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KMID : 1059519890330060623
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Journal of the Korean Chemical Society
1989 Volume.33 No. 6 p.623 ~ p.632
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A Study on the Hydrated and Dehydrated Mn2+-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 positions and interaction energies of framework atoms and water molecules of Mn2+-exchanged zeolite A were calculated using some potential energy functions and an optimization program. The sum of interaction energies of framework atoms in dehydrated Mn4.5Na3-A was approximately the same as those of thermally stable Ca2+-or Mg2+-exchanged zeolite A. Since Mn2+ ions can form good coordination bonds with framework oxygens even in dehydrated state, Mn2+-exchanged zeolite A is considered to be thermally stable. The optimized positions of framework atoms and ions in this work are agreed well with the crystallographic data. Three groups of water molecules are found in hydrated Mn2+-exchanged zeolite A; W(Ⅰ) group of water molecules having only hydrogen bonds, W(Ⅱ) group coordinated to Na+ ion, and W(Ⅲ) group coordinated to Mn2+ ion. The average binding energy of each group of water molecules decrease in the order of W(Ⅲ) > W(Ⅱ) > W(Ⅰ). The activation energies in the dehydration reaction of each group of water molecules increased in accordance with their binding energy.
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