STRUCTURAL INVESTIGATIONS OF SAPO-37 MOLECULAR-SIEVE BY COHERENCE-TRANSFER AND DIPOLAR-DEPHASING SOLID-STATE NUCLEAR-MAGNETIC-RESONANCE EXPERIMENTS

Citation
Ca. Fyfe et al., STRUCTURAL INVESTIGATIONS OF SAPO-37 MOLECULAR-SIEVE BY COHERENCE-TRANSFER AND DIPOLAR-DEPHASING SOLID-STATE NUCLEAR-MAGNETIC-RESONANCE EXPERIMENTS, Microporous materials, 5(1-2), 1995, pp. 29-37
Citations number
21
Categorie Soggetti
Chemistry Physical","Material Science","Chemistry Applied
Journal title
ISSN journal
09276513
Volume
5
Issue
1-2
Year of publication
1995
Pages
29 - 37
Database
ISI
SICI code
0927-6513(1995)5:1-2<29:SIOSMB>2.0.ZU;2-H
Abstract
In this work, dipolar-based coherence-transfer and dipolar-dephasing s olid-state nuclear magnetic resonance (NMR) experiments were performed to investigate the structure of the silicoaluminophosphate molecular sieve SAPO-37. The Al-27,Si-29 transferred-echo double-resonance (TEDO R) experiment directly proves, for the first time, that silicon substi tutes for phosphorus atoms in the framework via the SM2 mechanism. The Al-27 (P-31) and Al-27 (Si-29) dipolar-dephasing difference experimen ts and the two-dimensional Al-27-->P-31 TEDOR experiment indicate the presence of three types of aluminum environments: tetrahedral Al surro unded by symmetrical [4P] or [4Si] environments which give rise to a s harp resonance, tetrahedral Al surrounded by asymmetrical [3P, Si], [2 P, 2Si] or [P, 3Si] environments which give rise to a broad resonance, and also extra-framework amorphous octahedral Al.