TY - JOUR
T1 - Cation movements during dehydration and NO2 desorption in a Ba-Y,FAU zeolite
T2 - An in situ time-resolved X-ray diffraction study
AU - Wang, Xianqin
AU - Hanson, Jonathan C.
AU - Kwak, Ja Hun
AU - Szanyi, Janos
AU - Peden, Charles H.F.
N1 - Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.
PY - 2013/2/28
Y1 - 2013/2/28
N2 - Synchrotron-based in situ time-resolved X-ray diffraction and Rietveld analysis were used to probe the interactions between Ba-Y,FAU zeolite frameworks and H2O or NO2 molecules. These results provide information about the migration of the Ba2+ cations in the zeolite framework during dehydration and during NO2 adsorption/desorption processes in a water-free zeolite. In the hydrated structure, water molecules form four double rings of hexagonal icelike clusters [(H2O) 6] in the 12 ring openings of the supercage. These water rings interact with the cations and the zeolite framework through four cation/water clusters centered over the four six-membered rings of the supercage (site II). Interpenetrating tetrahedral water clusters [(H2O)4] and tetrahedral Ba cation clusters are observed in the sodalite cage. Consistent with the reported FT-IR results, three different ionic NOx species (NO+, NO+-NO2, and NO3-) are observed following NO2 adsorption by the dehydrated Ba-Y,FAU zeolite. The structure of the water and the NOx species are correlated with the interactions between the adsorbates, the cations, and the framework. The population of Ba2+ ions at different cationic positions strongly depends on the amount of bound water or NOx species. Both dehydration and NO2 adsorption/desorption result in facile migration of Ba2+ ions among the different cationic positions. Data obtained in this work have provided direct evidence for the Ba 2+ cation migration to accommodate the binding of gas molecules. This important feature may play a pivotal role in the strong binding of NO 2 to Ba-Y,FAU zeolite, a prerequisite for high catalytic activity in lean NOx reduction catalysis.
AB - Synchrotron-based in situ time-resolved X-ray diffraction and Rietveld analysis were used to probe the interactions between Ba-Y,FAU zeolite frameworks and H2O or NO2 molecules. These results provide information about the migration of the Ba2+ cations in the zeolite framework during dehydration and during NO2 adsorption/desorption processes in a water-free zeolite. In the hydrated structure, water molecules form four double rings of hexagonal icelike clusters [(H2O) 6] in the 12 ring openings of the supercage. These water rings interact with the cations and the zeolite framework through four cation/water clusters centered over the four six-membered rings of the supercage (site II). Interpenetrating tetrahedral water clusters [(H2O)4] and tetrahedral Ba cation clusters are observed in the sodalite cage. Consistent with the reported FT-IR results, three different ionic NOx species (NO+, NO+-NO2, and NO3-) are observed following NO2 adsorption by the dehydrated Ba-Y,FAU zeolite. The structure of the water and the NOx species are correlated with the interactions between the adsorbates, the cations, and the framework. The population of Ba2+ ions at different cationic positions strongly depends on the amount of bound water or NOx species. Both dehydration and NO2 adsorption/desorption result in facile migration of Ba2+ ions among the different cationic positions. Data obtained in this work have provided direct evidence for the Ba 2+ cation migration to accommodate the binding of gas molecules. This important feature may play a pivotal role in the strong binding of NO 2 to Ba-Y,FAU zeolite, a prerequisite for high catalytic activity in lean NOx reduction catalysis.
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U2 - 10.1021/jp308307m
DO - 10.1021/jp308307m
M3 - Article
AN - SCOPUS:84874586068
SN - 1932-7447
VL - 117
SP - 3915
EP - 3922
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 8
ER -