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

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 ABO(3) 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.