Effects of Reaction Temperature and Phosphoric Acid Catalyst Volume on Free Fatty Acid Reduction in Used Cooking Oil via Esterification
DOI:
https://doi.org/10.37577/sainteks.v8i02.1183Keywords:
used cooking oil, esterification, free fatty acid, phosphoric acid, reaction temperatureAbstract
Used cooking oil contains free fatty acids (FFAs), which can increase due to hydrolysis and repeated heating, thereby limiting its further use. This study descriptively evaluated the effects of reaction temperature (40 and 60 °C) and the volume of phosphoric acid catalyst (4 and 8 mL) on the reduction of FFAs through esterification with methanol. Each reaction used 100 mL of pretreated used cooking oil, 20 mL of methanol, and 85% H?PO? for 60 minutes at 500 rpm. FFA content was determined by alkalimetric titration, while FTIR was used for supporting qualitative characterization. The density and viscosity of the new oil and used oil were also compared. The initial FFA content was 2.11%. After esterification, the FFA contents were 1.33%, 0.88%, 0.70%; and 0.33% under the conditions of 4 mL–40 °C, 4 mL–60 °C, 8 mL–40 °C, and 8 mL–60 °C, with reported conversion rates ranging from 37.02% to 84.55%. The lowest FFA content was obtained at 60 °C with 8 mL of H?PO?. The FTIR spectra before and after treatment showed similar C=O and C–O ester bands because the triglycerides already contained ester groups; therefore, FFA titration was used as the primary indicator of esterification progress. Within the range of conditions tested, higher temperatures and catalyst volumes were associated with greater reductions in FFA.
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Abrante-Pascual, S., Nieva-Echevarría, B., & Goicoechea-Oses, E. (2024). Vegetable oils and their use for frying: A review of their compositional differences and degradation. Foods, 13(24), 4186. https://doi.org/10.3390/foods13244186.
Badan Standardisasi Nasional. (2019). SNI 7709:2019 Minyak goreng sawit. Jakarta: Badan Standardisasi Nasional.
Encinar, J. M., González, J. F., Martínez, G., & Nogales-Delgado, S. (2022). Transesterification of soybean oil through different homogeneous catalysts: Kinetic study. Catalysts, 12(2), 146. https://doi.org/10.3390/catal12020146.
Ferreira, M. J. A., Mota, M. F. S., Mariano, R. G. B., & Freitas, S. P. (2021). Evaluation of liquid-liquid extraction to reducing the acidity index of the tucuma (Astrocaryum vulgare Mart.) pulp oil. Separation and Purification Technology, 257, 117894. https://doi.org/10.1016/j.seppur.2020.117894.
Hájek, M., Vávra, A., de Paz Carmona, H., & Kocík, J. (2021). The catalysed transformation of vegetable oils or animal fats to biofuels and bio-lubricants: A review. Catalysts, 11(9), 1118. https://doi.org/10.3390/catal11091118.
Helwani, Z., Bahri, S., Kimia, J. T., & Riau, U. (2025). Jurnal Teknik Kimia USU Esterifikasi dan Transesterifikasi Minyak Kelapa Sawit Off-grade Menjadi Biodiesel Menggunakan Katalis Barium Hidroksida Esterification and Transesterification of Off-grade Palm Oil into Biodiesel Using Barium Hydroxide Catalyst. 14(1), 1–9.
Maduelosi, N. J., Ekezie, C. M., & Fred, O. (2024). Investigation of the effect of sequential heating on the chemical composition of vegetable oil. South African Journal of Chemistry, 78, Article a34. https://doi.org/10.17159/0379-4350/2024/v78a34.
Megawati, E., Putra, A. O. P., Effendi, N., & Yuniarti. (2021). Optimization of time in the esterification process of jelantah oil with ANOVA analysis. EduChemia (Jurnal Kimia dan Pendidikan), 6(2), 184–196. https://doi.org/10.30870/educhemia.v6i2.11331.
Metre, A. V., & Nath, K. (2015). Super phosphoric acid catalyzed esterification of Palm Fatty Acid Distillate for biodiesel production: Physicochemical parameters and kinetics. Polish Journal of Chemical Technology, 17(1), 88–96. https://doi.org/10.1515/pjct-2015-0013.
Nandiyanto, A. B. D., Oktiani, R., & Ragadhita, R. (2019). How to read and interpret FTIR spectroscope of organic material. Indonesian Journal of Science and Technology, 4(1), 97–118. https://doi.org/10.17509/ijost.v4i1.15806.
Nurfatihayati, Helwani, Z., & Bahri, S. (2025). Esterifikasi dan transesterifikasi minyak kelapa sawit off-grade menjadi biodiesel menggunakan katalis barium hidroksida. Jurnal Teknik Kimia USU, 14(1), 1–9. https://doi.org/10.32734/jtk.v14i1.17736.
Putri, Q. U., Augustin, D., & Hasanudin. (2022). Kinetika esterifikasi asam lemak bebas dari sludge industri Crude Palm Oil (CPO) menggunakan katalis komposit montmorillonite/karbon tersulfonasi dari tetes tebu. ALCHEMY Jurnal Penelitian Kimia, 18(1), 48–57. https://doi.org/10.20961/alchemy.18.1.50470.48-57.
Sánchez-Rodríguez, G., Domenzaín-González, J., Verónico-Sánchez, F. J., Pérez-López, H. I., Zúñiga-Moreno, A., & Elizalde-Solis, O. (2025). Density and viscosity in biodiesel + diesel mixtures from recycled feedstocks. Applied Sciences, 15(7), 3812. https://doi.org/10.3390/app15073812.
Santoso, A., Sumari, S., Asrori, M. R., & Wele, A. R. (2024). Synthesis of Biodiesel from Refined Waste Cooking Oil with Active Natural Zeolite as Catalyst. 11(3), 174–180. https://doi.org/10.30598//ijcr.
Supeno, M., Sihotang, J. P., Panjaitan, Y. V., Damanik, D. S. Y., Tarigan, J. B., & Sitepu, E. K. (2023). Room temperature esterification of high-free fatty acid feedstock into biodiesel. RSC Advances, 13(47), 33107–33113. https://doi.org/10.1039/D3RA06912E.
