Transforming lignocellulosic biomass into biofuels enabled by ionic liquid pretreatment

Processes that can convert lignocellulosic biomass into biofuels and chemicals are particularly attractive considering renewability and minimal environmental impact. Ionic liquids (ILs) have been used as novel solvents in the process development in that they can effectively deconstruct recalcitrant lignocellulosic biomass for high sugar yield and lignin recovery. From cellulose-dissolving ILs to choline-based and protic acidic ILs, extensive research in this field has been done, driven by the promising future of IL pretreatment. Meanwhile, shortcomings and technological hurdles are ascertained during research and developments. It is necessary to present a general overview of recent developments and challenges in this field. In this review paper, three aspects of advances in IL pretreatment are critically analyzed: biocompatible ILs, protic acidic ILs and combinatory pretreatments.