The Fischer-Tropsch reaction mechanism over an Iron based catalyst is investigated with the Steady State Isotopic Transient Kinetic Analysis (SSITKA) technique using a plug-flow fixed-bed reactor. This reactor is operated under differential and intrinsic conditions in the absence of severe pressure effects related to the abrupt change in isotopic feed composition. Emphasis is put on evolution of the labeled carbon 13C in the C1 to C5 hydrocarbon products, leading to a kinetic analysis of the Fischer-Tropsch mechanism. A plug-flow reactor model is used to describe the experimental results. Data is obtained at 330 °C, H2/CO ratios from 4 to 20, and a pressure of 1.2 bar. The results for the methanation reaction, which includes a reaction mech...