Single-crystal Structure of Partially Dehydrated Partially Mg²⁺-exchanged Zeolite Y (FAU), |Mg_30.5Na₁₄(H₂O)_2.5|[Si₁₁₇Al₇₅O₃₈₄]-FAU

Abstract

The single-crystal structure of partially dehydrated partially Mg 2+ -exchanged zeolite Y, |Mg 30.5 Na 14 (H 2 O) 2.5 | [Si 117 Al 75 O 384 ]-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 F o > 4σ(F o )) R 1 = 0.0377 (Based on F) and R 2 = 0.1032 (Based on F 2 ). About 30.5 Mg 2+ ions per unit cell are found at four different crystallographic sites. The 14 Mg 2+ 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 Mg 2+ ions are found at site I' in the sodalite cavity; the Mg 2+ ions are recessed 1.22 Å into the sodalite cavity from their 3-oxygen plane (Mg-O = 2.20(3) Å and O-Mg-O = 92.3(14) o ). Site II' positions (opposite single 6-rings in the sodalite cage) are occupied by 2.5 Mg 2+ ions, each coordinated to an H 2 O molecule (Mg-O = 2.187(20) Å and O-Mg-O = 114.2(16) o ). The 10 Mg 2+ 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 ).