Study On Preparation Of Core-shell Structure CuO@?-Al₂O₃ Particles And Composite Oxide For Methane Combustion

Core-shell nanoparticles show novel physical and chemical properties owing to the special structure,which has a broad application prospects in catalysis,biology,medicine,light and magnetism.In the last years,the use of nano packaging technique to assemble nanoparticles into core-shell structure catalytic material has become a hot research topic in the field of catalysis.Catalyst with a core-shell structure can not only obtain controlled catalytic reactions,but also achieve the integration of active sites to meet the complex catalytic reaction system by tuning the composition,structure of the shell and core particles.This thesis is aimed at catalysts for one-step synthesis of dimethyl ether from syngas.Core-shell structure CuO@?-Al₂O₃ composite particles were prepared by hydrothermal method.The influence of different copper salts and glucose dosage on preparation core-shell structure CuO@?-Al₂O₃ composite particles was investigated.Besides,the thesis also studied the influence of ion modulated composite oxide and methane catalytic performance.In the first chapter,the research progress of core-shell nanoparticles is reviewed,including classification,preparation and application of core@shell structure nanoparticles.Core-shell structure nanoparticles can broadly class into four types: inorganic@inorganic,organic@organic,inorganic@organic,organic@inorganic,in which the inorganic@inorganic core-shell nanoparticles are introduced in detail.Then,we have concluded the preparation method and the influence of particle size and distribution during the preparation process of core-shell structure nanoparticles.There are varied preparation methods for core-shell structure nanoparticles including sacrificial template assisted method,ship-in-a-bottle,and Ultrasonic spray pyrolysis.The effects of synthetic media,surface modifier concentration and pH value on the particle size and its distribution of core-shell particles were summarized.At last,we have summarized the application of core-shell structure nanoparticles,such as,in catalysis,biomedicine,electronics and other fields.Finally,the research content is described in detail according to the research purpose.In the second chapter,the CuO@?-Al₂O₃ composite particles were prepared by hydrothermal method.The effects of different copper sources on preparation of CuO@?-Al₂O₃ composite particles were mainly explored.The experiment results show that the copper dichloride as copper source to synthesis CuO@?-Al₂O₃ composite particles resulted in an irregular morphology,while cupric acetate under hydrothermal condition for 6h obtained a uniform one.EDS spectrum suggested that the surface has copper element when using copper dichloride as copper source,these results indicated that copper dichloride can drastically accelerate the dehydration and carbonization of glucose.Additionally,the experiment results also revealed that high amount of glucose probably inhibits the crystallization of ?-Al₂O₃.The third chapter is mainly introduced that cupric acetate as copper sources,different amount of glucose to synthesis CuO@?-Al₂O₃ composite particles.The experiment results show that different mass of glucose has a great influence on the morphology of CuO@?-Al₂O₃ composite particles.High amount of glucose and low amount of glucose is detrimental for synthesis CuO@?-Al₂O₃ composite particles.When the mole ratio of glucose and cupric acetate is 30,CuO@?-Al₂O₃ composite particles were proved to be a core-shell structure by TEM.The fourth chapter researched that effect of Co_1+xAl_2-xO₄ ion modulated composite oxide and its catalytic performance for methane.A serious of Co_1+xAl_2-xO₄?x=0-0.2?composite oxides were synthesized by sol-gel method.The structure,morphology and surface properties were characterized by XRD,SEM,XPS and Raman spectrum.The catalytic activity tests suggested that the catalytic activity of CoAl₂O₄ catalyst was significantly enhanced after Al³⁺ partially substituted by Co²⁺ cations.XPS revealed that the excellent catalytic activity for methane combustion may be attributed to the active octahedral coordinated Co³⁺ cations and surface oxygen vacancies,especially the active octahedral coordinated Co³⁺ cations predominantly determined for methane combustion.The fifth chapter investigated that effect of La_2-xSr_xCuO_4-? ion modulated composite oxide and its catalytic performance for methane.A serious of La_2-xSr_xCuO_4-??x=0-1.5?composite oxides were synthesized by sol-gel method.The structure,morphology and surface properties were characterized by XRD,SEM and XPS.The methane catalytic tests reveal that the substitution of Sr²⁺ for La³⁺ cations significantly promoted the catalytic performance of La2CuO4 for methane oxidation.XPS suggested that the excellent catalytic activity may be attributed to the surface oxygen vacancies.