Blending effects of biodiesels on oxidation stability and low temperature flow properties.

To improve the oxidation stability and the low temperature flow properties of a biodiesel mixture, the dependence of the oxidation stability and the cold filter plugging point (CFPP) on the fatty acid compositions was examined. Three different kinds of biodiesels, palm, rapeseed, and soybean biodiesels, were blended with the different weight ratios. The oxidation stability and the CFPP of the blended biodiesels had a close relationship with the compositions of the major fatty acid components. The oxidation stability of the blended biodiesels decreased as the total contents of the linoleic and linolenic acids increased. The correlation was obtained as Y=117.9295/X+2.5905 (0<X<100) where X is the content of the linoleic and linolenic acids (wt%) and Y is the oxidation stability (h). The CFPP decreased with the increase of the total unsaturated fatty acid contents. The correlation was obtained as Y=-0.4880X+36.0548 (0<X<or=88) and Y=-2.7043X+232.0036 (88<X<100) where X is the content of the unsaturated fatty acid (wt%) and Y is the CFPP (degrees C). If the compositions of the blended biodiesels are determined, it is possible to predict their oxidation stability and CFPP. Using the above three correlations, the blending ratios of biodiesel mixture having the specified properties can be determined.