Encapsulated acidic aspirin-based eutectic solvents for esterification of free fatty acid

Official URL: https://dx.doi.org/10.21894/jopr.2024.0047

The combination of high free fatty acid (FFA) palm oil and non-edible microalgae oil presents a promising avenue for sustainable biodiesel production. Efficient catalyst development and innovative technologies are crucial, particularly for the esterification reaction in feedstock pre-treatment processes. In this study, two novel active pharmaceutical ingredients (API)-based deep eutectic solvents (DESs) were introduced. They derived from p-toluenesulfonic acid monohydrate (PTSA) and benzenesulfonic acid (BZSA) combined with aspirin (ASA), encapsulated within medical capsules for safe handling and storage. These DESs effectively reduce FFA content from 11% to less than 2% under optimum conditions (1 wt% of DES catalyst dosage, 10:1 methanol-to-oil molar ratio, 60°C esterification reaction temperature and 60 min reaction time). The activation energies of the reaction using ASA:PTSA and ASA:BZSA based DES were determined as 53.11 and 39.20 kJ mol–1, respectively, according to the pseudo first order reaction rate. Furthermore, FFA to fatty acid methyl ester (FAME) conversion rates remained above 50% for both DESs even after three consecutive recycling runs. The utilisation of API-based DESs enhances catalyst physical properties, recyclability for FFA esterification reactions, underscoring their potential in advancing biodiesel production processes.