(557c) Insights Into Ionic Liquids Pretreatment On Lignocellulosic Biomass From Molecular Modeling Studies

A deeper mechanistic understanding of the lignocellulosic biomass dissolution in ionic liquids (ILs) is desired for the development of biorefining applications to enhance the efficiency of biofuel production. Previous work at the Joint BioEnergy Institute (JBEI) has demonstrated that certain ionic liquids (ILs) are efficient solvents for pretreating many types of biomass with high sugar yields. As a part of a broader effort to develop novel ILs and to improve IL process selectivity, biocompatibility, and economics, here we use an integrated experimental and computational approach to gain a fundamental understanding of the chemistry of biomass deconstruction. We use a multi-resolution computational approach to analyze (A) ions, and ion pairs (i.e. ILs) interactions with model lignin compound (B) interactions between ILs with crystalline cellulose, and (C) developing predictive models for ILs reactivity. In this study, quantum chemical calculations were carried out to probe the interactions of four ILs composed of 1-ethyl-3-methylimidazolium ([C₂mim]⁺) and cholinium ([Ch]⁺) cations combined with acetate ([OAc]^-) and lysinate ([Lys]^-) anions with dilignol. The mechanism for explaining the dissolution of cellulose in different [C₂mim][OAc]:water loading is deduced from the comprehensive fully-atomistic molecular dynamics simulations. Finally, we examined the relationship between the predicted Kamlet and Taft (K-T)   parameters (dipolarity/polarizability (π*), hydrogen bond donor acidity (α), and hydrogen bond basicity (β)) and experimentally tested K-T parameters on a series of imidazolium based and amino acid based ILs. The models developed in these studies will guide the targeted design of ILs on solubilizing lignocellulosic biomass and will advance the development of IL pretreatment technologies.