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A Single-Event MicroKinetic (SEMK) model has been extended towards the simulation of Steady State Isotopic Transient Kinetic Analysis (SSITKA) data for Co catalyzed Fischer-Tropsch Synthesis (FTS). The extended model considers two types of sites and both direct and H-assisted CO dissociation. Regression of the model parameters to the data obtained from 17 steady state and 11 SSITKA experiments resulted in physicochemically meaningful estimates for the activation energies and atomic chemisorption enthalpies. The application of the phenomenological UBI-QEP method allows to physically interpret the nature of the two site types considered in the model, i.e., terrace and step sites. A reaction path analysis shows that over 80 percent of the CO reacts on the step sites. Furthermore, chain growth exclusively occurs on these sites. The terrace sites are less reactive for CO dissociation and are identified as responsible for methane production. A fraction of the alkenes, produced on the step sites, is hydrogenated to alkanes on the terrace sites. Based on model simulations, the metal particle size effect, i.e., a lower TOF, higher methane selectivity and increasing alkane to alkene ratio with decreasing metal particle size, is attributed to an increasing relative importance of the terrace sites on the reaction kinetics.

The microkinetic of gas-solid Fischer-Tropsch synthesis on Fe–Cu–K–SiO2 catalyst was studied which was consisted of different elementary steps. The operation condition was in temperature of 523K, total pressures from 0.8 to 3.2 MPa, space velocity from 0.5 to 2.0 ×10 -3 Nm 3 kg -1 s -1 and H2/CO inlet ratios from 0.5 to 2 mol/mol. Unity bond indexquadratic exponential (UBI-QEP) and transition state theory (TST) was used to calculate heats of adsorption and initial estimates of some of the kinetic parameters. The pre-exponential factors were calculated based on statistical thermodynamics. The accuracy of the UBI-QEP method in calculating the energetic of the elementary reactions on catalyst surface was acceptable. The calculated activation energies to produce n-alkanes and 1-alkenes were in range of 19.57 to 25.68 and 19.53 to 20.45 kcal/mol respectively. These values were used to obtain the product distributions. However the application of the microkinetic study with molecular approach can provide better insight to the analysis of the FTS reaction mechanism.