CHARACTERIZATION OF LI CATIONS IN ZEOLITE LIX BY SOLID-STATE NMR-SPECTROSCOPY AND NEUTRON-DIFFRACTION

Lithium cations in the dehydrated zeolites LiX-1.0 [(SiAlO4)(96)Li-96] and LiX-1.25 [(Si-106-Al86O384)Li-86] are characterized by a combinat ion of neutron diffraction and magic-angle spinning (MAS) NMR spectros copy. Both samples show in the Li-6 and the Li-7 MAS NMR spectra three lines assigned to Li cations in three different crystallographic site s (SI', SII, and SIII'), The low-field component in Li-6 and Li-7 MAS NMR spectra recorded at a temperature of 295 K belongs to mobile Li ca tions, as proven by variable-temperature Li-7 MAS NMR spectra. Variabl e-temperature neutron diffraction experiments show a phase transition in the temperature range T = 220-230 K in case of LiX-1.0. Neutron dif fraction data recorded at 296 K were refined in the cubic space group Fd (3) over bar and data obtained at 20 K were refined in the orthorho mbic space group Fddd. No phase transitions were observed in the refin ement of the neutron diffraction data of zeolite LiX-1.25 (Fd (3) over bar) recorded at 10 K.