low temperature emission control to enable fuel-efficient ... · control to enable fuel-efficient...

ORNL is managed by UT-Battelle for the US Department of EnergyORNL is managed by UT-Battelle for the US Department of Energy

Low Temperature Emission Control to Enable Fuel-Efficient Engine Commercialization

Todd Toops(PI), Jim Parks, Jae-Soon Choi, Andrew Binder, Eleni Kyriakidou

Oak Ridge National Laboratory

ACE085June 11, 2015

Sponsors: Gurpreet Singh, Ken Howden, and Leo Breton

Advanced Combustion Engines ProgramU.S. Department of Energy

This presentation does not contain any proprietary, confidential, or otherwise restricted information

2 DOE VTO Annual Merit Review – ace085

Project Overview

• Started in FY2013• Expected to be ongoing

Timeline Budget

Partners

• FY2015: $373k• FY2014: $400k• FY2013: $400k

• BES-funded scientists Sheng Dai and Steve Overbury

• Johnson Matthey (Haiying Chen)• Low Temperature Aftertreatment Sub-

Team of US DRIVE Advanced Combustion and Emission Control Tech Team

• From DOE Vehicle Technologies Multi-Year Program Plan (2011-2015)− 2.3.1.B: Lack of cost-effective

emission control− 2.3.1.D: Durability

• Responsive to USDRIVE ACEC Tech Team Roadmap, Low Temperature Aftertreatment Workshop Report, and CLEERS Survey

• Overall, addressing emission compliance barrier to market for advanced fuel-efficient engine technologies

Barriers


Objectives and Relevance Develop emission control technologies that perform at low temperatures (<150ºC) to

enable fuel-efficient engines with low exhaust temperatures to meet emission regulationsGoal: 90% Conversion at 150ºC

• Advance catalysts to enable commercialization of advanced combustion engine vehicles

– Advanced combustion engines have greater efficiency and consequently lower exhaust temperature conditions

– At low temperatures, catalysis is challenging and emissions standards harder to meet

• Investigate “trap” material technologies that temporarily store emissions for later release and treatment Fu

el E

cono

my

Fuel Economy Standards

100

150

200

250

300

350

400

0 1 2 3 4 5 6

Turb

o O

utTe

mpe

ratu

re (C

)

BMEP (bar)

CDC

RCCI

Higher efficiency engines have lower exhaust temperatures*

*Reactivity Controlled Compression Ignition (RCCI) [a Low Temperature Combustion mode] vs. Conventional Diesel Combustion (CDC)

Em

issions EPA Tier 3 Emission Regulations

>70% less NOx

>85% less

NMOG

70% less PM

2017-2025 (phased in)

54.5 mpg CAFE by 2025

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=GRhlFhf1-UuTsM&tbnid=vLQ7YtRvXeEPWM:&ved=0CAUQjRw&url=http://wot.motortrend.com/official-2025-cafe-standards-finalized-fuel-economy-to-raise-gradually-to-54-5-mpg-253781.html&ei=0Ng5Uf2INOPV0gG7s4CACg&bvm=bv.43287494,d.dmQ&psig=AFQjCNHjAYLBeZDKdTtfLa7NmhRQObjzEw&ust=1362831933057311

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=GRhlFhf1-UuTsM&tbnid=vLQ7YtRvXeEPWM:&ved=0CAUQjRw&url=http://wot.motortrend.com/official-2025-cafe-standards-finalized-fuel-economy-to-raise-gradually-to-54-5-mpg-253781.html&ei=0Ng5Uf2INOPV0gG7s4CACg&bvm=bv.43287494,d.dmQ&psig=AFQjCNHjAYLBeZDKdTtfLa7NmhRQObjzEw&ust=1362831933057311


Relevance: Guiding Documents Define Needs

Identified Needs Addressed:• Lower temperature CO and HC

oxidation• Low temperature NOx reduction• Cold start emission trapping

technologies• Reduced PGM• Better thermal stability and

active site stability• Promote innovative catalytic

solutions via partnering with DOE BES programs

2013 CLEERS Industry Priorities Survey (New survey occurring this year)

USDRIVE ACEC Tech Team Roadmap (2013)

USDRIVE “The 150ºC Challenge” Workshop Report

Relative to all combustion approaches

cited in ACEC Tech Team Roadmap

Low Temperature Combustion (LTC)

Dilute Gasoline Combustion

Clean Diesel Combustion (CDC)


Approach: Challenge and advance novel approaches for low temperature emission control

Begin with catalysts and materials in literature,

BES program, and suggested by industry

Cost-effective and thermally stable

materials durable to multiple pollutants

Challenge

Understand

Innovate

This project is “high risk-high reward” by design

Experimental approach with emphasis on challenging…(1) In full exhaust mixture

(2) After hydrothermal aging(3) After sulfur exposure


Approach: Challenge and advance novel approaches for low temperature emission control

Begin with catalysts and materials in literature,

BES program, and suggested by industry

Cost-effective and thermally stable

materials durable to multiple pollutants

Challenge

Understand

Innovate

Inlet(1st ¼)

Outlet

TPR/TPO X-Ray Diffraction

Electron Microscopy

SXN1

SXN2

SXN3

SXN4

0.2

1800 1600 1400 1200 1000 Wavenumber (cm-1)

Abs

orba

nce

0.2

1800 1600 1400 1200 1000 Wavenumber (cm-1)

Abs

orba

nce

SXN1

SXN2

SXN3

SXN4

0.2

1800 1600 1400 1200 1000 Wavenumber (cm-1)

Abs

orba

nce

0.2

1800 1600 1400 1200 1000 Wavenumber (cm-1)

Abs

orba

nce

Sulfates

Carbonates

DRIFT Spectroscopy

Catalyst Reactors& BET/Active Surface Area


Approach: Specific Details• Recent approach modification based on feedback from project review with ACEC

Tech Team in FY2015Q1:– Research team reviewing literature* from notable catalysis, chemistry, and materials journals

to (1) provide science support to applied efforts, (2) fine tune strategy for project material studies, (3) identify new ideas to pursue

• Continuing approach to challenge materials in full exhaust with aging and poisons– CO oxidation is common metric in literature/BES program, but…EPA Tier 3 requires

dramatic reductions in HC & NOx [thus, we challenge materials in full conditions]

General Starting Point:CO

oxidation

Challenge with HCs and NOx

(full exhaust)

Study durability at

relevant exhaust temps

Study durability to

potential catalyst poisons

Candidate for engine application

Low Temperature Protocols will be used for experiments

Strategy ultimately aims to achieve EPA Tier 3 compliance

*backup slide has example list of journals reviewed


Approach: Specific Details• Recent approach modification based on feedback from project review with ACEC

Tech Team in FY2015Q1:– Research team reviewing literature* from notable catalysis, chemistry, and materials journals

to (1) provide science support to applied efforts, (2) fine tune strategy for project material studies, (3) identify new ideas to pursue

• Continuing approach to challenge materials in full exhaust with aging and poisons– CO oxidation is common metric in literature/BES program, but…EPA Tier 3 requires

dramatic reductions in HC & NOx [thus, we challenge materials in full conditions]

Candidate for engine application

Low Temperature Protocols will be used for experiments

Strategy ultimately aims to achieve EPA Tier 3 compliance

*backup slide has example list of journals reviewed

Downselectand/or

Combine

Innovative low-cost catalysts

Improved support stability

Trap (low temp) & treat (high temp)

Three different

technology approaches presented


Milestones • FY14 Quarterly Milestones:

– Q1: Synthesize SiO2 modified supports for improved thermal durability of Au catalysts

– Q2: Create synthesis process for hydrocarbon and NOx trapping materials

– Q3: Synthesize series of hydrocarbon and NOx trapping materials for evaluation

– Q4: Evaluate series of hydrocarbon and NOx trapping materials that will release at moderate temperatures

• FY15 Milestones:– {Key SMART milestone} Investigate individual roles of the components

in the CuCoCe ternary oxide and potential synergies with standard emissions control components (12/31/2014)

– Identify candidate materials for NH3 SCR catalysts that are active at low temperatures (9/30/2015)

complete

complete

complete

complete

complete

on track


Collaborations• DOE Basic Energy Sciences Program

– Sheng Dai and Steve Overbury (ORNL)– Center for Nanophase Material Science (ORNL)

• University of South Carolina– Professor John Regalbuto and student Andrew Wong

• International collaborations– UPMC, France (Dr. Cyril Thomas) & CNU, Korea (Prof. Sang-Wook Han)

• Johnson Matthey – Industry input from Haiying Chen

• CLEERS– Dissemination of data; presentation at CLEERS workshop

• USCAR/USDRIVE ACEC Tech Team Catalyst Sub-Team– Regarding low temperature protocols

• DOE-funded FOA Project led by Ford: Next Generation Three-Way Catalysts for Future, Highly Efficient Gasoline Engines– Catalysts being investigated for stoichiometric applications


Responses to 2014 Reviewers (5)• Approach (3.6/4.0): range of materials and range of techniques used is excellent…

good to see PNNL is on-board to capitalize on their strengths and know-how…demonstrating the performance under more realistic conditions earlier in the discovery process would minimize the amount of time characterizing a formulation that will not function in vehicle exhaust…investigating the individual and combined effects of HC and NOx on CO light-off is a great approach…investigating the thermal (and sulfur) durability of the new catalysts would be critical...for gasoline engines, the durability needed to be assessed under lean, stoichiometric, and rich conditions.

• Technical Accomplishments (3.5/4.0): results interesting…great progress in developing Au/Cu, CCC catalyst, and washcoat modifications with zirconium (Zr)…advances in performance are broad, and suggested more effort in aging and response to poisons would be useful…screened many materials; however, the project needs a more systematic approach to look into new materials with some rationale behind

• Collaborations (3.4/4.0): incorporating a supplier to provide guidance and advice was essential for these materials… CLEERS connection is a benefit...collaboration did not however seem to include a strong role from Johnson Matthey, and did not know exactly how the outcome was to be shared on a pre-competitive basis… The reviewer recommended that the project should have integrated major involvement from key catalyst suppliers (in a pre-competitive set-up) and/or a strong integration of a university catalysis R&D in the project (the role of the University of Tennessee is said to be a graduate student, but no explanation was provided on what exactly the graduate student contributed to the project.)

• Future plans (3.3/4.0): future work was clear and consistent with the remaining challenges and the overall target path…. sound technical path forward…project needed a more systematic plan and deliverables...for catalysts planned for gasoline applications, the project needs to assess the effect of high temperature rich operation on the catalyst. supported USCAR/U.S. DRIVE initiatives to address the need for low temperature aftertreatment to produce viable solutions for emerging, higher efficiency combustion strategies.

• Relevance (100%): this low-temperature catalyst project would be extremely important


Responses to 2014 Reviewers (5)• Approach (3.6/4.0): range of materials and range of techniques used is excellent…

good to see PNNL is on-board to capitalize on their strengths and know-how…demonstrating the performance under more realistic conditions earlier in the discovery process would minimize the amount of time characterizing a formulation that will not function in vehicle exhaust…investigating the individual and combined effects of HC and NOx on CO light-off is a great approach…investigating the thermal (and sulfur) durability of the new catalysts would be critical...for gasoline engines, the durability needed to be assessed under lean, stoichiometric, and rich conditions.

• Technical Accomplishments (3.5/4.0): results interesting…great progress in developing Au/Cu, CCC catalyst, and washcoat modifications with zirconium (Zr)…advances in performance are broad, and suggested more effort in aging and response to poisons would be useful…screened many materials; however, the project needs a more systematic approach to look into new materials with some rationale behind

• Collaborations (3.4/4.0): incorporating a supplier to provide guidance and advice was essential for these materials… CLEERS connection is a benefit...collaboration did not however seem to include a strong role from Johnson Matthey, and did not know exactly how the outcome was to be shared on a pre-competitive basis… The reviewer recommended that the project should have integrated major involvement from key catalyst suppliers (in a pre-competitive set-up) and/or a strong integration of a university catalysis R&D in the project (the role of the University of Tennessee is said to be a graduate student, but no explanation was provided on what exactly the graduate student contributed to the project.)

• Future plans (3.3/4.0): future work was clear and consistent with the remaining challenges and the overall target path…. sound technical path forward…project needed a more systematic plan and deliverables...for catalysts planned for gasoline applications, the project needs to assess the effect of high temperature rich operation on the catalyst. supported USCAR/U.S. DRIVE initiatives to address the need for low temperature aftertreatment to produce viable solutions for emerging, higher efficiency combustion strategies.

• Relevance (100%): this low-temperature catalyst project would be extremely important

Responsive Actions

Project aggressively challenging catalysts with realistic conditions and aging/poisons

Project approach modified to include systematic approach for materials selection based on literature

review of key journals (this feedback also given during ACEC Tech Team review of project)

Aging studies being performed (including sulfur exposure)

Collaborations growing: stronger involvement from Johnson Matthey and new university involvement (U.

of South Carolina)


PGM-Free CuOx-CoOy-CeO2 CatalystCo-precipitated CuOx, CoOy, and CeO2 (dubbed CCC catalyst) has shown to have both

high CO oxidation activity and exceptional tolerance for propylene.

• PGM-Free CCC (black) shows unique lack of inhibition by HCs; for reference, Pd/ZrO2-SiO2 catalyst (blue) shows inhibition which shifts light-off to higher temps

• Hydrocarbon oxidation, however, is still relatively high for CCC catalyst


CCC structure and composition

CoCe

Cu

• STEM analysis confirms interfacing regions of Co3O4 and CeO2 with high crystallinity for each phase.

• Ceria has a much smaller average particle size.

Co3O4 CeO2

• XRD analysis and EDX mapping shows that the Cu species is integrated into the lattices of both Co3O4 and CeO2 evenly.


C3H6 ox. CO ox.

PreferablyM1=Cu,Co M2=Ce

M1 = Co

C3H6 is not significantly influenced by oxide combination or Co3O4 particle size.Co3O4 surface is important for C3H6 conversion.

Low temperature CO ox. is significantly influenced by choice of oxide combination.Interface sites are important for CO oxidation.

Separated Active Sites?Binary catalyst comparisons indicate different sites are important for CO or C3H6

activity under simulated exhaust.


DRIFTS provides insights into CCC hydrocarbon inhibition resistance; initial aging results obtained

• DRIFTS data indicates a lower adsorption of C3H6on CCC (compared to Pd/ZrO2-SiO2) and almost no effect on the Cu-carbonyl binding site due to introduction of propene

• Short term (2 hr) thermal aging shows CCC to be very stable up to 700°C with major deactivation at 900°C

CO coverage to start; HC added


CCC + Pt/Al2O3 combination demonstrates the lowest combined CO and HC light-off temps

• Physical mixture of 50% CCC and 50% Pt(1% wt.)/Al2O3 allows for high CO and propene oxidation with half as much total Pt content vs. Pt/Al2O3

• C3H6 light-off greatly improved with CCC + Pt physical mixture

CCC+

PGM

CO HCsPhysical Mixture

CO2

Thermocouples

Quartz wool

Catalyst Bed

Temperature (°C)

100 150 200 250 300 350 400

Con

vers

ion

(%)

0

10

20

30

40

50

60

70

80

90

100

CO

Pt/Al2O3

CCC

CC

C+

Pt/A

l 2O3

Temperature (°C)100 150 200 250 300 350 400

Con

vers

ion

(%)

0

10

20

30

40

50

60

70

80

90

100

C3H6Pt/Al2O3

CCC

CCC+Pt/Al2O3

Temperature (°C)300 350 400 450 500 550 600

Con

vers

ion

(%)

0

10

20

30

40

50

60

70

80

90

100

C3H8

Pt/Al2O3

CCC

CO+HC+NOx Conditions: CO (1%), C3H6 (500ppm), C3H8 (500ppm), NO (500ppm), O2 (10%), H2O (5%)

SV ~150k/hr

CCC+Pt/Al2O3

gives best

light-off


• ZrO2 coating introduces surface acidity – High acidity: benefit on HC

oxidation vs. high basicity: high sulfur adsorption

– Pd/ZrO2 has both strong acidic and basic sites, while Pt/Si has neither

– Pd/ZrO2-SiO2 has acidic sites but negligible basic sites

– Favorable for Pd dispersion, HC oxidation, and sulfur tolerance

Accomplishment [Support Study]: Sulfur Tolerance of ZrO2coating on SiO2 improved Pd catalysts after deS at 600ºC

Reaction Conditions: 4000 ppm CO / 500 ppm NO / 1000 ppm C3H6 +4% O2 + 5% H2O in Ar, Total Flow: 200 sccm

Sulfation Conditions: 50 ppm SO2+4% O2+5% H2O in Ar, Total Flow: 200 sccm at 400 C

• Recall: in FY2014, reported approach of coating SiO2 with more S tolerant ZrO2

– FY2015 results shown here for amorphous SiO2 with ZrO2 catalyst (that did not provide 100% coating coverage of SiO2)

• Approach: optimize support for Pd catalysts by combining high acidity of ZrO2with high surface area of SiO2; coated SiO2 with ZrO2

100

150

200

250

300

Fresh Sulfated DeS 600ºC DeS 700ºC

C3H

6C

onve

rsio

n, T

90%

(ºC

)

Pd/ZrO₂

Pd/ZrO₂-SiO₂


*(Brij 30): Polyoxyethylene(4) lauryl ether**based on NOx TPD with UPMC method***with SiO2 removed

Synthesis of silica spheres

Accomplishment [Support Study]: New synthesis of SiO2@ZrO2core@shell improves ZrO2 coverage of SiO2 (vs. FY2014 results)

Silica core and zirconium oxide shell after calcination at 700 oC

Silica core and amorphous shell with zirconium hydroxide

• Successfully synthesized core@shell SiO2@ZrO2with more uniform ZrO2 coating than previousamorphous SiO2-ZrO2 catalyst

• Initial hydrothermal aging results good, but moreimportant evaluation of S tolerance (main objective)coming next

Material Surface Area (m2/g)

ZrO2 S. A.(m2/g)**

ZrO2 97 (97)

ZrO2-SiO2 402 60

SiO2@ZrO2 210 ---

@ZrO2*** 117 (117)

*

900 oC

SiO2[core]

ZrO2[shell]

100

150

200

250

300

350

Fresh Aged at 800ºC

Pd/ZrO₂Pd/ZrO₂-SiO₂Pd/SiO₂@ZrO₂

C3H

6C

onve

rsio

nT9

0% (º

C)


Accomplishment [Traps]: Baseline HC-trap materials selected to determine key controlling factors

• Zeolites chosen based on industry feedback and literature survey– Most studied materials in academic settings– Components of actual commercial technology (conventional ICEs)

• Systematic variation of key zeolite properties– Pore structure (Beta vs. ZSM-5)– Acidity (low vs. high SiO2/Al2O3)– Cation type (H+ vs. Ag+)

Beta (12-ring pore)

ZSM-5 (10-ring pore)

Large/medium pores allow easy HC transportZeolite

typeSiO2/Al2O3molar ratio

Nominal cation form

Surface area (m2/g)

Beta 25 H+ 680Beta 25 Ag+ NMBeta 300 H+ 620Beta 300 Ag+ NMZSM-5 30 H+ 405ZSM-5 30 Ag+ NMZSM-5 280 H+ 400ZSM-5 280 Ag+ NM

• Investigating performance trends will give Information necessary for designing HC-traps tailored to advanced ICEs

Trap loading: 25 mg/Total flow rate: 300 sccm300 ppm HC (C1 basis)

650 °C pretreatmentBase gas: 10% O2 + Ar balance (5% H2O, 5% CO2)

80 °C

adsorption

3 min 10 °C/min

desorption


Conditions: 167 ppm C3H6 +10% O2, Total Flow: 300 sccm

Ag added to zeolites improves C3H6 trapping desorption

• Beta zeolite stores more C3H6 than ZSM-5 • Ag increases both storage and desorption for beta zeolite• “Missing” C3H6 from TPD an important issue

– strongly held cokes a potential cause(1) Takamitsu, Y., Ariga, K., Yoshida, S., Ogawa, H., Sano, T. Bull. Chem. Jpn. 85(8), 869 (2012)(2) Moden, B., Donohue, J. M., Cormier, W. E., Li, H.-X. Top. Catal. 53, 1367 (2010)

0%

20%

40%

60%

80%

100%

0 1 2 3

Trap

ping

Eff

icie

ncy

(%)

Time (min)

Ag/BetaAg/ZSM-5

With 5% wt. Ag

0102030405060

100 200 300 400 500 600

C 3H

6Re

leas

ed (p

pm)

Temperature (ºC)

0102030405060

100 200 300 400 500 600

C 3H

6Re

leas

ed (p

pm)

Temperature (ºC)

0%

20%

40%

60%

80%

100%

0 1 2 3

Trap

ping

Eff

icie

ncy

(%)

Time (min)

BetaZSM-5

C3H6Trapping

Storage Capacity (mmol/g)

% Captured

% Released

Release TempPeak

Beta 26.2 74.2 14.4 345ºC

ZSM-5 25.1 66.7 4.0 135ºC

Ag/Beta 34.3 89.9 43.9 360ºC

Ag/ZSM-5 22.8 62.7 19.0 475ºC


Remaining Challenges and Future WorkAccomplished Remaining Future Work

(1) Unique lack of inhibition demonstrated

(2) Hydrothermally aged

(3) Physical mixture advantage shown

(1) S exposure(2) In series and

deposited PGM combination studies

(1) S studies(2) PGM

combination studies

(3) More fundamental studies

(1) Completed S studies of FY14 SiO2-ZrO2support

(2) New core-shell SiO2@ZrO2catalyst made

(1) S exposure on core-shell catalyst

(2) Hydrothermal aging (more)

(3) Characterization (more)

(1) S studies(2) Hydrothermally

aging studies(3) Characterization

of core-shell

(1) Two zeolites with and without Ag addition characterized

(2) Initial mixturespecies effects studied

(1) Characterizationof more materials

(2) Hydrothermalaging

(3) S exposure(4) Mixture species

studies (more)

(1) Mixture species studies

(2) Protocol development

(3) Aging and S exposure

(4) More materials

PGM

-Fre

e C

atal

yst

SiO

2-Zr

O2

Supp

ort

Zeol

ite

Trap

s









combination studies









of core-shell






studies (more)




(4) More materials

PGM

-Fre

e C

atal

yst

SiO

2-Zr

O2

Supp

ort

Zeol

ite

Trap

s

CCC

PGM

CO HCs

CO2 HCs

In Series

CCC+

PGM


CCCPGM

Deposited Particle

CO HCs

CO2

+ S

Preliminary experiments show H2O and CO2 decrease storage capacity and lower temperature of desorption


SummaryObjective: Develop emission control technologies that perform at low temperatures (<150ºC) to

enable fuel-efficient engines with low exhaust temperatures to meet emission regulations

Relevant To All ACEC Tech Team Combustion Techniques

SiO2-ZrO2Support

PGM-Free Catalyst

ZeoliteTraps

Low cost catalyst with no CO-HC inhibition continuing promise: hydrothermal aging and PGM combinations demo’d

UnderstandChallengeInnovateNovel Concepts

Real Conditions

Improved SiO2-ZrO2 catalyst synthesized as core-shell; initial hydrothermal studies good – S will be challenge of focus

Results for two zeolites with and without Ag obtained; more definition of study parameters continues – more materials too

Accomplishments

Future Work: continue challenges of full exhaust mixture, aging, and S


Technical Backup Slides


Select Journals for Literature Search to Support Project Approach (Not Complete List)

JournalsAngewandte ChemieChemistry of MaterialsACS – CatalysisJournal of CatalysisApplied Catalysis BJ Phys Chem CCatalysis Science & TechnologyPhysical Chemistry Chemical PhysicsApplied Catalysis ACatalysis CommunicationsCatalysis TodayCatalysis Letters

These journals and more being searched in project to:(1)provide science

support to applied efforts

(2) fine tune strategy for project material studies

(3) Identify new ideas to pursue


Experiment Detail: added thermocouple in catalyst bed and using as temperature measurement

Distinct exotherm (lower right) can be seen in the catalyst bed which is being used as reference point for conversion data (lower left) – sharper light-off

Thermocouples

Quartz wool

Catalyst Bed

CCC+

PGM


CO2

28 DOE VTO Annual Merit Review – ace085 *(Brij 30): Polyoxyethylene(4) lauryl ether

Synthesis of silica spheres

More Experiment Detail: Synthesis of SiO2@ZrO2core@shell Oxide Support

Silica core and zirconium oxide shell after calcination at 700 oC

Silica core and amorphous shell with zirconium hydroxide

700 oC

900 oC

• SiO2 is located in the core (Si: 14 amu) and ZrO2 in the shell(Zr: 40 amu).[Z contrast image shown]

• The ZrO2 shell seems to be porous.• Growth of SiO2@ZrO2 spheres. Shell is maintained. Diameter

at: 700 oC: ~220 nm900 oC: ~250 nm

Material Surface Area (m2/g)

ZrO2 97

ZrO2-SiO2 153

SiO2@ZrO2 210

@ZrO2 117

*









combination studies









of core-shell






studies (more)




(4) More materials

PGM

-Fre

e C

atal

yst

SiO

2-Zr

O2

Supp

ort

Zeol

ite

Trap

s