Further results on the reaction of H 2/CO on fused iron by the transient method

Abstract

Experiments have been continued on a CCI commercial, promoted, fused-iron catalyst. Catalyst stability and long-term activity are improved by an oxygen treatment at 500 °C prior to reduction at 500 °C. Water is a strong inhibitor of the initial reaction of H 2/CO ( 9 1 ) at 250 °C and 1 atm to hydrocarbons, and the steady-state catalyst is active for the shift reaction. Experiments with C 2H 4/H 2 and other olefins show that these reactants are both split into lower alkanes (including methane) and added to for the formation of alkanes of higher carbon number than the feed olefin. Reaction on a reduced catalyst at 250 °C does not lead to bulk carburization of the iron, whereas of course CO/H 2 under the same conditions forms bulk Fe 2C. These results support a mechanism in which the hydrogenation of surface carbon is the rate-limiting process, and chain growth occurs through C x H y fragments, present on the surface in low coverage. ESCA experiments show that the surface of the catalyst used at 250 °C has a high concentration of graphitic carbon and that the iron is at least partly oxidized.