Density and Volumetric Behavior of CO₂ + Undecane System from 313.15 to 353.15 K and Pressures up to 19 MPa

Abstract

Densities of compressed CO2 + undecane binary mixtures were measured using a magnetic suspension balance (MSB). Measurements were made at temperatures ranging from 313.15 to 353.15 K and pressures ranging from 8 to 19 MPa at CO2 mole fractions (x 1) of 0, 0.2483, 0.4641, 0.6797, and 0.8874. The mixture densities were found to increase linearly with pressure and decrease with temperature; this behavior is similar to that of CO2 + decane or dodecane mixtures. The mixture densities show a crossover with composition when the CO2 mole fraction is high. The densities of alkanes increase almost linearly with carbon number, as do the densities of CO2 + alkane mixtures. With the of CO2 mole fraction, the mixture densities increase at first, then decrease. The increase of pressure makes the excess molar volume less negative, whereas the increase of temperature makes it more negative. Densities calculated from the perturbed hard chain equation of state (PHSC EOS) with improved parameters are in good agreement with the experimental densities. Adopting the constant binary interaction parameter k ij for different alkanes in the PHSC EOS slightly enlarge the model deviation but simplifies the calculation.

Volumetric Properties and Solubility Parameters of Cyclohexane + CO2 Mixtures at High Pressures and Their Modeling with the Sanchez–Lacombe Equation of State

“…It should be noted that at 373 and 393 K the crossover pressure is not fully reached by 35 MPa. Such crossover phenomena have been reported for other mixtures of carbon dioxide with organic solvents. ,,,, …”

“…Similar trends are reported for mixtures of CO 2 with other hydrocarbons, such as decane or undecane . In mixtures of carbon dioxide with undecane, high negative excess volumes approaching −34 cm 3 mol –1 are reported for the mixtures with high CO 2 content …”

“…In the literature, the excess volume is often modeled with a Redlich–Kister-type equation, − which can be described by For binary mixtures, when the summation is limited to the first two terms, it reduces to This can be expanded into a third-order polynomial: Referring to CO 2 as component 1 and cyclohexane as component 2, the present excess volume data were fitted to this third-order polynomial and the parameters A 0 and A 1 were evaluated using mole fractions describing each composition. They were then fitted to the following second-order polynomials to describe the temperature dependence of these parameters: The coefficients a , b , c , d , e , and f were then fit to second-order polynomials of the form to describe their variations with pressure ( P ).…”

“…51 In mixtures of carbon dioxide with undecane, high negative excess volumes approaching −34 cm 3 mol −1 are reported for the mixtures with high CO 2 content. 51 In the literature, the excess volume is often modeled with a Redlich−Kister-type equation, 51−55 which can be described by…”

“…Among the specific mixtures that have been investigated in our laboratory are mixtures of carbon dioxide with ethanol, acetone, toluene, pentane, and, more recently, ethyl acetate . Among other mixtures that have been reported in the literature are mixtures of carbon dioxide with various hydrocarbons including (but not limited to) heptane, decane, − undecane, and tridecane . We are now reporting comprehensive data on the density and derived thermodynamic properties of mixtures of carbon dioxide with cyclohexane.…”