八面体
分解
煅烧
催化作用
化学
共沉淀
穆斯堡尔谱学
结晶学
离子
无机化学
三角双锥分子几何
钙钛矿(结构)
晶体结构
热分解
生物化学
有机化学
作者
Yan Zhang,Xiaodong Wang,Yanyan Zhu,Baolin Hou,Xiaofeng Yang,Xin Liu,Junhu Wang,Jun Li,Tao� Zhang
摘要
Compared to Ba-hexaaluminates with β-Al2O3 structure, La-hexaaluminates with magnetoplumbite (MP) structure have more substituted Al sites in the preferentially exposed mirror plane, which should favor N2O decomposition. In this regard, LaFexAl12–xO19 catalysts with x = 1 and 5 were herein prepared using the coprecipitation method. 57Fe Mössbauer spectroscopy and X-ray diffraction structure refinements revealed that Fe3+ ions originating in Fe2O3 species mainly entered tetrahedral Al(2) and trigonal bipyramidal Al(5) sites. Meanwhile, Fe3+ ions in octahedral sites of perovskite-type LaFeO3 intermediates preferentially accommodated in octahedral Al(3) sites in the mirror plane of La-hexaaluminates. Correlation of normalized rates (moles of N2O per hour per square meter) of the catalysts at 500 °C with the occupancy of Fe ions in different Al crystallographic sites of the MP phase indicated that Fe3+ ions in the Al(3) and Al(5) sites were highly active for N2O decomposition. In contrast, Fe2+ derived from a Fe3+ → Fe2+ reduction under high-temperature calcination played a negative role.
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