(213g) Understanding Water's Disruptive Role on Solubility in Ionic Liquids

Authors: 
Rabideau, B. D., RWTH Aachen University
Ismail, A. E., RWTH Aachen University

A number of ionic liquids (ILs) are currently being sought as solvents of biomass, with many potential advantages over traditional solvents, including low vapor pressure, low flammability and the ability to be tailored. As ILs dissolve biomass however, water that remains trapped within the matrix is released, mixing with the ionic liquid solvent. In small yet sufficient quantities water can significantly disrupt the dissolution process requiring removal of the water from the solvent, which is a costly process. This could potentially be improved through identification of ILs that are more water-tolerant or ways to stifle water’s disruptive mechanism, however a molecular understanding of these processes is first required.

Using molecular dynamics we study the ways in which ionic liquids interact with cellulose, a primary component of biomass. We study a set of 15 different alkylimidazolium based ILs with individual strands of cellulose while varying the concentration of water present in the system. We find that without water the anions form hydrogen bonds with cellulose through a complex series of formation and destruction mechanisms that allow these anions to find discrete and stable states. We outline this complex set of pathways and then show how the addition of water to the ionic liquids can significantly alter the transitions from one state to the next. Furthermore we explore water’s direct interaction with the ionic liquid that causes it to lose its effectiveness in dissolving cellulose.