Abstract

One of the main advantages of biodiesel is the high cetane number that allows for more complete combustion and wider energy release spectrum. To investigate the variation of cetane number with fatty acids profile, transesterification and blending with diesel fuel, the cetane number of cashew nut, egusi melon and rubber seed oils, their biodiesels, 10% (B10) and 20% (B20) blends with diesel fuel were determined analytically by using their distillation characteristics. The fatty acid profile of the three oils, their biodiesels and blends were determined using a chromatography analyzer. The results obtained shows that cetane number increases by an average of 10 to 40% after transesterification and the increase depends on the degree of unsaturation. Egusi melon oil methyl ester the most unsaturated had the lowest cetane number. Blending with diesel decreased cetane number to below that of diesel fuel for all the biodiesels. Highly unsaturated biodiesel tend to have lower cetane number increase after transesterification. They also have higher distillation temperature because they are long chained and have multiple bonds.

Key words: Cashew seed oil, rubber seed oil, melon seed oil, cetane number, fatty acid profile, biodiesel, blends