Density and Volumetric Behavior of Ternary CO₂ + <i>n</i>-Decane + <i>n</i>-Butylcyclohexane Mixtures at High Pressure and High Temperature

Abstract

This paper presents density experimental data for pure n-butylcyclohexane, along with carbon dioxide + n-decane + n-butylcyclohexane ternary mixtures, for temperature ranging from 298.15 to 423.15 K and pressure was up to 100.0 MPa. Density measurements were made using a vibrating tube densitometer. Ternary mixture compositions were defined in four different classes, as follows: (i) high CO2 content (xCO2= 0.60; xn-decane = 0.20; xn-butylcyclohexane = 0.20), (ii) high alkane content (xCO2= 0.20; xn-decane = 0.60; xn-butylcyclohexane = 0.20), (iii) high cycloparaffin content (xCO2= 0.20; xn-decane = 0.20; xn-butylcyclohexane = 0.60), and (iv) equimolar content (xCO2= xn-decane = xn-butylcyclohexane = 0.33). From these data sets, excess molar volumes were calculated showing negative values over the entire composition range for all ternary systems. Experimental density data were correlated to the modified Tammann–Tait equation as a function of temperature and pressure. The adjusted equation presented a maximum deviation (MD) of 1.12%. Additionally, isothermal compressibility (kT) and isobaric thermal expansion coefficient (αp) were calculated from the experimental density data. It was observed that isothermal compressibility (kT) increases by increasing temperature and isobaric thermal expansion coefficient (αp) remains constant for a pressure up to 55.0 MPa for all ternary systems studied here.