A Study of the Catalytic System HPWO/Quaternary Phosphonium Salts for the Epoxidation of Fatty Acid Methyl Esters-The Effect of the Molar Ratio of Hydrogen Peroxide to the Double Bond.

In the present work, the epoxidation of fatty acid methyl esters (biodiesel or FAMEs) with an iodine number of 96.4 g/100 g and containing approximately 11% palmitic acid, 4% stearic acid, 51% oleic acid, 25% linoleic acid, and 5% linolenic acid was studied with an aqueous HO solution and different quaternary phosphonium salts (QPSs) combined with the phosphotungstic heteropolyacid (HPA) HPWO in a biphasic system. The effect of the molar ratio of HO:C=C on the epoxidation of FAMEs was investigated. The effect of the molar ratio of HO:C=C on the epoxy number (EN) and iodine number (IN) was measured. Multiple regression analysis methods were used to determine the regression model describing the influence of the various independent variables. In the results obtained, it was found that the highest yields were obtained for [P6][Phosf]. The optimum conditions for the epoxidation process with the systems used were a time range of 30 ± 4 min and a HO/double bond molar ratio in the range of 1.8 ± 0.2. The formation of epoxidised fatty acid methyl esters (E-FAMEs) was confirmed by FT-IR, H NMR and C NMR analyses. In the FT-IR spectrum of the E-FAMEs, epoxy ring vibration signals were identified at 826 cm. In the H NMR spectrum, signals appeared in the range of 3.25-3.00 ppm, corresponding to epoxy ring formation in biodiesel, and in the range of 60-55 ppm in the C NMR spectrum.