CRYSTAL-STRUCTURE OF A PARTIALLY LITHIUM-EXCHANGED X ZEOLITE IN HYDRATED (25-DEGREES-C) AND DEHYDRATED (275-DEGREES-C) STATES

The crystal structures of a partially Li-exchanged X zeolite Li62Na30Al92Si100O384·200 H2O (h-LiNaX) and its dehydrated form (d-LiNaX) have been determined using single-crystal X-ray diffraction data. The dehydrated form was measured at 275°C. The crystal structures were refined by the least-squares method in the cubic space group Fd3 [a = 24.82(1) A ̊, h-LiNaX; a = 24.75(1) A ̊, d-LiNaX] with 385 and 190 reflections to final R-factors of 0.067 and 0.065 for the hydrated and dehydrated forms, respectively. In h-LiNaX, the Li ions are located in site I′ and displaced from the plane passing through the coordination oxygen atoms by 0.6(1) Å. In d-LiNaX, in addition to site I′, the Li+ ions occupy site II at the center of the six-membered rings. The large distortions of the zeolite framework occurring upon dehydration are related to the cation redistribution and strong interactions between Li ions and oxygen-framework atoms. © 1990.