Development of SCR on Diesel Particulate Filter
`System for Heavy Duty Applications
`
`2011-01-1312
`Published
`04/12/2011
`
`Mojghan Naseri, Sougato Chatterjee, Mario Castagnola, Hai-Ying Chen, Joseph Fedeyko,
`Howard Hess and Jianquan Li
`Johnson Matthey Inc.
`
`ABSTRACT
`Selective Catalytic Reduction (SCR) catalysts have been
`demonstrated as an effective solution for controlling NOx
`emissions from diesel engines. Typical 2010 Heavy Duty
`systems include a DOC along with a catalyzed soot filter
`(CSF) in addition to the SCR sub-assembly. There is a strong
`desire to further increase the NOx conversion capability of
`such systems, to enable additional fuel economy savings by
`allowing engines to be calibrated to higher engine-out NOx
`levels. One potential approach is to replace the CSF with a
`diesel particulate filter coated with SCR catalysts (SCR-DPF)
`while keeping the flow-through SCR elements downstream,
`which essentially increases the SCR volume in the after-
`treatment assembly without affecting the overall packaging. In
`this work, a system consisting of SCR-DPF was evaluated in
`comparison to the DOC + CSF components from a commercial
`2010 DOC + CSF + SCR system on an engine with the engine
`EGR on (standard engine out NOx) and off (high engine out
`NOx). The SCR-DPF system exhibited significantly higher
`NOx reduction efficiency than the CSF systems under both
`steady state and heavy duty FTP transient conditions when the
`engine operated at the same condition. The soot oxidation
`activity on these two systems was also evaluated. Net soot
`oxidation (ie more soot removed from the filter than entered it
`form the engine) was observed over the SCR-DPF system at
`400°C presumably because of the high NOx/PM ratio when
`the engine EGR was turned off. No net soot burn was observed
`for the 2010 CSF system when operating with standard EGR at
`the specific conditions chosen for these series of testing. The
`high passive filter regeneration activity of the SCR-DPF
`system with the engine operating at high engine-out NOx may
`result in less frequent active regeneration events and, hence,
`reduce the fuel penalty associated with active regeneration.
`The results of this work demonstrated that using SCR-DPF
`systems not only could meet current NOx reduction regulations
`but also improve fuel economy for heavy duty diesel vehicles
`
`Copyright © 2011 SAE International
`doi: 10.4271/2011-01-1312
`
`by allowing them to operate at higher engine out NOx
`conditions.
`
`INTRODUCTION
`To meet NOx emission requirements and regulations for heavy
`duty diesel engines, selective catalytic reduction (SCR)
`catalysts have been demonstrated to be an effective solution.
`Urea based SCRs for 2010 heavy duty applications consist of
`DOC along with a catalyzed soot filter (CSF) in addition to the
`SCR sub-assembly. Further decrease in NOx emission from an
`after-treatment system is desired to have additional fuel
`economy saving by allowing diesel engines operation at higher
`engine out NOx level. One approach is to replace the CSF with
`a diesel particulate filter coated with SCR (SCR-DPF) while
`keeping the flow-through SCR downstream. This approach
`helps in increasing the SCR volume, which can improve
`system NOx conversion, without changing the overall package
`size in a typical 2010 type system. Utilizing the SCR-DPF
`system could allow the diesel engine to operate at higher
`engine out NOx while still having the same emission targets
`and potentially improve the engine fuel economy. For the
`SCR-DPF system, high porosity filters are needed to enable
`the use of the high washcoat loadings necessary to get good
`performance and durability. These high porous filters need to
`have very good thermomechanical properties to enable them to
`survive the active regeneration events over the life of the
`system. Previous work has demonstrated that SCR-DPF
`catalysts have high NOx conversion capabilities [1, 4]. Also,
`many investigations have been conducted to understand the
`thermal durability of Cu-zeolite SCR catalysts and their
`activity after repeated soot regeneration [1, 2, 3, 4], which
`allows its use in the SCR-DPF system. It was also demonstrated
`that SCR-DPF has a similar characteristics as the CSF in that
`it has a low impact on back pressure [4]. However, limited
`work has been done to evaluate SCR-DPF for passive
`regeneration capability in heavy duty applications.
`
` SAE Int. J. Engines | Volume 4 | Issue 1
`
`1798
`
`BASF-2011.001
`
`

`
`In this work, a system containing an SCR-DPF was evaluated
`in comparison to a 2010 type CSF + SCR system on an engine
`with the engine EGR on (auto EGR) and off (high engine out
`NOx). The NOx conversion of these two systems during steady
`state and transient (HD FTP cycles) testing was studied to
`evaluate NOx conversion of the SCR-DPF as compared to the
`CSF system for heavy duty applications. In order to have the
`desired fuel economy, the SCR-DPF system must not only
`have high NOx conversion but also be able to passively
`regenerate via reaction with NO2. Therefore, passive soot
`oxidation activity of these two systems was evaluated.
`
`EXPERIMENTAL
`Cu-zeolite SCR was washcoated on a high porosity filter. The
`filter used for this study was a NGK cordierite C650, 300 cells
`per square inches and 12 mil wall thickness. This catalyst was
`compared to a current catalyzed soot filter (CSF) which was
`also coated on NGK cordierite filter substrate with 200 cells/
`
`in2 and 12 mil wall thickness. Both CSF and SCR-DPF were
`combined with diesel oxidation catalyst (DOC) upstream and
`Cu-SCR catalysts downstream. DOC, CSF and SCR-DPF
`were hydrothermally aged at 700°C for 150hrs while SCR
`catalysts were aged for 100hrs at 650°C. There was 10% water
`present during all hydrothermal aging. Table 1 shows catalyst
`dimensions and aging conditions.
`
`Testing was conducted using a 2007 MY heavy duty diesel
`engine with a 2007 calibration. The system configuration
`during all tests was DOC + SCR-DPF (or CSF) + SCRs, the
`configurations are shown in schematic diagrams 1 and 2. Urea
`was delivered and injected into exhaust by an air assisted
`Grundfos pump. The urea injection nozzle was located after
`the DOC for SCR-DPF system and after the CSF for the DOC
`+ CSF + SCR system. A six inch static mixer was placed after
`the injection nozzle and before SCR-DPF or SCR bricks to
`ensure good mixing and uniform distribution in the exhaust.
`
`Table 1. Catalysts Information
`
`Schematic Diagram 1. CSF System configuration
`
`SAE Int. J. Engines | Volume 4 | Issue 1
`
`1799
`
`BASF-2011.002
`
`

`
`Schematic Diagram 2. SCR-DPF System configuration
`
`Both steady state and transient testing were conducted to
`determine the performance of the two systems. The SCR-DPF
`system was tested with EGR off while the CSF system was
`tested both with EGR off and on. Steady-state tests were
`conducted at six different speeds and loads, A75, A25, B75,
`B25, C75 and C25. The ANR (ammonia to NOx ratio) was
`kept constant at 1.2 during steady state runs. The space velocity
`during steady-state testing varied between 20K hr−1-55K hr−1
`depending on the system and test condition. The two system
`performances were also determined during cold and hot HD
`FTP cycles. During transient cycles, urea over-dosing strategy
`at lower temperatures (200-220°C) was used to saturate the
`SCR and SCR-DPF components. The average ANR during
`transient cycles was 1.2 for both the CSF system (EGR on) and
`for the SCR-DPF system (EGR-off).
`
`For passive regeneration testing, the CSF or the SCR-DPF
`systems were loaded up to 3g soot/l. The passive regeneration
`capability of each system was studied at DOC inlet temperatures
`of 300°C and 400°C at speed B. Filters were weighed before
`and after soot loading and passive regeneration while still hot
`at around 180°C. The CSF system was passively regenerated
`with auto EGR (ie low NOx) while SCR-DPF was regenerated
`with EGR turned off (ie high NOx).
`
`The dynamometer utilized in this study was 800HP AC
`motoring dyno from Horiba. During transient testing, full
`dilution tunnel CVS (Horiba 4000 SCFM) was used, and
`intake air flow was measured with Sierra air flow meter
`ranging from 0-2400kg/hr with +_1% accuracy in full scale.
`Engine out emissions were measured using Horiba MEXA
`7500D dual bench (CO, HC and NOx) analyzers with +_1%
`accuracy across the full scale. System out emissions were also
`measured using an FTIR (MKS model 2030 HS). DPF
`backpressure was monitored using pressure transducers, Setra
`
`Model 206. Soot loadings/regenerations for the filters were
`measured by weighing the filters while still hot at 180°C. The
`scale used for weighing the filters was Mettler Toledo, ranging
`from 0-64Kg with 0.1g resolution. Temperatures in the system
`were measured using K type thermocouples.
`
`RESULTS
`
`NOx Performance During Steady State
`The NOx conversion over Cu-SCR for both SCR-DPF and CSF
`systems were measured during 6 mode steady state tests with
`ANR of 1.2. Before the start of steady state testing, the DPFs were
`actively regenerated at CSF/SCR-DPF inlet temperature of 600°C
`to remove soot. SCR-DPF performance was determined by
`turning off the EGR (to give a high NOx condition) while the CSF
`system was studied with both auto EGR and EGR off. Turning off
`the EGR resulted in approximately 5.0g/hp-hr engine out NOx
`while with auto EGR it was approximately 1.0g/hp-hr. Auto-EGR
`resulted in higher temperatures and lower exhausts flow as
`compared to EGR off as shown in Figure 1. The bars represent
`exhaust flow while dashed lines show SCR or SCR-DPF inlet
`temperatures. With EGR off, the exhaust flow increased at a
`minimum of 40% to over 100% in some cases. Consequently,
`with EGR off, exhaust temperature under these steady state
`conditions dropped anywhere from 30°C to over 100°C.
`
`Figure 2 shows NOx conversion for both systems at steady state
`with ANR of 1.2. For the majority of modes, the SCR-DPF
`system has equivalent NOx conversion as the CSF system even
`with high engine out NOx, higher exhaust flow and lower inlet
`temperatures. For example under C25 test condition, the SCR-
`DPF demonstrated almost similar (>93%) NOx conversion as the
`CSF system, even though the exhaust flow was more than double
`
` SAE Int. J. Engines | Volume 4 | Issue 1
`
`1800
`
`BASF-2011.003
`
`

`
`Figure 1. Exhaust flow and temperature at different engine operations
`
`with the SCR-DPF and exhaust temperature was over 30°C
`lower. Only under the very low temperatures for A25 and B25,
`the SCR-DPF system showed lower performance than the CSF
`system. This is due to very low temperature experienced by the
`SCR-DPF, approximately 214°C as compared to 290-300°C for
`the CSF system. However, the overall results suggested that there
`is a potential to achieve higher overall NOx conversion with the
`SCR-DPF system than the CSF+SCR systems. This is further
`examined by testing both systems under similar test conditions.
`
`Figure 3. NOx conversion for CSF and SCR-DPF
`systems (no EGR)
`
`Figure 3 shows the results of steady state testing of the CSF
`system versus the SCR-DPF system under similar EGR-off
`conditions. These tests were carried out to compare the
`performance of these two systems when subjected to similar
`temperatures and flow conditions. The exhaust flow conditions
`were those of the EGR-off conditions as shown in Figure 1.
`The exhaust temperatures at SCR inlet for each test conditions
`are shown in Figure 3. Note that the temperature was measured
`at SCR-DPF inlet for SCR-DPF system and at SCR inlet for
`CSF system. ANR was maintained at 1.2 for these tests. These
`results clearly showed the benefit in NOx reduction with the
`SCR-DPF system, especially under difficult low temperature
`conditions. Comparing A25 and B25 conditions with
`
`Figure 2. NOx conversion for CSF (auto-EGR) and
`SCR-DPF (no EGR)
`
`SAE Int. J. Engines | Volume 4 | Issue 1
`
`1801
`
`BASF-2011.004
`
`

`
`temperatures around 210°C, the SCR-DPF system exhibited
`significantly higher NOx reduction than the CSF system.
`Especially at B25 which had 50% higher flow than A25, the
`SCR-DPF system exhibited around 85% NOx reduction while
`the CSF system exhibited only about 70%. Similarly at C25,
`with even higher flow but temperatures around 237°C, the
`SCR-DPF system produced 93% NOx reduction while it was
`only 79% with the CSF system. As the temperature increased
`beyond 350°C, this difference was minimized.
`
`A light-off test comparison was also conducted to determine
`performance of the SCR-DPF as compared to the CSF system.
`The experiment was designed to have similar exhaust
`temperatures for both systems and space velocity was maintained
`approximately at 30,000/hr. EGR was turned off for SCR-DPF
`system while CSF system was tested with auto-EGR. ANR for
`
`each point was at 1.20. Figure 4 shows temperatures for each
`system during these tests. As is shown, the two systems had
`similar temperatures for most modes except the last mode,
`where the CSF system experienced higher temperature.
`
`Figure 5 shows NOx conversion for each system during light-off
`tests. These results suggested that the SCR-DPF system exhibits
`higher NOx conversion at lower temperatures from 200°C to
`about 280°C, as compared to the CSF system. For example, at
`200°C, the SCR-DPF system produced 77% NOx conversion
`whereas the CSF system showed only 62%. From 280°C
`onward, both systems have similar NOx conversion. However,
`at 340°C, there appears to be a slight drop in NOx conversion
`with the CSF system, which was not observed with the SCR-
`DPF system. This data has been repeated and is being further
`investigated. In general, these results indicate that the SCR-DPF
`system has a better light-off as compared to the CSF system.
`
`Figure 4. Exhaust temperature for SCR-DPF (EGR off) and CSF (Auto-EGR) during Light-off tests
`
`Figure 5. NOx conversion light-off comparison between SCR-DPF system (EGR off) and CSF system (Auto-EGR), ANR=1.2
`
` SAE Int. J. Engines | Volume 4 | Issue 1
`
`1802
`
`BASF-2011.005
`
`

`
`NOx Conversion During Transient Testing
`The NOx conversion over Cu-SCR for both the SCR-DPF and
`the CSF systems was measured during cold and hot HD FTP
`cycles. There was a warm FTP cycle between the cold and three
`hot FTP cycles. Again, the SCR-DPF system was tested with
`EGR off while the CSF system was tested with both auto EGR
`and EGR off. The engine out NOx was approximately 5g/hp-hr
`under hot FTP cycle with EGR off and it was 1.5g/hp-hr with
`auto EGR. Similar to steady state conditions, turning off the
`EGR resulted in lower exhaust temperature and higher flow, as
`compared to auto EGR. Figure 6 shows temperature traces and
`urea dosing for both systems at different engine operation
`conditions. The top traces (dotted lines) in the graph are SCR/
`SCR-DPF inlet temperatures (left Y-axis) while the traces at the
`bottom (solid lines) show urea dosing for both systems (right
`
`Y-axis). As is shown, SCR inlet temperature for the CSF system
`reaches 200°C sooner as compared to the SCR-DPF system.
`Figure 7 represents the histogram of exhaust temperature at two
`engine operating conditions; auto EGR (low NOx) and EGR
`off (high NOx). The lines indicate the percentage of time
`over certain temperature. The CSF system with auto EGR
`experienced more time over 200°C as compared to SCR-DPF
`system with EGR off condition. In the JM urea dosing system,
`urea is dosed at temperatures of 200°C or above. Therefore,
`in the CSF system with auto EGR, urea was dosed earlier.
`However, the dosing strategy was adjusted in order to have
`similar overall cycle ANR of 1.2 for both systems. This means,
`slightly higher Urea was dosed in the later part of the cycle with
`the SCR-DPF, which compensated for the late onset of dosing
`in this system.
`
`Figure 6. Exhaust temperature and urea dosing traces comparison between auto EGR and no EGR during Hot FTP
`
`Figure 7. Exhaust temperature histogram comparison between auto EGR and no EGR during Hot FTP
`
`SAE Int. J. Engines | Volume 4 | Issue 1
`
`1803
`
`BASF-2011.006
`
`

`
`Figure 8 compares the NOx conversion during cold, warm and
`hot HD FTP testing for the CSF and the SCR-DPF systems
`with auto EGR and EGR turned off, respectively. During these
`tests, the SCR-DPF system demonstrated slightly higher NOx
`conversion than the CSF system. This difference was more
`pronounced during the cold FTP cycle where the SCR-DPF
`system showed 63% NOx conversion as compared to 55% for
`the CSF system. During the hot FTP cycle, SCR-DPF still
`showed better NOx conversion as compared to the CSF,
`however the difference was minimal. Please note that these
`tests were not carried out with a dosing strategy fully optimized
`for SCR-DPF system. The dosing strategy was developed and
`optimized for CSF + SCR system. Authors believe that by
`optimizing the urea dosing strategy and taking advantage of
`NH3 storage of the system, SCR-DPF performance can further
`be improved under these conditions.
`
`Next, the SCR-DPF and the CSF systems were tested again
`under HD FTP transient cycles, but under similar engine
`operating conditions by turning the EGR off (in both cases).
`The exhaust flow was similar for both systems in these tests.
`The temperature profiles for these two systems were similar as
`well. The temperature histograms during hot FTP for both
`systems are shown in Figure 9. Exhaust temperature for the
`SCR-DPF system was measured at SCR-DPF inlet while it
`was measured at SCR inlet for the CSF system. As is shown in
`
`Figure 9, both systems experienced similar percentage time
`over temperature profile during the FTP tests, especially at
`200°C where urea injection starts. Due to similarity of the
`overall SCR temperature profiles between the two systems
`(unlike previous FTP tests with and without EGR) overall
`cycle ANR for the SCR-DPF and the CSF systems was s
`imilar. Please note that in these tests, the same Urea dosing
`strategy was utilized for both systems. The SCR-DPF system
`dosing was not optimized in any way to provide better
`performance.
`
`Figure 10 shows the NOx conversion comparison between
`these two systems under similar engine operating conditions
`with EGR turned off. The SCR-DPF system clearly exhibited
`higher overall NOx reduction than the CSF system during
`warm and hot FTP cycles. Comparing the hot cycles, the SCR-
`DPF produced 78-80% NOx reduction while the CSF system
`only produced 68 - 70% NOx reduction. In cold cycle tests, the
`late onset of Urea dosing with the SCR-DPF, probably
`minimized any benefit. This again indicated the benefit of the
`additional SCR catalyst volume in the SCR-DPF system. As
`mentioned previously, further enhancement in the urea dosing
`strategy can possibly help with additional improvement in
`NOx conversion with the SCR-DPF system. This will be
`investigated in the future.
`
`Figure 8. NOx Conversion during cold, warm and hot FTP cycles with CSF system
`(auto EGR) and SCR-DPF system (EGR off))
`
` SAE Int. J. Engines | Volume 4 | Issue 1
`
`1804
`
`BASF-2011.007
`
`

`
`Figure 9. Temperature histogram during Hot FTP cycle for CSF and SCR-DPF Systems
`
`Figure 10. NOx Conversion during cold and hot FTP cycles- EGR Off
`
`Passive Regeneration of Soot Via Reaction
`with NO2
`The passive regeneration capabilities of the SCR-DPF and
`CSF systems were determined under steady state conditions
`after loading the filters up to 3g soot/l. Passive regeneration
`was studied at DOC inlet temperatures of 300°C and 400°C
`with the engine running at speed A. Similar flow and
`temperature conditions were identified for the two systems for
`these tests. For the SCR-DPF system, passive regeneration
`capability was studied with and without urea injection. The
`passive regeneration duration for the SCR-DPF system was
`30 minutes with the EGR off. The CSF system was passively
`regenerated with the EGR on (ie low NOx condition). The CSF
`
`was regenerated for 30 minutes and the filter weight was
`measured while still hot at 180°C. Afterwards, the CSF was
`reinstalled and passively regenerated for a second 30 minute
`period and its weight was recorded. This was carried out to
`evaluate effect of additional time on the CSF passive
`regeneration process. As expected, turning off the EGR
`resulted in higher NOx/PM ratio for the SCR-DPF system as
`compared to the CSF system.
`
`Figure 11 shows passive regeneration capabilities of the two
`systems. The NO2/NOx ratio, space velocity, and engine out
`NOx for each system are shown in Table 2. In the SCR-DPF
`system, urea was dosed at ANR of 1.2 during the passive
`
`SAE Int. J. Engines | Volume 4 | Issue 1
`
`1805
`
`BASF-2011.008
`
`

`
`regeneration evaluation. This urea was dosed upstream of the
`SCR-DPF. There was no such urea dosing upstream of the CSF.
`During the 300°C passive regeneration tests, neither system
`demonstrated any net soot burn. In fact, both systems showed
`soot gain during this 30 minute period. There was up to 10%
`soot gain for the CSF at 300°C while the soot loading nearly
`double for the SCR-DPF, indicating significantly poorer passive
`regeneration for the SCR-DPF under these conditions. It appears
`that the higher increase in the soot load on the SCR-DPF system
`was due to urea dosing which allowed for significant reduction
`in NO2 across the SCR-DPF, before the same NO2 could be
`utilized for soot burn. During the 400°C passive regeneration
`testing, the CSF system still continued to show lack of passive
`regeneration and increased soot load by 24%. This appears to be
`due to reduced NO2 make from the DOC and CSF under this
`higher operating temperature. In contrast, the SCR-DPF system
`
`actually produced nearly 20% reduction in soot load under the
`400°C test condition. This can be attributed to higher NO2
`generation from the DOC under the SCR-DPF test conditions.
`Note that SCR-DPF had orders of magnitude higher engine out
`NOx with EGR off. It is known that higher NOx concentration
`helps to increase the NO oxidation to NO2, across a DOC under
`some temperature conditions. Accordingly, the DOC in the
`SCR-DPF system produced nearly 30% NO2 under the 400°C
`test condition. In addition, the overall NOx/PM ratio for the
`SCR-DPF condition was much higher than the CSF system.
`This combination resulted in significant passive regeneration
`with the SCR-DPF system than the CSF system at 400°C. Note
`that, this passive regeneration was observed even with urea
`dosing on the SCR-DPF. The SCR-DPF system also had a very
`high NOx conversion at both passive regeneration test
`conditions, as shown in Figure 12.
`
`Table 2. NO2/NOx, SV and Engine out Information during Passive Regeneration
`
`Figure 11. Passive regeneration characteristics of the two systems, 30minute regeneration time
`
` SAE Int. J. Engines | Volume 4 | Issue 1
`
`1806
`
`BASF-2011.009
`
`

`
`Figure 12. NOx Conversion for SCR-DPF during Passive Regeneration, ANR=1.2
`
`The SCR-DPF passive regeneration capability was further
`studied with and without urea injection at the same DOC inlet
`temperatures of 300°C and 400°C. The results are presented in
`Figure 13. These tests were carried out to understand the effect
`of Urea dosing on the SCR-DPF’s passive regeneration
`capability. As is shown (and as is expected), urea injection
`significantly reduced the net soot burn on the SCR-DPF. At
`300°C, there was only a slight soot gain of 5% without urea
`injection as compared to 20% increase in soot load with urea
`dosing. At 400°C, however, the SCR-DPF filter was passively
`regenerated with and without urea dosing. With urea dosing,
`
`the passive regeneration extent was reduced and 19% net soot
`was observed as compared to 25% net soot burn without urea.
`The lower soot burn with urea injection is attributed to NO2
`conversion via the SCR reaction as shown in Figure 14. Note
`that around 100% NOx conversion was observed through the
`SCR-DPF system in these experiments, as shown in Figure 12.
`
`The results shown in this section indicate that SCR-DPF has a
`promising potential for passive regeneration with engine out
`NOx control strategy, while still meeting high NOx conversion
`needed at tailpipe.
`
`Figure 13. SCR-DPF system passive regeneration capability with EGR off
`
`SAE Int. J. Engines | Volume 4 | Issue 1
`
`1807
`
`BASF-2011.010
`
`

`
`Figure 14. NO2/NOx ratio at different locations with DOC + SCR-DPF system with and without urea injection
`
`SUMMARY/CONCLUSIONS
`• In this paper, a DOC + CSF + SCR system was compared
`with a DOC + SCR-DPF + SCR system for heavy duty diesel
`engine applications. The SCR-DPF system was tested with
`high engine out NOx of approximately 5g/hp-hr (EGR off)
`while the CSF system was evaluated at an engine-out NOx
`level of 1-1.5g/hp-hr (EGR on) as well as under similar high
`NOx with EGR off.
`• Both steady state and transient results indicate that if engine
`conditions are similar for both systems (EGR-off), the SCR-
`DPF system enables higher NOx reduction as compared
`to the CSF system. The improved SCR-DPF performance
`is especially evident and more advantageous at lower
`temperatures, as demonstrated through steady state and light-
`off tests. This higher NOx conversion can be attributed towards
`the higher overall SCR volume in the SCR-DPF system.
`• The SCR-DPF system also exhibits very good potential
`for higher NOx conversion for future heavy duty systems.
`This was demonstrated during both steady state and transient
`testing. With further optimization of the urea dosing strategy
`for SCR-DPF system, the NOx conversion performance of
`heavy duty SCR-DPF system can be further improved. This
`can enable heavy duty engines to operate with higher engine
`out NOx while still meeting tailpipe emissions leading to
`improved vehicle fuel economy.
`• The SCR-DPF system demonstrated better passive
`regeneration capability under higher engine out NOx
`conditions as compared to the CSF system under lower engine
`out NOx. Therefore, when operated with higher engine out
`NOx (>2.5 g), the SCR-DPF system will experience less
`frequent active regeneration events and thus further reduce
`
`fuel penalty. It is off-course understood that the regeneration
`strategy with SCR-DPF needs to be optimized along with
`engine out emissions, in order to take advantage of this.
`
`REFERENCES
`1. Lee, J.H., Paratore, M.J., and Brown, D.B., “Evaluation
`of Cu-Based SCR/DPF Technology for Diesel Exhaust
`Emission Control,” SAE Int. J. Fuels Lubr. 1(1):96-101, 2008,
`doi:10.4271/2008-01-0072.
`2. Chang, R., Chen, H.Y., Fedeyko, J.M., Andersen, P.J.
`Thermal Durability and Deactivation of Cu-zeolite SCR
`Catalyst. 20th North American Catalysis Society Meeting,
`June 2007
`3. Cheng, Y., Lambert, C.K., Kwak, J.H., Peden, C.H.F..
`Understanding the Deactivation Mechanisms of Cu/Zeolite
`SCR Catalysts in Diesel Application. US Department of
`Energy Diesel Engine Emissions Reductions (DEER)
`Conference, Dearborn, August 2008
`4. Ballinger, T., Cox, J., Konduru, M., De, D., Manning, W.,
`Andersen, P. J.. Evaluation of SCR Catalyst Technology on
`Diesel Particulate Filters
`
`CONTACT INFORMATION
`Mojghan Naseri
`380 Lapp Rd
`Malvern, PA 19355
`Phone: (484) 320-2236
`naserm@jmusa.com
`
` SAE Int. J. Engines | Volume 4 | Issue 1
`
`1808
`
`BASF-2011.011
`
`

`
`ACKNOWLEDGMENTS
`The authors would like to thank everyone at Johnson Matthey
`who contributed to this work through catalyst preparation,
`characterization and evaluations. We would also like to thank
`Johnson Matthey for permission to publish this paper.
`
`DEFINITIONS/ABBREVIATIONS
`CSF
`
`Catalyzed Soot Filter
`
`SCR
`
`DPF
`
`Selective Catalytic Reduction
`
`Diesel Particulate Filter
`
`SCR-DPF
`SCR coated diesel particulate filter
`
`DOC
`
`NOx
`
`PM
`
`ANR
`
`SAE
`
`Diesel Oxidation Catalyst
`
`Nitrogen oxides
`
`Particulate matter
`
`Ammonia to NOx ratio
`
`SAE Int. J. Engines | Volume 4 | Issue 1
`
`1809
`
`BASF-2011.012