In:
The Journal of Chemical Physics, AIP Publishing, Vol. 128, No. 10 ( 2008-03-14)
Kurzfassung:
The study of inhomogeneity in supercritical fluids (SCFs) is of great importance. In this work, we propose the concept of local activity coefficients in supercritical (SC) solutions, which link thermodynamics and inhomogeneity in SC systems. The local activity coefficients of CO2+acetonitrile+phenol blue and CO2+aceticacid+phenol blue systems are investigated at 308.15K in critical region and outside critical region. To do this, the local compositions of CO2+acetonitrile and CO2+acetic acid mixed solvents around phenol blue are first estimated using UV-visible spectroscopy. Then it is considered that there exist bulk phase and local phase around phenol blue in the systems. The activity coefficients of CO2 and the cosolvents (acetonitrile or acetic acid) in bulk phase are calculated using Peng-Robinson equation of state. The local activity coefficients of CO2 and the cosolvents are then calculated on the basis of thermodynamic principles. It is demonstrated that in the critical region the local activity coefficients differ from bulk activity coefficients significantly and are sensitive to pressure. This can explain many unusual phenomena in SC systems in critical region thermodynamically.
Materialart:
Online-Ressource
ISSN:
0021-9606
,
1089-7690
Sprache:
Englisch
Verlag:
AIP Publishing
Publikationsdatum:
2008
ZDB Id:
3113-6
ZDB Id:
1473050-9
