Study on syngas methanation mechanism over Ni₄/MCM-41 catalyst based on the density functional theory

The density functional theory method is employed to systematically explore the mechanism of syngas methanation on the Ni₄/MCM-41 catalyst surface. The calculation results show that the optimal pathway of CH₄ formation is CO + H → CHO + H → CH₂O + H → CH₃O → CH₃ + H → CH₄ with the rate-determining step of CH₃O direct dissociation. Because the activation energy for the direct dissociation of CH₃O species is much lower than that for the CH₃OH formation (198.6 vs 264.8 kJ mol⁻¹), there is almost no by-product CH₃OH that appeared in the products of the syngas methanation over the Ni₄/MCM-41 catalyst. Compared with other conventional nickel-based methanation catalysts, Ni₄/MCM-41 catalyst is an excellent methanation catalyst with high selectivity of CH₄.