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What Makes Fe-Modified MgAl2O4 an Active Catalyst Support? Insight from X-ray Raman Scattering
ACS Catalysis ( IF 11.3 ) Pub Date : 2020-05-14 , DOI: 10.1021/acscatal.0c00759 Alessandro Longo 1, 2, 3 , Stavros Alexandros Theofanidis 1 , Chiara Cavallari 2 , Nadadur Veeraraghavan Srinath 1 , Jiawei Hu 1 , Hilde Poelman 1 , Maarten K. Sabbe 1 , Christoph J. Sahle 2 , Guy B. Marin 1 , Vladimir V. Galvita 1
ACS Catalysis ( IF 11.3 ) Pub Date : 2020-05-14 , DOI: 10.1021/acscatal.0c00759 Alessandro Longo 1, 2, 3 , Stavros Alexandros Theofanidis 1 , Chiara Cavallari 2 , Nadadur Veeraraghavan Srinath 1 , Jiawei Hu 1 , Hilde Poelman 1 , Maarten K. Sabbe 1 , Christoph J. Sahle 2 , Guy B. Marin 1 , Vladimir V. Galvita 1
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Fe-modified MgAl2O4 makes a surprisingly active catalyst support, likely linked to a structural effect of the Fe incorporation. Two catalyst supports, MgAl2O4 and MgFeAlO4, have been studied in fresh and reduced state to determine the effect of high-temperature H2 reduction upon ion distribution in the lattices. To this end, an X-ray Raman scattering study has been performed, focusing on the oxygen K edge and magnesium and aluminum L2,3 and iron M2,3 soft edges. MgAl2O4 shows a random cation distribution and only small changes occur at the Mg L2,3 and Al L2,3 edges upon reduction at 1073 K. The main oxygen signal does lose intensity and its simulation points to a lower O covalency and more confined state after reduction. Introducing 8.9 wt % Fe into the spinel pushes Mg towards mostly tetrahedral position in the MgFeAlO4 lattice, whereas Fe and Al share the octahedral sites. Concomitant lattice distortion is observable in the O signal. Reduction of MgFeAlO4 leads to enhanced distortion visible in the O and Al signals and the presence of 50% Fe2+. Both disorder and reduction lead to partial segregation of MgFeOx from the MgFeAlO4 lattice. This combination of distortion and phase restructuring in the Fe-modified MgFeAlO4 material facilitates the lattice oxygen mobility and hence its catalytic activity.
中文翻译：
是什么使铁改性的MgAl 2 O 4成为活性催化剂载体？X射线拉曼散射的见解
铁改性的MgAl 2 O 4提供了出乎意料的活性催化剂载体，这可能与掺入铁的结构效应有关。已经研究了两种催化剂载体MgAl 2 O 4和MgFeAlO 4处于新鲜和还原状态，以确定高温H 2还原对晶格中离子分布的影响。为此，已经进行了X射线拉曼散射研究，重点研究了氧K边缘，镁和铝L 2,3和铁M 2,3软边缘。MgAl 2 O 4显示出随机的阳离子分布，并且在Mg L 2,3处仅发生很小的变化Al 2，3在1073 K还原时边缘消失。主要的氧信号确实失去强度，其模拟表明还原后O价较低，状态更局限。在尖晶石中引入8.9 wt％Fe将Mg推向MgFeAlO 4晶格中的大部分四面体位置，而Fe和Al共享八面体位点。在O信号中可观察到伴随的晶格畸变。MgFeAlO 4的还原导致在O和Al信号中可见的变形增强，并且存在50％Fe 2+。无序和还原都导致MgFeO x与MgFeAlO 4晶格部分偏析。Fe修饰的MgFeAlO中畸变和相变的结合4材料有利于晶格氧的迁移，并因此促进其催化活性。
更新日期：2020-06-19
中文翻译：
是什么使铁改性的MgAl 2 O 4成为活性催化剂载体？X射线拉曼散射的见解
铁改性的MgAl 2 O 4提供了出乎意料的活性催化剂载体，这可能与掺入铁的结构效应有关。已经研究了两种催化剂载体MgAl 2 O 4和MgFeAlO 4处于新鲜和还原状态，以确定高温H 2还原对晶格中离子分布的影响。为此，已经进行了X射线拉曼散射研究，重点研究了氧K边缘，镁和铝L 2,3和铁M 2,3软边缘。MgAl 2 O 4显示出随机的阳离子分布，并且在Mg L 2,3处仅发生很小的变化Al 2，3在1073 K还原时边缘消失。主要的氧信号确实失去强度，其模拟表明还原后O价较低，状态更局限。在尖晶石中引入8.9 wt％Fe将Mg推向MgFeAlO 4晶格中的大部分四面体位置，而Fe和Al共享八面体位点。在O信号中可观察到伴随的晶格畸变。MgFeAlO 4的还原导致在O和Al信号中可见的变形增强，并且存在50％Fe 2+。无序和还原都导致MgFeO x与MgFeAlO 4晶格部分偏析。Fe修饰的MgFeAlO中畸变和相变的结合4材料有利于晶格氧的迁移，并因此促进其催化活性。
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