A Novel Approach for the Assessment of the Rate-Limiting Step in Fischer−Tropsch Slurry Process

Abstract

A novel approach to determine the rate-limiting step in the Fischer−Tropsch (F-T) slurry process was developed using a simple computer model. This approach, unlike others, takes into account the water gas shift (WGS) reaction in the calculation of the importance of the gas−liquid mass transfer and makes use of the “singular kinetic path” concept proposed by Espinoza in 1993 which incorporates F-T kinetic expressions from different investigators. The predictions of the computer model showed that CO was the likely limiting reactant when using iron-based catalyst, since it is consumed by Fischer−Tropsch and water gas shift reactions and has lower mass transfer coefficients than those of H2. It was also found that in the case of cobalt-based catalyst F-T synthesis is sensitive to the H2/CO ratio of the inlet gas and H2 was the likely limiting reactant, especially when the reactor was supplied with syngas having a H2/CO ratio lower than the stoichiometric value. The Fischer−Tropsch synthesis in a slurry phase ...