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

Abstract

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 CC 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.