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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 10, Number 3
BKCSDE 10(3)
March 20, 1989 

Crystallographic Evidence for the Reduction of CO in Partially Dehydratd Silver Zeolite A
Yang Kim*, Seong Hwan Song, Karl Seff
The crystal structure of Ag+-exchanged zeolite A vacuum-dehydrated at 370℃ and then treated with carbon monoxide at 23℃ has been determined by single crystal x-ray diffraction methods in the cubic space group Pm3m at 23(1)℃ ; a = 12.116 (2)Å. The structure was refined to the final error indices R1 = 0.061 and R2(weighted) = 0.068 using 349 independent reflections for which I > 3σ(I). 3.6 Ag+-CO complexes, where -CO may represent -CHO or -CH2OH, were found in each large cavity. By coordination to silver atoms followed by reaction with Ag°and H+ within the zeolite, carbon monoxide has been partially reduced. In about 28% of the sodalite units, a Ag6(Ag+)2 cluster may be present. In about 37% of the sodalite units, three Ag+ ions are found on threefold axes where they may be bridged by three water molecules. The remaining 35% of the sodalite units are empty of silver species. Two Ag+ ions per unit cell are associated with 8-ring oxygens. The remaining ca 3 Ag+ ions per unit cell have been reduced during the synthesis and have migrated to form small silver crystallities on the surface of the zeolite single crystal.
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