Investigation of reaction parameters for esterification of acidic crude palm oil using bubble column reactor

Acidic crude palm oil (ACPO) offers a sustainable option as a non-edible feedstock for biodiesel production. This study investigated a lab-scale bubble column reactor (BCR) for free fatty acid (FFA) esterification of APCO as a pretreatment step for biodiesel production. Air bubbles were sparged through the BCR column to facilitate homogeneous mixing of reactants, and the FFA esterification reaction was catalysed using sulphuric acid (H2SO4) and p-toluenesulfonic acid monohydrate (PTSA). Under optimised conditions, FFA esterification catalysed using H2SO4 required reaction conditions of 3 wt% catalyst dosage, 20:1 methanol-to-oil molar ratio, 30 min reaction time, 30 °C reaction temperature and 0.5 L/min air flow rate, achieving high FFA to FAME conversion of 84.06 %. PTSA-catalysed esterification reaction required similar reaction conditions as H2SO4, albeit at 5 wt% catalyst dosage and 15:1 methanol-to-oil molar ratio, achieving 79.51 % FFA conversion. Changes in the aspect ratio did not significantly affect the FFA conversion. The FFA esterification reaction trends were determined to fit the pseudo second-order reaction rate with activation energies of 28.59 and 22.23 kJ/mol for H2SO4 and PTSA, respectively. This study demonstrates the promising use of BCR for FFA esterification with lower reaction conditions and improved mixing.