Intrinsic kinetics of Fischer–Tropsch synthesis over an Fe–Cu–K catalyst

Abstract

A new method to obtain the intrinsic kinetics of Fischer–Tropsch (FT) synthesis over the Fe–Cu–K catalyst, which is sensitive to reaction temperature, has been developed. The initial activity of the fresh catalyst was depressed (passivated) under a pressure of 3.15 MPa and at a temperature of 573 K before measuring the kinetic data. The ‘lumping’(i.e. considering the reaction products in terms of six species; CH₄, CO₂, H₂O, C₂₊, C⁰₂₊ and C^OH₁₊) of chemical reactions was used to deal with kinetic models. On the basis of kinetic data for the fresh catalyst and the intrinsic kinetics for the passivated catalyst, the intrinsic kinetics over the Fe–Cu–K catalyst for the FT synthesis was proposed by regression of the pre-exponential factor, k₀ and the Arrhenius rate constant. The intrinsic kinetic model is in agreement with those obtained by enol theory. The intrinsic kinetic activation energy and enthalpy of adsorption are 66.52 kJ mol^–1 and –65.412 kJ mol^–1, respectively. The intrinsic kinetics indicates that the inhibition of the reaction by water is significant, but no inhibition by carbon dioxide was observed under the conditions investigated.