Non-uniform Aging on Super Duty Diesel Truck Aged Urea Cu/Zeolite SCR Catalysts

Yisun Cheng, Hungwen Jen, Mark Jagner, Christine LambertFord Motor Company

Ja Hun Kwak, Do Heui Kim, Charles H.F. PedenPacific Northwest National Laboratory

September 28, 20102010 DEER Conference

2

Background• Previous studies

– the deactivation of engine aged SCR catalysts is not uniform– the inlet section of the catalyst brick deactivating the most

• This study– to better understand this non uniform aging phenomena

especially the inlet section – Cu/zeolite SCR catalysts aged for 50K miles on a Super

Duty diesel truck – analyses including catalyst activity evaluation and catalyst

characterization, such as BET surface area, TPR, XRF, XPS and TEM.

3

0102030405060708090

100

100 150 200 250 300 350 400 450 500 550 600 650 700Inlet Gas Temperature, °C

NO

x C

onve

rsio

n, %

NOx conv M1

NOx conv M2

NOx conv M3

NOx conv M5

Non-uniform NOx ConversionNOx-NH3 SCR Steady State, SV=30K, 350ppm NO/350ppm NH3

inlet 1st inch

rest of brick

4

1st Inch Deactivated the MostNOx-NH3 SCR Steady State, SV=30K, 350ppm NO/350ppm NH3

0

10

20

30

40

50

60

70

80

90

100

100 150 200 250 300 350 400 450 500 550 600 650 700

Inlet Gas Temperature, °C

NO

x C

onve

rsio

n, %

NOx conv A1

NOx conv AM1

NOx conv M1

NOx conv CM1

inlet 1st inch from different location

5

0102030405060708090

100

100 150 200 250 300 350 400 450 500 550 600 650 700Inlet Gas Temperature, °C

NO

x C

onve

rsio

n, %

NOx 0-0.25 NOx 0.25-0.5NOx 0.5-0.75 NOx 0.75-1.0NOx 1.0-1.25 NOx 1.25-1.5

Inlet Section: Non-uniform NOx ConversionNOx-NH3 SCR Steady State, SV=120K, 350ppm NO/350ppm NH3

inlet 0.25 inch

6

0102030405060708090

100

100 150 200 250 300 350 400 450 500 550 600 650 700Inlet Gas Temperature, C

NO

x C

onve

rsio

n, %

NOx % 1st normal gas directionNOx % 1st reversed gas directionNOx % 6th normal gas directionNOx % 6th reversed gas direction

1st inch deactivation – the deterioration of NOx conversion on the 1st inch disappears after reversing the gas flow direction.

77

Surface Area

• Surface area decreased but the adsorption profiles are very similar → deactivation doesn’t arise from structural degradation.

• Exactly same surface area even after 1st section calcined at 550oC → deactivation likely not due to carbon deposition.

• Some surface area decrease likely arises from loss of the catalytic component by attrition.

• Deactivation is not related to changes in zeolite structure.

Surface area (m2/g)*

161

152

109

1101

123133131124122

Sample

Fresh

Lab aged

Engine aged

1st

2nd

3rd

4th

5th

6th

*Catalyst + support mixture1 after calcine at 550oC 2h

88

1st inch XPS&XRF – C, S, P, Zn

0

5

10

15

20

25

30

0

1

2

3

4

5

6

0 25 50 75 100 125 150

Con

cent

ratio

n(at

omic

%)

Length (mm)

C →

P

Zn

• Significant carbon deposition of front side(~ 7 % for fresh sample and ~ 1 % for lab aged sample).

• Carbon deposition may account for some activity loss, especially 1st run.

• P and Zn deposition on the inlet end of the monolith.

• Practically no sulfur in the samples.

XRF 1st 2nd 3rd 4th 5th 6th

P 0.043 0.020 0.015 0.010 0.009 0.006S 0.006 0.006 0.005 0.005 0.005 0.004Zn 0.008 0.003 0.003 0.002 0.002 0.002

99

1st inch XPS - Cu• Very front part of monolith

shows a very small Cu2+ peak related with Cu sintering(?)

• #1 located 0.5 mm from front end• Each spot spaced by 4 mm

1

7

1 inch

front

back

925930935940945950955960965970

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

Binding Energy (eV)

Nor

mal

ized

Inte

nsity

Position #2

Position #7 outlet

Position #1 inlet

Position #3

Position #4

Position #5

Position #6

Cu 2p3/2

Cu 2p1/2

1010

1st inch – TEM• Morphology shows little

change after engine aging other than perhaps including somewhat increased amorphous (or mixture with support(?)) areas.

• No evidence for Cu sintering

11

1st inch – TPRTPR with 10°C/min to 600°C using 9%H2/Ar

8.75

8.8

8.85

8.9

8.95

9

9.05

9.10 100 200 300 400 500 600

T (°C)

H2

(%)

Veh-50k-brk1-inlet-1/8 inch

Veh-50k-brk2-outlet

The change in TPR patterns indicates that the aging impacted the Cu in SCR catalyst differently from inlet to outlet.

12

Summary• The inlet section of SCR catalyst was deactivated the most. The

performance of the majority of SCR catalyst was uniform and as expected due to thermal aging.– Overall surface area drops due to loose the active component.– XPS results shows very small amount of 935.9eV band which will be related with

no evidence for Cu sintering in TEM. But, the change in TPR patterns clearly indicates that the different Cu states in the inlet section.

– Significant C, P and Zn in very front region of engine aged brick.– The deterioration of NOx conversion on the 1st inch disappeared after reversing

the gas flow direction.

• Changes of Cu state and high levels of C, P and Zn impurities in the very front region (no more than 1 inch) might explain the more severe deactivation of the inlet section of the SCR catalyst.

• The above results suggest that the inlet section of the brick experienced all the aging factors in the most severe way, and that this section deactivates in a more complicated manner than the rest of the brick.

1313

Acknowledgements• Funding from the U.S. Department of Energy (DOE),

Freedom Car and Vehicle Technologies Program. • Studies at PNNL were performed in the

Environmental Molecular Sciences Laboratory (EMSL), a National Scientific User Facility funded by U.S. DOE, Office of Science/Biological and Environmental Research.

• PNNL is a multi-program national laboratory operated for the U.S. Department of Energy by Battelle Memorial Institute under contract number DE-AC06-76RLO 1830.