Solution-combusted nanosized Ni–Al2O3 catalyst for slurry CO methanation: effects of alkali/alkaline earth metal chlorides

Solution combustion synthesis (SCS) possesses many advantages for preparation of nanosized materials. In the process of SCS, a large amount of heat release results in the agglomeration of particles. Thus, the controllable synthesis of solution combustion is necessary. In this study, Ni–Al2O3 nanoparticles with various metal chlorides, i.e., LiCl, NaCl, KCl, MgCl2 and CaCl2, were prepared by SCS method and performed for CO methanation reaction in a slurry-bed reactor. All of the introduced metal chlorides could absorb reaction heat during the combustion process, among which the addition of NaCl minimizes the combustion temperature for its high heat capacity. Moreover, the molten NaCl exerts a steric hindrance effect that restrains the agglomeration of NiO particles, leading to the highest Ni dispersion and smallest Ni particles. MgCl2-added sample exhibits the lowest reducibility and Ni dispersion and the worst methanation activity. The performance shows that, under a harsh condition of 310 °C and 9200 mL (gcat h)−1, NaCl-added Ni–Al2O3 catalyst exhibits the optimal CO conversion, which keeps stable at ca. 87% in a 100-h test. This study offers a new strategy for nanosized catalyst preparation via SCS by introducing metal chlorides.