IR study of Broensted acidity of Al-pillared montmorillonite
- Universita di Torino (Italy) Dipartimento di Scienza dei Materiali ed Ingegneria Chimica Politecnico di Torino (Italy)
- Ecole Nationale Superieure di Chimie de Montpellier (France)
Three different methods have been used to study the hydroxyls of montmorillonite, both as such and pillared with Al[sub 13] polycations. The methods are (i) formation of H-bonds with benzene, (ii) selective H/D exchange, and (iii) adsorption of pyridine. Besides nonacidic species, two reactive hydroxyls have been identified, characterized by stretching modes at 3738 and 3660 cm[sup [minus]1]. The former is ascribed to a species Al-O-Si-OH, resembling the hydroxyl on silica, and the latter to a species Si-O-Al-OH, similar to extraframework species in zeolites. Both arise from sealing the clay sheet and the Al pillar; their acidity comes from a synergic effect between the two constituents, as similar species in both silica and alumina are definitely less acidic. No bridged species Si(OH)Al is formed. Pyridine adsorption shows that (i) only the Si-O-Al-OH species may transfer protons, (ii) at least two distinct Lewis acid sites are present, and (iii) one of the related pyridine species reacts with a nearby hydroxyl to yield [alpha]-pyridone. 22 refs., 13 figs., 1 tab.
- OSTI ID:
- 7107536
- Journal Information:
- Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Vol. 147:1; ISSN 0021-9517; ISSN JCTLA5
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201* -- Chemical & Physicochemical Properties
ABSORPTION SPECTROSCOPY
ALUMINIUM COMPOUNDS
CHEMICAL REACTION YIELD
CLAYS
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
ISOTOPIC EXCHANGE
MATERIALS
MONTMORILLONITE
SORPTIVE PROPERTIES
SPECTROSCOPY
SURFACE PROPERTIES
YIELDS