Single-crystal structures of highly [formula omitted]-exchanged, fully deaminated, and fully Tl +-exchanged zeolite Y (FAU, Si/Al = 1.56), all fully dehydrated

Abstract

Single crystals of zeolite Y, |Na 75|[Si 117Al 75O 384]-FAU, with diameters up to 0.30 mm were grown from gels; Si/Al = 1.56. They were ion exchanged and fully dehydrated to generate |(NH 4) 67H 5Na 3|[Si 117Al 75O 384]-FAU (crystal 1, partially deaminated), |H 72Na 3|[Si 117Al 75O 384]-FAU (crystal 2, fully deaminated at 473 K) and |Tl 75|[Si 117Al 75O 384]-FAU (crystal 3). Their structures were determined crystallographically at 294 K using synchrotron X-radiation in the cubic space group Fd 3 ¯ m . They were refined to the final error indices R 1/ wR 2 = 0.037/0.126, 0.055/0.190, and 0.044/0.121 using 884, 723, and 851 reflections with F o > 4 σ( F o) for crystals 1, 2, and 3, respectively. In crystal 1, 67 NH 4 + and 3 Na + ions per unit cell are found at four different crystallographic sites. Six NH 4 + ions were found at the centers of double 6-rings (site I; N···O = 2.888(3) Å). Filling site I′ are 32 NH 4 + ions (N···O = 2.774(5) Å); each is recessed 1.59 Å into the sodalite cavity from the plane of the three oxygens to which it bonds. Filling site II in the supercages are 29 NH 4 + and 3 Na + ions, each of which extends 1.69 Å and 1.10 Å, respectively, into the supercage from its 3-oxygen plane (N···O = 2.818(5) Å, Na–O = 2.512(19) Å). The remaining 5 of the 72 NH 4 + ions originally present per unit cell have apparently been deaminated by vacuum dehydration at 294 K. NH 4 + ions simultaneously occupy sites I and I′ as K + ions did in |K 71|[Si 121Al 71O 384]-FAU, |K 92|[Si 100Al 92O 384]-FAU, and |K 96|[Si 96Al 96O 384]-FAU; the internitrogen distance is 3.36 Å. In crystal 2, three Na + ions per unit cell are found at site I′ (Na–O = 2.207(13) Å); no other cations were found so the deamination of NH 4 + is complete at 473 K. In crystal 3, 30, 30, 9, 4, and 2 Tl + ions were found at sites I′, II, and three sites III′ per unit cell, respectively. The total, 75, agrees with the results of EDX analysis to establish the framework composition (the Si/Al ratio) of these crystals.