Methanation of syngas (H₂/CO) over the different Ni-based catalysts

Methanation of syngas (H₂/CO) in a fixed-bed down-flow reactor under atmospheric atmosphere was investigated over a series of Ni-based catalysts with Fe and TiO₂ as the support. The prepared catalysts (Ni/Al₂O₃, Ni-Fe/Al₂O₃, and Ni-Fe/TiO₂-Al₂O₃) were characterized by N₂ adsorption-desorption, X-ray diffraction (XRD), temperature-programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS). The characteristics of the catalysts for the methanation process were investigated with the ratio of H₂/CO as 3:1 under an atmospheric pressure. The addition of Fe in the Ni/Al₂O₃ catalyst could promote the dispersion of Ni species and decrease the reduction temperature of catalyst. The optimal ratio for Ni-Fe/Al₂O₃ catalyst was estimated to be 1 due to the small-sized Ni particles and easily reducible β-type NiO species, giving the CO conversion of 97% and CH₄ selectivity of 94% at 262 °C. The addition of TiO₂ (10 wt%) in Ni-Fe/Al₂O₃ catalyst promotes the formation of Ni-Fe alloy, facilitating the methanation reaction at low temperatures and suppressing the coke deposition. This also results in the outstanding stability of the Ni-Fe/TiO₂-Al₂O₃ catalyst over other Ni-Fe/Al₂O₃ catalysts.