SYNTHESIS OF NOVEL LAYERED METAL HALIDE OXIDES AND THEIR APPLICATION AS CATALYSTS FOR SELECTIVE ALKANE OXIDATION

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(1) Utilization of Metal Halide Oxides as Solid Catalysts In order to obtain highly effective and functionalized solid catalysts based on layred metal halide oxides for selective oxidations of alkanes with molecular oxygen, fundamental informations on the metal halide oxides in terms of structure, catalytic activity, selectivity, stability, and role of halogen, were accumulated by the synthesis of various layred bismuth halide oxides including samples with novel structures. The bismuth-based halide oxides constitute a large family of layred compound, all of which crystallize into structures consisting of cation-oxygen layr sheets associated with the tetragonal PbO structure, alternating with single or multiple sheets of halide ions. As increasing the multiplicity of the halide ion sheet, the catalytic activity for methane oxidative coupling reaction and the selectivity to C_2-hydrocarbons increased prominently. However, reversely decreased the stability of the catalysts, the activities … More deeaying with the reaction time with the liberation of halogen form the catalyst. It was found that these catalysts were also very active and selective for the oxidative dehydrogenation of ethane to ethylene.(2) Structural Analysis with High Resolution Electron Microscopy(HREM) and Computer Graphics The synthesis of novel layred bismuth hallde oxides is a key issue of this work, thus structural analysis being very important. The structural analyzes has been carried out in the aid of high resolution electron microscopy(HREM) and computer graphics.Kinetics of Methane Oxidative Coupling over Layred Metal Halide Oxide Catalysts On the basis that halogen species liberated from the bulk of the catalyst were not involved in the reaction in the gas phase, it is concluded that halide ions on the surface constitute active site for the reaction and their abilities for the reaction strongly depend on the interaction to the oxygen sheet.(4) Catalytic Properties of Arppe's Phase-Type Metal Halide Oxides Three distinet examples of Arppe's pase(M_<24>O_<31>Cl_<10> ; M=Bi, La, Sm), which has a structure related to that of the layred oxychloride BiOCl, have been used as monophasic catalysts for the oxidative dehydrogenation of methane. The stability and performance of these catalysts rival those of the best catalysts previously described.(5) Catalytic Properties of Metal Halide Oxides Having Multiple Metal-Oxygen Sheet Several distinet types of bismuth-based chloride oxides, all of which have layred structures and are regulated on varying the thicknesses of infinite metal oxygen sheets, have been tested as monophasic catalysts for methane oxidation. It was found that the chlorine sheets between the metal oxygen sheets are responsible for the higher catalytic performance. On the basis of this results, highly integrated metal halide oxide catalysts have been designed for propane oxidation.(6) Intercalation of Halide Ion and Water into the Interlayr of Metal Halide Oxides Is was found that halide ion and water can intercalate into the interlayr between halide sheets of metal halide oxides by immersing in aqueous metal halide solution at ambient temperature. The phenomenon was investigated using XRD,EST and EXAFS.Catalytic Activities of Layred Metal Chloride Oxides for Dehydrohalogenation Various metal chloride oxides having layred structure have been tested as catalysts for the dehydrohalogenation of t-butyl chloride to form olefin and were found active for the reaction, depending on the metal constituents and the structure. Less