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Alcohol Oxidation and CO Oxidation over Supported Au and Ru Catalysts

Author: YangXiaoMin
Tutor: QiuJieShan；Jeroen A.van Bokhoven
School: Dalian University of Technology
Course: Chemical processes
Keywords: Heterogeneous catalysis selective oxidation of alcohols CO oxidation supported gold catalysts supported ruthenium catalysts in-situ characterization
CLC: O643.32
Type: PhD thesis
Year: 2010
Downloads: 607
Quote: 1
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Abstract


Due to increasing concern about environmental impact, there has been tremendous interest in developing environmentally friendly catalysts and processes in chemical synthesis and processing. Heterogeneous catalysis is a key to successful development of so-called "green chemistry". In this work, heterogeneous gold and ruthenium catalysis were investigated, which mainly focused on heterogeneous oxidation reactions such as alcohol oxidation and CO oxidation. Working gold catalysts were characterized by in situ spectroscopy, which may provide correlations between the catalyst structure and catalytic activity. Reaction mechanisms were further studied.Effective catalytic oxidation of alcohols under mild conditions has been realized in a special heterogeneous reaction system, in which supported gold or ruthenium catalysts function as catalysts, oxygen or air as oxidant, and water or the mixture of water and a kind of organic reagent like p-xylene or toluene as solvent. The unique and significant promotion effect of water has been evidenced by the selective oxidation of benzyl alcohol to benzaldehyde over Au/TiO2 and Ru/CNTs catalysts, respectively. Water helps to form unique emulsion droplets where the solid catalysts assemble at the interface. The interfaces of the emulsion droplets favor the mass transfer, resulting in the increase in the conversion of the substrate. Water facilitates O2 adsorption and activation over Au/TiO2. The present work has highlighted the potential of supported gold and ruthenium catalysts in aerobic oxidation of alcohols in the unique multiphase reaction system with water as promoting solvent.By making use of a novel microwave-assisted ethylene glycol approach (MW-EG), high performance Au/CNTs and Ru/CNTs catalysts that are novel and active for the selective oxidation of benzyl alcohol to benzaldehyde have been made. The as-prepared Au/CNTs catalysts have small gold particle size of 7 nm. The as-prepared Ru/CNTs catalysts have small ruthenium particle size of 1-2 nm. The catalytic activity of Au/CNTs by MW-EG method is much higher than that by impregnation method, deposition-precipitation method, and ethylene glycol approach. The catalytic activity of Ru/CNTs by MW-EG method is also much higher than that by traditional impregnation method. The microwave-assisted ethylene glycol approach to Au/CNTs and Ru/CNTs catalysts is novel and efficient, and will give a new impetus to the study of supported metal catalysts in the viewpoint of basic and applied science. Catalytic activities of Au/TiO2 for CO oxidation were studied. Reaction mechanisms of CO oxidation over supported gold catalysts were studied by in situ X-ray adsorption spectroscopy and infrared spectroscopy. Water helps to significantly improve the catalytic activity of Au/TiO2. Water has dual promotional functions in the reaction system:to increase the activation ability of the oxygen, and to inhibit the formation of these surface carbonate-like species and also help to their decomposition. The pronounced decrease of the initial activity of the supported gold catalysts was observed, which is caused by the accumulation of surface carbonate-like species on the surfaces of the supported gold catalysts.

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Chemical kinetics,catalysis > Catalytic > Catalytic reaction
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