Adsorption of oxygen in an activated europium ion-exchanged mordenite

The adsorption of oxygen in an activated europium ion-exchanged mordenite(Eu-M) was studied over the temperature range 25–600°C by the measurement of fluorescence of Eu₂₊ ion and a temperature programmed desorption (TPD) spectra of oxygen. When oxygen was exposed to a activated Eu-M, the intensity of emission band for Eu²⁺ ion extremely decreased. After the adsorption of oxygen at room temperature, the emission intensity was increased with a rise of degassing temperature and restored to the original emission intensity above 300°C. While, in Eu-M, at least four different states of adsorbed oxygen were indicated by the appearance of four TPD peaks with peak maxima located at about 70°C(α), 220°C(β), 300°C(γ) and >500°C(δ). The intensity of TPD peaks was dependent on the adsorption temperature. In the case of adsorption at 300°C or 600°C, the total amount of desorbed oxygen corresponded to one oxygen molecule adsorbing per Eu²⁺ ion.