyst below the catalyst below 850 ° C., and then the catalyst directly below was subjected to durability treatment for 150 hours and the catalyst below the floor was 50 hours. Then, each catalytic converter was installed in the position directly under the exhaust line of the vehicle for evaluation, and the position under the floor, and it evaluated in driving mode LA-4. The NOx purification performance of the catalyst is the total NOx removal performance of the direct catalyst and the underfloor catalyst. The average NOx purification rate in the acceleration region of the LA-4 mode is summarized in FIG.
Moreover, the relationship between the average particle diameter of barium sulfate in the barium sulfate-alumina of Comparative Example 1 shown in FIG. 1 and the average NOx purification rate of FIG. 14 is summarized in FIG. Further, the relationship between the correlation coefficient between Ba-Al of barium sulfate-alumina of Comparative Example 1 shown in FIG. 8 and the average NOx purification rate of FIG. 14 are summarized in FIG.
(Catalyst performance)
After storing the above-mentioned underfloor catalyst together with the direct catalyst in each catalytic converter, each converter is installed in the exhaust gas exhaust system of the durable gasoline engine at the position directly below and below the floor. The underfloor catalyst was durable for 50 hours at a catalyst bed temperature of 800 ° C. for 150 hours. Thereafter, each endurance-treated converter was installed immediately below the exhaust system of the vehicle for evaluation and below the floor, and the evaluation was performed in the driving mode LA-4. FIG. 14 shows the average NOx purification rate in the acceleration region during the LA-4 mode traveling. The underfloor catalyst using barium sulfate-alumina for comparison had a low denitration performance of 71.8%.
「結果と考察」
上記結果を示す図１から、本発明の実施例１〜５で得られた硫酸バリウム−アルミナは、粒子中の硫酸バリウムの平均分散粒子径がいずれも６００ｎｍ以下であった。一方、同様の方法で得られた比較例１の硫酸バリウム−アルミナは、硫酸バリウムの平均分散粒子径が１，０００ｎｍと本発明よりも大きかった。
また、図８から、実施例１〜５の硫酸バリウム−アルミナは、粒子内のＢａ−Ａｌ間の相関係数がいずれも０．３以上で正の相関を示した。一方、同様の方法で得られた比較例１の硫酸バリウム−アルミナは、粒子内のＢａ−Ａｌ間の相関係数が−０．６弱で負の相関を示した。"Results and discussion"
From FIG. 1 showing the above results, the barium sulfate-alumina obtained in Examples 1 to 5 of the present invention had an average dispersed particle diameter of barium sulfate in the particles of 600 nm or less. On the other hand, the barium sulfate-alumina of Comparative Example 1 obtained by the same method had an average dispersed particle diameter of barium sulfate of 1,000 nm, which was larger than that of the present invention.
Further, from FIG. 8, the barium sulfate-alumina of Examples 1 to 5 showed a positive correlation when the correlation coefficient between Ba-Al in the particles was 0.3 or more. On the other hand, the barium sulfate-alumina of Comparative Example 1 obtained by the same method showed a negative correlation with a correlation coefficient between Ba-Al in the particles of less than -0.6.
（Ｉ）硫酸バリウムを含むアルミナ材料について
本発明の実施例１〜５の硫酸バリウム−アルミナと比較例１の硫酸バリウム−アルミナは、平均粒子径と粒子内のＢａ−Ａｌ間の相関係数が上記のような差異を示しており、これらが、触媒反応と密接な関係を有するＢＥＴ比表面積の低下率や硫酸バリウムの分解温度に影響を及ぼしたことが分かる。
具体的には、図９及び１０から明らかなように、還元処理−酸化処理を施した耐久前後におけるＢＥＴ比表面積の低下率は、硫酸バリウム−アルミナ中の硫酸バリウムの平均粒子径が小さいほど低減し、硫酸バリウムの分解温度も硫酸バリウムの平均粒子径が小さいほど低くなった。但し、硫酸バリウムの混合比率が極端に増大すると、硫酸バリウム自体のＢＥＴ比表面積の低下により、ＢＥＴ比表面積の低下率は悪化した。
同様な現象は、硫酸バリウム−アルミナ中のＢａ−Ａｌ間の相関係数との関係においても見られ、図１１及び１２から明らかなように、平均粒子径が大きいほどＢａ−Ａｌ間の正の相関係数が低減し、また、Ｂａ−Ａｌ間の正の相関係数が大きくなるほどＢＥＴ比表面積の低下率は低減する傾向が見られた。
但し、硫酸バリウムの混合比率が極端に増大すると、硫酸バリウム自体のＢＥＴ比表面積の低下により、ＢＥＴ比表面積の低下率は悪化した。(I) About Alumina Material Containing Barium Sulfate The barium sulfate-alumina of Examples 1 to 5 of the present invention and the barium sulfate-alumina of Comparative Example 1 have an average particle diameter and a correlation coefficient between Ba-Al in the particles. The above differences are shown, and it can be seen that these had an effect on the reduction rate of the BET specific surface area and the decomposition temperature of barium sulfate, which are closely related to the catalytic reaction.
Specifically, as apparent from FIGS. 9 and 10, the reduction rate of the BET specific surface area before and after the endurance after the reduction treatment-oxidation treatment is reduced as the average particle size of barium sulfate in barium sulfate-alumina is smaller. The decomposition temperature of barium sulfate was lower as the average particle size of barium sulfate was smaller. However, when the mixing ratio of barium sulfate was extremely increased, the decrease rate of the BET specific surface area was deteriorated due to the decrease of the BET specific surface area of the barium sulfate itself.
A similar phenomenon is also observed in relation to the correlation coefficient between Ba-Al in barium sulfate-alumina. As is clear from FIGS. 11 and 12, the larger the average particle diameter, the more positive the Ba-Al relationship. There was a tendency that the decrease rate of the BET specific surface area decreased as the correlation coefficient decreased and the positive correlation coefficient between Ba and Al increased.
However, when the mixing ratio of barium sulfate was extremely increased, the decrease rate of the BET specific surface area was deteriorated due to the decrease of the BET specific surface area of the barium sulfate itself.
（ＩＩ）触媒について
これらアルミナ材料における結果は、硫酸バリウム−アルミナ中の硫酸バリウムの平均粒子径が１０〜８００ｎｍ、アルミナの平均粒子径が３００ｎｍ〜５μｍで、かつ、Ｂａ−Ａｌ間の相関係数が０．３以上の値を取るのであれば、耐久中のＢＥＴ比表面積の低下が抑制され、硫酸バリウムの分解も低い温度から生じることを示しており、バリウムが関与し、触媒が高温に曝される恐れのある触媒反応を促進するのに有効であることを示唆している。
実際に、本発明の実施例１〜４の硫酸バリウム−アルミナを用いて製造した実施例７〜１０の床下触媒は、ＬＡ−４モード走行時の加速領域の平均ＮＯｘ浄化率が７５％を超える高い性能を示した。一方、比較例１の硫酸バリウム−アルミナを用いて製造された比較例４の床下触媒は、実施例７〜１０の床下触媒と比べ、脱硝性能が低かった。
これらの結果を、硫酸バリウム−アルミナ中の硫酸バリウムの平均粒子径やＢａ−Ａｌ間の相関係数との比較で見てみると、図１５から明らかなように、実施例１〜４のように硫酸バリウム−アルミナ中の硫酸バリウムの平均粒子径が小さくなるほど脱硝性能が好転した。一方、本発明の硫酸バリウム−アルミナとＯＳＣの関係をみると、図１３の実施例６から、硫酸バリウム−アルミナがＯＳＣと物理的に混合している程度であれば、硫酸バリウムがＯＳＣに及ぼす悪影響は軽微であると考えられ、硫酸バリウム−アルミナ中のＢａ−Ａｌ間の相関係数が正の値で大きくなるほど脱硝性能が好転した。(II) Catalyst The results for these alumina materials are as follows: the average particle diameter of barium sulfate in barium sulfate-alumina is 10 to 800 nm, the average particle diameter of alumina is 300 nm to 5 μm, and the correlation coefficient between Ba and Al. Is 0.3 or more, it indicates that the decrease in the BET specific surface area during durability is suppressed, and that the decomposition of barium sulfate also occurs from a low temperature. Barium is involved, and the catalyst is exposed to a high temperature. This suggests that it is effective in promoting a catalytic reaction that may occur.
Actually, the underfloor catalysts of Examples 7 to 10 manufactured using the barium sulfate-alumina of Examples 1 to 4 of the present invention have an average NOx purification rate of 75% or more in the acceleration region during the LA-4 mode traveling. High performance was shown. On the other hand, the underfloor catalyst of Comparative Example 4 produced using the barium sulfate-alumina of Comparative Example 1 had lower denitration performance than the underfloor catalysts of Examples 7-10.
When these results are compared with the average particle diameter of barium sulfate in the barium sulfate-alumina and the correlation coefficient between Ba-Al, as shown in FIG. In addition, the denitration performance improved as the average particle size of barium sulfate in barium sulfate-alumina decreased. On the other hand, the relationship between the barium sulfate-alumina of the present invention and the OSC shows that, from Example 6 in FIG. 13, if the barium sulfate-alumina is physically mixed with the OSC, the barium sulfate affects the OSC. The adverse effect is considered to be minor, and the denitration performance improved as the correlation coefficient between Ba-Al in barium sulfate-alumina increased with a positive value.
こうした結果は、触媒に加えられた硫酸バリウムを含むアルミナ材料中の硫酸バリウムの粒子径やＢａ−Ａｌ間の相関係数が、脱硝性能の向上に重要な役割を果たしていることを示しており、具体的には、アルミナ材料中に分散している硫酸バリウムの平均粒子径が１０〜８００ｎｍ、アルミナの平均粒子径が３００ｎｍ〜５μｍで、かつ、Ｂａ−Ａｌ間の相関係数が０．３以上の値を取ることにより、優れた脱硝性能が期待できることを意味している。
また、アルミナ材料の耐久性能の更なる向上が必要な場合には、アルミナをγ−アルミナから更に耐熱性の高いθ−アルミナやδ−アルミナに変更することや、耐熱性を向上すると言われている酸化ランタン、セリア、酸化ネオジム、酸化プラセオジム、酸化イットリウムなどの希土類酸化物をアルミナに添加することも有効であると言える。These results show that the particle diameter of barium sulfate in the alumina material containing barium sulfate added to the catalyst and the correlation coefficient between Ba-Al play an important role in improving the denitration performance. Specifically, the average particle diameter of barium sulfate dispersed in the alumina material is 10 to 800 nm, the average particle diameter of alumina is 300 nm to 5 μm, and the correlation coefficient between Ba and Al is 0.3 or more. By taking this value, it means that excellent denitration performance can be expected.
In addition, when further improvement of the durability performance of the alumina material is required, it is said that changing the alumina from γ-alumina to θ-alumina or δ-alumina having higher heat resistance, or improving the heat resistance. It can be said that it is also effective to add rare earth oxides such as lanthanum oxide, ceria, neodymium oxide, praseodymium oxide, and yttrium oxide to alumina.
本発明の硫酸バリウムを含むアルミナ材料は、ガソリンエンジンなどの内燃機関から排出される排気ガス中の一酸化炭素（ＣＯ）、炭化水素（ＨＣ）、窒素酸化物（ＮＯｘ）の内、特にＮＯｘ浄化性能に優れる排気ガス浄化用触媒の原料として利用でき、吸着剤としても利用できる。また、本発明の排気ガス浄化用触媒は、自動車用途に限定されるものではなく、排気ガス中の窒素酸化物の脱硝技術にも広く適用可能である。 The alumina material containing barium sulfate according to the present invention is used to purify NOx among carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NOx) in exhaust gas discharged from an internal combustion engine such as a gasoline engine. It can be used as a raw material for an exhaust gas purification catalyst having excellent performance, and can also be used as an adsorbent. Further, the exhaust gas purifying catalyst of the present invention is not limited to automotive applications, and can be widely applied to a denitration technique for nitrogen oxides in exhaust gas.
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