Unusual water-assisted NO adsorption over Pd/FER calcined at high temperatures: The effect of cation migration

Inhak Song; Konstantin Khivantsev; Yiqing Wu; Mark Bowden; Yong Wang; János Szanyi

doi:10.1016/j.apcatb.2022.121810

Unusual water-assisted NO adsorption over Pd/FER calcined at high temperatures: The effect of cation migration

Inhak Song
, Konstantin Khivantsev
, Yiqing Wu
, Mark Bowden
, Yong Wang
, János Szanyi

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

19 Scopus citations

Abstract

Moisture contained in vehicle exhaust gas normally degrades the capacity and efficiency of Pd ion-exchanged zeolites as NO_x adsorbents by competitive adsorption on active sites. Here, we report a counterexample to this general proposition, in which moisture facilitates the storage of NO as a nitrosyl complex on hydrated Pd ions in high temperature calcined FER-type zeolites. Divalent Pd²⁺ cations upon elevated temperature (>800 °C) calcination occupy sterically constrained cationic position in the zeolite framework, and become inactive for the adsorption of probe molecules such as NO. These ‘hidden’ Pd ions, however, are accessible by NO when the zeolite is hydrated, but readily release NO as dehydration proceeds. Combined systematic in situ infra-red data with X-ray diffraction Rietveld analyses reveal that the high temperature-induced relocation of Pd ions to more stable cationic positions located near 6-membered ring of the ferrierite cage is responsible for this behavior.

Original language	English
Article number	121810
Journal	Applied Catalysis B: Environmental
Volume	318
DOIs	https://doi.org/10.1016/j.apcatb.2022.121810
State	Published - Dec 5 2022
Externally published	Yes

Funding

The authors gratefully acknowledge the US Department of Energy ( DOE ), Energy Efficiency and Renewable Energy , Vehicle Technologies Office for the support of this work. The research described in this paper was performed in the Environmental Molecular Sciences Laboratory ( EMSL ), a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory ( PNNL ). PNNL is operated for the US DOE by Battelle. The authors gratefully acknowledge the US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Vehicle Technologies Office for the support of this work. The research described in this paper was performed in the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated for the US DOE by Battelle.

Keywords

Cation migration
Ferrierite zeolite
NOx storage
Palladium
Passive NOx adsorber

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10.1016/j.apcatb.2022.121810

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title = "Unusual water-assisted NO adsorption over Pd/FER calcined at high temperatures: The effect of cation migration",

abstract = "Moisture contained in vehicle exhaust gas normally degrades the capacity and efficiency of Pd ion-exchanged zeolites as NOx adsorbents by competitive adsorption on active sites. Here, we report a counterexample to this general proposition, in which moisture facilitates the storage of NO as a nitrosyl complex on hydrated Pd ions in high temperature calcined FER-type zeolites. Divalent Pd2+ cations upon elevated temperature (>800 °C) calcination occupy sterically constrained cationic position in the zeolite framework, and become inactive for the adsorption of probe molecules such as NO. These {\textquoteleft}hidden{\textquoteright} Pd ions, however, are accessible by NO when the zeolite is hydrated, but readily release NO as dehydration proceeds. Combined systematic in situ infra-red data with X-ray diffraction Rietveld analyses reveal that the high temperature-induced relocation of Pd ions to more stable cationic positions located near 6-membered ring of the ferrierite cage is responsible for this behavior.",

keywords = "Cation migration, Ferrierite zeolite, NOx storage, Palladium, Passive NOx adsorber",

author = "Inhak Song and Konstantin Khivantsev and Yiqing Wu and Mark Bowden and Yong Wang and J{\'a}nos Szanyi",

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T1 - Unusual water-assisted NO adsorption over Pd/FER calcined at high temperatures

T2 - The effect of cation migration

AU - Song, Inhak

AU - Khivantsev, Konstantin

AU - Wu, Yiqing

AU - Bowden, Mark

AU - Wang, Yong

AU - Szanyi, János

PY - 2022/12/5

Y1 - 2022/12/5

N2 - Moisture contained in vehicle exhaust gas normally degrades the capacity and efficiency of Pd ion-exchanged zeolites as NOx adsorbents by competitive adsorption on active sites. Here, we report a counterexample to this general proposition, in which moisture facilitates the storage of NO as a nitrosyl complex on hydrated Pd ions in high temperature calcined FER-type zeolites. Divalent Pd2+ cations upon elevated temperature (>800 °C) calcination occupy sterically constrained cationic position in the zeolite framework, and become inactive for the adsorption of probe molecules such as NO. These ‘hidden’ Pd ions, however, are accessible by NO when the zeolite is hydrated, but readily release NO as dehydration proceeds. Combined systematic in situ infra-red data with X-ray diffraction Rietveld analyses reveal that the high temperature-induced relocation of Pd ions to more stable cationic positions located near 6-membered ring of the ferrierite cage is responsible for this behavior.

AB - Moisture contained in vehicle exhaust gas normally degrades the capacity and efficiency of Pd ion-exchanged zeolites as NOx adsorbents by competitive adsorption on active sites. Here, we report a counterexample to this general proposition, in which moisture facilitates the storage of NO as a nitrosyl complex on hydrated Pd ions in high temperature calcined FER-type zeolites. Divalent Pd2+ cations upon elevated temperature (>800 °C) calcination occupy sterically constrained cationic position in the zeolite framework, and become inactive for the adsorption of probe molecules such as NO. These ‘hidden’ Pd ions, however, are accessible by NO when the zeolite is hydrated, but readily release NO as dehydration proceeds. Combined systematic in situ infra-red data with X-ray diffraction Rietveld analyses reveal that the high temperature-induced relocation of Pd ions to more stable cationic positions located near 6-membered ring of the ferrierite cage is responsible for this behavior.

KW - Cation migration

KW - Ferrierite zeolite

KW - NOx storage

KW - Palladium

KW - Passive NOx adsorber

UR - https://www.scopus.com/pages/publications/85135316228

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DO - 10.1016/j.apcatb.2022.121810

M3 - Article

AN - SCOPUS:85135316228

SN - 0926-3373

VL - 318

JO - Applied Catalysis B: Environmental

JF - Applied Catalysis B: Environmental

M1 - 121810

ER -

Unusual water-assisted NO adsorption over Pd/FER calcined at high temperatures: The effect of cation migration

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