N₂O Abatement Over γ-Al₂O₃ Supported Catalysts: Effect of Reducing Agent and Active Phase Nature

A series of metal catalysts (Pd, Rh, Ru, Cu, Fe, In and Ni) supported on γ-Al₂O₃ carrier, were evaluated during N₂O catalytic conversion to N₂ in the absence and presence of excess oxygen and reducing agents (CH₄ or C₃H₈). Among all catalysts tested, Pd-, Ru- and Rh-based samples exhibited the best catalytic performance, in all reaction conditions examined. The reaction was inhibited by O₂, in particular at lower temperatures, while its effect was essentially negligible at higher ones. In the presence of reducing agents and under lean reaction conditions, N₂O conversion was comparably enhanced, with C₃H₈ being more efficient than CH₄; however even in the presence of hydrocarbons N₂O decomposition is the major pathway for N₂O abatement, since reducing agents mainly act as oxygen scavengers reducing and concurrently activating the metal sites. The influence of different co-existing gases (CO, H₂O and SO₂) on the performance of Pd supported catalysts was also investigated, whereas thermal stability tests in the presence of SO₂ indicate a gradual irreversible decrease in activity until a new steady state was established.