Tuning Potassium Concentration in Empowered Supports for Fischer‐Tropsch Synthesis

Abstract Potassium substitution in the A site of a LaAl 0.8 Mn 0.2 O 3‐δ perovskite was investigated as a strategy to anchor the promoter within a crystalline matrix thus suppressing its mobility under reaction conditions and enhancing the performance of iron‐based Fischer‐Tropsch (FT) catalysts. A series of La 1‐x K x Al 0.8 Mn 0.2 O 3‐δ ( x = 0 to 8 at.%) perovskites was prepared and subsequently loaded with pre‐synthesized iron oxide nanoparticles. Quantitative in situ X‐ray diffraction revealed that potassium incorporation delays the reduction of the Fe 3 O 4 phase and accelerates the rate of carburization, resulting in a higher crystalline iron carbide content at increased potassium concentrations. Under low temperature FT conditions (240 °C, 15 bar, H 2 /CO = 2) CO conversion and CO 2 selectivity increased with potassium loading, while C 5 + selectivity peaked at 2 at.% potassium in the A site of the perovskite lattice. At the same loading, thermal alkali desorption and X‐ray absorption spectroscopy studies revealed that potassium remains strongly anchored within the lattice yet sufficiently electronically active to enhance CO activation without over‐promoting the water‐gas shift (WGS) reaction, thereby maximizing chain growth selectivity. These results highlight the potential of fine‐tuning concentrations of promoters in empowered supports to optimize catalyst performance, offering a stable and controllable alternative to conventional deposition or impregnation methods.