Direct Production of Levulinic Acid in One Pot from Hemp Hurd by Dilute Acid in Ionic Liquids

Levulinic acid, a versatile platform chemical from renewable lignocellulose, can be used for the production of fuels, solvents, and pharmaceuticals. The complex chemical bonds of lignocellulose necessitate reaction conditions at high acid loading, low lignocellulose loading, and high temperature and/or pressure. These harsh reaction conditions degrade the intermediates (5-hydroxymethylfurfural (HMF) and glucose), resulting in a low yield of levulinic acid. Here, we show that combined lignocellulose dissolution in ionic liquids (1-ethyl-3-methylimidazolium chloride) and acid hydrolysis by HCl enables the conversion of hemp hurds to a high yield of levulinic acid (59%) in one pot under a mild reaction condition (120 degrees C and atmospheric pressure) without additional acid catalysts. The presence of HCl (Bronsted acid) catalyzed cellulose hydrolysis, glucose dehydration, and HMF rehydration in ionic liquid. The addition of Lewis acid catalysts (CrCl3, AlCl3, ZrCl4, and SnCl4) was not necessary. Compared with conventional processes for levulinic acid production, our approach has additional key advantages such as high solid loading (17.S wt %) and no need to separate intermediate products (glucose and HMF). Furthermore, the incorporation of a lignocellulose dissolution step in ionic liquids makes this one-pot strategy customizable for different types of lignocellulose.