CAREER: Understanding of Biomass-derived Deep Eutectic Solvents for Sustainable Biorefinery Strategies

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The need for sustainable supplies of clean energy and organic chemical feedstocks, together with the negative impact on the Earth’s climate by current manufacturing methods, constitute some of the most pressing problems faced by the world’s population. Biomass is a promising renewable alternative / supplement to fossil-based resources for transportation fuels, chemical products, and biodegradable materials. To extract the maximum fraction of useful biochemical components from chemically complicated biomass streams, effective separation (fractionation) of the major biomass components, including cellulose, hemicelluloses, and lignin, is essential. Unfortunately, current biorefinery technologies capable of carrying out this fractionation process consume significant amounts of non-renewable chemicals, energy, and capital, limiting the economic feasibility and sustainability of biomass utilization. In this program, the research team will pursue a completely new approach to producing a green biomass fractionation process based on deep eutectic solvents (non-volatile liquid mixtures produced from components that are otherwise solid) derived from the biomass itself. This unique approach will produce biomass-derived chemical products using a process that does not introduce non-bioderived processing agents. Education and outreach programs will integrate technical knowledge generated by this research with the goal of increasing the number and diversity of future technical leaders in sustainable chemical manufacturing methods.Biomass-derived solvents have the potential to play a key role in developing sustainable biorefining operations. The properties of biomass-derived deep eutectic solvents (DES) have been investigated using a range of experimental and computational methods; these studies, however, have examined a limited number of DES combinations and have not studied the mechanisms and kinetics of the reaction processes governing the conversion of biomass to DES. Intermolecular hydrogen bonding between the hydrogen bond donor (HBD) and hydrogen bond acceptor (HBA) species in a DES plays a primary role in the formation of the solvent and determining its physicochemical and thermal properties. The proposed research program will (a) pursue a mechanistic understanding of DES formation over a range of HBD and HBA structures by experimental and computational methods, (b) determine correlations between DES composition and the solvation, thermal transport, and rheological properties of the solvent by a comprehensive program of experimental characterization and machine learning-based modeling, and (c) elucidate the reaction mechanisms and kinetics of biomass-derived DES with biomass model components and natural biomass. The formation mechanism of DES will be investigated with diverse HBA and HBD pairs from biomass-derivable components and elucidated by nuclear magnetic resonance (NMR). The characteristics of the synthesized DES will be analyzed by differential scanning calorimetry, rheometry, and ion conductivity measurements. These experimental results will be used to develop a prediction model for the properties of DES by training an artificial neural network (ANN) model and validating its predictions. The chemical interactions of DES with biomass also will be investigated in reaction kinetic studies of the synthesized model compounds and real biomass using density functional theory (DFT) calculations. These findings will not only advance scientific knowledge in the fractionation properties of biomass-derived DES but also can be expanded to a wider range of sustainable, eco-friendly, and tunable industrial solvents for biorefining processes. Informed by the proposed research, an interdisciplinary curriculum for biorefining will be created to train the next generation of engineers and scientists in biorefining technologies. The research team plans to reach out to high school students through an annual summer workshop consisting of hybrid lectures and hands-on experiments to enhance participants’ understanding of sustainable biorefinery operations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.