Improveing The Low Temperature Flow Properties Of Biodiesel

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.