Abstract
A single crystal of zeolite Y, vertical bar Na-71 vertical bar[Si121Al71O384]-FAU, was ion exchanged to generate vertical bar(NH4)(38)Na-33 vertical bar[Si121Al71O384]-FAU. This was then vacuum dehydrated at 673 K, and, without re-exposure to the atmosphere, its structure was determined crystallographically using synchrotron X-radiation in the cubic space group Fd (3) over barm at 294 K. It was refined to the final error index R-1 = 0.0532 with 522 reflections for which F-o > 4 sigma(F-o). The composition ( best integers) is determined to be vertical bar Na33H26(Al5O4)vertical bar[Si126Al66O384]-FAU which means full dehydration, deamination, and dealumination were achieved. The 33 Na+ ions per unit cell were found at two crystallographically distinct positions: nine at site I ( in the centers of the D6Rs) and 24 at site II (in supercages opposite S6Rs). The 2.5 sodalite units contained a dimeric tetrahedral aluminate cation (Al-O = 1.40(8) and 1.60(8) angstrom) at its center. Each [Al5O4](7+) cation coordinates to framework oxygen of D6Rs with tetrahedral manner. This work demonstrates that it is possible to obtain large amount of dealuminated species within the H-Y zeolite framework which should enhance the acidity of adjacent sites for higher catalytic activity.