On the CO-Oxidation over Oxygenated Ruthenium
On the CO-Oxidation over Oxygenated Ruthenium
复制标题
含氧钌的共氧化
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
R. Schlögl
中科院分区：
文献类型：
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作者：
D. Rosenthal;F. Girgsdies;O. Timpe;R. Blume;G. Weinberg;D. Teschner;R. Schlögl
摘要采用填料床反应器和表面分析方法，研究了多晶二氧化钌（RuO2）粉末上一氧化碳的氧化反应。在常压下的原位x射线衍射（XRD）装置中，活性数据与体相相关。二氧化钌在1073 K的纯氧中预煅烧。在此阶段，RuO2对CO的氧化完全没有活性。在503 K的进料中经过长时间的诱导后，RuO2以100%的转化率变得有活性，而原位XRD显示RuO2的衍射图没有变化。在这一阶段，通过扫描电镜观察到选择性的RuO2表面粗化。很少也单侧面被粗糙。EDX显示高氧含量的顺序为：平坦的侧面>粗糙的侧面>粗糙的顶面。此外，在填充床反应器中进行的实验表明CO2生成速率存在振荡。根据XRD，在更高的还原进料温度（533-543 K）下，样品还原为金属钌。燃烧温度较低的还原颗粒非常粗糙，有裂纹和深星形孔。在点火温度下CO2生成速率的Arrhenius图显示，还原后的样品在质量单位上的活性明显高于活化的氧化样品，其表观活化能也低于活化的氧化样品。利用微点x射线光电子能谱（XPS）和XPS显微镜对Ru（0001）单晶在不同温度下暴露于氧气中进行了实验研究。虽然低能电子衍射（LEED）图像显示出强烈的1×1模式，但XPS数据显示出广泛的横向不均匀性，并且在次表层中存在不同程度的氧溶解。所有这些和文献数据都是在不同的活性状态和输运问题的背景下讨论的，以及在高催化活性条件下相混合物的亚稳性质。
Abstract The oxidation of carbon monoxide over polycrystalline ruthenium dioxide (RuO2) powder was studied in a packed-bed reactor and by bulk and surface analytical methods. Activity data were correlated with bulk phases in an in-situ X-ray diffraction (XRD) setup at atmospheric pressure. Ruthenium dioxide was pre-calcined in pure oxygen at 1073 K. At this stage RuO2 is completely inactive in the oxidation of CO. After a long induction period in the feed at 503 K RuO2 becomes active with 100% conversion, while in-situ XRD reveals no changes in the RuO2 diffraction pattern. At this stage selective roughening of apical RuO2 facets was observed by scanning electron microscopy (SEM). Seldom also single lateral facets are roughened. EDX indicated higher oxygen content in the following order: flat lateral facets > rough lateral facets > rough apical facets. Further, experiments in the packed bed reactor indicated oscillations in the CO2 formation rate. At even higher temperatures in reducing feed (533–543 K) the sample reduces to ruthenium metal according to XRD. The reduced particles exhibiting lower ignition temperature are very rough with cracks and deep star-shaped holes. An Arrhenius plot of the CO2 formation rate below the ignition temperature reveals the reduced samples to be significantly more active based on mass unit and shows lower apparent activation energy than the activated oxidized sample. Micro-spot X-ray photoelectron spectroscopy (XPS) and XPS microscopy experiments were carried out on a Ru(0001) single crystal exposed to oxygen at different temperature. Although low energy electron diffraction (LEED) images show a strong 1×1 pattern, the XPS data indicated a wide lateral inhomogeneity with different degree of oxygen dissolved in the subsurface layers. All these and the literature data are discussed in the context of different active states and transport issues, and the metastable nature of a phase mixture under conditions of high catalytic activity.