Cation distributions in fully hydrated Sr-and Rb- bicationic zeolites: an X-ray anomalous powder diffraction study

摘要

X-ray anomalous powder diffraction studies on bicationic X zeolites at high water loading has shown preference for occupation by Sr~(2+) cations of sites Ⅰ', Ⅱ and the disordered positions in the supercage (site~*) whatever the other cation (Ca~(2+), Rb~+). Rb~+ occupies preferentially site Ⅱ, then site~* if enough of these cations are present. Ca~(2+) shows strong preference for site Ⅰ' and site~* in SrCaX and RbCaX. In all samples studied, site Ⅱ' is mainly populated by water molecules.