Structural changes and grading mechanism of lignin during solid alkali-active oxygen extraction and grading

Area of Science:

• Biomass valorization and lignin chemistry.

Background:

• Biomass pretreatment is crucial for efficient component separation.
• Lignin yellow liquor requires effective grading for high-value applications.
• Existing methods may not fully preserve biomass integrity.

Purpose of the Study:

• To develop an efficient method for grading lignin fractions from biomass.
• To recover solid alkali and characterize separated lignin components.
• To assess the impact of the CAOSA process on lignin and carbohydrate stability.

Main Methods:

• Simultaneous acid-alkali graded separation applied to lignin yellow liquor.
• Cooking with Active Oxygen and Solid Alkali (CAOSA) pretreatment.
• Characterization of lignin fractions by dispersion coefficients, functional groups (Phenol hydroxyl group, Methoxy, β-aryl ether), and thermal properties.

Main Results:

• Achieved 67.25% solid alkali recovery.
• Lignin fractions exhibited smaller dispersion coefficients and enhanced stability.
• Low molecular weight lignin (L4) showed high Phenol hydroxyl group content (2.1 mmol/g) and antioxidant properties.
• CAOSA process prevented lignin condensation and protected carbohydrates from degradation.

Conclusions:

• The combined CAOSA and acid-alkali grading method offers efficient biomass component separation and lignin grading.
• This process preserves carbohydrate integrity, facilitating subsequent utilization.
• The study provides a theoretical basis for the high-value utilization of biomass and lignin.