High-temperature NMR study of zeolite Na-A: detection of a phase transition

• Published in: Journal of physical chemistry (1952) Vol. 93; no. 2; pp. 899 - 904
• Main Authors: Janssen, R, Tijink, G. A. H, Veeman, W. S, Maesen, T. L. M, Van Lent, J. F
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.01.1989
• Subjects: 400201 - Chemical & Physicochemical Properties; ALKALI METAL COMPOUNDS; ALKALI METAL ISOTOPES; ALUMINIUM 27; ALUMINIUM ISOTOPES; CATALYSIS; CATALYSTS; Chemistry; DATA; DIAGRAMS; EVEN-ODD NUCLEI; Exact sciences and technology; EXPERIMENTAL DATA; General and physical chemistry; INFORMATION; INORGANIC ION EXCHANGERS; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ION EXCHANGE MATERIALS; Ion-exchange; ISOTOPES; LIGHT NUCLEI; MAGNETIC RESONANCE; MATERIALS; MINERALS; NMR SPECTRA; NUCLEAR MAGNETIC RESONANCE; NUCLEI; NUMERICAL DATA; ODD-EVEN NUCLEI; Other ion exchangers: preparations and properties; PHASE DIAGRAMS; PHASE STUDIES; POTASSIUM COMPOUNDS; RESONANCE; SILICON 29; SILICON ISOTOPES; SODIUM 23; SODIUM COMPOUNDS; SODIUM ISOTOPES; SPECTRA; STABLE ISOTOPES; Surface physical chemistry; ZEOLITES; Zeolites: preparations and properties; Sodium Ions; Temperature; NMR spectrometry; Zeolite; Ion exchange; X ray diffraction; Phase transitions; Physical method; Molecular sieve; Modified material; Crystalline structure
• ISSN: 0022-3654; 1541-5740
• DOI: 10.1021/j100339a068

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.