MEASUREMENTS AND CALCULATIONS OF PHASE-EQUILIBRIA IN BINARY-MIXTURES OF PROPANE + TETRATRIACONTANE

This paper reports on the phase behaviour of binary mixtures of propan e and tetratriacontane (n-C34H70) in the near-critical region of propa ne. The measurements cover a temperature region from about 350 K up to 420 K. Pressures up to 10 MPa were applied. It has been found that in the binary mixture propane + tetratriacontane partial miscibility occ urs in the liquid phase, i.e. in this binary a three-phase equilibrium liquid + liquid + vapour (l1l2g) with a lower and upper critical endp oint exists. As well as the measurement of this three-phase equilibriu m, various types of two-phase boundaries and the three-phase equilibri um solid tetratriacontane + liquid + vapour (s(B)lg) have been determi ned experimentally. In addition simplified-perturbed-hard-chain theory (SPHCT) was applied to model the vapour + liquid equilibrium data. Th e results obtained are compared with similar calculations, using the P eng-Robinson (PR) equation of state. The calculations established that when modelling vapour + liquid equilibria of binaries with molecules differing largely in chain-length, the SPHCT equation of state should be preferred over the PR equation.