Acidic deep eutectic solvents with long carbon chains as catalysts and reaction media for biodiesel production

To overcome the mass transfer limit and saponification, acidic deep eutectic solvents (DESs) were prepared with p-Toluenesulfonic acid (p-TsOH) and quaternary ammonium salts with different carbon chains. The DESs acted as catalysts and reaction media for biodiesel production by transesterification of the cooked and waste vegetable oil. The DESs were characterized by 1H NMR, FT-IR and TG. In five DESs, TOAB/p-TsOH was found to enhance the direct contact between methanol and oil and have the highest catalytic activity due to its long carbon chain, which was chosen to further optimize. The suggested conditions given by the response surface methodology model were the reaction temperature of 70.5 °C, catalyst dosage of 24.6 wt%, and a molar ratio of 12.5, which reached the yield of 99.2%. Furthermore, the kinetic study of transesterification was studied and followed the pseudo-first-order reaction mechanism.