Andrzej Anderko

A simple equation of state incorporating association

Abstract A simple equation of state incorporating association effects in an explicit form is proposed. Parameters describing pure compound properties are determined from experimental vapour pressure and liquid density data. Besides the usual ability to reproduce pure compound vaporization enthalpy and second virial coefficients with considerable accuracy, the equation is able to predict the pressure dependence of gas phase thermal conductivity. For binary mixtures containing one associating component, the accuracy of representing vapor—liquid equilibria for a wide range of pressure with the use of one adjustable parameter is comparable with that obtained by correlation by means of activity coefficient methods. Fairly good prediction of vapour—liquid equilibrium can be obtained without the use of adjustable binary parameters.

Equation-of-state methods for the modelling of phase equilibria

Abstract The equation-of-state methods available for the representation of phase equilibria in multicomponent systems are reviewed. Various types of empirical and semi-empirical equations of state are evaluated with respect to their capability of representing pure component properties in the saturation region. Then, the performance of equations of state is examined for mixtures with special emphasis on systems containing polar and associating components. Various methods are discussed for extending equations of state to mixtures, viz. the classical quadratic and related mixing rules, mixing rules used in conjunction with the corresponding states theory, those derived from excess Gibbs energy models, density dependent mixing rules, improved conformal solution models and methods treating explicitly association and polarity. Attention is focussed on their capability of correlating and predicting multicomponent vapor—liquid and liquid—liquid equilibria over a wide range of pressure, temperature and molecular variety.

Phase equilibria in aqueous systems from an equation of state based on the chemical approach

Abstract A previously proposed equation of state incorporating association (AEOS) has been modified to extend its applicability to aqueous systems. The equation consists of two terms: a chemical one based on a generalized association model and a physical one which is equivalent to an equation of state for a monomeric fluid and is represented by a cubic equation of state for nonpolar compounds. The assumptions that are necessary to separate these terms have been discussed. The equation is able to present simultaneously vapor—liquid and liquid—liquid equilibria in aqueous hydrocarbon mixtures with only one adjustable binary parameter. A well-defined linear temperature dependence of the binary parameter makes it possible to reproduce VLE and LLE over large temperature and pressure intervals with good accuracy.

Extension of the AEOS model to systems containing any number of associating and inert components

Abstract The AEOS (association + equation of state) model is extended to mixtures containing any number of associating and inert components. The model is based on a continuous linear association scheme for molecules forming self-associates and cross-associates. The pure component parameters are determined from vapor pressure and liquid density data. The equation represents vapor—liquid equilibria over a wide pressure and temperature range with accuracy similar to that of experimental data. Results of calculating low-pressure vapor—liquid equilibria compare favorably with those obtained from activity coefficient methods. The well-established temperature dependence of the adjustable parameter makes possible a safe extrapolation beyond the experimental temperature range. Ternary vapor—liquid equilibria are accurately predicted from binary data. For mixtures containing chemically similar compounds vapor—liquid equilibria are fairly well predicted without any adjustable parameters.

Modeling phase equilibria using an equation of state incorporating association

Abstract A previosly proposed equation of state incorporating association in an explicit form (AEOS = Association + Equation of State) is applied to the calculation of vapor-liquid and liquid-liquid equilibria in mixtures containing water or alcohols and hydrocarbons. The AEOS model consists of two terms: a chemical one based on an association model and a physical one which is equivalent to an equation of state for nonassociating fluids. Attention is focused on the evaluation of pure component parameters which are crucial for mixture calculations. It is shown that the parameters should not only accurately reproduce pure component properties but also ensure the correct magnitude of the chemical and physical terms. A new algorithm is proposed to simplify the evaluation of pure component parameters. The AEOS equation, coupled with the new algorithm, is convenient for routine engineering calculations. It is capable of very accurately representing vapor-liquid and liquid-liquid equilibria over large temperature ranges. Only one binary parameter is needed. Moreover, the accuracy of predicting ternary equilibria using only binary parameters is very similar to the accuracy of correlating binary data.

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.

Calculation of vapor—liquid equilibria at elevated pressures by means of an equation of state incorporating association

Abstract A previously proposed simple equation of state incorporating association is applied to calculate vapor—liqud equilibria (VLE) at elevated pressures for systems formed by polar compounds and hydrocarbons. The pure-component parameters are calculated from experimental saturated vapor pressure and liquid density data. Such parameters are sufficient for the prediction of VLE with reasonable accuracy in binary systems formed by hydrogen sulfide, ammonia, carbon dioxide, carbon monoxide or sulfur dioxide with aliphatic hydrocarbons. All 26 systems formed by various hydrocarbons with the polar compounds analyzed in this paper can be represented within experimental accuracy when only one adjustable binary parameter is introduced. The binary parameter is generalized in terms of the critical temperature, pressure and acentric factor of the nonpolar (aliphatic or aromatic hydrocarbon) component. The equation also predicts saturated liquid and vapor densities with good accuracy.

Internally consistent representation of binary ion exchange equilibria

A model has been developed to obtain the thermodynamic parameters, i.e., the equilibrium constant and solid-phase activity coe

Excess volumes of (phenol + butylbenzene or propylbenzene or isopropylbenzene or 1,2,4-trimethylbenzene or ethylbenzene) at 318.15 and 348.15 K

cients, that describe binary ion exchange reactions. The model is based on the thermodynamic framework for adsorption exchange reactions developed by Gaines and Thomas (1953. Journal of Chemical Physics, 21, 714}718). The Wilson activity coe

(Vapour+liquid) equilibria of (phenol+butylbenzene or propylbenzene or isopropylbenzene or 1,2,4-trimethylbenzene or ethylbenzene) at 393.15 and 403.15 K

cient model is used for the adsorbed phase and the stoichiometry of the exchange reaction is taken into account. The solid solution model parameters are regressed with a new data reduction technique, based on the use of the Vanselow selectivity coe