Integration of an oxidation catalyst with Pd/zeolite-based passive NOx Adsorbers: Impacts on degradation resistance and desorption characteristics

Yuntao Gu; Silvia Marino; Marina Corteìs-Reyes; Izabela S. Pieta; Josh A. Pihl; William S. Epling

doi:10.1021/acs.iecr.0c05186

Integration of an oxidation catalyst with Pd/zeolite-based passive NOx Adsorbers: Impacts on degradation resistance and desorption characteristics

Yuntao Gu, Silvia Marino, Marina Corteìs-Reyes, Izabela S. Pieta, Josh A. Pihl, William S. Epling

Applied Catalysis&Emissions Res. Group

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

18 Scopus citations

Abstract

Fully ion-exchanged Pd/SSZ-13 model passive NOx adsorbers (PNA) exhibit significant NOx storage capability, achieving NOx-to-Pd ratios of 1, and NOx desorption at higher temperatures, where downstream NOx reduction catalysts are active, under simulated exhaust conditions. However, CO has been found to induce PNA degradation, which limits the potential for practical application. In this study, in an attempt to understand the consequences of limiting CO exposure, we integrated a model Pt/ Al2O3 diesel oxidation catalyst (DOC) with a Pd/SSZ-13 PNA and performed NOx adsorption and temperature-programmed desorption (TPD) cycles with the PNA, the DOC, and the DOC+PNA integrated system. Despite the high initial NOx-to-Pd ratio, Pd/ SSZ-13 experienced significant degradation over 15 adsorption and desorption cycles when including CO, with the NOx-to-Pd ratio dropping from 0.98 to 0.75. CO oxidation over the DOC+PNA integrated system lights off at significantly lower temperature compared to the PNA, limiting the PNA CO exposure at temperatures above 200 °C. As a result, the durability of the DOC+PNA integrated system is enhanced, and only a 0.02 decrease in NOx-to-Pd ratio was observed over the 15 test cycles. A further benefit with integration of the PNA with the DOC was a lower temperature NOx release, within a more practical temperature window. This is due to the enhanced oxidation activity of the DOC+PNA integrated system and consequently an early onset of NO2 formation, which was found to trigger the low temperature NOx release. Low temperature NOx adsorption and TPD experiments with controlled exposure of CO and NO2 reveal two types of NOx storage mechanisms, one of which is destabilized by the presence of NO2, leading to the evolution of a lower temperature NOx release. Overall, integrating the PNA with a highly active low temperature CO oxidation catalyst was beneficial by lowering the NOx release temperature window and leading to significantly less NOx capacity loss.

Original language	English
Pages (from-to)	6455-6464
Number of pages	10
Journal	Industrial and Engineering Chemistry Research
Volume	60
Issue number	18
DOIs	https://doi.org/10.1021/acs.iecr.0c05186
State	Published - May 12 2021

Funding

The authors acknowledge financial support by the Department of Energy Office of Energy Efficiency & Renewable Energy (DE-EE0008233). Collaboration with Oak Ridge National Lab funded by the U.S. Department of Energy Vehicle Technologies Office. This manuscript has been authored in part by UT-Battelle (J.A.P.), 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 nonexclusive, paid-up, irrevocable, worldwide 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 research used beamline 8-ID (ISS) of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704. M.C.-R. and I.S.P. acknowledge the Foundation for Polish Science cofinanced by the European Regional Development Fund under the Smart Growth Operational Programme PO IR (Project No. REINTEGRATION/2016-1/5). The authors would like to thank Prof. Robert J. Davis, Colby Whitcomb, and Dr. Gordon Brezicki for their assistance with the XAS experiments.

Funders	Funder number
Department of Energy Office of Energy Efficiency & Renewable Energy	DE-EE0008233
Smart Growth Operational Programme PO IR	REINTEGRATION/2016-1/5
U.S. Department of Energy
Office of Science
Brookhaven National Laboratory	DE-SC0012704
UT-Battelle	DE-AC05-00OR22725
Fundacja na rzecz Nauki Polskiej
European Regional Development Fund

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@article{b0cab230ba55462c810e8609b1d90170,

title = "Integration of an oxidation catalyst with Pd/zeolite-based passive NOx Adsorbers: Impacts on degradation resistance and desorption characteristics",

abstract = "Fully ion-exchanged Pd/SSZ-13 model passive NOx adsorbers (PNA) exhibit significant NOx storage capability, achieving NOx-to-Pd ratios of 1, and NOx desorption at higher temperatures, where downstream NOx reduction catalysts are active, under simulated exhaust conditions. However, CO has been found to induce PNA degradation, which limits the potential for practical application. In this study, in an attempt to understand the consequences of limiting CO exposure, we integrated a model Pt/ Al2O3 diesel oxidation catalyst (DOC) with a Pd/SSZ-13 PNA and performed NOx adsorption and temperature-programmed desorption (TPD) cycles with the PNA, the DOC, and the DOC+PNA integrated system. Despite the high initial NOx-to-Pd ratio, Pd/ SSZ-13 experienced significant degradation over 15 adsorption and desorption cycles when including CO, with the NOx-to-Pd ratio dropping from 0.98 to 0.75. CO oxidation over the DOC+PNA integrated system lights off at significantly lower temperature compared to the PNA, limiting the PNA CO exposure at temperatures above 200 °C. As a result, the durability of the DOC+PNA integrated system is enhanced, and only a 0.02 decrease in NOx-to-Pd ratio was observed over the 15 test cycles. A further benefit with integration of the PNA with the DOC was a lower temperature NOx release, within a more practical temperature window. This is due to the enhanced oxidation activity of the DOC+PNA integrated system and consequently an early onset of NO2 formation, which was found to trigger the low temperature NOx release. Low temperature NOx adsorption and TPD experiments with controlled exposure of CO and NO2 reveal two types of NOx storage mechanisms, one of which is destabilized by the presence of NO2, leading to the evolution of a lower temperature NOx release. Overall, integrating the PNA with a highly active low temperature CO oxidation catalyst was beneficial by lowering the NOx release temperature window and leading to significantly less NOx capacity loss.",

author = "Yuntao Gu and Silvia Marino and Marina Corte{\`i}s-Reyes and Pieta, {Izabela S.} and Pihl, {Josh A.} and Epling, {William S.}",

note = "Publisher Copyright: {\textcopyright} 2021 The Authors. Published by American Chemical Society.",

year = "2021",

month = may,

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doi = "10.1021/acs.iecr.0c05186",

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volume = "60",

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T1 - Integration of an oxidation catalyst with Pd/zeolite-based passive NOx Adsorbers

T2 - Impacts on degradation resistance and desorption characteristics

AU - Gu, Yuntao

AU - Marino, Silvia

AU - Corteìs-Reyes, Marina

AU - Pieta, Izabela S.

AU - Pihl, Josh A.

AU - Epling, William S.

PY - 2021/5/12

Y1 - 2021/5/12

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AB - Fully ion-exchanged Pd/SSZ-13 model passive NOx adsorbers (PNA) exhibit significant NOx storage capability, achieving NOx-to-Pd ratios of 1, and NOx desorption at higher temperatures, where downstream NOx reduction catalysts are active, under simulated exhaust conditions. However, CO has been found to induce PNA degradation, which limits the potential for practical application. In this study, in an attempt to understand the consequences of limiting CO exposure, we integrated a model Pt/ Al2O3 diesel oxidation catalyst (DOC) with a Pd/SSZ-13 PNA and performed NOx adsorption and temperature-programmed desorption (TPD) cycles with the PNA, the DOC, and the DOC+PNA integrated system. Despite the high initial NOx-to-Pd ratio, Pd/ SSZ-13 experienced significant degradation over 15 adsorption and desorption cycles when including CO, with the NOx-to-Pd ratio dropping from 0.98 to 0.75. CO oxidation over the DOC+PNA integrated system lights off at significantly lower temperature compared to the PNA, limiting the PNA CO exposure at temperatures above 200 °C. As a result, the durability of the DOC+PNA integrated system is enhanced, and only a 0.02 decrease in NOx-to-Pd ratio was observed over the 15 test cycles. A further benefit with integration of the PNA with the DOC was a lower temperature NOx release, within a more practical temperature window. This is due to the enhanced oxidation activity of the DOC+PNA integrated system and consequently an early onset of NO2 formation, which was found to trigger the low temperature NOx release. Low temperature NOx adsorption and TPD experiments with controlled exposure of CO and NO2 reveal two types of NOx storage mechanisms, one of which is destabilized by the presence of NO2, leading to the evolution of a lower temperature NOx release. Overall, integrating the PNA with a highly active low temperature CO oxidation catalyst was beneficial by lowering the NOx release temperature window and leading to significantly less NOx capacity loss.

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Integration of an oxidation catalyst with Pd/zeolite-based passive NOx Adsorbers: Impacts on degradation resistance and desorption characteristics

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