Lignin Extraction and Condensation as a Function of Temperature, Residence Time, and Solvent System in Flow-through...

Area of Science:

• Biomass Conversion and Biorefining
• Sustainable Chemistry
• Chemical Engineering

Background:

• Solvolytic extraction is crucial for lignin-first biorefining, particularly in reductive catalytic fractionation (RCF).
• Efficient lignin extraction and transfer to catalyst surfaces are key to minimizing undesirable lignin condensation reactions.
• Understanding the interplay between process parameters and lignin chemistry is vital for optimizing RCF.

Purpose of the Study:

• To investigate the impact of temperature, residence time, and solvent composition on lignin extraction and condensation during solvolysis.
• To identify optimal conditions for maximizing delignification while minimizing lignin condensation in a flow-through reactor.
• To provide insights for designing reactors and selecting solvents for efficient lignin-first biorefining.

Main Methods:

• Utilized a flow-through reactor to study solvolytic extraction of lignin from biomass.
• Varied temperature (175-250 °C), residence time (9-36 min), and solvent composition (methanol, methanol-water).
• Assessed total delignification, delignification rate, and extent of condensation (via monomer yield in hydrogenolysis).

Main Results:

• Delignification is primarily influenced by temperature; condensation extent is dictated by residence time.
• Methanol-water solvent systems showed increased lignin extraction and condensation compared to pure methanol.
• Lignin stability was observed in methanol up to 18 min at ≤225 °C; significant condensation occurred in methanol-water at 9 min and 200 °C.

Conclusions:

• Temperature and residence time are critical, independent parameters controlling lignin extraction and condensation, respectively.
• Solvent choice significantly impacts both extraction efficiency and the degree of lignin condensation.
• Findings guide the selection of reactor designs and solvents to optimize lignin separation and minimize condensation in biorefining.