Simultaneous Lignin Fractionation and Functionalization under Mild Conditions via Reactive Extraction

Area of Science:

• Biomass valorization and sustainable chemistry.
• Lignin chemistry and processing.
• Green chemistry and biorefining.

Background:

• Lignin valorization is crucial for biorefineries.
• Current methods often require harsh conditions.
• Reactive extraction (REx) offers a mild alternative.

Purpose of the Study:

• To investigate reactive extraction (REx) for simultaneous lignin fractionation and functionalization.
• To evaluate acetic acid, formic acid, and ethanol as solvent-reagents.
• To assess the use of Amberlyst 15 as a catalyst for REx.

Main Methods:

• Hydrothermally treated wood solids were refluxed with acetic acid, formic acid, or ethanol.
• Amberlyst 15 was tested as a heterogeneous acid catalyst.
• Product losses were minimized through optimized reaction setup.
• Lignin and cellulosic solids were characterized using NMR and molar mass analysis.

Main Results:

• Extracted lignins retained native linkages (28.8-46.4/100 Ar) and had molar masses of 2.8-13.7 kDa.
• Incorporation of ethoxy, acetyl, and formyl groups was confirmed by HSQC NMR.
• Residual cellulosic solids showed functionalization and reduced molar masses (DPw 2900-1000).

Conclusions:

• Reactive extraction is effective for mild lignin fractionation and functionalization.
• The process allows for the upgrade of both lignin and cellulosic fractions.
• This method presents a promising approach for sustainable biomass utilization.