Fractionation of biodiesel by urea inclusion to improve its cold flow properties and provide feedstocks for chemicals/polymers production

Abstract

Biodiesel is viewed as the alternative to petroleum diesel, but its poor cold flow properties constrained its utilization. Cloud point, the onset temperature of thermal crystallization, is one standard for evaluating cold flow properties. The saturated components significantly influence cloud point, and fractionation of biodiesel to remove saturated components effectively reduces the cloud point. Distillation and thermal crystallization are the fractionation based on the phase equilibrium and own the disadvantages of low yields and slow production rate. This work describes a unique method to fractionate FAME at room range temperatures by forming solid urea inclusion compounds (UIC). Urea inclusion fractionation provides a way to reduce the cloud point of mixtures of FAME by preferentially removing high melting-point linear saturated FAME components. Since soybean oil is the primary feedstock for biodiesel in the United States, the effects of the mass ratio of urea to FAMEs, the mass ratio of methanol to FAMEs, and the type of solvents on urea inclusion fractionation were carried out on FAMEs from soybean oil in urea inclusion fractionation. In addition, FAMEs from other sources were used to test the feasibility of urea inclusion fractionation on the cold flow properties. According to the experiments, the cloud point of biodiesel from soybean oil after urea fractionation could be as low as -52 °C. The separation efficiency and selectivity were measured according to the driving force in urea inclusion fractionation. Compared to distillation and thermal fractionation, urea inclusion fractionation could reach high yields and good cold flow properties.