Oxidation Degradation and Acid Generation in Diesel Fuel Containing 5% FAME

Compared with diesel fuel, FAME is relatively unstable and readily generates acids such as acetic acid and propionic acid. When FAME-blended diesel fuel is used in existing diesel vehicles, it is important to maintain the concentration of FAME-origin acid in the fuel at an appropriately low level to assure vehicle safety. In the present study, the oxidation of diesel fuel containing 5% FAME is investigated. Several kinds of FAMEs were examined, including reagents such as methyl linoleate and methyl linolenate, as well as commercially available products. The level of acid, peroxide, water, and methanol and the pressure of the testing vessel were measured. The result shows that unsaturated FAMEs that have two or more double bonds are unstable. Also, water is generated by oxidation of FAME blended diesel fuel, accelerating corrosion of the terne sheet. The effects of antioxidants and initial acid as well as the existence of metal and methanol as impurities were also examined in some cases. The addition of 20 to 40ppm of antioxidants to the fuel was effective in suppressing the oxidation. When some acids, such as acetic acid, are included in fuel with coexisting metals, oxidation degradation is accelerated.