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 CO 2 . 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 TiO 2 support with the same composition, requiring only a modest thermal treatment to activate it for FT synthesis. Cobalt supported on the MnTiO 3 shows significantly higher C 5+ selectivity and CO conversion than the equivalent conventional Co/Mn/TiO 2 catalyst. The MnTiO 3 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 MnTiO 3 support is re-oxidised to TiO 2 and MnO 2 , it subsequently reduces back to MnTiO 3 at low temperature, suggesting a structural memory for the MnTiO 3 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. Mn promotion in FT can direct products between oxygenates and paraffins. A simple in situ treatment forms MnTiO 3 while an ex situ support is demonstrated with the benefits of Mn inclusion while controlling activity and inhibiting alcohol selectivity.