R.N. Lichtenthaler

Phase equilibria and critical phenomena in fluid (n-hexane + water) at high pressures and temperatures

Abstract Phase equilibria in fluid ( n -hexane + water) were measured in the temperature range 610 to 675 K and at pressures from 15 to 140 MPa. The critical curve of the mixture starts at the critical point of pure water ( T c = 646.1 K; p c = 22.1 MPa) and runs via a temperature minimum at T = (627.8 ± 0.2) K and p = (31 ± 2) MPa to higher pressures, suggesting that (gas + gas) equilibria of the second kind occur. The results are discussed in view of phase equilibria of other ( n -alkane + water) mixtures. It is shown that the form of the critical line of (an n -alkane + water) changes systematically with the carbon number of the n -alkane.

Phase equilibria of (methane + n-hexadecane) and (p, Vm, T) of n-hexadecane

Abstract In this paper experimental results for several kinds of two-phase boundary in {methane (A) + n -hexadecane (B)} are presented. The measurements were performed in the temperature region from about 285 up to 360 K and pressures up to 85 MPa were applied. A Cailletet apparatus was used with autoclave equipment. The obtained experimental results allowed us to derive the course of the three-phase locus (s B +l+g). For pure liquid n -hexadecane ( p , V m ∗ , T ) were measured. Finally the Soave modification of the Redlich-Kwong equation of state was used to describe some of the experimental results.

Three phase equilibria in binary mixtures of ethane and higher n-alkanes

Abstract In binary mixtures of ethane + higher n-alkanes a systematic change in phase behaviour with increasing carbonnumber near the critical point of ethane can be observed. Binaries up to C 17 are completely miscible in the liquid phase and binaries up to C 23 show partial miscibility in the liquid phase with an upper and lower critical endpoint. In the binaries of ethane with C 24 and C 25 the three phase equilibrium solid n-alkane + liquid + vapour intersects the three phase equilibrium liquid + liquid + vapour and a quadruple point solid n-alkane + liquid + liquid + vapour can be observed. As the carbonnumber further increases stable liquid + liquid phasesplit will be obscured by solidification. In this contribution experimental results for the binaries C 2 + C 16 , C 2 + C 20 , C 2 + C 22 , C 2 + C 23 , C 2 + C 24 , C 2 + C 25 and C 2 + C 26 will be reported and shown to present a logical evolution in phase behaviour.

Phase equilibria and critical phenomena in fluid (n-alkane + water) systems at high pressures and temperatures

Abstract In fluid (n-alkane + water) mixtures (gas + gas) equilibria of the second type are found. Phase equilibria in fluid (n-pentane + water) and (n-heptane + water) were measured in the temperature range 600 to 675 K and at pressures from 15 to 170 MPa. The critical curve of these systems starts at the critical point of pure water and runs through a temperature minimum with increasing pressure. Experimental results are compared with previous studies and it is found that the data fit very well within the systematics of other (n-alkane + water) systems.

The influence of branching on high-pressure vapor-liquid equilibria in systems of ethylene and polyethylene

Abstract Cloud-point curves and critical curves in fluid systems of ethylene + branched polyethylene were measured in an optical high-pressure autoclave equipped with sapphire windows and magnetic stirring in the temperature range 380–445 K and at pressures from 90 to 200 MPa. From the experimental results, it is concluded that the cloud-point curves of a system with a branched polyethylene are at significantly lower pressures (10–40 MPa) than the cloud-point curves of a system with a linear polyethylene with comparable molecular-weight distribution.

Phase equilibria in binary mixtures of ethane and hexadecane

Abstract This paper reports experimental results of a study of the phase behaviour of binary mixtures of ethane + hexadecane. In the near-critical region of ethane liquid + vapour and solid hexadecane + liquid two-phase boundaries have been measured. Also the three-phase equilibrium solid hexadecane + liquid + vapour has been determined experimentally. The experimental data cover the complete mole fraction range. Pressures up to 18 MPa were applied and the investigation was performed in a temperature region from about 260 K up to 450 K.

Liquid-liquid equilibria in 2-methoxyethanol+alkane systems. I: Experimental results at pressures up to 400 MPa

Abstract In an optical high-pressure autoclave with sapphire windows and magnetic stirring, liquid-liquid equilibria and critical curves in binary systems of 2- methoxyethanol and different alkanes were measured in the temperature range 250–430 K and at pressures from 0.1–400 MPa. For all systems investigated upper critical solution temperatures and lower critical solution pressures were found. The upper critical solution temperature increases with increasing molecular weight of the alkane and decreases with increasing number of CH 3 -groups of the alkane.

The non-analytical statistical mechanical virial equation of state to calculate fluid phase equilibria

Abstract This contribution describes a new method to make use of the non-analytical statistical mechanical virial equation of state for calculating fluid phase equilibria of binary mixtures. The method proposed is such that a minimum of approximate relations is introduced. This method utilizes the advantages of perturbation theory as well as integral equations. Also a suitable numerical technique is introduced which allows us to handle the non-analytical virial equation of state for practical purposes.

Liquid + liquid equilibria in 2-methoxyethanol + alkane systems at high pressures

Abstract Liquid + liquid equilibria and critical curves have been measured in some 2-methoxyethanol + alkane systems in the temperature range 250 to 400 K and at pressures from .1 to 400 MPa. For all systems investigated, upper critical solution temperatures and lower critical solution pressures were found. The representation of the experimental results with a number of expressions for the excess Gibbs energy is discussed. A promising modification of the Uniquac equation is proposed.