Thermodynamische Untersuchungen ann-Alkan/n-Alkin-Systemen

The vapour-liquid equilibrium data obtained from isobarict-x-measurements have been used for calculation of the group UNIFAC parameters and excess free enthalpyG ^E of binary mixturesn-alkanes with isomericn-alkynes. The UNIFAC model gives satisfactory predictions for the systems studied. The temperature dependence ofG ^E was estimated on the basis of the heats of mixing measured earlier. The influence of the position of triple bond in the molecules ofn-alkynes on the excess thermodynamic functions is considered.

     

Application of a generalized van der Waals equation of state to several nonpolar mixtures

A generalized van der Waals equation of state, applied recently (Nguyen Van Nhu and Kohler, 1995) to the calculation of excess properties and phase equilibria for the mixture methane + ethane, is now extended to several nonpolar binary mixtures.Improved mixing rules for the van der Waals attractive term and for the correction term are proposed. With these mixing rules, the equation gives good agreement for vapour-liquid and liquid-liquid equilibria over a large temperature range for 29 binary mixtures. The agreement of mixture volumes and cross second virial coefficients is also satisfactory.     

New mixing rules in simple equations of state for representing vapour-liquid equilibria of strongly non-ideal mixtures

Huron, M.-J. and Vidal, J., 1979. New mixing rules in simple equations of state for representing vapour-liquid equilibria of strongly non-ideal mixtures. Fluid Phase Equilibria, 3: 255-271.Good correlations of vapour-liquid equilibria can be achieved by applying the same two-parameter cubic equation of state to both phases. The results primarily depend on the method used for calculating parameters and, for mixtures, on the mixing rule. True parameters are the covolume b and the energy parameter a/b. For this latter one, deviations from a linear weighting rule are closely connected to the excess free energy at infinite pressure. Thus any mixing rule gives a model for the excess free energy, or any accepted models for this property can be used as mixing rules.From the above, an empirical polynomial mixing rule is used for data smoothing and evaluation, while for practical work a local composition model is used. The mixing rule thus obtained can be reduced to the classical quadratic rule for some easily predicted values of the interaction energies. For highly polar systems, it includes three adjustable parameters. Using literature data, the new mixing rule is applied, in the low and high pressure range, to binary mixtures with one or two polar compounds, giving good data correlation and sometimes avoiding false liquid-liquid immiscibility.     

Modelling of the three phase LLV region for ternary hydrocarbon mixtures with the Soave-Redlich-Kwong equation of state

The prediction of the three phase liquid-liquid-vapour (L2L1V) region for the ternary mixtures ethane + propane + eicosane (C2 + C3 + C20) and methane + ethane + eicosane (C1 + C2 + C20) was performed using the Soave-Redlich-Kwong equation of state. A procedure for finding K- and L-points is presented. It is based on the solution of thermodynamic conditions for the K- and L-point using the Newton iteration technique with carefully chosen starting points. The calculations were performed with all binary interaction parameters set to zero and with binary interaction parameters fitted to vapour-liquid equilibrium data of the binary subsystems. In the latter case for all binary subsystems two adjustable parameters with classical mixing rules were used. The results obtained show only qualitative agreement with experimental data for both sets of interaction parameters.     

Measurements of vapour-liquid equilibria,densities, viscosities and dielectric properties of cyclohexanone + triethylamine mixtures with respect to keto-enol tautomerism

Densities, ?, kinematic viscosities ν, refractive indices n_D referred to the sodium D-line, static relative permittivities ε, specific conductances κ and vapour-liquid equilibrium data for cyclohexanone + triethylamine mixtures have been determined at two temperatures. Excess properties of mixing calculated from these data indicate that in such mixtures considerable amounts of enol-amine associates are formed. The permittivity data indicate that the formation of associates is an exothermic process, which also has a marked influence on the thermodynamic excess properties of the mixtures. The enol-amine associates may undergo electrolytic dissociation. A common evaluation of static relative permittivities and specific conductances shows that for the mixture the conductance data are affected considerably by the formation of undissociated ion pairs in the sense of Bjerrum theory, especially at concentrations of the mixture where it is less polar. The conductance data are also influenced considerably by the fact that the ion pairs are solvated if the molar ratio of triethylamine exceeds 0.5.     

New Thermodynamic Consistency Test for Isobaric Vapour-Liquid Equilibrium Data

A thermodynamic consistency test for the vapour-liquid equilibrium data obtained under isobaric conditions is proposed. According to this procedure, the coexistence equation with correction term for the nonideality of the vapour phase was used. The differential equation has two singulier points and was solved by numerical integration according to the method predictor-corrector Adams combined with the classical Runge-Kutta method. The nonideality of the vapour phase is considered by using the second coefficients from the virial equation of state. The residuals of the vapour phase obtained as differences between the calculated, respectively experimental values were statistically analysed to detect systematic and random errors. In this order Student and Abbe tests were used. A study of the influence of the method and the step of the integration is also presented. In this order Runge-Kutta and Adams methods were compared and for the estimation of the second virial coefficients different published procedures have been taken into account. In this paper the method of Tsonopoulos and Hayden - O'Connell are taken into account. A correlation analysis is performed to evaluate the results of this study. This revised version was published online in July 2006 with corrections to the Cover Date.     

The mixing properties of hexafluorobenzene with carbon tetrachloride and with perfluoromethylcyclohexane

Excess thermodynamic functions (free energies, enthalpies and entropies of mixing) have been obtained from measurements of vapour pressures, together with excess volumes of mixing, for mixtures of hexafluorobenzene with carbon tetrachloride and with perfluoromethyl-cyclohexane (tetradecafluoromethylcyclohexane). Deviations from thermodynamic ideality are large, although the systems are completely miscible. Critical temperatures of the mixtures are also reported. A correlation between the data, anticipated from a simple model for mixtures of asymmetric molecules, does not obtain.     

含醇溶液的热力学研究Ⅱ.醇的水溶液的超额焓

提出了一个醇与水混和的热力学模型，它由三步组成，分别考虑了醇与水的物 理混合，醇和水的自缔合破坏以及它们间的交叉缔合．据此建立了一个超额焓方程 ．检验的结果表明，它能满意地描述含醇水溶液的超额焓随组成和温度的变化规律．     

Density functional theory study on the structure and capillary phase transition of a polymer melt in a slitlike pore: effect of attraction

A density functional theory is proposed to investigate the effects of polymer monomer-monomer and monomer-wall attractions on the density profile, chain configuration, and equilibrium capillary phase transition of a freely jointed multi-Yukawa fluid confined in a slitlike pore. The excess Helmholtz energy functional is constructed by using the modified fundamental measure theory, Wertheim's first-order thermodynamic perturbation theory, and Rosenfeld's perturbative method, in which the bulk radial distribution function and direct correlation function of hard-core multi-Yukawa monomers are obtained from the first-order mean spherical approximation. Comparisons of density profiles and bond orientation correlation functions of inhomogeneous chain fluids predicted from the present theory with the simulation data show that the present theory is very accurate, superior to the previous theory. The present theory predicts that the polymer monomer-monomer attraction lowers the strength of oscillations for density profiles and bond orientation correlation functions and makes the excess adsorption more negative. It is interesting to find that the equilibrium capillary phase transition of the polymeric fluid in the hard slitlike pore occurs at a higher chemical potential than in bulk condition, but as the attraction of the pore wall is increased sufficiently, the chemical potential for equilibrium capillary phase transition becomes lower than that for bulk vapor-liquid equilibrium.     

多功能沸点仪的研究

本文提出了两种新型沸点仪——CP-Ⅰ型和CP-Ⅱ型沸点仪, 阐述了仪器各部分结构的设计思想和原理, 并对仪器的性能和各部分功能进行了较为完整的实验考核, 获得了预期的效果。     

The prediction of vapor-liquid equilibrium data from heat of mixing data for three non-ideal binary systems

The method of Hanks et al. was used with the heat of mixing data of McFall et al. for 1,3-butadiene + propylene, 1-butene + methyl tert.-butyl ether, and carbon disulfide + methanol to predict the vapor-liquid equilibrium behavior for these systems. The method involves curve-fitting an excess enthalpy model derived from an excess Gibbs energy model by means of the Gibbs-Helmholtz equation to the heat of mixing data, determining the adjustable parameters from this fit, and using the original excess Gibbs function equation to predict the vapor-liquid equilibrium behavior. The predicted vapor-liquid equilibrium values were compared with experimental values and good agreement was found.     

含醇溶液的热力学研究I.超额焓模型

提出了一个醇与烃混合的热力学模型,据此,得到了一个简单的超额焓方程, 它由物理和化学贡献两部分组成。这个方程具有一定的通用性,能够推广到其它含 醇溶液。方程不仅能满意地用来描述超额焓与组成间的关系,而且还能显示组分间 的相互作用。     

Vapour-liquid equilibria in nonpolar mixtures : II. Carbon tetrachloride with alkylbenzenes and n-alkanes at 313.15 K

Góral, M. and Zawadzki, S., 1993. Vapour-liquid equilibria in nonpolar mixtures. II. Carbon tetrachloride with alkylbenzenes and n-alkanes at 313.15 K. Fluid Phase Equilibria, 90: 355-364.

Total vapour pressure measurements using a modified static method at 313.15 K are reported for binary mixtures of CCl₄ with benzene, toluene, o-xylene, p-xylene, hexane, heptane, octane, nonane and decane. The results were correlated with the generalized Redlich-Kister equation for excess Gibbs energy. A comparison with literature vapour-liquid equilibrium data and excess enthalpy was made. Consistency within homologous series was checked. Predictions made using the UNIFAC method and the Hildebrand-Scatchard equation were compared.     

A modification of the martin equation of state for calculating vapour-liquid equilibria

A modification of the Martin (1979) equation of state suitable for vapour-liquid equilibrium calculations is presented. The temperature dependence of this modification is determined from the second virial coefficient correlation of Tsonopoulos (1974) and the pure-component vapour pressures. Excellent predictions of phase equilibria have been obtained for a number of binary systems, including a system containing hydrogen. For the systems tested, the equation of this study is more accurate than the Peng-Robinson (1976) equation of state.     

Vapour-liquid equilibria of binary systems of C1-C4 n-alcohols with 1,2-dichloroethane at 323.15 K

Isothermal vapour-liquid equilibrium data have been obtained for binary mixtures of methanol, ethanol, n-propanol or n-butanol with 1,2-dichloroethane at 323.15 K using a dynamic method. VLE data have been tested for thermodynamic consistency and also fitted to Wilson, NRTL and UNIQUAC equations. UNIFAC predictions and experimental data are compared.     

Isobaric Vapour-Liquid Equilibrium of Some Cyclic Ethers with Bromobenzene at Several Pressures

A dynamic recirculating still was employed to study the isobaric vapour-liquid equilibrium (VLE) at 40.0 and 101.3 kPa for the binary systems tetrahydrofuran, tetrahydropyran, 2-methyl-tetrahydrofuran and 2,5-dimethyl-tetrahydrofuran with bromobenzene. The experimental data were tested for thermodynamic consistency and correlated with the Wilson, NRTL and UNIQUAC equations. Predictions with the UNIFAC method were also obtained.     

Analytic solution of the mean spherical approximation for a multi-component plasma

The mean spherical approximation for a mixture of charged hard spheres in a uniform neutralizing background is solved analytically. The factor correlation functions and the excess thermodynamic properties are explicitly expressed through a single parameter, which can be obtained by solving an algebraic equation.     

A description of phase equilibria in nonideal systems with the use of integral equation theory

Integral equation theory for partial distribution functions was used to consider a method for calculations of vapor-liquid phase equilibrium conditions in binary Lennard-Jones systems with substantial deviations from the Berthelot-Lorentz mixing rules. Possible sources of errors in pressure and chemical potential values and methods for refining the results were analyzed. The required accuracy of calculations can be reached using two parameters only, one in the closure to the Ornstein-Zernike equation and the other in the equation for the chemical potential. These parameters are determined independently from two thermodynamic equations.     

Thermodynamic consistency of experimental VLE data for asymmetric binary mixtures at high pressures

A thermodynamic consistency of isothermal vapor–liquid equilibrium data for 9 non-polar and 8 polar binary asymmetric mixtures at high pressures has been evaluated. A method based on the isothermal Gibbs–Duhem equation was used for the test of thermodynamic consistency using a Φ–Φ approach. The Peng–Robinson equation of state coupled with the Wong–Sandler mixing rules were used for modeling the vapor–liquid equilibrium (VLE) within the thermodynamic consistency test. The VLE parameters calculations for asymmetric mixtures at high pressures were highly dependent on bubble pressure calculation, making more convenient to eliminate the data points yielding the highest deviations in pressure. However the results of the thermodynamic consistencies test of experimental data for many cases were found not fully consistent. As a result, the strategies for solving these problems were discussed in detailed.