The kinetic parameters of water-gas shift (WGS) reaction in the Fischer-Tropsch synthesis (FTS) on lanthanum promoted iron catalyst are analysis by size dependent thermodynamic method. A Langmuir–Hinshelwood kinetic equation is considered for the catalysts activity evaluation. A series of unsupported iron catalysts with different particle sizes are prepared via microemulsion method. These results show that the iron particle size has considerable effects on reactants adsorption and WGS kinetic parameters and WGS activity pass from a maximum by increasing the catalyst particle size. Finally, the analysis of data showed that by increasing the iron particle from 14 to 41 nm, the WGS activation energies and heats of adsorption of carbon monoxide and water on catalysts increased from 68 to 83 kJ/mol, 22 to 28 kJ/mol and from 75 to 94 kJ/mol, respectively.

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