Liquid Phase Equilibrium Research Articles

Synthesis, characterization and corrosion inhibition potential of two novel Schiff bases on mild steel in acidic medium

This study reports the synthesis of new Schiff bases namely 5-((4-chloro-3-nitrophenylimino)methyl)-2-methoxyphenol and 2-(4-hydroxy-3-methoxybenzylidineamino)-4-nitrophenol using solid–liquid phase equilibrium diagram and their characterization.

Vapour–Liquid Equilibrium for N, N-Dimethylformamide + Benzene + Thiophene via Gibbs Ensemble Molecular Simulation

The selection and design of an optimal solvent for extractive distillation require reliable vapour–liquid phase equilibrium data and knowledge of extraction mechanisms. Compared with time-consuming experiments, molecular simulation presents great potential in research on the properties of fluids. Therefore, in this work, Gibbs ensemble Monte Carlo was applied to successfully predict the vapour–liquid phase equilibrium data of binary and ternary systems containing benzene, thiophene and N, N-dimethylformamide (DMF) at P = 101.3 kPa. The explicit hydrogen version of the transferable potentials for phase equilibria potential model was chosen for benzene and thiophene, whereas the OPLS potential model was selected for DMF. The predicted phase diagrams were compared with experimental data and the UNIQUAC thermodynamic model. A good agreement was obtained, which corroborated the validity of the potential models. In addition, the extraction mechanism was explored by radial distribution function (RDF) of the liquid-phase structure. The RDFs showed that thiophene and benzene shared a similar liquid-phase structure because of the intermolecular interaction. The distinct difference between the RDFs of DMF/benzene and those of DMF/thiophene is that the oxygen atom of DMF is more associated with hydrogen atoms of thiophene than that of benzene, which may be responsible for the extraction effect of DMF.

Adsorption Characteristics of Activated Carbon for the Reclamation of Colored Effluents Containing Orange G and New Solid–Liquid Phase Equilibrium Model

Adsorption characteristics of activated carbon for the removal of orange G, an acid dye from aqueous solutions, have been investigated. The effect of initial dye concentration, temperature, and pH on the removal of orange G was investigated. The removal of orange G decreased from 95% to 82%, when the pH was increased from 2 to 12. The study of the effect of temperature and associated thermodynamic properties revealed the process of removal of dye is exothermic and spontaneous. Kinetic and mass transfer studies of the process were also carried out. The experimental data were used to develop a new solid–liquid phase equilibrium isotherm model. The average absolute relative deviation of the experimental data from the proposed model equation was 5.68%. In order to scale up the batch process for the removal of orange G, the concentration versus time data were analyzed to obtain mass transfer coefficient. The liquid-phase volumetric mass transfer coefficient (kLapL) was found to decrease from 0.008057 to 0.0028...

The measurements of vapor liquid phase equilibrium for R717 + R152a system at temperatures ranging from 253.150 K to 293.150 K

In contrast to pure ammonia, some additives into it may provide better solubility of the mineral oils, higher refrigeration capacity and lower discharge temperature of the compressor. In this paper, the vapor liquid phase equilibrium for the ammonia + 1,1-difluoroethane system at temperatures ranging from 253.150 K to 293.150 K were studied. The Peng–Robinson equation of state with the Huron–Vidal mixing rule involving the non-random two-liquid activity coefficient model was employed to describe the VLE behavior of the system concerned. The maximum average absolute relative deviation of pressure and average absolute deviation of vapor phase are 0.31% and 0.009, respectively. A positive azeotropic behavior was exhibited at the experimental temperature range.

Determination and correlation of solid-liquid phase equilibrium and phase diagram for multicomponent system of mixed dibasic acids. (III) Ternary system of succinic acid + glutaric acid + ethanol system

The solid-liquid phase equilibrium for ternary system of succinic acid+glutaric acid+ethanol was determined by an isothermal saturation method at the three temperatures of (283.15, 303.15 and 313.15)K under atmosphere pressure. Three isothermal phase diagrams were built based on the measured mutual solubility data. There were two pure solids formed in the ternary system at a certain temperature, which corresponded to pure succinic acid and pure glutaric acid and were confirmed by Schreinemaker’s method of wet residue and X-ray powder diffraction. The ternary phase diagram included one co-saturated point, two boundary curves, and three crystalline regions. The crystallization region of glutaric acid was smaller than that of succinic acid at each temperature. In addition, two thermodynamic models, NRTL and Wilson were employed to correlate and calculate the mutual solubility data for the ternary succinic acid+glutaric acid+ethanol system. The largest RMSD value for the ternary system of succinic acid+glutaric acid+ethanol was 0.43, and the maximum value of RAD was 3.0%. The Wilson model and NRTL model may all be employed to describe the mutual solubility behavior for the ternary system of succinic acid+glutaric acid+ethanol at various temperatures. Furthermore, the densities of the equilibrium liquid phase were obtained and correlated with an empirical equation.

Stable (solid + liquid) phase equilibrium for the ternary system (NaCl + RbCl + H2O) at T = (288.15, 298.15 and 308.15) K

The (solid+liquid) phase equilibrium of the ternary system (NaCl+RbCl+H2O) at T=(288.15, 298.15 and 308.15)K was studied by the method of isothermal solution saturation. Moreover, the density and refractive index of the solution was also determined. The solid phase was studied by the Schreinemaker’s wet residue method and verified by X-ray diffraction. The results show that each of the phase diagrams contains one invariant point, two univariant curves, and three crystallization regions. The crystallization region of NaCl increased obviously with the temperature increasing, while the crystallization regions of RbCl and the mixed crystallization region of (NaCl+RbCl) decreased a little. Furthermore, there are break points at the invariant points for density and refractive index curves.

Vapour–liquid phase equilibrium and surface tension of fully flexible Lennard–Jones chains

ABSTRACTWe report measurements of the vapour–liquid coexistence densities and surface tension of fully flexible Lennard–Jones chain molecules ranging in length from 4 to 60 beads. We demonstrate that the surface tension for all chain lengths collapses to a single master curve when plotted according to the universal parachor correlation. We find a universal parachor exponent 3.79 ± 0.05 for conditions close to the critical point, with a deviation observed for the longest chains far below the critical point.

Salt effects on extraction of trioxane from aqueous formaldehyde solutions

Extraction was a key step in industrial process of trioxane. NaOH was utilized in industrial production of trioxane to maintain appropriate pH to prevent trioxane decomposition. Here efforts were made to investigate the salt effects that can produce an alkaline medium to prevent trioxane decomposition and, simultaneously, can induce salting-out effect to considerably increase the efficiency of extraction of trioxane from aqueous formaldehyde solutions. The salt considered included K3PO4, Na3PO4, sodium tartrate (Na2C4H4O6) and sodium citrate (Na3C6H5O7). The decomposition measurements were made for the (trioxane + formaldehyde + salt + H2O) solutions at 323.15 K for 96 h. No trioxane decomposition was detectable over the whole experimental time. Extraction measurements were made using each of the selected salts or NaOH as accelerant salt and benzene, dichlorobenzene or dimethylbenzene as extraction solvent. The results showed that both the extraction efficiency and the distribution coefficient were considerably increased and that such effects followed the order Na3PO4 > K3PO4 > Na3C6H5O7 > Na2C4H4O6 > NaOH. The results also showed that the effects of these salts on the water content in the organic phase and on the organic phase residual in the water phase were generally similar to or even more favorable than those of NaOH. The liquid−liquid phase equilibrium data were measured for the (trioxane + formaldehyde + K3PO4 + H2O + benzene) solutions at (313.15, 323.15 and 333.15) K and were found to be well described by the Othmer−Toblas and the Hand equations.

Vapor-liquid equilibrium (VLE) of CO2 in aqueous solutions of benzylamine: New data and modeling using ENRTL-equation

In this work, new experimental data of carbon dioxide (CO2) solubility in aqueous benzylamine (BZA) solutions were generated at 313.15K, 323.15K, 333.15K and 343.15K, with the BZA concentrations of 5, 10, 20, 30mass% and pressure up to 190kPa. A rigorous thermodynamically consistent model based on Electrolyte Non-Random Two-Liquid (ENRTL) theory has been developed to correlate and predict the vapor liquid equilibrium behavior of CO2 in aqueous BZA. The model predicted CO2 solubility is in good agreement with experimental data showing 19% average absolute deviation (AAD). The model is also utilized to estimate equilibrium liquid phase speciation; pH of the CO2 loaded aqueous BZA solutions and heat of CO2 absorption (∼80kJ/mol).

Coupled phase-reaction equilibrium for dihydromyrcene hydration system

The solvent usually forms a large part of the heterogeneous hydration mixture in the biphasic hydration of liquid olefins, and solvent selection greatly affects the hydration conversion. In this work, the hydration of dihydromyrcene (DHM) in two different solvents, i.e., acetone and 1,4-dioxane, was investigated experimentally and mathematically. A theoretical model coupling liquid–liquid phase equilibrium and reaction equilibrium is proposed for evaluating the effects of the solvent on the heterogeneous hydration of DHM. Experiments were performed to obtain unreported parameters for the phase equilibrium and reaction equilibrium and the conversion of DHM in biphasic hydration was then predicted by the coupled model. The effects of the mass feed ratios on the total conversion X of DHM are discussed and varying conversions were observed when different solvents were employed. DHM was more soluble in the acetone system than in 1,4-dioxane, and the conversion of the hydration reaction was higher. This predictive evaluation process based on the overall equilibrium could provide a practical strategy for selecting the optimal solvent for the heterogeneous hydration of DHM and other liquid olefins.

Solid–liquid phase equilibrium and dissolution properties of ethyl vanillin in pure solvents

The solubility of ethyl vanillin (EVA) in eight pure solvents were determined in different temperature ranges from (273.15 to 318.15)K by a static analytical method. In the temperature ranges investigated, it was found that the solubility of EVA in all the selected solvents increased with the rising of temperature. Furthermore, four thermodynamic models were used to correlate the experimental solubility data and the calculation results showed that selected models can be used to correlate the solubility data with satisfactory accuracy. Finally, the dissolution thermodynamic properties, including dissolution Gibbs energy, dissolution enthalpy and dissolution entropy of EVA in the eight selected solvents were calculated.

Effect of operating parameters on a centrifugal partition chromatography separation

Centrifugal partition chromatography (CPC) is the branch of countercurrent chromatography (CCC) that works with single axis hydrostatic columns with rotary seals. The hydrodynamic of the liquid stationary phase-liquid mobile phase equilibrium in the CPC chambers has been studied theoretically and with specially designed CPC columns. In this work, we selected a simple analytical separation (no loading study) of three test solutes, coccine red, coumarin and carvone, with a commonly used heptane/ethyl acetate/methanol/water 1:1:1:1v/v biphasic liquid system and two different rotors: a commercially available 30-mL CPC instrument and a 80-mL prototype rotor designed for productivity. We fully studied this separation in many possible practical operating conditions of the two rotors, aiming at a generic column characterization. The rotor rotation was varied between 1000 and 2800rpm, the aqueous mobile phase flow rate was varied between 1 and 22mL/min with the 30-mL rotor and 10 and 55mL/min with the 80-mL rotor, the upper limits being mechanical constraints and some liquid stationary phase remaining in the rotor. The variations of Sf, the volume ratio of stationary phase in the rotor, were studied versus mobile phase flow rate and rotor rotation speed. A maximum mobile phase linear velocity was found to depend on the centrifugal field for the 30-mL rotor. This maximum velocity was not observed with the 80-mL rotor. Studying the changes in coumarin and carvone peak efficiencies, it is established that the number of cells required to make one theoretical plate, i.e. one chromatographic exchange, is minimized at maximal rotation speed and, to a lesser extent, at high mobile phase flow rate (or linear velocity). Considering the throughput, there is evidence of an optimal flow rate depending on the rotor rotation that is not necessarily the highest possible.

(Solid + Liquid) Phase Equilibria for the Systems CsBr + EuBr3 + H2O and CsBr + EuBr3 + HBr (∼12.3%) + H2O at 298.15 K and Atmospheric Pressure and Thermodynamic and Fluorescent Properties of the New Solid-Phase Compound

In this study, the (solid + liquid) phase equilibria for the two systems of CsBr + EuBr3 + H2O and CsBr + EuBr3 + HBr (∼12.3%) + H2O at 298.15 K and atmospheric pressure were determined by isothermal solubility method. Schreinemaker wet residue approach was used to determin the solid phases obtained from the studied systems. The related phase diagrams were depicted based upon the experimental data. There were two invariant points, three invariant curves, and three crystallization fields corresponding to CsBr, 5CsBr·2EuBr3·20H2O, and EuBr3·6H2O in the two phase diagrams. New double salt 5CsBr·2EuBr3·20H2O was incongruently soluble in the two systems. The content of EuBr3 in two invariant points decreased as the concentration of HBr in equilibrium liquid phase increased, while that of CsBr changed a little. The new solid-phase compound 5CsBr·2EuBr3·20H2O was investigated using chemical, XRD, and TG-DTG analyses. Additionally, the standard molar enthalpy of solution for 5CsBr·2EuBr3·20H2O in water was confir...

Phase equilibria for the pseudo-ternary system (NaCl + Na 2 SO 4 + H 2 O) of coal gasification wastewater at T = (268.15 to 373.15) K

Abstract The pseudo-ternary system (NaCl + Na2SO4 + H2O) of coal gasification wastewater was studied at T = (268.15 to 373.15) K. The solubility and density of the equilibrium liquid phase were determined by the isothermal solution saturation method. The equilibrium solids were also investigated by the Schreinemaker's method of wet residues and X-ray powder diffraction (XRD). According to the experimental data, the phase diagrams were determined. It was found that there was no significant solubility difference on the NaCl-rich side between the ternary system (NaCl + Na2SO4 + H2O) in coal gasification wastewater and in pure water. However, the solubility on the Na2SO4-rich side of coal gasification wastewater was apparently higher than that of pure water. The increase in the solubility of Na2SO4 was most likely caused by the effects of other impurities apart from NaCl and Na2SO4 in coal gasification wastewater. The measured data and phase equilibrium diagrams can provide fundamental basis for salt recovery in coal gasification wastewater.

Measurements and correlations of isothermal (vapour + liquid) equilibrium for the {isobutane (R600a) + cis-1,3,3,3-tetrafluoropropene (R1234ze(Z))} system at temperatures from (303.150 to 353.150) K

In this paper, the (vapour+liquid) phase equilibrium for the (isobutane+cis-1,3,3,3-tetrafluoropropene) system was measured by the static-analytical method at six temperatures from (303.150 to 353.150)K. The combined standard uncertainties of the temperature, pressure and composition were less than ±5mK, ±0.0005MPa and ±0.005, respectively. The experimental results were correlated by means of the Peng–Robison (PR) equation of state (EoS) with Van der Waals (VDW) mixing rule and Huron–Vidal (HV) mixing rule involving the non-random two-liquid (NRTL) activity coefficient model. Good consistency is found by both models. The average absolute relative deviations of pressure are between 0.44% and 0.58% for the PR-VDW model, while the average absolute relative deviations of pressure are between 0.12% and 0.44% for the PR-HV-NRTL model. The average absolute deviations of vapour phase mole fraction lay between 0.007 and 0.008 for the PR-VDW model, while the average absolute deviations of vapour phase mole fraction lay between 0.004 and 0.008 for the PR-HV-NRTL model. The results show that the PR-HV-NRTL model has better performance than that of the PR-VDW model for the binary system. Obviously an azeotropic behaviour can be observed for the system.

Thermodynamic representation of ionic liquids phase equilibrium with the Wilson-NRF model

Ionic liquids (ILs) with their limitless combinations of cations and anions can offer an optimal solvent for a specific purpose especially separation processes such as liquid-liquid extraction (LLE). The present work inquired phase behavior of 32-types ILs with various cations (including imidazolium, pyridinium, piperidinium, morpholinium, pyrrolidinium and phosphonium-based) and various anions (including Cl, FeCl4, BF4, B(CN)4, PF6, NTf2, FAP and alkylsulfates) in LLE systems. Calculation of LLE for 38 binary (220 Tie-Line) and 52 ternary (545 Tie-Line) systems were carried out using Wilson-Non-Random-Factor (Wilson-NRF) model. All the data were in the temperature range of 298.15–408.15K. Therefore, in order to obtain an temperature-independent interaction parameters, the adjustable parameter assumed to be as a function of T as: λij=aij+bij/T. All the interaction parameters either for binary or ternary systems were directly regressed from the experimental data using an optimization program based on two objective functions. All the results were expressed by root mean square deviation (rmsd) between the calculated and experimental compositions (the solubility data from the literature). The applied model had very good satisfactory results for ternary and binary systems with rmsd values of 8.78 and 4.08 respectively. Besides, the effect of cation-type, anion-type and the other organic compound on the model behavior was illustrated. Finally, the results represented that Wilson-NRF model could be satisfying model for evaluation of thermodynamic behavior of various LLE containing ILs.

Solid−liquid phase equilibrium and mixing properties of 2-Cyano-4′-methylbiphenyl in pure solvents

Solid–liquid equilibrium data of 2-Cyano-4′-methylbiphenyl (OTBN) are essential for the design and optimization of its production process. In this work, the solubility data of OTBN in pure solvents including 2-propanol, (R)-(−)-2-butanol (2-butanol, for short), methyl acetate, ethyl acetate, propyl acetate, butyl acetate, acetone and acetonitrile were determined in different temperature ranges from (268.05 to 303.25)K by using UV spectrometer method under atmospheric pressure. It was found that the order of OTBN solubility in these selected pure solvents at given temperature is acetone>methyl acetate>ethyl acetate>propyl acetate>butyl acetate>2-butanol>2-propanol and methyl acetate>acetonitrile>2-butanol. In the temperature range investigated, the solubility data of OTBN increase with the increasing of temperature in all eight solvents. Furthermore, the modified Apelblat equation, the Wilson model and the NRTL model were applied to correlate the experimental solubility data. The correlated results are consistent with the experimental results. Finally, the mixing thermodynamic properties of OTBN in different solvents were calculated and analyzed based on the experimental solubility data and the Wilson model.

Pyrolysis Oil Multiphase Behavior and Phase Stability: A Review

This paper reviews the literature related to the complex chemical composition and multiphase nature of bio-oils and their practical implications. Over time, bio-oil forms separated phases due to purely physical phenomena (phase stability) or chemical composition changes in storage (aging reactions). Bio-oil multiphase behavior and the formation of separated phases are controlled by the complex chemical composition of these oils. Fast pyrolysis oils from woody biomass are typically observed in a single phase. However, feedstocks with high extractives content and/or high ash content commonly produce oils with more than one phase (an aqueous phase, an upper layer, and a decanted heavy oily phase). The first part of this Review focuses on the effects of feedstock composition, particle size, type of pyrolysis reactor, and condensation systems on bio-oil chemical composition and their impact on stable oils production. The second section reviews our current understanding of fresh bio-oil multiphase behavior and the effect of aging reactions. The use of phase diagrams as a tool to predict bio-oil phase stability is discussed. The third section focuses on bio-oil upgrading strategies based on the use of solvents and the production of emulsions. In this section we discuss the factors affecting phase equilibrium. This review highlights the importance of developing systematic studies to better understand bio-oil liquid–liquid phase equilibrium and the advantages of using phase diagrams. This understanding could have significant impact on the development of new bio-oil separation processes, on the development of new tools to produce stable bio-oils, as well as on the production of bio-oil-derived fuels. Understanding the complex nature of bio-oil multiphase behavior has been progressing over the years; however, more work is still needed to control these phenomena.

Solid–Liquid Equilibrium on the Reciprocal Aqueous Quaternary System Li+, Mg2+//Cl–, and Borate–H2O at 323 K

The solid–liquid phase equilibrium in the reciprocal aqueous quaternary system Li+, Mg2+//Cl–, and borate–H2O at 323 K was completed with the isothermal dissolution method. The corresponding physiochemical properties (ρ, ηD) of solutions at equilibrium in the Li+, Mg2+//Cl–, and borate–H2O electrolyte mixtures were determined. The isothermal dissolution phase diagram, the water figure, and the figures for the physicochemical properties (ρ, ηD) depending on the composition were obtained according to values of the Janecke index. The stable phase diagram contains three invariant points, seven univariant curves, and five crystallization zones. The crystallographic forms of magnesium borate and lithium borate are tetraborate MgB4O5(OH)4·7H2O and Li2B4O7·3H2O, respectively. The size of MgB4O5(OH)4·7H2O crystallization field is the largest among the coexisting salts.

Salt effect on the liquid-liquid equilibrium of (water + diethanolamine + isobutanol/cyclohexanol) systems at T = (298.2 and 308.2) K

In this work, salt effect on the liquid phase equilibrium of (water+diethanolamine+isobutanol) and (water+diethanolamine+cyclohexanol) systems was investigated at T=(298.2 and 308.2) K. The liquid-liquid equilibrium data in the presence of KCl and NaCl salts for various ionic strength of 0.5, 1.0, 1.5, and 2.0mol·dm−3 and in absence of these salts were determined. The experimental results were correlated based on the Othmer-Tobias equation, Bachman equation and Pitzer ion-interaction model. Thermodynamic properties such as distribution coefficients and activity coefficients of diethanolamine in water+isobutanol and water+cyclohexanol mixtures were determined. In addition, the separation factor of the chosen solvents were obtained for the investigated systems.