Abstract
We report on the pretreatment of poplar wood with three different 1-ethyl-3-methylimidazolium ionic liquids, [EMim][OAc], [EMim][MeSO3], and [EMim][HSO4], at varying water contents from 0–40 wt% at 100 °C. The performance was evaluated by observing the lignin and hemicellulose removal, as well as enzymatic saccharification and lignin yield. The mechanism of pretreatment varied between the ionic liquids studied, with the hydrogen sulfate ionic liquid performing delignification and hemicellulose hydrolysis more effectively than the other solvents across the investigated water content range. The acetate ionic liquid produced superior glucose yield at low water contents, while the hydrogen sulfate ionic liquid performed better at higher water contents and produced a recoverable lignin. The methanesulfonate ionic liquid did not introduce significant fractionation or enhancement of saccharification yield under the conditions used. These findings help distinguish the roles of anion hydrogen bonding, solvent acidity, and water content on ionic liquid pretreatment and can aid with anion and water content selections for different applications.
Highlights
Glucose is a key substrate in biorefining, as it is readily fermented by a wide range of microbes into products, such as ethanol [1,2], butanol, sorbitol [3], and lactic acid [4]
This study shows that both the ionic liquid anion and water contents together have key influences on enabling the enzymatic saccharification and lignin isolation after pretreatment with dialkylated imidazolium ionic liquids
Our results indicate that dissolving ionic liquids such as [EMim][OAc] are active at lower temperatures than fractionating ILs
Summary
Glucose is a key substrate in biorefining, as it is readily fermented by a wide range of microbes into products, such as ethanol [1,2], butanol, sorbitol [3], and lactic acid [4]. Cellulose depolymerisation to glucose is possible using enzymes [5,6,7,8]; the enzymes can only access the cellulose contained in woody biomass after a pretreatment step. Cellulose-dissolving ILs have been found to be very effective in enabling fast and high-yielding sugar release from the pretreated material [12,13,14,15,16]. This has attracted a lot of interest in the research community, and a number of patents have been filed—for example, by Balensiefer et al as one of the first ones, with a priority date of 2008 [17]. During dissolving IL pretreatment, woody biomass is dissolved or substantially swollen, and a regenerated pulp produced upon addition of an antisolvent
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