Modeling Confined Fluids with the Multicomponent Potential Theory of Adsorption and the SAFT-VR Mie Equation of State

Abstract

In this work, the SAFT-VR Mie equation of state is combined with the Multicomponent Potential Theory of Adsorption (MPTA) in order to describe the phase equilibrium behavior of confined fluids due to their presence in an external field, namely a solid-fluid potential field. This is important for the understanding, modeling and design of fluids confined in micro- and meso-pores pertinent to applications in hydrocarbon reservoirs, membrane-based separations and heterogeneous catalytic systems, to name but a few. The problem specifications are the temperature of the system, volume of the pores, and the number of moles of each component in the system. The formulation results in the minimization of the Helmholtz energy of the system subject to mass and pore-volume conservation constraints. This formulation, in addition to treating supercritical fluids, tackles the problem of pore-condensation of subcritical systems by employing a Helmholtz-based global phase stability analysis which allows us to detect the presence of phase instability inside the pores as well as locate the spatial location at which it takes place.