Cuphea Oil as Source of Biodiesel with Improved Fuel Properties Caused by High Content of Methyl Decanoate†

Biodiesel, defined as the monoalkyl esters of vegetable oils and animal fats, is an alternative to conventional petroleum-based diesel fuel. Biodiesel has been prepared from numerous common vegetable oils or fats as well as new or less common feedstocks. Major issues facing biodiesel include several technical aspects such as cold flow and oxidative stability as well as availability of sufficient quantities of fuel. Solutions to the technical problems include the use of additives or modifying the fatty ester composition of biodiesel. While esters of oleic acid possess good fuel properties, esters of other fatty acids also exhibit advantageous fuel properties, even surpassing those of oleic acid esters. Decanoic acid has been shown to be an acid whose esters possess good fuel properties. In this work, a vegetable oil containing a high amount (approximately 65%) of decanoic acid, one of the many known varieties of cuphea oil (PSR 23; a cross of Cuphea Viscosissima × C. lanceolata), is reported for the first time as potential biodiesel feedstock. The methyl esters of cuphea oil (biodiesel) were prepared by conventional transesterification, and the 1H NMR spectrum of cuphea methyl esters is reported. The significant fuel properties influenced by fatty ester composition such as cetane number, kinematic viscosity, cold flow, as well as lubricity were determined and evaluated in comparison to biodiesel fuel standards. Cuphea methyl esters generally display more favorable fuel properties than do biodiesel fuels derived from other feedstocks due to the high content of methyl decanoate and as expressed by a cloud point around -9 to -10 °C. Although cuphea oil faces significant technical issues regarding its commercial availability, it appears to be a good potential feedstock for biodiesel and can serve as a model for other potential feedstocks with high decanoic acid content.