Superior cellulose-protective effects of cosolvent during enhanced dissolution in imidazolium ionic liquid

Abstract

To improve the solubility of cellulose at lower temperatures, several polar organic solvents were examined as cosolvents in imidazolium ionic liquid (IL). All tested cosolvents increased the solubilization efficiency of ILs at lower temperatures. Among these, N-methylimidazole, N-methyl-2-pyrrolidone, and dimethyl sulfoxide (DMSO) were notably efficient; in case of Avicel the solubility was increased, with 12–15% cellulose dissolution in 1-allyl-3-methylimidazolium chloride ([Amim]Cl) at 30°C. IR spectra of the regenerated celluloses from IL/cosolvent systems showed characteristic features of cellulose II and/or amorphous cellulose. Thermogravimetric analyses showed significantly higher thermal stability of regenerated cellulose from [Amim]Cl/DMSO compared with that without DMSO. Moreover, dimethylacetamide (DMAc) increased the solubility of filter paper pulp in 1-ethyl-3-methylimidazolium acetate ([Emim]OAc), with 12% pulp dissolution at 30°C. No decrease in the degree of polymerization (DP) of cellulose was observed with [Emim]OAc/DMAc, whereas 8–9% DP decrease was observed with [Emim]OAc, even at 30°C. These results indicate that some cosolvents including DMSO and DMAc increase solubilization efficiency and have superior cellulose-protective effects during enhanced dissolution in ILs.

Novel cellulose pretreatment solvent: phosphonium-based amino acid ionic liquid/cosolvent for enhanced enzymatic hydrolysis

“…However, without cosolvent, all of the AAILs failed to dissolve cellulose (Avicel), even at 120°C (Table 1, entries 1, 8, 15, and 17). Therefore, the above-mentioned aprotic polar organic solvents served as cosolvents because they increased the solubilization efficiency of 1-allyl-3-methylimidazolium chloride ([Amim]Cl) for cellulose dissolution (Tao et al 2016).…”

“…These results indicate that no significant degradation occurred during the dissolution process. Tao et al (2016) showed that polar organic cosolvents not only increase cellulose solubility in [Amim]Cl but also exhibit protective effects preventing DP decrement.…”

“…After vacuum filtration, the residual AAIL/cosolvent was washed with 100 ml distilled water three times. The regenerated cellulose was dried under vacuum over P 2 O 5 at r.t. for 24 h. The viscosimetric DP determination was performed in copper (II) ethylenediamine solution (Tao et al 2016). Each sample was measured in triplicate and the DPs in Table 1 are the averages of three runs.…”

Pretreatment of Lignocellulosic Biomass with Ionic Liquids and Ionic Liquid-Based Solvent Systems

“…They attributed the improved dissolving ability to the preferential solvation of the cations of the IL by the aprotic polar solvent, as is supported by the conductivity measurements. Tao et al found that DMSO could not only promote the dissolution of cellulose in ILs, but could also show a superior cellulose-protective effect [ 40 ]. The degree of polymerization (DP) of cellulose was unchanged after dissolution and regeneration from the solvent system [Emim]Ac/DMSO, while the obvious reduction of the DP of cellulose was observed in pure IL.…”

Enzymatic synthesis of methyl β-d-glucoside directly from cellulose pretreated with biocompatible amino acid ionic liquid/cosolvent

“…However, the poor solubility of cellulose in common solvents is the main obstacle to its further application. Ionic liquids (ILs) with negligible vapor pressure, strong solubilization efficiency, adjustable structure, and recyclability have been widely applied to lignocelluloses (Swatloski et al 2002;Zhang et al 2005;Fukaya et al 2006;Qu et al 2011Qu et al , 2012Qu et al , 2013aTao et al 2016a). After pretreatments with ILs, the highly crystalline structure of cellulose is altered to a disordered state with a more accessible surface area (Auxenfans et al 2012;Xiao et al 2012), which provides the possibility of transforming cellulose into advanced derivatives.…”