Keywords: Oleyl oleate; wax ester; respond surface methodology (RSM); Fourier transform infrared (FT-IR); nuclear magnetic resonance (NMR)

Abstract

Oleyl oleate, a liquid wax ester, was successfully synthesized via an esterification reaction between oleyl alcohol and oleic acid. Furthermore, the effects of essential reaction parameters on enhancing oleyl oleate formation were investigated. The reaction was optimized using the statistical approach of response surface methodology (RSM), relying on a 5-level, 4-variable central composite rotatable design (CCRD). This allowed for the evaluation of the interactive influence with regard to essential parameters in small-scale processing. The parameters studied included the reaction temperature, reaction time, molar ratios of the substrate (oleic acid:oleyl alcohol), and agitation speed, and the responses were oleyl oleate conversion. The maximum yield of 96.00% was accomplished with 3 hours 30 minutes reaction time, 53.9°C temperature, 172.9 rpm agitation speed, and a molar ratio of 2:24. The comparison between the anticipated and observed values demonstrated a strong alignment, suggesting that the empirical models formulated from RSM effectively capture the relationship between the factors as well as the outcome in the production process of oleyl oleate. Furthermore, the product was verified using spectroscopy methods, specifically Fourier transform infrared (FT-IR) as well as nuclear magnetic resonance (NMR). The absorption peak at 1712.18 cm-1 in the FT-IR spectrum demonstrated the characteristic ester carbonyl absorption in oleyl oleate. In addition, a peak at 173.2 ppm in the 13C-NMR spectrum confirmed the presence of an ester group, further confirming the identity of the product.