Preparation Of Metal Oxides With Different Morphologies And Their Catalytic Properties

With the continuous development of nanotechnology,metal oxides have received more and more attention because of their relatively low price and wide range of uses.In addition to the influence of the composition of its own atomic species,the properties of metal oxides are severely limited by the size,morphology and structure of the material.Therefore,the preparation of metal oxides with small size,multi-morphology and special structure is beneficial to the improvement of material properties and has important social and economic value.In this thesis,the transition metals of cobalt and iron oxides are mainly studied.The inexpensive cobalt salts and iron salts are used as the main raw materials,and optimization of synthesis conditions for synthesis of cobalt and iron oxides with different morphologies are implemented by simple hydrothermal or precipitation methods.And then,Pt salts impregnated on the obatained Co₃O₄ and FeO_x nanomaterials with different morphologies.TEM,SEM,XRD,BET and TPR techniques are used to characterize the material properties,which provide guidance for the subsequent structure-performance study.Then,the nitrobenzene liquid phase hydrogenation and CO₂ hydrogenation reaction are used as the model reactions to test the catalytic performances of Pt/Co₃O₄ and Pt/FeO_x.The research contents are as follows:Firstly,we used Co（NO₃）₂·6H₂O,CoCl₂·6H₂O,Co（CH₃COO）₂·4H₂O as the cobalt source to synthesize Co₃O₄ nancubes,nanorods,octahedral and hexagonal by simple hydrothermal or precipitation methods.After calcination at 350°C,the prepared samples still maintained theirs original morphologies and exhibited good thermal stability.Pt/Co₃O₄catalysts with the different carriers’morphologies were synthesized by loading Pt.This series of Pt/Co₃O₄ catalysts showed the differences of catalytic performances in liquid phase hydrogenation of nitrobenzene and hydrogenation of CO₂.Secondly,we used the inexpensive iron salts:FeCl₃·6H₂O and FeSO₄·7H₂O and Fe（NO₃）₃·9H₂O as raw materials and adjusted reducing agent or oxidizing agent to the synthesize iron oxides with the different morphologies.Fe₃O₄ nanopolyhedrons,nanooctahedrons,nanowires,andα-Fe₂O₃ nanocubes,nanrods,nanohexagons were successfully prepared by hydrothermal method.Pt/FeO_x catalysts were obtained by impregenting Pt on the above synthesized FeO_x with different morphologies,and hexagonal plate-like Fe₂O₃ nanomaterials supported Pt catalyst showed high catalytic performance in the liquid phase hydrogenation of nitrobenzene.