Ionic liquid pretreatment of lignocellulosic biomass with ionic liquid–water mixtures

Abstract

Ground lignocellulosic biomass (Miscanthus giganteus, pine (Pinus sylvestris) and willow (Salix viminalis)) was pretreated with ionic liquid-water mixtures of 1-butyl-3-methylimidazolium methyl sulfate and 1-butyl-3-methylimidazolium hydrogen sulfate. A solid fraction enriched in cellulose was recovered, which was subjected to enzymatic hydrolysis. Up to 90% of the glucose and 25% of the hemicellulose contained in the original biomass were released by the combined ionic liquid pretreatment and the enzymatic hydrolysis. After the pretreatment, the ionic liquid liquor contained the majority of the lignin and the hemicellulose. The lignin portion was partially precipitated from the liquor upon dilution with water. The amount of hemicellulose monomers in the ionic liquid liquor and their conversion into furfurals was also examined. The performance of ionic liquid-water mixtures containing 1,3-dialkylimidazolium ionic liquids with acetate, methanesulfonate, trifluoromethanesulfonate and chloride anions was investigated. The applicability of the ionic liquid 1-butylimidazolium hydrogensulfate for lignocellulose pretreatment was also examined. It was found that ionic liquid liquors containing methyl sulfate, hydrogen sulfate and methanesulfonate anions were most effective in terms of lignin/cellulose fractionation and enhancement of cellulose digestibility.

Characterization of Bamboo after Ionic Liquid-H2O Pretreatment for the Pyrolysis Process

“…In some chemical treatments of lignocellulose, chemical changes were evident in both hemicellulose and lignin, while the cellulose were retained in the pretreated samples. Differences in reactivity, depending on the anion, were observed (Brandt et al 2011;Brandt et al 2013). In the present study, in which ILs having the same cations were used, the lignin content was decreased significantly after pretreatment.…”

“…Most studies report reduced lignin and hemicellulose content in pretreated biomass, while the glucan fraction, which is mainly cellulose, is usually almost completely recovered. The effect of pH value (Zhang et al 2013), particle sizes (Bahcegul et al 2012;Hou et al 2013), water content, pretreatment time, and other influencing factors (Brandt et al 2011) have been investigated in grasses, hardwood, and softwood. The impact of ILs treatment on the composition of treated biomass was investigated in several studies (Fu et al 2010(Fu et al , 2011).…”

Design of low-cost ionic liquids for lignocellulosic biomass pretreatment

“…An increase in crystallinity index is often indicative of hemicellulose and/or lignin removal and hydrogen sulfate ionic liquids have been shown to be effective delignification agents in other studies. 3,15 Hence we investigated the composition of the recovered solid in more detail.…”

“…[1][2][3] Ionic liquids (ILs) have proven to be promising pretreatment solvents. 4,5 [C 2 C 1 im][OAc], also known as [Emim][Ac], is one of the most intensively studied candidates for use in cellulosic bio-refineries.…”

Manufacture of furfural in biphasic media made up of an ionic liquid and a co-solvent

“…In the past few years, growing attention has been paid to the utilization of acidic ionic liquids (AILs) owing to their ability to act as both a reaction media and a catalyst (Brandt et al, 2011). It can be noted that AILs utilization allows simpler operational schemes, since no stages of catalyst recovery have to be implemented, and other possible issues related to the catalysts (for example, environmental hazards) are avoided.…”