Stanisław Malanowski

Ebulliometers modified for the accurate determination of vapour—liquid equilibrium

Abstract The modifications of ebulliometers for the accurate determination of vapour—liquid equilibrium at pressures between 5 and 300 kPa and temperatures from 300 to 500 K are described. The measurements can be performed with or without the determination of the composition of the liquid and vapour phases at equilibrium. The proposed method is suitable for determinations at very low concentrations (limiting values of activity coefficients) and for whole range of concentrations. The ability of the proposed ebulliometers to reach the operation at steady state in a short time after changing the thermodynamic parameters makes possible isothermal as well as isobaric measurements. The procedure for the calculation of the composition of the liquid phase at equilibrium from the composition of the sample introduced into the ebulliometer is given. The accuracy of results obtained is limited only by the purity of the substances used and by the precision of weighing and introduction of the samples into the ebulliometer. To illustrate the performance of the proposed modified ebulliometers, the experimental results obtained for the systems N-methylpyrrolidone—cyclohexane, N-methylpyrrolidone—butylbenzene, and chlorobenzene—hexane are given.

Vapour—liquid equilibria in binary systems formed by N-Methylpyrrolidone with hydrocarbons and hydroxyl derivatives

Abstract The vapour—liquid equilibria (VLE) determined by an ebulliometric total pressure method under isothermal conditions for binary systems formed by N -methylpyrrolidone with hexane (333.25 and 343.15 K), dodecane (393.25 K), cyclohexane (333.25 and 354.15 K), methyl-cyclohexane (354.15 and 373.25 K), benzene (333.25 and 354.15 K), toluene (362.15 and 383.35 K), propylbenzene (352.15 and 373.75 K), butylbenzene (352.15 and 373.75 K), propanol-1 (354.15 K), hexanol-1 (351.75 and 393.35 K) and at 393.55 K for cyclohexanol, 4-methylphenol and 2,4-dimethylphenol are reported. The vapour pressures of the pure substances are given. The least squares analysis of VLE data by means of the Redlich-Kister equation is given.

A new equation for correlation of vapour-liquid equilibrium data of strongly non-ideal mixtures

Abstract A new equation for correlation of the thermodynamic excess functions of mixing, based on considerations of geometrical shape is proposed. Use of this equation for the correlation of heat of mixing data and vapour-liquid equilibrium data is proposed. The possibility of predicting multicomponent vapour-liquid equilibrium from binary data by using the proposed equation is shown. The equation is especially useful for correlating the excess functions of strongly non-ideal systems and for checking thermodynamic consistency of vapour-liquid equilibrium data.

Experimental methods for vapour-liquid equilibria. Part I. Circulation methods

Abstract A selection of experimental procedures available for the determination of vapour-liquid equilibrium at normal and low pressures by circulation methods is presented and recommendations are made. The development of vapour recirculation, condensate recirculation, and vapour and condensate recirculation methods is considered and critical evaluations are given. For selected recommended methods a detailed description and a discussion of accuracy and possible applications are given.

Calculation of solid-liquid, liquid-liquid and vapor-liquid equilibria by means of an equation of state incorporating association

Abstract AEOS, a previously proposed equation of state incorporating association in an explicit form is applied to calculate solid-liquid (SLE), liquid-liquid (LLE) and vapor-liquid equilibria (VLE) of strongly nonideal systems. The AEOS equation consists of two terms: a chemical one based on a continuous linear association model and a physical one represented by an equation of state for nonpolar fluids. The equation is able to reasonably predict the phase equilibria with the use of only pure component parameters. Only one adjustable binary parameter is sufficient for an accurate representation of mixture data. The obtained values of binary parameters are directly related to the acentric factor of inert components. The accuracy of simultaneous correlation of SLE, LLE and VLE is very satisfactory.

A new modification of the UNIQUAC equation including temperature dependent parameters

Abstract The UNIQUAC equation was modified by introduction of a linear temperature dependence of the volume and surface area parameters, ri and qi. The slope of ri and qi functions were found to be the same for hydrocarbons and pyridine. The modified equation was used for prediction of vapor–liquid equilibria (VLE) in binary mixtures of hydrocarbons and pyridine with hydrocarbons as well as for the prediction of the excess enthalpy (HE) in binary mixtures formed by pyridine with aliphatic alkanes. The results obtained were compared with predictions by UNIFAC and further with UNIQUAC equation and its modification involving temperature dependant coordination number z. The proposed temperature dependence of the ri and qi parameters enables prediction of the VLE at various temperatures and leads to reasonable values of HE. The necessary input reduces to one set of isothermal VLE data. One set of UNIQUAC interaction parameters uij is sufficient for representation of VLE in a wide range of temperature and to obtain a reasonable prediction of HE.

Development of a vapour-liquid equilibrium apparatus to work at pressures up to 3 MPa

Abstract An apparatus for vapour - liquid equilibrium measurement at elevated pressures was built. Construction was based on the Rogalski - Malanowski glass ebulliometer designed for precise measurements up to normal pressure. Experimental procedure was also developed. For the performance test of the proposed apparatus the vapour pressure was measured for four pure substances (benzene, heptane, cyclohexane and water) and the vapour - liquid equilibrium (VLE) was determined for two binary mixtures (benzene + heptane and benzene + cyclohexane). The results obtained were satisfactory.

Vapour pressure data for 1-butanol, cumene, n-octane and n-decane and their statistically consistent reduction with the antoine equation

Abstract Vapour pressures of pure substances: 1-butanol, cumene, n-octane and n-decane have been measured. A statistical consistent algorithm, based on the maximum likelihood principle, has been applied to data reduction and estimation of the Antoine equation parameters. The nonlinear correlating procedure, including estimation of true values of measured variables and error analysis, is proposed. A computational algorithm suitable for a personal computer is also presented.

Vapour—liquid equilibrium in binary mixtures formed by benzene or cyclohexane with 1-chloropropane or 1-chlorobutane

Abstract The vapour—liquid equilibria (VLE) for the binary systems formed by 1-chloropropane with benzene and cyclohexane at 308.15 K and 318.15 K, and for systems formed by 1-chlorobutane with the same hydrocarbons at 308.22 K, 328.27 K and 348.31 K have been determined by a total pressure ebulliometric method. The accuracy of these results was proved by comparing the heat of mixing data calculated from these VLE results with those obtained by direct measurements (Amaya, 1961; Grolier et al., 1973). The experimental data and the results of correlation by means of the Redlich—Kister equation are given. The systems with benzene were found to be nearly ideal, while those with cyclohexane exhibit positive deviations (GE = 220–260 J mole−1 for an equimolar mixture). New vapour pressure versus temperature data for 1-chlorobutane are reported.

Experimental methods for vapour-liquid equilibria. II. Dew- and bubble-point method

Abstract A description of the principles of the dew- and bubble-point method is given. Selected experimental procedures available for the determination of vapour-liquid equilibria using this method are evaluated critically.