Low Temperature Emission Control - Energy

Low TemperatureEmissions ControlTodd J. Toops (co-Principal Investigator)James E. Parks (co-Principal Investigator)J. Chris BauerOak Ridge National LaboratoryEnergy and Transportation Science DivisionGurpreet Singh and Ken HowdenAdvanced Combustion Engine ProgramU.S. Department of EnergyACE085May 16, 2013This presentation does not contain any proprietary,confidential, or otherwise restricted information

Project Overview TimelineStarted in FY2013 Reprogrammed project that wasunfunded in 2012 Prior project focused on effects ofadvanced combustion regimes onemissions control (Multi-mode)Budget 2FY2013: 400k (expected)FY2012: 0k BarriersFrom DOE Vehicle TechnologiesMulti-Year Program Plan (2011-2015) 2.3.1.B: Lack of cost-effectiveemission control 2.3.1.D: DurabilityResponsive to ACEC Tech Teamrequested emphasis on lowtemperature emissions controlPartnersBES-funded scientists Sheng Dai andSteve OverburyCenter for Nanophase MaterialsScience (CNMS) user project

Objectives and RelevanceDevelop emission control technologies that perform at low temperatures ( 150ºC) toenable fuel-efficient engines with low exhaust temperatures to meet emission regulations– Advanced combustion engines have greaterefficiency needed to meet CAFE consequently lower exhaust temperaturesEmissions Project aims to identify advancements intechnologies that will enable commercializationof advanced combustion engine vehicles– At low temperatures catalysis is challenging Perform research on strategies to improve lowtemperature catalysis for emission control– Need 90% conversion at T 150 C Investigate “trap” material technologies thatwould temporarily store emissions– Released and converted later under periodic hightemperature conditions3Fuel Economy emissions standards harder to meet, getting stricterTop: J.Kubsh, “Light-duty Vehicle Emission Standards”, 01/10/2013.Bottom: C. DiMaggio, “ACEC Low Temperature Aftertreatment Program”, 06/21/2012.

Improved vehicle efficiency leads to lowexhaust temperature Advanced combustion modes have greaterefficiency and consequently lower exhausttemperatures Low temperature exhaust is not simply astart-up problem Exhaust temperatures stay low throughoutthe FTP Further improvements in efficiency will beeven more challenging for emissions– Waste heat recovery (WHR)– ACEC: “Turbo Catalyst Refrigerator”TurboTURBO 4Top: C. Lambert, “Future Directions in SCR Systems”, 2012 CLEERS workshop, 05/01/2012.Bottom: M. Zammitt, “ACEC Future Aftertreatment Strategy Report”, 01/10/2012.Turbo: accelerate-by-80-could-make-up-40-of-global-of/

Current emissions control technologieshave limited activity at 150 CLNTTWCDOC(HC)SCR5All: M. Zammitt, “ACEC Future Aftertreatment Strategy Report”, 01/10/2012.

Approach:Pursue innovative catalyst technologies to improve lowtemperature emissions control Coordinate with BES-funded scientists to identifycatalysts/technologies that have potential– Transfer “science” findings to applied settings Evaluate promising catalysts/technologies underexhaust-relevant conditions– H2O, CO2, CO, HC, NOx Investigate durability– Sulfur, aromatics, hydrothermal cycling Characterize catalysts/technologies to understandfundamental behavior and limitations– Particularly when performance is being impeded– Materials and specific catalyst functionality/chemistry Redesign catalysts trying to overcome shortcomings6

Milestones Previous project scope was aimed at measuring the impact of advancedcombustion modes on emissions control– Low temperature reactivity seen to be a significant hurdle Example completed previous milestones are:– Comparison of Cu- and Fe-zeolite Urea-SCR catalyst performance for multimode dieselengine operation– Characterization of hydrocarbon oxidation efficiency of diesel oxidation catalyst for lowload operation with advanced combustion which results in lower exhaust temperatures Current direction is to identify novel/innovative technologies that can beimplemented to address the challenges of advanced combustion strategies FY13 Milestone: Characterization of performance and surfacemorphology for a novel candidate catalyst (September 30, 2013)– On target7

Collaborations Basic Energy Sciences [active]– Sheng Dai and Steve Overbury (ORNL)– Center for Nanophase Material Science (ORNL) Interactions with other fundamental catalysis groups [planned] CLEERS [active]– Dissemination of data; presentation at CLEERS workshop USCAR/USDRIVE [active and future activities]– Participation in US DRIVE 2012 Low Temperature Workshop ACEC catalyst sub-team (GM, Ford, Chrysler, PNNL, ORNL)– Guidance of critical technology needs8

Summary of Technical Accomplishments Investigated innovative Au@Cu (core@shell) catalyst for oxidation– Copper oxide surrounding Au core shows excellent low temperature CO oxidationbehavior In presence of CO2 and H2O– Inhibition by HC and NOx observed Could be potential CO-cleanup catalyst at tailpipe– Durability investigated up to 800 C Performance is good up to 700 C, but falls off 800 C; Sintering observed Demonstrated synergy of mixing of Au@Cu and Pt catalysts andpotential to overcome inhibitions– Pt inhibited by CO at low temperature; improved with AuCu– Very high NO to NO2 oxidation observed with mixture Synthesized and evaluated new catalysts using a new support– Improved hydrothermal durability using ceria-zirconia support9

Synthesis of AuCu/SiO2 Catalyst Supported Au nanoparticles serve as templates to synthesize smalland disperse intermetallic AuCu nanoparticles– Synthesized using aqueous/solution techniquesWhen reduced,catalyst forms aAuCu alloyInactive for COoxidationH2NSiO2Au(en)2Cl3pH 10(1.0 M NaOH)NH2AuH2NNHSiO2Reduce inH2 150 CWhen oxidized,catalyst formsAu@Cucore-shellACTIVE for COoxidation10amine ligand coats thesurface of goldNAuAuAuSiO2AuCu0NAuAuCu(C2H3O2)2 AuOrganic solutionat 300 CMetallicCu additionAuSiO2AuAuReductionH2 150 CH. Zhu et al. Applied Catalysis A: General 2007, 326, 89-99Bauer et al. Phys. Chem. Chem. Phys., 2011, 13, 2571-2581Reduced catalyst AuCu Alloy(Inactive)SiO2Oxidized catalystAu core CuOx shellSiO2Oxidation

AuCu/SiO2 catalyst is activated under leanconditions; forms core (Au) shell (CuOx) When oxidized, Aucore surroundedby amorphousCuOx shell afterheating at 500 COxidation pretreatment conditions:Flow Rate 75 sccm550 ̊C for 16 in 10% O2 1% H2O in Ar After H2 reductionat 300 C, AuCualloy forms– Time required tobe reduced– Brief rich periodwill not inactivatecatalyst11Au38.2 2θOxidationAuAuCu 40.3 2θAuCu40.1 2θAu38.2 2θACTIVECuOxReductionAuCualloyInactive

Au@Cu/SiO2 catalyst is excellent forlow temperature CO oxidation Au@Cu/SiO2 shows highactivity even at 50 C Similar loadings ofPt/Al2O3 catalyst showlittle activity below200 C– T50% 182-205 C– Pt/Al2O3 space velocity:W/F 0.5 g·h/mol is 27k h-10.90.8CO Conversion– Reactivity as low as 0 C1AuCu/SiO2W/F 0.50 g·h/mol0.70.60.5CO-onlyoxidationAuCu/SiO2W/F 0.25 g·h/mol0.40.30.20.10Pt/Al2O3W/F 0.50 g·h/mol0Pt/Al2O3W/F 0.25 g·h/mol50 100 150 200 250 300 350 400 450 500 550Temperature ( C)[weight catalyst (g)]W/F �––[molar gas flow (mol/h)]12Catalyst 50-100 mg10% O21% H2O1% COAr (balance)Flow Rate 75 sccm

Low temperature activity is limited in thepresence of NO and hydrocarbons Pt/Al2O3 displays less impact, but stillshows inhibition Strong inhibition by both NO and HCAuCu/SiO2CO Conversion0.81% CO0.61% CO1% CO 0.1% C3H60.41% CO 500 ppm NO1% CO 0.1% C3H6 0.05% NO0.2CO Conversion1.0Pt/Al2O31.01% CO0.81% CO 0.1% C3H61% CO 500 ppm NO1% CO 0.1% C3H6 0.05% NO0.6Catalyst 50 mg10% O21% H2OCO, NO, C3H6 as listedAr (balance)Flow Rate 75 sccm0.40.20.00.0050 100 150 200 250 300 350 400 450 500 550Temperature (oC)050 100 150 200 250 300 350 400 450 500 550Temperature (oC) Opportunity exists as a low temperature CO-cleanup catalyst for Au@Cu– Passive SCR approach presented by Jim Parks in prior talk (ACE033) shows CO-onlyexhaust concerns13

Combination of Au@Cu/SiO2 and Pt/Al2O3studied to explore potential synergies CO oxidation activityincreases comparedto Pt/Al2O3– but not as high asAu@Cu/SiO2 alone1CO Conversion Au@Cu/SiO2 andPt/Al2O3 werephysically 5W/F 0.50 g·h·mol-10.7Catalyst 100 mg10% O21% H2O1% COAr (balance)Flow Rate 75 sccmAu@Cu Pt0.40.30.2Pt/Al2O30.10075150225300375Temperature ( C)14450525

NO oxidation synergy observed withAu@Cu/SiO2 Pt/Al2O3 physical mixture Improved low temperature CO-oxidationin the presence of NO w/ Au@Cu Pt– Better than either individual catalystTheory:15 For Au@Cu Pt, NO oxidation to NO2approaches equilibrium limit at 250 C Considerably more active than Pt/Al2O31. NO oxidation inhibited by CO on Pt2. Au@Cu catalyst oxidizes CO, thus improving NO oxidation

Durability a concern with SiO2 support1.0 Catalyst relatively stable up to 700 C0.8– Only very low temperature activity (T 150 C)diminishes with increasing aging temperature Particles grow up to 25 nm in diameter afterthermally aged at 800 C for 10h (8-9 nm avg.)– Sulfur also shown to strongly deactivateCO Conversion Au@Cu/SiO2 aged in 10% O2 1% H2O in ArW/F 0.249 g·h/mol10% O21% H2O1% COAr (balance)Flow Rate 75 sccm0.40.275150225300375450525Intensity (Arb. Units)XRDTEMXRDTEMXRDTEMTemperature (oC)XRDTEMAvg. Particle Diameter (nm)16CO-onlyoxidation0.0 Improved metal support interactions needed1098765432100.6500 C,10h600C700C800C10h10h10hAging Temperature ( C)Au-CuO/SiO2 – 800 C, 10hAs-synthesized AuCu/SiO2Fresh800 ̊C, 10h50nm3040506070Degrees (2θ)8090

Supporting AuCu catalyst on ceriazirconia shows improved stability Same synthesis procedure asfollowed as described in slide 101.00.9 Even with low weight loading highactivity shown with unaged sample SV 95,000 h-1; denser than SiO2– T50% 60 C– T90% 98 C Activity drops after aging at 800 C,but is still very high– T50% 125 C– T90% 155 C17Aging Temp.0.8AuCu-550C 16h600C 16h700C 16h800C 16h0.7CO Conversion– W/F 0.25 g*h/molAu@Cu/CeO2(75)-ZrO2(25)0.60.5CO-only oxidation0.4W/F 0.25 g*h/mol10% O21% H2O1% COAr (balance)Flow Rate 75 sccm0.30.20.10.0050 100 150 200 250 300 350 400 450 500 550Temperature ( C)

Catalysts studied show promise, butchallenges remain 90% Oxidation of HCs and CO at150 C will continue to be difficult, butexploiting synergies of catalysts showpromise– Both Au@Cu/SiO2 and Pt/Al2O3 showimpact from NO and HCs Matching active catalysts with theright support shows promise forovercoming durability challenges– 90% conv. achieved w/ 800 C aging18300250Au@Cu/SiOAuCu/SiO2 lyCO NOCO NO HCAuCu/SiO2 2Au@Cu/SiOAu@Cu/Ceria-ZirconiaAuCu/CZGoal– Mixing catalysts results in 35 Cdrop in T-90CO-oxidation T-90 ( C)Goal– The lower the better350Goal– T-90 temperature where 90%conversion is achieved400CO-oxidation T-90 ( C) T-90 compared for each catalyst andcondition studied250200150100500FreshAged at 800 C

Future work Continue investigation on Au@Cu with ceria-zirconia and other supports– Activity in the presence of HC and NO– Physical mixture with Pt/Al2O3; Pt co-supported on ceria-zirconia– Additional supports while studying/characterizing metal support interactions Specifically interested in titania-modified SiO2 support– Discussed briefly last year and this year in CLEERS project (ACE022) Initial focus is on oxidation catalysts, but future efforts will move into trapmaterials and NOx reduction catalysts– Low temperature NOx and HC trap materials Release at moderate temperatures– NOx storage reduction catalysis with low temperature release and highly activereduction chemistry Goal is to move from powder catalysts to washcoated cores and further validationin engine exhaust– Developing washcoating capability19