Localization of benzene in sodium-Y-zeolite by powder neutron diffraction

Abstract

The structure of sodium-Y zeolite, Na56Si1360384A156, containing chemisorbed deuterated benzene has been studied for two different benzene coverages at 4 K and room temperature by powder neutron diffraction. The bare dehydrated zeolite has also been examined. The space group is Fd3m with cell parameters, at room temperature, of a = 24.85 (3) A, 24.83 (3) A, and 24.81 (3) 8, for the bare zeolite, low-coverage, and high-coverage samples, respectively. At 4 K a = 24.85 (3) 8, at low coverage and a = 24.81 (3) 8, for the high-coverage sample. The sodium ions are distributed over three sites whose positions at room temperature for the bare zeolite are Na(1) at 32e (x,x,x), x = 0.2345 (2); Na(2) at 32e, x = 0.0507 (4), and Na(3) at 16c (O,O,O), with fractional occupancies of 100 (2)%, 58 (2)%, and 44 (2)%, respectively.

Localization of ferrocene in NaY zeolite by powder x-ray and neutron diffraction

“…These slight decreases suggest an interaction between the adsorbed ferrocene molecules and the zeolite host. This effect has also been found for benzene in NaY zeolite 7 and pi-complexes in Y-type zeolites. 10 They suggest that this FIG.…”

“…We find for the bare zeolite a lattice parameter aϭ24.870 Å determined from x-ray diffraction and a ϭ24.815 Å determined from neutron diffraction, which is within the range 24.60-25.12 Å which is typically found in the literature. 7 After insertion of one ferrocene molecule per supercage the cell parameter decreases to aϭ24.767 Å and 24.770 Å determined from x-ray and neutron diffraction, respectively. Upon insertion of two ferrocene molecules per supercage the cell parameter further decreases to aϭ24.706 Å and aϭ24.713 Å as found from x-ray and neutron diffraction.…”

“…7 The spacegroup is Fd3m. The observed, calculated, and difference profiles for bare NaY zeolite are shown in Figs.…”

“…This migration of the sodium cations at the SII sites has also been found for benzene in NaY zeolite, where it was by 0.09 Å for loadings of 2.6 benzene molecules per supercage. 7 Figure 8 depicts the final result for the position and orientation of the ferrocene molecules in the zeolite supercage. Note that the position of the iron atom of the ferrocene molecule corresponds to the cross in Figs.…”

“…Since the sodium ions are positively charged it seems natural that the rings orient towards them by electrostatic interactions between the -systems of the aromatic rings and the ions, as with benzene. 7 In solid ferrocene the rings are rotated by 9°from the eclipsed orientation, where the rings are just on top of each other. 12 When adsorbed in a zeolite, the ferrocene rings take the eclipsed orientation.…”