Rancimat vs. rapid small scale oxidation test (RSSOT) correlation analysis, based on a comprehensive study of literature

摘要

Due to the fact that modern diesel engines require very well-defined fuel properties to ensure high efficiency, low emissions and a long durability, the fuel properties and their determination methods have to be standardized. Most diesel fuel standards allow a certain volume fraction of biodiesel that can be blended to fossil diesel fuel. Biodiesel consists of saturated and unsaturated fatty acid methyl esters (FAME) which are more susceptible to oxidation compared to fossil diesel fuel. Oxidation products formed by autoxidative processes can lead to higher emissions, a higher corrosiveness, fuel filter blocking, clogging of fuel injectors, the formation of deposits in the entire fuel system and a decreasing lubricity [1]. Therefore, oxidation needs to be prevented by the addition of oxidation inhibitors. These antioxidants are consumed during storage, resulting in partial loss of their efficiency against oxidative stress. After this induction period all antioxidants have been consumed and harmful oxidation products can be formed. For the determination of the long-term storage stability of diesel fuels rapid oxidation stability test methods were developed and defined by standards. In Europe, the most important determination methods are the Rancimat method and the rapid small scale oxidation test (RSSOT). Both methods differ in the construction of the measurement device and various parameters. However, it is not clear whether the results of both methods can be correlated in general. Due to the importance of the oxidation stability, we here describe the results of a literature research that was carried out using 17 literature sources. Possible correlation factors between the Rancimat and the RSSOT method were analyzed, showing that a universal correlation cannot be found. In contrast, a comparison of individual series of measurement, e.g. with the same antioxidant at various concentrations, can show a good correlation between the methods.