Abstract
•Bark and softwood bio-oil were distilled under vacuum (10 kPa).•Low molecular weight compounds (C1–C3) were isolated from bark and softwood bio-oil.•The heating value doubled in the residual bio-oil compared with the original bio-oil.•There was a significant reduction in water content and acidity in the residual bio-oil.
In this paper an analysis of short-path vacuum distillation for the isolation of low molecular weight compounds (C1–C3) from softwood and bark bio-oils is reported. The short-path vacuum distillation was performed at 60–100 °C under vacuum (10 kPa) for 0.5–1 h. Although methanol and acrolein distilled completely, acetic acid and acetol failed to do so after 1 h. The acetic acid content and the total acid number of the residual oils decreased and their heating values doubled (to 19.6 kJ/g). Short-path vacuum distillation is an efficient method to both isolate low molecular weight feedstocks/fuels, and improve the quality of the residual bio-oil for blending with petroleum or biofuels.