Harnessing the power of lignin from Litsea cubeba fruit residues: Characterization and valorization

Lignin is an important component of plants, and its utilization is essential for biorefinery. Litsea cubeba fruit residues (LSRs) are abundant renewable lignin-rich bioresource with enormous potential for producing value-added monophenols. Herein, the lignin from LFRs was isolated with organic solvent, which was characterized by two-dimensional HSQC-NMR, FT-IR, Py-GCMS and GPC. The results indicate that the lignin in LFRs is mainly composed of guaiacyl (G) subunits (93 %), with small amounts of syringyl (S)/ p -hydroxyphenyl (H) structural subunits. The reductive catalytic fractionation (RCF) of LFRs was investigated using methanol (MeOH) as the solvent and a commercial Pd/C (5 wt% Pd) catalyst. Two major phenolic compounds, 4- n -propylguaiacol and 4- n -propanolguaiacol derived from β-O-4 structure, were generated with high yield (19.4 wt%). This result was different from G-type pine wood powder, where 4- n -propanolguaiacol was the main product with a selectivity of 93.8 %. Besides, the influences about several important reaction parameters like time, temperature, solvent, H 2 pressure, and catalyst stability were also investigated based on monophenol yields and average molecular weight. Overall, the lignin components of Litsea cubeba fruit residues were identified and transformed into high functional phenolic chemicals in this work.