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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
  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/19—Catalysts containing parts with different compositions
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  • 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
  • B01D53/9418—Processes characterised by a specific catalyst for removing nitrogen oxides by selective catalytic reduction [SCR] using a reducing agent in a lean exhaust gas
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  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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  • 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
  • B01D53/944—Simultaneously removing carbon monoxide, hydrocarbons or carbon making use of oxidation catalysts
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  • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
  • B01J21/02—Boron or aluminium; Oxides or hydroxides thereof
  • B01J21/04—Alumina
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  • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
  • B01J21/12—Silica and alumina
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  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
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  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
  • B01J23/18—Arsenic, antimony or bismuth
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  • 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
  • B01J23/42—Platinum
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  • 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
  • B01J23/44—Palladium
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  • 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
  • B01J23/64—Platinum group metals with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
  • B01J23/644—Arsenic, antimony or bismuth
  • B01J23/6447—Bismuth
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  • B01J29/00—Catalysts comprising molecular sieves
  • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
  • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
  • B01J29/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65
  • B01J29/72—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65 containing iron group metals, noble metals or copper
  • B01J29/74—Noble metals
  • B01J29/7415—Zeolite Beta
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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
  • B01J37/0215—Coating
• • 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
  • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
  • F01N3/18—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 methods of operation; Control
  • F01N3/20—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 methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
  • F01N3/2066—Selective catalytic reduction [SCR]
• • 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
  • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
  • 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
  • F01N3/2803—Construction of catalytic reactors characterised by structure, by material or by manufacturing of catalyst support
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/10—Noble metals or compounds thereof
  • B01D2255/102—Platinum group metals
  • B01D2255/1021—Platinum
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01D2255/00—Catalysts
  • B01D2255/10—Noble metals or compounds thereof
  • B01D2255/102—Platinum group metals
  • B01D2255/1023—Palladium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/20—Metals or compounds thereof
  • B01D2255/209—Other metals
  • B01D2255/2096—Bismuth
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/40—Mixed oxides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/90—Physical characteristics of catalysts
  • B01D2255/902—Multilayered catalyst
  • B01D2255/9022—Two layers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/90—Physical characteristics of catalysts
  • B01D2255/903—Multi-zoned catalysts
  • B01D2255/9032—Two zones
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/90—Physical characteristics of catalysts
  • B01D2255/915—Catalyst supported on particulate filters
  • B01D2255/9155—Wall flow filters
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2258/00—Sources of waste gases
  • B01D2258/01—Engine exhaust gases
  • B01D2258/012—Diesel engines and lean burn gasoline engines
• • 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
  • B01D53/9477—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 separate bricks, e.g. exhaust systems
• • 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
  • F01N2370/00—Selection of materials for exhaust purification
  • F01N2370/02—Selection of materials for exhaust purification used in catalytic reactors
  • F01N2370/04—Zeolitic material
• • 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
  • F01N2510/00—Surface coverings
  • F01N2510/06—Surface coverings for exhaust purification, e.g. catalytic reaction
  • F01N2510/068—Surface coverings for exhaust purification, e.g. catalytic reaction characterised by the distribution of the catalytic coatings
• • 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
  • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
  • F01N3/103—Oxidation catalysts for HC and CO only

Definitions

• the present invention relates to a diesel oxidation catalyst comprising a plurality of catalytically active material zones, one material zone containing bismuth.
• the exhaust gas from motor vehicles that are operated with lean-burn internal combustion engines also contains components that result from the incomplete combustion of the fuel in the combustion chamber of the cylinder.
• residual hydrocarbons which are usually also predominantly in gaseous form, these include particle emissions, also referred to as “diesel soot” or “soot particles”.
• Hydrocarbons (HC) and carbon monoxide (CO) can be oxidized using diesel oxidation catalysts (DOC).
• DOC diesel oxidation catalysts
• Conventional diesel oxidation catalysts contain, in particular, platinum and/or palladium on a suitable carrier oxide, for example aluminum oxide.
• a known method for removing nitrogen oxides from exhaust gases in the presence of oxygen is selective catalytic reduction (SCR) using ammonia over a suitable catalyst.
• SCR selective catalytic reduction
• the nitrogen oxides to be removed from the exhaust gas are reacted with ammonia to form nitrogen and water.
• Soot particles can be very effectively removed from the exhaust gas with the help of diesel particle filters (DPF), with wall-flow filters made of ceramic materials having proven particularly effective.
• Particle filters can also be provided with catalytically active coatings. So describes For example, EP1820561 A1 describes the coating of a diesel particle filter with a catalyst layer that facilitates the burning off of the filtered soot particles. Diesel particulate filters can also be coated with SCR catalytic converters and are then referred to as SDPF for short.
• Exhaust gas aftertreatment systems are used for the exhaust gas aftertreatment of diesel engines, which are composed of two or more of the above-mentioned components.
• An important part of such a system is the diesel oxidation catalyst. Its main task is to convert carbon monoxide and hydrocarbons, but also to oxidize nitrogen monoxide (NO) to nitrogen dioxide (NO2), which is required by downstream components such as DPF, SCR and SDPF.
• NO nitrogen monoxide
• NO2 nitrogen dioxide
• EP 1 927 399 A2 discloses a support material comprising aluminum oxide and bismuth which carries platinum.
• US 2003/027719 relates to an oxidation catalyst containing palladium and silver and bismuth as the closest neighbor of palladium.
• US 2012/302439 discloses a palladium-gold catalyst which is doped with bismuth and/or manganese.
• WO 2017/064498 A1 discloses an oxidation catalyst containing bismuth or antimony and also a platinum group metal.
• the present invention relates to a catalyst comprising a support substrate having a length L extending between the ends a and b, and four material zones A, B, C and D, wherein
• material zone A extends from end a for part of length L and comprises platinum and no palladium, palladium and no platinum, or platinum and palladium;
• material zone C extends from end a for part of length L and comprises platinum and no palladium, palladium and no platinum, or platinum and palladium;
• Material zone A preferably comprises platinum and palladium, in particular in a weight ratio of 10:1 to 1:5, preferably 3:1 to 1:3.
• Platinum and palladium are preferably present in material zone A in amounts of 10 to 200 g/ft 3 , for example 20 to 180 g/ft 3 or 40 to 150 g/ft 3 , the amounts given being the sum of the amounts of platinum and palladium . If material zone A includes platinum and palladium, it preferably does not include bismuth.
• Platinum and palladium in material zone A are usually present on a carrier material. All materials familiar to the person skilled in the art for this purpose can be considered as carrier material. They have a BET surface area of 30 to 250 m 2 /g, preferably 100 to 200 m 2 /g (determined according to DIN 66132) and are in particular aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, cerium/titanium mixed oxides and mixtures or mixed oxides of at least two of these materials. Aluminum oxide, cerium/titanium mixed oxides, magnesium/aluminum mixed oxides and aluminum/silicon mixed oxides are preferred. If aluminum oxide is used, it is particularly preferably stabilized, for example with 1 to 6% by weight, in particular 4% by weight, of lanthanum oxide.
• an aluminum/silicon mixed oxide it has in particular a silicon oxide content of 5 to 30% by weight, preferably 5 to 10% by weight.
• Material zone A may be a material for storage of hydrocarbons, particularly at temperatures below the light-off of material zone A for the oxidation of hydrocarbons.
• Such storage materials are in particular zeolites whose channels are large enough to be able to absorb hydrocarbons. Preferred zeolites for this purpose belong to the BEA structure type.
• Material zone B comprises bismuth, for example in the form of bismuth oxide (BizOs), but in particular it is in the form of a composite oxide with aluminum or with aluminum and silicon, the silicon content being, for example, 5 to 30, preferably 5 to 15% by weight, based on the weight of aluminum and silicon oxide.
• Bismuth is present, for example, in an amount of 1 to 15, preferably 2 to 7% by weight, based on the composite oxide and calculated as elemental bismuth.
• the composite oxide ideally serves as a carrier material for the platinum.
• platinum is in particular in amounts of 10 to 200 g/ft 3 , for example 20 to 180 g/ft 3 or 40 to 150 g /ft 3 ago.
• Material zone B preferably does not include palladium.
• the lengths of the material zones LA and LB together correspond to the length L of the carrier substrate.
• the material zone LA has in particular a length of 20 to 80%, preferably 40 to 60% of the length L.
• LA and LB each extend over 50% of the length L.
• Material zone C preferably comprises platinum and no palladium or platinum and palladium, in particular in a weight ratio of 20:1 to 1:1, preferably 14:1 to 2:1.
• Platinum and palladium are preferably present in material zone C in amounts of 10 to 200 g/ft 3 , for example 20 to 180 g/ft 3 or 40 to 150 g/ft 3 , the amounts given being the amounts of platinum for the case in which material zone C includes platinum and no palladium or the sums of the amounts of platinum and palladium are for the case that material zone C includes platinum and palladium.
• Platinum and palladium in material zone C are usually present on a carrier material. All materials familiar to the person skilled in the art for this purpose can be considered as carrier material. They have a BET surface area of 30 to 250 m 2 /g, preferably 100 to 200 m 2 /g (determined according to DIN 66132) and are in particular aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, cerium/titanium mixed oxides and mixtures or mixed oxides of at least two of these materials. Aluminum oxide, cerium/titanium mixed oxides, magnesium/aluminum mixed oxides and aluminum/silicon mixed oxides are preferred. If aluminum oxide is used, it is particularly preferably stabilized, for example with 1 to 6% by weight, in particular 4% by weight, of lanthanum oxide.
• an aluminum/silicon mixed oxide it has in particular a silicon oxide content of 5 to 30% by weight, preferably 5 to 10% by weight.
• Material zone C may be a material for storage of hydrocarbons, particularly at temperatures below the light-off of material zone A for the oxidation of hydrocarbons.
• Such storage materials are in particular zeolites whose channels are large enough to be able to absorb hydrocarbons. Preferred zeolites for this purpose belong to the BEA structure type.
• Material zone D preferably comprises platinum and no palladium or platinum and palladium, in particular in a weight ratio of 20:1 to 1:1, preferably 14:1 to 2:1.
• Platinum and palladium are preferably present in material zone D in amounts of 10 to 200 g/ft 3 , for example 20 to 180 g/ft 3 or 40 to 150 g/ft 3 , the amounts given being the amounts of platinum in the event that material zone C includes platinum and no palladium or the sums of the amounts of platinum and palladium are for the case that material zone C includes platinum and palladium.
• Platinum and palladium in material zone D are usually present on a carrier material. All materials familiar to the person skilled in the art for this purpose can be considered as carrier material. They have a BET surface area of 30 to 250 m 2 /g, preferably 100 to 200 m 2 /g (determined according to DIN 66132) and are in particular aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, cerium/titanium mixed oxides and mixtures or mixed oxides of at least two of these materials. Aluminum oxide, cerium/titanium mixed oxides, magnesium/aluminum mixed oxides and aluminum/silicon mixed oxides are preferred. If aluminum oxide is used, it is particularly preferably stabilized, for example with 1 to 6% by weight, in particular 4% by weight, of lanthanum oxide.
• an aluminum/silicon mixed oxide it has in particular a silicon oxide content of 5 to 30% by weight, preferably 5 to 10% by weight.
• Material zone D may be a material for storage of hydrocarbons, particularly at temperatures below the light-off of material zone A for the oxidation of hydrocarbons.
• Such storage materials are in particular zeolites whose channels are large enough to be able to absorb hydrocarbons. Preferred zeolites for this purpose belong to the BEA structure type.
• the lengths of the material zones Lc and LD together correspond to the length L of the carrier substrate.
• the material zone Lc has in particular a length of 20 to 80%, preferably 40 to 60% of the length L.
• Lc and LD each extend over 50% of the length L.
• material zones C and D are identical, i.e., contain the identical components in the identical amounts.
• a uniform material zone extends over the entire length L of the carrier substrate and covers material zones A and B.
• material zone A also comprises bismuth and platinum and preferably no palladium.
• bismuth is also present in material zone A, for example in the form of bismuth oxide (BizCh), but in particular in the form of a composite oxide with aluminum. In the latter case, for example, bismuth is in an amount of 1 to 10, preferably 2 to 7% by weight, based on the composite oxide and calculated as elemental bismuth.
• zones of material A and B are identical, i.e., contain the identical ingredients in the identical amounts.
• a uniform material zone extends over the entire length L of the carrier substrate.
• the catalyst comprises a material zone E, which extends from end b of the support substrate over part of the length L over material zone D and comprises platinum and no palladium, palladium and no platinum, or platinum and palladium.
• Material zone E preferably comprises platinum and no palladium or platinum and palladium, in particular in a weight ratio of 20:1 to 1:1, preferably 14:1 to 2:1.
• Platinum and palladium are preferably present in material zone C in amounts of 10 to 200 g/ft 3 , for example 20 to 180 g/ft 3 or 40 to 150 g/ft 3 , the amounts given being the amounts of platinum for the case in which material zone C includes platinum and no palladium or the sums of the amounts of platinum and palladium are for the case that material zone C includes platinum and palladium.
• Platinum, palladium or platinum and palladium in material zone E are usually present on a carrier material. All materials familiar to the person skilled in the art for this purpose can be considered as carrier material. They have a BET surface area of 30 to 250 m 2 /g, preferably 100 to 200 m 2 /g (determined according to DIN 66132) and are in particular aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, cerium/titanium mixed oxides and mixtures or mixed oxides of at least two of these materials.
• Aluminum oxide, cerium/titanium mixed oxides, magnesium/aluminum mixed oxides and aluminum/silicon mixed oxides are preferred. If aluminum oxide is used, it is particularly preferably stabilized, for example with 1 to 6% by weight, in particular 4% by weight, of lanthanum oxide.
• an aluminum/silicon mixed oxide it has in particular a silicon oxide content of 5 to 30% by weight, preferably 5 to 10% by weight.
• Material zone E preferably extends from end b over 40 to 60% of length L.
• each of material zones A and B and material zones C and D are identical, i.e. material zones A and B contain the identical ingredients in identical amounts and material zones C and D contain identical ingredients in identical amounts .
• the catalyst comprises a zone E of material.
• the catalyst according to the invention comprises a support body. This can be a flow-through substrate or a wall-flow filter.
• a wall-flow filter is a support body comprising channels of length L extending in parallel between first and second ends of the wall-flow filter, which are alternately closed at either the first or second end and which are separated by porous walls.
• a flow-through substrate differs from a wall-flow filter in particular in that the channels of length L are open at both ends.
• wall-flow filters In the uncoated state, wall-flow filters have, for example, porosities of 30 to 80%, in particular 50 to 75%. Their average pore size in the uncoated state is 5 to 30 micrometers, for example.
• the pores of the wall flow filter are so-called open pores, which means they are connected to the channels. Furthermore, the Pores usually interconnected. On the one hand, this enables the inner pore surfaces to be easily coated and, on the other hand, an easy passage of the exhaust gas through the porous walls of the wall-flow filter.
• Flow-through substrates are known to those skilled in the art, as are wall-flow filters, and are commercially available. They consist, for example, of silicon carbide, aluminum titanate or cordierite.
• the catalyst according to the invention generally comprises no further metal, in particular no silver, gold, copper and iron.
• the present invention relates to a catalyst comprising a carrier substrate with a length L extending between the ends a and b, and four material zones A, B, C and D, wherein
• Material zone A extends from end a over 40 to 60% of length L and comprises platinum and palladium in a weight ratio of 3:1 to 1:3;
• material zone B extending from end b over 40 to 60% of length L and comprising platinum supported on a composite oxide of aluminum and bismuth or of aluminum, silicon and bismuth;
• LA + LB L, where LA is the length of material zone A and LB is the length of material zone B;
• material zone C extends from end a over 40 to 60% of length L and comprises platinum and palladium in a weight ratio of 14:1 to 2:1;
• the present invention relates to a catalyst comprising a carrier substrate with a length L extending between the ends a and b, and five material zones A, B, C, D and E, wherein
• Zone E of material comprises platinum and palladium in a weight ratio of 14:1 to 2:1; and wherein material zones C and D are disposed above material zones A and B and material zone E is disposed above material zone D.
• the material zones A, B, C, D and, if present, E are usually present in the form of coatings on the supporting body.
• Catalysts according to the invention in which the material zones A, B, C, D and, if present, E are present in the form of coatings on the carrier substrate, can be produced by methods familiar to the person skilled in the art, for example by the usual dip coating processes or pump and suction coating processes with subsequent thermal post-treatment (calcination).
• the average pore size and the average particle size of the materials to be coated can be coordinated so that they on the porous walls that the Forming channels of the wall-flow filter lie (on-wall coating).
• the mean particle size of the materials to be coated can also be chosen so that they are located in the porous walls that form the channels of the wall flow filter, so that the inner pore surfaces are coated (in-wall coating).
• the mean particle size of the materials to be coated must be small enough to penetrate the pores of the wall-flow filter.
• the carrier substrate is formed from the materials of material zones A and B and a matrix component, while material zones C and D are present in the form of a coating on the carrier substrate.
• Carrier substrates, flow-through substrates as well as wall-flow filters, which not only consist of inert material such as cordierite, but also contain a catalytically active material, are known to the person skilled in the art. To produce them, a mixture of, for example, 10 to 95% by weight of inert matrix component and 5 to 90% by weight of catalytically active material is extruded using methods known per se. All inert materials otherwise used for the production of catalyst substrates can be used as matrix components. These are, for example, silicates, oxides, nitrides or carbides, magnesium aluminum silicates being particularly preferred.
• a support substrate constructed from corrugated sheets of inert materials is used.
• carrier substrates are known to those skilled in the art as "corrugated substrates".
• Suitable inert materials are, for example, fibrous materials with an average fiber diameter of 50 to 250 ⁇ m and an average fiber length of 2 to 30 mm. Fibrous materials are preferred heat-resistant and consist of silicon dioxide, especially glass fibers.
• sheets of the fiber materials mentioned are corrugated in a known manner and the individual corrugated sheets are formed into a cylindrical, monolithically structured body with channels running through the body.
• a monolithic structured body having a crosswise corrugation structure is formed by laminating a number of the corrugated sheets into parallel layers with different orientation of corrugation between the layers.
• uncorrugated, i.e. flat, sheets may be interposed between the corrugated sheets.
• Corrugated sheet substrates can be coated directly with materials A and B, but preferably they are coated first with an inert material, such as titanium dioxide, and only then with the catalytic material.
• an inert material such as titanium dioxide
• the composite oxide can be obtained, for example, by contacting aluminum oxide or an aluminum oxide stabilized with silicon with an aqueous solution of a bismuth salt and then drying and calcining.
• Aluminum oxide or aluminum oxide stabilized with silicon can advantageously be brought into contact with an aqueous solution of a bismuth salt by spraying the aluminum oxide with the aqueous solution of the bismuth salt in a mixer.
• Suitable mixers are known to those skilled in the art. For example, powder mixers or devices for spray drying are suitable.
• the catalytic converter according to the invention is outstandingly suitable as a diesel oxidation catalytic converter which efficiently converts carbon monoxide and hydrocarbons even at low temperatures, but which can also be used for catalytic converters arranged on the downstream side, such as particle filters and SCR Catalysts, forms sufficient nitrogen dioxide.
• the catalyst according to the invention forms more nitrogen dioxide than a comparison catalyst which contains no bismuth in material zone B and is otherwise identical.
• the present invention also relates to a method for cleaning exhaust gases from motor vehicles that are operated with lean-burn engines, characterized in that the exhaust gas is passed over a catalytic converter as described above, the exhaust gas entering the catalytic converter at end a and at End b emerges from the catalyst.
• the present invention also relates to an exhaust system that includes a catalytic converter as described above, at the end b of which one or more further catalytic converters are connected, which are selected from the series consisting of a diesel particulate filter, a diesel particulate filter coated with an SCR catalytic converter, with a soot ignition temperature reducing coating of coated diesel particulate filters and a flow-through substrate located SCR catalyst.
• a catalytic converter as described above, at the end b of which one or more further catalytic converters are connected, which are selected from the series consisting of a diesel particulate filter, a diesel particulate filter coated with an SCR catalytic converter, with a soot ignition temperature reducing coating of coated diesel particulate filters and a flow-through substrate located SCR catalyst.
• the SCR catalytic converter in the exhaust system according to the invention can in principle be selected from all catalytic converters that are active in the SCR reaction of nitrogen oxides with ammonia, in particular from those that are known to the person skilled in the art in the field of automotive exhaust gas catalysis are known to be common.
• Embodiments of the present invention employ SCR catalysts containing a small pore zeolite having a maximum ring size of eight tetrahedral atoms and a transition metal.
• Such SCR catalysts are described, for example, in WO2008/106519 A1, WO2008/118434 A1 and WO2008/132452 A2.
• Particularly preferred zeolites belong to the framework types BEA, AEI, AFX, CHA, KFI, ERI, LEV, MER or DDR and are particularly preferably exchanged with cobalt, iron, copper or mixtures of two or three of these metals.
• zeolites also includes molecular sieves, which are sometimes also referred to as "zeolite-like" compounds. Molecular sieves are preferred if they belong to one of the framework types mentioned above. Examples are silica aluminum phosphate zeolites, known under the term SAPO, and aluminum phosphate zeolites , which are known under the term AIPO.
• Preferred zeolites are also those which have an SAR (silica-to-alumina ratio) value of 2 to 100, in particular 5 to 50.
• the zeolites or molecular sieves contain transition metal in particular in amounts of 1 to 10% by weight, in particular 2 to 5% by weight, calculated as metal oxide, ie for example as FezCh or CuO.
• Preferred embodiments of the present invention contain beta-type (BEA), chabazite-type (CHA), AEI, AFX or Levyne-type (LEV) zeolites or molecular sieves as SCR catalysts with copper, iron or copper and iron.
• Corresponding zeolites or molecular sieves are available, for example, under the designations ZSM-5, Beta, SSZ-13, SSZ-62, Nu-3, ZK-20, LZ-132, SAPO-34, SAPO-35, AIPO-34 and AIPO-35 known, see for example US 6,709,644 and US 8,617,474.
• an injection device for reducing agent is located in front of the SCR catalytic converter.
• the injection device can be chosen arbitrarily by a person skilled in the art, with suitable devices being found in the literature (see, for example, T. Mayer, solid SCR system based on ammonium carbamate, dissertation, TU Kaiserslautern, 2005, and EP 1 561 919 A1) .
• the ammonia may be introduced into the exhaust stream via the injector as such or in the form of a compound from which ammonia is formed at ambient conditions.
• Aqueous solutions of urea or ammonium formate for example, are suitable as such, as is solid ammonium carbamate.
• the reducing agent or a precursor thereof is kept in stock in an entrained container which is connected to the injection device.
• FIGS 1 and 2 show embodiments of the catalyst according to the invention with the following meanings:
• FIG. 1 shows a catalyst according to the invention with the material zones A, B, C and D, all material zones having the same length, namely 50% of the length of the carrier substrate.
• FIG. 2 shows a catalyst according to the invention with the material zones A, B, C, D and E, A and B and C and D being identical in each case.
• Example 1 A commercial cordierite flow-through substrate was coated from its first end for 50% of its length with 65 g/ft 3 platinum and palladium in a weight ratio of 2:1, supported on 72.65 g/l of a lanthanum oxide stabilized alumina, and 40 g/l of a ß-zeolite coated. b) The flow-through substrate obtained according to a) was coated starting from its second end over 50% of its length with 65 g/ft 3 of platinum, supported on 100 g/l of an aluminum oxide doped with 3% by weight of bismuth oxide, and 40 g/l of a ß-zeolites coated. c) The flow-through substrate obtained according to b) was coated over its entire length with 25 g/ft 3 of platinum and palladium in a weight ratio of 14:1, supported on 60 g/l of an aluminum oxide stabilized with lanthanum oxide.
• the total loading of platinum and palladium on the catalyst is 90 g/ft 3 .
• the material zones C and D are identical and form a coherent layer on the material zones A and B over the entire length of the flow-through substrate.
• Comparative Example 1 a) A commercially available flow-through substrate made of cordierite was coated over its entire length with 65 g/ft 3 of platinum and palladium in a weight ratio of 2:1, supported on 72.65 g/l of a lanthana-stabilized aluminum oxide and 40 g/l of a ß -Zeolite coated. b) The flow-through substrate obtained according to a) was coated over its entire length with 25 g/ft 3 of platinum and palladium in a weight ratio of 14:1, supported on 60 g/l of an aluminum oxide stabilized with lanthanum oxide.
• the total loading of platinum and palladium on the catalyst is 90 g/ft 3 .
• the material zones A and B, as well as C and D, are each identical.
• Catalyst VK1 contains no bismuth.
• Example 2 a) A commercially available flow-through substrate made of cordierite was coated, starting from its first end over 50% of its length, with 40 g/ft 3 of platinum and palladium in a weight ratio of 1:3 supported on Ce titanium oxide. b) The flow-through substrate obtained according to a) was coated starting from its second end over 50% of its length with 65 g/ft 3 of platinum, supported on 100 g/l of an aluminum oxide doped with 3% by weight of bismuth oxide, and 40 g/l of a ß-zeolites coated.
• the total loading of platinum and palladium on the catalyst is 100 g/ft 3 .
• the catalyst according to the invention thus obtained is referred to below as K2.
• Comparative Example 2 a) A commercially available flow-through substrate made of cordierite was coated over its entire length with 40 g/ft 3 of platinum and palladium in a weight ratio of 1:3 supported on Ce titanium oxide. b) The flow-through substrate obtained according to a) was coated over its entire length with 70 g/ft 3 of platinum and palladium in a weight ratio of 2:1 supported on 62.28 g/l of aluminum oxide and 25 g/l of ⁇ -zeolite. The total loading of platinum and palladium on the catalyst is 110 g/ft 3 .
• the comparison catalyst VK2 thus obtained, the material zones A and B, as well as C and D are identical. Catalyst VK2 contains no bismuth.
• Example 3 a) A commercially available flow-through substrate made of cordierite was coated over its entire length with 25 g/ft 3 of platinum supported on 25 g/l of an aluminum oxide doped with 3% by weight of bismuth oxide. b) The flow-through substrate obtained according to a) was coated over its entire length with 40 g/ft 3 of platinum and palladium in a weight ratio of 2:1 supported on 110 g/l of aluminum oxide. c) The flow-through substrate obtained according to b) was coated starting from its second end over 50% of its length with 50 g/ft 3 of platinum and palladium in a weight ratio of 12:1 on 50 g/l of a silica-stabilized alumina.
• the total loading of platinum and palladium on the catalyst is 90 g/ft 3 .
• the catalyst according to the invention thus obtained is referred to below as K3.
• the material zones A and B as well as C and D are identical in each case, with the material zones A and B containing bismuth.
• material zone D carries material zone E as a further material zone.
• FIG. 3 shows the NC/NOx ratios of Kl and VK1 in [%] downstream of the catalytic converter, measured on an engine test bench during an NEDC cycle.
• the black curve shows the result of VK1, the gray curve that of Kl.
• the gray curve of Kl shows a higher NO2/NOx ratio especially in the cycle between about 1125 seconds and 1500 seconds.
• FIG. 4 shows the NOz/NOx ratios of K2 and VK2 in [%] downstream of the catalytic converter, measured on an engine test bench during an NEDC cycle.
• the black curve shows the result of VK2, the gray curve that of K2.
• the gray curve shows a higher NO2/NOX ratio.

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• 2021
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