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Structural purification of technical lignins via fractional dissolution using non-azeotropic solvent mixtures
Reza Ebrahimi Majdar1, Federica Ferruti2, Marco Orlandi2,3
1University of Rome 'Tor Vergata', Department of Chemical Science and Technologies, Via della Ricerca Scientifica, 1, 00133 Rome, Italy. heiko.lange@unimib.it.
Novel fractionation of softwood kraft lignin (SKL) and wheat straw organosolv lignin (WSOSL) using tunable solvent mixtures yielded unique lignin fractions. This advanced Soxhlet extraction method enabled the isolation of distinct lignin carbohydrate complex (LCC) and high molecular weight lignin fractions.
Area of Science:
- Biomass Valorization
- Green Chemistry
- Polymer Science
Background:
- Technical lignins like softwood kraft lignin (SKL) and wheat straw organosolv lignin (WSOSL) are abundant biopolymers.
- Current fractionation methods often limit the diversity and purity of obtainable lignin fractions.
- Developing advanced fractionation techniques is crucial for unlocking the full potential of lignin in various applications.
Purpose of the Study:
- To develop an advanced Soxhlet extraction method for fractionating technical lignins.
- To explore the use of non-azeotropic solvent mixtures for enhanced lignin separation.
- To obtain novel lignin fractions with distinct structural and molecular characteristics.
Main Methods:
- Utilized a modified Soxhlet extractor with a piston pump for controlled solvent movement.
- Employed non-azeotropic solvent mixtures with tunable hydrogen-bond acceptor/donor characteristics and polarities.
- Fractionated softwood kraft lignin (SKL) and wheat straw organosolv lignin (WSOSL).
Main Results:
- Successfully obtained two SKL fractions with homogeneous structures but differing molecular weights using aqueous acetone.
- Achieved gradual purification of WSOSL, yielding a pure lignin carbohydrate complex (LCC) fraction.
- Isolated a purified high molecular weight lignin fraction from WSOSL.
Conclusions:
- The developed method allows for the fractionation of technical lignins into novel fractions not accessible by standard techniques.
- Tunable solvent mixtures offer precise control over lignin fractionation based on polarity and hydrogen bonding.
- This approach enhances the ability to isolate specific lignin-based materials, such as LCCs and high molecular weight fractions, for targeted applications.
