Ángeles Domínguez

Automatic implementation of thermodynamic models for reliable parameter estimation using computer algebra

Abstract An existing computer program for the automatic implementation of thermodynamic models, Thermath, was extended to allow the implementation of code compatible with the intbis / intlib package for the solution of sets of nonlinear equations using interval arithmetic. Using the extended program, we developed the scalar and interval subroutines needed to fit interaction parameters of the Wilson and UNIQUAC excess Gibbs free energy models. We could then use these codes to perform a reliable parameter estimation for these models, i.e. guaranteeing that the global minimum of the objective function was achieved inside an initially specified range for each model parameter. Our observations in the estimation of parameters for the Wilson model in binary systems confirm those of [Nonlinear parameter estimation using interval analysis, presented at FOCAPD-98, Snowbird, UT, USA (1998)] and [Fluid Phase Equilibria 168 (2000) 1], who found that the parameters presented for some systems in the Dechema Vapor–Liquid Equilibrium Data Collection [vol. I, Parts 1–8. Frankfurt/Main, Germany: DECHEMA (1977–1990)] do not correspond to the global optimum of the objective function used in that reference. Our experience with UNIQUAC allowed us to reach the same conclusion for this model.

Thermal Behaviour of Pure Ionic Liquids

The interest in ionic liquids (ILs) that has developed during in the past few decades is wellrecognized. This interest has developed mainly due to their special properties such as high thermal stability, high electrical conductivity, high heat capacity per unit volume, wide temperature range in a liquid state, good solvent properties and especially their negligible vapour pressure, which render them popular compounds. This popularity is reflected in the great deal of publications that relate the potential applications of ILs in different fields, among which can be highlighted their use as solvents, electrochemical applications and more recently, as heat transfer fluids.

Evaluation of [C3mim][NTf2] as Solvent for the Liquid-Liquid Extraction of Benzene from Mixtures of Benzene and Hexane

In this paper, the liquid-liquid extraction of benzene from hexane with 1-propyl-3-methylimidazolium bis{trifluoromethylsulfonyl}imide, [C3mim][NTf2], as solvent was studied. The liquid-liquid equilibrium (LLE) data of the ternary system [hexane + benzene + ionic liquid] were measured at 298.15 K and atmospheric pressure. From the experimental composition data, the selectivity and the solute distribution ratio were calculated. The reliability of the experimental LLE data was ascertained using the Othmer-Tobias equation, and the NRTL thermodynamic model was used to correlate the experimental data. Moreover, a comparison with literature data for the ternary systems [hexane + benzene + ionic liquid] was also carried out.

Liquid-liquid extraction of phenolic compounds from water using ionic liquids: Literature review and new experimental data using [C2mim]FSI

In this work, the capability of the ionic liquid, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide, [C2mim]FSI, to extract o-cresol, 2-chlorophenol, resorcinol and phenol from water, reaching the legal limit of 1 mg L-1 was analyzed. The extraction process was carried out for each one of these phenolic compounds varying the initial concentration in water from 3 mg L-1 to 1000 mg L-1, and for aqueous mixtures of the four phenolic compounds in the same concentration range. Because of the scarcity of physical properties of the [C2mim]FSI, density, speed of sound, dynamic viscosity and refractive index were measured from 293.15 to 343.15 K at atmospheric pressure. From the experimental data, the thermal expansion coefficient and the isentropic compressibility for the pure ionic liquid were calculated. Even though [C2mim]FSI is hydrophobic, it can solve small quantities of water that can hinder the recovery of the ionic liquid, consequently the solubility of water in the ionic liquid was determined at several temperatures and atmospheric pressure. In addition to experimental data, a literature review on the use of ionic liquids to extract phenolic compounds from water was performed.