EPR of O2-radicals in the zeolites NH4NaY and NH4CaA

Abstract

Activated and non-activated states of the zeolites NH4NaY and NH4CaA, and their NH+4 forms were prepared with an (NH4)2SO4 solution and were investigated by EPR after ?-irradiation. The formed radicals were attributed to O-2 supposed to be trapped near a trigonally coordinated framework of 27A1 (I = 5/2). Anisotropic O-2 spectra were observed, consisting of hyperfine structure due to the 27A1 framework, even at room temperature. This was attributed to the scarceness of NH+4 sites or trap sites because of the preparation of the NH+4 forms of the zeolites with an (NH4)2SO4 solution. The crystal field splittings were found and interpreted.