Water and Cation Distribution in Fully and Partially Hydrated Li-LSX Zeolite

Abstract

Faujasite type zeolite Li-LSX with unit cell composition Li96[Si96Al96O384]·xH2O is a very promising sorption material for heat storage and energy transformation. To understand the hydration and dehydration processes and to optimize the sorption properties, the structures of partially and fully hydrated Li-LSX with water loadings of x = 8, 16, 32, 48, 96, and 270 H2O/D2O were analyzed based on neutron and synchrotron powder data. In addition, forcefield simulations were performed. At low loading of water the cations occupy three sites: SIC (in the center of a 6-ring window of the β-cage), SIIC (in the center of another 6-ring window of the β-cage), and SIII (in front of the 4-ring of the β-cage). Increasing hydration leads to the disordering of Li+ at site SIII, which interacts with water molecules. As a consequence, Li+ moves from SIII sites to other crystallographic sites. In total six different crystallographic water sites (W1−W6) were identified. Nearly all water molecules occupy the supercage; 2.3 wa...