Data di Pubblicazione:
2003
Abstract:
The ambient temperature adsorption of acetonitrile, in its perdeuterated form (CD3CN), was used for
the surface characterization of both pure and sulfate-doped t-ZrO2. In most pure t-ZrO2 specimens, the
absence of terminal and bi-bridged surface hydroxyls hinders completely the base-catalyzedCD3CNreactions
which yield on other oxides either acetamide-like species or carbanionic surface species. In the case of
sulfated t-ZrO2, even if some terminal hydroxyls are present, the mentioned surface reactions are hindered
by the presence of acidic (sulfate) functionalities. On pure t-ZrO2, the predominant adsorbed species are
represented by CD3CN molecules Lewis-coordinated to coordinatively unsaturated (cus) surface cationic
sites. These sites are made available either by surface dehydration or by ligand-displacement of surfacecoordinated
(undissociated) water molecules. Lewis-coordinated CD3CN species dominate also on sulfated
t-ZrO2, and the relevant adsorbing sites are made available both through the two mechanisms active on
pure t-ZrO2 and through an additional ligand-displacement effect concerning polydentate surface sulfates.
On sulfated t-ZrO2 systems, there exists an abundant protonic (Brønsted) acidity, a fraction of which can
be revealed by CD3CN adsorption through the formation of a relatively strong H-bonded species. The CN
vibrational mode for these H-bonded species is distinct from that of weakly adsorbed H-bonded and/or
physisorbed species.
Tipologia CRIS:
03A-Articolo su Rivista
Keywords:
t-ZrO2; sulphated zirconia; acetonitrile adsorption
Elenco autori:
C. Morterra; G. Cerrato; E. Novarino; M. Peñarroya Mentruit
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