Cellulose amorphization by swelling in ionic liquid/water mixtures: a combined macroscopic and second-harmonic...

Area of Science:

• Biomass Pretreatment
• Green Chemistry
• Materials Science

Background:

• Cellulose pretreatment is crucial for efficient enzymatic digestion.
• Traditional dissolution-precipitation methods require energy-intensive steps and ionic liquid (IL) purification.
• Developing cost-effective and environmentally friendly pretreatment methods is essential for biomass valorization.

Purpose of the Study:

• To investigate the amorphization of cellulose via swelling in ionic liquid/water mixtures at room temperature.
• To evaluate this swelling method as an alternative to dissolution-precipitation for enzymatic digestion.
• To monitor the changes in cellulose crystallinity in situ using second-harmonic generation (SHG) microscopy.

Main Methods:

• Soaking microcrystalline cellulose in 1-ethyl-3-methylimidazolium acetate with 20 wt% water.
• Utilizing second-harmonic generation (SHG) microscopy for in situ monitoring of cellulose crystallinity.
• Comparing results with cellulose treated in pure ionic liquid and optical microscopy observations.

Main Results:

• Swelling cellulose in IL/water mixtures significantly reduced its crystallinity.
• Less than 4% of cellulose dissolved in the optimal IL/water mixture, eliminating the need for precipitation.
• Pure IL treatment resulted in complete cellulose dissolution, while the IL/water mixture yielded solid cellulose with reduced crystallinity.

Conclusions:

• Cellulose amorphization by swelling in IL/water mixtures is an effective pretreatment method.
• This swelling approach simplifies the pretreatment process by avoiding dissolution and purification steps.
• SHG microscopy is a valuable tool for monitoring structural changes in cellulose during pretreatment.