Vapor Pressures Of Solutions Research Articles

Measurement and Prediction of Vapor Pressure for H2O+CH3OH/C2H5OH+[BMIM][DBP] Ternary Working Fluids

The ionic liquid, 1-butyl-3-methylimidazolium dibutylphosphate ([BMIM][DBP]) was prepared and the vapor pressures of three set of binary solutions H2O(1)/CH3OH(1)/C2H5OH(1)+[BMIM][DBP](2) were measured at different temperature and in the ILs mole fraction range from 0.1 to 0.6 with a static equilibrium apparatus. The measured vapor pressures were correlated with Non-Random Two Liquid (NRTL) activity coefficient model and the average relative deviations (ARD) between experimental and correlated vapor pressures for these binary solutions were 3.19%, 2.42% and 2.95%, respectively. Then, the vapor pressures of two set of ternary solutions H2O(1)+CH3OH(2)/C2H5OH(2)+[BMIM][DBP](3) were measured with an inclined boiling apparatus and further predicted with NRTL activity coefficient model based on the binary interaction parameters coming from fitting the vapor pressures of the binary solutions. The results indicated that the ternary solutions containing [BMIM][DBP] were shown a strong negative deviation from Raoult's Law when the mole fraction of [BMIM][DBP] was larger than 0.2, which meant that ternary solutions could absorb the refrigerant vapors at the same or below solution temperature. Meanwhile, the average relative deviations between experimental and predicted vapor pressures for ternary solutions were 2.92% and 3.06%, respectively. Consequently, the NRTL active coefficient model used for non-electrolyte solutions was still valid for predicting vapor-liquid equilibrium of binary or ternary solutions containing ILs.

Experimental Analysis of Effects of Non-Structural Factors on Performance of Liquid-Gas Ejector Driven by Aqueous LiBr Solution

Miniaturization and high-efficiency plays an important role in the further development of absorption refrigeration. In order to improve the mass transfer efficiency, liquid-gas ejector is intended to be used in refrigeration system. Experimental analysis of effects of non-structural factors on Liquid-Gas Ejector driven by aqueous LiBr solution is presented. Solution concentration, solution temperature, evaporator temperature and back pressure are varied to analyze the ejector performance. The results show that the large difference between refrigerant vapor pressure and partial pressure of solution enhances absorption of water into aqueous lithium bromide solution. The optimal solution concentration range is 56.61wt%~57.61wt% when the throat diameter of convergent-divergent nozzle is 1.5mm. Cooling capacity increases with the decreasing of back pressure.

The Pressure Differential Analysis of LiCl Solution Absorption Process

To improve indoor air quality, mass transfer is an important part in air handling process, which is helpful for the control of humidity of air. This paper presents mass transfer dynamic analysis of isothermal and opposite flow process theoretically. The pressure difference analysis is used to show the changing of pressures of two phases in dehumidification process. It calculates the partial pressure of water vapor in wet air and the vapor pressure of LiCl solution. Also it gives the curves of pressure change in dehumidification of isothermal and opposite flow by lithium chloride. Results from this paper can be used as theoretical foundation for the experimental design of dehumidification of air by LiCl solution.

Absorption kinetics of carbon dioxide into aqueous ammonia solution: Addition of hydroxyl groups for suppression of vaporization

Aqueous ammonia can act as an alternative absorbent for CO2 removal, but it has high volatility and reduces the ammonia concentration. We analyzed the hydroxyl additives 2-amino-2-methyl-1-propanol (AMP), ethylene glycol, and glycerol to reduce the vapor pressure of ammonia solutions. In addition, absorption efficiency groups of aqueous ammonia solutions containing hydroxyl additives were investigated. The results show that the addition of AMP, ethylene glycol, or glycerol to NH3 reduced the vapor pressure of the absorbent by 14.0%, 22.7%, and 75.2%, respectively. The reaction rate constants of aqueous NH3 containing AMP, ethylene glycol, and glycerol additives at 293, 303, 313 and 323 K are given by k2, NH3/AMP=4.565×10 5 exp(�1396.5/T), k2, NH3/ethylene glycol=1.499×10 6 exp(�1978.7/T) and k2, NH3/glycerol= 7.078×10 6 exp(� 2413.3/T), respectively.

Modeling of Strong Electrolytes with ePPC-SAFT up to High Temperatures

An extension of the PPC-SAFT equation of state to treat strong electrolyte aqueous solutions is presented. It is capable of describing the behavior of such systems up to 473 K with a good precision and without requiring temperature-dependent model parameters. Long-range Coulombic interactions are taken into account using the mean spherical approximation (MSA) for a primitive model of the electrolyte solution, and the effect of solvation is described using short-range ion–water interactions mediated through association sites. Pairing between anions and cations is also treated through site–site interactions. A Born term is added to describe the change of dielectric constant resulting from solvation. A single ion-specific, temperature-independent model parameters are used, for 20 alkali-halide aqueous solutions. The Pauling ionic diameters are used for all terms (hard sphere, MSA, and Born). The dispersion energy of the ions is considered negligible. In the resulting ePPC-SAFT model, only the water–ion association energy is considered as an adjustable parameter. The results show coherent energy density behavior with respect to ionic size. The approach allows the calculation of the mean ionic activity coefficient, density, or vapor pressure of the aqueous solutions over a wide range of temperatures and molalities (298–573 K and 0–6 m). Moreover, salting out of carbon dioxide and methane in saline water can also be predicted accurately. A discussion of the changes in ion hydration at different salinity is also presented taking advantage of the model proposed that explicitly includes ion–water site–site interactions.

Application of the SAFT-VR equation of state in estimation of physiochemical properties of amino acid solutions

In the present study, the SAFT-VR equation of state has been utilized to examine the phase behavior of aqueous and aqueous-electrolyte solutions of amino acids and simple peptides. The main distinguishing feature of this model, is taking into account the range of interactions as a variable, in addition to other intrinsic qualities of these biomolecules such as diameter, number of segments per chain, energy of interaction and energy and volume of association. At the first stage of the simulation process, the optimized molecular parameters of water, amino acids and simple peptides are respectively obtained by correlating the experimental data of vapor pressure and activity coefficients. Subsequently, the solubility of amino acids in a wide range of temperature is correlated by means of enthalpy and entropy of dissolvation as the adjustable parameters. Afterwards, influence of pH variation on the solubility of amino acids and the phase behavior of one amino acid in the presence of another are predicted. Regarding the importance of equilibrium vapor pressure of aqueous solutions of amino acids in designing the separation units, activity and vapor pressure of water are also predicted. In the next step, the optimized molecular parameters of electrolytes are calculated by correlating the experimental mean ionic activity coefficient data and consequently the activity coefficients and solubility of amino acids in aqueous-electrolyte solutions are predicted.

Vapor pressures of aqueous blended-amine solutions containing (TEA/AMP/MDEA) + (DEA/MEA/PZ) at temperatures (303.15–343.15) K

In this study, a new set of data on the vapor pressure of aqueous blends of the most industrially important amines monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), methyldiethanolamine (MDEA), 2-amino-2-methyl-1-propanol (AMP), and piperazine (PZ) were presented. The blended-amines systems are mixtures of (TEA/AMP/MDEA)+(MEA/DEA/PZ), at total amine concentration=30wt% (10wt% amine 1+20wt% amine 2). Experimental data were obtained at atmospheric pressure and temperatures (303.15–343.15)K using a vapor pressure measurement apparatus. The apparatus consisted mainly of a degassing system and a vapor pressure measurement setup where the equilibrium experiment was performed. The vapor pressures of aqueous solutions of each of the six single-amine systems were also presented. Results showed that the addition of amine in water lead to the lowering of the vapor pressure. The vapor pressure increased with increasing temperature, and decreased with increasing mole fraction of amine in the solution. The vapor pressure data were correlated with temperature using the reliable Antoine equation, which yield an average absolute deviation of 0.09% for the aqueous single-amine systems, and 0.13% for the aqueous blended amine systems. The results presented in this work can be applied in engineering design calculations to have reliable vapor pressure estimates for the investigated amine systems in the temperature range (303.15–343.15)K.

Application of modified PHSC model in prediction of phase behavior of single and mixed electrolyte solutions

The modified perturbed hard sphere chain (e-PHSC) equation of state (EoS) has been used for correlation and prediction of thermo-physical properties of single and mixed aqueous electrolyte solutions. In order to take electrostatic contribution into account, the primitive mean spherical approximation (MSA) term has been utilized. The proposed electrolyte equation of state (e-EOS) has two ion-based parameters per each ion. Ion specific parameters were obtained by simultaneous adjustment using mean ionic activity coefficient (MIAC) and solution liquid density experimental data of single electrolyte solutions. In order to check the accuracy of the model, water activity, osmotic coefficient and vapor pressure of single electrolyte solutions have been calculated using adjusted parameters. Finally water activities, MIACs, solution liquid densities, osmotic coefficients and vapor pressures of various mixed electrolyte solutions were predicted. The results showed that using e-PHSC model, MIACs, osmotic coefficient, water activity and vapor pressure and liquid density of mixed electrolyte solutions up to 6.5, 10, 10, 10 and 5 of ionic strength can be well predicted without any additional adjustable parameters.

Thermodynamics of liquid-gas phase equilibria in the dipropylsulfoxide-water system in the range of 303.15 to 323.15 K

The saturation vapor pressure of pure dipropylsulfoxide (DPSO) is measured in the temperature range of 303.15 to 323.15 K. The boiling point of DPSO under normal pressure (479.15 K) is determined and the molar heat of vaporization of DPSO is calculated (ΔvH○ = 61.4 ± 3.1 kJ/mol) on the basis of data obtained via graphical extrapolation. The total saturation vapor pressure of aqueous solutions of DPSO of various concentrations at 303.15 and 308.15 K is measured. Partial pressures, the activity coefficients of DPSO and H2O, and the excess Gibbs energy of mixing are calculated on the basis of the obtained results.

The Water–18-Crown-6 System: Experimental Investigation and Thermodynamic Modeling

Vapor pressures of binary aqueous solutions containing 18-crown-6 over a wide concentration range up to saturation were measured at (293.15 and 298.15) K, and activities of solvent were calculated. Melting enthalpies of 18-crown-6 octa- and dodecahydrates have been determined by the differential scanning calorimetry (DSC) method. The new experimental data and previously published literature data (activities of water, enthalpies of dilution, and solubility data) were used for thermodynamic modeling of the water–18-crown-6 system. As a result the phase diagram of the water–18-crown-6 system was constructed using the universal quasichemical (UNIQUAC) expression for the excess Gibbs energy of the liquid phase.

A study of the evaporation of a solvent from a solution—Application to writing ink aging

When writing ink is placed on a substrate, a drying process begins. This process is dependent on the composition of the ink and of the substrate. Lociciro et al. provide an equation that describes the drying process based on models developed by earlier investigators. The work given here develops an equation for the drying process that is based on a different and rather simple model. This model considers the evaporation of a solution in an opened vertical container (e.g., a beaker) and consists of a volatile, non-hygroscopic solvent with a non-volatile solute dissolved in it. Three assumptions are made: (a) the rate of evaporation is proportional to the vapor pressure of the solution and to the solution's exposed surface area, (b) this solution vapor pressure is proportional to the solvent vapor pressure with the proportionality constant being the solvent mole fraction (Raoult's law), and (c) a small fraction of the solvent remains trapped in the solute after evaporation ceases. What results is a differential equation, which, when solved, gives the solvent weight W(t) as an implicit function. What emerges naturally from this treatment is the fact that the function W(t) can have a point of maximum acceleration. Prior to this point the drying process is fast and after this point, the drying process is slow. An approximation to W(t) is taken to be the sum of two exponential functions, one describing the fast drying region and the second describing the subsequent slow drying region. Upon including an additive constant, this approximation turns out to be similar to, but not the same as that provided by Lociciro et al. However, their equivalence is shown and then tested using the two inks examined by Lociciro et al. (the drying of a Bic and a Staedtler blue ballpoint ink). The examples of (solvent+solute) systems ("inks") given here consist of the solvent (2-phenoxyethanol) and a solute such as a dye (crystal violet) or a polymer resin such as synthetic resin SK or polyvinyl butyral. In the case of polymers, the Raoult's law assumption is replaced with one developed by the Flory-Huggins theory of solutions. Saturation and film formation, both of which slow the evaporation rate, are also discussed.

Vapor Pressure of Saturated Aqueous Solutions of Potassium Sulfate from 310 K to 345 K

The experimental evaluation of the vapor pressure of saturated aqueous solutions of potassium sulfate was carried out in the range of temperatures 310 K≤T≤345 K. The experimental data were used to determine the corresponding values of the water activity in such solutions. The analytical expressions as a function of temperature of both, vapor pressure and water activity, were obtained from the correlation of the experimental results. The vapor pressure expression was also extrapolated to a different temperature range in order to make a comparison with the results obtained by other authors.

(Vapour + liquid) equilibria, volumetric and compressibility behaviour of binary and ternary aqueous solutions of 1-hexyl-3-methylimidazolium chloride, methyl potassium malonate, and ethyl potassium malonate

(Vapour + liquid) equilibrium data (water activity, vapour pressure, osmotic coefficient, and activity coefficient) of binary aqueous solutions of 1-hexyl-3-methylimidazolium chloride ([C 6mim][Cl]), methyl potassium malonate, and ethyl potassium malonate and ternary {[C 6mim][Cl] + methyl potassium malonate} and {[C 6mim][Cl] + ethyl potassium malonate} aqueous solutions were obtained through the isopiestic method at T = 298.15 K. These results reveal that the ionic liquid behaves as surfactant-like and aggregates in aqueous solutions at molality about 0.4 mol · kg −1. The constant water activity lines of all the ternary systems investigated show small negative deviations from the linear isopiestic relation (Zdanovskii–Stokes–Robinson rule) derived using the semi-ideal hydration model. The density and speed of sound measurements were carried out on solutions of methyl potassium malonate and ethyl potassium malonate in water and of [C 6mim][Cl] in aqueous solutions of 0.25 mol · kg −1 methyl potassium malonate and ethyl potassium malonate at T = (288.15 to 308.15) K at atmospheric pressure. From the experimental density and speed of sound data, the values of the apparent molar volume, apparent molar isentropic compressibility and excess molar volume were evaluated and from which the infinite dilution apparent molar volume and infinite dilution apparent molar isentropic compressibility were calculated at each temperature. Although, there are no clear differences between the values of the apparent molar volume of [C 6mim][Cl] in pure water and in methyl potassium malonate or ethyl potassium malonate aqueous solutions, however, the results show a positive transfer isentropic compressibility of [C 6mim][Cl] from pure water to the methyl potassium malonate or ethyl potassium malonate aqueous solutions. The results have been interpreted in terms of the solute–water and solute–solute interactions.

Generalized Electrolyte-UNIQUAC-NRF model for calculation of solubility and vapor pressure of multicomponent electrolytes solutions

The Electrolyte-UNIQUAC-NRF model proposed by Haghtalab and Peyvandi, Fluid Phase Equilib., 281, 2009 is modified and extended to represent the excess Gibbs energy function of multicomponent electrolyte solutions. Using the experimental mean activity coefficient of aqueous binary electrolyte systems in the extensive domain of temperature and molality, the adjustable temperature dependent parameters are obtained for the several binary electrolyte systems. Furthermore, the osmotic coefficient and vapor pressure of some binary systems are predicted at the wide range of temperature and molality using the adjustable parameters. Having the binary interaction parameters, the solubility of electrolytes in ternary aqueous electrolyte solutions are predicted at 298 K and the higher temperatures so that the phase diagram of the salt solubility are obtained for the several ternary aqueous-salt systems. The results of the solubility, osmotic coefficient and vapor pressure for the electrolyte systems demonstrate that the generalized Electrolyte-UNIQUAC-NRF model can be successfully applied for prediction of the thermodynamic properties of multicomponent electrolyte systems with very good accuracy.

Water Activities in Binary and Ternary Aqueous Systems of Poly(ethylene glycol) Dimethyl Ether 2000 and Poly(propylene glycol) 400 at T = (298.15, 308.15, and 318.15) K

Isopiestic measurements were used to obtain activities for aqueous solutions of poly(ethylene glycol) dimethyl ether 2000 + poly(propylene glycol) 400 and their corresponding binary aqueous solutions at temperatures T = (298.15, 308.15, and 318.15) K. The data obtained were used to calculate the vapor pressure of solution as a function of concentration. The effect of temperature on the vapor–liquid equilibrium (VLE) of binary and ternary systems has been studied. Furthermore, the activity results for binary and ternary aqueous solutions were correlated to the Flory–Huggins and Wilson models.

Osmotic and activity coefficients in the binary solutions of 1-butyl-3-methylimidazolium chloride and bromide in methanol or ethanol at T=298.15K from isopiestic measurements

Abstract Osmotic coefficients of the binary solutions of two room-temperature ionic liquids (1-butyl-3-methylimidazolium chloride and bromide) in methanol and ethanol have been measured at T = 298.15 K by the isopiestic method. The experimental osmotic coefficient data have been correlated using a forth-order polynomial in terms of (molality)0.5, with both, ion interaction model of Pitzer and electrolyte non-random two liquid (e-NRTL) model of Chen. The values of vapor pressures of above-mentioned solutions have been calculated from the osmotic coefficients. The model parameters fitted to the experimental osmotic coefficients have been used for prediction of the mean ionic activity coefficients of those ionic liquids in methanol and ethanol.

Modeling of the Thermodynamic Properties of Aqueous Ionic Liquid Solutions with an Equation of State for Square-Well Chain Fluid with Variable Range

A new thermodynamic model based on an equation of state for square-well chain fluid with variable range (SWCF-VR) is proposed to describe the thermodynamic properties of aqueous solutions of ionic liquids. In this approach the electrostatic interactions are characterized via the mean spherical approximation and the ionic associations between the cations and anions of the ionic liquid are considered through the shield-sticky approach. The liquid densities, osmotic coefficients, and vapor pressures of aqueous solutions of nine ionic liquids (ILs) containing [Cxmim][Br] (x = 2, ..., 6), [C4mim][BF4] and [Cxmim][MSO4] (x = 1, 3, 4) have been modeled with the new model. Two ionic parameters for each anion and three for each cation of the ionic liquids were adjusted to experimental liquid densities and osmotic coefficients, and the corresponding average deviations are only 0.87% and 2.49%, respectively. Using the same ionic parameters, the vapor pressures of ionic liquid solutions are accurately predicted. The ...

Osmotic and activity coefficient of 1-ethyl-3-methylimidazolium chloride in aqueous solutions of tri-potassium phosphate, potassium carbonate, and potassium chloride at [formula omitted

Vapour–liquid equilibrium data (water activity, vapour pressure, osmotic coefficient, and activity coefficient) of the mixed electrolyte aqueous solutions, 1-ethyl-3-methylimidazolium chloride, (EmimCl) + tri-potassium phosphate, EmimCl + potassium carbonate, EmimCl + potassium chloride and their corresponding binary aqueous solutions have been measured by the isopiestic method at a temperature of 298.15 K. The osmotic coefficients for binary aqueous solutions were correlated to the Pitzer, modified Pitzer and TCPC models. The osmotic coefficient of mixed electrolyte with common anion was correlated to the Pitzer model. From these data, the corresponding mean activity coefficients, γ ± , have been calculated. The activity coefficients of mixed electrolytes were calculated by Scatchard’s neutral electrolyte method. A modified Pitzer model has been used to predict the osmotic and activity coefficients of mixed electrolyte solution with common anion.

Matrix assisted pulsed laser evaporation: the surface cluster problem

The unexpected presence of agglomerates in polymer films deposited by the Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique is discussed. Many experimental and theoretical works suggest that the simple model of individual molecule evaporation must be abandoned. Solute concentration, boiling temperature and vapor pressure of solvents, laser pulse number, and laser light penetration depth are important parameters to be considered to explain the morphology of the MAPLE deposited films. Nanorods films, which can be efficiently deposited on rough surfaces using the MAPLE technique, present more or less large surface droplets, also. Here, the reduced melting temperature of nanostructured materials can explain agglomeration even at low laser fluences.

Viscosity, vapour pressure and electronmicroscope studies of aqueous solutions of polyvinylpyrrolidone

Viscosity, vapour pressure and electronmicroscope studies of aqueous solutions of polyvinylpyrrolidone