Isotopic Exchange Study on the Kinetics of Fe Carburization and the Mechanism of the Fischer–Tropsch Reaction

The kinetics of the transformation metallic Fe to active carbide phase at start Fischer–Tropsch (FT) reaction were studied. diffusion rates C atoms going in or out lattice determined using 13C-labeled synthesis gas combination with measurements transient 12C and 13C contents by temperature-programmed hydrogenation. In initial 20 min, diffuses rapidly into occupying thermodynamically very stable interstitial sites. FT starts already during these early stages carburization. When reaching steady state, converge continues via two parallel mechanisms. It appears that outer layers are involved hydrocarbon formation a slow Mars–Van Krevelen-like contributing ?10% total activity, while remainder activity stems from fast Langmuir–Hinshelwood occurring over minor part catalyst surface.