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
  • F01N3/10—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
  • F01N3/18—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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/46—Removing components of defined structure
  • B01D53/54—Nitrogen compounds
  • B01D53/56—Nitrogen oxides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
  • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
• • 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
  • 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
  • F01N3/023—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 using means for regenerating the filters, e.g. by burning trapped particles
  • F01N3/0231—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 using means for regenerating the filters, e.g. by burning trapped particles using special exhaust apparatus upstream of the filter for producing nitrogen dioxide, e.g. for continuous filter regeneration systems [CRT]
• • 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
• • 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
• • 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
  • F01N2240/00—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being
  • F01N2240/30—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being a fuel reformer
• • 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
  • F01N2410/00—By-passing, at least partially, exhaust from inlet to outlet of apparatus, to atmosphere or to other device
• • 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
  • F01N2610/00—Adding substances to exhaust gases
  • F01N2610/03—Adding substances to exhaust gases the substance being hydrocarbons, e.g. engine fuel
• • 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 present invention relates to emissions treatment systems and methods useful for reducing contaminants in exhaust gas streams. Specifically, embodiments of the invention are directed to emissions treatment systems, and methods of use, for reducing NOx, the systems including hydrocarbon conversion over a partial oxidation catalyst to generate hydrogen and exhaust gas stream partition.
• NSR NOx storage reduction
• LNT lean NOx traps
• NSR NOx storage reduction
• LNT catalysts contain NOx sorbent materials capable of adsorbing or “trapping" oxides of nitrogen under lean conditions and platinum group metal components to provide the catalyst with oxidation and reduction functions.
• the LNT catalyst promotes a series of elementary steps which are depicted below in Equations 1-5.
• NO is oxidized to NO 2 (Equation 1), which is an important step for NOx storage.
• this reaction is typically catalyzed by a platinum group metal component, e.g., a platinum component.
• the oxidation process does not stop here.
• the platinum group metal component has the dual functions of oxidation and reduction. For its reduction role, the platinum group metal component first catalyzes the release of NOx upon introduction of a reductant, e.g., CO (carbon monoxide), H 2 (hydrogen) or HC (hydrocarbon) to the exhaust (Equation 3).
• a reductant e.g., CO (carbon monoxide), H 2 (hydrogen) or HC (hydrocarbon
• This step may recover some NOx storage sites but contribute to limited reduction of NOx species.
• the released NOx is then further reduced to gaseous N 2 in a rich environment (Equations 4 and 5).
• NOx release can be induced by fuel injection even in a net oxidizing environment.
• H 2 , CO or HC requires overall net rich conditions.
• a temperature surge can also trigger NOx release because metal nitrate is less stable at higher temperatures.
• NOx trap catalysis is a cyclic operation. Metal compounds are believed to undergo a carbonate/nitrate conversion, as a dominant path, during lean/rich operations.
• M represents a divalent metal cation
• M can also be a monovalent or ti ⁇ valent metal compound in which case the equations need to be rebalanced.
• SCR selective catalytic reduction
• the strategy has been proven effective as applied to stationary sources, e.g., treatment of flue gases.
• NO x is reduced with a reductant, e.g., NH 3 , to nitrogen (N 2 ) over an SCR catalyst that is typically composed of base metals.
• a reductant e.g., NH 3
• N 2 nitrogen
• This technology is capable OfNO x reduction greater than 90%, thus it represents one of the best approaches for achieving aggressive NO x reduction goals.
• Ammonia is one of the most effective reductants for NO x at lean condition using SCR technologies.
• HC-SCR hydrocarbons
• Ion-exchanged base metal zeolite catalysts e.g., Cu- ZSM5
• Catalysts employing platinum-group metals operate effectively over a narrow temperature window between 18O 0 C and 22O 0 C and are highly selective towards N 2 O production.
• Catalytic devices using alumina-supported silver have received attention because of their ability to selectively reduce NO x under lean exhaust conditions with a wide variety of hydrocarbon species.
• the use of hydrocarbons and alcoholSj aldehydes and functionalized organic compounds over AgZAl 2 O 3 allows reduction of NO x at temperatures below 45O 0 C.
• diesel fuel could also be used as a reductant. Diesel fuel does not require additional tanks for diesel-powered vehicles. The diesel fuel can be supplied to the emissions system by changing engine management or by supplying an additional injector of diesel fuel to the exhaust train.
• current HC-SCR catalyst systems exhibit insufficient durability. Catalyst coking caused by fuel decomposition and deposition on catalyst and sulfur poisoning derived from fuel and oil cause catalyst performance deterioration in relatively short periods of operation time. The catalyst has to undergo frequent and costly regeneration to sustain desirable performance.
• One or more embodiments of the invention are directed to emissions treatment systems for NOx abatement in an exhaust stream from a lean burn engine.
• One embodiment of a system comprises a main exhaust conduit in flow communication with the engine exhaust stream, and a hydrocarbon selective catalytic reduction catalyst (HC-SCR) in flow communication with the main exhaust conduit.
• a slip exhaust stream conduit branches off of the main exhaust conduit and is connected to the main exhaust conduit by a first junction to divert a portion of the exhaust stream from the main exhaust conduit into the slip exhaust stream conduit to provide a slip exhaust stream to flow through a catalytic partial oxidation (CPO) catalyst in flow communication with the slip exhaust stream conduit.
• a hydrocarbon injector is located upstream of the CPO catalyst in the slip stream.
• a second junction downstream from the first junction reintroduces the slip exhaust stream to the main exhaust conduit upstream of the HC-SCR.
• the CPO is effective to convert a portion of the hydrocarbons to carbon monoxide and hydrogen.
• the CPO is designed to provide sufficient hydrogen and adequate amount of hydrocarbons for the downstream HC-SCR catalyst.
• the hydrocarbon injector device includes a metering device adapted to control the amount of hydrocarbon injected into the slip exhaust stream conduit.
• the hydrocarbon is fuel according to one or more embodiments.
• the portion of the exhaust gas diverted into the slip exhaust stream conduit is up to about 10% of the total exhaust flow
• One or more embodiments further comprise a metering device at the first junction of the slip exhaust stream conduit to regulate the percentage of exhaust gas diverted to the slip exhaust stream conduit.
• the CPO catalyst contains platinum group metals. Examples of the platinum group metals of CPO catalyst include platinum, palladium, rhodium and mixtures thereof.
• one or both of the CPO catalyst and the HC-SCR are disposed on a flow through monolith.
• the system includes a diesel particulate filter (DPF) downstream of the HC-SCR catalyst.
• DPF diesel particulate filter
• the system includes a diesel particulate filter (DPF) upstream of the HC-SCR catalyst.
• the diesel particulate filter (DPF) is located between the first junction and the second junction in flow communication of the main exhaust conduit,
• the system includes a diesel oxidation catalyst (DOC) upstream of the DPF and HC-SCR catalyst.
• the system includes a diesel oxidation catalyst (DOC) upstream of the DPF and HC-SCR catalyst.
• the system includes a diesel oxidation catalyst (DOC) upstream of the DPF and HC-SCR catalyst.
• the system includes a diesel oxidation catalyst (DOC) upstream of the DPF and HC-SCR catalyst.
• the system includes the diesel oxidation catalyst (DOC) is located downstream of the fust junction in flow communication with the main exhaust conduit. In one or more embodiments, the system includes the diesel oxidation catalyst (DOC) is located downstream of the first junction in flow communication with the main exhaust conduit. In one or more embodiments, the system includes the diesel oxidation catalyst (DOC) is located downstream of the first junction in flow communication with the main exhaust conduit. [0017] In one or more embodiments, the system includes the diesel oxidation catalyst (DOC) is located downstream of the first junction and upstream of the DPF and in flow communication with the main exhaust conduit. In one or more embodiments, the system includes the DOC and DPF are integrated into a single component.
• the system includes a NH3-SCR catalyst downstream of the HC-SCR catalyst. In one or more embodiments, the system includes an oxidation catalyst downstream of the HC-SCR catalyst.
• Another aspect of the invention pertains to methods of treating an exhaust stream, In one method embodiment, the exhaust stream is passed through a main exhaust conduit and a portion of the exhaust stream through a slip exhaust stream conduit.
• the main exhaust conduit comprises a hydrocarbon selective catalytic reduction catalyst (HC-SCR), and the slip exhaust stream conduit comprises a catalytic partial oxidation (CPO) catalyst in flow communication with the slip stream conduit and a hydrocarbon injector upstream of the CPO.
• HC-SCR hydrocarbon selective catalytic reduction catalyst
• CPO catalytic partial oxidation
• the slip exhaust stream conduit branches-off of the main exhaust conduit at a first junction and is in flow communication with the CPO.
• the slip exhaust stream conduit rejoins the main exhaust conduit at a second junction upstream of the HC-SCR.
• the CPO is adapted to convert a portion of the hydrocarbons in the slip exhaust stream conduit to carbon monoxide and hydrogen.
• the amount of hydrocarbon injector into the slip exhaust stream conduit is controlled by a metering device.
• the hydrocarbon is onboard fuel in one or more embodiments.
• a first percentage of the exhaust stream passes through the main exhaust conduit and a second percentage of the exhaust stream passes through the slip exhaust stream conduit, where the first percentage is greater than the second percentage.
• the second percentage of the exhaust stream is controlled by a metering device located within the slip exhaust stream conduit near the first junction,
• One or more embodiments of the method further comprise passing the exhaust stream in the main exhaust conduit through a diesel particulate filter located upstream of the HC-SCR catalyst.
• One or more method embodiments may include passing the exhaust stream in the main exhaust conduit through a diesel particulate filter located downstream of the HC-SCR catalyst.
• One or more method embodiments may include passing the exhaust stream in the main exhaust conduit through a diesel particulate filter located downstream of the first junction and upstream of the second junction.
• One or more method embodiments may include passing the exhaust stream in the main exhaust conduit through a diesel oxidation catalyst located upstream of the diesel particulate filter.
• One or more method embodiments may include passing the exhaust stream in the main exhaust conduit through a diesel oxidation catalyst located upstream of the diesel particulate filter.
• One or more method embodiments may include passing the exhaust stream in the main exhaust conduit through a diesel oxidation catalyst located upstream of the diesel particulate filter.
• One or more method embodiments may include passing the exhaust stream in the main exhaust conduit through a diesel oxidation catalyst located downstream of the first junction.
• One or more method embodiments may include passing the exhaust stream in the main exhaust conduit through a diesel oxidation catalyst located downstream of the first junction.
• One or more method embodiments may include passing the exhaust stream in the main exhaust conduit through a diesel oxidation catalyst located downstream of the first junction.
• One or more method embodiments may include passing the exhaust stream in the main exhaust conduit through a diesel oxidation catalyst located downstream of the first junction and upstream of the diesel particulate filter.
• One or more method embodiments may include passing the exhaust stream in the main exhaust conduit through a diesel oxidation catalyst located downstream of the first junction and upstream of the diesel particulate filter.
• One or more method embodiments may include passing the exhaust stream in the main exhaust conduit through a diesel oxidation catalyst located downstream of the first junction and upstream of the diesel particulate filter.
• the diesel oxidation catalyst and the diesel particulate filter are integrated. In one or more method embodiments, the diesel oxidation catalyst and the diesel particulate filter are integrated.
• the method can comprise according to one or more embodiments passing the exhaust stream in the main exhaust conduit through a NH3-SCR catalyst located downstream of the HC- SCR catalyst.
• One or more method embodiments include passing the exhaust stream in the main exhaust conduit through an oxidation catalyst located downstream of the HC-SCR catalyst.
• the various embodiments of the invention may include, in a multitude of configurations, various components including, but not limited to, diesel oxidation catalysts, catalyzed soot filters, HC- selective catalytic reduction catalysts, NH3 - selective catalytic reduction catalyst and oxidation catalysts.
• the exhaust gas may be passed through these optional components in a variety of sequences.
• FIG. 1 is a schematic view showing an engine emission treatment system according to a detailed embodiment
• FIG. 2 is a schematic view showing an engine emission treatment system according to another embodiment
• FIG. 3 is a schematic view showing an integrated engine emission treatment system according to an embodiment
• FIG. 4 is an alternative emission treatment system according to one or more embodiments of the invention
• FIG. 5 is an alternative emission treatment system according to one or more embodiments of the invention
• FIG. 6 is an alternative emission treatment system according to one or more embodiments of the invention.
• FIG. 7 is an alternative emission treatment system according to one or more embodiments of the invention.
• FIG. 8 is an alternative emission treatment system according to one or more embodiments of the invention.
• FIG. 9 is an alternative emission treatment system according to one or more embodiments of the invention.
• FIG. 10 is an alternative emission treatment system according to one or more embodiments of the invention.
• FIG. 11 is an alternative emission treatment system according to one or more embodiments of the invention.
• FIG. 12 is an alternative emission treatment system according to one or more embodiments of the invention.
• FIG. 13 is a perspective view of a wall flow filter substrate;
• FIG. 14 is a cut-away view of a section of a wall flow filter substrate; and [0038] FIG. 15 shows a graph of the percent NOx conversion as a function of catalyst inlet temperature for an HC-SCR under various operating conditions.
• DETAILED DESCRIPTION [0039] Provided are emissions treatment systems that can be used for treating exhaust gas from lean burn engines, and methods of using these systems to treat engine exhaust.
• Lean burn engines include, but are not limited to, diesel engines, lean burn gasoline engines and locomotive engines.
• Small amount of hydrogen (typically ⁇ 2000 ppm) present in the lean exhaust can significantly enhance the performance of the HC-SCR catalyst, reversing damage done to the catalyst through normal operation.
• Embodiments of the invention are directed to systems and methods that can provide the fuel reductant and hydrogen to the HC-SCR catalyst.
• the system comprises a slip stream from the main exhaust to generate hydrogen with on-board fuel and a catalytic partial oxidation catalyst (CPO) iii a net reducing condition.
• CPO catalytic partial oxidation catalyst
• the slip stream containing unconverted fuel species and hydrogen is combined with the main exhaust to provide the favorable HC-SCR reaction conditions.
• Hydrogen can be generated from a hydrocarbon feed by a partial oxidation process in which a portion of the feed reacts with the oxygen in the slip stream under a fuel rich condition.
• FIG. 1 shows a schematic description of one aspect of the present invention and is described in greater detail below. Briefly, a slip stream (typically 1-10% of the total exhaust flow emanating from the engine) is bypassed upstream of a HC-SCR catalyst located downstream from the engine.
• a sufficient amount of the fuel is introduced into the slip stream to produce a fuel rich condition.
• a catalytic partial oxidation catalyst as described further below, is placed in the slipstream downstream of the point of fuel introduction.
• the slip stream containing unconverted fuel species and hydrogen is combined with the main exhaust and introduced to the HC-SCR catalyst.
• the HC-SCR may be placed downstream of a diesel oxidation catalyst and diesel particulate filter devices so that the HC-SCR can be regenerated at the same time as the regeneration of the DOC and
• the system can be optionally optimized with a bypass flow control valve and a fuel control delivery device to minimize the fuel penalty of the system.
• Lean NOx catalyst “LNC 11 , “hydrocarbon selective catalytic reduction catalyst” and “HC-SCR” may be used interchangeably within the specification. These are different than a lean NOx trap (LNT) which has a NOx storage and release function.
• LNT lean NOx trap
• Lean gaseous streams including lean exhaust streams mean gas streams that have a ⁇ > 1.0.
• Lean periods refer to periods of exhaust treatment where the exhaust gas composition is lean, i.e., has a ⁇ > 1.0.
• Platinum group metal components refer to platinum group metals or one of their oxides.
• Rare earth metal components refer to one or more oxides of the lanthanum series defined in the Periodic Table of Elements, including lanthanum, cerium, praseodymium and neodymium.
• Washcoat has its usual meaning in the art of a thin, adherent coating of a catalytic or other material applied to a refractory substrate, such as a honeycomb flow through monolith substrate or a filter substrate, which is sufficiently porous to permit the passage there through of the gas stream being treated.
• Flow communication means that the components and/or conduits are adjoined such that exhaust gases or other fluids can flow between the components and/or conduits.
• Downstream refers to a position of a component in an exhaust gas stream in a path further away from the engine than the component preceding component.
• upstream refers to a component that is located closer to the engine relate to another component.
• Reference to an " ammoni a- generati ng comp onent" means a part of the exhaust system that supplies ammonia (NH 3 ) as a result of its design and configuration driven by engine-out emissions and dosing of reductant (H 2 , CO and/or HC) via engine management or via injection into exhaust. Such a component excludes gas dosing or other externally supplied sources OfNH 3 .
• ammonia-generating components include NOx storage reduction (NSR) catalysts and lean NOx traps (LNT).
• FIG. 1 shows an emissions treatment system 2 for NOx abatement in an exhaust stream from a lean burn engine 4 according to one embodiment.
• An exhaust gas stream containing gaseous pollutants e.g., unburned hydrocarbons, carbon monoxide, nitrogen oxides
• gaseous pollutants e.g., unburned hydrocarbons, carbon monoxide, nitrogen oxides
• particulate matter is conveyed via a main exhaust conduit 6 in flow communication with a lean burn engine 4.
• the exhaust gas stream in the main exhaust conduit 6 is passed through a hydrocarbon selective catalytic reduction catalyst (HC-SCR) 8 in flow communication with the conduit 6.
• a slip exhaust stream conduit 10 branches off of the main exhaust conduit 6.
• the slip exhaust stream conduit 10 is connected to the main exhaust conduit 6 by a first junction 12 to divert a portion of the exhaust stream from the main exhaust conduit 6 into the slip exhaust stream conduit 10 to provide a slip exhaust stream.
• the slip exhaust stream flows through a catalytic partial oxidation (CPO) catalyst 14 in flow communication with the slip exhaust stream conduit 10.
• a second junction 16 downstream from the first junction 12 reintroduces the slip exhaust stream from the slip exhaust stream conduit 10 to the main exhaust conduit 6 upstream of the HC-SCR 8.
• Line 20 leads to the tail pipe and out of the system.
• Hydrocarbon feed can be introduced through the conduit 18 in the slip stream upstream of a CPO catalyst 14.
• the CPO 14 is effective to convert a portion of the hydrocarbons to carbon monoxide and hydrogen.
• the CPO 14 according to one or more embodiments is designed to provide sufficient hydrogen to enhance the performance of the HC-SCR 8.
• the main exhaust conduit 6 includes an optional additional exhaust system component 22 downstream of the first junction 12.
• the additional exhaust system component 22 can be, for example, one or more of a diesel oxidation catalyst, a diesel particulate filter, a reductant injector and an air injector in flow communication with the main exhaust conduit.
• the optional additional exhaust system component 22, for example, one or more of a diesel oxidation catalyst and a diesel particulate filter, can be placed upstream of the first junction 12 of the main exhaust conduit 6.
• the hydrocarbon injector 18 can include a metering device 24 adapted to control the amount of hydrocarbon injected into the slip exhaust stream conduit 10.
• the injected hydrocarbon is on-board fuel.
• Detailed embodiments of the invention include a metering device 26 at the first junction 12 of the slip exhaust stream conduit 10 to regulate the percentage of exhaust gas diverted to the slip exhaust stream conduit 10.
• the portion of the exhaust gas diverted from the main exhaust conduit 6 into the into the slip exhaust stream conduit 10 is up to about 10% of the total exhaust flow.
• the portion of the exhaust gas diverted from the main exhaust conduit 6 is in the range of about 0.5% to about 15%, or in the range of about 1% to about 10%.
• the portion of the exhaust gas diverted from the main exhaust conduit 6 is up to about 15%, 14%, 13%, 12% 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3% or 2% of the total exhaust flow.
• one or more of the CPO catalyst and the HC-SCR are disposed on a flow through monolith.
• the emissions treatment system of various embodiments further comprises a diesel particulate filter (DPF) 28 located between the first junction 12 and the second junction 16 in flow communication with the main exhaust conduit 6.
• a diesel oxidation catalyst (DOC) 30 is located downstream of the first junction 12 and upstream of the DPF 28 and in flow communication with the main exhaust conduit 6.
• the DOC 30 and DPF 28 are integrated into a single component or substrate 32.
• the DOC 30 and DPF 28 may be disposed in separate zones of the same substrate 32, where the DOC 30 is disposed on the upstream segment of the substrate 32, and the CSF 28 is disposed on the downstream segment of the substrate 32.
• Additional embodiments of the invention are directed to methods of treating an exhaust stream from a lean burn engine.
• the exhaust stream is passed through a main exhaust conduit 6 and a portion of the exhaust stream through a slip exhaust stream conduit 10.
• the main exhaust conduit 6 comprises a hydrocarbon selective catalytic reduction catalyst (HC-SCR) 8.
• the slip exhaust stream conduit 10 comprises a catalytic partial oxidation (CPO) catalyst 14 and hydrocarbons can be injected into the slip exhaust stream conduit 10 upstream of the CPO 14 using a hydrocarbon injector 18.
• the slip exhaust stream conduit 10 branches-off of the main exhaust conduit 6 at a first junction 12 and is in flow communication with the CPO 14.
• the slip exhaust stream conduit 10 rejoins the main exhaust conduit 6 at a second junction 16.
• the second junction 16 is located upstream of the HC-SCR 8.
• the CPO 14 is adapted to convert hydrocarbons in the slip exhaust stream conduit 10 to carbon monoxide and hydrogen.
• the amount of hydrocarbon injected into the slip exhaust stream conduit 10 may be controlled by a metering device 24.
• the hydrocarbon is on-broad fuel.
• a first percentage of the exhaust stream passes through the main exhaust conduit 6 and a second percentage of the exhaust stream passes through the slip exhaust stream conduit 10, where the first percentage is greater than the second percentage.
• the second percentage of the exhaust stream in some embodiments is controlled by a metering device 26 located within the slip exhaust stream conduit 10 near the first junction 12.
• Various embodiments of the invention further comprise passing the exhaust stream in the main exhaust conduit 6 through a diesel particulate filter 28 located downstream of the first junction 12 and upstream of the second junction 16.
• the exhaust stream in the main exhaust conduit 6 is passed through a diesel oxidation catalyst 30 located downstream of the first junction 12 and upstream of the diesel particulate filter 28.
• the diesel oxidation catalyst 30 and the diesel particulate filter 28 are integrated into a single component 32.
• the CPO 14, DOC 30, DPF 28 as well as optional components 22 can be made of compositions well known in the art and may comprise base metals (e.g., ceria) and/or platinum group metals as catalytic agents.
• the DOC and/or particulate filter provides several advantageous functions.
• the catalyst serves to oxidize unbumed gaseous and non-volatile hydrocarbons (i.e., the soluble organic fraction of the diesel particulate matter) and carbon monoxide to carbon dioxide and water. Removal of substantial portions of the SOF, in particular, assists in preventing too great a deposition of particulate matter on the HC-SCR 8.
• the platinum group metal is selected from the group consisting of platinum, palladium, rhodium and combinations thereof.
• one or more of the DOC 30, DPF 28 and optional components 22 are coated on a soot filter, for example, a wall flow filter to assist in the removal of the particulate material in the exhaust stream, and, especially the soot fraction (or carbonaceous fraction) of the particulate material.
• a soot filter for example, a wall flow filter to assist in the removal of the particulate material in the exhaust stream, and, especially the soot fraction (or carbonaceous fraction) of the particulate material.
• the DOC in addition to the other oxidation function mentioned above, lowers the temperature at which the soot fraction is oxidized to CO 2 and H 2 O. As soot accumulates on the filter, the catalyst coating assists in the regeneration of the filter.
• a DPF 28 may be located downstream of the HC-SCR 8 to convert the CO and unconverted fuel species.
• FIG. 6 shows another alternate embodiment where the DPF 28 is located upstream of the first junction 12 to minimize or prevent fouling of the downstream HC-SCR with particulate material
• FIG. 7 shows an alternate embodiment where a DOC 30 is located upstream of the first junction 12 and the HC-SCR 8 and DPF 28 are located downstream of the second junction.
• FIG. 8 shows an alternate embodiment where a DOC 30 and DPF 28 are located upstream of the first junction.
• the system further comprises a NH 3 -SCR catalyst downstream of the HC-SCR to convert any NH 3 emissions generated in the system.
• the system further comprises an oxidation catalyst downstream of the HC-SCR to oxidize CO and any unconverted fuel species.
• FIG. 11 shows an alternative embodiment of an emission treatment system comprising an ammonia oxidation (AMOX) catalyst 36 located downstream of the HC-SCR 8 catalyst.
• the ammonia oxidation catalyst 36 may be useful for removing or abating residual ammonia, which may be referred to as slipped ammonia through the system
• FIG. 12 shows an alternate embodiment where the hydrogen source 38 is an off-line source or component other than a CPO catalyst,
• the hydrogen source 38 as shown here, may include a metering device 40 capable of controlling the amount of hydrogen being injected into the main exhaust conduit 6.
• the off-line H 2 source (and HC reductant) can include the output from a CPO reaction (a partial oxidation of fuel with oxygen) as previously described.
• Various optional components 22 can be included in the exhaust conduit 6. These optional components 22 can be located upstream of the hydrogen injector 38, downstream of the hydrogen injector 38 or downstream of the HC-SCR catalyst 8. It is conceivable that an optional component may be located within the hydrogen injector 38 prior to the junction with the main exhaust conduit 6.
• the alternate embodiments shown are merely indicative of various ways the invention can be practiced and should not be taken as limiting. The components can arranged in other configurations and remain within the scope of the invention.
• the various metering devices may also be connected to a controller.
• the controller can include, amongst other components, sensors and processors.
• the sensors can be suitable for measuring the components of the gaseous composition and can be placed at various locations within the exhaust conduits.
• the processor can evaluate data from the sensors and adjust the metering devices to optimize the function of the various catalytic components.
• Optional components 22 for use with various embodiments of the invention can be, for example, one or more of a diesel oxidation catalyst, a diesel particulate filter, a reductant injector, an air injector, an ammonia oxidation catalyst, an ammonia selective catalytic reduction catalyst in flow communication with the main exhaust conduit. Additionally, the optional components 22 may be a combination of integrated components, including, but not limited to, those shown in FIG. 3. Substrates [0072] In detailed embodiments, any or all of the catalysts, including the HC-SCR 8, CPO 14, and DOC 30, are disposed on a substrate.
• the substrate may be any of those materials typically used for preparing catalysts, and will typically comprise a ceramic or metal honeycomb structure, for example, a flow through monolith.
• Any suitable substrate may be employed, such as a monolithic substrate of the type having fine, parallel gas flow passages extending therethrough from an inlet or an outlet face of the substrate, such that passages are open to fluid flow therethrough (referred to as honeycomb flow through substrates).
• honeycomb flow through substrates honeycomb flow through substrates.
• the passages which are essentially straight paths from their fluid inlet to their fluid outlet, are defined by walls on which the catalytic material is coated as a washcoat so that the gases flowing through the passages contact the catalytic material.
• the flow passages of the monolithic substrate are thin-walled channels, which can be of any suitable cross-sectional shape and size such as trapezoidal, rectangular, square, sinusoidal, hexagonal, oval, circular, etc.
• Such structures may contain from about 60 to about 600 or more gas inlet openings (i.e., cells) per square inch of cross section.
• FIGS. 13 and 14 illustrate a wall flow filter substrate 50 which has a plurality of alternately blocked channels 52 and can serve as a particulate filter.
• the passages are tubularly enclosed by the internal walls 53 of the filter substrate.
• the substrate has an inlet end 54 and an outlet end 56. Alternate passages are plugged at the inlet end 54 with inlet plugs 58 and at the outlet end 56 with outlet plugs to form opposing checkerboard patterns at the inlet 54 and outlet 56.
• a gas stream enters through the unplugged channel inlet 60, is stopped by outlet plug and diffuses through channel walls 53 (which are porous) to the outlet side. The gas cannot pass back to the inlet side of walls because of inlet plugs 58. If such substrate is utilized, the resulting system will be able to remove particulate matters along with gaseous pollutants.
• Wall flow filter substrates can be composed of ceramic-like materials such as cordierite, ⁇ -alumina, silicon carbide, aluminum titanate, silicon nitride, zirconia, mullite, spodumene, alumina-silica-magnesia or zirconium silicate, or of porous, refractory metal.
• Wall flow substrates may also be formed of ceramic fiber composite materials. Specific wall flow substrates are formed from cordierite, silicon carbide, and aluminum titanate. Such materials are able to withstand the environment, particularly high temperatures, encountered in treating the exhaust streams.
• Wall flow substrates for use in the inventive system can include thin porous walled honeycombs (monoliths) through which the fluid stream passes without causing too great an increase in back pressure or pressure across the article, Ceramic wall flow substrates used in the system can be formed of a material having a porosity of at least 40% (e.g., from 40 to 75%) having a mean pore size of at least 10 microns (e.g., from 10 to 30 microns).
• the substrates can have a porosity of at least 59% and have a mean pore size of between 10 and 20 microns.
• Typical wall flow filters in commercial use are typically formed with lower wall porosities, e.g., from about 42% to 50%. In general, the pore size distribution of commercial wall flow filters is typically very broad with a mean pore size smaller than 25 microns.
• the porous wall flow filter can be catalyzed in that the wall of the element has thereon or contained therein one or more catalytic materials.
• Catalytic materials may be present on the inlet side of the element wall alone, the outlet side alone, both the inlet and outlet sides, or the wall itself may consist all, or in part, of the catalytic material.
• This invention includes the use of one or more washcoats of catalytic materials and combinations of one or more washcoats of catalytic materials on the inlet and/or outlet walls of the element.
• the filter may be coated by any of a variety of means well known to the art.
• the substrates useful for the catalysts of the present invention may also be metallic in nature and be composed of one or more metals or metal alloys.
• the metallic substrates may be employed in various shapes such as corrugated sheet or monolithic form.
• Suitable metallic supports include the heat resistant metals and metal alloys such as titanium and stainless steel as well as other alloys in which iron is a substantial or major component.
• Such alloys may contain one or more of nickel, chromium and/or aluminum, and the total amount of these metals may advantageously comprise at least 15 wt.% of the alloy, e.g., 10-25 wt.% of chromium, 3-8 wt.% of aluminum and up to 20 wt.% of nickel.
• the alloys may also contain small or trace amounts of one or more other metals such as manganese, copper, vanadium, titanium and the like.
• the surface or the metal substrates may be oxidized at high temperatures, e.g., 1000 0 C and higher, to improve the resistance to corrosion of the alloys by forming an oxide layer on the surfaces the substrates. Such high temperature-induced oxidation may enhance the adherence of the refractory metal oxide support and catalytically promoting metal components to the substrate.
• one or all of the HC-SCR 8, CPO 14, DOC 30, DPF 28 and optional components 22 may be deposited on an open cell foam substrate. Such substrates are well known in the art, and are typically formed of refractory ceramic or metallic materials.
• CPO Catalyst [0081] The principle of the CPO catalyst is the reaction of fuel with oxygen to yield carbon monoxide and hydrogen according to Equation 8.
• the CPO 14 catalyst contains platinum and palladium.
• the platinum group metal loading is in the range of about 20 g/ft 3 to about 200 g/ft 3 .
• the platinum to palladium metal ratio in the CPO is in the range of about 1 : 9 to about 9:1.
• the CPO operates between 600° C and 700° C in excess of 100,000 hi- '1 space velocity (sometimes > 250,000 hr '1 ).
• the platinum to palladium metal ratio of detailed embodiments can be in the range of about 1:5 to about 5:1, or about 1 :4 to about 4:1, or about 1:3 to about 3:1, or about 1:2 to about 2:1, or about 1 :1.
• the CPO comprises a suitable high surface area refractory metal oxide support layer is deposited on a substrate as described above to serve as a support upon which finely dispersed catalytic metal may be distended.
• high surface area refractory metal oxide supports can be utilized, e.g., alumina support materials, also referred to as "gamma alumina” or “activated alumina,” typically exhibit a BET surface area in excess of 60 square meters per gram (“m 2 /g”), often up to about 200 m 2 /g or higher.
• Such activated alumina is usually a mixture of the gamma and delta phases of alumina, but may also contain substantial amounts of eta, kappa and theta alumina phases.
• Refractory metal oxides other than activated alumina can be used as a support for at least some of the catalytic components in a given catalyst.
• bulk ceria, zirconia, alpha alumina and other materials are known for such use. Although many of these materials suffer from the disadvantage of having a considerably lower BET surface area than activated alumina, that disadvantage tends to be offset by a greater durability or performance enhancement of the resulting catalyst.
• BET surface area has its usual meaning of referring to the Brunauer, Emmett, Teller method for determining surface area by N 2 adsorption. Pore diameter and pore volume can also be determined using BET-type N 2 adsorption or desorption experiments.
• a specific support coating is alumina, for example, a stabilized, high- surface area transition alumina, As used herein and in the claims, “transition alumina” includes gamma, chi, eta, kappa, theta and delta forms and mixtures thereof.
• transition alumina usually in amounts comprising from 2 to 10 weight percent of the stabilized coating
• oxides of one or more of lanthanum, cerium, praseodymium, calcium, barium, strontium and magnesium may be used as a stabilizer
• the platinum group metal catalytic component of the catalytic partial oxidation catalyst comprises palladium and platinum and, optionally, one or more other platinum group metals.
• platinum group metals means platinum, palladium, rhodium, iridium, osmium and ruthenium. Suitable platinum group metal components are palladium and platinum and, optionally, rhodium. Desirable catalysts for partial oxidation should have at least one or more of the following properties. They should be able to operate effectively under conditions varying from oxidizing at the inlet to reducing at the exit; they should operate effectively and without significant temperature degradation over a temperature range of about 427° C.
• Rhodium may optionally be included with the platinum and palladium. Under certain conditions, rhodium is an effective oxidation as well as a steam reforming catalyst, particularly for light olefins.
• the combined platinum group metal catalysts can catalyze the autothermal reactions at quite low ratios of H 2 O to carbon (atoms of carbon in the feed) and oxygen to carbon, without significant carbon deposition on the catalyst. This feature provides flexibility in selecting H 2 O to C and O.sub.2 to C ratios in the inlet streams to be processed.
• the platinum group metals employed in the catalysts of embodiments of the present invention may be present in the catalyst composition in any suitable form, such as the elemental metals, as alloys or intermetalHc compounds with the other platinum group metal or metals present, or as compounds such as an oxide of the platinum group metal.
• the terms palladium, platinum and/or rhodium "catalytic component” or “catalytic components” is intended to embrace the specified platinum group metal or metals present in any suitable form.
• reference in the claims or herein to platinum group metal or metals catalytic component or components embraces one or more platinum group metals in any suitable catalytic form.
• Suitable CPO catalysts are described in United States patent no. 4,522,894, the entire content of which is incorporated herein by reference.
• a HC-SCR catalyst comprising silver on an alumina support is generally useful for the emissions treatment system of this invention,
• the catalyst contains "well dispersed" silver species on the surface of an alumina.
• the catalyst substantially free of silver metal and/or silver aluminate.
• the catalyst may be prepared by impregnation of an alumina support with ionic silver.
• the alumina support can be any suitable alumina, including but not limited to, boehmite pseudoboehmite, diaspore, norstrandite, bayerite, gibbsite, hydroxylated alumina, calcined alumina, and mixtures thereof.
• An exemplary silver- alumina catalyst comprises about 3 to 4 weight percent (wt. %) silver on an Ag 2 O basis supported on alumina, In one embodiment, the catalyst is prepared by depositing ionic silver on highly hydroxylated alumina.
• hydroxylated means that the surface of the alumina has a high concentration of surface hydroxyl groups in the alumina as it is obtained, for example boehmite, pseudoboehmite or gelatinous boehmite, diaspore, nordstrandite, bayei ⁇ te, gibbsite, alumina having hydroxyl groups added to the surface, and mixtures thereof.
• Pseudoboehmite and gelatinous boehmite are generally classified as non-crystalline or gelatinous materials, whereas diaspore, nordstrandite, bayerite, gibbsite, and boehmite are generally classified as crystalline.
• aluminas are not subject to high temperature calcination, which would drive off many or most of the surface hydroxyl groups.
• the alumina may be of a type subject to higher temperature calcinations to provide gamma, delta, theta and alpha-alumina and combinations thereof.
• a temperature low enough to fix the silver and decompose the anion if possible.
• the nitrate salt this would be about 450-550 degrees centigrade to provide an alumina that has substantially no silver particles greater than about 20 nm in diameter.
• the diameter of the silver is less than 10 nm, and in other embodiments, the silver is less than about 2 nm in diameter.
• the processing is performed so that the silver is present in substantially ionic form and there is substantially no silver metal present as determined by UV spectroscopy. In one or more embodiments there is substantially no silver aluminate present. The absence of silver metal and silver aluminate can be confirmed by x-ray diffraction analysis. In the presence of small amount of hydrogen and adequate hydrocarbon fuel species, the catalyst can still perform well when it has been deposited with carbonaceous and sulfur species.
• the oxidation catalyst can be formed from any composition that provides effective combustion of unburned gaseous and non- volatile hydrocarbons (i.e., the VOF) and carbon monoxide.
• the oxidation catalyst should be effective to convert a substantial proportion of the NO of the NOx component to NO 2 .
• substantially conversion of NO of the NOx component to NO 2 means at least 20%, and specifically between 30 and 60%.
• Catalyst compositions having these properties are known in the art, and include platinum group metal- and base metal-based compositions.
• the catalyst compositions can be coated onto honeycomb flow-through monolith substrates formed of refractory metallic or ceramic (e.g., cordiei ⁇ te) materials.
• oxidation catalysts may be formed on to metallic or ceramic foam substrates which are well-known in the ait. These oxidation catalysts, by virtue of the substrate on which they are coated (e.g., open cell ceramic foam), and/or by virtue of their intrinsic oxidation catalytic activity provide some level of particulate removal, The oxidation catalyst may remove some of the particulate matter from the exhaust stream upstream of the wall flow filter, since the reduction in the particulate mass on the filter potentially extends the time before forced regenerations.
• One specific oxidation catalyst composition that may be used in the emission treatment system contains a platinum group component (e.g., platinum, palladium or rhodium components) dispersed on a high surface area, refractory oxide support (e.g., ⁇ -alumina) which is combined with a zeolite component (e.g., a beta zeolite),
• a platinum group component e.g., platinum, palladium or rhodium components
• a refractory oxide support e.g., ⁇ -alumina
• zeolite component e.g., a beta zeolite
• concentration of platinum group metal is typically from about 10 to 150 g/ft 3 .
• the platinum group metal is typically in the range of about 20 g/ft 3 to about 130 g/ft 3 , or about 30 g/ft 3 to about 120 g/ft 3 , or about 40 g/ft 3 to about 110 g/ft 3 or about 50 g/ft 3 to about 100 g/ft 3 .
• the platinum group metal is present in a concentration greater than about 10 g/ft 3 , about 20 g/ft 3 , about 30 g/ft 3 , about 40 g/ft 3 ; about 50 g/ft 3 , about 60 g/ft 3 , about 70 g/ft 3 , about 80 g/ft 3 , about 90 g/ft 3 , about 100 g/ft 3 , about 110 g/ft 3 or about 120 g/ft 3 .
• the platinum group metal is present in a concentration less than about 120 g/ft 3 , about 110 g/ft 3 , about 100 g/ft 3 , about 90 g/ft 3 , about 80 g/ft 3 , about 70 g/ft 3 , about 60 g/ft 3 , about 50 g/ft 3 , about 40 g/ft 3 , or about 30 g/ft 3 .
• the range of platinum group metal concentrations is between any combination of the previously listed minimum and maximum concentrations.
• compositions that have a mixture of platinum, palladium, rhodium, and ruthenium and an alkaline earth metal oxide such as magnesium oxide, calcium oxide, strontium oxide, or barium oxide with an atomic ratio between the platinum group metal and the alkaline earth metal of about 1 : 250 to about 1:1, and specifically about 1 : 60 to about 1:6.
• Catalyst compositions suitable for the oxidation catalyst may also be formed using base metals as catalytic agents. For example, U.S. Pat. No.
• oxidation catalyst compositions that include a catalytic material having a BET surface area of at least about 10 tn.sup.2/g and consist essentially of a bulk second metal oxide which may be one or more of titania, zirconia, ceria-zirconia, silica, alumina-silica, and ⁇ - alumina.
• a catalytic material having a BET surface area of at least about 10 tn.sup.2/g and consist essentially of a bulk second metal oxide which may be one or more of titania, zirconia, ceria-zirconia, silica, alumina-silica, and ⁇ - alumina.
• compositions that include a catalytic material containing ceria and alumina each having a surface area of at least about 10 m /g, for example, ceria and activated alumina in a weight ratio of from about 1.5:1 to 1:1.5.
• platinum may be included in the compositions described in the '907 patent in amounts effective to promote gas phase oxidation of CO and unbumed hydrocarbons but which are limited to preclude excessive oxidation Of SO 2 to SO3.
• palladium in any desired amount may be included in the catalytic material.
• the system may further comprise a NH 3 -SCR catalyst downstream of the HC-SCR catalyst.
• the NH 3 - SCR catalyst can prevent any NH 3 generated in the system from releasing to the environment.
• Suitable NH 3 -SCR catalysts can be any of the known SCR catalysts useful in the Urea-SCR application. It is advantageous that NFI 3 -SCR catalyst comprising molecular sieves with CHA X-ray crystal structures (e.g. Cu-CHA, Cu- SAPO) are employed. These molecular sieves with CHA structure exhibiting superior hydrothermal stability and durability are particularly useful in this invention.
• an exemplary system would include a system of the type shown in Figure 1, wherein exhaust from a lean bum engine is in flow communication with component 22, which may be a suitable catalyst for oxidizing carbon monoxides and hydrocarbons.
• component 22 which may be a suitable catalyst for oxidizing carbon monoxides and hydrocarbons.
• An example of a suitable catalyst for a gasoline engine is a three-way catalyst (TWC).
• TWC catalysts which exhibit good activity and long life comprise one or more platinum group metals (e.g., platinum or palladium, rhodium, ruthenium and iridium) located upon a high surface area, refractory oxide support, e.g., a high surface area alumina coating.
• platinum group metals e.g., platinum or palladium, rhodium, ruthenium and iridium
• the hydrogen may be generated by an external source or hydrogen generator.
• Suitable hydrogen sources include, but are not limited to, electrolyzers, plasma reformers, thermal decomposition devices, steam reformers, compressed gases container and liquefied gases containers.
• Electrolyzers such as proton exchange membranes (PEM) can be used to produce hydrogen on board the a vehicle. The PEM splits water into hydrogen and oxygen molecules which can then be compressed and injected into the exhaust. PEM systems require only small amounts of water maintained in the system.
• Plasma reformers convert gaseous hydrocarbons, like gasoline, diesel fuel, methane, ethane, etc., to hydrogen.
• a reaction chamber is charged with sufficient fuel and air and a plasma is ignited.
• the plasma based reaction results in hydrogen evolution.
• the hydrogen evolution can be optimized with catalytic components.
• Thermal decomposition devices can crack, or pyrolyze, fuel to yield hydrogen and carbon oxide species. Thermal decomposition generally requires high temperatures for efficient conversion.
• Steam reformers can generate hydrogen by reacting fuel with water. The reaction is exothermic, resulting in an increased reaction rate. Like electrolysis, a small onboard water source is required for this type of hydrogen injector.
• the available pore volume of the various supports was determined by titrating the bare support with water while mixing until incipient wetness was achieved. This resulted in a liquid volume per gram of support. Using the final target Ag 2 O level and the available volume per gram of support, the amount of IM AgNO 3 solution needed was calculated. DI water was added to the silver solution, if needed, so that the total volume of liquid was equal to amount needed to impregnate the support sample to incipient wetness. If the amount OfAgNO 3 solution needed exceeds the pore volume of the support, then multiple impregnations were done.
• the appropriate AgNO 3 solution was added slowly to the support with mixing. After incipient wetness is achieved, the resulting solid was dried at 90° C, for 16 h, then calcined at 540° C. for 2 hours.
• the catalyst was also optionally subjected to a flowing stream of about 10% steam in air for at least about, typically about 16 hours at 65O 0 C.
• Catalysts were prepared as described above using commercially available pseudoboehmite (Catapal.RTM. Cl, 270 m 2 /g, 0.41 cc/g pore volume, 6,1 nm average pore diameter, produced by Sasol, North America) and boehmite (P200 (from Sasol), 100 m 2 /g, 0.47 cc/g pore volume, 17.9 nm average pore diameter) alumina supports. Each alumina was processed until the silver content of the finished catalyst was about 3% by weight on an Ag 2 O basis. A monolith having about 300 cells per square inch was washcoated with the alumina, resulting in a loading of about 2 g/in 3 .
• pseudoboehmite Catalysts were prepared as described above using commercially available pseudoboehmite (Catapal.RTM. Cl, 270 m 2 /g, 0.41 cc/g pore volume, 6,1 nm average pore diameter, produced by
• the HC- SCR catalyst was placed in front of a DOC/DPF in a configuration in an engine exhaust system and aged on an engine for 50 hours. During the aging, a number of fuel burning cycles to simulate the regeneration of DOC/DPF were employed. [00106] The NOx conversion results are shown in FIG. 13. The engine aged sample as received without any treatment shows about 20% NOx conversion in the entire temperature range evaluated. The catalyst exhibits 10% better NOx conversion at 500 0 C, 20% better NOx conversion at 400 0 C, and 50% better NOx conversion at 300 0 C when 1000 ppm H 2 is introduced into the simulated exhaust. The presence of hydrogen in the exhaust drastically enhances the NOx performance of the severely deactivated catalyst.

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  • 2010-03-26 US US12/732,634 patent/US20100251700A1/en not_active Abandoned
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