Development of a biofuel blend using soybean methyl ester as the amphiphile in an ethanol-biodiesel-diesel microemulsion: EB-diesel

The oxygenation capability of ethanol-diesel fuel blends referred to as e-diesel significantly reduces particulate matter and reduces toxic gases like CO and NO_x during combustion. However, a major drawback with e-diesel is that ethanol is immiscible in diesel over a wide range of temperatures. In this study, the use of soybean based biodiesel (soybean methyl esters) as an amphiphile to form a stable ethanol-biodiesel-diesel microemulsion was investigated. Ternary phase diagrams were developed to represent the phase behavior of the ethanol-biodiesel-diesel pseudo three-component system. Effects of different components and physical properties of selected blends also were studied. The instantaneous phase behavior indicated that stable microemulsions are formed over a wide area in the phase triangle, revealing that biodiesel could be successfully used as an amphiphile in an ethanol-biodiesel-diesel (EB-diesel) fuel blend. In order to formulate a stable microemulsion, the ratio of biodiesel to ethanol in the system should be greater than one. Studies revealed that the blend concentration that had the highest stability to low temperatures and moisture was ethanol: biodiesel: diesel = 3.75%:25%:71.25% and 4.00%:20%:76.00% with low sulfur (0.05%) diesel reference fuel and ultra low sulfur (1.2 ppm) diesel fuel as the diesel component in the blends respectively. Analyses of fuel properties of the selected blends suggested that for both diesel fuel types, the blend energy contents were not significantly different when compared to their pure diesel forms. When #2 low sulfur diesel was used in the ethanol-biodiesel-diesel blend, the lubricity of this EB-diesel was 2.3 times better with a sulfur content reduction of 34% when compared to #2 low sulfur reference diesel fuel. When #2 ultra low sulfur diesel fuel was used in the blend, the lubricity was over four times better than reference ultra low sulfur diesel fuel. However, the blend sulfur content increased from 1.2 ppm to 18 ppm. The cetane numbers and flash points of the EB-diesel blends with both diesel types were reduced slightly in comparison to their pure forms.