Two Crystal Structures of Dehydrated Zn2+-Exchanged Zeolite X: Zn46Si100Al92O384 ?¤8ZnO and Zn13Tl66Si100Al92O384 ?¤ 2ZnO

摘要

The crystal structures of fully dehydrated fully Zn 2+ -exchanged zeolite X, Zn46Si100Al92O384 ·8ZnO(Zn46-X ·8ZnO; a = 24.710(4)∈), and that of fully dehydrated Zn 2+ -and Tl+ -exchanged zeolite X, Zn13Tl66Si100Al92O384 ·2ZnO(Zn13Tl66-X ·2ZnO; a = 24.984(4)∈), have been determined by single-crystal X-ray diffraction methods in the cubic space group Fd3 at 21(1)∩. Zn46-X ·8ZnO was prepared by ion exchange in a flowing stream of 0.05 M aqueous Zn(NO3)2 for 2 days. Zn13Tl66-X ·2ZnO was similarly prepared using a solution of 0.025 M each in Zn(NO3)2 and TlNO3. Each crystal was then dehydrated at 400 ∩ and 2 x 10-6 Torr for 2 days. Their structures were refined to the final error indices R1 = 0.052 and R2 = 0.047, with 292 reflections for Zn46-X ·8ZnO, and R1 = 0.039 and R2 = 0.034, with 382 reflections for Zn13Tl66-X ·2ZnO; I > 3 ヲ(I). In the structure of dehydrated Zn46-X ·8ZnO, Zn 2+ ions are located at four different crystallographic sites. Two Zn 2+ ions lie at the center of a double six-ring (site I, Zn-O = 2.584(10)∈, O-Zn-O = 103.2(4)。). Twenty-eight Zn 2+ ions are located at site I` displaced from a shared hexagonal face into a sodalite cavity (Zn-O = 1.984(12)∈, O-Zn-O = 108.0(4)。). Eight over-exchanged Zn 2+ ions, which lie at site II`, are recessed ca. 0.61∈ into the sodalite cavity from their three O(2) oxygen plane (Zn-O = 2.109(11)∈ and O-Zn-O = 109.1(4)。 ), and each associates with three framework oxygens and also with one nonframework oxygen deeper in the sodalite unit in a distorted tetrahedral arrangement. The remaining sixteen Zn 2+ ions are found at site II in a supercage (Zn-O = 1.986(10)∈ and O-Zn-O = 119.7(5)。). In the structure of a dehydrated Zn13Tl66-X·2 ZnO, thirteen Zn 2+ ions are found at site I` adjacent to D6R (Zn-O = 2.036(14)∈ and O-Zn-O = 119.8(5)∑). Two over-exchanged Zn 2+ ions, which lie at site II`, are recessed ca. 0.66 A into the sodalite cavity from their three O(2) oxygen plane (Zn-O = 2.276(36)∈ and O-Zn-O = 109.9(5)∑). Tl + ions are located at four different crystallographic sites. Nineteen Tl + ions lie at site I` in the sodalite cavity (Tl-O = 2.536(13)∈ and O-Tl-O = 88.0(4)∑). Thirty Tl + ions occupy site II, recessed 1.68∈ into a supercage from the three O(2) oxygen plane (Tl-O = 2.678(10)∈ and O-Tl-O = 88.0(4)∑). Four-teen Tl + ions are found at site III deep in the supercage (Tl-O = 2.835(14)∈, O-Tl-O = 75.4(4)∑). The remaining three Tl + ions are found at site III` in a supercage (Tl-O = 3.007(62)∈, Tl-O = 2.408(59)∈, O-Tl-O = 55.4(13)∑).