Effect of Mn-dopant on carburization of the Fe3O4 catalysts in Fischer-Tropsch synthesis. (August 2021) - Han, Xiaoxue
Highlights: The effect of Mn on carburization was studied by excluding the influence of particle size and support. Mn doping hinders the carburization of Fe3 O4 nanoparticles and stabilizes the intermediate at FeO. DFT calculation indicates Mn doping enhances Fe-O bonds and impedes oxygen removal. Abstract: By experimental and density functional theory (DFT) methods, we investigated the effect of Mn on the carburization of the Fe3 O4 catalysts in Fischer–Tropsch synthesis. Freshly prepared Mnx Fe3-x O4 (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 Fe3 O4 (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 Fe3 O4 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.