Separation of acid compounds for refining biomass pyrolysis oil

The large-scale utilization of biomass pyrolysis oil directly as high-grade energy resources has been quite limited due to its high water content and acidity. The water and acid compounds as a whole were separated from the pyrolysis oil by molecular distillation. One fraction obtained is rich in acid compounds, and the others are refined bio-oil I (heavy distillate fractions) and II (room temperature condensate), which have lower water content, weaker acidity, and higher heating value. The physical properties of the crude and refined bio-oil, such as the PH value, heating value, and water content were studied. The results indicated that water and acid compounds are separated effectively from the crude bio-oil. The content of carboxylic acids in crude bio-oil is about 18.85%, whereas that in the refined bio-oil I and II is decreased to 0.96% and 2.2%, respectively.