Microwave-Assisted One-Pot Synthesis of Alkyl Levulinates From Post-Harvest Vegetable Waste

The efficient production of fuels and chemical products from lignocellulosic biomass derivatives is a key objective in biorefinery research. Levulinic acid (LA), a valuable building block derived from lignocellulosic materials, serves as a precursor for alkyl levulinates via esterification with bio-alcohols. These esters are widely used in industry as fuel additives, solvents, and fragrances. In this work, a microwave-assisted one-pot protocol is presented for the valorization of post-harvest vegetable residues, specifically tomato, spinach, pepper, broccoli, red cabbage, beet, and artichoke, which are treated independently. The optimized reaction conditions for alkyl levulinate production, determined using the one-variable-at-a-time method, are as follows: 170 °C, 30 min, 150 mg of H3PWO40 (HPA), 2 mL of co-solvent, and 2 mL of alcohol based on 0.3 g of biomass. Under these conditions, complete substrate conversion is achieved, with alkyl levulinate yields ranging from 25% to 55%. Green metrics are employed to evaluate the sustainability of the process, demonstrating its alignment with green chemistry principles. The one-pot approach reduces intermediate separation steps, minimizing waste. These findings contribute to the development of more sustainable biomass-to-chemical conversion pathways, reinforcing the potential of alkyl levulinates as bio-based platform chemicals and contributing to the Sustainable Development Goals (SDG).