Infrared Structural Studies of Zeolite Frameworks

Mid-infrared spectroscopy has been applied to zeolite structural problems. The infrared spectrum in the region of 200 to 1300 cm-1 is a sensitive tool indicating structural features of zeolite frameworks. Preliminary interpretation suggests infrared specificity for zeolite structure type and group, and for structural subunits such as double rings and large pore openings. It is proposed that the major structural groups present in zeolites can be detected from their infrared pattern. This hypothesis is based on correlation of newly determined infrared spectra of synthetic zeolites with x-ray structure data for most of the known structural classes of zeolites. Other structural information obtained from infrared studies includes framework Si/Al composition, structural changes during thermal decomposition, and cation movement during dehydration and dehydroxylation.