Cellulose Regeneration in Imidazolium-Based Ionic Liquids and Antisolvent Mixtures: A Density Functional Theory Study

Abstract

Cellulose can be dissolved in ionic liquids (ILs), and it can be recovered by adding antisolvent such as water or alcohol. In addition, the regenerated cellulose can be used for textiles, degradable membranes, hydrogels/aerogels, etc. However, the regenerated mechanism of cellulose remains ambiguous. In this work, density functional theory (DFT) calculation is reported for the cellulose regeneration from a cellulose/1-n-butyl-3-methylimidazolium acetate (BmimOAc)/water mixture. To investigate the microscopic effects of the antisolvents, we analyzed the structures and H-bonds of BmimOAc-nH2O and cellobiose-ILs-nH2O (n = 0–6) clusters. It can be found that when n ≥ 5 in the BmimOAc-nH2O clusters, the solvent-separated ion pairs (SIPs) play a dominant position in the system. With the increasing numbers of water molecules, the cation–anion interaction can be separated by water to reduce the effects of ILs on cellulose dissolution. Furthermore, the BmimOAc-nH2O and cellobiose-ILs (n = 0–6) clusters tend to be a more stable structure with high hydration in an aqueous solution. When the water molecules were added to the system, H-bonds can be formed among H2O, the hydroxyl of cellulose, and the oxygen of OAc. Therefore, the interactions between cellulose and ILs will be decreased to promote cellulose regeneration. This work would provide some help to understand the mechanism of cellulose regeneration from the view of theoretical calculation.

Biomass and Cellulose Dissolution—The Important Issue in Renewable Materials Treatment

“…It leads to the aggregation of cellulose. Water can be applied as an antisolvent in the precipitation and regeneration of dissolved polymers [122][123][124][125].…”

Recent Advances in Cellulose-Based Hydrogels Prepared by Ionic Liquid-Based Processes

“…[95] Copyright © 2023, Elsevier, B.V.), fiber (B) (Reprinted with permission from ref. [129] Copyright © 2017 Wiley Periodicals, Inc.), membrane (C) (Reprinted with permission from ref. [130] Copyright © 2017 Wiley Periodicals, Inc.), and nonwoven mesh (D (Reprinted with permission from ref.…”

“…Ionic liquid-based preparation processes of cellulose hydrogels in the form of bulk (A) (Reprinted with permission from ref [95]. Copyright © 2023, Elsevier, B.V.), fiber (B) (Reprinted with permission from ref [129]. Copyright © 2017 Wiley Periodicals, Inc.), membrane (C) (Reprinted with permission from ref [130].…”

Ionic Pairing and Selective Solvation of Butylmethylimidazolium Chloride Ion Pairs in DMSO–Water Mixtures: A Comprehensive Examination via Molecular Dynamics Simulations and Potentials of Mean Force Analysis

“…However, the elevated viscosity characteristic of chloride-based ILs presents an obstacle to the efficient dissolution of biomass, notably within the realm of biofuel production. The incorporation of solvents, such as water and dimethyl sulfoxide (DMSO), into chloride-based ILs emerges as a promising avenue for mitigating IL viscosity, consequently amplifying the effectiveness of biomass component dissolution and regeneration. − The predominant approaches proposed for the extraction of cellulose from ILs involve the application of antisolvent precipitation methodologies . Moreover, the majority of aqueous and organic solvents are found to induce the precipitation of cellulosic biomass from mixtures containing ILs, thereby classifying them as antisolvents .…”

“…Moreover, the majority of aqueous and organic solvents are found to induce the precipitation of cellulosic biomass from mixtures containing ILs, thereby classifying them as antisolvents . Upon introduction of protic solvents, notably water into mixtures of ILs and cellulose, they perturb the favorable interactions between ILs and cellulose, consequently diminishing the cellulose-loading capability within IL–antisolvent mixtures. − ,− Solvents possessing hydrogen-bond-donating capabilities, such as water, form intimate associations with negatively charged IL anions. Upon amalgamation with ILs, protic solvents engage in competitive interactions with IL anions, impeding their efficacy in cellulose dissolution .…”