Evaluation of the star anise extract as a natural cold flow improver for enhancing the cold flow properties of diesel fuel

High-proportioned normal-alkanes in diesel are liable to crystallize and gel in cold climates, which considering as the major reasons for the poor cold flow properties (CFPs) of diesel. In this study, trans anethole (TA) was successful extracted from the naturally renewable substance of star anise, and first used to polymerize with alkyl methacrylate (C14MC) in different ratios. So, a novel kind of natural cold flow improvers (CFIs) of alkyl methacrylate-trans anethole copolymers (C14MC-TA) were prepared to enhance the CFPs of diesel. The depressing effects of these CFIs on cold filter plugging point (CFPP) and solid point (SP) of diesel were explored and discussed in-depth. The investigation concludes that the natural C14MC-TA as a CFI exerted positive effects on enhancing the CFPs of diesel. As the molar ratio of C14MC and TA was 1:1, C14MC-TA achieved the best optimal depressing effect at 2000 ppm dosage, and the reductions of CFPP and SP were up to 14 degrees C and 22 degrees C, respectively. The depressing mechanism of the natural CFIs were also discussed by polarizing optical microscope, differential scanning calorimeter, rheological analysis and X-ray diffractometer.