Study Of Phase Equilibria Research Articles

A phase equilibria study and thermodynamic assessment of the BaO–Al2O3 system

The liquidus in equilibrium with phase BaAl2O4, and the eutectic reaction, L→BaAl2O4+Ba3Al2O6, in the syste/m BaO–Al2O3 were measured and confirmed by equilibration–quenching method using SEM/EDS and EPMA. The samples with barium oxide rich compositions were investigated by XRD. A critical literature review was made on the phase diagram and thermodynamic properties for the BaO–Al2O3 system. Employing the reviewed literature data and present experimental results, the thermodynamic properties of the phases were optimized. Based on the obtained thermodynamic parameters, an improved phase diagram was derived and a thermodynamic description of the binary system was presented.

Study of phase equilibria and the physicochemical properties of selected pharmaceuticals

In this work the phase equlibria in binary system: (Drug+solvent) was examined and their physicochemical properties were analyzed. The investigated substances were: synephrine (SYN), isoprenaline hydrochloride (IPR) and metaraminol bitartrate (MET). Solubility of this drugs was determined in three solvents: water, ethanol and 1-octanol. The molecular structure of these drugs is based on a phenthylamine skeleton, therefore all studied pharmaceuticals have an aromatic structure with different amounts of hydroxyl groups located at an aromatic ring. They also have different substituents on the amino group inside the chemical chain. The amino-group confers basic properties of the molecule, whereas the phenolic OH group is weakly acidic. The tested substances belong to the group of adrenergic drugs (adrenomimetics) and stimulate the sympathetic nervous system.Solubilities of three drugs were measured in the temperature range from 270K to 450K at constant pH. All of studied systems were described as simple eutectic phase diagrams, with complete miscibility at liquid phase and non-miscibility in solid phase. The results are presenting as two phases in equilibrium as a function of temperature. These studies are necessity when the drugs are introducing into the pharmaceutical field. The obtained experimental data were correlated with three equations: Wilson, NRTL and UNIQUAC. Moreover dissociation constants and corresponding pKa values of drugs were obtained with Bates–Schwarzenbach method at temperature 298.15K in the buffer solutions.The DSC (differential scanning microcalorimetry) was used to measure thermal basic properties of pure drugs, that is: the glass-transition temperature, temperature of melting, enthalpy of fusion and the heat capacity at the glass-transition temperature.

Experimental and correlational study of phase equilibria in aqueous mixtures of phosphoric acid with aromatic hydrocarbons at various temperatures

Experimental solubility and tie-line data were obtained for (water+phosphoric acid+ethyl benzene or cumene) ternary systems at T=(298.15, 308.15 and 318.15)K and P=101.32kPa. The experimental tie-line values were correlated using the thermodynamic models of UNIQUAC and NRTL. The quality of the experimental results was determined through the Othmer–Tobias and Hand plots. Distribution coefficients and separation factors were evaluated over the immiscibility regions. The influence of temperature on biphasic region is found to be negligible.

China: Columbian – carbon black

Through the use of the electrum-tarnish method the following equation has been found to interrelate the composition of pyrrhotite, fugacity of sulfur, and temperature: In this equation fs2 is the fugacity of sulfur relative to the ideal diatomic gas at 1 atm, N is the mol fraction of FeS in pyrrhotite (in the system FeS-S2), and T the absolute temperature. The experimental uncertainty in the equation is 0–003 in N. The activity of FeS (aFeS) in pyrrhotite relative to the pure substance at the temperature of consideration follows from the above equation by virtue of the Gibbs-Duhem relation; it is given by:The electrum-tarnish method has permitted us to determine the fs2 vs. T curve for the univariant assemblage pyrrhotite-pyrite-vapor from 743 to 325°C. Our determinations of the composition of pyrrhotite are in excellent agreement with the results of Arnold. The activity of FeS in pyrite-saturated pyrrhotite is very different from unity, a fact that greatly influences the interpretation of some other phase equilibrium studies involving pyrrhotite and their application to sulfide mineral assemblages, but has little effect on the more general calculations of composition of hydrothermal or magmatic fluids.Pressure effects calculated from available volumetric data on the phases are small.

Study of phase equilibria in the CO(NH2)2-KH2PO4-K2HPO4-H2O system at 25°C using an optimized method of cross sections

Phase equilibria are studied in ternary contouring systems and in the CO(NH2)2-KH2PO4-K2HPO4-H2O quaternary system at 25°C using an optimized method of cross sections. It is found that an incongruent chemical compound forms between the components of a system with the composition 2KH2PO4 · K2HPO4. The compositions of eutonic and peritonic solutions and the solid phases saturating them are determined. The lines of monovariant equilibria and the crystallization surface of potassium dihydrogen phosphate are studied. The location of the eutonic and peritonic solutions and monovariant equilibrium lines near the plane are shown.

Prospects for Creating Materials in SiC–Me d Si2 Systems

Results are analyzed for an experimental study of phase equilibria within the volume of ternary systems Si–C–Me d , where Me d is W, Ta, Mo, Nb, Hf, and V. Information is summarized for the structure of SiC–Me d Si2 sections, and it is noted that all of them are quasibinary and are classified as a eutectic type. Correlation is established between eutectic temperatures in SiC–Me d Si2 systems, and also between Me d Si2 concentration within eutectic and Me d Si2 melting temperature. Equations are suggested describing this correlation.

Fractionation of orange essential oil using liquid–liquid extraction: Equilibrium data for model and real systems at 298.2 K.

Essential oils have many industrial applications and are basically composed of terpene hydrocarbons and oxygenated compounds. To improve their stability, sensorial quality, flavoring capacity and, consequently, their commercial value, the removal of hydrocarbon compounds is achieved by a fractionation process that can be performed by liquid–liquid extraction. In this work, a phase equilibrium study of real systems composed of crude orange essential oil and hydroalcoholic solvents (ethanol and water mixtures) was conducted and UNIQUAC and NRTL binary interaction parameters available in the literature were tested without success for the description of phase compositions. To obtain reliable parameters that provide a good description of the phase composition and can be used for computational simulation, liquid–liquid equilibrium data for model systems composed of limonene, linalool, ethanol and water at 298.2K were determined and used to adjust new binary interaction parameters of UNIQUAC and NRTL thermodynamic models. Concerning the physical–chemical behavior of the system, the increase in the water content of solvent was observed to promote a decrease in the migration of oxygenated compounds to the solvent-rich phase and in the mutual solubility of the compounds. The increase in the composition of the oxygenated compounds in the system resulted in an increased solubility of these oxygenated compounds and a consequent decreased solvent selectivity. The new set of parameters provided a satisfactory representation of the experimental data, with global deviations of up to a 0.0031 mass fraction in the prediction process, which indicates that these parameters may be very useful in the optimization of the fractionation process by computational simulation.

Self emulsifying drug delivery system (SEDDS) for phytoconstituents: a review.

The self emulsifying drug delivery system (SEDDS) is considered to be the novel technique for the delivery of lipophillic plant actives. The self emulsifying (SE) formulation significantly enhance the solubility and bioavailability of poorly aqueous soluble phytoconstituents. The self emulsifying drug delivery system (SEDDS) can be developed for such plant actives to enhance the oral bioavailability using different excipients (lipid, surfactant, co solvent etc.) and their concentration is selected on the basis of pre formulation studies like phase equilibrium studies, solvent capacity of oil for drug and mutual miscibility of excipients. The present review focuses mainly on the development of SEDDS and effect of excipients on oral bioavailability and aqueous solubility of poorly water soluble phytoconstituents/ derived products. A recent list of patents issued for self emulsifying herbal formulation has also been included. The research data for various self emulsifying herbal formulation and patents issued were reviewed using different databases such as PubMed, Google Scholar, Google patents, Scopus and Web of Science. In a nutshell, we can say that SEDDS was established as a novel drug delivery system for herbals and with the advances in this technique, lots of patents on herbal SEDDS can be translated into the commercial products.

Pressurized fluid extraction (PFE) of valonea tannin with binary H2O–CO2 and ternary H2O–CH3OH–CO2 systems and phase equilibrium studies

In this study, the effect of binary and ternary systems, solvent/feed (S/F) ratio (20–100w/w), time (2–3h) and pressure (10–200bar) were tested with subcritical and supercritical CO2 to produce valonea tannin from acorn cups. The best yield of phenolic contents (PCs) of the valonea tannin (34.73±0.02wt%) was obtained by H2O/CO2 binary system under the conditions of S/F=100(w/w) at 100bar for 3h with supercritical CO2. Phase equilibria of H2O/CH3OH/CO2 ternary system with different solvent fractions at different temperatures and pressures were also imaged in the high pressure view cell, where liquid–liquid–vapor phase behaviors were observed for all ratios of H2O and CH3OH from 60 to 100°C and 60 to 250bar. High tannin content isolated in a short time will decrease the waste load and provide great advantage in terms of reducing the cost of the tannin used in leather industry.

A study of phase equilibria in the Al–Pt–Rh alloy system

Phase equilibria in Al–Pt–Rh were studied in the whole compositional range at 1100°C and above 50 and 70at.% Al at 900 and 810°C, respectively. The continuous region of the fcc γ solid solutions extends from the Pt–Rh terminal up to 15at.% Al. At elevated temperatures the isostructural AlRh and high-temperature AlPt β-phases probably form a continuous compositional region. Wide ternary extensions of the phases Al4Pt, Al21Pt8, low-temperature AlPt (μ), Al3Pt5, AlPt2 and AlPt3 were revealed along approximately constant Al concentrations. In contrast, the dissolution of Rh in the Al2Pt phase (β∗) results in a visible decrease of its Al concentration. The Al–Rh C-phase and ε-phase dissolve up to 15 and 18at.%. Pt, respectively. Only the ε6 structural variant was observed at ternary compositions. The formation of the ternary χ-phase (P31c, a=1.2201, c=2.7243nm for Al75.5Pt16.9Rh7.6) was revealed in a compositional region between ∼Al75Pt21.5Rh3.5 and ∼Al76Pt6.5Rh17.5. The other ternary C2-phase (Fm3¯, a=1.5419nm) was revealed around Al69Pt9Rh22.

Фазовые равновесия и термодинамические свойства оксидов в системах на основе редкоземельных, щелочноземельных и 3d-переходных (Mn, Fe, Co) металлов. Краткий обзор

Review is dedicated studies of phase equilibria in the systems based on rare earth elements and 3d transition metals. It’s highlighted several structural families of these compounds and is shown that many were found interesting properties for practical application, such as high conductivity up to the superconducting state, magnetic properties, catalytic activity of the processes of afterburning of exhaust gases, the high mobility in the oxygen sublattice and more.

A Joint Theoretical and Experimental Study of Phase Equilibria and Evolution in Pt-Doped Calcium Titanate under Redox Conditions

Pseudoternary phase diagrams of the PtOx–CaO–TiOx system were constructed using first-principles theoretical methods to interpret experimental observations of phase formation and evolution in Pt-doped CaTiO3 made by aberration-corrected scanning transmission electron microscopy. In this system, promoted as a self-regenerative automotive exhaust-gas catalyst, Pt precipitates as metallic particles from the doped perovskite under reducing conditions and tends to redissolve under oxidizing conditions. Due to the likely influence of kinetic limitations on experimental observations, we focus on a restricted (metastable) phase diagram in which single and other unobserved oxides of Pt are intentionally excluded. Various titanate phases appear, however, and their presence helps inform the calculation of the phase diagrams, which in turn confirm that the self-regenerative effect is a consequence of thermodynamic phase stability under the specific redox environments examined.

Phase equilibria study of binary systems comprising an (ionic liquid + hydrocarbon)

In this study, the interaction of two ionic liquids with hydrocarbons has been investigated. With this aim, (solid+liquid) equilibria (SLE) and (liquid+liquid) equilibria (LLE) for binary systems of {1-methyl-1-propyl-pyrrolidinium triflate [PMPyr][CF3SO3]+heptane, or benzene, or thiophene, or benzothiophene} and {N-butyl-4-cyanopyridinium tricyanomethanide [BCN4Py][TCM]+heptane, or toluene, or 2-methylthiophene, or benzothiophene} were measured at ambient pressure. A dynamic method was used over a broad range of mole fractions and temperatures from (T=270 to 370)K. An upper critical solution temperature (UCST) was detected for all mutually immiscible systems. The immiscibility gap for [BCN4Py][TCM] in benzene and thiophene is larger than those for [PMPyr][CF3SO3]. Conversely, in heptane it is slightly larger for [PMPyr][CF3SO3]. The basic thermal properties of the pure ILs, i.e. melting and glass-transition temperatures as well as the enthalpy of fusion have been measured using a differential scanning microcalorimetry technique (DSC). The well-known NRTL model has been used to correlate the experimental SLE data points.

The TeO2‐Na2O System: Thermal Behavior, Structural Properties, and Phase Equilibria

Thermal behavior, structural properties, and phase equilibria of the (100−x)TeO2‐xNa2O system were studied in the 5 ≤ x ≤ 50 mol% composition range. Investigation of glass formation behavior in the binary system was realized, and the glass formation range was determined as 7.5 ≤ x ≤ 40 mol%. Differential thermal analysis (DTA) and Fourier transform infrared (FTIR) spectroscopy techniques were used for thermal and structural characterization of the glasses. Influence of Na2O content on glass transition temperature (Tg), glass stability (∆T), density (ρ), molar volume (VM), oxygen molar volume (VO), and oxygen packing density (OPD) values of sodium tellurite glasses was evaluated considering the structural transformations in the glass network. For the phase equilibria studies, DTA, X‐ray diffraction (XRD), and scanning electron microscopy/energy dispersive X‐ray (SEM/EDS) techniques were utilized to characterize the heat‐treated samples. According to the phase equilibria studies, three eutectic regions were detected in the 0 < x < 50 mol% composition range of the (100−x)TeO2‐xNa2O system. A new invariant endothermic reaction was detected for the compositions between 40 ≤ x ≤ 45 mol%. Na2O.8TeO2 (11.11 mol% Na2O) compound that was claimed to exist in the binary system in the literature was found to be the metastable δ‐TeO2 phase.

New type of ternary reciprocal system: Na,Ba‖BO2,F system

The congruent-melting compound Ba2Na3[B3O6]2F was found to exist when we studied phase equilibria in the Ba2Na3[B3O6]2F ternary reciprocal system. Inasmuch as the boundary binary systems are simple eutectic systems, the title ternary system is an example of a new, hitherto undescribed type of ternary system, which fails to fall within existing classifications. Ba2Na3[B3O6]2F forms stable quasi-binary sections with BaB2O4 and (NaBO2)2. Sections Ba2Na3[B3O6]2F-BaF2 and Ba2Na3[B3O6]2F-(NaF)2 are stable quasi-binary sections only in solid state.

Modeling vapor pressure of fatty acid and fatty acid methyl esters using cubic equations of state

AbstractBiodiesel is one of the most promising alternates to fossil fuels. Production process of biodiesel requires separation of fatty acids (FAs) and their esters from the other products and reactants. This requires the phase equilibrium studies of the FA and their esters. For phase equilibrium study through equation of state (EOS), accurate prediction of vapor pressure is necessary. It was shown that most of the predictive methods fail to estimate acceptable values of vapor pressure. Peng–Robinson EOS was used in the present study to predict the vapor pressure. Proper values of critical properties are required for accurate prediction of vapor pressure through cubic EOS. Obtaining experimental critical properties of FAs and their ester are difficult. Ten methods for the prediction of critical properties were compared, and suitable methods for FA, FAME, and their mixtures were proposed. For accurate prediction of vapor pressure using cubic EOS, one requires suitable cohesion factor model. Predictive cohesion factor models did not perform well; hence, four compound‐specific cohesion factor models were compared. Constants for all the four models for the compound considered were presented, and the models were compared for the accurate prediction of vapor pressure. It was observed that modified Trebble–Bishnoi type of cohesion factor model outperformed other models. Boiling points for pure FA and FAME were obtained with these four models. Prediction of boiling points for real‐world biodiesel was also carried out. Modified Trebble–Bishnoi type model was found to be suitable for predictions of boiling points as well. © 2014 Curtin University of Technology and John Wiley & Sons, Ltd.

Phase Equilibrium Study of Binary and Ternary Mixtures of Ionic Liquids + Acetone + Methanol

The vapor–liquid equilibrium (VLE) data for binary systems of acetone + 1-ethyl-3-methylimidazolebromine ([EMIM][Br]), methanol + 1-ethyl-3-methylimidazolebromine ([EMIM][Br]), acetone + 1-butyl-3-methylimidazolebromine ([BMIM][Br]), methanol + 1-butyl-3-methylimidazolebromine ([BMIM][Br]), and ternary VLE data for systems of acetone + methanol + 1-ethyl-3-methylimidazolebromine ([EMIM][Br]), acetone + methanol + 1-ethyl-3-butylimidazolebromine ([BMIM][Br]) were detected at 101.3 kPa in an all-glass dynamic recirculating still. With the addition of bromine–based ionic liquids, the relative volatility of acetone to methanol was enhanced and the azeotropy was eventually eliminated. As for the separating effect, [EMIM][Br] is better than [BMIM][Br]. The measured binary and ternary VLE data were correlated with the nonrandom two-liquid activity coefficient model, and the results demonstrated that the experimental data and the correlated data were in good agreement.

Phase equilibria studies of the “MnO”–Al2O3–SiO2 system in equilibrium with metallic alloy. Part 1: Development of the technique and determination of liquidus isotherms between 1 423 K and 1 523 K

Abstract Phase equilibria in the “MnO”–Al2O3–SiO2 pseudo-ternary system in equilibrium with metallic alloy have been experimentally investigated in the temperature range from 1 423 K to 1 523 K. This study is a part of a broader research program on the phase equilibria in the Al2O3–CaO–Li2O–“MnO”–SiO2 system, which is of importance to the slags used in a novel pyrometallurgical process for recycling of electric car batteries. The experimental procedures involve equilibration of high purity powder mixtures at high temperatures, rapid quenching, and accurate measurement of phase compositions using electron probe X-ray microanalysis, which allow the slag liquidus temperatures to be determined. This paper is part 1 of a series of two papers and focuses on the improvement of the experimental methodology. A number of elementary reactions taking place in the samples have been identified, including the formation of a tridymite ring around the alloy particles, manganese oxidation and manganese vaporization. This enabled relevant modifications to the experimental methodology to be introduced. The liquidus at 1 423 K, 1 473 K and 1 523 K in the high silica area and the solid solubility data in the tridymite and rhodonite phases have been reported.

New Hydrate Phase Equilibrium Data for Two Binary Gas Mixtures of Hydrogen and Propane Coupled with a Kinetic Study

A phase equilibrium (hydrate+liquid+vapor) study on hydrogen/propane mixed gas hydrates was conducted using the isochoric pressure search method. Equilibrium studies were conducted using two gas mixtures with varying hydrogen/propane compositions (0.905/0.095 and 0.65/0.35 mole fraction). For the gas mixture with lower propane concentration (0.095 mole fraction), equilibrium points were determined in the temperature range of 274.2 K to 281.2 K and the pressure range of 1.5 MPa to 9.0 MPa. Similarly for the gas mixture with 0.35 mole fraction of propane, equilbrium was determined between 274.2 K and 278.2 K and the corresponding pressures were in the range of 0.4 MPa to 1.2 MPa. Enthalpy of hydrate dissociation was calculated based on the Clausius–Clayperon equation to be 149.3 kJ/mol for the gas mixture with hydrogen/propane (0.905/0.095) and 179.0 kJ/mol for the gas mixture with hydrogen/propane (0.65/0.35). Kinetic studies were conducted to observe the effect of pressure and temperature on the formation...

Phase equilibria study of K–O–Si system in equilibrium with air

Abstract The binary phase diagram in the silica rich corner of K–O–Si system in equilibrium with air has been studied at temperatures between 770 °C and 1500 °C. Equilibration at high temperature in an appropriate containment material of pure silica, followed by rapid quenching and measurement of phase structures and assemblages using SEM-EDS confirmed by an electron probe X-ray microanalysis technique, was carried out to obtain the phase composition data at equilibrium. The results are in good agreement with previous experimental data and close to the earlier assessed phase equilibria at silica saturation.