Mechanistic Study of the Selective Methanation of CO over Ru/TiO2 Catalysts: Effect of Metal Crystallite Size on the Nature of Active Surface Species and Reaction Pathways
Mechanistic Study of the Selective Methanation of CO over Ru/TiO2 Catalysts: Effect of Metal Crystallite Size on the Nature of Active Surface Species and Reaction Pathways
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DOI：
10.1021/acs.jpcc.6b12091
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发表时间：
2017-03-09
影响因子：
3.7
通讯作者：
Verykios, Xenophon E.
中科院分区：
文献类型：
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作者：
Panagiotopoulou, Paraskevi;Verykios, Xenophon E.
采用原位FTIR和瞬态质谱技术研究了不同金属含量（0.5和5.0 wt %）和晶粒尺寸（2.1和4.5 nm）的Ru/TiO 2催化剂上金属晶粒尺寸对CO和CO竞争甲烷化反应机理的影响。结果表明，虽然这两种催化剂遵循相同的机理途径，反应中间体的相对人口不同。具体地，在与含CO/CO2的气体混合物相互作用时在催化剂表面上检测到的Rubonded羰基物质的性质对于两种催化剂是相同的。然而，它们的相对人口显着取决于钌微晶尺寸和决定催化活性。吸附在部分氧化的Ru网站（运行+-（CO）（x））的人口显着减少，而相反的是观察到的CO物种线性键合在还原Ru微晶（Ru-x-CO）。这与5%Ru/TiO 2催化剂的较高催化活性相关，因为已经提供了吸附在还原钌位点上的表面物质是甲烷的直接前体的证据。
The effect of metal crystallite size on the reaction mechanism of competitive methanation of CO and CO, is investigated over Ru/TiO2 catalysts of variable metal content (0.5 and 5.0 wt %) and crystallite size (2.1 and 4.5 nm) employing in situ FTIR and transient mass spectrometry techniques. Results show that although both catalysts follow the same mechanistic pathways, the relative population of reaction intermediates differs. Specifically, the nature of Rubonded carbonyl species detected on the catalyst surface upon interaction with the CO/CO2-containing gas mixtures is the same for both catalysts. However, their relative population depends significantly on ruthenium crystallite size and determines catalytic activity. The population of multicarbonyl species adsorbed on partially oxidized Ru sites (Run+-(CO)(x)) decreases significantly with increasing Ru crystallite size, whereas the opposite is observed for CO species linearly bonded on reduced Ru crystallites (Ru-x-CO). This is correlated with the higher catalytic activity found for the 5%Ru/TiO2 catalyst, since evidence has been provided that surface species adsorbed on reduced ruthenium sites are direct precursors of methane.