Evidence for two chain growth probabilities on iron catalysts in the Fischer-Tropsch synthesis

New data and reexamination of several previous studies in either fixed bed or slurry liquid reactors with iron catalysts show that the products frequently may be characterized as the sum of two Flory carbon number distributions. In many cases the dominating distribution shifts at about C10. At higher carbon numbers hydrocarbons are produced with a much higher probability of chain growth than for lower carbon numbers. Results are interpreted in terms of a two-site catalyst structure.