Production, optimization, and evaluation of thermal stability of palm oil biodiesel produced using a natural coconut oil–based surfactant

The prospect of depletion of fossil fuels and the global concern with reducing the emission of polluting gasses have aroused interest from governments and researchers in using alternative fuels. Biodiesel is considered an effective alternative as a partial or total replacement for petroleum-derived diesel because it is biodegradable, emits fewer greenhouse gasses, and is produced from renewable sources. In the biodiesel synthesis, the difference in the polarity of the reactants hinders the homogenization of the reaction system, which can negatively affect the transesterification reaction. Most surfactants used to improve the miscibility of reagents in transesterification reactions are toxic, dangerous, and are required in relatively high amounts. This study explored biodiesel production from palm oil and methanol in a new system containing a coconut oil–based natural surfactant, which is biodegradable, non-toxic, and derived from a fruit that is found worldwide. The experimental design, a full factorial design, was used to optimize the process, and using the thermogravimetric analysis, the isoconversional methods of Flynn–Wall–Ozawa and Kissinger were used in the kinetic study of thermal degradation of the biodiesel. The surfactant was efficient in low amounts, and the optimal conditions for biodiesel production were 30 min reaction time, potassium hydroxide 1 wt%, methanol and oil molar ratio of 8.28:1, and surfactant 1.05 wt%, which yielded 98.64% of biodiesel and 98.04% of fatty acid methyl esters. The properties of the biodiesel were according to EN 14,214. The biodiesel was thermally stable up to 200 °C, and waste generation was less than 2.2%. Graphical abstract