Powder x-ray diffraction and solid state NMR techniques for zeolite structure determination

The synthesis of zeolites, porous aluminosilicates, had a large impact on the development of catalyst materials. The framework structures of these systems consist of Si and Al atoms, referred to as T-atoms, tetrahedrally coordinated to oxygen atoms to form topologies with well defined and regular channel systems. Cations are necessary to satisfy the charge on the Al atoms and are exchangeable. The T-atoms may also consist of any atom capable of isomorphorus substitutions for Si. Since good quality large zeolite crystals are not available, powder X-ray diffraction is used to derive structural information, and with improvements in powder diffraction instrumentation and the availability of synchrotron and rotating anode high intensity Xray sources, much higher quality structure data is obtained. The combined application of solid state NMR which probes short-range order, X-ray diffraction which is a long-range order technique and Rietveld refinement has greatly increased both the quantity and quality of structural information available.