Bridging hydrodyl groups in zeolitic catalysts: a computer simulation of their structure, vibrational properties and acidity in protonated faujasites (HY zeolites)
✍ Scribed by Klaus-Peter Schröder; Joachim Sauer; Maurice Leslie; C. Richard; A. Catlow; John M. Thomas
- Publisher
- Elsevier Science
- Year
- 1992
- Tongue
- English
- Weight
- 517 KB
- Volume
- 188
- Category
- Article
- ISSN
- 0009-2614
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✦ Synopsis
The structure and properties of the four possible bridging hydroxyl groups in silicon-rich H-faujasite (zcolite Y ) are studied by lattice-energy minimization carried out within the classical shell model. The most likely proton-accepting sites are the 0 1 and 03 oxygens. Their hydroxyl stretching frequencies arc shown to be responsible for the characteristic high-frequency (HF) and lowfrequency (LF) bands, respectively, in the infrared spectra of H-faujasites. The variation of the OH stretching frequencies for the four isolated sites is correlated with changes of local geometry such as the O-H bond length and the Si-O(H)-AI and the Si-O-H angles. However, there appears to be no correlation with differences in the acid strength as evidenced by the values of the calculated deprotonation energy of the 0 ( I ) H and 0( 3 ) H hydroxyl groups for which only a minor difference is predicted.