Density and Volumetric Behavior of Binary CO₂ + n-Decane and Ternary CO₂ + n-Decane + Naphthalene Systems at High Pressure and High Temperature

Abstract

Densities of the carbon dioxide + n-decane binary system and carbon dioxide + n-decane + naphthalene ternary system have been measured up to 130 and 100 MPa, respectively, by using a vibrating tube densitometer. The measurements covered the molar compositions of CO2 of 0.1182, 0.3050, 0.6271, and 0.9539 for the first system, at temperatures from 318.15 to 358.15 K. While for the ternary mixtures, the measurements were performed for four compositions: high alkane, high aromatic, high CO2, and one equimolar content, at a temperature range of 328.15–423.15 K. From these data, excess molar volumes were calculated for both systems, showing positive values at lower temperatures and higher pressures for the binary mixtures, while negative values were observed for the ternary mixtures over the entire composition range. For both systems, the density was correlated by using a modified Tammann–Tait equation, as a function of temperature and pressure, presenting a maximum deviation of 0.63 and 1.72% for the binary and ternary systems, respectively. Additionally, isothermal compressibility and isobaric thermal expansivity were calculated from the experimental density data. It was observed that higher compressibility values were found at lower pressures and at higher CO2 content for both binary and ternary systems. Rich aromatic systems are less compressible when compared to rich CO2 systems. Regarding isobaric thermal expansivity, temperature dependence could be neglected for all binary mixtures. However, for the ternary mixtures, this dependence was strongly related to mixture composition.

Density and Volumetric Behavior of Ternary CO2 + n-Decane + cis-Decalin (or + trans-Decalin) Mixtures at High Pressure and High Temperature

“…These results indicate that the addition of CO 2 , above a certain molar composition, reaches a minimal difference regardless of decalin isomers studied ( cis -decalin or trans -decalin), i.e., structural isomerism has a minimal influence on the ternary system intermolecular interactions, and the CO 2 composition dominates the volumetric behavior. This is similar to the results obtained for the ternary system CO 2 + n -decane + naphthalene, as previously published . In the same way, for high- n -decane content mixtures, density data are almost the same for cis -decalin and trans -decalin, especially at pressure below 20 MPa.…”

“…The gas was injected at a constant pressure (10 MPa) at room temperature (298.15 K). A more detailed description could be found elsewhere . Finally, the mixture prepared has been pressurized until 50 MPa to reach a liquid-phase region.…”

“…Density uncertainty is ±0.1 kg/m 3 . Further apparatus details and the calibration process were addressed previously . Calibration was performed by using deionized water (resistivity of 18.2 ± 0.2 MΩ·cm at 298.15 K) and nitrogen (White Martins/Brazil, nominal purity of 99.996%).…”

“…Density measurements were carried out at a predefined temperature set point and following pressure steps from 15 to 100 MPa when the cell’s vibration period reached a plateau after, at least, 40 min. The schematic flow diagram and further details of the measurement assemble can be found elsewhere …”

Density of n-Heptane + n-Dodecane and Carbon Dioxide + n-Heptane + n-Dodecane Mixtures up to 70 MPa from (293.15 to 363.15) K

“…Their study reported the density of this mixture at temperatures from (293 to 318) K and pressure up to 100 MPa. Furthermore, the availability of density data for ternary or multicomponent mixtures comprising alkanes with dissolved CO 2 is even more restrictive. − …”