Preparation Of UO_x With Different Morphology And Size And Catalytic Removal Of NO

Uranium is a radioactive element.With the development of nuclear industry,the amount of the depleted urannium after extracting of U²³⁵ is keeping on increasing.To make full use of the depleted urannium has become an increasingly important issue.Exploring the performance of uranium oxide in catalysis is one of the important ways.Currently,environmental pollution problem incurred by pollutants like NO_x is getting more and more serious,for NO_x is not only one of the main substances to form acid rain,but also an important factor to form photochemical smog and to deplete ozone layer.It is expected to solve this kind of problem by removing NO_x based on catalytic process over on uranium oxides.The reported work on catalysis of uranium oxides is mainly directed to UO₂ and U₃O₈ and shows that these uranium oxides exhibit good catalytic performance in the removal of a variety of environmental pollutants,such as in the selective oxidation of hydrocarbons and the oxidation to eliminate of organic pollutants,the selective reduction of NO and so on.As a kind of metal oxide,it is an effective way to improve the catalytic activity of uranium oxide by preparing nanocrystalline to make it has high specific surface area,and to prepare such material with different morphologies to exhibit significantly different about the ability of selective recognition,adsorption,catalysis performance and so on.Therefore,the main contents of the present study are as follows:1.U₃O₈ nanocrystals with three different morphologies were prepared by hydrothermal method with different organic amines as well as by precipitation route,and characterized by XRD,SEM,HRTEM and H₂-TPR etc.The catalytic performance of U₃O₈ nanorods,nanocuboids and nanosheets for recduction NO by CO was evaluated to investigate the effect of morphology on their catalytic activities.Experimental results show that the catalytic performance for NO reduction is directly related to the morphology of U₃O₈ nanocrystals.U₃O₈ nanorods gives high NO conversion,at the space velocity GHSV=2500 h-1,and at 450 oC,the conversion rate can reach the maximum value 89 %.2.Spherical UO₂ nanocrystals with different sizes were prepared by modified hydrothermal route with different organic amines.Then it was characterized by XRD,SEM,BET,H₂-TPR,O₂-TPO and so on.Finally,their performance for catalytic reduction of NO was compared to the counterpart with introducing 5% Au on the surface by impregnation.