Optimizing lignin demethylation using a novel proton- based ionic liquid: 1, 2-propanediamine/glycolic acid catalyst.

Area of Science:

• Biomass Conversion and Valorization
• Green Chemistry
• Catalysis

Background:

• Lignin's high-value conversion is hindered by its recalcitrant structure.
• Demethylation is a key strategy to modify lignin's properties.
• Developing efficient and sustainable demethylation methods is crucial.

Purpose of the Study:

• To investigate a new proton-based ionic liquid (PIL), 1,2-propanediamine/glycolic acid (PD/GA), as a catalyst and solvent for targeted lignin oxidation.
• To optimize the demethylation process by modulating reaction parameters.
• To evaluate the physicochemical properties and performance of the modified lignin.

Main Methods:

• Utilized PD/GA as a dual-function catalyst and solvent for lignin demethylation.
• Optimized reaction conditions including acid-base molar ratio, temperature, and time.
• Characterized the treated lignin using Brunauer-Emmett-Teller (BET) surface area analysis and other techniques.
• Assessed the ultraviolet (UV) resistance and antioxidant activity of the modified lignin.

Main Results:

• PD/GA demonstrated higher selectivity and efficiency in lignin demethylation compared to conventional methods (e.g., ethanolamine/acetic acid).
• Optimal conditions (molar ratio 1.25, 60°C, 3h) significantly increased phenolic hydroxyl (PH)-content from 37.74% to 59.91%.
• PD/GA-treated lignin exhibited enhanced properties, including increased BET surface area (1.45 m²/g), pore volume (9.51*10⁻³ cm³/g), and mesoporous size (26.15 nm).
• The treated lignin showed maximum UV resistance and antioxidant activity.

Conclusions:

• PD/GA is a highly effective and recyclable system for green lignin demethylation.
• The enhanced lignin properties open avenues for its high-value applications.
• This approach offers a sustainable pathway for lignin valorization.