Humin-free synthesis of levulinic acid from fructose using heteropolyacid catalysts

Levulinic acid (LA) is one of the top bio-based platform molecules that can be converted into many valuable chemicals. Herein, we report the sustainable synthesis of LA acid from various sugars using heteropolyacid catalysts. By using a Box–Behnken design of experiment, both LA yield (up to 69 mol%) and complete suppression of parasitic humin formation could be achieved within a 5 h reaction time at 140°C using fructose as a substrate. The effects of various reaction parameters like temperature, sugar concentration, addition of organic co-solvent and reaction time on LA yield and humin formation were examined in a three-dimensional space. Moreover, the results could be successfully transferred to other sugars like glucose or cellobiose, paving the way for an atom-efficient and sustainable LA synthesis process.