EPR of O2-Radicals in the Zeolites NH4NaY and NH4CaA

Abstract

Activated and non-activated states of the zeolites NH<inf>4</inf>NaY and NH<inf>4</inf>CaA, and their NH+<inf>4</inf> forms were prepared with an (NH<inf>4</inf>)<inf>2</inf>SO<inf>4</inf> solution and were investigated by EPR after γ-irradiation. The formed radicals were attributed to O-<inf>2</inf> supposed to be trapped near a trigonally coordinated framework of 27A1 (I = 5/2). Anisotropic O-<inf>2</inf> spectra were observed, consisting of hyperfine structure due to the 27A1 framework, even at room temperature. This was attributed to the scarceness of NH+<inf>4</inf> sites or trap sites because of the preparation of the NH+<inf>4</inf> forms of the zeolites with an (NH<inf>4</inf>)<inf>2</inf>SO<inf>4</inf> solution. The crystal field splittings were found and interpreted.