Low pressure solubility and thermodynamics of solvation of oxygen,carbon dioxide,and carbon monoxide in fluorinated liquids

The solubility of oxygen, carbon dioxide, and carbon monoxide in three fluorinated liquids – perfluorohexylethane, perfluorooctane and bromoperfluorooctane – is presented. Mole fraction solubilities were calculated from new experimental Ostwald coefficient data for CO₂ and CO, and from previously published values for O₂, associated with original values of density and vapour pressure for the pure solvents. Carbon dioxide is the most soluble gas with mole fraction solubilities of the order of 10⁻². Oxygen and carbon monoxide are one order of magnitude less soluble. The measurements were done as a function of temperature between (288 and 313) K and from the variation of the calculated Henry’s law constants with temperature, the thermodynamic properties of solvation such as the Gibbs free energy, the enthalpy and the entropy were calculated. The precision of the experimental data, considered as the average absolute deviation of the Henry’s law constants from appropriate smoothing equations is of 1% for carbon dioxide and oxygen and of 3% for carbon monoxide. The data obtained here are judged accurate to within ±5%.     

Phase behavior of β-d galactose pentaacetate–carbon dioxide binary system

Phase behavior of β-d galactose pentaacetate–carbon dioxide binary system is investigated by dew-point and bubble-point measurements conducted in a high pressure variable volume sapphire cell. The phase envelope for solutions of β-d galactose pentaacetate in supercritical CO₂ is obtained for β-d galactose pentaacetate concentrations between 2 and 26 wt%, and for the temperature range of 308–323 K. The system exhibits lower critical solution temperature (LCST) behavior and high solubility of β-d galactose pentaacetate is observed. The densities of the system are also measured, and liquid-like densities (near 1 g/cm³) are observed for single-phase solutions of β-d galactose pentaacetate in supercritical CO₂ at concentrations of 18 wt% and higher. Viscosity is measured for solutions of 18 and 25 wt% β-d galactose pentaacetate in the single-phase region at 313 K and 17 MPa and the viscosity values, 0.095 and 0.103 cp, respectively, are similar in magnitude to the viscosity of pure carbon dioxide.     

High pressure phase equilibrium for δ-tocopherol + CO2

Vapour–liquid equilibrium compositions were measured for mixtures of δ-tocopherol and carbon dioxide, at pressures from 9 up to 27 MPa, and four temperatures between 306 and 333 K. The system exhibits liquid–liquid equilibrium at high pressures, similarly to previous results for mixtures of α-tocopherol with carbon dioxide. The results were correlated with the Peng–Robinson equation of state, using the Panagiotopoulos–Reid combination rules.Comparison of the solubilities of δ-tocopherol and α-tocopherol in supercritical carbon dioxide was performed using Chrastil’s equation to correlate the data. The number of solvent CO₂ molecules per solute molecule was calculated in both cases. An enthalpy of solvation per mole of CO₂ of −10 kJ mol⁻¹ was obtained.     

Measurement and correlation of antifungal drugs solubility in pure supercritical CO2 using semiempirical models

In the present study the solubilities of two antifungal drugs of ketoconazole and clotrimazole in supercritical carbon dioxide were measured using a simple static method. The experimental data were measured at (308 to 348) K, over the pressure range of (12.2 to 35.5) MPa. The mole fraction solubilities ranged from 0.2 · 10^?6 to 17.45 · 10^?5. In this study five density based models were used to calculate the solubility of drugs in supercritical carbon dioxide. The density based models are Chrastil, modified Chrastil, Bartle, modified Bartle and Mendez-Santiago and Teja (M–T). Interaction parameters for the studied models were obtained and the percentage of average absolute relative deviation (AARD%) in each calculation was displayed. The correlation results showed good agreement with the experimental data. A comparison among the five models revealed that the Bartle and its modified models gave much better correlations of the solubility data with an average absolute relative deviation (AARD%) ranging from 4.8% to 6.2% and from 4.5% to 6.3% for ketoconazole and clotrimazole, respectively. Using the correlation results, the heat of drug–CO₂ solvation and that of drug vaporization was separately approximated in the range of (?22.1 to ?26.4 and 88.3 to 125.9) kJ · mol^?1.     

Recent advances on synthesis of potentially non-bioaccumulable fluorinated surfactants

Fluorinated surfactants are exceptional compounds that have found many applications in everyday life. This review focuses on severe issues on the toxicity, persistency and bioaccumulation of these halogenated products, especially perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), the half-lives of which are several years in human serum. After an introduction on their productions, uses and hazards, this minireview updates non-exhaustive recent strategies of synthesis of original fluorosurfactants that may be potentially non-bioaccumulable. These routes have been devoted on: (i) the preparation of CF₃-X-(CH₂)_n-SO₃Na (with X = O, C₆H₄O or N(CF₃) and n = 8–12), (ii) the use of fluorinated polyethers (achieved either by oligomerization of hexafluoropropylene oxide (HFPO) or by ring opening cationic oligomerization of fluorinated oxetanes; (iii) the telomerization of vinylidene fluoride (VDF) with 1-iodoperfluoralkanes to produce C_nF_2n + 1-(VDF)₂-CH₂CO₂R (n = 2 or 4, R = H or NH₄), (iv) the radical telomerization of 3,3,3-trifluoropropene (TFP) with isoperfluoropropyliodide to prepare (CF₃)₂CF(TFP)_x-R_H, and (v) the radical cotelomerization of VDF and TFP, or their controlled radical copolymerization in the presence of either (CF₃)₂CFI or a fluorinated xanthate. In most cases, the surface tensions versus the surfactant concentrations have been assessed. These above pathways led to various highly fluorinated (but yet not perfluorinated) telomers or cooligomers, the chemical changes of which enabled to obtain original surfactants as novel alternatives to PFOA, ammonium perfluorooctanoate (APFO), or PFOS regarded as the PCBs of the XXIst century.     

Solubility of climbazole and triclocarban in supercritical carbon dioxide: Measurement and correlation

The supercritical technology has been considered as an appropriate alternative for separation of biomaterials from cosmetic, food, and pharmaceutical products. The solid solubility of biological compounds is the most important thermodynamic parameter in the supercritical extraction and purification. The equilibrium solubility of two biocides, climbazole, and triclocarban was measured in supercritical carbon dioxide with static method in the pressure range from (10 to 40) MPa and at temperatures equal to (313.2, 323.2, and 333.2) K. The experimental data were correlated by Peng–Robinson equation of state and quasi-chemical nonrandom lattice fluid model.     

Equilibrium solubility of carbon dioxide in the amine solvent system of (triethanolamine + piperazine + water)

In this study, a new set of data for the equilibrium solubility of carbon dioxide in the amine solvent system that consists of triethanolamine (TEA), piperazine (PZ), and water is presented. Equilibrium solubility values were obtained at T = (313.2, 333.2, and 353.2) K and pressures up to 153 kPa using the vapour-recirculation equilibrium cell. The TEA concentrations in the considered ternary (solvent) mixture were (2 and 3) kmol · m^?3 and those of PZ’s were (0.5, 1.0, and 1.5) kmol · m^?3. The solubility data (CO₂ loading in the amine solution) obtained were correlated as a function of CO₂ partial pressure, system temperature, and amine composition via the modified Kent–Eisenberg model. Results showed that the model applied is generally satisfactory in representing the CO₂ absorption into mixed aqueous solutions of TEA and PZ.     

High-pressure phase behaviour measurement of (CO2 + ethylene glycol dimethacrylate) and (CO2 + di-ethylene glycol dimethacrylate) binary mixture systems

Ethylene glycol dimethacrylate (EGDMA) and di-ethylene glycol dimethacrylate (DEGDMA) are two of the most wildly used di-functional monomers in the polymer industry. The EGDMA and DEGDMA are applied to cross-linking polymerisation for improving the physical and chemical properties of synthesized polymers. However, residual and unreacted EGDMA and DEGDMA applied to the synthesis of dental composite and super-absorption polymer poses a health threat. This problem can be solved by using supercritical CO₂, which has high diffusivity and causes polymer swelling. To design and operate the supercritical fluid extraction process using scCO₂, high pressure phase behaviour data are required. The pressure–composition (P–x) isotherms for the (CO₂ + EGDMA) and (CO₂ + DEGDMA) binary mixture systems were measured using the static method with a variable-volume view cell at temperatures ranging from (313.2 to 363.2) K. The experimental data correlation was performed using the Peng–Robinson equation of state (PR-EOS) and the Van der Waals one fluid mixing rule. The critical constants for the PR-EOS were estimated by the Joback method and the Marrero–Gani method. The acentric factor was estimated by the Lee–Kesler method. The Marrero–Gani method showed better correlation results than the Joback method and the EGDMA is more soluble in the supercritical carbon dioxide than the DEGDMA.     

Synthesis of fluorinated oligomers for supercritical carbon dioxide applications

Syntheses of various fluorine‐based surfactants, namely fluorinated‐segment‐containing block co‐oligomers, were achieved by the radical polymerization of mainly acrylate‐based monomers. These types of surfactants serve as stabilizers for supercritical carbon dioxide (scCO₂) media based applications, for which the effective solubilization of materials in the supercritical phase is generally not possible because of solubility problems faced when CO₂ is involved. Initially, a difunctional fluorinated initiator was synthesized in two steps. First, 4,4′‐azobis‐4‐cyanovaleric acid was chlorinated with SOCl₂, and then the product, 4,4′‐azobis‐4‐cyanovaleryl chloride, was reacted with a fluorinated alcohol to obtain the initiator for the polymerization reactions. The synthesized triblock co‐oligomers consisted of fluorinated side blocks and a hydrocarbon intermediate block. Efficient solubilization of the materials in scCO₂ was observed. It was experimentally shown that the solubility efficiency was affected by specific interactions between CO₂ and the oligomers, and these were determined by the nature and size of the inner block and by the chain length of the fluorinated side blocks in comparison with the inner block. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5312–5322, 2005     

Equilibrium solubility of carbon dioxide in a 30 wt.% aqueous solution of 2-((2-aminoethyl)amino)ethanol at pressures between atmospheric and 4400 kPa: An experimental and modelling study

New experimental equilibrium data were obtained for the solubility of carbon dioxide in an aqueous solution with 30 wt.% of 2-((2-aminoethyl)amino)ethanol (AEEA) at temperatures ranging from (313.2 to 368.2) K and CO₂ partial pressures ranging from above atmospheric to 4400 kPa. A thermodynamic model based on the Deshmukh–Mather method was applied to correlate and predict the CO₂ solubility in aqueous AEEA solutions. The binary interaction parameters and equilibrium constants for the proposed reactions were determined by data regression. Using the adjusted parameters, equilibrium partial pressures of CO₂ were calculated and compared with the corresponding experimental values at the selected temperatures and pressures. Values of carbon dioxide solubility at other temperatures reported in the literature were also calculated. The average absolute deviation for all of the data points was found to be 8.2%. The enthalpy change of the absorption of CO₂ in the 30 wt.% aqueous solution of AEEA was also estimated with our model.     

Solubility and diffusion of CO2 and H2S in the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate

The solubility and diffusion coefficient were determined for carbon dioxide and hydrogen sulfide gases in the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate ([emim][EtSO₄]) at temperatures ranging from (303.15 to 353.15) K and pressures up to 1.6 MPa. The Krichevsky–Kasarnovsky equation was used to correlate solubility data and Henry’s law constants at different temperatures were obtained. The partial molar thermodynamic functions of solution such as Gibbs free energy, enthalpy, and entropy were calculated using the solubility data. A semi-infinite volume approach is used to obtain the diffusion coefficients for CO₂ and H₂S and a correlation equation with temperature is presented for each gas. Comparison showed that H₂S is more soluble than CO₂ and its diffusion coefficient is about two orders of magnitude as that of CO₂ in the ionic liquid studied in this work.     

Solubility measurement of α-asarone in supercritical carbon dioxide

The solubility of α-asarone in supercritical CO₂ (sc-CO₂) has been measured using the dynamic method. The measurement was conducted in the pressure range from 9.0 to 18.0 MPa at temperature 35–49 °C. The experimental data were correlated using the Chrastil model. The results show that the solubility increases as the pressure rises and decreases as the temperature rises, which is well correlated with the Chrastil model.     

The co-solubility of 2-ethylhexanoic acid and some liquid alcohols in supercritical carbon dioxide

The co-solubility in supercritical carbon dioxide of 1-butanol, 1-pentanol, 2-ethyl-1-hexanol, or 1-decanol in the presence of 2-ethylhexanoic acid in the pressure range of 100–180 bar and at 313 or 323 K was measured. The solubility of these alcohols in the presence of 2-ethylhexanoic acid is lower than in the systems alcohol + CO₂ and remains nearly constant in the pressure range of 120–180 bar, with the exception of 1-decanol. The lower selectivities in the ternary systems are explained by strong intermolecular hydrogen bonding between alcohol molecules and 2-ethylhexanoic acid molecules. The FT-IR spectra of mixtures of alcohols and 2-ethylhexanoic acid at a 1:1 mole ratio in the liquid CCl₄ confirmed this conclusion.     

Gas solubility of CO2 in aqueous solutions of N-methyldiethanolamine and diethanolamine with 2-amino-2-methyl-1-propanol

Gas solubility of carbon dioxide in an aqueous solution of 32.5 wt.% N-methyldiethanolamine and 12.5 wt.% diethanolamine with 4, 6, and 10 wt.% 2-amino-2-methyl-1-propanol has been measured, at 313.15, 343.15, and 393.15 K, over a range of pressure from 3 to 2000 kPa, using a chromatographic method for analysis of the liquid phase. The results of the gas solubility are given as the partial pressure of CO₂ against its mole ratio α (mol CO₂/mol alkanolamine) and its mole fraction at each temperature studied. The solubility of CO₂ in all the systems studied decreases with an increase in temperature and increases with an increase in the partial pressure of CO₂ at a given temperature and it is a function of the concentration of the mixture of alkanolamines in solution. The enthalpy of solution of CO₂ has been calculated from the experimental solubility data.     

High-pressure phase equilibrium for the binary systems of {carbon dioxide (1) + dimethyl carbonate (2)} and {carbon dioxide (1) + diethyl carbonate (2)} at temperatures of 273 K, 283 K,and 293 K

Phase equilibrium data for the binary systems {carbon dioxide (CO₂) + dimethyl carbonate (DMC)} and {carbon dioxide (CO₂) + diethyl carbonate (DEC)} were measured at temperatures of 273 K, 283 K and 293 K in the pressure range of 0.5 MPa to 4.0 MPa. The measurements were carried out in a cylindrical autoclave with a moveable piston and an observation window. The experimental data were correlated with the Peng–Robison (PR) equation of state (EOS) and the Peng–Robinson–Stryjek–Vera (PRSV) equation of state with van der Waals-1 or Panagiotopoulos–Reid mixing rules. The correlations produced reasonable values for the interaction parameters. The comparisons between calculation results and experimental data indicate that the PRSV equation of state coupled with the Panagiotopoulos–Reid mixing rule produced the better correlated results.     

Solubility of CO2 in 1-(2-hydroxyethyl)-3-methylimidazolium ionic liquids with different anions

The solubility of carbon dioxide in a series of 1-(2-hydroxyethyl)-3-methylimidazolium ([hemim]⁺) based ionic liquids (ILs) with different anions, viz. hexafluorophosphate ([PF₆]^?), trifluoromethanesulfonate ([OTf]^?), and bis-(trifluoromethyl)sulfonylimide ([Tf₂N]^?) at temperatures ranging from 303.15 K to 353.15 K and pressures up to 1.3 MPa were determined. The solubility data were correlated using the Krichevsky–Kasarnovsky equation and Henry’s law constants were obtained at different temperatures. Using the solubility data, the partial molar thermodynamic functions of solution such as Gibbs free energy, enthalpy, and entropy were calculated. Comparison showed that the solubility of CO₂ in the ILs studied follows the same behaviour as the corresponding conventional 1-ethyl-3-methylimidazolium ([emim]⁺) based ILs with the same anions, i.e. [hemim][NTf₂] > [hemim][OTf] > [hemim][PF₆] > [hemim][BF₄].     

Measurements and predictions of density and carbon dioxide solubility in binary mixtures of ethanol and n-decane

The solubility of carbon dioxide (CO₂) in binary mixtures of ethanol and n-decane has been measured using an in-house developed pressure-volume-temperature (PVT) apparatus at pressures up to 6 MPa and two different temperatures (303.2 and 323.2 K). Three different binary mixtures of ethanol and n-decane were prepared, and the densities of the prepared mixtures were measured over the studied pressure and temperature ranges. The experimental data of CO₂ solubility in the prepared mixtures and their saturated liquid densities were then reported at each temperature and pressure. The solubility data indicated that the gas solubility reduced as the ethanol mole fraction in the liquid mixture increased. The dissolution of CO₂ in the liquid mixtures resulted in the increase in the saturated liquid densities. The impact of gas dissolution on the saturated liquid densities was more pronounced at the lower temperature and lower ethanol compositions. The experimental solubility and density data were compared with the results of two cubic equations of state (EOSs), Soave–Redlich–Kwong (SRK) and Peng–Robinson (PR). The modeling results demonstrated that both EOSs could predict the solubility data well, while the saturated liquid densities calculated with the PR EOS were much better than those predicted with the SRK EOS.     

Polymer-silica nanocomposite membranes for CO2 capturing

Reducing carbon dioxide (CO₂) is an area of great interest in current international efforts geared toward lowering emissions and combating global warming. In this work, amino-silica composite membranes were prepared and used to capture carbon dioxide. The surface of silica particles was chemically modified with amine to efficiently capture carbon dioxide. The phase separation technique was used to prepare the membranes from a composite containing polyvinylidene-fluoride-hexafluoropropylene (PVDF-HFP), amino-silica particles, acetone and water. SEM images revealed that the membranes composed of multilayers of porous polymer uniformly impregnated with silica particles. Both XRD and FTIR results have validated the perfect integration of silica particles within the polymeric network. The mechanical properties of the membrane are improved by the presence of silica particles as proved by the high tensile strength value (1.5 N/cm²) obtained for the PVDF-HFP/SiO₂ membrane compared to 0.9 N/cm² obtained for bare PVDF-HFP membrane. Also, we succeeded in recording SEM images to show that the plastic deformation of the film is associated with the formation of macro-holes. To the best of our knowledge this is the first time for such results to be monitored with SEM to observe the macroscopic evolution of the structure. Additionally, the surface area was significantly increased from 3.8 m²/g for bare PVDF-HFP membrane to 116.4 m²/g for PVDF-HFP impregnated with silica particles. Moreover, the CO₂ separation efficiency depends on both surface area and the quantity of amino-SiO₂ added to the membrane. The addition of amino-silica particles leads to a significant uptake of carbon dioxide compared to non-modified polymer membrane. The results obtained indicated that combing the phase separation with amino silica particles provided a cost-effective route to scaling up the synthesis of membranes that were mechanically stable and highly efficient at CO₂ capture.     

Solubility of hydrogen in toluene for the ternary system H2 + CO2 + toluene from 305 to 343 K and 1.2 to 10.5 MPa

The solubility of hydrogen in toluene in the presence of the compressed CO₂ at the temperatures from 305 to 343 K and the pressures from 1.2 to 10.5 MPa was measured by using a continuous flow technique. The obtained data indicate that more hydrogen could be dissolved in toluene at the pressures higher than a certain value depending on temperature and the molar ratio of H₂ to CO₂ in gas. The Peng–Robinson equation of state associated with the van der Waals mixing rule were found to correlate the VLE data of the ternary system H₂ + CO₂ + toluene satisfactorily. From the volume expansion resulted from the dissolution of CO₂ in toluene calculated by the proposed model, it was found that hydrogen solubility was generally increased with increasing volume expansion. A large volume expansion was required to enhance hydrogen solubility when the mole fraction of hydrogen in gas was low.