Impact of some common impurities on biodiesel cloud point

Commercial biodiesel is allowed to contain some impurities, such as free and bound glycerin, residual alcohol, soap and moisture within a limit specified in ASTM D6751. Compared to conventional diesel fuel, biodiesel has an unfavorable cold flow property. Cold flow properties of biodiesel depend both on fatty acid profile and, amount and types of impurities. This study reports the impact of biodiesel impurities on its cloud point. Commonly used biodiesel (methyl and ethyl esters of canola and soybean) and their blends were considered for viscosity, soap content, free and total glycerin, moisture content, and alcohol content test. The tests indicated that the blend level has the major impact on CP of the biodiesel. The presence of higher level of total glycerol in soy esters significantly increased CP (R ² ≈ 0.93), but no strong relation was observed for canola esters. The combined effect of total glycerol and moisture level improved the regression coefficients for all feedstock, but 95% confidence interval for moisture showed that the impact of moisture was negligible. The completeness of the transesterification reaction is essential to keep the total glycerol level low and to lower CP of the biodiesel. The impact of other impurities under study did not have significant effect on the biodiesel CP.