Adsorption of methanol on the nanocrystalline H–zeolite and alkali metal exchanged M–zeolites: Energetic, NBO and QTAIM analyses
✍ Scribed by H. Roohi; M. Azarpour
- Publisher
- Elsevier Science
- Year
- 2008
- Tongue
- English
- Weight
- 764 KB
- Volume
- 113
- Category
- Article
- ISSN
- 1387-1811
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✦ Synopsis
Adsorption of methanol on the H-zeolite and ion-exchanged M-zeolites (M = Li, Na, and K) has been investigated using 3T cluster model at the B3LYP/6-31++G(d,p) and MP2/6-31++G(d,p) levels and 5T cluster model at B3LYP/6-31++G(d,p) level of theory. The adsorption energy of methanol on the M-zeolites (M = Li, Na, and K) decreases when the cations (M + ) are changed from Li + to K + , in agreement with the weaker acidity of K + ion compared to the Li + ion. The proton jump between neighboring oxygen atoms of Al center has been studied in five cluster models. The electron density (q), Laplacian of electron density ($ 2 q) and energy density (H) estimated by AIM calculations, showed that both H M Á Á ÁO Z and O M Á Á ÁH Z hydrogen bonds are partially covalent and partially electrostatic in nature, whereas both O Z -H Z and O M -H M have covalent character. $ 2 q and H(r) values at MÁ Á ÁO M (M = Li, Na, and K) BCP of complexes are positive and decrease on going from complex Li + to complex K + . As a result, electrostatic nature of MÁ Á ÁO M interaction decreases on going from complex Li + to complex K + . Also, the interaction between methanol and the ZSM-5 zeolites has been examined using the natural bond orbital (NBO) analysis.