Comparative investigation on bio-oil production from eucalyptus via liquefaction in subcritical water and supercritical ethanol

The present work addresses the liquefaction of eucalyptus for the production of bio-oil, examining the effects of solvent on the conversion process. The liquefaction was conducted at 260-320 degrees C in subcritical water and supercritical ethanol, and the bio-oil produced was analyzed by elemental components, higher heating value, GC-MS, and FTIR. Results showed that reaction medium and temperature exhibited notable influence on the process. The optimum condition for the preparation of bio-oil from eucalyptus should be conducted under water at 300 degrees C for 30 min, which can produce a high bio-oil yield of 30.1%. As the hydrothermal liquefaction temperature increased, the contents of aldehydes, phenols, and alkanes in the heavy oil decreased, while those of esters and ketones increased. After liquefaction in ethanol, the main substances in the heavy oil were esters, phenols, ketones, alcohols, alkanes and olefins. In light oil, esters, alcohols, phenols and ketones were the main substances. The properties of the bio-oil produced made it suitable to be applied as a promising precursor of bio-based aromatics and/or phenolic-rich antioxidant.