Development of a NOx Adsorber System
for Dodge Ram 2007 Heavy Duty Pickup Truck
Aleksey Yezerets, Neal W. Currier, Bradlee J. Stroia, Junhui LiCummins Inc.
Howard Hess, Haiying Chen, Andy WalkerJohnson Matthey
2
NOx Adsorber Technology
Identified by the EPA 2007/2010 rulemaking process as a primary candidate for NOx emissions reduction
Major advancements in the fundamental understanding and application of the technology were required
Fundamental challenges[1]:
[1] Epling, Yezerets, Currier et al. “Overview of the Fundamental Reactions and Degradation Mechanisms of NOx Storage/ Reduction Catalysts”. Catalysis Reviews; V46(2004), p.163-245
Lean
Rich
NO > NO2 NO2 Storage Enrichment & ReductantEvolution
Lean
Rich Release Conversion
Lean
Rich
NO > NO2 NO2 Storage Enrichment & ReductantEvolution
Lean
Rich Release Conversion
Lean
Rich
NO > NO2 NO2 Storage Enrichment & ReductantEvolution
Lean
Rich Release Conversion
Multi-component, multi-functional catalyst: • At least 3 components,
with different functions• Both red-ox and acid-
base catalyst chemistry5 sequentially-coupled processSulfur poisoning/removal
3
LEV II-ULEV Certified Systemwith Cummins 6.7L Engine and A/T System
Close-Coupled Catalyst (2.1L)• Elliptical metallic substrate,
300 cpsi, by Emitec
NOx Adsorber Catalyst (5.2L)• Cordierite, 300cpsi by Corning
Catalyzed Diesel Particulate Filter (9.4L)• Cordierite, 200 cpsi by NGK
In-cylinder source of reductants and heat for A/T system control, enabled by:
Bosch 1800-bar Common Rail fuel system Cummins next-generation cooled EGRVariable Geometry Turbocharger
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Several Major Application Challenges
How to make NAC survive deSOx-related aging?
Trade-off between deSOx efficiency and thermal degradation
Different forms of sulfur
Reductant quality
Distribution of temperature and species across the catalyst
How to achieve maximum deNOx performance for a catalyst of a given age?
Catalyst diagnostics
Laboratory and on-board
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Tradeoff Between deSOxEfficiency and Thermal Deactivation
0
2 0 0
4 0 0
6 0 0
8 0 0
1 0 0 0
1 2 0 0
1 4 0 0
0 .0 1 .0 2 .0 3 .0 4 .0 5 .0tim e , m in
ppm
0
1 0
2 0
3 0
4 0
5 0
6 0
7 0
8 0
9 0
1 0 0
S re
mov
ed, %
S O 2 , p p m
H 2 S , p p m
C O S , p p m
S re m o ve d , % to ta l
0 5 /0 7 /0 4 - 6 0 0 C
0
2 0 0
4 0 0
6 0 0
8 0 0
1 0 0 0
1 2 0 0
1 4 0 0
0 .0 1 .0 2 .0 3 .0 4 .0 5 .0t im e , m in
ppm
0
1 0
2 0
3 0
4 0
5 0
6 0
7 0
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9 0
1 0 0
S re
mov
ed, %
S O 2 , p p m
H 2 S , p p m
C O S , p p m
S re m o v e d , % to ta l
0 4 /2 3 /0 4 - 7 5 0 C , H 2
0 2 4 6 8 1 0 1 2 1 4 1 60
5 0
1 0 0
1 5 0
2 0 0
2 5 0
3 0 0
3 5 0 7 0 0 oC
8 0 0 oC
9 0 0 oC
Pt c
ryst
allin
e si
ze (A
ngst
rom
)
T re a tin g t im e (h r )C a lc in a t io n T im e (h r)
Pt c
ryst
allit
e si
ze (A
ngst
rom
)
0 2 4 6 8 1 0 1 2 1 4 1 60
5 0
1 0 0
1 5 0
2 0 0
2 5 0
3 0 0
3 5 0 7 0 0 oC
8 0 0 oC
9 0 0 oC
Pt c
ryst
allin
e si
ze (A
ngst
rom
)
T re a tin g t im e (h r )C a lc in a t io n T im e (h r)
Pt c
ryst
allit
e si
ze (A
ngst
rom
)
600°C
750°C
deSOx T, °C
NO
x C
apac
ity
NOx Capacity Recovery after DeSOx
Sulfu
r rem
oval Therm
al
deactivation
0 2 4 6 8 1 0 1 20
2 0
4 0
6 0
8 0
1 0 0
7 0 0 o C
8 0 0 o C
9 0 0 o C4 m in 3 0 m in
NO
x up
take
(%)
O 2 t r e a t in g t im e ( h r )
700°C
800°C900°C
Unpublished Cummins dataD.H.Kim et.al. Ind.Eng.Chem.Res.2006,45, 8815
Comprehensive kinetic deSOxmodel developed by Cummins
DeSOx-related degradation understanding from PNNL/ Cummins/ JM CRADA
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S can exist on NOx adsorbercatalyst in different forms
Chemically uniform (sulfate)Morphologically different (surface/bulk)
Different Forms of Sulfur
020406080
100120140160180
400 600 800 1000T,C
ppm
020406080
100120140160180
400 600 800 1000T,C
ppm
LEAN/RICH
50/10 sec20 cycles
10min
Bypa
ss
5min
Performance test(same as previously)
LEAN
>920°CTPR
RICH4.25%H2, 5%H2O,
5%CO2, balance He
Complete removal of [S]
10°C/min
LEAN/RICH
50/10 sec20 cycles
10min
Bypa
ss
5min
Performance test(same as previously)
LEAN
>920°CTPR
RICH4.25%H2, 5%H2O,
5%CO2, balance He
Complete removal of [S]
10°C/min
[S] form depends on the formation conditions
Can be affected by subsequent re-distribution
Different forms of [S] have different impact on NOx performance
Examples of different forms of S
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0
30
60
90
120
150
1250 1350 1450 1550 1650 1750time, sec
ppm
Freshly degreened (different test)After SulfationAfter the 300 and 350C points
Original performance
After SO2Poisoning
After ~1h NOxcycling
Sulfated a “Degreened” LNT, Lost ~1/3 of NOx capacityApparent re-distribution of sulfur after ~1 hour normal NOx operation in the 300-400°C range
No sulfur loss confirmed by subsequent temperature-programmed reduction
Example: NOx Adsorber “Memory”
ppm
NO
x
8
Important to distinguish between forms of sulfur
No reason to attempt removing “bulk” sulfur –• Additional thermal
exposure
• Minimal advantage for the “dynamic” NOX capacity
Inherently non-homogeneous species distribution in an integral device
Different Forms of Sulfur/ Distribution Across catalyst
0-1" 1-2" 2-3" 3-4" 4-5"Distance from the inlet face
gS/L
Surface, g/L
Bulk, g/L
Micro-core analysis: minimally invasive (<1cm3 sample) NOx performance, [S] amount and formmultiple locations in the catalyst
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Gradients in integral devicesGas speciesTemperature Surface species
Pioneering role of NTRC(FEERC)/Cummins CRADA
Importance of Spatially-Resolved Measurements
6 0 &8
- 5
1 5
3 5
5 5
7 5
9 5
0 1 0 2 0 3 0 4 0 5 0 6 0 7 0
T im e
Tem
p o s 1p o s 2p o s 3p o s 4p o s 5p o s 8p o s 1 1p o s 1 4p o s 2 0
-5
15
35
55
75
95
Time, sec
ΔT,
°C
Rich
10 20 30 40 50 60
Pos 1 Pos 20
Sample for IR-thermography
6 0 &8
- 5
1 5
3 5
5 5
7 5
9 5
0 1 0 2 0 3 0 4 0 5 0 6 0 7 0
T im e
Tem
p o s 1p o s 2p o s 3p o s 4p o s 5p o s 8p o s 1 1p o s 1 4p o s 2 0
-5
15
35
55
75
95
Time, sec
ΔT,
°C
Rich
10 20 30 40 50 60
Pos 1 Pos 20
Sample for IR-thermography
Rich: 2% O2, 4%CO, 5%CO2, 5% H2O, N2, Tin=300°CSPACI-MSP-Thermography
Additional work sponsored by Cummins at U. Waterloo
IR thermographySpaRC
10
0
0.005
0.01
0.015
0.02
0.025
0.03
0 10000 20000 30000 40000 50000
Total Reductant (H2 equivalent), ppm
Nor
mal
ized
deS
Ox
rate
H2 CO
C3H6 C3H8
Reductant Quality
0
50
100
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400
0.0 1.0 2.0 3.0 4.0 5.0time, min
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COS, ppmH2S, ppm
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SO2, ppmCOS, ppmH2S, ppm
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1400
0.0 1.0 2.0 3.0 4.0 5.0time, min
ppm
SO2, ppmCOS, ppmH2S, ppm
H2
C3H6
C3H8
• CO and H2• C3H6 (model highly reactive HC) • C3H8 (model poorly reactive HC)
Use of efficient reductantsallows to minimize time at deSOx conditions
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Reductant Quality
In-situ H2 generation may play a major role in deSOx (and deNOx) efficiency
Complex spatial profileBalance in-cylinder and in-situ H2 generation options
J.Parks, M.Swartz, S.Huff, B.West. FEERC/ORNL. DEER 2006, August 20-24, 2006, Detroit, MI
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Summary: Balancing Sulfur Removal vs. Thermal Deactivation
Minimize excessive temperature exposure Accurate control of deSOx temperatureMinimize temperature gradients across the NACOptimize reductant qualityTarget only relevant forms of sulfur Capable laboratory diagnostic tools
Loading of removable sulfur
NO
xC
apac
ity Thermal
agingdeSOx
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SummaryUnderstanding the complexity of the system components (catalysts, sensors) during the design stage allows to develop robust, apparently simple solutions:
In the final product, complexity is reflected in the controls and diagnostics
Significant opportunities remain for further system optimization, e.g.:
Better understanding of the fundamentals of the components behavior (catalysts, sensors), including development of predictive models, would allow for tighter integration Laboratory and on-board diagnostics
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Acknowledgements
PNNL: Chuck Peden, Do Heui Kim, George Muntean, Tom Gallant, et al.
FEERC (ORNL) Bill Partridge, Jae-Soon Choi, Jim Parks et al.
HTML (ORNL): Tom Watkins, Larry Allard, Ray Johnson et al.
US DOE: Office of Freedom Car and Vehicle Technologies: Partial support through PNGV / Freedom Car program