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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 30, Number 6
BKCSDE 30(6)
June 20, 2009 

 
Title
Synthesis of Tellurium Sorption Complexes in Fully Dehydrated and Fully Ca2+-exchanged Zeolites A and X and their Single-crystal Structures
Author
Woo Taik Lim*, Jong Sam Park, Sang Hoon Lee, Ki Jin Jung, Nam Ho Heo*
Keywords
Zeolite A, Zeolite X, Tellurium, Ca2+, Structure
Abstract
Single crystals of fully dehydrated and fully Ca2+-exchanged zeolites A (|Ca6|[Si12Al12O48]-LTA) and X (|Ca46| [Si100Al92O384]-FAU) were brought into contact with Te in fine pyrex capillaries at 623 K and 673 K, respectively, for 5 days. Crystal structures of Te-sorbed Ca2+-exchanged zeolites A and X have been determined by single-crystal X-ray diffraction techniques at 294 K in the cubic space group Pm3 m (a = 12.288(2) A) and Fd 3 (a = 25.012(1) A), respectively. The crystal structures of pale red-brown |Ca6Te3|[Si12Al12O48]-LTA and black coloured |Ca46Te8| [Si100Al92O384]-FAU have been refined to the final error indices of R1/wR2 = 0.1096/0.2768 and R1/wR2 = 0.1054/ 0.2979 with 204 and 282 reflections for which Fo > 4σ(Fo), respectively. In the structure of |Ca6Te3|[Si12Al12O48]- LTA, 6 Ca2+ ions per unit cell were found at one crystallographic positions, on 3-fold axes equipoints of opposite 6-rings. In |Ca46Te8|[Si100Al92O384]-FAU, 46 Ca2+ ions per unit cell were found at four crystallographically distinct positions: 3 Ca2+ ions at Ca(1) fill the 16 equivalent positions of site I, 21 Ca2+ ions at Ca(2) fill the 32 equivalent positions of site I’, 10 and 12 Ca2+ ions at Ca(3) and Ca(4), respectively, fill the 32 equivalent positions of site II. The Te clusters are stabilized by interaction with cations and framework oxygen. In sodalite units, Te-Te distances of 2.86(10) and 2.69(4) A in zeolites A and X, respectively exhibited strong covalent properties due to their interaction with Ca2+ ions. On the other hand, in large cavity and supercage, those of 2.99(3) and 2.76(11) A in zeolites A and X, respectively, showed ionic properties because alternative ionic interaction was formed through framework oxygen at one end and Ca2+ cations at the other end.
Page
1274 - 1284
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