The microkinetic of gas-solid Fischer-Tropsch synthesis on Fe-Cu-K-SiO 2 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 H 2 /CO inlet ratios from 0.5 to 2 mol/mol. Unity bond index-quadratic exponential (UBI-QEP) and transition state theory (TST) was used to calculate heats of adsorption and initial estimates of some of the

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... netic 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.