Solubility of carbon dioxide in aqueous solution of 2-amino-2-methyl-1-propanol and piperazine

In this work, new experimental results of the vapour-liquid equilibrium (VLE) of CO₂ in aqueous 2-amino-2-methyl-1-propanol (AMP) and piperazine (PZ) have been presented in the temperature range of 298-328 K and PZ concentration range of 2-8 mass%, keeping the total amine concentration in the solution at 30 mass%. The partial pressures of CO₂ were in the range of 0.1-1450 kPa. A thermodynamic model was developed to correlate and predict the VLE of CO₂ in aqueous AMP + PZ. The electrolyte nonrandom two liquid (ENRTL) theory has been used to develop the VLE model for the quaternary system (CO₂ + AMP + PZ + H₂O) to describe the equilibrium behaviour of the solution. The experimental data from this work and data available in the literature were used to regress the ENRTL interaction parameters. The model predictions are in good agreement with the experimental data of CO₂ solubility in aqueous blends of this work as well as those reported in the literature. The current model can also predict speciation, heat of absorption, pH of the CO₂ loaded solution, and amine volatility.     

Measurement and correlation of solubility of artemisinin in supercritical carbon dioxide

Artemisinin is an effective antimalarial drug isolated from the herbal medicine Artemisia annua L. Supercritical fluid extraction is an environment-friendly method for the extraction of artemisinin. In this work, the solubility of artemisinin in supercritical carbon dioxide was determined by static method at three temperatures of 313 K, 323 K, 333 K and pressures from 11 to 31 MPa. The range of experimental solubility data was from 0.498 × 10⁻³ to 2.915 × 10⁻³ mol/mol under the above-mentioned conditions. Two density-based models (Chrastil and Mendez–Santiago–Teja models) were selected to correlate the experimental data of this work, and the average absolute relative deviation (AARD) was 8.32% and 8.33%, respectively. The correlation results showed good agreement with the experimental data.     

Solubility of HFCs in lower alcohols

This work is inserted in a research program that consists mainly in the experimental and theoretical study of the effect of association between solute and solvent molecules in the solubility of gases in liquids.The solubilities of hydrofluorocarbons, HFCs, (CH₃F, CH₂F₂, CHF₃) in lower alcohols (methanol, ethanol, 1-propanol, 1-butanol) have been determined in the temperature range [284, 313] K, at atmospheric pressure. An automated apparatus based on Ben-Naim-Baer and Tominaga et al. designs was used, which provides an accuracy of 0.6%. A precision of the same order of magnitude was achieved.To represent the temperature dependence of the mole fraction solubilities, the equation R ln x₂ = A + B/T + C ln T was used. From this equation, the experimental Gibbs energies, enthalpies and entropies of solution at 298 K and 1 atm partial pressure of the gas, were calculated.A semiempirical correlation has been developed between the solubilities of HFCs in alcohols at 298 K and the Gutmann acceptor number of solvents, AN, and reduced dipole moment of the gases, μ*.     

Vapor–liquid equilibrium data for the nitrogen + n-octane system from (344.5 to 543.5) K and at pressures up to 50 MPa

A static-analytical apparatus with visual sapphire windows and pneumatic capillary samplers has been used to obtain new vapor–liquid equilibrium data for the N₂ + n-octane system over the temperature range from (344.5 to 543.5) K and at pressures up to 50 MPa. Equilibrium phase compositions and vapor–liquid equilibrium ratios are reported. The new results were compared with solubility data reported by other authors. The comparison showed that the solubility data reported in this work at 344.5 K are in good agreement with those determined by others at 344.3 K. The experimental data were modeled with the PR and PC-SAFT equations of state by using one-fluid mixing rules and a single temperature-independent interaction parameter. Results from the modeling effort showed that the PC-SAFT equation was superior to the PR equation in correlating the experimental data of the N₂ + n-octane system.     

New isothermal vapor–liquid equilibria for the CO2 + n-nonane,and CO2 + n-undecane systems

Experimental vapor–liquid equilibria (VLE) for the CO₂ + n-nonane and CO₂ + n-undecane systems were obtained by using a 100-cm³ high-pressure titanium cell up to 20 MPa at four temperatures (315, 344, 373, and 418 K). The apparatus is based on the static-analytic method; which allows fast determination of the coexistence curve. For the CO₂ + n-nonane system, good agreement was found between the experimental data and those reported in literature. No literature data were available for the CO₂ + n-undecane system at high temperature and pressure. Experimental data were correlated with the Peng–Robinson equation of state using the classical and the Wong–Sandler mixing rules.     

Thermodynamic properties of the gaseous barium silicates BaSiO2 and BaSiO3

In the present study, the stability of gaseous barium silicates was confirmed by the high temperature mass spectrometry. On the basis of equilibrium constants measured for gas-phase reactions, the standard formation enthalpies were determined for gaseous barium silicates as (−510 ± 15) kJ · mol⁻¹ and (−884 ± 18) kJ · mol⁻¹ at 298 K; standard atomization enthalpies as (1637 ± 17) kJ · mol⁻¹ and (2318 ± 20) kJ · mol⁻¹ at 298 K for BaSiO₂ and BaSiO₃, respectively. Based on the results obtained the critical analysis of the literature data was carried out.     

The solubility of CO2 and N2O in olive oil

The solubility of CO₂ and N₂O in olive oil has been measured at temperatures of about 298, 310, and 323 K with a gravimetric microbalance under pressures up to 2 MPa. The molecular weight of olive oil has been analyzed and found to be about 882 g mol⁻¹ as a mixed oil compound. The observed solubility data have been correlated with a cubic equation of state (EOS) model. N₂O has a larger solubility than CO₂ in olive oil based on either the mole or mass fraction. The present results clarify some ambiguities from the previous N₂O solubility data in the literature.     

Densities and derived thermodynamic properties of ternary mixtures 1-butyl-3-methyl-imidazolium tetrafluoroborate + ethanol + water at seven pressures and two temperatures

This work is a continuation of our studies on experimental measurements of physical properties on binary mixtures of the ionic liquid (IL) family 1-alkyl-3-methyl imidazolium tetrafluoroborate (CnMIM-BF₄) with water and ethanol. Here, we present density for the ternary system Butyl-MIM-BF₄ + ethanol + water at two temperatures (298.15 K and 323.15 K) and seven pressures (from 0.1 to 30 MPa). It should be noted that BMIM-BF₄ is the only IL of the family CnMIM-BF₄ that can be mixed with water and ethanol in all range of concentrations at room conditions. From the density data measured in function of pressure and temperature other important derived thermodynamic properties can be calculated, such us excess molar volumes, isothermal compressibility, isobaric expansion and the thermal pressure coefficients. These properties for selected ternary mixtures will be discussed and compared with data from the scarce number of published results for similar ternary mixtures with this same IL.     

Equilibrium solubility of carbon dioxide in 2(methylamino)ethanol

In this paper the equilibrium solubility of carbon dioxide in 1.0 M, 2.0 M and 4.0 M 2(methylamino)ethanol (MAE) is measured at 303, 313 and 333 K, and at CO₂ partial pressures ranging from 1 to 100 kPa using stirred cell reactor. The Kent-Eisenberg model was used to predict the solubility of carbon dioxide in MAE solutions. The equilibrium constant representing hydrolysis of carbamate ion is correlated with temperature, CO₂ partial pressure and amine concentration by non-linear regression, using experimental results of carbamate ion concentrations. The model predicted results showed good agreement with the experimental solubility results. The solubility profile of CO₂ in MAE showed better performance when compared with other commercial amines.     

Vapor–liquid equilibrium in the n-butane + methanol system,measurement and modeling from 323.2 to 443.2 K

New experimental vapor–liquid equilibrium (VLE) data for the n-butane + methanol binary system are reported over a wide temperature range from 323.2 to 443.2 K and pressures up to 5.4 MPa. A static–analytic apparatus, taking advantage of two pneumatic capillary samplers, was used. The phase equilibrium data generated in this work are in relatively good agreement with previous data reported in the literature. Three different thermodynamic models have been used to represent the new experimental data. The first model is the cubic-based Peng–Robinson equation of state (EoS) combined with the Wong–Sandler mixing rules. The two other models are the non-cubic SAFT-VR and PC-SAFT equations of state. Temperature-dependent binary interaction parameters have been adjusted to the new data. The three models accurately represent the new experimental data, but deviations are seen to increase at low temperature. A similar evolution of the binary parameters with respect to temperature is observed for the three models. In particular a discontinuity is observed for the k_ij values at temperatures close to the critical point of butane, indicating the effects of fluctuations on the phase equilibria close to critical points.     

Experimental determination and prediction of the vapor pressure of some binary and quaternary aqueous solutions of alkaline nitrites and nitrates

Vapor pressure of H₂O + NaNO₃ and H₂O + NaNO₂ solutions were measured with static method from 298.1 to 353.1 K in a range of salt mass fractions between 0.05 and 0.50. As well, the vapor pressure was determined for quaternary mixtures LiNO₃ + NaNO₃ + KNO₃ + H₂O (salt mass ratio 53:5:42) and LiNO₃ + KNO₃ + NaNO₂ + H₂O (salt mass ratio 53:35:12) from 313.1 to 353.1 K and total salt mass fraction of 0.30, 0.40 and 0.50. The experimental vapor pressure data of binary systems were correlated with the temperature and the liquid-phase composition using an analytical polynomial equation. The capability of the electrolyte non-random two liquid model (Electrolyte-NRTL) to predict the vapor–liquid equilibrium was evaluated by comparing predicted and experimental data of the mixtures studied in this work.     

Thermodynamic properties of caffeine: Reconciliation of available experimental data

Molar enthalpies of sublimation of two crystal forms of caffeine were obtained from the temperature dependence of the vapour pressure measured by the transpiration method. A large number of primary experimental results on the temperature dependences of vapour pressure and phase transitions have been collected from the literature and have been treated in a uniform manner in order to derive sublimation enthalpies of caffeine at T = 298.15 K. This collection together with the new experimental results reported here has helped to resolve contradictions in the available sublimation enthalpies data and to recommend a consistent and reliable set of sublimation and formation enthalpies for both crystal forms under study. Ab initio calculations of the gaseous molar enthalpy of formation of caffeine have been performed using the G3MP2 method and the results are in excellent agreement with the selected experimental data.     

Physical properties of 3-methyl-N-butylpyridinium tricyanomethanide and ternary LLE data with an aromatic and an aliphatic hydrocarbon at T = (303.2 and 328.2) K and p = 0.1 MPa

Several physical properties were determined for the ionic liquid 3-methyl-N-butylpyridinium tricyanomethanide ([3-mebupy]C(CN)₃): liquid density, viscosity, surface tension, thermal stability and heat capacity in the temperature range from (283.2 to 363.2) K and at 0.1 MPa. The density and the surface tension could well be correlated with linear equations and the viscosity with a Vogel-Fulcher-Tamman equation. The IL is stable up to a temperature of 420 K.Ternary data for the systems {benzene + n-hexane, toluene + n-heptane, and p-xylene + n-octane + [3-mebupy]C(CN)₃} were determined at T = (303.2 and 328.2) K and p = 0.1 MPa. All experimental data were well correlated with the NRTL model. The experimental and calculated aromatic/aliphatic selectivities are in good agreement with each other.     

Chemistry in heterocyclic ammonium fluorohydrogenate room-temperature ionic liquid

Investigation on alkali fluoride-HF system has been initiated in the 19th century. The technique is currently utilized in fluorine-chemical industry. But, the problem is that this system readily releases hazardous HF. Although organic base, e.g., amine, with HF, which is mainly applied to fluorination treatment for organic compound, reduces the HF release, the solution still requires careful handling because of limited amount of free HF. Recently family of fluorohydrogenate room-temperature ionic liquid, XF(HF)_2.3, that consists of heterocyclic ammonium cation (X⁺), F(HF)₂⁻, and F(HF)₃⁻, has gotten a lot of attentions due to the interesting physicochemical properties such as negligible vapor pressure (<7.5 × 10⁻³ Torr (=1 Pa) at 298 K), high conductivity, and low corrosiveness. This novel solvent will greatly contribute to development of fluorine chemistry. In this article, fundamental techniques and physicochemical data on the fluorohydrogenate RTIL are summarized, and molecular science in the dialkylimidazolium fluorohydrogenates leading to the understanding of the unusual properties is reviewed based on recent experimental and theoretical considerations.     

Vapour pressure and excess Gibbs free energy of the ternary system {x1CH3F + x2HCl + x3N2O} at temperature of 182.33 K

The equilibrium pressure of ternary mixtures of {x₁CH₃F + x₂HCl + x₃N₂O} covering the entire composition range has been measured at temperature of 182.33 K by the static method. The system exhibits a minimum pressure for the binary {x₁CH₃F + x₂HCl}. The molar excess Gibbs free energy has been calculated from the experimental equilibrium pressure. For the equimolar mixture . The (p, x, y) surface for the ternary system and the corresponding curves for the three constituent binary mixtures obtained from the Peng-Robinson equation of state are in agreement with the experimental data.     

Solid–liquid phase equilibria in the system K2SO4–MnSO4–H2O at 298 K and 313 K

Phase equilibria studies of the system K₂SO₄–MnSO₄–H₂O published revealed discrepancies between the data presented in the literature regarding the solid phases formed at ambient temperatures. The solubility in the system at 298 K and 313 K was determined. At 298 K, the existence of the double salt K₂SO₄·3MnSO₄·5H₂O and of MnSO₄·H₂O was confirmed. The examinations at 313 K showed the formation of the stable solid phases MnSO₄·H₂O, K₂SO₄·2MnSO₄, K₂SO₄·MnSO₄·1.5H₂O, K₂SO₄ and the formation of a metastable phase K₂SO₄·MnSO₄·2H₂O.     

Crystal structure and phase transitions of strontium zirconium diorthophosphate, SrZr(PO4)2

The crystal structure of SrZr(PO₄)₂ at 298 K was determined from conventional X-ray powder diffraction data using direct methods, and it was further refined by the Rietveld method. The structure was triclinic (space group , Z=2) with a=0.77508(4) nm, b=0.78887(5) nm, c=0.51251(3) nm, α=95.754(3)°, β=90.228(2)°, γ=92.474(2)°, and V=0.31149(3) nm³. Final reliability indices were R_wp=8.51%, R_p=6.07%, and R_B=2.46%. The powder specimens were also examined by high-temperature XRD and differential thermal analysis to reveal the occurrence of phase transitions from triclinic to monoclinic at 405 K, then to hexagonal (or trigonal) at 1196 K during heating. Upon cooling, the reverse change of the latter transition occurred at 1175 K. The subsequent monoclinic-to-triclinic transition was martensitic and incomplete during further cooling to 298 K. The monoclinic phase is most probably isostructural with yavapaiite. The present paper has described, for the first time, the higher- and lower-temperature polymorphs of the yavapaiite-type structure.     

Thermodynamic properties of BaCeO3 and BaZrO3 at low temperatures

Specific heat capacities (C_p) of polycrystalline samples of BaCeO₃ and BaZrO₃ have been measured from about 1.6 K up to room temperature by means of adiabatic calorimetry. We provide corrected experimental data for the heat capacity of BaCeO₃ in the range T < 10 K and, for the first time, contribute experimental data below 53 K for BaZrO₃. Applying Debye's T³-law for T → 0 K, thermodynamic functions as molar entropy and enthalpy are derived by integration. We obtain C_p = 114.8 (±1.0) J mol⁻¹ K⁻¹, S° = 145.8 (±0.7) J mol⁻¹ K⁻¹ for BaCeO₃ and C_p = 107.0 (±1.0) J mol⁻¹ K⁻¹, S° = 125.5 (±0.6) J mol⁻¹ K⁻¹ for BaZrO₃ at 298.15 K. These results are in overall agreement with previously reported studies but slightly deviating, in both cases. Evaluations of C_p(T) yield Debye temperatures and identify deviations from the simple Debye-theory due to extra vibrational modes as well as anharmonicity. The anharmonicity turns out to be more pronounced at elevated temperatures for BaCeO₃. The characteristic Debye temperatures determined at T = 0 K are Θ₀ = 365 (±6) K for BaCeO₃ and Θ₀ = 402 (±9) K for BaZrO₃.     

Solubility of carbon dioxide in aqueous solutions of diisopropanolamine and methyldiethanolamine

The solubility of carbon dioxide in aqueous solutions of alkanolamines was measured by means of two experimental methods. The solubility of carbon dioxide was measured at 298 K with a static total pressure apparatus in solutions of water + diisopropanolamine (DIPA) having mass fraction of DIPA equal to 10.1%, 11.0% and 33.9%. The density of the water + DIPA solution was measured continuously during the experiments to investigate the changes in density introduced by the absorption of carbon dioxide. A correlation for the density of CO₂-loaded aqueous solutions of DIPA is presented.     

Enthalpy of mixing in 0.8[xB2O3-(1 − x)SiO2]-0.2K2O melts at 973 K

0.8[xB₂O₃-(1 − x)SiO₂]-0.2K₂O (with 0 ≤ x ≤ 1) glasses were synthesized by melt quenching techniques. DSC curves of the glasses exhibit only one glass transition. Calorimetric measurements of heats of dissolution in lead borate at 973 K indicated small negative enthalpies of mixing. Consequently phase separation was not observed over the whole composition range. The results are in good agreement with the structural data available in the literature.