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Upgrading of fast pyrolysis oil via catalytic hydrodeoxygenation: Effects of type of solvents

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Upgrading of fast pyrolysis oil was conducted in a batch reactor using Ru/C catalyst.

Using solvent in the HDO process could reduce or eliminate the self-polymerization.

Using ethanol as the solvent improved the heating value of the bio-oil products.

The lowest O/C ratio (0.08) is obtained by using ethanol as solvent.

The highest OF yield was obtained by using hydro-treated bio-oil as the solvent.


Effects of type of solvents (hydro-treated bio-oil and ethanol) and temperature (300 and 350 °C) on hydrodeoxygenation (HDO) of fast pyrolysis oil (PO) were studied. The presence of a solvent effectively reduced self-polymerization of the intermediates during the bio-oil HDO process. HDO of PO using hydro-treated oil as the solvent produced higher yields of oil fraction (OF) and consumed more H2 than those with ethanol. While the OF yields from all the HDO experiments ranged from 60 to 90 wt%, the highest OF yield was obtained using hydro-treated bio-oil as the solvent. Nevertheless, HDO of PO in ethanol is more promising as it improves the HHV (higher heating value) of the bio-oil substantially (from 21 to 38 MJ/kg), reduces the molecular weight of bio-oil, and the resulted OFs have the lowest O/C value (0.08). HDO upgrading of bio-oil in ethanol has similar effects as HDO operation at a higher temperature (350 °C) without solvent with respect to molar mass reduction for the bio-oil.

Graphical abstract

Van Krevelan plot of feeds (UO1 UO9) and HDO oil fractions (OF-UO1 OF-UO9) from all HDO tests using hydro-treated bio-oil (UO2 UO6) and ethanol (UO7 UO8) as solvents, respectively. UO1 and UO9 represent HDO tests without solvent at 300 °C and 350 °C, respectively.


  • Fast pyrolysis oil;
  • Hydro-treated bio-oil solvent;
  • Ethanol solvent;
  • Hydrodeoxygenation (HDO);
  • Upgrading;
  • Ru/C catalyst

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