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Abstract:
Sodium lignosulfonate (LS) was valorized to low molecular weight (Mw) fractions by combining solvothermal (SF) and catalytic hydrogenolysis/hydrogenation fragmentation (SHF) in continuous flow system. This achieved in either alcohol/water (EtOH2O or MeOH/H2O) as a solvent and Ni on nitrogen-doped carbon as a catalyst. The tunability according to 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 Mw was 2994 g mol-1 at 250°C with a dispersity (Đ) of 5.3 using MeOH/H2O. In catalytic SHF using MeOH/water, extremely low Mw was found (433 mg gLS-1) with Đ of 1.2 combined with 34 mg gLS-1. The monomer yield was improved to 42 mg gLS-1 using dual catalytic beds. These results is a direct evident that lignin is an unstable polymer at elevated temperature and could be efficiently deconstructed in hydrothermal conditions with and without catalyst.