Storage Stability of FAME Blended Diesel Fuels

The storage stability of diesel fuels containing 5% fatty acid methyl esters (FAMEs) was investigated at normal, high, and low temperatures. Unsaturated FAMEs such as rapeseed methyl ester (RME) or soy methyl ester (SME) oxidized to yield peroxides and acids during high-temperature (100 °C) storage. On the other hand, diesel fuels blended with a saturated FAME such as palm methyl ester (PME) showed stable oxidation performance during high-temperature storage. The cold flow properties of PME-blended diesel fuels, such as cold flow plugging point (CFPP) and pour point, deteriorated during the low-temperature storage; this led to deterioration of the drivability of vehicles using this type of diesel. Furthermore, in the PME-blended diesel fuels, crystals of saturated fatty acid glyceride were formed during normal-temperature storage (10 to 15 °C) above the cloud point (CP) of the fuels. The authors have shown that controlling the amount of saturated glyceride impurities in FAME is important for the suppression of precipitates above the CP during normal-temperature storage.