(700e) A Novel Method of Producing Levulinic Acid at High Concentrations and Yields from Corn Stover Hydrolysate

Ravikumar Gogar,¹ Sridhar Viamajala,¹ Patricia Relue,² and Sasidhar Varanasi¹

Department of Chemical and Environmental Engineering, ¹ Department of Bioengineering, ² University of Toledo, Toledo, OH 43606

Levulinic acid is a promising platform molecule that can be used to produce transportation fuels, resins, polymers, pharmaceuticals, and solvent precursors from biomass. In this work, dilute acid pre-treated corn stover was used as feed to obtain saccharified biomass hydrolysate. We developed a novel hybrid enzyme- and chemo-catalytic technology that isomerizes, isolates, and dehydrates the sugar to levulinic acid in high yields and concentrations. First, a simultaneous-isomerization-reactive-extraction (SIRE) step was used to convert glucose from biomass hydrolysate, using GXI enzyme at 60^o C and pH = 8.5, to fructose at higher yield (88%). This approach, which extracts the fructose into an immiscible octanol phase, as it is formed, not only overcomes the unfavorable equilibrium of the isomerization reaction, but also separates the sugar from the pretreatment-derived impurities in the hydrolyzate. Aryl Boronic Acids (ABA) and Aliquat® 336 are added to the octanol phase to facilitate the extraction of fructose selectively via preferential binding to ABA. Fructose was then transferred from the octanol into an immiscible phase of an acidic ionic liquid and aqueous mixture (at pH = 6) via back-extraction. Fructose was then converted in the IL-water phase, at facile reaction conditions (T = 95 C, P =1 atm), to Levulinic acid at high yield (63 mol%); levulinic acid was obtained at significant loading of 6.4%, thereby, reducing energy cost for its separation from the reaction mixture. The proposed process offers advantage of recyclable streams and catalyst, near complete utilization of feed by overcoming glucose to fructose equilibrium, and lower energy cost by providing levulinic acid at higher concentration, thereby making the process cost competitive.