Evaluation of biomass-derived solvents and protic ionic liquids as lignin-selective pretreatment agents for poplar fractionation

In this study, mixtures of protic ionic liquids (PILs) and biomass derived solvents; gamma-valerolactone (GVL), levulinic acid (LA) and H2O at different weight percentages were used to pretreat poplar. GVL addition up to 60% enhanced delignification in biomass that is subjected to MEAHSO(4)-GVL-H2O; cellulose content of the biomass increased from 42% to 74% with 67% lignin removal. Aqueous solution of LA used for the first time to pretreat a biomass performed better than TEAHSO(4)-H2O. LA-H2O at 80%-20% resulted in 70% lignin extraction and preserved 89% of the cellulose in the structure which were also verified with SEM, FTIR and XRD analysis displaying clear cellulose macrofibers, lignin signals with lower intensities and higher biomass crystallinity, respectively. Accordingly, enzymatic conversion of LA pretreated poplar released 43 g/L glucose at 10% substrate loading. Findings showed the potentials of biomass derived solvents, GVL and LA and PILs and their aqueous mixtures to selectively deconstruct poplar.