FTIR studies of thermal stability of the oils and methyl esters from Afzelia africana and Hura crepitans seeds

Fourier Transform Infrared (FTIR) spectroscopy was used to study thermal stability of the oils, methyl esters and esters/diesel blends from Afzelia africana and Hura crepitans seeds in comparison with petroleum diesel. Biodiesels are prone to oxidative degradation due to their chemical nature and the degree of this varies with feedstock. Information on the thermal stability of various potential biodiesel feedstocks is very vital for their application. In this study, the samples were exposed to high temperatures between 28 °C and 300 °C for a residence time of 10 min. Fuel degradation was monitored by tracking changes in peak intensities around 3442 cm−1, 1740 cm−1, and 734 cm−1 corresponding to OH of hydroperoxides, CO of carbonyl compounds and carbon-hydrogen bending out-of-plane of CC respectively. Thermal oxidation commenced at about 150 °C with hydroperoxides formation. CO and CC bonds in the samples were shown to be fairly stable within the exposure time. Hura crepitans showed higher thermal stability than Afzelia africana.