Comparison of SRK and CPA equations of state for phase equilibrium of binary and ternary systems containing aromatics

Abstract

In this work, the binary and ternary vapor–liquid and liquid–liquid equilibrium (VLE and LLE) data of different systems including N-formylmorpholine (NFM), alkanes, aromatics are collected from previously published literature and then modeled using two different equations of state including Soave–Redlich–Kwong (SRK) and cubic-plus-association (CPA). Since the main purpose of this work is set on the evaluation of the SRK and CPA EoS's capability for modeling of polar systems and to know the importance of association part of CPA EoS, binary and ternary systems of NFM are considered as the objective function. Besides, this investigation is directed in a way that a single “engineering approach” obtains for applying CPA to NFM–aromatic mixtures. Respect to this, different approaches are used to find the functionality of modeling using CPA EoS. These approaches including 3 association schemes for pure NFM (assuming a non-associating compound or a self-associating fluid with two or four association sites) and different possibilities to model mixtures of NFM+Ethylene Glycol (EG) and aromatics (application of just one interaction parameter kij or assuming cross-association interactions leads to obtain relevant parameters either via a combining rule). At last, based on the obtained results it is concluded that CPA is a powerful model that can be used for predictions of binary and ternary mixture properties even without adjustable interaction parameters. In addition, the results revealed that the functionality of the CPA EoS is higher than the SRK EoS in most of the cases especially for predicting the vapor pressure of NFM solvent.