Problem Statement and Objectives:
With growing demand for sustainable resources and reduced reliance on fossil fuels, the development of efficient biorefineries to convert lignocellulosic biomass, such as sugarcane bagasse, has become crucial. The main challenge lies in the selective separation of cellulose, hemicelluloses and lignin with minimal degradation. Conventional lignin degradation processes often require injecting external hydrogen (H₂) at high pressure, which adds significant complexity, risk, and operational costs. This study aims to introduce and evaluate a greener, safer catalytic fractionation strategy that does not require external hydrogen. This approach uses a ruthenium-based carbon catalyst (Ru/C) and formic acid as a hydrogen donor, focusing on comparing the effects of two renewable polyol solvents, glycerol and 1,4-butanediol, under identical operating conditions.


Materials and Methods:

The feedstock used was sugarcane bagasse with a known initial composition. The process was conducted in a batch stainless-steel reactor. In each experiment, defined amounts of bagasse, Ru/C catalyst, formic acid, and a solution containing one of the polyol solvents and water were mixed in the reactor. The mixture was stirred and heated to 200°C, where it was maintained for 5 hours. After the reaction, the reactor content was cooled, and the solid phase (cellulosic pulp) was separated from the liquid phase by filtration. The chemical composition of the pulp (cellulose, hemicelluloses, and lignin contents) was determined using the standard method of the U.S. National Renewable Energy Laboratory (NREL) and high-performance liquid chromatography (HPLC). The lignin oil was extracted from the liquid phase using dichloromethane, concentrated, and its components were identified and quantified by gas chromatography-mass spectrometry (GC-MS). Key performance indicators, including solid mass recovery, lignin removal percentage, hemicellulose removal, cellulose preservation, and yield of phenolic monomers, were calculated.

Results:
The results clearly showed that the choice of solvent completely controls the process selectivity. The 1,4-butanediol system achieved balanced performance through synergistic interaction with the catalytic system. This system resulted in 37.78% lignin removal and 76.10% hemicellulose removal, while preserving 63.8% of the initial cellulose. The produced pulp had a cellulose purity of approximately 70%. Furthermore, the overall yield of phenolic monomers in this system was significantly higher, with the product distribution primarily consisting of short-chain monomers such as guaiacol. In contrast, the glycerol system exhibited a completely different performance pattern. This system removed hemicelluloses exceptionally (91.92%) but showed only minimal lignin removal (3.28%). The formation of longer-chain monomers was prominent in this system. The data suggest that glycerol, due to its high viscosity and polarity, likely limited the catalyst’s penetration into the lignin structure, thus making hemicellulose hydrolysis the dominant pathway.

Conclusion:
This study empirically demonstrated that reaction environment engineering through the intelligent selection of solvents is a powerful tool for steering the selectivity of catalytic fractionation processes. 1,4-butanediol, as a solvent that enhances synergy, is recommended to achieve both high-quality cellulosic pulp and lignin oil rich in monomers in a single integrated process. The success of this process, which requires no external H₂ source and uses a liquid hydrogen donor system (formic acid + Ru/C), represents an important step toward developing safer, more practical, and sustainable biorefinery processes.