Comparison ofthe 17 O NMR spectra ofzeolites LTA and LSX

O NMR studies ofvarious cation-exchanged LTA and LSX zeolites have shown similarities between the two systems. LSX samples containing divalent cations contain resonances with similar chemical shifts to those previously assigned to 'bare' framework oxygen atoms in Ca-LTA and Sr-LTA. The assignments are consistent with the trends seen in the spectra ofmonovalent cation- containing LSX and LTA zeolites, which show an increase in the average chemical shift with increasing cationic radius. The spectrum ofLi-LSX, like Na-LSX, can be assigned based on the T-O-T bond angles. Gas sorption studies on Li-LSX are used to help identify the framework oxygen atoms that form the b-cages and demonstrate the sensitivity ofthe 17 O shifts to gas loading.