Lawrence Berkeley National Laboratory

The polymers found in plant cell walls represent the largest reserves of renewable carbon on Earth - it has been estimated that the United States has approximately 1.3 billion tons of plant biomass available per year. Ionic liquids (ILs) are salts with melting points less than 100oC, typically containing organic cations, that possess a wide range of extraordinary properties as compared to traditional organic solvents. The unusual catalytic and solvation properties of ionic liquids have attracted the biofuel and biomass communities because IL-pretreatment provides higher fermentable sugar yields than those obtained by acid- or alkali-pretreatment under similar severities. This research used lignin, a major by-product of the biofuel and pulping industries, as raw material for IL synthesis. The goal is to lower the cost of IL production, and enable a more "closed-loop" biorefinery. The lignin is oxidatively depolymerized, purified, and used to prepare a new class of renewable ILs. Biomass pretreatment was the target application for the lignin-derived ILs, while we continue to investigate additional applications within the growing IL market - process chemistry, biotechnology and materials recycling. When comparing our corn stover pretreatment data to recently published reports, we have shown comparable glucose and xylose yields by using neat and 10% aqueous solutions of lignin-derived ILs.