Optimization of softwood pretreatment by microwave-assisted deep eutectic solvents at high solids loading

Area of Science:

• Biomass Pretreatment
• Green Chemistry
• Lignocellulose Fractionation

Background:

• Deep eutectic solvents (DES) are emerging as efficient pretreatment agents for lignocellulose.
• Microwave-assisted DES pretreatment offers rapid and effective biomass fractionation.

Purpose of the Study:

• To optimize microwave-assisted deep eutectic solvent (DES) pretreatment using choline chloride:formic acid (ChCl:FA) for milled softwood mixture (MSM) fractionation.
• To achieve high glucan retention and purity in the residue while maximizing lignin and hemicellulose removal.

Main Methods:

• Fractionation of milled softwood mixture (MSM) using choline chloride:formic acid (ChCl:FA) deep eutectic solvent.
• Application of microwave irradiation to accelerate the pretreatment process.
• Optimization of key parameters including ChCl:FA ratio, temperature, time, microwave power, and solid loading.

Main Results:

• Optimal conditions (ChCl:FA 1:4, 140°C, 14 min, 800 W, 15% solid loading) yielded 96.2% hemicellulose removal, 90.1% delignification, and 93.5% glucan retention.
• Approximately 85% of lignin was recovered with 95% purity at 10-20% solid loading.
• High solid loading was demonstrated to be feasible for efficient fractionation.

Conclusions:

• Microwave-assisted ChCl:FA pretreatment is a highly effective and rapid method for lignocellulose fractionation.
• This approach enables the recovery of high-purity glucan-rich residues and valuable lignin.
• The optimized method shows significant potential for industrial applications in biomass valorization.