Cu on Co Improves C₅₊ Selectivity in the Fischer–Tropsch Synthesis

This research evaluates Cu as a low-cost promoter for a Co-based Fischer–Tropsch synthesis (FTS) catalyst. Co selectively produces alkenes and long hydrocarbon chains, while Cu’s affinity for H2 adsorption ensures Co remains in its metallic state. Moreover, Cu promotes Co to synthesize longer hydrocarbon chains, specifically in the C8–C16 range. The synergistic relationship between Cu and Co reduces the formation of undesirable products active at low and medium temperatures (<300 °C). We synthesized seven catalysts with varying Cu NPs loadings from 0 to 0.15 g g–1 of Cousing the ultrasonic impregnation method, controlling the size of the catalyst in the nanorange (<20 nm). Among them, Co15–Cu0.15 is the best-performing catalyst with a CO conversion of 66% and selectivity for C5+ paraffin of 29% while having the lowest selectivity for CH4 at 16%. Transmission electron microscopy (TEM) images showed uniformly dispersed CoCu NPs on the Al2O3 support before the reaction. Scanning transmission electron microscopy (STEM), X-ray diffraction (XRD), and temperature-programmed reduction (TPR) were also used to characterize the catalysts. Furthermore, we developed a kinetic model to evaluate the influence of Cu loading on the product distribution. Co15–Cu0.15 was determined to yield the most C5+ hydrocarbons and decrease the yield of C3+, complementing our experimental results.