O2 dosage as a descriptor of TWC performance under lean/rich dithering in stoichiometric natural gas engines

Jian Gong; Josh Pihl; Di Wang; Mi Young Kim; William P. Partridge; Junhui Li; Michael Cunningham; Krishna Kamasamudram; Neal Currier; Aleksey Yezerets

doi:10.1016/j.cattod.2020.02.022

O₂ dosage as a descriptor of TWC performance under lean/rich dithering in stoichiometric natural gas engines

Jian Gong, Josh Pihl, Di Wang, Mi Young Kim, William P. Partridge, Junhui Li, Michael Cunningham, Krishna Kamasamudram, Neal Currier, Aleksey Yezerets

Cummins Inc.

Research output: Contribution to journal › Article › peer-review

26 Scopus citations

Abstract

The effects of oscillations in gas composition, known as lean/rich dithering, on the performance of a commercial Pd-based three-way catalyst (TWC) for stoichiometric natural gas (NG) engines were evaluated using synthetic exhaust flow reactor experiments. Under simulated NG exhaust conditions, NO conversion was intimately correlated to CH₄ conversion at slightly fuel-rich operating conditions. CH₄ conversion significantly varied with lambda (or O₂ concentration) and depended on the direction of the lambda change. The dynamic CH₄ conversion is likely related to the change of catalyst oxidation state and structures of Pd active sites. The CH₄-NO cross-over point was found at a rich-biased lambda rather than stoichiometry. Compared to static operation, catalyst performance was much higher under a realistic dithering condition. The impacts of dithering parameters including amplitude and frequency on CH₄ and NO conversions were explored. O₂ dosage is proposed as an effective descriptor of the TWC dithering performance. In the O₂-dosage space, the performance of distinct dithering parameters collapse, helping to elucidate the fundamental influence of dithering parameters on TWC performance. With the help of O₂ dosage, an optimal operating window leading to high CH₄ and NO conversions was identified. A higher dithering amplitude is required to keep the catalyst in a reduced state for higher CH₄ and NO conversions, while an appropriate O₂ dosage that does not exceed the breakthrough OSC is necessary to avoid excess O₂ that results in NO slip. The dithering amplitude and O₂-dosage-metric maps provide a new method for studying dynamic TWC performance and identifying optimum operation strategies.

Original language	English
Pages (from-to)	294-304
Number of pages	11
Journal	Catalysis Today
Volume	360
DOIs	https://doi.org/10.1016/j.cattod.2020.02.022
State	Published - Jan 15 2021

Bibliographical note

Publisher Copyright:
© 2020 Elsevier B.V.

Funding

This manuscript has been authored in part by UT-Battelle (W.P. Partridge & J. Pihl), LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). This manuscript has been authored in part by UT-Battelle (W.P. Partridge & J. Pihl), LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ).

Funders	Funder number
DOE Public Access Plan
UT-Battelle
United States Government
U.S. Department of Energy
UT-Battelle	DE-AC05-00OR22725

Keywords

CH-NO cross-over point
Lean/rich dithering
Methane oxidation
Natural gas
Oxygen dosage
Three-way catalyst (TWC)

Access to Document

10.1016/j.cattod.2020.02.022

Cite this

@article{047d357e893e40be84d94df25786aea4,

title = "O2 dosage as a descriptor of TWC performance under lean/rich dithering in stoichiometric natural gas engines",

abstract = "The effects of oscillations in gas composition, known as lean/rich dithering, on the performance of a commercial Pd-based three-way catalyst (TWC) for stoichiometric natural gas (NG) engines were evaluated using synthetic exhaust flow reactor experiments. Under simulated NG exhaust conditions, NO conversion was intimately correlated to CH4 conversion at slightly fuel-rich operating conditions. CH4 conversion significantly varied with lambda (or O2 concentration) and depended on the direction of the lambda change. The dynamic CH4 conversion is likely related to the change of catalyst oxidation state and structures of Pd active sites. The CH4-NO cross-over point was found at a rich-biased lambda rather than stoichiometry. Compared to static operation, catalyst performance was much higher under a realistic dithering condition. The impacts of dithering parameters including amplitude and frequency on CH4 and NO conversions were explored. O2 dosage is proposed as an effective descriptor of the TWC dithering performance. In the O2-dosage space, the performance of distinct dithering parameters collapse, helping to elucidate the fundamental influence of dithering parameters on TWC performance. With the help of O2 dosage, an optimal operating window leading to high CH4 and NO conversions was identified. A higher dithering amplitude is required to keep the catalyst in a reduced state for higher CH4 and NO conversions, while an appropriate O2 dosage that does not exceed the breakthrough OSC is necessary to avoid excess O2 that results in NO slip. The dithering amplitude and O2-dosage-metric maps provide a new method for studying dynamic TWC performance and identifying optimum operation strategies.",

keywords = "CH-NO cross-over point, Lean/rich dithering, Methane oxidation, Natural gas, Oxygen dosage, Three-way catalyst (TWC)",

author = "Jian Gong and Josh Pihl and Di Wang and Kim, {Mi Young} and Partridge, {William P.} and Junhui Li and Michael Cunningham and Krishna Kamasamudram and Neal Currier and Aleksey Yezerets",

note = "Publisher Copyright: {\textcopyright} 2020 Elsevier B.V.",

year = "2021",

month = jan,

day = "15",

doi = "10.1016/j.cattod.2020.02.022",

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AU - Gong, Jian

AU - Pihl, Josh

AU - Wang, Di

AU - Kim, Mi Young

AU - Partridge, William P.

AU - Li, Junhui

AU - Cunningham, Michael

AU - Kamasamudram, Krishna

AU - Currier, Neal

AU - Yezerets, Aleksey

PY - 2021/1/15

Y1 - 2021/1/15

N2 - The effects of oscillations in gas composition, known as lean/rich dithering, on the performance of a commercial Pd-based three-way catalyst (TWC) for stoichiometric natural gas (NG) engines were evaluated using synthetic exhaust flow reactor experiments. Under simulated NG exhaust conditions, NO conversion was intimately correlated to CH4 conversion at slightly fuel-rich operating conditions. CH4 conversion significantly varied with lambda (or O2 concentration) and depended on the direction of the lambda change. The dynamic CH4 conversion is likely related to the change of catalyst oxidation state and structures of Pd active sites. The CH4-NO cross-over point was found at a rich-biased lambda rather than stoichiometry. Compared to static operation, catalyst performance was much higher under a realistic dithering condition. The impacts of dithering parameters including amplitude and frequency on CH4 and NO conversions were explored. O2 dosage is proposed as an effective descriptor of the TWC dithering performance. In the O2-dosage space, the performance of distinct dithering parameters collapse, helping to elucidate the fundamental influence of dithering parameters on TWC performance. With the help of O2 dosage, an optimal operating window leading to high CH4 and NO conversions was identified. A higher dithering amplitude is required to keep the catalyst in a reduced state for higher CH4 and NO conversions, while an appropriate O2 dosage that does not exceed the breakthrough OSC is necessary to avoid excess O2 that results in NO slip. The dithering amplitude and O2-dosage-metric maps provide a new method for studying dynamic TWC performance and identifying optimum operation strategies.

AB - The effects of oscillations in gas composition, known as lean/rich dithering, on the performance of a commercial Pd-based three-way catalyst (TWC) for stoichiometric natural gas (NG) engines were evaluated using synthetic exhaust flow reactor experiments. Under simulated NG exhaust conditions, NO conversion was intimately correlated to CH4 conversion at slightly fuel-rich operating conditions. CH4 conversion significantly varied with lambda (or O2 concentration) and depended on the direction of the lambda change. The dynamic CH4 conversion is likely related to the change of catalyst oxidation state and structures of Pd active sites. The CH4-NO cross-over point was found at a rich-biased lambda rather than stoichiometry. Compared to static operation, catalyst performance was much higher under a realistic dithering condition. The impacts of dithering parameters including amplitude and frequency on CH4 and NO conversions were explored. O2 dosage is proposed as an effective descriptor of the TWC dithering performance. In the O2-dosage space, the performance of distinct dithering parameters collapse, helping to elucidate the fundamental influence of dithering parameters on TWC performance. With the help of O2 dosage, an optimal operating window leading to high CH4 and NO conversions was identified. A higher dithering amplitude is required to keep the catalyst in a reduced state for higher CH4 and NO conversions, while an appropriate O2 dosage that does not exceed the breakthrough OSC is necessary to avoid excess O2 that results in NO slip. The dithering amplitude and O2-dosage-metric maps provide a new method for studying dynamic TWC performance and identifying optimum operation strategies.

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KW - Lean/rich dithering

KW - Methane oxidation

KW - Natural gas

KW - Oxygen dosage

KW - Three-way catalyst (TWC)

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