# A Study of the Catalytic System H3PW12O40/Quaternary Phosphonium Salts for the Epoxidation of Fatty Acid Methyl Esters—The Effect of the Molar Ratio of Hydrogen Peroxide to the Double Bond

## TL;DR

This study explores using a catalytic system to convert fatty acid methyl esters into epoxidized forms, finding optimal conditions for the reaction.

## Contribution

The novel contribution is identifying optimal molar ratios and catalyst combinations for efficient epoxidation of fatty acid methyl esters.

## Key findings

- The highest yields were achieved using [P6][Phosf] as the quaternary phosphonium salt.
- Optimal H2O2/double bond molar ratio was found to be 1.8 ± 0.2 with a reaction time of 30 ± 4 minutes.
- FT-IR and NMR analyses confirmed successful epoxy ring formation in the products.

## Abstract

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 H2O2 solution and different quaternary phosphonium salts (QPSs) combined with the phosphotungstic heteropolyacid (HPA) H3PW12O40 in a biphasic system. The effect of the molar ratio of H2O2:C=C on the epoxidation of FAMEs was investigated. The effect of the molar ratio of H2O2: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 H2O2/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, 1H NMR and 13C NMR analyses. In the FT-IR spectrum of the E-FAMEs, epoxy ring vibration signals were identified at 826 cm−1. In the 1H 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 13C NMR spectrum.