Liquefying Lignins: Determining Phase-Transition Temperatures in the Presence of Aqueous Organic Solvents

Under appropriate conditions of temperature and solvent composition, single-phase aqueous organic solvents are capable of liquefying lignin to form a lignin-rich liquid phase separate from the solvent phase, creating liquid-liquid equilibrium. The extent to which this phenomenon occurs when Kraft lignin is combined with the solvents methanol, ethanol, isopropanol, and acetone was determined, with solid-liquid (SL) to liquid-liquid (LL) phase-transition temperatures being measured over the range of applicable organic-water compositions. Lignins tested from a variety of biomass sources were all discovered to form this liquid-liquid equilibrium with aqueous ethanol solutions. The formation of such phase behavior between lignin and economical, green solvents creates new opportunities for the large-scale purification and fractionation of raw bulk (i.e., technical) lignins.

Automated summary

Under specific conditions, aqueous organic solvents can dissolve lignin to form a liquid phase separate from the solvent, creating liquid-liquid equilibrium. The formation of liquid-liquid equilibrium with alcohol solutions offers new opportunities for large-scale purification of raw lignins.