Extension of the PPR78 model (Predictive 1978, Peng–Robinson EOS with temperature dependent kij calculated through a group contribution method) to systems containing naphtenic compounds

In 2004, we started to develop a group contribution method aimed at estimating the temperature dependent binary interaction parameters (kij(T)) for the widely used Peng–Robinson equation of state (EOS). In this approach, the kij between two components i and j is a function of temperature (T) and of the pure component critical temperatures (Tc,i and Tc,j), critical pressures (Pc,i and Pc,j) and acentric factors (ωi, ωj). Because our model relies on the Peng–Robinson EOS as published by Peng and Robinson in 1978 and because the addition of a group contribution method to estimate the kij makes it predictive, this model was called PPR78 (predictive 1978, Peng–Robinson EOS). In our previous papers eight groups were defined: CH3, CH2, CH, C, CH4 (methane), C2H6 (ethane), CHaro and Caro. It was thus possible to estimate the kij for any mixture containing alkanes and aromatics whatever the temperature. In this study, the PPR78 model is extended to systems containing naphtenic (cyclic hydrocarbons) compounds. To do so, two new groups were added: CH2,cyclic and CHcyclic = Ccyclic.