Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Other
Publication Acceptance Date: 7/29/2003
Publication Date: 10/20/2003
Citation: Dunn, R.O., Knothe, G.H. 2003. Oxidative stability of biodiesel/jet fuel blends by oil stability index (osi) analysis. Journal of the American Oil Chemists' Society. 80(10):1047-1048. Interpretive Summary: Soy biodiesel (methyl soyate) as a renewable alternative fuel extender has potential in aviation fuel applications. During long-term storage, biodiesel readily reacts with oxygen present in ambient air and degrades. Extensive degradation can cause fuel operability and emissions problems. This study shows that measurement of the oil stability index (OSI), a standard parameter utilized by the fats and oils industry, is suitable for determining the relative resistance to oxidation of biodiesel in blends with jet fuel (JP-8) for up to 30 volume percent soy biodiesel. Block temperatures of 60 degrees Celsius for neat methyl soyate and 90 degrees Celsius for the methyl soyate/JP-8 fuel blends with up to 30 volume percent biodiesel were recommended for timely determination of OSI. This work is important because it 1) shows that OSI is suitable for measuring the relative resistance to oxidation of biodiesel in blends with jet fuel; 2) sets experimental conditions for measuring OSI of methyl soyate/JP-8 fuel blends; and 3) introduces a simple mathematical model for estimating relative resistance to oxidation. Results from this work will also directly benefit scientists and engineers seeking to define fuel property issues when designing aircraft engine performance and emissions tests for biodiesel/jet fuel blends.
Technical Abstract: Biodiesel, an alternative fuel made by transesterification of vegetable oil with methanol, is becoming more readily available for use in blends with conventional diesel fuel for transportation and other "off-road" applications. One such off-road application is in blends with aviation fuels to improve performance and reduce ground level emissions. Recently, concern among fuel suppliers and terminal operators has focused on effects of long-term storage on fuel quality of biodiesel and its blends with conventional fuels. This work investigates the oxidative stability of biodiesel made from soybean oil (SME) in blends with jet fuel (JP-8). Oil stability index (OSI) data were measured isothermally at 50, 60, 75, and 90 deg C for neat SME and 10, 20, and 30 vol% blends of SME in JP-8 fuel. Results showed that increasing temperature or SMW blend ratio decreases OSI. In accordance with timely acquisition of reliable OSI results, maximum temperatures were 60 deg C for neat SME and 90 deg C for 20-30 vol% blends. For 10 vol% blends, a minimum T = 90 deg C is recommended. Finally, slopes of regression lines from plotting ln (OSI) versus T for neat SME as well as the 20 and 30 vol% blends compared well with results from similar studies of fatty derivatives.