Microkinetic modeling of lean NO x trap chemistry

Richard S. Larson; V. Kalyana Chakravarthy; Josh A. Pihl; C. Stuart Daw

doi:10.1016/j.cej.2012.02.042

Microkinetic modeling of lean NO _x trap chemistry

Richard S. Larson, V. Kalyana Chakravarthy, Josh A. Pihl, C. Stuart Daw

Buildings and Transportation Science Div

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

14 Scopus citations

Abstract

A microkinetic chemical reaction mechanism capable of describing both the storage and regeneration processes in a fully formulated lean NO _x trap is presented. The mechanism includes steps occurring on the precious metal, NO _x storage, and oxygen storage sites of the catalyst. The complete reaction set is used with a transient plug flow reactor code (including boundary layer mass transfer) to simulate not only storage/regeneration cycles with a CO/H ₂ reductant, but also steady flow temperature sweep experiments that were previously analyzed with just a precious metal mechanism and a simpler steady state code. The results imply that NO _x storage was not negligible during some of the temperature ramps, necessitating a re-evaluation of the precious metal kinetic parameters. The parameters for the entire mechanism are inferred by finding the best overall fit to the complete set of experiments. Rigorous thermodynamic consistency is enforced for parallel reaction pathways and with respect to known data for all gas phase species. It is found that nearly all of the basic experimental observations can be reproduced with the transient simulations.

Original language	English
Pages (from-to)	134-147
Number of pages	14
Journal	Chemical Engineering Journal
Volume	189-190
DOIs	https://doi.org/10.1016/j.cej.2012.02.042
State	Published - May 1 2012

Funding

The authors thank Dr. Andrew Lutz, formerly of Sandia, for initial development of the Chemkin-based transient plug flow reactor code (TPLUG). The efforts at Oak Ridge were sponsored by the US Department of Energy (DOE) under contract number DE-AC05-00OR22725 with the Oak Ridge National Laboratory (ORNL), managed by UT-Battelle, LLC. The contribution of Josh A. Pihl was supported in part by an appointment to the ORNL Postgraduate Research Associates Program, administered jointly by the Oak Ridge Institute for Science and Education and ORNL. Research at both Oak Ridge and Sandia was sponsored specifically by Gurpreet Singh and Ken Howden of the US DOE's Vehicle Technologies Program. Sandia is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the US DOE's National Nuclear Security Administration under contract number DE-AC04-94AL85000.

Keywords

Catalysis
Kinetics
Lean NO trap
Mathematical modeling
NO storage reduction

Access to Document

10.1016/j.cej.2012.02.042

Cite this

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title = "Microkinetic modeling of lean NO x trap chemistry",

abstract = "A microkinetic chemical reaction mechanism capable of describing both the storage and regeneration processes in a fully formulated lean NO x trap is presented. The mechanism includes steps occurring on the precious metal, NO x storage, and oxygen storage sites of the catalyst. The complete reaction set is used with a transient plug flow reactor code (including boundary layer mass transfer) to simulate not only storage/regeneration cycles with a CO/H 2 reductant, but also steady flow temperature sweep experiments that were previously analyzed with just a precious metal mechanism and a simpler steady state code. The results imply that NO x storage was not negligible during some of the temperature ramps, necessitating a re-evaluation of the precious metal kinetic parameters. The parameters for the entire mechanism are inferred by finding the best overall fit to the complete set of experiments. Rigorous thermodynamic consistency is enforced for parallel reaction pathways and with respect to known data for all gas phase species. It is found that nearly all of the basic experimental observations can be reproduced with the transient simulations.",

keywords = "Catalysis, Kinetics, Lean NO trap, Mathematical modeling, NO storage reduction",

author = "Larson, {Richard S.} and Chakravarthy, {V. Kalyana} and Pihl, {Josh A.} and Daw, {C. Stuart}",

year = "2012",

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doi = "10.1016/j.cej.2012.02.042",

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AU - Larson, Richard S.

AU - Chakravarthy, V. Kalyana

AU - Pihl, Josh A.

AU - Daw, C. Stuart

PY - 2012/5/1

Y1 - 2012/5/1

N2 - A microkinetic chemical reaction mechanism capable of describing both the storage and regeneration processes in a fully formulated lean NO x trap is presented. The mechanism includes steps occurring on the precious metal, NO x storage, and oxygen storage sites of the catalyst. The complete reaction set is used with a transient plug flow reactor code (including boundary layer mass transfer) to simulate not only storage/regeneration cycles with a CO/H 2 reductant, but also steady flow temperature sweep experiments that were previously analyzed with just a precious metal mechanism and a simpler steady state code. The results imply that NO x storage was not negligible during some of the temperature ramps, necessitating a re-evaluation of the precious metal kinetic parameters. The parameters for the entire mechanism are inferred by finding the best overall fit to the complete set of experiments. Rigorous thermodynamic consistency is enforced for parallel reaction pathways and with respect to known data for all gas phase species. It is found that nearly all of the basic experimental observations can be reproduced with the transient simulations.

AB - A microkinetic chemical reaction mechanism capable of describing both the storage and regeneration processes in a fully formulated lean NO x trap is presented. The mechanism includes steps occurring on the precious metal, NO x storage, and oxygen storage sites of the catalyst. The complete reaction set is used with a transient plug flow reactor code (including boundary layer mass transfer) to simulate not only storage/regeneration cycles with a CO/H 2 reductant, but also steady flow temperature sweep experiments that were previously analyzed with just a precious metal mechanism and a simpler steady state code. The results imply that NO x storage was not negligible during some of the temperature ramps, necessitating a re-evaluation of the precious metal kinetic parameters. The parameters for the entire mechanism are inferred by finding the best overall fit to the complete set of experiments. Rigorous thermodynamic consistency is enforced for parallel reaction pathways and with respect to known data for all gas phase species. It is found that nearly all of the basic experimental observations can be reproduced with the transient simulations.

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KW - Kinetics

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