Insight and comprehensive study of Ni-based catalysts supported on various metal oxides for CO methanation.

In this study, nickel supported on various metal oxides were prepared by simple impregnation and the performance for CO methanation was tested. The oxide supports were all prepared by thermal decomposition of metal salts to provide comparable oxide properties such as surface area. Among the investigated oxides, nickel supported on CeO and YO showed the highest CO conversion of 90% at 320 °C with highest CH selectivity of 99%. The order of catalyst activity (X@320°C) was reported: Ni/CeO ~ Ni/YO > > Ni/LaO > Ni/ZrO > Ni/AlO > Ni/MgO > Ni/CaO > > Ni/MnO. The physicochemical properties of the catalysts were analyzed by TEM, BET, XRD, ICP, H-TPR, CO-TPD, H chemisorption, TGA, Raman, and XPS. From the characterization results, the catalyst activity was independent to specific surface area of catalyst and crystallite size of Ni. The amount of oxygen vacancies and weak-to-medium basic sites exhibited major roles for enhancing catalyst activity. The CeO and YO as reducible oxide supports not only provided abundant oxygen vacancies / basic sites, but also promoted Ni dispersion with appropriate interaction between metal and support, resulting in higher reducibility at low temperature. The reduction of catalyst at high temperature can significantly improve the performance of Ni supported on non-reducible MgO. However, the Ni/CeO and Ni/YO reduced at high temperature suffered from coalescence of CeO and YO, though Ni crystallite sizes are well preserved from sintering.