Redlich-Kwong-Peng-Robinson equation of state, towards two decades of its development and evolution

QUINZIO, MARTINA JULIETA; RODRIGUEZ REARTES, SABRINA BELÉN; CISMONDI, MARTÍN

La Pineda, Tarragona

Conferencia; 16th International Conference on Properties and Phase Equilibria for Product and Process Design; 2023

Universitat Rovira i Virgili and Khalifa University

The generalised Redlich-Kwong-Peng-Robinson (RKPR) equation is a three-parameter cubic equation of state (EoS), where its third parameter (δ1) allows connecting the density dependencies of the Soave-Redlinch-Kwong (SRK) and Peng-Robinson (PR) EoS. In it, the repulsive parameter (b) and parameter δ1 are constant for each compound, while the attractive parameter (a) has a simple dependence on temperature, through a fitting parameter (k) that is adjusted to reproduce the acentric factor (ω).The RKPR-EoS was developed and presented by Cismondi & Mollerup (2005). Originally it was recommended to use a simple ratio (Zcrat) between the experimental critical compressibility factor (Zc) and the one predicted by the EoS applied to non-associating fluids. This condition already determines δ1 for each fluid, while b and ac are obtained by setting the critical temperature (Tc) and critical pressure (Pc) to their experimental values. Later on, ratio Zcrat was not longer used and new specific correlations were developed for the δ1 parameter. To be used in mixtures, the RKPR-EoS was coupled to different mixing rules (mainly quadratic and cubic in mole fraction) to obtain the mixing parameters a and b, sometimes together with temperature-dependent interaction parameters.Since its development, RKPR-EoS was quickly adopted by the scientific community and used for numerous systems. In general, the different authors agree in recognizing its good predictive capability and its mathematical simplicity and practicality of application. As research progressed, some predictive parameter correlations were established for binary systems of homologous series, such as carbon dioxide + n-alkane and n-alkane + n-alkane and the predictive ability of RKPR-EoS in multicomponent mixtures was also explored. Furthermore, phase equilibrium modelling was extended to include the possibility of the occurrence of a solid phase. Also, RKPR-EoS was used in research in other areas of knowledge, obtaining satisfactory and promising results that drive new research aimed at extending its applications. Recently, it was shown that the cubic nature of PR-EoS is not the reason for its incorrect predictions in the deviations from ideality of athermal binary mixtures, since RKPR-EoS with the same repulsive term does not suffer from this limitation. Other studies show that it is also not necessary to resort to more complex mixing rules, but with a third parameter (δ1 in RKPR) it is possible to capture the appropriate evolution of the behaviour in the n-alkane family, and give flexibility to the model.RKPR-EoS in only two decades has come a long way both in terms of evolution and extension of its applications, as well as in its use as a practical tool for various investigations. In this paper we make a complete review of the scientific literature published so far retaled to RKPR-EoS and present the current state of knowledge.