黄连木生物柴油及其低温流动性能研究

Biodiesel derived from Pistacia chinensis and its low-temperature fluidity.

经分析,黄连木种子含油率49.3%,种子油酸值为每克油含41.04 mg KOH,含有较高的游离脂肪酸。种子油中脂肪酸组成主要为棕榈酸、亚油酸和油酸,其中主要不饱和脂肪酸含量高达82.4%。由于游离脂肪酸含量高,黄连木种子油采用酸碱催化剂分步甲酯化制备生物柴油。HPLC分析表明:第一步H2SO4催化反应主要转化游离脂肪酸,第二步碱催化通过酯交换完全转化为脂肪酸甲酯和甘油。黄连木生物柴油的燃油性能指标符合美国ASTMD6751-02生物柴油标准,表明黄连木是生产生物柴油的理想木本油料。研究评价了3种柴油降凝剂和乙醇对生物柴油低温流动性的影响,其中BJN-B降凝剂和乙醇能够有效降低黄连木生物柴油的凝点、倾点和冷滤点,加入1.40%BJN-B时能将黄连木生物柴油的冷滤点降低6℃。通过光学显微镜观察了不同实验条件下生物柴油的结晶情况,结果表明BJN-B降凝剂能够有效抑制晶体变大,并且分散晶体,从而改善生物柴油的低温流动性。

Pistacia chinensis seeds have an oil content of 49.3%,and the acid value of the seed oil is 41.04?mg KOH?g with a high content of free fatty acids.The seed oil is composed mainly of hexadecanoic acid,linoleic acid and 9-octadecenoic acid,in which the content of major unsaturated fatty acids accounts for 82.4%.Biodiesel was prepared in two steps from P.chinensis seed oil due to the high content of free fatty acids: firstly by an acid-catalyzed esterification and then by an base-catalyzed methanolysis.HPLC analyses showed that the first step(H_2SO_4 catalysis) converted free fatty acids into fatty acid methyl esters,and the second step(alkaline catalysis) converted the products of the first step into fatty acid methyl esters and glycerol.The fuel properties of obtained P.chinensis biodiesel accorded with the American standard ASTMD 6751-02,indicating that P.chinensis is an ideal raw material for production of biodiesel.Then effects of three pour point depressants and ethanol on the lowtemperature fluidity of P.chinensis biodiesel were evaluated.It was found that depressant BJN-B and ethanol could lower effectively the solidifying point,pour point and cold filter plugging point of the biodiesel,and an addition of 1.40% BJN-B could reduce the cold filter plugging point by about 6℃.Diesel crystallization under different conditions was observed under a light microscope,and the result indicated the BNJ-B depressant could inhibit effectively the magnification of crystals,disperse crystals,and thus improve the low-temperature fluidity of the bio-diesel.