Binary Mixtures Of Carbon Dioxide Research Articles

Vapor−Liquid Equilibrium (VLE) Data for the Carbon Dioxide (CO2) + 1,1,1,2-Tetrafluoroethane (R134a) System at Temperatures from 252.95 K to 292.95 K and Pressures up to 2 MPa

Isothermal vapor−liquid equilibrium data of the binary mixture of carbon dioxide (CO2)−1,1,1,2-tetrafluoroethane (R134a) at temperatures between 252.95 K and 292.95 K and pressures up to 2 MPa are measured and correlated. To obtain experimental data, we have used the static-analytic method with liquid and vapor phase sampling. The data are correlated using the Peng−Robinson (PR) equation of state and the classical mixing rules.

Experimental measurement and modeling of the vapor–liquid equilibrium of carbon dioxide + chloroform

Isothermal bubble and dew points, saturated molar volumes, and mixture critical points for binary mixtures of carbon dioxide+chloroform (trichloromethane) (CO 2/CHCl 3) have been measured in the temperature region 303.15–333.15 K and at pressures up to 100 bar. Mixture critical points are reported at 313.15, 323.15, and 333.15 K. The data were modeled with the Peng–Robinson equation of state using both the van der Waals-1 (vdW-1) mixing rule and the Wong–Sandler (WS) mixing rule incorporating the UNIQUAC excess free energy model. The WS mixing rule provided a better representation of the data than did the vdW-1 mixing rule, though with three adjustable parameters instead of one. The extrapolating ability of both of the mixing rules was investigated. Using the parameters regressed at 323.15 K, the WS mixing rule yielded better extrapolations for the composition dependence at 303.15, 313.15, and 333.15 K than the vdW-1 mixing rule.

Isothermal Vapor−Liquid Equilibria for Binary Mixtures of Carbon Dioxide with Hexyl Acetate, Cyclohexyl Acetate, or Phenyl Acetate at Elevated Pressures

Isothermal vapor−liquid equilibrium phase compositions were measured for three binary systems of carbon dioxide with different C6-acetateshexyl acetate, cyclohexyl acetate, and phenyl acetateat temperatures from 333.15 K to 413.15 K and pressures up to 20 MPa. The solubility isotherm of the acetates in the vapor phase exhibits a minimum value at subcritical pressures of carbon dioxide. Henry's constants were calculated by fitting the Krichevsky−Ilinskaya equation to the isothermal equilibrium data. The constants increase with increasing temperature for these three binary systems. The new phase equilibrium data were correlated with the Soave−Redlich−Kwong, the Peng−Robinson, and the Patel−Teja equations of state. The Peng−Robinson equation with two-parameter (ka12 and kb12) van der Waals mixing rules is marginally better than other methods for the investigated systems.

Densities and bubble points of binary mixtures of carbon dioxide and n-heptane and ternary mixtures of n-butane, n-heptane and n-hexadecane

The densities of three mixtures of carbon dioxide and n-heptane and three mixtures of n-butane, n-heptane and n-hexadecane were measured. The binary mixtures were studied over the temperature range of 302–459 K and the pressure range of 3.61–55.48 MPa at the following carbon dioxide mole fractions: 0.2918, 0.3888 and 0.4270. The ternary mixtures were studied over the temperature range of 405–469 K and the pressure range of 0.7–24 MPa at the following n-butane mole fractions: 0.0904, 0.1564 and 0.1856 and corresponding n-heptane mole fractions: 0.7358, 0.6825 and 0.6588. The measurements were carried out in an automated isochoric instrument and their accuracy is estimated to be better than ±0.1%. The bubble points of the mixtures were also determined from an analysis of the experimental isochores in the one- and two-phase regions. The new measurements have been used to assess the performance of the Peng–Robinson equation of state and the one-fluid corresponding states model. In single phase regions, the performance of the one-fluid model is found to be superior to that of the Peng–Robinson equation. The latter performs well for bubble points provided that optimised interaction parameters are used. As an interpolation tool, the one fluid model is found to reproduce the ternary mixtures within the experimental uncertainty.

Phase Behavior and Modeling of Supercritical Carbon Dioxide−Organic Acid Mixtures

Pressure−composition isotherms are obtained for binary mixtures of carbon dioxide with formic acid, acetic acid, butyric acid, valeric acid, caproic acid, and caprylic acid at temperatures of 35.0−120.0 °C and pressures up to 250 bar. The accuracy of the experimental apparatus was tested by comparing the measured phase equilibrium data of the carbon dioxide−acetic acid system at 40.0 and 60.0 °C with those of Laugier et al. These six carbon dioxide−polar solute systems exhibit type I phase behavior, which is characterized by an uninterrupted critical mixture curve that has a maximum in pressure. In each system, the mixture critical point increases as the temperatures increases, and also the mixture critical pressure increases as the molecular weight increases. On the contrary, the carbon dioxide−formic acid system shows a higher mixture critical pressure compared with those of the other systems. The experimental data are modeled using both the statistical associating fluid theory (SAFT) and the Peng−Robinson (P−R) equation of state. The SAFT equation of state reasonably models the pressure−composition isotherms for these six systems only if two temperature-independent mixture parameters are used for each system. The P−R equation of state calculated the phase behavior with one or two temperature-independent mixture parameters.

Vapor–liquid equilibria at elevated pressures of binary mixtures of carbon dioxide with methyl salicylate, eugenol, and diethyl phthalate

A semi-flow type apparatus was used to measure the vapor–liquid equilibria (VLE) of CO 2 with methyl salicylate, eugenol, and diethyl phthalate binary mixtures at 308.15, 318.15, and 328.15 K over the pressure range from 1.4 to 13 MPa. New VLE data for these binary mixtures are presented and the Henry's constants were determined from these results. The Soave–Redlich–Kwong and the Peng–Robinson equations of state, and the van der Waals, Panagiotopoulos–Reid and Huron–Vidal mixing rules are used to correlate these VLE data. It is shown that both equations of state with the van der Waals mixing rules and two adjustable parameters give satisfactory correlation results.

High-pressure viscosity of polystyrene solutions in toluene + carbon dioxide binary mixtures

High-pressure viscosity of polystyrene (Mw = 50,000, Mw/Mn ≤ 1.06) solutions in toluene and in mixtures of toluene + carbon dioxide was measured using a falling cylinder-type viscometer at 320, 340, and 360 K, and up to 35 MPa. Solutions with polystyrene concentrations of 3, 5, and 7 wt % were investigated. Carbon dioxide levels in the range from 0 to 14.7 wt % were evaluated. Viscosity was observed to vary linearly with pressure at the temperatures and polymer concentrations investigated. Viscosity of the polymer solutions decreased as the concentration of carbon dioxide in the mixture was increased. The largest viscosity reduction was observed at the lowest temperature and at the highest concentration of polymer. The viscosity of the solutions was correlated with the solution density for different compositions. It was found that solutions of the same density have different viscosities, depending upon the carbon dioxide concentration in the mixture. The solutions with the higher carbon dioxide content display the lower viscosities at a given density. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 306–315, 2000

Extraction of Coal Tar Pitch Using a Mixture of Compressed CO2 and Toluene

The removal of low-molecular-weight components from commercial pitches is a critical step in the production of suitable precursors for isotropic carbon fiber formation. A unique extraction process employing a one-phase binary mixture of carbon dioxide and toluene has been developed to remove low-molecular-weight components from coal tar pitch, with an ultimate goal of increasing the softening point of the pitch. The mass fraction of coal tar pitch extracted was determined as a function of extraction temperature (25−75 °C), pressure (8.7−14.9 MPa), and extractive solvent composition (40−70 wt % toluene) using a factorial experimental design. As much as 44 wt % of the coal tar pitch was removed at these extraction conditions, and softening points greater than 250 °C were achieved. The separation is controlled by the temperature and composition of the extractant solvent. This compressed gas/organic solvent extraction process removes low-molecular-weight material from the coal tar pitch using significantly milder solvents and reduced temperatures relative to traditional extractive processes.

Application of fluid opacity for determining the phase behavior of binary mixtures near their critical loci - CO 2 plus ethane and CO 2 plus propane

The rapid determination of critical data of binary mixtures of carbon dioxide plus propane and carbon dioxide plus ethane has been carried out using the opalescence effect of pure substances or mixtures near their critical loci. The experiments have been performed applying a heatable stainless-steel vessel equipped with two sapphire windows for optical observation of changes of state. The initial two-phase mixture is continuously heated and pressurized. The vessel content increasingly becomes opalescent and the critical point is characterized by a total opacity. Beyond this point the fluid instantly becomes clear; the one-phase supercritical state is reached.

Vapor–liquid equilibria for binary mixtures of carbon dioxide with 1,2-dimethoxybenzene, 2-methoxyphenol, or p-cresol at elevated pressures

Vapor–liquid equilibrium (VLE) phase compositions were measured for three binary systems of carbon dioxide with 1,2-dimethoxybenzene, 2-methoxyphenol, or p-cresol at temperatures from 323.15 to 423.15 K and pressures up to 20 MPa. The solubilities of these close-boiling heavy components in the vapor phase were compared over the experimental conditions. Henry's constants were calculated from the isothermal equilibrium data. The temperature effects on the Henry's constants and the solubilities of carbon dioxide in the liquid phase were discussed. The new phase equilibrium data were correlated by the Soave–Redlich–Kwong (SRK), the Peng–Robinson (PR), and the Patel–Teja (PT) equations of state (EOS) with the van der Waals (vdW) one-fluid mixing rules. The two-parameter ( k a 12 and k b 12 ) vdW mixing rule was found to yield satisfactory results for the investigated systems.

Influence of mobile phase composition on methylene group selectivity and homologous compound retention in near-critical mobile phases

A number of near-critical mobile phases were evaluated with respect to methylene group selectivity and overall eluotropic strength on a polymeric column. Binary mobile phases, consisting of mixtures of carbon dioxide and 1,1,1,2-tetrafluoroethane (HFC-134a), showed strong temperature and compositional dependence on both retention and selectivity. Binary mobile phases, consisting of mixtures of carbon dioxide and conventional modifiers such as alcohols, acetonitrile and tetrahydrofuran, also showed a strong temperature dependence on methylene group selectivity and relative retention. In contrast to the behavior observed using a polymeric column, a bonded silica-based stationary phase displayed significant deviations from the Martin rule, even with high order homologs. Of all the systems evaluated in this study, a binary mixture of carbon dioxide and 2-methoxyethanol proved to be optimal for obtaining a high degree of methylene group selectivity and strong eluotropic strength.

Evaluation of vapor—liquid equilibrium of CO 2 binary systems using UNIQUAC-based Huron—Vidal mixing rules

Since Huron and Vidal [M.J. Huron, J. Vidal, Fluid Phase Equilib. 3 (1979) 255] developed the basic idea of the so-called G E mixing rules, similar models have been proposed by different authors. In most of them, a group-contribution method like the UNIFAC model is used with the equation of state to enable the description of vapor-liquid equilibrium (VLE) at high temperatures and pressures including supercritical compounds. In this work we intended to use the UNIQUAC instead of the UNIFAC method as G E model in SRK equation of state. For comparison between Huron-Vidal-type mixing rules, we selected the modified Huron-Vidal first-order (MHV1) and second-order (MHV2) mixing rules proposed by Michelsen [M.L. Michelsen, Fluid Phase Equilib. 60 (1990a) 213; M.L. Michelsen, Fluid Phase Equilib. 60 (1990b) 42.] and PSRK mixing rule proposed by Holderbaum and Gmehling [T. Holderbaum, J. Gmehling, Fluid Phase Equilib. 70 (1991) 251.]. In other words, this paper investigates the ability of several mixing rules to predict and correlate the high-pressure vapor-liquid equilibrium used in combination with the UNIFAC and UNIQUAC models. For comparison of these mixing rules, the carbon dioxide binary mixtures have been chosen because carbon dioxide has numerous applications in supercritical fluid processes. The missing interaction parameters of UNIFAC and UNIQUAC were estimated through the regression of experimental vapor-liquid equilibrium data. For comparison of UNIQUAC-based mixing rules with each other, the interaction parameters of 51 carbon dioxide binary systems have been determined. Furthermore, a comparison between UNIFAC- and UNIQUAC-based SRK equation of state is presented. The results show that all of the UNIFAC- and UNIQUAC-based mixing rules, with parameters derived from VLE, can be used for reliable calculations of phase equilibrium. It is shown that the PSRK/UNIQUAC mixing rule can correlate the data for the best VLE results. Also, it is shown that the use of the second-order mixing rule in UNIQUAC-based SRK equation of state does not necessarily improve the results of VLE calculations.

97/03641 Thermal transformations of sulfur compounds during secondary pyrolysis of the products of oil shale retorting

Since Huron and Vidal [M.J. Huron, J. Vidal, Fluid Phase Equilib. 3 (1979) 255] developed the basic idea of the so-called GE mixing rules, similar models have been proposed by different authors. In most of them, a group-contribution method like the UNIFAC model is used with the equation of state to enable the description of vapor-liquid equilibrium (VLE) at high temperatures and pressures including supercritical compounds. In this work we intended to use the UNIQUAC instead of the UNIFAC method as GE model in SRK equation of state. For comparison between Huron-Vidal-type mixing rules, we selected the modified Huron-Vidal first-order (MHV1) and second-order (MHV2) mixing rules proposed by Michelsen [M.L. Michelsen, Fluid Phase Equilib. 60 (1990a) 213; M.L. Michelsen, Fluid Phase Equilib. 60 (1990b) 42.] and PSRK mixing rule proposed by Holderbaum and Gmehling [T. Holderbaum, J. Gmehling, Fluid Phase Equilib. 70 (1991) 251.]. In other words, this paper investigates the ability of several mixing rules to predict and correlate the high-pressure vapor-liquid equilibrium used in combination with the UNIFAC and UNIQUAC models. For comparison of these mixing rules, the carbon dioxide binary mixtures have been chosen because carbon dioxide has numerous applications in supercritical fluid processes. The missing interaction parameters of UNIFAC and UNIQUAC were estimated through the regression of experimental vapor-liquid equilibrium data. For comparison of UNIQUAC-based mixing rules with each other, the interaction parameters of 51 carbon dioxide binary systems have been determined. Furthermore, a comparison between UNIFAC- and UNIQUAC-based SRK equation of state is presented. The results show that all of the UNIFAC- and UNIQUAC-based mixing rules, with parameters derived from VLE, can be used for reliable calculations of phase equilibrium. It is shown that the PSRK/UNIQUAC mixing rule can correlate the data for the best VLE results. Also, it is shown that the use of the second-order mixing rule in UNIQUAC-based SRK equation of state does not necessarily improve the results of VLE calculations.

Solvatochromic characterization of the liquid phase in liquid—supercritical CO2 mixtures

AbstractThe 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 CO2‐rich conditions where compressibility effects are important.

Comparison of High-Pressure Vapor−Liquid Equilibria of Mixtures of CO2 or Propane with Nonane and C9 Alkylbenzenes

Vapor−liquid equilibria were measured for (1) binary mixtures of carbon dioxide with nonane, cumene, propylbenzene, or mesitylene, (2) binary mixtures of propane with nonane, cumene, or mesitylene, and (3) ternary mixtures of carbon dioxide, nonane, and cumene. For the carbon dioxide mixtures, vapor−liquid equilibria were measured at 70 °C and at pressures ranging from 3.7 MPa to 12.1 MPa. For the propane mixtures, vapor−liquid equilibria were measured at 104 °C and at pressures ranging from 0.9 MPa to 3.7 MPa. It was found that differences in the phase equilibria of the mixtures could be explained primarily by the self-association of the C9 components. The composition of the C9 components in the vapor phase compositions were found to be directly related to the volatility (self-association) of the C9 component. Liquid phase compositions were found to be enriched in carbon dioxide or propane content in the mixtures containing C9 compounds having the weakest self-association. Also presented in this paper are comparisons of measurements of vapor−liquid equilibria of carbon dioxide + decane and propane + decane with literature data as validation of the two experimental methods used. These measurements were made at 71 °C for the carbon dioxide + decane mixtures and at temperatures ranging from 38 °C to 120 °C for the propane + decane mixtures.

Volumetric Properties of Carbon Dioxide + Sulfur Hexafluoride at High Pressures

Volumetric properties of binary mixtures of carbon dioxide and sulfur hexafluoride have been determined using a specially designed high-pressure variable-volume view cell. The data are reported for...

Experimental Determination of Vapor-Liquid Equilibria in Binary Mixtures of Carbon Dioxide + Chloroform

In supercritical fluid extraction technology of pollutants from soils with carbon dioxide, chloroform might be a cosolvent candidate. For the modeling of systems consisting of a near-critical solvent, a cosolvent, and a solute, not only interaction parameters between the near-critical solvent and the solute have to be known, but also those between the near-critical solvent and the cosolvent. Bubble points of binary mixtures of carbon dioxide + chloroform at eight different mole fractions have been measured in the temperature region 280--370 K and at pressures up to 12 MPa by means of the synthetic method.

Adsorption Prediction of Binary Mixtures on Adsorbents Used in Respirator Cartridges and Air-Sampling Monitors

A mathematical method was developed for predicting the performance of respirator cartridges and air-sampling monitors in the presence of binary mixtures. This method uses only data for pure-component adsorption equilibrium to calculate the breakthrough curves of the two components in a binary vapor mixture. The Ideal Adsorbed Solution Theory was used to calculate the adsorption equilibria for the components in a binary mixture. The adsorption capacities were then used in expressions similar to the modified Wheeler equation for pure compounds to determine the breakthrough curves for the binary mixture. This technique applies to a wide variety of binary mixture/adsorbent systems. In the present study it was successfully applied to the adsorption of four binary mixtures of acetone and m–xylene on activated carbon, three binary mixtures of acetone and styrene on activated carbon, and a binary mixture of carbon dioxide and water vapor on a molecular sieve. The predicted breakthrough curves were in agreement wi...

High-pressure phase equilibria and densities of the binary mixtures carbon dioxide—oleic acid, carbon dioxide—methyl myristate, and carbon dioxide—methyl palmitate and of the ternary mixture carbon dioxide—methyl myristate—methyl palmitate

Densities and thermodynamic equilibrium compositions of both the gas and the liquid phases were determined for binary mixtures of carbon dioxide and oleic acid, methyl myristate, and methyl palmitate, and for the ternary system carbon dioxide—methyl myristate—methyl palmitate at pressures up to 130 bar. Binary equilibria and densities were measured at 40°C, 50°C, and 60°C; the ternary system was studied at 40°C and 50°C. High-pressure densities were also recorded for all pure components. The apparatus used for the experiments consisted of a high-pressure view cell through which both phases were recirculated. Compositions were determined from samples taken with the help of six-way valves. Densities were measured with a vibrating sensor tube. Solubilities increase with pressure at a given temperature; however, the separation of a mixture of methyl myristate and methyl palmitate becomes less selective. All numerical values are given in full detail.

High-pressure vapour-liquid equilibria in binary mixtures of carbon dioxide and benzene compounds: experimental data for mixtures with ethylbenzene, isopropylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, ethenylbenzene and isopropenylbenzene, and their correlation with the generalized Bender and Skjold-Jørgensen's group contribution equation of state

Bamberger, A., Schmelzer, J., Walther, D. and Maurer, G., 1994. High-pressure vapour—liquid Equilibria in binary mixtures of carbon dioxide and benzene compounds: experimental data for mixtures with ethylbenzene, isopropyl-benzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, ethenylbenzene and isopropenylbenzene, and their correlation with the generalized Bender and Skjold-Jørgensen's group contribution equation of state. Fluid Phase Equilibria, 97: 167-189. The binary vapour-liquid Equilibrium of six mixtures of carbon dioxide and a benzene derivative (ethylbenzene, isopropylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, ethenylbenzene and isopropenylbenzene) was studied by a flow technique at temperatures between 313 and 393 K and pressures between about 6 and 18 MPa. The experimental results are correlated using a generalized Bender equation of state and the group contribution equation of state (GC-EOS) by Skjold-Jørgensen. The application of that equation of state was extended by estimating new parameters for interactions between carbon dioxide and aromatic groups, using some of the new experimental results as well as literature data.