脱氢
催化作用
X射线光电子能谱
材料科学
咔唑
吸附
光化学
分解
尼亚尔
物理化学
结晶学
化学
化学工程
有机化学
金属间化合物
冶金
合金
工程类
作者
Marek Sobota,Ioannis Nikiforidis,Max Amende,Beatriz Sanmartín Zanón,Thorsten Staudt,Oliver Höfert,Yaroslava Lykhach,Christian Papp,Wolfgang Hieringer,Mathias Laurin,Daniel Assenbaum,Peter Wasserscheid,Hans‐Peter Steinrück,Andreas Görling,Jörg Libuda
标识
DOI:10.1002/chem.201101311
摘要
To elucidate the dehydrogenation mechanism of dodecahydro-N-ethylcarbazole (H(12)-NEC) on supported Pd catalysts, we have performed a model study under ultra high vacuum (UHV) conditions. H(12)-NEC and its final dehydrogenation product, N-ethylcarbazole (NEC), were deposited by physical vapor deposition (PVD) at temperatures between 120 K and 520 K onto a supported model catalyst, which consisted of Pd nanoparticles grown on a well-ordered alumina film on NiAl(110). Adsorption and thermally induced surface reactions were followed by infrared reflection absorption spectroscopy (IRAS) and high-resolution X-ray photoelectron spectroscopy (HR-XPS) in combination with density functional theory (DFT) calculations. It was shown that, at 120 K, H(12)-NEC adsorbs molecularly both on the Al(2)O(3)/NiAl(110) support and on the Pd particles. Initial activation of the molecule occurs through C-H bond scission at the 8a- and 9a-positions of the carbazole skeleton at temperatures above 170 K. Dehydrogenation successively proceeds with increasing temperature. Around 350 K, breakage of one C-N bond occurs accompanied by further dehydrogenation of the carbon skeleton. The decomposition intermediates reside on the surface up to 500 K. At higher temperatures, further decay to small fragments and atomic species is observed. These species block most of the absorption sites on the Pd particles, but can be oxidatively removed by heating in oxygen at 600 K, fully restoring the original adsorption properties of the model catalyst.
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