Solvent effects on improvement of fuel properties during hydrodeoxygenation process of bio-oil in the presence of Pt/C

Bio-oil was subjected to hydrodeoxygenation (HDO) reactions with polar protic (ethanol), polar aprotic (acetone), and nonpolar (ether) solvents in the presence of Pt/C catalyst. Mass balances (gas, light oil, heavy oil and char) of products were influenced by the solvent used. Subjecting the oil to HDO yielded improvement in the following heavy oil properties: water content, heating value, viscosity, acidity, and oxygen level. Especially, the viscosity was reduced from 29.6 cSt of the bio-oil to 2.2–4.4 cSt when ethanol was used, to 3.0–4.2 cSt when acetone was used, and to 6.5–6.7 cSt when ether was used. The initially acidic bio-oil was neutralized by HDO. Furthermore, HDO decreased the water and oxygen content of heavy oil, thereby improving its higher heating value (HHV). Because the polar protic solvent was able to react with bio-oil as a co-reactant during HDO, acid-type components in the bio-oil were converted into acid or ester forms, which were found in the light oil. In terms of carbon recovery from bio-oil to the heavy oil fraction, acetone was the most effective solvent, yielding 72.8% recovery, followed by ether (64.7%) and ethanol (55.3%).