THE ROLE OF CARBON ON IRON SURFACE IN METHANATION

The decomposition of carbon monoxide on a commercial fused iron catalyst for ammonia synthesis has been investigated in a flow system at 250 C under atmospheric pressurs. The decomposition proceeded in accordance with the Boudouard reaction, disproportionation of carbon monoxide to carbon dioxide and surface carbon (Hagg carbide) with irreversible adsorption of carbon monoxide during an initial period. The rate of the disproportionation showed first-order dependence on the partial pressure of carbon monoxide. The steady-state reduction of carbon monoxide with hydrogen to methane also has been carried out on the carbon-covered catalyst obtained by means of the Boudouard reaction at 250 C. With the increase in the amount of carbon on the surface, both rates of water and carbon dioxide formation decreased. On the other hand, the rate of methane formation was essentially independent of the amount of surface carbon up to 1.2m mole /g, and then decreased linearly. In the methane formation the carbon-covered catalyst showed a period of induction which depended on the amount of surface carbon. From this evidence it was deduced that some of the surface carbon contributed not to the formation of a reaction intermediate but to the formation of an actual active site on the fused iron catalyst