Ultraclean hybrid poplar lignins via liquid-liquid fractionation using ethanol-water solutions

As recovered from the byproducts stream of a cellulosic ethanol biorefinery, the renewable biopolymer lignin is too impure and polydisperse for many proposed applications. By mixing a hybrid poplar lignin with hot ethanol-water solutions, two liquid phases, one polymer-rich and one solvent-rich, are created. This liquid-liquid equilibrium phenomenon was used to generate solvated (and thus liquefied) lignin fractions of controlled molecular weight for which the impurities analyses for sugars and ash were near or below the limits of detection. Additionally, those carbohydrates and metals impurities end up highly concentrated in a single process stream also having potential value. Graphic abstract

Automated summary

By mixing hybrid poplar lignin with hot ethanol-water solutions, controlled molecular weight liquefied lignin fractions can be obtained, effectively removing impurities and concentrating carbohydrates and metal impurities in a process stream with potential value.