On the applicability of regular solution and Flory-Huggins theories to asphaltene liquid mixtures.

We critically review two classic, molecular-based solution theories, the regular solution theory and the Flory-Huggins theory, in the context of revealing their limited applicability to liquid mixtures containing asphaltenes, a significant fraction of crude oil. Asphaltene molecular structures, either as depicted by the Archipelago model or the island model, are non-linear (not chain-like) and rigid, making the application of the aforementioned theories to describe their phase behaviour problematic. In addition, since asphaltenes contain chemical moieties that are able to interact through directional dependent specific intermolecular interactions (e.g., hydrogen bonds), this renders the incorporation of Hildebrand solubility parameters into the theories inappropriate. As a result, the two theories do not always predict the onset and amount of asphaltene precipitation correctly for crude oil under different conditions (e.g., temperature, pressure, chemical composition of crude oil, solvent concentration). It is the hope of this author that researchers in the field channel their efforts into developing a brand-new solution theory for asphaltene liquid mixtures by taking the key molecular attributes of asphaltenes into account. [ABSTRACT FROM AUTHOR]