Fischer-Tropsch synthesis. Compositional changes in an iron catalyst during activation and use

The equilibrium phase compositions of iron have been calculated for gas compositions that could be encountered during the Fischer-Tropsch synthesis. The gas compositions measured experimentally for CO conversion levels in the 30-90% range show that iron should be present as the carbide phase. However, experimental characterization of iron catalysts show that a significant fraction of the iron is present as Fe3O4 following synthesis for several days. A model that can account for the experimental catalyst phase composition and the gases present in the reactor would have a core of Fe3O4 and an outer layer of iron carbides.