Fractionation of pyrolysis oil derived from lignin through a simple water extraction method

Great effort has been exerted to develop better, more effective fractionation techniques and improve the quality of bio-oil. Water extraction can be regarded as an effective method for bio-oil fractionation. In this study, fractionation of pyrolysis oil into water-soluble (WS) and water-insoluble (WI) phases by water extraction was investigated, and the influence of several factors, including water-to-oil ratio and water temperature, on the performance of the method were evaluated via several analytical techniques. When the water-to-oil ratio was 20:1 and the extraction temperature was 20 °C, polar and non-polar components were enriched in the WS (36.56 wt%) and WI (63.44 wt%) phases, respectively. Although extraction temperature had no significant effect on the properties of WS and WI, the distribution of polar and non-polar components was markedly affected by the dispersion and polarity of the compounds. 2D HSQC-NMR results revealed that side chain structures were more sensitive than aromatic structures to temperature. In view of these findings, an effective energy- and resource-saving extraction method featuring a water-to-oil ratio of 20:1 and extraction temperature of 20 °C is recommended for optimal water fractionation of pyrolysis oil.