Cellulose regeneration from a cellulose/ionic liquid mixture: the role of anti-solvents

Abstract

A molecular simulation study is reported to investigate the role of anti-solvents (water, ethanol, and acetone) in cellulose regeneration from a cellulose/1-n-butyl-3-methylimidazolium acetate ([BMIM][Ac]) mixture. Structural analysis based on radial distribution functions reveals that the interaction of cellulose–[BMIM][Ac] decreases in the order acetone > ethanol > water, with cellulose–[Ac]⁻ forming the smallest number of H-bonds in water. However, the interaction of cellulose–cellulose increases in the reverse order (acetone < ethanol < water), with the largest number of H-bonds between cellulose chains being observed in water. Among the three solvents, water is identified to be the most effective at breaking the cellulose–[Ac]⁻ H-bonds and leading to the subsequent formation of cellulose–cellulose H-bonds. Furthermore, the dynamic analysis based on survival time-correlation functions and mean-squared displacements demonstrates that [Ac]⁻ in water has the shortest residence time near cellulose and the highest mobility compared to [Ac]⁻ in ethanol and acetone. This simulation study suggests that water outperforms ethanol and acetone for cellulose regeneration, and provides a microscopic insight into the mechanism of cellulose regeneration.