Principles of Fischer–Tropsch synthesis—Constraints on essential reactions ruling FT-selectivity

Fischer–Tropsch synthesis has been performed with iron- and cobalt catalysts at varied conditions, and selectivity determined for steady state and the initial time of selforganization. Product composition has been analyzed in detail with high temporal resolution. Using the kinetic model of non-trivial surface polymerization, information about elemental reactions and their role in the reaction mechanism has been attained. Among the ruling principles, distinct constraints appear to be essential, as frustration of methanation, of desorption of chains in relation to their prolongation and of paraffin formation in relation to olefin desorption. Spatial constraints on the growth sites appear to control linear growth in relation to chain branching and also branching probability in dependence of chain length. With cobalt, selectivity and respectively the structure of active sites appear to be dynamic, to develop under reaction conditions and to respond to changes of conditions. With carbided iron, selectivity and respectively active sites appear to be of static nature. Information about secondary olefin reactions is also obtained as important for producing olefins through Fischer–Tropsch synthesis.