Encapsulated Paracetamol-Based Eutectic Solvents for the Treatment of Low-Grade Palm Oil Mixed with Microalgae Oil

The development of an efficient and green catalyst is a key step for the esterification of free fatty acid (FFA) in non-edible oil feedstocks. This study introduces a novel acidic deep eutectic solvent (DES) catalyst derived from an active pharmaceutical ingredient for FFA esterification. The DES was formed by paracetamol and p-toluenesulfonic acid monohydrate (PTSA), as the hydrogen bond acceptor (HBA) and the hydrogen bond donor (HBD) components, respectively. The DES was encapsulated in medical capsules for the loading and handling steps; and they utilized to esterify a high content of FFA (8.11%) in a low-grade palm oil-microalgae oil mixture to achieve an acceptable FFA limits (<2%) for transesterification reaction. The FFA content was decreased to < 2% under optimum conditions (catalyst dosage 2% wt/wt of catalyst to oil, 10:1 molar ratio of methanol to oil at 60 °C for 60 min reaction time). Paracetamol forms a eutectic mixture with PTSA and is an effective HBA component in the formation of the DES catalyst. The analysis of relative solubility screening, σ-profile and σ-potential confirm certain level of solubility and homogeneity of this DES in methanol during the pre-treatment process. The formation of the eutectic mixture endows the catalyst with advantages for the esterification reaction such as improvements in recyclability and hygroscopicity of PTSA.