Heterogeneous Esterification of Coconut Oil Fatty Acid Distillates (COFAD) Using Directly Sulfonated Cacao Shells

Abstract:

The valorization of agricultural byproducts presents a viable strategy to mitigate feedstock challenges in Philippine biodiesel production. One promising feedstock for the industry is coconut oil fatty acid distillate (COFAD), which can be optimized for conventional alkali transesterification through pre-treatment by acid-catalyzed esterification. This process involves converting free fatty acids (FFAs) into fatty acid methyl esters (FAMEs) using an innovative solid acid catalyst derived from directly sulfonated cacao shell (CS-SAC). A response surface methodology (RSM) approach was employed to systematically assess the influence of two key parameters—methanol-to-COFAD molar ratio (6.4 to 16.9 mol/mol) and catalyst loading (0.07 to 0.42 mmol H+/g COFAD)—on FFA conversion, while maintaining a constant temperature of 60°C and a reaction time of two (2) hours. Catalyst reusability was evaluated over four cycles under conditions that achieved the highest FFA conversion. Results indicated that an increase in the methanol-to-COFAD ratio initially enhanced FFA conversion. However, beyond a certain point, further increases in methanol concentration led to reduced conversion due to the dilution of the reaction medium. Regarding catalyst loading, a direct positive correlation with FFA conversion was observed across the tested range. The highest FFA conversion of 0.604 was achieved at the upper limits of the evaluated parameters, suggesting that further optimization beyond these ranges may further enhance conversion efficiency. CS-SAC demonstrated excellent stability, maintaining 90.25% of its initial conversion efficiency even after three reuse cycles. These findings underscore the potential of directly sulfonated CS-SAC as a robust catalyst for industrial-scale esterification of COFAD.

• Periodical: Engineering Chemistry (Volume 12)
• Pages: 73-99
• DOI: https://doi.org/10.4028/p-27Ar1w
• Online since: December 2025
• Authors: Ian Dominic F. Tabanag*, Jon Lionel O. Babanto, Kent Antonhel B. Catarig, James Anthony S. Solatorio, Jayhiel S. Malila
• Keywords: Coconut Oil Fatty Acid Distillate (COFAD/CFAD), Directly Sulfonated Cacao Shell Solid Acid Catalyst, Fatty Acid Methyl Esters, Response Surface Methodology – Central Composite Design (RSM-CCD), Reusability

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