Liquid-liquid equilibrium at high pressures of water/n-Decane system using Monte Carlo simulation

Liquid-liquid equilibrium (LLE) of two- and three-component systems containing short molecules has been previously studied by Monte Carlo simulations in the NPT ensemble with two simulation boxes; for systems with long-chain molecules have also been studied, but at low pressures and considering three simulation boxes, the third is a vapor phase that contains ghost molecules and acts only as a transfer medium between the two liquid phases. In this paper, the LLE at high pressures of the water/n-decane binary system is calculated using only two simulation boxes by the NPT-Gibbs ensemble combined with the Configurational Bias Monte Carlo method (CBMC). Besides, the molecular potential models used, and the simulation details allowed us to calculate the LLE properties of the system studied: the densities of the two phases in equilibrium, their compositions, and potential energies. The water/n-decane mixture is characterized by differences in molecular size and polarity, forming a highly non-ideal system. This is probably the reason for the difficulty of studying the LLE of water/n-alkane binary systems by Monte Carlo simulation, so to the best of our knowledge, this is the first study of the LLE of a binary water/n-alkane system using Monte Carlo simulation. Simulations were done at 573.2 K (from 121 to 303 bar) and 593.2 K (from 154 to 300 bar), and under these conditions, experimental data from the LLE is available, obtaining good predictions from simulations.