Abstract: The use of ionic liquids for CO 2 capture and natural gas sweetening is being object of intense research Within the enormous group of existing ionic liquids, those based on conjugate bases of carboxylic acids seem to be particularly promising This work addresses the study of the high pressure CO 2 solubility (up to 80 MPa) in two protic ionic liquids, N-methyl-2-hydroxyethylammonium formate and N-methyl-2-hydroxyethylammonium acetate, in a wide range of temperatures (293–353 K) A thermodynamic model based on the Peng–Robinson equation of state with the Wong–Sandler mixing rule, using the NRTL model for the activity coefficients, was here adopted to describe and evaluate the thermodynamic consistency of the experimental data Furthermore, the study of a ternary mixture of CO 2 + CH 4 + N-methyl-2-hydroxyethylammonium acetate was investigated showing a high selectivity from the IL towards these solutes

Abstract: To facilitate simulation, design, and optimization of chilled ammonia processes for CO2 capture, we develop a thermodynamic model for the NH3–CO2–H2O system with the electrolyte NRTL activity coefficient model. The thermodynamic model explicitly accounts for the solution chemistry which includes dissociations of H2O, NH3, and CO2, formation of ammonium carbamate, and precipitation of ammonium bicarbonate. The electrolyte NRTL activity coefficient model parameters are identified by fitting against selected experimental data for vapor–liquid equilibrium, heat of solution, and heat capacity of the NH3–H2O binary, solid–liquid equilibrium of the NH4HCO3–H2O binary, and vapor–liquid equilibrium and speciation of the NH3–CO2–H2O ternary. The model is further validated with additional VLE, speciation, heat capacity, and heat of solution data for the NH3–CO2–H2O system. Overall the model satisfactorily represents the thermodynamic properties of the NH3–CO2–H2O system with temperature up to 473 K, pressure up to 7...

Abstract: This paper is a continuation of our systematic investigations on piperidinium ionic liquids and presents new data on activity coefficients at infinite dilution for 43 solutes: linear and branched alkanes, cycloalkanes, alkenes, alkynes, benzene, alkylbenzenes, alcohols, water, thiophene, tetrahyrdofuran (THF), methyl tert-butyl ether (MTBE), linear ethers, acetone, and linear ketones in the ionic liquid 1-butyl-1-methylpiperidinium bis(trifluoromethylsulfonyl)imide, [BMPIP][NTf2]. The data were determined by gas–liquid chromatography (GLC) at temperatures from 308.15 to 358.15 K. These values were compared to those previously published for the bis(trifluoromethylsulfonyl)imide-based ionic liquids. The partial molar excess enthalpies ΔH1E,∞ and entropies ΔS1E,∞ at infinite dilution were calculated from the experimental γ13∞ values obtained over the temperature range. The values of the selectivities for different separation problems were calculated from γ13∞ and compared to literature values for N-methyl-2-...

Abstract: In this work, new solubility data of CO2 in aqueous piperazine (Pz) solutions were measured over a temperature range from T = (287.1 to 313.1) K and for amine concentrations from m = (0.10 to 2.00) mol·kg−1. The CO2 partial pressure was kept within PCO2 = (0.11 to 525.17) kPa using a vapor−liquid equilibrium (VLE) apparatus based on a static-synthetic method. These experimental data and those found in the literature for the ternary system Pz−CO2−H2O were correlated using a model combining the virial equation of state to calculate the fugacity coefficients with a modified Pitzer's thermodynamic model for the activity coefficients. With the new extended interaction parameters βi,j0 and βi,j1 that cover a wide range of temperature, CO2 partial pressure, and amine concentration, the model is able to correlate satisfactorily the available reliable experimental solubility data.

Abstract: Complexation of anions, cations and even ion pairs is now an active area of investigation in supramolecular chemistry; unfortunately it is an area fraught with complications when these processes are examined in low polarity organic media. Using a pseudorotaxane complex as an example, apparent K(a2) values (=[complex]/{[salt](o)-[complex]}{[host](o)-[complex]}) for pseudorotaxane formation from dibenzylammonium salts (2-X) and dibenzo-[24]crown-8 (1, DB24C8) in CDCl(3)/CD(3)CN 3:2 vary with concentration. This is attributable to the fact that the salt is ion paired, but the complex is not. We report an equilibrium model that explicitly includes ion pair dissociation and is based upon activities rather than molar concentrations for study of such processes in non-aqueous media. Proper analysis requires both a dissociation constant, K(ipd), for the salt and a binding constant for interaction of the free cation 2(+) with the host, K(a5); K(a5) for pseudorotaxane complexation is independent of the counterion (500 M(-1)), a result of the complex existing in solution as a free cation, but K(ipd) values for the salts vary by nearly two orders of magnitude from trifluoroacetate to tosylate to tetrafluoroborate to hexafluorophosphate anions. The activity coefficients depend on the nature of the predominant ions present, whether the pseudorotaxane or the ions from the salt, and also strongly on the molar concentrations; activity coefficients as low as 0.2 are observed, emphasizing the magnitude of their effect. Based on this type of analysis, a method for precise determination of relative binding constants, K(a5), for multiple hosts with a given guest is described. However, while the incorporation of activity coefficients is clearly necessary, it removes the ability to predict from the equilibrium constants the effects of concentration on the extent of binding, which can only be determined experimentally. This has serious implications for study of all such complexation processes in low polarity media.

Abstract: In this article, we present evolutionary models to predict the octanol-water partition coefficients (log P), water solubilities, and critical micelle concentrations (CMCs) of ionic liquids (ILs), as well as the anionic activity coefficients and hydrophobicities in pure water and octanol-water. They are based on a polyparameter linear free energy relationship (LFER) using measured and/or DFT-calculated LFER parameters: hydrogen-bonding acidity (A), hydrogen-bonding basicity (B), polarizability/dipolarity (S), excess molar refraction (E), and McGowan volume (V) of IL ions. With both calculated or experimental LFER descriptors of IL ions, the physicochemical parameters were predicted with an errors of 0.182-0.217 for the octanol-water partition coefficient and 0.131-0.166 logarithmic units for the water solubility. Because experimentally determined solute parameters of anions are not currently available, the CMC, anionic activity coefficient, and hydrophobicity were predicted with quantum-chemical methods with R(2) values of at least 0.99, as well as errors below 0.168 logarithmic units. These new approaches will facilitate the assessment of the technical applicability and environmental fate of ionic compounds even before their synthesis.

Abstract: The solubilities of decahydropyrazino[2,3-b]pyrazine (DHPP) in methanol, ethanol, and 2-propanol were measured at temperatures ranging from 274.95 to 354.75 K. The last crystal disappearance method was used to determine the solubility of DHPP. The experimental data were correlated by the van’t Hoff plot, λh (Buchowski) equation, modified Apelblat equation, and two local composition models (Wilson and NRTL). Moreover, the densities of (DHPP + water) solution were measured from 274.25 to 355.95 K, and the liquid molar volume of DHPP, Vm1(T), was obtained and used to calculate the parameters in the Wilson model. It was found that NRTL model gave the best correlation results. On the basis of the NRTL model and experimental data, the thermodynamic excess functions (ΔGE, ΔSE, and ΔHE) of DHPP + alcohols (methanol, ethanol, and 2-propanol) systems were determined. Furthermore, the infinite-dilution activity coefficient and the infinite-dilution reduced excess enthalpy (γ1∞ and ΔHE1∞) were derived.

Abstract: The Hildebrand solubility parameters have been calculated for eight ionic liquids. Retention data from the inverse gas chromatography measurements of the activity coefficients at infinite dilution were used for the calculation. From the solubility parameters, the enthalpies of vaporization of ionic liquids were estimated. Results are compared with solubility parameters estimated by different methods.

Abstract: The prediction of drug solubility in various pure and mixed solvents and the octanol−water partition coefficient (KOW) are evaluated using the recently revised conductor-like screening segment activity coefficient (COSMO-SAC) model. The solubility data of 51 drug compounds in 37 different solvents and their combinations over a temperature range of 273.15 K to 323.15 K (300 systems, 2918 data points) are calculated from the COSMO-SAC model and compared to experiments. The solubility data cover a wide range of solubility from (10−1 to 10−6) in mole fraction. When only the heat of fusion and the normal melting temperature of the drug are used, the average absolute error from the revised model is found to be 236 %, a significant reduction from that (388 %) of the original COSMO-SAC model. When the pure drug properties (heat of fusion and melting temperature) are not available, predictions can still be made with a similar accuracy using the solubility data of the drug in any other solvent or solvent mixture. T...

Abstract: The VLE data for the binary system of R1234ze(E) + R290 were measured with a recirculation method at four temperatures (258.150, 263.150, 273.150 and 283.150 K). The measured uncertainties of the temperature, pressure, and compositions are ±5 mK, ±0.0005 MPa, and ±0.005, respectively. All the experimental data were correlated by the Peng–Robinson (PR) EoS with the Huron–Vidal (HV) mixing rule involving the non-random two-liquid (NRTL) activity coefficient (PR–HV–NRTL) model. Azeotropic behavior can be found at the measured temperature range.

Abstract: The activity coefficients at infinite dilution, γ1,2∞, of 47 solutes including various (cyclo)alkanes, alkenes, alkynes, aromatic hydrocarbons, alcohols, water, thiophene, ethers, aldehydes, and ke...

Abstract: The expanded Hansen method was tested for determination of the solubility parameters of two non-steroidal anti-inflammatory drugs, naproxen and sodium diclofenac. This work describes for the first time the application of the method to the sodium salt of a drug. The original dependent variable of the expanded Hansen method, involving the activity coefficient of the drug, was compared with the direct use of the logarithm of the mole fraction solubility 1nX2 in the solubility models. The solubility of both drugs was measured in pure solvents of several chemical classes and the activity coefficient was obtained from the molar heat and the temperature of fusion. Differential scanning calorimetry was performed on the original powder and on the solid phase after equilibration with the pure solvents, enabling detection of possible changes of the thermal properties of the solid phase that might change the value of the activity coefficient. The molar heat and temperature of fusion of sodium diclofenac could not be determined because this drug decomposed near the fusion temperature. The best results for both drugs were obtained with the dependent variable 1nX2 in association with the four-parameter model which includes the acidic and basic partial-solubility parameters delta(a) and delta(b) instead of the Hansen hydrogen bonding parameter delta(h). Because the dispersion parameter does not vary greatly from one drug to another, the variation of solubility among solvents is largely a result of the dipolar and hydrogen-bonding parameters, a fact that is being consistently found for other drugs of small molecular weight. These results support earlier findings with citric acid and paracetamol that the expanded Hansen approach is suitable for determining partial-solubility parameters. The modification introduced in the expanded Hansen method, i.e. the use of 1nX2 as the dependent variable, provides better results than the activity coefficient used in the original method. This is advantageous for drugs such as sodium diclofenac for which the ideal solubility cannot be estimated. This paper shows for the first time that the method is suitable for determination of the partial-solubility parameters of a sodium salt of a drug, sodium diclofenac.

Abstract: Interactions of volatile organic compounds with the ionic liquid (IL) 1-butyl-1-methylpyrrolidinium dicyanamide [BMPYR][DCA] were explored through systematic gas–liquid chromatography retention measurements. Infinite dilution activity coefficients γ1∞ and gas–liquid partition coefficients KL of 30 selected hydrocarbons, alcohols, ketones, ethers, esters, haloalkanes, and nitrogen- or sulfur-containing compounds in [BMPYR][DCA] were determined at five temperatures in the range from (318.15 to 353.15) K. Partial molar excess enthalpies and entropies at infinite dilution were derived from the temperature dependence of the γ1∞ values. The linear free energy relationship (LFER) solvation model was used to correlate successfully the KL values. The LFER correlation parameters and excess thermodynamic functions were analyzed to disclose molecular interactions operating between the IL and the individual solutes. Among other ILs, [BMPYR][DCA] was identified to be a fairly cohesive solvent medium, which is capable o...

Abstract: The activity coefficients at infinite dilution (γ13∞) for 33 solutes: alkanes, alkenes, alkynes, cycloalkanes, aromatic hydrocarbons, alcohols, thiophene, ethers, ketones, and water in the ionic liquid, 1-butyl-1-methylpiperidinium thiocyanate ([BMPIP][SCN]), were determined by gas−liquid chromatography over the temperature range (318.15 to 358.15) K. The partial molar excess enthalpies at infinite dilution values (ΔH1E,∞) were calculated from the experimental γ13∞ values, obtained over the temperature range. The selectivities for heptane/benzene, cyclohexane/benzene, and heptane/thiophene separation problems were calculated from the γ13∞ and compared to the literature values for other ionic liquids with thiocyanate-based anion or with a butyl-methyl-substituted cation.