Wim Poot

Vapour-liquid equilibria and critical phenomena in methanol + n-alkane systems

Abstract Bubble point pressures and vapour-liquid critical points of {(1–x) CH 3 OH + x n-C m H 2m+2 , m = 6,7,8,9,10,12,14 } were measured visually over the temperature range from 425 to 540 K in a high pressure capillary glass tube apparatus by using the synthetic method. It is shown that the form of the vapour-liquid critical curve of binary methanol + n-alkane systems changes systematically with the carbon number of the n-alkane. In systems with m = 6,7,8 absolute azeotropy is found.

The pϱT properties of ethanol + hexane

Abstract The pϱT behavior of ethanol, hexane and its mixture has been investigated with the aim to cover the whole region from low pressure-low temperature thermodynamic excess properties up to the critical curve. The mixture exhibits a positive azeotrope which persists over the whole range. The positive excess volume shows a remarkable temperature dependence. Whereas the thermodynamic evaluation and the comparison to model calculations will be the subject of a future paper, all experimental results are put together in this paper.

High pressure phase equilibria of the binary systems N2 + benzene, N2 + p-xylene and N2 + naphthalene

Abstract (Liquid + vapour): (1+g) equilibria were measured in the systems N2 + benzene, N2 + p-xylene and N2 + naphthalene in the temperature range 370–440 K and pressures up to 165 MPa, 240 MPa and 165 MPa respectively. Also some (solid + liquid): (s+1) and (solid + liquid + gas): (s+1+g) equilibria in the system N2 + naphthalene are presented. The type of phase behaviour that can be deduced from the experiments is discussed in terms of (p, T) projections and compared to the behaviour in other binary N2 systems. Fluid phase equilibria up to 100 MPa were modelled using the Peng-Robinson equation of state.

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.

Liquid-liquid-vapor equilibria in binary families of SF6, CClF3, C2H3F3 and C2H4 with n-alkanes

Liquid–liquid–vapor equilibria were determined experimentally for binary and quasi-binary systems which consisted of a low-volatile n-alkane or mixture of n-alkanes with a more volatile component, chlorotrifluoromethane, sulfur hexafluoride, 1,1,1-trifluoroethane, and ethene. From the location of the critical end-points L2 = L1 + V and L2 + L1 = V of the three-phase curves, the coordinates of the tricritical point and the double critical endpoint of these families were estimated by extrapolation. For the families studied it was found that increasing the carbon number of the n-alkane leads to a transition from type II to type IV to type III fluid phase behavior.

Liquid–liquid–vapour equilibria in binary and quasi-binary systems of CHF3 with n-alkanes, phenylalkanes and alkanols

Liquid–liquid–vapour equilibria were determined experimentally for binary systems of trifluoromethane with n-alkanes, phenylalkanes and octanol, and for quasi-binary systems of trifluoromethane with mixtures of hexane and heptane. For the trifluoromethane+n-alkane family the coordinates of the tricritical point and the double critical endpoint were estimated by extrapolation from the location of the critical endpoints g(l2=l1) and (g=l1)l2 of the three-phase curves. It is found that in these families an increase in carbon number of the n-alkane leads to a transition from type II to type IV to type III fluid phase behaviour. The tricritical point is found at a carbon number of the n-alkane of 6.509 and the double critical endpoint at a carbon number of the n-alkane of 6.51. The system trifluoromethane+phenylpropane shows type II phase behaviour, and the systems trifluoromethane+phenylbutane, +phenylpentane and +phenyloctane show type III phase behaviour. The system trifluoromethane+octanol is a type II system.

Fluid-phase equilibria and critical phenomena in (tetrafluoromethane + n-butane)

Abstract Phase equilibria and critical phenomena in fluid (tetrafluoromethane + n -butane) were established in the temperature range 235 to 325 K at pressures up to 20 MPa. The mixture shows a three-phase curve (liquid + liquid + gas) which ends in an upper critical end point where one of the liquid phases and the gas phase become identical. The critical curve of the binary mixture has two branches: a (liquid + gas) branch which runs from the critical point of pure tetrafluoromethane to the upper critical end point, and a second branch of the type of (gas + gas) equilibria of the second kind which starts at the critical point of pure n -butane. The results are discussed in the context of fluid-phase equilibria of other {(1 − x )CF 4 + x C n H 2 n +2 } mixtures. The existence of a tricritical point in a quasi-binary mixture of {tetrafluoromethane + a mixture of (propane + n -butane)} is suggested.