Association and semiempirical equations of state

Abstract

An equation of state incorporating association in an explicit form (AEOS) has been derived from an infinite-equilibria association model coupled with a generalized van der Waals-type equation of state. The equation can be applied to associating or polar as well as non-polar compounds and their mixtures at gas- and liquid-like densities. The equation is able to represent accurately phase equilibria in mixtures with only one adjustable binary parameter while qualitative estimates can be obtained from pure component parameters alone. Excess volumes with composition dependence ranging from positive through S-shaped to negative are also reproduced for mixtures containing an associating and an inert component. A satisfactory simultaneous correlation of vapour–liquid equilibria and excess volumes is obtained with a linearly temperature dependent binary interaction parameter.