Cold-Flow Properties of Soybean Oil Fatty Acid Monoalkyl Ester Admixtures

Biodiesel is an alternative fuel. made from transesterification of vegetable oil or animal fat with an alcohol, that has many attractive fuel characteristics. However, biodiesel is more prone than petrodiesel to start-up and operability problems during cold weather. The present Study investigates the effects on cold-flow properties of biodiesel resulting from the mixture of soybean oil fatty acid methyl esters (SMEs) With fatty acid esters derived front transesterification of soybean oil with medium- and branched-chain alkyl alcohols. Admixtures of SMEs with 0-100 vol %, tallow fatty acid methyl esters and with n-propyl (SnPrE), isopropyl (SiPrE), n-butyl (SnBuE), isobutyl (SiBuE), and 2-butyl soyates (S2BuE) were analyzed for cloud and pour point (CP and PP). CP and apparent solidification point (SP = PP - 1) data were employed to construct temperature-composition phase diagrams for each admixture in SME. Soyates with branched-chain alkyl headgroup moieties were more effective in decreasing CP and PP (or SP) than those with straight-chain headgroups, compared to an unmixed SME. An admixture of 65 vol % SiPrE in SME decreased CP by more than 5 degrees C compared to an unmixed SME. In contrast, the same admixture with SnPrE decreased CP by only 1.9 degrees C. Furthermore, an admixture of 65 vol %; SnBuE in SME decreased CP by only 2.6 degrees C despite having an alkyl headgroup with a larger molecular weight than SiPrE. Analogous results were obtained from subambient differential scanning calorimetry analysis performed on mixtures of pure monoalkyl stearates in a methyl oleate solvent.