Controlling cobalt Fischer–Tropsch stability and selectivity through manganese titanate formation

Abstract

Fischer–Tropsch (FT) synthesis has gained renewed interest for its role in producing sustainable fuels from renewable feedstocks such as biomass, municipal waste and CO₂. This submission highlights a new catalyst support material for FT, which produces a novel switch in selectivity from oxygenated products to high quality linear paraffins. The manganese titanate support with a ABO₃ perovskite structure shows substantial differences in catalytic performance compared with the conventional Mn impregnated TiO₂ support with the same composition, requiring only a modest thermal treatment to activate it for FT synthesis. Cobalt supported on the MnTiO₃ shows significantly higher C₅₊ selectivity and CO conversion than the equivalent conventional Co/Mn/TiO₂ catalyst. The MnTiO₃ support material is shown to be able to be formed via either an in situ reactor treatment or from a targeted ex situ support preparation method. Interestingly, after the MnTiO₃ support is re-oxidised to TiO₂ and MnO₂, it subsequently reduces back to MnTiO₃ at low temperature, suggesting a structural memory for the MnTiO₃ phase after oxidation. The catalyst materials were fully analysed by in situ XAS, in situ XRD, TEM and TPR, while the FT products were analysed by GC and NMR. This work provides insights into the role of manganese in FT, particularly its impact on controlling selectivity when included in a preformed catalyst support material.