Phase Behavior Of Ternary System Research Articles

High pressure phase behaviour of ternary systems containing CO2 + fatty acid methyl esters

High pressure bubble- and dewpoint data were measured for ternary mixtures of CO2 + methyl palmitate + (methyl stearate or methyl oleate). The reported data were measured in the range T=308−348 K, p=7.1−21.8 MPa, and total solute (fatty acid methyl ester) mass fractions ranging from 0.020 to 0.618 g⋅g−1. The phase transition pressures in all the mixtures increase monotonically as temperature increases. Investigation of the ternary phase behaviour indicates that the differences observed between the binary CO2 + methyl stearate and CO2 + methyl oleate systems due to the presence of a C=C bond on methyl oleate, are translated to the ternary mixtures. The phase transition pressures also decrease almost linearly as the amount of methyl palmitate increases suggesting no significant interactions between the solutes. Prediction of the ternary data with the CPA equation of state are in good agreement with the experimental data provided binary CO2 + solute interaction parameters are fitted.

Equilibrium phase behavior of ternary systems formed by polyethylene glycol + choline salts + water

The economic and environmental potentialities of the application of choline salts in aqueous two-phase systems (ATPS), as well as the incipiency of works of these ionic liquids (ILs) combined with polyethylene glycol (PEG), are the reasons for the characterization of new “green” ATPS formed by PEG (400 and 1500 g.mol−1) combined with choline-based ILs (choline chloride, choline bitartrate, and choline dihydrogen citrate). Choline chloride was preferentially concentrated in the top phase, while the lower phase was rich in PEG. The opposite behavior was observed for bitartrate and dihydrogen citrate. ATPS formed by PEG1500 exhibits a significant increase in the biphasic area as the temperature increases; while for systems formed by PEG400, this same trend is slight, demonstrating that phase segregation has an endothermic character. The salting-out effect and the hydrophobicity of the polymer explain the increase of the biphasic area with increasing the charge density of the anion and increasing polymer molar mass, respectively. The data were fitted with good correlation using the Merchuk equation for the binodal curves and Guan equation for the tie-lines.

Thermodynamics and phase relationship of carbonaceous mesophase appearing during coal tar pitch carbonization

Carbonaceous mesophase appears as an intermediate product in production of electrical and mechanical carbon materials, needle coke for graphite electrodes used in electric-arc furnaces, pitch-based fibers and aluminum-smelting prebaked electrodes through carbonization process. A thermodynamic approach for phase behavior estimation of carbonaceous mesophase is presented to provide more insights and to lead to semi-quantitative modeling of this process. Phase behavior of binary, ternary and multi-component systems are described by minimization of the Gibbs free energy function proposed by Hu and Hurt for mesophase pitches which exhibits orientational energy contribution of molecules in mesophase. The model enables estimating the reversible phase transition of mesophase upon temperature cycling as suggested by Lewis. The capability of the model to estimate the molecular weight distribution of species in the phases in equilibrium and variation of mesophase content with thermal soaking time has been discussed. Estimated ternary isothermal sections showing isotropic-mesophase and iso-iso immiscibility are presented for the first time. The phase behavior of ternary systems with average molecular weight in the range of average molecular weight of coal tar pitches are described. The application of the model to phase diagram prediction of the specific systems which exhibit the miscibility gap has been studied.

Phase-equilibrium measurement of a carbon dioxide/toluene/polystyrene ternary system using laser turbidimetry

The phase behavior of a carbon dioxide (CO2)/toluene (Tol)/polystyrene (PS) ternary system was measured. The measurements were performed using a synthetic method combined with a reflected light intensity measurement. The bubble points were determined by visual observation, and the cloud points were determined from the change in the reflected light intensity. The phase boundaries were measured at temperatures ranging from 313.2 K to 373.2 K and CO2 weight fractions ranging from 0.10 to 0.41. The homogeneous phase area decreased when the molecular weight of PS and/or the ratio of PS to Tol increased. It was found that the phase behavior of ternary systems, especially the liquid-liquid phase separation behavior, was altered by a change in the mutual solubility between the three components.

Odd-even effect on the formation of aqueous biphasic systems formed by 1-alkyl-3-methylimidazolium chloride ionic liquids and salts.

This work provides a comprehensive evaluation of the effect of the cation alkyl side chain length of the 1-alkyl-3-methylimidazolium chloride series ([C n C1im]Cl, n = 2-14) of ionic liquids (ILs) on their capability to form aqueous biphasic systems (ABSs) with salts and self-aggregation derived properties. The liquid-liquid phase behavior of ternary systems composed of [C n C1im]Cl, water, and K3PO4 or K2CO3 and the respective Setschenow salting-out coefficients (ks ), a quantitative measure of the two-phase formation ability, were determined. An odd-even effect in the ks values along the number of methylene groups of the longest IL cation alkyl side chain was identified for the ABS formed by K2CO3, a weaker salting-out agent where the phenomenon is clearly identified. In general, cations with even alkyl side chains, being likely to display higher molar volumes, are more easily salted-out and thus more prone to undergo phase separation. The odd-even effect in the ks values is, however, more significant in ILs up to n = 6, where the nanostructuration/nanosegregation of ILs plays a less relevant role. Still, with the [C n C1im]Cl (n = 7-14) series of ILs, an odd-even effect was also identified in the ILs' ionization degree, molar conductivity, and conductivity at infinite dilution. In summary, it is shown here that the ILs' odd-even effect occurs in IL aqueous solutions and not just in neat ILs, an already well-established phenomenon occurring in a series of ILs' properties described as a result of the orientation of the terminal methyl groups to the imidazolium ring cation and consequent effect in the ILs' cohesive energy.

The analysis of liquid–liquid equilibria (LLE) of toluene + heptane + ionic liquid ternary mixture using intelligent models

This paper is to verify the applicability of three intelligence methods including artificial neural network (ANN), support vector machine (SVM) and least square support vector machine (LSSVM) in forecasting the thermodynamic phase behavior of LLE for toluene/heptane/ionic liquid ternary systems. The shuffled complex evolution (SCE), particle swarm optimization (PSO) and genetic algorithm (GA) are employed to acquire the optimal magnitudes of hyper parameters (σ2 and γ) which are embedded parts of SVM and LSSVM models, and the trial and error was employed to obtain the optimal numbers of neuron and layers for ANN intelligent model. Gathering and using 589 liquid–liquid equilibria (LLE) data, the comparison between the capability of applied intelligent models and NRTL thermodynamic model has also been made in giving the phase behavior of ternary system toluene/heptane/ionic liquid. The findings are indicative of a prefect agreement between the estimation from intelligent models and the experimental data. Comparison between these three investigated models reveals that the performance of SCE-LSSVM in prediction of LLE is somewhat better than other intelligent models (i.e., ANN and SVM) in prognosticating LLE behavior in those 40 studied ILs as the coefficient determination (R2) and root mean squared error (RMSE) are respectively 0.9895 and 0.0361 for test sets of data. This is likely due to the existence of structural risk minimization principle of LSSVM which is embodied in SVM algorithm and effectively minimizes upper bound of the generalization error, rather than minimizing the training error.

Molecular modeling of systems related to the biodiesel production using the PHSC equation of state

In this study, capability of the Perturbed Hard Sphere Chain (PHSC) equation of state (EoS) is investigated for thermodynamic modeling of binary and ternary systems related to the biodiesel processing. Vapor-liquid, liquid-liquid and solid-liquid equilibria (VLE, LLE and SLE, respectively) in mixtures containing fatty acid alkyl ester, non – polar and polar compounds are investigated. The PHSC model parameters are calculated for both fatty acid methyl ester (FAME) and Fatty acid ethyl ester (FAEE) molecules by fitting on the experimental pure liquid density and vapor pressure data. Using the obtained parameters, the phase behavior of binary systems over wide range of thermodynamic conditions is studied. The average deviation between model calculations and experimental equilibrium data of water + ester, alcohol + ester, ester + ester, hydrocarbon + ester and carbon dioxide + ester systems are about 5.57, 2.42, 0.31, 3.61 and 6.45%, respectively. Furthermore, the capability of the model has then been assessed by prediction of LLE phase behavior of ternary systems. The results show that, the predicted and correlated results are in good agreement with the experimental data. In the case of SLE, the melting and eutectic points of fatty acid ester systems have been predicted over wide range of composition.

Phase behavior of a TX-100/oleic acid/water based ternary system: A microstructure study

Abstract Present work reports the formation of different types of alcohol-free emulsions consisting of TX-100 (surfactant), oleic acid (oil phase) and water. The phase behavior of ternary system (water/oleic acid/TX-100) was observed which showed single phase, multiphase and gel phase regions. The prepared emulsions with a wide range of composition were thermodynamically stable. Investigations into the stability of emulsions under milder conditions showed that they remained stable over four months and even at high centrifugation. A progressive transformation of the water-in-oil (w/o) to bicontinuous phase and inversion to oil-in-water (o/w) microemulsions occurred upon dilution with water, which was confirmed by electrical conductivity, viscosity and microscopic measurements. A static percolation phenomenon was observed in the investigated alcohol-free-emulsion system and the water content at percolation threshold was determined.

Hydrothermal treatment of biomass for energy and chemicals

Pyrolysis oils are a product of fast pyrolysis or liquefaction of biomass. Those dark brown organic liquids are chemically a complex mixture and/or emulsion of water and degradation products of lignin (e.g. guaiacols, catechols, syringols, vanillins), cellulose (such as levoglucosan, dehydrated sugars, di-sugars, furancarboxaldehydes), and hemicellulose (such as acetic acid, formic acid). Composition strongly depends on conditions of pyrolysis process and great variety of biomass feedstock such as grasses and trees, and other sources of ligno-cellulosic material, derived from municipal waste, food processing wastes, forestry wastes and pulp and paper by-products. The present contribution will present an overview of current high pressure processes for treatment of biomass for production of energy and chemicals as well as the fundamental studies of phase equilibria of the systems pyrolysis oil/gas, which are crucial in biorefinery process design. In particular, phase equilibria of binary and ternary systems consisting of pyrolysis oil/supercritical fluid (pyrolysis oil/CO2) and (pyrolysis oil/H2) was studied in addition to the phase behavior of ternary systems of (pyrolysis oil/diesel/CO2) and (pyrolysis oil/tail water/CO2). These data are important for design of separation processes as well as for the application of these substances for commercial fuels.

Experimental investigations on the phase behavior of the aromatic mixtures regarding the performance enhancement of natural gas dehydration processes in petroleum industry

ABSTRACTThe phase behavior of ternary systems in three-phase separator including benzene-heptane-water and toluene-heptane-water are investigated at 298.15 K and 308.15 K. It is shown that the water solubility in hydrocarbon phase and the benzene and toluene solubilities in aqueous phase decrease considerably with increasing n-heptane concentration. Moreover, the discarded water phase from three-phase separator to the environment in azeotropic regeneration process is less contaminated by aromatic compounds (BTEX) in comparison with the one in the traditional dehydration process. It is shown that the n-heptane can be used as a stripping medium in the azeotropic regeneration process to achieve less than 1% water in the TEG solvent employed for natural gas dehydration process of gas refining plants.

Evidence for the impression of phase behavior of nonsolvent/solvent/polymer ternary system on morphology of polyethersulfone electrospun nanofibers

Polyethersulfone (PES) nanofibers are produced by electrospinning solutions of PES/dimethylforamide (DMF), PES/N-methylpyrrolidone (NMP) and PES/(NMP:DMF) (of different NMP:DMF ratios) at temperature of 40 °C and various levels of relative humidity (RH). The influence of environmental conditions on bead formation as well as surface and interior morphologies of electrospun fibers is discussed through the phase diagram of H2O/DMF/PES and H2O/NMP/PES systems. The former case has small miscibility area while the latter one has large of which. The results demonstrate the contribution of RH of operating environment to morphology evolution of nanofibers. If the size of miscibility area increases e.g. H2O/NMP/PES system, a higher values of RH is needed to stabilize the formation of fibers. For this system, low level of humidity leads to develop beads as well as bead-on-string morphology. Adding the second solvent i.e. DMF into the PES/NMP solution shifts the binodal boundary toward the polymer-solvent side meaning a smaller miscibility area. In consequence, formation of fiber can be stabilized under broad range of humidity levels i.e. from low to high level of humidity. Implications regarding formation of surface pores by manipulating phase behavior of ternary system as well as RH of ambient conditions are discussed related to physico-chemical nature of solvent.

Solubility of benzyl methacrylate/methacrylic acid copolymers in carbon dioxide-expanded acetone and correlation with the PC-SAFT equation of state

The high-pressure solid–liquid–vapor phase behavior of ternary systems comprising CO2, acetone, and benzyl methacrylate (BzMA)/methacrylic acid (MAA) copolymers has been probed experimentally and modeled with the PC-SAFT equation of state. Precipitation of BzMA/MAA copolymers required a larger overall CO2 mole fraction – and a correspondingly higher system pressure – in dilute solutions; however, a minimum in the precipitation pressure was observed for all copolymer compositions and temperatures near a CO2-free copolymer mass fraction of 0.05. These systems were characterized by a rapid reduction in copolymer solubility over a relatively narrow range of pressure (between 1.48MPa and 2.86MPa). The precipitation pressure increased with increasing temperature and BzMA mass fraction (per copolymer mass unit). The PC-SAFT EOS was successfully used to correlate the phase behavior data using binary interaction parameters with linear temperature dependence. The average relative error associated with the calculated precipitation pressure for each copolymer was 4.1% over the range of temperature and composition examined. Liquid phase carbon dioxide mole fraction was calculated to monotonically increase with increasing solid precipitation pressure, implying that carbon dioxide does not act as an antisolvent at higher (>5wt%) copolymer fractions.

Critical end line topologies for ternary systems

A ternary critical end line (T-CEL) is a line of Ternary critical end points (T-CEPs). T-CELs provide key information on the phase behavior of ternary systems, i.e., they are boundaries for the ternary three-phase equilibrium. A ternary system may have several T-CELs. It is desirable to have available a robust algorithm for computing complete ternary CELs, thus minimizing the need for user intervention. It is also important to reliably detect the key points where T-CELs originate or terminate. In this work, we propose to apply a numerical continuation method (NCM) for the fast and robust computation of T-CELs. We present calculated T-CELs for highly asymmetric systems showing the topologies that these lines define. We consider a model of the equation of state (EOS) type and use it over wide ranges of conditions. Such ranges are much wider than those previously considered in the literature. Our main conclusion is that models for the fluid phase equilibria of ternary systems may predict, for a given system, several T-CELs of varying types and topologies. Some of such topologies have been observed for the first time in this work.

Generation of characteristic maps of the fluid phase behavior of ternary systems

The main features of the fluid phase behavior of a given binary system can be grasped at a glance by looking at its (binary) characteristic map (B-CM), which is made of unary and binary univariant lines, i.e., by geometrical objects having only one degree of freedom. Binary univariant lines are critical and azeotropic lines and liquid–liquid–vapor equilibrium lines. These lines are customary shown in the pressure–temperature plane together with the pure-compound vapor–liquid equilibrium lines (unary lines). Similarly, ternary systems also have characteristic maps for their phase equilibrium behavior. Such ternary characteristic maps (T-CMs) are made of unary, binary and ternary univariant lines. Possible ternary univariant lines are the following: ternary four-phase equilibrium lines (T-4PLs), ternary critical end lines (T-CELs) and ternary homogeneous azeotropy lines (T-ALs). T-CMs also present invariant points as the following: pure compound critical points, binary critical endpoints (B-CEPs), ternary critical endpoints of four-phase equilibrium lines (T-CEP-4PLs), ternary tricritical endpoints (T-TCEP), and all possible endpoints of binary and ternary homogeneous azeotropy lines. Analogously to B-CMs for binary systems, T-CMs make possible to quickly identify the main features of the phase behavior of a given ternary system. In other words, T-CMs provide key information on the fluid phase equilibria of ternary systems. When dealing with models for the fluid phase behavior of ternary systems, it would be useful to generate the T-CMs, in a way as automated as possible, once a ternary system and a model are chosen, and the model parameter values are set. This would make possible, among other outcomes, to quickly evaluate the main features of the model performance. B-CMs can be efficiently generated, when using a model of the equation of state (EOS) type, by applying available algorithms. In this work we show how the univariant lines of T-CMs can be efficiently computed for a given ternary system, given EOS and EOS parameter values. In general, a ternary univariant line (T-UVL) is generated in this work by using a numerical continuation method (NCM). NCMs are able to build, in their full extent, highly non linear T-UVLs, with minimum user intervention. In particular, we describe in this work how T-TCEPs and T-CEP-4PLs are detected and computed, and how the calculation of T-4PLs is started off. Finally, an algorithm for the generation of computed T-CMs is presented. The algorithm relies on previously computed critical endpoints of the binary subsystems of the ternary system under study. We have not considered yet the detection and computation of T-ALs and of closed loop T-CELs. We provide examples of T-CMs computed over wide ranges of conditions. The results of this work show that relatively simple models can generate highly complex topologies for the phase behavior of ternary systems.

Extractive concentration of aqueous salt solutions in aqueous two phase systems

Concentration of aqueous salt solutions is among the most energy intensive processes in the chemical industry. We here report on extractive concentration as an alternative for the traditional technologies based on water evaporation or reverse osmosis. Extractive technologies are potentially energy-efficient, key is avoiding evaporation of (co-)extracted water during the recovery of the solvent. Polymers have been applied as solvents, because recovery may be done through mild temperature swing. For in total 53 commercially available polymers, the phase behavior of ternary systems containing water, salt (NaCl, Na2SO4, and FeCl3) and polymer was studied at room temperature (294K) and atmospheric pressure. Formation of aqueous two phase systems (ATPS) was studied for various solvent/feed ratios (mass) of (0.25<S/F<0.75), and initial salt concentrations of 5wt.%<[salt]initial<30wt.%. Several polyether (block co)polymers were found suitable for creating ATPS with NaCl and Na2SO4 with reasonable distributions of water and these systems were analyzed more detailed at 294K and 314K, showing concentration factors up to 7.70 in a single extraction step, and strong temperature dependency. Temperature responsive recovery by induced phase splitting was shown to be a promising option.

Measurements of the phase behavior of ternary systems of interest to the GAS process: III. The system CO2 + toluene + naphthalene

Systems consisting of a supercritical gas, an organic solvent and an organic solute are of interest for the gas-antisolvent (GAS) process. In this work the phase behavior of the ternary system carbon dioxide+toluene+naphthalene was studied in a Cailletet apparatus over the temperature range 283–343K and pressures varying between 2MPa and 12MPa. The system was investigated by means of a quasi-binary approach, in which the carbon dioxide mole fraction was kept constant. For three different mole fractions of carbon dioxide (0.3, 0.5 and 0.8) five different naphthalene/toluene ratios were added to give a certain overall composition. Additionally a mixture containing 77.5mol% carbon dioxide, 9.5mol% toluene and 13mol% naphthalene was studied. The experimental data show that in the ternary system carbon dioxide+toluene+naphthalene complex multiphase behavior occurs.

Measurements of the phase behavior of ternary systems of interest to the GAS process: II. The system CO2 + methanol + prednisolone

In this work, the phase behavior of the ternary system carbon dioxide+methanol+prednisolone has been studied experimentally. For this purpose, carbon dioxide has been chosen as the anti-solvent gas, methanol as the organic solvent, and prednisolone as the model drug that should be micronized using the GAS process. In each experiment, a solution of prednisolone in methanol was expanded using carbon dioxide as the anti-solvent. A synthetic method was used for measuring bubble point curves, and the solid (prednisolone)–liquid boundaries. Three-phase equilibrium data of solid (prednisolone)–liquid–vapor were obtained from the intersection of the two-phase isopleths vapor–liquid and solid–liquid. Results are reported for this ternary system at carbon dioxide concentrations ranging from 13.1 to 48.4mol%, and within temperature and pressure ranges of 293.1–367.0K and 2.4–9.9MPa, respectively.In one of the mixtures it was observed that the concentration of carbon dioxide has a great effect on the phase behavior of the solution: at lower concentrations, carbon dioxide has a co-solvency effect, therefore, increasing the carbon dioxide concentration decreases the precipitation temperature. However, at higher concentrations, carbon dioxide acts as an anti-solvent, thus precipitation temperature increases with increasing carbon dioxide concentration. Also, it is shown that at a proper temperature, it is possible to precipitate most of the dissolved solute with small changes in pressure.

Lyotropic liquid crystalline phases formed in ternary mixtures of N-alkyl-N-methylpyrrolidinium bromide/1-decanol/water

The phase behavior of ternary systems involving long-chain pyrrolidinium ionic liquids, N-alkyl-N-methylpyrrolidinium bromide (CnMPB, n = 12, 14, 16), water, and 1-decanol was investigated at 25 °C. Polarized optical microscopy (POM), small-angle X-ray scattering (SAXS), and rheological measurements were employed to investigate the lyotropic liquid crystalline (LC) phases. Lamellar phase (Lα) and hexagonal phase (H1) were found to exist in all the three systems, but the isotropic cubic phase only appears in the C12MPB and C14MPB systems. Greater surfactant content leads to a denser aggregation of the cylindrical units in the H1 phase, and the structural parameters of Lα phase depends on water content. The alkyl chain length of CnMPB also has interesting effect on the structural parameters and rheological properties of the LC phase. Compared with a similar ternary system of 1-hexadecyl-3-methylimidazolium chloride ([C16mim]Cl) and traditional cationic surfactants cetyltrimethylammonium bromide (C16TAB), the effect of the cationic group on the phase behavior was also investigated.

Effect of Glycerol on the Self-Assembly of P123 in a Room-Temperature Ionic Liquid [Bmim]PF&lt;sub&gt;6&lt;/sub&gt;

Phase behavior of ternary systems involving PEO-PPO-PEO block copolymer (Pluronic P123), room-temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate [Bmim]PF6, and glycerol is investigated at 25 °C by using small-angle X-ray scattering (SAXS) techniques. In this ternary system, the structures formed in the binary P123/[Bmim]PF6 system, hexagonal phase (H1) and lamellar phase (Lα), are still obtained. At lower P123/[Bmim]PF6 ratio, the H1 phase can accommodate more than 30 % glycerol. At higher P123/[Bmim]PF6 ratio, the Lα phase only accommodates less than 2 % glycerol and Lα changes to H1 with increasing the glycerol content. Moreover, a phase separation takes place at a higher glycerol content. Solvatophobic interactions between hydrophobic groups of [Bmim]PF6 and P123, coulombic force existing in the polyoxyethylene chain and imidazolium cation, H-bond between P123 and glycerol, accompanying with the force ascribe to the nitrogen of the imidazole ring and the oxygen of alcohol are helpful for the formation of long-range ordered structure.

Effect of L64 on the Phase Behavior of 1‐Dodecyl‐3‐methylimidazolium Chloride/Water System

AbstractPhase behavior of ternary system involving surfactant‐like ionic liquid 1‐dodecyl‐3‐methylimidazolium chloride ([C12mim]Cl), water, and nonionic surfactant PEO‐PPO‐PEO block copolymer (Pluronic L64) is investigated at 25°C. Hexagonal (H1) and lamellar liquid crystal phase (Lα) are found in [C12mim]Cl/H2O/L64 system by using polarized optical microscopy (POM), small‐angle X‐ray scattering (SAXS) techniques and 2H NMR spectra. The phase structure (H1 phase), which is formed in [C12mim]Cl/H2O binary system, is not changed when L64 with a low concentration is added. However, phase transitions will occur from hexagonal to multiphases of H1 and cubic phases (C), then to Lα+C phases with constant [C12mim]Cl/H2O ratio and increasing L64 concentration. Moreover, at given L64 (5%, 20%) concentration, the lattice parameter of H1 or Lα phase decreases with increasing [C12mim]Cl/H2O ratio. Fourier transform infrared (FTIR) spectra indicate that the H‐bonded network comprising an imidazolium ring, chloride ion and water formed in [C12mim]Cl/H2O binary system is disrupted upon addition of L64. This is helpful to the phase transition, due to the decreasing of interfacial curvature induced by dehydration of hydrated layer after the addition of PEO block of L64.