Controlled lignosulfonate depolymerization solvothermal fragmentation coupled with catalytic hydrogenolysis/hydrogenation in a continuous flow reactor

Sodium lignosulfonate (LS) was valorized to low molecular weight ( M w ) fractions by combining solvothermal (SF) and catalytic hydrogenolysis/hydrogenation fragmentation (SHF) in a continuous flow system. This was achieved in either alcohol/H 2 O (EtOH/H 2 O or MeOH/H 2 O) or H 2 O as a solvent and Ni on nitrogen-doped carbon as a catalyst. The tunability according to the temperature of both SF and catalytic SHF of LS has been separately investigated at 150 °C, 200 °C, and 250 °C. In SF, the minimal M w was 2994 g mol −1 at 250 °C with a dispersity ( ) of 5.3 using MeOH/H 2 O. In catalytic SHF using MeOH/H 2 O, extremely low M w was found (433 mg g LS −1 ) with a of 1.2 combined with 34 mg g LS −1 . The monomer yield was improved to 42 mg g LS −1 using dual catalytic beds. These results provide direct evidence that lignin is an unstable polymer at elevated temperatures and could be efficiently deconstructed under hydrothermal conditions with and without a catalyst. This study presents an efficient and controlled catalytic valorization of a real side product of the agroforestry industry, i.e. , sodium lignosulfonate (LS), in a continuous flow system to either monomers or oligomers.