Catalytic Performance Of Alumina Supported Nickel And Cobalt Catalysts In Methane Reforming With CO₂

The catalytic reforming of methane with CO₂ paves a promising way to transform CO₂ into valuable synthesis gas（syngas, a mixture of hydrogen and carbon monoxide） with lower H2/CO ratio which is suitable for the production of long-chain hydrocarbons and oxygenated derivatives. Meanwhile, it proves to be an effective way to reduce greenhouse gas（carbon dioxide CO₂） emission and relieve the burden on energy.The overall purpose of this study was to present an effective catalyst with high carbon resistance in the conversion of methane to synthesis gas via dry reforming. Catalysts cacinated under different temperature（500, 700, 800 °C respectively） and prepared by different precursors were studied to control the size and dispersion of Ni particles as well as the reduction behavior. It is verfied that the size of Ni particle greatly governs the catalytic behavior of the prepared catalysts and the catalyst Ni（CH₃COO）2/Al₂O₃ caclinated at 500 °C was proven as the most effective catalyst. Moreover, the optimum nickle loading was 4-6%.Furthermore, the catalytic performances of a-Al₂O₃ supported nickel- and cobalt-based catalysts modified with Y₂O₃ were investigated in this process. Sequential impregnation and co-impregnation of Y₂O₃ addition were employed during the catalyst preparation. The modification effect of Y₂O₃ and the preparation strategies on the surface structure, physico-chemical properties and coke deposition were revealed. For nickel catalysts, two impregnation methods of yttrium addition both greatly increased the activity and stability compared with counterpart Ni catalyst. Furthermore, the best performance over Ni/Y-Al₂O₃ catalyst prepared by sequential-impregnation was related to smaller metallic nickel particle and more basic sites, while its remarkable stability was due to the small degree of graphitization and the less amount of carbon deposit. This sintering-resistant and higher carbon-resistant nickel catalyst is potentially useful for methane conversion in high reaction temperature. On the contrary, the negative effect of Y₂O₃ was clearly found for Co/Al₂O₃ catalyst. The introduction of Y₂O₃ led to inadequate reduction and metal sintering in reduced and spent catalysts. Co/Y-Al₂O₃ prepared by sequential impregnation exhibited steep deactivation during the methane reforming reaction because of the obvious cobalt sintering and serious carbon deposition.