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The absorption capacity of the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate ([C2mim][BF4]) for the single gases carbon dioxide and hydrogen sulfide was measured at temperatures from (298 to 353) K and pressures up to about 2.0 MPa. The corresponding molar volumes of CO2/H2S-saturated liquid phase were also measured in the above temperature and pressure ranges. At the same temperature and pressure, the solubility of hydrogen sulfide in [C2mim][BF4], expressed on the molality scale, is more than three times that of CO2. The Henry’s law constants were determined from the new experimental data, which in turn were used to derive the change of some thermodynamic functions for dissolution of the gases in that particular ionic liquid. The partial molar volume at infinite dilution for CO2/H2S + [C2mim][BF4] mixtures was estimated from the measured molar volumes. The new experimental data were correlated by using two models: (a) a model comprised of the extended Henry’s law and Pitzer’s virial expansion for the excess Gibbs energy, and (b) a generic Redlich-Kwong (GRK) type of cubic equation of state. Both models adequately good correlate the experimental data; however, the first model shows a slightly higher correlative accuracy than the second one. The selectivity of [C2mim][BF4] to separate CO2 and H2S is also discussed on the basis of correlation results.

The synthetic method is used for the determination of the liquid phase solubility of methane in 1-octanol at three temperatures (273.25, 283.15, and 293.2) K and of methane in n-dodecane at 273.1 K at pressures up to about 10 MPa. The new gas solubility data is applied to evaluate the molality scale based Henry's constant of methane in those solvents: (4.31, 4.67, and 4.81 ± 0.05) MPa in 1-octanol and (2.75 ± 0.04) MPa in n-dodecane at the given temperatures, respectively. The experimental technique provides as well the density of the gas-saturated liquid phase and thus allows for evaluation of the partial molar volume of methane at infinite dilution in the solvent: (47, 49, and 49 ± 5) cm 3 /mol in 1-octanol and (45 ± 5) cm 3 /mol in n-dodecane, respectively. The experimental results are compared with the limited data from the open literature. At the investigated temperatures, the vapour phase can be treated as pure methane, and the extended Henry's law suffices to accurately correlate the new gas solubility data. However, that vapour-liquid equilibrium model is here expanded allowing to accurately predict the small vapour phase solubility of the solvent in compressed methane which is demonstrated by comparison with experimental data from the literature.

Different thermodynamic properties of aqueous solutions of butyltriacetonediamine (BuTAD), unloaded and loaded with carbon dioxide, are studied experimentally. For unloaded mixtures of BuTAD and water, protonation equilibrium constants between 283 and 333 K and liquid–liquid equilibria between 313 and 353 K, including the lower critical point, are determined at atmospheric pressure. Furthermore, the solubility of carbon dioxide in aqueous solutions of BuTAD between 313 and 393 K is determined at low loadings with an analytic method based on headspace gas chromatography and at high loadings with a synthetic method using a high pressure view cell. In the loaded system, solid precipitation, liquid–liquid phase split, and the presence of metastable states are observed in certain ranges. The data is interesting for assessing the aqueous solution of BuTAD as solvent for carbon capture. A short-cut method is used for comparing the new solvent with an aqueous solution of monoethanolamine (MEA) with respect to the...

New experimental results are presented for the solubility of methane in two single solvents (hexane and a petroleum benzine) at temperatures of about (273, 283, and 293) K and pressures up to about 10 MPa. The solubility of methane (in terms of moles of methane per kilogram of solvent at given temperature and pressure) is rather similar in both solvents. The experimental results are evaluated to determine Henry’s constant and the partial molar volume of methane in those solvents. A thermodynamic model, based on the extended Henry’s law, which accounts for interactions in both liquid and gaseous phases, is applied to correlate the experimental results.

New experimental results are presented for the solubility of methane in water at constant temperatures of 283 K and 298 K and pressures up to 10 MPa, and for the pressure–temperature coordinates of the three-phase (vapour + liquid + hydrate) equilibrium (when the liquid mainly consists of water) at temperatures between 274 K and 285 K. The new experimental results are compared with literature data. The gas solubility data are used to determine Henry’s constant and the partial molar volume of methane in water. Two thermodynamic models are used to describe the gas solubility. One model neglects the amount of water in the vapour whereas the other model describes the vapour as a binary mixture of (methane + water) and allows to predict the small fraction of water in the vapour phase. The prediction results are also compared with literature data.

New experimental results are presented for the solubility and the partial molar volume of carbon dioxide in an aqueous solution of phenol and sodium sulfate at temperatures of about (314, 354, and 395) K and pressures up to about 10 MPa. The composition of the solvent expressed as molality in water is about 0.5 mol · (kg H 2 O) −1 for phenol as well as for sodium sulfate. The experimental work is a continuation of investigations on the influence of organic components and strong electrolytes on the solubility of carbon dioxide in water. It extends a data base for developing and testing thermodynamic models to describe the solubility of gases in salt-free and salt-containing aqueous solutions of organic compounds. The experimental results are compared to prediction and correlation results from a thermodynamic model. That model is a combination of a model for the solubility of CO 2 in aqueous solutions of sodium sulfate on one side and a model for the solubility of CO 2 in aqueous solutions of phenol on the other side. When ternary interactions between CO 2 , phenol, and sodium sulfate are neglected, the model allows prediction of the pressure that is required to dissolve a given amount of CO 2 in the mixed aqueous solution. The prediction results reveal a reasonable agreement. However (and as in previous investigations with N,N-dimethylformamide instead of phenol as the organic solvent component or with sodium chloride instead of sodium sulfate as the dissolved electrolyte) adjusting a ternary parameter for interactions between the three solutes ( i.e. , CO 2 , phenol, and sodium sulfate) results in a correlation that allows description of the new experimental results almost within experimental uncertainty.

Experimental results are presented for the solubility of CO2 in an aqueous solution of phenol and NaOH (molalties in water: phenol: 0.5; NaOH: 1.0) at (314, 354, and 395) K and pressures up to 10 MPa. The experimental work extends recent investigations on the influence of phenol as well as of (phenol + NaCl) on the solubility of CO2 in water. In contrast to those previous investigations, the strong electrolyte reacts with carbon dioxide and also with phenol. The experimental results are compared with predictions from a thermodynamic model. That model combines a model for the “chemical” solubility of CO2 in aqueous solutions of NaOH with a model for the “physical” solubility of CO2 in aqueous solutions of phenol. An extension is introduced to account for the chemical reaction between the weak acid phenol and the strong base sodium hydroxide. The prediction results nicely agree with the new experimental data. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2832–2840, 2015

New experimental results are presented for the solubility and the partial molar volume of carbon dioxide in an aqueous solution of phenol and sodium chloride at temperatures of about (314, 354 and 395) K and pressures up to about 10 MPa. The composition of the solvent – expressed as molality in water – is about 0.5 mol/(kg H2O) for phenol and 1 mol/(kg H2O) for sodium chloride. The experimental work is a continuation of investigations on the influence of organic components and strong electrolytes on the solubility of carbon dioxide in water. It extends a data base for developing and testing thermodynamic models to describe the solubility of gases in salt-free and salt-containing aqueous solvents mixed with organic compounds. The experimental results are compared to predictions and correlations from a thermodynamic model which combines a model for the solubility of CO2 in aqueous solutions of NaCl with a model for the solubility of CO2 in aqueous solutions of phenol. The prediction results reveal a reasonable agreement. As in a previous investigation – with N,N-dimethylformamide instead of phenol as the organic solvent component – adjusting a ternary parameter for interactions between the three solutes (i.e. CO2, NaCl, and phenol) results in a correlation that allows to describe the new experimental data within experimental uncertainty.

The equilibrium swelling behavior of nine N-isopropyl acrylamide (NIPAAm) based copolymeric hydrogels containing the hydrophobic comonomer octadecyl acrylate (ODA) in aqueous solutions of ethanol was investigated experimentally at 298 K. The gels were produced by free radical polymerization in the solvent ethyl acetate using methylenebisacrylamide (MBA) for crosslinking. The mole fraction of octadecyl acrylate in the polymerizing substance yODA was varied between 0.01 and 0.3. The mole fraction of the crosslinker was either 0.01 or 0.02. The swelling behavior of such hydrogels in aqueous solutions of ethanol depends on its ODA content. As long as the concentration of ODA in (NIPAAm + ODA)-hydrogels is small (yODA

New experimental results are reported for the solubility of carbon dioxide in aqueous solutions of phenol and for the density of the corresponding liquid solvent mixtures at about (314, 354, and 395) K at pressures between about 0.2 MPa and 9.7 MPa. The experimental results are evaluated to determine Henry's constants for carbon dioxide (on the molality scale) and the partial molar volume of carbon dioxide at infinite dilution in such solutions at the same temperatures. Furthermore, correlations are presented that describe the new gas solubility data almost within experimental uncertainty.

New experimental results are reported for the solubility of carbon dioxide in phenol at 354 K and 395 K at pressures between about 0.15 MPa and 9 MPa and for the partial molar volume of carbon dioxide at infinite dilution in phenol at the same temperatures. Henry's constant for carbon dioxide in phenol is determined from the new solubility data and a correlation is presented that describes the new gas solubility data within experimental uncertainty.

The influence of single salts (either NaCl, K 2 CO 3 , KI, KSCN, KF and Na 2 SO 4 ) on the degree of swelling of some copolymeric hydrogels of N-isopropyl acrylamide (N-IPAAm) and a zwitterionic comonomer sulfobetaine (=[3-(methacryloylamino) propyl] dimethyl (3-sulfopropyl) ammonium hydroxide inner salt (MPSA)) in water at 298 K was investigated experimentally. As expected, the experimental results reveal that at low salt concentrations (mass fractions of salt in aqueous solution below about 10 −3 ) none of the investigated salts has an influence on the degree of swelling. As also expected, at high salt concentrations (mass fraction above ≈10 −1 ) the gels collapse. However, an increase of the degree of swelling at intermediate salt concentrations was found for all investigated gels in aqueous solutions of either KSCN or KI as well as for the gels with a high content of sulfobetaine in aqueous solutions of NaCl. This phenomenon is called “anti-polyelectrolyte” behavior. A previously developed thermodynamic model was extended to describe (i.e., correlate and predict) the experimental results for the swelling behavior. Calculation results for the degree of swelling are in good agreement with experimental data. In most cases the difference between the experimental and the calculation result for the degree of swelling is lower than the corresponding experimental uncertainty.

The influence of NaCl and pH on the swelling behavior of a series of chemically cross-linked ionic poly(N-IPAAm-allylglycine) hydrogels in aqueous solutions was investigated at 298 K. The hydrogels were synthesized by free radical polymerization using methylenebisacrylamide as crosslinker. For all investigated hydrogels, the mass fraction of polymerizable substances was constant (0.1). The hydrogels differ in the amount of crosslinker (mole fraction: 0.02 and 0.05, respectively) and in the amount of the comonomer allylglycine (mole fraction: from 0.05 to 0.2). The experimental results for the degree of swelling in aqueous salt solutions of NaCl exhibit two transitions: the first (second) transition occurs at salt mass fractions between about 10 −6 and 10 −4 (≈10 −2 ). The first transition reduces the degree of swelling by about 20%. That transition is caused by the screening of the charged amino and carboxylic groups of allylglycine by the salt ions. After that transition the gel still contains much water. In the second transition the gel collapses like non-ionic N-IPAAm – hydrogels. The swelling of the ionic hydrogels is also influenced by the pH of the aqueous solution. The degree of swelling reveals a minimum at 4

Aldehydes react with alcohols to hemiacetals and poly(oxymethylene) hemiacetals. The chemical reaction equilibria of such reactions, in particular in the liquid state, can have an essential influence on the thermodynamic properties and related phenomena like, for example, on the vapour + liquid phase equilibrium. Therefore, thermodynamic models that aim to describe quantitatively such phase equilibria have to consider the chemical reaction equilibrium in the coexisting phases. This is well known in the literature for systems such as, for example, formaldehyde and methanol. However, experimental information on the chemical reaction equilibria in mixtures with other aldehydes (than formaldehyde) and alcohols is extremely scarce. Therefore, quantitative NMR spectroscopy was used to investigate the chemical reaction equilibria in binary mixtures of acetaldehyde and a single alcohol (here either methanol, ethanol or 1-propanol) at temperatures between (255 and 295) K. The results reveal that the majority of the constituents of the mixture is present as hemiacetal and the first two poly(oxymethylene) hemiacetals: in an equimolar mixture of (acetaldehyde + methanol or ethanol or 1-propanol), between about 90% at T = 255 K and about 75% at 295 K. The mole-fraction based chemical reaction equilibrium constants for the formation of those species were determined and some derived properties are reported.

The solubility of two single gases carbon dioxide and hydrogen sulfide in the ionic liquid 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([C2mim][eFAP]) was experimentally determined at temperatures from (303 to 353) K and pressures up to about 2.0 MPa. Results show that hydrogen sulfide is more soluble in that particular ionic liquid than carbon dioxide. At fixed temperature and pressure, the amount of dissolved H2S is more than twice the amount of CO2. The new experimental data were used to determine the Henry’s law constants, which again were used to derive some thermodynamic functions of the gas/solvent systems, such as, for example, the change of the partial molar Gibbs free energy of the gases upon solution in the ionic liquid. Two models were used to correlate the new experimental data: (1) a model comprised of the extended Henry’s law and Pitzer's virial expansion for the excess Gibbs free energy, and (2) a generic Redlich–Kwong (RK) cubic equation of state recently proposed for gas-ionic liquid systems. Both models are equally suited to correlate the experimental results. The (CO2 + H2S) selectivity of [C2mim][eFAP] was calculated from the RK EoS at various temperatures, pressures and CO2/H2S feed ratios and compared with the recently reported results for the selectivity of other ionic liquids.

The chemical reactions of aldehydes with alcohols to (hemiacetals and poly(oxymethylene) hemiacetals) have an essential influence on the thermodynamic properties and related phenomena like, for example, the vapor + liquid phase equilibrium of such liquid mixtures. This is well known in the literature for systems such as, for example, formaldehyde and methanol. Experimental information on the chemical reaction equilibria in mixtures with aldehydes other than formaldehyde and alcohols is extremely scarce. Therefore, in the first part of this series, quantitative NMR spectroscopy was used to investigate the chemical reaction equilibrium in binary liquid mixtures of acetaldehyde and an alcohol (methanol or ethanol or 1-propanol) at temperatures between (255 and 295) K. That work is here extended to three other aldehydes, viz. (1-propanal, 1-butanal and 1-heptanal). The results confirm the expectations from the first part of this series, i.e., that the majority of the constituents of the mixture is present as hemiacetal and the first two poly(oxymethylene) hemiacetals. For example, in an equimolar liquid mixture of {1-heptanal + methanol (or + ethanol or + 1-propanol)} at T = 273 K about 88% (or 81% for both other alcohols) of the aldehyde is bound to hemiacetal and the first two poly(oxymethylene) hemiacetals, i.e., the conversion rates are nearly the same as in the previous investigations with acetaldehyde instead of 1-heptanal. In the series investigated of combinations of aldehydes and alcohols, the particular aldehyde has only a small influence on the conversion rate. In the series of alcohols investigated only methanol has a somewhat larger influence whereas the results (speciation and conversion) for ethanol and 1-propanol are very similar. The NMR-spectroscopic results were also evaluated to determine the mole-fraction based chemical reaction equilibrium constants for the formation of the hemiacetals and the first two poly(oxymethylene) hemiacetals and the chemical reaction enthalpies.

In the Hot Potassium Carbonate Process, carbon dioxide (CO2) is removed from gaseous streams by chemical absorption in an aqueous solution of potassium carbonate (K2CO3). It is common to activate the solvent by adding borates and vanadates as promoters. In the present investigation, we investigate the influence of borates and vanadates on the equilibrium solubility of CO2 in aqueous solutions of K2CO3. The solubility of CO2 in four activated aqueous solutions of K2CO3 was determined experimentally at two temperatures that are typical for CO2 absorption (343 K) and solvent regeneration (383 K) in the Hot Potassium Carbonate Process. The mass fraction of K2CO3 in the solvent was 0.26 g/g, and the mass fractions of boron (vanadium) was varied between 0.006 g/g and 0.013 g/g (0.01 g/g and 0.02 g/g). Two experimental setups were used: A headspace gas chromatography technique was applied to determine the solubility of CO2 at partial pressures of CO2 between 1 kPa and 140 kPa, and the synthetic gas solubility te...

Reliable data for the solubility of carbon dioxide in aqueous solutions of monoethanolamine are required for the design and evaluation of postcombustion carbon capture processes. As published experimental data for the solubility of carbon dioxide in aqueous solutions of monoethanolamine show considerable scatter, the solubility of carbon dioxide in aqueous solutions containing (15 and 30) mass percent of monoethanolamine; that is, (2.9 and 7.0) mol·(kg H2O)−1 respectively, was measured at molar ratios of carbon dioxide to monoethanolamine in the liquid solution from 0.1 to 1.3 at (313, 353 and 393) K. An apparatus based on headspace gas chromatography (on the synthetic gas solubility method) was used for the experiments at low (high) gas loadings, that is, at partial pressures of carbon dioxide from (1 to 80) kPa (from (0.4 to 8.6) MPa). The new experimental results are compared to literature data and used to parametrize a physicochemical thermodynamic model based on the extended Pitzer equation for the G...

The influence of sodium sulphate on the solubility of carbon dioxide in aqueous solutions of N,N-dimethylmethanamide {= N,N-dimethylformamide, (CH3)2N-C(H)O, DMF} was investigated experimentally at three temperatures (314 K, 354 K, and 395 K). The solvent was an aqueous solution of DMF (mole fraction of DMF in the salt-free solution ≈ 0.05) and sodium sulphate (molality ≈ 0.6 mol·(kgH2O)−1). The maximum pressure of the new experimental gas solubility data reaches nearly 10 MPa. A thermodynamic model that combines two models for the solubility of CO2 (in aqueous solutions of Na2SO4 on one side and in aqueous solutions of DMF on the other side) is used to predict the influence of Na2SO4 on the solubility of CO2 in aqueous solutions of DMF. The new experimental data are compared with such predictions and with calculations from an extension of that model where a single ternary parameter for interactions between the three solutes (i.e., CO2, Na2SO4, and DMF) is adjusted to improve the representation of the experimental data.

New experimental results are presented for the solubility of carbon dioxide in aqueous solutions of N,N-dimethylmethanamide {=N,N-dimethylformamide, (CH 3 ) 2 N C(H)O, DMF} and sodium chloride at temperatures of (314, 354, and 395) K, gas-free and salt-free solvent mixture DMF mole fractions of about (0.05, 0.1, and 0.25, respectively), and two salt molalities (about 2.2 and about 4.5 mol/kg water). The maximum pressure of the new experimental gas solubility data reaches nearly 10 MPa. The experimental work is to provide a data base for developing and testing thermodynamic models to describe the solubility of gases in salt-free and salt-containing mixed aqueous solvents, as well as to test screening methods based, for example, on molecular simulation. A particular thermodynamic model that combines a model for the solubility of CO 2 in aqueous solutions of NaCl with a model for the solubility of CO 2 in aqueous solutions of DMF is used to predict the influence of NaCl on the solubility of CO 2 in aqueous solutions of DMF. The new experimental data are compared with such predictions and with calculations from an extension of that model (where a single ternary parameter for interactions between the three solutes (i.e., CO 2 , NaCl and DMF) is introduced and fit to the new experimental data.

The “hot-potash” process is one of the most commonly used processes to remove carbon dioxide from gases in the chemical industry. The solvent of that absorption process is an aqueous solution of potassium carbonate. Dissolving carbon dioxide in an aqueous solution of K2CO3 results in the conversion of carbonate and CO2 to bicarbonate; that is, carbon dioxide is predominantly dissolved chemically. In industrial applications a single substance or a mixture of several substances are added to the solvent to improve the performance of the process. The specific role of such additives is often unknown, but it is well-established that some additives improve the performance of the “hot-potash” process. One of those additives is vanadium pentoxide. The influence of a small amount of vanadium pentoxide on the equilibrium solubility of carbon dioxide in aqueous solutions of potassium hydroxide was investigated at conditions that are typical for a “hot-ash” process. The experimental results reveal that vanadium pentox...

The solubility of hydrogen sulfide in an aqueous mixture of 2,2'-methyliminodiethanol (N-methyldiethanolamine, [CAS 105-59-9], MDEA) and 1,4-diazacyclohexane (piperazine, [CAS 110-85-0], PIPH 2 ) was measured over a wide range of gas-loadings (stoichiometric molar ratios of hydrogen sulfide to (MDEA + PIPH 2 ) between about 0.014 and 1.67) at three temperatures (about 313 K, 353 K, and 393 K) by headspace gas chromatography as well as by a synthetic gas solubility method. The molality of MDEA in the aqueous mixture was about 4.5 mol·(kg water) ―1 and that of PIPH 2 about 1.6 mol·(kg water) ―1 . The headspace gas chromatography technique was applied in the low pressure range (partial pressure of H 2 S between 0.64 and 125.7 kPa, stoichiometric molar ratio of H 2 S to (MDEA + PIPH 2 ) between about 0.014 and 0.73). The synthetic method was applied in the high pressure range (total pressure between 0.2 and 5.5 MPa, stoichiometric molar ratio of H 2 S to (MDEA + PIPH 2 ) between about about 0.51 and 1.67). The new experimental results are compared to prediction results from a thermodynamic model that was parametrized using only experimental results for the solubility of H 2 S data in the aqueous solution of the single amines in the high pressure range.

New experimental results are presented for the solubility of carbon dioxide in pure liquid N,N-dimethylmethanamide {= N,N-dimethylformamide, (CH3)2NC(H)O, DMF} and in solvent mixtures of (water + DMF) at gas-free solvent mixture DMF mole fractions of about (0.05, 0.1, 0.25, 0.5, 0.75, and 0.9), temperatures of (314, 354, and 395) K, and total pressures up to about 10 MPa. Numerical values are reported for the (molality scale based) Henry's constant of CO2 in DMF and in (water + DMF) liquid mixtures resulting from the new experimental data by applying a common 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 aqueous solvents, as well as to test screening methods based, for example, on molecular simulation.

Experimental results are presented for the (liquid + liquid), (solid + liquid) and (solid + liquid + liquid) equilibria occurring in the downstream process of a typical example for the Biphasic Acid Scavenging Utilizing Ionic Liquids (BASIL)-processes. In a BASIL process an organic base is used to catalyze a chemical reaction and, at the same time, to scavenge an acid that is an undesired side product of that reaction. The particular example of a BASIL process treated here is the reaction of 1-butanol and acetylchloride to butylacetate and hydrochloric acid, where the acid is scavenged by the organic base 1-methyl imidazole (1-MIM) resulting in the ionic liquid 1-methyl imidazolium chloride. The reaction results in a two-phase system as butylacetate and the ionic liquid reveal a large liquid–liquid miscibility gap. The organic base has to be recovered. This is commonly achieved by treating the ionic liquid–rich liquid phase with an aqueous solution of sodium hydroxide (i.e., converting the ionic liquid to the organic base) and extracting the organic base by an appropriate organic solvent (e.g., 1-propanol). The work presented here deals in experimental work with the (liquid + liquid), (solid + liquid) and (solid + liquid + liquid) phase equilibria that are encountered in such extraction processes. Experimental results are reported for temperatures between about 298 K and 333 K: for the solubility of NaCl in several solvents (1-propanol, 1-MIM), (water + 1-MIM), (1-propanol + 1-MIM), (water + 1-propanol), and (water + 1-propanol + 1-MIM) and for the (liquid + liquid) equilibrium as well as for the (solid + liquid + liquid) equilibrium of the ternary system (NaCl + water + 1-propanol) and of the quaternary system (NaCl + water + 1-propanol + 1-MIM).

Untersuchungen zur gasinduzierten Phasentrennung bzw. zum Aussalzen mit nahekritischen Gasen wurden an verschiedenen wassrigen Losungen (auch mit ionischem Fluid) durchgefuhrt. Ziel war der Nachweis und die Charakterisierung von Hochdruckmehrphasengleichgewichten, die sich fur eine technische Anwendung eignen. Kriterien hierfur sind Auftreten des Flussig/flussig-Phasenzerfalls bei relativ niedrigem Druck, seine Existenz uber einen weiten Druck- und Zusammensetzungsbereich und damit verbunden eine druckinduzierte Anderung der Zusammensetzung der koexistierenden Flussigphasen. Die eingesetzten ionischen Fluide zeigen zwar das gewunschte Phasenverhalten, erfullen die Kriterien aber nur teilweise. Im Vorgriff auf eine mogliche Anwendung wurde die Verteilung eines hochmolekularen, amphiprotischen Naturstoffs auf die koexistierenden Flussigphasen untersucht und durch Einstellung des pH-Werts gezielt verandert. Investigations on gas-induced phase split, i.e., salting out by a nearcritical gas, were carried out for several aqueous solutions (including an ionic liquid). The research aimed to verify and characterize high-pressure multiphase equilibria that might be suitable for technical applications. The respective criteria are occurrence at relatively low pressures and the existence of the phase equilibrium phenomenon over a significant region of both composition and pressure, which is related to a pressure-induced significant alteration of the compositions of the coexisting liquid phases. The employed ionic liquids revealed the expected phase behavior but without full compliance of all criteria. In anticipation of an application, the partitioning of an amphiprotic, high-molecular biomolecule to the coexisting liquid phases was successfully administered via a pH variation.

The solubility of a single gas as well as the simultaneous solubility of several gases in an ionic liquid is of great interest in many areas of chemical engineering, particularly in heterogeneous catalysis. One of the most interesting features involved in the study of the simultaneous solubility of several gases in a pure ionic liquid is the difference between experimental data and predictions for the simultaneous solubility (based on experimental data for the solubility of the single gases). The well soluble gas might act as a cosolvent or as an antisolvent for a sparsely soluble second gas. New experimental results and a correlation are presented for the simultaneous solubility of hydrogen (i.e., a sparsely soluble gas) and carbon dioxide (a well soluble gas) in the ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([hmim][Tf2N]) at temperatures between 293 K and 373 K and pressures up to about 9.2 MPa. The experimental results reveal that carbon dioxide acts as a cosolvent for hydrogen in that particular ionic liquid. A correlation shows that the cosolvency effect can be modeled by considering interaction parameters between hydrogen and carbon dioxide in liquid [hmim][Tf2N]. The correlation can also be used to quantify that cosolvency effect: one mole of carbon dioxide in 1000 g of [hmim][Tf2N] increases the solubility of (small amounts of) hydrogen by about 20%.

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...

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 liq...

A thermodynamic model for the solubility of carbon dioxide in aqueous solutions of (N-methyldiethanolamine (MDEA) + piperazine (PIPH2)) is presented. The model combines and extends previous models for the solubility of CO2 in aqueous solutions of the single amines and also accounts for the volatility of both amines. Model parameters are estimated from previously published experimental results for the solubility of CO2 in aqueous solutions of both amines (for MDEA molalities up to 8 mol kg−1 of water and for PIPH2 molalities up to 4 mol kg−1 of water, temperatures between 313 and 393 K, and pressures up to about 10 MPa).

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.

Experimental results are presented for the liquid–liquid equilibrium of a ternary system (N-vinylpyrrolidone + sodium sulfate + water) and three quaternary systems composed of (N-vinylpyrrolidone + poly(vinylpyrrolidone) + sodium sulfate + water) at 25 °C. The quaternary systems differ in the number averaged molecular mass of the poly(vinylpyrrolidones). That molecular mass was between about 4 000 and 140 000. The experimental results are described with a semi-empirical model (VERS model) for the excess Gibbs energy.

The high-pressure phase equilibrium of two ternary systems—(ethene + water + acetone) and (ethane + water + acetone)—was investigated by a static−analytical method. Both systems exhibit the “salting-out” phenomenon upon pressurization by the gaseous compound. The composition of the two coexisting liquid phases L1 and L2 of the high-pressure liquid−liquid−vapor (L1L2V) equilibrium was determined at (293, 313, and 333) K over the entire pressure range that spans from about (2.9 to 8.0) MPa for (ethene + water + acetone) and from about (2.3 to 5.8) MPa for (ethane + water + acetone), respectively. Additionally, the coordinates of both critical end point lines (i.e., the lower ((L1 = L2)V) and the upper (L1(L2 = V)), respectively) bordering the L1L2V equilibrium were recorded between (278 and 353) K. For both systems, it was found that, at constant temperature, increasing the pressure has a stronger impact on the L2 phase (resulting in higher contents of the gas), whereas the composition of the water-rich L1 ...

Hydrogels are crosslinked polymers of hydrophilic monomers. Hydrogels can swell and shrink in aqueous solutions. The swelling behavior of hydrogels and the encountered phase behavior are of interest in many areas, e.g., in biotechnology, membrane science and controlled drug release. This contribution presents the criteria for such phase equilibria and a previously developed thermodynamic model for correlating/predicting the swelling and shrinking of hydrogels. The application of the method is demonstrated by describing the swelling equilibrium of some synthetic, non-ionic N-isopropyl acrylamide (N-IPAAm) hydrogels in aqueous solutions of sodium chloride at 298 K. Furthermore, new experimental results are presented for the degree of swelling of synthetic hydrogels that contain – besides the non-ionic monomer N-IPAAm – either a combination of a cationic comonomer (here, N-[3-(dimethylamino)propyl]methacrylamide (DMAPMA)) and an anionic comonomer (here, 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS)) or a zwitterionic comonomer (here, [3-(methacryloylamino)propyl]dimethyl(3-sulfopropyl)ammonium hydroxide inner salt (MPSA)). These gels were equilibrated with aqueous solutions of sodium chloride at 298 K.

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.

Some homogeneous liquid mixtures of an ionic liquid and a lower alkanol (e.g., methanol) can be forced to undergo a liquid–liquid phase split (resulting in a three-phase liquid–liquid–vapor (L1L2V) equilibrium) by pressurization with a gas. Such systems exhibit the phenomenon of “salting out by a nearcritical gas”. That phenomenon is often observed at temperatures around the critical temperature of the gas in liquid mixtures where at least one of the liquid components is a good solvent for that gas. New experimental results for both the L1L2V equilibrium and the corresponding critical endpoint lines of the two ternary systems (carbon dioxide + methanol + 1-n-butyl-3-methylimidazolium hexafluorophosphate [bmim][PF6]) and (carbon dioxide + 1-butanol + 1-n-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide [hmim][Tf2N]) at temperatures between 293 and 333 K are reported. The experiments were performed with an “analytical method”. The liquid–liquid phase split exists only at pressures between a lower critical endpoint line (where both liquid phases become critical and coexist with a vapor phase) and an upper critical endpoint line (where one of the phases becomes critical with the vapor phase while the critical phases coexist with another liquid phase). The compositions of the coexisting three phases L1, L2, and V differ considerably; a high-density, ionic liquid-rich liquid phase (L1) coexists with an alkanol-rich liquid phase (L2) of lower density and a vapor phase (V) that is virtually ionic liquid-free. For both systems, it was observed that, at constant temperature, increasing pressure shifts the L1 phase towards higher contents of ionic liquid and gas and less alkanol, whereas in the L2 phase the mole fractions of ionic liquid and alkanol decrease. Higher temperatures result in a smaller difference between the pressures of both critical endpoint lines. Experimental results for both critical endpoint lines and for the compositions of the coexisting liquid phases are reported.

Lysozyme precipitation induced by the addition of the volatile salt ammonium carbamate was studied through cloud-point measurements and precipitation assays. Phase equilibrium experiments were carried out at 5.0, 15.0 and 25.0 °C and the compositions of the coexisting phases were determined. A complete separation of the coexisting liquid and solid phases could not be achieved. Nevertheless it was possible to determine the composition of the solid precipitate through the extensions of experimental tie lines. The same precipitate was found at all temperatures. Lysozyme enzymatic activities of the supernatant and precipitate phases were also determined. The activity balance suggests that ammonium carbamate preserves lysozyme activity after the salting-out precipitation.

The influence of the amino acid d,l-methionine on the solubility of carbon dioxide in pure water and in aqueous solutions of potassium carbonate was investigated. The solubility was measured with a high-pressure view-cell technique operating on the synthetic method. Temperature and total pressure ranged from about 353 to 393 K and 1 to 10 MPa, respectively. The molality of methionine was between about 0.42 mol·(kg H2O)−1 and 0.83 mol·(kg H2O)−1. The molality of potassium carbonate was about 1.25 and 2.5 mol·(kg H2O)−1. The solubility of carbon dioxide in aqueous solutions of potassium carbonate and methionine is influenced by chemical reactions: On one side, dissolving carbon dioxide in an aqueous solution of potassium carbonate shifts the chemical reaction equilibrium from carbonate to bicarbonate and, on the other side, methionine is a zwitterionic substance. The new experimental results are correlated using an extension of a previously published thermodynamic model for the solubility of carbon dioxide ...

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 PIPH2 between 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 %.

The salt-induced precipitation of lysozyme from aqueous solutions was studied through precipitation assays in which the equilibrium compositions of the coexisting phases were determined. Lysozyme precipitation experiments were carried out at 5, 15 and 25 °C and pH 7.0 with ammonium sulfate, sodium sulfate and sodium chloride as precipitating agents. In these experiments a complete separation of the coexisting phases (liquid and solid) could not be achieved. Nevertheless it was possible to determine the composition of the precipitate. The enzymatic activity of lysozyme in the supernatant phase as well as in the precipitate phase was also determined. The activity balance suggests that there is a relationship between the composition of the true precipitate and the total activity recovery.

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 CO2 varied 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).

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][Tf 2 N]) 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][Tf 2 N] is more than 1 order of magnitude higher than the solubility of hydrogen. Carbon dioxide becomes less soluble in [bmpy][Tf 2 N] 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][Tf 2 N] (on the molality scale) are represented within the experimental uncertainty (about 0.8 % for carbon dioxide and 1.3 % for hydrogen) by In(k (0) H,CO2 /MPa) = 8.5128 - 2057/(T/K) - 0.004274·(T/K) and In(k (0) H, H2 /MPa) = 3.5746 + 343/(T/K) - 0.0008·(T/K), respectively.

A new model for the excess Gibbs energy of aqueous solutions of polyelectrolytes is presented and applied for the correlation of the activity of water in aqueous solutions of polyelectrolytes without as well as with an added (single) salt. The model considers the phenomenon of counterion condensation, i.e., the partial dissociation of highly charged polyelectrolytes in water. Three parameters (a binary interaction parameter between polymer segments, the equilibrium constant of the dissociation reaction and a parameter which accounts for the polymer configuration) were fitted to the experimental results. The model allows for a reliable correlation of experimental results for the osmotic coefficient of aqueous solutions of a single polyelectrolyte (without as well as with an added salt).

The esterification of ethanol, 1-propanol and 1-butanol with acetic acid in three ionic liquids with HSO4 - anion and 1-alkyl-3-methylimidazolium cation was investigated. The ionic liquids are 1-methylimidazolium hydrogen sulfate [HMIM][HSO4], 1-ethyl-3-methylimidazolium hydrogen sulfate [EMIM][HSO4] and 1-butyl-3-methylimidazolium hydrogen sulfate [BMIM][HSO4], which have catalytic activity. Data and modeling on the reaction conversions and the distribution of the compounds between the phases is reported here. Trends for the change in the liquid-liquid equilibrium, with parameters like alkyl chain length on the cation or the alcohol, are discussed and used to estimate the phase behavior of similar esterification systems.

Thermodynamic properties have always played essential roles in the engineering of chemical products and in the processes that manufacture them. Further, contemporary and future chemical technologies depend more than ever on property model formulation and application. This work explores how properties are utilized in process and product engineering, including opportunities and constraints of current property models, the current status of data availability and needs, and the interplay of data and models. Several case studies are given to illustrate underlying concepts, strategies for development, and methods of application to some industrial systems.

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 intermolecula...

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)...

The partial molar volume of a gas that is dissolved at high dilution in a solvent is required to express the influence of pressure on Henry's constant as well as to describe the volume change (expansion) of the liquid caused by the dissolved gas. The correlations of recently published experimental results for the solubility of some selected gases (CO 2 , Xe, CH 4 , CF 4 , H 2 , CO, O 2 ) in three imidazolium-based ionic liquids (1- n -butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF 6 ]), 1- n -butyl-3-methylimidazolium methyl sulfate ([bmim][CH 3 SO 4 ]), and 1- n -hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([hmim][Tf 2 N])) determined by the synthetic method were re-evaluated by also considering the experimentally determined volumetric properties. The new evaluation does not change the published results for Henry's constants, but additionally yields reliable information on the partial molar volume of those gases in the mentioned ionic liquids at temperatures from about 293 to 413 K.