Comparative Analysis on the Epoxidation of Soybean Oil using Formic and Acetic Acids

Abstract

The objective of this study was to make a comparative analysis of the effect of formic and acetic acids as oxygen carriers on the epoxidation of soybean oil used with hydrogen peroxide as the oxygen donor. Comparative analysis between the use of formic acid (FA) and acetic acid (AA) was studied to obtain the most effective oxygen carrier that yielded high oxirane oxygen contents (OOC). The epoxidation reaction was carried out using a stoichiometric ratio of 1:0.5:1, 1:0.5:0.5, and 1:0.5:2 of soybean oil: formic/acetic acid: hydrogen peroxide. The synthesis was performed at three reaction times (2, 4 and 6 h) at a constant temperature of 50°C. Samples prepared using FA and AA were characterized using ASTM D1652-11 and confirmed by Fourier transform infrared (FTIR) spectroscopy. The result of this study proved FA to be an effective oxygen carrier compared to that of AA based on the high OOC and percent yield achieved. The optimum epoxidized soybean oil (ESO) sample using FA was obtained at a reaction time of 6 h using 2 moles of H2O2, yielding an OOC of 7.45 at a relative conversion to oxirane of 98%. Samples of FA were further characterized to prove the optimum parameters that gave the highest OOC using rheology and gel permeation chromatography (GPC). Rheology data revealed an increase in the viscosity that implied an increase in the degree of epoxidation. GPC indicated an increase in the molecular weight at low reaction times, then a decrease resulting in a change in the structure of the triglyceride and consequently an increase in the extent of epoxidation.