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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 32, Number 10
BKCSDE 32(10)
October 20, 2011 

Single-crystal Structure of Partially Dehydrated Partially Mg2+-exchanged Zeolite Y (FAU), |Mg30.5Na14(H2O)2.5|[Si117Al75O384]-FAU
Hu Sik Kim, Seong Oon Ko, Woo Taik Lim *
Zeolite Y, Ion exchange, Dehydrated, Structure, Magnesium
The single-crystal structure of partially dehydrated partially Mg2+-exchanged zeolite Y, |Mg30.5Na14(H2O)2.5| [Si117Al75O384]-FAU per unit cell, a = 25.5060(1) Å, dehydrated at 723 K and 1 × 10−4 Pa, has been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd m at 100(1) K. The structure was refined using all intensities to the final error indices (using only the 561 reflections with Fo > 4σ(Fo)) R1 = 0.0377 (Based on F) and R2 = 0.1032 (Based on F2). About 30.5 Mg2+ ions per unit cell are found at four different crystallographic sites. The 14 Mg2+ ions occupy at site I at the center of double 6-ring (Mg-O = 2.231(3) Å, O-Mg-O = 89.15(11)o and 90.85(11)o). Four Mg2+ ions are found at site I' in the sodalite cavity; the Mg2+ ions are recessed 1.22 Å into the sodalite cavity from their 3-oxygen plane (Mg-O = 2.20(3) Å and OMg- O = 92.3(14)o). Site II' positions (opposite single 6-rings in the sodalite cage) are occupied by 2.5 Mg2+ ions, each coordinated to an H2O molecule (Mg-O = 2.187(20) Å and O-Mg-O = 114.2(16)o). The 10 Mg2+ ions are nearly three-quarters filled at site II in the supercage, being recessed 0.12 Å into the supercage (Mg-O = 2.123(4) Å and O-Mg-O = 119.70(19)o). About 14 Na+ ions per unit cell are found at one crystallographic site; the Na+ ions are located at site II in the supercage (Na-O = 2.234(7) Å and O-Mg-O = 110.5(4)o).
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