Thermal Stability of NH4-Chabazite

Abstract

The thermal stability of NH4-chabazite has been examined by i.r. spectroscopy and thermal analysis combined with mass spectrometry. Dehydration occurs in two and deammoniation in four steps. Disregarding a very small water loss during deammoniation, dehydroxylation is completely separable from deammoniation and occurs in two distinct steps. Two OH stretching bands at 3540 and 3630 cm–1 appear during deammoniation and could be related to distinct ammonium ions having bending vibrations at 1420 and 1460 cm–1 respectively. The hydroxyls showing a band at 3540 cm–1 are formed at lower temperatures and are less thermostable than other hydroxyls.