Comparison study and mechanisms insight of AlCl-catalyzed different organosolv pretreatment of lignocellulose: Enhancing enzymatic hydrolysis, lignin fractionation, and furfural production.

Organosolv pretreatment has emerged as a highly effective strategy for deconstructing lignocellulose compactness, enabling enhanced enzymatic hydrolysis and facilitating the downstream production of valuable biochemicals. This study systematically investigates the effects of AlCl-catalyzed organosolv pretreatment using ethanol, ethylene glycol, and 1,4-butanediol (1,4-BDO) on LCB's fractionation efficiency, enzymatic hydrolysis, lignin structural alteration, and furfural production. Results showed that the AlCl/1,4-BDO system with stronger solvation achieved superior delignification (81.7 %), hemicellulose removal (93.0 %), and cellulose retention (90.3 %) at 120 °C, outperforming the other two systems. Theoretical calculations revealed that AlCl/1,4-BDO exhibited higher total energy density for lignin-carbohydrate complexes (-8692.4 kcal/mol) and more stable hydrogen bonds, facilitating solvent-biomass interactions and promoting efficient component fractionation. Lignin structural characterization verified that organic solvents can graft and stabilize reactive intermediates, obtain a high purity, and preserve β-O-4 linkages, especially in the AlCl/1,4-BDO system yielding lignin enriched with more aliphatic and phenolic hydroxyl groups. Furthermore, due to the enhanced substrate's pore enlargement and increased surface area in AlCl/1,4-BDO pretreatment, the pretreated substrates achieved the highest glucose yield after enzymolysis. Additionally, the AlCl/1,4-BDO system achieved a great furfural yield, attributed to selective adsorption/desorption and its lowest total energy (-9969.6 kcal/mol) with minimal torsion energy (-1.6 kcal/mol), reflecting its stability and reduced side reactions during conversion. The combined experimental and simulation-based approach provides valuable mechanistic insights and offers a theoretical foundation for enhancing the efficiency of organosolv pretreatment in lignocellulose biorefinery applications.