One-step synthesis of bulk Mo and Ni–Mo carbides for methanation

Abstract

β-Mo₂C and Ni/β-Mo₂C catalysts were prepared by a single-step thermal decomposition method using hexamethylenetetramine (HMT) as a reducing agent and carbon source. The synthesized carbides were detailedly characterized and their catalytic performances in methanation were evaluated. The results showed that serious carbon deposition was observed in β-Mo₂C, while for Ni/β-Mo₂C, the carbon content was insufficient and Ni₃Mo₃N was produced. With respect to catalytic performances in methanation, the β-Mo₂C catalyst exhibited a high CO conversion, but its CH₄ selectivity was low and its activity was not stable due to hydrogenation of the carbidic carbon. While the Ni/β-Mo₂C catalyst exhibited excellent activity and stability, the CO conversion and CH₄ selectivity increased from 67.41% and 33.54% on β-Mo₂C to 92.51% and 52.73% on Ni/β-Mo₂C. This is ascribed to Ni₃Mo₃N in Ni/β-Mo₂C, which is more active and stable during methanation.