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KMID : 1059519890330040357
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Journal of the Korean Chemical Society
1989 Volume.33 No. 4 p.357 ~ p.365
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The Structures and Thermal Properties of Divalent Ion Exchanged Zeolite A
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Park Jong-Yul
Kim Yang
Kim Un-Sik
Choi Sang-Gu
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Abstract
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The positional parameters of framework atoms, cations, and water molecules in hydrated and dehydrated Mg4Na4-A, Ca6-A, Zn5Na2-A and Co4Na4-A were determined by the optimization technique using some potential energy functions and VAIOA optimization program. Upon dehydration, cations in hydrated states move toward the framework oxygens of 6 rings. Frameworks of fully dehydrated zeolite A are more stable than those of fully dehydrated divalent cation exchanged Zeolite A. There are three different kinds of water molecules in divalent cation exchanged Zeolite A; W(Ⅲ) (water molecules having hydrogen bonds), W(Ⅱ) (water molecules associated with Na+ ions), and W(Ⅰ) (water molecules associated with divalent cations). Three different DTA endothermic peaks were observed corresponding to the dehydration of three different kinds of water molecules in divalent cation exchanged Zeolite A.
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