Thermodynamic representation of ionic liquids phase equilibrium with the PDH-UNIQUAC-NRF model

Abstract

This article uses four thermodynamic predictive models to calculate the interaction parameters of 4 binary (28 Tie-Line) and 71 ternary (889 Tie-Line) systems. Two specific properties were kept in mind when collecting the systems: 1. A Thiophene (BenzoThiophene) component is contained in all the systems; 2. Ionic liquids are used as the extracting factor.All systems were carried out using UNIQUAC, UNIQUAC-NRF, PDH-UNIQUAC and PDH-UNIQUAC-NRF models. In these models, the long-range contribution is accounted by Pitzer–Debye–Hückel (PDH) equation while the short-range contribution is considered by nonelectrolyte UNIQUAC and UNIQUAC-NRF. The present work inquired phase behavior of 36-types of ILs with various cations (imidazolium, pyrrolidinium, piperidinium, pyridinium, morpholinium phosphonium and Ammonium-Based cations) and various anions (Cl, FeCl4, BF4, B(CN)4, PF6, NTf2, FAP, OAc, DEP, EtSO4, H2PO4, TCM, CH3COO, SCN, TCB, CF3SO3 and MeSO4) in LLE systems. All the temperatures were in the range of 298.15–364.70 K. Therefore, in order to obtain temperature-independent interaction parameters, the adjustable parameter assumed to be as a function of T. This work uses a hybrid optimization approach for computing the interaction parameters. This approach benefits from both the capabilities of Genetic Algorithm (GA) as a global optimization technique while making use of a local search technique like Nelder-Mead Algorithm (NMA). All the interaction parameters for both binary and ternary systems were directly regressed from the experimental data using an optimization program based on two objective functions. Comparison of the results is expressed by root mean square deviation (rmsd) between the experimental and calculated compositions. The applied UNIQUAC, UNIQUAC-NRF, PDH-UNIQUAC and PDH-UNIQUAC-NRF models yielded to quite satisfactory results for ternary and binary systems, with rmsd values of 10.85, 10.54, 10.96 and 10.25 for binary systems, and 20.49, 11.55, 20.50 and 11 for ternary systems respectively. It is demonstrated that the PDH-UNIQUAC-NRF model presents quite satisfactory results.