Direct N2O decomposition over La2NiO4-based perovskite-type oxides

Direct decomposition of N₂O by perovskite-structure catalysts including La₂NiO₄, LaSrNiO₄, and La_0.7Ce_0.3SrNiO₄ was investigated. The catalysts were prepared by the Pechini method and characterized by x-ray diffraction (XRD), BET, scanning electron microscopy (SEM), and O₂-TPD. Experimental results indicate that the properties of La₂NiO₄ are significantly improved by partially substituting La with Sr and Ce. N₂O decomposition efficiencies achieved with LaSrNiO₄ and La_0.7Ce_0.3SrNiO₄ are 44 and 36%, respectively, at 400ºC. As the temperature was increased to 600ºC, N₂O decomposition efficiency achieved with LaSrNiO₄ and La_0.7Ce_0.3SrNiO₄ reached 100% at an inlet N₂O concentration of 1,000 ppm, while the space velocity was fixed at 8,000 hr^?1. In addition, effects of various parameters including oxygen, water vapor, and space velocity were also explored. The results indicate that N₂O decomposition efficiencies achieved with LaSrNiO₄ and La_0.7Ce_0.3SrNiO₄ are not significantly affected as space velocity is increased from 8,000 to 20,000 hr^?1, while La_0.7Ce_0.3SrNiO₄ shows better tolerance for O₂ and H₂O_(g). On the other hand, N₂ yield with LaSrNiO₄ as catalyst can be significantly improved by doping Ce. At a gas hour space velocity of 8,000 hr^?1, and a temperature of 600ºC, high N₂O decomposition efficiency and N₂ yield were maintained throughout the durability test of 60 hr, indicating the long-term stability of La_0.7Ce_0.3SrNiO₄ for N₂O decomposition.

Implications:Nitrous oxide (N₂O) not only has a high global warming potential (GWP₁₀₀ = 310), but also potentially destroys ozone in the stratosphere. Pervoskite-type catalysts including La₂NiO₄, LaSrNiO₄, and La_0.7Ce_0.3SrNiO₄ are applied for direct N₂O decomposition. The results show that N₂O decomposition can be enhanced as Sr and Ce are doped into La₂NiO₄. At 600ºC, N₂O decomposition efficiencies achieved with LaSrNiO₄ and La_0.7Ce_0.3SrNiO₄ reach 100%, demonstrating high activity and good potential for direct N₂O decomposition. Effects of O₂ and H₂O_(g) contents on catalytic activities are also evaluated and discussed.