Refractive indices and molar refractions of binary mixtures formed by some cyclic ethers and isomeric chlorobutanes

Refractive indices of binary mixtures formed by a cyclic ether (tetrahydrofuran or tetrahydropyran) and each of the isomeric chlorobutanes (1-chlorobutane, 2-chlorobutane, 1-chloro-2-methylpropane and 2-chloro-2-methylpropane) have been measured at two temperatures, 298.15?K and 313.15?K. From experimental data, refractive index deviations and molar refractions have been calculated. Furthermore, several common mixing rules have been used to predict refractive indices of the mixtures from their experimental densities reported previously.     

Surface study of mixtures containing cyclic ethers and isomeric chlorobutanes

Experimental surface tensions and the corresponding surface tensions deviations for the mixtures containing 1,3-dioxolane or 1,4-dioxane and 1-chlorobutane, 2-chlorobutane, 1-chloro-2-methylpropane or 2-chloro-2-methylpropane, measured with a drop volume tensiometer, are reported at the temperatures of 298.15 K and 313.15 K. The excess surface concentrations of isomeric chlorobutanes are also evaluated using a monolayer model.     

Solid-liquid equilibrium using the SAFT-VR equation of state: Solubility of naphthalene and acetic acid in binary mixtures and calculation of phase diagrams

A solid-liquid equilibrium (SLE) thermodynamic model based on the SAFT-VR equation of state (EOS) is presented. The model allows for the calculation of solid-liquid phase equilibria in binary mixtures at atmospheric pressure. The fluid (liquid) phase is treated with the SAFT-VR approach, where molecules are modelled as associating chains of tangentially bonded spherical segments interacting via square-well potentials of variable range. The equilibrium between the liquid and solid phase is treated following a standard thermodynamic method that requires the experimental temperature and enthalpy of fusion of the solute. The model is used to calculate the solubilities of naphthalene and acetic acid in common associating and non-associating organic solvents and to determine the solid-liquid phase behaviour of binary mixtures with simple eutectics. The SAFT-VR pure component model parameters are determined by comparison to experimental vapour pressure and saturated liquid density data with the choice of association models according to the nature of the molecule; in addition, an unlike adjustable parameter (k_ij) is used to model the solutions. The solubility data of naphthalene and acetic acid in both associating and non-associating solvents are reproduced essentially within the accuracy of the experimental measurements. The phase boundaries and the position of the eutectic points in the binary mixtures considered are, in most cases, reproduced with the accuracy commensurate with the industrial applications. Overall, the results presented show that the SAFT-VR EOS can be used with confidence for the prediction of the SLE of binary systems at atmospheric pressure.     

Surface tension of quantum fluids from molecular simulations

We present the first molecular simulations of the vapor-liquid surface tension of quantum liquids. The path integral formalism of Feynman was used to account for the quantum mechanical behavior of both the liquid and the vapor. A replica-data parallel algorithm was implemented to achieve good parallel performance of the simulation code on at least 32 processors. We have computed the surface tension and the vapor-liquid phase diagram of pure hydrogen over the temperature range 18-30 K and pure deuterium from 19 to 34 K. The simulation results for surface tension and vapor-liquid orthobaric densities are in very good agreement with experimental data. We have computed the interfacial properties of hydrogen-deuterium mixtures over the entire concentration range at 20.4 and 24 K. The calculated equilibrium compositions of the mixtures are in excellent agreement with experimental data. The computed mixture surface tension shows negative deviations from ideal solution behavior, in agreement with experimental data and predictions from Prigogine's theory. The magnitude of the deviations at 20.4 K are substantially larger from simulations and from theory than from experiments. We conclude that the experimentally measured mixture surface tension values are systematically too high. Analysis of the concentration profiles in the interfacial region shows that the nonideal behavior can be described entirely by segregation of H(2) to the interface, indicating that H(2) acts as a surfactant in H(2)-D(2) mixtures.     

Predicting mixture phase equilibria and critical behavior using the SAFT-VRX approach

The SAFT-VRX equation of state combines the SAFT-VR equation with a crossover function that smoothly transforms the classical equation into a nonanalytical form close to the critical point. By a combinination of the accuracy of the SAFT-VR approach away from the critical region with the asymptotic scaling behavior seen at the critical point of real fluids, the SAFT-VRX equation can accurately describe the global fluid phase diagram. In previous work, we demonstrated that the SAFT-VRX equation very accurately describes the pvT and phase behavior of both nonassociating and associating pure fluids, with a minimum of fitting to experimental data. Here, we present a generalized SAFT-VRX equation of state for binary mixtures that is found to accurately predict the vapor-liquid equilibrium and pvT behavior of the systems studied. In particular, we examine binary mixtures of n-alkanes and carbon dioxide + n-alkanes. The SAFT-VRX equation accurately describes not only the gas-liquid critical locus for these systems but also the vapor-liquid equilibrium phase diagrams and thermal properties in single-phase regions.     

Liquid mixtures of xenon with fluorinated species: xenon + sulfur hexafluoride

The vapor-liquid equilibrium of binary mixtures of xenon + SF6 has been measured at nine temperatures from 235.34 to 295.79 K and pressures up to 6.5 MPa. The mixture critical line is found to be continuous between the critical points of the pure components, and hence, the system can be classified as type I phase behavior in the scheme of van Konynenburg and Scott. The excess Gibbs free energies have been calculated, and the experimental results have been interpreted using the statistical associating fluid theory for potentials of variable range (SAFT-VR). Additionally, the SAFT-VR equation has been used to model other systems involving SF6 and alkanes, illustrating the predictability of the approach and further demonstrating the transferability of parameters between binary mixtures involving alkanes and xenon.     

Isobaric vapor–liquid equilibria for binary systems α-phenylethylamine + toluene and α-phenylethylamine + cyclohexane at 100 kPa

In this paper the results of the vapor–liquid equilibria study at 100 kPa are presented for two binary systems: α-phenylethylamine(1) + toluene (2) and (α-phenylethylamine(1) + cyclohexane(2)). The binary VLE data of the two systems were correlated by the Wilson, NRTL, and UNIQUAC models. For each binary system the deviations between the results of the correlations and the experimental data have been calculated. For the both binary systems the average relative deviations in temperature for the three models were lower than 0.99%. The average absolute deviations in vapour phase composition (mole fractions) and in temperature T were lower than 0.0271 and 1.93 K, respectively. Thermodynamic consistency has been tested for all vapor-liquid equilibrium data by the Herrington method. The values calculated by Wilson and NRTL equations satisfied the thermodynamics consistency test for the both two systems, while the values calculated by UNIQUAC equation didn’t.     

Experimental data of isobaric vapour–liquid equilibrium for binary mixtures containing tetrahydrofuran and isomeric chlorobutanes

Isobaric vapour–liquid equilibrium (VLE) measurements for mixtures formed by tetrahydrofuran and isomeric chlorobutanes at 40.0?kPa (except for the mixture containing 2-methyl-2-chloropropane) and 101.3?kPa are reported. The activity coefficients were calculated from experimental data. The mixture containing 2-chlorobutane at 40.0?kPa presents an azeotrope. The VLE measurements have been found thermodynamically consistent according to Van Ness test. Wilson, NRTL, and UNIQUAC equations have been used to correlate the activity coefficients and we have obtained satisfactory results.     

Isothermal measurements of vapor-liquid equilibria for three n-alkane-chloroalkane mixtures

Results of isothermal vapor-liquid equilibrium (VLE) measurements for 1-chlorobutane with n-hexane and n-heptane at three temperatures and for 1,2-dichloroethane with n-heptane at two temperatures are reported.New constants of the Antoine vapor pressure equation for 1,2-dichloroethane are presented. The consistency of the new vapor-pressure data with published experimental data of heat of vaporization is checked.The VLE data are used for the determination of group interaction parameters of UNIFAC and of the quasichemical group surface interaction model (QUAGSIM).     

甲醇—乙醇—水—盐体系的等压气液平衡

木文采用CPⅡ型沸点仪测定了在93.33kPa下甲醇-乙醇-水-盐(NaCl,NaBr,Nal,LiCl,CaCl_2)体系的气液平衡数据。实验证明,当三元混合溶剂的相对组成固定时,体系的沸点与加入的盐量呈线性关系,用热力学理论导出了该线性方程,用Gibbs相律探讨了该线性关系的起因。     

Thermodynamic behaviour of ethanol+methanol+2-ethoxy-2-methylpropane system. Physical properties and phase equilibria

The densities, refractive indices and speeds of sound of ternary ethanol+methanol+2-ethoxy-2-methylpropane (ETBE) mixtures were determined at 298.15 K and atmospheric pressure, and were used to calculate the corresponding excess molar volumes and the deviations of the molar refractive index and isentropic compressibility from linear dependence on concentration. These excess and deviational quantities were best predicted by the equations of Radojkovic, Kohler and Jacob and Fitzner. Vapour–liquid equilibrium (VLE) data were obtained for the ternary system at 101.32 kPa, shown to pass thermodynamic consistency tests, correlated by means of the equations Wilson, NRTL and UNIQUAC, and compared with the results predicted by the ASOG-KT and original and modified UNIFAC methods and by the equations of Wilson, NRTL and UNIQUAC with interaction parameters obtained from data for the relevant binary systems. The agreement between the experimental data and the latter predictions was as good as was achieved by ASOG-KT and UNIFAC-Dortmund, which were the best of the group contribution methods.     

极性非质子溶剂与甲醇或1,2-二氯乙烷的汽液平衡

使用双沸点仪测定了丙酮、乙酸乙酯、对二氧六环、乙腈或三乙胺与甲醇或1,2→二氯乙烷以及二者混合物等十一组二元体系在99.3 kPa下的汽液平衡数据(T,x,p), 计算了有关体系的过量吉布斯自由能。结果表明, 六种非质子溶剂与甲醇组成的二元系GE>0; 乙腈或三乙胺与1,2-二氯乙烷组成的二元系GE>0, 而丙酮、乙酸乙酯或对二氧六环与1,2-二氯乙烷的二元混合物GE<0。从同种分子间或不同种分子间的缔合作用对上述结果进行了讨论。本文还在固定极性非质子溶剂(第三组分)物质的量浓度的条件下, 测定了非质子溶剂+1,2-二氯乙烷+甲醇三元混合物的汽液平衡数据, 考察了非质子溶剂的加入对甲醇+1,2-二氯乙烷二元系GE的影响。     

Pressure dependence of the vapor-liquid-liquid phase behavior in ternary mixtures consisting of n-alkanes, n-perfluoroalkanes, and carbon dioxide

Expansion of an organic solvent by an inert gas can be used to tune the solvent's liquid density, solubility strength, and transport properties. In particular, gas expansion can be used to induce miscibility at low temperatures for solvent combinations that are biphasic at standard pressure. Configurational-bias Monte Carlo simulations in the Gibbs ensemble were carried out to investigate the vapor-liquid-liquid equilibria and microscopic structures for two ternary systems: n-decane/n-perfluorohexane/CO2 and n-hexane/n-perfluorodecane/CO2. These simulations employed the united-atom version of the transferable potential for phase equilibria (TraPPE-UA) force field. Initial simulations for binary mixtures of n-alkanes and n-perfluoroalkanes showed that special mixing parameters are required for the unlike interactions of CHx and CFy pseudoatoms to yield satisfactory results. The calculated upper critical solution pressures for the ternary mixtures at a temperature of 298 K are in excellent agreement with the available experimental data and predictions using the SAFT-VR (statistical associating fluid theory of variable range) equation of state. The simulations yield asymmetric compositions for the coexisting liquid phases and different degrees of microheterogeneity as measured by local mole fraction enhancements.     

Surface and bulk behaviour of some (n-hexane + chloroalkane) mixtures

Surface tensions at the temperatures of (283.15, 288.15, 293.15, 298.15, 303.15, 308.15, and 313.15) K and isothermal (vapour + liquid) equilibrium at the temperatures of (288.15, 298.15, and 308.15) K of n-hexane with 1-chlorobutane or 1-chloropentane mixtures have been measured. Surface tension measurements were carried out with a drop volume tensiometer while the (vapour + liquid) equilibrium was obtained using an all-glass dynamic recirculating type still. Several bulk thermodynamic properties of the studied mixtures have been used together with the experimental measurements to analyse the results. Furthermore, a thermodynamic study of surface formation, including interesting properties such as excess surface compositions and excess properties of surface formation, is also presented.     

A modified clausius equation of state for calculation of multicomponent refrigerant vapor-liquid equilibria

Gow, A.S., 1993. A modified Clausius equation of state for calculation of multicomponent refrigerant vapor-liquid equilibria. Fluid Phase Equilibria, 90: 219-249.

A modified Clausius equation of state with a single temperature dependent energy-volume parameter a(T) in the attractive term was designed to describe the vapor pressure vs. temperature relationship of 39 pure refrigerant fluids including elementary cryogenic materials (e.g. He, Ar, N₂, CO₂, CH₄, etc.), chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), hydrochlorofluorocarbons (HCFCs), fluorocarbons (FCs), and various other simple cryogenic compounds. The equation developed represents the vapor-liquid coexistence dome, and the superheated vapor compressibility factor and enthalpy for pure refrigerants.

The vapor-liquid equilibrium for refrigerant mixtures is calculated using a “phi-phi” method with “one fluid” van der Waals mixing and combining rules for the equation of state parameters a_M(T), b_M and c_M. A single interaction constant k₁₂ is used to describe non-ideal behavior of each binary. The binary interaction constant, which is a strong function of temperature, and the sign of which signifies the type of deviations from Raoult's law, is obtained by correlating experimental bubble point data for isothermal binary refrigerant mixtures. The proposed equation of state generally describes binary P-x,y data more accurately the higher the temperature for a given system. The method presented is extended to predict vapor-liquid equilibria for the R14-R23-R13 ternary system at 198.75 K using binary interaction constants at this temperature for the three binaries involved.     

Modeling the phase behavior of H2S+n-alkane binary mixtures using the SAFT-VR+D approach

A statistical associating fluid theory for potential of variable range has been recently developed to model dipolar fluids (SAFT-VR+D) [Zhao and McCabe, J. Chem. Phys. 2006, 125, 104504]. The SAFT-VR+D equation explicitly accounts for dipolar interactions and their effect on the thermodynamics and structure of a fluid by using the generalized mean spherical approximation (GMSA) to describe a reference fluid of dipolar square-well segments. In this work, we apply the SAFT-VR+D approach to real mixtures of dipolar fluids. In particular, we examine the high-pressure phase diagram of hydrogen sulfide+n-alkane binary mixtures. Hydrogen sulfide is modeled as an associating spherical molecule with four off-center sites to mimic hydrogen bonding and an embedded dipole moment (micro) to describe the polarity of H2S. The n-alkane molecules are modeled as spherical segments tangentially bonded together to form chains of length m, as in the original SAFT-VR approach. By using simple Lorentz-Berthelot combining rules, the theoretical predictions from the SAFT-VR+D equation are found to be in excellent overall agreement with experimental data. In particular, the theory is able to accurately describe the different types of phase behavior observed for these mixtures as the molecular weight of the alkane is varied: type III phase behavior, according to the scheme of classification by Scott and Konynenburg, for the H2S+methane system, type IIA (with the presence of azeotropy) for the H2S+ethane and+propane mixtures; and type I phase behavior for mixtures of H2S and longer n-alkanes up to n-decane. The theory is also able to predict in a qualitative manner the solubility of hydrogen sulfide in heavy n-alkanes.