Single-crystal Structure of Fully Dehydrated and Largely NH_4~+-exchanged Zeolite Y (FAU, Si/Al = 1.70), |(NH4)_(60)Na_(11)|[Si_(121)Al_(71)O_(384)]-FAU

摘要

The single-crystal structure of largely ammonium-exchanged zeolite Y dehydrated at room temperature (293 K) and 1 X 10~(-6) Torr. has been determined using synchrotron X-radiation in the cubic space group Fd3m (a = 24.9639(2) A) at 294 K. The structure was refined to the final error index R1 = 0.0429 with 926 reflections where F_o > 4 sigma(F_o); the composition (best integers) was identified as [(NH4)_(60)Na_(11)|[Si_(121)Al_(71)O_(384)]-FAU. The 11 Na~+ ions per unit cell were found at three different crystallographic sites and 60 NH_~4+ ions were distributed over three sites. The 3 Na~+ ions were located at site I, the center of the hexagonal prism (Na-O = 2.842(5) A and O-Na-O = 85.98(12)°). The 4 Na~+ and 22 NH_4~+ ions were found at site I' in the sodalite cavity opposite the double 6-rings, respectively (Na-O = 2.53(13) A, O-Na-O = 99.9(7)°, N-O = 2.762(11) A, and O-N-O = 89.1(5)°). About 4 Na~+ ions occupied site II (Na-O = 2.40(4) A and O-Na-O = 108.9(3)°) and 29 NH_4~+ ions occupy site II (N-O = 2.824(9) A and O-N-O = 87.3(3)°) opposite to the single 6-rings in the supercage. The remaining 9 NH_~4+ ions were distributed over site III' (N-O = 2.55(3), 2.725(13) A and O-N-O = 94.1(13), 62.16(15), 155.7(14)°).