Preparation Of Uranium Oxides With Different Morphologies And Their Adsorption Properties For PVA And Catalytic Dehydrogenation Of Cyclohexane

Uranium is a radioactive element.With the development of nuclear industry,the use of the"waste"of the large amount of depleted uranium remaining after the extraction of ²³⁵U has become an increasingly important issue for countries related to nuclear.At the same time,the current environmental pollution problem is becoming increasingly serious.Among them,widely used polyvinyl alcohol（PVA）is a water-soluble macromolecule that is difficult to biodegrade.In water,PVA can increase its viscosity,increase surface foam,affect water reoxygenation ability and microbial health,and also affect the migration of heavy metals,bringing a series of environmental pollution problems.In addition,the organic hydride cyclohexane has a hydrogen storage capacity of up to 7.1%by weight,which is convenient for storage and transportation.There is no release of CO and CO₂ during hydrogen storage and hydrogen supply.It is a good medium for storing and transporting large quantities of H₂.Now,its hydrogen storage（ie,hydrogenation of benzene to cyclohexane）has become more mature.However,there is a lack of efficient and cheap dehydrogenation catalysts in this process.Structure-rich uranium oxides can produce suitable interactions with a variety of molecules.Focusing on"turning waste into treasure",in this study,uranium oxides with different morphologies were prepared,and their adsorption properties of PVA were determined.Considering that uranium is a polyvalent element,the redox capacity of its oxides can be easily adjusted.In order to further expand the application of uranium,the H2-TPR study of uranium oxide is planned to evaluate its performance for catalytic dehydrogenation of cyclohexane.The main research contents of this thesis are as follows:1.Uranium oxides in the form of flakes,rods,spheres and waist drums were successfully prepared by hydrothermal synthesis.SEM,XRD,H₂-TPR,BET and other characterizations of uranium oxides with different morphologies were performed,and the results showed that the main exposure planes of uranium oxides with different morphologies were different.2.The influence of morphology on the adsorption of polyvinyl alcohol by uranium oxide was investigated.Experiments using rod-shaped,spherical-shaped and plate-shaped uranium oxides as adsorbents to adsorb polyvinyl alcohol under the same conditions,were carried out and with the aim to compare their performance.The adsorption kinetics and thermodynamics were analyzed,and the optimal conditions for the adsorption of polyvinyl alcohol were established.3.The catalytic ability of uranium oxide for cyclohexane dehydrogenation was studied.The performance of dehydrogenation of cyclohexane over rod-shaped,spherical and plate-shaped uranium oxides were evaluated under the same conditions.Preliminary correlation the catalytic results with their H₂-TPR characteristics indicated there exists a direct structure-activity relationship of the catalytic performance of cyclohexane dehydrogenation with surface reducibility.