Catalytic hydrothermal liquefaction of eucalyptus to prepare bio-oils and product properties

Highlights: • Hydrothermal liquefaction of eucalyptus was performed in NaOH, KOH, and Pd/C. • The C and H contents of heavy oils were higher than those in light oils. • Light oils contained more phenolics than heavy oils. • Bio-oils contained mainly carboxylic acids, aldehydes, ketones, phenols and esters. -- Abstract: Catalytic hydrothermal liquefaction of eucalyptus was performed in the presence of NaOH, KOH, and Pd/C at 260 and 300 °C. The influences of catalyst and temperature on the process were thoroughly investigated regarding product distribution and characteristics of the bio-oil obtained. The yields of bio-oils obtained using NaOH and KOH were 61.2% and 57.7% for the liquefaction at 260 °C, respectively. For the liquefaction with alkali catalysts, as the liquefaction temperature increased, the yields of bio-oils and solid residue decreased, while the amounts of gas and losses increased. The C and H contents of heavy oils were higher than those in light oils, and the O content was lower than those in light oils. GC–MS analysis of the sample indicated that the bio-oils contained large amounts of carboxylic acids, aldehydes, ketones, phenols, and esters. The liquid products are promising bio-fuel precursors for further utilization.