Prediction of Interfacial Properties of Ternary, Sulfur-containing Mixtures

Abstract

Sulfur-containing gases, like SO 2 and H 2 S are toxic; therefore, experimental data are rare. However, these gases are important in many technical processes, for instance in enhanced oil recovery, where information about the phase behavior and the interfacial properties of mixtures with these gases are required. In this contribution, we investigated these properties theoretically using PCP-SAFT-EOS in combination with density gradient theory. We focus on ternary systems made of sulfurcontaining molecules, carbon dioxide and n-heptane representing the oil. With purecomponent parameters taken from the literature and binary interaction parameters taken also from the literature, except these for SO 2 + heptane and H 2 S + heptane, which were fitted in this work, the phase behavior of the corresponding ternaries over a large temperature and pressure range was predicted. Additionally, the interfacial tension as well as the partial density profiles across the interface were studied. The presence of sulfur compounds leads to a reduction of interfacial tension in comparison with the binary subsystem CO 2 + heptane. Additionally to the predictions polynomial expressions for calculation of surface tension as a function of liquid composition, temperature and pressure are provided in this work. This approach allows the representation of the surface tension of ternary systems very precisely with reduced numerical effort.

Enrichment at vapour–liquid interfaces of mixtures: establishing a link between nanoscopic and macroscopic properties

“…At least, no contrary evidence has been reported yet to the best of our knowledge. In the case of multicomponent mixtures, a simultaneous enrichment has been reported for several low-boiling components [16,[70][71][72][73][74][75].…”

“…The density profiles ρ i (z) were obtained from different theoretical methods (molecular simulations, DGT, DFT, or a combination of those). Since data on ternary and multicomponent mixtures have been reported relatively scarcely in the literature [36,54,[70][71][72][73][74][75][87][88][89][90][91][92][93], they are not listed in Table 1.…”

Vapor-liquid interfacial properties of the system cyclohexane + CO2: Experiments, molecular simulation and density gradient theory

“…Density gradient theory [84,85] is a widely used method for computing the surface tension of both pure substances [6,46,86,87] and mixtures [42,43,49,51,53,54,[88][89][90]. Also, nanoscopic interfacial properties can be obtained from DGT, namely the density profiles across the interface.…”

Vapor−Liquid Interface of the Lennard-Jones Truncated and Shifted Fluid: Comparison of Molecular Simulation, Density Gradient Theory, and Density Functional Theory

“…Density gradient theory [66][67][68] is a widely used framework for calculating surface tensions for pure substances [69][70][71] and mixtures [72][73][74][75][76][77][78] based on an EoS, especially for real substances. For a comprehensive introduction we refer to.…”