Ethanoled gasoline bubble pressure determination: Experimental and Monte Carlo modeling

In this work, we present some experimental and modeling studies of ethanoled gasoline bubble pressures (ethanol + gasoline blends) at various temperatures and ethanol contents. Modelings are carried out using Monte Carlo simulations in a specific bubble-point pseudo ensemble and using the AUA4 force field. This method is first validated on the prediction of binary mixture bubble pressures (ethanol + n-hexane, ethanol + propylene, ethanol + toluene, ethanol + isooctane). It is shown that a good accuracy is reached without introducing empirical binary interaction parameter, demonstrating the predictivity of the approach. Then, simulations of ethanoled gasolines have been performed. The molecular representation of the gasoline is obtained using a lumping scheme from the detailed composition of a commercial gasoline. Simulation results are compared to experimental bubble pressures measured in this work on this commercial gasoline in which various proportions of ethanol have been added. From a qualitative point of view, the azeotropic behavior of such fuels is observed both experimentally and by simulations. From a quantitative point of view, an average deviation of 15% between experimental and simulation data is found. Such results show that Monte Carlo simulation using an accurate force field is an efficient method to predict phase equilibrium of complex mixtures such as oxygenated gasolines. This methodology can thus be seen as an efficient tool that can be used by engineers for fuel formulation or for equation of state or process model calibration.