NA-23 SYNCHRONIZED DOUBLE-ROTATION NMR-STUDY OF CS+, CA2+, AND LA3+ CATION-EXCHANGED SODIUM ZEOLITE-Y

High-resolution, Na-23 synchronized double-rotation NMR (DOR) experiments provide site-specific information on cation-exchange processes in sodium zeolite Y. The Na-23 NMR spectra of Na56Y, progressively exchanged with Cs+, Ca2+, and La3+ cations, respectively, indicate significantly different cation distributions in the exchanged materials. Cs+ cations preferably deplete Na+ cations from the supercage, while Ca2+ cations initially replace Na+ cations in the hexagonal prisms. La3+ cation-exchange, by contrast, is least disturbing to the relative distribution of the Na+ cations. Cs-133 magic angle spinning (MAS) experiments provide additional information on the cation distributions in the Cs+ cation-exchanged sodium zeolite Y. Interestingly, the positions of the Cs-133 resonance exhibit a significant sensitivity with respect to coexisting extraframework cations in the zeolite.