Study On Nickel-based Catalysts And Reaction Conditions Of Methane Catalytic Partial Oxidation To Syngas

Compared with methane reforming with steam or carbon dioxide, catalytic partial oxidation of methane to syngas is a better approach for methane utilization, for it has many advantages such as higher space velocity, lower power cost, smaller reactor and H₂/CO ratio of syngas close to 2.0, which is favorable to synthesis of methanol or other high-grade alcohol. In this work, a series of Ni/MgO-CeO₂-CaO-Al₂O₃ catalysts were prepared, and their physico-chemical properties were characterized by means of TPR,XRD,TEM,TG,BET and catalytic performance evaluation. Additionally, the reaction conditions for partial oxidation of methane were optimized. Calcinations temperature is an important factor for catalyst preparation. With the increase of calcinations temperature for Ni/MgO-CeO₂-CaO-Al₂O₃ catalysts, the interaction between nickel species and support became stronger. Compared with γ-alumina, the catalysts showed larger specific surface area even at higher calcinations temperature due to the formation of spinel, such as NiAl₂O₄ and MgAl2O4. The formation NiAl₂O₄ spinel benefited to the dispersion of nickel, and so smaller nickel crystallites would be formed after reduction. In the partial oxidation of methane to syngas, the catalysts calcined at higher temperature exhibited better stability, especially calcined at 950℃. Moreover, the hotspot temperature of bed for the catalysts calcinated at high temperature declined, which is favorable to prevent the catalysts from sintering. Compared with incipient impregnation, physical-mixing and sol-gel methods, wet-mix preparation favored to obtain high catalytic performance as well as simplified the preparation of the catalysts. With MgA_l2O₄ instead of γ-alumina as support, the catalyst also showed higher reactivity and lower hotspot temperature. It was found that POM-1 catalyst displayed better catalytic performance under the conditions of GHSV 4.35×10⁵h^-1, 800oC, 1.75 for CH₄/O₂ ratio and 16.7 for Db/Dp. Besides, when the catalysts were isothermally reduced at the temperature close to catalyst calcinations temperature, smaller nickel crystallites would be obtained, which benefited to the catalytic performance of the catalysts.