Development of new comprehensive kinetic models for Fischer–Tropsch synthesis process over Fe–Co/γ-Al2O3 nanocatalyst in a fixed-bed reactor

Abstract

Kinetics and mechanisms of Fischer–Tropsch synthesis were investigated over a %10Fe/%10Co/%80γ-Al2O3 nano catalyst prepared by the impregnation method in a fixed bed micro-reactor. The ranges of operating conditions varied as T = 573.15–643.15 K, P = 1–7 bar, H2/CO feed ratio =1–2, and GHSV=3000 h−1. The kinetic expressions for CH4, olefins, paraffins formation, and water gas shift reaction (WGSR) were developed based on the occupied sites in three steps. According to this theory, eighteen rate expressions for WGSR, CO consumption, and products formation were tested, and finally, the ethylene production and water step gave the best fitted kinetic model. The Levenberg–Marquardt algorithm was used to estimate the activation energy (66.01 kJ/mol) and the kinetic parameters. It was found that the proposed model could perfectly predict the effects of water and ethylene. These models can be applied to determine the optimum conditions and products in the reactor. Characterization of catalysts was carried out using different techniques, including BET and SEM.