High-temperature NMR study of zeolite Na-A: detection of a phase transition
1989
The zeolite Linde 4A is studied by {sup 23}Na, {sup 27}al, and {sup 29}Si NMR at temperatures up to 953 K. {sup 23}Na NMR shows that the quadrupole interaction of sodium ions sited at 6-rings decreases when the temperature increases. With the aid of two-dimensional nutation and exchange experiments it can be shown that large-amplitude motions of the sodium ions, which in principle could explain a decrease of quadrupole interactions, do not occur. The decrease of the quadrupole interaction can be interpreted in terms of a phase transition. From a comparison of the NMR spectra of {sup 23}Na and {sup 27}Al it is concluded that the zeolite framework undergoes a major structural change upon increasing the temperature, before the sodium ions are displaced at higher temperatures. The exchange of sodium ions for potassium ions shifts this transition to higher temperatures.
Keywords:
- Correction
- Source
- Cite
- Save
- Machine Reading By IdeaReader
0
References
22
Citations
NaN
KQI