Submitted to: Annual Meeting and Expo of the American Oil Chemists' Society
Publication Type: Abstract Only
Publication Acceptance Date: May 4, 2003
Publication Date: May 4, 2003
Citation: DUNN, R.O., KNOTHE, G.H. OIL STABILITY INDEX (OSI) STUDIES ON THE OXIDATIVE STABILITY OF BIODIESEL. ANNUAL MEETING AND EXPO OF THE AMERICAN OIL CHEMISTS SOCIETY. 2003. Abstract. pp.80-81. Technical Abstract: Biodiesel made from transesterification of vegetable oil with methanol is rapidly increasing in availability as an alternative fuel in blends with petroleum diesel for "on-road" transportation applications. In 2002, consumption of biodiesel in the United States was projected to increase to 47.5 million liters (12.5 million gal) even though production capacities were estimated to be as high as 230-300 million liters (60-80 million gal). Hence, storage stability with respect to oxidative degradation has become a leading concern for many fuel producers, marketers, and terminal operators. The present work investigates determination of relative oxidative stability of biodiesel made from soybean oil (SME) under accelerated isothermal conditions by measuring the oil stability index (OSI). Mixtures of SME with antioxidants tert-butylhydroquinone (TBHQ) and a-tocopherol were also studied at loadings 200, 500, and 1000 ppm. OSI data (in hours) were measured at block temperatures 50, 60, 75, and 90ºC in accordance with a modified American Oil Chemists' Society method Cd 12b-92. Results indicated first order reaction kinetics were present at lower block temperatures (50-75ºC) for neat SME and higher temperatures (60-90ºC) for SME + TBHQ. First-order kinetics were also present at all four block temperatures for SME + a-tocopherol. This work recommends the following maximum block temperatures for reliable determination of the relative oxidative stability of biodiesel under accelerated isothermal conditions: 1) 60ºC for neat SME or SME + 200 ppm a-tocopherol; 2) 75ºC for SME + 200 ppm TBHQ or SME + 500 or 1000 ppm a-tocopherol; and 3) 90ºC for SME + 500 or 1000 ppm TBHQ.