Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 25, 1995
Publication Date: N/A
Interpretive Summary: Esters made from triglycerides such as soybean oil or animal tallow may be utilized as fuels or extenders for combustion in direct-injection compresssion ignition (diesel) type engines. This work examines problems relating to fuel flow and operability developed during periods of cooler ambient temperatures. Experimental studies were conducted to establish the severity of potential flow problems and to establish a foundation for performing laboratory-scale research and development of approaches for improving low-temperature operability. These studies include cloud point, pour point, low-temperature filterability and viscosity measurements. This work shows that esters may develop flow problems at temperatures in the range 12-15C (20-25F) warmer than unblended distillates. Esters can only be blended with distillates in relatively small volumes (20 to 30 vol% maximum) before the properties are compromised. Evidence suggests that an empirical correlation exists between cloud points and expected minimum operability temperatures. This finding is significant because it suggests that approaches to improving low-temperature operability of esters should primarily focus on lowering their cloud points, even when the esters are blended with distillates.
Technical Abstract: This work examines low-temperature properties of triglyceride oil- derived alternate fuels for direct-injection compression-ignition engines. Methyl esters from transesterified soybean oil were investigated both in neat form and blended with either No. 1 or No. 2 diesel fuel. Some mixed methyl ester formulations were studied by adding 5-30 vol% tallowate to the soyate. Pour points, cloud points and kinematic viscosities were measured. Viscosities were also measured at cooler temperatures to evaluate effects of sustained exposure. Low- temperature filterability studies were conducted according to the following two standard methods: the North American standard, the low- temperature flow test (LTFT); and its European equivalent, the cold filter plugging point (CFPP). Relative to cold-flow properties of methyl esters, blending them with middle distillates is limited to relatively small ester-contents before the properties become preclusive. Under most conditions, cold-flow properties relative to soyate esters were not greatly affected by mixing them with up to 30 vol% tallowate (before blending). Formulations studied in this work showed a good correlation between LTFT-results and cloud points. This result may prove crucial in efforts to improve low-temperature flow properties of alternate diesel fuels containing fatty methyl esters from triglyceride oils.