Fate of iron during hydrothermal liquefaction of hemin

Hemin, an iron porphyrin, was used as a model compound to study the fate of iron during hydrothermal liquefaction (HTL). Hemin decomposed hydrothermally and produced an oil-phase with appreciable iron content only at temperatures exceeding 250 °C. Both the temperature of and the time in the hydrothermal environment affect the iron concentration in the oil from hemin HTL, with severe conditions leading to lower iron concentrations. Catalysts (Ni/Al₂O₃-SiO₂) and solvents (MTBE) that were effective in algal HTL biocrude demetallation also reduced iron concentrations in oil from hemin HTL. Iron porphyrinic species were identified in the oil from hemin HTL. They were much less prevalent when a Ni/Al₂O₃-SiO₂ catalyst was also used, which points to the effectiveness of catalytic HTL for demetallation of the oil. In addition, there were many species in the oil products with two nitrogen atoms, which formed from hemin decomposition.