Ionic Liquids for Lignin Processing: Dissolution, Isolation, and Conversion

Abstract

We present a review on the multifunctional use of ionic liquids with respect to lignin processing. In a biorefinery context, lignocellulosics could be used to provide sustainable sources of fuels such as bioethanol, and feedstock molecules for the chemical industry such as phenols and other aromatics. However, separation of lignin from cellulose and hemicellulose is a vital step. Ionic liquids can dissolve extensive quantities of biomass, and even be designed to be multifunctional solvents. We highlight the use of ionic liquids in selectively or non-selectively dissolving lignin, the depolymerization reactions that have been attempted on lignin in ionic liquids, and the effect ionic liquids have been observed to have on such processes. Finally, we present some of the challenges and issues that must be addressed before the informed and large-scale application of ionic liquids can be realized for lignin processing.

Enhanced Cellulase Production by a Novel Thermophilic Bacillus licheniformis 2D55: Characterization and Application in Lignocellulosic Saccharification

“…Lignocellulosic materials are one of the most abundant renewable sources of biomass, and they are composed mainly of cellulose, hemicellulose, and lignin (Hossain and Aldous 2012). Global production of agro-waste and its by-products amounts to about 180 billion tons per year (Kim et al 2006).…”

Novel and Efficient Diethylene Glycol/H2O Solvent for Lignin Dissolution

“…Lignin is composed of three types of monolignols including coniferyl alcohol, paracoumaryl alcohol, and sinapyl alcohol. The relative ratios of each of these monolignols depend on the origin of the biomass, and it is also the only native biopolymer on the earth that contains aromatic phenolpropanoid monomers (Metzger et al 1992;Pu et al 2007;Hossain and Aldous 2012). With the increasing depletion of petroleum resources, rising environmental awareness, and health concerns, the exploitation of low-cost and biorenewable bioresources such as lignin have received great attention (Graca et al 2012;Rozite et al 2013).…”

“…Lignin is one of three main components (cellulose, hemicellulose, and lignin) of lignocellulosic biomass, and it protects cellulose and hemicellulose by providing hydrophobicity, mechanical strength, and indigestibility to plant cell walls (Ragauskas et al 2006;King et al 2009;Kim et al 2011;Hossain and Aldous 2012). Lignin is composed of three types of monolignols including coniferyl alcohol, paracoumaryl alcohol, and sinapyl alcohol.…”

5th Australasian Symposium on Ionic Liquids

“…[6] The potential use of ILs for energy-based applications has also attracted considerable attention in the field of biomassderived energy, as reviewed by Hossain and Aldous. [7] In particular, the ability to tailor the physical properties of ILs through adjusting the cation and anion structure, and the possibility of thus being able to control different aspects of the processing of lignin, is particularly attractive. [7] In this special issue, Amano and coworkers [8] report preparation of regenerated celluloses prepared from microcrystalline cellulose by treatment with four different ILs, and the effect of the IL on the crystallinity of the regenerated cellulose.…”

“…[7] In particular, the ability to tailor the physical properties of ILs through adjusting the cation and anion structure, and the possibility of thus being able to control different aspects of the processing of lignin, is particularly attractive. [7] In this special issue, Amano and coworkers [8] report preparation of regenerated celluloses prepared from microcrystalline cellulose by treatment with four different ILs, and the effect of the IL on the crystallinity of the regenerated cellulose. Kondo and coworkers [9] demonstrate the preparation of bacterial cellulose membranes containing an IL, and the properties of the resulting membranes for the separation of organic nitrogen compounds.…”