Oxidative stability of biodiesel

Although there are numerous publications on the effect of natural and synthetic antioxidants on the stability of oils and fats used as food and feed, until recently relatively little publicly available information was available on the effect of antioxidants on the oxidative stability of biodiesel. One of the earliest studies reporting of the effects of antioxidants on biodiesel was that of Du Plessis et aL (1985), which examined storage stability of sunflower oil methyl esters (SFME) at various temperatures for 90 d. Effects of air temperature, presence of light, addition of TBHQ (see Figure 1.1) and contact with steel were evaluated by analysis of free fatty acid content, PV, kinematic viscosity, anisidine value, and induction period. Addition of TBHQ delayed oxidation of samples stored at moderate temperatures (<30°C). In contrast, under unfavorable (50°C) conditions, TBHQ was ineffective. 

Dunn, R. O. 2006a. Oxidative Stability of Biodiesel by Dynamic Mode Pressurized-Differential Scanning Calorimetry (P-DSC). Trans. ASABE, 49,1633-1641. 

Oxidative stability of biodiesel has been the subject of considerable research. This issue affects biodiesel primarily during extended storage. The effects of parameters, such as the presence of air, heat, traces of metals, antioxidants, peroxides as well as the nature of the storage container, were investigated in the aforementioned studies. Generally, factors, such as presence of air, elevated temperatures or the presence of metals, facilitate oxidation. 

Bondioli. R L. Folegatti. Evaluating the oxidation stability of biodiesel. An experimental contribution. Riv. Ital. Sostanze Grasse 1996, 73, 349—353. 

Dunn, R.O. Oxidative stability of biodiesel by dynamic mode pressurized-differential scanning calorimetry (p-dsc). Trans. ASABE 20XiE, 49, 1633—1641. 

The presence of unsaturated fatty acids in biodiesel makes it susceptible to oxidation or autoxidation during long-term storage. Several studies carried out by assaying different antioxidants to improve the oxidative stability of biodiesel have shown the usefulness of PG for this purpose [48-50],... 

Y. All et al.. Fuel properties of tallow and soybean oil esters. J. Am. Oil Chem. Soc. 72 (1995) P. Bondioli, L. Folegatti, Evaluating the oxidation stability of biodiesel. An experimental contribution. Riv. Ital. Sostanze Grasse 73, 349-353 (1996)... 

The oxidative stability of biodiesel has been the subject of considerable research as it is, besides cold flow, one of the major technical issues with biodiesel. Some recent overview articles are (Knothe, 2007 Dunn, 2008 Jain and Sharma, 2010 Xin and Saka, 2010). This issue affects biodiesel primarily during extended storage. The influence of parameters such as the presence of air, heat, traces of metal, antioxidants, and peroxides as well as the nature of the storage container was investigated in the aforementioned studies. Generally, factors such as the presence of air, elevated temperatures, or the presence of metals facilitate oxidation. Studies performed with the automated Oil Stability Index (OSI) method confirmed the catalyzing effect of metals on oxidation, however, the influence of compound structure of the fatty esters, especially unsaturation, as discussed later, was even greater (Knothe and Dunn, 2(X)3). 

Kivevele, T.T., Mbarawa, M.M., et al., 201 lb. Impact of antioxidant additives on the oxidation stability of biodiesel produced from Croton megalocarpus oil. Fuel Processing Technology 92 (6), 1244-1248. 

---