(127b) Selective Production of Levulinic Acid from Furfuryl Alcohol in Aprotic Solvent Systems Using Solid Acid Catalysts

The use of organic solvents is pervasive in the chemical industry, and it has recently been shown that organic solvents are beneficial for the selective chemical upgrading of lignocellulosic biomass.^[1] We have previously reported that the use of polar aprotic solvents, such γ-valerolactone (GVL) and tetrahydrofuran (THF), leads to improved activity and selectivity during homogeneous acid-catalyzed biomass conversion reactions compared to reactions carried out in aqueous media.^[2,3] By studying the reaction kinetics of these systems, we have determined that the observed increases in product yields are due to advantageous increases in relative reaction rates. We propose that these increased rates stem from changes in the relative stabilization of the acidic proton catalyst versus stabilization of the protonated transition states.

In addition, we have observed increases in reactivity and selectivity using heterogeneous acid catalysts in polar aprotic solvents; however, the behavior of heterogeneous acid catalysts in polar aprotic solvents is not well understood. This presentation will demonstrate the use of solid acid catalysts for the production of levulinic acid by furfuryl alcohol hydrolysis in monophasic THF-H₂O solvent systems. We show that H-ZSM-5 zeolite is selective for levulinic acid production (>70% yield) even at high reactant concentrations (1 M).^[4] Through reaction kinetics studies using H-ZSM-5, we identify important catalytic parameters leading to high levulinic acid yields, including the hydrophobicity and structural properties of the catalyst. Based on these results, we provide new insight into the synergistic relationship between aprotic solvents and heterogeneous catalysts for acid-catalyzed hydrolysis reactions. Ultimately, this insight will act as a template for rational catalyst design for furfuryl alcohol conversion into levulinic acid as well as other acid-catalyzed reactions.

^[1] Schwartz, T. J.; O'Neill, B. J.; Shanks, B. H.; Dumesic, J. A. ACS Catal. 2014, 4, 2060-2069.

^[2] Mellmer, M. A.; Sener, C.; Gallo, J. M. R.; Luterbacher, J. S.; Alonso, D. M.; Dumesic, J. A. Angew. Chem., Int. Ed. 2014, 53, 11872-11875; Angew. Chem. 2014, 126, 12066-12069.

^[3] Mellmer, M. A.; Alonso, D. M.; Luterbacher, J. S.; Gallo, J. M. R.; Dumesic, J. A. Green Chem. 2014, 16, 4659-4662.

^[4] Mellmer, M. A.; Gallo, J. M. R.; Alonso, D. M.; Dumesic, J. A. ACS Catal. 2015, 5, 3354-3359.