FTIR investigation of the interaction at 77 K of diatomic molecular probes on MCM-22 zeolite
✍ Scribed by B. Onida; F. Geobaldo; F. Testa; F. Crea; E. Garrone
- Publisher
- Elsevier Science
- Year
- 1999
- Tongue
- English
- Weight
- 348 KB
- Volume
- 30
- Category
- Article
- ISSN
- 1387-1811
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✦ Synopsis
Three different Si(OH )Al sites have been singled out in MCM-22, absorbing at 3628, 3618 and 3585 cm-1, tentatively assigned to hydroxyls located in supercages, 10-membered ring channels and six-membered rings, respectively. FTIR study of the adsorption of CO and N 2 at the nominal temperature of 77 K allowed the measurement of their acidity, which appears close to that measured for H-ZSM-5 by means of the same technique, and it is not modified by dealumination. Lewis sites are present in small amounts in vacuum-activated samples. After dealumination, no Lewis sites are present, being extraframework Al3+ species coordinatively saturated by OH groups.