摘要
本文研究了生物柴油组成结构对生物柴油的性能的影响,结果显示：高熔点的饱和脂肪酸甲酯是影响生物柴油低温流动性能的主要因素,饱和脂肪酸异丙酯化后能够有效地降低熔点,棕榈酸异丙酯、硬脂酸异丙酯的熔点较棕榈酸甲酯、硬脂酸甲酯分别降低了17.74℃、17.72℃；脂肪酸碳链越长,热值越大,然而脂肪酸不饱和程度、烷基醇结构对饱和脂肪酸酯的热值影响不大。
通过对生物柴油的结构的调整来改进它的低温流动性能,具体方法为：先通过尿素包合法分离游离脂肪酸,并使用正交试验优化尿素包合条件,对尿素包合法分离得到的富含饱和脂肪酸的部分进行异丙酯化处理,富含不饱和脂肪酸的部分进行甲酯化处理。结果显示：脂肪酸甲酯异丙酯形成的混合酯的冷滤点为2℃,较对照产品纯脂肪酸甲酯降低了8℃。
本文通过筛选优化低温流动改进剂、掺混法和尿素包合法这三种方法来改进以地沟油为原料生产的生物柴油的低温流动性能,结果显示：1、改进效果最好的低温流动改进剂是灵智5003,在添加量为0.75%时,能够使生物柴油的冷滤点由原来的3℃降低至-2℃；2、部分掺混0#柴油或航空煤油能够有效地降低生物柴油的冷滤点,当0#柴油或航空煤油的掺混比例达到80%时,混合油的冷滤点分别降至-9℃、-16℃,并且,添加适量的低温流动改进剂,混合油的冷滤点能够进一步地降低；3、尿素包合法的最佳条件为：生物柴油：尿素：甲醇(W/W/V)=1：1：5,搅拌时间：50min,搅拌温度：50℃,包合温度20℃,包合时间：2h。得到的富含不饱和脂肪酸甲酯的部分的收率为47.4%,该部分不饱和脂肪酸甲酯含量由原来的73.6%提高到87%。性能改进的生物柴油的冷滤点为-7℃,降低了10℃。实验证明：乙醇可以作为替代溶剂替代甲醇进行尿素包合,再次利用的尿素的使用效果不好。
为了将酶催化后的脂肪酸甲酯含量约为85%的粗甲酯产品用于锅炉和工业用炉等设备,通过部分掺混废机油、碳九(C9)进行调制,结果显示：掺混后的混合燃料油的理化性能很接近锅炉和工业用炉设备的燃料油,可见85%粗甲酯作为锅炉和工业用炉设备的燃料油的替代物还是很有潜力的。
In this paper, we studied the influence of the structures of biodiesel to it's properties. Results showed that the high-melting-point saturated fatty acid methyl esters were the main factors to influence the low temperature flow properties. To change saturated fatty acid methyl esters to saturated fatty acid isopropyl esters could reduce their melting points effectively. The melting points of isopropyl palmitate and isopropyl stearate, compare to the melting points of corresponding methyl palmitate and methyl stearate, had a decrease of 17.74℃and 17.72℃, respectively; The longer carbon chain of the fatty acids had the greater heat value. The degree of unsaturated fatty acids and the alkyl alcohols moieties had little effect on the heat value of saturated fatty acid esters.
To improve the low temperature flow properties of biodiesel, we changed the structures of biodiesel. Firstly, we separated free fatty acids via urea complexation, optimizing the conditions through the orthogonal test. Then we esterified two parts of the fatty acid mixture with methanol and isopropanol respectively. After the cold filter plugging point(CFPP) tests, the results demonstrated that the mixed esters'CFPP was 2℃, a decrease of 8℃, compare to conventional fatty acid methyl ester's (10℃).
In this paper, we improved the low temperature flow properties of biodiesel made from waste cooking oil through optimizing flow improvers, mixing method and the method of urea complexation. Results showed that the best flow improver was LingZhi 5003. When adding the optimum dosage 0.75%, the CFPP of biodiesel could drop to-2℃from 3℃; With the 0# diesel or jet fuel blending ratio increasing, the CFPP of the mixed oil showed a gradual decline. When the 0# diesel or jet fuel blending ratio reached 80%, the CFPPs of mixed oil were reduced to -9℃,-16℃respectively. And adding the right amount of cold flow improvers,the CFPP of mixed oil could be further reduced; The optimum conditions of urea complexation were:biodiesel:urea:methanol(W/W/V)=1:1:5,50min stirring time, 50℃stirring temperature,20℃crystallization temperature, and 2h crystallization time. The yield of non-urea complexes was 47.4%, and the content of the unsaturated fatty acid methyl esters increased to 87% from 73.6%. The CFPP of the treated biodiesel was -7℃, a decrease of 10℃. Ethanol could be the solvent instead of methanol, and the urea of recycling was not effective.
In order to use the after-enzyme-catalyzed crude methyl ester products which the content of fatty acid methyl ester was about 85% to boilers, industrial furnaces and other equipments, we improved their properties through blending waste engine oil and alkane with nine carbon atoms. Results showed that the mixed fuel oil's physical and chemical properties were very close to the boiler and industrial furnace equipment's fuel oil's. It was clear that the crude methyl ester products as a alternative to boiler and industrial furnace equipment's fuel oil was promising.
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