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

In this paper, the activity and stability of Ru supported on La1.6Sr0.4NiO4 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.