Crystal structure of dehydrated Rb+ -exchanged zeolite X, Rb71Na21Si100Al92O384

The crystal structure of dehydrated Rb+ -exchanged zeolite x, stoichiometry Rb71Na21-X (Rb71Na21Si100O384)per unit cell, has been determined from single-crystal X-ray diffraction data gathered by counter methods. The structure was solved and refined in the cubic space group Fd3, a=25.007(3) A at 21(1).deg.C. The crystal was prepared by ion exchange in a flowing stream using a 0.05 M aqueous RbOH solution (pH=12.7). The crystal was then dehydrated at 360.deg.C and 2x106 torr for two days. The structure was refined to the final error in dices, R1=0.047 and R2=0.040 with 239 reflections for which I>3σ(I). In this structure, 71 Rb+ ions per unit cell are found at six different crystallographic sites and 21 Na+ ions per unit cell are found at two different crystallographic sites. Four and a half Rb+ ions are located at site I, the center of the hexagonal prism. Nine Rb+ ions are found at site I' in the sodalite cavity (Rb-O=2.910(15) A and O-Rb-O=78.1(4).deg.). Eighteen Rb+ ions are found at site II in the supercage (Rb-O=2.789(9) A and O-Rb-O=92.1)4.deg.). Two and a half Rb+ ions, which lie at site II', are recessed ca. 2.07 A into the sodalite cavity from their three O(2) oxygen planes (Rb-O=3.105(37) A and O-Rb-O=80.6(5).deg.). Thirty-two Rb+ ions are found at site III deep in the supercage (Rb-O=2.918(12) A and O-Rb-O=71.9(4).deg.), and five Rb+ ions are found at site III'. Seven Na+ ions also lie at site I. Fourteen Na+ ions are found at site II in the supercage (Na-O =2.350(19) A and O-Na-O=117.5(6).deg.)