Effect of Metals in the Oxidation Stability and Lubricity of Biodiesel Fuel

The introduction to the European market of higher levels of biodiesel blends focuses the research interest on the compatibility problems of the diesel fuel distribution system. The influence of metals in the oxidation stability and lubricity of two different types of commercially available FAMEs (without antioxidant additive) was investigated. Zinc (Zn), Copper (Cu) and Tin (Sn), were added in the form of solid metals (heterogeneous catalysis in liquid phase oxidation) and examined for their impact on the oxidation stability of biodiesel fuel. Oxidation stability was determined by Rancimat accelerated oxidation method, according to European Standard EN14214. Additionally, in order to examine the effect of the above mentioned metals in the presence of antioxidant additive, BHT was added in both biodiesel samples and oxidation stability determinations were carried out, as well. Alterations in the lubricating properties of the oxidized biodiesel were determined by the lubricity test according to High Frequency Reciprocating Rig (HFRR) standard method. The oxidized biodiesel samples were blended with Ultra Low Sulfur Diesel (ULSD) at a concentration of 5% v/v in order to investigate the lubricating properties of the final blends.