The Epoxidation of Walnut Oil (WNO) and the Analysis on the Epoxidized Oil with the Fourier Transform Infrared Spectroscopy

Abstract

Growing interest in renewable feedstocks has encouraged the chemical modification of vegetable oils for potential use in polymeric materials. Walnut oil contains unsaturated fatty acids that provide reactive carbon–carbon double bonds suitable for epoxidation. This report describes the epoxidation of walnut oil (WNO) and the analysis of the oil using Fourier transform infrared spectroscopy (FTIR). Walnut oil, containing 61–70% lipid, 13–19% protein, 18.2% linoleic acid, and small amounts of carbohydrate, fibre, and moisture, was epoxidised using hydrogen peroxide as the oxygen donor. The oil was extracted from walnut using a Soxhlet apparatus with hexane as the solvent. The formation and presence of the epoxy or oxirane group in the epoxidised oil were confirmed by the characteristic C–O absorption of the epoxy group at 1244 cm−1. This absorption was absent from the spectrum of the unepoxidised oil. Moreover, the reduced intensity of the C–H absorption bands between 2920 cm−1 and 2850 cm−1 in the spectrum of the epoxidised oil, compared with that of the unepoxidised oil, can be attributed to a reduction in the concentration of these bonds as epoxides formed. The reaction conducted under ambient laboratory conditions showed a broad O–H band between 3423 cm−1 and 3352 cm−1, indicating hydroxylation of some oxirane rings. The highest reported value for the walnut oil (WNO) product was 32.4% (wt). Factories producing basic chemicals such as hydrogen peroxide and acetic acid should be established in Nigeria to make these chemicals available at affordable prices.