Probing Lewis acidity and reactivity of Sn- and Ti-beta zeolite using industrially important moieties: A periodic density functional study
IR@CECRI: CSIR-Central Electrochemical Research Institute, Karaikudi
View Archive Info| Field | Value | |
| Title |
Probing Lewis acidity and reactivity of Sn- and Ti-beta zeolite using industrially
important moieties: A periodic density functional study
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| Creator |
Bhakti, S.
Kulkarni, S. Sailaja, K. Sourav, P. |
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| Subject |
Electrochemical Materials Science
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| Description |
The Lewis acidic nature and reactivity of two industrially important catalysts, viz., Sn and Ti substituted
beta zeolite (T-BEA) are analyzed using a unique combination of structural parameters, energetics and
reactivity descriptors. To achieve this purpose, we adsorb the industrially important moieties (L) namely
NH3, H2O, CH3OH, CH3CN on the active sites of T-BEA. The calculations were performed using a periodic
density functional method where the valence electrons are described using a plane wave basis set in
conjunction with pseudo-potentials for the core electrons. The analysis of the structural properties of
these complexes reveals that TO4 shows typical characteristic splitting 120◦/90◦, close to bipyramidal
geometry as compared to tetrahedral symmetry observed in the bare T-BEA. This is associated with small
variations in the framework bond lengths (≥0.08 Å) and a substantially large variation of bond angles
(≤10◦) in all the ligand-zeolite complexes. Further in both cases of Sn and Ti substituted beta zeolite,
ligand interacts at optimum inter-atomic bond distance. Our interaction energies show that adsorption
of all ligand moieties is stronger at Sn center than that of Ti. In general, the order of stability of the different
T-BEA adducts isNH3 >H2O>CH3OH>CH3CN. The ligand interaction is associated with the corresponding
bond elongation and bond reduction of the adsorbed molecules on catalyst active site, which can be taken
as measure of red or blue shifted frequencies. Finally, the global descriptors of reactivity justify the fact
that soft acid, Sn-BEA, interacts strongly with soft bases following the Pearson’s HSAB principle. However,
hard acid, Ti-BEA interacts with soft bases to form a stable Lewis adduct. Furthermore, the HOMO–LUMO
gap of all Sn-BEA–L adducts is lower than that of Ti-BEA–L adducts indicating to its higher Lewis acidic
nature compared to Ti-BEA.
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| Publisher |
Elsevier B.V.
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| Date |
2010
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| Type |
Article
PeerReviewed |
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| Format |
application/pdf
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| Identifier |
http://cecri.csircentral.net/467/1/2010-094.pdf
Bhakti, S. and Kulkarni, S. and Sailaja, K. and Sourav, P. (2010) Probing Lewis acidity and reactivity of Sn- and Ti-beta zeolite using industrially important moieties: A periodic density functional study. Journal of Molecular Catalysis, 329. pp. 36-43. |
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| Relation |
http://cecri.csircentral.net/467/
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