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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 19, Number 1
BKCSDE 19(1)
January 20, 1998 

 
Title
Crystal Structure of Dehydrated Rb+-Exchanged Zeolite X, Rb71Na21Si100Al92O384
Author
Seok Hee Lee, Yang Kim, Duk-Soo Kim, Karl Seff
Keywords
Abstract
The crystal structure of dehydrated Rb+-exchanged zeolite X, stoichiometry Rb71Na21-X (Rb71Na21Si100Al92O384) per unit cell, has been determined from single-crystal X-ray diffraction date gathered by counter methods. The structure was solved and refined in the cubic space group Fd3, a=25.007(3) Å at 21(1) ℃. 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 ℃ and 2×10-6 torr for two days. The structure was refined to the final error indices, 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) Å and O-Rb-O=78.1(4)°). Eighteen Rb+ ions are found at site Ⅱ in the supercage (Rb-O=2.789(9) Å and O-Rb-O=92.1(4)°). Two and a half Rb+ ions, which lie at site Ⅱ', are recessed ca. 2.07 Å into the sodalite cavity from their three O(2) oxygen planes (Rb-O=3.105(37) Å and O-Rb-O=80.6(5)°). Thirty-two Rb+ ions are found at site Ⅲ deep in the supercage (Rb-O=2.918(12) Å and O-Rb-O=71.9(4)°), 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) Å and O-Na-O=117.5(6)°).
Page
98 - 103
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