Comparative investigation on hydrothermal and alkali catalytic liquefaction of bagasse: Process efficiency and product properties

•A significant enhancement of bagasse hydrothermal liquefaction is shown with MgMnO2.•93.7% of the bagasse is liquefied yielding 59.5% of the water-soluble fraction.•Lignin, the main component of residue without catalyst, can be degraded over MgMnO2.•The volatile product is substantially different with MgMnO2 catalyst.•No obvious catalytic activity loss exhibits even up to five consecutive reuses.

In this study, we propose a novel and efficient process for bagasse liquefaction in subcritical water over the solid alkali catalyst of MgMOx (M = Mn, Ni, Fe, Cr, Zn and Al). The intensification effect of the catalyst was investigated via hydrothermal liquefaction, where the product distribution and composition of volatiles and residue were compared using GC-MS, GPC, FT-IR and elemental analysis. The results show that the materials substantially promote bagasse liquefaction. Under optimized conditions (250 °C for 15 min), MgMnO2 liquefied 93.7% of the bagasse yielding a water-soluble fraction of 59.5%. Of particular note, lignin, the most recalcitrant fragment in biomass hydrothermal liquefaction, is efficiently depolymerized to volatile phenolic monomers with these catalysts. Furthermore, the MgMnO2 catalyst shows good recyclability, where no significant activity loss is demonstrated even after the fifth run.

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