Investigations On Praseodymium(Pr)-based Oxide Nanostructures For Their Controllable Preparation And CO Catalytic Oxidation

Rare earth material is a mineral resource with great potential for industrial application,and has the advantages of wide distribution,abundant reservation and rich types.Praseodymium oxide has the highest oxygen migration rate in all the undoped rare earth oxides.In this thesis,the following research work was carried out for praseodymium?Pr?-based oxide nanostructures:1.The praseodymium hydroxide nanorods were prepared by using hydrothermal synthesis method,and the optimal annealing temperature range was found between Pr?OH?₃-NRs and Pr₆O₁₁-NRs.The morphology effect for Pr₆O₁₁-NRs and Pr₆O₁₁-NPs on the CO catalytic oxidation was investigated.Pr₆O₁₁-NRs,with high specific surface area,have more significant catalytic performance than Pr₆O₁₁-NPs.The catalytic activity of Pr₆O₁₁-NRs increased after 260°C.As the reaction temperature is above 350°C,the CO conversion rate was larger than 50%;as for the Pr₆O₁₁-NPs catalyst,it is not active until 275°C,while the CO conversion rate is only 25%at 350°C.2.Based on the above experiments,praseodymium oxide is treated as catalyst support,and loaded with a certain amount of Ag nanoparticles to further enhance the catalytic activity.We explored the relationship between Ag and Pr₆O₁₁ support.The Pr₆O₁₁-NRs support with higher specific surface area is more favorable for faciliating the uniform distribution of Ag nanoparticles.The amount of effective active sites(the interface between Ag and Pr₆O₁₁)increased significantly.As a result,the contact area of catalysts and reaction gases increased significantly during the catalytic reaction.Praseodymium oxide support have excellent capability to store and release oxygen,and the synergistic action between Ag and supports contributes to effective CO catalytic oxidation.3.The morphology and specific surface area of praseodymium oxide were further regulated by introducing Fe elements,and the Pr₆O₁₁/PrFeO₃ microspheres with core-shell structure were synthesized by hydrothermal method.It was found that the process of growth followed such a mechanism:nucleus formation?agglomeration growth?exothecium cladding?kernel dissolution.Pr₆O₁₁/PrFeO₃ microspheres have high specific surface area and abundant diffusion channels.As a consequence,more active sites are provided for CO catalytic oxidation towards the improvement of catalytic performance.