Characterization of silicon sites in monoclinic zeolite ZSM-5 using 29Si magic angle spinning (MAS) nuclear magnetic resonance (NMR) and molecular modelling
✍ Scribed by C. Sivadinarayana; V.R. Choudhary; R. Vetrivel; S. Ganapathy
- Book ID
- 104357991
- Publisher
- Elsevier Science
- Year
- 1998
- Tongue
- English
- Weight
- 290 KB
- Volume
- 13
- Category
- Article
- ISSN
- 0926-2040
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✦ Synopsis
An attempt has been made to correlate the experimentally observed 29Si MAS NMR chemical shifts of monoclinic phase of highly siliceous ZSM-5 with their electronic properties. In order to incorporate the influence of next neighbor atoms on the 29Si chemical shielding of central SiO4, a pentameric cluster model (H12Si5O16) has been chosen. Each of the 24 crystallographically distinct Si sites, of ZSM-5 framework has been modelled by such cluster models. Based on semi-empirical quantum chemical calculations, a multiple linear regression analysis of the various electronic properties with the 29Si chemical shifts has been attempted. The relative difference in 29Si chemical shifts for the Si sites in ZSM-5 is reasonably accounted, although quantitative prediction may require non-empirical quantum chemical calculations.