Isothermal vapour–liquid equilibria for the binary system benzene–n-octane

Vapour–liquid equilibrium data were determined at three isothermal conditions for the binary system benzene–n-octane using a modified Gillespie still. Non-ideality of the vapour phase was evaluated and log γ values were correlated.     

Symmetrical-area tests for the consistency of vapour–liquid equilibrium data. I. Isothermal data

The need to test experimentally determined vapour–liquid equilibrium data for thermodynamic consistency is now widely recognised. This paper is concerned with general integral tests based on the Duhem–Margules equation and not with particular algebraic solutions of that equation. A family of ‘symmetrical-area’ tests is presented; these new tests are more powerful tools for the examination of experimental data than the area tests previously developed by the author, and can be used to examine part of a composition range and to identify regions of poor observation. Moreover, the tests can sometimes be used to identify the quantities that are in error. They are applicable to systems with miscibility gaps.     

Prediction of isobaric and isothermal vapour–liquid equilibria from limited experimental data

Malesinski's method for prediction of isobaric vapour–liquid equilibrium data using a single experimental datum on a T–x isobar has been modified and extended to a more general case where the molar entropies of vaporisation of the components are not necessarily equal and the non-ideality in the vapour phase is considered. However, it is assumed that the solution behaves like a strictly regular one over the temperature range in question, that is, the constant A in the expression for excess free energy: g^E=Ax₁x₂ is independent of temperature. The method has been illustrated for several systems and is found to be highly satisfactory for non-polar–non-polar as well as polar–non-polar systems in which the boiling points of the pure components are not much different. Incorporating temperature dependence of the constants in the Redlich–Kister equation for excess free energy, a method has been developed for predicting isothermal vapour–liquid equilibrium data at several temperature levels from equilibrium values at a single pressure. For testing the validity of this method, predicted results have been compared with the available experimental data for zeotropic as well as azeotropic systems comprising non-polar–non-polar, polar–non-polar and polar–polar mixtures, and the method has been found to be satisfactory for all systems.     

A data bank for high pressure vapour—liquid equilibria

The Berlin Thermodynamics Data Bank (die Berliner Datenbank Thermodynamik, BDBT) records experimental data on high pressure vapour—liquid equilibria of binary, ternary and multi-element mixtures. The information contained in the data bank is useful for several purposes:(1) as a reference for process design;(2) as a basis for fitting binary parameters in correlations;(3) as a data file for checking the accuracy of correlations.The structure of the data bank, the fitting procedures for binary parameters and the tabular or graphical representation of the comparison of calculated and experimental data are shown and discussed. The Data Bank is available from the INKA (Informations-System Karlsruhe), from Dechema, Frankfurt, and from FIZ Chemie, West Berlin. Part of the BDBT has been published in the Dechema Data Series.     

Ternary vapour–liquid equilibrium data for the system: n-butanol–n-butyl acetate–1,2-propylene glycol

Vapour–liquid equilibrium data for the ternary system n-butanol–n-butyl acetate–1,2-propylene glycol are reported at pressures between 725 and 735 mm Hg. The activity coefficient data are satisfactorily correlated by Wohl's two-suffix van Laar equation. Thermodynamic consistency is checked by both the McDermott & Ellis point-to-point consistency test and by the Li & Lu closed-loop method.     

Isothermal vapour-liquid equilibria for the isopropyl benzene-ammonia system

Vapour-liquid equilibrium data were obtained for the isopropyl benzene-ammonia system at 273.15, 288.15, 293.15 and 298.15 K. This system has an upper critical solution temperature at 293.15 K. Since the liquid mixture changes from two liquid phases to one liquid phase with rising temperature, vapour-liquid-liquid equilibria also are evaluated. Experimental vapour-liquid equilibrium data were compared with calculated values from the UNIQUAC equation, and show good agreement.     

Binary liquid–liquid equilibria of aniline–paraffin and furfural–paraffin systems

Binary liquid-liquid-equilibria data for several aniline-paraffin and furfural-paraffin systems have been taken. These data along with data for other aniline-hydrocarbon and furfural-hydrocarbon systems from literature have been correlated using UNIFAC model. The UNIFAC group interaction parameters have been found to have a linear temperature dependence. The CH₂ groups in cyclo and non cyclo paraffins require different interaction parameters. It was also found that a scaling of the combinatorial term is necessary for higher molecular weight hydrocarbons.     

A phase model for the gas–liquid equilibria in the ammonia–carbon dioxide–water–urea system in chemical equilibrium at urea synthesis conditions. I. Theory

A ternary phase model of the reciprocal salt-pair type (square composition plane) is presented to describe the gas–liquid equilibria of the ammonia–carbon dioxide–water–urea system in chemical equilibrium at urea synthesis conditions. The components of the model are CO₂, H₂O and (2NH₃). Urea is represented by the equation:. and is therefore located at the corner of the composition square diagonally opposed to water. Characteristic of this phase model (at constant temperature) is the occurrence of minimum bubble- and dew-points in planes located parallel to the (2NH₃)-CO₂ diagonal. The point of tangency of the bubble- and dew-point lines formed by these points forms the ternary azeotropic point. Intercepting the azeotropic point is a plane parallel to the urea–water diagonal; at the azeotropic point the bubble-point line in this plane reaches a maximum pressure value. The ternary azeotrope is of the saddle type.     

Representation of vapor–liquid and liquid–liquid equilibria for binary systems containing polymers: Applicability of an extended flory–huggins equation

For some binary systems, an extended Flory–Huggins equation is applicable to both vaporliquid equilibria (VLE) and liquid–liquid equilibria (LLE) using the same adjustable parameters. New LLE and VLE data are reported for polystyrene (PS) (MW = 100,000)/cyclohexane and for poly(ethylene glycol) (PEG) (MW = 8,000)/water. Experimental results for the PS/cyclohexane system agree well with the semiempirical model, whereas those for PEG/water do not, probably because, for PEG/water, the temperature range of the VLE data is about 55°C lower than that of the LLE data. Excellent fits were obtained for our previously published experimental results for PS/cyclohexane (upper critical solution temperature, UCST), PS/ethyl acetate (lower critical solution temperature, LCST), PS/tert-butyl acetate and PS/methyl acetate (both UCST and LCST), and PEG/water (closed-loop). The semiempirical model also fits well with new data obtained for the polymer blend PS/poly(vinyl methyl ether). © 1993 John Wiley & Sons, Inc.     

Alcell® lignin solubility in ethanol–water mixtures

The lignin solubility in aqueous solutions of different ethanol concentrations was studied. The concept of the solubility parameter was applied to account for the effect of ethanol concentration on the lignin solubility. Experimental results showed that the lignin solubility increased strongly as the ethanol concentration increased from 9.5 to 47.5% then, it increased much more slowly until a maximum was reached at an ethanol concentration of about 70%. Further increase in the ethanol concentration resulted in a slight decrease in the lignin solubility. Based on the lignin molecular formula, the solubility parameter (δ-value) of the ALCELL® lignin was 13.7 (cal/cm³)^1/2. The δ-value of aqueous ethanol solutions of increased ethanol concentration was calculated and was found to decrease continuously from 22.31 (cal/cm³)^1/2 for pure water to 12.08 (cal/cm³)^1/2 for pure ethanol. The effect of ethanol concentration on the solubility of the ALCELL lignin was then explained based on the theory that lignin exhibited the maximum solubility when the δ-value of the solvent was close to that of the ALCELL lignin and the H-bonding capacity of the solutions with different ethanol concentrations was similar. © 1995 John Wiley & Sons, Inc.     

A phase model for the gas–liquid equilibria in the ammonia–carbon dioxide–water–urea system in chemical equilibrium at urea synthesis conditions. II. Experimental verification

Bubble- and critical-points in the ammonia–carbon dioxide plane and ammonia–urea system are presented as well as bubble-points in the carbon dioxide–urea system. In order to confirm the form of a previously presented phase model a large number of bubble- and dew-points were measured at various ammonia–carbon dioxide–water–urea compositions (including those most important to the urea industry) in the range of 140 ? T ? 200°C and 15 < P < 400 atm. All of the measurements were carried out under conditions of complete chemical equilibrium. The results are in agreement with the ternary phase model presented in a previous article.     

Phase equilibria in the two-phase system polystyrene—liquid sulphur dioxide

The concentration and molecular weight distribution (GPC) of polystyrene (PS) in the two phases of the PS-SO₂ (δ)-system were determined. Typical concentrations of PS in the upper phase were around 30%, while the lower phase contained at most 1% PS. An exception was a PS-grade with a low molecular weight (MW 3.5 · 10³), which dissolved homogeneously. The molecular weight of PS in the lower phase was substantially below an the one found in the concentrated phase. Mechanical agitation was necessary to attain an equilibrium state; during the equilibration the upper phase became more diluted. At the same time the molecular weight of the lower phase PS-fraction increased, while the MW value in the upper phase remained practically unchanged and equal to that of the virgin sample. The fractionation with regard to the molecular weight between the two phases was also reflected in the Tg-values of the fractions. The value of X(Flory-Huggins parameter) determined from vapour pressure data above the concentrated phase was 0.8–1.     

An improved prediction result of entropic‐FV model for vapor–liquid equilibria of solvent–polymer systems

In this work, entropic expressions of UNIFAC‐FV and Entropic‐FV models were evaluated by using an extensive database of infinite dilution vapor–liquid equilibrium (VLE) data of athermal systems containing polypropylene, polyethylene, and polyisobutylene. For the infinite dilution athermal systems, performance of the Entropic‐FV model was better than that of the UNIFAC‐FV model. Then, finite concentration VLE data of non‐athermal systems that consisted of 16 polymers and 36 solvents containing a large variety of solvent–polymer systems ranging from nonpolar to polar substances were considered to optimized 46 pairs of group interaction parameters of the Entropic‐FV model. For systems containing polar solvents of three types of solvents studied, revised group interaction parameters gave significant improvements from 17.9 to 13.0% average absolute deviation (AAD) of solvent activities. For overall results, improvements were achieved from 15.1 to 12.4% AAD. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1145–1153, 2005     

Experimental phase equilibria studies of the PbO–SiO2 system

Phase equilibria of the PbO–SiO₂ system have been established for a wide range of compositions: (i) liquid in equilibrium with silica polymorphs (quartz, tridymite, and cristobalite) between 740°C and 1580°C, at 60‐90 mol% SiO₂; (ii) with lead silicates (PbSiO₃, Pb₂SiO₄, and Pb₁₁Si₃O₁₇) and lead oxide (PbO) between 700°C and 810°C. A high‐temperature equilibration/quenching/electron probe X‐ray microanalysis (EPMA) technique has been used to accurately determine the compositions of the phases in equilibrium in the system. Significantly, no liquid immiscibility has been found in the high‐silica range, and the liquidus in this high‐silica region has been accurately measured. The phase equilibria information in the PbO–SiO₂ system is of practical importance for the improvement of the existing thermodynamic database of lead‐containing slag systems (Pb–Zn–Fe–Cu–Si–Ca–Al–Mg–O).     

Modeling of solid–liquid equilibria for polyethylene and polypropylene solutions with equations of state

We modeled solid–liquid equilibria (SLEs) in polyethylene and polypropylene solutions with a Soave–Redlich–Kwong (SRK) cubic equation of state (EOS) and a perturbed‐chain statistical associating fluid theory (PC‐SAFT) EOS. Two types of mixing rules were used with SRK EOS: The Wong–Sandler mixing rule and the linear combination of the Vidal and Michelsen mixing rules (LCVM), both of which incorporated the Bogdanic and Vidal activity coefficient model. The performance of these models was evaluated with atmospheric‐pressure and high‐pressure experimental SLE data obtained from literature. The basic SLE equation was solved for the equilibrium melting temperature instead of for the composition. The binary interaction parameters of SRK and PC‐SAFT EOS were estimated to best describe the experimental equilibrium behavior of 20 different polymer–solvent systems at atmospheric pressure and 31 other polymer–solvent systems at high pressure. A comparison with experimental data showed that SRK–LCVM agreed very well with the atmospheric SLE data and that PC‐SAFT EOS was more efficient in high‐pressure conditions. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The vapour—liquid equilibria of the binary,ternary and quaternary systems formed by acetone,methanol, propan-2-ol,and water

The vapour-liquid equilibrium data of the binary, ternary and quaternary systems that may be formed by combination of the components acetone, methanol, propan-2-ol and water, have been determined at 760 mmHg by means of an equilibrium still based on the principle of circulation of both phases. The binary data have been correlated by means of the Margules and of the Wilson equation. The data of the ternary and quaternary systems have been predicted by these equations. The results of both equations are discussed and compared.     

Swelling behavior of pervaporation membranes in ethanol–water mixtures

Novel hydrophobic composite membranes made of crosslinked poly(dimethylsiloxane) and poly(methyl hydrogen siloxane) (PDMS–PMHS) with various amounts of catalyst were prepared. Pervaporation experiments with water–ethanol mixtures revealed that an optimum ratio of catalyst to polymer base existed. Both swelling behavior and dynamic–mechanical properties of these silicone films were studied. The swelling experiments in different mixtures of ethanol and water determined that ethanol is preferentially sorbed and that the membranes are only capable to absorb a limited quantity of solvent. Equilibrium swelling data were also used in combination with the analysis of the viscoelastic relaxation of the swollen samples to obtain the dependence of the dynamic–mechanical properties of the silicone films on the quantity of permeants sorbed into the membrane. It was observed that the permselective parameters were related with the mobility of the chains and the free volume. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1424–1433, 2000     

Real-time inferencing of solid–liquid phase equilibria in solution polymerization of polyethylene

An algorithm for the real-time prediction of multi-component solid–liquid equilibrium (SLE) in a polyethylene (PE) process flowsheet has been attempted. While most of the available literature assumes the polymer to possess a single average molecular weight and lump the entire polymer as a single component, the present work proposes to consider a polydispersed multi-component fraction, characterized by the pseudo-component approach. The SLE model has been used to study the effects of monomer and polymer polydispersity in solution polymerization process. At first, it has been validated on the solubility data of n-alkanes in n-hexane, polyethylene in M-xylene and on wax precipitation from a mixture of n-paraffins. The SLE model is based on perturbed chain SAFT (PC–SAFT) equation of state (EOS). An algorithm for the real-time prediction of SLE phase boundaries in solution polymerization has been subsequently presented. A simulation experiment on the polyethylene flowsheet highlighted the potential of real-time inferencing for industrial applications.