Modeling the Phase Behavior of Asphaltene + Toluene + Polystyrene Mixtures—A Depletion Flocculation Approach

Abstract

Mixtures of polystyrene + Maya and Athabasca pentane asphaltene + toluene split into two stable phases, one toluene + polymer rich and one toluene + asphaltene rich. This phase behavior was attributed to depletion flocculation, previously, and a Fleer-Tuinier based model was used to simulate the phase diagrams including one-phase to two-phase boundaries, tie lines, critical points, and relative phase volumes in the two-phase region. The distribution of asphaltenes between molecular and aggregated species and the variation of the mean size and size distribution of aggregated asphaltene species with global composition are not known a priori. This knowledge gap presents a key conceptual challenge. Consequently, the variation of the fraction of asphaltenes participating in the depletion flocculation mechanism, γ(η), and variation of asphaltene mean size Rs(η) with asphaltene volume fraction, η, are fitted parameters introduced in the phase behavior model. In this work, the phase behavior modeling approach is ...