An evaluation of the performance of the Cubic-Plus-Association equation of state in mixtures of non-polar, polar and associating compounds: Towards a single model for non-polymeric systems

The aim of this work is to investigate the possibility of identifying a single model that will be able to accurately describe the phase equilibrium in non-polymeric systems, which involve non-polar, polar and hydrogen bonding compounds. To this purpose the Cubic-Plus-Association (CPA) EoS, developed in this laboratory about 10 years ago, is examined in the correlation of phase equilibrium in binary systems and prediction of multicomponent phase equilibrium from binary data. When possible the results of the CPA EoS are compared with those obtained from the PC-SAFT EoS.To account for dipolar or quadrupolar interactions, present when molecules such as acetone or carbon dioxide are involved, these molecules are treated using the concept of “pseudo-association”, i.e. as being able to act as associating compounds. This approach renders CPA applicable to systems that involve polar compounds without the need of extra terms to account for polar and/or quadrupolar interactions.It is concluded that CPA, coupled with the “pseudo-association” approach for polar molecules, represents a model that is able to accurately describe the phase equilibrium in a variety of binary systems involving non-polar, polar and hydrogen bonding compounds and provide satisfactory prediction of multicomponent phase equilibrium from binary data.