Stabilization of the aqueous phase fraction of pine wood bio-oil using zirconia-supported Fe/Cu/Pd nano-catalysts under mild conditions

Bio-oil has high potential for fuel and chemical production by hydroprocessing, but its high acidity and oxygen level require a stabilization stage before its upgrading. The hydrogenation of the water fraction of bio-oil (WBO) was studied in the presence of mono- and bimetallic catalysts (Cu, Fe, Pd, PdCu and PdFe) on a zirconia support at 50 bar H₂ at 100 °C. 96% of C present in the liquid phase was retained after a reaction time of 240 minutes using the PdFe bi-metallic catalyst without a decrease in catalytic activity. Fe/ZrO₂ and FePd/ZrO₂ were able to reduce WBO acids (−45%) and levoglucosan (−50%) and maintain their activity for the whole 360 min, while the Pd, Cu and PdCu based catalysts deactivated relatively fast. PdFe/ZrO₂ was the catalyst that produced more cyclohexanes (after 240 min), suggesting that Fe promoted by Pd is active for the hydrogenation of C[double bond, length as m-dash]C bonds, leading to the saturation of aromatic rings at low temperature. The LTMP hydrogenation activity of PdFe/ZrO₂ can be linked to the good dispersion of Fe and Pd nanoparticles of a few nm size and Pd–Fe–ZrO₂ synergistic activity. The results suggest that particularly PdFe on ZrO₂ is an attractive catalyst for the stabilization of WBO at low temperatures.