Understanding Zeolite Properties Through Structural Analysis
Barbara A. Reisner,§ Nick D. Hutson, A. Tripathi,° Brian H. Toby,§ J.B. Parise° and Ralph T. Yang
§ Center for Neutron Research, National
Institute of Standards and Technology, Gaithersburg, MD 20899-8562
Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109
° Department of Geosciences, State University of New York, Stony Brook, NY 11794-2100
The presence of extraframework cations are known to strongly affect the properties of zeolites. For example, the addition of copper to ZSM-5, a member of the MFI family of zeolites, is known to catalyze decomposition of NOx into N2 and O2. Silver exchanged zeolites with the faujasite topology (FAU) exhibit enhanced nitrogen adsorption. Zeolites that exhibit this property are used in commercial separations of air. In order to understand the role of extraframework cations on zeolite properties, we need to understand their coordination chemistry. In this poster we demonstrate how structural analysis can be used to understand zeolite properties. Specific systems to be discussed include silver coordination in FAU, alkali metal cation coordination in framework materials with the RHO topology, and copper coordination in ZSM-5. All materials were synthesized and ion-exchanged, then crystallographic analysis was performed using neutron powder diffraction and the Rietveld technique. Structural results, in combination with valence bond analysis, reveal how the properties of these materials are strongly affected by the presence and identity of extraframework cations.