Single-Crystal Structure of |Li50Na25|[Si117Al75O384]-FAU
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The single-crystal structure of fully dehydrated partially Li+-exchanged zeolite Y, |Li50Na25|[Si117Al75O384]-FAU, was determined by single-crystal synchrotron X-ray diffraction techniques in the cubic space group Fd3m at 100(1) K. Ion exchange was accomplished by flowing stream of 0.1 M aqueous LiNO3 for 2 days at 293 K, followed by vacuum dehydration at 623 K and 1×10-6 Torr for 2 days. The structure was refined using all intensities to the final error indices (using only the 801 reflections with (Fo > 4σ(Fo)) R1/R2 = 0.043/0.140. The 50 Li+ ions per unit cell are found at three different crystallographic sites. The 19 Li+ ions occupy at site I’ in the sodalite cavity: the Li+ ions are recessed 0.30 Å into the sodalite cavity from their 3-oxygens plane (Li-O = 1.926(5) Å and O-Li-O = 117.7(3)°). The 20 Li+ ions are found at site II in the supercage, being recessed 0.23 Å into the supercage (Li-O= 2.038(5) Å and O-Li-O = 118.7(3)°). Site III’ positions are occupied by 11 Li+ ions: these Li+ ions bind strongly to one oxygen atom (Li-O = 2.00(8) Å). About 25 Na+ ions per unit cell are found at four different crystallographic sites: 4 Na+ ions are at site I, 5 at site I’, 12 at site II, and the remaining 4 at site III’.
Abstract
The single-crystal structure of fully dehydrated partially Li+-exchanged zeolite Y, |Li50Na25|[Si117Al75O384]-FAU, was determined by single-crystal synchrotron X-ray diffraction techniques in the cubic space group Fd3m at 100(1) K. Ion exchange was accomplished by flowing stream of 0.1 M aqueous LiNO3 for 2 days at 293 K, followed by vacuum dehydration at 623 K and 1×10-6 Torr for 2 days. The structure was refined using all intensities to the final error indices (using only the 801 reflections with (Fo > 4σ(Fo)) R1/R2 = 0.043/0.140. The 50 Li+ ions per unit cell are found at three different crystallographic sites. The 19 Li+ ions occupy at site I’ in the sodalite cavity: the Li+ ions are recessed 0.30 Å into the sodalite cavity from their 3-oxygens plane (Li-O = 1.926(5) Å and O-Li-O = 117.7(3)°). The 20 Li+ ions are found at site II in the supercage, being recessed 0.23 Å into the supercage (Li-O= 2.038(5) Å and O-Li-O = 118.7(3)°). Site III’ positions are occupied by 11 Li+ ions: these Li+ ions bind strongly to one oxygen atom (Li-O = 2.00(8) Å). About 25 Na+ ions per unit cell are found at four different crystallographic sites: 4 Na+ ions are at site I, 5 at site I’, 12 at site II, and the remaining 4 at site III’.
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