A facile method for the recovery of ionic liquid and lignin from biomass pretreatment

Abstract

Persil Çetinkol, Özgül (Dogus Author)In the biochemical conversion of lignocellulosic biomass to biofuels, the process of pretreatment is currently one of the most difficult and expensive operations. The use of ionic liquids (ILs) in biomass pretreatment has received considerable attention recently because of their effectiveness at decreasing biomass recalcitrance to subsequent enzymatic hydrolysis. In addition, ILs have the potential for decreasing the need for corrosive or toxic chemicals and associated waste streams that can be generated by other pretreatment methods that utilize acids and/or bases. In this article, we address two significant challenges to the realization of a practical IL pretreatment process. First, we describe a mixture containing specific proportions of a ketone and an alcohol that precipitates cellulose and lignocellulosic biomass from solutions of the IL 1-ethyl-3-methylimidazolium acetate without the formation of intermediate gel phases. Second, an IL recovery process is described that removes lignin and most residual IL solutes and that minimizes energy and solvent use. These two techniques are demonstrated by the pretreatment of 100 g of corn stover with the recovery of 89% of the initial IL and separate corn stover fractions rich in glucans, xylans, lignin, and non-polar substances. These results highlight one potential approach towards the realization of a scalable ionic liquid pretreatment process technology that enables ionic liquid recovery and reuse

Substrate-Specific Development of Thermophilic Bacterial Consortia by Using Chemically Pretreated Switchgrass

“…The green waste consisted of yard trimmings and discarded food waste from an end-stage compost pile. Samples were transported to the lab at room temperature and inoculated within 24 h. The ionic-liquid (IL)-pretreated switchgrass was prepared by heating switchgrass with 1-ethyl-3-methylimidazolium acetate as previously described and washed with water to remove the ionic liquid (11). Ammonium fiber expansion (AFEX)-pretreated switchgrass was prepared as previously described and washed with water after pretreatment to remove readily solubilized compounds (14).…”

“…Pretreatment reorients the physical structure of the plant cell wall and reduces the recalcitrance of the polysaccharides, cellulose, and hemicellulose (10). Depending on the pretreatment, some plant polymers, primarily hemicellulose and lignin, are depolymerized, and the resulting substrate is enriched in cellulose (11). Two prominent chemical pretreatments of biomass are ammonia fiber expansion (AFEX) pretreatment, in which gaseous ammonia disrupts the plant cell wall while maintaining the composition of the biomass (10,12,13), and ionic-liquid (IL) pretreatment, in which molten organic salts are used to achieve partial dissolution of biomass, yielding a cellulose-enriched substrate in which the polysaccharides are much more accessible than in the native biomass.…”

Ionic liquids as a tool for lignocellulosic biomass fractionation

“…As previously mentioned the reconstituted material presents a gelatinous phase, thus it is hard to separate it from the viscous liquid after regeneration. Dibble et al developed an antisolvent mixture with specific proportions of an alcohol (ethanol) and ketone (acetone) that provided the regeneration of solid precipitates with porous appearance and easily dispersed in the liquid with no gel formation [68]. A rapid separation was attained and a lower volume of antisolvent mixture was used in comparison with other antisolvent used.…”

“…Therefore, the IL recovery is largely dependent on the antisolvent used, as well as on the pre-treatment conditions applied that guides to certain extend carbohydrates dissolution, lignin removal and biomass degradation products present in the liquid stream. Focused on maximising IL recovery, several processes were developed and further reuse pre-treatments were performed to evaluate the pretreatment efficiency after recycle [48,68,78,91,93]. Figure 4 represents three processes of IL recovery that were developed up to present.…”

Studies to optimize the process of biofuel production from castor stalk

“…In previous reports up to a maximum of 89 % of IL was recovered with the impurity of water [52]. In our study 95 % of IL was recovered by a method in which the filtrate was thoroughly mixed with silica gel (in acetonitrile) and then passed through a sintered crucible (see Suppl.…”