Abstract:
Biodiesel has become one of the comparatively ideal partial alternative fuels for diesel engines because of its environmental benefits and the fact that it is a product made from renewable resources. However the less favorable cold flow properties or the low temperature operability of biodiesel fuel compared to conventional diesel is a major drawback limiting its use. The poor flow properties of biodiesel at cold temperatures are mainly due to fatty acid methyl ester composition. In order to quantify the relation between biodiesel composition and its cold filter plugging point (CFPP), fatty acid methyl ester composition, CFPP, and the influence of composition on CFPP were analyzed by gas chromatography-mass spectrometry and a cold filter plugging point test method. Correlation between fatty acid methyl ester composition and CFPP was studied with multivariate linear regression. The study shows that biodiesel is mainly fatty acid methyl ester (FAME) that is composed of 14-24 even number carbon atoms. Saturated fatty acid methyl esters (SFAMEs) are mainly C14:0~C24:0 and unsaturated fatty acid methyl ester (UFAMEs) are mainly C16:1~C22:1, C18:2~C20:2 and C18:3. The cold flow property of biodiesel is mainly determined by the content and distribution of FAME. The CFPP increases linearly with increasing SFAME, and the longer the carbon chains are, the greater the increase will be. In addition, CFPP decreases linearly with the increasing unsaturated fatty acid methyl esters (UFAME), and the higher the degree of unsaturation, the greater the decrease. Among the 120 kinds of biodiesel we studied, the CFPP of sapium sebiferum methyl ester (SSME) was the lowest (-14℃) and the CFPP of peanut methyl ester (PNME) was the highest (13℃).