Cross Second Virial Coefficients and Dilute Gas Transport Properties of the (CH₄+ C₃H₈) and (CO₂+ C₃H₈) Systems from Accurate Intermolecular Potential Energy Surfaces

Abstract

Accurate values for the cross second virial coefficients and dilute gas shear viscosities, thermal conductivities, and binary diffusion coefficients of the (CH 4 + C 3 H 8 ) and (CO 2 + C 3 H 8 ) systems were determined at temperatures from (150 to 1200) K using state-of-the-art computational approaches. The cross second virial coefficients were calculated semiclassically using the Mayer-sampling Monte Carlo method, while the transport properties were computed by means of the classical trajectory approach in conjunction with the kinetic theory of molecular gases. The required intermolecular potential energy surfaces (PESs) for the CH 4 −C 3 H 8 and CO 2 −C 3 H 8 interactions are reported in this work, whereas those for the CH 4 −CH 4 , CO 2 −CO 2 , and C 3 H 8 −C 3 H 8 interactions were taken from our previous work on the pure gases. All PESs are based on high-level quantum-chemical ab initio calculations and were fine-tuned to the best experimental data for the second virial and cross second virial coefficients. Overall, the agreement of the calculated thermophysical property values with the few available experimental data is satisfactory.

Ab initio intermolecular potential energy surface for the CO2—N2 system and related thermophysical properties

“…The high-temperature data (T > 298 K) of Kestin and Ro are known to suffer from a design flaw 71 in their viscometer that resulted in viscosity values that are always systematically too high above room temperature by up to about 1%. 5,10,13,14,16,17,65 This is consistent with the observed deviations. We conservatively estimate the combined standard uncertainty of the scaled values to vary from 0.2% for pure CO 2 to 0.15% for pure N 2 between 300 K and 700 K, increasing to 1% for pure CO 2 and 0.5% for pure N 2 , respectively, outside of this temperature range.…”

“…Binary diffusion coefficients measured by the Dunlop group are consistently in excellent agreement with theoretically calculated values as illustrated for other dilute gas systems. 17,93 The other experimental data shown in Fig. 7 exhibit larger scatter and have larger uncertainties than that of Robjohns and Dun-lop, especially the high-temperature data of Pakurar and Ferron, which have quoted uncertainties of 10%.…”

“…Recently, Hellmann and co-workers have extended their work on pure gases 1,[4][5][6][7][8][9][10][11][12][13] to binary mixtures, namely CH 4 -N 2 , 14,15 CH 4 -CO 2 , 16 CH 4 -H 2 S, 16 H 2 S-CO 2 , 16 CH 4 -C 3 H 8 , 17 and CO 2 -C 3 H 8 , 17 and successfully validated the respective kinetic theory expressions for the transport properties. [14][15][16] The extension of the calculations to binary mixtures provides not only accurate thermophysical property data for such systems, but also all the input data for the calculation of thermophysical properties of any multicomponent mixture consisting of species for which the binary properties are available.…”

“…Similar weighting functions were already employed by Hellmann in previous works. 8,9,17 An additional weight factor of 100 was used for the energies of both minimum configurations to ensure a perfect match. Figure 2 shows the distance dependence of the ab initio interaction energies and of the fitted analytical potential function for 8 of the 93 considered angular configurations.…”

Reference Values for the Second Virial Coefficient and Three Dilute Gas Transport Properties of Ethane from a State-of-the-Art Intermolecular Potential Energy Surface

“…In our previous studies of intermolecular PESs involving hydrocarbons, ,,,, we observed systematic positive deviations of the ab initio calculated values for the second virial and cross second virial coefficients from most of the experimental data. This is mainly due to the use of rigid monomers, resulting in the neglect of important vibrational contributions to the dispersion coefficients, see ref and references therein.…”