Microkinetic Modeling of the Fischer-Tropsch Synthesis over Cobalt Catalysts

We present a detailed microkinetic analysis of the Fischer-Tropsch synthesis on a Co/gamma-Al2O3 catalyst over the full range of syngas conversions. The experiments were performed in a Carberry spinning basket batch reactor at initial H-2/CO ratios between 1.8 and 2.9, temperatures of 469 and 484 K, and initial pressures of 2 MPa. A reaction mechanism based on the H-2-assisted CO activation pathway, which comprises 128 elementary reactions with 85 free parameters, was proposed to explain the experimental results. Each of these elementary re-actions belongs to one of the following reaction groups: adsorption-desorption, monomer formation, chain growth, hydrogenation-hydrogen abstraction, or water-gas shift. A two-stage parameter estimation method, based on a quasi-random global search followed by a gradient-free local optimization, has been used to calculate the values of pre-exponential factors and activation energies. The use of data obtained from batch experiments enabled an effective analysis of dominating reactions at different stages of syngas conversions.