| In recent years,bimetallic catalysts have been widely concerned because of the more optimal selectivity,stability and reactivity than mono metallic catalysts.Au-Pd alloy catalysts is increasingly used in bimetallic catalysts research.because its can form a solid solution in any mole ratio,the addition of the second metal can effectively change the bimetallic nanoparticles'characteristics of electronic and geometric properties.But in the process of preparation of gold palladium bimetallic it is easy to form core-shell structure bimetallic nanoparticles,because of the palladium reduction more easily and the palladium nuclear gold shell structure has the lowest formation,it will affect the activity and selectivity of the catalyst.In addition,some factors will make the catalytic nature activity of gold palladium alloy is complicated,such as the interaction between metal and carrier,protective agent residues,alloy composition form is not unified,nanometer particle size is differed.This work,a synthetic procedure is presented for preparing Au-Pd alloy NPs that have high activity and high stability supported on mesoporous carbon based matrix.In the catalysts,the gold and palladium elements are evenly distributed and the size of the nanoparticles is uniform.Benzene methanol oxidation in base free water as probe reaction,combined with the XPS,EXAFS characterization methods explore the active source of Au-Pd alloy.The full text is divided into four chapters,the first chapter is literature review,mainly introduced the application of the bimetallic nanoparticles,the research progress of Au-Pd alloy NPs and mesoporous carrier material.The second chapter introduces the solvent-induced self-assembly method to obtain the ordered palladium-supported alloy catalyst with ordered mesoporous silica-silica composite.The use of mercapto coordination and mesoporous hole wall physical limit,limiting the growth of nanoparticles,to avoid the use of protective agent;through high temperature roasting to eliminate the coordination agent and restore the metal,the catalyst obtained in the nano-particles in the distribution of gold and palladium,The size of nanoparticles is uniform,and the interaction between gold and palladium alloy and carrier carbon silica composites is weak.XPS,EXAFS and other characterization results show that by adjusting the molar ratio of gold and palladium in gold palladium alloy,the bond energy,bond length and coordination number of the catalyst change to varying degrees,and modify the electronic properties of gold and palladium alloy.In the third chapter,the catalytic activity of gold and palladium alloy is explored by XPS and EXAFS.By adjusting the molar ratio of gold and palladium in the material,the gold and palladium alloy catalysts with different gold and palladium molar ratios were obtained.The catalysts have the same specific surface area,pore volume and highly ordered mesoporous structure,and the size of the nanoparticles in each catalyst is the same,which eliminates the influence of the carrier morphology and particle size on the catalytic activity of the catalyst.In the selective oxidation of benzyl alcohol in the base-free aqueous phase,the molar ratio of gold to palladium in the catalyst is related to the catalytic activity.When the gold-palladium molar ratio is close to 1:1,the catalyst is exhibited in the oxidation reaction of benzyl alcohol in the alkali-free aqueous phase,and the catalytic effect of the palladium-palladium alloy is improved when the gold-palladium alloy is almost unaltered.The catalytic conversion frequency?TOF?reached 265 h-1 after 4 h reaction at 90?under normal pressure.When the conversion is 60%or less,the selectivity of the catalyst to benzaldehyde is up to 100%.After repeated six times of the catalyst,no significant morphological changes and decreased catalytic activity were observed.Indicating that the catalyst has a very high stability.Chapter 4 summarizes the full text. |
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