catalyst directions for low nox emissions...0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 t2b5...

Catalyst Directions for Low NOx Emissions

Tom Pauly

September 20, 2018

Topics

Low NOx Requirements and Challenges

System and Technologies

Technology Details

• SCR

• SCR on Filter (SDPF)

• PNA

Conclusion

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T2B

5

T2B

4

T2B

3

T2B

2

T2B

1

LE

V

UL

EV

SU

LE

V

LE

V160

UL

EV

125

UL

EV

70

UL

EV

50

SU

LE

V30

SU

LE

V20

NM

OG

+N

Ox (

g/m

i)

NO

xN

MO

G

FED T2 LEVIII / FED T3 LEVII

NOx Emission Standards

Light Duty

100%

0%

Sa

les s

ha

re

2010 20202010 California and Federal

Heavy Duty

ARB

Voluntary Potential

Greenhouse Gas RegulationsEfforts to reduce CO2 increase challenges to meet ‘Low NOx’

CAFE/CO2

Light Duty Heavy Duty

Freeze at 2021 levels?

Challenges to Achieving Low NOx

5

Cold Start FTP:Example NOx Performance

(above)FTP performance requirements

for a 3.3g NOx /bhp-hr engine

Heavy Duty

NOx Efficiency requirements of ~

>95% cFTP & ~100% hFTP cycles (below)

Light Duty

Heavy Duty

SAE INTERNATIONAL

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1800

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50

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250

300

1600 1800 2000 2200 2400 2600 2800 3000 3200

NO

x M

ass

Rat

e,

g/h

r

Tem

pe

ratu

re, d

egC

Time, sec

Turbine Out T Aftertreatment In T Aftertreatment Out T TP NOx EO NOx

Low Load / Vocational / Urban Driving (Heavy Duty)

6

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x M

ass

Rat

e,

g/h

r

Tem

pe

ratu

re, d

egC

Time, sec


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800 900 1000 1100 1200 1300 1400 1500 1600

NO

x M

ass

Rat

e,

g/h

r

Tem

pe

ratu

re, d

egC

Time, sec


Stage 1 ULN (burner off)

96% conversion

Current – 47% conversion

Low Load Profile – 6% max powerLow Load Profile – 9% max power

Current – 83% conversion

• Significant portion of operations at Low Load

• Large contribution to NOX emission inventories

• Gap between certification and Low Load field performance

• Consensus among all parties that Low Load “gap” should be

addressed

• Low Load cycles, updated in-use requirements

• Example data from in-use Low Load profiles based on real-

world vehicle data

27%

50%

28%

57%

79%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

3 5 7 10 15 20 30 40 50 60 70 80 90 100

Cu

mu

lati

ve P

erc

en

tage

of

Tota

l

MAW Average Power, % max

MAW Count NOX

In-Use Data

Courtesy C.Sharp, SwRI

Topics



Technology Details

• SCR


• PNA

Conclusion

Catalyst System Configurations

8

?Diesel Oxidation Catalyst (DOC)

Catalyzed Particulate Filter (CDPF)

Selective Catalytic Reduction (SCR)

NOx Storage Catalyst (NSC)

Ammonia Slip Catalyst (ASC)

Diesel Exhaust Fluid (DEF)

Passive NOx Adsorber (PNA)

Serial Design

Light/Med Duty Heavy Duty

https://www.arb.ca.gov/research/veh-

emissions/low-nox/low-nox.htm

Catalysts Technologies for Low NOxApproaches and Challenges

9

SCR:

• Continued improvements to low temperature NOx performance

• Moving SCR function to high temperature location


• Close Coupled SCR

NOx Storage:

• Passive NOx adsorption during cold cycles with thermal release as temperature increases

General Challenges:

• NOx Conversion at <<200 °C

• Near 100% conversion in peak NOx events

• NH3 availability at temps << 200 °C

• Impact of NH4NO3 formation

Increasing Durability

• Increased warranty and useful life expectancy for HD (~1M miles)

• LD experience for most stringent Tier III regulations are often accompanied with a shift to more severe aging requirements

• Greater “Impact” of the non-thermal aging mechanisms

Topics



Technology Details

• SCR


• PNA

Conclusion

0

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50

60

70

80

90

100

150 200 250 300 350 400 450 500 550 600 650

NO

x-C

on

ve

rsio

n [%

]

Temperature [°C]

CuSCR

Next_Gen

SCR Catalyst DevelopmentNext Generation of SCR Catalysts

Material and catalyst development continues

to further extend NOx performance window to

low (and high) temperatures

Aged 16Hr750C,HT

Test Conditions

S.V.k hr-1 60

NO [ppm] 500

C3H6 [ppm] 100

NH3 [ppm] 500

O2 [%] 5

H2O [%] 5

Long Term ageing stability:

Aged 250Hr650C, HT

0

10

20

30

40

50

60

70

80

90

100

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

NO

x-C

on

vers

ion

[%

]Temperature [°C]

Next_Gen Future (sim)

SCR Catalyst DevelopmentNext Generation of SCR Catalysts

Non-zeolite materials also investigated as they

provide interesting properties resulting in a

unique performance window when compared to

Cu-SCR

• “Future” sample results (right) are

simulated on cores from experimental

powder studies

Challenges:

• Highest NOx conversion efficiency

• N2O make (not shown)

Aged 16Hr750C,HT

Temperature: 225C

“Load Jump” Conditions:

• NOx: 200 400 ppm

• NH3: 240 480 ppm

• NO2: 20 5%

• O2: 8 2%

• SV: 30 60 kh-1

SCR Catalyst DevelopmentSimulating NOx Flux during Accelerations (Load Jump)

NH3 raw

NOx raw

O2

NO2 ratio

RP: 570s

LJ: 30s

CuSCR

Next Gen

SCR Catalyst DevelopmentSimulating NOx Flux during Accelerations (Load Jump)

NH3 raw

NOx raw

O2

NO2 ratio

RP: 570s

LJ: 30s

40

50

60

70

80

90

100

0 2 4 6 8 10 12 14

avg

. N

Ox

con

vers

ion

[%

]

# Load Jump [-]

Reference fresh

Reference aged 16h700°C

SCR D-404_V04 fresh

SCR D-404_V04 aged 16h700°C

Next gen fresh

Next gen 16hrs 700C

CUSCR fresh

CUSCR 16hrs 700C

Temperature: 225C

Cycle

SCR Catalyst DevelopmentSulfur Tolerance and Recovery

After Sulfation, Cores removed and

analyzed for NOx performance at

250C, ANR = 1.0

6.7L engine

EuroVI

7 g/kWh NOx

270°C

250ppm

S fuel

DOC use for Maximum SO3

Sulfur Exposure = 2g S /L SCR

0

10

20

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50

60

70

80

90

100

350°C 400°C 450°C 500°C 550°C 600°C 650°C

NO

xco

nv.

@ 2

50

°C [

%]

Regeneration temperatures

CuSCR40

SCR D-404Next Gen

CuSCR

= 30 min

Dyno Sulfation, SGB Evaluation

0% NO2

25%NO2

50%NO2

175°C

225°C

300°C

175°C

175°C

225°C

300°C

0% NO2

25%NO2

50%NO2

SCR Catalyst DevelopmentFe-SCR

High activity with NO2/NOx at 50%

• Low N2O per NOx Converted

• Must avoid excess NO2/NOx

• Dynamic response for NOx conversion

at optimum N2O

Potential first SCR brick of hybrid system with

CuSCR

HC Storage must be managed

Aged 100h, 550°C HT

SCR Catalyst DevelopmentFe-SCR for Hybrid Fe-CuSCR System

Fe-SCR can offer superior NOx conversion if

adequate NO2 and offers benefits for low N2O

emissions per NOx conversion (vs. CuSCR)A)

B)

25% Fe/75% CuTest Procedure

• 5 WHTChot in series (NH3/NOx = 1.2)

• 6. 7 L engine, 7 g/kWh NOx

• Aged 100hr580C, HT

• 2 DOC/DPFs for different NO2 Ratio

FeS

CR

100% Cu

Low Temperature NOxNH4NO3 Formation (Fe-SCR Sample)

200°C, NO2/NO = 0;

200°C, NO2/NO = 1;

200°C, NO2/NO = 2;

175°C, NO2/NO = 2;

150°C, NO2/NO = 2

16 h, GHSV 60 k, alpha = 1.1, 1100 ppm NH3, 5% H2O, 10% O2

N2O

2.26

1.52

1.121.01

0.26 0.21 0.19 0.20 0.300.0

0.5

1.0

1.5

2.0

2.5

0.4/0.8 0.6/0.6 0.8/0.4 0.9/0.3 0/1.2 (SCRT)Sp

ec.

NO

x [g

/kW

h]

Dosing split [SCR1/SCR2]

SCR1 (VWT)

SCR2 (Cu-Zeo)

SCR Catalyst Development2 Stage SCR of “Close Coupled SCR”

7.7L, 258 KW

3.7 g/kWh

NOx (FTPhot) 23V

100h580°C (HT)

29Cu

50h700°C (HT)

ANR = 1.2 (Constant)

Potential for High Efficiency ATS (High NOx Engines)

V-SCR used here of interest for GHG PII

• High NOx Conversion/Low N2O

Low NOx likely to require NOx Conversion ≥ CuSCR

• Low Temp, “Digital” conversion w/ dosing…

Dual dosing approach allows for management of

DPF for passive soot oxidation

-40%

Topics



Technology Details

• SCR


• PNA

Conclusion

SCR on Filter (SDPF) DevelopmentNext Generation of SCR Catalysts

AS

C

DO

C

SC

R

SD

PF

DEF

0

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NO

x-C

on

vers

ion

[%

]

Temperature [°C]

CuSDPF

Next Gen SDPF0

0.2

0.4

0.6

0.8

1

1.2

Re

lative

In

cre

ase

in

Re

str

ictio

nSubstrates, washcoat and coating processes

improved to minimize flow restriction and

increased NOx Conversion

Average NOx conversion on

Step 2 of 4 Step protocol;

• t = 0 to x (10 ppm NH3 slip)

Aged 16hr800C,HT

SCR on Filter (SDPF) DevelopmentDyno Evaluation: Low and High Temperature

Next Gen

CuSDPF

Aged 16hr800C,HT

EOP LT HT

T [°C] 200 610

NO2 [%] <5 <5

SV [1k/h] 50 131

NOx [ppm] 70 500

Low Temp (LT) High Temp (HT)

SCR on Filter (SDPF)

Date

Application

SDPF established in Light

Duty applications and in few

off road application in EU

Source: Audi AG (23rd Aachen Colloquium)

Active Soot Regen

Thermal Durability, f(T)

Passive Soot Regen

Long Duration, f(t)

Light Duty

ApplicationsHeavy Duty

Fleet/Delivery…Heavy Duty

Line Haul

NO/NO2

C N2

plugs

CO2NH3

SCR PGM

sensitivity

SCR On Filter (SDPF)HDD Challenge

Significant drop in NO2 assisted soot removal, “Passive Soot Regeneration”

• Fast SCR reaction dominates the reaction limiting NO2 + C interactions

• Negatively impacts fuel economy (soot restriction and active regeneration)

Current SDPF technologies are a better fit where active soot regeneration exists at a high level

• Light/med duty, delivery vehicles and other low load operating applications

Dual urea (reductant) dosing could provide an independent tool to help manage soot

SCR On Filter (SDPF)Impact of NH3 & SCR washcoat

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

x 104

0

200

400

600

T /

°C

an

d m

ole

fra

ction

/ p

pm

time / s

0 10 20 30 40 50 60 70 80 90 1000

2

4

6x 10

-4

soot burn

rate

/ g

L-1

s-1

rel. soot loading / %

SDPF

DPF w NH3

DPF w/o NH3

time window for bottom plot

NH3 impact

SCR washcoat

impact

compared at 72 % initial loading

26

CONFIDENTIAL

SCR Materials DevelopmentImproved Zeolites via Process Improvements

16h, 750°C 16h, 800°C

Improved Synthesis

Commercial Material

27CONFIDENTIAL

SCR Materials DevelopmentNew Material Types (SDPF, LDD)

0

0.4

0.8

1.2

1.6

2

2.4

2.8

3.2

3.6

4

4.4

4.8

Reacti

on

rate

(10

-12 m

ol/g

*s),

175 C

aged 900°C fresh

Development effort proves that

further improvement of the low

temperature performance and

high temperature stability is

possible.

Topics



Technology Details

• SCR


• PNA

Conclusion

Assisted NOx release/reduction w/ purge

Thermal release of NOx still present

Focused storage window

Rich conditioning beneficial for HC/CO LO

DNC

Passive

Control

Active

Control

29

NOx Storage and Control: Brick OneActive vs. Passive DeNOx and DeSOx

NOx Emissions

HC

Em

issio

ns

PNADOC

NSC

DNC

DOC:

• Heatup (HU) and temp hold

for SCR function

• HU for CDPF Regeneration

• HU for OBD

Thermal release of NOx

Lowest T storage window

NOx reduction via rich purge

Broadest storage window

Rich conditioning beneficial for HC/CO LO

Highest desulfation temperature

NSC

PNA

Heatup (HU)

HU for CDPF Regeneration & OBD

DOC

Passive NOx Adsorber DevelopmentLow Temperature NOx Control pre-SCR Lightoff

NOx desorption

*Catalyst Volume

*

Passive NOx Adsorber DevelopmentChallenges

Cycle Challenges:

• Light Duty FTP75

• Rapid Heatup limits cold operation

• FTP72 prep cycle beneficial for SCR (NH3) not beneficial for PNA (NOx)

• Higher peak temperature exposure

• Heavy Duty FTP

• Cold operation favorable but high NOx flux rapidly fills catalyst

• Low Load Operation

• Continuous cold operation results in saturated catalyst

Technology Challenges:

• NOx capacity

• Adsorption/desorption kinetics and thermodynamics

DOC In

SCR In

CLEERS Low Temperature Protocol*

UMI_PZ1

UMI_PZ2

Conclusion

SCR will continue to be the dominant technology for future targets

• Advances continue to be made to expand the performance window into the low temperature area while also improving the ability to convert high NOx peak

• NH3 availability and NH4NO3 formation will need to be addressed

SCR on Filter (SDPF) improvements will enable introduction to applications currently in the active soot arena

• Challenges for passive soot oxidation will need to be addressed for introduction into the applications dependent on passive regeneration

• Dual urea dosing provides an independent tool to manage soot

PNA performance is promising though the NOx capacity and kinetics require noticeable improvements for the benefits to truly be realized on the transient applications

32

Thank You

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