EP2560755A1 - Novel mixed oxide materials for the selective catalytic reduction of nitrogen oxides in exhaust gases - Google Patents
Novel mixed oxide materials for the selective catalytic reduction of nitrogen oxides in exhaust gasesInfo
- Publication number
- EP2560755A1 EP2560755A1 EP11716376A EP11716376A EP2560755A1 EP 2560755 A1 EP2560755 A1 EP 2560755A1 EP 11716376 A EP11716376 A EP 11716376A EP 11716376 A EP11716376 A EP 11716376A EP 2560755 A1 EP2560755 A1 EP 2560755A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- oxide
- zeolite
- catalyst
- compound
- catalytically active
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 title claims abstract description 113
- 239000007789 gas Substances 0.000 title claims abstract description 55
- 238000010531 catalytic reduction reaction Methods 0.000 title claims abstract description 15
- 239000000463 material Substances 0.000 title description 4
- 239000003054 catalyst Substances 0.000 claims abstract description 133
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims abstract description 62
- 239000000203 mixture Substances 0.000 claims abstract description 45
- 229910021529 ammonia Inorganic materials 0.000 claims abstract description 29
- 150000001875 compounds Chemical class 0.000 claims abstract description 25
- 229910052761 rare earth metal Inorganic materials 0.000 claims abstract description 16
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 claims abstract description 15
- 229910000420 cerium oxide Inorganic materials 0.000 claims abstract description 14
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical class O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 claims abstract description 14
- 150000002910 rare earth metals Chemical class 0.000 claims abstract description 14
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 claims abstract description 13
- 229910001928 zirconium oxide Inorganic materials 0.000 claims abstract description 13
- 229910000484 niobium oxide Inorganic materials 0.000 claims abstract description 12
- URLJKFSTXLNXLG-UHFFFAOYSA-N niobium(5+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Nb+5].[Nb+5] URLJKFSTXLNXLG-UHFFFAOYSA-N 0.000 claims abstract description 12
- 238000002485 combustion reaction Methods 0.000 claims abstract description 9
- 238000000576 coating method Methods 0.000 claims description 50
- 239000011248 coating agent Substances 0.000 claims description 44
- 239000010457 zeolite Substances 0.000 claims description 33
- 229910021536 Zeolite Inorganic materials 0.000 claims description 32
- -1 Zeolite compound Chemical class 0.000 claims description 23
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims description 14
- 230000003197 catalytic effect Effects 0.000 claims description 14
- 239000003638 chemical reducing agent Substances 0.000 claims description 11
- 239000011230 binding agent Substances 0.000 claims description 7
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 6
- 150000001768 cations Chemical class 0.000 claims description 5
- 238000000746 purification Methods 0.000 claims description 5
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 4
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 claims description 4
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 claims description 4
- 229910052739 hydrogen Inorganic materials 0.000 claims description 4
- 239000000377 silicon dioxide Substances 0.000 claims description 3
- 239000011149 active material Substances 0.000 abstract description 3
- 238000006243 chemical reaction Methods 0.000 description 43
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 26
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 20
- 230000000052 comparative effect Effects 0.000 description 19
- 238000003860 storage Methods 0.000 description 17
- 238000000034 method Methods 0.000 description 15
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 14
- 229910052760 oxygen Inorganic materials 0.000 description 14
- 239000001301 oxygen Substances 0.000 description 14
- 238000012360 testing method Methods 0.000 description 14
- RCFVMJKOEJFGTM-UHFFFAOYSA-N cerium zirconium Chemical compound [Zr].[Ce] RCFVMJKOEJFGTM-UHFFFAOYSA-N 0.000 description 13
- 229910052757 nitrogen Inorganic materials 0.000 description 13
- 230000032683 aging Effects 0.000 description 12
- 230000006399 behavior Effects 0.000 description 10
- 230000008569 process Effects 0.000 description 10
- 239000000725 suspension Substances 0.000 description 10
- 239000010949 copper Substances 0.000 description 9
- 239000000919 ceramic Substances 0.000 description 8
- 229910052742 iron Inorganic materials 0.000 description 8
- 238000005259 measurement Methods 0.000 description 8
- 229910001935 vanadium oxide Inorganic materials 0.000 description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 8
- XHCLAFWTIXFWPH-UHFFFAOYSA-N [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] XHCLAFWTIXFWPH-UHFFFAOYSA-N 0.000 description 7
- 230000009467 reduction Effects 0.000 description 7
- 238000006722 reduction reaction Methods 0.000 description 7
- 210000004027 cell Anatomy 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 6
- 239000010937 tungsten Substances 0.000 description 6
- 229910001930 tungsten oxide Inorganic materials 0.000 description 6
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 5
- 238000007598 dipping method Methods 0.000 description 5
- 239000011733 molybdenum Substances 0.000 description 5
- QGLKJKCYBOYXKC-UHFFFAOYSA-N nonaoxidotritungsten Chemical compound O=[W]1(=O)O[W](=O)(=O)O[W](=O)(=O)O1 QGLKJKCYBOYXKC-UHFFFAOYSA-N 0.000 description 5
- PBYZMCDFOULPGH-UHFFFAOYSA-N tungstate Chemical compound [O-][W]([O-])(=O)=O PBYZMCDFOULPGH-UHFFFAOYSA-N 0.000 description 5
- 229910052721 tungsten Inorganic materials 0.000 description 5
- 229910052720 vanadium Inorganic materials 0.000 description 5
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 5
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 4
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 4
- 239000004202 carbamide Substances 0.000 description 4
- 210000002421 cell wall Anatomy 0.000 description 4
- XTVVROIMIGLXTD-UHFFFAOYSA-N copper(II) nitrate Chemical compound [Cu+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O XTVVROIMIGLXTD-UHFFFAOYSA-N 0.000 description 4
- 238000001125 extrusion Methods 0.000 description 4
- 229910052750 molybdenum Inorganic materials 0.000 description 4
- 229910052726 zirconium Inorganic materials 0.000 description 4
- 229910052684 Cerium Inorganic materials 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 3
- 229910052691 Erbium Inorganic materials 0.000 description 3
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical group [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 3
- 229910001593 boehmite Inorganic materials 0.000 description 3
- 238000004140 cleaning Methods 0.000 description 3
- 229910052802 copper Inorganic materials 0.000 description 3
- 229930195733 hydrocarbon Natural products 0.000 description 3
- 150000002430 hydrocarbons Chemical class 0.000 description 3
- FAHBNUUHRFUEAI-UHFFFAOYSA-M hydroxidooxidoaluminium Chemical compound O[Al]=O FAHBNUUHRFUEAI-UHFFFAOYSA-M 0.000 description 3
- 229910052746 lanthanum Inorganic materials 0.000 description 3
- 229910052748 manganese Chemical group 0.000 description 3
- 239000011572 manganese Chemical group 0.000 description 3
- 229910000069 nitrogen hydride Inorganic materials 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- 238000009997 thermal pre-treatment Methods 0.000 description 3
- 238000007669 thermal treatment Methods 0.000 description 3
- 229910052719 titanium Inorganic materials 0.000 description 3
- 239000010936 titanium Substances 0.000 description 3
- 238000011144 upstream manufacturing Methods 0.000 description 3
- 229910052727 yttrium Inorganic materials 0.000 description 3
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 2
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
- 229910017493 Nd 2 O 3 Inorganic materials 0.000 description 2
- 229910052779 Neodymium Inorganic materials 0.000 description 2
- 229910052772 Samarium Inorganic materials 0.000 description 2
- 229910004298 SiO 2 Inorganic materials 0.000 description 2
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 2
- 229910052769 Ytterbium Inorganic materials 0.000 description 2
- 230000004913 activation Effects 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- QVQLCTNNEUAWMS-UHFFFAOYSA-N barium oxide Chemical compound [Ba]=O QVQLCTNNEUAWMS-UHFFFAOYSA-N 0.000 description 2
- 238000001354 calcination Methods 0.000 description 2
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 2
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 2
- 239000000292 calcium oxide Substances 0.000 description 2
- 229910002091 carbon monoxide Inorganic materials 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 2
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 description 2
- 230000003750 conditioning effect Effects 0.000 description 2
- 238000006731 degradation reaction Methods 0.000 description 2
- 230000007062 hydrolysis Effects 0.000 description 2
- 238000006460 hydrolysis reaction Methods 0.000 description 2
- AMWRITDGCCNYAT-UHFFFAOYSA-L hydroxy(oxo)manganese;manganese Chemical compound [Mn].O[Mn]=O.O[Mn]=O AMWRITDGCCNYAT-UHFFFAOYSA-L 0.000 description 2
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 229910000476 molybdenum oxide Inorganic materials 0.000 description 2
- 229910052758 niobium Inorganic materials 0.000 description 2
- 239000010955 niobium Substances 0.000 description 2
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 2
- 230000000737 periodic effect Effects 0.000 description 2
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- IATRAKWUXMZMIY-UHFFFAOYSA-N strontium oxide Chemical compound [O-2].[Sr+2] IATRAKWUXMZMIY-UHFFFAOYSA-N 0.000 description 2
- 229910052717 sulfur Inorganic materials 0.000 description 2
- 239000011593 sulfur Substances 0.000 description 2
- 238000003878 thermal aging Methods 0.000 description 2
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 description 2
- 229910001887 tin oxide Inorganic materials 0.000 description 2
- 239000004408 titanium dioxide Substances 0.000 description 2
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- QPLDLSVMHZLSFG-UHFFFAOYSA-N Copper oxide Chemical compound [Cu]=O QPLDLSVMHZLSFG-UHFFFAOYSA-N 0.000 description 1
- 239000005751 Copper oxide Substances 0.000 description 1
- 229910052692 Dysprosium Inorganic materials 0.000 description 1
- 241000282326 Felis catus Species 0.000 description 1
- 229910052688 Gadolinium Inorganic materials 0.000 description 1
- 229910052689 Holmium Inorganic materials 0.000 description 1
- 229910052765 Lutetium Inorganic materials 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 229910052777 Praseodymium Inorganic materials 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 229910052771 Terbium Inorganic materials 0.000 description 1
- 229910052775 Thulium Inorganic materials 0.000 description 1
- 229910010413 TiO 2 Inorganic materials 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical class [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 description 1
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 229910000310 actinide oxide Inorganic materials 0.000 description 1
- DNXNYEBMOSARMM-UHFFFAOYSA-N alumane;zirconium Chemical compound [AlH3].[Zr] DNXNYEBMOSARMM-UHFFFAOYSA-N 0.000 description 1
- CSDREXVUYHZDNP-UHFFFAOYSA-N alumanylidynesilicon Chemical compound [Al].[Si] CSDREXVUYHZDNP-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- BVCZEBOGSOYJJT-UHFFFAOYSA-N ammonium carbamate Chemical compound [NH4+].NC([O-])=O BVCZEBOGSOYJJT-UHFFFAOYSA-N 0.000 description 1
- VZTDIZULWFCMLS-UHFFFAOYSA-N ammonium formate Chemical compound [NH4+].[O-]C=O VZTDIZULWFCMLS-UHFFFAOYSA-N 0.000 description 1
- 239000012752 auxiliary agent Substances 0.000 description 1
- XFHGGMBZPXFEOU-UHFFFAOYSA-I azanium;niobium(5+);oxalate Chemical compound [NH4+].[Nb+5].[O-]C(=O)C([O-])=O.[O-]C(=O)C([O-])=O.[O-]C(=O)C([O-])=O XFHGGMBZPXFEOU-UHFFFAOYSA-I 0.000 description 1
- 229910052788 barium Inorganic materials 0.000 description 1
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 1
- 239000000440 bentonite Substances 0.000 description 1
- 229910000278 bentonite Inorganic materials 0.000 description 1
- SVPXDRXYRYOSEX-UHFFFAOYSA-N bentoquatam Chemical compound O.O=[Si]=O.O=[Al]O[Al]=O SVPXDRXYRYOSEX-UHFFFAOYSA-N 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- KXDHJXZQYSOELW-UHFFFAOYSA-N carbonic acid monoamide Natural products NC(O)=O KXDHJXZQYSOELW-UHFFFAOYSA-N 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 229910000423 chromium oxide Inorganic materials 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 229910000431 copper oxide Inorganic materials 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000003795 desorption Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- UYAHIZSMUZPPFV-UHFFFAOYSA-N erbium Chemical compound [Er] UYAHIZSMUZPPFV-UHFFFAOYSA-N 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000009472 formulation Methods 0.000 description 1
- 230000006870 function Effects 0.000 description 1
- 238000004868 gas analysis Methods 0.000 description 1
- 238000012812 general test Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000005470 impregnation Methods 0.000 description 1
- 229910003437 indium oxide Inorganic materials 0.000 description 1
- PJXISJQVUVHSOJ-UHFFFAOYSA-N indium(iii) oxide Chemical compound [O-2].[O-2].[O-2].[In+3].[In+3] PJXISJQVUVHSOJ-UHFFFAOYSA-N 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 238000005342 ion exchange Methods 0.000 description 1
- SZQUEWJRBJDHSM-UHFFFAOYSA-N iron(3+);trinitrate;nonahydrate Chemical compound O.O.O.O.O.O.O.O.O.[Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O SZQUEWJRBJDHSM-UHFFFAOYSA-N 0.000 description 1
- 229910000311 lanthanide oxide Inorganic materials 0.000 description 1
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
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- 150000004706 metal oxides Chemical class 0.000 description 1
- 239000006262 metallic foam Substances 0.000 description 1
- QHMGFQBUOCYLDT-RNFRBKRXSA-N n-(diaminomethylidene)-2-[(2r,5r)-2,5-dimethyl-2,5-dihydropyrrol-1-yl]acetamide Chemical compound C[C@@H]1C=C[C@@H](C)N1CC(=O)N=C(N)N QHMGFQBUOCYLDT-RNFRBKRXSA-N 0.000 description 1
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 1
- 229910000480 nickel oxide Inorganic materials 0.000 description 1
- 150000002822 niobium compounds Chemical class 0.000 description 1
- ZKATWMILCYLAPD-UHFFFAOYSA-N niobium pentoxide Inorganic materials O=[Nb](=O)O[Nb](=O)=O ZKATWMILCYLAPD-UHFFFAOYSA-N 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 229910000487 osmium oxide Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- PQQKPALAQIIWST-UHFFFAOYSA-N oxomolybdenum Chemical compound [Mo]=O PQQKPALAQIIWST-UHFFFAOYSA-N 0.000 description 1
- GNRSAWUEBMWBQH-UHFFFAOYSA-N oxonickel Chemical compound [Ni]=O GNRSAWUEBMWBQH-UHFFFAOYSA-N 0.000 description 1
- JIWAALDUIFCBLV-UHFFFAOYSA-N oxoosmium Chemical compound [Os]=O JIWAALDUIFCBLV-UHFFFAOYSA-N 0.000 description 1
- DYIZHKNUQPHNJY-UHFFFAOYSA-N oxorhenium Chemical compound [Re]=O DYIZHKNUQPHNJY-UHFFFAOYSA-N 0.000 description 1
- BPUBBGLMJRNUCC-UHFFFAOYSA-N oxygen(2-);tantalum(5+) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Ta+5].[Ta+5] BPUBBGLMJRNUCC-UHFFFAOYSA-N 0.000 description 1
- 235000011837 pasties Nutrition 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- CHWRSCGUEQEHOH-UHFFFAOYSA-N potassium oxide Chemical compound [O-2].[K+].[K+] CHWRSCGUEQEHOH-UHFFFAOYSA-N 0.000 description 1
- 229910001950 potassium oxide Inorganic materials 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- PUDIUYLPXJFUGB-UHFFFAOYSA-N praseodymium atom Chemical compound [Pr] PUDIUYLPXJFUGB-UHFFFAOYSA-N 0.000 description 1
- 239000012041 precatalyst Substances 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 229910001404 rare earth metal oxide Inorganic materials 0.000 description 1
- 229910003449 rhenium oxide Inorganic materials 0.000 description 1
- KZUNJOHGWZRPMI-UHFFFAOYSA-N samarium atom Chemical compound [Sm] KZUNJOHGWZRPMI-UHFFFAOYSA-N 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000011973 solid acid Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 238000010561 standard procedure Methods 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 1
- 229910001936 tantalum oxide Inorganic materials 0.000 description 1
- GZCRRIHWUXGPOV-UHFFFAOYSA-N terbium atom Chemical compound [Tb] GZCRRIHWUXGPOV-UHFFFAOYSA-N 0.000 description 1
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 1
- PMTRSEDNJGMXLN-UHFFFAOYSA-N titanium zirconium Chemical compound [Ti].[Zr] PMTRSEDNJGMXLN-UHFFFAOYSA-N 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 229910052723 transition metal Inorganic materials 0.000 description 1
- 150000003624 transition metals Chemical class 0.000 description 1
- 230000007306 turnover Effects 0.000 description 1
- 150000003682 vanadium compounds Chemical class 0.000 description 1
- NAWDYIZEMPQZHO-UHFFFAOYSA-N ytterbium Chemical compound [Yb] NAWDYIZEMPQZHO-UHFFFAOYSA-N 0.000 description 1
- 150000003754 zirconium Chemical class 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
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Definitions
- the invention relates to the use of mixed oxides as a catalytically active material for the selective catalytic reduction of nitrogen oxides with ammonia or a decomposable to ammonia compound as a reducing agent in the exhaust gas of predominantly lean-burn internal combustion engines in motor vehicles.
- the invention also relates to catalytically active compositions comprising a mixed oxide and a zeolite compound and / or a zeolite-like compound, as well as various embodiments of catalysts prepared from said mixed oxides or compositions.
- Exhaust gases from motor vehicles with a predominantly lean-burn internal combustion engine contain not only the usual primary emissions of carbon monoxide CO, hydrocarbons HC and nitrogen oxides NO x a relatively high oxygen content of up to 15 vol .-%. Carbon monoxide and hydrocarbons can easily be neutralized by oxidation. The reduction of nitrogen oxides to nitrogen is more difficult because of the high oxygen content.
- One known method of removing nitrogen oxides from exhaust gases in the presence of oxygen is the Selective Catalytic Reduction (SCR) process using ammonia on a suitable catalyst, abbreviated to SCR catalyst.
- SCR Selective Catalytic Reduction
- the nitrogen oxides to be removed from the exhaust gas are reacted with ammonia to nitrogen and water.
- the ammonia used as the reducing agent can be made available by metering into the exhaust gas stream a compound which is decomposable to ammonia, for example urea, ammonium carbamate or ammonium formate, and subsequent hydrolysis.
- exhaust-gas cleaning concepts for motor vehicles are known in which ammonia is generated during a rich operating phase of the engine on an upstream catalytic converter, for example a nitrogen oxide storage catalytic converter, as secondary emission and stored in the SCR catalytic converter until the point of consumption during the lean operating phases.
- an upstream catalytic converter for example a nitrogen oxide storage catalytic converter
- the use in a discontinuous SCR system in which the ammonia used as a reducing agent is generated exclusively as a secondary emission in the exhaust system requires SCR catalysts whose ammonia storage capacity is sufficient to provide as much as possible of the total reducing agent need for Abgasentstickung during the lean phase.
- Particularly suitable for this purpose are zeolite-based SCR catalysts, as are known from numerous publications and patent applications. For example, US Pat. No.
- 4,961,917 describes a method for reducing nitrogen oxides with ammonia using a catalyst which contains iron and / or copper as promoter in addition to a zeolite having defined properties.
- SCR catalysts based on transition metal-exchanged zeolites and processes for the selective catalytic reduction using such SCR catalysts are described, for example, in EP 1 495 804 A1, US Pat. No. 6,914,026 B2 or EP 1 147 801 B1.
- the SCR catalyst it is not necessary for the SCR catalyst to have a large ammonia storage capacity. Accordingly, efforts are being made to avoid the use of zeolite-based SCR catalysts, which are very expensive because of the high production prices of zeolite compounds.
- SCR catalysts containing vanadium oxide in addition to titanium dioxide or tungsten oxide or mixtures thereof are suitable.
- EP 0 385 164 B1 describes such a catalyst which, in addition to titanium dioxide, contains at least one oxide of tungsten, silicon, boron, aluminum, phosphorus, zirconium, barium, yttrium, lanthanum or cerium, and at least one oxide of vanadium, niobium, molybdenum, Contains iron or copper and is prepared as a shaped body by compression or extrusion of the components optionally after addition of suitable auxiliaries.
- EP 1 153 648 A1 describes a structured SCR catalyst which contains, under a hydrolysis catalyst coating, a reduction coating whose composition corresponds to the formulation known from EP 0 385 164 B1.
- EP 0 246 859 describes an SCR catalyst containing vanadium applied to a mixture of ceria and alumina.
- vanadium-containing SCR catalysts for cleaning the exhaust gases of motor vehicles is the possible emission of volatile, toxic vanadium compounds at higher exhaust gas temperatures, which must be expected to be harmful to humans and the environment. Accordingly, the acceptance of vanadium-containing autocatalysts in the market is decreasing. Efforts to provide cost-effective vanadium-free SCR catalysts have been around for some time. Thus, some mixed oxide compositions based on cerium-zirconium mixed oxide and their use in the SCR reaction are already known in the art.
- WO 2008/049491 discloses homogeneous cerium-zirconium mixed oxides containing 10 to 90% by weight of cerium oxide, based on the total weight of the cerium-zirconium mixed oxide, and by incorporating sulfur or a transition metal selected from the group consisting of chromium, molybdenum, Tungsten or mixtures thereof or combinations thereof are activated for the SCR reaction.
- Particularly preferred embodiments of these mixed oxides contain 0.02 to 3 wt .-% sulfur and / or 5 to 15 wt .-% molybdenum or tungsten and 0.5 to 3 wt .-% iron or copper, each based on the total weight of cerium -Zirkon mixed oxide.
- Cerium-zirconium mixed oxides containing 45-55% by weight of CeO 2 and 1-9% by weight of rare earth oxide are particularly preferably used for the preparation of the SCR-active compounds.
- EP 2 116 293 discloses a vanadium-free SCR catalyst which contains tungsten oxide WO 3 and a homogeneous cerium-zirconium mixed oxide (Ce, Zr) O 2 , the content of tungsten oxide WO 3 being between 5 and 25% by weight, the content of the homogeneous cerium-zirconium mixed oxide can be between 50 and 95% by weight.
- Cerium-zirconium mixed oxides having a weight ratio of cerium oxide CeO 2 to zirconium oxide ZrO 2 between 0.67 and 1.5 are preferred.
- EP 2 072 120 likewise discloses a temperature-stable catalyst for the reduction of nitrogen oxides in the presence of ammonia, which contains 10 to 30% by weight of cerium oxide and 5 to 14% of tungsten oxide, and zirconium oxide as complex oxide.
- WO 2008/051752 discloses a NO x reduction catalyst comprising a cerium-zirconium-based mixed oxide of the formula Ce a Zr b R t AiMeO x wherein R is tungsten or manganese and A is molybdenum, tantalum or niobium, optionally also tungsten, if R is manganese.
- M denotes a trivalent rare earth ion, preferably selected from Sm, Gd, Dy, Er, Yb, Ho, Er, Tm and Lu, but not La or Y.
- the mixed oxide of This composition is catalytically active and is suitable for the selective catalytic reduction of nitrogen oxides with ammonia. It can be used in a corresponding exhaust aftertreatment system either as an essential component of the catalytically active coating of an SCR catalyst or as part of the coating of a catalytically active particulate filter.
- EP 0 277 765 discloses a process for removing nitrogen oxides from the exhaust gas of diesel engines by catalytic reduction over a honeycomb catalyst containing as active material 60 to 95% by weight of an oxide selected from TiO 2 , ZrO 2 , (Ti, Zr ) 0 2 , (Ti, Si) 0 2 and (Ti, Zr, Si) 0 2 . Furthermore, the catalyst contains 0.5 to 40 wt .-% vanadium, tungsten, molybdenum, manganese, cerium and / or tin oxide.
- US 5,552,128 describes a process for reacting nitrogen oxides to nitrogen by contacting the nitrogen oxides with a reducing agent in the presence of a catalyst which effectively catalyzes the reduction of the nitrogen oxides.
- the catalyst consists essentially of solid acid components comprising a metal oxide of the 4th subgroup of the Periodic Table of the Elements, which is modified with an oxyanion of a metal of the 6th subgroup and further at least one metal selected from the 1st, the 5th, the 7th or contains the 8th subgroup or even the 4th main group of the periodic table of the elements.
- US 2006/0228283 describes a catalyst system and a method for reducing nitrogen oxides in exhaust gases by reduction with hydrocarbons or oxygen-containing organic compounds.
- the "modification catalyst” comprises a "modification oxide” selected from the group consisting of iron oxide, cerium oxide, copper oxide, manganese oxide, chromium oxide, lanthanide oxides, actinide oxides, molybdenum oxide, Tin oxide, indium oxide, rhenium oxide, tantalum oxide, osmium oxide, barium oxide, calcium oxide, strontium oxide, potassium oxide, calcium oxide, vanadium oxide, nickel oxide, tungsten oxide, and mixtures thereof.
- This "modifying oxide” is applied to inorganic carrier oxides, at least one acidic and preferably selected from the group consisting of titanium-zirconium mixed oxide, zirconium-aluminum mixed oxide, sulphated zirconium oxide, phosphated zirconium oxide, tungsten-modified zirconium mixed oxide, silicon-alumin
- the invention has for its object to provide cost-effective, vanadium-free SCR catalysts available, which are characterized by dynamic light-off while aging resistant ammonia storage capacity and can also be produced as exhaust gas purification components with low back pressure.
- cerium-zirconium mixed oxides can show an effect catalyzing the selective catalytic reduction of nitrogen oxides after a targeted activation.
- the inventors have now surprisingly found that the targeted Veresell- tion of the aforementioned mixed oxides with niobium (V) oxide (Nb 2 0 5 ) to a mixed oxide of ceria, zirconia, rare earth sesquioxide and niobium oxide, which without an additional activation step an excellent Activity with high aging stability in the SCR reaction shows.
- Such mixed oxides are described in US Pat. No. 6,468,941 B1, but are not used there to catalyze the selective catalytic reduction of nitrogen oxides, but as oxygen-ion-conducting or oxygen-storing materials in three-way catalysts.
- the present invention accordingly relates to the use of a catalytically active mixed oxide consisting of cerium oxide, niobium oxide, rare earth sesquioxide and zirconium oxide for the selective catalytic reduction of nitrogen oxides.
- the use according to the invention takes place, for example, in such a way that the mixed oxide is contained in the form of a fully extruded, catalytically active honeycomb body in a catalyst.
- the use according to the invention takes place in such a way that the mixed oxide is contained in a catalytically active coating which is applied to a catalytically inert support body which forms a catalyst together with the coating.
- the preparation of the mixed oxide used according to the invention can be carried out by the simplest means.
- a suitable complex mixed oxide is obtained, for example, by impregnation of a commercially available cerium-zirconium mixed oxide, which is doped with rare earth sesquioxide for stabilization, with an aqueous solution of a water-soluble niobium compound and subsequent calcination of the (wet) powder thus obtained.
- Preferred mixed oxides to be used according to the invention which are very suitable for catalyzing the selective reduction of nitrogen oxides in lean exhaust gases, have the following composition of their components, calculated as parts by weight of the primary oxides: 15-50% by weight CeO 2 , 3 25 wt .-% Nb 2 0 5l 3 - 10 wt .-% SE 2 0 3 and rest Zr0 2 , where SE is a rare earth element.
- the mixed oxides contain 25-45 wt .-% Ce0 2 , 3 - 20 wt .-% Nb 2 0 5l 3 - 10 wt .-% SE 2 0 3 and the radical Zr0 2 , and most preferably 35- 40 wt % Ce0 2 , 10-15% by weight Nb 2 0 5 , 3-6% by weight SE 2 O 3 and the radical ZrO 2 .
- the mixed oxides to be used according to the invention are processed, for example, into a mechanically stable catalyst.
- Preferred embodiments of such a catalyst are obtained by applying at least one catalytically active coating which contains the mixed oxide to be used according to the invention to a catalytically inert support body.
- a catalytically inert support preferably ceramic or metallic fürflußwaben redesign, ceramic Wandflußfiltersubstrate and ceramic or metallic foam structures are used.
- preferred embodiments of the catalyst are obtained when a catalytically active, monolithic honeycomb body is produced by extrusion from the mixed oxide to be used according to the invention. These embodiments are characterized by a particularly low back pressure.
- an extrudable, pasty mass is produced which in addition to the catalytically active composition optionally extrusion aids such For example, bentonite, boehmite, ⁇ -alumina, zirconium oxide or conventional cerium-zirconium mixed oxide contains.
- extrusion aids such for example, bentonite, boehmite, ⁇ -alumina, zirconium oxide or conventional cerium-zirconium mixed oxide contains.
- the catalysts prepared in this way exhibit excellent NO x conversion rates in the temperature range from 250 ° C to 450 ° C. They are characterized in particular by excellent aging stability under hydrothermal conditions.
- the combination of these properties causes a dynamic light-off behavior of the catalyst in the SCR reaction after metering of the reductant from a source independent of the engine (e.g., in the form of urea injection into the exhaust line) at all important operating points.
- a source independent of the engine e.g., in the form of urea injection into the exhaust line
- the metering strategy for the reducing agent can be made significantly simpler than in the systems according to the prior art in which, for example, exclusively zeolite-based SCR catalysts are used.
- the mixed oxide to be used according to the invention can be used in combination with a zeolite compound and / or a zeolite-like compound.
- the present invention also relates to a catalytically active composition
- a catalytically active composition comprising (i) a mixed oxide consisting of cerium oxide, niobium oxide, rare earth sesquioxide and zirconium oxide and (ii) a zeolite compound and / or a zeolite-like compound containing exchangeable cations selected from the group consisting of H + , NH 4 ⁇ Fe 2+ , Fe 3+ , Cu + , Cu 2+ , Ag + or mixtures thereof.
- the present invention further relates to a catalyst characterized in that it comprises (i) a mixed oxide consisting of cerium oxide, niobium oxide, rare earth sesquioxide and zirconium oxide and (ii) a zeolite compound and / or a zeolite-like compound which contains exchangeable cations selected from the group consisting of H + , NH 4 + , Fe 2+ , Fe 3+ , Cu + , Cu 2+ , Ag + or mixtures thereof.
- Preferred catalytically active compositions according to the invention and preferred catalysts according to the invention comprise the mixed oxides described above as being preferred or particularly preferred.
- the zeolite compound and / or the zeolite-like compound particularly preferably contains H + , Fe- and / or Cu cations.
- the zeolite compound and / or the zeolite-like compound itself is preferably selected from the group consisting of zeolite beta, USY, ZSM-5, CHA, FER, ERI, SAPO-11, SAPO-17, SAPO-34, SAPO-56, ALPO- 11, ALPO-17, ALPO-34 and ALPO-56. Particular preference is given to zeolite beta, CHA, FER and SAPO-34.
- the mixed oxide consisting of cerium oxide, niobium oxide, rare earth sesquioxide and zirconium oxide in the form of a fully extruded, catalytically active honeycomb body is present and the zeolite compound and / or zeolite-like compound is contained in a catalytically active coating applied to the honeycomb body.
- the catalyst according to the invention is present as a coated inert supporting body, wherein the mixed oxide is contained in at least one catalytically active coating applied thereto, and the zeolite compound and / or the zeolite-like compound is contained in a spatially separate, further catalytically active coating ,
- the mixed oxide is contained in at least one catalytically active coating applied thereto
- the zeolite compound and / or the zeolite-like compound is contained in a spatially separate, further catalytically active coating
- so-called "zone catalysts” in which the catalytically active coatings are designed as zones following one another in the flow direction of the exhaust gas on the support body ( Figure 1).
- so-called “layered catalysts” may also be preferred, in which the catalytically active coatings are arranged on the support body as layers lying one above the other over the entire length of the component (FIG. 2).
- FIGS. 1 and 2 show embodiments in which (A) is the coating containing the mixed oxide composition according to the invention, while (B) is the coating which is spatially separated therefrom and which comprises the zeolite compound and / or zeolite-like compound contains.
- Embodiments according to FIG. 1 a) or FIG. 2 a), in which the coating containing the mixed oxide composition first comes into contact with the inflowing exhaust gas, are preferably used in applications with medium operating temperatures, in which a dynamic light-off behavior and rapid ignition With such an arrangement of the coatings, the maximum NO x conversion in the SCR reaction that is characteristic for the corresponding operating temperature can be achieved in the shortest possible time
- the downstream zone in the flow direction of the exhaust gas or layer (B) containing the zeolite compound and / or the zeolite-like compound is used in such applications mainly to store unreacted ammonia in the first zone or layer and to break through by the first zone or layer Nitrogen oxides at operating points with particularly high ⁇ quantities and / or ge to provide characteristic NO x conversions and to catalyze the corresponding reaction.
- Embodiments according to Figures 1 b) and 2b), in which the coating, which is the zeolite and / or the zeolite-like compound is contained, from the inflowing Exhaust gas is first contacted are preferred when a high ammonia storage is required to maintain the SCR reaction, for example, in very cold operating conditions (long cold start phases, low temperature applications), in which due to a low exhaust gas temperature level no urea can be metered.
- An arrangement according to Figure 1 b) is further preferred in arrangements in which the SCR catalyst is exposed to very high exhaust gas temperatures.
- the coating which contains the more age stable zeolite compounds and exhibits lower tendencies to overoxidize ammonia, is placed in the hotter upstream zone, while the downstream zone serves to complete the SCR reaction.
- the catalytically active composition according to the invention is present in the form of a coating on a catalytically inert support body, it may be advantageous to add a binder to the coating in order to ensure improved adhesion of the catalytically active coating to the catalytically inert support body. This is especially true when metallic support bodies are used.
- the binder is preferably selected from the group consisting of alumina, zirconia and silica. Silica is used in particular in the form of silica sol.
- the mixed oxide of cerium oxide, zirconium oxide, rare earth sesquioxide and niobium oxide or the catalytically active composition according to the invention which additionally contains a zeolite compound and / or a zeolite-like compound, is particularly suitable for the selective catalytic reduction of nitrogen oxides.
- the catalysts which can be produced therefrom in the described manner are particularly suitable for purifying the exhaust gases of predominantly lean-burn internal combustion engines, as used, for example, in motor vehicles (diesel vehicles, predominantly lean-burn gasoline vehicles).
- the preferred field of application of these catalysts is the selective catalytic reduction of nitrogen oxides in the exhaust gas of predominantly lean-burn internal combustion engines after the addition of ammonia as reducing agent to the exhaust gas to be purified, optionally in the form of a decomposable compound to ammonia.
- zone catalysts wherein (A) represents the catalytically active coating containing the composition of ceria, zirconia, rare earth sesquioxide and niobium oxide, while (B) represents a spatially separated catalytically active coating comprising a zeolite compound and / or a zeolite-like compound contains;
- a schematic section of a monolithic fürflußwaben redesign whose flow channels are separated by gas-impermeable walls on which the catalytically active coatings (A) and (B) are applied is shown schematically.
- Embodiments of layered catalysts according to the invention wherein (A) represents the catalytically active coating containing the composition of cerium oxide, zirconium oxide, rare earth sesquioxide and niobium oxide, while (B) is one of spatially separated catalytically active coating comprising a zeolite compound and / or a zeolite-like compound contains;
- a schematic section of a monolithic Siriflußwaben endeavor whose flow channels are separated by gas-impermeable walls on which the catalytically active coatings (A) and (B) are applied is shown schematically.
- Nitrogen oxide conversions in the SCR reaction measured on a composition of 38 wt .-% Ce0 2 , 14.5 wt .-% Nb 2 0 5 , 4.5 wt .-% Nd 2 0 3 and 43 wt. % Zr0 2 freshly prepared (K1 (f)), after aging at 750 ° C / 16 h (K1 (A-1)) and after aging at 600 ° C / 200 h (K1 (A-2)).
- FIG. 7 Difference of the NH 3 storage capacity between the fresh catalyst
- K3 (f) and its thermally pretreated at 750 ° C for 16 hours K3 (A-1) and its thermally pretreated at 750 ° C for 16 hours (K3 (A-1)) compared to VK3 (f) / VK3 (A-1).
- FIG. 8 Dynamic light-off behavior after NH 3 -dosing of the
- FIG. 9 Dynamic light-off behavior after NH 3 -dosing of the
- the mixed oxide compositions prepared in the Examples and Comparative Examples described below were suspended in water, ground and applied to a ceramic honeycomb body having a volume of 0.5 L and a cell number of 62 cells per square centimeter with a wall thickness of 0.17 mm. After calcination of the honeycomb body at 500 ° C for two hours in air, cylindrical cores were removed from the coated honeycomb body for testing in a model gas plant having a diameter of 25.4 mm and a length of 76.2 mm.
- the testing was carried out in a laboratory model gas plant under the following conditions.
- the nitrogen oxide concentrations of the model exhaust gas were detected after catalyst with a suitable analysis. From the known, metered nitrogen oxide contents, which were verified during conditioning at the beginning of the respective test run with a pre-catalyst exhaust gas analysis, and the measured nitrogen oxide contents after catalyst, the nitrogen oxide conversion, based on the ratio of NH 3 to NO, calculated over the catalyst for each temperature measuring point as follows:
- a commercially available cerium-zirconium mixed oxide having a weight ratio of Ce0 2 : Zr0 2 of 1: 1, 1 and a Nd 2 0 3 content of 5.3 wt .-% was impregnated with an aqueous solution of ammonium niobium oxalate and at 500 ° C calcined for a period of 2 hours.
- the mixed oxide composition according to the invention thus obtained consisted of 38% by weight of CeO 2 , 14.5% by weight of Nb 2 O s , 4.5% by weight of Nd 2 O 3 and 43% by weight of ZrO 2 . From the mixed oxide, a coating suspension was prepared and thus coated a catalytically inert honeycomb body.
- the catalyst thus prepared was taken from three cores. From a first drill core (K1 (f)) the catalytic activity according to the previously described test routine in the freshly prepared state was investigated. A second core (K1 (A-1)) was thermally treated in nitrogen at 750 ° C for 16 hours in an oven in an atmosphere containing 10% by volume of oxygen and 10% by volume of steam in the presence of catalytic activity. A third core (K1 (A-2)) was also thermally treated prior to analysis of catalytic activity. He became, however subjected to a thermal treatment adapted to the SCR application in the diesel vehicle, ie a thermal treatment at 600 ° C.
- Figure 3 shows the result of the investigations of the catalytic activity:
- the catalyst according to the invention already exhibits a nitrogen oxide conversion of more than 97% at 250 ° C.
- the temperature window between> 250 ° C. and 400 °
- the nitrogen oxides are completely converted by ° C.
- the conversion curves of the thermally pretreated drill cores also show that the catalyst according to the invention has a very, very high aging stability
- the catalyst reaches after the shortened aging at high temperatures (750 ° C, K1 (A-1)) loss of sales in the low temperature range up to 250 ° C and reach ht above 300 ° C complete NO x conversion.
- K1 (A-2) After prolonged aging at lower temperatures (K1 (A-2)), in contrast, in the low-temperature range up to 400 ° C. virtually no conversion degradation due to thermal aging can be observed. Aging of the catalyst under these conditions can only be observed by a faster drop in the NO x conversion curve in the high-temperature range above 400 ° C.
- Example 2 Analogously to the procedure described in Example 1, a mixed oxide of the following composition was obtained: 38% by weight CeO 2 , 14.5% by weight Nb 2 O 5 , 4.5% by weight Y 2 O 3 and 43% by weight. -% Zr0 2 .
- Example 2 From the mixed oxide, a coating suspension was prepared as indicated in Example 1 and thus coated a catalytically inert honeycomb body.
- the catalyst thus obtained is hereinafter referred to as K2.
- Example 1 As indicated in Example 1, here again, a second core (K2 (A-1)) was tested for 16 hours in an oven in an atmosphere containing 10% by volume of oxygen and 10% by volume of water vapor in nitrogen thermally treated at 750 ° C.
- the catalytic performance of the inventive catalysts according to Examples 1 and 2 in the SCR reaction was compared with two prior art catalysts:
- a commercial SCR catalyst was selected based on vanadium oxide, which contained a catalytically active coating consisting of V 2 0 5 , W0 3 , Ti0 2 and Si0 2 .
- a second comparative catalyst according to WO 2008/051752 was prepared which comprises a catalytically active coating consisting of 15% by weight WO 3 , 46.75% by weight ZrO 2 , 27.2% by weight CeO 2 , 5, 1 wt .-% Y 2 0 3 and 5.95 wt .-% Nb 2 0 3 on a catalytically inert honeycomb body contained.
- the catalyst was also sampled from two cores, one of which was tested as freshly prepared (VK2 (f)), and the second core (VK2 (A-1)) was placed in an oven in an atmosphere containing 10 for 16 hours prior to testing Vol .-% oxygen and 10 vol .-% steam in nitrogen at 750 ° C was thermally treated.
- FIG. 4 shows a comparison of the NO x conversion powers of the freshly prepared catalysts K1 (f), VK1 (f) and VK2 (f).
- the catalyst according to the invention shows the highest working temperature window with a complete NO x conversion in the range> 250 to 400 ° C.
- the catalyst according to the invention by far the best NO x -Konvert ists excel in the low temperature range up to 250 ° C. In the temperature range above 450 ° C, a marked “kinking" of the NO x conversion curve is observed - a reaction behavior of the comparative catalyst according to WO 2008/051752 (VK2 (f)) corresponds.
- FIG. 5 shows a comparison of the inventive catalyst K1 (A-2) aged at 600 ° C.
- FIG. 6 shows a comparison of the inventive catalysts K1 (A-1) and K2 (A-1) aged at 750 ° C. (16 hours) with the correspondingly aged comparative catalyst VK2 (A-1) according to WO 2008/051752. While the activity of the comparative catalyst according to WO 2008/051752 has clearly collapsed (maximum of 86% NO x conversion at 400 ° C.), the catalysts according to the invention still still reach NO x after this hot thermal treatment in the temperature range between 300 and 400 ° C. Sales close to 100% and over 95%.
- Example 1 a second core (VK3 (A-1)) was also tested for 16 hours in an oven in an atmosphere containing 10% by volume of oxygen and 10% by volume of steam in nitrogen thermally treated at 750 ° C.
- a layered catalyst according to FIG. 2a was produced.
- a catalyst obtained analogously to Comparative Example 3 (amount applied 150 g / l instead of 222 g / l) was provided with an additional coating by applying a coating suspension according to Example 1 in an amount of 70 g / l again by means of a conventional dipping method and was calcined.
- the layered catalyst thus obtained is hereinafter referred to as K3.
- a second core (K3 (A-1)) was tested for 16 hours in an oven in an atmosphere containing 10% by volume of oxygen and 10% by volume of water vapor in nitrogen thermally treated at 750 ° C.
- the thermal stability of the NH 3 storage capacity of K3 compared to VK3 was determined as follows:
- test was carried out on supported catalysts in a laboratory model gas facility.
- test gas compositions were adjusted:
- Phase 1 empty memory, hold time 10 min (600 ° C)
- Phase 2 cooling to target temperature (1 OK / min), hold time 5 min
- Phase 3 NH 3 adsorption phase, holding time 20 min
- Phase 5: heating to 600 ° C
- the concentration is determined that leaves at padded memory the catalyst: c (NH 3) Ph3, e nd-
- the stored amount of NH 3 at any time t is given by the difference between c (NH 3) Ph3, e nd and after the catalyst detected amount of NH 3 c (NH 3) 3 P, t:
- a layered catalyst according to FIG. 2b) was produced.
- the coating described in Example 2 was applied to a ceramic fürflußwaben redesign with 62 cells per square centimeter and a cell wall thickness of 0.17 millimeters in an amount of 70 g / L and calcined as described in Example 3 by a conventional dipping method.
- a suspension containing an iron-containing ⁇ -zeolite was then applied to this coating in a quantity of 150 g / l by means of a conventional dipping process, dried and calcined as indicated in Comparative Example 3.
- a zone catalyst according to FIG. 1a) was produced.
- the coating described in Example 2 was applied to a ceramic fürflußwaben redesign with 62 cells per square centimeter and a cell wall thickness of 0.17 millimeters in an amount of 200 g / L, but starting from the entrance end face of the honeycomb body only 50% of its length.
- the coating suspension described in Comparative Example 4 was then applied by a conventional dipping method, but starting from the exit end face of the honeycomb body to 50% of its length, i. up to the coating applied in the first step.
- the zone catalyst thus obtained is referred to as K5.
- a second core K5 (A-1) was also used in an oven for 16 hours prior to analysis of catalytic activity Atmosphere containing 10 vol .-% oxygen and 10 vol .-% steam in nitrogen at 750 ° C thermally treated.
- Example 5 The process described in Example 5 was repeated with the difference that in the second step, instead of the coating suspension described in Comparative Example 4, the coating suspension described in Comparative Example 3 was applied.
- the zone catalyst thus obtained is referred to as K6.
- a second core (K6 (A-1)) was tested for 16 hours in an oven in an atmosphere containing 10% by volume of oxygen and 10% by volume of water vapor in nitrogen thermally treated at 750 ° C.
- a coating suspension was prepared by suspending commercially available SAPO-34 in water and adding an aqueous copper (II) nitrate solution. The added amount of the copper nitrate solution was calculated such that the final catalyst contained 2% by weight of Cu based on the total weight of the exchanged zeolite-like compound.
- the suspension was stirred for 30 minutes to complete the ion exchange, and then, after adding silica sol as a binder, directly to a ceramic flow honeycomb body of 62 cells per square centimeter and cell wall thickness of 0.165 millimeters, having a diameter of 92.96 millimeters and a length of 76 , 2 millimeters, applied.
- the thus coated honeycomb body was dried at 90 ° C, calcined at 350 ° C and annealed for 2 hours at 640 ° in air.
- the catalyst thus obtained is designated as VK4.
- a second core VK4 (A-1) was also tested for 16 hours in an oven in an atmosphere containing 10% by volume of oxygen and 10% by volume of steam in nitrogen thermally treated at 750 ° C.
- the dynamic light-off behavior after NH 3 dosing of the inventive catalysts K2 (A-1) and K6 (A-1), and of the comparative catalyst VK3 (A-1) was determined as follows:
- test gas composition was adjusted:
- phases A through D The test was conducted at different temperatures, which were tuned to the most application-relevant target temperature range for an SCR system downstream of other exhaust gas purification units in an exhaust system, namely 250 ° C, 300 ° C and 350 ° C. At each temperature, a cycle has been run through four distinct phases, hereafter referred to as phases A through D:
- Phase A gas mixture 1; Duration: 5 minutes;
- Phase B Nhb-SCR phase: gas mixture 2; Duration: up to a NHh breakthrough of 20 vppm or break-off by time;
- Phase C gas mixture 3; Empty the NH3 storage tank by temperature ramp up
- Phase D gas mixture 3; Adjustment of the next measurement temperature Within a cycle, the catalyst temperature was first adjusted to the defined target temperature. Then, the catalyst was charged with gas mixture 1 for 5 minutes (phase A). In Phase B, gas mixture 2 was switched to determine the Nhh-SCR conversion. This phase was terminated either by detection of an NH3 breakthrough of 20 Vppm or by a previously fixed time criterion ended. Then gas mixture 3 was adjusted and the catalyst heated to 500 ° C to empty the ammonia storage (Phase C). Subsequently, the catalyst was cooled down to the next temperature to be tested (phase D), the next cycle started with phase A by adjusting the gas mixture 1 after adjusting the target temperature. The dynamic NOx conversion was determined for all measurement temperatures from the concentrations of the respective exhaust gas components before and after the catalyst determined during phase B.
- the NOx conversion X (NOx) is calculated, which results from the measured NOx concentration 5 seconds after the start of phase B.
- FIG. 8 shows the determined characteristic numbers for K2 (A-1), K6 (A-1) and VK3 (A-1), in each case at 250 and 300X.
- SCR catalysts with good properties are also obtained by replacing the mixed oxide described there in each case by one of the mixed oxides of Examples 7 to 13 in Examples 3 to 6.
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Abstract
The invention relates to the use of mixed oxides made of cerium oxide, zirconium oxide, rare earth sesquioxide and niobium oxide as catalytically active materials for the selective catalytic reduction of nitrogen oxides with ammonia or a compound that can decompose to form ammonia in the exhaust gas of internal combustion engines in motor vehicles that are predominantly leanly operated, and to compositions or catalysts which contain said mixed oxides in combination with zeolite compounds and/or zeolite-like compounds and are suitable for the denitrogenation of lean motor vehicle exhaust gases in all essential operating states.
Description
Neue Mischoxid-Materialien zur selektiven katalytischen Reduktion von New mixed oxide materials for the selective catalytic reduction of
Stickoxiden in Abgasen Nitrogen oxides in exhaust gases
Beschreibung Die Erfindung betrifft die Verwendung von Mischoxiden als katalytisch aktives Material zur selektiven katalytischen Reduktion von Stickoxiden mit Ammoniak oder einer zu Ammoniak zersetzlichen Verbindung als Reduktionsmittel im Abgas von überwiegend mager betriebenen Verbrennungsmotoren in Kraftfahrzeugen. Die Erfindung betrifft außerdem katalytisch aktive Zusammensetzungen umfassend ein Mischoxid und eine Zeolithverbbindung und/oder eine zeolithähnliche Verbindung, sowie verschiedene Ausführungsformen von Katalysatoren, die aus den genannten Mischoxiden bzw. Zusammensetzungen hergestellt werden. The invention relates to the use of mixed oxides as a catalytically active material for the selective catalytic reduction of nitrogen oxides with ammonia or a decomposable to ammonia compound as a reducing agent in the exhaust gas of predominantly lean-burn internal combustion engines in motor vehicles. The invention also relates to catalytically active compositions comprising a mixed oxide and a zeolite compound and / or a zeolite-like compound, as well as various embodiments of catalysts prepared from said mixed oxides or compositions.
Abgase von Kraftfahrzeugen mit einem überwiegend mager betriebenem Verbren- nungsmotor enthalten neben den üblichen Primäremissionen Kohlenmonoxid CO, Kohlenwasserstoffe HC und Stickoxide NOx einen relativ hohen Sauerstoffgehalt von bis zu 15 Vol.-%. Kohlenmonoxid und Kohlenwasserstoffe können durch Oxidation leicht unschädlich gemacht werden. Die Reduktion der Stickoxide zu Stickstoff ist wegen des hohen Sauerstoffgehaltes schwieriger. Exhaust gases from motor vehicles with a predominantly lean-burn internal combustion engine contain not only the usual primary emissions of carbon monoxide CO, hydrocarbons HC and nitrogen oxides NO x a relatively high oxygen content of up to 15 vol .-%. Carbon monoxide and hydrocarbons can easily be neutralized by oxidation. The reduction of nitrogen oxides to nitrogen is more difficult because of the high oxygen content.
Ein bekanntes Verfahren zur Entfernung von Stickoxiden aus Abgasen in Gegenwart von Sauerstoff ist das Verfahren der selektiven katalytischen Reduktion (SCR-Ver- fahren; Selective Catalytic Reduction) mittels Ammoniak an einem geeigneten Katalysator, kurz als SCR-Katalysator bezeichnet. Bei diesem Verfahren werden die aus dem Abgas zu entfernenden Stickoxide mit Ammoniak zu Stickstoff und Wasser umgesetzt. Das als Reduktionsmittel verwendete Ammoniak kann durch Eindosierung einer zu Ammoniak zersetzlichen Verbindung wie beispielsweise Harnstoff, Ammo- niumcarbamat oder Ammoniumformiat in den Abgasstrang und anschließende Hydrolyse verfügbar gemacht werden. Außerdem sind Abgasreinigungskonzepte für Kraft- fahrzeuge bekannt, in denen Ammoniak während einer fetten Betriebsphase des Motors an einem vorgeschalteten Katalysator, zum Beispiel einem Stickoxidspeicher- katalysator, als Sekundäremission erzeugt und im SCR-Katalysator bis zum Verbrauchszeitpunkt während der mageren Betriebsphasen zwischengespeichert wird.
Der Einsatz in einem diskontinuierlich arbeitenden SCR-System, in dem das als Reduktionsmittel verwendete Ammoniak ausschließlich als Sekundäremission in der Abgasanlage erzeugt wird, erfordert SCR-Katalysatoren, deren Ammoniakspeicherfähigkeit ausreicht, um möglichst den gesamten Reduktionsmittelbedarf für die Abgasentstickung während der Magerphase vorzuhalten. Hierzu eignen sich insbesondere Zeolith-basierte SCR-Katalysatoren, wie sie aus zahlreichen Publikationen und Patentanmeldungen bekannt sind. Beispielsweise beschreibt die US 4,961 ,917 eine Methode zur Reduktion von Stickoxiden mit Ammoniak unter Verwendung eines Katalysators, der neben einem Zeolith mit definierten Eigenschaften Eisen und/oder Kupfer als Promotor enthält. Weitere SCR-Katalysatoren auf der Basis Übergangs- metall-ausgetauschter Zeolithe und Verfahren zur selektiven katalytischen Reduktion unter Verwendung solcher SCR-Katalysatoren sind beispielsweise beschrieben in der EP 1 495 804 A1 , der US 6,914,026 B2 oder der EP 1 147 801 B1. Für den Einsatz in Abgasreinigungsanlagen mit Dosiereinrichtungen für Harnstoff oder andere zu Ammoniak zersetzliche Verbindungen, die die kontinuierliche Versorgung des Systems mit Reduktionsmittel ermöglichen, ist es nicht erforderlich, dass der SCR- Katalysator eine große Ammoniakspeicherkapazität aufweist. Dementsprechend ist man bestrebt, den Einsatz Zeolith-basierter SCR-Katalysatoren zu vermeiden, da diese wegen der hohen Herstellungspreise für Zeolithverbindungen sehr teuer sind. One known method of removing nitrogen oxides from exhaust gases in the presence of oxygen is the Selective Catalytic Reduction (SCR) process using ammonia on a suitable catalyst, abbreviated to SCR catalyst. In this method, the nitrogen oxides to be removed from the exhaust gas are reacted with ammonia to nitrogen and water. The ammonia used as the reducing agent can be made available by metering into the exhaust gas stream a compound which is decomposable to ammonia, for example urea, ammonium carbamate or ammonium formate, and subsequent hydrolysis. In addition, exhaust-gas cleaning concepts for motor vehicles are known in which ammonia is generated during a rich operating phase of the engine on an upstream catalytic converter, for example a nitrogen oxide storage catalytic converter, as secondary emission and stored in the SCR catalytic converter until the point of consumption during the lean operating phases. The use in a discontinuous SCR system, in which the ammonia used as a reducing agent is generated exclusively as a secondary emission in the exhaust system requires SCR catalysts whose ammonia storage capacity is sufficient to provide as much as possible of the total reducing agent need for Abgasentstickung during the lean phase. Particularly suitable for this purpose are zeolite-based SCR catalysts, as are known from numerous publications and patent applications. For example, US Pat. No. 4,961,917 describes a method for reducing nitrogen oxides with ammonia using a catalyst which contains iron and / or copper as promoter in addition to a zeolite having defined properties. Further SCR catalysts based on transition metal-exchanged zeolites and processes for the selective catalytic reduction using such SCR catalysts are described, for example, in EP 1 495 804 A1, US Pat. No. 6,914,026 B2 or EP 1 147 801 B1. For use in emission control systems with urea dosing devices or other ammonia-decomposable compounds that allow continuous supply of the system with reducing agent, it is not necessary for the SCR catalyst to have a large ammonia storage capacity. Accordingly, efforts are being made to avoid the use of zeolite-based SCR catalysts, which are very expensive because of the high production prices of zeolite compounds.
Hierfür eignen sich SCR-Katalysatoren, die Vanadiumoxid neben Titandioxid oder Wolframoxid oder Mischungen davon enthalten. Beispielsweise beschreibt die EP 0 385 164 B1 einen solchen Katalysator, der neben Titandioxid mindestens ein Oxid von Wolfram, Silizium, Bor, Aluminium, Phosphor, Zirkonium, Barium, Yttrium, Lanthan oder Cer, sowie mindestens ein Oxid von Vanadium, Niob, Molybdän, Eisen oder Kupfer enthält und der als Formkörper durch Verpressung beziehungsweise Extrusion der Komponenten gegebenenfalls nach Zusatz geeigneter Hilfsstoffe hergestellt wird. Die EP 1 153 648 A1 beschreibt einen strukturierten SCR-Katalysator, der unter einer Hydrolysekatalysator-Beschichtung eine Reduktionsbeschichtung enthält, deren Zusammensetzung der aus der EP 0 385 164 B1 bekannten Rezeptur entspricht. EP 0 246 859 beschreibt einen SCR-Katalysator, der Vanadium aufgebracht auf eine Mischung von Ceroxid und Aluminiumoxid enthält. For this purpose, SCR catalysts containing vanadium oxide in addition to titanium dioxide or tungsten oxide or mixtures thereof are suitable. For example, EP 0 385 164 B1 describes such a catalyst which, in addition to titanium dioxide, contains at least one oxide of tungsten, silicon, boron, aluminum, phosphorus, zirconium, barium, yttrium, lanthanum or cerium, and at least one oxide of vanadium, niobium, molybdenum, Contains iron or copper and is prepared as a shaped body by compression or extrusion of the components optionally after addition of suitable auxiliaries. EP 1 153 648 A1 describes a structured SCR catalyst which contains, under a hydrolysis catalyst coating, a reduction coating whose composition corresponds to the formulation known from EP 0 385 164 B1. EP 0 246 859 describes an SCR catalyst containing vanadium applied to a mixture of ceria and alumina.
Ein wesentliches Problem bei der Verwendung der Vanadium-haltigen SCR-Kataly- satoren zur Reinigung der Abgase von Kraftfahrzeugen ist die mögliche Emission von
flüchtigen, toxischen Vanadiumverbindungen bei höheren Abgastemperaturen, wodurch mit Beeinträchtigungen von Mensch und Umwelt gerechnet werden muß. Dementsprechend sinkt die Akzeptanz von Vanadium-haltigen Autoabgaskatalysatoren am Markt. Bemühungen, kostengünstige Vanadium-freie SCR-Katalysatoren zur Verfü- gung zu stellen, gibt es bereits seit längerem. So sind einige Mischoxid-Zusammensetzungen auf der Basis von Cer-Zirkon-Mischoxid und ihre Verwendung in der SCR- Reaktion im Stand der Technik bereits bekannt. A major problem with the use of the vanadium-containing SCR catalysts for cleaning the exhaust gases of motor vehicles is the possible emission of volatile, toxic vanadium compounds at higher exhaust gas temperatures, which must be expected to be harmful to humans and the environment. Accordingly, the acceptance of vanadium-containing autocatalysts in the market is decreasing. Efforts to provide cost-effective vanadium-free SCR catalysts have been around for some time. Thus, some mixed oxide compositions based on cerium-zirconium mixed oxide and their use in the SCR reaction are already known in the art.
WO 2008/049491 offenbart homogene Cer-Zirkon-Mischoxide, welche 10 - 90 Gew.-% Ceroxid bezogen auf das Gesamtgewicht des Cer-Zirkon-Mischoxids enthalten und durch Einbringen von Schwefel oder einem Übergangsmetall ausgewählt aus der Gruppe bestehend aus Chrom, Molybdän, Wolfram oder Mischungen davon oder durch Kombinationen davon für die SCR-Reaktion aktiviert sind. Besonders bevorzugte Ausführungsformen dieser Mischoxide enthalten 0,02 bis 3 Gew.-% Schwefel und/oder 5 bis 15 Gew.-% Molybdän oder Wolfram und 0,5 bis 3 Gew.-% Eisen oder Kupfer, jeweils bezogen auf das Gesamtgewicht des Cer-Zirkon-Mischoxids. Zur Herstellung der SCR-aktiven Verbindungen werden besonders bevorzugt Cer-Zirkon-Mischoxide eingesetzt, die 45 - 55 Gew.-% Ce02 und 1 - 9 Gew.-% Selten-Erd-Oxid enthalten. EP 2 116 293 offenbart einen Vanadium-freien SCR-Katalysator, welcher Wolframoxid W03 und ein homogenes Cer-Zirkon-Mischoxid (Ce, Zr)02 enthält, wobei der Gehalt an Wolframoxid W03 zwischen 5 und 25 Gew.-%, der Gehalt des homogenen Cer-Zirkon- Mischoxides zwischen 50 und 95 Gew.-% liegen kann. Bevorzugt werden Cer-Zirkon- Mischoxide mit einem Gewichtsverhältnis von Ceroxid Ce02 zu Zirkonoxid Zr02 zwischen 0,67 und 1 ,5. WO 2008/049491 discloses homogeneous cerium-zirconium mixed oxides containing 10 to 90% by weight of cerium oxide, based on the total weight of the cerium-zirconium mixed oxide, and by incorporating sulfur or a transition metal selected from the group consisting of chromium, molybdenum, Tungsten or mixtures thereof or combinations thereof are activated for the SCR reaction. Particularly preferred embodiments of these mixed oxides contain 0.02 to 3 wt .-% sulfur and / or 5 to 15 wt .-% molybdenum or tungsten and 0.5 to 3 wt .-% iron or copper, each based on the total weight of cerium -Zirkon mixed oxide. Cerium-zirconium mixed oxides containing 45-55% by weight of CeO 2 and 1-9% by weight of rare earth oxide are particularly preferably used for the preparation of the SCR-active compounds. EP 2 116 293 discloses a vanadium-free SCR catalyst which contains tungsten oxide WO 3 and a homogeneous cerium-zirconium mixed oxide (Ce, Zr) O 2 , the content of tungsten oxide WO 3 being between 5 and 25% by weight, the content of the homogeneous cerium-zirconium mixed oxide can be between 50 and 95% by weight. Cerium-zirconium mixed oxides having a weight ratio of cerium oxide CeO 2 to zirconium oxide ZrO 2 between 0.67 and 1.5 are preferred.
EP 2 072 120 offenbart ebenfalls einen temperaturstabilen Katalysator zur Reduktion von Stickoxiden in Gegenwart von Ammoniak, der 10 bis 30 Gew.-% Ceroxid und 5 bis 14 % Wolframoxid, sowie Zirkonoxid als komplexes Oxid enthält. EP 2 072 120 likewise discloses a temperature-stable catalyst for the reduction of nitrogen oxides in the presence of ammonia, which contains 10 to 30% by weight of cerium oxide and 5 to 14% of tungsten oxide, and zirconium oxide as complex oxide.
WO 2008/051752 offenbart einen NOx-Reduktionskatalysator, der ein Cer-Zirkon- basiertes Mischoxid der Formel CeaZrbRtAiMeOx enthält, worin R Wolfram oder Mangan und A Molybdän, Tantal oder Niob ist, gegebenenfalls auch Wolfram, falls R Mangan ist. M bezeichnet ein dreiwertiges Selten-Erd-Ion, bevorzugt ausgewählt aus Sm, Gd, Dy, Er, Yb, Ho, Er, Tm und Lu, nicht jedoch La oder Y. Das Mischoxid der
genannten Zusammensetzung ist katalytisch aktiv und eignet sich zur selektiven kata- lytischen Reduktion von Stickoxiden mit Ammoniak. Es kann in einem entsprechenden Abgasnachbehandlungssystem entweder als wesentlicher Bestandteil der katalytisch aktiven Beschichtung eines SCR-Katalysators oder als Bestandteil der Beschichtung eines katalytisch aktiven Partikelfilters eingesetzt werden. WO 2008/051752 discloses a NO x reduction catalyst comprising a cerium-zirconium-based mixed oxide of the formula Ce a Zr b R t AiMeO x wherein R is tungsten or manganese and A is molybdenum, tantalum or niobium, optionally also tungsten, if R is manganese. M denotes a trivalent rare earth ion, preferably selected from Sm, Gd, Dy, Er, Yb, Ho, Er, Tm and Lu, but not La or Y. The mixed oxide of This composition is catalytically active and is suitable for the selective catalytic reduction of nitrogen oxides with ammonia. It can be used in a corresponding exhaust aftertreatment system either as an essential component of the catalytically active coating of an SCR catalyst or as part of the coating of a catalytically active particulate filter.
EP 0 277 765 offenbart ein Verfahren zur Entfernung von Stickoxiden aus dem Abgas von Dieselmotoren durch katalytische Reduktion über einem Wabenkörper-Katalysator, der als aktives Material 60 bis 95 Gew.-% eines Oxids ausgewählt aus Ti02, Zr02, (Ti, Zr)02, (Ti, Si)02 und (Ti, Zr, Si)02 enthält. Desweiteren enthält der Katalysator 0,5 bis 40 Gew.-% Vanadium-, Wolfram-, Molybdän-, Mangan-, Cer- und/oder Zinnoxid. EP 0 277 765 discloses a process for removing nitrogen oxides from the exhaust gas of diesel engines by catalytic reduction over a honeycomb catalyst containing as active material 60 to 95% by weight of an oxide selected from TiO 2 , ZrO 2 , (Ti, Zr ) 0 2 , (Ti, Si) 0 2 and (Ti, Zr, Si) 0 2 . Furthermore, the catalyst contains 0.5 to 40 wt .-% vanadium, tungsten, molybdenum, manganese, cerium and / or tin oxide.
US 5,552,128 beschreibt ein Verfahren zur Umsetzung von Stickoxiden zu Stickstoff durch in Kontakt bringen der Stickoxide mit einem Reduktionsmittel in Gegenwart eines Katalysators, der die Reduktion der Stickoxide wirksam katalysiert. Der Katalysator besteht im wesentlichen aus Festsäurekomponenten umfassend ein Metalloxid der 4. Nebengruppe des Periodensystems der Elemente, das mit einem Oxyanion eines Metalls der 6. Nebengruppe modifiziert ist und weiterhin mindestens ein Metall ausgewählt aus der 1., der 5., der 7. oder der 8. Nebengruppe oder auch der 4. Haupt- gruppe des Periodensystems der Elemente enthält. Als Beispiele für entsprechende Katalysatoren nennt die Patentschrift mit Wolframat und Eisen modifiziertes Zirkonoxid; nur mit Wolframat modifiziertes Zirkonoxid; mit Wolframat und Cer modifiziertes Zirkonoxid; mit Wolframat und Nickel modifiziertes Zirkonoxid; mit Wolframat und Zinn modifiziertes Zirkonoxid und mit Wolframat, Eisen und Mangan modifiziertes Zirkonoxid. US 5,552,128 describes a process for reacting nitrogen oxides to nitrogen by contacting the nitrogen oxides with a reducing agent in the presence of a catalyst which effectively catalyzes the reduction of the nitrogen oxides. The catalyst consists essentially of solid acid components comprising a metal oxide of the 4th subgroup of the Periodic Table of the Elements, which is modified with an oxyanion of a metal of the 6th subgroup and further at least one metal selected from the 1st, the 5th, the 7th or contains the 8th subgroup or even the 4th main group of the periodic table of the elements. As examples of corresponding catalysts, the patent mentions tungstate and iron-modified zirconium oxide; only tungstate modified zirconia; tungstate and cerium modified zirconia; tungstate and nickel modified zirconia; zirconia modified with tungstate and tin, and zirconia modified with tungstate, iron and manganese.
US 2006/0228283 beschreibt ein Katalysatorsystem und ein Verfahren zur Verminderung von Stickoxiden in Abgasen durch Reduktion mit Kohlenwasserstoffen oder Sauerstoff-haltigen organischen Verbindungen. Es wird ein Katalysatorsystem aus einem Silber-haltigen Katalysator und einem „Modifizierungskatalysator" eingesetzt. Der„Modifizierungskatalysator" enthält ein„Modifizierungsoxid" ausgewählt aus der Gruppe bestehend aus Eisenoxid, Ceroxid, Kupferoxid, Manganoxid, Chromoxid, Lan- thanidoxide, Actinidoxide, Molybdänoxid, Zinnoxid, Indiumoxid, Rheniumoxid, Tantaloxid, Osmiumoxid, Bariumoxid, Calciumoxid, Strontiumoxid, Kaliumoxid, Kalziumoxid, Vanadiumoxid, Nickeloxid, Wolframoxid und Mischungen davon. Diese „Modifizie- rungsoxid" ist auf anorganischen Trägeroxiden aufgebracht, wobei mindestens eines
sauer und bevorzugt ausgewählt ist aus der Gruppe bestehend aus Titan-Zirkon- Mischoxid, Zirkon-Aluminium-Mischoxid, sulphatisiertes Zirkonoxid, phosphatiertes Zirkonoxid, Wolfram-modifiziertes Zirkonmischoxid, Silizium-Aluminium-Mischoxid, Zeolith oder Mischungen davon. US 2006/0228283 describes a catalyst system and a method for reducing nitrogen oxides in exhaust gases by reduction with hydrocarbons or oxygen-containing organic compounds. The "modification catalyst" comprises a "modification oxide" selected from the group consisting of iron oxide, cerium oxide, copper oxide, manganese oxide, chromium oxide, lanthanide oxides, actinide oxides, molybdenum oxide, Tin oxide, indium oxide, rhenium oxide, tantalum oxide, osmium oxide, barium oxide, calcium oxide, strontium oxide, potassium oxide, calcium oxide, vanadium oxide, nickel oxide, tungsten oxide, and mixtures thereof.This "modifying oxide" is applied to inorganic carrier oxides, at least one acidic and preferably selected from the group consisting of titanium-zirconium mixed oxide, zirconium-aluminum mixed oxide, sulphated zirconium oxide, phosphated zirconium oxide, tungsten-modified zirconium mixed oxide, silicon-aluminum mixed oxide, zeolite or mixtures thereof.
Der Erfindung liegt die Aufgabe zugrunde, kostengünstige, Vanadium-freie SCR- Katalysatoren zur Verfügung zu stellen, die sich durch dynamisches Anspringverhalten bei zugleich alterungsstabiler Ammoniak-Speicherkapazität auszeichen und sich auch als Abgasreinigungsbauteile mit geringem Staudruck herstellen lassen. The invention has for its object to provide cost-effective, vanadium-free SCR catalysts available, which are characterized by dynamic light-off while aging resistant ammonia storage capacity and can also be produced as exhaust gas purification components with low back pressure.
Im Stand der Technik ist bekannt, dass ausgewählte, gegebenenfalls mit Seltenerd- sesquioxiden dotierte Cer-Zirkon-Mischoxide nach einer gezielten Aktivierung eine die selektive katalytische Reduktion von Stickoxiden katalysierende Wirkung zeigen können. Die Erfinder haben nun überraschend festgestellt, dass die gezielte Vergesell- schaftung der vorstehend genannten Mischoxide mit Niob(V)-oxid (Nb205) zu einem Mischoxid aus Ceroxid, Zirkonoxid, Seltenerdsesquioxid und Nioboxid führt, welches ohne einen zusätzlichen Aktivierungsschritt eine hervorragende Aktivität bei zugleich hoher Alterungsstabilität in der SCR-Reaktion zeigt. It is known in the prior art that selected cerium-zirconium mixed oxides, optionally doped with rare earth sesquioxides, can show an effect catalyzing the selective catalytic reduction of nitrogen oxides after a targeted activation. The inventors have now surprisingly found that the targeted Veresell- tion of the aforementioned mixed oxides with niobium (V) oxide (Nb 2 0 5 ) to a mixed oxide of ceria, zirconia, rare earth sesquioxide and niobium oxide, which without an additional activation step an excellent Activity with high aging stability in the SCR reaction shows.
Solche Mischoxide sind in US 6,468,941 B1 beschrieben, werden dort aber nicht zur Katalyse der selektiven katalytischen Reduktion von Stickoxiden verwendet, sondern als Sauerstoffionen leitende bzw. Sauerstoff speichernde Materialien in Dreiwegekatalysatoren. Such mixed oxides are described in US Pat. No. 6,468,941 B1, but are not used there to catalyze the selective catalytic reduction of nitrogen oxides, but as oxygen-ion-conducting or oxygen-storing materials in three-way catalysts.
Die vorliegende Erfindung betrifft demnach die Verwendung eines katalytisch aktiven Mischoxides bestehend aus Ceroxid, Nioboxid, Seltenerdsesquioxid und Zirkonoxid zur selektiven katalytischen Reduktion von Stickoxiden. The present invention accordingly relates to the use of a catalytically active mixed oxide consisting of cerium oxide, niobium oxide, rare earth sesquioxide and zirconium oxide for the selective catalytic reduction of nitrogen oxides.
Die erfindungsgemäße Verwendung erfolgt beispielsweise dergestalt, dass das Mischoxid in Form eines vollextrudierten, katalytisch aktiven Wabenkörpers in einem Katalysator enthalten ist. Insbesondere erfolgt die erfindungsgemäße Verwendung aber so, dass das Mischoxid in einer katalytisch aktiven Beschichtung enthalten ist, die auf einen katalytisch inerten Tragkörper aufgebracht ist, der zusammen mit der Beschichtung einen Katalysator bildet.
Die Herstellung des erfindungsgemäß verwendeten Mischoxids kann mit einfachsten Mitteln erfolgen. So erhält man ein geeignetes komplexes Mischoxid beispielsweise durch Imprägnierung eines kommerziell erhältlichen Cer-Zirkon-Mischoxides, welches zur Stabilisierung mit Seltenerdsesquioxid dotiert ist, mit einer wässrigen Lösung einer in Wasser löslichen Niobverbindung und anschließende Kalzination des so erhaltenen (feuchten) Pulvers. The use according to the invention takes place, for example, in such a way that the mixed oxide is contained in the form of a fully extruded, catalytically active honeycomb body in a catalyst. In particular, however, the use according to the invention takes place in such a way that the mixed oxide is contained in a catalytically active coating which is applied to a catalytically inert support body which forms a catalyst together with the coating. The preparation of the mixed oxide used according to the invention can be carried out by the simplest means. Thus, a suitable complex mixed oxide is obtained, for example, by impregnation of a commercially available cerium-zirconium mixed oxide, which is doped with rare earth sesquioxide for stabilization, with an aqueous solution of a water-soluble niobium compound and subsequent calcination of the (wet) powder thus obtained.
Bevorzugte erfindungsgemäß zu verwendende Mischoxide, die sich sehr gut zur Katalyse der selektiven Reduktion von Stickoxiden in mageren Abgasen eignen, weisen die folgende Zusammensetzung ihrer Komponenten, berechnet als Gewichtsanteile der primären Oxide, auf: 15 - 50 Gew.-% Ce02, 3 - 25 Gew.-% Nb205l 3 - 10 Gew.-% SE203 und Rest Zr02, worin SE für ein Seltenerdelement steht. Besonders bevorzugt enthalten die Mischoxide 25 - 45 Gew.-% Ce02, 3 - 20 Gew.-% Nb205l 3 - 10 Gew.-% SE203 und Rest Zr02, und ganz besonders bevorzugt 35 - 40 Gew.-% Ce02, 10 - 15 Gew.-% Nb205, 3 - 6 Gew.-% SE203 und Rest Zr02. Bevorzugt eingesetzte Seltenerdsesquioxide SE203 sind Seltenerdsesquioxide des Yttriums, des Ytterbiums, des Lanthans, des Praseodyms (als Pr6O = 4 Pr02 · Pr203), des Neodyms, des Samariums, des Terbiums und des Erbiums. Besonders bevorzugt eingesetzt werden Yttriumsesquioxid Y203 und Neodymsesquioxid Nd203. Preferred mixed oxides to be used according to the invention, which are very suitable for catalyzing the selective reduction of nitrogen oxides in lean exhaust gases, have the following composition of their components, calculated as parts by weight of the primary oxides: 15-50% by weight CeO 2 , 3 25 wt .-% Nb 2 0 5l 3 - 10 wt .-% SE 2 0 3 and rest Zr0 2 , where SE is a rare earth element. Particularly preferably, the mixed oxides contain 25-45 wt .-% Ce0 2 , 3 - 20 wt .-% Nb 2 0 5l 3 - 10 wt .-% SE 2 0 3 and the radical Zr0 2 , and most preferably 35- 40 wt % Ce0 2 , 10-15% by weight Nb 2 0 5 , 3-6% by weight SE 2 O 3 and the radical ZrO 2 . Seltenerdsesquioxide SE 2 0 3 are preferably used are Seltenerdsesquioxide of yttrium, ytterbium, lanthanum, praseodymium (as Pr 6 O 4 = Pr0 2 · Pr 2 0 3), neodymium, samarium, terbium and erbium. Particular preference is given Yttriumsesquioxid Y 2 0 3 and Nd 2 0 Neodymsesquioxid. 3
Zum Einsatz in der katalytischen Abgasreinigung beispielsweise von Fahrzeugen mit überwiegend mager betriebenem Verbrennungsmotor werden die erfindungsgemäß zu verwendenden Mischoxide zum Beispiel zu einem mechanisch stabilen Katalysator verarbeitet. For use in catalytic exhaust gas purification, for example of vehicles with a predominantly lean-burn internal combustion engine, the mixed oxides to be used according to the invention are processed, for example, into a mechanically stable catalyst.
Bevorzugte Ausgestaltungen eines solchen Katalysators erhält man durch Aufbringen mindestens einer katalytisch aktiven Beschichtung, die das erfindungsgemäß zu verwendende Mischoxid enthält, auf einen katalytisch inerten Tragkörper. Als katalytisch inerte Tragkörper kommen bevorzugt keramische oder metallische Durchflußwabenkörper, keramische Wandflußfiltersubstrate und keramische oder metallische Schaumstrukturen zum Einsatz. Desweiteren erhält man bevorzugte Ausgestaltungen des Katalysators, wenn aus dem erfindungsgemäß zu verwendenden Mischoxid durch Extrusion ein katalytisch aktiver, monolithischer Wabenkörper hergestellt wird. Diese Ausführungsformen zeichnen sich durch einen besonders geringen Staudruck aus. Zu ihrer Herstellung wird eine extrusionsfähige, pastöse Masse erzeugt, die neben der katalytisch aktiven Zusammensetzung gegebenenfalls Extrusionshilfsstoffe wie
beispielsweise Bentonit, Böhmit, γ-Aluminiumoxid, Zirkonoxid oder auch herkömmliches Cer-Zirkon-Mischoxid enthält. Sowohl Verfahren zur Beschichtung von katalytisch inerten Tragkörpern als auch Verfahren zur Herstellung von katalytisch aktiven, monolithischen Wabenkörpern durch Extrusion gehören zum Stand der Technik und sind dem Fachmann bekannt. Preferred embodiments of such a catalyst are obtained by applying at least one catalytically active coating which contains the mixed oxide to be used according to the invention to a catalytically inert support body. As a catalytically inert support preferably ceramic or metallic Durchflußwabenkörper, ceramic Wandflußfiltersubstrate and ceramic or metallic foam structures are used. Furthermore, preferred embodiments of the catalyst are obtained when a catalytically active, monolithic honeycomb body is produced by extrusion from the mixed oxide to be used according to the invention. These embodiments are characterized by a particularly low back pressure. For their preparation, an extrudable, pasty mass is produced which in addition to the catalytically active composition optionally extrusion aids such For example, bentonite, boehmite, γ-alumina, zirconium oxide or conventional cerium-zirconium mixed oxide contains. Both processes for coating catalytically inert support bodies and processes for producing catalytically active, monolithic honeycomb bodies by extrusion belong to the prior art and are known to the person skilled in the art.
Die derart hergestellten Katalysatoren zeigen hervorragende NOx-Konvertierungsraten im Temperaturbereich von 250°C bis 450°C. Sie zeichnen sich insbesondere durch eine hervorragende Alterungsstabilität unter hydrothermalen Bedingungen aus. The catalysts prepared in this way exhibit excellent NO x conversion rates in the temperature range from 250 ° C to 450 ° C. They are characterized in particular by excellent aging stability under hydrothermal conditions.
Eine weitere Eigenschaft dieser Katalysatoren, die für ihre Applikation zur Reinigung der Abgase von Fahrzeugen mit überwiegend mager betriebenem Verbrennungsmotor von besonderer Bedeutung ist, ist die hohe thermische Stabilität ihrer Ammoniak- Speicherkapazität. Zwar weisen sie eine im Vergleich zu Zeolith-basierten SCR- Katalysatoren um mindestens 30 % verringerte Ammoniak-Speicherkapazität auf, so dass sie weniger bevorzugt sind für den Einsatz in Passiv-SCR-Verfahren, in denen das als Reduktionsmittel genutzte Ammoniak nur während ausgewählter Betriebszustände an dafür geeigneten, vorgeschalteten Katalysatoren als Sekundäremission erzeugt wird. Diese geringe, für Aktiv-SCR-Verfahren jedoch vollkommen ausreichende Ammoniak-Speicherkapazität ist dafür nach thermischer bzw. nach hydrothermaler Alterung ausgesprochen stabil. Die Kombination dieser Eigenschaften bedingt ein dynamisches Anspringverhalten des Katalysators in der SCR-Reaktion nach Dosierung des Reduktionsmittels aus einer vom Motor unabhängigen Quelle (z.B. in Form von Harnstoffeinspritzung in den Abgasstrang) in allen wichtigen Betriebspunkten. Dadurch kann die Dosierstrategie für das Reduktionsmittel deutlich einfacher gestaltet werden, als bei den Systemen nach dem Stand der Technik, in denen beispielsweise ausschließlich Zeolith-basierte SCR-Katalysatoren zum Einsatz kommen. Another property of these catalysts, which is of particular importance for their application for cleaning the exhaust gases of vehicles with predominantly lean-burn internal combustion engine, is the high thermal stability of their ammonia storage capacity. While they have at least 30% reduced ammonia storage capacity compared to zeolite-based SCR catalysts, they are less preferred for use in passive SCR processes where the ammonia used as the reductant is only during selected operating conditions is produced on suitable, upstream catalysts as secondary emission. However, this small, sufficient for active SCR process but sufficient ammonia storage capacity is very stable for thermal or after hydrothermal aging. The combination of these properties causes a dynamic light-off behavior of the catalyst in the SCR reaction after metering of the reductant from a source independent of the engine (e.g., in the form of urea injection into the exhaust line) at all important operating points. As a result, the metering strategy for the reducing agent can be made significantly simpler than in the systems according to the prior art in which, for example, exclusively zeolite-based SCR catalysts are used.
Wird in der konkreten Anwendung ein höherer Ammoniakspeicher oder eine Verbrei- terung des Aktivitätstemperaturbereiches des oben beschriebenen Katalysators benötigt, so kann das erfindungsgemäß zu verwendende Mischoxid in Kombination mit einer Zeolithverbindung und/oder einer zeolithähnlicher Verbindung eingesetzt werden. Die vorliegende Erfindung betrifft demnach auch eine katalytisch aktive Zusammensetzung umfassend (i) ein Mischoxid bestehend aus Ceroxid, Nioboxid, Seltenerdsesquioxid und Zirkonoxid und (ii) eine Zeolithverbindung und/oder eine
zeolithähnlichen Verbindung, welche austauschbare Kationen ausgewählt aus der Gruppe bestehend aus H+, NH4\ Fe2+, Fe3+, Cu+, Cu2+, Ag+ oder Mischungen davon enthält. Die vorliegende Erfindung betrifft darüber hinaus einen Katalysator, der dadurch gekennzeichnet ist, dass er (i) ein Mischoxid bestehend aus Ceroxid, Nioboxid, Seltenerdsesquioxid und Zirkonoxid und (ii) eine Zeolithverbindung und/oder eine zeolithähnlichen Verbindung, welche austauschbare Kationen ausgewählt aus der Gruppe bestehend aus H+, NH4 +, Fe2+, Fe3+, Cu+, Cu2+, Ag+ oder Mischungen davon enthält. If a higher ammonia storage or a broadening of the activity temperature range of the above-described catalyst is required in the specific application, the mixed oxide to be used according to the invention can be used in combination with a zeolite compound and / or a zeolite-like compound. Accordingly, the present invention also relates to a catalytically active composition comprising (i) a mixed oxide consisting of cerium oxide, niobium oxide, rare earth sesquioxide and zirconium oxide and (ii) a zeolite compound and / or a zeolite-like compound containing exchangeable cations selected from the group consisting of H + , NH 4 \ Fe 2+ , Fe 3+ , Cu + , Cu 2+ , Ag + or mixtures thereof. The present invention further relates to a catalyst characterized in that it comprises (i) a mixed oxide consisting of cerium oxide, niobium oxide, rare earth sesquioxide and zirconium oxide and (ii) a zeolite compound and / or a zeolite-like compound which contains exchangeable cations selected from the group consisting of H + , NH 4 + , Fe 2+ , Fe 3+ , Cu + , Cu 2+ , Ag + or mixtures thereof.
Bevorzugte erfindungsgemäße katalytisch aktive Zusammensetzungen und bevorzugte erfindungsgemäße Katalysatoren enthalten die oben als bevorzugt bzw. besonders bevorzugt bezeichneten Mischoxide. Preferred catalytically active compositions according to the invention and preferred catalysts according to the invention comprise the mixed oxides described above as being preferred or particularly preferred.
Besonders bevorzugt enthält die Zeolithverbindung und/oder die zeolithähnliche Verbindung H+, Fe- und/oder Cu-Kationen. Die Zeolithverbindung und/oder die zeolithähnliche Verbindung selbst wird bevorzugt ausgewählt aus der Gruppe bestehend aus Zeolith beta, USY, ZSM-5, CHA, FER, ERI, SAPO-11 , SAPO-17, SAPO-34, SAPO-56, ALPO-11 , ALPO-17, ALPO-34 und ALPO-56, Besonders bevorzugt sind Zeolith beta, CHA, FER und SAPO-34. The zeolite compound and / or the zeolite-like compound particularly preferably contains H + , Fe- and / or Cu cations. The zeolite compound and / or the zeolite-like compound itself is preferably selected from the group consisting of zeolite beta, USY, ZSM-5, CHA, FER, ERI, SAPO-11, SAPO-17, SAPO-34, SAPO-56, ALPO- 11, ALPO-17, ALPO-34 and ALPO-56. Particular preference is given to zeolite beta, CHA, FER and SAPO-34.
In einer Ausführungsform des erfindungsgemäßen Katalysators liegt das Mischoxid bestehend aus Ceroxid, Nioboxid, Seltenerdsesquioxid und Zirkonoxid in Form eines vollextrudierten, katalytisch aktiven Wabenkörpers vor und die Zeolithverbindung und/oder zeolithähnliche Verbindung ist in einer auf den Wabenkörper aufgebrachten katalytisch aktiven Beschichtung enthalten. In one embodiment of the catalyst according to the invention, the mixed oxide consisting of cerium oxide, niobium oxide, rare earth sesquioxide and zirconium oxide in the form of a fully extruded, catalytically active honeycomb body is present and the zeolite compound and / or zeolite-like compound is contained in a catalytically active coating applied to the honeycomb body.
In einer weiteren Ausführungsform des erfindungsgemäßen Katalysators liegt er als beschichteter inerter Tragkörper vor, wobei das Mischoxid in mindestens einer darauf aufgebrachten katalytisch aktiven Beschichtung enthalten ist, und die Zeolithverbindung und/oder die zeolithähnliche Verbindung in einer räumlich davon getrennten, weiteren katalytisch aktiven Beschichtung enthalten ist.
Je nach Zielanwendung kann es besonders vorteilhaft sein, sogenannte„Zonenkatalysatoren" zu verwenden, in denen die katalytisch aktiven Beschichtungen als in Strömungsrichtung des Abgases horizontal aufeinander folgende Zonen auf dem Tragkörper ausgeführt sind (Figur 1 ). Ändern sich Betriebs- und Applikationsbedingungen des Katalysators, so können jedoch auch sogenannte „Schichtkatalysatoren" zu bevorzugen sein, in denen die katalytisch aktiven Beschichtungen als vertikal über die gesamte Länge des Bauteils übereinander liegende Schichten auf dem Tragkörper angeordnet sind (Figur 2). Welche konkrete Ausgestaltung des Katalysators zu wählen ist, um ein möglichst optimales Abgasreinigungsergebnis zu erzielen, hängt, wie schon erwähnt, von den Betriebsbedingungen des Katalysators in der Zielanwendung ab und sollte nach einer Evaluierung durch den Fachmann mit den ihm bekannten Standardmethoden festgelegt werden. In den Figuren 1 und 2 sind Ausführungsformen gezeigt, in denen (A) die Beschichtung ist, die die erfindungsgemäße Mischoxid-Zusammensetzung enthält, während (B) die davon räumlich getrennt aufgebrachte Beschichtung ist, die die Zeo- lithverbindung und/oder die zeolithähnliche Verbindung enthält. In a further embodiment of the catalyst according to the invention, it is present as a coated inert supporting body, wherein the mixed oxide is contained in at least one catalytically active coating applied thereto, and the zeolite compound and / or the zeolite-like compound is contained in a spatially separate, further catalytically active coating , Depending on the target application, it may be particularly advantageous to use so-called "zone catalysts" in which the catalytically active coatings are designed as zones following one another in the flow direction of the exhaust gas on the support body (Figure 1). however, so-called "layered catalysts" may also be preferred, in which the catalytically active coatings are arranged on the support body as layers lying one above the other over the entire length of the component (FIG. 2). Which concrete configuration of the catalytic converter is to be selected in order to achieve the best possible exhaust gas purification result depends, as already mentioned, on the operating conditions of the catalytic converter in the target application and should be determined after evaluation by the person skilled in the art using the standard methods known to him. FIGS. 1 and 2 show embodiments in which (A) is the coating containing the mixed oxide composition according to the invention, while (B) is the coating which is spatially separated therefrom and which comprises the zeolite compound and / or zeolite-like compound contains.
Ausführungsformen entsprechend Figur 1 a) oder Figur 2a), in denen die Beschichtung, die die Mischoxidzusammensetzung enthält, mit dem anströmenden Abgas zuerst in Kontakt kommt, kommen bevorzugt in Anwendungen mit mittleren Betriebstemperaturen zum Einsatz, in denen ein dynamisches Anspringverhalten und ein schnelles„Zünden" des SCR-Katalysators von besonderer Bedeutung ist. Mit einer solchen Anordnung der Beschichtungen kann in kürzester Zeit der für die entspre- chende Betriebstemperatur charakteristische maximale NOx-Umsatz in der SCR-Reak- tion erreicht werden. Die in Strömungsrichtung des Abgases nachgelagerte Zone bzw. Schicht (B), die die Zeolithverbindung und/oder die zeolithähnliche Verbindung enthält, dient in solchen Anwendungen vor allem dazu, in der ersten Zone bzw. Schicht nicht umgesetztes Ammoniak zu speichern und zur Reduktion von durch die erste Zone bzw. Schicht durchbrechenden Stickoxiden in Betriebspunkten mit besonders hohen ΝΟχ-Mengen und/oder geringen charakteristischen NOx-Umsätzen zur Verfügung zu stellen, sowie die entsprechende Reaktion zu katalysieren. Embodiments according to FIG. 1 a) or FIG. 2 a), in which the coating containing the mixed oxide composition first comes into contact with the inflowing exhaust gas, are preferably used in applications with medium operating temperatures, in which a dynamic light-off behavior and rapid ignition With such an arrangement of the coatings, the maximum NO x conversion in the SCR reaction that is characteristic for the corresponding operating temperature can be achieved in the shortest possible time The downstream zone in the flow direction of the exhaust gas or layer (B) containing the zeolite compound and / or the zeolite-like compound is used in such applications mainly to store unreacted ammonia in the first zone or layer and to break through by the first zone or layer Nitrogen oxides at operating points with particularly high ΝΟχ quantities and / or ge to provide characteristic NO x conversions and to catalyze the corresponding reaction.
Ausführungsformen gemäß den Figuren 1 b) und 2b), in denen die Beschichtung, die den Zeolith und/oder die zeolithähnliche Verbindung enthalten ist, vom anströmenden
Abgas zuerst kontaktiert wird, sind bevorzugt, wenn ein hoher Ammoniak-Speicher benötigt wird, um die SCR-Reaktion beispielsweise in sehr kalten Betriebspunkten (lange Kaltstartphasen; Niedertemperaturanwendungen) zu unterhalten, in denen aufgrund eines zu geringen Abgastemperaturniveaus kein Harnstoff dosiert werden kann. Eine Anordung gemäß Figur 1 b) wird desweiteren in Anordnungen bevorzugt, in denen der SCR-Katalysator sehr hohen Abgastemperaturen ausgesetzt wird. In diesem Fall wird die Beschichtung, die die zumeist alterungsstabileren Zeolithverbindungen enthält und geringere Neigungen zur Überoxidation von Ammoniak zeigt, in der heißeren an- strömseitigen Zone angeordnet, während die abströmseitige Zone zur Vervoll- ständigung der SCR-Reaktion dient. Embodiments according to Figures 1 b) and 2b), in which the coating, which is the zeolite and / or the zeolite-like compound is contained, from the inflowing Exhaust gas is first contacted are preferred when a high ammonia storage is required to maintain the SCR reaction, for example, in very cold operating conditions (long cold start phases, low temperature applications), in which due to a low exhaust gas temperature level no urea can be metered. An arrangement according to Figure 1 b) is further preferred in arrangements in which the SCR catalyst is exposed to very high exhaust gas temperatures. In this case, the coating, which contains the more age stable zeolite compounds and exhibits lower tendencies to overoxidize ammonia, is placed in the hotter upstream zone, while the downstream zone serves to complete the SCR reaction.
Liegt die erfindungsgemäße katalytisch aktive Zusammensetzung in Form einer Beschichtung auf einem katalytisch inerten Tragkörper vor, so kann es vorteilhaft sein, der Beschichtung desweiteren einen Binder zuzusetzen, um eine verbesserte Haft- fähigkeit der katalytisch aktiven Beschichtung auf dem katalytisch inerten Tragkörper zu gewährleisten. Dies gilt im besonderen, wenn metallische Tragkörper verwendet werden. Der Binder wird bevorzugt ausgewählt aus der Gruppe bestehend aus Aluminiumoxid, Zirkonoxid und Siliciumdioxid. Siliciumdioxid wird insbesondere in Form von Silikasol eingesetzt. If the catalytically active composition according to the invention is present in the form of a coating on a catalytically inert support body, it may be advantageous to add a binder to the coating in order to ensure improved adhesion of the catalytically active coating to the catalytically inert support body. This is especially true when metallic support bodies are used. The binder is preferably selected from the group consisting of alumina, zirconia and silica. Silica is used in particular in the form of silica sol.
Das erfindungsgemäß zu verwendenden Mischoxid aus Ceroxid, Zirkonoxid, Seltenerdsesquioxid und Nioboxid bzw. die erfindungsgemäße katalytisch aktive Zusammensetzung, die zusätzlich eine Zeolithverbindung und/oder eine zeolithähnlichen Verbindung enthält ist insbesondere geeignet zur selektiven kataly- tischen Reduktion von Stickoxiden. Die daraus in beschriebener Weise herstellbaren Katalysatoren eignen sich besonders gut zur Reinigung der Abgase von überwiegend mager betriebenen Verbrennungsmotoren, wie sie beispielsweise in Kraftfahrzeugen (Dieselfahrzeuge, überwiegend mager betriebene Benzinfahrzeuge) zum Einsatz kommen. Das bevorzugte Anwendungsfeld dieser Katalysatoren ist die selektive kata- lytische Reduktion von Stickoxiden im Abgas von überwiegend mager betriebenen Verbrennungsmotoren nach Zusatz von Ammoniak als Reduktionsmittel zum zu reinigenden Abgas, gegebenenfalls in Form einer zu Ammoniak zersetzlichen Verbindung. The mixed oxide of cerium oxide, zirconium oxide, rare earth sesquioxide and niobium oxide or the catalytically active composition according to the invention, which additionally contains a zeolite compound and / or a zeolite-like compound, is particularly suitable for the selective catalytic reduction of nitrogen oxides. The catalysts which can be produced therefrom in the described manner are particularly suitable for purifying the exhaust gases of predominantly lean-burn internal combustion engines, as used, for example, in motor vehicles (diesel vehicles, predominantly lean-burn gasoline vehicles). The preferred field of application of these catalysts is the selective catalytic reduction of nitrogen oxides in the exhaust gas of predominantly lean-burn internal combustion engines after the addition of ammonia as reducing agent to the exhaust gas to be purified, optionally in the form of a decomposable compound to ammonia.
Die Erfindung wird nachfolgend anhand einiger Figuren und Beispiele weitergehend erläutert. Es zeigen:
Ausführungsformen erfindungsgemäßer Zonenkatalysatoren, wobei (A) die katalytisch aktive Beschichtung darstellt, die die Zusammensetzung aus Ceroxid, Zirkonoxid, Seltenerdsesquioxid und Nioboxid enthält, während (B) eine davon räumlich getrennte, katalytisch aktive Beschichtung darstellt, welche eine Zeolithverbindung und/oder eine zeolithähnliche Verbindung enthält; gezeigt wird schematisch ein Ausschnitt aus einem monolithischen Durchflußwabenkörper, dessen Strömungskanäle durch gasundurchlässige Wände getrennt sind, auf denen die katalytisch aktiven Beschichtungen (A) und (B) aufgebracht sind. The invention will be explained below with reference to some figures and examples. Show it: Embodiments of zone catalysts according to the present invention, wherein (A) represents the catalytically active coating containing the composition of ceria, zirconia, rare earth sesquioxide and niobium oxide, while (B) represents a spatially separated catalytically active coating comprising a zeolite compound and / or a zeolite-like compound contains; A schematic section of a monolithic Durchflußwabenkörper whose flow channels are separated by gas-impermeable walls on which the catalytically active coatings (A) and (B) are applied is shown schematically.
Ausführungsformen erfindungsgemäßer Schichtkatalysatoren, wobei (A) die katalytisch aktive Beschichtung darstellt, die die Zusammensetzung aus Ceroxid, Zirkonoxid, Seltenerdsesquioxid und Nioboxid enthält, während (B) eine davon räumlich getrennte, katalytisch aktive Beschichtung darstellt, welche eine Zeolithverbindung und/oder eine zeolithähnliche Verbindung enthält; gezeigt wird schematisch ein Ausschnitt aus einem monolithischen Durchflußwabenkörper, dessen Strömungskanäle durch gasundurchlässige Wände getrennt sind, auf denen die katalytisch aktiven Beschichtungen (A) und (B) aufgebracht sind. Embodiments of layered catalysts according to the invention, wherein (A) represents the catalytically active coating containing the composition of cerium oxide, zirconium oxide, rare earth sesquioxide and niobium oxide, while (B) is one of spatially separated catalytically active coating comprising a zeolite compound and / or a zeolite-like compound contains; A schematic section of a monolithic Durchflußwabenkörper whose flow channels are separated by gas-impermeable walls on which the catalytically active coatings (A) and (B) are applied is shown schematically.
Stickoxid-Umsätze in der SCR-Reaktion, gemessen an einer Zusammensetzung aus 38 Gew.-% Ce02, 14,5 Gew.-% Nb205, 4,5 Gew.-% Nd203 und 43 Gew.-% Zr02 in frisch hergestelltem Zustand (K1 (f)), nach Alterung bei 750°C / 16 h (K1 (A-1)) und nach Alterung bei 600°C / 200 h (K1(A-2)). Nitrogen oxide conversions in the SCR reaction, measured on a composition of 38 wt .-% Ce0 2 , 14.5 wt .-% Nb 2 0 5 , 4.5 wt .-% Nd 2 0 3 and 43 wt. % Zr0 2 freshly prepared (K1 (f)), after aging at 750 ° C / 16 h (K1 (A-1)) and after aging at 600 ° C / 200 h (K1 (A-2)).
Stickoxid-Umsätze in der SCR-Reaktion an einem Katalysator K1 (f), einem kommerziellen Vanadiumoxid-basierten SCR-Katalysator VK1(f) und einem Vergleichskatalysator VK2(f) gemäß WO 2008/05 752 in frisch hergestelltem Zustand. Nitrogen oxide conversions in the SCR reaction on a catalyst K1 (f), a commercial vanadium oxide-based SCR catalyst VK1 (f) and a comparative catalyst VK2 (f) according to WO 2008/05 752 in a fresh state.
Stickoxid-Umsätze in der SCR-Reaktion an einem Katalysator K1 (A-2) und einem kommerziellen Vanadiumoxid-basierten Katalysator VK1 (A- 2), beide nach einer thermischen Vorbehandlung bei 600°C für die Dauer von 200 Stunden. Nitrogen oxide conversions in the SCR reaction on a catalyst K1 (A-2) and a commercial vanadium oxide-based catalyst VK1 (A-2), both after a thermal pretreatment at 600 ° C for a period of 200 hours.
Stickoxid-Umsätze in der SCR-Reaktion an den Katalysatoren K1 (A-1) und K2(A-1), sowie einem Vergleichskatalysator VK2(A-1) gemäß WO
2008/051752, alle nach einer thermischen Vorbehandlung bei 750°C für die Dauer von 16 Stunden. Nitrogen oxide conversions in the SCR reaction on the catalysts K1 (A-1) and K2 (A-1), and a comparative catalyst VK2 (A-1) according to WO 2008/051752, all after a thermal pretreatment at 750 ° C for 16 hours.
Figur 7: Differenz der NH3-Speicherkapazität zwischen dem frischen Katalysator FIG. 7: Difference of the NH 3 storage capacity between the fresh catalyst
K3(f) und seiner bei 750°C für die Dauer von 16 Stunden thermisch vorbehandelten Version (K3(A-1 )) im Vergleich mit VK3(f) / VK3(A-1 ). K3 (f) and its thermally pretreated at 750 ° C for 16 hours (K3 (A-1)) compared to VK3 (f) / VK3 (A-1).
Figur 8: Dynamisches Anspringverhalten nach NH3 - Dosierung der FIG. 8: Dynamic light-off behavior after NH 3 -dosing of the
Katalysatoren K2(A-1), K6(A-1) und VK3(A-1), gemessen bei 250 und Catalysts K2 (A-1), K6 (A-1) and VK3 (A-1), measured at 250 and
300°C. 300 ° C.
Figur 9: Dynamisches Anspringverhalten nach NH3 - Dosierung der FIG. 9: Dynamic light-off behavior after NH 3 -dosing of the
Katalysatoren K2(A-1), K5(A-1) und VK4(A-1), gemessen bei 250 und Catalysts K2 (A-1), K5 (A-1) and VK4 (A-1), measured at 250 and
350°C. 350 ° C.
Untersuchung des Stickoxid-Umsatzes als Maß für die SCR-Aktivität: Examination of nitric oxide turnover as a measure of SCR activity:
Die in den nachstehend beschriebenen Beispielen und Vergleichsbeispielen herge- stellten Mischoxidzusammensetzungen wurden in Wasser suspendiert, gemahlen und auf einen keramischen Wabenkörper mit einem Volumen von 0,5 L und einer Zellzahl von 62 Zellen pro Quadratzentimeter bei einer Wandstärke von 0,17 mm aufgebracht. Nach Kalzination des Wabenkörpers bei 500°C für die Dauer von zwei Stunden in Luft wurden dem beschichteten Wabenkörper zylinderförmige Bohrkerne für die Testung in einer Modellgasanlage mit einem Durchmesser von 25,4 mm und einer Länge von 76,2 mm entnommen. The mixed oxide compositions prepared in the Examples and Comparative Examples described below were suspended in water, ground and applied to a ceramic honeycomb body having a volume of 0.5 L and a cell number of 62 cells per square centimeter with a wall thickness of 0.17 mm. After calcination of the honeycomb body at 500 ° C for two hours in air, cylindrical cores were removed from the coated honeycomb body for testing in a model gas plant having a diameter of 25.4 mm and a length of 76.2 mm.
Die Testung erfolgte in einer Labor-Modellgasanlage unter den folgenden Bedingungen. The testing was carried out in a laboratory model gas plant under the following conditions.
Zusammensetzung des Modellgases Composition of the model gas
NO [Vol.-ppm]: 500 NO [ppm by volume]: 500
NH3 [Vol.-ppm]: 450 NH 3 [vol. Ppm]: 450
02 [Vol.-%]: 5 0 2 [vol.%]: 5
H20 [Vol.-%] 1 ,3 H 2 0 [vol.%] 1, 3
N2: Rest N 2 : rest
Allgemeine Testbedingungen General test conditions
Raumgeschwindigkeit [h"1]: 30.000
Temperatur [°C]: 500; 450; 400; 350; 300; 250; 200; 175; 150Space velocity [h "1 ]: 30,000 Temperature [° C]: 500; 450; 400; 350; 300; 250; 200; 175; 150
Konditionierung vor Meßbeginn: Modellgas-Atmosphäre; 600°C; einige MinutenConditioning before start of measurement: model gas atmosphere; 600 ° C; a few minutes
Während der Messung wurden die Stickoxid-Konzentrationen des Modellabgases nach Katalysator mit einer geeigneten Analytik erfasst. Aus den bekannten, dosierten Stickoxid-Gehalten, die während der Konditionierung zu Beginn des jeweiligen Prüflaufs mit einer Vor-Katalysator-Abgasanalytik verifiziert wurden, und den gemessenen Stickoxid- Gehalten nach Katalysator wurde der Stickoxid-Umsatz, bezogen auf das Verhältnis von NH3 zu NO, über den Katalysator für jeden Temperaturmeßpunkt wie folgt berechnet: During the measurement, the nitrogen oxide concentrations of the model exhaust gas were detected after catalyst with a suitable analysis. From the known, metered nitrogen oxide contents, which were verified during conditioning at the beginning of the respective test run with a pre-catalyst exhaust gas analysis, and the measured nitrogen oxide contents after catalyst, the nitrogen oxide conversion, based on the ratio of NH 3 to NO, calculated over the catalyst for each temperature measuring point as follows:
CAusgang (NOx) 1 CAus gang ( N Ox) 1
Eingang (NOx) mit CEingang/AusgangfNOx) = CEin/Aus(NO) +
.. . Die erhaltenen Stickoxid-Umsatz-Werte UNOx [%] wurden zur Beurteilung der SCR- Aktivität der untersuchten Materialien als Funktion der vor Katalysator gemessenen Temperatur aufgetragen. Input (NO x ) with CE input / output fNOx) = C on / off (NO) + ... The resulting nitrogen oxide conversion values U NOx [%] were plotted to evaluate the SCR activity of the materials studied as a function of the temperature measured before the catalyst.
Beispiel 1 example 1
Ein kommerziell erhältliches Cer-Zirkon-Mischoxid mit einem Gewichtsverhältnis von Ce02 : Zr02 von 1 : 1 ,1 und einem Nd203-Gehalt von 5,3 Gew.-% wurde mit einer wässrigen Lösung von Ammoniumnioboxalat imprägniert und bei 500°C für die Dauer von 2 Stunden kalziniert. Die derart erhaltene erfindungsgemäße Mischoxid-Zusammensetzung bestand aus 38 Gew.-% Ce02, 14,5 Gew.-% Nb2Os, 4,5 Gew.-% Nd203 und 43 Gew.-% Zr02. Aus dem Mischoxid wurde eine Beschichtungssuspension angefertigt und damit ein katalytisch inerter Wabenkörper beschichtet. Dem derart hergestellten Katalysator wurden drei Bohrkerne entnommen. Von einem ersten Bohrkern (K1 (f)) wurde die kata- lytische Aktivität gemäß der vorstehend beschriebenen Testroutine im frisch hergestellten Zustand untersucht. Ein zweiter Bohrkern (K1(A-1)) wurde vor der Untersuchung der katalytischen Aktivität für 16 Stunden in einem Ofen in einer Atmosphäre enthaltend 10 Vol.-% Sauerstoff und 10 Vol.-% Wasserdampf in Stickstoff bei 750°C thermisch behandelt. Ein dritter Bohrkern wurde (K1 (A-2)) wurde ebenfalls vor der Untersuchung der katalytischen Aktivität thermisch behandelt. Er wurde jedoch
einer der SCR-Anwendung im Dieselfahrzeug angepassten thermischen Alterung unterzogen, d.h. einer thermischen Behandlung bei 600°C für die Dauer von 200 Stunden in einem mit 10 Vol.-% Sauerstoff und 10 Vol.-% Wasserdampf in Stickstoff durchströmten Ofen (mittlere Raumgeschwindigkeit: 2.200 h"1). Figur 3 zeigt das Ergebnis der Untersuchungen der katal tischen Aktivität. Im frisch hergestellten Zustand zeigt der erfindungsgemäße Katalysator bei 250°C bereits einen Stickoxid-Umsatz von mehr als 97 %. Im Temperaturfenster zwischen > 250°C und 400°C werden die Stickoxide vollständig umgesetzt. Erst ab 450°C tritt eine leichte Degradation des Umsatzes ein. Die Umsatzkurven der thermisch vorbehandelten Bohrkerne zeigen darüber hinaus, dass der erfindungsgemäße Katalysator eine sehr, sehr hohe Alterungsstabilität aufweist. Der Katalysator erreicht nach der verkürzten Alterung bei hohen Temperaturen (750°C; K1(A-1)) Umsatzeinbußen im Tieftemperaturbereich bis 250°C und erreicht erst oberhalb von 300°C vollständigen NOx-Umsatz. Nach einer längeren Alterung bei tieferen Temperaturen (K1 (A-2)) ist dagegen im Tieftemperaturbereich bis 400°C praktisch keine Umsatzdegradation infolge thermischer Alterung zu beobachten. Eine Alterung des Katalysators wird unter diesen Bedingungen lediglich durch ein schnelleres Abfallen der NOx-Umsatzkurve im Hochtemperaturbereich oberhalb von 400°C beobachtbar. A commercially available cerium-zirconium mixed oxide having a weight ratio of Ce0 2 : Zr0 2 of 1: 1, 1 and a Nd 2 0 3 content of 5.3 wt .-% was impregnated with an aqueous solution of ammonium niobium oxalate and at 500 ° C calcined for a period of 2 hours. The mixed oxide composition according to the invention thus obtained consisted of 38% by weight of CeO 2 , 14.5% by weight of Nb 2 O s , 4.5% by weight of Nd 2 O 3 and 43% by weight of ZrO 2 . From the mixed oxide, a coating suspension was prepared and thus coated a catalytically inert honeycomb body. The catalyst thus prepared was taken from three cores. From a first drill core (K1 (f)) the catalytic activity according to the previously described test routine in the freshly prepared state was investigated. A second core (K1 (A-1)) was thermally treated in nitrogen at 750 ° C for 16 hours in an oven in an atmosphere containing 10% by volume of oxygen and 10% by volume of steam in the presence of catalytic activity. A third core (K1 (A-2)) was also thermally treated prior to analysis of catalytic activity. He became, however subjected to a thermal treatment adapted to the SCR application in the diesel vehicle, ie a thermal treatment at 600 ° C. for a period of 200 hours in an oven through which 10% by volume of oxygen and 10% by volume of steam flow in nitrogen (average space velocity: 2,200 h "1 ) Figure 3 shows the result of the investigations of the catalytic activity: In the freshly prepared state, the catalyst according to the invention already exhibits a nitrogen oxide conversion of more than 97% at 250 ° C. In the temperature window between> 250 ° C. and 400 ° The nitrogen oxides are completely converted by ° C. The conversion curves of the thermally pretreated drill cores also show that the catalyst according to the invention has a very, very high aging stability The catalyst reaches after the shortened aging at high temperatures (750 ° C, K1 (A-1)) loss of sales in the low temperature range up to 250 ° C and reach ht above 300 ° C complete NO x conversion. After prolonged aging at lower temperatures (K1 (A-2)), in contrast, in the low-temperature range up to 400 ° C. virtually no conversion degradation due to thermal aging can be observed. Aging of the catalyst under these conditions can only be observed by a faster drop in the NO x conversion curve in the high-temperature range above 400 ° C.
Beispiel 2 Example 2
Analog zu der in Beispiel 1 angegebenen Verfahrensweise wurde ein Mischoxid folgender Zusammensetzung erhalten: 38 Gew.-% Ce02, 14,5 Gew.-% Nb205, 4,5 Gew.-% Y203 und 43 Gew.-% Zr02. Analogously to the procedure described in Example 1, a mixed oxide of the following composition was obtained: 38% by weight CeO 2 , 14.5% by weight Nb 2 O 5 , 4.5% by weight Y 2 O 3 and 43% by weight. -% Zr0 2 .
Aus dem Mischoxid wurde eine Beschichtungssuspension wie in Beispiel 1 angegeben angefertigt und damit ein katalytisch inerter Wabenkörper beschichtet. Der so erhaltene Katalysator wird nachfolgend als K2 bezeichnet. From the mixed oxide, a coating suspension was prepared as indicated in Example 1 and thus coated a catalytically inert honeycomb body. The catalyst thus obtained is hereinafter referred to as K2.
Wie in Beispiel 1 angegeben wurde auch hier ein zweiter Bohrkern (K2(A-1)) vor der Untersuchung der katalytischen Aktivität für 16 Stunden in einem Ofen in einer Atmosphäre enthaltend 10 Vol.-% Sauerstoff und 10 Vol.-% Wasserdampf in Stickstoff bei 750°C thermisch behandelt.
Die katalytische Leistung der erfindungsgemäßen Katalysatoren gemäß Beispielen 1 und 2 in der SCR-Reaktion wurde mit zwei Katalysatoren aus dem Stand der Technik verglichen: As indicated in Example 1, here again, a second core (K2 (A-1)) was tested for 16 hours in an oven in an atmosphere containing 10% by volume of oxygen and 10% by volume of water vapor in nitrogen thermally treated at 750 ° C. The catalytic performance of the inventive catalysts according to Examples 1 and 2 in the SCR reaction was compared with two prior art catalysts:
Vergleichsbeispiel 1 Comparative Example 1
Als erster Vergleichskatalysator wurde ein kommerzieller SCR-Katalysator auf Vanadiumoxid-Basis gewählt, der eine katalytisch aktive Beschichtung bestehend aus V205, W03, Ti02 und Si02 enthielt. As a first comparative catalyst, a commercial SCR catalyst was selected based on vanadium oxide, which contained a catalytically active coating consisting of V 2 0 5 , W0 3 , Ti0 2 and Si0 2 .
Aus dem kommerziellen Katalysator wurden zwei Bohrkerne entnommen, von denen ein Bohrkern im frisch hergestellten Zustand (VK1 (f)) getestet wurde, während der zweite Bohrkern (VK1 (A-2)) vor Testung einer thermischen Vorbehandlung unterzogen wurde bei 600°C für die Dauer von 200 Stunden in einem mit 10 Vol.-% Sauerstoff und 10 Vol.-% Wasserdampf in Stickstoff durchströmten Ofen (mittlere Raumgeschwindigkeit: 2.200 h"1). From the commercial catalyst, two cores were taken, one of which was tested as freshly prepared (VK1 (f)), while the second core (VK1 (A-2)) was subjected to thermal pretreatment at 600 ° C before testing the duration of 200 hours in an oven with 10 vol .-% oxygen and 10 vol .-% steam in nitrogen flowed through (average space velocity: 2,200 h "1 ).
Vergleichsbeispiel 2 Comparative Example 2
Es wurde ein zweiter Vergleichskatalysator gemäß der WO 2008/051752 hergestellt, der eine katalytisch aktive Beschichtung bestehend aus 15 Gew.-% W03, 46,75 Gew.- % Zr02, 27,2 Gew.-% Ce02, 5,1 Gew.-% Y203 und 5,95 Gew.-% Nb203 auf einem katalytisch inerten Wabenkörper enthielt. A second comparative catalyst according to WO 2008/051752 was prepared which comprises a catalytically active coating consisting of 15% by weight WO 3 , 46.75% by weight ZrO 2 , 27.2% by weight CeO 2 , 5, 1 wt .-% Y 2 0 3 and 5.95 wt .-% Nb 2 0 3 on a catalytically inert honeycomb body contained.
Dem Katalysator wurden ebenfalls zwei Bohrkerne entnommen, von denen ein Bohrkern im frisch hergestellten Zustand (VK2(f)) getestet wurde, während der zweite Bohrkern (VK2(A-1)) vor Testung für 16 Stunden in einem Ofen in einer Atmosphäre enthaltend 10 Vol.-% Sauerstoff und 10 Vol.-% Wasserdampf in Stickstoff bei 750°C thermisch behandelt wurde. The catalyst was also sampled from two cores, one of which was tested as freshly prepared (VK2 (f)), and the second core (VK2 (A-1)) was placed in an oven in an atmosphere containing 10 for 16 hours prior to testing Vol .-% oxygen and 10 vol .-% steam in nitrogen at 750 ° C was thermally treated.
Figur 4 zeigt einen Vergleich der NOx-Konvertierungsleistungen der frisch hergestellten Katalysatoren K1 (f), VK1 (f) und VK2(f). Der erfindungsgemäße Katalysator zeigt mit einem vollständigen NOx-Umsatz im Bereich >250 bis 400°C das größte Arbeitstemperaturfenster. Außerdem weist der erfindungsgemäße Katalysator die mit Abstand beste NOx-Konvertierungsleistung im Tieftemperaturbereich bis 250°C auf. Im Temperaturbereich oberhalb von 450°C wird ein deutliches„Abknicken" der NOx-Um- satzkurve beobachtet - ein Reaktionsverhalten des dem Vergleichskatalysator gemäß WO 2008/051752 (VK2(f)) entspricht.
Figur 5 zeigt einen Vergleich des bei 600°C (200 Stunden) gealterten erfindungsgemäßen Katalysators K1 (A-2) mit dem unter entsprechenden Bedingungen gealterten Vanadiumoxid-basierten, kommerziellen Katalysator. Der Vergleich der Konvertierungsleistungen nach Alterung zeigt, dass das Arbeitstemperaturfenster der erfindungsgemäßen Katalysators nach Alterung um ca. 50° zu geringeren Temperaturen verschoben ist, d.h. es wird eine erhebliche bessere NOx-Konversion im Tieftemperaturbereich bis 300°C und ein schnelleres Erreichen des Vollumsatzes bei zugleich etwas früher eintretender Degradation des Umsatzes beobachtet. FIG. 4 shows a comparison of the NO x conversion powers of the freshly prepared catalysts K1 (f), VK1 (f) and VK2 (f). The catalyst according to the invention shows the highest working temperature window with a complete NO x conversion in the range> 250 to 400 ° C. In addition, the catalyst according to the invention by far the best NO x -Konvertierungsleistung in the low temperature range up to 250 ° C. In the temperature range above 450 ° C, a marked "kinking" of the NO x conversion curve is observed - a reaction behavior of the comparative catalyst according to WO 2008/051752 (VK2 (f)) corresponds. FIG. 5 shows a comparison of the inventive catalyst K1 (A-2) aged at 600 ° C. (200 hours) with the vanadium oxide-based commercial catalyst aged under appropriate conditions. The comparison of the conversion performance after aging shows that the working temperature window of the catalyst according to the invention is shifted by aging to about 50 ° to lower temperatures, ie there is a considerable better NO x conversion in the low temperature range up to 300 ° C and a faster achievement of full conversion At the same time, a slightly earlier degradation of sales was observed.
Figur 6 zeigt einen Vergleich der bei 750°C (16 Stunden) gealterten erfindungs- gemäßen Katalysatoren K1 (A-1) und K2(A-1) mit dem entsprechend gealterten Vergleichskatalysator VK2(A-1) gemäß WO 2008/051752. Während die Aktivität des Vergleichskatalysators gemäß WO 2008/051752 deutlich zusammengebrochen ist (max. 86 % NOx-Konvertierung bei 400°C), erreichen die erfindungsgemäßen Katalysatoren selbst nach dieser heißen thermischen Behandlung im Temperaturbereich zwischen 300 und 400°C noch immer NOx-Umsätze nahe 100 % bzw. über 95%. FIG. 6 shows a comparison of the inventive catalysts K1 (A-1) and K2 (A-1) aged at 750 ° C. (16 hours) with the correspondingly aged comparative catalyst VK2 (A-1) according to WO 2008/051752. While the activity of the comparative catalyst according to WO 2008/051752 has clearly collapsed (maximum of 86% NO x conversion at 400 ° C.), the catalysts according to the invention still still reach NO x after this hot thermal treatment in the temperature range between 300 and 400 ° C. Sales close to 100% and over 95%.
Die Messungen zeigen, dass die erfindungsgemäßen Katalysatoren sowohl im Vergleich zu kommerziellen Vanadiumoxid-basierten SCR-Katalysatoren als auch im Vergleich zu Vanadium-freien Mischoxid-Zusammensetzungen nach dem Stand der Technik erheblich verbesserte Eigenschaften aufweist. Dies gilt insbesondere hinsichtlich der erreichbaren NOx-Konvertierungsraten, der Breite des Arbeitstemperaturfensters, in dem annähernd vollständiger Umsatz erreicht wird, und hinsichtlich der thermischen Alterungsstabilität des Katalysators. Vergleichsbeispiel 3 The measurements show that the catalysts according to the invention have significantly improved properties both compared to commercial vanadium oxide-based SCR catalysts and compared to vanadium-free mixed oxide compositions according to the prior art. This applies in particular with regard to the achievable NO x conversion rates, the width of the working temperature window in which almost complete conversion is achieved, and the thermal aging stability of the catalyst. Comparative Example 3
Es wurden ein kommerziell erhältlicher Si02-Binder und ein kommerziell erhältlicher Böhmit-Binder als Beschichtungshilfsstoffe, sowie Eisen(lll)-nitrat-nonahydrat und kommerziell erhältlicher ß-Zeolith mit einem molaren Si02/Al203-Verhältnis (SAR) von 25 in Wasser suspendiert und nach einem herkömmlichen Tauchverfahren auf einen keramischen Durchflußwabenkörper mit 62 Zellen pro Quadratzentimeter und einer Zellwandstärke von 0,17 Millimetern in einer Menge von 222 g/L aufgebracht. Das beschichtete Bauteil wurde zunächst für 15 Minuten bei 350°C, dann für die Dauer von 2 Stunden bei 500°C kalziniert. Die Beschichtung bestand zu 90% aus ß-Zeolith und hatte einen Eisengehalt, berechnet als Fe203, von 4,5 Gew.-%.
Der so erhaltene Katalysator wird nachstehend als VK3 bezeichnet. There were a commercially available Si0 2 binder and a commercially available boehmite binder as coating aids, and iron (III) nitrate nonahydrate and commercially available β-zeolite with a molar Si0 2 / Al 2 0 3 ratio (SAR) of 25 suspended in water and applied by a conventional dipping method to a ceramic Durchflußwabenkörper with 62 cells per square centimeter and a cell wall thickness of 0.17 millimeters in an amount of 222 g / L. The coated component was first calcined for 15 minutes at 350 ° C, then for 2 hours at 500 ° C. The coating consisted of 90% of beta-zeolite and had an iron content, calculated as Fe 2 0 3 , of 4.5 wt .-%. The catalyst thus obtained is hereinafter referred to as VK3.
Wie in Beispiel 1 angegeben wurde auch hier ein zweiter Bohrkern (VK3(A-1 )) vor der Untersuchung der katalytischen Aktivität für 16 Stunden in einem Ofen in einer Atmosphäre enthaltend 10 Vol.-% Sauerstoff und 10 Vol.-% Wasserdampf in Stickstoff bei 750°C thermisch behandelt. As indicated in Example 1, a second core (VK3 (A-1)) was also tested for 16 hours in an oven in an atmosphere containing 10% by volume of oxygen and 10% by volume of steam in nitrogen thermally treated at 750 ° C.
Beispiel 3 Example 3
Es wurde ein Schichtkatalysator gemäß Figur 2a) hergestellt. Hierzu wurde ein analog Vergleichsbeispiel 3 erhaltener Katalysator (aufgebrachte Menge 150 g/L statt 222 g/L) mit einer zusätzlichen Beschichtung versehen, indem eine Beschichtungssuspension gemäß Beispiel 1 in einer Menge von 70 g/L wiederum im Wege eines herkömmlichen Tauchverfahrens aufgebracht und wie angegeben kalziniert wurde. A layered catalyst according to FIG. 2a) was produced. For this purpose, a catalyst obtained analogously to Comparative Example 3 (amount applied 150 g / l instead of 222 g / l) was provided with an additional coating by applying a coating suspension according to Example 1 in an amount of 70 g / l again by means of a conventional dipping method and was calcined.
Der so erhaltene Schichtkatalysator wird nachfolgend als K3 bezeichnet. The layered catalyst thus obtained is hereinafter referred to as K3.
Wie in Beispiel 1 angegeben wurde auch hier ein zweiter Bohrkern (K3(A-1 )) vor der Untersuchung der katalytischen Aktivität für 16 Stunden in einem Ofen in einer Atmosphäre enthaltend 10 Vol.-% Sauerstoff und 10 Vol.-% Wasserdampf in Stickstoff bei 750°C thermisch behandelt. As indicated in Example 1, here again, a second core (K3 (A-1)) was tested for 16 hours in an oven in an atmosphere containing 10% by volume of oxygen and 10% by volume of water vapor in nitrogen thermally treated at 750 ° C.
Die thermische Stabilität der NH3-Speicherkapazität von K3 im Vergleich zu VK3 wurde wie folgt bestimmt: The thermal stability of the NH 3 storage capacity of K3 compared to VK3 was determined as follows:
Der Test wurde an Trägerkatalysatoren in einer Labormodellgasanlage vorgenommen. Dabei wurde die folgende Testgaszusammensetzungen eingestellt: The test was carried out on supported catalysts in a laboratory model gas facility. The following test gas compositions were adjusted:
Vor dem Test wird eine Feedgasmessung über Bypass durchgeführt. Gleichzeitig wird der Reaktor auf 600°C aufgeheizt. Danach wird die Gasmischung auf den Reaktor umgeschaltet und durchläuft die oben angegebenen Phasen 1 bis 6. Insgesamt werden drei verschiedene Zieltemperaturen angefahren: 400°C, 300°C und 200°C. Der gesamte Test läuft wie folgt ab: Before the test, a feed gas measurement is performed via bypass. At the same time the reactor is heated to 600 ° C. Thereafter, the gas mixture is switched to the reactor and runs through the above-mentioned phases 1 to 6. In total, three different target temperatures are approached: 400 ° C, 300 ° C and 200 ° C. The entire test is as follows:
Phase 1 : Speicher leeren, Haltezeit 10 min (600°C) Phase 1: empty memory, hold time 10 min (600 ° C)
Phase 2: Abkühlen auf Zieltemperatur (1 OK/min), Haltezeit 5 min Phase 2: cooling to target temperature (1 OK / min), hold time 5 min
Phase 3: = NH3-Adsorptionsphase, Haltezeit 20 min Phase 3: = NH 3 adsorption phase, holding time 20 min
Phase 4: = NH3-Desorptionsphase: NH3 abschalten, Haltezeit 20 min Phase 4: = NH 3 desorption phase: switch off NH3, holding time 20 min
Phase 5: = Aufheizen auf 600°C Phase 5: = heating to 600 ° C
Phase 6: = Speicher leeren: NO zuschalten, Haltezeit 10min Phase 6: = empty memory: switch on NO, hold time 10min
Wiederholung der Phasen 2 bis 6 bis zum letzten Temperaturpunkt. Danach Repeat phases 2 to 6 until the last temperature point. After that
Gasmischung auf Bypass schalten, Aufnahme einer zweiter Feedgasmessung. Switch gas mixture to bypass, recording a second feed gas measurement.
Zum Ende der Haltezeit in Phase 3 wird die Konzentration bestimmt, die bei aufgefülltem Speicher den Katalysator verlässt: c(NH3)Ph3, end- Die zu jedem Zeitpunkt t gespeicherte Menge NH3 ergibt sich aus der Differenz aus c(NH3)Ph3, end und nach dem Katalysator detektierter Menge NH3 c(NH3)P 3, t : The end of the dwell time in phase 3, the concentration is determined that leaves at padded memory the catalyst: c (NH 3) Ph3, e nd- The stored amount of NH 3 at any time t is given by the difference between c (NH 3) Ph3, e nd and after the catalyst detected amount of NH 3 c (NH 3) 3 P, t:
Δ c(NH3)Ph3i t = c(NH3)ph3i end - c(NH3)Ph3, f Δ c (NH 3 ) Ph 3i t = c (NH 3 ) p h 3i end - c (NH 3 ) Ph 3, f
Aus dem Integral der Auftragung Ac(NH3)Ph3i t gegen die Zeit t für die Phase 3 ergibt sich nach entsprechender Umrechnung der Konzentration c(NH3) in Masse m(NH3) die gesamte Speicherkapazität m(NH3) [mg/L Kat] für den betrachteten Temperaturpunkt. Die NH3-Speicherkapazität wird für die untersuchten Katalysator-Bohrkerne sowohl im frischen (f) als auch im gealterten Zustand (A-1) bestimmt. Als Maß für die thermische Stabilität der NH3-Speicherkapazität wird die Differenz der nach obigem Test bestimmten NH3-Speicherkapazitäten für jede Messtemperatur bestimmt: From the integral of the plot Ac (NH 3 ) Ph3i t against the time t for the phase 3 results in the corresponding total conversion capacity m (NH 3 ) [mg / m] after appropriate conversion of the concentration c (NH 3 ) in mass m (NH 3 ). L cat] for the considered temperature point. The NH 3 storage capacity is determined for the investigated catalyst cores in both the fresh (f) and aged states (A-1). As a measure of the thermal stability of the NH 3 storage capacity, the difference of the determined according to the above test NH 3 storage capacities for each measurement temperature is determined:
Am(NH3) = m(NH3)frisch - m(NH3) gealtert
Figur 7 zeigt die bei 200, 300 und 400°C erhaltenen Am-Werte von K3 und VK3. Wie daraus hervorgeht zeichnet sich K3 im Vergleich zu VK3 bei allen Temperaturen durch eine deutlich bessere thermische Stabilität der NH3-Speicherkapazität aus. Beispiel 4 Am (NH 3 ) = m (NH 3 ) fresh - m (NH 3 ) aged Figure 7 shows the Am values of K3 and VK3 obtained at 200, 300 and 400 ° C. As can be seen, K3 shows a much better thermal stability of the NH 3 storage capacity compared to VK3 at all temperatures. Example 4
Es wurde ein Schichtkatalysator gemäß Figur 2b) hergestellt. Hierzu wurde die in Beispiel 2 beschriebene Beschichtung nach einem herkömmlichen Tauchverfahren auf einen keramischen Durchflußwabenkörper mit 62 Zellen pro Quadratzentimeter und einer Zellwandstärke von 0,17 Millimetern in einer Menge von 70 g/L aufgebracht und wie in Beispiel 3 beschrieben kalziniert. A layered catalyst according to FIG. 2b) was produced. For this purpose, the coating described in Example 2 was applied to a ceramic Durchflußwabenkörper with 62 cells per square centimeter and a cell wall thickness of 0.17 millimeters in an amount of 70 g / L and calcined as described in Example 3 by a conventional dipping method.
Auf diese Beschichtung wurde nunmehr eine einen Eisen-haltigen ß-Zeolithen enthaltende Suspension im Wege eines herkömmlichen Tauchverfahrens in einer Menge von 150 g/L aufgebracht, getrocknet und wie in Vergleichsbeispiel 3 angegeben kalziniert. A suspension containing an iron-containing β-zeolite was then applied to this coating in a quantity of 150 g / l by means of a conventional dipping process, dried and calcined as indicated in Comparative Example 3.
Zur Herstellung der einen Eisen-haltigen ß-Zeolithen enthaltenden Suspension wurde ein kommerziell erhältlicher Fe-Beta-Zeolith mit 1 ,3% Fe203 und SAR = 40 zusammen mit Al203 und Si02 basierten Bindern als Hilfsstoffe (0,8% AIOOH (Böhmit), 4% Si02 (amorph), 9% Si02 (Sol)) in Wasser suspendiert. Beispiel 5 To prepare the suspension containing an iron-containing β-zeolite, a commercially available Fe-Beta zeolite with 1.3% Fe 2 O 3 and SAR = 40 together with Al 2 O 3 and SiO 2- based binders as auxiliary agents (0, 8% AIOOH (boehmite), 4% SiO 2 (amorphous), 9% SiO 2 (sol)) suspended in water. Example 5
Es wurde ein Zonenkatalysator gemäß Figur 1a) hergestellt. Hierzu wurde in einem ersten Arbeitsschritt die in Beispiel 2 beschriebene Beschichtung nach einem herkömmlichen Tauchverfahren auf einen keramischen Durchflußwabenkörper mit 62 Zellen pro Quadratzentimeter und einer Zellwandstärke von 0,17 Millimetern in einer Menge von 200 g/L aufgebracht, jedoch von der Eintrittsstirnfläche des Wabenkörpers ausgehend nur auf 50 % seiner Länge. A zone catalyst according to FIG. 1a) was produced. For this purpose, in a first step, the coating described in Example 2 was applied to a ceramic Durchflußwabenkörper with 62 cells per square centimeter and a cell wall thickness of 0.17 millimeters in an amount of 200 g / L, but starting from the entrance end face of the honeycomb body only 50% of its length.
In einem zweiten Arbeitsschritt wurde dann die in Vergleichsbeispiel 4 beschriebene Beschichtungssuspension nach einem herkömmlichen Tauchverfahren aufgebracht, jedoch von der Austrittsstirnfläche des Wabenkörpers ausgehend auf 50 % seiner Länge, d.h. bis zu der im ersten Schritt aufgebrachten Beschichtung. In a second step, the coating suspension described in Comparative Example 4 was then applied by a conventional dipping method, but starting from the exit end face of the honeycomb body to 50% of its length, i. up to the coating applied in the first step.
Der so erhaltene Zonenkatalysator wird als K5 bezeichnet. The zone catalyst thus obtained is referred to as K5.
Wie in Beispiel 1 angegeben wurde auch hier ein zweiter Bohrkern (K5(A-1)) vor der Untersuchung der katalytischen Aktivität für 16 Stunden in einem Ofen in einer
Atmosphäre enthaltend 10 Vol.-% Sauerstoff und 10 Vol.-% Wasserdampf in Stickstoff bei 750°C thermisch behandelt. As indicated in Example 1, a second core (K5 (A-1)) was also used in an oven for 16 hours prior to analysis of catalytic activity Atmosphere containing 10 vol .-% oxygen and 10 vol .-% steam in nitrogen at 750 ° C thermally treated.
Beispiel 6 Example 6
Das in Beispiel 5 beschriebene Verfahren wurde wiederholt mit dem Unterscheid, dass im zweiten Arbeitsschritt an Stelle der in Vergleichsbeispiel 4 beschriebenen Be- schichtungssuspension die in Vergleichsbeispiel 3 beschriebene Beschichtungs- suspension aufgetragen wurde. The process described in Example 5 was repeated with the difference that in the second step, instead of the coating suspension described in Comparative Example 4, the coating suspension described in Comparative Example 3 was applied.
Der so erhaltene Zonenkatalysator wird als K6 bezeichnet. The zone catalyst thus obtained is referred to as K6.
Wie in Beispiel 1 angegeben wurde auch hier ein zweiter Bohrkern (K6(A-1)) vor der Untersuchung der katalytischen Aktivität für 16 Stunden in einem Ofen in einer Atmosphäre enthaltend 10 Vol.-% Sauerstoff und 10 Vol.-% Wasserdampf in Stickstoff bei 750°C thermisch behandelt. As indicated in Example 1, here again, a second core (K6 (A-1)) was tested for 16 hours in an oven in an atmosphere containing 10% by volume of oxygen and 10% by volume of water vapor in nitrogen thermally treated at 750 ° C.
Vergleichsbeispiel 4 Comparative Example 4
Es wurde eine Beschichtungssuspension durch Suspendieren von kommerziell erhältlichem SAPO-34 in Wasser und Zugabe einer wässrigen Kupfer(ll)-nitratlösung hergestellt. Die zugegebene Menge der Kupfernitratlösung wurde so berechnet, das der fertige Katalysator 2 Gew.-% Cu, bezogen auf das Gesamtgewicht der ausgetauschten zeolithähnlichen Verbindung, enthielt. Die Suspension wurde zur Vervollständigung des lonenaustausches 30 Minuten gerührt und dann nach Zugabe von Silica-Sol als Binder direkt auf einen keramischen Durchflußwabenkörper mit 62 Zellen pro Quadratzentimeter und eienr Zellwandstärke von 0,165 Millimetern, der einen Durchmesser von 92,96 Millimeter und eine Länge von 76,2 Millimeter aufwies, aufgebracht. Der so beschichtete Wabenkörper wurde bei 90°C getrocknet, bei 350°C kalziniert und 2 Stunden bei 640° an Luft getempert. A coating suspension was prepared by suspending commercially available SAPO-34 in water and adding an aqueous copper (II) nitrate solution. The added amount of the copper nitrate solution was calculated such that the final catalyst contained 2% by weight of Cu based on the total weight of the exchanged zeolite-like compound. The suspension was stirred for 30 minutes to complete the ion exchange, and then, after adding silica sol as a binder, directly to a ceramic flow honeycomb body of 62 cells per square centimeter and cell wall thickness of 0.165 millimeters, having a diameter of 92.96 millimeters and a length of 76 , 2 millimeters, applied. The thus coated honeycomb body was dried at 90 ° C, calcined at 350 ° C and annealed for 2 hours at 640 ° in air.
Der so erhaltene Katalysator wird als VK4 bezeichnet. Wie in Beispiel 1 angegeben wurde auch hier ein zweiter Bohrkern (VK4(A-1)) vor der Untersuchung der katalytischen Aktivität für 16 Stunden in einem Ofen in einer Atmosphäre enthaltend 10 Vol.-% Sauerstoff und 10 Vol.-% Wasserdampf in Stickstoff bei 750°C thermisch behandelt.
Das dynamische Anspringverhalten nach NH3-Dosierung der erfindungsgemäßen Katalysatoren K2(A-1) und K6(A-1 ), sowie des Vergleichskatalysators VK3(A-1 ) wurde wie folgt bestimmt: The catalyst thus obtained is designated as VK4. As indicated in Example 1, a second core (VK4 (A-1)) was also tested for 16 hours in an oven in an atmosphere containing 10% by volume of oxygen and 10% by volume of steam in nitrogen thermally treated at 750 ° C. The dynamic light-off behavior after NH 3 dosing of the inventive catalysts K2 (A-1) and K6 (A-1), and of the comparative catalyst VK3 (A-1) was determined as follows:
Der Test wurde an Trägerkatalysatoren in einer Labormodellgasanlage vorgenommen. Dabei wurde die folgende Testgaszusammensetzung eingestellt: The test was carried out on supported catalysts in a laboratory model gas facility. The following test gas composition was adjusted:
Der Test wurde bei verschiedenen Temperaturen durchgeführt, die auf den anwendungsrelevantesten Zieltemperaturbereich für ein SCR-System, das in einer Abgasanlage anderen Abgasreinigungsaggregaten nachgeschaltet ist, abgestimmt waren, nämlich bei 250°C, 300°C und 350°C. Bei jeder Temperatur wurde ein Zyklus aus vier unterschiedlichen Phasen durchlaufen, die nachfolgend als Phasen A bis D bezeichnet werden: The test was conducted at different temperatures, which were tuned to the most application-relevant target temperature range for an SCR system downstream of other exhaust gas purification units in an exhaust system, namely 250 ° C, 300 ° C and 350 ° C. At each temperature, a cycle has been run through four distinct phases, hereafter referred to as phases A through D:
Phase A: Gasmischung 1 ; Dauer: 5 Minuten; Phase A: gas mixture 1; Duration: 5 minutes;
Phase B: Nhb-SCR-Phase: Gasmischung 2; Dauer: bis zu einem NHh-Durchbruch von 20 Vppm oder Abbruch nach Zeit; Phase B: Nhb-SCR phase: gas mixture 2; Duration: up to a NHh breakthrough of 20 vppm or break-off by time;
Phase C: Gasmischung 3; Leeren des NH3-Speichers durch Temperaturrampe bis Phase C: gas mixture 3; Empty the NH3 storage tank by temperature ramp up
500°C; 500 ° C;
Phase D: Gasmischung 3; Einregeln der nächsten Messtemperatur Innerhalb eines Zyklus wurde zuerst die Katalysatortemperatur auf die definierte Zieltemperatur eingeregelt. Dann wurde der Katalysator für 5 Minuten mit Gasmischung 1 beaufschlagt (Phase A). In Phase B wurde auf Gasmischung 2 umgeschaltet, um den Nhh-SCR-Umsatz zu ermitteln. Diese Phase wurde entweder bei Detektion eines NH3-Durchbruchs von 20 Vppm abgebrochen oder durch ein zuvor
festgelegtes Zeitkriterium beendet. Dann wurde Gasmischung 3 eingestellt und der Katalysator auf 500°C aufgeheizt, um den Ammoniakspeicher zu entleeren (Phase C). Anschließend wurde der Katalysator auf die nächste zu untersuchende esstemperatur heruntergekühlt (Phase D), der nächste Zyklus begann mit Phase A durch Einstellen der Gasmischung 1 nach Einregeln der Zieltemperatur. Der dynamische NOx-Umsatz wurde für alle Messtemperaturen aus den während Phase B ermittelten Konzentrationen der entsprechenden Abgaskomponenten vor und nach Katalysator ermittelt. Phase D: gas mixture 3; Adjustment of the next measurement temperature Within a cycle, the catalyst temperature was first adjusted to the defined target temperature. Then, the catalyst was charged with gas mixture 1 for 5 minutes (phase A). In Phase B, gas mixture 2 was switched to determine the Nhh-SCR conversion. This phase was terminated either by detection of an NH3 breakthrough of 20 Vppm or by a previously fixed time criterion ended. Then gas mixture 3 was adjusted and the catalyst heated to 500 ° C to empty the ammonia storage (Phase C). Subsequently, the catalyst was cooled down to the next temperature to be tested (phase D), the next cycle started with phase A by adjusting the gas mixture 1 after adjusting the target temperature. The dynamic NOx conversion was determined for all measurement temperatures from the concentrations of the respective exhaust gas components before and after the catalyst determined during phase B.
Als Kennzahl für ein dynamisches Anspringverhalten wird der NOx-Umsatz X(NOx) berechnet, der sich aus der gemessenen NOx Konzentration 5 Sekunden nach Beginn der Phase B ergibt. Figur 8 zeigt die ermittelten Kennzahlen für K2(A-1), K6(A-1) und VK3(A-1 ), jeweils bei 250 und 300X. As a characteristic for a dynamic light-off behavior, the NOx conversion X (NOx) is calculated, which results from the measured NOx concentration 5 seconds after the start of phase B. FIG. 8 shows the determined characteristic numbers for K2 (A-1), K6 (A-1) and VK3 (A-1), in each case at 250 and 300X.
Das frühere Anspringverhalten der erfindungsgemäßen Katalysatoren K2(A-1 ) und K6(A-1) zeigt sich in dem bereits nach 5 Sekunden deutlich höheren NOx-Umsatz X(NOx) im Vergleich zu VK3(A-1 ). The earlier light-off behavior of the catalysts K2 (A-1) and K6 (A-1) according to the invention is evident in the significantly higher NOx conversion X (NOx) already after 5 seconds compared to VK3 (A-1).
In analoger Weise wurde auch das dynamische Anspringverhalten nach NH3- Dosierung der erfindungsgemäßen Katalysatoren K2(A-1 ) und K5(A-1), sowie des Vergleichskatalysators VK4(A-1) bestimmt, wobei allerdings die Kennzahlen bei 250 und 350°C ermittelt wurden. Die Ergebnisse sind Figur 9 zu entnehmen. K2(A-1 ) und K5(A-1) zeichnen sich durch ein früheres Anspringverhalten im Vergleich zu VK4(A-1) aus. The dynamic light-off behavior after NH 3 dosing of the novel catalysts K2 (A-1) and K5 (A-1) and of the comparative catalyst VK4 (A-1) was determined in an analogous manner, although the characteristic numbers at 250 and 350 ° C were determined. The results are shown in FIG. 9. K2 (A-1) and K5 (A-1) are characterized by earlier light-off behavior compared to VK4 (A-1).
Analog zu den vorstehenden Beispielen 1 und 2 können auch die in den nachfolgenden Beispielen 7 bis 13 beschriebenen Mischoxide bzw. diese enthaltende Katalysatoren erhalten werden. Sie zeichnen sich ebenfalls durch gute Eigenschaften als SCR-Katalysatoren aus: Analogously to Examples 1 and 2 above, the mixed oxides described in Examples 7 to 13 or catalysts containing them can also be obtained. They are also characterized by good properties as SCR catalysts:
CeOz Nb205 SE2Oz/ Zr02 CeO z Nb 2 0 5 SE 2 Oz / Zr0 2
Beispiel example
[Gew.-%] [Gew.-%] [Gew.-%] [Gew.-%] [Wt%] [wt%] [wt%] [wt%]
7 38 14,5 La203/4,5 437 38 14,5 La 2 0 3 / 4,5 43
8 25 15 YzOa/I O 508 25 15 YzOa / I O 50
9 45 15 Nd2O3/10 309 45 15 Nd 2 O 3/10 30
10 45 3 Nd203/9 4310 45 3 Nd 2 0 3/9 43
1 1 40 15 Y203/3 42
1 1 40 15 Y 2 0 3/3 42
SCR-Katalysatoren mit guten Eigenschaften werden auch erhalten, wenn man in den Beispielen 3 bis 6 das dort jeweils beschriebene Mischoxid durch eines der Mischoxide der Beispiele 7 bis 13 ersetzt.
SCR catalysts with good properties are also obtained by replacing the mixed oxide described there in each case by one of the mixed oxides of Examples 7 to 13 in Examples 3 to 6.
Claims
Patentansprüche claims
Verwendung eines katalytisch aktiven Mischoxides bestehend aus Ceroxid, Nioboxid, Seltenerdsesquioxid und Zirkonoxid zur selektiven katalytischen Reduktion von Stickoxiden. Use of a catalytically active mixed oxide consisting of cerium oxide, niobium oxide, rare earth sesquioxide and zirconium oxide for the selective catalytic reduction of nitrogen oxides.
Verwendung nach Anspruch 1 , dadurch gekennzeichnet, dass das Mischoxid aus Ce02: 15 - 50 Gew.-%; Use according to claim 1, characterized in that the mixed oxide of Ce0 2 : 15 - 50 wt .-%;
Nb205: 3 - 25 Gew.-%; Nb 2 0 5 : 3 - 25 wt .-%;
SE203: 3 - 10 Gew.-%; SE 2 0 3 : 3 - 10% by weight;
Zr02: Rest, Zr0 2 : rest,
jeweils berechnet als primäre Oxide, besteht. each calculated as primary oxides.
Verwendung nach Anspruch 1 und/oder 2, dadurch gekennzeichnet, dass das Mischoxid in einer katalytisch aktiven Beschichtung enthalten ist, die auf einen katalytisch inerten Tragkörper aufgebracht ist, der zusammen mit der Use according to claim 1 and / or 2, characterized in that the mixed oxide is contained in a catalytically active coating which is applied to a catalytically inert support body, which together with the
Beschichtung einen Katalysator bildet. Coating forms a catalyst.
Katalytisch aktive Zusammensetzung umfassend (i) ein Mischoxid bestehend aus Ceroxid, Nioboxid, Seltenerdsesquioxid und Zirkonoxid und (ii) eine A catalytically active composition comprising (i) a mixed oxide consisting of ceria, niobium oxide, rare earth sesquioxide and zirconia, and (ii) a
Zeolithverbindung und/oder eine zeolithähnlichen Verbindung, welche Zeolite compound and / or a zeolite-like compound which
austauschbare Kationen ausgewählt aus der Gruppe bestehend aus H+, NH4 +, Fe2+, Fe3+, Cu\ Cu2+, Ag+ oder Mischungen davon enthält. exchangeable cations selected from the group consisting of H + , NH 4 + , Fe 2+ , Fe 3+ , Cu \ Cu 2+ , Ag + or mixtures thereof.
Katalysator enthaltend (i) ein Mischoxid bestehend aus Ceroxid, Nioboxid, Seltenerdsesquioxid und Zirkonoxid und (ii) eine Zeolithverbindung und/oder eine zeolithähnlichen Verbindung, welche austauschbare Kationen ausgewählt aus der Gruppe bestehend aus H+, NH4 +, Fe2+, Fe3+, Cu+, Cu2+, Ag+ oder Mischungen davon. Catalyst comprising (i) a mixed oxide consisting of cerium oxide, niobium oxide, rare earth sesquioxide and zirconium oxide and (ii) a zeolite compound and / or a zeolite-like compound which contains exchangeable cations selected from the group consisting of H + , NH 4 + , Fe 2+ , Fe 3+ , Cu + , Cu 2+ , Ag + or mixtures thereof.
Katalysator nach Anspruch 5, dadurch gekennzeichnet, dass die Catalyst according to claim 5, characterized in that the
Zeolithverbindung und/oder die zeolithähnliche Verbindung ausgewählt ist aus der Gruppe bestehend aus Zeolith beta, USY, ZSM-5, CHA, FER, ERI, SAPO-11, SAPO-17, SAPO-34, SAPO-56, ALPO-11 , ALPO-17, ALPO-34 und ALPO-56. Zeolite compound and / or the zeolite-like compound is selected from the group consisting of zeolite beta, USY, ZSM-5, CHA, FER, ERI, SAPO-11, SAPO-17, SAPO-34, SAPO-56, ALPO-11, ALPO -17, ALPO-34 and ALPO-56.
Katalysator nach Anspruch 5 oder 6, dadurch gekennzeichnet, dass er als beschichteter inerter Tragkörper vorliegt, wobei das Mischoxid in mindestens
einer darauf aufgebrachten katalytisch aktiven Beschichtung enthalten ist, und die Zeolithverbindung und/oder die zeolithähnliche Verbindung in einer räumlich davon getrennten, weiteren katalytisch aktiven Beschichtung enthalten ist. Catalyst according to claim 5 or 6, characterized in that it is present as a coated inert supporting body, wherein the mixed oxide in at least a catalytically active coating applied thereto, and the zeolite compound and / or zeolite-like compound is contained in a spatially separate, further catalytically active coating.
8. Katalysator nach Anspruch 7, dadurch gekennzeichnet, dass die katalytisch 8. A catalyst according to claim 7, characterized in that the catalytic
aktiven Beschickungen als in Strömungsrichtung des Abgases horizontal aufeinander folgende Zonen auf dem Tragkörper ausgeführt sind active feeds are designed as horizontally successive zones in the flow direction of the exhaust gas on the support body
(„Zonenkatalysator"). ( "Zone catalyst").
9. Katalysator nach Anspruch 7, dadurch gekennzeichnet, dass die katalytisch 9. A catalyst according to claim 7, characterized in that the catalytic
aktiven Beschichtungen als vertikal über die gesamte Länge des Bauteils übereinander liegenden Schichten auf dem Tragkörper angeordnet sind active coatings are arranged as vertically over the entire length of the component superposed layers on the support body
(„Schi chtkatalysato r" ) . ("Schichkatalysato r").
10. Katalysator nach einem der Ansprüche 7 bis 9, dadurch gekennzeichnet, dass in mindestens einer katalytisch aktiven Beschichtung ein Binder ausgewählt aus der Gruppe bestehend aus Aluminiumoxid, Zirkonoxid und Siliciumdioxid enthalten ist. 10. A catalyst according to any one of claims 7 to 9, characterized in that in at least one catalytically active coating, a binder selected from the group consisting of alumina, zirconia and silica is included.
11. Verwendung eines Katalysators nach einem der Ansprüche 5 bis 10 zur Reinigung der Abgase von überwiegend mager betriebenen Verbrennungsmotoren. 11. Use of a catalyst according to one of claims 5 to 10 for the purification of the exhaust gases of predominantly lean-burn internal combustion engines.
12. Verwendung eines Katalysators nach einem der Ansprüche 5 bis 10 zur selektiven katalytischen Reduktion von Stickoxiden im Abgas von überwiegend mager betriebenen Verbrennungsmotoren nach Zusatz von Ammoniak als Reduktionsmittel zum zu reinigenden Abgas, gegebenenfalls in Form einer zu Ammoniak zersetzlichen Verbindung.
12. Use of a catalyst according to one of claims 5 to 10 for the selective catalytic reduction of nitrogen oxides in the exhaust gas of predominantly lean internal combustion engines after addition of ammonia as a reducing agent to be cleaned exhaust gas, optionally in the form of a decomposable to ammonia compound.
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2011
- 2011-04-16 WO PCT/EP2011/001944 patent/WO2011131324A1/en active Application Filing
- 2011-04-16 EP EP11716376A patent/EP2560755A1/en not_active Withdrawn
- 2011-04-16 KR KR1020127030255A patent/KR20130097076A/en not_active Application Discontinuation
- 2011-04-16 US US13/642,048 patent/US8617497B2/en active Active
- 2011-04-16 BR BR112012027087A patent/BR112012027087A2/en not_active IP Right Cessation
- 2011-04-16 JP JP2013505359A patent/JP5771267B2/en active Active
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WO2011116907A2 (en) * | 2010-03-26 | 2011-09-29 | Umicore Ag & Co. Kg | Zrox, ce-zrox, ce-zr-reox as host matrices for redox active cations for low temperature, hydrothermally durable and poison resistant scr catalysts |
Also Published As
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CN102844112A (en) | 2012-12-26 |
CN102844112B (en) | 2015-05-13 |
JP2013527799A (en) | 2013-07-04 |
BR112012027087A2 (en) | 2016-07-26 |
JP5771267B2 (en) | 2015-08-26 |
US8617497B2 (en) | 2013-12-31 |
WO2011131324A1 (en) | 2011-10-27 |
US20130121902A1 (en) | 2013-05-16 |
KR20130097076A (en) | 2013-09-02 |
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