Experimental determination and theoretical predictions of the isothermal (344.15 K) mass densities and
interfacial tensions for the sys
tem carbon dioxide (CO2) with heptol (n
-
heptane + toluene) mixtures
varying liquid volume fraction compositions of toluene (0, 25, 50, 75, 100 % v/v) and over the pressure
range 0.1 to 8 MPa are reported. Measurements are carried out on a high
-
pressure dev
ice that includes a
vibrating tube densimeter and a pendant drop tensiometer. Theoretical modeling of mass densities phase
equilibria and interfacial properties (i.e., interfacial tension and interfacial concentration profiles) are
performed by employing t
he Square Gradient Theory using an extension of the Statistical Associating
Fluid Theory equation of state that accounts for ring fluids. The experimental bulk phase equilibrium
densities and interfacial tensions obtained are in very good agreement with th
e theoretical predictions.
Although there are no previous experimental data of these mixtures at the conditions explored herein, the
results follow the same trends observed from experimental data at other conditions. The combination of
experimental and mod
eling approaches provides a route to simultaneously predict phase equilibrium and
interfacial properties within acceptable statistical deviations.
For the systems and conditions studied here, we observe that the phase equilibrium of the mixtures
display z
eotropic vapor
-
liquid equilibria with positive deviations from ideal behavior. The mass bulk
densities behave ordinarily whereas the interfacial tensions decrease as the pressure or liquid mole
fraction of CO2 increases and/or the ratio toluene/heptane dec
reases. The interfacial concentration along
the interfacial region exhibits a remarkable high excess adsorption of CO2, which increases with pressure
and it is larger in n
-
heptane than in toluene. Toluene does not exhibit any special adsorption activity wh
ereas n
-
heptane displays surface activity only at low pressure in a very narrow range for the case of
CO2 + (25% n
-
heptane + 75% toluene) mixture.