Vapor-liquid Equilibrium Behavior Research Articles

Isothermal measurement and modeling of VLE properties for 2,3,3,3-tetrafluoroprop-1-ene + trifluoromethane + tetrafluoromethane ternary system at temperatures from 253.15 K to 273.15 K

Abstract At present, the difficulty in the research of auto cascade refrigeration system lies in the selection of the mixed refrigerant ratio and the design of system process. Accurate thermodynamic data is the key to solve those problems. In this paper, isothermal vapor liquid equilibrium (VLE) behavior was experimentally studied for the strongly-zeotropic ternary mixture 2,3,3,3-tetrafluoroprop-1-ene (R1234yf) + trifluoromethane (R23) + tetrafluoromethane (R14) at 253.15 K, 263.15 K, and 273.15 K. The pressures and the vapor mass fractions were found to be thermodynamically consistent and were satisfactorily correlated with the NRTL-RK model and the MUNIFAC-SRK model. The average absolute relative deviations of pressure (AARD-p), and the average absolute deviations of vapor phase mass fraction (AAD-y1, AAD-y2 and AAD-y3) are less than 0.25%, 0.0032, 0.0048 and 0.0040 for the MUNIFAC-SRK model, respectively, which are better than those of 0.4%, 0.0138, 0.0198 and 0.0049 for the NRTL-RK model. The results of the MUNIFAC-SRK model showed excellent agreement with the experimental values. The isothermal three-dimensional VLE behavior and the isothermal-isobaric ternary VLE diagrams under 1500 kPa were also established using a flash calculation method.

Modeling the acentric factor of binary and ternary mixtures of ionic liquids using advanced intelligent systems

Ionic liquids (ILs) have found application in wide range of areas including petroleum industry, extractive distillation, raw material processing, additives for lubricants, functional materials, and catalyst for organic processes. Despite their applications in various fields of science, the use of ILs has been of questionable existence due to their induced toxic effects. To study the phase behavior of these ILs, various methods of obtaining data have been proposed. Notably, the main source of data comes from the laboratory experiments. Despite the existence of experimental methods to quantify the vapor-liquid equilibrium behavior of a fluid – IL system, it is necessary to build a model that can predict the behavior of the system at various states such as, changing temperature, pressure, and volume. Notwithstanding the huge cost and time required during experiments, thermodynamic model has found increasing use for modeling complex mixtures and/or compounds. One of the key parameters of the various thermodynamic models is the acentric factor, which dictates the level of sphericity of a molecule. In this study, the authors explored two different intelligent systems to estimate this key property for binary and ternary mixtures. The algorithm considered in this study include the least square support vector machine and artificial neural network. The input parameters considered include the critical temperature and volume, mole fraction of the solvent(s) and ionic liquid, molecular weight, density of the mixture, and temperature of the fluid. The comparison between the best model and experimental data point indicates very low root mean square error of 0.0164 and 0.0005 for the binary and ternary mixtures respectively. Similarly, the best model produced a very high correlation coefficient of 0.9826 and 1.0000 for the binary and ternary mixtures respectively.

Molecular Mechanism for Azeotrope Formation in Ethanol/Benzene Binary Mixtures through Gibbs Ensemble Monte Carlo Simulation.

Azeotropes have been studied for decades due to the challenges they impose on separation processes but fundamental understanding at the molecular level remains limited. Although molecular simulation has demonstrated its capability of predicting mixture vapor-liquid equilibrium (VLE) behaviors, including azeotropes, its potential for mechanistic investigation has not been fully exploited. In this study, we use the united atom transferable potentials for phase equilibria (TraPPE-UA) force field to model the ethanol/benzene mixture, which displays a positive azeotrope. Gibbs ensemble Monte Carlo (GEMC) simulation is performed to predict the VLE phase diagram, including an azeotrope point. The results accurately agree with experimental measurements. We argue that the molecular mechanism of azeotrope formation cannot be fully understood by studying the mixture liquid-state stability at the azeotrope point alone. Rather, azeotrope occurrence is only a reflection of the changing relative volatility between the two components over a much wider composition range. A thermodynamic criterion is thus proposed on the basis of the comparison of partial excess Gibbs energy between the components. In the ethanol/benzene system, molecular energetics shows that with increasing ethanol mole fraction, its volatility initially decreases but later plateaus, while benzene volatility is initially nearly constant and only starts to decrease when its mole fraction is low. Analysis of the mixture liquid structure, including a detailed investigation of ethanol hydrogen-bonding configurations at different composition levels, reveals the underlying molecular mechanism for the changing volatilities responsible for the azeotrope.

Improved Design of Maximum-Boiling Phenol/Cyclohexanone Separation with Experimentally Verified Vapor–Liquid Equilibrium Behaviors

There are very few papers in the open literature studying the design of extractive distillation system for separating maximum-boiling mixtures. Using the knowledge of the curvature of the distillat...

Energy-efficient design of extraction-distillation process for 2,2,3,3-tetrafluoro-1-propanol/water separation with thermodynamically verified liquid-liquid and vapor-liquid equilibrium behaviors

Design of 2,2,3,3-tetrafluoro-1-propanol (TFP)/water separation process by energy-saving hybrid extraction-distillation system is investigated in this paper. Solvent extraction is one of the most promising energy-efficient separation methods because the major part of this separation is achieved through an extraction column without needing of reboiler duty. Thus, by utilizing a hybrid extraction-distillation separation process, huge economic potential can be realized with an important prerequisite of finding an effective solvent for the liquid-liquid separation. In this work, an efficient solvent of diisopropyl ether (DIPE) is found for this separation process. The thermodynamic model used in the investigation not only satisfies the experimental data of ternary liquid-liquid equilibrium, but also predicts well the behavior of binary vapour-liquid equilibrium, showing the credibility of simulation study. Another important aspect of this paper is to also consider the way to achieve a minimum density difference of liquid-liquid extraction in the analysis. It is found that the proposed extraction-distillation system by utilizing DIPE as solvent not only can achieve over 100 kg/m3 density difference in the extraction column, but also can significantly reduce total annual cost by 51.1%, as compared to that of a heterogeneous dividing-wall column system recently published in open literature.

Vapor phase and two-phase PvTz measurements of difluoromethane + 2,3,3,3-tetrafluoroprop-1-ene

This paper provides 217 PvTz points for the binary systems of difluoromethane (R32) and 2,3,3,3-tetrafluoroprop-1-ene (R1234yf) both in the two-phase and superheated vapor regions. The R32 + R1234yf data were measured along eleven isochores (0.029794, 0.029936, 0.030724, 0.032113, 0.061323, 0.063915, 0.102150, 0.111536, 0.116592, 0.144796, 0.280627) m3·kg−1 for temperatures from (263 to 383) K for eleven R32 mole fractions (0.1214, 0.1330, 0.1792, 0.2712, 0.3432, 0.5229, 0.6231, 0.6489, 0.7020, 0.8122, 0.9460). From the measurements in the two-phase region, the vapor-liquid equilibrium behavior of the studied binary systems was derived by applying the flash method with the Carnahan–Starling–De Santis equation of state, the Peng–Robinson equation of state and a two-parameter cubic equation of state proposed by Stryjek. The representation of the vapor – liquid equilibrium for the studied binary systems obtained from the isochoric data is consistent with the experimental vapor – liquid equilibrium data available in the literature. The superheated vapor data were correlated using the virial equation of state, in addition to the aforementioned equations of state. The vapor phase data showed good agreement with the values calculated with the equations of state and the predictions provided by REFPROP 10.0.

Vapour-liquid equilibrium study of tertiary amines, single and in blend with 3-(methylamino)propylamine, for post-combustion CO2 capture

This work studies the potential of using the tertiary amines 3-dimethylamino-1-propanol (3DMA1P), 3-diethylamino-1-propanol (3DEA1P) and 1-(2-hydroxyethyl)pyrrolidine (1-(2HE)PRLD) as an alternative to 2-(diethylamino)ethanol (DEEA) in the blend with 3-(methylamino)propylamine (MAPA). Vapour pressure of the three tertiary amines and vapour-liquid equilibrium (VLE) of the binary mixtures 3DMA1P/H2O, 3DEA1P/H2O and 1-(2HE)PRLD/H2O at T = (353, 363 and 373) K were measured in a modified Swietoslawski ebulliometer. The vapour pressure of the pure amines was fitted to the Antoine equation, and the P-T-x-y data were fitted to NRTL equations. VLE of the CO2 loaded blended amines were measured in the temperature range of T = 313 to 393 K, and speciation data of equilibrated samples at different CO2 loadings were obtained by NMR spectroscopy.The study showed that the tertiary amines 3DMA1P, 3DEA1P and 1-(2HE)PRLD in the binary amine/H2O system were less volatile than DEEA in aqueous solution. The CO2 loaded blended amines showed comparable VLE behaviour, as well as speciation, and obtained a cyclic capacity higher than that of 30 wt% MEA but similar to most of the blended amines studied in the literature. The overall results indicated that the tertiary amines studied in this work can be used as an alternative to DEEA.

Isobaric Vapor–Liquid Equilibria for the Quaternary System Water + Ethanol + Ethylene Glycol + Choline Chloride and the Ternary System Water + Ethanol + Choline Chloride at 101.3 kPa

An organic salt choline chloride (ChCl) was introduced in ethylene glycol (EG) for improving the entrainer performance for ethanol dehydration by extractive distillation. The mixed solvent EG + ChCl with molar ratios of 8:1, 4:1, 2:1, and 4:3 were tested through vapor–liquid equilibrium (VLE) measurement for the quaternary system water + ethanol + EG + ChCl at 101.3 kPa. Data were also measured for the ternary system water + ethanol + ChCl. VLE behavior of the quaternary system was modeled successfully using the NRTL equation. The mean absolute deviations for the quaternary data were 0.24 K for equilibrium temperature and 0.0041 for vapor mole fraction of ethanol, while deviations for the ternary data were 0.15 K and 0.0032. As compared with EG alone, the existence of ChCl in the mixed solvent decreases the activity coefficient of water and increases the activity coefficient of ethanol, both leading to the enhancement of the relative volatility of ethanol to water. The azeotrope of water + ethanol can be removed with the addition of EG + ChCl 4:3 at a solvent mass fraction of 0.062, showing favorable entrainer performance for ethanol dehydration by extractive distillation.

CO2 Solubility in Physicochemical Absorbent: Dibutyl Ether/N-Methylethanolamine/Ethanol

In this work, a physicochemical absorbent was proposed for CO2 capture, which consists of dibutyl ether as physical solvent, N-methylethanolamine (NMEA) as chemical additive, and ethanol as dissolvent. The vapor–liquid equilibrium behavior of this CO2 + physicochemical absorbent system was measured using an isothermal synthetic apparatus. The solubility data of CO2 in ethanol at 313.15 K were measured and compared with literature data to verify the validity of this method. Then, the CO2 solubility data of above system with varying NMEA mass fractions of 15 %, 25 %, and 50 % were, respectively, measured at 298.15 K. It shows that the CO2 solubility increases when NMEA mass fraction goes up. The CO2 solubility data in the absorbent with 25 % NMEA mass fraction were measured at a temperature range from 298.15 K to 328.15 K with the interval of 10 K and at a pressure range from 0 MPa to 3 MPa. The result shows that CO2 turns out to be more soluble in the physicochemical absorbents than in dibutyl ether at the same conditions of temperature and pressure.

Measurement and correlation of the isobaric vapor-liquid equilibria of methanol + methyl carbonate + Bis(trifluoromethylsulfonyl)imide-based ionic liquidsat 101.3 kPa

Isobaric vapor-liquid equilibria (VLE) for the azeotropic system of methanol + methyl carbonate and the ternary systems of methanol + methyl carbonate + 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][NTf2]) and methanol + methyl carbonate + 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([HMIM][NTf2]) have been obtained using an Othmer Still. Methyl carbonate could be separated from the azeotropic system with [BMIM][NTf2] and [HMIM][NTf2] due to the existence of cross-salt effect. The experimental data were in good agreement with the correlated data using the NRTL model. The model results indicated that the minimum mole fractions required for [BMIM][NTf2] and [HMIM][NTf2] to eliminate azeotropes were 0.048 and 0.043, respectively. The separation capacity of [HMIM][NTf2] was much higher than that of [BMIM][NTf2]. This work provided a general method to understand the effect of ionic liquids (ILs) on the isobaric VLE behavior of methanol + methyl carbonate, and a promising way to the industrial application of ILs in extractive distillation.

Effect of Ionic Liquids on the Isobaric Vapor-Liquid Equilibrium Behavior of Acetone-Chloroform

Isobaric vapor-liquid equilibrium (VLE) data of the ternary system acetone + chloroform + 1,3-dimethylimidazolium dimethylphosphate ([MMIM][DMP]) or 1-ethyl-3-methylimidazolium diethylphosphate ([EMIM][DEP]) were obtained at 101.3 kPa. Results indicated that the addition of [MMIM][DMP] or [EMIM][DEP] could eliminate the azeotropic point of the binary system of acetone + chloroform when the mole fraction of ionic liquids (ILs) was above 0.15. Besides, the experimental data could be well correlated by the nonrandom two-liquid (NRTL) model. The structures as well as interactions between molecular solvents (acetone, chloroform) and the ion pairs ([MMIM][DMP], [EMIM][DEP]) were studied by quantum chemical calculations. The result indicated that the interaction energies (ΔE) follow the order of ΔE(acetone + [EMIM][DEP]) > ΔE(acetone + [MMIM][DMP]) > ΔE(chloroform + [EMIM][DEP]) ≈ ΔE(chloroform + [MMIM][DMP]), and chloroform had stronger affinity to ionic liquids than acetone.

Vapor-liquid and liquid-liquid equilibrium modeling of systems involving ethanol, water, and ethyl valerate (valeric acid) using the PC-SAFT equation of state

Valeric biofuels are renewable and environmental friendly fuels whose production avoids the competition with the food industry for edible oils since its route of production uses lignocellulose of residue from crops as raw material. After the reaction steps several purification operations are necessary for the valeric biofuels to meet purity standards. Therefore, it is of utter importance the knowledge of both liquid-liquid (LLE) and vapor-liquid (VLE) equilibrium behavior of species present in the process, such as ethyl valerate, valeric acid, ethanol and water. In this sense, the objective of this work is to provide a general overview for the phase equilibria of the system aforementioned using experimental data collected as background for the thermodynamic modeling. Experimental data concerning to LLE were evaluated at local atmospheric pressure (around 90.9 kPa) and 293.15 K and 318.15 K, while VLE data were collected at several different controlled pressures, ranging from approximately 7 kPa to local atmospheric pressure (around 91 kPa). UNIFAC and PC-SAFT (Perturbed Chain form of the Statistical Associating Fluid Theory) were used to perform the thermodynamic modeling. The results obtained in this work are helpful to prove the importance of carefully evaluate the interactions between the molecules present in the system. Otherwise, the design of unit operations could underestimate the number of stages required for the purification, causing the products to not reach purity specifications.

Screening of ionic liquids as entrainers for the separation of 1-propanol + water and 2-propanol + water mixtures using COSMO-RS model

ABSTRACTThe COSMO-RS model was used to screen potential ionic liquids for the separation of aqueous azeotropic mixtures 1-propanol + water and 2-propanol + water. A combination of 22 cations (involving imidazolium, pyridinium, pyrrolidinium, quinolinium, and ammonium) and 36 anions were investigated. The anions chloride [Cl] and dihydrogen phosphate [H2O4P] were found to strongly influence the vapor liquid equilibrium behavior, whereas the ammonium-based cations diethanol ammonium [(Et)2AMM]+ and tetra methyl ammonium [M4AMM]+ were the most promising cations. In addition, the study of mixing enthalpy and excess Gibbs free energy confirmed that the molecular interaction of ionic liquids with water was found to be much larger than that with alcohols 1-propanol and 2-propanol, indicating the presence of a strong hydrogen bonding between the ionic liquids and water. Further, the addition of ionic liquids to the alcohol–water mixture reduces the activity coefficient of water and increases the relative volatility of the mixture, facilitating easier separation. Ionic liquids [(Et)2AMM][Cl], [(Et)2AMM][H2O4P], [M4AMM][Cl], and [M4AMM][H2O4P] are expected to be effective entrainers for the separation of the industrially important 1-propanol + water and 2-propanol + water systems.

Investigation of the solute-solute and solute-solvent interactions in ternary {saccharide + ionic liquid + water} systems

The aim of this work is to investigate the salt effect resulted by addition of ionic liquids to aqueous saccharide solutions. To achieve this goal, systematic studies have been made on ternary {saccharide+ionic liquid+water} system using the available vapor-liquid equilibrium (VLE) data published recently. Vapor pressure depression, osmotic and activity coefficient data for the ionic liquids and saccharides in the binary solutions are used to investigate ionic liquid-water and saccharide–water interactions. For ternary solutions, the calculated activity coefficient of saccharides in presence of ionic liquids, transfer Gibbs energies, pair and triplet interaction parameters and salting constants are used to investigate saccharide-ionic liquid interactions. The variety of ionic liquids based on imidazolium and pyridinium have been considered. To extent the number of systems considered in this work, we have also included vapor-liquid equilibrium studies on the new systems {d-fructose+1-butyl-4-methyl pyridinium bromide+H2O} and {sucrose+1-butyl-4-methyl pyridinium bromide+H2O} from which experimental water activity data are measured. The aforementioned properties were also calculated for these new systems. In this article, the effect of stereochemistry of sugar, cation (imidazolium or pyridinium), chain length and anion of ionic liquids on vapor-liquid equilibrium behavior of these ternary systems and saccharide-ionic liquid interactions have been discussed. Generally, we found that there is a relationship between soluting-in or soluting-out behavior of ionic liquids and their hydration so that soluting-in effect is observed in ionic liquids with longer chain length and with anions having smaller values of osmotic coefficient. Soluting-out effect is observed in ionic liquids with shorter chain length and with anions having larger values of osmotic coefficient. From the VLE results we conclude that soluting-out effect of ionic liquids also depends on the hydration of saccharides and is observed in saccharides with high tendency to interact with water.

Investigation on vapor liquid equilibrium for strongly-zeotropic ternary mixture of 2,3,3,3-tetrafluoroprop-1-ene (R1234yf) + trifluoromethane (R23) + tetrafluoromethane (R14)

The cubic equation of state/excess Gibbs free energy (CEoS/GE) model is a new idea to predict non-ideal systems. In this study, the Peng-Robinson (PR) EoS combined with the Wong-Sandler (WS) mixing rule and the modified UNIFAC group contribution activity model was used to calculate the vapor liquid equilibrium (VLE) data. The average absolute relative deviations (AARD) of pressure and the average absolute deviations (AAD) of the vapor phase mass fraction between the calculated results and experimental data are 0.87% and 0.005 for fluoroethane (R161)+2,3,3,3-tetrafluoroprop-1-ene (R1234yf) over the temperature range of (283.15–323.15K) and at pressures varying from 0.4MPa to 1.8MPa, respectively. The liquid and vapor phase mass fraction deviations are within ±0.028 and ±0.025 for difluoromethane (R32)+pentafluoroethane (R125)+1,1,1,2-tetrafluoroethane (R134a) system at temperatures of (205–350K), respectively. The VLE behavior for the strongly-zeotropic mixture of 2,3,3,3-tetrafluoroprop-1-ene (R1234yf)+trifluoromethane (R23)+tetrafluoromethane (R14) which is suitable for the three-stage auto cascade refrigeration system was calculated at pressures of (0.2–2.2MPa) and the corresponding three-dimensional phase diagrams were constructed. It was found that the sliding temperature increases with the decrease of pressure and the maximum predicted sliding temperature reached 73K.

Isobaric Vapor–Liquid Equilibrium for the Binary and Ternary System with Isobutyl Alcohol, Isobutyl Acetate and Dimethyl Sulfoxide at 101.3 kPa

The isobaric vapor–liquid equilibrium (VLE) data for the binary systems isobutyl alcohol + dimethyl sulfoxide (DMSO), isobutyl acetate + DMSO, and ternary system isobutyl alcohol + isobutyl acetate + DMSO were measured at 101.3 kPa. All of the binary VLE data passed Wisniak’s modifed Herington area test and Wisniak point and area test. Ternary VLE data passed Wisniak point test. The VLE data of binary systems were correlated with NRTL, UNIQUAC, and Wilson models. The ternary VLE behavior were successfully predicted by the correlated binary parameters. The VLE data for the binary and ternary systems predicted by the correlated interaction parameters were in good agreement with all the experimental data. The relative volatility of isobutyl acetate to isobutyl alcohol can be greatly increased by DMSO and the azeotropic point of isobutyl acetate and isobutyl alcohol will disappear if the mole fraction of DMSO is greater than 0.36. DMSO is a promising solvent for separating the azeotrope of isobutyl alcohol an...

Evaluation of the Capability of Ionic Liquid-Amino Acid Aqueous Systems for the Formation of Aqueous Biphasic Systems and Their Applications in Extraction.

To obtain further experimental evidence for a better understanding of the molecular mechanisms responsible for the soluting-out effect phenomena in ternary systems composed of an ionic liquid (IL), amino acid, and water, systematic studies on the vapor-liquid, liquid-liquid, and solid-liquid equilibrium behavior of aqueous solutions of several ILs were carried out in the presence of a range of amino acids. Water activities for binary and ternary aqueous solutions containing 1-butyl-3-methylimidazolium chloride, [C4mim]Cl, 1-hexyl-3-methylimidazolium chloride, [C6mim]Cl, 1-butyl-3-methyl-imidazolium trifluoromethanesulfonate, [C4mim][CF3SO3], l-Ser, Gly, Ala, and l-Pro were measured using both vapor pressure osmometry and isopiestic methods. All of the ternary IL + amino acid + water systems show negative deviations from semi-ideal behavior and therefore soluting-out effects have been observed in these systems. In the case of the [C4mim][CF3SO3] + amino acids aqueous systems, the IL is soluted-out by the amino acids and the soluting-out effect appears by aqueous biphasic system formation. For these systems, the phase diagram and partition coefficient of caffeine were measured at 298.15 K. However, for the [C4mim]Cl and [C6mim]Cl containing systems, the amino acids are soluted-out by the ILs and the soluting-out effect appears by precipitation of the amino acids from the solution, and the solubilities of the amino acids in the aqueous solutions decrease in the presence of [C4mim]Cl and [C6mim]Cl.

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).

A green process for recovery of 1-propanol/2-propanol from their aqueous solutions: Experimental and MD simulation studies

In the present study, we have found that a common and relatively inexpensive biological buffer tris(hydroxymethyl)aminomethane (TRIS) is potentially applicable to shift the azeotrope compositions of aqueous solutions of 1-propanol and 2-propanol. By taking the advantage of our findings, we are proposing a green process for the recovery of these organics from their respective aqueous solutions. In order to confirm the effect of TRIS buffer on vapor–liquid equilibrium behavior of the aqueous propanol systems, we measured the isobaric vapor–liquid equilibrium (VLE) data at 101.3kPafor the 1-proponol+water+TRIS and 2-propanol+water+TRIS systems over the azeotropic range with various concentrations of TRIS (0.02, 0.04, 0.08, and 0.12 in mole fraction). The binary interaction parameters were obtained for TRIS with water, TRIS with 1-propanol, and TRIS with 2-propanol by correlating the new VLE data with the NRTL model. The isobaric VLE properties for the investigated propanol+water mixtures in the presence of various concentrations of TRIS were also predicted with the conductor-like screening model COSMO-RS. Based on the predicted excess molar enthalpies (HEm) from the COSMO-RS, the interactions between all constituent pairs of molecules were estimated. To explore the mechanism of TRIS-based separation of 1-propanol/2-propanol from their aqueous solutions, the interactions between different pairs of molecules were also investigated by using fluorescence analysis and Molecular Dynamic (MD) simulation. In comparison with the conventional corrosive inorganic salts and volatile organic entrainers, TRIS is non-corrosive, non-volatile, and almost totally recyclable. With the aid of TRIS, a cleaner separation process is proposed in the present study for recovery of 1-propanol and 2-propanol from their aqueous solutions based on buffer-swing distillation.

Vapor Pressure of Dichlorosilane, Trichlorosilane, and Tetrachlorosilane from 300 K to 420 K

The method for the preparation of elemental silicon of sufficient purity for the fabrication of electronic devices is by first converting silicon oxide to silicon–hydrogen-chloride compounds, purifying the material as a fluid mixture, and then converting the product to solid silicon. During the purification process a mixture of dichlorosilane (SiH2Cl2), trichlorosilane (SiHCl3), and tetrachlorosilane or silicon tetrachloride (SiCl4) are formed with each of the components in significant quantities. Models that describe the vapor–liquid equilibrium behavior for the mixtures are required to design appropriate separation and purification processes. Pure fluid properties form the starting point for most mixture models, hence the importance of vapor pressures for the pure materials. In this work we report measurements of the vapor pressures for three of the most important fluids in the silicon production process, dichlorosilane, trichlorosilane, and tetrachlorosilane. Our results are compared with measurements ...