Supercritical water depolymerization of black liquor, refining and comprehensive analysis of products including biopolyols

Abstract

Black liquor (BL) has valuable lignin and its derived compounds, which can be used for many purposes, such as polyol synthesis. Herein, we reveal polyols presence in depolymerized black liquor (DBL) and propose a fast and scalable approach to increase the yield of this fraction. Hydrothermal treatment (HTL) of black liquor (385°C, 26 MPa) was performed in a custom designed supercritical water (SCW) pilot-plant with rapid reaction times of around 0.4 s. Ash-free, total ethyl acetate extracted bio-oil yield was found 77% w/w. In addition to the contribution of the detailed fractionation methods, this study highlights continuous operation (>1 hour), and short reaction times (∼0.4 s) of raw black liquor in SCW to produce biopolyols and aromatic bio-oil.