Effect of Mn-dopant on carburization of the Fe3O4 catalysts in Fischer-Tropsch synthesis

Abstract

By experimental and density functional theory (DFT) methods, we investigated the effect of Mn on the carburization of the Fe₃O₄ catalysts in Fischer–Tropsch synthesis. Freshly prepared Mn_xFe_3-xO₄ (x = 0, 0.27 and 1) nanoparticles as representative model bulk FTS catalysts were carburized by exposing to syngas. The oxide nanoparticles and the corresponding carburized samples were then characterized using XRD, XPS, TEM and MES. To mimic the experiments, a slab modelling the Fe₃O₄(3 1 1) surface doped with different number of Mn atoms were constructed in the DFT calculations. Our results showed that Mn doping hindered the carburization of Fe₃O₄ nanoparticles and stabilizes the reduction intermediate at FeO. This is attributed to the enhanced affinity of O atoms in the presence of Mn-dopant, making removal of O difficult. The work provides guidance for catalysts design and activation for FTS process.