FeOx/Al2O3 catalysts for high-temperature decomposition of N2O under conditions of NH3 oxidation in nitric acid production

Abstract

The catalytic activity of a series of FeO_x/Al₂O₃ prepared under various conditions was evaluated for high temperature decomposition of N₂O (HT-deN₂O) in a complex gas mixture produced by oxidation of ammonia. Thus the relevant step in the industrial nitric acid production process was simulated. The catalyst stability during long-term exposure (12 days) to reaction conditions relevant to HT-deN₂O was studied. Both fresh and aged FeO_x/Al₂O₃ exhibited more than 90% conversion of N₂O in the 750–900 °C temperature range. Structural analysis showed that the prepared FeO_x/Al₂O₃ catalysts contained various proportions of δ, θ and α alumina phases and up to four individual iron species. In the δ and θ Al₂O₃ phases, well stabilized Fe(III) in T_d or O_h coordination was identified as the active species in HT-deN₂O.