No abstract

On the basis of Eyring's absolute reaction rate theory, a new model for the Maxwell−Stefan diffusivity has been developed. This model, an extension of the Vignes equation, describes the concentration dependence of the diffusion coefficient in terms of the diffusivities at infinite dilution and an additional excess Gibbs energy contribution. This energy part allows the explicit consideration of thermodynamic nonidealities within the modeling of this transport property. If the same set of interaction parameters, which has been derived from vapor−liquid equilibrium (VLE) data, is applied for this part and for the thermodynamic correction, a theoretically sound modeling of VLE and diffusion can be achieved. The influence of viscosity and thermodynamics on the model accuracy is thoroughly investigated. For this purpose, diffusivities of 85 binary mixtures consisting of alkanes, cycloalkanes, halogenated alkanes, aromatics, ketones, and alcohols are computed. The average relative deviation between experimental data and computed values is approximately 8% depending on the choice of the g E model. These results indicate that this model is superior to some widely used methods.

On the basis of Eyring's absolute reaction rate theory, a new mixture viscosity model has been developed. The nonidealities of the mixture are accounted for with the thermodynamically consistent COSMOSPACE approach. The required model and component parameters are derived from sigma profiles, which form the basis of the a priori predictive method COSMO-RS. To improve the model performance, two segment parameters are determined from a least-squares analysis of experimental viscosity data, where a constraint optimization procedure is applied. In this way, the parameters retain their physical meaning. Finally, the viscosity calculations of this approach are compared to the findings of the Eyring−UNIQUAC model for a broad range of chemical mixtures. These results show that the new Eyring−COSMOSPACE approach is superior to the frequently employed Eyring−UNIQUAC method.

Accurate diffusion coefficient data are reported for highly nonideal binary mixtures. The mixtures consist of an alcohol (ethanol, 1-propanol, 1-butanol) dissolved in hexane, cyclohexane, carbon tetrachloride, or toluene. All measurements have been conducted over the whole concentration range at various temperatures, (25, 30, and 35) °C, by means of the Taylor dispersion technique. The uncertainty of the reported data is estimated to be within 3·10-11 m2·s-1.