Calcination conditions and stability of supported Ni4La oxide for catalytic decomposition of N2O

Abstract

A series of novel supported Ni₄La oxide catalysts (S-Ni₄La for short) with the same mass loading amount of 10%, using pretreated cordierite ceramics as carrier, was prepared by an impregnation method and tested for catalytic decomposition of N₂O at low temperature. The effects of calcination temperature and atmosphere on the catalytic performance were mainly studied, and the stability of the S-Ni₄La in reaction was evaluated. Meanwhile, the solid-phase structure, micro-structure morphology, redox properties, valence and content of ions were characterized by the techniques of XRD, SEM, H₂-TPR, N₂O-TPD and XPS, respectively. Moreover, the catalytic mechanism for N₂O decomposition over the S-Ni₄La was discussed. The results showed that the S-Ni₄La calcined at 400 °C in a nitrogen atmosphere completely decomposed N₂O at 375 °C, which successfully breaks the technical bottleneck that low-cost supported metal oxides were not able to completely decompose N₂O at below 400 °C. La₂O₃ and LaNiO₃ were not active phases for catalytic decomposition of N₂O, while NiO was a major active phase in reaction. The reducing atmosphere decreased crystallization and refined the grain size, so as to increase the effective specific surface area, thereby improving the catalytic performance. Furthermore, the La_n+1Ni_nO_3n+1+σ formed possessed a perfect migration performance of oxygen species, particularly for the catalyst calcined in a nitrogen atmosphere, and consequently the S-Ni₄La calcined in a nitrogen atmosphere revealed a much better catalytic performance.