Single-crystal Structure of Partially Dehydrated Partially Mg2+-exchanged Zeolite Y (FAU), |Mg30.5Na14(H2O)2.5|[Si117Al75O384]-FAU

Abstract

The single-crystal structure of partially dehydrated partially <TEX>$Mg^{2+}$</TEX>-exchanged zeolite Y, <TEX>${\mid}Mg{30.5}Na_{14}(H_2O)_{2.5}{\mid}$</TEX> [<TEX>$Si_{117}Al_{75}O_{384}$</TEX>]-FAU per unit cell, <TEX>${\alpha}$</TEX> = 25.5060(1) <TEX>${\AA}$</TEX>, dehydrated at 723 K and <TEX>$1{\times}10^{-4}$</TEX> Pa, has been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd<TEX>$\bar{3}$</TEX> m at 100(1) K. The structure was refined using all intensities to the final error indices (using only the 561 reflections with <TEX>$F_{\circ}$</TEX> > <TEX>$4{\sigma}(F_{\circ})$</TEX>) <TEX>$R_1$</TEX> = 0.0377 (Based on F) and <TEX>$R_2$</TEX> = 0.1032 (Based on <TEX>$F^2$</TEX>). About 30.5 <TEX>$Mg^{2+}$</TEX> ions per unit cell are found at four different crystallographic sites. The 14 <TEX>$Mg^{2+}$</TEX> ions occupy at site I at the center of double 6-ring (Mg-O = 2.231(3) <TEX>${\AA}$</TEX>, O-Mg-O = <TEX>$89.15(11)^{\circ}$</TEX> and <TEX>$90.85(11)^{\circ}$</TEX>). Four <TEX>$Mg^{2+}$</TEX> ions are found at site I' in the sodalite cavity; the <TEX>$Mg^{2+}$</TEX> ions are recessed 1.22 <TEX>${\AA}$</TEX> into the sodalite cavity from their 3-oxygen plane (Mg-O = 2.20(3) <TEX>${\AA}$</TEX> and O-Mg-O = <TEX>$92.3(14)^{\circ}$</TEX>). Site II' positions (opposite single 6-rings in the sodalite cage) are occupied by 2.5 <TEX>$Mg^{2+}$</TEX> ions, each coordinated to an <TEX>$H_2O$</TEX> molecule (Mg-O = 2.187(20) <TEX>${\AA}$</TEX> and O-Mg-O = <TEX>$114.2(16)^{\circ}$</TEX>). The 10 <TEX>$Mg^{2+}$</TEX> ions are nearly three-quarters filled at site II in the supercage, being recessed 0.12 <TEX>${\AA}$</TEX> into the supercage (Mg-O = 2.123(4) A and O-Mg-O = <TEX>$119.70(19)^{\circ}$</TEX>). About 14 <TEX>$Na^+$</TEX> ions per unit cell are found at one crystallographic site; the <TEX>$Na^+$</TEX> ions are located at site II in the supercage (Na-O = 2.234(7) <TEX>${\AA}$</TEX> and O-Mg-O = <TEX>$110.5(4)^{\circ}$</TEX>).