US20150252706A1 - Scr exhaust-gas aftertreatment device and motor vehicle with such an scr exhaust-gas aftertreatment device - Google Patents

Scr exhaust-gas aftertreatment device and motor vehicle with such an scr exhaust-gas aftertreatment device Download PDF

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Publication number
US20150252706A1
US20150252706A1 US14/714,190 US201514714190A US2015252706A1 US 20150252706 A1 US20150252706 A1 US 20150252706A1 US 201514714190 A US201514714190 A US 201514714190A US 2015252706 A1 US2015252706 A1 US 2015252706A1
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Prior art keywords
scr
particulate filter
exhaust
scr catalytic
catalytic converter
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US14/714,190
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English (en)
Inventor
Martina Kösters
Jovina Addo-Mensah
Thorsten Düsterdiek
Frank Piritz
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Volkswagen AG
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Volkswagen AG
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Assigned to VOLKSWAGEN AKTIENGESELLSCHAFT reassignment VOLKSWAGEN AKTIENGESELLSCHAFT ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: ADDO-MENSAH, JOVINA, DÜSTERDIEK, Thorsten, KÖSTERS, Martina, PIRITZ, FRANK
Publication of US20150252706A1 publication Critical patent/US20150252706A1/en
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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
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/033—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices
    • F01N3/035—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices with catalytic reactors, e.g. catalysed diesel particulate filters
    • 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
    • F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F01N13/009—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series
    • F01N13/0093—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series the purifying devices are of the same type
    • 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
    • F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F01N13/009—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series
    • F01N13/0097—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series the purifying devices are arranged in a single housing
    • 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
    • F01N2250/00—Combinations of different methods of purification
    • F01N2250/02—Combinations of different methods of purification filtering and catalytic conversion
    • 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
    • F01N2340/00—Dimensional characteristics of the exhaust system, e.g. length, diameter or volume of the apparatus; Spatial arrangements of exhaust apparatuses
    • F01N2340/02—Dimensional characteristics of the exhaust system, e.g. length, diameter or volume of the apparatus; Spatial arrangements of exhaust apparatuses characterised by the distance of the apparatus to the engine, or the distance between two exhaust treating apparatuses
    • 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
    • F01N3/105—General auxiliary catalysts, e.g. upstream or downstream of the main catalyst
    • F01N3/106—Auxiliary oxidation catalysts
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

Definitions

  • the invention relates to an exhaust-gas aftertreatment device for an aftertreatment of an exhaust-gas of an internal combustion engine and a motor vehicle with such an exhaust-gas aftertreatment device, wherein the exhaust-gas aftertreatment device operates in accordance with the principle of the selective catalytic reduction.
  • a known NO x exhaust-gas aftertreatment provides for the use of NO x storage catalytic converters which store nitrogen oxides in the form of nitrates during lean operation (at ⁇ >1) and, during short intervals with a rich exhaust-gas atmosphere ( ⁇ 1), desorb the stored nitrogen oxides and reduce them to nitrogen N 2 in the presence of reducing agents, which are present in the rich exhaust-gas.
  • catalytic converter systems which operate in accordance with the principle of the selective catalytic reduction (SCR selective catalytic reduction).
  • SCR selective catalytic reduction include at least an SCR catalytic converter which selectively converts, in the presence of a reducing agent, usually ammonia NH 3 , which is fed to the exhaust-gas, the nitrogen oxides of the exhaust-gas into nitrogen and water.
  • the ammonia can be added in a metered manner from an aqueous ammonia solution to the exhaust-gas flow or can be obtained by way of thermolysis and hydrolysis from a precursor compound, for example urea in the form of an aqueous solution or solid pellets.
  • a more recent approach to storing ammonia in the vehicle includes NH 3 storage materials that reversibly bind ammonia as a function of the temperature.
  • metal amine storage systems are known in this context, for example, MgCl 2 , CaCl 2 and SrCl 2 , which store ammonia in the form of a complex compound, in order to then be available for example as MgCl 2 (NH 3 ) x , CaCl 2 (NH 3 ) x or SrCl 2 (NH 3 ) x .
  • the ammonia can be released again from these compounds by the application of heat.
  • a positioning of the SCR catalytic converter close to the engine is also known, in particular by integrating an SCR catalytic coating in the particulate filter.
  • SCR catalytically coated particulate filter also called SCR particulate filter, SCR/PF, or SPF
  • SCR/PF SCR particulate filter
  • the temperature gradient across the particulate filter substrate compared to that of the flow-through substrate is greater because of the greater substrate length of the filter, which has an adverse effect on the NO x conversion.
  • the substrate temperature in the rear area of the particulate filter can be so low that only low conversion rates are achieved in that area.
  • the coating of the particulate filter substrate with the SCR catalytic material in contrast to the coating of a flow-through substrate (honeycomb body), is limited to smaller amounts of coating, so that the exhaust-gas back pressure across the particulate filter is within acceptable ranges.
  • the NO x efficiency of the SCR particulate filter is limited and a downstream SCR catalytic converter, in particular at an underfloor position of the vehicle, is still required.
  • the downstream SCR catalytic converter also serves to prevent the emission of a reducing agent slip of the SCR unit which is close to the engine.
  • U.S. Patent Application Publication No. US 2008/0060348 A1 describes an exhaust-gas system having two series-connected SCR catalytic converters and having a particulate filter disposed between them. By an appropriate selection of the SCR catalytic coatings of the two SCR catalytic converters, the upstream SCR catalytic converter has a temperature window at lower temperatures than the downstream SCR catalytic converter.
  • U.S. Patent Application Publication No. US 2008/0060348 A1 proposes to provide the particulate filter with an SCR catalytic coating and thereby eliminate the first upstream SCR catalytic converter.
  • an exhaust-gas system of a diesel engine which has a first “SCR catalytic converter” (HC-SCR catalytic converter) which reduces nitrogen oxides in the presence of hydrocarbons, which are supplied to the exhaust-gas flow by a fuel metering.
  • HC-SCR catalytic converter Downstream of the HC-SCR catalytic converter is an oxidation catalytic converter, a second SCR catalytic converter (NH 3 -SCR catalytic converter) and a diesel particulate filter downstream from that.
  • the SCR catalytic coating of the NH 3 -SCR catalytic converter is provided on a wall-flow filter substrate.
  • German Patent Application No. DE 10 2010 039 972 A1 corresponding to U.S. Patent Application Publication No. US 2011/0064632 A1
  • German Patent Application No. DE 10 2010 039 972 A1 describes a configuration which has a first oxidation catalytic converter, an SCR/DPF (selective catalytic reduction/diesel particulate filter) connected downstream thereof, and, downstream of that, an SCR catalytic converter and, optionally, a second oxidation catalytic converter.
  • SCR/DPF selective catalytic reduction/diesel particulate filter
  • SCR catalytic converter on a particulate filter substrate (SCR/PF) with a downstream-connected SCR catalytic converter on a flow-through substrate.
  • SCR/PF particulate filter substrate
  • an exhaust-gas aftertreatment device for an aftertreatment of an exhaust-gas of an internal combustion engine including:
  • an SCR catalytic converter having an SCR catalytic coating for a selective reduction of nitrogen oxides in a presence of a reducing agent added to the exhaust-gas in a metered manner, the SCR catalytic converter having a flow-through substrate, the SCR catalytic coating of the SCR catalytic converter being disposed on the flow-through substrate;
  • an SCR particulate filter downstream of the SCR catalytic converter having an SCR catalytic coating for a selective reduction of nitrogen oxides in a presence of the reducing agent added to the exhaust-gas in a metered manner
  • the SCR particulate filter having a particulate filter substrate, the SCR catalytic coating of the SCR particulate filter being disposed on the particulate filter substrate.
  • an exhaust-gas aftertreatment device for the aftertreatment of exhaust-gases of an internal combustion engine wherein the exhaust-gas aftertreatment device includes:
  • an SCR catalytic converter having an SCR catalytic coating for the selective reduction of nitrogen oxides NO x in the presence of a reducing agent added to the exhaust-gas in a metered manner, wherein the SCR catalytic coating is disposed on a flow-through substrate, and
  • SCR-PF SCR particulate filter having an SCR catalytic coating for the selective reduction of NO x in the presence of the reducing agent added to the exhaust-gas in a metered manner, wherein the SCR catalytic coating is disposed on a particulate filter substrate.
  • the SCR particulate filter is in this case provided downstream of the SCR catalytic converter.
  • the SCR catalytic converter in accordance with the invention is thus provided upstream of the SCR particulate filter, and is thus located at a position closer to the engine.
  • the SCR catalytic converter close to the engine (close-coupled position) in front, i.e. upstream, of the SCR particulate filter By positioning the SCR catalytic converter close to the engine (close-coupled position) in front, i.e. upstream, of the SCR particulate filter, the NO x conversion performance of the SCR catalytic converter is improved due to the lower temperature gradient in the flow-through substrate of the SCR catalytic converter. This applies in particular in the case of low exhaust-gas temperatures, for example after a cold start of the internal combustion engine.
  • the configuration according to the invention furthermore allows for the reduction or even the absence of heating measures of the SCR catalytic converter, as a result of which fuel advantages and thus lower CO 2 emissions are achieved.
  • the upstream SCR catalytic converter also results in an improvement of the contact times between the NO x molecules of the exhaust-gas and the activity centers of the SCR catalytic coating, which also results in the improvement of the NO x conversion already at low temperatures. Since the flow-through substrate of the upstream SCR catalytic converter, when compared to the particulate filter substrate of the SCR particulate filter, permits a larger amount of SCR coating in relation to the substrate volume, the exhaust-gas back pressure of the entire exhaust-gas aftertreatment device, with the same total amount of the SCR catalytic coating, is reduced when compared to a single SCR particulate filter.
  • a flow-through substrate is understood to be a catalyst carrier which includes uninterrupted, continuous flow channels from an inflow face side to an outflow face side, wherein the flow channels are in particular disposed parallel to one another.
  • This can be a ceramic monolith or a metallic catalyst carrier.
  • a particulate filter substrate is understood to be a carrier whose flow channels are closed.
  • the particulate filter substrate can be embodied in the form of a so-called wall-flow filter, whose parallel flow channels are closed alternately on the inlet side or on the outlet side. In this case, a flow channel closed on the outlet side is disposed adjacent to flow channels closed on the inlet side and vice versa.
  • Exhaust-gas which flows into the flow channels closed on the outlet side is thus forced to penetrate through the lateral channel walls, so as to enter the flow channels dosed on the inlet side and thus exit the filter.
  • particulate constituents of the exhaust-gas in particular soot particles, are retained on and in the porous channel walls.
  • Particulate filter substrates are usually manufactured from a ceramic material.
  • At least the SCR catalytic converter is disposed at a position close to the engine.
  • the light-off temperature of the SCR catalytic converter is quickly achieved after an engine cold start, and a cooling down of the catalytic converter during operation is avoided.
  • This permits the elimination of additional heating measures for the targeted heat input into the catalytic converter.
  • what is meant by being positioned or disposed close to the engine is a position within the exhaust-gas channel, wherein the position is located upstream of an underfloor position of a vehicle.
  • the SCR catalytic converter dose to the engine is disposed so that a distance between a cylinder-side inlet opening of an exhaust-gas manifold of the exhaust-gas aftertreatment device and an inflow face side of the SCR catalytic converter is at most 100 cm, preferably at most 80 cm. In specific embodiments, this distance can even be reduced to values of at most 70 cm. The distance is in this case measured by the exhaust-gas travel length, i.e. the path length to be traveled by the exhaust-gas between the cylinder-side inlet opening of the exhaust-gas manifold and the inflow face side of the SCR catalytic converter.
  • an exhaust-gas aftertreatment device for an aftertreatment of an exhaust-gas of the internal combustion engine wherein the exhaust-gas aftertreatment device includes:
  • an SCR catalytic converter having an SCR catalytic coating for a selective reduction of nitrogen oxides in a presence of a reducing agent added to the exhaust-gas in a metered manner, the SCR catalytic converter having a flow-through substrate, the SCR catalytic coating of the SCR catalytic converter being disposed on the flow-through substrate;
  • an SCR particulate filter downstream of the SCR catalytic converter having an SCR catalytic coating for a selective reduction of nitrogen oxides in a presence of the reducing agent added to the exhaust-gas in a metered manner, the SCR particulate filter having a particulate filter substrate, the SCR catalytic coating of the SCR particulate filter being disposed on the particulate filter substrate;
  • At least the SCR catalytic converter being disposed in a position close to the internal combustion engine.
  • the internal combustion engine has an exhaust-gas manifold with a cylinder-side inlet opening
  • the SCR catalytic converter has an inflow face side
  • a distance between the cylinder-side inlet opening of the exhaust-gas manifold and the inflow face side of the SCR catalytic converter is at most 100 cm, preferably at most 80 cm.
  • downstream SCR particulate filter is also disposed at a position close to the engine, in which case the distance between the cylinder-side inlet opening of the exhaust-gas manifold and the inflow face side of the SCR particulate filter is at most 120 cm, preferably at most 100 cm.
  • the SCR catalytic converter has a smaller volume than the downstream SCR particulate filter. With this measure, a very quick light-off of the SCR catalytic converter is achieved after a cold start.
  • the volume of the SCR catalytic converter is at most 75%, preferably at most 60% of the volume of the SCR particulate filter.
  • the SCR catalytic converter and the SCR particulate filter each have a respective volume
  • the volume of the SCR catalytic converter is smaller than the volume of the SCR particulate filter.
  • the volume of the SCR catalytic converter is at most 75% of the volume of the SCR particulate filter.
  • the volume of the SCR catalytic converter is at most 60% of the volume of the SCR particulate filter.
  • the SCR catalytic converter has at least the same or a larger amount of the SCR catalytic coating in relation to the substrate volume than the SCR particulate filter.
  • This embodiment takes account of the fact that flow-through substrates can accommodate a larger amount of coating per substrate volume than filter substrates, without causing unacceptable exhaust-gas back pressures across the substrate.
  • the SCR catalytic converter has a greater amount of SCR catalytic coating than the SCR particulate filter, the amount being greater by a factor of at least 1.2, preferably by a factor of at least 1.5.
  • the flow-through substrate and the particulate filter substrate each have a respective substrate volume; and the SCR catalytic converter and the SCR particulate filter each have a respective amount of the SCR catalytic coating in relation to the respective substrate volume, the amount of the SCR catalytic coating in relation to the substrate volume of the flow-through substrate of the SCR catalytic converter is at least equal to or larger than the amount of the SCR catalytic coating in relation to the substrate volume of the particulate filter substrate of the SCR particulate filter.
  • the amount of the SCR catalytic coating in relation to the substrate volume of the flow-through substrate of the SCR catalytic converter is larger by a factor of at least 1.2 than the amount of the SCR catalytic coating in relation to the substrate volume of the particulate filter substrate of the SCR particulate filter.
  • the amount of the SCR catalytic coating in relation to the substrate volume of the flow-through substrate of the SCR catalytic converter is larger by a factor of at least 1.5 than the amount of the SCR catalytic coating in relation to the substrate volume of the particulate filter substrate of the SCR particulate filter.
  • the flow-through substrate of the SCR catalytic converter has a greater cell count (cell density) than the particulate filter substrate of the SCR particulate filter. Due to the greater cell count of the SCR catalytic converter, a large surface area of the cell walls of the flow channels is achieved, which facilitates the accommodation of a comparatively large amount of SCR coating.
  • the flow-through substrate has a cell count which is greater by a factor of at least 1.1 and preferably by a factor of at least 1.2 than the cell count of the particulate filter substrate.
  • the flow-through substrate of the SCR catalytic converter and the particulate filter substrate of the SCR particulate filter each have a respective cell count
  • the cell count of the flow-through substrate is greater than the cell count of the particulate filter substrate.
  • the cell count of the flow-through substrate is greater by a factor of at least 1.1 than the cell count of the particulate filter substrate.
  • the cell count of the flow-through substrate is greater by a factor of at least 1.2 than the cell count of the particulate filter substrate.
  • the cell count of the flow-through substrate of the SCR catalytic converter is at least 300 cpsi (cells per square inch), preferably at least 350 cpsi and particularly preferably at least 650 cpsi.
  • the particulate filter substrate of the SCR particulate filter has in particular a cell count of at least 250 cpsi, preferably at least 300 cpsi and particularly preferably at least 350 cpsi.
  • the flow-through substrate of the SCR coating has a smaller wall thickness than the particulate filter substrate of the SCR particulate filter.
  • a preferred wall thickness of the particulate filter substrate of the SCR particulate filter is at most 30 mil, in particular at most 15 mil and more preferably at most 13 mil.
  • the porosity of the particulate filter substrate is in a preferred embodiment at most 65%, in particular at most 61%.
  • the mean pore radius is preferably ⁇ 25 ⁇ m, in particular ⁇ 20 ⁇ m.
  • the SCR catalytic converter and the SCR particulate filter are disposed in separate housings connected in series. According to a preferred embodiment, however, the SCR catalytic converter and the SCR particulate filter are disposed in a common housing, because this results in a further temperature advantage as well as a lower exhaust-gas backpressure.
  • the exhaust-gas aftertreatment device includes a common housing, wherein the SCR catalytic converter and the SCR particulate filter are disposed in the common housing.
  • the exhaust-gas aftertreatment device further includes a reducing agent metering device, which is configured to add the reducing agent, or a precursor compound thereof, in a metered manner to the exhaust-gas upstream of the SCR catalytic converter.
  • a reducing agent metering device which is configured to add the reducing agent, or a precursor compound thereof, in a metered manner to the exhaust-gas upstream of the SCR catalytic converter.
  • it is a common metering device for both, the SCR catalytic converter and the downstream SCR particulate filter.
  • the exhaust-gas aftertreatment device thus includes a reducing agent metering device, wherein the reducing agent metering device is configured to add the reducing agent or a precursor compound of the reducing agent in a metered manner to the exhaust-gas upstream of the SCR catalytic converter.
  • the reducing agent that is added in a metered manner is preferably ammonia NH 3 or a precursor compound thereof, wherein in this case in particular urea is suitable.
  • the urea may be used in the form of solid urea pellets, but preferably used in the form of an in particular an aqueous urea solution.
  • the urea that is added in a metered manner reacts by way of thermolysis and hydrolysis while releasing NH 3 . It is within the scope of the invention that the reducing agent ammonia can in principle also be stored up through the use of NH 3 storage materials that reversibly bind or, respectively, release ammonia as a function of the temperature. Corresponding metal amine storages have already been explained above.
  • the exhaust-gas aftertreatment device further includes an oxidation catalytic converter.
  • the oxidation catalytic converter is preferably disposed upstream of the SCR catalytic converter. In this manner it is achieved that the NO 2 /NO ratio of the exhaust-gas is increased, thus achieving an improved NO x conversion performance of the downstream SCR components. If furthermore the oxidation catalytic converter is provided downstream of the reducing agent metering, the oxidation catalytic converter additionally results in an improved homogenization of the supplied reducing agent in the exhaust-gas before it enters the SCR catalytic converter.
  • the exhaust-gas aftertreatment device includes an oxidation catalytic converter.
  • the oxidation catalytic converter is preferably disposed upstream of the SCR catalytic converter.
  • the invention further relates to a motor vehicle with an intemal combustion engine for driving the vehicle and an exhaust-gas aftertreatment device according to the invention.
  • a motor vehicle including:
  • an exhaust-gas aftertreatment device for an aftertreatment of an exhaust-gas of the internal combustion engine, the exhaust-gas aftertreatment device including an SCR catalytic converter and an SCR particulate filter;
  • the SCR catalytic converter having an SCR catalytic coating for a selective reduction of nitrogen oxides in a presence of a reducing agent added to the exhaust-gas in a metered manner, the SCR catalytic converter having a flow-through substrate, the SCR catalytic coating of the SCR catalytic converter being disposed on the flow-through substrate;
  • the SCR particulate filter being disposed downstream of the SCR catalytic converter, the SCR particulate filter having an SCR catalytic coating for a selective reduction of nitrogen oxides in a presence of the reducing agent added to the exhaust-gas in a metered manner, the SCR particulate filter having a particulate filter substrate, the SCR catalytic coating of the SCR particulate filter being disposed on the particulate filter substrate.
  • the internal combustion engine is an internal combustion engine that is operated permanently or at least temporarily in a lean-burn mode, in particular a diesel engine.
  • the exhaust-gas aftertreatment device according to the invention can in principle also be advantageously used for Otto-cycle engines that are temporarily operated in a lean-burn mode, in particular Otto-cycle engines capable of stratified charge operation.
  • FIG. 1 is a schematic illustration of an exhaust-gas aftertreatment device according to a first embodiment of the invention
  • FIG. 2 is a schematic illustration of an exhaust-gas aftertreatment device according to a second embodiment of the invention.
  • FIG. 3 is a graph illustrating temporal courses of the NO x untreated emission of an internal combustion engine and the NO x final emission in an exhaust-gas aftertreatment device according to the invention with a combination of an SCR particulate filter with an upstream SCR catalytic converter (dashed lines) as well as a comparison system without an upstream SCR catalytic converter (solid lines).
  • FIG. 1 there is shown a motor vehicle which is only schematically indicated and is overall designated with reference numeral 10 , wherein the motor vehicle is driven by an internal combustion engine 12 as a traction source, in particular a diesel engine, and wherein the internal combustion engine is at least temporarily operated in a lean-burn mode.
  • the internal combustion engine 12 has in this case, for example, four cylinders, however any different number of cylinders is also possible.
  • the motor vehicle 10 further has an exhaust-gas aftertreatment device according to the invention, which is overall designated by reference numeral 14 , for the catalytic aftertreatment of an exhaust-gas of the internal combustion engine 12 .
  • the exhaust-gas aftertreatment device 14 includes an exhaust-gas manifold 16 , which connects the individual cylinder outlets of the cylinders of the internal combustion engine 12 to an exhaust-gas channel 18 .
  • the exhaust-gas channel 18 has a section 20 close to the engine and has an underfloor section 22 , which is shown here in a shortened form and which ends in an exhaust pipe that is not shown here.
  • an oxidation catalytic converter 24 Downstream of the exhaust-gas manifold 16 , an oxidation catalytic converter 24 is disposed in the exhaust-gas channel 18 .
  • the oxidation catalytic converter 24 has a flow-through substrate which is coated with a catalytic coating which catalyzes the oxidation of exhaust-gas components.
  • the catalytic coating is suited to convert unburned hydrocarbons HC and carbon monoxide CO into CO 2 and H 2 O.
  • the catalytic coating of the oxidation catalytic converter 24 is configured to oxidize NO and N 2 O to NO 2 in order to increase the NO 2 /NO ratio.
  • the catalytic coating of the oxidation catalytic converter 24 contains as a catalytic component in particular at least one element of the platinum group metals Pt, Pd, Rh, Ru, Os, or Ir or a combination of these, in particular Pt and/or Pd.
  • the catalytic coating further contains a washcoat which includes a porous ceramic matrix having a large specific surface area, for example on the basis of zeolite that is doped with the catalytic component.
  • the flow-through substrate of the oxidation catalytic converter 24 can be a metallic substrate or a ceramic monolith, in particular with a honeycomb-like structure having a plurality of continuous, parallel flow channels. Suitable ceramic materials include aluminum oxide, cordierite, mullite and silicon carbide. Suitable metal substrates are made for example from stainless steel or iron-chromium alloys.
  • an SCR catalytic converter 26 Downstream of the oxidation catalytic converter 24 , an SCR catalytic converter 26 is disposed in the section 20 of the exhaust-gas channel 18 that is close to the engine.
  • the SCR catalytic converter 26 has, just like the oxidation catalytic converter 24 , a flow-through substrate on metallic basis or ceramic basis, preferably on ceramic basis. Suitable ceramic or metallic materials correspond to those mentioned in connection with the oxidation catalytic converter.
  • the flow-through substrate of the SCR catalytic converter 26 has a cell count of preferably ⁇ 350 cpsi and a wall thickness of ⁇ 5.5 mil.
  • the walls of the parallel and continuous flow channels of the flow-through substrate of the SCR catalytic converter 26 are coated with an SCR catalytic coating.
  • washcoat made of a porous ceramic matrix having a large specific surface area (for example a zeolite on the basis of aluminum silicate) and catalytic substances disposed thereon in a distributed manner.
  • Suitable SCR catalytic substances include, in particular base metals such as Fe, Cu, Va, Cr, Mo, W, and combinations of these. These are deposited on the zeolite and/or the zeolite metals are partially replaced by ion exchange by the corresponding base metals.
  • the SCR particulate filter 28 Downstream of the SCR catalytic converter 26 is an SCR particulate filter 28 which is also disposed in the section 20 of the exhaust-gas channel 18 that is close to the engine.
  • the SCR particulate filter has a particulate filter substrate, which is, for example, a wall-flow filter.
  • the particulate filter substrate has parallel flow channels that are closed alternately on the inlet side and the outlet side.
  • the particulate filter substrate is made of a porous ceramic material such as cordierite, ⁇ -aluminum oxide, silicon carbide, silicon nitride, zirconium oxide, mullite, spodumene, aluminum oxide-silicon oxide-magnesium oxide (alumina-silica-magnesia) or zirconium silicate.
  • the cell count of the particulate filter substrate is preferably ⁇ 300 cpsi, wherein the cell count is smaller by at least a factor of 1.1 than that of the flow-through substrate of the SCR catalytic converter 26 .
  • the wall thickness of the particulate filter substrate is preferably at most 15 mil and has a porosity of ⁇ 61% with a mean pore radius of ⁇ 20 ⁇ m.
  • the flow channels of the particulate filter substrate are coated with an SCR catalytic coating, which in principle can have the same chemical composition as that of the SCR catalytic converter 26 .
  • the amount of the catalytic coating of the SCR particulate filter 28 in relation to the substrate volume is less than that of the SCR catalytic converter 26 , in particular by a factor of at least 1.5.
  • the particulate filter substrate of the SCR particulate filter 28 can be coated with the SCR catalytic coating over the whole area or only in sections, for example, only in an inlet-side section.
  • the SCR catalytic converter 26 and the SCR particulate filter 28 are disposed in a position close to the engine (close-coupled position).
  • the distance D between a cylinder-side inlet opening of the exhaust-gas manifold 16 and an inflow face side of the SCR catalytic converter 26 is at most 80 cm.
  • Crucial for the measurement of this distance D is the actual path length to be covered by the exhaust-gas (the distance D is in this case illustrated in a simplified manner).
  • the SCR catalytic converter 26 and the SCR particulate filter 28 are disposed in a common housing 30 , which has a conical inlet funnel expanding in the exhaust-gas flow direction and a conically tapering outlet funnel via which funnels it is connected with the exhaust-gas channel 18 .
  • the exhaust-gas aftertreatment device 14 further includes a reducing agent metering device 32 , with which the reducing agent or a precursor compound thereof is added to the exhaust-gas in a metered manner.
  • the reducing agent is introduced into the exhaust-gas flow through the use of a nozzle upstream of the SCR catalytic converter 26 .
  • the reducing agent is typically ammonia NH 3 , which is added in a metered manner in the form of a precursor compound, in particular in the form of urea.
  • the urea in the form of an aqueous solution, is fed from a reservoir, which is not shown, and is added in a metered manner.
  • thermolysis and hydrolysis the urea is decomposed in the hot exhaust-gas to NH 3 and CO 2 .
  • the metered adding of the reducing agent by the metering device 32 is usually carried out by a control unit which is not illustrated here and which controls the device 32 in dependence on an operating point of the engine 12 , in particular in dependence on a current NO x concentration of the exhaust-gas.
  • the exhaust-gas aftertreatment device 14 can also have various exhaust-gas sensors and temperature sensors, such as NO x sensors upstream and/or downstream of the SCR components 26 / 28 .
  • FIG. 2 An exhaust-gas aftertreatment device 14 according to a second embodiment of the present invention is shown in FIG. 2 .
  • corresponding components are designated with the same reference characters as in FIG. 1 and are not discussed in detail again.
  • the SCR catalytic converter 26 and the SCR particulate filter 28 in FIG. 2 are disposed separately, each in its own housing 30 .
  • exhaust-gas aftertreatment device 14 envisage providing the oxidation catalytic converter 24 downstream of the reducing agent metering device 32 .
  • further exhaust-gas aftertreatment components can be present, for example, at the underfloor position 22 of the exhaust-gas channel 18 .
  • FIG. 3 shows cumulative NO x emissions of the exhaust-gas as a function of time t measured after an engine cold start at time to in a standardized test cycle (here NEDC New European Driving Cycle).
  • NO x emissions of an exhaust-gas aftertreatment device 14 according to the invention corresponding to FIG. 1 dashed lines 2 and 4
  • solid lines 1 and 3 were measured.
  • the total amount of the catalytic coating of the SCR particulate filter of the comparison experiment corresponded to the sum of the catalytic coatings of the SCR catalytic converter 26 and the SCR particulate filter 28 of the configuration according to the invention.
  • the curves 1 and 2 show the respective NO x untreated emissions (raw emissions), i.e. the NO x emissions in the untreated exhaust-gas that are generated by the internal combustion engine 12 .
  • the curves 3 and 4 show the respective NO x final emissions measured downstream of the SCR particulate filter.
  • the curves of the NO x final emissions correspond to that of the NO x untreated emission 1 , 2 .
  • the SCR catalytic coatings have in each case not yet reached their light-off temperature, so that no significant NO x conversion takes place.
  • the light-off temperature of the SCR components is reached, so that the NO x final emissions 3 and 4 are considerably lower than the NO x untreated emissions 1 , 2 .
  • the curves of the final emissions 3 and 4 separate from one another, wherein the NO x final emissions of exhaust-gas aftertreatment according to the invention are significantly below the comparison system. From this it is evident, that despite an identical amount of catalytic material, the exhaust-gas aftertreatment device according to the invention has an improved NO x conversion.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Exhaust Gas After Treatment (AREA)
US14/714,190 2012-11-26 2015-05-15 Scr exhaust-gas aftertreatment device and motor vehicle with such an scr exhaust-gas aftertreatment device Abandoned US20150252706A1 (en)

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DE102012023049.4 2012-11-26
DE102012023049.4A DE102012023049A1 (de) 2012-11-26 2012-11-26 SCR-Abgasnachbehandlungseinrichtung sowie Kraftfahrzeug mit einer solchen
PCT/EP2013/072611 WO2014079664A1 (de) 2012-11-26 2013-10-29 Scr-abgasnachbehandlungseinrichtung sowie kraftfahrzeug mit einer solchen

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US20210229079A1 (en) * 2017-03-20 2021-07-29 Basf Corporation Selective catalytic reduction articles and systems
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US10823030B2 (en) 2018-06-11 2020-11-03 Faurecia Emissions Control Technologies, Usa, Llc Method and apparatus to control valve operation for close coupled SCR
US10823031B2 (en) 2018-09-20 2020-11-03 Faurecia Emissions Control Technologies, Usa, Llc Method and apparatus for turbo bypass valve operation strategy for close coupled SCR

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CN104884752A (zh) 2015-09-02
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