Anisotropic Chemical Shielding, M-Site Ordering, and Characterization of Extraframework Cations in ETS-10 Studied through MAS/MQ-MAS NMR and Molecular Modeling Techniques
IR@IIP: CSIR-Indian Institute of Petroleum, Dehradun
View Archive Info| Field | Value | |
| Creator |
Ganapathy,S
Vetrivel R Ray,S.S Sen,T Sivasankar,S Delevoye,L Fernandez,C Amoureur,J.P |
|
| Date |
2009-06-23T05:02:27Z
2009-06-23T05:02:27Z 2009-06-23T05:02:27Z |
|
| Identifier |
http://hdl.handle.net/123456789/242
|
|
| Description |
The local structural characteristics of Si and Ti sites in ETS-10 as derived from a combination of
high-resolution magic angle spinning (MAS) NMR spectroscopic and molecular modeling studies are reported.
Pure and highly crystalline ETS-10 and aluminum-substituted ETS-10 (ETAS-10), devoid of impurity ETS-4
phase, were synthesized and fully studied by MAS and multiple-quantum magic angle spinning (MQ-MAS)
NMR. More accurate assignments of the experimentally observed 29Si resonances to the crystallographically
nonequivalent Si sites are made, and a correlation with T-site geometry is established. 29Si slow MAS NMR
is shown to be a very general and powerful methodology to unequivocally establish heteroatom substitution
in the zeolite lattice, and this was used to probe the local symmetry and chemical shielding at different Si sites
in ETS-10 and ETAS-10. 29Si and 27Al MAS NMR spectral analysis of ETAS-10 is used to confirm that the
aluminum substitution occurs only in Si[4Si,0Ti] silicon sites. This, in turn, was used to generate cluster
models for computer graphics techniques. The electronic structure of such cluster models and the calculated
aluminum substitution energy values pinpoint the topographical location of aluminum in ETAS-10. The acidity
of ETAS-10 is predicted on the basis of the quantum chemical cluster model calculations. The first application
of MQ-MAS NMR to study cation environments in molecular sieves is also reported and is used in the present
study to investigate the local structural characteristics of sodium cations in ETS-10 and ETAS-10.
|
|
| Language |
en_US
|
|
| Subject |
NMR
|
|
| Title |
Anisotropic Chemical Shielding, M-Site Ordering, and Characterization of Extraframework Cations in ETS-10 Studied through MAS/MQ-MAS NMR and Molecular Modeling Techniques
|
|
| Type |
Article
|
|