Pressure-induced hydration and cation migration in a Cs+ exchanged gallosilicate zeolite LTL: Sychrotron X-ray powder diffraction study at ambient and high pressures
- Pressure-induced hydration and cation migration in a Cs+ exchanged gallosilicate zeolite LTL: Sychrotron X-ray powder diffraction study at ambient and high pressures
- 성동훈; 이용문; 김선진; 이현위; 안도천; 신남수; Thomas Vogt; 이용재
- Zeolite LTL; Cs-exchange; High-pressure; Synchrotron; Powder diffraction
- Issue Date
- Microporous and mesoporous materials
- VOL 136, NO 1-3, 75-82
- The ambient and high pressure structures of a partially cesium-exchanged K-gallosilicate with a zeolite
LTL framework topology (Cs0.65K0.35–GaSi–LTL) was studied using synchrotron X-ray powder diffraction.
In contrast to the cation distribution present in the aluminosilicate analogues, the larger cesium cations
replace part of the potassium cations in the narrow 8-ring channel as well as in the main 12-ring channel
of the gallosilicate LTL. Under hydrostatic pressures mediated by a pore-penetrating alcohol and water
mixture, anomalous compression behavior is observed with a slight increase in the unit cell volume upon
initial compression, i.e., 0.15% expansion at 0.44 GPa. This is the result of the continuous increase of the aaxis
length up to 2 GPa and is found to be related to the gradual pressure-induced hydration (PIH) occurring
inside the main 12-ring channel, where the water content increases from 15.9(1) H2O at ambient
conditions to 26.7(1) H2O per formula unit at 2.83 GPa. During PIH, part of the cesium cations along
the main 12-ring channel migrate into the narrow 8-ring channel. Compared to the structural changes
observed in K–GaSi–LTL, the degree of pressure-induced hydration and the accompanying cation migration
is found to be diminished in Cs0.65K0.35–GaSi–LTL.
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