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首页> 外文期刊>The journal of physical chemistry, C. Nanomaterials and interfaces >XPD and XANES Studies of Ce0.9Zr0.1O2 Nanocatalysts under Redox and Catalytic CH4 Oxidation Conditions
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XPD and XANES Studies of Ce0.9Zr0.1O2 Nanocatalysts under Redox and Catalytic CH4 Oxidation Conditions

机译：CE0.9ZR0.1O2氧化铈下XPD和XANES研究氧化还原和催化CH4氧化条件下的CE0.9ZR0.1O2纳米催化剂

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The aim of this work is to take further insight into the structural stability of cerium zirconium catalysts under reducing, oxidizing and reaction conditions. In situ synchrotron based techniques (XANES and XPD) were used in order to determine the stability of crystal structure and the oxidation state of cerium cations in the reaction conditions prevailing in the catalytic studies. In situ XPD studies in 5 mol % H-2 atmosphere revealed that no structural changes occur until 870 degrees C. At this temperature, the sample synthesized with glycine, which presents lower crystallite agglomeration, segregated a small quantity of a reduced phase. On the contrary, the solid synthesized with lysine, with more agglomerated crystallites, does not show structural changes in all the temperature range. Reoxidation treatments in 5 mol % O-2 revealed that at 750 degrees C the segregated phase disappears and that the original cubic structure is restored. In situ XANES studies in the Ce L-III absorption edge indicate that under catalytic reaction conditions, the degree of reduction of Ce4+ is low, allowing the occurrence of methane oxidation. The solid is capable to deliver the oxygen of its structure when no oxygen is fed into the reactor until the 50% of cerium cations become reduced, triggering the deactivation process. Therefore, it is clear for these studies that the Ce4+ to Ce3+ ratio in the lattice is governing the catalytic behavior of the solid. The catalytic results collected during in situ XANES experiments are in excellent agreement with our previous catalytic studies performed with a laboratory fixed bed reactor.
机译：这项工作的目的是进一步了解降低，氧化和反应条件下铈锆催化剂的结构稳定性。原位同步基于同步技术（XANES和XPD）用于确定催化研究中普遍存在的反应条件下晶体结构的稳定性和铈阳离子的氧化状态。原位XPD在5摩尔％H-2气氛中的研究表明，在该温度下，没有发生结构变化，直到870℃。用甘氨酸合成的样品，其呈较低的微晶附聚，少量减少阶段。相反，用赖氨酸合成的固体，具有更加凝聚的微晶，不显示所有温度范围内的结构变化。 5摩尔％O-2中的再氧化处理显示，在750℃下，分离相消失，恢复原始立方体结构。原位XANES在CE L-III吸收边缘表明，在催化反应条件下，CE4 +的还原程度低，允许发生甲烷氧化。当没有氧气进入反应器中，固体能够递送其结构的氧气直至50％的铈阳离子减少，引发失活过程。因此，晶格中的CE4 +至Ce3 +比对于这些研究是明确的，晶格中的CE4 +与固体的催化行为有影响。在原位XANES实验中收集的催化结果与我们以前的催化研究进行了良好的一致性，该研究用实验室固定床反应器进行。

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