Rationalization of the catalytic behavior of lanthanide oxides and praseodymium molybdates in total and selective oxidation of isobutene
Rationalization of the catalytic behavior of lanthanide oxides and praseodymium molybdates in total and selective oxidation of isobutene
复制标题
镧系氧化物和钼酸镨在异丁烯全氧化和选择性氧化中催化行为的合理化
DOI：
10.1021/jp0124600
复制
发表时间：
2001
影响因子：
3.3
通讯作者：
M. Devillers
中科院分区：
文献类型：
--
作者：
F. Smet;B. Delmon;P. Ruiz;M. Devillers
这项工作的目的是严格研究电离势或绝对硬度与含有镧系元素 (Ln) 的二元和三元氧化物在烯烃氧化中的催化行为之间的相关性。五种镧系氧化物（La2O3、Sm2O3、Pr6O11、Tb4O7 和 CeO2）和三种钼酸镨（Pr-2-Mo3O12、Pr6MoO12 和 Pr2MoO6）以纯相或与 MoO3 的混合物形式用于异丁烯的部分和完全氧化。它们与 MoO3 的混合物的催化性能描述于在“远程控制机制”的背景下，根据该机制，镧系元素氧化物被认为是溢出氧的供体，其供体能力通过对异丁烯醛选择性的协同效应进行评估，并与上述物理性质相关。对于钼酸镨等三元氧化物，提出了平均电离能和平均绝对硬度的概念，以考虑电子密度和移动表面氧物质的反应性受到影响的事实。就机械混合物而言，纯 Ln 基氧化物获得的结果与文献中的电离能和绝对硬度概念一致，表明上述关系与“远程控制”概念相结合，可以全面了解电离能或绝对硬度对表现出相合作的单相催化剂的影响。
The purpose of this work is to examine critically the correlations between ionization potential or absolute hardness and the catalytic behavior of binary and ternary oxides containing lanthanides (Ln) in alkene oxidation. Five lanthanide oxides (La2O3, Sm2O3, Pr6O11, Tb4O7, and CeO2) and three praseodymium molybdates (Pr-2-Mo3O12, Pr6MoO12, and Pr2MoO6, were used as pure phases or in mixtures with MoO3 in the partial and total oxidation of isobutene. The catalytic performances of their mixtures with MoO3 are described in the context of the "remote control mechanism", according to which the lanthanide-based oxides are identified as donors of spillover oxygen. Their donor ability is evaluated through the synergetic effects on methacrolein selectivity and correlated with the physical properties mentioned above. In the case of ternary oxides such as praseodymium molybdates, the concepts of average ionization energy and average absolute hardness are proposed to take into account the fact that the electron density and therefore the reactivity of mobile surface oxygen species are influenced by the presence of both metals in the lattice. The results obtained with the pure Ln-based oxides are in line with the literature concepts of ionization energy and absolute hardness. As far as the mechanical mixtures are concerned, it is shown that the above correlations, when combined with the "remote control" concepts, provide a comprehensive view of the influence of ionization energy or absolute hardness for both single phase and biphasic catalysts exhibiting phase cooperation.