Tunability of Gas-Expanded Liquids under Confinement: Phase Equilibrium and Transport Properties of Ethylene-Expanded Methanol in Mesoporous Silica

Using grand canonical Monte Carlo (GCMC) and molecular dynamics simulation, we examine the phase equilibrium and transport of a gas-expanded liquid under confinement. The system chosen is ethylene-expanded methanol confined in model silica mesopores, but in equilibrium with the bulk mixture—a system that has received recent interest as a reaction medium, e.g., for epoxidation of ethylene. This system was studied at 20 °C and pressures ranging from 5 to 55 bar. In addition, two different pore surface chemistries were examined: a hydrophilic pore, in which the silica dangling bonds were terminated by −OH groups, and a model “hydrophobic” pore, in which the charges on the pore atoms (including the −OH groups) were turned off. The chemical potentials for the mixture necessary to perform the GCMC simulations were obtained using a novel Gibbs–Duhem integration method along a previously calculated binary vapor–liquid equilibrium curve. We find that the pressure significantly affects the ethylene mole fraction in...