Vapor-liquid equilibria of α-tocopherol in transportation fuels surrogates: An experimental and modeling study

The environmental performance of advanced engines in terms of combustion and emissions relies strongly on fuel phase change properties, which can be improved by specific additives. Among sustainable additives, tocopherols are particularly promising since they exhibit high dispersion, low toxicity and antioxidant properties, which may allow their introduction as multifunctional additives in engine fuel and lubricants. The present work aims at studying the α-tocopherol synergy with surrogate automotive fuels and the volatility of the resulting ternary blends. This study deals with the experimental measurements and modeling of the phase behavior of n-pentane + ethanol + α-tocopherol mixtures: the n-pentane + ethanol mixture is considered as a base surrogate fuel, and α-tocopherol is the additive. The Peng-Robinson (PR) equation of state combined with the MHV1 mixing rules and the predictive UNIFAC and COSMO-SAC dsp activity coefficient models, is used to determine the vapor–liquid equilibria (VLE) of the n-pentane + ethanol + α-tocopherol mixture. Reid vapor pressures and distillation curves based on the ASTM D86 protocol are predicted for α-tocopherol + fuel systems. It is observed that the addition of α-tocopherol induces a change in the distillation curve (shift to higher temperatures) for large fractions of distillate volumes. The validated model allows to tailor multifunctional additives to improve fuel distillation curves.