HIGH-PRESSURE SOLID-FLUID AND VAPOR-LIQUID-EQUILIBRIA IN THE SYSTEM (METHANE PLUS TETRACOSANE)

Experimental vapour-liquid, solid-fluid, and solid-liquid-vapour equil ibrium data of the binary system (methane + tetracosane) in the temper ature range 315-450K and for pressures up to 200MPa are presented. The experiments were carried out for various mixtures with compositions r anging from almost pure methane to pure tetracosane. It was found that the (solid alpha-to-solid beta) transition of pure tetracosane has ha rdly any influence on the shape of the (solid + fluid/fluid) boundary curves and the three-phase equilibrium curve (solid tetracosane + liqu id + vapour) of the binary system. The second critical endpoint of the three-phase curve (s(C24) + 1 = g), where solid tetracosane is in equ ilibrium with a critical fluid phase was located at a temperature of T = (322.60 +/- 0.25) K, a pressure of p = (104.7 +/- 0.4) MPa, and a m ole fraction of tetracosane in the critical fluid phase of x(C24) = (0 .041 +/- 0.003).