Modeling the phase behavior, excess enthalpies and Henry's constants of the H2O + H2S binary mixture using the SAFT-VR+D approach

M. Carolina dos Ramos, Clare McCabe*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

19 Citations (Scopus)

Abstract

The high-pressure phase diagram and other thermodynamic properties of the binary systems of water + hydrogen sulphide have been examined using the SAFT-VR+D equation of state [Zhao and McCabe, J. Chem. Phys. 125 (2006) 104504]. The SAFT-VR+D approach is based on a version of the statistical associating fluid theory that was developed to model dipolar fluids by explicitly accounting for dipolar interactions and their effect on the thermodynamics and structure of a fluid. In the SAFT-VR+D equation this is achieved through the use of the generalized mean spherical approximation (GSMA) to describe a monomer fluid of dipolar square-well segments. In the present work, we further develop the SAFT-VR+D equation to study mixtures of dipolar associating fluids of arbitrary size using the analytical solution of the Ornstein-Zernike equation due to Cummings and Blum [J. Chem. Phys. 84, 1833 (1986)]. The high-pressure phase diagram and other thermodynamic properties of the water + hydrogen sulphide binary mixture are then examined. Both components, hydrogen sulphide and water, are naturally modeled as associating spherical molecules with four off-centre sites to mimic hydrogen bonding and an embedded dipole moment (μ) to describe their polarity. Using simple Lorentz-Berthelot combining rules, the theory is able to predict the phase behavior of the H2O + H2S system from pure component parameters. Specifically, type III phase behavior according to the classification of Scott and van Konynenburg is observed, with a three-phase line at low temperatures that terminates at an upper critical end point and two separate critical lines, one at high temperatures that runs continuously from a gas-liquid critical line to a liquid-liquid critical line at high pressures and a second gas-liquid critical line located at low temperatures. The phase behavior predicted by the SAFT-VR+D approach is in excellent agreement with the experimental data, without requiring any fitted binary interaction parameters. In addition, the theory is also able to describe the excess molar enthalpies and the most important features of the Henry's constants as a function of temperature.

Original languageEnglish
Pages (from-to)137-147
Number of pages11
JournalFluid Phase Equilibria
Volume290
Issue number1-2
DOIs
Publication statusPublished - 25 Mar 2010

Keywords

  • Equation of state
  • Excess enthalpy
  • Henry's constants
  • Hydrogen sulphide
  • Phase behavior
  • Polar systems
  • SAFT-VR+D
  • Solubility
  • Water

ASJC Scopus subject areas

  • General Chemical Engineering
  • General Physics and Astronomy
  • Physical and Theoretical Chemistry

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