Accessibility of lithium cations in high-silica zeolites investigated using the NMR paramagnetic shift effect of adsorbed oxygen

被引：24

作者：

Accardi, RJ ^{[1
]}

Lobo, RF ^{[1
]}

机构：

[1] Univ Delaware, Ctr Catalyt Sci & Technol, Dept Chem Engn, Newark, DE 19716 USA

来源：

MICROPOROUS AND MESOPOROUS MATERIALS | 2000年 / 40卷 / 1-3期

基金：

美国国家科学基金会;

关键词：

ZSM-5; beta; Li-7 MAS NMR spectroscopy; paramagnetic shift; cation accessibility; high-silica zeolites; adsorption;

D O I：

10.1016/S1387-1811(00)00234-1

中图分类号：

O69 [应用化学];

学科分类号：

081704 ;

摘要：

The accessibility of lithium cations in the high-silica zeolites ZSM-5 and beta was investigated using Li-7 MAS NMR spectroscopy. The samples are investigated in vacuum and in the presence of adsorbed oxygen molecules. The paramagnetic shift effect due to the oxygen molecules was exploited to determine the fractions of accessible lithium cations. Approximately 85% of lithium cations in Al-ZSM-5 (Si/Al= 50) are accessible to oxygen molecules, while none of the cation sites in zeolite Al-beta (Si/Al = 18 and 8) and only a small fraction in B-beta (Si/B = 15) were available for adsorption. This difference indicates a very distinct coordination environment for Li+ in zeolite beta as compared to ZSM-5. (C) 2000 Elsevier Science B.V. All rights reserved.

引用

页码：25 / 34

页数：10

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