Direct solvolysis of papermaking black liquor in strong alkali coupled with catalytic hydrodeoxygenation to produce aviation fuel-range arenes

During the chemical pulping of lignocellulose, a lot of papermaking black liquor (pH 13–14) was generated, containing a substantial amount of low molecular weight lignin, which has potential for the production of aviation fuels. Herein, black liquor was converted into aviation fuel-range arenes via a two-step process including direct solvolysis in strong alkali followed by catalytic hydrodeoxygenation of the products. In the solvolysis step, the black liquor (20 % solids content, pH 14) could directly produce lignin oil (mainly consisting of alkylphenols and oligomers linked by β-O-4 and β-5 linkages) with a high yield (67.3 wt%) at 280 °C under hydrogen atmosphere in a methanol/ n -hexane (2:1, v/v) mixed solvent, which was much higher than that of the other lignin feedstocks. In the second step, the obtained lignin oil from the black liquor was efficiently hydrodeoxygenated into arenes (80.1 % selectivity) over a CoMoS/γ-Al 2 O 3 catalyst at 320 °C under 2 MPa H 2 , achieving a deoxygenation degree of 97.7 %, and CoMoS/γ-Al 2 O 3 efficiently promoted the cleavage of C ar -O bonds in lignin-derived phenols. Techno-economic analysis and life cycle assessment further emphasized the actual feasibility of the two-step process. This work presents a novel strategy for converting papermaking black liquor into aviation fuels.