Comparison of the Effects of Different Biofuel on the Oxidation Stability of a Hydrocarbon Fuel
In this work, the effects of the addition of biofuels belonging to different chemical families on the oxidation stability of a conventional fuel surrogate (n-decane) have been investigated. Experiments have been performed in a PetroOxy apparatus, which is one of the references Rapid Small Scale Oxidation Test of the ASTM 7545 methods. When the pressure in the cell of the device decreases by 10% of the maximum pressure recorded, the time measured to reach this target value defines the Induction Period (IP). IP constitutes a quantitative measure of the oxidation stability of the fuel. In addition to the IP measurements for each biofuel / hydrocarbon fuel blend, organic peroxides produced in the liquid sample were quantified at the IP, using iodometric titration and ultraviolet-visible spectrophotometry.
Different oxygenated biofuels have been studied in this work: diethyl ether, n-butanol, and cyclopentanone. Cyclohexane addition has also been considered to probe the effects of a non-oxygenated additive. For each type of biofuel, the proportion added to n-decane, the surrogate fuel, was varied from 0.2 to 20%vol. For each blend, the IP and the total peroxide content in the liquid have been systematically measured.
This study demonstrates an unexpected diversity of the effects of oxygenates biofuels: n-butanol strongly enhances the oxidation stability of the surrogate fuel (up to a factor of 6) while diethyl ether and cyclopentanone decrease the stability of n-decane. The experimental results show also that variations in the proportions of biofuel additives lead to non-linear variations in the measured IPs. Organic peroxide measurements confirmed that a similar reaction mechanism underpins the oxidation of all the biofuel/fuel surrogate blends.