La₂O₃‐Promoted Ni/Al₂O₃ Catalyst for CO Methanation: Enhanced Catalytic Activity and Stability

Abstract

To simultaneously inhibit Ni sintering and coke formation, while maintaining high catalytic activity, Ni–La 2 O 3 /Al 2 O 3 catalysts are prepared by a modified deposition–precipitation (DP) method and applied for the CO methanation reaction. The activity of the catalyst prepared by the DP method is much higher than those prepared by the traditional impregnation and co‐impregnation methods due to the promotion of La 2 O 3 as well as its unique dispersion on the surface of the catalyst. In the 100 h‐lifetime test under the conditions of 450 °C, 0.1 MPa, a weight hourly space velocity (WHSV) of 120 000 mL g −1 h −1 , the Ni–La 2 O 3 /Al 2 O 3 catalyst prepared by the DP method shows high catalytic stability. The characterization results show that La 2 O 3 species can be deposited on the surface of the catalyst during the preparation process and can act as a physical barrier to prevent sintering of Ni particles and coke formation during high‐temperature reduction and reaction. La 2 O 3 species can improve the reducibility of Ni particles and decrease the Ni particle sizes, resulting in larger H 2 uptake and higher catalytic activity. Furthermore, the La 3+ /La 2+ redox can also decrease coke formation by increasing the active oxygen species on the Ni surface.