Ordered Silicon Vacancies in the Framework Structure of the Zeolite Catalyst SSZ-74
Physico-chemical characterization of the high-silica zeolite catalyst SSZ-74 (ref. 1) suggested that it, like the related materials TNU-9 (ref. 2) and IM-5 (ref. 3), has a multidimensional 10-ring channel system4. Such pore systems are ideal for many petrochemical applications, and indeed SSZ-74 has been shown to be a good catalyst for a wide variety of reactions1. The elucidation of its framework structure, however, proved to be difficult. Comparable problems were encountered with TNU-9 and IM-5, which were synthesized with related structure-directing agents. Their framework structures, which are the two most complex ones known, both have 24 Si atoms in the asymmetric unit, and were finally solved by combining high-resolution powder diffraction data with information derived from high-resolution electron microscopy images5, 6. Therefore, a similar approach, using the powder charge-flipping algorithm7 to combine the two types of data and molecular modelling to help to locate the structure-directing agent, was applied to SSZ-74. This procedure eventually revealed a most unusual 23-Si-atom framework structure (|(C16H34N2)4|[Si92square4O184(OH)8]) with ordered Si vacancies.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 960061
- Report Number(s):
- BNL-83047-2009-JA; TRN: US201016%%1205
- Journal Information:
- Nature Materials, Vol. 7
- Country of Publication:
- United States
- Language:
- English
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