Tailor-­Designed Oxidation Catalysts for Lean/Low Temperature Combustion

Engines

William Epling, Sung Bong Kang, Melanie Hazlett, Courtney Littlejohn, Vence Easterling

and Christos Kalamaras

University of Houston and Saudi Aramco

Background• Advanced combustion engines• Improved fuel economy• Fuel type varies• Emissions vary

• The Advanced Combustion and Emission Control (ACEC) Technical Team, Low-­Temperature Aftertreatment Group• Protocols developed• DOE 150C Challenge

Background

Oak Ridge National Laboratories (ORNL)

Methodology• Feed (ORNL/SA concentrations, SA speciation)

• MKS 2030 for analysis (calibrated)

Species Type Amount/Representative

CO 5500 ppm CO

Short alkene 150 ppm C2H4

Short alkane 150 ppm C2H6

Long alkane 260 ppm C6H14

Aromatic 50 ppm C7H8

NOx 30 ppm NO

The usual suspects 10% O2, 5% CO2, 5% H2O bal N2

SV 50,000 hr-­‐1

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Methodology• Samples

• Pt, 3:1 Pt:Pd, 1:1 Pt:Pd, 1:3 Pt:Pd, Pd• 1 wt% Pt metal basis• Consistent molar basis (0.54 wt% Pd for Pd-­only sample)• Aged: 14% O2, 5% H2O and N2 bal. at 700oC for 24h• Before each expt: 14% O2, 5% H2O and N2 bal. at 600oC for 1h

• Monolith-­supported (1.5 g/in3 Al2O3 washcoated bricks supplied by JMI, PM added via incipient wetness)

• Liquid components injected using Bronkhorst CEM systems

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Results -­ TPO

-­ CO oxidation observed first, then C2H4, then C7H8-­ CO adsorption strength

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Results – TPO (3:1 Pt:Pd)

-­ CO oxidation observed first, then C2H4 ~ C7H8-­ C6H14 lowered conversion

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Results – TPO (Pd)

-­ CO oxidation observed first, then C7H8 then C2H4

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Results – TPO summary

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Results – TPO summary

-­ Stereotypically: Pd good for CO oxidation;; Pt (in the bimetallics) for HCs

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Results – TPO – interesting trends

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Results – “simpler” feed TPO

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Results – “simpler” feed TPO

Significant differences when comparing data sets between single vs multi-­component mixtures • CO later than C2H4 and NO?• NO in general (NO2 as an oxidant)

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Results – “simpler” feed TPO

Significant differences when comparing data sets between single vs multi-­component mixtures • CO back in front;; Pd less sensitive to CO poisoning• C2H4 vs C7H8

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Results – “simpler” feed TPO

• CO trend à identical. CO as the strong adsorbate covers the low T surface

• C2H4 trend• Under the C2H4 only scenario, Pd is less active• Under the full mix scenario, CO poisoning and the exotherm play a role.

CLEERS 2016 Workshop

Results – “simpler” feed TPO

• C6H14 trend à similar to C2H4• C7H8 trend

• By itself, bimetallics are more active• Full mix à similar to CO (lights off just after CO)

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Results – TPO – interesting trends

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Intermediate buildup causing C2H4 oxid trend?

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Intermediate buildup causing C2H4 oxid trend?

Answer = no

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Intermediate buildup causing C2H4 oxid trend?

Answer = noSo….see Melanie’s poster this afternoon!

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Conclusions• Trends in reactant mixture data are complex, but can/do exist• CO is the primary PITA – its coverage/inhibition stops the other components from oxidizing

• Pd is less sensitive to this, but is less active toward other HC oxidation reactions

• Trends in single component results à do not correlate well to mixture data

• Buildup in surface partial oxidation species has been observed and does correlate to performance• But is a f(Pt vs. Pd)

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AcknowledgmentsJim Parks – initial exhaust concentration dataJohnson Matthey – washcoated substratesSaudi Aramco – financial support

CLEERS 2016 Workshop