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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 9, Number 6
BKCSDE 9(6)
June 20, 1988 

 
Title
Two Crystal Structures of Dehydrated Ag+ and K+ Exchanged Zeolite A, Ag12-xKx-A, x = 1.3 and 2.7
Author
Yang Kim*, Seong-Hwan Song, Jong-Yul Park, Un-Sik Kim
Keywords
Abstract
Two crystal structures of fully dehydrated silver and potassium exchanged zeolite A, stoichiometries of Ag9.3K2.7-A (a = 12.282(2) Å) and Ag10.7K1.3-A (a = 12.287(2) Å) per unit cell, have been determined from 3-dimensional x-ray diffraction data gathered by counter methods. All structures were solved and refined in the cubic space group Pm3m at 21(1) ℃. The crystals of Ag9.3K2.7-A and Ag10.7K1.3-A were prepared by flow method using exchange solutions in which mole ratios of AgNO3 and KNO3 were 1:10 and 1:5, respectively, with total concentration of 0.05M. The structures of the dehydrated Ag9.3K2.7-A and Ag10.7K1.3-A were refined to yield the final error indices R1 = 0.037 and R2 = 0.040 with 321 reflections, and R1 = 0.042 and R2 = 0.043 with 371 reflections, repectively, for which I > 3σ(Ⅰ). In both structures, eight Ag+ ions are found nearly at 6-ring centers and each Ag+ ion is nearly in the (1 1 1) plane at its O(3) ligands. The 8-ring sites are preferentially occupied by K+ ions in both structures. 1.3 and 1.7 reduced silver atoms per unit cell were found inside of sodalite units of Ag9.3K2.7-A and that of Ag10.7K1.3-A, respectively. These reduced silver species were presumably formed from the reduction of Ag+ ions by oxide ions of residual water molecule or of the zeolite framework. These two crystals may be presented as hexasilver cluster in 21.7% and 28.3% of sodalite unit cells for Ag9.3K2.7-A and Ag10.7K1.3-A, repectively.
Page
338 - 341
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