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Characterization of Brønsted and Lewis acidity in zeolites by solid-state NMR and the recent progress in the REDOR technique

✍ Scribed by A. L. Blumenfeld; J. J. Fripiat

Publisher
John Wiley and Sons
Year
1999
Tongue
English
Weight
110 KB
Volume
37
Category
Article
ISSN
0749-1581

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✦ Synopsis

Because of their use as catalysts, the volume of papers published on the nature of the acid sites in zeolites is impressive. The number of acid sites is correctly estimated and their chemical nature is known. There are however numerous domains still largely unexplored, such as the structural description (topology) of the disordered surface of a real catalyst. 29 Si and 27 Al REDOR NMR from chemisorbed ammonia provide the spatial arrangement of the base with respect to either the Si/Al distribution in the lattice or the coordination in the nonframework Al nano-particles, shedding light on the nature of the Brønsted and Lewis sites. In particular they explain the main features ruling the strength of the Brønsted sites and the 'dispersion' of Lewis sites, that is the ratio of the number of sites to the number of nonframework aluminum.

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