Statistical-mechanics-based equation binaries

We have applied some of these principles to the extraction of 1-butene from a binary mixture of 1,3-butadiene/1-butene. Various mixtures of sc solvents (e.g., ethane, carbon dioxide, ethylene) are used in combination with a strongly polar solvent gas like ammonia. The physical properties of these components are shown in Table I. The experimental results were then compared with VLE predictions using a newly developed equation of state (18). The key feature of this equation is a new set of mixing rules based on statistical mechanical arguments. We have been able to demonstrate its agreement with a number of binary and ternary systems described in the literature, containing various hydrocarbon compounds, a number of selected polar compounds and a supercritical component. 

Although equations of state based on statistical mechanics, like the Perturbed Hard Chain and Chain of Rotators equations of state are good at predicting phase equilibria at conditions far from the critical point of mixtures, a critical evaluation of six of these type of equations of state showed that they are rather inaccurate in the mixture critical region[3]. Satisfactory correlation of the data is obtained with a Peng Robinson equation of state using two interaction parameters per binary as proposed by Shibata and Sandler[4], The correlations of Huang[5] were used for the pure component parameters. 

---