+ All Categories
Home > Documents > Investigation of Sulfur Deactivation on Cu/Zeolite SCR ... · PDF fileInvestigation of Sulfur...

Investigation of Sulfur Deactivation on Cu/Zeolite SCR ... · PDF fileInvestigation of Sulfur...

Date post: 28-Mar-2018
Category:
Upload: trinhduong
View: 230 times
Download: 3 times
Share this document with a friend
19
Investigation of Sulfur Deactivation on Cu/Zeolite SCR Catalysts in Diesel Application Yisun Cheng, Christine Lambert Ford Motor Company Do Heui Kim, Ja Hun Kwak, Charles H.F. Peden Pacific Northwest National Laboratory August 4, 2009 2009 DEER Conference
Transcript
Page 1: Investigation of Sulfur Deactivation on Cu/Zeolite SCR ... · PDF fileInvestigation of Sulfur Deactivation on Cu/Zeolite SCR Catalysts in Diesel Application. ... Fe Zeolite catalyst

Investigation of Sulfur Deactivation on Cu/Zeolite SCR Catalysts in Diesel Application

Yisun Cheng, Christine Lambert

Ford Motor Company

Do Heui Kim, Ja Hun Kwak, Charles H.F. Peden

Pacific Northwest National Laboratory

August 4, 2009

2009 DEER Conference

Page 2: Investigation of Sulfur Deactivation on Cu/Zeolite SCR ... · PDF fileInvestigation of Sulfur Deactivation on Cu/Zeolite SCR Catalysts in Diesel Application. ... Fe Zeolite catalyst

Urea SCR Catalysts in Diesel Application

• Cu, Fe Zeolite catalyst

• Leading candidate for treatment of NOx emission for North America Diesel applications.

• Better options for Heavy-duty Diesel Engines

• Already commercialized in Europe

• Durability issues: – Dealumination and zeolite structure collapse due to

hydrothermal aging at high temperature

– Cu sintering due to the reducing agents

– Poisonings: such as S, P, Zn

2

Page 3: Investigation of Sulfur Deactivation on Cu/Zeolite SCR ... · PDF fileInvestigation of Sulfur Deactivation on Cu/Zeolite SCR Catalysts in Diesel Application. ... Fe Zeolite catalyst

SOx on Cu/zeolite SCR catalysts

• Sulfur poisoning is still a durability issue for base metal/zeolite SCR catalysts, especially for Cu/Zeolite SCR catalysts.

• Most studies have been based on SO2.

• As DOCs are employed upstream of the SCR catalysts, it is likely that a portion of the SO2 are oxidized into SO3.

• Investigation of the impact of SO3 on Cu/zeolite SCR catalysts is important.

3

Page 4: Investigation of Sulfur Deactivation on Cu/Zeolite SCR ... · PDF fileInvestigation of Sulfur Deactivation on Cu/Zeolite SCR Catalysts in Diesel Application. ... Fe Zeolite catalyst

Experimental

• Catalysts: – Fully formulated monolith Cu/zeolite.

– Six (6) 1x1 samples.

• Procedure: – Hydrothermal aging at 670C for 20 hr. – S poisoning:

• 40ppm for 1.5hr with SO2 or SO3 at

• 200°C, 300°C, 400°C

• Total S throughput equivalent to 500 miles with 350ppm sulfur fuel

– DeSOx: 170°C to 770°C at 5°C/min.

• Characterization: – XPS, Cu XAFS, Cu XANES

4

Page 5: Investigation of Sulfur Deactivation on Cu/Zeolite SCR ... · PDF fileInvestigation of Sulfur Deactivation on Cu/Zeolite SCR Catalysts in Diesel Application. ... Fe Zeolite catalyst

SCR Activity Testing Sequence

Hydrothermal Aging

Test #1: Baseline

Sulfation with SO2 or SO3

Test #2: Sulfation effect 770 oC

De-Sulfation with O2, H2O and CO2 up to 770C: TPD SOx

desorption

Test #3: DeSOx effect 200 oC

5

Page 6: Investigation of Sulfur Deactivation on Cu/Zeolite SCR ... · PDF fileInvestigation of Sulfur Deactivation on Cu/Zeolite SCR Catalysts in Diesel Application. ... Fe Zeolite catalyst

NOx Activity After Thermal Aging

100

90 Almost 100% conversion after 200C

80

70 Test1, Sample 1

60 Test1, Sample 2

50 Test1, Sample 3

40 Test1, Sample 4

30 Test1, Sample 5

20 Test1, Sample 6 10

0

100 125 150 175 200 225 250 275 300 325 350

Inlet Gas Temperature (ºC) 6

NO

x C

on

ve

rsio

n (

%)

Page 7: Investigation of Sulfur Deactivation on Cu/Zeolite SCR ... · PDF fileInvestigation of Sulfur Deactivation on Cu/Zeolite SCR Catalysts in Diesel Application. ... Fe Zeolite catalyst

     

300 325 350

SO2 vs. SO3 – The impacts on NOx conversion N

Ox C

on

ve

rsio

n (

%)

200C SO2, T2

300C SO2, T2

400C SO2, T2

200C SO3, T2

300C SO3, T2

400C SO3, T2

T1

Significant deactivation by SO3!

100

90

80

70

60

50

40

30

20

10

0

100 125 150

NOx Conversion SV = 30,000/hr - NO only

175 200 225 250 275

Inlet Gas Temperature (ºC) 7

Page 8: Investigation of Sulfur Deactivation on Cu/Zeolite SCR ... · PDF fileInvestigation of Sulfur Deactivation on Cu/Zeolite SCR Catalysts in Diesel Application. ... Fe Zeolite catalyst

275 300 325 350

NOx Activity Recovered after DeSOx

0

10

20

30

40

50

60

70

80

90

100

NO

x C

on

vers

ion

(%

)

Test1, after thermal aging

Test2, after SO3 aging at 400C

Test3, after deSOx

100 125 150 175 200 225 250

Inlet Gas Temperature (ºC) 8

Page 9: Investigation of Sulfur Deactivation on Cu/Zeolite SCR ... · PDF fileInvestigation of Sulfur Deactivation on Cu/Zeolite SCR Catalysts in Diesel Application. ... Fe Zeolite catalyst

SO2 vs. SO3 – Sulfur released during deSOx

SO2 Measurement During DeSOx

45 More SO2 desorption for the sample sulfated with SO3

40 SO2/200C/ afterT2

35 SO2/300C/ afterT2

SO2/400C/ afterT2 30

SO3/200C/ afterT2

SO3/300C/ afterT2 25 SO3/400C/ afterT2

20

15

10

5

0

150 250 350 450 550 650 7509

Inlet Gas T, C

SO

2, P

PM

Page 10: Investigation of Sulfur Deactivation on Cu/Zeolite SCR ... · PDF fileInvestigation of Sulfur Deactivation on Cu/Zeolite SCR Catalysts in Diesel Application. ... Fe Zeolite catalyst

10

Sulfated with SO3: XPS S 2p region

3500

3000

2500

2000

1500

1000

500

0

165 170 175 180

c/s

Hydrothermal aging

Sulfated with SO3 at 200C

Sulfated with SO3 at 300C

No observable sulfur for the

sample sulfated with SO2

Binding Energy (eV)

Only sulfates exists, only if sulfated with SO3. The sample sulfated with

SO2 does not contain sulfur on the catalyst.

Sulfates formed during reaction at 200C is larger than those at 300C.

Page 11: Investigation of Sulfur Deactivation on Cu/Zeolite SCR ... · PDF fileInvestigation of Sulfur Deactivation on Cu/Zeolite SCR Catalysts in Diesel Application. ... Fe Zeolite catalyst

NOx Conversion: sulfated with SO3 at different T

0

10

20

30

40

50

60

70

80

90

100

NO

x C

onvers

ion (

%)

Test2, SO3 aged at 200C

Test2, SO3 aged at 300C

Test2, SO3 aged at 400C

Test1, Before Sulfur Aging

100 125 150 175 200 225 250 275 300 325 350

Inlet Gas Temperature (ºC)

Not much difference in NOx conversion in spite of higher amount of sulfates over the sample aged at 200C than that at 300C.

11

Page 12: Investigation of Sulfur Deactivation on Cu/Zeolite SCR ... · PDF fileInvestigation of Sulfur Deactivation on Cu/Zeolite SCR Catalysts in Diesel Application. ... Fe Zeolite catalyst

After DeSOx: XPS S 2p region

Inte

nsity (

A. U

.)

Sulfated at 300 oC

Desulfated (300 oC)

Desulfated (200 oC)

175 170 165

Binding Energy (eV)

•Sulfur is completely removed after desulfation for both samples.

•Full recovery of NOx conversion after deSOx can be explained by

the complete removal of sulfate after deSOx.

12

Page 13: Investigation of Sulfur Deactivation on Cu/Zeolite SCR ... · PDF fileInvestigation of Sulfur Deactivation on Cu/Zeolite SCR Catalysts in Diesel Application. ... Fe Zeolite catalyst

13

ZCuSO4 Most stable adsorbed SOx species

better than ZCuSO3 or ZCuSO2

Can we identify the species

(structure) with XAFS?

Page 14: Investigation of Sulfur Deactivation on Cu/Zeolite SCR ... · PDF fileInvestigation of Sulfur Deactivation on Cu/Zeolite SCR Catalysts in Diesel Application. ... Fe Zeolite catalyst

       

               

         

XAFS (X­ray absorption fine structure)

XAFS = XANES (X­ray absorption near­edge spectroscopy) +

EXAFS (extended X­ray absorption fine structure)

• EXAFS can give information about bond lengths, element and coordination number surrounding the atom.

• XANES yields information about the electronic structure of the absorbing atom, including valence and oxidation state.

• XAFS works for a wide variety of samples: amorphous and crystalline; solid, liquid, and gas; magnetic and nonmagnetic, etc..

14

Page 15: Investigation of Sulfur Deactivation on Cu/Zeolite SCR ... · PDF fileInvestigation of Sulfur Deactivation on Cu/Zeolite SCR Catalysts in Diesel Application. ... Fe Zeolite catalyst

15

How about the state of Cu?: Cu XANES study

Normalized spectra Derivative spectra

Not much change in Cu after DeSOx

Not like bulk CuSO4, but highly dispersed CuO

Page 16: Investigation of Sulfur Deactivation on Cu/Zeolite SCR ... · PDF fileInvestigation of Sulfur Deactivation on Cu/Zeolite SCR Catalysts in Diesel Application. ... Fe Zeolite catalyst

Cu XAFS: aged, sulfated with SO3, DeSOx

16

Informative, but the 2nd shell structure

is not obtained due to the noise signal.

Distance (nm)

0.0 0.1 0.2 0.3 0.4 0.5 0.6

FT

in

ten

sit

y (

a. u

.) Distance (nm) 0.30 0.32 0.34 0.36 0.38 0.40 0.42 0.44

FT

in

ten

sit

y (a

. u

.)

Page 17: Investigation of Sulfur Deactivation on Cu/Zeolite SCR ... · PDF fileInvestigation of Sulfur Deactivation on Cu/Zeolite SCR Catalysts in Diesel Application. ... Fe Zeolite catalyst

Summary of XAFS curve fitting for Cu sample

Sample Pair CN1 r (nm)2 σσσσ2(pm2)3 ΔΔΔΔE (eV)

Cu aged Cu-O 3.5±±±±0.5 0.195±±±±0.001 57±±±±11 -3.4±±±±2.1

Cu DeSOx Cu-O 3.4±±±±0.3 0.195±±±±0.001 54±±±±8 -3.4±±±±1.4

Cu sulfated Cu-O 3.5±±±±0.3 0.195±±±±0.001 46±±±±6 -3.5±±±±1.2

1Coordination number. 2Coordination distance. 3The Debye-Waller factor accounting thermal and statistical

vibration. *The many body reduction factor was fixed to 0.9. The fitting ranges were 20 - 139 nm-1 for Δk and 0.100 – 0.300 nm for Δr, respectively. The restraint was applied to the Debye-Waller factor for the multiple scattering.

Only 1st shell information, which is the same among the samples, is

available due to the noisy signal.

17

Page 18: Investigation of Sulfur Deactivation on Cu/Zeolite SCR ... · PDF fileInvestigation of Sulfur Deactivation on Cu/Zeolite SCR Catalysts in Diesel Application. ... Fe Zeolite catalyst

Summary

• SCR activity was significantly reduced for samples poisoned

by SO3 compared with those by SO2, indicating that sulfur poisoning by SO2 and SO3 are not equivalent, with different poisoning mechanisms and impacts.

• Upon the sulfation with SO3, Sulfur exists as sulfate forms (not bulk CuSO4 form, but highly dispersed CuSO4), but maintain its highly dispersed Cu-O species during SOx and DeSOx, which can explain the reversible recovery of activity after desorption as SO2 at elevated temp.

• This study raises an important sulfur poisoning concern for the systems with DOCs in front of on Cu/zeolite SCR catalysts in diesel engine applications.

18

Page 19: Investigation of Sulfur Deactivation on Cu/Zeolite SCR ... · PDF fileInvestigation of Sulfur Deactivation on Cu/Zeolite SCR Catalysts in Diesel Application. ... Fe Zeolite catalyst

Acknowledgement • Clifford Montreuil and Giovanni Cavataio (Ford) for some testing.

• Prof. Sung June Cho (ChonNam Nat. Unv. of Korea) for analyzing XAFS.

• Funding from the U.S. Department of Energy (DOE), Freedom Car and Vehicle Technologies Program.

• NSLS for the beam time at X19A.

• 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.

19


Recommended