Pacific Northwest National Laboratory U.S. Department of Energy

Low-Temperature Hydrocarbon/COOxidation Catalysis in Support of HCCI

Emission Control CRADA: PNNL – Caterpillar

PNNL: Ken Rappé, Liyu Li, Jonathan Male

Caterpillar:Ron Silver, Svetlana Zemskova, Colleen Eckstein,

Bethanie Moss

2007 DEER (Diesel Engine-Efficiency &Exhaust Reduction) Conference

Detroit, MichiganAugust 15, 2007

Low-Temperature Hydrocarbon/COOxidation Catalysis in Support of HCCI

Emission ControlCRADA: PNNL – Caterpillar

PNNL:Ken Rappé, Liyu Li, Jonathan Male

Caterpillar:Ron Silver, Svetlana Zemskova, Colleen Eckstein,

Bethanie Moss

2007 DEER (Diesel Engine-Efficiency &Exhaust Reduction) Conference

Detroit, MichiganAugust 15, 2007

Overview

Low-Temperature Oxidation Catalysts for HCCIEmissions Control

HCCI shows promise for meeting 2010 HD NOx limits (Duffy et al., DEER 2004)z One of the major hurdles with implementation is high hydrocarbon (up

to 2000 ppm C1) and CO emissions (0.1-0.4%) z Low exhaust temperatures are below typical light-off for standard

oxidation catalysts

Program initiated Summer 2004 (at PNNL) to survey workin low temperature oxidation (CO) and propose roadmap

2

350

3

CO Conversion

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

50 100 150 200 250 300

Catalyst Face Temperature (deg C)

Con

vers

ion

%

Oxicat A

Oxicat B

Oxicat C

Oxicat D

Oxicat E

Target

Specifications to vendors: HC oxidation: 90% at 175oC and higherHC light-off: 50% at < 150oC CO oxidation: 99% at higher temperaturesCO light-off: 50% at < 150oC

Akin to the cold start problem, except the exhaust never reaches light-offtemperatures on commercial catalysts.

Objectives Develop low-temperature HC & CO oxidationcatalysts to enable HCCI application

4

Technical Summary Low Temperature CO/HC Oxidation Catalyst

Literature Survey - Multi-component Pt systems - Nano-phase Au systems - Other PGM (e.g. Pd, Ru) - Non PGM (e.g. Co, Cu, Ag, Sn)

Extensive catalyst synthesis & screening efforts(>75 formulations to date): Supports z Engelhard γ-Al2O3, Aldrich SnO2, Davison SiO2 z Multiple CeO2 formulations z Multiple CeXSnYO2, CeXPrYO2, CeXTbYO2 blends z CeO2/γ-Al2O3 sequential formulations z Other supports employed: ZnO2, ZrO2, Ce-Y zeolite, ZSM-5

Metals z Predominantly Pt- & Pd-based; multiple Rh & Ru formulations also

interrogated z Multi-component formulations combining PGMs Pd, Pt, Rh, Ru, & non-PGMs

Mn, Co, Ni z Multi-component Pt/Sn, Pt/Ce, & Pd/Ce on γ-Al2O3 and CeO2

5

Technical Summary Nano-Phase Gold (Au) Catalyst Investigations

Testing currently in progress to evaluate durability and suitability for monolith coating.

Extensive literature search assisted in narrowing selection for study. Four (4) 1-5% Au catalyst supports interrogated; *2%Pt/γ-Al2O3 tested & shown for comparison. Various formulations include variables such as precursor materials, preparation/drying conditions and calcination temperature.

T 50 ,

°C

Gold Catalyst Formulation/Support Type Iron oxide Silica Alumina Titania *

500

400

300

200

100

0

CO T50 Data (SV = 75,000/hr)

Technical Summary Initial Screening Efforts – CO, C3H6, C3H8 & CH4 investigated

>99% CO Oxidation >95% C3H8 Oxidation

400,000/hr

2%Pt / Al2O3 2%Pt / SnO2 2%Pt / CeO2 2%Pd / CeO2

2%Pd / Ce0.7Sn0.3O2 2%Pt / Ce0.7Sn0.3O2

2%Pt / 20%SnO2 / CeO2 (co) 2%Pt / 10%SnO2 / CeO2 (co) 2%Pt / 23%CeO2 / Al2O3 (seq) 2%Pt / 12%CeO2 / Al2O3 (seq) 2%Pt / 20%SnO2 / Al2O3 (co) 2%Pt / 20%SnO2 / Al2O3 (seq) 2%Pt / 10%SnO2 / Al2O3 (seq)

400,000/hr

40 60 80 100 120 140 160 180 200 200 250 300 350 400 450 500 550 Catalyst Temperature, °C Catalyst Temperature, °C

Completed screening activities on initial catalyst formulations. GHSV 400K shown; 200K & 800K GHSV also characterized. Targeted activity achieved for CO. z 50% oxidation at < 150°C; 99% oxidation at higher temperatures

Pt/CeO2 & Pd/CeO2 systems show promise, warrant furtherinvestigation

6

Technical Accomplishment Summary – PNNL

Target system: Pd/CeO2 – CO & C3H8 activity shown >99% CO Oxidation >95% C3H8 Oxidation

400,000/hr

2%Pt / 30%CeO2 / Al2O3 (62D) 2%Pd / 30%CeO2 / Al2O3 (62B)

2%Pt / CeO2 (62C) 2%Pt / CeO2 (22) 2%Pd / CeO2 (10) 2%Pd / CeO2 (62A) 2%Pd / CeO2 (72B) 2%Pd / CeO2 (72A) 2%Pd / CeO2 (78) 2%Pd / CeO2 (77) 2%Pd / CeO2 (88) 2%Pd / CeO2 (88B)

2%Pt / 20%SnO2 / CeO2 (co) 2%Pt / 10%SnO2 / CeO2 (co) 2%Pt / 23%CeO2 / Al2O3 (seq) 2%Pt / 12%CeO2 / Al2O3 (seq)

400,000/hr

40 60 80 100 120 140 200 250 300 350 400 450 500 550 Catalyst Temperature, °C Catalyst Temperature, °C

GHSV 400K hr-1 shown; 200K & 800K hr-1 also characterized Screening efforts include additional 10+ Pd/Pt CeO2–based formulations Excellent low-temperature activity achieved with re-formulatedPd/CeO2 system; showing improvement with C3H8 activity

7

Pd(NH3)4(NO3)2

cination of Ce(NO3)3, 650°C4hrs

no rod (58897B)

4A)

8

Technical Accomplishment Summary

-

0

20

40

60

80

100

120

Pd(NH3)4(NO3)2 Tem

p 10

0% C

O c

onve

rsio

n

Ce(NO3)3.6H2O

CeO2 nano-rod

CeO2 longer nano-rod

2%Pd/CeO2 System Summary of Pd- and Ce-source investigations

Pd-source: 9 Pd(NO3)2 9 Pd(NH3)4(NO3)2 z Pd-acetyl acetonate (PdACAC)

Ce-source: z Calcination of CeO2 sol and surfactant mixture 9 Decomposition of Ce(NO3)3•6H2O z Calcination of CeO2 nano-rod solution z Calcination of CeO2 longer nano-rod solution

Significant improvements made in low temperature activity[T99(CO)~60°C]; need to improve higher temperature HCactivity (e.g. C3H8).

9

Technical Summary 2%Pd/CeXPr1-XO2 System Investigations Addition of transition metals praseodymium (Pr) and terbium (Tb)

believed to enhance low-temperature REDOX capacity of the CeO2 catalyst, improving the low-temperature oxidation capacity.

X = 1 [CeO2], 0.98, 0.95, 0.9, 0.8, 0.7, 0.5, 0 [PrO2]

Pd source: Pd(NH3)4(NO3)2

Ce/PrO2 source: decomposition of Ce & Pr(NO3)3•6H2O solutions

Ferrer, V. et al Catal. Today 2005, 107-108, 487-492

Logan, A. D. et al J. Mater. Res. 1994, 9, 468-475

50

100

150

200

250

300

350

0% 20% 40% 60% 80% 100% % Pr in CeXPr1-XO2 Support

T ~10

0 (C

O, C

3 H 6 )

50

150

250

350

450

550

650

T ~10

0 (C

3 H 8 ,

CH

4 )

CO C3H6

C3H8

CH4

*

10

Technical Summary

2%Pd/CeXPr1-XO2 System Investigations TPO studies

Shoulder at 159-171°C is due to Pr, and more noticeable upon ↑ Pr.

This is seen again by Pd oxidation at 64-74°C.

200-228°C is Pd oxidation and more readily oxidized as Pr ↑ (i.e. ↑ Pr increased interaction of Pd with CeO2 support).

7.00

7.05

7.10

7.15

7.20

7.25

50 100 150 200 250 300 350 Temperature (deg C)

TCD

(a.u

.) N

OR

M

228°C

2%Pd/CeO2

208°C 200°C

159°C

171°C 187°C97°C

74°C

64°C

2%Pd/Ce0.8Pr0.2O2

2%Pd/Ce0.9Pr0.1O2

CeO2Ce0.8Pr0.2O2

11

Technical Summary 2%Pd/CeXPr1-XO2 System: BET Results

Small amounts of Pr (0-20%) believed to not reduce surface area of CeO2, larger amounts (>20%) impact the surface up to 100% PrO2 with surface area <10 m2/g.

Total pore volume reaches maximum (*) at 10% Pr.

0

10

20

30

40

50

60

70

80

0% 20% 40% 60% 80% 100% % Pr in CeXPr1-XO2 Support

Surf

ace

Are

a [m

2 /g]

Pore

Siz

e [n

m]

0

0.025

0.05

0.075

0.1

0.125

0.15

0.175

0.2

Pore Volume [cm

3]

Surface Area Pore Size Pore Volume

*

12

Technical Summary 2%Pd/CeXPr1-XO2 System: Pore Distribution

2%Pd/Ce0.8Pr0.2O2

Pore

Vol

ume

(cm

3 /g)

Pore Diameter (nm)

2%Pd/Ce0.9Pr0.1O2

Pore Diameter (nm)

Pore

Vol

ume

(cm

3 /g)

2%Pd/CeO2

Pore

Vol

ume

(cm

3 /g)

Pore Diameter (nm)

2%Pd/Ce0.7Pr0.3O2

Pore

Vol

ume

(cm

3 /g)

Pore Diameter (nm)

Pore

Vol

ume

(cm

3 /g)

2%Pd/Ce0.5Pr0.5O2

Pore Diameter (nm)

2%Pd/PrO2

Pore

Vol

ume

(cm

3 /g)

Pore Diameter (nm)

10%-20% Pr brings in larger (≥ 20nm) pores, shifts the maxima slightly to larger pores asymmetrically. >20% significantly decreases the maxima with drastic broadening of the peak towards the larger pore sizes asymmetrically.

13

Technical Summary 2%Pd/CeXPr1-XO2 System: Pd Dispersion

Pd metal dispersion in 2%Pd/CexPr1-xO2 system

0

20

40

60

80

100

120

140

160

0 20 40 60 80 100 Pr in support (balance Ce)

Pd d

ispe

rsio

n (%

)

0

0.5

1

1.5

2

2.5

3

H 2 c

hem

sorb

ed,

ml(S

TP)/g

met

al

*

Optimal metal-support interaction at 10-20% Pr loading.

Effective Pd dispersion maximized at 10-20% Pr loadingin CeXPr1-XO2 support. Increased synergy ofPd with support at 10­20% Pr loading; ‘spill­over’ effect* results in >100% effective dispersion. *Gatica, J. et al J. Phys. Chem. B 2001, 105, 1191-1199 De Leitenburg, C. et al J. Cat. 1997, 166, 98-107 Eriksson, S. et al Appl. Cat. A: Gen.2007, 326, 8-16

14

Crystal cell parameter (cubic structure)

5.4

5.41

5.42

5.43

5.44

5.45

5.46

5.47

5.48

0 20 40 60 80 100 % Pr in 2%Pd/CeXPr1-XO2

Cel

l par

amet

er a

=b=c

, A

Technical Summary 2%Pd/CeXPr1-XO2 System: XRD Analyses

10%-20% Pr results in ‘swelling’ of the crystal structure.

This is lost with >20% Pr.

Structure similar to PrO2 (versus PrO1.83) would account for no XRD shift from 10-50% Pr.

2000 COC2H4CO2

uncoated 21.5 wt% coated21.5 wt% coated

15

0

400

800

1200

1600

50 100 150 200 250

Catalyst Temperature, °C

CO

, C2 H

4 Con

cent

ratio

n, p

pm

7.80

7.90

8.00

8.10

8.20

8.30

8.40

8.50

8.60

CO

2 Con

cent

ratio

n, %

CO C2H4

CO2

Technical Summary Catalyst core test efforts – preliminary results

uncoated 22.2 wt% coated CO activity very similar to 200,000 hr-1

on powder catalyst; powder & core bench correlate well with one another. CO target <150°C achieved

Core test bench on-line Currently testing first cores z 2%Pd / Ce0.8Pr0.2O2 z 2.0 g catalyst on 9.0 g core

(22.2 wt%) z Catalyst thickness ~77μm (ρ

~ 1.3 g/cm3) z SV = 25,000/hr

- - -

- -

-

-

- -

16

>99% CO Oxidation

60

80

100

120

140

160

180

200,000 400,000 800,000

Cat

alys

t Tem

pera

ture

, °C

hr-1

1%Pd

1%Pd

1%

Mn

1%Pd

1%Pd

-1%

Mn

1%Pd

-1%

Mn

1%Pd

1%Pd

1%

Co

1%Pd

-1%

Co

1%Pd

-1%

Co

1%Pd

1%

Ni

1%Pd

-1%

Ni

1%Pd

-1%

Ni

2%Pd 2%

Pd 2%Pd

hr-1 hr-1

Technical Summary 2%Pd/Ce0.8Pr0.2O2 System Non-PGMs

Investigation into replacing PGM with a non-PGM (Mn, Co, Ni).

No significant improvement.

This represents just a glimpse; not comprehensive.

>95% C3H8 Oxidation

100

150

200

250

300

350

400

450

500

200,000 400,000 800,000

Cat

alys

t Tem

pera

ture

, °C

hr-1

1%Pd

1%Pd

-1%

Mn

1%Pd

1%Pd

-1%

Mn

1%Pd

-1%

Mn

1%Pd

1%Pd

1%

Co

1%Pd

1%

Co

1%Pd

1%

Co

1%Pd

1%

Ni

1%Pd

1%

Ni

1%Pd

1%

Ni

2%Pd 2%

Pd 2%Pd

hr-1 hr-1

17

>99% CO Oxidation

60

80

100

120

140

160

180

200,000 400,000 800,000

Cat

alys

t Tem

pera

ture

, °C

hr-1 hr-1 hr-1

1%Pd

2%Pd

2%Pt

2%R

h1%

Pd/1

%Pt

1%Pd

/1%

Rh

1%Pt

/1%

Rh

1%Pd

/1%

Ru

1%Pt

/1%

Ru

1%Pd

2%Pd

2%Pt

2%R

h1%

Pd/1

%Pt

1%Pd

/1%

Rh

1%Pt

/1%

Rh

1%Pd

/1%

Ru

1%Pt

/1%

Ru

1%Pd

2%Pd

2%Pt

2%R

h1%

Pd/1

%Pt

1%Pd

/1%

Rh

1%Pt

/1%

Rh

1%Pd

/1%

Ru

1%Pt

/1%

Ru

Technical Summary 2%Pd/Ce0.8Pr0.2O2 System Other-PGMs

Investigation into the effect of other PGMs, including Pt, Rh, Ru.

Pt excellent for CO, olefin oxidation. Rh excellent for paraffin oxidation. Pt/Rh catalyst is promising.

>95% C3H8 Oxidation

60

100

140

180

220

260

300

340

380

420

460

500

200,000 400,000 800,000

Cat

alys

t Tem

pera

ture

, °C

hr-1 hr-1 hr-1

1%Pd

2%Pd

2%Pt

2%R

h1%

Pd/1

%Pt

1%Pd

/1%

Rh

1%Pt

/1%

Rh

1%Pd

/1%

Ru

1%Pt

/1%

Ru

1%Pd

2%Pd

2%Pt

2%R

h1%

Pd/1

%Pt

1%Pd

/1%

Rh

1%Pt

/1%

Rh

1%Pd

/1%

Ru

1%Pt

/1%

Ru

1%Pd

2%Pd

2%Pt

2%R

h1%

Pd/1

%Pt

1%Pd

/1%

Rh

1%Pt

/1%

Rh

1%Pd

/1%

Ru

1%Pt

/1%

Ru

100% CO 100% C3H6 100% C3H8

200K GHSV

400K GHSV

800K GHSV

100% CO 100% C3H6 100% C3H8

200K GHSV

400K GHSV

800K GHSV

18

Technical Summary 2%Pd/CeXPr1-XO2 System: Preliminary Durability Investigations

2%Pd / CeO2

50

100

150

200

250

300

350

400

450

Cat

alys

t Tem

pera

ture

, °C

>99% CO >95% C3H6 >95% C3H8

200K GHSV

400K GHSV

800K GHSV

Fres

hA

ged

Fres

hA

ged

Fres

hA

ged

Fres

hA

ged

Fres

hA

ged

Fres

hA

ged

Fres

hA

ged

Fres

hA

ged

Fres

hA

ged

2%Pt / Ce0.8Pr0.2O2

50

100

150

200

250

300

350

400

450

500

Cat

alys

t Tem

pera

ture

, °C

>99% CO >95% C3H6 >95% C3H8

200K GHSV

400K GHSV

800K GHSV

Fres

hA

ged

Fres

hA

ged

Fres

hA

ged

Fres

hA

ged

Fres

hA

ged

Fres

hA

ged

Fres

hA

ged

Fres

hA

ged

Fres

hA

ged

Results of hydrothermal aging tests. Samples aged in 10% H2O in air at 350°C for 100 hours.

Effect of aging: z Minimal effect on Pd. z Slight deactivation of Pt.

19

Summary

Identified CeO2 system as promising area forinvestigation. Results of incorporating Pr into supporthas decreased the temperature required for activity.

Employing characterization tools (BET,XRD, TPO/TPR,etc.) for the assessment of structure-property activityrelationships.

Blending in of 10% to 20% Pr ‘swells’ the oxide crystal structure; >20% Pr appears to cause loss of smallerpores (<20nm) and loss of surface area.

Increased synergy of precious metal with 10% to 20% Prblended into the CeO2 support.

Beginning core-configured investigations.

Pacific Northwest National Laboratory U.S. Department of Energy

Tom Paulson, Dennis Endicott, Christie Ragle– Caterpillar, Inc.

Ken Howden – DOE OFCVT

Tom Paulson, Dennis Endicott, Christie Ragle– Caterpillar, Inc.

Ken Howden– DOE OFCVT

Acknowledgements

21

Caterpillar speciation efforts complete for HCCI exhaust characterization. Vendor supplied catalysts tested.

Appendix HCCI emission hydrocarbon speciation efforts

HCCI: FTIR Emissions 1200 rpm; 1/4 load

0

50

100

150

200

250

300

350

9 11 13 15 17 19 21 23 25 27 29 Setups

0.0

1000.0

2000.0

3000.0

4000.0

5000.0

6000.0

7000.0

NOx Ethene Ethyne Methane THC Carbon CO

A B C

Trade-off: NOx versus CO levels

31.722.624.613.816.810.6Pore size, nm

0.050.110.160.180.200.15Pore volume,

cc/g

5.9419.726.453.847.056.8BET, m2/g

97 2Pd­

Tb0.5Ce0.5O2

96 2Pd­

Pr0.5Ce0.5O2

99B 2Pd­

Pr0.3Ce0.7O2

94A 2Pd­

Pr0.2Ce0.8O2

99A, 2Pd­

Pr0.1Ce0.9O2

88C, 2Pd­CeO2

Cat ID and composition

22