Mechanism of chain growth and product formation for the Fischer-Tropsch reaction over iron catalysts

Abstract

Schulz-Flory-Anderson (SFA) product distributions with high percentages of alkenes are often observed for the Fischer-Tropsch (FT) reaction over promoted iron catalysts. This type of product distribution is inconsistent with carbide mechanisms involving alkyl groups as the growing chains. In order to explain these product distributions, the chain growth and product formation steps must be kinetically separated. We propose a straightforward carbide mechanism consistent with the experimentally observed product distributions. In this mechanism, the growing hydrocarbon chains are multiply bonded to the metal surface, the termination step is hydrogenation of the growing chain to a metal-bound alkyl species, and product formation occurs from this alkyl species