Effect of deep eutectic solvents-regulated lignin structure on subsequent pyrolysis products selectivity

Area of Science:

• Biomass Conversion
• Chemical Engineering
• Materials Science

Background:

• Lignin structure significantly impacts pyrolysis product distribution.
• Controlling lignin pyrolysis selectivity is crucial for efficient biomass valorization.
• Deep eutectic solvents (DESs) offer a tunable medium for biomass modification.

Purpose of the Study:

• To investigate the effect of DESs on softwood kraft lignin (SKL) structure and pyrolysis behavior.
• To explore the potential of DESs in enhancing bio-oil yield and altering pyrolysis product distribution.
• To understand how DESs modify lignin's chemical structure and thermal properties.

Main Methods:

• Treatment of softwood kraft lignin (SKL) with various DESs: choline chloride/ethylene glycol (CE), zinc chloride/ethylene glycol (ZE), and choline chloride/acetic acid.
• Systematic characterization of treated lignin using techniques to assess chemical structure, molecular weight, and thermal stability.
• Analysis of lignin pyrolysis products to determine product distribution, bio-oil yield, and char content.

Main Results:

• DES treatments increased the hydrogen-to-carbon ratio, reduced molecular weight, and decreased β-O-4 linkages in SKL.
• CE and ZE treatments specifically enhanced the yield of H-phenols and C-phenols, respectively.
• DES pretreatment increased monomer aromatic hydrocarbons and improved bio-oil yield while reducing char content.

Conclusions:

• DESs are effective agents for modifying lignin structure, improving its pyrolysis efficiency.
• CE and ZE treatments show distinct advantages in producing specific phenolic compounds from lignin pyrolysis.
• DES pretreatment presents a viable strategy for enhancing bio-oil production and reducing char formation in lignin valorization.