Pretreatment and Fractionation of Wheat Straw Using Various Ionic Liquids

Abstract

Pretreatment of lignocellulosic biomass with ionic liquids (ILs) is a promising and challenging process for an alternative method of biomass processing. The present work emphasizes the examination of wheat straw pretreatment using ILs, namely, 1-butyl-3-methylimidazolium hydrogensulfate ([bmim][HSO4]), 1-butyl-3-methylimidazolium thiocyanate ([bmim][SCN]), and 1-butyl-3-methylimidazolium dicyanamide ([bmim][N(CN)2]). Only [bmim][HSO4] was found to achieve a macroscopic complete dissolution of wheat straw during pretreatment. The fractionation process demonstrated to be dependent on the IL used. Using [bmim][SCN], a high-purity lignin-rich material was obtained. In contrast, [bmim][N(CN)2] was a good solvent to produce high-purity carbohydrate-rich fractions. When [bmim][HSO4] was used, a different behavior was observed, exhibiting similarities to an acid hydrolysis pretreatment, and no hemicellulose-rich material was recovered during fractionation. A capillary electrophoresis (CE) technique allowed for a better understanding of this phenomenon. Hydrolysis of carbohydrates was confirmed, although an extended degradation of monosaccharides to furfural and hydroxymethylfurfural (HMF) was observed.

Relevance of the acidic 1-butyl-3-methylimidazolium hydrogen sulphate ionic liquid in the selective catalysis of the biomass hemicellulose fraction

“…[6][7][8][9][10][11][12][13][14][15][16][17][18][19]40 Recently, the ILs containing [HSO 4 ] anion became an appealing option to be used in the biomass pre-treatment, and the acidic properties of this IL allows for the catalytic conversion of biomass. [6][7][8][9][10][11][12][13][14][15][16][17][18][19]40 Recently, the ILs containing [HSO 4 ] anion became an appealing option to be used in the biomass pre-treatment, and the acidic properties of this IL allows for the catalytic conversion of biomass.…”

“…4 However, to achieve this goal various challenges must be addressed. 5 One of the approaches is the use of more sustainable solvents such as ionic liquids [6][7][8][9][10][11][12][13][14][15][16][17][18][19] and supercritical uids. In addition, the choice of pre-treatment should consider the overall compatibility of feedstocks, enzymes and organisms to be applied, overall economic assessment and environmental impact.…”

“…17 Thus, the pre-treatment of biomass with ILs offers advantages over conventional methods allowing the alteration of physicochemical properties of the biomass macromolecular components, such as reduction of the cellulose crystallinity, extraction of specic macromolecules such as lignin and hemicellulose and execution of different fractionation approaches aer biomass dissolution in ILs. 18,45 Furthermore, [HSO 4 ]-based ILs have been procured increasingly not only because of their acidic properties, but also due to their low cost when compared to other ILs. Acidic ILs can behave as both solvents and catalysts because they combine the advantages of mineral acid and IL.…”

Pre-treatment and extraction techniques for recovery of added value compounds from wastes throughout the agri-food chain

“…297 An example is lignocellulosic biomass processing with ILs that allows for the efficient fractionation into main components, such cellulose, hemicellulose, lignin and phenolic compounds. [298][299][300][301][302][303][304] Besides the ability of ILs to dissolve and pre-treat, the solvent power and high selectivity of ILs also allows for the extraction of specific targeted biomolecules from biomass, as demonstrated in literature. 305 In fact, the heterogeneity of food waste generally leads to the disadvantage of adopting multi-step fractionation strategies to obtain target compounds.…”

Loblolly pine pretreatment by ionic liquid-glycerol mixtures

“…In addition, the peak at 1734 cm −1 decreases with increasing [C2mim][O2CH] concentration. Da Costa Lopes et al [60] have suggested that this peak should be assigned to esterlinked acetyl, feruloyl and p-coumaroyl groups between hemicelluloses and lignin. The peak at 1457 cm −1 (lignin and xylan) similarly decreases with increasing [C2mim][O2CH] concentration [54,59,61].…”