A Langmuir–Hinshelwood–Hougen–Watson (LHHW) kinetic model for FTS hydrocarbon production rates is developed. The concept of dual Anderson- Schulz- Flory (ASF) distribution with two chain growth probabilities is used for developing of kinetic model. The experiences carried out in the continuous spinning basket reactor. The iron catalyst promoted by lanthanum as a low basic promoter is used for activity evaluations. The results show that the kinetic model developed by dual ASF products distributions is more consistent than simple ASF with experimental results. The activation energy for formation of methane, ethane and ethylene are calculated as 68, 76 and 72 kJ mol-1, which can explain the lower selectivity of ethane than ethylene. The activation energy for paraffin formation with carbon number lower than break is 91 kJ mol-1 and for paraffin formation with carbon number greater than break is 102 kJ mol-1 which can explain the lower selectivity of heavy paraffin. Also, the activation energy of light olefin formation is 98 kJ mol-1 and the activation energy of heavy olefin formation, is 148 kJ mol-1.

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