Hydrothermal Synthesis Of Several Metal Oxides And Their Applications In The Decomposition Of Greenhouse Gases Such As N₂O,NF₃ And SF₆

N₂O,NF₃ and SF₆ are the greenhouse gases restricted by the Kyoto Protocol.They have high global warming potential?GWP?and long life-time.The catalytic decomposition is an effective method to eliminate N₂O,and the thermal decomposition without water is an effective method to destruct NF₃ and SF₆.The focuses in this thesis are as follows:?1?Co₃O₄ catalysts with certain morphology were hydrothermally synthesized by using CTAB as soft template for catalytic decomposition N₂O.The effect of CTAB solution concentration,molar ratio of CTAB to cobalt,molar ratio of urea to cobalt,and potassium additive on catalytic activity was optimized.?2?The defluorinated reagent of Al₂O₃ and Mn/Al₂O₃ were hydrothermally synthesized by using carbon sphere as hard template.The effect of manganese loadings and crystallization temperatures on the reactivity of Mn/Al₂O₃ for NF₃decomposition was investigated.?3?CaO nanoparticles were synthesized by hydrothermal method using carbon sphere as template,in which CaO nanoparticles were prepared by adjusting the mass ratio of calcium to carbon spheres,molar ratio of urea to calcium and crystallization temperatures.Then,the ternary reagent of NaF-Si-CaO was prepared by mechanical mixing for SF₆ decomposition.In addition,a binary reagent of NaF-Si was used for SF₆ decomposition.The catalysts and defluorinated reagents were characterized by BET,XRD,SEM-EDX,H₂-TPR,O₂-TPD,XPS and so on.The main results are obtained as follows:?1?In the N₂O catalytic decomposition,Co₃O₄ catalysts were prepared with different parameters.Of the Co₃O₄ catalysts,the one by 0.05mol/L CTAB solution,molar ratio1 of CTAB to cobalt,and molar ratio 4 of urea to cobalt ion revealed high N₂O decomposition activity.In addition,K modified-Co₃O₄ catalyst exhibited much better activity and stability than bare Co₃O₄.?2?The de-fluorinated reagents of Al₂O₃ and Mn/Al₂O₃ were hydrothermally synthesized by using carbon sphere as hard template and urea as precipitator.The5%Mn/Al₂O₃ reagent crystallized at 160?exhibited high reactivity for NF₃decomposition,in detail,the full conversion time of NF₃ reached 620 min and the utilization percentage of de-fluorinated reagent is about 98%.?3?CaO nanoparticles were synthesized by hydrothermal method at different crystallization temperatures with carbon sphere as template and urea as precipitator.The time of SF₆ total conversion on NaF-Si-CaO was 260 min.When the ratio of NaF/Si was in the range of 0.5¹.5,the complete conversion time of SF₆ reached 460 min,revealing the higher reactivity of binary NaF-Si than ternary NaF-Si-CaO.