TY - JOUR
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
N1 - Publisher Copyright:
© 2022
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 - http://www.scopus.com/inward/record.url?scp=85135316228&partnerID=8YFLogxK
U2 - 10.1016/j.apcatb.2022.121810
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 -