EP2399012A1 - Système de post-traitement de gaz d'échappement - Google Patents

Système de post-traitement de gaz d'échappement

Info

Publication number
EP2399012A1
EP2399012A1 EP10707152A EP10707152A EP2399012A1 EP 2399012 A1 EP2399012 A1 EP 2399012A1 EP 10707152 A EP10707152 A EP 10707152A EP 10707152 A EP10707152 A EP 10707152A EP 2399012 A1 EP2399012 A1 EP 2399012A1
Authority
EP
European Patent Office
Prior art keywords
exhaust gas
engine
nox
treatment system
particulate matter
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP10707152A
Other languages
German (de)
English (en)
Inventor
Douglas M. Beall
Achim K. Heibel
Charles M. SORENSEN Jr
Pushkar Tandon
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Corning Inc
Original Assignee
Corning Inc
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Corning Inc filed Critical Corning Inc
Publication of EP2399012A1 publication Critical patent/EP2399012A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • 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
    • 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
    • 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
    • F01N13/011—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 purifying devices arranged in parallel
    • 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
    • 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
    • F01N3/0821—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents combined with 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
    • 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
    • F01N2250/00—Combinations of different methods of purification
    • F01N2250/12—Combinations of different methods of purification absorption or adsorption, 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
    • F01N2250/00—Combinations of different methods of purification
    • F01N2250/14—Combinations of different methods of purification absorption or adsorption, and filtering
    • 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
    • F01N2570/00—Exhaust treating apparatus eliminating, absorbing or adsorbing specific elements or compounds
    • F01N2570/10—Carbon or carbon oxides
    • 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
    • F01N2570/00—Exhaust treating apparatus eliminating, absorbing or adsorbing specific elements or compounds
    • F01N2570/12—Hydrocarbons
    • 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
    • F01N2570/00—Exhaust treating apparatus eliminating, absorbing or adsorbing specific elements or compounds
    • F01N2570/14—Nitrogen oxides
    • 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 disclosure relates generally to engine exhaust after-treatment systems, and more particularly to porous honeycomb ceramics used in catalytic converters and particulate filters of engine exhaust after-treatment systems.
  • lean DISI engines have two emission issues that must be addressed: the difficulty of converting NOx under excess oxygen conditions by conventional three-way catalyst systems, and production of relatively high levels of ultra-fine (e.g., nanometer sized) particulate matter (PM).
  • ultra-fine (e.g., nanometer sized) particulate matter PM
  • Stoichiometric gasoline engines also produce significant amounts of nanometer sized particulate matter.
  • DISI engines With respect to generation of particulate matter, DISI engines produce carbon soot as a component of their exhaust emissions. The emission of ultra-fine particles into the atmosphere is considered a health issue due to the respiration of these particles into the lungs of people. In addition, the production of carbon black particles is thought to contribute to global climate change. Although the total mass of soot produced and the number of ultra-fine particles emitted by DISI engines is generally lower than those produced by diesel engines (measured, for example, as mass or number of particles emitted per distance driven or per time operated), it is significantly higher than emissions from port-fuel injected gasoline engines, and from diesel engines equipped with particle filtration devices. Thus an exhaust after-treatment filtration system that reduces the emission of ultra- fine particles from vehicles that are powered by DISI engines is desirable.
  • One aspect of embodiments described herein provide an exhaust gas after-treatment system for a gasoline engine comprising a three-way catalyst close-coupled to the gasoline engine; a particulate matter control device positioned downstream of the three-way catalyst; and a NOx control system positioned downstream of the particulate matter control device.
  • embodiments described herein provide a method for cleaning an engine exhaust gas flow, comprising: operating a gasoline engine in a stoichiometric condition upon start-up of the engine; conducting an exhaust gas flow generated by the engine through an exhaust system comprising, successively, a flow-through substrate having a three-way catalytic coating, a wall-flow particulate filter, and a NOx control system; and operating the gasoline engine in a lean-burn condition after the NOx control system attains a minimum operating temperature.
  • FIG. 1 is a schematic illustration of one embodiment of an exhaust gas after-treatment system for a gasoline engine.
  • FIG. 2 is a schematic illustration of another embodiment of an exhaust gas after- treatment system for a gasoline engine.
  • the term ""stoichiometric" combustion means the point at which the air to fuel ratio is such that the fuel is fully oxidized with no remaining oxygen.
  • stoichiometric combustion in gasoline engines typically occurs at an air-fuel mass ratio of about 14.7:1, although it will be recognized by those skilled in the art that the air- fuel ratio in stoichiometric gasoline cars equipped with three-way catalysts require a small oscillation of air-fuel ratio about the stoichiometric point.
  • lean combustion conditions result when the air to fuel ratio during combustion is greater than at the stoichiometric point (i.e., excess air), while “rich” combustion conditions result when the air to fuel ratio during combustion is less than at the stoichiometric point (i.e., excess fuel).
  • Exhaust gases resulting from lean combustion include excess oxygen and relatively small amounts of NOx, hydrocarbons, and carbon monoxide due to nearly complete combustion of the hydrocarbon fuel.
  • Proposed regulations set forth both particle number and particle mass based limits for gasoline engines. For example, Euro 6 regulations slated for implementation in 2014 limit particle number and mass based emissions to 6 x 10 11 particles/km and 4.5 mg/km, respectively, based on the NEDC regulatory drive cycle and the PMP test protocols for particulates measurement.
  • Exhaust after-treatment systems for removing particulate matter from diesel engine exhaust are well known.
  • DISI engines operate in both stoichiometric and lean-burn modes, while diesel engines operate only in lean-burn.
  • Compression ratios of DISI engines are generally less than 12 (although the compression ratio of some high performance engines maybe as high as 15), while the compression ratios of diesel engines are much higher, making DISI engines more sensitive to exhaust system backpressure.
  • the temperature of DISI engine exhaust is generally higher than the temperature of diesel engine exhaust
  • the volume of exhaust gas from a DISI engine is generally higher than a comparably sized diesel engine
  • the generation of particulate matter and NOx differs for DISI and diesel engines.
  • solid soot particles produced by DISI engines are smaller than solid soot particles produced by diesel engines. It is theorized that the particle size difference may be caused by factors such as differences in fuel chemistry, molecular weight, and combustion dynamics. Differences in the aerosolized particulate matter (e.g. liquid droplets) produced by DISI engines also exist, but are less known.
  • soot production rates of lean DISI engines are significantly (i.e., about an order of magnitude) lower than soot production rates of diesel engines.
  • the soot accumulation rate in a particulate filter used in a DISI system is expected to be much lower than the soot accumulation rate in a diesel system. This means that the need for frequent filter regeneration is reduced in DISI systems, or that filter regeneration can be initiated at much lower soot loading levels than required in a diesel system.
  • NOx levels produced by DISI engines are higher than those of diesel engines due to the DISI engine's higher cylinder combustion temperature.
  • the ratio of NOx to carbonaceous soot in the exhaust is an important factor in passive filter regeneration (via the reaction of 2NO2 + C ⁇ CO2 + 2NO).
  • NOx to soot ratio is higher than in a diesel engine.
  • the amount of passive regeneration of carbonaceous soot by nitrogen dioxide (NO2) is relatively high, and consequently the soot accumulation rate in a gasoline system is even lower than in a diesel system.
  • Gasoline engines can also be operated at exhaust temperatures whereby continuous oxidation of soot by oxygen occurs when temperatures in the filter exceed about 600 0 C and excess O2 is present.
  • the present disclosure provides embodiments of exhaust after-treatment systems suitable for gasoline engines in general, and gasoline direct injection (DISI) engines in particular, that operate in both stoichiometric and lean modes, some of such embodiments including particulate filters having relatively low thermal mass (as compared to existing diesel filters).
  • filter wall thickness, inherent material density, total porosity, and product length to diameter ratios are manipulated to control thermal mass and/or pressure drop.
  • After-treatment system 10 includes a close-coupled catalyst 14 (e.g., a three-way catalyst (TWC)), a NOx control system 16 (e.g., a lean NOx trap (LNT)) 16, and a particulate matter control device 18 (e.g., a wall-flow filter) connected to each other via an exhaust pipe 20.
  • a close-coupled catalyst 14 e.g., a three-way catalyst (TWC)
  • NOx control system 16 e.g., a lean NOx trap (LNT)
  • LNT lean NOx trap
  • particulate matter control device 18 e.g., a wall-flow filter
  • At least one of close-coupled catalyst 14, NOx control system 16, and particulate filter 18 comprise a honeycomb body. In one embodiment, all of close-coupled catalyst 14, NOx control system 16, and particulate filter 18 comprise honeycomb bodies. In one embodiment, at least one of close-coupled catalyst 14, NOx control system 16, and particulate filter 18 comprise a ceramic body. In one embodiment, all of close-coupled catalyst 14, NOx control system 16, and particulate filter 18 comprise ceramic bodies.
  • Three-way catalysts (TWC) are designed to simultaneously convert three pollutants to harmless emissions: reduction of nitrogen oxides to nitrogen and oxygen, oxidation of carbon monoxide to carbon dioxide, and oxidation of unburned hydrocarbons (HC) to carbon dioxide and water. Suitable catalyst formulations include three-way compositions having an oxygen storage component such as cerium oxide, and precious metals such as palladium, platinum, or rhodium.
  • Samples A-I nine different particulate matter control devices are referenced (Samples A-I).
  • Samples A-G and I comprise ceramic materials, while sample H comprises a metal material having a tortuous path flow-through type configuration (PM-MetalitTM available from Emitec).
  • Samples A-E and G are configured as wall-flow filters.
  • samples F and I were configured as flow-through substrates to determine whether the number and mass of particulates might be reduced by a high performance emission substrate.
  • Sample F provided a discontinuous channel wall
  • Sample I provided a continuous channel wall.
  • sample I was coated with a catalytic material to determine the efficacy of substrates for reducing particulate matter through catalytic oxidation.
  • Specific materials and geometries (cell density, wall thickness, porosity, median pore size, diameter and length) of the samples are provided in Table 1.
  • particulates were measured in the exhaust gas prior to and immediately after the particulate matter control device 18.
  • Candidate particulate matter control devices were positioned after existing close-coupled and underbody catalysts and the NOx sensor used in the commercial BMW 118i exhaust system.
  • the mufflers were removed from the exhaust system.
  • Candidate particulate matter control devices were canned using a modular canning design and standard mat materials. Taps for pressure, temperature, and gas analyzer measurements were provided for measurements upstream and downstream of the particulate matter control device 18. Filtration efficiency and pressure drop were measured at both low and high exhaust gas flow rates of approximately 18 and 72 kg/hr respectively.
  • Table 1 summarizes results from the filtration efficiency testing.
  • the measured filtration efficiencies in Table 1 are based on accumulation mode particle numbers (e.g. the number of carbonaceous soot and inorganic ash particles).
  • full wall-flow filters i.e., samples A-E and G
  • partial filters i.e., samples H
  • flow-through substrates i.e., samples F and I
  • filtration efficiencies greater than about 92% are required to meet the proposed Euro-6 particulate matter regulations if such regulations were applied to the 2007 Mercedes CLS350 and BMW 12Oi & 118i vehicles.
  • Wall-flow filters with high cell densities and thin walls provide the necessary filtration efficiency, but at the penalty of a higher pressure drop. Because of their higher geometric surface area, bodies with high cell densities (i.e., over about 300 cpsi in one embodiment) will have utility as coated or catalyzed components, thereby providing multi-functional devices having both particulate matter filtration and HC/CO/NOx emission control features in DISI engine emission after-treatment systems.
  • FIG. 2 shows an exhaust system configuration used to further test the performance of uncatalyzed wall flow filter devices with gasoline engines.
  • an exhaust system 100 for direct injection gasoline engine 12 includes a close-coupled catalyst 14, particulate matter control device 18, and NOx control system 16.
  • a supplementary NOx catalyst 16' was installed in the system 100 of FIG. 2 to maximize the ratio of NO2 to NO via the interconversion of these species by reaction with oxygen.
  • NOx control system 16 is selected from any suitable NOx control technology such as, for example, a lean NOx trap (LNT), a lean NOx catalyst (LNC), a selective catalytic reduction (SCR) system, or a combination of one or more of these or other NOx control systems.
  • LNT lean NOx trap
  • LNC lean NOx catalyst
  • SCR selective catalytic reduction
  • LNT Lean NOx traps
  • exemplary NOx-absorbents are often associated with a catalyst for oxidizing nitrogen monoxide (NO) to nitrogen dioxide (NO2), e.g. platinum (Pt), and, optionally, also a catalyst such as rhodium, for reducing NOx to N2 with a suitable reductant (e.g., a hydrocarbon) especially when the system operates close to stoichiometric conditions.
  • a catalyst for oxidizing nitrogen monoxide (NO) to nitrogen dioxide (NO2) e.g. platinum (Pt)
  • Pt platinum
  • a catalyst such as rhodium
  • LNC Lean NOx catalysts
  • the hydrocarbons maybe those naturally present in the exhaust gas (i.e., "native" hydrocarbons) or hydrocarbons may be added to the exhaust gas.
  • LNC catalysts must be selective for NOx reduction compared to competing reactions that might oxidize the hydrocarbons to CO2 and water thus rendering them unable to facilitate conversion of NOx to di-nitrogen.
  • SCR Selective catalytic reduction
  • Ammonia or an ammonia precursor is the primary reductant used in SCR systems.
  • Ammonia-SCR systems react ammonia (NH 3 ) with the NOx to form nitrogen (N 2 ) and water (H 2 O).
  • Suitable de-NOx formulations include the use of barium oxide with platinum for lean- NOx reduction, or SCR systems based on zeolites such as ZSM-5, Zeolite Beta, ZSM-35, ZSM- 12, mordenite, faujasite Y-type zeolite, ferrierite, chabazite, or alternatively SCR with base metal oxide systems using tungsten, vanadium, and titanium oxides.
  • SCR systems based on zeolites such as ZSM-5, Zeolite Beta, ZSM-35, ZSM- 12, mordenite, faujasite Y-type zeolite, ferrierite, chabazite, or alternatively SCR with base metal oxide systems using tungsten, vanadium, and titanium oxides.
  • the close-coupled catalyst 14 has a cell density in the range of about 400 cpsi to about 900 cpsi, a web thickness in the range of about 2 mil to about 4 mil, platinum group metals (PGM) coating formulation, and alumina, zirconia, or ceria wash coat having oxygen storage capability.
  • PGM platinum group metals
  • particulate matter control device 18 has a cell density in the range of about 200 cpsi to about 600 cpsi, and a web thickness in the range of about 3 mil to about 15 mil. Cell densities at the higher end of the range (e.g., in excess of about 300 cpsi) are preferred when particulate matter control device 18 is to provide both particulate matter filtration and HC/CO/NOx emission control features (i.e., when particulate matter control device 18 is to be coated or catalyzed). Total porosity of particulate matter control device 18 is greater than about 30%, and may approach about 60-65% when particulate matter control device 18 is to be coated or catalyzed.
  • particulate matter control device 18 is provided with a length to diameter (L: D) in the range of about 0.5 to about 2.
  • the particulate matter control device 18 may be provided with an asymmetric cell design (i.e., inlet channels having a larger hydraulic diameter than outlet channels) for increased ash capture and storage to extend the life of the filter.
  • the ratio of inlet hydraulic diameter to outlet hydraulic diameter is in the range from about 1.1 :1 to about 1.5:1.
  • particulate matter control device 18 provides a catalytic functionality in addition to filtering particulates from the exhaust stream.
  • particulate matter control device 18 is provided with a platinum group metals (PGM) coating formulation.
  • PGM platinum group metals
  • particulate matter control device 18 has an alumina, zirconia, or ceria washcoat, or combinations thereof, having oxygen storage capability.
  • particulate matter control device 18 has a lean NOx trap (LNT) functionality provided by, for example, barium oxide.
  • washcoats and catalysts are preferentially located within particulate matter control device 18, such as near the inlet side of the device.
  • Close-coupled catalyst 14 A primary function of close-coupled catalyst 14 is to control emissions from engine 12 during the first minutes of engine start-up (i.e., cold-start emissions). In most instances, at start-up, engine 12 will operate under stoichiometric conditions. The near engine position of close-coupled catalyst 14 allows close-coupled catalyst 14 to quickly reach operating (i.e., light-off) temperatures and begin converting at least about 90% of the hydrocarbon, CO, and NOx emissions within about four minutes from engine start-up.
  • particulate matter control device 18 As the components of exhaust system 100 continue to heat-up, catalyst functionality (if present) on particulate matter control device 18 becomes active.
  • particulate matter control device 18 is provided with a three-way catalyst (TWC) precious metal and wash coat formulation
  • the particulate matter control device 18 helps to further convert hydrocarbon, CO, and NOx emissions, while simultaneously capturing solid particulate matter in the exhaust gasses.
  • TWC three-way catalyst
  • the NOx control system 16 downstream of the particulate filter reaches its minimum operating temperature and begins reducing NOx in the exhaust gasses.
  • engine 12 can begin operating in lean-burn combustion mode, thus providing improved fuel economy and better performance (e.g. torque and horsepower) that come from lean-burn combustion.
  • TWC three-way catalysts
  • NOx is controlled by the combination of close- coupled catalyst 14 and NOx control system 16, together with any catalyst functionality provided on particulate matter control device 18.
  • Data in Table 2 show the effectiveness of the uncatalyzed wall flow filters tested in the system configuration of FIG. 2.
  • the measured filtration efficiencies in Table 2 are based on accumulation mode particle numbers (e.g. the number of carbonaceous soot and inorganic ash particles), nucleation mode particle numbers (e.g., the number of aerosolized gasoline and oil particles), and particle mass.
  • Samples A, D and H of Table 2 are of the same configuration as Samples A, D and H described with reference to Table 1.
  • filtration efficiencies in excess of 90% may be achieved.

Abstract

L'invention concerne un système de post-traitement de gaz d'échappement (l0) pour un moteur à essence (12) comprenant un catalyseur à trois voies (14) couplé étroitement au moteur à essence, un dispositif de contrôle de matière particulaire (18) positionné en aval du catalyseur à trois voies, un système de contrôle d'oxyde d'azote (NOx) (16) positionné en aval du dispositif de contrôle de matière particulaire. Selon un procédé de fonctionnement, le moteur à essence fonctionne de façon stœchiométrique lors du démarrage du moteur, le flux de gaz d'échappement généré par le moteur est conduit à travers le système d'échappement, et ensuite le moteur à essence (12) fonctionne dans un état de mélange pauvre lorsque le système de contrôle NOx (16) atteint une température de fonctionnement minimale.
EP10707152A 2009-02-23 2010-02-19 Système de post-traitement de gaz d'échappement Withdrawn EP2399012A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US15454409P 2009-02-23 2009-02-23
PCT/US2010/024710 WO2010096641A1 (fr) 2009-02-23 2010-02-19 Système de post-traitement de gaz d'échappement

Publications (1)

Publication Number Publication Date
EP2399012A1 true EP2399012A1 (fr) 2011-12-28

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US (1) US20120247088A1 (fr)
EP (1) EP2399012A1 (fr)
WO (1) WO2010096641A1 (fr)

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