Fuel Properties of Biodiesel/Ultra-Low Sulfur Diesel (ULSD) Blends

Biodiesel is an alternative fuel and fuel extender easily derived from vegetable oil or animal fat. In 2006, the US Environmental Protection Agency mandated that maximum sulfur content of diesel fuels be reduced to 15 ppm to protect catalysts employed in exhaust after-treatment devices. Processing to produce this ultra-low sulfur petrodiesel (ULSD) alters fuel lubricity, density, cold flow, viscosity, and other properties. Consequently, there is a need to develop a better understanding of the basic fuel properties of biodiesel/ULSD blends. This work evaluates the effects of biodiesel volumetric blend ratio (V (BD)) on cloud point (CP), kinematic viscosity (nu), specific gravity (SG), and refractive index (RI) of blends with petrodiesel. Properties measured for various blends of methyl esters of soybean oil (SME) and used cooking oil (UCOME) in ULSD were compared with those for blends with low sulfur (a parts per thousand currency sign500 ppm) petrodiesel fuel (LSD). With respect to increasing V (BD), CP and SG increased and RI decreased with each parameter demonstrating a linear correlation. In contrast, nu showed a curvilinear relationship with respect to increasing V (BD). Calibration curves were derived from regression analyses to determine V (BD) in biodiesel/ULSD blends from measurements of each individual property. While the models had generally high coefficients of regression (R (2) > 0.986), SG models were most accurate for predicting V (BD) to within 1.3 vol%.