Global phase diagrams of model and real binary fluid mixtures -: Part II.: Non-Lorentz-Berthelot mixtures of attractive hard spheres

The global phase diagram of a binary mixture of attractive hard spheres described by the Boublik-Mansoori-Carnahan-Starling-Leland equation of state with a van der Waals mean field attractive term is investigated in its dependence on the ratio of the hard-sphere diameters and the strength of the attraction. Two values of the energetic combining rule parameter k(12), determining the deviation from the geometric mean rule, are considered. In addition to phenomena reported recently for k(12)=1, the shield region of quadruple points is investigated for k(12)=0.8, along with its associated azeotropic phenomena. For k(12)=1.15, the mixture exhibits a rich set of low-temperature azeotropic phenomena: cusps on the p-T projections of azeotropic lines, exchange of branches of azeotropic lines, zero-temperature limited azeotropy, and double critical azeotropic points. Some of these azeotropic phenomena are described here for the first time.