Study On Low-temperature Flow Properties Of Biodiesel

Biodiesel is an alternative diesel fuel derived from vegetable oils or animal fats. There has been a considerable interest in developing biodiesel as an alternative fuel in recent years, due to its environmental benefits and also because it is derived from renewable resources such as vegetable oils or animal fats. Nevertheless, the use of neat biodiesel is limited by its poor low-temperature flow characteristics. Crystallization of biodiesel components at relatively higher temperature during cold seasons causes fuel starvation and operability problems, as solidified materials clog fuel lines and filters. Adding pour point depressant (PPD) is a effective and available method for improving the low-temperature flow properties of biodiesel. Therefore, study on effect and mechanism of PPD on biodiesel is of great significance for developing new biodiesel PPDs.The major research results are as follows:(1) Soybean methyl esters (SME) was synthesized by transesterification by soybean oil and methanol using NaOH. It was found that the impact of PPD on SME was different with both kind and dosage. The effect of10-320,10-330, Haote1, Haote2were better, producing a descent of cold filter plugging point (CFPP) of3℃and a descent of solidifying point (SP) of9℃.(2) The impact on CFPP of combining two PPDs of above four PPDs was as much as the single PPD. The impact on SP of combining10-320with both Haote1and Haote2was obvious. Adding1%PPD in biodiesel blends, the low-temperature flow properties of biodiesel blends was improved compared with biodiesel. It was also found that adding1%10-320in B60produced a CFPP of-10℃,and adding0.6%10-320in B20produced a SP of-29℃.(3) The mechanism of Haote1PPD on SME was investigated by DSC, low-temperature XRD, polarizing optical microscope. The results show that the starting temperature of the peak (Onset) in curves was stable. The slope of peak was lessening. Solid-liquid phase change energy and the area of peak was lessening. It implies that the process of crystallization was changed. The content of crystal decreased and the system was more stable. The wax crystals appeared almost spherical, dispersed better, not easy to crosslink between wax crystals and reduced the cold filter plugging point (CFPP) and solidification point (SP) of bio-diesel.(4) Tetradecyl methacrylate polymer, hexadecyl methacrylate polymer, octadecyl methacrylate polymer and its anhydride copolymer were synthesized. The structure and extent of polymerization of them were decided by IR. The impact of polymer on SME were not obvious. It may because the molecular weight and distribution of the polymer was not optimum and the impat on SME of molecular weight of PPD is very significant, so further improvements of polymerization conditions are needed.