Methanation of carbon deposited directly from CO₂ on rhodium-bearing activated magnetite

Abstract

Methanation reactivity was studied for the surface carbon deposited from CO₂ on the surface of Rh-bearing activated magnetite. The most active material (Rh=0.83 wt %) for methanation was prepared by the impregnation method at 60°C and showed 98% conversion at 300°C. The surface carbon was composed of elemental carbon (α-carbon) and polymerized carbon (β-carbon), the proportion being dependent on the density of carbon deposited. In temperature-programmed surface reaction, the extent of conversion of the α- and β-carbon to CH₄ was 0.34 (α-carbon) and 0.53 (β-carbon), respectively, and the total conversion was 0.87. This result indicates that not only elemental carbon but polymerized carbon (β-carbon) could be converted to CH₄ on the Rh-bearing activated (α-carbon) magnetite, whereas β-carbon is not hydrogenated on activated magnetite.