Kinetics Modeling of Fischer–Tropsch Synthesis on the Cobalt Catalyst Supported on Functionalized Carbon Nanotubes

Resumo

An active cobalt catalyst supported on functionalized carbon nanotubes was prepared and tested for CO hydrogenation to produce liquid hydrocarbons in the Fischer–Tropsch synthesis. The catalyst characterization was carried out using different methods including X-ray diffraction, transmission electron microscopy and BET surface area equation. The kinetic experiments were performed in a fixed-bed reactor under following conditions: T =200–240°C, P = 15–30 bars, GHSV = 0.5–1.5 nL \({\text{g}}_{{{\text{cat}}}}^{{ - 1}}\) h^–1 and H₂/CO feed ratio (mol/mol) = 1–2.5. Based on various mechanisms and Langmuir–Hinshelwood–Hougen–Watson type rate equations, eleven kinetic expressions for CO consumption were tested and the best-fitted model is achieved. In kinetic rate development, various rate-determining steps (RDS) are considered for evaluation of RDS effects. The kinetic parameters were estimated with nonlinear regression method using Levenberg–Marquardt method to make refined optimization. The obtained energy of activation was 78 kJ/mol for optimal kinetic model. The obtained results show that the best models for proposed elementary reactions involve the formation of surface species as RDS rather than syngas adsorption.