ISSN:0005-9021    

DOI:10.1002/bbpc.19840880902

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractThe “Supercritical solvency” is connected to the liquid‐like density of gases at high pressure, and to the high sensitivity of this density to temperature and pressure in the near critical range of the solvent. The dissolution of the supercritical solvent in the liquid phase may also lead to liquid liquid equilibria, whose continuity with vapour liquid equilibria has been shown. – Simple methods, like cubic equations of state give a qualitative representation of such properties. However new formulations of the equation of state should be used to obtain a satisfactory prediction of thepVTproperties in the critical range, while maintaining the simplicity of the cubic equation of state. The classical mixing rules cannot take into account the intermolecular forces existing between the solutes and the solvent, which often greatly differ in size, shape and polarity, and our experience of the classical liquid‐liquid equilibria can help us in the formulation of new and effective methods, such as the “density dependant local composition” mixing rules. Such theories contain empirical binary parameters and their application needs experimental data. – However, prediction methods based on the concept of group contribution are being developed, and can help the selection of selective supercr

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880904

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractBy integrating an equation of state, an expression for the Gibbs energy of binary fluid mixtures is derived and used to define the thermodynamic conditions of phase equilibrium. These conditions are solved numerically for the equilibrium concentrations. The same equation of state is used for liquid and vapour phases. From additional solid density data and the sublimation/melting pressure, solid‐liquid and solid‐gas equilibria can be calculated, provided that no miscibility occurs in the solid state. ‐ Calculations of phase equilibria have been carried out for several binary mixtures of nonpolar substances (noble gases, CO2hydrocarbons) for pressures up to 200 MPa, using the Redlich‐Kwong equation and our own equation of state, which has been published earlier [1]. ‐ The Redlich‐Kwong equation represents the experimental phase equilibrium data at low pressures only, whereas the other equation achieves good agreement over the whole pressure range. I f the molecules differ very much in size, deviations from one‐fluid theory can be accounted for by using the Leland‐Mansoori‐Carnahan‐Starling function for rigid sphere mixtures in the repulsion term of ou

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880905

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractSupercritical‐fluid extraction is a useful process for upgrading heavy multicomponent mixtures such as high‐boiling petroleum fractions. Design‐oriented calculations are reported for an extraction process using propane to extract intermediate components from a petroleum fraction with molecular weights in the range 150‐−500. The composition of the heavy‐hydrocarbon mixture is described by two continuous distribution functions of molecular weight, one for paraffinic and one for aromatic components. Process calculations are based on a recently developed thermodynamic framework for mixtures with very many components, coupled with an equation of state of the van der Waals form. Particular attention is given to multicomponent phase equilibria in the retrograde region where solvent recovery is favorable. Quantitative results are given for solvent capacity and selectivity as a function of operating

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880906

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractThe group contribution equation of state (GC‐EOS) is used for the prediction of phase equilibria related to supercritical extraction of ethanol from aqueous solutions. The calculations show that it is not possible to design an economically favourable alternative to distillation processes using CO2as the supercritical solvent. This is in accordance with the available experimental evidence. – Further calculations indicate that the use of light hydrocarbons as supercritical or near‐critical solvents may be a very attractive alternative for the recovery of pure alcohol from dilute aqueous solu

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880907

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractA 1−4−12 association model for methanol is proposed and applied in the equation‐of‐state method to calculate high‐pressure phase equilibria. An equation of the van der Waals type is used. Tests are performed in systems containing methanol + methane, ethane, propane, butane, ethene, propene, nitrogen, carbon monoxide, hydrogen, carbon dioxide and hydrogen sulfide. One single adjustable parameter is used for a binary system; this parameter is temperature independent and is zero for mixtures of methanol with alkanes. The method yields satisfactory predictions except for carbon dioxide and hydrogen sulfide where association between unlike molecules should be taken into account. Critical pressures in binary systems are over

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880908

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractThe use (and limitations) of equations of state for collating and predicting liquid/liquid and liquid/dense fluid equilibria is discussed with reference to 15 binary pairs (including some new data for the Carbon dioxide/Hexadecane system at 60°C) and three ternary combinations. It is concluded that the estimation of some of the parameters required for these calculations would be difficult if the solute was a complex substance about which little was known apart from its structural formula. ‐ An alternative procedure is to apply activity coefficient expressions of the “regular solution” or UNIFAC type to each phase. Preliminary calculations along these lines are described and the physical basis for applying these methods under the relevant conditions is discussed. The “UNIFAC” approach in particular has been found to be encouraging, though the interaction parameters must be regarded as pressure

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880909

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractA survey is given of selected thermophysical properties of supercritical solvents which have been determined more recently and which may have technical interest. The static dielectric permittivity of water and of supercritical water‐benzene mixtures to 400°C and several 1000 bar is shown. The transport properties viscosity and thermal conductivity of water at high pressures and extending into the supercritical region are discussed. Of binary systems anthracene as a model solute in ten different highly compressed sub‐ and supercritical fluids is discussed and results presented as “enhancement” factors and virial coefficientsB12. Critical curves of binary aqueous systems are shown and methods for calculations indicated. The binary systems water‐nitrogen and water‐oxygen were determined to 2000 bar and excess volumes of water‐methane and water‐benzene measure

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880910

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractMeasurements of the excess enthalpyHEof mixtures of water + hydrocarbon vapour in the region 363 to 698 K and at pressures up to 12 MPa are described. Results obtained at low temperatures and pressures yield values of the cross term second virial coefficientB12. Analysis of results on several mixtures containing steam show that in its interaction with n‐alkane water has effective Lennard‐Jones parameters ε/k= 285 K and σ = 0.27 nm. Combining rules for ε12in the water + alkane interaction are established. For alkanes above n‐pentane the isothermalHE(x= 0.5),pcurves show maxima at pressures well below saturation. Results for all mixtures can be fitted using a new association model.HEmeasurements on water + benzene show clear evidence of a specific interaction. The enthalpy of formation of the water + benzene complex is ΔH=

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880911

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractBinary diffusion coefficients of benzene and heptane in supercritical CO2were measured by photon correlation spectroscopy. The measurements were carried out along isochores in the dense gas region at concentrations less than 5 mole percent hydrocarbon. The results of an analysis of data using mode‐mode‐coupling theory indicated that the exponent of the correlation length, ν = 0.67 ± 0.03 on the critical isochore. On the other hand, ν = 0.86 ± 0.05 was obtained on isochores that were not critical and the background contribution became sign

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880912

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY