The effect of fatty acid composition on biodiesel oxidative stability

Concerning their environmental impact, native based fuels and lubricants show immense potential. In fact, these products are highly exposed to oxidative processes during storage or application [1, 2]. One way to raise oxidative stabilities is the addition of synthetic antioxidants. Another way may be the modification of the fatty acid composition, since polyunsaturated fatty acids show a much higher proneness to autoxidation. In order to decrease the content of polyunsaturated and to raise the content of saturated components, experiments for fractional distillation and crystallisation as well as for hydrogenation of fatty acid methyl esters have been carried out. In distillation experiments with separation columns the methyl esters performed good separation of the lower-boiling esters with a chain-length up to 16C-atoms, from the C-18 fraction, causing a degree of saturation up to 75 wt-% in the distillate. In tests with fractional crystallisation, the rate of saturation could be raised up to 92.8 wt-%. Using the process of catalytic hydrogenation, a rate of saturation up to 100 wt-% could be achieved, depending on the duration of the hydrogenation process. By partial hydrogenation of the polyunsaturated components, products with high oxidation stability and low pour point could be produced within relatively short hydrogenation time.