Corresponding State Behaviour of Vapour- Liquid Phase Equilibria of Bulk and Confined Alkanes

Abstract

In this work, we have investigated the corresponding state behaviour of vapour-liquid phase equilibria of bulk and confined alkanes using grand-canonical transition-matrix Monte carlo simulation and histogram reweighting method. In this work,Buckingham exponential-6 potential model is used to describe the interaction between alkane’s molecules and Steele potential is used for the interaction between confining surface and alkane molecules.In this investigation methane, n-butane and n-octane are subjected under graphite and mica slit pores of varying slit width. In case of methane, slit width varied from 40A0 to 5.4A0,n- butane from 40A0 to 6A0 and for n-octane 50A0 to 10A0. In these investigations deviations from corresponding state behaviour in vapour-liquid phase equilibria is observed with larger pore widths, irrespective of type of fluid under consideration. On the other hand, with smaller pore width insignificant deviations from corresponding state behaviour in vapour-liquid phase equilibria is observed.We have also compared the saturation vapour pressure in confinement with respect to bulk, in a corresponding state plot.Saturation vapour pressure under either type of confinement (graphite & mica) show positive deviation (with larger pore width) and negative deviation (with smaller pore width) with respect to the corresponding bulk value at a given reduced temperature.