ABSTRACT Levulinic acid (LA) is at the forefront of biorefinery research as an important carbohydrate‐derived platform chemical for the synthesis of biofuels, sustainable chemicals, and renewable polymers. Several studies have attempted to maximize the selectivity and yield of LA by using additives that influence the mechanistic pathway of the acid‐catalyzed dehydration of sugars. This work used formic acid (FA), a biogenic carboxylic acid, as an additive to significantly improve LA yield from various terrestrial and marine carbohydrates. The balanced electrophilicity and nucleophilicity of FA are believed to play a crucial role in stabilizing the reactive intermediates, steering them toward LA, and minimizing side reactions. Under optimized conditions (1 g substrate, 120°C, 4 h, 18 mL 20% aq. HCl, 2 mL FA), an 86% yield of LA was obtained from glucose in a closed batch reactor, whereas the control reactions (i.e., without FA) gave a 79% yield of LA. Polymeric carbohydrates (e.g., cellulose), also afforded significantly better yield of LA in the presence of FA. The reactions also showed a similar trend under microwave irradiation. Insoluble humin formed in noticeably lower amounts in the presence of FA, hinting at the positive influence of FA toward the synthesis of LA.
Aranha et al. (Sun,) studied this question.