生物柴油低温凝固机理探讨

采用气相色谱法研究菜籽油生物柴油、大豆油生物柴油和花生油生物柴油中脂肪酸甲酯的分布和含量；采用多功能低温性能测定仪和旋转粘度计研究生物柴油的低温流动性及粘温性。结果表明，生物柴油低温流动性与其脂肪酸甲酯相对含量关系密切；温度高于生物柴油冷滤点时，其表观粘度与温度关系不大；温度低于生物柴油冷滤点时，其表观粘度随温度降低而增大；随温度降低，生物柴油中析出针状蜡晶，并逐渐聚结形成三维网状结构，将液态的生物柴油吸附于其中，使生物柴油整体上失去流动性。

A PRELIMINARY STUDY OF THE SOLIDIFICATION MECHANISM OF BIODIESEL AT LOW TEMPERATURE

The fatty acid methyl ester compositions of rapeseed biodiesel, soybean biodiesel and peanut biodiesel were determined by gas chromatography. Low temperature fluidity and viscosity-temperature properties of biodiesels were studied by a low-temperature flow tester and a rotatory viscometer. The phase transition of biodiesels was investigated by a differential scanning calorimeter. Polarizing microscope was applied for real-time observing the crystal morphologies of biodiesels at low temperature. The solidification mechanism of biodiesel was discussed. Results indicate that the cold flow properties of biodiesels are related to the compositions of saturated and unsaturated fatty acid methyl esters. The influence of temperature on appearance viscosity is varied, when temperature is higher than the cold filter plugging point (CFPP) of biodiesel, the influence of temperature is not significant, yet when the temperature is lower than CFPP, the appearance viscosity increases with the decrease of temperature. The primary reason for biodiesel to lose fluidity at low temperature might be ascribed to the precipitation of wax crystal and finally, the liquid biodiesel is absorbed by the formed spongy waxy crystal matrix.