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The solubility of hydrogen sulfide in 2 m(about 0.146 mass fraction) aqueous solutions of 1,4-diazacyclohexane (piperazine, PIPH2) was measured at low gas loadings (at stochiometric molar ratios of hydrogen sulfide to PIPH2between about 0.14 and 1.04) and low partial pressures of hydrogen sulfide (from about (1.3 to 98.7) kPa) at (313.5 and 392.2) K by headspace gas chromatography. The new experimental results are a supplement to previously published data in the high gas-loading region. The new experimental data are compared to prediction results from a thermodynamic model that was based only on gas solubility data in the high gas-loading area. That thermodynamic model for describing the vapor−liquid equilibrium uses Pitzer’s molality-based equation for the excess Gibbs energy of the aqueous solution. The average relative deviation between the new experimental results and the predictions for the partial pressure of hydrogen sulfide amounts to 10 %. [ABSTRACT FROM AUTHOR]

Adding some salt to a homogeneous aqueous liquid solution of an organic solvent often results in a liquid–liquid phase split. However, such a phase split can also be achieved by charging such a liquid with a gas, in particular when the temperature is close to the critical temperature of that specific gas. This phenomenon is called “salting out by a near-critical gas”. It might be applied in a high-pressure extraction process, for example, to separate and recover valuable biomolecules from aqueous phases. Using a neutral gas like, for example, ethene for pressurizing additionally allows to adjust the pH of the coexisting liquid phases and to influence the partitioning of biomolecules when they change their electric net charge with the pH of the solution. The design of such separation processes requires not only reliable information on the phase forming system, that is, the ternary system (near-critical gas water organic solvent), but also on the partitioning of typical solutes to the coexisting phases. The present publication reports data (from an experimental study with a static-analytical device) for the partitioning of four biomolecules, that is, l-histidine, Aspirin, cimetidine, and 4-dimethylaminoantipyrine (at nearly infinite dilution) to coexisting liquid phases of the high-pressure three-phase liquid–liquid–vapor (L1L2V) equilibrium of the ternary system (ethene water 2-propanol) at (293 and 333) K and pressures from about (5.5 to 17) MPa. The coexisting liquid phases are characterized by distinctly different compositions, the aqueous phase being more hydrophilic than the alkanol-rich phase. Moreover, electrolytes were additionally added to adjust the pH conditions in the liquid phases. The pH-dependent dissociation equilibrium and the related net charge of the biomolecules primarily determine the partitioning behavior: The pH effect is stronger than the impact of varying pressure or temperature. For example, a switch from basic to acidic conditions can invert the partitioning, if that switch at the same time effects a change in the net charge of the solute, for example, from an ionic to a neutral molecule (or vice versa). The ionic solute is more hydrophilic (and thus prefers the aqueous phase), whereas the neutral or zwitterionic solute is less hydrophilic (i.e., more lipophilic) and consequently prefers the propanol-rich liquid phase. [ABSTRACT FROM AUTHOR]

A high-pressure-cell technique based on the analytical method was used to investigate the simultaneous solubility of the chemically reacting gases ammonia and carbon dioxide in solvent mixtures of (water + methanol). Seven (gas-free) solvent compositions were considered (methanol mole fractions of about 0, 0.05, 0.25, 0.5, 0.75, 0.95, and 1). The temperatures were approximately (313, 353, and 393) K. In the isothermal experimental series, carbon dioxide was added stepwise to a cell containing a mixture of (water + methanol + ammonia). The stoichiometric molality of ammonia in the solvent mixture of (water + methanol) was approximately (6 and 12) mol·(kg of solvent mixture)−1. The carbon dioxide loading (i.e., the ratio of the stoichiometric molalities of carbon dioxide and ammonia) ranged up to 1.07. The total pressure ranged up to 5.5 MPa. Vapor−liquid equilibrium data, including partial pressures of all components, are reported. [ABSTRACT FROM AUTHOR]

The solubility of carbon dioxide in aqueous mixtures of 2,2′-methyliminodiethanol (N-methyldiethanolamine, MDEA) and 1,4-diazacyclohexane (piperazine, PZ) was measured at low gas loadings (at stoichiometric molar ratios of carbon dioxide to (MDEA PZ) between about 0.02 and 0.83) and consequently low partial pressures of carbon dioxide (from about (0.1 to 150) kPa) at three temperatures (313 K, 353 K, and 393 K) by headspace gas chromatography. The molality of MDEA in the aqueous mixture was varied between (2 and 8) mol·(kg of water)−1and the molality of piperazine was varied between (1 and 4) mol·(kg of water)−1. The new experimental data supplement recently published high-pressure data for the same systems. Comparisons with prediction results from a formerly published thermodynamic model reveal that the set of model parameters from that previous publication should be revised. [ABSTRACT FROM AUTHOR]

A synthetic technique was used to measure the solubility of carbon dioxide in three aqueous solutions of 2,2′-methyliminodiethanol (N-methyldiethanolamine, MDEA) and piperazine (PZ) at around (313, 333, 353, and 393) K and pressures between about (0.2 and 10) MPa. The molalities of (MDEA + PZ) in the aqueous solutions were (2.2 + 1.97), (4.22 + 2.01), and (7.83 + 2.07), respectively. The loading of the amines by carbon dioxide (i.e., the molar ratio of (MDEA + PZ) and CO2varied between 0.2 and 2.0 The new experimental results are to supplement previously published experimental data of our research group for a single solution of both amines {molalities of (MDEA + PZ) in the aqueous solutions: (2.0 + 2.0)}. The new experimental results are compared to predictions from a model that combines previously published models for (CO2+ MDEA + H2O) and (CO2+ PZ + H2O). [ABSTRACT FROM AUTHOR]

The correlation and prediction of the solubility of gases in (nonelectrolyte as well as in electrolyte) aqueous/organic solvent mixtures is an important topic in many areas of chemical engineering. Despite the importance of that field, comparatively little attention has been given to that area in both classical thermodynamics (i.e., correlation methods that are based on semiempirical expressions for the excess Gibbs energy) and molecular simulation (where gas solubility can be predicted from intermolecular pair potentials). In the work presented here, recently published experimental data for the solubility of carbon dioxide in aqueous solutions of acetone (covering temperatures from 313 to 395 K at pressures ranging up to about 9 MPa) are used for testing a semiempirical, classical method (for the correlation of such gas solubility phenomena) as well as the Gibbs ensemble Monte Carlo method (GEMC) (for predicting the solubility of carbon dioxide in aqueous solutions of acetone from published intermolecular pair potentials without using any adjustable binary interaction parameter). The correlation method reproduces the experimental data (nearly) within experimental uncertainty, as was expected. The predictions by the GEMC method also agree well with the experimental data. [ABSTRACT FROM AUTHOR]

Experimental results are presented for the liquid−liquid equilibrium of aqueous two-phase systems containing a synthetic polyelectrolyte (polysodium acrylate, polysodium methacrylate, and polysodium ethylene sulfonate) and polyethylene glycol at (298.2 and 323.2) K. A total of 40 phase diagrams were obtained, comprising data both of the binodal curve (obtained through cloud-point measurements) and of equilibrium compositions. The influences of temperature, the nature of the polyelectrolyte monomer unit, and the chain length of both types of polymers are analyzed and discussed. [ABSTRACT FROM AUTHOR]

Activity coefficients at infinite dilution were measured for eight alkanols (methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, and 2-methyl-2-propanol) in the three ionic liquids 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF 6]), 1-butyl-3-methylimidazolium methyl sulfate ([bmim][CH 3SO 4]), and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl) amide ([hmim][Tf 2N]) between (293.15 and 353.15) K using the dilutor technique. The results are presented and, as far as possible, compared with literature data. [ABSTRACT FROM AUTHOR]

Experimental results for the activity of water in aqueous solutions of 10 single, synthetic polyelectrolytes (polysodium acrylate, polysodium methacrylate, polyammonium acrylate, polysodium ethylene sulfonate, and polysodium styrene sulfonate) and sodium chloride at 298.2 K are presented. The experimental work was performed by applying the isopiestic method with sodium chloride as a reference substance. As expected, the activity of water decreases when the concentration of a polyelectrolyte and/or sodium chloride increases. At constant concentration of a polyelectrolyte and sodium chloride, the activity of water depends on the monomer unit and the molecular mass of the polyelectrolyte. The new data are to be used in future work to develop and test models for the Gibbs excess energy of aqueous solutions of polyelectrolytes. [ABSTRACT FROM AUTHOR]

Experimental results for the activity of water in aqueous solutions of 10 single polyelectrolytes (two polysodium acrylates, two polysodium methacrylates, three polyammonium acrylates, two polysodium ethylene sulfonates, and one polysodium styrene sulfonate) at (298.2 and 323.2) K are reported. The isopiestic method was employed in these experiments with aqueous solutions of sodium chloride as references. The polyelectrolytes were characterized by three averaged molecular masses determined by gel permeation chromatography. Furthermore, the density and the refractive index increments of the aqueous polyelectrolyte solutions are reported. Although a similar pattern for the activity of water was observed for all systems (i.e., the osmotic coefficient increases with rising polyelectrolyte concentration), the experimental results show that this property depends on the monomer type as well as on the size of the polymer chain. The temperature (varied from (298.2 to 323.2) K) has only a small influence on the activity of water. [ABSTRACT FROM AUTHOR]

This paper reports experimental data for the activity of water in aqueous solutions of 3-methyl-1-vinylimidazolium methyl sulfate (QVI) at (298 and 338) K and the solid−liquid equilibrium for the ternary system (QVI sodium sulfate water) at the same temperatures. QVI is an ionic monomer which is gaining importance as a monomer for water-soluble polymers. The experimental data presented here are to contribute to a database which is needed to develop and test thermodynamic models for the description/prediction of phase equilibrium in aqueous solutions of such polyelectrolytes. The new experimental results for the activity of water are described by the VERS model of Gromann et al. for the excess Gibbs energy of aqueous solutions. Two interaction parameters were adjusted to correlate that data. The data set comprising the solid−liquid equilibrium was used for determining another set of interaction parameters (between that vinylimidazolium salt and sodium sulfate). [ABSTRACT FROM AUTHOR]

New experimental liquid−liquid-phase equilibrium data are reported for aqueous systems containing poly(vinyl pyrrolidone)of different molecular massand sodium sulfate at (298 and 338) K together with parameters for a semiempirical model for the excess Gibbs energy which is used to describe the experimental data. [ABSTRACT FROM AUTHOR]

New experimental results are presented for the solubility of carbon dioxide in pure liquid acetone 2-propanone, (CH3)2CO and in solvent mixtures of (acetone water) at gas-free solvent mixture acetone mole fractions of about (0.05, 0.1, 0.25, 0.5, 0.75, 0.9, and 0.95), temperatures of (313.75, 354.35, and 395.0) K, and total pressures up to about 10 MPa. Numerical values are reported for the (molality scale based) Henry's constant of CO2in acetone and in (acetone water) at vanishing amount of the gas in the liquid mixture resulting from the new experimental data by applying the well-known extrapolation procedure. The experimental work is to provide a database for developing and testing thermodynamic models to describe the gas solubility in salt-free and salt-containing mixed solvents as well as to test screening methods based, for example, on molecular simulation. [ABSTRACT FROM AUTHOR]

The solubility of carbon dioxide in pure methanol, and in aqueous solutions of methanol, was computed using the Gibbs ensemble Monte Carlo (GEMC) technique for 313, 354, and 395 K at pressures up to 9 MPa. Three solvent mixtures (of methanol and water) with methanol mole fractions of 10, 50, and 75 mole percent (in the gas-free solvent mixture) were studied. The Monte Carlo simulations were conducted in an isothermal−isobaric ensemble applying effective pair potentials for the pure components from literature. Common mixing rules without any adjustable binary interaction parameters were used to describe the interactions between the mixture components. Overall, a good agreement between simulation results and recently published experimental data is achieved. [ABSTRACT FROM AUTHOR]

Experimental results are reported for the solubility of carbon dioxide in liquid mixtures of water and the ionic liquid 1-n-butyl-3-methylimidazolium methylsulfate ([bmim][CH3SO4]). Three (gas-free) solvent compositions were considered with mass fractions of [bmim][CH3SO4] of w′ ≈ 0.15, 0.50, and 0.87 (mole fractions x′ ≈ 0.013, 0.066, and 0.33). In the isothermal experimental series, the temperature was about (293, 333, and 373) K. The total pressure ranged up to about 10 MPa. The molality of carbon dioxide in the solvent mixture of (water [bmim][CH3SO4]) (the mole fraction of carbon dioxide in the liquid) ranged up to approximately 1.64 mol·kg–1(about 0.0332). The experimental results are used to determine Henry's constant of carbon dioxide in the liquid mixtures of (water [bmim][CH3SO4]) as well as the partial molar volume of that gas at infinite dilution in those solvent mixtures. The phase equilibrium is described by applying an extension (to solvent mixtures) of Pitzer's molality scale-based equation for the Gibbs excess energy. [ABSTRACT FROM AUTHOR]

Experimental results (and a correlation) are presented for the liquid−liquid equilibrium of an example for the Biphasic Acid Scavenging utilizing Ionic Liquids (BASIL) process: for the binary system (butylacetate 1-methyl imidazolium chloride) and for the partitioning of 1-butanol and 1-methyl imidazole to the coexisting liquid phases at temperatures from (363 to 373) K. [ABSTRACT FROM AUTHOR]

Experimental data for the solubility of the two single gases carbon dioxide and hydrogen in the ionic liquid 1-n-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([bmpy][Tf2N]) are reported for temperatures between (293.1 and 413.2) K. The maximum pressure (the maximum gas molality in the solvent) was 10.8 MPa (4.43 mol·kg−1) for carbon dioxide and 8.9 MPa (0.14 mol·kg−1) for hydrogen. The experiments were performed using a high-pressure view-cell technique operating on the synthetic method. The solubility of carbon dioxide in [bmpy][Tf2N] is more than 1 order of magnitude higher than the solubility of hydrogen. Carbon dioxide becomes less soluble in [bmpy][Tf2N] with increasing temperature, whereas hydrogen shows the opposite effect. An extension of Henry’s law is employed to correlate the solubility pressures. The final results for the Henry’s constant (at zero pressure) of carbon dioxide and hydrogen in [bmpy][Tf2N] (on the molality scale) are represented within the experimental uncertainty (about 0.8 % for carbon dioxide and 1.3 % for hydrogen) by ln(kH,CO2(0)/MPa) = 8.5128 − 2057/(T/K) − 0.004274·(T/K) and ln(kH, H2(0)/MPa) = 3.5746 + 343/(T/K) − 0.0008·(T/K), respectively. [ABSTRACT FROM AUTHOR]

Experimental data for the solubility of the two single gases carbon monoxide and oxygen in the ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([hmim][Tf2N]) are reported for temperatures between (293.25 and 413.2) K. The maximum pressure (the maximum gas molality) was 9.8 MPa (0.27 mol·kg−1) for carbon monoxide and 9.1 MPa (0.31 mol·kg−1) for oxygen. The experiments were performed using a high-pressure view-cell technique operating on the synthetic method. Oxygen shows a slightly higher solubility than carbon monoxide under all conditions investigated, but the solubility generally remains very low. Both gases become less soluble in [hmim][Tf2N] with increasing temperature; however, the effect is not very pronounced and becomes ambiguous for carbon monoxide above 373 K. An extension of Henry’s law is employed in correlating the solubility pressures. The final results for the Henry’s constant (at zero pressure) of carbon monoxide and oxygen in [hmim][Tf2N] (on the molality scale) are represented within the experimental uncertainty (1 % for both gases) by ln(kH,CO(0)/MPa) = 5.3954 − 364.2/(T/K) − 0.002356 (T/K) and ln(kH,O2(0)/MPa) = 5.7618 − 505.1/(T/K) − 0.002802 (T/K), respectively. [ABSTRACT FROM AUTHOR]

New experimental results are reported for the influence of two single salts (sodium chloride and sodium sulfate) on the solubility of ammonia in liquid mixtures of water and methanol at 353 and 393 K. The mole fractions of methanol in the (gas-free and salt-free) solvent mixture of water and methanol were about 0.25, 0.5, and 0.75 in the experiments with sodium chloride and about 0.05 and 0.25 in the experiments with sodium sulfate. The molality of the salt varied between about 0.25 and 2 (0.15 and 1) mol/kg of the solvent mixture in the systems with sodium chloride (sodium sulfate). The maximum molality of ammonia was about 6.7 mol/kg of (water + methanol) for both temperatures and for both salts. The maximum total pressure above the liquid solutions was about 0.3 MPa (1 MPa) in the system containing sodium chloride at 353 K (393 K) and about 0.2 MPa (0.7 MPa) in the system with sodium sulfate at 353 K (393 K). The experimental results are used to test a thermodynamic framework which allows the influence of both single strong electrolytes on the solubility of ammonia in liquid mixtures of water and methanol to be predicted. The prediction results are in good agreement with the new experimental data. [ABSTRACT FROM AUTHOR]

Aqueous two-phase systems of poly(ethylene) glycol and a salt are considered as extraction media for large-scale downstream processing of industrially important enzymes. The present paper deals with one of such two-phase systems. New experimental results are presented for the composition of the coexisting liquid phases of the system (water + poly(ethylene glycol) + sodium citrate) at 298.15 K for three poly(ethylene) glycols of different molar masses of about (600, 1500, and 3000) g·mol −1, respectively. The experimental results are described within experimental uncertainty by a semiempirical expression for the excess Gibbs energy. [ABSTRACT FROM AUTHOR]

Experimental results for the solubility of tetrafluoromethane (CF4, R14) in the ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (hmimTf2N) are presented for temperatures between 293.3 and 413.3 K, at pressures (gas molalities) up to 9.6 MPa (0.22 mol kg-1). The experimental results were determined with a high-pressure view-cell technique operating on the synthetic method. The experimental data were used to determine Henry's constant of tetrafluoromethane in hmimTf2N. The results for the Henry's constant (at zero pressure) are correlated (on the molality scale) within the experimental uncertainty (i.e., about 1.1%) by ln(%@mt;sys@%%@ital@%k%@rsf@%%@sx@%H,%@/hd@%CF%@sb@%4%@sbx@%%@be@%%@/hd@%%@fn;(;vis;full;auto@%0%@fnx;);vis;full@%%@/hd@%%@sxx@%%@mx@%/MPa) 7.537 − 893.8/(T/K) − 0.003977(T/K). Henry's law was also extended to describe the gas solubility at higher pressures. Furthermore, a cubic equation of state was used to correlate the gas solubility over the entire range of experimentally investigated temperature and pressure. Both methods proved suited for a reliable correlation of the new experimental data. [ABSTRACT FROM AUTHOR]

This work reports new experimental results for the solubility of two single gases (methane and xenon) in the ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (hmimTf2N). The solubility was measured with a high-pressure view-cell technique operating on the synthetic method. The temperature ranged from 293.3 to 413.3 K, and the maximum pressure (the maximum gas molality) was 9.3 MPa (0.51 mol·kg-1) for methane and 9.6 MPa (2.08 mol·kg-1) for xenon. Xenon shows a significantly higher solubility than methane at all conditions investigated. Both gases become less soluble in hmimTf2N with rising temperature. An extension of Henry's law is employed to correlate the solubility pressures. The final results for the Henry's constants (at zero pressure) of methane and xenon in hmimTf2N (on the molality scale) are represented within the experimental uncertainty (about 1.2% for methane and 1% for xenon) by ln(%@mt;sys@%%@ital@%k%@rsf@%%@sx@%H,%@/hd@%CH%@sb@%4%@sbx@%%@be@%%@/hd@%%@fn;(;vis;full;auto@%0%@fnx;);vis;full@%%@/hd@%%@sxx@%%@mx@%/MPa) 6.4929 − 835.9/(T/K) − 0.003471(T/K) and ln(%@mt;sys@%%@ital@%k%@rsf@%%@sx@%H,%@/hd@%Xe%@be@%%@/hd@%%@fn;(;vis;full;auto@%0%@fnx;);vis;full@%%@/hd@%%@sxx@%%@mx@%/MPa) 6.3357 − 1321.4/(T/K) − 0.00265(T/K), respectively. [ABSTRACT FROM AUTHOR]

Solubility measurements of methane and of xenon in the ionic liquid 1-n-butyl-3-methylimidazolium methyl sulfate (bmimCH3SO4) were performed with a high-pressure view-cell technique based on the synthetic method. The temperature ranged from 293.1 K to 413.2 K, and the maximum pressure (the maximum gas molality) was 8.9 MPa (0.19 mol·kg-1) for methane and 11.3 MPa (0.65 mol·kg-1) for xenon. Both gases become less soluble in bmimCH3SO4with rising temperature, but xenon shows a significantly higher solubility at all conditions investigated. An extension of Henry's law is employed to correlate the solubility pressures in both cases. The final results for the Henry's constant (at zero pressure) of methane and xenon in bmimCH3SO4(on the molality scale) are correlated within the experimental uncertainty (about ± 1.3 %) by ln(%@mt;sys@%%@ital@%k%@rsf@%%@sx@%H,%@/hd@%CH%@sb@%4%@sbx@%%@be@%%@/hd@%%@fn;(;vis;full;auto@%0%@fnx;);vis;full@%%@/hd@%%@sxx@%%@mx@%/MPa) 6.216 − 564.5/(T/K) − 0.002566(T/K) and ln(%@mt;sys@%%@ital@%k%@rsf@%%@sx@%H,%@/hd@%Xe%@be@%%@/hd@%%@fn;(;vis;full;auto@%0%@fnx;);vis;full@%%@/hd@%%@sxx@%%@mx@%/MPa) 5.5906 − 928/(T/K) − 0.00141(T/K), respectively. [ABSTRACT FROM AUTHOR]

A high-pressure view-cell technique based on the synthetic method was used to determine the solubility of ammonia in liquid methanol (total pressure at a preset temperature and liquid-phase composition). The solubility pressure ranges up to about 4.2 MPa. The temperature amounts to (313.75, 354.35, and 395.0) K. The molality of ammonia in methanol (the mole fraction of ammonia in the liquid) ranges up to about 66.4 mol·kg-1(about 0.68). Furthermore, a high-pressure cell technique based on the analytical method was used to investigate the vapor−liquid equilibrium of that same system (equilibrium pressure as well as liquid- and gas-phase compositions at a preset temperature). The solubility pressure ranges up to about 1.6 MPa. The temperature amounts to (353.1 and 393.1) K. The molality of ammonia in methanol (the mole fraction of ammonia in the liquid) ranges up to 13 mol·kg-1(about 0.3). The experimental results are used to determine Henry's constant of ammonia in methanol. Furthermore, the experimental data are correlated by applying Pitzer's molality scale based equation for the Gibbs excess energy. [ABSTRACT FROM AUTHOR]

A high-pressure view-cell technique based on the synthetic method was used to determine the total pressure above aqueous solutions of two single salts (potassium chloride and potassium carbonate) and carbon dioxide. In the series of measurements with potassium chloride, the molality of the salt amounted to about (2 and 4) mol·(kg of water)-1, the temperature ranged from about (313 to 433) K, and the molality of carbon dioxide ranged up to about 1 mol·(kg of water)-1, corresponding to a maximum pressure of about 9.4 MPa. In the series of measurements with potassium carbonate, the stoichiometric molality of that salt amounted to about (0.43 and 1.7) mol·(kg of water)-1(stoichiometric mass fraction of the salt of about 0.056 and 0.19, respectively), the temperature ranged from about (313 to 393) K, and the ratio of the stoichiometric molalities of carbon dioxide to potassium carbonate ranged from about 0.7 to 3.6, corresponding to pressures from about (0.27 to 9.2) MPa. The vapor−liquid equilibrium of the systems (CO2KCl H2O) and (CO2K2CO3H2O) (the latter allowing for the precipitation of KHCO3that is important in connection with the “Hot Potassium Carbonate (Benfield) Process” and its modifications by activating additives) is described by means of a thermodynamic model based on Pitzer's molality scale based equation for the Gibbs excess energy of the aqueous phase. Model parameters are determined from the new carbon dioxide solubility data as well as from an extensive database adopted from the literature. [ABSTRACT FROM AUTHOR]