Post on 16-Oct-2020
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