Synthesis and crystal structure of dehydrated, deaminated, and dealuminated zeolite Y (FAU): single-crystal structure of |Na33H26(Al5O4)|[Si126Al66O384]-FAU

A single crystal of zeolite Y, |Na 71 |[Si 121 Al 71 O 384 ]-FAU, was ion exchanged to generate |(NH 4 ) 38 Na 33 |[Si 121 Al 71 O 384 ]-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 m at 294 K. It was refined to the final error index R 1 = 0.0532 with 522 reflections for which F o > 4σ( F o ). The composition (best integers) is determined to be |Na 33 H 26 (Al 5 O 4 )|[Si 126 Al 66 O 384 ]-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) Å) at its center. Each [Al 5 O 4 ] 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.