Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 22, 1996
Publication Date: N/A
Interpretive Summary: Methyl esters from soybean oil are attractive as an alternative diesel fuel. However, operability problems develop when the esters are exposed to temps near 0 C (32 F). In contrast, petroleum diesel develops similar problems at temps near -15 C (5 F). This work explores approaches for improving the cold flow properties of methyl esters. Winterization trials greatly reduced the cloud point of methyl esters. Although yields were relatively low, they may be boosted by pre-treating the esters or by enhancing the removal of saturated components. Additives marketed for distillates also improved the pour point of methyl esters. These results showed that mechanisms for wax formation and growth may be similar between distillates and methyl esters. Although treatment of distillate/methyl ester blends did not affect filtrability limits, treatment of neat methyl esters may improve limits by 5-6 C. Nevertheless, this work supports earlier conclusions reporting that approaches seeking to improve cold flow properties of methyl esters should focus on reducing the cloud point.
Technical Abstract: This work explores approaches for improving the cold flow properties of vegetable oil-derived fuels for direct-injection compression-ignition (diesel) engines. Methyl esters from transesterified soybean oil were evaluated as a neat fuel and in blends with petroleum middle distillates. Winterization showed that the cloud point (CP) of methyl soyate may be reduced to -16 C. Twelve cold flow additives distillates were tested by standard methods including CP, pour point (PP), kinematic viscosity, cold filter plugging point (CFPP) and low-temp flow test (LTFT). Additive-treatment significantly improved the PP of the blends; however, additives did not greatly affect CP or viscosity. Both CFPP and LTFT were nearly linear functions of CP, a result that compares well with earlier studies with untreated distillate/methyl ester blends. Furthermore, additive-treatment can reduce LTFT of neat methyl esters by 5-6 C. Finally, this work supports earlier observations on how cold flow properties of methyl esters may be improved; that is, effective approaches should be initially focus on reducing CP.