Esterification of Acidic Crude Palm Oil Using Trickle Bed Reactor Packed With Supported p-Toluenesulfonic Acid Monohydrate-Based Deep Eutectic Solvent

Trickle bed reactors (TBRs) are widely employed in oleochemical processing due to their continuous operation and high efficiency. However, further improvements are needed to develop sustainable packing materials for TBR systems. In this study, a TBR packed with activated carbon impregnated with a deep eutectic solvent (DES) was used for the treatment of acidic crude palm oil (ACPO). An ammonium-based DES was synthesized from p-toluenesulfonic acid monohydrate (PTSA) and choline chloride (ChCl). The successful impregnation of –SO₃H groups onto activated carbon was evidenced by FESEM, verified by EDX through the detection of sulfur and further confirmed by FTIR analysis showing characteristic sulfonic peaks. Under optimal conditions using 8 g of DES-loaded activated carbon, a reaction temperature of 60 °C, and flow rates of 4 mL/min for ACPO and 3 mL/min for methanol, the free fatty acid (FFA) content was reduced from 9 to 1%. Compared to the batch process, the system showed lower catalyst consumption (17.86 mg/g over 37 mg/g) and higher treated ACPO yield (86 ± 0.1%). These results highlight the TBR-DES system as a promising and sustainable approach for upgrading low-grade palm oil to biodiesel feedstock.