The Effects of Water Concentration On the Properties of Imidazolium-Based Ionic Liquids

 In the conversion process of production of tailor-made biofuels from waste biomass , cellulose is solvated and broken down into glucose units using solvents such as ionic liquids (ILs). Because this process releases trapped water molecules from the cellulose matrix , and because water is known to inhibit the dissolution of cellulose in IL’s , study of the effect of water content on local interactions between individual components of the system has an important role in understanding the details of the mechanism of cellulose dissolution using ILs. In this work , we have analyzed the results of series of molecular dynamics (MD) simulations of twelve different commercially available imidazolium-based ILs: a combinatorial set of four cations: [dmim] , [emim] , [pmim] , and [bmim] and three anions: [DMP] , Cl , and [Ac]. For each IL , we have tested the effect of presence of water molecules on structural properties and dynamics of systems with water mole fractions ranging from 0.0% to 99.9%. Particularly , we have examined bulk properties (density) , structural properties (radial distribution functions , water clustering and hydrogen bonding) and dynamical properties (shear viscosity and diffusion coefficients) of those mixtures and have made direct comparisons with experimental works whenever possible. We have observed for each IL a critical concentration , usually at water mole fractions between 70% and 80% , at which the mixture undergoes a transition from water dispersed in IL to an aqueous solution.