Tailoring iron-based catalysts via support variation and metal loading for efficient gasoline-like hydrocarbons production from oleic acid

This study investigates the effect of Fe metal loading and support type on the characteristics and catalytic behavior of Fe-based catalysts to produce gasoline-like hydrocarbons (GHCs) via the hydrodeoxygenation (HDO) of oleic acid. The catalysts were prepared by the wet impregnation method using HZSM-5, mordenite (MOR), and amorphous silica-alumina (SiAl) supports, with Fe loadings of 3, 6, and 9 wt%. The HDO reaction was conducted under mild operating conditions at atmospheric pressure. Characterization results indicate that Fe impregnation does not significantly alter the crystalline structure of the supports, as confirmed by XRD analysis. However, SEM observations reveal an increase in surface roughness after metal loading. An increase in Fe content leads to a decrease in surface area and total acidity, likely due to partial pore blockage and reduced accessibility of acid sites. Catalytic performance evaluation shows that both catalytic and non-catalytic experiments achieve high oleic acid conversion (>95%), indicating a significant contribution from thermal decomposition under the applied reaction conditions. Among all catalysts, Fe6/HZSM-5 exhibits the highest GHCs selectivity of 73%, outperforming Fe6/MOR (46.60%) and Fe9/SiAl (56.20%). The superior performance of Fe6/HZSM-5 is attributed not solely to acidity, but rather to the combined effects of pore structure, metal–support interaction, and the presence of Fe species that facilitate deoxygenation pathways and subsequent hydrocarbon formation. Overall, this study provides valuable insights into optimizing support selection and Fe metal loading for designing efficient catalysts for fatty acid-based gasoline-like hydrocarbons production under mild operating conditions.