Fischer–tropsch synthesis in a three-phase slurry reactor: Fe/HAp versus commercial Nanocat® for liquid hydrocarbon production

In this study, hydroxyapatite (HAp) is investigated as a catalyst support for Fischer–Tropsch synthesis (FTS) using iron as the active metal. The reaction is performed in a continuous stirred-tank reactor (CSTR), providing superior temperature control and enhanced gas–solid interactions. The Fe/HAp catalyst is benchmarked against a commercial ferric oxide catalyst (Nanocat®), and the effects of the CO/H 2 feed ratio, temperature, and gas space velocity (SV) on the catalytic performance are evaluated. X-ray diffraction (XRD) analysis reveals strong Fe–HAp interactions, leading to iron phosphide (Fe 2 P) formation, which enhances iron dispersion and mitigates sintering. Scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy (STEM-EDS) confirms a uniform iron distribution with an average particle size of 5 nm. Performance tests show that Fe/HAp maintains stable CO conversion (40 %) at a high SV (12,050 mL·g −1 ·h −1 , 250 °C), whereas Nanocat® deactivates rapidly, mainly due to severe sintering. Both catalysts exhibit high C 5+ hydrocarbon selectivity (>90 %); Fe/HAp favors gasoline (32 %), while Nanocat® favors diesel (33 %) at 250 °C. Notably, Fe/HAp promotes olefin selectivity (50 %) at 220 °C and an H 2 /CO ratio of 1, whereas increasing the H 2 /CO ratio to 2 enhances oxygenate formation (35 %). These findings highlight HAp as a promising support for modifying Fischer–Tropsch selectivity while ensuring catalyst stability.