Improving bio-oil stability by fractional condensation and solvent addition

A three-stage condensation system was employed in this study to investigate the improvement effect of fractional condensation on the stability of bio-oil obtained through the pyrolysis of rice husk. The fractional bio-oil obtained from the second condenser was selected for aging experiments and compared with crude bio-oil collected via one-stage condensation at 0 degrees C. The bio-oil viscosity, moisture content, and organic composition were recorded and analyzed as characteristic parameters of the aging process. The results demonstrate that the aging reactions of the fractional bio-oil were suppressed or delayed because the bio-oil components involved in the aging reactions were effectively separated in the other two condensers. Subsequently, the fractional bio-oil was further upgraded via the addition of ethanol, ethyl acetate, or mixtures of these two solvents. It was observed that the addition of ethanol and ethyl acetate at a mass ratio of 1:1 significantly improved the stability of the fractional bio-oil, and the resulting modified bio-oil was found to be rich in high value-added components, such as 2-methyl-3-buten-2-ol, furfural, and phenol. Overall, this research facilitates a better understanding of the bio-oil aging mechanism and provides a new method to improve bio-oil stability.