Fluid Mixtures at High Pressure. Phase Separation and Critical Phenomena in Binary Mixtures of a Polar Component with Supercritical Carbon Dioxide, Ethane, and Ethene up to 1000 Bar.

Abstract

Fluide ilrlischiinyen I Holie Driicke I Kritische Erscheinunyen I PhasenumH.andlunger1 I ThermodynomikIn order to study the polarity effect on the critical phase behaviour of fluid binary systems the critical temperatures of binary mixtures of carbon dioxide, ethane, ethene. hexane, or 1-hexene with a second component of very different polarity such as methanol, 2-hexano1, 2-octanol. 2.5-hexanediol, nitromethane, N,N-dimethylformamide, or N-methylacetamide were determined as a function of pressure up to 1000 bar. The critical p ( T ) curves obtained exhibit a whole pattern of different transition types between liquid-gas, liquid-liquid, and gas-gas equilibria; they are compared with data for other systems taken from the literature. The results verify a previous hypothesis that there are continuous transitions between liquid-gas, liquid-liquid, and gas-gas critical phenomena in fluid binary mixtures at high pressures. The measurements are of interest for fluid extraction and supercritical fluid chromatography (SFC). Lwischen Fliissig-Gas-, Fliissig-Flussig-und Gas-Gas-Gleichgewichten; sie werden im Vergleich zu Literaturdaten fur andere Systeme diskutiert. Die Ergebnisse bestatigen eine friihere Hypothese, wonach kontinuierliche Ubergange zwischen Fliissig-Gas-, Flussig-Flussig-und GasGas-Gleichgewichten in fluiden Mischsystemen unter hohen Drucken existieren. Die Messungen sind von Interesse fur die Fluidextraktion und die Fluidchromatographie (SFC). Zur Untersuchung des Polaritatseffektes auf das kritische

The application of a shear mode piezoelectric sensor to monitoring the high-pressure phase behaviour of asymmetric binary systems

“…In addition, this system shows a liquid-liquid critical curve at temperatures between 275.2 and 279.6 K, and pressures up to 95 MPa. Therefore, it has been suggested [65] that the system of 2-octanol + CO 2 may belong to Type II. The liquid-liquid immiscibility at lower temperatures should not interfere with the measurements for the vapour-liquid critical points.…”

“…Our research interest was initially focused on the measurements of the critical points of this system because the reaction rate and selectivity may be related to the phase behaviour, particularly the critical points of the mixtures [31,43]. The phase behaviour of this system has been studied in the literature using the synthetic method [65], and sampling [66], and it is reported that this binary system exhibits a non-interrupted critical curve for the vapour-liquid equilibrium, running though the usual pressure maximum. In addition, this system shows a liquid-liquid critical curve at temperatures between 275.2 and 279.6 K, and pressures up to 95 MPa.…”

Fluid Phase Equilibria of Mixtures at High Pressure

“…3). Whereas the ethane+ methanol system [17] belo ngs to type 2 in Fig. lf and the ethane + water system [18] to type 2 in Fig.…”

“…lh (the latter corresponding to a gas-gas equilibrium system of the second kind) all other ethane binaries in Fig. 4 [17] show intermediate types of phase behavior; e.g., ethane+ nitromethane exhibits a phase behavior of type 1 in Fig. lh.…”

“…*Invited paper. [17]. Legend: p(x) isotherms; critical curve of binary mixtures; ---vapor pressure curve of pure component; three-phase line llg; C critical endpoint).…”