Effect of poly-alpha-olefin pour point depressant on cold flow properties of waste cooking oil biodiesel blends

Improving the flow ability at a low temperature is vital for the utilization and popularization of biodiesel. The cold flow properties of waste cooking oil biodiesel-0# diesel blends with poly-alpha-olefin (PAO) pour point depressants were studied. Here results showed that B20 (20 vol.% biodiesel-80 vol.% diesel) treated with 400 ppm PAO exhibited the best depression in cloud point, cold filter plugging point and pour point by 8 °C, 9 °C and 7 °C, respectively. The other fuel properties of B20 were also determined and compared with the limits indicated in the ASTM D7467 standard. Viscosity-temperature curves, polarized optical microscopy, low-temperature X-ray diffraction, and differential scanning calorimetry were used to explore the performance mechanism of PAO in biodiesel blends; and results presented that PAO could effectively lower the low-temperature viscosity, delay the aggregation of wax crystals and modify their crystallization behavior by transforming the shape of crystals and depressing the formation of large wax crystals.