Biomass fractionation through an ionic liquid process

An efficient biomass fractionation process is crucial to produce biofuels and bio-based products from lignocellulosic feedstock. Ionic liquids (ILs) have been investigated and developed as a media to pretreat and/or fractionate lignocellulosic biomass for generating high purity cellulose, hemicellulose or lignin fraction.  Although various IL processes have been designed regarding this purpose, one major goal of these processes to be yet achieved is to produce high yield and purity of both, lignin and hemicellulose fractions. The value-added derived products from lignin and hemicellulose would improve the economic viability and sustainability of biorefineries. In this study, a fractionation process with 1-ethyl-3-methylimidazolium acetate ([C₂mim][OAc]) was designed to fractionate lignocellulosic biomass to high purity fractions with minor degradation and modification. First, approximately 50% of hemicellulose was extracted by autohydrolysis at 160 ^oC for 60 min with minor degradation of lignin and cellulose. The hemicellulose-extracted biomass was then treated with [C₂mim][OAc] at 60 ^oC for 3 h followed by an enzymatic saccharification to hydrolyze the carbohydrate fraction into monosugars and generate a lignin-rich fraction. The enzymatic saccharification kinetic data revealed that a combination of both, autohydrolysis and IL treatment, significantly reduced the recalcitrance of the IL-regenerated hemicellulose-extracted biomass making it more susceptible to enzymatic hydrolysis than the untreated biomass or each treatment separately. Quantitative analyses showed that the fractionation process was able to isolate 87% of the cellulose and 81% of the hemicellulose in a monosugars form, and 70% of the lignin with a purity of 90%.