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KMID : 1059519950390010007
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Journal of the Korean Chemical Society
1995 Volume.39 No. 1 p.7 ~ p.13
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Crystal Structures of Fully Dehydrated Ca2+-Exchanged Zeolite X, Ca46-X, and Ca2+ and K+-Exchanged Zeolite X, Ca32K28-X
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Jang Se-Bok
Song Seung-Hwan
Kim Yang
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Abstract
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The crystal sructures of Ca46-X (Ca46Al92Si100O384) and Ca32K28-X (Ca32K28Al92Si100O384) dehydrated at 360℃ and 2×10-6 Torr have been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd3 at 21(1)℃. Their structures were refined to the final error indices, R1=0.096 andRw=O.068 with 166 reflections, and R1=0.078 and Rw=O.056 with 130 reflections, respectively, for which I > 3σ(I). In dehydrated Ca48-X, Ca2+ ions are located at two different sites opf high occupancies. Sixteen Ca2+ ions are located at site Ⅰ, the centers of the double six rings (Ca(1)-O(3)=2.51(2)Å and thirty Ca2+ ions are located at site Ⅱ, the six-membered ring faces of sodalite units in the supercage. Latter Ca2+ ions are recessed 0.44Å into the supercage from the three O(2) oxygen plane (Ca(2)-O(2)= 2.24(2)Å and O(2)-Ca(2)-O(2)=119(l)°). In the structure of Ca32K28-X, all Ca2+ ions and K+ ions are located at the four different crystallographic sites: 16 Ca2+ ions are located in the centers of the double six rings, another sixteen Ca2+ ions and sixteen K+ ions are located at the site Ⅱ in the supercage. These Ca2+ ions adn K+ ions are recessed 0.56Å and 1.54Å, respectively, into the supercage from their three O(2) oxygen planes (Ca(2)-O(2)=2.29(2)Å, O(2)-Ca(2)-O(2)=119(1)°, K(1)-O(2)=2.59(2)Å, and O(2)-K(1)-O(2)=99.2(8)°). Twelve K+ ions lie at the site Ⅲ, twofold axis of edge of the four-membered ring ladders inside the supercage (K(2)-O(4)=3.11(6)Å and O(1)-K(2)-O(1)=128(2)°).
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