Effect of sodium perborate monohydrate concentrations on product distributions from the hydrothermal liquefaction of Scotch pine wood

The hydrothermal liquefaction of biomass was carried out using sodium perborate monohydrate (NaBO3⋅H2O) at 250, 300 and 350 °C. The effects of temperature and additive concentrations on the product distributions were investigated. NaBO3⋅H2O was found to be very effective for the hydrothermal liquefaction of biomass at 300 and 350 °C. The use of NaBO3⋅H2O in the liquefaction of woody biomass increased the yields of bio-oils and decreased the solid residue yields at 300 and 350 °C. All concentrations of NaBO3⋅H2O showed high catalytic performance at 300 and 350 °C. The identified compounds in bio-oils (light bio-oils and heavy bio-oils) were mostly oxygenated hydrocarbons for both the thermal and NaBO3⋅H2O runs. Furfural, 5-methyl furfural, and 5-(hydroxymethyl)furfural were only observed in the thermal run. Most of the identified compounds in the light bio-oils obtained from the thermal and NaBO3⋅H2O runs were phenolic compounds. The highest heating value of the resultant heavy bio-oils was approximately 32 MJ/kg, which was obtained from the hydrothermal liquefaction of biomass at 350 °C with NaBO3⋅H2O.