A Highly Effective Antioxidant and Artificial Marker for Biodiesel

Biodiesel is composed of saturated and unsaturated methyl esters of fatty acids formed via transesterification of vegetable oil or animal fat. This chemical nature makes biodiesel much more susceptible to oxidation or autoxidation during long-term storage than conventional petrodiesel. Increasing resistance to oxidation therefore requires the use of antioxidants. This paper investigates the effectiveness of the N,N′-di-sec-butyl-p-phenylenediamine (1) as a antioxidant to improve the oxidative stability of soybean, sunflower and canola biodiesel. Results indicate that the induction period for oxidation of soybean and canola biodiesel is significantly improved with the addition of only 0.2 ppm of the 1, reaching the oxidative stability specification (6 h by the Rancimat test). For sunflower biodiesel, 2.0 ppm of the 1 was necessary. This additive is also shown to be efficiently detected by the easy ambient sonic-spray ionization mass spectrometry technique, indicating that 1 and its analogues and derivatives could also be used as versatile artificial markers of biodiesel.