Niobium oxide acidity studied by proton broad-line NMR at 4 K and MAS NMR at room temperature

被引:17
作者
Batamack, P
Vincent, R
Fraissard, J
机构
关键词
niobic acid; acidity; H-1 broad-line NMR; H-1 MAS NMR;
D O I
10.1007/BF00807209
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The quantitative study of the Bronsted acidity of niobic acid (Nb2O5 . xH(2)O) using broad-line H-1 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-line H-1 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 Bronsted and Lewis acid sites. These results are compared with those of some HY zeolites with or without framework defects.
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页码:81 / 86
页数:6
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