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Temperature-Independent Colloidal Phase Behavior of Maya Asphaltene + Toluene + Polystyrene Mixtures

Pouralhosseini, Sajjad, Shaw, John M.
Energy & Fuels 2015 v.29 no.8 pp. 4864-4873
ambient temperature, models, polystyrenes, toluene
Polystyrene, a non-adsorbing polymer, has been shown to cause Maya and Athabasca asphaltene + toluene mixtures to split into two stable liquid phases at room temperature. One phase is enriched in polystyrene and toluene. The other phase is enriched in asphaltene and toluene. The phase boundaries, tie lines, and critical points for Maya asphaltene + toluene + polystyrene (Mw = 393 000 and 700 000 g/mol) and Athabasca asphaltene + toluene + polystyrene (Mw = 393 000 g/mol) have also been simulated at room temperature using a modified Fleer–Tuinier colloid phase behavior model. In this work, the temperature dependence of the depletion flocculation-driven phase behavior is investigated for Maya asphaltene + toluene + polystyrene (Mw = 393 000 g/mol) mixtures both experimentally and theoretically. The coincidence of experimental two-phase to one-phase boundaries, including liquid–liquid critical points and tie lines at 248 and 298 K, illustrates the temperature-independent nature of this phase behavior. This outcome is interpreted and predicted in terms of the known temperature dependence of the radius of gyration of polymer molecules, possible impacts of temperature variation on mean asphaltene aggregate size, and relative importance of steric repulsion and depletion attraction effects in determining the phase behavior of asphaltene + toluene + polystyrene mixtures. Experimental and modeling outcomes are discussed.