Investigation of NO adsorption and desorption phenomena on a Pd/ZSM-5 passive NOx adsorber

Yuntao Gu; Sreshtha Sinha Majumdar; Josh A. Pihl; William S. Epling

doi:10.1016/j.apcatb.2021.120561

Investigation of NO adsorption and desorption phenomena on a Pd/ZSM-5 passive NOx adsorber

Yuntao Gu, Sreshtha Sinha Majumdar, Josh A. Pihl, William S. Epling

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

31 Scopus citations

Abstract

Pd-based zeolite materials have gained significant attention as passive NOx adsorbers (PNAs) for diesel-engine cold-start NOx mitigation due to their ability to store NOx at low temperatures. Pd/ZSM-5 is a promising PNA candidate, however, the NO adsorption mechanism over this material is not well understood. This study combines flow reactor experiments and surface spectroscopy to investigate NO adsorption under a variety of conditions. The state of hydration of the Pd cations played an important role in determining the impact of H₂O and CO concentration on the PNA performance. Below 150 °C, the inhibition effect of H₂O on NO adsorption was mitigated by CO. Due to dehydration, neither H₂O nor CO had an impact on NO uptake at 150 °C, where maximum NO storage capacity of the PNA was also observed. The observed gas composition and temperature effects on NO adsorption and formation of surface intermediates ultimately inform a proposed mechanism.

Original language	English
Article number	120561
Journal	Applied Catalysis B: Environmental
Volume	298
DOIs	https://doi.org/10.1016/j.apcatb.2021.120561
State	Published - Dec 5 2021

Funding

This research was supported by the DOE Office of Energy Efficiency and Renewable Energy (EERE) Vehicle Technologies Office (VTO) and used resources at the National Transportation Research Center, a DOE-EERE User Facility at Oak Ridge National Laboratory, under the Cross-cut Lean Exhaust Emissions Reduction Simulations (CLEERS) initiative. The authors gratefully acknowledge guidance and support from Ken Howden, Siddiq Khan, and Gurpreet Singh at DOE VTO and Hai-Ying Chen at Johnson Matthey. This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US 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 US 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 ).

Funders	Funder number
DOE-EERE
Ken Howden
Siddiq Khan
U.S. Department of Energy
Office of Energy Efficiency and Renewable Energy
Oak Ridge National Laboratory

Keywords

Adsorption mechanism
Cold start
Emissions
NOx storage
Palladium zeolite catalyst
Passive NOx adsorber

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10.1016/j.apcatb.2021.120561

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title = "Investigation of NO adsorption and desorption phenomena on a Pd/ZSM-5 passive NOx adsorber",

abstract = "Pd-based zeolite materials have gained significant attention as passive NOx adsorbers (PNAs) for diesel-engine cold-start NOx mitigation due to their ability to store NOx at low temperatures. Pd/ZSM-5 is a promising PNA candidate, however, the NO adsorption mechanism over this material is not well understood. This study combines flow reactor experiments and surface spectroscopy to investigate NO adsorption under a variety of conditions. The state of hydration of the Pd cations played an important role in determining the impact of H2O and CO concentration on the PNA performance. Below 150 °C, the inhibition effect of H2O on NO adsorption was mitigated by CO. Due to dehydration, neither H2O nor CO had an impact on NO uptake at 150 °C, where maximum NO storage capacity of the PNA was also observed. The observed gas composition and temperature effects on NO adsorption and formation of surface intermediates ultimately inform a proposed mechanism.",

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AU - Sinha Majumdar, Sreshtha

AU - Pihl, Josh A.

AU - Epling, William S.

PY - 2021/12/5

Y1 - 2021/12/5

N2 - Pd-based zeolite materials have gained significant attention as passive NOx adsorbers (PNAs) for diesel-engine cold-start NOx mitigation due to their ability to store NOx at low temperatures. Pd/ZSM-5 is a promising PNA candidate, however, the NO adsorption mechanism over this material is not well understood. This study combines flow reactor experiments and surface spectroscopy to investigate NO adsorption under a variety of conditions. The state of hydration of the Pd cations played an important role in determining the impact of H2O and CO concentration on the PNA performance. Below 150 °C, the inhibition effect of H2O on NO adsorption was mitigated by CO. Due to dehydration, neither H2O nor CO had an impact on NO uptake at 150 °C, where maximum NO storage capacity of the PNA was also observed. The observed gas composition and temperature effects on NO adsorption and formation of surface intermediates ultimately inform a proposed mechanism.

AB - Pd-based zeolite materials have gained significant attention as passive NOx adsorbers (PNAs) for diesel-engine cold-start NOx mitigation due to their ability to store NOx at low temperatures. Pd/ZSM-5 is a promising PNA candidate, however, the NO adsorption mechanism over this material is not well understood. This study combines flow reactor experiments and surface spectroscopy to investigate NO adsorption under a variety of conditions. The state of hydration of the Pd cations played an important role in determining the impact of H2O and CO concentration on the PNA performance. Below 150 °C, the inhibition effect of H2O on NO adsorption was mitigated by CO. Due to dehydration, neither H2O nor CO had an impact on NO uptake at 150 °C, where maximum NO storage capacity of the PNA was also observed. The observed gas composition and temperature effects on NO adsorption and formation of surface intermediates ultimately inform a proposed mechanism.

KW - Adsorption mechanism

KW - Cold start

KW - Emissions

KW - NOx storage

KW - Palladium zeolite catalyst

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Investigation of NO adsorption and desorption phenomena on a Pd/ZSM-5 passive NOx adsorber

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