In this work, we propose a new predictive entropy-scaling approach for Newtonian shear viscosities based on group contributions. The approach is based on Rosenfeld’s original work [Rosenfeld, Y. Phys. Rev. A 1977, 15, 2545−2549]. The entropy scaling is formulated as third order polynomial in terms of the residual entropy as calculated from a group-contribution perturbed-chain polar statistical associating fluid theory (PCP-SAFT) equation of state. In this study, we analyze the course of entropy scaling parameters within homologous series and suggest suitable mixing rules for the parameters of functional groups. The viscosity of nonpolar, of polar, and of self-associating (hydrogen bonding) components are considered. In total, 22 functional groups are parametrized to viscosity data of 110 pure substances, from 12 different chemical families. The mean absolute relative deviations (MADs) to experimental viscosity data are typically around 5%. For three chemical families, namely, branched alkanes, 1-alcohols,...

Group Contribution Method for Viscosities Based on Entropy Scaling Using the Perturbed-Chain Polar Statistical Associating Fluid Theory

High-pressure viscosities and densities of n-butane, n-pentane, n-hexane, and n-octane have been measured with a specially designed falling cylinder viscometer. Data cover the pressure range from 10 to 70 MPa at temperatures from 310 to 450 K. When the viscosity is plotted as a function of density, the data at all temperatures and pressures are shown to reduce to a single curve for each alkane. An exponential relationship of the form η = B
1 x exp(B
2xρ) + B
3 is used to describe the density dependence of viscosity. The logarithmic viscosity of the alkanes changes linearly with the inverse temperature at all pressures. The density shows a linear dependence on temperature.

High-pressure viscosity and density of n -alkanes

Viscosity and thermal conductivity coefficients for binary, ternary, and quaternary n-alkane mixtures are predicted over extended ranges of temperature and pressure, in excellent agreement with experiment, by extension of a method recently described for the correlation of n-alkane transport coefficients. The outstanding advantage of this approach is that there are no adjustable parameters. Furthermore, in contrast with other mixture viscosity equations, this scheme does not require experimental viscosity coefficient data for the pure components under the same conditions of temperature and pressure.

Correlation and prediction of dense fluid transport coefficients. III. n-alkane mixtures

A previously described method, based on consideration of hard-sphere theory, is used for the simultaneous correlation of the coefficients of self-diffusion, viscosity, and thermal conductivity for benzene, toluene, o-, m-, and p-xylene, mesitylene, and ethylbenzene in excellent agreement with experiment, over extended temperature and pressure ranges. Values are given for the roughness factors R

 D
 , R
η, and R
λ, and the characteristic volume, V
0, is expressed as a function of both carbon number and temperature.

Correlation and prediction of dense fluid transport coefficients. V : Aromatic hydrocarbons

In the present study, the simultaneous and accurate determination of liquid viscosity and surface tension of the n-alkanes n-hexane (n-C6H14), n-octane (n-C8H18), n-decane (n-C10H22), and n-hexadecane (n-C16H34) by surface light scattering (SLS) in thermodynamic equilibrium is demonstrated. Measurements have been performed over a wide temperature range from 283.15 K up to 473.15 K for n-C6H14, 523.15 K for n-C8H18, and 573.15 K for n-C10H22 as well as n-C16H34. The liquid dynamic viscosity and surface tension data with average total measurement uncertainties (k = 2) of (2.0 and 1.7) % agree with the available literature and contribute to a new database at high temperatures. Over the entire temperature range, a Vogel-type equation for the dynamic viscosity and a modified van der Waals equation for the surface tension represent the measured data for the four n-alkanes within experimental uncertainties. By also considering our former SLS data for n-dodecane (n-C12H26) and n-octacosane (n-C28H58), empirical models for the liquid viscosity and surface tension of n-alkanes were developed as a function of temperature and carbon number covering values between 6 and 28. Agreement between these models and reference correlations for further selected n-alkanes which were not included in the development procedure was found.

Dag Arne Berstad

Papers

Viscosity and density of n-hexane, cyclohexane and benzene, and their binary mixtures with methane