Niobium oxide acidity studied by proton broad-line NMR at 4 K and MAS NMR at room temperature |
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Authors: | Patrice Batamack Robert Vincent Jacques Fraissard |
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Affiliation: | (1) Laboratoire de Chimie des Surfaces associé au CNRS, URA1428, Université Pierre et Marie Curie, Tour 55,4 Place Jussieu, 75252 Paris Cedex05, France |
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Abstract: | The quantitative study of the Brønsted acidity of niobic acid (Nb2O5·xH2O) using broad-line1H NMR at 4 K has been performed by interacting niobic acid, pretreated at 573 K under vacuum, with water molecules. The number of oxyprotonated species (H3O+ and H2O...HO species formed, unreacted acidic OH groups or excess H2O molecules) deduced from the simulations of the broad-line1H NMR spectra shows a continuous increase in the number of H3O+ species with adsorbed water molecules. This increase may be due to a classical dilution effect or to a synergistic interaction between Brønsted and Lewis acid sites. These results are compared with those of some HY zeolites with or without framework defects. |
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Keywords: | niobic acid acidity 1H broad-line NMR 1HMASNMR |
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