Preparation And Properties Research Of Manganese Dioxdeand Manganese Dioxde Supported Noble Metal Catalysts

Transition metal oxide nanomaterials have attracted a lot of attention in science and technology because of their unique electrochemical,optic,and catalytic properties.It is extremely significant for synthesis of nanomaterials to regulate the phase,size,and dimension because it guides to optimize the performance of materials and design new materials with unique functions.This dissertation selected MnO₂ as the research issue in consideration of its characters of high stability,cheapness and easy acquisition,and prepared a variety of MnO₂ with different phases,achieving the controllable preparation for crystal phase and morphology.Then,a research for catalytic performance of MnO₂ that acts as the main catalyst and catalyst support has been carried out and confirmed the influence regulation of different phases in catalytic performance.Afterward,a possible reaction mechanism has been proposed by relating the experimental result and the microstructure of nanocatalysts.The second chapter in this dissertation introduced the synthesis of?,?,?,?-MnO₂ with nanowaires,nanorods and other kinds of morphologies by oxidation of Mn2+ or reduction of high valance of Mn.Oxidation reaction of benzyl alcohol has been selected into the research to evaluate the distinction of catalytic performance among the different phase.The result showed that?-MnO₂ exhibited the best catalytic activity.Meanwhile,?-MnO₂ performed the best cycle stability.On the basis of the experimental result,the microstructure of MnO₂,and property of benzyl alcohol oxidation,a possible reaction mechanism has been proposed.This work can provide experimental support for selecting the optimized phase in related reactions catalyzed by MnO₂.Besides the research of MnO₂ catalytic performance as the main catalysts,the paper also studied their catalytic behaviors in 1,4-butandiol cyclization when they acted as the support.In third chapter,monodisperse palladiumnanoparticles have been successfully prepared and supported on the surface of MnO₂.Au/?-MnO₂ was also prepared by deposition-precipitation method.These as-prepared catalysts were used in the cyclization reaction of 1,4-butandiol in high-pressure condition so as to study the influence of different supports for catalytic performance.The research results showed that Pd/?-MnO₂ exhibited the best activity and all catalysts have good cycle stability.Meanwhile,calcination temperature has no effect on the catalytic performance of Au/?-MnO₂.Afterwards,a possible mechanism for the reaction has been presented by combining the microstructure information and experimental results.This work has provided experimental data for revealing the interconnection between noble metal catalyst and the support.