US009039982B2
`
`(12) United States Patent
`US 9,039,982 B2
`(10) Patent No.:
`Patchett et al.
`(45) Date of Patent:
`*May 26, 2015
`
`(54)
`
`(71)
`
`(72)
`
`CATALYZED SCR FILTER AND EMISSION
`TREATMENT SYSTEM
`
`Applicant: BASF Corporation, Florham Park, NJ
`(US)
`
`Inventors: Joseph A. Patchett, Basking Ridge, NJ
`(US); Joseph C. Dettling, Howell, NJ
`(US); Elizabeth A. Przybylski, Edison,
`NJ (US)
`
`(2015.01); B01D 5/0054 (2013.01); B01D
`5/009 (2013.01); B01D 19/0005 (2013.01);
`(Continued)
`
`(58) Field of Classification Search
`CPC
`F01N 2370/04; F01N 3/2066; F01N 3/106;
`F01N 13/009; B01D 2255/9205; B01D 5/009;
`B01D 5/0054
`USPC ................ 422/177, 180, 472, 502/74, 77, 79,
`60/286, 297, 301
`See application file for complete search history.
`
`(73)
`
`Assignee:
`
`BASF CORPORATION, Florham Park,
`NJ (US)
`
`(56)
`
`(*)
`
`Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`This patent is subject to a terminal dis-
`claimer.
`
`(21)
`
`Appl. No.: 14/497,454
`
`(22)
`
`Filed:
`
`Sep. 26, 2014
`
`(65)
`
`(60)
`
`Prior Publication Data
`
`US 2015/0011377 A1
`
`Jan. 8,2015
`
`Related U.S. Application Data
`
`Continuation of application No. 13/274,635, filed on
`Oct. 17, 2011, now Pat. No. 8,899,023, which is a
`continuation of application No. 11/676,798, filed on
`Feb. 20, 2007, which is a division of application No.
`10/634,659, filed on Aug. 5, 2003, now Pat. No.
`7,229,597.
`
`Int. Cl.
`
`(51)
`
`B01D 50/00
`F01N 3/28
`
`U.S. Cl.
`
`(52)
`
`(2006.01)
`(2006.01)
`(Continued)
`
`References Cited
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`
`FOREIGN PATENT DOCUMENTS
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`
`12/2004
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`
`(Continued)
`OTHER PUBLICATIONS
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`Non-certified English Translation of Petition for Invalidation of
`Korean Patent No. 1121397, dated Jan. 23,2015, 37 pages.
`(Continued)
`
`Primary Examiner 7 Tom P Duong
`(74) Attorney, Agent, or Firm 7 Melanie L. Brown
`
`(57)
`
`ABSTRACT
`
`Provided is a catalyst article for simultaneously remediating
`the nitrogen oxides (NOx), particulate matter, and gaseous
`hydrocarbons present in diesel engine exhaust streams. The
`catalyst article has a soot filter coated with a material effective
`in the Selective Catalytic Reduction (SCR) of NOx by a
`reductant, e.g., ammonia.
`
`CPC ......... F01N 3/2892 (2013.01); Y10T29/49345
`
`27 Claims, 7 Drawing Sheets
`
`
`
`ENGINE
`
`
`
`
`JM 1001
`
`1
`
`JM 1001
`
`

`

`US 9,039,982 B2
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`Page 2
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`(51)
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`(200601)
`(200601)
`(2006.01)
`(2006.01)
`(200601)
`(200601)
`(2006.01)
`(2006.01)
`(201001)
`
`Int, Cl.
`301D 5/00
`301019/00
`B01D 53/94
`BOIJZ9/76
`301137/02
`F01N3/023
`F01N3/10
`F01N3/20
`F01N13/00
`(52) U.S.Cl.
`CPC ........ B01D19/0036 (2013.01); B01D 53/9418
`(2013.01);B01D53/945(2013.01);BOID
`53/9477(2013.01);BOID 2251/2062 (2013.01);
`BOID 2251/2067 (2013.01); BOID 2255/102
`(2013.01); BOID 2255/20715(2013.01); 301D
`2255/20738 (2013.01); BOID 2255/2076]
`(2013.01);BOID 2255/502(2013.01);BOID
`2255/9155 (2013 01)~B01D 2255/9202
`‘
`’
`(2013~01);301D 2255/9205(2013~01);301D
`2258/012 (2013.01); B01129/7615 (2013.01);
`B01137/0246(2013.01);F01N3/0231
`(201301); F01N3/106 (201301); F01N
`3/2066(2013~01)§F01N2370/04 (201301);
`F01N2510/063 (201301); F01N2610/02
`(2013.01);F01N 2610/08 (2013.01); YIOS
`55/30 (2013.01); YIOS55/10(2013.01); Y02T
`10/22(2013.01); Y02T10/24(2013.01);F01N
`13/009 (2014~06);B01129/76 (201301); F01N
`3/10 (2013.01);F01N3/2828 (2013.01); FOIN
`2330/06 (2013.01); F01N 2330/30 (2013.01)
`
`6,314,722 B1
`6,375,910 B1
`6,415,602 B1
`6,419,890 B1
`6,696,031 B1
`6,745,560 B2
`6,753,294 B1
`6,805,849 B1
`6,813,884 B2
`6,826,906 B2
`6,843,971 B2
`6,928,806 B2
`6,946,013 B2
`6,946,107 B2
`7,062,904 B1
`7,078,004 32
`33%;; E;
`7:229:597 B2
`7,264,785 B2
`7,265,580 B2
`7,306,771 32
`7’625’529 BZ
`7,727,498 B2
`7,902,107 B2
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`US 9,039,982 B2
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`* cited by examiner
`
`4
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`U.S. Patent
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`May 26, 2015
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`US 9,039,982 B2
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`US. Patent
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`May 26, 2015
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`US 9,039,982 B2
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`US. Patent
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`May 26, 2015
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`U.S. Patent
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`Sheet 5 of 7
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`US 9,039,982 B2
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`U.S. Patent
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`May 26, 2015
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`US 9,039,982 B2
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`US. Patent
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`May 26, 2015
`
`Sheet 7 of7
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`US 9,039,982 B2
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`US 9,039,982 B2
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`1
`CATALYZED SCR FILTER AND EMISSION
`TREATMENT SYSTEM
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`This application is a continuation of US. application Ser.
`No. 13/274,635, filed Oct. 17, 2011, which is a continuation
`ofU.S. application Ser. No. 11/676,798, filed Feb. 20, 2007,
`which is a divisional application of US. application Ser. No.
`10/634,659, filedAug. 5, 2003, now US. Pat. No. 7,229,597,
`issued Jun. 12, 2007, the contents of each ofwhich are hereby
`incorporated by reference in their entireties.
`
`BACKGROUND
`
`The present invention relates to an emission treatment sys-
`tem having an oxidation catalyst upstream of a soot filter
`coated with a material effective in the Selective Catalytic
`Reduction (SCR) of NOx by a reductant, e.g., ammonia. In
`one embodiment, the system provides an effective method of
`simultaneously remediating the nitrogen oxides (NOx), par-
`ticulate matter, and gaseous hydrocarbons present in diesel
`engine exhaust streams.
`Diesel engine exhaust is a heterogeneous mixture which
`contains not only gaseous emissions such as carbon monox-
`ide (“CO”), unburned hydrocarbons (“HC”) and nitrogen
`oxides (“NOX”), but also condensed phase materials (liquids
`and solids) which constitute the so-called particulates or par-
`ticulate matter. Often, catalyst compositions and substrates
`on which the compositions are disposed are provided in diesel
`engine exhaust systems to convert certain or all of these
`exhaust components to innocuous components. For example,
`diesel exhaust systems can contain one or more of a diesel
`oxidation catalyst, a soot filter and a catalyst for the reduction
`of NOx.
`
`Oxidation catalysts that contain platinum group metals,
`base metals and combinations thereof are known to facilitate
`
`the treatment of diesel engine exhaust by promoting the con-
`version of both HC and CO gaseous pollutants and some
`proportion of the particulate matter through oxidation of
`these pollutants to carbon dioxide and water. Such catalysts
`have generally been contained in units called diesel oxidation
`catalysts (DOC’s), which are placed in the exhaust of diesel
`engines to treat the exhaust before it vents to the atmosphere.
`In addition to the conversions of gaseous HC, CO and par-
`ticulate matter, oxidation catalysts that contain platinum
`group metals (which are typically dispersed on a refractory
`oxide support) also promote the oxidation of nitric oxide
`(NO) to N02.
`The total particulate matter emissions of diesel exhaust are
`comprised of three main components. One component is the
`solid, dry, solid carbonaceous fraction or soot fraction. This
`dry carbonaceous matter contributes to the visible soot emis-
`sions commonly associated with diesel exhaust. A second
`component of the particulate matter is the soluble organic
`fraction (“SOF”). The soluble organic fraction is sometimes
`referred to as the volatile organic fraction (“VOF”), which
`terminology will be used herein. The VOF can exist in diesel
`exhaust either as a vapor or as an aerosol (fine droplets of
`liquid condensate) depending on the temperature ofthe diesel
`exhaust. It is generally present as condensed liquids at the
`standard particulate collection temperature of 52° C.
`in
`diluted exhaust, as prescribed by a standard measurement
`test, such as the US. Heavy Duty Transient Federal Test
`Procedure. These liquids arise from two sources: (1) lubricat-
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`ing oil swept from the cylinder walls of the engine each time
`the pistons go up and down; and (2) unburned or partially
`burned diesel fuel.
`
`The third component of the particulate matter is the so-
`called sulfate fraction. The sulfate fraction is formed from
`
`small quantities of sulfur components present in the diesel
`fuel. Small proportions of SO3 are formed during combustion
`ofthe diesel, which in turn combines rapidly with water in the
`exhaust to form sulfuric acid. The sulfuric acid collects as a
`
`condensed phase with the particulates as an aerosol, or is
`adsorbed onto the other particulate components, and thereby
`adds to the mass of TPM.
`
`One key aftertreatment technology in use for high particu-
`late matter reduction is the diesel particulate filter. There are
`many known filter structures that are effective in removing
`particulate matter from diesel exhaust, such as honeycomb
`wall flow filters, wound or packed fiber filters, open cell
`foams, sintered metal filters, etc. However, ceramic wall flow
`filters, described below, receive the most attention. These
`filters are capable of removing over 90% of the particulate
`material from diesel exhaust. The filter is a physical structure
`for removing particles from exhaust, and the accumulating
`particles will increase the back pressure from the filter on the
`engine. Thus, the accumulating particles have to be continu-
`ously or periodically burned out of the filter to maintain an
`acceptable back pressure. Unfortunately, the carbon soot par-
`ticles require temperatures in excess of 500° C. to burn under
`oxygen rich (lean) exhaust conditions. This temperature is
`higher than what is typically present in diesel exhaust.
`Provisions are generally introduced to lower the soot bum-
`ing temperature in order to provide for passive regeneration of
`the filter. The presence of a catalyst promotes soot combus-
`tion, thereby regenerating the filters at temperatures acces-
`sible within the diesel engine’s exhaust under realistic duty
`cycles. In this way a catalyzed soot filter (CSF) or catalyzed
`diesel particulate filter (CDPF) is effective in providing for
`>80% particulate matter reduction along with passive burning
`of the accumulating soot, and thereby promoting filter regen-
`eration.
`
`Future emissions standards adopted throughout the world
`will also address NOx reductions from diesel exhaust. A
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`proven NOx abatement technology applied to stationary
`sources with lean exhaust conditions is Selective Catalytic
`Reduction (SCR). In this process, NOx is reduced with
`ammonia (NH3) to nitrogen (N2) over a catalyst typically
`composed of base metals. The technology is capable of NOx
`reduction greater than 90%, and thus it represents one of the
`best approaches for achieving aggressive NOx reduction
`goals. SCR is under development for mobile applications,
`with urea (typically present in an aqueous solution) as the
`source of ammonia. SCR provides efficient conversions of
`NOx as long as the exhaust temperature is within the active
`temperature range of the catalyst.
`While separate substrates each containing catalysts to
`address discrete components of the exhaust can be provided
`in an exhaust system, use of fewer substrates is desirable to
`reduce the overall size of the system, to ease the assembly of
`the system, and to reduce the overall cost of the system. One
`approach to achieve this goal is to coat the soot filter with a
`catalyst composition effective for the conversion of NOx to
`innocuous components. With this approach, the catalyzed
`soot filter assumes two catalyst functions: removal of the
`particulate component of the exhaust stream and conversion
`of the NOx component of the exhaust stream to N2.
`Coated soot filters that can achieve NOx reduction goals
`require a sufficient loading of SCR catalyst composition on
`the soot filter. The gradual loss ofthe catalytic effectiveness of
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`US 9,039,982 B2
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`3
`the compositions that occurs over time through exposure to
`certain deleterious components of the exhaust stream aug-
`ments the need for higher catalyst loadings of the SCR cata-
`lyst composition. However, preparation of coated wall flow
`soot filters with higher catalyst loadings can lead to unaccept-
`ably high back pressure within the exhaust system. Coating
`techniques that allow higher catalyst loadings on the wall
`flow filter, yet still allow the filter to maintain flow character-
`istics that achieve acceptable back pressures are therefore
`desirable.
`
`An additional aspect for consideration in coating the wall
`flow filter is the selection of the appropriate SCR catalyst
`composition. First, the catalyst composition must be durable
`so that it maintains its SCR catalytic activity even after pro-
`longed exposure to higher temperatures that are characteristic
`of filter regeneration. For example, combustion of the soot
`fraction of the particulate matter often leads to temperatures
`above 700° C. Such temperatures render many commonly
`used SCR catalyst compositions such as mixed oxides of
`vanadium and titanium less catalytically effective. Second,
`the SCR catalyst compositions preferably have a wide enough
`operating temperature range so that they can accommodate
`the variable temperature ranges over which the vehicle oper-
`ates. Temperatures below 300° C. are typically encountered,
`for example, at conditions of low load, or at startup. The SCR
`catalyst compositions are preferably capable ofcatalyzing the
`reduction of the NOx component of the exhaust to achieve
`NOx reduction goals, even at lower exhaust temperatures.
`The prior art contains descriptions of the use of SCR cata-
`lyst compositions, soot filters and combinations thereof for
`the abatement ofboth the NOx and particulate components of
`diesel exhaust. These references are described below.
`
`Japanese Kokai 3-130522, for example, discloses the treat-
`ment of diesel exhaust gases characterized by use of an
`ammonia injector and porous ceramic filter having a denitra-
`tion catalyst within the pores. The filter is installed in the
`wake of the diesel engine exhaust. The ceramic porous filter
`comprises an up stream fine pore path layer, and a downstream
`side course ceramic particle layer on which the denitration
`catalyst was supported. The fine layer can support a platinum
`or palladium or other hydrocarbon combustion catalyst. The
`diesel exhaust gas containing unburned carbon flows through
`the porous ceramic filter and the carbon particles are filtered
`onto the surface. The gas containing nitric oxides and the
`ammonia passes through the denitration catalyst containing
`side of the filter and the nitric oxides are reduced to nitrogen
`and water. The oxidation catalyst on the upstream side causes
`the particulate component to burn off catalytically.
`US. Pat. No. 4,912,776 discloses an oxidation catalyst, an
`SCR catalyst downstream and adjacent to the SCR catalyst,
`and a reductant source introduced to the exhaust stream
`
`between the oxidation catalyst and the SCR catalyst. Provid-
`ing a higher feed containing a high proportion of N02 to NO
`to the SCR reactor is said to allow the use of lower tempera-
`tures and higher space velocities than is possible with a feed
`of NO.
`
`WO 99/39809 discloses a system for treating combustion
`exhaust gas containing NOx and particulates that has an oxi-
`dation catalyst effective to convert at least a portion ofthe NO
`in the NOx to N02, a particulate trap, a source of reductant
`fluid and an SCR catalyst. The particulate trap is downstream
`of the oxidation catalyst; the reductant fluid source is down-
`stream of the particulate trap; and the SCR catalyst is down-
`stream of the reductant fluid source. Reductant fluids dis-
`closed include ammonia, urea, ammonium carbamate and
`hydrocarbons (e.g., diesel fuel).
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`A catalytic wall flow filter for an exhaust system of a
`combustion engine is described in WO 01/12320. The wall
`flow filter has channels that are in honeycomb arrangement,
`where some of the channels are blocked at the upstream end
`and some of the channels that are unblocked at the upstream
`end are blocked at the downstream end. An oxidation catalyst
`is disposed on a gas impermeable zone at an upstream end of
`channels that are blocked at the downstream end. The filter
`
`has a gas permeable filter zone that is downstream of the
`oxidation catalyst that is for trapping soot. The oxidation
`catalyst is described to be capable (when in an exhaust sys-
`tem) of generating NO2 from NO to combust the trapped soot
`continuously at temperatures below 400° C. The oxidation
`catalyst preferably includes a platinum group metal. Exhaust
`streams containing NO are initially passed over the oxidation
`catalyst to convert NO to NO2 prior to filtering to remove soot.
`The exhaust gas then containing N02 is used to combust the
`soot trapped on the filter.
`In some embodiments of the wall flow filter described in
`W0 01/ 12320 the downstream channels of the soot filter
`
`contain a catalyst for a NOx absorber and an SCR catalyst
`downstream of the NOx absorber. The SCR catalyst can be a
`copper-based material, platinum, a mixed oxide of vanadium
`and titania or a zeolite, or mixtures of two or more thereof.
`
`SUMMARY OF THE INVENTION
`
`In one aspect, the invention relates to an emission treatment
`system for treatment of an exhaust stream that contains NOx
`and particulate matter. The emission treatment system
`includes an oxidation catalyst, an injector that periodically
`meters ammonia or an ammonia precursor into the exhaust
`stream; and a wall flow monolith. The injector is in fluid
`communication with the oxidation catalyst, and is positioned
`downstream ofthe oxidation catalyst. The wall flow monolith
`contains an SCR catalyst composition, is in fluid communi-
`cation with the injector, and is positioned downstream of the
`injector.
`The wall flow monolith has a plurality of longitudinally
`extending passages formed by longitudinally extending walls
`bounding and defining said passages. The passages include
`inlet passages that have an open inlet end and a closed outlet
`end, and outlet passages that have a closed inlet end and an
`open outlet end. The wall flow monolith contains an SCR
`catalyst composition that permeates the walls at a concentra-
`tion of at least 1.3 g/in3 (and preferably from 1.6 to 2.4 g/in3).
`The wall flow monolith has a wall porosity of at least 50%
`with an average pore size of at least 5 microns. Preferably, the
`SCR catalyst composition permeates the walls of the wall
`flow monolith so that the walls have a wall porosity offrom 50
`to 75% with an average pore size of from 5 to 30 microns.
`In a preferred embodiment of the emission treatment sys-
`tem, the SCR catalyst composition contains a zeolite and base
`metal component selected from one or more of a copper and
`iron component. Preferably, the base metal component is a
`copper component. Preferred zeolites of the SCR catalyst
`composition have a silica to alumina ratio of at least about 10.
`For instance, a beta zeolite can be used in the SCR catalyst
`composition.
`Among other things, the oxidation catalyst ofthe system is
`useful for combusting substantial portions of the particulate
`matter, and in particular, the VOF, entrained in the exhaust. In
`addition, a substantial portion of the NO in the NOx compo-
`nent is oxidized to NO2 over the oxidation catalyst. In pre-
`ferred embodiments, the oxidation catalyst is disposed on a
`honeycomb flow through monolith substrate or an open cell
`foam substrate. Preferably, the oxidation catalyst includes a
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`US 9,039,982 B2
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`5
`platinum group metal component, and in particular, a plati-
`num component. In some embodiments, the oxidation cata-
`lyst can also contain a zeolite component.
`In another preferred embodiment ofthe emission treatment
`system, the system also has a diesel engine which is located
`upstream of, and in fluid communication with the oxidation
`catalyst.
`Another aspect of the invention relates to a method for
`treating emissions produced in an exhaust stream that con-
`tains NOx and particulate matter. The method includes:
`(a) passing the exhaust stream through an oxidation cata-
`lyst wherein a substantial portion of NO is oxidized to
`NO2 to provide an NOz-enriched exhaust stream;
`(b) metering at periodic intervals, ammonia or an ammonia
`precursor into the NO2-enriched exhaust stream; and,
`(c) subsequently passing the exhaust stream through a wall
`flow monolith wherein particulate matter is filtered and
`a substantial portion of NOx is reduced to N2.
`Here again, the wall flow monolith has a plurality of lon-
`gitudinally extending passages formed by longitudinally
`extending walls bounding and defining said passages. The
`passages include inlet passages that have an open inlet end
`and a closed outlet end, and outlet passages that have a closed
`inlet end and an open outlet end. The wall flow monolith
`contains an SCR catalyst composition that permeates the
`walls at a concentration of at least 1.3 g/in3 (and preferably
`from 1.6 to 2.4 g/in3). The wall flow monolith has a wall
`porosity of at least 50% with an average pore size of at least
`5 microns. Preferably, the SCR catalyst composition perme-
`ates the walls of the wall flow monolith so that the walls have
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`a wall porosity of from 50 to 75% with an average pore size of
`from 5 to 30 microns.
`
`In another aspect, the invention relates to a method for
`disposing an SCR catalyst composition on a wall flow mono-
`lith. The method includes:
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`(a) immersing the wall flow monolith in an aqueous slurry
`comprising the SCR catalyst composition from a first
`direction to deposit the SCR catalyst composition on the
`inlet passages;
`(b) r