Effect of praseodymium and europium doping in La1−xLnxMnO3+δ (Ln: Pr or Eu, 0 ≤ x ≤ 1) perosvkite catalysts for total methane oxidation
Effect of praseodymium and europium doping in La1−xLnxMnO3+δ (Ln: Pr or Eu, 0 ≤ x ≤ 1) perosvkite catalysts for total methane oxidation
复制标题
La1−xLnxMnO3+δ (Ln: Pr 或 Eu, 0 ≤ x ≤ 1) 钙钛矿催化剂中镨和铕掺杂对甲烷全氧化的影响
DOI：
10.1016/j.apcata.2013.09.014
复制
发表时间：
2014
影响因子：
5.5
通讯作者：
Jean‐Marc Giraudon
中科院分区：
文献类型：
--
作者：
H. Najjar;H. Batis;J. Lamonier;O. Mentré;Jean‐Marc Giraudon
采用溶液燃烧合成法制备了钙钛矿型La1−xLnxMnO3 +δ（Ln: Pr或Eu， 0≤x≤1）氧化物，用x射线衍射、氧解吸、x射线光电子能谱对其进行了表征，并进行了甲烷深度氧化测试。XRD谱图在整个Ln取代度范围内均显示出钙钛矿结构。与镨相比，铕的引入增加了钙钛矿晶格畸变，这与它较小的离子半径有关。化学滴定结果显示，B亚晶格中存在Mn3+和Mn4+混合物，所有固体的氧超化学计量值均为δ>。发现催化剂活性取决于取代度和A位的Ln性质。在所研究的化合物中，含铕20%的化合物表现出最高的催化活性。将催化性能与氧化物的结构特征联系起来是可能的。α2-氧的释放量（即通过晶格转移到表面还原位点导致Mn4+→Mn3+暂时还原的物质）和La、Pr、Eu和Mn在表面的偏析在序列上表现出差异，这似乎是影响催化活性的最重要因素。pr改性催化剂的较低的催化性能可能是由于Pr3+向表面的高度偏析。对于thex= 0.2催化剂而言，Mn4+的稳定性以及La和Eu的局部最小值和Mn的最大值的存在是提高甲烷深度氧化催化活性的关键原因。
Perovskite-type La1 −xLnxMnO3 +δ(Ln: Pr or Eu, 0 ≤x≤ 1) oxides were prepared using solution combustion synthesis, characterized by X-ray diffraction, oxygen desorption, X-ray photoelectron spectroscopy and tested for methane deep oxidation. XRD patterns showed perovskite structure over the whole range of Ln substitution degree. Compared to praseodymium, introduction of europium increased the perovskite lattice distortion in relation to its smaller ionic radius. Chemical titration results revealed oxygen over-stoichiometry (δ> 0) for all solids and the presence of Mn3+and Mn4+mixture in B sublattice. The catalyst activity was found to depend on the degree of substitution and the Ln nature in the A sites. Among the investigated compositions, the 20% containing europium compound showed the highest catalytic activity. It was possible to correlate catalytic performances with the structural characteristics of the oxides. The released α2-oxygen (i.e. species transported through the lattice to the surfacial reduction site leading to temporary Mn4+→ Mn3+reduction) and the La, Pr, Eu and Mn segregation at the surface, showed differences along the series and seem to be the most important determining factors concerning the catalytic activity. The relatively low catalytic performances of Pr-modified catalysts should be due to the high segregation of Pr3+toward the surface. The stability of Mn4+and the existence of a local minimum of La and Eu and a maximum of Mn segregations for thex= 0.2 catalyst should be considered as the key reasons enhancing the catalytic activity in methane deep oxidation.
DOI：
10.1016/0001-6160(53)90006-6
发表时间：
1953-01-01
期刊：
ACTA METALLURGICA
影响因子：
--
作者：
WILLIAMSON, GK;HALL, WH
通讯作者：
HALL, WH