Study on cold flow properties of typical materials biodiesel and its blends

The chemical compositions of biodiesel are analyzed by gas chromatograph-mass spectrometer (GC-MS), and theirs molecular structure are investigated on the basis of the hybrid orbital theory. Cold filter plugging point (CFPP) of biodiesel is studied by CFPP tester, the solution crystallization theory and the similarity-intermiscibility principle. Good correlation models are proposed for prediction biodiesel CFPP by chemical compositions and CFPP of biodiesel-petrodiesel blends by biodiesel ratio. The study shows that biodiesel is mainly composed of SFAME (C-14:0-C-24:0) and UFAME (C-16.1-C-22.1, C-18.2 and C-18:3). Carbon atoms of the alkyl for SFAME arrange in a zigzag pattern by angle CCC=109.5 degrees. C-C carbon atoms of the alkyl arrange in a zigzag pattern by angle CCC=109.5 degrees, too, carbon chain is curved by C=C in angle CCC=122.0 degrees, and curved degree increases with increasing unsaturated degree. CFPP of biodiesel is mainly determined by chemical compositions. CFPP increases with the amount and carbon chain length of SFAME. CFPP of biodiesel-petrodiesel blends is mainly determined by chemical compositions and ratio of biodiesel. To lower SFAME(C >= 20) biodiesel, such as PME, CSME, WME, SBME and RME, it blending with -10PD can formed a eutectic mixture. CFPP of the eutectic mixture is -12 degrees C. The biodiesel ratio for the lowest CFPP rang increases with decreasing SFAME. Such as, SFAME contents in PME, CSME, WME, SBME and RME are 35.86, 32.12, 31.04, 18.29 and 14.69 w% respectively,. and the range of biodiesel ratio is 5-20, 10-20, 20-30, 30-50 and 40-60 v% respectively. To higher SFAME(C >= 20) biodiesel, such as PNME, CFPP increases with PNME ratio.