Characterization of Fe Substitution into La-Hexaaluminate Systems and the Effect on N2O Catalytic Decomposition

详细信息    查看全文

• 作者：Yan Zhang ; Xiaodong Wang ; Yanyan Zhu ; Baolin Hou ; Xiaofeng Yang ; Xin Liu ; Junhu Wang ; Jun Li ; Tao Zhang
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：January 30, 2014
• 年：2014
• 卷：118
• 期：4
• 页码：1999-2010
• 全文大小：659K
• ISSN：1932-7455

文摘

Compared to Ba-hexaaluminates with 尾-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, LaFe_xAl_12鈥?i>xO₁₉ catalysts with x = 1 and 5 were herein prepared using the coprecipitation method. ⁵⁷Fe M枚ssbauer 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 掳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⁺ 鈫?Fe²⁺ reduction under high-temperature calcination played a negative role.