Decomposition Of SF₆ And N₂O As Green-House Gases Over Some Metal Oxides

SF₆ and N₂O gases with high global warming potential?GWP? and long atmospheric lifetime are limited by Kyoto Protocol. The decomposition of SF₆ without water and catalytic decomposition of N₂O are suggested to be the effective methods to destruct SF₆ and N₂O, respectively.In the present thesis, the decomposition of SF₆ over Al₂O₃, CaO and other single metal oxides, as well as ternary mixture de-fluorinated reagents such as Na F-Si-CaO, KF-Si-Ca O was investigated. Cu-Fe, Ni-Fe spinel oxides were prepared and tested in the N₂O catalytic decomposition by optimizing the compositions of catalysts in terms of catalytic activity and stability; Ce-Co-Al mixed oxides catalysts were tested for N₂O decomposition and the preparation parameters such as catalyst compositions, pH values of mother liquid, and K loadings were screened. XRD, BET, SEM, H2-TPR, O2-TPD, XPS techniques were used to characterize these de-fluorinated reagents and catalysts. In addition, the adsorption of N₂O on Co₃O₄?110? was calculated by GGA-PBE function method. The following results are drawn:?1? The reaction temperature has a great impact on SF₆ thermal decomposition over Al₂O₃, and the reactivity is enhanced with the increasing temperature. SF₆ can be decomposed over Al₂O₃, MgO, CaO, La₂O₃ at 650 °C, followed by the order of CaO > La₂O₃ > MgO > Al₂O₃.The reactivity of KF-Si-Ca O is lower than that of NaF-Si-CaO because the more active KF than Na F reacted with other reactants to produce several inert phases such as K₂SiF₆ and KCaF₃, then declined the content of KF sharply, and reduced the reactivity.?2? Among the Cu-Fe, Ni-Fe catalysts with different compositions, the optimal catalysts are CuFe₂O₄ and NiFe₂O₄, respectively. Furthermore, the initial activity and stability of NiFe₂O₄ is superior to CuFe₂O₄.The optimal catalyst of K-modified Ce-Co-Al catalyst was prepared with Ce_0.05Co_1.95AlO₄ at mother liquid value of 2 and K/?Co+Ce? molar ratio of 0.05. In contrast to bare Ce_0.05Co_1.95AlO₄, the K-modified catalyst with better reducibility of Co³⁺-O^- and easier oxygen desorption performs higher catalytic activity.?3? The calculation results of N₂O adsorption over Co₃O₄?110? suggest the possible adsorption style of N₂O is N-Co²⁺-O^-Co²⁺.