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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 22, Number 2
BKCSDE 22(2)
February 20, 2001 

 
Title
Crystal Structures of Ni2+ - and Tl+ - Exchanged Zeolite X, Ni17Tl58Si100Al92O384 and Ni12Tl68Si100Al92O384
Author
Mee Kyung Song, Bo young Yoon, Yang Kim
Keywords
Structure, Zeolite X, Nickel, Thallium, Ion-exchange.
Abstract
The crystal structures of fully dehydrated Ni2+- and Tl+ -exchanged zeolite X (Ni17Tl58-X, and Ni12Tl68-X; X=Si100Al92O384) have been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd3 at 21(1)℃ (a=24.380(4) Å, 24.660(4) Å, respectively). Their structures have been refined to the final error indices R1=0.037 and R2=0.043 with 485 reflections, and R1=0.039 and R2=0.040 with 306 reflections, respectively, for which I >3б(I). In Ni17Tl58-X, 17 Ni2+ ions per unit cell were found at only two sites: 15 at site I at the center of the hexagonal prism (Ni-O=2.203(9) Å) and the remaining 2 at site Ⅱ near single six-oxygen rings in the supercage (Ni-O=2.16(3) Å). Fifty-eight Tl+ ions were found at five crystallographic sites: 28 at site II (Tl-O=2.626(8) Å), 2 at site I' in the sodalite cavity near the hexagonal prism (Tl-O=2.85(1) Å), another 2 at site Ⅱ' in the sodalite cavity (Tl-O=2.77(1) Å). The remaining 26 were found at two nonequivalent Ⅲ' sites with occupancies of 23 and 3. In Ni12Tl68-X, 12 Ni2+ ions per unit cell were found at two sites: 10 at site I (Ni-O=2.37(2) Å) and the remaining 2 at site Ⅱ (Ni-O=2.13(2) Å). Sixty-eight Tl+ ions were found at five crystallographic sites: 28 at site II (Tl-O=2.63(1) Å), 12 at site I' (Tl-O=2.62(1) Å), 2 at site Ⅱ' (Tl-O=3.01(2) Å), and the remaining 26 at two Ⅲ' sites with occupancies of 23 and 3. It appears that Ni 2+ ions prefer to occupy site I and Ⅱ, in that order. The large Tl+ ions occupy the remaining sites, I', Ⅱ, Ⅱ' and two different Ⅲ' sites. In both crystals, only the Ni2+ ions at site II were reduced and migrated to the external surface of zeolite X when these crystals were treated with hydrogen gas.
Page
164 - 170
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