2011 DOE AMR Review - US Department of Energy · 2011-05-25 · 1 Enhanced High Temperature Performance of NOx Storage/Reduction (NSR) Materials 2011 DOE AMR Review. This presentation

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Enhanced High Temperature Performance of NOx Storage/Reduction (NSR) Materials

2011 DOE AMR Review

This presentation does not contain any proprietary, confidential, orotherwise restricted information.

The work was funded by the U.S. Department of Energy (DOE) Office of FreedomCar and Vehicle Technologies.

Program Managers: Ken Howden and Gurpreet Singh

May 11, 2011

Do Heui Kim, George Muntean, Chuck PedenInstitute for Interfacial CatalysisPacific Northwest National Laboratory

Neal Currier, Junhui Li,Alex YezeretsCummins Inc.

Hai-Ying Chen, Howard HessJohnson Matthey

ACE026

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Project Overview

Timeline

BudgetPartners

Barriers• Start – March 2009• Finish – Feb 2012• 70% complete

• Matched 50/50 by Cummins as per CRADA agreement

• DOE funding in FY11 WAS:• $200K

• Discussed on next slide

• Pacific Northwest National Laboratory• Cummins, Inc.

• w/Johnson Matthey

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Barriers - Relevance

• In looking forward to 2012 and beyond with expected more stringent regulations, a critical need for future NSR systems will be significantly improved higher temperature performanceand stability. For example, current NSR catalyst formulations are not effective for NOx removal during high temperature system maintenance events, including desulfation. The possibility of using NSR systems for natural gas engines will also require higher temperature performance.

• It is important to reduce system costs by, for example, minimizing the precious metal content while maintaining, even improving, performance and long-term stability.

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Barriers - Relevance

Higher Temperature Lean NOx Performance: Better NOx storage at higher temperatures

• Modify the NSR storage and/or support material to expand NOx trapping at higher temperatures?

• Improved NOx storage means enhanced SOxstability – enhance thermal stability to higher temperature deSOx?

• Develop selectivity to NOx over SOx? Do something else at higher temperature for lean

NOx removal rather than trapping?

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Goals and Objectives• Develop a fundamental understanding of candidate next

generation NSR materials operated at high temperatures for NOx after-treatment for light-duty lean-burn (including diesel) engines.

• Focus on characterizing and understanding the following specific issues:

– mechanisms for deactivation in NOx storage performance in alternative LNT materials for high-temperature application;

– the sulfur adsorption and regeneration mechanisms for modified and/or alternative storage materials;

– the effects of high temperatures on the precious metal and storage elements in their various roles;

– the various roles for the precious metals.

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Approach• Prepare and Process High Temperature NSR Materials

– Fully formulated catalyst has been provided by Johnson Matthey (NOTE that the composition of this catalyst is proprietary and unknown to Cummins and PNNL).

– Based on prior PNNL results and published literature, PNNL is preparing model HT NSR catalysts, including changes to the storage element and support material.

– These materials are studied:• Fresh, as-received (AR) and degreened• Variably sulfated (thermally-aged)

• Utilize expertise and state-of-the-art catalyst characterization and testing facilities at PNNL’s IIC to address mechanisms and structure/function

• XRD, XPS, NMR, TEM/EDX and SEM/EDX• NO2 TPD, H2 TPRX• Synchrotron based techniques (in situ time-resolved XRD)• Lab reaction system

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Collaborations/Interactions

PNNL

Cummins Inc.

Johnson Matthey

Provide results of current

performance testing of NOx

adsorber systems

Engine dynamometer testing of new formulations.

Supply catalyst materials, and

provide information on their preparation

and initial characterization

Carry out and disseminate

results of mechanistic

studies using catalyst

characterization and testing

BNLSynchrotron-based in situ experiment

• Conference calls were held typically once every month or two to discuss the results.

• The most recent annual face-to-face CRADA Review was held in Devon, PA (October, 2010).

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Collaborations/Interactions

PNNL

Cummins Inc.

Johnson Matthey

Provide results of current

performance testing of NOx

adsorber systems

Engine dynamometer testing of new formulations.

Supply catalyst materials, and

provide information on their preparation

and initial characterization

Carry out and disseminate

results of mechanistic

studies using catalyst

characterization and testing

BNLSynchrotron-based in situ experiment

• Conference calls were held typically once every month or two to discuss the results.

• The most recent annual face-to-face CRADA Review was held in Devon, PA (October, 2010).

Results obtained on similar model catalyst formulations in more fundamental CLEERS-funded studies are essential for this program’s success.

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Technical Accomplishments

• Fully formulated high temperature NSR catalysts supplied from JM – baseline studies for comparison with new materials– Explore the storage behavior of a fresh developmental catalyst sample as a

function of temperature.– Investigate the effects of thermal aging and sulfation/desulfation on the NOx

storage activity.

• High temperature NSR catalysts prepared by PNNL – Studies of the effects of storage elements and various supports on the NOx

storage activity, are being carried out as part of PNNL’s CLEERS activities.– Detailed studies of the deactivation mechanisms in these high temperature

NOx storage materials. These studies involve activity testing, thermal treatments, variable desulfation processing, and extensive catalyst characterization.

Reaction Protocol:

LEAN/RICH

50/10 sec20 cycles

LEAN

10min

Bypa

ss

5min

LEA

N LEAN/RICH

50/10 sec20 cycles

10min

Bypa

ss

Initial performance tests

Repeat performance tests (aged)

LEAN

Lean6,7,8, 900 °C

•Lean: 1min

•Rich: 10min

•2 cycles

Simulated DeSOx

• As received

• Initial performance tests measured at 500, 450, 400, 350, 300, 250 and then 570 ºC

Repeated while raising the temperature

15min

LEAN

Fresh brick: 0.7906 g (4x4 cell), sealed around the sample with quartz wool

Gas flow:• Total gas flow: 400 sccm (~ 30k h-1 G.H.S.V)• Lean: 5%O2, 5%CO2, 5%H2O, 150 ppm NO, • Rich: 0%O2, 5%CO2, 5%H2O, 4.25%H2

0 1000 2000 3000 40000

20

40

60

80

100

120

140

160

NOx

conc

. (pp

m)

Time (sec)

500 450 400 350 300 250 570

250 300 350 400 450 500 5500

1

2

3

4

NOx

upta

ke (c

m3 / g

cat

)Temperature (oC)

Note: NOx uptake = total NOx uptake up to 20% NOx ‘breakthrough’

Technical Accomplishments/ Progress/Results

A fully formulated developmental H-T NSR catalyst system, supplied from JM, shows highest activities between 400 and 450 ºC. These catalysts were also tested after thermal aging at elevated temperature to understand the thermal stability.

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250 300 350 400 450 500 5500

1

2

3

4 fresh 700 C 800 C 900 C

NOx

upta

ke (c

m3 / g

cat

)

Temperature (oC)0 500 1000 1500 2000 2500

0

20

40

60

80

100

120

140

160

NO

x co

nc. (

ppm

)

Time (sec)

700 C 800 C 900 C Fresh

• NOx uptakes decrease significantly with increasing aging temperatures.

• Thermal treatment over 700 °C deteriorates NOxuptakes in these samples.

• However, this is compared to fresh (NOT de-greened) catalyst.

Thermal stability of the NSR sample from JM


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Which treatment is more detrimental, oxidizing or reducing?

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0 500 1000 1500 2000 2500 3000 3500 40000

20

40

60

80

100

120

140

Oxidizing Reducing

NOx

conc

. (pp

m)

Time (sec)

After treating the sample at 700 ºC under oxidizing or reducing conditions.

Loss in activity (%)7870

Oxidizing conditions gives rise to a somewhat greater loss in NOx uptake, compared with reducing conditions.

Reaction protocol: sulfation-desulfation1) Degreening: at 700 °C, Lean/Rich (1 min/10min) cycling for ~16hrs

2) Sulfation: SO2 exposure at 400 ºC for 7 hrs (7.5 ppm) 1.08 cm3 of SO2 in total Periodic activity measurements during sulfation

3) Desulfation: see below

LEAN/RICH

50/10 sec20 cycles

LEAN

10min

Bypa

ss

5min

LEA

N LEAN/RICH

50/10 sec20 cycles

10min

Bypa

ss

Performance test (SO2 for 7 hrs)

Performance test (no SO2)

LEAN

Lean6,7,8, 900 °C

•Lean: 1min

•Rich: 10min

•2 cycles

DeSOx

• Activity at 400 ºC

• De-greening at 700 ºC

• 86 pulses (10 min rich/1min lean)

Sulfation

Repeated while raising the temperature

15min

LEAN

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NOx storage in a degreened JM catalyst sample monotonically decreases with incremental increases in SO2 exposure; even relatively small amounts of SO2 can deteriorate NOx storage performance.

0 500 1000 1500 2000 25000

100

200

300

400

NOx

conc

. (pp

m)

Time (sec)

0.5 h 1.5 h 2.5 h 3.5 h 4.5 h 5.5 h 6.5 h

0 20 40 60 80 1000

100

200

300

400

NOx

conc

. (pp

m)

Time (sec)

0 1 2 3 4 5 6 70.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

NOx

upta

ke (c

m3 N

Ox/

g c

atal

)

Sulfation time (hr)

Less NOx puff with sulfation

Monotonic decrease!

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The activities after sulfation followed by desulfation at 600 and 700 ºC are slightly higher than a degreened one before any sulfation. Activities after desulfationabove 800 ºC are significantly lower due to detrimental thermal aging effects.

1200 1400 1600 1800 20000

20

40

60

80

100

120

NOx

conc

. (pp

m)

Time (sec)

fresh degreening 600 C 700 C 800 C 900 C

600 700 800 9000.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Desulfation temperature (oC)

Degreening

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0 5 10 15 20

lean(1min)

rich (10 min)

H2S

MS

signa

l (a.

u.)

Time (min)

600 C 700 C 800 C 900 C

rich (10 min)

lean(1min)

600 700 800 900

Inte

grat

ed H

2S s

igna

l

Temperature (oC)

During isothermal desulfation, the primary sulfur-containing product, H2S, is emitted early during desulfation at 600 ºC, and this sulfur removal results in regenerated activity. Lower amounts of H2S evolve at higher desulfation temperatures. However, removal of sulfur above 700 ºC is harmful rather than helpful.


Desulfation as a function of temperature

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Technical Accomplishments

• Fully formulated high temperature NSR catalysts supplied from JM – baseline studies for comparison with new materials– Explore the storage behavior of a fresh developmental catalyst sample as a

function of temperature.– Investigate the effects of thermal aging and sulfation/desulfation on the NOx

storage activity.

• High temperature NSR catalysts prepared by PNNL (Pt-K(10)/MgAl2O4)

– Studies of the effects of storage elements and various supports on the NOxstorage activity, are being carried out as part of PNNL’s CLEERS activities.

– Detailed studies of the deactivation mechanisms in these PNNL-prepared model high temperature NOx storage materials. These studies involve activity testing, thermal treatments, variable desulfation processing, and extensive catalyst characterization

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1000 1500 2000 25000

20

40

60

80

100

NOx

conc

. (pp

m)

Time (sec)

0 0.5 hr 1.67 hr 2.83 hr 4.67 hr

0 1 2 3 4 55

6

7

8

NOx

upta

ke (c

m3

NO3/

g ca

tal)

Sulfur exposure time (hr)

SO2 effects on NOx uptake for PNNL-prepared model HT-NSR catalyst material (Pt-K(10)/MgAl2O4)

Like the sample from JM, even small exposures of SO2 gives rise to a decrease in NOx uptake.

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H2S begins to be formed around 500 ºC and has a maximum peak around 800 ºC, which is higher than Ba-based LNTs.

300 400 500 600 700 800 9000.000

0.001

0.002

0.003

0.004

0.005

H2S

(m/e

= 3

4)

Temperature (oC)

Desulfation Behavior:H2 TPRX after sulfation PNNL-prepared

model HT-NSR catalyst material (Pt-K(10)/MgAl2O4)

0 500 1000 1500 2000 25000

50

100

150

NO

x co

ncen

tratio

n (p

pm)

Time (min)

500C_1st 500C_2nd after 600C after 700C after 800C

500 600 700 8000

2

4

6

8

10

NO

x up

take

(cm

3)/ g

cat

al

Treated temperature (oC)

After 1st measurement

• NOx uptake begins to decrease gradually after treatment above 600 ºC.• After treatment at 800 ºC, about 80% loss in activity.

Thermal stability of model HT NSR catalyst: Activity at 500 ºC after thermal treatment at each T for 1 hr (lean)

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0 500 1000 1500 2000 2500 30000

50

100

150

NO

x co

nc. (

ppm

) 3 mon. after calc. 4 days after calc. (May) 2 days after calc. (Aug.)

Time (sec)

•Sample just after calcination has higher NOx uptake.

•This result suggests that the sample is changing with time, which has a negative effect on NOx uptake.•Some changes observed in XRD data.•More characterization studies underway.

NOx uptake change: PNNL HT-NSRPt-K(10)/MgAl2O4 after calcination

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•After calcination

•3 months after calc.

•With time •KNO3 Niter phase

•Rhombohedral

•orthorhombic

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Planned Future Work

1. Preparation and characterization of High temperature NSR materials at PNNL- Detailed comparative characterization of K/MgAl2O4 and K/Al2O3 catalysts

after high temperature thermal treatments and sulfation/desulfationexperiments.

- Investigate support and K-loading effects with respect to nitrate and sulfate adsorption/desorption behavior at high temperatures.

2. Characterization of high temperature NSR materials supplied from JM- Understanding of sulfation/desulfation behavior at various sulfur loadings,

and relationship of sulfur loading with thermal stability- Determination of optimum conditions for regeneration (sulfur removal) with

minimized thermal deactivation.

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Summary• A critical need for future NSR systems will be significantly improved

higher temperature performance and stability, since current NSR systems are not effective during high temperature system maintenance events (desulfations and/or upstream soot filter regenerations).

• PNNL’s role has been to prepare and characterize model NSR catalysts known for enhanced performance at higher temperatures, and provide fundamental insights into specific issues concerning HT-NSR catalyst deactivation due to sulfur poisoning and/or thermal degradation.

• Technical highlights from this project included:– PNNL prepared and evaluated a number of candidate materials, which led to a

choice of a HT-NSR catalyst, Pt-K/MgAl2O4, as a promising model system. In addition, comparative behavior of Pt-K/Al2O3 is being studied. Some sulfur and high temperature aging has been observed and these are now being characterized in detail.

– We are also evaluating proprietary HT-NSR materials supplied from JM regarding the durability issues of thermal aging and sulfation/desulfation.

Documents

2011 DOE AMR Review - US Department of Energy · 2011-05-25 · 1 Enhanced High Temperature Performance of NOx Storage/Reduction (NSR) Materials 2011 DOE AMR Review. This presentation