Characterization of isolated Ag cations in homoionic Ag-Y zeolites: A combined anomalous XRPD and EXAFS study

In this contribution we report a structural characterization of a homoionic Ag-Y zeolite (Si/Al = 2.63) on. both short (EXAFS) and long range (XRD) scales. Our study shows that the zeolite is a near-100% exchanged silver faujasite, showing almost isolated Ag+ counterions (EXAFS estimates that clustered species represent less than 2% of the whole silver). Synchrotron radiation XRPD measurements (ESRF, BM16), performed at the Ag-K edge (lambda = 0.486103(2) Angstrom), just before (lambda = 0.486093(2) Angstrom) and far away (lambda = 0.491153(2) Angstrom), allowed us to locate the near totality of the expected Ag+ counterions: 51.9(4) out of 52.9 per unit cell, located in five different sites. The output of the Rietveld refinement has been used successfully to simulate the Ag-K edge EXAFS spectra (ESRF, BM29). (C) 2002 Elsevier Science B.V. All rights reserved.