The Preparation Of Some Metal Oxides And Their Application In The Decomposition Of Greenhouse Gases Such As N₂O And NF₃

N₂O and NF₃ with high global warming potiential?GWP?and long lifetime are important greenhouse gases and their emissions are limited.Catalytic decomposition of N₂O and thermal decomposition of NF₃ are effective methods for the destruction of N₂O and NF₃,respectively.In this thesis,the following experiments were carried out:?1?Mg-Co and Mg-Mn-Co spinel mixed oxides were prepared by using sol-gel method,and their catalytic activity for de-N₂O was test.The effect of catalyst preparation parameters,such as composition of catalysts,K loadings on catalytic activity was investigated.?2?By using carbon sphere as template and urea as precipitant,Mg-Co composite oxides were prepared by hydrothermal method and used for catalytic decomposition of N₂O.The effect of catalyst preparation parameters,such as metal salt solution concentration and content of urea on catalytic activity,was investigated.?3?The reagent of Al₂O₃ with shell structure was prepared by hydrothermal method using carbon sphere as template and used in NF₃ decomposition without water.The effect of de-fluorinated reagent preparation parameters,such as metal salt concentration,urea content,crystallization temperature on de-fluorinated reactivity,was investigated.In addition,the techniques such as XRD,BET,SEM,XPS,H₂-TPR,and O₂-TPD were used to characterize the above catalysts and de-fluorinated reagents.The following conclusions are drawn:?1?MgCo₂O₄ and MgMn_0.2Co_1.8O₄ show better activity for N₂O decomposition than other catalysts in the family of Mg-Co and Mg-Mn-Co mixed oxides,respectively.In K-modified MgMn_0.2Co_1.8O₄ catalysts,the one with K/?Mn+Co?=0.02?atomic ratio?exhibits high activity and stability.?2?MgCo₂O₄ catalysts were hydrothermally prepared by using carbon sphere as hard template at 120°C.The results show that the catalyst prepared with mass ratio 0.192 of cobalt and magnesium to carbon sphere,and molar ratio 2 of urea to cobalt and magnesium cations,exhibits higher catalytic activity for N₂O decomposition than others.The catalyst of 0.02K/MgCo₂O₄ by potassium modification reveals good stability.?3?Al₂O₃ reagents with thin shell morphology were hydrothermally prepared by using carbon sphere as hard template and applied in NF₃ thermal decomposition without water.It is found that the Al₂O₃ reagent prepared with mass ratio 0.182 of aluminum to carbon sphere,molar ratio 4 of urea to aluminum,and crystallization temperature 120°C,exhibits high reactivity.