Gaudencio Eliosa-Jiménez

An equation-of-state-based viscosity model for non-ideal liquid mixtures

Abstract A viscosity model based on the Eyring’s theory and a cubic equation of state (Peng–Robinson–Stryjek–Vera) has been applied to the correlation and prediction of experimental liquid viscosities of binary mixtures containing polar fluids within a wide range of temperature, pressure and composition (encompassing low-pressure and compressed liquid conditions). Highly non-idealities of the binary mixtures considered in this study were conveniently handled via the application of the Wong–Sandler approach for the mixing rules used in the cubic equation of state. The results obtained were highly satisfactory for various non-ideal binary mixtures over the whole composition range at a low pressure. The predictive capabilities of the present approach were also verified in the representation of liquid viscosities at elevated pressures preserving the same model parameters previously obtained at low pressure.

Modeling of microemulsion phase diagrams from excess Gibbs energy models

Abstract Projects on tertiary oil recovery by means of microemulsions have been mainly concerned with, first, the ability of a microemulsion to dissolve oil and water simultaneously and, second, the attainment of very low interfacial tensions. Therefore, the design and analysis of chemical flooding processes for enhanced oil recovery must be based on calculations of phase equilibria for these systems, which are composed of water (brine), oil, surfactant and co-surfactant (usually an alcohol). Consequently, the understanding of phase behavior of these systems is of fundamental importance to the development of any surfactant-based chemical flooding process. The purpose of this work was to give a thermodynamic analytical representation of the phase diagram of microemulsion systems similar to those used in enhanced oil recovery. The algorithms presented for the calculation of multiphase liquid equilibria and the methods for the estimation of the excess Gibbs energy model interaction parameters were successfully tested for the representation of experimental multiphase liquid equilibrium data of an oil−brine−surfactant−alcohol model system. In addition, to represent effectively the phase diagram of this system, an empirical expression was introduced into the selected excess Gibbs energy model to account for the specific role of the surfactant in these complex systems.

An efficient flash procedure using cubic equations of state

Abstract A robust and highly efficient procedure to solve the isothermal two-phase flash problem at critical and sub-critical conditions is proposed in this work. From a calculated initialization, an accelerated successive substitution method is applied until either the solution is achieved or the change in the Gibbs free energy becomes positive, i.e. the Gibbs energy increases. From this point, an unconstrained optimization method is applied where the Hessian is kept positive definite and a line search method is implemented to guarantee a decrease in the Gibbs function. Using cubic equations of state to calculate the required thermodynamic properties has broadly tested the approach. Three hydrocarbon binary systems and a five-component mixture are used in this work to show the robustness of this procedure.

Henry's law constant for propane and butane in solutions of n-methylpyrrolidone with alkanolamines

Abstract Eliosa-Jimenez, G. and Trejo, A., 1992. Henrys Law constant for propane and butane in solutions of N-methylpyrrolidone with alkanolamines. Fluid Phase Equilibria, 00: 000-000. Using the gas-stripping or exponential dilutor technique values of Henrys Law constant have been determined for propane and butane independently in mixtures of known composition made up of N-methylpyrrolidone with monoethanolamine or with diethanolamine at several temperatures in the range 293 to 373 K. The results show a clear dependence with the size of the hydrocarbon, the composition of the mixture, the type of amine, and the temperature.

Étude des modèles thermodynamiques pour représenter des mélanges contenant des hydrocarbures, de l’eau et des alcools: I. Traitement général et représentation des équilibres liquide–vapeur et des enthalpies de mélange des systèmes binaires sous basse pression

Abstract The aim of this work was to indicate some thermodynamic models based on the formalism ‘Equation of state–Excess function’ able to represent thermodynamic properties of complex systems. First, we have developed the characteristics of the corrected Peng–Robinson equation of state for pure components as well as the conditions of its extension to mixtures by using excess function models such as those of van Laar, NRTL, Adachi–Sugie, Schwartzentruber–Renon and that of the ‘Surrounded Molecule’. Afterwards, we have studied the simultaneous representation of vapor–liquid equilibria and mixing enthalpies of binary systems containing non-polar, polar or associated compounds by using a temperature-dependence of the parameters for all models considered. The obtained results allow thus to establish what classes of compounds need the use of excess functions depending of one, two or three binary interaction parameters.