Catalytic Exhaust Gas Recirculation-Loop Reforming for High Efficiency in a Stoichiometric Spark-Ignited Engine through Thermochemical Recuperation and Dilution Limit Extension, Part 1: Catalyst Performance

Yan Chang; James P. Szybist; Josh A. Pihl; D. William Brookshear

doi:10.1021/acs.energyfuels.7b02564

Catalytic Exhaust Gas Recirculation-Loop Reforming for High Efficiency in a Stoichiometric Spark-Ignited Engine through Thermochemical Recuperation and Dilution Limit Extension, Part 1: Catalyst Performance

Yan Chang, James P. Szybist, Josh A. Pihl, D. William Brookshear

Buildings and Transportation Science Div

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

20 Scopus citations

Abstract

The use of fuel reformate from catalytic processes is known to have beneficial effects on the spark-ignited combustion process through enhanced dilution tolerance and decreased combustion duration, but, in many cases, reformate generation can incur a significant fuel penalty. In this two-part investigation, we demonstrate that efficient catalytic fuel reforming can result in improved brake engine efficiency while maintaining stoichiometric exhaust under the right conditions. In Part 1 of this investigation, we used a combination of thermodynamic equilibrium calculations and experimental fuel catalytic reforming measurements on an engine to characterize the best possible reforming performance and energetics over a range of equivalence ratios and O₂ concentrations. Ideally, one might expect the highest levels of thermochemical recuperation for the highest catalyst equivalence ratios. However, reforming under these conditions is highly endothermic, and the available enthalpy for reforming is constrained. Thus, for relatively high equivalence ratios, more methane and less H₂ and CO are produced. Our experiments revealed that this suppression of H₂ and CO could be countered by adding small amounts of O₂, yielding as much as 15 vol % H₂ at the catalyst outlet for 4 < φ_catalyst < 7 under quasi-steady-state conditions. Under these conditions, the H₂ and CO yields were highest and there was significant water consumption, confirming the presence of steam reforming reactions. Analyses of the experimental catalyst measurements indicated the possibility of both endothermic and exothermic reaction stages and global reaction rates sufficient to enable the utilization of higher space velocities than those employed in our experiments. In a companion paper detailing Part 2 of this investigation, we present results for the engine dilution tolerance and brake engine efficiency impacts of the reforming levels achieved.

Original language	English
Pages (from-to)	2245-2256
Number of pages	12
Journal	Energy and Fuels
Volume	32
Issue number	2
DOIs	https://doi.org/10.1021/acs.energyfuels.7b02564
State	Published - Feb 15 2018

Funding

The authors gratefully acknowledge the support of the U.S. Department of Energy Vehicle Technologies Office, particularly program managers Gurpreet Singh and Mike Weismiller. The authors also gratefully acknowledge John Nunan (Umicore) for providing catalyst samples and Galen Fisher (University of Michigan) for supporting our efforts to obtain substrates and catalysts. Yan Chang was also enrolled as a Ph.D. candidate at the University of Michigan at the time of this publication. *E-mail: [email protected]. ORCID James P. Szybist: 0000-0002-3550-4423 Josh A. Pihl: 0000-0002-9798-4012 Author Contributions ‡The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. These authors contributed equally. Notes This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC0500OR22725 with the U.S. Department of Energy (DOE). The U.S. government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for U.S. government purposes. DOE 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). The authors declare no competing financial interest. The authors gratefully acknowledge the support of the U.S. Department of Energy Vehicle Technologies Office, particularly program managers Gurpreet Singh and Mike Weismiller. The authors also gratefully acknowledge John Nunan (Umicore) for providing catalyst samples and Galen Fisher (University of Michigan) for supporting our efforts to obtain substrates and catalysts. Yan Chang was also enrolled as a Ph.D. candidate at the University of Michigan at the time of this publication; she would like to express her gratitude for the strong support she received from her coadvisors, Prof. Andre Boehman and Dr. Stani Bohac.

Funders	Funder number
U.S. Department of Energy Vehicle Technologies Office
UT-Battelle
U.S. Department of Energy
University of Michigan

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@article{d6eab661ec854b59a747a9e96f343589,

title = "Catalytic Exhaust Gas Recirculation-Loop Reforming for High Efficiency in a Stoichiometric Spark-Ignited Engine through Thermochemical Recuperation and Dilution Limit Extension, Part 1: Catalyst Performance",

abstract = "The use of fuel reformate from catalytic processes is known to have beneficial effects on the spark-ignited combustion process through enhanced dilution tolerance and decreased combustion duration, but, in many cases, reformate generation can incur a significant fuel penalty. In this two-part investigation, we demonstrate that efficient catalytic fuel reforming can result in improved brake engine efficiency while maintaining stoichiometric exhaust under the right conditions. In Part 1 of this investigation, we used a combination of thermodynamic equilibrium calculations and experimental fuel catalytic reforming measurements on an engine to characterize the best possible reforming performance and energetics over a range of equivalence ratios and O2 concentrations. Ideally, one might expect the highest levels of thermochemical recuperation for the highest catalyst equivalence ratios. However, reforming under these conditions is highly endothermic, and the available enthalpy for reforming is constrained. Thus, for relatively high equivalence ratios, more methane and less H2 and CO are produced. Our experiments revealed that this suppression of H2 and CO could be countered by adding small amounts of O2, yielding as much as 15 vol % H2 at the catalyst outlet for 4 < φcatalyst < 7 under quasi-steady-state conditions. Under these conditions, the H2 and CO yields were highest and there was significant water consumption, confirming the presence of steam reforming reactions. Analyses of the experimental catalyst measurements indicated the possibility of both endothermic and exothermic reaction stages and global reaction rates sufficient to enable the utilization of higher space velocities than those employed in our experiments. In a companion paper detailing Part 2 of this investigation, we present results for the engine dilution tolerance and brake engine efficiency impacts of the reforming levels achieved.",

author = "Yan Chang and Szybist, {James P.} and Pihl, {Josh A.} and Brookshear, {D. William}",

note = "Publisher Copyright: {\textcopyright} 2017 American Chemical Society.",

year = "2018",

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day = "15",

doi = "10.1021/acs.energyfuels.7b02564",

language = "English",

volume = "32",

pages = "2245--2256",

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Catalytic Exhaust Gas Recirculation-Loop Reforming for High Efficiency in a Stoichiometric Spark-Ignited Engine through Thermochemical Recuperation and Dilution Limit Extension, Part 1: Catalyst Performance. / Chang, Yan; Szybist, James P.; Pihl, Josh A. et al.
In: Energy and Fuels, Vol. 32, No. 2, 15.02.2018, p. 2245-2256.

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

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T1 - Catalytic Exhaust Gas Recirculation-Loop Reforming for High Efficiency in a Stoichiometric Spark-Ignited Engine through Thermochemical Recuperation and Dilution Limit Extension, Part 1

T2 - Catalyst Performance

AU - Chang, Yan

AU - Szybist, James P.

AU - Pihl, Josh A.

AU - Brookshear, D. William

PY - 2018/2/15

Y1 - 2018/2/15

N2 - The use of fuel reformate from catalytic processes is known to have beneficial effects on the spark-ignited combustion process through enhanced dilution tolerance and decreased combustion duration, but, in many cases, reformate generation can incur a significant fuel penalty. In this two-part investigation, we demonstrate that efficient catalytic fuel reforming can result in improved brake engine efficiency while maintaining stoichiometric exhaust under the right conditions. In Part 1 of this investigation, we used a combination of thermodynamic equilibrium calculations and experimental fuel catalytic reforming measurements on an engine to characterize the best possible reforming performance and energetics over a range of equivalence ratios and O2 concentrations. Ideally, one might expect the highest levels of thermochemical recuperation for the highest catalyst equivalence ratios. However, reforming under these conditions is highly endothermic, and the available enthalpy for reforming is constrained. Thus, for relatively high equivalence ratios, more methane and less H2 and CO are produced. Our experiments revealed that this suppression of H2 and CO could be countered by adding small amounts of O2, yielding as much as 15 vol % H2 at the catalyst outlet for 4 < φcatalyst < 7 under quasi-steady-state conditions. Under these conditions, the H2 and CO yields were highest and there was significant water consumption, confirming the presence of steam reforming reactions. Analyses of the experimental catalyst measurements indicated the possibility of both endothermic and exothermic reaction stages and global reaction rates sufficient to enable the utilization of higher space velocities than those employed in our experiments. In a companion paper detailing Part 2 of this investigation, we present results for the engine dilution tolerance and brake engine efficiency impacts of the reforming levels achieved.

AB - The use of fuel reformate from catalytic processes is known to have beneficial effects on the spark-ignited combustion process through enhanced dilution tolerance and decreased combustion duration, but, in many cases, reformate generation can incur a significant fuel penalty. In this two-part investigation, we demonstrate that efficient catalytic fuel reforming can result in improved brake engine efficiency while maintaining stoichiometric exhaust under the right conditions. In Part 1 of this investigation, we used a combination of thermodynamic equilibrium calculations and experimental fuel catalytic reforming measurements on an engine to characterize the best possible reforming performance and energetics over a range of equivalence ratios and O2 concentrations. Ideally, one might expect the highest levels of thermochemical recuperation for the highest catalyst equivalence ratios. However, reforming under these conditions is highly endothermic, and the available enthalpy for reforming is constrained. Thus, for relatively high equivalence ratios, more methane and less H2 and CO are produced. Our experiments revealed that this suppression of H2 and CO could be countered by adding small amounts of O2, yielding as much as 15 vol % H2 at the catalyst outlet for 4 < φcatalyst < 7 under quasi-steady-state conditions. Under these conditions, the H2 and CO yields were highest and there was significant water consumption, confirming the presence of steam reforming reactions. Analyses of the experimental catalyst measurements indicated the possibility of both endothermic and exothermic reaction stages and global reaction rates sufficient to enable the utilization of higher space velocities than those employed in our experiments. In a companion paper detailing Part 2 of this investigation, we present results for the engine dilution tolerance and brake engine efficiency impacts of the reforming levels achieved.

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ER -

Catalytic Exhaust Gas Recirculation-Loop Reforming for High Efficiency in a Stoichiometric Spark-Ignited Engine through Thermochemical Recuperation and Dilution Limit Extension, Part 1: Catalyst Performance

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