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

Abstract

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.