Opportunities of Ionic Liquids for Lignin Utilization from Biorefinery

Abstract

The development of economically viable biorefineries for the transformation of lignocellulose into sustainable biofuels, chemicals and materials requires effective valorization of lignin. The high solubility of lignocelluloses and lignin in ionic liquids has created new probabilities, which renders the essential significance of understanding the cell structure of biomass, isolation of lignin from biomass (IL-lignin), elucidation of the chemical structure of wood and lignin, and valorization of IL-lignin. In this review, we first give an overview of lignin chemistry, and then describe the current development of structural elucidation of lignin with IL-mediations, extraction fractionation and its catalytic conversion. This review also highlight the relationship between the research challenges, lignin utilization and the properties of ILs, on which a brief conclusion and perspectives are drawn.

The Role of Ionic Liquids in the Lignin Separation from Lignocellulosic Biomass

“…Lignin has the potential substrate for the production of valuable chemicals to use in different applications. However, deeper understanding of lignin as a substrate, its fractionation and subsequent valorization is still an inevitable challenge when it comes to establishing efficient and cost-competitive biorefineries [34].…”

“…Several studies have presented that different solvents like ethylene glycol, DMSO [80], ILs [81], g-valerolactone [34] and Tween-80/H 2 O are able to dissolve up to 70 wt% lignin [82]. Among these solvents, ILs have acquired especial levels of interest due to their particular chemo-physical properties when compared to traditional molecular solvents.…”

“…Different strategies can be applied during or after IL-aided fractionation in order to produce fuels, chemicals, and materials. These include the extraction of lignin from lignocelluloses, catalytic delignification to acquire separated lignin components from biomass, and the saccharification of polysaccharides that are attached to lignin fragments [34]. Delignification causes disruption of lignin structure, resulting in biomass swelling, which is not feasible in a sense of native lignin.…”

“…The anionic part of the solvent breaks down the intramolecular hydrogen bonding network in LC, thereby making possible the dissolution of the lignin [32]. According to Varanasi et al the order of efficiency in terms of reducing the lignin molecular weight of specific anions is as follows: sulphates > lactates > acetates > chlorides > phosphates [34]. Pyridinium and pyrrolidinium cations are relatively cheaper than conventional ILs.…”

From Current Science to School – the Facets of Green Chemistry on the Example of Ionic Liquids

“…A reason for the absence of lignin utilization is its insolubility in many solvents. With ILs as powerful, inert and recoverable solvents for lignin, novel strategies for the usage of the aromatic biopolymer are discussed in the scientific community [33]. These approaches utilize either cracking into useable chemicals by different methods, to have a fossil-fuel independent, large-scale source for aromatic molecules or the incorporation into biodegradable polymers.…”