Structural Studies of Zeolites using Combined Neutron and Synchrotron Rietveld Refinements. Brian H. Toby and Nazy Khosrovani, Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg MD 20899 USA.

Zeolites and related molecular sieves are used in a wide variety of commercial applications. They are used as catalysts in production of gasoline, pharmaceuticals, and other non-commodity chemicals. Zeolites also have ion exchange capabilities. For this reason they are used in detergents to reduce hardness of water. Industrial-scale separation of gases is also performed using zeolites.

NIST is currently certifying three Zeolite Standard Reference Materials, as well as issuing nine additional Reference Materials, in response to a request from the industrial and academic zeolite research community. Synchrotron and Neutron diffraction measurements will play a primary role in the certification of these materials.

Results from our studies of cation and guest molecule siting in zeolite systems as well as new instrumentation at NIST designed for powder diffraction study of these systems will be also presented.