Carbon chain growth reaction of synthesis of lower olefins from syngas on Fe-Co catalyst

In recent years, the Fischer-Tropsch synthesis of lower olefins (FTO) has been an attractive non-oil-based process to produce lower olefins. Fe-based catalysts doped with Co promotor used for synthesis of lower olefins from syngas are studied in this work. We have used a combination of density functional theory (DFT) and kinetic Monte Carlo (kMC) simulations to explore the role of Co and Fe-Co catalytic activity in this reaction. DFT calculation results suggest that energy barriers of CHx coupling decrease significantly with the addition of Co while energy barriers of CHx hydrogenation decrease slightly, indicating that the addition of Co improves the ability of carbon chain growth. The results of kMC simulation show that the addition of Co increases reaction rates, and the carbon chain grows not only by CH2 coupling, but also by coupling of CH2 and CH3 in the presence of Co atoms. The appropriate Co content can increase the proportion of C-2 hydrocarbons and C2H4 in the three main products. In summary, the appropriate addition of Co is beneficial to carbon chain growth, and the appropriate amount of Co can improve olefins selectivity effectively, which provides a theoretical basis for the preparation of Fe-Co catalyst for synthesis of lower olefins.