Thermochemical properties of ammonium exchanged type omega zeolite

Abstract

The thermochemical properties of ammonium exchanged Ω zeolite have been examined by infrared spectroscopy, thermal analysis and high temperature X-ray diffractometry. Differential thermal analysis in air shows a complex exotherm near 550°C due to the oxidation of volatile cations (NH⁺₄ and TMA⁺). Thermogravimetric analysis indicates loss of volatile cations and dehydroxylation overlap. I.r. spectra show that water can be removed by evacuation at room temperature and that the principal hydroxy group band shifts in frequency from 3624 to 3605 cm^–1 with increasing temperature. Shifts in the framework i.r. region suggest that aluminium is removed from the framework during calcination. High temperature X-ray diffractometry indicates that crystal collapse occurs near 500°C prior to dehydroxylation. It is possible to obtain a more stable crystal structure by calcination in a deep bed configuration.