Phase Equilibria of Mixtures Containing Organic Sulfur Species (OSS) and Water/Hydrocarbons: VLE Measurements and Modeling Using the Cubic-Plus-Association Equation of State

Abstract : We report new vapor-liquid equilibrium (VLE) data for dimethyl sulfide (DMS) in pure water, performed at three temperatures (303, 330, and 362 K) in the 1-8 MPa pressure range. The total system pressure was maintained introducing CH4. The inlet mole fraction of DMS was the same in all experiments, around 1.5 × 10-3 in the liquid phase. A “static-analytic” method was used for performing all of the measurements. The objective is to provide experimental VLE data for the dimethyl sulfide + CH4 + water system, for which no data are available in the open literature. These data will allow industry to model sulfur emissions. The new VLE data as well as the VLE data of some binary systems from the literature containing organic sulfur species + hydrocarbon, organic sulfur species + water, and some ternary systems containing organic sulfur species in hydrocarbons and water have been modeled successfully with the cubic-plus-association (CPA) equation of state. Useful remarks are presented about the application of Henry's constant values to estimate binary interaction parameters of the CPA EoS for the description of whole vapor-liquid equilibria. The results using CPA EoS show that the cross association interactions in the methyl mercaptan + water system and ethyl mercaptan + water system should be considered. In aqueous mixtures of higher mercaptans, the consideration of such interactions does not improve the calculations, indicating that they are rather weak.