Enhanced Lignin Recovery from Saccharum officinarum via Organosolv Fractionation with Using Low-Acid Catalyst...

We report the investigation of the organosolv fractionation of Saccharum officinarum for the simultaneous recovery of cellulose and lignin and compared commercially produced organosolv lignin (CPOL) with our extracted lignin (AEL). The effects of the catalyst concentration, and reaction temperature and reaction time on fractionation efficiency were systematically evaluated. Hydrochloric acid (HCl; concentration = 0.05%-0.15%) was used as a catalyst in the temperature range of 145 °C-185 °C for 1 h. The highest cellulose yield (86.2%) was obtained using 0.05% HCl at 145 °C, whereas increasing the acid concentration and temperature caused partial cellulose degradation. In contrast, maximum lignin recovery (82.4%) and lignin removal efficiency (84.1%) were achieved using 0.10% HCl at 165 °C. Extending the reaction time to 1.5 h further improved lignin recovery, although an extended duration caused lignin degradation. Pyrolysis-gas chromatography-mass spectrometry analysis revealed the relative abundance of syringyl (S), guaiacyl (G), and p-hydroxyphenyl (H) units in CPOL (49.8%) and AEL (48.2%). S was dominant in both samples, with S/G/H ratios of 1.33 for CPOL and 1.28 for AEL, indicating comparable structural characteristics with a slightly higher S content in CPOL. The crystallinity index of cellulose increased from 54.6% in the untreated sample to 61.8% after acid-catalyzed fractionation, suggesting effective removal of amorphous components. These findings demonstrated that less-acid organosolv fractionation enabled efficient lignin recovery while preserving cellulose integrity. The direct comparison between CPOL and AEL provided insight into the structural consistency of lignin obtained from different sources, supporting the potential of this approach for sustainable biomass valorization.