Vapor–Liquid Equilibrium of the Hydrogen Sulfide (H₂S) – Benzene (C₆H₆) Binary System: Experimental and Modeling Study

The phase behavior of the hydrogen sulfide (H₂S) - benzene (C₆H₆) binary system is critical for optimizing gas sweetening, aromatic solvent recovery, and high-pressure reservoir in the petroleum industry, while ensuring environmental compliance. This study presents new isothermal vapor-liquid equilibrium (VLE) measurements for the H₂S - C₆H₆ system at 278.21 K, 298.36 K, 323.38 K, and 343.39 K, covering pressures up to 4.5 MPa. The experimental data were obtained using a static-analytic method with two magnetic capillary samplers (ROLSI®), enabling precise sampling and analysis of both liquid and vapor phases via gas chromatography. The measurements have uncertainties of u(T, k=2)= 0.02 K for temperature, u(P, k=2)= 0.0008 MPa for pressure, and u(z) = 0.006 for molar compositions. The VLE data were modeled using the Peng–Robinson equation of state with classical van der Waals mixing rules and an alternative approach combining modified Huron–Vidal mixing rules with the NRTL model for the liquid phase. In addition, the predictive PPR78 and PSRK models were evaluated against the experimental dataset. With optimized binary interaction parameters, all models reproduced the measured data with acceptable deviations, effectively capturing the strongly non-ideal behavior of the H₂S–C₆H₆ system. These results extend the experimental database for H₂S–C₆H₆ mixtures, validate robust EOS-based and predictive modeling frameworks, and provide a reliable foundation for industrial process design, simulation, and optimization.