High-pressure densities and interfacial tensions of binary systems containing carbon dioxide + n-alkanes: (n-Dodecane, n-tridecane, n-tetradecane)

Abstract

Experimental isothermal densities and interfacial tensions for the binary systems carbon dioxide+n-dodecane, carbon dioxide+n-tridecane and carbon dioxide+n-tetradecane at 344.15K and over the pressure range 0.1 to 12, 13 and 14MPa, are reported. Measurements are carried out on a combined device that includes a high-pressure vibrating tube densimeter and a high-pressure pendant drop tensiometer. The theoretical modeling is based on the use of square gradient theory as applied to the statistical associated fluid theory (SAFT) equation of state. The experimental bulk phase equilibrium densities and interfacial tensions obtained are in very good agreement with the theoretical modeling. By seamlessly combining experimental and modeling approaches we are able to simultaneously predict phase equilibrium and interfacial properties. For the systems and conditions studied we do not observe mass nor molar barotropic inversion; the interfacial tensions decrease as the pressure (or liquid mole fraction of carbon dioxide) and/or as the n-alkane molecular chain length increases. The surface relative Gibbs adsorption of the species along the interfacial region is reported; carbon dioxide is adsorbed along the interfacial region, whereas n-alkanes (n-dodecane, or n-tridecane or n-tetradecane) do not exhibit any special adsorption activity. The adsorption of carbon dioxide increases with pressure and with the chain length of the n-alkane.