Phase behaviour of the ternary system {poly(ε-caprolactone) + carbon dioxide + dichloromethane}

Recently, production of biocompatible and biodegradable polymer microparticles has been a matter of growing interest in pharmaceutical and food areas such as drug or active compounds delivery. To conduct production of microparticles, polymeric particle coating, impregnation of active compounds in polymeric films, the knowledge of phase behaviour involving the biodegradable polymer in supercritical carbon dioxide in the presence of a modifier may be needed to allow developing new industrial applications. In this sense, the aim of this work was to investigate the phase behaviour of the ternary system formed by the biodegradable polymer poly(ε-caprolactone) in (carbon dioxide + dichloromethane). Experimental phase transition (bubble and cloud point) values were obtained by applying the static-synthetic method using a variable-volume view cell over the temperature range of (303 to 343) K and pressures up to 21 MPa, in the CO₂ overall composition range of (25–46) wt%, while polymer concentrations studied were (1, 3, 5, and 7) wt%. For the system investigated, depending on the polymer concentration, vapour–liquid, liquid–liquid, and vapour–liquid–liquid phase transitions were verified.     

(Vapour + liquid) equilibria for the binary mixtures (cis-pinane + α-pinene) and (cis-pinane + 1-butanol)

The isothermal and isobaric (vapour + liquid) equilibria for (cis-pinane + α-pinene) and (cis-pinane + 1-butanol) measured with an inclined ebulliometer are presented. The experimental results are analysed using the UNIQUAC equation with the temperature-dependence binary parameters with satisfactory results. Experimental vapour pressures of cis-pinane are also included.     

Experimental determination of the liquidus of the binary system (Cu2O + CaO) in air at temperature from (1050 to 1500) °C

The liquidus of the binary system (Cu₂O + CaO) has been experimentally investigated over the temperature range from (1050 to 1500) °C in air. The liquidus has been quantified by the equilibration/quench/analysis technique. Equilibrated specimens were quenched in brine solution of 10 wt% NaCl. Specimens were then examined by Energy-Dispersive X-ray Spectroscopy (EDS) and Electron probe micro-analyzer (EPMA) to quantify liquid chemical compositions. This work reveals that the solubility of CaO in the liquid phase of the binary (Cu₂O + CaO) at higher temperatures is lower than previously reported, and the deviation systematically increases with a corresponding increase in temperature. This is predominant at temperatures between (1300 and 1500) °C where a deviation of up to 5 wt% in CaO solubility is observed. The solubility of Cu₂O in liquid phase for the cuprite saturated section of the binary however is consistent with all the previous authors.     

Modelling (vapour + liquid) and (vapour + liquid + liquid) equilibria of {water (H2O) + methanol (MeOH) + dimethyl ether (DME) + carbon dioxide (CO2)} quaternary system using the Peng–Robinson EoS with Wong–Sandler mixing rule

The (vapour + liquid) equilibria (VLE) and (vapour + liquid + liquid) equilibria (VLLE) binary data from literature were correlated using the Peng–Robinson (PR) equation of state (EoS) with the Wong–Sandler mixing rule (WS). Two group contribution activity models were used in the PRWS: UNIFAC–PSRK and UNIFAC–Lby. The systems were successfully extrapolated from the binary systems to ternary and quaternary systems. Results indicate that the PRWS–UNIFAC–PSRK generally displays a better performance than the PRWS–UNIFAC–Lby.     

Vapor–liquid equilibrium of the (water + ethanol + glycerol) system: Experimental and modelling data at normal pressure

In this work, vapor-liquid equilibrium data of the ethanol–water–glycerol system were measured in an Othmer-type ebulliometer at normal pressure. The choice for this system was due to the importance of the ethanol–water separation. The samples analyses were done in a digital densimeter, and the methodology was previously validated with data available in the literature. Since the mean relative deviation was less than 5% in temperature and vapor composition, new data from mixtures of ethanol–water–glycerol were obtained. The experiments showed that glycerol is a promising solvent to ethanol dehydration since it eliminates the azeotrope and promotes the production of anhydrous ethanol. A thermodynamic model for this system was developed using the NRTL model to describe the non-ideality of the liquid phase. The modeling results were compared with experimental data and the deviations were lower than 7%. In this way, the model developed in this work can be used for simulation of ethanol dehydration.     

Ebulliometric determination and prediction of (vapor + liquid) equilibria for binary and ternary mixtures containing alcohols (C1–C4) and dimethyl carbonate

(Vapor + liquid) equilibrium (VLE) data for a ternary mixture, namely {methanol + propan-1-ol + dimethyl carbonate (DMC)}, and four binary mixtures, namely an {alcohol (C₃ or C₄) + DMC}, containing the binary constituent mixtures of the ternary mixture, were measured at p = (40.00 to 93.32) kPa using a modified Swietoslawski-type ebulliometer. The experimental data for the binary systems were correlated using the Wilson model. The Wilson model was also applied to the ternary system to predict the VLE behavior using parameters from the binary mixtures. The modified UNIFAC (Dortmund) model was also tested for the predictions of the VLE behavior of the binary and ternary mixtures. In addition, the experimental VLE data for the ternary and constituent binary mixtures were correlated using the extended Redlich–Kister (ERK) model, which can completely represent the azeotropic points. For the ternary system, a comparison of the experimental and the predicted or correlated boiling points obtained using the Wilson and ERK models showed that the ERK model is more accurate. The valley line, i.e., the curve which divides the patterns of vapor–liquid tie lines, was found in the (methanol + propan-1-ol + DMC) system. This valley line could be represented by the ERK model. Finally, the composition profile for simple distillation of this ternary mixture was obtained by analysis of the residue curves from the estimated Wilson parameters of the constituent binary mixtures.     

Vapor–liquid equilibrium for binary system of tetrahydrothiophene + 2,2,4-trimethylpentane and tetrahydrothiophene + 2,4,4-trimethyl-1-pentene at 358.15 and 368.15 K

Isothermal vapor–liquid equilibrium (VLE) for tetrahydrothiophene + 2,2,4-trimethylpentane and tetrahydrothiophene + 2,4,4-trimethyl-1-pentene at 358.15 and 368.15 K were measured with a circulation still. All systems studied exhibit positive deviation from Raoult's law. No azeotropic behavior was found in all systems at the measured temperatures. The experimental results were correlated with the Wilson model and compared to COSMO-SAC predictive model. Analyses of liquid and vapor phase composition were determined with gas chromatography. All VLE measurements passed the three thermodynamic consistency tests used. The activity coefficients at infinite dilution are also presented.     

(Solid + liquid) equilibria for the ternary system (CsBr + LnBr3 + H2O) (Ln = Pr,Nd, Sm) at T = 298.2 K and atmospheric pressure,thermal and fluorescent properties of Cs2LnBr5·10H2O

The (solid + liquid) phase equilibria of the ternary systems (CsBr + LnBr₃ + H₂O) (Ln = Pr, Nd, Sm) at T = 298.2 K were studied by the isothermal solubility method. The solid phases formed in the systems were determined by the Schreinemakers wet residues technique, and the corresponding phase diagrams were constructed based on the measured data. Each of the phase diagrams, with two invariant points, three univariant curves, and three crystallization regions corresponding to CsBr, Cs₂LnBr₅·10H₂O and LnBr₃·nH₂O (n = 6, 7), respectively, belongs to the same category. The new solid phase compounds Cs₂LnBr₅·10H₂O are incongruently soluble in water, and they were characterized by chemical analysis, XRD and TG-DTG techniques. The standard molar enthalpies of solution of Cs₂PrBr₅·10H₂O, Cs₂NdBr₅·10H₂O and Cs₂SmBr₅·10H₂O in water were measured to be (52.49 ± 0.48) kJ · mol⁻¹, (49.64 ± 0.49) kJ · mol⁻¹ and (50.17 ± 0.48) kJ · mol⁻¹ by microcalorimetry under the condition of infinite dilution, respectively, and their standard molar enthalpies of formation were determined as being −(4739.7 ± 1.4) kJ · mol⁻¹, −(4728.4 ± 1.4) kJ · mol⁻¹ and −(4724.4 ± 1.4) kJ · mol⁻¹, respectively. The fluorescence excitation and emission spectra of Cs₂PrBr₅·10H₂O, Cs₂NdBr₅·10H₂O and Cs₂SmBr₅·10H₂O were measured. The results show that the upconversion spectra of the three new solid phase compounds all exhibit a peak at 524 nm when excited at 785 nm.     

Near critical measurements of HmEandVmE for { xCO2 + (1 − x)SF6} and measurements made over the pressure range 2.5 to 10.0 MPa at the temperature T = 301.95 K

A flow mixing calorimeter, followed by a vibrating tube densimeter, has been used to measure excess molar enthalpies H_m^Eand excess molar volumesV_m^E of {xCO₂ +  (1  − x)SF₆}. Measurements over a range of mole fraction x have been made at the temperatures T =  302.15 K and T =  305.65 K at the pressures (3.76, 5.20, 6.20, and 7.38) MPa. The lowest pressure 3.76 MPa is close to thecritical pressure of SF₆ and the highest pressure 7.38 MPa is close to the critical pressure of CO ₂. Measurements atx =  0.5 have been made over the pressure range (2.5 to 10.0) MPa at the temperature 301.95 K. Some of the measurements are very close to the critical locus of the mixture. The measurements are compared with the Patel–Teja equation of state which reproduces the main features of the excess function curves as well as it does for similar measurements on {xCO₂ +  (1  − x)C₂H₆} and{xCO₂ +  (1  − x)C₂H₄} . The equation was used to calculate residual enthalpies and residual volumes for the pure components and for the mixture, and inspection of the way these combine to give excess enthalpies and volumes assisted the interpretation of the pressure scan measurements.     

Physicochemical properties of (1-butyl-1-methylpyrrolydinium dicyanamide + γ-butyrolactone) binary mixtures

Experimental densities, electrical conductivities and dynamic viscosities of the pure 1-butyl-1-methylpyrrolydinium dicyanamide ionic liquid, [bmpyrr][DCA], and its binary liquid mixtures with γ-butyrolactone (GBL) were measured at temperatures from (273.15 to 323.15) K and at pressure of 0.1 MPa over the whole composition range. From the experimental density data the related excess molar volumes were calculated and fitted using Redlich–Kister’s polynomial equation. Obtained values are negative in the whole range of ionic liquid mole fraction and at all temperatures. Other volumetric properties, such as isobaric thermal expansion coefficients, partial molar volumes and partial molar volumes at infinite dilution were also calculated, in order to obtain information about the interactions between GBL and the selected ionic liquid. Negative values of these properties for both components indicate stronger interactions between GBL and IL compared to the pure components and better packing due to the differences in size and shape of the studied molecules. From the viscosity results, the Angell strength parameter was calculated and found to be 5.47 indicating that [bmpyrr][DCA] is a “fragile” liquid. All the results are compared with those obtained for binary mixtures of 1-butyl-1-methylpyrrolydinium bis(trifluoromethylsulfonyl)imide, [bmpyrr][NTf₂], with GBL.     

Volumetric properties of the water-ethylene glycol mixtures in the temperature range 278–333.15 K at atmospheric pressure

Density of the water-ethylene glycol binary mixtures was measured in the entire range of compositions in the temperature range 278–333.15 K (6 values) at atmospheric pressure using a vibration densimeter. Mixtures with low concentrations of ethylene glycol were studied at 15 temperatures in the range of 274–333.15 K. Excess molar volumes V _m ^E , the partial molar volumes of water -V ₁ and ethylene glycol, -V ₂, the coefficients of thermal volume expansion α of the mixture, the partial molar volume coefficients of thermal expansion of water $ \bar V_1 $ \bar V_1 and ethylene $ \bar V_2 $ \bar V_2 were calculated. Excess molar volumes were described using the Redlich-Kister equation. The density ρ of the mixture was found to increase with the increasing ethylene glycol concentration at all temperatures, but at low content of ethylene glycol the dependence ρ = f(T) of the mixture at ∼276.5 K passed through a maximum. The coefficient α increases sharply in the composition range 0 < x < 0.2, in the range 0.5 < x <1 remains almost unchanged, and at T > 277 K is positive for all compositions. The dependences $ \bar \alpha _1 $ \bar \alpha _1 = f (x) and $ \bar \alpha _2 $ \bar \alpha _2 = f (x) are complex in whole temperature range and are characterized by the presence of an extremum. V _m ^E values are negative at all temperatures, and upon increase in the temperature the deviation from ideality decreases (x is the mole fraction of ethylene glycol).     

Calorimetric and Volumetric Studies of the Interactions of Propionamide in Aqueous Alkan-1-ol Solutions at 298.15 K

Enthalpies of solution and apparent molar volumes have been determined for propionamide in aqueous methanol, ethanol and propanol solutions at 298.15 K using a C-80 microcalorimeter and a DMA60/602 vibrating-tube digital densimeter. The enthalpic and volumetric interaction coefficients have been calculated. Using the present results along with results from previous studies for formamide, the pair-interaction coefficients are discussed from the perspective of dipole-dipole and structural interactions. In addition, the triplet interaction coefficients are interpreted by using the solvent-separated association mechanism.     

Phase diagram of the eutectic benzoic acid-naphthalene system in the temperature range of 300–400 K

Liquid-solid phase equilibria are studied in the eutectic benzoic acid-naphthalene system by means of thermic analysis (DTA, CTA), on the basis of which the liquidus line and eutectic point (x _e ≈ 50 mol %, T _e ± 340 K) are determined and the phase diagram is constructed. Average precrystallization supercooling temperatures ΔT _L ^? of the liquid phase relative to liquidus temperature T _L are determined, allowing us to locate the region of solution metastability on the phase diagram. Excessive functions of the components in the liquid phase are found via thermodynamic modeling using the Margules equation and experimental data. The boundaries of the region of liquid solution metastability are estimated from the thermodynamic conditions of solution stability.