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, |Na71|[Si121Al71O384]-FAU, was ion exchanged to generate |(NH4)38Na33|[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 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ Fd\bar{3} $$\end{document}m at 294  K. It was refined to the final error index R1 = 0.0532 with 522 reflections for which Fo > 4σ(Fo). The composition (best integers) is determined to be |Na33H26(Al5O4)|[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) Å) 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.