Acidic properties of [Al], [Ga] and [Fe] isomorphously substituted zeolites. Density functional model cluster study of the complexes with a probe CO molecule
✍ Scribed by Paul Strodel; Konstantin M. Neyman; Helmut Knözinger; Notker Rösch
- Publisher
- Elsevier Science
- Year
- 1995
- Tongue
- English
- Weight
- 577 KB
- Volume
- 240
- Category
- Article
- ISSN
- 0009-2614
No coin nor oath required. For personal study only.
✦ Synopsis
The Brensted acid strength and related characteristics of bridging hydroxyl groups in [Al]-, [Gal-and [Fe]-frameworksubstituted zeolites have been studied using a model cluster density functional approach based on a gradient-corrected exchange-correlation energy functional. The acidity is found to decrease in the order Al(OH)Si > Ga(OH)Si > Fe(OH)Si in agreement with existing experimental and theoretical results. The present quantification is based on the calculated deprotonation energy of H,Si(OH)TH,, on the adsorption energy of a CO probe molecule as well as on the changes of the vibrational frequencies and absolute IR intensities of the O-H and of the C-O modes induced by CO adsorption. The vibrational parameters of the carbonyl adsorption complex in [Fe]-zeolites are predicted.