Abstract
BackgroundBiomass pretreatment using certain ionic liquids (ILs) is very efficient, generally producing a substrate that is amenable to saccharification with fermentable sugar yields approaching theoretical limits. Although promising, several challenges must be addressed before an IL pretreatment technology can become commercially viable. One of the most significant challenges is the affordable and scalable recovery and recycle of the IL itself. Pervaporation (PV) is a highly selective and scalable membrane separation process for quantitatively recovering volatile solutes or solvents directly from non-volatile solvents that could prove more versatile for IL dehydration.ResultsWe evaluated a commercially available PV system for IL dehydration and recycling as part of an integrated IL pretreatment process using 1-ethyl-3-methylimidazolium acetate ([C2C1Im][OAc]) that has been proven to be very effective as a biomass pretreatment solvent. Separation factors as high as 1500 were observed. We demonstrate that >99.9 wt% [C2C1Im][OAc] can be recovered from aqueous solution (≤20 wt% IL) and recycled five times. A preliminary technoeconomic analysis validated the promising role of PV in improving overall biorefinery process economics, especially in the case where other IL recovery technologies might lead to significant losses.ConclusionsThese findings establish the foundation for further development of PV as an effective method of recovering and recycling ILs using a commercially viable process technology.
Highlights
Biomass pretreatment using certain ionic liquids (ILs) is very efficient, generally producing a substrate that is amenable to saccharification with fermentable sugar yields approaching theoretical limits
The effective membrane surface area used in the membrane stability experiments conducted at the Joint BioEnergy Institute (JBEI) is ~90 cm2, while it is 60 cm2 in the experiments conducted at Compact Membrane System (CMS)
The results show that when the proper care is taken of the membrane, 5 h of IL treatment resulted in water content as low as 4.7 ± 0.2 wt% (Additional file 1: Figure S3b)
Summary
Biomass pretreatment using certain ionic liquids (ILs) is very efficient, generally producing a substrate that is amenable to saccharification with fermentable sugar yields approaching theoretical limits. Certain ionic liquids (ILs), e.g., 1-ethyl-3-methylimidazolium acetate ([C2C1Im][OAc]) and 1-butyl-3-methylimidazolium chloride ([C4C1Im]Cl), have been demonstrated to be very effective at pretreating a wide range of lignocellulosic biomass feedstocks that are capable of generating very high yields of fermentable sugars suitable for biofuel production via fermentation (Fig. 1) [1,2,3], and have been widely used recently [4]. Sun et al Biotechnol Biofuels (2017) 10:154 Separation technologies such as evaporation/distillation, electrodialysis (ED), reverse osmosis (RO) have been investigated for concentrating ILs [12,13,14,15]. It is challenging to achieve both highly concentrated ILs and quantitative IL recovery by distillation [21]
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