STRUCTURAL DEFECTS AND CATION-EXCHANGE CAPACITY IN DEALUMINATED Y-ZEOLITES

Y zeolites obtained from solution and vapor phase dealumination treatments were characterized using cation exchange capacity, standard chemical analysis, X-ray powder diffraction, and Si-29 magic angle spinning nuclear magnetic resonance techniques. Both dealumination treatments produce nonframework silica as well as nonframework alumina. By taking into account not only the isomorphic. Al by Si substitutions but also the nonframework species, the calculated lattice charge is in agreement with the cation exchange capacity for Si:Al > 3. The crystallinity seems mainly related to the amount of dislodged silicon.