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Interpreting gas-saturation vapor-pressure measurements using virial coefficients derived from molecular models

Published

Author(s)

Shu Yang, Andrew J. Schultz, David A. Kofke, Allan H. Harvey

Abstract

Gas-saturation measurements of apparent vapor pressures of heavy organic molecules are found to depend on the carrier gas when interpreted with an ideal-gas model of the vapor mixture, indicating that treatment of non-ideality is needed to interpret the experimental data properly. The virial equation of state (VEOS) for mixtures presents a convenient means to develop such an approach. Coefficients of this equation can be computed from molecular models, which provides a good foundation for applications to both pure fluids and mixtures. We examine VEOS for helium (He), carbon dioxide (CO2), nitrogen (N2) and sulfur hexafluoride (SF6), which are sometimes used as carrier gases in experimental measurements. For the heavy organic, we examine normal tetradecane (C14H30) and normal eicosane (C20H42) as prototype molecules. Both the pure virial coefficients of every species and the cross virial coefficients of He/CO2/N2/SF6 with n-eicosane binaries are calculated up to the 3rd order; cross virial coefficients of SF6 with n-tetradecane binaries are calculated at 2nd order. Using these coefficients, we calculate corrections to the vapor pressure of n-tetradecane at 283.15, 293.15, 303.15, and 313.15 K for an SF6 carrier gas, and n-eicosane at 323.15 K for all four carrier gases.
Citation
Journal of Chemical and Engineering Data
Volume
59

Keywords

gas saturation, molecular modeling, nonideality, vapor pressure, virial coefficients

Citation

Yang, S. , Schultz, A. , Kofke, D. and Harvey, A. (2014), Interpreting gas-saturation vapor-pressure measurements using virial coefficients derived from molecular models, Journal of Chemical and Engineering Data, [online], https://doi.org/10.1021/je500245f (Accessed August 3, 2021)
Created July 2, 2014, Updated June 2, 2021