Activity and deactivation of Ru supported on La1.6Sr0.4NiO4 perovskite-like catalysts prepared by different methods for decomposition of N2O

Abstract

In this paper, the activity and stability of Ru supported on La_1.6Sr_0.4NiO₄ perovskite-like catalysts prepared by two different methods, incipient wetness procedures with the addition of ethylene glycol (Ru/LSN-EG) and without ethylene glycol (Ru/LSN), were investigated for the decomposition of N₂O. The catalysts were fully characterized by means of XRD, elemental analysis, N₂-physisorption, TEM, H₂-TPR, N₂O-TPD and XPS. The Ru/LSN-EG catalyst retained high activity for 10 h without deactivation, which is attributed to the stable Ru³⁺ species, the much higher mobility of lattice oxygen and the regeneration ability of oxygen vacancies. However, the Ru/LSN catalyst presented deactivation; the initial N₂O conversion of about 95% was only maintained for the first hour and decreased with time to 55% after 6 h. The reasons for this deactivation were investigated by a series of experiments and characterizations. The results indicate that the deactivation of the Ru/LSN catalyst can be ascribed to the difficult desorption of the oxygen species derived from N₂O decomposition on the active sites; moreover, all the metallic Ru and Ru³⁺ species are oxidized to high oxidation state Ru⁴⁺ species. All the results demonstrated that the Ru³⁺ species was more favorable for N₂O decomposition. Furthermore, the effects of O₂ and H₂O on the decomposition of N₂O were also evaluated over the Ru/LSN-EG catalyst. High stability and no irreversible deactivation of the Ru/LSN-EG catalyst, even in the presence of O₂ and H₂O, were found.