Properties of palm oil biodiesels derived from different alcohols

The palm oil biodiesels with different ester alkyls were prepared through transesterification of palm oil with methanol, ethanol, isopropanol and isobutanol. The crystallization behavior and cold flow properties of the palm oil biodiesels were characterized by differential scanning calorimeter (DSC) and stress controlled rheometer; the effect of ester alkyl on certain important properties such as the oxidation stability, kinematic viscosity (40℃) and density (20℃) was then investigated. The results suggested that the palm oil biodiesels with larger ester alkyls exhibit lower crystal precipitation temperature and gelation point than those biodiesels with ester methyl; especially, the crystal precipitation temperature and gelation point for the palm oil biodiesel derived from isobutanol reach -2.57 and -8.09℃, respectively. An increase in the length of ester alkyl chain in alcohol moiety can significantly improve the cold flow properties of the palm oil biodiesels, by slightly prolonging the oxidation induction period and enhancing the oxidative stability. The palm oil biodiesels with different ester alkyls are also different in their kinematic viscosity and density; however, all these values can meet the requirement from the biodiesel standard of China.