XRPD study on cation location in Na-Rb-Y zeolite under carefully controlled atmospheres: vacuum, H2O and NH3

High quality XRD data of a dehydrated Na-Rb-Y zeolite with Si/Al = 2.7, collected at the ESRF BM16 beamline, are illustrated. The quality of the Rietveld refinement is very satisfactory, as confirmed by the low R-wp and R-p parameters (7.72 and 5.98 %, respectivly) and by the comparison of the Rb+/Na+ ratio (1.32) with the experimental one (1.38) obtained with analytical methods. We have found that 8.44 Na+ cations are located in site SI, 9.44 Na+ and 5.17 Rb+ cations in site SI' and 2.75 Na+ and 22.08 Rb+ cations in site SII. No cations have been observed in site Sm. Less than 4 cations out of 51.8 remain to be located in the unit cell, which has a cell parameter of a = 24.767(4) Angstrom (V = 15192(9) Angstrom(3)). Th, effect of interaction with 1 Torr of H2O and NH3 on the XRD pattern is marked, so indicating a strong interaction between guest molecules and cations