Methanation of CO2 with H2-reduced magnetite

The methanation reaction of CO₂ was studied with H₂-reduced magnetite. A high conversion ratio of about 0.9 (in 30 min of the reaction time) with a selectivity of nearly 100% was obtained at 300°C and at 0.1 MPa for H₂-reduced magnetite which had been prepared by passing H₂ gas for 1–5 h at 300°C. From the results of X-ray diffractometry and Mössbauer spectroscopy, and from chemical analysis of the deposited carbon, H₂-reduced magnetite is considered to decompose adsorbed CO₂ into carbon, and to incorporate the oxygen of the CO₂ into the spinel-type structure of the magnetite, associated with oxidation of the Fe²⁺ ion into Fe³⁺ ion in the magnetite. The high conversion ratio in the methanation reaction is considered to come from a higher reactivity of the elementary carbon deposited on the surface of the H₂-reduced magnetite.