Solid-state rubidium exchange of zeolite NH4Y

NH4Y has been ion exchanged by reaction with solid Rb2CO3 to form RbY. This process has been followed with X-ray powder diffraction, mass spectrometry and NMR. Both H-1 and Rb-87 MAS NMR are very sensitive to the hydration le vel of the zeolite and have been used to investigate the solid-state exchan ge process. Rb-87 NMR shows that exchange begins instantaneously on grindin g the two solids together: decomposition of Rb2CO3 is observed, together wi th the migration of Rb+ into the zeolite pores. X-ray diffraction indicates that the reaction proceeds to completion by 400 degreesC. The structure of the final RbY product has been refined with Rietveld analysis and rubidium cations have been located at the SI' SII and SIII' positions. Residual sod ium cations from the incomplete exchange of the ammonium starting material have been located at the SI position; this result was confirmed by Na-23 MA S NMR. No evidence for Rb occupation of the Sl positions was observed. Cons iderable disorder is observed in the cages of the zeolite during the ion-ex change process, but refinements of the structures, using the in situ data, indicate that Rb+ cations have entered the socialite cages by 200 degreesC. (C) 2001 Published by Elsevier Science B.V.