Crystal-chemical studies of cation-exchanged zeolite A

Abstract

Powder and single crystals of K and NH4 exchanged zeolite A were prepared by static exchange methods. The crystal structure of hydrated zeolite K,Na-A and NH4-A were investigated by X-ray diffraction methods (space group Fm-3c) at ambient temperature. The refinement results indicated that all cations and large proportion of water molecules were located in the big grc units. The residual water molecules resided on the 6-fold axes in the toc units. In zeolite NH4-A, dealumination process occurred when the crystal stored in air. The thermal behavior of zeolite K-A, NH4-A and intermediate samples were studied by means of in situ X-ray powder diffraction combined with thermal gravimetric analyses in air and under vacuum conditions. Heavy atoms (Ba2 and Sr2 ) exchanged zeolite A were prepared. The results showed that the low X-ray intensity compared with zeolite Na-A was due to the high absorption coefficient of heavy atoms for X-rays.