Thermophysical Properties of Low-Density Pure Alkanes and Their Binary Mixtures Calculated by Means of an (n-6) Lennard-Jones Temperature-Dependent Potential

Abstract

Self-consistent calculations of interaction pVT-virial coefficients B 12 (T ), viscosities η mix (T ), and diffusion coefficients D 12 (T ) of binary mixtures of the alkanes C n H 2n+2 (n < 6) are presented. This study is based on the recently developed model of the (n-6) Lennard-Jones temperature-dependent potential (LJTDP) and uses already obtained potential parameters of the pure alkanes as input data. The well-known and simple Lorentz-Berthelot (LB) and the more elaborate Tang-Toennies (TT) mixing rules are applied to the potential parameters of the pure alkanes in order to determine those of the mixtures. The new Hohm-Zarkova-Damyanova (HZD) mixing rule, which is an extension of the TT-mixing rule, is also considered. The HZD takes into account that for the LJTDP model, in general, the repulsive parameter is an independent variable whose value n = 12. As in a recent examination of binary mixtures of globular molecules, the LB-mixing rule is superior to TT-and HZD-mixing rules when calculating equilibrium properties such as B 12 (T ). For the transport properties η mix (T ) and D 12 (T ), the new mixing rule performs slightly better.

Effective (n-6) Lennard-Jones Potentials with Temperature-Dependent Parameters Introduced for Accurate Calculation of Equilibrium and Transport Properties of Ethene, Propene, Butene, and Cyclopropane

“…The LJTDP has been successfully applied before to a number of pure gases like the alkanes , and perfluoroalkanes . We have shown that it performs also very well in the prediction of B , η, and D of binary mixtures of alkanes and other gases. , To give a comprehensive overview on the molecules with sum formula C m H 2 m , we not only consider the alkenes but also try to include the two cyclic compounds cyclopropane (C 3 H 6 ) and cyclobutane (C 4 H 8 ) in our studies. These two molecules are also of some importance in industry − and basic research …”

Viscosity, SecondpVTVirial Coefficient, and Diffusion of Binary Mixtures of Small Alkanes CH4, C2H6, C3H8,n-C4H10,i-C4H10,n-C5H12,i-C5H12, and C(CH3)4Predicted by Means of an Isotropic Temperature-Dependent Potential

“…Once R mAA (eff) ( T ), ε AA (eff) ( T ), and n AA are known for the pure substances, the parameters R mAB (eff) ( T ), ε AB (eff) ( T ), and n AB describing the interaction between unlike molecules can be deduced via mixing rules. In this work, we use our recently developed Hohm−Zarkova−Damyanova (HZD) mixing rules . For the unlike interaction parameters we have with and where α A and α B are the dipole-polarizabilities and C 6 AA and C 6 BB are the dispersion-interaction energy constants of molecules A and B, respectively.…”

“…To handle the vast number of different binary mixtures containing alkanes, mixing rules of the intermolecular interaction potential parameters are often used which relate the unlike interaction AB between two particles A and B to the like interactions AA and BB . Although it is now accepted that the very simple Lorentz−Berthelot mixing rules do not give the correct potential parameters of unlike interactions, they are still widely used because in some cases they nevertheless allow for a reliable prediction of some thermophysical properties of binary mixtures. – Despite their partial success, in many cases extensions of the Lorentz−Berthelot mixing rules or completely different combination rules give better results for binary alkane mixtures. – In our recent work on the thermophysical properties of low-density binary alkane mixtures, we have developed a flexible extension of the physically reasonable Tang−Toennies mixing rules. , This new scheme is called Hohm−Zarkova−Damyanova (HZD) mixing rules.…”

“…Although it is now accepted that the very simple Lorentz−Berthelot mixing rules do not give the correct potential parameters of unlike interactions, they are still widely used because in some cases they nevertheless allow for a reliable prediction of some thermophysical properties of binary mixtures. – Despite their partial success, in many cases extensions of the Lorentz−Berthelot mixing rules or completely different combination rules give better results for binary alkane mixtures. – In our recent work on the thermophysical properties of low-density binary alkane mixtures, we have developed a flexible extension of the physically reasonable Tang−Toennies mixing rules. , This new scheme is called Hohm−Zarkova−Damyanova (HZD) mixing rules. We have shown that in general these more sophisticated HZD mixing rules work better compared to the old Lorentz−Berthelot combination scheme as long as the thermophysical properties B , η, and D of binary mixtures are considered .…”

“… , This new scheme is called Hohm−Zarkova−Damyanova (HZD) mixing rules. We have shown that in general these more sophisticated HZD mixing rules work better compared to the old Lorentz−Berthelot combination scheme as long as the thermophysical properties B , η, and D of binary mixtures are considered . The present paper is a considerable extension of our preliminary study on the binary mixtures of small alkanes .…”