Premium
Solvatochromic characterization of the liquid phase in liquid—supercritical CO 2 mixtures
Author(s) -
Kelley Sean P.,
Lemert Richard M.
Publication year - 1996
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690420725
Subject(s) - supercritical fluid , solvatochromism , characterization (materials science) , liquid liquid , liquid phase , phase (matter) , materials science , chromatography , chemical engineering , chemistry , analytical chemistry (journal) , organic chemistry , thermodynamics , nanotechnology , solvent , physics , engineering
The solvatochromic dye phenol blue (N, N‐dimethylindoaniline) is used to characterize the solvent strength (polarity) of the saturated liquid phase in a series of solvent–carbon dioxide binary mixtures. Data were obtained at 35 and 55°C and at pressures up to ∼70 bar. Five solvents were investigated—acetone, cyclohexane, methanol, THF, and toluene. The polarity of the liquid phase decreases significantly with increasing pressure due to the increasing carbon dioxide content of this phase at equilibrium. For example, the polarity of acetone saturated with carbon dioxide at 35°C and ∼60 bar is equivalent to the polarity of pure cyclohexane at ambient pressure. The local environment about the dye is significantly richer in the polar liquid component than the bulk composition would indicate. The degree of enrichment reflects concentration effects at low pressure, and both concentration and pressure effects at high pressure where the mixtures are highly compressible. The NRTL model of Renon and Prausnitz is able to predict these local compositions with reasonable accuracy except at CO 2 ‐rich conditions where compressibility effects are important.