This article presents experimental viscosity and density data for binary systems containing ethanol and one of the following 1-alkanols as the second component: butan-1-ol, pentan-1-ol, heptan-1-ol, octan-1-ol, nonan-1-ol, and decan-1-ol. These properties were measured at 0.1 MPa and at five different temperatures, ranging from 283.15 K to 313.15 K. The viscosity data have also been correlated by a model which combines Eyring's theory of viscous flow with a thermodynamic framework (Ind. Eng. Chem. Res. 2000, 39, 849). The model binary interaction parameters, for each of the binary systems, are also reported. The agreement between calculated and experimental data was rather good. The overall mean relative standard deviations did not exceed 0.01. The experimental viscosity deviations, obtained by the difference between the viscosity of the mixture and the mole fraction average of the pure component viscosities, were adjusted by means of Redlich−Kister polynomials. For all the systems studied negative values of viscosity deviations were obtained, for all temperatures, and over the whole mole fraction range.

Abstract

ABSTRACT:In this work, we propose a new model to calculate viscosity of dense fluids based on the reference part of the Weeks-Chandler-Andersen perturbation theory. The reference fluid intermolecular interactions are given by a repulsive soft-sphere potential. The viscosity is calculated by means of a Chapman-Enskog equation corrected to high densities coupled with a density-and temperature-dependent effective diameter. The viscosity is also calculated by molecular dynamics simulations in a wide range of temperatures and densities for fluids interacting by repulsive soft-spheres potential. These results, obtained from molecular dynamics, are used to optimize the parameters of the effective diameter equation. To compute the contribution due to attractive intermolecular interactions, we use a temperature-dependent term, obtained by the Stokes-Einstein relation and the results published by Straub (1992) for the self-diffusion coefficient. The proposed model correlated experimental viscosity data from literature with absolute deviations less than 4%.

It is well known that colloids can show phase transitions similar to the ones observed in molecular systems. Colloid-diluted and colloid-concentrated phases can coexist in thermodynamic equilibrium at certain conditions. In a previous work, the authors of this research have used this concept to study petroleum emulsions stability, applying thermodynamic perturbation theories to calculate a phase diagram of water-in-oil emulsions under the influence of an electric field. In this work, it was used a similar thermodynamic formalism coupled with the Lifshitz theory to perform a qualitative analysis of the influence of some variables on emulsion stability. Among the variables studied were temperature, applied electric field, and salt concentration. This research found that droplet diameter is a key parameter in studying thermodynamic stability. Variables like temperature and oil composition can have an opposite effect on thermodynamic and kinetic stability. The application of an electric field can destabilize thermodynamically the emulsion. It can also induce meta-stable transitions, which are important for the calculation of droplet coagulation rate. The results presented in this work are in accordance with trends of experimental and industrial observations, and seek to promote a better understanding of water-in-oil emulsion stability.

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