Binary systems supercritical carbon dioxide

The NMR method we have developed gives a direct, in situ determination of the solubility and also allows us to obtain phase data on the system. In this study we have measured the solubilities of solid naphthalene in supercritical carbon dioxide along three isotherms (50.0, 55.0, and 58.5°C) near the UCEP temperature over a pressure range of 120-500 bar. We have also determined the pressure-temperature trace of the S-L-G phase line that terminates with the UCEP for the binary mixture. Finally, we have performed an analysis of our data using a quantitative theory of solubility in supercritical fluids to help establish the location of the UCEP. 

Experimental results are presented for high pressure phase equilibria in the binary systems carbon dioxide - acetone and carbon dioxide - ethanol and the ternary system carbon dioxide - acetone - water at 313 and 333 K and pressures between 20 and 150 bar. A high pressure optical cell with external recirculation and sampling of all phases was used for the experimental measurements. The ternary system exhibits an extensive three-phase equilibrium region with an upper and lower critical solution pressure at both temperatures. A modified cubic equation of a state with a non-quadratic mixing rule was successfully used to model the experimental data. The phase equilibrium behavior of the system is favorable for extraction of acetone from dilute aqueous solutions using supercritical carbon dioxide. 

A recirculation apparatus for the determination of high pressure phase equilibrium data for mixtures of water, polar organic liquids and supercritical fluids was constructed and operated for binary and ternary systems with supercritical carbon dioxide. 

A high-pressure circulation-type apparatus was designed and constructed to investigate the vapor-liquid equilibria (VLE) of systems containing limonene, linalool and supercritical carbon dioxide. VLE data of binary and ternary systems of these compounds can be determined in the ranges of pressure and temperature of interest for the deterpenation of cold-pressed orange oil. The preliminary results obtained for the binaries CC -linalool and C02-limonene were compared to data already published with acceptable accuracy and well correlated by a modified Soave-Redlich-Kwong (SRK) equation of state. 

Chrisochoou AA, Schaber K, Stephan K. Phase equilibria with supercritical carbon dioxide for the enzymatic production of an enantiopure pyrethroid component. 1. Binary systems. J Chem Eng Data 1997 42 551-557. 

Strubinger JR, Song H, Parcher JF. High pressure phase distribution isotherms for supercritical fluid chromatographic systems. 2. Binary isotherms of carbon dioxide and methanol. Anal Chem 1991 63 104-108. 

This chemical and physico-chemical behavior of the binary H2O-CO2 mixture [38] suggests that water is an attractive liquid to be combined with supercritical carbon dioxide in multiphase catalysis. CO2/H2O systems have adequate mass-transfer properties, especially if emulsions or micro-emulsions can be formed ([39] and refs, therein). The low pH of aqueous phases in the presence of compressed CO2 (pH ca. 3-3.5 [40]) must be considered and the use of buffered solutions can be beneficial in the design of suitable catalytic systems, as demonstrated for colloid-catalyzed arene hydrogenation in water-scC02 [41]. 

A second type of ternary electrolyte systems is solvent -supercritical molecular solute - salt systems. The concentration of supercritical molecular solutes in these systems is generally very low. Therefore, the salting out effects are essentially effects of the presence of salts on the unsymmetric activity coefficient of molecular solutes at infinite dilution. The interaction parameters for NaCl-C02 binary pair and KCI-CO2 binary pair are shown in Table 8. Water-electrolyte binary parameters were obtained from Table 1. Water-carbon dioxide binary parameters were correlated assuming dissociation of carbon dioxide in water is negligible. It is interesting to note that the Setschenow equation fits only approximately these two systems (Yasunishi and Yoshida, (24)). 

During the 1940s, a large amount of solubility data was obtained by Francis (6, 7), who carried out measurements on hundreds of binary and ternary systems with liquid carbon dioxide just below its critical point. Francis (6, 7) found that liquid carbon dioxide is also an excellent solvent for organic materials and that many of the compounds studied were completely miscible. In 1955, Todd and Elgin (8) reported on phase equilibrium studies with supercritical ethylene and a number of... 

We have applied some of these principles to the extraction of 1-butene from a binary mixture of 1,3-butadiene/1-butene. Various mixtures of sc solvents (e.g., ethane, carbon dioxide, ethylene) are used in combination with a strongly polar solvent gas like ammonia. The physical properties of these components are shown in Table I. The experimental results were then compared with VLE predictions using a newly developed equation of state (18). The key feature of this equation is a new set of mixing rules based on statistical mechanical arguments. We have been able to demonstrate its agreement with a number of binary and ternary systems described in the literature, containing various hydrocarbon compounds, a number of selected polar compounds and a supercritical component. 

In the present study, we tested the validity of the EOS-Ge models by applying different treatments for 21 binary solid/supercritical fluid systems listed in table 2. In those systems, the supercritical component is one of the following fluids carbon dioxide, ethane, fluoroform and chlorotrifluoromethane and the solid component is either a nonpolar compound... 

The first chiral separation using pSFC was published by Caude and co-workers in 1985 [3]. pSFC resembles HPLC. Selectivity in a chromatographic system stems from different interactions of the components of a mixture with the mobile phase and the stationary phase. Characteristics and choice of the stationary phase are described in the method development section. In pSFC, the composition of the mobile phase, especially for chiral separations, is almost always more important than its density for controlling retention and selectivity. Chiral separations are often carried out at T < T-using liquid-modified carbon dioxide. However, a high linear velocity and a low pressure drop typically associated with supercritical fluids are retained with near-critical liquids. Adjusting pressure and temperature can control the density of the subcritical/supercritical mobile phase. Binary or ternary mobile phases are commonly used. Modifiers, such as alcohols, and additives, such as adds and bases, extend the polarity range available to the practitioner. 

An analytic method has been used to produce pVTxy measurements for binary systems containing methyl oleate and supercritical solvents. A micro dual-sampling system has been added to our apparatus for taking vapor and liquid samples. The systems ethane-methyl oleate and carbon dioxide-methyl oleate were studied along isotherms at 313.15 K and 343.15 K up to pressures substantially greater than the critical pressures of the pure solvents. Comparisons are made between the experimental data and predictions using the Peng-Robinson equation of state. 

The results for the carbon dioxide and propane binary system, shown as dashed lines in Figure 4.2.2, on the other hand are not as good. When compared with the performance of the IPVDW model (solid lines in Figure 4.2.2), the use of the same parameters for all isotherms leads to inferior results at higher temperatures despite the use of an extra parameter in the Huron-Vidal model. This indicates that, for the mixtures containing supercritical components, the HVO mixing rule, when combined... 

Figure 3.21 Examples of binary solid-supercritical fluid systems with a temperature minimum in the SLV line (a) carbon dioxide-solid systems (McHugh and Yogan, 1984) (b) methane-naphthalene system (van Hest and Diepen, 1963).

Radically different binary phase behavior is found for the methane-TMB and the methane-methanol systems. This suggests that TMB can be extracted from methanol. To verify this conjecture experimental information was obtained on the TMB-methanol-methane system to ascertain whether the weak TMB-methanol complex can be broken by nonpolar methane. Interestingly, carbon dioxide, ethane, and ethylene, all much better supercritical solvents than methane, dissolve both methanol and TMB to such a large extent that they are not selective for either component. But with methane, the interactions between methane and TMB are strong enough to maintain a constant concentration of TMB in the extract phase as TMB is removed from the methanol-rich liquid phase. This means that the distribution coefficient for TMB increases as the concentration in the liquid phase decreases. We know of no other system that exhibits this type of distribution coefficient behavior. 

Yonker, C. R., and R. D. Smith. 1988. Solvatochromic behavior of binary supercritical fluids The carbon dioxide/2-propanol system. J. Phys. Chem. 92 2374-2378. 

Lam, D.H., JangkamoUculchai, A. and Luks, K.D. (1990) Liquid-liquid-vapor phase equilibrium behavior of certain binary carbon dioxide + n-alkanol mixtures. Fluid Phase Equilibria, 60,131-141. Gurdial, G.S., Foster, N.R., Jimmy Yun, S.L. and Tilly, KJ3. (1993) Phase behavior of supercritical fluid-entrainer systems, in Siqtercritical Fluid Engineering Science, Fundamentals and Applications, E. Kiran and JJ. Brennecke (Eds.), ACS Symposium Series No. 514, pp. 34-45. 

The most investigated binary ionic liquid systems are mixtures with carbon dioxide (CO2). In 1999, Blanchard et al showed that the solubility of CO2 in imidazolium-based ionic liquids is very high, however, CO2 is not able to dissolve any ionic liquid. Therefore, it was found possible to extract a solute from an ionic liquid using supercritical CO2 without any contamination by the ionic liquid. ... 

SEC has also been used for the separation of phenols [105-107]. The supercritical fluid normally used is carbon dioxide with some modifier, for example, methanol or chlorodi-fluoromethane (Freon 22) [106]. Berger and Deye tested binary and tertiary supercritical mixtures, among them methanol/carbon dioxide mixtures containing very polar additives [107]. Ong et al. used chlorodifluoromethane as the supercritical fluid [105]. In most studies, UV detection was used and did not measure up to the required sensitivity. To bypass this problem, an online system with SPE cormected to the SFC instrmnentation was designed. Some of these systems are presented in the following section. 

In this section the experimental data and modeling of the solubilities of diamondoids in supercritical solvents such as carbon dioxide, methane, and ethane are presented first, followed by the solubilities of these components in liquid organic solvents. In the last part of this section high-pressure phase behavior of the binary systems of diamondoids containing butane and isobutene is explained. 

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