GB2476573A - NOx trap with an upstream and downstream zone - Google Patents
NOx trap with an upstream and downstream zone Download PDFInfo
- Publication number
- GB2476573A GB2476573A GB1021604A GB201021604A GB2476573A GB 2476573 A GB2476573 A GB 2476573A GB 1021604 A GB1021604 A GB 1021604A GB 201021604 A GB201021604 A GB 201021604A GB 2476573 A GB2476573 A GB 2476573A
- Authority
- GB
- United Kingdom
- Prior art keywords
- zone
- rare earth
- nox
- nox trap
- upstream
- 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.)
- Granted
Links
- 238000011144 upstream manufacturing Methods 0.000 title abstract description 21
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 abstract description 37
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 abstract description 37
- 239000000758 substrate Substances 0.000 abstract description 32
- 229910001404 rare earth metal oxide Inorganic materials 0.000 abstract description 24
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical group [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 abstract description 20
- 238000011068 loading method Methods 0.000 abstract description 18
- 229910052684 Cerium Inorganic materials 0.000 abstract description 14
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 abstract description 14
- 230000000694 effects Effects 0.000 abstract description 12
- 239000006185 dispersion Substances 0.000 abstract description 11
- 229910052751 metal Inorganic materials 0.000 abstract description 11
- 239000002184 metal Substances 0.000 abstract description 11
- 238000002485 combustion reaction Methods 0.000 abstract description 7
- 238000000034 method Methods 0.000 abstract description 7
- 229910002091 carbon monoxide Inorganic materials 0.000 abstract description 6
- 239000011232 storage material Substances 0.000 abstract description 6
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 abstract description 5
- 229930195733 hydrocarbon Natural products 0.000 abstract description 3
- 150000002430 hydrocarbons Chemical class 0.000 abstract description 3
- 239000010410 layer Substances 0.000 description 27
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 24
- 239000005864 Sulphur Substances 0.000 description 20
- 239000007789 gas Substances 0.000 description 20
- 238000006243 chemical reaction Methods 0.000 description 17
- 239000003054 catalyst Substances 0.000 description 13
- 229910052761 rare earth metal Inorganic materials 0.000 description 12
- 238000003860 storage Methods 0.000 description 11
- MXQGCMQXTPTJJT-UHFFFAOYSA-N 1-(2,3-dihydro-1,4-benzodioxin-3-ylmethyl)-3-hydroxythieno[3,2-d]pyrimidine-2,4-dione Chemical compound C1OC2=CC=CC=C2OC1CN1C(=O)N(O)C(=O)C2=C1C=CS2 MXQGCMQXTPTJJT-UHFFFAOYSA-N 0.000 description 8
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 8
- 238000001035 drying Methods 0.000 description 8
- 238000010304 firing Methods 0.000 description 8
- 239000000446 fuel Substances 0.000 description 7
- 101150094154 lnt2 gene Proteins 0.000 description 7
- 239000000203 mixture Substances 0.000 description 7
- 239000002245 particle Substances 0.000 description 7
- 239000010948 rhodium Substances 0.000 description 7
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 6
- 101150035458 lnt1 gene Proteins 0.000 description 6
- 230000018537 nitric oxide storage Effects 0.000 description 6
- 229910052760 oxygen Inorganic materials 0.000 description 6
- 239000001301 oxygen Substances 0.000 description 6
- 229910052703 rhodium Inorganic materials 0.000 description 6
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 6
- 230000003197 catalytic effect Effects 0.000 description 5
- 239000011248 coating agent Substances 0.000 description 5
- 238000000576 coating method Methods 0.000 description 5
- 230000003647 oxidation Effects 0.000 description 5
- 238000007254 oxidation reaction Methods 0.000 description 5
- 229910052697 platinum Inorganic materials 0.000 description 5
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 4
- 239000007864 aqueous solution Substances 0.000 description 4
- 239000003225 biodiesel Substances 0.000 description 4
- HSJPMRKMPBAUAU-UHFFFAOYSA-N cerium(3+);trinitrate Chemical compound [Ce+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O HSJPMRKMPBAUAU-UHFFFAOYSA-N 0.000 description 4
- 238000007906 compression Methods 0.000 description 4
- 230000006835 compression Effects 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 4
- 229910052763 palladium Inorganic materials 0.000 description 4
- 230000010718 Oxidation Activity Effects 0.000 description 3
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 3
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 3
- 229910052788 barium Inorganic materials 0.000 description 3
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 3
- 229910000420 cerium oxide Inorganic materials 0.000 description 3
- 230000001627 detrimental effect Effects 0.000 description 3
- 238000009472 formulation Methods 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 238000007726 management method Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 description 3
- 230000001737 promoting effect Effects 0.000 description 3
- 229910052726 zirconium Inorganic materials 0.000 description 3
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 2
- 229910052783 alkali metal Inorganic materials 0.000 description 2
- 150000001340 alkali metals Chemical class 0.000 description 2
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 2
- 150000001342 alkaline earth metals Chemical class 0.000 description 2
- IWOUKMZUPDVPGQ-UHFFFAOYSA-N barium nitrate Chemical compound [Ba+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O IWOUKMZUPDVPGQ-UHFFFAOYSA-N 0.000 description 2
- QVQLCTNNEUAWMS-UHFFFAOYSA-N barium oxide Chemical compound [Ba]=O QVQLCTNNEUAWMS-UHFFFAOYSA-N 0.000 description 2
- TZCXTZWJZNENPQ-UHFFFAOYSA-L barium sulfate Chemical compound [Ba+2].[O-]S([O-])(=O)=O TZCXTZWJZNENPQ-UHFFFAOYSA-L 0.000 description 2
- 229910052792 caesium Inorganic materials 0.000 description 2
- TVFDJXOCXUVLDH-UHFFFAOYSA-N caesium atom Chemical compound [Cs] TVFDJXOCXUVLDH-UHFFFAOYSA-N 0.000 description 2
- 229910052878 cordierite Inorganic materials 0.000 description 2
- 238000000151 deposition Methods 0.000 description 2
- 239000002283 diesel fuel Substances 0.000 description 2
- JSKIRARMQDRGJZ-UHFFFAOYSA-N dimagnesium dioxido-bis[(1-oxido-3-oxo-2,4,6,8,9-pentaoxa-1,3-disila-5,7-dialuminabicyclo[3.3.1]nonan-7-yl)oxy]silane Chemical compound [Mg++].[Mg++].[O-][Si]([O-])(O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2)O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2 JSKIRARMQDRGJZ-UHFFFAOYSA-N 0.000 description 2
- 239000003502 gasoline Substances 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 229910052749 magnesium Inorganic materials 0.000 description 2
- 239000011777 magnesium Substances 0.000 description 2
- 239000003345 natural gas Substances 0.000 description 2
- -1 platinum group metals Chemical class 0.000 description 2
- 229910052700 potassium Inorganic materials 0.000 description 2
- 239000011591 potassium Substances 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 229910052712 strontium Inorganic materials 0.000 description 2
- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 description 2
- 229910052717 sulfur Inorganic materials 0.000 description 2
- 239000011593 sulfur Substances 0.000 description 2
- 229910021653 sulphate ion Inorganic materials 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- 229910052779 Neodymium Inorganic materials 0.000 description 1
- 229910052777 Praseodymium Inorganic materials 0.000 description 1
- 230000010757 Reduction Activity Effects 0.000 description 1
- 229910052772 Samarium Inorganic materials 0.000 description 1
- ROLJWXCAVGNMAK-UHFFFAOYSA-N [Ce]=O Chemical compound [Ce]=O ROLJWXCAVGNMAK-UHFFFAOYSA-N 0.000 description 1
- 239000006096 absorbing agent Substances 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- CSSYLTMKCUORDA-UHFFFAOYSA-N barium(2+);oxygen(2-) Chemical class [O-2].[Ba+2] CSSYLTMKCUORDA-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000006260 foam Substances 0.000 description 1
- 230000020169 heat generation Effects 0.000 description 1
- 238000005470 impregnation Methods 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 239000000314 lubricant Substances 0.000 description 1
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 description 1
- 150000002823 nitrates Chemical class 0.000 description 1
- MMKQUGHLEMYQSG-UHFFFAOYSA-N oxygen(2-);praseodymium(3+) Chemical compound [O-2].[O-2].[O-2].[Pr+3].[Pr+3] MMKQUGHLEMYQSG-UHFFFAOYSA-N 0.000 description 1
- 231100000572 poisoning Toxicity 0.000 description 1
- 230000000607 poisoning effect Effects 0.000 description 1
- PUDIUYLPXJFUGB-UHFFFAOYSA-N praseodymium atom Chemical compound [Pr] PUDIUYLPXJFUGB-UHFFFAOYSA-N 0.000 description 1
- 229910003447 praseodymium oxide Inorganic materials 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 150000002910 rare earth metals Chemical class 0.000 description 1
- KZUNJOHGWZRPMI-UHFFFAOYSA-N samarium atom Chemical compound [Sm] KZUNJOHGWZRPMI-UHFFFAOYSA-N 0.000 description 1
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 238000009827 uniform distribution Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 238000013316 zoning Methods 0.000 description 1
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
- B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
- B01J23/56—Platinum group metals
- B01J23/58—Platinum group metals with alkali- or alkaline earth metals
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
- F01N3/0871—Regulation of absorbents or adsorbents, e.g. purging
- F01N3/0885—Regeneration of deteriorated absorbents or adsorbents, e.g. desulfurization of NOx traps
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/46—Removing components of defined structure
- B01D53/60—Simultaneously removing sulfur oxides and nitrogen oxides
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
- B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
- B01D53/9404—Removing only nitrogen compounds
- B01D53/9409—Nitrogen oxides
- B01D53/9413—Processes characterised by a specific catalyst
- B01D53/9422—Processes characterised by a specific catalyst for removing nitrogen oxides by NOx storage or reduction by cyclic switching between lean and rich exhaust gases (LNT, NSC, NSR)
-
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
- B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
- B01D53/9445—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC]
- B01D53/9454—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC] characterised by a specific device
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
- B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
- B01D53/9459—Removing one or more of nitrogen oxides, carbon monoxide, or hydrocarbons by multiple successive catalytic functions; systems with more than one different function, e.g. zone coated catalysts
- B01D53/9463—Removing one or more of nitrogen oxides, carbon monoxide, or hydrocarbons by multiple successive catalytic functions; systems with more than one different function, e.g. zone coated catalysts with catalysts positioned on one brick
- B01D53/9472—Removing one or more of nitrogen oxides, carbon monoxide, or hydrocarbons by multiple successive catalytic functions; systems with more than one different function, e.g. zone coated catalysts with catalysts positioned on one brick in different zones
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/10—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of rare earths
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
- B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
- B01J23/46—Ruthenium, rhodium, osmium or iridium
- B01J23/464—Rhodium
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
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- B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
- B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
- B01J23/56—Platinum group metals
- B01J23/63—Platinum group metals with rare earths or actinides
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- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/19—Catalysts containing parts with different compositions
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/50—Catalysts, in general, characterised by their form or physical properties characterised by their shape or configuration
- B01J35/56—Foraminous structures having flow-through passages or channels, e.g. grids or three-dimensional monoliths
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/02—Impregnation, coating or precipitation
- B01J37/024—Multiple impregnation or coating
- B01J37/0242—Coating followed by impregnation
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/02—Impregnation, coating or precipitation
- B01J37/024—Multiple impregnation or coating
- B01J37/0244—Coatings comprising several layers
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
- F01N3/0814—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
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- F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
- F01N3/28—Construction of catalytic reactors
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- F01N3/2828—Ceramic multi-channel monoliths, e.g. honeycombs
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Abstract
A NOx trap comprises components comprising at least one platinum group metal, at least one NOx storage material and bulk ceria or a bulk cerium-containing mixed oxide deposited uniformly in a first layer on a honeycombed substrate monolith, the uniformly deposited components in the first layer having a first, upstream, zone having increased activity relative to a second, downstream zone for oxidising hydrocarbons and carbon monoxide, and a second, downstream, zone having increased activity to generate heat during a desulphation event, relative to the first, upstream, zone, wherein the second, downstream, zone comprises a dispersion of rare earth oxide, wherein the rare earth oxide loading in the second, downstream zone is greater than the rare earth oxide loading in the first, upstream zone. An exhaust system for a lean burn internal combustion engine, a vehicle comprising a lean burn internal combustion engine and the exhaust system and methods of making the NOx trap according to the invention are also claimed.
Description
NOx TRAP The present invention concerns improvements in NOx traps forming part of an internal combustion exhaust gas aftertreatment system, and more especially concerns NOx traps having an improved ability to be regenerated in respect of stored sulphur.
The use of in-line NOx storage units, often called Lean NOx Traps but now more commonly called NOx traps or NOx Absorber Catalysts (NAC), is now well known in exhaust gas aftertreatment systems for lean burn internal combustion engines. Possibly the earliest patent publication is Toyota's EP 0 560 991, which describes how a NOx storage unit may be constructed by incorporating materials such as barium oxide which react with NOx to form nitrates, and a NOx conversion catalyst such as platinum. The trap is periodically regenerated by modulating the fuel/air ratio (commonly called "lambda" or X) to stoichiometric (X = 1) or rich (X> 1), so that NOx is released and simultaneously reduced by contact with the catalyst to nitrogen gas.
A conventional NOx trap is constructed by depositing NOx trapping components, including oxygen storage components ("OSC") and catalytic components onto a honeycombed flow-through substrate monolith, in similar manner to coating honeycombed substrate monoliths with an exhaust gas catalyst. We have previously disclosed that, in some circumstances at least, it may be advantageous to form a NOx trap by utilising selected layers of materials.
The present invention may be applied to gasoline, spark ignition engines, but has particular relevance to compression ignition engines, generally known as Diesel engines, though some compression ignition engines can operate on other fuels, such as natural gas, biodiesel or Diesel fuel blended with biodiesel and/or Fischer-Tropsch fuels. Compression ignition engines operate with lean fuellair ratios, and give good fuel economy, but present greater difficulties than gasoline-fuelled engines in NOx storage and conversion, because of the resulting lean exhaust gases. Gasoline-fuelled engines are generally operated closer to X 1, and although NOx conversion presents slightly fewer difficulties than with Diesel, sulphur accumulation on, and release from, NOx traps may present some difficulties.
Although Diesel fuels are now commonly refined and formulated as "low sulphur" or "ultra low sulphur", the fuels, and consequently the exhaust gases, do contain sulphur compounds. The lubricants used in the engine can also contribute sulphur components to the exhaust gases. The NOx traps, which generally contain barium oxides, and ceria as an oxygen storage component ("OSC"), effectively but coincidentally, trap sulphur compounds by reaction. This may be regarded as "poisoning" by sulphur, or simply as reducing the NOx storage capacity of the NOx trap by sulphur competing with the NOx storage sites. As barium sulphate is more stable than barium nitrate in vehicular exhaust gas conditions, sulphur has to be removed periodically using more aggressive (richer, longer and/or hotter exhaust gas temperatures) than are used to release stored NOx. Accordingly, the state of the art NOx storage trap technology includes sulphur release events, in order to maintain the effectiveness of the NOx trap. Such events are periods of operation of the engine such that the sulphur is released from the NOx trap, and generally involve raising the temperature of the NOx trap whilst frequently modulating X ("leanlrich" switching), which can generate exotherms within the NOx trap. The temperature of the NOx trap in such a sulphur release event is generally increased to at least 5500 C. A number of companies have been working on improving sulphur release from NOx traps, concentrating on initiating and terminating the sulphur release event and the engine management necessary for successful sulphur release. Reference is made to U520090445 18 (Peugeot Citroen Automobiles SA) as an example. However, it is not believed that any such improvement made has involved changing the structure of the NOx trap itself For a typical state of the art NOx trap having a uniform distribution of components throughout, there is a time lag between the front (upstream end) of the NOx trap reaching the desired sulphur release temperature, and the rear of the NOx trap reaching that temperature. In practical terms, therefore, accumulated sulphur is moved through the trap, and there is a tendency for the rear of the trap not to be fully desulphated.
The inventors have noted that temperature propagation through the length of a NOx trap substrate is slow. It would therefore be desirable to improve the heat generation in the downstream part of the NOx trap, rather than to rely on conventional heat transfer from the front of the trap during a desulphation event. An aim of the present invention is to realise an improved NOx trap, offering the ability to release trapped sulphur more efficiently and/or with a less demanding desulphation event.
The present invention provides a NOx trap comprising components comprising at least one platinum group metal, at least one NO storage material and bulk ceria or a bulk cerium-containing mixed oxide deposited uniformly in a first layer on a honeycombed substrate mono lith, the uniformly deposited components in the first layer having a first, upstream, zone having increased activity relative to a second, downstream zone for oxidising hydrocarbons and carbon monoxide, and a second, downstream, zone having increased activity to generate heat during a desulphation event, relative to the first, upstream, zone, wherein the second, downstream, zone comprises a dispersion of rare earth oxide, wherein the rare earth oxide loading in gin3 in the second, downstream zone is greater than the rare earth oxide loading in the first, upstream zone.
As used herein the term "bulk" to refer to a reducible oxide such as ceria (or any other component) means that the ceria is present as solid particles thereof These particles are usually very fine, of the order of at least 90 percent of the particles being from about 0.5 to 15 microns in diameter. The term "bulk" is intended to distinguish from the situation in which ceria is "dispersed" on a refractory support material e.g. by being impregnated into the support material from a solution e.g. cerium nitrate or some other liquid dispersion of the component and then dried and calcined to convert the impregnated cerium nitrate to a dispersion of ceria particles on a surface of the refractory support. The resultant ceria is thus "dispersed" onto and, to a greater or lesser extent, within a surface layer of the refractory support. The dispersed ceria is not present in bulk form, because bulk ceria comprises fine, solid particles of ceria.
The dispersion can also take the form of a sol, i.e. finely divided particles of e.g. ceria on the nanometer scale.
GB 2450578 discloses a lean NOx trap system comprising two individual substrates wherein an upstream substrate has a lower cerium oxygen storage component and a lower platinum group metal loading than a downstream substrate.
However, none of the Examples in GB 578 investigates the benefits claimed of dividing the total ceria loading in the lean NOx trap system between upstream and downstream substrates. Moreover, it is not clear whether by "cerium" in the lean NOx trap the authors intended to mean "bulk" ceria, dispersed ceria or both. In the NOx trap of the present invention, the inventors have found that the presence of "bulk" ceria or a bulk cerium-containing mixed oxide deposited uniformly in a first layer on a honeycombed substrate monolith improves rich NO conversion. By removing it, rich NO conversion is undesirably lower.
US 2004/0082470 discloses a two zone NOx trap that appears to have been designed primarily for use in a gasoline engine, which NOx trap having an upstream zone without oxygen storage component and a downstream zone having "a small amount of mixed oxides of zirconium and cerium". For the reasons discussed above, the inventors believe that the absence of OSC, e.g. ceria, in the upstream zone would lower the overall NO reduction activity of the NOx trap. Furthermore, the PGM loading in the upstream zone appears to be greater than that of the downstream zone.
In embodiments, the rare earth oxide dispersion can comprise oxides of elements selected from the group consisting of cerium, praseodymium, neodymium, lanthanum, samarium and mixtures thereof. Preferred rare earth oxides include cerium oxide and/or praseodymium oxide with cerium oxide particularly preferred.
The rare earth oxide dispersion can be present, for example, as an impregnation of components in the NOx trap (wherein one or more components of the NOx trap supports the rare earth oxide) or as a sol (particles of finely divided rare earth oxide on the nanometer scale).
The inventors have noted that the presence of e.g. dispersed rare earth oxides such as ceria is detrimental to oxidation of HC and CO in e.g. Pt or PtPd/CeZrO2.
They also noted that a key to promoting NO storage is to remove HC and CO from the exhaust gas. As a result of this observation, the skilled person might consider disposing platinum group metal in a higher loading at the inlet end. However, this increases cost to little benefit. Equally, removing platinum group metal from the second, downstream zone entirely is also detrimental to overall NO storage, because total NO storage is catalyst volume-dependent and platinum group metal is required to oxidise NO to NO2 to promote NO storage. Preferably, therefore, the loading of the dispersion of rare earth oxide in the first, upstream zone in gin3 is zero. However, in certain embodiments e.g. for use in an exhaust system comprising a close-coupled Diesel Oxidation Catalyst followed by a NOx trap in an underfloor location (see also hereinbelow), rare earth oxide can be present also in the first, upstream zone but at a lower loading than the second, downstream zone e.g. at <30%, such as 5-25%, <20% or 10-20% of the loading in gin3 of the dispersion of the rare earth oxide in the second, downstream zone.
By locating most, if not all, of the rare earth oxide dispersion in the second, downstream zone, the hydrocarbon and carbon monoxide oxidation activity of the first, upstream zone is improved relative to the second, downstream zone.
Additionally, the rare earth oxide dispersion in the second, downstream zone increases activity to generate heat to promote desulphation during a desulphation event. Also, the inventors believe that the rare earth oxide can generate hydrogen (e.g. via the water gas shift) which can also destabilise sulphate present on the NOx trap, thereby also promoting desulphation.
Depending upon the arrangement most appropriate for use on a vehicle (e.g. maximum exhaust gas temperature, exhaust gas temperature window (i.e. temperature range from high to low), space velocity, location in the exhaust system (close-coupled or underfloor location), the proportions of the first and second zones, by length of the first layer, can be from 20:80 to 80:20, preferably 30:70 to 70:30, especially 50:50.
In further embodiments, the platinum group metals in the uniformly deposited components in the first layer comprise platinum and/or palladium. Combinations of platinum and palladium are preferred as palladium reduces the tendency of platinum to sinter, losing surface area and activity.
The bulk ceria and cerium-containing mixed oxide components are reducible oxides having oxygen storage activity, i.e. in the exhaust gas environment they release oxygen when the exhaust gas is rich of the stoichiometric lambda set point and absorb oxygen from the exhaust gas when the exhaust gas is lean of the stoichiometric lambda set point. A preferred component for combining with cerium in mixed oxides to improve the hydrothermal stability of the bulk cerium oxide is zirconium, and depending upon the ratio of cerium to zirconium used, optionally one or more rare earth elements may also be included.
The or each at least one NOx storage material may be selected from the group consisting of alkaline earth metals and alkali metals. Suitable alkaline earth metals include barium, strontium, calcium and magnesium with barium and/or strontium preferred. Alkali metals may be selected from the group consisting of potassium, caesium, sodium and lithium with potassium and/or caesium preferred.
To improve hydrothermal stability of the NOx trap, it is preferred that the uniformly deposited components in the first layer comprise magnesium aluminate.
To improve NOx reduction at relatively high temperatures and to maintain NOx reduction following hydrothermal ageing, preferably the second layer overlying the first layer comprises a supported rhodium component. The rhodium support can be alumina or zirconia, optionally doped with one or more rare earth elements.
Preferably, the support for the rhodium or the washcoat containing the rhodium includes a reducible oxide such as ceria. Where the ceria is not present in the rhodium support, it can be included in the washcoat e.g. as a sol.
To further improve heat management, the second, downstream, zone may have a lower thermal mass than the first, upstream, zone, for example, a lower washcoat loading may be applied.
The honeycombed substrate monolith can be made from a ceramic material such as cordierite or silicon carbide, or a metal such as FecralloyTM. The arrangement is preferably a so-called flow-through configuration, in which a plurality of channels extend in parallel from an open inlet end to an open outlet end. However, the honeycombed substrate monolith may also take the form of a filtering substrate such as a so-called wall-flow filter or a ceramic foam.
According to a further aspect, the invention provides an exhaust system for a lean burn internal combustion engine, which exhaust system comprising a NOx trap according to the invention wherein the first, upstream, zone is oriented to receive exhaust gas from the engine before the second, downstream, zone. The NOx trap according to the invention has particular application when located in the so-called close-coupled position, i.e. within 50cm or so of the engine exhaust manifold to maximise heat utilisation for promoting catalytic activity. An alternative, less preferred, alTangement would be to locate the NOx trap in the so-called underfloor position, i.e. slung below the vehicle under-body, with a Diesel oxidation catalyst located upstream (optionally close-coupled to the engine) of the underfloor NOx trap.
In this latter arrangement it is desirable to disperse some rare earth oxide also in the first, upstream zone, according to the invention.
According to another aspect, the invention provides a vehicle comprising a lean burn internal combustion engine and an exhaust system according to the present invention, wherein the engine comprises engine management means configured, when the engine is in use, intermittently to modulate an engine fuel/air ratio from a normal lean running (lambda <1) mode to a richer running mode (lambda <1, lambda = 1 or lambda >1) for the purposes of releasing sulphur inadvertently stored on the NOx trap. The lean burn internal combustion engine of the vehicle is preferably a compression ignition engine, such as a Diesel engine, it can also be fuelled with natural gas, biodiesel or blends of Diesel and biodiesel and/or Fischer-Tropsch-based fuel blends.
According to a further aspect, the invention provides a method of making a NOx trap according to any preceding claim, which method comprising the steps of: (a) coating a honeycombed substrate monolith with a uniform washcoat comprising at least one platinum group metal, at least one NOx storage material and bulk ceria or a bulk cerium-containing mixed oxide; (b) drying and firing the coated substrate monolith; (c) impregnating a second zone of the coated substrate monolith with an aqueous solution of a rare earth element; or contacting a second zone of the coated substrate monolith with a sol of a rare earth element oxide; and (d) drying and firing the coated substrate monolith of step (c).
In one embodiment, an additional step is inserted between steps (c) and (d), wherein a first zone of the coated substrate monolith is impregnated with an aqueous solution of a rare earth element; or a first zone of the coated substrate monolith is contacted with a sol of rare earth element oxide, and in either case the resulting rare earth oxide loading in gin3 (i.e. excluding the bulk ceria or bulk cerium-containing mixed oxide) in the first zone is: (i) <30% the rare earth oxide loading in the second zone; or (ii) >70% the rare earth oxide loading in the second zone.
According to another aspect, the invention provides a method of making a NOx trap according to the invention, which method comprising the steps of: (a) coating a first zone of a honeycombed substrate monolith from a first end with a washcoat comprising at least one platinum group metal, at least one NOx storage material and bulk ceria or a bulk cerium-containing mixed oxide; (b) drying and firing the part-coated substrate monolith; (c) coating a second zone of the part-coated substrate monolith from a second end thereof with a washcoat comprising at least one platinum group metal, at least one NOx storage material, bulk ceria or a bulk cerium-containing mixed oxide and an aqueous solution of a rare earth element or a sol of a rare earth element oxide; and (d) drying and firing the coated substrate monolith of step (c).
In one embodiment, the washcoat of step (a) comprises an aqueous solution of rare earth element or a sol of a rare earth element oxide at a concentration resulting in a rare earth oxide loading in gin3 (i.e. excluding the ceria or cerium-containing mixed oxide) in the first, upstream, zone that is: (i) <30% the rare earth oxide loading in the second zone; or (ii) >70% the rare earth loading in the second zone.
In embodiments of either method of making a NOx trap according to the present invention, a further step comprises of coating the substrate monolith coated with the first layer with a second layer comprising a supported rhodium component and drying and firing the resulting substrate monolith.
The first and second zones may be readily formed by utilising known techniques for differential deposition of catalyst and other components for exhaust gas catalysts, for example using the Applicant's WO 99/47260, i.e. comprising the steps of (a) locating a containment means on top of a support, (b) dosing a pre-determined quantity of a liquid component into said containment means, either in the order (a) then (b) or (b) then (a), and (c) by applying pressure or vacuum, drawing said liquid component into at least a portion of the support, and retaining substantially all of said quantity within the support.
In order that the invention may be more fully understood, the following Examples are provided by way of illustration only and with reference to the accompanying drawings, wherein: Figure 1 is a graph showing the loss of NO conversion due to repeated SO/deSO cycles plotted against the number of desulphation events at 500°C on a synthetic catalytic activity test apparatus for two, two-layer lean NOx traps, one having ceria sol present in the bottom layer; and Figure 2 is a graph comparing the CO conversion of an 800°C aged lower-layer of a lean NOx trap with and without ceria sol.
EXAMPLES
EXAMPLE 1 -Lean NOx Trap Formulation A 400 cells per square inch flow-through cordierite substrate monolith was coated with a two layer NOx trap formulation comprising a first, lower layer comprising 2gin3 alumina, 2gin3 particulate ceria, 90gft3 Pt, 25gft3 Pd and 800gft3 Ba and a second layer comprising 0.5 gin3 85wt% zirconia doped with rare earth elements, 10gft3 Rh and 400gft3 ceria so!. The first layer was coated on the virgin substrate monolith using the method disclosed in WO 99/47260 followed by drying for 30 minutes in a forced air drier at 100°C and then by firing at 500°C for 2 hours before the second layer was applied and the same drying a firing procedure was repeated. This NOx trap was labelled LNT1.
LNT2 was prepared using an identical procedure except in that 400gft3 ceria sol was also added to the lower layer formulation.
EXAMPLE 2 -Synthetic Catalytic Activity Test (SCAT) repeat SO/deSQ Test A core was cut from each of LNT1 and LNT2 and each core was tested in turn using on a Synthetic Catalytic Activity Test (SCAT) apparatus using the following conditions: 1) Cycle between 300 seconds leanl2O seconds rich at an inlet temperature of 350°C -5 cycles with no sulphur to evaluate clean NOx performance; and -5 cycles with sulphur to sulphate sample to 2g/litre 2) Desulphate at 500°C for 5 minutes Cycle between 50 seconds richll0 seconds lean 3) 300 seconds leanl20seconds rich at 350°C -5 cycles with no sulfur to evaluate desulfated NOx performance; and -5 cycles with sulfur to sulfate to 2g/l 4) Repeat The gas conditions used are set out in Table 1.
Table 1
Lean Rich Lean Rich desuiphation desuiphation Length (secs) 300 20 10 50 NO (ppm) 100 200 --CO(%) 0.03 2 1 2 C02(%) 6 10 6 10 C3H6 (ppm) 50 1700 50 1700 H2 (%) 0 0.4 0 0.4 02(%) 11 1.5 6 1.5 H20(%) 12 12 6.6 12 Flow rate 47 39 47 39 (1/mm) The results of repeated sulphation/desuiphation cycles and its effect on NO conversion is shown in Figure 1, in which it can be seen that after repeated desuiphations, LNT2 retains more NO conversion activity than LNT 1. That is, the presence of additional dispersed ceria in the lower layer of LNT2 assists in retaining NO conversion after repeated SO/deSO cycles. The inventors infer from this observation that the dispersed ceria assists in desulphation by generating an exotherm and/or hydrogen during the desuiphation events that assists in desuiphating the NOx trap.
EXAMPLE 3 -NOx Trap Lower Layer CO Oxidation Activity Substrate monoliths coated with the lower layers only of LNT1 and LNT2 following drying and firing prepared as described in Example 1 were aged at 800°C for 5 hours in 10% H20, l0%02, balance N2. The substrate monoliths were each tested on a laboratory bench-mounted 1.9 litre Euro 4 Diesel engine by removing an existing NOx trap and replacing it with the LNT1 (lower layer) or LNT2 (lower layer) substrate monoliths.
An engine speed of 1200rpm was selected and the engine torque was varied to achieve a desired catalyst inlet temperature. The evaluation started with a catalyst .* *I inlet temperature of 350°C. The engine torque was adjusted to ramp the inlet temperature down to < 150°C, sufficient to achieve carbon monoxide oxidation "light- **. : out". In practice this was done by reducing the engine torque from lOONm to 5Nm * 25 over 10 minutes. Following "light-out", the engine torque was ramped back up at a rate of approximately 7°C/mm to 3 50°C to achieve carbon monoxide oxidation "light-off". Exhaust gas composition, mass flow rate, temperature etc. were all monitored * . using a vehicle dynamometer.
The results of CO conversion (%) for this test procedure are shown in Figure 2, from which it can be seen that after lighting out at <150°C, the catalyst's CO oxidation activity "lights off' again as the test ramps up above about 165°C and the CO conversion activity of LNT1 lower layer never drops below 80% conversion over the entire test. However, after the CO conversion activity of the LNT2 lower layer, which contains ceria sol in addition to the other washcoat components of LNT1, lights-out at <150°C, the catalyst fails to light-off again to a similar degree as the LNT 1 lower layer until about 180°C, and CO conversion efficiency falls to below 50%.
The results of Examples 1, 2 and 3 taken together show that for a lean NOx trap comprising Pt, Pd, and a barium NO storage component supported on alumina and bulk ceria, the presence of dispersed ceria is both detrimental to CO conversion activity and beneficial to desulphation. By "zoning" the dispersed ceria to the rear of a substrate monolith carrying the NO trap, an advantageous combination of functionalities is obtained.
For the avoidance of any doubt, the entire contents of every patent document referenced herein is incorporated herein by reference.
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GBGB0922195.3A GB0922195D0 (en) | 2009-12-21 | 2009-12-21 | Improvements in NOx traps |
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GB1021604.2A Expired - Fee Related GB2476573B (en) | 2009-12-21 | 2010-12-21 | NOx trap |
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JP (1) | JP5735983B2 (en) |
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EP2516043A1 (en) | 2012-10-31 |
DE102010063805A1 (en) | 2011-09-01 |
US20110154807A1 (en) | 2011-06-30 |
RU2554576C2 (en) | 2015-06-27 |
CN102740953A (en) | 2012-10-17 |
BR112012015195A2 (en) | 2021-06-01 |
KR20120116965A (en) | 2012-10-23 |
WO2011077139A1 (en) | 2011-06-30 |
GB201021604D0 (en) | 2011-02-02 |
GB0922195D0 (en) | 2010-02-03 |
JP2013514881A (en) | 2013-05-02 |
US20170043322A1 (en) | 2017-02-16 |
JP5735983B2 (en) | 2015-06-17 |
GB2476573B (en) | 2014-04-09 |
RU2012131133A (en) | 2014-01-27 |
CN102740953B (en) | 2015-11-25 |
KR101838558B1 (en) | 2018-03-14 |
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