1

Urea SCR and DPF System for Tier 2 Diesel Light-Duty Trucks

Christine Lambert, Giovanni Cavataio, Yisun Cheng, Douglas Dobson, James Girard, Paul Laing,

Joseph Patterson, Scott WilliamsDiesel Exhaust Aftertreatment

Ford Research & Adv Engineering

August 24, 2006

DEER 2006 8/24/2006

2

Presentation Overview

1.Department of Energy Program Overview

2.Final System Durability and Results 3.Post Mortem Phase 4.On-going Catalyst Development 5.Conclusions

DEER 2006 8/24/2006

3

1. DOE Program Overview

DEER 2006 8/24/2006

4

Tier 2 Emission Standards

• Tier 2 Bin 5 / LEVII standards represent 90-95% NOx and PM reduction from Tier 1 standards for diesels.

Standard NOx (g/mi) PM (g/mi) Tier 1 (100k mi) 1.25 0.10 Tier 2 Bin 5 (120k mi) 0.07 0.01

• NOx and PM control remain a challenge for diesels.

DEER 2006 8/24/2006

5

Program Objectives (2001)

• 0.07 g/mi NOx

• 0.01 g/mi PM

• 120,000 miles of durability

DEER 2006 8/24/2006

6

Aftertreatment Selection

• Particulate Control – catalyzed DPF (CDPF)

• NOx Control 1 – HC SCR using diesel fuel

• NOx Control 2 – Lean NOx Trap (LNT)

• NOx Control 3 – SCR with ammonia-based reductant

(SCR = Selective Catalytic Reduction)

DEER 2006 8/24/2006

7

Typical Performance Curves of Slightly Aged Catalysts

NO

x C

onve

rsio

n (%

)

100Urea SCR 90

80HD Dyno

Cert 120k Std.

70

60LNT

50

40

HC SCR30

20 LD FTP LD US0650k and10 4k Std.120k Stds.

0

0 100 200 300 400 500 600 700

Catalyst Temperature (°C)

DEER 2006 8/24/2006

8

Simulated FTP NOx Conversion vs. FTP-75 Fuel Economy Penalty

0.0% 2.0% 4.0% 6.0% 8.0% 10.0% FTP Fuel Economy Penalty

0 10 20 30 40 50 60 70 80 90

100

FTP

N O

x C

onv e

rs io

n (%

)

LNT + filter

HC SCR + filter

Urea SCR + filter

3% due to filter

DEER 2006 8/24/2006

9

Urea SCR Chemistry urea decomposition:

O

heat HNCO + NH3C

heatH2N NH2 H2Ourea CO2 + NH3

NO reduction: x

4NO + 4NH3 + O2 4N2 + 6H2O 6NO2+ 8NH3 7N2 + 12H2O 2NH3 + NO + NO2 2N2 + 3H2O “fast SCR”

SCR Catalyst Types: 1) vanadia and 2) base metal/zeolite

DEER 2006 8/24/2006

10

NOx Activity Profiles for Cu, Fe, and V Based SCR FormulationsHTA 64hrs @ 670°C, 30,000/h

300 350 400 450 500 550 600 650

Inlet Gas Temperature (ºC)

• Cu/zeolites are best at low temperatures

• Fe/zeolites perform well at high temperatures

• Vanadium based SCRs are not appropriate for North America

100

90

80

70

60

50

40

30

20

10

0

100 150 200 250

Cu-Based SCR

Fe- Based SCR

Vanadium Based SCR

FTP US06

Gro

ss N

Ox

conv

ersi

on (%

)

DEER 2006 8/24/2006

11

LDT Exhaust System (NOx)90% FTP NOx conversion, 0.07 g/mi TP NOx

urea

DOC

NOx sensor

SCR

DOC DOC

CDPF

Spray Target

exhaust flow Base Metal/

Zeolite

to engine intake

• Engine-out NOx lowered by 40% with increased EGR • Low tailpipe NOx achieved with rapid warm-up strategy

• lower thermal mass upstream of catalyst system • engine calibration changes during cold start (post injection & inc. idle speed)

DEER 2006 8/24/2006

12

Diesel Fuel Properties

• ExxonMobil blended 14,000 gallon batch to represent typical 2007 ULSD

Est. Avg. Proposed Program Proposed ‘06 Diesel DOE Prog. Fuel 2007

Fuel Property Properties Min/Max Delivered Cert. Fuel Sulfur, ppm 15* 10 / 15 12.5 7 / 15 Density, kg/m3 850 820 / 850 841.1 839 / 865 Aromatics, vol. % 32 25 / 32 29.5 27 min Polyaromatics, wt. % 10 6 / 11 11.0 no spec Cetane number 46 44 / 48 44.9 40 / 50 T50, C 267 250 / 280 249 243 / 282 T90, C 306 300 / 320 307 293 / 332

* As delivered to the vehicle

DEER 2006 8/24/2006

EPA

-75

Wei

ghte

d (g

/mile

)

13

Weighted Tailpipe Emissionswith Low-mileage Catalysts on LDT

0.055

0.60

0.83

0.45

0.76

0.17

0.062

0.85

0.015

0.16 0.14

0.047 0.042

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

NMHC CO NOX

System 1

3' Injector to SCR

Deflector/mixer, long inlet cone

Larger DOC, upstream injection with spray target Turbo & EGR modifications, post injection

2.01

Reduced tailpipe

NOx

PM: 2-5 mg/mi

Increased distance to SCR

Baseline system FT

P-75

DEER 2006 8/24/2006

14

Low-mileage FTP-75 Emissions with 6000 lb LDT gr

ams/

mile

0.20

0.18

0.16

0.14

0.12

0.10

0.08

0.06

0.04

0.02

0.00

0.129 (92%)

0.055

0.024

1.99

0.019 (81%)

0.051

0.013 (94%)

.022

0.015 (86%)

0.042 (97%)

0.014

THC

4.2 2.00 (78%)

CO

Bag 3 Bag 2 Bag 1

Tier 2 - Bin 5 Standard, 120k

(Catalyst efficiency)0.047 (89%)

PM ~ 2 mg/mi

NOX NMHC

• Emissions were below 120k mi Tier 2 Bin 5 standards

DEER 2006 8/24/2006

15

2. Final System Durability and Results

DEER 2006 8/24/2006

16

Durability Test Definition (Dyno Aging) • Full-size Urea SCR – CDPF system was aged for 120k mi on

engine dyno with a total of 643 CDPF regenerations.

vehi

cle

spee

d (m

ph)

Ford High Speed Cycle (HSC)90

80

70

60

50

40

30

20

10

0 0 250 500 750 1000

time (s)

• Typical time at high temperature in SCR ~ 6 min per regen

• 643 regens x 6 min/regen xh/60min = 64 h

DEER 2006 8/24/2006

17

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14 Ta

ilpip

e N

Ox

(g/m

i)

Increase due to loss of post injection control

4K 4K 50K 120K

4K DOC, 120K SCR

Improvement with fresh DOC

Aging Summary: FTP-75 Weighted NOx

• Loss of DOC activity resulted in higher NOx emissions at 120k mi

DEER 2006 8/24/2006

18

Emissions With 120k mi Catalystson 6000 lb LDT (No Warmup)

4.2 2.50 (78%)

THC NMHC CO NOX

• Emissions were below 120k mi Tier 2 Bin 5 standards except for NOx

0.058

0.023

0.059 (61%)

0.055 0.042 (81%)

.027

0.027 (77%)

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

gram

s/m

ile Bag 3 Bag 2 Bag 1

Tier 2 - Bin 5 Standard, 120k

(Catalyst efficiency)

0.141 (82%) 0.128 (74%)

0.029 (96%) Tailpipe NH3: 0 N2O selectivity: 15% PM: 1.2 mg/mile

DEER 2006 8/24/2006

19

Emissions With 120k mi DOC and Lab Aged Improved SCR on 6000 lb LDT (No Warmup)

gram

s/m

ile0.20

0.18

0.16

0.14

0.12

0.10

0.08

0.06

0.04

0.02

0.00

0.092 (87%)

0.051 (68%)

0.015 0.036 (78%)

0.013 (95%) 0.037 (91%)

0.017 (88%) 0.018 (87%)

0.018 (97%)

THC NMHC

4.2 1.67 (81%)

CO

Bag 3 Bag 2 Bag 1

0.081 (85%)

Tier 2 - Bin 5 Standard, 120k

(Catalyst efficiency)

NOX

• Improved SCR catalyst was less sensitive to NO2/NOx ratio

DEER 2006 8/24/2006

20

3. Post Mortem Phase

DEER 2006 8/24/2006

21

DOC HC and CO OxidationHC/CO Light-Off Conversion

DOC ABDOE Vehicle 120K Miles

100% T80:HC: ~70oC shift

75%

50% NMHC Conv - Inlet

T50: NMHC Conv - OutletCO Conv - Inlet

HC: ~65oC CO Conv - Outlet

shift 25%

0% 100 150 200 250 300 350 400 450 500

Temperature (Deg C)

• Key deactivation of inlet is chemical poisoning due to phosphorous deposition. • Key deactivation of outlet is due to fuel combustion required for DPF regen.

Con

vers

ion

Effic

ienc

y

DEER 2006 8/24/2006

22

DOC NO OxidationNO2:NOx

DOC AB : 120K Miles

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

% N

O2 o

f Tot

al N

Ox

Inlet Core Outlet Core

Better

100 200 300 400 500 600 700

Temperature (C)

• NO oxidation is more deactivated at the outlet of the 120k mi engine aged DOC

DEER 2006 8/24/2006

23

DOC Fuel Quench Temperature FQT Results

DOC AB : 120K Miles

0

50

100

150

200

250

300

350

400

450 M

inim

um S

afe

FQT

Tem

pera

ture

(deg

C)

DOC AB Inlet 1 DOC AB Outlet 1

Better

• DOC outlet requires an inlet of 425°C to maintain DPF regeneration conditions.

DEER 2006 8/24/2006

24 Post Mortem of 120k mi SCR – Core#1 NO only and SV=30,000/hr

-40

-20

0

20

40

60

80

100

Gro

ss N

Ox

conv

ersi

on (%

)

Inlet

Mid1

OutletFresh Mid2

100 150 200 250 300 350 400 450 500 550 600 650

Inlet Gas Temperature (ºC)

• 120k mi engine aging of SCR catalyst upstream of filter was non-uniform • Outlet of engine aged SCR correlates well to the 64hr/670°C hydrothermal aging • Inlet was most severely aged – work ongoing to understand

DEER 2006 8/24/2006

25

-40

-20

0

20

40

60

80

100 G

ross

NO

x co

nver

sion

(%)

Core #1 Core #2

Core #3

Deactivation of Inlet of 120k mi SCR NO only and SV=30,000/hr

100 150 200 250 300 350 400 450 500 550 600 650

Inlet Gas Temperature (ºC)

• Severe deactivation is observed at inlet and across the radius

DEER 2006 8/24/2006

26

Next Steps for DOC and SCR Post Mortem

• Investigate possible deactivation mechanisms: • Thermal deactivation due to DPF regeneration events

• Chemical poisoning from oil contamination

• Washcoat adhesion

• Contamination from urea by-products (SCR only)

• Develop new formulations that are more robust

DEER 2006 8/24/2006

27

4. On-going Catalyst Development

DEER 2006 8/24/2006

28

DOC DevelopmentC

onve

rsio

n Ef

ficie

ncy

HC/CO Light-Off Conversion NO2:NOxComparison of DOC Improvements Comparison of DOC Improvements 100%

CO 100%

90% DOE Program DOC AB New Formulation DOC AV

75% 80%

50%

25%

HC

% N

O2 o

f Tot

al N

Ox 70%

60%

50%

40%

30%

20% 0% CO DOE Formulation AB

CO New Formulation AV 10%100 150 200 250 300 350 400 450 500 HC DOE Formulation AB

HC New Formulation AV 0%

-25% 100 200 300 400 500 600

Temperature (Deg C) Temperature (C)

• HC and CO light-off has • NO2 generation has improved by ~ 20°C improved by ~10%.

DEER 2006 8/24/2006

29

SCR Development: Importance of NH3 Storage

0

10

20

30

40

50

60

70

80

90

100 %

NO

x C

onve

rsio

n

Increasing NH3 exposure

0 100 200 300 400 500 600

Inlet Temperature, °C

• NOx Conversion of SCRs is strongly related to NH3 storage

DEER 2006 8/24/2006

30

40

30

SCR Development: Benefits of Over-Dosing NH3 at High Temperature Low Temperature SCRSteady State Performance

Aged 64hrs@ 670°C, SV=30,000/hr, NO only

NOx Conversion - All FG NOx as NO - Varied Alpha, 350 ppm NO NH3 Slip - All FG NOx as NO - Varied Alpha, 350 ppm NO NOx Conversion NH3 Slip 100 800

Alpha = 0.7Alpha = 0.9Alpha = 1.0Alpha = 1.1Alpha = 1.2Alpha = 1.5Alpha = 2.0

SV=30k

No NH3 Slip

90 700

80 600

70

NO

x co

nver

sion

(%)

60

50

NH

3 Slip

(ppm

) 500

400

Alpha = 0.7Alpha = 0.9Alpha = 1.0

300 SV=30k

Alpha = 1.1 200 20 Alpha = 1.2

Alpha = 1.510 100Alpha = 2.0

0 0 100 150 200 250 300 350 400 450 500 550 600 650 100 150 200 250 300 350 400 450 500 550 600 650

Catalyst Temperature (ºC) Catalyst Temperature (ºC)

• Excess gas phase NH3 helps high • NH3 slip is controlled when over-temperature but no improvement is dosing above 450°C possible below 200°C

DEER 2006 8/24/2006

31

SCR Development - Never-to-Exceed Temperature1hr Aging - SV = 30,000/hr - NO only

0

10

20

30

40

50

60

70

80

90

100 G

ross

NO

x co

nver

sion

(%)

NTE = 800°C 650C

750C

800C

850C

900C

950C

100 150 200 250 300 350 400 450 500 550 600 650

Inlet Gas Temperature (ºC)

• Robustness to occasional high temperatures during DPF regeneration is required

DEER 2006 8/24/2006

32

Conclusions• Urea SCR has most potential to reach Tier 2 for light-duty trucks. Base metal

zeolites are superior to vanadia for NA applications.

• After 120k mi of engine aging, a DOC-SCR-DPF system met Tier 2 standards except for NOx. A new SCR formulation that was less sensitive to inlet NO2/NOx ratio resulted in tailpipe NOx that approached the standard.

• Post-mortem testing of the 120k mi catalysts revealed non-uniform activity. The outlet of the DOC and inlet of SCR were most severely deactivated.

• Improvements were made in DOC formulation for HC, CO and NO oxidation.

• Pre-stored NH3 and overdosing of NH3 increased overall activity of base metal/zeolite SCR catalysts.

• Base metal/zeolites are robust enough to handle DPF regeneration temperatures.

DEER 2006 8/24/2006

33

Acknowledgements

DOE DE-FC26-01NT41103

Ford Brendan Carberry, Dick Chase, Bob Hammerle, Dave Kubinski, Santhoji Katare, Jeong Kim, Cliff Montreuil, Rick Soltis, Devesh Upadhyay, Michiel van Nieuwstadt, and many others

FEV Erik Koehler, Dean Tomazic

Exxon Mobil Rich Grosser, Marcus Moore, Mike Noorman, Charlie Schleyer

DEER 2006 8/24/2006