Feasibility of additive winterization of biodiesel fuel derived from various eatable oils and fat

Abstract

For simple removal of saturated fatty acid methyl esters (FAMEs) from a FAME mixture, our previous research described winterization using sorbitan palmitate without agitation. However, limited information exists on additive winterization of real oil biodiesels and their separation performance. We demonstrated the additive winterization of biodiesel fuel derived from commercial eatable oils and fat (palm, lard, cottonseed, rice, and soybean). Five biodiesel fuels were prepared through a transesterification reaction under alkali conditions. The biodiesel-additive mixtures were air-cooled over 48 h at a temperature equal to or several degrees lower than the cloud point (CP) of the biodiesel without agitation. The palm biodiesel showed a marked similarity to a simulated FAME mixture, and was separated into saturated FAME-rich solid fuel and unsaturated FAME-rich liquid fuel. The CP of the recovered liquid decreased by 6–10.5 °C, and the separation factors were between 2.4 and 7.7. The kinetic viscosity of the resultant liquid increased slightly because of the oleate fraction but was in the range of the biodiesel standard. These results indicate that additive winterization is useful for the separation and purification of biodiesel. Because the separation factor of the lard biodiesel winterization using sorbitan palmitate decreased (1.3–1.9), the separation improver retains scope for improvement under high stearate conditions. The relatively lower saturated FAME biodiesels (cottonseed, rice, and soybean) were predisposed to form a slurry during the winterization. However, the CP of the recovery liquid decreased 2–5 °C from the initial biodiesels. The separation factor and liquid recovery rate will increase with the use of a proper mechanical separation method such as filtration.